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

Purpose: To explore the N6-methyladenosine (mA) 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.

Methods: high glucose (HG)-treated HK-2 cell models and db/db mice models injected with rAAV-METTL3 the tail vein were established. The expression levels were determined by RT-qPCR, western blot, and immunohistochemical staining. RNA mA 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.

Results: METTL3 and TUG1 expression levels decreased in the kidneys of diabetic mice and HG-treated HK-2 cells. Mechanistically, METTL3-mediated mA modification increased the stability of TUG1 in an insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2)-dependent manner. METTL3-mediated mA 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.

Conclusion: METTL3 targets TUG1/PGC-1α and ameliorates mitochondrial dysfunction in diabetic nephropathy in an IGF2BP2-dependent manner.