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Title: Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula

Author
item YANG, CHENGBO - University Of Guelph
item YANG, XIAOJIAN - University Of Guelph
item LACKEYRAM, DALE - University Of Guelph
item RIDEOUT, TODD - University Of Guelph
item WANG, ZIRONG - Xinjiang Agricultural University
item STOLL, BARBARA - Children'S Nutrition Research Center (CNRC)
item YIN, YULONG - Chinese Academy Of Sciences
item Burrin, Douglas - Doug
item FAN, MING - University Of Guelph

Submitted to: Amino Acids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/29/2016
Publication Date: 3/16/2016
Publication URL: http://handle.nal.usda.gov/10113/62808
Citation: Yang, C., Yang, X., Lackeyram, D., Rideout, T.C., Wang, Z., Stoll, B., Yin, Y., Burrin, D.G., Fan, M.Z. 2016. Expression of apical Na(+)-L-glutamine co-transport activity, B(0)-system neutral amino acid co-transporter (B(0)AT1) and angiotensin-converting enzyme 2 along the jejunal crypt-villus axis in young pigs fed a liquid formula. Amino Acids. 48(6):1491-1508.

Interpretive Summary: The intestinal digestion of dietary protein and absorption of amino acids is a vital process to sustain optimal growth for infants. The process of amino acid absorption occurs by many specialized proteins designed to transport specific free amino acids from the intestine into the bloodstream. It is difficult to study the activity of these proteins in human infant intestine because it is not ethical to collect intestinal tissue from healthy infants early after birth. We used the neonatal piglet to study the activity of these transport proteins since pigs are an excellent model of human infants. In this study, we used a technique to isolate specific cells within the neonatal piglet intestine and measure the activity and protein expression of a specific protein called system sodium-neutral AA transporter (B(0) AT1) that transports the neutral amino acids, especially glutamine. Glutamine is a major energy fuel for intestinal cells. Our result showed that the activity of sodium glutamine transport was higher in more mature villus intestinal cells than in immature crypt cells. The amount of protein was not different, but the gene for BoAT1 was higher in more mature cells than in immature cells. These results provide a clue about the cell mechanism that explains how rapidly growing intestinal cells transport dietary amino acids.

Technical Abstract: Gut apical amino acid (AA) transport activity is high at birth and during suckling, thus being essential to maintain luminal nutrient-dependent mucosal growth through providing AA as essential metabolic fuel, substrates and nutrient stimuli for cellular growth. Because system-B(0) Na(+)-neutral AA co-transporter (B(0)AT1, encoded by the SLC6A19 gene) plays a dominant role for apical uptake of large neutral AA including L-Gln, we hypothesized that high apical Na(+)-Gln co-transport activity, and B(0)AT1 (SLC6A19) in co-expression with angiotensin-converting enzyme 2 (ACE2) were expressed along the entire small intestinal crypt-villus axis in young animals via unique control mechanisms. Kinetics of Na(+)-Gln co-transport activity in the apical membrane vesicles, prepared from epithelial cells sequentially isolated along the jejunal crypt-villus axis from liquid formula-fed young pigs, were measured with the membrane potential being clamped to zero using thiocyanate. Apical maximal Na(+)-Gln co-transport activity was much higher ("p" < 0.05) in the upper villus cells than in the middle villus (by 29 %) and the crypt (by 30 %) cells; whereas, Na(+)-Gln co-transport affinity was lower ("p" < 0.05) in the upper villus cells than in the middle villus and the crypt cells. The B(0)AT1 (SLC6A19) mRNA abundance was lower ("p" < 0.05) in the crypt (by 40-47 %) than in the villus cells. There were no significant differences in B(0)AT1 and ACE2 protein abundances on the apical membrane among the upper villus, the middle villus and the crypt cells. Our study suggests that piglet fast growth is associated with very high intestinal apical Na(+)-neutral AA uptake activities via abundantly co-expressing B(0)AT1 and ACE2 proteins in the apical membrane and by transcribing the B(0)AT1 (SLC6A19) gene in the epithelia along the entire crypt-villus axis.