ANXA1 improves mitochondrial homeostasis through uncoupling protein 1 in diabetic nephropathy

Diabetic nephropathy (DN) is a major public health concern. Our previous study found that annexin A1 (ANXA1) alleviated DN by improving mitochondrial homeostasis. However, the underlying mechanism is not fully clear yet.

This study aimed to explore mechanisms by which ANXA1 improves mitochondrial homeostasis and identify novel therapeutic targets for DN.

Diabetic Anxa1^-/-/uncoupling protein 1 (Ucp1)^-/- mice and renal Ucp1/cardiolipin synthase 1 (Crls1)-overexpressing mice were constructed. Diabetes was established using high-fat diet (HFD) plus streptozotocin (STZ). CL316243 was used to upregulate UCP1 in db/db mice. Knockdown and overexpression in proximal tubular epithelial cells (PTECs) were constructed. Metabolomics and lipidomics were applied.

Transcriptomics revealed that Ucp1 was the most significantly downregulated mitochondria-associated gene in kidneys of diabetic Anxa1-KO mice. Functional validation demonstrated that local overexpression of Ucp1 in kidneys alleviated urine albumin-to-creatine ratio (uACR), kidney injuries in histopathology and mitochondrial fission in Anxa1-KO diabetic mice. In vitro, UCP1 silencing abolished the improvements of human recombinant ANXA1 on high glucose (HG)-induced inflammation, fibrosis and mitochondrial dysfunction in PTECs. Silencing/overexpression of ANXA1 reduced/increased the stability of transcription factor GATA binding protein 3 (GATA3) in HK-2 cells under HG conditions, respectively. GATA3 could bind to the proximal promoter region of UCP1, thereby enhancing its transcriptional activity. UCP1 was significantly upregulated in kidneys of DN patients and mice. UCP1 deficiency reduced renal cardiolipin and exacerbated diabetes-induced kidney injury, including aggravated uACR, interstitial inflammation and fibrosis, and enhanced mitochondrial fission. Mechanistically, UCP1 upregulated CRLS1 by modulating aristaless-related homeobox (ARX), thereby promoting cardiolipin biosynthesis and reducing mitochondrial fission. Therapeutically, pharmacological upregulation of UCP1 by CL316243 attenuated established DN in db/db mice.

ANXA1 stabilized GATA3 to upregulate UCP1, which promoted cardiolipin biosynthesis through the ARX/CRLS1 axis, inhibited mitochondrial fission, thereby alleviated DN. This study highlighted the therapeutic potential of targeting UCP1 in DN.