Effect of soybean hull product on obesity and gut microbiome in high-fat diet induced obese mice

Background and objectives: In recent years, the global obesity population has increased rapidly. Obesity increases the risk of developing cardiovascular diseases, therefore it is important to prevent or ameliorate obesity. Soybean hulls are by-product produced during the processing of soybean products. Although soybean hulls contain a high content of dietary fibre, most of them are wasted. Several studies have reported that the intake of dietary fibre improves high-fat diet induced obesity and gut microbiome composition, however few studies have reported about the effect of soybean hulls on obesity and microbiome. Therefore, in this study, we investigated the effects of soybean hull product on obesity and gut microbiome in high-fat diet induced obese mice. Methods: 7-week-old male C57BL/6J mice were fed a standard diet (ST), a high-fat diet (HFD), or HFD with 5% (w/w) or 10% (w/w) soybean hull product (5% or 10%) for 10 weeks. After 10 weeks of the respective dietary treatment, mice were sacrificed. For the measurement of fecal short chain fatty acids (SCFAs) contents and the analysis of gut microbiome composition, feces were collected at 10 weeks of treatment. The gut microbiome composition was analyzed by 16S rRNA gene sequencing. Results: Dietary supplementation of 10% soybean hull product significantly reduced the body weight gains, weights of subcutaneous, epididymal, and perirenal adipose tissues compared to the HFD group. In 10% group, the content of major SCFAs such as acetate, propionate, and butyrate significantly increased. Furthermore, the overall gut microbiome composition changed with the dietary treatment, especially 10% group showed the significant increase of the relative abundance of potentially beneficial bacteria such as SCFAs producing bacteria. Conclusions: Consumption of soybean hull product suppressed the weight gain and fat accumulation caused by a high-fat diet intake and altered gut microbiome composition. These results suggest that soybean hull product can be a functional food material which helps prevent high-fat diet induced obesity and utilize wasted food material.