Acute effects of a mixed meal on arterial stiffness and central hemodynamics in healthy adults

Effects of pre-exercise intake of plant- and animal-based foods on arterial function and aerobic exercise capacity in healthy young men: a randomized cross-over trial

The purpose of this study was to examine the effects of plant- versus animal-based food intake before exercise on arterial function and subsequent aerobic exercise capacity. Eleven healthy adult males (mean age, 22.6 ± 1.8 years) participated in this study. A plant- or animal-based randomized meal type crossover comparison was conducted on separate days with a uniform protein, fat, and carbohydrate balance. Both carotid-femoral pulse wave velocity (cfPWV), femoral-ankle pulse wave velocity (faPWV), and brachial artery flow-mediated dilatation (FMD) were measured as indexes of aortic and peripheral arterial stiffness and vascular endothelial function, respectively, before and at 120 min after the meal. After these measurements, maximal oxygen uptake was assessed using a graded power test on an electronically braked cycle ergometer. The results revealed that cfPWV was significantly lower, whereas FMD was significantly higher, at 120 min after compared with before the plant-based meal (p = 0.01 and 0.02, respectively). By contrast, cfPWV and FMD did not change at 120 min after compared with before the animal-based meal. In addition, faPWV did not change at 120 min after compared with before the meal for either meal type. Maximal oxygen uptake was higher in the plant- than in the animal-based meal type (p = 0.02). These results suggest that pre-exercise plant-based food intake may improve central arterial stiffness and vascular endothelial function, which may have favorable implications for aerobic exercise capacity.

Acute regulation of erythropoietin via lower body negative pressure: Influence of sex and age

The regulation of erythropoiesis via hemodynamic stimuli such as reduced central blood volume (CBV) remains uncertain in women and elderly individuals. This study assessed the acute effects of lower body negative pressure (LBNP) on key endocrine biomarkers regulating erythropoiesis, that is, erythropoietin (EPO) and copeptin, in young and older women and men (n = 87). Transthoracic echocardiography and hemodynamics were assessed throughout incremental LBNP levels for 1 hour, or until presyncope, with established methods. Venous blood samples were collected at baseline and immediately after termination of the orthostatic tolerance (OT) test for subsequent hormone analyses. The average age of young women and men (33.1 ± 6.0 vs. 29.5 ± 6.9 yr) and older women and men (63.8 ± 8.0 vs. 65.3 ± 8.9 yr) as well as their physical activity levels were matched within each age and sex group. CBV, as determined by right atrial volume, was reduced in all individuals at the end of the OT test (p < 0.001). The average OT time ranged from 50.1 to 58.1 min in all individuals. LBNP increased circulating EPO in young women (p = 0.023) but not in young men or older individuals. Copeptin was increased in all individuals with LBNP but was exclusively associated with EPO in men (r = 0.39, p = 0.013). The present study indicates that the acute hemodynamic regulation of EPO production is both sex- and age-dependent.

Hemodynamics and Arterial Stiffness in Response to Oral Glucose Loading in Individuals with Type II Diabetes and Controlled Hypertension

INTRODUCTION

Type 2 diabetes (T2D), the fastest growing pandemic, is typically accompanied by vascular complications. A central hallmark of both T2D and vascular disease is insulin resistance which causes impaired glucose transport and vasoconstriction concomitantly. Those with cardiometabolic disease display greater variation in central hemodynamics and arterial elasticity, both potent predictors of cardiovascular morbidity and mortality, which may be exacerbated by concomitant hyperglycemia and hyperinsulinemia during glucose testing. Thus, elucidating central and arterial responses to glucose testing in those with T2D may identify acute vascular pathophysiologies triggered by oral glucose loading.

AIM

This study compared hemodynamics and arterial stiffness to an oral glucose challenge (OGC: 50g glucose) between individuals with and without T2D. 21 healthy (48 ± 10 years) and 20 participants with clinically diagnosed T2D and controlled hypertension (52 ± 8 years) were tested.

METHODS

Hemodynamics and arterial compliance were assessed at baseline, and 10, 20, 30, 40, 50, and 60 min post-OGC.

RESULTS

Heart rate increased between 20 and 60 post-OGC in both groups (p < 0.05). Central systolic blood pressure (SBP) decreased in the T2D group between 10 and 50 min post-OGC while central diastolic blood pressure (DBP) decreased in both groups from 20 to 60 post-OGC. Central SBP decreased in T2D between 10 and 50 min post-OGC and central DBP decreased in both groups between 20 and 60 min post-OGC. Brachial SBP decreased between 10 and 50 min in healthy participants, whereas both groups displayed decreases in brachial DBP between 20 and 60 min post-OGC. Arterial stiffness was unaffected.

CONCLUSIONS

An OGC alters central and peripheral blood pressure in healthy and T2D participants similarly with no changes in arterial stiffness.

Device-guided slow breathing alters postprandial oxidative stress in young adult males: A randomized sham-controlled crossover trial

BACKGROUND AND AIMS

Slow, deep breathing (SDB) lowers blood pressure (BP) though the underlying mechanisms are unknown. Redox improvements could facilitate hemodynamic adjustments with SDB though this has not been investigated. The purpose of this randomized, sham-controlled trial was to examine the acute effects of SDB on oxidative stress and endothelial function during a physiological perturbation (high-fat meal) known to induce oxidative stress.

METHODS AND RESULTS

Seventeen males (ages 18-35 years) were enrolled, and anthropometric measurements and 7-day physical activity monitoring were completed. Testing sessions consisted of 24-h diet recalls (ASA24), blood sample collection for superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS) analysis, and flow-mediated dilation (FMD). High-fat meals were ingested and 2-min breathing exercises (SDB or sham control breathing) were completed every 15 min during the 4-h postprandial phase. Blood sample collection and FMD were repeated 1-, 2-, and 4-h post meal consumption. Mean body mass index and step counts were 25.6 ± 4.3 kg/m2 and 8165 ± 4405 steps per day, respectively. Systolic and diastolic BP and nutrient intake 24 h prior were similar between conditions. No time or time by condition interaction effects were observed for FMD. The total area under the curve (AUC) for SOD was significantly lower during SDB compared to the sham breathing condition (p < 0.01). No differences were observed in TBARS AUC (p = 0.538).

CONCLUSIONS

Findings from the current investigation suggest that SDB alters postprandial redox in the absence of changes in endothelial function in young, healthy males.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04864184.

CLINICAL TRIALS IDENTIFIER

NCT04864184.

Feasibility of home-based tracking of insulin resistance from vascular stiffness estimated from the photoplethysmographic finger pulse waveform

In this study, we explored the utility of post-prandial vascular stiffness as a surrogate measure for the estimation of insulin resistance (IR), which is a pre-diabetic condition. A cohort of 51 healthy young adults of varying Body mass index values (BMI) were studied by fasting plasma values of insulin and glucose; fasting and post-meal finger photoplethysmography (PPG), and electrocardiogram (ECG). Insulin resistance was estimated by Homeostatic model assessment-Insulin resistance 2 (HOMA-IR2) using fasting plasma insulin and glucose. Vascular stiffness was estimated by reciprocal of pulse arrival time (rPAT) from ECG and finger PPG at five time points from fasting to 2-hours post oral glucose ingestion. We examined if insulin resistance is correlated with meal induced vascular stiffness changes supporting the feasibility of using finger PPG for the estimation of insulin resistance. HOMA-IR2 was found to be positively correlated with early rise (0- to 30- minutes post meal) and delayed fall (30- to 120-minutes) of rPAT. Correlation persisted even after the effect of BMI has been partialled out in sub-group analysis. We conclude that finger PPG based pulse waveform and single lead ECG has the potential to be used as a non-invasive method for the assessment of insulin resistance. As both signals viz., ECG and PPG can be easily acquired using wearable and other low-cost sensing systems, the present study can serve as a pointer for the development of accessible methods of monitoring and longitudinal tracking of insulin resistance in health and pathophysiological states.

Acute and long-term effects of saxagliptin on a set of cardiovascular targets measured at fasting and post-prandially in obese patients with impaired glucose tolerance: A placebo-controlled study

BACKGROUND AND AIMS

Studies of dipeptidyl peptidase inhibitors (DPP4is) report heterogeneous effects on cardiovascular targets in type 2 diabetes. This study aimed to investigate, in patients with impaired glucose tolerance (IGT), whether saxagliptin, a DPP4i, had beneficial cardiovascular effects at fasting and during the post-prandial state.

METHODS AND RESULTS

In this randomized, placebo-controlled, double-blind, single-center pilot exploratory study, we included obese individuals with IGT. Twenty-four individuals (BMI 36.8 ± 4.8 kg/m²) were randomized to receive for 12 weeks either saxagliptin 5 mg a day or placebo. They were explored before and after a standardized breakfast for biological markers; microcirculatory blood flow at baseline and after transcutaneous administration of acetylcholine (Periflux System 5000® PERIMED); post-occlusive digital reactive hyperhemia (Endopat2000®); pulse wave velocity, augmentation index, central pulse pressure and subendocardial viability ratio (Sphygmocor®); cardiac hemodynamic parameters and cardiovascular autonomic nervous system activity (Task force monitor®). The results of all the investigations were similar after breakfast in the two groups at Visit 1 (acute post-prandial effects, after the first tablet) and Visit 2 (long-term post-prandial effects), and at fasting at Visit 1 and 2 (long-term effects, after 12 weeks of treatment). Only at Visit 2 the decrease in cardiac vagal activity occurring after breakfast was more sustained in the saxagliptin group than in the placebo group (interaction between treatment and time effect: p = 0.016).

CONCLUSION

In obese patients with IGT, the effects of saxagliptin on the large set of cardiovascular parameters measured are neutral, except for a more marked post-prandial depression of vagal activity.

CLINICAL TRIAL REGISTRATION NUMBER

NCT01521312.

Sex differences in workload-indexed blood pressure response and vascular function among professional athletes and their utility for clinical exercise testing

Purpose

Sex differences in blood pressure (BP) regulation at rest have been attributed to differences in vascular function. Further, arterial stiffness predicts an exaggerated blood pressure response to exercise (BPR) in healthy young adults. However, the relationship of vascular function to the workload-indexed BPR and potential sex differences in athletes are unknown.

Methods

We examined 47 male (21.6 ± 1.7 years) and 25 female (21.1 ± 2 years) athletes in this single-center pilot study. We assessed vascular function at rest, including systolic blood pressure (SBP). Further, we determined the SBP/W slope, the SBP/MET slope, and the SBP/W ratio at peak exercise during cycling ergometry.

Results

Male athletes had a lower central diastolic blood pressure (57 ± 9.5 vs. 67 ± 9.5 mmHg, p < 0.001) but a higher central pulse pressure (37 ± 6.5 vs. 29 ± 4.7 mmHg, p < 0.001), maximum SBP (202 ± 20 vs. 177 ± 15 mmHg, p < 0.001), and ΔSBP (78 ± 19 vs. 58 ± 14 mmHg, p < 0.001) than females. Total vascular resistance (1293 ± 318 vs. 1218 ± 341 dyn*s/cm⁵, p = 0.369), pulse wave velocity (6.2 ± 0.85 vs. 5.9 ± 0.58 m/s, p = 0.079), BP at rest (125 ± 10/76 ± 7 vs. 120 ± 11/73.5 ± 8 mmHg, p > 0.05), and the SBP/MET slope (5.7 ± 1.8 vs. 5.1 ± 1.6 mmHg/MET, p = 0.158) were not different. The SBP/W slope (0.34 ± 0.12 vs. 0.53 ± 0.19 mmHg/W) and the peak SBP/W ratio (0.61 ± 0.12 vs. 0.95 ± 0.17 mmHg/W) were markedly lower in males than in females (p < 0.001).

Conclusion

Male athletes displayed a lower SBP/W slope and peak SBP/W ratio than females, whereas the SBP/MET slope was not different between the sexes. Vascular functional parameters were not able to predict the workload-indexed BPR in males and females.

The effect of oral glucose tolerance testing on changes in arterial stiffness and blood pressure in elderly women with hypertension and relationships between the stage of diabetes and physical fitness levels

[Purpose]

The purpose of this study was to assess changes in blood glucose level, blood pressure, and arterial stiffness after a 75 g oral glucose tolerance test (OGTT) in elderly women aged over 65 years with hypertension and either normal glycemic control, impaired fasting glucose tolerance, or diabetes mellitus. We also wished to investigate the relationship between stages of diabetes and physical fitness.

[Methods]

A total of 24 elderly women with hypertension were assigned to a control group (CON; n=7), impaired fasting glucose group (IFG; n=9), and diabetes mellitus group (DM; n=8). In each group, blood glucose level, brachial ankle pulse wave velocity (PWV), and blood pressure were measured at baseline as well as 60 and 120 minutes after a 75 g OGTT. Physical fitness factors such as hand grip strength, balance test, 4 m gait speed test, chair stand test, short physical performance battery, and 6-minute walking test were subsequently assessed.

[Results]

In all three groups, blood glucose levels were significantly increased at 60 and 120 minutes after a 75 g OGTT. In the DM group, blood glucose levels were significantly higher before and after a 75 g OGTT than in the CON group. In the CON group, PWV was significantly increased at 60 minutes after a 75 g OGTT; however, there were no changes in other groups after glucose ingestion. In the CON group, systolic and diastolic blood pressures were significantly decreased at 60 and 120 minutes after a 75 g OGTT compared to baseline. However, there was no change in blood pressure after ingestion in the DM group. The IFG group had greater grip strength than the CON group; however, there were no differences in other variables between the groups.

[Conclusion]

After a 75 g OGTT, elderly women with hypertension and diabetes maintain higher blood glucose levels compared to those with hypertension alone. Unlike elderly women with hypertension alone, those with hypertension and diabetes did not show changes in arterial stiffness and blood pressure after a 75 g OGTT. Therefore, elderly women with hypertension and diabetes may not be able to control their blood vessels following a 75 g OGTT due to impaired vascular endothelial function. Moreover, there was no association between diabetes stage and physical fitness in elderly women with hypertension.

Acute Changes in Carotid-Femoral Pulse-Wave Velocity Are Tracked by Heart-Femoral Pulse-Wave Velocity

Background: Carotid-femoral pulse-wave velocity (cfPWV) is the reference standard measure of central arterial stiffness. However, it requires assessment of the carotid artery, which is technically challenging, and subject-level factors, including carotid artery plaque, may confound measurements. A promising alternative that overcomes these limitations is heart-femoral PWV (hfPWV), but it is not known to what extent changes in cfPWV and hfPWV are associated.

Objectives: To determine, (1) the strength of the association between hfPWV and cfPWV; and (2) whether change in hfPWV is associated with change in cfPWV when central arterial stiffness is perturbed.

Methods: Twenty young, healthy adults [24.0 (SD: 3.1) years, 45% female] were recruited. hfPWV and cfPWV were determined using Doppler ultrasound at baseline and following a mechanical perturbation in arterial stiffness (120 mmHg thigh occlusion). Agreement between the two measurements was determined using mixed-effects regression models and Bland-Altman analysis.

Results: There was, (1) strong (ICC > 0.7) agreement between hfPWV and cfPWV (ICC = 0.82, 95%CI: 0.69, 0.90), and, (2) very strong (ICC > 0.9) agreement between change in hfPWV and cfPWV (ICC = 0.92, 95%CI: 0.86, 0.96). cfPWV was significantly greater than hfPWV at baseline and during thigh occlusion (both P < 0.001). Inspection of the Bland-Altman plot, comparing cfPWV and corrected hfPWV, revealed no measurement magnitude bias.

Discussion: The current findings indicate that hfPWV and cfPWV are strongly associated, and that change in cfPWV is very strongly associated with change in hfPWV. hfPWV may be a simple alternative to cfPWV in the identification of cardiovascular risk in clinical and epidemiological settings.

A Protein/Lipid Preload Attenuates Glucose-Induced Endothelial Dysfunction in Individuals with Abnormal Glucose Tolerance

Postprandial hyperglycemia interferes with vascular reactivity and is a strong predictor of cardiovascular disease. Macronutrient preloads reduce postprandial hyperglycemia in subjects with impaired glucose tolerance (IGT) or type 2 diabetes (T2D), but the effect on endothelial function is unknown. Therefore, we examined whether a protein/lipid preload can attenuate postprandial endothelial dysfunction by lowering plasma glucose responses in subjects with IGT/T2D. Endothelial function was assessed by the reactive hyperemia index (RHI) at fasting, 60 min and 120 min during two 75 g oral glucose tolerance tests (OGTTs) preceded by either water or a macronutrient preload (i.e., egg and parmesan cheese) in 22 volunteers with IGT/T2D. Plasma glucose, insulin, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), glucagon, free fatty acids, and amino acids were measured through each test. RHI negatively correlated with fasting plasma glucose. During the control OGTT, RHI decreased by 9% and its deterioration was associated with the rise in plasma glucose. The macronutrient preload attenuated the decline in RHI and markedly reduced postprandial glycemia. The beneficial effect of the macronutrient preload on RHI was proportional to the improvement in glucose tolerance and was associated with the increase in plasma GLP-1 and arginine levels. In conclusion, a protein/lipid macronutrient preload attenuates glucose-induced endothelial dysfunction in individuals with IGT/T2D by lowering plasma glucose excursions and by increasing GLP-1 and arginine levels, which are known regulators of the nitric oxide vasodilator system.

Antioxidant cocktail following a high-sodium meal does not affect vascular function in young, healthy adult humans: a randomized controlled crossover trial

Chronic high sodium intake is a risk factor for cardiovascular disease as it impairs vascular function through an increase in oxidative stress. The objective of this study was to investigate the acute effects of a high-sodium meal (HSM) and antioxidant (AO) cocktail on vascular function. We hypothesized that a HSM would impair endothelial function, and increase arterial stiffness and wave reflection, while ingestion of the AO cocktail would mitigate this response. Healthy adults ingested either an AO cocktail (vitamin C, E, alpha-lipoic acid) or placebo (PLA) followed by a HSM (1500 mg) in a randomized crossover blinded design. Blood pressure (BP), endothelial function (flow-mediated dilation; FMD) and measures of arterial stiffness (pulse wave velocity; PWV) and wave reflection (augmentation index; AIx) were made at baseline and 30, 60, 90, and 120 min after meal consumption. Forty-one participants (20M/21W; 24 ± 1 years; BMI 23.4 ± 0.4 kg/m²) completed the study. Mean BP increased at 120 min relative to 60 min (60 min: 79 ± 1; 120 min: 81 ± 1 mmHg; time effect P = .01) but was not different between treatments (treatment × time interaction P = .32). AIx decreased from baseline (time effect P < .001) but was not different between treatments (treatment × time interaction P = .31). PWV (treatment × time interaction, P = .91) and FMD (treatment × time interaction P = .65) were also not different between treatments. In conclusion, a HSM does not acutely impair vascular function suggesting young healthy adults can withstand the acute impact of sodium on the vasculature and therefore, the AO cocktail is not necessary to mitigate the response.

Self-reported sleep quality is associated with central hemodynamics in healthy individuals

BACKGROUND

Insufficient sleep is associated with arterial stiffness and elevated cardiovascular disease risk. Central hemodynamics are influenced by arterial stiffness, yet independently predict cardiovascular risk. Relationships between sleep characteristics and central hemodynamic parameters are largely unexplored. We aimed to characterize the relationship between self-reported sleep quality and central hemodynamics in healthy individuals. To explore the secondary hypothesis that impairments in glucose metabolism may underlie relationships between sleep and central hemodynamic variables, we also explored associations between self-reported sleep quality and fasting blood glucose values.

METHODS

Thirty-one healthy study subjects (20 to 69 years, 17 men) were free from metabolic or cardiovascular disease and did not take sleep medication. Self-reported sleep quality was obtained using the Pittsburgh Sleep Quality Index (PSQI) with normal sleepers defined by PSQI scores 0-5 and poor sleepers by PSQI score > 5. Relationships were assessed between PSQI, central hemodynamic profiles (systolic and diastolic blood pressures, pulse and augmentation pressures, augmentation index) estimated from oscillometric pulse wave analysis, and blood glucose values.

RESULTS

Central pulse pressure was significantly elevated in poor (PSQI score > 5) compared with that in normal (PSQI scores 0-5) sleepers (P < 0.05). Linear regression models, adjusted for age, gender, and body mass index, demonstrated PSQI score to be an independent predictor (P < 0.05) of both central pulse (β = 0.469) and augmentation (β = 0.364) pressures. Global PSQI scores were not related to fasting blood glucose values (r = 0.045; P > 0.05).

CONCLUSIONS

Significant relationships between central pulse and augmentation pressures and self-reported sleep quality highlight the importance of considering sleep when examining lifestyle contributors to central hemodynamics.

Hemodynamic Response to Glucose-Insulin Infusion and Meals during Hemodialysis

Introduction: Intradialytic nutrition may improve nutritional status and reduce mortality in patients on maintenance hemodialysis (HD) but has been associated with adverse events, mainly hemodynamic instability. Some dialysis centers therefore restrict intradialytic meals. In 2 clinical studies, we investigated the effects of intradialytic glucose-insulin infusion (GII) and meal intake on blood pressure (BP), pulse wave velocity (PWV), pulse wave analysis (PWA), and cardiac output (CO). PWA yielded augmentation index standardized with heart rate 75 (AIx@HR75). Methods: In the GII study, 12 nondiabetic HD patients had BP, PWV, PWA, and CO measured during 3 HD sessions: standard HD, HD with glucose infusion, and HD with GII. In the Meal study, 12 nondiabetic patients had BP and PWA measured on 3 study days: meal alone (non-HD), meal and HD, 2 meals and HD. Twelve matched healthy controls completed the non-HD day. Findings: In the GII study, glucose or GII had no additional effects on hemodynamic parameters compared with standard HD. HD resulted in a decrease in systolic BP of 13%, in diastolic BP of 9%, in AIx@HR75 of 17%, and CO of 18%. PWV was reduced by only 5%. In the Meal study, a meal alone did not change BP, whereas the combined influence of HD and meal intake reduced systolic BP with 22% and diastolic BP with 19%. Furthermore, AIx@HR75 decreased by 37% on HD days and by 36% in controls, but was unaffected on non-HD days. Discussion: In the GII study, HD significantly reduced BP, AIx@75, and CO, whereas PWV remained almost constant. No additional effects were observed by concomitant GII during HD. BP reductions seemed larger in the Meal study compared with the GII study. Taken together, HD per se appears as the main discriminant for intradialytic hypotension but in hemodynamically unstable patients the timing and route of nutrition provision should be considered carefully.

The Effects of Nut Consumption on Vascular Function

Vascular stiffness can be measured using numerous techniques including assessments of central haemodynamics, aortic arterial stiffness, and indices of aortic wave reflection and endothelial dilatation. Impaired vascular function is associated with increased risk of cardiovascular disease (CVD). Epidemiological studies indicate that regular nut consumption reduces CVD risk, with one of the proposed mechanisms being via improvements in vascular function. This narrative review summarizes the evidence from a systematic search of the literature of the effects of tree nut and peanut consumption on measures of vascular function excluding flow mediated dilatation. A total of 16 studies were identified, with a mix of acute controlled studies (n = 3), an uncontrolled pre/post chronic study (n = 1), chronic crossover (n = 7) and parallel studies (n = 5). Nut types tested included almonds, peanuts, pine nuts, pistachios and walnuts, with dose and length of supplementation varying greatly across studies. Most studies (n = 13) included individuals at risk for CVD, according to various criteria. Findings were inconsistent, with ten studies reporting no significant changes in vascular function and six studies (one acute and five chronic studies) reporting improvements in at least one measure of vascular function. In summary, nuts have the potential to improve vascular function and future studies should consider the population, dose and length of nut supplementation as well as suitability of the different vascular function techniques.

Resting sympathetic activity is associated with the sympathetically mediated component of energy expenditure following a meal

Individuals with high plasma norepinephrine (NE) levels at rest have a smaller reduction in resting energy expenditure (REE) following β‐adrenergic blockade. If this finding extends to the response to a meal, it could have important implications for the role of the sympathetic nervous system in energy balance and weight gain. We hypothesized high muscle sympathetic nerve activity (MSNA) would be associated with a low sympathetically mediated component of energy expenditure following a meal. Fourteen young, healthy adults completed two visits randomized to continuous saline (control) or intravenous propranolol to achieve systemic β‐adrenergic blockade. Muscle sympathetic nerve activity and REE were measured (indirect calorimetry) followed by a liquid mixed meal (Ensure). Measures of energy expenditure continued every 30 min for 5 h after the meal and are reported as an area under the curve (AUC). Sympathetic support of energy expenditure was calculated as the difference between the AUC during saline and β‐blockade (AUC_Propranolol–AUC_Saline, β‐REE) and as a percent (%) of control (AUC_Propranolol÷AUC_Saline × 100). β‐REE was associated with baseline sympathetic activity, such that individuals with high resting MSNA (bursts/100 heart beats) and plasma NE had the greatest sympathetically mediated component of energy expenditure following a meal (MSNA: β‐REE R = −0.58, P = 0.03; %REE R = −0.56, P = 0.04; NE: β‐REE R = −0.55, P = 0.0535; %REE R = −0.54, P = 0.0552). Contrary to our hypothesis, high resting sympathetic activity is associated with a greater sympathetically mediated component of energy expenditure following a liquid meal. These findings may have implications for weight maintenance in individuals with varying resting sympathetic activity.

Ingesting a small amount of beer reduces arterial stiffness in healthy humans

Epidemiological studies reveal a J-shaped association between alcohol consumption and arterial stiffness, with arterial stiffening lower among mild-to-moderate drinkers than heavy drinkers or nondrinkers. This study aimed to examine the effects of ingesting a small amount of beer, corresponding to the amount consumed per day by a mild drinker, on arterial stiffness. Eleven men (20-22 years) participated, in random order and on different days, in four separate trials. The participants each drank 200 or 350 mL of alcohol-free beer (AFB200 and AFB350) or beer (B200 and B350), and were monitored for 90 min postingestion. There were no significant changes in arterial stiffness among trials that ingested AF200 or AF350. However, among trials ingesting B200 and B350, breath alcohol concentrations increased significantly, while indexes of arterial stiffness decreased significantly for approximately 60 min: carotid-femoral pulse wave velocity (B200: -0.6 ± 0.2 m/sec; B350: -0.6 ± 0.2 m/sec); brachial-ankle pulse wave velocity (B200: -53 ± 18 cm/sec; B350: -57 ± 19 cm/sec); and cardio-ankle vascular index (B200: -0.4 ± 0.1 unit; B350: -0.3 ± 0.1 unit). Furthermore, AFB showed no effect on arterial stiffness, regardless of whether or not it contained sugar, and no significant difference in antioxidant capacity was found between AFB and B. This is the first study to demonstrate that acute ingestion of relatively small amounts of beer reduces arterial stiffness (for approximately 60 min). Our data also suggest that the reduction in arterial stiffness induced by ingestion of beer is largely attributable to the effects of alcohol.

Dynamic changes in retinal vessel diameter during acute hyperglycemia in type 1 diabetes

AIMS

To investigate changes in retinal vessel diameter during acute hyperglycemia in patients with type 1 diabetes.

METHODS

We conducted a study on 11 subjects with type 1 diabetes. Euglycemia was maintained for 3h followed by induction of hyperglycemia and simultaneous bolus of rapid acting insulin. Two fundus photos were captured during euglycemia and five fundus photos, blood glucose and blood pressure were taken every 30min for 2.5h post-prandial. Central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) were measured over the study visit and examined using generalized linear mixed models.

RESULTS

In a multivariate mixed model, mean CRAE and CRVE were reduced at 90min post-prandial in both zones B and C. In repeated measures analysis, arterioles exhibited a significant association with change in vessel caliber per change in blood glucose. Inconsistent effects of blood pressure on vessel diameter were also measured.

CONCLUSIONS

We document a change in retinal vessel diameter during acute hyperglycemia in persons with type 1 diabetes. Larger controlled studies are required to further investigate this phenomenon and to more accurately assess if hyperglycemia has direct effects on retinal vessel diameter.

The association between brain-derived neurotrophic factor and central pulse pressure after an oral glucose tolerance test

BACKGROUND

Arterial stiffening blunts postprandial vasodilatation. We hypothesized that brain-derived neurotrophic factor (BDNF) may modulate postprandial central pulse pressure, a surrogate marker for arterial stiffening.

METHODS

A total of 82 non-diabetic subjects received a 75-g oral glucose tolerance test (OGTT) after overnight fasting. Serum BDNF concentrations were determined at 0, 30, and 120min to calculate the area under the curve (AUC). Brachial and central blood pressures were measured using a noninvasive central blood pressure monitor before blood withdrawals at 0 and 120min.

RESULTS

With the median AUC of BDNF of 45(ng/ml)∗h as the cutoff value, the central pulse pressure after glucose intake was significantly higher in the subjects with a low BDNF than in those with a high BDNF (63±16 vs. 53±11mmHg, P=0.003), while the brachial pulse pressure was not significantly different between the 2 groups (P=0.099). In a multivariate linear regression model, a lower AUC of BDNF was an independent predictor of a higher central pulse pressure after oral glucose intake (linear regression coefficient-0.202, 95% confidence interval-0.340 to -0.065, P=0.004).

CONCLUSION

After oral glucose challenge, a lower serum BDNF response is significantly associated with a higher central pulse pressure.

Postprandial Effects of Breakfast Glycemic Index on Vascular Function among Young Healthy Adults: A Crossover Clinical Trial

This study aimed to evaluate the postprandial effects of high and low glycemic index (GI) breakfasts on vascular function. It was a crossover trial that included 40 young healthy adults (50% women), aged 20-40 years, who were recruited at primary care settings. They consumed three experimental breakfasts in randomized order, each one separated by a 1-week washout period: (1) control conditions (only water); (2) low GI (LGI) breakfast (29.4 GI and 1489 KJ energy); and (3) high GI (HGI) breakfast (64.0 GI and 1318 KJ energy). Blood samples were collected at 60 and 120 min after each breakfast to determine glucose and insulin levels. Vascular parameters were measured at 15 min intervals. Augmentation index (AIx) was studied as a primary outcome. Secondary outcomes comprised glucose, insulin, heart rate (HR) and pulse pressures (PPs). We found a trend toward increased AIx, HR and PPs for the HGI versus the LGI breakfast. A significant interaction between the type of breakfast consumed and all measured parameters was identified (p < 0.05) except for central PP. Stratifying data by sex, this interaction remained significant for AIx and augmentation pressure only in males (p < 0.05). In conclusion, breakfast GI could affect postprandial vascular responses in young healthy adults.

Combined effects of physical inactivity and acute hyperglycemia on arterial distensibility

Arterial distensibility, an independent predictor of cardiovascular events, is transiently increased with acute hyperglycemia (AHG) in healthy individuals. Whether this response interacts with physical inactivity remains unknown. We examined the effects of short-term bed rest (BR) on the response of carotid artery distensibility (CD) to AHG, and the influence of underlying changes in insulin resistance and blood volume. CD was assessed with ultrasonography before as well as 30 and 120 minutes following ingestion of 75 g of glucose prior to and after 3 days of BR in 15 healthy male volunteers. Plasma insulin/glucose concentrations and blood volumes were concomitantly determined. On day 4 of BR, blood volume was re-established to pre-BR levels by albumin infusion and CD and insulin/glucose concentrations were determined as in the previous experimental days. Basal CD was not affected by BR. AHG increased CD before and after BR but reached a higher peak increment after BR (12% vs 60% at 30 min OGTT, p=0.028). BR also increased the plasma insulin concentration during AHG ( p=0.007). In regression analyses, plasma insulin and glucose concentrations were positively correlated to CD, particularly after BR ( r=0.31, p<0.05). Restoration of the BR-induced loss (5%) in blood volume did not affect the response of CD to AHG. In conclusion, short-term physical inactivity strongly accentuates the initial increase in CD in response to AHG in healthy individuals. This effect is associated with concomitant increases in circulating insulin concentration attributable to early insulin resistance.

Sources of inaccuracy in the measurement of adult patients' resting blood pressure in clinical settings: a systematic review

BACKGROUND

To interpret blood pressure (BP) data appropriately, healthcare providers need to be knowledgeable of the factors that can potentially impact the accuracy of BP measurement and contribute to variability between measurements.

METHODS

A systematic review of studies quantifying BP measurement inaccuracy. Medline and CINAHL databases were searched for empirical articles and systematic reviews published up to June 2015. Empirical articles were included if they reported a study that was relevant to the measurement of adult patients' resting BP at the upper arm in a clinical setting (e.g. ward or office); identified a specific source of inaccuracy; and quantified its effect. Reference lists and reviews were searched for additional articles.

RESULTS

A total of 328 empirical studies were included. They investigated 29 potential sources of inaccuracy, categorized as relating to the patient, device, procedure or observer. Significant directional effects were found for 27; however, for some, the effects were inconsistent in direction. Compared with true resting BP, significant effects of individual sources ranged from -23.6 to +33 mmHg SBP and -14 to +23 mmHg DBP.

CONCLUSION

A single BP value outside the expected range should be interpreted with caution and not taken as a definitive indicator of clinical deterioration. Where a measurement is abnormally high or low, further measurements should be taken and averaged. Wherever possible, BP values should be recorded graphically within ranges. This may reduce the impact of sources of inaccuracy and reduce the scope for misinterpretations based on small, likely erroneous or misleading, changes.

Influence of sympathetic nerve activity on aortic hemodynamics and pulse wave velocity in women

Central (aortic) blood pressure, arterial stiffness, and sympathetic nerve activity increase with age in women. However, it is unknown if the age-related increase in sympathetic activity influences aortic hemodynamics and carotid-femoral pulse wave velocity (cfPWV), an index of central aortic stiffness. The goal of this study was to determine if aortic hemodynamics and cfPWV are directly influenced by sympathetic nerve activity by measuring aortic hemodynamics, cfPWV, and muscle sympathetic nerve activity (MSNA) in women before and during autonomic ganglionic blockade with trimethaphan camsylate. We studied 12 young premenopausal (23 ± 4 yr) and 12 older postmenopausal (57 ± 3 yr) women. These women did not differ in body mass index or mean arterial pressure (P > 0.05 for both). At baseline, postmenopausal women had higher aortic pulse pressure, augmented pressure, augmentation index adjusted for a heart rate of 75 beats/min, wasted left ventricular pressure energy, and cfPWV than young women (P < 0.05). During ganglionic blockade, postmenopausal women had a greater decrease in these variables in comparison to young women (P < 0.05). Additionally, baseline MSNA was negatively correlated with the reductions in aortic pulse pressure, augmented pressure, and wasted left ventricular pressure energy during ganglionic blockade in postmenopausal women (P < 0.05) but not young women. Baseline MSNA was not correlated with the changes in augmentation index adjusted for a heart rate of 75 beats/min or cfPWV in either group (P > 0.05 for all). Our results suggest that some aortic hemodynamic parameters are influenced by sympathetic activity to a greater extent in older postmenopausal women than in young premenopausal women.NEW & NOTEWORTHY Autonomic ganglionic blockade results in significant decreases in multiple aortic pulse wave characteristics (e.g., augmented pressure) and central pulse wave velocity in older postmenopausal women but not in young premenopausal women. Certain aortic pulse wave parameters are negatively influenced by sympathetic activity to a greater extent in older postmenopausal women.

Eating and arterial endothelial function: a meta-analysis of the acute effects of meal consumption on flow-mediated dilation

Given that endothelial dysfunction precedes atherosclerotic cardiovascular disease, exploring the parameters that modify postprandial flow-mediated dilation (FMD) is important for public health. The objectives of the study are to estimate the population effect of meal ingestion on FMD and to determine how the effect varied based on patient characteristics and modifiable methodological features. Articles published before June 2015 were located using MEDLINE, PubMed and Web of Science. One hundred fifty-four effects were derived from 78 articles involving 2,548 subjects were selected. Included articles required measurement of FMD in adults before and after meal ingestion. Effects were analysed using an unstandardized mean gain random effects model, and significant moderators were analysed using meta-regression. Meal consumption significantly reduced FMD by a heterogeneous mean effect size delta (Δ) of -2.03 (95% CI: [-2.28, -1.77]), an ~2% reduction in FMD. FMD reductions were larger among normal weight individuals, males, those with a cardio-metabolic disorder, those with elevated baseline FMD, and individuals with impaired glucose tolerance at baseline. Macronutrient meal ingestion significantly reduced FMD, an effect that was moderated by body mass index, sex and two-way interactions between disease status and both baseline FMD and baseline blood glucose levels.

Postprandial effect of breakfast glycaemic index on vascular function, glycaemic control and cognitive performance (BGI study): study protocol for a randomised crossover trial

Background

Postprandial glycaemic response affects cognitive and vascular function. The acute effect of breakfast glycaemic index on vascular parameters is not sufficiently known. Also, the influence of breakfasts with different glycaemic index on cognitive performance has been mostly studied in children and adolescents with varying results. Therefore, the purpose of this study is to analyse the postprandial effect of high and low glycaemic index breakfasts on vascular function and cognitive performance and their relationship with postprandial glycaemic response in healthy young adults.

Methods/design

This is a crossover clinical trial targeting adults (aged 20–40 years, free from cardiovascular disease) selected by consecutive sampling at urban primary care health clinics in Salamanca (Spain). Each subject will complete three interventions with a washout period of one week: a control condition (consisting of water); a low glycaemic index breakfast (consisting of dark chocolate, walnuts, yogurt and an apple, with an overall glycaemic index of 29.4 and an energy contribution of 1489 kJ); and a high glycaemic index breakfast (consisting of bread, grape juice and strawberry jam, with an overall glycaemic index of 64.0 and an energy contribution of 1318 kJ). The postprandial effect will be assessed at 60 and 120 minutes from each breakfast including blood sampling and cognitive performance evaluations. Measurements of arterial stiffness and central haemodynamic parameters will be taken at –10, 0, 15, 30, 45, 60, 75, 90, 105 and 120 minutes.

Discussion

The differences in postprandial glycaemic response due to breakfast glycaemic index could affect vascular parameters and cognitive performance with important applications and implications for the general population. This could provide necessary information for the establishment of new strategies in terms of nutritional education and work performance improvement.

Trial registration

ClinicalTrials.gov: NCT02616276. Registered on 19 November 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1649-x) contains supplementary material, which is available to authorized users.

High trans but not saturated fat beverage causes an acute reduction in postprandial vascular endothelial function but not arterial stiffness in humans

A diet high in trans-fatty acids (TFAs) is associated with a higher risk of cardiovascular disease (CVD) than a diet high in saturated fatty acids (SFAs), but the mechanisms remain unclear. We hypothesized that a beverage high in TFAs would cause a larger reduction in postprandial endothelial function and an increase in arterial stiffness, in part from greater reductions in insulin sensitivity, compared with a beverage high in SFAs. Eleven healthy adults (aged 47±5 years) ingested a warm test beverage (520 kcal, 56 g total fat, 5 g carbohydrate, 1 g protein) high in either TFAs or SFAs in a randomized cross-over study. Ingestion of the beverage high in TFAs (p<0.01) but not high in SFAs (p=0.49) decreased endothelial function (brachial artery flow-mediated dilation, mmΔ) at 3-4 hours (p<0.01 for time; p=0.034 for interaction), but did not alter aortic stiffness or carotid β-stiffness. The homeostasis model of insulin resistance (interaction p=0.062) tended to decrease after SFAs but not TFAs. A beverage high in TFAs but not SFAs results in a postprandial reduction in endothelial function and a trend for decreased insulin sensitivity, potentially explaining the higher risk of CVD with a diet high in TFAs.

Reduction of Central Blood Pressure in Response to Oral Glucose Loading Is Blunted in Patients With Diabetes Mellitus

BACKGROUND

Recent studies have shown that arterial stiffness is reduced after meal intake. We evaluated the acute response of central hemodynamics to glucose loading and the variation in their responses among normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and diabetes mellitus (DM).

METHODS

The study enrolled 85 patients with known or suspected coronary artery disease who underwent a 75-g oral glucose tolerance test. Central hemodynamic measurements were assessed using radial applanation tonometry at fasting, 60, and 120 minutes after glucose loading.

RESULTS

Glucose loading decreased the augmentation index normalized to a heart rate of 75 bpm (AIx@75) (81.6±13.9 to 74.5±14.1%, P < 0.01) and central systolic blood pressure (SBP) (115±22 to 109±21mm Hg, P < 0.01) at 120 minutes without a significant change in brachial SBP (126±25 to 125±25mm Hg, P = 0.93). Glucose loading decreased central SBP in NGT and IGT groups but did not affect the DM group. Change in AIx@75 at 120 minutes after glucose loading was blunted in IGT and DM groups compared with the NGT group (-5.7±4.4 vs. -3.6±4.1 vs. -9.3±6.2%, P < 0.01). Multivariate logistic regression analysis identified DM as an independent factor associated with the presence of blunted response of AIx to glucose loading.

CONCLUSIONS

Oral glucose loading decreased central SBP and AIx@75 without a significant change in brachial SBP, and these central hemodynamic responses were blunted in patients with DM.

Postprandial effects on arterial stiffness parameters in healthy young adults

Postprandial lipemia has been associated with acute endothelial dysfunction. Endothelial dysfunction, in turn, is associated with increased arterial stiffness. However, the relationship between postprandial lipemia and acute changes in arterial stiffness has not been extensively investigated. Therefore, we conducted a pilot study on the effects of postprandial lipemia on arterial stiffness in 19 healthy young adults before and after consumption of a high-fat mixed meal. Arterial stiffness was assessed locally with echo-tracking carotid arterial strain (CAS) and globally with carotid–femoral pulse wave velocity (PWV). As assessed by these two benchmark parameters, arterial stiffness did not differ significantly postprandially. However, the arterial distension period (ADP) was significantly lower 2 hours after mixed meal ingestion. In addition, slopes of carotid artery area (CAA) curves were significantly steeper postprandially. Therefore, we concluded that ADP may be a more sensitive marker of arterial stiffness in healthy young adults when compared to PWV and CAS.

Effect of sodium and potassium supplementation on vascular and endothelial function: a randomized controlled trial

BACKGROUND

It is known that increased potassium and reduced sodium intakes can improve postprandial endothelial function. However, the effect of increasing potassium in the presence of high sodium in the postprandial state is not known.

OBJECTIVE

We aimed to determine the effect of high potassium and high sodium on postprandial endothelial function as assessed by using flow-mediated dilatation (FMD) and arterial compliance as assessed by using pulse wave velocity (PWV) and central augmentation index (AIx).

DESIGN

Thirty-nine healthy, normotensive volunteers [21 women and 18 men; mean ± SD age: 37 ± 15 y; BMI (in kg/m(2)): 23.0 ± 2.8] received a meal with 3 mmol K and 65 mmol Na (low-potassium, high-sodium meal (LKHN)], a meal with 38 mmol K and 65 mmol Na [high-potassium, high-sodium meal (HKHN)], and a control meal with 3 mmol K and 6 mmol Na (low-potassium, low-sodium meal) on 3 separate occasions in a randomized crossover trial. Brachial artery FMD, carotid-femoral PWV, central AIx, and blood pressure (BP) were measured while participants were fasting and at 30, 60, 90, and 120 min after meals.

RESULTS

Compared with the LKHN, the addition of potassium (HKHN) significantly attenuated the postmeal decrease in FMD (P-meal by time interaction < 0.05). FMD was significantly lower after the LKHN than after the HKHN at 30 min (P < 0.01). AIx decreased after all meals (P < 0.05). There were no significant differences in AIx, PWV, or BP between treatments over time.

CONCLUSION

The addition of potassium to a high-sodium meal attenuates the sodium-induced postmeal reduction in endothelial function as assessed by FMD. This trial was registered at http://www.anzctr.org.au/ as ACTRN12613000772741.