Changes in Tight Junction Protein Expression Levels but Not Distribution in Commercial White and Brown Laying Hens Supplemented with Chondrus crispus or Ascophyllum nodosum Seaweed

Simple Summary: The intestinal epithelium is the layer of cells that line the digestive tract, and it acts both as a selective filter to facilitate the absorption of nutrients and a protective barrier to toxins and infection. The functional integrity of this constantly renewing cell layer depends on so-called tight junction proteins, a class that includes two regulatory proteins called occludin and zonula occludens-1 (ZO-1). We studied the effect of two different prebiotic seaweed supplements for 41 weeks on occludin and ZO-1 expression in two genetic lines of laying hen. Differences between genetic lines in the level of occludin in a highly absorptive section of the small intestine called the jejunum were found. There also were differences due to seaweed supplementation in the ZO-1 protein, and red seaweed supplementation appeared to have more impact in the brown laying hen strain than in the white strain. Overall, our results are consistent with previous studies showing genetic differences in diet response. It is proposed that prebiotic diet supplements improve intestinal function, in part by improving the barrier function of the intestinal epithelium with an associated increase in the expression of tight junction proteins, including occludin and zonula occludens-1 (ZO-1). We examined the expression of these proteins in two strains of laying hens (Lohman LSL-lite (White) and Lohman Brown-lite (Brown)) who were supplemented or not with 3% Chondrus crispus or 0.5% Ascophyllum nodosum seaweeds from 31 to 72 weeks of age. Occludin was localized to the lateral surfaces and across the intestinal epithelium in all animals. Reactivity for ZO-1 was concentrated at the apicolateral epithelial cell membrane border. Mood's median test indicated that White hens may express more occludin in villus epithelium (median intensity 3.5 vs. 2.5 in Brown hens, p = 0.06) but less ZO-1 in the deep cryptal epithelium (median intensity 1.5 vs. 2.5 in Brown hens, p = 0.06). Western blotting also showed higher levels of occludin in White than Brown hens (p < 0.05). A decrease in ZO-1 Western blot expression was associated with Chondrus crispus supplementation in comparison to controls (p < 0.05), but not with Ascophyllum nodosum supplementation (p > 0.05). In conclusion, genetic strain and dietary seaweed supplements affect tight junction regulatory protein expression levels but do not impact the anatomical distribution, as seen in cryosections.