title: 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.
authors.affiliation: Institut National de Recherche Agronomique, AgroParisTech, Centre de Recherche en Nutrition Humaine-Ile de France, UMR 914 Physiologie de Nutrition et du Comportement Alimentaire, Paris, France.
authors.forename: Mireille
authors.initials: M
authors.lastname: Andriamihaja
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Davila
authors.forename: Mamy
authors.initials: M
authors.lastname: Eklou-Lawson
authors.forename: Nathalie
authors.initials: N
authors.lastname: Petit
authors.forename: Serge
authors.initials: S
authors.lastname: Delpal
authors.forename: Fadhila
authors.initials: F
authors.lastname: Allek
authors.forename: Anne
authors.initials: A
authors.lastname: Blais
authors.forename: Corine
authors.initials: C
authors.lastname: Delteil
authors.forename: Daniel
authors.initials: D
authors.lastname: Tomé
authors.forename: François
authors.initials: F
authors.lastname: Blachier
mesh_terms: D000641:Ammonia / Q000032:analysis / Q000494:pharmacology; D000818:Animals; D001834:Body Water; D048430:Cell Shape / Q000187:drug effects*; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects* / Q000502:physiology; D005766:Gastrointestinal Contents / Q000737:chemistry / Q000187:drug effects*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
chemical_list: D004044:Dietary Proteins; D000641:Ammonia; D005974:Glutamate-Ammonia Ligase