Aging of the nitric oxide system: are we as old as our NO?

The impact of prediabetes and diabetes on endothelial function in a large population-based cohort

BACKGROUND

Diabetes and prediabetes are well-recognized risk factors for cardiovascular disease (CVD) and are marked by vascular endothelial dysfunction (ED). However, there is a scarcity of thorough population-based studies examining ED in individuals with diabetes/prediabetes free from manifest CVD. Here, we examined the association between ED assessed by reactive hyperaemia index (RHI) in the finger and diabetes/prediabetes in a large middle-aged population cohort.

METHODS

Within the Malmö Offspring Study, following the exclusion of participants <30 years and participants with prevalent CVD, 1384 participants had complete data on all covariates. The RHI was calculated using pulse amplitude tonometry. ED was defined as RHI < 1.67. Multivariable logistic and linear regression models were conducted to investigate associations between ED and RHI with diabetes and prediabetes.

RESULTS

The study population had a mean age of 53.6 ± 7.6 years (53% women). In study participants with manifest diabetes (n = 121) and prediabetes (n = 514), ED was present in 42% and 25% respectively, compared to 23% in those with normal glucometabolic status. In multivariable logistic regression analyses, prevalent diabetes was significantly associated with ED (OR 1.95; 95%CI 1.57-3.39; p = 0.002), as well as with lower RHI (β-coeff. -0.087; p = 0.002). However, prediabetes showed no association with neither ED nor RHI.

CONCLUSION

In a population free from CVD, vascular endothelial dysfunction was primarily associated with manifest diabetes, but not with prediabetes, implying that finger ED may develop when diabetes is established, rather than being an early sign of glucose intolerance. Further research is needed to explore whether addressing glucose intolerance could potentially delay or prevent vascular ED onset.

Inflammaging, immunosenescence, and cardiovascular aging: insights into long COVID implications

Aging leads to physiological changes, including inflammaging-a chronic low-grade inflammatory state with significant implications for various physiological systems, particularly for cardiovascular health. Concurrently, immunosenescence-the age-related decline in immune function, exacerbates vulnerabilities to cardiovascular pathologies in older individuals. Examining the dynamic connections between immunosenescence, inflammation, and cardiovascular aging, this mini-review aims to disentangle some of these interactions for a better understanding of their complex interplay. In the context of cardiovascular aging, the chronic inflammatory state associated with inflammaging compromises vascular integrity and function, contributing to atherosclerosis, endothelial dysfunction, arterial stiffening, and hypertension. The aging immune system's decline amplifies oxidative stress, fostering an environment conducive to atherosclerotic plaque formation. Noteworthy inflammatory markers, such as the high-sensitivity C-reactive protein, interleukin-6, interleukin-1β, interleukin-18, and tumor necrosis factor-alpha emerge as key players in cardiovascular aging, triggering inflammatory signaling pathways and intensifying inflammaging and immunosenescence. In this review we aim to explore the molecular and cellular mechanisms underlying inflammaging and immunosenescence, shedding light on their nuanced contributions to cardiovascular diseases. Furthermore, we explore the reciprocal relationship between immunosenescence and inflammaging, revealing a self-reinforcing cycle that intensifies cardiovascular risks. This understanding opens avenues for potential therapeutic targets to break this cycle and mitigate cardiovascular dysfunction in aging individuals. Furthermore, we address the implications of Long COVID, introducing an additional layer of complexity to the relationship between aging, immunosenescence, inflammaging, and cardiovascular health. Our review aims to stimulate continued exploration and advance our understanding within the realm of aging and cardiovascular health.

Sarcopenic obesity in older adults: a clinical overview

Sarcopenic obesity is characterized by a concurrent decline in muscle mass and function, along with increased adipose tissue. Sarcopenic obesity is a growing concern in older adults owing to significant health consequences, including implications for mortality, comorbidities and risk of developing geriatric syndromes. A 2022 consensus statement established a new definition and diagnostic criteria for sarcopenic obesity. The pathophysiology of this condition involves a complex interplay between muscle, adipose tissue, hormonal changes, inflammation, oxidative stress and lifestyle factors, among others. Sarcopenic obesity is treated with a range of management approaches, such as lifestyle interventions, exercise, nutrition and medical therapies. Emerging therapies that were developed for treating other conditions may be relevant to sarcopenic obesity, including novel pharmacological agents and personalized approaches such as precision medicine. In this Review, we synthesize the current knowledge of the clinical importance of sarcopenic obesity, its assessment and diagnosis, along with current and emerging management strategies.

Dietary High Salt Intake Exacerbates SGK1-Mediated T Cell Pathogenicity in L-NAME/High Salt-Induced Hypertension

Sodium chloride (NaCl) activates Th17 and dendritic cells in hypertension by stimulating serum/glucocorticoid kinase 1 (SGK1), a sodium sensor. Memory T cells also play a role in hypertension by infiltrating target organs and releasing proinflammatory cytokines. We tested the hypothesis that the role of T cell SGK1 extends to memory T cells. We employed mice with a T cell deletion of SGK1, SGK1fl/fl × tgCD4cre mice, and used SGK1fl/fl mice as controls. We treated the mice with L-NAME (0.5 mg/mL) for 2 weeks and allowed a 2-week washout interval, followed by a 3-week high-salt (HS) diet (4% NaCl). L-NAME/HS significantly increased blood pressure and memory T cell accumulation in the kidneys and bone marrow of SGK1fl/fl mice compared to knockout mice on L-NAME/HS or groups on a normal diet (ND). SGK1fl/fl mice exhibited increased albuminuria, renal fibrosis, and interferon-γ levels after L-NAME/HS treatment. Myography demonstrated endothelial dysfunction in the mesenteric arterioles of SGK1fl/fl mice. Bone marrow memory T cells were adoptively transferred from either mouse strain after L-NAME/HS administration to recipient CD45.1 mice fed the HS diet for 3 weeks. Only the mice that received cells from SGK1fl/fl donors exhibited increased blood pressure and renal memory T cell infiltration. Our data suggest a new therapeutic target for decreasing hypertension-specific memory T cells and protecting against hypertension.

Dual-Acting Nitric Oxide Donor and Phosphodiesterase Inhibitor TOP-N53 Increases Lifespan and Health Span of Caenorhabditis elegans

The quest for extending lifespan and promoting a healthy aging has been a longstanding pursuit in the field of aging research. The control of aging and age-related diseases by nitric oxide (NO) and cGMP signaling is a broadly conserved process from worms to human. Here we show that TOP-N53, a dual-acting NO donor and PDE5 inhibitor, can increase both lifespan and health span in C. elegans .

Associations between Aging and Vitamin D Status with Whole-Body Nitric Oxide Production and Markers of Endothelial Function

BACKGROUND

Aging and vitamin D deficiency have been associated with reduced nitric oxide (NO) synthesis and impaired endothelial function (EF) but the evidence in humans remains weak.

OBJECTIVES

Two independent cross-sectional studies were designed to evaluate the association between age, sex, and plasma vitamin D concentrations with physiological and biochemical biomarkers of NO synthesis and EF in young and older healthy participants (Study 1) and in overweight and obese postmenopausal females (Study 2).

METHODS

In Study 1, 40 young (20-49 y) and older (50-75 y) males and females (10 participants per age and sex group) were included. Resting blood pressure and ear-to-finger peripheral pulse wave velocity (PWV) were measured. A stable-isotopic method was used to determine whole-body NO production. Plasma 25-hydroxyvitamin D (25(OH)D), nitrate, nitrite, and asymmetric dimethylarginine (ADMA) concentrations were determined. In Study 2, 80 older overweight and obese females (age 61.2 ± 6.2 y, body mass index 29.5 ± 4.4 kg/m2) were recruited. Postocclusion reactive hyperemia (PORH) and peripheral PWV were measured. Plasma concentrations of 25(OH)D, nitrate, cyclic guanosine monophosphate, 3-nitrotyrosine (3-NT), endothelin-1, vascular endothelial growth factor, and ADMA were determined.

RESULTS

In Study 1, whole-body NO production was significantly greater in young compared with older participants (0.61 ± 0.30 μmol·h-1·kg-1 compared with 0.39 ± 0.10 μmol·h-1·kg-1, P = 0.01) but there was no evidence of a sex difference (P = 0.81). Plasma 25(OH)D concentration was not associated with PWV (r = 0.18, P = 0.28) or whole-body NO production (r = -0.20, P = 0.22). Plasma ADMA concentration was associated positively with age (r = 0.35, P = 0.03) and negatively with whole-body NO production (r = -0.33, P = 0.04). In Study 2, age was associated with lower PORH (r = -0.28, P = 0.02) and greater ADMA concentrations (r = 0.22, P = 0.04). Plasma 25(OH)D concentration was inversely associated with 3-NT concentrations (r = -0.31, P = 0.004).

CONCLUSIONS

Older age was associated with lower whole-body NO production. Plasma vitamin D concentrations were not associated with NO production or markers of EF but showed a weak, significant correlation with oxidative stress in postmenopausal overweight females.

Nitric Oxide as a Determinant of Human Longevity and Health Span

The master molecular regulators and mechanisms determining longevity and health span include nitric oxide (NO) and superoxide anion radicals (SOR). L-arginine, the NO synthase (NOS) substrate, can restore a healthy ratio between the dangerous SOR and the protective NO radical to promote healthy aging. Antioxidant supplementation orchestrates protection against oxidative stress and damage-L-arginine and antioxidants such as vitamin C increase NO production and bioavailability. Uncoupling of NO generation with the appearance of SOR can be induced by asymmetric dimethylarginine (ADMA). L-arginine can displace ADMA from the site of NO formation if sufficient amounts of the amino acid are available. Antioxidants such as ascorbic acids can scavenge SOR and increase the bioavailability of NO. The topics of this review are the complex interactions of antioxidant agents with L-arginine, which determine NO bioactivity and protection against age-related degeneration.

The Effect of Aging on Nitric Oxide Production during Cerebral Ischemia and Reperfusion in Wistar Rats and Spontaneous Hypertensive Rats: An In Vivo Microdialysis Study

Nitric oxide (NO) is involved in the pathogenesis of cerebral ischemic injury. Here, we investigated the effects of aging on NO production during cerebral ischemia-reperfusion (IR). Male Wister rats (WRs) were assigned to 12-month-old (older; n = 5) and 3-month-old (younger; n = 7) groups. Similarly, male spontaneous hypertensive rats (SHRs) were allocated to 12-month-old (older; n = 6) and 3-month-old (younger; n = 8) groups. After anesthesia, their NO production was monitored using in vivo microdialysis probes inserted into the left striatum and hippocampus. Forebrain cerebral IR injuries were produced via ligation of the bilateral common carotid arteries, followed by reperfusion. The change in the NO3- of the older rats in the SHR groups in the striatum was less compared to that of the younger rats before ischemia, during ischemia, and after reperfusion (p < 0.05). In the hippocampus, the change in the NO3- of the older rats in the SHR groups was lower compared to that of the younger rats after reperfusion (p < 0.05). There were no significant differences between the two WR groups. Our findings suggested that aging in SHRs affected NO production, especially in the striatum, before and during cerebral ischemia, and after reperfusion. Hypertension and aging may be important factors impacting NO production in brain IR injury.

Coronary "Microvascular Dysfunction": Evolving Understanding of Pathophysiology, Clinical Implications, and Potential Therapeutics

Until recently, it has been generally held that stable angina pectoris (SAP) primarily reflects the presence of epicardial coronary artery stenoses due to atheromatous plaque(s), while acute myocardial infarction (AMI) results from thrombus formation on ruptured plaques. This concept is now challenged, especially by results of the ORBITA and ISCHEMIA trials, which showed that angioplasty/stenting does not substantially relieve SAP symptoms or prevent AMI or death in such patients. These disappointing outcomes serve to redirect attention towards anomalies of small coronary physiology. Recent studies suggest that coronary microvasculature is often both structurally and physiologically abnormal irrespective of the presence or absence of large coronary artery stenoses. Structural remodelling of the coronary microvasculature appears to be induced primarily by inflammation initiated by mast cell, platelet, and neutrophil activation, leading to erosion of the endothelial glycocalyx. This leads to the disruption of laminar flow and the facilitation of endothelial platelet interaction. Glycocalyx shedding has been implicated in the pathophysiology of coronary artery spasm, cardiovascular ageing, AMI, and viral vasculitis. Physiological dysfunction is closely linked to structural remodelling and occurs in most patients with myocardial ischemia, irrespective of the presence or absence of large-vessel stenoses. Dysfunction includes the impairment of platelet and vascular responsiveness to autocidal coronary vasodilators, such as nitric oxide, prostacyclin, and hydrogen sulphide, and predisposes both to coronary vasoconstriction and to a propensity for microthrombus formation. These findings emphasise the need for new directions in medical therapeutics for patients with SAP, as well as a wide range of other cardiovascular disorders.

Phenotypic characteristics of asthma and morbidity are associated with distinct longitudinal changes in L-arginine metabolism

BACKGROUND

The L-arginine metabolome is dysregulated in asthma, though it is not understood how longitudinal changes in L-arginine metabolism differ among asthma phenotypes and relate to disease outcomes.

OBJECTIVES

To determine the longitudinal associations between phenotypic characteristics with L-arginine metabolites and their relationships with asthma morbidity.

METHODS

This is a prospective cohort study of 321 patients with asthma followed semiannually for over 18 months with assessments of plasma L-arginine metabolites, asthma control, spirometry, quality of life and exacerbations. Metabolite concentrations and ratios were transformed using the natural logarithm.

RESULTS

There were many differences in L-arginine metabolism among asthma phenotypes in the adjusted models. Increasing body mass index was associated with increased asymmetric dimethylarginine (ADMA) and depleted L-citrulline. Latinx was associated with increased metabolism via arginase, with higher L-ornithine, proline and L-ornithine/L-citrulline levels, and was found to have higher L-arginine availability compared with white race. With respect to asthma outcomes, increasing L-citrulline was associated with improved asthma control and increasing L-arginine and L-arginine/ADMA were associated with improved quality of life. Increased variability in L-arginine, L-arginine/ADMA, L-arginine/L-ornithine and L-arginine availability index over 12 months were associated with increased exacerbations, OR 4.70 (95% CI 1.35 to 16.37), OR 8.69 (95% CI 1.98 to 38.08), OR 4.17 (95% CI 1.40 to 12.41) and OR 4.95 (95% CI 1.42 to 17.16), respectively.

CONCLUSIONS

Our findings suggest that L-arginine metabolism is associated with multiple measures of asthma control and may explain, in part, the relationship between age, race/ethnicity and obesity with asthma outcomes.

Carotid dysfunction in senescent female mice is mediated by increased α1A-adrenoceptor activity and COX-derived vasoconstrictor prostanoids

α-Adrenergic receptors are crucial regulators of vascular hemodynamics and essential pharmacological targets for cardiovascular diseases. With aging, there is an increase in sympathetic activation, which could contribute to the progression of aging-associated cardiovascular dysfunction, including stroke. Nevertheless, there is little information directly associating adrenergic receptor dysfunction in the blood vessels of aged females. This study determined the role of a-adrenergic receptors in carotid dysfunction of senescent female mice (accelerated-senescence prone, SAMP8), compared with a nonsenescent (accelerated-senescence prone, SAMR1). Vasoconstriction to phenylephrine (Phe) was markedly increased in common carotid artery of SAMP8 [area under the curve (AUC), 527 ± 53] compared with SAMR1 (AUC, 334 ± 30, P = 0.006). There were no changes in vascular responses to the vasoconstrictor agent U46619 or the vasodilators acetylcholine (ACh) and sodium nitroprusside (NPS). Hyperactivity to Phe in female SAMP8 was reduced by cyclooxygenase-1 and cyclooxygenase-2 inhibition and associated with augmented ratio of TXA2/PGI2 release (SAMR1, 1.1 ± 0.1 vs. SAMP8, 2.1 ± 0.3, P = 0.007). However, no changes in cyclooxygenase expression were seen in SAMP8 carotids. Selective α_1A-receptor antagonism markedly reduced maximal contraction, whereas α_1D antagonism induced a minor shift in Phe contraction in SAMP8 carotids. Ligand binding analysis revealed a threefold increase of α-adrenergic receptor density in smooth muscle cells (VSMCs) of SAMP8 vs. SAMR1. Phe rapidly increased intracellular calcium (Ca_i²⁺) in VSMCs via the α_1A-receptor, with a higher peak in VSMCs from SAMP8. In conclusion, senescence intensifies vasoconstriction mediated by α_1A-adrenergic signaling in the carotid of female mice by mechanisms involving increased Ca_i²⁺ and release of cyclooxygenase-derived prostanoids.NEW & NOTEWORTHY The present study provides evidence that senescence induces hyperreactivity of α₁-adrenoceptor-mediated contraction of the common carotid. Impairment of α₁-adrenoceptor responses is linked to increased Ca²⁺ influx and release of COX-derived vasoconstrictor prostanoids, contributing to carotid dysfunction in the murine model of female senescence (SAMP8). Increased reactivity of the common carotid artery during senescence may lead to morphological and functional changes in arteries of the cerebral microcirculation and contribute to cognitive decline in females. Because the elderly population is growing, elucidating the mechanisms of aging- and sex-associated vascular dysfunction is critical to better direct pharmacological and lifestyle interventions to prevent cardiovascular risk in both sexes.

Extracellular Vesicles and Cardiac Aging

Global population aging is a major challenge to health and socioeconomic policies. The prevalence of diseases progressively increases with aging, with cardiovascular disease being the major cause of mortality among elderly people. The allostatic overload imposed by the accumulation of cardiac senescent cells has been suggested to play a pivotal role in the aging-related deterioration of cardiovascular function. Senescent cells exhibit intrinsic disorders and release a senescence-associated secretory phenotype (SASP). Most of these SASP compounds and damaged molecules are released from senescent cells by extracellular vesicles (EVs). Once secreted, these EVs can be readily incorporated by recipient neighboring cells and elicit cellular damage or otherwise can promote extracellular matrix remodeling. This has been associated with the development of cardiac dysfunction, fibrosis, and vascular calcification, among others. The molecular signature of these EVs is highly variable and might provide important information for the development of aging-related biomarkers. Conversely, EVs released by the stem and progenitor cells can exert a rejuvenating effect, raising the possibility of future anti-aging therapies.

Effects of Fermented Garlic Extract Containing Nitric Oxide Metabolites on Blood Flow in Healthy Participants: A Randomized Controlled Trial

Aged or fermented garlic extract (FGE) is a natural remedy that improves vascular function through increasing vascular nitric oxide (NO) bioavailability. This is because nitrite (NO2-), a NO metabolite, can be produced through bioconversion with macrobacteria during the fermentation of foods like garlic. We aimed to evaluate the effects of NO2- in FGE on blood flow (BF), blood pressure (BP), velocity of the common carotid artery (CCA) and internal carotid artery (ICA), regional cerebral BF (rCBF), and peripheral BF (PBF). The study was divided into two parts: (1) Thirty healthy adults were divided into FGE and placebo groups to compare BP and velocity of the CCA and ICA; and (2) Twenty-eight healthy adults were divided into FGE and placebo groups to compare rCBF and PBF and determine changes before/after ingestion. Significant changes were noted in BP and the velocity of both CCA 30-60 min after FGE ingestion. FGE ingestion resulted in significant increases in rCBF and increases in body surface temperature through alterations in PBF. No detectable clinical side effects were noted. Overall, oral administration of NO2- containing FGE demonstrated acute positive effects in upregulating BF, including the CCA, BP, rCBF, and PBF. Follow-up studies with larger sample sizes and long-term ingestion may be needed.

Pathophysiology and genetics of salt-sensitive hypertension

Most hypertensive cases are primary and heavily associated with modifiable risk factors like salt intake. Evidence suggests that even small reductions in salt consumption reduce blood pressure in all age groups. In that regard, the ACC/AHA described a distinct set of individuals who exhibit salt-sensitivity, regardless of their hypertensive status. Data has shown that salt-sensitivity is an independent risk factor for cardiovascular events and mortality. However, despite extensive research, the pathogenesis of salt-sensitive hypertension is still unclear and tremendously challenged by its multifactorial etiology, complicated genetic influences, and the unavailability of a diagnostic tool. So far, the important roles of the renin-angiotensin-aldosterone system, sympathetic nervous system, and immune system in the pathogenesis of salt-sensitive hypertension have been studied. In the first part of this review, we focus on how the systems mentioned above are aberrantly regulated in salt-sensitive hypertension. We follow this with an emphasis on genetic variants in those systems that are associated with and/or increase predisposition to salt-sensitivity in humans.

ET-1 as a Sex-Specific Mechanism Impacting Age-Related Changes in Vascular Function

Aging is a primary risk factor for cardiovascular disease (CVD), which is the leading cause of death in developed countries. Globally, the population of adults over the age of 60 is expected to double by the year 2050. CVD prevalence and mortality rates differ between men and women as they age in part due to sex-specific mechanisms impacting the biological processes of aging. Measures of vascular function offer key insights into cardiovascular health. Changes in vascular function precede changes in CVD prevalence rates in men and women and with aging. A key mechanism underlying these changes in vascular function is the endothelin (ET) system. Studies have demonstrated sex and sex hormone effects on endothelin-1 (ET-1), and its receptors ETA and ETB. However, with aging there is a dysregulation of this system resulting in an imbalance between vasodilation and vasoconstriction. Thus, ET-1 may play a role in the sex differences observed with vascular aging. While most research has been conducted in pre-clinical animal models, we describe more recent translational data in humans showing that the ET system is an important regulator of vascular dysfunction with aging and acts through sex-specific ET receptor mechanisms. In this review, we present translational evidence (cell, tissue, animal, and human) that the ET system is a key mechanism regulating sex-specific changes in vascular function with aging, along with therapeutic interventions to reduce ET-mediated vascular dysfunction associated with aging. More knowledge on the factors responsible for the sex differences with vascular aging allow for optimized therapeutic strategies to attenuate CVD risk in the expanding aging population.

Nitric oxide, aging and aerobic exercise: Sedentary individuals to Master's athletes

Aging is associated with a decline in physiological function and exercise performance. These effects are mediated, at least in part, by an age-related decrease in the bioavailability of nitric oxide (NO), a ubiquitous gasotransmitter and regulator of myriad physiological processes. The decrease in NO bioavailability with aging is especially apparent in sedentary individuals, whereas older, physically active individuals maintain higher levels of NO with advancing age. Strategies which enhance NO bioavailability (including nutritional supplementation) have been proposed as a potential means of reducing the age-related decrease in physiological function and enhancing exercise performance and may be of interest to a range of older individuals including those taking part in competitive sport. In this brief review we discuss the effects of aging on physiological function and endurance exercise performance, and the potential role of changes in NO bioavailability in these processes. We also provide a summary of current evidence for dietary supplementation with substrates for NO production - including inorganic nitrate and nitrite, l-arginine and l-citrulline - for improving exercise capacity/performance in older adults. Additionally, we discuss the (limited) evidence on the effects of (poly)phenols and other dietary antioxidants on NO bioavailability in older individuals. Finally, we provide suggestions for future research.

Effect of Vitamin C and Protein Supplementation on Plasma Nitrate and Nitrite Response following Consumption of Beetroot Juice

Beetroot juice is a food high in nitrate and is associated with cardiometabolic health benefits and enhanced exercise performance through the production of nitric oxide in the nitrate−nitrite−nitric oxide pathway. Since various food components influence this pathway, the aim of this trial was to study the effect of beetroot juice alone and in conjunction with vitamin C or protein on the acute response to plasma nitrate and nitrite levels in healthy middle- to older-aged adults. In this cross-over trial, each participant received, in a randomized order, a single dose of Beet It Sport® alone; Beet It Sport®, plus a 200 mg vitamin C supplement; and Beet It Sport® plus 15 g of whey protein. Plasma levels of nitrate and nitrite were determined prior to and at 1 and 3 h after intervention. Log plasma nitrate and nitrite was calculated to obtain data that were normally distributed, and these data were analyzed using two-way within-factors ANOVA, with time and treatment as the independent factors. There were no statistically significant differences for log plasma nitrate (p = 0.308) or log plasma nitrite (p = 0.391) values across treatments. Log plasma nitrate increased significantly from pre-consumption levels after 1 h (p < 0.001) and 3 h (p < 0.001), but plasma nitrate was lower at 3 h than 1 h (p < 0.001). Log plasma nitrite increased from pre to 1 h (p < 0.001) and 3 h (p < 0.001) with log values at 3 h higher than at 1 h (p = 0.003). In this cohort, we observed no differences in log plasma nitrate and nitrite at 1 h and 3 h after co-ingesting beetroot juice with vitamin C or a whey protein supplement compared to beetroot juice alone. Further research needs to be undertaken to expand the blood-sampling time-frame and to examine factors that may influence the kinetics of the plasma nitrate to nitrite efficacy, such as differences in fluid volume and osmolarity between treatments employed.

Cardiovascular Inflammaging: Mechanisms and Translational Aspects

Aging is one of the major non-reversible risk factors for several chronic diseases, including cancer, type 2 diabetes, dementia, and cardiovascular diseases (CVD), and it is a key cause of multimorbidity, disability, and frailty (decreased physical activity, fatigue, and weight loss). The underlying cellular mechanisms are complex and consist of multifactorial processes, such as telomere shortening, chronic low-grade inflammation, oxidative stress, mitochondrial dysfunction, accumulation of senescent cells, and reduced autophagy. In this review, we focused on the molecular mechanisms and translational aspects of cardiovascular aging-related inflammation, i.e., inflammaging.

Impairment of Anti-Aggregatory Responses to Nitric Oxide and Prostacyclin: Mechanisms and Clinical Implications in Cardiovascular Disease

The propensity towards platelet-rich thrombus formation increases substantially during normal ageing, and this trend is mediated by decreases in platelet responsiveness to the anti-aggregatory nitric oxide (NO) and prostacyclin (PGI₂) pathways. The impairment of soluble guanylate cyclase and adenylate cyclase-based signalling that is associated with oxidative stress represents the major mechanism of this loss of anti-aggregatory reactivity. Platelet desensitization to these autacoids represents an adverse prognostic marker in patients with ischemic heart disease and may contribute to increased thrombo-embolic risk in patients with heart failure. Patients with platelet resistance to PGI₂ also are unresponsive to ADP receptor antagonist therapy. Apart from ischemia, diabetes and aortic valve disease are also associated with impaired anti-aggregatory homeostasis. This review examines the association of impaired platelet cyclic nucleotide (i.e., cGMP and cAMP) signalling with the emerging evidence of thromboembolic risk in cardiovascular diseases, and discusses the potential therapeutic strategies targeting this abnormality.

α-Klotho, Plasma Asymmetric Dimethylarginine, and Kidney Disease Progression

Rationale & Objective

We aimed to explore the associated factors of endothelial injury in chronic kidney disease (CKD) and the relationship between endothelial dysfunction and CKD prognosis.

Study Design

A prospective observational cohort study.

Setting & Participants

77 adults with CKD stages 1-5 were enrolled January 2010 to December 2010 and followed up until December 2015.

Exposure

Serum asymmetric dimethylarginine (ADMA) level at baseline, α-klotho, sodium-phosphorus synergistic transporter, and dimethylarginine-dimethylamine hydrolase expression in kidney biopsy samples.

Outcome

Initiation of kidney replacement therapy (KRT).

Analytical Approach

Kaplan-Meier analysis was used for evaluation of the incidence rate of KRT. All tests were 2 tailed, and statistical significance was defined as P < 0.05.

Results

Mean serum ADMA level of 77 patients was 64.3 ± 34.6 ng/mL. ADMA level increased with CKD stages (P = 0.06) and declining kidney function (r = −0.267; P = 0.02). The expression of α-klotho in kidney biopsy specimens also decreased. Median follow-up time was 56 (interquartile range, 50.5-62) months. Kaplan-Meier analyses showed that during a total follow-up of 6 years, the incidence of KRT initiation in the high-ADMA group was significantly higher than that in the low group (35.9% vs 13.2%; P = 0.03). ADMA level was negatively correlated with α-klotho (r = −0.233; P = 0.04) and positively correlated with phosphorus level (r = 0.243; P = 0.04). The expression of sodium-phosphorus synergistic transporter in kidney tubules, which promoted phosphorus reabsorption, and the expression of dimethylarginine-dimethylamine hydrolase isoform 1, which regulated ADMA, were decreased. Correlation analysis also showed that ADMA level decreased while age increased at baseline (r = −0.292; P = 0.01).

Limitations

Small sample size with limited longer-term follow-up.

Conclusions

Serum ADMA levels increased as kidney function declined, and high serum ADMA level was associated with incident kidney failure. Low tissue α-klotho and high levels of plasma phosphorus or tissue expression of type II sodium/phosphate cotransporter in the kidney are associated with higher circulating ADMA levels, suggesting that they may be involved in the pathogenesis of endothelial dysfunction in patients with CKD.

Serum nitrite and nitrate: A potential biomarker for post-covid-19 complications?

Nitric oxide (NO) plays an important role in cardiovascular and immune systems. Quantification of blood nitrite and nitrate, two relatively stable metabolites of NO (generally as NO_x), has been acknowledged, in part, representing NO bioactivity. Dysregulation of NO_x had been reported in SARS-CoV-2 infected populations, but whether patients recovered from COVID-19 disease present with restored NO_x is unknown. In this study, serum NO₂^- and NO₃^- were quantified and analyzed among 109 recovered adults in comparison to a control group of 166 uninfected adults. Nitrite or nitrate levels were not significantly different among mild-, common-, severe- and critical-type patients. However, these recovered patients had dramatically lower NO₂^- and NO₂^-/NO₃^- than the uninfected group (p < 0.0001), with significantly higher NO₃^- levels (p = 0.0023) than the uninfected group. Nitrate and nitrite/nitrate were positively and negatively correlated with patient age, respectively, with age 65 being a turning point among recovered patients. These results indicate that low NO₂^-, low NO₂^-/NO₃^- and high NO₃^- may be potential biomarkers of long-term poor or irreversible outcomes after SARS-CoV-2 infection. It suggests that NO metabolites might serve as a predictor to track the health status of recovered COVID-19 patients, highlighting the need to elucidate the role of NO after SARS-CoV-2 infection.

Transcriptional Regulation of Structural and Functional Adaptations in a Developing Adulthood Myocardium

The development of the heart follows a synergic action of several signaling pathways during gestational, pre- & postnatal stages. The current study aimed to investigate whether the myocardium experiences transcriptional changes during the transition from post-natal to adult hood stages. Herein, we used C57/B16/J mice at 4 (28- days; post-natal/PN) and 20 weeks (adulthood/AH) of ages and employed the next generation RNAseq (NGS) to profile the transcriptome and echocardiography analysis to monitor the structural/functional changes in the heart. NGS-based RNA-seq revealed that 1215 genes were significantly upregulated and 2549 were down regulated in the AH versus PN hearts, indicating a significant transcriptional change during this transition.

A synchronized cardiac transcriptional regulation through cell cycle, growth hormones, redox homeostasis and metabolic pathways was noticed in both PN and AH hearts. Echocardiography reveals significant structural and functional (i.e. systolic/diastolic) changes during the transition of PN to adult stage. Particularly, a progressive decline in ejection fraction and cardiac output was observed in AH hearts. These structural adaptations are in line with critical signaling pathways that drive the maturation of heart during AH. Overall, we have presented a comprehensive transcriptomic analysis along with structural-functional relationship during the myocardial development in adult mice.

An Overview of NO Signaling Pathways in Aging

Nitric Oxide (NO) is a potent signaling molecule involved in the regulation of various cellular mechanisms and pathways under normal and pathological conditions. NO production, its effects, and its efficacy, are extremely sensitive to aging-related changes in the cells. Herein, we review the mechanisms of NO signaling in the cardiovascular system, central nervous system (CNS), reproduction system, as well as its effects on skin, kidneys, thyroid, muscles, and on the immune system during aging. The aging-related decline in NO levels and bioavailability is also discussed in this review. The decreased NO production by endothelial nitric oxide synthase (eNOS) was revealed in the aged cardiovascular system. In the CNS, the decline of the neuronal (n)NOS production of NO was related to the impairment of memory, sleep, and cognition. NO played an important role in the aging of oocytes and aged-induced erectile dysfunction. Aging downregulated NO signaling pathways in endothelial cells resulting in skin, kidney, thyroid, and muscle disorders. Putative therapeutic agents (natural/synthetic) affecting NO signaling mechanisms in the aging process are discussed in the present study. In summary, all of the studies reviewed demonstrate that NO plays a crucial role in the cellular aging processes.

Inhaled nasopharyngeal nitric oxide concentrations during unilateral nostril breathing - A pilot study

The yogic pranayama technique of unilateral nostril breathing (UNB) has previously demonstrated improvements in language and anxiety in stroke sufferers, as well as reduced blood pressure and increased heart rate in normal healthy adults. The nose typically passes different amounts of air through each nostril with the greater amount of air passing through the 'patent' side, and a lesser amount through the 'congested' side. Each side of the nose periodically takes turns at carrying the dominant tidal air flow in what is termed the' nasal cycle'. The nasal sinuses are a rich source of inhaled nitric oxide, a colourless and odourless gas that acts as a bronchodilator, vasodilator, and neurotransmitter. Nasal derived nitric oxide (NO) may contribute to the benefits attributed to UNB. This investigation seeks to assess the influence the nasal cycle has on inhaled nasopharyngeal NO concentrations during UNB by comparing unobstructed bilateral nostril breathing to patent-side and congested-side UNB in healthy individuals demonstrating a nasal cycle. After determining the patent and congested nasal sides in healthy adult volunteers, and sampling air at both nostrils, nasopharyngeal inhaled NO concentrations were then assessed during normal nasal at-rest tidal breathing during three different nasal breathing states: first both nostrils, then allocated in randomised order, patent side only, and congested side with only UNB. Nasopharyngeal NO concentrations were found to be consistently higher on both exhalation and inhalation during congested side UNB, when compared with either unilateral patent side UNB or breathing through both nostrils.

Deficiency of Endothelial Nitric Oxide Synthase (eNOS) Exacerbates Brain Damage and Cognitive Deficit in A Mouse Model of Vascular Dementia

Vascular Dementia (VaD) accounts for nearly 20% of all cases of dementia. eNOS plays an important role in neurovascular remodeling, anti-inflammation, and cognitive functional recovery after stroke. In this study, we investigated whether eNOS regulates brain damage, cognitive function in mouse model of bilateral common carotid artery stenosis (BCAS) induced VaD. Late-adult (6-8 months) C57BL/6J and eNOS knockout (eNOS-/-) mice were subjected to BCAS (n=12/group) or sham group (n=8/group). BCAS was performed by applying microcoils to both common carotid arteries. Cerebral blood flow (CBF) and blood pressure were measured. A battery of cognitive functional tests was performed, and mice were sacrificed 30 days after BCAS. Compared to corresponding sham mice, BCAS in wild-type (WT) and eNOS-/- mice significantly: 1) induces short term, long term memory loss, spatial learning and memory deficits; 2) decreases CBF, increases ischemic cell damage, including apoptosis, white matter (WM) and axonal damage; 3) increases blood brain barrier (BBB) leakage, decreases aquaporin-4 (AQP4) expression and vessel density; 4) increases microglial, astrocyte activation and oxidative stress in the brain; 5) increases inflammatory factor interleukin-1 receptor-associated kinase-1(IRAK-1) and amyloid beta (Aβ) expression in brain; 6) increases IL-6 and IRAK4 expression in brain. eNOS-/-sham mice exhibit increased blood pressure, decreased iNOS and nNOS in brain compared to WT-sham mice. Compared to WT-BCAS mice, eNOS-/-BCAS mice exhibit worse vascular and WM/axonal damage, increased BBB leakage and inflammatory response, increased cognitive deficit, decreased iNOS, nNOS in brain. eNOS deficit exacerbates BCAS induced brain damage and cognitive deficit.

The Potential Role of Creatine in Vascular Health

Creatine is an organic compound, consumed exogenously in the diet and synthesized endogenously via an intricate inter-organ process. Functioning in conjunction with creatine kinase, creatine has long been known for its pivotal role in cellular energy provision and energy shuttling. In addition to the abundance of evidence supporting the ergogenic benefits of creatine supplementation, recent evidence suggests a far broader application for creatine within various myopathies, neurodegenerative diseases, and other pathologies. Furthermore, creatine has been found to exhibit non-energy related properties, contributing as a possible direct and in-direct antioxidant and eliciting anti-inflammatory effects. In spite of the new clinical success of supplemental creatine, there is little scientific insight into the potential effects of creatine on cardiovascular disease (CVD), the leading cause of mortality. Taking into consideration the non-energy related actions of creatine, highlighted in this review, it can be speculated that creatine supplementation may serve as an adjuvant therapy for the management of vascular health in at-risk populations. This review, therefore, not only aims to summarize the current literature surrounding creatine and vascular health, but to also shed light onto the potential mechanisms in which creatine may be able to serve as a beneficial supplement capable of imparting vascular-protective properties and promoting vascular health.

COVID-19: A Challenge to Physiology of Aging

The death toll of the current COVID-19 pandemic is strongly biased toward the elderly. COVID-19 case fatality rate (CFR) increases with age exponentially, its doubling time being about 7 years, irrespective of countries and epidemic stages. The same age-dependent mortality pattern known as the Gompertz law is featured by the total mortality and its main constituents attributed to cardiovascular, metabolic, neurological, and oncological diseases. Among patients dying of COVID-19, most have at least one of these conditions, whereas none is found in most of those who pass it successfully. Thus, gerontology is indispensable in dealing with the pandemic, which becomes a benchmark for validating the gerontological concepts and advances. The two basic alternative gerontological concepts imply that either aging results from the accumulation of stochastic damage, or is programmed. Based on these different grounds, several putative anti-aging drugs have been proposed as adjuvant means for COVID-19 prevention and/or treatment. These proposals are reviewed in the context of attributing the molecular targets of these drugs to the signaling pathways between the sensors of resource availability and the molecular mechanisms that allocate resources to storage, growth and reproduction or to self-maintenance and repair. Each of the drugs appears to reproduce only a part of the physiological responses to reduced resource availability caused by either dietary calories restriction or physical activity promotion, which are the most robust means of mitigating the adverse manifestations of aging. In the pathophysiological terms, the conditions of the endothelium, which worsen as age increases and may be significantly improved by the physical activity, is a common limiting factor for the abilities to withstand both physical stresses and challenges imposed by COVID-19. However, the current anti-epidemic measures promote sedentary indoor lifestyles, at odds with the most efficient behavioral interventions known to decrease the vulnerability to both the severe forms of COVID-19 and the prevalent aging-associated diseases. To achieve a proper balance in public health approaches to COVID-19, gerontologists should be involved in crosstalk between virologists, therapists, epidemiologists, and policy makers. The present publication suggests a conceptual background for that.

Urinary nitrate concentration as a marker for kidney transplant rejection

BACKGROUND

Early identification and treatment of kidney transplant rejection episodes is vital to limit loss of function and prolong the life of the transplanted kidney and recipient. Current practice depends on detecting a creatinine rise. A biomarker to diagnose transplant rejection at an earlier time point than current practice, or to inform earlier decision making to biopsy, could be transformative. It has previously been shown that urinary nitrate concentration is elevated in renal transplant rejection. Nitrate is a nitric oxide (NO) oxidation product. Transplant rejection upregulates NO synthesis via inducible nitric oxide synthase leading to elevations in urinary nitrate concentration. We have recently validated a urinary nitrate concentration assay which could provide results in a clinically relevant timeframe. Our aim was to determine whether urinary nitrate concentration is a useful tool to predict renal transplant rejection in the context of contemporary clinical practice.

METHODS

We conducted a prospective observational study, recruiting renal transplant participants over an 18-month period. We made no alterations to the patients' clinical care including medications, immunosuppression, diet and frequency of visits. We collected urine samples from every clinical attendance. We assessed the urinary nitrate to creatinine ratio (uNCR) between patient groups: routine attendances, biopsy proven rejection, biopsy proven no rejection and other call backs. uNCR was examined over time for those with biopsy proven transplant rejection. These four groups were compared using an ANOVA test.

RESULTS

A total of 2656 samples were collected. uNCR during biopsy proven rejection, n = 15 (median 49 μmol/mmol, IQR 23-61) was not significantly different from that of routine samples, n = 164 (median 55 μmol/mmol, IQR 37-82) (p = 0.55), or biopsy proven no rejection, n = 12 (median 39 μmol/mmol, IQR 21-89) (P = 0.77). Overall uNCR was highly variable with no diagnostic threshold for kidney transplant rejection. Furthermore, within-patient uNCR was highly variable over time, and thus it was not possible to produce individualised patient thresholds to identify rejection. The total taking Tacrolimus was 204 patients, with no statistical difference between the uNCR of all those on Tacrolimus, against those not, p = 0.18.

CONCLUSION

The urinary nitrate to creatinine ratio is not a useful biomarker for renal transplant rejection.

Anthocyanins attenuate vascular and inflammatory responses to a high fat high energy meal challenge in overweight older adults: A cross-over, randomized, double-blind clinical trial

BACKGROUND & AIMS

Postprandial metabolic imbalances are important indicators of later developing cardiovascular disease (CVD). This study investigated the effects of food anthocyanins on vascular and microvascular function, and CVD associated biomarkers following a high fat high energy (HFHE) meal challenge in overweight older adults.

METHODS

Sixteen subjects (13 female, 3 male, mean age 65.9 SD 6.0 and body mass index 30.6 kg/m² SD 3.9) participated in a crossover, randomized, controlled, double-blind clinical trial (registered under Australian New Zealand Clinical Trials Registry, identifier no. ACTRN12620000437965). Participants consumed a HFHE meal with a 250 mL dose of either intervention (anthocyanins-rich Queen Garnet Plum) or control (apricot) juice. Blood samples and blood pressure measures were collected at baseline, 2 h and 4 h following the HFHE meal. Vascular and microvascular function were evaluated at baseline and 2 h after the HFHE meal.

RESULTS

Participants had a higher 2 h postprandial flow-mediated dilatation (+1.14%) and a higher microvascular post-occlusive reactive hyperaemia (+0.10 perfusion units per mmHg) when allocated to the anthocyanin compared to the control arm (P = 0.019 and P = 0.049, respectively). C-reactive protein was lower 4 h postprandially in the anthocyanins (1.80 mg/L, IQR 0.90) vs control arm (2.30 mg/L, IQR 1.95) (P = 0.026), accompanied by a trend for lower concentrations of interleukin-6 (P = 0.075). No significant postprandial differences were observed between treatments for blood pressure, triacylglycerol, total cholesterol, serum derivatives of reactive oxidative metabolites, tumor necrosis factor alpha, interleukin-1 beta, or maximum microvascular perfusion following iontophoresis of acetylcholine.

CONCLUSION

Fruit-based anthocyanins attenuated the potential postprandial detrimental effects of a HFHE challenge on parameters of vascular and microvascular function, and inflammatory biomarkers in overweight older adults. Anthocyanins may reduce cardiovascular risk associated with endothelial dysfunction and inflammatory responses to a typical high fat 'Western' meal. Further studies are required to better elucidate the clinical implications of postprandial biomarkers of CVD.

New insights into RhoA/Rho-kinase signaling: a key regulator of vascular contraction

While Rho-signalling controlling vascular contraction is a canonical mechanism, with the modern approaches used in research, we are advancing our understanding and details into this pathway are often uncovered. RhoA-mediated Rho-kinase is the major regulator of vascular smooth muscle cells and a key player manoeuvring other functions in these cells. The discovery of new interactions, such as oxidative stress and hydrogen sulphide with Rho signalling are emerging addition not only in the physiology of the smooth muscle, but especially in the pathophysiology of vascular diseases. Likewise, the interplay between ageing and Rho-kinase in the vasculature has been recently considered. Importantly, in smooth muscle contraction, this pathway may also be affected by sex hormones, and consequently, sex-differences. This review provides an overview of Rho signalling mediating vascular contraction and focuses on recent topics discussed in the literature affecting this pathway such as ageing, sex differences and oxidative stress.

The Evolving Applications of Creatine Supplementation: Could Creatine Improve Vascular Health?

Creatine is a naturally occurring compound, functioning in conjunction with creatine kinase to play a quintessential role in both cellular energy provision and intracellular energy shuttling. An extensive body of literature solidifies the plethora of ergogenic benefits gained following dietary creatine supplementation; however, recent findings have further indicated a potential therapeutic role for creatine in several pathologies such as myopathies, neurodegenerative disorders, metabolic disturbances, chronic kidney disease and inflammatory diseases. Furthermore, creatine has been found to exhibit non-energy-related properties, such as serving as a potential antioxidant and anti-inflammatory. Despite the therapeutic success of creatine supplementation in varying clinical populations, there is scarce information regarding the potential application of creatine for combatting the current leading cause of mortality, cardiovascular disease (CVD). Taking into consideration the broad ergogenic and non-energy-related actions of creatine, we hypothesize that creatine supplementation may be a potential therapeutic strategy for improving vascular health in at-risk populations such as older adults or those with CVD. With an extensive literature search, we have found only four clinical studies that have investigated the direct effect of creatine on vascular health and function. In this review, we aim to give a short background on the pleiotropic applications of creatine, and to then summarize the current literature surrounding creatine and vascular health. Furthermore, we discuss the varying mechanisms by which creatine could benefit vascular health and function, such as the impact of creatine supplementation upon inflammation and oxidative stress.

Integrated metabolomics reveals altered lipid metabolism in adipose tissue in a model of extreme longevity

Adipose tissue plays an essential role in metabolic health. Ames dwarf mice are exceptionally long-lived and display metabolically beneficial phenotypes in their adipose tissue, providing an ideal model for studying the intersection between adipose tissue and longevity. To this end, we assessed the metabolome and lipidome of adipose tissue in Ames dwarf mice. We observed distinct lipid profiles in brown versus white adipose tissue of Ames dwarf mice that are consistent with increased thermogenesis and insulin sensitivity, such as increased cardiolipin and decreased ceramide concentrations. Moreover, we identified 5-hydroxyeicosapentaenoic acid (5-HEPE), an ω-3 fatty acid metabolite, to be increased in Ames dwarf brown adipose tissue (BAT), as well as in circulation. Importantly, 5-HEPE is increased in other models of BAT activation and is negatively correlated with body weight, insulin resistance, and circulating triglyceride concentrations in humans. Together, these data represent a novel lipid signature of adipose tissue in a mouse model of extreme longevity.

A randomized controlled trial of nitrate supplementation in well-trained middle and older-aged adults

Purpose

Nitrate (NO₃^-), through its conversion to nitrite (NO₂^-) and nitric oxide, has been shown to increase exercise tolerance in healthy younger adults and older diseased patients. Nitrate’s effect in well-trained middle to older-aged adults has not been studied. Therefore, the purpose of this investigation was to examine the effects of a NO₃^- rich beverage on submaximal constant work rate exercise time in well-trained middle to older-aged adults.

Methods

This was a randomized controlled cross-over trial with 15 well-trained middle to older-aged adults, 41–64 year-old, who received one of two treatments (NO₃^- rich beverage then placebo or placebo then NO₃^- rich beverage), after which an exercise test at 75 percent of the subject’s maximal work rate was completed.

Results

The NO₃^- rich beverage increased plasma NO₃^- and NO₂^- levels by 260 μM and 0.47 μM, respectively (p<0.001). Exercise time was not significantly different (p = 0.31) between the NO₃^- rich versus placebo conditions (1130±151 vs 1060±132 sec, respectively). Changes in exercise time between the two conditions ranged from a 55% improvement to a 40% decrease with the NO₃^- rich beverage. Oxygen consumption and rating of perceived exertion were not significantly different between the two conditions.

Conclusion

In middle to older-aged well-trained adults, NO₃^- supplementation has non-significant, albeit highly variable, effects on exercise tolerance.

ClinicalTrials.gov Identifier: NCT03371966

Nitroxyl: A Novel Strategy to Circumvent Diabetes Associated Impairments in Nitric Oxide Signaling

Diabetes is associated with an increased mortality risk due to cardiovascular complications. Hyperglycemia-induced oxidative stress underlies these complications, leading to an impairment in endogenous nitric oxide (NO•) generation, together with reductions in NO• bioavailability and NO• responsiveness in the vasculature, platelets and myocardium. The latter impairment of responsiveness to NO•, termed NO• resistance, compromises the ability of traditional NO•-based therapeutics to improve hemodynamic status during diabetes-associated cardiovascular emergencies, such as acute myocardial infarction. Whilst a number of agents can ameliorate (e.g. angiotensin converting enzyme [ACE] inhibitors, perhexiline, statins and insulin) or circumvent (e.g. nitrite and sGC activators) NO• resistance, nitroxyl (HNO) donors offer a novel opportunity to circumvent NO• resistance in diabetes. With a suite of vasoprotective properties and an ability to enhance cardiac inotropic and lusitropic responses, coupled with preserved efficacy in the setting of oxidative stress, HNO donors have intact therapeutic potential in the face of diminished NO• signaling. This review explores the major mechanisms by which hyperglycemia-induced oxidative stress drives NO• resistance, and the therapeutic potential of HNO donors to circumvent this to treat cardiovascular complications in type 2 diabetes mellitus.

Impaired l-arginine-nitric oxide pathway contributes to the pathogenesis of resistant hypertension

The precise mechanisms underlying resistant hypertension remain elusive. Reduced nitric oxide (NO) bioavailability is frequently documented in chronic kidney disease, obesity, diabetes and advanced age, all of which are risk factors for resistant hypertension. Sympathetic overactivity and chronic activation of the renin-angiotensin system are salient features of resistant hypertension. Interestingly, recent data indicate that renal sympathetic overactivity can reduce the expression of neuronal nitric oxide synthase in the paraventricular nucleus. Reduced NO levels in the paraventricular nucleus can increase sympathetic outflow and this can create a vicious cycle contributing to resistant hypertension. Angiotensin II can reduce l-arginine transport and hence NO production. Reduced NO levels may reduce the formation of angiotensin 1-7 dampening the cardio-protective effects of the renin-angiotensin system contributing to resistant hypertension. In addition, interleukin-6 (IL-6) is demonstrated to be independently associated with resistant hypertension, and IL-6 can reduce NO synthesis. Despite this, NO levels have not been quantified in resistant hypertension. Findings from a small proof of concept study indicate that NO donors can reduce blood pressure in patients with resistant hypertension but more studies are required to validate these preliminary findings. In the present paper, we put forward the hypothesis that reduced NO bioavailability contributes substantially to the development of resistant hypertension.

Influence of Genetic Variation in PDE3A on Endothelial Function and Stroke

We aimed to characterize the genetics of endothelial function and how this influences risk for cardiovascular diseases such as ischemic stroke. We integrated genetic data from a study of ultrasound flow-mediated dilatation of brachial artery in adolescents from ALSPAC (Avon Longitudinal Study of Parents and Children; n=5214) with a study of ischemic stroke (MEGASTROKE: n=60 341 cases and 452 969 controls) to identify variants that confer risk of ischemic stroke through altered endothelial function. We identified a variant in PDE3A (Phosphodiesterase 3A), encoding phosphodiesterase 3A, which was associated with flow-mediated dilatation in adolescents (9-12 years of age; β[SE], 0.38 [0.070]; P=3.8×10-8) and confers risk of ischemic stroke (odds ratio, 1.04 [95% CI, 1.02-1.06]; P=5.2×10-6). Bayesian colocalization analyses showed the same underlying variation is likely to lead to both associations (posterior probability, 97%). The same variant was associated with flow-mediated dilatation in a second study in young adults (age, 24-27 years; β[SE], 0.47 [0.23]; P=0.047) but not in older adults (β[SE], -0.012 [0.13]; P=0.89). We conclude that a genetic variant in PDE3A influences endothelial function in early life and leads to increased risk of ischemic stroke. Subtle, measurable changes to the vasculature that are influenced by genetics also influence risk of ischemic stroke.

Targeting heme-oxidized soluble guanylate cyclase to promote osteoblast function

The enzyme soluble guanylate cyclase (sGC) plays an essential part in the nitric oxide (NO) signaling pathway by binding to the prosthetic heme group; thereby catalyzing the synthesis of cyclic guanosine monophosphate (cGMP)-dependent protein kinases. Impaired NO-sGC-cGMP signaling could lead to osteoblast apoptosis by mechanisms involving the oxidative-stress-induced shift of the redox state of the reduced heme to oxidized sGC, leading to diminished heme binding to the enzyme and rendering the sGC unresponsive to NO. Targeting oxidized sGC to enhance cGMP production could restore proliferation and differentiation of osteoblasts into osteocytes. Here, the potential role of sGC activators of an oxidized or heme-free sGC as a target for promoting osteoblast function is reviewed and strategies for delivering drugs to bone are identified.

Nitric Oxide Metabolites and Lung Cancer Incidence: A Matched Case-Control Study Nested in the ESTHER Cohort

Studies suggest that nitric oxide (NO) may have a possible role in lung carcinogenesis. This study is aimed to evaluate the association of the NO metabolites, namely, nitrite and nitrate, with lung cancer incidence. We conducted a matched case-control study (n = 245 incident lung cancer cases and n = 735 controls) based on the German ESTHER cohort (n = 9,940). Controls were matched to cases on age, sex, smoking status (never/former/current smoking), and pack-years of smoking. The sum of nitrite and nitrate was measured in urine samples using a colorimetric assay and was standardized for renal function by urinary creatinine. Conditional logistic regression models, adjusted for lifestyle factors, asthma prevalence, and family history of lung cancer, were used to estimate odds ratios (ORs) and 95% confidence intervals (95% CI). Among incident lung cancer cases, high nitrite/nitrate levels were statistically significantly associated with current smoking, a low BMI, and the oxidative stress biomarker 8-isoprostane levels. Nitrite/nitrate levels in the top quintile were statistically significantly associated with lung cancer incidence: the OR (95% CI) was 1.37 (1.04-1.82) for comparison with the bottom quintile. This association was unaltered after additional adjustment for 8-isoprostane levels and C-reactive protein (CRP). In conclusion, this large cohort study suggested that subjects with high urinary nitrite/nitrate concentrations had an increased risk of lung cancer and this association was independent of smoking, CRP, 8-isoprostane levels, and other established lung cancer risk factors. Further studies are needed to validate these findings and to confirm the hypothesis that pathologically high levels of NO are involved in lung cancer development.

The Effects of Beetroot Juice on Blood Pressure, Microvascular Function and Large-Vessel Endothelial Function: A Randomized, Double-Blind, Placebo-Controlled Pilot Study in Healthy Older Adults

Dietary nitrate (NO₃⁻) has been reported to improve endothelial function (EF) and blood pressure (BP). However, most studies only assess large-vessel EF with little research on the microvasculature. Thus, the aim of the present pilot study is to examine NO₃⁻ supplementation on microvascular and large-vessel EF and BP. Twenty older adults (63 ± 6 years) were randomized to a beetroot juice (BRJ) or placebo (PLA) group for 28 (±7) days and attended three laboratory visitations. Across visitations, blood pressure, microvascular function and large-vessel EF were assessed by laser Doppler imaging (LDI) with iontophoresis of vasoactive substances and flow-mediated dilatation (FMD), respectively. Plasma NO₃⁻concentrations, BP and the presence of NO₃⁻ reducing bacteria were also assessed. Plasma NO₃⁻ increased following two weeks of BRJ supplementation (p = 0.04) along with a concomitant decrease in systolic and diastolic BP of approximately −6 mmHg and −4 mmHg, respectively (p = 0.04; p = 0.01, respectively). BP remained unchanged in the PLA group. There were no significant differences in endothelium-dependent or endothelium-independent microvascular responses between groups. FMD increased by 1.5% following two weeks of BRJ (p = 0.04), with only a minimal (0.1%) change for the PLA group. In conclusion, this pilot study demonstrated that medium-term BRJ ingestion potentially improves SBP, DBP and large-vessel EF in healthy older adults. The improvements observed in the present study are likely to be greater in populations presenting with endothelial dysfunction. Thus, further prospective studies are warranted in individuals at greater risk for cardiovascular disease.

Asymmetric (ADMA) and Symmetric (SDMA) Dimethylarginines in Chronic Kidney Disease: A Clinical Approach

Asymmetric dimethylarginine (ADMA) and its enantiomer, Symmetric dimethylarginine (SDMA), are naturally occurring amino acids that were first isolated and characterized in human urine in 1970. ADMA is the most potent endogenous inhibitor of nitric oxide synthase (NOS), with higher levels in patients with end-stage renal disease (ESRD). ADMA has shown to be a significant predictor of cardiovascular outcome and mortality among dialysis patients. On the other hand, although initially SDMA was thought to be an innocuous molecule, we now know that it is an outstanding marker of renal function both in human and in animal models, with ESRD patients on dialysis showing the highest SDMA levels. Today, we know that ADMA and SDMA are not only uremic toxins but also independent risk markers for mortality and cardiovascular disease (CVD). In this review, we summarize the role of both ADMA and SDMA in chronic kidney disease along with other cardiovascular risk factors.

The Post-amyloid Era in Alzheimer's Disease: Trust Your Gut Feeling

The amyloid hypothesis, the assumption that beta-amyloid toxicity is the primary cause of neuronal and synaptic loss, has been the mainstream research concept in Alzheimer's disease for the past two decades. Currently, this model is quietly being replaced by a more holistic, “systemic disease” paradigm which, like the aging process, affects multiple body tissues and organs, including the gut microbiota. It is well-established that inflammation is a hallmark of cellular senescence; however, the infection-senescence link has been less explored. Microbiota-induced senescence is a gradually emerging concept promoted by the discovery of pathogens and their products in Alzheimer's disease brains associated with senescent neurons, glia, and endothelial cells. Infectious agents have previously been associated with Alzheimer's disease, but the cause vs. effect issue could not be resolved. A recent study may have settled this debate as it shows that gingipain, a Porphyromonas gingivalis toxin, can be detected not only in Alzheimer's disease but also in the brains of older individuals deceased prior to developing the illness. In this review, we take the position that gut and other microbes from the body periphery reach the brain by triggering intestinal and blood-brain barrier senescence and disruption. We also surmise that novel Alzheimer's disease findings, including neuronal somatic mosaicism, iron dyshomeostasis, aggressive glial phenotypes, and loss of aerobic glycolysis, can be explained by the infection-senescence model. In addition, we discuss potential cellular senescence targets and therapeutic strategies, including iron chelators, inflammasome inhibitors, senolytic antibiotics, mitophagy inducers, and epigenetic metabolic reprograming.

Decline of popliteal artery flow-mediated dilation with aging and possible involvement of asymmetric dimethylarginine in healthy men

Purpose

We examined the influences of age and gender on flow-mediated endothelial function and the involvement of the competitive inhibition of l-arginine in endothelial function.

Methods

We measured brachial and popliteal flow-mediated vasodilation (FMD) responses, nitrate/nitrite (NOx) concentrations, and plasma levels of asymmetric dimethylarginine (ADMA) in four healthy, nonsmoking groups: young men (mean 26 ± 2 years, n = 17), middle-aged men (mean 50 ± 3 years, n = 19), young women (mean 27 ± 2 years, n = 16), and middle-aged women (mean 51 ± 2 years, n = 18).

Results

In young men, we found no significant differences between brachial and popliteal artery FMDs (10.6 ± 1.5 vs 8.7 ± 1.6%, p = 0.06). However, the popliteal artery FMD was significantly lower than the brachial artery FMD in middle-aged men (11.4 ± 1.5 vs 6.4 ± 1.0%, p < 0.001). In women, we found no significant differences between brachial and popliteal artery FMDs in young and middle-aged individuals (young, p = 0.17; middle-aged, p = 0.08). Popliteal artery FMD correlated with plasma NOx and ADMA levels as well as with the NOx/ADMA ratio in men but not in women (r = 0.485, − 0.544, and 0.672, respectively).

Conclusion

We concluded that a decrease in flow-mediated endothelial function in arteries of the lower extremities was evident in healthy middle-aged men, but not in middle-aged women. The competitive inhibition of l-arginine may contribute to this decrease in men.

Extracellular matrix roles in cardiorenal fibrosis: Potential therapeutic targets for CVD and CKD in the elderly

Whereas hypertension, diabetes, and dyslipidemia are age-related risk factors for cardiovascular disease (CVD) and chronic kidney disease (CKD), aging alone is an independent risk factor. With advancing age, the heart and kidney gradually but significantly undergo inflammation and subsequent fibrosis, which eventually results in an irreversible decline in organ physiology. Through cardiorenal network interactions, cardiac dysfunction leads to and responds to renal injury, and both facilitate aging effects. Thus, a comprehensive strategy is needed to evaluate the cardiorenal aging network. Common hallmarks shared across systems include extracellular matrix (ECM) accumulation, along with upregulation of matrix metalloproteinases (MMPs) including MMP-9. The wide range of MMP-9 substrates, including ECM components and inflammatory cytokines, implicates MMP-9 in a variety of pathological and age-related processes. In particular, there is strong evidence that inflammatory cell-derived MMP-9 exacerbates cardiorenal aging. This review explores the potential therapeutic targets against CVD and CKD in the elderly, focusing on ECM and MMP roles.

Age- and sex-dependent alteration of functions and epigenetic modifications of vessel and endothelium related biomarkers

Aging is a main risk factor for development of cardiovascular diseases associated with the impairment of endothelial function in both sexes. In the present study, age-related changes in vascular responsiveness, epigenetic modifications of vessel wall, and blood biomarkers related to endothelial functions were examined in an age- and sex-dependent manner. Acetylcholine (ACh)-induced relaxations of the aorta were decreased in 3-, 6-, and 12-month-old rats compared to those in 1-month-old female rats. In males, maximum relaxations related to ACh were higher in 1- and 6-month-old rats than in 3- and 12-month-old rats. Plasma levels of nitric oxide (NO) and asymmetric dimethylarginine (ADMA) decreased with age in female rats, and total antioxidant capacity (TAC) and hydrogen sulfide (H 2S) levels displayed biphasic alterations. In male rats, plasma levels of NO, TAC, and ADMA decreased with age, and H2S levels increased. Aging also caused a sex-dependent alteration in epigenetic modification of vessels. Expressions of H3K27me2, H3K27me3, H3K36me2, and H3K36me3 were much higher in vessels of 12-month-old female rats compared to those in younger age groups. These results indicate that vascular functions, epigenetic modifications of vessels, and plasma levels of endothelium-related biomarkers are affected by age and sex. These findings could be important for the assessment of vascular status over the course of the life span.

Increased risk of atrial fibrillation among patients undergoing coronary artery bypass graft surgery while receiving nitrates and antiplatelet agents

Background

Postoperative atrial fibrillation (POAF) is a frequent complication of coronary artery bypass graft (CABG) surgery. This arrhythmia occurs more frequently among patients who receive perioperative inotropic therapy (PINOT). Administration of nitrates with antiplatelet agents reduces the conversion rate of cyclic guanosine monophosphate to guanosine monophosphate. This process is associated with increased concentrations of free radicals, catecholamines, and blood plasma volume. We hypothesized that patients undergoing CABG surgery who receive PINOT may be more susceptible to POAF when nitrates are administered with antiplatelet agents.

Methods

Clinical records were examined from a prospectively maintained cohort of 4,124 patients undergoing primary isolated CABG surgery to identify POAF-associated factors.

Results

POAF risk was increased among patients receiving PINOT, and the greatest effect was observed when nitrates were administered with antiplatelet therapy. Adjustment for comorbidities did not substantively change the study results.

Conclusions

Administration of nitrates with certain antiplatelet agents was associated with an increased POAF risk among patients undergoing CABG surgery. Additional studies are needed to determine whether preventive strategies such as administration of antioxidants will reduce this risk.

Effects of Vitamin D3 on asymmetric- and symmetric dimethylarginine in arterial hypertension

BACKGROUND AND AIMS

Accumulating evidence has proposed a correlation between vitamin D (25(OH)D) insufficiency and cardiovascular (CV) disease. Vitamin D associated effects on endothelial function have been suggested to be a possible culprit. The present study investigated the association of vitamin D3 treatment on markers of endothelial dysfunction in patients with arterial hypertension.

METHODS AND RESULTS

The Styrian Vitamin D Hypertension Trial is a double-blind, placebo-controlled, single-centre study conducted at the Medical University of Graz, Austria. A total of 200 study participants with arterial hypertension and 25(OH)D levels below 30ng/mL were enrolled. The study participants were randomized to receive 2800 IU of vitamin D3 per day as oily drops (n=100) or placebo (n=100) for a duration of eight weeks. The present study uses an analysis of covariance (ANCOVA) to investigate the effect of vitamin D3 treatment on symmetric (SDMA) and asymmetric dimethylarginine (ADMA). A total of 187 participants (mean [SD] age 60.0 [11.3] years; 47% women; 25(OH)D 21.2 [5.6]ng/mL; mean systolic blood pressure of 131.4 [8.9] mmHg on a median of 2 antihypertensive drugs) completed the trial. Mean treatment effect was -0.004 (95%CI [-0.03 to 0.04]; P=0.819) on ADMA and 0.001 (95%CI [-0.05 to 0.05]; P=0.850) on SDMA. In the subgroup analysis patients with a 25(OH)D concentration <20ng/mL had a significant increase in their log l-arginine/ADMA ratio (mean treatment effect 18.4 95%CI [1.84-34.9]μmol/L/μmol/L; P=0.030). ClinicalTrials.gov Identifier: NCT02136771 EudraCT number: 2009-018125-70 CONCLUSIONS: Vitamin D3 supplementation in hypertensive patients with low 25-hydroxyvitamin D has no significant effect on ADMA and SDMA.