Diets high in fermentable protein and fibre alter tight junction protein composition with minor effects on barrier function in piglet colon.
Protein fermentation end products may damage the colonic mucosa, which could be counteracted by dietary inclusion of fermentable carbohydrates (fCHO). Although fermentable crude protein (fCP) and fCHO are known to affect microbial ecology, their interactive effects on epithelial barrier function are unknown. In the present study, in a 2 × 2 factorial experiment, thirty-two weaned piglets were fed low-fCP/low-fCHO (14·5 % crude protein (CP)/14·5 % total dietary fibre (TDF)), low-fCP/high-fCHO (14·8 % CP/16·6 % TDF), high-fCP/low-fCHO (19·8 % CP/14·5 % TDF) and high-fCP/high-fCHO (20·1 % CP/18·0 % TDF) diets. After 21-23 d, samples of proximal and distal colonic mucosae were investigated in Ussing chambers with respect to the paracellular and transcytotic passages of macromolecules and epithelial ion transport. The high-fCHO diets were found to reduce the permeability of the distal colon to the transcytotic marker horseradish peroxidase (HRP, 44 kDa; P <0·05) and also reduce the paracellular permeation of N-hydroxysuccinimide-biotin into the submucosa (443 Da; P <0·05), whereas that of HRP was decreased by the high-fCP diets (P <0·01). Short-circuit current (active ion transport), transepithelial resistance (barrier function) and charge selectivity were largely unaffected in both the segments. However, the high-fCP diets were found to suppress the aldosterone-induced epithelial Na channel activity (P <0·01) irrespective of fCHO inclusion. The high-fCP diets generally reduced the expression of colonic claudin-1, claudin-2 and claudin-3 (P <0·01), while that of claudin-4 was increased by the high-fCHO diets (P <0·01). The high-fCHO diets also altered the ratio between occludin forms (P <0·05) and increased the expression of tricellulin in the proximal colon, which was not observed with high-fCP diets. In conclusion, dietary fCHO and fCP exerted few and largely independent effects on functional measurements, but altered tight junction protein composition in a compensatory way, so that colonic transport and barrier properties were only marginally affected.
Institute of Anatomy II, University of Jena, Teichgraben 7, 07743 Jena, Germany.
Jan F
JF
Richter
Department of Veterinary Medicine, Institute of Animal Nutrition, Freie Universität Berlin, Königin-Luise-Straße 49, 14195 Berlin, Germany.
Robert
R
Pieper
Institute of Clinical Physiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Silke S
SS
Zakrzewski
Institute of Clinical Physiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Dorothee
D
Günzel
Division of Nutritional Medicine, Department of Gastroenterology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Joerg D
JD
Schulzke
Department of Animal and Poultry Science, University of Saskatchewan, 51 Campus Drive, Saskatoon, Saskatchewan, Canada S7N 5A8.
Andrew G
AG
Van Kessel
D000818:Animals; D003106:Colon / Q000737:chemistry / Q000502:physiology*; D004032:Diet / Q000662:veterinary; D004043:Dietary Fiber / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D005285:Fermentation; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000502:physiology; D008297:Male; D034421:Sus scrofa / Q000502:physiology*; D062725:Tight Junction Proteins / Q000032:analysis*
D004043:Dietary Fiber; D004044:Dietary Proteins; D062725:Tight Junction Proteins