Serum gamma-glutamyltransferase, oxidized LDL and mortality in the elderly

Background: Serum gamma-glutamyltransferase (GGT) is a liver enzyme involved in the metabolism of glutathione (GSH), a major antioxidant in humans. GGT is a risk factor for mortality in young and middle-aged individuals but this association has been poorly investigated in the elderly. Methods: We studied the relationship between GGT and all-cause mortality and tested whether oxidized low-density lipoproteins (oxLDL) modify this association in a cohort of 1038 elderly individuals. Results: During the observation time (median 9 years), 401 individuals died. In a Cox regression model adjusting for potential confounders, GGT was an independent risk factor for all-cause mortality [HR (20U/L increase in serum GGT): 1.11, 95% CI 1.02-1.21, P = 0.02]. Furthermore, increasing levels of oxLDL amplified the risk excess for all-cause mortality associated with GGT (P for the effect modification = 0.003). Conclusions: In the elderly, serum GGT is an independent risk factor for all-cause mortality and circulating oxLDL amplify the magnitude of this association.