No abstract

Chronic kidney disease (CKD) has been recognized as a significant public health problem, with 20 million Americans, or 11% of the adult population, currently living with CKD. Life expectancy in patients with CKD is limited by the development of disturbances of mineral metabolism, which occurs in virtually all patients during the progression of their disease, and is associated with bone loss and fractures, cardiovascular disease, immune suppression, and increased mortality. As kidney disease develops, there is decreased functional renal mass and a reduction in renal 1alpha-hydroxylase activity and thus in renal production of calcitriol at very early CKD stages. Recently, a potentially important role of vitamin D receptor activation (VDRa) in the survival of patients undergoing dialysis has been suggested. Beyond the effect on parathyroid hormone suppression, the pleiotropic effect of vitamin D has been associated with improvement of cardiovascular risk factors, including increased renin activity, hypertension, inflammation, insulin resistance, diabetes, and albuminuria. However, the current K/DOQI and KDIGO recommendations limit the administration of VDRa agents for treatment of hyperparathyroidism only. The role of vitamin D administration in the different CKD stages will be discussed in this review.

High adenine phosphate (HAP) diet serves as an animal model of chronic renal failure (RF). Induction of RF and establishment of end organ damage require long exposure periods to this diet. Previously, we have shown that RF is reversible after diet cessation even after protracted administration. In this study, we explored the underlying renal changes and cellular pathways occurring during administration and after cessation of the diet. Kidneys were obtained from rats fed HAP diet for 7 weeks, and from rats fed HAP diet followed a 10 week recovery period on normal diet. The kidneys of HAP diet group were significantly enlarged due to tubular injury characterized by massive cystic dilatation and crystal deposition. Kidney injury was associated with markers of apoptosis as well as with activation of apoptosis related pathways. Diet cessation was associated with a significant reduction in kidney size, tubules diameter, and crystals deposition. The recovery from renal injury was coupled with regression of apoptotic features. This is the first study showing the potential reversibility of long standing RF model, allowing optimal evaluation of uremia-chronic effects.

Osteoporosis (OP), the most frequent bone disease affecting the general population, is associated with high fracture risk. Patients with impaired kidney function have bone and mineral disturbances leading to extraskeletal calcifications and complex changes in bone turnover that predispose them to increased fracture risk accompanied by increased morbidity and mortality. The combination of these two bone disorders seems to have an additive effect with regard to fracture risk and its outcome, so that appropriate diagnosis and treatment of this disorder should be of primary concern when approaching patients with kidney disease. Nevertheless, the clinical and laboratory diagnostic tools used to identify OP in the general population do not suit the requirement for detecting the complex bone and metabolic changes that occur with chronic kidney disease, leading to the lack of or the initiation of inappropriate therapy. This review will focus on the bone pathophysiologic processes involved in OP and renal osteodystrophy and address some of the problems associated with our current diagnostic tools and aspects of the therapeutic approaches.