Elevated atopy in healthy obese women

Abstract

Allergic disorders, including asthma, have increased dramatically in the United States in the past 20 y. Epidemiologic studies have found body mass index (body weight in kg/height squared in m) to be a positive independent correlate of atopy in women but not in men. We investigated the prevalence of atopy among healthy obese and nonobese women and its relation to fat mass (FM), insulin resistance, and plasma concentrations of 17beta-estradiol, interleukin 4 (IL-4), and leptin. A cross-sectional study of 21 obese (> or = 30% body fat) and 22 nonobese (< 30% body fat) women (18-41 y of age) was performed. The following measurements were taken: FM by plethysmography, total and specific immunoglobulin E (IgE) by automated immunosorbent analysis, and blood glucose, insulin, C-peptide, 17beta-estradiol, sex hormone-binding globulin, and IL-4. Insulin sensitivity was determined on the basis of the fasting insulin resistance index and with an oral-glucose-tolerance test. The frequency of specific IgE in the obese group was almost 3 times that in the nonobese group (P = 0.008). The total IgE concentration was not significantly different between groups. Plasma concentrations of 17beta-estradiol, the ratio of 17beta-estradiol to sex hormone-binding globulin, the fasting insulin resistance index, and C-peptide and leptin concentrations were higher in the obese than in the nonobese group (P < 0.05) after adjustment for oral contraceptive use. All factors correlated positively with FM. Logistic regression showed FM to be the only positive predictor of specific IgE (P = 0.01). The findings confirm a direct relation between obesity and a T helper 2 cell immune response in women.