The effect of a soy protein diet on attenuation of obesity-related pathologies in obese Zucker rats.

The purpose of this study was to determine how a soy-based diet modifies tissue-specific adipogenesis and the impact on the development of type 2 diabetes mellitus and non-alcoholic fatty liver disease in obese male lean and obese Zucker rats. Animals were randomly assigned to three diet groups for 17 weeks: casein control, whey control and soy protein. Physiological data were collected throughout the study and at week 14 animals were subjected to an OGTT. As previously demonstrated, obese soy-fed animals had greater final body weights and adiposity, and exhibited an increased food intake. Despite hypertrophic adipocytes in all obese animals, those fed soy protein presented with a benign obesity phenotype. Soy diets attenuated obesity-induced hepatic lipid accumulation and markers of inflammation. The obese soy-fed rats had greater adipocyte hypertrophy without an increase in adipocyte density (number per area), suggesting adipocyte hyperplasia in this group. This corresponded with maintenance of glucose tolerance and serum lipid profiles in the obese soy-fed group despite the greater adiposity. Transcript abundance of adipogenic regulatory genes revealed no significant diet effect at 17 weeks in adipose tissue, but did show greater modification of Wnt/β-catenin signaling in the liver. These results demonstrate benefits of a soy protein diet in amelioration of obesity-related pathologies such as non-alcoholic fatty liver and impaired insulin sensitivity. Furthermore, these outcomes may be mediated through an interaction of soy with the Wnt/β-catenin signaling