Burosumab vs Phosphate/Active Vitamin D in Pediatric X-Linked Hypophosphatemia: A Subgroup Analysis by Dose Level

CONTEXT

In an open-label, randomized, controlled, phase 3 trial in 61 children aged 1 to 12 years with X-linked hypophosphatemia (XLH), burosumab improved rickets vs continuing conventional therapy with active vitamin D and phosphate.

OBJECTIVE

We conducted an analysis to determine whether skeletal responses differed when switching to burosumab vs continuing higher or lower doses of conventional therapy.

METHODS

Conventional therapy dose groups were defined as higher-dose phosphate [greater than 40 mg/kg] (HPi), lower-dose phosphate [40 mg/kg or less] (LPi), higher-dose alfacalcidol [greater than 60 ng/kg] or calcitriol [greater than 30 ng/kg] (HD), and lower-dose alfacalcidol [60 ng/kg or less] or calcitriol [30 ng/kg or less] (LD).

RESULTS

At week 64, the Radiographic Global Impression of Change (RGI-C) for rickets was higher (better) in children randomly assigned to burosumab vs conventional therapy for all prebaseline dose groups: HPi (+1.72 vs +0.67), LPi (+2.14 vs +1.08), HD (+1.90 vs +0.94), LD (+2.11 vs +1.06). At week 64, the RGI-C for rickets was also higher in children randomly assigned to burosumab (+2.06) vs conventional therapy for all on-study dose groups: HPi (+1.03), LPi (+1.05), HD (+1.45), LD (+0.72). Serum alkaline phosphatase (ALP) also decreased in the burosumab-treated patients more than in the conventional therapy group, regardless of on-study phosphate and active vitamin D doses.

CONCLUSION

Prior phosphate or active vitamin D doses did not influence treatment response after switching to burosumab among children with XLH and active radiographic rickets. Switching from conventional therapy to burosumab improved rickets and serum ALP more than continuing either higher or lower doses of phosphate or active vitamin D.

Long-Term Safety and Efficacy of Recombinant Human Parathyroid Hormone (1-84) in Adults With Chronic Hypoparathyroidism

Context

Chronic hypoparathyroidism is conventionally treated with oral calcium and active vitamin D to reach and maintain targeted serum calcium and phosphorus levels, but some patients remain inadequately controlled.

Objective

To assess long-term safety and efficacy of recombinant human parathyroid hormone (1-84) (rhPTH(1-84)) treatment.

Methods

This was an open-label extension study at 12 US centers. Adults (n = 49) with chronic hypoparathyroidism were included. The intervention was rhPTH(1-84) for 6 years. The main outcome measures were safety, biochemical measures, oral supplement doses, bone indices.

Results

Thirty-eight patients (77.6%) completed the study. Throughout 72 months, mean albumin-adjusted serum calcium was within 2.00 to 2.25 mmol/L (8.0-9.0 mg/dL). At baseline, 65% of patients with measurements (n = 24/37) were hypercalciuric; of these, 54% (n = 13/24) were normocalciuric at month 72. Mean serum phosphorus declined from 1.6 ± 0.19 mmol/L at baseline (n = 49) to 1.3 ± 0.20 mmol/L at month 72 (n = 36). Mean estimated glomerular filtration rate was stable. rhPTH(1-84)-related adverse events were reported in 51.0% of patients (n = 25/49); all but 1 event were mild/moderate in severity. Mean oral calcium supplementation reduced by 45% ± 113.6% and calcitriol by 74% ± 39.3%. Bone turnover markers declined by month 32 to a plateau above pretreatment values; only aminoterminal propeptide of type 1 collagen remained outside the reference range. Mean bone mineral density z score fell at one-third radius and was stable at other sites.

Conclusion

6 years of rhPTH(1-84) treatment was associated with sustained improvements in biochemical parameters, a reduction in the percentage of patients with hypercalciuria, stable renal function, and decreased supplement requirements. rhPTH(1-84) was well tolerated; no new safety signals were identified.

Bmi-1 Overexpression Improves Sarcopenia Induced by 1,25(OH)2 D3 Deficiency and Downregulates GATA4-Dependent Rela Transcription

Sarcopenia increases with age, and an underlying mechanism needs to be determined to help with designing more effective treatments. This study aimed to determine whether 1,25(OH)₂ D₃ deficiency could cause cellular senescence and a senescence-associated secretory phenotype (SASP) in skeletal muscle cells to induce sarcopenia, whether GATA4 could be upregulated by 1,25(OH)₂ D₃ deficiency to promote SASP, and whether Bmi-1 reduces the expression of GATA4 and GATA4-dependent SASP induced by 1,25(OH)₂ D₃ deficiency in skeletal muscle cells. Bioinformatics analyses with RNA sequencing data in skeletal muscle from physiologically aged and young mice were conducted. Skeletal muscles from 2-month-old young and 2-year-old physiologically aged wild-type (WT) mice and 8-week-old WT, Bmi-1 mesenchymal transgene (Bmi-1^Tg ), Cyp27b1 homozygous (Cyp27b1^-/- ), and Bmi-1^Tg Cyp27b1^-/- mice were observed for grip strength, cell senescence, DNA damage, and NF-κB-mediated SASP signaling of skeletal muscle. We found that muscle-derived Bmi-1 and vitamin D receptor (VDR) decreased with physiological aging, and DNA damage and GATA4-dependent SASP activation led to sarcopenia. Furthermore, 1,25(OH)₂ D₃ deficiency promoted DNA damage-induced GATA4 accumulation in muscles. GATA4 upregulated Rela at the region from -1448 to -1412 bp at the transcriptional level to cause NF-κB-dependent SASP for aggravating cell senescence and muscular dysfunction and sarcopenia. Bmi-1 overexpression promoted the ubiquitination and degradation of GATA4 by binding RING1B, which prevented cell senescence, SASP, and dysfunctional muscle, and improved sarcopenia induced by 1,25(OH)₂ D₃ deficiency. Thus, Bmi-1 overexpression improves sarcopenia induced by 1,25(OH)₂ D₃ deficiency, downregulates GATA4-dependent Rela transcription, and sequentially inhibits GATA4-dependent SASP in muscle cells. Therefore, Bmi-1 overexpression could be used for translational gene therapy for the ubiquitination of GATA4 and prevention of sarcopenia. © 2023 American Society for Bone and Mineral Research (ASBMR).

Real-World Analysis of Outcomes and Economic Burden in Patients with Chronic Kidney Disease with and without Secondary Hyperparathyroidism among a Sample of the Italian Population

This real-world analysis evaluated the clinical and economic burden of non-dialysis-dependent CKD patients with and without secondary hyperparathyroidism (sHPT) in Italy. An observational retrospective study was conducted using administrative databases containing a pool of healthcare entities covering 2.45 million health-assisted individuals. Adult patients with hospitalization discharge diagnoses for CKD stages 3, 4, and 5 were included from 1 January 2012 to 31 March 2015 and stratified using the presence/absence of sHPT. Of the 5710 patients, 3119 were CKD-only (62%) and 1915 were CKD + sHPT (38%). The groups were balanced using Propensity Score Matching (PSM). Kaplan-Meier curves revealed that progression to dialysis and cumulative mortality had a higher incidence in the CKD + sHPT versus CKD-only group in CKD stage 3 patients and the overall population. The total direct healthcare costs/patient at one-year follow-up were significantly higher in CKD + sHPT versus CKD-only patients (EUR 8593 vs. EUR 5671, p < 0.001), mostly burdened by expenses for drugs (EUR 2250 vs. EUR 1537, p < 0.001), hospitalizations (EUR 4628 vs. EUR 3479, p < 0.001), and outpatient services (EUR 1715 vs. EUR 654, p < 0.001). These findings suggest that sHPT, even at an early CKD stage, results in faster progression to dialysis, increased mortality, and higher healthcare expenditures, thus indicating that timely intervention can ameliorate the management of CKD patients affected by sHPT.

Utility of monthly minodronate for osteoporosis after gastrectomy: Prospective multicenter randomized controlled trials

AIM

Osteoporosis in patients after gastrectomy is increasing with the aging of gastric cancer patients. Bisphosphonates are effective treatments for osteoporosis; however, their safety or efficacy in postgastrectomy patients has not been established. The purpose of this multicenter prospective intervention study was to investigate the impact of monthly minodronate on osteoporosis after gastrectomy.

METHODS

Of the 261 enrolled gastric cancer patients, 164 patients were diagnosed with osteoporosis based on criteria of the Japan Society of Osteoporosis. They were randomly assigned 1:1 to groups treated with active vitamin D (VD group) or monthly minodronate (MIN group). The primary endpoint was changes in lumbar bone mineral density (L-BMD) 12 mo after the start of administration. The secondary endpoints were changes in bone metabolism markers, adverse events (AEs), or treatment completion rates.

RESULTS

There was no significant difference in patient background between the VD (n = 82) and MIN (n = 82) groups. In the MIN group, the increase in L-BMD was significantly higher than that in the VD group (4.52% vs 1.72%, P = .001), with a significant reduction in bone metabolism markers; blood NTX (-25.6% vs -1.6%, P < .01) and serum bone-specific alkaline phosphatase (-34.3% vs -20.1%, P < .01). AEs were observed in 26.8% and 9.3% of the patients and treatment completion rates were 77.5% and 89.3% in the MIN and VD groups, respectively. Serious AEs were not observed in either group.

CONCLUSION

This study demonstrated the safety and efficacy of monthly minodronate, suggesting that this treatment may be useful for osteoporosis after gastrectomy (UMIN000015517).

Hypoparathyroidism in Pregnancy and Lactation: Current Approach to Diagnosis and Management

Background: Hypoparathyroidism is an uncommon endocrine disorder. During pregnancy, multiple changes occur in the calcium-regulating hormones, which may affect the requirements of calcium and active vitamin D during pregnancy in patients with hypoparathyroidism. Close monitoring of serum calcium during pregnancy and lactation is ideal in order to optimize maternal and fetal outcomes. In this review, we describe calcium homeostasis during pregnancy in euparathyroid individuals and also review the diagnosis and management of hypoparathyroidism during pregnancy and lactation. Methods: We searched the MEDLINE, CINAHL, EMBASE, and Google scholar databases from 1 January 1990 to 31 December 2020. Case reports, case series, book chapters, and clinical guidelines were included in this review. Conclusions: During pregnancy, rises in 1,25-dihydroxyvitamin D (1,25-(OH)2-D3) and PTH-related peptide result in suppression of PTH and enhanced calcium absorption from the bowel. In individuals with hypoparathyroidism, the requirements for calcium and active vitamin D may decrease. Close monitoring of serum calcium is advised in women with hypoparathyroidism with adjustment of the doses of calcium and active vitamin D to ensure that serum calcium is maintained in the low-normal to mid-normal reference range. Hyper- and hypocalcemia should be avoided in order to reduce the maternal and fetal complications of hypoparathyroidism during pregnancy and lactation. Standard of care therapy consisting of elemental calcium, active vitamin D, and vitamin D is safe during pregnancy.

Immunomodulatory Agents Combat Multidrug-Resistant Tuberculosis by Improving Antimicrobial Immunity

Background

Multidrug-resistant (MDR) tuberculosis has low treatment success rates, and new treatment strategies are needed. We explored whether treatment with active vitamin D₃ (vitD) and phenylbutyrate (PBA) could improve conventional chemotherapy by enhancing immune-mediated eradication of Mycobacterium tuberculosis.

Methods

A clinically relevant model was used consisting of human macrophages infected with M. tuberculosis isolates (n = 15) with different antibiotic resistance profiles. The antimicrobial effect of vitD+PBA, was tested together with rifampicin or isoniazid. Methods included colony-forming units (intracellular bacterial growth), messenger RNA expression analyses (LL-37, β-defensin, nitric oxide synthase, and dual oxidase 2), RNA interference (LL-37-silencing in primary macrophages), and Western blot analysis and confocal microscopy (LL-37 and LC3 protein expression).

Results

VitD+PBA inhibited growth of clinical MDR tuberculosis strains in human macrophages and strengthened intracellular growth inhibition of rifampicin and isoniazid via induction of the antimicrobial peptide LL-37 and LC3-dependent autophagy. Gene silencing of LL-37 expression enhanced MDR tuberculosis growth in vitD+PBA–treated macrophages. The combination of vitD+PBA and isoniazid were as effective in reducing intracellular MDR tuberculosis growth as a >125-fold higher dose of isoniazid alone, suggesting potent additive effects of vitD+PBA with isoniazid.

Conclusions

Immunomodulatory agents that trigger multiple immune pathways can strengthen standard MDR tuberculosis treatment and contribute to next-generation individualized treatment options for patients with difficult-to-treat pulmonary tuberculosis.

Pathological role of excessive DNA as a trigger of keratinocyte proliferation in psoriasis

Psoriasis is characterized by excessive growth and aberrant differentiation of epidermal keratinocytes due to persistent inflammation. However, the underlying mechanism that triggers immune activation in psoriasis is not clear. In this study, we explored excessive DNA as a potential trigger of psoriasis using cultured human keratinocytes and psoriatic skin tissues. We demonstrated that human genomic DNA fragments induced tumour necrosis factor (TNF)-α expression, hyperproliferation and over-expression of heparin-binding epidermal-like growth factor (HB-EGF) and transforming growth factor (TGF)-α, accompanied by defective expression of keratins 1 and 10 in cultured normal human epidermal keratinocytes, which have a similar phenotype to that of keratinocytes in psoriatic skin lesions. In psoriatic lesions, we found high levels of double-stranded (ds)DNA fragments, accompanying keratinocytes expressing Ki-67, HB-EGF and TNF-α. In addition, we showed that 1,25-dihydroxyvitamin D₃ inhibited genomic DNA fragment-induced TNFA and interleukin-1β (IFNB) expression in human keratinocytes, and an intact function of cathelicidin anti-microbial peptide (CAMP) was required for this effect. These results suggest that excessive dsDNA fragments probably act as a risk factor for immune activation in psoriasis, and the active form of vitamin D can prevent genomic DNA-mediated skin inflammation via CAMP.

Efficacy and safety of active vitamin D supplementation in chronic spontaneous urticaria patients

Background: Chronic spontaneous urticaria (CSU) is a common skin disorder affecting negatively patients' lives. Vitamin D deficiency has been reported to be associated to many allergic skin disorders.Objective: This study aimed to evaluate the association between the serum level of 25 hydroxy vitamin D and CSU and to assess the efficacy and safety of active vitamin D in management of CSU.Methods: The study was conducted on 77 patients with CSU and 67 healthy controls, then the 77 CSU patients were randomized to either the study group that received 0.25 µg alfacalcidol daily or the placebo group that received oral placebo for 12 weeks.Results: Serum 25(OH) D was significantly lower in CSU as compared to healthy controls and was negatively correlated to the urticarial severity. After alfacalcidol administration, the study group showed significant higher level of 25(OH) D compared to the placebo group. In addition, the mean serum level of IL6, hsCRP and TNFα significantly decreased in the study group in comparison to the placebo group and as compared to their baseline results.Conclusion: Vitamin D deficiency is more common in CSU patients as compared to healthy people and hence, alfacalcidol might have a beneficial role as add on therapy in CSU management with no reported side effects.

Efficacy and safety of cinacalcet and active vitamin D in the treatment of secondary hyperparathyroidism in patients with chronic kidney disease: a network meta-analysis

Background

We conducted a network meta-analysis (NMA) to evaluate the efficacy and safety of cinacalcet, active vitamin D and cinacalcet plus active vitamin D in the treatment of secondary hyperparathyroidism (SHPT) in patients with chronic kidney disease (CKD).

Methods

A systematic literature search was performed using the Cochrane Library, PubMed, EMBASE, Web of Science, Google Scholar, China National Knowledge Internet (CNKI) and Wanfang databases. In total, eight randomized controlled trials (RCTs) with 1,443 patients were eligible for this meta-analysis. Pairwise meta-analysis was performed to evaluate the compliance of intact parathyroid hormone (iPTH), Ca, P, etc., and the mortality and safety of cinacalcet plus active vitamin D and active vitamin D alone. Then, NMA was used to estimate the safety and efficacy of the administration of active vitamin D and different drugs in the control group.

Results

The results of the pairwise meta-analysis revealed that compared with active vitamin D monotherapy, cinacalcet plus active vitamin D did not improve the survival of patients but significantly improved the blood calcium compliance rate [relative risk (RR) =1.82, 95% confidence interval (CI): 1.51-2.21, P<0.00001]. Furthermore, it is worth noting that compared with the corresponding incidence with other treatments, the incidence of vomiting was significantly increased with cinacalcet plus active vitamin D treatment (RR =2.07, 95% CI: 1.18-3.65, P=0.01). Through direct and indirect comparisons, the NMA revealed the following results: (I) compared with oral or intravenous (IV) administration of vitamin D, the solely oral administration of active vitamin D increased mortality, and (II) cinacalcet monotherapy increased the risk of hypocalcemia, and that risk was even higher for cinacalcet plus active vitamin D. However, the results should be treated with caution because the prediction interval (PrI) crossed the invalid line.

Conclusions

This pairwise meta-analysis and NMA provided a comprehensive analysis of the currently utilized CKD-SHPT treatment interventions. This network identified some highly ranked interventions through analyses that were included in a small number of trials; these interventions merit further examination on a larger scale in the context of well-designed RCTs.

Active vitamin D regulates macrophage M1/M2 phenotypes via the STAT-1-TREM-1 pathway in diabetic nephropathy

AIM

Imbalance of M1/M2 macrophages phenotype activation is a key point in diabetic nephropathy (DN). This study aimed to investigate whether active vitamin D (VD) suppresses macrophage transition to the M1 phenotype via inhibiting the high glucose-induced STAT-1 phosphorylation to reduce TREM-1 expression.

METHODS

In vivo, pathological changes in kidney tissue were detected and the expression of CD68 TREM-1, STAT-1, M1 makers, and M2 makers were acquired in renal tissue of patients with DN and 18w DN rats. In vitro, RAW 264.7 cells were incubated in the presence of high glucose with or without VD_. Silencing and overexpression of TREM-1 and silencing and activate of STAT-1 were explored to elucidate the underlying mechanism. The expression of TREM-1 and STAT-1 and the changes of macrophage phenotype were examined separately by western blot and immunofluorescence staining.

RESULTS

(a) Expression of TREM-1, p-STAT-1, and M1 markers (iNOS and TNF-α) were increased and positively correlated in kidneys from patients with DN. (b) In DN rats, the enlargement of glomerular surface area, expansion of glomerular mesangial matrix, the expression of CD68, TREM-1, p-STAT-1, and M1 marker (iNOS) were significantly increased in comparison with the normal control group, whereas above changes were markedly decreased in the diabetic group treated with the VD group. (c) In vitro, VD significantly decreased high glucose-induced CD68, TREM-1, p-STAT-1, and M1 marker (iNOS) expression. However, above-mentioned effects of VD are abolished when TREM-1 is overexpressed or STAT-1 is activated. Reductions in STAT-1 expression decreased the TREM-1 expression.

CONCLUSION

VD can inhibit macrophage transition to the M1 phenotype through the STAT-1/TREM-1 pathway.

Low Vitamin D Levels Are Associated With the Development of Deep Venous Thromboembolic Events in Patients With Ischemic Stroke

The objective is to determine whether a low serum 25-hydroxyvitamin D (25(OH)D) level is associated with an increased incidence of deep venous thromboembolic events in patients with ischemic stroke. One hundred eighty persons admitted consecutively for inpatient rehabilitation at the Department of Rehabilitation of the First Affiliated Hospital of Wenzhou Medical University with a diagnosis of ischemic stroke from January 2015 to December 2015 were enrolled. The following demographic data were collected: age, sex, body mass index, and history of risk factors. The levels of 25(OH)D and the presence of deep vein thrombosis (DVT) by routine duplex imaging were also recorded. The value of 25(OH)D needed to predict DVT was analyzed using logistic regression analysis, after adjusting for the possible confounders. We found that 80% of patients admitted to the acute inpatient rehabilitation unit had low levels of vitamin D. Forty-seven patients had DVT, and the incidence of DVT was 26.1% within 3 weeks after the stroke event. With all patients taken together, DVT occurrence as a dependent variable with the sufficient group as the reference used for vitamin D levels in the logistic analysis, deficiency of vitamin D was independently associated with the development of DVT (odds ratio = 4.683, 95% confidence interval: 1.396-15.703, P = .012). In conclusion, low serum 25(OH)D levels were independent predictors of DVT in patients with ischemic stroke during inpatient rehabilitation stay in China. This finding reveals the critical role played by 25(OH)D in the pathogenesis of DVT.

Milk-alkali syndrome (MAS) as a complication of the treatment of hypoparathyroidism - a case study

Milk-alkali syndrome (MAS), characterized by renal failure, metabolic alkalosis and hypercalcemia, is a severe and life-threatening complication of the treatment of hypoparathyroidism. The clinical course is often sudden and is not preceded by any prodromal symptoms. Occurrence does not depend on the duration of hypoparathyroidism treatment, although it is closely related to the applied therapy, especially the dose of calcium carbonate and active vitamin D preparations. Drugs influencing the glomerular filtration rate (angiotensin receptor blockers, sartans, aldosterone receptor antagonists, thiazide diuretics), lack of adequate routine control, changing the calcium carbonate supplementation, dehydration, a diet rich in pH-basic foods (i.e. vegetarian diet), pregnancy and other associated conditions are listed among the factors triggering MAS. A higher calcium carbonate dose is directly associated with an increased risk of milk-alkali syndrome. In case of a high calcium demand it is necessary to control renal function and monitor the level of calcium in the serum more frequently, aiming for the lower end of the reference range. If MAS has been confirmed or if there are alarming neurological symptoms suggestive of hypercalcemia, the patient must be sent to the hospital immediately. Treatment of MAS involves: discontinuation of calcium and vitamin D supplementation, and intravenous infusion of normal saline solution to eliminate volume deficiencies and to achieve forced diuresis while maintaining proper fluid balance. As soon as there is improvement in the patient's clinical condition, it is necessary to begin the treatment of comorbidities increasing the risk of renal failure or alkalosis (i.e. vomiting, diarrhea).

Moderator's view: Vitamin D deficiency treatment in advanced chronic kidney disease: a close look at the emperor's clothes

Two recent vitamin D supplementation (ergocalciferol) trials in stage G5D CKD patients with vitamin D insufficiency showed that this sterol effectively increases serum 25-hydroxyvitamin D [25(OH)D] but fails to modify serum PTH and other clinical outcomes. The Pro side of this polar view emphasizes that the duration of these studies was too short to allow sensible analyses based on a clinical endpoint. Furthermore, he notes that in the second study, the use of active forms of vitamin D, phosphate binders and cinacalcet could have hindered appreciation of the effect of ergocalciferol supplementation per se The Con side produces an updated meta-analysis showing that inactive vitamin D forms largely fail to reduce serum PTH and affect various relevant endpoints, including muscle strength, functional capacity, quality of life and hospitalization. Studies suggesting an effect of inactive vitamin D forms in advanced CKD are either very small and mainly based on sequential, uncontrolled observations or inherently weak, simple pre/post studies. No biological or clinical evidence exists that 25(OH)D may exert meaningful effects in CKD patients who are being treated with active forms of vitamin D. Careful a etiologic studies based on the omics sciences, i.e. precise pathophysiological profiling of individual CKD patients followed by consequential, well-targeted intervention(s) in the precision medicine scenario, will likely provide a definitive answer to the lingering question of whether inactive vitamin D forms may have biological effects beyond those produced by their proximate metabolite 1,25-dihydroxyvitamin D3.

High-phosphorus diet maximizes and low-dose calcitriol attenuates skeletal muscle changes in long-term uremic rats

Although disorders of mineral metabolism and skeletal muscle are common in chronic kidney disease (CKD), their potential relationship remains unexplored. Elevations in plasma phosphate, parathyroid hormone, and fibroblastic growth factor 23 together with decreased calcitriol levels are common features of CKD. High-phosphate intake is a major contributor to progression of CKD. This study was primarily aimed to determine the influence of high-phosphate intake on muscle and to investigate whether calcitriol supplementation counteracts negative skeletal muscle changes associated with long-term uremia. Proportions and metabolic and morphological features of myosin-based muscle fiber types were assessed in the slow-twitch soleus and the fast-twitch tibialis cranialis muscles of uremic rats (5/6 nephrectomy, Nx) and compared with sham-operated (So) controls. Three groups of Nx rats received either a standard diet (0.6% phosphorus, Nx-Sd), or a high-phosphorus diet (0.9% phosphorus, Nx-Pho), or a high-phosphorus diet plus calcitriol (10 ng/kg 3 day/wk ip, Nx-Pho + Cal) for 12 wk. Two groups of So rats received either a standard diet or a high-phosphorus diet (So-Pho) over the same period. A multivariate analysis encompassing all fiber-type characteristics indicated that Nx-Pho + Cal rats displayed skeletal muscle phenotypes intermediate between Nx-Pho and So-Pho rats and that uremia-induced skeletal muscle changes were of greater magnitude in Nx-Pho than in Nx-Sd rats. In uremic rats, treatment with calcitriol preserved fiber-type composition, cross-sectional size, myonuclear domain size, oxidative capacity, and capillarity of muscle fibers. These data demonstrate that a high-phosphorus diet potentiates and low-dose calcitriol attenuates adverse skeletal muscle changes in long-term uremic rats.

Effect of active vitamin D on cardiovascular outcomes in predialysis chronic kidney diseases: A systematic review and meta-analysis

AIM

Vitamin D deficient patients present an increased risk of cardiovascular disease. We conducted this systematic review and meta-analysis to evaluate the effect of active vitamin D analogue on cardiovascular outcomes in predialysis chronic kidney disease.

METHODS

Pubmed, Embase, the Cochrane Library, CNKI, and article reference lists were searched for randomized controlled trials (RCTs) that compared active vitamin D analogues with placebo or no treatment for patients with predialysis chronic kidney disease. A meta-analysis was conducted using the standard methods consistent with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Reviewer Manager Software, ver. 5.2, was used.

RESULTS

Seven RCTs (five studies with paricalcitol and two studies with calcitriol, 731 patients) were included. Compared with control groups, active vitamin D reduced the incidence of cardiovascular events (RR, 0.27; 95% CI, 0.13-0.59), induced an increase in those with proteinuria reduction (RR, 1.9; 95% CI, 1.34-2.71), but did not alter left ventricular mass index and systolic function (MD, 0.42 g/m^2.7 ; 95% CI, -0.23-1.07 g/m^2.7 , P = 0.21 for left ventricular mass index and MD, -0.33; 95% CI, -0.74-0.07, P = 0.1 for left ventricular ejection fraction). Neither systolic blood pressure nor diastolic blood pressure was reduced by active vitamin D (MD, 0.3 mmHg; 95% CI, -4.95-5.56 mmHg; MD, -0.24 mmHg; 95% CI: -6.21-5.72 mmHg, respectively). Increased probability of hypercalcaemia after paricalcitol therapy was found (RR, 7.85; 95% CI, 2.92-21.10).

CONCLUSION

Active vitamin D reduced the incidence of cardiovascular events and induced a reduction in proteinuria, but its long-term effect on cardiac structure and function needed further confirmation. Increased probability of hypercalcaemia after paricalcitol therapy was found.

Estimated GFR and circulating 24,25-dihydroxyvitamin D3 concentration: a participant-level analysis of 5 cohort studies and clinical trials

BACKGROUND

Decreased glomerular filtration rate (GFR) leads to reduced production of 1,25-dihydroxyvitamin D3 from 25-hydroxyvitamin D3 (25[OH]D3). Effects of low GFR on vitamin D catabolism are less well understood. We tested associations of estimated GFR (eGFR) with the circulating concentration of 24,25-dihydroxyvitamin D3 (24,25[OH]2D3), the most abundant product of 25(OH)D3 catabolism, across populations with a wide range of GFRs.

STUDY DESIGN

Cross-sectional study.

SETTING & PARTICIPANTS

9,596 participants in 5 cohort studies and clinical trials: the Diabetes Control and Complications Trial (N=1,193), Multi-Ethnic Study of Atherosclerosis (N=6,470), Cardiovascular Health Study (N=932), Seattle Kidney Study (N=289), and Hemodialysis Study (N=712).

PREDICTOR

eGFR.

OUTCOME

Circulating 24,25(OH)2D3 concentration.

MEASUREMENTS

GFR was estimated from serum creatinine using the Chronic Kidney Disease Epidemiology Collaboration equation. Vitamin D metabolites were measured by mass spectrometry.

RESULTS

Circulating 24,25(OH)2D3 concentration was correlated with circulating 25(OH)D3 concentration (Pearson r range, 0.64-0.88). This correlation was weaker with lower eGFRs. Moreover, the increment in 24,25(OH)2D3 concentration associated with higher 25(OH)D3 concentration (slope) was lower with lower eGFRs: 2.06 (95% CI, 2.01-2.10), 1.77 (95% CI, 1.74-1.81), 1.55 (95% CI, 1.48-1.62), 1.17 (95% CI, 1.05-1.29), 0.92 (95% CI, 0.74-1.10), 0.61 (95% CI, 0.22-1.00), and 0.37 (95% CI, 0.35-0.39) ng/mL of 24,25(OH)2D3 per 10 ng/mL of 25(OH)D3 for eGFRs≥90, 60-89, 45-59, 30-44, 15-29, and <15 mL/min/1.73 m2 and end-stage renal disease treated with hemodialysis, respectively. As a result, at a 25(OH)D3 concentration of 20 ng/mL, mean 24,25(OH)2D3 concentrations were 2.92 (95% CI, 2.87-2.96), 2.68 (95% CI, 2.64-2.72), 2.35 (95% CI, 2.26-2.45), 1.92 (95% CI, 1.74-2.10), 1.69 (95% CI, 1.43-1.95), 1.14 (95% CI, 0.62-1.66), and 1.04 (95% CI,1.02-1.07) ng/mL for each category, respectively. This interaction was independent of other relevant clinical characteristics. Race, diabetes, urine albumin excretion, and circulating parathyroid hormone and fibroblast growth factor 23 concentrations more modestly modified the association of 24,25(OH)2D3 with 25(OH)D3.

LIMITATIONS

Lack of direct pharmacokinetic measurements of vitamin D catabolism.

CONCLUSIONS

Lower eGFR is associated strongly with reduced vitamin D catabolism, as measured by circulating 24,25(OH)2D3 concentration.

Treatment of Hypophosphatemic Rickets with Phosphate and Active Vitamin D in Japan: A Questionnaire-based Survey

Hereditary hypophosphatemic rickets represented by X-linked hypophosphatemic rickets (XLH) is a rare disorder characterized by hypophosphatemia, elevated alkaline phosphatase (ALP) and undermineralization of bone. Active vitamin D and phosphate are administered to correct hypophosphatemia and elevation of ALP. Overtreatment with phosphate leads to secondary hyperparathyroidism, and a large dose of active vitamin D has a risk of hypercalciuria. To understand the situation concerning treatment of patients with hereditary hypophosphatemic rickets in Japan, we conducted a questionnaire survey of pediatric endocrinologists. Answers were obtained from 53 out of 68 hospitals where the pediatric endocrinologists worked. One hundred and thirty-five patients were treated in 28 hospitals during November 2009 and May 2010; 126 patients suffered from hereditary hypophosphatemic rickets, and 9 had hypophosphatemia caused by other miscellaneous reasons. The distribution of patient age was as follows: 27 (21%) were between 6 mo and 6 yr of age, 39 (31%) were between 6 and 12 yr of age, and 60 (48%) were more than 12 yr of age. Active vitamin D was given to 123 patients, and phosphate was given to 106 patients. As for the dose of phosphorus, 37.2–58.1 mg/kg/d was given divided into 2 to 6 aliquots. There were various control targets of treatment, including serum phosphate, serum ALP, rachitic change, urinary Ca/Cr, parathyroid hormone and growth. It is very important to avoid side effects of these treatments. No evidence is available about the optimal dose of phosphate or number of administrations in the treatment of patients with hypophosphatemic rickets. Although there is a recommendation for clinical management of patients with hypophosphatemic rickets, we should set a clinical guideline for it in Japan.

Paricalcitol in the treatment of secondary hyperparathyroidism

Secondary hyperparathyroidism is a common complication of both chronic kidney and end-stage renal disease. Vitamin D appears to play a central role in the pathogenesis of this condition and active vitamin D replacement is usually a necessary component of its treatment. The ability to administer active vitamin D is limited by increases in calcium and phosphorus, predisposing patients to vascular calcifications and cardiovascular disease. Paricalcitol is a new vitamin D analog designed to suppress parathyroid secretion with less effect on serum levels of calcium and phosphorus. The application of paricalcitol in chronic kidney disease may slow the clinical course of secondary hyperparathyroidism and allow more effective suppression of parathyroid hormone while minimizing the concommitant risks of hypercalcemia and hyperphosphatemia. This article reviews the pathogenesis of secondary hyperparathyroidism and the data supporting the role of oral and intravenous paricalcitol in the treatment of secondary hyperparathyroidism in both chronic kidney disease and end-stage renal disease patients.