The miRNA expression profile directly reflects the energy metabolic differences between slow and fast muscle with nutritional regulation of the Chinese perch (Siniperca chuatsi)

Fish skeletal muscles are composed of two distinct types, slow and fast muscles, and they play important roles in maintaining the body's movement and energy metabolism. The two types of muscle are easy to separate, so they are often used as the model system for studies on their physiological and functional characteristics. In this study, we revealed that the carbohydrate and lipid metabolic KEGG pathways are different between slow and fast muscles of Chinese perch with transcriptome analysis. In fast muscle, glucose metabolism was catabolic with higher glycolysis capacity, while in slow muscle, glucose metabolism was anabolic with more glycogen synthesis. In addition, oxidative metabolism in slow muscle was stronger than that in fast muscle. By analyzing the expression levels of 40 miRNAs involved in metabolism in the muscles of Chinese perch, 18 miRNAs were significantly upregulated and 7 were significantly downregulated in slow muscle compared with fast muscle. Based on functional enrichment analysis of their target genes, the differential expression levels of 17 miRNAs in slow and fast muscles were reflected in their carbohydrate and lipid metabolism. Among these, 15 miRNAs were associated with carbohydrate metabolism, and 6 miRNAs were associated with lipid metabolism. After 3 days of starvation, the expression levels of 15 miRNAs involved in glucose metabolism in fast and slow muscles increased. However, after 7 days of starvation, the mRNA levels of miR-22a, miR-23a, miR-133a-3p, miR-139, miR-143, miR-144, miR-181a and miR-206 decreased to basal levels. Our data suggest that the possible reason for the difference in glucose and lipid metabolism is that more miRNAs inhibit the expression of target genes in slow muscle.