Regulation Of Hepatic Gluconeogenesis By MiR-21 And The Underlying Mechanism

MicroRNAs is a class of single-stranded,endogenous non-coding RNA molecules of about 22 nucleotides,and their sequences are highly conserved.Mature microRNA(miRNA)is mainly combined with target gene mRNA through the base complementary pairing.It can mediate the process of cell differentiation,proliferation,apoptosis and metabolism by regulating the expression of mRNA and inhibiting the transcription process.More and more studies have shown that the abnormal expression of miRNAs is also involved in the occurrence and development of diabetes and its complications.MiR-21 is widely present in a variety of plants and animals,maintaining a high degree of conservation among multiple species,and is involved in the development and progression of many diseases,especially cancer.MiR-21 is also an early diagnostic molecular marker of diabetic nephropathy.The study found that there is an abnormal activation of hepatic gluconeogenesis in fasting blood glucose of type 2 diabetes.However,the potential mechanism of microRNAs in the pathogenesis of glycogen is unclear.In this paper,Taqman real-time PCR method showed that in the liver,compared with normal control mice(C57BL/6J),mice in type 2 diabetes mellitus(db/db and ob/ob)and obese mice induced by high fat diet model(HFD),the expression of miR-21 were downregulated.According to this,we speculated that miR-21 may play an important role in the pathogenesis of diabetes.In order to verify this conjecture,silencing of miR-21 resulted in a further increase the blood glucose level in HFD mice by the classic peritoneal glucose tolerance test,insulin tolerance test and pyruvate tolerance test.MiR-21 may have a negative effect on blood glucose.Furthermore,adenovirus-mediated overexpression of mi R-21 in C57BL/6J mice,db / db mice and HFD mice reduced fasting blood glucose levels in mice and improved glucose tolerance,insulin tolerance and pyruvate tolerance.In order to further confirm the molecular mechanism of miR-21 hypoglycemia,the 3'-UTR of FOXO1 was cloned and tested by double luciferase reporter gene and Western blotting,it was confirmed that FOXO1 was the target of miR-21.In primary mouse liver cells and liver of db/db mice and HFD mice,adenovirus-mediated overexpression of miR-21 significantly inhibited the key glucose-specific gene peroxisome proliferator-activated receptor coactivator 1?(PGC-1?),glucose-6-phosphatase(G6Pase)and phosphoenolpyruvate(PEPCK)mRNA expression levels,and reduced glucose output and increased insulin stimulation of AKT phosphorylation levels.It is suggested that miR-21 targets the signal pathway of the key regulation of gluconeogenesis by targeting FOXO1 gene.Further,in primary mouse hepatocytes,miRNA sponge-mediated miR-21 silencing resulted in an increase expression levels of these two key gluconeogenesis mRNAs and reduced the level of insulin-stimulated AKT phosphorylation.In summary,miR-21 targets the FOXO1 gene,which regulates gluconeogenesis-related genes PGC-1?,G6 Pase and PEPCK,increases insulin-stimulated AKT phosphorylation levels,inhibits glucose production,regulates blood glucose under hunger conditions levels,improved glucose tolerance in diabetic mice,insulin tolerance and pyruvate tolerance and promote insulin sensitivity.MiR-21 plays an important role in regulating blood glucose balance and hepatic insulin sensitivity.