MiR-338-3p mediates gluconeogenesis via targeting of PP4R1 in hepatocytes

Abstract

Hyperglycaemia is a characteristic of type 2 diabetes. In hepatocytes, impaired insulin sensitivity leads to increased gluconeogenesis and decreased glycogenesis. MicroRNA (miR)-338-3p is associated with tumour necrosis factor (TNF)-α-induced suppression of hepatic glycogenesis via regulation of protein phosphatase 4 regulatory subunit 1 (PP4R1). However, the effect of miR-338-3p on gluconeogenesis in hepatocytes remains unknown. In a previous study, it was demonstrated that miR-338-3p is downregulated in the livers of mice and in mouse HEPA1-6 hepatocytes following treatment with TNF-α. In the present study, the effect of miR-338-3p on TNF-α-induced gluconeogenesis in hepatocytes was investigated. The levels of phosphorylated-FOXO1/FOXO1, phosphoenolpyruvate carboxykinase (PEPCK), peroxisome proliferator-activated receptor γ coactivator (PGC-1α) and glucose-6-phosphatase (G6Pase) were measured by western blotting. The mRNA levels of PEPCK, PGC-1α and G6Pase were determined by quantitative polymerase chain reaction. Pyruvate tolerance testing was used to determine the gluconeogenesis of mouse livers. The results demonstrated that treatment with TNF-α resulted in increased levels of gluconeogenesis in the livers of mice and decreased miR-338-3p expression levels in HEPA1-6 cells. Overexpression of miR-338-3p reversed TNF-α-induced glucose production via enhancement of phosphorylated forkhead box O1 levels and downregulation of the expression levels of genes associated with gluconeogenesis, including peroxisome proliferator-activated receptor γ coactivator-1α, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. However, inhibition of miR-338-3p expression was revealed to enhance gluconeogenesis in the livers of mice and in HEPA1-6 cells. Furthermore, downregulation of PP4R1 was revealed to attenuate the effect on glucose production following treatment with miR-338-3p inhibitors. In conclusion, the results of the present study revealed that miR-338-3p may be involved in TNF-α-mediated gluconeogenesis via targeting of PP4R1 in hepatocytes.