Association of sympathovagal imbalance with obesity indices, and abnormal metabolic biomarkers and cardiovascular parameters

Autonomic Function in Obese Children and Adolescents: Systematic Review and Meta-Analysis

Background: Obesity is invariably accompanied by autonomic dysfunction, although data in pediatric populations are conflicting. Methods: We conducted a systematic review and meta-analysis of 12 studies (totaling 1102 participants) comparing obese and normal-weight subjects (5-18 years of age), defined as body mass index >95th or <85th percentile, respectively. Using a random-effects model, we report the standardized mean differences (SMD) of sympathetic and vagal indices of heart rate variability. Results: Autonomic dysfunction was present in the obesity group, based on the average SMD in the standard deviation of sinus intervals (at -0.5340), and on the ratio of low (LF)- to high (HF)-frequency spectra (at 0.5735). There was no difference in sympathetic activity, but the heterogeneity among the relevant studies weakens this result. SMD in HF (at 0.5876), in the root mean square of successive differences between intervals (at -0.6333), and in the number of times successive intervals exceeded 50 ms divided by the total number of intervals (at -0.5867) indicated lower vagal activity in the obesity group. Conclusions: Autonomic dysfunction is present in obese children and adolescents, attributed to lower vagal activity. Further studies are needed in various pediatric cohorts, placing emphasis on sympathetic activity.

Obesity: Heart Rate Variability during standardized psychosocial stress induction

Obesity is related to a higher risk of cardiovascular diseases (CVD). An altered stress reactivity of the parasympathetic nervous system (PNS) is a promising predictor of CVD and other negative health outcomes. Therefore, the aim of this study was to compare heart rate (HR) and heart rate variability parameters, root mean square successive differences (RMSSD) and power in the high frequency range 0.15-0.4 Hz (HF-HRV), of individuals with obesity and healthy weight controls during psychosocial stress induction. Thirty-four obese men and women (BMI: 33.80 ± 4.62 kg/m²), and thirty-four age- and gender-matched healthy weight controls (BMI: 22.29 ± 1.81 kg/m²) underwent the Trier Social Stress Test (TSST). Before, during, and after the TSST, their HR, RMSSD, and HF-HRV were measured. The individuals with obesity showed a lower stress reactivity in HR, and less stress recovery in RMSSD, compared to healthy weight controls. Obesity appears related to blunted HR reactivity, which is associated with CVD. In addition, impaired recovery of RMSSD also found in individuals with obesity may reflect health-damaging processes as well.

Adipose Tissue and Biological Factors. Possible Link between Lymphatic System Dysfunction and Obesity

The World Health Organization (WHO) has recognised obesity as one of the top ten threats to human health. Obesity is not only a state of abnormally increased adipose tissue in the body, but also of an increased release of biologically active metabolites. Moreover, obesity predisposes the development of metabolic syndrome and increases the incidence of type 2 diabetes (T2DM), increases the risk of developing insulin resistance, atherosclerosis, ischemic heart disease, polycystic ovary syndrome, hypertension and cancer. The lymphatic system is a one-directional network of thin-walled capillaries and larger vessels covered by a continuous layer of endothelial cells that provides a unidirectional conduit to return filtered arterial and tissue metabolites towards the venous circulation. Recent studies have shown that obesity can markedly impair lymphatic function. Conversely, dysfunction in the lymphatic system may also be involved in the pathogenesis of obesity. This review highlights the important findings regarding obesity related to lymphatic system dysfunction, including clinical implications and experimental studies. Moreover, we present the role of biological factors in the pathophysiology of the lymphatic system and we propose the possibility of a therapy supporting the function of the lymphatic system in the course of obesity.

A critical role of hepatic GABA in the metabolic dysfunction and hyperphagia of obesity

Hepatic lipid accumulation is a hallmark of type II diabetes (T2D) associated with hyperinsulinemia, insulin resistance, and hyperphagia. Hepatic synthesis of GABA, catalyzed by GABA-transaminase (GABA-T), is upregulated in obese mice. To assess the role of hepatic GABA production in obesity-induced metabolic and energy dysregulation, we treated mice with two pharmacologic GABA-T inhibitors and knocked down hepatic GABA-T expression using an antisense oligonucleotide. Hepatic GABA-T inhibition and knockdown decreased basal hyperinsulinemia and hyperglycemia and improved glucose intolerance. GABA-T knockdown improved insulin sensitivity assessed by hyperinsulinemic-euglycemic clamps in obese mice. Hepatic GABA-T knockdown also decreased food intake and induced weight loss without altering energy expenditure in obese mice. Data from people with obesity support the notion that hepatic GABA production and transport are associated with serum insulin, homeostatic model assessment for insulin resistance (HOMA-IR), T2D, and BMI. These results support a key role for hepatocyte GABA production in the dysfunctional glucoregulation and feeding behavior associated with obesity.

Effect of air pollution on the autonomic modulation of heart rate in overweight adults

Objective:

To analyze the effect of air pollution on heart rate variability in overweight individuals.

Methods:

A total of 46 adult individuals, both sexes, aged between 18 and 49 years and with body mass index >25kg/m² were analyzed. All volunteers were students from public schools of two cities in the state of São Paulo. The clinical, demographic and anthropometric data of each individual, as well as heart rate variability through time domain, geometric and frequency indices were collected. For the air quality analysis, the following variables were investigated: concentration of carbon dioxide, particulate matter, temperature and relative humidity. The analysis was carried out with descriptive and analytical statistics, adopting a level of significance of 5%.

Results:

There was a reduction in overall heart rate variability in overweight individuals by the following indices: mean standard deviation of all normal RR intervals, long-term standard deviation of continuous RR intervals, ratio of short-and long-term standard deviation of continuous RR intervals. In addition, the indices responsible for parasympathetic control showed a downward trend in their values, as well as the low frequency index, which represented sympathetic action, although not significant.

Conclusion:

Overweight individuals exposed to air pollution had lower heart rate variability than the Control Group.

Increased osteoprotegerin level is associated with impaired cardiovagal modulation in type-2 diabetic patients treated with oral antidiabetic drugs

Background

An increased osteoprotegerin (OPG) level has been reported in both type-2 diabetes mellitus (T2DM) and cardiovascular diease (CVD) that are linked to sympathovagal imbalance (SVI). We explored the link of osteoprotegerin with cardiovagal modulation in T2DM.

Methods

We assessed fasting serum OPG, high-sensitive C-reactive protein (hsCRP), glucose, insulin and lipid profile in patients having T2DM receiving oral antidiabetic drugs (OAD) (n = 42) compared with age, gender and body composition-matched healthy participants without diabetes (n = 42). Rate pressure product (RPP), spectral indices of heart rate variability (HRV) and body composition were recorded in both the groups. Association of HOMA-IR and OPG with various parameters were assessed.

Results

Osteoprotegerin, HOMA-IR, hsCRP, coronary lipid risk factor were significantly increased, markers of cardiovagal modulation (TP, SDNN, RMSSD) were considerably decreased, ratio of low-frequency to high-frequency (LH-HF ratio), the indicator of SVI, and RPP, the marker of myocardial work stress were significantly higher in patients with diabetes, suggesting an overall elevated CVD risks in them. HOMA-IR was correlated with RMSSD, lipid risk factors and OPG. Rise in OPG was correlated with decreased cardiovagal modulation in patients with diabetes. There was significant contribution of OPG in decreasing TP, suggesting impaired cardiovagal modulation.

Conclusion

T2DM patients receiving OAD had higher cardiometabolic risks compared to age, gender and body composition-matched healthy individuals. Increased level of OPG is linked to decreased cardiovagal modulation in T2DM patients.

Risk Factors Associated with Cardiac Autonomic Modulation in Obese Individuals

Obesity leads to an imbalance in the autonomic nervous system, especially in increased sympathetic modulation and decreased vagal tone, and some anthropometric, metabolic, and lifestyle variables may increase the risk of developing cardiovascular disease. Objective. To analyze the association between cardiovascular autonomic modulation and biochemical and anthropometric markers, food intake, and physical activity level in severely obese individuals. Methodology. The present study is a cutout of a randomized clinical trial "Effect of nutritional intervention and olive oil in severe obesity" (DieTBra Trial), where the baseline data were analyzed. Anthropometric data, biochemical exams, heart rate variability (HRV), accelerometry, and 24 h recall (R24H) of obese patients (body mass index BMI ≥35 kg/m2) were collected. Results. 64 obese patients were analyzed, with a mean age of 39.10 ± 7.74 years (27 to 58 years). By HRV analysis, in the frequency domain, the obese had a higher predominance of sympathetic autonomic modulation (low frequency (LF) 56.44 ± 20.31 nu) and lower parasympathetic modulation (high frequency (HF) 42.52 ± 19.18 nu). A negative association was observed between the variables Homeostasis Evaluation Model (HOMA-IR) and HF (p = 0.049). In the physical activity analysis, there was a negative association between moderate to vigorous physical activity and the sympathetic component (p = 0.043), and for sedentary time (ST), there was a negative association with HF (p = 0.049) and LF/HF (p = 0.036) and a positive association with LF (p = 0.014). For multiple linear regression, waist circumference (WC) and HOMA-IR values were negatively associated with HF (β = -0.685, p = 0.010; β = -14.989, p = 0.010; respectively). HOMA-IR (β = 0.141, p = 0.003) and the percentage of lipids ingested (β = -0.030, p = 0.043) were negatively associated with LF/HF. Conclusion. Among the cardiovascular risk variables studied, insulin resistance and central adiposity showed the greatest influence on cardiac autonomic modulation of obese, increasing the risk for cardiovascular disease.

The effects of acetylcholinesterase inhibitors on the heart in acute myocardial infarction and heart failure: From cells to patient reports

Cardiovascular diseases remain a major cause of morbidity and mortality worldwide. Cardiovascular diseases such as acute myocardial infarction, ischaemia/reperfusion injury and heart failure are associated with cardiac autonomic imbalance characterized by sympathetic overactivity and parasympathetic withdrawal from the heart. Increased parasympathetic activity by electrical vagal nerve stimulation has been shown to provide beneficial effects in the case of cardiovascular diseases in both animals and patients by improving autonomic function, cardiac remodelling and mitochondrial function. However, clinical limitations for electrical vagal nerve stimulation exist because of its invasive nature, costly equipment and limited clinical validation. Therefore, novel therapeutic approaches which moderate parasympathetic activities could be beneficial for in the case of cardiovascular disease. Acetylcholinesterase inhibitors inhibit acetylcholinesterase and hence increase cholinergic transmission. Recent studies have reported that acetylcholinesterase inhibitors improve autonomic function and cardiac function in cardiovascular disease models. Despite its potential clinical benefits for cardiovascular disease patients, the role of acetylcholinesterase inhibitors in acute myocardial infarction and heart failure remediation remains unclear. This article comprehensively reviews the effects of acetylcholinesterase inhibitors on the heart in acute myocardial infarction and heart failure scenarios from in vitro and in vivo studies to clinical reports. The mechanisms involved are also discussed in this review.

Android Fat Deposition and Its Association With Cardiovascular Risk Factors in Overweight Young Males

Objective

Excess adiposity increases the risk of type-2 diabetes and cardiovascular disease development. Beyond the simple level of adiposity, the pattern of fat distribution may influence these risks. We sought to examine if higher android fat distribution was associated with different hemodynamic, metabolic or vascular profile compared to a lower accumulation of android fat deposits in young overweight males.

Methods

Forty-six participants underwent dual-energy X-ray absorptiometry and were stratified into two groups. Group 1: low level of android fat (<9.5%) and group 2: high level of android fat (>9.5%). Assessments comprised measures of plasma lipid and glucose profile, blood pressure, endothelial function [reactive hyperemia index (RHI)] and muscle sympathetic nerve activity (MSNA).

Results

There were no differences in weight, BMI, total body fat and lean mass between the two groups. Glucose tolerance and insulin resistance (fasting plasma insulin) were impaired in group 2 (p < 0.05). Levels of plasma triglycerides and 5 lipid species were higher in group 2 (p < 0.05). Endothelial function was less in group 2 (RHI: 1.64 vs. 2.26, p = 0.003) and heart rate was higher (76 vs. 67 bpm, p = 0.004). No difference occurred in MSNA nor blood pressure between the 2 groups.

Conclusion

Preferential fat accumulation in the android compartment is associated with increased cardiovascular and metabolic risk via alteration of endothelial function.

Evaluating the Impact of Different Hypercaloric Diets on Weight Gain, Insulin Resistance, Glucose Intolerance, and its Comorbidities in Rats

Animal experimentation has a long history in the study of metabolic syndrome-related disorders. However, no consensus exists on the best models to study these syndromes. Knowing that different diets can precipitate different metabolic disease phenotypes, herein we characterized several hypercaloric rat models of obesity and type 2 diabetes, comparing each with a genetic model, with the aim of identifying the most appropriate model of metabolic disease. The effect of hypercaloric diets (high fat (HF), high sucrose (HSu), high fat plus high sucrose (HFHSu) and high fat plus streptozotocin (HF+STZ) during different exposure times (HF 3 weeks, HF 19 weeks, HSu 4 weeks, HSu 16 weeks, HFHSu 25 weeks, HF3 weeks + STZ) were compared with the Zucker fatty rat. Each model was evaluated for weight gain, fat mass, fasting plasma glucose, insulin and C-peptide, insulin sensitivity, glucose tolerance, lipid profile and liver lipid deposition, blood pressure, and autonomic nervous system function. All animal models presented with insulin resistance and dyslipidemia except the HF+STZ and HSu 4 weeks, which argues against the use of these models as metabolic syndrome models. Of the remaining animal models, a higher weight gain was exhibited by the Zucker fatty rat and wild type rats submitted to a HF diet for 19 weeks. We conclude that the latter model presents a phenotype most consistent with that observed in humans with metabolic disease, exhibiting the majority of the phenotypic features and comorbidities associated with type 2 diabetes in humans.

Is the Brain a Key Player in Glucose Regulation and Development of Type 2 Diabetes?

Ever since Claude Bernards discovery in the mid 19th-century that a lesion in the floor of the third ventricle in dogs led to altered systemic glucose levels, a role of the CNS in whole-body glucose regulation has been acknowledged. However, this finding was later overshadowed by the isolation of pancreatic hormones in the 20th century. Since then, the understanding of glucose homeostasis and pathology has primarily evolved around peripheral mechanism. Due to scientific advances over these last few decades, however, increasing attention has been given to the possibility of the brain as a key player in glucose regulation and the pathogenesis of metabolic disorders such as type 2 diabetes. Studies of animals have enabled detailed neuroanatomical mapping of CNS structures involved in glucose regulation and key neuronal circuits and intracellular pathways have been identified. Furthermore, the development of neuroimaging techniques has provided methods to measure changes of activity in specific CNS regions upon diverse metabolic challenges in humans. In this narrative review, we discuss the available evidence on the topic. We conclude that there is much evidence in favor of active CNS involvement in glucose homeostasis but the relative importance of central vs. peripheral mechanisms remains to be elucidated. An increased understanding of this field may lead to new CNS-focusing pharmacologic strategies in the treatment of type 2 diabetes.

Isolated Obesity Is Not Enough to Impair Cardiac Autonomic Modulation in Metabolically Healthy Men

PURPOSE

To evaluate whether excess body mass influences the heart rate variability (HRV) indexes at rest, and to correlate adiposity indicators and the aerobic fitness with cardiac autonomic variables in metabolically healthy young adults.

METHOD

In all, 41 untrained males (M_age = 21.80, SD = 2.14 years), 14 normal weight (M_BMI = 22.28, SD = 1.86 kg∙m^-2), 11 overweight (M_BMI = 26.95, SD = 1.43 kg∙m^-2), and 16 obese (M_BMI = 33.58, SD = 3.06 kg∙m^-2) metabolically healthy (normal values of blood pressure, fasting blood glucose, triglycerides, and total cholesterol), underwent evaluations of the HRV at rest and of the peak oxygen consumption (VO₂ peak) during maximal exercise on a cycle ergometer.

RESULTS

Blood pressure, heart rate, HRV indexes, casual blood glucose, oxidative stress, and antioxidant activity did not differ among the groups. The VO₂ peak (mL∙kg^-1∙min^-1) was lower in the obese group compared with the normal weight and overweight groups. The body mass (r = -.40 to -.45) and abdominal circumference (r = -.39 to -.52) were slightly to moderately correlated with SD1, SD2, RMSSD, SDNN, pNN50, LF, and HF indexes and total power. The VO₂ peak (mL∙kg^-1∙min^-1) was slightly to moderately correlated (r = .48 to .51) with SD2, SDNN, and LF indexes in the individuals with excess body mass.

CONCLUSION

Cardiac autonomic modulation at rest was preserved in metabolically healthy obese young men. However, the indicators of adiposity, as well as the aerobic fitness were correlated with cardiac autonomic modulation in the individuals with excess body mass.

Contribution of insulin resistance to decreased baroreceptor sensitivity & cardiometabolic risks in pre-obesity & obesity

Background & objectives:

Although insulin resistance (IR) is a known complication in obesity, the physiological mechanisms linking IR with cardiometabolic risks in obesity have not been well studied. This study was conducted to assess the difference in cardiovascular (CV) risk profile in IR and non-IR (NIR) conditions, and contribution of IR to cardiometabolic risks in pre-obese and obese individuals.

Methods:

Basal CV, blood pressure variability, autonomic function test and cardiometabolic parameters were recorded in pre-obese (n=86) and obese (n=77) individuals during 2012 and 2015. The association of altered cardiometabolic parameters with homeostatic model for IR (HOMA-IR) in pre-obese and obese groups and with baroreceptor sensitivity (BRS) in IR and NIR groups was calculated by appropriate statistical analysis.

Results:

Decreased BRS, a known CV risk and cardiometabolic parameters were significant in IR (pre-obese and obese) group compared to the NIR group. Sympathovagal imbalance in the form of increased sympathetic and decreased parasympathetic activities was observed in individuals with IR. There was no significant difference in the level of independent contribution of HOMA-IR to cardiometabolic parameters in pre-obese and obese groups. Adiponectin and inflammatory markers had an independent contribution to BRS in IR group.

Interpretation & conclusions:

Findings of the present study demonstrated that the intensity of cardiometabolic derangements and CV risk were comparable between IR, pre-obese and obese individuals. Pro-inflammatory state, dyslipidaemia and hypoadiponectinaemia might contribute to CV risk in these individuals with IR. IR could possibly be the link between altered metabolic profile and increased CV risks in these individuals independent of the adiposity status.

Waist-Stature Ratio And Its Relationship With Autonomic Recovery From Aerobic Exercise In Healthy Men

Autonomic modulation and cardiorespiratory variables are influenced by numerous factors, including anthropometric variables. We investigated autonomic recovery following aerobic exercise in healthy men with different waist-stature ratio (WSR) values. The study was conducted with 52 healthy men aged 18 to 30 years, divided into groups according to the WSR: G1 – between 0.40 and 0.449 (N = 19), G2 – between 0.45 and 0.50 (N = 28) and G3 – between 0.5 and 0.56 (N = 5). The subjects endured 15 minutes seated and at rest followed by an aerobic exercise and then remained seated for 60 minutes and at rest during recovery from exercise. Heart rate (HR) variability (HRV) (rMSSD, SD1, HF [ms²]) and cardiorespiratory variables were analyzed before and after exercise. Recovery of respiratory rate, diastolic blood pressure, SD1 and HF indices were delayed in G2. G3 presented delayed recovery after the maximal effort test while no difference with G2 was noted in the moderate intensity. Correlation and linear regression analysis indicated association of WSR, body mass index and waist circumference with HRV indices in the recovery from aerobic exercise (45 to 60 minutes after exercise) in G2. In conclusion, healthy men with higher WSR accomplished delayed autonomic recovery following maximal effort exercise.

The association of non-alcoholic fatty liver disease and atrial fibrillation: a review

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent and causes an enormous burden to human health and health-care systems all over the world. A great proportion of this burden results from increased risk of cardiovascular diseases. Atrial fibrillation (AF) is the most common chronic heart arrhythmia globally and it increases the risk of embolic stroke and heart failure. Recent studies have explored the association between NAFLD and AF with somewhat conflicting results. However, ultrasound-verified prospective studies concur that NAFLD is associated with the incidence of AF. According to epidemiological evidence, the greater the prevalence of NALFD in a population, the stronger the association with AF incidence and prevalence. Specifically, diabetic individuals with NAFLD are at the greatest risk of AF. Additionally, the risk of AF may concentrate most in individuals with advanced NAFLD, particularly those with liver fibrosis. The possible mechanistic factors between NAFLD and AF, particularly obesity and systemic inflammation, are diverse and form a complex interplaying network. However, further studies are needed to elucidate whether NAFLD has a causative role in the development of AF. The purpose of this article is to review and discuss the epidemiologic evidence and possible mechanistic links between these two conditions. KEY MESSAGES Although epidemiologic studies have provided conflicting results on the association of NAFLD and AF, prospective studies with ultrasound-verified NAFLD concur that NAFLD is associated with about 2-fold greater incidence of AF among general population and about 6-fold greater incidence among subjects with type 2 diabetes. The risk of AF among individuals with NAFLD is increased by other cardiovascular risk factors, especially type 2 diabetes and advanced age. The possible mechanistic links between NALFD and AF are diverse, with obesity and systemic inflammation having a significant role, but further studies are needed until NAFLD can be established as a causal factor in the incidence of AF.

The short-term effects of indoor size-fractioned particulate matter and black carbon on cardiac autonomic function in COPD patients

BACKGROUND

Previous studies have reported adverse health effects of indoor air pollutants especially particulate matter (PM) and black carbon (BC). Patients with chronic obstructive pulmonary disease (COPD) have been shown to be more likely with cardiovascular comorbidities in which cardiac autonomic dysfunction plays an important role. However, there is little evidence for the effect of indoor PM and BC exposures on cardiac autonomic function in COPD patients.

OBJECTIVES

To evaluate the association between exposure to indoor size-fractioned PM and BC and changes in HRV and HR in COPD patients.

METHODS

Forty-three doctor diagnosed, stable COPD patients were recruited and measured for 24-h HRV and HR. Real-time indoor size-fractioned PM and BC were monitored on the day before and the day of performing health measurements. Mixed-effects models were used to estimate the associations between indoor PM and BC and HRV indices and HR after controlling for potential confounders.

RESULTS

Increasing levels of size-fractioned PM and BC were associated with decreased HRV indices and increased HR. An IQR (3.14μg/m³) increase in 8-h BC moving average and an IQR (20.72μg/m³) increase in 5-min PM_0.5 moving average concentrations were associated with declines of 7.45% (95% CI: -10.89%, -3.88%) and 16.40% (95% CI: -21.06%, -11.41%) in LF, respectively. The smaller the particles size, the greater effects on HRV indices and HR. Patients' BMI modified the associations between size-fractioned PM and BC and their HRV and HR. For an IQR increase in PM_0.5, there was decline in HF of 34.85% (95% CI: -39.08%, -30.33%) in overweight patients, compared to a 2.01% (95% CI: -6.44%, 11.19%) increase in normal-weight patients.

CONCLUSIONS

Exposures to indoor PM and BC were associated with altered cardiac autonomic function in COPD patients, and the associations for HRV measures of parasympathetic activity (e.g., HF) were more apparent in overweight patients.

Sympathetic neural activity, metabolic parameters and cardiorespiratory fitness in obese youths

OBJECTIVE

The main objective of this cross-sectional study is to assess the cardiac autonomic neural activity in the presence of abnormally increased body weight in youths and its relationship to metabolic risk factors and cardiorespiratory fitness (CRF).

METHODS

Sixty-four overweight and obese patients, aged 9-17 years, of both sexes, stratified according to the international BMI cut-off, were enrolled. Continuous ECG was recorded during 15 min in resting conditions, and the heart rate variability (HRV) was measured in the time domain, frequency domain and for nonlinear dynamics. In addition, cardiometabolic risk factors and CRF in effort conditions were assessed.

RESULTS

Among the overweight and obese youths, no significant differences were observed regarding metabolic parameters and heart rate, although CRF was the lowest in the severely obese youths. Likewise, no significant differences were observed in HRV, independent of how it was assessed. A positive and significant relationship, independent of the degree of obesity, pubertal stage and breathing rate under resting conditions, has been observed among sympathovagal balance, insulin and the homeostatic model assessment index. Furthermore, CRF assessed by volume oxygen peak was associated with insulin levels (r = -0.273; P < 0.05), the SD of the NN interval series (r = 0.268, P < 0.05) and the long-term variation using the Poincaré plot (PS1: r = 0.275, P < 0.05; PS2: r = 0.273, P < 0.05).

CONCLUSION

The key findings of the present study were the presence of a link among fasting insulin, HRV and CRF independent of the degree of obesity, indicating the heterogeneity of obese children and adolescents.

Correlation of Adiposity Indices with Electrocardiographic Ventricular Variables and Vascular Stiffness in Young Adults

INTRODUCTION

Excess adiposity constitute an important public health problem because of the associated increased risk of hypertension, coronary heart disease, type 2 diabetes and other disorders. Not only the contribution of general measures of adiposity but also central measures of adiposity have been observed.

AIM

To compare and correlate the central and general adiposity indices with ventricular electrocardiographic variables and vascular stiffness indices in normal, overweight and obese young adults.

MATERIALS AND METHODS

This was a cross-sectional study. Nearly ninety subjects were enrolled and were divided into 30 normal weight, 30 overweight and 30 obese group based on the BMI classification of WHO for Asian population with their age ranging from 18-25 years. Waist and hip circumferences were measured using stretchable tape. Two novel indices-conicity index and abdominal volume index were calculated using standard formula. ECG and pulse wave were recorded using the Physiopac - Medicaid systems. Statistical analysis was done using SPSS version 19.0 software. ANOVA test was done to compare the variables among three groups. Pearson's correlation coefficients were applied to establish the correlations between variables.

RESULTS

In our study Body Mass Index (BMI) and Conicity Index (CI) was significantly and strongly correlated with the ventricular electrocardiographic variables especially with QRS duration, QTc interval and with vascular stiffness indices. These indices can be used to assess the electrocardiographic abnormalities and vascular stiffness status.

CONCLUSION

Excess adipose tissue in young adults was closely linked to ventricular depolarization and repolarization abnormalities and also to increased vascular stiffness. Adiposity indices in particular (BMI, CI) provide a simple and non invasive approach to assess these abnormalities at the earliest in order to prevent future complications.

Caracterização da variabilidade da frequência cardíaca em indivíduos com síndrome metabólica

RESUMO Introdução: A variabilidade da frequência cardíaca (VFC) tem sido considerada um mecanismo de modulação do sistema nervoso autônomo. A diminuição da VFC pode estar associada à síndrome metabólica (SM). Objetivo: Comparar a VFC e variáveis de saúde em indivíduos com e sem SM. Métodos: Cento e dezenove participantes foram divididos em dois grupos: sem SM (SSM, n = 68) e com SM (CSM, n = 51). Foi avaliada a análise espectral da VFC em repouso, durante teste cardiopulmonar de exercício (TCPE) e na recuperação em bandas de baixa frequência (LF = 0,04-0,15 Hz), alta frequência (HF = 0,15-0,4 Hz) e razão LF/HF. Adicionalmente, a frequência cardíaca (FC) de repouso (FCrep), FC máxima (FCmáx), pressão arterial sistólica (PAS) e diastólica (PAD), glicemia, perfil lipídico, consumo de oxigênio pico (VO2pico) e composição corporal foram avaliados. Resultados: A FCrep e o VO2pico não apresentaram diferenças entre o CSM e o SSM (73,3 ± 9,1 vs. 70,1 ± 11,0 bpm) (26,8 ± 4,6 vs. 28,1 ± 6,6 ml.kg-1.min-1), respectivamente. A VFC foi similar entre os grupos nos diferentes momentos analisados. A glicemia (99,8 ± 22,5 vs. 87,6 ± 8,6 mg/dl) foi superior no CSM comparado ao SSM. Os valores de triglicérides (159,5 ± 68,8 vs. 89,2 ± 34,3 mg/dl) e VLDL-c (31,9 ± 13,8 vs. 17,8 ± 6,9 mg/dl) foram superiores no CSM comparado ao SSM. O HDL-c (40,7 ± 11,5 vs. 49,3 ± 9,8 mg/dl) foi menor no CSM comparado ao SSM. O IMC (33,1 ± 4,7 vs. 30,8 ± 3,8 Kg/m²) foi superior no CSM comparado ao SSM. A PAS (128,6 ± 12,9 vs. 119,5 ± 11,3 mmHg) e a PAD (77,2 ± 10,5 vs. 72,9 ± 8,1 mmHg) foram superiores no CSM comparado ao SSM, p < 0,05. Conclusão: Os resultados sugerem que a presença de SM não é suficiente para provocar alterações nos índices de VFC em repouso, durante teste cardiopulmonar de exercício (TCPE) e na recuperação quando os pacientes são comparados a indivíduos sem a doença.

Synergistic effect of energy drinks and overweight/obesity on cardiac autonomic testing using the Valsalva maneuver in university students

BACKGROUND

Obesity and caffeine consumption may lead to autonomic disturbances that can result in a wide range of cardiovascular disorders.

OBJECTIVES

To determine autonomic disturbances produced by the synergistic effects of overweight or obesity (OW/OB) and energy drinks.

DESIGN

Cross-sectional, analytical.

SETTING

Physiology department at a university in Saudi Arabia.

SUBJECTS AND METHODS

University students, 18-22 years of age, of normal weight (NW) and OW/OB were recruited by convenience sampling. Autonomic testing by the Valsalva ratio (VR) along with systolic and diastolic blood pressure, pulse pressure, and mean arterial blood pressure were measured at baseline (0 minute) and 60 minutes after energy drink consumption.

MAIN OUTCOME MEASURE(S)

Autonomic disturbance, hemodynamic changes.

RESULTS

In 50 (27 males and 23 females) subjects, 21 NW and 29 OW/OB, a significant decrease in VR was observed in OW/OB subjects and in NW and OW/OB females at 60 minutes after energy drink consumption. Values of systolic and diastolic blood pressure, pulse pressure and mean arterial blood pressure were also significantly higher in OW/OB and in females as compared to NW and males. BMI was negatively correlated with VR and diastolic blood pressure at 60 minutes.

CONCLUSION

Obesity and energy drinks alter autonomic functions. In some individuals, OW/OB may augment these effects.

LIMITATIONS

Due to time and resource restraints, only the acute effects of energy drinks were examined.

Acute cyclooxygenase inhibition and baroreflex sensitivity in lean and obese adults

PURPOSE

Obese adults exhibit increased levels of inflammation, which may negatively affect blood pressure regulation. Based on existing literature, we hypothesized: (1) baroreflex sensitivity would be lower in obese adults when compared to lean adults; (2) acute ibuprofen (IBU, a cyclooxygenase inhibitor and nonsteroidal antiinflammatory agent) administration would increase baroreflex sensitivity in obese adults, with no effect in lean adults.

METHODS

Seven lean (4 male, 3 female) and six obese (5 M, 1 F) adults completed two visits randomized to control (CON) or IBU (800 mg oral). On each visit, blood pressure (intra-arterial catheter), heart rate (ECG), and muscle sympathetic nerve activity (MSNA, microneurography) were measured continuously. Sympathetic and cardiac baroreflex sensitivities were assessed using the modified Oxford technique.

RESULTS

Measures of systemic inflammation [C-reactive protein (CRP) and interleukin-6 (IL-6)] were higher in obese adults when compared to lean adults and tended to decrease with IBU (IL-6: p < 0.05; CRP: p = 0.14). Cardiac baroreflex sensitivity was lower in obese adults (14 ± 2 vs. 24 ± 2 ms/mmHg, p = 0.02), whereas sympathetic baroreflex sensitivity was higher in obese adults (-3.6 ± 0.5 vs. -2.1 ± 0.5 bursts/100 beats/mmHg, p = 0.03) when compared to lean. There was no effect of IBU on cardiac or sympathetic baroreflex sensitivity in either group (p value range 0.20-0.71).

CONCLUSION

Despite obese individuals exhibiting higher levels of systemic inflammation and lower cardiac baroreflex sensitivity when compared to lean adults, an acute dose of IBU has no effect on cardiac or sympathetic baroreflex sensitivity.

Exaggerated sympathoexcitatory reflexes develop with changes in the rostral ventrolateral medulla in obese Zucker rats

Obesity leads to altered autonomic reflexes that reduce stability of mean arterial pressure (MAP). Sympathoinhibitory reflexes such as baroreflexes are impaired, but reflexes that raise MAP appear to be augmented. In obese Zucker rats (OZR) sciatic nerve stimulation evokes larger increases in MAP by unknown mechanisms. We sought to determine the autonomic underpinnings of this enhanced somatic pressor reflex and whether other sympathoexcitatory reflexes are augmented. We also determined whether their final common pathway, glutamatergic activation of the rostral ventrolateral medulla (RVLM), was enhanced in male OZR compared with lean Zucker rats (LZR). Sciatic nerve stimulation or activation of the nasopharyngeal reflex evoked larger rises in splanchnic sympathetic nerve activity (SNA) (79% and 45% larger in OZR, respectively; P < 0.05) and MAP in urethane-anesthetized, ventilated, paralyzed adult OZR compared with LZR. After elimination of baroreflex feedback by pharmacological prevention of changes in MAP and heart rate, these two sympathoexcitatory reflexes were still exaggerated in OZR (167% and 69% larger, respectively, P < 0.05). In adult OZR microinjections of glutamate, AMPA, or NMDA into the RVLM produced larger rises in SNA (∼61% larger in OZR, P < 0.05 for each drug) and MAP, but stimulation of axonal fibers in the upper thoracic spinal cord yielded equivalent responses in OZR and LZR. In juvenile OZR and LZR, sympathoexcitatory reflexes and physiological responses to RVLM activation were comparable. These data suggest that the ability of glutamate to activate the RVLM becomes enhanced in adult OZR and may contribute to the development of exaggerated sympathoexcitatory responses independent of impaired baroreflexes.

Current Approaches to Quantifying Tonic and Reflex Autonomic Outflows Controlling Cardiovascular Function in Humans and Experimental Animals

The role of the autonomic nervous system in the pathophysiology of human and experimental models of cardiovascular disease is well established. In the recent years, there have been some rapid developments in the diagnostic approaches used to assess and monitor autonomic functions. Although most of these methods are devoted for research purposes in laboratory animals, many have still found their way to routine clinical practice. To name a few, direct long-term telemetry recording of sympathetic nerve activity (SNA) in rodents, single-unit SNA recording using microneurography in human subjects and spectral analysis of blood pressure and heart rate in both humans and animals have recently received an overwhelming attention. In this article, we therefore provide an overview of the methods and techniques used to assess tonic and reflex autonomic functions in humans and experimental animals, highlighting current advances available and procedure description, limitations and usefulness for diagnostic purposes.

Decreased baroreflex sensitivity is linked to sympathovagal imbalance, body fat mass and altered cardiometabolic profile in pre-obesity and obesity

OBJECTIVE

Though decreased baroreflex sensitivity (BRS), the predictor of cardiac morbidities and mortality has been reported in obesity, the mechanisms and metabolic biomarkers influencing BRS have not been studied. We aimed to assess the difference in cardiovascular (CV) risk profile in pre-obesity and obesity, and the contribution of body composition and cardiometabolic factors to CV risks in these two conditions.

METHODS

Obesity indices, body composition, blood pressure variability and autonomic function test parameters were recorded in 223 subjects divided into controls (n=72), pre-obese (n=77) and obese (n=74) groups. Insulin resistance (HOMA-IR), atherogenic index (AI), leptin, adiponectin, inflammatory and oxidative stress parameters were measured. Association and independent contribution of altered cardiometabolic parameters with BRS were performed by Pearson's correlation and multiple regression analysis, respectively.

RESULTS

BRS was significantly decreased in pre-obese and obese group compared to controls. Sympathovagal imbalance (SVI) in the form of increased sympathetic and decreased parasympathetic cardiac drives was observed in pre-obesity and obesity. There was significant difference in general markers of obesity (body mass index, and waist-to-hip ratio), between pre-obese and obese group, however no such difference was observed in body composition and cardiometabolic parameters between the two groups. AI, high sensitive C-reactive protein (hs-CRP) and ratio of basal metabolism to body fat (BM/BF) in pre-obese group, and AI, HOMA-IR, leptin, adiponectin, ratio of basal metabolism to body weight (BM/BW), BM/BF, inflammatory and oxidative stress markers in obese group had independent contribution to BRS. Among these metabolic biomarkers, BRS had maximum association with leptin (β=0.532, p=0.000) in the obese group and hs-CRP (β=0.445, p=0.022) in the pre-obese group.

CONCLUSIONS

The present study demonstrates decreased BRS, an important marker of increased CV risk in pre-obesity and obesity. The intensity of cardiometabolic derangements and CV risk was comparable between pre-obese and obese subjects. BM/BF ratio appears to be a better marker of metabolic activity in pre-obesity and obesity. SVI and increased basal metabolism appear to be the physiological link between metabolic derangements and CV risks in both pre-obesity and obesity.

Effects of energy drink consumption on corrected QT interval and heart rate variability in young obese Saudi male university students

BACKGROUND AND OBJECTIVES

Consumption of energy drinks has adverse effects on the heart that might be potentiated in obese individuals. Since the incidence of obesity and use of energy drinks is high among Saudi youth, we used non-invasive tests to study hemodynamic changes produced by altered autonomic cardiac activ.ity following consumption of energy drinks in obese male students.

DESIGN AND SETTING

This cross-sectional study was carried out at Department of Physiology, College of Medicine, University of Dammam, Saudi Arabia, over a one-year period from December 2013 to December 2014.

SUBJECTS AND METHODS

In Saudi male university students we measured continuous ECG recordings and a one-minute deep breathing maneuver to measure the expiratory-to-inspiratory ratio, the mean heart rate range (MHRR), the mean percentage variability. (M%VHR) and the corrected QT interval (QTc) at 0, 30 and 60 minutes after consumption of energy drink.

RESULTS

We enrolled 31 students (18 overweight/obese and 13 normal weights. QTc was significantly in.creased at 60 min as compared with the resting state in overweight/obese subjects (P=.006). Heart rate variability was significantly less in obese as compared with normal weight subjects at 60 minutes as indicated by E:I ratio, (P=.037), MHRR (P=.012), M%VHR (P=.040) after energy drink consumption. Significant increases in diastolic (P=.020) and mean arterial blood pressure (P=.024) were observed at 30 minutes in the obese group.

CONCLUSION

Hemodynamic changes after intake of energy drinks in obese subjects indicate that obesity and energy drinks could synergistically induce harmful effects. This finding warrants efforts to caution the obese on intake of energy drinks and timely intervention to motivate changes in lifestyle.