Can vitamin D slow down the progression of chronic kidney disease?

Association between dietary inflammation index and albuminuria: results from the National Health and Nutrition Examination Survey

Background

The Dietary Inflammation Index (DII) is a tool for evaluating the potential for dietary inflammation, and inflammation is a major cause of exacerbation in chronic kidney disease. Our study aimed to investigate the relationship between DII and albuminuria.

Methods

Data were obtained from the 2005-2018 National Health and Nutrition Examination Survey (NHANES) after excluding pregnant, minors, and missing data of urinary albumin-creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), and DII were enrolled in our study. Albuminuria was defined as ACR > 30 mg/g. DII was calculated and divided into tertiles. After fully adjusted, multivariate logistic regression analysis and subgroup analysis were performed to investigate the association between DII and albuminuria.

Results

A total of 22,607 participants including 2,803 (12.40%) with and 19,804 (87.60%) without albuminuria were enrolled in our study. The albuminuria increased with the increasing DII tertiles (Tertile 1: 10.81%; Tertile 2: 12.41%; Tertile 3:13.97%, P < 0.001). After fully adjusting for covariates, multivariate logistic regression showed that the higher the DII, the greater the odds of albuminuria (OR = 1.19; 95% CI, 1.00-1.41, P < 0.001). Subgroup analysis and interaction test of participants found that the positive correlation between DII and albuminuria was not significantly related to gender, age, BMI, hypertension, diabetes, and eGFR (P for interaction >0.05).

Conclusion

Elevated DII is associated with high odds of albuminuria. Further large-scale prospective studies are still needed to analyze the role of DII in albuminuria.

The Impact of Serum Levels of Vitamin D3 and Its Metabolites on the Prognosis and Disease Severity of COVID-19

Vitamin D is among the increasingly consumed dietary supplements during the COVID-19 pandemic. It plays a regulatory role in the immune system and moderates the renin-angiotensin system, which is implicated in infection pathogenesis. However, the investigation of serum levels of vitamin D3 forms and their relative ratios in COVID-19 patients is worth investigation to understand the impacts of disease severity. Hence, we investigated the serum levels of vitamin D3 (cholecalciferol) and its metabolites (calcifediol and calcitriol), in addition to their relative ratios and correlations with angiotensin-converting enzyme 2 (ACE2), interleukin-6 (Il-6), and neutrophil-lymphocyte ratio (NLR) in COVID-19 patients compared with healthy controls. Oropharyngeal specimens were collected from the study subjects for polymerase chain reaction testing for COVID-19. Whole blood samples were obtained for blood count and NLR testing, and sera were used for the analysis of the levels of the vitamin and its metabolites, ACE2, and IL-6. We enrolled 103 patients and 50 controls. ACE2, Il-6, and NLR were significantly higher in the patients group (72.37 ± 18.67 vs. 32.36 ± 11.27 U/L, 95.84 ± 25.23 vs. 2.76 ± 0.62 pg/mL, and 1.61 ± 0.30 vs. 1.07 ± 0.16, respectively). Cholecalciferol, calcifediol, and calcitriol were significantly lower in patients (18.50 ± 5.36 vs. 29.13 ± 4.94 ng/mL, 14.60 ± 3.30 vs. 23.10 ± 3.02 ng/mL, and 42.90 ± 8.44 vs. 65.15 ± 7.11 pg/mL, respectively). However, their relative ratios were normal in both groups. Levels of the vitamin and metabolites were strongly positively, strongly negatively, and moderately negatively correlated with ACE2, Il-6, and NLR, respectively. COVID-19 infection severity is associated with a significant decrease in vitamin D3 and its metabolites in a parallel pattern, and with a significant increase in ACE2, Il-6, and NLR. Higher levels of vitamin D and its metabolites are potentially protective against severe infection.

Acute kidney injury in children with chronic kidney disease is associated with faster decline in kidney function

BACKGROUND

This study aimed to investigate the association of acute kidney injury (AKI) with change in estimated glomerular filtration rate (eGFR) in children with advanced chronic kidney disease (CKD).

METHODS

Single centre, retrospective longitudinal study including all prevalent children aged 1-18 years with nondialysis CKD stages 3-5. Variables associated with CKD were analysed for their potential effect on annualised eGFR change (ΔGFR/year) following multiple regression analysis. Composite end-point including 25% reduction in eGFR or progression to kidney replacement therapy was evaluated.

RESULTS

Of 147 children, 116 had at least 1-year follow-up in a dedicated CKD clinic with mean age 7.3 ± 4.9 years with 91 (78.4%) and 77 (66.4%) with 2- and 3-year follow-up respectively. Mean eGFR at baseline was 29.8 ± 11.9 ml/min/1.73 m² with 79 (68%) boys and 82 (71%) with congenital abnormalities of kidneys and urinary tract (CAKUT). Thirty-nine (33.6%) had at least one episode of AKI. Mean ΔGFR/year for all patients was - 1.08 ± 5.64 ml/min/1.73 m² but reduced significantly from 2.03 ± 5.82 to - 3.99 ± 5.78 ml/min/1.73 m² from youngest to oldest age tertiles (P < 0.001). There was a significant difference in primary kidney disease (PKD) (77% versus 59%, with CAKUT, P = 0.048) but no difference in AKI incidence (37% versus 31%, P = 0.85) between age tertiles. Multiple regression analysis identified age (β = - 0.53, P < 0.001) and AKI (β = - 3.2, P = 0.001) as independent predictors of ΔGFR/year. 48.7% versus 22.1% with and without AKI reached composite end-point (P = 0.01).

CONCLUSIONS

We report AKI in established CKD as a predictor of accelerated kidney disease progression and highlight this as an additional modifiable risk factor to reduce progression of kidney dysfunction. Graphical abstract.

Association of vitamin D with the modulation of the disease severity in COVID-19

In late 2019, SARS-CoV-2 started to spread throughout the world causing the COVID-19 that has taken a considerable number of lives. Results obtained from several investigations have explained the virus origin, pathogenicity, and transmission. Similar to SARS coronavirus, the pulmonary angiotensin converting enzyme (ACE) 2 was introduced as the virus receptor for entering the cell. An increased body of epidemiological and clinical evidences has shown modulating effects of vitamin D in lung injuries through several mechanisms. Several clinical symptoms as well as molecular factors have shown to be related to the disease transmission and severity. In this study, vitamin D, ACE concentrations, and neutrophil to lymphocyte ratio (NLR) were measured in patients with confirmed COVID-19 in comparison with control group. Results demonstrated significant alterations in vitamin D and ACE levels as well as NLR in the patients' group. Contribution of those factors with the prognosis and severity of the disease has been shown.

Immune Dysfunction in Uremia 2020

Cardiovascular disease and infections are major causes for the high incidence of morbidity and mortality of patients with chronic kidney disease. Both complications are directly or indirectly associated with disturbed functions or altered apoptotic rates of polymorphonuclear leukocytes, monocytes, lymphocytes, and dendritic cells. Normal responses of immune cells can be reduced, leading to infectious diseases or pre-activated/primed, giving rise to inflammation and subsequently to cardiovascular disease. This review summarizes the impact of kidney dysfunction on the immune system. Renal failure results in disturbed renal metabolic activities with reduced renin, erythropoietin, and vitamin D production, which adversely affects the immune system. Decreased kidney function also leads to reduced glomerular filtration and the retention of uremic toxins. A large number of uremic toxins with detrimental effects on immune cells have been identified. Besides small water-soluble and protein-bound compounds originating from the intestinal microbiome, several molecules in the middle molecular range, e.g., immunoglobulin light chains, retinol-binding protein, the neuropeptides Met-enkephalin and neuropeptide Y, endothelin-1, and the adipokines leptin and resistin, adversely affect immune cells. Posttranslational modifications such as carbamoylation, advanced glycation products, and oxidative modifications contribute to uremic toxicity. Furthermore, high-density lipoprotein from uremic patients has an altered protein profile and thereby loses its anti-inflammatory properties.

Vitamin D status of children with moderate to severe chronic Kidney Disease at a Tertiary Pediatric Center in Cape Town

The prevalence of suboptimal Vitamin D levels is higher in patients with chronic kidney disease (CKD) than in the general population. Recent findings suggest that progression of CKD is linked to a suboptimal Vitamin D level. A high percentage of CKD patients have severe Vitamin D deficiency. These patients also have a low level of 25-hydroxy-vitamin D [25(OH)D] and consequently, a reduced ability to form active 1,25-dihydroxyvitamin D. Various factors underlie the low level of 25(OH)D, including a sedentary lifestyle, decreased intake of Vitamin D due to CKD-related dietary restrictions, and decreased synthesis of Vitamin D in skin due to uremia. All these factors may be particularly influential in patients with progressively worsening CKD, including those receiving chronic dialysis. The objective of our study is to determine the prevalence of Vitamin D deficiency in children with CKD stages three to five and those receiving chronic dialysis, to ascertain whether there is a relationship between Vitamin D deficiency and the stage of CKD, and to identify any clinical correlates associated with the Vitamin D status. A single-center, retrospective review was conducted of 46 children (younger than 18 years) with CKD stages 3-5D who attended the renal clinic of the Red Cross Children's Hospital between October 2013 and November 2014. In total, 73.9% of the study population had suboptimal Vitamin D levels (43.5% and 30.4% had Vitamin D deficiency and insufficiency, respectively). The prevalence of Vitamin D deficiency was significantly higher in older children (≥10 years of age) than in younger children (P = 0.000) but did not significantly differ between males and females (P = 0.693). In total, 12 of 15 black children (80%), 19 of 26 colored children (73.1%), two of four white children (50%), and one Asian child (100%) had suboptimal Vitamin D levels. Neither white nor Asian child had Vitamin D deficiency. In addition, 90% of patients undergoing chronic dialysis, 80% of whom were receiving peritoneal dialysis, had suboptimal Vitamin D levels. Age, weight, height, and the albumin concentration were significantly associated with the Vitamin D level. There was a positive linear relationship between the Vitamin D level and the serum albumin concentration (Spearman's rho correlation coefficient = 0.397, P = 0.007). In total, 87.5% of patients with nephrotic-range proteinuria had suboptimal Vitamin D levels, and 80% were Vitamin D deficient (P = 0.004). A higher percentage of Vitamin D deficiency/insufficiency cases was documented during the winter (24/34, 70.6%) than during the summer (10/34, 29.4%); however, this difference was not statistically significant (P = 0.685). Sub-optimal Vitamin D is high among children with moderate to severe CKD and significantly higher in those undergoing chronic dialysis. The emerging evidence of the role of Vitamin D in slowing progression of CKD highlights the need for monitoring and correction of Vitamin D levels in predialysis children.

The Relationship Between Vitamin D Deficiency and Glycated Hemoglobin Levels in Patients with Type 2 Diabetes Mellitus

PURPOSE

The aims of this study were to determine the relationship between 25-hydroxyvitamin D [25(OH) D] and glycated hemoglobin (HbA1c) levels in male and female patients with type 2 diabetes mellitus (T2DM).

PATIENTS AND METHODS

The participants were adults diagnosed with T2DM recruited from Hebei General Hospital. Patient information and information regarding blood indicators were collected. The subjects were divided into no vitamin D deficiency group [25(OH) D >20 ng/mL] and vitamin D deficiency group [25(OH) D <20 ng/mL], and these groups were then further subdivided into male-only or female-only subgroups. And then, the subjects were divided into male group and female group in different 25(OH) D levels.

RESULTS

HbA1c levels in the vitamin D deficiency group were significantly higher than those in the no vitamin D deficiency group for all subjects. The same was true for female patients but not for male patients. There was no difference in HbA1c levels between male and female patients with T2DM, regardless of 25(OH) D deficiency. A negative correlation existed between 25(OH) D and HbA1c in all subjects, as well as in the male-only and female-only subgroups. Vitamin D deficiency was associated with high HbA1c levels before and after adjusting for confounding factors in all participants and in the female-only subgroup, but not in the male-only subgroup.

CONCLUSION

This study confirmed that vitamin D deficiency was related with high HbA1c levels in patients with T2DM, and this relationship differs between female and male patients.

Ultraviolet B Exposure Inhibits Angiotensin II-Induced Abdominal Aortic Aneurysm Formation in Mice by Expanding CD4+Foxp3+ Regulatory T Cells

Background

Pathogenic immune responses are known to play an important role in abdominal aortic aneurysm (AAA) development. Ultraviolet B (UVB) irradiation has been demonstrated to have therapeutic potential not only for cutaneous diseases but also for systemic inflammatory diseases in mice by suppressing immunoinflammatory responses. We investigated the effect of UVB irradiation on experimental AAA.

Methods and Results

We used an angiotensin II–induced AAA model in apolipoprotein E–deficient mice fed a high‐cholesterol diet. Mice aged 10 weeks were irradiated with 5 kJ/m²UVB once weekly for 6 weeks (UVB‐irradiated, n=38; nonirradiated, n=42) and were euthanized for evaluation of AAA formation at 16 weeks. Overall, 93% of angiotensin II–infused mice developed AAA, with 60% mortality possibly because of aneurysm rupture. UVB irradiation significantly decreased the incidence (66%) and mortality (29%) of AAA (P=0.004 and P=0.006, respectively). UVB‐irradiated mice had significantly smaller diameter AAA (P=0.008) and fewer inflammatory cells in the aortic aneurysm tissue than nonirradiated mice, along with systemic expansion of CD4⁺Foxp3⁺ regulatory T cells and decreased effector CD4⁺CD44^highCD62L^low T cells in para‐aortic lymph nodes. Genetic depletion of regulatory T cells abrogated these beneficial effects of UVB treatment, demonstrating a critical role of regulatory T cells.

Conclusions

Our data suggest that UVB‐dependent expansion of regulatory T cells has beneficial effects on experimental AAA and may provide a novel strategy for the treatment of AAA.

Design and implementation of a custom next generation sequencing panel for selected vitamin D associated genes

Background

Biologically active vitamin D has an important regulatory role within the genome. It binds the vitamin D receptor (VDR) in order to control the expression of a wide range of genes as well as interacting with the epigenome to modify chromatin and methylation status. Vitamin D deficiency is associated with several human diseases including end-stage renal disease.

Methods

This article describes the design and testing of a custom, targeted next generation sequencing (NGS) panel for selected vitamin D associated genes. Sequencing runs were used to determine the effectiveness of the panel for variant calling, to compare efficiency and data across different sequencers, and to perform representative, proof of principle association analyses. These analyses were underpowered for significance testing. Amplicons were designed in two pools (163 and 166 fragments respectively) and used to sequence two cohorts of renal transplant recipients on the Ion Personal Genome Machine (PGM)™ and Ion S5™ XL desktop sequencers.

Results

Coverage was provided for 43.8 kilobases across seven vitamin D associated genes (CYP24A1, CUBN, VDR, GC, NADSYN1, CYP27B1, CYP2R1) as well as 38 prioritised SNPs. Sequencing runs provided sufficient sequencing quality, data output and validated the effective library preparation and panel design.

Conclusions

This novel, custom-designed, validated panel provides a fast, cost effective, and specific approach for the analysis of vitamin D associated genes in a wide range of patient cohorts. This article does not report results from a controlled health-care intervention.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2664-z) contains supplementary material, which is available to authorized users.

Clinical practice recommendations for native vitamin D therapy in children with chronic kidney disease Stages 2-5 and on dialysis

Vitamin D deficiency is widely prevalent and often severe in children and adults with chronic kidney disease (CKD). Although native vitamin D {25-hydroxyvitamin D [25(OH)D]} is thought to have pleiotropic effects on many organ systems, its skeletal effects have been most widely studied. The 25(OH)D deficiency is causally linked with rickets and fractures in healthy children and those with CKD, contributing to the CKD-mineral and bone disorder (MBD) complex. There are few studies to provide evidence for vitamin D therapy or guidelines for its use in CKD. A core working group (WG) of the European Society for Paediatric Nephrology (ESPN) CKD-MBD and Dialysis WGs have developed recommendations for the evaluation, treatment and prevention of vitamin D deficiency in children with CKD. We present clinical practice recommendations for the use of ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) in children with CKD Stages 2-5 and on dialysis. A parallel document addresses treatment recommendations for active vitamin D analogue therapy. The WG has performed an extensive literature review to include meta-analyses and randomized controlled trials in healthy children as well as children and adults with CKD, and prospective observational studies in children with CKD. The Grading of Recommendation, Assessment, Development and Evaluation (GRADE) system has been used to develop and grade the recommendations. In the absence of applicable study data, the opinion of experts from the ESPN CKD-MBD and Dialysis WGs is provided, but clearly GRADE-ed as such and must be carefully considered by the treating physician, and adapted to individual patient needs as appropriate.

Oral paricalcitol: expanding therapeutic options for pediatric chronic kidney disease patients

The complex pathophysiology of progressive chronic kidney disease (CKD) and the development of mineral and bone disorder, abbreviated as CKD-MBD, is of vital importance to a pediatric patient. Paricalcitol, the 19 nor-1,25(OH)₂D₂ analogue was shown to be effective and safe in the treatment of secondary hyperparathyroidism (SHPT) in adults almost two decades ago. It also significantly improved survival in dialysis patients compared to the standard calcitriol. The successful treatment of CKD-MBD in children is essential if they are to grow and survive into adulthood. It can be argued that it is more important for children with CKD than adults since they have early and prolonged disease risk exposure. In this issue of Pediatric Nephrology, Webb et.al. report a dual trial of the safety, efficacy, and pharmacokinetics of paricalcitol in children aged 10-16 years with moderate but significant efficacy in meeting the endpoint of >30% decrease in parathyroid hormone (PTH) levels from baseline with minimal adverse events. Much more research needs to be done to expand and develop clinical pharmaceutical trials in the use of paricalcitol in children, especially in the younger age categories. This current study has done much to open the doors for future studies, with the caveat that it has been long coming and much more needs to be done to compensate for this delay in the treatment of children with CKD-MBD and cardiovascular and renal disease progression.

The Prevalence of 25-hydroxyvitamin D Deficiency in Japanese Patients with Diabetic Nephropathy

Objective The purpose of this study was to measure serum 25-hydroxyvitamin D [25(OH)D] levels in Japanese patients with diabetic nephropathy and determine the relationship between 25(OH)D concentrations and various factors. Methods The study subjects included 442 patients with type 2 diabetes. Their serum levels of creatinine, HbA1c, intact-parathyroid hormone, urinary albumin, 25(OH)D, and 1,25-dihydroxyvitamin D [1,25(OH)2D] were measured and their estimated glomerular filtration rate (eGFR) was determined. The patients were divided into four groups based on the risk for progression to chronic kidney disease (CKD): low, moderate, high, very high, based on their eGFR and their level of albuminuria. Results The median 25(OH)D level was 14.6 ng/mL; 11% of the patients had 25(OH)D deficiency (<10 ng/mL), and 2% of patients had active vitamin D deficiency, as defined by a 1,25(OH)2D level of <22 pg/mL. The serum 25(OH)D level was correlated with the serum 1,25(OH)2D level in patients with a very high risk for CKD, but not in those with a moderate or high risk for CKD. Conclusion Although the vitamin D levels of the Japanese patients with diabetic nephropathy and CKD were low, the prevalence of vitamin D deficiency, as defined by the 1,25(OH)2D level, was low. Albuminuria, younger age, and female gender were associated with a low 25(OH)D level. The serum level of 25(OH)D should be monitored to assess the vitamin D status of patients with nephropathy and CKD.

Normal 25-Hydroxyvitamin D Levels Are Associated with Less Proteinuria and Attenuate Renal Failure Progression in Children with CKD

Angiotensin-converting enzyme inhibitors (ACEi) for renin-angiotensin-aldosterone system (RAAS) blockade are routinely used to slow CKD progression. However, vitamin D may also promote renoprotection by suppressing renin transcription through cross-talk between RAAS and vitamin D-fibroblast growth factor-23 (FGF-23)-Klotho pathways. To determine whether vitamin D levels influence proteinuria and CKD progression in children, we performed a post hoc analysis of the Effect of Strict Blood Pressure Control and ACE Inhibition on Progression of CKD in Pediatric Patients (ESCAPE) cohort. In 167 children (median eGFR 51 ml/min per 1.73 m(2)), serum 25-hydroxyvitamin D (25(OH)D), FGF-23, and Klotho levels were measured at baseline and after a median 8 months on ACEi. Children with lower 25(OH)D levels had higher urinary protein/creatinine ratios at baseline (P=0.03) and at follow-up (P=0.006). Levels of 25(OH)D and serum vitamin D-binding protein were not associated, but 25(OH)D ≤50 nmol/L associated with higher diastolic BP (P=0.004). ACEi therapy also associated with increased Klotho levels (P<0.001). The annualized loss of eGFR was inversely associated with baseline 25(OH)D level (P<0.001, r=0.32). Five-year renal survival was 75% in patients with baseline 25(OH)D ≥50 nmol/L and 50% in those with lower 25(OH)D levels (P<0.001). This renoprotective effect remained significant but attenuated with ACEi therapy (P=0.05). Renal survival increased 8.2% per 10 nmol/L increase in 25(OH)D (P=0.03), independent of eGFR; proteinuria, BP, and FGF-23 levels; and underlying renal diagnosis. In children with CKD, 25(OH)D ≥50 nmol/L was associated with greater preservation of renal function. This effect was present but attenuated with concomitant ACEi therapy.

Serum vitamin D and parathyroid hormone profiles in patients with various stages of renal disease

BACKGROUND

The prevalence of vitamin D deficiency among Saudi population has increased recently. The social and pathological factors, including kidney disease that may have influenced the vitamin status have not been investigated in the Hail population.

AIMS

The present study aims to: (1) investigate changes in the serum vitamin D, parathyroid hormone, serum calcium, and phosphate levels in Saudi patients with kidney disease; and (2) elucidate the other possible physiological factors that may have influence on the vitamin status.

METHODS

A cross-sectional study was carried out in King Khalid Hospital in Hail, Saudi Arabia. The database of kidney disease patients that attended the Kidney Unit between September 2012 and June 2013 was searched and data classified according to the estimated glomerular filtration rate into stages 1-4. Beside the kidney function parameters, serum calcium, phosphorus, vitamin D, and parathyroid hormone were measured.

RESULTS

Out of the 167 patients who visited the kidney unit, the data of 96 patients was included in the study. The results exhibited significant reductions in serum vitamin D level in stage 4 patients by 52.05 per cent with significant increase in the serum PTH level amounting to 3.5-fold. Kidney impairment at stage 4 caused significant increase in the serum phosphate level by 15.74 per cent and the serum calcium by 8.17 per cent. Significant correlations were observed between serum creatinine and Log PTH (r=0.704, p<0.0001) and a negative correlation between creatinine and log vitamin D (r=-0.373, p=0.001).

CONCLUSION

The results exhibited depletion of serum vitamin D concentration accompanied with the development of severe secondary hyperparathyroidism with the progression in kidney disease. The vitamin D deficiency was more prominent in females, older ages, and advanced kidney disease.

Is the renin-angiotensin system actually hypertensive?

The historical view of the renin-angiotensin system (RAS) is that of an endocrine hypertensive system that is controlled by renin and mediated via the action of angiotensin II on its type 1 receptor. Numerous new angiotensins (Ang) and receptors have been described, the majority being hypotensive and natriuretic, namely Ang-(1-7) and its receptor rMas. Renin and its precursor (pro-renin) can bind their common receptor. In addition to the production of Ang II, this receptor triggers intracellular effects. Given the control of renin production by intracellular calcium, calcium homeostasis is of particular importance. Ang-(1-12), which is not controlled by renin, is converted to several different angiotensin peptides and is a new pathway of the RAS. Local RAS enzymes produce or transform the different hyper- or hypotensive angiotensin within vessels and organs, but also in blood through circulating forms of the enzymes. In the kidney, a powerful local vascular RAS allows for the independence of renal vascularization from systemic control. Moreover, the kidney also contains an independent urinary RAS, which counterbalances the systemic RAS and coordinates proximal and distal sodium reabsorption. The systemic and local effects of renal RAS cannot be analyzed without taking into account the antagonistic effect of renalase. Our concept of RAS needs to evolve to take into account its dual potentiality (hyper- or hypotensive).

Chronic kidney disease: a new look at pathogenetic mechanisms and treatment options

The concept of renoprotection has evolved significantly, driven by improved understanding of the pathophysiology of chronic kidney disease (CKD) and the advent of novel treatment options. Glomerular hyperfiltration, hypertension and proteinuria represent key mediators of CKD progression. It is increasingly recognized that proteinuria may actually be pathological and etiological in CKD progression and not just symptomatic. It initiates a sequence of events involving activation of proinflammatory and profibrotic signaling pathways in proximal tubular epithelial cells with transmission of the disease to the tubulointerstitium and progression to end-stage kidney disease (ESKD). Although the etiology and epidemiology of pediatric CKD differs to that in adults, studies in the various animal models of kidney disease, from obstructive uropathy to glomerulonephritis, have revealed that many common proinflammatory and profibrotic pathways are induced in progressive proteinuric CKD, irrespective of the primary disease. This pathomechanistic overlap therefore translates into the potential for common treatment targets for a wide spectrum of kidney diseases. In this review we therefore discuss the experimental and clinical evidence for an array of prospective future drug treatments of CKD progression. While conceptually promising, clear definitive evidence beyond preclinical data does not exist for many of these treatments, and others are limited by serious adverse effects. More studies are needed before general recommendations can be given.

Calcitriol, calcidiol, parathyroid hormone, and fibroblast growth factor-23 interactions in chronic kidney disease

Objective

To review the inter-relationships between calcium, phosphorus, parathyroid hormone (PTH), parent and activated vitamin D metabolites (vitamin D, 25(OH)-vitamin D, 1,25(OH)₂-vitamin D, 24,25(OH)₂-vitamin D), and fibroblast growth factor-23 (FGF-23) during chronic kidney disease (CKD) in dogs and cats.

Data Sources

Human and veterinary literature.

Human Data Synthesis

Beneficial effects of calcitriol treatment during CKD have traditionally been attributed to regulation of PTH but new perspectives emphasize direct renoprotective actions independent of PTH and calcium. It is now apparent that calcitriol exerts an important effect on renal tubular reclamation of filtered 25(OH)-vitamin D, which may be important in maintaining adequate circulating 25(OH)-vitamin D. This in turn may be vital for important pleiotropic actions in peripheral tissues through autocrine/paracrine mechanisms that impact the health of those local tissues.

Veterinary Data Synthesis

Limited information is available reporting the benefit of calcitriol treatment in dogs and cats with CKD.

Conclusions

A survival benefit has been shown for dogs with CKD treated with calcitriol compared to placebo. The concentrations of circulating 25(OH)-vitamin D have recently been shown to be low in people and dogs with CKD and are related to survival in people with CKD. Combination therapy for people with CKD using both parental and activated vitamin D compounds is common in human nephrology and there is a developing emphasis using combination treatment with activated vitamin D and renin-angiotensin-aldosterone-system (RAAS) inhibitors.

Chronic kidney disease: mineral and bone disorder in children

Childhood and adolescence are crucial times for the development of a healthy skeletal and cardiovascular system. Disordered mineral and bone metabolism accompany chronic kidney disease (CKD) and present significant obstacles to optimal bone strength, final adult height, and cardiovascular health. Early increases in bone and plasma fibroblast growth factor 23 (FGF23) are associated with early defects in skeletal mineralization. Later in the course of CKD, secondary hyperparathyroidism--caused by a combination of declining calcitriol values and phosphate retention--results in high-turnover renal osteodystrophy whereas increased levels of both phosphate and FGF23 contribute to cardiovascular disease. Treatment of hyperphosphatemia and secondary hyperparathyroidism improves high-turnover bone disease but fails to correct defects in skeletal mineralization. Because overtreatment may result in adynamic bone disease, growth failure, hypercalcemia, and progression of cardiovascular calcifications, therapy therefore must be titrated carefully to maintain optimal serum biochemical parameters according to stage of CKD. Newer therapeutic agents and new treatment paradigms may suppress serum PTH levels effectively while limiting intestinal calcium absorption and skeletal FGF23 stimulation and may provide future therapeutic alternatives for children with CKD.

Calcidiol deficiency in end-stage organ failure and after solid organ transplantation: status quo

Among patients with organ failure, vitamin D deficiency is extremely common and frequently does not resolve after transplantation. This review crystallizes and summarizes existing data on the status quo of vitamin D deficiency in patients with organ failure and in solid organ transplant recipients. Interventional studies evaluating different treatment strategies, as well as current clinical practice guidelines and recommendations on the management of low vitamin D status in these patients are also discussed.

An update on the pathomechanisms and future therapies of Alport syndrome

Alport Syndrome (AS) is an inherited progressive disease that is caused by mutations of the genes encoding the key collagen chains, α3, α4, and α5, which are necessary for the composition of collagen type IV to form a robust glomerular basement membrane (GBM), capable of withstanding the significant biomechanical strain to which the glomerulus is subjected. Progressive loss of the filtration barrier allows excessive proteinuria, which ultimately leads to end-stage kidney disease (ESKD). The evidence for a beneficial renoprotective effect of renin-angiotensin-aldosterone system (RAAS) blockade by angiotensin-converting enzyme (ACE) inhibition and/or angiotensin receptor blockers (ARBs) is well established in AS and recent evidence has shown that it can significantly delay the time to onset of renal replacement therapy and ESKD. Future potential treatments of AS disease progression are evaluated in this review.

Cardiovascular risk assessment in children with chronic kidney disease

Chronic kidney disease (CKD) is a major factor contributing to cardiovascular (CV) morbidity and mortality with the highest risk in patients on dialysis. An estimation of CV risk is important not only to identify potential modifiable risk factors but also to evaluate the effect of treatments aimed to reduce the risk. Non-invasive methods of measuring vascular changes and circulating biomarkers are available to assess the presence and severity of cardiovascular damage. These include measures of structural (carotid intima-media thickness and coronary artery calcification score) and functional (aortic pulse wave velocity, 24-h ambulatory blood pressure monitoring, ambulatory arterial stiffness index, heart rate variability and flow-mediated dilatation) changes in the vessel wall. In addition, a number of circulating biomarkers of vascular damage and its progression have been studied. Many of these tests are well validated as surrogate markers of future cardiovascular events and death in adult CKD patients, but need technical adaptation, standardization and validation for use in children. With our current state of knowledge, these are best reserved for research studies and scarce clinical resources may be better utilized for preventative strategies to reduce the modifiable risk factors for calcification from early CKD stages.

Vitamin D supplementation in pre-dialysis chronic kidney disease: A systematic review

Vitamin D deficiency is associated with a variety of skeletal, cardiometabolic, and immunologic co-morbidities that are present in chronic kidney disease (CKD). We performed a systematic review to investigate the effects of vitamin D supplementation, in the form of ergocalciferol or cholecalciferol, on various health outcomes in early CKD. Seventeen clinical trials were identified, only two of which were randomized, placebo controlled trials. The majority of studies supplementing with > 2,000 IU/day of cholecalciferol achieved optimal vitamin D status, whereas studies supplementing with ergocalciferol were less consistent. Studies varied widely in their effects on lowering serum parathyroid hormone concentrations. Few studies investigated effects of vitamin D treatment on other clinical health indicators in early CKD. Rigorous studies are necessary to investigate optimal vitamin D dosing strategies in early CKD for the maintenance of adequate vitamin D status, management of secondary hyperparathyroidism and improvement of non-skeletal related clinical outcomes.

Vitamin D status in children with chronic kidney disease

BACKGROUND

The role of vitamin D status in patients with renal insufficiency and its relation to dietary intake and parathyroid hormone (PTH) secretion is of utmost interest given the morbidity and mortality associated with the disordered mineral metabolism seen in chronic kidney disease (CKD).

METHODS

We conducted a cross-sectional study of 100 pediatric patients with a diagnosis of CKD stage 1-5 at Children's Hospital Boston, measuring blood levels of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)(2)D], and parathyroid hormone and obtaining data on nutrient intake and other variables related to vitamin D status.

RESULTS

Subjects ranged in age from 6 months to 18 years, and 60 were male, 40 female. Of the 100 patients, 16 % were deficient in 25(OH)D (≤ 20 ng/mL) and another 24 % were insufficient (≤ 30 ng/mL), with 40 % in the suboptimal range. Serum 25(OH)D and dietary vitamin D intake were not correlated.

CONCLUSIONS

We found a high prevalence of hyperparathyroidism in early-stage CKD and a significant relationship between 25(OH)D and PTH regardless of calcitriol level. Our study results support the suggestion that optimization of vitamin D levels may provide additional benefit in preventing or improving hyperparathyroidism in patients with early CKD and likely remains important as an adjunctive therapy in children with advanced CKD.