METTL3 alleviates renal tubular mitochondrial dysfunction by regulating the TUG1/PGC-1a axis in an IGF2BP2-dependent manner in diabetic nephropathy

To explore the N6-methyladenosine (m6A) modification mechanism of taurine upregulated gene 1 (TUG1) and whether methyltransferase 3 (METTL3) can promote peroxisome proliferators-activated receptor γ coactivator 1 alpha (PGC-1α) transcription and alleviate mitochondrial dysfunction. In vitro high glucose (HG)-treated HK-2 cell models and in vivo db/db mice models injected with rAAV-METTL3 via the tail vein were established. The expression levels were determined by RT–qPCR, western blot, and immunohistochemical staining. RNA m6A modification was analyzed by the RNase Mazf. The biochemical indicators of mice were detected by enzyme-linked immunosorbent assay. Cell apoptosis was detected by flow cytometry. Histopathological staining was performed to evaluate kidney injury. mtDNA content, mitochondrial complex activity, and ATP were detected by RT–qPCR and detection kits, respectively, per the manufacturer’s instructions. Mitochondrial reactive oxygen species production in HK-2 cells incubated with MitoSOX Red and mitochondrial morphology were observed under a fluorescence microscope and transmission electron microscope, respectively. Molecular interactions were verified through RNA immunoprecipitation, RNA pull-down, and dual-luciferase reporter gene assay. METTL3 and TUG1 expression levels decreased in the kidneys of diabetic mice and HG-treated HK-2 cells. Mechanistically, METTL3-mediated m6A modification increased the stability of TUG1 in an insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2)-dependent manner. METTL3-mediated m6A modification of TUG1 promotes PGC-1α activation, thereby alleviating mitochondrial dysfunction in HG-treated HK-2 cells and db/db mice. Moreover, METTL3 overexpression alleviated kidney injury in db/db mice. METTL3 targets TUG1/PGC-1α and ameliorates mitochondrial dysfunction in diabetic nephropathy in an IGF2BP2-dependent manner.