Maltose promotes crucian carp survival against Aeromonas sobrial infection at high temperature

Abstract

Temperature influences fish's susceptibility to infectious disease through an immune response. However, the mechanism underlying this regulation is yet to be elucidated. In this study, we compared the susceptibility of crucian carp that were grown at 18°C and 33°C, respectively, to Aeromonas sobrial infection and found that crucian carp was more susceptible when grown at 33°C. These distinct susceptibilities of fish at different temperatures to infection may partially be explained by their differences in the metabolism as revealed by comparative metabolomics profiling: crucian carp demonstrated enhanced TCA cycle but reduced fatty acid biosynthesis; Our study also found that maltose was the most suppressed metabolite in fish grown at 33°C. Importantly, exogenous injection of maltose enhances crucian carp survival grown at 33°C by 30%. Further study showed that exogenous maltose downregulated the production of several cytokines but enhanced the lysozyme (lyz) and complement component c3, which involves the humoral innate immunity. Our results suggest that maltose promotes the survival of crucian carp likely through fine tuning the immune gene expression, and this finding provides a novel approach to manage bacterial infection.

Keywords: Aeromonas sobrial; Metabolomics; crucian carp; immune response; maltose.

Figure 1.

Percent survival of crucian carp to A.sobrial infection at 18°C and 33°C. Crucian carp were acclimated at 18°C or 33°C for 7 days and then were challenged with saline or A.sobrial (1 × 10⁶CFU/dose; n = 30 for each treatment). The percent survival was monitored for 15 days.

Figure 2.

Crucian carp had different metabolomics profiling when cultured at different temperatures.

Figure 2.

Crucian carp had different metabolomics profiling when cultured at different temperatures.

Figure 3.

Pathway analysis of differential metabolites.

Figure 3.

Pathway analysis of differential metabolites.

Figure 4.

Metabolic network of the metabolites with differential abundance, and measurement of the activities of enzymes of the TCA cycle.

Figure 4.

Metabolic network of the metabolites with differential abundance, and measurement of the activities of enzymes of the TCA cycle.

Figure 5.

Maltose promotes fish survival against A. sobrial infection.

Figure 5.

Maltose promotes fish survival against A. sobrial infection.

Figure 6.

Maltose promotes fish survival against A.sobrial infection.

Figure 7.

Maltose does not promote the activity of TCA cycle.

Figure 8.

Maltose modulates innate immune response at 33°C.