Vascular Dysfunction In Chronic Kidney Disease Research Articles

Targeting Uremic Toxins to Prevent Peripheral Vascular Complications in Chronic Kidney Disease.

Chronic kidney disease (CKD) exhibits progressive kidney dysfunction and leads to disturbed homeostasis, including accumulation of uremic toxins, activated renin-angiotensin system, and increased oxidative stress and proinflammatory cytokines. Patients with CKD are prone to developing the peripheral vascular disease (PVD), leading to poorer outcomes than those without CKD. Cumulative evidence has showed that the synergy of uremic milieu and PVD could exaggerate vascular complications such as limb ischemia, amputation, stenosis, or thrombosis of a dialysis vascular access, and increase mortality risk. The role of uremic toxins in the pathogenesis of vascular dysfunction in CKD has been investigated. Moreover, growing evidence has shown the promising role of uremic toxins as a therapeutic target for PVD in CKD. This review focused on uremic toxins in the pathophysiology, in vitro and animal models, and current novel clinical approaches in reducing the uremic toxin to prevent peripheral vascular complications in CKD patients.

Nutraceuticals as a potential adjunct therapy toward improving vascular health in CKD.

Chronic kidney disease (CKD) is a major public health epidemic and increases risk for developing cardiovascular disease (CVD). Vascular dysfunction is a major independent risk factor toward increased risk for CVD in CKD. Several mechanisms have been postulated to result in vascular dysfunction in CKD, including oxidative stress-mediated inflammation by redox imbalance and reduced nitric oxide (NO) bioavailability and synthesis. Therefore, strategies that decrease oxidative stress and/or increase NO bioactivity may have major clinical implications toward improving vascular health and reducing the burden of CVD in CKD. Nutraceutical therapy in the form of polyphenols, dietary nitrates, or selective mitochondria-targeting therapies has recently been shown to improve vascular function by reducing oxidative stress and/or increasing NO bioavailability and synthesis. This review, therefore, highlights these three emerging nutraceuticals recently implicated in pathophysiological improvement of vascular function in CKD. This review also describes those pathophysiological mechanisms thought to be responsible for the beneficial effects on the vasculature and possible experimental considerations that may exist within human CKD populations. It is clear throughout this review that human-based mechanistic preclinical and health-related clinical studies are lacking regarding whether nutraceuticals do indeed improve vascular function in patients with CKD. As such, a comprehensive, detailed, and fully integrated understanding of nutraceuticals and vasculature function is necessary in patients with CKD. Many opportunities exist for original mechanistic and therapeutic discoveries and investigations on select nutraceuticals and their impact on vascular outcomes in patients with CKD, and these will remain exciting avenues of research in the future.

Abstract 209: NAD(P)H Oxidase-Derived Superoxide Contributes to Impaired Cutaneous Microvascular Function in Chronic Kidney Disease

Endothelial dysfunction occurs in chronic kidney disease (CKD) and cardiovascular disease is the most common cause of death in these patients. Oxidative stress has been shown to be a mechanism of vascular dysfunction in CKD. We utilized the cutaneous circulation to test the hypothesis that superoxide derived from NAD(P)H oxidase and xanthine oxidase impair nitric oxide (NO)-dependent cutaneous vasodilation patients with CKD. Twenty subjects, 10 stage 3 and 4 CKD patients (61±4 years; 5 male/5 female; eGFR: 39 ± 4 ml·min -1 ·1.73m -2 ) and 10 healthy controls (HC) (55±2 years; 4 male/6 female; eGFR: >60 ml·min -1 ·1.73m -2 ) were instrumented with 4 intradermal microdialysis fibers in the forearm for the local delivery of 1) Ringers solution (Control), 2) 10 μM Tempol to scavenge superoxide, 3) 100 μM apocynin to inhibit NAD(P)H oxidase, and 4) 10 μM allopurinol to inhibit xanthine oxidase. Red blood cell (RBC) flux was measured via laser Doppler flowmetry during standardized local heating (42°C). After the local heating response was established, 10 mM L-NAME was infused into all four sites to quantify the NO-dependent portion of the response. Cutaneous vascular conductance (CVC) was calculated as RBC flux/mean arterial pressure and all data are presented as a percentage of maximum CVC achieved during 28mM sodium nitroprusside infusion at 43°C. The plateau in cutaneous vasodilation was attenuated in CKD at the control site (CKD: 77±3 vs. HC: 88±3 %, p<0.05). Tempol and apocynin augmented the plateau in cutaneous vasodilation in CKD patients (Tempol: 88±2, apocynin: 91±2 %, p<0.05 vs. CKD control site) but had no effect in the healthy control group. The NO-dependent portion of the response was reduced in CKD at the control site (CKD: 41±4 vs. HC: 58±2 %, p<0.05). Tempol and apocynin augmented NO-dependent portion of the response in CKD patients (Tempol: 58±3, apocynin: 58±4 %, p<0.05 vs. CKD control site) but had no effect in the healthy control group. Inhibition of xanthine oxidase did not alter the plateau in cutaneous vasodilation in either group (p>0.05). These data suggest that NAD(P)H oxidase is a source of superoxide and contributes to microvascular dysfunction in CKD.

Insulin Resistance, Inflammation, and Blood Pressure Determine Vascular Dysfunction in CKD

Conventional cardiovascular risk equations underestimate the risk for cardiovascular disease (CVD) in patients with chronic kidney disease (CKD), implying a role for novel risk factors. Our aim was to compare vascular function and arterial compliance, known markers of CVD, between patients with CKD and healthy controls and examine their association with traditional and novel CVD risk factors. Vascular function was determined by using high-resolution ultrasonography to measure brachial artery endothelial-dependent flow-mediated dilatation (FMD) and endothelial-independent glyceryl trinitrate (GTN)-mediated dilatation. Arterial compliance was measured by using pulse contour analysis to generate large-artery (C1) and small-artery (C2) compliance. We also examined the relationship between vascular function, arterial compliance and blood pressure, lipid and lipoprotein levels, insulin resistance, inflammation, oxidative stress, and calcium and phosphate levels in 105 patients with CKD and 40 healthy controls. Vascular function and arterial compliance were significantly impaired in patients with CKD compared with healthy controls: mean FMD, 3.8% +/- 0.3% (SE) versus 5.7% +/- 0.6%; GTN-mediated dilatation, 15.7% +/- 0.9% versus 19.6% +/- 1.0%; C1, geometric mean, 12.1 mL/mm Hg; 95% confidence interval (CI), 11.2 to 13.1 versus 15.1 mL/mm Hg; 95% CI, 13.7 to 16.5; and C2, 3.8 mL/mm Hg; 95% CI, 3.4 to 4.3 versus 5.0 mL/mm Hg; 95% CI, 4.2 to 6.0; all P < 0.05. Patients with CKD had greater waist-hip ratios, systolic blood pressures (SBPs), pulse pressures, triglyceride levels, oxidized low-density lipoprotein levels, high-sensitivity interleukin 6 levels, and Homeostasis Model Assessment (HOMA) scores (all P < 0.05) and lower high-density lipoprotein levels (P < 0.001). In patients with CKD, HOMA score and SBP were associated negatively with FMD (model R(2) = 0.28; P < 0.001), and SBP and waist-hip ratio were associated negatively with GTN-mediated dilatation (model R(2) = 0.25; P < 0.001). Pulse pressure was associated negatively with C1 (R(2) = 0.37; P < 0.001), and pulse pressure and high-sensitivity interleukin 6 level were associated negatively with C2 (model R(2) = 0.36; P < 0.001). Insulin resistance, inflammation, systolic hypertension, and increased pulse pressure, but not dyslipidemia, were associated with vascular dysfunction and may be targets for future interventional strategies to reduce CVD risk in patients with CKD.