Nitrite and nitric oxide metabolism in peripheral artery disease

L-Arginine and Intermittent Hypoxia Are Stress-Limiting Factors in Male Wistar Rat Models

The aim of this study was to evaluate the combined effects of L-arginine, intermittent hypoxia training (IHT), and acute stress on oxygen-dependent processes in rats, including mitochondrial oxidative phosphorylation, microsomal oxidation, and the intensity of lipoperoxidation processes. In addition, our study investigated how the modulatory effect of the NO synthase mechanism on the concentration of catecholamines (CA), such as adrenaline and noradrenaline, and their biosynthetic precursors (DOPA, dopamine) varies depending on the cholinergic (acetylcholine, Ach-acetylcholinesterase, AChE) status in rats. This study investigated the protective stress-limiting effects of L-arginine impact and IHT in the blood and liver of rats. The results showed that L-arginine promoted the maintenance of NAD-dependent oxidation in mitochondria, which was detrimental compared to succinate oxidation, and was accompanied by depletion of respiratory activity reserves under stress induced by high concentrations of CA. The interdependence of SC-dependent oxidation and the functional role of NAD-dependent substrate oxidation in the mitochondrial respiratory chain in stress conditions induced using inhibitors revealed the importance of the NO system. Administration of L-arginine during the IHT course prior to stress exposure increased the compensatory capacity of the organism. L-arginine increased the compensatory capacity of the sympathoadrenal system in stress-exposed rats. In the early stages of IHT, modulation of the CA concentration was observed with a concomitant increase in lipoperoxidation processes, and in the final stages of IHT, the CA concentrations increased, but there was also an inhibition of lipoperoxidation, which was particularly enhanced by the administration of L-arginine. The increase in blood concentrations of CA and ACh was accompanied by a decrease in AChE activity at different stages of adaptation to hypoxia induced by IHT (days 5, 10, and 14). Thus, the IHT method significantly mobilises the reserve capacity of oxygen-dependent processes through the system of CA, ACh-AChE mediated by nitric oxide.

Redox signaling regulates the skeletal tissue development and regeneration

Skeletal tissue development and regeneration in mammals are intricate, multistep, and highly regulated processes. Various signaling pathways have been implicated in the regulation of these processes, including redox. Redox signaling is the signal transduction by electron transfer reactions involving free radicals or related species. Redox homeostasis is essential to cell metabolic states, as the ROS not only regulates cell biological processes but also mediates physiological processes. Following a bone fracture, redox signaling is also triggered to regulate bone healing and regeneration by targeting resident stromal cells, osteoblasts, osteoclasts and endothelial cells. This review will focus on how the redox signaling impact the bone development and bone regeneration.

Nitrate: "the source makes the poison"

Interest in the role of dietary nitrate in human health and disease has grown exponentially in recent years. However, consensus is yet to be reached as to whether consuming nitrate from various food sources is beneficial or harmful to health. Global authorities continue to recommend an acceptable daily intake (ADI) of nitrate of 3.7 mg/kg-bw/day due to concerns over its carcinogenicity. This is despite evidence showing that nitrate consumption from vegetable sources, exceeding the ADI, is associated with decreased cancer prevalence and improvements in cardiovascular, oral, metabolic and neurocognitive health. This review examines the paradox between dietary nitrate and health and disease and highlights the key role of the dietary source and food matrix in moderating this interaction. We present mechanistic and epidemiological evidence to support the notion that consuming vegetable-derived nitrate promotes a beneficial increase in nitric oxide generation and limits toxic N-nitroso compound formation seen with high intakes of nitrate added during food processing or present in contaminated water. We demonstrate the need for a more pragmatic approach to nitrate-related nutritional research and guidelines. Ultimately, we provide an overview of our knowledge in this field to facilitate the various therapeutic applications of dietary nitrate, whilst maintaining population safety.

Power-Doppler Ultrasonic Imaging of Peripheral Perfusion in Diabetic Mice

OBJECTIVE

We explored the capabilities of power-Doppler ultrasonic (PD-US) imaging without contrast enhancement for monitoring changes in muscle perfusion over time.

METHODS

Ischemic recovery was observed in healthy and type II diabetic male and female mice with and without exercise. In separate studies, perfusion was measured during and after 5-min ischemic periods and during four-week recovery periods following irreversible femoral ligation. A goal was to assess how well PD-US estimates tracked the diabetic-related changes in endothelial function that influenced perfusion.

RESULTS

The average perfusion recovery time following femoral ligation increased 47% in diabetic males and 74% in diabetic females compared with non-diabetic mice. Flow-mediated dilation in conduit arteries and the reactive hyperemia index in resistive vessels each declined by one half in sedentary diabetic mice compared with sedentary non-diabetic mice. We found that exercise reduced the loss of endothelial function from diabetes in both sexes. The reproducibility of perfusion measurements was limited primarily by our ability to select the same region in muscle and to effectively filter tissue clutter.

CONCLUSIONS/SIGNIFICANCE

PD-US measurements can precisely follow site-specific changes in skeletal muscle perfusion related to diabetes over time, which fills the need for techniques capable of regularly monitoring atherosclerotic changes leading to ischemic vascular pathologies.

Effects of short-term dietary nitrate supplementation on exercise and coronary blood flow responses in patients with peripheral artery disease

Background

Peripheral arterial disease (PAD) is a prevalent vascular disorder characterized by atherosclerotic occlusion of peripheral arteries, resulting in reduced blood flow to the lower extremities and poor walking ability. Older patients with PAD are also at a markedly increased risk of cardiovascular events, including myocardial infarction. Recent evidence indicates that inorganic nitrate supplementation, which is abundant in certain vegetables, augments nitric oxide (NO) bioavailability and may have beneficial effects on walking, blood pressure, and vascular function in patients with PAD.

Objective

We sought to determine if short-term nitrate supplementation (via beetroot juice) improves peak treadmill time and coronary hyperemic responses to plantar flexion exercise relative to placebo (nitrate-depleted juice) in older patients with PAD. The primary endpoints were peak treadmill time and the peak coronary hyperemic response to plantar flexion exercise.

Methods

Eleven PAD patients (52-80 yr.; 9 men/2 women; Fontaine stage II) were randomized (double-blind) to either nitrate-rich (Beet-IT, 0.3 g inorganic nitrate twice/day; BRnitrate) or nitrate-depleted (Beet-IT, 0.04 g inorganic nitrate twice/day, BRplacebo) beetroot juice for 4 to 6 days, followed by a washout of 7 to 14 days before crossing over to the other treatment. Patients completed graded plantar flexion exercise with their most symptomatic leg to fatigue, followed by isometric handgrip until volitional fatigue at 40% of maximum on day 4 of supplementation, and a treadmill test to peak exertion 1-2 days later while continuing supplementation. Hemodynamics and exercise tolerance, and coronary blood flow velocity (CBV) responses were measured.

Results

Although peak walking time and claudication onset time during treadmill exercise did not differ significantly between BRplacebo and BRnitrate, the diastolic blood pressure response at the peak treadmill walking stage was significantly lower in the BRnitrate condition. Increases in CBV from baseline to peak plantar flexion exercise after BRplacebo and BRnitrate showed a trend for a greater increase in CBV at the peak workload of plantar flexion with BRnitrate (p = 0.06; Cohen's d = 0.56).

Conclusion

Overall, these preliminary findings suggest that inorganic nitrate supplementation in PAD patients is safe, well-tolerated, and may improve the coronary hyperemic and blood pressure responses when their calf muscles are most predisposed to ischemia.Clinical trial registration:https://clinicaltrials.gov/, identifier NCT02553733.

Systemic nitric oxide metabolites and the chance of pre-diabetes regression to normoglycemia: A 9-year cohort study

Introduction

We aimed to track longitudinal changes of glycemic status in subjects with pre-diabetes (Pre-DM) in relation to their baseline levels of systemic nitric oxide (NO) production [i.e., measured as serum NO metabolites (NOx), crude and body weight (BW)-adjusted NOx to creatinine ratio (NOx-to-Cr)] over 9 years.

Methods

This cohort study included 541 middle-aged Iranian men and women with Pre-DM, recruited in 2006-2008 and followed up to 2015-2017. The colorimetric Griess method was used to measure serum NOx concentration. Multinomial logistic regression analyses estimated the odds ratios (OR) of Pre-DM regression and progression across tertiles (tertile 3 vs. tertile 1 and tertile 2) of serum NOx, crude, and BW-adjusted NOx-to-Cr ratio.

Results

Participants who regressed to normoglycemia (NG) had a higher BW-adjusted NOx-to-Cr ratio than those who developed type 2 diabetes (T2D) or those who remained Pre-DM (0.52±0.34 vs. 0.43±0.25 and 0.48±0.29, P=0.023). Higher BW-adjusted NOx-to-Cr increased chance of returning to NG (OR=2.05, 95% CI= 0.98-4.32, P=0.058) and decreased levels of 2h-serum glucose over time (P time×group=0.025), as well as the decreased overall mean of fasting (106, 95% CI=103-109 vs. 110, 95% CI=108-112 mg/dL, P=0.008) and 2h-serum glucose (153, 95% CI=146-159 vs. 163, 95% CI=158-168 mg/dL, P=0.018).

Conclusion

A higher endogenous NO production (i.e., indirectly measured by BW- and Cr-adjusted serum NOx concentration) in Pre-DM subjects is associated with the chance of returning to NG.

Translational Relevance of Advanced Age and Atherosclerosis in Preclinical Trials of Biotherapies for Peripheral Artery Disease

Approximately 6% of adults worldwide suffer from peripheral artery disease (PAD), primarily caused by atherosclerosis of lower limb arteries. Despite optimal medical care and revascularization, many PAD patients remain symptomatic and progress to critical limb ischemia (CLI) and risk major amputation. Delivery of pro-angiogenic factors as proteins or DNA, stem, or progenitor cells confers vascular regeneration and functional recovery in animal models of CLI, but the effects are not well replicated in patients and no pro-angiogenic biopharmacological procedures are approved in the US, EU, or China. The reasons are unclear, but animal models that do not represent clinical PAD/CLI are implicated. Consequently, it is unclear whether the obstacles to clinical success lie in the toxic biochemical milieu of human CLI, or in procedures that were optimized on inappropriate models. The question is significant because the former case requires abandonment of current strategies, while the latter encourages continued optimization. These issues are discussed in the context of relevant preclinical and clinical data, and it is concluded that preclinical mouse models that include age and atherosclerosis as the only comorbidities that are consistently present and active in clinical trial patients are necessary to predict clinical success. Of the reviewed materials, no biopharmacological procedure that failed in clinical trials had been tested in animal models that included advanced age and atherosclerosis relevant to PAD/CLI.

Effects of aerobic and combined training on pain-free walking distance and health-related quality of life in patients with peripheral artery disease: a randomized clinical trial

Background

Decreased walking ability in patients with peripheral arterial disease is often a clinical problem and limits the quality of life and daily activities of these subjects. physical exercise is important in this scenario, as it improves both the daily walking distance and the ability to withstand intermittent claudication related to the limitations of the peripheral disease.

Objectives

Our aim was to compare the effects of two types of exercise training (aerobic training and aerobic training combined with resistance exercises) on pain-free walking distance (PFWD) and health-related quality of life (HRQoL) in a sample composed of patients with peripheral artery disease (PAD).

Methods

Twenty patients with claudication symptoms were randomized to either aerobic control (AC) N= 9, or combined training (CT) N= 8, (24 sixty-minute sessions, twice a week). The total walking distance until onset of pain due to claudication was assessed using the 6-minute walk test and HRQoL was measured using the WHOQOL-bref questionnaire (general and specific domains) at baseline and after training. We used generalized estimating equations (GEE) to assess the differences between groups for the PFWD and HRQoL domains, testing the main group and time effects and their respective interaction effects. P values < 0.05 were considered statistically significant.

Results

Seventeen patients (mean age 63±9 years; 53% male) completed the study. Both groups experienced improvement in claudication, as reflected by a significant increase in PFWD: AC, 149 m to 299 m (P<0.001); CT, 156 m to 253 m (P<0.001). HRQoL domains also improved similarly in both groups (physical capacity, psychological aspects, and self-reported quality of life; P=0.001, P=0.003, and P=0.011 respectively).

Conclusions

Both aerobic and combined training similarly improved PFWD and HRQoL in PAD patients. There are no advantages in adding strength training to conventional aerobic training. This study does not support the conclusion that combined training is a good strategy for these patients when compared with classic training.

Effect of Dietary Supplements Which Upregulate Nitric Oxide on Walking and Quality of Life in Patients with Peripheral Artery Disease: A Meta-Analysis

This systematic review pooled evidence from randomised controlled trials (RCTs) on the effectiveness of dietary upregulators of nitric oxide (NO) in improving the walking and quality of life of patients with peripheral artery disease (PAD). RCTs examining the effect of dietary upregulators of NO in patients with PAD were included. The primary outcome was the maximum walking distance. Secondary outcomes were the initial claudication distance, the six-minute walking distance, quality of life, the ankle-brachial pressure index (ABI), adverse events and risk of mortality, revascularisation or amputation. Meta-analyses were performed using random effects models. The risk of bias was assessed using Cochrane's ROB-2 tool. Leave-one-out and subgroup analyses were conducted to assess the effect of individual studies, the risk of bias and intervention type on pooled estimates. Thirty-four RCTs involving 3472 participants were included. Seven trials tested NO donors, nineteen tested antioxidants, three tested NO synthase inducers and five tested enhancers of NO availability. Overall, the dietary supplements significantly improved the initial claudication (SMD 0.34; 95%CI 0.04, 0.64; p = 0.03) but not maximum walking (SMD 0.13; 95%CI -0.17, 0.43; p = 0.39) distances. Antioxidant supplements significantly increased both the maximum walking (SMD 0.36; 95%CI 0.14, 0.59; p = 0.001) and initial claudication (SMD 0.58; 95%CI 0.26, 0.90; p < 0.001) distances. The dietary interventions did not improve the physical function domain of the Short Form-36 (SMD -0.16; 95%CI -0.32, 0.00; p = 0.38), ABI or risk of adverse events, mortality, revascularisation or amputation. Dietary NO upregulators, especially antioxidants, appear to improve the initial claudication distance in patients with PAD. Larger high-quality RCTs are needed to fully examine the benefits and risks of these treatments. PROSPERO Registration: CRD42022256653.

The association of calcium channel blocker with risk of adverse limb events in patients with chronic limb-threatening ischemia after endovascular treatment

Symptoms of lower-extremity artery disease (LEAD) emerge from impaired vascularization in distal circulation of the extremities. Calcium channel blockers (CCB) can improve distal circulation when used as adjunctive therapy with endovascular treatment (EVT), but few studies have evaluated that. We investigated the relationship between CCB therapy and post-EVT outcomes. Through a consecutive EVT registry, we evaluated those relationships in whole cohort and the following 2 subgroups; the patients suffered from intermittent claudication (IC) or chronic limb-threatening ischemia (CLTI), with adjusting baseline characteristics by propensity score matchings. The primary endpoints were major adverse cardiac and cerebrovascular events (MACCE, a composite endpoint of all death, nonfatal myocardial infarction, and nonfatal stroke), and major adverse limb event (MALE, a composite of major amputation, acute limb ischemia, and surgical reintervention). The group that received CCB had less MALE in whole cohort (HR 0.31; 95% confidence interval (CI) 0.20-0.47), and less MACCE and MALE in CLTI cohort (HR 0.67; 0.50-0.89 and 0.32; 0.20-0.52 respectively) compared to the group that did not receive CCB. The relationships were common in the cohorts with baseline adjustment. MACCE and MALE in IC (HR 1.01; 0.57-1.80 and 0.60; 0.25-1.45, respectively) showed no significant differences both with and without baseline adjustment. CCB use was related to fewer MACCE and MALE events in adjusted patients who underwent EVT, and the trend was more evident, especially in the adjusted CLTI cohort. This study highlights the necessity of future studies regarding CCB. Clinical Trial Registration: URL: https://www.umin.ac.jp ; Unique identifiers: UMIN000015100.

Outcomes following supervised exercise and home-based exercise for patients with intermittent claudication

INTRODUCTION

Intermittent claudication (IC) is the most common symptom of peripheral arterial disease (PAD) which presents as a consequence of muscle ischaemia resulting from the atherosclerotic obstruction to arterial flow. High-quality evidence (Lane et al., 2017) shows that exercise programmes provide important benefits compared with usual care in improving pain-free and maximum walking distance in people with IC, but do not improve ankle-brachial pressure index (ABPI).

METHODS

Retrospective data were analysed to examine walking and ABPI outcomes for participants who completed a 12-week course of supervised or home-based exercise. All participants had a history of IC.

RESULTS

46 participants (mean age 69±11 years; 76% male; 29% current smokers) referred for exercise were assessed, completed a 12-week course of exercise (home-based or supervised) and subsequently attended for re-assessment. Claudication onset distance (COD) increased by 363% (mean improvement 344.7 ± 265.1m; p < .001) and peak walking distance (PWD) by 324.4% in the supervised exercise group; COD increased by 30.6% (mean improvement 32.8 ± 57.2 m; p = 0.026) and PWD by 31.5% in the home-based exercise group. Resting ABPI for the total cohort significantly improved from 0.82 ± 0.25 at A1 to 0.88 ± 0.25 at A2 (p = 0.027).

DISCUSSION

A 12-week course of supervised exercise results in significantly greater walking distance outcomes (COD and PWD) than unmonitored home-based exercise. In contrast with previous findings (Lane et al. 2017), this retrospective study demonstrated a significant improvement in resting ABPI with both supervised exercise as well as home-based exercise.

CONCLUSION

A 12-week programme of exercise favourably influenced walking and ABPI outcomes for patients with IC. Both home-based exercise and supervised individualised exercise increased walking distances, but the magnitude of the improvement in walking outcomes was greater in individuals who attended supervised exercise therapy.

Topical Biological Agents as Adjuncts to Improve Wound Healing in Chronic Diabetic Wounds: A Systematic Review of Clinical Evidence and Future Directions

Diabetes is a leading chronic illness in the modern world and 19-34% develop chronic diabetic foot ulcers (DFUs) in their lifetime, often necessitating amputation. The reduction in tissue growth factors and resulting imbalance between proteolytic enzymes and their inhibitors, along with systemic factors impairing healing appear particularly important in chronic wounds. Growth factors applied topically have thus been suggested to be a non-invasive, safe, and cost-effective adjunct to improve wound healing and prevent complications. Comprehensive database searches of MEDLINE via PubMed, EMBASE, Cochrane, and ClinicalTrials.gov were performed to identify clinical evidence and ongoing trials. The risk of bias analysis included randomized controlled trials (RCTs) was performed using the Cochrane Risk of Bias 2.0 tool. We included randomized controlled trials that compared the use of a topical biologic growth factor-containing regimen to any other regimen. Primary outcomes of interest were time to wound closure, healing rate, and time. Secondary outcomes included the incidence of adverse events such as infection. A total of 41 trials from 1992-2020 were included in this review, with a total recorded 3,112 patients. Platelet-derived growth factors (PDGF) in the form of becaplermin gel are likely to reduce the time of closure, increase the incidence of wound closure, and complete wound healing. Human umbilical cord-related treatments, dehydrated human amnion and chorion allograft (dHACA), and hypothermically stored amniotic membrane (HSAM), consistently increased the rates and incidence of complete ulcer healing while reducing ulcer size and time to complete ulcer healing. Fibroblast growth factor-1 (FGF1) showed only a slight benefit in multiple studies regarding increasing complete ulcer healing rates and incidence while reducing ulcer size and time to complete ulcer healing, with a few studies showing no statistical difference from placebo. Platelet-rich fibrin (PRF) is consistent in reducing the time to complete ulcer healing and increasing wound healing rate but may not reduce ulcer size or increase the incidence of complete ulcer healing. Targeting the wound healing pathway via the extrinsic administration of growth factors is a promising option to augment wound healing in diabetic patients. Growth factors have also shown promise in specific subgroups of patients who are at risk of significantly impaired wound healing such as those with a history of secondary infection and vasculopathy. As diabetes impairs multiple stages of wound healing, combining growth factors in diabetic wound care may prove to be an area of interest. Evidence from this systematic literature review suggests that topical adjuncts probably reduce time to wound closure, reduce healing time, and increase the healing rate in patients with chronic DFUs.

The lncRNA Punisher Regulates Apoptosis and Mitochondrial Homeostasis of Vascular Smooth Muscle Cells via Targeting miR-664a-5p and OPA1

Long noncoding RNAs (lncRNAs) are important regulators of various cellular functions. Recent studies have shown that a novel lncRNA termed Punisher is highly expressed in cardiovascular progenitors and has potential role in cardiovascular diseases. However, its role, especially in molecular mechanism, is unclear. In our present study, we observed that Punisher was obviously downregulated in atherosclerotic plaques. Further research proved that it can suppress the apoptosis of VSMCs potentially contributing to the progression of atherosclerosis. Intriguingly, Punisher revealed to regulate mitochondria fission as well as mitochondrial functions induced by hydrogen peroxide (H₂O₂) in VSMCs. Mechanistically, Punisher was further proved to serve as a ceRNA which directly binds to miR-664a-5p and consequently regulates its target OPA1, and finally contributes to the biological function of VSMCs. Particularly, Punisher overexpression distinctly suppressed neointima formation and VSMC apoptosis in vivo. Encouragingly, these results were in accordance with findings obtained with the clinical evaluation of patients with atherosclerosis. Our data provides the significant relationship among OPA1, mitochondrial homeostasis, VSMC apoptosis, and atherosclerosis. And lncRNA Punisher and miR-664a-5p could serve as the novel and potential targets in the diagnosis and treatment of cardiovascular diseases.

Remodeling Osteoarthritic Articular Cartilage under Hypoxic Conditions

Osteoarthritis (OA) is one of the leading joint diseases induced by abnormalities or inflammation in the synovial membrane and articular cartilage, causing severe pain and disability. Along with the cartilage malfunction, imbalanced oxygen uptake occurs, changing chondrocytes into type I collagen- and type X collagen-producing dedifferentiated cells, contributing to OA progression. However, mounting evidence suggests treating OA by inducing a hypoxic environment in the articular cartilage, targeting the inhibition of several OA-related pathways to bring chondrocytes into a normal state. This review discusses the implications of OA-diseased articular cartilage on chondrocyte phenotypes and turnover and debates the hypoxic mechanism of action. Furthermore, this review highlights the new understanding of OA, provided by tissue engineering and a regenerative medicine experimental design, modeling the disease into diverse 2D and 3D structures and investigating hypoxia and hypoxia-inducing biomolecules and potential cell therapies. This review also reports the mechanism of hypoxic regulation and highlights the importance of activating and stabilizing the hypoxia-inducible factor and related molecules to protect chondrocytes from mitochondrial dysfunction and apoptosis occurring under the influence of OA.

Update on the pathophysiology and medical treatment of peripheral artery disease

Approximately 6% of adults worldwide have atherosclerosis and thrombosis of the lower limb arteries (peripheral artery disease (PAD)) and the prevalence is rising. PAD causes leg pain, impaired health-related quality of life, immobility, tissue loss and a high risk of major adverse events, including myocardial infarction, stroke, revascularization, amputation and death. In this Review, I describe the pathophysiology, presentation, outcome, preclinical research and medical management of PAD. Established treatments for PAD include antithrombotic drugs, such as aspirin and clopidogrel, and medications to treat dyslipidaemia, hypertension and diabetes mellitus. Randomized controlled trials have demonstrated that these treatments reduce the risk of major adverse events. The drug cilostazol, exercise therapy and revascularization are the current treatment options for the limb symptoms of PAD, but each has limitations. Novel therapies to promote collateral and new capillary growth and treat PAD-related myopathy are under investigation. Methods to improve the implementation of evidence-based medical management, novel drug therapies and rehabilitation programmes for PAD-related pain, functional impairment and ischaemic foot disease are important areas for future research.

Supplemental nitrite increases choroidal neovascularization in mice

Low doses of nitrite, close to physiological levels, increase blood flow in normal and ischemic tissues through a nitric oxide (NO) dependent mechanism. Given that nitrite therapy and dietary supplementation with vegetables high in nitrate (e.g. beets) are gaining popularity we decided to determine if low doses of nitrite impact the development of choroidal neovascularization (CNV), a key feature of wet age related macular degeneration (AMD). Sodium nitrite (at 50 mg/L, 150 mg/L, and 300 mg/L), nitrate (1 g/L) or water alone were provided in the drinking water of C57BL/6 J mice aged 2 or 12 months. Mice were allowed to drink ad libitum for 1 week at which time laser-induced choroidal neovascularization (L-CNV) was induced. The mice continued to drink the supplemented water ad libitum for a further 14 days at which point optical coherence tomography (OCT) was performed to determine the volume of the CNV lesion. Blood was drawn to determine nitrite and nitrate levels and eyes taken for histology. CNV volume was 2.86 × 10⁷ μm³ (±0.4 × 10⁷) in young mice on water alone but CNV volume more than doubled to >6.9 × 10⁷ μm³ (±0.8 × 10⁷) in mice receiving 300 mg/L nitrite or 7.34 × 10⁷ μm³ (±1.4 × 10⁷) in 1 g/L nitrate (p < 0.01). A similar trend was observed in older mice. CNV volume was 5.3 × 10⁷ μm³ (±0.5 × 10⁷) in older mice on water alone but CNV volume almost doubled to approximately 9.3 × 10⁷ μm³ (±1.1 × 10⁷) in mice receiving 300 mg/L nitrite or 8.7 × 10⁷ μm³ (±0.9 × 10⁷) 1 g/L nitrate (p < 0.01). Plasma nitrite levels were highest in young mice receiving 150 mg/L in the drinking water with no changes in plasma nitrate observed. In older mice, drinking water nitrite did not significantly change plasma nitrite, but plasma nitrate was increased. Plasma nitrate was elevated in both young and old mice provided with nitrate supplemented drinking water. Our data demonstrate that the CNV lesion is larger in older mice compared to young and that therapeutic levels of oral nitrite increase the volume of CNV lesions in both young and older mice. Therapeutic nitrite or nitrate supplementation should be used with caution in the elderly population prone to CNV.

The role of metabolism in chondrocyte dysfunction and the progression of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by low-grade inflammation and high levels of clinical heterogeneity. Aberrant chondrocyte metabolism is a response to changes in the inflammatory microenvironment and may play a key role in cartilage degeneration and OA progression. Under conditions of environmental stress, chondrocytes tend to adapt their metabolism to microenvironmental changes by shifting from one metabolic pathway to another, for example from oxidative phosphorylation to glycolysis. Similar changes occur in other joint cells, including synoviocytes. Switching between these pathways is implicated in metabolic alterations that involve mitochondrial dysfunction, enhanced anaerobic glycolysis, and altered lipid and amino acid metabolism. The shift between oxidative phosphorylation and glycolysis is mainly regulated by the AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR) pathways. Chondrocyte metabolic changes are likely to be a feature of different OA phenotypes. Determining the role of chondrocyte metabolism in OA has revealed key features of disease pathogenesis. Future research should place greater emphasis on immunometabolism and altered metabolic pathways as a means to understand the pathophysiology of age-related OA. This knowledge will advance the development of new drugs against therapeutic targets of metabolic significance.

Acceptability and Feasibility of a 13-Week Pilot Randomised Controlled Trial Testing the Effects of Incremental Doses of Beetroot Juice in Overweight and Obese Older Adults

Nitrate-rich food can increase nitric oxide production and improve vascular and brain functions. This study examines the feasibility of a randomised controlled trial (RCT) testing the effects of prolonged consumption of different doses of dietary nitrate (NO3-) in the form of beetroot juice (BJ) in overweight and obese older participants. A single-blind, four-arm parallel pilot RCT was conducted in 62 overweight and obese (30.4 ± 4 kg/m2) older participants (mean ± standard deviation (SD), 66 ± 4 years). Participants were randomized to: (1) high-NO3- (HN: 2 × 70 mL BJ/day) (2) medium-NO3- (MN: 70 mL BJ/day), (3) low-NO3- (LN: 70 mL BJ on alternate days) or (4) Placebo (PL: 70 mL of NO3--depleted BJ on alternate days), for 13 weeks. Compliance was checked by a daily log of consumed BJ, NO3- intake, and by measuring NO3- and NO2- concentrations in plasma, saliva, and urine samples. Fifty participants completed the study. Self-reported compliance to the interventions was >90%. There were significant positive linear relationships between NO3- dose and the increase in plasma and urinary NO3- concentration (R2 = 0.71, P < 0.001 and R2 = 0.46 P < 0.001, respectively), but relationships between NO3- dose and changes in salivary NO3- and NO2- were non-linear (R2 = 0.35, P = 0.002 and R2 = 0.23, P = 0.007, respectively). The results confirm the feasibility of prolonged BJ supplementation in older overweight and obese adults.

Association of Carboxyhemoglobin Levels with Peripheral Arterial Disease in Chronic Smokers Managed at Dr George Mukhari Academic Hospital

Chronic cigarette smokers (CCS) are known to have elevated levels of carboxyhemoglobin (COHb). However, it is not known whether increased levels of COHb are associated with endothelial dysfunction (ED), and therefore the development of peripheral arterial disease (PAD). The aim of the study was to investigate the association of blood COHb and plasma nitric oxide (NO) levels, and whether it is an independent risk factor in the development of PAD among CCS at Dr George Mukhari Academic Hospital (DGMAH). A sample of 120 CCS with PAD and a convenience sample of 100 CCS without PAD were recruited into the study. Blood COHb levels were measured using the ABL 90 FLEX CO-oximeter automated spectroscopy. Plasma nitric oxide (NO) levels were measure using ELISA. Logistic regression analysis was used to investigate the association of blood COHb and plasma NO with PAD. Blood COHb levels of CCS with PAD were significantly higher than those of CCS without PAD, and the NO levels of CCS with PAD were significantly lower than those of CCS without PAD. Although both the blood COHb and plasma NO in CCS were significantly associated with PAD in bivariate logistic analysis, only plasma NO was independently associated with PAD in multivariate logistic analysis. This finding is consistent with the hypothesis that COHb is a cause of arterial damage in PAD, leading to reduced NO, and therefore reduced arterial dilation.

Protocol and recruitment results from a 13-week randomized controlled trial comparing the effects of different doses of nitrate-rich beetroot juice on cognition, cerebral blood flow and peripheral vascular function in overweight and obese older people

BACKGROUND

Nitrate-rich food can increase NO production and may induce positive effects on brain function. This study examined the feasibility of a randomized clinical trial (RCT) testing the effects of prolonged consumption of incremental doses of dietary nitrate (NO3 -) in overweight and obese older participants. Secondary aims tested dose-dependent changes in cognitive, vascular and pulmonary functions and cerebral blood flow (CBF).

METHODS

This was a single blind, four-arm parallel RCT conducted in 60 overweight and obese older participants. Eligible participants were randomized to:1) high NO3 - (140 ml of beetroot juice (BJ) per day, ~800 mg of NO3 -/day), 2) moderate NO3 - (70 ml of BJ per day, ~400 mg of NO3 -/day), 3) low NO3 - (70 ml on alternate days, ~400 mg of NO3 -) or 4) NO3 - depleted (70 ml on alternate days, ~0.001 mg of NO3). Measurements of cognitive, vascular and pulmonary functions and CBF were conducted at baseline and 13-weeks NO3 - intake was assessed by six 24-h recalls, and by measuring NO3 - intake biomarkers. Feasibility was assessed by obtaining qualitative feedback and evaluating trial recruitment, retention, compliance with study visits and measurement protocols.

RESULTS

Participant recruitment started in July 2018 and ended in April 2019. Of all the recruitment strategies that were used, advertisement of the study via Facebook generated the highest response rate. Sixty-two participants consented and were enrolled. Overall, characteristics of included participants matched our recruitment criteria.

CONCLUSION

The findings from this study provide evidence of the acceptability and feasibility of an intervention investigating the effects of incremental doses of high-nitrate BJ over a prolonged period.

TRIAL REGISTRATION

The intervention study was registered with clinical trial ISRCTN registry (ISRCTN14746723) on 27 December 2018.

Circulating markers of nitric oxide homeostasis and cardiometabolic diseases: insights from population-based studies

Emerging data suggest that impaired nitric oxide (NO) homeostasis has a key role in development of cardiometabolic disorders. The association between circulating levels of NO metabolites, i.e. nitrate and nitrite (NOx), and risk of chronic diseases has not yet been fully clarified. This work aims to address epidemiologic aspects of NO metabolism and discusses different physiologic and pathophysiologic conditions influencing circulating NOx. Further, cross-sectional associations of serum NOx with metabolic disorders are described and along the way, potential short-term and long-term power of serum NOx for predicting cardiometabolic outcomes are reviewed. Results from population-based studies show that circulating NOx is affected by aging, smoking habits, pregnancy, menopause status, thyroid hormones, and various pathologic conditions including type 2 diabetes, insulin resistance, hypertension, and renal dysfunction. Lifestyle factors, especially dietary habits, but also smoking habits and the degree of physical activity influence NO homeostasis and the circulating levels of NOx. Elevated serum NOx, due to increased iNOS activity, is associated with increased incidence of metabolic syndrome, different obesity phenotypes, and cardiovascular events.

Circulating nitric oxide metabolites and the risk of cardiometabolic outcomes: a prospective population-based study

Aim: This study was conducted to investigate whether serum NO metabolites (NOx) could predict the occurrence of type 2 diabetes (T2DM), hypertension (HTN) and metabolic syndrome (MetS). Methods: We measured serum NOx concentrations in the Tehran Lipid and Glucose Study participants (aged ≥19 years) and followed them for a median of 7.7 years for the incidence of outcomes. To determine the appropriate cut-off points of serum NOx for predicting clinical events, a random sampling method (50:50 ratio) was used for the population and for analysis, receiver operator characteristic curve was used. Multivariable Cox proportional hazard models were used to estimate the hazard ratios (HRs) with 95% confidence intervals (95% CIs) of T2DM, HTN and MetS in response to serum NOx values. Results: The optimal cut-off points of serum NOx levels for predicting T2DM, HTN and MetS were 26.5, 25.5 and 25.5 µmol/L, respectively. Participants with serum NOx levels ≥25.5 µmol/L had increased risk of MetS (HR = 1.31, 95% CI = 1.01-1.72). No evidence was found for any association of serum NOx with incidence of T2DM and HTN (HR = 1.03, 95% CI = 0.83-1.77 and HR = 1.09, 95% CI = 0.88-1.35). Conclusion: In this prospective population-based investigation, a higher circulating NOx was associated with development of MetS.

Endothelial function and lipid profile of individuals with schizophrenia participating in a supported employment program

Background

The social function of individuals with schizophrenia is usually poor and this population exhibits a sedentary lifestyle. Social participation, inclusion in the world of work in particular, might favorably interfere with the lives of these individuals by reducing sedentarism and improving their state of health.

Objective

To analyze the lipid profile and endothelial function markers among individuals with schizophrenia enrolled in a supported employment program.

Methods

Quantitative quasi-experimental study conducted with 14 individuals with schizophrenia enrolled in a labor inclusion program. Participants were assessed before enrolment (time-point 1) and one year later (time-point 2). Total cholesterol and fractions, triglycerides, serum nitrates and nitrites (endothelial function markers) were measured. The data were analyzed with software SPSS 20.

Results

The high-density lipoprotein (HDL) and low-density lipoprotein (LDL) levels exhibited significant changes one year after inclusion in the labor market. HDL increased from 82.30 to 98.60 mg/dL (p<0.01) and LDL decreased from 54.50 to 44.45 mg/dL (p<0.02). The triglyceride and total cholesterol levels remained stable. The nitrate and nitrite level exhibited significant reduction from 15.20 to 14.48 µMol (p<0.01).

Conclusion

Participation in the supported employment program might have favorably influenced the participants' lipid profile and endothelial function. Nitrites have been described as mediators in the neural inflammatory process, and reduction of their levels is associated with better prognosis of chronic diseases such as schizophrenia.

Nitric oxide donors for peripheral artery disease

Current management of peripheral arterial disease involves risk factor modification and revascularisation, but many patients are still left with debilitating symptoms. Therefore, new treatment strategies are needed. The importance of nitric oxide, and its role in regulating endothelial function, is well-established. Altering the nitric oxide pathway has been extensively studied as a means of treating vascular disease, including peripheral arterial disease. Statins and ACE inhibitors have been shown to enhance endogenous nitric oxide and improve intermittent claudication symptoms. Studies using l-arginine have produced differing results, for reasons for yet fully understood. A greater understanding of the nitric oxide pathway, and its enzymatic control, has generated more potential therapeutic targets to alter NO levels.

Dietary nitrate supplementation in cardiovascular health: an ergogenic aid or exercise therapeutic?

Oral consumption of inorganic nitrate, which is abundant in green leafy vegetables and roots, has been shown to increase circulating plasma nitrite concentration, which can be converted to nitric oxide in low oxygen conditions. The associated beneficial physiological effects include a reduction in blood pressure, modification of platelet aggregation, and increases in limb blood flow. There have been numerous studies of nitrate supplementation in healthy recreational and competitive athletes; however, the ergogenic benefits are currently unclear due to a variety of factors including small sample sizes, different dosing regimens, variable nitrate conversion rates, the heterogeneity of participants’ initial fitness levels, and the types of exercise tests used. In clinical populations, the study results seem more promising, particularly in patients with cardiovascular diseases who typically present with disruptions in the ability to transport oxygen from the atmosphere to working tissues and reduced exercise tolerance. Many of these disease-related, physiological maladaptations, including endothelial dysfunction, increased reactive oxygen species, reduced tissue perfusion, and muscle mitochondrial dysfunction, have been previously identified as potential targets for nitric oxide restorative effects. This review is the first of its kind to outline the current evidence for inorganic nitrate supplementation as a therapeutic intervention to restore exercise tolerance and improve quality of life in patients with cardiovascular diseases. We summarize the factors that appear to limit or maximize its effectiveness and present a case for why it may be more effective in patients with cardiovascular disease than as ergogenic aid in healthy populations.

Thiadiazoline- and Pyrazoline-Based Carboxamides and Carbothioamides: Synthesis and Inhibition against Nitric Oxide Synthase

Two new families of pyrazoline and thiadiazoline heterocycles have been developed. Their inhibitory activities against two different isoforms of nitric oxide synthase (inducible and neuronal NOS) are reported. The novel derivatives were synthesized combining the arylthiadiazoline or arylpyrazoline skeleton and a carboxamide or carbothioamide moiety, used as starting material ethyl 2-nitrobenzoates or substituted nitrobenzaldehydes, respectively. The structure-activity relationships of final molecules are discussed in terms of the R1 radical effects in the aromatic ring, the Y atom in the heterocyclic system, the X heteroatom in the main chain, and the R2 substituent in the carboxamide or carbothioamide rest. In general, thiadiazolines (5a–e) inhibit preferentially the neuronal isoform; among them, 5a is the best nNOS inhibitor (74.11% at 1 mM, IC50 = 420 μM). In contrast, pyrazolines (6a–r) behave better as iNOS than nNOS inhibitors, 6m being the best molecule of this series (76.86% at 1 mM of iNOS inhibition, IC50 = 130 μM) and the most potent of all tested compounds.

Hybrid Nitric Oxide Donor and its Carrier for the Treatment of Peripheral Arterial Diseases

Nitric oxide (NO) has been known to promote physiological angiogenesis to treat peripheral arterial diseases (PAD) by increasing the vascular endothelial growth factor (VEGF) level in endothelial cells (ECs) and preventing platelet adherence and leukocyte chemotaxis. However, the ongoing ischemic event during peripheral ischemia produces superoxide and diminishes the NO bioavailability by forming toxic peroxynitrite anion. Here we disclose an efficacious hybrid molecule 4-(5-Amino-1,2,3-oxadiazol-3-yl)-2,2,6,6-tetramethyl-1-piperidinol (SA-2) containing both antioxidant and NO donor functionalities that provide a therapeutic level of NO necessary to promote angiogenesis and to protect ECs against hydrogen peroxide-induced oxidative stress. Compound SA-2 scavenged reactive oxygen species, inhibited proliferation and migration of smooth muscle cells (SMCs) and promoted the tube formation from ECs. Copolymer poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with SA-2 provided a sustained release of NO over days, improved aqueous stability in serum, protected ECs against oxidative stress, and enhanced angiogenesis under stress conditions as compared to that of the control in the in vitro matrigel tube formation assay. These results indicated the potential use of SA-2 nanoparticles as an alternative therapy to treat PAD.

Inorganic nitrate as a treatment for acute heart failure: a protocol for a single center, randomized, double-blind, placebo-controlled pilot and feasibility study

Background

Acute heart failure (AHF) is a frequent reason for hospitalization worldwide and effective treatment options are limited. It is known that AHF is a condition characterized by impaired vasorelaxation, together with reduced nitric oxide (NO) bioavailability, an endogenous vasodilatory compound. Supplementation of inorganic sodium nitrate (NaNO₃) is an indirect dietary source of NO, through bioconversion. It is proposed that oral sodium nitrate will favorably affect levels of circulating NO precursors (nitrate and nitrite) in AHF patients, resulting in reduced systemic vascular resistance, without significant hypotension.

Methods and outcomes

We propose a single center, randomized, double-blind, placebo-controlled pilot trial, evaluating the feasibility of sodium nitrate as a treatment for AHF. The primary hypothesis that sodium nitrate treatment will result in increased systemic levels of nitric oxide pre-cursors (nitrate and nitrite) in plasma, in parallel with improved vasorelaxation, as assessed by non-invasively derived systemic vascular resistance index. Additional surrogate measures relevant to the known pathophysiology of AHF will be obtained in order to assess clinical effect on dyspnea and renal function.

Discussion

The results of this study will provide evidence of the feasibility of this novel approach and will be of interest to the heart failure community. This trial may inform a larger study.

Protective effects of physiological testosterone on advanced glycation end product‑induced injury in human endothelial cells

The effect of testosterone, a sex steroid, on endothelial cells is controversial as it is uncertain if it has a protective effect on them. Whether physiological testosterone can inhibit the deleterious effects of advanced glycation end products (AGEs) on endothelial cells remains to be elucidated. The present study focused on elucidating the effect of testosterone on the injury of endothelial cells induced by AGEs. Human umbilical vein endothelial cells (HUVECs) were cultured in vitro and treated with AGEs in the presence or absence of various concentrations of testosterone. The cell viability in each group was measured using an MTS assay. Early-stage apoptosis was detected using flow cytometry with Annexin V-fluorescein isothiocyanate/propidium iodide double staining, and the expression levels of apoptosis-associated proteins, B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax) and caspase-3, were determined using western blot analysis. Oxidative stress and pro-inflammatory parameters in the medium were evaluated using an enzyme-linked immunosorbent assay. The MTS results showed that AGEs significantly decreased the proliferation of HUVECs, whereas a physiological concentration of testosterone alleviated this damage. Physiological concentrations of testosterone protected the HUVECs from AGE-induced apoptosis, mediated by caspase-3 and Bax/Bcl-2. In addition, treatment of the HUVECs with AGEs caused a significant decrease in anti-oxidative parameters, but increased the concentrations of malondialdehyde and tumor necrosis factor-α. The activation of Janus kinase 2 and signal transducer and activator of transcription 3 was significantly increased by incubation with AGEs. However, pre-incubation with a physiological concentration of testosterone attenuated these changes. Therefore, the data obtained in the present study established the potential role of physiological testosterone in ameliorating AGE-induced damage in HUVECs.

Altered distribution of adrenergic constrictor responses contributes to skeletal muscle perfusion abnormalities in metabolic syndrome

PURPOSE

Although studies suggest elevated adrenergic activity paralleling metabolic syndrome in OZRs, the moderate hypertension and modest impact on organ perfusion question the multi-scale validity of these data.

METHODS

To understand how adrenergic function contributes to vascular reactivity in OZR, we utilized a multi-scale approach to investigate pressure responses, skeletal muscle blood flow, and vascular reactivity following adrenergic challenge.

RESULTS

For OZR, adrenergic challenge resulted in increased pressor responses vs LZRs, mediated via α₁ receptors, with minimal contribution by either ROS or NO bioavailability. In situ gastrocnemius muscle of OZR exhibited blunted functional hyperemia, partially restored with α₁ inhibition, although improved muscle performance and VO₂ required combined treatment with TEMPOL. Within OZR in situ cremaster muscle, proximal arterioles exhibited a more heterogeneous constriction to adrenergic challenge, biased toward hyperresponsiveness, vs LZR. This increasingly heterogeneous pattern was mirrored in ex vivo arterioles, mediated via α₁ receptors, with roles for ROS and NO bioavailability evident in hyperresponsive vessels only.

CONCLUSIONS

These results support the central role of the α₁ adrenoreceptor for augmented pressor responses and elevations in vascular resistance, but identify an increased heterogeneity of constrictor reactivity in OZR that is presently of unclear purpose.

Dietary nitrate supplementation: impact on skeletal muscle vascular control in exercising rats with chronic heart failure

Chronic heart failure (CHF) results in central and peripheral derangements that ultimately reduce skeletal muscle O2 delivery and impair exercise tolerance. Dietary nitrate (NO3 (-)) supplementation improves skeletal muscle vascular function and tolerance to exercise. We tested the hypothesis that NO3 (-) supplementation would elevate exercising skeletal muscle blood flow (BF) and vascular conductance (VC) in CHF rats. Myocardial infarction (MI) was induced (coronary artery ligation) in young adult male rats. After 21 days of recovery, rats randomly received 5 days of NO3 (-)-rich beetroot juice (CHF + BR, n = 10) or a placebo (CHF, n = 10). Mean arterial pressure (carotid artery catheter) and skeletal muscle BF (radiolabeled microspheres) were measured during treadmill exercise (20 m/min, 5% grade). CHF-induced dysfunction, as determined by myocardial infarction size (29 ± 3% and 33 ± 4% in CHF and CHF + BR, respectively) and left ventricular end-diastolic pressure (18 ± 2 and 18 ± 2 mmHg in CHF and CHF + BR, respectively), and exercising mean arterial pressure (131 ± 3 and 128 ± 4 mmHg in CHF and CHF + BR, respectively) were not different (P > 0.05) between groups. Total exercising hindlimb skeletal muscle BF (95 ± 5 and 116 ± 9 ml·min(-1)·100 g(-1) in CHF and CHF + BR, respectively) and VC (0.75 ± 0.05 and 0.90 ± 0.05 ml·min(-1)·100 g(-1)·mmHg(-1) in CHF and CHF + BR, respectively) were 22% and 20% greater in BR-supplemented rats, respectively (P < 0.05). During exercise, BF in 9 and VC in 10 hindlimb muscles and muscle portions were significantly greater in the CHF + BR group. These results provide strong evidence that dietary NO3 (-) supplementation improves skeletal muscle vascular function during exercise in rats with CHF and, thus, support the use of BR as a novel therapeutic modality for the treatment of CHF.

Vasoactive enzymes and blood flow responses to passive and active exercise in peripheral arterial disease

BACKGROUND

Peripheral arterial disease (PAD) is characterised by impaired leg blood flow, which contributes to claudication and reduced exercise capacity. This study investigated to what extent vasoactive enzymes might contribute to altered blood flow in PAD (Fontaine stage II).

METHODS

We compared femoral artery blood flow during reactive hyperaemia, leg-extension exercise and passive leg movement, and determined the level of vasoactive enzymes in skeletal muscle samples from the vastus lateralis in PAD (n = 10, 68.5 ± 6.5 years) and healthy controls (CON, n = 9, 62.1 ± 12.3 years). Leg blood flow was measured with Doppler ultrasound and muscle protein levels of phosphorylated endothelial nitric oxide synthase, NADPH oxidase, cyclooxygenase 1 and 2, thromboxane synthase, and prostacyclin synthase were determined.

RESULTS

Leg blood flow during the initial 90 s of passive leg movement (242 ± 33 vs 441 ± 75 ml min(-1), P = 0.03) and during reactive hyperaemia (423 ± 100 vs 1255 ± 175 ml min(-1), P = 0.002) was lower in PAD than CON, whereas no significant difference was observed for leg blood flow during exercise (1490 ± 250 vs 1887 ± 349 ml min(-1), P = 0.37). PAD had higher NADPH oxidase than CON (1.04 ± 0.19 vs 0.50 ± 0.06 AU, P = 0.02), with no differences for other enzymes. Leg blood flow during exercise was correlated with prostacyclin synthase (P = 0.001).

CONCLUSION

Elevated NADPH oxidase indicates that oxidative stress may be a primary cause of low nitric oxide availability and impaired blood flow in PAD.

Effects of nitrite infusion on skeletal muscle vascular control during exercise in rats with chronic heart failure

Chronic heart failure (CHF) reduces nitric oxide (NO) bioavailability and impairs skeletal muscle vascular control during exercise. Reduction of NO2 (-) to NO may impact exercise-induced hyperemia, particularly in muscles with pathologically reduced O2 delivery. We tested the hypothesis that NO2 (-) infusion would increase exercising skeletal muscle blood flow (BF) and vascular conductance (VC) in CHF rats with a preferential effect in muscles composed primarily of type IIb + IId/x fibers. CHF (coronary artery ligation) was induced in adult male Sprague-Dawley rats. After a >21-day recovery, mean arterial pressure (MAP; carotid artery catheter) and skeletal muscle BF (radiolabeled microspheres) were measured during treadmill exercise (20 m/min, 5% incline) with and without NO2 (-) infusion. The myocardial infarct size (35 ± 3%) indicated moderate CHF. NO2 (-) infusion increased total hindlimb skeletal muscle VC (CHF: 0.85 ± 0.09 ml·min(-1)·100 g(-1)·mmHg(-1) and CHF + NO2 (-): 0.93 ± 0.09 ml·min(-1)·100 g(-1)·mmHg(-1), P < 0.05) without changing MAP (CHF: 123 ± 4 mmHg and CHF + NO2 (-): 120 ± 4 mmHg, P = 0.17). Total hindlimb skeletal muscle BF was not significantly different (CHF: 102 ± 7 and CHF + NO2 (-): 109 ± 7 ml·min(-1)·100 g(-1) ml·min(-1)·100 g(-1), P > 0.05). BF increased in 6 (∼21%) and VC in 8 (∼29%) of the 28 individual muscles and muscle parts. Muscles and muscle portions exhibiting greater BF and VC after NO2 (-) infusion comprised ≥63% type IIb + IId/x muscle fibers. These data demonstrate that NO2 (-) infusion can augment skeletal muscle vascular control during exercise in CHF rats. Given the targeted effects shown herein, a NO2 (-)-based therapy may provide an attractive "needs-based" approach for treatment of the vascular dysfunction in CHF.

Skeletal Muscle Vascular Control During Exercise: Impact of Nitrite Infusion During Nitric Oxide Synthase Inhibition in Healthy Rats

The nitric oxide synthase (NOS)-independent pathway of nitric oxide (NO) production in which nitrite (NO2 (-)) is reduced to NO may have therapeutic applications for those with cardiovascular diseases in which the NOS pathway is downregulated. We tested the hypothesis that NO2 (-) infusion would reduce mean arterial pressure (MAP) and increase skeletal muscle blood flow (BF) and vascular conductance (VC) during exercise in the face of NOS blockade via L-NAME. Following infusion of L-NAME (10 mg kg(-1), L-NAME), male Sprague-Dawley rats (3-6 months, n = 8) exercised without N(G)-nitro-L arginine methyl ester (L-NAME) and after infusion of sodium NO2 (-) (7 mg kg(-1); L-NAME + NO2 (-)). MAP and hindlimb skeletal muscle BF (radiolabeled microsphere infusions) were measured during submaximal treadmill running (20 m min(-1), 5% grade). Across group comparisons were made with a published control data set (n = 11). Relative to L-NAME, NO2 (-) infusion significantly reduced MAP (P < 0.03). The lower MAP in L-NAME+NO2 (-) was not different from healthy control animals (control: 137 ± 3 L-NAME: 157 ± 7, L-NAME + NO2 (-): 136 ± 5 mm Hg). Also, NO2 (-) infusion significantly increased VC when compared to L-NAME (P < 0.03), ultimately negating any significant differences from control animals (control: 0.78 ± 0.05, L-NAME: 0.57 ± 0.03, L-NAME + NO2 (-); 0.69 ± 0.04 mL min(-1) 100 g(-1) mm Hg(-1)) with no apparent fiber-type preferential effect. Overall, hindlimb BF was decreased significantly by L-NAME; however, in L-NAME + NO2 (-), BF improved to a level not significantly different from healthy controls (control: 108 ± 8, L-NAME: 88 ± 3, L-NAME + NO2 (-): 94 ± 6 mL min(-1) 100 g(-1), P = 0.38 L-NAME vs L-NAME + NO2 (-)). Individuals with diseases that impair NOS activity, and thus vascular function, may benefit from a NO2 (-)-based therapy in which NO bioavailability is elevated in an NOS-independent manner.

Cell-specific impact of nitric oxide-dependent guanylyl cyclase on arteriogenesis and angiogenesis in mice

Nitric oxide (NO) acts as essential regulator of vasculogenesis and angiogenesis and is critical for arteriogenesis. Whether NO's effects in vivo are mediated through NO-sensitive guanylyl cyclase (NO-GC) and thus by cGMP-dependent mechanisms has been only poorly addressed. Mice lacking NO-GC globally or specifically in smooth muscle cells (SMC) or endothelial cells (EC) were subjected to two established models for arteriogenesis and angiogenesis, namely hindlimb ischemia and oxygen-induced retinopathy. Our data clearly show the involvement of NO-GC in the recovery of blood flow after hindlimb ischemia, and this effect could be attributed to NO-GC in SMC. In the retina, global deletion of NO-GC led to reduced oxygen-induced vessel loss and hypoxia-induced capillary regrowth, whereas pathological neovascularization was increased. These effects were also seen in mice with SMC-specific NO-GC deletion but not in animals lacking NO-GC in EC. Intriguingly, NO-GC was found to be strongly expressed in retinal pericytes. Our data prove the involvement of NO-GC in growth and plasticity of hindlimb and retinal vasculature after ischemic/hypoxic insult.

Endothelial health in childhood acute lymphoid leukemia survivors: pilot evaluation with peripheral artery tonometry

BACKGROUND

Childhood cancer survivors are a growing population at risk for poor cardiac outcomes. Acute lymphoid leukemia (ALL) survivors are among those at increased risk of cardiovascular complications. Early identification of impaired vascular health may allow for interventions to improve these outcomes. The purpose of this study was to evaluate vascular health using peripheral artery tonometry in ALL survivors and compare results with healthy siblings.

PROCEDURE

Sixteen ALL survivor, healthy sibling pairs, aged 8 to 20 years, were evaluated for vascular health and cardiovascular risk factors (body mass index, central adiposity, blood pressure, and fitness). One-tailed paired t test was used to compare the groups.

RESULTS

Survivors were similar to siblings in cardiovascular risk measures but had poorer vascular health as measured by reactive hyperemia index (survivor RHI 1.54 vs. sibling 1.77; P=0.0474).

CONCLUSION

This study reveals that even among survivors who are comparable to their healthy siblings in other traditional cardiovascular risks, there is evidence of poorer vascular health.

A session of resistance exercise increases vasodilation in intermittent claudication patients

No study has shown the effects of acute resistance exercise on vasodilatory capacity of patients with peripheral artery disease. The aim of this study was to analyse the effects of a single session of resistance exercise on blood flow, reactive hyperemia, plasma nitrite, and plasma malondialdehyde in patients with peripheral artery disease. Fourteen peripheral artery disease patients underwent, in a random order, 2 experimental sessions: control (rest for 30 min) and resistance exercise (8 exercises, 2 sets of 10 repetitions at an intensity of 5–7 in the OMNI Resistance Exercise Scale). Blood flow, reactive hyperemia, plasma nitrite, and malondialdehyde were measured before and 40 min after the interventions in both sessions. Data were compared between sessions by analysis of covariance, using pre-intervention values as covariates. The increases in blood flow, reactive hyperemia, and log plasma nitrite were greater (p ≤ 0.05) after resistance exercise than the control session (3.2 ± 0.1 vs. 2.7 ± 0.1 mL·100 mL−1tissue·min−1, 8.0 ± 0.1 vs. 5.7 ± 0.1 AU, and 1.36 ± 0.01 vs. 1.26 ± 0.01 μmol∙L−1, respectively). On the other hand, malondialdehyde was similar between sessions (p > 0.05). In peripheral arterial disease patients, a single session of resistance exercise increases blood flow and reactive hyperemia, which seems to be mediated, in part, by increases in nitric oxide release.

Sildenafil improves skeletal muscle oxygenation during exercise in men with intermittent claudication

Endothelial dysfunction caused by defective nitric oxide (NO) signaling plays a pivotal role in the pathogenesis of intermittent claudication (IC). In the present study, we evaluated the acute effects of sildenafil, a phosphodiesterase type 5 inhibitor that acts by prolonging NO-mediated cGMP signaling in vascular smooth muscle, on blood pressure (BP), skeletal muscle oxygenation, and walking tolerance in patients with IC. A randomized, double-blind, crossover study was conducted in which 12 men with stable IC received two consecutive doses of 50 mg of sildenafil or matching placebo and underwent a symptom-limited exercise test on the treadmill. Changes in gastrocnemius deoxy-hemoglobin by near-infrared spectroscopy estimated peripheral muscle O2delivery-to-utilization matching. Systolic BP was significantly lower during the sildenafil trial relative to placebo during supine rest (∼15 mmHg), submaximal exercise (∼14 mmHg), and throughout recovery (∼18 mmHg) ( P < 0.05). Diastolic BP was also lower after sildenafil during upright rest (∼6 mmHg) and during recovery from exercise (∼7 mmHg) ( P < 0.05). Gastrocnemius deoxygenation was consistently reduced during submaximal exercise (∼41%) and at peak exercise (∼34%) following sildenafil compared with placebo ( P < 0.05). However, pain-free walking time (placebo: 335 ± 42 s vs. sildenafil: 294 ± 35 s) and maximal walking time (placebo: 701 ± 58 s vs. sildenafil: 716 ± 62 s) did not differ between trials. Acute administration of sildenafil lowers BP and improves skeletal muscle oxygenation during exercise but does not enhance walking tolerance in patients with IC. Whether the beneficial effects of sildenafil on muscle oxygenation can be sustained over time and translated into positive clinical outcomes deserve further consideration in this patient population.

Evaluation of endothelial function by peripheral arterial tonometry and relation with the nitric oxide pathway

Endothelial dysfunction is an important component in the development of cardiovascular diseases. Endothelial function may be evaluated by peripheral arterial tonometry (PAT) which measures the vasodilator function in the microvasculature of the fingertip during reactive hyperaemia. The reactive hyperaemia index (RHI) is decreased in the presence of cardiovascular risk factors and thus far several studies have shown that PAT-RHI may provide reliable prediction of outcome. The technique is operator independent and easy to perform. Abnormalities measured by PAT follow the same trend as those measured by flow-mediated dilation in the brachial artery, but the two methods are not interchangeable. We have reviewed the recent literature in an effort to evaluate peripheral arterial tonometry as a method to assess the function of the endothelium and additionally suggest directions for future research. Special attention will be directed to the nitric oxide dependency of the reactive hyperaemia index obtained by peripheral arterial tonometry.

Dark chocolate acutely improves walking autonomy in patients with peripheral artery disease

Background

NOX‐2, the catalytic subunit of NADPH oxidase, has a key role in the formation of reactive oxidant species and is implicated in impairing flow‐mediated dilation (FMD). Dark chocolate exerts artery dilatation via down‐regulating NOX2‐mediated oxidative stress. The aim of this study was to investigate whether dark chocolate improves walking autonomy in peripheral artery disease (PAD) patients via an oxidative stress‐mediated mechanism.

Methods and Results

FMD, serum levels of isoprostanes, nitrite/nitrate (NOx) and sNOX2‐dp, a marker of blood NOX2 activity, maximal walking distance (MWD) and maximal walking time (MWT) were studied in 20 PAD patients (14 males and 6 females, mean age: 69±9 years) randomly allocated to 40 g of dark chocolate (>85% cocoa) or 40 g of milk chocolate (≤35% cocoa) in a single blind, cross‐over design. The above variables were assessed at baseline and 2 hours after chocolate ingestion. Dark chocolate intake significantly increased MWD (+11%; P<0.001), MWT (+15%; P<0.001), serum NOx (+57%; P<0.001) and decreased serum isoprostanes (−23%; P=0.01) and sNOX2‐dp (−37%; P<0.001); no changes of the above variables were observed after milk chocolate intake. Serum epicatechin and its methylated metabolite significantly increased only after dark chocolate ingestion. Multiple linear regression analysis showed that Δ of MWD was independently associated with Δ of MWT (P<0.001) and Δ of NOx (P=0.018). In vitro study demonstrated that HUVEC incubated with a mixture of polyphenols significantly increased nitric oxide (P<0.001) and decreased E‐selectin (P<0.001) and VCAM1 (P<0.001).

Conclusion

In PAD patients dark but not milk chocolate acutely improves walking autonomy with a mechanism possibly related to an oxidative stress‐mediated mechanism involving NOX2 regulation.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01947712.

Active invasion of oral and aortic tissues by Porphyromonas gingivalis in mice causally links periodontitis and atherosclerosis

Atherosclerotic vascular disease is a leading cause of myocardial infarction and cerebrovascular accident, and independent associations with periodontal disease (PD) are reported. PD is caused by polymicrobial infections and aggressive immune responses. Genomic DNA of Porphyromonas gingivalis, the best-studied bacterial pathogen associated with severe PD, is detected within atherosclerotic plaque. We examined causal relationships between chronic P. gingivalis oral infection, PD, and atherosclerosis in hyperlipidemic ApoE^null mice. ApoE^null mice (n = 24) were orally infected with P. gingivalis for 12 and 24 weeks. PD was assessed by standard clinical measurements while the aorta was examined for atherosclerotic lesions and inflammatory markers by array. Systemic inflammatory markers serum amyloid A, nitric oxide, and oxidized low-density lipoprotein were analyzed. P. gingivalis infection elicited specific antibodies and alveolar bone loss. Fluorescent in situ hybridization detected viable P. gingivalis within oral epithelium and aorta, and genomic DNA was detected within systemic organs. Aortic plaque area was significantly increased in P. gingivalis-infected mice at 24 weeks (P<0.01). Aortic RNA and protein arrays indicated a strong Th2 response. Chronic oral infection with P. gingivalis results in a specific immune response, significant increases in oral bone resorption, aortic inflammation, viable bacteria in oral epithelium and aorta, and plaque development.

Inorganic nitrite supplementation for healthy arterial aging

Aging is the major risk factor for cardiovascular diseases (CVD). This is attributable primarily to adverse changes in arteries, notably, increases in large elastic artery stiffness and endothelial dysfunction mediated by inadequate concentrations of the vascular-protective molecule, nitric oxide (NO), and higher levels of oxidative stress and inflammation. Inorganic nitrite is a promising precursor molecule for augmenting circulating and tissue NO bioavailability because it requires only a one-step reduction to NO. Nitrite also acts as an independent signaling molecule, exerting many of the effects previously attributed to NO. Results of recent studies indicate that nitrite may be effective in the treatment of vascular aging. In old mice, short-term oral sodium nitrite supplementation reduces aortic pulse wave velocity, the gold-standard measure of large elastic artery stiffness, and ameliorates endothelial dysfunction, as indicated by normalization of NO-mediated endothelium-dependent dilation. These improvements in age-related vascular dysfunction with nitrite are mediated by reductions in oxidative stress and inflammation, and may be linked to increases in mitochondrial biogenesis and health. Increasing nitrite levels via dietary intake of nitrate appears to have similarly beneficial effects in many of the same physiological and clinical settings. Several clinical trials are being performed to determine the broad therapeutic potential of increasing nitrite bioavailability on human health and disease, including studies related to vascular aging. In summary, inorganic nitrite, as well as dietary nitrate supplementation, represents a promising therapy for treatment of arterial aging and prevention of age-associated CVD in humans.

Risk of recurrence and long-term outcomes after colonic diverticular bleeding

PURPOSE

Diverticular disease is one of the most common causes of acute lower gastrointestinal bleeding. We aimed to evaluate the natural history, follow-up, and risk factors associated with re-bleeding (recurrence) in patients with colonic diverticular bleeding.

METHODS

We reviewed patients with proven colonic diverticular hemorrhage from September 1993 to June 2012 at our institution. Recurrence was the main outcome measure.

RESULTS

We identified 78 out of 95 patients with proven diverticular bleed who were treated non-operatively and were followed up for a median of 57.1 months. Thirty-seven (47 %) of these patients with a median age of 67 years developed recurrent diverticular bleed after a median time of 8.1 months. The bleeding originated from the left colon in 78 (83 %) out of 95 patients in the first bleeding episode and 31(84 %) out of 37 patients during the recurrent bleeding episode. Thirty-six patients (97 %) with recurrent diverticular bleed required surgical intervention. Old age at the time of initial bleeding was associated with recurrence (p = 0.001). Patients with diverticulitis (p < 0.0001), peripheral vascular (p = 0.01), and chronic renal diseases (p = 0.047) were found to have an increased risk for recurrent colonic diverticular bleed. We only had one perioperative mortality due to postoperative sepsis. All other mortalities were not directly associated with surgery.

CONCLUSION

Patients with a history of colonic diverticular bleed are prone to recur shortly thereafter. Certain risk factors including increased age, documented diverticulitis, history of peripheral vascular disease, and chronic renal failure may predispose to recurrence.

Diabetes status differentiates endothelial function and plasma nitrite response to exercise stress in peripheral arterial disease following supervised training

AIMS

To determine if type 2 diabetes mellitus (T2D) differentiates endothelial function and plasma nitrite response (a marker of nitric oxide bioavailability) during exercise in peripheral arterial disease (PAD) subjects prior to and following 3 months supervised exercise training (SET).

METHODS

In subjects with T2D+PAD (n = 13) and PAD-only (n = 14), endothelial function was measured using brachial artery flow-mediated dilation. On a separate day, venous blood draws were performed at rest and 10 min following a symptom-limited graded treadmill test (SL-GXT). Plasma samples were snap-frozen for analysis of nitrite by reductive chemiluminescence. All testing was repeated following 3 months of SET.

RESULTS

Prior to training both groups demonstrated endothelial dysfunction, which was correlated with a net decrease in plasma nitrite following a SL-GXT (p ≤ 0.05). Following SET, the PAD-only group demonstrated an improvement in endothelial function (p ≤ 0.05) and COT (p ≤ 0.05), which was related to a net increase in plasma nitrite following the SL-GXT (both p ≤ 0.05). The T2D+PAD group had none of these increases.

CONCLUSIONS

T2D in the presence of PAD attenuated improvements in endothelial function, net plasma nitrite, and COT following SET. This suggests that T2D maybe associated with an inability to endogenously increase vascular NO bioavailability to SET.

Nitrite reductase and nitric-oxide synthase activity of the mitochondrial molybdopterin enzymes mARC1 and mARC2

Mitochondrial amidoxime reducing component (mARC) proteins are molybdopterin-containing enzymes of unclear physiological function. Both human isoforms mARC-1 and mARC-2 are able to catalyze the reduction of nitrite when they are in the reduced form. Moreover, our results indicate that mARC can generate nitric oxide (NO) from nitrite when forming an electron transfer chain with NADH, cytochrome b5, and NADH-dependent cytochrome b5 reductase. The rate of NO formation increases almost 3-fold when pH was lowered from 7.5 to 6.5. To determine if nitrite reduction is catalyzed by molybdenum in the active site of mARC-1, we mutated the putative active site cysteine residue (Cys-273), known to coordinate molybdenum binding. NO formation was abolished by the C273A mutation in mARC-1. Supplementation of transformed Escherichia coli with tungsten facilitated the replacement of molybdenum in recombinant mARC-1 and abolished NO formation. Therefore, we conclude that human mARC-1 and mARC-2 are capable of catalyzing reduction of nitrite to NO through reaction with its molybdenum cofactor. Finally, expression of mARC-1 in HEK cells using a lentivirus vector was used to confirm cellular nitrite reduction to NO. A comparison of NO formation profiles between mARC and xanthine oxidase reveals similar Kcat and Vmax values but more sustained NO formation from mARC, possibly because it is not vulnerable to autoinhibition via molybdenum desulfuration. The reduction of nitrite by mARC in the mitochondria may represent a new signaling pathway for NADH-dependent hypoxic NO production.

Sodium nitrite in patients with peripheral artery disease and diabetes mellitus: safety, walking distance and endothelial function

Nitrite stores decrease after exercise in patients with peripheral artery disease (PAD) and diabetes represents decreased nitric oxide (NO) bioavailability that may contribute to endothelial dysfunction and limit exercise duration. The primary objective of this placebo-controlled study was the safety and tolerability of multiple doses of oral sodium nitrite in patients with PAD, predominantly with diabetes, over a period of 10 weeks. The primary efficacy endpoint was endothelial flow-mediated dilatation (FMD) and secondary efficacy endpoints included a 6-minute walk test and quality of life assessment. Of the 55 subjects, the most common side effects attributed to sodium nitrite were a composite of headache and dizziness occurring in 21% with the 40 mg dose and 44% with the 80 mg dose. There was no clinically significant elevation of methemoglobin. FMD non-significantly worsened in the placebo and 40 mg groups, but was stable in the 80 mg group. Diabetic patients receiving 80 mg had significantly higher FMD compared with the placebo and 40 mg groups. There was no significant change in 6-minute walk test or quality of life parameters over time compared to placebo. In conclusion, sodium nitrite therapy is well tolerated in patients with PAD. The possible clinical benefit of sodium nitrite should be studied in a larger and fully powered trial.