Marked suppression of secondary hyperparathyroidism by intravenous administration of 1,25-dihydroxy-cholecalciferol in uremic patients

Calcitriol resistance in hemodialysis patients with secondary hyperparathyroidism

Nonselective vitamin D receptor activators (VDRA), such as calcitriol and alfacalcidol, have been successfully used in the treatment of secondary hyperparathyroidism (SHPT) in hemodialysis. Despite their beneficial effects on the control of serum PTH levels, their use has been limited by intolerance (development of hypercalcemia and hyperphosphatemia with consecutive cardiovascular toxicity). Apart from becoming intolerant, in 20-30 % of patients who use nonselective VDRA, serum PTH levels do not decrease appropriately despite increasing doses of these agents. These patients are considered calcitriol-resistant patients. Thus, calcitriol resistance and intolerance are two sides of the same coin: active vitamin D failure. Despite the clinical relevance of active vitamin D failure, definitions of resistance and intolerance are imprecise and have varied over time. More selective VDRA claim to produce less hypercalcemia and hyperphosphatemia and could help clinicians to overcome intolerance. Also, some studies have also shown that paricalcitol can be even useful in resistant patients. Significant limitations of iPTH as a reliable and useful clinical biomarker have been increasingly appreciated. There is evidence that intact PTH concentration must differ by 72 % between any two measurements before it can be considered a significant change. VDR polymorphisms could be involved in the development of SHPT in CKD patients. Interestingly, a higher incidence of the b allele of the VDR BsmI gene variant has been shown to be present in SHPT. The BsmI genotype can also affect the response of hemodialysis to IV calcitriol. A challenge for the future will be to establish biomarkers such as laboratory determinations or ultrasound findings that can help us to early identify those patients who will not respond appropriately to calcitriol or exhibit intolerable side effects .

Vitamin D receptor activation, left ventricular hypertrophy and myocardial fibrosis

BACKGROUND

Left ventricular hypertrophy (LVH), a common complication in chronic kidney disease (CKD), is associated with high cardiovascular mortality. The aim of this experimental study was to analyze the effect of different vitamin D receptor activators (VDRAs) on both LVH and myocardial fibrosis in chronic renal failure (CRF).

METHODS

Male Wistar rats with CRF, carried out by 7/8 nephrectomy, were treated intraperitoneally with equivalent doses of VDRAs (calcitriol, paricalcitol and alfacalcidol, 5 days per week) during 4 weeks. A placebo group (CRF + vehicle) and a Sham group with normal renal function served as controls. Biochemical, morphological, functional and molecular parameters associated with LVH were evaluated, as well as cardiac fibrosis, collagen I, transforming growth factor β1 (TGFβ1) and matrix metalloproteinase-1 (MMP1) expression.

RESULTS

All VDRAs treatment prevented LVH, with values of cardiomyocyte size, LV wall and septum thickness and heart-body weight ratio similar to those observed in the Sham group. At molecular levels, all VDRAs attenuated atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression compared with CRF + vehicle. The phosphorylation of ERK1/2, a signal for activating growth, was stimulated in the CRF + vehicle group; VDRAs use prevented this activation. Paricalcitol was the only VDRA used that maintained in the normal range all parameters associated with myocardial fibrosis (total collagen, collagen I, TGFβ1 and MMP1).

CONCLUSIONS

Our findings demonstrated that the three VDRAs used induced similar changes in bone metabolic parameters and LVH. In addition, paricalcitol was the only VDRA which showed a relevant beneficial effect in the reduction of myocardial fibrosis, a key factor in the myocardial dysfunction in CKD patients.

Impaired vitamin D metabolism in CKD

Vitamin D metabolism consists of both production and catabolism, which are enzymatically driven and highly regulated. Renal vitamin D metabolism requires filtration and tubular reabsorption of 25-hydroxyvitamin D and is regulated by parathyroid hormone, fibroblast growth factor-23, and 1,25-dihydroxyvitamin D. In chronic kidney disease, renal production of 1,25-dihydroxyvitamin D from 25-hydroxyvitamin D is reduced. In addition, pharmacokinetic studies and epidemiologic studies of 24,25-dihydroxyvitamin D, the most abundant product of 25-hydroxyvitamin D catabolism by CYP24A1, suggest that vitamin D catabolism also is reduced. New insights into the mechanisms and regulation of vitamin D metabolism may lead to novel approaches to assess and treat impaired vitamin D metabolism in chronic kidney disease.

Efficacy and safety of oral doxercalciferol in the management of secondary hyperparathyroidism in chronic kidney disease stage 4

This study was carried out to evaluate the efficacy and safety of doxercalciferol as therapy for secondary hyperparathyroidism (SHPT) in patients with chronic kidney disease (CKD) stage 4 in a prospective clinical trial. A total of 35 CKD-4 patients who had a baseline parathyroid hormone (iPTH) >150 pg/mL and had not received any vitamin D analog in the preceding 8 weeks were followed up at intervals of 6 weeks for 18 weeks on oral therapy with doxercalciferol. The starting dose was 1.5 μg/day, and the dose was increased in steps of 1 μg/day if iPTH did not decrease by at least 30% on the subsequent visit. Doxercalciferol was stopped temporarily if low iPTH (<70 pg/mL), hypercalcemia (>10.7 mg/dL), or severe hyperphosphatemia (>8.0 mg/dL) occurred, and was restarted at a lower dose on reversal of these abnormalities. Calcium acetate was the only phosphate binder used. Mean iPTH decreased by 35.4 ± 4.4% from 381.7 ± 31.3 pg/mL to 237.9 ± 25.7 pg/mL (P < 0.001). The proportion of patients who achieved 30% and 50% suppression of iPTH levels was 83% and 72%, respectively. Mean serum calcium, phosphorus, and calcium-phosphorus product values did not differ significantly from the baseline values. Four, two, and nine patients developed hypercalcemia, severe hyperphosphatemia, and high CaxP (>55), respectively. Almost all patients recovered to an acceptable level within 2 weeks of stopping doxercalciferol and adjusting the phosphate binder dose. In all, 21 patients required temporary stoppage of therapy. Most of them were restarted on therapy at a reduced dose during the study. It can, therefore, be concluded that doxercalciferol is effective in controlling SHPT in CKD-4 patients with an acceptable risk of hyperphosphatemia and hypercalcemia.

Randomized controlled trial to compare the efficacy and safety of oral paricalcitol with oral calcitriol in dialysis patients with secondary hyperparathyroidism

AIM

The objective of the study was to compare the efficacy and safety of oral paricalcitol with oral calcitriol for treating secondary hyperparathyroidism.

METHODS

We conducted the first multicenter open-labelled parallel group randomized controlled trial in 66 patients on dialysis. Patients were randomized to paricalcitol or calcitriol at a 3:1 dose ratio and adjusted to maintain intact parathyroid hormone (iPTH) level between 150-300 pg/mL, serum calcium ≤2.74 mmol/L and calcium-phosphate product ≤5.63 mmol(2) /L(2). The primary end point was the proportion of patients who achieved >30% reduction in iPTH.

RESULTS

At 24 weeks, 22 (61.1%) patients in the paricalcitol and 22 (73.3%) in the calcitriol group had achieved the primary end-point (P-value = 0.29). The cumulative proportion of patients who achieved the end-point at 6 weeks, 12 weeks and 24 weeks were 50%, 80.6% and 86.1%, respectively, in paricalcitol and 53.3%, 86.7% and 86.7%, respectively, in the calcitriol group (P-value = 0.67). Median time to the end-point was 6 weeks in both groups. There were no significant differences in iPTH level at any time during the study. The median reduction in iPTH at 24 weeks was 48.4% in the paricalcitol group and 41.9% in the calcitriol group (P-value = 0.6). The median maximal iPTH reduction was 77.1% (paricalcitol) and 83.7% (calcitriol), P-value = 0.3. Serum calcium and incidence of hypercalcaemia did not differ between groups. 16.7% of patients in both groups had at least one episode of hypercalcaemia (serum calcium >2.74 mmol/L). Other adverse events were similar between groups.

CONCLUSION

Our study suggests that oral paricalcitol has similar efficacy and safety to oral calcitriol.

Effect of paricalcitol on renin and albuminuria in non-diabetic stage III-IV chronic kidney disease: a randomized placebo-controlled trial

BACKGROUND

Vitamin D receptor activators reduce albuminuria, and may improve survival in chronic kidney disease (CKD). Animal studies suggest that these pleiotropic effects of vitamin D may be mediated by suppression of renin. However, randomized trials in humans have yet to establish this relationship.

METHODS

In a randomized, placebo-controlled, double-blinded crossover study, the effect of oral paricalcitol (2 μg/day) was investigated in 26 patients with non-diabetic, albuminuric stage III-IV CKD. After treatment, plasma concentrations of renin (PRC), angiotensin II (AngII) and aldosterone (Aldo) were measured. GFR was determined by 51Cr-EDTA clearance. Assessment of renal NO dependency was performed by infusion of NG-monomethyl-L-arginine (L-NMMA). Albumin excretion rate (AER) was analyzed in 24-h urine and during 51Cr-EDTA clearance.

RESULTS

Paricalcitol did not alter plasma levels of renin, AngII, Aldo, or urinary excretion of sodium and potassium. A modest reduction of borderline significance was observed in AER, and paricalcitol abrogated the albuminuric response to L-NMMA.

CONCLUSIONS

In this randomized, placebo-controlled trial paricalcitol only marginally decreased AER and did not alter circulating levels of renin, AngII or Aldo. The abrogation of the rise in albumin excretion by paricalcitol during NOS blockade may indicate that favourable modulation of renal NO dependency could be involved in mediating reno-protection and survival benefits in CKD.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01136564.

Mineral metabolic abnormalities and mortality in dialysis patients

The survival rate of dialysis patients, as determined by risk factors such as hypertension, nutritional status, and chronic inflammation, is lower than that of the general population. In addition, disorders of bone mineral metabolism are independently related to mortality and morbidity associated with cardiovascular disease and fracture in dialysis patients. Hyperphosphatemia is an important risk factor of, not only secondary hyperparathyroidism, but also cardiovascular disease. On the other hand, the risk of death reportedly increases with an increase in adjusted serum calcium level, while calcium levels below the recommended target are not associated with a worsened outcome. Thus, the significance of target levels of serum calcium in dialysis patients is debatable. The consensus on determining optimal parathyroid function in dialysis patients, however, is yet to be established. Therefore, the contribution of phosphorus and calcium levels to prognosis is perhaps more significant. Elevated fibroblast growth factor 23 levels have also been shown to be associated with cardiovascular events and death. In this review, we examine the associations between mineral metabolic abnormalities including serum phosphorus, calcium, and parathyroid hormone and mortality in dialysis patients.

Meta-analysis: the efficacy and safety of paricalcitol for the treatment of secondary hyperparathyroidism and proteinuria in chronic kidney disease

Introduction. Previous studies have demonstrated the safety and efficacy of using Paricalcitol for the treatment of secondary hyperparathyroidism (SHPT) in patients on dialysis. The aim of the current meta-analysis was to assess the safety and efficacy of Paricalcitol for the management of SHPT in patients with chronic kidney disease (CKD) not yet on dialysis. A secondary aim was to determine if sufficient data was available to assess the effect of Paricalcitol for the management of proteinuria. Methods. A meta-analysis was conducted using the Cochrane Collaboration's RevMan 4.2 software. Results. Paricalcitol is effective in lowering PTH in patients with CKD not yet on dialysis and is also effective in lowering proteinuria in diabetic CKD patients. However, we uncovered a safety signal identifying an elevated calcium phosphate product and a trend towards the development of hypercalcemia. A phosphate elevation was not demonstrated because the target used in the clinical studies was a P > 5.5 mg/dl, a value appropriate for dialysis patients and not CKD patients. Conclusion. Although Paricalcitol is effective in lowering PTH, we advise caution in the use of any active Vitamin D analogues in patients with CKD because of the potential risk of exacerbating vascular calcification.

The serum 24,25-dihydroxyvitamin D concentration, a marker of vitamin D catabolism, is reduced in chronic kidney disease

Chronic kidney disease is characterized, in part, as a state of decreased production of 1,25-dihydroxyvitamin D (1,25(OH)(2)D); however, this paradigm overlooks the role of vitamin D catabolism. We developed a mass spectrometric assay to quantify serum concentration of 24,25-dihydroxyvitamin D (24,25(OH)(2)D), the first metabolic product of 25-hydroxyvitamin D (25(OH)D) by CYP24A1, and determined its clinical correlates and associated outcomes among 278 participants with chronic kidney disease in the Seattle Kidney Study. For eGFRs of 60 or more, 45-59, 30-44, 15-29, and under 15 ml/min per 1.73 m(2), the mean serum 24,25(OH)(2)D concentrations significantly trended lower from 3.6, 3.2, 2.6, 2.6, to 1.7 ng/ml, respectively. Non-Hispanic black race, diabetes, albuminuria, and lower serum bicarbonate were also independently and significantly associated with lower 24,25(OH)(2)D concentrations. The 24,25(OH)(2)D concentration was more strongly correlated with that of parathyroid hormone than was 25(OH)D or 1,25(OH)(2)D. A 24,25(OH)(2)D concentration below the median was associated with increased risk of mortality in unadjusted analysis, but this was attenuated with adjustment for potential confounding variables. Thus, chronic kidney disease is a state of stagnant vitamin D metabolism characterized by decreases in both 1,25(OH)(2)D production and vitamin D catabolism.

Pharmacotherapy of chronic kidney disease and mineral bone disorder

INTRODUCTION

Disturbances of the bone and mineral metabolism are a common complication of chronic kidney disease (CKD); these disturbances are known as CKD-mineral bone disorder (CKD-MBD). A better understanding of the pathophysiological mechanisms of CKD-MBD, along with its negative impact on other organs and systems, as well as on survival, has led to a shift in the treatment paradigm of this disorder. The use of phosphate binders changed dramatically over the last decade when noncalcium-containing phosphate binders, such as sevelamer and lanthanum carbonate, became possible alternative treatments to avoid calcium overload. Vitamin D receptor activators, such as paricalcitol and doxercalciferol, with fewer calcemic and phosphatemic effects, have also been introduced to control parathormone production and the interest in native vitamin D supplementation has grown. Furthermore, a new drug class, the calcimimetics, has recently been introduced into the therapeutic arsenal for treating secondary hyperparathyroidism.

AREAS COVERED

This review discusses the advantages and disadvantages of the above pharmacological options to treat CKD-MBD.

EXPERT OPINION

The individual-based use of phosphate binders, vitamin D and calcimimetics, separately or in combination, constitute a reasonable approach to treat CKD-MBD. These treatments aim to achieve a rigorous control of phosphorus and parathormone levels, while avoiding calcium overload.

Mild renal dysfunction is a risk factor for a decrease in bone mineral density and vertebral fractures in Japanese postmenopausal women

CONTEXT

The effect of mild renal dysfunction on bone mineral density and fracture risk is uncertain.

OBJECTIVE

We evaluated whether mild renal dysfunction would affect bone mineral density (BMD) and the risk of vertebral fractures (VFs) in 659 postmenopausal women.

MAIN OUTCOME MEASURES

Creatinine clearance (CCr) and the estimated glomerular filtration rate (eGFR) were calculated using the Cockcroft-Gault and the Modification of Diet in Renal Disease formulas, respectively. BMD was measured by dual-energy x-ray absorptiometry. Renal function was categorized by the criteria of the Kidney Disease Outcomes Quality Initiative Committee.

RESULTS

Comparison of fracture prevalence by chronic kidney disease stages revealed that the group of stage 3 or greater by eGFR had a significantly higher rate of VFs (45.3%) than stages 1 (23.8%) and 2 (25.3%) groups. In the stage 2 group, there were significant positive correlations between eGFR and BMD values at the femoral neck and radius as well as between CCr and BMD values at all sites. Moreover, postmenopausal women with VFs had lower eGFR and CCr than those without VFs in stage 2. When multivariable logistic regression analysis was performed with the presence of VFs as a dependent variable and CCr levels adjusted for years after menopause, smoking habit, alcohol intake, and lumbar spine BMD as an independent variable, CCr levels were identified as a factor associated with the presence of VFs in postmenopausal women with chronic kidney disease stage 2.

CONCLUSIONS

The present study indicates that postmenopausal women with mild renal dysfunction are at increased risk for BMD decrease and VFs.

Comparison of active vitamin D compounds and a calcimimetic in mineral homeostasis

The differential effects between cinacalcet and active vitamin D compounds on parathyroid function, mineral metabolism, and skeletal function are incompletely understood. Here, we studied cinacalcet and active vitamin D compounds in mice expressing the null mutation for Cyp27b1, which encodes 25-hydroxyvitamin D-1α-hydroxylase, thereby lacking endogenous 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. Vehicle-treated mice given high dietary calcium had hypocalcemia, hypophosphatemia, and marked secondary hyperparathyroidism. Doxercalciferol and 1,25(OH)(2)D(3) each normalized these parameters and corrected both the abnormal growth plate architecture and the diminished longitudinal bone growth observed in these mice. In contrast, cinacalcet suppressed serum parathyroid hormone (PTH) cyclically and did not correct the skeletal abnormalities and hypocalcemia persisted. Vehicle-treated mice given a "rescue diet" (high calcium and phosphorus, 20% lactose) had normal serum calcium and PTH levels; cinacalcet induced transient hypocalcemia and mild hypercalciuria. The active vitamin D compounds and cinacalcet normalized the increased osteoblast activity observed in mice with secondary hyperparathyroidism; cinacalcet, however, increased the number and activity of osteoclasts. In conclusion, cinacalcet reduces PTH in a cyclical manner, does not eliminate hypocalcemia, and does not correct abnormalities of the growth plate. Doxercalciferol and 1,25(OH)(2)D(3) reduce PTH in a sustained manner, normalize serum calcium, and improve skeletal abnormalities.

Cholecalciferol supplementation in hemodialysis patients: effects on mineral metabolism, inflammation, and cardiac dimension parameters

BACKGROUND AND OBJECTIVES

Vitamin D deficiency is highly prevalent in chronic kidney disease. The aim of this study was to evaluate the effects of oral cholecalciferol supplementation on mineral metabolism, inflammation, and cardiac dimension parameters in long-term hemodialysis (HD) patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This 1-year prospective study included 158 HD patients. Serum levels of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)(2)D], intact parathyroid hormone, and plasma brain natriuretic peptide as well as circulating bone metabolism and inflammation parameters were measured before and after supplementation. Baseline 25(OH)D and 1,25(OH)(2)D levels were measured twice (end of winter and of summer, respectively). Therapy with paricalcitol, sevelamer, and darbepoietin was evaluated.

RESULTS

There was an increase in serum 25(OH)D and 1,25(OH)(2)D levels after supplementation. Conversely, serum calcium, phosphorus, and intact parathyroid hormone were decreased. There was a reduction in the dosage and in the number of patients who were treated with paricalcitol and sevelamer. Darbepoietin use was also reduced, with no modification of hemoglobin values. Serum albumin increased and C-reactive protein decreased during the study. Brain natriuretic peptide levels and left ventricular mass index were significantly reduced at the end of the supplementation.

CONCLUSIONS

Oral cholecalciferol supplementation in HD patients seems to be an easy and cost-effective therapeutic measure. It allows reduction of vitamin D deficiency, better control of mineral metabolism with less use of active vitamin D, attenuation of inflammation, reduced dosing of erythropoiesis-stimulating agents, and possibly improvement of cardiac dysfunction.

Effect of paricalcitol and cinacalcet on serum phosphate, FGF-23, and bone in rats with chronic kidney disease

Calcimimetics activate the calcium-sensing receptor (CaR) and reduce parathyroid hormone (PTH) by increasing the sensitivity of the parathyroid CaR to ambient calcium. The calcimimetic, cinacalcet, is effective in treating secondary hyperparathyroidism in dialysis patients [chronic kidney disease (CKD 5)], but little is known about its effects on stage 3-4 CKD patients. We compared cinacalcet and paricalcitol in uremic rats with creatinine clearances "equivalent" to patients with CKD 3-4. Uremia was induced in anesthetized rats using the 5/6th nephrectomy model. Groups were 1) uremic control, 2) uremic + cinacalcet (U+Cin; 15 mg x kg(-1) x day(-1) po for 6 wk), 3) uremic + paricalcitol (U+Par; 0.16 microg/kg, 3 x wk, ip for 6 wk), and 4) normal. Unlike U+Par animals, cinacalcet promoted hypocalcemia and marked hyperphosphatemia. The Ca x P in U+Cin rats was twice that of U+Par rats. Both compounds suppressed PTH. Serum 1,25-(OH)(2)D(3) was decreased in both U+Par and U+Cin rats. Serum FGF-23 was increased in U+Par but not in U+Cin, where it tended to decrease. Analysis of tibiae showed that U+Cin, but not U+Par, rats had reduced bone volume. U+Cin rats had similar bone formation and reduced osteoid surface, but higher bone resorption. Hypocalcemia, hyperphosphatemia, low 1,25-(OH)(2)D(3), and cinacalcet itself may play a role in the detrimental effects on bone seen in U+Cin rats. This requires further investigation. In conclusion, due to its effects on bone and to the hypocalcemia and severe hyperphosphatemia it induces, we believe that cinacalcet should not be used in patients with CKD without further detailed studies.

Monthly cholecalciferol administration in haemodialysis patients: a simple and efficient strategy for vitamin D supplementation

BACKGROUND

There is growing evidence of the usefulness of vitamin D supplementation in dialysis patients who are most often vitamin D deficient. Due to the long half-life of vitamin D, there is much interest in administering it intermittently for long-term adherence. However, there are no data to indicate which dosage would be most efficient. Objective. The aim was to assess the long-term efficiency and safety of a monthly oral dose of cholecalciferol (100 000 IU) in vitamin D-deficient haemodialysis (HD) patients.

METHODS

HD patients with a serum 25-hydroxyvitamin D (25(OH)D) level <75 nmol/L were enrolled in a 15-month prospective study. The exclusion criteria were as follows: use of any vitamin D derivatives, prescription of cinacalcet and bisphosphonates, uncontrolled hypercalcaemia (>2.55 mmol/L), hyperphosphataemia (>2 mmol/L) and severe secondary hyperparathyroidism (SHPT; serum PTH >600 pg/mL). Biological data were recorded in the following months: M-3, M0, M1, M3, M9 and M15. We aimed to maintain stable levels of the phosphate binder and oral and dialysate calcium during the course of the study.

RESULTS

Of the 250 patients screened, 161 were enrolled, and the results from 107 were recorded at the end of the study. Of these 107 patients, 56% were males, and the average age of the patient group was 66.4 +/- 15 years. Diabetics accounted for 36% of the total patients. The dialysis schedule ranged from 3 x 5 to 3 x 8 h, with a mean dialysate calcium concentration of 1.48 +/- 0.6 mmol/L. After 15 months, the mean serum 25(OH)D level increased from 32 +/- 13 to 105.8 +/- 27 nmol/L (P < 0.001) and plateaued after M3. Of the patients, 91% had a level higher than the target level (>75 nmol/L), while none had levels >200 nmol/L. The serum calcitriol (1,25(OH)(2)D) level increased from 13.7 +/- 14 to 45 +/- 13 pmol/L (P < 0.001) and plateaued after M9. The levels of serum PTH (median 295-190 pg/mL, P < 0.001), bone alkaline phosphatase (20.5 +/- 9-17.1 +/- 7 microg/L, P < 0.05) and beta-cross-laps (2.5 +/- 1-2.07 +/- 0.8 microg/L, P < 0.05) decreased significantly. No significant changes were observed in the values of the following: calcaemia, phosphataemia, blood pressure, serum albumin, haemoglobin and C-reactive protein.

CONCLUSIONS

Long-term monthly administration of oral cholecalciferol (100 000 IU) was a safe, effective, inexpensive and simple method for correcting vitamin D deficiency in almost 90% of the HD patients in this study and led to optimal compliance. The most evident consequences were a slight decrease in the levels of PTH and bone markers and an increase in the level of serum 1,25(OH)(2)D.

Vitamin D metabolism and vitamin D traditional and nontraditional, target organs: implications for kidney patients

Vitamin D plays an absolute essential role in human physiology. More than 60 types of cells possess vitamin D receptors (VDR) and more than 200 genes represent the target for VDR activation. The principle of the biological effect of vitamin D is gene control. In general, VDR activation inhibits cell differentiation and proliferation while promoting cell maturation and it also participates in the regulation of apoptosis (programmed cell death). Conventionally, vitamin D status is assessed according to the serum 25-hydroxyvitamin D concentration. Values between 30-60 ng/ml (70-150 nmol/l) are optimal. Low vitamin D status is associated with bone and mineral disturbances and also with many other pathological conditions. Studies have described association with susceptibility to some infections; higher risk of autoimmune diseases, association with some malignancies and many other complications. Low vitamin D status is common, but usually underestimated. The native vitamin D undergoes two-step hydroxylation to become biologically active. The second metabolic conversion is dependent on functional renal parenchyma. In advanced stages of chronic kidney disease (CKD) the renal activation of vitamin D sharply decreases regardless of the stores of native vitamin D, resulting in low concentration of active vitamin D. The parathyroid hyperactivity in advanced CKD represents the approved indication for pharmacological VDR activation. The therapeutic window of nonselective VDR activators is narrow. On the contrary, the effect of selective VDR activators (paricalcitol) in the intestine is much lower and therefore the activators are safer in terms of maintaining serum concentration of calcium and phosphate. Several recent observational studies demonstrated survival benefits of selective VDR activation in CKD patients. Theoretically, these drugs may, at least, partly cover the need for the systemic activation of VDR in kidney patients, but this assumption must be carefully examined. At present, the possible cardioprotectivity, renoprotectivity and other benefits of selective VDR activators are being intensively studied.

The calcimimetic AMG 641 abrogates parathyroid hyperplasia, bone and vascular calcification abnormalities in uremic rats

Calcimimetics and vitamin D sterols reduce serum parathyroid hormone (PTH) in patients with secondary hyperparathyroidism receiving dialysis, a disease state associated with parathyroid hyperplasia, vascular calcification, bone disease, and increased mortality. The aim of this study was to determine the effects of the research calcimimetic AMG 641 (Amgen, Inc., Thousand Oaks, CA) or calcitriol (Sigma Aldrich Corporation, St. Louis, MO) on vascular calcification in a rodent model of progressive uremia with accompanying secondary hyperparathyroidism induced by dietary adenine. Treatment effects on parathyroid gland hyperplasia and bone loss were also investigated. Rats were treated daily with vehicle, calcitriol (10 ng), AMG 641 (3 mg/kg), or no treatment during the 4 week period the animals were fed adenine. The uremia-induced increases in serum PTH levels were significantly attenuated by both AMG 641 (>90%) and calcitriol (approximately 50%). AMG 641 significantly reduced calcium-phosphorus product (CaxP) and significantly attenuated the development of both parathyroid hyperplasia and vascular calcification. In addition, AMG 641 prevented the defects in trabecular bone volume, trabecular number, and bone mineralization, as well as increases in trabecular spacing in this rodent model of secondary hyperparathyroidism. Calcitriol (10 ng/rat) decreased osteoid surface/bone surface, but had no effects on other bone parameters, or parathyroid hyperplasia (likely due to the lower PTH suppressive effect of calcitriol at the dose used in this study). However, this dose of calcitriol significantly exacerbated vascular calcification. These results suggest that calcimimetics can reduce the development of vascular calcification, parathyroid hyperplasia and bone abnormalities associated with secondary hyperparathyroidism.

Role of vitamin D in chronic kidney disease

Decline in renal function is related directly to cardiovascular mortality. However, traditional risk factors do not fully account for the high mortality in these patients. Activated vitamin D, a hormone produced by the proximal convoluted tubule of the kidney, appears to have beneficial effects beyond suppressing parathyroid hormone (PTH). However, activated vitamin D also can cause hypercalcemia and hyperphosphatemia in chronic kidney disease. Newer agents such as vitamin D receptor activators (eg, paricalcitol) suppress PTH with reduced risk of hypercalcemia and hyperphosphatemia. Recent evidence from animal and preliminary human studies supports an association between vitamin D receptor activators and reduced risk of cardiovascular disease deaths, irrespective of PTH levels. New pathways of vitamin D regulation also have been discovered, involving fibroblast growth factor-23 and klotho. Although considerable work has been performed to advance our understanding of the effects of vitamin D in health and chronic kidney disease, more investigations and randomized trials need to be performed to elucidate the mechanistic underpinnings of these effects.

Vitamin D's role in cell proliferation and differentiation

Vitamin D has pleiotropic effects that go beyond its traditional role in calcium homeostasis. Hundreds of genes with vitamin D receptor response elements directly or indirectly influence cell cycling and proliferation, differentiation, and apoptosis. Vitamin D compounds also have effects on cell function that are nongenomic. The noncalcemic actions of vitamin D influence normal and pathological cell growth, carcinogenesis, immune function, and cardiovascular physiology. This review examines many of the various mechanisms by which vitamin D alters cellular growth and differentiation and explores cell-specific factors that influence responsiveness to vitamin D.

Immunomodulation by a novel, dissociated Vitamin D analogue

The biologically active metabolite of vitamin D3, 1alpha,25-dihydroxyvitamin D3, has potent immunomodulatory activity; however, its clinical use is limited because of its hypercalcaemic activity in anti-inflammatory active doses. Here, we present ZK203278, a novel, structurally different vitamin D3 analogue with profound immunomodulatory activities. It potently inhibits lymphocyte proliferation in the mixed lymphocyte reaction, and release of cytokines that are central in inflammation, such as TNFalpha and IL-12 in the low nanomolar range. Similarly, expression of cell-surface molecules involved in cell adhesion and antigen presentation, e.g. to T cells, is down-regulated on human monocytes by low nanomolar concentrations of ZK203278. Potent anti-inflammatory activity has been demonstrated also in vivo in rodent disease models. ZK203278 inhibited allergic contact dermatitis in rodents after oral administration in doses approximately two orders of magnitude below the hypercalcaemic threshold dose. Moreover, ZK203278 significantly prolonged skin allograft survival in rats in well-tolerated doses. Altogether ZK203278, in contrast to 1alpha,25-dihydroxyvitamin D3, exerts considerable immunomodulatory activity at non-hypercalcaemic dosages and may have therapeutic potential for immune disorders or transplant rejection.

1-Alpha, 25-dihydroxy vitamin D3 inhibits osteoclastogenesis through IFN-beta-dependent NFATc1 suppression

1-Alpha, 25-dihydroxy vitamin D(3) (1alpha,25(OH)(2)D(3)), an active form of vitamin D(3), plays a critical role in calcium and bone metabolism. Although 1alpha,25(OH)(2)D(3) has been used for osteoporosis therapy, the direct role of 1alpha,25(OH)(2)D(3) on human osteoclastogenesis has not been well characterized. Here we show that 1alpha,25(OH)(2)D(3) treatment significantly inhibited human osteoclast formation at the early stage of differentiation in a concentration-dependent manner. 1alpha,25(OH)(2)D(3) inhibited the expression of nuclear factor of activated T cells c1 (NFATc1, also referred as NFAT2), an essential transcription factor for osteoclast differentiation, and upregulated the expression of interferon-beta (IFN-beta), a strong inhibitor of osteoclastogenesis in osteoclast progenitors. Inhibitory effects of 1alpha,25(OH)(2)D(3) on osteoclastogenesis and NFATc1 expression were restored by treatment with an antibody against IFN-beta, suggesting that upregulation of IFN-beta by 1alpha,25(OH)(2)D(3) treatment results in inhibition of NFATc1 expression, in turn interfering with osteoclast formation. Thus, our study may provide a molecular basis for the treatment of human bone diseases by 1alpha,25(OH)(2)D(3) through regulation of the IFN-beta and NFATc1 axis.

Treatment of secondary hyperparathyroidism in CKD patients with cinacalcet and/or vitamin D derivatives

The discovery of the calcium-sensing receptor (CaR) 15 yr ago was rapidly followed by the development of drugs modulating its activity, the so-called calcimimetics (increasing the CaR signal) and calcilytics (decreasing the CaR signal). The indication for calcimimetics is treatment of primary and secondary hyperparathyroidism, whereas calcilytics have potential for treatment of osteoporosis. A large number of clinical studies has shown that cinacalcet, the only presently available calcimimetic, effectively reduces serum parathyroid hormone in dialysis patients with secondary hyperparathyroidism. In contrast to the effect of active vitamin D derivatives, it simultaneously decreases serum calcium and phosphorus. Experimental studies showed a concomitant decrease in parathyroid hyperplasia. In the treatment of secondary hyperparathyroidism of dialysis patients, important questions remain unresolved, for example, whether there are reasons to prefer calcimimetics to active vitamin D derivatives and whether combined administration offers advantages compared with calcimimetics or active vitamin D given in isolation. For lowering parathyroid hormone, available evidence from recent studies suggests that combination therapy should be preferred to single drug treatment because of less side-effects and greater efficacy in controlling parathyroid overfunction. Future randomized controlled trial must answer whether calcimimetics impact on cardiovascular events or survival and whether in this respect there are differences between vitamin D sterols and calcimimetics.

Percutaneous ethanol injection therapy for advanced renal hyperparathyroidism in Japan: 2004 survey by the Japanese Society for Parathyroid Intervention

Background. Marked hyperplasia of the parathyroid gland (PTG) is a characteristic feature of severe hyperparathyroidism in patients under chronic haemodialysis treatment. Percutaneous ethanol injection therapy (PEIT) is now becoming popular in Japan as a treatment option for secondary hyperparathyroidism (SHPT) and its cost is covered by the National Health Insurance (NHI) System. The Japanese Society for Parathyroid Intervention surveyed its membership in 2004 to revise the guidelines for the use of PEIT.

Methods. The project was approved by the Executive Committee of the Society, and the primary questionnaire was addressed to 3268 centres (departments) affiliated with the Japanese Society for Dialysis Therapy. A follow-up questionnaire was sent to all the centres that responded.

Results. Although the number of centres to which the questionnaire was sent in 2004 was 3268, compared with 2653 in 1998, the number of responses decreased from 1425 (53.7%) in 1998 to 962 (29.4%) in 2004. To the question of whether the centre performed PEIT, 114 (11.9%) answered ‘Yes’ and 848 (88.1%) answered ‘No’ in 2004. It was an increase from 1998 when only 83 (5.8%) of 1425 centres answered ‘Yes’. In the 1998 survey, 612 patients underwent PEIT at 74 centres, and in 2004, 2098 patients underwent PEIT at 111 centres.

Conclusions. PEIT may become the frequently performed treatment for SHPT patients who become resistant to medical therapy. However, the same problems as in 1998 remain unsolved; that is, recurrent nerve paralysis, difficulty of post-PEIT PTx and lack of evidence showing the long-term effectiveness of PEIT.

Molecular and morphological approach of uremia-induced hyperplastic parathyroid gland following direct maxacalcitol injection

The mechanisms explaining the clinical effects of direct maxacalcitol (OCT) injection into the hyperplastic parathyroid gland (PTG) in uremic patients with advanced secondary hyperparathyroidism (SHPT) were investigated by molecular and morphological examination. PTG of uremia-induced SHPT model rats were treated by a direct injection of OCT (DI-OCT) or vehicle (DI-vehicle). The changes in serum intact parathyroid hormone (intact-PTH) level, vitamin D and Ca-sensing receptor (VDR and CaSR, respectively) expression levels in PTG, and the calcium (Ca)-PTH response curve were examined; the induction of apoptosis in parathyroid cells (PTC) was also analyzed by the TUNEL method, DNA electrophoresis, and electron microscopic examination. Serum intact-PTH level following DI-OCT significantly decreased. Upregulation of both VDR and CaSR, a clear shift to the left downward in the Ca-PTH curve, and many apoptotic PTCs were observed in the DI-OCT-treated PTGs. However, these findings were not observed in the DI-vehicle-treated PTGs. Moreover, these effects were confirmed by the DI-OCT into one PTG and DI-vehicle alone into another PTG in the same rat. DI-OCT may introduce simultaneous VDR and CaSR upregulation and the regression of hyperplastic PTG, and these effects may provide a strategy for strongly suppressing PTH level in uremia-induced advanced SHPT.

Secondary contributors to bone loss in osteoporosis related hip fractures

Osteoporosis treatment of patients with hip fractures is necessary to prevent subsequent fractures. Secondary causes for bone loss are present in more than 80% of patients with hip fractures, and therefore, assessment of Vitamin D status, disorders in calcium absorption and excretion, monoclonal gammopathies, and renal function should be performed. Identifying and managing these disorders will improve detection and enhance treatment aimed at reducing the risk of recurrent fractures in older adults.

INTRODUCTION

The purpose of this study was to determine the prevalence of disorders affecting bone and mineral metabolism in individuals with osteoporotic hip fractures.

METHODS

Community dwelling individuals with hip fractures (HFx) 50 years of age and older. Assessment for vitamin D, renal and parathyroid status, calcium absorption, and plasma cell disorders.

RESULTS

Of 157 HFx, mean age 70 +/- 10 years, HFx had higher creatinine (p = 0.002, 95% C.I. -0.09, 0.05); lower 25 OH vitamin D (p = 0.019, 95% C.I. 6.5, 2.7), albumin (p = 0.007, 95% C.I. 0.36, 0.009), and 24-h urine calcium (p = 0.024, 95% CI 51, 21) as compared to controls. More than 80% of HFx had at least one previously undiagnosed condition, with vitamin D insufficiency (61%), chronic kidney disease (16%) (CKD), monoclonal gammopathy (6%), and low calcium absorption (5%) being the most common. One case each of multiple myeloma and solitary plasmocytoma were identified.

CONCLUSIONS

Osteoporosis treatment of HFx is necessary to prevent subsequent fractures. Secondary causes for bone loss are remarkably common in HFx; therefore, assessment of vitamin D status, disorders in calcium absorption and excretion, protein electrophoresis, and renal function should be performed. Identifying and correcting these disorders will improve detection and enhance treatment aimed at reducing the risk of recurrent fractures in older adults.

Cholecalciferol (vitamin D3) therapy and vitamin D insufficiency in patients with chronic kidney disease: a randomized controlled pilot study

OBJECTIVE

To investigate the efficacy of cholecalciferol (vitamin D3) in raising serum 25-hydroxyvitamin D (25[OH)]D) levels and reducing parathyroid hormone (PTH) levels in patients with chronic kidney disease (CKD).

METHODS

In this double-blind, randomized controlled pilot study, participants with CKD stage 3 and 4 (estimated glomerular filtration rate, 15-59 mL/min/1.73 m2), vitamin D insufficiency (serum 25[OH]D <30 ng/mL), and serum intact PTH levels >70 pg/mL were randomly assigned to receive either 50 000 IU of cholecalciferol or placebo once weekly for 12 weeks. Primary outcomes (25[OH]D and PTH levels) were measured at baseline, week 6, and week 12. Secondary outcomes (1,25-dihydroxvitamin D and bone turnover markers) were measured at baseline and week 12. Because of skewed data distribution, statistical analyses were performed on a logarithmic scale. The difference between the group means was exponentiated to provide the geometric mean ratio. A linear mixed model using an unstructured variance-covariance matrix was used to examine change in the primary and secondary outcomes over time.

RESULTS

Geometric mean serum 25(OH)D concentrations of the study groups were similar at baseline (P = .77). At week 6, a significant difference between the treatment and placebo groups was detected (P = .001); this difference was maintained at week 12 (P = .002). Among cholecalciferol-treated participants, serum 25(OH)D concentration increased on average from 17.3 ng/mL (95% confidence interval [CI], 11.8-25.2) at baseline to 49.4 ng/mL (95% CI, 33.9-72.0) at week 12. As-treated analysis indicated a trend toward lower PTH levels among cholecalciferol-treated participants (P = .07).

CONCLUSION

Weekly cholecalciferol supplementation appears to be an effective treatment to correct vitamin D status in patients with CKD.

Pharmacological control of secondary hyperparathyroidism in chronic hemodialysis patients: cinacalcet is coming to Japan

Secondary hyperparathyroidism has a significant impact on morbidity and mortality due to skeletal and extraskeletal manifestations. Cinacalcet, a newly developed calcimimetic, is reported to decrease parathyroidism, as well as serum levels of phosphorus (P) and calcium (Ca) and therefore Ca x P product. Available evidence has shown that cinacalcet decreases the rate of parathyroidectomy and bone fracture in hemodialysis patients, but the death rate remains the same. Although, it is not yet available in Japan, cinacalcet is expected to be available as a possible drug for patients undergoing hemodialysis due to secondary hyperparathyroidism associated with refractory hyperphosphatemia and hypercalcemia. Except for the high cost, cinacalcet will be a welcome therapeutic option for end-stage renal disease and probably also for pre-end-stage renal disease patients. Dietary phosphate restriction and adequate hemodialysis, however, are still the main strategy for the control of hyperphosphatemia and secondary hyperparathyroidism.

Secondary hyperparathyroidism disease stabilization following calcimimetic therapy

Standard therapy for secondary hyperparathyroidism (SHPT) includes dietary calcium supplementation, active vitamin D, and phosphate binders; however, these are often insufficient to allow patients to achieve their serum parathyroid hormone (PTH), calcium and calcium-phosphorus product (Ca × P) targets. Recent preclinical studies have demonstrated that treatment with type II calcimimetics that increase the sensitivity of the calcium-sensing receptor (CaR) to calcium can reverse the alterations in CaR and vitamin D receptor expression and parathyroid cell proliferation that are associated with SHPT. These data suggest that calcimimetic treatment could stabilize disease progression and improve maintenance of treatment goals. In clinical trials involving SHPT patients, the calcimimetic cinacalcet has been shown to decrease PTH, calcium, phosphorus and Ca × P. Significant improvements were seen regardless of initial disease severity, and benefits were maintained over the course of long-term therapy (up to 4 years), indicating effective disease stabilization. In conclusion, preclinical and clinical data provide both theoretical and empirical support for the use of calcimimetics in moderate and advanced SHPT to effectively stabilize disease.

A new paradigm for the treatment of secondary hyperparathyroidism

The global rise in chronic kidney disease makes secondary hyperparathyroidism (SHPT) a growing medical concern. Conventional therapies for treating SHPT are limited and include calcium-based and calcium-free phosphate binders for reducing serum phosphorus and vitamin D or its analogues for simultaneous stimulation of calcium absorption and suppression of parathyroid hormone (PTH) gene expression. Control of SHPT using these therapies has typically been poor. Recent studies have demonstrated that use of calcimimetics that reduce PTH secretion by increasing the sensitivity of the parathyroid gland calcium-sensing receptor to circulating calcium allow improved control of serum PTH, calcium, phosphorus and calcium-phosphorus product. This review describes experimental data and the clinical rationale supporting novel strategies for the integration of calcimimetics with conventional therapies to improve control of SHPT.

1,25-dihydroxyvitamin D-mediated hypercalcemia in ovarian dysgerminoma

Humoral hypercalcemia of malignancy (HHM) is a rare complication of malignant pediatric tumors, specifically those that secrete humoral factor(s), such as parathyroid hormone-related peptide (PTHrP). The authors report a case of severe hypercalcemia associated with ovarian dysgerminoma in a 10-year-old girl. In this case, the humoral factor was considered to be 1,25-dihydroxyvitamin D. HHM is extremely resistant to medical therapy. Therefore, tumor resection or volume reduction is necessary to control serum calcium levels.

Intraperitoneal Calcitriol in Infants on Peritoneal Dialysis

Background

Calcitriol has long been used as the main therapy in renal osteodystrophy, but the efficacy of the oral route is not always as high as expected.

Objective

To asses the safety and efficacy of intraperitoneal calcitriol in infants undergoing peritoneal dialysis (PD).

Patients and Methods

PD patients on oral calcitriol therapy, with serum parathyroid hormone (PTH) >1000 pg/mL during the previous 3 months of treatment, were switched to intraperitoneal calcitriol therapy, 1 μg twice per week. Dose was increased to 1 μg three times per week if PTH remained >1000 pg/mL, and was later readjusted. Target PTH was 200 – 300 pg/mL according DOQI guidelines. Statistics: All results are expressed as mean ± SE. The Wilcoxon signed rank test was used to evaluate differences in measurements for each pair of values. The confidence interval for differences between population medians was 96.9%. A p value less than 0.05 was considered significant.

Results

Six male children, mean age 17 ± 3.86 months, completed a 12-month follow-up. Mean pretreatment PTH was 1654 ± 209 pg/mL. Mean PTH at months 0, 3, 6, 9, and 12 was 1448 ± 439*, 1277 ± 723, 910 ± 704, 582 ± 282*, and 465 ± 224* pg/mL, respectively (*p < 0.05). Twelve hypercalcemic and 10 hyperphosphatemic episodes were successfully treated.

Conclusion

Infants on PD who fail to respond to oral calcitriol therapy can be safely treated with intraperitoneal administration of active vitamin D.

Expanding role for vitamin D in chronic kidney disease: importance of blood 25-OH-D levels and extra-renal 1alpha-hydroxylase in the classical and nonclassical actions of 1alpha,25-dihydroxyvitamin D(3)

Recent advances in the understanding of vitamin D have revolutionized our view of this old nutritional factor and suggested that it has much wider effects on the body than ever believed before. In addition to its well-known effects on calcium/phosphate homeostasis, vitamin D, through its hormonal form, 1alpha,25-dihydroxyvitamin D(3) or calcitriol, is a cell differentiating factor and anti-proliferative agent with actions on a variety of tissues around the body (e.g., skin, muscle, immune system). By influencing gene expression in multiple tissues, calcitriol influences many physiological processes besides calcium/phosphate homeostasis including muscle and keratinocyte differentiation, insulin secretion, blood pressure regulation, and the immune response. The incidence of various diseases including epithelial cancers, multiple sclerosis, muscle weakness as well as bone-related disorders has been correlated with vitamin D deficiency/insufficiency and has led to a re-evaluation of recommended daily intakes both in the normal subject and CKD patient. Critical developments have been the emergence of the value of blood 25-OH-D measurement as a tool in predicting vitamin D-related problems and this has in turn emphasized the importance of the extra-renal version of the 1alpha-hydroxylase, the enzyme responsible for the final step in vitamin D activation. The widespread expression of this extra-renal enzyme supports the view that it exists to boost intracellular concentrations of calcitriol within some target tissues in order to modulate a unique set of genes specifically in those tissues, a process which is therefore dependent upon circulating 25-OH-D. For CKD patients with their tendency to vitamin D substrate insufficiency coupled with their documented loss of the renal 1alpha-hydroxylase in late stages, this new information has profound implications. Physicians must start to manage the vitamin D insufficiency by vitamin D supplements throughout stages 1-5 whilst continuing to provide calcitriol replacement therapy, in the form of calcitriol or its analogs, in stages 3-5.