Activation of peroxisome proliferator-activated receptor gamma/small heterodimer partner pathway prevents high fat diet-induced obesity and hepatic steatosis in Sprague-Dawley rats fed soybean meal.

Soybeans are a complete nutritional resource and soybean proteins are known to affect lipid metabolism via multiple mechanisms. Soybean meal (SBM) is produced after extraction of soybean oil and in this study, we investigated the ability whether the SBM could prevent high fat diet-induced obesity and understand the underlying mechanisms. Male Sprague-Dawley rats, aged 5 weeks, were randomly divided into three groups (n=8 each) and fed one of three diets for 28 days: Cont (AIN-93G), HFD (high fat diet with 40% of calories derived from fat) and HFD+SBM (HFD with 30% SBM). White adipose tissue weight as well as plasma and hepatic triglycerides were significantly decreased in HFD+SBM rats. Expression of hepatic SREBP-1 and its target genes was significantly decreased in HFD+SBM rats. Meanwhile, expression of SHP gene expression was significantly increased in HFD+SBM, and there was a negative correlation between SHP and SREBP-1 expression. Together these results suggest that hepatic SREBP-1 gene expression is negatively regulated by SHP. Expression of PPARG, the transcriptional factor that regulates SHP expression, was increased in HFD+SBM rats. Furthermore, expression of genes controlled by PPARG/SHP, such as those involved in hepatic gluconeogenesis, was also significantly decreased in HFD+SBM rats. Therefore, in addition to the previous findings of SBM on obesity here we show an additional mechanism which by changing the expression of genes involved in lipid metabolism via the PPARG/SHP pathway in the liver.