Effects of early low temperature exposure on the growth, glycolipid metabolism and growth hormone (gh) gene methylation in the late stage of Chinese perch (Siniperca chuatsi).

Temperature is an important factor affecting the early development, growth and physiology of fish, as well as on aspects of feeding and metabolism. Here, we investigated the impact of low temperature on the growth, glycolipid metabolism and growth hormone (gh) gene methylation in the late stage of Chinese perch (Siniperca chuatsi). Chinese perch larvae were exposed to temperatures with 21 °C (low temperature group (LT)) and 25 °C (control group) for 7 days, and then the LT group was slowly heated to 25 °C and raised at this temperature for two months. Results indicated that the LT group exhibited significantly lower growth rate and weight gain rate than the control group (p < 0.05), but no obvious food intake (FI) were detected yet between LT group and control group. The larvae exposed at 21 °C relative to the 25 °C group had significant decreased transcript levels of GH-IGF axis genes (gh, igf1 and igf2) in Chinese perch juvenile (p < 0.05). Further analysis of the DNA methylation levels of gh showed that the LT group had higher at the CpG sites of -3029 and - 3032 than the control group in larvae (p < 0.05), whereas the DNA methylation levels at CpG sites of -2982 and - 3039 of gh were significantly lower compared with the control group in juveniles (p < 0.05). In addition, the plasma glucose was significantly increased in the LT group (p < 0.05), suggesting the metabolism of blood glucose slowed at low temperature. In larvae, the expressions of glycolipid metabolism genes (ins-ra and ins-rb) in LT group were significantly up-regulated compared to control group in larvae (p < 0.05), while down-regulated in juveniles (p < 0.05). The expression level of ucp2 mRNA was continuously up-regulated under low temperature stress. All these data demonstrate that early exposure to low temperature affected the growth and glycolipid metabolism of Chinese perch.