Active vitamin D and accelerated progression of aortic stiffness in hemodialysis patients: a longitudinal observational study

Can we reverse arterial stiffness by intervening on CKD-MBD biomarkers?

The increased cardiovascular risk of chronic kidney disease may in part be the consequence of arterial stiffness, a typical feature of kidney failure. Deranged homeostasis of minerals and hormones involved (CKD-MBD), are also strongly associated with this increased risk. It is well established that CKD-MBD is a main driver of vascular calcification, which in turn worsens arterial stiffness. However, there are other contributors to arterial stiffness in CKD than calcification. An overlooked possibility is that CKD-MBD may have detrimental effects on this potentially better modifiable component of arterial stiffness. In this review, the individual contributions of short-term changes in calcium, phosphate, PTH, vitamin D, magnesium, and FGF23 to arterial stiffness, in most studies assessed as pulse wave velocity, is summarized. Indeed, there is evidence from both observational studies and interventional trials that higher calcium concentrations can worsen arterial stiffness. This, however, has not been shown for phosphate, and it seems unlikely that, apart from being a contributor to vascular calcification and having effects on the microcirculation, phosphate has no acute effect on large artery stiffness. Several interventional studies, both by infusing PTH and by abrupt lowering PTH by calcimimetics or surgery, virtually ruled out direct effects on large artery stiffness. A well-designed trial using both active and nutritional vitamin D as intervention found a beneficial effect for the latter. Unfortunately, the study had a baseline imbalance and other studies did not support its finding. Both magnesium and FGF23 do not seem do modify central arterial stiffness.

Outcomes of elderly peritoneal dialysis patients: 65-74 years old versus ≥ 75 years old

OBJECTIVE

To analyze the clinical data of elderly patients with peritoneal dialysis (PD) and compare patient and technique survival rates between Group 1 (65-74 years old) and Group 2 (≥75 years old).

METHODS

This retrospective study enrolled 296 elderly patients (≥65 years old) on maintenance PD who were admitted to the Peritoneal Dialysis Center of the Second Hospital of Soochow University. The patients were categorized by outcome into ongoing PD, changed to hemodialysis, renal recovery dialysis stopped, or death groups. The patients were divided into Group 1 (65-74 years old) and Group 2 (≥75 years old). Patient survival and technique survival rates were calculated by the Kaplan-Meier method. Factors associated with patient survival were analyzed using the Cox regression model.

RESULTS

There were 176 (59.5%) subjects in Group 1 and 120 (40.5%) subjects in Group 2. The primary causes of death were cardiovascular events, peritonitis, and other infections. The patient survival rates at 1, 3, and 5 years were 91.2%, 68.0%, and 51.3% in Group 1 and 76.8%, 37.5%, and 17.6% in Group 2 (p < 0.001, HR 0.387, 95% CI 0.282-0.530). There was no statistically significant difference in the technique survival rate between the two groups (p = 0.54).

CONCLUSION

The elderly PD patients in this cohort mostly died from cardiovascular events, with a higher patient survival rate in Group 1 and similar technique survival in both groups. Older age, lower prealbumin, higher creatinine, not being on activated vitamin D, and high Charlson's comorbidity index (CCI) score were independent risk factors for death.

The Correlation between Serum Sclerostin Level and Arterial Stiffness in Peritoneal Dialysis Patients

Objective

To study the correlation between serum sclerostin (SO) and arterial stiffness in peritoneal dialysis (PD) patients.

Methods

The study included 50 Parkinson's disease (PD) patients on continuous ambulatory peritoneal dialysis (CAPD) for more than 6 months at the nephrology department of our hospital. Without regard for age, the eligible patients were assigned to a low PWV group and a high PWV group with brachial-ankle pulse wave velocity (Ba PWV) of 1400 cm/s as the cutoff value. Patient characteristics such as age, gender, height, weight, BMI, smoking history, dialysis age, systolic blood pressure (SBP), diastolic blood pressure (DBP), urea clearance index (Kt/V), residual renal function (RRF), and diabetes mellitus (DM) were analyzed. Biochemical indices for analysis include hemoglobin (Hb), albumin (ALB), total cholesterol (TC), urea nitrogen (BUN), creatinine (CREA), triglyceride (TG), uric acid (UA), parathyroid hormone (PTH), blood phosphorus(P), fasting blood glucose (GLU), corrective calcium (Ca), calcium-phosphorus product, low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), SO, and arterial stiffness.

Results

There were 9 males and 16 females in the low PWV group and 12 males and 13 females in the high PWV group. Statistical significance was absent in patient characteristics despite more males in the high PWV group (P=0.055). The low PWV group had significantly lower mean age, SBP, SO, and PWV level, fewer diabetic patients, and higher CREA than the control group. Analysis of PWV-related factors showed that PWV was positively correlated with age, P, Ca, GLU, SBP, PTH, and SO while negatively correlated with CREA. Multiple stepwise regression analysis showed that age, SO, and SBP demonstrated great potential to predict PWV (P < 0.05).

Conclusion

The degree of vascular sclerosis is highly correlated with SO level in Parkinson's disease patients, which might provide a theoretical basis for the evaluation of cardiovascular illness in Parkinson's disease patients. High serum sclerostin level is a risk factor for deteriorated arterial stiffness. Given the limited sample size, the relevant results require further validation by expanding the sample size.

Mineral Bone Abnormalities and Vascular Calcifications

Vascular calcification (VC) is common in chronic kidney disease, increases in prevalence as patients progress to end-stage renal disease, and is significantly associated with mortality. VC is a complex and highly regulated process similar to bone formation whereby hydroxyapatite crystals deposit in the intimal or medial layer of arteries. Mineral bone abnormalities are common in chronic kidney disease; reduction in glomerular filtration rate and changes in vitamin D, parathyroid hormone, and fibroblast growth factor 23 result in the dysregulation of phosphorus and calcium metabolism. Cell culture studies, animal models, and observational and clinical studies all suggest this abnormal mineral metabolism plays a role in the initiation and progression of VC in kidney disease. This review will focus on these mineral bone abnormalities and how they may contribute to mechanisms that induce VC in kidney disease.

High calcium, phosphate and calcitriol supplementation leads to an osteocyte-like phenotype in calcified vessels and bone mineralisation defect in uremic rats

A link between vascular calcification and bone anomalies has been suggested in chronic kidney disease (CKD) patients with low bone turnover disease. We investigated the vascular expression of osteocyte markers in relation to bone microarchitecture and mineralization defects in a model of low bone turnover CKD rats with vascular calcification. CKD with vascular calcification was induced by 5/6 nephrectomy followed by high calcium and phosphate diet, and vitamin D supplementation (Ca/P/VitD). CKD + Ca/P/VitD group (n = 12) was compared to CKD + normal diet (n = 12), control + normal diet (n = 8) and control + Ca/P/VitD supplementation (n = 8). At week 6, tibia, femurs and the thoracic aorta were analysed by Micro-Ct, histomorphometry and for expression of osteocyte markers. High Ca/P/VitD treatment induced vascular calcification only in CKD rats, suppressed serum parathyroid hormone levels and led to higher sclerostin, DKK1 and FGF23 serum levels. Expression of sclerostin, DKK1 and DMP1 but not FGF23 were increased in calcified vessels from CKD + Ca/P/VitD rats. Despite low parathyroid hormone levels, tibia bone cortical thickness was significantly lower in CKD + Ca/P/VitD rats as compared to control rats fed a normal diet, which is likely the result of radial growth impairment. Finally, Ca/P/VitD treatment in CKD rats induced a bone mineralization defect, which is likely explained by the high calcitriol dose. In conclusion, Ca/P/VitD supplementation in CKD rats induces expression of osteocyte markers in vessels and bone mineralisation anomalies. Further studies should evaluate the mechanisms of high dose calcitriol-induced bone mineralisation defects in CKD.

Prognostic value of bone- and vascular-derived molecular biomarkers in hemodialysis and renal transplant patients: a systematic review and meta-analysis

Background

Patients undergoing hemodialysis and kidney graft recipients are high-risk populations for cardiovascular and all-cause mortality. Fibroblast growth factor 23 (FGF23), osteoprotegerin (OPG), RANK ligand, osteopontin (OPN), Klotho protein and bone morphogenetic protein-7 (BMP-7) are bone- and vascular-derived molecular biomarkers that have been shown to be associated with cardiovascular surrogate end points; however, currently available data on the prognostic value of these biomarkers is inconsistent. The aim of the present study was to conduct a systematic review and meta-analysis in order to summarize the available evidence on the association of molecular biomarkers with mortality in individuals undergoing hemodialysis and renal transplant patients.

Methods

Two databases (MEDLINE and Embase) were systematically searched. Studies were eligible if the association of biomarker and mortality was reported as time-to-event data [hazard Ratio (HR)] or as effect size with a fixed time of follow-up [odds Ratio (OR)]. Abstracted HRs were converted onto a standard scale of effect and combined using a random effects model.

Results

From a total of 1170 studies identified in initial searches, 21 met the inclusion criteria. In hemodialysis patients, comparing the lower third with the upper third of baseline FGF23 distribution, pooled HRs (95% confidence intervals) were 1.94 (1.47, 2.56) for all-cause mortality and 2.4 (1.64, 3.51) for cardiovascular mortality. For the same comparison of baseline OPG distribution, pooled HRs were 1.8 (0.95, 3.39) for all-cause mortality and 2.53 (1.29, 4.94) for cardiovascular mortality. Reported risk estimates of RANK ligand, OPN, Klotho protein and BMP-7 were not suitable for pooling; however, only Klotho protein was significantly related to mortality. For kidney graft recipients, four studies that investigated the relationship of FGF23 and OPG with mortality were identified, all of which reported a significant association.

Conclusions

In hemodialysis patients, FGF23 is a predictor of all-cause and cardiovascular mortality, whereas the predictive value of OPG is restricted to cardiovascular mortality. Further studies are needed in order to gain insight into the prognostic value of these biomarkers in renal transplant recipients.

Association Between Serum 25-Hydroxy Vitamin D Levels and Blood Pressure Among Adolescents in Two Resource-Limited Settings in Peru

INTRODUCTION

Serum 25-hydroxyvitamin D (25OHD) deficiency (<50 nmol/l or 20 ng/ml) has been associated with increased blood pressure (BP) in observational studies. A paucity of data on this relationship is available in Latin American or child populations. This study investigates the association between 25OHD levels and BP in adolescents at risk for vitamin D deficiency in 2 Peruvian settings.

METHODS

In a population-based study of 1,441 Peruvian adolescents aged 13-15 years, 1,074 (75%) provided a serum blood sample for 25OHD analysis and BP measurements. Relationships between 25OHD and BP metrics were assessed using multiple linear regressions, adjusted for anthropometrics and sociodemographic factors.

RESULTS

25OHD deficiency was associated with an elevated diastolic BP (DBP) (1.09 mm Hg increase, 95% confidence interval: 0.04 to 2.14; P = 0.04) compared to nondeficient adolescents. Systolic BP (SBP) trended to increase with vitamin D deficiency (1.30 mm Hg increase, 95% confidence interval: -0.13 to 2.72; P = 0.08). Mean arterial pressure (MAP) was also greater in adolescents with 25OHD (1.16 mm Hg increase, 95% confidence interval: 0.10 to 2.22; P = 0.03). SBP was found to demonstrate a U-shaped relationship with 25OHD, while DBP and MAP demonstrated inverse J-shaped relationships with serum 25OHD status. The association between 25OHD deficiency and BP was not different across study sites (all P ≥ 0.19).

DISCUSSION

Adolescents deficient in 25OHD demonstrated increased DBP and MAP and a trend toward increased SBP, when compared to nondeficient subjects. 25OHD deficiency early in life was associated with elevated BP metrics, which may predispose risk of hypertension later in adulthood.