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BACKGROUND. Cytochrome P450 family 8 subfamily B member 1 (CYP8B1) generates 12[alpha]-hydroxylated bile acids (BAs) that are associated with insulin resistance in humans. METHODS. To determine whether reduced CYP8B1 activity improves insulin sensitivity, we sequenced CYP8B1 in individuals without diabetes and identified carriers of complete loss-of-function (CLOF) mutations utilizing functional assays. RESULTS. Mutation carriers had lower plasma 12[alpha]-hydroxylated/non-12[alpha]-hydroxylated BA and cholic acid (CA)/ chenodeoxycholic acid (CDCA) ratios compared with age-, sex-, and BMI-matched controls. During insulin clamps, hepatic glucose production was suppressed to a similar magnitude by insulin, but glucose infusion rates to maintain euglycemia were higher in mutation carriers, indicating increased peripheral insulin sensitivity. Consistently, a polymorphic CLOF CYP8B1 mutation associated with lower fasting insulin in the AMP-T2D-GENES study. Exposure of primary human muscle cells to mutationcarrier CA/CDCA ratios demonstrated increased FOXO1 activity, and upregulation of both insulin signaling and glucose uptake, which were mediated by increased CDCA. Inhibition of FOXO1 attenuated the CDCA-mediated increase in muscle insulin signaling and glucose uptake. We found that reduced CYP8B1 activity associates with increased insulin sensitivity in humans. CONCLUSION. Our findings suggest that increased circulatory CDCA due to reduced CYP8B1 activity increases skeletal muscle insulin sensitivity, contributing to increased whole-body insulin sensitization. FUNDING. Biomedical Research Council/National Medical Research Council of Singapore., Introduction Bile acids (BAs) are products of cholesterol catabolism, accounting for approximately 50% of daily cholesterol turnover in humans, and act as surfactants to promote intestinal lipid absorption (1). The [...]

Disruption of a key bile acid synthesis enzyme, CYP8B1, results in the absence of cholic acid (CA), increased levels of chenodeoxycholic acid (CDCA) and improved glucose metabolism in mice. However, the mechanism by which the BAs affect glucose metabolism remains unclear. We found that the absence of CYP8B1 increases insulin sensitivity in chow-fed mice, making them phenotypically similar to antibiotic-treated wild type mice, suggesting a role for the microbiome in the beneficial effect derived from CYP8B1 depletion. The aim of this study is to determine if the gut microbiome contributes to the increased insulin sensitivity observed in the absence of CYP8B1. Ten to twelve weeks old female CYP8B1-/- and CYP8B1+/+ mice (n=8-10/group) were fed chow diet ad libitum and OGTT, ITT and GSIS were evaluated. The C2C12 mouse myotubes were exposed to either CA or CDCA, and Insr and Tgr5 levels were measured by qPCR. Moreover, 10 to 12 weeks old female CYP8B1-/- and CYP8B1+/+ mice (n=8-10/group) received a cocktail of antibiotics (1 g/L) in drinking water. Plasma bile acids were measured by GC-MS and ITT was evaluated every two weeks. CYP8B1-/- mice showed significantly increased insulin sensitivity compared to wild type littermates (p<0.001) but no differences in OGTT and GSIS. In addition, the in vitro studies show that exposure of the myotubes to CDCA resulted in significant increases in Insr (t-test, p=0.009) and Tgr5 (t-test, p=0.02). We found that the alteration of the gut microbiome by antibiotics in the wild type mice abolished the difference in ITT between CYP8B1-/- and CYP8B1+/+ mice (p=0.08). Furthermore, the antibiotic-treated wild type mice displayed a significant increase in the CA:CDCA ratio (p<0.0001), mimicking the bile acid pool composition of the untreated CYP8B1-/- littermates. Our results suggest that the specific microbiome composition in the absence of CYP8B1 might play a critical role in enhancing the insulin sensitivity, and therefore glucose metabolism in mice. Disclosure: M. Corlianò: None. S. Zhong: None. R.R. Singaraja: None. [ABSTRACT FROM AUTHOR]

Lipids are hydrophobic and amphiphilic molecules involved in diverse functions such as membrane structure, energy metabolism, immunity, and signaling. However, altered intra-cellular lipid levels or composition can lead to metabolic and inflammatory dysfunction, as well as lipotoxicity. Thus, intra-cellular lipid homeostasis is tightly regulated by multiple mechanisms. Since most peripheral cells do not catabolize cholesterol, efflux (extra-cellular transport) of cholesterol is vital for lipid homeostasis. Defective efflux contributes to atherosclerotic plaque development, impaired β-cell insulin secretion, and neuropathology. Of these, defective lipid efflux in macrophages in the arterial walls leading to foam cell and atherosclerotic plaque formation has been the most well studied, likely because a leading global cause of death is cardiovascular disease. Circulating high density lipoprotein particles play critical roles as acceptors of effluxed cellular lipids, suggesting their importance in disease etiology. We review here mechanisms and pathways that modulate lipid efflux, the role of lipid efflux in disease etiology, and therapeutic options aimed at modulating this critical process. Unlabelled Image [ABSTRACT FROM AUTHOR]

Prior experimental work showed that Bi 2 Se 3 , as a sister compound of the best room-temperature thermoelectric material Bi 2 Te 3 , has remarkably improved thermoelectric performance by Sb-Br codoping. But the relationship between its crystalline structure and thermoelectric properties is still unclear to date. Here, we use first-principles calculations to explore the possible reasons for such improvement. The electronic structures of Bi 2- x Sb x (Se 1- y Br y ) 3 ( x = 0, 1, 2; y = 0, 0.08) are systematically investigated. Significant effects of 8% Br codoping in BiSbSe 3 are found. First, the Br atom acts as an electron donor, thus greatly increasing the carrier concentration. Second, similar to the effect of Sb doping, Br codoping further improves greatly the degeneracy of the conduction band edge, which leads to a remarkably increased density-of-states effective mass without deterioration of the carrier mobility, and simultaneously preserves a large Seebeck coefficient of ∼-254 μV K -1 at 800 K. In addition, the Br codoping softens the chemical bonds, which enhances anharmonic scattering and further reduces the lattice thermal conductivity. We predict that the maximum zT of BiSb(Se 0.92 Br 0.08 ) 3 at 800 K can reach 0.96 with the carrier concentration of 9.22 × 10 19 cm -3 . This study rationalizes a potential strategy to improve the thermoelectric performance of Bi 2 Se 3 -based thermoelectric materials., Competing Interests: The authors declare no competing interests., (This journal is © The Royal Society of Chemistry.)

Four DNA extraction methods namely SDS-hyperhaline method (I), modified SDS-hyperhaline method (II), indirect method (III), alkaline lysis method (IV) were evaluated by comparing DNA yield, spectrophotometric quality, genomic integrity and PCR suitability in this paper. The results showed that high DNA yields were obtained by method I, II and IV. However, higher quality of DNA was gained by method III and IV. Based on the results of the Pulsed-Field Gel Electrophoresis (PFGE), the completeness of DNA extracted by method IV was the best. About 6.0 microg DNA can be recovered from 1.0 g soil by method IV which involved to lysis cell by SDS and to precipitate impurities by adding potassium acetate and magnesium chloride Therefore, it is confirmed that method IV is a novel, reliable and versatile method for large-scale DNA extraction involving less purification steps for various soil samples., (Copyright 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)