Relationship between unexplained elevations in alanine aminotransferase and serum leptin in US adults - Results from the Third National Health and Nutrition Examination Survey (NHANES III)

Introduction: There has been an interest to explore whether serum leptin plays any role in the pathogenesis of chronic liver disease. We conducted a case-control study to evaluate the relationship between unexplained elevations in ALT and serum leptin in NHANES III participants. Methods: A total of 6343 adults who bad fasting serum leptin and ALT measured as part of NHANES III constituted our study group. From this database, we have constructed cohorts of patients with unexplained elevations in ALT according to published criteria and compared their serum leptin levels to matched controls without liver disease and matched controls with hepatitis C. Leptin was also compared between patients with unexplained elevations in ALT with and without metabolic syndrome. Results: Serum leptin in 288 patients with unexplained elevations in ALT was 13.3 +/- 9.9 ng/mL and was not significantly different than 720 controls without liver disease (13.6 +/- 11.9 ng/mL, P = 0.6). Serum leptin in another group of patients with unexplained elevations in ALT and hepatitis C controls was also not significantly different (8.0 +/- 4.8 vs. 8.8 +/- 7.4 ng/mL, respectively, P = 0.5). There was no independent relationship between the presence of metabolic syndrome and serum leptin in individuals with unexplained elevations in ALT (P = 0.8). Conclusions: individuals with unexplained elevations in ALT did not have higher levels of serum leptin than the matched controls. As unexplained elevations in ALT may signify the presence of nonalcoholic fatty liver disease in NHANES III participants, our data provide indirect evidence against a role for serum leptin in the pathogenesis of nonalcoholic fatty liver disease.