HDL steady state levels are not affected, but HDL apoA-I turnover is enhanced by Lifibrol in patients with hypercholesterolemia and mixed hyperlipidemia

Lifibrol (4-(4′-tert-butylphenyl)-1-(4′carboxyphenoxy)-2-butanol) is a new hypocholesterolemic drug effectively reducing total cholesterol, LDL cholesterol, and apolipoprotein (apo) B in experimental animals and in humans. In contrast to fibrates and HMG-CoA reductase inhibitors the cholesterol and triglyceride lowering effect of Lifibrol is not accompanied by increases in HDL cholesterol and apoA-I levels. We examined the impact of Lifibrol on the metabolism of HDL apoA-I in patients with hyperlipoproteinemia, using endogenous labeling with stable isotopes. Kinetic studies were performed in five male hypercholesterolemic individuals (type IIa), before and on treatment with 450 mg of Lifibrol daily for 4 weeks and in five male individuals suffering from mixed hyperlipidemia (type IIb), before and on therapy, for 12 weeks. Lifibrol reduced total cholesterol by 14% ( P=0.02) and LDL cholesterol by 16% ( P=0.014) in all patients, and decreased triglycerides by 34% in type IIb patients. During Lifibrol therapy, HDL cholesterol and ApoA-I concentrations did not change. Tracer kinetics revealed that the fractional catabolic rate (FCR) of HDL apoA-I increased by 22% ( P=0.013). This increase in the apoA-I FCR was accompanied by a 23% increase in HDL apoA-I production rate ( P=0.006). We conclude that Lifibrol, although not changing HDL steady state concentrations, enhances the turnover of apoA-I containing HDL particles.