MiR-143-3p/FNDC5 axis: a novel regulator of insulin sensitivity

Insulin resistance is a key hallmark in type 2 diabetes. In recent decades, there have been numerous studies of the causes of insulin resistance. microRNAs (miRNAs) participate in the regulation of multiple aspects of energy metabolism and miR-143-3p has been shown to induce insulin resistance. We aimed to predict the downstream targets of miR-143-3p and found a miR-143-3p binding site on the 3'-untranslated region of FNDC5 (Fibronectin type III domain containing 5) mRNA.

We first confirmed that FNDC5 mRNA is a target of miR-143-3p using a double luciferase experiment, then constructed a prokaryotic expression system for the mature form of FNDC5, irisin, and expressed and purified irisin protein. We transfected a miR-143-3p mimic into HepG2-NTCP (Na+-taurocholate cotransporting polypeptide) cells using an NTCP targeting vector, then 24 h later, the glucose concentration of the culture medium, western blot analysis was analyzed. We next co-incubated the cells transfected with the miR-143-3p mimic with irisin for 12 h following by the assay of glucose uptake and AKT phosphorylation.

The glucose concentration of the culture medium was higher than that associated with control miRNA-transfected cells (p < 0.01). Western blot analysis showed that the miR-143-3p mimic significantly reduced the expression of FNDC5 (p < 0.05) and the phosphorylation of AKT (Protein kinase B) (p < 0.05), implying impaired insulin signaling. which increased the glucose uptake (p < 0.0001) and AKT phosphorylation in the cells (p < 0.05).

We conclude that FNDC5 is a direct target of miR-143-3p and that miR-143-3p induces insulin resistance by reducing its expression.