Phosphate as a cardiovascular risk factor: effects on vascular and endothelial function

Chronic kidney disease (CKD) is prevalent affecting 8.5% of the population in the UK and it is associated with premature cardiovascular disease (CVD) and death. The association between CKD and accelerated CVD arises as a consequence of traditional and non-traditional cardiovascular (CV) risk factors, including serum phosphate. Currently, there is no therapeutic intervention which has been shown to effectively reverse the increased CV risk in CKD. Phosphate metabolism is disordered in CKD particularly in the advanced stages (CKD 4 and 5). Even at the upper limit of the normal reference range, serum phosphate has been shown to be associated with CV mortality and morbidity including left ventricular hypertrophy, vascular calcification (VC) and endothelial dysfunction (ED). These associations also extend to populations without CKD. Serum phosphate is an appealing CV risk factor because it can be modified by dietary and pharmacological therapies. However, there has been no study linking lowered phosphate with improved outcomes and whilst several small mechanistic studies have suggested a role of phosphate in VC, oxidative stress and more recently ED, the precise mechanism of action of phosphate as a CV risk factor remains elusive. Our lack of understanding of the mechanism of action of phosphate makes it difficult to ascertain how to best manage phosphate. The hypothesis of this thesis is that long term exposure to elevated phosphate is associated with endothelial and vascular dysfunction and it is this which contributes to the elevated CV risk seen in CKD. Endothelial and vascular dysfunction will be evident in individual cell lines and in blood vessels as well as in humans, who have been exposed to sustained oral phosphate. This hypothesis has been explored in a translational manner in three ways: 1. The function of resistance vessels from rats and from humans, with and without CKD, has been studied. Experiments were performed looking at endothelium dependent and independent relaxation of vessels exposed to either normal or high phosphate concentration medium. The anti-oxidant, ascorbic acid and zaprinast, a phosphodiesterase 5 inhibitor were studied in the rat vessels to assess if these additions altered the vessels’ relaxation response. 2. Cells were cultured in normal and high phosphate concentration medium from the outset to mimic the chronicity of the uraemic environment. The nitric oxide (NO) pathway was studied considering eNOS expression, VEGF and cGMP production, intracellular calcium concentration and NO production. Proliferation and cell growth pathways have also been studied. 3. A cross-over clinical trial was performed in 19 healthy volunteers, without CKD. Volunteers attended for three visits. Prior to each visit, they fasted for 12 hours and performed a 24 hour urine collection. Bloods were drawn and endothelial function was measured with flow mediated dilatation and vascular stiffness with pulse wave velocity and analysis. There was a baseline visit and then two further visits. Prior to visit two, volunteers were randomised to take phosphate supplementation or phosphate binding medication for two weeks, followed by a wash out period and then volunteers took the other tablet for two weeks, before attending for a final visit. In rat vessels, there was impaired endothelium dependent and independent relaxation in vessels exposed to high phosphate concentration medium. Vessels in high phosphate produced less basal NO and less cGMP. The impaired relaxation could be ameliorated with the addition of a phosphodiesterase 5 inhibitor. This suggests reversibility of the detrimental effects of phosphate. In human vessels from patients without CKD, there was similarly attenuated endothelium dependent and independent relaxation. In vessels from patients with CKD, there was impaired endothelium dependent relaxation but independent relaxation was preserved. The CKD vessels exposed to normal phosphate medium relaxed to the same degree as their counterparts from patients without CKD, again suggesting that the effects of phosphate may be reversible. These effects are independent of intracellular calcium concentration which was found to be similar in cells cultured in normal or high phosphate medium. There was evidence of disruption to the NO pathway with reduced eNOS expression in human and rat endothelial cells and reduced protein kinase G expression in vascular smooth muscle cells. NO measured by the Griess reaction was lower in cells cultured in high phosphate medium. NO has an inhibitory effect on growth and cells cultured in high phosphate proliferated more (measured with the MTT assay) and were bigger than cells cultured in normal phosphate medium. Gene expression studies showed alterations in growth genes and cell cycle regulators. ED was demonstrated in healthy volunteers exposed to sustained oral phosphate loading. This was independent of serum phosphate level which was unchanged. Urinary phosphate and fibroblast growth factor 23 level independently predicted ED and suggest that whilst the normal homeostatic mechanisms maintain serum phosphate within the normal reference range, total body phosphate was elevated and urinary phosphate excretion was a surrogate for this. These relationships are novel and have not been demonstrated previously. It has previously been difficult to separate the effects of phosphate from other effects of the uraemic environment, including acidosis. The studies in this thesis have achieved this and the results provide strong evidence of an association between phosphate and ED. There is also evidence that these effects may be reversible. In contrast to conventional thinking that the effects of phosphate, like VC, are largely irreversible, these studies suggest that there may be dynamic effects of phosphate. This may be explained by alterations in intracellular phosphate. These findings have important implications for patients with CKD because they provide a sound explanation for the increased CV risk seen with phosphate and advocate further study of phosphate lowering (and outcome) as a therapeutic strategy to reverse this elevated CV risk

Effect of left atrial and ventricular abnormalities on renal transplant recipient outcome—a single-center study

Background: Premature cardiovascular (CV) death is the commonest cause of death in renal transplant recipients. Abnormalities of left ventricular (LV) structure (collectively termed uremic cardiomyopathy) and left atrial (LA) dilation, a marker of fluid status and diastolic function, are risk factors for reduced survival in patients with end stage renal disease (ESRD). In the present analysis, we studied the impact of pre-transplant LA and LV abnormalities on survival after successful renal transplantation (RT).<p></p> Methods: One hundred nineteen renal transplant recipients (first transplant, deceased donors) underwent cardiovascular MRI (CMR) as part of CV screening prior to inclusion on the waiting list. Data regarding transplant function and patient survival after transplantation were collected.<p></p> Results: Median post-transplant follow-up was 4.3 years (interquartile range (IQR) 1.9, 6.2). During the post-transplant period, 13 patients returned to dialysis after graft failure and 23 patients died with a functioning graft. Survival analyses, censoring for patients returning to dialysis, showed that pre-transplant LV hypertrophy and elevated LA volume were significantly associated with reduced survival after transplantation. Multivariate Cox regression analyses demonstrated that longer waiting time, poorer transplant function, presence of LV hypertrophy and higher LA volume on screening CMR and female sex were independent predictors of death in patients with a functioning transplant.<p></p> Conclusions: Presence of LVH and higher LA volume are significant, independent predictors of death in patients who are wait-listed and proceed with renal transplantation.<p></p> METHODS: One hundred nineteen renal transplant recipients (first transplant, deceased donors) underwent cardiovascular MRI (CMR) as part of CV screening prior to inclusion on the waiting list. Data regarding transplant function and patient survival after transplantation were collected.<p></p> RESULTS: Median post-transplant follow-up was 4.3 years (interquartile range (IQR) 1.9, 6.2). During the post-transplant period, 13 patients returned to dialysis after graft failure and 23 patients died with a functioning graft. Survival analyses, censoring for patients returning to dialysis, showed that pre-transplant LV hypertrophy and elevated LA volume were significantly associated with reduced survival after transplantation. Multivariate Cox regression analyses demonstrated that longer waiting time, poorer transplant function, presence of LV hypertrophy and higher LA volume on screening CMR and female sex were independent predictors of death in patients with a functioning transplant.<p></p> CONCLUSIONS: Presence of LVH and higher LA volume are significant, independent predictors of death in patients who are wait-listed and proceed with renal transplantation

Activated Protective Fabric

Disclosed are fibrous activated materials that can remove and/or deactivate potentially dangerous airborne agents from a gas or air stream. Disclosed materials are multi-layer materials that include a fibrous nonwoven interceptor layer and an active layer immediately adjacent the interceptor layer. The interceptor layer is a fibrous membrane of very low basis weight and defines a relatively low porosity, and the active layer describes geometries, chemistries, etc. that can entrap and/or decontaminate compounds contained in an airstream passing through the material. Disclosed materials can be utilized in forming protective garments, face masks, and the like

Serum phosphate and social deprivation independently predict all-cause mortality in chronic kidney disease

Background: Hyperphosphataemia is linked to cardiovascular disease and mortality in chronic kidney disease (CKD). Outcome in CKD is also affected by socioeconomic status. The objective of this study was to assess the associations between serum phosphate, multiple deprivation and outcome in CKD patients. Methods: All adult patients currently not on renal replacement therapy (RRT), with first time attendance to the renal outpatient clinics in the Glasgow area between July 2010 and June 2014, were included in this prospective study. Area socioeconomic status was assessed as quintiles of the Scottish Index of Multiple Deprivation (SIMD). Outcomes were all-cause and cardiovascular mortality and commencement of RRT. Results: The cohort included 2950 patients with a median (interquartile range) age 67.6 (53.6–76.9) years. Median (interquartile range) eGFR was 38.1 (26.3–63.5) ml/min/1.73 m 2 , mean (±standard deviation) phosphate was 1.13 (±0.24) mmol/L and 31.6 % belonged to the most deprived quintile (SIMD quintile I). During follow-up 375 patients died and 98 commenced RRT. Phosphate ≥1.50 mmol/L was associated with all-cause (hazard ratio (HR) 2.51; 95 % confidence interval (CI) 1.63-3.89) and cardiovascular (HR 5.05; 95 % CI 1.90–13.46) mortality when compared to phosphate 0.90–1.09 mmol/L in multivariable analyses. SIMD quintile I was independently associated with all-cause mortality. Phosphate did not weaken the association between deprivation index and mortality, and there was no interaction between phosphate and SIMD quintiles. Neither phosphate nor SIMD predicted commencement of RRT. Conclusions Multiple deprivation and serum phosphate were strong, independent predictors of all-cause mortality in CKD and showed no interaction. Phosphate also predicted cardiovascular mortality. The results suggest that phosphate lowering should be pursued regardless of socioeconomic status

Non-contrast renal magnetic resonance imaging to assess perfusion and corticomedullary differentiation in health and chronic kidney disease

AIMS Arterial spin labelling (ASL) MRI measures perfusion without administration of contrast agent. While ASL has been validated in animals and healthy volunteers (HVs), application to chronic kidney disease (CKD) has been limited. We investigated the utility of ASL MRI in patients with CKD. METHODS We studied renal perfusion in 24 HVs and 17 patients with CKD (age 22-77 years, 40% male) using ASL MRI at 3.0T. Kidney function was determined using estimated glomerular filtration rate (eGFR). T1 relaxation time was measured using modified look-locker inversion and xFB02;ow-sensitive alternating inversion recovery true-fast imaging and steady precession was performed to measure cortical and whole kidney perfusion. RESULTS T1 was higher in CKD within cortex and whole kidney, and there was association between T1 time and eGFR. No association was seen between kidney size and volume and either T1, or ASL perfusion. Perfusion was lower in CKD in cortex (136 ± 37 vs. 279 ± 69 ml/min/100 g; p < 0.001) and whole kidney (146 ± 24 vs. 221 ± 38 ml/min/100 g; p < 0.001). There was significant, negative, association between T1 longitudinal relaxation time and ASL perfusion in both the cortex (r = -0.75, p < 0.001) and whole kidney (r = -0.50, p < 0.001). There was correlation between eGFR and both cortical (r = 0.73, p < 0.01) and whole kidney (r = 0.69, p < 0.01) perfusion. CONCLUSIONS Significant differences in renal structure and function were demonstrated using ASL MRI. T1 may be representative of structural changes associated with CKD; however, further investigation is required into the pathological correlates of reduced ASL perfusion and increased T1 time in CKD

Risk factors of ischemic stroke and subsequent outcome in hemodialysis patients

Background and purpose: End stage renal disease (ESRD) requiring hemodialysis (HD) carries up to a 10-fold greater risk of stroke than normal renal function. Knowledge concerning risk factors and management strategies derived from the general population may not be applicable to those with ESRD. We studied a large ESRD population to identify risk factors and outcomes for stroke. Methods: All adult patients receiving HD for ESRD from 01/01/2007 to 31/12/2012 were extracted from the electronic patient record. Variables associated with stroke were identified by survival analysis; demographic, clinical, imaging and dialysis related variables were assessed and case-fatality determined. Follow-up was until 31/12/2013. Results: 1382 patients were identified (mean age 60.5 years, 58.5% male). The prevalence of AF was 21.2% and 59.4% were incident HD patients. 160 (11.6%) experienced a stroke during 3471 patient-years of follow-up (95% ischemic). Stroke incidence was 41.5/1000 patient-years in prevalent and 50.1/1000 patient-years in incident HD patients. Factors associated with stroke on regression analysis were prior stroke, diabetes and age at starting renal replacement therapy. AF was not significantly associated with stroke and warfarin did not affect stroke risk in warfarin treated patients. Fatality was 18.8% at 7, 26.9% at 28 and 56.3% 365 days after stroke.<p></p> Conclusions: Incidence of stroke is high in patients with ESRD on HD with high case-fatality. Incident HD patients had the highest stroke incidence. Many, but not all, important risk factors commonly associated with stroke in the general population were not associated with stroke in patients receiving HD

Results from a Phase 1 Study of Sodium Selenite in Combination with Palliative Radiation Therapy in Patients with Metastatic Cancer.

In preclinical studies, selenite had single agent activity and radiosensitized tumors in vivo. Here we report results from a Phase 1 trial in 15 patients with metastatic cancer treated with selenite (5.5 to 49.5 mg) orally as a single dose 2 hours before each radiation therapy (RT) treatment. Patients received RT regimens that were standard of care. The primary objective of the study was to assess the safety of this combination therapy. Secondary objectives included measurement of pharmacokinetics (PK) and evaluation of efficacy. Endpoints included assessment of PK, toxicity, tumor response, and pain before and after treatment. The half-life of selenite was 18.5 hours. There were no adverse events attributable to selenite until the 33 mg dose level, at which the primary toxicities were grade 1 GI side effects. One patient treated with 49.5 mg had grade 2 GI toxicity. Although this was not a DLT, it was felt that the highest acceptable dose in this patient population was 33 mg. Most patients had stabilization of disease within the RT fields, with some demonstrating objective evidence of tumor regression. Most patients had a marked improvement in pain and seven out of nine patients with prostate cancer had a decrease in PSA ranging from 11-78%. Doses up to 33 mg selenite were well tolerated in combination with RT. A randomized, well controlled study is needed at the 33 mg dose level to determine if selenite results in clinically meaningful improvements in the response to palliative RT

The Earth Microbiome Project: Meeting report of the "1 EMP meeting on sample selection and acquisition" at Argonne National Laboratory October 6 2010.

This report details the outcome the first meeting of the Earth Microbiome Project to discuss sample selection and acquisition. The meeting, held at the Argonne National Laboratory on Wednesday October 6(th) 2010, focused on discussion of how to prioritize environmental samples for sequencing and metagenomic analysis as part of the global effort of the EMP to systematically determine the functional and phylogenetic diversity of microbial communities across the world

Research methods of Talking About The Smokes: an International Tobacco Control Policy Evaluation Project study with Aboriginal and Torres Strait Islander Australians

Objective: To describe the research methods and baseline sample of the Talking About The Smokes (TATS) project.Design: The TATS project is a collaboration between research institutions and Aboriginal community-controlled health services (ACCHSs) and their state and national representative bodies. It is one of the studies within the International Tobacco Control Policy Evaluation Project, enabling national and international comparisons. It includes a prospective longitudinal study of Aboriginal and Torres Strait Islander smokers and recent ex-smokers; a survey of non-smokers; repeated cross-sectional surveys of ACCHS staff; and descriptions of the tobacco policies and practices at the ACCHSs. Community members completed face-to-face surveys; staff completed surveys on paper or online. We compared potential biases and the distribution of variables common to the main community baseline sample and unweighted and weighted results of the 2008 National Aboriginal and Torres Strait Islander Social Survey (NATSISS). The baseline survey (Wave 1) was conducted between April 2012 and October 2013.Setting and participants: 2522 Aboriginal and Torres Strait Islander people in 35 locations (the communities served by 34 ACCHSs and one community in the Torres Strait), and 645 staff in the ACCHSs.Main outcome measures: Sociodemographic and general health indicators, smoking status, number of cigarettes smoked per day and quit attempts.Results: The main community baseline sample closely matched the distribution of the Aboriginal and Torres Strait Islander population in the weighted NATSISS by age, sex, jurisdiction and remoteness. There were inconsistent differences in some sociodemographic factors between our sample and the NATSISS: our sample had higher proportions of unemployed people, but also higher proportions who had completed Year 12 and who lived in more advantaged areas. In both surveys, similar percentages of smokers reported having attempted to quit in the past year, and daily smokers reported similar numbers of cigarettes smoked per day.Conclusion: The TATS project provides a detailed and nationally representative description of Aboriginal and Torres Strait Islander smoking behaviour, attitudes, knowledge and exposure to tobacco control activities and policies, and their association with quitting

Deleterious effects of phosphate on vascular and endothelial function via disruption to the nitric oxide pathway

Background: Hyperphosphataemia is an independent risk factor for accelerated cardiovascular disease in chronic kidney disease (CKD), although the mechanism for this is poorly understood. We investigated the effects of sustained exposure to a high-phosphate environment on endothelial function in cellular and preclinical models, as well as in human subjects. Methods: Resistance vessels from rats and humans (± CKD) were incubated in a normal (1.18 mM) or high (2.5 mM) phosphate concentration solution and cells were cultured in normal- (0.5 mM) or high-phosphate (3 mM) concentration media. A single-blind crossover study was performed in healthy volunteers, receiving phosphate supplements or a phosphate binder (lanthanum), and endothelial function measured was by flow-mediated dilatation. Results: Endothelium-dependent vasodilatation was impaired when resistance vessels were exposed to high phosphate; this could be reversed in the presence of a phosphodiesterase-5-inhibitor. Vessels from patients with CKD relaxed normally when incubated in normal-phosphate conditions, suggesting that the detrimental effects of phosphate may be reversible. Exposure to high-phosphate disrupted the whole nitric oxide pathway with reduced nitric oxide and cyclic guanosine monophosphate production and total and phospho endothelial nitric oxide synthase expression. In humans, endothelial function was reduced by chronic phosphate loading independent of serum phosphate, but was associated with higher urinary phosphate excretion and serum fibroblast growth factor 23. Conclusions: These directly detrimental effects of phosphate, independent of other factors in the uraemic environment, may explain the increased cardiovascular risk associated with phosphate in CKD