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Circulating bile acids as biomarkers for disease diagnosis and prevention.

CONTEXT
Bile acids (BAs) are pivotal signalling molecules that regulate energy metabolism and inflammation. Recent epidemiological studies have reported specific alterations in circulating BA profiles in certain disease states, including obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease, and Alzheimer's disease. In the past decade, breakthroughs have been made regarding the translation of BA profiling into clinical use for disease prediction. In this review, we summarise and synthesise recent data on variation in circulating BA profiles in patients with various diseases to evaluate the value of these biomarkers in human plasma for early diagnosis.


EVIDENCE ACQUISITION
This review is based on a collection of primary and review literature gathered from a PubMed search for BAs, obesity, type 2 diabetes mellitus (T2DM), insulin resistance, non-alcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC), cholangiocarcinoma (CCA), colon cancer, and Alzheimer's disease (AD), among other keywords.


EVIDENCE SYNTHESIS
Subjects with obesity, T2DM, HCC, CCA, or AD showed specific alterations in circulating BA profiles. These alterations may have existed long before the initial diagnosis of the above diseases. The intricate relationship between obesity, IR, and NAFLD complicates the establishment of clear and independent associations between BA profiles and NASH. Alterations in the levels of TBAs and several BA species were seen across the entire spectrum of NAFLD, demonstrating significant increases with the worsening of histological features.


CONCLUSIONS
Aberrant circulating BA profiles are an early event in the onset and progression of obesity, T2DM, HCC, and AD. The pleiotropic effects of BAs explain these broad connections. Circulating BA profiles could provide a basis for the development of biomarkers for the diagnosis and prevention of a wide range of diseases.