Objective: To explore the correlations of serum alanine aminotransferase (ALT), insulin resistance and pancreatic B-cell function.
Methods: A total of 351 first-degree relatives of type 2 diabetes mellitus received a standard oral glucose tolerance test (OGTT) at our outpatient clinic. All subjects were analyzed for the parameters of body mass index (BMI), waist-hip ratio, blood pressure (BP), serum lipids, ALT, aspartate aminotransferase (AST), plasma glucose (PG), true-insulin and proinsulin. Homeostasis model assessment (HOMA) was applied to assess the status of insulin resistance and pancreatic B-cell function. They were divided into 4 groups according to the quartiles of ALT: ALT1 group (< 12.9 U/L), ALT2 group (12.9 - 17.3 U/L), ALT3 group (17.4 - 24.2 U/L) and ALT4 group (≥ 24.2 U/L). The diagnosis of metabolic syndrome was made according to the definition of Chinese Diabetic Society.
Results: With the rising serum ALT levels (ALT4 vs ALT1), the levels of BMI [(26.3 ± 2.9) kg/m(2) vs (23.2 ± 3.7) kg/m(2), P < 0.01], HOMA-IR [1.93 (1.21 - 3.26) vs 1.06 (0.65 - 1.54), P < 0.01] and LnHOMA-beta (2.00 ± 0.32 vs 1.87 ± 0.28, P < 0.05) were elevated; BP, serum lipids, PG, true-insulin and proinsulin also increased (P < 0.05 or P < 0.01). The levels of serum ALT [23.3 (16.3 - 37.6) vs 14.3 (10.3 - 18.5) U/L, P < 0.01] and AST [21.5 (18.3 - 32.8) U/L vs 17.9 (15.5 - 22.1) U/L, P < 0.01] increased with the rising number of metabolic disorders (0 vs 3 - 4 metabolic disorders). After adjustments for gender, age, BMI and waist-hip ratio, serum ALT were still positively correlated with BP, serum lipids, PG, fasting true-insulin, 2 h proinsulin, 2 h proinsulin/true-insulin, HOMA-IR and the numbers of metabolic disorder (r = 0.117 - 0.236, P < 0.05 or P < 0.01). After adjustments for gender, age, BMI, waist-hip ratio and HOMA-IR, the serum ALT level remained positively correlated with the numbers of metabolic disorders (r = 0.120, P < 0.05). Multiple stepwise regression analysis showed that triglyceride, HOMA-IR, total cholesterol and 2 h-proinsulin were the independent risk factors for the level of serum ALT (P < 0.05 or P < 0.01).
Conclusion: The elevated levels of serum ALT are significantly correlated with metabolic syndrome, insulin resistance and compensatory increases of pancreatic B-cell function. Independently of insulin resistance, the serum ALT level is correlated with metabolic syndrome.