Correlates and reference limits of plasma gamma-glutamyltransferase fractions from the Framingham Heart Study

Background: We assessed GGT fractions correlates and their reference values in the Offspring Cohort of the Framingham Heart Study. Methods: Correlates of GGT fractions were assessed by multivariable regression analysis in 3203 individuals [47% men, mean age (SD): 59 (10) years]. GGT fractions reference values were established by empirical quantile analysis in a reference group of 432 healthy subjects [45% men, 57 (10) years]. Results: Fractional GGT levels were higher in men than in women (P<0.0001). In both sexes, fractions were associated with: triglycerides were associated with b-GGT, alcohol consumption with m-, s- and f-GGT. C-reactive protein with m- and s-GGT, while plasminogen activator inhibitor-1 with b- and f-GGT. Body mass index, blood pressure, glucose and triglycerides correlated with b- and f-GGT. In comparison with the reference group [b-GGT/s-GGT median (Q1-Q3): 0.51 (0.35-0.79) U/L], subjects affected by cardiovascular disease or diabetes showed no change of b/s ratio [0.52 (0.34-0.79) U/L, 0.57 (0.40-0.83) U/L, respectively]. The b/s ratio was higher in presence of metabolic syndrome [0.61 (0.42-0.87) U/L, P<0.0001], while lower in heavy alcohol consumers [0.41 (0.28-0.64) U/L, P<0.0001]. Conclusions: Metabolic and cardiovascular risk markers are important correlates of GGT fractions, in particular of b-GGT.