Exaggerated Exercise Blood Pressure as a Marker of Baroreflex Dysfunction in Normotensive Metabolic Syndrome Patients

Introduction

Exaggerated blood pressure response to exercise (EEBP = SBP ≥ 190 mmHg for women and ≥210 mmHg for men) during cardiopulmonary exercise test (CPET) is a predictor of cardiovascular risk. Sympathetic hyperactivation and decreased baroreflex sensitivity (BRS) seem to be involved in the progression of metabolic syndrome (MetS) to cardiovascular disease.

Objective

To test the hypotheses: (1) MetS patients within normal clinical blood pressure (BP) may present EEBP response to maximal exercise and (2) increased muscle sympathetic nerve activity (MSNA) and reduced BRS are associated with this impairment.

Methods

We selected MetS (ATP III) patients with normal BP (MetS_NT, n = 27, 59.3% males, 46.1 ± 7.2 years) and a control group without MetS (C, n = 19, 48.4 ± 7.4 years). We evaluated BRS for increases (BRS+) and decreases (BRS−) in spontaneous BP and HR fluctuations, MSNA (microneurography), BP from ambulatory blood pressure monitoring (ABPM), and auscultatory BP during CPET.

Results

Normotensive MetS (MetS_NT) had higher body mass index and impairment in all MetS risk factors when compared to the C group. MetS_NT had higher peak systolic BP (SBP) (195 ± 17 vs. 177 ± 24 mmHg, P = 0.007) and diastolic BP (91 ± 11 vs. 79 ± 10 mmHg, P = 0.001) during CPET than C. Additionally, we found that MetS patients with normal BP had lower spontaneous BRS− (9.6 ± 3.3 vs. 12.2 ± 4.9 ms/mmHg, P = 0.044) and higher levels of MSNA (29 ± 6 vs. 18 ± 4 bursts/min, P < 0.001) compared to C. Interestingly, 10 out of 27 MetS_NT (37%) showed EEBP (MetS_NT+), whereas 2 out of 19 C (10.5%) presented (P = 0.044). The subgroup of MetS_NT with EEBP (MetS_NT+, n = 10) had similar MSNA (P = 0.437), but lower BRS+ (P = 0.039) and BRS− (P = 0.039) compared with the subgroup without EEBP (MetS_NT−, n = 17). Either office BP or BP from ABPM was similar between subgroups MetS_NT+ and MetS_NT−, regardless of EEBP response. In the MetS_NT+ subgroup, there was an association of peak SBP with BRS− (R = −0.70; P = 0.02), triglycerides with peak SBP during CPET (R = 0.66; P = 0.039), and of triglycerides with BRS− (R = 0.71; P = 0.022).

Conclusion

Normotensive MetS patients already presented higher peak systolic and diastolic BP during maximal exercise, in addition to sympathetic hyperactivation and decreased baroreflex sensitivity. The EEBP in MetS_NT with apparent well-controlled BP may indicate a potential depressed neural baroreflex function, predisposing these patients to increased cardiovascular risk.

Effect of Metaboreflex on Cardiovascular System in Subjects of Metabolic Syndrome

INTRODUCTION

Metaboreflex is a reflex in which muscle receptors send signals regarding metabolic (metabolites accumulation like lactic acid, potassium, adenosine) conditions of the muscles to nucleus tractus solitarius via afferent III and IV fibres to cause haemodynamic adjustments in order to regulate blood flow on the basis of the status of contracting muscle. Dysregulation in its mechanism in metabolic syndrome is demonstrated.

AIM

To study the effect of metaboreflex by both isometric and rhythmic handgrip exercise on CVS parameters {Blood Pressure (BP), Cardiac Output (CO) and Systemic Vascular Resistance (SVR)} in subjects of metabolic syndrome.

MATERIALS AND METHODS

In this study, 27 subjects aged 25 to 45 years were enrolled after ethical clearance and proper consent. They were divided into: a) subjects without metabolic syndrome; and b) subjects with metabolic syndrome. Impedance cardiovasography was done to assess cardiac parameters (systolic and diastolic blood pressure, cardiac output, systemic vascular resistance). Pre-exercise parameters were assessed followed by isometric exercise and post-isometric exercise parameter measurement. Again after rest, rhythmic exercise was followed. Finally post exercise parameters were assessed. Student paired t-test for comparison between pre and post exercise parameters were done.

RESULTS

Changes in diastolic BP following exercise were statistically significant in subjects without metabolic syndrome (p-value 0.01 and 0.001 following isometric and rhythmic exercise respectively). In subjects with metabolic syndrome also these changes were significant, but to a lesser extent (p-value 0.1 and 0.01 respectively for isometric and rhythmic exercise). Changes in systolic BP following exercise were statistically significant in subjects without metabolic syndrome (p-value 0.001 and 0.001 following isometric and rhythmic exercise respectively). In subjects with metabolic syndrome also these changes were significant (p-value 0.01 and 0.001 respectively for isometric and rhythmic exercise).

CONCLUSION

Diminished pressor response is found after exercise in subjects with metabolic syndrome.

Predictors for diagnosing metabolic syndrome among hypertensive patients in a tertiary care centre

Metabolic syndrome (MS) was present in 71% of adult hypertensive subjects according to modified National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP-III) criteria in a tertiary care health centre. Female gender and higher body mass index (BMI) were predictors for MS among these patients. BMI cut off of 23 (overweight) had sensitivity of 94% and positive predictive value of 75% for diagnosing MS among them.

Meta-analysis of prospective studies on the effects of nut consumption on hypertension and type 2 diabetes mellitus

BACKGROUND

Inconclusive reports have been published on the consumption of nuts and the risk of hypertension and type 2 diabetes mellitus (T2DM). We performed a meta-analysis of prospective studies to assess the effects of nut consumption on hypertension and T2DM risks.

METHODS

A PUBMED and EMBASE database search was performed. Summary relative risks (SRRs) and 95% confidence intervals (CIs) were calculated using a random-effects model. Q and I2 statistics were used to examine between-study heterogeneity.

RESULTS

A total of eight articles with nine prospective cohort studies (three hypertension studies and six T2DM studies) were selected. Using random effects models, we found that compared with never/rare consumers of nuts, those consuming >2 servings per week had an 8% lower risk of hypertension (SRR = 0.92, 95% CI: 0.87-0.97, P(heterogeneity)  = 0.590, I2  = 0%), while consumption of nuts at one serving per week had similar risk (SRR = 0.97, 95% CI: 0.83-1.13). In addition, nuts consumption was not associated with risk of T2DM (SRRs = 0.98, 95% CI: 0.84-1.15; P(heterogeneity)  = 0.008, I2  = 67.7%) on the basis of the highest versus lowest analysis. This null association was also shown in the dose-response analysis.

CONCLUSION

Findings from this meta-analysis indicate that consumption of nuts (>2 servings/week) may be inversely associated with hypertension risk, but not with T2DM risk.

Exercise-mediated vasodilation in human obesity and metabolic syndrome: effect of acute ascorbic acid infusion

We tested the hypothesis that infusion of ascorbic acid (AA), a potent antioxidant, would alter vasodilator responses to exercise in human obesity and metabolic syndrome (MetSyn). Forearm blood flow (FBF, Doppler ultrasound) was measured in lean, obese, and MetSyn adults (n = 39, 32 ± 2 yr). A brachial artery catheter was inserted for blood pressure monitoring and local infusion of AA. FBF was measured during dynamic handgrip exercise (15% maximal effort) with and without AA infusion. To account for group differences in blood pressure and forearm size, and to assess vasodilation, forearm vascular conductance (FVC = FBF/mean arterial blood pressure/lean forearm mass) was calculated. We examined the time to achieve steady-state FVC (mean response time, MRT) and the rise in FVC from rest to steady-state exercise (Δ, exercise - rest) before and during acute AA infusion. The MRT (P = 0.26) and steady-state vasodilator responses to exercise (ΔFVC, P = 0.31) were not different between groups. Intra-arterial infusion of AA resulted in a significant increase in plasma total antioxidant capacity (174 ± 37%). AA infusion did not alter MRT or steady-state FVC in any group (P = 0.90 and P = 0.85, respectively). Interestingly, higher levels of C-reactive protein predicted longer MRT (r = 0.52, P < 0.01) and a greater reduction in MRT with AA infusion (r = -0.43, P = 0.02). We concluded that AA infusion during moderate-intensity, rhythmic forearm exercise does not alter the time course or magnitude of exercise-mediated vasodilation in groups of young lean, obese, or MetSyn adults. However, systemic inflammation may limit the MRT to exercise, which can be improved with AA.

Neural control of blood flow during exercise in human metabolic syndrome

α-Adrenergic-mediated vasoconstriction is greater during simulated exercise in animal models of metabolic syndrome (MetSyn) when compared with control animals. In an attempt to translate such findings to humans, we hypothesized that adults with MetSyn (n = 14, 35 ± 3 years old) would exhibit greater α-adrenergic responsiveness during exercise when compared with age-matched healthy control subjects (n = 16, 31 ± 3 years old). We measured muscle sympathetic nerve activity (MSNA; microneurography) and forearm blood flow (Doppler ultrasound) during dynamic forearm exercise (15% of maximal voluntary contraction). α-Adrenergic agonists (phenylephrine and clonidine) and an antagonist (phentolamine) were infused intra-arterially to assess α-adrenergic receptor responsiveness and restraint, respectively. Resting MSNA was ∼35% higher in adults with MetSyn (P < 0.05), but did not change in either group with dynamic exercise. Clonidine-mediated vasoconstriction was greater in adults with MetSyn (P < 0.01). Group differences in vascular responses to phenylephrine and phentolamine were not detected (P > 0.05). Interestingly, exercise-mediated vasodilatation was greater in MetSyn (P < 0.05). Adults with MetSyn exhibit greater resting MSNA and clonidine-mediated vasoconstriction, yet preserved functional sympatholysis and higher exercise blood flow during low-intensity hand-grip exercise when compared with age-matched healthy control subjects. These results suggest that adults with MetSyn exhibit compensatory vascular control mechanisms capable of preserving blood flow responses to exercise in the face of augmented sympathetic adrenergic activity.

Mechanical and metabolic reflex activation of the sympathetic nervous system in younger adults with metabolic syndrome

AIM

Based on reports of exaggerated blood pressure responses to whole-body exercise in patients with metabolic syndrome (MetSyn), we tested the hypothesis that MetSyn adults would exhibit augmented sympathetic and pressor responses to mechanoreflex and metaboreflex activation when compared with healthy, age-matched control subjects.

METHODS

We studied 12 adults with MetSyn (34±3years) and 12 healthy control subjects (34±3years). Heart rate (HR; ECG), blood pressure (BP; finger photoplethysmography), and MSNA (microneurography of the peroneal nerve) were measured during: (1) static handgrip exercise at 15% of maximal voluntary contraction (MVC), and (2) static handgrip exercise at 30% MVC to fatigue, followed by post-exercise ischemia (PEI). Increases in MSNA, HR, and BP were assessed.

RESULTS

During static exercise at both 15 and 30% MVC, increases in MSNA, HR, and BP were not different between groups. MSNA remained significantly elevated from baseline during PEI and responses were not different between groups.

CONCLUSION

Sympathetic and pressor responses to mechanoreflex and metaboreflex activation are not augmented in younger adults with MetSyn.

RETRACTED: Nut consumption with risk of hypertension and type 2 diabetes mellitus: A meta-analysis of prospective cohort studies

Background

The consumption of nuts was reported to be associated with risk of hypertension and type 2 diabetes mellitus (T2DM), but the results were inconclusive. The aim of this study was to systematically examine longitudinal studies investigating nut intake in relation to risk of hypertension and T2DM.

Methods

A systematic search of the PubMed and EMBASE databases to 31 March 2013 was performed. Reference lists of retrieved articles were also screened. Summary relative risks (SRRs) and 95% confidence intervals (CIs) were calculated using a random-effects model. Q and I2 statistics were used to examine between-study heterogeneity.

Results

A total of nine prospective cohort studies (three for hypertension and six for T2DM) were identified. Using random effects models, we found that based on the highest vs lowest analysis, nut consumption were inversely associated with risk of hypertension (SRR = 0.84, 95% CI: 0.76–0.93, pheterogeneity = 0.831, I2 = 0%). Dose-response analyses indicated that nut consumption at more than two servings/wk, but not ne serving/wk, had a preventative role in the hypertension. In addition, nut consumption was not associated with risk of T2DM (SRRs = 0.98, 95% CI: 0.84–1.15; pheterogeneity = 0.008, I2 = 67.7%) on the basis of the highest vs lowest analysis. This null association was also shown in the dose-response analysis.

Conclusion

In our meta-analysis, nut consumption is found to be inversely associated with hypertension risk but is not associated with the risk of T2DM.

Increased mean arterial pressure response to dynamic exercise in normotensive subjects with multiple metabolic risk factors

Metabolic syndrome (MS) may influence vascular reactivity and might cause an excessive increase in blood pressure (BP) during dynamic exercise. We examined this hypothesis in 698 normotensive men (mean age: 43 years) free of cardiovascular disease, diabetes mellitus and renal disease. The response of BP to exercise was assessed by the mean arterial pressure (MAP) during bicycle ergometry. The MAP values were expressed as z-scores normalized to the relative increases in heart rate. High-normal BP, dyslipidemia and hyperglycemia were diagnosed according to the Japan-specific MS criteria. The z-score of MAP was significantly higher in subjects with high-normal BP (+0.57, P<0.001), dyslipidemia (+0.18, P<0.001) and hyperglycemia (+0.24, P<0.001) than in those without MS component (-0.38). In the high-normal BP subjects, the addition of dyslipidemia and/or hyperglycemia was associated with a progressive increase in the z-score of exercise MAP, whereas no such association was observed in the normal-BP subjects (P=0.033, two-way ANOVA). Multivariate regression analysis revealed that a greater number of MS components (β=0.102, P=0.010) was an independent determinant of increased MAP z-score after adjustment for potential confounders, including age (β=0.123, P<0.001), body mass index (β=0.145, P<0.001) and high-normal BP (β=0.410, P<0.001). These results suggest that accumulation of MS components may alter vascular structure and function and lead to the significant elevation of MAP during dynamic exercise even before clinical manifestation of arterial hypertension.