title: The role of insulin receptor substrate-1 gene (IRS1) in type 2 diabetes in Pima Indians.
abstract: The insulin receptor substrate-1 (IRS1) is a critical element in insulin-signaling pathways, and mutations in the IRS1 gene have been reported to have a role in determining susceptibility to traits related to type 2 diabetes. In gene expression studies of tissue biopsies from nondiabetic Pima Indians, IRS1 mRNA levels were reduced in adipocytes from obese subjects compared with lean subjects, and IRS1 mRNA levels were also reduced in skeletal muscle from insulin-resistant subjects compared with insulin-sensitive subjects (all P < 0.05). Based on these expression differences and the known physiologic role of IRS1, this gene was investigated as a candidate gene for susceptibility to type 2 diabetes in Pima Indians, a population with an extremely high incidence and prevalence of type 2 diabetes. Thirteen variants were identified, and among these variants, several were in complete linkage disequilibrium. Four genotypically unique variants were further genotyped in 937 DNA samples from full-heritage Pima Indians. Three of the variants were modestly associated with type 2 diabetes (P < 0.05), one of which was additionally associated with 2-h plasma insulin and glucose as well as insulin action at physiologic and maximally stimulating insulin concentrations (all P < 0.05). The association of variants in IRS1 with type 2 diabetes and type 2 diabetes-related phenotypes and the differential expression of IRS1 in adipocytes and skeletal muscle suggest a role of this gene in the pathogenesis of type 2 diabetes in Pima Indians.
authors.affiliation: Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona 85016, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Kovacs
authors.forename: Robert L
authors.initials: RL
authors.lastname: Hanson
authors.forename: Yong-Ho
authors.initials: YH
authors.lastname: Lee
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Yang
authors.forename: Sayuko
authors.initials: S
authors.lastname: Kobes
authors.forename: Paska A
authors.initials: PA
authors.lastname: Permana
authors.forename: Clifton
authors.initials: C
authors.lastname: Bogardus
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Baier
mesh_terms: D017667:Adipocytes / Q000378:metabolism; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D004247:DNA / Q000235:genetics; D003920:Diabetes Mellitus / Q000378:metabolism / Q000473:pathology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000208:ethnology* / Q000235:genetics*; D020022:Genetic Predisposition to Disease / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D007198:Indians, North American / Q000235:genetics*; D007328:Insulin / Q000097:blood; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D015810:Linkage Disequilibrium; D018482:Muscle, Skeletal / Q000378:metabolism; D009765:Obesity; D010641:Phenotype; D010750:Phosphoproteins / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D001786:Blood Glucose; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D004247:DNA