japplphysiol.00286.2016.pdf

 Increased endothelin-1 (ET-1) and reduced endothelial nitric oxide phosphorylation (peNOS) are hypothesized to reduce insulin-stimulated blood flow in type 2 diabetes (T2D), but studies examining these links in humans are limited. We sought to assess basal and insulin-stimulated endothelial signaling proteins (ET-1 and peNOS) in skeletal muscle from T2D patients. Ten obese T2D [glucose disposal rate (GDR): 6.6 ? 1.6 mg·kg lean body mass (LBM)?1 ·min?1 ] and 11 lean insulin-sensitive subjects (Lean GDR: 12.9 ? 1.2 mg·kg LBM?1 ·min?1 ) underwent a hyperinsulinemic-euglycemic clamp with vastus lateralis biopsies taken before and 60 min into the clamp. Basal biopsies were also taken in 11 medication-naïve, obese, non-T2D subjects. ET-1, peNOS (Ser1177), and eNOS protein and mRNA were measured from skel?etal muscle samples containing native microvessels. Femoral artery blood flow was assessed by duplex Doppler ultrasound. Insulin?stimulated blood flow was reduced in obese T2D (Lean: ?50.7 ? 6.5% baseline, T2D: ?20.8 ? 5.2% baseline, P ? 0.05). peNOS/eNOS content was higher in Lean under basal conditions and, although not increased by insulin, remained higher in Lean during the insulin clamp than in obese T2D (P ? 0.05). ET-1 mRNA and peptide were 2.25 ? 0.50- and 1.52 ? 0.11-fold higher in obese T2D com?pared with Lean at baseline, and ET-1 peptide remained 2.02 ? 1.9- fold elevated in obese T2D after insulin infusion (P ? 0.05) but did not increase with insulin in either group (P ? 0.05). Obese non-T2D subjects tended to also display elevated basal ET-1 (P ? 0.06). In summary, higher basal skeletal muscle expression of ET-1 and re?duced peNOS/eNOS may contribute to a reduced insulin-stimulated leg blood flow response in obese T2D patients.