OB GENE NOT LINKED TO HUMAN OBESITY IN MEXICAN-AMERICAN AFFECTED SIB PAIRS FROM STARR COUNTY, TEXAS

Obesity is a highly prevalent disease, which is associated with a numb er of chronic conditions and, as such, represents a major public healt h burden. Numerous studies indicate that there is a genetic component contributing to interindividual variability in obesity. The discovery of the ob gene in mice, mutations in which produce extreme obesity and non-insulin-dependent diabetes mellitus (NIDDM), provides a prime can didate gene for human obesity. We investigated linkage between the hum an OB gene and obesity in a sample of Mexican Americans from Starr Cou nty, Texas. Markers D7S635 and D7S1875, estimated to lie within a regi on approximately 290 to 400 kb proximal to the OB gene, were used to g enotype 177 obese individuals distributed in 64 sibships. Obesity was defined as a body mass index (BMI) above 30 kg/m(2). Linkage analyses for affected sibling pairs provided no evidence for linkage in this sa mple. In addition, differences between siblings for weight, BMI, systo lic and diastolic blood pressure, percent body fat, waist-to-hip ratio , and blood lipid measures were not significantly related to number of alleles shared identical by state (IBS) for either of the two markers . While the OB gene may be involved in the metabolic sequences leading to obesity, the present linkage results do not support the existence of common genetic variation at or near the OB locus that increases ris k for human obesity.