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

Heart rate variability after bariatric surgery: The add-on value of exercise

PURPOSE

To assess the impact of bariatric surgery and an added supervised exercise training programme on heart rate variability (HRV) in patients with severe obesity.

METHODS

Fifty-nine patients who underwent bariatric surgery were randomised in the post-operative period to a 12-week supervised exercise training programme (moderate intensity combination aerobic/resistance exercise training programme) or a control group. Indices of HRV including time-domain, spectral-domain, and nonlinear parameters were measured preoperatively, and at 3, 6, and 12 months.

RESULTS

After the surgical procedure, both groups improved anthropometric parameters. Type 2 diabetes, hypertension, and dyslipidemia resolutions were similar between groups. Total body weight loss at 6 and 12 months were also comparable between groups (6 months: 28 ± 6 vs. 30 ± 6%; 12 months: 38 ± 9 vs. 38 ± 10%; control vs. intervention group respectively). Bariatric surgery improved HRV parameters at 12 months compared to the pre-operative values in the intervention group: standard deviation of R-R interval (SDNN) (156.0 ± 46.4 vs. 122.6 ± 33.1 ms), low frequency (LF) (6.3 ± 0.8 vs. 5.8 ± 0.7 ms²), and high frequency (HF) (5.1 ± 0.8 vs. 4.7 ± 0.9 ms²) (all p<0.001). For the control patients, similar improvements in SDNN (150.0 ± 39.4 vs. 118.8 ± 20.1 ms), LF (6.1 ± 0.9 vs. 5.7 ± 0.8 ms²), and HF (5.0 ± 0.9 vs. 4.7 ± 0.9 ms²) were obtained (all p<0.001). However, there was no add-on impact of the supervised exercise training programme on HRV after 12 months (p>0.05 for all HRV parameters).

CONCLUSION

Bariatric surgery is associated with an improvement in HRV. A supervised exercise training programme in the post-operative period did not modulate further the benefits of bariatric surgery regarding HRV parameters.

Does bariatric surgery improve cardiac autonomic modulation assessed by heart rate variability? A systematic review

Our study aimed to explore the influence of bariatric surgery (BS) on heart rate (HR) variability (HRV) through a systematic review. Manuscripts were selected based on electronic searches of the MEDLINE, EMBASE, and CINAHL databases from the inception of each database up to year 2020, and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Searching of these studies was systematized using the Population Intervention Comparison Outcome Study Design strategy. We selected randomized and nonrandomized controlled trials and cohorts from prospective studies that reported the influence of BS on HRV. We assessed the quality rating using the Black and Downs questionnaire. Following the screening and eligibility stages, 14 studies were included in the review. All studies agreed that BS promotes an increase in parasympathetic HR control and HRV and a decrease in HR. Yet the literature does not provide evidence that these outcomes are directly caused by the surgical procedure. There is limited evidence to support that patients with type 2 diabetes have greater improvement in HRV as an interim measure, to individuals without. The decrease in insulin resistance was correlated with the increase in HRV in some studies, but, other studies are unsupportive of this outcome. Improvements in 2 metabolic parameters (e.g., leptin, N-terminal pro B-type natriuretic peptide) were connected with superior increases in HRV. This review demonstrated that BS promotes an increase in HRV, indicating improved autonomic control of HR.

Obesity, Hypertension, and Bariatric Surgery

PURPOSE OF REVIEW

Obesity increases the risk of hypertension. However, blood pressure decreases before any significant loss of body weight after bariatric surgery. We review the mechanisms of the temporal dissociation between blood pressure and body weight after bariatric surgery.

RECENT FINDINGS

Restrictive and bypass bariatric surgery lower blood pressure and plasma leptin levels within days of the procedure in both hypertensive and normotensive morbidly obese patients. Rapidly decreasing plasma leptin levels and minimal loss of body weight point to reduced sympathetic nervous system activity as the underlying mechanism of rapid blood pressure decline after bariatric surgery. After the early rapid decline, blood pressure does not decrease further in patients who, while still obese, experience a steady loss of body weight for the subsequent 12 months. The divergent effects of bariatric surgery on blood pressure and body weight query the role of excess body weight in the pathobiology of the obesity phenotype of hypertension. The decrease in blood pressure after bariatric surgery is moderate and independent of body weight. The lack of temporal relationship between blood pressure reduction and loss of body weight for 12 months after sleeve gastrectomy questions the nature of the mechanisms underlying obesity-associated hypertension.

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

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

Early blood pressure response to isometric exercise is attenuated in obese individuals who have undergone bariatric surgery

Blood pressure (BP) reactivity is predictive of the development of cardiovascular disease. We hypothesized that the BP response at the onset of isometric handgrip exercise would occur earlier and to a lesser degree in individuals who underwent bariatric surgery compared with obese adults and that the reliance on total peripheral resistance (TPR) would be attenuated. Twenty-six individuals (7 nonobese, 11 obese, 8 postbariatric surgery) completed isometric handgrip exercise (40% maximum voluntary contraction) to exhaustion. Heart rate (HR, ECG) and arterial BP (brachial catheter) were measured continuously. Stroke volume was estimated from the pressure waveform, and cardiac output (CO) and TPR were calculated. Peak change, time to peak, and rate of rise in BP were assessed during the first 30 s of exercise. Obese adults exhibited a slower rise in BP and higher peak BP at exercise onset compared with nonobese controls ( P < 0.05). Peak BP and the rate of rise were not different between individuals who underwent bariatric surgery and nonobese controls ( P > 0.05). Nonobese controls exhibited an exercise-mediated increase in CO, whereas obese adults increased TPR ( P < 0.05). The increases in CO and TPR were less apparent in individuals who underwent bariatric surgery ( P > 0.05). In contrast to obese adults, individuals who underwent bariatric surgery exhibit a rapid rise in BP at exercise onset. This rapid increase in BP is associated with a fall in TPR and results in lower peak BP at the onset of isometric exercise. These data suggest that bariatric surgery improves BP reactivity via changes in the time course of hemodynamic responses. NEW & NOTEWORTHY Bariatric surgery has been shown to reduce the blood pressure (BP) response to isometric handgrip exercise. By examining the time course of the BP response to exercise, we found, in contrast to obese adults, individuals who underwent bariatric surgery exhibit a rapid rise in BP at exercise onset, which is associated with a fall in total peripheral resistance and results in lower peak BP at the onset of isometric exercise. These data suggest that bariatric surgery improves BP reactivity via reflex autonomic adjustments.

The Role of the Autonomic Nervous System in the Pathophysiology of Obesity

Obesity is reaching epidemic proportions globally and represents a major cause of comorbidities, mostly related to cardiovascular disease. The autonomic nervous system (ANS) dysfunction has a two-way relationship with obesity. Indeed, alterations of the ANS might be involved in the pathogenesis of obesity, acting on different pathways. On the other hand, the excess weight induces ANS dysfunction, which may be involved in the haemodynamic and metabolic alterations that increase the cardiovascular risk of obese individuals, i.e., hypertension, insulin resistance and dyslipidemia. This article will review current evidence about the role of the ANS in short-term and long-term regulation of energy homeostasis. Furthermore, an increased sympathetic activity has been demonstrated in obese patients, particularly in the muscle vasculature and in the kidneys, possibily contributing to increased cardiovascular risk. Selective leptin resistance, obstructive sleep apnea syndrome, hyperinsulinemia and low ghrelin levels are possible mechanisms underlying sympathetic activation in obesity. Weight loss is able to reverse metabolic and autonomic alterations associated with obesity. Given the crucial role of autonomic dysfunction in the pathophysiology of obesity and its cardiovascular complications, vagal nerve modulation and sympathetic inhibition may serve as therapeutic targets in this condition.

Effect of a weight reduction program on baseline and stress-induced heart rate variability in children with obesity

OBJECTIVE

Autonomic dysregulation is a well-established feature in adults with obesity but not in children. Since this dysregulation could contribute to weight dynamics, this study aimed to compare autonomic regulation in children with obesity and normal-weight peers and to track autonomic status during weight reduction.

METHODS

Sixty children with obesity and 27 age- and sex-matched normal-weight healthy participants were included. Heart rate variability (HRV) was assessed at baseline and during a mental stress test and a subsequent recovery period. Children with obesity were investigated both upon admission and discharge.

RESULTS

Upon admission, no significant differences in HRV parameters were found for normal-weight participants and those with obesity. Inpatient treatment led to significant changes in HRV with increase in general variability (standard deviation of the normal-to-normal interval (SDNN), P < 0.001) as well as of parasympathetic regulation (root mean square successive difference (RMSSD) and high frequency power (logHF), P < 0.01). Children with obesity had sympathetic activation similar to normal-weight controls during mental stress with subsequent return to baseline values, and weight loss did not affect this profile.

CONCLUSIONS

A weight reduction program induced a change in autonomic activity in children with obesity toward parasympathetic dominance but had no influence on autonomic nervous system reactivity during stress conditions.

Impact of body weight on antidiabetic treatment and predictors of weight control under real-world conditions: a 2-year follow-up of DiaRegis cohort

AIMS

Treatment strategies for obese patients with type 2 diabetes mellitus aim to increase physical activity, reduce body weight, and improve glucose control using weight-beneficial antidiabetic drugs. The objective of this study was to determine whether these strategies are implemented, and to identify factors predictive of glucose control and body weight management in a large, real-world patient population.

METHODS

The prospective DiaRegis cohort study included 3807 patients with type 2 diabetes in whom the treating physician decided to intensify and optimize treatment because of insufficient glucose control.

RESULTS

Antidiabetic treatment of overweight and obese patients was compared with that of normal-weight patients over a 2-years follow-up period, and multivariate analyses were performed to identify predictors of body weight loss. Among the 3807 participants, 92.5 % were overweight or obese. Normal-weight participants were more often treated with sulfonylureas or insulin, and overweight and obese patients with metformin or glucagon-like peptide (GLP)-1 analogues. Predictors of weight loss were body mass index (BMI) ≥30 kg/m(2) and any reported physical activity.

CONCLUSIONS

DiaRegis study shows that under real-world conditions, antidiabetic drug therapy is performed dependent on body weight. This strategy results in adequate glucose control and moderate weight reductions in overweight and obese patients. Weight loss is affected by treatment with weight-beneficial drugs, but also by any reported physical activity. However, only a small subgroup of patients perform physical activity. Initiation and maintenance of a physically active lifestyle remains a significant challenge for physicians, and patients with type 2 diabetes.

Bariatric surgery and prevention of cardiovascular events and mortality in morbid obesity: mechanisms of action and choice of surgery

AIMS

Obesity is associated with increased cardiovascular (CV) morbidity and mortality. Weight loss improves several risk factors for CV diseases, but anti-obesity medications and lifestyle interventions have failed to modify primary CV endpoints. This paper reviews bariatric surgery in prevention of CV diseases and CV mortality, and analyzes the possible mechanisms involved.

DATA SYNTHESIS

In morbidly obese patients bariatric surgery results in stable weight loss and in long-term reduction in the prevalence and incidence of obesity-related comorbidities; controlled trials have shown superiority of bariatric surgery over medical therapy in inducing significant weight loss and improvement of CV risk factors. Bariatric surgery induces several metabolic improvements (resolution of type 2 diabetes mellitus, improvement of lipid metabolism and of insulin resistance, reduction of visceral fat, of subclinical endothelial dysfunction and inflammation), and functional improvements (reduction of hypertension, of sympathetic overactivity, of left and right ventricular hypertrophy), which can explain the protective effect towards CV disease.

CONCLUSIONS

Reduction of CV diseases is mediated by the pleiotropic effects of weight loss through surgery. Available data do not allow conclusions on the comparative efficacy of different surgical techniques; the choice of the surgical technique for a single patient remains an open question, and it is likely that the degree of prevention of CV diseases depends, among other factors, on the baseline conditions of patients. Large prospective studies are needed to address this issue in morbidly obese patients.

Heart rate variability in overweight health care students: correlation with visceral fat

BACKGROUND AND OBJECTIVES

Increased sympathetic activity, decreased parasympathetic activity and sympathovagal imbalance (SVI) has been reported in obese individuals. However, the SVI and its association with visceral fat in overweight health care students have not been explored. Therefore, in the present study, we have assessed heart rate variability (HRV) and its association with visceral fat in overweight health care students.

MATERIALS AND METHODS

Frequency domain parameters of HRV, body fat distribution and baseline anthropometric parameters were recorded in the control (n=40) and overweight (n=40) individuals. Further, the association of visceral fat with HRV was analysed.

RESULTS

There was no significant difference in age and height of overweight group and control group (p = 0.732). The baseline heart rate and blood pressure (p<0.001) were higher in the overweight group. Total body fat, subcutaneous fat and visceral fat were higher in the overweight group (p<0.001). Among frequency domain parameter of HRV, LFnu and LF: HF were more in the overweight group (p<0.001). Further, HFnu was less in the overweight group (p<0.001).

CONCLUSION

Sympathovagal imbalance due to increased sympathetic activity and its association with visceral fat was observed in overweight individuals.

Outcomes of bariatric surgery in type 2 diabetic patients with diminished pancreatic secretory reserve

Although the marked and durable effects of bariatric surgery on early type 2 diabetes is known, there are limited data on the impact of surgery in patients with reduced beta-cell function/reserve. Clinical outcomes of 15 morbidly obese patients with poorly controlled diabetes who underwent bariatric surgery in a 10-year period and had a baseline fasting serum c-peptide ≤0.5 ng/mL were assessed. All patients had glycated hemoglobin >7 % and were on insulin before surgery. Surgical procedures included laparoscopic gastric bypass (n = 9), sleeve (n = 5), and banding (n = 1) without any intraoperative complications. At a mean follow-up of 39.6 ± 22.9 months, a mean reduction in body mass index of 25.1 ± 9.2 % and a mean percent excess weight loss of 61.5 ± 19.7 % were associated with a significant improvement in daily insulin requirement and lipid profile. At the last follow-up point, three patients (20 %) were off insulin, five patients (33.3 %) had a glycated hemoglobin ≤7 %, and one patient (6.7 %) had remission of diabetes. Hypertension resolved or improved in 5 of 11 (45.5 %) hypertensive patients. In conclusion, bariatric surgery can result in improvement of glycemic status and comorbid conditions of obese diabetic patients with diminished beta-cell reserve and may facilitate medical management of diabetes.

Prevention of type 2 diabetes in obese at-risk subjects: a systematic review and meta-analysis

Different intervention strategies can prevent new cases of type 2 diabetes (T2DM) in obese subjects. The present systematic review and meta-analysis evaluates the effectiveness of different strategies in prevention of type 2 diabetes in obese subjects. Studies were grouped into five different strategies: (1) physical activity ± diet; (2) anti-diabetic drugs (glitazones, metformin, glinides, alfa-glucosidase inhibitors); (3) antihypertensive drugs (ACE inhibitors, ARB); (4) weight loss-promoting drugs and lipid-lowering drugs (orlistat, bezafibrate, phentermine/topiramate controlled release); and (5) bariatric surgery. Only controlled studies, dealing with subjects BMI ≥ 30 kg/m(2), were included in the analysis, whether randomized or non-randomized studies. Appropriate methodology (PRISMA statement) was adhered to. Publication bias was formally assessed. Eighteen studies (43,669 subjects, 30,774 with impaired glucose tolerance and/or impaired fasting glucose), published in English language as full papers, were analyzed to identify predictors of new cases of T2DM and were included in a meta-analysis (random-effects model) to study the effect of different strategies. Intervention effect (new cases of diabetes) was expressed as odds ratio (OR), with 95 % confidence intervals (CIs). In obese subjects, non-surgical strategies were able to prevent T2DM, with different effectiveness [OR from 0.44 (0.36-0.52) to 0.86 (0.80-0.92)]; in morbidly obese subjects, bariatric surgery was highly effective [OR = 0.10 (0.02-0.49)]. At meta-regression analysis, factors associated with effectiveness were weight loss, young age and fasting insulin levels. Publication bias was present only when considering all studies together. These data indicate that several strategies, with different effectiveness, can prevent T2DM in obese subjects.

Long-term sympathoinhibitory effects of surgically induced weight loss in severe obese patients

Weight loss improves insulin sensitivity and exerts sympathomodulatory effects. No data, however, are available on the effects of the weight loss induced by vertical sleeve gastrectomy on sympathetic neural drive, insulin sensitivity, and their reciprocal cross talks. In 10 severe obese hypertensives (age, 54.0±2.3 years [mean±SEM]), we measured sphygmomanometric blood pressure, heart rate, body mass index, homeostatic model assessment index, plasma leptin, muscle sympathetic nerve traffic (microneurography), and baroreflex sensitivity (vasoactive drug technique). Measurements were performed 2 to 3 days before surgery and repeated 6 and 12 months after the procedure. Ten matched hypertensive obeses not undergoing gastrectomy served as controls. Six months after bariatric surgery, a significant (P<0.05) reduction in body mass index (-9.1±1.4 kg/m(2)), sphygmomanometric systolic blood pressure (-10.2±4.5 mm Hg), heart rate (-11.0±2.4 bpm), homeostatic model assessment index (-3-3±1.3 AU), plasma leptin (-53.6±8.8 μg/L), and muscle sympathetic nerve traffic (-15.0±3.4 bursts/100 heart beats) was observed. The weight loss, the plasma leptin reduction, and the sympathetic inhibition were maintained after 12 months, whereas homeostatic model assessment index showed a tendency to return toward presurgery values. A significant improvement in baroreflex control of sympathetic nerve traffic was observed both 6 (+32.1%; P<0.05) and 12 months (+60.7%; P<0.01) after gastrectomy. No significant changes in the above-mentioned variables were detected in the control group. These data provide evidence that massive weight loss induced by sleeve gastrectomy triggers profound sympathoinhibitory effects, associated with a stable and significant reduction in plasma leptin levels, whereas the improvement in insulin sensitivity was attenuated with time and unrelated to the sympathoinhibition.

Preliminary evidence that obese patients with obstructive sleep apnea/hypopnea syndrome are refractory to the acute beneficial metabolic effects of a very low calorie diet

Since obesity seems to play a causal role in both obstructive sleep apnea/hypopnea syndrome (OSAHS) and type 2 diabetes, the question arises whether diet-induced weight loss is equally efficacious in type 2 diabetic patients with and without OSAHS. The present study was aimed to investigate the effect of 1 week very low calorie diet (VLCD) on oxygen desaturation index (ODI) and on glucose regulation in OSAHS versus non-OSAHS patients. Fourteen patients with type 2 diabetes mellitus and morbid obesity were enrolled. According to ODI, patients were divided into 2 groups (with and without OSAHS) and evaluated by a hyperglycemic clamp study, before and after a 7 day-VLCD. After a VLCD, a significant reduction of anthropometric parameters, in the overall group and in subgroups, was observed. M-value and acute insulin response increased significantly only in patients without obstructive sleep apnea (990.10 ± 170.19 vs. 1,205.22 ± 145.73 μmol min(-1) m(-2), p = 0.046; -1.05 ± 8.40 vs. 48.26 ± 11. 90 pmol/L, p = 0.028, respectively). The average 24-h heart rate (24-h HR) fell significantly (p = 0.05), primarily because of a decrease during daytime (p = 0.041), in the whole group. In conclusion, we observed that morbidly obese patients with type 2 diabetes and OSAHS are specifically resistant to the acute beneficial effects of VLCD on metabolic parameters. Our preliminary observation deserves further investigation to clarify the pathogenetic mechanisms involved.