Treatment of primary mixed hyperlipidemia with etophylline clofibrate: effects on lipoprotein-modifying enzymes, postprandial lipoprotein metabolism, and lipoprotein distribution and composition

Lipid lowering therapy in type 2 diabetes

The primary defect underlying abnormalities in lipoprotein transport in type 2 diabetes is insulin resistance, which leads to increased triglycerides in the fasting and postprandial states, preponderance of small, dense LDL and low concentrations of dysfunctional HDL. Concentrations of LDL-cholesterol (LDL-C) are most often not remarkably abnormal. Based on this lipoprotein profile, it seems somewhat counterintuitive to prioritize LDL-C lowering in type 2 diabetes. Nevertheless, ≈20 years of statins trials in >18,000 diabetic patients have unequivocally established this priority. Patients with type 2 diabetes without manifest atherosclerosis should reach an LDL-C goal <100 mg/dl or a Non-HDLcholesterol (NHDL-C) goal <130 mg/dl. If their baseline LDL-C is already between 70 and 100 mg/dl LDL-C should be lowered by 30 to 40%. Thus, the majority of these patients can be managed successfully with monotherapy using standard-intensity statins (e.g. simvastatin 40 mg/d). Patients with type 2 diabetes with manifest CHD should reach an LDL-C goal <70 mg/dl or an NHDL-C goal <100 mg/dl. A sizable fraction of these patients will require high-intensity statins (e.g. atorvastatin 80 mg/d or rosuvastatin 20-40 mg/d). If LDL-C goals are still not reached or high-intensity statins are not tolerated, combination of statins with ezetimibe is advisable. In patients with persistent pronounced dyslipidemic features, i.e. high TG/low HDL-C despite maximal lifestyle intervention and optimized statin dosage, pioglitazone should be incorporated in the antidiabetic management and combinations of statins with either niacin or fenofibrate should be considered. However, it has to be recognized that evidence supporting HDL-raising therapy is currently still much weaker than evidence supporting LDL lowering with statins.

Effect of three consecutive meals on the physicochemical properties of HDL and LDL in individuals with the metabolic syndrome and patients with type 2 diabetes

BACKGROUND/OBJECTIVES

Postprandial hyperlipidemia, which is exaggerated and prolonged in insulin-resistant individuals, has been associated with cardiovascular disease. The objective of this study was to investigate whether and how the composition, size and function of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles are affected in the postprandial state among males with the metabolic syndrome (MetS) or type 2 diabetes (T2DM), compared with controls.

SUBJECTS/METHODS

A total of 14 males with T2DM, 14 with the MetS and 14 age-matched controls were given three standardized high-fat mixed meals (900 kcal; 50-g fat, 75-g carbohydrate and 35-g protein) as breakfast, lunch and dinner. Blood sampling was performed just before each meal, and 4 and 8 h after the last meal. HDL and LDL were isolated by ultracentrifugation and analyzed for their composition, particle diameter and functional properties.

RESULTS

Postprandial triglycerides levels in plasma, HDL and LDL particles increased significantly in all groups (P<0.01). Compared with the control subjects, patients with T2DM had smaller LDL particles, and in agreement, a lower cholesterol-to-protein content in both fasting and postprandial samples. A prolonged increase in susceptibility of LDL to oxidation was found in all subjects, but was most evident in T2DM. The postprandial effect on LDL oxidation was associated with an increase in LDL triglyceride (r=0.29, P<0.05). In T2DM the anti-oxidative capacity of HDL trended to impairment after the third meal.

CONCLUSIONS

Postprandial increases in triglycerides, especially in T2DM, are accompanied by pro-atherosclerotic functional changes in HDL and LDL particles.

Therapeutic effects of fibrates in postprandial lipemia

Hypertriglyceridemia is observed in many metabolic diseases such as the metabolic syndrome, diabetes mellitus, or mixed dyslipidemia frequently leading to premature coronary heart disease (CHD). Additionally, several studies have shown that postprandial hypertriglyceridemia is pronounced in patients with CHD, metabolic syndrome, hypertension, and other pathologic conditions. The triglyceride-rich lipoprotein remnants accumulating in the postprandial state seem to be involved in atherogenesis and in events leading to thrombosis. Since abnormal postprandial lipemia is associated with pathologic conditions, its treatment is of clinical importance.Fibrates are of significant help in managing hypertriglyceridemia. This review summarizes the effect of fibric acid derivatives on postprandial lipemia. Fibrates decrease the production of and enhance the catabolism of triglyceride-rich lipoproteins through the activation of peroxisome proliferator-activated receptor-alpha. Results of clinical studies with fibrates have confirmed their action in decreasing postprandial triglyceride levels by increasing lipoprotein lipase activity, decreasing apolipoprotein CIII production, and by increasing fatty acid oxidation in the liver.It is concluded that fibrates are effective agents in lowering the postprandial increase in remnant lipoprotein particles and retinyl palmitate. Furthermore, fibrates can also affect the postprandial lipid profile by increasing hepatic lipase levels and in some cases, by reducing cholesterol ester transfer protein activity. The main target of fibrate therapy is to improve fasting hypertriglyceridemia, which is an essential component associated with improving postprandial lipemia. Fibrates are well tolerated by patients and adverse effects have been reported rarely after their administration.

Enantiomeric separation of some demethylated analogues of clofibric acid by capillary zone electrophoresis and nano-liquid chromatography

The enantiomeric separation of some demethylated analogues of clofibric acid, namely 2-(6-chloro-benzothiazol-2-ylsulfanyl)-, 2-(6-methoxy-benzothiazol-2-ylsulfanyl)-, 2-(quinolin-2-yloxy)-, 2-(6-chloro-quinolin-2-yloxy)-, 2-(7-chloro-quinolin-4-yloxy)-propionic acid (compounds A-E, respectively), has been studied by CZE and nano-LC using for the first technique two beta-CD derivatives and vancomycin added to the BGE and vancomycin-modified silica particles for the second one, with the aim to find the optimum experimental conditions for the baseline resolution. The type and the concentration of the chiral selector added to the BGE, the buffer pH, the type of organic modifier and its concentration, the capillary temperature and the applied voltage played a very important role in the enantioresolution of the analysed compounds. The use of 6-monodeoxy-6-monoamino-beta-CD allowed to achieve baseline resolution of four of five clofibric acid derivatives in less than 10 min while heptakis-(2,3,6-tri-O-methyl)-beta-CD partially resolved the same compounds in their enantiomers. Employing vancomycin as the chiral selector in CZE, the counter-current partial filling method was chosen achieving baseline resolution of four analytes. All the studied compounds were enantioresolved employing a capillary column packed with vancomycin stationary phase by nano-LC, and the resolution was strongly influenced by the concentration of the organic modifier and by the pH of the mobile phase. The best results were achieved at pH 4.5 in presence of 60% of methanol (MeOH). However, longer analysis times were observed in the experiments carried out by nano-LC.

Postprandial lipemia--effect of lipid-lowering drugs

Exaggerated postprandial hyperlipidemia has been associated with cardiovascular disease. The mechanisms underlying this association are likely to depend on a multitude of effects. Potentially atherogenic remnants of triglyceride-rich lipoproteins (TRL) accumulate in the postprandial state. In addition, TRL may promote the formation of small dense LDL. There are some indications that the postprandial period is a hypercoagulable state and endothelial function seems to be hampered after acute fat intake. Conventional lipid lowering drugs such as statins and fibrates have the potency of reducing postprandial hyperlipidemia, but the fibrates seem to be more effective in this respect. There is a complete lack of prospective studies linking inefficient postprandial lipid metabolism with clinical endpoints and there is also a need to include investigations of postprandial lipid metabolism in the evaluation of novel drugs affecting lipid metabolism and insulin resistance.

Effects of etofibrate upon the metabolism of chylomicron-like emulsions in patients with coronary artery disease

Slow chylomicron intravascular catabolism has been associated with coronary artery disease and screening for drugs that can speed-up this process can be important. In this study, the effects of etofibrate upon chylomicron metabolism was tested by determination of the plasma kinetics of a chylomicron-like emulsion model in 12 patients with coronary artery disease, aged 59+/-11 years, (total cholesterol: 240+/-41 mg/dl; triglycerides: 188+/-42 mg/dl) submitted to a randomized, crossover, double-blind, placebo-controlled study with administration of 1 g per day etofibrate or placebo for 1-month. A 1-month washout period was inserted between the treatment periods. Patients were intravenously injected a chylomicron-like emulsion doubly labeled with 14C-cholesteryl oleate and 3H-triolein at baseline and after treatments. After etofibrate treatment, there was decrease of total cholesterol and triglyceride plasma levels and a trend to increase high-density lipoprotein cholesterol plasma levels. Etofibrate elicited 62% enhancement of post-heparin lipolytic activity and 100% increase of 3H-triglyceride fractional clearance rate compared with placebo treatment. 14C-cholesterol ester fractional clearance rate was 260% greater after etofibrate than after placebo. Therefore, a potent effect of etofibrate on both chylomicron lipolysis and remnant removal was achieved, indicating that this drug can be used to improve this metabolism in future prospective studies.

Effects of chronic di(2-ethylhexyl) phthalate intake on the secretion and removal rate of triglyceride-rich lipoproteins in rats

This work intends to characterize the nature of the plasma triglyceride level decrease in male Wistar rats fed with diets supplemented with 2% (w/w) di(2-ethylhexyl) phthalate (DEHP), a packaged-food chemical contaminant. After being fed for 21 days, the animals were assessed to determine plasma and liver lipids or to quantify the in vivo hepatic secretion and in vitro plasma removal of triglyceride-rich lipoproteins. The liver cholesterol and triglyceride contents in DEHP-fed rats were closely similar to those found in controls, co-existing with a decrease in plasma cholesterol (19%), phospholipid (14%) and triglyceride (36%) levels. The decrease of the plasma triglyceride pool size was not associated with a reduction in hepatic secretion of triglyceride. The total triglyceride lipase activity rose (32%) due to a remarkable increase (100%) of the extrahepatic lipoprotein lipase activity. We can conclude that extrahepatic lipoprotein lipase activity accounts for the hypotriglyceridaemic effect of DEHP through an increase of triglyceride removal rate.