The Relationships Between Serum Liver Enzyme Levels And Liver Fat Accumulation, Insulin Resistance, And Metabolic Disorders In Obese Adults

ObjectiveNonalcoholic fatty liver disease (NAFLD) is characterized by an increase in intrahepatic triglyceride contents (IHTC) accumulation. NAFLD is associated with insulin resistance and metabolic syndrome. Meanwhile, NAFLD is frequently accompanied with elevating liver enzymes(ALT, AST and GGT). This study aimed to determine the associations of serum liver enzyme levels with NAFLD and its related metabolic disorders in obese adults.Study design and methodsWe recruited1061subjects at age of40-65years with waist circumference of greater than90cm for men and85cm for women. Questionnaires were adopted to collect information on health status, medical history and life styles. Anthropometric parameters, blood biochemical indexes and abdominal ultrasonography were measured. Of those,475subjects were received auxiliary examinations including measurement of IHTC by1H-MRS, abdominal fat areas by CT and body fat mass by Dual Energy X-Ray Absorptiometry (DEXA).Results1. The association of serum liver enzyme levels with IHTCCompared to subjects without NAFLD, subjects with NAFLD had higher serum ALT, AST and GGT levels (all p<0.01).By dividing the distribution of IHTC into quartiles, serum ALT, AST and GGT levels at the highest quartile of IHTC were significantly elevated as compared with those in the lowest quartile (all p<0.01). Serum ALT, AST and GGT levels were positively correlated with IHTC (r=0.43,0.25and0.19, respectively, all p<0.01). Multivariate regression analysis demonstrated that serum ALT, but not AST or GGT was independently associated with IHTC (β=0.30±0.05, p<0.01). By logistic regression analysis the odds ratio for higher IHTC was increased by1.727times per1S.D increase in serum ALT level after adjusting for multiple confounding factors [OR (95%CI):2.727(1.693-4.392)]. However, this relationship could not be observed in serum AST or GGT levels. 2. The association of serum liver enzyme levels with metabolic disorders.By dividing the distribution of liver enzymes into quartiles, SBP, DBP, TG,2hPG and HOMA-IR were increased gradually with the increase of serum ALT, AST or GGT levels(all p<0.01). Serum HDL-C level were reduced gradually with increase of serum ALT or GGT levels (all p<0.01). TC and FBP progressively increased across the quartiles of serum ALT or GGT levels (all p<0.01). LDL-C only correlated with serum GGT level (p<0.01). By logistic regression analysis, the odds ratio for higher prevalence rate of MS were respectively increased by40.8%per1S.D increase in serum ALT level and58.9%per1S.D increase in serum GGT level after adjustment for multivariate metabolic factors (both p<0.01); Meanwhile, the odds ratio for higher insulin resistance were increased respectively by59.2%in serum ALT,34.9%in serum AST and49.7%in serum GGT (all p<0.01). Furthermore, the odds ratio for higher visceral fat area was increased by33.5%per1S.D increase in serum ALT level after adjusting for multiple confounding factors [OR (95%CI):1.335(1.016-1.755), p<0.05]. However, these relationships did not remain in serum AST or GGT levels.ConclusionsThe results demonstrated that serum ALT level was positively associated with hepatic triglyceride contents in obese subjects. Meanwhile, serum ALT, AST and GGT levels might be regarded as surrogate markers of insulin resistant. Serum ALT and GGT were associated with an increased risk for metabolic syndrome. Serum ALT level rather than AST and GGT was independently associated with visceral fat area and liver fat contents.