Gemfibrozil treatment potentiates oxidative resistance of high-density lipoprotein in hypertriglyceridemic patients

BACKGROUND

Studies suggest that both oxidized low and high density lipoprotein (LDL and HDL) play a role in the pathogenesis of atherosclerosis. Gemfibrozil is widely used and is reported to increase cholesterol of LDL and HDL in hypertriglyceridemic patients. The aim of this study was to investigate the effect of gemfibrozil treatment on the oxidative status of lipoprotein particles in Fredrickson phenotype IV hypertriglyceridemic patients.

METHODS

Twenty-two patients, aged 38-64 years, with fasting plasma triglyceride concentrations between 2.90 and 8.97 mmol L(-1), were recruited and were given gemfibrozil 300 mg three times daily for 12 weeks. Venous blood samples were collected before gemfibrozil treatment, after 4, 8, or 12 weeks of treatment, and 4 weeks after termination of treatment, and used to analyse the plasma lipid profile, isolate lipoproteins, and analyse the chemical composition and in vitro oxidation of lipoprotein particles.

RESULTS

Gemfibrozil treatment resulted in a decrease in plasma total triglyceride levels and the triglyceride content of all lipoproteins. Plasma total cholesterol levels were decreased as a result of a decrease in very low density lipoprotein (VLDL) cholesterol levels. A slight increase in LDL cholesterol levels was observed, whereas the thiobarbituric acid-reactive substances (TBARS) of LDL were decreased and the lag and peak time of LDL to oxidation were unchanged and maximal diene production was decreased. Plasma HDL cholesterol levels, the surface-to-core ratio of HDL particles, and the resistance of HDL to oxidation were increased.

CONCLUSION

The decreased TBARS and diene production of LDL, increased HDL cholesterol levels, and increased resistance of HDL to oxidation may, in part, explain why gemfibrozil treatment was found to be generally beneficial in terms of protection against coronary heart disease.

Effect of gemfibrozil on the composition and oxidation properties of very-low-density lipoprotein and high-density lipoprotein in patients with hypertriglyceridemia

Recent studies suggest that both oxidized very-low-density lipoprotein (VLDL) and oxidized high-density lipoprotein (HDL) may play a role in the pathogenesis of atherosclerosis. Gemfibrozil is widely used and is reported to decrease VLDL levels and increase HDL levels. The aim of this study was to investigate the effect of gemfibrozil on the chemical composition and oxidative susceptibility of VLDL and HDL and their relationship with atherosclerosis. Twenty patients with hypertriglyceridemia were treated with 300 mg gemfibrozil, 3 times daily, for 12 weeks. Venous blood samples were collected before treatment, at the end of treatment, and 4 weeks after the end of treatment. Gemfibrozil effectively lowered concentrations of plasma lipid, apolipoprotein (apo) B, and apo E. The lipid and protein content of VLDL were also decreased, but not by the same extent. The surface-to-core ratio and apo E/apo B ratio of VLDL particles were increased after gemfibrozil treatment. HDL(2) cholesteryl ester and HDL(3) apo A-II content were also increased. Gemfibrozil treatment lowered levels of lipid peroxides in both VLDL and HDL particles. The susceptibility of VLDL to oxidation was unchanged, whereas maximal peroxide production was decreased. The oxidative susceptibility of both HDL(2) and HDL(3) decreased with gemfibrozil treatment. These results indicate that after gemfibrozil treatment, VLDL and HDL particles in patients with hypertriglyceridemia are less atherogenic, which may explain why gemfibrozil treatment is beneficial in terms of coronary heart disease in hypertriglyceridemia.

The seventh copy of IS1 in Escherichia coli W3110 belongs to the IS1 A (IS1E) type which is the only IS1 type that transposes from chromosome to plasmids

In the Escherichia coli K-12 chromosome, six copies of IS1 (IS1A - IS1F) have been identified and characterized. According to their nucleotide (nt) sequences, the six IS1 copies can be classified into four types, IS1A(IS1E), IS1B(IS1C), IS1D and IS1F type. Zuber and Schumann (1993) identified the seventh IS1 copy at 49.6 minutes on the E. coli W3110 genetic map. Unfortunately, only the end 21-bp sequence as well as the neighboring 120-bp E. coli sequence were reported. We therefore designed two oligonucleotide primers to specifically amplify the seventh IS1 copy by PCR. One primer is homologous to the first sixteen bases of the IRL sequence of IS1A(IS1E), IS1B(IS1C) and IS1D. The other primer is complementary to the eighteen bases of E. coli sequence adjacent to IRR of the seventh IS1 copy. An 800-bp PCR fragment was obtained and its nt sequence determined, revealing an identical nucleotide sequence to that of IS1A(IS1E). A plasmid system was then used to isolate insertion mutations caused by insertions of the chromosomal insertion sequences. Of the 142 plasmid insertion mutants isolated, thirty-eight were insertions of chromosomal IS5, ten were IS30, and ninety-four were IS1. Detailed restriction mapping indicates that all ninety-four plasmid IS1 insertions were insertions of IS1 of the IS1A(IS1E) type.