Normal serum alanine aminotransferase activity in uncomplicated obesity.

Aim: To evaluate serum alanine aminotransferase (ALT) activity in a well-characterized group of uncomplicated obese subjects and its correlation with insulin resistance, plasma adiponectin, and leptin concentrations.

Methods: One hundred and five uncomplicated obese subjects (87 women, 18 men, age 34.3+/-9.6 years, BMI 39.9+/-8.3 kg/m(2)) were studied. Serum ALT activity was evaluated. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp (M index) and fasting insulin. Plasma leptin and adiponectin levels were also measured.

Results: Serum ALT concentration in the whole group of uncomplicated obese subjects was 17.73+/-6.33 U/L with none of the subjects presenting ALT levels greater than 43 U/L and only 9 (11%) women and 3 (19%) men showed ALT levels >19 and >30 U/L for women and men, respectively. No significant difference was detected in serum ALT levels between severe obese subjects (BMI >40 kg/m(2)) and those with BMI <40 kg/m(2) (18.63+/-6.25 vs 17.26+/-6.02 U/L). ALT was significantly correlated with fasting insulin (r = 0.485, P = 0.02) and triglycerides (r = 0.358, P = 0.03).

Conclusion: Serum ALT activity is practically normal in uncomplicated obese subjects, independently of their obesity degree. These findings suggest the role of obesity-related comorbidities and not of BMI as main risk factors for elevated ALT levels in obese subjects.