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

Background: Peripheral arterial disease (PAD) is a prevalent vascular disorder characterized by atherosclerotic occlusion of peripheral arteries, resulting in reduced blood flow to the lower extremities and poor walking ability. Older patients with PAD are also at a markedly increased risk of cardiovascular events, including myocardial infarction. Recent evidence indicates that inorganic nitrate supplementation, which is abundant in certain vegetables, augments nitric oxide (NO) bioavailability and may have beneficial effects on walking, blood pressure, and vascular function in patients with PAD. Objective: We sought to determine if short-term nitrate supplementation (via beetroot juice) improves peak treadmill time and coronary hyperemic responses to plantar flexion exercise relative to placebo (nitrate-depleted juice) in older patients with PAD. The primary endpoints were peak treadmill time and the peak coronary hyperemic response to plantar flexion exercise. Methods: Eleven PAD patients (52-80 yr.; 9 men/2 women; Fontaine stage II) were randomized (double-blind) to either nitrate-rich (Beet-IT, 0.3 g inorganic nitrate twice/day; BRnitrate) or nitrate-depleted (Beet-IT, 0.04 g inorganic nitrate twice/day, BRplacebo) beetroot juice for 4 to 6 days, followed by a washout of 7 to 14 days before crossing over to the other treatment. Patients completed graded plantar flexion exercise with their most symptomatic leg to fatigue, followed by isometric handgrip until volitional fatigue at 40% of maximum on day 4 of supplementation, and a treadmill test to peak exertion 1-2 days later while continuing supplementation. Hemodynamics and exercise tolerance, and coronary blood flow velocity (CBV) responses were measured. Results: Although peak walking time and claudication onset time during treadmill exercise did not differ significantly between BRplacebo and BRnitrate, the diastolic blood pressure response at the peak treadmill walking stage was significantly lower in the BRnitrate condition. Increases in CBV from baseline to peak plantar flexion exercise after BRplacebo and BRnitrate showed a trend for a greater increase in CBV at the peak workload of plantar flexion with BRnitrate (p = 0.06; Cohen's d = 0.56). Conclusion: Overall, these preliminary findings suggest that inorganic nitrate supplementation in PAD patients is safe, well-tolerated, and may improve the coronary hyperemic and blood pressure responses when their calf muscles are most predisposed to ischemia.Clinical trial registration:https://clinicaltrials.gov/, identifier NCT02553733.

Effects of acute hyperoxia on autonomic function and coronary tone in patients with peripheral artery disease.

Numerous studies have shown that oxidative stress plays an important role in peripheral artery disease (PAD). Prior reports suggested autonomic dysfunction in PAD. We hypothesized that responses of the autonomic nervous system and coronary tone would be impaired in patients with PAD during exposure to acute hyperoxia, an oxidative stressor. In 20 patients with PAD and 16 healthy, sex- and age-matched controls, beat-by-beat heart rate (HR, from ECG) and blood pressure (BP, with Finometer) were recorded for 10 min during room air breathing and 5 min of hyperoxia. Cardiovagal baroreflex sensitivity and HR variability (HRV) were evaluated as measures of autonomic function. Transthoracic coronary echocardiography was used to assess peak coronary blood flow velocity (CBV) in the left anterior descending coronary artery. Cardiovagal baroreflex sensitivity at rest was lower in PAD than in healthy controls. Hyperoxia raised BP solely in the patients with PAD, with no change observed in healthy controls. Hyperoxia induced an increase in cardiac parasympathetic activity assessed by the high-frequency component of HRV in healthy controls but not in PAD. Indices of parasympathetic activity were lower in PAD than in healthy controls throughout the trial as well as during hyperoxia. Hyperoxia induced coronary vasoconstriction in both groups, while the coronary perfusion time fraction was lower in PAD than in healthy controls. These results suggest that the response in parasympathetic activity to hyperoxia (i.e., oxidative stress) is blunted and the coronary perfusion time is shorter in patients with PAD.NEW & NOTEWORTHY Patients with peripheral artery disease (PAD) showed consistently lower parasympathetic activity and blunted cardiovagal baroreflex sensitivity compared with healthy individuals. Notably, hyperoxia, which normally boosts parasympathetic activity in healthy individuals, failed to induce this response in patients with PAD. These data suggest altered autonomic responses during hyperoxia in PAD.

Aortic blood pressure and pulse wave indices responses to exercise in peripheral artery disease.

Peripheral artery disease (PAD) refers to obstructed blood flow in peripheral arteries typically due to atherosclerotic plaques. How PAD alters aortic blood pressure and pressure wave propagation during exercise is unclear. Thus, this study examined central blood pressure responses to plantar flexion exercise by investigating aortic pulse wave properties in PAD. Thirteen subjects with PAD and 13 healthy [age-, sex-, body mass index (BMI) matched] subjects performed rhythmic plantar flexion for 14 min or until fatigue (20 contractions/min; started at 2 kg with 1 kg/min increment up to 12 kg). Brachial (oscillometric cuff) and radial (SphygmoCor) blood pressure and derived-aortic waveforms were analyzed during supine rest and plantar flexion exercise. At rest, baseline augmentation index (P = 0.0263) and cardiac wasted energy (P = 0.0321) were greater in PAD due to earlier arrival of the reflected wave (P = 0.0289). During exercise, aortic blood pressure (aMAP) and aortic pulse pressure showed significant interaction effects (P = 0.0041 and P = 0.0109, respectively). In particular, PAD had a greater aMAP increase at peak exercise (P = 0.0147). Moreover, the tension time index was greater during exercise in PAD (P = 0.0173), especially at peak exercise (P = 0.0173), whereas the diastolic time index (P = 0.0685) was not different between the two groups. Hence, during exercise, the subendocardial viability ratio was lower in PAD (P = 0.0164), especially at peak exercise (P = 0.0164). The results suggest that in PAD, the aortic blood pressure responses and myocardial oxygen demand during exercise are increased compared with healthy controls.

Calorie restriction and pravastatin administration during pregnancy in obese rhesus macaques modulates maternal and infant metabolism and infant brain and behavioral development.

Background: Maternal obesity has been associated with a higher risk of pregnancy-related complications in mothers and offspring; however, effective interventions have not yet been developed. We tested two interventions, calorie restriction and pravastatin administration, during pregnancy in a rhesus macaque model with the hypothesis that these interventions would normalize metabolic dysregulation in pregnant mothers leading to an improvement in infant metabolic and cognitive/social development. Methods: A total of 19 obese mothers were assigned to either one of the two intervention groups (n = 5 for calorie restriction; n = 7 for pravastatin) or an obese control group (n = 7) with no intervention, and maternal gestational samples and postnatal infant samples were compared with lean control mothers (n = 6) using metabolomics methods. Results: Gestational calorie restriction normalized one-carbon metabolism dysregulation in obese mothers, but altered energy metabolism in her offspring. Although administration of pravastatin during pregnancy tended to normalize blood cholesterol in the mothers, it potentially impacted the gut microbiome and kidney function of their offspring. In the offspring, both calorie restriction and pravastatin administration during pregnancy tended to normalize the activity of AMPK in the brain at 6 months, and while results of the Visual Paired-Comparison test, which measures infant recognition memory, was not significantly impacted by either of the interventions, gestational pravastatin administration, but not calorie restriction, tended to normalize anxiety assessed by the Human Intruder test. Conclusions: Although the two interventions tested in a non-human primate model led to some improvements in metabolism and/or infant brain development, negative impacts were also found in both mothers and infants. Our study emphasizes the importance of assessing gestational interventions for maternal obesity on both maternal and offspring long-term outcomes.

Neonatal immune signatures differ by sex regardless of neurodevelopmental disorder status: Macrophage migration inhibitory factor (MIF) alone reveals a sex by diagnosis interaction effect.

Immune dysregulation, including aberrant peripheral cytokine/chemokine levels, is implicated in neurodevelopmental disorders (NDD) such as autism spectrum disorder (ASD). While the diagnosis of ASD is more common in males compared to females, sex effects in immune dysregulation related to neurodevelopment remain understudied. The aim of this exploratory study was to determine whether there are sex-specific effects in neonatal immune dysregulation with respect to an ASD or delayed development (DD) diagnosis. We utilized the data from the Early Markers for Autism study, a population based case-control study of prenatal and neonatal biomarkers of ASD. The immune profile of newborns later diagnosed with ASD (n = 482, 91 females), DD (n = 140, 61 females) and sex-matched general population controls (GP; n = 378, 67 females) were analyzed using neonatal bloodspots (NBS) via 42-plex multiplex assay. Multiple linear regression analysis was performed to identify whether sex was associated with differences in cytokine/chemokine levels of children with ASD, DD, and GP. A sex by diagnosis interaction effect was observed only for the chemokine macrophage migration inhibitory factor (MIF), with males displaying higher levels of NBS MIF than females in the GP control group (p = 0.02), but not in ASD (p = 0.52) or DD (p = 0.29) groups. We found that regardless of child diagnosis, newborn bloodspot eluates from females had a significantly higher concentration than males with the same diagnosis of the chemokines granulocyte chemotactic protein 2 (GCP-2; p < 0.0001), macrophage inflammatory protein 2-alpha (GROß; p = 0.002), interferon-inducible t-cell alpha chemoattractant (I-TAC; p < 0.0001), stromal cell-derived factor 1 alpha and beta (SDF-1α-ß; p = 0.03), innate inflammatory chemokines interferon-gamma induced protein 10 (IP-10; p = 0.02), macrophage inflammatory protein 1-alpha (MIP-1α; p = 0.02), and Th1-related pro-inflammatory cytokine interleukin-12 active heterodimer (IL-12p70; p = 0.002). In contrast, males had a higher concentration than females of secondary lymphoid-tissue chemokine (6CKINE; p = 0.02), monocyte chemotactic protein 1 (MCP-1; p = 0.005) and myeloid progenitor inhibitory factor 1 (MPIF-1; p = 0.03). Results were similar when analyses were restricted to NBS from DD and ASD further classified as ASD with intellectual disability (ID), ASD without ID, and DD (GCP-2, p = 0.007; I-TAC, p = 0.001; IP-10, p = 0.005; IL-12p70, p = 0.03 higher in females; MPIF-1, p = 0.03 higher in male). This study is the first to examine sex differences in neonatal cytokine/chemokine concentrations, and whether these differences are associated with neurodevelopmental outcomes. Results highlight the importance of considering sex as a critical factor in understanding the immune system as it relates to child development.

Maternal Immune Dysregulation and Autism-Understanding the Role of Cytokines, Chemokines and Autoantibodies.

Autism spectrum disorder (ASD) is acknowledged as a highly heterogeneous, behaviorally defined neurodevelopmental disorder with multiple etiologies. In addition to its high heritability, we have come to recognize a role for maternal immune system dysregulation as a prominent risk factor for the development of ASD in the child. Examples of these risk factors include altered cytokine/chemokine activity and the presence of autoantibodies in mothers that are reactive to proteins in the developing brain. In addition to large clinical studies, the development of pre-clinical models enables the ability to evaluate the cellular and molecular underpinnings of immune-related pathology. For example, the novel animal models of maternal autoantibody-related (MAR) ASD described herein will serve as a preclinical platform for the future testing of targeted therapeutics for one 'type' of ASD. Identification of the cellular targets will advance precision medicine efforts toward tailored therapeutics and prevention. This minireview highlights emerging evidence for the role of maternal immune dysregulation as a potential biomarker, as well as a pathologically relevant mechanism for the development of ASD in offspring. Further, we will discuss the current limitations of these models as well as potential avenues for future research.

Inorganic nitrate supplementation and blood flow restricted exercise tolerance in post-menopausal women.

Exercise tolerance appears to benefit most from dietary nitrate (NO3-) supplementation when muscle oxygen (O2) availability is low. Using a double-blind, randomized cross-over design, we tested the hypothesis that acute NO3- supplementation would improve blood flow restricted exercise duration in post-menopausal women, a population with reduced endogenous nitric oxide bioavailability. Thirteen women (57-76 yr) performed rhythmic isometric handgrip contractions (10% MVC, 30 per min) during progressive forearm blood flow restriction (upper arm cuff gradually inflated 20 mmHg each min) on three study visits, with 7-10 days between visits. Approximately one week following the first (familiarization) visit, participants consumed 140 ml of NO3- concentrated (9.7 mmol, 0.6 gm NO3-) or NO3-depleted beetroot juice (placebo) on separate days (≥7 days apart), with handgrip exercise beginning 100 min post-consumption. Handgrip force recordings were analyzed to determine if NO3- supplementation enhanced force development as blood flow restriction progressed. Nitrate supplementation increased plasma NO3- (16.2-fold) and NO2- (4.2-fold) and time to volitional fatigue (61.8 ± 56.5 s longer duration vs. placebo visit; p = 0.03). Nitrate supplementation increased the rate of force development as forearm muscle ischemia progressed (p = 0.023 between 50 and 75% of time to fatigue) with non-significant effects thereafter (p = 0.052). No effects of nitrate supplementation were observed for mean duration of contraction or relaxation rates (all p > 0.150). These results suggest that acute NO3- supplementation prolongs time-to-fatigue and speeds grip force development during progressive forearm muscle ischemia in postmenopausal women.

Neonatal chemokine markers predict subsequent diagnosis of autism spectrum disorder and delayed development.

Immune dysregulation has been found to be related to a diagnosis of autism spectrum disorder (ASD). However, investigations in very early childhood examining immunological abnormalities such as altered neonatal cytokine/chemokine profiles in association with an aberrant developmental trajectory, are sparse. We assessed neonatal blood spots from 398 children, including 171 with ASD, which were subdivided according to severity (121 severe, 50 mild/moderate) and cognitive/adaptive levels (144 low-functioning, 27 typical to high-functioning). The remainder were 69 children with developmental delay (DD), and 158 with typical development (TD), who served as controls in the Childhood Autism Risks from Genetics and the Environment (CHARGE) study. Exploratory analysis suggested that, in comparisons with TD and DD, CTACK (CCL27) and MPIF-1 (CCL23), respectively, were independently associated with ASD. Higher neonatal levels of CTACK were associated with decreased odds of ASD compared to TD (odds ratio [OR] = 0.40, 95% confidence interval [Cl] 0.21, 0.77), whereas higher levels of MPIF-1 were associated with increased odds of ASD (OR = 2.38, 95% Cl 1.42, 3.98) compared to DD but not to TD. MPIF-1 was positively associated with better scores in several developmental domains. Dysregulation of chemokine levels in early life can impede normal immune and neurobehavioral development, which can lead to diagnosis of ASD or DD. This study collectively suggests that certain peripheral chemokines at birth are associated with ASD progression during childhood and that children with ASD and DD have distinct neonatal chemokine profiles that can differentiate their diagnoses.

Renal medullary oxygenation decreases with lower body negative pressure in healthy young adults.

One in three Americans suffer from kidney diseases such as chronic kidney disease, and one of the etiologies is suggested to be long-term renal hypoxia. Interestingly, sympathetic nervous system activation evokes a renal vasoconstrictor effect that may limit oxygen delivery to the kidney. In this report, we sought to determine if sympathetic activation evoked by lower body negative pressure (LBNP) would decrease cortical and medullary oxygenation in humans. LBNP was activated in a graded fashion (LBNP; -10, -20, and -30 mmHg), as renal oxygenation was measured (T2*, blood oxygen level dependent, BOLD MRI; n = 8). At a separate time, renal blood flow velocity (RBV) to the kidney was measured (n = 13) as LBNP was instituted. LBNP significantly reduced RBV (P = 0.041) at -30 mmHg of LBNP (Δ-8.17 ± 3.75 cm/s). Moreover, both renal medullary and cortical T2* were reduced with the graded LBNP application (main effect for the level of LBNP P = 0.0008). During recovery, RBV rapidly returned to baseline, whereas medullary T2* remained depressed into the first minute of recovery. In conclusion, sympathetic activation reduces renal blood flow and leads to a significant decrease in oxygenation in the renal cortex and medulla.NEW & NOTEWORTHY In healthy young adults, increased sympathetic activation induced by lower body negative pressure, led to a decrease in renal cortical and medullary oxygenation measured by T2*, a noninvasive magnetic resonance derived index of deoxyhemoglobin levels. In this study, we observed a significant decrease in renal cortical and medullary oxygenation with LBNP as well as an increase in renal vasoconstriction. We speculate that sympathetic renal vasoconstriction led to a significant reduction in tissue oxygenation by limiting oxygen delivery to the renal medulla.

Myelin as a regulator of development of the microbiota-gut-brain axis.

Myelination in the peripheral and central nervous systems is critical in regulating motor, sensory, and cognitive functions. As myelination occurs rapidly during early life, neonatal gut dysbiosis during early colonization can potentially alter proper myelination by dysregulating immune responses and neuronal differentiation. Despite common usage of antibiotics (Abx) in children, the impact of neonatal Abx-induced dysbiosis on the development of microbiota, gut, brain (MGB) axis, including myelination and behavior, is unknown. We hypothesized that neonatal Abx-induced dysbiosis dysregulates host-microbe interactions, impairing myelination in the brain, and altering the MGB axis. Neonatal C57BL/6 mice were orally gavaged daily with an Abx cocktail (neomycin, vancomycin, ampicillin) or water (vehicle) from postnatal day 7 (P7) until weaning (P23) to induce gut dysbiosis. Behavior (cognition; anxiety-like behavior), microbiota sequencing, and qPCR (ileum, colon, hippocampus and pre-frontal cortex [PFC]) were performed in adult mice (6-8 weeks). Neonatal Abx administration led to intestinal dysbiosis in adulthood, impaired intestinal physiology, coupled with perturbations of bacterial metabolites and behavioral alterations (cognitive deficits and anxiolytic behavior). Expression of myelin-related genes (Mag, Mog, Mbp, Mobp, Plp) and transcription factors (Sox10, Myrf) important for oligodendrocytes were significantly increased in the PFC region of Abx-treated mice. Increased myelination was confirmed by immunofluorescence imaging and western blot analysis, demonstrating increased expression of MBP, SOX10 and MYRF in neonatally Abx-treated mice compared to sham controls in adulthood. Finally, administration of the short chain fatty acid butyrate following completion of the Abx treatment restored intestinal physiology, behavior, and myelination impairments, suggesting a critical role for the gut microbiota in mediating these effects. Taken together, we identified a long-lasting impact of neonatal Abx administration on the MGB axis, specifically on myelin regulation in the PFC region, potentially contributing to impaired cognitive function and bacterial metabolites are effective in reversing this altered phenotype.

Patients With Peripheral Arterial Disease With Exaggerated Pressor Response Have Greater Ambulatory Dysfunction Than Patients With Lower Pressor Response.

We determined whether patients with peripheral arterial disease (PAD) who have either an exaggerated or a negative pressor response during treadmill walking have shorter peak walking time (PWT) and claudication onset time (COT) than patients with a normal pressor response, independent of comorbid conditions. A total of 249 patients were categorized to 1 of 3 groups based on systolic blood pressure (SBP) responses at 2 minutes of treadmill walking (speed = 2 mph, grade = 0%): group 1 (negative pressor response, SBP < 0 mm Hg), group 2 (normal pressor response, SBP 18 mm Hg), and group 3 (exaggerated pressor response, SBP > 18 mm Hg). After adjusting for comorbid conditions, group 3 (exaggerated) had significantly reduced COT (P = .011) and PWT (P = .002) compared to group 2 (normal), while group 1 (negative) and group 2 (normal) were not different. Patients with symptomatic PAD with an increase in SBP > 18 mm Hg after 2 minutes of treadmill walking experience claudication earlier and thus have greater ambulatory dysfunction, compared to patients with PAD with a normal pressor response, whereas patients with PAD with negative pressor response had a similar walking performance. The implication is that the magnitude of pressor response to only 2 minutes of treadmill walking can partially explain the degree of ambulatory dysfunction in patients with PAD.

Systemic and regional hemodynamic response to activation of the exercise pressor reflex in patients with peripheral artery disease.

Patients with peripheral artery disease (PAD) have an accentuated exercise pressor reflex (EPR) during exercise of the affected limb. The underlying hemodynamic changes responsible for this, and its effect on blood flow to the exercising extremity, are unclear. We tested the hypothesis that the exaggerated EPR in PAD is mediated by an increase in total peripheral resistance (TPR), which augments redistribution of blood flow to the exercising limb. Twelve patients with PAD and 12 age- and sex-matched subjects without PAD performed dynamic plantar flexion (PF) using the most symptomatic leg at progressive workloads of 2-12 kg (increased by 1 kg/min until onset of fatigue). We measured heart rate, beat-by-beat blood pressure, femoral blood flow velocity (FBV), and muscle oxygen saturation (SmO2) continuously during the exercise. Femoral blood flow (FBF) was calculated from FBV and baseline femoral artery diameter. Stroke volume (SV), cardiac output (CO), and TPR were derived from the blood pressure tracings. Mean arterial blood pressure and TPR were significantly augmented in PAD compared with control during PF. FBF increased during exercise to an equal extent in both groups. However, SmO2 of the exercising limb remained significantly lower in PAD compared with control. We conclude that the exaggerated pressor response in PAD is mediated by an abnormal TPR response, which augments redistribution of blood flow to the exercising extremity, leading to an equal rise in FBF compared with controls. However, this increase in FBF is not sufficient to normalize the SmO2 response during exercise in patients with PAD.NEW & NOTEWORTHY In this study, peripheral artery disease (PAD) patients and healthy control subjects performed graded, dynamic plantar flexion exercise. Data from this study suggest that previously reported exaggerated exercise pressor reflex in patients with PAD is driven by greater vasoconstriction in nonexercising vascular territories which also results in a redistribution of blood flow to the exercising extremity. However, this rise in femoral blood flow does not fully correct the oxygen deficit due to changes in other mechanisms that require further investigation.

Hydrodealkenylative C(sp3)-C(sp2) bond fragmentation.

Chemical synthesis typically relies on reactions that generate complexity through elaboration of simple starting materials. Less common are deconstructive strategies toward complexity-particularly those involving carbon-carbon bond scission. Here, we introduce one such transformation: the hydrodealkenylative cleavage of C(sp3)-C(sp2) bonds, conducted below room temperature, using ozone, an iron salt, and a hydrogen atom donor. These reactions are performed in nonanhydrous solvents and open to the air; reach completion within 30 minutes; and deliver their products in high yields, even on decagram scales. We have used this broadly functionality tolerant transformation to produce desirable synthetic intermediates, many of which are optically active, from abundantly available terpenes and terpenoid-derived precursors. We have also applied it in the formal total syntheses of complex molecules.

Vascular Inflammation, Calf Muscle Oxygen Saturation, and Blood Glucose are Associated With Exercise Pressor Response in Symptomatic Peripheral Artery Disease.

We determined whether calf muscle oxygen saturation (StO2) and vascular biomarkers of inflammation and oxidative stress were associated with an exercise pressor response during treadmill walking in 179 patients with symptomatic peripheral artery disease (PAD). The exercise pressor response was measured as the change in blood pressure from rest to the end of the first 2-minute treadmill stage (2 mph, 0% grade). There was a wide range in the change in systolic blood pressure (-46 to 50 mm Hg) and in diastolic blood pressure (-23 to 38 mm Hg), with mean increases of 4.3 and 1.4 mm Hg, respectively. In multiple regression analyses, significant predictors of systolic pressure included glucose (P < .001) and insulin (P = .039). Significant predictors of diastolic pressure included cultured endothelial cell apoptosis (P = .019), the percentage drop in exercise calf muscle (StO2; P = .023), high-sensitivity C-reactive protein (P = .032), and glucose (P = .033). Higher levels in pro-inflammatory vascular biomarkers, impaired calf muscle StO2 during exercise, and elevated blood glucose were independently associated with greater exercise pressor response in patients with symptomatic PAD. The clinical implication is that exercise and nutritional interventions designed to improve inflammation, microcirculation, and glucose metabolism may also lower blood pressure during exercise in patients with symptomatic PAD.

Effects of acute dietary nitrate supplementation on aortic blood pressures and pulse wave characteristics in post-menopausal women.

PURPOSE: Consumption of nitrate-rich beetroot juice can lower blood pressure in peripheral as well as central arteries and may exert additional hemodynamic benefits (e.g. reduced aortic wave reflections). The specific influence of nitrate supplementation on arterial pressures and aortic wave properties in postmenopausal women, a group that experiences accelerated increases in these variables with age, is unknown. Accordingly, the primary aim of this study was to determine the effect of consuming nitrate-rich beetroot juice on resting brachial and aortic blood pressures (BP) and pulse wave characteristics in a group of healthy postmenopausal women, in comparison to a true (nitrate-free beetroot juice) placebo. METHODS: Brachial (oscillometric cuff) and radial (SphygmoCor) pressures and derived-aortic waveforms were measured during supine rest in thirteen healthy postmenopausal women (63 ±â€¯1 yr) before and 100 min after consumption of 140 ml of either nitrate-rich (9.7 mmol, 0.6 gm NO3-) or nitrate-depleted beetroot juice on randomized visits approximately 10 days apart (cross-over design). Ten young premenopausal women (22 ±â€¯1 yr) served as a reference (non-supplemented) cohort. RESULTS: Brachial and derived-aortic variables showed the expected age-associated differences in these women (all p < 0.05). In post-menopausal women, nitrate supplementation reduced (p < 0.05 vs. placebo visit) brachial systolic BP (BRnitrate -4.9 ±â€¯2.1 mmHg vs BRplacebo +1.1 ± 1.8 mmHg), brachial mean BP (BRnitrate -4.1 ±â€¯1.7 mmHg vs BRplacebo +0.9 ± 1.3 mmHg), aortic systolic BP (BRnitrate -6.3 ±â€¯2.0 mmHg vs BRplacebo +0.5 ± 1.7 mmHg) and aortic mean BP (BRnitrate -4.1 ±â€¯1.7 mmHg vs BRplacebo +0.9 ± 1.3 mmHg), and increased pulse pressure amplification (BRnitrate +4.6 ± 2.0% vs BRplacebo +0.7 ± 2.5%, p = 0.04), but did not alter aortic pulse wave velocity or any other derived-aortic variables (e.g., augmentation pressure or index). CONCLUSIONS: Dietary nitrate supplementation favorably modifies aortic systolic and mean blood pressure under resting conditions in healthy postmenopausal women. Acute supplementation of nitrate does not, however, appear to restore indices of aortic stiffness in this group. Future work should evaluate chronic, long-term effects of this non-pharmacological supplement.

Retrograde and oscillatory shear increase across the menopause transition.

Declines in endothelial function can take place rapidly across the menopause transition, placing women at heightened risk for atherosclerosis. Disturbed patterns of conduit artery shear, characterized by greater oscillatory and retrograde shear, are associated with endothelial dysfunction but have yet to be described across menopause. Healthy women, who were not on hormone therapy or contraceptives, were classified into early perimenopausal, late perimenopausal, and early postmenopausal stage. Resting antegrade, retrograde, and oscillatory shear were calculated from blood velocity and diameter measured in the brachial and common femoral artery using Doppler ultrasound. Serum was collected for measurements of estradiol, follicle-stimulating hormone (FSH), and luteinizing hormone. After adjusting for age, brachial artery oscillatory shear was significantly higher in early postmenopausal women (n = 15, 0.17 ± 0.08 a.u.) than both early (n = 12, 0.08 ± 0.05 a.u., P < 0.05) and late (n = 8, 0.08 ± 0.04 a.u) perimenopausal women, and retrograde shear was significantly greater in early postmenopausal versus early perimenopausal women (-19.47 ± 12.97 vs. -9.62 ± 6.11 sec-1 , both P < 0.05). Femoral artery oscillatory and retrograde shear were greater, respectively, in early postmenopausal women (n = 15, 0.19 ± 0.08 a.u.; -13.57 ± 5.82 sec-1 ) than early perimenopausal women (n = 14, 0.11 ± 0.08 a.u.; -8.13 ± 4.43 sec-1 , P < 0.05). Further, Pearson correlation analyses revealed significant associations between FSH and both retrograde and oscillatory shear, respectively, in the brachial (r = -0.40, P = 0.03; r = 0.43, P = 0.02) and common femoral artery (r = -0.45, P = 0.01; r = 0.56, P = 0.001). These results suggest menopause, and its associated changes in reproductive hormones, adversely influences conduit arterial shear rate patterns to greater oscillatory and retrograde shear rates.

Greater Exercise Pressor Response Is Associated With Impaired Claudication Outcomes in Symptomatic Peripheral Artery Disease.

We determined whether a greater exercise pressor response during a constant-load treadmill test was associated with lower peak walking time (PWT) and claudication onset time (COT) measured during a graded maximal treadmill test in 304 patients with symptomatic peripheral artery disease (PAD). The exercise pressor response was assessed by measuring heart rate and blood pressure (BP) at rest and during a constant-load treadmill test (speed = 2 mph, grade = 0%). After only 2 minutes of walking, mean heart rate increased by 26 beats/min from rest and mean systolic BP increased by 16 mm Hg. In adjusted analyses, increases in systolic BP (P = .021), heart rate (P = .002), mean arterial pressure (P = .034), and rate-pressure product (P < .001) from rest to 2 minutes of constant-load exercise were negatively associated with COT. Similarly, increases in heart rate (P = .012) and rate-pressure product (P = .018) from rest to 2 minutes of constant-load exercise were negatively associated with PWT. A greater exercise pressor response observed after only 2 minutes of walking at no incline was independently associated with impaired claudication outcomes in patients with symptomatic PAD. The implication is that the exercise pressor response is an important and easily obtained clinical measurement that partially explains differences in PWT and COT.

Peripheral revascularization attenuates the exercise pressor reflex and increases coronary exercise hyperemia in peripheral arterial disease.

Peripheral arterial disease (PAD) is associated with augmented blood pressure (BP) and impaired coronary blood flow responses to exercise, which may increase cardiovascular risk. We investigated the effects of leg revascularization on the BP and coronary blood flow responses to exercise in PAD. Seventeen PAD patients (11 men, 66 ± 2 yr) performed single-leg plantar flexion exercise 24 h before and 1 mo following leg revascularization. BP and heart rate (HR) were measured continuously, and rate pressure product (systolic BP × HR) was calculated as an index of myocardial oxygen demand. Coronary blood velocity was obtained by transthoracic Doppler echocardiography in 8/17 subjects. The mean BP response to plantar flexion exercise was attenuated by leg revascularization (pre-revascularization: 15 ± 4 vs. post-revascularization: 7 ± 3 mmHg, P = 0.025). The HR response to plantar flexion was also attenuated following leg revascularization (pre-revascularization: 9 ± 1 vs. post-revascularization: 6 ± 1 beats/min, P = 0.006). The change in coronary blood velocity with exercise was greater at the post-revascularization visit: 4 ± 1 vs. pre-revascularization: -1 ± 2 cm/s ( P = 0.038), even though the change in rate pressure product was not greater following revascularization in these subjects (pre-revascularization: 2,796 ± 871 vs. post-revascularization: 1,766 ± 378 mmHg·beats/min, P = 0.082). These data suggest that leg revascularization alters reflex control of BP, HR, and coronary blood flow in response to exercise in patients with PAD. NEW & NOTEWORTHY We found that peripheral revascularization procedures lowered exercise blood pressure and improved coronary blood flow in patients with peripheral arterial disease.

Blood pressure and leg deoxygenation are exaggerated during treadmill walking in patients with peripheral artery disease.

The purpose of this study was to investigate blood pressure (BP) and leg skeletal muscle oxygen saturation (Smo2) during treadmill walking in patients with peripheral artery disease (PAD) and healthy subjects. Eight PAD patients (66 ± 8 yr, 1 woman) and eight healthy subjects (65 ± 7 yr, 1 woman) walked on a treadmill at 2 mph (0.89 m/s). The incline increased by 2% every 2 min, from 0 to 15% or until maximal discomfort. BP was measured every 2 min with an auscultatory cuff. Heart rate (HR) was recorded continuously with an ECG. Smo2 in the gastrocnemius muscle was measured on each leg using near-infrared spectroscopy. The change in systolic BP from seated to peak walking time (PWT) was greater in PAD (healthy: 23 ± 9 vs. PAD: 44 ± 19 mmHg, P = 0.007). HR was greater in PAD patients compared with controls at PWT (P = 0.011). The reduction in Smo2 (PWT - seated) was greater in PAD (healthy: 15 ± 12 vs. PAD: 49 ± 5%, P < 0.001) in the most affected leg and in the least affected leg (healthy: 12 ± 11 vs. PAD: 32 ± 18%, P = 0.003). PAD patients have an exaggerated decline in leg Smo2 during walking compared with healthy subjects, which may elicit the exaggerated rise in BP and HR during walking in PAD.NEW & NOTEWORTHY This is the first study to simultaneously measure skeletal muscle oxygen saturation and blood pressure (BP) during treadmill exercise in patients with peripheral arterial disease. We found that BP and leg deoxygenation responses to slow-paced, graded treadmill walking are greater in patients with peripheral arterial disease compared with healthy subjects. These data may help explain the high cardiovascular risk in patients with peripheral arterial disease.

Brainstem neurons survive the identical ischemic stress that kills higher neurons: insight to the persistent vegetative state.

Global ischemia caused by heart attack, pulmonary failure, near-drowning or traumatic brain injury often damages the higher brain but not the brainstem, leading to a 'persistent vegetative state' where the patient is awake but not aware. Approximately 30,000 U.S. patients are held captive in this condition but not a single research study has addressed how the lower brain is preferentially protected in these people. In the higher brain, ischemia elicits a profound anoxic depolarization (AD) causing neuronal dysfunction and vasoconstriction within minutes. Might brainstem nuclei generate less damaging AD and so be more resilient? Here we compared resistance to acute injury induced from simulated ischemia by 'higher' hippocampal and striatal neurons versus brainstem neurons in live slices from rat and mouse. Light transmittance (LT) imaging in response to 10 minutes of oxygen/glucose deprivation (OGD) revealed immediate and acutely damaging AD propagating through gray matter of neocortex, hippocampus, striatum, thalamus and cerebellar cortex. In adjacent brainstem nuclei, OGD-evoked AD caused little tissue injury. Whole-cell patch recordings from hippocampal and striatal neurons under OGD revealed sudden membrane potential loss that did not recover. In contrast brainstem neurons from locus ceruleus and mesencephalic nucleus as well as from sensory and motor nuclei only slowly depolarized and then repolarized post-OGD. Two-photon microscopy confirmed non-recoverable swelling and dendritic beading of hippocampal neurons during OGD, while mesencephalic neurons in midbrain appeared uninjured. All of the above responses were mimicked by bath exposure to 100 µM ouabain which inhibits the Na+/K+ pump or to 1-10 nM palytoxin which converts the pump into an open cationic channel. Therefore during ischemia the Na+/K+ pump of higher neurons fails quickly and extensively compared to naturally resilient hypothalamic and brainstem neurons. The selective survival of lower brain regions that maintain vital functions will support the persistent vegetative state.