Short-term manipulation of plasma free fatty acids does not change skeletal muscle concentrations of ceramide and glucosylceramide in lean and overweight subjects

Context: Increased plasma free fatty acid (FFA) concentrations may be in part responsible for the increased levels of ceramide in skeletal muscle of obese subjects. Objective: We studied the effect of lowering and increasing plasma FFA levels on muscle ceramide and glucosylceramide concentrations in lean and obese subjects. Design: Plasma FFAs were either increased or decreased for 6 h by infusing a lipid emulsion or using Acipimox, respectively. Muscle biopsies were performed before and after the intervention for measurements of ceramide and glucosylceramide. Study Subjects: Eight lean [body mass index 21.9 (range, 19.6 - 24.6) kg/m(2)] and six overweight/obese [body mass index 34.4 (27.8 - 42.5) kg/m(2)] subjects without type 2 diabetes mellitus participated in the study. Main Outcome Measure: Differences in muscle ceramide and glucosylceramide upon manipulation of plasma FFAs were measured. Results: There were no differences in muscle ceramide and glucosylceramide between lean and obese subjects, respectively. Increasing or decreasing plasma FFAs for 6 h had no effect on ceramide [high FFAs: 24 (19 - 25) vs. 24 (22 - 27) pmol/mg muscle, P = 0.46; and 22 (20 - 28) vs. 24 (18 - 26) pmol/mg muscle, P = 0.89 in lean and obese, respectively; low FFAs: 26 (24 - 35) vs. 23 (18 - 27) pmol/mg muscle, P = 0.17 and 24 (15 - 44) vs. 24 (19 - 42) pmol/mg muscle, P = 0.6 in lean and obese, respectively] and glucosylceramide [high FFAs: 2.0 (1.7 - 4.3) vs. 3.4 (2.1 - 4.6) pmol/mg muscle, P = 0.17; and 3.0 (1.3 - 6.7) vs. 2.6 (1.2 - 3.9) pmol/mg muscle, P = 0.89 in lean and obese, respectively; low FFAs: 2.2 (1.0 - 4.4) vs. 1.7 (1.4 - 3.0) pmol/mg muscle, P = 0.92; and 6.6 (1.0 - 25.0) vs. 4.3 (1.3 - 7.6) pmol/mg muscle, P = 0.7 in lean and obese, respectively] concentrations in skeletal muscle. Conclusion: Short-term manipulation of plasma FFAs has no effect on ceramide and glucosylceramide concentrations in skeletal muscle from lean and obese subjects.