Identification of Novel Regulatory Cholesterol Metabolite, 5-Cholesten, 3β,25-Diol, Disulfate

Oxysterol sulfation plays an important role in regulation of lipid metabolism and inflammatory responses. In the present study, we report the discovery of a novel regulatory sulfated oxysterol in nuclei of primary rat hepatocytes after overexpression of the gene encoding mitochondrial cholesterol delivery protein (StarD1). Forty-eight hours after infection of the hepatocytes with recombinant StarD1 adenovirus, a water-soluble oxysterol product was isolated and purified by chemical extraction and reverse-phase HPLC. Tandem mass spectrometry analysis identified the oxysterol as 5-cholesten-3β, 25-diol, disulfate (25HCDS), and confirmed the structure by comparing with a chemically synthesized compound. Administration of 25HCDS to human THP-1-derived macrophages or HepG2 cells significantly inhibited cholesterol synthesis and markedly decreased lipid levels in vivo in NAFLD mouse models. RT-PCR showed that 25HCDS significantly decreased SREBP-1/2 activities by suppressing expression of their responding genes, including ACC, FAS, and HMG-CoA reductase. Analysis of lipid profiles in the liver tissues showed that administration of 25HCDS significantly decreased cholesterol, free fatty acids, and triglycerides by 30, 25, and 20%, respectively. The results suggest that 25HCDS inhibits lipid biosynthesis via blocking SREBP signaling. We conclude that 25HCDS is a potent regulator of lipid metabolism and propose its biosynthetic pathway

Rifaximin Exerts Beneficial Effects Independent of its Ability to Alter Microbiota Composition

Rifaximin has clinical benefits in minimal hepatic encephalopathy (MHE) but the mechanism of action is unclear. The antibiotic-dependent and -independent effects of rifaximin need to be elucidated in the setting of MHE-associated microbiota. To assess the action of rifaximin on intestinal barrier, inflammatory milieu and ammonia generation independent of microbiota using rifaximin

Profiling of Urinary Glucuronidated Bile Acids across Age Groups

We investigated the age-dependent changes in urinary excretion of glucuronidated bile acids at the C-3 position. Bile acid 3-glucuronides accounted for 0.5% of urinary bile acids in neonates, and the proportion of bile acid 3-glucuronides plateaued at 1–3 years of age. The 3-glucuronides of secondary bile acids were first secreted at 3 months of age, the same time as the establishment of the gut bacterial flora in infants. A considerable portion of bile acid 3-glucuronides were present as non-amidated forms. Our results indicate dynamic hepatic enzyme activity in which the levels of uridine 5′-diphospho-glucuronosyltransferases (UGTs) differ by age group, with higher glucuronidation activity of UGTs towards nonamidated bile acids than amidated bile acids

StarD5: an ER stress protein regulates plasma membrane and intracellular cholesterol homeostasis

How plasma membrane (PM) cholesterol is controlled is poorly understood. Ablation of the gene encoding the ER stress steroidogenic acute regulatory-related lipid transfer domain (StarD)5 leads to a decrease in PM cholesterol content, a decrease in cholesterol efflux, and an increase in intracellular neutral lipid accumulation in macrophages, the major cell type that expresses StarD5. ER stress increases StarD5 expression in mouse hepatocytes, which results in an increase in accessible PM cholesterol in WT but not in StarD5-/- hepatocytes. StarD5-/- mice store higher levels of cholesterol and triglycerides, which leads to altered expression of cholesterol-regulated genes. In vitro, a recombinant GST-StarD5 protein transfers cholesterol between synthetic liposomes. StarD5 overexpression leads to a marked increase in PM cholesterol. Phasor analysis of 6-dodecanoyl-2-dimethylaminonaphthalene fluorescence lifetime imaging microscopy data revealed an increase in PM fluidity in StarD5-/- macrophages. Taken together, these studies show that StarD5 is a stress-responsive protein that regulates PM cholesterol and intracellular cholesterol homeostasis

Analysis of chemically synthesized 25HCDS: MS spectrum and ¹H NMR spectrum of 25HCDS.

<p>(<b>A</b>) Negative ion flow injection mass spectrum of 25HCDS. m/z, 583(M+Na-2H), 561 (M-H) 481 (M-S) and 463 (M-S-S-H2O) were observed as major ions. This fragmentation pattern is similar to that obtained from the nuclear compound (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103621#pone-0103621-g003" target="_blank">Fig. 1C</a>); (<b>B</b>) 1H NMR spectrum of 25HCDS; the sulfated 3α-H resonated at 4.14 ppm which was ca 0.7ppm downfield compared to that of unsulfated 3α-H in 25HC. All other chemical shifts and their spin couplings observed were similar to those of 25HC and 25HC3S; and (<b>C</b>) 13C NMR spectrum of 25HCDS; the C-3 and C-25 resonated at 86 and 80 ppm, which were δ 14 ppm and δ 9 ppm downfield, respectively, indicating that both positions are sulfated.</p

Relative Hepatic mRNA Expression Involved in Lipid Metabolism in Mice Fed on a HFD with or without 25HCDS.

<p>Animals were treated as described in Methods.</p><p>All values are expressed as the mean ± SD; n = 6–7.</p><p>* p<0.05 compared with HFD mice.</p><p>Abbreviations: HFD, high fat diet.</p