Paricalcitol aggravates perivascular fibrosis in rats with renal insufficiency and low calcitriol

Paricalcitol Attenuates Metabolic Syndrome-Associated Heart Failure through Enhanced Mitochondrial Fusion

Objectives

Transition from cardiac hypertrophy to failure involves adverse metabolic reprogramming involving mitochondrial dysfunction. We have earlier shown that vitamin D deficiency induces heart failure, at least in part, through insulin resistance. However, whether activation of vitamin D receptor (VDR) can attenuate heart failure and underlying metabolic phenotype requires investigation. Thus, we aimed to assess the cardioprotective potential of paricalcitol, a vitamin D receptor-activator, against cardiac hypertrophy and failure in high-fat high-fructose-fed rats.

Methods

Male Sprague Dawley rats were fed control (Con) or high-fat high-fructose (HFHFrD) diet for 20 weeks. After 12 weeks, rats from HFHFrD group were divided into the following: HFHFrD, HFHFrD+P (paricalcitol i.p. 0.08 μg/kg/day) and HFHFrD+E (enalapril maleate i.p. 10 mg/kg/day). Intraperitoneal glucose tolerance test, blood pressure measurement, and 2D echocardiography were performed. Cardiac fibrosis was assessed by Masson's trichrome staining of paraffin-embedded heart sections. Mitochondrial DNA and proteins, and citrate synthase activity were measured in rat hearts. VDR was silenced in H9c2 cardiomyoblasts, and immunoblotting was performed.

Results

Paricalcitol improved glucose tolerance, serum lipid profile, and blood pressure in high-fat high-fructose-fed rats. Paricalcitol reduced cardiac wall thickness and increased ejection fraction in high-fat high-fructose-fed rats but had no effect on perivascular fibrosis. PGC1-α was upregulated in the HFHFrD+P group compared to the HFHFrD group, but there was no significant difference in mitochondrial content. Citrate synthase activity was significantly higher in the HFHFrD+P group compared to the HFHFrD group. Rat hearts of the HFHFrD+P group had significantly higher expression of mitofusins. H9c2 cells with VDR knockdown showed significantly lower expression of Mfn2. Improvement in the HFHFrD+P group was comparable with that in the HFHFrD+E group.

Conclusions

Paricalcitol reverses cardiac dysfunction in rats with metabolic syndrome by enhancing mitochondrial fusion. We demonstrate repurposing potential of the drug currently used in end-stage kidney disease.

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.

Maxacalcitol (22-Oxacalcitriol (OCT)) Retards Progression of Left Ventricular Hypertrophy with Renal Dysfunction Through Inhibition of Calcineurin-NFAT Activity

PURPOSE

Left ventricular hypertrophy (LVH) is a cardiovascular complication highly prevalent in patients with chronic kidney disease (CKD). Previous studies analyzing 1α-hydroxylase or vitamin D receptor (Vdr) knockout mice revealed active vitamin D as a promising agent inhibiting LVH progression. Paricalcitol, an active vitamin D analog, failed to suppress the progression of LV mass index (LVMI) in pre-dialysis patients with CKD. As target genes of activated VDR differ depending on its agonists, we examined the effects of maxacalcitol (22-oxacalcitriol: OCT), a less calcemic active vitamin D analog, on LVH in hemodialysis patients and animal LVH models with renal insufficiency.

METHODS

In retrospective cohort study, patients treated with OCT who underwent hemodialysis were enrolled. Using cardiac echocardiography, LV mass was evaluated by the area-length method. In animal study, angiotensin II (Ang II)-infused Wister rats with heminephrectomy or Ang II-stimulated neonatal rat ventricular myocytes (NRVM) were treated with OCT.

RESULTS

OCT significantly inhibited the progression of LVMI in hemodialysis patients. In Ang II-infused heminephrectomized rats, OCT suppressed the progression of LVH in a blood pressure-independent manner. OCT also suppressed the activity of calcineurin in the left ventricle of model rats. Specifically, OCT reduced the protein levels of calcineurin A, but not the mRNA levels of Ppp3ca (calcineurin Aα). Luciferase assays showed that OCT increased the promoter activity of Fbxo32 (atrogin1), an E3 ubiquitin ligase targeting calcineurin A. Finally, OCT promoted ubiquitination and degradation of calcineurin A.

CONCLUSION

Our works indicated that OCT retards progression of LVH through calcineurin-NFAT pathway, which reveal a novel aspect of OCT in attenuating pathological LVH.

Vitamin D Attenuates Loss of Endothelial Biomarker Expression in Cardio-Endothelial Cells

Vitamin D is associated with cardiovascular health through activating the vitamin D receptor that targets genes related to cardiovascular disease (CVD). The human cardiac microvascular endothelial cells (HCMECs) were used to develop mechanically and TGF-β1-induced fibrosis models, and the rat was used as the isoproterenol (ISO)-induced fibrosis model. The rats were injected with ISO for the first five days, followed by vitamin D injection for the consecutive three weeks before being sacrificed on the fourth week. Results showed that mechanical stretching reduced endothelial cell marker CD31 and VE-cadherin protein expressions, as well as increased α-smooth muscle actin (α-SMA) and fibronectin (FN). The transforming growth factor-β1 (TGF-β1) reduced CD31, and increased α-SMA and FN protein expression levels. Vitamin D presence led to higher protein expression of CD31, and lower protein expressions of α-SMA and FN compared to the control in the TGF-β1-induced fibrosis model. Additionally, protein expression of VE-cadherin was increased and fibroblast-specific protein-1 (FSP1) was decreased after vitamin D treatment in the ISO-induced fibrosis rat. In conclusion, vitamin D slightly inhibited fibrosis development in cell and animal models. Based on this study, the beneficial effect of vitamin D may be insignificant; however, further investigation of vitamin D’s effect in the long-term is required in the future.

Arrhythmia and Sudden Death in Hemodialysis Patients: Protocol and Baseline Characteristics of the Monitoring in Dialysis Study

BACKGROUND

Dialysis patients have high rates of cardiovascular morbidity and mortality, but data on arrhythmia burden, arrhythmia type, arrhythmia triggers, and the identity of terminal arrhythmias have historically been limited by an inability to monitor heart rhythm for prolonged periods.

OBJECTIVES

To investigate arrhythmia and its association with sudden death in dialysis-dependent ESRD, describe the potential for implantable devices to advance study of dialysis physiology, review the ethical implications of using implantable devices in clinical studies, and report on the protocol and baseline results of the Monitoring in Dialysis Study (MiD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this multicenter, interventional-observational, prospective cohort study, we placed implantable loop recorders in patients undergoing long-term hemodialysis. The proportion of patients experiencing clinically significant arrhythmias was the primary endpoint. For 6 months, we captured detailed data on the primary endpoint, symptomatic arrhythmias, other electrocardiographic variables, dialysis prescription, electrolytes, dialysis-related variables, and vital signs. We collected additional electrocardiographic data for up to 1 year.

RESULTS

Overall, 66 patients underwent implantation in sites in the United States and India. Diabetes was present in 63.6% of patients, 12.1% were age ≥70 years, 69.7% were men, and 53.0% were black. Primary and secondary endpoint data are expected in 2016.

CONCLUSIONS

Cardiac arrhythmia is an important contributor to cardiovascular morbidity and mortality in dialysis patients, but available technology has previously limited the ability to estimate its true burden and triggers and to define terminal rhythms in sudden death. Use of implantable technology in observational studies raises complex issues but may greatly expand understanding of dialysis physiology. The use of implantable loop recorders in MiD is among the first examples of such a trial, and the results are expected to provide novel insights into the nature of arrhythmia in hemodialysis patients.

Preventive effects of vitamin D treatment on bleomycin-induced pulmonary fibrosis

Patients with pulmonary fibrosis often have low vitamin D levels, the effects of which are largely unknown. We here report that early vitamin D supplementation significantly reduced the severity of pulmonary fibrosis and inflammatory cell accumulationin in the bleomycin-induced pulmonary fibrosis mouse model on supplementary days 14, 21 and 28 (P < 0.001). Vitamin D supplementation also prevented some ultrastructural changes in response to bleomycin administration, including basement membrane thickening, interstitial fibrin deposition and microvilli flattening or disappearance on days 14, 21 and 28, and lamellar body swelling or vacuolation on days 21 and 28. The bleomycin group had rising hydroxyproline level on days 14, 21 and 28, whereas the vitamin D treatment group showed consistently lower hydroxyproline level but still higher than that of the control group (P < 0.001). Our immunohistochemistry and densitometry analyses showed less staining for α-smooth muscle actin, a myofibroblast marker, in the vitamin D group compared to the bleomycin group (P < 0.001). Thus, vitamin D treatment could prevent bleomycin-induced pulmonary fibrosis by delaying or suppressing ultrastructural changes, as well as attenuating hydroxyproline accumulation and inhibiting myofibroblastic proliferation. These data further our understanding of the roles of vitamin D in pulmonary fibrogenesis and in the treatment of pulmonary fibrosis.

Effect of paricalcitol and enalapril on renal inflammation/oxidative stress in atherosclerosis

AIM: To investigate the protective effect of paricalcitol and enalapril on renal inflammation and oxidative stress in ApoE-knock out mice.

METHODS: Animals treated for 4 mo as group (1) ApoE-knock out plus vehicle, group (2) ApoE-knock out plus paricalcitol (200 ng thrice a week), (3) ApoE-knock out plus enalapril (30 mg/L), (4) ApoE-knock out plus paricalcitol plus enalapril and (5) normal. Blood pressure (BP) was recorded using tail cuff method. The kidneys were isolated for biochemical assays using spectrophotometer and Western blot analyses.

RESULTS: ApoE-deficient mice developed high BP (127 ± 3 mmHg) and it was ameliorated by enalapril and enalapril plus paricalcitol treatments but not with paricalcitol alone. Renal malondialdehyde concentrations, p22^phox, manganese-superoxide dismutase, inducible nitric oxide synthase (NOS), monocyte chemoattractant protein-1, tumor necrosis factor-alpha and transforming growth factor-β1 levels significantly elevated but reduced glutathione, CuZn-SOD and eNOS levels significantly depleted in ApoE-knock out animals compared to normal. Administration of paricalcitol, enalapril and combined together ameliorated the renal inflammation and oxidative stress in ApoE-knock out animals.

CONCLUSION: Paricalcitol and enalapril combo treatment ameliorates renal inflammation as well as oxidative stress in atherosclerotic animals.

Vitamin D and the heart

Vitamin D receptors (VDR) are found in cells throughout the cardiovascular system. A variety of experimental studies indicate that the liganded VDR may play an important role in controlling cardiac hypertrophy and fibrosis, regulating blood pressure, and suppressing the development of atherosclerosis. Some, but not all, observational studies in humans provide support for these experimental findings, raising the possibility that vitamin D or its analogs might prove useful therapeutically in the prevention or treatment of cardiovascular disease.

Submaximal suppression of parathyroid hormone ameliorates calcitriol-induced aortic calcification and remodeling and myocardial fibrosis in uremic rats

BACKGROUND AND OBJECTIVE

In subtotally nephrectomized rats, we studied to what extent high-dose calcitriol-induced cardiovascular disease can be modulated by almost complete suppression of parathyroid hormone (PTH), mediated by either cinacalcet (CINA) or parathyroidectomy (PTX).

METHODS

Five groups were studied: sham-operated controls, uremic (U), uremic with calcitriol (U+1,25D), uremic and calcitriol with CINA (U+1,25D+CINA) and uremic and calcitriol with PTX (U+1,25D+PTX). Treatments lasted 14 weeks.

RESULTS

Compared with U group animals, PTH was significantly lower with calcitriol treatment and almost completely suppressed in animals treated with either PTX or CINA. Serum calcium and phosphorus levels were similarly elevated in all groups receiving calcitriol. Renal function in uremic animals was significantly more impaired in the U+1,25D group. Aortic calcifications were pronounced in U+1,25D animals and reduced by more than 50% by concomittant treatment with CINA or PTX. Chondrocytes were observed near areas of calcification (>90%) and endochondral bone formation was confirmed by positive immunofluorescence for chondrocytic transcription factor sox9 and matrix protein collagen X. Altered arterial (aneurysmatic) geometry with a significant increase in wall/lumen and lumen/body weight ratio was found only in the U+1,25D group. Myocardial fibrosis was present in all uremic groups with a significant increase in the U+1,25D group. Connective tissue growth factor messenger RNA was significantly upregulated only in the U+1,25D group.

CONCLUSION

Submaximal suppression of PTH by either CINA or PTX reduced vascular calcifications, arterial remodeling and myocardial fibrosis to a similar degree and independent of the serum calcium and phosphorus levels. These data do not indicate vasculotropic effects of calcimimetics independent of PTH suppression.

The vitamin D receptor activator paricalcitol prevents fibrosis and diastolic dysfunction in a murine model of pressure overload

BACKGROUND

Activation of the vitamin D-vitamin D receptor (VDR) axis has been shown to reduce blood pressure and left ventricular (LV) hypertrophy. Besides cardiac hypertrophy, cardiac fibrosis is a key element of adverse cardiac remodeling. We hypothesized that activation of the VDR by paricalcitol would prevent fibrosis and LV diastolic dysfunction in an established murine model of cardiac remodeling.

METHODS

Mice were subjected to transverse aortic constriction (TAC) to induce cardiac hypertrophy. Mice were treated with paricalcitol, losartan, or a combination of both for a period of four consecutive weeks.

RESULTS

The fixed aortic constriction caused similar increase in blood pressure, both in untreated and paricalcitol- or losartan-treated mice. TAC significantly increased LV weight compared to sham operated animals (10.2±0.7 vs. 6.9±0.3 mg/mm, p<0.05). Administration of either paricalcitol (10.5±0.7), losartan (10.8±0.4), or a combination of both (9.2±0.6) did not reduce LV weight. Fibrosis was significantly increased in mice undergoing TAC (5.9±1.0 vs. sham 2.4±0.8%, p<0.05). Treatment with losartan and paricalcitol reduced fibrosis (paricalcitol 1.6±0.3% and losartan 2.9±0.6%, both p<0.05 vs. TAC). This reduction in fibrosis in paricalcitol treated mice was associated with improved indices of LV contraction and relaxation, e.g. dPdtmax and dPdtmin and lower LV end diastolic pressure, and relaxation constant Tau. Also, treatment with paricalcitol and losartan reduced mRNA expression of ANP, fibronectin, collagen III and TIMP-1.

DISCUSSION

Treatment with the selective VDR activator paricalcitol reduces myocardial fibrosis and preserves diastolic LV function due to pressure overload in a mouse model. This is associated with a reduced percentage of fibrosis and a decreased expression of ANP and several other tissue markers.

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

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

Mineral and bone disorders in children with chronic kidney disease

As children with chronic kidney disease (CKD) have a long lifespan, optimal control of bone and mineral homeostasis is essential not only for the prevention of debilitating skeletal complications and for achieving adequate growth but also for preserving long-term cardiovascular health. As the growing skeleton is highly dynamic and at particular risk of deterioration, close control of bone and mineral homeostasis is required in children with CKD. However, assessment of bone disease is hampered by the limited validity of biochemical parameters-major controversy exists on key issues such as parathyroid hormone target ranges and the lack of useful imaging techniques. The role of newly discovered factors in bone and mineral homeostasis, such as fibroblast growth factor 23, is not yet established. Even though scientific evidence is limited in children with CKD, ergocalciferol or cholecalciferol supplementation and the use of calcium-free phosphate binders is recommended. The new drug cinacalcet is highly promising; however, pediatric experience is still limited to observational data and the effect of cinacalcet on longitudinal growth and pubertal development is unknown. Randomized, controlled trials are underway, including studies of cinacalcet pharmacokinetics and pharmacodynamics in infants.

Defective renal maintenance of the vitamin D endocrine system impairs vitamin D renoprotection: a downward spiral in kidney disease

In kidney disease, the progressive loss of renal capacity to produce calcitriol, the vitamin D hormone, is a key contributor to elevations in parathyroid hormone (PTH) and mineral and skeletal disorders predisposing to renal and cardiovascular damage, ectopic calcifications, and high mortality rates. Thus, the safe correction of calcitriol deficiency to suppress PTH has been the treatment of choice for decades. However, recent epidemiological and experimental data suggest that calcitriol replacement may improve outcomes through renal and cardioprotective actions unrelated to PTH suppression. Furthermore, a striking incidence of vitamin D deficiency occurs in kidney disease and associates more strongly than calcitriol deficiency with a higher risk for kidney disease progression and death. Despite the translational relevance of these findings, no prospective trials are currently available in support of the efficacy of vitamin D supplementation and/or calcitriol replacement to safely halt/moderate renal disease progression. This review updates the pathophysiology behind the vicious cycle by which kidney injury impairs the maintenance of normal vitamin D and calcitriol levels, which in turn impedes vitamin D/calcitriol renoprotective actions, a requirement for the design of prospective trials to improve current recommendations for vitamin D interventions at all stages of kidney disease.

Vitamin D, chronic kidney disease and survival: a pluripotent hormone or just another bone drug?

It is now about 40 years ago that the mechanism of renal 1-α-hydroxylation of vitamin D was discovered and characterized. After this seminal observation, the key role of the active vitamin D derivative 1, 25-(OH)2-vitamin D (calcitriol) in calcium homeostasis and bone mineralization, and its specific role in the course of chronic kidney disease (CKD) and renal osteopathy, was unraveled step by step, while the precursor 25-OH-vitamin D (calcidiol) was gradually ignored. Calcitriol and its synthetic analogue alfa-calcidol became the first-line standard drug to tackle secondary hyperparathyroidism (sHPT) in CKD. Potential side-effects, including hypercalcemia, hyperphosphatemia, and vascular calcification, were partly abrogated by developing less calcemic substances such as paricalcitol or maxacalcitol. Thus, TIME Magazine surprised when nominating vitamin D, with regard to its newly discovered pleiotropic actions, as one of the "top medical breakthroughs" in the December issue of 2007. This vote was driven by novel and spectacular insights into the pivotal regulatory role of vitamin D with regard to autoimmune diseases, immune defense, cancer development and progression, and cardiovascular function and disease. More than 30 cell types express the vitamin D receptor (VDR), and more than ten organs in addition to the kidney are capable of paracrine 1-α-hydroxylation. More than 200 genes are under the control of calcitriol. A MEDLINE search performed in December 2009 focusing on the keywords "vitamin D-and-kidney-and-2009" yielded 523 hits. This review intends to give a subjective and CKD-related update on novel biological and clinical insights with relevance to the steroid hormone vitamin D.

Kidney bone disease and mortality in CKD: revisiting the role of vitamin D, calcimimetics, alkaline phosphatase, and minerals

Recent evidence suggests that the traditional syndromes known as renal osteodystrophy, secondary hyperparathyroidism, and vitamin D deficiency are related to mortality in persons with moderate to advanced chronic kidney disease (CKD). The so-called 'kidney bone disease', also known as 'mineral and bone disorders', is defined to include bone disorders, mineral disarrays, and vascular calcification. We have identified 14 common and clinically relevant conditions of contemporary nature that are related to the kidney bone disease, including calcitriol (active vitamin D) deficiency, 25(OH)-vitamin D deficiency, biochemical hyperparathyroidism, relatively low parathyroid hormone (PTH) level, increased serum alkaline phosphatase (hyperphosphatasemia), elevated fibroblast growth factor (FGF)-23, high turnover bone disease, adynamic bone disease, uremic osteoporosis, vascular calcification, hyper- and hypophosphatemia, and hyper- and hypocalcemia. We present a critical review of these 14 conditions with emphasis on patient survival and other pertinent clinical outcomes. We also review unresolved controversies surrounding the management of these conditions by administration of nutritional vitamin D (ergocalciferol and cholecalciferol), vitamin D receptor activators (calcitriol, alphacalcidiol, doxercalciferol), D-mimetics (paricalcitol, maxacalcitol), calcimimetics (cinacalcet), recombinant PTH (teriparatide), and receptor activator of nuclear factor-kappaB ligand modulators (denosumab); compare mortality predictability of PTH and alkaline phosphatase; and examine potential risks of bone disorders and mineral disarrays in CKD patients.

Combination therapy with paricalcitol and trandolapril reduces renal fibrosis in obstructive nephropathy

Growing evidence suggests that active vitamin D slows the progression of chronic kidney diseases. Here we compared the individual renal protective efficacy of paricalcitol and trandolapril (an angiotensin-converting enzyme inhibitor) in obstructive nephropathy, and examined any potential additive effects of their combination on attenuating renal fibrosis and inflammation. Mice underwent unilateral ureteral obstruction and were treated individually with paricalcitol or trandolapril or their combination. Compared to vehicle-treated controls, monotherapy with paricalcitol or trandolapril inhibited the expression and accumulation of fibronectin and type I and type III collagen, suppressed alpha-smooth muscle actin, vimentin, and Snail1 expression, and reduced total collagen content in the obstructed kidney. Combination therapy led to a more profound inhibition of all parameters. Monotherapy also suppressed renal RANTES (regulated on activation, normal T cell expressed and secreted) and tumor necrosis factor (TNF)-alpha expression and inhibited renal infiltration of T cells and macrophages, whereas the combination had additive effects. Renin expression was induced in the fibrotic kidney and was augmented by trandolapril. Paricalcitol blocked renin induction in the absence or presence of trandolapril. Our study indicates that paricalcitol has renal protective effects, comparable to that of trandolapril, in reducing interstitial fibrosis and inflammation. Combination therapy had additive efficacy in retarding renal scar formation during obstructive nephropathy.

A new role for vitamin D receptor activation in chronic kidney disease

Vitamin D has proven to be much more than a simple "calcium hormone." The fact that the vitamin D receptor has been found in cells not related to mineral metabolism supports that statement. The interest of nephrologists in vitamin D and its effects beyond mineral metabolism has increased over the last few years, evidencing the importance of this so-called "sunshine hormone." In the present review, we highlight the most recent developments in the traditional use of vitamin D in chronic kidney disease (CKD) patients, namely, the control of secondary hyperparathyroidism (sHPT). Furthermore, we also explore the data available regarding the new possible therapeutic uses of vitamin D for the treatment of other complications present in CKD patients, such as vascular calcification, left ventricular hypertrophy, or proteinuria. Finally, some still scarce but very promising data regarding a possible role of vitamin D in kidney transplant patients also are reviewed. The available data point to a potential beneficial effect of vitamin D in CKD patients beyond the control of mineral metabolism.

Vitamin D reduces the expression of collagen and key profibrotic factors by inducing an antifibrotic phenotype in mesenchymal multipotent cells

Hypovitaminosis D is an important public health problem. Serum 25-hydroxyvitamin D (25-OHD) is now recognized as an independent predictor for cardiovascular and related diseases (CVD) as well as other chronic medical conditions. However, the biologic pathways through which these effects are mediated remain poorly understood. We hypothesized that exposing mesenchymal multipotent cells (MMCs) to the active form of vitamin D would increase the expression of selected antifibrotic factors that in turn would ameliorate the progression of chronic diseases. MMCs were primed with 5'-azacytidine to induce a fibrotic phenotype and then treated with active vitamin D (1,25D) or ethanol <0.1% as vehicle in a time course manner (30 min, 1, 5, and 24 h, and for 4 and 7 days). The addition of 1,25D to MMCs promotes: a) increased expression and nuclear translocation of the vitamin D receptor; b) decreased expression of TGFB1 and plasminogen activator inhibitor (SERPINE1), two well-known profibrotic factors; c) decreased expression of collagen I, III and other collagens isoforms; and d) increased expression of several antifibrotic factors such as BMP7 a TGFB1 antagonist, MMP8 a collagen breakdown inducer and follistatin, an inhibitor of the profibrotic factor myostatin. In conclusion, the addition of 1,25D to differentiated MMCs displays a decreased profibrotic signaling pathway and gene expression, leading to decrease in collagen deposition. This study highlights key mechanistic pathways through which vitamin D decreases fibrosis, and provides a rationale for studies to test vitamin D supplementation as a preventive and/or early treatment strategy for CVD and related fibrotic disorders.

Calcitriol ameliorates capillary deficit and fibrosis of the heart in subtotally nephrectomized rats

BACKGROUND

Remodelling of the heart, characterized by hypertrophy, fibrosis and capillary/myocyte mismatch, is observed in patients with chronic renal failure. Low vitamin D levels have been associated with increased cardiovascular risk. In the present experimental study, we studied the effects of non-hypercalcaemic doses of calcitriol on microvascular disease and interstitial fibrosis of the heart.

METHODS

Three-month-old male Sprague-Dawley rats were randomized to subtotal nephrectomy (SNX) or sham operation and received calcitriol (6 ng/kg) or vehicle starting immediately thereafter. Blood pressure was measured by tail pletysmography. Albuminuria was measured by rat-specific ELISA. Capillary length density, volume density of interstitial tissue, immunohistochemistry and western blots (vitamin D receptor, collagen I, III, TGF-beta(1), MAP kinases and nitrotyrosine) were assessed after 12 weeks of treatment.

RESULTS

After SNX blood pressure, albuminuria and heart weight were elevated, capillary length density reduced and interstitial fibrosis increased. Treatment with calcitriol reduced albuminuria and prevented reduction of capillary density and expansion of interstitium without affecting significant blood pressure and heart weight after perfusion fixation. Calcitriol left high VEGF unchanged, but upregulated VEGF receptor 2 (presumably reversing VEGF resistance). Calcitriol reduced expression of profibrotic TGF-beta(1) and the accumulation of collagens I and III.

CONCLUSIONS

Non-hypercalcaemic doses of calcitriol ameliorated, directly or indirectly, cardiac remodelling in sub- totally nephrectomized rats.

Current Approaches in the Treatment of Chronic Kidney Disease Mineral and Bone Disorder

Patients with chronic kidney disease (CKD) develop mineral and bone disorder (MBD), a common and important complication, as a result of impaired phosphorus excretion and reduced vitamin D activation. Altered mineral metabolism is now recognized as an independent cardiovascular risk factor in end-stage renal disease patients and contributes to the risk for accelerating vascular calcification. CKD patients are at high risk for cardiovascular disease and vascular calcification which account for the high morbidity and mortality in this patient population. Pharmacotherapeutic interventions are necessary to manage and treat the condition. Multiple classes of agents including phosphorus binders, vitamin D analogs, and calcimimetics are now available to treat CKD-MBD. Recent data have shown that treatment with sevelamer and vitamin D analogs are associated with a reduction in calcification and cardiovascular mortality and improved survival. This article provides an overview of the strategies and considerations for the management of CKD-MBD, as well as their implications on clinical outcomes.

Vitamin D receptor activation and survival in chronic kidney disease

Replacement of activated vitamin D has been the cornerstone of therapy for secondary hyperparathyroidism (SHPT). Recent findings from several large observational studies have suggested that the benefits of vitamin D receptor activators (VDRA) may extend beyond the traditional parathyroid hormone (PTH)-lowering effect, and could result in direct cardiovascular and metabolic benefits. The advent of several new analogs of the activated vitamin D molecule has widened our therapeutic armamentarium, but has also made therapeutic decisions more complicated. Treatment of SHPT has become even more complex with the arrival of the first calcium-sensing receptor (CSR) agonist (cinacalcet hydrochloride) and with the uncovering of novel mechanisms responsible for SHPT. We provide a brief overview of the physiology and pathophysiology of SHPT, with a focus on vitamin D metabolism, and discuss various practical aspects of VDRA therapy and its reported association with survival in recent observational studies. A detailed discussion of the available agents is aimed at providing the practicing physician with a clear understanding of the advantages or disadvantages of the individual medications. A number of open questions are also analyzed, including the present and future roles of CSR agonists and 25(OH) vitamin D replacement.