Fructose bad effects reversed by DHA, an omega-3 fatty acid

Despite alarm signals raised by various groups and organizations regarding the dangers of the presence of sugars – particularly fructose derived from corn syrup – in almost every food in the markets, only in the past decade there has been some serious evidence against high consumption of fructose.

A bitter-sweet (sic!) paper comes from Meng et al. (2016) who, in addition to showing some bad things that fructose does to brain and body, it also shows some rescue from its deleterious effects by DHA (docosahexaenoic acid), an omega-3 fatty acid.

The authors had 3 groups of rodents: one group got fructose in their water for 6 weeks, another group got fructose and DHA, and another group got their normal chow. The amount of fructose was calculated to be ecologically valid, meaning that they fed the animals the equivalent of 1 litre soda bottle per day (130 g of sugar for a 60 Kg human).

The rats that got fructose had worse learning and memory performance at a maze test compared to the other two groups.

The rats that got fructose had altered gene expression in two brain areas: hypothalamus (involved in metabolism) and hippocampus (involved in learning and memory) compared to the other two groups.

The rats that got fructose had bad metabolic changes that are precursors for Type 2 diabetes, obesity and other metabolic disorders (high blood glucose, triglycerides, insulin, and insulin resistance index) compared to the other two groups.

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The genetic analyses that the researchers did (sequencing the RNA and analyzing the DNA methylation) revealed a whole slew of the genes that had been affected by the fructose treatment. So, they did some computer work that involved Bayesian modeling  and gene library searching and they selected two genes (Bgn and Fmod) out of almost a thousand possible candidates who seemed to be the drivers of these changes. Then, they engineered mice that lacked these genes. The resultant mice had the same metabolic changes as the rats that got fructose, but… their learning and memory was even better than that of the normals? I must have missed something here. EDIT: Well… yes and no. Please read the comment below from the Principal Investigator of the study.

It is an ok paper, done by the collaboration of 7 laboratories from 3 countries. But there are a few things that bother me, as a neuroscientist, about it. First is the behavior of the genetic knock-outs. Do they really learn faster? The behavioral results are not addressed in the discussion. Granted, a genetic knockout deletes that gene everywhere in the brain and in the body, whereas the genetic alterations induced by fructose are almost certainly location-specific.

Which brings me to the second bother: nowhere in the paper (including the supplemental materials, yeas, I went through those) are any brain pictures or diagrams or anything that can tell us which nuclei of the hypothalamus the samples came from. Hypothalamus is a relatively small structure with drastically different functional nuclei very close to one another. For example, the medial preoptic nucleus that deals with sexual hormones is just above the suprachiasmatic nucleus that deals with circadian rhythms and near the preoptic is the anterior nucleus that deals mainly with thermoregulation. The nuclei that deal with hunger and satiety (the lateral and the ventromedial nucleus, respectively) are located in different parts of the hypothalamus. In short, it would matter very much where they got their samples from because the transcriptome and methylome would differ substantially from nucleus to nucleus. Hippocampus is not so complicated as that, but it also has areas with specialized functions. So maybe they messed up the identification of the two genes Bgn and Fmod as drivers of the changes; after all, they found almost 1 000 genes altered by fructose. And that mess-up might have been derived by their blind hypothalamic and hippocampal sampling. EDIT: They didn’t mess up,  per se. Turns out there were technical difficulties of extracting enough nucleic acids from specific parts of hypothalamus for analyses. I told you them nuclei are small…

Anyway, the good news comes from the first experiment, where DHA reverses the bad effects of fructose. Yeay! As a side note, the fructose from corn syrup is metabolized differently than the fructose from fruits. So you are far better off consuming the equivalent amount on fructose from a litre of soda in fruits. And DHA comes either manufactured from algae or extracted from cold-water oceanic fish oils (but not farmed fish, apparently).

If anybody that read the paper has some info that can help clarify my “bothers”, please do so in the Comment section below. The other media outlets covering this paper do not mention anything about the knockouts. Thanks! EDIT: The last author of the paper, Dr. Yang, was very kind and clarified a bit of my “bothers” in the Comments section. Thanks again!

Reference: Meng Q, Ying Z, Noble E, Zhao Y, Agrawal R, Mikhail A, Zhuang Y, Tyagi E, Zhang Q, Lee J-H, Morselli M, Orozco L, Guo W, Kilts TM, Zhu J, Zhang B, Pellegrini M, Xiao X, Young MF, Gomez-Pinilla F, Yang X (2016). Systems Nutrigenomics Reveals Brain Gene Networks Linking Metabolic and Brain Disorders. EBioMedicine, doi: 10.1016/j.ebiom.2016.04.008. Article | FREE fulltext PDF | Supplementals | Science Daily cover | NeuroscienceNews cover

By Neuronicus, 24 April 2016

Pic of the day: Abundant vertebrate

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Fish Reference: Nelson, J. S. (2006). Fishes of the World. 4th ed. John Wiley & Sons, p. 209

Bird Reference: Strycker, N. (2014). The Thing with Feathers: The Surprising Lives of Birds and What They Reveal About Being Human. Riverhead Books

Putative mechanism for decreased spermatogenesis following SSRI

fishThe SSRIs (selective serotonin reuptake inhibitors) are the most commonly prescribed antidepressants around the world. Whether is Prozac, Zoloft or Celexa, chances are that 1 in 4 Americans (or 1 in 10, depending on the study) will be making a decision during their lifetime to start an antidepressant course or not. And yet adherence to treatment is significantly low, as many people get off the SSRI due to their side effects, one of the main complains being sexual dysfunction in the form of low libido and pleasure.

Now a new study finds a mechanism for an even more worrisome effect of citalopram, (Celexa), an SSRI: the reduction of spermatogenesis. Prasad et al. (2015) used male zebrafish as a model and exposed them to citalopram in 3 different doses for 2- or 4-weeks period. They found out that the expression in the brain of the serotonin-related genes (trp2 and sert) and gonadotropin genes (lhb, sdhb, gnrh2, and gnrh3) were differently affected depending on the dose and durations of treatment. In the testes, the “long-term medium- and high-dose citalopram treatments displayed a drastic decrease in the developmental stages of spermatogenesis as well as in the matured sperm cell count” (p. 5). The authors also looked at how the neurons are organized and they found out that the serotonin fibers are associated with the fibers of the neurons that release gonadotropin-releasing hormone 3 (GnRH3) in preoptic area, a brain region in the hypothalamus heavily involved in sexual and parental behavior in both humans and fish.

Shortly put, in the brain, the citalopram affects gene expression profiles and fiber density of the serotonin neurons, which in turn decreases the production of GnRH3, which may account for the sexual dysfunctions that follow citalopram. In the testes, citalopram may act directly by binding to the local serotonin receptors and decrease spermatogenesis.

Reference: Prasad P, Ogawa S, & Parhar IS. (Oct 2015, Epub 8 Jul 2015). Serotonin Reuptake Inhibitor Citalopram Inhibits GnRH Synthesis and Spermatogenesis in the Male Zebrafish. Biololy of Reproduction. 93(4):102, 1-10. doi: 10.1095/biolreprod.115.129965. Article | FREE FULLTEXT PDF

By Neuronicus, 11 November 2015