Decreased oxidation susceptibility of plasma low density lipoproteins in patients with Gilbert's syndrome

Abstract

The association of hyperbilirubinemia in Gilbert's syndrome (GS) with a decrease in prevalence of coronary artery disease is a well-known phenomenon. In this study, the state of low-density lipoprotein (LDL) oxidation which has been postulated to be a significant determinant at the etiopathogenesis of atherosclerotic disorders was investigated among individuals with GS. For this purpose, serum cholesterol, LDL cholesterol, high-density lipoprotein cholesterol, triglycerides, uric acid, apolipoprotein A and B, bilirubins, thiobarbituric acid-reactive substances, and the sensitivity of LDL oxidation levels, as well as serum alanine aminotransferase, aspartate aminotranserfase, gamma glutamyl transferase, and alkaline phosphatase activities, were determined in 17 patients with Gilbert's syndrome and 15 healthy adults. There was no significant difference between the groups except the indirect bilirubin parameter (P < 0.001). In comparison with the healthy individuals, LDL oxidation levels between 75 and 120 min were significantly lower (P < 0.005) along with prolonged lag-phase in GS patients, indicating a delay in oxidation susceptibility. It is suggested that the chronic hyperbilirubinemia leading to a lag-phase prolongation in LDL oxidation and a decrease in LDL oxidation may be reason for the low percentage of coronary artery disease.