Rimonabant is a dual inhibitor of acyl CoA:cholesterol acyltransferases 1 and 2

Robust differentiation of human enteroendocrine cells from intestinal stem cells

Enteroendocrine (EE) cells are the most abundant hormone-producing cells in humans and are critical regulators of energy homeostasis and gastrointestinal function. Challenges in converting human intestinal stem cells (ISCs) into functional EE cells, ex vivo, have limited progress in elucidating their role in disease pathogenesis and in harnessing their therapeutic potential. To address this, we employed small molecule targeting of the endocannabinoid receptor signaling pathway, JNK, and FOXO1, known to mediate endodermal development and/or hormone production, together with directed differentiation of human ISCs from the duodenum and rectum. We observed marked induction of EE cell differentiation and gut-derived expression and secretion of SST, 5HT, GIP, CCK, GLP-1 and PYY upon treatment with various combinations of three small molecules: rimonabant, SP600125 and AS1842856. Robust differentiation strategies capable of driving human EE cell differentiation is a critical step towards understanding these essential cells and the development of cell-based therapeutics.

The role of exercise training and the endocannabinoid system in atherosclerotic plaque burden and composition in Apo-E-deficient mice

INTRODUCTION

We investigated the effect of combining exercise training and treatment with an endocannabinoid receptor 1 inhibitor (Rimonabant) on atherosclerosis burden and composition.

METHODS

Forty-eight apolipoprotein E-deficient (ApoE-/-) mice were kept on a 16-week high-fat diet. Mice were then placed on a normal diet and were randomized to the following groups with n=12 mice for 6 more weeks: 1) Control (Co) - no intervention; 2) Exercise (Ex) - exercise training on treadmill; 3) Rimonabant (Ri) - oral administration of rimonabant (10 mg/kg/day); or 4) Rimonabant+Exercise (RiEx) - combination of Ri and Ex groups treatment. At the end, all animals were sacrificed, and blood samples, as well as aortic root specimens, were obtained for histomorphometric analysis and quantification of the serum and plaque content of matrix metalloproteinases (MMPs).

RESULTS

The mean plaque area was significantly smaller (RiEx: 43.18±1.72%, Ri: 44.66±3.1%, Ex: 49±4.10%, Co: 70.43±2.83%) in all active treatment groups relative to the Co group (p<0.01). Conversely, the relative concentrations of collagen and elastin were increased significantly across all treatment groups compared to Co (p<0.05). Immunohistochemical analysis revealed significantly reduced macrophage content within plaques after all interventions, with the most pronounced effect observed after combined treatment (RiEx: 9.4±3.92%, Ri: 15±2.45%, Ex: 19.78±2.79%, Co: 34.25±4.99%; p<0.05). Within plaques, the TIMP-1 concentration was significantly upregulated in exercise-treated groups. MMP-3 and MMP-9 concentrations were equivalently decreased in all three active treatment groups compared to controls (p<0.001).

DISCUSSION

Both exercise and rimonabant treatments induced plaque regression and promoted plaque stability. The combined treatment failed to show additive or synergistic benefits relative to either intervention alone.

Macrophage-mediated cholesterol handling in atherosclerosis

Formation of foam cells is a hallmark at the initial stages of atherosclerosis. Monocytes attracted by pro-inflammatory stimuli attach to the inflamed vascular endothelium and penetrate to the arterial intima where they differentiate to macrophages. Intimal macrophages phagocytize oxidized low-density lipoproteins (oxLDL). Several scavenger receptors (SR), including CD36, SR-A1 and lectin-like oxLDL receptor-1 (LOX-1), mediate oxLDL uptake. In late endosomes/lysosomes of macrophages, oxLDL are catabolysed. Lysosomal acid lipase (LAL) hydrolyses cholesterol esters that are enriched in LDL to free cholesterol and free fatty acids. In the endoplasmic reticulum (ER), acyl coenzyme A: cholesterol acyltransferase-1 (ACAT1) in turn catalyses esterification of cholesterol to store cholesterol esters as lipid droplets in the ER of macrophages. Neutral cholesteryl ester hydrolases nCEH and NCEH1 are involved in a secondary hydrolysis of cholesterol esters to liberate free cholesterol that could be then out-flowed from macrophages by cholesterol ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 and SR-BI. In atherosclerosis, disruption of lipid homoeostasis in macrophages leads to cholesterol accumulation and formation of foam cells.

[Microbial metabolites that inhibit sterol biosynthesis, their chemical diversity and characteristics of mode of action]

Inhibitors of sterol biosynthesis (ISB) are widespread in nature and characterized by appreciable diversity both in their chemical structure and mode of action. Many of these inhibitors express noticeable biological activity and approved themselves in development of various pharmaceuticals. In this review there is a detailed description of biologically active microbial metabolites with revealed chemical structure that have ability to inhibit sterol biosynthesis. Inhibitors of mevalonate pathway in fungous and mammalian cells, exhibiting hypolipidemic or antifungal activity, as well as inhibitors of alternative non-mevalonate (pyruvate gliceraldehyde phosphate) isoprenoid pathway, which are promising in the development of affective antimicrobial or antiparasitic drugs, are under consideration in this review. Chemical formulas of the main natural inhibitors and their semi-synthetic derivatives are represented. Mechanism of their action at cellular and biochemical level is discussed. Special attention is given to inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase (group of lovastatin) and inhibitors of acyl-CoA-cholesterol-acyl transferase (ACAT) that possess hypolipidemic activity and could be affective in the treatment of atherosclerosis. In case of inhibitors of late stages of sterol biosynthesis (after squalene formation) special attention is paid to compounds possessing evident antifungal and antitumoral activity. Explanation of mechanism of anticancer and antiviral action of microbial ISB, as well as the description of their ability to induce apoptosis is given.

HPLC-FLD determination of NBD-cholesterol, its ester and other metabolites in cellular lipid extracts

22-[N(-7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol), a fluorescent cholesterol analog, was an extragenous cholesterol tracer used to study cholesterol absorption and metabolism in cultured cells. In order to measure free intracellular cholesterol and its esters, a precise and sensitive method employing high-performance liquid chromatography/fluorescence detection (HPLC-FLD) was developed for the first time. Method validation showed a limit of detection at 30 ng/mL. The calibration curve was linear within the range of 0.0625-10.0 µg/mL (r(2) = 0.999). Accuracy and precision were highlighted by good recovery and low variations. Apart from NBD-cholesteryl oleate, two additional cellular metabolites of NBD-cholesterol, probably an isomer and an oxidation product, were determined in the lipid extracts of Caco-2 human colon adenocarcinoma cells according to mass spectrometry. In AC29 mouse malignant mesothelioma cells overexpressing acyl-CoA:cholesterol acyltransferase-1 (ACAT1) or ACAT2, only the oxidized metabolite was detected. Using the newly developed method, YIC-C8-434, a known ACAT inhibitor, was shown to inhibit ACAT activity in Caco-2 cells, as well as in AC29/ACAT1 or AC29/ACAT2 cells. In conclusion, the sensitive and specific HPLC-FLD method is a powerful tool for simultaneous quantification of intracellular NBD-cholesterol and its oleoyl-ester.

Fatty acyl esterification and deesterification of 17β-estradiol in human breast subcutaneous adipose tissue

CONTEXT

Adipose tissue has an important role in peripheral estrogen synthesis. One of the metabolic pathways of estradiol (E(2)) is its conversion to lipophilic fatty acyl esters.

OBJECTIVE

The aim was to study the metabolism of E(2) fatty acyl esters in adipose tissue and, specifically, the role of hormone-sensitive lipase (HSL) in steroid ester hydrolysis.

DESIGN AND SETTING

Tissue samples were obtained during elective surgery in University Central Hospital in the years 2008-2011.

PATIENTS

Women undergoing reduction mammoplasty (n = 27) or surgery for breast cancer (n = 16) participated in the study.

INTERVENTIONS

Two sc adipose tissue samples were taken from different quadrants of the breast. Radiolabeled steroids were incubated with tissue homogenate (esterase assay) or microsomal fraction (acyl transferase assay). E(2) and E(2) fatty acyl ester concentrations were determined by fluoroimmunoassay or liquid chromatography-tandem mass spectrometry.

MAIN OUTCOME MEASURES

We evaluated the hydrolysis rate of E(2) fatty acyl esters as well as the esterification rate of E(2); we also related tissue concentrations of E(2) and E(2) esters to serum estrogen concentrations.

RESULTS

Compared to esters of dehydroepiandrosterone and cholesterol, the hydrolysis of E(2) esters was much slower, whereas the esterification rate of E(2) was higher. The hydrolysis of E(2) esters in adipose tissue was reduced by 33-51% by inhibition of HSL. Estrogen concentration in sc adipose tissue was higher than in serum in both pre- and postmenopausal women.

CONCLUSIONS

E(2) fatty acyl esters in adipose tissue surrounding the mammary gland may act as a reservoir for conversion back to biologically active E(2). This is partly dependent on HSL activity.

Cannabinoids and atherosclerotic coronary heart disease

Marijuana is the most abused recreational drug in the United States. Cannabinoids, the active ingredients of marijuana, affect multiple organ systems in the human body. The pharmacologic effects of marijuana, based on stimulation of cannabinoid receptors CB1 and CB2, which are widely distributed in the cardiovascular system, have been well described. Activation of these receptors modulates the function of various cellular elements of the vessel wall, and may contribute to the pathogenesis of atherosclerosis. Clinically, there are reports linking marijuana smoking to the precipitation of angina and acute coronary syndromes. Recently, large published clinical trials with CB1 antagonist rimonabant did not show any significant benefit of this agent in preventing progression of atherosclerosis. In light of these findings and emerging data on multiple pathways linking cannabinoids to atherosclerosis, we discuss the literature on the role of cannabinoids in the pathophysiology of atherosclerosis. We also propose a marijuana paradox, which implies that inhalation of marijuana may be linked to precipitation of acute coronary syndromes, but modulation of the endocannabinoid system by a noninhalation route may have a salutary effect on the development of atherosclerosis.