Cholesterol ester transfer protein (CETP), postprandial lipemia and hypolipidemic drugs

Cholesterol ester transfer protein (CETP) plays a significant role in high density lipoprotein (HDL) metabolism and reverse cholesterol transport (RCT). A reduction in CETP activity leads to an increase in HDL-cholesterol levels. However, the relationship between reduced CETP function and atherosclerosis is complex and confusing. In the hypertriglyceridemic state, CETP is highly expressed and RCT leads to the formation of small dense low density lipoprotein (LDL) and small dense HDL, both of which are involved in the progression of atherosclerosis. Significant associations of the B1B1 genotype with higher plasma CETP concentration and/or CETP activity and lower HDL cholesterol were reported in several, but not all, studies. The magnitude of postprandial lipemia is also associated with plasma CETP concentration and lipoprotein content and size. Several conditions such as metabolic syndrome, hypertension, insulin resistance, obesity and familial hypercholesterolaemia are characterized by a more pronounced postprandial hypertriglyceridemia and delayed TG clearance than normal states. Thus, CETP is considered as a candidate target for drug therapy. A number of synthetic CETP inhibitors (CGS25159 and JTT-705) were evaluated in animals with satisfactory results. In humans, two CETP inhibitors were evaluated, JTT-705 and torcetrapib, leading to HDL increase. However, torcetrapib administration was associated with an increase in blood pressure and other "off-target" effects. It is also not clear whether the HDL produced during treatment with torcetrapib is bioactive (i.e. an "on target" undesirable action). In the current review, CETP function regarding lipid metabolism (in fasting and fed states) from human and animal studies as well as the current knowledge on CETP inhibitors are discussed. We also discuss gender influence on the action of hypolipidemic drugs and their effect on CETP mass and activity, as well as on the lipid profile.

Tangier Disease Four Decades of Research: A Reflection of the Importance of HDL

Reduced circulating levels of high density lipoprotein cholesterol (HDL-C) are a frequent lipoprotein disorder in coronary heart disease patients and can be caused by either genetic and/or environmental factors (sedentary lifestyle, diabetes mellitus, smoking, obesity or a diet enriched in carbohydrates). Extremely low serum HDL-C levels occur in patients with Tangier disease (TD), which is caused by mutations in the adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1). Clinical manifestations are related to the storage of cholesteryl esters in reticuloendothelial tissues and to peripheral neuropathy. This review focuses on the genetic and lipid abnormalities of TD, the consequence of these on clinical outcome and the possible treatment options. These abnormalities reflect the importance of HDL in the pathogenesis of vascular disease.

Heterozygote men with familial hypercholesterolaemia may have an abnormal triglyceride response post-prandially. Evidence for another predictor of vascular risk in familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is associated with premature coronary heart disease (CHD). Post-prandial hypertriglyceridaemia has also been associated with cardiovascular disease. Thus, an abnormal post-prandial triglyceride (TG) clearance may contribute to the heterogeneity in the risk of CHD in heterozygous (h) FH. Therefore, we investigated the response of TG levels to a fatty meal in men with hFH. We studied 26 Greek men divided into two groups: the hFH group of 14 men, mean age 39 (SD = 11) years and the control group of 12 healthy men, mean age 43 (50:5) years. An increased TG response to the fatty meal was defined as a post-prandial TG concentration (at 4, 6 or 8 h) greater than the highest TG concentration in any hour in any control individual. All hFH patients had normal baseline fasting TG levels. However, seven hFH men showed an abnormal TG response after the fatty meal; these patients had higher baseline fasting TG levels than others [1.5 (0.2) vs. 1.0 (0.4) mmol/l, p = 0.005]. The hFH men constituted a heterogeneous group regarding their TG response to the fatty meal compared with healthy men because 50% with higher, but nevertheless 'normal' basal TG levels, had an abnormal post-prandial TG response. The reduced activity of low-density lipoprotein receptors in hFH together with other defects in TG handling may explain the abnormal rise of TG levels post-prandially.