Predictive factors requiring high-dose evocalcet in hemodialysis patients with secondary hyperparathyroidism.

The dosage of evocalcet required to control serum parathyroid hormone (PTH) levels varies among secondary hyperparathyroidism (SHPT) patients. This post hoc analysis evaluated the dose-dependent efficacy of evocalcet on serum intact PTH (iPTH) levels, corrected calcium (Ca) and phosphate (P) levels, and safety, in an evaluation period (week 28 to week 30) by stratifying the previous phase 3 data with the final evocalcet dosages (low 1-2 mg [131 patients], medium 3-4 mg [90 patients], high 5-8 mg [92 patients]), and identified pre-treatment patient characteristics predicting the use of higher final evocalcet dosages via univariate and multivariate logistic regression models. At the end of the study at week 30, the median serum iPTH level was higher and the achievement ratio for the target range of Japanese Society for Dialysis Therapy (60-240 pg/mL) was lower in the final high-dose subgroup (216 pg/mL and 58%, respectively) than in the other subgroups (low: 149 pg/mL and 79%; medium: 149 pg/mL and 73%, respectively). Among the three subgroups, the mean serum corrected Ca and P levels demonstrated similar trends, and similar ratio of patients achieved the target range (corrected Ca, 8.4-10 mg/dL; P, 3.5-6.0 mg/dL) from week 28 to week 30. No dose-dependent safety concerns were identified. Younger age, prior cinacalcet use, higher serum levels of iPTH and corrected Ca, procollagen type 1 N-terminal propeptide, intact fibroblast growth factor-23, and larger maximum parathyroid gland volume were significantly associated with final high-dose evocalcet (p < 0.05 in all cases). Patients requiring final high-dose evocalcet had pre-treatment characteristics indicating severe SHPT, leading to a lower final achievement rate for the target PTH levels of Japanese Society for Dialysis Therapy. Therefore, the early initiation of evocalcet treatment for SHPT is critical. Trial registration: This trial was registered as follows: ClinicalTrials.gov: NCT02549391 and JAPIC: JapicCTI-153013.

Protective Roles of Xenotropic and Polytropic Retrovirus Receptor 1 (XPR1) in Uremic Vascular Calcification.

Cellular phosphate transporters play critical roles in the pathogenesis of vascular calcification (VC) in chronic kidney disease (CKD). However, the mechanistic link between VC and xenotropic and polytropic receptor 1 (XPR1), a newly identified phosphate exporter, remains unknown. We developed a new mouse model with rapidly progressive uremic VC in C57BL/6 mice and examined the roles of XPR1. The combination of surgical heminephrectomy and 8 weeks of feeding a customized warfarin and adenine-based diet induced extensive aortic VC in almost all mice. The XPR1 mRNA level in the aorta of CKD mice was significantly lower than those in control mice as early as week 2, when there was no apparent VC, which progressively declined thereafter. Dietary phosphate restriction increased XPR1 mRNA expression in the aorta but reduced aortic VC in CKD mice. In cultured vascular smooth muscle cells (VSMCs), a calcifying medium supplemented with high phosphate and calcium did not affect XPR1 mRNA expression. The XPR1 mRNA expression in cultured VCMCs was also unaffected by administration of indoxyl sulfate or calcitriol deficiency but was decreased by 1-34 parathyroid hormone or fibroblast growth factor 23 supplementation. Furthermore, XPR1 deletion in the cultured VSMCs exacerbated calcification of the extracellular matrix as well as the osteogenic phenotypic switch under the condition of calcifying medium. Our data suggest that XPR1 plays protective roles in the pathogenesis of VC and its decrease in the aorta may contribute to the progression of VC in CKD.

Rapid progression of vascular and soft tissue calcification while being managed for severe and persistent hypocalcemia induced by denosumab treatment in a patient with multiple myeloma and chronic kidney disease.

We herein present the case of a patient with myeloma and chronic kidney disease (CKD) who developed rapidly progressive vascular and soft tissue calcification during the course of treatment for severe hypocalcemia induced by the administration of denosumab for myeloma and hypercalcemia. Because a large amount of supplementation with active vitamin D and calcium was required to correct the severe hypocalcemia, rapidly progressive vascular calcification developed. Seeing that patients with CKD are prone to developing severe and prolonged hypocalcemia after denosumab treatment, physicians should closely monitor the patients' serum calcium levels and manage their hypocalcemia appropriately so as to avoid the development of significant ectopic calcification.

Systemic Aldosterone, But Not Angiotensin II, Plays a Pivotal Role in the Pathogenesis of Renal Injury in Chronic Nitric Oxide-Deficient Male Rats.

Chronic inhibition of nitric oxide synthase by N(ω)-nitro-L-arginine methyl ester (L-NAME) causes progressive renal injury and systemic hypertension. Angiotensin II (Ang II) has been conventionally regarded as one of the primary causes of renal injury. We reported previously that such renal injury was almost completely suppressed by both an Ang II type I receptor blocker and an aldosterone antagonist. The aldosterone antagonist also inhibited the systemic Ang II elevation. Therefore, it remains to be elucidated whether Ang II or aldosterone directly affects the development of such renal injury. In the present study, we investigated the role of aldosterone in the pathogenesis of renal injury induced by L-NAME-mediated chronic nitric oxide synthase inhibition in male Wistar rats (aged 10 wk). Serial analyses demonstrated that the renal injury and inflammation in L-NAME-treated rats was associated with elevation of both Ang II and aldosterone. To investigate the direct effect of aldosterone on the renal injury, we conducted adrenalectomy (ADX) and aldosterone supplementation in L-NAME-treated rats. In ADX rats, aldosterone was undetectable, and renal injury and inflammation were almost completely prevented by ADX, although systemic and local Ang II and blood pressure were still elevated. Aldosterone supplementation reversed the beneficial effect of ADX. The present study indicates that aldosterone rather than Ang II plays a central and direct role in the pathogenesis of renal injury by L-NAME through inflammation, independent of its systemic hemodynamic effects.

Cerebral oxidative stress induces spatial working memory dysfunction in uremic mice: neuroprotective effect of tempol.

BACKGROUND: Chronic kidney disease (CKD) is frequently associated with uremic encephalopathy and cognitive impairment. Recent studies have demonstrated that cerebral oxidative stress contributes to cognitive dysfunction. Although oxidative stress has been reported to increase in the uremic rat brain, the relationship between increased oxidative stress and cognitive impairment in uremia is unclear. In the present study, the effects of tempol (TMP), an antioxidant drug, were investigated in uremic mice. METHODS: CKD was induced in male C57BL/6 mice (n = 8) by left nephrectomy and 2/3 electrocoagulation of the right renal cortex. Working memory performance was tested by the radial arm water maze test. We have prepared two protocols ('time course study' and 'treatment study'). First, we examined the working memory test and histological examination of mouse brains after 4 and 8 weeks. Next, we investigated the effect of TMP (3 mM) against uremia-induced neurodegeneration and oxidative stress in the mouse brain. RESULTS: Eight weeks after CKD induction, vehicle-treated mice made significantly more errors than sham-operated control mice, while TMP improved working memory performance in CKD mice. CKD was associated with accumulation of 8-hydroxy-2'-deoxyguanosine in the hippocampal neuronal cells, but not in TMP-treated CKD mice. Increased numbers of pyknotic neuronal cells were observed in the hippocampus of CKD mice at 8 weeks, but pyknotic neuronal cell numbers were decreased under the influence of TMP in uremic mice. CONCLUSIONS: The present study provided evidence that uremia is associated with spatial working memory dysfunction in mice and that treatment with TMP protects against cerebral oxidative stress and improves cognitive dysfunction in uremic mice, suggesting their potential usefulness for the treatment of cognitive dysfunction in uremia.

Severe metabolic alkalosis, hypokalemia, and respiratory acidosis induced by the Chinese herbal medicine yokukansan in an elderly patient with muscle weakness and drowsiness.

Yokukansan is a Chinese herbal medicine containing licorice that has been shown to alleviate the behavioral and psychological symptoms of Alzheimer's disease, with few adverse effects. Increasing numbers of patients with Alzheimer's disease in Japan are now being treated with this drug. However, yokukansan should be used with caution because of its potential to induce pseudoaldosteronism through the inhibition of 11-beta-hydroxysteroid dehydrogenase type 2, which metabolizes cortisol into cortisone. We present the case of an 88-year-old woman with a history of Alzheimer's disease who was transferred to our emergency department because of drowsiness, anorexia, and muscle weakness. Her blood pressure was 168/90 mmHg. Laboratory data showed serum potassium of 1.9 mmol/l, metabolic alkalosis (pH 7.54; HCO 3- , 50.5 mmol/l; chloride, 81 mmol/l; sodium, 140 mmol/l), and respiratory disorders (pCO2, 60.5 mmHg; pO2, 63.8 mmHg). Plasma renin activity and aldosterone concentration were suppressed, and urinary potassium excretion was 22 mmol/l (calculated transtubular potassium gradient 12.9). An electrocardiogram showed flat T-waves and U-waves with ventricular premature contractions. Echocardiography denied volume depletion. Medical interview disclosed that she had been treated with a Chinese herbal medicine (yokukansan) containing licorice. The final diagnosis was pseudoaldosteronism and respiratory acidosis induced by licorice. Hypokalemia, metabolic alkalosis, and respiratory acidosis all subsided shortly after the discontinuation of yokukansan and initiation of intravenous potassium replacement. This case highlights the need for nephrologists to consider the possible involvement of Chinese herbal medicines, including yokukansan, when they encounter hypokalemia in elderly patients.

Defective renal maintenance of the vitamin D endocrine system impairs vitamin D renoprotection: a downward spiral in kidney disease.

In kidney disease, the progressive loss of renal capacity to produce calcitriol, the vitamin D hormone, is a key contributor to elevations in parathyroid hormone (PTH) and mineral and skeletal disorders predisposing to renal and cardiovascular damage, ectopic calcifications, and high mortality rates. Thus, the safe correction of calcitriol deficiency to suppress PTH has been the treatment of choice for decades. However, recent epidemiological and experimental data suggest that calcitriol replacement may improve outcomes through renal and cardioprotective actions unrelated to PTH suppression. Furthermore, a striking incidence of vitamin D deficiency occurs in kidney disease and associates more strongly than calcitriol deficiency with a higher risk for kidney disease progression and death. Despite the translational relevance of these findings, no prospective trials are currently available in support of the efficacy of vitamin D supplementation and/or calcitriol replacement to safely halt/moderate renal disease progression. This review updates the pathophysiology behind the vicious cycle by which kidney injury impairs the maintenance of normal vitamin D and calcitriol levels, which in turn impedes vitamin D/calcitriol renoprotective actions, a requirement for the design of prospective trials to improve current recommendations for vitamin D interventions at all stages of kidney disease.

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.

Intravenous calcitriol therapy in an early stage prevents parathyroid gland growth.

BACKGROUND: Both the phenotypic alterations of parathyroid (PT) cells, e.g. down-regulation of the calcium-sensing receptor, and the increase of the PT cell number in nodular hyperplasia are the main causes of refractory secondary hyperparathyroidism. It is of great importance to prevent PT growth in an early stage. METHODS: To examine a more effective method of calcitriol therapy for the prevention of PT hyperplasia, we randomized haemodialysis patients with mild hyperparathyroidism to receive either daily orally administered calcitriol (n = 33) or intravenous calcitriol (n = 27) over a 12-month study period. Calcitriol was modulated so as to keep the serum intact PTH level between 100 and 150 pg/ml. RESULTS: Both groups showed similar reductions of the serum PTH level and similar increases in serum calcium. In both groups, there were no significant changes in the serum phosphate level. Long-term daily oral calcitriol therapy failed to prevent the increase of both maximum PT volume and total volume, as assessed by ultrasonography; however, intravenous calcitriol therapy successfully suppressed this progression. In the daily, oral group, both the bone-specific alkaline phosphatase (BAP) and the N-telopeptide cross-linked of type I collagen (NTX) significantly decreased, which was probably due to the PTH suppression. However, these bone metabolism markers remained stable in the intravenous group. The total dosage of calcitriol during the study was comparable in both groups. CONCLUSIONS: These data indicate that intravenous calcitriol therapy in an early stage of secondary hyperparathyroidism is necessary to prevent PT growth and to keep a good condition of bone metabolism.

Parathyroid cell growth in patients with advanced secondary hyperparathyroidism: vitamin D receptor, calcium sensing receptor, and cell cycle regulating factors.

The parathyroid gland (PTG) is a unique endocrine organ in which the quiescent glandular cells begin to proliferate in response to the demand for maintaining calcium (Ca) homeostasis in the progressive course of renal failure, leading to secondary hypereparathyroidism (SHPT). SHPT is characterized with continuous over-secretion of parathyroid hormone (PTH) and high turn-over bone disease, osteitis fibrosa, and the major factors include a deficiency of active vitamin D, hypocalcemia, and phosphate retention. With long-term end-stage renal failure, SHPT becomes resistant to conventional medical treatment such as phosphate binders and active vitamin D supplementation, and the growth of the PTG accelerates with the pattern of hyperplasia changing from diffuse to nodular type. In this process, the sigmoid curve between extracellular Ca concentration (exCa) and the plasma level of PTH shifts to the upper-rightward, indicating both an absolute increase in PTH secretion and the resistance of PT cells to exCa. Many experimental and human studies have revealed down-regulation of vitamin D receptor (VDR), calcium-sensing receptor (CaSR), and retinoid X receptor (RXR) in PT cells. The sustained proliferation of PT cells after obtaining autonomicity is another characteristic feature of SHPT. In this context, it has been demonstrated that the cell cycle is markedly progressed, where the expression of cyclin-dependent kinase inhibitor (CDKI), p21 and p27, is depressed in a VDR-dependent manner. These pathological features are most evident in nodular hyperplasia, in which monoclonal proliferation is obvious, indicating the phenotypic changes have occured in PT cells. It has been observed by Fukagawa and colleagues that pharmacologically high dose of active vitamin D administered orally can cause small-size PTG hyperplasia to regress in patients with advanced SHPT. Successful renal transplantation may also restore VDR and CaSR expressions in the diffuse type, in association with increasing TUNEL-positive cells. Thus, it is important to vigorously treat SHPT when the PT cell proliferation is in the reversible stage of diffuse hyperplasia.

Different effects of 22-oxacalcitriol and calcitriol on the course of experimental chronic renal failure.

Calcitriol, 1,25(OH)(2)D(3), has been reported to have a beneficial effect on bone histology in patients with predialysis chronic renal failure; however, such treatment involves a risk of hypercalcemia. To investigate the effects of 1,25(OH)(2)D(3) and 22-oxacalcitriol (OCT) on the progression of histologic deterioration, we administered intraperitoneal 1,25(OH)(2)D(3) or OCT, three times a week, to rats with adriamycin-induced progressive renal failure, from the 10th week after the induction of ADR-induced nephropathy. The rats were divided into the following groups: (1) high-dose 1,25(OH)(2)D(3), 0.2 microg/kg (group D(3)-0.2); (2) low-dose 1,25(OH)(2)D(3), 0.04 microg/kg (group D(3)-0.04); (3) high-dose OCT, 0.2 microg/kg (group OCT-0.2); (4) low-dose OCT, 0.04 microg/kg (group OCT-0.04); and (5) ADR-induced nephropathy (group ADR). The death rate at week 20 in group D(3)-0.2 was 50%, significantly higher than the death rates in the other groups, except for group D(3)-0.04 (P <.05). The serum creatinine and blood urea nitrogen levels were the highest in group D(3)-0.2, although the difference was not significant. In contrast, in groups OCT-0.2 and OCT-0.04, tubular changes and interstitial volume were smaller than in groups D(3)-0.2 and D(3)-0.04 (P <.05). Although calcium deposits increased in group D(3)-0.2, the difference was not significant. Glomerular expression of transforming growth factor-beta1 (TGF-beta1) expression was less in groups OCT-0.2 and OCT-0.04 than in groups D(3)-0.2 and D(3)-0.04 (P <.05). Glomerular fibronectin expression was less in group OCT-0.2 than in groups D(3)-0.2 and ADR (P <.05). Tubulointerstitial expression of TGF-beta1 was greater in group D(3)-0.2 than in group ADR and greater in group D(3)-0.04 than in group OCT-0.04 (P <.05). We conclude that a high dose of 1,25(OH)(2)D(3) accelerated the progressive renal deterioration of ADR-induced nephropathy, and, as a result, OCT was able to attenuate renal histologic lesions.