Abstract
The Megalobrama amblycephala (M. amblycephala) is one of the most important economic freshwater fish in China. The molecular mechanism under the glucose intolerance responses which affects the growth performance and feed utilization is still confused. miR-34a was reported as a key regulator in the glucose metabolism, but how did the miR-34a exert its function in the metabolism of glucose/insulin in M. amblycephala was still unclear. In this study, we intraperitoneally injected the miR-34a inhibitor (80 nmol/100 g body weight) into M. amblycephala (fed with high starch diet, 45% starch) for 12 h, and then analyzed the gene expression profiling in livers by RNA-seq. The results showed that miR-34a expression in M. amblycephala livers was inhibited by injection of miR-34a inhibitor, and a total of 2212 differentially expressed genes (DEGs) were dysregulated (including 1183 up- and 1029 downregulated DEGs). Function enrichment analysis of DEGs showed that most of them were enriched in the peroxisome proliferator-activated receptor (PPAR), insulin, AMP-activated protein kinase (AMPK) and janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathways, which were all associated with the glucose/lipid metabolic and biosynthetic processes. In addition, we examined and verified the differential expression levels of some genes involved in AMPK signaling pathway by qRT-PCR. These results demonstrated that the inhibition of miR-34a might regulate glucose metabolism in M. amblycephala through downstream target genes.
Highlights
Carbohydrates are the main source of energy in most animal diets [1], and its properties such as digestion and absorption rate, viscosity, structural features, water-binding capacity and fermentation ability in the gastrointestinal tract are of critical importance in the effect of nutrition [2]
Our results suggested that the injection of miR-34a inhibitor (80 nmol/100 g body weight) for 12, 24, and 48 h showed significant effect on miR-34a expression level in livers of fishes treated with high starch diet (HSD, 45% wheat starch, Figure 1, p < 0.001)
We had previously performed a next-generation sequencing study between normal starch diet and high starch diet treated fishes, and identified hundreds of differentially expressed miRNAs (DEMs) that responded to HSD treatment in intestine, liver, and brain in M. amblycephala, respectively, suggesting that miRNAs might play crucial roles in glucose metabolism [9]
Summary
Carbohydrates are the main source of energy in most animal diets [1], and its properties such as digestion and absorption rate, viscosity, structural features, water-binding capacity and fermentation ability in the gastrointestinal tract are of critical importance in the effect of nutrition [2]. M. amblycephala is typical herbivorous feeding habit [8], and its digestive function and disease resistance ability are related to high-fat and -glucose diets [9]. Our previous study provided a miRNA profiling in response to high starch treatment in M. amblycephala, and showed that miRNAs might play crucial roles in glucose metabolism [9]. 124 differentially expressed miRNAs (DEMs) were identified in liver tissue between fishes fed with normal and high starch diets and a noteworthy upregulated miRNA, miR-34a, was found in the DEMs list [9]. There might be association between miR-34a upregulation and glucose metabolism
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