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Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) is a key enzyme in triacylglycerol (TG) biosynthesis. Here we show that genetic deficiency and pharmacological inhibition of DGAT1 in mice alters cholesterol metabolism. Cholesterol absorption, as assessed by acute cholesterol uptake, was significantly decreased in the small intestine and liver upon DGAT1 deficiency/inhibition. Ablation of DGAT1 in the intestine (I-DGAT1(-/-)) alone is sufficient to cause these effects. Consequences of I-DGAT1 deficiency phenocopy findings in whole-body DGAT1(-/-) and DGAT1 inhibitor-treated mice. We show that deficiency/inhibition of DGAT1 affects cholesterol metabolism via reduced chylomicron size and increased trans-intestinal cholesterol excretion. These effects are independent of cholesterol uptake at the apical surface of enterocytes but mediated through altered dietary fatty acid metabolism. Our findings provide insight into a novel role of DGAT1 and identify a pathway by which intestinal DGAT1 deficiency affects whole-body cholesterol homeostasis in mice. Targeting intestinal DGAT1 may represent a novel approach for treating hypercholesterolemia., (Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.)

The β-lactam cholesterol absorption inhibitor ezetimibe is so far the only representative of this class of compounds on the market today. The goal of this work was to synthesize new amide ezetimibe analogs from trans-3-amino-(3R,4R)-β-lactam and to test their cytotoxicity and activity as cholesterol absorption inhibitors. We synthesized six new amide ezetimibe analogs. All new compounds exhibited low toxicity in MDCKIIwt, hNPC1L1/MDCKII and HepG2 cell lines and showed significant inhibition of cholesterol uptake in hNPC1L1/MDCKII cells. In addition, we determined the activity of the three compounds to inhibit cholesterol absorption in vivo. Our results demonstrate that these compounds considerably reduce cholesterol concentrations in liver and small intestine of mice. Thus, our newly synthesized amide ezetimibe analogs are cholesterol absorption inhibitors in vitro and in vivo., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Two new trans-(3R,4R)-amino-β-lactam derivatives and their diastereoisomeric mixtures were synthesized as ezetimibe bioisosteres and tested in in vitro and in vivo experiments as novel β-lactam cholesterol absorption inhibitors. Both compounds exhibited low cytotoxicity in MDCKII, hNPC1L1/MDCKII, and HepG2 cell lines and potent inhibitory effect in hNPC1L1/MDCKII cells. In addition, these compounds markedly reduced cholesterol absorption in mice, resulting in reduced cholesterol concentrations in plasma, liver, and intestine. We determined the crystal structure of one amino-β-lactam derivative to establish unambiguously both the absolute and relative configuration at the new stereogenic centre C17, which was assigned to be S. The pKa values for both compounds are 9.35, implying that the amino-β-lactam derivatives and their diastereoisomeric mixtures are in form of ammonium salt in blood and the intestine. The IC50 value for the diastereoisomeric mixture is 60 μM. In vivo, it efficiently inhibited cholesterol absorption comparable to ezetimibe., (Copyright © 2014 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Aberrant oxysterol biosynthesis is implicated in the pathogenesis of neurodegenerative diseases. During the present study we have investigated the effects of exogenously added 25-hydroxycholesterol (25-HC) on transcription of cholesterol biosynthetic genes, sterol-regulatory element binding protein (SREBP) processing and cholesterol biosynthesis in the murine CATH.a neuronal cell line. A single i.p. injection of lipopolysaccharide resulted in robust induction of cholesterol 25-hydroxylase mRNA and protein levels in brains of treated mice. In vitro, 25-HC upregulated the transcription of ATP-binding cassette transporter A1 (ABCA1) and (to a lesser extent) apolipoprotein E (apoE) in CATH.a neurons. Cholesterol biosynthetic gene expression (squalene synthase, HMG-CoA synthase, HMG-CoA reductase, and SREBP2) was downregulated by 25-HC. 25-HC also significantly attenuated proteolytic processing of SREBP2. Finally, 25-HC downregulated cholesterol biosynthesis in CATH.a neurons. Our results demonstrate that 25-HC is a potent effector oxysterol of neuronal cholesterol homeostasis., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Hormone sensitive lipase (HSL) regulates the hydrolysis of acylglycerols and cholesteryl esters (CE) in various cells and organs, including enterocytes of the small intestine. The physiological role of this enzyme in enterocytes, however, stayed elusive. In the present study we generated mice lacking HSL exclusively in the small intestine (HSLiKO) to investigate the impact of HSL deficiency on intestinal lipid metabolism and the consequences on whole body lipid homeostasis. Chow diet-fed HSLiKO mice showed unchanged plasma lipid concentrations. In addition, feeding with high fat/high cholesterol (HF/HC) diet led to unaltered triglyceride but increased plasma cholesterol concentrations and CE accumulation in the small intestine. The same effect was observed after an acute cholesterol load. Gavaging of radioactively labeled cholesterol resulted in increased abundance of radioactivity in plasma, liver and small intestine of HSLiKO mice 4h post-gavaging. However, cholesterol absorption determined by the fecal dual-isotope ratio method revealed no significant difference, suggesting that HSLiKO mice take up the same amount of cholesterol but in an accelerated manner. mRNA expression levels of genes involved in intestinal cholesterol transport and esterification were unchanged but we observed downregulation of HMG-CoA reductase and synthase and consequently less intestinal cholesterol biosynthesis. Taken together our study demonstrates that the lack of intestinal HSL leads to CE accumulation in the small intestine, accelerated cholesterol absorption and decreased cholesterol biosynthesis, indicating that HSL plays an important role in intestinal cholesterol homeostasis., (Copyright © 2012 Elsevier B.V. All rights reserved.)