Gamma-glutamyltransferase, insulin resistance and cardiometabolic risk profile in a middle-aged African population

Background Mechanisms linking liver functions with cardiometabolic risk may involve insulin resistance (IR) and non-alcoholic fatty liver disease. We assessed the associations of gamma-glutamyltransferase (GGT) levels with IR and metabolic syndrome (MetS) in an adult South African urban cohort. Methods 1198 participants aged >15 years (297 men) were drawn from the Bellville-South suburb (Cape Town). The homeostatic model assessment of insulin (HOMA-IR), -cells function (HOMA-B%), fasting insulin resistance index (FIRI) and the quantitative insulin-sensitivity check index (QUICKI) were calculated, and MetS defined according to the Join Interim Statement 2009 criteria. Associations of GGT levels with covariates were assessed on a continuous scale and across sex-specific quarters of GGT, with adjustment for confounders via generalized linear and logistic regressions. Results Indicators of IR (HOMA-IR, FIRI and fasting insulin) increased, whereas those for insulin sensitivity (Sib and QUICKI) diminished significantly linearly and across increasing GGT quarters. In multivariable-adjusted models, adjustment for sex, age, BMI, cigarette smoking and alcohol intake yielded the strongest, significant associations between GGT and all markers of IR/IS and glycemia excluding glucose insulin ratio. In a similar level of adjustments, with/without further adjustment for markers of IR/insulin sensitivity, the prevalence of MetS significantly increased across quarters of GGT. Conclusions GGT levels were independently associated with insulin sensitivity and MetS in this population. Unaccounted, chronic elevation of GGT may therefore be a cue to screen and monitor individuals for MetS and diabetes, and may warrant consideration as an indicator of high risk for the development of these metabolic disorders.