text:
Difference between revisions of "2017 Group 3 Project"
|Line 77:
|Line 77:
[[File:Microscopic structure of pancreas.JPG|thumb|
[[File:Microscopic structure of pancreas.JPG|thumb|||'''Figure 1.''' Microscopic image of the pancreas, which reveals the structure of a blood vessel, acini, pancreatic islet and duct. Image is reprinted with permission from<ref name="Gittes">Gittes, G. (2009). Developmental Biology of the Pancreas: a Comprehensive Review. Dev. Biol.: 326(1);4-35</ref>.]]
Among most species, pancreatic islets are generally characterised by an oval shape although the distribution of cells, within the endocrine pancreas, are subject to variation across animals. In most mammals, the islet contains a core of beta cells, which is encircled by a mantle of non-beta cells. Conversely, in humans and primates, cells are dispersed with greater complexity and deviate from the mammalian mantle-core arrangement to a composite of several mantle-core subunits. Due to such cellular organisation, pancreatic islets within humans and primates may be of oval or clover-leaf shape. Islets of Langerhans are highly vascularised structures, which contain capillaries that are lined by endothelial cells comprising of mitochondria*, ergastoplams*, a golgi complex* and a nucleus*. The peripheral extensions of the cytoplasm* of such endothelial cells are typically thinner and lack these organelles however, they contain several fenestrae or openings. While it is not confirmed whether these fenestrae vary in quantity and/or distribution, it is predicted that they represent areas for communication and allow the transfer of materials between the bloodstream and the extravascular space.
Among most species, pancreatic islets are generally characterised by an oval shape although the distribution of cells, within the endocrine pancreas, are subject to variation across animals. In most mammals, the islet contains a core of beta cells, which is encircled by a mantle of non-beta cells. Conversely, in humans and primates, cells are dispersed with greater complexity and deviate from the mammalian mantle-core arrangement to a composite of several mantle-core subunits. Due to such cellular organisation, pancreatic islets within humans and primates may be of oval or clover-leaf shape. Islets of Langerhans are highly vascularised structures, which contain capillaries that are lined by endothelial cells comprising of mitochondria*, ergastoplams*, a golgi complex* and a nucleus*. The peripheral extensions of the cytoplasm* of such endothelial cells are typically thinner and lack these organelles however, they contain several fenestrae or openings. While it is not confirmed whether these fenestrae vary in quantity and/or distribution, it is predicted that they represent areas for communication and allow the transfer of materials between the bloodstream and the extravascular space.
Revision as of 16:17, 26 May 2017
2017 Projects: Group 1 - Delta | Group 2 - Duct | Group 3 - Beta | Group 4 - Alpha
- 1 Introduction
- 2 Structure
- 3 Pancreatic and Beta Cell Development
- 4 Function
- 5 Signalling
- 6 Role in Pathology
- 7 Current Research
- 8 Review Quiz
- 9 Glossary
- 10 References
Beta cells, abbreviated as β-cells, are one of the four major cells found within the endocrine* portion of the human pancreas*. The human pancreas is a composite organ, which extends from the distal foregut endoderm and is composed of an exocrine* and endocrine portion. The exocrine tissue consists of copious amounts of acinar cells, that discharge digestive fluid, and a complementary duct complex through which the secreted fluid drains into the intestine. The endocrine portion of the pancreas is composed of islets of Langerhans*, or pancreatic islets (reviewed in[1]). These islets of Langerhans constitute approximately 1-2% of the pancreas and are dispersed throughout it[2]. They contain multiple endocrine cells; alpha, beta, delta, gamma and epsilon cells, which secrete the hormones; glucagon, insulin, somatostatin, pancreatic polypeptides and ghrelin, respectively[1]. The pancreatic islets also host several endothelial cells, nerves and fibroblasts hence deeming them highly vascularised structures, which vary in size from small clusters to larger clusters, containing up to several thousand islets and reaching diameters of 300-400 μm. As the majority of pancreatic islets are typically less than 160 μm in diameter, islets which exceed this diameter are considered to be responsible for the majority of islet's total mass[3].
Currently, it is predicted that adult humans have approximately 2 million islets of Langerhans, which contributes to 2% of their total pancreatic weight[4]. Within these islets, approximately 60-70% of the total islet-cell population can be attributed to beta cells[5]. Beta cells, or insulin-secreting cells, are thus key cells within the pancreas and are predominately responsible for preserving normoglycaemia* by neutralizing blood glucose levels with appropriate quantities of insulin secretion[6]. While glucose levels are the chief driver, insulin secretion and synthesis by beta cells may occasionally occur in response to other factors such as nervous stimuli, hormones and nutrients[4].
|Video 1. Introductory Video on the Role of the Pancreas:
|Table 1. History of Pancreatic and Beta Cell Development
|Historical Event
|The islets of Langerhans, or pancreatic islets, were first discovered by German anatomist Paul Langerhans, within rabbits, as anatomical formations with no direct connection to the duct. At that moment, no function was attributed to them[7]. Prior to the discovery, the pancreas was solely recognised as an exocrine organ[8].
|Joseph Von Mering and Oskar Minkowski successfully completed the first pancreatectomy* in a dog. Through this, they discovered that the removal of the pancreas induced diabetes in the dog . This discovery was paramount as it irrevocably established that the pancreas and diabetes were affiliated [9].
|Edouard Laguesse, who located islets in the human pancreas, suggested that they were responsible for the internal secretions that regulate glycemia*, and named them Langerhans, after their discoverer [10].
|1907 and 1911
|Lane and Bensley developed staining techniques to analyse the structure of the pancreas at a cellular level. These stains revealed at least two different granular cell types; A cells, which contained granules preserved by alcohol, and B cells, which contained granules preserved by chrome sublimate*[9].
|Homans noticed that B-cells were involved in experimental diabetes and thus attributed the sugar regulating function to them[8].
|Best and Banting isolated insulin from the canine pancreas after ductal ligation. Their discovery of insulin was awarded the Nobel Prize in Medicine in 1923[9].
|Dunn et al. selectively destroyed beta cells by administration of alloxan*, which led to diabetes[8].
|Morphological features of the islet cell types were established through multiple studies utilising electron microscopy. Their structure and the appearance of their cytoplasmic secretory granules were observed[10].
|First case of insulin independence by pancreas transplantation by William Kelly and Richard Lillehei into a 28 year old uremic* woman at the University of Minnesota[11].
|Pictet and Rutter analysed the ultrastructural development of the pancreas by transmission electron microscopy and found that both the endocrine and exocrine cells of the pancreas were derived from a common progenitor*; alpha cells were the first endocrine cells to differentiate[9].
|Cudworth et al. made a crucial step in the etiological* classification of diabetes; introducing the terms type 1 and type 2 diabetes[12].
|Sharp et al. led further advances in transplantation achieving clinical insulin independence, lasting 1 month, through islet transplantation[13].
|Shapiro et al. utilise the "Edmonton protocol*" where 7 patients with type 1 diabetes receive islets and all recipients achieve insulin independence. The study utilised immunosuppression drugs to prevent rejection[14].
|Pagliuca et al. conduct the first successful generation of functional human pancreatic beta cells in vitro*, potentially providing an unprecedented cell source for drug discovery and cell transplantation therapy in diabetes [15].
|Research continues into stem cell therapeutics for diabetes (refer to "Current Research").
Among most species, pancreatic islets are generally characterised by an oval shape although the distribution of cells, within the endocrine pancreas, are subject to variation across animals. In most mammals, the islet contains a core of beta cells, which is encircled by a mantle of non-beta cells. Conversely, in humans and primates, cells are dispersed with greater complexity and deviate from the mammalian mantle-core arrangement to a composite of several mantle-core subunits. Due to such cellular organisation, pancreatic islets within humans and primates may be of oval or clover-leaf shape. Islets of Langerhans are highly vascularised structures, which contain capillaries that are lined by endothelial cells comprising of mitochondria*, ergastoplams*, a golgi complex* and a nucleus*. The peripheral extensions of the cytoplasm* of such endothelial cells are typically thinner and lack these organelles however, they contain several fenestrae or openings. While it is not confirmed whether these fenestrae vary in quantity and/or distribution, it is predicted that they represent areas for communication and allow the transfer of materials between the bloodstream and the extravascular space.
The beta cell, itself, is enclosed by a continuous plasma membrane and includes, within its cytoplasm, several membrane-bound organelles such as the endoplasmic reticulum*, mitochondria, a nucleus, golgi complex and secretory granules*. The endoplasmic reticulum, also called the ergastoplasm, is composed of two lamellar membranes that have ribosomes attached to their exterior surface. In comparison to the mitochondria present within adjacent acinar cells, the mitochondria of the beta cells are relatively smaller in size. However they are easily identifiable by the cristae within their matrix. The golgi complex and beta granules are similarly composed of smooth membranous sacs, although the latter is sequestered from the cytoplasm by the walls of these sacs. The beta granules are additionally dispersed throughout the entire cytoplasm. The nucleus contains a double-layered nuclear membrane and also several nuclear pores, which allow continuity and interaction between the nucleoplasm and cytoplasm of the beta cell.
Adjacent beta cells are connected to each other at distributed focal points, termed desmosomes, along their plasma membrane. Between two successive desmosomes, an intercellular space exists and its size is reliant upon the respective activity of the cells. The capillaries present within the islets of Langerhans are detached from the beta cells by two basement membranes; one related to the endothelium and the other to the capillary surface. Typically, between these two basement membranes, cross-sections of fibroblasts* and unmyelinated* nerve fibres can be detected. In some instances, unmyelinated nerve fibres have also been identified beneath the basement membrane and in close contact with the cell's plasma membrane. Although presently unconfirmed, this is considered to indicate synapses between the nerve fibres and the beta cell[5].
Structural Modifications with Age
Extensive studies conducted on human pancreases, from the prenatal period through to adulthood, have revealed that the anatomical architecture of pancreatic islets resemble their adult form by the age of 2. As a direct result of this, the pancreas experiences substantial beta cell proliferation* during the first 2 years after its conception, which enables significant increases in beta cell mass and area. Increased beta cell production thus manifests as an increase in the diameter of existing pancreatic islets, rather than the formation of new islets. In fact, while 10% of beta cell mass increase during early life can be attributed to islet development, a sizeable 90% can be linked to an increase in islet size. Although, beta cell replication continues throughout life, the replication rate notably decreases after adolescence and hereafter beta cell mass remains relatively constant between the ages of 20 – 100 (reviewed in[17]).
Structural Comparison between Humans and Mice
Consequential of the clinical importance of pancreas-associated disease (refer to "Pathology"), the structure of the pancreas is studied extensively within medical science. Studies of the human pancreas, nevertheless, are restricted due to the inherent ethical and medical limitations present in obtaining pancreatic samples at specific and intermittent intervals. As a result of scarce human pancreatic samples, animal models are increasingly used in scientific studies. Within current pancreatic research, mice are the most frequently studied animal models. As a sizeable portion of scientific knowledge concerning the human pancreas is derived from studies conducted on mice, it is thereby imperative to identify and understand the distinction between the human and mouse pancreas[17].
Macroscopic Comparison
At a macroscopic level, the human pancreas is a well-defined organ, which contains three key structural components: the anterior and posterior head, body and tail (reviewed in[18]). The left border of the superior mesenteric artery borders the head and body of the pancreas, while the midpoint of the pancreatic body and tail, combined, is understood as the border between the body and the tail. Reflecting a C-shape, the pancreatic head is continuous with the upper curvature of duodenum whereas the pancreatic tail touches the hilum of the spleen. The narrow and flat pancreatic body locates itself underneath the stomach and extends in such a manner that it crosses with the superior mesenteric artery and vein, abdominal aorta, inferior vena cava and portal vein.
Contradictorily, the mouse pancreas is less defined than its human counterpart, see Figure 2. and Figure 3., and in a dendritic manner, is uniquely diffused along the mesentery of the proximal small intestine of mice. Analogous to the human pancreas, it can also be distinguished into three key structural components. However, these are termed 'lobes' and are identified as the duodenal, splenic and gastric lobe. The largest lobe, the splenic lobe, extends between the duodenum and the spleen and is homologous to the body and the tail of the human pancreas. The second largest lobe, the duodenal lobe, is located within the mesentery, that surrounds the duodenum, and is homologous to the human pancreatic head. Additionally, the gastric lobe, which is the smallest observable lobe, is considered to be a component of the splenic lobe, from which it originally develops, and is homologous to the auricle of the human pancreas. Characteristically, patches of adipose*, connective and lymphatic tissue separate these three main pancreatic lobes in mice[17].
Microscopic Comparison
Microscopically analysed, each lobe of the pancreas contains numerous smaller lobules, which vary in size respective to the organism and measure 1-10 mm in diameter in humans and 0.5-1.5 mm in diameter in mice. Dome-resembling clusters of pyramidal acinar cells are dispersed throughout these pancreatic lobules. They secrete various digestive enzymes, which are ultimately released into the duodenum by successive movement through intercalated ducts, intralobular ducts, interlobar ducts and finally the pancreatic duct, thus forming the exocrine pancreas. The endocrine portion of the pancreas, predominately constituting islets of Langerhans, is embedded within the exocrine tissue. Notably, the size and distribution of pancreatic islets is congruous between humans and mice. With distinctly irregular cross-sections, they are home to thousands of hormone-secreting endocrine cells, which may also be singularly and randomly scattered across acinar and ductal tissues. While a minimum of five different polypeptide endocrine cells can be identified within the islets, beta cells, which synthesize and secrete insulin, form the majority and account for 60-70% of the islet cell population in humans and 60-80% in mice.
The spatial organization of beta cells has continuous focus for scientific research. In mice, the mantle component of pancreatic islets contain non-beta cells while the core component exclusively comprises beta cells. In humans, it was initially perceived that, alongside a similar mantle-core pattern, beta cells additionally formed ribbon-like clusters and were scattered throughout islets in an unorganised manner. However, consequential of recent studies, the current scientific consensus is that human pancreatic islets form trilmainar plates, which are folded into a U- or O-shape, and within which there are two layers of alpha cells that enclose a single beta cell layer. The reason for this specific organisation is considered to be the promotion of heterologous contact between both endocrine cells. Alternatively, in mice, there is homologous contact among alpha cells within the mantle of the islet and beta cells within the core of the islet. It is proposed that this specific type of spatial arrangement promotes alpha-cell-stimulation of beta cell functional activity[17].
|Table 2. Summary Table of Key Comparisons between Human and Mice Pancreas
|Macroscopic Pancreatic Structure
|Well-defined organ with three structural components: the head, body and tail
|Less-defined structure with three lobes: duodenal, splenic and gastric lobe
|Diameter of Lobules
|1 - 10 mm
|0.5 - 1.5 mm
|Beta Cells as a % of Pancreatic Cell Population
|60 - 70%
|60 - 80%
|Microarchitecture of Islets
|Trilaminar islets predominate
|Mantle islets predominate
|Contact between Alpha and Beta Cells
|Heterologous contact between endocrine cells as two layers of alpha cells enclose a single beta cell layer
|homologous contact among alpha cells within the mantle of the islet and beta cells within the core of the islet
Pancreatic and Beta Cell Development
The ultimate architecture of the complete adult pancreas is the outcome of several necessary embryologic events (reviewed in[19]). During embryonic days 8.5 and 9, the emerging embryo moves from a lordotic position to a fetal position[20], which causes the endoderm layer to fold on itself and form a primitive gut tube that is divided into the foregut, midgut and hind-gut. Upon the establishment of the gut tube, the development of the dorsal pancreas is hereafter controlled by the notochord[19], which is the source of permissive signals that enable the differentiation of the foregut endoderm into a pancreas. The removal of the notochord is scientifically evidenced to eliminate the expression of pancreatic genes thus inhibiting pancreatic development and preventing the formation of all pancreatic cells, including beta cells[21]).
Of the three divisions of the gut tube, the foregut is the most essential[22] as the first morphological process in pancreatic formation, and beta cell development, is a condensation of the mesenchyme covering the dorsal aspect of the endodermal gut tube in the foregut. Succeeding this condensation, at 26 days post-conception, the endoderm evaginates into the mesenchyme and dorsal and ventral buds arise from the foregut. The buds are marked by transcription factors, such as pancreatic and duodenal homeobox factor 1 (PDX1) [22], SRY (sex-determining region Y)-box 9 (SOX9) and GATA binding protein 4 (GATA4), which are all necessary for pancreatic growth[23]. The epithelium, which constructs the mesenchyme surrounding the pancreas, coelomic epithelium, also begins to compartmentalise the pancreas away from non-gut structures and a substantial increase in the proliferation of mesenchymal cells, between the coelomic epithelium and pancreatic epithelium, is seen[19].
At approximately 37 to 42 days after gestation, the proximal portion of the dorsal bud form small accessory ducts called ducts of Santorini, while the remainder of the dorsal bud and ventral bud fuse to form the duct of Wirsung, which runs across the entire pancreas. Hereafter, the cellular architecture of the pancreas undergoes significant change and a major amplification in the amount of endocrine cells, particularly β-cells, is observed. Pancreatic acinar cells also undergo cell differentiation and gene expression for acinar enzymes increase in an exponential manner. The rough endoplasmic reticulum and zymogen granules also begin forming, consequently causing the pancreas to become opaque to the naked-eye due to high zymogen granule concentrations.
Although pancreatic alpha cells are differentiated and observed before beta cells, the earliest endocrine cells of the pancreas are collectively found in an admixture of endocrine, exocrine and epithelial cells, which all maintain close contact with the lumen. Eventual morphological transitions, however, allow endocrine cells to become distinct from epithelial cells and lose connection with the lumen[19]. At this stage in development, a down regulation of PDX1, which marks pluripotent precursor cells, is detected in endocrine progenitor cells as they become non-epithelial. Throughout pancreatic maturation, PDX1 remains principally expressed in the beta cells of the pancreas population[24], which is considered to be necessary for proper endocrine differentiation[20]. As the developmental process nears conclusion, endocrine cells aggregate in pancreatic ducts, as shown in Figure 4., and form islets of Langerhans[19].
On a hormonal level, at around 52 days after the conception of the human pancreas, Neurogenin-3 (NGN3), a regulator of pancreatic islet differentiation and regeneration is first detected in the pancreas[25]. Although the expression of the transcription factor PDX1 precedes them[24], insulin, glucagon and somatostatin are the first pancreatic hormones expressed. Pancreatic polypeptide is not detected until about 10 weeks post-conception. At around 12 weeks into the gestation period, at the point where pancreatic islet formation reaches its peak, all four hormones are expressed and thus the total number of hormone expressing cells, present within the islets, is increased[26].
The overall function of the pancreas is to maintain glucose levels within the blood and beta cells play a specialised role within this process. The insulin gene, which provides instructions for the manufacture of the hormone insulin, is solely expressed in the endocrine portion of the pancreas within the beta cells of pancreatic islets. Insulin, a polypeptide hormone, is a key regulator of metabolism as it promotes the storage of excess glucose, amino acids and fatty acids, by acting on the liver, muscles and adipose tissue. Insulin release into the bloodstream predominantly occurs as a consequence of increased blood glucose levels. Glucose phosphorylation, by glucokinase, is currently understood to act as the glucose sensor, as it adjusts the rate of metabolic activity to the extracellular concentration of glucose. Glucose metabolism generates intracellular signals in beta cells, which subsequently initiates insulin secretion, insulin mRNA translation and insulin gene transcription.
|Video 2. Video Elucidating the Function of Insulin in the Human Body:
Insulin Gene Expression
In the late 1980s, the 5' flanking region of the insulin gene was identified in transgenic mice. This proved to be an extraordinary breakthrough as it allowed the general location of binding sites, for transcription factors, to be discovered. The transcription factor binding sites, which direct beta-cell-specific expression, were eventually located to be between −520 and +1 base pairs relative to the transcription initiation site. In later studies, congruous expression data was collected for the human insulin gene. Both results thus collectively indicate that there are sequences conserved between mammalian insulin genes, which lie within 350bp of the transcription start site and control the specific cell-type expressions. The enhancer region in mammalian insulin genes is located between nucleotides -340 and -91. While the transcription factors that bind onto this region principally determine the glucose-regulated expression properties of the gene, the activity of the enhancer can be additionally up-regulated and/or down-regulated by cellular activity. For example, through autocrine signalling, the insulin secreted from beta cells may increase insulin transcription in the same beta cells, by positively influencing enhancer-mediated activation [27].
Insulin Biosynthesis
In the 1950s, insulin (as show in Fig. x) became the first protein to have its structure clearly revealed. The discovery exposed insulin as a two-chain hormone and consequently triggered widespread speculation in the scientific community on the underlying mechanisms contributing to such a structure. Succeeding the discovery of single-chain precursor proteins, which occurred in 1967, insulin synthesis was finally understood to occur through several reactions with multiple single-chained precursor proteins, including preproinsulin and proinsulin.
During insulin biosynthesis, the initial product formed instantaneously after insulin mRNA translation is preproinsulin, which contains a hydrophobic N-terminal 24 residue signal peptide. The signal peptide engages with the signal recognition particle (SRP), a ribonucleoprotein particle that is located within the cytosol, which enables the separation of the preproinsulin polypeptide chain from the cytosolic compartment into the secretory pathway. From here, the preprohormone is translocated across the membrane of the rough endoplasmic retiticulum (RER) and into its lumen, via a peptide-conducting channel. A specialized signal peptidase, situated on the surface of the RER membrane, cleaves and rapidly degrades the signal sequence. Inside the RER, several chaperone proteins, catalyse the folding of proinsulin and facilitate its manufacture of three disulfide bonds, which largely contribute to the development of its native structure.
Within a time period of ~10-20 minutes, proinsulin is rapidly transported from the RER to the Golgi apparatus. Here, proinsulin is packaged into immature secretory vesicles [REF] and cleaved to form equimolar amounts of insulin and connecting polypeptide (C-peptide) [28]. The predominant route for proinsulin processing is via cleavage at the junctions resulting in a 32,33 proinsulin peptide split, followed by the removal of 2 amino acids resulting in Des-31,32 proinsulin which finally becomes mature C-peptide and insulin with the action of pro-protein convertase-2 (PC2) and carboxypeptide-E (CPE). The alternative pathway which occurs less commonly is where the 2 amino acids are removed first (see Figure X) [29].
While proinsulin and insulin have a direct biological effect, C-peptide has no effect on homologous or heterologous tissue and no ability to influence the concentration or action of beta cell hormones (reviewed in [30]). Although small volumes of proinsulin and its immediate cleavage forms, C-peptide and insulin are collectively stored in the secretion granules of beta cells, insulin is the predominant hormone released after signalling.
The formation of insulin from its precursor, proinsulin, is initiated approximately 20 minutes after the synthesis of preproinsulin and typically lasts for 1-2 hours, independent of additional protein synthesis.
Notably, proinsulin and insulin share similarities with respect to many of their properties, including solubility, isoelectric point, self-associative properties and relative reactivity with insulin antiserum. The insulin moiety found within proinsulin is also highly similar to the one present in insulin itself, as indicated by nuclear magnetic resonance (NMR) imaging.
Image Proinsulin and Image insulin
Cell Biology of Insulin Biosynthesis
Congruous to other neurosecretory cells, the Golgi apparatus plays a substantial role in the formation of secretory granules in beta cells. However, its dynamic nature and the underlying mechanisms, which facilitate the transport and sorting of secretory products within it, is currently only partly understood. With further research, new models for Golgi progression are continuously proposed. Currently, a scientifically favoured model presents a form of the Golgi apparatus wherein individual cisternae, containing their secretory contents, migrate from cis to trans while small, coated vesicles transport various Golgi resident proteins and enzymes in an opposite manner from trans to cis. Relative to this model, while secretory products mature, they are kept in the same compartment and only exit from it as they dissipate into the trans Golgi network into immature secretory granules. Recent immunocyto-chemical studies have established that newly synthesized clathrin-clad granules in the trans Golgi cisternal network (TGN) are rich in proinsulin, which confirms the proposal that conversion to insulin occurs principally during the maturation of the secretory granules. The proteolytic processing of proinsulin may be prevented by energy poisons, which block their transfer into secretory vesicles. Nevertheless, once newly manufactured proinsulin has reached the trans Golgi, energy is no longer required to convert it to insulin. While proinsulin conversion may begin in the trans compartment of the Golgi apparatus, it is now confirmed that it occurs predominantly within newly manufactured secretory vesicles as they leave the Golgi region and mature biochemically in the cytosol (see Fig y.) [28].
Quantitative Aspects of Insulin Secretion
In the late 1960s, the dynamics of insulin secretion, in response to glucose stimulation was studied and results demonstrated that glucose infused into the pancreas for extended amount of time, led to two different phases of insulin release. The first phase was characterised by rapid insulin release for 2 minutes, why the latter phase involved the continuous release of insulin, which slowly increased in rate until the termination of the glucose stimulus [31].
This was the first indication that insulin release from beta cells follows a biphasic pattern [32]. Insulin release in the initial phase is due to ATP-dependent potassium channels, which allow increased calcium influx and the discharge of ready and releasable insulin-containing granules. The second phase involves preparing granules for release and is thought to include the translocation of the granules and checks to ensure that they are competent for exocytosis. Insulin secretion in the second phase therefore occurs over a greater length of time. In fact, in mouse islets, of the 13 000 granules present in beta cells, only ~100 are ready for release in phase one and thus the others must be finalized in phase two [33]. Quantitative comparisons can be made between both phases of insulin release by reports, which state that first and second phase insulin secretion in mouse islets are 0.14%/min and 0.05%/min, respectively [32].
The Stimulus-Secretion Coupling Mechanism
Stimulus-secretion coupling refers to glucose-dependent insulin secretion from beta cells. Congruous to muscle cells, beta cells are also dependent on electrical activity and calcium entry in order to discharge insulin into the body. As a result, they have specific ion channels located in their plasma membrane, which enable the flow of calcium and potassium ions into and out of the cell. As these ions are electrically charged, their movement across the membrane causes action potentials, which are sharp changes in voltage [34].
In pancreatic beta cells, an increase in blood glucose levels blocks ATP-dependent potassium channels thus leading to the depolarisation of the membrane. Initially identified in ventricular myocytes, ATP-sensitive potassium channels are potassium channels that are inhibited by high intracellular concentrations of ATP (reviewed in[35]. As the activation of these channels disallow the production of action potentials, their inhibition, by glucose, stimulates action potentials by triggering voltage-dependent calcium channels in the membrane to open and thus allow increased calcium influx into the cell (reviewed in[36]). Within the cell, the calcium ions act on exocytotic machinery to stimulate the merging of vesicles, containing insulin, with the plasma membrane, thereby preparing them for secretion into the blood stream [32].
Conversely, as the electrical activity induced in beta cells is mainly due to calcium ion influx [37], decreased extracellular levels of calcium ions prevent the firing of action potentials and thus, by extension, inhibit insulin secretion [34].
Glucose Metabolism and Potassium Channels
As glucose breakdown is imperative for insulin secretion, the inhibition of mitochondrial metabolism prevents insulin from being secreted by beta cells. Adenosine triphosphate (ATP) is the major product of glucose metabolism and therefore is a key factor that links the mitochondrial metabolism of glucose and ATP-sensitive potassium channels. ATP-dependent potassium channels contain four pore-forming subunits alongside four accessory sulfonylurea receptor subunits (SUR1). These SUR1 subunits are essential components of beta cells, as they are the focus site for anti-diabetic sulphonylurea drugs, which aim to increase insulin secretion by replication the effect of glucose in order to block ATP-sensitive potassium channels [34].
While increased glucose levels generate a high cytoplasmic concentration of ATP and depolarize beta cells by blocking ATP-sensitive potassium channels[38], under low concentrations of glucose, these channels are open and enable the outward flux of potassium, causing a negative cellular membrane potential of ~ -70 mV. At this point, action potentials cease to occur and insulin exocytosis is inhibited. The membrane potential is only increased to more positive values once glucose-induced increases in ATP drive the closure ATP-sensitive potassium channels. Hereafter, L-type voltage-dependent calcium channels, which are predominately expressed in beta cells, allow the release of insulin into the blood in order to maintain glucose homeostasis[34].
Un-Coupling Glucose Metabolism and ATP Production in Beta Cells
As mentioned above, the voltage of the cell membrane is dependent upon changes in the intracellular concentration of ATP. As a result of this, perturbations of metabolic pathways that produce ATP can, by extension, impact insulin secretion by beta cells. In all cells, ATP is generated in the mitochondria[34], which produces approximately 95% of the cell's energy and is therefore colloquially termed "powerhouse of the cell" [39]. Within the mitochondria, the electron transport chain (ETC) is the central machinery responsible for ATP production (reviewed in [40]) and is heavily reliant upon a proton gradient across the mitochondrial membrane[34].
The ETC is composed of four enzyme complexes that transfer electrons from donors, such as NADH, to the ultimate electron accepter, oxygen. Throughout this transfer of electron, the ETC concurrently pumps protons, or hydrogen ions (H+), into the inter-membrane space, which subsequently generates a gradient across the inner mitochondrial membrane. ATPase, an enzyme, then harnesses this gradient to drive ATP synthesis[41] (as shown in Figure. X and further explain in Video 3.).
Specifically within beta cells, the uncoupling protein-2 (UCP2) can largely impair the generation of ATP via the mitochondrial ETC as it enables a proton leakage across the mitochondrial membrane [34] and therefore inhibits the necessary formation of a proton gradient. The overexpression of UCP2 can therefore bypass the production of ATP, which is reinforced by studies that report a 50% reduction in the ATP content in the cells of UCP-2-induced pancreatic islets [42]), On the other hand, a loss of UCP2 expression is hence responsible for increased intracellular ATP concentrations and glucose-stimulated insulin secretion by beta cells, which serves to decrease levels of glycemia [43]). It has also been discovered that the expression of Sirt1in beta cells downregulates UCP2 expression, further enhancing insulin secretion [34].
|Video 3. Explanation of the Mitochondrial Electron Transport Chain:
Role in Pathology
To reiterate the sections above, insulin is vital in the maintenance of glucose levels. Through signalling of liver, muscle and fat cells, insulin allows for the uptake of glucose, allowing for its use as an energy source. When the body has a sufficient amount of energy, insulin signals the liver to take up glucose and store it as glycogen. Thus in the absence of insulin or responsiveness to insulin, glucose remains in the blood stream resulting in a rise of blood-glucose levels. Refer to the video below for a visual conceptual explanation of the relationship between insulin, glucose and diabetes.
|Video 4. Video to understand the connection between insulin and diabetes:
|Type 1 Diabetes Mellitus (T1DM)
|Type 2 Diabetes Mellitus (T2DM)
Type 1 diabetes is one of the most common chronic childhood diseases
Type 1 diabetes varies dramatically on a global scale with more than 350-fold variation in incidence among reporting countries; overall:
Type 1 diabetes results from an insulin deficiency that is caused by the loss of pancreatic beta cells
Early familial and twin studies supported the importance of both genetic and environmental risk factors. [50]
In the normal healthy body, beta-cells are able to function at a greater capacity when glucose increases, thus producing more insulin to maintain glucose homeostasis; beta cells are able to adapt resulting in a compensatory response in insulin production. Beta-cell dysfunction is seen inType 2 diabetes as the compsenatory response results in gradual failure of beta cells, primarily due to insulin resistance within the individual [51]
Primarily lifestyle factors cause this insulin resistance to occur;
Recent increase in occurence of type 2 diabetes may also be attributed to environmental factors as reveiwed by Olokoba et al. (2012) [53].
The pathogenesis of autoimmune type 1 diabetes has been extensively studied through the use of animal models; nonobese diabetic mouse and diabetes-prone BioBreeding rat. Exact mechanisms of initiation and progression remain unclear, however through the animal studies it is generally believed that beta-cell autoantigens macrophages, dendritic cells, B lymphocytes, and T lymphocytes are involved in the beta-cell specific autoimmune process. As seen in Figure 3, the beta-cell autoantigens are processed by the macrophages, dendritic cells or B cells in the pancreatic islets, and then presented to the autoreactive CD4+ T cells in the peripheral lymphoid system. These cells are consequently activated leading to the secretion of cytokines which can activate beta-cell specific cytotoxic CD8+ T cells. Activated T cells recruit at the iselts, producing cytokines which further activate macrophages and other T cells; all contributing to the destruction of pancreatic beta-cells. [55]
The evolution of beta-cell dysfunction is marked by 5 stages as identified by Weir & Bonner-Weir (2004) [56]:
Pancreatogenic (Type 3c) Diabetes
Unlike T1DM and T2DM, Type 3c Diabetes Mellitus (T3cDM) is a form of secondary mellitus that is caused by underlying pancreatic diseases such as acute or chronic pancreatitis, cystic fibrosis, pancreatic cancer or any other pancreatic trauma leading to loss of pancreatic tissue; the most common cause being chronic pancreatits (CP). CP accounts for 75-80% of T3cDM cases while pancreatic carncinoma accounts for 8%. [57] T3cDM was previously believed to have a lower prevalence of approximately 0.5-1.2 percent among diabetes cases in North America, however recent studies suggest higher occurences with a recent 2013 study finding a 5-10% prevalece among all diabetic subjects in Western populations. [58] A review by Anderson et al. (2013) suggest previous underestimations may be attributed to the fact that it has become easier to detect exocrine pancreatic pathology with the advancements in imaging technology and noninvasive screening methods to quantify exocrine dysfunction. [59]
Also unlike T1DM and T2DM the endocrinopathy is far more complex in T3cDM due to additional comorbidties. [60] Due to the cross over in risk factors for T2DM and T3cDM such as obesity and the similar symptom associated with all three forms of diabetes; difficulties with glucose homeostasis, a method of discrimination between the diseases is required.
Proposed criteria:
- presence of exocrine pancreatic insufficency (monoclonal fecal elasttase-1 test)
- Pathological pancreatic imaging (endoscopic ultrasound, MRI, CT)
- Absence of type 1 diabetes mellitus associated autoimmune markers
- Impaired beta cell function
- No excessive insulin resistance
- Impaired secretion of incretins
- Low serum levels of lipid soluable vitamuns
However even with these criteria in place, overlapping still occurs as people suffering from T1DM and T2DM for an extended period of time are also associated with pancreatic failure and are at risk of acute and chronic pancreatitis. Additionally, patients with pancreatitis may develop T1DM or T2DM independently. Thus the best discriminator seems to be the pancreatic polypeptide (PP) response to nutrients. [61]
A study found that isolated hepatic insulin resistance coexisted with clinical studies of T3cDM [62]. This has been documentated to be due to CP, pancreatic cancer and cystic fibrosis resulting in unsuppressed hepatic glucose production. PP deficiency was also found to coincide and thus was identified as a likely mediator of the hepatic defect. Animal studies confirmed that PP deficiency results in diminished hepatic insulin receptor availability and thus PP administration reversed hepatic insulin resistance in patience with CP, resulting in improved glucose tolerance. [63]
How cancer induces T3cDM
The most likely explanation for the consequential occurence of diabetes in pancreactic ductal adenocarcinoma (PDAC) is a paraneoplastic phenomenon caused by tumor-secreted products. One such product that results in beta-cell dysfunction is adrenomedullin; a pluripotent hormone with homology to amylin, which is overexpressed in PDAC. Adrenomedullin receptors are found on beta cells, which studies have found with the external administration of adrenomedulin in animal studies cause the inhibition of insulin secretion. [64] One such study performed by identified adreninedulin (AM) to impair insulin secretion from beta cell and cintributing to the insulin inhibitory effect of pancreatic cancer cells in vitro and in vivo* (as seen in Figure 5) [65]. These finding support that adrenomedulin is mediator of beta cell dysfunction in PDAC.
How chronic pancreatitis induces T3cDM
Development of diabetes in chronic pancreatitis mainly occurs due to the destruction of islet cells by pancreatic inflammation. Additionally maldigestion caused by pancreatitis leads to diminished insulin release. [66] GLP-1 is an incretin hormone secreted by the L-cells of the distal intestine, and has the effect of stimulating insulin gene expression and proinsulin biosynthesis. GLP-1 also has proliferative and anti-apoptotic effects on the beta-cell. [67] Thus maldigestion leads to an impaired incretin secretion and therefore diminished insulin release of the remaining beta-cells. [66] In contrast to auto-immune destruction of beta-cells in T1DM, gulcagon secreting alpha cells and PP cells are also subject to destruction in CP leading to a complex metabolic situation.
Insulin Therapy
Insulin injections are used in place of the insulin that would normally be produced by the body. Individualised treatment plans are suggested however generally T1DM patients would take 3-4 injections per day to provide optimal glucose control, while T2DM generally would take 2 injections per day if not in conjunction with medication. [68][69] Review Article https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2901025/#!po=72.5000 Insulin shots are most effective when administered when food enters the blood such as 30 minutes before eating. Also particular sites of injections provide better results, such as the addomen, while insulin taken at the arms and thighs take a longer period of time to arrive into the blood stream. [70]
However insulin vial and syringes provide an inconvenience to patients, providing adverse psychological and social impact in using a syringe as well as incorrect insulin use and dosage could also result in risks. Insulin pens were thus developed to counter these issues, providing rapid, long acting insulin. [71] On the other hand, insulin pens become more costly per unit of insulin compared to the insulin supplied in vials. [70]
Insulin pumps are also another alternative to provide insulin however it is in the form of continuous treatment; also known as continuous subcutaneous insulin infusion (CSII). This method is mainly utilised by patients with T1DM. Insulin pumps send insulin through tubing into an infusion set that delivers insulin to the body. A plastic tube is connected to the insulin reservour and insulin flows into the subcutaneous tissue through the infusion set. However pumps are not only costly but require commitment to self-management with frequent blood glucose checks throughout the day. Many adolescents also may feel uncomfortable with the notion of being attached to a foreign object.
Pancreatic Transplantation
As there is no definite cure for diabetes, many of the current research on Beta Cells focus on developing new and better treatments for patients with diabetes. One of the most promising treatments that is still under research and experimentation is pancreatic transplantation. [72] Insulin pumps also have the potential to over or undermedicate if they are to malfunction or are used improperly. Thus potential complications of use include ketoacidoses and hypoglycemia. [73]
The development of more physiological routes of insulin administration, use of artificial pancreas or pancreas/beta cell transplantation thus become important for ongoing research.
1. Pancreatic Islet Transplantation [74]
This method is specifically aimed to treat patients with type-1 diabetes mellitus. The pancreatic islet is responsible for the endocrine function of the pancreas. This is isolated within the donated pancreas, and the exocrine functioning part of the pancreas is removed. The isolated pancreatic islet is then transported to the liver of the patient by the blood of the vein.
In a study performed by Shapiro et al. the Edmonton protocol was established which was taken on by islet trancplant centers around the world and has greatly increased islet transplant. [74] The protocol involves the islet transplantation in conjunction with immunosuppressive drugs in order to counteract rejection. The procedure of transplantation involves the isolation of islets with cold purified collagenase, which is then digested and purified in xenoprotein-free medium, and transplanted immediately through a catheter; a small plastic tube using ultrasound for guidance, through the upper abdomen and into the liver (see Figure 6). This procedure only requires a local anesthetic, Alternatively some surgeons will create a small incision using general anesthetics. Once implanted, the beta cells in the islet begin to make and release insulin. Ultimately the transplant succefully results in insulin independence with excellent metabolic control. [14]
However currently many limitations remain with this procedure, two of which include islet rejection and supply of islets for transplantation. Although current immunosuppressive regimens exist, they are expensive and may increase the risk or particular malignancies and opportunistic infections. Also as a contradiction, some drugs also impair normal islet function and insulin action, combined with other unwanted side effects such as anemia, weight loss, hypertension, diarrhea and fatigue. [14] More importantly are the concerns of renal failure associated with umminnosuppressive agents, as renal function is a crucial factor in determining long-term outcomes for the patients. [75] As for the limitation of islet donors; statistics highlight at least 1 million american have T1DM however only a few thousand pancreas donors are available each year. To resolve this issues researchers continue to look for alternative means such as growing islets, or at least cells capable of physiologically regulated insulin sectrion - in vitro.
2. Transplantation using Embryonic Pig Pancreatic Tissue [76]
Instead of using human tissue or organ for transplantation, this method uses pancreatic tissue of an embryonic pig. Although previous clinical studies failed to provide successful results in treating diabetes, this study sought to examine the potential, functionality and immunogenicit of pig embryonic pancreatic tissue harvested different stages of the embryonic pig development.
Through the use of implantation of the varying embryonic pancreatic tissues in SCID mice, the 42nd day of gestation (E42) enabled a substantial growth of pig islets for a prolonged period of time and restored noromoglycemia in the diabetic mice as seen in Figure 7. Also the study reveal reduced rejection was seen at this stage of embryonic tissue implantation, as opposed to E56 or later stages. Ultimately the fully immunocompetent diabetic mice with E42 implanted pancreatic tissue that were simultaneously treated with immunosuppression protocol attained normal glucose levels and elimated the need for insulin.
Thus these results highlight the theraputic potential of E42 embryonic pig pancreatic tissue transplantation in diabetes.
Stem Cell Research
Another recent endeavour into a promising anti-diabetic therapeutic is within stem cell research. has also been conducted in the search for anti-diabetic therapeutics. Mitutsova et al. (2017) investigated the possible use of muscle-derived stem cells (MDSC) from adult mice to differentiate in vitro into beta cells when transplanted as undifferentiated stem cells in vivo to compensate for beta-cell deficiency. Within their study they successfully found in vitro cultured MDSC to spontaneously differentiate into insulin-expressing islet like cell clusters under the control of an insulin promoter. Differentiated clusters of beta-like cells co-expressing insuling with transcription factors were shown to secrete significant levels of insulin in response to glucose challenges. Additionally, in vivo undifferentiated MDSC injected into streptozotocin* treated mice engrafted within 48 hours specifically to damaged pancreatic islets and were also shown to differentiate and express insulin within 10-12 days after injection. Also to add to the successful results, injection of MDSC into hyperglycemic diabetic mice was shown to reduce blood glucose levels for 2-4 weeks. Ultimately the study successfully showed MDSC as capable of differenctiating into mature pancreatic beta islet-like cells, both in vivo and in vitro highlighting a promising avenue in stem-cell based treated of beta-cell deficiencies. [77]
Current Research
Generation of Functional Beta-like Cells
In a recent study by Lima et. al. (2016) the generation of mature and functional beta-like cells from the human exocrine pancreas was assessed for being a viable avenue for treatment of type 1 diabetes. The pivotal finding of the study was that knockdown of transcription factor ARX expression combined with over expression of transcription factor Pax4 considerably enhances the production of functional insulin secreting beta-like cells with the accompanying suppression of alpha cells.The beta-like cells produced were shown to efficiently exhibit glucose responsive insulin secretion and an immediate as well as prolonged effect in normalising blood glucose levels upon transplantation into diabetic mice. The study estimated approximately 3 billion of these cells would have an immediate therapeutic effect following implantation in T1DM patients and potentially one pancreas could provide enough tissue for numerous transplants.
The ability to reprogram exocrine pancreas tissue could circumvent the necessity for multiple pancreas donors to treat a single patient, allowing one pancreas to treat several patients instead. The study although could not achieve exact human islet response levels, did succeed in attaining results of 15-30% insulin levels of that of the normal human islet. This response could potentially have therapeutic benefits for a patient with T1DM as reinstating even a fraction of the normal beta-cell mass would have a therapeutic effect.
Ultimately this study produced functional beta-like cells that efficiently processed proinsulin to insulin, contained insulin storage granules, secreted insulin in response to glucose and rescued diabetes in a streptozotocin mouse model. Essential this inexpensive relatively simple protocol, for cell preparation could provide an avenue to bypass the obstacle of pancreas donors as one donor could provide numerous islet grafts. [78]
Glibenclamide as Potential Prevention of Diabetes
A study by Lamprianou et al. (2016) utilised previous study's findings in the importance of Cx35 as an enhancement factor of insulin secretion, promoting resistance of beta cells against pro-inflammatory cytokines, and furthered this by studying whether glibenclamide could protect beta cells since it is shown to promote the assembly and function of Cx36 channels. The study utilised untreated NOD mice to model type 1 diabetes, and found the glibenclamide to:
- protect Cx36 loss in vitro usually induced by Th1 cytokines
- prevent the development of hyperglycemia through the prevention of loss of beta cells, shown to rapidly develop in the aging untreated NOD mice
- modified the proportion of CD4+ and CD8+ T cells in pancreatic draining lymph nodes
Figure X highlights the highly successful results, comparing the before and after of islet and beta cell mass. The images of the islets in Figure Xa highlight the substantial increase of islet number and size after dose 1 and 2 of glibenclamide compared to the control. Figure Xb and c also highlight the numerical density changes in islet and beta cells respectively emphasising a spike of approximately 66% islet density and 50% beta cell density after dose 2.
Ultimately the study establishes a plausible avenue for therapeutics as seen through the testing of the therapeutic value of glibenclamide effects. [79]
RA index to Determine Beta-Cell Functionality
This study aims to identify parameters which influence the function of beta-cells in order to potentially find markers of disease progression or targets for intervention. Although body mass index (BMI) and increased energy intake considered risk factors associated with beta-cell dysfunction, evidence of direct numerical correlation remain undefined. Thus Curran et al. (2016) recognised the necessity for identification markers to allow for beta-cell function assessment.
Beta cells were calculated as a ratio of the incremental insulin to glucose response over 30 minutes of the OGTT. Insulin sensitivity and beta-cell homeostatic assessment of insulin resistance was calculated as well as C-peptide. Ultimately after all else was accounted for a RA index was formulated as a ratio of resistin to adiponectin at fasting levels. Ultimately the findings were that RA index was very strongly associated with pancreatic beta-cell function; in vitro studies correlated RA index to insulin secretion. Previous studies have found the RA index to correlate to T2DM however this study was first to make the connection to beta-cell function.
The study concluded with the venture to examine potential mechanisms for modulating the RA index which consequentially may lead to new avenues/interventions for improving beta-cell function. [51]
Review Quiz
Try to attempt these questions from memory!
|Bodily tissue which stores brown or white fat
|Edmonton Procedure
|Researchers use specialised enzymes to remove islets from the pancreas of a deceased donor and transplant to patient via catheter through to small incision through to liver as treatment for type 1 diabetes.
|The study of distribution and determinant of diseases
|In vitro
|Performed or taking place in a test tube, culture dish, or elsewhere outside the living organism
|In vivo
|Performed within a living organism
|Islets of Langerhans
|A cluster of endocrine pancreatic cells, which secrete the hormones insulin and glucagon
|A large gland within organisms which has an exocrine portion that secretes digestive enzymes and an endocrine portion that secretes the hormones insuln and glucagon
|The manner of development of a disease
|Plasma glucose
|The concentration of glucose in blood measured in milligram per deciliter or milimole per litre. (normal fasting is >100 mg/dL (5.55 mmol/L).
|Abnormally increased thirst symptomatic of disease
|Excessive eating or appetite symptomatic of disease
|The production of abnormally large volumes of dilute urine ( >2.5L per day)
|Oral Glucose Tolerance Test (OGTT)
|Test determining the body's capacity to maintain glucose levels; results noted after overnight fasting and 4 times after administration (usually through sweet liquid) of 75g of glucose (100g for pregnant woman).
|A naturally occurring chemical that is particularly toxic to the insulin-producing beta cells of the pancreas in mammals
- ↑ 1.0 1.1 <pubmed>26395141</pubmed>
- ↑ Brissova, M. & Powers, A. C. (2008). Architecture of Pancreatic Islets. Pancreatic Beta Cell in Health and Disease (pp. 3-4).
- ↑ Bell, G., Seino, S., & SpringerLink. (2008). Pancreatic Beta Cell in Health and Disease.
- ↑ 4.0 4.1 <pubmed>14687913</pubmed>
- ↑ 5.0 5.1 <pubmed>5333806</pubmed>
- ↑ <pubmed>22460761</pubmed>
- ↑ <pubmed>6993583</pubmed>
- ↑ 8.0 8.1 8.2 <pubmed><4192603></pubmed>
- ↑ 9.0 9.1 9.2 9.3 <pubmed>19765178</pubmed>
- ↑ 10.0 10.1 <pubmed>26216133</pubmed>
- ↑ <pubmed>5338113</pubmed>
- ↑ <pubmed>67403</pubmed>
- ↑ <pubmed>2108071</pubmed>
- ↑ 14.0 14.1 14.2 <pubmed>10911004</pubmed>
- ↑ <pubmed>25303535 </pubmed>
- ↑ Gittes, G. (2009). Developmental Biology of the Pancreas: a Comprehensive Review. Dev. Biol.: 326(1);4-35
- ↑ 17.0 17.1 17.2 17.3 17.4 17.5 <pubmed>26030186</pubmed>
- ↑ <pubmed>16547676</pubmed>
- ↑ 19.0 19.1 19.2 19.3 19.4 19.5 <pubmed>19013144</pubmed>
- ↑ 20.0 20.1 <pubmed>3420142</pubmed>
- ↑ <pubmed>9334273</pubmed>
- ↑ 22.0 22.1 <pubmed>17185316</pubmed>
- ↑ <pubmed>26395141</pubmed>
- ↑ 24.0 24.1 <pubmed> PMC232449</pubmed>
- ↑ <pubmed>23630303</pubmed>
- ↑ <pubmed>15072563</pubmed>
- ↑ Artner, I. & Stein, R. (2008). Transcriptional Regulation of Insulin Gene. Pancreatic Beta Cell in Health and Disease (pp. 13-16).
- ↑ 28.0 28.1 Steiner, D. (2008). The Biosynthesis of Insulin. Pancreatic Beta Cell in Health and Disease (pp. 31-37).
- ↑ <pubmed>26216140</pubmed>
- ↑ <pubmed>403392</pubmed>
- ↑ <pubmed>4877098</pubmed>
- ↑ 32.0 32.1 32.2 <pubmed>12879249</pubmed>
- ↑ <pubmed>11815463</pubmed>
- ↑ 34.0 34.1 34.2 34.3 34.4 34.5 34.6 34.7 <pubmed>1363709</pubmed>
- ↑ <pubmed>3662377</pubmed>
- ↑ <pubmed>1779997</pubmed>
- ↑ <pubmed>1309425</pubmed>
- ↑ <pubmed>2417189</pubmed>
- ↑ <pubmed>22901785</pubmed>
- ↑ <pubmed>24372303</pubmed>
- ↑ <pubmed>4522279</pubmed>
- ↑ <pubmed>11375330</pubmed>
- ↑ <pubmed>11440717</pubmed>
- ↑ <pubmed>18502302</pubmed>
- ↑ 45.0 45.1 <pubmed>9914216</pubmed>
- ↑ <pubmed>20723815</pubmed>
- ↑ <pubmed>20622160</pubmed>
- ↑ <pubmed>11742409</pubmed>
- ↑ <pubmed>22315720</pubmed>
- ↑ 50.0 50.1 <pubmed>7193616</pubmed>
- ↑ 51.0 51.1 <pubmed>27536890</pubmed>
- ↑ <pubmed>18055651</pubmed>
- ↑ 53.0 53.1 <pubmed>23071876</pubmed>
- ↑ <pubmed>9203460</pubmed>
- ↑ <pubmed>16280652</pubmed>
- ↑ <pubmed>15561905</pubmed>
- ↑ <pubmed>22121010</pubmed>
- ↑ <pubmed>23375619</pubmed>
- ↑ <pubmed> 24152948</pubmed>
- ↑ <pubmed>16954337</pubmed>
- ↑ <pubmed>23890130</pubmed>
- ↑ <pubmed>21757968</pubmed>
- ↑ <pubmed>22226275</pubmed>
- ↑ <pubmed>23528347</pubmed>
- ↑ <pubmed> 22960655</pubmed>
- ↑ 66.0 66.1 <pubmed>6997121</pubmed>
- ↑ <pubmed>25401335</pubmed>
- ↑ <pubmed>25040034</pubmed>
- ↑ <pubmed>20589066 </pubmed>
- ↑ 70.0 70.1 <pubmed>20513314</pubmed>
- ↑ <pubmed>17594200</pubmed>
- ↑ <pubmed>19196588</pubmed>
- ↑ <pubmed>16774616 </pubmed>
- ↑ 74.0 74.1 <pubmed>15630467</pubmed>
- ↑ <pubmed>12954741</pubmed>
- ↑ <pubmed>16768546</pubmed>
- ↑ <pubmed>28420418</pubmed>
- ↑ <pubmed>27243814</pubmed>
- ↑ <pubmed>28006000</pubmed>


text:
'Thought-out UI.'
'Landscape screen can feel cramped.'
'Viewing angles are adequate, and the quality of the screen itself is fine.'
'Dedicated Facebook button.'
'Okay material quality.'
ReviewGist helps you find the best products to buy by making sense of online reviews.
We are currently aggregating 376,500 reviews
covering over 29,474 products.
© 2020 ReviewGist.com. All Rights Reserved.

subset: commoncrawl


text:
cape town blog RSS
Trailblazers Hiking Club x FORD x Atlantis Dunes - Cape Town South Africa
Its common knowledge that the Trailblazers live on adventure so when Ford called us up looking to test out their new off road ready Ranger we knew just what to do with it. We headed straight out into the open road looking for the first space we could play in to find out apart from just good looks, what this beauty was really made of. What happens when you take a bunch of adventure loving friends, load them into a bi turbo, double cab, 10 speed, 157kw adventure wagon and send them out in to the open lands filled with layers of...
IKAMVA YOUTH Outreach and Educational Experience - Hiking Cape Town South Africa
On the 13th of October, Trailblazers Hiking Club spent the day taking IkamvaYouth South Africa into the great outdoors. This is an organisation that provides a safe space for learners to be after class ends, where they receive help with their homework and a host of other services and support to ensure they succeed. IkamvaYouth is HOME to learners who often come from difficult environments and when they enter Ikamva Youth's doors they receive the seldom feeling of being noticed and valued. At Ikamva Youth, learners are validated and celebrated for who they are and as celebrating individuality and...
Trailblazers Hiking Club Colab CAPE NATURE Kogelberg Nature Reserve - Hiking Cape Town South Africa
The TrailBlazers Hiking Club joined Cape Nature this winter for an exciting collaboration, the goal was to experience and expose the great trails Cape Nature has to offer and promote the beauty of the outdoor culture and their #LoveNature campaign. On Saturday the 11th of August the Trailblazers set off towards Kogelberg Nature Reserve to enjoy a day out of the hustle and bustle of the city and spend some time in the tranquillity of nature courtesy of Cape Nature. As soon as you drive through the gates it's easy to see why Kogelberg Nature Reserve is considered by...
Trailblazers Hiking Club VALKEN LABYRINTH HIKE - Hiking Cape Town South Africa
Valken Labyrinth A beautiful hike we did via Pipe Track, then up Diagonal Ravine onto Porcupine Ravine. We then crossed over Jubilee Traverse and onto Barrier Ravine where we reached the top. Enter the Valken Labyrinth through the Oracles Gate....check out the video to see what we got up to :)
GEAR REVIEW - HITEC Atlas Mid Crossover Boots - Hiking Cape Town South Africa
The TrailBlazers Hiking Club has had a busy month both on and off the mountain and this time around we had the chance to test out Hitec's new Atlas Mid. As soon as we received the drop for these boots we immediately put them on and got to business. So what did the Trailblazers think of the boot? Looks At first glance we have to admit, it really is good-looking and one of the more stylish options of boots that we have worn. Its styles echos that of the original P.C.T, that has remained a classic for so many years. Often...
- All
- 4X4 adventures
- adventure blogger
- adventure cape town
- Atlantis Dunes
- Biosphere
- blog
- blog post
- blog review
- blogger
- blogging
- boot review
- Cape Nature
- cape town
- cape town adventure
- cape town blog
- coast
- explore
- explore cape town
- flora fauna
- Ford
- Ford Adventures
- Ford Ranger 4x4
- Ford South Africa
- Ford Wildtrack
- fynbos
- hiking
- hiking adventure blog
- hiking boot review
- hiking cape town
- hiking culture
- hiking life
- hiking review
- hiking trail
- hiking video
- hitec
- hitec review
- kogelberg nature reserve
- mountain
- mountain adventures
- Nature
- nature blog
- Outdoor adventure
- overland adventures
- palmiet
- palmiet river trail
- product review
- review
- river
- south africa
- sunrise
- trail
- Trailblazers Hiking Club
- trek


text:
NEW YORK (Reuters) - Swiss bank UBS AG UBSN.VX is expected to cut up to 10,000 jobs, or 16 percent of its workforce, as it contends with shrinking revenue and rising capital requirements, a source familiar with the matter said, in what would be one of the largest layoffs by a bank since the financial crisis.
Switzerland's biggest bank is expected to make the cuts across the firm globally, but the bulk of the losses are likely to occur in its hard-hit trading and investment banking areas.
The cuts will accompany a restructuring that will lop off much of UBS' massive fixed-income operations into a separate unit to be wound down over time, according to the Financial Times, which first reported the news.
That unit is expected to be led by Carsten Kengeter, a co-head of the investment bank, the paper said.
Andrea Orcel, who joined from Bank of America BAC.N this year to work alongside Kengeter in restructuring the trading activities, will run the equities, fixed income, foreign exchange and advisory businesses that will remain active, the paper said.
UBS pledged last year to cut more than 5 percent of its workforce, or about 3,500 jobs. The new cuts are expected to supplement that target, the paper said.
UBS, which has more than 60,000 employees, is likely to provide details of the cutbacks when it reports its third-quarter results on October 30, the source said.
The moves are being engineered by Sergio Ermotti, the 52-year-old chief executive who took the top job just 13 months ago. The bank has been withdrawing from the riskier and more capital-intensive parts of its business to meet tighter capital rules and a dearth of deals affecting the securities industry globally. It has said it will dedicate most of its resources to its wealth management, private banking and asset management businesses.
The expected cuts will add to the tens of thousands of jobs the financial sector has shed globally since the crisis of 2008. In the United States alone, financial companies have announced plans to eliminate 28,000 jobs through the first nine months of this year, according to outplacement firm Challenger, Gray & Christmas. That compared with 54,000 job losses through the first nine months of 2011.
"I think we are still in the early innings of this," said Nancy Bush, a veteran bank analyst and contributing editor at SNL Financial. "The whole structure of the financial services industry has got to change. We are in the meat cleaver stage right now."
UBS is following on the heels of other financial companies worldwide that have been retrenching, as they struggle to reduce expenses amid a weak economy, new regulations and reduced trading activity.
Credit Suisse Group AG CSGN.VX, UBS' largest Swiss rival, said this week that "repeated shocks" in the global economy has led it to increase its cost-cutting efforts by 1 billion Swiss francs ($1.1 billion) en route to reaching 4 billion francs of expense savings by 2015.
Credit Suisse, which has cut about 7 percent of its workforce since 2011, said more employees will lose their jobs as a result of the new target.
UBS has had more than its share of crises in the past few years, suffering billions of dollars in trading losses, management mishaps and scandals since the financial crisis.
Ermotti replaced Oswald Gruebel, a former Credit Suisse executive who was tasked with strengthening the bank's risk controls following a $50 billion loss at the start of the crisis and allegations of creating tax-avoidance schemes.
Those plans were shattered in September 2011, when a UBS trader was arrested and later charged by London police for allegedly hiding up to $2.3 billion of losses.
On Friday, the London-based trader, Kweku Adoboli, tearfully said in court that his trading was intended to benefit the bank.
Reporting by Jed Horowitz, Rick Rothacker, Lauren Tara LaCapra and Paritosh Bansal; Editing by Dan Grebler
Our Standards: The Thomson Reuters Trust Principles.


text:
Shameful, even for MSNBC...
Via Newsbusters:
BASHIR: Mr. Romney's spokesperson has just said that he believes everyone needs to be civil. But no sign yet of him rejecting Nugent's endorsement.
You have to hand it to Mitt and Ann Romney. Even their righteous indignation is as fake and as two-faced as everything else that marks their presidential campaign.


text: Cam Cam creates high quality, architect designed, bed linen for children and adults. The company is founded by architect Sara Giese Camre, who personally designs all Cam Cam Copenhagen products. Each design is inspired by Japanese patterns and French refinement, combined with beautiful Scandinavian minimalism. A blend of sweet romance with a graphic simplicity is the recipe for Cam Cam's int... View more CAM CAM COPENHAGEN


text:
We produce a lot of posts every month. Most of them disappear quickly. Some of them don't. Here are the 10 most popular posts from January, ranked low to high
Topic addressed in this edition of Drew's mailbag: Would Drew turn cannibal to save his own life? Answer: "FUCK AND YES, I WOULD. I'd go right for the thighs."
Topic addressed in in this edition of Drew's mailbag: How many gallons of ejaculate might Drew produce in his lifetime? Answer: "If I live another 44 years and my prostate doesn't give way, I could end up producing 375 gallons of little Drews. And that would still leave me 25 gallons short of what a blue whale can do in a single money shot. Stupid whale. THINK YOU'RE SO VIRILE, DO YOU?!!!"
The Awl's Choire Sicha appraised the exposed dongs of our professional sports figures. Grady Sizemore, Choire wrote, "basically is his own cock, as these pictures reveal, in the way that any narcissist is just an extension of his own penis."
/dick joke
Topics addressed in this edition of Drew's mailbag: Who is the comely lady in Verizon's Football Zone commercials, and what is Drew's personal vision of heaven? Answers: Rebecca Grant; "Like, you die, and then you go up to heaven, and God knows PRECISELY which girls in your life would have had sex with you if you had simply gone for it."
Topic addressed in this edition of Drew's mailbag: How do Drew's readers express their gratitude? Answer: "Enclosed is a pic of my girlfriend's awesome boobage. Those are D's."
Drew launched a new feature, "Great Moments In Drunken Hookup Failure," which has given the world such memorable phrases as, "Oh my god I can't believe you EXFOLIATED MY ASS."
Those of you longing to see the slightly exposed areola of the mother of a decent American League catcher finally got your wish.
Those of you longing to see a photo of an occasionally healthy NBA center perched on some sort of large stanchion finally got your wish.
Boise State bowl victories are a powerful aphrodisiac. If these guys ever win a BCS title, the field will look like the sauna room at Plato's Retreat.
Barry Petchesky did to Venus Williams's ass what Ida Tarbell did to Standard Oil, by which I mean that he, too, wrote an exhaustive exposé of big business.


text:
Neighborhood Resources
Our online Neighborhood Resources is a collection of our favorite how-to guides, grant opportunities, workshops, city services and more. New York City is home to a wealth of resources—gather the tools to better your community here!
Know of other resources that are worth sharing?
Di Cui at
or 212-822-9563
Explore the Citizens Committee Resource Library
Grants for School Gardens
Grow to Learn NYC provides grants from $500 to $2,000 to fund start-up and existing school gardens. Registered schools are also eligible to receive materials and expert assistance from GreenThumb.
Type: Grants & Funding
Grants for Brooklyn Groups
The Brooklyn Community Foundation awards grants to the borough's most innovative nonprofits in five distinct "fields of interest" funds that focus on improving the quality of life for Brooklynites. They also offer $500 or less Micro Grants on a rolling basis.
Type: Grants & Funding
Fund Your Neighborhood Environmental Project
ioby is a crowdfunding platform that connects donors and volunteers to environmental projects in their neighborhoods.
Type: Grants & Funding
- ‹ previous
- …
- 6
- 7
- 8
- 9


text:
So I was on my flight to San Francisco for the 2013 Microsoft Build Conference and was working on my laptop, totally disconnected from the web, punching in User Stories and Tasks in a Microsoft Excel spreadsheet that I had previously connected to TFS 2012 before heading out. I click on File > Save and it gives me a connection error for obvious reasons, I mean, I am on a plane after all. When I get to my hotel and connect to the WiFi, I click on File > Save again, and bam, all the work I had done on the plane was saved to TFS ready for my team to work on. No double entry required! That alone lead me to believe this was going to be a great trip.
Now, at the Moscone Center in downtown San Francisco, I sit in for the Day 1 Keynote and man, the progress Microsoft has made in the last 8 months since the last Build conference in Seattle is astonishing! I'm blown away with even just the subtle differences between Windows 8.0 and Windows 8.1, just one min version, yet it seems like a major version release. New features such as dual screen support for the modern view (formerly metro), multi-view snapping with variable width support, native 3d printer support, hands free mode, lock screen slide show, Skype call answering from lock screen without having to login and much more. The Search results from the charm are incredible for example, search "New York" from your desktop or device and a pseudo app will be created on the fly with aggregated data from your machine, social accounts, xbox as well as Bing search results and more as the Bing API is now open to developers to build on top of those search results.
One thing I wasn't happy about was the come back of the start button, I was the only one in the crowd booing that one as everyone else clapped. I personally wish they would just get rid of the desktop altogether. I've been looking at it for over a decade, on Windows and various Linux flavors including Macs, it's all the same, I'm over the whole icons and menu bar on a desktop view! Let's move on people!
As for tooling, the updates in VS and TFS 2013 are great. There's finally decent async debugging! In addition, there are over 1,500 new API's for us to play with. I can go on and on but one thing that really amazed me was Project Spark. Wow! This is definitely a game changer (no pun intended) as it's a platform that allows anyone to build games on a tablet using touch gestures for example then seamlessly share and play it on an XBox console. My son already develops virtual worlds to play in online via Roblox but what Microsoft has done with Project Spark simply blows Roblox out of the water. The graphics are what you would expect of an XBox game and literally no programming knowledge is required.
If you're interested in learning more about Project Spark, go to https://joinprojectspark.com.
For videos and other details on the Microsoft Build Conference, go to http://buildwindows.com.


text:
I'm trying to use that extension lo use compressed textures on Android platform, but I'm unable of finding its specification neither any example of the file format that this extension provides.
I really would appreciate if somebody could point me to the spec or to a fragment of code that loads that formats, as well as a tool to convert standard textures into compressed ones, compatibles with that extension.
Thank you very much.


text:
Keep Tabs on Your Blood Sugar
Regular glucose monitoring is an important part of controlling diabetes. Learn how to make blood sugar testing a routine part of every day, no matter how hectic your schedule.
People with type 2 diabetes have ready access to the best equipment ever made for home blood sugar testing. In fact, performing your own blood sugar reading has become a cornerstone of diabetes management. Blood sugar testing helps you maintain safe blood glucose levels and avoid the systemic damage that comes from uncontrolled diabetes. The key is to make testing as easy as possible so that you'll do it and feel like you're in control, rather than feeling as though your diabetes is controlling you.
Why Blood Sugar Testing Is Important
Although you might think of blood sugar testing as a nuisance, its importance cannot be overstated. Obtaining regular blood sugar readings gives you a basic understanding of how diabetes is affecting your body and how you can best control it.
Using a blood sugar, or blood glucose, monitor daily — or several times a day as needed — can help you:
- Understand how different foods affect your blood glucose levels
- Make better choices regarding the type of insulin you use and the dosage you require
- Predict how exercise or stress will affect your blood sugar
- Prevent having low blood sugar at night
- Precisely control your blood glucose to prevent diabetes complications
If you don't perform blood sugar testing on a regular basis, you're flying blind in your diabetes treatment. You will have to rely on physical symptoms to tell you when your blood sugar levels are too high or too low and, as a result, you will not be aware as soon as you could be that elevated blood sugars are causing damage to your body.
Blood Sugar Testing Burnout
Self-testing for blood glucose levels has been made easier as glucose monitoring device technology has improved. Of course, the testing still requires a lot of effort. You have to:
- Take time out of your busy day
- Remember when you need to test
- Stick yourself repeatedly with lancets
- Respond to the test with medicine or food
This can lead to diabetes burnout, a situation in which those with type 2 diabetes decide that controlling the disease is just too much effort. Signs of burnout include feeling out of control and powerless, losing interest in activities you usually enjoy, or being just plain unhappy.
Strategies for Better Blood Sugar Testing
You can cope with the demands placed on you by your type 2 diabetes. To help fit regular blood sugar testing into your daily life, try these ideas:
- Set realistic goals. It's good to be proactive about getting frequent blood sugar readings, but set a schedule that is realistic. Don't beat yourself up if you miss a reading. The key is to stay motivated, while also acknowledging that no one's perfect.
- Find reminders for testing. Memory aids can help you remember your blood sugar testing. Link the test to things you do at the same time every day, such as eating meals or brushing your teeth. You also can create rituals around your blood sugar tests by doing certain things in a set order every time. Or use a timer to remind you when your next test is due. You can even create a daily chart and check off boxes as you do each one.
- Identify barriers to regular testing. If you find that keeping a set schedule is the best way to perform regular blood sugar testing, avoid situations that disrupt your schedule. For example, if you need to test following meals, be sure that you eat at about the same time every day.
- Ask for help. Those around you may not understand the importance of testing your blood glucose at specific times or after specific events like eating or exercise. Explain it to them and ask for their help remembering to perform the tests.
Always keep in mind why you test: Tightly controlling your blood sugar allows you to protect your long-term health and get the most out of life. When your resolve falters, remembering this one fact can help you get back on track.


text:
Over countless backyard BBQ's, nights out at NY's best watering holes, and a mutual love for all things ridiculous, these two forged out a solid and life-long friendship that has consistently grown, but hardly matured. The name of the Bar comes from a woman that the two "gentlemen" both "dated", aptly named "Rochelle". About 6 months back, when we were in our initial concepts, Stephen was stuck on a name, and kept saying it should be something that connects us, and our skills. Brett responded, "well, I can think of 100 right now, but let's leave Rochelle out of it." And so, a legend was born…
Brett and Stephen's mission was simple. Take away the airs of pretense and take the bar business back to it's basic roots; Great cocktails, delicious in their simplicity, hearty food not to turn off the masses but instead encourage their palates, and a place you'd be happy to come not just on a Friday night, but also a Monday. With the former 205 space as it's backdrop, it was a no-brainer to continue a 25 year nightlife legacy in a historic space. Teaming up with Delshah was a natural fit, and one of the best working relationships of recent memory. Brett and Steve hope to take their expected success with Rochelles and grow not only within the company, but as well the city that they've learned to love, and have made such a good name for themselves.
Brett David Creative Director
Brett David is a 10+ years Hospitality veteran, Graduate of CUNY Baruch, and a life-long NY'er. His true loves are serving people, his dog (Napoleon), tattoo culture, and the city he loves. His restaurant resume includes stints as the GM of Sons of Essex, and most recently, Maitre D' at EMM Group's The General. Prior to that, he had a successful 8 year run with his own Model Waitstaff and full service catering company; Brett David Staffing. He's been involved and associated with the latest and greatest, most notably as a personal waiter/butler to Anna Wintour from 2004-2009. Brett's keen service skills, attention to detail, and leadership abilities have guided him to such accolades as leading the CFDA and Met Costume Gala for several years, and taking the lead role in charge of Chelsea Clinton's Wedding. A true New Yorker with a servant's heart, the undertaking of Rochelle's was the next logical step for an already impressive career.
Stephen Yorsz Creative Director
Stephen Yorsz has been in the bar and restaurant business for over 15 years. He started in the NY nightlife scene in 1996 at the infamous Marylou's while he attended NYU's Stern School of Business. After a brief stint as a financial advisor, Stephen came back to his true passion; the bar/nightclub business. Over the years Steven bartended at many of New York's hottest joints, including Le 'Souk, HOME, Guest House, Boom, Gemini Lounge, STK, The Inn, and Citrine, just to name a few. In 2008 Stephen took his bar and restaurant knowledge and focused it specifically on whiskey, becoming Maker's mark brand ambassador for NY. HE continued his work in the spirits industry, working on such notable brands as Templeton Rye, Fernet Branca, Wild Turkey, and most recently Alibi American Whiskey. Stephen's vast knowledge of spirits, especially whiskey, has afforded him the opportunities of teaching classes and seminars on the subject for the Culinary Institute of America, Whiskey Live, Whiskey Fest, and Tales of the Cocktail.


text:
We hear a lot of words like "authenticity" and "failure" thrown around when talking about careers and businesses.
But these words are often used in big-picture terms, as though someone just starting out in her career should know what we mean when we use them. Today's Q&A is part two of a career mini-series (see part one from last week here) that focuses on words in the context of careers and really getting specific about them.
I'm chatting with One Woman Shop founder Cristina Roman, whose community for creative solopreneurs addresses one word in particular: isolation. See what Cristina has to say below.
Briefly tell us your story and how you came to become so laser-focused on what you wanted to pursue for a career.
I think my friends and family would crack up if they heard someone call me "laser-focused"! I've always struggled with being pulled in a ton of different directions. Luckily, there's a name for this kind of person, which I really identify with: multipassionate. It's for those of us who love to dabble in various projects, always have our fingers in many pies, and love to learn just about everything.
That being said, I have found the common thread in my various projects and interests relatively recently: working with young women to find and thrive in careers and businesses that they love. Even more specifically, I now work almost exclusively with women who are starting or running their own solo businesses.
I do this through running One Woman Shop, a resource hub and community for female solopreneurs and freelancers, and offering business and career coaching and consulting, e-courses, and seminars through CMR Strategies in the areas of digital marketing, productivity, and personal branding.
And of the best parts of running my own business is that I can incorporate in any new interests I have willy nilly. That's how my Unique Hobbies blog series and my Cultivating Happiness email series both came about, for example.
One thing your business touches on is something many people don't talk about in entrepreneurship—loneliness and isolation. How does self-employment lend itself to those things and how can entrepreneurs combat them?
I would say that's the number-one complaint of solo business owners and is how our tagline "going it alone doesn't have to be lonely" came about. Entrepreneurs often start out working alone, either by choice or by necessity, and this can lead to a feeling of isolation, especially if friends and family don't share the same passion for discussing the ins and outs of email marketing, the pros and cons of different legal designations, and the best strategies for finding a virtual assistant!
It can be tough working from home alone day in and day out, often going to a coffee shop doesn't have quite the same feel as being in an office, and coworking spaces (shared office spaces for freelancers and entrepreneurs) can be expensive.
My advice for combatting this feeling of isolation: Meet other solo business owners in your area through Meetup, Twitter (try using FollowerWonk to search by area), and other local events; plan work dates and coffee dates to get out of the house; collaborate with other solopreneurs on projects and events, and set up periodic phone calls with people who motivate and inspire you (some of my most productive days have come after early morning phone calls that lit me up!).
We place a high value on authenticity in business these days, but that can seem like a double-edged sword for anyone just starting out who doesn't want to offend potential clients or employers. How can any entrepreneur or corporate ladder climber walk that fine line while keeping her personality intact?
I think it comes down to making a decision: if there is a part of you that has the potential to offend or alienate someone – like your dirty jokes, your strong religious beliefs, or your political affiliation – and you choose to bring that into your business or the workplace, you need to own all of the possible repercussions. That could include not getting hired by a certain client or a company you want to work for.
Some people have made very successful careers for themselves by being 100% their "not suitable for work" selves – like Ash of the Middle Finger Project. This works for them, but it doesn't mean you need to be the same way. It's not inauthentic to have slightly different versions of yourself in your everyday life and your work life, as long as you don't feel weird about it.
People talk a lot about failure as a positive thing. But what do you think they mean by that? Is there good failure and bad failure, and how can we use both to our advantage?
Failure sure is having its heyday, huh? It's a complicated discussion because failure is all about perspective. For example, a $10,000 product launch could be an utter flop for one business owner, while it's a gold mine for another. It's also a matter of attitude – what one person considers failure, another may consider a learning experience. Basically, I think it's all subjective!
The idea behind thinking of failure as a positive thing is that if you are putting out there over and over, you're bound to fail sometimes. If you're not failing occasionally, it probably means you didn't really put yourself out there. In my opinion, it's not absolutely necessary to fail, but it's important to not be afraid to fail. And when you do fail, it's crucial to learn from your mistakes.
At the risk of sounding too cheesy, we can use every failure to our advantage by learning from it. For example, I offered paid membership on One Woman Shop from the very beginning and exactly one person became a member in the first six months – pretty big failure, right? I learned that I needed to have a solid base of active individuals, prove that I provide valuable content, and poll my audience about what they were looking for in a paid membership site. Now that we've done those things, we're relaunching our paid membership component!
How can someone just starting out build a community (online and in the real world) that will give her not only the audience, but the relationships necessary for upward growth?
Great question – we're actually launching a coaching program around this idea! I think the first step is to cultivate resourcefulness and the ability to see the opportunities around you. Once you realize that opportunities to connect are everywhere, things get rolling pretty quickly. Another important piece is to make building a strong community around you a priority, not just something that falls to the wayside.
I firmly believe that community building is not a one-size-fits-all thing; for example, some people love online networking, while others thrive on making in-person connections. Some people build community through blogging, while others have find Instagram to be more suited to them. It's all about finding your fit while still being willing to experiment.
Hands-down, my #1 recommendation is to get incredibly comfortable with direct outreach, whether it's to ask people to join your email list, be a guest on your podcast, let you speak to their organization, or partner with you on a collaboration.
At One Woman Shop, we've been putting a lot of effort into high-impact activities, such as guest posting on sites like Design*Sponge, setting up a pop-up on the site, doing direct outreach to women we think would be a good fit for the community, and partnering with solo business owners on things like our 28 Tips for Growing Your Community freebie.
Thanks, Cristina!
Enjoy what she had to say or have any thoughts of your own? Let us know in the comments. And if this series hasn't touched on something you'd like to see covered, let me know that, too!


text:
I found this post about a TEDx Speech by motivational speaker and author Simon Sinek entitled, "Entrepreneurs: It's Not What You Do, It's Why You Do It". He talks about his concept "The Golden Circle" (3 circles representing the different ways we think about a product/goal (watch the video)), goes into the Diffusion of Innovations theory and explains it all quite well.
It's a philosophy I have always felt and more recently started following myself for a while and, among other things, explains why past business partnerships I've made eventually failed and why I've decided to be solo for good. This whole talk refers to and explains (MUCH better than I could) why I say "old school" all the time; this is what I mean, people I say are old school are working for the paycheck, not for what they believe. Living in the top 10% and trying to do business with somebody in the last 16%… let's just say you don't quite see eye-to-eye.
Anyways it's good and I thought it needed to be here for you.
Quote from Speech:
"There are leaders and there are those that lead.
Leaders hold a position of power or authority, but those who lead – inspire us.
We follow those who lead not because we have to but because we want to, we follow those who lead not for them but for ourselves."
Check out his book on Amazon: "Start With Why"
Watch the whole speech:
Part in speech regarding type of people to hire: 08:02
Part in speech regarding the Law of Diffusion of Innovation: 11:05
Posted 2010-01-18 in Entrepreneurship, written by: Chuck Reynolds


text:
S. S. Van Dine was the pseudonym of Willard Huntington Wright (October 15, 1888 - April 11, 1939), a U.S. art critic and author. He created the once immensely popular fictional detective Philo Vance, who first appeared in books in the 1920s, then in movies and on the radio.
Willard Huntington Wright was born to Archibald Davenport Wright and Annie Van Vranken Wright on October 15, 1888, in Charlottesville,… (more)