Linolenic acid improves growth performance and immune status of Penaeus vannamei infected by Enterocytozoon hepatopenaei

Abstract Hepatopancreatic microsporidiosis (HPM) caused by Enterocytozoon hepatopenaei (EHP) leads to significant growth retardation of Penaeus vannamei and is increasing the economic losses in the shrimp aquaculture. Our previous metabolomic results showed that 24 metabolites including linolenic acid (LNA) significantly decreased in EHP-infected shrimp compared with healthy groups. This study aims to evaluate whether LNA can improve the growth performance and immune status of EHP-infected shrimp. The EHP-infected shrimp was fed with dietary LNA (0, 1.2, 2.4 and 4.8 g/kg diet) for 30 days. The results showed that compared to the other groups, the body length and weight of shrimp in groups of 2.4 g LNA/kg diet were significantly increased. The copy numbers of EHP were significantly reduced in group of 1.2, 2.4 and 4.8 LNA g/kg diet compared to without LNA group. Further study showed that when shrimp were fed with 2.4 g LNA/kg diet, growth-related genes (farnesoic acid O-methyltransferase and ecdysteroid-regulated protein) were down-regulated, but juvenile hormone esterase-like carboxylesterase 1 up-regulated, suggesting that LNA could improve the growth ability of EHP-infected shrimp. More importantly, three immune genes (peritrophin-44-like protein, lysozyme, and cathepsin C) in shrimp were significantly up-regulated after fed with addition of LNA. In addition, the enzyme activity of superoxide dismutase and catalase in the hepatopancreas of P. vannamei was obviously increased after fed with different concentrations of LNA. Overall, the appropriate LNA content in the feed (2.4 g/kg diet) can improve the growth of P. vannamei and enhance its non-specific immunity and antioxidant activity. These findings indicate that LNA could be used as a potential metabolic modulator for controlling the HMP caused by EHP, and shed some light on host metabolic prevention to infectious diseases.