Effects of Long-Term, High Doses of Nitrate Administration on Adiposity Index in Female Rats

Despite higher prevalence of obesity in women, the anti-obesity effects of nitrate have mostly been studied in male animals, using low doses of nitrate for short durations. This study aims at determining effects of long-term (6 months), administration of high doses of nitrate on the obesity indices of normal adult female rats. Female Wistar rats were divided into 3 groups (n=10/group): Control group received tap water and the two treatment groups received water containing 250 and 500 mg/L sodium nitrate for 6 months. Body weight, food intake, and water consumption were measured weekly. Naso-anal length, body mass index (BMI), Lee index, as well as abdominal and thoracic circumferences were determined every two months. Weights of white adipose tissue (WAT) and brown adipose tissue (BAT) were measured at the end of study and adiposity index was calculated. Administration of nitrate had no effect on food intake but significantly (p<0.001) increased water consumption in female rats. Compared to the control group, there was no significant difference in body weight and nasal-to-anal length in the nitrate-treated rats. At the end of study, compared to controls, in nitrate-treated rats, BMI (23%), Lee index (7%), adiposity index (36%), weight of WAT as well as abdominal (5%) and thoracic (6%) circumferences were significantly lower. Weight of BAT was also significantly higher in the interscapular region, i.e 0.23±0.02, 0.39±0.03 and 0.32±0.02 gram in the control and nitrate groups (250 and 500 mg/L), respectively. and in the axillary region 0.24±0.03, 0.33±0.02 and 0.30±0.03 gram in the control and nitrate groups (250 and 500 mg/L), respectively. Nitrate administration prevents increase in adiposity in normal adult female rats, beneficial effects which may be associated with increased browning of WAT.