The effect of laparoscopic gastric banding surgery on plasma levels of appetite-control, insulinotropic, and digestive hormones

The Interplay Between Psychological and Neurobiological Predictors of Weight Regain: A Narrative Review

Introduction: Obesity is a global health problem requiring effective interventions to achieve weight loss and maintain it in the long term. A major challenge for clinicians is weight regain (WR), defined as progressive weight gain following successful weight loss. WR is affected by multiple factors, including psychological traits linked to specific brain alterations. Understanding these mechanisms is crucial in developing strategies to prevent WR and to ensure effective weight control. Objectives: This narrative review aims to gather current findings on the psychological and neurobiological determinants of WR and to discuss the interplay between these factors. Methods: A literature search was conducted on PubMed, Medline, and Web of Science for English-language studies published between December 1990 and November 2024. Results: WR is driven by interconnected psychological and neurobiological factors that influence eating behavior and the regulation of body weight. Certain personality traits and emotional patterns are associated with specific changes in brain activity, which together affect vulnerability to WR. Although distinct mechanisms can be identified, the complexity of homeostatic and nonhomeostatic appetite control suggests that no single factor predominates. Conclusions: This review highlights the dynamic interplay between psychological and neurobiological predictors of WR. However, due to the narrative nature of this review, the focus on selected determinants, and the limited quality and size of the available studies, further research is needed to comprehensively understand causality and to improve relapse prevention strategies.

Duodenal enteroendocrine cells and GIP as treatment targets for obesity and type 2 diabetes

The duodenum is an important source of endocrine and paracrine signals controlling digestion and nutrient disposition, notably including the main incretin hormone glucose-dependent insulinotropic polypeptide (GIP). Bariatric procedures that prevent nutrients from contact with the duodenal mucosa are particularly effective interventions to reduce body weight and improve glycaemic control in obesity and type 2 diabetes. These procedures take advantage of increased nutrient delivery to more distal regions of the intestine which enhances secretion of the other incretin hormone glucagon-like peptide-1 (GLP-1). Preclinical experiments have shown that either an increase or a decrease in the secretion or action of GIP can decrease body weight and blood glucose in obesity and non-insulin dependent hyperglycaemia, but clinical studies involving administration of GIP have been inconclusive. However, a synthetic dual agonist peptide (tirzepatide) that exerts agonism at receptors for GIP and GLP-1 has produced marked weight-lowering and glucose-lowering effects in people with obesity and type 2 diabetes. This appears to result from chronic biased agonism in which the novel conformation of the peptide triggers enhanced signalling by the GLP-1 receptor through reduced internalisation while reducing signalling by the GIP receptor directly or via functional antagonism through increased internalisation and degradation.

Significance of Hormone Alteration Following Bariatric Surgery

The prevalence of obesity has increased significantly over the last several decades, and with its increase comes a wide variety of comorbidities, such as diabetes and cardiovascular disease. Traditionally, diet and exercise have been prescribed for individuals to try and regain control of their weight and health status. Despite this successful method, the compliance rate is significantly below the desired amount. Over the last few decades, a new treatment has been offered to significantly decrease an individual's weight to an optimal BMI between 18 and 25 kg/m2. Bariatric surgery has been proposed to be the most appropriate treatment for obesity, and there are several different types of bariatric surgery: Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion with duodenal switch (BPD-DS), adjustable gastric band (AGB), and sleeve gastrectomy (SG). Hormones may be significantly involved in losing and maintaining weight loss. This paper aims to evaluate hormone changes in appetite suppression, appetite activation, glycemic control, and lipid metabolism and how these impact overall weight loss concerning the most prominent surgeries. The hormones assessed were ghrelin, insulin, leptin, GLP-1, PYY, and adiponectin, and their levels before and after each surgery were compared. RYGB is one of the most successful types of bariatric surgeries, and this correlates with it having the most suppressed levels of ghrelin, insulin, and leptin following surgery with a slow return to normal. RYGB has also led to the most significant increased levels of PYY, pre- and post-prandial GLP-1, and adiponectin. Hormones following SG followed the hormone trend after RYGB but were not as prominent. BDP-DS has the highest success rate. However, numerous adverse effects have limited the amount of studies assessing the surgery. What was present was not as significant as RYGB, possibly due to manipulation.

Mechanisms of bariatric surgery for weight loss and diabetes remission

Obesity and type 2 diabetes(T2D) lead to defects in intestinal hormones secretion, abnormalities in the composition of bile acids (BAs), increased systemic and adipose tissue inflammation, defects of branched-chain amino acids (BCAAs) catabolism, and dysbiosis of gut microbiota. Bariatric surgery (BS) has been shown to be highly effective in the treatment of obesity and T2D, which allows us to view BS not simply as weight-loss surgery but as a means of alleviating obesity and its comorbidities, especially T2D. In recent years, accumulating studies have focused on the mechanisms of BS to find out which metabolic parameters are affected by BS through which pathways, such as which hormones and inflammatory processes are altered. The literatures are saturated with the role of intestinal hormones and the gut-brain axis formed by their interaction with neural networks in the remission of obesity and T2D following BS. In addition, BAs, gut microbiota and other factors are also involved in these benefits after BS. The interaction of these factors makes the mechanisms of metabolic improvement induced by BS more complicated. To date, we do not fully understand the exact mechanisms of the metabolic alterations induced by BS and its impact on the disease process of T2D itself. This review summarizes the changes of intestinal hormones, BAs, BCAAs, gut microbiota, signaling proteins, growth differentiation factor 15, exosomes, adipose tissue, brain function, and food preferences after BS, so as to fully understand the actual working mechanisms of BS and provide nonsurgical therapeutic strategies for obesity and T2D.

The effects of glucagon like peptide-1 (GLP-1) on cardiac remodeling: exploring the role of medication and physiological modulation after metabolic surgery

Obesity and associated comorbidities reach epidemic proportions nowadays. Several treatment strategies exist, but bariatric surgery has the only longstanding effects. Since a few years, there is increasing interest in the effects of gastro-intestinal hormones, in particular Glucagon-Like Peptide-1 (GLP-1) on the remission of Type 2 Diabetes (T2DM) and its effects on cardiac cardiovascular morbidity, cardiac remodeling, and mortality. In the past years several high quality multicenter randomized controlled trials were developed to assess the effects of GLP-1 receptor agonist therapy on cardiovascular morbidity and mortality. Most of the trials were designed and powered as non-inferiority trials to demonstrate cardiovascular safety. Most of these trials show a reduction in cardiovascular morbidity in patients with T2DM. Some follow-up studies indicate potential beneficial effects of GLP-1 receptor agonists on cardiovascular function in patients with heart failure, however the results are contradictory, and we need long-term studies to make firm conclusions about the pleiotropic properties of incretin-based therapies. However, it seems that GLP-1 receptor agonists have different effects than the increased GLP-1 production after bariatric surgery on cardiovascular remodeling. One of the hypotheses is that the blood concentrations of GLP-1 receptor agonists are three times higher compared to GLP-1 increase after bariatric and metabolic surgery. The purpose of this narrative review is to summarize the effects of GLP-1 on cardiovascular morbidity, mortality and remodeling due to medication but also due to bariatric and metabolic surgery. The second objective is to explain the possible differences in effects of GLP-1 agonists and bariatric and metabolic surgery.

Body Weight and Prandial Variation of Plasma Metabolites in Subjects Undergoing Gastric Band-Induced Weight Loss

BACKGROUND

Bariatric procedures are safe and effective treatments for obesity, inducing rapid and sustained loss of excess body weight. Laparoscopic adjustable gastric banding (LAGB) is unique among bariatric interventions in that it is a reversible procedure in which normal gastrointestinal anatomy is maintained. Knowledge regarding how LAGB effects change at the metabolite level is limited.

OBJECTIVES

To delineate the impact of LAGB on fasting and postprandial metabolite responses using targeted metabolomics.

SETTING

Individuals undergoing LAGB at NYU Langone Medical Center were recruited for a prospective cohort study.

METHODS

We prospectively analyzed serum samples from 18 subjects at baseline and 2 months after LAGB under fasting conditions and after a 1-hour mixed meal challenge. Plasma samples were analyzed on a reverse-phase liquid chromatography time-of-flight mass spectrometry metabolomics platform. The main outcome measure was their serum metabolite profile.

RESULTS

We quantitatively detected over 4,000 metabolites and lipids. Metabolite levels were altered in response to surgical and prandial stimuli, and metabolites within the same biochemical class tended to behave similarly in response to either stimulus. Plasma levels of lipid species and ketone bodies were statistically decreased after surgery whereas amino acid levels were affected more by prandial status than surgical condition.

CONCLUSIONS

Changes in lipid species and ketone bodies postoperatively suggest improvements in the rate and efficiency of fatty acid oxidation and glucose handling after LAGB. Further investigation is necessary to understand how these findings relate to surgical response, including long term weight maintenance, and obesity-related comorbidities such as dysglycemia and cardiovascular disease.

Neurohormonal Changes in the Gut-Brain Axis and Underlying Neuroendocrine Mechanisms following Bariatric Surgery

Obesity is a complex, multifactorial disease that is a major public health issue worldwide. Currently approved anti-obesity medications and lifestyle interventions lack the efficacy and durability needed to combat obesity, especially in individuals with more severe forms or coexisting metabolic disorders, such as poorly controlled type 2 diabetes. Bariatric surgery is considered an effective therapeutic modality with sustained weight loss and metabolic benefits. Numerous genetic and environmental factors have been associated with the pathogenesis of obesity, while cumulative evidence has highlighted the gut-brain axis as a complex bidirectional communication axis that plays a crucial role in energy homeostasis. This has led to increased research on the roles of neuroendocrine signaling pathways and various gastrointestinal peptides as key mediators of the beneficial effects following weight-loss surgery. The accumulate evidence suggests that the development of gut-peptide-based agents can mimic the effects of bariatric surgery and thus is a highly promising treatment strategy that could be explored in future research. This article aims to elucidate the potential underlying neuroendocrine mechanisms of the gut-brain axis and comprehensively review the observed changes of gut hormones associated with bariatric surgery. Moreover, the emerging role of post-bariatric gut microbiota modulation is briefly discussed.

Do Gut Hormones Contribute to Weight Loss and Glycaemic Outcomes after Bariatric Surgery?

Bariatric surgery is an effective intervention for management of obesity through treating dysregulated appetite and achieving long-term weight loss maintenance. Moreover, significant changes in glucose homeostasis are observed after bariatric surgery including, in some cases, type 2 diabetes remission from the early postoperative period and postprandial hypoglycaemia. Levels of a number of gut hormones are dramatically increased from the early period after Roux-en-Y gastric bypass and sleeve gastrectomy—the two most commonly performed bariatric procedures—and they have been suggested as important mediators of the observed changes in eating behaviour and glucose homeostasis postoperatively. In this review, we summarise the current evidence from human studies on the alterations of gut hormones after bariatric surgery and their impact on clinical outcomes postoperatively. Studies which assess the role of gut hormones after bariatric surgery on food intake, hunger, satiety and glucose homeostasis through octreotide use (a non-specific inhibitor of gut hormone secretion) as well as with exendin 9–39 (a specific glucagon-like peptide-1 receptor antagonist) are reviewed. The potential use of gut hormones as biomarkers of successful outcomes of bariatric surgery is also evaluated.

Revisiting the Ghrelin Changes Following Bariatric and Metabolic Surgery

Since the description of ghrelin in 1999, several studies have dug into the effects of this hormone and its relationship with bariatric surgery. While some aspects are still unresolved, a clear connection between ghrelin and the changes after metabolic surgery have been established. Besides weight loss, a significant amelioration in obesity-related comorbidities following surgery has also been reported. These changes in patients occur in the early postoperative period, before the weight loss appears, so that amelioration may be mainly due to hormonal changes. The purpose of this review is to go through the current body of knowledge of ghrelin's physiology, as well as to update and clarify the changes that take place in ghrelin concentrations following bariatric/metabolic surgery together with their potential consolidation to outcomes.

GIP analogues and the treatment of obesity-diabetes

The potential application of glucose-dependent insulinotropic polypeptide (gastric inhibitory polypeptide, GIP) in the management of obesity and type 2 diabetes has been controversial. Initial interest in the therapeutic use of GIP was dampened by evidence that its insulinotropic activity was reduced in type 2 diabetes and by reports that it increased glucagon secretion and adipose deposition in non-diabetic individuals. Also, attention was diverted away from GIP by the successful development of glucagon-like peptide-1 (GLP-1) receptor agonists, and a therapeutic strategy for GIP became uncertain when evidence emerged that both inhibition and enhancement of GIP action could prevent or reverse obese non-insulin dependent forms of diabetes in rodents. Species differences in GIP receptor responsiveness complicated the extrapolation of evidence from rodents to humans, but initial clinical studies are investigating the effect of a GIP antagonist in non-diabetic individuals. A therapeutic role for GIP agonists was reconsidered when clinical studies noted that the insulinotropic effect of GIP was increased if near-normal glycaemia was re-established, and GIP was found to have little effect on glucagon secretion or adipose deposition in obese type 2 diabetes patients. This encouraged the development of designer peptides that act as GIP receptor agonists, including chimeric peptides that mimic the incretin partnership of GIP with GLP-1, where the two agents exert complementary and often additive effects to improve glycaemic control and facilitate weight loss. Polyagonist peptides that exert agonism at GIP, GLP-1 and glucagon receptors are also under investigation as potential treatments for obese type 2 diabetes.

Circulating levels of gastrointestinal hormones in response to the most common types of bariatric surgery and predictive value for weight loss over one year: Evidence from two independent trials

AIMS

Bariatric surgery leads to profound and sustainable weight loss. Gastrointestinal hormones are involved in energy and glucose homeostasis, thus postoperative changes of their circulating levels may be mediating future weight loss. To investigate how the circulating concentrations of gastrointestinal hormones change in response to the most common types of bariatric operation and whether these changes can predict future weight loss.

MATERIALS AND METHODS

We measured circulating GLP-1, GLP-2, oxyntomodulin, glicentin, glucagon, major proglucagon fragment (MPGF), ghrelin, GIP, PYY after overnight fasting and/or after a mixed meal test (MMT) in: a) 14 subjects that have undergone either an adjustable gastric banding [AGB] (n = 9) or a Roux-en-Y bypass (RYGB) (n = 5) (Pilot study 1), b) 28 subjects that have undergone either a vertical sleeve gastrectomy (n = 17) or a RYGB (n = 11) before and three, six and twelve months after surgery.

RESULTS

In addition to the expected associations with GLP-1, the most robust increases were observed in postprandial levels of oxyntomodulin and glicentin three months after VSG or RYGB (but not after AGB) and are associated with degree of weight loss. Oxyntomodulin and glicentin levels at the third and sixth month postoperative visit are positively associated with feeling of satiety which may be underlying the observed associations with future weight loss.

CONCLUSION

Beyond GLP-1, early postprandial changes in circulating oxyntomodulin and glicentin are predictors of weight loss after bariatric surgery, possibly through regulation of satiety. Further studies should focus on underlying mechanisms, and their potential as attractive therapeutic tools against obesity and related comorbidities.

Cardiac remodeling in obesity and after bariatric and metabolic surgery; is there a role for gastro-intestinal hormones?

Introduction: Obesity is associated with various diseases such as type 2 diabetes, hypertension, obstructive sleep apnea syndrome (OSAS), metabolic syndrome, and cardiovascular diseases. It affects several organ systems, including the pulmonary and cardiac systems. Furthermore, it induces pulmonary and cardiac changes that can result in right and/or left heart failure.Areas covered: In this review, authors provide an overview of obesity and cardiovascular remodeling, the individual actions of the gut hormones (like GLP-1 and PYY), the effects after bariatric/metabolic surgery and its influence on cardiac remodeling. In this review, we focussed and searched for literature in Pubmed and The Cochrane library (from the earliest date until April 2019), regarding cardiac function changes before and after bariatric surgery and literature regarding changes in gastrointestinal hormones.Expert opinion: Regarding the surgical treatment of obesity and metabolic diseases there is recognition of the importance of both weight loss (bariatric surgery) and improvement in metabolic milieu (metabolic surgery). A growing body of evidence further suggests that bariatric surgical procedures [like the Sleeve Gastrectomy (SG), Roux-en Y Gastric Bypass (RYGB), or One Anastomosis Gastric Bypass (OAGB)] have can improve outcomes of patients suffering from a number of cardiovascular diseases, including heart failure.

Helicobacter pylori and nutrition: a bidirectional communication

Helicobacter pylori (HP) is a gram-negative flagellated pathogen acid-resistant bacterium; it belongs to the order Campylobacterales that is wide spread all over the world, infecting more than 50% of the world population. HP infection is etiologically associated with non-atrophic and atrophic gastritis, peptic ulcer and with 3 to 6-fold increased relative risk for developing gastric adenocarcinoma and mucosa-associated lymphoid tissue (MA LT) lymphoma. For this reason HP is recognized by the World Health Organization as a Class I human carcinogen. In the last years a lot of studies clarified the role of this pathogen in nutrition and metabolism; particularly, it has been shown that it is able to induce malabsorption of several nutrients like iron, cobalamin, vitamin C and vitamin E, with strong consequences on nutritional status. Interesting, this bacterium is able to produce different biological effects on hormones like ghrelin and leptin controlling both appetite and growth, mostly depending on the time of acquisition of the infection and of its treatment. In this review, the authors focused their attention on nutritional effects of HP infection and particularly on the role that diet, food, plants and specific nutrients can play in its treatment, considering that HP eradication rates, with standard triple-therapy, have fallen to a low level in the last years.

The Gut-Brain Axis, the Human Gut Microbiota and Their Integration in the Development of Obesity

Obesity is a global epidemic, placing socioeconomic strain on public healthcare systems, especially within the so-called Western countries, such as Australia, United States, United Kingdom, and Canada. Obesity results from an imbalance between energy intake and energy expenditure, where energy intake exceeds expenditure. Current non-invasive treatments lack efficacy in combating obesity, suggesting that obesity is a multi-faceted and more complex disease than previously thought. This has led to an increase in research exploring energy homeostasis and the discovery of a complex bidirectional communication axis referred to as the gut-brain axis. The gut-brain axis is comprised of various neurohumoral components that allow the gut and brain to communicate with each other. Communication occurs within the axis via local, paracrine and/or endocrine mechanisms involving a variety of gut-derived peptides produced from enteroendocrine cells (EECs), including glucagon-like peptide 1 (GLP1), cholecystokinin (CCK), peptide YY3-36 (PYY), pancreatic polypeptide (PP), and oxyntomodulin. Neural networks, such as the enteric nervous system (ENS) and vagus nerve also convey information within the gut-brain axis. Emerging evidence suggests the human gut microbiota, a complex ecosystem residing in the gastrointestinal tract (GIT), may influence weight-gain through several inter-dependent pathways including energy harvesting, short-chain fatty-acids (SCFA) signalling, behaviour modifications, controlling satiety and modulating inflammatory responses within the host. Hence, the gut-brain axis, the microbiota and the link between these elements and the role each plays in either promoting or regulating energy and thereby contributing to obesity will be explored in this review.

Mechanisms of weight loss and improved metabolism following bariatric surgery

Bariatric surgery is increasingly recognized as one of the most effective interventions to help patients achieve significant and sustained weight loss, as well as improved metabolic and overall health. Unfortunately, the cellular and physiological mechanisms by which bariatric surgery achieves weight loss have not been fully elucidated, yet are critical to understanding the central role of the intestinal tract in whole-body metabolism and to developing novel strategies for the treatment of obesity. In this review, we provide an overview of potential mechanisms contributing to weight loss, including effects on regulation of energy balance and both central and peripheral nervous system regulation of appetite and metabolism. Moreover, we highlight the importance of the gastrointestinal tract, including alterations in bile acid physiology, secretion of intestinally derived hormones, and the microbiome, as a potent mediator of improved metabolism in postbariatric patients.

Potential Hormone Mechanisms of Bariatric Surgery

PURPOSE OF REVIEW

In recent years, the role of the gastrointestinal (GI) tract in energy homeostasis through modulation of the digestion and absorption of carbohydrates and the production of incretin hormones is well recognized.

RECENT FINDINGS

Bariatric surgery for obesity has been a very effective method in substantially improving weight, and numerous studies have focused on intestinal adaptation after bariatric procedures. A number of structural and functional changes in the GI tract have been reported postsurgery, which could be responsible for the altered hormonal responses. Furthermore, the change in food absorption rate and the intestinal regions exposed to carbohydrates may affect blood glucose response. This review hopes to give new insights into the direct role of gut hormones, by summarising the metabolic effects of bariatric surgery.

A prospective 4-year study of insulin resistance and adipokines in morbidly obese diabetic and non-diabetic patients after gastric banding

Introduction

There are insufficient data regarding the changes in adipokine levels after laparoscopic adjustable gastric banding (LAGB) in diabetic and non-diabetic patients and their effects on insulin resistance and type 2 diabetes remission.

Aim

To assess leptin, adiponectin, and insulin resistance changes after LAGB in diabetic and non-diabetic morbidly obese patients.

Material and methods

One hundred and three patients (37 with and 66 without type 2 diabetes) underwent LAGB from January 2009 to January 2010. Glycated hemoglobin, insulin, adipokine levels and insulin resistance were evaluated preoperatively, and 1 and 4 years after LAGB.

Results

The mean patient age was 45.9 ±11.7 years and mean preoperative body mass index was 47.5 ±7.3 kg/m². A total of 80 of 103 patients (77.6%) completed the 4-year follow-up. After 4 years the mean excess weight loss was 38.8% and 39.5% in diabetic and non-diabetic patients respectively. Leptin levels decreased significantly in both groups at 1 year, but after 4 years this was noted only in non-diabetic patients. After 1 year adiponectin levels increased significantly only in non-diabetic patients (p = 0.003) and remained almost the same at 4 years. A significant decrease in insulin resistance was noted in both groups 1 year after LAGB and diabetes remission was observed in 23 (62.1%) patients. There was a negative correlation between preoperative insulin resistance and adiponectin levels throughout the follow-up period. Leptin levels positively correlated with BMI throughout the study period (baseline r = 0.45; p < 0.001; after 1 year r = 0.71; p < 0.001; after 4 years r = 0.68; p < 0.001). There was no significant correlation between leptin and adiponectin concentrations preoperatively or after 1 year; however, at 4 years it was significant (r = 0.27; p < 0.02).

Conclusions

The most significant metabolic changes occurred within 1 year after LAGB. The 4-year follow-up revealed stabilization in metabolic indices rather than significant improvement.

Distinctive microbiomes and metabolites linked with weight loss after gastric bypass, but not gastric banding

Roux-en-Y gastric bypass (RYGB) and laparoscopic adjustable gastric banding (LAGB) are anatomically different bariatric operations. RYGB achieves greater weight loss compared with LAGB. Changes in the gut microbiome have been documented after RYGB, but not LAGB, and the microbial contribution to sustainable surgical weight loss warrants further evaluation. We hypothesized that RYGB imposes greater changes on the microbiota and its metabolism than LAGB, and that the altered microbiota may contribute to greater weight loss. Using multi-omic approaches, we analyzed fecal microbial community structure and metabolites of pre-bariatric surgery morbidly obese (PreB-Ob), normal weight (NW), post-RYGB, and post-LAGB participants. RYGB microbiomes were significantly different from those from NW, LAGB and PreB-Ob. Microbiome differences between RYGB and PreB-Ob populations were mirrored in their metabolomes. Diversity was higher in RYGB compared with LAGB, possibly because of an increase in the abundance of facultative anaerobic, bile-tolerant and acid-sensible microorganisms in the former. Possibly because of lower gastric acid exposure, phylotypes from the oral cavity, such as Escherichia, Veillonella and Streptococcus, were in greater abundance in the RYGB group, and their abundances positively correlated with percent excess weight loss. Many of these post-RYGB microorganisms are capable of amino-acid fermentation. Amino-acid and carbohydrate fermentation products-isovalerate, isobutyrate, butyrate and propionate-were prevalent in RYGB participants, but not in LAGB participants. RYGB resulted in greater alteration of the gut microbiome and metabolome than LAGB, and RYGB group exhibited unique microbiome composed of many amino-acid fermenters, compared with nonsurgical controls.

The effect of bariatric surgery on gastrointestinal and pancreatic peptide hormones

Bariatric surgery for obesity has proved to be an extremely effective method of promoting long-term weight reduction with additional beneficial metabolic effects, such as improved glucose tolerance and remission of type 2 diabetes. A range of bariatric procedures are in common use, including gastric banding, sleeve gastrectomy and the Roux-en-Y gastric bypass. Although the mechanisms underlying the efficacy of bariatric surgery are unclear, gastrointestinal and pancreatic peptides are thought to play an important role. The aim of this review is to summarise the effects of different bariatric surgery procedures upon gastrointestinal and pancreatic peptides, including ghrelin, gastrin, cholecystokinin (CCK), glucose-dependent insulinotropic hormone (GIP), glucagon-like peptide 1 (GLP-1), peptide YY (PYY), oxyntomodulin, insulin, glucagon and somatostatin.

Effect of bariatric surgery on humoral control of metabolic derangements in obese patients with type 2 diabetes mellitus: How it works

Obesity and diabetes is a co-pandemic and a major health concern that is expanding. It has many psychosocial and economic consequences due to morbidity and mortality of this disease combination. The pathophysiology of obesity and related diabetes is complex and multifactorial. One arm of this disease process is the genetic susceptibility. Other arm is dependent on the intricate neuro-humoral factors that converge in the central nerve system. Gut hormones and the adipose tissue derived factors plays an important role in this delicate network. Bariatric surgery provides the only durable option for treatment of obesity and furthermore it provides a remission in the concomitant diseases that accompany obesity. This review provides a brief insight to all these mechanisms and tries to deduce the possible reasons of remission of type 2 diabetes after bariatric surgery.

Peripheral signals mediate the beneficial effects of gastric surgery in obesity

Obesity is nowadays a public health problem both in the industrialized world and developing countries. The different treatments to fight against obesity are not very successful with the exception of gastric surgery. The mechanism behind the achievement of this procedure remains unclear although the modifications in the pattern of gastrointestinal hormones production appear to be responsible for the beneficial effect. The gastrointestinal tract has emerged in the last time as an endocrine organ in charge of response to the different stimulus related to nutritional status by the modulation of more than 30 signals acting at central level to modulate food intake and body weight. The production of some of these gastric derived signals has been proved to be altered in obesity (ghrelin, CCK, and GLP-1). In fact, bariatric surgery modifies the production of both gastrointestinal and adipose tissue peripheral signals beyond the gut microbiota composition. Through this paper the main peripheral signals altered in obesity will be reviewed together with their modifications after bariatric surgery.

Could the improvement of obesity-related co-morbidities depend on modified gut hormones secretion?

Obesity and its associated diseases are a worldwide epidemic disease. Usual weight loss cures - as diets, physical activity, behavior therapy and pharmacotherapy - have been continuously implemented but still have relatively poor long-term success and mainly scarce adherence. Bariatric surgery is to date the most effective long term treatment for morbid obesity and it has been proven to reduce obesity-related co-morbidities, among them nonalcoholic fatty liver disease, and mortality. This article summarizes such variations in gut hormones following the current metabolic surgery procedures. The profile of gut hormonal changes after bariatric surgery represents a strategy for the individuation of the most performing surgical procedures to achieve clinical results. About this topic, experts suggest that the individuation of the crosslink among the gut hormones, microbiome, the obesity and the bariatric surgery could lead to new and more specific therapeutic interventions for severe obesity and its co-morbidities, also non surgical.

Relationship between gut hormones and glucose homeostasis after bariatric surgery

Type 2 diabetes mellitus (T2D) is emerging as a worldwide public health problem, and is mainly associated with an increased incidence of obesity. Bariatric surgery is currently considered the most effective treatment for severely obese patients. After bariatric surgery, T2D patients have shown a significant improvement in glycemic control, even before substantial weight loss and often discontinuation of medication for diabetes control. A central role for enteroendocrine cells from the epithelium of the gastrointestinal tract has been speculated in this postoperative phenomenon. These cells produce and secrete polypeptides - gut hormones - that are associated with regulating energy intake and glucose homeostasis through modulation of peripheral target organs, including the endocrine pancreas. This article reviews and discusses the biological actions of the gut hormones ghrelin, cholecystokinin, incretins, enteroglucagon, and Peptide YY, all of which were recently identified as potential candidates for mediators of glycemic control after bariatric surgery. In conclusion, current data reinforce the hypothesis that T2D reversion after bariatric surgery may be related to glycemic homeostasis developed by the intestine.

Metabolic surgery: action via hormonal milieu changes, changes in bile acids or gut microbiota? A summary of the literature

Obesity and type 2 diabetes remain epidemic problems. Different bariatric surgical techniques causes weight loss and diabetes remission to varying degrees. The underlying mechanisms of the beneficial effects of bariatric surgery are complex, and include changes in diet and behaviour, as well as changes in hormones, bile acid flow, and gut bacteria. We summarized the effects of multiple different bariatric procedures, and their resulting effects on several hormones (leptin, ghrelin, adiponectin, glucagon-like peptide 1 (GLP-1), peptide YY, and glucagon), bile acid changes in the gut and the serum, and resulting changes to the gut microbiome. As much as possible, we have tried to incorporate multiple studies to try to explain underlying mechanistic changes. What emerges from the data is a picture of clear differences between restrictive and metabolic procedures. The latter, in particular the roux-en-Y gastric bypass, induces large and distinctive changes in most measured fat and gut hormones, including early and sustained increase in GLP-1, possible through intestinal bile acid signalling. The changes in bile flow and the gut microbiome are causally inseparable so far, but new studies show that each contributes to the effects of weight loss and diabetes resolution.

Effects of bariatric surgery on the level of hormones that regulate body weight. What is the basis of success?

The growth of obesity and type 2 diabetes incidence has made bariatric surgery a widespread method of treatment. The effectiveness of bariatricoperations in the treatment of obesity and related metabolic diseases is thoroughly highlighted in medical literature. However, the resultsof surgery do not always correlate with type of operation. As before, the mechanisms have not been fully studied of how the bariatric surgeryinfluence on insulinresistance, entero-insulin axes, adipokines. Understanding such mechanisms will allow us to determine more precisely theindications relating to surgical treatment, and enhance the effectiveness of surgery in specific patient. The review is focusing on the influence ofvarious types of bariatric surgery on the level of adipokines and incretines that participate in regulation of appetite and of fat and carbohydratemetabolism. The article elaborates modern concepts related to the impact of bariatric operations on metabolic disorders in obesity.

Impairment of ghrelin synthesis in Helicobacter pylori-colonized stomach: New clues for the pathogenesis of H. pylori-related gastric inflammation

Ghrelin, the ligand of growth hormone secretagogue receptor 1a, takes part in several functions of the digestive system, including regulation of appetite, energy homeostasis, gastric acid secretion and motility. Ghrelin has also immunoregulatory properties and is supposed to inhibit some inflammatory pathways that can mediate gastric damage. Interestingly, ghrelin synthesis is reduced in the gastric mucosa of patients with Helicobacter pylori (H. pylori) infection, a worldwide condition inducing a T helper (Th)1/Th17 cell response-driven gastritis, which may evolve towards gastric atrophy and cancer. In this article, we review the available data on the expression of ghrelin in H. pylori infection and discuss how the defective ghrelin synthesis may contribute to sustain the ongoing inflammatory response in this disease.

Hormonal responses and test meal intake among obese teenagers before and after laparoscopic adjustable gastric banding

BACKGROUND

Relatively little is known about changes in eating behavior or hormonal responses to food after bariatric surgery in adolescents.

OBJECTIVE

This study compared eating behavior and hormones among adolescents in a bariatric surgery program with those in nonoverweight control adolescents and evaluated changes before and after laparoscopic adjustable gastric banding (LAGB).

DESIGN

Fasting leptin, peptide YY (PYY), and ghrelin concentrations were obtained, and postprandial ghrelin and PYY area under the curve (AUC) were assessed after a single-item breakfast. Intake from an ad libitum lunchtime multi-item meal was measured.

RESULTS

Compared with controls (n = 9), all presurgical candidates (n = 20) had significantly greater fasting leptin, lower fasting ghrelin, and lower AUC ghrelin but similar PYY and AUC PYY. Preoperative candidates did not differ from controls in total energy consumed during the test meal. Postoperatively, among the 11 participants with data both before and after surgery, BMI (in kg/m(2)) decreased by 3.5 (P < 0.001), significantly less energy was consumed in the test meal, and a smaller number of foods were selected. AUC ghrelin and PYY did not significantly change before or after LAGB.

CONCLUSIONS

Few significant short-term changes were observed in appetitive hormones after LAGB. It is unclear whether objective measures of eating behavior will prove useful in evaluating the impact of bariatric surgery on outcomes. This trial was registered at clinicaltrials.gov as CT00764127.

Bariatric surgery, bone loss, obesity and possible mechanisms

Bariatric surgery remains the most effective treatment for severely obese patients. However, the potential long-term effects of bariatric surgical procedures on health, including bone health, are only partially understood. The goal of this review was to present data on the impact of bariatric surgery on bone metabolism and to analyse possible reasons for the loss of bone mass that frequently occurs after bariatric surgery. Such factors include nutritional deficiencies, rapid weight loss per se, effects of fat-derived adipokines and gut-derived appetite-regulatory hormones. However, the relative roles of these factors in skeletal regulation and the mechanisms by which they work are not yet fully defined. Our review was focussed on the complex relationship between body weight, fat mass and bone mass, as well as peripheral and central mediators potentially involved in the dual regulation of both energy and bone homeostasis. We also review the data on the inverse relationship between central obesity, bone marrow fat and osteoporosis. As the number of bariatric operations increases, it is imperative to recognize mechanisms responsible for bariatric surgery-induced bone loss, with careful monitoring of bone health including long-term fracture incidence in patients undergoing these procedures.

Comparison of Bariatric Surgical Procedures for Diabetes Remission: Efficacy and Mechanisms

Bariatric surgery induces a mean weight loss of 15-30% of initial body weight (depending on the procedure), as well as a 45-95% rate of diabetes remission. Procedures that induce greater weight loss are associated with higher rates of diabetes remission. Improvements in glucose homeostasis after bariatric surgery are likely mediated by a combination of caloric restriction (followed by weight loss) and the effects of altered gut anatomy on the secretion of glucoregulatory gut hormones.

Effects of laparoscopic gastric band applications on plasma and fundic acylated ghrelin levels in morbidly obese patients

BACKGROUND

It has been proposed that laparoscopic adjustable gastric banding (LAGB) procedure might play a role in modulation of fundic ghrelin production. To test this hypothesis, we examined plasma and tissue concentrations of acylated ghrelin in morbidly obese patients before and 6 months after LAGB. Baseline levels of acylated ghrelin in morbidly obese patients were also compared with those in age-matched, healthy, non-obese controls.

METHODS

We studied 21 patients who had been operated on for morbid obesity (M/F = 9/12, BMI = 49.3 ± 5.3 kg/m(2)) and 16 healthy, non-obese persons (M/F = 7/9, BMI = 23.0 ± 1.7 kg/m(2)). Fasting blood samples were collected once from the non-obese controls as well as the morbidly obese patients before and 6 months after the LAGB. The morbidly obese patients and their respective controls underwent gastroscopy for fundic biopsy. The plasma and fundic acylated ghrelin levels were evaluated in these groups by enzyme-linked immunosorbent assay.

RESULTS

The plasma and fundic acylated ghrelin concentrations were significantly lower in obese patients than in non-obese controls (2.8 ± 1.0 ng/ml, 727 ± 171.7 ng/g tissue, respectively; p = 0.000). These parameters were significantly increased in morbidly obese patients 6 months after LAGB (4.1 ± 1.2 ng/ml and p = 0.001; 999 ± 292.1 ng/g tissue and p = 0.003, respectively).

CONCLUSIONS

We showed that fundic production of acylated ghrelin was significantly increased in morbidly obese patients 6 months after LAGB. Moreover, the weight loss after LAGB occurred in spite of the significant increase in the plasma and fundic acylated ghrelin levels. The potential role of ghrelin as being responsible for the weight loss after bariatric surgery needs to be elucidated in further studies.

[Bariatric surgery for the treatment of type 2 diabetes mellitus]

Weight loss can improve metabolic control in patients with type 2 diabetes mellitus but the results of conventional therapy in this respect have been discouraging. Besides achieving significant and sustained weight loss, bariatric surgery can improve or resolve type 2 diabetes mellitus in the majority of patients. Anatomical modifications and changes in the secretion of intestinal hormones can explain the superiority of malabsorptive techniques. Currently, bariatric surgery offers a therapeutic alternative for type 2 diabetes patients with severe obesity and poor metabolic control under conventional therapy. Ongoing research will provide insights regarding the effect of intestinal hormones, new surgery techniques and the possible benefits of bariatric surgery in non-obese patients.

Physiology of weight loss surgery

The clinical outcomes achieved by bariatric surgery have been impressive. However, the physiologic mechanisms and complex metabolic effects of bariatric surgery are only now beginning to be understood. Ongoing research has contributed a large amount of data and shed new light on the science behind obesity and its treatment, and this article reviews the current understanding of metabolic and bariatric surgery physiology.

Mechanisms responsible for excess weight loss after bariatric surgery

Obesity has increased alarmingly in the United States and is increasing in many countries of the world. Because obesity is an important risk factor for type 2 diabetes and other chronic diseases, it is important to develop approaches to counter the rapid increase in adiposity. One approach is bariatric surgery, the most successful clinical intervention known for treating obesity. Surgery can result in impressive weight loss and improvement of obesity-related comorbidities. Yet the mechanisms responsible for this remarkable effect of surgery remain controversial. It is now clear that caloric restriction, per se, does not explain all the reduction in stored fat mass after surgery. A number of gastrointestinal hormones, including glucagon-like peptide (GLP)-1, peptide YY, oxyntomodulin, GLP-2, glucose-dependent insulinotropic polypeptide, ghrelin, and others, can play roles in energy homeostasis and could be involved in bariatric-surgery-related weight loss and weight loss maintenance. Vagal innervation may play a role. In addition, there may be other yet-uncharacterized factors that could participate. This review discusses the possible roles of these hormonal mechanisms in various types of bariatric surgery to help elucidate some of the potential mechanisms at play in short-term and long-term post-bariatric surgery weight loss. Understanding such mechanisms could lead to new and efficacious means to control or even reduce the epidemic of obesity.

Metabolic surgery-principles and current concepts

INTRODUCTION

In the almost six decades of bariatric surgery, a variety of surgical approaches to treating morbid obesity have been developed.

HISTORY AND EVOLUTION

Rather than prior techniques being continually superseded by new ones, a broad choice of surgical solutions based on restrictive, malabsorptive, humoral effects, or combinations thereof, is now available. In fact, in recent years, the advent of surgically modifying human metabolism promises new approaches to ameliorate traditionally medically treated metabolic entities, i.e., diabetes, even in the non-obese. The understanding of the various metabolic effects have led to a paradigm shift from bariatric surgery as a solely weight-reducing procedure to metabolic surgery affecting whole body metabolism.

CONCLUSION

The bariatric surgeon now faces the challenge and opportunity of selecting the most suitable technique for each individual case. To assist in such decision-making, this review, Metabolic surgery-principles and current concepts, is presented, tracing the historical development; describing the various surgical techniques; elucidating the mechanisms by which glycemic control can be achieved that involve favorable changes in insulin secretion and insulin sensitivity, gut hormones, adipokines, energy expenditure, appetite, and preference for low glycemic index foods; as well as exploring the fascinating future potential of this new interdisciplinary field.

GIP and bariatric surgery

Bariatric surgery is the most effective modality of achieving weight loss as well as the most effective treatment for type 2 diabetes mellitus (T2DM). Glucose-dependent insulinotropic polypeptide (GIP) is an incretin and is implicated in the pathogenesis of obesity and T2DM. Its role in weight loss and resolution of T2DM after bariatric surgery is very controversial. We have made an attempt to review the physiology of GIP and its role in weight loss and resolution of T2DM after bariatric surgery. We searched PubMed and included all relevant original articles (both human and animal) in the review. Whereas most human studies have shown a decrease in GIP post-malabsorptive bariatric surgery, the role of GIP in bariatric surgery done in animal experiments remains inconclusive.

Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy: understanding weight loss and improvements in type 2 diabetes after bariatric surgery

Obesity increases the likelihood of diseases like type 2 diabetes (T2D), heart disease, and cancer, and is one of the most serious public health problems of this century. In contrast to ineffectual prevention strategies, lifestyle modifications, and pharmacological therapies, bariatric surgery is a very effective treatment for morbid obesity and also markedly improves associated comorbidities like T2D. However, weight loss and resolution of T2D after bariatric surgery is heterogeneous and specific to type of bariatric procedure performed. Conventional mechanisms like intestinal malabsorption and gastric restriction do not fully explain this, and potent changes in appetite and the enteroinsular axis, as a result of anatomical reorganization and altered hormonal, neuronal, and nutrient signaling, are the portended cause. Uniquely these signaling changes appear to override vigorous homeostatic defenses of stable body weight and compelling self-gratifying motivations to eat and to reverse defects in beta-cell function and insulin sensitivity. Here we review mechanisms of weight loss and T2D resolution after Roux-en-Y gastric bypass and laparoscopic sleeve gastrectomy bariatric surgery, two markedly different procedures with robust clinical outcomes.

Changes in neurohormonal gut peptides following bariatric surgery

The rising prevalence of obesity has reached pandemic proportions, with an associated cost estimated at up to 7% of health expenditures worldwide. Bariatric surgery is currently the only effective long-term treatment for obesity and obesity-related co-morbidities in clinically severely obese patients. However, the precise physiological mechanisms underlying the postsurgical reductions in caloric intake and body weight are poorly comprehended. It has been suggested that changes in hormones involved in hunger, food intake and satiety via the neurohormonal network may contribute to the efficacy of bariatric procedures. In this review, we consider how gastrointestinal hormone concentrations, involved in appetite and body weight regulation via the gut-brain axis, are altered by different bariatric procedures. Special emphasis is placed on neurohormonal changes following Roux-en-Y gastric bypass surgery, which is the most common and effective procedure used today.

Bariatric surgery: results in obesity and effects on metabolic parameters

PURPOSE OF REVIEW

The use of bariatric surgery is increasing at an enormous rate in all countries but the indications for the operation on the basis of metabolic derangements are not clear as only one controlled randomized trial has been performed so far. Thus, it is not clear whether bariatric surgery should be performed on obese patients with long-standing type 2 diabetes or poorly controlled hypertension or hypertriglyceridemia. The mechanism for the immediate improvement in glucose tolerance after gastric bypass is not clear but is being actively investigated.

RECENT FINDINGS

Gastric bypass appears to enhance glucagon-like peptide-1 production and suppress glucose-dependent insulinotropic polypeptide production. It appears that patients with type 2 diabetes and a greater BMI gain more benefit from the operation.

SUMMARY

Bariatric surgery, particularly gastric bypass, has powerful and usually persistent effects on type 2 diabetes, dyslipidemia, and hypertension but randomized controlled trials with predefined metabolic entry criteria and planned comprehensive follow-up are required.

Helicobacter pylori infection and circulating ghrelin levels - a systematic review

BACKGROUND

The nature of the association between ghrelin, an orexigenic hormone produced mainly in the stomach, and Helicobacter pylori (H pylori), a bacterium that colonises the stomach, is still controversial. We examined available evidence to determine whether an association exists between the two; and if one exists, in what direction.

METHODS

We reviewed original English language studies on humans reporting circulating ghrelin levels in H pylori infected and un-infected participants; and circulating ghrelin levels before and after H pylori eradication. Meta-analyses were conducted for eligible studies by combining study specific estimates using the inverse variance method with weighted average for continuous outcomes in a random effects model.

RESULTS

Seventeen out of 27 papers that reported ghrelin levels in H pylori positive and negative subjects found lower circulating ghrelin levels in H pylori positive subjects; while 10 found no difference. A meta-analysis of 19 studies with a total of 1801 participants showed a significantly higher circulating ghrelin concentration in H pylori negative participants than in H pylori positive participants (Effect estimate (95%CI) = -0.48 (-0.60, -0.36)). However, eradicating H pylori did not have any significant effect on circulating ghrelin levels (Effect estimate (95% CI) = 0.08 (-0.33, 0.16); Test for overall effect: Z = 0.67 (P = 0.5)).

CONCLUSIONS

We conclude that circulating ghrelin levels are lower in H pylori infected people compared to those not infected; but the relationship between circulating ghrelin and eradication of H pylori is more complex.

Helicobacter pylori infection and circulating ghrelin levels - a systematic review

Background

The nature of the association between ghrelin, an orexigenic hormone produced mainly in the stomach, and Helicobacter pylori (H pylori), a bacterium that colonises the stomach, is still controversial. We examined available evidence to determine whether an association exists between the two; and if one exists, in what direction.

Methods

We reviewed original English language studies on humans reporting circulating ghrelin levels in H pylori infected and un-infected participants; and circulating ghrelin levels before and after H pylori eradication. Meta-analyses were conducted for eligible studies by combining study specific estimates using the inverse variance method with weighted average for continuous outcomes in a random effects model.

Results

Seventeen out of 27 papers that reported ghrelin levels in H pylori positive and negative subjects found lower circulating ghrelin levels in H pylori positive subjects; while 10 found no difference. A meta-analysis of 19 studies with a total of 1801 participants showed a significantly higher circulating ghrelin concentration in H pylori negative participants than in H pylori positive participants (Effect estimate (95%CI) = -0.48 (-0.60, -0.36)). However, eradicating H pylori did not have any significant effect on circulating ghrelin levels (Effect estimate (95% CI) = 0.08 (-0.33, 0.16); Test for overall effect: Z = 0.67 (P = 0.5)).

Conclusions

We conclude that circulating ghrelin levels are lower in H pylori infected people compared to those not infected; but the relationship between circulating ghrelin and eradication of H pylori is more complex.

The neurohormonal regulation of energy intake in relation to bariatric surgery for obesity

Obesity has reached pandemic proportions, with bariatric surgery representing the only currently available treatment demonstrating long-term effectiveness. Over 200,000 bariatric procedures are performed each year in the US alone. Given the reliable and singular success of bariatric procedures, increased attention is being paid to identifying the accompanying neurohormonal changes that may contribute to the resulting decrease in energy intake. Numerous investigations of postsurgical changes in gut peptides have been conducted, suggesting greater alterations in endocrine function in combination restrictive and malabsorptive procedures (e.g., Roux-en-Y gastric bypass) as compared to purely restrictive procedures (e.g., gastric banding), which may contribute to the increased effectiveness of combination procedures. However, very few studies have been performed and relatively little is known about changes in neural activation that may result from bariatric procedures, which likely interact with changes in gut peptides to influence postsurgical caloric intake. This review provides a background in the neurohormonal regulation of energy intake and discusses how differing forms of bariatric surgery may affect the neurohormonal network, with emphasis on Roux-en-Y gastric bypass, the most commonly performed procedure worldwide. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.

Superior appetite hormone profile after equivalent weight loss by gastric bypass compared to gastric banding

The goal of this study was to understand the mechanisms of greater weight loss by gastric bypass (GBP) compared to gastric banding (GB) surgery. Obese weight- and age-matched subjects were studied before (T0), after a 12 kg weight loss (T1) by GBP (n = 11) or GB (n = 9), and at 1 year after surgery (T2). peptide YY(3-36) (PYY(3-36)), ghrelin, glucagon-like peptide-1 (GLP-1), leptin, and amylin were measured after an oral glucose challenge. At T1, glucose-stimulated GLP-1 and PYY levels increased significantly after GBP but not GB. Ghrelin levels did not change significantly after either surgery. In spite of equivalent weight loss, leptin and amylin decreased after GBP, but not after GB. At T2, weight loss was greater after GBP than GB (P = 0.003). GLP-1, PYY, and amylin levels did not significantly change from T1 to T2; leptin levels continued to decrease after GBP, but not after GB at T2. Surprisingly, ghrelin area under the curve (AUC) increased 1 year after GBP (P = 0.03). These data show that, at equivalent weight loss, favorable GLP-1 and PYY changes occur after GBP, but not GB, and could explain the difference in weight loss at 1 year. Mechanisms other than weight loss may explain changes of leptin and amylin after GBP.

Mechanisms facilitating weight loss and resolution of type 2 diabetes following bariatric surgery

Bariatric surgery is the most effective treatment modality for obesity, resulting in durable weight loss and amelioration of obesity-associated comorbidities, particularly type 2 diabetes mellitus (T2DM). Moreover, the metabolic benefits of bariatric surgery occur independently of weight loss. There is increasing evidence that surgically induced alterations in circulating gut hormones mediate these beneficial effects of bariatric surgery. Here, we summarise current knowledge on the effects of different bariatric procedures on circulating gut hormone levels. We also discuss the theories that have been put forward to explain the weight loss and T2DM resolution following bariatric surgery. Understanding the mechanisms mediating these beneficial outcomes of bariatric surgery could result in new non-surgical treatment strategies for obesity and T2DM.

Bariatric surgery and the gut-brain communication--the state of the art three years later

OBJECTIVE

This review analyzes the literature concerning gut peptides and bariatric surgery, from 2005 to July 2009. In particular, we are interested in whether, and how, gastrointestinal peptide alterations following surgery interfere with appetite/satiety, and what role they might play in the resolution of comorbidities.

RESEARCH METHODS AND PROCEDURE

PubMed/MEDLINE and ISI Web of Knowledge were used to search for human studies concerning gut peptides profiles after any bariatric operation technique.

RESULTS

Most of the studies reviewed had longitudinal design, short follow-up, and low statistical power. The diversity of study results may be partially explained by methodological aspects. Glucagon-like peptide-1, gastric inhibitory peptide, and peptide YY alterations may contribute to the excellent results in glycemic control of diabetics. Results do vary depending on bariatric operation technique; this is particularly evident in the case of ghrelin, which has been much studied in recent years. Ghrelin suppression has been linked to increased satiety, alterations in energy homeostasis, and better glucose metabolism.

CONCLUSIONS

There is a lack of long-term data on gastrointestinal hormone profiles after bariatric surgery and the studies have many methodological pitfalls. We still need prospective, long-term, good methodological studies in this area.

Early effects of gastric banding (LGB) and of biliopancreatic diversion (BPD) on insulin sensitivity and on glucose and insulin response after OGTT

BACKGROUND

Bariatric surgery improves glucose metabolism.

METHODS

To assess the direct role of surgery (i.e., independently of significant weight loss) on insulin sensitivity (homeostasis model assessment (HOMA) insulin resistance (IR) and oral glucose insulin sensitivity (OGIS)), on glucose and insulin response (area under the curve (AUC) blood glucose (BG) and AUC insulin (Ins)) to oral glucose tolerance test (OGTT), and on glucose tolerance, 11 subjects underwent OGTT (75 g, p.o.) before and 5 days after laparoscopic gastric banding (LGB; no change of initial body mass index (BMI), 46.7 +/- 2.21 kg/m(2)), and ten subjects underwent OGTT before and 7 days after biliopancreatic diversion (BPD; BMI decreased from 54.5 +/- 3.75 to 52.1 +/- 4.03 kg/m(2)). As controls, we considered OGTT performed twice over a 30-45-day period in two groups of subjects [BMI 43.0 +/- 0.41 (n = 13, matched with LGB subjects for BMI) and 48.2 +/- 0.49 kg/m(2) (n = 14, matched with BPD subjects for BMI), respectively] with stable weight (+/-1.5 kg); a further control group was made of 11 subjects with a spontaneous weight loss similar to BPD subjects (BMI from 55.5 +/- 1.27 to 52.2 +/- 1.35 kg/m(2)).

RESULTS

Fasting BG and OGIS improved in BPD subjects and in subjects with spontaneous weight loss, not in LGB subjects or in weight-stable controls; HOMA-IR, AUC BG, and AUC Ins only decreased in BPD subjects. Glucose tolerance was not affected in a different way in the various groups of subjects.

CONCLUSIONS

These data indicate an early effect of BPD different from LGB on insulin sensitivity and on glucose and on insulin response to OGTT, mostly independent of weight loss.