Obesity, hypertension, and sympathetic nervous system activity

Modulation of Sirt1 and FoxO1 on Hypothalamic Leptin-Mediated Sympathetic Activation and Inflammation in Diet-Induced Obese Rats

Background Hypothalamic leptin-mediated signaling contributes to the exaggerated sympatho-excitation and increased blood pressure in obesity-associated hypertension. The aim of the study was to investigate the roles of energy-sensing enzyme sirtuin1 (Sirt1) and forkhead box protein O1 (FoxO1) on the hypothalamic leptin-mediated high sympathetic nerve activity and inflammation in obesity. Methods and Results Sprague Dawley rats were fed with high-fat diet (HFD) for 12 weeks. In vivo, the potential of Srit1 and FoxO1 in the sympathetic effects of leptin was investigated via siRNA injection to knockdown Sirt1 or FoxO1 gene in the arcuate nucleus (ARCN) of hypothalamus in rats. In vitro, the effects of Sirt1 or FoxO1 on leptin-mediated inflammation were observed in proopiomelanocortin (POMC) and microglial cells. Knockdown Sirt1 by siRNA significantly reduced the renal sympathetic nerve activity (RSNA) and blood pressure responses to leptin injection in the ARCN in the HFD rats. Conversely, knockdown FoxO1 significantly enhanced the RSNA and blood pressure responses to leptin injection in the HFD rats. Knockdown Sirt1 reduced the levels of pro-inflammatory cytokines interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), C1q/TNF-related protein-1 (CTRP1), and immune cell infiltration in the ARCN in the HFD rats. Knockdown FoxO1 significantly increased the level of IL-6 in the ARCN of HFD rats. In cultured hypothalamic POMC and microglial cells, knockdown Sirt1 significantly reduced leptin-induced IL-6 expression, affected the levels of AMP-activated protein kinase (AMPK) and serine/threonine-specific protein kinase (Akt). Knockdown FoxO1 significantly increased leptin-induced IL-6 in both POMC cells and microglial cells. Conclusions These data suggest that both Sirt1 and FoxO1 are the key modulators of leptin signaling in the hypothalamus contributed to the over sympathetic activation and inflammation in obesity.

Cadmium exposure negatively affects the microarchitecture of trabecular bone and decreases the density of a subset of sympathetic nerve fibers innervating the developing rat femur

Cadmium (Cd) is toxic to the skeletal system resulting in bone loss and pain. We aimed at determining the effect of chronic Cd exposure on bone density and microarchitecture along with changes in the density of a subset of sensory and sympathetic nerve fibers innervating the developing rat femur. Newborn male Wistar rats were injected daily for 49 days with CdCl₂ (1 mg/kg i.p.) or saline solution (control group). At the day of sacrifice, levels of Cd in the right femur, liver and kidney were determined by atomic absorption spectrophotometry. Additionally, microCT followed by immunohistochemical analyses were performed in the left femur. Results showed Cd accumulation in trabecular bone neared levels seen in liver and kidney. Cd concentration in cortical bone was significantly lower versus trabecular bone. MicroCT analysis revealed that Cd-exposed rats had a significant decrease in trabecular bone parameters at the distal femoral metaphysis; however, most of the cortical bone parameters were not significantly affected. Cd-exposed rats showed a significant loss of TH⁺ sympathetic nerve fibers, but not of CGRP⁺ sensory nerve fibers, at the level of bone marrow of the femoral diaphysis as compared to control rats. This study shows that Cd negatively affects bone density and microarchitecture of trabecular bone and decreases the density of sympathetic nerve fibers innervating rat femur. Future studies are warranted to determine the toxigenic mechanisms of Cd on sympathetic nerves and how sympathetic denervation influences bone loss in animals exposed to Cd.

Coexistence of fibromyalgia and metabolic syndrome in females: The effects on fatigue, clinical features, pain sensitivity, urinary cortisol and norepinephrine levels: A cross-sectional study

Objectives

This study aims to evaluate the coexistence of metabolic syndrome (MetS) and fibromyalgia syndrome (FMS) and determine the effects of this coexistence on neuroendocrine levels and clinical features of FMS.

Patients and methods

One-hundred female FMS patients (mean age 40.1±7.8 years; range, 24 to 58 years) and 38 healthy females (mean age 40.4±5.8 years; range, 30 to 55 years) were included in this cross-sectional study. MetS was identified by using the criteria from the Adult Treatment Panel III. Widespread pain index, symptom severity score and number of tender points were determined. Visual analog scale, Fibromyalgia Impact Questionnaire, Fatigue Severity Scale, Beck Depression Inventory, and pain pressure threshold were used as the outcome measures. The severity of FMS was assessed with total myalgic score (TMS) and control point score.

Results

Twenty-four (24%) of the 100 FMS patients and three (7.9%) of the 38 control patients fulfilled the MetS criteria (p=0.047). The coexistence of FMS and MetS was associated with higher symptom severity score (p=0.004), widespread pain index (p=0.001), number of tender points (p=0.039), and lower total myalgic score (p=0.029) values. There was a significant association between the occurrence of FMS and MetS (odds ratio=3.76; 95% confidence interval: 1.04-13.4; p=0.043).

Conclusion

We found that patients with FMS had a nearly four times higher risk for MetS and the coexisting MetS may increase the severity of FMS. In clinical practice, when evaluating a patient with FMS, metabolic characteristics should also be evaluated.

Leptin-Mediated Sympathoexcitation in Obese Rats: Role for Neuron-Astrocyte Crosstalk in the Arcuate Nucleus

Introduction

Accumulated evidence indicates that obesity is associated with enhanced sympathetic activation. Hypothalamic leptin-mediated signaling may contribute to the exaggerated sympathoexcitation of obesity. The goal of this study was to investigate the "neuron-astrocyte" interaction affecting leptin-mediated sympathoexcitation within the arcuate nucleus (ARCN) of the hypothalamus in obese rats.

Methods and Results

Obesity was induced by high-fat diet (HFD, 42% of calories from fat) in Sprague Dawley rats. Twelve weeks of HFD produced hyperleptinemia, hyperlipidemia, and insulin resistance. In anesthetized rats, microinjections of leptin into the ARCN induced increases in heart rate (HR), renal sympathetic nerve activity (RSNA), and mean arterial pressure (MAP) in both control and HFD rats. However, microinjections of leptin in HFD rats elicited higher responses of RSNA and arterial pressure than control-fed rats. It also caused the inhibition of astrocytes within the ARCN using an astrocytic metabolic inhibitor, fluorocitrate, and reduced leptin-induced sympathetic activity and blood pressure responses. Moreover, the expression of the leptin receptor in the ARCN of HFD-fed rats was significantly increased compared to rats fed a control diet. Immunohistochemistry analysis revealed leptin receptor localization from both neurons and astrocytes of the ARCN. HFD rats exhibited increased protein expression of glial fibrillary acidic protein (GFAP) in the ARCN. We also found that the expression of astrocyte-specific glutamate transporters and excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2) were decreased within the ARCN of the HFD rats. In cultured astrocytic C6 cells, 24 h of leptin treatment increased the protein expression of GFAP and reduced the expression of EAAT1 and EAAT2.

Conclusion

The results suggest that central leptin signaling occurs via neuron-astrocyte interactions in the ARCN and contributing to the exaggerated sympathoexcitation observed in obese rats. The effects may be mediated by the action of leptin on regulating astrocytic glutamate transporters within the ARCN of the hypothalamus.

Hypertension Prevalence Based on Three Separate Visits and Its Association With Obesity Among Chinese Children and Adolescents

Background: Clinical practice guidelines recommended that hypertension in children and adolescents should be defined based on elevated blood pressure (BP) on at least three separate occasions. Therefore, in the present study, we aimed to estimate the prevalence of hypertension based on three separate visits among Chinese children and adolescents and to examine its relationship with obesity. Methods: A school-based cross-sectional survey was performed in children and adolescents in Jinan, China between September 2012 and September 2014. A total of 7,832 children and adolescents aged 6-17 years were included. Anthropometric data and BP were measured by trained examiners. Elevated BP was defined as BP ≥ 95th percentile for age and sex based on the Chinese reference data. Participants with elevated BP at the first visit underwent a second visit 2 weeks later, and a third visit was conducted if BP was still high at the second visit. Hypertension was defined as having an elevated BP at all three visits. Obesity was defined in three ways by using body mass index, waist circumference, and waist-to-height ratio. Results: The prevalence of elevated BP decreased substantially across three separate visits, with the prevalence of 17.2, 8.6, and 4.9%, respectively. Obesity was an independent risk factor for elevated BP during each visit. Based on the body mass index, obesity was associated with higher risk of elevated BP, with the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of 8.6 (6.8-11.0), 12.5 (9.1-17.3), and 14.0 (8.9-22.2), respectively, at the first, second and third visit. The ORs of elevated BP were similar in association with obesity defined by waist circumference or waist-to-height ratio. Conclusions: The prevalence of hypertension based on three visits was ~5% in Chinese children and adolescents. There was a dose-response relationship between obesity and elevated BP across three visits.

Maternal protein malnutrition induced-hypertension: New evidence about the autonomic and respiratory dysfunctions and epigenetic mechanisms

Maternal protein malnutrition during the critical stages of development (pregnancy, lactation and first infancy) can lead to adult hypertension. Studies have shown that renal and cardiovascular dysfunctions can be associated to the development of hypertension in humans and rats exposed to maternal protein malnutrition. The etiology of hypertension, however, includes a complex network involved in central and peripheral blood pressure control. Recently, the hyperactivity of the sympathetic nervous system in protein-restricted rats has been reported. Studies have shown that protein malnutrition during pregnancy and/or lactation alters blood pressure control through mechanisms that include central sympathetic-respiratory dysfunctions and epigenetic modifications, which may contribute to adult hypertension. Thus, this review will discuss the historical context, new evidences of neurogenic disruption in respiratory-sympathetic activities and possible epigenetic mechanisms involved in maternal protein malnutrition induced- hypertension.

Effect of maternal dyslipidaemia on the cardiorespiratory physiology and biochemical parameters in male rat offspring

The present study evaluated the effects of maternal dyslipidaemia on blood pressure (BP), cardiorespiratory physiology and biochemical parameters in male offspring. Wistar rat dams were fed either a control (CTL) or a dyslipidaemic (DLP) diet during pregnancy and lactation. After weaning, both CTL and DLP offspring received standard diet. On the 30th and 90th day of life, blood samples were collected for metabolic analyses. Direct measurements of BP, respiratory frequency (RF), tidal volume (VT) and ventilation (VE) under baseline condition, as well as during hypercapnia (7 % CO2) and hypoxia (KCN, 0·04 %), were recorded from awake 90-d-old male offspring. DLP dams exhibited raised serum levels of total cholesterol (TC) (4·0-fold), TAG (2·0-fold), VLDL+LDL (7·7-fold) and reduced HDL-cholesterol (2·4-fold), insulin resistance and hepatic steatosis at the end of lactation. At 30 d of age, the DLP offspring showed an increase in the serum levels of TC (P<0·05) and VLDL+LDL (P<0·05) in comparison with CTL offspring. At 90 d of age, DLP offspring exhibited higher mean arterial pressure (MAP, approximately 34 %). In the spectral analysis, the DLP group showed augmented low-frequency (LF) power and LF:high-frequency (HF) ratio when compared with CTL offspring. In addition, the DLP animals showed a larger delta variation in arterial pressure after administration of the ganglionic blocker (P=0·0003). We also found that cardiorespiratory response to hypercapnia and hypoxia was augmented in DLP offspring. In conclusion, the present data show that maternal dyslipidaemia alters cardiorespiratory physiology and may be a predisposing factor for hypertension at adulthood.

Early Reverse Cardiac Remodeling Effect of Laparoscopic Sleeve Gastrectomy

BACKGROUND

This study evaluated the early postoperative benefits of laparoscopic sleeve gastrectomy (LSG) on the left ventricular (LV) function and left atrial (LA) structural, mechanical, and electrical functions in severely obese patients.

METHODS

Thirty-two patients with severe obesity who were consecutively scheduled for LSG and 30 healthy controls were included in the study. LV global longitudinal strain (LGS), peak atrial longitudinal strain (PALS), and strain rates (S-Sr, E-Sr, and A-Sr) of the lateral and septal LA walls, and intra- and interatrial dyssynchrony periods for all subjects were evaluated using strain echocardiography. The measurements were repeated in patients 1 month after surgery.

RESULTS

LGS of the LV was significantly depressed in the patient group compared with the control group (p < 0.001). LA peak septal and lateral wall strain values were significantly lower in patients than in controls (both p values <0.001). LA intra- and interatrial dyssynchrony periods were longer in patients than in controls (p = 0.012 and p = 0.004, respectively). LGS significantly improved after LSG (p < 0.001). Significant reductions were noted in the LA antero-posterior diameter (p < 0.001), LA volume index (LAVI, p = 0.001), and in the mitral velocity to the early diastolic velocity of the mitral annulus ratio (E/e' ratio, p = 0.046). The PALS of the septal and lateral LA walls significantly increased (p = 0.001 and p < 0.001, respectively). S-Sr, E-Sr, and A-Sr values of the septal LA wall (p = 0.049, p < 0.001, and p = 0.001, respectively) and the lateral LA wall (p = 0.009, p = 0.007, and p = 0.002, respectively) significantly improved postoperatively. Intra- and interatrial dyssynchrony significantly decreased (p = 0.001 and p < 0.001, respectively). Weight loss positively correlated with changes in LGS (R = 0.39, p = 0.039), LAVI (R = 0.39, p = 0.034), intra-atrial dyssynchrony (R = 0.45, p = 0.021), interatrial dyssynchrony (R = 0.42, p = 0.038), septal LA wall peak strain (R = 0.44, p = 0.027), lateral LA wall peak strain (R = 0.46, p = 0.017), septal LA wall A-Sr (R = 0.43, p = 0.028), and lateral LA wall A-Sr (R = 0.46, p = 0.019). The comparison of postoperative findings of the patients with controls revealed that the LA diameter, both LA volume and volume index (LAVI), E/e' ratio, S-Sr and E-Sr of both lateral and septal LA walls, intra- and interatrial LA dyssynchrony of the patient group became similar to the control group (all p value >0.05). Postoperative A-Sr values of both LA walls (both p value <0.001) were higher in patients than controls.

CONCLUSION

The benefits of LSG on LV and LA function may be observed even in the early postoperative phase. The resulting weight loss correlates with LV and LA reverse remodeling in severely obese patients.

New Insights on the Use of Dietary Polyphenols or Probiotics for the Management of Arterial Hypertension

Arterial hypertension (AH) is one of the most prevalent risk factors for cardiovascular diseases (CD) and is the main cause of deaths worldwide. Current research establish that dietary polyphenols may help to lower blood pressure (BP), thus contributing to the reduction of cardiovascular complications. In addition, the health benefits of probiotics on BP have also attracted increased attention, as probiotics administration modulates the microbiota, which, by interacting with ingested polyphenols, controls their bioavalability. The aim of the present mini-review is to summarize and clarify the effects of dietary polyphenols and probiotics administration on BP using combined evidence from clinical and experimental studies, as well as to discuss the current debate in the literature about the usefulness of this nutritional approach to manage BP. Clinical trials and experimental studies have demonstrated that consuming dietary polyphenols or probiotics in adequate amounts may improve BP, ranging from modest to greater effects. However, the mechanisms linking probiotic intake and reduced BP levels need to be further elucidated as a definitive consensus on the link between intake of polyphenols or probiotics and improvement of AH has not been reached yet.

Stress and salt sensitivity in primary hypertension

As the development of hypertension and target organ damage becomes more prevalent, it becomes exceedingly important to determine the underlying mechanisms through which this detrimental development occurs. Specifically, our studies and others have explored mechanisms through which stress elicits a salt-sensitive response in approximately 20-30 % of the population, resulting in the early development of hypertension and target organ damage. Data associated with this stress-induced cardiovascular response pattern have recently demonstrated additional effects across the body systems including factors contributing to the development of osteoporosis, obesity, autoimmune disease, and chronic inflammation. As each of these diseases become more prevalent in conjunction with hypertension, further research may discover stress and salt sensitivity to be at the "heart" of the matter for the development of many of today's most deadly conditions.

Increased peripheral vascular disease risk progressively constrains perfusion adaptability in the skeletal muscle microcirculation

To determine the impact of progressive elevations in peripheral vascular disease (PVD) risk on microvascular function, we utilized eight rat models spanning "healthy" to "high PVD risk" and used a multiscale approach to interrogate microvascular function and outcomes: healthy: Sprague-Dawley rats (SDR) and lean Zucker rats (LZR); mild risk: SDR on high-salt diet (HSD) and SDR on high-fructose diet (HFD); moderate risk: reduced renal mass-hypertensive rats (RRM) and spontaneously hypertensive rats (SHR); high risk: obese Zucker rats (OZR) and Dahl salt-sensitive rats (DSS). Vascular reactivity and biochemical analyses demonstrated that even mild elevations in PVD risk severely attenuated nitric oxide (NO) bioavailability and caused progressive shifts in arachidonic acid metabolism, increasing thromboxane A2 levels. With the introduction of hypertension, arteriolar myogenic activation and adrenergic constriction were increased. However, while functional hyperemia and fatigue resistance of in situ skeletal muscle were not impacted with mild or moderate PVD risk, blood oxygen handling suggested an increasingly heterogeneous perfusion within resting and contracting skeletal muscle. Analysis of in situ networks demonstrated an increasingly stable and heterogeneous distribution of perfusion at arteriolar bifurcations with elevated PVD risk, a phenomenon that was manifested first in the distal microcirculation and evolved proximally with increasing risk. The increased perfusion distribution heterogeneity and loss of flexibility throughout the microvascular network, the result of the combined effects on NO bioavailability, arachidonic acid metabolism, myogenic activation, and adrenergic constriction, may represent the most accurate predictor of the skeletal muscle microvasculopathy and poor health outcomes associated with chronic elevations in PVD risk.

The influence of high versus low sodium intake on blood pressure and haemodynamics in patients with morbid obesity

BACKGROUND

Many patients with morbid obesity (BMI > 40 kg/m) have hypertension. The complex pathophysiological abnormalities linking hypertension to obesity have not been fully clarified, but abnormal sodium handling could be an important mechanism.

METHOD

Therefore, we examined changes in body fluid compartments and haemodynamic responses (at rest and during exercise) after 5 days of a low-sodium diet (90 mmol/day) and 5 days of a high-sodium diet (250 mmol/day) in 12 morbidly obese, hypertensive patients; 12 morbidly obese, normotensive patients and 12 nonobese controls.

RESULTS

High sodium intake as compared to low sodium intake was associated with an increase in plasma volume (obese, hypertensive patients: 5 ± 4%; obese, normotensive patients: 10 ± 11%; nonobese controls: 7 ± 6%), cardiac output (CO) (obese, hypertensive patients: 17 ± 12%; obese, normotensive patients: 20 ± 16%; nonobese controls: 13 ± 14%) and stroke volume (SV) (obese, hypertensive patients: 27 ± 26%; obese, normotensive patients: 27 ± 24%; nonobese controls: 18 ± 27%) in all three groups with no differences between the groups. Despite an increase in CO during high salt intake, 24-h blood pressure (BP) was unchanged in patients and controls as a result of a reduction in total peripheral resistance (obese, hypertensive patients: -11 ± 11%; obese, normotensive patients: -10 ± 12%; nonobese controls: -5 ± 14%). Similar changes were observed during an incremental bicycle exercise test wherein CO and SV were higher, whereas mean arterial BP was unchanged at each exercise level during high sodium intake.

CONCLUSION

Despite substantial increases in CO and SV, we did not observe any significant change in BP during high sodium intake, neither in morbid obese patients nor in lean individuals.

Effects of bariatric surgery on right ventricular structure and function

AIM

Left ventricular (LV) changes associated with obesity, including LV hypertrophy and impaired LV function, have been shown to be reverted by bariatric surgery. Little is known about the effects of bariatric procedures on right ventricle (RV). We analyzed the literature in order to provide a comprehensive information on RV structural and functional changes, as assessed by imaging techniques, after bariatric surgery.

METHODS AND RESULTS

The studies were identified by the following search terms: 'bariatric surgery', 'obesity', 'left ventricle', 'right ventricle', 'left ventricular hypertrophy', 'right ventricular hypertrophy', 'cardiac hypertrophy', 'ventricular dysfunction', 'echocardiography', 'magnetic resonance imaging' and 'cardiac imaging techniques'.In a pooled population of 537 obese patients with preserved systolic function enrolled in eight studies, bariatric surgery induced beneficial effects on RV morphology and function; the procedures reverted obesity-related right ventricular hypertrophy as suggested by a significant decrease in RV mass, and improved systolic and diastolic RV performance as assessed by traditional and newer echocardiographic indexes. Decrements in body mass index and improvement in obstructive sleep apnea were major factors independently related to the improved RV structure and function.

CONCLUSION

The present review shows that bariatric surgery exerts beneficial effects on RV structure and function in morbidly obese patients. As RV changes are independent predictors of outcomes, improvement of RV structure and function may contribute to the cardioprotective effects of bariatric surgery.

Renal denervation for resistant hypertension and beyond

Despite the availability of more than 125 approved antihypertensive medications, 36 million (48%) of 75 million people with hypertension, including 16 million treated with antihypertensive medications in the United States, do not achieve guideline blood pressure goals known to reduce cardiovascular morbidity and mortality and progression of kidney disease; 3% to 6% of these 75 million hypertensive individuals are estimated to have resistant hypertension. A major contributing factor for poor blood pressure control, besides inadequate diuretic therapy, is failure of antihypertensive agents to inhibit the sympathetic nervous system effectively. Consequently, alternative device-driven approaches have been developed. Recent technical advances targeting renal sympathetic nerves, that is, renal denervation therapy, are the focus of more invasive therapies to treat resistant hypertension. Encouraging results from the SYMPLICITY HTN-2 trial, regarding efficacy and safety of renal denervation therapy, were countered by disappointing efficacy results of SYMPLICITY HTN-3. Reasons for these divergent results and the future of the field are discussed.

Cardiovascular effects of high-fructose intake in rats with nitric oxide deficiency

The aim of this study was to evaluate the involvement of nitric oxide (NO) system damage in the deleterious effects of high-fructose intake in rats. Fructose was administered as 10% solution in drinking water to twelve-week-old male Wistar rats for the period of 8 weeks. Blood pressure was measured by tail-cuff plethysmography. After sacrificing the rats at the end of the treatment, relative weights of heart and liver and biochemical parameters in blood plasma were determined. Reactivity of isolated conduit arteries was measured using a force-displacement transducer for recording isometric tension. Fructose drinking rats had increased blood pressure and impaired acetylcholine-induced relaxation of the thoracic aorta in comparison with control rats drinking just tap water. Relative liver weight and plasma concentrations of glucose and triglycerides were also elevated after fructose administration. In a further group of Wistar rats, inhibition of NO production by administration of N^G-nitro-L-arginine methyl ester (L-NAME; 40 mg/kg/day) was performed throughout fructose intake. L-NAME treatment itself induces increase in blood pressure and relative heart weight as well as impairment in arterial relaxation and contractility. However, in these rats, fructose administration did not cause further elevation of blood pressure and other abnormalities observed in rats receiving fructose without L-NAME. Our results showed that in the state of NO deficiency (induced by L-NAME administration) fructose does not induce cardiovascular and metabolic alterations which develop in rats with a functional NO system. This indicates that impairment of the NO system may participate in many of the adverse effects induced by high-fructose intake.

Association between nocturnal blood pressure dipping and insulin resistance in children affected by NAFLD

The aim of this study was to analyse the relationship between insulin-glucose metabolism, nocturnal blood pressure dipping and nonalcoholic fatty liver disease (NAFLD) in obese adolescents without diabetes. One hundred one consecutive children, with biopsy-proven NAFLD, were included in this study. Blood samples were drawn for the analyses of liver function tests, insulin-glucose metabolism and lipid profile appraisal. An ambulatory blood pressure measurement (ABPM) was performed. Seventy-six children (75.3 %) were systolic nondippers, and 23 of them were diastolic nondippers (30.3 %). No differences were found in the anthropometric parameters between the two groups. When compared to the systolic dippers, the systolic nondippers had higher medians of mean nocturnal blood pressure, glucose at 0, 60 and 120 min in the oral glucose tolerance test (OGTT), OGTT insulin at all time points and insulin-resistance values. No correlation of histopathological features with dipping/nondipping statuses was found.

CONCLUSIONS

We found an association between a nocturnal blood pressure fall and measures of insulin levels, independent of obesity, or daytime blood pressure levels, among the obese patients with NAFLD. Although no association between nondipping profiles and NAFLD was observed in our study, further studies with a longer term follow-up are needed, to better elucidate the complex link between these particular entities.

Left-ventricular hypertrophy and obesity: a systematic review and meta-analysis of echocardiographic studies

AIM

Left-ventricular hypertrophy (LVH) is a frequent complication in obese individuals; an updated review and meta-analysis focusing on this issue is lacking. Thus, we analysed the literature in order to provide a comprehensive information on the left-ventricular structural changes, as assessed by echocardiography, associated to obesity.

DESIGN

A literature search using the keywords 'left ventricle', 'left-ventricular hypertrophy', 'cardiac hypertrophy', 'obesity', 'hypertension' and 'echocardiography' was performed in order to identify relevant papers. Full articles published in English language in the past 12 years reporting studies in adult obese individuals were considered.

RESULTS

A total of 22 studies including 5486 obese individuals were considered. Overall, in the pooled obese population, prevalence of LVH, defined by 12 criteria, was 56.0% (range 20.0-85.0%). Data provided by 15 studies (n = 4999 obese individuals), including 6623 non-obese controls, showed that the probability of having LVH was much higher in cases than in non-obese counterparts (odds ratio 4.19, 95% confidence interval 2.67-6.53, P < 0.01). A meta-regression analysis (n = 2214; 14 studies) showed a direct correlation between BMI and left-ventricular mass (P < 0.01). Among obese patients with LVH (n = 1930; 15 studies), eccentric hypertrophy was more frequent than the concentric phenotype (66 versus 34%; P < 0.01).

CONCLUSIONS

Our analysis shows that LVH is present in a consistent fraction of the obese population and that eccentric hypertrophy prevails over the concentric phenotype. As obesity-related LVH is a powerful risk factor for systolic/diastolic dysfunction, the prevention/treatment of obesity may have a strong, favourable impact on incident heart failure.

The complex interaction between overweight, hypertension, and sympathetic overactivity

There is ample evidence in the epidemiological and clinical literature that hypertension and overweight are closely and causally interrelated. Sympathetic nervous system (SNS) overactivity has been well documented in both hypertension and overweight, but it is not clear whether this is a coincidental finding or whether the association reflects a mechanistic role of SNS in these two interrelated clinical conditions. Whereas in this review we focus on the evidence for a primary role of SNS in the development of hypertension and overweight, it is clear that the process can be initiated from other starting points such as primary overeating or sleep apnea. After overweight evolves, hormones secreted by fat cells further accelerate SNS overactivity, weight gain, and blood pressure increase. The main thesis of this article is that regardless of where the process started, the same clinical picture of hypertension, overweight, and SNS overactivity will emerge. There is good evidence that in genetically prone individuals, prolonged SNS stimulation elicits a down regulation of beta-adrenergic receptors. This in turn decreases the ability to dissipate calories and diminishes the beta-adrenoceptor-mediated vasodilatation. We hypothesize that beta-adrenoceptor downregulation is the linchpin in the association of SNS with overweight and hypertension.

Dysregulation of the Autonomic Nervous System Can Be a Link between Visceral Adiposity and Insulin Resistance

OBJECTIVE

To evaluate the interplay among abdominal adipose tissue distribution, the cortisol axis, the autonomic nervous system, and insulin resistance.

RESEARCH METHODS AND PROCEDURES

Two age-, sex-, and BMI-matched groups were studied. Fifteen subjects were first-degree relatives of patients with type 2 diabetes (R), and 15 had no family history of diabetes (controls, C). A hyperinsulinemic euglycemic clamp, cortisol measurements, and analysis of heart rate variability (HRV) were performed. Computed tomography was performed in a subgroup (n = 9 + 9) to determine abdominal adipose tissue distribution.

RESULTS

R tended to be less insulin-sensitive than C (M value 9.2 +/- 1.0 vs 10.3 +/- 0.7 mg/kg per minute, not significant). Stimulation with tetracosactin or corticotropin releasing hormone yielded lower peak serum cortisol levels in R (p = 0.03 and p = 0.06, respectively). The amount of visceral abdominal fat (VAT) tended to be greater in R. In all subjects, VAT was negatively correlated to insulin sensitivity (r = -0.93, p < 0.001). There was a positive association between VAT and resting heart rate (r = 0.70, p = 0.003) and sympathetic/parasympathetic ratio in HRV assessment after tilt (r = 0.53, p = 0.03). Subcutaneous abdominal tissue was not associated with insulin sensitivity or any of the hormonal or HRV assessments.

DISCUSSION

Subjects genetically predisposed for type 2 diabetes had a tendency toward a larger amount of VAT and to lower insulin sensitivity compared with control subjects. The amount of visceral fat was strongly associated with insulin resistance and signs of a high ratio of sympathetic vs. parasympathetic reactivity. A large amount of visceral fat may act in concert with sympathetic/parasympathetic imbalance to promote the development of insulin resistance, and this may be partly independent of genetic background.

The Relation between Fructose-Induced Metabolic Syndrome and Altered Renal Haemodynamic and Excretory Function in the Rat

This paper explores the possible relationships between dietary fructose and altered neurohumoral regulation of renal haemodynamic and excretory function in this model of metabolic syndrome. Fructose consumption induces hyperinsulinemia, hypertriglyceridaemia, insulin resistance, and hypertension. The pathogenesis of fructose-induced hypertension is dubious and involves numerous pathways acting both singly and together. In addition, hyperinsulinemia and hypertension contribute significantly to progressive renal disease in fructose-fed rats. Moreover, increased activity of the renin-angiotensin and sympathetic nervous systems leading to downregulation of receptors may be responsible for the blunted vascular sensitivity to angiotensin II and catecholamines, respectively. Various approaches have been suggested to prevent the development of fructose-induced hypertension and/or metabolic alteration. In this paper, we address the role played by the renin-angiotensin and sympathetic nervous systems in the haemodynamic alterations that occur due to prolonged consumption of fructose.

Non-dipping pattern in ambulatory blood pressure monitoring is associated with metabolic abnormalities in a random sample of middle-aged subjects

A reduction in the blood pressure decline at night (<10% from daytime systolic blood pressure (SBP)) during 24-h ambulatory blood pressure monitoring (ABPM) ('non-dipping pattern') is associated with cardiovascular morbidity. Our aim was to evaluate whether ABPM characteristics are associated with metabolic abnormalities in subjects without known hypertension or type 2 diabetes mellitus (T2DM). This is a cross-sectional population-based study on middle-aged subjects (n=462). Two distinct definitions of metabolic syndrome (MetS) were used: National Cholesterol Education Program-Third Adult Treatment Panel (NCEP-ATPIII) and International Diabetes Federation (IDF) criteria. Results suggested that subjects characterized by non-dipping in 24 h ABPM were more obese (P=0.014). After adjustment for body mass index, age and sex, non-dippers had higher very-low-density lipoprotein (VLDL)-cholesterol (P=0.003), total (P=0.029)-and VLDL-triglycerides (P=0.026) and oral glucose tolerance test 2 h blood glucose (P=0.027) compared with dippers. Non-dipping status was more common among subjects with MetS (P< or =0.01), impaired glucose tolerance (IGT) (P<0.05) and in those with the combination of IGT-T2DM (P< or =0.01) than among those without these abnormalities. ABPM non-dipping status was an independent predictor of IGT in multivariate models (P<0.05). With respect to MetS components, high triglycerides (P< or =0.005) and low high density lipoprotein-cholesterol (P<0.05) were associated with a non-dipping pattern. The percentage decline in blood pressure from day to night decreased with the number of metabolic abnormalities (P=0.012). In conclusion, ABPM non-dipping status is an independent predictor of glucose intolerance. It is also associated with several other metabolic abnormalities. Whether non-dipping pattern is causally related to these metabolic aberrations remains to be explored in a future prospective follow-up of this cohort.

Time-course changes in macronutrient metabolism induced by a nutritionally balanced low-calorie diet in obese women

The use of low-calorie diets is a common strategy for body-weight reduction purposes, but the time-course of the metabolic changes induced by moderately energy-restricted, otherwise balanced, diets is still poorly known. The aim of this nutritional intervention design was to study in obese women the effect of a balanced low-calorie diet on the metabolic rate, and metabolic fuel utilization changes during the weight loss process through the application of breath tests with stable isotope-labeled tracers. Seven obese (body mass index >30 kg/m(2)) women were assigned to a 10-week dietary hypoenergetic intervention regime supplying 55% of energy as carbohydrate, 30% as fat and 15% as protein. Metabolic rate and substrate utilization were evaluated for 6 h in separate occasions during the weight loss program by indirect calorimetry and after 13C-labeled glucose, triolein and leucine administration. Body weight loss after 10 weeks was 4.2+/-1.1 kg, while the percent body fat decrease was about 5%. Slimming was accompanied by a marked decrease in fasting leptin (about 25%). Postprandial carbohydrate utilization after the administration of a test meal with the same macronutrient distribution as the experimental low-energy diet was decreased (24.1%, P<0.05) as a consequence of the dietary restriction, which was associated with lower insulin plasma levels (P<0.05). Although protein and lipid oxidation were not significantly different after weight reduction (day 1 versus day 70), the metabolic utilization of these substrates tended to increase. Moreover, marginally significant indications obtained on days 15 and 45 suggest that the weight and body composition changes are attributable to a shift in endogenous and exogenous glucose utilization in favor of lipid burning. The breath tests determinations, which were performed on different occasions along the experimental trial, confirmed that the cumulative 13C output decreased for labeled tracers with time, being only statistically significant for the glucose utilization between days 15 and 45. In summary, the weight and fat mass losses were associated with a lower carbohydrate oxidation, which were probably compensated by an increase in lipid oxidation without major changes in protein mobilization.

G protein-coupled receptor kinase 2 expression and activity are associated with blood pressure in black Americans

Hypertension occurs with higher prevalence and morbidity in black Americans compared with other groups. Alterations in the signal transduction pathways of 7-transmembrane spanning receptors are found in hypertensive patients. G protein-coupled receptor kinases (GRKs) play an important role in regulating this receptor signaling. The 2 most abundantly expressed GRKs in the cardiovascular system are GRK2 and GRK5, and each has unique substrates. Understanding changes in expression may give us insight into activated receptors in the pathophysiological progression of hypertension. In heart failure and white hypertensives, increased GRK2 expression arises because of neurohormonal stimulation of particular receptors. GRK2 subsequently desensitizes specific receptors, including beta-adrenergic receptors. In blood pressure control, beta-adrenergic receptor desensitization could lead to increased blood pressure. GRK2 and GRK5 mRNA were evaluated in lymphocytes of black Americans via quantitative real-time PCR. GRK2 mRNA expression directly correlated with systolic blood pressure and norepinephrine levels. GRK2 was elevated >30% among those with systolic blood pressure > or =130 mm Hg. No significant correlation between GRK5 mRNA expression and blood pressure or catecholamines was observed. Diabetic status, age, sex, and body mass index were also compared with GRK2 expression using univariate and multivariate analyses. GRK2 protein expression was elevated 2-fold in subjects with higher blood pressure, and GRK activity was increased >40%. Our data suggest that GRK2, but not GRK5, is correlated with increasing blood pressure in black Americans. Understanding the receptors stimulated by increased neurohormonal activation may give insight into the pathophysiology of hypertension in this at-risk population.

Catecholamine alterations in pediatric obstructive sleep apnea: effect of obesity

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) elicits increased sympathetic activity in adults and increased urinary catecholamines. Moreover, urinary catecholamine excretion is altered in obese patients. We hypothesized that morning urine catecholamine levels would be correlated with the severity of obstructive sleep apnea and degree of obesity in children.

METHODS

Children referred to the pediatric sleep center for habitual snoring underwent overnight polysomnography, and the first morning voided urine sample was collected. Urinary concentrations of norepinephrine, epinephrine and dopamine were measured and corrected for creatinine levels. In a subset of children, blood samples were drawn and gene expression of catecholamine-relevant genes analyzed by quantitative real-time PCR.

RESULTS

One hundred fifty-nine children were recruited and completed the protocol. Children with OSA had significantly higher urinary norepinephrine and epinephrine levels, but not dopamine, compared to habitual snorers (norepinephrine: 40.1 +/- 24.7 ng/mg creatinine vs. 31.6 +/- 16.2 ng/mg creatinine, P < 0.01; epinephrine: 6.4 +/- 10.5 ng/mg vs. 4.5 +/- 0.5 ng/mg, P < 0.01). There was a positive correlation between norepinephrine and epinephrine values and polysomnographic indices, but no effect of obesity on catecholamine levels. In addition, expression of several of the major genes involved in synthesis and transport of catecholamines, as well as in selected receptors were compatible with increased bioavailability of catecholamines.

CONCLUSIONS

In children with OSA, morning urinary norepinephrine and epinephrine levels are significantly higher than those without OSA, and correlate with the severity of the disease. Gene expression patterns are in agreement with such findings. Urine catecholamine levels do not appear to be influenced by the presence of obesity. Thus, altered sympathetic activity in OSA patients appears to occur independently of the presence of obesity.

Indexation of left ventricular mass to body surface area and height to allometric power of 2.7: is the difference limited to obese hypertensives?

Whether left ventricular mass (LVM) should be normalized to different indexes in relation to body size is still debated. We sought to evaluate the prevalence of left ventricular hypertrophy (LVH) defined by different indexation criteria in a cohort of hypertensive subjects categorized according to body mass index (BMI). A total of 2213 essential hypertensive subjects included in the Evaluation of Target Organ Damage in Hypertension (ETODH) were divided in three groups according to BMI thresholds (<25, 25-29.9 and >or=30 kg m(-2)). All patients underwent extensive investigations including quantitative echocardiography. LVH was defined as an LVM index equal to or higher than (1) 125 g m(-2) in men and 110 g m(-2) in women, (2) 51 g m(-2.7) in men and 47 g m(-2.7) in women. Overall, 687 out of 2213 patients (31.0%) were found to have LVH when LVM was indexed to body surface area (BSA) and 1030 (46.5%) when indexed to height(2.7). A total of 845 patients (38.2%) had normal BMI, 954 patients (43.1%) were overweight and 414 (18.7%) were obese. Prevalence rates of LVH in the three groups were 25.1, 31.6, 41.2% by indexation to BSA and 29.9, 50.5, 71.8% by indexation to height(2.7), respectively. LVM indexed to BSA markedly underestimates LVH prevalence in obese as well as overweight hypertensive patients. To avoid a systematic misclassification of cardiovascular risk, LVM should be routinely indexed to height(2.7) in overweight and obese patients representing a large percentage of the hypertensive population.

Inhibition of vascular smooth muscle G protein-coupled receptor kinase 2 enhances alpha1D-adrenergic receptor constriction

G protein-coupled receptor kinase 2 (GRK2) is a serine/theorinine kinase that phosphorylates and desensitizes agonist-bound G protein-coupled receptors. GRK2 is increased in expression and activity in lymphocytes and vascular smooth muscle (VSM) in human hypertension and animal models of the disease. Inhibition of GRK2 using the carboxyl-terminal portion of the protein (GRK2ct) has been an effective tool to restore compromised beta-adrenergic receptor (AR) function in heart failure and improve outcome. A well-characterized dysfunction in hypertension is attenuation of betaAR-mediated vasodilation. Therefore, we tested the role of inhibition of GRK2 using GRK2ct or VSM-selective GRK2 gene ablation in a renal artery stenosis model of elevated blood pressure (BP) [the two-kidney, one-clip (2K1C) model]. Use of the 2K1C model resulted in a 30% increase in conscious BP, a threefold increase in plasma norepinephrine levels, and a 50% increase in VSM GRK2 mRNA levels. BP remained increased despite VSM-specific GRK2 inhibition by either GRK2 knockout (GRK2KO) or peptide inhibition (GRK2ct). Although betaAR-mediated dilation in vivo and in situ was enhanced, alpha(1)AR-mediated vasoconstriction was also increased. Further pharmacological experiments using alpha(1)AR antagonists revealed that GRK2 inhibition of expression (GRK2KO) or activity (GRK2ct) enhanced alpha(1D)AR vasoconstriction. This is the first study to suggest that VSM alpha(1D)ARs are a GRK2 substrate in vivo.

Activation of transient receptor potential vanilloid type-1 channel prevents adipogenesis and obesity

We tested the hypothesis that activation of transient receptor potential vanilloid type-1 (TRPV1) by capsaicin prevents adipogenesis. TRPV1 channels in 3T3-L1-preadipocytes and visceral adipose tissue from mice and humans were detected by immunoblotting and quantitative real-time RT-PCR. The effect of TRPV1 on cytosolic calcium was determined fluorometrically in 3T3-L1-preadipocytes and in human visceral fat tissue. Adipogenesis in stimulated 3T3-L1-preadipocytes was determined by oil red O-staining of intracellular lipid droplets, triglyceride levels, expression of peroxisome proliferator-activated receptor-gamma, and expression of fatty acid synthase. Long-term feeding experiments were undertaken in wild-type mice and TRPV1 knockout mice. We detected TRPV1 channels in 3T3-L1-preadipocytes and visceral adipose tissue from mice and humans. In vitro, the TRPV1 agonist capsaicin dose-dependently induced calcium influx and prevented the adipogenesis in stimulated 3T3-L1-preadipocytes. RNA interference knockdown of TRPV1 in 3T3-L1-preadipocytes attenuated capsaicin-induced calcium influx, and adipogenesis in stimulated 3T3-L1-preadipocytes was no longer prevented. During regular adipogenesis TRPV1 channels were downregulated which was accompanied by a significant and time-dependent reduction of calcium influx. Compared with lean counterparts in visceral adipose tissue from obese db/db and ob/ob mice, and from obese human male subjects we observed a reduced TRVP1 expression. The reduced TRPV1 expression in visceral adipose tissue from obese humans was accompanied by reduced capsaicin-induced calcium influx. The oral administration of capsaicin for 120 days prevented obesity in male wild type mice but not in TRPV1 knockout mice assigned to high fat diet. We conclude that the activation of TRPV1 channels by capsaicin prevented adipogenesis and obesity.

Metabolic syndrome in women with chronic pain

Fibromyalgia is a prevalent syndrome characterized by chronic pain, fatigue, and insomnia. Patients with fibromyalgia commonly have an elevated body mass index and are physically inactive, 2 major risk factors for metabolic syndrome. Yet little is known about the relationship between chronic pain conditions and metabolic disturbances. Our study evaluated the risk for, and neuroendocrine correlates of, metabolic syndrome in this patient population. Women with fibromyalgia (n = 109) were compared with control healthy women (n = 46), all recruited from the community. Metabolic syndrome was identified by using criteria from the Adult Treatment Panel III with glycosylated hemoglobin concentrations substituted for serum glucose. Catecholamine and cortisol levels were determined from 12-hour overnight urine collections. Women with fibromyalgia were 5.56 times more likely than healthy controls to have metabolic syndrome (95% confidence interval, 1.25-24.74). Fibromyalgia was associated with larger waist circumference (P = .04), higher glycosylated hemoglobin (P = .01) and serum triglyceride (P < .001) levels, and higher systolic (P = .003) and diastolic (P = .002) blood pressure. Total and low-density lipoprotein cholesterol were also significantly higher in women with fibromyalgia (P = .001 and .02, respectively), although high-density lipoprotein cholesterol was in the reference range. These associations were not accounted for by age or body mass index. Meeting criteria for more metabolic syndrome components was related to higher urinary norepinephrine (NE)/epinephrine and NE/cortisol ratios (P < .001 and P = .009, respectively). Women with chronic pain from fibromyalgia are at an increased risk for metabolic syndrome, which may be associated with relatively elevated NE levels in conjunction with relatively reduced epinephrine and cortisol secretion.

A case of sleep apnea syndrome manifesting severe hypertension with high plasma norepinephrine levels

A 55-year-old female was admitted to our hospital with severe hypertension (274/140 mmHg). Endocrinological examination revealed that her plasma levels of norepinephrine (NE) was elevated with high levels of urinary NE, normetanephrine and vanillylmandelic acid (VMA), suggesting the presence of pheochromocytoma. However, neither computed tomography nor MIBG scintigraphy detected any catecholamine-producing tumor in or outside the adrenal glands. She was screened with full polysomnography because of heavy snoring, and the diagnosis of severe obstructive sleep apnea syndrome (OSAS) was made. She was treated with calcium channel blocker for three weeks, but severe hypertension persisted. After treatment with nasal continuous positive airway pressure (CPAP) was added, her blood pressure gradually lowered week by week. Concomitantly, the levels of plasma and urinary NE, urinary normetanephrine and urinary VMA were normalized following nasal CPAP therapy for 2 weeks. Additional treatments with alpha-adrenergic blocker further decreased her home blood pressure. After a year, she continued nasal CPAP therapy and her blood pressure was nearly below 160/100 mmHg. Urinary NE level was slightly above normal range and other catecholamines stayed within the normal range. This case shows that patients with OSAS could develop severe hypertension through elevated sympathetic tone, mimicking pheochromocytoma. Nasal CPAP therapy is recommended not only to improve hypertension and catecholamine excess but also to distinguish the condition from pheochromocytoma.

Modelos experimentais de resistência à insulina e obesidade: lições aprendidas

Para melhor compreender o papel de cada um dos elementos envolvidos na fisiopatologia da obesidade e da resistência à insulina, pesquisadores utilizam-se de modelos experimentais, que podem determinar de maneira controlada o papel de cada um dos componentes da resistência à insulina e obesidade e, desta maneira, fornecer subsídios para a melhor compreensão da fisiopatolologia e tratamento da resistência à insulina e obesidade. A obesidade e a resistência à insulina experimentais podem ser verificadas quando ocorre diminuição da resposta à leptina, seja por menor produção ou alteração no seu receptor, modificações no receptor de insulina, por deleção do receptor ou alteração da transdução dos seu sinal, exacerbação do efeito de peptídeos orexígenos e/ou menor ação de peptídeos anorexígenos no hipotálamo, ou ainda secundária à hipertensão arterial, como nos ratos espontaneamente hipertensos. O excesso de glicocorticóides, a adição de uma dieta rica em frutose, ou ainda uma dieta hipercalórica, além da lesão hipotalâmica induzida pela administração neonatal de monoglutamato de sódio, são exemplos de obesidade e resistência à insulina induzidos.

AT1-receptor antagonism reverses the blood pressure elevation associated with diet-induced obesity

Previous studies in our laboratory demonstrated that rats exhibiting obesity in response to a moderately high-fat (MHF) diet developed hypertension associated with activation of the local and systemic renin-angiotensin system. In this study, we examined the effect of the angiotensin type 1 (AT(1))-receptor antagonist, losartan, on blood pressure in obesity-prone (OP) and obesity-resistant (OR) rats fed a MHF diet. Using telemetry monitoring, we characterized the evolution of blood pressure elevations during the development of obesity. Male Sprague-Dawley rats were implanted with telemetry transducers for chronic monitoring of blood pressure, and baseline measurements were obtained. Rats were then switched to the MHF diet (32% kcal as fat) and were segregated into OP and OR groups at week 5. At week 9 on the MHF diet, OP rats exhibited significantly greater 24-h mean arterial blood pressure compared with OR rats (OP: 105 +/- 4 mmHg, OR: 96 +/- 2 mmHg; P < 0.05). Elevations in blood pressure in OP rats were manifest as an increase in systolic pressure. Administration of losartan to all rats at week 9 resulted in a reduction in blood pressure; however, losartan had the greatest effect in OP rats (percent decrease in mean arterial pressure by losartan; OP: 19 +/- 4, OR: 10 +/- 2%; P < 0.05). These results demonstrate that elevations in blood pressure occur subsequent to established obesity in rats fed a high-fat diet. Moreover, these results demonstrate the ability of losartan to reverse the blood pressure increase from diet-induced obesity, supporting a primary role for the renin-angiotensin system in obesity-associated hypertension.

Pleiotrophin is a major regulator of the catecholamine biosynthesis pathway in mouse aorta

To better understand the phenotype of pleiotrophin (PTN the protein, Ptn the gene) genetically deficient mice (Ptn -/-), we compared the transcriptional profiles of aortae obtained from Ptn -/- and wild type (WT, Ptn +/+) mice using a 14,400 gene microarray chip (Affymetrix) and confirmed the analysis of relevant genes by real time RT-PCR. We identified a dramatic upregulation of expression of tyrosine hydroxylase (TH), DOPA decarboxylase, and dopamine beta-hydroxylase in aortae of Ptn -/- mice in comparison with WT (Ptn +/+) mice. In contrast, transcripts of phenylethanolamine-N-methyltransferase, the enzyme catalyzing the conversion of norepinephrine into epinephrine, were not detected in aortae in either mouse strain. These findings suggest that Ptn gene expression has a critical role in determining the levels of expression of the enzymes of catecholamine biosynthesis in aorta and through this mechanism, PTN may regulate levels of endogenous catecholamine synthesis and potentially the vascular tone of aorta.

Hiperreactividad cardiovascular en pacientes con antecedentes familiares de hipertensión arterial

BACKGROUND AND OBJECTIVE

The association between family history of essential high blood pressure (FH of HBP) and the cardiovascular hyperactivity to the isometric exercise is not well known; that is why the aim of this study was to describe this relation and to determine whether it is independent of the presence of cardiovascular risk factors.

PATIENTS AND METHOD

We carried out a correlational descriptive study with a sample of 1855 people of both sexes between 18 and 70 years of age. The cardiovascular hyperactivity, expression of the cardiovascular response to the activity of the sympathetic nervous system (SNS), was determined by means of the test of the sustained weight (TSW). Comparisons of the values of cardiovascular reactivity were developed between individuals with and without FH of HBP and a model of logistical regression. The level of statistical significance was 95%.

RESULTS

The arterial blood pressure at the end of the TSW was higher in individuals with FH of HBP independently of the age group. The cardiovascular hyperactivity, measured by means of they systolic index of cardiovascular reactivity, was also significantly higher in subjects with FH of HBP. Finally, individuals with FH of HBP showed a higher risk (more than 5 times) of having cardiovascular hyperactivity (OR = 5.16; CI 95%, 3.51-7.59), this association being independent of other cardiovascular factors of risk.

CONCLUSIONS

The FH of HBP is independently related to the cardiovascular hyperactivity, to the isometric exercise, of other cardiovascular risks factors. These elements help explain the relationship between cardiovascular hyperactivity, the activity of SNS and essential high blood pressure, at least in an important group of people.

Activation of the systemic and adipose renin-angiotensin system in rats with diet-induced obesity and hypertension

In obesity-related hypertension, activation of the renin-angiotensin system (RAS) has been reported despite marked fluid volume expansion. Adipose tissue expresses components of the RAS and is markedly expanded in obesity. This study evaluated changes in components of the adipose and systemic RAS in diet-induced obese hypertensive rats. RAS was quantified in adipose tissue and compared with primary sources for the circulating RAS. Male Sprague-Dawley rats were fed either a low-fat (LF; 11% kcal as fat) or moderately high-fat (32% kcal as fat) diet for 11 wk. After 8 wk, rats fed the moderately high-fat diet segregated into obesity-prone (OP) and obesity-resistant (OR) groups based on their body weight gain (body weight: OR, 566 ± 10; OP, 702 ± 20 g; P < 0.05). Mean arterial blood pressure was increased in OP rats (LF: 97 ± 2; OR: 97 ± 2; OP: 105 ± 1 mmHg; P < 0.05). Quantification of mRNA expression by real-time PCR demonstrated a selective increase (2-fold) in angiotensinogen gene expression in retroperitoneal adipose tissue from OP vs. OR and LF rats. Similarly, plasma angiotensinogen concentration was increased in OP rats (LF: 390 ± 48; OR: 355 ± 24; OP: 530 ± 22 ng/ml; P < 0.05). In contrast, other components of the RAS were not altered in OP rats. Marked increases in the plasma concentrations of angiotensin peptides were observed in OP rats (angiotensin II: LF: 95 ± 31; OR: 59 ± 20; OP: 295 ± 118 pg/ml; P < 0.05). These results demonstrate increased activity of the adipose and systemic RAS in obesity-related hypertension.

Epinephrine infusion increases adipose interleukin-6 gene expression and systemic levels in humans

Exercise increases IL-6 mRNA in subcutaneous adipose tissue; however, the immediate signal for the IL-6 induction is unknown. We, therefore, explored the possible role of epinephrine in the induction of IL-6 in adipose tissue. Subcutaneous adipose tissue biopsies and blood samples were obtained from eight healthy men (mean age 27 yr, mean height 184 cm, mean weight 83 kg) in response to epinephrine infusion or in response to saline infusion. The rate of epinephrine infusion was such that circulating epinephrine concentrations mimicked that typically seen during exercise. The level of IL-6 mRNA in subcutaneous adipose tissue increased 26-fold (95% confidence interval, 9- to 166-fold) at 3 h of epinephrine infusion compared with controls ( P = 0.028). In addition, plasma levels of IL-6 increased in response to epinephrine infusion ( P < 0.001). However, epinephrine did not affect the IL-6 receptor mRNA. In conclusion, epinephrine acutely increases IL-6 mRNA levels in subcutaneous adipose tissue as well as circulating IL-6 levels in healthy men.

Adrenal medullary function and expression of catecholamine-synthesizing enzymes in mice with hypothalamic obesity

The mechanisms underlying the onset of obesity are complex and not completely understood. An imbalance of autonomic nervous system has been proposed to be a major cause of great fat deposits accumulation in hypothalamic obesity models. In this work we therefore investigated the adrenal chromaffin cells in monosodium glutamate (MSG)-treated obese female mice. Newborn mice were injected daily with MSG (4 mg/g body weight) or saline (controls) during the first five days of life and studied at 90 days of age. The adrenal catecholamine content was 56.0% lower in the obese group when compared to lean controls (P < 0.0001). Using isolated adrenal medulla we observed no difference in basal catecholamine secretion percentile between obese and lean animals. However, the percentile of catecholamine secretion stimulated by high K+ concentration was lower in the obese group. There was a decrease in the tyrosine hydroxylase enzyme expression (57.3%, P < 0.004) in adrenal glands of obese mice. Interestingly, the expression of dopamine beta-hydroxylase was also reduced (47.0%, P < 0.005). Phenylethanolamine N-methyltransferase expression was not affected. Our results show that in the MSG model, obesity status is associated with a defective adrenal chromaffin cell function. We conclude that in MSG obesity the low total catecholamine content is directly related to a decrease of key catecholamine-synthesizing enzymes, which by its turn may lead to a defective catecholamine secretion.

Relation between cardiac sympathetic activity and hypertensive left ventricular hypertrophy

BACKGROUND

Left ventricular (LV) hypertrophy is an independent risk factor for cardiovascular morbidity and mortality in hypertensive subjects. Sympathetic activation has been suggested to contribute to LV hypertrophy, but this has not yet been conclusively validated in humans.

METHODS AND RESULTS

We comprehensively assessed total systemic and regional sympathetic activity by radiotracer dilution methods and microneurography in 15 untreated hypertensive subjects with echocardiographic evidence of LV hypertrophy (EH+), 11 hypertensive subjects with similar blood pressure but without LV hypertrophy (EH-), and 10 age-matched normotensive control subjects (NT). LV mass index was 87+/-15 g/m2 in NT, 106+/-11 g/m2 in EH-, and 138+/-17 g/m2 in EH+ (P<0.001). Total body and renal norepinephrine spillover were higher in both hypertensive groups compared with NT (total norepinephrine spillover, NT 223+/-145 versus EH- 418+/-135 versus EH+ 497+/-303 ng/min; renal norepinephrine spillover, NT 38.8+/-25.3 versus EH- 88.6+/-58.0 versus EH+ 103.4+/-56.2 ng/min; both P<0.05). However, muscle sympathetic nerve activity (NT 25+/-6 versus EH- 38+/-20 versus EH+ 57+/-19 bursts per 100 heartbeats; P<0.01) and cardiac norepinephrine spillover (NT 11.7+/-6.2 versus EH- 13.1+/-7.2 versus EH+ 28.6+/-17.4 ng/min; P<0.01) were only increased in EH+. Cardiac norepinephrine spillover correlated positively with LV mass index in all subjects (r=0.52; P<0.001).

CONCLUSIONS

Our findings demonstrate that hypertensive LV hypertrophy is associated with increased sympathetic activity largely confined to the heart, suggesting that increased cardiac norepinephrine release is related to the development of LV hypertrophy.

Weight loss and weight maintenance, ambulatory blood pressure and cardiac autonomic tone in obese persons with the metabolic syndrome

BACKGROUND

Cardiac autonomic function may play a role in obesity-associated hypertension. Most studies on the effects of weight loss on blood pressure and autonomic function do not distinguish between acute or continuing weight loss and steady-state weight maintenance after weight loss.

OBJECTIVES

We sought to clarify the changes in ambulatory blood pressure, heart rate and heart rate variability as assessed by spectral analysis during rapid weight loss and extended weight maintenance.

PARTICIPANTS

Abdominally obese (body mass index 35.2 +/- 2.1 kg/m2, waist 114.3 +/- 9.0 cm) men and women (n = 41) with the metabolic syndrome.

METHODS AND RESULTS

The 34 men and women completing the 1-year weight maintenance period lost 14.6 +/- 3.5 kg during the 9-week very-low-calorie diet and maintained a 12.5 +/- 7.5 kg weight loss to the end of the trial. Ambulatory 24-h blood pressure decreased dramatically during the diet (-9.0 +/- 8.0/-4.6 +/- 4.9 mmHg), but had risen to near baseline levels by the end of weight maintenance (-2.2 +/- 8.2 /-1.2 +/- 6.1 mmHg). Night-time heart rate decreased (-5.5 +/- 9.6 beats/min, P = 0.012), and heart rate variability total and low-frequency power measured during 5 min of controlled breathing increased by 46-56% (P = 0.003-0.09) during rapid weight loss. These changes gradually attenuated during weight maintenance, and only the change in night-time heart rate was still of borderline significance after 1 year of weight maintenance (-3.6 +/- 8.6 beats/min, P = 0.063). Heart rate variability high-frequency power tended to increase during weight loss and weight maintenance.

CONCLUSION

Despite successful weight maintenance, the decrease in ambulatory blood pressure after rapid weight loss was largely transient. The increase in parasympathetic tone was more sustained, but also gradually attenuated during 1 year of weight maintenance.

Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children

OBJECTIVE

To determine the factors that contribute to the pathogenesis of isolated systolic hypertension in children.

METHODS

School-based measurement was performed of blood pressure (BP), heart rate, weight, and height in 2460 students (49% Hispanic, 31% black, 13% white) 12 to 16 years of age in 8 urban public schools. An independent group of 71 untreated children underwent 24-hour ambulatory BP monitoring (ABPM) to confirm clinic hypertension and assess circadian BP patterns.

RESULTS

Hypertension and obesity were found in 17% and 23% of students, respectively. Among hypertensive students, 88% (363/413) had isolated systolic hypertension. Hypertension was more prevalent in obese than nonobese students (33% vs 11%, P <.0001). Obese hypertensive students had higher resting heart rate than nonobese normotensive patients (85.9 vs 79.6 beats/min, P <.001). Among patients who underwent ABPM, isolated systolic hypertension was found in 51% (36/71) by clinic BP and in 62% (18/29) with confirmed hypertension by ABPM. Blood pressure variability during daytime and sleep periods was higher in obese than nonobese patients for systolic BP (P <.01) and diastolic BP (P <.05).

CONCLUSIONS

The findings of increased heart rate and BP variability in obese children with isolated systolic hypertension suggest that sympathetic nervous system hyperactivity may contribute to its pathogenesis.

Selective aspects of the insulin resistance syndrome

There is increasing recognition of new features in the insulin resistance syndrome and its association with new disease states or treatment modalities. Recent additions to the list of features in the insulin resistance syndrome include elevated non-esterified fatty acids, abnormalities in visceral fat metabolism, elevated uric acid, elevated hematocrit, endothelial dysfunction, abnormalities in glucocorticoids, and differences in the phenotypic expression of the syndrome between men and women. A critical factor that may be inherent in the syndrome is the distribution and metabolism of visceral fat. This finding is also accompanied by the recognition of the role of non-esterified fatty acids as a cause of many of the risk factors in the insulin resistance syndrome. Elevated non-esterified fatty acids contribute to hypertension, glucose intolerance and increased arteriosclerosis. Elevated cortisol levels and disrupted metabolism, as well as abnormalities in the hypothalamic-pituitary-adrenal axis are seen in the insulin resistance syndrome. In women, adipose cells express fewer glucocorticoid receptors and less of the enzyme that metabolizes cortisol, 11beta-hydroxysteroid dehydrogenase. Several inflammatory factors such as tumor necrosis factor-alpha may be an etiologic link in the risk found in the insulin resistance syndrome. Certain cases of the syndrome appear to be related to specific drug therapies (steroids, immunosuppressive agents and antiretroviral agents), as seen in transplant patients and HIV-infected individuals.

Contrasting clinical properties and exercise responses in obese and lean hypertensive patients

OBJECTIVES

We sought to test whether the differences in activity of the renin-angiotensin and sympathetic nervous systems at rest or during exercise can explain the differing cardiovascular properties and outcomes of lean and obese hypertensive patients.

BACKGROUND

Although lean hypertensive patients have fewer metabolic abnormalities than obese hypertensive patients, paradoxically they appear to have a poorer cardiovascular prognosis.

METHODS

To evaluate the heightened risks in lean hypertensive patients, this study compared metabolic, neuroendocrine and cardiovascular characteristics at rest and during a standardized treadmill protocol in obese (body mass index [BMI] = 32.5 +/- 0.3 kg/m2, n = 55) and lean (BMI = 24.3 +/- 0.2 kg/m2, n = 66) hypertensive patients. Normotensive obese (n = 21) and lean (n = 55) volunteers served as control subjects.

RESULTS

Compared with the lean normotensive subjects, the lean and obese hypertensive patients had greater left ventricular mass index (LVMI) values, but on multivariate analysis, LVMI correlated with plasma renin activity (p < 0.001) and plasma norepinephrine (PNE) (p < 0.01) in the lean but not the obese hypertensive patients. Arterial compliance (stroke volume/pulse pressure ratio) was reduced in the lean hypertensive patients, in whom it correlated (p = 0.033) with PNE. The PNE rose less (22%) in the obese than in the lean (55%) hypertensive patients in response to standing (p < 0.05). Likewise, during treadmill exercise, there were lesser increases in renin (65% vs. 145%, p < 0.01) and epinephrine (200% vs. 500%, p < 0.05) in the obese hypertensive patients. These changes were also less in obese patients than in lean control subjects, indicating attenuated neurohormonal responses to stress in obesity.

CONCLUSIONS

Compared with obese hypertensive patients, cardiovascular properties in lean hypertensive patients are more dependent on catecholamines and the renin system. The different neuroendocrine responses to dynamic stimuli in lean and obese patients also might help to explain the disparity in their cardiovascular outcomes.