Effects of regular exercise on vascular function with aging: Does sex matter?

Vascular aging, featuring endothelial dysfunction and large elastic artery stiffening, is a major risk factor for the development of age-associated cardiovascular diseases (CVDs). Vascular aging is largely mediated by an excessive production of reactive oxygen species (ROS) and increased inflammation leading to reduced bioavailability of the vasodilatory molecule nitric oxide and remodeling of the arterial wall. Other cellular mechanisms (i.e., mitochondrial dysfunction, impaired stress response, deregulated nutrient sensing, cellular senescence), termed "hallmarks" or "pillars" of aging, may also contribute to vascular aging. Gonadal aging, which largely impacts women but also impacts some men, modulates the vascular aging process. Regular physical activity, including both aerobic and resistance exercise, is a first-line strategy for reducing CVD risk with aging. Although exercise is an effective intervention to counter vascular aging, there is considerable variation in the vascular response to exercise training with aging. Aerobic exercise improves large elastic artery stiffening in both middle-aged/older men and women and enhances endothelial function in middle-aged/older men by reducing oxidative stress and inflammation and preserving nitric oxide bioavailability; however, similar aerobic exercise training improvements are not consistently observed in estrogen-deficient postmenopausal women. Sex differences in adaptations to exercise may be related to gonadal aging and declines in estrogen in women that influence cellular-molecular mechanisms, disconnecting favorable signaling in the vasculature induced by exercise training. The present review will summarize the current state of knowledge on vascular adaptations to regular aerobic and resistance exercise with aging, the underlying mechanisms involved, and the moderating role of biological sex.

Electronic hookah (waterpipe) vaping reduces vascular endothelial function: the role of nicotine.

Vaping has risen substantially in recent years, particularly among young adults. Electronic (e-) hookahs are a newer category of vaping devices touted as safer tobacco alternatives. Although e-hookah vaping acutely reduces endothelial function, the role of nicotine and the mechanisms by which it may impair endothelial function remain understudied. In a randomized crossover study, we investigated the acute effects of vaping e-hookah, with and without nicotine, as compared with sham on endothelial function assessed by brachial artery flow-mediated dilation (FMD), among 18 overtly healthy young adults. To determine the role of changes in circulating factors in plasma on endothelial cell function, human umbilical vein endothelial cells (HUVECs) were cultured with participants' plasma, and acetylcholine-stimulated nitric oxide (NO) production and basal reactive oxygen species (ROS) bioactivity were assessed. Plasma nicotine was measured before and after the sessions. E-hookah vaping with nicotine, which acutely increased heart rate (HR) by 8 ± 3 beats/min and mean arterial pressure (MAP) by 7 ± 2 mmHg (means ± SE; P < 0.05), decreased endothelial-dependent FMD by 1.57 ± 0.19%Δ (P = 0.001), indicating impairment in endothelial function. Vaping e-hookah without nicotine, which mildly increased hemodynamics (HR, 2 ± 2 beats/min and MAP 1 ± 1 mmHg; P = ns), did not significantly impair endothelial function. No changes were observed after sham vaping. HUVECs cultured with participants' plasma after versus before e-hookah vaping with nicotine, but not without nicotine or sham vaping, exhibited reductions in endothelial cell NO bioavailability and increases in ROS bioactivity (P < 0.05). Plasma nicotine concentrations increased after vaping e-hookah with nicotine (6.7 ± 1.8 ng/mL; P = 0.002), whereas no changes were observed after vaping e-hookah without nicotine or sham (P = ns). Acute e-hookah vaping induces endothelial dysfunction by impairing NO bioavailability associated with increased ROS production, and these effects are attributable to nicotine, not to nonnicotine constituents, present in the flavored e-liquid.NEW & NOTEWORTHY Despite safety claims heavily advertised by the hookah tobacco industry, acute e-hookah vaping induces in vivo endothelial dysfunction by impairing ex vivo NO bioavailability associated with increased ROS production. These effects are attributable to nicotine, not to nonnicotine constituents, present in the flavored e-liquid.

Role of the circulating milieu in age-related arterial dysfunction: a novel ex vivo approach.

The circulating milieu, bioactive molecules in the bloodstream, is altered with aging and interfaces constantly with the vasculature. This anatomic juxtaposition suggests that circulating factors may actively modulate arterial function. Here, we developed a novel, translational experimental model that allows for direct interrogation of the influence of the circulating milieu on age-related arterial dysfunction (aortic stiffening and endothelial dysfunction). To do so, we exposed young and old mouse arteries to serum from young and old mice and young and midlife/older (ML/O) adult humans. We found that old mouse and ML/O adult human, but not young, serum stiffened young mouse aortic rings, assessed via elastic modulus (mouse and human serum, P = 0.003 vs. young serum control), and impaired carotid artery endothelial function, assessed by endothelium-dependent dilation (EDD) (mouse serum, P < 0.001; human serum, P = 0.006 vs. young serum control). Furthermore, young mouse and human, but not old, serum reduced aortic elastic modulus (mouse serum, P = 0.009; human serum, P < 0.001 vs. old/MLO serum control) and improved EDD (mouse and human serum, P = 0.015 vs. old/MLO serum control) in old arteries. In human serum-exposed arteries, in vivo arterial function assessed in the human donors correlated with circulating milieu-modulated arterial function in young mouse arteries (aortic stiffness, r = 0.634, P = 0.005; endothelial function, r = 0.609, P = 0.004) and old mouse arteries (aortic stiffness, r = 0.664, P = 0.001; endothelial function, r = 0.637, P = 0.003). This study establishes novel experimental approaches for directly assessing the effects of the circulating milieu on arterial function and implicates changes in the circulating milieu as a mechanism of in vivo arterial aging.NEW & NOTEWORTHY Changes in the circulating milieu with advancing age may be a mechanism underlying age-related arterial dysfunction. Ex vivo exposure of young mouse arteries to the circulating milieu from old mice or midlife/older adults impairs arterial function whereas exposure of old mouse arteries to the circulating milieu from young mice or young adults improves arterial function. These findings establish that the circulating milieu directly influences arterial function with aging.

The complete guide to hosting a guest speaker.

The ability to effectively host a guest speaker is an important but underemphasized aspect of career development in the physiological and broader biomedical sciences. Currently, there is scant information available to guide early-career scientists through this multifaceted, subtlety-filled process. In this Personal View on Training and Mentoring, I first describe the importance and benefits of hosting visiting speakers. I then discuss the many considerations involved in selecting an appropriate speaker and how to formulate the invitation to present. The key activities involved in planning and preparing for a speaker's visit are described next, including information that must be obtained from the speaker, the logistics of travel and lodging, constructing an effective itinerary, food/meals, and how the presentation will be advertised. I then delve into the essential components of host responsibilities during the visit: best practices for introducing speakers, other hosting duties associated with the presentation, tips for enhancing trainee interactions with the speaker, and keys to properly completing the visit on the right note. I next discuss events occurring after the visit, including speaker expenses, reimbursements, and honoraria. Last, the distinct aspects of virtual visits (i.e., remote presentations and meetings) compared with in-person visits are noted. Overall, this viewpoint is intended to provide a comprehensive guide to successfully hosting a guest speaker that should help advance the professional development of students, postdoctoral fellows, and other early-stage investigators.NEW & NOTEWORTHY This Personal View on Training and Mentoring provides a comprehensive guide to successfully hosting a guest speaker that should help inform and advance the professional development of students, postdoctoral fellows, and other early-stage investigators.

Novel whole blood transcriptome signatures of changes in maximal aerobic capacity in response to endurance exercise training in healthy women.

Maximal aerobic exercise capacity [maximal oxygen consumption (V̇o2max)] is one of the strongest predictors of morbidity and mortality. Aerobic exercise training can increase V̇o2max, but inter-individual variability is marked and unexplained physiologically. The mechanisms underlying this variability have major clinical implications for extending human healthspan. Here, we report a novel transcriptome signature related to ΔV̇o2max with exercise training detected in whole blood RNA. We used RNA-Seq to characterize transcriptomic signatures of ΔV̇o2max in healthy women who completed a 16-wk randomized controlled trial comparing supervised, higher versus lower aerobic exercise training volume and intensity (4 training groups, fully crossed). We found significant baseline gene expression differences in subjects who responded to aerobic exercise training with robust versus little/no ΔV̇o2max, and differentially expressed genes/transcripts were mostly related to inflammatory signaling and mitochondrial function/protein translation. Baseline gene expression signatures associated with robust versus little/no ΔV̇o2max were also modulated by exercise training in a dose-dependent manner, and they predicted ΔV̇o2max in this and a separate dataset. Collectively, our data demonstrate the potential utility of using whole blood transcriptomics to study the biology of inter-individual variability in responsiveness to the same exercise training stimulus.

Chronic mitochondria antioxidant treatment in older adults alters the circulating milieu to improve endothelial cell function and mitochondrial oxidative stress.

Excessive reactive oxygen species production by mitochondria (mtROS) is a key contributor to age-related vascular endothelial dysfunction. We recently showed in a crossover design, placebo-controlled clinical trial in older adults that 6 wk of treatment with the mitochondria-targeted antioxidant (MitoQ) improved endothelial function, as measured by nitric oxide (NO)-mediated endothelium-dependent dilation (EDD), by lowering mtROS and was associated with reduced circulating levels of oxidized low-density lipoprotein (oxLDL). Here, we conducted an ancillary analysis using plasma samples from our clinical trial to determine if MitoQ treatment-mediated changes in the "circulating milieu" (plasma) contribute to improvements in endothelial function and the mechanisms involved. With the use of an ex vivo model of endothelial function, acetylcholine-stimulated NO production was quantified in human aortic endothelial cells (HAECs) exposed to plasma collected after chronic MitoQ and placebo supplementation in 19 older adults (67 ± 1 yr; 11 females). We also assessed the influence of plasma on endothelial cell (EC) mtROS bioactivity and the role of lower circulating oxLDL in plasma-mediated changes. NO production was ∼25% higher (P = 0.0002) and mtROS bioactivity was ∼25% lower (P = 0.003) in HAECs exposed to plasma collected from subjects after MitoQ treatment versus placebo. Improvements in NO production ex vivo and NO-mediated EDD in vivo with MitoQ were correlated (r = 0.4683; P = 0.0431). Increasing oxLDL in plasma collected after MitoQ to placebo levels abolished MitoQ treatment effects on NO production and mtROS bioactivity, whereas inhibition of endogenous oxLDL binding to its lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) prevented these effects. These findings provide novel insight into the mechanisms by which MitoQ treatment improves endothelial function in older adults.NEW & NOTEWORTHY Chronic supplementation with a mitochondria-targeted antioxidant (MitoQ) improves vascular endothelial function in older adults, but the mechanisms of action are incompletely understood. Here, we show that MitoQ supplementation leads to changes in the circulating milieu (plasma), including reductions in oxidized low-density lipoprotein that enhance nitric oxide production and reduce mitochondrial oxidative stress in endothelial cells. These findings provide new information regarding the mechanisms by which MitoQ improves age-related endothelial dysfunction.

Time-efficient, high-resistance inspiratory muscle strength training increases cerebrovascular reactivity in midlife and older adults.

Aging is associated with increased risk for cognitive decline and dementia due in part to increases in systolic blood pressure (SBP) and cerebrovascular dysfunction. High-resistance inspiratory muscle strength training (IMST) is a time-efficient, intensive respiratory training protocol (30 resisted inspirations/day) that lowers SBP and improves peripheral vascular function in midlife/older adults with above-normal SBP. However, whether, and by what mechanisms, IMST can improve cerebrovascular function is unknown. We hypothesized that IMST would increase cerebrovascular reactivity to hypercapnia (CVR to CO2), which would coincide with changes to the plasma milieu that improve brain endothelial cell function and enhance cognitive performance (NIH Toolbox). We conducted a 6-wk double-blind, randomized, controlled clinical trial investigating high-resistance IMST [75% maximal inspiratory pressure (PImax); 6×/wk; 4 females, 5 males] vs. low-resistance sham training (15% PImax; 6×/wk; 2 females, 5 males) in midlife/older adults (age 50-79 yr) with initial above-normal SBP. Human brain endothelial cells (HBECs) were exposed to participant plasma and assessed for acetylcholine-stimulated nitric oxide (NO) production. CVR to CO2 increased after high-resistance IMST (pre: 1.38 ± 0.66 cm/s/mmHg; post: 2.31 ± 1.02 cm/s/mmHg, P = 0.020). Acetylcholine-stimulated NO production increased in HBECs exposed to plasma from after vs. before the IMST intervention [pre: 1.49 ± 0.33; post: 1.73 ± 0.35 arbitrary units (AU); P < 0.001]. Episodic memory increased modestly after the IMST intervention (pre: 95 ± 13; post: 103 ± 17 AU; P = 0.045). Cerebrovascular and cognitive function were unchanged in the sham control group. High-resistance IMST may be a promising strategy to improve cerebrovascular and cognitive function in midlife/older adults with above-normal SBP, a population at risk for future cognitive decline and dementia.NEW & NOTEWORTHY Midlife/older adults with above-normal blood pressure are at increased risk of developing cognitive decline and dementia. Our findings suggest that high-resistance inspiratory muscle strength training (IMST), a novel, time-efficient (5-10 min/day) form of physical training, may increase cerebrovascular reactivity to CO2 and episodic memory in midlife/older adults with initial above-normal blood pressure.

Female C57BL/6N mice are a viable model of aortic aging in women.

The aorta stiffens with aging in both men and women, which predicts cardiovascular mortality. Aortic wall structural and extracellular matrix (ECM) remodeling, induced in part by chronic low-grade inflammation, contribute to aortic stiffening. Male mice are an established model of aortic aging. However, there is little information regarding whether female mice are an appropriate model of aortic aging in women, which we aimed to elucidate in the present study. We assessed two strains of mice and found that in C57BL/6N mice, in vivo aortic stiffness (pulse wave velocity, PWV) was higher with aging in both sexes, whereas in B6D2F1 mice, PWV was higher in old versus young male mice, but not in old versus young female mice. Because the age-related stiffening that occurs in men and women was reflected in male and female C57BL/6N mice, we examined the mechanisms of stiffening in this strain. In both sexes, aortic modulus of elasticity (pin myography) was lower in old mice, occurred in conjunction with and was related to higher plasma levels of the elastin-degrading enzyme matrix metalloproteinase-9 (MMP-9), and was accompanied by higher numbers of aortic elastin breaks and higher abundance of adventitial collagen-1. Plasma levels of the inflammatory cytokines interferon-γ, interleukin 6, and monocyte chemoattractant protein-1 were higher in both sexes of old mice. In conclusion, female C57BL/6N mice exhibit aortic stiffening, reduced modulus of elasticity and structural/ECM remodeling, and associated increases in MMP-9 and systemic inflammation with aging, and thus are an appropriate model of aortic aging in women.NEW & NOTEWORTHY Our study demonstrates that with aging, female C57BL/6N mice exhibit higher in vivo aortic stiffness, reduced modulus of elasticity, aortic wall structural and extracellular matrix remodeling, and elevations in systemic inflammation. These changes are largely reflective of those that occur with aging in women. Thus, female C57BL/6N mice are a viable model of human aortic aging and the utility of these animals should be considered in future biomedical investigations.

Publishing particulars: Part 3. General writing tips, editing, and responding to peer review.

In Part 3 of this Perspective on Publishing Particulars, I begin by providing several general writing tips to consider when developing a manuscript for publication. I then discuss the process involved in rigorously editing research papers and advance some important considerations for manuscript submission. I next share my thoughts and recommendations when attempting to interpret and respond to comments from the manuscript peer review process. Finally, I discuss author responsibilities after a manuscript is accepted for publication. Overall, this portion of the 3-part commentary seeks to complete a broader discussion on publishing in the biomedical sciences aimed at better informing early-stage investigators about many of the nuances of this critical area of professional development.

Publishing particulars: Part 2. Tips for effective manuscript development.

In Part 2 of this Perspective on Publishing Particulars, I share several recommendations with early-career stage investigators for how to successfully develop a competitive manuscript for publication. In the initial section, I first discuss how to organize content most effectively for an original research article by creating a "storyboard" of the key results, including the sequence in which they will be presented. I then emphasize the importance of rigorously outlining all the information to be presented in the manuscript before attempting to write the text. In the second section, I comprehensively discuss tactical approaches for developing the specific component parts of an original research paper, including the Abstract, Introduction, Methods, Results and illustrations, and Discussion, as well as strategies for referencing the text. In the final section, I provide suggestions for how to best develop a compelling review article. The topics discussed include how to view the opportunity; selecting authors and defining their respective roles; identifying the foundational components of the text; conducting a comprehensive review of the target published literature; and organizing, writing, and illustrating the article.

Publishing particulars: Part 1. The big picture.

In Part 1 of this Perspective on Publishing Particulars, I share my thoughts on several key issues related to publishing in academic biomedical research for early-career stage investigators. Among the topics discussed are the importance of publishing peer-reviewed manuscripts, considerations associated with different types of publications, how frequently you should publish, how to select a scientific journal for your manuscript, and navigating authorship questions, including who should be an author, authorship order, and who should write a manuscript. The goal of this first part of the Perspective is to lay a "foundation" of basic knowledge on the publication process from which to discuss more specific aspects of manuscript development in Parts 2 and 3.

Ponderings on peer review. Part 2. Manuscript critiques.

In part 1 of this Perspective, I discussed general principles of scientific peer review in the biomedical sciences aimed at early-stage investigators (i.e., graduate students, postdoctoral fellows, and junior faculty). Here in part 2, I share my thoughts specifically on the topic of peer review of manuscripts. I begin by defining manuscript peer review and discussing the goals and importance of the concept. I then describe the organizational structure of the process, including the two distinct stages involved. Next, I emphasize several important considerations for manuscript reviewers, both general points and key considerations when evaluating specific types of papers, including original research manuscripts, reviews, methods articles, and opinion pieces. I then advance some practical suggestions for developing the written critique document, offer advice for making an overall recommendation to the editor (i.e., accept, revise, reject), and describe the unique issues involved when assessing a revised manuscript. Finally, I comment on how best to gain experience in the essential academic research skill of manuscript peer review. In part 3 of the series, I will discuss the topic of reviewing grant applications submitted to research funding agencies.

Ponderings on peer review: Part I. Basic principles.

In Part 1 of this Perspective, I share my thoughts on several basic principles of scientific peer review for early career-stage investigators. I begin by defining scientific peer review and its primary goals and briefly discuss the historical development of peer review. I then describe the reputed benefits of the process for science and society. Next, I characterize the "2-stage" structure of peer review, as well as the most prevalent evaluation formats used for determining scientific merit of peer-reviewed documents, including grant applications and manuscripts. I then discuss the primary responsibilities and core values of scientific peer review and offer several general tips for how to be an effective scientific peer reviewer. I next share commonly voiced concerns about the peer review process and oft-cited suggestions for improving the system. I finish the commentary by emphasizing numerous benefits of having a sound working knowledge of peer review for enhancing research career development and describe various opportunities for obtaining experience in peer review. This discussion of general issues is intended to lay a proper foundation upon which to address specific aspects of peer review of manuscripts in part 2 and grant applications in part 3 of the Perspective.

Ponderings on peer review: Part 3. Grant critiques.

In Part 1 of this Perspective, I discussed basic principles of scientific peer review. In Part 2, I focused specifically on the peer review of manuscripts. Here in Part 3, I complete the Perspective by sharing my thoughts on peer review of grant applications. I begin by emphasizing the goals of grant peer review and then describe the two-stage organizational structure involved. The objective of stage 1 of the process is to establish the scientific merit of the grant proposal. For that phase, I discuss grant review panels, reviewer qualifications and responsibilities, how reviewers are identified and selected, prereview meeting activities, activities during the review panel meeting, grant review criteria and scoring scales, and postmeeting activities. I also note two mechanisms that provide "prepeer review" advice and recommendations for grant applications under development. I then describe the events associated with stage 2 of the peer review process in which grant funding agencies consider application merit scores (from stage 1) along with other factors including their (the funding agency's) research mission, priority areas of investigation, and available funds. Tips for early career reviewers are discussed next and include questions to ask before accepting a review assignment, the importance of following reviewer guidelines, considerations when working through applications, issues involved in writing the critique, scoring the application, and how to approach evaluating resubmitted grant applications. Finally, I identify options for gaining skills and experience in peer review of grant proposals.

Neurovascular and hemodynamic responses to mental stress and exercise in severe COVID-19 survivors.

Previous studies show that COVID-19 survivors have elevated muscle sympathetic nerve activity (MSNA), endothelial dysfunction, and aortic stiffening. However, the neurovascular responses to mental stress and exercise are still unexplored. We hypothesized that COVID-19 survivors, compared with age- and body mass index (BMI)-matched control subjects, exhibit abnormal neurovascular responses to mental stress and physical exercise. Fifteen severe COVID-19 survivors (aged: 49 ± 2 yr, BMI: 30 ± 1 kg/m2) and 15 well-matched control subjects (aged: 46 ± 3 yr, BMI: 29 ± 1 kg/m2) were studied. MSNA (microneurography), forearm blood flow (FBF), and forearm vascular conductance (FVC, venous occlusion plethysmography), mean arterial pressure (MAP, Finometer), and heart rate (HR, ECG) were measured during a 3-min mental stress (Stroop Color-Word Test) and during a 3-min isometric handgrip exercise (30% of maximal voluntary contraction). During mental stress, MSNA (frequency and incidence) responses were higher in COVID-19 survivors than in controls (P < 0.001), and FBF and FVC responses were attenuated (P < 0.05). MAP was similar between the groups (P > 0.05). In contrast, the MSNA (frequency and incidence) and FBF and FVC responses to handgrip exercise were similar between the groups (P > 0.05). MAP was lower in COVID-19 survivors (P < 0.05). COVID-19 survivors exhibit an exaggerated MSNA and blunted vasodilatory response to mental challenge compared with healthy adults. However, the neurovascular response to handgrip exercise is preserved in COVID-19 survivors. Overall, the abnormal neurovascular control in response to mental stress suggests that COVID-19 survivors may have an increased risk to cardiovascular events during mental challenge.

NAD+-boosting compounds enhance nitric oxide production and prevent oxidative stress in endothelial cells exposed to plasma from patients with COVID-19.

SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), induces vascular endothelial dysfunction, but the mechanisms are unknown. We tested the hypothesis that the "circulating milieu" (plasma) of patients with COVID-19 would cause endothelial cell dysfunction (characterized by lower nitric oxide (NO) production), which would be linked to greater reactive oxygen species (ROS) bioactivity and depletion of the critical metabolic co-substrate, nicotinamide adenine dinucleotide (NAD+). We also investigated if treatment with NAD+-boosting compounds would prevent COVID-19-induced reductions in endothelial cell NO bioavailability and oxidative stress. Human aortic endothelial cells (HAECs) were exposed to plasma from men and women (age 18-85 years) who were hospitalized and tested positive (n = 34; 20 M) or negative (n = 13; 10 M) for COVID-19. HAECs exposed to plasma from patients with COVID-19 also were co-incubated with NAD+ precursors nicotinamide riboside (NR) or nicotinamide mononucleotide (NMN). Acetylcholine-stimulated NO production was 27% lower and ROS bioactivity was 54% higher in HAECs exposed to plasma from patients with COVID-19 (both p < 0.001 vs. control); these responses were independent of age and sex. NAD+ concentrations were 30% lower in HAECs exposed to plasma from patients with COVID-19 (p = 0.001 vs. control). Co-incubation with NR abolished COVID-19-induced reductions in NO production and oxidative stress (both p > 0.05 vs. control). Co-treatment with NMN produced similar results. Our findings suggest the circulating milieu of patients with COVID-19 promotes endothelial cell dysfunction, characterized by lower NO bioavailability, greater ROS bioactivity, and NAD+ depletion. Supplementation with NAD+ precursors may exert a protective effect against COVID-19-evoked endothelial cell dysfunction and oxidative stress.

Initiation of 3,3-dimethyl-1-butanol at midlife prevents endothelial dysfunction and attenuates in vivo aortic stiffening with ageing in mice.

Vascular dysfunction: develops progressively with ageing; increases the risk of cardiovascular diseases (CVD); and is characterized by endothelial dysfunction and arterial stiffening, which are primarily mediated by superoxide-driven oxidative stress and consequently reduced nitric oxide (NO) bioavailability and arterial structural changes. Interventions initiated before vascular dysfunction manifests may have more promise for reducing CVD risk than interventions targeting established dysfunction. Gut microbiome-derived trimethylamine N-oxide (TMAO) induces vascular dysfunction, is associated with higher CV risk, and can be suppressed by 3,3-dimethyl-1-butanol (DMB). We investigated whether DMB supplementation could prevent age-related vascular dysfunction in C57BL/6N mice when initiated prior to development of dysfunction. Mice received drinking water with 1% DMB or normal drinking water (control) from midlife (18 months) until being studied at 21, 24 or 27 months of age, and were compared to young adult (5 month) mice. Endothelial function [carotid artery endothelium-dependent dilatation (EDD) to acetylcholine; pressure myography] progressively declined with age in control mice, which was fully prevented by DMB via higher NO-mediated EDD and lower superoxide-related suppression of EDD (normalization of EDD with the superoxide dismutase mimetic TEMPOL). In vivo aortic stiffness (pulse wave velocity) increased progressively with age in controls, but DMB attenuated stiffening by ∼ 70%, probably due to preservation of endothelial function, as DMB did not affect aortic intrinsic mechanical (structural) stiffness (stress-strain testing) nor adventitial abundance of the arterial structural protein collagen. Our findings indicate that long-term DMB supplementation prevents/attenuates age-related vascular dysfunction, and therefore has potential for translation to humans for reducing CV risk with ageing. KEY POINTS: Vascular dysfunction, characterized by endothelial dysfunction and arterial stiffening, develops progressively with ageing and increases the risk of cardiovascular diseases (CVD). Interventions aimed at preventing the development of CV risk factors have more potential for preventing CVD relative to those aimed at reversing established dysfunction. The gut microbiome-derived metabolite trimethylamine N-oxide (TMAO) induces vascular dysfunction, is associated with higher CV risk and can be suppressed by supplementation with 3,3-dimethyl-1-butanol (DMB). In mice, DMB prevented the development of endothelial dysfunction and delayed and attenuated in vivo arterial stiffening with ageing when supplementation was initiated in midlife, prior to the development of dysfunction. DMB supplementation or other TMAO-suppressing interventions have potential for translation to humans for reducing CV risk with ageing.

Direct advice for directing an academic biomedical research laboratory.

This Perspective shares "insider" thoughts and recommendations for success with early-career stage scientists on directing an independent biomedical research laboratory.

Talking the talk: tips for effective oral presentations in biomedical research.

In this Perspective, I share several personal thoughts and recommendations with early-career stage investigators for developing and delivering effective oral research presentations in the biomedical sciences. I begin by emphasizing the importance of this professional skill and describing numerous opportunities for gaining experience as well as sources of guidance and feedback. I then discuss considerations for deciding whether and when to present, tips for developing a fundamentally sound presentation, and suggestions on preparing for and delivering a compelling talk. Lastly, I provide my insights on optimal performance during the Q&A (question and answer) period, discuss the concept of "audience good will," and provide advice on how to best maintain that good will during your presentation.

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.