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

Associations of serum 25-hydroxyvitamin D and vitamin D receptor polymorphisms with risks of cardiovascular disease and mortality among patients with chronic kidney disease: a prospective study

BACKGROUND

Evidence regarding the relationships of serum 25-hydroxyvitamin D [25(OH)D] with cardiovascular diseases (CVD) and mortality among patients with chronic kidney disease (CKD) is limited and inconsistent.

OBJECTIVES

This study aimed to investigate the associations between serum 25(OH)D and CVD incidence and mortality among patients with CKD.

METHODS

This prospective study included 21,507 participants with CKD and free of CVD in the UK Biobank. Incidences of total and subtypes of CVD and mortality were ascertained via electronic health records. Cox proportional hazard regression models were used to estimate the hazard ratios (HRs) and 95% confidential intervals (CIs) for CVD incidence and mortality.

RESULTS

The median serum 25(OH)D concentration was 44.0 nmol/L (interquartile range: 30.1, 60.6 nmol/L). After multivariable adjustment, compared with CKD patients with serum 25(OH)D concentrations of <25 nmol/L, those with serum 25(OH)D ≥75 nmol/L had HRs (95% CIs) of 0.80 (0.71, 0.90) for total CVD incidence, 0.82 (0.69, 0.97) for ischemic heart disease, 0.56 (0.41, 0.77) for stroke, 0.64 (0.46, 0.88) for myocardial infarction, 0.62 (0.49, 0.80) for heart failure, 0.60 (0.43, 0.85) for CVD mortality, and 0.62 (0.52, 0.74) for all-cause mortality. In addition, these associations were not modified by vitamin D receptor polymorphisms, with no significant interaction detected.

CONCLUSIONS

Higher serum 25(OH)D concentrations were significantly associated with lower risks of total and subtypes of CVD incidence and mortality among individuals with CKD. These findings highlight the importance of maintaining adequate vitamin D status in the prevention of CVD and mortality in patients with CKD.

The influence of uremic toxins on low bone turnover disease in chronic kidney disease

Uremic toxins play a crucial role in the development of low bone turnover disease in chronic kidney disease (CKD) through the induction of oxidative stress. This oxidative stress disrupts the delicate balance between bone formation and resorption, resulting in a decline in both bone quantity and quality. Reactive oxygen species (ROS) activate nuclear factor kappa-B and mitogen-activated protein kinase signaling pathways, promoting osteoclastogenesis. Conversely, ROS hinder osteoblast differentiation by facilitating the binding of Forkhead box O proteins (FoxOs) to β-catenin, triggering apoptosis through FoxOs-activating kinase phosphorylation. This results in increased osteoblastic receptor activator of nuclear factor kappa-B ligand (RANKL) expression and decreased nuclear factor erythroid 2-related factor 2 levels, compromising antioxidant defenses against oxidative damage. As CKD progresses, the accumulation of protein-bound uremic toxins such as indoxyl sulfate (IS) and p-cresyl sulfate (PCS) intensifies oxidative stress, primarily affecting osteoblasts. IS and PCS directly inhibit osteoblast viability, induce apoptosis, decrease alkaline phosphatase activity, and impair collagen 1 and osteonectin, impeding bone formation. They also reduce cyclic adenosine 3',5'-monophosphate (cAMP) production and lower parathyroid hormone (PTH) receptor expression in osteoblasts, resulting in PTH hyporesponsiveness. In summary, excessive production of ROS by uremic toxins not only reduces the number and function of osteoblasts but also induces PTH hyporesponsiveness, contributing to the initiation and progression of low bone turnover disease in CKD.

Biochemical spectrum of parathyroid hormone disorders in patients attending Tribhuvan University Teaching Hospital, Kathmandu, Nepal

Objectives

This study intends to determine the association of parathormone with vitamin D and other biochemical parameters (calcium and phosphate) and evaluate the relationship between low vitamin D and parathormone levels.

Methods

A hospital-based cross-sectional study was conducted among 310 study participants over the period of 1 year. Patients who underwent laboratory investigations for vitamin D, parathormone, calcium, and phosphate in the Clinical Biochemistry Laboratory at the Institute of Medicine, Tribhuvan University Teaching Hospital were included. Serum intact parathyroid hormone, vitamin D, calcium, and phosphate were measured in Abbott Architect (ci4100) integrated system autoanalyzer.

Results

Among the 310 study participants, 177 (57%) were males and 43% were females. The mean age of the patient was 47.09 ± 19.01 years. High intact parathyroid hormone (>68 pg/ml) was observed in 73% of the patients. Low vitamin D (<20 ng/ml) was present in 30.2% of the patients. The findings from our study depict that there is a negative significant correlation between intact parathyroid hormone levels, vitamin D, and calcium levels and a positive correlation between intact parathyroid hormone and phosphate levels (p < 0.001).

Conclusions

The findings from our study illustrate that there is a swapping drift in the profile of hyperparathyroidism in the Nepalese population. We report the presence of hyperparathyroidism in the middle age group than in the older age group contradictory to that reported in the literature.

Role of nutritional vitamin D in chronic kidney disease-mineral and bone disorder: A narrative review

Chronic kidney disease-mineral and bone disorder has complex and diverse clinical manifestations, including the simplest abnormalities of calcium, phosphorus and parathyroid hormone detected in blood, abnormalities of bone transformation and mineralization in bone, and calcification of blood vessels or other soft tissues detected on imaging. Patients with CKD-MBD combined low bone mineral density and fragility fractures are referred to as CKD-MBD with low bone mineral density. Vascular calcification refers to ectopic deposition of calcium phosphate in the blood vessel walls and heart valves. The degree of vascular calcification was inversely proportional to bone mineral density. The more severe the degree of vascular calcification, the lower the bone mineral density, and the higher the risk of death, indicating that the bone-vascular axis exists. Activation and alteration of the Wnt signaling pathway are central to the treatment of vascular diseases in uremia. Vitamin D supplementation can prevent secondary hyperparathyroidism, activate osteoblasts, relieve muscle weakness and myalgia, and reduce vascular calcification. Nutritional vitamin D may improve vascular calcification in uremia patients by regulating Wnt signaling pathway.

Comparison of biochemical markers and technetium 99m methoxyisobutylisonitrile imaging in primary and secondary hyperparathyroidism

OBJECTIVE

To investigate the differences in biochemical marker levels and the extent of lesion visualization on technetium 99m methoxyisobutylisonitrile (^99mTc-MIBI) imaging between primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism (SHPT).

METHODS

Nineteen patients with PHPT and 14 patients with SHPT were enrolled in the study, all of whom underwent routine ^99mTc-MIBI dual-phase planar imaging, single-photon emission computed tomography combined with computed tomography (SPECT/CT fusion) imaging, and serum biochemical and hormonal investigations prior to surgery. The target-to-non-target (T/NT) ratios were calculated based on images from the early and delayed phases of ^99mTc-MIBI planar imaging and also based on SPECT/CT fusion imaging. The volume of the parathyroid glands was measured following their excision.

RESULTS

A total of 62 parathyroid glands were removed: 14 parathyroid adenomas and five parathyroid carcinomas in PHPT patients; and 18 parathyroid adenomas, 17 parathyroid hyperplasia lesions, and eight instances of nodular hyperplasia with adenoma in SHPT patients. The median volume of the lesions in PHPT and SHPT was 1.69 cm³ and 0.52 cm³ respectively, and the difference between them was statistically significant (P = 0.001). The median T/NT ratios calculated at the early phase of ^99mTc-MIBI planar imaging, the delayed phase of ^99mTc-MIBI planar imaging, and the subsequent SPECT/CT fusion imaging were 1.51, 1.34, and 2.75, respectively, in PHPT, and 1.46, 1.30, and 1.38, in SHPT, respectively. The T/NT ratio difference between PHPT and SHPT on the SPECT/CT fusion imaging was statistically significant (P = 0.002). The histopathology subtypes of the lesions were associated with significant differences in two areas: the T/NT ratios on the SPECT/CT fusion imaging and the volume of the lesions (P=0.002, P<0.001).

CONCLUSION

The proportion of positive findings on ^99mTc-MIBI dual-phase planar imaging and the T/NT ratios of ^99mTc-MIBI SPECT/CT fusion imaging were higher in PHPT than in SHPT. The volume of parathyroid lesions in SHPT was smaller than in PHPT.

Expression of risk genes linked to vitamin D receptor super-enhancer regions and their association with phenotype severity in multiple sclerosis

Multiple sclerosis (MS) is a chronic debilitating neurological condition with a wide range of phenotype variability. A complex interplay of genetic and environmental factors contributes to disease onset and progression in MS patients. Vitamin D deficiency is a known susceptibility factor for MS, however the underlying mechanism of vitamin D-gene interactions in MS etiology is still poorly understood. Vitamin D receptor super-enhancers (VSEs) are enriched in MS risk variants and may modulate these environment-gene interactions. mRNA expression in total of 64 patients with contrasting MS severity was quantified in select genes. First, RNA-seq was performed on a discovery cohort (10 mild, 10 severe MS phenotype) and ten genes regulated by VSEs that have been linked to MS risk were analyzed. Four candidates showed a significant positive association (GRINA, PLEC, PARP10, and LRG1) in the discovery cohort and were then quantified using digital droplet PCR (ddPCR) in a validation cohort (33 mild, 11 severe MS phenotype). A significant differential expression persisted in the validation cohort for three of the VSE-MS genes: GRINA (p = 0.0138), LRG1 (p = 0.0157), and PLEC (p = 0.0391). In summary, genes regulated by VSE regions that contain known MS risk variants were shown to have differential expression based on disease severity (p<0.05). The findings implicate a role for vitamin D super-enhancers in modulating disease activity. In addition, expression levels may have some utility as prognostic biomarkers in the future.

Endocrine manifestations of chronic kidney disease and their evolving management: A systematic review

BACKGROUND

Chronic Kidney Disease (CKD) shows a wide range of renal abnormalities including the excretory, metabolic, endocrine, and homeostatic function of the kidney. The prognostic impact of the 'endocrine manifestations' which are often overlooked by clinicians cannot be overstated.

METHODS AND OBJECTIVES

A systematic review was attempted to provide a comprehensive overview of all endocrine abnormalities of CKD and their evolving principles of management, searching databases of PubMed, Embase, and Scopus and covering the literature between 2002 and 2022.

RESULTS

The endocrine derangements in CKD can be attributed to a myriad of pathologic processes, in particular decreased clearance, impaired endogenous hormone production, uremia-induced cellular dysfunction, and activation of systemic inflammatory pathways. The major disorders include anemia, hyperprolactinemia, insulin resistance, reproductive hormone deficiency, thyroid hormone deficiency, and serum FGF (Fibroblast Growth Factor) alteration. Long-term effects of CKD also include malnutrition and increased cardiovascular risk. The recent times have unveiled their detailed pathogenesis and have seen an evolution in the principles of management which necessitates a revision of current guidelines.

CONCLUSION

Increased advertence regarding the pathology, impact, and management of these endocrine derangements can help in reducing morbidity as well as mortality in the CKD patients by allowing prompt individualized treatment. Moreover, with timely and appropriate intervention, a long-term reduction in complications, as well as an enhanced quality of life, can be achieved in patients with CKD.

Vitamin D for Recovery of COVID-19 in Patients With Chronic Kidney Disease

The severity of coronavirus disease 2019 (COVID-19) is determined not only by viral damage to cells but also by the immune reaction in the host. In addition to therapeutic interventions that target the viral infection, immunoregulation may be helpful in the management of COVID-19. Vitamin D exerts effects on both innate and adaptive immunity and subsequently modulates immune responses to bacteria and viruses. Patients with chronic kidney disease (CKD) frequently have vitamin D deficiency and increased susceptibility to infection, suggesting a potential role of vitamin D in this vulnerable population. In this paper, we review the alterations of the immune system, the risk of COVID-19 infections and mechanisms of vitamin D action in the pathogenesis of COVID-19 in CKD patients. Previous studies have shown that vitamin D deficiency can affect the outcomes of COVID-19. Supplementing vitamin D during treatment may be protective against COVID-19. Future studies, including randomized control trials, are warranted to determine the effect of vitamin D supplementation on the recovery from COVID-19 in CKD patients.

Serum Phosphorus, Parathyroid Hormone, and Serum Fibroblast Growth Factor-23 in Egyptian Patients Six Months after Undergoing Living-donor Kidney Transplantation

End-stage renal disease is a major health problem with many complications. Previous studies emphasized the relationship of cardiovascular disease and mortality among these patients to dysregulated phosphate homeostasis. Even after successful renal transplantation, the risk is not eliminated. Several factors seem to interplay to regulate serum phosphorus levels after renal transplantation. Fibroblast growth factor-23 (FGF-23) is a hormone with the major function of inhibiting the reabsorption of phosphate by the renal tubules. Parathormone reduces the reabsorption of phosphate from the proximal tubule of the kidney. The aim of our study was to explore the changes that occurred in FGF-23 and intact parathyroid hormone (iPTH) levels in a cohort of Egyptian patients undergoing renal transplantation and to examine the effect of these factors on posttransplant serum phosphorus levels. The study was carried out prospectively on 37 candidates for live-donor renal transplantation. Serum levels of calcium, phosphorus, iPTH, and FGF-23 were measured before and 6 months after renal transplantation. Statistically significant differences were detected in serum calcium, phosphorus, FGF-23, and iPTH before and 6 months after transplantation (P < 0.001, P < 0.001, P < 0.001, and P < 0.001, respectively). The results also showed a statistically significant correlation between FGF-23 levels and phosphorus levels before transplantation. The interplay between FGF-23 and iPTH has an impact on posttransplant serum phosphorus levels.

Klotho/FGF23 and Wnt in SHPT associated with CKD via regulating miR-29a

OBJECTIVE

Recently, the interaction between Klotho/fibroblast growth factor 23 (FGF-23) axis and Wnt signaling has been recognized to be responsible for chronic kidney disease (CKD)-associated comorbidities, including secondary hyperparathyroidism (SHPT). This study aimed to investigate the molecular mechanism of the interaction between Klotho/FGF23 axis and Wnt.

METHODS

A SHPT model was successfully established with a high-phosphorus diet plus 5/6 nephrectomy. Cell counting Kit-8 (CCK-8) assay and calcium deposit experiment were applied to detect the proliferation and calcium levels. Quantitative real-time PCR (qRT-PCR), Western blotting and immunofluorescence (IF) were used to determine the expression or location of FGF23, calcification-related factors and β-catenin after lentivirus-mediated Klotho overexpression. Luciferase reporter assay was performed to further validate the transcriptional regulation between microRNA-29a (miR-29a) and Dickkopf-1 (DDK1).

RESULTS

We found increased serum biochemical factors including parathyroid hormone (PTH), phosphorus, calcium, enhanced parathyroid calcification, and decreased expressions of Klotho in a rat model of secondary hyperparathyroidism. Moreover, genetic-induced upregulation of Klotho inhibited the proliferation, reduced the calcification and the alkaline phosphatase (ALP) activity, and downregulated Wnt/β-catenin signaling in parathyroid cells.

CONCLUSIONS

Mechanistically, Klotho suppressed miR-29a expression, led to upregulated expression of Wnt/β-catenin signaling inhibitor DKK1, and finally downregulated the activity of Wnt/β-catenin signaling. These findings suggest a novel molecular mechanism in the pathogenesis of CKD-associated SHPT, which provides a potential therapeutic target in the future.

Indoxyl-Sulfate-Induced Redox Imbalance in Chronic Kidney Disease

The accumulation of the uremic toxin indoxyl sulfate (IS) induces target organ damage in chronic kidney disease (CKD) patients, and causes complications including cardiovascular diseases, renal osteodystrophy, muscle wasting, and anemia. IS stimulates reactive oxygen species (ROS) production in CKD, which impairs glomerular filtration by a direct cytotoxic effect on the mesangial cells. IS further reduces antioxidant capacity in renal proximal tubular cells and contributes to tubulointerstitial injury. IS-induced ROS formation triggers the switching of vascular smooth muscular cells to the osteoblastic phenotype, which induces cardiovascular risk. Low-turnover bone disease seen in early CKD relies on the inhibitory effects of IS on osteoblast viability and differentiation, and osteoblastic signaling via the parathyroid hormone. Excessive ROS and inflammatory cytokine releases caused by IS directly inhibit myocyte growth in muscle wasting via myokines’ effects. Moreover, IS triggers eryptosis via ROS-mediated oxidative stress, and elevates hepcidin levels in order to prevent iron flux in circulation in renal anemia. Thus, IS-induced oxidative stress underlies the mechanisms in CKD-related complications. This review summarizes the underlying mechanisms of how IS mediates oxidative stress in the pathogenesis of CKD’s complications. Furthermore, we also discuss the potential role of oral AST-120 in attenuating IS-mediated oxidative stress after gastrointestinal adsorption of the IS precursor indole.

Current treatment options for secondary hyperparathyroidism in patients with stage 3 to 4 chronic kidney disease and vitamin D deficiency

Introduction: Secondary hyperparathyroidism (SHPT) represents a complication of chronic kidney disease (CKD). Vitamin D system is altered since early CKD, and vitamin D deficiency is an established trigger of SHPT. Although untreated SHPT may degenerate into tertiary hyperparathyroidism with detrimental consequences in advanced CKD, best treatments for counteracting SHPT from stage 3 CKD are still debated. Enthusiasm on prescription of vitamin D receptor activators (VDRA) in non-dialysis renal patients, has been mitigated by the risk of low bone turnover and positive calcium-phosphate balance. Nutritional vitamin D is now suggested as first-line therapy to treat SHPT with low 25(OH)D insufficiency. However, no high-grade evidence supports the best choice between ergocalciferol, cholecalciferol, and calcifediol (in its immediate or extended-release formulation).Areas covered: The review discusses available data on safety and efficacy of nutritional vitamin D, VDRA and nutritional therapy in replenishing 25(OH)D deficiency and counteracting SHPT in non-dialysis CKD patients.Expert opinion: Best treatment for low 25(OH)D and SHPT remains unknown, due to incomplete understanding of the best homeostatic, as mutable, adaptation of mineral metabolism to CKD progression. Nutritional vitamin D and nutritional therapy appear safest interventions, whenever contextualized with single-patient characteristics. VDRA should be restricted to uncontrolled SHPT by first-line therapy.

The Interplay Between Nutrition, Metabolic, and Endocrine Disorders in Chronic Kidney Disease

The kidneys are responsible for maintaining our bodies' homeostasis through excretion, biodegradation, and synthesis of different hormones. Therefore, a decline in renal function often results in significant derangements in hormone levels. The most common metabolic and endocrine abnormalities seen in patients with chronic kidney disease include deficiencies in erythropoietin, calcitriol, triiodothyronine, testosterone, and estrogen. In addition, accumulation of hormones such as adiponectin, leptin, triglycerides, and prolactin also is seen. Subsequently, this can lead to the development of a wide range of clinical consequences including but not limited to anemia, hyperparathyroidism, insulin resistance, anorexia-cachexia, infertility, bone disorders, and cardiovascular diseases. These disorders can negatively affect the prognosis and quality of life of patients with chronic kidney disease, and, thus, early diagnosis, nutritional intervention, and pharmacologic treatment is imperative.

Effects of calcifediol supplementation on markers of chronic kidney disease-mineral and bone disorder in dogs with chronic kidney disease

Background

Chronic kidney disease‐mineral and bone disorder (CKD‐MBD) in dogs is associated with hypovitaminosis D, increased parathyroid hormone (PTH), and increased fibroblast growth factor‐23 (FGF‐23) concentrations. Best practice for vitamin D metabolite supplementation in CKD‐MBD remains unknown.

Objective

To provide an extended‐release calcifediol supplement to dogs with CKD and to measure its effects on variables indicative of CKD‐MBD.

Animals

Ten dogs with International Renal Interest Society stages 2 and 3 CKD.

Methods

In a prospective study, dogs received a calcifediol supplement for 84 days. Serum 25‐hydroxyvitamin D (25[OH]D), 1,25‐dihydroxyvitamin D (1,25[OH]₂D), 24,25‐dihydroxyvitamin D (24,25[OH]₂D), creatinine, calcium, phosphorus, PTH, plasma FGF‐23 concentrations, and urine profiles were measured monthly during supplementation. Urine calcium to creatinine (UCa/Cr) ratios and fractional excretion of calcium, phosphorus, and sodium were determined.

Results

All serum vitamin D metabolite concentrations increased significantly by day 84 (P < .001): [25(OH)D (median 249.9 ng/mL; range, 149.7‐469.9 ng/mL) compared to baseline (median 50.2 ng/mL; range, 31.3‐66.0 ng/mL); 1,25(OH)₂D (median 66.1 pg/mL; range, 56.9‐88.1 pg/mL) compared to baseline (median 37.3 pg/mL; range, 29.3‐56.7 pg/mL); 24,25(OH)₂D (median 81.4 ng/mL; range, 22.1‐151.7 ng/mL) compared to baseline (median 15.4 ng/mL; range, 6.9‐40.6 ng/mL)]. There were no significant differences in calcium, phosphorus, PTH concentrations, UCa/Cr or fractional excretion of calcium. No dog developed ionized hypercalcemia. Plasma FGF‐23 concentrations increased by day 84 (median 1219 pg/mL; range, 229‐8824 pg/mL) compared to baseline (median 798 pg/mL; range, 103‐4.145 pg/mL) (P < .01).

Conclusions and Clinical Importance

Calcifediol supplementation for 84 days was well‐tolerated in dogs with IRIS stages 2 and 3 CKD. It remains to be determined how long‐term supplementation would affect CKD progression and QOL.

Endocrine myopathies: clinical and histopathological features of the major forms

Endocrinopathies, such as thyroid and parathyroid diseases, disorders of the adrenal axis, and acromegaly are included among the many causes of myopathy. Muscle disturbances caused by endocrine disorders are mainly due to alterations in the protein and carbohydrate metabolisms. Either a deficiency or excess of hormones produced by the glands can cause muscle dysfunction that can be reversed by starting hormone replacement therapy or acting on hormone dysfunction. The diagnosis is usually easy if a muscle disorder occurs in an overt endocrinopathy; however, in few patients, myopathy could be the first manifestation of the underlying endocrinopathy. In this article we discuss pathophysiology, clinical features and management of muscle involvement related to the major endocrine diseases.

The role of 18F-FCH PET/CT in patients with uremic hyperparathyroidism compared with 99mTc-sestaMIBI SPECT/CT and ultrasonography

BACKGROUND

The aim of this study was to evaluate the diagnostic efficacy of ¹⁸F-fluorocholine (¹⁸F-FCH) PET/CT for uremic hyperparathyroidism (uHPT) compared to ^99mTc-sestaMIBI SPECT/CT and ultrasonography (US).

METHODS

A total of 17 uHPT patients with stage 5 chronic kidney disease (CKD) were prospectively enrolled. All patients underwent US, ^99mTc-sestaMIBI SPECT/CT, and ¹⁸F-FCH within 2 months and received surgical treatment. Visual and quantitative methods were used for image analyses. Intraoperative localization and postoperative histological results of the reference standard as well as the sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of the three modalities were analyzed using Pearson's χ² tests. In addition, the diagnostic efficacy of ¹⁸F-FCH PET/CT for uHPT was evaluated. The relationships between PET parameters and laboratory parameters were assessed using the Spearman correlation coefficient.

RESULTS

A total of 63 parathyroid hyperplasia lesions were resected in 17 uHPT patients, and 53 lesions were detected using ¹⁸F-FCH PET/CT with no false-positive results. The sensitivity, specificity, accuracy, PPV, and NPV were 84.13%, 100%, 86.49%, 100%, and 52.38%, respectively. In comparison, the corresponding values for ^99mTc-sestaMIBI SPECT/CT and US were 63.49%, 90.91%, 67.57%, 97.56%, and 30.30% and 61.90%, 81.82%, 64.86%, 95.12%, and 27.27%, respectively. The volume of hyper-functioning parathyroid glands was significantly different between lesions positive in ¹⁸F-FCH PET/CT and negative in ¹⁸F-FCH PET/CT (mean volume 1.36 ± 0.55 cm³ vs. 0.83 ± 0.26 cm³; P = 0.019). US misidentified intrathyroidal parathyroid hyperplasia as thyroid nodules in three patients, while ¹⁸F-FCH PET correctly identified the anatomy. No significant associations were observed between PET parameters and laboratory parameters in uHPT.

CONCLUSION

¹⁸F-FCH PET/CT was more sensitive and accurate for uHPT than ^99mTc-sestaMIBI SPECT/CT and US, and had better preoperative diagnostic efficacy, particularly for lesions diagnosed as a thyroid nodule by US.

Antiproteinuria Effect of Calcitriol in Patients With Chronic Kidney Disease and Vitamin D Deficiency: A Randomized Controlled Study

OBJECTIVE

Vitamin D has been demonstrated to lessen proteinuria severity in chronic kidney disease (CKD). Compared with healthy populations, patients with CKD may have lower serum levels of 1,25-dihydroxy vitamin D (1,25-(OH)2 D) and 25-hydroxy vitamin D (25-(OH) D). We investigated the effect of  oral low-dose active vitamin D (calcitriol at 0.25 μg, 3 times weekly) on urinary protein excretion.

DESIGN AND METHODS

We conducted a nonblinded and non-placebo-controlled study. In total, 60 patients with CKD (average estimated glomerular filtration rate of >15 mL/min) who received a stable dose of angiotensin receptor blocker (ARB) or angiotensin-converting enzyme inhibitor (ACEI) were enrolled in this 24-week study. We randomly assigned these patients to the vitamin D group (oral calcitriol at 0.25 μg 3 times weekly with an ACEI or ARB) or the control group (ACEI or ARB). Change in the urine protein/creatinine ratio (uPCR) was the primary endpoint in this study.

RESULTS

The mean baseline uPCRs of the 2 groups were comparable (1.84 ± 0.83 g/g vs. 2.02 ± 0.97 g/g, control vs. vitamin D group; P = .46). After the 24-week treatment, the uPCRs were significantly lower than the baseline values in the vitamin D group (1.35 ± 0.64 g/g; P < .05) but not in the control group. The values of uPCR decreased significantly at 8, 16, and 24 weeks (P < .05 vs. baseline) in the vitamin D group. The values of uPCRs were significantly lower in the vitamin D group than in the control group at 8, 16, and 24 weeks (P < .05). A positive correlation was discovered between reduction in uPCRs at 24-week and baseline 25-(OH) D serum level in the vitamin D group (r = 0.738, P < .001).

CONCLUSION

Supplementary low-dose active vitamin D could reduce proteinuria in CKD patients with low serum 25-(OH) D levels.

Inflammation-Related Patterns in the Clinical Staging and Severity Assessment of Chronic Kidney Disease

Chronic kidney disease (CKD) is an irreversible loss of kidney function, and it represents a major global public health burden due to both its prevalence and its continuously increasing incidence. Mineral bone disorders (MBDs) constitute a hallmark of CKD, and alongside cardiovascular complications, they underlie a poor prognosis for these patients. Thus, our study focused on novel CKD biomarker patterns and their impact on the clinical staging of the disease. As a first testing approach, the relative expression levels of 105 proteins were assessed by the Proteome Profiler Cytokine Array Kit for pooled CKD stage 2–4 serum samples to establish an overall view regarding the proteins involved in CKD pathogenesis. Among the molecules that displayed significant dysregulation in the CKD stages, we further explored the involvement of Dickkopf-related protein 1 (Dkk-1), a recognised inhibitor of the Wnt signalling pathway, and its crosstalk with 1,25OH₂D₃ (calcitriol) as new players in renal bone and vascular disease. The serum levels of these two molecules were quantified by an ELISA (76 samples), and the results reveal decreasing circulating levels of Dkk-1 and calcitriol in advanced CKD stages, with their circulating expression showing a downward trend as the CKD develops. In the next step, we analysed the inflammation and MBD biomarkers' expression in CKD (by xMAP array). Our results show that the molecules involved in orchestrating the inflammatory response, interleukin-6 (IL-6) and tumour necrosis factor alpha (TNFα), as well as the mineral biomarkers osteoprotegerin (OPG), osteocalcin (OC), osteopontin (OPN), and fibroblast growth factor 23 (FGF-23), correlate with Dkk-1 and calcitriol, raising the possibility of them being potential useful CKD biomarkers. These results reveal the impact of different biomarker patterns in CKD staging and severity, thus opening up novel approaches to be explored in CKD clinical management.

Effect of Resistance Exercise Plus Cholecalciferol on Nutritional Status Indicators in Adults With Stage 4 Chronic Kidney Disease

OBJECTIVE

Decreased serum concentrations of 25-hydroxyvitamin D (25(OH)D) affect people with chronic kidney disease (CKD); lower concentrations of 25(OH)D have been associated with decrease in nutritional status indicators. On the other hand, muscle resistance exercise has improved the nutritional status of patients with CKD.The aim of this study was to evaluate the effect of resistance exercise and dietary supplementation with cholecalciferol on nutritional status indicators in adults with stage 4 CKD.

METHODS

Patients with an estimated glomerular filtration rate between 15 and 29 mL/min/1.73 m² in an open-label clinical trial were followed for 12 weeks. The intervention group received exercise resistance training sessions three times per week with oral cholecalciferol supplementation each day. The control group only received standard medical care. The outcomes were anthropometric measurements, handgrip strength, and bioelectrical impedance analysis.

RESULTS

Thirty-nine patients of a median age of 48 (36-52) years had an estimated glomerular filtration rate of 21.8 ± 6.5 mL/min/1.73 m². A total of 57.5% of the patients were women. In 41% of the patients, the etiology of CKD was diabetes. After 12 weeks, in the intervention group, the adherence to the resistance training was 77%, and the adherence to the supplementation with cholecalciferol was 96.2%. Significant improvements in 25(OH)D serum concentrations and in handgrip strength were detected in the intervention group (P < .05). In the control group, a decrease in 25(OH)D serum concentrations and a loss in handgrip strength were observed, although the difference was not statistically significant. Anthropometrics and biochemical and dietary indicators, but not bioelectrical impedance data, exhibited changes.

CONCLUSION

Supplementation with cholecalciferol improves serum concentrations of 25(OH)D and, when combined with resistance exercise, improved muscle function as measured by handgrip strength in a study of patients with CKD not on dialysis.