Abstract
Previous studies have paid much attention to the associations between high intake of meat and host health. Our previous study showed that the intake of meat proteins can maintain a more balanced composition of gut bacteria as compared to soy protein diet. However, the associations between dietary protein source, gut bacteria, and host health were still unclear. In this study, we collected colonic contents from the growing rats fed with casein, beef, chicken or soy proteins for 90 days, and analyzed the compositions of gut microbiota and metabolites. Compared to the casein group (control), the chicken protein group showed the highest relative abundance of Lactobacillus and the highest levels of organic acids, including lactate, which can in turn promote the growth of Lactobacillus. The soy protein group had the highest relative abundance of Ruminococcus but the lowest relative abundance of Lactobacillus. Long-term intake of soy protein led to the up-regulation of transcription factor CD14 receptor and lipopolysaccharide-binding protein (LBP) in liver, an indicator for elevated bacterial endotoxins. In addition, the intake of soy protein also increased the levels of glutathione S-transferases in liver, which implicates elevated defense and stress responses. These results confirmed that meat protein intake may maintain a more balanced composition of gut bacteria and reduce the antigen load and inflammatory response from gut bacteria to the host.
Highlights
In recent years, excessive intake of meat and meat products has been suggested to be associated with some metabolic disorders (Tilman and Clark, 2014)
We found that the soy protein group had higher levels of short chain fatty acids (923, 779, 666, and 645 μmol/L for the soy, casein, beef, and chicken protein groups, respectively, P < 0.05)
The casein group had the highest levels of amino acids, while the chicken protein group had the lowest levels of these amino acids (P < 0.05)
Summary
Excessive intake of meat and meat products has been suggested to be associated with some metabolic disorders (Tilman and Clark, 2014). N-nitroso-compounds and heterocyclic amines, which were formed during cooking of red meat at high temperatures, could be critical factors for an elevated risk of mortality of colorectal cancer (Pan et al, 2012; Bastide et al, 2015). It is the fact that meat has many biological functions in terms of highly bioavailable nutrients, including essential amino acids, heme iron, and vitamins (Pereira and Vicente, 2013). The gastrointestinal tract and residing bacteria have been shown to play a crucial role in extracting and metabolizing dietary ingredients (Muegge et al, 2011; Tyakht et al, 2012; Tang et al, 2013). There is about 12–18 g of protein entering into human colon every day, consisting of residual dietary
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