Cholesterol metabolism in familial hypertriglyceridemia: effects of obesity versus triglyceride level

Treatment of lipid disorders in obesity

Obesity is the most common cause of secondary hyperlipidemia. Atherogenic dyslipidemia refers to elevated triglycerides, low HDL-cholesterol and small dense LDL associated with visceral obesity and metabolic syndrome. Obesity may also be associated with isolated low HDL-cholesterol or high triglycerides and postprandial hyperlipidemia. While some obese patients have high LDL cholesterol concentrations, obesity has a more pronounced effect on other atherogenic lipids and lipoproteins. Obesity may aggravate familial lipid disorders. Lipid disorders in obesity are responsive to weight loss, pharmacotherapy and weight loss surgery. Statins are the lipid-lowering drug of choice, together with lifestyle change. Hard clinical end point data to support combinations of statins with other drugs is lacking. After weight loss surgery, the absolute risk of cardiovascular disease should be reassessed, but tools to facilitate risk assessment need to be developed.

Fish oil increases bile acid synthesis in male patients with hypertriglyceridemia

Fibrates are drugs of choice in patients with hypertriglyceridemia (HTG), but may increase the risk for gallstones by decreasing bile acid synthesis. Fish oil might be a therapeutic alternative, but its effect on bile acid metabolism in humans is unknown. We compared the effects of triglyceride-lowering therapy by fish oil or bezafibrate on cholesterol synthesis and bile acid metabolism in HTG. Cholesterol synthesis, bile acid pool sizes, and synthesis rates were compared between 9 male HTG patients and 10 normolipidemic controls matched for age, sex, and BMI. Effects of bezafibrate or fish oil were studied only in HTG patients in a randomized crossover trial. Patients had 14-fold higher serum triglyceride concentrations and greater cholesterol synthesis, as indicated by a 107% higher ratio of serum lathosterol to cholesterol (P < 0.01) than controls. The groups did not differ in bile acid metabolism. Both bezafibrate and fish oil reduced serum TG concentration (-68 and -51% vs. baseline, respectively). Compared with baseline, bezafibrate therapy was associated with reduced cholesterol synthesis (-25%, P = 0.009) without changes in bile acid synthesis rate and pool size. In contrast, fish oil increased bile acid synthesis (+31% vs. baseline, P = 0.07 and +53% vs. bezafibrate, P = 0.02) and altered bile acid distribution, as reflected by an increased ratio of the cholic acid (CA) synthesis rate to the chenodeoxycholic acid (CDCA) synthesis rate (+35% vs baseline, P = 0.05 and + 32% vs bezafibrate, P = 0.07) without effects on bile acid pool size or cholesterol synthesis. In conclusion, cholesterol synthesis is greater in HTG patients than in controls, whereas bile acid synthesis does not differ. Bezafibrate and fish oil have similar triglyceride-lowering capacities, but distinct effects on cholesterol synthesis. Bile acid synthesis is increased by fish oil, but not by bezafibrate therapy.

Comparative pharmacokinetics and pharmacodynamics of propranolol and atenolol in normolipaemic and hyperlipidaemic obese subjects

The lipophilic beta-adrenoreceptor antagonist propranolol and hydrophilic atenolol have been studied to define their pharmacokinetic and pharmacodynamic characteristics in obese patients. A total of 43 subjects were allocated into three study groups: (1) healthy, lean, normolipaemic volunteers, (2) obese normolipaemic subjects, and (3) obese patients with lipid disorders. A crossover method with an interval of 2 weeks was applied for oral 80 mg propranolol and oral 100 mg atenolol administration. Heart rate as well as systolic and diastolic blood pressure were recorded during 24 h. At each time-point of measurement blood serum concentration of propranolol and atenolol were evaluated. Pharmacokinetic parameters of the drugs were calculated using a one-compartment open model for extravascular administration. There were no statistically significant differences in blood serum concentrations of propranolol between the studied groups. The concentrations of atenolol were significantly lower in both normolipaemic and hyperlipidaemic obese subjects. A trend towards increase in Vd/F and Cl/F of propranolol in obese patients with hyperlipidaemia were noted. In the case of water-soluble atenolol, the AUC, C(max), Cl/(F x BW) were significantly lower in obese hyperlipidaemic and normolipaemic patients in comparison with lean subjects. The pharmacodynamic effects of propranolol and atenolol in obese and lean subjects were of similar magnitude. The observed differences between obese and non-obese persons were clinically not relevant.