Vitamin D receptor attenuates renal fibrosis by suppressing the renin-angiotensin system

ACSL4 mediates inflammatory bowel disease and contributes to LPS-induced intestinal epithelial cell dysfunction by activating ferroptosis and inflammation

Background

The pathogenesis of inflammatory bowel disease (IBD) is closely associated with the dysfunction of the intestinal epithelial barrier, leading to increased bacterial translocation, leukocyte infiltration, and mucosal injury, which may act as a pivotal or incipient event in the pathophysiology of the disorder. The primary objective of this study is to examine the key genes implicated in IBD and the perturbation of intestinal epithelial cell function.

Methods

The genes associated with ferroptosis were identified through the utilization of the Gene Expression Omnibus (GEO) database and the GeneCard database. Additionally, an in vitro model of IBD was established by stimulating Caco-2 cells with lipopolysaccharides (LPSs) to investigate the molecular mechanisms underlying intestinal epithelial cell dysfunction.

Results

We discovered evidence that establishes a connection between ferroptosis and the inflammatory responses associated with the development of IBD. This evidence suggests that IBD patients who exhibit an inflammatory response have higher expression of the acyl-CoA synthetase long-chain family member 4 (ACSL4) gene compared to IBD patients without an inflammatory response or healthy individuals. Exposure to LPS at concentrations of 1 or 10 μg/mL resulted in a significant upregulation of ferroptosis-related genes ACSL4, GPX4, and SLC7A11, as well as an increase in ferroptosis biomarkers MDA and a decrease in CAT and GSH-Px levels compared to the control group. Inhibition of ACSL4 using si-ACSL4 or rosiglitazone demonstrated protective effects against LPS-induced ferroptosis and NF-κB-mediated inflammatory response.

Conclusion

ACSL4 shows potential as a promising target for ferroptosis in the prevention and treatment of IBD and dysfunction of intestinal epithelial cells.

Paricalcitol prevents renal tubular injury induced by ischemia-reperfusion: Role of oxidative stress, inflammation and AT1R

The vitamin D receptor (VDR) is associated with antioxidative and anti-inflammatory effects and modulation of the renin-angiotensin-aldosterone system. This study evaluated whether VDR agonist paricalcitol protects renal ischemia-reperfusion (IR) induced tubular injury in rats by evaluating: 1) ATP-dependent tubular Na+ transport; 2) renal redox signaling; 3) renal content of proinflammatory cytokines TNF-α and IL-6; and 4) renal content of renin and angiotensin II receptor type 1 (AT1R). Paricalcitol prevented IR-induced tubular injury, evidenced by the prevention of histopathological changes and renal fibrosis with preservation of the activity of ATP-dependent Na+ transporters in the renal cortex. Paricalcitol decreased renal oxidative stress by reducing NADPH oxidase activity and increasing catalase. Paricalcitol also decreased the renal content of TNF-α, IL-6, and AT1R. The NADPH oxidase inhibitor apocynin did not present additive protection to paricalcitol-induced effects. The protective effects of paricalcitol on tubular injury induced by renal IR may dependent on the modulation of redox and proinflammatory signaling and renal angiotensin II/AT1R signaling.

Association of serum 25-hydroxyvitamin D with cardiovascular mortality and kidney outcome in patients with early stages of CKD

PURPOSE

While serum 25-hydroxyvitamin D (25[OH]D) deficiency is prevalent in chronic kidney disease (CKD), the effects of 25(OH)D deficiency on cardiovascular mortality and kidney outcomes in patients with early-stage CKD remain incompletely understood.

METHODS

This multicenter retrospective cohort study included adult patients with stages 1-3 CKD from 19 medical centers across China between January 2000 and May 2021. The primary outcome was cardiovascular mortality. The secondary study outcome included CKD progression (defined as a sustained > 40% eGFR decrease from baseline or progress to end-stage kidney disease), and annual percentage change of eGFR.

RESULTS

Of 9229 adults with stages 1-3 CKD, 27.0% and 38.9% had severe (< 10 ng/mL) and moderate (10 to < 20 ng/mL) serum 25(OH)D deficiency, respectively. Compared with patients having 25(OH)D ≥ 20 ng/mL, a significantly higher risk of cardiovascular mortality (hazard ratio [HR] 1.90, 95% CI 1.37-2.63), CKD progression (HR 2.20, 95% CI 1.68-2.88), and a steeper annual decline in eGFR (estimate - 7.87%; 95% CI - 10.24% to - 5.51% per year) was found in those with serum 25(OH)D < 10 ng/mL. Similar results were obtained in subgroups and by sensitivity analyses.

CONCLUSIONS

25(OH)D deficiency is associated with increased risks of cardiovascular mortality and CKD progression in patients with early-stage CKD. Studies are needed to determine whether early intervention for 25(OH)D deficiency could improve the prognosis of patients with early-stage CKD.

Vitamin D metabolism in critically ill patients with acute kidney injury: a prospective observational study

BACKGROUND

Vitamin D deficiency in critically ill patients is associated with poor outcomes, and vitamin D supplementation is recommended for patients with chronic kidney disease. Whether acute kidney injury (AKI) is associated with altered Vitamin D metabolism is unknown. We aimed to compare the longitudinal profiles of serum 25(OH)D and 1,25(OH)2D concentrations in critically ill patients with and without moderate to severe AKI and explore the impact of renal recovery and parathyroid hormone (PTH).

METHODS

In this prospective, observational study in two centres in the UK, critically ill patients with and without AKI underwent serial measurement of serum 25(OH)D and 1,25(OH)2D and plasma PTH concentrations for 5 days. Linear mixed model analysis and sensitivity analyses were performed.

RESULTS

Serial data of 137 patients were analysed. Seventy-one patients had AKI stage II/III of whom 23 recovered kidney function during the 5-day study period; 66 patients did not have AKI at enrolment of whom 14 developed new AKI. On day of enrolment, patients' serum 25(OH)D concentrations were low (median 18 nmol/L) but there was no significant difference between patients with and without AKI. Median serum 1,25(OH)2D levels were significantly lower in patients with AKI II/III (41 pmol/L [IQR 26, 58]) compared to similarly unwell patients without AKI (54 pmol/L [IQR 33, 69]) during the 5-day period. Recovery of kidney function in patients with AKI was associated with a rise in 1,25(OH)2D concentrations. Plasma PTH results were impacted by serum calcium and magnesium levels but not associated with 1,25(OH)2D levels.

CONCLUSIONS

Critically ill patients with moderate-to-severe AKI have significantly lower serum 1,25(OH)2D concentrations than similarly sick patients without AKI but there was no difference in serum 25(OH)D concentrations. Recovery of AKI was associated with a rise in serum 1,25(OH)2D concentrations. More research is needed to investigate the health benefits and safety of supplementation with active vitamin D in critically ill patients with moderate-to-severe AKI. Trial registration Clinicaltrials.gov (NCT02869919), registered on 16 May 2016.

Suppression of DNMT1 combined with ATM or ATR inhibitor as a therapeutic combination of acute myeloid leukemia

The potential treatment option of targeting DNA methyltransferase 1 (DNMT1) has been explored, but further investigation is required to assess the efficacy of combination therapy in acute myeloid leukemia (AML). In this study, bioinformatics and online databases were utilized to select the combined therapeutic targets. The potential kinases associated with DNMT1-related genes in AML were analyzed using the Cancer Genome Atlas (TCGA) database and X2K Appyter (Expression2Kinases) database. In-vitro evaluations were conducted to assess the synergistic effects between DNMT1 and ATR/ATM in five AML cell lines (MOLM-16, NB-4, HEL 92.1.7, HEL, EOL-1). In our study, ATR and ATM are primarily the kinases associated with DNMT1-related genes in AML. We observed a significant upregulation of DNMT1, ATR, and ATM expression in AML tissues and cell lines. The five AML cell lines demonstrated sensitivity to monotherapy with GSK-368, AZD-1390, or AZD-6738 (EC50 value ranges from 5.461 to 7.349 nM, 5.821 to 10.120 nM, and 7.618 to 10.100 nM, respectively). A considerable synergistic effect was observed in AML cell lines when combining GSK-368 and AZD-1390, GSK-368 and AZD-6738, or AZD-1390 and AZD-6738, resulting in induced cell apoptosis and inhibited cell growth. DNMT1, ATM, and ATR possess potential as therapeutic targets for AML. Both individual targeting and combination targeting of these molecules have been confirmed as promising therapeutic approaches for AML.

Reduction of renal interstitial fibrosis by targeting Tie2 in vascular endothelial cells

BACKGROUND

Tie2, a functional angiopoietin receptor, is expressed in vascular endothelial cells and plays an important role in angiogenesis and vascular stability. This study aimed to evaluate the effects of an agonistic Tie2 signal on renal interstitial fibrosis (RIF) and elucidate the underlying mechanisms.

METHODS

We established an in vivo mouse model of folic acid-induced nephropathy (FAN) and an in vitro model of lipopolysaccharide-stimulated endothelial cell injury, then an agonistic Tie2 monoclonal antibody (Tie2 mAb) was used to intervent these processes. The degree of tubulointerstitial lesions and related molecular mechanisms were determined by histological assessment, immunohistochemistry, western blotting, and qPCR.

RESULTS

Tie2 mAb attenuated RIF and reduced the level of fibroblast-specific protein 1 (FSP1). Further, it suppressed vascular cell adhesion molecule-1 (VCAM-1) and increased CD31 density in FAN. In the in vitro model, Tie2 mAb was found to decrease the expression of VCAM-1, Bax, and α-smooth muscle actin (α-SMA).

CONCLUSIONS

The present findings indicate that the agonistic Tie2 mAb exerted vascular protective effects and ameliorated RIF via inhibition of vascular inflammation, apoptosis, and fibrosis. Therefore, Tie2 may be a potential target for the treatment of this disease.

IMPACT

This is the first report to confirm that an agonistic Tie2 monoclonal antibody can reduce renal interstitial fibrosis in folic acid-induced nephropathy in mice. This mechanism possibly involves vascular protective effects brought about by inhibition of vascular inflammation, apoptosis and fibrosis. Our data show that Tie2 signal may be a novel, endothelium-specific target for the treatment of tubulointerstitial fibrosis.

Modulation of the vitamin D receptor by traditional Chinese medicines and bioactive compounds: potential therapeutic applications in VDR-dependent diseases

The Vitamin D receptor (VDR) is a crucial nuclear receptor that plays a vital role in various physiological functions. To a larger extent, the genomic effects of VDR maintain general wellbeing, and its modulation holds implications for multiple diseases. Current evidence regarding using vitamin D or its synthetic analogs to treat non-communicable diseases is insufficient, though observational studies suggest potential benefits. Traditional Chinese medicines (TCMs) and bioactive compounds derived from natural sources have garnered increasing attention. Interestingly, TCM formulae and TCM-derived bioactive compounds have shown promise in modulating VDR activities. This review explores the intriguing potential of TCM and bioactive compounds in modulating VDR activity. We first emphasize the latest information on the genetic expression, function, and structure of VDR, providing a comprehensive understanding of this crucial receptor. Following this, we review several TCM formulae and herbs known to influence VDR alongside the mechanisms underpinning their action. Similarly, we also discuss TCM-based bioactive compounds that target VDR, offering insights into their roles and modes of action.

Relationship of Vitamin-D Deficiency with Kidney Disease in Patients with Type-2 Diabetes Mellitus (T2DM) in the Makkah Region: A Cross-Sectional Study

Aim

Vitamin D deficiency is linked with type 2 diabetes mellitus (T2DM) and the occurrence of complications in patients with type 2 diabetes mellitus. None of the studies have focused on the association between vitamin D levels in patients with type 2 diabetes mellitus and diabetic nephropathy (DN) in the Makkah region, Saudi Arabia. Hence, the purpose of this study is to investigate the relationship of vitamin D with kidney disease in patients with T2DM in the Makkah region, of Saudi Arabia.

Materials and Methods

This descriptive cross-sectional study was conducted at different hospitals in the Makkah region on T2DM patients from 2021 to 2022. In total, 328 patients with confirmed diabetes were enrolled in this study. T2DM patients over the aged>18 to 92 years were included in the study. General laboratory characteristics of the study population were measured, including fasting blood sugar, HbA1C (Glycated hemoglobin), vitamin D, kidney function (BUN-Blood urea nitrogen and creatinine), and lipid profiles (cholesterol, triglycerides, LDL-Low density lipoprotein, and HDL-High density lipoprotein).

Results

46.6% (n=153) of participants had normal serum vitamin D levels. Insufficient and deficient serum vitamin D level were observed in 43.9% (n=144) and 9.5% (n=31) of participants, respectively. Of the participants, 25.9% (n=85) had good glycemic control (<7.0%). Moderate and poor glycemic control were observed in 39.9% (n=131) and 34.1% (n=112) of the participants, respectively. A significant negative correlation (p<0.5) was found between vitamin D levels and kidney function test results (blood urea nitrogen and serum creatinine levels). An inverse relationship was observed between HbA1c levels and vitamin D deficiency.

Conclusion

Nephropathy is more likely to develop in people with type 2 diabetes mellitus and vitamin D deficiency.

Vitamin D/Vitamin D receptor mitigates cisplatin-induced acute kidney injury by down-regulating C5aR

Cisplatin (DDP) is a potent chemotherapeutic; however, it can also cause acute kidney injury (AKI). Because of the complexity of the toxicity it induces, few effective methods exist for ameliorating any form of DDP-induced AKI. Recent research has suggested that the complement system is a potential molecular target for such amelioration. In the study here, in vivo (male ICR mice) and in vitro (HK-2 cells) models of DDP-induced AKI were established to investigate the potential therapeutic effects of Vitamin D (VD) against this form of AKI. Endpoints assessed in vivo/in vitro included overall renal function, degree of renal damage, and complement receptor C5aR expression using histology, immunohistochemistry, immunofluorescence, RT-PCR, and Western blots. The data indicated that the use of VD treatment could reduce renal pathological damage along with expression of TNFα, IL-1β, IL-18, and C5aR; however, an over-expression of C5aR weakened the protective effects of VD/VD receptor (VDR) against oxidative damage and inflammatory cell infiltration. Using a luciferase reporter gene assay and ChIP analysis, it was demonstrated that C5aR was transcriptionally inhibited by VDR. In conclusion, VD/VDR could delay DDP-induced AKI by inhibiting the expression of C5aR through transcriptional regulation and reducing the production of downstream pro-inflammatory cytokines. The present study revealed the regulatory mechanism of VD/VDR in acute renal inflammation and provides new insights into its therapeutic function in DDP-induced AKI.

Vitamin D Status Modestly Regulates NOD-Like Receptor Family with a Pyrin Domain 3 Inflammasome and Interleukin Profiles among Arab Adults

Vitamin D (VD) deficiency has been associated with inflammation and dysregulation of the immune system. The NLRP3 inflammasome, a critical immune response component, plays a pivotal role in developing inflammatory diseases. VD hinders NLRP3 inflammasome activation and thus exerts anti-inflammatory effects. This study aimed to analyze the effect of VD deficiency on circulating levels of NLRP3 inflammasomes (NLRP3 and caspase-1) and associated interleukins (IL-1α, IL-1β, IL-18, IL-33 and IL-37) in Saudi adults. Methods: A total of 338 Saudi adults (128 males and 210 females) (mean age = 41.2 ± 9.1 years and mean BMI 31.2 ± 6.5 kg/m2) were included. Overnight-fasting serum samples were collected. Participants were stratified according to their VD status. Serum levels of NLRP3 inflammasomes and interleukins of interest were assessed using commercially available immuno-assays. Individuals with VD deficiency had significantly lower mean 25(OH)D levels than those with a normal VD status (29.3 nmol/L vs. 74.2 nmol/L, p < 0.001). The NLRP3 levels were higher in the VD-deficient group than their VD-sufficient counterparts (0.18 vs. 0.16, p = 0.01). Significant inverse associations were observed between NLRP3 levels with age (r = -0.20, p = 0.003) and BMI (r = -0.17, p = 0.01). Stepwise regression analysis identified insulin (β = 0.38, p = 0.005) and NLRP3 (β = -1.33, p = 0.03) as significant predictors of VD status, explaining 18.3% of the variance. The findings suggest that the VD status modestly regulates NLRP3 inflammasome and interleukin activities. This may provide novel insights into the pathogenesis and management of inflammatory disorders.

Vitamin D deficiency contributes to the diabetic kidney disease progression via increase ZEB1/ZEB2 expressions

BACKGROUND

Diabetic kidney disease (DKD) remains one of the main causes of end-stage renal disease (ESRD) and mortality in diabetic patients worldwide. Vitamin D deficiency (VitDD) is one of the main consequences of different chronic kidney disease (CKD) types and is associated with rapid progression to ESRD. Nevertheless, the mechanisms that lead to this process are poorly understood. This study aimed to characterize a model of diabetic nephropathy progression in VitDD and the epithelial-mesenchymal-transition (EMT) role in these processes.

METHODS

Wistar Hannover rats received a diet with or without VitD before type 1 diabetes (T1D) induction. After this procedure, the rats were accompanied for 12 and 24 weeks after T1D induction and the renal function, structure, cell transdifferentiating markers and zinc finger e-box binding homeobox 1/2 (ZEB1/ZEB2) contribution to kidney damage were evaluated during the DKD progression.

RESULTS

The results showed an increase in glomerular tuft, mesangial and interstitial relative areas and renal function impairment in VitD-deficient diabetic rats compared to diabetic rats that received a VitD-containing diet. These alterations can be associated with increased expression of EMT markers, ZEB1 gene expression, ZEB2 protein expression and TGF-β1 urinary excretion. Decreased miR-200b expression, an important post-transcriptional regulator of ZEB1 and ZEB2 was also observed.

CONCLUSION

Our data demonstrated that VitD deficiency contributes to the rapid development and progression of DKD in diabetic rats induced by increase ZEB1/ZEB2 expressions and miR-200b downregulation.

Vitamin D status and biomarkers of renal graft function after kidney transplantation: a longitudinal study

Introduction

Introduction: Low 25-hydroxyvitamin D [25(OH)D] levels occur after kidney transplantation (KTx), and can be associated with increase the risk of graft loss. This longitudinal study aimed to evaluate the vitamin D status and association with biomarkers of the renal graft function after KTx. Methods: this longitudinal study included 42 patients evaluated at baseline, 3 and 6 months after KTx. Biodemographic, clinical, and biochemical parameters such as 25(OH)D and parathyroid hormone (PTH), and biomarkers of renal graft function, such as creatinine, estimated glomerular filtration rate (eGFR), and albumin/creatinine ratio (ACR), were assessed. Sun exposure was also evaluated. Patients were categorized according to their 25(OH)D levels. Results: at baseline, 25(OH)D levels < 30 ng/mL were found in 43 % patients, and 38 % of these patients failed to improve their 25(OH)D levels by 6 months after KTx. Low 25(OH)D levels occurred regardless of sun exposure. Further, 44 % patients developed albuminuria at 6 months. An increased ACR was observed in patients with 25(OH)D levels < 30 ng/mL (p = 0.002) compared to that in patients with 25(OH)D > 30 ng/mL. Additionally, 25(OH)D levels were negatively correlated with ACR at 6 months post-KTx (r = -0.444; p = 0.003). Twelve (28.6 %) patients with 25(OH)D levels < 30 ng/mL showed no eGFR recovery until 6 months after KTx. Conclusion: low vitamin D levels and increased albuminuria were observed at 6 months after KTx, even in a region with high sun exposure. The association between vitamin D status and biomarkers of renal graft function after KTx should be explored in further studies.

Vitamin D, Cellular Senescence and Chronic Kidney Diseases: What Is Missing in the Equation?

As life expectancy increases in many countries, the prevalence of age-related diseases also rises. Among these conditions, chronic kidney disease is predicted to become the second cause of death in some countries before the end of the century. An important problem with kidney diseases is the lack of biomarkers to detect early damage or to predict the progression to renal failure. In addition, current treatments only retard kidney disease progression, and better tools are needed. Preclinical research has shown the involvement of the activation of cellular senescence-related mechanisms in natural aging and kidney injury. Intensive research is searching for novel treatments for kidney diseases as well as for anti-aging therapies. In this sense, many experimental shreds of evidence support that treatment with vitamin D or its analogs can exert pleiotropic protective effects in kidney injury. Moreover, vitamin D deficiency has been described in patients with kidney diseases. Here, we review recent evidence about the relationship between vitamin D and kidney diseases, explaining the underlying mechanisms of the effect of vitamin D actions, with particular attention to the modulation of cellular senescence mechanisms.

Latest Knowledge on the Role of Vitamin D in Hypertension

Hypertension is the third leading cause of the global disease burden, and while populations live longer, adopt more sedentary lifestyles, and become less economically concerned, the prevalence of hypertension is expected to increase. Pathologically elevated blood pressure (BP) is the strongest risk factor for cardiovascular disease (CVD) and related disability, thus making it imperative to treat this disease. Effective standard pharmacological treatments, i.e., diuretics, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blocker (ARBs), beta-adrenergic receptor blockers (BARBs), and calcium channel blockers (CCBs), are available. Vitamin D (vitD) is known best for its role in bone and mineral homeostasis. Studies with vitamin D receptor (VDR) knockout mice show an increased renin-angiotensin-aldosterone system (RAAS) activity and increased hypertension, suggesting a key role for vitD as a potential antihypertensive agent. Similar studies in humans displayed ambiguous and mixed results. No direct antihypertensive effect was shown, nor a significant impact on the human RAAS. Interestingly, human studies supplementing vitD with other antihypertensive agents reported more promising results. VitD is considered a safe supplement, proposing its great potential as antihypertensive supplement. The aim of this review is to examine the current knowledge about vitD and its role in the treatment of hypertension.

Structural characterization and protective effect against renal fibrosis of polysaccharide from Ligustrum lucidum Ait

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Ligustri Lucidi (FLL), the fruit of Ligustrum lucidum Ait., is a traditional Chinese medicine that has been used for tonifying the kidney and liver for decades.

AIM OF THE STUDY

This study aimed to explore and identify polysaccharides from FLL and elucidate its protective effect against renal fibrosis.

MATERIALS AND METHODS

Polysaccharides were extracted and isolated from FLL. The purified fraction was identified by serial phytochemical work, such as gel-permeation chromatography, ion chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance. Mice with unilateral ureteral obstruction (UUO) were applied as a renal fibrosis model. The male UUO mice were pretreated with heteropolysaccharide (Poly) 1 week prior to surgery and continuously treated for 7 days after the operation. Renal fibrosis was assessed by Periodic Acid-Schiff (PAS) staining and Masson's trichrome staining in paraffin-embedded slides. The murine mesangial cells SV40-MES13 upon angiotensin II (Ang II) treatment were developed as an in vitro fibrotic model. The cells were treated by Poly in the presence of Ang II. Molecular expression was detected by RT-PCR, immunoblotting, and immunofluorescence staining.

RESULTS

We identified a heteropolysaccharide composed of arabinose and galactose (molar ratio, 0.73:0.27) with a predicted chemical structure characterized by a backbone composed of 1,5-α-Araf, 1,3,5-α-Araf, 1,6-α-Galp, and 1,3,6-β-Galp and side chains comprised of T-α-Araf, T-α-Arap, and 1,3-α-Araf. Pretreatment of UUO mice with Poly effectively alleviated glomerulosclerosis and tubulointerstitial fibrosis. Moreover, Poly pretreatment down-regulated the expression of extracellular matrix (ECM) protein fibronectin (FN), profibrotic factor VEGF, proinflammatory cytokines MCP-1 and Rantes in the obstructed kidney. Similarly, the incubation of SV40-MES13 cells with Poly significantly inhibited Ang II-induced elevation in accumulation and expression level of FN and attenuated Ang II-evoked up-regulation in protein expression of MCP-1 and Rantes.

CONCLUSIONS

Our study isolated and identified a naturally occurring heteropolysaccharide in FLL and revealed its potential in protecting the kidneys from fibrosis.

Double blind control trial of vitamin D fortified milk on the expression of lncRNAs and adiponectin for patients with metabolic syndrome

BACKGROUND

Metabolic syndrome (Mets) is a common metabolic disorder in which hypoadiponectinemia is one of the consequences for the body caused by inflammation, and vitamin D may help improve inflammatory symptoms. LncRNAs (long non-coding RNA) play several different regulatory roles in the body. The goal of this study was to see how adding vitamin D to milk affected the levels of adiponectin and inflammatory lncRNAs in the serum of people with Mets.

METHODS

This clinical trial was conducted on staff and students between the ages of 30 and 50 at Mashhad University of Medical Sciences and met the International Diabetes Federation's criteria for Mets. Eighty-two Mets were assigned randomly to one of two groups for ten weeks: fortified milk (FM) with 1500 IU vitamin D or non-fortified milk (NFM). Total RNA was extracted from both frozen clinical samples using Trizol reagent. APQ AS and MALAT1 lncRNA gene expression were measured by Real-Time PCR.

RESULTS

Serum adiponectin levels in the FM group increased significantly compared to the NFM group (p = 0.01). Also, the expression of APQ AS and MALAT1 genes decreased after ten weeks, which showed a significant decrease in APQ AS (p = 0.036).

CONCLUSION

As in FM, vitamin D may have anti-inflammatory effects and increase adiponectin levels in people with Mets via decreasing APQ AS gene expression.

Modulation of cardiometabolic risk and CardioRenal syndrome by oral vitamin D3 supplementation in Black and White Southern Sahara residents with chronic kidney disease Stage 3: focus on racial and ethnic disparities

OBJECTIVES

Several studies have shown that cholecalciferol supplementation (25OHD-S) in chronic kidney disease (CKD) improves kidney injury by reducing fibrosis-related vascular calcification and declining apoptosis-linked nephron damage.

METHODS

The oral 25OHD-S was evaluated in 60,000 IU/month/36 weeks versus in 2000 IU/d/24 weeks in CKD Stage 3 with serum 25OHD level < 20 ng/mL. The study was undertaken on 156 black subjects and 150 white subjects Southern Sahara (SS). All biomarkers of cardiometabolic (CMet) and cardiorenal (CRenal) syndrome, Renin-angiotensin-aldosterone system (RAAS) profile, secondary hyperparathyroidism (SHPT), N-terminal pro B-type natriuretic peptide (NT-proBNP), Troponin T (cTnT) and atherogenicity risk were assessed by biochemical methods. Estimate glomerular filtration rate (eGFR) by chronic CKD-EPI equation formula. Total serum vitamin D by liquid chromatography-tandem mass spectrometry (MS).

RESULTS

Vitamin D deficiency alters in the same manner CMet, CRenal, and others biomarkers in both groups SS; however, these disorders are more acute in blacks compared to whites SS. Oral 25OHD-S a highlighted improvement of eGFR drop, SHPT decrease, decline proteinuria, and cardiac failure risk (NT-proBNP and cTnT) attenuation. Concomitantly, 25OHD-S normalizes Renin, Aldosterone, and Angiotensin System (RAAS) activity. Nevertheless, homocysteine and Lp (a) do not modulate by 25OHD-S.

CONCLUSIONS

The oral vitamin D3 supplementation, according the dose, and the treatment duration does not like in black-skinned people versus to white-skinned inhabitants, while the 02 groups are native to the same Saharan environment. It emerge that a high intermittent dose through an extensive supplementation (60,000 IU/36 weeks) was more effective in black subjects. At opposite, a lower dose during a short period supplementation is sufficient (2000 IU/24 weeks) in white subjects.

The Role of Vitamin D in SARS-CoV-2 Infection and Acute Kidney Injury

Vitamin D has been described as an essential nutrient and hormone, which can cause nuclear, non-genomic, and mitochondrial effects. Vitamin D not only controls the transcription of thousands of genes, directly or indirectly through the modulation of calcium fluxes, but it also influences the cell metabolism and maintenance specific nuclear programs. Given its broad spectrum of activity and multiple molecular targets, a deficiency of vitamin D can be involved in many pathologies. Vitamin D deficiency also influences mortality and multiple outcomes in chronic kidney disease (CKD). Active and native vitamin D serum levels are also decreased in critically ill patients and are associated with acute kidney injury (AKI) and in-hospital mortality. In addition to regulating calcium and phosphate homeostasis, vitamin D-related mechanisms regulate adaptive and innate immunity. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have a role in excessive proinflammatory cell recruitment and cytokine release, which contribute to alveolar and full-body endothelial damage. AKI is one of the most common extrapulmonary manifestations of severe coronavirus disease 2019 (COVID-19). There are also some correlations between the vitamin D level and COVID-19 severity via several pathways. Proper vitamin D supplementation may be an attractive therapeutic strategy for AKI and has the benefits of low cost and low risk of toxicity and side effects.

Insights Into Vascular Anomalies, Cancer, and Fibroproliferative Conditions: The Role of Stem Cells and the Renin-Angiotensin System

Cells exhibiting embryonic stem cell (ESC) characteristics have been demonstrated in vascular anomalies (VAs), cancer, and fibroproliferative conditions, which are commonly managed by plastic surgeons and remain largely unsolved. The efficacy of the mTOR inhibitor sirolimus, and targeted therapies that block the Ras/BRAF/MEK/ERK1/2 and PI3KCA/AKT/mTOR pathways in many types of cancer and VAs, further supports the critical role of ESC-like cells in the pathogenesis of these conditions. ESC-like cells in VAs, cancer, and fibroproliferative conditions express components of the renin-angiotensin system (RAS) – a homeostatic endocrine signaling cascade that regulates cells with ESC characteristics. ESC-like cells are influenced by the Ras/BRAF/MEK/ERK1/2 and PI3KCA/AKT/mTOR pathways, which directly regulate cellular proliferation and stemness, and interact with the RAS at multiple points. Gain-of-function mutations affecting these pathways have been identified in many types of cancer and VAs, that have been treated with targeted therapies with some success. In cancer, the RAS promotes tumor progression, treatment resistance, recurrence, and metastasis. The RAS modulates cellular invasion, migration, proliferation, and angiogenesis. It also indirectly regulates ESC-like cells via its direct influence on the tissue microenvironment and by its interaction with the immune system. In vitro studies show that RAS inhibition suppresses the hallmarks of cancer in different experimental models. Numerous epidemiological studies show a reduced incidence of cancer and improved survival outcomes in patients taking RAS inhibitors, although some studies have shown no such effect. The discovery of ESC-like cells that express RAS components in infantile hemangioma (IH) underscores the paradigm shift in the understanding of its programmed biologic behavior and accelerated involution induced by β-blockers and angiotensin-converting enzyme inhibitors. The findings of SOX18 inhibition by R-propranolol suggests the possibility of targeting ESC-like cells in IH without β-adrenergic blockade, and its associated side effects. This article provides an overview of the current knowledge of ESC-like cells and the RAS in VAs, cancer, and fibroproliferative conditions. It also highlights new lines of research and potential novel therapeutic approaches for these unsolved problems in plastic surgery, by targeting the ESC-like cells through manipulation of the RAS, its bypass loops and converging signaling pathways using existing low-cost, commonly available, and safe oral medications.

The Role of Vitamin D in Diabetic Nephropathy: A Translational Approach

According to several animal and human studies, vitamin D appears to play a significant role in the development of diabetic nephropathy. However, the possible renoprotective effect of vitamin D and its influence on the reversal of already existing renal damage remains doubtful. At this moment, there are a few hypotheses concerning the underlying molecular and genetic mechanisms including the link between vitamin D and inflammation, oxidative stress, and extracellular matrix accumulation. The present review aims to investigate the potential role of vitamin D in the development of diabetic kidney disease from a translational approach.

Vitamin D/Vitamin D Receptor Signaling Attenuates Skeletal Muscle Atrophy by Suppressing Renin-Angiotensin System

The nutritional level of vitamin D may affect musculoskeletal health. We have reported that vitamin D is a pivotal protector against tissue injuries by suppressing local renin-angiotensin system (RAS). This study aimed to explore the role of the vitamin D receptor (VDR) in the protection against muscle atrophy and the underlying mechanism. A cross-sectional study on participants (n = 1034) in Shanghai (China) was performed to analyze the association between vitamin D level and the risk of low muscle strength as well as to detect the circulating level of angiotensin II (Ang II). In animal studies, dexamethasone (Dex) was applied to induce muscle atrophy in wild-type (WT) and VDR-null mice, and the mice with the induction of muscle atrophy were treated with calcitriol for 10 days. The skeletal muscle cell line C2C12 and the muscle satellite cells were applied in in vitro studies. The increased risk of low muscle strength was correlated to a lower level of vitamin D (adjusted odds ratio [OR] 0.58) accompanied by an elevation in serum Ang II level. Ang II impaired the myogenic differentiation of C2C12 myoblasts as illustrated by the decrease in the area of myotubes and the downregulation of myogenic factors (myosin heavy chain [MHC] and myogenic differentiation factor D [MyoD]). The phenotype of muscle atrophy induced by Dex and Ang II was aggravated by VDR ablation in mice and in muscle satellite cells, respectively, and mediated by RAS and its downstream phosphatidylinositol 3-kinase/protein kinase B/forkhead box O1 (PI3K/Akt/FOXO1) signaling. Calcitriol treatment exhibited beneficial effects on muscle function as demonstrated by the increased weight-loaded swimming time, grip strength, and fiber area, and improved fiber type composition via regulating ubiquitin ligases and their substrates MHC and MyoD through suppressing renin/Ang II axis. Taken together, VDR protects against skeletal muscle atrophy by suppressing RAS. Vitamin D could be a potential agent for the prevention and treatment of skeletal muscle atrophy. © 2021 American Society for Bone and Mineral Research (ASBMR).

Assessing and counteracting fibrosis is a cornerstone of the treatment of CKD secondary to systemic and renal limited autoimmune disorders

Chronic kidney disease (CKD) is an increasing cause of morbidity and mortality worldwide. Besides the higher prevalence of diabetes, hypertension and aging worldwide, immune mediated disorders remain an important cause of kidney disease and are especially prevalent in young adults. Regardless of the initial insult, final pathway to CKD and kidney failure is always the loss of normal tissue and fibrosis development, in which the dynamic equilibrium between extracellular matrix synthesis and degradation is disturbed, leading to excessive production and accumulation. During fibrosis, a multitude of cell types intervene at different levels, but myofibroblasts and inflammatory cells are considered critical in the process. They exert their effects through different molecular pathways, of which transforming growth factor β (TGF-β) has demonstrated to be of particular importance. Additionally, CKD itself promotes fibrosis due to the accumulation of toxins and hormonal changes, and proteinuria is simultaneously a manifestation of CKD and a specific driver of renal fibrosis. Pathways involved in renal fibrosis and CKD are closely interrelated, and although important advances have been made in our knowledge of them, it is still necessary to translate them into clinical practice. Given the complexity of this process, it is highly likely that its treatment will require a multi-target strategy to control the origin of the damage but also the mechanisms that perpetuate it. Fortunately, rapid technology development over the last years and new available drugs in the nephrologist's armamentarium give reasons for optimism that more personalized assistance for CKD and renal fibrosis will appear in the future.

Developmental Vitamin D Deficiency in Pregnant Rats Does Not Induce Preeclampsia

Preeclampsia is a pregnancy disorder characterized by hypertension. Epidemiological studies have associated preeclampsia with an increased risk of neurodevelopmental disorders in offspring, such as autism and schizophrenia. Preeclampsia has also been linked with maternal vitamin D deficiency, another candidate risk factor also associated with autism. Our laboratory has established a gestational vitamin-D-deficient rat model that shows consistent and robust behavioural phenotypes associated with autism- and schizophrenia-related animal models. Therefore, we explored here whether this model also produces preeclampsia as a possible mediator of behavioural phenotypes in offspring. We showed that gestational vitamin D deficiency was not associated with maternal blood pressure or proteinuria during late gestation. Maternal and placental angiogenic and vasculogenic factors were also not affected by a vitamin-D-deficient diet. We further showed that exposure to low vitamin D levels did not expose the placenta to oxidative stress. Overall, gestational vitamin D deficiency in our rat model was not associated with preeclampsia-related features, suggesting that well-described behavioural phenotypes in offspring born to vitamin-D-deficient rat dams are unlikely to be mediated via a preeclampsia-related mechanism.

Nuclear Receptors and Transcription Factors in Obesity-Related Kidney Disease

Both obesity and chronic kidney disease are increasingly common causes of morbidity and mortality worldwide. Although obesity often co-exists with diabetes and hypertension, it has become clear over the past several decades that obesity is an independent cause of chronic kidney disease, termed obesity-related glomerulopathy. This review defines the attributes of obesity-related glomerulopathy and describes potential pharmacologic interventions. Interventions discussed include peroxisome proliferator-activated receptors, the farnesoid X receptor, the Takeda G-protein-coupled receptor 5, and the vitamin D receptor.

Vitamin D Analogs Can Retard the Onset or Progression of Diabetic Kidney Disease: A Systematic Review

Introduction

Previous studies have shown that vitamin D analogs (such as paricalcitol) can reduce albuminuria in patients with diabetes mellitus and retard the progression of diabetic kidney disease (DKD). A recent systematic review reported significant improvement of renal function in patients with DKD who received vitamin D or its analogs. Study-driven data about their use in improving DKD outcomes have continued to accumulate over the years.

Aim

This paper aims to systematically review the contemporary evidence about the effectiveness of vitamin D analogs in retarding the onset or progression of DKD.

Methods

With appropriate descriptors, two electronic databases (PubMed and Google Scholar) were searched for articles published between 2015 and 2021 in the English language. Primary studies that fulfilled the inclusion criteria were selected; their titles and abstracts were screened, and duplicates were removed. Relevant data were retrieved from the final selected studies using a preconceived data-extraction form.

Results

A total of eight studies (three randomized-controlled trials, one prospective study, and four cross-sectional studies) were reviewed. A total of 6,243 participants were investigated in the eight studies and comprised young adults, middle-aged adults, and the elderly with a male-gender predominance. One randomized controlled trial reported that paricalcitol significantly improved renal function in type 1 diabetes patients with renal impairment when combined with renin-angiotensin-aldosterone system (RAAS) blockers. A strong correlation between vitamin D deficiency and DKD risk was noted in the majority of the cross-sectional studies. High doses of cholecalciferol (4,000 or 10,000 IU/day), given early in DKD, significantly reduced disease prevalence.

Conclusion

Paricalcitol may retard the onset or progression of DKD, especially if administered in combination with RAAS blockers. The association of vitamin D deficiency with DKD risk also supports this therapeutic effect. Future systematic reviews are still needed to strengthen the current evidence on therapeutic benefit of vitamin D or its analogs in DKD.

Prevalence of vitamin D deficiency and impact on clinical outcomes after kidney transplantation: a systematic review and meta-analysis

CONTEXT

The prevalence of vitamin D deficiency (VDD) and its impact on clinical outcomes after kidney transplant (KT) remain poorly defined.

OBJECTIVES

We conducted a meta-analysis to evaluate the impact of early VDD on clinical outcomes after KT.

DATA SOURCES

Electronic databases (PubMed, Embase, Web of Science, and The Cochrane Library) were systematically searched for eligible publications up to April 30, 2020.

DATA EXTRACTION

Relative risk was presented as hazard ratios (HRs) or odds ratios (ORs) and 95%CIs for dichotomous outcomes. Mean difference (MD) and 95%CIs were presented for continuous outcomes.

RESULTS

A total of 28 studies (13 prospective and 15 retrospective) were included. VDD was common early after KT, with a prevalence of 52% (95%CI: 41%-64%) at transplant, 34% (95%CI: 17%-51%) at 3 months, and 23% (95%CI: 10%-35%) at 6 months. Early VDD was associated with higher mortality rate after KT (HR, 1.56; 95%CI: 1.32-1.84; P < 0.001). In addition, early VDD led to higher risk of bacterial infection (OR, 1.82; 95%CI: 1.40-2.36; P < 0.001), BK polyomavirus infection (OR, 2.11, 95%CI: 1.23-3.61; P = 0.006), and cytomegalovirus infection (OR, 1.69; 95%CI: 1.24-2.31; P = 0.001). Early VDD increased the risk of acute rejection as well (HR, 2.28; 95%CI: 1.57-3.30; P < 0.001). Recipients with early VDD had lower estimated glomerular filtration rates (mean difference: -5.06; 95%CI: -7.28 to 2.83 mL/min; P < 0.001). Sensitivity analyses showed good stability of the pooled results.

CONCLUSION

VDD was common early after KT and associated with higher risk of death and adverse outcomes.

The effect of cholecalciferol supplementation on allograft function in incident kidney transplant recipients: A randomized controlled study

It is unknown whether cholecalciferol supplementation improves allograft outcomes in kidney transplant recipients (KTRs). We conducted a single-center randomized, double-blind, placebo-controlled trial of daily 4000 IU cholecalciferol supplementation in KTRs at 1-month posttransplant. The primary endpoint was the change in eGFR from baseline to 12-month posttransplant. Secondary endpoints included severity of interstitial fibrosis and tubular atrophy (IFTA) at 12-month posttransplant and changes in urinary biomarkers. Of 193 randomized patients, 180 participants completed the study. Changes in eGFR were 1.2 mL/min/1.73 m² (95% CI; -0.7 to 3.1) in the cholecalciferol group and 1.8 mL/min/1.73 m² (95% CI, -0.02 to 3.7) in the placebo group, with no significant between-group difference (-0.7 mL/min/1.73 m² [95% CI; -3.3 to 2.0], p = 0.63). Subgroup analyses showed detrimental effects of cholecalciferol in patients with eGFR <45 mL/min/1.73 m² (P_interaction <0.05, between-group difference; -4.3 mL/min/1.73 m² [95% CI; -7.3 to -1.3]). The degree of IFTA, changes in urine albumin-to-creatinine ratio, or adverse events including hypercalcemia and infections requiring hospitalization did not differ between groups. In conclusion, cholecalciferol supplementation did not affect eGFR change compared to placebo among incident KTRs. These findings do not support cholecalciferol supplementation for improving allograft function in incident KTRs. Clinical trial registry: This study was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) as UMIN000020597 (please refer to the links below). UMIN-CTR: https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000023776.

Vitamin D-VDR (vitamin D receptor) regulates defective autophagy in renal tubular epithelial cell in streptozotocin-induced diabetic mice via the AMPK pathway

Diabetic nephropathy (DN) has become a major cause of end-stage renal disease, and autophagy disorder is implicated in the pathogenesis of DN. Our previous studies found that vitamin D (VD) and VDR (vitamin D receptor) played a renoprotective role by inhibiting inflammation and fibrosis. However, whether VD-VDR regulates autophagy disorders in DN remains unclear. In this study, we established a streptozotocin (STZ)-induced diabetic model in vdr knockout (vdr-KO) mice and VDR specifically overexpressed in renal proximal tubular epithelial cells (Vdr-OE) mice. Our results showed that paricalcitol (an activated vitamin D analog) or Vdr-OE could alleviate STZ-induced ALB (albumin) excretion, renal tubule injury and inflammation, while these were worsened in vdr-KO mice. Defective autophagy was observed in the kidneys of STZ mice, which was more pronounced in vdr-KO mice and could be partially restored by paricalcitol or Vdr-OE. In high glucose-induced HK-2 cells, defective autophagy and decreased PRKAA1/AMPK phosphorylation was observed, which could be partially restored by paricalcitol in a VDR-dependent manner. AMPK inhibitor abolished paricalcitol-induced autophagy activation, and AMPK activator restored the defective autophagy in high glucose-induced HK-2 cells. Furthermore, paricalcitol-mediated AMPK activation was abrogated by CAMKK2/CaMKKβ inhibition, but not by STK11/LKB1 knockout. Meanwhile, paricalcitol rescued the decreased Ca²⁺ concentration induced by high glucose. In conclusion, VD-VDR can restore defective autophagy in the kidney of STZ-induced diabetic mice, which could be attributed to the activation of the Ca²⁺-CAMKK2-AMPK pathway in renal tubular epithelial cells.

Abbreviations: ACTB/β-actin: actin beta;AGE: advanced glycation end-products;AMPK: AMP-activated protein kinase;CAMKK2/CaMKKβ: calcium-calmodulin dependent protein kinase kinase 2;CQ: chloroquine;DN: diabetic nephropathy;HG: high levels of glucose;KO: knockout;LG: low levels of glucose;MAP1LC3/LC3: microtubule associated protein 1 light chain 3;NOD2: nucleotide binding oligomerization domain containing 2;OE: overexpression;PAS: periodic acid Schiff; Pari: paricalcitol;PTECs: proximal renal tubule epithelial cells;RT: room temperature;SQSTM1/p62: sequestosome 1;STK11/LKB1: serine/threonine kinase 11;STZ: streptozotocin;TEM: transmission electron microscopy;VD: vitamin D;VDR: vitamin D receptor;WT: wild-type

Vitamin D suppresses bleomycin-induced pulmonary fibrosis by targeting the local renin-angiotensin system in the lung

Idiopathic pulmonary fibrosis (IPF) is a severe disorder leading to progressive and irreversible loss of pulmonary function. In this study we investigated the anti-fibrotic effect of vitamin D using a mouse model of IPF. Lung fibrosis was induced with bleomycin in vitamin D-sufficient and vitamin D-deficient C57BL/6 mice. We found that treatment with active vitamin D analog paricalcitol prevented mouse body weight loss and alleviated lung fibrosis, whereas vitamin D deficiency severely aggravated lung injury. At the molecular level, paricalcitol treatment suppressed the induction of fibrotic inducer TGF-β and extracellular matrix proteins α-SMA, collagen type I and fibronectin in the lung, whereas vitamin D deficiency exacerbated the induction of these proteins. Interestingly, bleomycin treatment activated the local renin–angiotensin system (RAS) in the lung, manifested by the induction of renin, angiotensinogen, angiotensin II and angiotensin receptor type 1 (AT1R). Paricalcitol treatment suppressed the induction of these RAS components, whereas vitamin D deficiency enhanced the activation of the lung RAS. We also showed that treatment of bleomycin-induced vitamin D-deficient mice with AT1R antagonist losartan relieved weight loss, substantially ameliorated lung fibrosis and markedly blocked TGF-β induction in the lung. Moreover, we demonstrated that in lung fibroblast cultures, TGF-β and angiotensin II synergistically induced TGF-β, AT1R, α-SMA, collagen type I and fibronectin, whereas 1,25-dihydroxyvitamin D markedly suppressed the induction of these fibrotic markers. Collectively, these observations strongly suggest that vitamin D mitigates lung fibrosis by blocking the activation of the lung RAS in this mouse model of IPF.

Effects of calcitriol and paricalcitol on renal fibrosis in CKD

BACKGROUND

In chronic kidney disease, the activation of the renin-angiotensin-aldosterone system (RAAS) and renal inflammation stimulates renal fibrosis and the progression to end-stage renal disease. The low levels of vitamin D receptor (VDR) and its activators (VDRAs) contribute to worsen secondary hyperparathyroidism and renal fibrosis.

METHODS

The 7/8 nephrectomy model of experimental chronic renal failure (CRF) was used to examine the anti-fibrotic effects of treatment with two VDRAs, paricalcitol and calcitriol, at equivalent doses (3/1 dose ratio) during 4 weeks.

RESULTS

CRF increased the activation of the RAAS, renal inflammation and interstitial fibrosis. Paricalcitol treatment reduced renal collagen I and renal interstitial fibrosis by decreasing the activation of the RAAS through renal changes in renin, angiotensin receptor 1 (ATR1) and ATR2 mRNAs levels and renal inflammation by decreasing renal inflammatory leucocytes (CD45), a desintegrin and metaloproteinase mRNA, transforming growth factor beta mRNA and protein, and maintaining E-cadherin mRNA levels. Calcitriol showed similar trends without significant changes in most of these biomarkers.

CONCLUSIONS

Paricalcitol effectively attenuated the renal interstitial fibrosis induced by CRF through a combination of inhibitory actions on the RAAS, inflammation and epithelial/mesenchymal transition.

Vitamin D/VDR in Acute Kidney Injury: A Potential Therapeutic Target

Despite many strategies and parameters used in clinical practice, the incidence and mortality of acute kidney injury (AKI) are still high with poor prognosis. With the development of molecular biology, the role of vitamin D and vitamin D receptor (VDR) in AKI is drawing increasing attention. Accumulated researches have suggested that Vitamin D deficiency is a risk factor of both clinical and experimental AKI, and vitamin D/VDR could be a promising therapeutic target against AKI. However, more qualitative clinical researches are needed to provide stronger evidence for the clinical application of vitamin D and VDR agonists in the future. Issues like the route and dosage of administration also await more attention. The present review aims to summarize the current works on the role of vitamin D/VDR in AKI and provides some new insight on its therapeutic potential.

Health implication of vitamin D on the cardiovascular and the renal system

Vitamin D regulates the calcium and phosphorus balance in the body. The activated form of vitamin D (1 α,25-dihydroxyvitamin D) binds to vitamin D receptor which regulates genes that control cell proliferation, differentiation and apoptosis. In the cardiovascular system, the vitamin D receptor is present in cardiomyocytes and the arterial wall. A clear correlation between vitamin D level and cardiovascular diseases is established. Vitamin D deficiency affects the renin-angiotensin system leading to ventricular hypertrophy and eventually to stroke. While clinical trials highlighted the positive effects of vitamin D supplements on cardiovascular disease these still need to be confirmed. This review outlines the association between vitamin D and cardiovascular and renal disease summarising the experimental data of selective cardiovascular disorders.

Vitamin D and Acute Kidney Injury: A Two-Way Causality Relation and a Predictive, Prognostic, and Therapeutic Role of Vitamin D

Background: Acute kidney injury (AKI) constitutes a multi-factorially caused condition, which significantly affects kidney function and can lead to elevated risk of morbidity and mortality. Given the rising scientific evidence regarding vitamin D's (VitD's) multisystemic role, the connection between AKI and VitD is currently being studied, and the complex relation between them has started to be unraveled.

Methods: A systematic review had been conducted to identify the pathogenetic relation of VitD and AKI and the potential role of VitD as a biomarker and therapeutic–renoprotective factor.

Results: From 792 articles, 74 articles were identified that fulfilled the inclusion criteria. Based on these articles, it has been found that not only can VitD disorders (VitD deficiency or toxicity) cause AKI but, also, AKI can lead to great disruption in the metabolism of VitD. Moreover, it has been found that VitD serves as a novel biomarker for prediction of the risk of developing AKI and for the prognosis of AKI's severity. Finally, animal models showed that VitD can both ameliorate AKI and prevent its onset, suggesting its renoprotective effect.

Conclusion: There is a complex two-way pathogenetic relation between VitD disorders and AKI, while, concomitantly, VitD serves as a potential novel predictive–prognostic biomarker and a treatment agent in AKI therapy.

Vitamin D/VDR attenuate cisplatin-induced AKI by down-regulating NLRP3/Caspase-1/GSDMD pyroptosis pathway

Vitamin D/Vitamin D receptor (VDR) has been shown to inhibit the NF-κB-mediated inflammatory effects. Up-regulation of the NLRP3(Recombinant NLR Family, Pyrin Domain Containing Protein 3)/Caspase-1/GSDMD (Gasdermin D) pathway through NF-κb is one of the key mechanisms leading to pyroptosis. This study aims to explore the effects of vitamin D/VDR on the pyroptosis pathway in cisplatin induced acute kidney injury (AKI) models. Our results showed that in wide type mice, renal function loss, tissue injury and cell death induced by cisplatin were alleviated by pretreatment of high-dose paricalcitol(a VDR agonist) accompanied with up-regulated VDR and decreased expression of NLRP3, GSDMD-N, Cleaved-Caspase-1 and mature Interleukin- 1β (features of pyroptosis). While, in VDR knock out mice, cisplatin induced more severer renal injury and further increased pyroptosis related protein than the wild type mice and the effect of paricalcitol were also eliminated. In tubular cell specific VDR-over expressing mice, those renal injury index as well as pyroptosis phenotype were significantly reduced by low-dose paricalcitol pretreatment with upregulated VDR expression compared with WT mice. In vitro data using gain and lose function experiments in Human tubular epithelial cell (HK-2) were consistent with the observation as in vivo work. Our further experiments in both animal and cell culture work has found that the level of IκBα(Inhibitor of NF-κB) were decreased and the nuclear level of NF-κB p65 of renal tubular cells were increased after cisplatin injury while VDR activation by paricalcitol could reverse up-regulation of nuclear NF-κB p65 with reduced cell pyroptosis. These data suggested that vitamin D/VDR could alleviate cisplatin-induced acute renal injury partly by inhibiting NF-κB-mediated NLRP3/Caspase-1/GSDMD pyroptosis.

The Blockade of TACE-Dependent EGF Receptor Activation by Losartan-Erlotinib Combination Attenuates Renal Fibrosis Formation in 5/6-Nephrectomized Rats Under Vitamin D Deficiency

Chronic kidney disease (CKD) has been considered a major public health issue. In addition to cardiovascular diseases and infections, hypovitaminosis D has been considered a non-traditional aggravating factor for CKD progression. Interstitial fibrosis is a hallmark of CKD strongly correlated with deterioration of renal function. Transforming growth factor β (TGF-β) is the major regulatory profibrotic cytokine in CKD. Many injurious stimuli converge on the TGF-β pathway, which has context-dependent pleiotropic effects and interacts with several related renal fibrosis formation (RFF) pathways. Epidermal growth factor receptor (EGFR) is critically involved in CKD progression, exerting a pathogenic role in RFF associated with TGF-β-related fibrogenesis. Among others, EGFR pathway can be activated by a disintegrin and a metalloproteinase known as tumor necrosis factor α-converting enzyme (TACE). Currently no effective therapy is available to completely arrest RFF and slow the progression of CKD. Therefore, we investigated the effects of a double treatment with losartan potassium (L), an AT1R antagonist, and the tyrosine kinase inhibitor erlotinib (E) on the alternative pathway of RFF related to TACE-dependent EGFR activation in 5/6-nephrectomized rats under vitamin D deficiency (D). During the 90-day protocol, male Wistar rats under D, were submitted to 5/6 nephrectomy (N) on day 30 and randomized into four groups: N+D, no treatment; N+D+L, received losartan (50 mg/kg/day); N+D+E, received erlotinib (6 mg/kg/day); N+D+L+E received losartan+erlotinib treatment. N+D+L+E data demonstrated that the double treatment with losartan+erlotinib not only blocked the TACE-dependent EGF receptor activation but also prevented the expression of TGF-β, protecting against RFF. This renoprotection by losartan+erlotinib was corroborated by a lower expression of ECM proteins and markers of phenotypic alteration as well as a lesser inflammatory cell infiltrate. Although erlotinib alone has been emerging as a renoprotective drug, its association with losartan should be considered as a potential therapeutic strategy on the modulation of RFF.

Role of the renin-angiotensin-aldosterone system in bone metabolism

With the acceleration of population aging, the incidence of osteoporosis has gradually increased, and osteoporosis and fractures caused by osteoporosis have gradually become a serious social public health problem. The classic role of the renin-angiotensin-aldosterone system (RAAS) is to keep blood pressure stable. However, as the components of RAAS were found in bone tissues, their functions of stimulating osteoclast formation and inhibiting osteoblast activity thus inducing bone loss have gradually emerged. RAAS blockers can prevent osteoporotic fractures which may be related to angiotensin type 1 (AT1) receptor, osteoprotegerin (OPG)/nuclear factor-κB ligand (RANKL), and angiotensin-converting enzyme 2 (ACE2)/angiotensin (1-7) (Ang (1-7))/G protein-coupled receptor (Mas) cascade. However, some studies suggest that RAAS blockers do not prevent osteoporotic fractures. This article reviews the effects of RAAS and RAAS inhibitors on bone metabolism and provides new ideas for the prevention of osteoporosis.

Association between 25(OH) vitamin D and graft survival in renal transplanted children

BACKGROUND

In children, vitamin D deficiency is common after renal transplantation. Besides promoting bone and muscle development, vitamin D has immunomodulatory effects, which could protect kidney allografts. The purpose of this study was to assess the association between vitamin D status and the occurrence of renal rejection.

METHODS

We studied a retrospective cohort of 123 children, who were transplanted at a single institution between September 2008 and April 2019. Patients did not receive vitamin D supplementation systematically. In addition, factors influencing vitamin D status were analyzed using univariate and multivariate analyses.

RESULTS

Median 25-hydroxy-vitamin D (25-OH-D) concentration was close to reference values at the time of transplantation (30 ng/mL (min-max 5-100)), but rapidly decreased within the first 3 months to 19 ng/mL (min-max 3-91) (P < .001). The overall acute rejection rate was 7%. The clinical rejection rate (5% vs 9%), subclinical rejection (12% vs 36%), and borderline changes (21% vs 28%) were not statistically different during the follow-up between the 3-month 25-OH-D < 20 ng/mL and 3-month 25-OH-D > 20 ng/mL groups. There was a correlation between the 25-OH-D levels and PTH concentration at 3 months (r = -.2491, P = .01), but no correlation between the 3-month 25-OH-D and the season of the year (F = 0.19, P = .90; F = 1.34, P = .27, respectively). Multivariate analyses revealed that age and mGFR at 3 months, were independent predictors of mGFR at 12 months.

CONCLUSION

Our data show that vitamin D deficiency can develop rapidly after transplantation; vitamin D levels at 3 months are not associated with lower mGFR or a higher rejection rate at 1 year in children as opposed to adult recipients.

Understanding the Biological Activities of Vitamin D in Type 1 Neurofibromatosis: New Insights into Disease Pathogenesis and Therapeutic Design

Vitamin D is a fat-soluble steroid hormone playing a pivotal role in calcium and phosphate homeostasis as well as in bone health. Vitamin D levels are not exclusively dependent on food intake. Indeed, the endogenous production-occurring in the skin and dependent on sun exposure-contributes to the majority amount of vitamin D present in the body. Since vitamin D receptors (VDRs) are ubiquitous and drive the expression of hundreds of genes, the interest in vitamin D has tremendously grown and its role in different diseases has been extensively studied. Several investigations indicated that vitamin D action extends far beyond bone health and calcium metabolism, showing broad effects on a variety of critical illnesses, including cancer, infections, cardiovascular and autoimmune diseases. Epidemiological studies indicated that low circulating vitamin D levels inversely correlate with cutaneous manifestations and bone abnormalities, clinical hallmarks of neurofibromatosis type 1 (NF1). NF1 is an autosomal dominant tumour predisposition syndrome causing significant pain and morbidity, for which limited treatment options are available. In this context, vitamin D or its analogues have been used to treat both skin and bone lesions in NF1 patients, alone or combined with other therapeutic agents. Here we provide an overview of vitamin D, its characteristic nutritional properties relevant for health benefits and its role in NF1 disorder. We focus on preclinical and clinical studies that demonstrated the clinical correlation between vitamin D status and NF1 disease, thus providing important insights into disease pathogenesis and new opportunities for targeted therapy.

Association between vitamin D metabolites, vitamin D binding protein, and proteinuria in dogs

BACKGROUND

Proteinuria has been associated with progression of renal disease and increased morbidity and mortality in dogs and people. In people, proteinuria also has been associated with hypovitaminosis D. Little is known about the relationship between vitamin D metabolism and proteinuria in dogs.

OBJECTIVES

To further elucidate vitamin D status in dogs with protein-losing nephropathy (PLN) and minimal to no azotemia. We hypothesized that vitamin D metabolites would be lower in dogs with PLN compared to healthy dogs.

ANIMALS

Twenty-three client-owned adult dogs with PLN and 10 healthy control dogs.

METHODS

Serum 25-hydroxyvitamin D (25[OH]D), 1,25-dihydroxyvitamin D (1,25[OH]₂ D), 24,25-dihydroxyvitamin D (24,25[OH]₂ D), serum vitamin D binding protein (VDBP), and urine 25(OH)D concentrations were measured.

RESULTS

Compared to healthy dogs, dogs with PLN had lower concentrations of all vitamin D metabolites (P < .01). Correlations (rho; 95% confidence interval [CI]) in dogs with PLN are reported. Serum 25(OH)D and 24,25(OH)₂ D concentrations were positively correlated with albumin (r = 0.47; 0.07-0.74), and 24,25(OH)₂ D was negatively correlated with urine protein-to-creatinine ratio (UPC; r = -0.54; -0.78 to -0.16). Urine 25(OH)D-to-creatinine ratio was negatively correlated with serum albumin concentration (r = -0.77; -0.91 to -0.50) and positively correlated with UPC (r = 0.79; 0.53-0.91). Serum VDBP concentration was positively correlated with serum albumin concentration (r = 0.53; 0.05-0.81).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with PLN have decreased serum concentrations of vitamin D metabolites. Urine 25(OH)D-to-creatinine ratio and UPC are correlated in PLN dogs. Future studies are needed to assess additional management strategies for dogs with PLN.

The Emerging Role of Vitamin D and Vitamin D Receptor in Diabetic Nephropathy

Diabetic nephropathy (DN), one of the most common and severe microvascular complications of diabetes mellitus (DM), is an important risk factor for DM patient's death. Nowadays, DN has become the leading cause of end-stage renal disease (ESRD) in most countries without effective therapeutic methods. Recently, the renoprotective effects mediated by vitamin D (VD) and vitamin D receptor (VDR) have been evidenced. VD, a kind of steroid with the active form 1,25(OH)₂D₃, has been known for the crucial roles in the modulation of serum calcium and phosphorus concentrations. It exerts important functions by binding with its receptor VDR.VDR, a transcription factor located at chromosome 12 containing 9 exons, is one of the nonsteroid nuclear hormone receptor superfamily, which participates in transcriptional regulation of genes in tissue- and cell-specific ways. Increasing evidences have demonstrated that VD/VDR signaling pathway possesses a variety of kidney-protective effects in DN patients, such as antiproteinuria, antifibrosis, anti-inflammatory, and preventing podocyte damage. Although there are many studies on the role of the VD/VDR signaling pathway in DN, the effects and mechanisms still need to be further explained. This review summarized the multiple roles of VD/VDR in podocyte injury, tubule lesions, interstitial fibrosis, and inflammation, as well as the clinical applications about DN to explore much more and effective therapeutic methods for DN.

Phenol glycosides extract of Fructus Ligustri Lucidi attenuated depressive-like behaviors by suppressing neuroinflammation in hypothalamus of mice

Depression is partially caused by inflammation in central nervous system. This study investigated the ameliorative effects of phenol glycosides (PG) from Ligustrum lucidum Ait. (Oleaceae) on neuroinflammation and depressive-like behavior in mice hypothalamus as well as the molecular mechanism. Mice were administered with PG extract for 2 weeks prior to treatment with LPS. The mice treated with PG extract showed resistance to LPS-induced reduction in body weight and LPS-induced depressive-like behaviors shown by sucrose preference, tail suspension test, forced swimming test and open field test. LPS-induced activation of microglial cells and elevation in protein expression of inflammatory cytokines including IL-1β, RANTES and MCP-1 in hypothalamus of mice were abrogated by pre-treatment with PG extract. This extract down-regulated expression of TLR4, MyD88, NLRP3, renin and angiotensin II and decreased proportional area of Iba-1⁺ microglias in hypothalamus. Pre-treatment with PG extract inhibited LPS-triggered activation of CaSR/G_α11 signaling, stimulated 1-OHase expression in hypothalamus, and enhanced circulating 1,25(OH)₂ D₃ level. Overall, pre-treatment with PG extract ameliorated LPS-induced depressive-like behaviors by repressing neuroinflammation in mice hypothalamus which was attributed to its suppression on activation of microglia and production of inflammatory cytokines via acting on TLR4 pathway, CaSR and RAS cascade associated with improving vitamin D metabolism.

Daily and seasonal mitochondrial protection: Unraveling common possible mechanisms involving vitamin D and melatonin

From an evolutionary point of view, vitamin D and melatonin appeared very early and share functions related to defense mechanisms. In the current clinical setting, vitamin D is exclusively associated with phosphocalcic metabolism. Meanwhile, melatonin has chronobiological effects and influences the sleep-wake cycle. Scientific evidence, however, has identified new actions of both molecules in different physiological and pathological settings. The biosynthetic pathways of vitamin D and melatonin are inversely related relative to sun exposure. A deficiency of these molecules has been associated with the pathogenesis of cardiovascular diseases, including arterial hypertension, neurodegenerative diseases, sleep disorders, kidney diseases, cancer, psychiatric disorders, bone diseases, metabolic syndrome, and diabetes, among others. During aging, the intake and cutaneous synthesis of vitamin D, as well as the endogenous synthesis of melatonin are remarkably depleted, therefore, producing a state characterized by an increase of oxidative stress, inflammation, and mitochondrial dysfunction. Both molecules are involved in the homeostatic functioning of the mitochondria. Given the presence of specific receptors in the organelle, the antagonism of the renin-angiotensin-aldosterone system (RAAS), the decrease of reactive species of oxygen (ROS), in conjunction with modifications in autophagy and apoptosis, anti-inflammatory properties inter alia, mitochondria emerge as the final common target for melatonin and vitamin D. The primary purpose of this review is to elucidate the common molecular mechanisms by which vitamin D and melatonin might share a synergistic effect in the protection of proper mitochondrial functioning.

Muscone Ameliorates LPS-Induced Depressive-Like Behaviors and Inhibits Neuroinflammation in Prefrontal Cortex of Mice

Depression is partially caused by inflammation in the central nervous system. Early study demonstrated that musk, glandular secretion from male musk deer, exerted an antidepressant-like effect. The aim of this study was to investigate if muscone, a bioactive ingredient in musk, could ameliorate neuroinflammation and depressive-like behaviors as well as explore the potential action mechanism. Mice were intraperitoneally (i.p.) injected with muscone for 2 weeks prior to administration of lipopolysaccharides (LPS, 1mg/kg, i.p.). Pre-treatment with muscone reversed the LPS-induced decrease in body weight within 24h and ameliorated depressive-like behaviors shown by sucrose preference, tail suspension test, and forced swimming test. LPS-induced activation of microglial cells and elevation in expression of inflammatory cytokines including IL-1β, RANTES, and MCP-1 in the prefrontal cortex of mice were effectively abrogated by muscone, which significantly down-regulated expression of TLR4, MyD88, Caspase-1, NLRP3, renin, and Ang II. In addition, treatment of BV2 microglia cells with muscone markedly attenuated the LPS-induced rise in protein expression of TLR4, Ang II, and IL-1β. This study revealed that muscone could ameliorate LPS-induced depressive-like behaviors by repressing neuroinflammation in the prefrontal cortex of mice caused by its suppression on microglia activation and production of inflammatory cytokines via acting on TLR4 pathway and RAS cascade.

1,25(OH)2D3 provides protection against diabetic kidney disease by downregulating the TLR4-MyD88-NF-κB pathway

The over-activation of Toll-like receptors (TLRs) is a typical immune response to injury. Previous work has suggested that controlling the over-activation of TLR4-MyD88-NF-κB may represent a new therapeutic option for diabetic kidney disease (DKD). 1,25(OH)₂D₃ has also been shown to exert a protective effect on DKD, although the mechanism involved has yet to be elucidated. The aim of this study was to investigate whether 1,25(OH)₂D₃ protects against DKD by down-regulating the innate immune TLR-NF-κB pathway. NRK-52E cells were cultured under normal or high-glucose conditions. We then used siRNA to knock down TLR4 expression under high-glucose conditions. NRK-52E cells cultured under high-glucose conditions, and streptozotocin (STZ)-induced diabetic rats, were treated with different doses of 1,25(OH)₂D₃ and used as in vitro and in vivo models, respectively. Renal biochemical indicators were then measured to evaluate the influence of 1,25(OH)₂D₃ treatment on DKD in diabetic rats. Histological analysis was also performed to determine the extent of infiltration by inflammatory cells and tubulointerstitial fibrosis. Using RT-qPCR, western blotting, immunohistochemistry and immunofluorescence, we determined the expression levels of TLR4, MyD88, NF-κB p65, MCP-1 and α-SMA to investigate whether 1,25(OH)₂D₃ could reduce the development of tubulointerstitial fibrosis. Knocking down TLR4 abolished the tubulointerstitial fibrosis caused by high-glucose conditions. High doses of 1,25(OH)₂D₃ consistently reduced the expression of TLR4-MyD88-NF-κB in NRK-52E cells. Moreover, high doses of 1,25(OH)₂D₃ had an obvious protective effect on kidney injury and inhibited the infiltration of inflammatory cells and tubulointerstitial fibrosis in diabetic rats. In conclusion, high doses of 1,25(OH)₂D₃ protected against tubulointerstitial fibrosis both in vitro and in vivo by downregulating the expression of TLR4-MyD88-NF-κB.

Changes in the whole/intact parathyroid hormone ratio and their clinical implications in patients with chronic kidney disease

BACKGROUND

Although a previous study has reported the relationship between intact parathyroid hormone (iPTH) and whole parathyroid hormone (wPTH) levels in patients undergoing dialysis, the w/i PTH ratio (whole/intact PTH ratio) among predialysis chronic kidney disease (CKD) patients remains unclear. The present study therefore aimed to examine the relationship between w/i PTH ratio and kidney function and determine other factors affecting the w/i PTH ratio.

METHODS

An observational study including 773 predialysis CKD patients was conducted. The correlation between w/i PTH ratio and kidney function, as well as clinical factors at different CKD stages, were assessed using univariate and multivariate analyses. In addition, the relationship between w/i PTH ratio and composite renal outcome [kidney transplantation, dialysis, and 30% decline in estimated glomerular filtration rate (eGFR)] was examined.

RESULTS

The w/i PTH ratio decreased as the CKD stage progressed. Patients in each CKD stage (1/2, 3, 4, and 5) had a w/i PTH ratio of 0.85, 0.81, 0.78, and 0.59, respectively. The inflection point in the correlation lines between eGFR and w/i PTH ratio was 24.1 mL/min/1.73 m². In multivariate analysis, the w/i PTH ratio was significantly correlated with serum calcium levels only in the CKD5 group and with eGFR in the CKD3, CKD4 and CKD5 group. Furthermore, w/i PTH ratio, eGFR, serum phosphate levels, and urinary protein/creatinine ratio were determined to be significant independent predictors for composite renal outcome.

CONCLUSIONS

Our study demonstrated that changes in the w/i PTH ratio were associated with kidney function, abnormal mineral metabolism, and renal outcome.

Comparison of the effects of valsartan plus activated vitamin D versus valsartan alone in IgA nephropathy with moderate proteinuria

BACKGROUND/AIMS

To compare the effects of valsartan plus activated vitamin D with valsartan alone on urinary protein excretion and eGFR in IgA nephropathy with moderate proteinuria.

METHODS

A prospective, single-center, randomized, controlled study was performed between Jan, 2008 and Jan, 2018 on patients with IgA nephropathy who had moderate proteinuria with urinary protein excretion 1.0-3.0 g/24 h. These IgAN patients were randomly assigned to receive either valsartan 160 mg/day treatment or valsartan 160 mg/day plus activated vitamin D (calcitriol) 0.5 μg/day treatments. The changes of the clinical, biochemical data, and the adverse events during the observation period were all analyzed in the two groups. The primary endpoint was defined as changes in urinary protein excretion at week 24 compared with the baseline and the secondary endpoint was to observe the changes in estimated glomerular filtration rate (eGFR) between baseline and the end of the study.

RESULTS

Baseline characteristics between the two groups were comparable. At the end of the treatment period, urinary protein excretion in both two groups decreased significantly (P < 0.05). However, there was a more significant decrease in proteinuria in IgAN patients who received valsartan plus activated vitamin D treatment (from 2.39 ± 0.77 to 1.43 ± 0.57 g/24 h, P < 0.01) compared to valsartan treatment alone (from 2.46 ± 0.81 to 1.78 ± 0.60 g/24 h, P < 0.05). The percentage change in urine protein excretion at week 24 was  - 40.2% in valsartan plus activated vitamin D treatment group (P < 0.01) and - 27.6% in valsartan treatment group (P < 0.05). No significant change in blood pressure, estimated glomerular filtration rate, serum calcium, and serum potassium was observed. The incidence of adverse events was similar between the two groups, respectively (P > 0.05).

CONCLUSION

Combination therapy with valsartan plus activated vitamin D is more effective than valsartan alone in reduction of moderate proteinuria in IgA nephropathy and without more adverse events.

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.

LC3 promotes the nuclear translocation of the vitamin D receptor and decreases fibrogenic gene expression in proximal renal tubules

Diabetic nephropathy (DN) is a major cause of end-stage renal disease (ESRD). Vitamin D receptor (VDR) belongs to the nuclear receptor superfamily and exerts a renoprotective effect through inhibiting fibrosis. Microtubule-associated protein 1 light chain 3 (LC3), a key regulator of autophagy, is abundant in the nucleus, although its primary function is in the cytoplasm. The role of nuclear LC3 and the mechanism by which LC3 shuttles between the cytoplasm and nucleoplasm has not been fully elucidated. We found that LC3 binds to VDR in an LC3-interacting region (LIR)-independent manner and promotes the nuclear translocation of VDR. Further study indicated that LC3 promotes the formation of the VDR:retinoid X receptor (RXR) heterodimer and inhibits fibrogenic genes expression in HK-2 cells induced by high glucose. Our result demonstrates that LC3 is a negative regulator of high glucose-induced fibrogenic genes expression through its ability to promote VDR signaling.

Native Hypovitaminosis D in CKD Patients: From Experimental Evidence to Clinical Practice

Native hypovitaminosis D (n-hVITD) is frequently found from the early stages of chronic kidney disease (CKD) and its prevalence increases with CKD progression. Even if the implications of n-hVITD in chronic kidney disease-mineral bone disorder (CKD-MBD) have been extensively characterized in the literature, there is a lot of debate nowadays about the so called "unconventional effects" of native vitamin D (25(OH)VitD) supplementation in CKD patients. In this review, highlights of the dimension of the problem of n-hVITD in CKD stages 2-5 ND patients will be presented. In addition, it will focus on the "unconventional effects" of 25(OH)VitD supplementation, the clinical impact of n-hVITD and the most significant interventional studies regarding 25(OH)VitD supplementation in CKD stages 2-5 ND.

Activation of vitamin D receptor attenuates high glucose-induced cellular injury partially dependent on CYP2J5 in murine renal tubule epithelial cell

AIMS

Vitamin D and its receptor, vitamin D receptor (VDR), have renoprotection effect against diabetic nephropathy (DN). But the exact mechanism has not been fully elucidated. Epoxyeicosatrienoic acids (EETs) are cytochrome P450 (CYP) epoxygenase-derived metabolites of arachidonic acid, protecting against diabetes and DN. Herein, we hypothesized that activation of VDR attenuated high glucose-induced cellular injury in renal tubular epithelial cells partially through up-regulating CYP2J5 expression.

MAIN METHODS

Streptozotocin (STZ) was injected to induce diabetic in wild type and Vdr^-/- mice. The effects of VDR knockout and an activator of VDR, paricalcitol, on the renal injury were detected. In vitro, a murine kidney proximal tubule epithelial cell line BU.MPT induced by high glucose were treated with or without paricalcitol (30 mM) for 12 h or 24 h.

KEY FINDINGS

The expression of CYP2J5 was significantly decreased both in wild type and Vdr^-/- diabetic mice induced by STZ. The STZ-induced kidney architecture damage and apoptosis rate in Vdr^-/- mice were more severe. In vitro, high glucose treatment strongly reduced the CYP2J5 expression and the synthesis of 14,15-EET in BU.MPT cells. Supplement of 14,15-EET significantly reduced the lactate dehydrogenase (LDH) release induced by high glucose in BU.MPT cells. Furthermore, treatment with paricalcitol attenuated cellular injury and restored the expression of CYP2J5 reduced by high glucose in BU.MPT cells.

SIGNIFICANCE

We conclude that activation of VDR attenuates high glucose-induced cellular injury partially dependent on CYP2J5 in murine renal tubule epithelial cells and paricalcitol may represent a potential therapy for DN.