Dietary choline deficiency aggravated the intestinal apoptosis in association with the MAPK signalling pathways of juvenile grass carp (Ctenopharyngodon idella)

Abstract

To investigate the effects and potential mechanisms of apoptosis in the intestines of juvenile grass carp (Ctenopharyngodon idella) for dietary choline, fish were fed different choline-containing diets (142.2, 407.4, 821.6, 1215.8, 1589.3, and 1996.6 mg kg−1) for 70 days. Results revealed that dietary choline deficiency (1) decreased the contents of choline, phosphatidylcholine, betaine, and acetylcholine (not in distal intestine [DI]) in grass crap intestines; down-regulated the mRNA abundances of choline transportations, such as high-affinity choline transporter CHT1 (not in proximal intestine[PI] and DI), choline transporter-like proteins such as CTL-1, CTL-2, CTL-4 (not in DI), and CTL-5 in grass crap intestines; (2) enhanced the degree of DNA fragments. Moreover, it up-regulated the activities of caspase-3, −8, and-9; reduced mRNA levels of caspase-3, −7, −8 (not in DI), and − 9, Fas ligand (FASL) (not in PI), and apoptotic protease activating factor-1(Apaf1), as well as the protein level of cytochrome c (Cty c). Dietary choline deficiency also down-regulated myeloid cell leukemia-1 (Mcl-1) (not in PI), B-cell lymphoma-2 (Bcl-2), and the inhibitor of apoptosis protein (IAP) mRNA levels in grass carp intestines, suggesting that choline inhibited cell apoptosis in fish intestines; (3) increased p38MAPK and JNK(not in mid intestine [MI]) mRNA level, as well as p-p38MAPK and T-p38MAPK protein levels in the PI and the ratio of p-p38MAPK/T-p38MAPK in the MI and DI, indicating that choline deficiency aggravated cell apoptosis in association with the MAPK signalling pathway in fish intestines; In conclusion, choline insufficiency promotion of intestinal apoptosis might be related to MAPK signalling pathways in fish. Moreover, the requirements of choline for resist intestinal apoptosis indices (caspase-8 and capase-9 activities) of grass carp (9.28–108.97 g) were calculated to be (1162.13–1780.93) mg kg−1 diet, respectively.