The relevance of the insulin gene (INS) variable number tandem repeat (VNTR) polymorphism to indexes of body size and adult obesity is inconclusive. Given the equivocal reports on the association between the VNTR class genotype at the insulin gene locus and indexes of body size and obesity, we assessed these associations in a series of cohort studies based on 7,999 middle-aged men and women. We found no convincing evidence that INS VNTR class genotype was associated with indexes of body size and adult obesity. These data suggest that INS VNTR class is not an important determinant of size and body weight regulation in middle-aged men and women. Diabetes 54:2812-2815, 2005 E xperimental and observational studies have suggested that insulin signaling is involved in regulation of somatic growth and body weight (1). The variable number tandem repeat (VNTR) polymorphism, lying 396 base pairs 5Ј to the insulin gene on chromosome 11p15.5, is thought to influence insulin expression (2,3). This minisatellite polymorphism has also been associated with altered expression of the nearby IGF-II, a key regulator of fetal growth and development (4,5). Collectively, observational studies have reported conflicting associations between the INS VNTR class genotype and indexes of body size in childhood and obesity (4,6 -8). Importantly, the relevance of INS VNTR class to indexes of body size and obesity in adults is also inconclusive. Given these equivocal results, we assessed the association between INS VNTR class genotype and indexes of body size and adult obesity in a series of cohort studies based on 7,999 middle-aged men and women.
RESEARCH DESIGN AND METHODSWe used data from the Norfolk cohort of the European Prospective Investigation into Cancer (EPIC) and the Ely Study. EPIC is an ongoing prospective cohort study of ϳ25,000 people aged 45-75, resident in Norfolk, and recruited from general practice registers between 1993 and 1997 (9). It is an ethnically homogeneous Caucasian population. These participants completed a health examination. In January 1998, we invited the cohort for a second health examination, and 15,786 people had attended by October 2000. All participants gave informed consent. Details of recruitment, anthropometric measurements, and health examinations following standardized protocols have been published (9). All participants completed a detailed health and lifestyle questionnaire, which included a question on birth weight. A D-loop nonstretch fiberglass tape was used for the head circumference measures. DNA was extracted from the 15,786 whole blood/EDTA samples (Whatman Biosciences, Ely, U.K.) taken at the second health examination. BMI was calculated from the weight and height measures.For the purposes of this analysis, we examined data from two subcohorts of the 15,786 EPIC study participants who attended the second health examination (9). EPIC1 comprises 3,744 participants with fully arrayed DNA available for genotyping. EPIC2 is a random sample of 5,000 participants who were free of baseline disease (ca...