Abstract: In order to explore the role of Isthmin-1 (Ism-1) in glucose and lipid metabolism of grass carp, we cloned the open reading frame (ORF) of Ism-1 by RT-PCR, and the sequence was analyzed by bioinformatics technology. The distribution characteristics of Ism-1 in different tissues of grass carp were detected by RT-qPCR, and the expression of Ism-1 under different nutritional conditions were analyzed in vitro and in vivo. In this study, ORF region of Ism-1 was successfully cloned. Sequence analysis showed that the ORF region of Ism-1 was 1380 bp, encoding 459 amino acids, and the relative molecular weight of protein was 50.96 kD. Amino acid multiple sequence alignment and phylogenetic tree analysis showed that the evolutionary relationship of Ism-1 between grass carp and fathead minnow was the closest (amino acid similarity was up to 96.51%). Ism-1 was widely expressed in multiple tissues, and had higher expression in red muscle, next were gill, brain and white muscle of grass carp. The fasting and refeeding experiment indicated the expression of Ism-1 in hepatopancreas was significantly upregulated after 14 days of starvation treatment (P<0.05), and the expression decreased after refeeding, but was still significantly higher than that of control group (P<0.05). The expression ofIsm-1 in white muscle was significantly up-regulated after starvation and refeeding (P<0.05). The results of intraperitoneal injection of glucagon experiment eventuated that the expression ofIsm-1 in hepatopancreas was significantly downregulated compared with control group (P<0.05). In addition, the expression ofIsm-1 was significantly decreased (P<0.001) in hepatocytes after treatment with 80 μg/mL oleic acid for 24h. Overall, this research confirmedIsm-1 may be involved in the regulation of glucose and lipid metabolism of grass carp, which would provide essential data for the following study of the function of Ism-1.