Ethnic differences in insulinemia and sympathetic tone as links between obesity and blood pressure

Limited evidence for sympathetic neural overactivation in older patients with type 2 diabetes mellitus

Introduction

Mechanistic studies suggested that excess sympathetic activity promotes arterial hypertension while worsening insulin sensitivity. Older patients with type 2 diabetes are at particularly high cardiovascular and metabolic risk. However, data on sympathetic activity in this population is scarce.

Methods

We studied 61 patients with type 2 diabetes mellitus (22 women, 60.9 ± 1.4 years; 39 men, 60.9 ± 1.4 years). They had to have diabetes for at least 2 years, a hemoglobin A1c of 6.5-10%, a body-mass-index of 20-40 kg/m², and had to be treated with stable doses of metformin only. We recorded ECG, finger and brachial blood pressure, and muscle sympathetic nerve activity (MSNA).

Results

MSNA was 37.5 ± 2.5 bursts/min in women and 39.0 ± 2.0 bursts/min in men (p = 0.55). MSNA expressed as burst incidence was 52.7 ± 2.0 bursts/100 beats in women and 59.2 ± 3.1 bursts/100 beats in men (p = 0.21). Five out of 39 men (12.8%) and two out of 22 women (9.1%) exhibited resting MSNA measurements above the 95th percentile for sex and age. In the pooled analysis, MSNA was not significantly correlated with systolic blood pressure, diastolic blood pressure, body mass index, waist circumference, body composition, or HbA1c (r ² < 0.02, p > 0.26 for all).

Discussion

We conclude that relatively few older patients with type 2 diabetes mellitus exhibit increased MSNA. The large interindividual variability in MSNA cannot be explained by gender, blood pressure, body mass index, or glycemic control.

Race and sex differences in cardiovascular autonomic regulation

Racial and ethnic differences in cardiovascular morbidity and mortality persist despite advances in risk factor identification and implementation of evidence-based treatment strategies. African American men and women are disproportionately affected by cardiovascular risk factors, particularly hypertension. In this context, previous studies have identified sex and racial differences in autonomic cardiovascular regulation which may contribute to the development of hypertension and its high morbidity burden among African Americans. In this review, we provide a comprehensive evaluation of the potential pathophysiological mechanisms of blood pressure control and their differences based on sex and race. These mechanisms include obesity-induced sympathetic activation, sympatho-vascular transduction, baroreflex sensitivity and adrenoreceptor vascular sensitivity, which have been the subjects of prior investigation in this field. Understanding the racial differences in the pathophysiology of hypertension and its co-morbid conditions would allow us to implement better treatment strategies tailored to African Americans, with the ultimate goal of reducing cardiovascular mortality in this population.

Skin sympathetic nerve activity in patients with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is associated with increased cardiac arrhythmia and sudden cardiac death. We recently developed a new method (neuECG) to noninvasively measure electrocardiogram and skin sympathetic nerve activity (SKNA).

OBJECTIVE

The purpose of this study was to test the hypothesis that SKNA measured during sleep study is higher in patients with OSA than in those without OSA.

METHODS

We prospectively recorded neuECG and polysomnography in 26 patients undergoing a sleep study. Sleep stages were scored into rapid eye movement (REM), and non-REM sleep stages 1 (N1), 2 (N2), and 3 (N3). Average voltage of skin sympathetic nerve activity (aSKNA) and SKNA burst area were calculated for quantification. Apnea/hypopnea index (AHI) >5 per hour was used to diagnose OSA.

RESULTS

There was a positive correlation (r = 0.549; P = .018) between SKNA burst area and the arousal index in OSA but not in the control group. aSKNA during sleep was 0.61 ± 0.09 μV in OSA patients (n = 18) and 0.53 ± 0.04 μV in control patients (n = 8; P = .025). Burst area was 3.26 (1.90-4.47) μV·s/min in OSA patients and 1.31 (0.67-1.94) μV·s/min in control (P = .047). More apparent differences were found during N2, when the burst area in OSA (3.06 [1.46-5.52] μV·s/min) was much higher than that of the control (0.89 [0.79-1.65] μV·s/min; P = .03).

CONCLUSION

OSA patients have higher SKNA activity than control patients, with the most pronounced differences observed during N2. Arousal at the end of apnea episodes is associated with large SKNA bursts. Overlaps of aSKNA and SKNA burst area between groups suggest that not all OSA patients have increased sympathetic tone.

Relationships between metabolic markers and obesity measures in two populations that differ in stature-The SAMINOR Study

Background

The relationships between metabolic markers and obesity measures may differ by ethnicity, sex, and height. Questions have been posed whether these relationships differ by ethnicity in the population in Northern Norway, but this has not been explored yet.

Objectives

Investigate the relationships between metabolic markers and obesity measures in Sami and non‐Sami and explore the impact of stature.

Methods

In total, 13 921 men and women aged 30 and 36 to 79 years (22.0% Sami) from a population‐based cross‐sectional survey in Norway, the SAMINOR 1 Survey (2003‐2004, 57.2% attendance), were included. Relationships between triglycerides, high‐density lipoprotein cholesterol, glucose, systolic/diastolic blood pressure (BP), metabolic syndrome and diabetes mellitus as outcomes, and body mass index (BMI), waist circumference (WC), and waist‐to‐height ratio (WHtR), respectively, were modelled using fractional polynomial regression. Appropriate interaction analyses and adjustments were made.

Results

The non‐Sami were approximately 6 cm taller than the Sami. No interactions were found between ethnicity and obesity. At the same levels of WC, BMI, or WHtR, levels of lipids and BP differed marginally between Sami and non‐Sami, but these were eliminated by height adjustment, with one exception: At any given WC, BMI, or WHtR, Sami had approximately 1.4 mmHg (95% CI, −2.1 to −0.7) lower systolic BP than non‐Sami (P values < .001).

Conclusions

Height explained the marginal ethnic differences in metabolic markers at the same level of obesity, except for systolic BP, which was lower in Sami than in non‐Sami at any given BMI, WC, or WHtR.

Metabolically Healthy Obesity (MHO)-New Research Directions for Personalised Medicine in Cardiovascular Prevention

PURPOSE OF REVIEW

To discuss new findings on the heterogeneity of obesity and associated risks.

RECENT FINDINGS

Obesity is a public health problem of immense importance on a global scale. However, epidemiological findings and clinical studies have revealed that obesity is a heterogeneous phenotype and that not all obese subjects run the same risk for complications. Current research has tried to describe so-called metabolically healthy obesity (MHO), defined by lack of risk factors included in the metabolic syndrome. These subjects will not escape long-term complications, but mortality risk is not increased. However, a new definition of MHO has recently been proposed, based on the lack of hospitalisation for somatic disease for decades in middle life. MHO subjects defined in this way are characterised by being "fat and fit" and also run a lower risk of long-term complications. If MHO could be better understood, this could contribute to a more diverse clinical approach to obesity based on personalised medicine.

Obesity, kidney dysfunction and hypertension: mechanistic links

Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal and renal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin-angiotensin-aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.

Obesity-related hypertension: a review of pathophysiology, management, and the role of metabolic surgery

Obesity is a significant public health challenge worldwide and is inextricably linked to adverse cardiovascular outcomes. The relationship between excess adiposity and increased blood pressure is well established, and it is estimated that obesity accounts for 65-78% of cases of primary hypertension. The mechanisms through which obesity causes hypertension are complex and include sympathetic nervous system overactivation, stimulation of the renin-angiotensin-aldosterone system, alterations in adipose-derived cytokines, insulin resistance, and structural and functional renal changes. Weight loss is the primary goal of treatment for obesity-related hypertension, although few individuals achieve success with nonpharmacological management alone. Specific considerations apply when selecting the most appropriate pharmacological therapy for obese hypertensive patients. Metabolic surgery has proved to be the most effective means of ensuring substantial and sustained weight loss and has also been shown to confer beneficial effects in type 2 diabetes mellitus. Increasing evidence suggests that metabolic surgery may also be an effective treatment for obesity-related hypertension, although prospective data on long-term blood pressure outcomes are awaited. This review will discuss the pathophysiological mechanisms that link obesity with hypertension and will provide an overview of treatment strategies, with a focus on metabolic surgery.

Limited contribution of insulin resistance and metabolic parameters to obesity-associated increases in ambulatory blood pressure in a black African community

Although accounting for a striking proportion of obesity effects on blood pressure (BP) in other populations, the extent to which obesity-associated increases in BP are explained by insulin resistance and metabolic changes in populations of African ancestry is uncertain. We determined the contribution of insulin resistance and associated metabolic abnormalities to variations in office or ambulatory BP in a black African community with prevalent obesity and hypertension. In 1225 randomly selected participants of black South African ancestry (age>16years, 43.1% obese, 47.4% abdominal obesity), we assessed adiposity indexes, the homeostasis model of insulin resistance (HOMA-IR) and associated metabolic abnormalities and office or ambulatory (n ​= ​798) BP. In separate models, waist circumference (p ​< ​0.0005-<0.0001) and HOMA-IR (p ​< ​0.51–0.005), were independently associated with office, 24 ​h, day or night systolic (SBP) or diastolic (DBP) BP. However, whilst a one standard deviation increase in waist circumference translated into a 1.47–3.08 ​mm Hg increased in office, 24-h SBP or DBP, in mediation analysis HOMA-IR accounted for only 0.12–0.30 ​mm Hg of the impact of a one standard deviation effect of waist circumference on office, and 24-h SBP and 0.003–0.17 ​mm Hg of the impact of a one standard deviation effect of waist circumference on office and 24-h DBP. In conclusion, in a black African community, insulin resistance accounts for a negligible proportion of the impact of obesity on office or ambulatory BP.

Regulation of alternative splicing in obesity-induced hypertension

Obesity is the result of genetics which predisposes an individual to obesity and environmental factors, resulting in excessive weight gain. A well-established linear relationship exists between hypertension and obesity. The combined burden of hypertension and obesity poses significant health and economic challenges. Many environmental factors and genetic traits interact to contribute to obesity-linked hypertension. These include excess sodium re-absorption or secretion by the kidneys, a hypertensive shift of renal-pressure and activation of the sympathetic nervous system. Most individuals suffering from hypertension need drugs in order to treat their raised blood pressure, and while a number of antihypertensive therapeutic agents are currently available, 50% of cases remain uncontrolled. In order to develop new and effective therapeutic agents combating obesity-induced hypertension, a thorough understanding of the molecular events leading to adipogenesis is critical. With the advent of whole genome and exome sequencing techniques, new genes and variants which can be used as markers for obesity and hypertension are being identified. This review examines the role played by alternative splicing (AS) as a contributing factor to the metabolic regulation of obesity-induced hypertension. Splicing mutations constitute at least 14% of the disease-causing mutations, thus implicating polymorphisms that effect splicing as indicators of disease susceptibility. The unique transcripts resulting from the alternate splicing of mRNA encoding proteins that play a key role in contributing to obesity would be vital to gain a proper understanding of the genetic causes of obesity. A greater knowledge of the genetic basis for obesity-linked hypertension will assist in the development of appropriate diagnostic tests as well as the identification of new personalized therapeutic targets against obesity-induced hypertension.

Target Organ Damage and Cardiovascular Risk in a Hypertensive Roma Sample Population in Romania

Background

The largest European Roma community resides in Romania, but there is still little published data on cardiovascular (CV) risk factors and disease in this group. This study addresses the prevalence of arterial hypertension, associated CV disease risk, and target organ damage (TOD) in a Roma community from Bucharest, Romania.

Methods

This is a cross-sectional community-based participatory research to assess for CV risk factors, TOD and CV disease, including 806 Roma ethnics (18-83 years) integrated in the local community, 36.16% males. Evaluation included physical examination with blood pressure, pulse wave velocity and anklebrachial measurements, laboratory tests, ECG, echocardiography and fundoscopy.

Results

Prevalence of hypertension was 33.62%, awareness 76.38%, higher in females (p>0.01), and control rate 44.39%. Compared to age-matched normotensives, hypertensives had more left ventricle hypertrophy and more frequently increased pulse pressure. Differences in TOD were attenuated between newly and previously diagnosed, controlled and uncontrolled, hypertensives. Cardiovascular disease was almost absent in normotensives. Ten-year risk for fatal CV disease followed an increasing trend from normotension to long standing hypertension.

Conclusion

This is the first dedicated study to thoroughly assess TOD and risk for fatal CV disease in a Romanian Roma population. Hypertension was less prevalent than in the general population, with similar awareness, possibly as a consequence of integration in the surrounding community. Fatal CV disease risk followed the trend of increasing prevalence of risk factors, and hypertension played an important role in its modulation.

Renal function and its association with blood pressure in Middle Eastern immigrants and native Swedes

BACKGROUND

Iraqi-born immigrants residing in Sweden are at high risk for type 2 diabetes, obesity and hyperlipidemia compared with native Swedes. Paradoxically, hypertension is less prevalent in this immigrant population. The aim of this study was to investigate differences in renal function and further if differences in blood pressure (BP) levels were associated with differences across ethnicities in renal function as a possible explanation to the paradox.

METHODS

A population-based, cross-sectional study of men and women, born in Iraq or Sweden, aged 30-75 years was conducted in Malmö, Sweden, from 2010 to 2012. Blood samples were drawn, physical examinations performed and self-administrated questionnaires were assessed. Estimated glomerular filtration rate (eGFR) was calculated from the Caucasian Asian Pediatric Adult cohort formula based on cystatin C.

RESULTS

Participants without history of cardiovascular disease born in Iraq (n = 1214), irrespective of age and sex, presented with higher eGFR than participants born in Sweden (n = 659), (96.5 ml/min per 1.73 m vs. 93.6, P = 0.009). Furthermore, eGFR showed weaker association with BP in Iraqis than in Swedes, especially for SBP. The relationship was confirmed by a significant interaction between eGFR and country of birth (Pinteraction country of birth × eGFRcystatinC = 0.004).

CONCLUSION

The current study shows differences across ethnicities in renal function and its associations with BP. More studies are needed to understand mechanisms contributing to BP regulation and renal function in populations of different ethnic backgrounds.

Autonomic Blockade Reverses Endothelial Dysfunction in Obesity-Associated Hypertension

Impaired nitric oxide (NO) vasodilation (endothelial dysfunction) is associated with obesity and thought to be a factor in the development of hypertension. We previously found that NO synthesis inhibition had similar pressor effects in obese hypertensives compared with healthy control during autonomic blockade, suggesting that impaired NO vasodilation is secondary to sympathetic activation. We tested this hypothesis by determining the effect of autonomic blockade (trimethaphan 4 mg/min IV) on NO-mediated vasodilation (increase in forearm blood flow to intrabrachial acetylcholine) compared with endothelial-independent vasodilation (intrabrachial sodium nitroprusside) in obese hypertensive subjects (30<body mass index<40 kg/m(2)). Acetylcholine and sodium nitroprusside were given at equipotent doses (10, 30, and 50 μg/min and 1, 2, and 3 μg/min, respectively) to 14 obese subjects (49±3.6 years, 34±1 kg/m(2), 165/94±7/6 mm Hg), on separate occasions 1 month apart, randomly assigned. Autonomic blockade increased basal forearm blood flow (from 3.9±0.7 to 5.2±1.2 mL/100 mL per minute, P=0.078). As expected, NO-mediated vasodilation was blunted on the intact day compared with NO-independent vasodilation; forearm blood flow increased from 3.6±0.6 to 10.1±1.1 with the highest dose of nitroprusside, but only from 3.7±0.4 to 7.2±0.8 mL/100 mL per minute with the highest dose of acetylcholine, P<0.05. In contrast, forearm blood flow responses to acetylcholine were restored by autonomic blockade and were no longer different to nitroprusside (from 6.2±1.1 to 11.4±1.6 mL/100 mL per minute and from 5.2±0.9 to 12.5±0.9, respectively, P=0.58). Our results support the concept that sympathetic activation contributes to the impairment in NO-mediated vasodilation seen in obesity-associated hypertension and provides further rationale to explore it as a therapeutic target.

New developments in the pathogenesis of obesity-induced hypertension

Obesity is a disorder that develops from the interaction between genotype and environment involving social, behavioral, cultural, and physiological factors. Obesity increases the risk for type 2 diabetes mellitus, hypertension, cardiovascular disease, cancer, musculoskeletal disorders, chronic kidney and pulmonary disease. Although obesity is clearly associated with an increased prevalence of hypertension, many obese individuals may not develop hypertension. Protecting factors may exist and it is important to understand why obesity is not always related to hypertension. The aim of this review is to highlight the knowledge gap for the association between obesity, hypertension, and potential genetic and racial differences or environmental factors that may protect obese patients against the development of hypertension and other co-morbidities. Specific mutations in the leptin and the melaninocortin receptor genes in animal models of obesity without hypertension, the actions of α-melanocyte stimulating hormone, and SNS activity in obesity-related hypertension may promote recognition of protective and promoting factors for hypertension in obesity. Furthermore, gene-environment interactions may have the potential to modify gene expression and epigenetic mechanisms could also contribute to the heritability of obesity-induced hypertension. Finally, differences in nutrition, gut microbiota, exposure to sun light and exercise may play an important role in the presence or absence of hypertension in obesity.

Cardiometabolic crosstalk in obesity-associated arterial hypertension

Abdominal obesity and elevated blood pressure commonly occur in the same patient and are key components of the metabolic syndrome. However, the association between obesity and increased blood pressure is variable. We review mechanisms linking cardiovascular and metabolic disease in such patients including altered systemic and regional hemodynamic control, neurohumoral activation, and relative natriuretic peptide deficiency. Moreover, we discuss recent results using omics techniques providing insight in molecular pathways linking adiposity, metabolic disease, and arterial hypertension. Recognition of the mechanisms orchestrating the crosstalk between cardiovascular and metabolic regulation in individual patients may lead to better and more precise treatments. It is reassuring that recently developed cardiovascular and metabolic medications may in fact ameliorate, both, cardiovascular and metabolic risks.

Risk Factors in Adolescent Hypertension

Hypertension is a complex and multifaceted disease, with many contributing factors. While diet and nutrition are important influences, the confounding effects of overweight and obesity, metabolic and genetic factors, racial and ethnic predispositions, socioeconomic status, cultural influences, growth rate, and pubertal stage have even more influence and make diagnosis quite challenging. The prevalence of hypertension in adolescents far exceeds the numbers who have been diagnosed; studies have found that 75% or more go undiagnosed. This literature review summarizes the challenges of blood pressure classification in adolescents, discusses the impact of these confounding influences, and identifies actions that will improve diagnosis and treatment outcomes.

Sympathetic Activity Assessed during Exercise Recovery in Young Obese Females

OBJECTIVE

To evaluate differences in sympathetic activity, as assessed by an exercise recovery index (ERI; heart rate/oxygen consumption [VO2] plateau), between black and white obese female adolescents. An additional aim was to determine the association of ERI with insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR]), cardiovascular fitness per fat-free mass (VO2 per fat-free mass), systolic blood pressure (SBP), and percent body fat (%FAT) in both black and white obese adolescents.

STUDY DESIGN

Sixty-one females volunteered to participate in this study. HOMA-IR, SBP, and %FAT were assessed during resting conditions in black (n = 49, 13.7 ± 1.6 years, 38.1 ± 6.1 kg/m(2)) and white (n = 12, 13.3 ± 2.2 years, 34.3 ± 4.9 kg/m(2)) obese adolescents. An ERI was calculated during a 5-minute passive recovery period immediately following a graded treadmill exercise test to exhaustion.

RESULTS

The ERI was significantly greater in black compared with white obese adolescent females (29.8 ± 6.4 vs 24.1 ± 3.1 bpm·mLO2(-1)·min(-1), P = .004). Using multiple linear regression modeling, there was a significant independent association between ERI and VO2 per fat-free mass (r = -0.310, P = .027) and %FAT (r = 0.326, P = .020) in black obese adolescents after controlling for HOMA-IR and SBP.

CONCLUSIONS

These results suggest that black obese adolescent females have greater sympathetic activity, as assessed by an ERI, than white obese adolescent females. These findings support the need for weight management efforts aimed at both reducing %FAT and improving fitness in obese adolescents, specifically black females.

TRIAL REGISTRATION

Registered with Clinicaltrials.gov: NCT00562293.

Surgical Treatment of Cervical Spondylotic Myelopathy Associated Hypertension--A Retrospective Study of 309 Patients

Hypertension is the most prevalent cardiovascular disease, and various risk factors are known to be involved in it. Cervical spondylotic myelopathy (CSM) is the most common non-traumatic cause of myelopathy, which displays neurological symptoms and may induce systemic symptoms. To date, it is still unknown whether CSM is associated with hypertension, and if so, whether the decompression operations can attenuate CSM associated hypertension. Here, a total of 309 patients with CSM who received anterior or posterior decompression surgery were enrolled as subjects. Blood pressure measurements were performed before and within one week after the surgery. Among the 309 subjects, 144 (46.6%) of them exhibited hypertension before surgery, a significantly higher ratio than that of the whole population. One week after surgery, blood pressure of 106 (73.6%) patients turned back to normal. Blood pressure of another 37(25.7%) patients decreased with different degrees, although still higher than normal. Moreover, it appears that both approaches were effective in improving blood pressure, while the posterior approach was more effective in decreasing systolic blood pressure. We speculate this type of hypertension might result from hyperactivity of sympathetic nervous system as the heart rate of these patients decreased after surgery as well. Collectively, compression of spinal cord in CSM patients might be associated with hypertension, and decompression surgery largely attenuated this type of hypertension. These findings prove CSM to be a potential associated factor of high blood pressure and may shed light on therapies of hypertension in clinics.

The sympathetic nervous system alterations in human hypertension

Several articles have dealt with the importance and mechanisms of the sympathetic nervous system alterations in experimental animal models of hypertension. This review addresses the role of the sympathetic nervous system in the pathophysiology and therapy of human hypertension. We first discuss the strengths and limitations of various techniques for assessing the sympathetic nervous system in humans, with a focus on heart rate, plasma norepinephrine, microneurographic recording of sympathetic nerve traffic, and measurements of radiolabeled norepinephrine spillover. We then examine the evidence supporting the importance of neuroadrenergic factors as promoters and amplifiers of human hypertension. We expand on the role of the sympathetic nervous system in 2 increasingly common forms of secondary hypertension, namely hypertension associated with obesity and with renal disease. With this background, we examine interventions of sympathetic deactivation as a mode of antihypertensive treatment. Particular emphasis is given to the background and results of recent therapeutic approaches based on carotid baroreceptor stimulation and radiofrequency ablation of the renal nerves.

Therapeutic interventions for hypertension in metabolic syndrome: a comprehensive approach

Hypertension is a major component of the metabolic syndrome and a major cardiovascular risk factor. Both disorders are rapidly increasing in frequency, with hypertension affecting nearly 60 million Americans and over 1 billion people worldwide, and metabolic syndrome affecting 44% of the US population above the age of 60 years. Sedentary lifestyle, together with obesity and aging of the population, are the major contributing factors for this growing epidemic. Hypertension in metabolic syndrome possesses unique pathophysiological aspects that have considerable implications on therapy of this disease. In this article, we review the pathophysiology and provide a rationale for the current therapeutic options in light of the most recent clinical trials in the field.

Hypertension: physiology and pathophysiology

Despite major advances in understanding the pathophysiology of hypertension and availability of effective and safe antihypertensive drugs, suboptimal blood pressure (BP) control is still the most important risk factor for cardiovascular mortality and is globally responsible for more than 7 million deaths annually. Short-term and long-term BP regulation involve the integrated actions of multiple cardiovascular, renal, neural, endocrine, and local tissue control systems. Clinical and experimental observations strongly support a central role for the kidneys in the long-term regulation of BP, and abnormal renal-pressure natriuresis is present in all forms of chronic hypertension. Impaired renal-pressure natriuresis and chronic hypertension can be caused by intrarenal or extrarenal factors that reduce glomerular filtration rate or increase renal tubular reabsorption of salt and water; these factors include excessive activation of the renin-angiotensin-aldosterone and sympathetic nervous systems, increased formation of reactive oxygen species, endothelin, and inflammatory cytokines, or decreased synthesis of nitric oxide and various natriuretic factors. In human primary (essential) hypertension, the precise causes of impaired renal function are not completely understood, although excessive weight gain and dietary factors appear to play a major role since hypertension is rare in nonobese hunter-gathers living in nonindustrialized societies. Recent advances in genetics offer opportunities to discover gene-environment interactions that may also contribute to hypertension, although success thus far has been limited mainly to identification of rare monogenic forms of hypertension.

Health of Indigenous Circumpolar Populations

Indigenous circumpolar populations have experienced profound transitions in lifeways over the past half-century as a result of economic development. Although there have been positive aspects of this social transformation, most circumpolar groups today have a triple burden of disease, with a modestly elevated infectious disease level, an elevated and increasing burden of chronic conditions such as obesity and cardiovascular disease, and high rates of mental health–related challenges. The health of contemporary circumpolar populations is not easily characterized because of dramatic regional differences that stem from socioeconomic disparities among nonindigenous groups, individual population histories, lifestyle factors, environmental pollution, and underlying biological variation. Overall health and well-being range from excellent among the Sami of Sweden and Norway to extremely poor among marginalized native populations in northern Russia. Circumpolar groups today are not only threatened by continued regional economic development and pollution, but also uniquely vulnerable to global climate change.

Chronic kidney disease, obesity, and hypertension: the role of leptin and adiponectin

Chronic kidney disease is a major public health problem and characterized by a progressive loss in renal function over a period of months or years as defined by structural or functional abnormalities of the kidney. Several elements contribute to determine a progression of the kidney injury, inducing a worsening of renal damage and accelerating the decline of renal function: obesity and hypertension are two known factors of kidney progression. Remarkable improvements have been recently achieved in the study of the endocrine features of the adipose tissue and have been able to produce hormone-like peptides named adipokines or adipocytokines. Among these adipocytokines, which represent a link between obesity, hypertension, and chronic nephropathy, leptins and adiponectin appear to play an important role. Leptin not only is a prohypertension element (renal progression factor) through the activation sympathetic nervous, but also is able to induce prosclerotic effects directly on the kidney. In contrast, a decline of adiponectin levels has been shown to be related to a picture of hypertension: an endothelial dysfunction has been described as the main pathogenic mechanism responsible for this phenomenon.

Obesity-related hypertension and its remission following gastric bypass surgery - a review of the mechanisms and predictive factors

It is well established that hypertension and obesity appear to be associated. The exact mechanism by which they are linked is unclear and remains a topic of a great deal of research. Current NICE guidelines recommend that patients with a BMI in excess of 35 kg/m(2) should be considered for bariatric surgery if they have a concomitant obesity-associated condition, of which hypertension is one. The commonest bariatric procedure in the UK is the Roux-en-Y gastric bypass, which has been shown to result in long-standing remission of hypertension in up to 93% of patients. This paper summarizes the existing literature on the main theories as to how obesity leads to hypertension as well as the literature concerning the effects of gastric bypass surgery on hypertension.

Joint statement of the European Association for the Study of Obesity and the European Society of Hypertension: obesity and difficult to treat arterial hypertension

Obese patients are prone to arterial hypertension, require more antihypertensive medications, and have an increased risk of treatment-resistant arterial hypertension. Obesity-induced neurohumoral activation appears to be involved. The association between obesity and hypertension shows large inter-individual variability, likely through genetic mechanisms. Obesity affects overall cardiovascular and metabolic risk; yet, the relationship between obesity and cardiovascular risk is complex and not sufficiently addressed in clinical guidelines. The epidemiological observation that obesity may be protective in patients with established cardiovascular disease is difficult to translate into clinical experience and practice. Weight loss is often recommended as a means to lower blood pressure. However, current hypertension guidelines do not provide evidence-based guidance on how to institute weight loss. In fact, weight loss influences on blood pressure may be overestimated. Nevertheless, weight loss through bariatric surgery appears to decrease cardiovascular risk in severely obese patients. Eventually, most obese hypertensive patients will require antihypertensive medications. Data from large-scale studies with hard clinical endpoints on antihypertensive medications specifically addressing obese patients are lacking and the morbidity from the growing population of severely obese patients is poorly recognized or addressed. Because of their broad spectrum of beneficial effects, renin-angiotensin system inhibitors are considered to be the most appropriate drugs for antihypertensive treatment of obese patients. Most obese hypertensive patients require two or more antihypertensive drugs. Finally, how to combine weight loss strategies and antihypertensive treatment to achieve an optimal clinical outcome is unresolved.

Microneurographic research in women

This article reviews microneurographic research on sympathetic neural control in women under both physiological and pathophysiological conditions across the lifespan. Specifically, the effects of sex, age, race, the menstrual cycle, oral contraceptives, estrogen replacement therapy, and normal pregnancy on neural control of blood pressure in healthy women are reviewed. In addition, sympathetic neural activity during neurally mediated (pre)syncope, the Postural Orthostatic Tachycardia Syndrome (POTS), obesity, the Polycystic Ovary Syndrome (PCOS), gestational hypertension, and preeclampsia, chronic essential hypertension, heart failure, and myocardial infarction in women are also reviewed briefly. It is suggested that microneurographic studies provide valuable information regarding autonomic circulatory control in women of different ages and in most cases, excessive sympathetic activation is associated with specific medical conditions regardless of age and sex. In some situations, sympathetic inhibition or withdrawal may be the underlying mechanism. Information gained from previous and recent microneurographic studies has significant clinical implications in women's health, and in some cases could be used to guide therapy if more widely available.

Mechanisms linking obesity to hypertension

Obesity-related hypertension is increasingly recognized as a distinct hypertensive phenotype requiring a modified approach to diagnosis and management. In this review rapidly evolving insights into the complex and interdependent mechanisms linking obesity to hypertension are discussed. Overweight and obesity are associated with adipose tissue dysfunction, characterized by enlarged hypertrophied adipocytes, increased infiltration by macrophages and marked changes in secretion of adipokines and free fatty acids. This results in chronic vascular inflammation, oxidative stress, activation of the renin-angiotensin-aldosterone system and sympathetic overdrive, eventually leading to hypertension. These mechanisms may provide novel targets for anti-hypertensive drug treatment. Recognition of obesity-related hypertension as a distinct diagnosis enables tailored therapy in clinical practice. This includes lifestyle modification and accommodated choice of blood pressure-lowering drugs.

Hypertension in obesity

Obesity and HTN are on the rise in the world. HTN seems to be the most common obesity-related health problem and visceral obesity seems to be the major culprit. Unfortunately, only 31% of hypertensives are treated to goal. This translates into an increased incidence of CVD and related morbidity and mortality. Several mechanisms have been postulated as the causes of obesity-related HTN. Activation of the RAAS, SNS, insulin resistance, leptin, adiponectin, dysfunctional fat, FFA, resistin, 11 Beta dehydrogenase, renal structural and hemodynamic changes, and OSA are some of the abnormalities in obesity-related HTN. Many of these factors are interrelated. Treatment of obesity should begin with weight loss via lifestyle modifications, medications, or bariatric surgery. According to the mechanisms of obesity-related HTN, it seems that drugs that blockade the RAAS and target the SNS should be ideal for treatment. There is not much evidence in the literature that one drug is better than another in controlling obesity-related HTN. There have only been a few studies specifically targeting the obese hypertensive patient, but recent trials that emphasize the importance of BP control have enrolled both overweight and obese subjects. Until we have further studies with more in-depth information about the mechanisms of obesity-related HTN and what the targeted treatment should be, the most important factor necessary to control the obesity-related HTN pandemic and its CVD and CKD consequences is to prevent and treat obesity and to treat HTN to goal.

Association of adiposity with pulse pressure amongst gujarati Indian adolescents

BACKGROUND AND AIM

The current study was conducted to determine the effect of adiposity on vascular distensibility in Gujarati Indian adolescents as research indicating the pathogenesis of hypertension among overweight and/or obese Indian adolescents is scant and ethnic differences exist in the pathogenesis of hypertension

MATERIALS AND METHODS

A cross-sectional study was conducted on 488 Gujarati Indian adolescents of 16-19 years age group. Adiposity was assessed in terms of BMI, Body Fat %, Fat Mass, Fat Mass Index and Waist Circumference. Arterial blood pressure was recorded and pulse pressure (PP) was calculated using the standard equation based on the difference between systolic blood pressure (SBP) and diastolic blood pressure (DBP). Pearson's correlation coefficient was determined to find the association between the markers of adiposity and SBP, DBP and PP.

RESULT

A significant positive correlationship was found between adiposity and PP in boys. However, no significant correlationship was found between adiposity and PP in girls.

CONCLUSION

An increase in total as well as visceral adiposity is probably associated with a decrease in vascular distensibility in the Gujarati Indian adolescent boys but not in girls, thus indicating a protective role of female sex hormone estrogen which has been shown earlier to protect the vasculature from atherosclerosis, endothelial dysfunction which occurs with increase in adiposity.

Obesity-related hypertension: epidemiology, pathophysiology, and clinical management

The prevalence of obesity, including childhood obesity, is increasing worldwide. Weight gain is associated with increases in arterial pressure, and it has been estimated that 60-70% of hypertension in adults is attributable to adiposity. Centrally located body fat, associated with insulin resistance and dyslipidemia, is a more potent determinant of blood pressure elevation than peripheral body fat. Obesity-related hypertension may be a distinct hypertensive phenotype with distinct genetic determinants. Mechanisms of obesity-related hypertension include insulin resistance, sodium retention, increased sympathetic nervous system activity, activation of renin-angiotensin-aldosterone, and altered vascular function. In overweight individuals, weight loss results in a reduction of blood pressure, however, this effect may be attenuated in the long term. An increasing number of community-based programs (including school programs and worksite programs) are being developed for the prevention and treatment of obesity. Assessment and treatment of the obese hypertensive patient should address overall cardiovascular disease (CVD) risk. There are no compelling clinical trial data to indicate that any one class of antihypertensive agents is superior to others, and in general the principles of pharmacotherapy for obese hypertensive patients are not different from nonobese patients. Future research directions might include: (i) development of effective, culturally sensitive strategies for the prevention and treatment of obesity; (ii) clinical trials to identify the most effective drug therapies for reducing CVD in obese, hypertensive patients; (iii) continued search for the genetic determinants of the obese, hypertensive phenotype.

Regulatory effects of Y4 receptor agonist (BVD-74D) on food intake

The objective of this study was to clarify the role of a novel agonist with high selectivity and affinity for Y4 receptors in the regulation of food intake. The Y4 receptor agonist BVD-74D was administered to C57BL/6J mice that were fed with a normal or high-fat diet, and to fatty liver Shionogi (FLS)-ob/ob mice; the food intake, water intake, and body weight gain were measured in these mice. In the mice fed with a normal diet, the cumulative food intake significantly decreased at 20 min and 1 h after the administration of 1 mg/kg of BVD-74D and at 1, 2, 4, 8, and 24 h after the administration of 10 mg/kg of BVD-74D. Moreover, the cumulative water intake and body weight gain significantly decreased in these mice. Among the mice that were fed with a high-fat diet, the cumulative food intake and water intake significantly decreased 1, 2, and 4 h after BVD-74D (10 mg/kg) administration. Furthermore, the cumulative food intake significantly decreased 2 and 4 h after BVD-74D (10 mg/kg) administration in the FLS-ob/ob mice. Thus, we propose that the novel Y4 receptor agonist BVD-74D has suppressive effects on food intake, water intake, and weight gain in normal mice fed with normal diets and on food intake in normal mice fed with high-fat diets and in FLS-ob/ob mice. These findings indicate that the Y4 receptor and its agonist would be promising targets for obesity.

Mechanisms of obesity-induced hypertension

The relationship between obesity and hypertension is well established both in children and adults. The mechanisms through which obesity directly causes hypertension are still an area of research. Activation of the sympathetic nervous system has been considered to have an important function in the pathogenesis of obesity-related hypertension. The arterial-pressure control mechanism of diuresis and natriuresis, according to the principle of infinite feedback gain, seems to be shifted toward higher blood-pressure levels in obese individuals. During the early phases of obesity, primary sodium retention exists as a result of increase in renal tubular reabsorption. Extracellular-fluid volume is expanded and the kidney-fluid apparatus is resetted to a hypertensive level, consistent with a model of hypertension because of volume overload. Plasma renin activity, angiotensinogen, angiotensin II and aldosterone values display significant increase during obesity. Insulin resistance and inflammation may promote an altered profile of vascular function and consequently hypertension. Leptin and other neuropeptides are possible links between obesity and the development of hypertension. Obesity should be considered as a chronic medical condition, which is likely to require long-term treatment. Understanding of the mechanisms associated with obesity-related hypertension is essential for successful treatment strategies.

Adiposity-independent sympathetic activity in black men

Obesity is thought to lead to sympathetic overactivity as a compensatory adjustment to weight gain. However, most of the experimental support for the hypothesis has been derived from white cohorts. Our previous study in blacks indicated that sympathetic nerve activity (SNA) is closely correlated with body mass index only in women, whereas, in black men, SNA is elevated and dissociated from adiposity (Abate et al., Hypertension 38: 379-383, 2001). To further determine whether total and regional adiposity are determinants of SNA in blacks, we performed a prospective weight loss study in 12 normotensive obese black men and 9 obese black women. SNA, body mass index, and abdominal fat mass were measured before and 16 wk after hypocaloric diet. The major new findings are that, in obese black men, the dietary-induced weight loss of 11.3+/-0.8 kg resulted in reduction in plasma leptin, insulin, and visceral abdominal fat but had no effect on SNA (from baseline of 26+/-4 to 28+/-3 bursts/min, P=not significant). In contrast, in black women, weight loss of 8.0+/-0.9 kg caused similar reductions in plasma leptin, insulin, and visceral abdominal fat and led to a reduction in SNA by 40% (from baseline of 22+/-2 to 13+/-3 bursts/min, P<0.05). In conclusion, these new data from this prospective study provide strong support for a major adiposity-independent sympathetic activity in black men and adiposity-related sympathetic activity in black women.

Autonomic dysregulation in ob/ob mice is improved by inhibition of angiotensin-converting enzyme

The leptin-deficient ob/ob mice are insulin resistant and obese. However, the control of blood pressure in this model is not well defined. The goal of this study was to evaluate the role of leptin and of the renin-angiotensin system in the cardiovascular abnormalities observed in obesity using a model lacking leptin. To this purpose, we measured blood pressure in ob/ob and control animals by radiotelemetry combined with fast Fourier transformation before and after both leptin and enalapril treatment. Autonomic function was assessed pharmacologically. Blood pressure during daytime was slightly higher in the ob/ob compared to control mice, while no difference in heart rate was observed. Blood pressure response to trimetaphane and heart rate response to metoprolol were greater in ob/ob mice than in control littermates indicating an activated sympathetic nervous system. Heart rate response to atropine was attenuated. Baroreflex sensitivity and heart rate variability were blunted in ob/ob mice, while low frequency of systolic blood pressure variability was found increased. Chronic leptin replacement reduced blood pressure and reversed the impaired autonomic function observed in ob/ob mice. Inhibition of angiotensin-converting enzyme by enalapril treatment had similar effects, prior to the loss of weight. These findings suggest that the renin-angiotensin system is involved in the autonomic dysfunction caused by the lack of leptin in ob/ob mice and support a role of this interplay in the pathogenesis of obesity, hypertension, and metabolic syndrome.

Biochemical risk factors for development of obesity in first-episode schizophrenia

Obesity is a serious health issue for many patients with schizophrenia. There is a lack of predictors for and understanding of the development of obesity in the early phase of the illness. Therefore we investigated a set of routine biochemistry variables in blood as predictors of the development of obesity and weight gain over 5 years in an observational cohort study of patients with first-episode schizophrenia (n=59). Twelve percent of the patients were obese at baseline and 37% were obese at the 5-year follow-up. The mean body mass index (BMI) change over 5 years was a 4.1 kg/m(2) increase (4.5 SD). Obesity was predicted by baseline hemoglobin levels (odds ratio per standard deviation [OR/SD] 3.3, 95% confidence interval [CI] 1.4 to 7.5), red blood cell count (OR/SD 2.6, 95% CI 1.2 to 5.5), hematocrit (OR/SD 2.8, 95% CI 1.3 to 5.9), gamma-glutamyltransferase (OR/SD 2.8, 95% CI 1.2-6.3) and creatinine (OR/SD 3.1, 95% CI 1.2 to 8.0). After adjustment for baseline BMI, the associations were attenuated for gamma-glutamyltransferase and creatinine. Low baseline BMI was associated with a greater BMI increase. The major conclusion is that easily available routine biochemistry markers can be useful in predicting the development of obesity in first-episode schizophrenia. The mechanisms underlying the observed associations are unknown, but the predictors identified in this study could signify dehydration or insulin resistance. These observations open a new window to future research on the mechanisms underlying the development of obesity in schizophrenia.

Is obesity associated with lower body temperatures? Core temperature: a forgotten variable in energy balance

The global increase in obesity, along with the associated adverse health consequences, has heightened interest in the fundamental causes of excessive weight gain. Attributing obesity to "gluttony and sloth", blaming the obese for overeating and limiting physical activity, oversimplifies a complex problem, since substantial differences in metabolic efficiency between lean and obese have been decisively demonstrated. The underlying physiological basis for these differences have remained poorly understood. The energetic requirements of homeothermy, the maintenance of a constant core temperature in the face of widely divergent external temperatures, accounts for a major portion of daily energy expenditure. Changes in body temperature are associated with significant changes in metabolic rate. These facts raise the interesting possibility that differences in core temperature may play a role in the pathophysiology of obesity. This review explores the hypothesis that lower body temperatures contribute to the enhanced metabolic efficiency of the obese state.

Sympathetic nervous system behavior in human obesity

The sympathetic nervous system (SNS) plays an essential role in the regulation of metabolic and cardiovascular homeostasis. Low SNS activity has been suggested to be a risk factor for weight gain and obesity development. In contrast, SNS activation is characteristic of a number of metabolic and cardiovascular diseases that occur more frequently in obese individuals. Until recently, the relation between obesity and SNS behavior has been controversial because previous approaches for assessing SNS activity in humans have produced inconsistent findings. Beginning in the early 1990s, many studies using state of the art neurochemical and neurophysiological techniques have provided important insight. The purpose of the present review is to provide an overview of our current understanding of the region specific alterations in SNS behavior in human obesity. We will discuss findings from our own laboratory which implicate visceral fat as an important depot linking obesity with skeletal muscle SNS activation. The influence of weight change on SNS behavior and the potential mechanisms and consequences of region specific SNS activation in obesity will also be considered.

Mediators of sympathetic activation in metabolic syndrome obesity

The metabolic syndrome represents a major public health burden because of its high prevalence in the general population and its association with cardiovascular disease and type 2 diabetes. Accumulated evidence based on biochemical, neurophysiologic, and indirect measurements of autonomic activity indicate that visceral obesity and the metabolic syndrome are associated with enhanced sympathetic neural drive and vagal impairment. The mechanisms linking metabolic syndrome with sympathetic activation are complex and not completely understood, and cause-effect relationships need further clarification from prospective trials. Components of the metabolic syndrome that may directly or indirectly enhance sympathetic drive include hyperinsulinemia, leptin, nonesterified fatty acids, proinflammatory cytokines, angiotensinogen, baroreflex impairment, and obstructive sleep apnea. beta-Adrenoceptor polymorphisms have also been associated with adrenoceptor desensitization, increased adiposity, insulin resistance, and enhanced sympathetic activity. Because chronic sympathetic activation contributes to hypertension and its target-organ damage, sympathoinhibition remains an important goal in the therapeutic management of the metabolic syndrome.

Blunted sympathetic neural response to oral glucose in obese subjects with the insulin-resistant metabolic syndrome

BACKGROUND

Glucose ingestion stimulates sympathetic nervous system (SNS) activity in lean subjects, whereas blunted responses have been reported in the obese.

OBJECTIVE

The objective was to investigate the impact of insulin resistance on the SNS response to oral glucose.

DESIGN

Nineteen insulin-resistant (IR) and 12 insulin-sensitive (IS) obese subjects with the metabolic syndrome and matched for age, sex, and blood pressure participated. Simultaneous measurements of muscle sympathetic nerve activity (MSNA) by microneurography, whole-body norepinephrine spillover rate, cardiac baroreflex sensitivity (BRS), calf blood flow, and arterial blood pressure were made at baseline and 30, 60, 90, and 120 min after a 75-g glucose load.

RESULTS

IR subjects had a higher insulin area under the curve from 0 to 120 min (AUC(0-120): 13,468 +/- 677 compared with 6399 +/- 612 mU/L . min; P < 0.001), glucose AUC(0-120) (P < 0.05), and resting MSNA (41 +/- 3 compared with 31 +/- 3 bursts/min; P = 0.03) than did IS subjects. MSNA and the norepinephrine spillover rate increased from baseline (by 29 +/- 7% and 40 +/- 13%, respectively; P < or = 0.001 for both) in IS subjects after the glucose load. In contrast, there was a blunted and delayed sympathetic response in IR subjects. Cardiac BRS and diastolic blood pressure decreased, whereas calf blood flow increased after the glucose load and by a similar magnitude in both groups (P < 0.01). Body mass index, abdominal fat, and insulin AUC(0-120) were independent (inverse) predictors of the SNS response.

CONCLUSIONS

IR subjects with the metabolic syndrome have a blunted SNS response to oral glucose compared with IS subjects with the metabolic syndrome, which is related to central adiposity and the insulin response but not to differences in skeletal muscle vasodilation or BRS.

Influences of gender on the interaction between sympathetic nerve traffic and central adiposity

CONTEXT

Sympathetic activation promotes insulin resistance and arterial hypertension with increasing adiposity. A difference in the relationship between adiposity and sympathetic activity between women and men could contribute to the known gender difference in cardiovascular disease risk.

OBJECTIVE

We tested whether muscle sympathetic nerve activity (MSNA) is correlated differently with waist circumference, waist to hip ratio (WHR), and body mass index (BMI) in women and men.

DESIGN AND SETTING

We pooled data from two microneurography centers (Berlin, Germany; Gdansk, Poland) for a cross-sectional study.

PARTICIPANTS

We studied 111 normotensive, healthy Caucasian subjects (70 males and 41 females). Age ranged between 19 and 62 yr and BMI ranged between 18 and 40 kg/m(2).

INTERVENTION

No intervention was applied during the study.

MEASUREMENTS

Supine heart rate, blood pressure, and MSNA were recorded after at least 30 min rest.

RESULTS

MSNA in bursts per minute was age dependent in both sexes [r (male) = 0.56, r (female) = 0.34, P < 0.01]. Controlling for waist and hip circumferences, age dependence remained highly significant in men (r = 0.43) and women (r = 0.43). Adjusting for age, in men, waist circumference (r = 0.29), WHR (r = 0.39), and BMI (r = 0.31) were predictive for MSNA and directly correlated (P < 0.01) but not in women. Adjusting for BMI, in men, only WHR (r = 0.40) remained predictive for MSNA.

CONCLUSION

These data support the hypothesis of a gender difference in the regulation of the sympathetic nervous system, in which MSNA mainly relates to WHR in men but not women. The phenomenon may contribute to the sexual dimorphism in cardiovascular disease risk.

Comparison of diagnostic criteria of the metabolic syndrome in 3 ethnic groups of Canada

The metabolic syndrome (MetS) is a cluster of metabolic abnormalities in which visceral obesity is a prominent feature. Although a matter of debate, the MetS essentially represents "at risk obesity." The purpose of this study was to compare the various definitions of MetS, with a special focus on abdominal obesity, and to explore sex and ethnic differences in the prevalence and nature of this syndrome in 3 ethnic groups residing in the Canadian province of Québec. The study population included adult participants of 3 cross-sectional health surveys conducted in southern Québec, James Bay, and Nunavik between 1990 and 1992. A total of 2613 adults (18-74 years old) were included: 1417 Quebecers, 817 Indian Crees, and 379 Inuit. The prevalence of MetS varied by definitions, and the highest agreement was observed between the National Cholesterol Education Program-Adult Treatment Panel III and the International Diabetes Federation (79%). Most women (25%), regardless of ethnic origin, presented with a "triad" profile characterized by high waist circumference, elevated triglycerides, and low high-density lipoprotein, whereas 20% of men had the "deadly quartet" of high blood pressure with the triad mentioned above. Furthermore, our results highlight an obvious difference in the impact of the increased abdominal obesity on metabolic parameters such as insulin resistance measured by the homeostasis model assessment according to ethnic origin (P < .001). These 3 unique population-based samples suggest that abdominal obesity does not have a similar deleterious impact according to ethnicity, suggesting the need for an ethnic-based MetS definition.

Hypertension in obesity

Hypertension and obesity are major components of the cardiometabolic syndrome and are both on the rise worldwide, with enormous consequences on global health and the economy. The relationship between hypertension and obesity is multifaceted; the etiology is complex and it is not well elucidated. This article, reviews the current knowledge on obesity-related hypertension. Further understanding of the underlying mechanisms of this epidemic will be important in devising future treatment avenues.

A sympathetic view of the sympathetic nervous system and human blood pressure regulation

New ideas about the relative importance of the autonomic nervous system (and especially its sympathetic arm) in long-term blood pressure regulation are emerging. It is well known that mean arterial blood pressure is normally regulated in a fairly narrow range at rest and that blood pressure is also able to rise and fall 'appropriately' to meet the demands of various forms of mental, emotional and physical stress. By contrast, blood pressure varies widely when the autonomic nervous system is absent or when key mechanisms that govern it are destroyed. However, 24 h mean arterial pressure is still surprisingly normal under these conditions. Thus, the dominant idea has been that the kidney is the main long-term regulator of blood pressure and the autonomic nervous system is important in short-term regulation. However, this 'renocentric' scheme can be challenged by observations in humans showing that there is a high degree of individual variability in elements of the autonomic nervous system. Along these lines, the level of sympathetic outflow, the adrenergic responsiveness of blood vessels and individual haemodynamic patterns appear to exist in a complex, but appropriate, balance in normotension. Furthermore, evidence from animals and humans has now clearly shown that the sympathetic nervous system can play an important role in longer term blood pressure regulation in both normotension and hypertension. Finally, humans with high baseline sympathetic traffic might be at increased risk for hypertension if the 'balance' among factors deteriorates or is lost. In this context, the goal of this review is to encourage a comprehensive rethinking of the complexities related to long-term blood pressure regulation in humans and promote finer appreciation of physiological relationships among the autonomic nervous system, vascular function, ageing, metabolism and blood pressure.