Increased mucin‐degrading bacteria by high protein diet leads to thinner mucus layer and aggravates experimental colitis

Abstract

Background and Aim: Westernized high-fat diet increases the risk for inflammatory bowel diseases (IBDs), yet with insufficient understanding of the role of high-protein diet. We aimed to identify the effect of high-protein diets from different dietary proteins (casein, whey protein, soy protein) on experimental colitis and its impact on microbiota, structure and function of colonic mucus layer. Methods: Female BALB/c mice were fed by standard diet, high-casein diet (HCD), high whey protein diet or high soy protein diet for 4 weeks. The susceptibility of dextran sulfate sodium (DSS)-induced colitis in mice and thickness of colonic mucus layer were compared after different dietary interventions, associated with the identification of the reversal effect of broad-spectrum antibiotic intervention (0.5 g/L of vancomycin and 1 g/L of neomycin sulfate, metronidazole and ampicillin in drinking water). Further analysis was performed on the synthesis of mucin, microbiota and sialidase involved in degradation of mucus layer. Results: High-protein diets aggravated acute DSS-induced colitis independent of protein composition, while broad-spectrum antibiotics reversed this effect. HCD significantly altered the composition of bacteria in the colonic mucus layer, especially Bacteroides thetaiotaomicron and total mucin-degrading bacteria; besides, it increased sialidase concentration and reduced the thickness of mucus layer. However, it exhibited no significant effect on the synthesis of Muc2. Broad-spectrum antibiotics decreased the abundance of mucin-degrading bacteria and sialidase concentration while increased the thickness of mucus layer. Conclusion:High-protein diet shifts microbial composition and thickness of colonic mucus layer, leading to the aggravation of acute DSS-induced colitis.High protein diet and mucin degrading bacteria L Chen et al.

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“…Most of the studies found the negative effect of excessive intake of animal protein, especially red meat, while soy-pea protein was considered having a protective effect [ 53 ]. However, a study showed that a high-protein diet, no matter whether derived from casein mainly from animal food or whey from milk or soy, could aggravate acute DSS-induced colitis [ 54 ]. They also found that a high-casein diet had no significant effect on the synthesis of Mucin-2 but impaired the mucus barrier by decreasing Bacteroides thetaiotaomicron and total mucin-degrading bacteria, which encode sialidase, an enzyme in the first step of mucin degradation [ 54 ].…”

“…However, a study showed that a high-protein diet, no matter whether derived from casein mainly from animal food or whey from milk or soy, could aggravate acute DSS-induced colitis [ 54 ]. They also found that a high-casein diet had no significant effect on the synthesis of Mucin-2 but impaired the mucus barrier by decreasing Bacteroides thetaiotaomicron and total mucin-degrading bacteria, which encode sialidase, an enzyme in the first step of mucin degradation [ 54 ]. However, two studies have shown that low red meat intake had no protective effect on IBD, without data of gut microbiota changes.…”

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“…Dietary components can modulate the composition and metabolome of the gut microbiota, as well as affect the intestinal epithelium, goblet cells and innate immune system [12]. Dietary factors present in Western diets may decrease the production of mucins or cause more permeable mucous and antimicrobial peptides, as well as reshaping the microbiota [13,19]. Turner et al demonstrated that patients with severe UC have an increased relative abundance of Gammaproteobacteria [7].…”

Exploration of the Potential Relationship Between Gut Microbiota Remodeling Under the Influence of High-Protein Diet and Crohn’s Disease

“…This may be due to the cross-feeding of gut microbes ( D’Souza et al, 2018 ) or due to the limitation of sample size. Our previous study found that the antibiotics can reduce damage of mucus layer caused by a high-protein diet ( Chen et al, 2021 ). However, gut microbes are a complex community in which the altruistic behavior and community effects of drug-resistant bacteria need to be taken into account ( Lee et al, 2010 ; Frost et al, 2018 ).…”