Metabolism and Nutrition I: Amino Acids

The intestinal peptide transporter, PepT1, is known to be regulated by a variety of dietary factors, including protein quantity, protein quality, and feed intake. The objective of this experiment was to determine the effect of dietary protein composition on mRNA abundance of chicken PepT1. From day of hatch to day 8, chicks from 2 genetic lines (A and B, selected under different dietary conditions) were given ad-libitum access to a commercial corn-soy diet. From day 8 to day 15, birds were fed 1 of 3 diets (24% CP) that differed only in protein source. Protein sources included whey protein concentrate (Whey), a partial whey hydrolysate (Hydro) consisting of mainly small peptides, or a mixture of free amino acids (AA) identical to the composition of the whey protein. Intake of all diets was restricted to the group that consumed the least (Line B, AA diet). Intestinal samples were collected at day 8 (before random assignment to dietary treatment), and days 9, 11, 13, and 15. Abundance of PepT1 mRNA was assayed by real time PCR. Quantities of PepT1 mRNA were greater (P = 0.0001) in Line B chicks as compared with Line A chicks. Abundance of PepT1 mRNA was greater in chicks that consumed the Hydro diet as compared with chicks that consumed the Whey (P = 0.06) or AA diet (P = 0.008). There was a line × diet interaction where PepT1 mRNA showed the greatest (P = 0.005) induction in Line B birds consuming the Hydro diet. Line B birds were heavier (P = 0.03) than Line A birds, but BW did not differ among treatments. These data demonstrate that dietary protein composition influences expression of the intestinal peptide transporter, PepT1. In particular, the Hydro diet accentuated the difference in gene expression between genetic lines.