Douglas R Seals's research while affiliated with University of Colorado at Boulder and other places

Publications (245)

Key points summary: Age-related arterial dysfunction, characterized by oxidative stress- and inflammation-mediated endothelial dysfunction and arterial stiffening, is the primary risk factor for cardiovascular diseases (CVD). To investigate whether age-related changes in the gut microbiome may mediate arterial dysfunction, we suppressed gut microbiota in young and old mice with a cocktail of broad-spectrum, poorly-absorbed antibiotics in drinking water for 3-4 weeks. In old mice, antibiotic treatment reversed endothelial dysfunction and arterial stiffening and attenuated vascular oxidative stress and inflammation. To provide insight into age-related changes in gut microbiota that may underlie these observations, we show that aging altered abundance of microbial taxa associated with gut dysbiosis and increased plasma levels of the adverse gut-derived metabolite trimethylamine-N-oxide. Our results provide the first proof-of-concept evidence that the gut microbiome is an important mediator of age-related arterial dysfunction and therefore may be a promising therapeutic target to preserve arterial function with ageing, thereby reducing CVD risk. Abstract: Oxidative stress-mediated arterial dysfunction, e.g. endothelial dysfunction and large elastic artery stiffening, is the primary mechanism driving age-related cardiovascular disease. Accumulating evidence suggests the gut microbiome modulates host physiology, as dysregulation ("gut dysbiosis") has systemic consequences, including promotion of oxidative stress. Aim: To determine whether the gut microbiome modulates arterial function with ageing. Methods: We measured arterial function in young and older mice following 3-4 weeks treatment with broad-spectrum, poorly-absorbed antibiotics to suppress the gut microbiome. To identify potential mechanistic links between the gut microbiome and age-related arterial dysfunction, we sequenced microbiota from young and older mice and measured plasma levels of the adverse gut-derived metabolite trimethylamine-N-oxide (TMAO). Results: In old mice, antibiotics reversed endothelial dysfunction (area-under-the-curve carotid artery dilation to acetylcholine in young: 345±16A.U. vs. old control [OC]: 220±34A.U., p<0.01; vs. old antibiotic-treated [OA]: 334±15A.U.; p<0.01 vs. OC), and arterial stiffening (aortic pulse wave velocity in young: 3.62±0.15m. s-1 vs. OC: 4.43±0.38m. s-1 vs. OA: 3.52±0.35m. s-1 ; p = 0.03). These improvements were accompanied by lower oxidative stress and greater antioxidant enzyme expression. Ageing altered abundance of gut microbial taxa associated with gut dysbiosis. Lastly, plasma TMAO was higher with ageing (young: 2.6±0.4 vs. OC: 7.2±2.0μmol. L-1 ; p<0.0001) and suppressed by antibiotic treatment (OA: 1.2±0.2μmol. L-1 ; p<0.0001 vs. OC). Conclusion: Our results provide the first evidence for the gut microbiome as an important mediator of age-related arterial dysfunction and oxidative stress and suggest therapeutic strategies targeting gut microbiome health may hold promise for preserving arterial function and reducing cardiovascular risk with ageing in humans. This article is protected by copyright. All rights reserved.
This review summarizes a presentation given at the 2016 Gerontological Society of America Annual Meeting as part of a Vascular Aging Workshop. The development of age-related vascular dysfunction increases the risk of cardiovascular disease as well as other chronic age-associated disorders, including chronic kidney disease and Alzheimer's disease. Healthy lifestyle behaviors, most notably regular aerobic exercise and certain dietary patterns, are considered "first-line" strategies for the prevention and/or treatment of vascular dysfunction with aging. Despite the well-established benefits of these strategies, however, many older adults do not meet the recommended guidelines for exercise or consume a healthy diet. Therefore, it is important to establish alternative and/or complementary evidence-based approaches to prevent or reverse age-related vascular dysfunction. Time-efficient forms of exercise training, hormetic exposure to mild environmental stress, fasting "mimicking" dietary paradigms, and nutraceutical/pharmaceutical approaches to favorably modulate cellular and molecular pathways activated by exercise and healthy dietary patterns may hold promise as such alternative approaches. Determining the efficacy of these novel strategies is important to provide alternatives for adults with low adherence to conventional healthy lifestyle practices for healthy vascular aging.
Obesity and the metabolic syndrome are characterized by chronic, low-grade inflammation mainly originating from expanding adipose tissue and resulting in inhibition of insulin signaling and disruption of glycemic control. Transgenic mice expressing human interleukin 37 (IL-37), an anti-inflammatory cytokine of the IL-1 family, are protected against metabolic syndrome when fed a high-fat diet (HFD) containing 45% fat. Here, we examined whether treatment with recombinant IL-37 ameliorates established insulin resistance and obesity-induced inflammation. Wild-type mice were fed a HFD for 22 weeks and then treated daily with IL-37 (1 μg/mouse) during the last 2 weeks. Compared with vehicle only-treated mice, IL-37-treated mice exhibited reduced insulin in the plasma and had significant improvements in glucose tolerance, and insulin content of the islets. The IL-37 treatment also increased the levels of circulating IL-1 receptor antagonist. Cultured adipose tissues revealed that IL-37 treatment significantly decreases spontaneous secretions of IL-1β, tumor necrosis factor α (TNFα), and C-X-C motif chemokine ligand 1 (CXCL-1). We also fed mice a 60% fat diet with concomitant daily IL-37 for 2 weeks and observed decreased secretion of IL-1β, TNFα, and IL-6 and reduced intracellular levels of IL-1α in the liver and adipose tissue, along with improved plasma glucose clearance. Compared with vehicle treatment, these IL-37-treated mice had no apparent weight gain. In human adipose tissue cultures, the presence of 50 pM IL-37 reduced spontaneous release of TNFα and 50% of lipopolysaccharide-induced TNFα. These findings indicate that IL-37's anti-inflammatory effects can ameliorate established metabolic disturbances during obesity.
Advancing age is associated with impairments in numerous physiological systems, leading to an increased risk of chronic disease and disability, and reduced healthspan (the period of high functioning healthy life). The plasma metabolome is thought to reflect changes in the activity of physiological systems that influence healthspan. Accordingly, we utilized an LC-MS metabolomics analysis of plasma collected from healthy young and older individuals to characterize global changes in small molecule abundances with age. Using a weighted gene correlation network analysis, similarly expressed metabolites were grouped into modules that were related to indicators of healthspan, including clinically-relevant markers of morphology (body mass index, body fat, lean mass), cardiovascular health (systolic/diastolic blood pressure, endothelial function), renal function (glomerular filtration rate), and maximal aerobic exercise capacity in addition to conventional clinical blood markers (e.g., fasting glucose and lipids). Investigation of metabolic classes represented within each module revealed amino acid and lipid metabolism as significantly associated with age and indicators of healthspan. Further LC-MS/MS targeted analyses of the same samples were used to identify specific metabolites related to age and indicators of healthspan, including methionine and nitric oxide pathways, fatty acids and ceramides. Overall, these results demonstrate that plasma metabolomics profiles in general, and amino acid and lipid metabolism in particular, are associated with aging and indicators of healthspan in healthy adults.
Excess reactive oxygen species production by mitochondria is a key mechanism of age-related vascular dysfunction. Our laboratory has shown that supplementation with the mitochondrial-targeted antioxidant MitoQ improves vascular endothelial function by reducing mitochondrial reactive oxygen species and ameliorates arterial stiffening in old mice, but the effects in humans are unknown. Here, we sought to translate our preclinical findings to humans and determine the safety and efficacy of MitoQ. Twenty healthy older adults (60–79 years) with impaired endothelial function (brachial artery flow–mediated dilation <6%) underwent 6 weeks of oral supplementation with MitoQ (20 mg/d) or placebo in a randomized, placebo-controlled, double-blind, crossover design study. MitoQ was well tolerated, and plasma MitoQ was higher after the treatment versus placebo period (P<0.05). Brachial artery flow–mediated dilation was 42% higher after MitoQ versus placebo (P<0.05); the improvement was associated with amelioration of mitochondrial reactive oxygen species–related suppression of endothelial function (assessed as the increase in flow-mediated dilation with acute, supratherapeutic MitoQ [160 mg] administration; n=9; P<0.05). Aortic stiffness (carotid–femoral pulse wave velocity) was lower after MitoQ versus placebo (P<0.05) in participants with elevated baseline levels (carotid–femoral pulse wave velocity >7.60 m/s; n=11). Plasma oxidized LDL (low-density lipoprotein), a marker of oxidative stress, also was lower after MitoQ versus placebo (P<0.05). Participant characteristics, endothelium-independent dilation (sublingual nitroglycerin), and circulating markers of inflammation were not different (all P>0.1). These findings in humans extend earlier preclinical observations and suggest that MitoQ and other therapeutic strategies targeting mitochondrial reactive oxygen species may hold promise for treating age-related vascular dysfunction.
Aortic stiffening is a major independent risk factor for cardiovascular diseases, cognitive dysfunction and other chronic disorders of aging. Mitochondria-derived reactive oxygen species are a key source of arterial oxidative stress which may contribute to arterial stiffening by promoting adverse structural changes—including collagen overabundance and elastin degradation—and enhancing inflammation, but the potential for mitochondria-targeted therapeutic strategies to ameliorate aortic stiffening with primary aging is unknown. We assessed aortic stiffness (pulse-wave velocity (aPWV)), ex vivo aortic intrinsic mechanical properties (elastic modulus (EM) of collagen and elastin regions), and aortic protein expression in young (~ 6 mo) and old (~27 mo) male c57BL/6 mice consuming normal drinking water (YC and OC) or water containing mitochondria-targeted antioxidant MitoQ (250 µM; YMQ and OMQ) for 4 weeks. Following the intervention, aPWV was higher in OC versus YC (482 ± 21 vs. 420 ± 5 cm/sec, p<0.05). MitoQ had no effect in young mice but reduced aPWV in old mice (426 ± 20, p<0.05 vs. OC). MitoQ did not affect the age-associated increases in aortic collagen-region EM, collagen expression, or pro-inflammatory cytokine expression, but partially attenuated the age-associated decreases in elastin-region EM and elastin expression. Together, these results indicate that the reduction in in vivo aortic stiffness in old mice following MitoQ treatment was at least partially mediated by attenuation/reversal of age-related elastin degradation, and suggest that mitochondria-targeted antioxidants may represent a novel, promising therapeutic strategy for reducing aortic stiffness with primary aging and, possibly, age-related clinical disorders in humans.
This review summarizes the opening keynote presentation overview of the American Physiological Society conference on Cardiovascular Aging: New Frontiers and Old Friends held in Westminster, CO, in August 2017. Age is the primary risk factor for cardiovascular diseases (CVD). Without effective intervention, increased numbers of older adults in the future will translate to greater prevalence of CVD and related disorders. Advancing age increases the risk of CVD partly via direct effects on the heart and through increases in blood pressure; however, much of the risk is mediated by arterial dysfunction, including large elastic artery stiffening and both macro- and micro-vascular endothelial dysfunction. Although excessive superoxide-related oxidative stress and chronic low-grade inflammation are the major processes driving cardiovascular aging, the upstream mechanisms involved represent new frontiers of investigation and potential therapeutic targets. Lifestyle practices, including aerobic exercise, energy intake (caloric) restriction, and healthy diet composition are the most evidence-based strategies (old friends) for optimal cardiovascular aging, but adherence is poor in some groups. Healthy lifestyle "mimicking" approaches, including novel forms of physical training, intermittent fasting paradigms, exercise/healthy diet-inspired nutraceuticals (functional foods and natural supplements), as well as controlled environmental stress exposure (e.g., heat therapy), may hold promise, but are unproven. Mitigating the adverse effects of aging on cardiovascular function and health is a high biomedical priority.
Nicotinamide adenine dinucleotide (NAD+) has emerged as a critical co-substrate for enzymes involved in the beneficial effects of regular calorie restriction on healthspan. As such, the use of NAD+precursors to augment NAD+bioavailability has been proposed as a strategy for improving cardiovascular and other physiological functions with aging in humans. Here we provide the evidence in a 2 × 6-week randomized, double-blind, placebo-controlled, crossover clinical trial that chronic supplementation with the NAD+precursor vitamin, nicotinamide riboside (NR), is well tolerated and effectively stimulates NAD+metabolism in healthy middle-aged and older adults. Our results also provide initial insight into the effects of chronic NR supplementation on physiological function in humans, and suggest that, in particular, future clinical trials should further assess the potential benefits of NR for reducing blood pressure and arterial stiffness in this group.
Background: Recent studies suggest curcumin is a promising nutraceutical for improving important clinical and physiological markers of healthy aging, including motor and cognitive function. Objective: To determine if curcumin supplementation improves motor and cognitive function in healthy middle-aged and older adults. Methods: 39 healthy men and postmenopausal women (45-74 yrs) were randomized to 12 weeks of placebo (n = 19) or curcumin supplementation (2000 mg/day Longvida®; n = 20) with motor and cognitive function assessed at week 0 and 12. Results: Using measures of the NIH Toolbox and other standardized tests, there were no changes in muscle strength and rate of torque development, dexterity, fatigability, mobility, endurance, and balance between the placebo and curcumin groups after 12 weeks (all P > 0.05). Additionally, there were no changes after 12 weeks of placebo and curcumin supplementation in measures of fluid cognitive ability, a cognitive domain that declines with age, including processing speed, executive function, working memory, and episodic memory (all P > 0.3). There were marginal changes in language, a measure of crystallized cognitive ability that is stable with age, following the intervention, wherein reading decoding increased 3% in the curcumin group (post: 2428±35 vs. pre: 2357±34, P = 0.003), but was unchanged in the placebo group (post: 2334±39 vs. pre: 2364±40, P = 0.07). Conclusions: Overall, 12 weeks of curcumin supplementation does not improve motor and cognitive functions in healthy middle-aged and older adults. It is possible that curcumin may enhance these functions in groups with greater baseline impairments than those studied here, including adults greater than 75 years of age and/or patients with clinical disorders.
Aortic stiffening is a major independent risk factor for cardiovascular diseases, cognitive dysfunction and other chronic disorders of aging. Mitochondria-derived reactive oxygen species are a key source of arterial oxidative stress which may contribute to arterial stiffening by promoting adverse structural changes-including collagen overabundance and elastin degradation-and enhancing inflammation, but the potential for mitochondria-targeted therapeutic strategies to ameliorate aortic stiffening with primary aging is unknown. We assessed aortic stiffness (pulse-wave velocity (aPWV)), ex-vivo aortic intrinsic mechanical properties (elastic modulus (EM) of collagen and elastin regions), and aortic protein expression in young (~ 6 mo) and old (~27 mo) male c57BL/6 mice consuming normal drinking water (YC and OC) or water containing mitochondria-targeted antioxidant MitoQ (250 µM; YMQ and OMQ) for 4 weeks. Both baseline and post-intervention aPWV values were higher in OC versus YC (post: 482 ± 21 vs. 420 ± 5 cm/sec, p<0.05). MitoQ had no effect in young mice but reduced aPWV in old mice (OMQ, 426 ± 20, p<0.05 vs. OC). MitoQ did not affect age-associated increases in aortic collagen-region EM, collagen expression, or pro-inflammatory cytokine expression, but partially attenuated age-associated decreases in elastin-region EM and elastin expression. Our results demonstrating that MitoQ reverses in vivo aortic stiffness in old mice suggest that mitochondria-targeted antioxidants may represent a novel, promising therapeutic strategy for reducing aortic stiffness with primary aging and, possibly, age-related clinical disorders in humans. The de-stiffening effects of MitoQ treatment may be at least partially mediated by attenuation/reversal of age-related aortic elastin degradation.
Cellular senescence is emerging as a key mechanism of age-related vascular endothelial dysfunction, but evidence in healthy humans is lacking. Moreover, the influence of lifestyle factors such as habitual exercise on endothelial cell (EC) senescence is unknown. We tested the hypothesis that EC senescence increases with sedentary, but not physically active, aging and is associated with vascular endothelial dysfunction. Protein expression (quantitative immunofluorescence) of p53, a transcription factor related to increased cellular senescence, and the cyclin dependent kinase inhibitors p21 and p16 were 116%, 119%, and 128% greater (all P<0.05), respectively, in ECs obtained from antecubital veins of older sedentary (n=12, 60±1 yrs) vs. young sedentary (n=9, 22±1 yrs) adults. These age-related differences were not present (all P>0.05) in venous ECs from older exercising adults (n=13, 57±1 yrs). Furthermore, venous EC protein levels of p53 (r=-0.49, P=0.003), p21 (r=-0.38, P=0.03), and p16 (r=-0.58, P=0.002) were inversely associated with vascular endothelial function (brachial artery flow-mediated dilation). Similarly, p53 and p21 protein expression were 26% and 23% higher (both P<0.05), respectively, in ECs sampled from brachial arteries of healthy older sedentary (n=18, 63±1 yrs) vs. young sedentary (n=9, 25±1 yrs) adults; age-related changes in arterial EC p53 and p21 expression were not observed (P>0.05) in older habitually exercising adults (n=14, 59±1 yrs). These data indicate that EC senescence is associated with sedentary aging and is linked to endothelial dysfunction. Moreover, these data suggest that prevention of EC senescence may be one mechanism by which aerobic exercise protects against endothelial dysfunction with age.
Background and objectives: High circulating vitamin D levels are associated with lower cardiovascular mortality in CKD, possibly by modifying endothelial function. We examined the effect of calcitriol versus cholecalciferol supplementation on vascular endothelial function in patients with CKD. Design, setting, participants, & measurements: We performed a prospective, double-blind, randomized trial of 128 adult patients with eGFR=15-44 ml/min per 1.73 m(2)and serum 25-hydroxyvitamin D level <30 ng/ml at the University of Colorado. Participants were randomly assigned to oral cholecalciferol (2000 IU daily) or calcitriol (0.5 μg) daily for 6 months. The primary end point was change in brachial artery flow-mediated dilation. Secondary end points included changes in circulating markers of mineral metabolism and circulating and cellular markers of inflammation. Results: One hundred and fifteen patients completed the study. The mean (SD) age and eGFR of participants were 58±12 years old and 33.0±10.2 ml/min per 1.73 m(2), respectively. There were no significant differences between groups at baseline. After 6 months, neither calcitriol nor cholecalciferol treatment resulted in a significant improvement in flow-mediated dilation (mean±SD percentage flow-mediated dilation; calcitriol: baseline 4.8±3.1%, end of study 5.1±3.6%; cholecalciferol: baseline 5.2±5.2%, end of study 4.7±3.6%); 25-hydroxyvitamin D levels increased significantly in the cholecalciferol group compared with the calcitriol group (cholecalciferol: 11.0±9.5 ng/ml; calcitriol: -0.8±4.8 ng/ml; P<0.001). Parathyroid hormone levels decreased significantly in the calcitriol group compared with the cholecalciferol group (median [interquartile range]; calcitriol: -22.1 [-48.7-3.5] pg/ml; cholecalciferol: -0.3 [-22.6-16.9] pg/ml; P=0.004). Conclusions: Six months of therapy with calcitriol or cholecalciferol did not improve vascular endothelial function or improve inflammation in patients with CKD.
Adaptation to stress is identified as one of the seven pillars of aging research. Our viewpoint discusses the importance of the distinction between stress resistance and resilience, highlights how integration of physiological principles is critical for further understanding in vivo stress resistance and resilience, and advocates for the use of early warning signs to prevent a tipping point in stress resistance and resilience.
The accumulation of damaged proteins can perturb cellular homeostasis and provoke aging and cellular damage. Quality control systems, such as the unfolded protein response (UPR), inflammatory signaling and protein degradation, mitigate the residence time of damaged proteins. In the present study, we have examined the UPR and inflammatory signaling in the liver of young (~6 mo.) and old (~28 mo.) mice (n=8/group), and the ability of trehalose, a compound linked to increased protein stability and autophagy, to counteract age-induced effects on these systems. When used, trehalose was provided for 4 wks in the drinking water immediately prior to sacrifice (n=7/group). Livers from old mice were characterized by activation of the UPR, increased inflammatory signaling and indices of liver injury. Trehalose treatment reduced the activation of the UPR and inflammatory signaling, and reduced liver injury. Reductions in proteins involved in autophagy and proteasome activity observed in old mice were restored following trehalose treatment. The autophagy marker, LC3B-II, was increased in old mice treated with trehalose. Metabolomics analyses demonstrated that reductions in hexosamine biosynthetic pathway metabolites and nicotinamide in old mice were restored following trehalose treatment. Trehalose appears to be an effective intervention to reduce age-associated liver injury and mitigate the need for activation of quality control systems that respond to disruption of proteostasis.
IL-1 family member interleukin 37 (IL-37) has broad antiinflammatory properties and functions as a natural suppressor of innate inflammation. In this study, we demonstrate that treatment with recombinant human IL-37 reverses the decrease in exercise performance observed during systemic inflammation. This effect was associated with a decrease in the levels of plasma and muscle cytokines, comparable in extent to that obtained upon IL-1 receptor blockade. Exogenous administration of IL-37 to healthy mice, not subjected to an inflammatory challenge, also improved exercise performance by 82% compared with vehicle-treated mice (P = 0.01). Treatment with eight daily doses of IL-37 resulted in a further 326% increase in endurance running time compared with the performance level of mice receiving vehicle (P = 0.001). These properties required the engagement of the IL-1 decoy receptor 8 (IL-1R8) and the activation of AMP-activated protein kinase (AMPK), because both inhibition of AMPK and IL-1R8 deficiency abrogated the positive effects of IL-37 on exercise performance. Mechanistically, treatment with IL-37 induced marked metabolic changes with higher levels of muscle AMPK, greater rates of oxygen consumption, and increased oxidative phosphorylation. Metabolomic analyses of plasma and muscles of mice treated with IL-37 revealed an increase in AMP/ATP ratio, reduced levels of proinflammatory mediator succinate and oxidative stress-related metabolites, as well as changes in amino acid and purine metabolism. These effects of IL-37 to limit the metabolic costs of chronic inflammation and to foster exercise tolerance provide a rationale for therapeutic use of IL-37 in the treatment of inflammation-mediated fatigue.
Increasing age is associated with declines in multiple domains of physiological function leading to an increased risk of morbidity, disability, and mortality in older adults. Central to these declines in physiological function is a reduction in the bioavailability of the ubiquitous signaling molecule nitric oxide (NO). Supplementation with precursors of NO, nitrate, and nitrite, improves select vascular, physical, and cognitive functions in middle-aged and older adults and may improve age-associated inflammation and oxidative stress. Collectively, current evidence suggests that nitrate and nitrite supplementation represent promising therapeutic strategies for enhancing physiological function with aging and reducing the risk of age-associated disability and risk of chronic diseases.
Fig. S1 Glucose tolerance in young and old untreated and rapamycin treated mice. Table S1 Total blood count and differential from old untreated and rapamycin (Rap) treated mice.
The compliance of large elastic arteries in the cardiothoracic circulation declines, whereas sympathetic nervous system activity increases markedly with advancing age in adult humans. We tested the hypothesis that the reduction in compliance of the large elastic arteries with age is associated with elevations in sympathetic tone to vascular smooth muscle in 16 young and 17 older adults. Carotid arterial compliance (via ultrasonography) was 45% lower in healthy older compared with young men (P<0.001), and was inversely related to sympathetic nerve activity (via microneurography) (r=−0.51; P<0.005). Statistically correcting for sympathetic nerve activity abolished the age-related difference in arterial compliance (P=0.35). Our results suggest that increases in the sympathetic tone of vascular smooth muscle may have a mechanistic role in the age-related reduction in large artery compliance.
We hypothesized that curcumin would improve resistance and conduit artery endothelial function and large elastic artery stiffness in healthy middle-aged and older adults. Thirty-nine healthy men and postmenopausal women (45-74 yrs) were randomized to 12 weeks of curcumin (2000 mg/day Longvida®; n=20) or placebo (n=19) supplementation. Forearm blood flow response to acetylcholine infusions (FBFACh; resistance artery endothelial function) increased 37% following curcumin supplementation (107±13 vs. 84±11 AUC at baseline, P=0.03), but not placebo (P=0.2). Curcumin treatment augmented the acute reduction in FBFACh induced by the nitric oxide synthase inhibitor NG monomethyl-L-arginine (L-NMMA; P=0.03), and reduced the acute increase in FBFACh to the antioxidant vitamin C (P=0.02), whereas placebo had no effect (both P>0.6). Similarly, brachial artery flow-mediated dilation (conduit artery endothelial function) increased 36% in the curcumin group (5.7±0.4 vs. 4.4±0.4% at baseline, P=0.001), with no change in placebo (P=0.1). Neither curcumin nor placebo influenced large elastic artery stiffness (aortic pulse wave velocity or carotid artery compliance) or circulating biomarkers of oxidative stress and inflammation (all P>0.1). In healthy middle-aged and older adults, 12 weeks of curcumin supplementation improves resistance artery endothelial function by increasing vascular nitric oxide bioavailability and reducing oxidative stress, while also improving conduit artery endothelial function.
Mitochondrial dysregulation and associated excessive reactive oxygen species (mtROS) production is a key source of oxidative stress in aging arteries that reduces baseline function and may influence resilience (ability to withstand stress). We hypothesized that voluntary aerobic exercise would increase arterial resilience in old mice. An acute mitochondrial stressor (rotenone) caused greater (further) impairment in peak carotid EDD in old (~27 mo., OC, n=12; -32.5±-10.5%) versus young (~7 mo., YC n=11; -5.4±- 3.7%) control male mice, whereas arteries from young and old exercising (YVR n=10 and OVR n=11, 10-wk voluntary running; -0.8±-2.1% and -8.0±4.9%, respectively) mice were protected. Ex-vivo simulated Western diet (WD, high glucose and palmitate) caused greater impairment in EDD in OC (-28.5±8.6%) versus YC (-16.9±5.2%) and YVR (-15.3±2.3%), whereas OVR (-8.9±3.9%) were more resilient (not different versus YC). Simultaneous ex-vivo treatment with mitochondria-specific antioxidant MitoQ attenuated WD-induced impairments in YC and OC, but not YVR or OVR, suggesting that exercise improved resilience to mtROS-mediated stress. Exercise normalized age-related alterations in aortic mitochondrial protein markers PGC-1α, SIRT-3 and Fis1 and augmented cellular antioxidant and stress response proteins. Our results indicate that arterial aging is accompanied by reduced resilience and mitochondrial health, which are restored by voluntary aerobic exercise.
New & noteworthy: This is the first study to demonstrate that habitual aerobic exercise may not protect against age/menopause-related whole forearm microvascular endothelial dysfunction in healthy nonobese estrogen-deficient postmenopausal women, consistent with recent findings regarding macrovascular endothelial function. This is in contrast to what is observed in healthy middle-aged and older aerobic exercise-trained men.
As our world’s population ages, cardiovascular diseases (CVD) will become an increasingly urgent public health problem. A key antecedent to clinical CVD and many other chronic disorders of aging is age-related arterial dysfunction, characterized by increased arterial stiffness and impaired arterial endothelial function. Accumulating evidence demonstrates that diet and nutrition may favorably modulate these arterial functions with aging, but many important questions remain. In this review, we will summarize the available information on dietary patterns and nutritional factors that have been studied for their potential to reduce arterial stiffness and improve endothelial function with age, with an emphasis on: 1) underlying physiological mechanisms, and 2) emerging areas of research on nutrition and arterial aging that may hold promise for preventing age-related CVD.
Inhibition of mammalian target of rapamycin, mTOR, extends lifespan and reduces age-related disease. It is not known what role mTOR plays in the arterial aging phenotype or if mTOR inhibition by dietary rapamycin ameliorates age-related arterial dysfunction. To explore this, young (3.8 ± 0.6 months) and old (30.3 ± 0.2 months) male B6D2F1 mice were fed a rapamycin supplemented or control diet for 6-8 weeks. Although there were few other notable changes in animal characteristics after rapamycin treatment, we found that glucose tolerance improved in old mice, but was impaired in young mice, after rapamycin supplementation (both P < 0.05). Aging increased mTOR activation in arteries evidenced by elevated S6K phosphorylation (P < 0.01), and this was reversed after rapamycin treatment in old mice (P < 0.05). Aging was also associated with impaired endothelium-dependent dilation (EDD) in the carotid artery (P < 0.05). Rapamycin improved EDD in old mice (P < 0.05). Superoxide production and NADPH oxidase expression were higher in arteries from old compared to young mice (P < 0.05), and rapamycin normalized these (P < 0.05) to levels not different from young mice. Scavenging superoxide improved carotid artery EDD in untreated (P < 0.05), but not rapamycin-treated, old mice. While aging increased large artery stiffness evidenced by increased aortic pulse-wave velocity (PWV) (P < 0.01), rapamycin treatment reduced aortic PWV (P < 0.05) and collagen content (P < 0.05) in old mice. Aortic adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and expression of the cell cycle-related proteins PTEN and p27kip were increased with rapamycin treatment in old mice (all P < 0.05). Lastly, aging resulted in augmentation of the arterial senescence marker, p19 (P < 0.05), and this was ameliorated by rapamycin treatment (P < 0.05). These results demonstrate beneficial effects of rapamycin treatment on arterial function in old mice and suggest these improvements are associated with reduced oxidative stress, AMPK activation and increased expression of proteins involved in the control of the cell cycle.
a major goal of graduate education is the development of students as “stewards of the discipline,” scholars who can create and preserve knowledge and responsibly translate it through writing, teaching, and practical applications ([5][1]). These qualities are consistent with the American
Calorie restriction (CR) in the absence of malnutrition exerts a multitude of physiological benefits with aging in model organisms and in humans including improvements in vascular function. Despite the well-known benefits of chronic CR, long-term energy restriction is likely not a feasible healthy lifestyle strategy in humans due to poor sustained adherence, and presents additional concerns if applied to normal weight older adults. The purpose of this review will be to summarize what is known about the effects of CR on vascular function with aging including the underlying molecular “energy- and nutrient-sensing” mechanisms, and to discuss the limited but encouraging evidence for alternative pharmacological and lifestyle interventions that may improve vascular function with aging by mimicking the beneficial effects of long-term CR. This article is protected by copyright. All rights reserved
We hypothesized that supplementation with trehalose, a disaccharide that reverses arterial aging in mice, would improve vascular function in middle-aged and older (MA/O) men and women. Thirty-two healthy adults aged 50-77 years consumed 100 g/day of trehalose (n=15) or maltose (n=17, isocaloric control) for 12 weeks (randomized, double-blind). In subjects with Δbody mass less than 2.3kg (5 lb.), resistance artery endothelial function, assessed by forearm blood flow to brachial artery infusion of acetylcholine (FBFACh), increased ~30% with trehalose (13.3±1.0 vs. 10.5±1.1 AUC, P=0.02), but not maltose (P=0.40). This improvement in FBFACh was abolished when endothelial nitric oxide (NO) production was inhibited. Endothelium-independent dilation, assessed by FBF to sodium nitroprusside (FBFSNP), also increased ~30% with trehalose (155±13 vs. 116±12 AUC, P=0.03) but not maltose (P=0.92). Changes in FBFACh and FBFSNP with trehalose were not significant when subjects with Δbody mass ≥ 2.3kg were included. Trehalose supplementation had no effect on conduit artery endothelial function, large elastic artery stiffness or circulating markers of oxidative stress or inflammation (all P>0.1) independent of changes in body weight. Our findings demonstrate that oral trehalose improves resistance artery (microvascular) function, a major risk factor for cardiovascular diseases, in MA/O adults, possibly through increasing NO bioavailability and smooth muscle sensitivity to NO.
We tested the hypothesis that supplementation of nicotinamide mononucleotide (NMN), a key NAD(+) intermediate, increases arterial SIRT1 activity and reverses age-associated arterial dysfunction and oxidative stress. Old control mice (OC) had impaired carotid artery endothelium-dependent dilation (EDD) (60 ± 5% vs. 84 ± 2%), a measure of endothelial function, and nitric oxide (NO)-mediated EDD (37 ± 4% vs. 66 ± 6%), compared with young mice (YC). This age-associated impairment in EDD was restored in OC by the superoxide (O2-) scavenger TEMPOL (82 ± 7%). OC also had increased aortic pulse wave velocity (aPWV, 464 ± 31 cm s(-1) vs. 337 ± 3 cm s(-1) ) and elastic modulus (EM, 6407 ± 876 kPa vs. 3119 ± 471 kPa), measures of large elastic artery stiffness, compared with YC. OC had greater aortic O2- production (2.0 ± 0.1 vs. 1.0 ± 0.1 AU), nitrotyrosine abundance (a marker of oxidative stress), and collagen-I, and reduced elastin and vascular SIRT1 activity, measured by the acetylation status of the p65 subunit of NFκB, compared with YC. Supplementation with NMN in old mice restored EDD (86 ± 2%) and NO-mediated EDD (61 ± 5%), reduced aPWV (359 ± 14 cm s(-1) ) and EM (3694 ± 315 kPa), normalized O2- production (0.9 ± 0.1 AU), decreased nitrotyrosine, reversed collagen-I, increased elastin, and restored vascular SIRT1 activity. Acute NMN incubation in isolated aortas increased NAD(+) threefold and manganese superoxide dismutase (MnSOD) by 50%. NMN supplementation may represent a novel therapy to restore SIRT1 activity and reverse age-related arterial dysfunction by decreasing oxidative stress.
We hypothesised that differences in cardiac baroreflex sensitivity (BRS) would be independently associated with aortic stiffness and augmentation index (AI), clinical biomarkers of cardiovascular disease risk, among young sedentary and middle-aged/older sedentary and endurance-trained adults. A total of 36 healthy middle-aged/older (age 55-76 years, n=22 sedentary and n=14 endurance-trained) and 5 young sedentary (age 18-31 years) adults were included in a cross-sectional study. A subset of the middle-aged/older sedentary adults (n=12) completed an 8-week-aerobic exercise intervention. Invasive brachial artery blood pressure waveforms were used to compute spontaneous cardiac BRS (via sequence technique), estimated aortic pulse wave velocity (PWV) and AI (AI, via brachial-aortic transfer function and wave separation analysis). In the cross-sectional study, cardiac BRS was 71% lower in older compared with young sedentary adults (P<0.05), but only 40% lower in older adults who performed habitual endurance exercise (P=0.03). In a regression model that included age, sex, resting heart rate, mean arterial pressure (MAP), body mass index and maximal exercise oxygen uptake, estimated aortic PWV (β±s.e.=-5.76±2.01, P=0.01) was the strongest predictor of BRS (model R(2)=0.59, P<0.001). The 8-week-exercise intervention improved BRS by 38% (P=0.04) and this change in BRS was associated with improved aortic PWV (r=-0.65, P=0.044, adjusted for changes in MAP). Age- and endurance-exercise-related differences in cardiac BRS are independently associated with corresponding alterations in aortic PWV among healthy adults, consistent with a mechanistic link between variations in the sensitivity of the baroreflex and aortic stiffness with age and exercise.Journal of Human Hypertension advance online publication, 25 February 2016; doi:10.1038/jhh.2016.3.
Insufficient nitric oxide (NO) bioavailability plays an important role in endothelial dysfunction and arterial stiffening with aging. Supplementation with sodium nitrite, a precursor of NO, ameliorates age-related vascular endothelial dysfunction and arterial stiffness in mice, but effects on humans, including the metabolic pathways altered, are unknown. The purpose of this study was to determine the safety, feasibility and efficacy of oral sodium nitrite supplementation for improving vascular function in middle-aged and older adults, and to identify related circulating metabolites. Ten weeks of sodium nitrite (80 or 160 mg/day, capsules, TheraVasc, Inc., randomized, placebo-control, double-blind) increased plasma nitrite acutely (5- to 15-fold, p<0.001 vs. placebo) and chronically (p<0.10), and was well-tolerated without symptomatic hypotension or clinically-relevant elevations in blood methemoglobin. Endothelial function, measured by brachial artery flow-mediated dilation, increased 45-60% vs. baseline (p<0.10) without changes in body mass or blood lipids. Measures of carotid artery elasticity (ultrasound and applanation tonometry) improved (decreased β-stiffness index, increased cross-sectional compliance, p<0.05) without changes in brachial or carotid artery blood pressure. Aortic pulse wave velocity was unchanged. Nitrite-induced changes in vascular measures were significantly related to 11 plasma metabolites identified by untargeted analysis. Baseline abundance of multiple metabolites, including glycerophospholids and fatty acyls, predicted vascular changes with nitrite. This study provides evidence that sodium nitrite supplementation is well-tolerated, increases plasma nitrite concentrations, improves endothelial function and lessens carotid artery stiffening in middle-aged and older adults, perhaps by altering multiple metabolic pathways, thereby warranting a larger clinical trial.
Mounting evidence suggests that curcumin, an anti-inflammatory ingredient in the Indian spice tumeric, has vascular protective effects in aging animals and humans. We tested the hypothesis that curcumin improves vascular endothelial function, as assessed by endothelium-dependent dilation (EDD), in middle-aged and older (MA/O) adults (45-74 yrs) by enhancing bioavailability of the vasodilatory and vascular protective molecule, nitric oxide (NO). Conduit and resistance artery EDD were assessed by brachial artery flow-mediated dilation (FMDba) and forearm blood flow in response to incremental brachial artery infusions of acetylcholine (FBFach), respectively, before and after 12 weeks of curcumin (2000 mg/day-Longvida®; n=16) or placebo (n=13) supplementation. FMDba was increased by 34% (P<0.01 vs. placebo; 5.6±0.5 compared to 4.6±0.4% at baseline, P<0.001) in the curcumin group, whereas no change was observed with placebo (P>0.05). Similarly, FBFach increased by 44% following curcumin (P<0.05 vs. placebo; 222±74 vs. 170±57 AUC at baseline, P=0.06) and this improvement was mediated in part by an increase in NO bioavailability as indicated by a greater ΔFBFach AUC during co-infusion of the NO synthase inhibitor, NG monomethyl-L-arginine (-34 vs. -5%; P=0.08). In contrast, there was no change in either FBFach or NO bioavailability in the placebo group (both P>0.05). Conduit (sublingual nitroglycerin) and resistance artery (incremental brachial artery infusions of sodium nitroprusside) endothelium-independent dilation were unchanged in both groups (all P>0.05), suggesting an endothelium-specific effect of curcumin. Our findings indicate that 12 weeks of curcumin supplementation improves EDD in MA/O adults and this is mediated, in part, by an increase in NO bioavailability.
Objective: Aortic pulse-wave velocity (aPWV) increases with age and is a strong independent predictor of incident cardiovascular diseases (CVDs) in healthy middle-aged and older adults. aPWV is lower in middle-aged and older adults who perform regular aerobic exercise than in their sedentary peers. As exercise is associated with reduced systemic inflammation, we hypothesized that suppression of the pro-inflammatory transcription factor nuclear factor κ B (NFκB) may mediate this process. Methods: aPWV was measured in young sedentary [n = 10, blood pressure (BP) 108 ± 3/59 ± 2 mmHg; mean ± SEM], middle-aged and older sedentary (n = 9, 124 ± 7/73 ± 5 mmHg) and middle-aged and older aerobic exercise-trained (n = 12, 110 ± 4/67 ± 2 mmHg) healthy, nonhypertensive men and women. Results: Baseline aPWV increased with age [626 ± 14 (young sedentary) vs. 859 ± 49 (middle-aged and older sedentary) cm/s, P < 0.001] but was 20% lower in middle-aged and older trained (686 ± 30 cm/s) than in middle-aged and older sedentary (P < 0.005). Short-term (4 days x 2500-4500 mg) treatment with the NFκB inhibitor salsalate (randomized, placebo-controlled cross-over design) reduced aPWV (to 783 ± 44 cm/s, P < 0.05) without changing BP (P = 0.40) or heart rate (P = 0.90) in middle-aged and older sedentary, but had no effect in young sedentary (623 ± 19) or middle-aged and older trained (699 ± 30). Following salsalate treatment, aPWV no longer was significantly different in middle-aged and older sedentary vs. middle-aged and older trained (P = 0.29). The reduction in aPWV with salsalate administration was inversely related to baseline (placebo) aPWV (r = -0.60, P < 0.001). Conclusion: These results support the hypothesis that suppressed NFκB signalling may partially mediate the lower aortic stiffness in middle-aged and older adults who regularly perform aerobic exercise. Because aPWV predicts incident cardiovascular events in this population, this suggests that tonic suppression of NFκB signalling in middle-aged and older exercising adults may potentially lower cardiovascular risk.
Despite dedicated efforts to identify interventions to delay aging, most promising interventions yielding dramatic life-span extension in animal models of aging are often ineffective when translated to clinical trials. This may be due to differences in primary outcomes between species and difficulties in determining the optimal clinical trial paradigms for translation. Measures of physical function, including brief standardized testing batteries, are currently being proposed as biomarkers of aging in humans, are predictive of adverse health events, disability, and mortality, and are commonly used as functional outcomes for clinical trials. Motor outcomes are now being incorporated into preclinical testing, a positive step toward enhancing our ability to translate aging interventions to clinical trials. To further these efforts, we begin a discussion of physical function and disability assessment across species, with special emphasis on mice, rats, monkeys, and man. By understanding how physical function is assessed in humans, we can tailor measurements in animals to better model those outcomes to establish effective, standardized translational functional assessments with aging. © The Author 2015. Published by Oxford University Press on behalf of the Gerontological Society of America. All rights reserved. For permissions, please email: journals.permissions@oup.com.
Metabolomics is a relatively new field of "-omics" research, focusing on high-throughput identification of small molecular weight metabolites. Diet has both acute and chronic effects on metabolic profiles; however, alterations in response to dietary sodium restriction (DSR) are completely unknown. The goal of this study was to explore changes in urine metabolites in response to DSR, as well as their association with previously reported improvements in vascular function with DSR. Using stored urine samples from a 10-week randomized placebo-controlled crossover study of DSR in 17 middle-aged/older adults (six men and 11 women; mean age 62±8 years) who had moderately elevated systolic BP (130-159 mmHg) and were otherwise healthy, a liquid chromatography/mass spectrometry-based analysis of 289 metabolites was performed. This study identified metabolites that were significantly altered between the typical (153±29 mmol/d) and low (70±29 mmol/d) sodium conditions, as well as their baseline (typical sodium) association with responsiveness to previously reported improvements in vascular endothelial function (brachial artery flow-mediated dilation) and large elastic artery stiffness (aortic pulse wave velocity). Of the 289 metabolites surveyed, 10 were significantly altered (nine were upregulated and one was downregulated) during the low sodium condition, and eight of these exceeded our prespecified clinically significant threshold of a >40% change. These metabolites were involved in biologic pathways broadly related to cardiovascular risk, nitric oxide production, oxidative stress, osmotic regulation, and metabolism. One metabolite, serine, was independently (positively) associated with previously reported improvements in the primary vascular outcome of brachial artery flow-mediated dilation. This proof-of-concept study provides the first evidence that DSR is a stimulus that induces significant changes in urinary metabolomic profiles. Moreover, serine was independently associated with corresponding changes in vascular endothelial function after DSR. Larger follow-up studies will be required to confirm and further elucidate the metabolic pathways that are altered in response to DSR. Copyright © 2015 by the American Society of Nephrology.
Aging causes macro- and microvascular endothelial dysfunction, as assessed by endothelium-dependent dilation (EDD), which can be prevented and reversed by habitual aerobic exercise (AE) in men. However, a beneficial effect of AE on macrovascular EDD has not been consistently shown in estrogen-deficient postmenopausal women, and microvascular EDD has not been assessed. We determined forearm blood flow in response to incremental brachial artery infusion of acetylcholine (FBFACh), a measure of microvascular EDD, and brachial artery flow-mediated dilation (FMD), an assessment of macrovascular EDD, in 8 premenopausal sedentary (PrS; 25.5±2 yrs; VO2max = 36.9±2.6 ml/kg/min), 28 estrogen-deficient postmenopausal sedentary (PoS; 61.8±1 yrs; VO2max = 24.5±0.9 ml/kg/min), and 7 estrogen-deficient postmenopausal trained (PoT; 58.6±2 yrs; VO2max = 40.6±2.4 ml/kg/min) women. Peak and area under the curve (AUC) FBFACh was lower in PoS vs. PrS (19.5±1.2 vs. 29.9 ml/100 ml tissue/min and 133.4±8.8 vs. 211.5±28.7 AUC, respectively, P<0.05) women. In PoT, peak and AUC FBFACh was lower than PrS, but not different from PoS (20.1 ml/100 ml tissue/min and 102.8±21.8 AUC, respectively, P<0.05 and P>0.05, respectively) women. FMD was 28% and 42% lower in PoS and PoT, respectively, vs. PrS women, and there was no difference in FMD between PoS and PoT (P>0.05) women. These findings suggest that habitual AE does not protect against age-related macro- and microvascular endothelial dysfunction in estrogen-deficient postmenopausal women.
We tested the hypothesis that short-term oral sodium nitrite supplementation would improve vascular dysfunction in obese, diabetic mice. Vascular function was determined in control mice and in db/db mice receiving drinking water with or without sodium nitrite (50 mg/L) for 5 weeks. Nitrite supplementation increased plasma nitrite concentrations in db/db mice (0.19±0.02 µM vs 0.80±0.26 µM; p < 0.05). Db/db mice had lower endothelium-dependent dilation (EDD) in response to increasing doses of acetylcholine versus heterozygous control mice (71.2% ± 14.3% vs 93% ± 7.0%; p < 0.05), and sodium nitrite supplementation restored endothelium-dependent dilation to control levels (92.9% ± 2.3% vs 93% ± 7.0%; p < 0.05). The improvement in endothelial function was accompanied by a reduction in intrinsic stiffness, but not by alterations in plasma or vascular markers of inflammation. These data suggest that sodium nitrite may be a novel therapy for treating diabetes-related vascular dysfunction; however, the mechanisms of improvement are unknown. © The Author(s) 2015.
Most nations of the world are undergoing rapid and dramatic population aging, which presents great socio-economic challenges, as well as opportunities, for individuals, families, governments and societies. The prevailing biomedical strategy for reducing the healthcare impact of population aging has been “compression of morbidity” and, more recently, to increase healthspan, both of which seek to extend the healthy period of life and delay the development of chronic diseases and disability until a brief period at the end of life. Indeed, a recently established field within biological aging research, “Geroscience”, is focused on healthspan extension. Superimposed on this background are new attitudes and demand for “optimal longevity”—living long, but with good health and quality of life. A key obstacle to achieving optimal longevity is the progressive decline in physiological function that occurs with aging, which causes functional limitations (e.g., reduced mobility) and increases the risk of chronic diseases, disability and mortality. Current efforts to increase healthspan center on slowing the fundamental biological processes of aging such as inflammation/oxidative stress, increased senescence, mitochondrial dysfunction, impaired proteostasis and reduced stress resistance. We propose that optimization of physiological function throughout the lifespan should be a major emphasis of any contemporary biomedical policy addressing global aging. Effective strategies should delay, reduce or abolish reductions in function with aging (primary prevention) and/or improve function or slow further declines in older adults with already impaired function (secondary prevention). Healthy lifestyle practices featuring regular physical activity and ideal energy intake/diet composition represent first-line function-preserving strategies, with pharmacological agents, including existing and new pharmaceuticals and novel “nutraceutical” compounds, serving as potential complementary approaches. Future research efforts should focus on defining the temporal patterns of functional declines with aging, identifying the underlying mechanisms and modulatory factors involved, and establishing the most effective lifestyle practices and pharmacological options for maintaining function. Continuing development of effective behavioral approaches for enhancing adherence to healthy aging practices in diverse populations, and ongoing analysis of the socio-economic costs and benefits of healthspan extension will be important supporting goals. To meet the demands created by rapid population aging, a new emphasis in physiological geroscience is needed, which will require the collaborative, interdisciplinary efforts of investigators working throughout the translational research continuum from basic science to public health.This article is protected by copyright. All rights reserved
Cardiovascular diseases (CVDs) remain the leading cause of death in the United States and other modern societies. Advancing age is the major risk factor for CVD, primarily due to stiffening of the large elastic arteries and the development of vascular endothelial dysfunction. In contrast, regular aerobic exercise protects against the development of large elastic artery stiffness and vascular endothelial dysfunction with advancing age. Moreover, aerobic exercise interventions reduce arterial stiffness and restore vascular endothelial function in previously sedentary middle-aged/older adults. Aerobic exercise exerts its beneficial effects on arterial function by modulating structural proteins, reducing oxidative stress and inflammation, and restoring nitric oxide bioavailability. Aerobic exercise may also promote "resistance" against factors that reduce vascular function and increase CVD risk with age. Preventing excessive increases in abdominal adiposity, following healthy dietary practices, maintaining a low CVD risk factor profile, and, possibly, selective use of pharmaceuticals and nutraceuticals also play a major role in preserving vascular function with aging. Copyright © 2014 The American Physiological Society.
Aging is associated with motor declines that lead to functional limitations and disability, necessitating the development of therapies to slow/reverse these events. We tested the hypothesis that sodium nitrite supplementation attenuates declines in motor function in older C57BL/6 mice. Motor function was assessed using a battery of tests (grip strength, open-field distance, rota-rod endurance) in old animals (20-24mo) at baseline and after eight-weeks sodium nitrite (Old Nitrite: n=22, 50mg/L) or no treatment (Old Control: n=40), and in young reference animals (Young Reference: 3mo, n=87). Eight-weeks sodium nitrite supplementation improved grip strength (Old Nitrite: +12.0±14.9% vs. Old Control: +1.5±15.2%, p<0.05) and open field distance (Old Nitrite: +9.5±7.7%, p<0.01 vs. Old Control: -28.1±2.0%) and completely restored rota-rod endurance-run time (Old Nitrite: +3.2±7.1%, p<0.01 vs. Old Control: -21.5±7.2%; Old Nitrite post treatment p>0.05 vs. Young Reference). Inflammatory cytokines were markedly increased in quadriceps of old compared with young (ELISA; interleukin-1β [IL-1β]: 3.86±2.34 vs. 1.11±0.74, p < 0.05; interferon-gamma [INFγ]: 8.31±1.59 vs. 3.99±2.59, p <0.01; tumor necrosis factor-alpha [TNFα]: 1.69±0.44 vs. 0.76±0.30 pg/mL, p < 0.01), but were reduced to Young Reference levels post-treatment (Old Nitrite: IL-1β: 0.67±0.95, INFγ: 5.22±2.01, TNFα: 1.21±0.39 pg/mL, p < 0.05 vs. Old Control, p > 0.05 vs. Young Reference). Cytokine expression and treatment (Old Nitrite vs. Old Control) predicted strength (R(2)=0.822, p<0.001, IL-1β, INFγ, group), open field distance (R(2)=0.574, p<0.01, IL-1β, group) and endurance-run time (R(2)=0.477, p<0.05, INFγ). Our results suggest that sodium nitrite improves motor function in old mice, in part by reducing low-grade inflammation in muscle.
Reductions in arterial SIRT1 expression and activity with aging are linked to vascular endothelial dysfunction. We tested the hypothesis that the specific SIRT1 activator, SRT1720, improves endothelial function (endothelium-dependent dilation, EDD) in old mice. Young (4-9 months) and old (29-32 months) male B6D2F1 mice treated with SRT1720 (100 mg/kg BW) or vehicle for four weeks were studied with a group of young controls. Compared with the young controls, aortic SIRT1 expression and activity were reduced (p < 0.05) and EDD was impaired (83 ± 2% vs. 96 ± 1%, p < 0.01) in old vehicle-treated animals. SRT1720 normalized SIRT1 expression/activity in old mice, and restored EDD (95 ± 1%) by enhancing cyclooxygenase (COX)-2 mediated dilation and protein expression in the absence of changes in nitric oxide bioavailability. Aortic superoxide production and expression of NOX4 were increased in old vehicle mice (p < 0.05), and ex vivo administration of the superoxide scavenger TEMPOL restored EDD in that group. SRT1720 normalized aortic superoxide production in old mice, without altering NOX4, and abolished the improvement in EDD with TEMPOL, while selectively increasing aortic antioxidant enzymes. Aortic nuclear factor κB (NF-κB) activity and tumor necrosis factor-α (TNF-α) were increased in old vehicle mice (p < 0.05), whereas SRT1720 normalized NF-κB activation and reduced TNF-α in old animals. SIRT1 activation with SRT1720 ameliorates vascular endothelial dysfunction with aging in mice by enhancing COX-2 signaling and reducing oxidative stress and inflammation. Specific activation of SIRT1 is a promising therapeutic strategy for age-related endothelial dysfunction in humans.
Among individuals, biological aging leads to cellular and organismal dysfunction and an increased risk of chronic degenerative diseases and disability. This sequence of events in combination with the projected increases in the number of older adults will result in a worldwide healthcare burden with dire consequences. Superimposed on this setting are the adults now reaching traditional retirement ages--the baby boomers--a group that wishes to remain active, productive and physically and cognitively fit as they grow older. Together, these conditions are producing an unprecedented demand for increased healthspan or what might be termed "optimal longevity"-to live long, but well. To meet this demand, investigators with interests in the biological aspects of aging from model organisms to human epidemiology (population aging) must work together within an interactive process that we describe astranslational geroscience. An essential goal of this new investigational platform should be the optimization and preservation of physiological function throughout the lifespan, including integrative physical and cognitive function, which would serve to increase healthspan, compress morbidity and disability into a shorter period of late-life, and help achieve optimal longevity. To most effectively utilize this new approach, we must rethink how investigators and administrators working at different levels of the translational research continuum communicate and collaborate with each other, how best to train the next generation of scientists in this new field, and how contemporary biological-biomedical aging research should be organized and funded.
Stiffening of large elastic arteries with age increases the risk of cardiovascular diseases (CVD), but the underlying mechanisms are incompletely understood. We investigated the role of mitochondrial quality control (QC, i.e., mitophagy and biogenesis) in arterial stiffening with aging. In C57BL6 mice, aging was associated with impaired aortic expression of mitochondrial QC mediators, greater activation of the mitochondrial redox/stress sensor p66shc, elevated superoxide production and increased arterial stiffness-as indicated by ~20% higher aortic pulse wave velocity (aPWV). In old mice, supplementation with trehalose, a nutraceutical reported to enhance mitophagy, normalized mitochondrial QC markers, p66shc activation and superoxide production, and reduced aPWV and aortic collagen I (a structural protein that confers stiffness). In vitro experiments indicated that mitochondrial QC processes were enhanced in the aorta from old trehalose-treated mice, and in aortic rings studied ex vivo, both aging and treatment with the mitochondrial stressor rotenone were associated with increases in p66shc activation and intrinsic mechanical stiffness, whereas co-incubation with trehalose prevented these effects. Taken together, these findings suggest that mitochondrial stress/dysfunction as a result of impaired mitochondrial QC contributes to large elastic artery stiffening with age. Enhancing mitochondrial QC with agents such as trehalose may be a novel strategy for reducing age-associated arterial stiffness and CVD.
Endothelial dysfunction develops with age and increases the risk of age-associated vascular disorders. Nitric oxide insufficiency, oxidative stress, and chronic low-grade inflammation, induced by upregulation of adverse cellular signaling processes and imbalances in stress resistance pathways, mediate endothelial dysfunction with aging. Healthy lifestyle behaviors preserve endothelial function with aging by inhibiting these mechanisms, and novel nutraceutical compounds that favorably modulate these pathways hold promise as a complementary approach for preserving endothelial health.
Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this is only partially explained by traditional CVD risk factors. Vascular dysfunction is an important non-traditional risk factor, characterized by vascular endothelial dysfunction (most commonly assessed as impaired endothelium-dependent dilation [EDD]) and stiffening of the large elastic arteries. While various techniques exist to assess EDD and large elastic artery stiffness, the most commonly used are brachial artery flow-mediated dilation (FMDBA) and aortic pulse-wave velocity (aPWV), respectively. Both of these noninvasive measures of vascular dysfunction are independent predictors of future cardiovascular events in patients with and without kidney disease. Patients with CKD demonstrate both impaired FMDBA, and increased aPWV. While the exact mechanisms by which vascular dysfunction develops in CKD are incompletely understood, increased oxidative stress and a subsequent reduction in nitric oxide (NO) bioavailability are important contributors. Cellular changes in oxidative stress can be assessed by collecting vascular endothelial cells from the antecubital vein and measuring protein expression of markers of oxidative stress using immunofluorescence. We provide here a discussion of these methods to measure FMDBA, aPWV, and vascular endothelial cell protein expression.
Habitual aerobic exercise prevents age-related impairments in endothelium-dependent dilation (EDD). We hypothesized that the pro-inflammatory transcription factor nuclear factor κB (NF-κB) impairs EDD with sedentary aging and habitual aerobic exercise prevents this age-related suppression of EDD by NF-κB. To test this hypothesis, we inhibited NF-κB signaling via oral salsalate administration in healthy older aerobic exercise-trained adults (OT, n=14, 58±2 years), older non-exercising adults (ON, n=16, 61±1 years) and young non-exercising controls (YN, n=8, 23±1 years). Salsalate reduced endothelial cell expression of NF-κB p65 by ~25% in ON (P<0.05), but did not significantly change expression in OT or YN (P>0.05). EDD, assessed by brachial artery flow-mediated dilation (FMD), was improved by salsalate in ON (4.0±0.7% vs. 6.8±0.7%, placebo vs. salsalate, P<0.001), but did not change with salsalate in OT or YN (OT: 7.2±0.7% vs. 7.7±0.6%; YN: 7.6±0.9% vs. 8.1±0.8%; placebo vs. salsalate, P>0.05). Endothelium-independent dilation was not affected by salsalate in any group (P>0.05). In ON, vitamin C infusion improved FMD by ~30% during placebo (P<0.001), but had no affect during salsalate (P>0.05). In OT and YN, vitamin C infusion did not affect FMD during either placebo or salsalate (P>0.05). Salsalate reduced endothelial cell nitrotyrosine content by ~25% and NADPH oxidase p47phox expression by ~30% in ON (P<0.05), but had no effect in OT or YN (P>0.05). Our results suggest that endothelial NF-κB signaling is associated with oxidative stress-related impairment of EDD in healthy non-exercising, but not aerobically exercising older adults. This may be a key mechanism by which regular aerobic exercise preserves endothelial function and reduces cardiovascular risk with aging.
Cardiovascular diseases (CVD) remain the leading cause of morbidity and mortality in modern societies, and advancing age is the major risk factor for CVD. Arterial dysfunction, characterized by large elastic artery stiffening and endothelial dysfunction, is the key event leading to age-associated CVD. Our work shows that regular aerobic exercise inhibits large elastic artery stiffening with aging (optimizes arterial compliance) and preserves endothelial function. Importantly, among previously sedentary late middle-aged and older adults, aerobic exercise improves arterial stiffness and enhances endothelial function in most groups and, therefore, also can be considered a treatment for age-associated arterial dysfunction. The mechanisms by which regular aerobic exercise de-stiffens large elastic arteries are incompletely understood, but existing evidence suggests that reductions in oxidative stress associated with decreases in both adventitial collagen (fibrosis) and advanced glycation endproducts (structural protein cross-linking molecules), play a key role. Aerobic exercise preserves endothelial function with aging by maintaining nitric oxide bioavailability via suppression of excessive superoxide-associated oxidative stress, and by inhibiting the development of chronic low-grade vascular inflammation. Recent work from our laboratory supports the novel hypothesis that aerobic exercise may exert these beneficial effects by directly inducing protection to aging arteries against multiple adverse factors to which they are chronically exposed. Regular aerobic exercise should be viewed as a "first line" strategy for prevention and treatment of arterial aging, and a vital component of a contemporary public health approach for reducing the projected increase in population CVD burden.
Using only indirect, static markers of the dynamic cellular quality control system, autophagy, we have reported impaired autophagy in biopsied vascular endothelial cells (EC) of humans with aging that is related to endothelial dysfunction, as indicated by reduced endothelium-dependent dilation (EDD), and oxidative stress. Here, we estimated dynamic autophagic flux in EC from 10 healthy adults aged 51-73 by calculating the within-subject difference in the expression of microtubule-associated protein light chain 3 (LC3 ratio) between ECs incubated in the absence vs. presence of chloroquine (50 μM 1.5 hrs) to inhibit autophagy. EDD was assessed by: 1) brachial artery flow-mediated dilation (FMD); and 2) forearm blood flow (FBF) to incremental brachial artery infusions of acetylcholine. Oxidative stress-suppression of EDD was determined by ∆FBF to co-infusion of vitamin C (vitC). The LC3 ratio was positively related to FMD (r=0.76, P<0.05) and FBF (r=0.56, P<0.05), but not endothelium-independent dilation to NO donors (both P>0.05). The LC3 ratio also was inversely related to ∆FBF with vitC (r=-0.57, P<0.05). These findings provide novel evidence that greater EC autophagic flux is associated with improved endothelial function linked to reduced oxidative stress in healthy middle-aged/older adults.
Aging causes physiological dysfunction, some of which can be prevented or reduced by habitual aerobic exercise (AE). However, the molecular mechanisms underlying these effects remain largely unknown, particularly in humans. We used a novel high-throughput molecular assay (SOMAscan v3.0, SomaLogic Inc., Boulder, CO) to characterize the effects of age and regular AE on the plasma proteome of healthy adult humans. From 1129 analytes, the expression of 48 proteins was greater and 37 lower in older (O; 64±6 yr; n=16) vs. young (Y; 24±4 yr; n=16) healthy men (false discovery rate [FDR] < 15%, p<0.01). Expression of the non-collagenous extracellular matrix (ECM) protein dermatopontin was greater in O vs. Y (P=0.007), but was lower in older AE-trained men (63±7 yr; n=8; VO2max = 49.6±3.7 mL/kg⋅min) compared with their sedentary counterparts (VO2max = 27.4±2.4 mL/kg⋅min) (FDR < 1.28%, p<0.001). Within O, no other group differences in plasma protein expression associated with exercise status met our FDR threshold (>35%). These preliminary results suggest that normal human aging is associated with several changes to the plasma proteome that may serve as molecular biomarkers of physiological dysfunction or disease risk. Regular AE status influences age-related changes in circulating dermatopontin, a possible mediator of age-related ECM remodeling.
Age-related arterial endothelial dysfunction, a key antecedent to the development of cardiovascular diseases (CVD), is largely due to a reduction in nitric oxide (NO) bioavailability as a consequence of oxidative stress. Mitochondria are a major source and target of vascular oxidative stress when dysregulated. Mitochondrial dysregulation is associated with primary aging, but its role in age-related endothelial dysfunction is unknown. Our aim was to determine the efficacy of a mitochondria-targeted antioxidant, MitoQ, for ameliorating vascular endothelial dysfunction in old mice. Ex vivo carotid artery endothelium-dependent dilation (EDD) to increasing doses of acetylcholine was impaired ∼30% in old (∼27 mo.) compared to young (∼8 mo.) mice due to reduced NO bioavailability (P < 0.05). Acute (ex vivo) and chronic (4 weeks in drinking water) administration of MitoQ completely restored EDD in older mice by improving NO bioavailability. There were no effects of age or MitoQ on endothelium-independent dilation to sodium nitroprusside. The improvements in endothelial function with MitoQ supplementation were associated with normalization of age-related increases in total and mitochondria-derived arterial superoxide production and oxidative stress (nitrotyrosine abundance), as well as increases in markers of vascular mitochondrial health, including antioxidant status. MitoQ also reversed the age-related increase in endothelial susceptibility to acute mitochondrial damage (rotenone-induced impairment in EDD). Our results suggest that mitochondria-derived oxidative stress is an important mechanism underlying the development of endothelial dysfunction with primary aging. Mitochondria-targeted antioxidants such as MitoQ represent a promising, novel strategy for preserving vascular endothelial function with advancing age and preventing age-related CVD.This article is protected by copyright. All rights reserved
Table S1 Arterial morphology and blood pressure in young, old and old TEMPOL-treated mice. Table S2 Arterial morphology and blood pressure in young recipient mice after transplanted with PVAT from young, old or old TEMPOLtreated donors for 8 weeks. Fig. S1 Adventitial collagen I expression in young, old and old TEMPOL-treated mice. Fig. S2 Superoxide production in adipocytes isolated from PVAT of young and old mice. Fig. S3 Cytokine secretion profile of cultured PVAT from young and old mice. Fig. S4 Adventitial collagen I expression in young recipient mice transplanted with PVAT from young, old or old TEMPOL donors.
Aging is the major risk factor for cardiovascular diseases (CVD). This is attributable primarily to adverse changes in arteries, notably increases in large elastic artery stiffness and endothelial dysfunction mediated by inadequate concentrations of the vascular-protective molecule, nitric oxide (NO), and higher levels of oxidative stress and inflammation. Inorganic nitrite is a promising precursor molecule for augmenting circulating and tissue NO bioavailability because it requires only a one-step reduction to NO. Nitrite also acts as an independent signaling molecule, exerting many of the effects previously attributed to NO. Results of recent studies indicate that nitrite may be effective in the treatment of vascular aging. Short-term oral sodium nitrite supplementation reduces aortic pulse wave velocity, the gold-standard measure of large elastic artery stiffness, in old mice and ameliorates endothelial dysfunction, as indicated by normalization of NO-mediated endothelium-dependent dilation. These improvements in age-related vascular dysfunction with nitrite are mediated by reductions in oxidative stress and inflammation, and may be linked to increases in mitochondrial biogenesis and health. Increasing nitrite levels via dietary intake of nitrate appears to have similarly beneficial effects in many of the same physiological and clinical settings. Several clinical trials are being performed to determine the broad therapeutic potential of increasing nitrite bioavailability on human health and disease, including studies related to vascular aging. In summary, inorganic nitrite, as well as dietary nitrate, supplementation represents a promising therapy for treatment of arterial aging and prevention of age-associated CVD in humans.
Translational research has become the preferred model worldwide for organizations supporting biomedical science. As a field, we should look for opportunities to integrate translational approaches into physiological research to most effectively gain insight into mechanisms of interest, study relations between genotype and phenotype, establish the efficacy of interventions, and maximize the impact of our work on public health.
We tested the hypothesis that superoxide signaling within aortic perivascular adipose tissue (PVAT) contributes to large elastic artery stiffening in old mice. Young (4-6 mo), old (26-28 mo), and old treated with TEMPOL, a superoxide scavenger (1mM in drinking water for 3 weeks), male C57BL6/N mice were studied. Compared with young, old had greater large artery stiffness assessed by aortic pulse wave velocity (aPWV, 436±9 vs. 344±5 cm/s) and intrinsic mechanical testing (3821±427 vs. 1925±271 kPa) (both P<0.05). TEMPOL treatment in old reversed both measures of arterial stiffness. Aortic PVAT superoxide production was greater in old (P<0.05 vs. Y), which was normalized with TEMPOL. Compared with young, old controls had greater pro-inflammatory proteins in PVAT conditioned media (P<0.05). Young recipient mice transplanted with PVAT from old compared with young donors for 8 weeks had greater aPWV (409±7 vs. 342±8 cm/s) and intrinsic mechanical properties (3197±647 vs. 1889±520 kPa) (both P<0.05), which was abolished with TEMPOL supplementation in old donors. Tissue-cultured aortic segments from old in the presence of PVAT had greater mechanical stiffening compared with old cultured in the absence of PVAT and old with PVAT and TEMPOL (both, P<0.05). In addition, PVAT-derived superoxide was associated with arterial wall hypertrophy and greater adventitial collagen I expression with aging that was attenuated by TEMPOL. Aging or TEMPOL treatment did not affect blood pressure. Our findings provide evidence for greater age-related superoxide production and pro-inflammatory proteins in PVAT, and directly link superoxide signaling in PVAT to large elastic artery stiffness. This article is protected by copyright. All rights reserved.
We tested the hypothesis that vascular endothelial function and oxidative stress are related to dietary niacin intake among healthy middle-aged and older adults. In 127 men and women aged 48-77 years, brachial artery flow-mediated dilation (FMD) was positively related to dietary niacin intake (%Δ: r=0.20, P<0.05; mmΔ: r=0.25, P<0.01). In subjects with above-average dietary niacin intake (≥22mg/day, NHANES III), FMD was 25% greater than in subjects with below-average intake (P<0.05). Stepwise linear regression revealed that dietary niacin intake (above- vs. below-average) was an independent predictor of FMD (%Δ: β=1.8; mmΔ: β=0.05, both P<0.05). Plasma oxidized low-density lipoprotein, a marker of systemic oxidative stress, was inversely related to niacin intake (r=-0.23, P<0.05) and was lower in subjects with above- vs. below-average niacin intake (48±2 vs. 57±2 mg/dL, P<0.01). Intravenous infusion of the antioxidant vitamin C improved brachial FMD in subjects with below-average niacin intake (P<0.001, n=33), but not above-average (P>0.05, n=20). In endothelial cells sampled from the brachial artery of a subgroup, dietary niacin intake was inversely related to nitrotyrosine, a marker of peroxynitrite-mediated oxidative damage (r=-0.30, P<0.05, n=55), and expression of the pro-oxidant enzyme, NADPH oxidase (r=-0.44, p<0.01, n=37), and these markers were lower in subjects with above- vs. below-average niacin intake (nitrotyrosine: 0.39±0.05 vs. 0.56±0.07; NADPH oxidase: 0.38±0.05 vs. 0.53±0.05 [ratio to HUVEC control], both P<0.05). Our findings support the hypothesis that higher dietary niacin intake is associated with greater vascular endothelial function related to lower systemic and vascular oxidative stress among healthy middle-aged and older adults.
Motor function in humans can be characterized with tests of locomotion, strength, balance, and endurance. The aim of our project was to establish an analogous test battery to assess motor function in mice. Male C57BL/6 mice were studied at 3 (n = 87), 20 (n = 48) and 26 (n = 43) months of age. Tests assessed locomotion, strength, balance/coordination, and endurance capacity in mice. Motor function was reduced in the older groups of mice for the locomotion, strength, and endurance subdomains (p < 0.001). As indicated with a summary score, motor function declined by 7.4 % from 3 to 20 months and by 13.5 % from 20 to 26 months. Based on comparison with previously published data in humans, the magnitude and relative time course of changes were similar in mice and humans in each subdomain except balance/coordination. Power calculations confirmed that the age-associated differences depicted by several of the individual tests and domain summary scores would be sufficient to assess the efficacy of interventions aimed at prevention or treatment of motor dysfunction with aging. The current study describes a mouse model that characterizes age-associated changes in clinically relevant domains of motor function and indicates that the preclinical model can be used to test strategies to attenuate age-associated declines in motor function.
Objective: In contrast to age-matched men, endurance exercise training is not consistently associated with enhanced endothelial function in estrogen-deficient postmenopausal women. We determined whether endurance exercise training improves endothelial function in postmenopausal women treated with estrogen. In a substudy, we determined if oxidative stress is mechanistically linked to endothelial function adaptations to endurance exercise training. Participants and design: Brachial artery flow-mediated dilation (FMD) was measured in 36 sedentary, estrogen-deficient postmenopausal women (45-65 y) at study entry (baseline), after 12 weeks of either placebo, oral (1 mg/d) estradiol, or transdermal estradiol (0.05 mg/d) (randomized), and after an additional 12 weeks of continued estradiol or placebo treatment with concurrent endurance exercise training. In subgroups of women, FMD also was measured during the infusion of ascorbic acid at baseline and following estradiol/placebo plus endurance exercise training, and in seven habitually endurance-trained estrogen-deficient controls. Results: FMD increased in the estrogen-treated groups (both P < .01) after 12 weeks and remained unchanged in placebo. FMD further increased following 12 weeks of endurance exercise training in estrogen-treated (both P < .025), but not placebo-treated women (P = .55). In the substudy, baseline FMD was similar between sedentary and endurance-trained controls. Ascorbic acid increased FMD at baseline in sedentary women and endurance-trained controls, and following endurance exercise training in placebo-treated, but not in estrogen-treated women. Conclusions: Estrogen status appears to play an important modulatory role in improvements in endothelial function with endurance exercise training in postmenopausal women. The restored endurance exercise training adaptation in estrogen-treated postmenopausal women may be related to mitigation of oxidative stress.
We tested the hypothesis that aging will exacerbate the negative vascular consequences of exposure to a common physiological stressor, i.e., consumption of a "western" (high fat/high sucrose) diet (WD) by inducing superoxide-associated reductions in nitric oxide (NO) bioavailability, and that this would be prevented by voluntary aerobic exercise. Incremental stiffness and endothelium-dependent dilation (EDD) were measured in the carotid arteries of young (5.4±0.3 mo, N=20) and old (30.4±0.2 mo, N=19) male B6D2F1 mice fed normal chow (NC: 17% fat, 0% sucrose) or a western diet (40% fat, 19% sucrose) diet and housed in either standard cages or cages equipped with running wheels for 10-14weeks. Incremental stiffness was higher in old NC (P<0.05) and both young (P<0.01) and old (P<0.01) WD fed mice compared with young NC mice, but WD did not further increase stiffness in the old mice. In cage control mice, EDD was 17% lower in both NC fed old mice and young WD fed mice (P<0.05). Consumption of WD by old mice led to a further 20% reduction in EDD (P<0.05). Incremental stiffness was 28% lower and EDD was 38% greater in old WD fed mice with access to running wheels vs. old WD fed control mice (P<0.05) and not different from young NC fed controls. Wheel running also tended to improve EDD (+9%, P=0.11), but not incremental stiffness in young WD fed mice. Ex vivo treatment with the superoxide scavenger TEMPOL and NO inhibitor L-NAME abolished these respective effects of age, WD and voluntary running on EDD. Ingestion of a WD induces similar degrees of endothelial dysfunction in old and young adult B6D2F1 mice, and these effects are mediated by a superoxide-dependent impairment of NO bioavailability. However, the combination of old age and WD, a common occurrence in our aging society, results in a marked, additive reduction in endothelial function. Importantly, regular voluntary aerobic exercise reduces arterial stiffness and protects against the adverse influence of WD on endothelial function in old animals by preventing superoxide suppression of NO. These findings may have important implications for arterial aging and the prevention of age-associated cardiovascular diseases.
Systolic BP and large elastic artery stiffness both increase with age and are reduced by dietary sodium restriction. Production of the natriuretic hormone marinobufagenin, an endogenous α1 Na+,K+-ATPase inhibitor, is increased in salt-sensitive hypertension and contributes to the rise in systolic BP during sodium loading. The hypothesis was that dietary sodium restriction performed in middle-aged/older adults (eight men and three women; 60±2 years) with moderately elevated systolic BP (139±2/83±2 mmHg) would reduce urinary marinobufagenin excretion as well as systolic BP and aortic pulse-wave velocity (randomized, placebo-controlled, and crossover design). This study also explored the associations among marinobufagenin excretion with systolic BP and aortic pulse-wave velocity across conditions of 5 weeks of a low-sodium (77±9 mmol/d) and 5 weeks of a normal-sodium (144±7 mmol/d) diet. Urinary marinobufagenin excretion (weekly measurements; 25.4±1.8 versus 30.7±2.1 pmol/kg per day), systolic BP (127±3 versus 138±5 mmHg), and aortic pulse-wave velocity (700±40 versus 843±36 cm/s) were lower during the low- versus normal-sodium condition (all P<0.05). Across all weeks, marinobufagenin excretion was related with systolic BP (slope=0.61, P<0.001) and sodium excretion (slope=0.46, P<0.001). These associations persisted during the normal- but not the low-sodium condition (both P<0.005). Marinobufagenin excretion also was associated with aortic pulse-wave velocity (slope=0.70, P=0.02) and endothelial cell expression of NAD(P)H oxidase-p47phox (slope=0.64, P=0.006). These results show, for the first time in humans, that dietary sodium restriction reduces urinary marinobufagenin excretion and that urinary marinobufagenin excretion is positively associated with systolic BP, aortic stiffness (aortic pulse-wave velocity), and endothelial cell expression of the oxidant enzyme NAD(P)H oxidase. Importantly, marinobufagenin excretion is positively related to systolic BP over ranges of sodium intake typical of an American diet, extending previous observations in rodents and humans fed experimentally high-sodium diets.
Context: Activation of the unfolded protein response (UPR) is emerging as an important molecular signature of cardiometabolic diseases associated with obesity. However, despite the well-established role of the vascular endothelium in obesity-related cardiometabolic dysfunction, it is unclear whether the UPR is activated in endothelial cells of obese adults. Objective: The objective of the study was to determine whether markers of UPR activation are increased in endothelial cells (ECs) of nondiabetic obese adults with impaired endothelial function. Design, setting, and participants: Endothelial cells were obtained from antecubital veins of the nondiabetic obese adults [body mass index (BMI) ≥ 30 kg/m(2), n = 12] with impaired endothelial function and from their nonobese peers (BMI < 30 kg/m(2), n = 14). Main outcome variables: UPR activation via expression (quantitative immunofluorescence) of the proximal UPR sensors, inositol-requiring endoplasmic reticulum (ER)-to-nucleus signaling protein 1 (IRE1), RNA-dependent protein kinase-like ER eukaryotic initiation factor-2α kinase (PERK), and activating transcription factor 6 (ATF6), were the main outcome variables. Results: IRE1 expression was greater in obese vs nonobese individuals (0.84 ± 0.09 vs 0.47 ± 0.02 IRE1 intensity/human umbilical vein EC (HUVEC) intensity (n = 10/8, P < .01). Obese individuals also had greater EC activation of UPR stress sensors PERK and ATF6, indicated by increased expression of phosphorylated PERK [p-PERK; 0.49 ± 0.05 vs 0.36 ± 0.03, p-PERK (threonine 981) intensity/HUVEC intensity, n = 10 men, 13 women, P < .05] and nuclear localization of ATF6 (0.38 ± 0.05 vs 0.23 ± 0.02, nuclear ATF6 intensity/HUVEC intensity, n = 5 men, 9 women, P < .01), respectively. Stepwise linear regression analysis revealed that indices of body fat (BMI and waist circumference) were the strongest independent predictors of all 3 UPR mediators, explaining between 18% and 59% of the variance in endothelial cell expression of IRE1, p-PERK, and nuclear ATF6 localization. Conclusion: These results provide novel evidence for UPR activation in the endothelial cells of nondiabetic obese adults with vascular endothelial dysfunction.
The term 'translational research' was coined 20 years ago and has become a guiding influence in biomedical research. It refers to a process by which the findings of basic research are extended to the clinical research setting (bench to bedside) and then to clinical practice and eventually health policy (bedside to community). It is a dynamic, multidisciplinary research approach. The concept of translational physiology applies the translational research model to the physiological sciences. It differs from the traditional areas of integrative and clinical physiology by its broad investigative scope of basic research to community health. Translational physiology offers exciting opportunities, but presently is under-developed and -utilized. A key challenge will be to expand physiological research by extending investigations to communities of patients and healthy (or at risk) individuals. This will allow bidirectional physiological investigation throughout the translational continuum: basic research observations can be studied up to the population level, and mechanisms can be assessed by 'reverse translation' in clinical research settings and preclinical models based on initial observations made in populations. Examples of translational physiology questions, experimental approaches, roadblocks and strategies for promotion are discussed. Translational physiology provides a novel framework for physiology programs and an investigational platform for physiologists to study function from molecular events to public health. It holds promise for enhancing the completeness and societal impact of our work, while further solidifying the critical role of physiology in the biomedical research enterprise.
We recently published an original research article reporting that short-term fenofibrate improves flow-mediated dilation (FMD) in healthy normolipidemic older adults.1 By assessing the response to vitamin C infusion before and after fenofibrate treatment, we determined that the mechanism for the improvements in FMD was reduced oxidative stress. We also assessed the influence of changes in clinical characteristics on the improvements in FMD. On the basis of these analyses, we concluded that oxidative stress was the primary mechanism for the improvements in FMD in response to fenofibrate. In a letter to the editor, Dr Kawada2 recently stated concerns about our statistical analyses. Specifically, there was a concern that the distributions for circulating factors may not be normal. In …
Aging impairs arterial function through oxidative stress and diminished nitric oxide (NO) bioavailability. Life-long caloric restriction (CR) reduces oxidative stress, but its impact on arterial aging is incompletely understood. We tested the hypothesis that life-long CR attenuates key features of arterial aging. Blood pressure, pulse wave velocity (PWV) (arterial stiffness), carotid artery wall thickness and endothelium-dependent dilation (EDD) (endothelial function) were assessed in young (Y: 5-7 mo), old ad libitum (Old AL: 30-31 mo.) and life-long 40% CR old (30-31 mo.) B6D2F1 mice. Blood pressure was elevated with aging (P<0.05) and was blunted by CR (P<0.05 vs. Old AL). PWV was 27% greater in old vs. young AL fed mice (P<0.05), and CR prevented this increase (P<0.05 vs. Old AL). Carotid wall thickness was greater with age (P<0.05), and CR reduced this by 30%. CR effects were associated with amelioration of age-related changes in aortic collagen and elastin. Nitrotyrosine, a marker of cellular oxidative stress, and superoxide production was greater in old AL vs. young (P<0.05) and CR attenuated this increase. Carotid artery EDD was impaired with age (P<0.05); CR prevented this by enhancing NO and reducing superoxide-dependent suppression of EDD (Both P<0.05 vs. Old AL). This was associated with a smaller age-related increase in NADPH oxidase activity and p67 expression, with increases in superoxide dismutase (SOD), total SOD and catalase activities (All P<0.05 Old CR vs. Old AL). Lastly, CR normalized age-related changes in the critical nutrient sensing pathways SIRT-1 and mTOR (P<0.05 vs. Old AL). Our findings demonstrate that CR is an effective strategy for attenuation of arterial aging. This article is protected by copyright. All rights reserved.
We hypothesized that demographic/anthropometric parameters can be used to estimate effective reflecting distance (EfRD), required to derive aortic pulse wave velocity (APWV), a prognostic marker of cardiovascular risk, from peripheral waveforms and that such estimates can discriminate differences in APWV and EfRD with aging and habitual endurance exercise in healthy adults. Ascending aortic pressure waveforms were derived from peripheral waveforms (brachial artery pressure, n=25; and finger volume pulse, n=15) via a transfer function and then used to determine the time delay between forward- and backward-traveling waves (Δtf-b). True EfRDs were computed as directly measured carotid-femoral pulse wave velocity (CFPWV) x 1/2Δtf-b and then used in regression analysis to establish an equation for EfRD based on demographic/anthropometric data (EfRD=0.173*age + 0.661*BMI + 34.548 cm; BMI: body mass index). We found good agreement between true and estimated APWV (Pearson's R(2)=0.43; intraclass correlation ICC=0.64; both P<0.05) and EfRD (R(2)=0.24; ICC=0.40; both P<0.05). In young sedentary (22±2 years, n=6), older sedentary (62±1 years, n=24), and older endurance-trained (61±2 years, n=14) subjects, EfRD (from demographic/anthropometric parameters), APWV, and 1/2Δtf-b (from brachial artery pressure waveforms) were 52.0±0.5, 61.8±0.4 and 60.6±0.5 cm; 6.4±0.3, 9.6±0.2, and 8.1±0.2 m/sec; and 82±3, 65±1 and 76±2 ms (all P<0.05), respectively. Our results demonstrate that APWV derived from peripheral waveforms using age and BMI to estimate EfRD correlates with CFPWV in healthy adults. This method can reliably detect the distal shift of the reflecting site with age and the increase in APWV with sedentary aging that is attenuated with habitual endurance exercise.
Arterial aging, characterized by stiffening of large elastic arteries and the development of arterial endothelial dysfunction, increases cardiovascular disease (CVD) risk. We tested the hypothesis that spermidine, a nutrient associated with the anti-aging process autophagy, would improve arterial aging. Aortic pulse wave velocity (aPWV), a measure of arterial stiffness, was ∼20% greater in old (O, 28 months) compared with young C57BL6 mice (Y, 4 months, P<0.05). Arterial endothelium-dependent dilation (EDD), a measure of endothelial function, was ∼25% lower in O (P<0.05 vs. Y) due to reduced nitric oxide (NO) bioavailability. These impairments were associated with greater arterial oxidative stress (nitrotyrosine), superoxide production, and protein cross-linking (advanced glycation end-products, AGEs) in O (all P<0.05). Spermidine supplementation normalized aPWV, restored NO-mediated EDD and reduced nitrotyrosine, superoxide, AGEs and collagen in O. These effects of spermidine were associated with enhanced arterial expression of autophagy markers, and in vitro experiments demonstrated that vascular protection by spermidine was autophagy-dependent. Our results indicate that spermidine exerts a potent anti-aging influence on arteries by increasing NO bioavailability, reducing oxidative stress, modifying structural factors and enhancing autophagy. Spermidine may be a promising nutraceutical treatment for arterial aging and prevention of age-associated CVD.
We tested the hypothesis that curcumin supplementation would reverse arterial dysfunction and vascular oxidative stress with aging. Young (Y, 4-6 mo) and old (O, 26-28 mo) male C57BL6/N mice were given normal or curcumin supplemented (0.2%) chow for 4weeks (n=5-10/group/measure). Large elastic artery stiffness, assessed by aortic pulse wave velocity (aPWV), was greater in O (448±15 vs. 349±15cm/s) and associated with greater collagen I and advanced glycation end-products and less elastin (all P<0.05). In O, curcumin restored aPWV (386±15cm/s), collagen I and AGEs to levels not different vs. Y. Ex vivo carotid artery acetylcholine (ACh)-induced endothelial-dependent dilation (EDD, 79±3 vs. 94±2%), nitric oxide (NO) bioavailability and protein expression of endothelial NO synthase (eNOS) were lower in O (all P<0.05). In O, curcumin restored NO-mediated EDD (92±2%) to levels of Y. Acute ex vivo administration of the superoxide dismutase (SOD) mimetic TEMPOL normalized EDD in O control mice (93±3%), but had no effect in Y control or O curcumin treated animals. O had greater arterial nitrotyrosine abundance, superoxide production and NADPH oxidase p67 subunit expression, and lower manganese SOD (all P<0.05), all of which were reversed with curcumin. Curcumin had no effects on Y. Curcumin supplementation ameliorates age-associated large elastic artery stiffening, NO-mediated vascular endothelial dysfunction, oxidative stress and increases in collagen and AGEs in mice. Curcumin may be a novel therapy for treating arterial aging in humans.
Vascular endothelial dysfunction develops with aging, as indicated by impaired endothelium-dependent dilation, and is related to increased cardiovascular disease risk. We hypothesized that short-term treatment with fenofibrate, a lipid-lowering agent with potential pleiotropic effects, would improve endothelium-dependent dilation in middle-aged and older normolipidemic adults by reducing oxidative stress. Brachial artery flow-mediated dilation, a measure of endothelium-dependent dilation, was assessed in 22 healthy adults aged 50 to 77 years before and after 7 days of fenofibrate (145 mg/d; n=12) or placebo (n=10). Brachial flow-mediated dilation was unchanged with placebo, but improved after 2 and 7 days of fenofibrate (5.1±0.7 versus 2 days: 6.0±0.7 and 7 days: 6.4±0.6%Δ; both P<0.005). The improvements in flow-mediated dilation after 7 days remained significant (P<0.05) after accounting for modest changes in plasma total and low-density lipoprotein cholesterol. Endothelium-independent dilation was not affected by fenofibrate or placebo (P>0.05). Intravenous infusion of the antioxidant vitamin C improved brachial flow-mediated dilation at baseline in both groups and during placebo treatment (P<0.05), but not after 2 and 7 days of fenofibrate (P>0.05). Fenofibrate treatment also reduced plasma-oxidized low-density lipoprotein, a systemic marker of oxidative stress, compared with placebo (P<0.05). In vascular endothelial cells sampled from peripheral veins of the subjects, endothelial nitric oxide synthase protein expression was unchanged with placebo and after 2 days of fenofibrate, but was increased after 7 days of fenofibrate (0.54±0.03 versus 2 days: 0.52±0.04 and 7 days: 0.76±0.11 intensity/human umbilical vein endothelial cell control; P<0.05, 7 days). Short-term treatment with fenofibrate improves vascular endothelial function in healthy normolipidemic middle-aged and older adults by reducing oxidative stress and induces an increase in endothelial nitric oxide synthase.
OBJECTIVES: This study sought to determine the efficacy of dietary sodium restriction (DSR) for improving vascular endothelial dysfunction in middle-aged/older adults with moderately elevated systolic blood pressure (SBP; 130-159 mm Hg) and the associated physiological mechanisms. BACKGROUND: Vascular endothelial dysfunction develops with advancing age and elevated SBP, contributing to increased cardiovascular risk. DSR lowers BP, but its effect on vascular endothelial function and mechanisms involved are unknown. METHODS: Seventeen subjects (11 men and 6 women; mean age, 62 ± 7 years) completed a, randomized crossover study of 4 weeks of both low (DSR) and normal sodium intake. Vascular endothelial function (endothelium-dependent dilation; EDD), nitric oxide (NO)/tetrahydrobiopterin (BH(4)) bioavailability, and oxidative stress-associated mechanisms were assessed following each condition. RESULTS: Urinary sodium excretion was reduced by ∼50% (to 70 ± 30 mmol/day), and conduit (brachial artery flow-mediated dilation [FMD(BA)]) and resistance (forearm blood flow responses to acetylcholine [FBF(ACh)]) artery EDD were 68% and 42% (peak FBF(ACh)) higher following DSR (p < 0.005). Low sodium markedly enhanced NO-mediated EDD (greater ΔFBF(ACh) with endothelial NO synthase inhibition) without changing endothelial NO synthase expression/activation (Ser 1177 phosphorylation), restored BH(4) bioactivity (less ΔFMD(BA) with acute BH(4)), abolished tonic superoxide suppression of EDD (less ΔFMD(BA) and ΔFBF(ACh) with ascorbic acid infusion), and increased circulating superoxide dismutase activity (all p < 0.05). These effects were independent of ΔSBP. Other subject characteristics/dietary factors and endothelium-independent dilation were unchanged. CONCLUSIONS: DSR largely reversed both macro- and microvascular endothelial dysfunction by enhancing NO and BH(4) bioavailability and reducing oxidative stress. Our findings support the emerging concept that DSR induces "vascular protection" beyond that attributable to its BP-lowering effects.
We tested the hypothesis that age-associated vascular endothelial dysfunction is exacerbated by impaired fasting plasma glucose (IFG) and that regular aerobic exercise prevents this effect. Data were analyzed from a cohort of 131 nonsmoking men and women without overt clinical disease. Compared with young adult controls (age=24±1years, mean±SE, n=29), brachial artery flow-mediated dilation (FMD), a measure of conduit artery endothelium-dependent dilation, was 33% lower (7.93±0.33 vs. 5.27±0.37%∆, P<0.05) in middle-aged/older adults with normal fasting plasma glucose (≤99 mg/dl, 62±1 years, n=35). In middle-aged/older adults with IFG (100-125 mg/dl, 64±1 years, n=28), FMD was 30% lower (3.37±0.35%∆) than in their peers with normal fasting plasma glucose and 58% lower than young controls (P<0.05). Brachial artery FMD was greater (6.38±0.35%∆) in middle-aged/older adults with normal fasting plasma glucose who regularly performed aerobic exercise (<45 min/day for ≥5 days/week, 62±1 years, n=23) compared with their non-exercising peers and only slightly less than young controls (P<0.05). Most importantly, FMD was completely preserved in middle-aged/older adults with IFG who regularly performed aerobic exercise (6.99±0.69%∆, 65±1 years, n=16). In the pooled sample, fasting plasma glucose was inversely related to FMD (r=-0.42, p<0.01) and was the strongest independent predictor of FMD (R2=0.32). Group differences in FMD were not affected by other subject characteristics or brachial artery properties, including brachial artery dilation to sublingual nitroglycerin (i.e., endothelium-independent dilation). IFG significantly exacerbates age-associated vascular endothelial dysfunction and this adverse effect is completely prevented in middle-aged/older adults who regularly perform aerobic exercise.
Vascular smooth muscle responsiveness to nitric oxide, as assessed by nitroglycerin-induced dilation (NID), is impaired in clinical cardiovascular disease, but its relation to adiposity is unknown. We determined the relation of NID to total and abdominal adiposity in healthy adults varying widely in adiposity. In 224 men and women [age, 18-79 years; body mass index (BMI), 16.4-42.2 kg/m(2)], we measured NID (brachial artery dilation to 0.4 mg sublingual nitroglycerin), total body adiposity [BMI and percent body fat (percent BF via dual-energy X-ray absorptiometry)], and indexes of abdominal adiposity [waist circumference (WC) and waist-to-hip ratio (WHR)]. In a subgroup (n = 74), we also measured total abdominal fat (TAF), abdominal visceral fat (AVF), and subcutaneous fat (ASF) using computed tomography. Based on multiple linear regression, NID was negatively related to BMI [part correlation coefficient (r(part)) = -0.19, P = 0.004] and abdominal adiposity (WC, r(part) = -0.22; WHR, r(part) = -0.19; TAF, r(part) = -0.36; AVF, r(part) = -0.36; and ASF, r(part) = -0.30; all P ≤ 0.009) independent of sex, but only tended to be related to total percent BF (r(part) = -0.12, P = 0.07). In a subgroup of subjects with the highest compared with the lowest amount of AVF, NID was 35% lower (P = 0.003). Accounting for systolic blood pressure, HDL cholesterol, glucose, insulin resistance, adiponectin, and brachial artery diameter reduced or abolished some of the relations between NID and adiposity. In conclusion, NID is or tends to be negatively associated with measures of total adiposity (BMI and percent BF, respectively) but is consistently and more strongly negatively associated with abdominal adiposity. Adiposity may influence NID in part via other cardiovascular risk factors.
Hysterectomy, with or without oophorectomy, is associated with increased cardiovascular disease (CVD) risk due, in part, to an adverse CVD risk factor profile. Large artery stiffening, a biomarker of vascular aging, increases the risk for CVD. We determined whether hysterectomy with or without bilateral oophorectomy (BLO) is associated with arterial stiffening in healthy postmenopausal women. We conducted a cross-sectional study including estrogen-deficient postmenopausal women who had a hysterectomy with ovarian preservation (n = 24; mean ± SE age, 59 ± 1 y) or with BLO (n = 21; 58 ± 2 y) and had no hysterectomy/no BLO (n = 58; 58 ± 1 y). Arterial stiffness (arterial compliance and β stiffness index) was measured by ultrasonography of the carotid artery. Carotid artery compliance was lower in women with hysterectomy alone and in women with hysterectomy with BLO compared with women with no hysterectomy (0.66 ± 0.03 and 0.71 ± 0.06 vs 0.89 ± 0.03 mm/mm Hg × 10, respectively, both P < 0.05). There were no differences in traditional CVD risk factors (ie, adiposity, blood pressure and fasted lipids and lipoproteins, glucose, and insulin) between the groups. After adjustment for age, menopause duration, previous menopausal hormone therapy duration, parity, waist-to-hip ratio, systolic blood pressure, and sex hormone-binding globulin, hysterectomy status remained a significant predictor of arterial compliance. These results indicate that hysterectomy status (with or without BLO) is associated with greater arterial stiffening in estrogen-deficient postmenopausal women. The greater arterial stiffening with hysterectomy was not related to an adverse CVD risk profile. Large artery stiffening may be an important mechanism by which hysterectomy increases the risk of CVD in postmenopausal women.
Background We performed a pilot study to test the hypothesis that acute oral ingestion of tetrahydrobiopterin (BH(4)), a key cofactor modulating vascular nitric oxide (NO) synthase activity, improves large elastic artery stiffness with aging in men.Methods Healthy older (63 ± 2 years; n = 8) and young (age 25 ± 1 years; n = 6) men were studied 3 h after ingestion of BH(4) (10 mg·kg(-1) body weight) or placebo on separate days in a randomized, placebo-controlled, double-blind study.ResultsBaseline carotid artery compliance was 37% lower (0.17 ± 0.02 vs. 0.22 ± 0.02 mm/mm Hg·10(-1)) and β-stiffness was 42% higher (7.3 ± 1.1 vs. 4.2 ± 0.5 AU) in the older men (both P < 0.05). BH(4) ingestion markedly increased circulating BH(4) concentrations in both groups (17-19-fold, P < 0.05), but increased compliance (+39% to 0.23 ± 0.02 mm/mm Hg(.)10(-1), P < 0.01) and decreased β-stiffness index (-27% to 5.3 ± 0.7 AU, P < 0.01) only in the older men. BH(4) also reduced carotid systolic blood pressure (SBP) in the older men (P < 0.05).Conclusions These preliminary results support the possibility that limited BH(4) bioavailability contributes to impaired carotid artery compliance in healthy older men. Further studies are needed to determine if increasing BH(4) bioavailability though oral BH(4) supplementation may have therapeutic efficacy for improving large elastic artery compliance and reducing central SBP with aging.American Journal of Hypertension 2012; doi:10.1038/ajh.2012.70.
We tested the hypothesis that sodium nitrite treatment reverses large elastic artery stiffening in old mice via reductions in collagen I, increases in elastin and/or decreases in advanced glycation end products (AGEs) mediated by reduced oxidative stress. Aortic pulse wave velocity (aPWV), a measure of large elastic artery stiffness, was greater in old (26-28months) compared with young (4-6months) control animals (520±9 vs. 405±6cm/s, p<0.05), and this was reversed by 3weeks of sodium nitrite treatment (50mg/L) (435±17cm/s). Age-related increases (p<0.05) in aortic superoxide production were associated with greater total and adventitial nitrotyrosine staining, all of which were reversed by nitrite treatment. Total and adventitial transforming growth factor β and collagen I were increased, and total and medial elastin were reduced with aging (p<0.05), but were unaffected by sodium nitrite. Aorta from old mice had increased total, adventitial and medial AGEs (p<0.05 vs. young), which were normalized by sodium nitrite treatment. In aortic segments from young mice in vitro, pyrogallol (10μM), a superoxide generator, induced an "aging-like" increase in AGEs, and direct treatment with AGEs induced vascular stiffening; these effects were prevented by incubation with sodium nitrite. De-stiffening of aged large elastic arteries by short-term sodium nitrite therapy is mediated in part by normalization of AGEs secondary to amelioration of oxidative stress.
Ageing causes arterial endothelial dysfunction that increases the risk of cardiovascular diseases (CVD), but the underlying mechanisms are incompletely understood. The aim of the present study was to determine the role of autophagy, the cellular process of recycling damaged biomolecules, in endothelial dysfunction with ageing. In older humans, expression of autophagy markers in arterial endothelial cells was impaired by ∼50% (P <0.05) and was associated with an ∼30% (P <0.05) reduction in arterial endothelium-dependent dilatation (EDD). Similarly, in C57BL/6 control mice ageing was associated with an ∼40% decrease (P <0.05) in arterial markers of autophagy and an ∼25% reduction (P <0.05) in EDD. In both humans and mice, impaired EDD was mediated by reduced nitric oxide (NO) bioavailability and was associated with increased oxidative stress and inflammation (P <0.05). In old mice, treatment with the autophagy-enhancing agent trehalose restored expression of autophagy markers, rescued NO-mediated EDD by reducing oxidative stress, and normalized inflammatory cytokine expression. In cultured endothelial cells, inhibition of autophagy increased oxidative stress and reduced NO production, whereas trehalose enhanced NO production via an autophagy-dependent mechanism. These results provide the first evidence that autophagy is impaired with ageing in vascular tissues. Our findings also suggest that autophagy preserves arterial endothelial function by reducing oxidative stress and inflammation and increasing NO bioavailability. Autophagy-enhancing strategies may therefore have therapeutic efficacy for ameliorating age-associated arterial dysfunction and preventing CVD.
Exercise restores endothelium-dependent dilation (EDD) in old mice by reducing oxidative stress and increasing nitric oxide (NO) bioavailability. Adenosine monophosphate protein kinase (AMPK) activation mimics some effects of exercise. Old (28-30 months) B6D2F1 mice had reduced arterial AMPK expression and superoxide-mediated suppression of EDD vs. young (3-6 months) controls. Pharmacological activation of AMPK by aminoimidazole carboxamide ribonucleotide (AICAR) for 2 weeks increased arterial AMPK and reversed this superoxide-induced impairment of EDD. The improvement in EDD was independent of NO or prostaglandin signaling, suggesting enhanced endothelium-dependent hyperpolarizing factor-related dilation. AMPK activation may represent a novel therapy for treating age-associated vascular dysfunction.
Dietary sodium restriction (DSR) improves carotid artery compliance (CC) in middle-aged and older adults (MA/O) with moderately elevated systolic blood pressure (SBP), but the mechanisms of action are unknown. Reduced tetrahydrobiopterin (BH4) bioactivity contributes to age-associated vascular dysfunction. We hypothesized that increased BH4 bioavailability may contribute to improvements in CC with DSR. SBP was reduced following 4 weeks of a low sodium (LS; 56±11 mmol/day; 125±2 mmHg) vs. normal sodium (NS; 160±7 mmol/day; 141±4 mmHg) diet (p<0.001; randomized, cross-over design; 5M/4F; 61±3 yrs). Baseline CC was 43% greater during the LS vs. NS condition (0.14±0.02 vs. 0.097±0.02 mm/mmHg, p=0.05). Acute oral BH4 administration (10 mg/kg) improved CC vs. placebo during the NS condition (0.13±0.02 mm/mmHg, p<0.05) to levels not significantly different than the LS placebo state, but had no effect on CC during the LS condition (0.14±0.02 mm/mmHg). BH4 had no significant influence on SBP in either condition (LS, 127±3 mmHg, p=0.30; NS, 138±3 mmHg; p=0.13). Results were similar when presented as the β-stiffness index, a more BP-independent expression of carotid artery distensibility. These findings are consistent with the hypothesis that DSR improves CC in MA/O with moderately elevated SBP in part by enhancing BH4 bioavailability.
A senescent phenotype in endothelial cells is associated with increased apoptosis, reduced endothelial nitric oxide synthase (eNOS) and inflammation, which are implicated in arterial dysfunction and disease in humans. We tested the hypothesis that changes in microRNAs are associated with a senescent phenotype in human aortic endothelial cells (HAEC). Compared with early-passage HAEC, late-passage HAEC had a reduced proliferation rate and increased staining for senescence-associated beta-galactosidase and the tumor suppressor p16(INK4a). Late-passage senescent HAEC had reduced expression of proliferation-stimulating/apoptosis-suppressing miR-21, miR-214 and miR-92 and increased expression of tumor suppressors and apoptotic markers. eNOS-suppressing miR-221 and miR-222 were increased and eNOS protein and eNOS activation (phosphorylation at serine1177) were lower in senescent HAEC. Caveolin-1 inhibiting miR-133a was reduced and caveolin-1, a negative regulator of eNOS activity, was elevated in senescent HAEC. Inflammation-repressing miR-126 was reduced and inflammation-stimulating miR-125b was increased, whereas inflammatory proteins were greater in senescent HAEC. Development of a senescent arterial endothelial cell phenotype featuring reduced cell proliferation, enhanced apoptosis and inflammation and reduced eNOS is associated with changes in miRNAs linked to the regulation of these processes. Our results support the hypothesis that miRNAs could play a critical role in arterial endothelial cell senescence.
The demographics of ageing are changing dramatically such that there will be many more older adults in the near future. This setting is projected to produce a new 'boomer-driven' epidemic of physiological dysfunction, disability and risk of chronic degenerative disorders, including cardiovascular diseases. Standing out against this dreary biomedical forecast are Masters athletes, a group of middle-aged and older adults who engage in regular vigorous physical training and competitive sport. Compared with their sedentary/less active (untrained) peers, Masters athletes who perform endurance training-based activities demonstrate a more favourable arterial function-structure phenotype, including lower large elastic artery stiffness, enhanced vascular endothelial function and less arterial wall hypertrophy. As such, they may represent an exemplary model of healthy or 'successful' vascular ageing. In contrast, Masters athletes engaged primarily/exclusively in intensive resistance training exhibit less favourable arterial function-structure than their endurance-trained peers and, in some instances, untrained adults. These different arterial properties are probably explained in large part by the different intravascular mechanical forces generated during endurance versus resistance exercise-related training activities. The more favourable arterial function-structure profile of Masters endurance athletes may contribute to their low risk of clinical cardiovascular diseases.
Some experimental evidence suggests that uric acid impairs endothelial function. It is controversial if high uric acid levels and impaired endothelial function are related in healthy adults. In addition, the effect of uric acid on endothelial cells (ECs) of humans is unexplored. Data of 107 healthy adult volunteers were analyzed. The association between serum uric acid and endothelial-dependant dilation (EDD) and endothelial-independent dilation (EID) was evaluated by linear regression models. We also examined the relations between uric acid and systemic and cellular markers of inflammation and oxidative stress in all or subsets of participants. Uric acid levels and EDD were not related in unadjusted or adjusted models. There was a significant negative correlation between uric acid and EID in the pooled sample (r = -0.34, P = 0.005). This correlation remained significant after adjusting for demographics (P = 0.04) and was attenuated after adjusting for other cardiac risk factors (P = 0.12). Higher serum uric acid levels were found to correlate significantly with C-reactive protein (CRP) (r = 0.31, P = 0.002). Serum uric acid levels were not associated with brachial artery EC nuclear factor-κB (NF-κB) p65 or NADPH oxidase p47(phox) expression or with nitrotyrosine staining, but were inversely associated with EC manganese superoxide dismutase (MnSOD) expression (r = -0.5, P = 0.01, n = 25). Elevated serum uric acid is not associated with endothelial dysfunction among healthy adults, but is inversely related to EID and EC MnSOD, and positively related to systemic inflammation. These findings may have implications for cardiovascular risk in healthy adults.
Thickening of the intimal layer of arteries characterized by expression of smooth muscle α-actin (SMαA), collagen deposition, and inflammation is an important pathophysiological change with aging assumed to be mediated by smooth muscle cells migrating from the medial layer. We tested the novel hypothesis that these characteristics could also reflect an endothelial-mesenchymal (smooth muscle-like) transition (EnMT). Late ('old') compared with early ('young') passage (45.0 ± 1.2 vs. 27.1 ± 0.5 population doublings) human aortic endothelial cells demonstrated greater smooth muscle (spindle) morphological changes, expression of SMαA and collagen I, nuclear factor-κB activation, and transforming growth factor-β (TGF-β) (all p < 0.05). Based on increases in SMαA, stimulation with the proinflammatory cytokine tumor necrosis factor-α, but not with TGF-β, induced EnMT in early passage cells similar to that observed in late passage cells. Here, we present the first evidence for EnMT induced in a model of endothelial cell aging and provide support for proinflammatory signaling in mediating this phenotypic change.

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Affiliations

University of Colorado Boulder
Department
  • Department of Integrative Physiology
University of Iowa
Department
  • Department of Health and Human Physiology
Emory University
Department
  • Division of Cardiothoracic Surgery
Maastricht University
Department
  • Department of Human Biology
University of Texas at Austin
Department
  • Department of Kinesiology and Health Education
The University of Arizona
Department
  • Department of Pharmacology