Cholecalciferol Additively Reduces Serum Parathyroid Hormone Levels in Severe Secondary Hyperparathyroidism Treated with Calcitriol and Cinacalcet among Hemodialysis Patients

Does Native Vitamin D Supplementation Have Pleiotropic Effects in Patients with End-Stage Kidney Disease? A Systematic Review of Randomized Trials

Vitamin D has been shown to have multiple pleiotropic effects beyond bone and mineral metabolism, with purported roles in cardiovascular disease, cancer, and host immunity. Vitamin D deficiency is common in patients with end-stage kidney disease (ESKD); however, current clinical practice has favored the use of the active hormone. Whether vitamin D deficiency should be corrected in patients with ESKD remains unclear, as few randomized trials have been conducted. In this systematic review, we summarize the current evidence examining whether vitamin D supplementation improves outcomes, beyond mineral metabolism, in patients with ESKD. Data from randomized controlled trials of adults with ESKD were obtained by searching Ovid MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, and the Web of Science Core Collection from inception to February 2023. Twenty-three trials composed of 2489 participants were identified for inclusion. Data were synthesized by two independent reviewers and summarized in tables organized by outcome. Outcomes included measures of mortality, cardiovascular disease, inflammation, muscle strength/function, nutrition, patient well-being, and outcomes specific to ESKD including erythropoietin usage, pruritus, and dialysis access maturation. The Cochrane risk of Bias Tool (RoB 2, 2019) was used to assess study quality. Overall, our findings indicate a minimal and varied benefit of native vitamin D supplementation. From the largest studies included, we determine that vitamin D has no demonstrated effect on patient-reported measures of well-being or utilization of erythropoietin, nor does it change levels of the inflammation biomarker C-reactive protein. Included trials were heterogeneous with regards to outcomes, and the majority studied small participant populations with a relatively short follow-up. We conclude that vitamin D supplementation corrects vitamin D deficiency and is safe and well-tolerated in humans with ESKD. However, it is not clear from clinical trials conducted to date that a causal pathway exists between 25(OH)D and pleiotropic effects that is responsive to vitamin D treatment.

Serum nuclear factor IB as a novel and noninvasive indicator in the diagnosis of secondary hyperparathyroidism

BACKGROUND

Chronic renal failure (CRF) referred to chronic progressive renal parenchymal damage caused by various causes, with metabolite retention and imbalance of water, electrolyte, and acid-base balance as the main clinical manifestations. Secondary hyperparathyroidism (sHPT) was a common complication in maintenance hemodialysis patients with CRF. Nuclear factor IB (NFIB) was a newly found tumor suppressor gene in various cancers. The present study aimed to illustrate the role of NFIB in sHPT clinical diagnosis and treatment response.

METHODS

A retrospective, case-control study, including 189 patients with sHPT and 106 CRF patients without sHPT, compared with 95 controls. Serum NFIB and 1,25(OH)₂ D₃ levels were measured by RT-qPCR and ELISAs, respectively. ROC analysis was conducted to verify the diagnostic value of NFIB in sHPT. Spearman's correlation analysis was conducted to verify the association between NFIB and bone mineral density (BMD) scores. After 6 months of treatment, the variance of NFIB and 1,25(OH)₂ D₃ in different groups was recorded.

RESULTS

The expression of NFIB was significantly lower in serum samples from sHPT and non-sHPT CRF patients, compared to controls. Clinicopathological information verified sHPT was associated with NFIB, parathyroid hormone (PTH), serum calcium, serum phosphorus, time of dialysis, and serum 1,25(OH)₂ D₃ levels. Spearman's correlation analysis illustrated the positive correlation between NFIB levels and BMD scores. At receiver operator characteristic (ROC) curve analysis, the cutoff of 1.6508 for NFIB was able to identify patients with sHPT from healthy controls; meanwhile, NFIB could also discriminate sHPT among CRF patients as well (cutoff = 1.4741). Furthermore, we found that during 6 months of treatment, NFIB levels were gradually increased, while PTH and serum P levels were decreased.

CONCLUSIONS

Serum NFIB was a highly accurate tool to identify sHPT from healthy controls and CRF patients. Due to its simplicity, specificity, and sensitivity, this candidate can be proposed as a first-line examination in the diagnostic workup in sHPT.

Therapeutic Effect of Calcimimetics on Osteoclast-Osteoblast Crosslink in Chronic Kidney Disease and Mineral Bone Disease

We have previously demonstrated calcimimetics optimize the balance between osteoclastic bone resorption and osteoblastic mineralization through upregulating Wingless and int-1 (Wnt) signaling pathways in the mouse and cell model. Nonetheless, definitive human data are unavailable concerning therapeutic effects of Cinacalcet on chronic kidney disease and mineral bone disease (CKD-MBD) and osteoclast-osteoblast interaction. We aim to investigate whether Cinacalcet therapy improves bone mineral density (BMD) through optimizing osteocytic homeostasis in a human model. Hemodialysis patients with persistently high intact parathyroid hormone (iPTH) levels > 300 pg/mL for more than 3 months were included and received fixed dose Cinacalcet (25 mg/day, orally) for 6 months. Bone markers presenting osteoclast-osteoblast communication were evaluated at baseline, the 3rd and the 6th month. Eighty percent of study patients were responding to Cinacalcet treatment, capable of improving BMD, T score and Z score (16.4%, 20.7% and 11.1%, respectively). A significant correlation between BMD improvement and iPTH changes was noted (r = -0.26, p < 0.01). Nonetheless, baseline lower iPTH level was associated with better responsiveness to Cinacalcet therapy. Sclerostin, an inhibitor of canonical Wnt/β-catenin signaling, was decreased from 127.3 ± 102.3 pg/mL to 57.9 ± 33.6 pg/mL. Furthermore, Wnt-10b/Wnt 16 expressions were increased from 12.4 ± 24.2/166.6 ± 73.3 pg/mL to 33.8 ± 2.1/217.3 ± 62.6 pg/mL. Notably, procollagen type I amino-terminal propeptide (PINP), a marker of bone formation and osteoblastic activity, was increased from baseline 0.9 ± 0.4 pg/mL to 91.4 ± 42.3 pg/mL. In contrast, tartrate-resistant acid phosphatase isoform 5b (TRACP-5b), a marker of osteoclast activity, was decreased from baseline 16.5 ± 0.4 mIU/mL to 7.7 ± 2.2 mIU/mL. Moreover, C-reactive protein levels were suppressed from 2.5 ± 0.6 to 0.8 ± 0.5 mg/L, suggesting the systemic inflammatory burden may be benefited after optimizing the parathyroid-bone axis. In conclusion, beyond iPTH suppression, our human model suggests Cinacalcet intensifies BMD through inhibiting sclerostin expression and upregulating Wnt-10b/Wnt 16 signaling that activates osteoblastic bone formation and inhibits osteoclastic bone resorption and inflammation. From the perspective of translation to humans, this research trial brings a meaningful insight into the osteoblast-osteoclast homeostasis in Cinacalcet therapy for CKD-MBD.

Effect of cholecalciferol on serum hepcidin and parameters of anaemia and CKD-MBD among haemodialysis patients: a randomized clinical trial

In this multicentre double-blind randomized clinical trial, we investigated the effects of oral cholecalciferol supplementation on serum hepcidin and parameters related to anaemia and CKD-MBD among haemodialysis patients. Participants were assigned in a 2:2:1:1 ratio to either (1) thrice-weekly 3,000-IU cholecalciferol, (2) once-monthly cholecalciferol (equivalent to 9,000 IU/week), (3) thrice-weekly placebo, or (4) once-monthly placebo. We also examined the effect modifications by selected single nucleotide polymorphisms in vitamin D-related genes. Out of 96 participants, 94 were available at Month 3, and 88 completed the 6-month study. After adjustment for baseline values, serum hepcidin levels were higher at Day 3 in the combined cholecalciferol (vs. placebo) group, but were lower at Month 6 with increased erythropoietin resistance. Cholecalciferol increased serum 1,25(OH)₂D levels, resulting in a greater proportion of patients who reduced the dose of active vitamin D at Month 6 (31% vs. 10% in the placebo group). Cholecalciferol also suppressed intact PTH only among patients with severe vitamin D deficiency. In conclusion, cholecalciferol supplementation increases serum hepcidin-25 levels in the short term and may increase erythropoietin resistance in the long term among haemodialysis patients. Both thrice-weekly and once-monthly supplementation effectively increases serum 1,25(OH)₂D levels, and hence, reduces active vitamin D drugs.

Clinical Trial Registry: This study was registered at ClinicalTrials.gov and University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) as NCT02214563 (registration date: 12/08/2014) and UMIN000011786 (registration date: 15/08/2014), respectively (please refer to the links below). ClinicalTrials.gov: https://clinicaltrials.gov/ct2/show/record/NCT02214563. UMIN-CTR: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&type=summary&recptno=R000017152&language=E.

Sirtuin-1 and Its Relevance in Vascular Calcification

Vascular calcification (VC) is highly associated with cardiovascular disease and all-cause mortality in patients with chronic kidney disease. Dysregulation of endothelial cells and vascular smooth muscle cells (VSMCs) is related to VC. Sirtuin-1 (Sirt1) deacetylase encompasses a broad range of transcription factors that are linked to an extended lifespan. Sirt1 enhances endothelial NO synthase and upregulates FoxOs to activate its antioxidant properties and delay cell senescence. Sirt1 reverses osteogenic phenotypic transdifferentiation by influencing RUNX2 expression in VSMCs. Low Sirt1 hardly prevents acetylation by p300 and phosphorylation of β-catenin that, following the facilitation of β-catenin translocation, drives osteogenic phenotypic transdifferentiation. Hyperphosphatemia induces VC by osteogenic conversion, apoptosis, and senescence of VSMCs through the Pit-1 cotransporter, which can be retarded by the sirt1 activator resveratrol. Proinflammatory adipocytokines released from dysfunctional perivascular adipose tissue (PVAT) mediate medial calcification and arterial stiffness. Sirt1 ameliorates release of PVAT adipokines and increases adiponectin secretion, which interact with FoxO 1 against oxidative stress and inflammatory arterial insult. Conclusively, Sirt1 decelerates VC by means of influencing endothelial NO bioavailability, senescence of ECs and VSMCs, osteogenic phenotypic transdifferentiation, apoptosis of VSMCs, ECM deposition, and the inflammatory response of PVAT. Factors that aggravate VC include vitamin D deficiency-related macrophage recruitment and further inflammation responses. Supplementation with vitamin D to adequate levels is beneficial in improving PVAT macrophage infiltration and local inflammation, which further prevents VC.

Cinacalcet plus vitamin D versus vitamin D alone for the treatment of secondary hyperparathyroidism in patients undergoing dialysis: a meta-analysis of randomized controlled trials

BACKGROUND

Secondary hyperparathyroidism (SHPT) is a common and serious complication of chronic kidney disease, particularly in end-stage renal disease. Currently, both cinacalcet and vitamin D are used to treat SHPT via two different mechanisms, but it is still unclear whether the combination use of these two drugs can be a safe and effective alternative to vitamin D alone. Therefore, the aim of this meta-analysis was to assess the efficacy and safety of cinacalcet plus vitamin D in the treatment of SHPT.

METHODS

Four electronic databases, including PubMed, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science, were searched for eligible publications. All randomized-controlled trials comparing cinacalcet plus vitamin D with vitamin D alone in SHPT patients undergoing dialysis were included. Mean difference (MD) with 95% confidence intervals (CIs) and risk ratios (RRs) with 95% CIs were calculated using a random-effects model or fixed-effects model. Sensitivity analysis was conducted by removing any one study successively to estimate the stability of the pooled results, and subgroup analysis was carried out to explore potential sources of heterogeneity, and funnel plots were used to test publication bias.

RESULTS

A total of 8 randomized-controlled trials involving 1480 patients were included in the study. Compared with vitamin D treatment, the combination use of cinacalcet and vitamin D significantly lowered serum calcium (MD - 0.82, 95% CI - 1.02 to - 0.61, P < 0.001), phosphorus (MD - 0.57, 95% CI - 0.97 to - 0.18, P = 0.005), and calcium × phosphorus product (MD - 9.41, 95% CI - 10.00 to - 8.82, P < 0.001). However, there was no difference in serum parathyroid hormone (PTH, MD 43.99, 95% CI - 49.22 to 137.20, P = 0.35), ≥ 30% reduction in PTH (RR 1.02, 95% CI 0.69-1.52, P = 0.91), and PTH achieve 150-300 pg/ml (RR 0.88, 95% CI 0.68-1.15, P = 0.35). Moreover, the combination therapy did not increase the risk of all adverse events, all-cause mortality, diarrhea, muscle spasms, and headache (all P > 0.05), but had a higher risk of hypocalcemia (RR 17.98, 95% CI 5.68-56.99, P < 0.001), and nausea or vomiting (RR 3.47, 95% CI 2.25-5.35, P < 0.001).

CONCLUSIONS

In comparison with vitamin D alone, the combination use of cinacalcet and vitamin D significantly lowered serum calcium, phosphorus, and the calcium × phosphorus product, and did not increase the risk of all adverse events, all-cause mortality, diarrhea, muscle spasms, and headache, whereas had no effect on serum PTH and increased the risk of hypocalcemia and nausea or vomiting. Future studies are needed to assess the effects of cinacalcet plus vitamin D on PTH level, cardiovascular events, and other clinical outcomes in larger samples with longer durations.

Osteoclast-Released Wnt-10b Underlies Cinacalcet Related Bone Improvement in Chronic Kidney Disease

Secondary hyperparathyroidism (SHPT) relates to high turnover bone loss and is responsible for most bone fractures among chronic kidney disease (CKD) patients. Changes in the Wingless/beta-catenin signaling (Wnt/β-catenin) pathway and Wnt inhibitors have been found to play a critical role in CKD related bone loss. A calcimimetic agent, cinacalcet, is widely used for SHPT and found to be similarly effective for parathyroidectomy clinically. A significant decrease in hip fracture rates is noted among US hemodialysis Medicare patients since 2004, which is probably related to the cinacalcet era. In our previous clinical study, it was proven that cinacalcet improved the bone mineral density (BMD) even among severe SHPT patients. In this study, the influence of cinacalcet use on bone mass among CKD mice was determined. Cinacalcet significantly reduced the cortical porosity in femoral bones of treated CKD mice. It also improved the whole-bone structural properties through increased stiffness and maximum load. Cinacalcet increased femoral bone wingless 10b (Wnt10b) expression in CKD mice. In vitro studies revealed that cinacalcet decreased osteoclast bone resorption and increased Wnt 10b release from osteoclasts. Cinacalcet increased bone mineralization when culturing the osteoblasts with cinacalcet treated osteoclast supernatant. In conclusion, cinacalcet increased bone quantity and quality in CKD mice, probably through increased bone mineralization related with osteoclast Wnt 10b secretion.

Supplementary nutrients for prevention of vascular calcification in patients with chronic kidney disease

Vascular calcification (VC) and malnutrition associated with cardiovascular disease are common in patients with chronic kidney disease (CKD) treated with dialysis. VC, which reflects vascular aging, and malnutrition are also encountered in the non-CKD elderly population. This similarity of clinical findings suggests that the progression of CKD is related to aging and the existence of a causal relationship between VC and malnutrition. To retard renal progression, a low- or very-low-protein diet is usually recommended for CKD patients. Dietary education may induce malnutrition and deficiency of important nutrients, such as vitamins K and D. Menaquinone-7, a type of vitamin K2, is under investigation for inhibiting VC in elderly patients without CKD, as well as for prevention of VC in patients with CKD. Nutritional vitamin D, such as cholecalciferol, may be considered to decrease the required dose of active vitamin D, which increases the risk of VC due to increased calcium and phosphate loads. Omega-3 fatty acids are important nutrients and their ability to inhibit VC needs to be evaluated in clinical trials. This review focuses on the ability of supplementary nutrients to prevent VC in patients with CKD, in whom dietary restriction is essential.

The Emerging Role of Nutritional Vitamin D in Secondary Hyperparathyroidism in CKD

In chronic kidney disease (CKD), hyperphosphatemia induces fibroblast growth factor-23 (FGF-23) expression that disturbs renal 1,25-dihydroxy vitamin D (1,25D) synthesis; thereby increasing parathyroid hormone (PTH) production. FGF-23 acts on the parathyroid gland (PTG) to increase 1α-hydroxylase activity and results in increase intra-gland 1,25D production that attenuates PTH secretion efficiently if sufficient 25D are available. Interesting, calcimimetics can further increase PTG 1α-hydroxylase activity that emphasizes the demand for nutritional vitamin D (NVD) under high PTH status. In addition, the changes in hydroxylase enzyme activity highlight the greater parathyroid 25-hydroxyvitmain D (25D) requirement in secondary hyperparathyroidism (SHPT); the higher proportion of oxyphil cells as hyperplastic parathyroid progression; lower cytosolic vitamin D binding protein (DBP) content in the oxyphil cell; and calcitriol promote vitamin D degradation are all possible reasons supports nutritional vitamin D (NVD; e.g., Cholecalciferol) supplement is crucial in SHPT. Clinically, NVD can effectively restore serum 25D concentration and prevent the further increase in PTH level. Therefore, NVD might have the benefit of alleviating the development of SHPT in early CKD and further lowering PTH in moderate to severe SHPT in dialysis patients.

Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis

BACKGROUND

The effects of vitamin D on fractures, falls, and bone mineral density are uncertain, particularly for high vitamin D doses. We aimed to determine the effect of vitamin D supplementation on fractures, falls, and bone density.

METHODS

In this systematic review, random-effects meta-analysis, and trial sequential analysis, we used findings from literature searches in previously published meta-analyses. We updated these findings by searching PubMed, Embase, and Cochrane Central on Sept 14, 2017, and Feb 26, 2018, using the search term "vitamin D" and additional keywords, without any language restrictions. We assessed randomised controlled trials of adults (>18 years) that compared vitamin D with untreated controls, placebo, or lower-dose vitamin D supplements. Trials with multiple interventions (eg, co-administered calcium and vitamin D) were eligible if the study groups differed only by use of vitamin D. We excluded trials of hydroxylated vitamin D analogues. Eligible studies included outcome data for total or hip fractures, falls, or bone mineral density measured at the lumbar spine, total hip, femoral neck, total body, or forearm. We extracted data about participant characteristics, study design, interventions, outcomes, funding sources, and conflicts of interest. The co-primary endpoints were participants with at least one fracture, at least one hip fracture, or at least one fall; we compared data for fractures and falls using relative risks with an intention-to-treat analysis using all available data. The secondary endpoints were the percentage change in bone mineral density from baseline at lumbar spine, total hip, femoral neck, total body, and forearm.

FINDINGS

We identified 81 randomised controlled trials (n=53 537 participants) that reported fracture (n=42), falls (n=37), or bone mineral density (n=41). In pooled analyses, vitamin D had no effect on total fracture (36 trials; n=44 790, relative risk 1·00, 95% CI 0·93-1·07), hip fracture (20 trials; n=36 655, 1·11, 0·97-1·26), or falls (37 trials; n=34 144, 0·97, 0·93-1·02). Results were similar in randomised controlled trials of high-dose versus low-dose vitamin D and in subgroup analyses of randomised controlled trials using doses greater than 800 IU per day. In pooled analyses, there were no clinically relevant between-group differences in bone mineral density at any site (range -0·16% to 0·76% over 1-5 years). For total fracture and falls, the effect estimate lay within the futility boundary for relative risks of 15%, 10%, 7·5%, and 5% (total fracture only), suggesting that vitamin D supplementation does not reduce fractures or falls by these amounts. For hip fracture, at a 15% relative risk, the effect estimate lay between the futility boundary and the inferior boundary, meaning there is reliable evidence that vitamin D supplementation does not reduce hip fractures by this amount, but uncertainty remains as to whether it might increase hip fractures. The effect estimate lay within the futility boundary at thresholds of 0·5% for total hip, forearm, and total body bone mineral density, and 1·0% for lumbar spine and femoral neck, providing reliable evidence that vitamin D does not alter these outcomes by these amounts.

INTERPRETATION

Our findings suggest that vitamin D supplementation does not prevent fractures or falls, or have clinically meaningful effects on bone mineral density. There were no differences between the effects of higher and lower doses of vitamin D. There is little justification to use vitamin D supplements to maintain or improve musculoskeletal health. This conclusion should be reflected in clinical guidelines.

FUNDING

Health Research Council of New Zealand.

Effect of uremic toxin-indoxyl sulfate on the skeletal system

Chronic kidney disease-mineral bone disorders (CKD-MBD) exhibit abnormalities in the circulating mineral levels, vitamin D metabolism, and parathyroid function that contribute to the formation of a bone lesion. The uremic toxin, indoxyl sulfate (IS), accumulates in the blood in cases of renal failure and leads to bone loss. The bone and renal responses to the action of the parathyroid hormone (PTH) are progressively decreased in CKD in spite of increasing PTH levels, a condition commonly called PTH resistance. There is a high prevalence of low bone turnover or adynamic bone disease in the early stages of CKD. This could be due to the inhibition of bone turnover, such as in PTH resistance, reduced active vitamin D levels, diabetes, aluminum, and, increased IS. With an increase in IS, there is a decrease in the osteoblast Wnt/b-catenin signaling and increase in the expression of Wnt signaling inhibitors, such as sclerostin and Dickkopf-1 (DKK1). Thus, a majority of early CKD patients exhibit deterioration of bone quality owing to the action of IS, this scenario could be termed uremic osteoporosis. However, this mechanism is complicated and not fully understood. With progressive deterioration in the renal function, IS accumulates along with persistent PTH secretion, potentially leading to high-turnover bone disease because high serum PTH levels have the ability of overriding peripheral PTH resistance and other inhibitory factors of bone formation. Finally, it leads to deterioration in bone quantity with prominent bone resorption in end stage renal disease. Uremic toxins adsorbents may decelerate oxidative stress and improve bone health in CKD patients. This review article focuses on IS and bone loss in CKD patients.