Mineral Metabolites, Angiotensin II Inhibition and Outcomes in Advanced Chronic Kidney Disease.

BACKGROUND: Evidence suggests that the renin-angiotensin-aldosterone system (RAAS) interacts with the vitamin D-fibroblast growth factor 23-Klotho axis. We investigated whether circulating mineral metabolism markers modify outcomes in response to RAAS inhibition in subjects with advanced chronic kidney disease (CKD). METHODS: In this retrospective cohort study, we analyzed the association of angiotensin-converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB) use with all-cause mortality and dialysis initiation among 1,753 subjects (1,099 CKD, estimated glomerular filtration rate 18 ± 6 ml/min/1.73 m(2) and 654 end-stage renal disease [ESRD]) from the Homocysteine in Kidney and End Stage Renal Disease (HOST) study. A propensity score analysis accounted for indication bias and Cox regression models adjusted for mineral metabolism markers. RESULTS: Mean follow-up was 3.2 years; 714 (41%) subjects died and 615 (56%) initiated dialysis. In adjusted analyses, all subjects treated with ACEI/ARB had a significantly lower hazard of death (hazards ratio (HR) 0.81, 95% CI 0.70-0.95, p = 0.007). Those with CKD not on dialysis and treated with ACEI/ARB trended toward a lower hazard of dialysis initiation (HR 0.86, 95% CI 0.73-1.01, p = 0.06). The association with mortality did not differ by level of mineral metabolism marker (p for interaction >0.16); however, the relationship with dialysis initiation differed according to the median serum phosphorus level (p for interaction <0.001). CONCLUSIONS: RAAS inhibition was associated with decreased all-cause mortality independent of disordered mineral metabolism among mostly male HOST subjects with advanced CKD and ESRD. However, among those with CKD not requiring dialysis, the renoprotection associated with RAAS inhibition was attenuated by higher serum phosphorus levels. Further studies are needed to confirm this association.

Renal outcomes and dietary potassium: the overshadowed electrolyte?

Smyth et al. examined the association between urinary sodium and potassium excretion and adverse renal outcomes in adults at high cardiovascular risk. They found no association between urinary sodium excretion and adverse renal outcomes, but a reduced odds of adverse renal outcomes with higher urinary potassium excretion. It will be important to ascertain whether this finding holds true in individuals free from vascular disease and diabetes, as well as in patients with chronic kidney disease.

Regular aerobic exercise protects against impaired fasting plasma glucose-associated vascular endothelial dysfunction with aging.

In the present study, we tested the hypothesis that age-associated vascular endothelial dysfunction is exacerbated by IFG (impaired fasting plasma glucose) and that regular aerobic exercise prevents this effect. Data were analysed from a cohort of 131 non-smoking men and women without overt clinical disease. Compared with young adult controls (age=24±1 years, n=29; values are means±S.E.M.), brachial artery FMD (flow-mediated dilation), a measure of conduit artery EDD (endothelium-dependent dilation), was 33% lower [7.93±0.33 against 5.27±0.37%Δ (% change), P<0.05] in MA/O (middle-aged/older) adults with NFG (normal fasting plasma glucose) (≤99 mg/dl, 62±1 years, n=35). In MA/O adults with IFG (100-125 mg/dl, 64±1 years, n=28), FMD was 30% lower (3.37±0.35%Δ) than in their peers with NFG and 58% lower than young controls (P<0.05). Brachial artery FMD was greater (6.38±0.35%Δ) in MA/O adults with NFG who regularly performed aerobic exercise (>45 min/day for ≥5 days/week, 62±1 years, n=23) compared with their non-exercising peers and only slightly less than young controls (P<0.05). Most importantly, FMD was completely preserved in MA/O adults with IFG who regularly performed aerobic exercise (6.99±0.69%Δ, 65±1 years, n=16). In the pooled sample, fasting plasma glucose was inversely related to FMD (r=-0.42, P<0.01) and was the strongest independent predictor of FMD (R(2)=0.32). Group differences in FMD were not affected by other subject characteristics or brachial artery properties, including brachial artery dilation to sublingual NTG (nitroglycerine, i.e. endothelium-independent dilation). IFG exacerbates age-associated vascular endothelial dysfunction and this adverse effect is completely prevented in MA/O adults who regularly perform aerobic exercise.

Aging and vascular endothelial function in humans.

Advancing age is the major risk factor for the development of CVD (cardiovascular diseases). This is attributable, in part, to the development of vascular endothelial dysfunction, as indicated by reduced peripheral artery EDD (endothelium-dependent dilation) in response to chemical [typically ACh (acetylcholine)] or mechanical (intravascular shear) stimuli. Reduced bioavailability of the endothelium-synthesized dilating molecule NO (nitric oxide) as a result of oxidative stress is the key mechanism mediating reduced EDD with aging. Vascular oxidative stress increases with age as a consequence of greater production of reactive oxygen species (e.g. superoxide) without a compensatory increase in antioxidant defences. Sources of increased superoxide production include up-regulation of the oxidant enzyme NADPH oxidase, uncoupling of the normally NO-producing enzyme, eNOS (endothelial NO synthase) (due to reduced availability of the cofactor tetrahydrobiopterin) and increased mitochondrial synthesis during oxidative phosphorylation. Increased bioactivity of the potent endothelial-derived constricting factor ET-1 (endothelin-1), reduced endothelial production of/responsiveness to dilatory prostaglandins, the development of vascular inflammation, formation of AGEs (advanced glycation end-products), an increased rate of endothelial apoptosis and reduced expression of oestrogen receptor α (in postmenopausal females) also probably contribute to impaired EDD with aging. Several lifestyle and biological factors modulate vascular endothelial function with aging, including regular aerobic exercise, dietary factors (e.g. processed compared with non-processed foods), body weight/fatness, vitamin D status, menopause/oestrogen deficiency and a number of conventional and non-conventional risk factors for CVD. Given the number of older adults now and in the future, more information is needed on effective strategies for the prevention and treatment of vascular endothelial aging.

Cytochrome P-450 2C9 signaling does not contribute to age-associated vascular endothelial dysfunction in humans.

Oxidative stress impairs endothelium-dependent dilation (EDD) with aging in healthy sedentary adults. Increased cytochrome P-450 2C9 (CYP 2C9) signaling can contribute to oxidative stress-mediated suppression of EDD, but its role in aging is unknown. We hypothesized that inhibition of CYP 2C9 signaling with sulfaphenazole would improve EDD in older, but not young, healthy sedentary adults. At baseline, increases in forearm blood flow (FBF; venous occlusion plethysmography) in response to brachial artery infusions of ACh (1, 2, 4, and 8 microg.100 ml forearm volume(-1).min(-1)), an endothelium-dependent dilator, were smaller in older [n = 14, 63 +/- 1 (SE) yr] than in young (n = 11, 23 +/- 2 yr) adults (P < 0.05), with a reduction in peak FBF of 32% (11.8 +/- 1.7 vs. 17.3 +/- 2.3 ml.100 ml tissue(-1).min(-1)). Infusion of sulfaphenazole at doses that block CYP 2C9 signaling in humans did not affect the FBF responses to ACh in the older (peak FBF = 13.0 +/- 4.3 ml.100 ml tissue(-1).min(-1), P = 0.41) or the young (peak FBF = 17.1 +/- 1.9 ml.100 ml tissue(-1).min(-1), P = 0.55) adults. Coadministration of the nitric oxide inhibitor l-NMMA and sulfaphenazole decreased the FBF response to ACh in young and older subjects (P < 0.05); the effect was smaller in the older subjects, but group differences in EDD remained (P < 0.05). Endothelium-independent dilation assessed with sodium nitroprusside was not different in the young and older subjects. These results provide the first support for the concept that increased CYP 2C9 signaling does not contribute to impairments in EDD with aging in healthy adults.

High-dose ascorbic acid infusion abolishes chronic vasoconstriction and restores resting leg blood flow in healthy older men.

Resting whole leg blood flow and vascular conductance decrease linearly with advancing age in healthy adult men. The potential role of age-related increases in oxidative stress in these changes is unknown. Resting leg blood flow during saline and ascorbic acid infusion was studied in 10 young (25 +/- 1 yr) and 11 older (63 +/- 2 yr) healthy normotensive men. Plasma oxidized LDL, a marker of oxidative stress, was greater in the older men (P < 0.05). Absolute resting femoral artery blood flow at baseline (iv saline control infusion) was 25% lower in the older men (238 +/- 25 vs. 316 +/- 38 ml/min; P < 0.05), and it was inversely related to plasma oxidized LDL (r = -0.56, P < 0.01) in all subjects. Infusion of supraphysiological concentrations of ascorbic acid increased femoral artery blood flow by 37% in the older men (to 327 +/- 52 ml/min; P < 0.05), but not in the young men (352 +/- 41 ml/min; P = 0.28), thus abolishing group differences (P = 0.72). Mean arterial blood pressure was greater in the older men at baseline (86 +/- 4 vs. 78 +/- 2 mmHg; P < 0.05), but it was unaffected by ascorbic acid infusion (P >/= 0.70). As a result, the lower baseline femoral artery blood flow in the older men was mediated solely by a 32% lower femoral artery vascular conductance (P < 0.05). Baseline femoral vascular conductance also was inversely related to plasma oxidized LDL (r = -0.65, P < 0.01). Ascorbic acid increased femoral vascular conductance by 36% in the older men (P < 0.05) but not in the young men (P = 0.31). In conclusion, ascorbic acid infused at concentrations known to scavenge reactive oxygen species restores resting femoral artery blood flow in healthy older adult men by increasing vascular conductance. These results support the hypothesis that oxidative stress plays a major role in the reduced resting whole leg blood flow and increased leg vasoconstriction observed with aging in men.

Effect of dietary sodium restriction on human urinary metabolomic profiles.

BACKGROUND AND OBJECTIVES: Metabolomics is a relatively new field of "-omics" research, focusing on high-throughput identification of small molecular weight metabolites. Diet has both acute and chronic effects on metabolic profiles; however, alterations in response to dietary sodium restriction (DSR) are completely unknown. The goal of this study was to explore changes in urine metabolites in response to DSR, as well as their association with previously reported improvements in vascular function with DSR. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Using stored urine samples from a 10-week randomized placebo-controlled crossover study of DSR in 17 middle-aged/older adults (six men and 11 women; mean age 62±8 years) who had moderately elevated systolic BP (130-159 mmHg) and were otherwise healthy, a liquid chromatography/mass spectrometry-based analysis of 289 metabolites was performed. This study identified metabolites that were significantly altered between the typical (153±29 mmol/d) and low (70±29 mmol/d) sodium conditions, as well as their baseline (typical sodium) association with responsiveness to previously reported improvements in vascular endothelial function (brachial artery flow-mediated dilation) and large elastic artery stiffness (aortic pulse wave velocity). RESULTS: Of the 289 metabolites surveyed, 10 were significantly altered (nine were upregulated and one was downregulated) during the low sodium condition, and eight of these exceeded our prespecified clinically significant threshold of a >40% change. These metabolites were involved in biologic pathways broadly related to cardiovascular risk, nitric oxide production, oxidative stress, osmotic regulation, and metabolism. One metabolite, serine, was independently (positively) associated with previously reported improvements in the primary vascular outcome of brachial artery flow-mediated dilation. CONCLUSIONS: This proof-of-concept study provides the first evidence that DSR is a stimulus that induces significant changes in urinary metabolomic profiles. Moreover, serine was independently associated with corresponding changes in vascular endothelial function after DSR. Larger follow-up studies will be required to confirm and further elucidate the metabolic pathways that are altered in response to DSR.

Reduced large elastic artery stiffness with regular aerobic exercise in middle-aged and older adults: potential role of suppressed nuclear factor κ B signalling.

OBJECTIVE: Aortic pulse-wave velocity (aPWV) increases with age and is a strong independent predictor of incident cardiovascular diseases (CVDs) in healthy middle-aged and older adults. aPWV is lower in middle-aged and older adults who perform regular aerobic exercise than in their sedentary peers. As exercise is associated with reduced systemic inflammation, we hypothesized that suppression of the pro-inflammatory transcription factor nuclear factor κ B (NFκB) may mediate this process. METHODS: aPWV was measured in young sedentary [n = 10, blood pressure (BP) 108 ±â€Š3/59 ±â€Š2 mmHg; mean ± SEM], middle-aged and older sedentary (n = 9, 124 ±â€Š7/73 ±â€Š5 mmHg) and middle-aged and older aerobic exercise-trained (n = 12, 110 ±â€Š4/67 ±â€Š2 mmHg) healthy, nonhypertensive men and women. RESULTS: Baseline aPWV increased with age [626 ±â€Š14 (young sedentary) vs. 859 ±â€Š49 (middle-aged and older sedentary) cm/s, P < 0.001] but was 20% lower in middle-aged and older trained (686 ±â€Š30 cm/s) than in middle-aged and older sedentary (P < 0.005). Short-term (4 days  x  2500-4500 mg) treatment with the NFκB inhibitor salsalate (randomized, placebo-controlled cross-over design) reduced aPWV (to 783 ±â€Š44 cm/s, P < 0.05) without changing BP (P = 0.40) or heart rate (P = 0.90) in middle-aged and older sedentary, but had no effect in young sedentary (623 ±â€Š19) or middle-aged and older trained (699 ±â€Š30). Following salsalate treatment, aPWV no longer was significantly different in middle-aged and older sedentary vs. middle-aged and older trained (P = 0.29). The reduction in aPWV with salsalate administration was inversely related to baseline (placebo) aPWV (r = -0.60, P < 0.001). CONCLUSION: These results support the hypothesis that suppressed NFκB signalling may partially mediate the lower aortic stiffness in middle-aged and older adults who regularly perform aerobic exercise. Because aPWV predicts incident cardiovascular events in this population, this suggests that tonic suppression of NFκB signalling in middle-aged and older exercising adults may potentially lower cardiovascular risk.

Recent advances in the management of hemodialysis patients: a focus on cardiovascular disease.

The number of patients requiring chronic hemodialysis is rapidly growing worldwide. Hemodialysis both greatly reduces quality of life and is associated with extremely high mortality rates. Management of care of patients requiring chronic hemodialysis is complex, and randomized controlled trials aimed at reducing primary outcomes of cardiovascular disease events, mortality, or both in this population have largely been unsuccessful. Topics of major concern in the management of maintenance hemodialysis patients as related to these outcomes include the overall cardiovascular disease burden, blood pressure control, anemia, abnormalities in mineral metabolism, and inflammation. The focus of this review is a discussion of these topics on the basis of current recommendations from major organizations, expert opinion, and the available randomized controlled trials to date. These issues are further complicated by sometimes conflicting observational and randomized controlled trial data. Overall, treatment options for reducing these endpoints in maintenance hemodialysis patients are limited, and future randomized controlled trials are essential to continuing to advance care in this population, with the goal of ultimately improving hard outcomes. Such trials should consider new therapies to better target these factors, additional risk factors that have not been well tested to date, and therapies with new targets, including inflammation.

Assessment of vascular function in patients with chronic kidney disease.

Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this is only partially explained by traditional CVD risk factors. Vascular dysfunction is an important non-traditional risk factor, characterized by vascular endothelial dysfunction (most commonly assessed as impaired endothelium-dependent dilation [EDD]) and stiffening of the large elastic arteries. While various techniques exist to assess EDD and large elastic artery stiffness, the most commonly used are brachial artery flow-mediated dilation (FMDBA) and aortic pulse-wave velocity (aPWV), respectively. Both of these noninvasive measures of vascular dysfunction are independent predictors of future cardiovascular events in patients with and without kidney disease. Patients with CKD demonstrate both impaired FMDBA, and increased aPWV. While the exact mechanisms by which vascular dysfunction develops in CKD are incompletely understood, increased oxidative stress and a subsequent reduction in nitric oxide (NO) bioavailability are important contributors. Cellular changes in oxidative stress can be assessed by collecting vascular endothelial cells from the antecubital vein and measuring protein expression of markers of oxidative stress using immunofluorescence. We provide here a discussion of these methods to measure FMDBA, aPWV, and vascular endothelial cell protein expression.

Vascular calcification in end-stage renal disease.

Vascular calcification is highly prevalent in end-stage renal disease and independently predictive of future cardiovascular events and mortality. Calcification can occur in both the intimal and medial layers of vasculature, but medial calcification is the major form in end-stage renal disease. Medial calcification increases large elastic artery stiffness and pulse-pressure, promotes left ventricular hypertrophy, reduces perfusion of the coronary arteries, and ultimately promotes increased cardiovascular mortality via increased risk of myocardial infarction and heart failure. It results not from a passive deposition of calcium and phosphate due to increased circulating levels, but rather is an active cell-mediated process involving vascular smooth muscle cell apoptosis and vesicle release, a shift in the balance of inhibitors and promoters of vascular calcification, and vascular smooth muscle cell differentiation from a contractile to osteochondrogenic phenotype. This phenotypic shift requires phosphate, as well as the uptake of phosphate by the sodium-dependent phosphate cotransporter PiT-1, which is upregulated by proinflammatory cytokines and the uremic milieu. Further research is needed to determine if targeting these processes can ultimately reduce vascular calcification in this high cardiovascular risk population.

Dietary sodium restriction reverses vascular endothelial dysfunction in middle-aged/older adults with moderately elevated systolic blood pressure.

OBJECTIVES: This study sought to determine the efficacy of dietary sodium restriction (DSR) for improving vascular endothelial dysfunction in middle-aged/older adults with moderately elevated systolic blood pressure (SBP) (130-159 mm Hg) and the associated physiological mechanisms. BACKGROUND: Vascular endothelial dysfunction develops with advancing age and elevated SBP, contributing to increased cardiovascular risk. DSR lowers BP, but its effect on vascular endothelial function and mechanisms involved are unknown. METHODS: Seventeen subjects (11 men and 6 women; mean age, 62 ± 7 years) completed a, randomized crossover study of 4 weeks of both low (DSR) and normal sodium intake. Vascular endothelial function (endothelium-dependent dilation; EDD), nitric oxide (NO)/tetrahydrobiopterin (BH(4)) bioavailability, and oxidative stress-associated mechanisms were assessed following each condition. RESULTS: Urinary sodium excretion was reduced by ≈ 50% (to 70 ± 30 mmol/day), and conduit (brachial artery flow-mediated dilation [FMD(BA)]) and resistance (forearm blood flow responses to acetylcholine [FBF(ACh)]) artery EDD were 68% and 42% (peak FBF(ACh)) higher following DSR (p < 0.005). Low sodium markedly enhanced NO-mediated EDD (greater ΔFBF(ACh) with endothelial NO synthase inhibition) without changing endothelial NO synthase expression/activation (Ser 1177 phosphorylation), restored BH(4) bioactivity (less ΔFMD(BA) with acute BH(4)), abolished tonic superoxide suppression of EDD (less ΔFMD(BA) and ΔFBF(ACh) with ascorbic acid infusion), and increased circulating superoxide dismutase activity (all p < 0.05). These effects were independent of ΔSBP. Other subject characteristics/dietary factors and endothelium-independent dilation were unchanged. CONCLUSIONS: DSR largely reversed both macro- and microvascular endothelial dysfunction by enhancing NO and BH(4) bioavailability and reducing oxidative stress. Our findings support the emerging concept that DSR induces "vascular protection" beyond that attributable to its BP-lowering effects.

Dietary sodium restriction and association with urinary marinobufagenin, blood pressure, and aortic stiffness.

BACKGROUND AND OBJECTIVES: Systolic BP and large elastic artery stiffness both increase with age and are reduced by dietary sodium restriction. Production of the natriuretic hormone marinobufagenin, an endogenous α1 Na+,K+-ATPase inhibitor, is increased in salt-sensitive hypertension and contributes to the rise in systolic BP during sodium loading. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: The hypothesis was that dietary sodium restriction performed in middle-aged/older adults (eight men and three women; 60 ± 2 years) with moderately elevated systolic BP (139 ± 2/83 ± 2 mmHg) would reduce urinary marinobufagenin excretion as well as systolic BP and aortic pulse-wave velocity (randomized, placebo-controlled, and crossover design). This study also explored the associations among marinobufagenin excretion with systolic BP and aortic pulse-wave velocity across conditions of 5 weeks of a low-sodium (77 ± 9 mmol/d) and 5 weeks of a normal-sodium (144 ± 7 mmol/d) diet. RESULTS: Urinary marinobufagenin excretion (weekly measurements; 25.4 ± 1.8 versus 30.7 ± 2.1 pmol/kg per day), systolic BP (127 ± 3 versus 138 ± 5 mmHg), and aortic pulse-wave velocity (700 ± 40 versus 843 ± 36 cm/s) were lower during the low- versus normal-sodium condition (all P<0.05). Across all weeks, marinobufagenin excretion was related with systolic BP (slope=0.61, P<0.001) and sodium excretion (slope=0.46, P<0.001). These associations persisted during the normal- but not the low-sodium condition (both P<0.005). Marinobufagenin excretion also was associated with aortic pulse-wave velocity (slope=0.70, P=0.02) and endothelial cell expression of NAD(P)H oxidase-p47phox (slope=0.64, P=0.006). CONCLUSIONS: These results show, for the first time in humans, that dietary sodium restriction reduces urinary marinobufagenin excretion and that urinary marinobufagenin excretion is positively associated with systolic BP, aortic stiffness (aortic pulse-wave velocity), and endothelial cell expression of the oxidant enzyme NAD(P)H oxidase. Importantly, marinobufagenin excretion is positively related to systolic BP over ranges of sodium intake typical of an American diet, extending previous observations in rodents and humans fed experimentally high-sodium diets.

Vascular endothelial function is not related to serum uric acid in healthy adults.

BACKGROUND: Some experimental evidence suggests that uric acid impairs endothelial function. It is controversial if high uric acid levels and impaired endothelial function are related in healthy adults. In addition, the effect of uric acid on endothelial cells (ECs) of humans is unexplored. METHODS: Data of 107 healthy adult volunteers were analyzed. The association between serum uric acid and endothelial-dependant dilation (EDD) and endothelial-independent dilation (EID) was evaluated by linear regression models. We also examined the relations between uric acid and systemic and cellular markers of inflammation and oxidative stress in all or subsets of participants. RESULTS: Uric acid levels and EDD were not related in unadjusted or adjusted models. There was a significant negative correlation between uric acid and EID in the pooled sample (r = -0.34, P = 0.005). This correlation remained significant after adjusting for demographics (P = 0.04) and was attenuated after adjusting for other cardiac risk factors (P = 0.12). Higher serum uric acid levels were found to correlate significantly with C-reactive protein (CRP) (r = 0.31, P = 0.002). Serum uric acid levels were not associated with brachial artery EC nuclear factor-κB (NF-κB) p65 or NADPH oxidase p47(phox) expression or with nitrotyrosine staining, but were inversely associated with EC manganese superoxide dismutase (MnSOD) expression (r = -0.5, P = 0.01, n = 25). CONCLUSION: Elevated serum uric acid is not associated with endothelial dysfunction among healthy adults, but is inversely related to EID and EC MnSOD, and positively related to systemic inflammation. These findings may have implications for cardiovascular risk in healthy adults.

Tetrahydrobiopterin supplementation enhances carotid artery compliance in healthy older men: a pilot study.

BACKGROUND: We performed a pilot study to test the hypothesis that acute oral ingestion of tetrahydrobiopterin (BH(4)), a key cofactor modulating vascular nitric oxide (NO) synthase activity, improves large elastic artery stiffness with aging in men. METHODS: Healthy older (63 ± 2 years; n = 8) and young (age 25 ± 1 years; n = 6) men were studied 3 h after ingestion of BH(4) (10 mg·kg(-1) body weight) or placebo on separate days in a randomized, placebo-controlled, double-blind study. RESULTS: Baseline carotid artery compliance was 37% lower (0.17 ± 0.02 vs. 0.22 ± 0.02 mm/mm Hg·10(-1)) and ß-stiffness was 42% higher (7.3 ± 1.1 vs. 4.2 ± 0.5 AU) in the older men (both P < 0.05). BH(4) ingestion markedly increased circulating BH(4) concentrations in both groups (17-19-fold, P < 0.05), but increased compliance (+39% to 0.23 ± 0.02 mm/mm Hg·10(-1), P < 0.01) and decreased ß-stiffness index (-27% to 5.3 ± 0.7 AU, P < 0.01) only in the older men. BH(4) also reduced carotid systolic blood pressure (SBP) in the older men (P < 0.05). CONCLUSIONS: These preliminary results support the possibility that limited BH(4) bioavailability contributes to impaired carotid artery compliance in healthy older men. Further studies are needed to determine if increasing BH(4) bioavailability though oral BH(4) supplementation may have therapeutic efficacy for improving large elastic artery compliance and reducing central SBP with aging.

25-Hydroxyvitamin D deficiency is associated with inflammation-linked vascular endothelial dysfunction in middle-aged and older adults.

We tested the hypothesis that vascular endothelial function, assessed by endothelium-dependent dilation, is related to serum vitamin D status among middle-aged and older adults without clinical disease, and that this is linked to inflammation. Brachial artery flow-mediated dilation, a measure of endothelium-dependent dilation, was lower (P<0.01) in vitamin D-insufficient (3.7 ± 0.2%; serum 25-hydroxyvitamin D [25(OH)D]: 20 to 29 ng/mL; 62 ± 1 years of age; n = 31; mean± SE) and vitamin D-deficient (3.2 ± 0.3%; 25(OH)D: <20 ng/mL; 63 ± 2 years of age; n = 22) versus vitamin D-sufficient (4.6 ± 0.4%; 25(OH)D: >29 ng/mL; 61 ± 1 years of age; n = 22) subjects, whereas endothelium-independent dilation (brachial dilation to sublingual nitroglycerine) did not differ (P = 0.45). Among all subjects, brachial flow-mediated dilation was positively related to serum 25(OH)D (%Δ: r = 0.35; P<0.01) but not 1,25-dihydroxyvitamin D (r = -0.06; P = 0.61), the active form of vitamin D. Vascular endothelial cell expression of the proinflammatory transcription factor nuclear factor κB was greater in deficient versus sufficient subjects (0.59 ± 0.07 versus 0.44 ± 0.05; P<0.05), and inhibition of nuclear factor κB (4 days oral salsalate) improved flow-mediated dilation to a greater extent in subjects with lower versus higher 25(OH)D (+3.7 ± 0.6 versus +2.0 ± 0.2%; P<0.05). Endothelial cell expression of the downstream proinflammatory cytokine interleukin-6 also was higher in deficient versus sufficient subjects (0.67 ± 0.08 versus 0.47 ± 0.05; P<0.01) and inversely related to serum 25(OH)D level (r = -0.62; P<0.01), whereas vitamin D receptor and 1-α hydroxylase, the 25(OH)D to 1,25-dihydroxyvitamin D converting enzyme, were lower (P<0.05). Inadequate serum 25(OH)D is associated with vascular endothelial dysfunction among healthy middle-aged/older adults, and this is mediated in part by nuclear factor κB-related inflammation. Reduced vitamin D receptor and 1-α hydroxylase may be molecular mechanisms linking vitamin D insufficiency to endothelial dysfunction.

Low dietary sodium intake is associated with enhanced vascular endothelial function in middle-aged and older adults with elevated systolic blood pressure.

BACKGROUND: Age and increasing systolic blood pressure (BP) are associated with vascular endothelial dysfunction, but the factors involved are incompletely understood. We tested the hypothesis that vascular endothelial function is related to dietary sodium intake among middle-aged and older adults (MA and O) with elevated systolic BP. METHODS: Data were analyzed on 25 otherwise healthy adults aged 48-73 years with high normal systolic BP or stage I systolic hypertension (130-159 mmHg). Self-reported sodium intake was <100 mmol/d in 12 (7 M) subjects (low sodium, 73+/-6 mmol/d) and between 100 and 200 mmol/d in 13 (9 M) subjects (normal sodium, 144+/-6 mmol/d). RESULTS: Groups did not differ in other dietary factors, age, body weight and composition, BP, metabolic risk factors, physical activity and maximal aerobic capacity. Plasma concentrations of norepinephrine, endothelin-1, oxidized low-density lipoproteins (LDL), antioxidant status and inflammatory markers did not differ between groups. Brachial artery flow-mediated dilation (FMD) was 42% (mm Delta) to 52% (% Delta) higher in the low versus normal sodium group (p < 0.05). In all subjects, brachial artery FMD was inversely related to dietary sodium intake (FMD mm Delta r =-0.40, p < 0.05; %Delta r =-0.53, p < 0.01). Brachial artery FMD was not related to any other variable. In contrast, endothelium-independent dilation did not differ between groups (p >or= 0.24) and was not related to sodium intake in the overall group (p >or= 0.29). CONCLUSIONS: Low sodium intake is associated with enhanced brachial artery FMD in MA and O with elevated systolic BP. These results suggest that dietary sodium restriction may be an effective intervention for improving vascular endothelial function in this high-risk group.