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

Weight-Loss Strategies for Prevention and Treatment of Hypertension: A Scientific Statement From the American Heart Association

Hypertension is a major risk factor for cardiovascular and renal diseases in the United States and worldwide. Obesity accounts for much of the risk for primary hypertension through several mechanisms, including neurohormonal activation, inflammation, and kidney dysfunction. As the prevalence of obesity continues to increase, hypertension and associated cardiorenal diseases will also increase unless more effective strategies to prevent and treat obesity are developed. Lifestyle modification, including diet, reduced sedentariness, and increased physical activity, is usually recommended for patients with obesity; however, the long-term success of these strategies for reducing adiposity, maintaining weight loss, and reducing blood pressure has been limited. Effective pharmacotherapeutic and procedural strategies, including metabolic surgeries, are additional options to treat obesity and prevent or attenuate obesity hypertension, target organ damage, and subsequent disease. Medications can be useful for short- and long-term obesity treatment; however, prescription of these drugs is limited. Metabolic surgery is effective for producing sustained weight loss and for treating hypertension and metabolic disorders in many patients with severe obesity. Unanswered questions remain related to the mechanisms of obesity-related diseases, long-term efficacy of different treatment and prevention strategies, and timing of these interventions to prevent obesity and hypertension-mediated target organ damage. Further investigation, including randomized controlled trials, is essential to addressing these questions, and emphasis should be placed on the prevention of obesity to reduce the burden of hypertensive cardiovascular and kidney diseases and subsequent mortality.

Acute Physical Effort Increases Sympathovagal Balance Responses to Autonomic Stimulation in Metabolic Syndrome

BACKGROUND

There is little evidence of how metabolic syndrome (MS) affects sympathovagal balance responses to acute physical effort (APE) and autonomic stimulation (AS). This study aimed to evaluate the heart rate variability (HRV) responses to the combined APE and AS challenges.

METHODS

Fourteen subjects (8 men; 49.15 ± 8.67 years) divided into two groups: 7 healthy volunteers [control group (CG)] and 7 patients with MS. Sympathovagal balance [low frequency (LF)/high frequency (HF) ratio] was accessed by HRV through the beat-to-beat heart rate (HR) electrocardiogram. Other variables analyzed were as follows: HR, RR-interval variance (VAR/ms²), LF and HF normalized units (un). The APE consisted of a 30-min walk at 65%-75% of the age-predicted maximal HR. The AS was achieved by changing from the supine to standing position (activity orthostatic position).

RESULTS

At rest, all HRV variables differ with on MS, but after APE and AS LF (nu) and HF (nu) become similar to the CG. However, the LF/HF ratio responses to the AS were significantly different after APE, but only in the MS (CG rest: 367% ± 59% vs. recovery 495% ± 116%, P > 0.05; MS rest: 316% ± 88% vs. recovery: 665% ± 165%; P = 0.045). Comparing the difference between AS in rest and recovery (ΔAS = rest - recovery), the LF/HF ratio was notably higher in the MS group (CG: 94% ± 29% vs. MS: 415% ± 76%; P < 0.0001).

CONCLUSIONS

The APE and AS induced by body posture changes activated a clear distinction in sympathovagal balance response in MS.

Feeling the pressure: (patho) physiological mechanisms of weight gain and weight loss in humans

Obesity is an ongoing global epidemic and has adverse consequences for cardiovascular health. Obesity is often associated with hypertension, which is, itself, a common condition and an important cause of morbidity and mortality worldwide. Although animal models of obesity have provided extensive data on the links between obesity and hypertension, a greater understanding of the pathways linking obesity and hypertension in humans is likely to assist translation of animal data, and may, itself, identify important treatment strategies. Ultimately, this could have a substantial impact on human health, both at an individual and population level. The current review will focus specifically on studies of experimental weight gain and weight loss in humans and the following key areas, which are strongly related to blood pressure: cardiovascular function, autonomic nervous system function, metabolic function and the impact of cardiorespiratory fitness.

Blood pressure reduction after gastric bypass surgery is explained by a decrease in cardiac output

Blood pressure (BP) decreases in the first weeks after Roux-and-Y gastric bypass surgery. Yet the pathophysiology of the BP-lowering effects observed after gastric bypass surgery is incompletely understood. We evaluated BP, systemic hemodynamics, and baroreflex sensitivity in 15 obese women[mean age 42 ± 7 standard deviation (SD) yr, body mass index 45 ± 6 kg/m²] 2 wk before and 6 wk following Roux-and-Y gastric bypass surgery. Six weeks after gastric bypass surgery, mean body weight decreased by 13 ± 5 kg (10%, P < 0.001). Office BP decreased from 137 ± 10/86 ± 6 to 128 ± 12/81 ± 9 mmHg (P < 0.001, P < 0.01), while daytime ambulatory BP decreased from 128 ± 14/80 ± 9 to 114 ± 10/73 ± 6 mmHg (P = 0.01, P = 0.05), whereas nighttime BP decreased from 111 ± 13/66 ± 7 to 102 ± 9/62 ± 7 mmHg (P = 0.04, P < 0.01). The decrease in BP was associated with a 1.6 ± 1.2 l/min (20%, P < 0.01) decrease in cardiac output (CO), while systemic vascular resistance increased (153 ± 189 dyn·s·cm^-5, 15%, P < 0.01). The maximal ascending slope in systolic blood pressure decreased (192 mmHg/s, 19%, P = 0.01), suggesting a reduction in left ventricular contractility. Baroreflex sensitivity increased from 9.0 [6.4-14.3] to 13.8 [8.5-19.0] ms/mmHg (median [interquartile range]; P < 0.01) and was inversely correlated with the reductions in heart rate (R = -0.64, P = 0.02) and CO (R = -0.61, P = 0.03). In contrast, changes in body weight were not correlated with changes in either BP or CO. The BP reduction following Roux-and-Y gastric bypass surgery is correlated with a decrease in CO independent of changes in body weight. The contribution of heart rate to the reduction in CO together with enhanced baroreflex sensitivity suggests a shift toward increased parasympathetic cardiovascular control.

NEW & NOTEWORTHY

The reason for the decrease in blood pressure (BP) in the first weeks after gastric bypass surgery remains to be elucidated. We show that the reduction in BP following surgery is caused by a decrease in cardiac output. In addition, the maximal ascending slope in systolic blood pressure decreased suggesting a reduction in left ventricular contractility and cardiac workload. These findings help to understand the physiological changes following gastric bypass surgery and are relevant in light of the increased risk of heart failure in these patients.

Multidisciplinary Treatment of the Metabolic Syndrome Lowers Blood Pressure Variability Independent of Blood Pressure Control

Blood pressure (BP) variability (BPV) contributes to target organ damage independent of BP. The authors examined the effect of a 1-year multidisciplinary intervention on BPV in patients with the metabolic syndrome (MetS) as defined by criteria from the Third Report of the Adult Treatment Panel. Forty-four nondiabetic patients underwent clinical and biochemical profiling, 24-hour ambulatory BP monitoring (ABPM), body composition, carotid intima-media thickness, and carotid-femoral pulse wave velocity (PWV). The intervention targeted all MetS components. BPV was assessed by the standard deviation of daytime systolic BP derived from ABPM. Patients with low and high BPV (lower or higher than the median daytime standard deviation of 11.6 mm Hg) did not differ in regards to systolic and diastolic BP, age, fasting glucose, glycated hemoglobin, and body mass index, but the high-variability group had higher values of low-density lipoprotein and leg fat. The 1-year intervention resulted in weight reduction but not BP-lowering. BPV declined in the high-variability group in association with lowering of PWV, C-reactive protein, glycated hemoglobin, alanine aminotransferase, asymmetric dimethylarginine, and increased high-density lipoprotein cholesterol. A multidisciplinary intervention independent of BP-lowering normalized BPV, lowered PWV, and enhanced metabolic control.

Effect of a 1-Year Obesity Intervention (KLAKS Program) on Preexisting Autonomic Nervous Dysfunction in Childhood Obesity

Childhood obesity may involve autonomic nervous system dysfunction. Whether it improves following weight loss remains unclear. Thirty-one obese children (body mass index standard deviation scores 2.33 ± 0.47; age 11.2 ± 2.0) completed a 1-year lifestyle intervention (KLAKS: Concept Leipzig: Adiposity Therapy for School-Aged Children). Anthropometric/biochemical parameters and autonomic nervous system function (heart rate variability, quantitative pupillography) were assessed at baseline and follow-up. A multivariate model for changes in body mass index standard deviation scores considered age, gender, and changes in autonomic nervous system function. Weight status (Δ body mass index standard deviation scores: 0.16 [0.05, 0.29], P = .008), glycemic control, and free fatty acids (all P < .05) improved after the intervention. Redilation velocity increased by 0.22 mm/s [0.06, 0.38] (P = .008), and changes tended to be negatively associated with Δ body mass index standard deviation scores (P = .08 [-0.61, 0.03]). Relative reflex amplitude (23.4 vs 26.3, P = .004) and constriction velocity (4.97 mm/s vs 5.47 mm/s, P < .001) also improved. Our data provide preliminary evidence that lifestyle-intervention induced improvement of weight status/metabolic risk factors may ameliorate some parameters of autonomic nervous system dysfunction in childhood obesity.

Heart rate variability and the metabolic syndrome: a systematic review of the literature

BACKGROUND

A number of cross-sectional studies have examined associations between heart rate variability and metabolic syndrome, but differences in study populations, data collection and analysis methodologies make synthesis difficult. The purpose of this study was to systematically review published primary research examining associations between heart rate variability and metabolic syndrome or its individual risk factors.

METHODS

A systematic literature search of PubMed and EMBASE was conducted to identify relevant articles published from January 1999 to December 2012. Studies were included if they examined associations between heart rate variability analysed by standard protocols and metabolic syndrome risk factors according to published definitions. All papers were scored with a modified Downs and Black instrument, and data were extracted.

RESULTS

Fourteen studies were included. Heart rate variability generally was reduced in women with metabolic syndrome compared to those without, while results in men were inconsistent. Time and frequency domain heart rate variability parameters were associated with individual metabolic syndrome risk factors, though sex differences exist. Only two studies considered nonlinear and Poincaré plot heart rate variability parameters, which were reduced in metabolic syndrome.

CONCLUSIONS

Heart rate variability is altered differently in men and women with metabolic syndrome. Future studies should follow consistent heart rate variability analysis protocols and metabolic syndrome definitions and include more comprehensive analyses to investigate potential mechanisms.

Effect of weight loss on sympatho-vagal balance in subjects with grade-3 obesity: restrictive surgery versus hypocaloric diet

Few and mostly uncontrolled studies indicate that weight loss improves heart rate variability (HRV) in grade-3 obesity. The aim of this study was to compare in grade-3 obesity surgery and hypocaloric diet on clinical and metabolic variables and on autonomic indices of HRV. Twenty-four subjects (body mass index, BMI 45.5 ± 9.13 kg/m(2)) underwent surgery (n = 12, gastric banding, LAGB) or received hypocaloric diet (n = 12, 1,000-1,200 kg/day). Clinical [BMI, systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate] and metabolic variables [glucose, cholesterol, HDL- and LDL-cholesterol, triglycerides, AST and ALT transaminases] and 24-h Holter electrocardiographic-derived HRV parameters [R-R interval, standard deviation of R-R intervals (SDNN); low/high-frequency (LF/HF) ratio, and QT interval] were measured at baseline and after 6 months. The two groups were identical at baseline. BMI (-7.5 ± 3.57 kg/m(2), mean ± SD), glucose (-24.1 ± 26.77 mg/dL), SBP (-16.7 ± 22.19 mmHg) and DBP (-6.2 ± 8.56 mmHg) decreased in LAGB subjects (p < 0.05) and remained unchanged in controls. At 6 months, SDNN increased in LAGB subjects (+25.0 ± 37.19 ms, p < 0.05) and LF/HF ratio diminished (2.9 ± 1.84 vs. 4.9 ± 2.78; p = 0.01), with no change in controls; LF (daytime) and HF (24 h and daytime) increased in LAGB subjects, with no change in controls. Decrease in BMI correlated with SBP and DBP decrease (p < 0.05), and DBP decrease correlated with HR decrease (p < 0.05) and QT shortening (p < 0.05). Weight loss is associated with improvement of glucose metabolism, of blood pressure, and with changes in time and frequency domain parameters of HRV; all these changes indicate recovery of a more physiological autonomic control, with increase in parasympathetic and reduction in sympathetic indices of HRV.

The defence of body weight: a physiological basis for weight regain after weight loss

Although weight loss can usually be achieved by restricting food intake, the majority of dieters regain weight over the long-term. In the hypothalamus, hormonal signals from the gastrointestinal tract, adipose tissue and other peripheral sites are integrated to influence appetite and energy expenditure. Diet-induced weight loss is accompanied by several physiological changes which encourage weight regain, including alterations in energy expenditure, substrate metabolism and hormone pathways involved in appetite regulation, many of which persist beyond the initial weight loss period. Safe effective long-term strategies to overcome these physiological changes are needed to help facilitate maintenance of weight loss. The present review, which focuses on data from human studies, begins with an outline of body weight regulation to provide the context for the subsequent discussion of short- and long-term physiological changes which accompany diet-induced weight loss.

Diabetes and technology for increased activity study: the effects of exercise and technology on heart rate variability and metabolic syndrome risk factors

This study tested the hypothesis that an 8-week exercise intervention supported by mobile health (mHealth) technology would improve metabolic syndrome (MetS) risk factors and heart rate variability (HRV) in a population with MetS risk factors. Participants (n = 12; three male; aged 56.9 ± 7.0 years) reported to the laboratory for assessment of MetS risk factors and fitness (VO2max) at baseline (V 0) and after 8-weeks (V 2) of intervention. Participants received an individualized exercise prescription and a mHealth technology kit for remote monitoring of blood pressure (BP), blood glucose, physical activity, and body weight via smartphone. Participants underwent 24-h ambulatory monitoring of R-R intervals following V 0 and V 2. Low and high frequency powers of HRV were assessed from the recording and the ratio of low-to-high frequency powers and low and high frequency powers in normalized units were calculated. One-way repeated measures analysis of variance showed that waist circumference (V 0: 113.1 ± 11.0 cm, V 2: 108.1 ± 14.7 cm; p = 0.004) and diastolic BP (V 0: 81 ± 6 mmHg, V 2: 76 ± 11 mmHg; p = 0.04) were reduced and VO2max increased (V 0: 31.3 ml/kg/min, V 2: 34.8 ml/kg/min; p = 0.02) with no changes in other MetS risk factors. Low and high frequency powers in normalized units were reduced (V 0: 75.5 ± 12.0, V 2: 72.0 ± 12.1; p = 0.03) and increased (V 0: 24.5 ± 12.0, V 2: 28.0 ± 12.1; p = 0.03), respectively, with no other changes in HRV. Over the intervention period, changes in systolic BP were correlated negatively with the changes in R-R interval (r = -0.600; p = 0.04) and positively with the changes in heart rate (r = 0.611; p = 0.03), with no other associations between MetS risk factors and HRV parameters. Thus, this 8-week mHealth supported exercise intervention improved MetS risk factors and HRV parameters, but only changes in systolic BP were associated with improved autonomic function.

Cardiorespiratory fitness and heart rate recovery in obese premenopausal women

Post-exercise heart rate recovery (HRR) has been proposed as a measure of cardiac autonomic dysfunction in apparently healthy adults. We aimed to determine the effects of a lifestyle intervention on HRR among clinically obese premenopausal women. A randomized controlled trial was conducted to investigate the effects of a 3-month non-dieting lifestyle intervention program on cardiorespiratory fitness (CRF) and HRR among healthy clinically obese premenopausal women. Thirty-one were randomly assigned to 3-month intensive lifestyle intervention and 31 served as controls. Sixty-one participants performed a maximal treadmill walking test with metabolic gas exchange. Baseline anthropometric measures were closely related to HRR at 1 min, which may indicate reduced parasympathetic reactivation. Post-exercise HRR at 60 s (HRR60) increased from 21.3 ± 6.2 to 27.8 ± 10.2 bpm in the intervention group compared with a smaller reduction (26.8 ± 12.3 to 24.5 ± 9.9 bpm) in controls (test for interaction P = 0.0001). HRR120 showed a significant effect of time (P = 0.0002) with no significant interaction with lifestyle intervention. A significant increase in VO2 peak was evident in the lifestyle group (21.6 to 23.6 mL/kg/min) compared with a modest reduction in the controls (22.6 to 21.6 mL/kg/min; test for interaction, P = 0.001). Clinically obese healthy premenopausal women achieved significant improvements in HRR60 and VO peak following a 3-month intensive lifestyle intervention.

Methodological implications of nonlinear dynamical systems models for whole systems of complementary and alternative medicine

This paper focuses on the worldview hypotheses and research design approaches from nonlinear dynamical complex systems (NDS) science that can inform future studies of whole systems of complementary and alternative medicine (WS-CAM), e.g., Ayurveda, traditional Chinese medicine, and homeopathy. The worldview hypotheses that underlie NDS and WS-CAM (contextual, organismic, interactive-integrative - Pepper, 1942) overlap with each other, but differ fundamentally from those of biomedicine (formistic, mechanistic). Differing views on the nature of causality itself lead to different types of study designs. Biomedical efficacy studies assume a simple direct mechanistic cause-effect relationship between a specific intervention and a specific bodily outcome, an assumption less relevant to WS-CAM outcomes. WS-CAM practitioners do not necessarily treat a symptom directly. Rather, they intervene to modulate an intrinsic central imbalance of the person as a system and to create a more favorable environmental context for the emergence of health, e.g., with dietary changes compatible with the constitutional type. The rebalancing of the system thereby fosters the emergence of indirect, diffuse, complex effects throughout the person and the person's interactions with his/her environment. NDS theory-driven study designs thus have the potential for greater external and model validity than biomedically driven efficacy studies (e.g., clinical trials) for evaluating the indirect effects of WS-CAM practices. Potential applications of NDS analytic techniques to WS-CAM include characterizing different constitutional types and documenting the evolution and dynamics of whole-person healing and well-being over time. Furthermore, NDS provides models and methods for examining interactions across organizational scales, from genomic/proteomic/metabolomic networks to individuals and social groups.

Exercise augments weight loss induced improvement in renal function in obese metabolic syndrome individuals. J Hypertens. 2011;29:553-564. [PMID: 21119532 DOI: 10.1097/hjh.0b013e3283418875]

OBJECTIVE

Metabolic syndrome (MetS) obesity is an independent risk factor for chronic kidney disease. This study was conducted to examine the effects of lifestyle interventions on renal parameters and putative metabolic, neuroadrenergic and hemodynamic mediators of renal injury.

METHODS

Untreated men and women (mean age 55 ± 1 years; BMI 32.7 ± 0.6 kg/m) without pre-existing renal dysfunction, who fulfilled MetS criteria were randomized to dietary weight loss (WL, n = 13), weight loss combined with aerobic exercise (WL + EX, n = 13), or no treatment (control, n = 12). Estimated glomerular filtration rate (eGFR), 24 h urinary albumin excretion, plasma renin activity (PRA), muscle sympathetic nerve activity (MSNA), baroreflex sensitivity (BRS), anthropometric, metabolic and fitness variables were measured at baseline and week 12.

RESULTS

Body weight decreased by -8.2 ± 0.8% in the WL and -10.7 ± 0.9% in the WL + EX groups (both P < 0.001). Fitness (maximal oxygen consumption) increased by 15 ± 5% and BRS by 5.5 ± 2.4 ms/mmHg in the WL + EX group only (P < 0.05). Serum creatinine decreased by -8.1 ± 4.8%, (WL, P = 0.016) and -14.9 ± 3.0% (WL + EX, P < 0.001). Estimated GFR increased commensurately but the increment was greater in the WL + EX group (P = 0.04). Albuminuria (P < 0.05) and MSNA (P < 0.001) decreased similarly in both groups, whereas PRA, high sensitivity C-reactive protein, uric acid and DBP decreased only in the WL + EX group (all P < 0.05).

CONCLUSION

Moderate weight loss in obese MetS patients is associated with a reduction in albuminuria and an improvement in eGFR which is augmented by exercise co-intervention.

The effects of weight loss versus weight loss maintenance on sympathetic nervous system activity and metabolic syndrome components

CONTEXT

Sympathetic nervous system (SNS) overactivity participates in both the pathogenesis and adverse clinical complications of metabolic syndrome (MetS) obesity.

OBJECTIVE

We conducted a prospective lifestyle intervention trial to compare the effects of active weight loss and extended weight loss maintenance on SNS function and MetS components.

METHODS

Untreated subjects (14 males, four females; mean age, 53 ± 1 yr; body mass index, 30.9 ± 0.9 kg/m(2)) who fulfilled Adult Treatment Panel III criteria were randomized to 12-wk hypocaloric diet alone (n = 8) or together with aerobic exercise training (n = 10). This was followed by a 4-month weight maintenance period. Measurements of muscle sympathetic nerve activity (MSNA) by microneurography, whole-body norepinephrine kinetics, substrate oxidation by indirect calorimetry, baroreflex sensitivity, plasma renin activity (PRA), and MetS components were performed.

RESULTS

Body weight decreased by 9.3 ± 0.8% at wk 12 (P < 0.001), and this was maintained. During active weight loss, norepinephrine spillover rate decreased by 23 ± 16% (P = 0.004), MSNA by 25 ± 3 bursts per 100 heartbeats (P < 0.001), and PRA by 0.25 ± 0.09 ng/ml · h (P = 0.007), whereas baroreflex sensitivity increased by 5.2 ± 2.2 msec/mm Hg (P = 0.005). After weight maintenance, beneficial effects of weight loss on norepinephrine spillover rate were preserved, whereas PRA and MSNA rebounded (by 0.24 ± 0.11 ng/ml · h, P = 0.02; and 20 ± 5 bursts/100 heartbeats, P = 0.0003), and baroreflex sensitivity was attenuated.

CONCLUSIONS

Divergent effects of successful weight loss maintenance on whole-body norepinephrine spillover rate and MSNA suggest organ-specific differentiation in SNS adaptation to weight loss under conditions of negative vs. stable energy balance.

Moderate weight loss improves heart rate variability in overweight and obese adults with type 2 diabetes

The objective of this study was to determine the effects of weight loss on heart rate variability (HRV) and its association with traditional cardiovascular disease risk factors in overweight and obese patients with type 2 diabetes. Forty five patients [body mass index (BMI) 35.4 ± 0.7 kg/m²; age 56.5 ± 1.1 yr] with type 2 diabetes followed an energy-restricted diet (6-7 MJ/day) for 16 wk. Body weight, blood pressure, glucose, insulin, insulin resistance [homeostasis model assessment index 2 (HOMA2)], glycosylated hemoglobin (HbA1c), total cholesterol, low-density lipoproteins (LDL), high-density lipoproteins (HDL), triglycerides, resting HR, and HRV were measured before and after the intervention period. Mean reduction in body weight was 11.1 ± 1.0 kg (10%), with significant reductions in blood pressure (-10%), total cholesterol (-15.9%), LDL (-17.7%), HDL (-7.5%), triglycerides (-21.2%), glucose (-23.4%), insulin (-37.6%), HOMA2 (-40.1%), and HbA1c (-14.5%) (P ≤ 0.05 for all variables). There were increases in several HRV components, including total power (1,370 ± 280 to 2,045 ± 280 ms²), low-frequency power (345 ± 70 to 600 ± 108 ms²), SD of normal to normal intervals (SDNN; 35.0 ± 2.5 to 43.0 ± 2.7 s), and square root of the mean squared differences of successive normal to normal intervals (RMSSD; 23.0 ± 3.5 to 32.0 ± 3.1 s), and a decrease in HR (69.0 ± 1.3 to 60.0 ± 1.2 beats/min) (P ≤ 0.03 for all variables). Changes in HR, SDNN, total power, and low-frequency power correlated with change in BMI (P < 0.05). In addition to improvements in traditional cardiovascular and metabolic risk factors, weight loss improves HRV in overweight and obese patients with type 2 diabetes.

Neuroadrenergic dysfunction in obesity: an overview of the effects of weight loss

PURPOSE OF REVIEW

The prevalence of obesity is rising to epidemic proportions worldwide, and in tandem so is that of type 2 diabetes. Neuroadrenergic abnormalities, comprising increased resting sympathetic nervous system activity and blunted sympathetic neural responsiveness are recognized features of metabolic syndrome obesity, which contribute importantly to both the pathophysiology and adverse clinical prognosis of this high-risk population. Weight loss is recommended as first-line treatment for obesity. This review examines the effects of nonpharmacological weight loss on sympathetic nervous system function under basal and stimulated conditions.

RECENT FINDINGS

Human weight loss trials show that even moderate weight reduction is accompanied by significant attenuation in resting whole-body norepinephrine spillover rate and muscle sympathetic nerve activity, an improvement in cardiac autonomic modulation, and a reversal of blunted sympathetic responsiveness at both peripheral and central nervous system levels. Recent findings underscore the relevance of insulin resistance in mediating blunted sympathetic responsiveness to endogenous hyperinsulinemia induced by glucose ingestion. Impaired insulin transport across the blood-brain barrier may be one mechanism mediating these effects. Weight loss reverses blunted sympathetic responsiveness to glucose, which has implications for postprandial energy expenditure and body weight homeostasis.

SUMMARY

The autonomic dysfunction of obesity is reversible with weight loss, highlighting the importance of lifestyle intervention as a key therapeutic modality.

Effect of diet-induced weight loss on plasma apelin and cytokine levels in individuals with the metabolic syndrome

BACKGROUND AND AIMS

Adipose tissue is an active endocrine organ that secretes signaling molecules involved in the regulation of insulin sensitivity, food intake and inflammation. Apelin is a peptide secreted by adipose tissue that has been shown to modulate cardiovascular tone in animals. The aim of this study was to measure abdominal fat, blood pressure and circulating apelin, adiponectin, leptin, ghrelin, TNF-alpha and IL-6 levels in patients with the metabolic syndrome after a diet-induced weight loss.

METHODS AND RESULTS

35 obese individuals with the metabolic syndrome underwent an 8-week very-low-calorie diet (VLCD) and a 6-month weight maintenance period (WM) with 120mg orlistat or placebo administered 3 times daily. VLCD and WM (-15.1+/-1.0kg) decreased mean arterial pressure (MAP), insulin, leptin, triglycerides and visceral and subcutaneous adipose tissue. Moreover, adiponectin increased in response to the weight loss. However, the overall changes in plasma apelin, TNF-alpha and IL-6 were non-significant. A correlation between plasma apelin and TNF-alpha was observed at baseline (0.41, p<0.05), and the minor changes in plasma apelin levels were associated with changes in BMI during VLCD and MAP and TNF-alpha during VLCD and WM periods.

CONCLUSION

Despite reductions in BMI, body adiposity, MAP and enhancement of glucose metabolism and adiponectin in response to weight loss, no significant changes in plasma apelin, TNF-alpha and IL-6 were observed. However, apelin significantly correlated with TNF-alpha and MAP. These results suggest that apelin may not be that strongly correlated with the fat mass as an adipokine like the more abundant adipokines adiponectin or leptin and it might be involved in the regulation of inflammation and cardiovascular tone.

Higher heart rate may predispose to obesity and diabetes mellitus: 20-year prospective study in a general population

BACKGROUND

Emerging evidence indicates an association between sympathetic activation and metabolic syndrome. However, sympathetic activation in metabolic syndrome may be a cause, consequence, or just epiphenomenon. To elucidate this issue, the predictive power of resting heart rate for the development of abnormal glucose and lipid metabolisms after 20 years was evaluated in a general population.

METHODS

A total of 637 participants (>20 years old) underwent a health examination in 1979 including measurements of blood chemistries. Resting heart rate (bpm) was measured by an electrocardiogram. In 1999, all of the study participants again underwent a health examination, including electrocardiogram and blood chemistries. Because four of them had atrial fibrillation, and 19 subjects were taking antihypertensive medication in 1979, they were excluded from analysis. Therefore, a complete dataset of 614 subjects was available.

RESULTS

As was reported in our previous article, in 1999 we found a linear and significant (P < 0.05) cross-sectional relationship between resting heart rate and a cluster of cardiometabolic risk factors (blood pressure (BP), free fatty acid (FFA), plasma glucose, and homeostasis model assessment (HOMA) index). Baseline higher heart rate (heart rate >or=80 bpm in 1979) predicted the development of obesity, diabetes mellitus (DM), and insulin resistance in 1999 after adjustments for age, sex, and other confounders.

CONCLUSION

This is one of the first prospective reports demonstrating that higher heart rate may predispose to the development of obesity and DM, suggesting that the sympathetic nerve system may play a role in the development of obesity and DM.

Independent evolution of heart autonomic function and insulin sensitivity during weight loss

In order to investigate the improvement of insulin resistance and cardiac autonomic function along massive weight loss, 12 obese women were evaluated before, and 3 and 12 months after Roux-en-Y gastric bypass. The 12-month values were compared to those of BMI-matched controls. Insulin sensitivity was assessed by euglycemic clamp and the cardiac autonomic function by the analysis of the Heart Rate Variability (HRV). After surgery, glucose uptake progressively increased from 4.3 +/- 0.5 mg/kg lean body mass (LBM)/min preoperative (pre-op) to 4.9 +/- 0.5 and 7.0 +/- 0.5, 3- and 12-month postoperative (post-op) (P = 0.04 and P = 0.006 vs. pre-op), whereas the cardiac autonomic function showed a biphasic pattern. HRV values increased 3 months post-op, and decreased at 12 months, thus indicating an early sympathetic withdrawal followed by a later reactivation (e.g., the standard deviation of the normal-to-normal intervals was 116 +/- 7 ms in pre-op, 161 +/- 10 at 3 months, P = 0.008 vs. pre-op, and 146 +/- 15 at 12 months, P = 0.03 vs. pre-op and P = 0.02 vs. 3 m). Insulin sensitivity was significantly related to body weight (P = 0.02), whereas the cardiac indexes were significantly linked to the profile of energy intake (e.g., HRV triangular index vs. energy intake P = 0.003). No significant relationship linked insulin sensitivity to the cardiac autonomic indexes. Insulin sensitivity and cardiac parameters of the 12-month post-op patients were similar to their matched controls. During massive weight loss, the cardiac autonomic deregulation and insulin resistance improved concomitantly but independently from each other. Our results suggest that the extent of the improvement is associated with the final body weight.

Randomized clinical trials of weight loss maintenance: a review

The problem of overweight and obesity has reached epidemic proportions in the United States and globally, and the high prevalence is due in part to the recidivism associated with weight loss treatment. Approximately one-third of lost weight is often regained in the first year after treatment and, at times, continues. Because a plethora of comorbid diseases are associated with obesity, in particular, cardiovascular disease, hypertension, and hyperlipidemia, clinicians and researchers have attempted to find useful strategies for maintaining weight loss. This review presents the findings from 42 randomized clinical trials of weight loss maintenance from 1984 through 2007 using interventions that include (1) the Internet, (2) strategies after a very low calorie diet, (3) pharmacotherapy, (4) behavioral strategies, (5) physical activity, and (6) alternative strategies. The results of the reviewed trials revealed that treatment with orlistat or sibutramine combined with dietary modification, caffeine or protein supplementation, consuming a diet lower in fat, adherence to physical activity routines, prolonged contact with participants, problem-solving therapy, and the alternative treatment of acupressure were efficacious in reducing weight regain after weight loss treatment. The limitations of some studies may reduce the robustness of their findings, and future studies are necessary to replicate and support these results so that individuals are able to maintain weight loss and retain the health benefits associated with a lower weight.

Effects of short-term hypocaloric diet on sympatho-vagal interaction assessed by spectral analysis of heart rate and blood pressure variability during stress tests in obese hypertensive patients

We examined the effects of a short-term low-calorie diet on the activity of the autonomic nervous system during stress tests in obese patients with hypertension by analysis of heart rate and blood pressure variability. Eighteen obese inpatients with essential hypertension were given a regular-calorie diet (1,600 kcal, NaCl 7 g) for 4 days, and then a low-calorie diet (1,100 kcal, NaCl 7 g) for 11 days. During both the regular-calorie diet and low-calorie diet, power spectral analysis of heart rate and blood pressure variability at rest and during mental arithmetic test, deep breathing test, isometric handgrip test or cold pressor test was performed. Body weight and 24-h ambulatory blood pressure were significantly lower during the low-calorie diet than during the regular-calorie diet. Systolic and diastolic blood pressure significantly increased over the handgrip test and cold pressor test during both diets. The low frequency component (LF) of systolic blood pressure, a marker of sympathetic activity to the vasculature, during the deep breathing test and cold pressor test were significantly lower on the low-calorie diet than the regular-calorie diet. The blood leptin concentration was also significantly lower on the low-calorie diet than the regular-calorie diet. The decrease in body weight was positively correlated with the decrease in blood leptin concentration. The LF/high frequency component (HF) ratio of the RR interval at rest on the regular-calorie diet was negatively correlated with the decrease in blood leptin concentration. These results suggest that the autonomic nervous function assessed by analysis of heart rate and blood pressure variability during stress tests may be improved by weight loss due to a short-term low-calorie diet in obese patients with hypertension.

Impaired ex vivo leukotriene B4 production characterizes the metabolic syndrome and is improved after weight reduction

CONTEXT

Neutrophil (polymorphonuclear neutrophil) production of leukotriene B4 (LTB4) may be associated with alterations in immune and inflammatory function that characterize the metabolic syndrome (MetS).

OBJECTIVE

We investigated whether polymorphonuclear neutrophil production of LTB(4) and its metabolites 20-hydroxy-LTB4 (20-OH-LTB4) and 20-carboxyl-LTB4 were altered in subjects with features of the MetS before and after weight reduction.

DESIGN, SETTING, PATIENTS, AND INTERVENTION

In a case-controlled comparison, men and postmenopausal women with features of the MetS were matched with controls. Subjects with MetS were then matched and randomly assigned to either a 12-wk weight reduction study followed by 4-wk weight stabilization or 16-wk weight maintenance.

MAIN OUTCOME MEASURES

Measurements were performed at baseline and at the end of the 16-wk period. Stimulated neutrophil LTB4 and its metabolites were measured by HPLC.

RESULTS

In the case-controlled study, body mass index, waist circumference, blood pressure, fasting triglycerides, and glucose were all significantly increased in subjects with features of the MetS (P < 0.05). Production of LTB4 and 20-OH-LTB4 was significantly lower compared with controls (P < 0.005). The weight loss intervention resulted in a 4.6-kg reduction in body weight and 6.6-cm decrease in waist circumference relative to controls and a significant increase in LTB4 and 20-OH-LTB4.

CONCLUSIONS

Subjects with features of the MetS have lower stimulated LTB4, which is not due to increased metabolism of LTB4. Weight reduction restored the production of neutrophil LTB4, suggesting that in addition to modifying cardiovascular risk, weight loss may also help with the management of perturbed inflammatory responses in overweight subjects.

Role of genetic and environmental influences on heart rate variability in middle-aged men

Our aim was to estimate causal relationships of genetic factors and different specific environmental factors in determination of the level of cardiac autonomic modulation, i.e., heart rate variability (HRV), in healthy male twins and male twins with chronic diseases. The subjects were 208 monozygotic (MZ, 104 healthy) and 296 dizygotic (DZ, 173 healthy) male twins. A structured interview was used to obtain data on lifetime exposures of occupational loading, regularly performed leisure-time sport activities, coffee consumption, smoking history, and chronic diseases from 12 yr of age through the present. A 5-min ECG at supine rest was recorded for the HRV analyses. In univariate statistical analyses based on genetic models with additive genetic, dominance genetic, and unique environmental effects, genetic effects accounted for 31–57% of HRV variance. In multivariate statistical analysis, body mass index, percent body fat, coffee consumption, smoking, medication, and chronic diseases were associated with different HRV variables, accounting for 1–11% of their variance. Occupational physical loading and leisure-time sport activities did not account for variation in any HRV variable. However, in the subgroup analysis of healthy and diseased twins, occupational loading explained 4% of the variability in heart periods. Otherwise, the interaction between health status and genetic effects was significant for only two HRV variables. In conclusion, genetic factors accounted for a major portion of the interindividual differences in HRV, with no remarkable effect of health status. No single behavioral determinant appeared to have a major influence on HRV. The effects of medication and diseases may mask the minimal effect of occupational loading on HRV.

Baroreflex sensitivity in obesity: relationship with cardiac autonomic nervous system activity

OBJECTIVE

The aim of this study was to test the hypothesis that baroreflex sensitivity (BRS), assessed by indirect measurement of aortic pressure, is blunted in obesity. Additionally, the potential effect of cardiac autonomic nervous system (ANS) activity, aortic compliance, and metabolic parameters on BRS of obese subjects was investigated.

RESEARCH METHODS AND PROCEDURES

A group of 30 women with BMI>30 kg/m2 and a group of 30 controls with BMI<25 kg/m2 were examined. BRS was estimated by the sequence technique, cardiac ANS activity by short-term spectral analysis of heart rate variability (HRV), and aortic compliance by the method of applanation tonometry.

RESULTS

BRS was lower in obese women (9.18+/-3.77 vs. 19.63+/-9.16 ms/mm Hg, p<0.001). The median values (interquartile range) of the power of both the high-frequency and low-frequency components of the HRV were higher in the lean than in the obese participants [1079.2 (202.7 to 1716.9) vs. 224.1 (72.7 to 539.6) msec2, p=0.001 and 411.8 (199.3 to 798.0) vs. 235.8 (99.4 to 424.5) msec2, p=0.01 respectively]. Low-to-high-frequency ratio values were higher in the obese subjects [0.82 (0.47 to 2.1) vs. 0.57 (0.28 to 0.89), p=0.02]. Aortic augmentation values were not significantly different between lean and obese subjects. Multivariate analysis demonstrated a significant and independent association between BRS and age (p=0.003), BMI (p<0.001), and high-frequency power of HRV (p<0.001). These variables explained 72% of the variation of BRS values.

DISCUSSION

BRS is severely reduced in obese subjects. BMI, age, and the parasympathetic nervous system activity are the main determinants of BRS. Baroreflex behavior is of clinical relevance because an attenuated BRS represents a negative prognostic factor in cardiovascular diseases, which are common in obesity.

Physical activity, diet, and incident diabetes in relation to an ADRA2B polymorphism

PURPOSE

The 12Glu9 polymorphism of the alpha2B-adrenergic receptor gene may impair insulin secretion and modify the effects of a lifestyle intervention on the risk of type 2 diabetes, but the interaction with specific lifestyle components is unknown. We assessed the associations of leisure-time physical activity (LTPA), dietary changes, and weight loss on the risk of type 2 diabetes according to the 12Glu9 polymorphism in 481 participants of the Finnish Diabetes Prevention Study.

METHODS AND RESULTS

The lifestyle intervention decreased the risk of diabetes in 9Glu carriers (9Glu9, intervention vs control, relative risk (RR) = 0.23, 95% confidence interval (CI) 0.09-0.62), but not in 12Glu12 homozygotes. In the combined intervention and control groups, increased total LTPA as estimated with a questionnaire decreased the risk of diabetes in 12Glu carriers (12Glu12, upper vs lower third, RR = 0.12, 95% CI 0.03-0.53) but not in 9Glu9 homozygotes (P for the interaction 0.033). In contrast, favorable dietary changes, estimated using a dietary score, reduced the risk of diabetes in those with the 9Glu9 genotype (upper vs lower third, RR = 0.21, 95% CI 0.06-0.75) but not in those with the 12Glu allele. Weight loss significantly decreased the risk of diabetes only in 12Glu carriers.

CONCLUSION

Increased LTPA decreased the risk of type 2 diabetes more in those with the 12Glu allele of the ADRA2B gene, whereas dietary changes may have mediated the greater risk reduction of the lifestyle intervention in 9Glu homozygotes.

The altered homeostatic theory: A hypothesis proposed to be useful in understanding and preventing ischemic heart disease, hypertension, and diabetes – including reducing the risk of age and atherosclerosis

Evidence will be presented to support the usefulness of the altered homeostatic theory in understanding basic pathogenetic mechanisms of ischemic heart disease (IHD), hypertension, and diabetes, and in improving prevention of these disorders. The theory argues that: IHD, hypertension, and diabetes share the same basic pathogenesis; risk factors favor a sympathetic homeostatic shift; preventative factors favor a parasympathetic homeostatic shift; risk and preventative factors oppose each other through a dynamic risk/prevention balance; and prevention should be based on improving the risk/prevention balance. Prevention based on improving the risk/prevention balance should be more effective, as this method is regarded as reflecting more accurately basic pathogenetic mechanisms. As example, the theory argues that the risk of supposedly nonmodifiable risk factors as age and the risk of relatively nonmodifiable atherosclerosis can be reduced significantly. The possible validity of the altered homeostatic theory was tested by a study based on multiple associations. Findings support a common pathogenesis for IHD, hypertension, and diabetes based on a sympathetic homeostatic shift, and the usefulness of prevention based on improving the risk/prevention balance by using standard pharmaceutical and lifestyle preventative measures. The same set of multiple and diverse risk factors favored IHD, hypertension, and diabetes, and the same set of multiple and diverse pharmaceutical and lifestyle preventative measures prevented these disorders. Also, the same set of preventative agents generally improved cognitive function and bone density, and reduced the incidence of Alzheimer's disease, atrial fibrillation, and cancer. Unexpectedly, evidence was developed that four major attributes of sympathetic activation represent four major risk factors; attributes of sympathetic activation are a tendency toward thrombosis and vasoconstriction, lipidemia, inflammation, and hyperglycemia, and corresponding risk factors are endothelial dysfunction (which expresses thrombosis/vasoconstriction and epitomizes this tendency), dyslipidemia, inflammation, and insulin resistance. These findings, plus other information, provide evidence that dyslipidemia acts mainly as a marker of risk of IHD, rather than being the basic mechanism of this disorder. However, prevention generally is based solely on improvement of dyslipidemia; basing prevention on dyslipidemia relatively underemphasizes the importance of other significant risk factors and, by certifying its validity, discourages alternate pathogenetic approaches. Also, development of myocardial infarction is approached differently. It seems generally accepted that dyslipidemia results rather automatically in infarction through the sequence of atherosclerosis, atherosclerotic complications, and thrombosis. In contrast, distinction is made between development of atherosclerosis and acute induction of infarction--where atherosclerosis is only one of multiple risk factors.

Sympathetic System Activity in Obesity and Metabolic Syndrome

Obesity is a very common disease worldwide, resulting from a disturbance in the energy balance. The metabolic syndrome is also a cluster of abnormalities with basic characteristics being insulin resistance and visceral obesity. The major concerns of obesity and metabolic syndrome are the comorbidities, such as type 2 diabetes, cardiovascular disease, stroke, and certain types of cancers. Sympathetic nervous system (SNS) activity is associated with both energy balance and metabolic syndrome. Sympathomimetic medications decrease food intake, increase resting metabolic rate (RMR), and thermogenic responses, whereas blockage of the SNS exerts opposite effects. The contribution of the SNS to the daily energy expenditure, however, is small ( approximately 5%) in normal subjects consuming a weight maintenance diet. Fasting suppresses, whereas meal ingestion induces SNS activity. Most of the data agree that obesity is characterized by SNS predominance in the basal state and reduced SNS responsiveness after various sympathetic stimuli. Weight loss reduces SNS overactivity in obesity. Metabolic syndrome is characterized by enhanced SNS activity. Most of the indices used for the assessment of its activity are better associated with visceral fat than with total fat mass. Visceral fat is prone to lipolysis: this effect is mediated by catecholamine action on the sensitive beta(3)-adrenoceptors found in the intraabdominal fat. In addition, central fat distribution is associated with disturbances in the hypothalamo-pituitary-adrenal axis, suggesting that a disturbed axis may be implicated in the development of the metabolic syndrome. Furthermore, SNS activity induces a proinflammatory state by IL-6 production, which in turn results in an acute phase response. The increased levels of inflammatory markers seen in the metabolic syndrome may be elicited, at least in part, by SNS overactivity. Intervention studies showed that the disturbances of the autonomic nervous system seen in the metabolic syndrome are reversible.

Vagal modulation and aging

Cardiovascular disease accounts for approximately 30% of all deaths worldwide, and will only worsen as the world's population ages. It is well-established that age, per se, is a major risk factor and contributor to all cardiovascular morbidities and mortalities. However, environmental factors, including a lack of exercise, appear to play a critical role in the onset and progression of cardiovascular disease. This paper reviews the literature on cardiac variability and aging and addresses risk factors associated with aging that can be modified and possibly attenuate the decline of heart rate variability with aging, including exercise training to increase vagal modulation. Thus, results of the studies described in this review support a potential benefit of increasing or maintaining fitness in order to slow the decline of parasympathetic control of HR with normal aging.

Weight loss improves heart rate recovery in overweight and obese men with features of the metabolic syndrome

BACKGROUND

Heart rate recovery (HRR) is an independent risk factor for cardiovascular disease (CVD) and mortality, but whether it is modifiable and can improve with weight loss is unclear. We sought to determine the effects of weight loss on HRR and its association with traditional CVD risk markers.

METHODS

Heart rate recovery (defined as the decrease in heart rate from peak heart rate to that measured 1 minute after a standardized graded treadmill test) and a range of established cardiovascular risk factors were measured in 42 overweight and obese men (body mass index 33.8 +/- 0.6 kg/m2, mean age 46.5 +/- 1.3 years) who had no symptoms of CVD but had components of the metabolic syndrome before and after 12 weeks of weight loss.

RESULTS

There was a 9% weight reduction (P < .001), with losses of 6.3 +/- 0.6 kg of fat mass (P < .001) and 3.1 +/- 0.6 kg of non-bone fat-free mass (P < .001). There were significant reductions in waist circumference, blood pressure, plasma triglycerides, total cholesterol, low-density lipoprotein cholesterol, triglyceride/high-density lipoprotein ratio, C-reactive protein, plasma insulin, glucose, and insulin resistance (P < .05). Although peak heart rate remained unchanged, HRR at 1 minute improved from 33.1 +/- 1.4 to 36.9 +/- 1.3 beats/min (P < .001) after weight loss. There was no change in cardiorespiratory fitness (P = .30); neither was there any change in physical activity levels (P = .67). The improvement in HRR was significantly correlated with decreases in body weight, body mass index, waist circumference, plasma glucose, serum triglycerides, and triglyceride/high-density lipoprotein ratio; however, it was only independently associated with changes in weight and plasma glucose concentrations.

CONCLUSION

In addition to improving a range of well-accepted cardiovascular and metabolic risk factors, weight loss also improves HRR after exercise, a less recognized risk factor.

High serum high-sensitivity C-reactive protein concentrations are associated with relative cardiac sympathetic overactivity during the early morning period in type 2 diabetic patients with metabolic syndrome

Sympathetic activation is associated with metabolic syndrome (MS) and increased risk of cardiovascular disease. The aim of this study was to investigate whether cardiac autonomic activity or sympathovagal balance, as estimated by a 24-hour power spectral analysis of heart rate variation, is associated with serum concentrations of high-sensitivity C-reactive protein (hs-CRP), a sensitive predictor for cardiovascular events, in type 2 diabetic patients with and without MS. We studied 104 type 2 diabetic patients (50 female and 54 male). The diagnosis of MS was based on the National Cholesterol Education Program Adult Treatment Panel III criteria. Based on the serum hs-CRP, diabetic patients were also divided into 3 groups: low risk (CRP < 1.0 mg/L), moderate risk (1.0 < or = CRP < or = 3.0), and high risk (CRP > 3.0). Heart rate variation was determined automatically every 5 minutes over 24 hours using an ambulatory Holter electrocardiographic recording. Power spectral analysis of the R-R intervals was performed by fast Fourier transformation. Low frequency (LF, both sympathetic and parasympathetic activities), high frequency (HF, pure parasympathetic activity), and the ratio of LF to HF, an index of sympathovagal balance, were used as indices of cardiac autonomic activity. Blood concentrations of hs-CRP, interleukin 6, and plasminogen activator inhibitor 1 were higher in diabetic patients with than in those without MS (P < .0001, P = .0056, and P < .0001, respectively). Both the 24-hour mean LF and the LF-to-HF ratio were also significantly higher in diabetic patients with than in those without MS (P = .0397 and P = .0483, respectively). The LF-to-HF ratio at 6:00 am was significantly higher in diabetic patients with a high CRP concentration than in those with a low or moderate CRP concentration (P < .001 and P < .01, respectively). Only urinary albumin and hs-CRP were independent factors predicting the LF-to-HF ratio at 6:00 am in diabetic patients. In conclusion, type 2 diabetic patients with MS have elevated markers of inflammation and evidence of cardiac sympathetic predominance. High serum concentrations of hs-CRP are associated with relative cardiac sympathetic overactivity during the early morning in type 2 diabetic patients.

Hypothesis: the systemic circulation as a regulated free-market economy. A new approach for understanding the long-term control of blood pressure

1. The purpose of the present paper is to discuss the long-term regulation of arterial blood pressure. Current thinking on the topic favours the theory that tight regulation is achieved through the action of a central (or primary) controller, usually assumed to be in either the brain or kidneys. 2. Here, an alternative explanation is considered; namely, that the average long-term level of arterial pressure is an emergent property of a decentralized control system. The goal of the system is to deliver nutrient-rich blood to distinct vascular regions based on their energy demand. 3. Specifically, the circulation is conceptualized as a free-market economy where tissues 'compete' for a scarce resource (the energy contained in blood) supplied by the heart-lung unit; the 'price' of the resource (analogous to the reciprocal of arterial pressure) is determined primarily by the dynamic relationship between supply and demand, not by a central mechanism. 4. Based on this concept of the circulation as an energy market, economic analogies are used to suggest novel mechanisms by which the brain and kidney may affect the long-term control of blood pressure. 5. Market-based control, a process derived from quantitative theoretical analysis of the performance of economic markets, is proposed as a new, potentially useful strategy for mathematically modelling the behaviour of the circulation.

Weight change and changes in the metabolic syndrome as the French population moves towards overweight: the D.E.S.I.R. cohort

BACKGROUND

How weight change affects the metabolic syndrome (MS) and its parameters is unknown, particularly, in a leaner European population such as the French prospective D.E.S.I.R. cohort.

METHODS

In 3770 D.E.S.I.R. participants (sex ratio=1) averaging 47.5 years (range 30-64), with measured weight and MS parameters at baseline (D0) and at 6 year follow-up (D6), we assessed this relationship across five weight-change classes, using stable weight as the referent group (-2 to +2 kg). We used analysis-of-covariance to assess changes in each MS parameter and logistic regression to assess incident MS, according to the National Cholesterol Education Program (NCEP). We also assessed weight-change effect on MS status between D0 and D6.

RESULTS

At D0, average weight was 68.4 kg (SD 12.3); BMI was 24.8 kg/m2 (SD 3.5). From D0-D6, the cohort gained a mean 2.1 kg (median 2.0; SD 4.4). After adjustment for age and D0 weight, there was a strong linear relationship with weight change and worsening of the following MS parameters at D6: fasting insulin, waist girth, fasting glucose, fasting triglycerides, HDL cholesterol, and systolic and diastolic blood pressure (P<0.0001). After age adjustment, for every kilogram gained over 6 years, risk of developing the NCEP Syndrome increased 22% (OR 1.22; 95% CI 1.18-1.25). NCEP-MS was incident in 3% of those with stable weight compared with 21% among those gaining >9 kg; 10% of those who lost >2 kg reverted to non-NCEP-MS.

CONCLUSIONS

All continuous MS measures are linearly related to weight change, and MS can resolve with modest weight loss, underscoring the importance of maintaining lifelong normal weight.

Clinical Implications of Obesity With Specific Focus on Cardiovascular Disease

Obesity adversely affects cardiac function, increases the risk factors for coronary heart disease, and is an independent risk factor for cardiovascular disease. The risk of developing coronary heart disease is directly related to the concomitant burden of obesity-related risk factors. Modest weight loss can improve diastolic function and affect the entire cluster of coronary heart disease risk factors simultaneously. This statement from the American Heart Association Council on Nutrition, Physical Activity, and Metabolism reviews the relationship between obesity and the cardiovascular system, evaluates the effect of weight loss on coronary heart disease risk factors and coronary heart disease, and provides practical weight management treatment guidelines for cardiovascular healthcare professionals. The data demonstrate that weight loss and physical activity can prevent and treat obesity-related coronary heart disease risk factors and should be considered a primary therapy for obese patients with cardiovascular disease.

Changes in sex hormone-binding globulin and testosterone during weight loss and weight maintenance in abdominally obese men with the metabolic syndrome

BACKGROUND

Mild hypoandrogenism in men, usually defined by low levels of testosterone, is a peculiar feature of abdominal obesity that independently predicts the development of insulin resistance and diabetes mellitus. Little is known about the short- and long-term effects of weight loss on sex steroids in abdominally obese men, however.

OBJECTIVES

We assessed the effect of rapid weight loss and sustained weight maintenance on the plasma concentrations of testosterone and other sex hormones in 58 abdominally obese men (age, 46.3 +/- 7.5 years; body mass index, 36.1 +/- 3.8 kg/m(2); waist girth, 121 +/- 10 cm) with the metabolic syndrome.

RESULTS

The men lost on average 16.3 +/- 4.5 kg during a 9-week very low-calorie diet (VLCD) and maintained 14.3 +/- 9.1 kg weight loss after a 12-month maintenance period (vs. baseline, p < 0.001). Sex hormone-binding globulin (SHBG) increased from 27.6 +/- 11.9 to 48.1 +/- 23.5 nmol/l during the VLCD but decreased to 32.6 +/- 12.9 nmol/l during weight maintenance, which was still higher than at baseline (p < 0.001). Free testosterone (fT) increased from 185 +/- 66 to 208 +/- 70 pmol/l (p = 0.002) during the VLCD and remained high after 1 year of weight maintenance (212 +/- 84 pmol/l, p = 0.002). Total testosterone levels followed a pattern intermediate between fT and SHBG. Plasma estradiol and dehydroepiandrosterone sulphate concentrations changed only transiently or not at all.

CONCLUSIONS

Rapid weight loss with successful weight maintenance in abdominally obese men with the metabolic syndrome brings about a sustained increase in fT levels. The dramatic increase in SHBG attenuated initially during weight maintenance but remained elevated. These findings may be important with regard to prevention of progressive metabolic decompensation and cardiovascular disease associated with obesity and the metabolic syndrome.

Obesity and hypertension: two epidemics or one?

The association between obesity and hypertension is well documented, although the exact nature of this relation remains unclear. Sympathetic nervous and renin-angiotensin-aldosterone system activation appear to play an important role in the sodium and water retention, rightward shift in the pressure-natriuresis, and blood pressure elevation observed in obese individuals. Visceral obesity and the ectopic deposition of adipose tissue may be important in the activation of these systems and in the target organ damage that ensues. Weight loss is critical in the effective management of obesity hypertension and the accompanying target organ damage, although recidivism rates are high. However, prevention of weight gain should be the major priority for combating hypertension and its consequences in the future. The present review will provide an overview of our understanding of the etiology, pathophysiology, and treatment of obesity hypertension. Our focus is on the state of knowledge in humans. The potential role of abdominal obesity is considered throughout our review. We refer to relevant animal literature for supportive evidence and where little or no data in humans are available.

Comparison of efficacy of sibutramine or orlistat versus their combination in obese women

OBJECTIVE

Sibutramine and orlistat are currently used for weight loss. We aimed to investigate the effect of orlistat and sibutramine combination therapy in treatment of obese women.

SUBJECTS AND DESIGN

Study population consisted of 89 obese women who had a body mass index > or = 30 kg/m2, were normotensive, and had normal glucose tolerance. All patients were placed on a diet which contained fat approximately 30% of total calorie intake and the diet was designed to cause an energy deficit of approximately 2.51-3.56 megajoule/day. At the first month of diet (baseline), all patients were randomly divided into three therapy groups: Diet + Orlistat (group 1; n = 30 patients), Diet + Sibutramine (group 2; n = 29 patients), Diet + Orlistat + Sibutramine (group 3; n = 30 patients). Body weight, body fat distribution and serum lipid levels were evaluated baseline and after six months in all subjects.

RESULTS

Mean weight loss was 5.5 +/- 4.9 kg (p = 0.024) in group 1, 10.1 +/- 3.6 kg (p < 0.001) in group 2, 10.8 +/- 6.6 kg (p < 0.001) in group 3 after the six months. Weight loss was significantly greater in group 2 (p = 0.003) and group 3 (p = 0.002) when compared with group 1. Percentage of mean weight loss was 5.5 +/- 3.1% in group 1, 10.2 +/- 4.8% in group 2, 10.6 +/- 5.7% in group 3. Percentage of weight loss was higher in group 2 (p = 0.01) and group 3 (p = 0.009) when compared with group 1. Weight loss and percentage of weight loss were not different between group 2 and group 3.

CONCLUSION

These three regimens had different results on weight loss in obese women. Combination drug therapy and sibutramine therapy were both more effective than orlistat therapy alone. However, no significant difference was noted between combination drug therapy and sibutramine treatment groups.

Changes in body weight and onset of hypertension in perimenopausal women

We assessed the determinants of onset of hypertension in a large, prospective population-based study of perimenopausal women from the Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study. The data collection started in 1989, when a baseline postal inquiry was sent to all women aged 47-56 years (n=14 220) residing in the Kuopio Province in Eastern Finland. Names, social security numbers and addresses were obtained from the Population Register Centre of Finland. A total of 11 798 women responded at baseline and at 5-year follow-up in 1994. After the exclusion of 1777 women with prevalent hypertension at baseline and women with missing height or weight information, the study population consisted of 9485 without established hypertension at baseline. New cases of established hypertension during the follow-up (n=908) were ascertained with the Registry of Specially Refunded Drugs of the Finnish Social Insurance Institution (SII). According to the National Health Insurance, the SII granted 90% reimbursement for drug costs in defined chronic illnesses necessitating continuous medication, like arterial hypertension. Weight and weight gain both raised the risk by 5% per kg (P<0.001). Weight gain of 4-6 kg increased the risk of hypertension 1.25 times and a gain of more than 7 kg 1.65 times compared with the control (zero) group. To conclude, the onset of hypertension in peri- and early postmenopausal women was related to an increase in body weight despite controlling for initial body weight, reported physical activity and use of HRT. Therefore, preventing weight gain by dietary means and exercise is of great importance at menopausal age.