Human muscle fiber type–specific insulin signaling: impact of obesity and type 2 diabetes

PH Albers, AJT Pedersen, JB Birk, DE Kristensen… - Diabetes, 2015 - Am Diabetes Assoc
PH Albers, AJT Pedersen, JB Birk, DE Kristensen, BF Vind, O Baba, J Nøhr, K Højlund…
Diabetes, 2015Am Diabetes Assoc
Skeletal muscle is a heterogeneous tissue composed of different fiber types. Studies
suggest that insulin-mediated glucose metabolism is different between muscle fiber types.
We hypothesized that differences are due to fiber type–specific expression/regulation of
insulin signaling elements and/or metabolic enzymes. Pools of type I and II fibers were
prepared from biopsies of the vastus lateralis muscles from lean, obese, and type 2 diabetic
subjects before and after a hyperinsulinemic-euglycemic clamp. Type I fibers compared with …
Skeletal muscle is a heterogeneous tissue composed of different fiber types. Studies suggest that insulin-mediated glucose metabolism is different between muscle fiber types. We hypothesized that differences are due to fiber type–specific expression/regulation of insulin signaling elements and/or metabolic enzymes. Pools of type I and II fibers were prepared from biopsies of the vastus lateralis muscles from lean, obese, and type 2 diabetic subjects before and after a hyperinsulinemic-euglycemic clamp. Type I fibers compared with type II fibers have higher protein levels of the insulin receptor, GLUT4, hexokinase II, glycogen synthase (GS), and pyruvate dehydrogenase-E1α (PDH-E1α) and a lower protein content of Akt2, TBC1 domain family member 4 (TBC1D4), and TBC1D1. In type I fibers compared with type II fibers, the phosphorylation response to insulin was similar (TBC1D4, TBC1D1, and GS) or decreased (Akt and PDH-E1α). Phosphorylation responses to insulin adjusted for protein level were not different between fiber types. Independently of fiber type, insulin signaling was similar (TBC1D1, GS, and PDH-E1α) or decreased (Akt and TBC1D4) in muscle from patients with type 2 diabetes compared with lean and obese subjects. We conclude that human type I muscle fibers compared with type II fibers have a higher glucose-handling capacity but a similar sensitivity for phosphoregulation by insulin.
Am Diabetes Assoc