Efficacy of dietary vitamin D3 and 25(OH)D3 on reproductive capacities, growth performance, immunity and bone development in pigs.

Vitamin D3 (Vit D3) and 25(OH)D3 are used as dietary sources of active vitamin D (1,25(OH)2D3) in pig husbandry. Although acting primarily on intestine, kidney and bone, their use in pig nutrition has shown a wide range of effects also in peripheral tissues. However, there is an ambiguity in the existing literature about whether the effects of Vit D3 and 25(OH)D3 differ in attributing the molecular and phenotypic outcomes in pigs. We searched Web of Science and PubMed databases concerning the efficacy of Vit D3 in comparison with 25(OH)D3 on pig physiology, i.e. reproductive capacities, growth performance, immunity and bone development. Dietary intake of Vit D3 or 25(OH)D3 did not influence the reproductive capacity of sows. Unlike Vit D3, the maternal intake of 25(OH)D3 significantly improved the growth performance of piglets, which might be attributed to maternally induced micronutrient efficiency. Consequently, even in the absence of maternal vitamin D supplementation, 25(OH)D3-fed offspring also demonstrated better growth than the offspring received Vit D3. Moreover, a similar superior impact of 25(OH)D3 was seen with respect to serum markers of innate and humoral immunity. Last but not least, supplements containing 25(OH)D3 were found to be more effective than Vit D3 to improve bone mineralisation and formation, especially in pigs receiving basal diets low in Ca and phosphorus. The insights are of particular value in determining the principal dietary source of vitamin D to achieve its optimum utilisation efficiency, nutritional benefits and therapeutic potency and to further improve animal welfare across different management types.

Naturally occurring stable calcium isotope ratios are a novel biomarker of bone calcium balance in chronic kidney disease.

Dysregulated calcium homeostasis is common in chronic kidney disease and causally associated with disorders of bone mineralization. However, radiological measures and biomarkers do not allow accurate evaluation of bone calcium balance. Non-radioactive calcium isotopes, 42Ca and 44Ca, are present in our diet and sequestered into body compartments following principles of kinetic isotope fractionation. Isotopically light 42Ca is preferentially incorporated into bone, while heavier 44Ca is excreted. The ratio (44/42Caserum) increases when bone formation exceeds resorption and vice versa, reflecting bone calcium balance. We measured these calcium isotopes by inductively coupled plasma mass-spectrometry in blood, urine and feces of 42 children with chronic kidney disease and 92 receiving dialysis therapy. We compared the isotope ratios with bone biomarkers and determined total bone mineral content by dual-energy x-ray absorptiometry and peripheral quantitative CT expressed as age-adjusted z-scores. The 44/42Caserum ratio positively correlated with serum calcium, 25-hydroxyvitamin D and alkaline phosphatases and inversely with serum parathyroid hormone and other bone resorption markers. The 44/42Caserum ratio positively correlated with age-adjusted z-scores of tibial trabecular bone mineral density and total bone mineral content measured by peripheral quantitative CT, and hip bone mineral density measured by dual-energy X-ray absorptiometry. Significant and independent predictors of total bone mineral content, measured by, were the 44/42Caserum ratio and parathyroid hormone. The 44/42Caserum ratio, repeated after four weeks, highly correlated with baseline values. When adjusted for calcium-containing medications and kidney impairment, the 44/42Caserum ratio in patients receiving dialysis was 157% lower than that of age-matched children and 29% lower than levels in elderly women with osteoporosis, implying significantly lower bone mineral content. Thus, calcium isotope ratios may provide a novel, sensitive and non-invasive method of assessing bone calcium balance in chronic kidney disease.

3D optical scanning as an objective and reliable tool for volumetry of the foot and ankle region.

BACKGROUND: Edema development of the foot and ankle region should be evaluated by an objective measurement. We hypothesized, that 3D optical scanning of this region can serve as an alternative to clinically established measurement techniques. METHODS: Two investigators determined the volume by 3D optical scanning and the figure-of-eight method in a random order at 2 separate time points. Plots were created and ICCs were calculated for determination of reliability. The Pearson correlation coefficient served as a measure of the association between both measures. RESULTS: 40 healthy volunteers with mean age of 28.3±9.9 years underwent four sequences of measurements. The inter- and intraobserver reliability of both methods was excellent with high intraclass correlation coefficients (ICC 3,1). A strong correlation (r=0.96, P<0.001) between measured ankle volumes was noted. CONCLUSION: 3D optical scanning turned out to be more reliable than the figure-of-eight method in a preclinical set-up. A clinical use should be aimed at.

Active vitamin D is cardioprotective in experimental uraemia but not in children with CKD Stages 3-5.

BACKGROUND: Uraemic cardiac remodelling is associated with vitamin D and Klotho deficiency, elevated fibroblast growth factor 23 (FGF23) and activation of the renin-angiotensin system (RAS). The cardioprotective properties of active vitamin D analogues in this setting are unclear. METHODS: In rats with 5/6 nephrectomy (5/6Nx) treated with calcitriol, the cardiac phenotype and local RAS activation were investigated compared with controls. A nested case-control study was performed within the Cardiovascular Comorbidity in Children with Chronic Kidney Disease (4C) study, including children with chronic kidney disease (CKD) Stages 3-5 [estimated glomerular filtration rate (eGFR) 25 mL/min/1.73 m2] treated with and without active vitamin D. Echocardiograms, plasma FGF23 and soluble Klotho (sKlotho) were assessed at baseline and after 9 months. RESULTS: In rats with 5/6Nx, left ventricular (LV) hypertrophy, LV fibrosis and upregulated cardiac RAS were dose-dependently attenuated by calcitriol. Calcitriol further stimulated FGF23 synthesis in bone but not in the heart, and normalized suppressed renal Klotho expression. In the 4C study cohort, treatment over a mean period of 9 months with active vitamin D was associated with increased FGF23 and phosphate and decreased sKlotho and eGFR compared with vitamin D naïve controls, whereas LV mass index did not differ between groups. CONCLUSIONS: Active vitamin D ameliorates cardiac remodelling and normalizes renal Klotho expression in 5/6Nx rats but does not improve the cardiac phenotype in children with CKD Stages 3-5. This discrepancy may be due to further enhancement of circulating FGF23 and faster progression of CKD associated with reduced sKlotho and higher serum phosphate in vitamin D-treated patients.

Diabetes Mellitus and Hypertension-A Case of Sugar and Salt?

The majority of patients with diabetes mellitus (DM) have hypertension (HTN). A specific mechanism for the development of HTN in DM has not been described. In the Zucker, Endothel, und Salz (sugar, endothelium, and salt) study (ZEuS), indices of glucose metabolism and of volume regulation are recorded. An analysis of these parameters shows that glucose concentrations interfere with plasma osmolality and that changes in glycemic control have a significant impact on fluid status and blood pressure. The results of this study are discussed against the background of the striking similarities between the regulation of sugar and salt blood concentrations, introducing the view that DM is probably a sodium-retention disorder that leads to a state of hypervolemia.

FGF23-Mediated Activation of Local RAAS Promotes Cardiac Hypertrophy and Fibrosis.

Patients with chronic kidney disease (CKD) are prone to developing cardiac hypertrophy and fibrosis, which is associated with increased fibroblast growth factor 23 (FGF23) serum levels. Elevated circulating FGF23 was shown to induce left ventricular hypertrophy (LVH) via the calcineurin/NFAT pathway and contributed to cardiac fibrosis by stimulation of profibrotic factors. We hypothesized that FGF23 may also stimulate the local renin-angiotensin-aldosterone system (RAAS) in the heart, thereby further promoting the progression of FGF23-mediated cardiac pathologies. We evaluated LVH and fibrosis in association with cardiac FGF23 and activation of RAAS in heart tissue of 5/6 nephrectomized (5/6Nx) rats compared to sham-operated animals followed by in vitro studies with isolated neonatal rat ventricular myocytes and fibroblast (NRVM, NRCF), respectively. Uremic rats showed enhanced cardiomyocyte size and cardiac fibrosis compared with sham. The cardiac expression of Fgf23 and RAAS genes were increased in 5/6Nx rats and correlated with the degree of cardiac fibrosis. In NRVM and NRCF, FGF23 stimulated the expression of RAAS genes and induced Ngal indicating mineralocorticoid receptor activation. The FGF23-mediated hypertrophic growth of NRVM and induction of NFAT target genes were attenuated by cyclosporine A, losartan and spironolactone. In NRCF, FGF23 induced Tgfb and Ctgf, which were suppressed by losartan and spironolactone, only. Our data suggest that FGF23-mediated activation of local RAAS in the heart promotes cardiac hypertrophy and fibrosis.

Impaired Microcirculation in Children After Kidney Transplantation: Everolimus Versus Mycophenolate Based Immunosuppression Regimen.

BACKGROUND/AIMS: Whether the immunosuppressive regimen is associated with micro- and macro-vascular status in pediatric kidney transplant recipients (KTx) is unknown. METHODS: We performed a cross-sectional, case-control study in 44 pediatric KTx patients on either everolimus (EVR) plus calcineurin inhibitor or standard treatment, i.e. mycophenolate mofetil plus calcineurin inhibitor. Measurement of carotid intima-media thickness (cIMT) via ultrasound, central pulse wave velocity (PWV) by a cuff-based oscillometric technique, and skin microvascular blood flow during local heating via laser-Doppler-fluximetry (LDF) served as marker of subclinical vascular disease. Serum concentrations of angiopoietin-1 and -2, fibroblast-growth factor 23 (FGF23) and soluble klotho were measured. RESULTS: EVR-treated patients exhibited a similar degree of hypertension, increased cIMT, elevated pro-inflammatory angiopoietin-2, and diminished endothelial survival factor angiopoietin-1 compared to healthy children but presented with a twofold more reduced skin micro-vascular function compared to standard treatment (each p< 0.001). By contrast, PWV and soluble klotho levels were normal in both groups. CONCLUSION: Endothelial dysfunction seems more frequent in KTx patients on EVR-based immunosuppressive regimen compared to standard immunosuppression.

Vitamin D treatment attenuates cardiac FGF23/FGFR4 signaling and hypertrophy in uremic rats.

BACKGROUND: Vitamin D deficiency and excess of circulating fibroblast growth factor 23 (FGF23) contribute to cardiovascular mortality in patients with chronic kidney disease (CKD). FGF23 activates FGF receptor 4 and (FGFR4) calcineurin/nuclear factor of activated T cells (NFAT) signaling in cardiac myocytes, thereby causing left ventricular hypertrophy (LVH). Here, we determined if 1,25-dihydroxyvitamin D (calcitriol) inhibits FGF23-induced cardiac signaling and LVH. METHODS: 5/6 nephrectomized (5/6 Nx) rats were treated with different doses of calcitriol for 4 or 10 weeks and cardiac expression of FGF23/FGFR4 and activation of calcineurin/NFAT as well as LVH were analyzed. FGFR4 activation and hypertrophic cell growth were studied in cultured cardiac myocytes that were co-treated with FGF23 and calcitriol. RESULTS: In 5/6Nx rats with LVH, we detected elevated FGF23 expression in bone and myocardium, increased cardiac expression of FGFR4 and elevated cardiac activation of calcineurin/NFAT signaling. Cardiac expression levels of FGF23 and FGFR4 significantly correlated with the presence of LVH in uremic rats. Treatment with calcitriol reduced LVH as well as cardiac FGFR4 expression and calcineurin/NFAT activation. Bone and cardiac FGF23 expression were further stimulated by calcitriol in a dose-dependent manner, but levels of intact cardiac FGF23 protein were suppressed by high-dose calcitriol. In cultured cardiac myocytes, co-treatment with calcitriol blocked FGF23-induced activation of FGFR4 and hypertrophic cell growth. CONCLUSIONS: Our data suggest that in CKD, cardioprotective effects of calcitriol stem from its inhibitory actions on the cardiac FGF23/FGFR4 system, and based on their counterbalancing effects on cardiac myocytes, high FGF23 and low calcitriol synergistically contribute to cardiac hypertrophy.

Endothelial dysfunction during long-term follow-up in children with STEC hemolytic-uremic syndrome.

BACKGROUND: Shiga-toxin-producing Escherichia coli (STEC)-associated hemolytic-uremic syndrome (HUS) is a major cause of acute kidney injury (AKI), especially in children. Its long-term outcome with respect to endothelial damage remains largely elusive. METHODS: This was a cross-sectional study in 26 children who had suffered from STEC-HUS in the past and achieved a complete recovery of renal function (eGFR >90 ml/min/1.73 m2). Skin microcirculation after local heating was assessed by laser Doppler fluximetry, carotid-femoral pulse wave velocity (PWV), carotid intima media thickness (cIMT), 24-h ambulatory blood pressure, and angiopoietin (Ang) 1 and 2 serum levels after a median follow-up period of 6.1 years. The results were compared to those of healthy controls. RESULTS: All patients were normotensive, mean eGFR was 102 (range 91-154) ml/min/1.73 m2, and 13 of the 26 patients showed albuminuria. Endothelial dysfunction was present in 13 patients, and the mean serum Ang2/Ang1 ratio was increased compared to healthy children (each p < 0.05). In contrast, mean values for PWV and cIMT in the patients did not differ from those of the controls. Endothelial dysfunction was significantly associated with younger age at STEC-HUS manifestation, time after HUS, and presence of albuminuria. CONCLUSION: The results of this study highlight the need for long-term follow-up of STEC-HUS patients even after complete recovery of eGFR and lack of hypertension with respect to microvascular damage.

[Visual Analysis of Retinal OCT Data]. / Visuelle Analyse von retinalen OCT-Daten.

Optical coherence tomography (OCT) enables noninvasive high-resolution 3D imaging of the human retina, and thus plays a fundamental role in ophthalmology. Via OCT examination, even subtle retinal changes can be captured, which occur in very early stages of different diseases (e.g., glaucoma, diabetes mellitus, or age-related macular degeneration). Yet, analyzing the resulting data is challenging. Conventionally, OCT data are strongly aggregated via automated methods. While this reduces the amount of information to be analyzed, it also makes it difficult, if not impossible, to identify small and localized retinal changes. This might lead to wrong diagnoses, since these methods do not account for patient-specific characteristics. We address this problem by providing new and efficient visual-interactive methods. Particularly, we introduce dedicated visualizations that show different aspects of the data. In addition, we support patient-specific selections of relevant data regions. Selected regions are emphasized, or separately visualized to inspect retinal substructures in detail. By visually comparing the regions to reference data, even very small retinal changes can be detected. We demonstrate the utility of our approach by applying it to data of a study with pediatric patients suffering from diabetes mellitus type 1. Our results show that visual-interactive methods indeed help to analyze subtle retinal changes and, thus, support the diagnosis of diseases in an early stage.

Induction of cardiac FGF23/FGFR4 expression is associated with left ventricular hypertrophy in patients with chronic kidney disease.

BACKGROUND: In chronic kidney disease (CKD), serum concentrations of fibroblast growth factor 23 (FGF23) increase progressively as glomerular filtration rate declines, while renal expression of the FGF23 coreceptor Klotho decreases. Elevated circulating FGF23 levels are strongly associated with mortality and with left ventricular hypertrophy (LVH), which is a major cause of cardiovascular death in CKD patients. The cardiac FGF23/FGF receptor (FGFR) system and its role in the development of LVH in humans have not been addressed previously. METHODS: We conducted a retrospective case-control study in 24 deceased patients with childhood-onset end-stage renal disease (dialysis: n = 17; transplanted: n = 7), and 24 age- and sex-matched control subjects. Myocardial autopsy samples of the left ventricle were evaluated for expression of endogenous FGF23, FGFR isoforms, Klotho, calcineurin and nuclear factor of activated T-cells (NFAT) by immunohistochemistry, immunofluorescence microscopy, qRT-PCR and western blotting. RESULTS: The majority of patients presented with LVH (67%). Human cardiomyocytes express full-length FGF23, and cardiac FGF23 is excessively high in patients with CKD. Enhanced myocardial expression of FGF23 in concert with Klotho deficiency strongly correlates with the presence of LVH. Cardiac FGF23 levels associate with time-averaged serum phosphate levels, up-regulation of FGFR4 and activation of the calcineurin-NFAT signaling pathway, an established mediator of cardiac remodelling and LVH. These changes are detected in patients on dialysis but not in those with a functioning kidney transplant. CONCLUSIONS: Our results indicate a strong association between LVH and enhanced expression levels of FGF23, FGFR4 and calcineurin, activation of NFAT and reduced levels of soluble Klotho in the myocardium of patients with CKD. These alterations are not observed in kidney transplant patients.

Arterial stiffness is increased in asthmatic children.

UNLABELLED: Altered arterial stiffness is a recognized risk factor of poor cardiovascular health. Chronic inflammation may increase arterial stiffness. We tested whether arterial stiffness is increased children with asthma, a chronic disease characterized by fluctuating airway and systemic inflammation. Arterial stiffness, expressed as carotid-femoral pulse wave velocity (PWVcf), was measured in 37 mild-to-moderate asthmatic children: 11 girls, median (range) age 11.1 years (6-15). PWVcf in asthma was compared to PWVcf in 65 healthy controls matched for age, height, and gender previously studied in Germany and was correlated with airway inflammation and obstruction. PWVcf was higher in asthmatic children compared to controls: PWVcf median (interquartile range) was 4.7 m/s (4.5-4.9) vs. 4.3 m/s (4.1-4.7), p < 0.0001. In asthmatic children, PWVcf was inversely associated (r (2) = 0.20, p = 0.004) with forced expiratory volume in 1 s (FEV1). This association remained significant after adjusting for possible confounders including body mass index, blood pressure, steroid use, and FeNO. CONCLUSION: Arterial stiffness is increased in children with mild-to-moderate asthma. The association between impaired lung function and increased arterial stiffness suggests that severity of disease translates into detrimental effects on the cardiovascular system.

Exposure to artificial ultraviolet-B light mediates alterations on the hepatic transcriptome and vitamin D metabolism in pigs.

In the currently prevailing pig husbandry systems, the vitamin D status is almost exclusively dependent on dietary supply. Additional endogenous vitamin D production after exposure to ultraviolet-B (UVB) light might allow the animals to utilize minerals in a more efficient manner, as well as enable the production of functional vitamin D-enriched meat for human consumption. In this study, growing pigs (n = 16) were subjected to a control group or to a daily narrowband UVB exposure of 1 standard erythema dose (SED) for a period of 9 weeks until slaughter at a body weight of 105 kg. Transcriptomic profiling of liver with emphasis on the associated effects on vitamin D metabolism due to UVB exposure were evaluated via RNA sequencing. Serum was analyzed for vitamin D status and health parameters such as minerals and biochemical markers. The serum concentration of calcidiol, but not calcitriol, was significantly elevated in response to UVB exposure after 17 days on trial. No effects of UVB exposure were observed on growth performance and blood test results. At slaughter, the RNA sequencing analyses following daily UVB exposure revealed 703 differentially expressed genes (DEGs) in liver tissue (adjusted p-value < 0.01). Results showed that molecular pathways for vitamin D synthesis (CYP2R1) rather than cholesterol synthesis (DHCR7) were preferentially initiated in liver. Gene enrichment (p < 0.05) was observed for reduced cholesterol/steroid biosynthesis, SNARE interactions in vesicular transport, and CDC42 signaling. Taken together, dietary vitamin D supply can be complemented via endogenous production after UVB exposure in pig husbandry, which could be considered in the development of functional foods.

Force loss and distribution of load in the hands of patients with cubital tunnel syndrome.

Manugraphy with three different cylinder sizes was used to quantify the contribution of fingers, thumb and palm to grip force in patients with unilateral cubital tunnel syndrome. Forces in the affected and contralateral hands differed by up to 29%. Although grip force is usually maximal when gripping small handles, ulnar nerve palsy resulted in similar absolute grip forces using the 100-mm and 200-mm cylinders. The contact area between the affected hand and the cylinders was reduced by 5%-9%. We noted a high correlation between the contact area and grip force, visible atrophy and permanently impaired sensibility. The load distribution differed significantly between both hands for all cylinder sizes. When gripping large objects, the main functional impairment in cubital tunnel syndrome is weakness in positioning and stabilizing the thumb. Weak intrinsic finger muscles are responsible for loss of force when gripping small objects. Level of evidence: III.

Cardiovascular risk and mineral bone disorder in patients with chronic kidney disease.

The term chronic kidney disease-mineral bone disorder has been coined recently to highlight that the disturbed mineral and bone metabolism is a major contributor to vascular calcification and finally cardiovascular disease. This syndrome is characterized by clinical, biochemical and/or histological findings, i.e. i) biochemical alterations in the homeostasis of calcium, phosphate and their key player parathyroid hormone (PTH), Fibroblast growth factor-23 (FGF-23), klotho and vitamin-D, ii) the occurrence of vascular and/or soft tissue calcification, and iii) an abnormal bone structure and/or turnover. Apart from the combined and synergistic action of "traditional" and uremia-related risk factors, promoters and inhibitors of calcification have to be considered as well. This review will focus on the disturbed mineral metabolism as the triggering force behind distortion of vascular integrity and cardiovascular malfunction in CKD patients.

Circulating suPAR in two cohorts of primary FSGS.

Overexpression of soluble urokinase receptor (suPAR) causes pathology in animal models similar to primary FSGS, and one recent study demonstrated elevated levels of serum suPAR in patients with the disease. Here, we analyzed circulating suPAR levels in two cohorts of children and adults with biopsy-proven primary FSGS: 70 patients from the North America-based FSGS clinical trial (CT) and 94 patients from PodoNet, the Europe-based consortium studying steroid-resistant nephrotic syndrome. Circulating suPAR levels were elevated in 84.3% and 55.3% of patients with FSGS patients in the CT and PodoNet cohorts, respectively, compared with 6% of controls (P<0.0001); inflammation did not account for this difference. Multiple regression analysis suggested that lower suPAR levels associated with higher estimated GFR, male sex, and treatment with mycophenolate mofetil. In the CT cohort, there was a positive association between the relative reduction of suPAR after 26 weeks of treatment and reduction of proteinuria, with higher odds for complete remission (P=0.04). In the PodoNet cohort, patients with an NPHS2 mutation had higher suPAR levels than those without a mutation. In conclusion, suPAR levels are elevated in geographically and ethnically diverse patients with FSGS and do not reflect a nonspecific proinflammatory milieu. The associations between a change in circulating suPAR with different therapeutic regimens and with remission support the role of suPAR in the pathogenesis of FSGS.

Randomized Controlled Clinical Trial of the Effect of Treatment with Vitamin K2 on Vascular Calcification in Hemodialysis Patients (Trevasc-HDK).

Introduction: Vitamin K deficiency among patients on hemodialysis (HD) affects the function of matrix GLA protein (MGP), a potent vitamin K-dependent inhibitor of vascular calcification (VC). Methods: We conducted a single-center randomized controlled trial (RCT) on maintenance HD patients to examine if vitamin K2 supplementation can reduce progression of coronary artery calcification (CAC) over an 18-month study period. Patients were randomized to vitamin K2 group receiving menaquinone-7360 µg 3 times/wk or control group. The primary outcome was CAC scores at the end of the study period. The secondary outcomes were aortic valve calcification (AVC), carotid-femoral pulse wave velocity (cfPWV), aortic augmentation index (AIx), dephosphorylated undercarboxylated MGP (dp-ucMGP) levels, major adverse cardiac events (MACE), and vascular access events. Results: Of the 178 patients randomized, follow-up was completed for 138 patients. The CAC scores between the 2 groups were not statistically different at the end of 18 months (relative mean difference [RMD] 0.85, 95% CI 0.55-1.31). The secondary outcomes did not differ significantly in AVC (RMD 0.82, 95% CI 0.34-1.98), cfPWV (absolute mean difference [AMD] 0.55, 95% CI -0.50 to 1.60), and AIx (AMD 0.13, 95% CI -3.55 to 3.80). Supplementation with vitamin K2 did reduce dp-ucMGP levels (AMD -86, 95% CI -854 to -117). The composite outcome of MACE and mortality was not statistically different between the 2 groups (Hazard ratio = 0.98, 95% CI 0.50-1.94). Conclusion: Our study did not demonstrate a beneficial effect of vitamin K2 in reducing progression of VC in this population at the studied dose and duration.

Arterial microcalcification in atherosclerotic patients with and without chronic kidney disease: a comparative high-resolution scanning X-ray diffraction analysis.

Vascular calcification, albeit heterogeneous in terms of biological and physicochemical properties, has been associated with ageing, lifestyle, diabetes, and chronic kidney disease (CKD). It is unknown whether or not moderately impaired renal function (CKD stages 2-4) affects the physiochemical composition and/or the formation of magnesium-containing tricalcium phosphate ([Ca,Mg](3)[PO(4)](2), whitlockite) in arterial microcalcification. Therefore, a high-resolution scanning X-ray diffraction analysis (European Synchrotron Radiation Facility, Grenoble, France) utilizing histological sections of paraffin-embedded arterial specimens derived from atherosclerotic patients with normal renal function (n = 15) and CKD (stages 2-4, n = 13) was performed. This approach allowed us to spatially assess the contribution of calcium phosphate (apatite) and whitlockite to arterial microcalcification. Per group, the number of samples (13 vs. 12) with sufficient signal intensity and total lengths of regions (201 vs. 232 µm) giving rise to diffractograms ("informative regions") were comparable. Summarizing all informative regions per group into one composite sample revealed calcium phosphate/apatite as the leading mineral phase in CKD patients, whereas in patients with normal renal function the relative contribution of whitlockite and calcium phosphate/apatite was on the same order of magnitude (CKD, calcium phosphate/apatite 157 µm, whitlockite 38.7 µm; non-CKD, calcium phosphate/apatite 79.0 µm, whitlockite 94.1 µm; each p < 0.05). Our results, although based on a limited number of samples, indicate that chronic impairment of renal function affects local magnesium homeostasis and thus contributes to the physicochemical composition of microcalcification in atherosclerotic patients.

Serum fetuin-A and vitamin D in children with mild-to-severe chronic kidney disease: a cross-sectional study.

BACKGROUND: Fetuin-A and vitamin D are significant correlates of cardiovascular morbidity in paediatric chronic kidney disease (CKD) patients. It is thus far unknown, whether or not serum fetuin-A is affected by the vitamin D status or treatment with vitamin D preparations in these patients. METHODS: In a cross-sectional study, serum concentrations of fetuin-A, 25-hydroxyvitamin D(3) (25OHD) and 1,25-dihydroxyvitamin D(3) (calcitriol) levels were determined in 112 paediatric patients with mild-to-severe CKD (Stages 1-5) and after renal transplantation. A25OHD supplementation and/or calcitriol treatment were given in 64% of the patients. RESULTS: Fetuin-A levels were clearly reduced in dialysis patients but were comparable to healthy controls in those with moderate CKD and after transplantation. Although 64 and 46% of all patients received 25OHD and/or calcitriol treatment, 48 and 20% of patients were 25OHD and/or calcitriol deficient, respectively. Within the whole patient cohort, fetuin-A correlated with serum calcium and yearly weight-related 25OHD dosage (each P < 0.01) but not with the vitamin D status per se. Multiple regression analysis revealed the need for dialysis treatment and cumulative 25OHD dosage as independent predictors of fetuin-A concentrations (model r(2) = 0.17). In dialysis patients, fetuin-A was inversely correlated with serum C-reactive protein but positively correlated with cumulative calcitriol dosage and serum parathormone (each P < 0.01). CONCLUSIONS: Fetuin-A levels are clearly reduced in children on dialysis but not in those with moderate CKD and after transplantation. Besides the degree of microinflammation, the cumulative intake of 25OHD and calcitriol are significantly correlated to fetuin-A in these patients. The impact of vitamin D treatment appears to be at least partly mediated by serum calcium.