Increases in Nitric Oxide Concentrations Correlate Strongly with Body Fat in Obese Humans

NO is produced in many different cells and is involved in the regulation of such physiological and pathophysiological processes as inflammation, vasodilation, and metabolism (1). Depending on the cell type, NO is produced in an enzymatic reaction catalyzed by one of the three isoforms of NO synthase (NOS): neuronal NOS, endothelial NOS, and inducible NOS (2). Measurement of the NO metabolites, nitrate and nitrite (NOx), is also important as a marker of NOS enzyme activity. Obesity is a condition involving an excess accumulation of body fat, and the prevalence of obesity is rapidly increasing worldwide. Excessive weight and obesity are leading to nutrition-related disorders of clinical and public health concern. Recent studies have suggested a role for NO in the regulation of food intake in an animal experiment (3)(4). Endothelial and inducible NOS have been shown to be present in adipose tissue of the rat (5), suggesting that adipose tissue may be a potential source of NO production. Previous reports demonstrated that NOS activity and inducible NOS protein were also present in human subcutaneous adipose tissue (6) and showed that inhibition of NOS led to increased lipolysis in this tissue (7). However, how NO production changes as body mass index (BMI) increases in apparently healthy subjects has not been studied extensively. Moreover, correlation studies of serum NOx concentrations, body fat mass, and blood lipid concentrations in healthy subjects are limited. Therefore, in the present study, we investigated the changes in NOx concentrations according to BMI and evaluated the relationships among NOx concentrations, total body fat, and lipid profiles in adolescents. We measured serum NOx concentrations, complete blood cell counts, iron markers, and serum lipid profiles in 185 males and 178 females, 14–19 years of age, selected from 1473 students attending middle or high school. Eight anthropometric measurements were …