RESPONSE OF PEPTIDE TRANSPORTER (SLC15A1) IN THE INTESTINAL EPITHELIAL CELLS OF TILAPIA Oreochromis mossambicus TO FASTING AND REFEEDING  

Amino acids are essential for growth, homeostasis, and metabolic and other physiological processes in fish. Amino acids from dietary proteins are absorbed mainly as peptides in the intestinal epithelial cells by the peptide transporters. Knowledge on how these transporters adapt to changes in nutritional condition is essential for the elucidation of mechanisms for possible in vitro (e.g. control of pathways) or in vivo (e.g. diet modification) regulation to improve amino acid absorption and therefore growth and other physical conditions of fish.   

In this study, a 14-day fasting and 3-day refeeding experiments were conducted to investigate the response of peptide transporter (SLC15A1) in the intestinal epithelial cells of tilapia Oreochromis mossambicus to the change in nutritional condition. The expression level of SLC 15a1 was checked at day 0, day 1, day 2, day 4, day 7, and day 14 during fasting and day 1 and day 3 after refeeding using real time PCR. The intestine was divided into 5 segments: hepatic loop (HL), proximal major coil (PMC), gastric loop (GL), distal major coil (DMC) and terminal segment (TS).

SLC15A1 is highly expressed at HL and PMC suggesting higher absorption of peptides in these intestinal segments. A temporary increase during the first day of fasting and a decrease at the second day was observed (Figure 1). The expression level became stable from day 4 to day 7. Previous studies reported decrease of peptide transporter during fasting. In this study, the temporary increase at the beginning of fasting might be vital information for a better understanding of the mechanisms involved in the regulation of peptide and amino acid absorption by the transporters.

After re-feeding SLC15A1 expressions increased (Figure 2). This result might suggest a coping strategy that contributes to mechanisms driving compensatory growth in tilapia.