Vitamin D deficiency may predict a poorer outcome of IgA nephropathy

Association of vitamin D status with disease severity and outcome in Indian patients with IgA nephropathy

BACKGROUND

Vitamin D deficiency has been examined as a risk factor for severity and progression of kidney disease due to its immunomodulatory effects. There is paucity of data about its impact in IgA nephropathy (IgAN).

METHODS

In a retrospective cohort study, 25 (OH) vitamin D assay was performed in bio-banked baseline serum samples collected during kidney biopsy of 105 adult patients with primary IgAN diagnosed between 2015 and 2019. A level of < 10 ng/mL was defined as Vitamin D deficiency.

RESULTS

Mean age of patients was 34 ± 10.6 years, 69.5% were males. Mean baseline 25(OH) Vitamin D levels was 15.9 ± 11.9 ng/mL and 41(39%) patients had vitamin D deficiency. Serum albumin level was lower in vitamin D deficient patients compared to those who had higher vitamin D levels (3.7 ± 0.9 vs 4.1 ± 0.7 g/dl, p = 0.018)but there was no significant difference in baseline proteinuria and eGFR. Crescentic lesions were more frequent in vitamin D deficient group (19.5% vs 6.3%, p = 0.022). At median follow up of 21.5 months (6 - 56 months), there was no difference in remission (68.3% vs 65.6%, p = 0.777) and disease progression (12.5% vs 9.4%, p = 0.614) in those with and without Vitamin D deficiency respectively. On multivariate cox proportional hazard analysis, vitamin D deficiency was not a significant risk factor for renal survival (HR-1.79, 95% confidence interval:0.50-6.34, p = 0.368).

CONCLUSION

There was no association between vitamin D deficiency and disease profile as well as renal outcome in Indian patients with IgAN.

Nuclear receptors in renal health and disease

As a major social and economic burden for the healthcare system, kidney diseases contribute to the constant increase of worldwide deaths. A deeper understanding of the underlying mechanisms governing the etiology, development and progression of kidney diseases may help to identify potential therapeutic targets. As a superfamily of ligand-dependent transcription factors, nuclear receptors (NRs) are critical for the maintenance of normal renal function and their dysfunction is associated with a variety of kidney diseases. Increasing evidence suggests that ligands for NRs protect patients from renal ischemia/reperfusion (I/R) injury, drug-induced acute kidney injury (AKI), diabetic nephropathy (DN), renal fibrosis and kidney cancers. In the past decade, some breakthroughs have been made for the translation of NR ligands into clinical use. This review summarizes the current understanding of several important NRs in renal physiology and pathophysiology and discusses recent findings and applications of NR ligands in the management of kidney diseases.

Vitamin D receptor gene polymorphisms in chronic kidney disease Egyptian children: effect on biochemical markers of bone mineral disorders

INTRODUCTION

The aim of this study was to assess the association between four vitamin D receptor (VDR) single nucleotide polymorphisms BsmI (rs1544410), ApaI (rs7975232), FokI (rs2228570) and TaqI (rs731236) and the susceptibility to chronic kidney disease (CKD) in Egyptian children and to evaluate their association with mineral status in these patients.

MATERIAL AND METHODS

The current study included 305 patients with CKD and 100 apparently healthy children. We measured the serum vitamin D (VD), para-thyroid hormone (PTH) level and fibroblast growth factor 23 (FGF-23) levels by ELISA method. The genotyping of the four VDR gene variants was carried out by PCR-RFLP technique.

RESULTS

The TaqI AG &amp; the BsmI TT genotypes were associated with a significantly higher risk of CKD. The expression of 25-OH D serum level was decreased in patients with TaqI GG &amp; AG genotypes groups and in patients with BsmI TT genotype group The expression of PTH serum level was increased in patients with BsmI CT genotype group. The expression of FGF-23 serum level was increased in patients with Taq1 AG genotype group. We found 3 specific haplotypes; AGCA, AGCC and GGCA for healthy controls.

CONCLUSIONS

Our study showed an association between VDR TaqI, BsmI polymorphisms and the susceptibility to CKD. The existence of VDR vari-ants affected the protein expression of VD, FGF-23 and PTH. The AGCA, AGCC and GGCA haplotypes were considered as protec-tive factors against the development of renal nephropathy in our population.

Narrative review of recent studies on the role of vitamin D in the prevention of cardiac and renal risk and additional considerations for COVID-19 vulnerability

The role of vitamin D in maintaining a healthy cardiovascular (CV) and the renal system has received increasing attention. Low vitamin D levels are associated with the incidence of hypertension, cardiac remodeling, and chronic congestive heart failure. Low vitamin D levels also influence renal disease progression and albuminuria deterioration. Moreover, recent research indicates that vitamin D deficiency can be a potential risk factor for coronavirus disease-19 (COVID-19) infection and poorer outcomes. Data are inconclusive as to whether supplementation with vitamin D agents reduces CV disease risk or COVID-19 severity. Conversely, in patients with kidney disease, vitamin D supplementation is associated with improved kidney function and albuminuria. This narrative review considers recent data on the effects of vitamin D on the CV and renal system, as well as its possible role regarding COVID-19 complications.

A randomised controlled unblinded multicentre non-inferiority trial with activated vitamin D and prednisolone treatment in patients with minimal change nephropathy (ADAPTinMCN)

BACKGROUND

Minimal change nephropathy (MCN) is a common cause of nephrotic syndrome in both adults and children. International guidelines recommend treatment with prednisolone 1 mg/kg/day to adults. This dose is derived from an empirically established dose in children, although children generally attain remission faster and relapse more rapidly than adults. Prednisolone is associated with multiple and serious adverse events. Activated vitamin D has been shown to reduce albuminuria in other glomerular renal diseases with a minimum of adverse events. This study tests the hypothesis that a new treatment regimen in MCN combining reduced dose prednisolone and active vitamin D is as efficient in inducing remission and has fewer and less severe adverse events than standard prednisolone. Furthermore, we aim to establish models allowing for more personalized medicine based on assessment of the individual's prednisolone metabolism.

METHODS

A randomised controlled multicentre non-inferior unblinded trial including 96 adult, incident patients with biopsy-proven MCN, albuminuria > 3 g/day, and an estimated glomerular filtration rate (eGFR) > 30 ml/min from renal departments in Denmark. Patients are randomised to standard prednisolone (1 mg/kg/day) or reduced prednisolone (0.5 mg/kg/day) and alfacalcidol (0.5 μg/day). The primary outcome is the rate of remissions after 16 weeks and the time from diagnosis to remission. The study will include a saliva test to characterise prednisolone pharmacokinetics and compare them to genetic variations in specific liver enzymes responsible for prednisolone metabolism.

DISCUSSION

Reducing the prednisolone dose is expected to reduce the number of severe adverse events. This study will examine if reduced prednisolone dose with active vitamin D but without additional immunosuppression is feasible in the treatment of MCN and will reduce the number of adverse events. The findings can potentially change current guidelines for treatment of MCN in adults. Additional outcomes on inter-individual pharmacokinetic and metabolic variations may allow for a more personalised treatment strategy.

TRIAL REGISTRATION

EudraCT 2017-001206-16, ClinicalTrials.gov NCT03210688 . Registered on June 3, 2017.

Expression of renal vitamin D receptors and metabolizing enzymes in IgA nephropathy

AIM

One of the main causes of end-stage renal disease (ESRD) in the world is IgA nephropathy (IgAN). Since kidney is a key player in vitamin D metabolism, we investigated the expression of renal vitamin D receptors (VDR) and metabolizing enzymes in IgA nephropathy patients (IgAN-P).

METHODS

The sample included twelve IgAN-P who underwent ultrasound-guided renal biopsies and five controls who underwent nephrectomy due to clear renal carcinoma. Immunofluorescent staining was used to determine the expression of VDR, 25-hydroxyvitamin D3 -alpha-hydroxylase (1alpha-OHase) and vitamin D3 24-hydroxylase (CYP24A1).

RESULTS

Significant increase in expression of VDR, which was prominent in distal tubular cells (DTCs) in tissues from IgAN-P, was found in comparison to the controls (p = 0.0368). The expression of 1alpha-OHase, calcitriol synthesizing enzyme, was significantly lower in IgAN-P, in comparison with controls (p < 0.0001). The opposite, expression of CYP24A1 (vitamin D degrading enzyme), was significantly higher in IgAN-P in comparison with controls (p = 0.0003). Additionally, we found significant negative correlation between percentage of CYP24A1 immunoreactive nuclei in proximal tubular cells (PTCs) and estimated glomerular filtration rate (eGFR) in IgAN-P (r = -0.6139; p = 0.0337).

CONCLUSIONS

Our research indicates substantially decreased renal calcitriol production and increased vitamin D degradation in kidneys of IgAN-P, but larger studies are needed to confirm our results.

Vitamin D and Glomerulonephritis

Vitamin D presents a plethora of different functions that go beyond its role in skeletal homeostasis. It is an efficient endocrine regulator of the Renin–Angiotensin–Aldosterone System (RAAS) and erythropoiesis, exerts immunomodulatory effects, reduces the cardiovascular events and all-cause mortality. In Chronic Kidney Disease (CKD) patients, Vitamin D function is impaired; the renal hydrolyzation of its inactive form by the action of 1α-hydroxylase declines at the same pace of reduced nephron mass. Moreover, Vitamin D major carrier, the D-binding protein (DBP), is less represented due to Nephrotic Syndrome (NS), proteinuria, and the alteration of the cubilin–megalin–amnionless receptor complex in the renal proximal tubule. In Glomerulonephritis (GN), Vitamin D supplementation demonstrated to significantly reduce proteinuria and to slow kidney disease progression. It also has potent antiproliferative and immunomodulating functions, contributing to the inhibitions of kidney inflammation. Vitamin D preserves the structural integrity of the slit diaphragm guaranteeing protective effects on podocytes. Activated Vitamin D has been demonstrated to potentiate the antiproteinuric effect of RAAS inhibitors in IgA nephropathy and Lupus Nephritis, enforcing its role in the treatment of glomerulonephritis: calcitriol treatment, through Vitamin D receptor (VDR) action, can regulate the heparanase promoter activity and modulate the urokinase receptor (uPAR), guaranteeing podocyte preservation. It also controls the podocyte distribution by modulating mRNA synthesis and protein expression of nephrin and podocin. Maxalcalcitol is another promising alternative: it has about 1/600 affinity to vitamin D binding protein (DBP), compared to Calcitriol, overcoming the risk of hypercalcemia, hyperphosphatemia and calcifications, and it circulates principally in unbound form with easier availability for target tissues. Doxercalciferol, as well as paricalcitol, showed a lower incidence of hypercalcemia and hypercalciuria than Calcitriol. Paricalcitol demonstrated a significant role in suppressing RAAS genes expression: it significantly decreases angiotensinogen, renin, renin receptors, and vascular endothelial growth factor (VEGF) mRNA levels, thus reducing proteinuria and renal damage. The purpose of this article is to establish the Vitamin D role on immunomodulation, inflammatory and autoimmune processes in GN.

Monitoring Immune Responses in IgA Nephropathy: Biomarkers to Guide Management

IgA nephropathy (IgAN) is the commonest biopsy-reported primary glomerulonephritis worldwide. It has an incidence which peaks among young adults, and 30 to 40% of patients' progress to end stage kidney disease within twenty years of diagnosis. Ten-year kidney survival rates have been reported to be as low as 35% in some parts of the world. The successful management of IgAN is limited by an incomplete understanding of the pathophysiology of IgAN and a poor understanding of how pathophysiology may vary both from patient to patient and between patient groups, particularly across races. This is compounded by a lack of rigorously designed and delivered clinical trials in IgAN. This is slowly changing, with a number of Phase 2 and 3 clinical trials of novel therapies targeting a number of different putative pathogenic pathways in IgAN due to report in the next 5 years. From our current, albeit limited, understanding of the pathophysiology of IgAN it is unlikely a single therapy will be effective in all patients with IgAN. The successful management of IgAN in the future is, therefore, likely to be reliant on targeted therapies, carefully selected based on an individualized understanding of a patient's risk of progression and underlying pathophysiology. The potential role of biomarkers to facilitate personalization of prognostication and treatment of IgAN is immense. Here we review the progress made over the past decade in identifying and validating new biomarkers, with a particular focus on those that reflect immunological responses in IgAN.

Emerging role of vitamin D in autoimmune diseases: An update on evidence and therapeutic implications

Vitamin D plays a key role in in calcium homeostasis and, thus, provides an important support in bone growth by aiding in the mineralization of the collagen matrix. However, vitamin D performs various immunomodulatory, anti-inflammatory, antioxidant and anti-fibrotic actions. Autoimmune diseases result from an aberrant activation of the immune system, whereby the immune response is directed against harmless self-antigens. Does vitamin D play a role in the pathophysiology of autoimmune diseases? And, if so, what is its role? In the last decade, researchers' interest in vitamin D and its correlations with autoimmune diseases has considerably increased. We conducted a literature review, covering the period January 1, 2009 through March 30, 2019, in PubMed. We analyzed more than 130 studies in order to find a correlation between vitamin D levels and its effect upon several autoimmune diseases. The analysis demonstrated an inverse association between vitamin D and the development of several autoimmune diseases, such as SLE, thyrotoxicosis, type 1 DM, MS, iridocyclitis, Crohn's disease, ulcerative colitis, psoriasis vulgaris, seropositive RA, polymyalgia rheumatica. International multicenter study could allow us to confirm the data already present in the literature in the single clinical studies and to evaluate when to effectively supplement vitamin D in patients who do not take corticosteroids.

Association between VDR gene FokI polymorphism and renal function in patients with IgA nephropathy

Background

Studies have shown that the occurrence and development of IgA nephropathy (IgAN) are genetically susceptible, but the relationship between vitamin D receptor (VDR) gene polymorphisms and renal function in IgAN patients is unclear.

Methods

We investigated the relationship between VDR FokI (rs2228570) single nucleotide polymorphism (SNP) and renal function and related clinicopathologic parameters in IgAN patients. Clinical and pathological data of 282 IgAN patients treated at the First Affiliated Hospital of Guangxi Medical University were collected, and FokI genotypes were determined by PCR and direct sequencing. Patients were divided into the renal dysfunction group and normal renal function (control) group by estimated glomerular filtration rate (eGFR) and serum creatinine level.

Results

Frequencies of TT genotype and T allele in the renal dysfunction group were higher than those of the control group. Blood urea nitrogen, serum phosphorus (P), proportions of mesangial cell proliferation, interstitial fibrosis/tubular atrophy and crescents in T allele carriers were higher than those in non-T allele carriers, while eGFR and 25-Hydroxyvitamin D3 were lower in T allele carriers than non-T allele carriers. Multiple linear regression analysis showed that eGFR was affected by FokI genotypes in IgAN patients. Logistics regression analysis showed that middle and elderly age, elevated P, intact parathyroid hormone and TT genotype were independent risk factors for renal dysfunction in IgAN patients; the odds ratio of carrying the TT genotype was as high as 84.77 (P < 0.05 for all).

Conclusions

IgA nephropathy patients carrying the VDR FokI TT genotype have an increased risk of renal dysfunction. VDR FokI SNP is closely related to renal function, calcium-phosphate metabolism, and related pathological damage in IgAN patients.

Calcitriol Ameliorates AngiotensinII-Induced Renal Injury Partly via Upregulating A20

Inflammation and reactive oxygen species (ROS) play crucial roles in the progression of chronic kidney diseases. Vitamin D has been shown anti-inflammatory effects, but the underlying mechanism is not fully understood. Here, we investigated whether calcitriol exerts protective effects via upregulating A20 in angiotensinII (AngII)-induced renal injury. Male C57BL/6 mice were infused with vehicle or AngII for 10 days. Calcitriol reduced infiltration of T lymphocytes and macrophages. This reduction of inflammatory cells was accompanied by elevated A20 and decreased pro-inflammatory cytokines (PICs) and reactive oxygen species (ROS). Calcitriol could inhibit NF-κB activation and necroptotic pathway. Induction of A20 was located primarily to the tubular epithelial cells. In rat proximal tubular epithelial cells (NRK-52E), calcitriol stably upregulated A20 and reduced the PICs and ROS. Inhibitory effect of A20 on PICs and ROS depended on suppressing NF-κB pathway and necroptotic pathway, respectively. A20 knockdown diminished the effect of calcitriol on suppressing NF-κB and necroptotic pathways. However, A20 deficiency could not abrogate the inhibitory effect of calcitriol on NF-κB and necroptotic pathways. Our results established that A20 is involved in the renoprotective effect by calcitriol via negatively modulating the NF-κB pathway and necroptotic pathway in AngII-induced renal injury.

Maternal vitamin D deficiency increases the risk of adverse neonatal outcomes in the Chinese population: A prospective cohort study

BACKGROUND

Although vitamin D (vitD) deficiency is a common problem in pregnant women, in China, few studies have focused on the relationship between maternal vitD deficiency throughout the three trimesters and subsequent neonatal outcomes in China.

METHODS

Between 2015 and 2016, maternal serum and neonate cord blood samples were collected from 1978 mother-neonate pairs from Liuzhou city.

RESULTS

The mean concentrations of 25-hydroxy vitD (25(OH)D) were 16.17±6.27 and 15.23±5.43 ng/ml in the mother and neonate groups, respectively, and the prevalence values of vitD deficiency in the two groups were 78.18% and 83.27%, respectively. Logistic regression showed that maternal vitD deficiency independently increased the risk of gestational diabetes mellitus (GDM) (adjust OR, aOR 1.08; P = 0.026). A relatively lower risk of vitD deficiency was observed in the third trimester than in the first and second trimester (aOR 0.80; P = 0.004). VitD-calcium cosupplementation during pregnancy improves the vitD deficiency in both the maternal and neonatal groups (aOR 0.56, 0.66; P<0.001 and 0.021, respectively). Maternal vitD deficiency significantly increased the risk of neonatal low birth weight (LBW) (aOR 2.83; P = 0.005) and small-for-gestational-age (SGA) (aOR 1.17; P = 0.015). There was a positive correlation between maternal and neonatal vitD deficiency (r = 0.879, P<0.001). VitD supplementation during pregnancy significantly reduced the risk of giving birth to LBW infants (OR = 0.47, 95%CI = 0.33-0.68, P<0.001).

CONCLUSIONS

Further research focusing on the consumption of vitD with calcium during pregnancy and the consequential clinical outcomes in Chinese pregnant women is warranted.

The association between serum vitamin D levels and renal tubular dysfunction in a general population exposed to cadmium in China

Cadmium exposure can cause renal tubular dysfunction. Recent studies show that vitamin D can play multiple roles in the body. However, the association between serum vitamin D levels and renal tubular dysfunction in a general population exposed to cadmium has not been clarified. We performed study to assess the effects of cadmium on serum 25(OH) D levels and the association between serum 25(OH) D levels and renal tubular dysfunction in a population environmentally exposed to cadmium. A total of 133 subjects living in control area and two cadmium polluted areas were included in the present study. Cadmium in urine (UCd) and blood (BCd), urinary β2Microglobulin (UBMG), urinary retinol binding protein (URBP) and serum 25 (OH) D were determined. Logistic regression was used to estimate the association between 25 (OH) D and prevalence of renal tubular dysfunction. No significant differences were observed in serum 25(OH) D levels among the four quartile of UCd and BCd after adjusting with cofounders. After adjusted with the confounders, the odds ratio (OR) of subjects with 25(OH) D ≥ 40 ng/ml were 0.20 (95%CI: 0.1–0.8) if UBMG was chosen as indicators of renal dysfunction and 0.28 (95%CI: 0.1–1.1) if URBP was chosen as indicators of renal dysfunction, compared with those with 25(OH) D < 30 ng/ml, respectively. Similar results were observed in those subjects living in cadmium polluted areas or with high level of UCd or BCd. Our data indicated that cadmium exposure did not affect serum 25(OH) D level and high 25 (OH) D levels were associated with a decreased risk of renal tubular dysfunction induced by cadmium.

Vitamin D Receptor: A Novel Therapeutic Target for Kidney Diseases

BACKGROUND

Kidney disease is a serious problem that adversely affects human health, but critical knowledge is lacking on how to effectively treat established chronic kidney disease. Mounting evidence from animal and clinical studies has suggested that Vitamin D Receptor (VDR) activation has beneficial effects on various renal diseases.

METHODS

A structured search of published research literature regarding VDR structure and function, VDR in various renal diseases (e.g., IgA nephropathy, idiopathic nephrotic syndrome, renal cell carcinoma, diabetic nephropathy, lupus nephritis) and therapies targeting VDR was performed for several databases.

RESULT

Included in this study are the results from 177 published research articles. Evidence from these papers indicates that VDR activation is involved in the protection against renal injury in kidney diseases by a variety of mechanisms, including suppression of RAS activation, anti-inflammation, inhibiting renal fibrogenesis, restoring mitochondrial function, suppression of autoimmunity and renal cell apoptosis.

CONCLUSION

VDR offers an attractive druggable target for renal diseases. Increasing our understanding of VDR in the kidney is a fertile area of research and may provide effective weapons in the fight against kidney diseases.

Effect of Vitamin D and Tacrolimus Combination Therapy on IgA Nephropathy

Background

To explore the effects and the mechanism of vitamin D (VD) and tacrolimus (TAC) combinatorial therapy in the treatment of IgA nephropathy (IgAN) in a rat model.

Material/Methods

IgAN rat models constructed by oral immunization with bovine serum albumin (BSA) and lipopolysaccharide (LPS) (n=30) and were treated with: saline (model group), TAC (TAC group), or TAC+VD therapy (TAC+VD group) through gavage daily for 14 days. Serum creatinine (Scr), albumin (ALB), blood urea nitrogen (BUN), and urinary protein (UAE) levels were determined. Histopathology of renal tissues was examined after hematoxylin and eosin (H&E) staining. The levels of cytokines TGF-β1, IL-5, IFN-γ, and IL-4 in serum were detected by enzyme-linked immunosorbent assay (ELISA). Changes in TLR4/NF-κB pathway were evaluated by western blot.

Results

Both TAC and TAC+VD treatment significantly restored the dysregulated Scr, ALB, BUN, and UAE levels in IgAN rats. TAC+VD therapy more prominently restored Scr and UAE levels (p<0.05). TAC+VD therapy demonstrated superior efficacy in reducing glomerular mesangial cells hyperplasia, reducing thickening of the glomerular basement membrane and glomerular infiltration of inflammatory cells. Thymus and spleen indexes were also increased (p<0.05). The levels of TGF-β1, IL-5, and IL-4 of the TAC+VD group were also lower than those of the TAC group (p<0.05). The TAC+VD group also demonstrated increased IFN-γ, and decreased p-P65/P65 and TLR4 compared to the TAC group.

Conclusions

TAC+VD combinatorial therapy can effectively alleviate renal tissue damage in IgAN rats by regulating immune response and the NF-κB/TLR4 pathway.