Objective: To test the hypothesis that hepatic steatosis is associated with risk factors for type 2 diabetes in overweight and obese youth, mediated by cardiorespiratory fitness.
Research design and methods: This was a cross-sectional study comparing insulin sensitivity between 30 overweight and obese adolescents with hepatic steatosis, 68 overweight and obese adolescents without hepatic steatosis, and 11 healthy weight adolescents without hepatic steatosis. Cardiorespiratory fitness was determined by a graded maximal exercise test on a cycle ergometer. Secondary outcomes included presence of metabolic syndrome and glucose response to a 75-g oral glucose challenge.
Results: The presence of hepatic steatosis was associated with 55% lower insulin sensitivity (P = 0.02) and a twofold greater prevalence of metabolic syndrome (P = 0.001). Differences in insulin sensitivity (3.5 vs. 4.5 mU ⋅ kg(-1) ⋅ min(-1), P = 0.03), prevalence of metabolic syndrome (48 vs. 20%, P = 0.03), and glucose area under the curve (816 vs. 710, P = 0.04) remained between groups after matching for age, sex, and visceral fat. The association between hepatic steatosis and insulin sensitivity (β = -0.24, t = -2.29, P < 0.025), metabolic syndrome (β = -0.54, t = -5.8, P < 0.001), and glucose area under the curve (β = 0.33, t = 3.3, P < 0.001) was independent of visceral and whole-body adiposity. Cardiorespiratory fitness was not associated with hepatic steatosis, insulin sensitivity, or presence of metabolic syndrome.
Conclusions: Hepatic steatosis is associated with type 2 diabetes risk factors independent of cardiorespiratory fitness, whole-body adiposity, and visceral fat mass.