Intestinal IMINO transporter SIT1 is not expressed in human newborns

Area of Science:

• Gastroenterology
• Developmental Biology
• Molecular Biology

Background:

• Amino acid transporter expression in the human newborn small intestine remains uncharacterized.
• The maturation of imino acid (proline) transport in the neonatal gut is unknown, with potential parallels to delayed maturation in the kidney proximal tubule.

Purpose of the Study:

• To investigate the expression and maturation of amino acid transporters, particularly imino acid transporter SIT1 (SLC6A20), in the human newborn small intestine.
• To compare neonatal small intestinal transporter expression with adult levels and assess the impact of intestinal atresia on this expression.

Main Methods:

• Utilized small intestinal tissue from newborns with jejunal or ileal atresia and adult terminal ileum tissue.
• Analyzed gene expression (mRNA) of various amino acid transporters and accessory proteins.
• Determined protein expression of key transporters (B0AT1, SIT1) and ACE2 using immunofluorescence.

Main Results:

• Luminal imino and amino acid transporter SIT1 (SLC6A20) mRNA was threefold lower in newborns compared to adults.
• Protein levels of the major luminal neutral amino acid transporter B0AT1 (SLC6A19) and ACE2 were similar in newborns and adults.
• SIT1 protein was undetectable in the newborn small intestine, contrasting with its presence in adults. Intestinal atresia did not alter the expression of other tested transporters.

Conclusions:

• The imino acid transporter SIT1 (SLC6A20) is not expressed in the human newborn small intestine, a finding consistent with its absence in the kidney proximal tubule and potentially leading to iminoglycinuria.
• The expression of most other luminal and basolateral amino acid transporters is established by birth and is not significantly affected by intestinal obstruction or lack of amniotic fluid passage.