Vitamin D Auto-/Paracrine System Is Involved in Modulation of Glucocorticoid-Induced Changes in Angiogenesis/Bone Remodeling Coupling

Figure 6

A schematic summary of the results obtained in the study. Osteoporosis was characterized by an impairment of angiogenesis/osteoblastogenesis/osteoclastogenesis coupling that led to a decrease in whole-bone biomechanical parameters of femurs and bone turnover characteristics; vitamin D₃ demonstrated ameliorative action in prednisolone-induced osteoporosis. 25(OH)D: 25-dihydroxyvitamin D; ALP: alkaline phosphatase; Ca⁺⁺: calcium; CYP27B1: 25(OH)D-1α-hydroxylase; P_i: inorganic phosphate; RANK: receptor activator of nuclear factor κB; VDR: vitamin D receptor; VEGF-A: vascular endothelial growth factor A. Blue normal arrows indicate a positive effect; black normal arrows indicate a link/influence;  ⟶: direct;  ↔: bidirectional; ?: points that need to be addressed by future research.