Importance of abnormal bone metabolism in the acceleration of atherosclerosis in hemodialysis patients.

Increases in serum calcium and phosphate are known as main risk factors for cardiovascular mortality in hemodialysis patients. However, increased phosphate, a definite mortality risk in the general population, should be more remarkable in hemodialysis patients, as their renal capacity to excrete phosphate into urine is negligible. Phosphate acts directly and indirectly to cause vascular injury by stimulating the apoptosis of vascular endothelial cells and the vascular calcification of vascular smooth muscle cells. Bone releases not only phosphate but also calcium during bone resorption. An increased calcium load reduces bone turnover by suppressing parathyroid function, resulting in the formation of adynamic bone disease. Adynamic bone disease is a major risk factor for ectopic calcification in areas including the vascular wall by diminishing the capacity of bone to absorb surplus calcium and phosphate in the circulation. Therefore, it is recognized that the maintenance of bone turnover within a normal range might be the most important strategy to protect against the development of vascular calcification and to attenuate the load of phosphate and calcium, particularly in hemodialysis patients.