[Correlation between ectopic fat accumulation and insulin sensitivity in obese individuals with different glucose...

To investigate the correlation between liver and skeletal muscle fat contents and insulin resistance in obese individuals with different levels of glucose tolerance.

RESULTS: Ten non-obese individuals with normal glucose tolerance (NGT), 9 obese individuals with NGT, and 7 obese individuals with impaired glucose tolerance (IGT) were enrolled in this study. All the participants were examined for insulin sensitivity by hyperinsulinemic-euglycemic clamp and for liver and skeletal muscle fat accumulation quantified by proton magnetic resonance spectroscopy (1H MRS). The data were collected from the subjects including somatometric measurements, fasting plasma glucose, 2-h plasma glucose (2hPG), fasting insulin, and blood biochemistry. Linear correlation analysis and multiple linear stepwise regression analysis were used to analyze the relationship between ectopic fat accumulation and insulin resistance.

The glucose infusion rates (GIR, presented as the M value) differed significantly among IGT-obese (3.95∓1.66 mg·kg^-1·min^-1), NGT-obese (6.14∓1.90 mg·kg^-1·min^-1) and NGT-non-obese (8.78∓2.46 mg·kg^-1·min^-1) groups (P<0.05). The 3 groups also showed significant differences in liver fat contents [(15.23∓3.09)%, (6.25∓0.38)%, and (1.89∓0.90)%, respectively, P<0.05] and intramyocellular lipids in the tibialis anterior (2.69∓0.95, 2.61∓1.45, and 1.54∓0.66 mmol/kg, respectively, P<0.05). Linear analysis revealed that liver fat content, but not skeletal muscle fat content, was significantly correlated with the M value. Multiple linear stepwise regression analysis using M value as the dependent variable (Y) revealed that liver fat content (X) was an independent factor inversely correlated with the M value (regression equation: Y=-30.562X+9.007, R²=0.717, P<0.01).

Liver fat accumulation, but not skeletal muscle fat accumulation, is correlated with insulin resistance and impaired glucose metabolism.