Effects of obesity and short‐term dietary manipulations on serum insulin and leptin levels in female Zucker rats following DMBA treatment

Abstract

Several epidemiological and animal studies have suggested that circulating insulin and leptin play an important role in the promotion and progression of breast cancer. The main objective of this experiment was to investigate the role of obesity and diet on serum insulin and leptin levels following 7,12-dimethylbenz(a)anthracene (DMBA) exposure. Obese (n=6) and lean (n=6) female Zucker rats were maintained on either regular chow, casein or soy protein diet for two weeks. All rats were orally gavaged at age 50 days with 65 mg/kg DMBA. All rats were sacrificed 24 hrs post-DMBA treatment. Blood was collected and serum insulin and leptin levels were measured by ELISA. Lean and obese rats fed casein or soy based diets had significantly increased serum insulin level compared to rats fed the chow diet (P<0.05). Also, obesity caused a significant increase in serum insulin regardless of the respective diet (P<0.05). Serum leptin levels were not significantly affected by dietary manipulation in lean rats. However, in obese rats fed casein or soy diets had significantly increased serum leptin levels compared to obese rats fed the chow diet. Our results suggest that short term dietary manipulation can play an important role in the elevation of insulin and leptin levels in obese animals. Other mechanisms responsible for increasing insulin and leptin levels in obese rats which are involved in mammary carcinogenesis are under investigation.