Soy Protein Health Benefits Are in Part Dependent of the Gut Microbiota

Objectives Several studies have demonstrated that the consumption of soy protein decreases LDL-cholesterol, improves insulin sensitivity and attenuates body weight gain. Also, soy protein consumption can modify the gut microbiota, however it has not been established whether the changes in gut microbiota are in part responsible of the health effects of soy protein. Thus, the aim of the present study was to understand whether the metabolic effects of soy protein are reduced by the use of an antibiotic treatment. Methods Rats were fed for 16 weeks with one of the 4 experimental diets: 1) Casein control diet (C), 2) Soy protein diet (S), 3) C high-fat diet, and 4) S high-fat diet. Each group was sub-divided at the end of the 16 weeks in 2 groups. One subgroup continue with the same diet, and the other received the antibiotic treatment (Ampicillin/Neomycin) for 4 weeks. During the study body weight, food intake, body composition, energy expenditure and glucose tolerance were measured. Fecal samples were collected before and after the antibiotic treatment to determine the gut microbiota using the Illumina platform. At the end of the study blood samples were obtained to measure several biochemical variables. Also, liver and adipose tissue samples were obtained to assess the abundance of mRNA and proteins involved in lipid, glucose and thermogenesis. Results Rats fed S or S high fat diet had significant lower body weight gain, body fat, energy expenditure, glucose tolerance, blood lipids, increased expression of thermogenic genes and decreased serum lipopolisacharide than the control or high fat groups fed C diets. The antibiotic treatment abolished the health benefits observed in rats fed the S diets, particularly energy expenditure and weight gain. These changes were associated with changes in the gut microbiota, since S consumption increased the abundance of the Akkermansia and Bifidobacterium genus. This effect on the gut microbiota was prevented by the antibiotic treatment and rats developed metabolic endotoxemia. Finally, the antibiotic treatment reduced the expression of thermogenic genes, particularly in rats fed S high fat diet. Conclusions This study indicates that the beneficial effects of soy protein consumption on health are significantly dependent on the gut microbiota. Funding Sources CONACYT, INCMNSZ.