Oxoglutarate dehydrogenase-L regulates mitochondrial metabolism reprogramming of renal tubular epithelial cells to alleviate renal fibrosis

To investigate the role and underlying mechanisms of oxoglutarate dehydrogenase-L (OGDHL) in renal fibrosis.

Twelve male wild-type C57BL/6J mice (8 weeks old, weighting about 25 g) were randomly divided into control group and model group (n=6). A mouse model of renal fibrosis was established by unilateral ureteral obstruction (UUO). HE staining, immunofluorescence assay, and immunohistochemical and Masson staining were applied to assess the extent of renal fibrosis. Human kidney-2 proximal tubule cell line (HK-2) were randomly divided into blank plasmid group (Vector), OGDHL overexpression group (OGDHL OE), blank plasmid + TGF-β1 treatment group (TGF-β1+Vector), TGF-β1 treatment and OGDHL overexpression group (TGF-β1+OGDHL OE). Transmission electron microscopy (TEM) was employed to observe mitochondrial morphology. RT-qPCR, Western blotting and immunofluorescence assay were used to detect the expression levels of OGDHL and mitochondrial metabolism-related genes. Adenosine triphosphate (ATP) level, oxygen consumption rate (OCR), extracellular acidification rate (ECAR) and other mitochondrial metabolism-related indicators were detected with corresponding reagent kits and Agilent Seahorse.

UUO operation resulted in obvious thinning of the renal cortex, significant hydronephrosis. HE staining revealed that tubular atrophy accompanied by dilated tubular lumens in the kidneys. Immunofluorescence, immunohistochemical and Masson staining showed obvious renal fibrosis after UUO operation. In the mouse model of renal fibrosis, the expression of OGDHL was decreased by 82.9% at mRNA level (P<0.001) and 81.9% at protein level (P<0.001), the production of mitochondrial ATP was reduced by 0.970±0.151 µmol/L (P<0.01), and notable damaged mitochondrial structure was observed, with maximum breathing capacity decreased by 25.260±1.920 pmol/min (P<0.001), expression levels of fatty acid oxidation-related genes were declined by 50.2% (P<0.05), while glycolysis was enhanced, with the genes related to glycolysis increased by 2.5 times when compared with those in the control group (P<0.05). After OGDHL overexpression, mitochondrial morphological damage was significantly improved, ATP production was increased by 0.980±0.090 µmol/L (P<0.05), with significantly alleviated energy metabolism disorder and renal fibrosis (P<0.05).

OGDHL regulates mitochondrial metabolic reprogramming of renal tubular epithelial cells to alleviate fibrosis, suggesting that OGDHL may be a new therapeutic target for renal fibrosis.