Effects Of Milk-Borne Bioactive Peptides On The Small Intestinal Development In Neonatal Pigs And Its Mechanism

Studies in recent years found that the milk-borne bioactive peptides might regulate the development of gastrointestinal tract, however, its mechanism remains unknown. We studied the effect of naturally suckling, intrauterine growth retardation, insulin and pre-hydrolyzed casein, on some growth-related gene expressions in the tissue of small intestine and liver to explore the underground mechanism of the regulation effect of the bioactive peptides on the intestinal development.Our studies included five sections presented as follows:In section one, we explored the underground mechanism of the rapid development of gastrointestinal tract in neonatal pigs. Ten newborn piglets were selected and divided into group 1 (D0, n=5) and 2 (D3, n=5). The piglets of DO were slaughtered within 2~4 hours after birth and those of D3 were reared by sows for three days and then slaughtered. The contents of DNA, RNA, and protein, the activities of lactase, maltase and L-leucine aminopeptidase (LAP) were determined. The expressions of receptors for growth hormone (GH), insulin and insulin-like growth factor I (IGF-I), IGF-I and LAP in the intestinal mucosa, GH receptor and IGF-I in the liver were quantified by the method of RT- PCR. The results showed that the length and the weight of small intestine, the contents of DNA, RNA, and protein, the activities of lactase, maltase and LAP in the small intestinal mucosa of DO were higher (P<0.05 or P<0.01) than that of D3. In the mocosa of small intestine, expressions of IGF-I receptor, IGF-I and LAP in D3 were higher than that of D0. In liver, the expression of IGF-I in D3 was up regulated (P<0.01) compared with D0. These results suggest that the fast development of gastrointestinal tract in neonatal pigs is related to the up-regulation of IGF-I receptor, IGF-I expression in the small intestinal mucosa, and also may be related to the up-regulation of IGF-I expression in the liver. The increase of LAP activity is partially the result of up-regulation of LAP gene expression.In section two, we examined the influences of intrauterine growth retardation (IUGR)...