"What are the yanks doing?" the U.S. experience with implantable gastric stimulation (IGS) for the treatment of obesity - update on the ongoing clinical trials

Standardization of Bariatric Metabolic Procedures: World Consensus Meeting Statement

BACKGROUND

Standardization of the key measurements of a procedure's finished anatomic configuration strengthens surgical practice, research, and patient outcomes. A consensus meeting was organized to define standard versions of 25 bariatric metabolic procedures.

METHODS

A panel of experts in bariatric metabolic surgery from multiple continents was invited to present technique descriptions and outcomes for 4 classic, or conventional, and 21 variant and emerging procedures. Expert panel and audience discussion was followed by electronic voting on proposed standard dimensions and volumes for each procedure's key anatomic alterations. Consensus was defined as ≥ 70% agreement.

RESULTS

The Bariatric Metabolic Surgery Standardization World Consensus Meeting (BMSS-WOCOM) was convened March 22-24, 2018, in New Delhi, India. Discussion confirmed heterogeneity in procedure measurements in the literature. A set of anatomic measurements to serve as the standard version of each procedure was proposed. After two voting rounds, 22/25 (88.0%) configurations posed for consideration as procedure standards achieved voting consensus by the expert panel, 1 did not attain consensus, and 2 were not voted on. All configurations were voted on by ≥ 50% of 50 expert panelists. The Consensus Statement was developed from scientific evidence collated from presenters' slides and a separate literature review, meeting video, and transcripts. Review and input was provided by consensus panel members.

CONCLUSIONS

Standard versions of the finished anatomic configurations of 22 surgical procedures were established by expert consensus. The BMSS process was undertaken as a first step in developing evidence-based standard bariatric metabolic surgical procedures with the aim of improving consistency in surgery, data collection, comparison of procedures, and outcome reporting.

In Vivo Validation of a Less Invasive Gastrostimulator

Gastrointestinal stimulator implants have recently shown promising results in helping obese patients lose weight. However, to place the implant, the patient currently needs to undergo an invasive surgical procedure. We report a less invasive procedure to stimulate the stomach with a gastrostimulator. After attempting fully endoscopic implantation, we more recently focused on a single incision percutaneous procedure. In both cases, the challenges in electronic design of the implant are largely similar. This article covers the work achieved to meet these and details the in vivo validation of a gastrostimulator aimed to be endoscopically placed and anchored to the stomach.

Design and Implementation of a Less Invasive Gastrostimulator

Gastrointestinal stimulator implants have recently shown positive results in helping obese patients lose weight. However, to place the implant, the patient currently needs to undergo an invasive surgical procedure. Our team is aiming for a less invasive procedure to stimulate the stomach with a gastrostimulator. Attempts covered fully endoscopic implantation and, more recently, we have focussed on a single incision laparoscopic procedure. Whatever the chosen implantation solution, the electronic design of the implant system shares many challenges. This paper covers the work achieved to meet these.

Neurostimulation of the gastrointestinal tract: review of recent developments

OBJECTIVE

Neurostimulation is one manifestation of neuromodulation of the gastrointestinal (GI) tract. This manuscript reviews the history of neurostimulation of the GI tract with emphasis on current methods of stimulation.

MATERIALS AND METHODS

A review was completed of the current research on GI neurostimulation methods with an emphasis on their clinical applications.

RESULTS

Upper GI disorders can be modulated with both temporary (placed endoscopically or surgically) or permanent (placed surgically) gastric electrical stimulation (GES) devices. The current GI neurostimulation of stomach (GES) devices have been used in both children and adults, and some patients have been followed in excess of 15 years with good long-term results. Similar GES devices also have been used for a variety of lower GI disorders, including constipation and fecal incontinence, for a number of years.

CONCLUSIONS

GI neurostimulation, as a type of neuromodulation, has been demonstrated to function at several locations in the GI tract for a variety of disorders. The future of neurostimulation in the GI tract will likely be influenced by a better understanding of pathophysiology as well as the development of new techniques and devices for neuromodulation.

The effects of individualized gastric electrical stimulation on food craving and gastrointestinal peptides in dogs

BACKGROUND

Using an adjustable stimulator with a wide range of stimulation parameters, the aims of this study were 1) to investigate the effects of long-term gastric electrical stimulation (GES) on appetite and differential food cravings for three different foods and 2) to investigate the effects of GES on plasma gastrointestinal peptide concentrations.

METHODS

The study was performed in eight Beagle dogs implanted with one pair of serosal electrodes. They were followed during GES and sham GES sessions in a crossover design. GES was conducted using a series of individualized parameters. Food intake and food cravings were observed to evaluate the effects of long-term GES. Enzyme-linked immunosorbent assay was used to measure the plasma concentrations of gastrointestinal peptides.

RESULTS

Dogs on GES for three months ate significantly less food than those on sham GES for three months (p < 0.05). A significant change in food cravings was induced by GES. Dogs with GES ate significantly less high-fat food. However, there was no significant difference in consumption of high-carbohydrate food or balanced food between the periods of GES and sham GES. The plasma concentrations of ghrelin, peptide YY3-36, and glucagon-like peptide 1 did not differ significantly between the periods of GES and sham GES.

CONCLUSIONS

Food intake and food craving were changed significantly by adjustable GES. GES may be used for treating obesity by changing food preferences. Further clinical studies are necessary to highlight the effect of adjustable GES on eating behavior.

Parameter selection and stimulating effects of an adjustable gastric electrical stimulator in dogs

BACKGROUND

Gastric electrical stimulation (GES) has been proposed as a promising therapeutic option in treating obesity for 20 years. Currently, the available device of GES cannot meet the clinical needs. The purpose of this study is to verify the effect of a new type of adjustable gastric electrical stimulator in reducing food intake and body weight.

METHODS

Eight beagle dogs randomly followed GES and sham GES for 3 months in a crossover design. Parameters were adjusted and individualized during the experiment. Symptoms of GES were recorded, and the effective parameters were selected. Resistance to GES was assessed. Food intake and body weight were measured to evaluate the effect of GES.

RESULTS

The effective parameters were varied among the dogs. Resistance to GES was observed in different periods in dogs. Parameters needed to be adjusted every 10.2 ± 2.1 days during the period of GES. Food intake during GES for 3 months was significantly reduced than that during sham GES of 3 months (P < 0.05). With the decreased food intake, body weight was significantly reduced by the end of GES of 3 months compared with that of sham GES of 3 months (P < 0.05).

CONCLUSIONS

Food intake and body weight of dogs are significantly reduced by adjustable GES. Individual parameters and resistance during GES are required to be considered. The new adjustable device may have good prospects of clinical application for obesity.

Food intake and body weight responses to intermittent vs. continuous gastric electrical stimulation in diet-induced obese rats

BACKGROUND

Gastric electrical stimulation (GES) has recently been introduced as a potential therapy for the treatment of obesity. The main challenge for the new generation of devices is to achieve desired clinical outcomes at a suitably low level of energy consumption. The aim of this study is to compare the effectiveness of GES with continuous and intermittent duty cycles in reducing food intake and body weight in diet-induced obesity-prone rats.

METHODS

In macro duty cycle experiment, 40 rats were divided into groups to receive a sham GES, continuous GES, or intermittent GES (15 min On-45 min Off or 15 min On-15 min Off) for 28 days. In micro duty cycle experiment, 18 rats received cross-over treatment of continuous stimulation, 60 % time cycle or 40 % time cycle. Food intake, body weight, gastric emptying and ghrelin level were measured to evaluate the effect of different GES.

RESULTS

GES with macro duty cycle intensity-dependently reduced mean daily food intake increase by 18.6, 10.2 and -6.0 % compared to 42.7 % with sham GES and body weight gain by 6.1 %, 3.4 and -0.8 % compared to 5 % with sham GES. Daily food intake decreased with increasing micro duty cycle intensity, averaging 16.5, 15.6 and 13.7 g/day under 40 % cycle, 60 % cycle and continuous stimulation respectively. Gastric emptying was intensity-dependently delayed by GES. GES has no effect in modulating plasma ghrelin level.

CONCLUSIONS

GES energy-dependently reduces food intake, body weight and gastric emptying. Peripheral modulation of plasma ghrelin level is not related to the GES effects.

An update on less invasive and endoscopic techniques mimicking the effect of bariatric surgery

Obesity (BMI 30-35 kg/m(2)) and its associated disorders such as type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular disease have reached pandemic proportions worldwide. For the morbidly obese population (BMI 35-50 kg/m(2)), bariatric surgery has proven to be the most effective treatment to achieve significant and sustained weight loss, with concomitant positive effects on the metabolic syndrome. However, only a minor percentage of eligible candidates are treated by means of bariatric surgery. In addition, the expanding obesity epidemic consists mostly of relatively less obese patients who are not (yet) eligible for bariatric surgery. Hence, less invasive techniques and devices are rapidly being developed. These novel entities mimic several aspects of bariatric surgery either by gastric restriction (gastric balloons, gastric plication), by influencing gastric function (gastric botulinum injections, gastric pacing, and vagal nerve stimulation), or by partial exclusion of the small intestine (duodenal-jejunal sleeve). In the last decade, several novel less invasive techniques have been introduced and some have been abandoned again. The aim of this paper is to discuss the safety, efficacy, complications, reversibility, and long-term results of these latest developments in the treatment of obesity.

Implantable gastric stimulator does not prevent the increase in plasma ghrelin levels that occurs with weight loss

The SHAPE (Screened Health Assessment and Pacer Evaluation) trial was a 24 month randomized multicenter placebo-controlled study to determine the efficacy of an implantable gastric stimulator (IGS) for weight loss. This report is an investigator-initiated sub-study at one site designed to assess whether IGS affects plasma levels of ghrelin and peptide YY (PYY). The device was implanted in all subjects but was activated in the TREATMENT group (n = 7, BMI = 41.5 ± 2.0 kg/m2) and remained inactive in the CONTROL (n = 6, BMI = 39.5 ± 1.7 kg/m2) during the first 12 months. IGS was activated in both groups during months 12-24. Fasting venous blood was drawn at months 0, 12, and 24 and an oral glucose tolerance test (OGTT) was performed at month 12. Although there was no difference in weight loss at 6 months (

CONTROL

-6.6 ± 1.5% vs.

TREATMENT

-6.2 ± 1.4%), at 24 months the CONTROL group exhibited weight gain from baseline (+2.2 ± 1.5%) that was significantly different from the weight loss in the TREATMENT group (-1.9 ± 1.4%; P < 0.05). At 12 months, fasting ghrelin was significantly increased (P < 0.05) in the TREATMENT group (285 ± 35 to 336 ± 35 pg/ml; weight change, -4.9 ± 1.4%), but not in the CONTROL (211 ± 36 to 208 ± 35 pg/ml; weight change, -3.4 ± 1.5%). No significant change was observed in postprandial suppression of plasma ghrelin or in fasting and postprandial PYY levels. In conclusion, IGS does not prevent the increase in fasting plasma ghrelin levels associated with weight loss. Further studies are needed to determine whether changes in technology can improve weight loss and maintenance, perhaps using gut hormones as biomarkers of possible efficacy.

Duodenum electrical stimulation delays gastric emptying, reduces food intake and accelerates small bowel transit in pigs

Duodenum electrical stimulation (DES) has been shown to delay gastric emptying and reduce food intake in dogs. The aim of this study was to investigate the effects of DES on gastric emptying, small bowel transit and food intake in pigs, a large animal model of obesity. The study consisted of three experiments (gastric emptying, small bowel transit, and food intake) in pigs implanted with internal duodenal electrodes for DES and one or two duodenal cannulas for gastric emptying and small bowel transit. We found that (i) gastric emptying was dose-dependently delayed by DES of different stimulation parameters; (ii) small bowel transit was significantly accelerated with continuous DES in proximal intestine but not with intermittent DES; (iii) DES significantly reduced body weight gain with 100% duty cycle (DC), but not with DES with 40% DC. A marginal difference was noted in food intake among 100% DC session, 40% DC session, and control session. DES with long pulses energy-dependently inhibits gastric emptying in pigs. DES with appropriate parameters accelerates proximal small bowel transit in pigs. DES reduces body weight gain in obese pigs, and this therapeutic effect on obesity is mediated by inhibiting gastric emptying and food intake, and may also possibly by accelerating intestinal transit. DES may have a potential application to treat patients with obesity.

Effects and mechanisms of electrical stimulation of the stomach, duodenum, ileum, and colon on gastric tone in dogs

Previous studies have shown that gastric tone is inhibited by the electrical stimulation of some parts of the gut. The aims of this study were to investigate the effects of gastric electrical stimulation (GES), duodenal electrical stimulation (DES), ileal electrical stimulation (IES), and colonic electrical stimulation (CES) on gastric tone and the possible mechanism of electrical stimulation on gastric tone. Experiments were performed to study: (1) the effects of the four stimulations (GES, DES, IES, CES) on gastric tone; (2) the role of the nitrergic pathway's involvement in the effect of IES on gastric tone. Each dog was implanted with one pair of gastric, duodenal, ileal, and colonic electrodes and a gastric cannula. A computerized barostat was used to assess gastric tone by measuring the gastric intra-balloon volume. We found that: (1) all methods of stimulation significantly inhibited gastric tone; (2) the percentage of increase in gastric volume was highest with CES and lowest with DES; however, there was no significant difference in the percentage of inhibition among the four stimulations; (3) the inhibitory effect of IES on gastric tone was abolished by intravenous nitric oxide synthase inhibitor. It was concluded that electrical stimulation of the stomach, intestine, or colon with long pulses has an inhibitory effect on gastric tone, and the most effective stimulation is CES. The inhibitory effect is not organ-specific and is unrelated to the distance between the stimulation site and the affected organ. The inhibitory effect of IES on gastric tone is mediated by the nitrergic pathway.

Surgery for obesity

BACKGROUND

Bariatric (weight loss) surgery for obesity is considered when other treatments have failed. The effects of the available bariatric procedures compared with medical management and with each other are uncertain. This is an update of a Cochrane review first published in 2003 and previously updated in 2005.

OBJECTIVES

To assess the effects of bariatric surgery for obesity.

SEARCH STRATEGY

Studies were obtained from computerized searches of multiple electronic bibliographic databases, supplemented with searches of reference lists and consultation with experts in obesity research.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing different surgical procedures, and RCTs, controlled clinical trials and prospective cohort studies comparing surgery with non-surgical management for obesity.

DATA COLLECTION AND ANALYSIS

Data were extracted by one reviewer and checked independently by two reviewers. Two reviewers independently assessed trial quality.

MAIN RESULTS

Twenty six studies were included. Three RCTs and three prospective cohort studies compared surgery with non-surgical management, and 20 RCTs compared different bariatric procedures. The risk of bias of many trials was uncertain; just five had adequate allocation concealment. A meta-analysis was not appropriate.Surgery results in greater weight loss than conventional treatment in moderate (body mass index greater than 30) as well as severe obesity. Reductions in comorbidities, such as diabetes and hypertension, also occur. Improvements in health-related quality of life occurred after two years, but effects at ten years are less clear.Surgery is associated with complications, such as pulmonary embolism, and some postoperative deaths occurred.Five different bariatric procedures were assessed, but some comparisons were assessed by just one trial. The limited evidence suggests that weight loss following gastric bypass is greater than vertical banded gastroplasty or adjustable gastric banding, but similar to isolated sleeve gastrectomy and banded gastric bypass. Isolated sleeve gastrectomy appears to result in greater weight loss than adjustable gastric banding. Evidence comparing vertical banded gastroplasty with adjustable gastric banding is inconclusive. Data on the comparative safety of the bariatric procedures was limited.Weight loss and quality of life were similar between open and laparoscopic surgery. Conversion from laparoscopic to open surgery may occur.

AUTHORS' CONCLUSIONS

Surgery is more effective than conventional management. Certain procedures produce greater weight loss, but data are limited. The evidence on safety is even less clear. Due to limited evidence and poor quality of the trials, caution is required when interpreting comparative safety and effectiveness.

Methods of gastric electrical stimulation and pacing: a review of their benefits and mechanisms of action in gastroparesis and obesity

Development of gastric electrical stimulation techniques for treatment of gastric dysmotility syndromes and obesity has been a long-standing goal of investigators and clinicians. Depending on stimulus parameters and sites of stimulation, such methods have a range of theoretical benefits including entrainment of intrinsic gastric electrical activity, eliciting propagating contractions and reducing symptomatology in patients with gastroparesis and reducing appetite and food intake in individuals with morbid obesity. Additionally, gastric stimulation parameters have extragastrointestinal effects including alteration of systemic hormonal and autonomic neural activity and modulation of afferent nerve pathways projecting to the central nervous system that may represent important mechanisms of action. Numerous case series and smaller numbers of controlled trials suggest clinical benefits in these two conditions, however better controlled trials are mandated to confirm their efficacy. Current research is focusing on novel stimulation methods to better control symptoms in gastroparesis and promote weight reduction in morbid obesity.

Gastric electrical stimulation for obesity: the need for a new device using wider pulses

Gastric electrical stimulation (GES) has been proposed as a therapeutic option for obesity. However, its clinical efficacy is not proven, and its mechanisms remain largely unknown. To compare the peripheral and central neural and behavioral effects in rats of GES with a pulse width currently used in clinical trials (GES-A: 6 mA, 0.3 ms, 40 Hz, 2 s on, 3 s off) and GES with a wider pulse (GES-B: same as GES-A, except that the pulse width is 3 ms). Experiment 1: assessing gastric volume changes as a result of GES. Experiment 2: recording the extracellular potentials of a single neuron in the paraventricular nucleus (PVN) with GES. Experiment 3: determining the effects of GES on oxytocin-immunoreactive (OT-IR) neuron expression in the hypothalamus. Experiment 4: determining the effects of GES on food intake and body weight. GES-B, but not GES-A, significantly increased gastric volume. GES-B activated a higher percentage of gastric distention-responsive neurons in the PVN (93% vs. 81%, P = 0.021) and elicited more intensive neuronal responses than GES-A. The number of OT-IR neurons was significantly increased in the PVN and supraoptic nucleus with both methods of GES compared with control groups. The increase in OT-IR neurons in the PVN was higher with GES-B than with GES-A. A 1-week GES treatment significantly reduced daily food intake and body weight. GES-B was more potent than GES-A in producing weight loss (P < 0.001). The effects of GES depend on the stimulation pulse width. GES with a wider pulse is more effective both peripherally and centrally and more potent in reducing body weight in rats.

Improvement in glycemic control by gastric electrical stimulation (TANTALUS) in overweight subjects with type 2 diabetes

BACKGROUND

The TANTALUS system (MetaCure Ltd.) is a minimally invasive implantable gastric stimulation modality that does not exhibit malabsorptive or restrictive characteristics. The device applies gastric contractility modulation (GCM) signals to the stomach antrum. The signals are delivered in synchronization to the native electrical activity of the stomach during meals. Retrospective analysis of previous studies indicated that type 2 diabetes mellitus (T2DM) subjects on oral medication with hemoglobin A1c (HbA1c) between 7.5% and 9.5% are the population with most potential benefit from the treatment. The current study includes subjects enrolled prospectively within that range of HbA1c.

AIM

To prospectively investigate the potential effect of the TANTALUS system on glycemic control and weight in overweight subjects with T2DM.

METHODS

In this European multicenter, open-label study, 13 T2DM obese (6 male, 7 female, BMI 37.2 +/- 1.0 kg/m(2), range 30.4-44.0 kg/m(2)) subjects treated with oral antidiabetic medications but with poor glycemic control (HbA1c > or = 7%, range 7.3-9.5%) were implanted laparoscopically with the TANTALUS system.

RESULTS

Thirteen subjects that had completed 3 months of treatment showed a significant reduction in HbA1c from 8.0 +/- 0.2% to 6.9 +/- 0.1% (p < 0.05), whereas fasting blood glucose decreased from 175 +/- 6 mg/dL to 127 +/- 8 mg/dL (p < 0.05). The glycemic improvement was accompanied by reduction in weight from 104.4 +/- 4.4 kg to 99.7 +/- 4.8 kg, and in waist circumference from 122.3 +/- 3.2 cm to 117.0 +/- 3.0 cm.

CONCLUSIONS

Interim results with the TANTALUS system suggest that this stimulation regime can potentially improve glucose levels and induce moderate weight loss in obese T2DM subjects on oral antidiabetic therapy with poor glycemic control. Further evaluation is required to determine whether this effect is due to induced weight loss and/or due to direct signal-dependent mechanisms.

Neuromodulatory processes of the brain-gut axis

Brain-gut axis represents a complex reflex circuit that integrates the communication between cortex and the digestive system. Disturbances of the neuromodulatory processes in the brain-gut axis generate functional digestive disorders mainly centered on the pain symptoms and motility disorders. This article reviews structural and patho-physiological aspects of the brain-gut axis and explains how the neuromodulatory interventions currently used in order to treat GI conditions related to the brain-gut axis disturbances. The neuromodulation can be realized by pharmacological targeting mainly receptors in the periphery or using electrical stimulation applied at different levels of the nervous system or directly in the muscular layers of the bowels resulting in modulation of the digestive system activity. The efficacy of the methods using electrostimulation is dependent on the parameters of the physical system used: amplitude, frequency, burst time of the electrical current and also the positioning of the electrodes. While pharmacological interventions are largely used at the moment, neuromodulatory interventions involving electrical stimulation showed clinical efficacy in research trials and have promise.

Inhibitory effects of gastrointestinal electrical stimulation on rectal tone are both organ-specific and distance-related in dogs

PURPOSE

A phenomenon of cross-talk has been noted that electrical stimulation of one part of the gut affects another part of the gut. This study was designed to investigate whether the effect of electrical stimulation of one part of the gut on another part of the gut was related to the organ or the distance between the stimulation site and the affected organ, and the mechanism of ileum electrical stimulation on rectal tone.

METHODS

This study was performed in 13 healthy dogs (16-28 kg) in the fasting state. Experiments were performed to study 1) effects of gastric electrical stimulation, duodenal electrical stimulation, ileum electrical stimulation, and colonic electrical stimulation on rectal tone, and 2) the sympathetic and nitrergic pathways involved in the effects of ileum electrical stimulation on rectal tone. A computerized barostat was used to assess rectal tone.

RESULTS

All methods of stimulations significantly inhibited rectal tone. Duodenal electrical stimulation was least effective in reducing rectal tone. The percentage of increase in rectal volume was distance-related with duodenal electrical stimulation, ileum electrical stimulation, and colonic electrical stimulation but organ-specific with gastric electrical stimulation. The inhibitory effect of ileum electrical stimulation on rectal tone was abolished by N omega-nitro-L-arginine but not guanethidine.

CONCLUSIONS

Electrical stimulation of the stomach, intestine, or colon with long pulses has an inhibitory effect on rectal tone. This inhibitory effect is organ-specific as well as associated with the distance between stimulation site and affected organs. The inhibitory effect of ileum electrical stimulation on rectal tone is mediated by the nitrergic but not sympathetic pathway.

Potential of intestinal electrical stimulation for obesity: a preliminary canine study

OBJECTIVE

The aims of this study were to investigate the therapeutic potential of intestinal electrical stimulation (IES) for obesity. Experiments were performed to investigate the effects of IES on food intake, gastric tone, gastric accommodation, and its possible pathway.

RESEARCH METHODS AND PROCEDURES

Ten normal dogs and six dogs with truncal vagotomy were used in this study. Each dog was equipped with a gastric cannula for the measurement of gastric tone and accommodation by barostat and one pair of duodenal serosal electrodes for IES. The experiment on food intake was composed of both control session without IES and IES session after a 28-hour fast. The experiment on gastric tone and accommodation was performed in the fasting and fed states and composed of three sessions: control, IES, and IES with N(G)-nitro-l-arginine.

RESULTS

IES significantly reduced food intake in the normal dogs (459.0 vs. 312.6 grams, p < 0.001). The food intake was negatively correlated with the fasting gastric volume during IES. IES significantly decreased fasting gastric tone in the normal dogs reflected as a decrease in gastric volume (89.1 vs. 261.3 mL, p < 0.01), which was abolished by vagotomy and N(G)-nitro-l-arginine.

DISCUSSION

IES reduces food intake and inhibits gastric tone in the fasting state. The inhibitory effect of IES on gastric tone is mediated by both vagal and nitrergic pathway.

Laparoscopically Implanted Gastric Pacemaker after Kidney-Pancreas Transplantation: Treatment of Morbid Obesity and Diabetic Gastroparesis

Combined kidney-pancreas transplantation is the treatment of choice for end-stage diabetic nephropathy. Weight gain post-transplant increases the risk for post-transplant complications and death due to cardiovascular events. Gastric pacemakers have been used for therapy of diabetic gastropathy and for the treatment of moderate morbid obesity. We report a patient who experienced significant weight gain following successful kidney-pancreas transplantation and was thereafter successfully treated for diabetic gastroparesis and morbid obesity by use of a laparoscopically implanted gastric pacemaker.

Surgery for obesity: a review of the current state of the art and future directions

The number of patients undergoing surgery for the treatment of obesity, and the proportion of the health care budget dedicated to this health problem, is growing exponentially. There are several competing surgical approaches for the management of morbid obesity. We review the literature relating to four of these: gastric bypass, biliopancreatic diversion, gastric banding, and gastric pacing. Our review finds that while enhancing the malabsorptive activity of these procedures may induce an incremental increase in excess body weight loss, the proportion of patients who fail to lose more than 50% of their excess body weight is similar no matter how radical is the surgery performed. There is little guidance from the literature as to appropriate patient selection for the varying procedures, and anonymously reported registries have yet to show that patients who undergo bariatric surgery have enhanced longevity. To date, the bariatric surgical community has not conducted adequately powered randomized prospective trials to elucidate key elements of the surgical procedure such as optimal bypass length, to determine whether mixed operations are superior to those that offer intake restriction only, and to define what constitutes success after bariatric surgery. As a public health measure, bariatric surgery in the United States is being pursued in an irrational manner, being concentrated in areas where there are fewer morbidly obese patients, and used disproportionately among the population of white obese females.

Electrical stimulation as treatment for obesity and diabetes

The prevalence of obesity is growing, is driving an increase in the prevalence of diabetes, and is creating a major public health crisis in the United States. Lifestyle and behavior therapy rarely give durable weight loss. There are few medications approved for the treatment of obesity. Those that exist are limited in efficacy and using them in combination does not result in greater weight loss. Surgical treatments for obesity are effective and give durable weight loss, but are accompanied by measurable morbidity and mortality. Several pacing approaches are being tried and are an outgrowth of pacing for gastroparesis. The Transcend(R) pacemaker blocks vagal efferents and delays gastric emptying, giving a 40% loss of excess body weight, if certain screening procedures are employed. The Tantulus pacemaker is still in development but increases antral muscular contractions and delays gastric emptying by stimulation during the absolute refractory period. Weight loss has been 30% of excess body weight, and glycohemoglobin decreased 1.6% in a trial of obese type 2 diabetes. Stimulation to the subdiaphragmatic sympathetics, vagal nerve stimulation with or without unilateral vagotomy, and intestinal pacing are other approaches that are still being evaluated preclinically. Clearly a safe, effective, and durable treatment for obesity is desperately needed. Electrical pacing of the gastrointestinal tract is promising therapeutically, and because pacemakers work through different mechanisms, combining pacemaker treatments may be possible. Rapid progress is being made in the field of electrical stimulation as a treatment for obesity and even greater progress can be expected in the foreseeable future.

Gastric or intestinal electrical stimulation-induced increase in gastric volume is correlated with reduced food intake

OBJECTIVE

Satiation has recently been shown to be associated with gastric volume or gastric tone. Electrical stimulation has been shown to reduce food intake and increase gastric volume, or reduce gastric tone. The aim of this study was to investigate the correlation between gastric or intestinal electrical stimulation (GES/IES)-induced increase in gastric volume and food intake.

MATERIAL AND METHODS

GES/IES was performed on 14 dogs implanted with electrodes and a gastric cannula. Food intake was measured and gastric volume was assessed using barostat with or without GES/IES.

RESULTS

Food intake was correlated to weight (r = 0.62, p = 0.02) as well as the fasting gastric volume (r = 0.59, p = 0.02). GES/IES reduced food intake (240.8 versus 445.0 g, p < 0.005) and increased gastric volume in the fasting state (263.4 versus 74.4 ml, p < 0.0001). Reduced food intake was correlated to the preprandial gastric volume (r = - 0.58, p = 0.02) and postprandial increase in gastric volume with GES/IES (r = 0.56, p = 0.03). CONCLUSIONS. GES/IES reduces food intake and increases gastric volume measured by barostat. The GES/IES-induced increase in gastric volume (or reduced gastric tone) is correlated with reduced food intake during GES/IES.

Potential role of new therapies in modifying cardiovascular risk in overweight patients with metabolic risk factors

The serotonin, norepinephrine, dopamine, and endocannabinoid systems, as well as a host of other systems, mediate hunger and satiety signals. Weight loss agents that modulate appetite through pure central nervous system pathways (e.g., APD356, a selective serotonin receptor agonist) and peripheral signals to central nervous system pathways (e.g., cholecystokinin receptor agonists and ghrelin receptor antagonists) are in preclinical or early phase studies. Both devices and pharmacological compounds that facilitate weight loss and/or target multiple components of metabolic risk also are in development. One of the medications that has completed extensive phase III clinical trials and may become available in the foreseeable future is rimonabant, a selective cannabinoid 1-receptor antagonist. Drugs that improve adipose tissue function or fatty acid metabolism (e.g., AOD9604) also are in clinical trials. Some currently available medications may reduce metabolic complications without treating obesity per se (e.g., acipimox, pioglitazone). Surgically implanted gastric pacemaker systems that modulate vagus nerve activity and delay gastric emptying are under study.

Looking to the future: electrical stimulation for obesity

Among all classes of therapies for morbid obesity-behavioral, drugs, devices, and surgery-devices for electrical stimulation are a relatively new approach. This article reviews the history of electrical therapies for the gastrointestinal tract with an emphasis on the development of stimulation for obesity. Based on similar animal work, electrical stimulation of the gastrointestinal tract has been applied to treat morbid obesity much in the way it has been used to treat nausea and vomiting. The current status of gastrointestinal electrical stimulation for the treatment of morbid obesity is reviewed, with an emphasis on human studies. The physics of electrical stimulation and the possible mechanism of stimulation in the gastrointestinal tract, including for the treatment of morbid obesity, are also discussed. Future work on stimulation for obesity offers the opportunity for better understanding of possible mechanisms of action.