MTERF1 Regulates Podocyte Mitochondrial DNA Replication Impairment and Mitochondrial Dysfunction in Diabetic...

This study was carried out with an objective to clarify the mechanism of mitochondrial transcription termination factor 1 (MTERF1) in regulating mitochondrial DNA (mtDNA) replication and mitochondrial function of podocytes in diabetic nephropathy (DN).

To establish a type I diabetes model, C57BL/6J mice were injected intraperitoneally with streptozotocin (STZ). Eight weeks after STZ injection, blood glucose levels and renal function were assessed in mice. Mouse renal tissues were analyzed via hematoxylin-eosin, periodic acid-Schiff, and TdT-mediated dUTP nick-end labeling staining. Immunohistochemistry/Western blot were employed for the detection of MTERF1 expression. MPC-5 cells were treated with high glucose (HG) (30 mM) to establish the cellular model. MTERF1-overexpressing MPC-5 cells were constructed and treated with HG and the AMP-activated protein kinase (AMPK) inhibitor compound C (CC) for 24 h. Cell apoptosis was assessed by flow cytometry, cell viability by the cell counting kit-8 assay, mtDNA copy number by real-time quantitative PCR, adenosine triphosphate (ATP) production by ultraviolet spectrophotometric method, mitochondrial reactive oxygen species (mtROS) by MitoSox, and mitochondrial membrane potential (MMP) by JC-1. MTERF1 protein expression and AMPK/mammalian target of rapamycin (mTOR) signaling pathway activity were measured via Western blot.

The model group (relative to the control group) exhibited a significant rise in blood glucose, urine volume, urinary albumin, and urine albumin-creatinine ratio, along with significantly aggravated glomerular injury and markedly increased glycogen deposition and decreased MTERF1 expression in mouse renal tissue. In in vitro experiments, compared with the normal glucose (NG) group, the HG group showed increased apoptosis and reduced cell activity, accompanied by significantly decreased MTERF1 protein expression, mtDNA copy number, and ATP content. Compared to the HG+oe-NC group, the HG+oe-MTERF1 group showed significant increases in mtDNA copy number, ATP content, MMP, and AMPK/mTOR signaling pathway activity, while demonstrating decreased mtROS production. The HG+oe-MTERF1+CC group exhibited significant reductions in mtDNA copy number, ATP production, and AMPK/mTOR signaling pathway activity compared to the HG+oe-MTERF1 group, but displayed elevated mtROS levels.

Over-expression of MTERF1 can alleviate HG-induced damage of mtDNA replication and mitochondrial dysfunction in podocytes via activating the AMPK/mTOR signaling pathway, thus improving DN.