Abstract

Objective: To determine the relationship between plasma liver enzyme concentrations, insulin sensitivity and intra-abdominal fat (IAF) distribution.

Research Design and Methods: Plasma gamma-glutamyl transferase (GGT), aspartate transaminase (AST), alanine transaminase (ALT) levels, insulin sensitivity (S_I), IAF and subcutaneous fat (SCF) areas were measured on 177 non-diabetic subjects (75M/102, 31-75 years) with no history of liver disease. Based on BMI (< or ≥27.5 kg/m²) and S_I (< or ≥7.0x10^-5 min^-1 pM^-1) subjects were divided into lean insulin sensitive (LIS, n=53), lean insulin resistant (LIR, n=60) and obese insulin resistant (OIR, n=56) groups.

Results: All three liver enzymes were higher in men than women (p<0.0001 for each). In men, GGT levels were higher in insulin resistant than insulin sensitive subjects (p<0.01). In women, GGT levels were higher in the OIR vs. LIS (p<0.01) but no different in LIR. There was no difference in ALT and AST levels between LIS, LIR and OIR. GGT was associated with S_I (r=-0.26, p<0.0001), IAF (r=0.22, p<0.01), waist-hip ratio (WHR) (r=0.25, p=0.001), BMI (r=0.17, p<0.05), and SCF (r=0.16, p<0.05) after adjusting for age and gender. In men, only S_I (r=-0.29, p<0.05) remained independently correlated with GGT in multiple regression analysis. In women, IAF (r=0.29, p<0.01) and WHR (r=0.29, p<0.01) were independently associated with GGT, but S_I was not.

Conclusions: In non-diabetic men GGT levels, but not AST or ALT levels, are inversely related to insulin sensitivity independent of IAF. However in women, GGT is related to measures of central body fat rather than insulin sensitivity.