Anemia and fibroblast growth factor 23 elevation in chronic kidney disease: homeostatic interactions and emerging therapeutics

Anemia of Chronic Kidney Disease-A Narrative Review of Its Pathophysiology, Diagnosis, and Management

Anemia is one of the most common chronic kidney disease (CKD) complications. It negatively affects patients' quality of life and clinical outcomes. The pathophysiology of anemia in CKD involves the interplay of various factors such as erythropoietin (EPO) deficiency, iron dysregulation, chronic inflammation, bone marrow dysfunction, and nutritional deficiencies. Despite recent advances in understanding this condition, anemia still remains a serious clinical challenge in population of patients with CKD. Several guidelines have been published with the aim to systematize the diagnostic approach and treatment of anemia; however, due to emerging data, many recommendations vary between publications. Recent studies indicate a potential of novel biomarkers to evaluate anemia and related conditions such as iron deficiency, which is often present in CKD patients. Our article aims to summarize the pathophysiology of anemia in CKD, as well as the diagnosis and management of this condition, including novel therapeutic approaches such as hypoxia-inducible factor-prolyl hydroxylase inhibitors (HIF-PHI). Understanding these complex subjects is crucial for a targeted approach to diagnose and treat patients with anemia in CKD effectively.

Fibroblast Growth Factor 23 Bone Regulation and Downstream Hormonal Activity

Mineral homeostasis of calcium and phosphate levels is one critical component to the maintenance of bone mineral density (BMD) and strength. Diseases that disrupt calcium and phosphate balanced have highlighted not only the role these minerals play in overall bone homeostasis, but also the factors, hormones and downstream transporters, responsible for mineral metabolism. The key phosphaturic hormone elucidated from studying rare heritable disorders of hypophosphatemia is Fibroblast Growth Factor 23 (FGF23). FGF23 is predominantly secreted from bone cells in an effort to maintain phosphate balance by directly controlling renal reabsorption and indirectly affecting intestinal uptake of this mineral. Multiple factors have been shown to enhance bone mRNA expression; however, FGF23 can also undergo proteolytic cleavage to control secretion of the biologically active form of the hormone. The review focuses specifically on the regulation of FGF23 and its secretion from bone as well as its hormonal actions under physiological and disease conditions.

Dapagliflozin Ameliorates Renal Tubular Ferroptosis in Diabetes via SLC40A1 Stabilization

Tubular injury has been shown to play a critical role in the morbidity of diabetic kidney disease (DKD); ferroptosis often occurs in tubules during renal disease development. This study was aimed at evaluating the inhibitory effects and potential mechanism of dapagliflozin (DAPA) against diabetic-related ferroptosis in the kidney. C57BL/6 mice were fed a high-fat diet (HFD) for 12 weeks, administered a small dose of streptozocin (STZ) for three consecutive days by intraperitoneal injection, and then orally administered dapagliflozin (10 mg/kg/day) for 8 weeks. Mouse blood and urine samples were collected, and their renal cortices were harvested for subsequent investigations. The effects of DAPA were also evaluated in HK-2 cells subjected to simulated diabetic conditions through excess glucose or palmitic acid (PA) administration. DAPA significantly ameliorated tubular injury independently of glycemic control in diabetic model mice. In vivo and in vitro investigations showed that dapagliflozin ameliorated tubular injury by inhibiting ferroptosis. Docking experiments demonstrated that dapagliflozin and SLC40A1 could bind with each other and may consequently reduce ubiquitination degradation. In conclusion, in this study, the tubular protective effects of DAPA, irrespective of glycemic control, were observed in a diabetic mouse model. DAPA ameliorated ferroptosis during diabetic tubular injury via SLC40A1 stabilization, and this may be the mechanism underlying its action. To the best of our knowledge, this is the first study to investigate the ferroptosis inhibitory effects of DAPA in the treatment of DKD.