Heat stress alters the gene expression of nutrient transporters along the chicken small intestine and dietary galacto-oligosaccharides are able to modulate this response

Introduction/Objective: One of the primary functions of the intestinal epithelium is transport of fluids, nutrients and electrolytes from and to the intestinal lumen. These transport processes are facilitated by different membrane nutrient transporters and nutrient transporters might be altered under stress conditions. This study aimed to investigate the effect of heat stress (HS) on the expression of intes-tinal brush border nutrient transporters, including intestinal peptide transporter (PepT-1), glutamate/aspartate amino acid transporter-3 (EAAT-3), fructose transporter (GLUT-5) and sodium-dependent glucose transporter 1 (SGLT-1) in jejunum and ileum of broiler chickens. In addition, the expression of the liver-expressed antimicrobial peptide (LEAP-2), as a representative of antimicrobial peptides that play a key role in the innate host defence mechanism in the chicken intestines, was measured. Materials and Methods: All parameters were determined in chickens under control and HS conditions with or without dietary galacto-oligosaccharides (GOS) in their diet. Chickens were fed a control diet or diet supplemented with 1% or 2.5% GOS for 6 days prior to and during a HS challenge for 5 days(38-39°C,8 h per day). mRNA levels of PepT-1, EAAT-3, GLUT-5, SGLT-1 and LEAP-2 were examined in jejunum and ileum by qRT-PCR. Moreover, the correlation of PepT-1 mRNA expression was determined compared to the mRNA expression of pro-inflammatory cytokines of IL-6 and IL-8 in jejunum and ileum. Results and Conclusions: The mRNA levels of PepT-1 and GLUT-5 were significantly upregulated in jejunum and ileum of HS-exposed broilers. Upregulation of Pep-T1 mRNA significantly correlated with the mRNA expression of IL-6 and IL-8 both in jejunum and ileum. In contrast, LEAP-2 mRNA levels were decreased under HS conditions. Feed supplementation with GOS significantly attenuated the HS-induced upregulation of PepT-1 and GLUT-5 mRNA in chicken jejunum and prevented the HS-induced downregulation of LEAP-2 mRNA expression. The presented results demonstrate that HS selectively modifies the mRNA expression of nutrient transporters along the broiler small intestine and dietary GOS mitigates these HS-induced alterations in nutrient transporters in the jejunum. Additionally, correlation of PepT-1 and the pro-inflammatory cytokines mRNA expressions in the intestines might describe the potential involve-ment of Pep-T1 in pathophysiology of HS-related intestinal inflammatory disorders.