Colon luminal content and epithelial cell morphology are markedly modified in rats fed with a high-protein diet

Abstract

Hyperproteic diets are used in human nutrition to obtain body weight reduction. Although increased protein ingestion results in an increased transfer of proteins from the small to the large intestine, there is little information on the consequences of the use of such diets on the composition of large intestine content and on epithelial cell morphology and metabolism. Rats were fed for 15 days with either a normoproteic (NP, 14% protein) or a hyperproteic isocaloric diet (HP, 53% protein), and absorptive colonocytes were observed by electron microscopy or isolated for enzyme activity studies. The colonic luminal content was recovered for biochemical analysis. Absorbing colonocytes were characterized by a 1.7-fold reduction in the height of the brush-border membranes (P = 0.0001) after HP diet consumption when compared with NP. This coincided in the whole colon content of HP animals with a 1.8-fold higher mass content (P = 0.0020), a 2.2-fold higher water content (P = 0.0240), a 5.2-fold higher protease activity (P = 0.0104), a 5.5-fold higher ammonia content (P = 0.0008), and a more than twofold higher propionate, valerate, isobutyrate, and isovalerate content (P < 0.05). The basal oxygen consumption of colonocytes was similar in the NP and HP groups, but ammonia was found to provoke a dose-dependent decrease of oxygen consumption in the isolated absorbing colonocytes. The activity of glutamine synthetase (which condenses ammonia and glutamate) was found to be much higher in colonocytes than in small intestine enterocytes and was 1.6-fold higher (P = 0.0304) in colonocytes isolated from HP animals than NP. Glutaminase activity remained unchanged. Thus hyperproteic diet ingestion causes marked changes both in the luminal environment of colonocytes and in the characteristics of these cells, demonstrating that hyperproteic diet interferes with colonocyte metabolism and morphology. Possible causal relationships between energy metabolism, reduced height of colonocyte brush-border membranes, and reduced water absorption are discussed.

Relevance of protein fermentation to gut health

“…Recently, rats fed a high-protein diet (53% protein versus 14% in a normal diet) had a marked decrease of the height of the colonocyte brush-border membranes (p 5 0.0001) which coincided with a higher colonic protease activity (p 5 0.01) and an increased NH 3 content in the colonic lumen (p 5 0.0008) [55]. The relationship between the different measured parameters was not further investigated.…”

Chronic feeding with protein-restricted diets affect ileal amino acid digestibility and the expression of nutrient-sensing, hormone secretion, gastrointestinal digestive enzyme, and nutrient transporter genes in young weaned pigs

“…Young mammals (including infant and weaned pigs) have often been reported to exhibit gastrointestinal tract (GIT) dysfunction, including alterations intestinal morphology, the immune system, and absorption functions, when fed a high-protein diet [1][2][3][4][5]. A reduction in dietary crude protein (CP) levels can reduce diarrhea and nitrogen (N) excretion and repair digestive and immune function by enhancing the gene expression levels of digestive enzymes and amino acid (AA) transporters in young pigs [4,6].…”

“…For weaned pigs, it has been suggested that the CP levels in their diets can be reduced by 2-3 points without affecting average daily gain (ADG) [4,6], feed efficiency, or gastrointestinal health when the diets are supplemented with AAs [7,8]. However, reductions exceeding 3 points have produced no effects on ADG, feed efficiency and the mRNA levels of digestive enzymes (including trypsinogen, chymotrypsin B, and dipeptidase-II and III) and AA transporters [2,4,[9][10][11][12][13], although these trends have not been observed in all studies [14][15][16]. These findings suggest that the reduction of dietary CP levels and supplementation with AAs may be an alternative method for decreasing N excretion and improving GIT digestive function while maintaining performance in young pigs.…”

The impact of long-term dietary pattern of fecal donor on in vitro fecal fermentation properties of inulin

“…15 Ammonia and BCFA may change the morphology of intestinal tissues and act as a tumor promoter in the gut. 16 Proteolyic fermentation also results in the formation of amines, which are the precursors to carcinogenic nitrosamine formation.…”