maxacalcitol and Cardiovascular-Diseases

The 'classical' effects of vitamin D receptor activator or agonist (VDRA) therapy for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease primarily involves suppressive effects on the parathyroid gland, and regulation of calcium and phosphorus absorption in the intestine and mobilisation in bone. Observational studies in haemodialysis patients report improved cardiovascular and all-cause survival among those receiving VDRA therapy compared with those not on VDRA therapy. Among VDRAs, the selective VDRA paricalcitol has been associated with greater survival than nonselective VDRAs, such as calcitriol (1,25-dihydroxyvitamin D(3)). The survival benefits of paricalcitol appear to be linked, at least in part, to 'nonclassical' actions of VDRAs, possibly through VDRA-mediated modulation of gene expression. In cardiovascular tissues, VDRAs are reported to have beneficial effects such as anti-inflammatory and antithrombotic effects, inhibition of vascular smooth muscle cell proliferation, inhibition of vascular calcification and stiffening, and regression of left ventricular hypertrophy. VDRAs are also reported to negatively regulate the renin-angiotensin system, which plays a key role in hypertension, myocardial infarction and stroke. The selective VDRAs, paricalcitol and maxacalcitol, are associated with direct protective effects on glomerular architecture and antiproteinuric effects in response to renal damage. Paricalcitol regulates several cardiovascular and renal parameters more favourably than nonselective VDRAs. Complex nonclassical effects, which are not clearly understood, possibly contribute to the improved survival seen with VDRAs, especially paricalcitol.

Topics: Animals; Bone Density Conservation Agents; Calcitriol; Cardiovascular Diseases; Chronic Disease; Ergocalciferols; Humans; Hydroxycholecalciferols; Hyperparathyroidism, Secondary; Kidney Diseases; Receptors, Calcitriol; Survival Rate

Although it effectively suppresses parathyroid hormone (PTH) secretion, vitamin D [1,25(OH)(2)D(3)] therapy often causes tissue calcification over the long term. In patients on chronic dialysis, cardiovascular calcification is clearly linked to an unfavourable prognosis. In pre-dialysis patients, renal calcification of the kidney leads to the deterioration of renal function.. We compared the propensities of 22-oxacalcitriol (OCT), with lesser calcaemic action, and 1,25(OH)(2)D(3) for producing their potential side effects in rats: (i) metastatic calcification of heart and aorta, and (ii) renal dysfunction with nephrocalcinosis, using the same effective doses for hyperparathyroidism. OCT (1.25 and 6.25 micro g/kg) or 1,25(OH)(2)D(3) (0.125 and 0.625 micro g/kg) solutions were administered intravenously to subtotally nephrectomized (SNX) rats three times weekly for 2 weeks.. Despite the suppression of PTH to comparable levels, the calcification of the hearts, aortas and kidneys in the 1,25(OH)(2)D(3)-treated group was significantly greater than in the OCT-treated group. Of interest was that, in the OCT (6.25 micro g/kg) group, the degree of calcification in hearts, aortas and kidneys were distinctly lower than those in the 1,25(OH)(2)D(3) (0.125 micro g/kg) group despite the comparable serum Ca x Pi products. Therefore, there may be different mechanisms behind the calcifications resulting from OCT and 1,25(OH)(2)D(3). Deterioration of renal function, tubular changes, and atypical hyperplasia of proximal tubules associated with calcification were more severe in the 1,25(OH)(2)D(3)-treated group than in the OCT-treated group.. These results indicate that OCT may be an effective agent for the suppression of PTH with a lesser risk of cardiovascular calcification or deterioration of residual renal function.

Topics: Animals; Calcinosis; Calcitriol; Cardiovascular Diseases; Cardiovascular System; Kidney; Kidney Diseases; Male; Nephrectomy; Parathyroid Hormone; Rats; Rats, Sprague-Dawley; Vitamins