title: Insulin receptor autophosphorylation in cultured myoblasts correlates to glucose disposal in Pima Indians.
abstract: In a previous study [Youngren, J. F., I. D. Goldfire, and R. E. Pratley. Am. J. Physiol. 273 (Endocrinol. Metab. 36): E276-E283, 1997] of skeletal muscle biopsies from insulin-resistant, nondiabetic Pima Indians, we demonstrated that diminished insulin receptor (IR) autophosphorylation correlated with in vivo insulin resistance. In the present study, to determine whether decreased IR function is a primary trait of muscle, and not secondary to an altered in vivo environment, we cultured myoblasts from 17 nondiabetic Pima Indians in whom insulin-stimulated glucose disposal (M) was measured during hyperinsulinemic-euglycemic glucose clamps. Myoblast IR autophosphorylation was determined by a highly sensitive ELISA. IR autophosphorylation directly correlated with M (r = 0.56, P = 0.02) and inversely correlated with the fasting plasma insulin (r = -0.58, P < 0.05). The relationship between M and IR autophosphorylation remained significant after M was adjusted for the effects of percent body fat (partial r = 0.53, P < 0.04). The relationship between insulin resistance and the capacity for myoblast IR autophosphorylation in nondiabetic Pima Indians suggests that variations in IR-signaling capacity may be intrinsic characteristics of muscle that contribute to the genetic component determining insulin action in this population.
mesh_terms: D000328:Adult; D001706:Biopsy; D001786:Blood Glucose / Q000378:metabolism*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007198:Indians, North American; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008137:Longitudinal Studies; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010766:Phosphorylation; D011972:Receptor, Insulin / Q000378:metabolism*