Embryonic vitamin D deficiency programs hematopoietic stem cells to induce type 2 diabetes.

Environmental factors may alter the fetal genome to cause metabolic diseases. It is unknown whether embryonic immune cell programming impacts the risk of type 2 diabetes in later life. We demonstrate that transplantation of fetal hematopoietic stem cells (HSCs) made vitamin D deficient in utero induce diabetes in vitamin D-sufficient mice. Vitamin D deficiency epigenetically suppresses Jarid2 expression and activates the Mef2/PGC1a pathway in HSCs, which persists in recipient bone marrow, resulting in adipose macrophage infiltration. These macrophages secrete miR106-5p, which promotes adipose insulin resistance by repressing PIK3 catalytic and regulatory subunits and down-regulating AKT signaling. Vitamin D-deficient monocytes from human cord blood have comparable Jarid2/Mef2/PGC1a expression changes and secrete miR-106b-5p, causing adipocyte insulin resistance. These findings suggest that vitamin D deficiency during development has epigenetic consequences impacting the systemic metabolic milieu.

Serum and Urinary Soluble α-Klotho as Markers of Kidney and Vascular Impairment.

This study was designed to investigate the controversy on the potential role of sKlotho as an early biomarker in Chronic Kidney Disease-Mineral Bone Disorder (CKD-MBD), to assess whether sKlotho is a reliable marker of kidney α-Klotho, to deepen the effects of sKlotho on vascular smooth muscle cells (VSMCs) osteogenic differentiation and to evaluate the role of autophagy in this process. Experimental studies were conducted in CKD mice fed a normal phosphorus (CKD+NP) or high phosphorus (CKD+HP) diet for 14 weeks. The patients' study was performed in CKD stages 2-5 and in vitro studies which used VSMCs exposed to non-calcifying medium or calcifying medium with or without sKlotho. The CKD experimental model showed that the CKD+HP group reached the highest serum PTH, P and FGF23 levels, but the lowest serum and urinary sKlotho levels. In addition, a positive correlation between serum sKlotho and kidney α-Klotho was found. CKD mice showed aortic osteogenic differentiation, together with increased autophagy. The human CKD study showed that the decline in serum sKlotho is previous to the rise in FGF23. In addition, both serum sKlotho and FGF23 levels correlated with kidney function. Finally, in VSMCs, the addition of sKlotho prevented osteogenic differentiation and induced autophagy. It can be concluded that serum sKlotho was the earliest CKD-MBD biomarker, a reliable indicator of kidney α-Klotho and that might protect against osteogenic differentiation by increasing autophagy. Nevertheless, further studies are needed to investigate the mechanisms of this possible protective effect.

Role of Klotho and AGE/RAGE-Wnt/ß-Catenin Signalling Pathway on the Development of Cardiac and Renal Fibrosis in Diabetes.

Fibrosis plays an important role in the pathogenesis of long-term diabetic complications and contributes to the development of cardiac and renal dysfunction. The aim of this experimental study, performed in a long-term rat model, which resembles type 1 diabetes mellitus, was to investigate the role of soluble Klotho (sKlotho), advanced glycation end products (AGEs)/receptor for AGEs (RAGE), fibrotic Wnt/ß-catenin pathway, and pro-fibrotic pathways in kidney and heart. Diabetes was induced by streptozotocin. Glycaemia was maintained by insulin administration for 24 weeks. Serum and urine sKlotho, AGEs, soluble RAGE (sRAGE) and biochemical markers were studied. The levels of Klotho, RAGEs, ADAM10, markers of fibrosis (collagen deposition, fibronectin, TGF-ß1, and Wnt/ß-catenin pathway), hypertrophy of the kidney and/or heart were analysed. At the end of study, diabetic rats showed higher levels of urinary sKlotho, AGEs and sRAGE and lower serum sKlotho compared with controls without differences in the renal Klotho expression. A significant positive correlation was found between urinary sKlotho and AGEs and urinary albumin/creatinine ratio (uACR). Fibrosis and RAGE levels were significantly higher in the heart without differences in the kidney of diabetic rats compared to controls. The results also suggest the increase in sKlotho and sRAGE excretion may be due to polyuria in the diabetic rats.

MicroRNA-145 and microRNA-486 are potential serum biomarkers for vascular calcification.

INTRODUCTION: MicroRNAs (miRs) regulate vascular calcification (VC), and their quantification may contribute to suspicion of the presence of VC. METHODS: The study was performed in four phases. Phase 1: miRs sequencing of rat calcified and non-calcified aortas. Phase 2: miRs with the highest rate of change, plus miR-145 [the most abundant miR in vascular smooth muscle cells (VSMCs)], were validated in aortas and serum from rats with and without VC. Phase 3: the selected miRs were analyzed in epigastric arteries from kidney donors and recipients, and serum samples from general population. Phase 4: VSMCs were exposed to different phosphorus concentrations, and miR-145 and miR-486 were overexpressed to investigate their role in VC. RESULTS: miR-145, miR-122-5p, miR-486 and miR-598-3p decreased in the rat calcified aortas, but only miR-145 and miR-486 were detected in serum. In human epigastric arteries, miR-145 and miR-486 were lower in kidney transplant recipients compared with donors. Both miRs inversely correlated with arterial calcium content and with VC (Kauppila index). In the general population, the severe VC was associated with the lowest serum levels of both miRs. The receiver operating characteristic curve showed that serum miR-145 was a good biomarker of VC. In VSMCs exposed to high phosphorus, calcium content, osteogenic markers (Runx2 and Osterix) increased, and the contractile marker (α-actin), miR-145 and miR-486 decreased. Overexpression of miR-145, and to a lesser extent miR-486, prevented the increase in calcium content induced by high phosphorus, the osteogenic differentiation and the loss of the contractile phenotype. CONCLUSION: miR-145 and miR-486 regulate the osteogenic differentiation of VSMCs, and their quantification in serum could serve as a marker of VC.

Bodas de plata: 25 años de la primera demostración del efecto directo del fósforo en la célula paratiroidea / Silver jubilee: 25 years of the first demonstration of the direct effect of phosphate on the parathyroid cell

Aunque el fósforo es un elemento indispensable para la vida, en la naturaleza no se encuentra en estado nativo sino combinado en forma de fosfatos inorgánicos (PO43−), con niveles plasmáticos estrechamente regulados que se asocian a efectos deletéreos y mortalidad cuando estos se encuentran fuera de la normalidad. El interés creciente sobre el acúmulo de PO43− en la fisiopatología humana se originó en el papel que se le atribuyó en la patogenia del hiperparatiroidismo secundario a la enfermedad renal crónica. En este artículo revisamos los mecanismos por los cuales se justificaba dicho efecto y conmemoramos la importante contribución de un grupo español liderado por el Dr. M. Rodríguez, ahora hace justo 25 años, cuando demostraron por primera vez el efecto directo del PO43− sobre la regulación de la síntesis y secreción de hormona paratiroidea (manteniendo la integridad estructural de las glándulas paratiroides en su nuevo modelo experimental. Además de demostrar la importancia del ácido araquidónico (AA) y la vía de la fosfolipasa A2-AA como mediadora de respuestas en la glándula paratiroidea, estos hallazgos fueron predecesores de la reciente descripción del importante papel del PO43− sobre la actividad del receptor-sensor de calcio y alimentaron asimismo diversas líneas de investigación sobre la importancia de la sobrecarga de PO43−, no solo en la fisiopatología del hiperparatiroidismo secundario sino también en su papel patogénico sistémico. (AU)

Although phosphorus is an essential element for life, it is not found in nature in its native state but rather combined in the form of inorganic phosphates (PO43−), with tightly regulated plasma levels that are associated with deleterious effects and mortality when these are out of bounds. The growing interest in the accumulation of PO43− in human pathophysiology originated in its attributed role in the pathogenesis of secondary hyperparathyroidism in chronic kidney disease. In this article, we review the mechanisms by which this effect was justified and we commemorate the important contribution of a Spanish group led by Dr. M. Rodríguez, just 25 years ago, when they first demonstrated the direct effect of PO43− on the regulation of the synthesis and secretion of parathyroid hormone by maintaining the structural integrity of the parathyroid glands in their original experimental model. In addition to demonstrating the importance of arachidonic acid (AA) and the phospholipase A2-AA pathway as a mediator of parathyroid gland response, these findings were predecessors of the recent description of the important role of PO43− on the activity of the calcium sensor-receptor, and also fueled various lines of research on the importance of PO43− overload not only for the pathophysiology of secondary hyperparathyroidism but also of its systemic pathogenic role. (AU)

Association of α-klotho with subclinical carotid atherosclerosis in subjects with type 1 diabetes mellitus.

BACKGROUND: Compelling evidence suggests that the fibroblast growth factor 23 (FGF23) / α-klotho axis is impaired in subjects with diabetes mellitus. We examined the relationship between parameters related to calcium/phosphate homeostasis, including FGF23 and α-klotho, and subclinical carotid atherosclerosis burden in type 1 diabetes mellitus (T1D) subjects. METHODS: This cross-sectional study involved 226 subjects with T1D and 147 age-, sex- and plaque-matched, non-diabetic (non-T1D) subjects, both with normal renal function. Carotid ultrasound was performed to determine the presence and burden of atheromatous plaques. Concentrations of the intact form of FGF23 and α-klotho were assessed by ELISA. Calcium, phosphate, parathyroid hormone, and vitamin D levels were also determined. Negative binomial regression models were used to examine relationship between parameters studied and subclinical carotid atherosclerosis. RESULTS: Only FGF23 was increased in T1D compared with non-diabetic subjects (> 2-fold; p < 0.05). α-klotho was higher in subjects with subclinical carotid atherosclerosis (1.4-fold, p < 0.05). Regression analysis revealed that the log α-klotho concentration was positively associated with the presence of subclinical carotid atherosclerosis both in T1D subjects (incidence rate ratio [IRR]: 1.41; 95% confidence interval [CI], 1.06-1.89; p < 0.05) and in non-T1D subjects (IRR: 1.65; 95% CI, 1.02-2.75; p < 0.05). The models also showed that age, smoking and albuminuria-to-creatinine ratio were positively associated with subclinical carotid atherosclerosis in T1D subjects. Interestingly, sex-related protection against plaque was also revealed in T1D women. CONCLUSION: Higher α-klotho was associated with subclinical carotid atherosclerotic in the absence of kidney dysfunction. This finding also points to a new pathophysiological pathway involved in the development and progression of this complication.

Vitamin D Treatment Prevents Uremia-Induced Reductions in Aortic microRNA-145 Attenuating Osteogenic Differentiation despite Hyperphosphatemia.

In chronic kidney disease, systemic inflammation and high serum phosphate (P) promote the de-differentiation of vascular smooth muscle cells (VSMC) to osteoblast-like cells, increasing the propensity for medial calcification and cardiovascular mortality. Vascular microRNA-145 (miR-145) content is essential to maintain VSMC contractile phenotype. Because vitamin D induces aortic miR-145, uremia and high serum P reduce it and miR-145 directly targets osteogenic osterix in osteoblasts, this study evaluated a potential causal link between vascular miR-145 reductions and osterix-driven osteogenic differentiation and its counter-regulation by vitamin D. Studies in aortic rings from normal rats and in the rat aortic VSMC line A7r5 exposed to calcifying conditions corroborated that miR-145 reductions were associated with decreases in contractile markers and increases in osteogenic differentiation and calcium (Ca) deposition. Furthermore, miR-145 silencing enhanced Ca deposition in A7r5 cells exposed to calcifying conditions, while miR-145 overexpression attenuated it, partly through increasing α-actin levels and reducing osterix-driven osteogenic differentiation. In mice, 14 weeks after the induction of renal mass reduction, both aortic miR-145 and α-actin mRNA decreased by 80% without significant elevations in osterix or Ca deposition. Vitamin D treatment from week 8 to 14 fully prevented the reductions in aortic miR-145 and attenuated by 50% the decreases in α-actin, despite uremia-induced hyperphosphatemia. In conclusion, vitamin D was able to prevent the reductions in aortic miR-145 and α-actin content induced by uremia, reducing the alterations in vascular contractility and osteogenic differentiation despite hyperphosphatemia.

Silver jubilee: 25 years of the first demonstration of the direct effect of phosphate on the parathyroid cell.

Although phosphorus is an essential element for life, it is not found in nature in its native state but rather combined in the form of inorganic phosphates (PO43-), with tightly regulated plasma levels that are associated with deleterious effects and mortality when these are out of bounds. The growing interest in the accumulation of PO43- in human pathophysiology originated in its attributed role in the pathogenesis of secondary hyperparathyroidism (SHPT) in chronic kidney disease. In this article, we review the mechanisms by which this effect was justified and we commemorate the important contribution of a Spanish group led by Dr. M. Rodríguez, just 25 years ago, when they first demonstrated the direct effect of PO43- on the regulation of the synthesis and secretion of parathyroid hormone by maintaining the structural integrity of the parathyroid glands in their original experimental model. In addition to demonstrating the importance of arachidonic acid (AA) and the phospholipase A2-AA pathway as a mediator of parathyroid gland response, these findings were predecessors of the recent description of the important role of PO43- on the activity of the calcium sensor-receptor, and also fueled various lines of research on the importance of PO43- overload not only for the pathophysiology of SHPT but also in its systemic pathogenic role.

Non-classical Vitamin D Actions for Renal Protection.

Chronic Kidney Disease (CKD), a disorder that affects 11% of the world's population, is characterized by an acceleration in skeletal, immune, renal, and cardiovascular aging that increases the risk of cardiovascular mortality by 10- to 20-fold, compared to that in individuals with normal renal function. For more than two decades, the progressive impairment in renal capacity to maintain normal circulating levels of the hormonal form of vitamin D (1,25-dihydroxyvitamin D or calcitriol) was considered the main contributor to the reduced survival of CKD patients. Accordingly, calcitriol administration was the treatment of choice to attenuate the progression of secondary hyperparathyroidism (SHPT) and its adverse impact on bone health and vascular calcification. The development of calcitriol analogs, designed to mitigate the resistance to calcitriol suppression of PTH associated with CKD progression, demonstrated survival benefits unrelated to the control of SHPT or skeletal health. The exhaustive search for the pathophysiology behind survival benefits associated with active vitamin D analogs has identified novel anti-inflammatory, anti-hypertensive, anti-aging actions of the vitamin D endocrine system. A major paradigm shift regarding the use of calcitriol or active vitamin D analogs to improve survival in CKD patients emerged upon demonstration of a high prevalence of vitamin D (not calcitriol) deficiency at all stages of CKD and, more significantly, that maintaining serum levels of the calcitriol precursor, 25(OH)vitamin D, above 23 ng/ml delayed CKD progression. The cause of vitamin D deficiency in CKD, however, is unclear since vitamin D bioactivation to 25(OH)D occurs mostly at the liver. Importantly, neither calcitriol nor its analogs can correct vitamin D deficiency. The goals of this chapter are to present our current understanding of the pathogenesis of vitamin D deficiency in CKD and of the causal link between defective vitamin D bioactivation to calcitriol and the onset of molecular pathways that promote CKD progression independently of the degree of SHPT. An understanding of these mechanisms will highlight the need for identification of novel sensitive biomarkers to assess the efficacy of interventions with vitamin D and/or calcitriol(analogs) to ameliorate CKD progression in a PTH-independent manner.

Mortality in Hemodialysis Patients with COVID-19, the Effect of Paricalcitol or Calcimimetics.

BACKGROUND: In COVID-19 patients, low serum vitamin D (VD) levels have been associated with severe acute respiratory failure and poor prognosis. In regular hemodialysis (HD) patients, there is VD deficiency and markedly reduced calcitriol levels, which may predispose them to worse outcomes of COVID-19 infection. Some hemodialysis patients receive treatment with drugs for secondary hyperparathyroidism, which have well known pleiotropic effects beyond mineral metabolism. The aim of this study was to evaluate the impact of VD status and the administration of active vitamin D medications, used to treat secondary hyperparathyroidism, on survival in a cohort of COVID-19 positive HD patients. METHODS: A cross-sectional retrospective observational study was conducted from 12 March to 21 May 2020 in 288 HD patients with positive PCR for SARS-CoV2. Patients were from 52 different centers in Spain. RESULTS: The percent of HD patients with COVID-19 was 6.1% (288 out of 4743). Mortality rate was 28.4% (81/285). Three patients were lost to follow-up. Serum 25(OH)D (calcidiol) level was 17.1 [10.6-27.5] ng/mL and was not significantly associated to mortality (OR 0.99 (0.97-1.01), p = 0.4). Patients receiving active vitamin D medications (16/94 (17%) vs. 65/191(34%), p = 0.003), including calcimimetics (4/49 (8.2%) vs. 77/236 (32.6%), p = 0.001), paricalcitol or calcimimetics (19/117 (16.2%) vs. 62/168 (36.9%); p < 0.001), and also those on both paricalcitol and calcimimetics, to treat secondary hyperparathyroidism (SHPTH) (1/26 (3.8%) vs. 80/259 (30.9%), p < 0.001) showed a lower mortality rate than patients receiving no treatment with either drug. Multivariate Cox regression analysis confirmed this increased survival. CONCLUSIONS: Our findings suggest that the use of paricalcitol, calcimimetics or the combination of both, seem to be associated with the improvement of survival in HD patients with COVID-19. No correlation was found between serum VD levels and prognosis or outcomes in HD patients with COVID-19. Prospective studies and clinical trials are needed to support these findings.

Novel Immune Cell Subsets Exhibit Different Associations With Vascular Outcomes in Chronic Kidney Disease Patients-Identifying Potential Biomarkers.

Background and Aims: Alterations in novel immune cell subsets, such as angiogenic T cells (Tang), senescent T cells (CD4+CD28null), and monocyte subsets are associated with impaired vascular homeostasis in several inflammatory conditions. However, mediators underlying vascular deterioration in chronic kidney disease (CKD) are poorly characterized. This study assessed their role in the vascular deterioration of CKD using a broad spectrum of surrogate markers ranging from altered functionality to overt calcification. Methods: Tang (CD3+CD31+CXCR4+), CD4+CD28null cells, and monocytes [CD14/CD16 subsets and angiotensin-converting enzyme (ACE) expression] were measured in peripheral blood by flow cytometry in 33 CKD stage 5 patients undergoing peritoneal dialysis (CKD5-PD) and 15 healthy controls (HCs). Analyses were replicated in a hemodialysis cohort. Vascular surrogate markers (including adventitial vasa vasorum, pulse wave velocity, intima-media thickness, and vascular calcification) were assessed by appropriate imaging methods. Results: In CKD5-PD, decreased Tang levels (p < 0.001) were unrelated to clinical features or traditional cardiovascular (CV) risk factors but correlated negatively with troponin T levels (r = -0.550, p = 0.003). Instead, CD4+CD28null frequency was increased (p < 0.001), especially in those with vascular calcifications. Quantitative and qualitative differences were also observed within the monocyte pool, a shift toward CD16+ subsets and ACE expression being found in CKD. Equivalent results were observed in the replication cohort. Each subset associated distinctly with adverse vascular outcomes in univariate and multivariate analyses: while Tang depletion was linked to poor vascular function and subclinical atherosclerosis, increases in CD4+CD28null were associated with overt vascular thickening and calcification. Monocytes were not independently associated with vascular outcomes in CKD patients. Conclusions: Novel T cell and monocyte subsets are altered in CKD. Altered T-cell subpopulations, but not monocytes, exhibited distinct associations with different vascular outcomes in CKD. Tang are emerging biomarkers of subclinical vascular deterioration in CKD.

Role of the RANK/RANKL/OPG and Wnt/ß-Catenin Systems in CKD Bone and Cardiovascular Disorders.

In the course of chronic kidney disease (CKD), alterations in the bone-vascular axis augment the risk of bone loss, fractures, vascular and soft tissue calcification, left ventricular hypertrophy, renal and myocardial fibrosis, which markedly increase morbidity and mortality rates. A major challenge to improve skeletal and cardiovascular outcomes in CKD patients requires a better understanding of the increasing complex interactions among the main modulators of the bone-vascular axis. Serum parathyroid hormone (PTH), phosphorus (P), calcium (Ca), fibroblast growth factor 23 (FGF23), calcidiol, calcitriol and Klotho are involved in this axis interact with RANK/RANKL/OPG system and the Wnt/ß-catenin pathway. The RANK/RANKL/OPG system controls bone remodeling by inducing osteoblast synthesis of RANKL and downregulating OPG production and it is also implicated in vascular calcification. The complexity of this system has recently increased due the discovery of LGR4, a novel RANKL receptor involved in bone formation, but possibly also in vascular calcification. The Wnt/ß-catenin pathway plays a key role in bone formation: when this pathway is activated, bone is formed, but when it is inhibited, bone formation is stopped. In the progression of CKD, a downregulation of the Wnt/ß-catenin pathway has been described which occurs mainly through the not coincident elevations of sclerostin, Dickkopf1 (Dkk1) and the secreted Frizzled Related Proteins (sFRPs). This review analyzes the interactions of PTH, P, Ca, FGF23, calcidiol, calcitriol and Klotho with the RANKL/RANKL/OPG system and the Wnt/ß-catenin, pathway and their implications in bone and cardiovascular disorders in CKD.

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.

The receptor activator of nuclear factor κΒ ligand receptor leucine-rich repeat-containing G-protein-coupled receptor 4 contributes to parathyroid hormone-induced vascular calcification.

BACKGROUND: In chronic kidney disease, serum phosphorus (P) elevations stimulate parathyroid hormone (PTH) production, causing severe alterations in the bone-vasculature axis. PTH is the main regulator of the receptor activator of nuclear factor κB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system, which is essential for bone maintenance and also plays an important role in vascular smooth muscle cell (VSMC) calcification. The discovery of a new RANKL receptor, leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4), which is important for osteoblast differentiation but with an unknown role in vascular calcification (VC), led us to examine the contribution of LGR4 in high P/high PTH-driven VC. METHODS: In vivo studies were conducted in subtotally nephrectomized rats fed a normal or high P diet, with and without parathyroidectomy (PTX). PTX rats were supplemented with PTH(1-34) to achieve physiological serum PTH levels. In vitro studies were performed in rat aortic VSMCs cultured in control medium, calcifying medium (CM) or CM plus 10-7 versus 10-9 M PTH. RESULTS: Rats fed a high P diet had a significantly increased aortic calcium (Ca) content. Similarly, Ca deposition was higher in VSMCs exposed to CM. Both conditions were associated with increased RANKL and LGR4 and decreased OPG aorta expression and were exacerbated by high PTH. Silencing of LGR4 or parathyroid hormone receptor 1 (PTH1R) attenuated the high PTH-driven increases in Ca deposition. Furthermore, PTH1R silencing and pharmacological inhibition of protein kinase A (PKA), but not protein kinase C, prevented the increases in RANKL and LGR4 and decreased OPG. Treatment with PKA agonist corroborated that LGR4 regulation is a PTH/PKA-driven process. CONCLUSIONS: High PTH increases LGR4 and RANKL and decreases OPG expression in the aorta, thereby favouring VC. The hormone's direct pro-calcifying actions involve PTH1R binding and PKA activation.

Effect of Oat ß-Glucan Supplementation on Chronic Kidney Disease: A Feasibility Study.

OBJECTIVE: Dietary supplementation with grains containing high ß-glucan fiber has been shown to attenuate the progression of chronic kidney disease (CKD) and vascular calcification in animal models. The aim of this study was to investigate the feasibility of consuming an oat ß-glucan supplement and to assess its effects on certain uremic toxins and markers of mineral metabolism in patients with CKD. DESIGN: This is a 20-week, nonrandomized, single-center, pretest-posttest study. Twenty-eight subjects with CKD stages 3-4 were enrolled. The mean age was 67.6 ± 8.9 years, and the mean estimated glomerular filtration rate was 35 ± 14 mL/min/1.73 m2. Subjects received a dietary supplement containing 3 g of oat ß-glucan per day for 12 weeks. The 4-week period before the start of the intervention was used as a baseline comparison for each subject. The primary outcome was pre-post supplement changes in plasma levels of two uremic toxins: trimethylamine N-oxide (TMAO) and asymmetric dimethylarginine. Secondary outcomes were pre-post supplement changes in serum calcium, phosphorus, and Klotho levels. Repeated-measures analysis of variance was used to test the differences in outcomes over the three-month-long intervention. RESULTS: Serum levels of TMAO decreased by a median of -17% (interquartile range: -46%, 7%) at the end of the intervention. A nonstatistically significant change was observed for asymmetric dimethylarginine (median -0.6% [-12%, 20%]) and serum Klotho (median -3% [-8%, 7%]). There were no changes in serum levels of calcium and phosphorus. One month after discontinuation of ß-glucan therapy, TMAO levels increased by a median of 16% (-12%, 36%) but remained slightly below the pretreatment levels. Eight subjects experienced side effects and discontinued the treatment. CONCLUSION: A diet supplemented with ß-glucan is safe and potentially efficacious in lowering serum concentrations of TMAO in patients with CKD. Larger trials with longer follow-up times are needed to determine whether such reductions translate into clinical benefits.

Barley-ß-glucans reduce systemic inflammation, renal injury and aortic calcification through ADAM17 and neutral-sphingomyelinase2 inhibition.

In chronic kidney disease (CKD), hyperphosphatemia-induced inflammation aggravates vascular calcification (VC) by increasing vascular smooth muscle cell (VSMC) osteogenic differentiation, ADAM17-induced renal and vascular injury, and TNFα-induction of neutral-sphingomyelinase2 (nSMase2) to release pro-calcifying exosomes. This study examined anti-inflammatory ß-glucans efficacy at attenuating systemic inflammation in health, and renal and vascular injury favoring VC in hyperphosphatemic CKD. In healthy adults, dietary barley ß-glucans (Bßglucans) reduced leukocyte superoxide production, inflammatory ADAM17, TNFα, nSMase2, and pro-aging/pro-inflammatory STING (Stimulator of interferon genes) gene expression without decreasing circulating inflammatory cytokines, except for γ-interferon. In hyperphosphatemic rat CKD, dietary Bßglucans reduced renal and aortic ADAM17-driven inflammation attenuating CKD-progression (higher GFR and lower serum creatinine, proteinuria, kidney inflammatory infiltration and nSMase2), and TNFα-driven increases in aortic nSMase2 and calcium deposition without improving mineral homeostasis. In VSMC, Bßglucans prevented LPS- or uremic serum-induced rapid increases in ADAM17, TNFα and nSMase2, and reduced the 13-fold higher calcium deposition induced by prolonged calcifying conditions by inhibiting osteogenic differentiation and increases in nSMase2 through Dectin1-independent actions involving Bßglucans internalization. Thus, dietary Bßglucans inhibit leukocyte superoxide production and leukocyte, renal and aortic ADAM17- and nSMase2 gene expression attenuating systemic inflammation in health, and renal injury and aortic calcification despite hyperphosphatemia in CKD.

A subset of low density granulocytes is associated with vascular calcification in chronic kidney disease patients.

Inflammation is central to chronic kidney disease (CKD) pathogenesis and vascular outcomes, but the exact players remain unidentified. Since low density granulocytes (LDGs) are emerging mediators in inflammatory conditions, we aimed to evaluate whether LDGs may be altered in CKD and related to clinical outcomes as biomarkers. To his end, LDGs subsets were measured in peripheral blood by flow cytometry and confocal microscopy in 33 CKD patients undergoing peritoneal dialysis and 15 healthy controls (HC). Analyses were replicated in an additional cohort. DEF3 (marker of early granulopoiesis) gene expression on PBMCs was quantified by qPCR. Total CD15+ LDGs and both CD14lowCD16+ and CD14-CD16- subsets were expanded in CKD. The relative frequency of the CD14-CD16- subpopulation was higher among the CD15+ pool in CKD. This alteration was stable over-time. The increased CD14-CD16-CD15+ paralleled Kauppila scores and DEF3 expression, whereas no association was found with CD14lowCD16+ CD15+. Both subsets differed in their CD11b, CD10, CD35, CD31, CD62L, IFNAR1 and CD68 expression, FSC/SSC features and nuclear morphology, pointing to different origins and maturation status. In conclusion, LDGs were expanded in CKD showing a skewed distribution towards a CD14-CD16-CD15+ enrichment, in association with vascular calcification. DEF3 expression in PBMC can be a marker of LDG expansion.

Vitamin D Receptor Polymorphism and DHCR7 Contribute to the Abnormal Interplay Between Vitamin D and Lipid Profile in Rheumatoid Arthritis.

Emerging evidence suggests a role for 7-dehydrocholesterol reductase (DHCR7) in the crosstalk between cholesterol and vitamin D. Our aim was to evaluate the impact of vitamin D-related polymorphisms and DHCR7 levels in the association between vitamin D deficiency and altered lipid profile in rheumatoid arthritis (RA). Serum 25(OH)-vitamin D, DHCR7 levels and vitamin D-related polymorphisms (VDR-rs2228570, CYP27A1-rs933994, CYP2R1-rs10741657 and DHCR7-rs12785878) were analyzed in 211 RA patients,94 controls and in a prospective cohort of 13 RA patients undergoing TNFα-blockade. Vitamin D was decreased in RA (p < 0.001), correlated to HDL-cholesterol (r = 0.217, p < 0.001) and total-/HDL-cholesterol ratio (r = -0.227, p = 0.004). These correlations were restricted to the VDR-rs2228570 status. Vitamin D deficiency was associated with lower HDL-cholesterol (p = 0.028), higher tender (p = 0.005) and swollen (p = 0.002) joint counts, higher DAS28 (p = 0.018) and HAQ (p = 0.024) in AG/AA-patients but not in their GG-counterparts. The associations among DHCR7, vitamin D and lipid profile followed a seasonal pattern, decreased DHCR7 (p = 0.008) and vitamin D (p < 0.001) and increased total-cholesterol (p = 0.025) being found in winter/spring. Increasing vitamin D upon TNFα-blockade paralleled RA clinical improvement (r = -0.610, p = 0.027) and DHCR7 elevation (r = 0.766, p = 0.002). In conclusion, vitamin D-related polymorphisms and DHCR7 are pivotal to understand the complex, seasonal associations between vitamin D and lipid profile in RA.

High-serum phosphate and parathyroid hormone distinctly regulate bone loss and vascular calcification in experimental chronic kidney disease.

BACKGROUND: In chronic kidney disease (CKD), increases in serum phosphate and parathyroid hormone (PTH) aggravate vascular calcification (VC) and bone loss. This study was designed to discriminate high phosphorus (HP) and PTH contribution to VC and bone loss. METHODS: Nephrectomized rats fed a HP diet underwent either sham operation or parathyroidectomy and PTH 1-34 supplementation to normalize serum PTH. RESULTS: In uraemic rats fed a HP diet, parathyroidectomy with serum PTH 1-34 supplementation resulted in (i) reduced aortic calcium (80%) by attenuating osteogenic differentiation (higher α-actin; reduced Runx2 and BMP2) and increasing the Wnt inhibitor Sclerostin, despite a similar degree of hyperphosphataemia, renal damage and serum Klotho; (ii) prevention of bone loss mostly by attenuating bone resorption and increases in Wnt inhibitors; and (iii) a 70% decrease in serum calcitriol levels despite significantly reduced serum Fgf23, calcium and renal 24-hydroxylase, which questions that Fgf23 is the main regulator of renal calcitriol production. Significantly, when vascular smooth muscle cells (VSMCs) were exposed exclusively to high phosphate and calcium, high PTH enhanced while low PTH attenuated calcium deposition through parathyroid hormone 1 receptor (PTH1R) signalling. CONCLUSIONS: In hyperphosphataemic CKD, a defective suppression of high PTH exacerbates HP-mediated osteogenic VSMC differentiation and reduces vascular levels of anti-calcifying sclerostin.

Serum phosphate optimal timing and range associated with patients survival in haemodialysis: the COSMOS study.

BACKGROUND: Serum phosphate is a key parameter in the management of chronic kidney disease-mineral and bone disorder (CKD-MBD). The timing of phosphate measurement is not standardized in the current guidelines. Since the optimal range of these biomarkers may vary depending on the duration of the interdialytic interval, in this analysis of the Current management of secondary hyperparathyroidism: a multicentre observational study (COSMOS), we assessed the influence of a 2- (midweek) or 3-day (post-weekend) dialysis interval for blood withdrawal on serum levels of CKD-MBD biomarkers and their association with mortality risk. METHODS: The COSMOS cohort (6797 patients, CKD Stage 5D) was divided into two groups depending upon midweek or post-weekend blood collection. Univariate and multivariate Cox's models adjusted hazard ratios (HRs) by demographics and comorbidities, treatments and biochemical parameters from a patient/centre database collected at baseline and every 6 months for 3 years. RESULTS: There were no differences in serum calcium or parathyroid hormone levels between midweek and post-weekend patients. However, in post-weekend patients, the mean serum phosphate levels were higher compared with midweek patients (5.5 ± 1.4 versus 5.2 ± 1.4 mg/dL, P < 0.001). Also, the range of serum phosphate with the lowest mortality risk [HR ≤ 1.1; midweek: 3.5-4.9 mg/dL (95% confidence interval, CI: 2.9-5.2 mg/dL); post-weekend: 3.8-5.7 mg/dL (95% CI: 3.0-6.4 mg/dL)] showed significant differences in the upper limit (P = 0.021). CONCLUSION: Midweek and post-weekend serum phosphate levels and their target ranges associated with the lowest mortality risk differ. Thus, clinical guidelines should consider the timing of blood withdrawal when recommending optimal target ranges for serum phosphate and therapeutic strategies for phosphate control.