Marcelo Rodrigues dos Santos

Glu298Asp eNOS gene polymorphism causes attenuation in nonexercising muscle vasodilatation

The influence of Glu298Asp endothelial nitric oxide synthase (eNOS) polymorphism in exercise-induced reflex muscle vasodilatation is unknown. We hypothesized that nonexercising forearm blood flow (FBF) responses during handgrip isometric exercise would be attenuated in individuals carrying the Asp298 allele. In addition, these responses would be mediated by reduced eNOS function and NO-mediated vasodilatation or sympathetic vasoconstriction. From 287 volunteers previously genotyped, we selected 33 healthy individuals to represent three genotypes: Glu/Glu [n = 15, age 43 +/- 3 yr, body mass index (BMI) 22.9 +/- 0.3 kg/m(2)], Glu/Asp (n = 9, age 41 +/- 3 yr, BMI 23.7 +/- 1.0 kg/m(2)), and Asp/Asp (n = 9, age 40 +/- 4 yr, BMI 23.5 +/- 0.9 kg/m(2)). Heart rate (HR), mean blood pressure (MBP), and FBF (plethysmography) were recorded for 3 min at baseline and 3 min during isometric handgrip exercise. Baseline HR, MBP, FBF, and forearm vascular conductance (FVC) were similar among genotypes. FVC responses to exercise were significantly lower in Asp/Asp when compared with Glu/Asp and Glu/Glu (Delta = 0.07 +/- 0.14 vs. 0.64 +/- 0.20 and 0.57 +/- 0.09 units, respectively; P = 0.002). Further studies showed that intra-arterial infusion of NG-monomethyl-L-arginine (L-NMMA) did not change FVC responses to exercise in Asp/Asp, but significantly reduced FVC in Glu/Glu (Delta = 0.79 +/- 0.14 vs. 0.14 +/- 0.09 units). Thus the differences between Glu/Glu and Asp/Asp were no longer observed (P = 0.62). l-NMMA + phentolamine increased similarly FVC responses to exercise in Glu/Glu and Asp/Asp (P = 0.43). MBP and muscle sympathetic nerve activity increased significant and similarly throughout experimental protocols in Glu/Glu and Asp/Asp. Individuals who are homozygous for the Asp298 allele of the eNOS enzyme have attenuated nonexercising muscle vasodilatation in response to exercise. This genotype difference is due to reduced eNOS function and NO-mediated vasodilatation, but not sympathetic vasoconstriction.

Mechanisms of Blunted Muscle Vasodilation During Peripheral Chemoreceptor Stimulation in Heart Failure Patients

We described recently that systemic hypoxia provokes vasoconstriction in heart failure (HF) patients. We hypothesized that either the exaggerated muscle sympathetic nerve activity and/or endothelial dysfunction mediate the blunted vasodilatation during hypoxia in HF patients. Twenty-seven HF patients and 23 age-matched controls were studied. Muscle sympathetic nerve activity was assessed by microneurography and forearm blood flow (FBF) by venous occlusion plethysmography. Peripheral chemoreflex control was evaluated through the inhaling of a hypoxic gas mixture (10% O(2) and 90% N(2)). Basal muscle sympathetic nerve activity was greater and basal FBF was lower in HF patients versus controls. During hypoxia, muscle sympathetic nerve activity responses were greater in HF patients, and forearm vasodilatation in HF was blunted versus controls. Phentolamine increased FBF responses in both groups, but the increase was lower in HF patients. Phentolamine and N(G)-monomethyl-l-arginine infusion did not change FBF responses in HF but markedly blunted the vasodilatation in controls. FBF responses to hypoxia in the presence of vitamin C were unchanged and remained lower in HF patients versus controls. In conclusion, muscle vasoconstriction in response to hypoxia in HF patients is attributed to exaggerated reflex sympathetic nerve activation and blunted endothelial function (NO activity). We were unable to identify a role for oxidative stress in these studies.

Abnormal Neurovascular Control in Anabolic Androgenic Steroids Users

PURPOSE Previous studies showed that anabolic androgenic steroids (AAS) increase vascular resistance and blood pressure (BP) in humans. In this study, we tested the hypotheses 1) that AAS users would have increased muscle sympathetic nerve activity (MSNA) and reduced forearm blood flow (FBF) compared with AAS nonusers and 2) that there would be an association between MSNA and 24-h BP. METHODS Twelve AAS users aged 31 +/- 2 yr (means +/- SE) and nine age-matched AAS nonusers aged 29 +/- 2 yr participated in the study. All individuals were involved in strength training for at least 2 yr. AAS was determined by urine test (chromatography-mass spectrometry). MSNA was directly measured by microneurography technique. FBF was measured by venous occlusion plethysmography. BP monitoring consisted of measures of BP for 24 h. RESULTS MSNA was significantly higher in AAS users than that in AAS nonusers (29 +/- 3 vs 20 +/- 1 bursts per minute, P = 0.01). FBF (1.92 +/- 0.17 vs 2.77 +/- 0.24 mL x min(-1) x 100 mL(-1), P = 0.01) and forearm vascular conductance (2.01 +/- 0.17 vs 2.86 +/- 0.31 U, P = 0.02) were significantly lower in AAS users than that in AAS nonusers. Systolic (131 +/- 4 vs 120 +/- 3 mm Hg, P = 0.001), diastolic (74 +/- 4 vs 68 +/- 3 mm Hg, P = 0.02), and mean BP (93 +/- 4 vs 86 +/- 3 mm Hg, P = 0.005) and heart rate (74 +/- 3 vs 68 +/- 3 bpm, P = 0.02) were significantly higher in AAS users when compared with AAS nonusers. Further analysis showed that there was a significant correlation between MSNA and 24-h mean BP (r = 0.75, P = 0.002). CONCLUSIONS AAS increases MSNA and reduces muscle blood flow in young individuals. In addition, the increase in BP levels in AAS users is associated with augmented sympathetic outflow. These findings suggest that AAS increases the susceptibility for cardiovascular disease in humans.

Dynamic Cerebral Autoregulation Changes during Sub-Maximal Handgrip Maneuver

Purpose We investigated the effect of handgrip (HG) maneuver on time-varying estimates of dynamic cerebral autoregulation (CA) using the autoregressive moving average technique. Methods Twelve healthy subjects were recruited to perform HG maneuver during 3 minutes with 30% of maximum contraction force. Cerebral blood flow velocity, end-tidal CO2 pressure (PETCO2), and noninvasive arterial blood pressure (ABP) were continuously recorded during baseline, HG and recovery. Critical closing pressure (CrCP), resistance area-product (RAP), and time-varying autoregulation index (ARI) were obtained. Results PETCO2 did not show significant changes during HG maneuver. Whilst ABP increased continuously during the maneuver, to 27% above its baseline value, CBFV raised to a plateau approximately 15% above baseline. This was sustained by a parallel increase in RAP, suggestive of myogenic vasoconstriction, and a reduction in CrCP that could be associated with metabolic vasodilation. The time-varying ARI index dropped at the beginning and end of the maneuver (p<0.005), which could be related to corresponding alert reactions or to different time constants of the myogenic, metabolic and/or neurogenic mechanisms. Conclusion Changes in dynamic CA during HG suggest a complex interplay of regulatory mechanisms during static exercise that should be considered when assessing the determinants of cerebral blood flow and metabolism.

The influence of aetiology on the benefits of exercise training in patients with heart failure

Background Exercise training improves neurovascular control and functional capacity in heart failure (HF) patients. However, the influence of the aetiology on these benefits is unknown. We compared the effects of exercise training on neurovascular control and functional capacity in idiopathic, ischaemic and hypertensive HF patients. Design Subjects consisted of 45 exercise-trained HF patients from our database (2000–2015), aged 40–70 years old, functional class II/III and ejection fraction ≤40%, and they were divided into three groups: idiopathic (n = 11), ischaemic (n = 18) and hypertensive (n = 16). Methods Functional capacity was determined by cardiopulmonary exercise testing. Muscle sympathetic nerve activity (MSNA) was recorded by microneurography. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Results Four months of exercise training significantly reduced MSNA and significantly increased FBF in all groups. However, the relative reduction in MSNA was greater in hypertensive patients compared with that in idiopathic patients (frequency: −34% vs. −15%, p = 0.01; incidence: −31% vs. −12%, p = 0.02). No differences were found between hypertensive patients and ischaemic patients. The relative increase in FBF was greater in hypertensive patients than in ischaemic and idiopathic patients (42% vs. 15% and 17%, respectively, p = 0.02). The relative increase in forearm vascular conductance was greater in hypertensive patients compared with those in ischaemic and idiopathic patients (57% vs. 13% and 26%, respectively, p = 0.001). Exercise training significantly and similarly increased peak oxygen consumption in all groups. Conclusion The exercise-induced improvement in neurovascular control is more pronounced in hypertensive HF patients than in idiopathic and ischaemic HF patients. The increase in functional capacity is independent of aetiology.

Testosterone deficiency increases hospital readmission and mortality rates in male patients with heart failure.

Background Testosterone deficiency in patients with heart failure (HF) is associated with decreased exercise capacity and mortality; however, its impact on hospital readmission rate is uncertain. Furthermore, the relationship between testosterone deficiency and sympathetic activation is unknown. Objective We investigated the role of testosterone level on hospital readmission and mortality rates as well as sympathetic nerve activity in patients with HF. Methods Total testosterone (TT) and free testosterone (FT) were measured in 110 hospitalized male patients with a left ventricular ejection fraction < 45% and New York Heart Association classification IV. The patients were placed into low testosterone (LT; n = 66) and normal testosterone (NT; n = 44) groups. Hypogonadism was defined as TT < 300 ng/dL and FT < 131 pmol/L. Muscle sympathetic nerve activity (MSNA) was recorded by microneurography in a subpopulation of 27 patients. Results Length of hospital stay was longer in the LT group compared to in the NT group (37 ± 4 vs. 25 ± 4 days; p = 0.008). Similarly, the cumulative hazard of readmission within 1 year was greater in the LT group compared to in the NT group (44% vs. 22%, p = 0.001). In the single-predictor analysis, TT (hazard ratio [HR], 2.77; 95% confidence interval [CI], 1.58–4.85; p = 0.02) predicted hospital readmission within 90 days. In addition, TT (HR, 4.65; 95% CI, 2.67–8.10; p = 0.009) and readmission within 90 days (HR, 3.27; 95% CI, 1.23–8.69; p = 0.02) predicted increased mortality. Neurohumoral activation, as estimated by MSNA, was significantly higher in the LT group compared to in the NT group (65 ± 3 vs. 51 ± 4 bursts/100 heart beats; p < 0.001). Conclusion These results support the concept that LT is an independent risk factor for hospital readmission within 90 days and increased mortality in patients with HF. Furthermore, increased MSNA was observed in patients with LT.

Effects of Intradialytic Resistance Exercise on Protein Energy Wasting, Physical Performance and Physical Activity in Ambulatory Patients on Dialysis: A Single‐Center Preliminary Study in a Japanese Dialysis Facility

Patients under hemodialysis present protein‐energy wasting (PEW), which is related with higher mortality rates. The study aimed to determine whether intradialytic resistance exercise training could improve physical performance, physical activity, and PEW in hemodialysis patients. In single center study, 75 hemodialysis patients were enrolled in an intradialytic resistance exercise training consisting of 20 min of adapted leg press, with a gymnastic ball, 3 days/week, during 9 months on the same day of hemodialysis therapy. Physical performance by short physical performance battery (SPPB), physical activity by life space assessment (LSA), and PEW score based on the nomenclature proposed by the International Society of Renal Nutrition and Metabolism in 2008 were assessed at baseline and after 9 months. Intradialytic resistance exercise training significantly improved SPPB score, LSA score, and PEW score (all, P < 0.05). In addition, intradialytic resistance exercise training improved SPPB score in patients with moderate and severe PEW subgroups (P < 0.05), associated with reduced prevalence of the patients with moderate to severe PEW (53% vs. 36%, P < 0.05). Intradialytic resistance exercise training was safe and effective to improve physical performance, physical activity, and PEW in hemodialysis patients.

Regular physical exercise improves cardiac autonomic and muscle vasodilatory responses to isometric exercise in healthy elderly

The objective of this study was to evaluate cardiac autonomic control and muscle vasodilation response during isometric exercise in sedentary and physically active older adults. Twenty healthy participants, 10 sedentary and 10 physically active older adults, were evaluated and paired by gender, age, and body mass index. Sympathetic and parasympathetic cardiac activity (spectral and symbolic heart rate analysis) and muscle blood flow (venous occlusion plethysmography) were measured for 10 minutes at rest (baseline) and during 3 minutes of isometric handgrip exercise at 30% of the maximum voluntary contraction (sympathetic excitatory maneuver). Variables were analyzed at baseline and during 3 minutes of isometric exercise. Cardiac autonomic parameters were analyzed by Wilcoxon and Mann–Whitney tests. Muscle vasodilatory response was analyzed by repeated-measures analysis of variance followed by Tukey’s post hoc test. Sedentary older adults had higher cardiac sympathetic activity compared to physically active older adult subjects at baseline (63.13±3.31 vs 50.45±3.55 nu, P=0.02). The variance (heart rate variability index) was increased in active older adults (1,438.64±448.90 vs 1,402.92±385.14 ms, P=0.02), and cardiac sympathetic activity (symbolic analysis) was increased in sedentary older adults (5,660.91±1,626.72 vs 4,381.35±1,852.87, P=0.03) during isometric handgrip exercise. Sedentary older adults showed higher cardiac sympathetic activity (spectral analysis) (71.29±4.40 vs 58.30±3.50 nu, P=0.03) and lower parasympathetic modulation (28.79±4.37 vs 41.77±3.47 nu, P=0.03) compared to physically active older adult subjects during isometric handgrip exercise. Regarding muscle vasodilation response, there was an increase in the skeletal muscle blood flow in the second (4.1±0.5 vs 3.7±0.4 mL/min per 100 mL, P=0.01) and third minute (4.4±0.4 vs 3.9±0.3 mL/min per 100 mL, P=0.03) of handgrip exercise in active older adults. The results indicate that regular physical activity improves neurovascular control of muscle blood flow and cardiac autonomic response during isometric handgrip exercise in healthy older adult subjects.

Blunted peripheral blood supply and underdeveloped skeletal muscle in Fontan patients: The impact on functional capacity

BACKGROUND Changes in circulatory physiology are common in Fontan patients due to suboptimal cardiac output, which may reduce the peripheral blood flow and impair the skeletal muscle. The objective of this study was to investigate the forearm blood flow (FBF), cross-sectional area (CSA) of the thigh and functional capacity in asymptomatic clinically stable patients undergoing Fontan surgery. METHODS Thirty Fontan patients and 27 healthy subjects underwent venous occlusion plethysmography, magnetic resonance imaging of the thigh musculature and maximal cardiopulmonary exercise testing. Muscle sympathetic nerve activity (MSNA), norepinephrine measures, cardiovascular magnetic resonance, handgrip strength and 6-minute walk test were also performed. RESULTS Fontan patients have blunted FBF (1.59 ± 0.33 vs 2.17 ± 0.52 mL/min/100 mL p < 0.001) and forearm vascular conductance (FVC) (1.69 ± 0.04 vs 2.34 ± 0.62 units p < 0.001), reduced CSA of the thigh (81.2 ± 18.6 vs 116.3 ± 26.4 cm2p < 0.001), lower peak VO2 (29.3 ± 6 vs 41.5 ± 9 mL/kg/min p < 0.001), walked distance (607 ± 60 vs 701 ± 58 m p < 0.001) and handgrip strength (21 ± 9 vs 30 ± 8 kgf p < 0.001). The MSNA (30 ± 4 vs 22 ± 3 bursts/min p < 0.001) and norepinephrine concentration [265 (236-344) vs 222 (147-262) pg/mL p = 0.006] were also higher in Fontan patients. Multivariate linear regression showed FVC (β = 0.653; CI = 0.102-1.205; p = 0.022) and stroke volume (β = 0.018; CI = 0.007-0.029; p = 0.002) to be independently associated with reduced CSA of the thigh adjusted for body mass index. The CSA of the thigh adjusted for body mass index (β = 5.283; CI = 2.254-8.312; p = 0.001) was independently associated with reduced peak VO2. CONCLUSION Patients with Fontan operation have underdeveloped skeletal muscle with reduced strength that is associated with suboptimal peripheral blood supply and diminished exercise capacity.

Resting spontaneous baroreflex sensitivity and cardiac autonomic control in anabolic androgenic steroid users

OBJECTIVES: Misuse of anabolic androgenic steroids in athletes is a strategy used to enhance strength and skeletal muscle hypertrophy. However, its abuse leads to an imbalance in muscle sympathetic nerve activity, increased vascular resistance, and increased blood pressure. However, the mechanisms underlying these alterations are still unknown. Therefore, we tested whether anabolic androgenic steroids could impair resting baroreflex sensitivity and cardiac sympathovagal control. In addition, we evaluate pulse wave velocity to ascertain the arterial stiffness of large vessels. METHODS: Fourteen male anabolic androgenic steroid users and 12 nonusers were studied. Heart rate, blood pressure, and respiratory rate were recorded. Baroreflex sensitivity was estimated by the sequence method, and cardiac autonomic control by analysis of the R-R interval. Pulse wave velocity was measured using a noninvasive automatic device. RESULTS: Mean spontaneous baroreflex sensitivity, baroreflex sensitivity to activation of the baroreceptors, and baroreflex sensitivity to deactivation of the baroreceptors were significantly lower in users than in nonusers. In the spectral analysis of heart rate variability, high frequency activity was lower, while low frequency activity was higher in users than in nonusers. Moreover, the sympathovagal balance was higher in users. Users showed higher pulse wave velocity than nonusers showing arterial stiffness of large vessels. Single linear regression analysis showed significant correlations between mean blood pressure and baroreflex sensitivity and pulse wave velocity. CONCLUSIONS: Our results provide evidence for lower baroreflex sensitivity and sympathovagal imbalance in anabolic androgenic steroid users. Moreover, anabolic androgenic steroid users showed arterial stiffness. Together, these alterations might be the mechanisms triggering the increased blood pressure in this population.