Lipoprotein composition and oxidative modification during therapy with gemfibrozil and lovastatin in patients with combined hyperlipidaemia.

AIM

To evaluate the resistance to oxidation of human lipoproteins after hypolipidaemic therapy.

METHODS

VLDL and LDL samples were obtained from patients with Familial Combined Hyperlipidaemia included in a randomized, double-blind, cross-over study, with 8 weeks of active treatment (gemfibrozil, 600 mg twice daily, or lovastatin, 40 mg daily) and a 4-week wash-out period. Oxidation related analytes after Cu-induced oxidation of VLDL and LDL have been investigated. Further, in order to relate possible changes in oxidative behaviour to lipoprotein composition, the proportion of the lipid species transported by lipoproteins (triglycerides, phospholipids, and cholesteryl esters), the molar composition of fatty acids for each lipoprotein lipid, and the content of antioxidant vitamins in plasma (vitamin C) and lipoproteins (vitamin E) have been studied.

RESULTS

Both drugs reduced the plasma concentration of apo-B lipoproteins (-23% gemfibrozil, -26% lovastatin), but whereas lovastatin affected mainly LDL-cholesterol (-30%), gemfibrozil reduced triglycerides (-49%) and VLDL-cholesterol (-48%). Lovastatin treatment had no effect on the lipid and protein composition, the fatty acid profile, or the vitamin E content of either VLDL or LDL; likewise, lipoprotein oxidation markers (Cu-induced conjugated dienes, thiobarbituric acid reactive substances formation, and lysine residues) were similar before and after lovastatin treatment. Gemfibrozil therapy also had no effect on lipoprotein oxidation; nevertheless, it consistently: a) decreased the proportion of LDL-triglycerides (-32%), and b) increased the proportion (molar%) of 18:3 n-6 in VLDL triglycerides (+140%), phospholipids (+363%) and cholesteryl esters (+53%).

CONCLUSIONS

Based on these results, lovastatin and gemfibrozil do not adversely affect lipoprotein oxidation in patients with mixed dyslipidaemia. In the case of gemfibrozil, this occurs in spite of an increased proportion of some polyunsaturated fatty acids in VLDL. In the context of a fixed dietary intake, such modifications suggest that the drug influences liver enzyme activities involved in fatty acid chain synthesis (elongases and desaturases).