Study of vegetal and animal high protein-based diets on a human gastrointestinal ex vivo model over gut microbiota composition (Probiotics and Enterobacteria) and metabolites profile (biogenic amines and fatty acids).

Abstract

For the last years, the trend of high protein diets (HPD) has been widely adopted by the general population as well as by recreational and professional athletes as a strategy to lose weight and gain muscle mass. Nevertheless, during this type of diet a relatively high amount of protein could reach the large intestine, increasing protein fermentation by gut microbiota, which in contrast to carbohydrate fermentation, potentially leads to dysbiosis because of the concomitant reduction of beneficial microbial metabolites (e.g. Short-chain fatty acids) and the increase in the production of harmful ones, such as biogenic amines. These compounds derived from amino acid decarboxylation, have mainly been investigated in fermented foods. However, recently its production by human isolated bacteria has been discovered. The objectives of this work were to study the effect of animal and vegetal high protein diets on probiotics (Bifidobacterium and Lactobacillus) and Enterobacteria concentrations as well as the evaluation of short and branched chain fatty acids, and biogenic amines (putrescine, tyramine, cadaverine, and histamine), on an ex vivo model of the human gastrointestinal tract. For this purpose, three human digestive simulators (ARIS, CIATEJ) were inoculated with human microbiota, and after that, fed with three diets for a period of 24 days. The diets consisted of two high-protein diets (50% protein, 30%, carbohydrates, and 20% fat), either with an animal or vegetal protein, and a control diet (19% protein, 56 % carbohydrates, and 25% fat). The vegetal protein isolate consisted of a mixture of black bean protein, obtained through alkaline extraction and acid precipitation procedure, and corn protein (zein). Whereas, the animal protein was obtained from freeze-dried and defatted (with hexane) beef. The amino acid profile of the dehydrated beef was used to formulate a vegetal protein with a similar amino acid profile. Samples from the digestors corresponding to the large intestine were collected every 72 h and stored at -20°C until gas chromatography analysis (short and branched chain fatty acids), HPLC analysis (biogenic amines), and Real-time qPCR (bacteria concentration). The production, at the end of the fermentation (24 day), of short chain fatty acids (SCFA) and branched-chain fatty acids (BCFA) was higher in the section of the descending colon of the three diets evaluated. In this regard, acetic and butyric acid were the main SCFA produced in the animal protein-based diet. Whereas, butyric acid was the main SCFA in the vegetal protein-based diet. On the other hand, both diets led to similar concentrations of BCFA, caproic, and valeric acid from which the last one, was the acid mostly produced in both diets. Regarding biogenic amines ,both high protein diets lead to similar concentrations, and the main amines were putrescine and cadaverine. Finally, the probiotics concentrations ended (24 day) with similar concentrations in both colon segments of the three diets, and the same was observed with the concentration of Enterobacteria. In this respect, among the bacteria evaluated, the concentrations of Enterobacteria showed the highest decrease in comparison to the probiotics in both colon segments of the three diets.