Devices for the treatment of obesity: will understanding the physiology of satiety unravel new targets for intervention?

Biomechanical Investigation of the Stomach Following Different Bariatric Surgery Approaches

Background: The stomach is a hollow organ of the gastrointestinal tract, on which bariatric surgery (BS) is performed for the treatment of obesity. Even though BS is the most effective treatment for severe obesity, drawbacks and complications are still present because the intervention design is largely based on the surgeon’s expertise and intraoperative decisions. Bioengineering methods can be exploited to develop computational tools for more rational presurgical design and planning of the intervention. Methods: A computational mechanical model of the stomach was developed, considering the actual complexity of the biological structure, as the nonhomogeneous and multilayered configuration of the gastric wall. Mechanical behavior was characterized by means of an anisotropic visco-hyperelastic constitutive formulation of fiber-reinforced conformation, nonlinear elastic response, and time-dependent behavior, which assume the typical features of gastric wall mechanics. Model applications allowed for an analysis of the influence of BS techniques on stomach mechanical functionality through different computational analyses. Results: Computational results showed that laparoscopic sleeve gastrectomy and endoscopic sleeve gastroplasty drastically alter stomach capacity and stiffness, while laparoscopic adjustable gastric banding modestly affects stomach stiffness and capacity. Moreover, the mean elongation strain values, which are correlated to the mechanical stimulation of gastric receptors, were elevated in laparoscopic adjustable gastric banding compared to other procedures. Conclusions: The investigation of stomach mechanical response through computational models provides information on different topics such as stomach capacity and stiffness and the mechanical stimulation of gastric receptors, which interact with the brain to control satiety. These data can provide reliable support to surgeons in the presurgical decision-making process.

The GAMMA concept (gastrointestinal activity manipulation to modulate appetite) preliminary proofs of the concept of local vibrational gastric mechanical stimulation

BACKGROUND

Mechanical stimulation of the stretch receptors of the gastric wall can simulate the presence of indigested food leading to reduced food intake. We report the preliminary experimental results of an innovative concept of localized mechanical gastric stimulation.

METHODS

In a first survival study, a biocompatible bulking agent was injected either in the greater curvature (n = 8) or in the cardia wall (n = 8) of Wistar rats. Six animals served as sham. Changes of bulking volume, leptin levels and weight gain were monitored for 3 months. In a second acute study, a micro-motor (n = 10; MM) or a size-paired inactive device (n = 10; ID) where applied on the cardia, while 10 additional rats served as sham. Serum ghrelin and leptin were measured at baseline and every hour (T0-T1-T2-T3), during 3 h. In a third study, 24 implants of various shapes and sizes were introduced into the gastric subserosa of 6 Yucatan pigs. Monthly CT scans and gastroscopies were done for 6 months.

RESULTS

Weight gain in the CW group was significant lower after 2 weeks and 3 months when compared to the shame and GC (p = 0.01/p = 0.01 and p = 0.048/p = 0.038 respectively). Significant lower increase of leptin production occurred at 2 weeks (p = 0.01) and 3 months (p = 0.008) in CW vs. SG. In the MM group significant reduction of the serum ghrelin was seen after 3 h. Leptin was significantly increased in both MM and ID groups after 3 h, while it was significantly reduced in sham rats. The global device retention was 43.5%. Devices with lower profile and with a biocompatible coating remained more likely in place without complications.

CONCLUSIONS

Gastric mechanical stimulation induced a reduced weight gain and hormonal changes. Low profile and coated devices inserted within the gastric wall are more likely to be integrated.

Different types of soluble fermentable dietary fibre decrease food intake, body weight gain and adiposity in young adult male rats

BACKGROUND

Dietary fibre-induced satiety offers a physiological approach to body weight regulation, yet there is lack of scientific evidence. This experiment quantified food intake, body weight and body composition responses to three different soluble fermentable dietary fibres in an animal model and explored underlying mechanisms of satiety signalling and hindgut fermentation.

METHODS

Young adult male rats were fed ad libitum purified control diet (CONT) containing 5% w/w cellulose (insoluble fibre), or diet containing 10% w/w cellulose (CELL), fructo-oligosaccharide (FOS), oat beta-glucan (GLUC) or apple pectin (PECT) (4 weeks; n = 10/group). Food intake, body weight, and body composition (MRI) were recorded, final blood samples analysed for gut satiety hormones, hindgut contents for fermentation products (including short-chain fatty acids, SCFA) and intestinal tissues for SCFA receptor gene expression.

RESULTS

GLUC, FOS and PECT groups had, respectively, 10% (P < 0.05), 17% (P < 0.001) and 19% (P < 0.001) lower food intake and 37% (P < 0.01), 37% (P < 0.01) and 45% (P < 0.001) lower body weight gain than CONT during the four-week experiment. At the end they had 26% (P < 0.05), 35% (P < 0.01) and 42% (P < 0.001) less total body fat, respectively, while plasma total glucagon-like peptide-1 (GLP-1) was 2.2-, 3.2- and 2.6-fold higher (P < 0.001) and peptide tyrosine tyrosine (PYY) was 2.3-, 3.1- and 3.0-fold higher (P < 0.001). There were no differences in these parameters between CONT and CELL. Compared with CONT and CELL, caecal concentrations of fermentation products increased 1.4- to 2.2-fold in GLUC, FOS and PECT (P < 0.05) and colonic concentrations increased 1.9- to 2.5-fold in GLUC and FOS (P < 0.05), with no consistent changes in SCFA receptor gene expression detected.

CONCLUSIONS

This provides animal model evidence that sustained intake of three different soluble dietary fibres decreases food intake, weight gain and adiposity, increases circulating satiety hormones GLP-1 and PYY, and increases hindgut fermentation. The presence of soluble fermentable fibre appears to be more important than its source. The results suggest that dietary fibre-induced satiety is worthy of further investigation towards natural body weight regulation in humans.

Bariatric surgery for obese children and adolescents: a review of the moral challenges

BACKGROUND

Bariatric surgery for children and adolescents is becoming widespread. However, the evidence is still scarce and of poor quality, and many of the patients are too young to consent. This poses a series of moral challenges, which have to be addressed both when considering bariatric surgery introduced as a health care service and when deciding for treatment for young individuals. A question based (Socratic) approach is applied to reveal underlying moral issues that can be relevant to an open and transparent decision making process.

DISCUSSION

A wide range of moral issues with bariatric surgery for children and adolescents is identified in the literature. There is a moral imperative to help obese minors avoiding serious health problems, but there is little high quality evidence on safety, outcomes, and cost-effectiveness for bariatric surgery in this group. Lack of maturity and family relations poses a series of challenges with autonomy, informed consent, assent, and assessing the best interest of children and adolescents. Social aspects of obesity, such as medicalization, prejudice, and discrimination, raise problems with justice and trust in health professionals. Conceptual issues, such as definition of obesity and treatment end-points, present moral problems. Hidden interests of patients, parents, professionals, industry, and society need to be revealed.

SUMMARY

Performing bariatric surgery for obese children and adolescents in order to discipline their behavior warrants reflection and caution. More evidence on outcomes is needed to be able to balance benefits and risks, to provide information for a valid consent or assent, and to advise minors and parents.

A pathway to endoscopic bariatric therapies

The American Society for Gastrointestinal Endoscopy (ASGE) is dedicated to advancing patient care and digestive health by promoting excellence in gastrointestinal endoscopy. The American Society for Metabolic and Bariatric Surgery (ASMBS) is dedicated to improving public health and well-being by lessening the burden of the disease of obesity and related diseases. They are the largest professional societies for their respective specialties of gastrointestinal endoscopy and bariatric surgery in the world. The ASGE/ASMBS task force was developed to collaboratively address opportunities for endoscopic approaches to obesity, reflecting the strengths of our disciplines, to improve patient and societal outcomes. This white paper is intended to provide a framework for, and a pathway towards, the development, investigation, and adoption of safe and effective endoscopic bariatric therapies (EBT).

Bariatric surgery in obese adolescents

PURPOSE OF REVIEW

Bariatric surgery is gaining acceptance as an effective and well tolerated treatment of morbid obesity in adults yet experience in obese children is still lacking. The purpose of this review is to highlight recent findings in this exciting field and identify the knowledge gaps.

RECENT FINDINGS

One randomized controlled trial and several case series have been published in the last 2 years regarding bariatric surgery for obese adolescents. These studies demonstrate relative safety along with significant weight loss. In addition, the vast majority of obesity-related comorbidities are resolved following these procedures. Adverse psychological effects of these procedures are probably more common than those in adults and need to be addressed.

SUMMARY

These publications indicate that bariatric surgical procedures, mainly gastric banding and gastric bypass, when performed on the right patients by skilled surgeons along with the appropriate ancillary staff, show positive metabolic effects and are well tolerated. Precise patient selection criteria, choice of the procedure and the extent of the multidisciplinary preoperative and postoperative care, are yet to be defined.