No abstract

A delayed clearance of postprandial lipoproteins from the plasma may play a role in the etiology of premature coronary atherosclerosis. To address this hypothesis, we studied chylomicron (remnant) metabolism in two groups of 20 selected normolipidemic men aged 35-65 years, a group of coronary artery disease (CAD) patients, and a matched control group with documented minimal coronary atherosclerosis. Subjects received an oral fat load supplemented with cholesterol and retinyl palmitate. Plasma samples obtained during the next 24-hour period were analyzed for total as well as d less than 1.019 g/ml and d greater than 1.019 g/ml triacylglycerol, cholesterol, and retinyl ester concentrations. Although both groups of patients responded identically in terms of the appearance of gut-derived lipids in the plasma, CAD patients showed a marked delay in the clearance of retinyl esters as well as in the normalization of plasma triacylglycerol concentrations. Postheparin plasma hepatic lipase activity was significantly lower in the CAD group. Apolipoprotein E phenotype measurements did not reveal marked differences in frequency between both groups. The frequency distribution was not unusual in comparison with the normal Dutch population. The magnitude of the postprandial responses of triacylglycerol and retinyl esters was correlated positively with the fasting levels of plasma triacylglycerol and negatively with high density lipoprotein subfraction 2 cholesterol concentrations. These data indicate that the clearance of postprandial lipoproteins in normolipidemic CAD patients as selected in the present study is delayed as compared with that of controls without coronary atherosclerosis and suggest that postprandial lipoproteins may play a role in the etiology of their disease.

Despite widespread use of statins to reduce low-density lipoprotein cholesterol (LDL-C) and associated atherosclerotic cardiovascular risk, many patients do not achieve sufficient LDL-C lowering due to muscle-related side effects, indicating novel treatment strategies are required. Bempedoic acid (ETC-1002) is a small molecule intended to lower LDL-C in hypercholesterolemic patients, and has been previously shown to modulate both ATP-citrate lyase (ACL) and AMP-activated protein kinase (AMPK) activity in rodents. However, its mechanism for LDL-C lowering, efficacy in models of atherosclerosis and relevance in humans are unknown. Here we show that ETC-1002 is a prodrug that requires activation by very long-chain acyl-CoA synthetase-1 (ACSVL1) to modulate both targets, and that inhibition of ACL leads to LDL receptor upregulation, decreased LDL-C and attenuation of atherosclerosis, independently of AMPK. Furthermore, we demonstrate that the absence of ACSVL1 in skeletal muscle provides a mechanistic basis for ETC-1002 to potentially avoid the myotoxicity associated with statin therapy.

No abstract

Peroxisome proliferator-activated receptors (PPARs) control the transcription of genes involved in lipid metabolism. Activation of PPAR ␦ may have antiatherogenic effects through the increase of plasma HDL, theoretically promoting reverse cholesterol transport from peripheral tissues toward the liver for removal via bile and feces. Effects of PPAR ␦ activation by GW610742 were evaluated in wild-type and Abca1-deficient ( Abca1 ؊ / ؊ ) mice that lack HDL. Treatment with GW610742 resulted in an ‫ف‬ 50% increase of plasma HDL-cholesterol in wild-type mice, whereas plasma cholesterol levels remained extremely low in Abca1 ؊ / ؊ mice. Yet, biliary cholesterol secretion rates were similar in untreated wild-type and Abca1 ؊ / ؊ mice and unaltered upon treatment. Unexpectedly, PPAR ␦ activation led to enhanced fecal neutral sterol loss in both groups without any changes in intestinal Abca1 , Abcg5 , Abcg8 , and 3-hydroxy-3-methylglutaryl-coenzyme A reductase expression. Moreover, GW610742 treatment resulted in a 43% reduction of fractional cholesterol absorption in wild-type mice, coinciding with a significantly reduced expression of the cholesterol absorption protein NiemannPick C1-like 1 ( Npc1l1 ) in the intestine. PPAR ␦ activation is associated with increased plasma HDL and reduced intestinal cholesterol absorption efficiency that may be related to decreased intestinal Npc1l1 expression. Thus, PPAR ␦ is a promising target for drugs aimed to treat or prevent atherosclerosis. -van der Veen, J. N., J. K. Kruit, R. Havinga, J. Plasma levels of HDL-cholesterol are inversely related to the development of atherosclerosis (1). This protective effect has been attributed to a role of HDL in reverse cholesterol transport (RCT), defined as the flux of excess cholesterol from peripheral cells to nascent HDL particles followed by transport to the liver. The liver is able to secrete cholesterol into bile, either as free cholesterol or after conversion into bile salts, for removal via the feces. Stimulation of HDL-mediated cholesterol efflux is considered an attractive approach to diminish the development of atherosclerosis.ABCA1 is considered to be essential in RCT (2). ABCA1 is ubiquitously expressed and probably involved in the formation of pre ␤ -HDL particles and the efflux of cholesterol from peripheral tissues toward HDL (3). HDL is considered a major source for bile-destined cholesterol (4). However, we recently demonstrated that, despite the absence of HDL, hepatobiliary cholesterol flux and fecal sterol excretion are not affected in Abca1-deficient ( Abca1 Ϫ / Ϫ ) mice (5, 6). The ABCG5/ABCG8 heterodimer was recently shown to be of crucial importance for hepatobiliary cholesterol secretion and for transport of cholesterol from enterocytes back into the intestinal lumen, thereby promoting net cholesterol removal from the body (7,8).Several genes involved in the control of cholesterol meAbbreviations: Abca1 Ϫ / Ϫ , Abca1-deficient; FPLC, fast-protein liquid chromatography; Hmgr, 3-hydroxy-3-methylglutaryl-coenzyme...

Fractalkine/CX3C-chemokine ligand 1 is expressed as a membrane-spanning adhesion molecule that can be cleaved from the cell surface to produce a soluble chemoattractant. Within the vasculature, fractalkine is known to be generated by endothelial cells, but to date there are no reports describing its expression by smooth muscle cells (SMC). In this study we demonstrate that IFN-γ and TNF-α, but not IL-1β, cooperate synergistically to induce fractalkine mRNA and protein expression in cultured aortic SMC. We also report the release of functional, soluble fractalkine from the membranes of stimulated SMC. This release is inhibited by the zinc metalloproteinase inhibitor batimastat, resulting in the accumulation of membrane-associated fractalkine on the SMC surface. Therefore, an SMC-derived metalloproteinase activity is involved in fractalkine shedding. While soluble fractalkine present in SMC-conditioned medium is capable of inducing calcium transients in cells expressing the fractalkine receptor (CX3CR1), blocking experiments using neutralizing Abs reveal that it can be inactivated without affecting the chemotactic activity of SMC-conditioned media on monocytes. However, membrane-bound fractalkine plays a major role in promoting adhesion of monocytic cells to activated SMC. This fractalkine-mediated adhesion is further enhanced in the presence of batimastat, indicating that shedding of fractalkine from the cell surface down-regulates the adhesive properties of SMC. Hence, during vascular inflammation, the synergistic induction of fractalkine by IFN-γ and TNF-α together with its metalloproteinase-mediated cleavage may finely control the recruitment of monocytes to SMC within the blood vessel wall.

We describe here a classical molecular modeling exercise that was carried out to provide a basis for the design of novel antagonist ligands of the CCR2 receptor. Using a theoretical model of the CCR2 receptor, docking studies were carried out to define plausible binding modes for the various known antagonist ligands, including our own series of indole piperidine compounds. On the basis of these results, a number of site-directed mutations (SDM) were designed that were intended to verify the proposed docking models. From these it was clear that further refinements would be necessary in the model. This was aided by the publication of a crystal structure of bovine rhodopsin, and a new receptor model was built by homology to this structure. This latest model enabled us to define ligand-docking hypotheses that were in complete agreement with the results of the SDM experiments.

Kuipers. Differential effects of pharmacological liver X receptor activation on hepatic and peripheral insulin sensitivity in lean and ob/ob mice.