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Impact of different high fiber diets on intestinal cell proliferation and differentiation in finishing pigs
Feeding diets high in fiber (DF) increases mucin secretion and alters intestinal morphology. This study aimed to investigate the impact of different sources of DF on intestinal epithelial proliferation and differentiation in finishing pigs. Forty-six finishing pigs (BW 84 ± 7 kg) were fed 1 of 4 diets: control (corn-soybean; CON; n = 12), wheat straw (23%; WS; n = 11), corn distillers dried grains with solubles (55%; DDGS; n = 11), and soybean hulls (30%; SBH; n = 12). The WS, SBH, or corn DDGS was the only DF containing ingredient in each diet, CON and DF diets were formulated to contain 8.5 and 17% NDF, respectively. Pigs were fed an amount equal to 2.5% of initial BW for 14-d in metabolism cages. Ileum samples were collected for histology and gene expression analysis after euthanasia. Data were analyzed using non-parametric tests in GraphPad Prism 6. Overall, DF diets were not different in proliferation (positive cells for Ki67/crypt) compared with CON. However, proliferation was greater (P < 0.05) for pigs fed DDGS (13.3 ± 0.8) than those fed SBH (10.0 ± 1.2). Presence of goblet cells (% area of mucosa) was greater (P < 0.05) in WS (11.5 ± 0.9) and DDGS (9.2 ± 0.5) diets compared with CON (8.2 ± 0.3) diet, WS diet was also greater (P < 0.05) than SBH (10.9 ± 0.6) diet. Furthermore, the expression of the mucin Muc2 was greater (P < 0.05) in all DF diets compared with CON. The expansion of the progenitor cell pool was tested by Olfm4 expression. Compared with CON, SBH decreased (P < 0.05) and DDGS increased Olfm4 (P < 0.05); and SBH showed lower (P < 0.05) expression than WS and DDGS diets. This suggests that DDGS induced Notch signaling. Enterocyte differentiation was demonstrated by changes in functional marker Fabp, and differentiation driver Hes1. No differences were observed in Fabp expression, but SBH decreased (P < 0.05) and DDGS tended to increase (P = 0.06) Hes1 compared with CON. These observations suggest that feeding SBH may reduce, and DDGS may promote swine intestinal enterocyte differentiation. Secretory cell expansion is indicated by cell markers Muc2, ChgA, and Lyz, and differentiation drivers Atoh1, Dll4 and Sox9. Compared with CON, DDGS was a stronger inducer while SBH was a stronger repressor of secretory cells. These results indicate that sources of DF modulate different aspects of epithelial cell proliferation and differentiation.
Keywords: dietary fiber, cell proliferation, cell differentiation