Cholesterol-lowering effects of taurine through the reduction of ileal FXR signaling due to the alteration of ileal bile acid composition

Sodium alginate improves lipid disruption and alters the composition of the gut microbiota in farnesoid X receptor-null mice

Seaweed-derived dietary fibre sodium alginate (SA) has been shown to present with health benefits in food-derived disease models. To determine whether SA improves the disease rather than merely suppressing its progression, we assessed its effects using farnesoid X receptor (FXR)-deficient mice to provide a model of advanced hyperlipidaemia. Fxr-null mice were fed with a 5% SA-supplemented diet for nine weeks and showed significant decreases in the levels of liver triglycerides (p < 0.05), total cholesterol (p < 0.05), serum low-density lipoprotein-cholesterol (p < 0.001). The expression levels of fatty acid-synthesizing genes (Fas and Scd1) and cholesterol-metabolizing genes (Hmgcr, Hmgcs, and Abca1), were significantly reduced. Furthermore, the SA supplementation has altered the gut microbiota and significantly increased the abundance of the genus Oscillospira (p < 0.001) and Parabacteroides (p < 0.01). These results suggest that SA improves lipid disruption and influences the composition of the gut microbiota in the Fxr-null mice.

Taurine alleviates dysfunction of cholesterol metabolism under hyperuricemia by inhibiting A2AR-SREBP-2/CREB/HMGCR axis

Dysfunctional cholesterol metabolism is highly prevalent in patients with hyperuricemia. Both uric acid and cholesterol are independent risk factors for atherosclerosis, contributing to an increased incidence of cardiovascular disease in hyperuricemia. Investigating the pathological mechanisms underlying cholesterol metabolism dysfunction in hyperuricemia is essential. This study identified adenosine and inosine, two major purine metabolites, as key regulators of cholesterol biosynthesis. These metabolites upregulate 3-hydroxy-3-methylglutaryl-CoA. Further mechanistic studies revealed that adenosine/inosine up-regulated the expression of 3-hydroxy-3-methylglutaryl-CoA by activating adenosine A2A receptor via the Srebp-2/Creb axis in hyperuricemia. Additionally, we found that taurine deficiency contributes to cholesterol metabolism dysfunction in hyperuricemia. Taurine administration in hyperuricemia mice significantly reduced cholesterol elevation by inhibiting adenosine A2A receptor. This study provides a promising strategy for treating comorbid hypercholesterolemia and hyperuricemia.

Trimethylamine N-oxide ameliorates hepatic damage including reduction of hepatic bile acids and cholesterol in Fxr-null mice

There are conflicting animal experiments on the effect of trimethylamine N-oxide (TMAO), the dietary metabolite, on non-alcoholic fatty liver disease (NAFLD). This study aims to determine the effect of TMAO on NAFLD. A diet containing 0.3% TMAO was fed to farnesoid X receptor (Fxr)-null mice, a model of NAFLD, for 13 weeks. Fxr-null mice fed TMAO showed significant reductions in liver damage markers but not wild-type mice. Hepatic bile acid and cholesterol levels were significantly decreased, and triacylglycerol levels tended to decrease in TMAO-fed Fxr-null mice. Changes in mRNA levels of hepatic bile acid and cholesterol transporters and synthetic enzymes were observed, which could explain the decreased hepatic bile acid and cholesterol levels in Fxr-null mice given the TMAO diet but not in the wild-type mice. These results suggest that TMAO intake ameliorates liver damage in Fxr-null mice, further altering bile acid/cholesterol metabolism in an FXR-independent manner.

Taurine supplementation reduces adiposity and hepatic lipid metabolic activity in adult offspring following maternal cafeteria diet

Maternal taurine supplementation has been shown to exert protective effects following a maternal obesogenic diet on offspring growth and metabolism. However, the long-term effects of maternal cafeteria diet on adiposity, metabolic profile, and hepatic gene expression patterns following supplementation of taurine in adult offspring remains unclear. In this study, we hypothesized that exposure to maternal taurine supplementation would modulate the effects of maternal cafeteria diet by reducing adiposity and hepatic gene expression patterns involved in lipid metabolism in adult offspring. Female Wistar rats were fed a control diet, control diet supplemented with 1.5% taurine in drinking water, cafeteria diet (CAF) or CAF supplemented with taurine (CAFT) from weaning. After 8 weeks, all animals were mated and maintained on the same diets during pregnancy and lactation. After weaning, all offspring were fed with control chow diet until the age of 20 weeks. Despite similar body weights, CAFT offspring had significantly lower fat deposition and body fat when compared with CAF offspring. Microarray analysis revealed that genes (Akr1c3, Cyp7a1, Hsd17b6, Cd36, Acsm3, and Aldh1b1) related to steroid hormone biosynthesis, cholesterol metabolism, peroxisome proliferator-activated receptor signaling pathway, butanoate metabolism, and fatty acid degradation were down-regulated in CAFT offspring. The current study shows that exposure to maternal cafeteria diet promoted adiposity and taurine supplementation reduced lipid deposition and in both male and female offspring and led to alterations in hepatic gene expression patterns, reducing the detrimental effects of maternal cafeteria diet.

Cul5 mediates taurine-stimulated mTOR mRNA expression and proliferation of mouse mammary epithelial cells

Cullin5 (Cul5) protein can regulate multiple signaling pathways; however, it is still largely unknown the role and molecule mechanism of Cul5 in regulation of the mTOR signaling. In this study, we determined the effect of Cul5 on the proliferation of HC11 cells, a mouse mammary epithelial cell line, and explored the corresponding molecular mechanism. We found that Cul5 was highly expressed in mammary gland tissues in the lactation stage compared with that in puberty and involution. Using gene knockdown and activation methods, we showed that Cul5 promoted proliferation of HC11 cells, mRNA expression and protein phosphorylation of mTOR. Taurine (Tau) affected Cul5 mRNA and protein levels in a dose-dependent manner. Cul5 localized to the nucleus and knockdown of Cul5 almost totally blocked the stimulation of Tau on mTOR mRNA expression and protein phosphorylation. PI3K inhibition almost totally abolished the stimulation of Tau on Cul5 expression. In summary, our data uncover that Cul5 is a positive regulator of proliferation of HC11 cells, and mediates the stimulation of Tau on mRNA expression and subsequent protein phosphorylation of mTOR. Our data lay a new theoretical foundation for regulating mammary cell proliferation and promoting milk yield.

Dietary Oyster (Crassostrea gigas) Extract Ameliorates Dextran Sulfate Sodium-Induced Chronic Experimental Colitis by Improving the Composition of Gut Microbiota in Mice

Previously, we have reported that the intake of oyster extract (OE), prepared from Pacific oysters (Crassostrea gigas), can attenuate symptoms of dextran sulfate sodium (DSS)-induced acute experimental colitis in mice. Herein, we aimed to evaluate whether OE intake ameliorates chronic experimental colitis induced by repeated DSS administration in mice. Male C57BL/6J (4-week-old) mice were fed either the standard diet AIN93G (control diet) or the control diet containing 5.0% (w/w) OE (OE diet). After 21 days of diet feeding, chronic experimental colitis was induced by three cycles of 2.0% (w/w) DSS solution administration (5 days), followed by distilled water (5 days). Mice fed OE alleviated the shortened colonic length, increased the relative weight of the spleen, colonic histopathological score (regeneration), and blood in the stool score compared with mice fed control diet. A tendency to improve the α-diversity of fecal microbiota, which was exacerbated by colitis, was observed in mice fed OE. Correlation analysis suggested that the anti-colitis effect of OE intake could be related to the valeric acid content and relative abundances of Ruminococcus and Enterococcus in the feces. In conclusion, OE could ameliorate DSS-induced chronic experimental colitis by improving the gut environment, including the microbiota community and SCFA composition.

Aberrant Cholesterol Metabolic Genes Regulation in a Negative Feedback Loop Induced by an Alphacoronavirus

Porcine epidemic diarrhea virus (PEDV) is an alphacoronavirus that causes acute inflammation and severe diarrhea in newborn piglets with a high mortality rate. Given that cholesterol is required for coronavirus infection in vitro, the role of endogenous cholesterol metabolism in regulating coronavirus infection and the mechanism behind it ought to be elucidated. In this study, we found that the levels of cholesterol and bile acids were both elevated in the livers of PEDV-infected piglets compared to those of the control group. Consistently, in the livers of PEDV-infected piglets, the expression of key genes involved in cholesterol metabolism was significantly increased. Transcriptomic analysis indicated that the cholesterol homeostasis pathway was among the most enriched pathways in the livers of PEDV-infected piglets. Unexpectedly, the expression of key genes in the cholesterol metabolic pathway was downregulated at the messenger RNA (mRNA) level, but upregulated at the protein level. While the primary transcriptional factors (TFs) of cholesterol metabolism, including SREBP2 and FXR, were upregulated at both mRNA and protein levels in response to PEDV infection. Further Chromatin Immunoprecipitation Quantitative Real-time PCR (ChIP-qPCR) analysis demonstrated that the binding of these TFs to the locus of key genes in the cholesterol metabolic pathway was remarkably inhibited by PEDV infection. It was also observed that the occupancies of histone H3K27ac and H3K4me1, at the locus of the cholesterol metabolic genes HMGCR and HMGCS1, in the livers of PEDV-infected piglets, were suppressed. Together, the PEDV triggers an aberrant regulation of cholesterol metabolic genes via epigenetic inhibition of SREBP2/FXR-mediated transcription, which provides a novel antiviral target against PEDV and other coronaviruses.

Human Cytochrome P450 2C9 and Its Polymorphic Modifications: Electroanalysis, Catalytic Properties, and Approaches to the Regulation of Enzymatic Activity

The electrochemical properties of cytochrome P450 2C9 (CYP2C9) and polymorphic modifications P450 2C9*2 (CYP2C9*2) and P450 2C9*3 (CYP2C9*3) were studied. To analyze the comparative electrochemical and electrocatalytic activity, the enzymes were immobilized on electrodes modified with a membrane-like synthetic surfactant (didodecyldimethylammonium bromide (DDAB)). An adequate choice of the type of modified electrode was confirmed by cyclic voltammetry of cytochromes P450 under anaerobic conditions, demonstrating well-defined peaks of reduction and oxidation of the heme iron. The midpoint potential, Emid, of cytochrome P450 2C9 is −0.318 ± 0.01 V, and Emid = −0.324 ± 0.01 V, and Emid = −0.318 ± 0.03 V for allelic variant 2C9*2 and allelic variant 2C9*3, respectively. In the presence of substrate diclofenac under aerobic conditions, cytochrome P450 2C9 and its polymorphic modifications P450 2C9*2 and P450 2C9*3 exhibit catalytic properties. Stimulation of the metabolism of diclofenac by cytochrome P450 2C9 in the presence of antioxidant medications mexidol and taurine was shown.

Long-Term Dietary Taurine Lowers Plasma Levels of Cholesterol and Bile Acids

Cholesterol is an essential lipid in vertebrates, but excess blood cholesterol promotes atherosclerosis. In the liver, cholesterol is metabolized to bile acids by cytochrome P450, family 7, subfamily a, polypeptide 1 (CYP7A1), the transcription of which is negatively regulated by the ERK pathway. Fibroblast growth factor 21 (FGF21), a hepatokine, induces ERK phosphorylation and suppresses Cyp7a1 transcription. Taurine, a sulfur-containing amino acid, reportedly promotes cholesterol metabolism and lowers blood and hepatic cholesterol levels. However, the influence of long-term feeding of taurine on cholesterol levels and metabolism remains unclear. Here, to evaluate the more chronic effects of taurine on cholesterol levels, we analyzed mice fed a taurine-rich diet for 14-16 weeks. Long-term feeding of taurine lowered plasma cholesterol and bile acids without significantly changing other metabolic parameters, but hardly affected these levels in the liver. Moreover, taurine upregulated Cyp7a1 levels, while downregulated phosphorylated ERK and Fgf21 levels in the liver. Likewise, taurine-treated Hepa1-6 cells, a mouse hepatocyte line, exhibited downregulated Fgf21 levels and upregulated promoter activity of Cyp7a1. These results indicate that taurine promotes cholesterol metabolism by suppressing the FGF21/ERK pathway followed by upregulating Cyp7a1 expression. Collectively, this study shows that long-term feeding of taurine lowers both plasma cholesterol and bile acids, reinforcing that taurine effectively prevents hypercholesterolemia.