Insulin resistance directly correlates with increased saturated fatty acids in skeletal muscle triglycerides

A close relationship between elevated plasma free fatty acid (FFA) levels a nd insulin resistance is commonly reported in obese subjects. The aim of th e present study was to evaluate the role of intramuscular triglyceride (mTG ) and FFA levels in insulin sensitivity in 30 nondiabetic normal-weight or obese subjects (18 with body mass index [BMI] = 21.8 +/- 3.3 kg/m(2) and 12 with BMI = 34.6 +/- 2.7 kg/m(2)) who underwent minor abdominal surgery. Bo dy composition was estimated by isotopic dilution, substrate oxidation by i ndirect calorimetry, and whole-body glucose uptake by euglycemic-hyperinsul inemic clamp (EHC). Glucose uptake (M) value negatively correlated with the MTG level (R-2 = -.56, P < .0001), which was increased in obese patients ( 11.6 +/- 2.2 v 6.2 +/- 1.4 mu mol/g wet weight muscle tissue, P < .0001). T he TG fatty acid profile was significantly different in the 2 groups: an in creased concentration of saturated fat was present in obese patients (unsat urated to saturated ratio, 1.89 +/- 0.40 v2.19 +/- 0,07, P < .0001). Stepwi se linear regression analysis of total mTGs and palmitic and oleic fraction s on the M value showed that only mTGs and palmitic acid were significantly related to glucose uptake (R-2 = 66, P < .0001), Furthermore, among the ot her anthropometric variables, only the BMI was significantly correlated wit h MTGs (R-2 = .71, P < ,0001). In conclusion, not only the MTG concentratio n but also the FFA pattern seems to affect insulin-mediated glucose uptake. A pivotal role might be played by a high saturated fatty acid content in t he TGs, Copyright (C) 2000 by W.B. Saunders Company.