Plasma FFA utilization and fatty acid-binding protein content are diminished in type 2 diabetic muscle

In this study, we investigated the hypothesis that impairments in forearm s keletal muscle free fatty acid (FFA) metabolism are present in patients wit h type 2 diabetes both in the overnight fasted state and during beta-adrene rgic stimulation. Eight obese subjects with type 2 diabetes and eight nonob ese controls (Con) were studied using the forearm balance technique and ind irect calorimetry during infusion of the stable isotope tracer [U-C-13] pal mitate after an overnight fast and during infusion of the nonselective beta -agonist isoprenaline (Iso, 20 ng . kg lean body mass(-1) . min(-1)). Addit ionally, activities of mitochondrial enzymes and of cytoplasmatic fatty aci d-binding protein (FABP) were determined in biopsies from the vastus latera lis muscle. Both during fasting and Iso infusion, the tracer balance data s howed that forearm muscle FFA uptake (Con vs. type 2: fast 449 +/- 69 vs. 2 58 +/- 42 and Iso 715 +/- 129 vs. 398 +/- 70 nmol . 100 ml tissue(-1) . min (-1), P< 0.05) and FFA release were lower in type 2 diabetes compared with Con. Also, the oxidation of plasma FFA by skeletal muscle was blunted durin g Iso infusion in type 2 diabetes (Con vs. type 2: Iso 446 +/- 274 vs. 16 /- 70 nmol . 100 ml tissue(-1) . min(-1), P< 0.05). The net forearm glycero l release was increased in type 2 diabetic subjects (P< 0.05), which points to an increased forearm lipolysis. Additionally, skeletal muscle cytoplasm atic FABP content and the activity of muscle oxidative enzymes were lowered in type 2 diabetes. We conclude that the uptake and oxidation of plasma FF A are impaired in the forearm muscles of type 2 diabetic subjects in the ov ernight fasted state with and without Iso stimulation.