title: The insulin gene variable number tandem repeat class I/III polymorphism is in linkage disequilibrium with birth weight but not Type 2 diabetes in the Pima population.
abstract: The insulin gene variable number tandem repeat (INS-VNTR) is proposed to exert pleiotropic genetic effects on birth weight and diabetes susceptibility. In our study, we examined the influence of a polymorphism in tight linkage disequilibrium with INS-VNTR (-23Hph1) on birth weight and type 2 diabetes in the Pima population. A parent-offspring "trio" design was used to assess parent-of-origin effects and population stratification. The presence of the -23Hph1 T-allele was associated with lower birth weight (n = 192; -140 g per copy of the T-allele; P = 0.04), even after adjustment for effects of population stratification (P = 0.03). The effects of paternally transmitted T-alleles were greater than those of maternally transmitted alleles (paternally transmitted: -250 g, P = 0.05; maternally transmitted: -111 g, P = 0.43), but this difference was not statistically significant (P = 0.50). The -23Hph1 T-allele was associated with an increased prevalence of type 2 diabetes (P = 0.009), which family-based association analysis suggested was attributable to population structure (P = 0.04) without significant evidence of linkage disequilibrium between diabetes prevalence and genotype (P = 0.86). Thus allelic variation of the INS gene is associated with lower birth weight and increased prevalence of type 2 diabetes. Significant linkage disequilibrium was found between -23Hph1 and birth weight but not type 2 diabetes, an observation that supports a potential functional role of INS polymorphisms in the regulation of birth weight.
authors.affiliation: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona 85014, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Lindsay
authors.forename: Robert L
authors.initials: RL
authors.lastname: Hanson
authors.forename: Chris
authors.initials: C
authors.lastname: Wiedrich
authors.forename: William C
authors.initials: WC
authors.lastname: Knowler
authors.forename: Peter H
authors.initials: PH
authors.lastname: Bennett
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Baier
mesh_terms: D000328:Adult; D001724:Birth Weight / Q000235:genetics*; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics* / Q000473:pathology; D005260:Female; D006801:Humans; D007198:Indians, North American / Q000235:genetics*; D007328:Insulin / Q000235:genetics*; D015810:Linkage Disequilibrium; D008297:Male; D008875:Middle Aged; D018598:Minisatellite Repeats; D011110:Polymorphism, Genetic / Q000235:genetics*
chemical_list: D007328:Insulin