Arginine affects growth and integrity of grass carp enterocytes by regulating TOR signaling pathway and tight junction proteins
Dietary arginine (Arg) could improve the intestinal structure and absorption of grass carp (Ctenopharyngodon idellus); however, the mechanism of Arg on intestinal morphology improvement was unclear. The present study aimed to explain the possible mechanism of the positive effect of Arg on intestinal epithelial cells of grass carp. An in vitro study was conducted through a primary culture model to assess the growth, cell viability, mRNA expressions of TOR signal pathway, and tight junction proteins of enterocytes after culture in the medium with 6 levels of Arg (0, 0.1, 0.2, 0.5, 1.0, and 2.0 mmol/L). The results showed that 0.5 mmol/L Arg improved the cell number and decreased the lactate dehydrogenase and creatine kinase activities in culture medium (P < 0.05). The alkaline phosphatase activity in cell lysis buffer was depressed by 1 and 2 mmol/L Arg (P < 0.05). The nitric oxide (NO) content showed an increasing trend with the Arg content (P < 0.05), whereas the NO synthase activity showed an opposite trend to NO. TOR expression was higher in 0.2 and 0.5 mmol/L groups, whereas S6K1 expression in 1.0 mmol/L and 2.0 mmol/L groups were lower (P < 0.05). The mRNA expressions of occludin, claudin 3, and claudin c in 0.5 mmol/L group were the highest, while ZO-1 and claudin b expressions were higher in 0.2 and 0.5 mmol/L groups (P < 0.05). This study indicated that Arg enhanced the growth and integrity of intestinal epithelial cells of grass carp through upregulation of mRNA expression of TOR signal pathway and tight junction proteins at an optimal Arg content of 0.2–0.5 mmol/L.
KeywordsArginine Grass carp Intestinal epithelial cell TOR signal pathway Tight junctions
This study was supported by Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of China, the Fundamental Research Funds for the Central Universities (2662016PY105), and National Undergraduate Innovation and Entrepreneurship Training Plan of Huazhong Agricultural University (201510504044).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving animals were conducted under principles of good laboratory animal care and were approved by the Ethical Committee for Laboratory Animals Care and Use of Huazhong Agricultural University.
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