tauromuricholate and Insulin-Resistance

Previous studies have linked dietary capsaicin (CAP) intake to improved glucose homeostasis and insulin sensitivity. However, the underlying mechanisms remain unclear.. Type 2 diabetic db/db mice are fed a chow diet with or without CAP treatment for 8 weeks. CAP administration markedly improves glucose tolerance and insulin sensitivity through decreasing gluconeogenesis and increasing glycogen synthesis in the liver. Furthermore, CAP inhibits the increase in abundance of the genus Lactobacillus and its bile salt hydrolase (BSH) activity compared with levels in chow-fed mice, thereby leading to the accumulation of tauro-β-muricholic acid (TβMCA), a natural antagonist of the farnesoid X receptor (FXR) that is involved in the regulation of BA and glucose metabolism. CAP-induced suppression of enterohepatic FXR-fibroblast growth factor 15 (FGF15) signaling contributes to the increased BA pool size, followed by increases in the expression of cholesterol 7α-hydroxylase (CYP7A1) and hepatic BA synthesis. Additionally, depleting gut microbiota by antibiotics administration abolishes the beneficial effects of CAP on BA metabolism and glucose homeostasis.. CAP-induced improvements in BA and glucose metabolism are partially mediated by the gut microbiota-BA-enterohepatic FXR axis in db/db mice.

Topics: Animals; Bile Acids and Salts; Capsaicin; Diabetes Mellitus, Type 2; Fibroblast Growth Factors; Gastrointestinal Microbiome; Glucose; Insulin Resistance; Male; Mice; Mice, Inbred C57BL; Receptors, Cytoplasmic and Nuclear; Signal Transduction; Taurocholic Acid

Bile acid synthesis is the major pathway for catabolism of cholesterol. Cholesterol 7α-hydroxylase (CYP7A1) is the rate-limiting enzyme in the bile acid biosynthetic pathway in the liver and plays an important role in regulating lipid, glucose and energy metabolism. Transgenic mice overexpressing CYP7A1 (CYP7A1-tg mice) were resistant to high-fat diet (HFD)-induced obesity, fatty liver, and diabetes. However the mechanism of resistance to HFD-induced obesity of CYP7A1-tg mice has not been determined. In this study, metabolomic and lipidomic profiles of CYP7A1-tg mice were analyzed to explore the metabolic alterations in CYP7A1-tg mice that govern the protection against obesity and insulin resistance by using ultra-performance liquid chromatography-coupled with electrospray ionization quadrupole time-of-flight mass spectrometry combined with multivariate analyses. Lipidomics analysis identified seven lipid markers including lysophosphatidylcholines, phosphatidylcholines, sphingomyelins and ceramides that were significantly decreased in serum of HFD-fed CYP7A1-tg mice. Metabolomics analysis identified 13 metabolites in bile acid synthesis including taurochenodeoxycholic acid, taurodeoxycholic acid, tauroursodeoxycholic acid, taurocholic acid, and tauro-β-muricholic acid (T-β-MCA) that differed between CYP7A1-tg and wild-type mice. Notably, T-β-MCA, an antagonist of the farnesoid X receptor (FXR) was significantly increased in intestine of CYP7A1-tg mice. This study suggests that reducing 12α-hydroxylated bile acids and increasing intestinal T-β-MCA may reduce high fat diet-induced increase of phospholipids, sphingomyelins and ceramides, and ameliorate diabetes and obesity. This article is part of a Special Issue entitled Linking transcription to physiology in lipodomics.

Topics: Animals; Bile Acids and Salts; Cholesterol 7-alpha-Hydroxylase; Diabetes Mellitus; Diet, High-Fat; Female; Glucose; Homeostasis; Insulin Resistance; Intestinal Mucosa; Lipid Metabolism; Liver; Male; Metabolome; Metabolomics; Mice; Mice, Inbred C57BL; Mice, Transgenic; Obesity; Rats; Signal Transduction; Taurocholic Acid