Role of hyperphosphatemia-mediated vascular calcification in cardiovascular outcomes and its management

Manifestations of left ventricular dysfunction and arrhythmia in patients with chronic hypoparathyroidism and pseudohypoparathyroidism: a preliminary study

BACKGROUND

Cardiac damage triggered by severe hypocalcemia is well known. However, the role of chronic hypoparathyroidism (HP) and pseudohypoparathyroidism (PHP) in cardiac health is still unclear. We investigated the effect of chronic HP and PHP on cardiac structure and conductive function in patients compiling with treatment.

METHODS

The study included 18 patients with HP and eight with PHP aged 45.4 ± 15.4 and 22.1 ± 6.4 years, respectively with a previously regular follow-up. In addition, 26 age- and sex-matched healthy controls were included. General characteristics and biochemical indices were recorded. Cardiac function and structure were assessed by estimation of myocardial enzymes, B-type natriuretic peptide (BNP), and echocardiography. The 12-lead electrocardiogram and 24-h Holter electrocardiography were performed to evaluate the conductive function.

RESULTS

Levels of serum calcium in HP and PHP were 2.05 ± 0.16 mmol/L and 2.25 ± 0.19 mmol/L, respectively. The levels of myocardial enzyme and BNP were within the normal range. Adjusting for age at evaluation and body mass index, all M-mode measurements, left ventricular mass (LVM), LVM index (LVMI) and relative wall thickness (RWT) were comparable between patients and controls. Prolongation of corrected QT (QTc) intervals occurred in 52.6% (10/19) of patients, and 6.7% (1/15) of patients manifested more than 100 episodes of supraventricular and ventricular extrasystoles, as well as supraventricular tachycardia. None of the above arrhythmias was related to a severe clinical event.

CONCLUSIONS

From this pilot study, patients diagnosed with HP and PHP and well-controlled serum calcium levels manifested normal cardiac morphology and ventricular function, except for prolonged QTc intervals, and a small percentage of mild arrhythmias needing further investigation.

Factors influencing pathological ankle-brachial index values along the chronic kidney disease spectrum: the NEFRONA study

Background

The ankle-brachial index (ABI) is widely used to diagnose subclinical peripheral artery disease (PAD) in the general population, but data assessing its prevalence and related factors in different chronic kidney disease (CKD) stages are scarce. The aim of this study is to evaluate the prevalence and associated factors of pathological ABI values in CKD patients.

Methods

NEFRONA is a multicentre prospective project that included 2445 CKD patients from 81 centres and 559 non-CKD subjects from 9 primary care centres across Spain. A trained team collected clinical and laboratory data, performed vascular ultrasounds and measured the ABI.

Results

PAD prevalence was higher in CKD than in controls (28.0 versus 12.3%, P < 0.001). Prevalence increased in more advanced CKD stages, due to more patients with an ABI ≥1.4, rather than ≤0.9. Diabetes was the only factor predicting both pathological values in all CKD stages. Age, female sex, carotid plaques, higher carotid intima-media thickness, higher high-sensitivity C-reactive protein (hsCRP) and triglycerides, and lower 25-hydroxi-vitamin D were independently associated with an ABI ≤0.9. Higher phosphate and hsCRP, lower low-density lipoprotein (LDL)-cholesterol and dialysis were associated with an ABI ≥1.4. A stratified analysis showed different associated factors in each CKD stage, with phosphate being especially important in earlier CKD, and LDL-cholesterol being an independent predictor only in Sage 5D CKD.

Conclusions

Asymptomatic PAD is very prevalent in all CKD stages, but factors related to a low or high pathological ABI differ, revealing different pathogenic pathways. Diabetes, dyslipidaemia, inflammation and mineral-bone disorders play a role in the appearance of PAD in CKD.

Activation of the Nrf2-ARE Signaling Pathway Prevents Hyperphosphatemia-Induced Vascular Calcification by Inducing Autophagy in Renal Vascular Smooth Muscle Cells

This study investigates the effect of nuclear factor erythroid 2-related factor 2-antioxidant response element (Nrf2-ARE) signaling pathway in vascular calcification (VC) via inducing Autophagy in renal vascular smooth muscle cells (VSMCs). VSMCs were assigned into six experimental groups: the normal control, high phosphorus, si-negative control (si-NC), Nrf2-siRNA, over-expressed Nrf2, and negative control (NC) groups. RT-PCR was applied to detect the mRNA expressions of the desired Nrf2-ARE signaling pathway-related genes (Nrf2, NQO-1, HO-1, γ-GCS). The protein products of these genes: apoptosis-related genes (LC3I and LC3II), osteogenic marker proetins (Runt-related transcription factor 2) Runx2 and BMP2 were all detected by Western blotting. Autophagosomes in VSMCs were observed under a transmission electron microscope. We discovered an increased calcium ion concentration and upregulated Runx2, BMP2, Nrf2, HO-1, γ-GCS, NQO-1, and LC3II/LC3I expressions in the high phosphorous, si-NC and Nrf2-siRNA, and NC groups, compared with the normal control group. Compared to the high phosphorus and si-NC groups, higher levels of Runx2 and BMP2 but decreased Nrf2, HO-1, γ-GCS, NQO-1, and LC3II/LC3I expressions were detected in the Nrf2-siRNA group. The high phosphorus, si-NC and over-expressed Nrf2 experimental groups all had increased Nrf2, NQO-1, HO-1, γ-GCS, and LC3II/LC3I expressions as well as high numbers of autophagosomes compared with the normal control group. Finally, we detected a lower amount of autophagosomes presence and Nrf2, NQO-1, HO-1 γ-GCS, and LC3II/LC3 protein expression of Nrf2-siRNA group than that of the high phosphorus and si-NC groups. Activation of Nrf2-ARE signaling pathway may prevent hyperphosphatemia-induced VC by inducing autophagy in VSMCs. J. Cell. Biochem. 118: 4708-4715, 2017. © 2017 Wiley Periodicals, Inc.

Preclinical studies of VS-505: a non-absorbable highly effective phosphate binder

BACKGROUND AND PURPOSE

Phosphate imbalance is often present in chronic kidney disease (CKD), and it contributes to a higher cardiovascular mortality rate. A phosphate binder is typically part of a treatment strategy for controlling phosphate imbalance. However, safety concerns and low compliance are two well-recognized disadvantages of on-market phosphate binders. This report describes the preclinical studies of VS-505, a non-absorbable, calcium- and aluminum-free, plant-derived polymer currently being evaluated in haemodialysis patients in Australia.

EXPERIMENTAL APPROACH

Normal Sprague Dawley (SD) rats or uraemic SD rats induced by 5/6 nephrectomy fed a high-phosphate diet were treated with VS-505 or sevelamer (0.05-10% in food) for 5 and 28 days respectively.

KEY RESULTS

Urinary and serum phosphate levels were significantly elevated in untreated rats, and were decreased by VS-505 and sevelamer. VS-505 increased faecal phosphate levels in a dose-dependent manner. High-phosphate diet also caused an increase in serum FGF-23 and parathyroid hormone in nephrectomized (NX) rats, effects prevented by VS-505 or sevelamer. Significant aortic calcification was observed in NX rats treated with 5% sevelamer, whereas VS-505 at all doses tested did not show effects. VS-505 had no effects on small intestine histomorphology and intestinal sodium-dependent phosphate cotransporter gene expression. In vitro characterizations showed that VS-505 has a relatively high density and low expansion volume when exposed to simulated gastric fluid.

CONCLUSIONS AND IMPLICATIONS

VS-505 is a safe and effective phosphate binder and may offer the advantage of having a reduced pill burden and minimal GI side effects for CKD patients.