Risk factors for developing osteoporosis in diabetic kidney disease and its correlation with calcium-phosphorus metabolism, FGF23, and Klotho

BACKGROUND The progression of diabetic kidney disease (DKD) affects the patient's kidney glomeruli and tubules, whose normal functioning is essential for maintaining normal calcium (Ca) and phosphorus (P) metabolism in the body. The risk of developing osteoporosis (OP) in patients with DKD increases with the aggravation of the disease, including a higher risk of fractures, which not only affects the quality of life of patients but also increases the risk of death. AIM To analyze the risk factors for the development of OP in patients with DKD and their correlation with Ca-P metabolic indices, fibroblast growth factor 23 (FGF23), and Klotho. METHODS One hundred and fifty-eight patients with DKD who were admitted into the Wuhu Second People's Hospital from September 2019 to May 2021 were selected and divided into an OP group (n = 103) and a normal bone mass group (n = 55) according to their X-ray bone densitometry results. Baseline data and differences in Ca-P biochemical indices, FGF23, and Klotho were compared. The correlation of Ca-P metabolic indices with FGF23 and Klotho was discussed, and the related factors affecting OP in patients with DKD were examined by multivariate logistic regression analysis. RESULTS The OP group had a higher proportion of females, an older age, and a longer diabetes mellitus duration than the normal group (all P < 0.05). Patients in the OP group exhibited significantly higher levels of intact parathyroid hormone (iPTH), blood P, Ca-P product (Ca x P), fractional excretion of phosphate (FeP), and FGF23, as well as lower estimated glomerular filtration rate, blood Ca, 24-hour urinary phosphate excretion (24-hour UPE), and Klotho levels (all P < 0.05). In the OP group, 25-(OH)-D3, blood Ca, and 24-hour UPE were negatively correlated with FGF23 and positively correlated with Klotho. In contrast, iPTH, blood Ca, Ca x P, and FeP exhibited a positive correlation with FGF23 and an inverse association with Klotho (all P < 0.05). Moreover, 25-(OH)-D3, iPTH, blood Ca, FePO4, FGF23, Klotho, age, and female gender were key factors that affected the lumbar and left femoral neck bone mineral density. CONCLUSION The Ca-P metabolism metabolic indexes, FGF23, and Klotho in patients with DKD are closely related to the occurrence and development of OP.