Mechanistic insight into the gut microbiome and its interaction with host immunity and inflammation

The intestinal tract is a host to 100 trillion of microbes that have co-evolved with mammals over the millennia.These commensal organisms are critical to the host survival.The roles that symbiotic microorganisms play in the digestion,absorption,and metabolism of nutrients have been clearly demonstrated.Additionally,commensals are indispensable in regulating host immunity.This is evidenced by the poorly developed gut immune system of germ-free mice,which can be corrected by transplantation of specific commensal bacteria.Recent advances in our understanding of the mechanism of host emicrobial interaction have provided the basis for this interaction.This paper reviews some of these key studies,with a specific focus on the effect of the microbiome on the immune organ development,nonspecific immunity,specific immunity,and inflammation.

Vitamin D_3 increased intestinal Na/Pi-Ⅱb and CYP27B1 mRNA level in rats fed low-phosphorus diets

The objective of the study was to determine the role of vitamin D3(VD3) in regulating adaptation and mechanism of rats to low-phosphorus(P) diets. Rats were assigned to 4 diets containing 0.2%, 0.4%, 0.6%,or 0.8% P consisting of 5 replicate cages with 6 rats per replicate cage and fed for 7 days. Four rats from each replicate cage were treated with ethane-1-hydroxy-1,1-diphosphonicacid, tetrasodium salt(EHDP)and 2 rats remained untreated. Twelve hours prior to preparation on d 7, two of the EHDP-treated rats received an intraperitoneal injection of VD3 [1,25-(OH)_2 D_3] at 600 ng per kg body weight, while two rats did not receive the injection. Rats that did not receive VD_3 injection had decreased(P < 0.001) P absorption, but injection of VD3 resulted in increased(P < 0.001) absorption. The effect of VD3 injection was greater(P < 0.001) for rats fed 0.2% P diet than rats fed 0.8% P diet in ileum. Sodium dependent phosphate cotransporter type IIb(Na/Pi-IIb) and 25-hydroxyvitamin D 1-α hydroxylase(CYP27 B1) mRNA level showed the same trend with P absorption. Serum concentration of VD3 and la-hydroxylase activity in rats fed 0.2% P diet were lower than those fed 0.8% P diet. The injection of VD3 increased(P < 0.001)serum concentration of VD3 and la-hydroxylase activity. Thus, VD3 increased Na/Pi-Ⅱb and CYP27 B1 mRNA level and improved serum concentration of VD3 and la-hydroxylase activity in rats fed low-P diets.

Enzyme activity and phosphate uptake in the small intestine of Sprague Dawley rats improved by supplementation of infant formula with prebiotics

This study was to identify the effects of prebiotics supplemented in infant formula on enzyme activity and phosphate uptake in the small intestine of Sprague Dawley(SD) rats. Forty-eight healthy SD rats at15 days old(a week before weaning) with similar weight were randomly divided into 3 groups: A(control group), B, C, with 16 rats per group. Rats in groups A, B, C were fed a standard infant formula, the standard infant formula supplemented with oligosaccharides, and the standard infant formula supplemented with polysaccharides, respectively. The feeding test was conducted for 28 d. Compared with group A, the results showed the following: 1) the activities of sucrose and lactase in the small intestine were significantly increased in SD rats of group C(P < 0.05); 2) the relative expressions of lactase gene in the anterior and posterior segments of the small intestine were significantly increased by 1.68 and 2.26 in SD rats of group C(P < 0.05), and the relative expression of Mgam gene in the posterior segment of the small intestine was significantly increased by 0.99 in SD rats of group C(P < 0.05); 3) the relative expressions of Na/Pi-IIb gene in the anterior and posterior segments of the small intestine were significantly increased by 1.85 and 2.28 in SD rats of group C(P < 0.05). These results indicate that the supplementation of infant formula with prebiotics can promote enzyme activity in the small intestine by increasing the relative expression of enzyme gene or by decreasing intestinal injury, and can increase the relative expression of Na/Pi-IIb gene. The effect of polysaccharides is better than that of oligosaccharides.