2096 DIABETES, VOL. 48, OCTOBER 1999 Brief Genetics Report Tumor Necrosis Factor- -238 and -308 Polymorphisms Do Not Associate With Traits Related to Obesity and Insulin Resistance Jeremy Walston, Michael Seibert, Chung-Jen Yen, Lawrence J. Cheskin, and Ross E. Andersen Tumor necrosis factor- (TNF-) is expressed primar- ily in adipocytes, and elevated levels of this cytokine have been linked to obesity and insulin resistance. The purpose of this investigation was to test whether the TNF--308 polymorphism (previously linked to insulin resistance and increased leptin levels) and the TNF-- 238 polymorphism (linked to decreased insulin resis- tance) were associated with insulin resistance or obesity-related traits in 424 subjects self-referred to the Johns Hopkins Weight Management Center (JHWMC). There were no differences in allele frequencies of either polymorphism by obesity category in the JHWMC and a lean control group. Despite previous smaller studies that have linked insulin resistance and the 308 allele, we found no such relationship in the JHWMC population. Instead, homozygotes for this allele had a significantly lower BMI than their coun- terparts without the polymorphism. In addition, we found no relationship between the 238 polymorphism and BMI, fasting glucose, or log of fasting insulin. Diabetes 48:2096–2098, 1999 O besity is increasing in prevalence among Amer- icans and is associated with several adverse health problems, including type 2 diabetes, hyperlipidemia, and hypertension (1–3). The influence of obesity on the development of type 2 diabetes is complex and is likely due to an interaction of genetic, nutri- tional, and metabolic factors (4). Much attention has been focused on the identification of molecular pathways that contribute to the development of obesity and type 2 diabetes (5–8). The cytokine tumor necrosis factor- (TNF-) is expressed primarily in adipocytes, where it is an important modulator of gene expression (9–11). In obese individuals, TNF- expression is elevated and correlates strongly with hyperinsulinemia (10). Recently, two polymorphisms were identified in the 5' regulatory region of the TNF- gene. The first, found at position 308 (guanine [G] adenine [A]) of the TNF- gene, may increase expression of this cytokine in fat tissue and influence fat mass and insulin resistance (12). Fernández-Real et al. (8) recently reported that in 38 subjects (19 men and 19 women), this polymorphism was associated with increased insulin resistance, elevated percent body fat, and increased serum leptin levels. The second polymorphism was recently reported by Day et al. (13) to associate with decreased insulin resistance among family members who carried the 238 (guanine [G] adenine [A]) polymorphism. The purpose of this study was to determine the relationship of these variant TNF- alleles to traits related to obesity and type 2 diabetes in an obese cohort. The Johns Hopkins Weight Management Center (JHWMC) participants (n = 424) were >18 years of age, nondiabetic by American Diabetes Association criterion, and mostly female (65%). All signed institutional review board consent forms for genotyping. Characteristics of this population have been described elsewhere (7). A lean (BMI <25 kg/m 2 ) control group (n = 210) of age- and sex-matched nondiabetic indi- viduals was identified from the east Baltimore area to study allele frequency differences. Genotype frequencies in the JHWMC population were 0.18 overall for the 308 variant (Caucasian 0.17, n = 362; African-American 0.18, n = 62). The 238 TNF- allele fre- quencies were 0.06 for both Caucasians and African-Ameri- cans. The frequencies of each allele were in Hardy-Weinberg equilibrium. To examine whether the variant alleles were more common in patients with morbid obesity, we stratified the JHWMC participants by BMI classifications of obesity according to Wensier (14) and compared with the lean group (BMI <25 kg/m 2 ) of volunteers. A  2 analysis revealed no sig- nificant differences in gene frequencies across the four grades of obesity (Table 1) for either the TNF--308 or the TNF--238 polymorphism. Analysis of covariance (ANCOVA) with adjustment for age, BMI, ethnicity, and sex revealed no significant differences in the JHWMC participants among genotype for waist-to-hip ratio, fasting glucose levels, or log of fasting insulin levels (Table 2). We used a two-factor ANCOVA to test for interactions between these two poly- morphisms and found no significant interactions between From the Divisions of Geriatric Medicine and Gerontology (J.W., M.S., C.-J.Y., R.E.A.) and Gastroenterology (L.J.C.), Johns Hopkins Medical Insti- tutions, Baltimore, Maryland. Address correspondence and reprint requests to Jeremy Walston, MD, Johns Hopkins Geriatrics Center, 5505 Bayview Cir., Baltimore, MD 21224. E-mail: jwalston@welchlink.welch.jhu.edu. Received for publication 10 December 1998 and accepted for publication 11 June 1999. ANCOVA, analysis of covariance; JHWMC, John Hopkins Weight Man- agement Center; PCR, polymerase chain reaction; TNF- , tumor necrosis factor-.