EPO and diabetic kidney disease: HIF-1α, the principal regulatory component for hypoxic adaptation, plays a significant role in the pathogenesis and progression of DKD through several mechanisms, including the induction of angiogenesis, upregulation of erythropoietin (EPO) expression, suppression of oxidative stress and inflammatory responses, regulation of apoptosis, promotion of mitochondrial autophagy, and inhibition of fibrosis and vascular calcification.