High concentrate diet induced mucosal injuries by enhancing epithelial apoptosis and inflammatory response in the hindgut of goats.

It is widely accepted that lipopolysaccharide and volatile fatty acids (VFA) accumulate in the digestive tract of ruminants fed diets containing high portions of grain. Compared to the ruminal epithelium, the hindgut epithelium is composed of a monolayer structure that is more "leaky" for lipopolysaccharide and susceptible to organic acid-induced damage. The aim of this study was to investigate changes in epithelial structure, apoptosis and inflammatory response in the hindgut of goats fed a high-concentrate diet for 6 weeks.Eight local Chinese goats with rumen cannulas were randomly assigned to two groups: one group was fed a high-concentrate diet (65% concentrate of dry matter, HC) and the other group was fed a low-concentrate diet (35% concentrate of dry matter, LC) for 6 wks. Ruminal fluid, plasma, and hindgut mucosa tissues were collected. Histological techniques, real-time PCR and western blotting were used to evaluate the tissues structure, cell apoptosis and local inflammation in the hindguts.Feeding HC diet for 6 wks resulted in a significant decrease of ruminal pH (p<0.01), and ruminal lipopolysaccharide concentrations were significantly increased in HC goats (p<0.05). Obvious damage was observed to mucosal epithelium of the hindgut and the intercellular tight junctions in HC, but not in LC, goats. The expression of MyD88 and caspase-8 mRNA was increased in colonic epithelium of HC goats compared to LC (p<0.05), and the expression of TLR-4 and caspase-3 showed a tendency to increase. In the cecum, interleukin-1β mRNA expression was decreased (p<0.05), and caspase-3 showed a potential increase (p = 0.07) in HC goats. The level of NF-κB protein was increased in colonic epithelium of HC goats. Caspase-3 activity was elevated in both colon and cecum, whereas caspase-8 activity was statistically increased only in colon.Feeding a high-concentrate diet to goats for 6 wks led to hindgut mucosal injuries via activating epithelial cells apoptosis and local inflammatory response

LPS concentrations in ruminal fluid (A) and plasma (B).

<p>The results were expressed as mean ± SEM. Data were analyzed for differences due to diet, time, and their interactions by ANOVA using the General Linear Models of SPSS 11.0 for Windows (StatSoft Inc, Tulsa, OK, USA). Data was considered statistically significant when P<0.05, n = 4. * P<0.05 between two groups.</p

PCR primer sequences of the target genes.

<p>TLR4, Toll-like receptor 4; MyD88, myeloid differentiating factor 88; TNF-α, tumor necrosis factor alpha; IL-1β, interleukin-1 beta; TLR2, Toll-like receptor 2.</p><p>PCR primer sequences of the target genes.</p

Comparisons of morphology of the hindgut mucosa (colon and cecum) between HC and LC goats.

<p>Hindgut (n = 4) from each group were processed for morphological evaluation: colon section of the (A, C) LC group; (B, D) HC group and cecum section of the (E, G) LC group; (F, H) HC group (transmission electron microscopy, ×10000). Arrow indicates the location of the TJs (Scale bar = 500 nm).</p

pH value in ruminal fluid after 2 (A) and 6 weeks (B) feeding regime.

<p>Data was analyzed for differences due to diet, time, and their interactions by ANOVA using the General Linear Models of SPSS 11.0 for Windows (StatSoft Inc, Tulsa, OK, USA). Data was considered statistically significant when P<0.05, n = 4.</p

Protein expression of NF-κB p65 in colon and cecum mucosa.

<p>Results of NF-κB p65 protein levels expressed as arbitrary units relative to β-actin protein. Values are mean ± SEM. The data were analyzed by Independent-Samples T test using the Compare Means of SPASS 11.0 for Windows (StaSoft Inc, Tulsa, OK, USA). <i>^#p<0.1</i>, *<i>p<0.05</i> vs. LC.</p