Acute effects of MitoQ on vascular endothelial function are influenced by cardiorespiratory fitness and baseline FMD in middle-aged and older adults.

A key mechanism promoting vascular endothelial dysfunction is mitochondrial-derived reactive oxygen species (mtROS). Aerobic exercise preserves endothelial function in preclinical models by lowering mtROS. However, the effects of mtROS on endothelial function in exercising and non-exercising adults is limited. In a double-blind, randomized, placebo-controlled crossover study design 23 (10 M/13 F, age 62.1 ± 11.5 years) middle-aged and older (MA/O, ≥45 years) adults were divided into two groups: exercisers (EX, n = 11) and non-exercisers (NEX, n = 12). All participants had endothelial function (brachial artery flow-mediated dilatation, FMDBA) measured before and ∼1 h after mitoquinone mesylate (MitoQ) (single dose, 80 mg) and placebo supplementation. A two-way repeated measures ANOVA was used to determine the effects of MitoQ and placebo on FMDBA. Pearson correlations assessed the association between the change in FMDBA with MitoQ and baseline FMDBA and cardiorespiratory fitness (CRF). Compared with placebo, MitoQ increased FMDBA in NEX by + 2.1% (MitoQ pre: 4.9 ± 0.4 vs. post: 7.0 ± 0.4 %, P = 0.004, interaction) but not in EX (P = 0.695, interaction). MitoQ also increased endothelial function in adults with a FMDBA <6% (P < 0.0001, interaction) but not >6% (P = 0.855, interaction). Baseline FMDBA and CRF were correlated (r = 0.44, P = 0.037), whereas the change in FMDBA with MitoQ was inversely correlated with CRF (r = -0.66, P < 0.001) and baseline FMDBA (r = -0.73, P < 0.0001). The relationship between the change in FMDBA and baseline FMDBA remained correlated after adjusting for CRF (r = -0.55, P = 0.007). These data demonstrate that MitoQ acutely improves FMDBA in NEX and EX adults who have a baseline FMDBA <6%. KEY POINTS: A key age-related change contributing to increased cardiovascular disease (CVD) risk is vascular endothelial dysfunction due to increased mitochondrial-derived reactive oxygen species (mtROS). Aerobic exercise preserves endothelial function via suppression of mtROS in preclinical models but the evidence in humans is limited. In the present study, a single dose of the mitochondria-targeted antioxidant, mitoquinone mesylate (MitoQ), increases endothelial function in non-exercisers with lower cardiorespiratory fitness (CRF) but not in exercisers with higher CRF. The acute effects of MitoQ on endothelial function in middle-aged and older adults (MA/O) are influenced by baseline endothelial function independent of CRF. These data provide initial evidence that the acute MitoQ-enhancing effects on endothelial function in MA/O adults are influenced, in part, via CRF and baseline endothelial function.

Short-term vascular responses to spring and fall daylight savings time shifts.

Daylight saving time (DST) is a Western biannual time transition, setting the clock back 1 h in the fall and forward 1 h in the spring. There is an epidemiological link between DST and acute myocardial infarction risk in the first week following the spring shift; however, the mechanisms underlying the effect of DST on cardiovascular function remain unclear. The purpose of this study was to explore the short-term cardiovascular changes induced by fall and spring shifts in DST in a convenience sample of healthy adults. We hypothesized that spring, but not fall, DST shifts would acutely increase central pulse wave velocity, the gold standard measurement of central arterial stiffness. Twenty-one individuals (fall: n = 10; spring: n = 11) participated in four visits, occurring 1 wk before and at +1, +3, and +5 days after spring and fall time transitions. Central, brachial, and radial pulse wave velocity as well as carotid augmentation index were assessed with applanation tonometry. Sleep quality and memory function were assessed via questionnaire and the Mnemonic Similarities Task, respectively. Neither fall or spring transition resulted in changes to cardiovascular variables (carotid-femoral pulse wave velocity, carotid-brachial pulse wave velocity, carotid-radial pulse wave velocity, heart rate, mean arterial pressure, or augmentation index), sleep quality, or cognitive function (all P > 0.05). Our findings do not provide evidence that DST shifts influence cardiovascular outcomes in healthy adults. This study emphasizes the need for further research to determine the mechanisms of increased cardiovascular disease risk with DST that help explain epidemiological trends.NEW & NOTEWORTHY The debate of whether to abolish daylight savings time (DST) is, in part, motivated by the population-level increase in all-cause mortality and incidence of cardiovascular events following DST; however, there is an absence of data to support a physiological basis for risk. We found no changes in pulse wave velocity or augmentation index during the subacute window of DST. Large multisite trials are necessary to address the small, but meaningful, effects brought on by a societal event.

Statin administration improves vascular function in heart failure with preserved ejection fraction.

Heart failure with preserved ejection fraction (HFpEF) is characterized by impaired vascular endothelial function that may be improved by hydroxy-methylglutaryl-CoA (HMG-CoA) reductase enzyme inhibition. Thus, using a parallel, double-blind, placebo-controlled design, this study evaluated the efficacy of 30-day atorvastatin administration (10 mg daily) on peripheral vascular function and biomarkers of inflammation and oxidative stress in 16 patients with HFpEF [Statin: n = 8, 74 ± 6 yr, ejection fraction (EF) 52-73%; Placebo: n = 8, 67 ± 9 yr, EF 56-72%]. Flow-mediated dilation (FMD) and sustained-stimulus FMD (SS-FMD) during handgrip (HG) exercise, reactive hyperemia (RH), and blood flow during HG exercise were evaluated to assess conduit vessel function, microvascular function, and exercising muscle blood flow, respectively. FMD improved following statin administration (pre, 3.33 ± 2.13%; post, 5.23 ± 1.35%; P < 0.01), but was unchanged in the placebo group. Likewise, SS-FMD, quantified using the slope of changes in brachial artery diameter in response to increases in shear rate, improved following statin administration (pre: 5.31e-5 ± 3.85e-5 mm/s-1; post: 8.54e-5 ± 4.98e-5 mm/s-1; P = 0.03), with no change in the placebo group. Reactive hyperemia and exercise hyperemia responses were unchanged in both statin and placebo groups. Statin administration decreased markers of lipid peroxidation (malondialdehyde, MDA) (pre, 0.652 ± 0.095; post, 0.501 ± 0.094; P = 0.04), whereas other inflammatory and oxidative stress biomarkers were unchanged. Together, these data provide new evidence for the efficacy of low-dose statin administration to improve brachial artery endothelium-dependent vasodilation, but not microvascular function or exercising limb blood flow, in patients with HFpEF, which may be due in part to reductions in oxidative stress.NEW & NOTEWORTHY This is the first study to investigate the impact of statin administration on vascular function and exercise hyperemia in patients with heart failure with preserved ejection fraction (HFpEF). In support of our hypothesis, both conventional flow-mediated dilation (FMD) testing and brachial artery vasodilation in response to sustained elevations in shear rate during handgrip exercise increased significantly in patients with HFpEF following statin administration, beneficial effects that were accompanied by a decrease in biomarkers of oxidative damage. However, contrary to our hypothesis, reactive hyperemia and exercise hyperemia were unchanged in patients with HFpEF following statin therapy. These data provide new evidence for the efficacy of low-dose statin administration to improve brachial artery endothelium-dependent vasodilation, but not microvascular reactivity or exercising muscle blood flow in patients with HFpEF, which may be due in part to reductions in oxidative stress.

Acute inspiratory resistance training enhances endothelium-dependent dilation and retrograde shear rate in healthy young adults.

Inspiratory resistance training (IRT) yields significant reductions in resting blood pressure and improves vascular endothelial function. Our objective was to quantify the acute effects of IRT on brachial artery flow-mediated dilation (FMD) and shear rates (SRs) in healthy men and women. Twenty young adults (22.9 ± 3.4 years; 10 male, 10 female) completed a single bout of IRT or Rest condition in a randomized crossover design. Brachial artery FMD was performed before, 10 min after, and 40 min after the assigned condition. Brachial artery blood flow velocities were collected during IRT, separated by breathing cycle phase, and converted into SRs. FMD improved 10 min post-IRT (+1.86 ± 0.61%; p = 0.025) but returned to baseline by 40 min post-IRT (p = 0.002). Anterograde SR decreased by 10% and retrograde SR increased 102% during resisted inspiration, relative to baseline SR (p < 0.001). Anterograde SR increased by 7% in men and women (p < 0.001) and retrograde SR decreased by 12% in women but not men (p = 0.022) during unresisted expiration, relative to baseline SR. A single bout of IRT elicits a transient enhancement in FMD in both men and women. Acute IRT-related enhancements in SRs may contribute to sustained improvements in FMD that have been reported previously.

Measurements of Arterial Occlusion Pressure Using Hand-Held Devices.

ABSTRACT: Vehrs, PR, Reynolds, S, Allen, J, Barrett, R, Blazzard, C, Burbank, T, Hart, H, Kasper, N, Lacey, R, Lopez, D, and Fellingham, GW. Measurements of arterial occlusion pressure using hand-held devices. J Strength Cond Res 38(5): 873-880, 2024-Arterial occlusion pressure (AOP) of the brachial artery was measured simultaneously using Doppler ultrasound (US), a hand-held Doppler (HHDOP), and a pulse oximeter (PO) in the dominant (DOM) and nondominant (NDOM) arms of males ( n = 21) and females ( n = 23) using continuous (CONT) and incremental (INCR) cuff inflation protocols. A mixed-model analysis of variance revealed significant ( p < 0.05) overall main effects between AOP measured using a CONT (115.7 ± 10.9) or INCR (115.0 ± 11.5) cuff inflation protocol; between AOP measured using US (116.3 ± 11.2), HHDOP (115.4 ± 11.2), and PO (114.4 ± 11.2); and between males (120.7 ± 10.6) and females (110.5 ± 9.4). The small overall difference (1.81 ± 3.3) between US and PO measures of AOP was significant ( p < 0.05), but the differences between US and HHDOP and between HHDOP and PO measures of AOP were not significant. There were no overall differences in AOP between the DOM and NDOM arms. Trial-to-trial variance in US measurements of AOP was not significant when using either cuff inflation protocol but was significant when using HHDOP and PO and a CONT cuff inflation protocol. Bland-Altman plots revealed reasonable limits of agreement for both HHDOP and PO measures of AOP. The small differences in US, HHDOP, and PO measurements of AOP when using CONT or INCR cuff inflation protocols are of minimal practical importance. The choice of cuff inflation protocol is one of personal preference. Hand-held Doppler of PO can be used to assess AOP before using blood flow restriction during exercise.

Does perceived caloric and nutrient intake influence the acute effect of beverage consumption on cardiovascular function?

Our objective was to explore whether consuming the same high-fat/sugar beverage affects endothelial function differently depending on whether it is presented as "unhealthy" [accurate high calorie (kcal), fat, and sugar information displayed] versus "healthy" (inaccurate low kcal, fat, and sugar information displayed). Twenty-five, young (21 ± 2 yr), healthy, food-stress/shame-prone women completed three conditions: milkshake consumption (540 kcal, 80 g sugar, and 14 g fat) where correct, "unhealthy" nutritional information was shown to participants (milkshake condition), consumption of the same milkshake but with incorrect, "healthy" information shown to participants (100 kcal, 3 g sugar, and 4 g fat; sham-nutrishake condition), and water consumption (control condition). Pre- and postbeverage we assessed 1) endothelial function via standard brachial artery flow-mediated dilation (FMD); 2) perceived shame, stress, beverage healthiness, and harm; and 3) blood (plasma) glucose, insulin, triglycerides and oral fluid cortisol, and tumor necrosis factor-alpha (TNFα) receptor binding. Glucose, triglycerides, and insulin increased in the milkshake and sham-nutrishake conditions (P < 0.05). The milkshake was perceived as less healthy (P < 0.001) and more harmful (P < 0.001) than the sham-nutrishake. Shame, stress, oral fluid cortisol and TNFα receptor binding did not increase postconsumption. FMD decreased after the milkshake condition (pre: 7.4 ± 3.3%; post-60 min: 4.9 ± 2.9%; post-90 min: 4.5 ± 3.1%, P < 0.001) but not the sham-nutrishake (pre: 5.7 ± 2.2%; post-60 min: 5.5 ± 2.6%; post-90 min: 5.0 ± 2.4%, P = 0.43) or control conditions (pre: 7.0 ± 2.6%; post-60 min: 6.6 ± 4.1%; post-90 min: 6.0 ± 3.2%, P = 0.29). Shear rate stimulus covariation did not alter FMD results. Lower perceived beverage healthiness was significantly associated with a greater reduction in FMD (ρ = 0.36, P = 0.002). In conclusion, a high-fat/sugar milkshake reduced FMD only when presented as high in fat, sugar, and calories. This suggests that perceptions about nutritional information contribute to the impact of food intake on endothelial function and that nocebo effects could be involved in cardiovascular disease etiology.NEW & NOTEWORTHY This was the first study to investigate how perceived nutritional content influences the impact of a high-sugar/fat beverage on endothelial function. We found that a high-sugar/fat beverage only reduced endothelial function when it was presented to participants as high in calories, fat, and sugar. This suggests that perceived nutritional information contributes to the impact of high sugar and fat intake on endothelial function.

The vascular response to acute sauna heating is similar in young and middle-aged adults.

Sauna has been linked to a reduction of cardiovascular disease risk and is a promising nonpharmacological treatment for populations at risk of cardiovascular disease. This study examined the vascular response to an acute bout of sauna heating in young and middle-aged individuals. Ten young (25 ± 4 yr, 6 males and 4 females) and eight middle-aged adults (56 ± 4 yr, 4 males and 4 females) underwent 40 min of sauna exposure at 80°C. Esophageal and intramuscular temperatures, brachial and superficial femoral artery blood flow, artery diameter, and shear rates were recorded at baseline and following heat exposure. Brachial artery flow-mediated dilation (FMD) was measured at baseline and following 90 min of recovery. Esophageal and muscle temperatures increased similarly in the young and middle-aged adults by 1.5 ± 0.53 and 1.95 ± 0.70°C, respectively (P < 0.05). The shear rate increased by 170-200% (P < 0.001), while blood flow increased by 180-390% (P < 0.001) in the superficial femoral and brachial arteries, respectively, and did not differ between age groups (P = 0.190-0.899). Systolic blood pressure was reduced from 135 ± 17 to 122 ± 20 mmHg (P = 0.017) in middle-aged participants. These data indicate that young and middle-aged adults have similar vascular responses to acute sauna heating.NEW & NOTEWORTHY Sauna therapy has been shown to improve cardiovascular health and function in older adults and individuals with cardiovascular disease risk factors. Specifically, improvements in vascular function have been reported and have been attributed to the increased hemodynamic stimuli on the vasculature associated with thermal stress. The present study quantified this hemodynamic response to a sauna protocol associated with improved cardiovascular health across the lifespan. Our data show that middle-aged adults have the same shear rate and blood flow response to sauna as young adults.

Accurate detection of Korotkoff sounds reveals large discrepancy between intra-arterial systolic pressure and simultaneous noninvasive measurement of blood pressure with brachial cuff sphygmomanometry.

Cardiovascular disease is the number 1 cause of death globally, with elevated blood pressure (BP) being the single largest risk factor. Hence, BP is an important physiological parameter used as an indicator of cardiovascular health. Noninvasive cuff-based automated monitoring is now the dominant method for BP measurement and irrespective of whether the oscillometric or the auscultatory method is used, all are calibrated according to the Universal Standard (ISO 81060-2:2019), which requires two trained operators to listen to Korotkoff K1 sounds for SBP and K4/K5 sounds for DBP. Hence, Korotkoff sounds are fundamental to the calibration of all NIBP devices. In this study of 40 lightly sedated patients, aged 64.1 ±â€Š9.6 years, we compare SBP and DBP recorded directly by intra-arterial fluid filled catheters to values recorded from the onset (SBP-K) and cessation (DBP-K) of Korotkoff sounds. We demonstrate that whilst DBP-K measurements are in good agreement, with a mean difference of -0.3 ±â€Š5.2 mmHg, SBP-K underestimates true intra-arterial SBP (IA-SBP) by an average of 14 ±â€Š9.6 mmHg. The underestimation arises from delays in the re-opening of the brachial artery following deflation of the brachial cuff to below SBP. The reasons for this delay are not known but appear related to the difference between SBP and the pressure under the cuff as blood first begins to flow, as the cuff deflates. Linear models are presented that can correct the underestimation in SBP resulting in estimates with a mean difference of 0.2 ±â€Š7.1 mmHg with respect to intra-arterial SBP.

Optimization and validation of a suprasystolic brachial cuff-based method for noninvasively estimating central aortic blood pressure.

Clinical studies have extensively demonstrated that central aortic blood pressure (CABP) has greater clinical significance in comparison with peripheral blood pressure. Despite the existence of various techniques for noninvasively measuring CABP, the clinical applications of most techniques are hampered by the unsatisfactory accuracy or large variability in measurement errors. In this study, we proposed a new method for noninvasively estimating CABP with improved accuracy and reduced uncertain errors. The main idea was to optimize the estimation of the pulse wave transit time from the aorta to the occluded lumen of the brachial artery under a suprasystolic cuff by identifying and utilizing the characteristic information of the cuff oscillation wave, thereby improving the accuracy and stability of the CABP estimation algorithms under various physiological conditions. The method was firstly developed and verified based on large-scale virtual subject data (n = 800) generated by a computational model of the cardiovascular system coupled to a brachial cuff, and then validated with small-scale in vivo data (n = 34). The estimation errors for the aortic systolic pressure were -0.05 ± 0.63 mmHg in the test group of the virtual subjects and -1.09 ± 3.70 mmHg in the test group of the patients, both demonstrating a good performance. In particular, the estimation errors were found to be insensitive to variations in hemodynamic conditions and cardiovascular properties, manifesting the high robustness of the method. The method may have promising clinical applicability, although further validation studies with larger-scale clinical data remain necessary.

Intermediate versus morning chronotype has lower vascular insulin sensitivity in adults with obesity.

AIM: Chronotype reflects a circadian rhythmicity that regulates endothelial function. While the morning chronotype (MORN) usually has low cardiovascular disease risk, no study has examined insulin action on endothelial function between chronotypes. We hypothesized intermediate chronotypes (INT) would have lower vascular insulin sensitivity than morning chronotype (MORN). MATERIALS AND METHODS: Adults with obesity were classified per Morningness-Eveningness Questionnaire (MEQ) as either MORN (n = 27, 22 female, MEQ = 63.7 ± 4.7, 53.8 ± 6.7 years, 35.3 ± 4.9 kg/m2) or INT (n = 29, 23 female, MEQ = 48.8 ± 6.7, 56.6 ± 9.0 years, 35.7 ± 6.1 kg/m2). A 120 min euglycaemic-hyperinsulinaemic clamp (40 mU/m2/min, 90 mg/dl) was conducted to assess macrovascular insulin sensitivity via brachial artery flow-mediated dilation (%FMD; conduit artery), post-ischaemic flow velocity (resistance arteriole), as well as microvascular insulin sensitivity via contrast-enhanced ultrasound [e.g. microvascular blood volume (perfusion)]. Fasting plasma arginine and citrulline, as well as fasting and clamp-derived plasma endothelin-1 and nitrate/nitrite, were assessed as surrogates of vasoconstriction and nitric oxide-mediated vasodilation. Aerobic fitness (VO2max) and body composition (dual-energy X-ray absorptiometry) were also collected. RESULTS: MORN had a higher VO2max compared with INT (p < .01), although there was no difference in fat mass. While fasting FMD was similar between groups, insulin lowered FMD corrected to shear stress and microvascular blood volume in INT compared with MORN after co-varying for VO2max (both p ≤ .02). INT also had a lower fasting nitrate (p = .03) and arginine (p = .07). Higher MEQ correlated with elevated FMD (r = 0.33, p = .03) and lower post-ischaemic flow velocity (r = -0.33, p = .03) as well as shear rate (r = -0.36, p = .02) at 120 min. CONCLUSION: When measured during the morning, INT had a lower vascular insulin sensitivity than MORN. Additional work is needed to understand endothelial function differences among chronotypes to optimize cardiovascular disease risk reduction.

Comparison of cuff inflation and cuff deflation brachial sphygmomanometry with intra-arterial blood pressure as reference.

Conventional sphygmomanometry with cuff deflation is used to calibrate all noninvasive BP (NIBP) instruments and the International Standard makes no mention of calibrating methods specifically for NIBP instruments, which estimate systolic and diastolic pressure during cuff inflation rather than cuff deflation. There is however increasing interest in inflation-based NIBP (iNIBP) instruments on the basis of shorter measurement time, reduction in maximal inflation pressure and improvement in patient comfort and outcomes. However, we have previously demonstrated that SBP estimates based on the occurrence of the first K1 Korotkoff sounds during cuff deflation can underestimate intra-arterial SBP (IA-SBP) by an average of 14 ±â€Š10 mmHg. In this study, we compare the dynamics of intra-arterial blood pressure (IABP) measurements with sequential measurement of Korotkoff sounds during both cuff inflation and cuff deflation in the same individual. In 40 individuals aged 64.1 ±â€Š9.6 years (range 36-86 years), the overall dynamic responses below the cuff were similar, but the underestimation error was significantly larger during inflation than deflation, increasing from 14 ±â€Š10 to 19 ±â€Š12 mmHg ( P  < 0.0001). No statistical models were found which could compensate for this error as were found for cuff deflation. The statistically significant BP differences between inflation and deflation protocols reported in this study suggest different behaviour of the arterial and venous vasculature between arterial opening and closing which warrant further investigation, particularly for iNIBP devices reporting estimates during cuff inflation. In addition, measuring Korotkoff sounds during cuff inflation represents significant technical difficulties because of increasing pump motor noise.

Sex-specific microvascular and hemodynamic responses to passive limb heating in young adults.

OBJECTIVE: We examined sex-specific microvascular reactivity and hemodynamic responses under conditions of augmented resting blood flow induced by passive heating compared to normal blood flow. METHODS: Thirty-eight adults (19 females) completed a vascular occlusion test (VOT) on two occasions preceded by rest with or without passive heating in a randomized, counterbalanced order. Skeletal muscle tissue oxygenation (StO2, %) was assessed with near-infrared spectroscopy (NIRS), and the rate of desaturation and resaturation as well as maximal StO2 (StO2max) and prolonged hypersaturation (area under the curve, StO2AUC) were quantified. Before the VOT, brachial artery blood flow (BABF), vascular conductance, and relative BABF (BABF normalized to forearm lean mass) were determined. Sex × condition ANOVAs were used. A p-value ≤.05 was considered statistically significant. RESULTS: Twenty minutes of heating increased BABF compared to the control (102.9 ± 28.3 vs. 36.0 ± 20.9 mL min-1; p < .01). Males demonstrated greater BABF than females (91.9 ± 34.0 vs. 47.0 ± 19.1 mL min-1; p < .01). There was no sex difference in normalized BABF. There were no significant interactions for NIRS-VOT outcomes, but heat did increase the rate of desaturation (-0.140 ± 0.02 vs. -0.119 ± 0.03% s-1; p < .01), whereas regardless of condition, males exhibited greater rates of resaturation and StO2max than females. CONCLUSIONS: These results suggest that blood flow is not the primary factor causing sex differences in NIRS-VOT outcomes.

Elevated blood flow in people with type 1 and type 2 diabetes.

AIMS: The study aimed to evaluate blood flow (BF) and microvascular function in the forearm of people with type 1 and type 2 diabetes at rest and after ischemia. Microvascular function plays a crucial role in regulating BF in peripheral tissues based on metabolic demand. METHODS: People with diabetes and sex-matched healthy controls were recruited. Brachial artery diameter and blood velocity were continuously measured at rest and after ischemia by an automatic tracking system. BF and vascular conductance were then calculated. RESULTS: Forty-nine people with diabetes and 49 controls were enrolled. BF at rest and after ischemia was significantly higher in people with diabetes than controls: Type 1, 243 ± 116 and 631 ± 233 ml/min; controls, 180 ± 106 and 486 ± 227 ml/min; Type 2, 332 ± 149 and 875 ± 293 ml/min; controls 222 ± 106 and 514 ± 224 ml/min. Vascular conductance was significantly higher in Type 2 than in controls at rest and after ischemia. CONCLUSIONS: People with diabetes exhibited significantly increased BF, with Type 2 also showing heightened vascular conductance. Activating metabolic pathways triggered by hyperglycemia may lead to distinct vascular redistribution, potentially impairing blood flow over time. These findings of the study underscore the importance of understanding overall vascular dynamics in diabetes and its implications for vascular health.

Skipping breakfast does not accelerate the hyperglycemia-induced endothelial dysfunction but reduces blood flow of the brachial artery in young men.

PURPOSE: Postprandial hyperglycemia is assumed to have a negative impact on flow-mediated dilation (FMD), an index of endothelial function, and blood flow of the peripheral conduit arteries. This study aimed to determine whether the enhancement of postprandial hyperglycemia by skipping breakfast accelerates endothelial dysfunction and reduces the blood flow in the brachial artery in young men. METHODS: Using a randomized cross-over design, ten healthy men completed two trials: with and without breakfast (Eating and Fasting trials, respectively). Venous blood sampling and brachial FMD tests were conducted before, 30, 60, 90, and 120 min after a 75-g oral glucose tolerance test (OGTT). RESULTS: Skipping breakfast boosted post-OGTT glucose levels than having breakfast (P = 0.01). The magnitude of the decrease in FMD via OGTT did not vary between trials (main effect of trial P = 0.55). Although brachial blood flow tended to decrease after OGTT in both trials (interaction and main effect of time P = 0.61 and P = 0.054, respectively), the decrease in blood flow following OGTT was greater in the Fasting trial than in the Eating trial (main effect of trial, mean difference = - 15.8 mL/min [95%CI = - 25.6 to - 6.0 mL/min], P < 0.01). CONCLUSION: Skipping breakfast did not enhance the magnitude of the decrease in FMD following glucose loading, but did accelerate hyperglycemia-induced reduction in brachial blood flow. Current findings suggest that even missing one breakfast has negative impacts on the blood flow regulation of the peripheral conduit arteries in young men who habitually eat breakfast.

Impact of a cuff-based device calibration method on the agreement between invasive and noninvasive aortic and brachial pressure.

INTRODUCTION: Brachial cuff-based methods are increasingly used to estimate aortic systolic blood pressure (aoSBP). However, there are several unresolved issues. AIMS: to determine to what extent the scheme used to calibrate brachial records (1) can affect noninvasive obtained aoSBP levels, and consequently, the level of agreement with the aoSBP recorded invasively, and (2) how different ways of calibrating ultimately impact the relationship between aoSBP and cardiac properties. METHODS: brachial and aortic blood pressure (BP) was simultaneously obtained by invasive (catheterisation) and noninvasive (brachial oscillometric-device) methods (89 subjects). aoSBP was noninvasive obtained using three calibration schemes: 'SD': diastolic and systolic brachial BP, 'C': diastolic and calculated brachial mean BP (bMBP), 'Osc': diastolic and oscillometry-derived bMBP. Agreement between invasive and noninvasive aoSBP, and associations between BP and echocardiographic-derived parameters were analysed. CONCLUSIONS: 'C' and 'SD' schemes generated aoSBP levels lower than those recorded invasively (mean errors: 6.9 and 10.1 mmHg); the opposite was found when considering 'Osc'(mean error: -11.4 mmHg). As individuals had higher invasive aoSBP, the three calibration schemes increasingly underestimated aoSBP levels; and viceversa. The 'range' of invasive aoSBP in which the calibration schemes reach the lowest error level (-5-5 mmHg) is different: 'C': 103-131 mmHg; 'Osc': 159-201 mmHg; 'SD':101-124 mmHg. The calibration methods allowed reaching levels of association between aoSBP and cardiac characteristics, somewhat lower, but very similar to those obtained when considering invasive aoSBP. There is no evidence of a clear superiority of one calibration method over another when considering the association between aoSBP and cardiac characteristics.

Assessment of Endothelial Reactivity by Measurement of Vascular Material Response to Shear Stress: A Feasibility Study.

Flow-mediated dilation (FMD) evaluates the relative change in arterial diameter during hyperemia to assess the endothelial response due to a shear stimulus. However, conventional FMD measures diameter response alone and the alterations in the arterial wall's material properties during reactive hyperemia, which also influence dilation, go unaddressed. In this work, we examine the material response (MR) of the artery during reactive hyperemia using clinically relevant stiffness markers for the assessment of endothelial reactivity (ER). For this, we have developed an in-house brachial cuff control (BCC) system to continuously acquire brachial pressure which can be integrated with simultaneous measurement of brachial diameter and used to quantify the relative changes in wall property during hyperemia non-invasively. The assessment of endothelial reactivity using material response (ERAMR) was conducted on 20 healthy participants (12M/8F) and the results were compared with conventional FMD (FMD%). The mean pressure response gave an inverse trend to that of diameter response with varying magnitudes during reactive hyperemia (18.71% from baseline for diameter and 2.45% for pressure), there was a significant difference in the measurement of FMD and ERAMR (P < 0.05). The larger distribution of ERAMR compared to FMD% in box-plots further implies the inclusion of within-subject variations. Hence, ERAMR can be a potential estimate of ER, given the need for intensive validations in this line on larger cohorts.Clinical Relevance- This study demonstrates the independent role of arterial wall material properties to quantify endothelial reactivity in response to a shear stimulus.

Comparison of effects of peripheral vasculature on tonometric radial pulse and cuff-based brachial pulse waveform as used in estimation of central aortic pressures.

OBJECTIVE: Aortic pressure estimation requires reliable peripheral pulse waveform acquisition. The peripheral waveform can change with local vascular effects that can be independent of aortic pressure. This study quantifies the effects of peripheral vasculature changes on radial and brachial waveforms. DESIGN AND METHOD: In 20 subjects (37± 15 years, 7 female), brachial volumetric displacement (cuff-based) and radial tonometry waveforms were simultaneously measured whilst a cuff around the hand on the same arm was inflated to induce transmural pressures of -60, -30, -15, 0, 15 and 30 mmHg, altering local peripheral resistance and compliance by graded arterial wall unloading. Aortic blood pressure (BP), augmentation index (AIx) and ejection duration were calculated from the measurements using a generalized transfer function. The parameters under unloaded conditions were compared to baseline measurements. RESULTS: Brachial systolic and diastolic BP did not change throughout the experiment. Altering peripheral resistance and compliance did not significantly change calculated aortic BP values, although changes were nominally greater for radial (maximum +8±1 mmHg) compared to brachial (maximum +2±1 mmHg) waveforms. AIx at 0 mmHg transmural pressure (maximum arterial wall unloading) was higher when derived from radial waveforms (+24±3%, p<0.001) but not when derived from brachial waveforms. CONCLUSIONS: Localized changes in peripheral resistance and compliance affect tonometer acquired radial waveforms but not volumetric displacement acquired brachial pressure waveforms, as judged by computed central aortic augmentation pressure parameters. This suggests aortic pressure estimation from the brachial cuff waveform is less sensitive to peripheral vasculature disturbances that alter the peripheral arterial pulse morphology.

Reduction in peripheral arterial stiffness after reactive hyperemia is dependent on increases in blood flow.

The acute reduction in peripheral arterial stiffness during reactive hyperemia is assumed to be flow-mediated; however, the mechanism remains unproven. We hypothesized that restricting the blood flow increase during reactive hyperemia would abolish the reduction in peripheral arterial stiffness. Fourteen healthy young adults (5 females, 25 ± 5 years, mean ± SD) underwent reactive hyperemia with a rapid-release cuff on the upper arm inflated to 220 mmHg for 5 min: once with unrestricted blood flow and once with restricted blood flow by manually applying pressure to the brachial artery. Brachial-radial pulse wave velocity (PWV) was measured with tonometers over brachial and radial arteries before cuff inflation and at 5, 15, and 30 min after release. Brachial blood flow was monitored with Doppler ultrasound. Baseline brachial-radial PWV was similar between conditions (10.3 ± 1.8 vs. 10.7 ± 1.7 m/s). With unrestricted flow, PWV decreased 5 min post-reactive hyperemia (8.6 ± 1.1 m/s; p < 0.05) and returned near baseline at 15 and 30 min post (p < 0.05). With restricted flow, PWV did not change (p > 0.05) post-reactive hyperemia. Reactive hyperemia acutely reduced peripheral arterial stiffness, but not when brachial artery blood flow increase was restricted. This suggests that the reduction in peripheral arterial stiffness during reactive hyperemia depends on increased blood flow.

Mechanistic, participant, and movement-related factors that contribute to low-flow-mediated constriction.

Endothelial function is commonly determined via the ultrasound-based flow-mediated dilation (FMD) technique which assesses arterial dilation in response to a hyperemia response following distal cuff occlusion. However, the low-flow-mediated constriction (L-FMC) response during cuff-induced ischemia is often overlooked. L-FMC provides unique information regarding endothelial function, but vascular researchers may be unclear on what this metric adds. Therefore, the objective of this review was to examine the mechanistic determinants and participant-level factors of L-FMC. Existing mechanistic studies have demonstrated that vasoreactivity to low flow may be mediated via non-nitric oxide vasodilators (i.e., endothelial hyperpolarizing factors and/or prostaglandins), inflammatory markers, and enhancement of vasoconstriction via endothelin-1. In general, participant-level factors such as aging and presence of cardiovascular conditions generally are associated with attenuated L-FMC responses. However, the influence of sex on L-FMC is unclear with divergent results between L-FMC in upper versus lower limb vessels. The ability of aerobic exercise to augment L-FMC (i.e., make more negative) is well supported, but there is a major gap in the literature concerning the mechanistic underpinnings of this observation. This review summarizes that while larger L-FMC responses are generally healthy, the impact of interventions to augment/attenuate L-FMC has not included mechanistic measures that would provide insight into non-nitric oxide-based endothelial function. Clarifications to terminology and areas of further inquiry as it relates to the specific pharmacological, individual-level factors, and lifestyle behaviors that impact L-FMC are highlighted. A greater integration of mechanistic work alongside applied lifestyle interventions is required to better understand endothelial cell function to reductions in local blood flow.

Acute upper and lower limb hemodynamic responses during single sessions of low- versus high-intensity inspiratory muscle strength training.

Inspiratory muscle strength training (IMST) has shown potential to improve both respiratory and cardiovascular function in health and disease. Less is known about acute hemodynamic responses to a single IMST session, therefore we assessed upper and lower limb blood flow via Doppler ultrasound in the brachial and popliteal arteries, respectively. Mean, anterograde, and retrograde blood flow (BF) and shear rate (SR) were assessed relative to baseline during low-intensity (15% maximal inspiratory pressure - PImax) and high-intensity (75% PImax) IMST. During low-intensity IMST, popliteal BF and SR were reduced by ∼10%, and brachial BF and SR were reduced by ∼40%. During high-intensity IMST, popliteal BF and SR were reduced by ∼20%, and brachial BF and SR were reduced by ∼35%. BF and SR responses were not statistically different between low-intensity and high-intensity training for either blood vessel (P > 0.05). In addition, anterograde BF and SR were significantly decreased in the brachial artery for both low-intensity and high-intensity training (P < 0.05), but not the popliteal artery (P > 0.05). Finally, during IMST retrograde BF and SR were significantly increased in both the upper and lower limbs during low-intensity and high-intensity training (P < 0.05). These data provide novel insight into the acute BF and SR responses to a single bout of IMST and may enhance our understanding of the mechanism(s) by which IMST imparts its beneficial chronic effects on cardiovascular function.NEW & NOTEWORTHY Herein, we demonstrate for the first time that upper and lower limb blood flow and shear rate patterns are altered during a single bout of IMST, at low- and high-intensity training. Specifically, anterograde blood flow and shear rate are significantly reduced in the brachial artery, whereas retrograde blood flow is significantly elevated in both the brachial and popliteal arteries. These findings provide insight into the vascular impact of IMST, which may inform future mechanistic studies.