Prospective study of gut hormone and metabolic changes after adjustable gastric banding and Roux-en-Y gastric bypass

Randomized double-blind placebo-controlled study of leptin administration after gastric bypass

OBJECTIVE

Obese individuals have high levels of circulating leptin and are resistant to the weight-reducing effect of leptin administration at physiological doses. Although Roux-en-Y gastric bypass (RYGB) is an effective weight loss procedure, there is a plateau in weight loss and most individuals remain obese. This plateau may be partly due to the decline in leptin resulting in a state of relative leptin insufficiency. The main objective of this study was to determine whether leptin administration to post-RYGB patients would promote further weight reduction.

DESIGN AND METHODS

This was a randomized, double-blind, placebo-controlled cross-over study of 27 women who were at least 18 months post-RYGB and lost on average 30.8% of their presurgical body weight. Subjects received either leptin or placebo via subcutaneous injection twice daily for 16 weeks, then crossed over to receive the alternate treatment for 16 weeks.

RESULTS

Weight change after 16 weeks of placebo was not significantly different from that after 16 weeks of leptin. No changes were observed in percent fat mass, resting energy expenditure, thyroid hormones, or cortisol levels.

CONCLUSION

Contrary to our hypothesis, we did not observe a significant effect of leptin treatment on body weight in women with relative hypoleptinemia after RYGB.

Roux-en-Y gastric bypass normalizes the blunted postprandial bile acid excursion associated with obesity

BACKGROUND

Bile acids (BAs) are nutrient-responsive hormones that modulate energy balance through cell surface and nuclear receptors. Postprandial plasma BAs have been found to be decreased in obesity.

OBJECTIVE

We aimed to determine whether meal-stimulated circulating BA levels are altered by Roux-en-Y gastric bypass (RYGB), an operation that modifies the neurohumoral determinants of food intake and energy expenditure to cause significant and durable weight loss.

DESIGN

Longitudinal study measuring fasting and postprandial plasma BAs before and after RYGB.

SUBJECTS

Five obese surgical patients and eight lean controls underwent frequent blood sampling after a standard liquid meal. Obese subjects were also tested at 1, 4 and 40 weeks after RYGB. Primary and secondary circulating BAs, as well as their glycine and taurine conjugates, were measured via reverse-phase high-performance liquid chromatography/mass spectroscopy.

RESULTS

We found that postprandial excursion of conjugated BAs was 52.4% lower in obese than in lean individuals by area-under-the-curve (AUC) analysis (378 vs 793 μmol min l(-1), respectively, P<0.05). By 40 weeks after RYGB, the meal-induced rise in conjugated BAs increased by 55.5% to the level of healthy lean controls (378 pre-op vs 850 μmol min l(-) post-op by AUC analyses, P<0.05). In contrast, postprandial concentrations of unconjugated BAs were similar in lean and obese individuals and were not affected by surgery.

CONCLUSION

In light of the growing evidence that BAs have key roles in glucose, lipid and energy homeostasis, the observation that RYGB normalizes the blunted postprandial circulating BA response in obesity suggests that BAs may contribute to the improvement in meal-related physiology seen after RYGB. Further studies are warranted to examine this hypothesis and to determine the degree to which an augmented BA response to nutrient ingestion may mediate the increased incretin response, brown adipose tissue activation and thermic effect of feeding that has been observed after this operation.

Metabolic surgery for type 2 diabetes: efficacy and risks

PURPOSE OF REVIEW

Bariatric surgery has emerged as a highly effective treatment for obesity and is increasingly recognized to have benefits for glycemic management in patients with pre-existing type 2 diabetes mellitus (T2DM), and for diabetes prevention. This article will review the efficacy and mechanisms of metabolic surgery for the treatment of T2DM.

RECENT FINDINGS

Recent small randomized studies with 1-2 years of follow-up begin to provide level 1 data of the effects of surgical procedures compared to medical management on glycemic control. Physiology studies using sophisticated metabolic techniques to evaluate insulin secretion, action, and entero-endocrine changes in patients preoperatively and postoperatively have shed light on the mechanisms that lead to changes in glycemia observed after bariatric surgery.

SUMMARY

Understanding the efficacy and physiologic effects of bariatric surgery on metabolism will help guide patient management in the context of a growing epidemic of obesity and T2DM, and may also ultimately enable us to develop less invasive but equally effective therapeutic strategies for weight loss and metabolic control.

Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient--2013 update: cosponsored by American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery

The development of these updated guidelines was commissioned by the AACE, TOS, and ASMBS Board of Directors and adheres to the AACE 2010 protocol for standardized production of clinical practice guidelines (CPG). Each recommendation was re-evaluated and updated based on the evidence and subjective factors per protocol. Examples of expanded topics in this update include: the roles of sleeve gastrectomy, bariatric surgery in patients with type-2 diabetes, bariatric surgery for patients with mild obesity, copper deficiency, informed consent, and behavioral issues. There are 74 recommendations (of which 56 are revised and 2 are new) in this 2013 update, compared with 164 original recommendations in 2008. There are 403 citations, of which 33 (8.2%) are EL 1, 131 (32.5%) are EL 2, 170 (42.2%) are EL 3, and 69 (17.1%) are EL 4. There is a relatively high proportion (40.4%) of strong (EL 1 and 2) studies, compared with only 16.5% in the 2008 AACE-TOS-ASMBS CPG. These updated guidelines reflect recent additions to the evidence base. Bariatric surgery remains a safe and effective intervention for select patients with obesity. A team approach to perioperative care is mandatory with special attention to nutritional and metabolic issues.

Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient--2013 update: cosponsored by American Association of Clinical Endocrinologists, the Obesity Society, and American Society for Metabolic & Bariatric Surgery

The development of these updated guidelines was commissioned by the AACE, TOS, and ASMBS Board of Directors and adheres to the AACE 2010 protocol for standardized production of clinical practice guidelines (CPG). Each recommendation was re-evaluated and updated based on the evidence and subjective factors per protocol. Examples of expanded topics in this update include: the roles of sleeve gastrectomy, bariatric surgery in patients with type-2 diabetes, bariatric surgery for patients with mild obesity, copper deficiency, informed consent, and behavioral issues. There are 74 recommendations (of which 56 are revised and 2 are new) in this 2013 update, compared with 164 original recommendations in 2008. There are 403 citations, of which 33 (8.2%) are EL 1, 131 (32.5%) are EL 2, 170 (42.2%) are EL 3, and 69 (17.1%) are EL 4. There is a relatively high proportion (40.4%) of strong (EL 1 and 2) studies, compared with only 16.5% in the 2008 AACE-TOS-ASMBS CPG. These updated guidelines reflect recent additions to the evidence base. Bariatric surgery remains a safe and effective intervention for select patients with obesity. A team approach to perioperative care is mandatory with special attention to nutritional and metabolic issues.

Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient--2013 update: cosponsored by American Association of Clinical Endocrinologists, the Obesity Society, and American Society for Metabolic & Bariatric Surgery

The development of these updated guidelines was commissioned by the AACE, TOS, and ASMBS Board of Directors and adheres to the AACE 2010 protocol for standardized production of clinical practice guidelines (CPG). Each recommendation was re-evaluated and updated based on the evidence and subjective factors per protocol. Examples of expanded topics in this update include: the roles of sleeve gastrectomy, bariatric surgery in patients with type-2 diabetes, bariatric surgery for patients with mild obesity, copper deficiency, informed consent, and behavioral issues. There are 74 recommendations (of which 56 are revised and 2 are new) in this 2013 update, compared with 164 original recommendations in 2008. There are 403 citations, of which 33 (8.2%) are EL 1, 131 (32.5%) are EL 2, 170 (42.2%) are EL 3, and 69 (17.1%) are EL 4. There is a relatively high proportion (40.4%) of strong (EL 1 and 2) studies, compared with only 16.5% in the 2008 AACE-TOS-ASMBS CPG. These updated guidelines reflect recent additions to the evidence base. Bariatric surgery remains a safe and effective intervention for select patients with obesity. A team approach to perioperative care is mandatory with special attention to nutritional and metabolic issues.

Ghrelin and eating disorders

There is growing evidence supporting a multifactorial etiology that includes genetic, neurochemical, and physiological components for eating disorders above and beyond the more conventional theories based on psychological and sociocultural factors. Ghrelin is one of the key gut signals associated with appetite, and the only known circulating hormone that triggers a positive energy balance by stimulating food intake. This review summarizes recent findings and several conflicting reports on ghrelin in eating disorders. Understanding these findings and inconsistencies may help in developing new methods to prevent and treat patients with these disorders.

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.

Interdisciplinary European Guidelines on metabolic and bariatric surgery

In 2012, an outstanding expert panel derived from IFSO-EC (International Federation for the Surgery of Obesity-European Chapter) and EASO (European Association for the Study of Obesity), composed by key representatives of both Societies including past and present presidents together with EASO's OMTF (Obesity Management Task Force) chair, agreed to devote the joint Medico-Surgical Workshop of both institutions to the topic of metabolic surgery as a pre-satellite of the 2013 European Congress on Obesity (ECO) to be held in Liverpool given the extraordinarily advancement made specifically in this field during the past years. It was further agreed to revise and update the 2008 Interdisciplinary European Guidelines on Surgery of Severe Obesity produced in cooperation of both Societies by focusing in particular on the evidence gathered in relation to the effects on diabetes during this lustrum and the subsequent changes that have taken place in patient eligibility criteria. The expert panel composition allowed the coverage of key disciplines in the comprehensive management of obesity and obesity-associated diseases, aimed specifically at updating the clinical guidelines to reflect current knowledge, expertise and evidence-based data on metabolic and bariatric surgery.

The novel GLP-1-gastrin dual agonist, ZP3022, increases β-cell mass and prevents diabetes in db/db mice

AIM

Diabetes is characterized by β-cell deficiency, and therefore restoration of β-cell function has been suggested as a potential therapy. We hypothesized that a novel glucagon-like peptide-1 (GLP-1)-gastrin dual agonist, ZP3022, improves glycaemic control via improvement of β-cell status in db/db mice.

METHODS

Diabetic mice were studied following short- or long-term treatment with either the GLP-1-gastrin dual agonist or the commercially available GLP-1 agonists (exendin-4 and liraglutide). The effects on glycaemic control were addressed by repeated glucose tolerance tests and/or measurements of HbA1c levels, and pancreatic islet and β-cell masses were determined by stereology.

RESULTS

ZP3022 and the pure GLP-1 agonists improved glycaemic control after both short- and long-term treatment compared with vehicle. Interestingly, the effect was sustainable only in mice treated with ZP3022. Stereology data displayed a dose-dependent increase of β-cell mass (p < 0.05) following treatment with ZP3022, whereas no significant effect of liraglutide was observed (β-cell mass: vehicle 3.7 ± 0.2 mg; liraglutide (30 nmol/kg) 3.4 ± 0.5 mg; ZP3022 (30 nmol/kg) 4.3 ± 0.4 mg and ZP3022 (100 nmol/kg) 5.2 ± 0.4 mg).

CONCLUSION

The novel GLP-1-gastrin dual agonist, ZP3022, improved glycaemic control in db/db mice, and pancreatic islet and β-cell mass increased significantly following treatment with ZP3022 compared with vehicle.

Roux-en-Y gastric bypass surgery increases number but not density of CCK-, GLP-1-, 5-HT-, and neurotensin-expressing enteroendocrine cells in rats

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery is very effective in reducing excess body weight and improving glucose homeostasis in obese subjects. Changes in the pattern of gut hormone secretion are thought to play a major role, but the mechanisms leading to both changed hormone secretion and beneficial effects remain unclear. Specifically, it is not clear whether changes in the number of hormone-secreting enteroendocrine cells, or changes in the releasing stimuli, or both, are important.

METHODS

We estimated numbers of enteroendocrine cells after immunohistochemical staining in fixed tissue samples from rats at 10-11 months after RYGB.

KEY RESULTS

Numbers of glucagon-like peptide-1 (GLP-1) (L-cells, co-expressing peptide YY (PYY)), cholecystokinin (CCK), neurotensin, and 5-HT-immunoreactive cells were significantly increased in the Roux and common limbs, but not the biliopancreatic limb in RYGB rats compared with sham-operated, obese rats fed high-fat diet, and chow-fed controls. This increase was mostly accounted for by general hyperplasia of all intestinal wall layers of the nutrient-perfused Roux and common limbs, and less to increased density of expression. The number of ghrelin cells in the bypassed stomach was not different among the three groups.

CONCLUSIONS & INFERENCES

The findings suggest that the number of enteroendocrine cells increases passively as the gut adapts, and that the increased total number of L- and I-cells is likely to contribute to the higher circulating levels of GLP-1, PYY, and CCK, potentially leading to suppression of food intake and stimulation of insulin secretion. Whether changes in releasing stimuli also contribute to altered circulating levels will have to be determined in future studies.

Peripheral Pathways in the Food-Intake Control towards the Adipose-Intestinal Missing Link

In the physiological state a multitude of gut hormones are released into the circulation at the same time depending on the quality and quantity of the diet. These hormones interact with receptors at various points in the "gut-brain axis" to affect short-term and intermediate-term feelings of hunger and satiety. The combined effects of macronutrients on the predominant gut hormone secretion are still poorly understood. Besides, adipokines form an important part of an "adipoinsular axis" dysregulation which may contribute to β -cell failure and hence to type 2 diabetes mellitus (T2DM). Even more, gestational diabetes mellitus (GDM) and T2DM seem to share a genetic basis. In susceptible individuals, chronic exaggerated stimulation of the proximal gut with fat and carbohydrates may induce overproduction of an unknown factor that causes impairment of incretin production and/or action, leading to insufficient or untimely production of insulin, so that glucose intolerance develops. The bypass of the duodenum and jejunum might avoid a putative hormone overproduction in the proximal foregut in diabetic patients that might counteract the action of insulin, while the early presentation of undigested or incompletely digested food to the ileum may anticipate the production of hormones such as GLP1, further improving insulin action.

Ghrelin, the proglucagon-derived peptides and peptide YY in nutrient homeostasis

Dysregulation of nutrient homeostasis is implicated in the current epidemics of obesity and type 2 diabetes mellitus. The maintenance of homeostasis in the setting of repeated cycles of feeding and fasting occurs through complex interactions between metabolic, hormonal and neural factors. Although pancreatic islets, the liver, muscle, adipocytes and the central nervous system are all key players in this network, the gastrointestinal tract is the first tissue exposed to ingested nutrients and thus has an important role. This Review focuses on several of the endocrine hormones released by the gastrointestinal tract prior to or during nutrient ingestion that have key roles in maintaining energy balance. These hormones include the gastric orexigenic hormone, ghrelin, and the distal L cell anorexigenic and metabolic hormones, glucagon-like peptide (GLP)-1, GLP-2, oxyntomodulin and peptide YY. Each of these hormones exerts a distinct set of biological actions to maintain nutrient homeostasis, the properties of which are currently, or might soon be, exploited in the clinic for the treatment of obesity and type 2 diabetes mellitus.

Suppression of food intake by glucagon-like peptide-1 receptor agonists: relative potencies and role of dipeptidyl peptidase-4

Administration of the glucagon-like peptide-1 (GLP-1) receptor agonists GLP-1 and exendin-4 (Ex-4) directly into the central nervous system decreases food intake. But although Ex-4 potently suppresses food intake after peripheral administration, the effects of parenteral GLP-1 are variable and not as strong. A plausible explanation for these effects is the rapid inactivation of circulating GLP-1 by dipeptidyl peptidase-4 (DPP-4), an enzyme that does not alter Ex-4 activity. To test this hypothesis, we assessed the relative potency of Ex-4 and GLP-1 under conditions in which DPP-4 activity was reduced. Outbred rats, wild-type mice, and mice with a targeted deletion of DPP-4 (Dpp4(-/-)) were treated with GLP-1 alone or in combination with the DPP-4 inhibitor vildagliptin, Ex-4, or saline, and food intake was measured. GLP-1 alone, even at high doses, did not affect feeding in wild-type mice or rats but did reduce food intake when combined with vildagliptin or given to Dpp4(-/-) mice. Despite plasma clearance similar to DPP-4-protected GLP-1, equimolar Ex-4 caused greater anorexia than vildagliptin plus GLP-1. To determine whether supraphysiological levels of endogenous GLP-1 would suppress food intake if protected from DPP-4, rats with Roux-en-Y gastric bypass and significantly elevated postprandial plasma GLP-1 received vildagliptin or saline. Despite 5-fold greater postprandial GLP-1 in these animals, vildagliptin did not affect food intake in Roux-en-Y gastric bypass rats. Thus, in both mice and rats, peripheral GLP-1 reduces food intake significantly less than Ex-4, even when protected from DPP-4. These findings suggest distinct potencies of GLP-1 receptor agonists on food intake that cannot be explained by plasma pharmacokinetics.

ESR1 gene and insulin resistance remission are associated with serum uric acid decline for severely obese patients undergoing bariatric surgery

BACKGROUND

Hyperuricemia is associated with obesity. Few studies have reported the effects of different types of bariatric surgery on uric acid metabolism. The aim of our study was to determine the relationships between serum uric acid reduction and estrogen receptor-α (ESR1) gene polymorphism, as well as the type of bariatric surgery received. The potential physiological pathways involved in postsurgery serum uric acid reduction were also discussed.

METHODS

A total of 508 severely obese Han Chinese patients, aged 20 to 50 years, with a body mass index (BMI)≥35 kg/m(2) were selected. Patients received either laparoscopic adjustable gastric banding (LAGB; n = 164) or laparoscopic mini-gastric bypass (LMGB; n = 344). A 12-month follow-up was performed to explore the effects of the type of bariatric surgery and ESR1 polymorphism on serum uric acid reduction.

RESULTS

The rs712221 polymorphism of ESR1 affects serum uric acid reduction after bariatric surgery. The LMGB group exhibited a greater reduction in serum uric acid level compared with the LAGB counterpart after adjusting for sex, age, and metabolic confounders (-2.3 ± 2.1 mg/dL versus-1.2 ± 1.1 mg/dL; P = .002). Patients with the rs712221 genotype exhibited better glycemic control and a greater serum uric acid reduction at 12 months after surgery. The effects of the rs712221 polymorphism in LMGB patients resulted in the greatest serum uric acid reduction (-2.7 ± 1.4 mg/dL).

CONCLUSIONS

For severely obese Han Chinese patients, bariatric surgery appears to reduce serum uric acid levels, potentially mediated by synergic effects of surgery type, BMI reduction, rs712221 locus, insulin sensitivity, and changed dietary factors via an unknown mechanism.

Alcohol reward is increased after Roux-en-Y gastric bypass in dietary obese rats with differential effects following ghrelin antagonism

Roux-en-Y gastric bypass (RYGB) is one of the most successful treatments for severe obesity and associated comorbidities. One potential adverse outcome, however, is increased risk for alcohol use. As such, we tested whether RYGB alters motivation to self-administer alcohol in outbred dietary obese rats, and investigated the involvement of the ghrelin system as a potential underlying mechanism. High fat (60%kcal from fat) diet-induced obese, non-diabetic male Sprague Dawley rats underwent RYGB (n = 9) or sham operation (Sham, n = 9) and were tested 4 months after surgery on a progressive ratio-10 (PR10) schedule of reinforcement operant task for 2, 4, and 8% ethanol. In addition, the effects of the ghrelin-1a-receptor antagonist D-[Lys3]-GHRP-6 (50, 100 nmol/kg, IP) were tested on PR10 responding for 4% ethanol. Compared to Sham, RYGB rats made significantly more active spout responses to earn reward, more consummatory licks on the ethanol spout, and achieved higher breakpoints. Pretreatment with a single peripheral injection of D-[Lys3]-GHRP-6 at either dose was ineffective in altering appetitive or consummatory responses to 4% ethanol in the Sham group. In contrast, RYGB rats demonstrated reduced operant performance to earn alcohol reward on the test day and reduced consummatory responses for two subsequent days following the drug. Sensitivity to threshold doses of D-[LYS3]-GHRP-6 suggests that an augmented ghrelin system may contribute to increased alcohol reward in RYGB. Further research is warranted to confirm applicability of these findings to humans and to explore ghrelin-receptor targets for treatment of alcohol-related disorders in RYGB patients.

Advances in the surgical treatment of morbid obesity

Due to the rapidly expanding prevalence of obesity, bariatric surgery is becoming an increasingly popular treatment option. Bariatric surgeries including Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) produce long-term weight loss and metabolic improvement, reducing mortality. This review discusses the important benefits and risks of RYGB and VSG, highlighting hypothesized mechanisms for these effects. We present data suggesting that VSG, albeit a newer procedure, may be as effective as RYGB with fewer adverse effects including less surgical risk, reduced nutritional deficiency, and less incidence of dumping syndrome. This may position VSG as an increasingly important procedure, particularly for the treatment of pediatric obesity.

Effect of vertical sleeve gastrectomy on food selection and satiation in rats

Vertical sleeve gastrectomy (VSG) is a restrictive procedure that reduces food intake to produce weight loss. Here we assess volume and nutrient effects on the ingestive behavior of VSG and sham surgery animals. Rats given access to Ensure or pelleted chow were used to determine if liquid foods would adversely affect weight loss after surgery. Volume effects were studied by altering the caloric density of Ensure, and dietary preferences for fat and carbohydrate (sucrose) were assessed using a two-bottle test. c-Fos was used to measure neuronal activation in the nucleus of the solitary tract and area postrema in response to intragastric infusions of water, sucrose, or Intralipid. The degree of colocalization with catecholaminergic neurons was also assessed. VSG rats did not show the expected preference for a liquid diet over chow and lacked dietary preferences for fat seen in shams. Preferences for carbohydrate/sucrose solutions were unaffected by surgery. Meal size was reduced by VSG; however, VSG rats were able to alter their volume of intake to compensate for changes in caloric density, and intragastric infusions of water produced similar levels of neuronal activation among VSG, sham, and pair-fed rats. In comparison, nutrient-induced c-Fos activation was substantially increased by VSG. Colocalization between c-Fos and catecholaminergic-expressing neurons was similar among rats treated with water, sucrose, or Intralipid. VSG alters nutrient sensing in a manner that lowers the threshold for satiety and reduces fat preference to induce and maintain weight loss.

Effects of bariatric surgery on glucose homeostasis and type 2 diabetes

Obesity is an important risk factor for type 2 diabetes mellitus (T2DM). Weight loss improves the major factors involved in the pathogenesis of T2DM, namely insulin action and beta cell function, and is considered a primary therapy for obese patients who have T2DM. Unfortunately, most patients with T2DM fail to achieve successful weight loss and adequate glycemic control from medical therapy. In contrast, bariatric surgery causes marked weight loss and complete remission of T2DM in most patients. Moreover, bariatric surgical procedures that divert nutrients away from the upper gastrointestinal tract are more successful in producing weight loss and remission of T2DM than those that simply restrict stomach capacity. Although upper gastrointestinal tract bypass procedures alter the metabolic response to meal ingestion, by increasing early postprandial plasma concentrations of glucagon-like peptide 1 and insulin, it is not clear whether these effects make an important contribution to long-term control of glycemia and T2DM once substantial surgery-induced weight loss has occurred. Nonetheless, the effects of surgery on body weight and metabolic function indicate that bariatric surgery should be part of the standard therapy for T2DM. More research is needed to advance our understanding of the physiological effects of different bariatric surgical procedures and possible weight loss-independent factors that improve metabolic function and contribute to the resolution of T2DM.

Bariatric surgery and the central nervous system

Bariatric procedures are now known to have an effect on hunger as well as on metabolism. The role of central nervous pathways in causing these effects after bariatric surgery is now being elucidated. A brief overview of these pathways has been presented for the sake of bariatric surgeons. A PubMed search was made using various search phrases to retrieve all original articles concerning the effect of bariatric surgery on the neural pathways. The mechanisms regulating the food intake and energy expenditure can be broadly divided into homeostatic and hedonic systems. The effect of bariatric surgery on the homeostatic system in animal models is not clear. A decrease in preference for sweet taste and high calorie foods has been demonstrated in animal models. The effect of bariatric surgery on the hedonic system in humans has been consistent with decreased activation of the hedonic system being demonstrated by functional MRI and decreased preference for intake of high energy foods also being observed post-surgery. The effect of bariatric surgery on dopamine signaling, which is involved in the hedonic system, is however not clear. Functional MRI studies have also demonstrated increased activation of the hypothalamus after surgery. Various studies utilizing questionnaires have demonstrated increased satiety and decreased hunger after bariatric surgery.

Neural responsivity to food cues in fasted and fed states pre and post gastric bypass surgery

Reductions in mesolimbic responsivity have been noted following Roux-en-Y gastric bypass (RYGB; Ochner et al., 2011a). Given potential for postoperative increases in postprandial gut (satiety) peptides to affect mesolimbic neural responsivity, we hypothesized that: (1) post RYGB changes in mesolimbic responsivity would be greater in the fed relative to the fasted state and; (2) fasted vs. fed state differences in mesolimbic responsivity would be greater post-relative to pre-surgery. fMRI was used to asses neural responsivity to high- and low-calorie food cues in five women 1 mo pre- and 1 mo post-RYGB. Scans were repeated in fasted and fed states. Significant post RYGB decreases in the insula, ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC) responsivity were found in the fasted state. These changes were larger than neural changes in the fed state, which were non-significant. Preoperatively, fasted vs. fed differences in neural responsivity were greater in the precuneus, with large but nonsignificant clusters in the vmPFC and dlPFC. Postoperatively, however, no fasted vs. fed differences in neural responsivity were noted. Results were opposite to that predicted and appear inconsistent with the initial hypothesis that postoperative increases in postprandial gut peptides are the primary driver of postoperative changes in neural responsivity.

Obesity and appetite control

Obesity is one of the major challenges to human health worldwide; however, there are currently no effective pharmacological interventions for obesity. Recent studies have improved our understanding of energy homeostasis by identifying sophisticated neurohumoral networks which convey signals between the brain and gut in order to control food intake. The hypothalamus is a key region which possesses reciprocal connections between the higher cortical centres such as reward-related limbic pathways, and the brainstem. Furthermore, the hypothalamus integrates a number of peripheral signals which modulate food intake and energy expenditure. Gut hormones, such as peptide YY, pancreatic polypeptide, glucagon-like peptide-1, oxyntomodulin, and ghrelin, are modulated by acute food ingestion. In contrast, adiposity signals such as leptin and insulin are implicated in both short- and long-term energy homeostasis. In this paper, we focus on the role of gut hormones and their related neuronal networks (the gut-brain axis) in appetite control, and their potentials as novel therapies for obesity.

All bariatric surgeries are not created equal: insights from mechanistic comparisons

Despite considerable scientific progress on the biological systems that regulate energy balance, we have made precious little headway in providing new treatments to curb the obesity epidemic. Diet and exercise are the most popular treatment options for obesity, but rarely are they sufficient to produce long-term weight loss. Bariatric surgery, on the other hand, results in dramatic, sustained weight loss and for this reason has gained increasing popularity as a treatment modality for obesity. At least some surgical approaches also reduce obesity-related comorbidities including type 2 diabetes and hyperlipidemia. This success puts a premium on understanding how these surgeries exert their effects. This review focuses on the growing human and animal model literature addressing the underlying mechanisms. We compare three common procedures: Roux-en-Y Gastric Bypass (RYGB), vertical sleeve gastrectomy (VSG), and adjustable gastric banding (AGB). Although many would group together VSG and AGB as restrictive procedures of the stomach, VSG is more like RYGB than AGB in its effects on a host of endpoints including intake, food choice, glucose regulation, lipids and gut hormone secretion. Our strong belief is that to advance our understanding of these procedures, it is necessary to group bariatric procedures not on the basis of surgical similarity but rather on how they affect key physiological variables. This will allow for greater mechanistic insight into how bariatric surgery works, making it possible to help patients better choose the best possible procedure and to develop new therapeutic strategies that can help a larger portion of the obese population.

Obesity and appetite control

Obesity is one of the major challenges to human health worldwide; however, there are currently no effective pharmacological interventions for obesity. Recent studies have improved our understanding of energy homeostasis by identifying sophisticated neurohumoral networks which convey signals between the brain and gut in order to control food intake. The hypothalamus is a key region which possesses reciprocal connections between the higher cortical centres such as reward-related limbic pathways, and the brainstem. Furthermore, the hypothalamus integrates a number of peripheral signals which modulate food intake and energy expenditure. Gut hormones, such as peptide YY, pancreatic polypeptide, glucagon-like peptide-1, oxyntomodulin, and ghrelin, are modulated by acute food ingestion. In contrast, adiposity signals such as leptin and insulin are implicated in both short- and long-term energy homeostasis. In this paper, we focus on the role of gut hormones and their related neuronal networks (the gut-brain axis) in appetite control, and their potentials as novel therapies for obesity.

Association of ghrelin receptor promoter polymorphisms with weight loss following Roux-en-Y gastric bypass surgery

BACKGROUND

Ghrelin plays a role in appetite and has been hypothesized to play a role in the mechanism of Roux-en-Y gastric bypass (RYGB) surgery. Single nucleotide polymorphisms (SNPs) in the promoter region of its receptor gene (growth hormone secretagogue receptor type 1a--GHSR) have also been associated with weight loss outcomes following long-term dietary intervention in adults with impaired glucose tolerance. Our objectives were to evaluate changes in serum ghrelin levels and determine the effect of GHSR promoter polymorphisms on post-RYGB surgery weight loss.

METHODS

Preoperative and 6-month postoperative serum ghrelin levels were measured in 37 patients with extreme obesity undergoing RYGB surgery. Total ghrelin was also measured in liver tissue collected intraoperatively. Association analysis between genotypes for SNPs rs9819506 and rs490683 in the promoter region of the GHSR gene and weight loss outcomes in the 30 months following surgery was performed in over 650 RYGB patients.

RESULTS

Serum ghrelin levels increased after RYGB surgery. Weight loss trajectories were significantly different using an additive model for both ghrelin SNPs, with patients homozygous for the rs490683 CC genotype exhibiting the most weight loss. Weight loss trajectories were also different using a dominant model. The rs490683 risk allele demonstrated decreased promoter activity in vitro.

CONCLUSIONS

The role of increased ghrelin levels in weight loss outcomes following RYGB surgery may be influenced by variation in the GHSR gene.

Gut microbial communities modulating brain development and function

Mammalian brain development is initiated in utero and internal and external environmental signals can affect this process all the way until adulthood. Recent observations suggest that one such external cue is the indigenous microbiota which has been shown to affect developmental programming of the brain. This may have consequences for brain maturation and function that impact on cognitive functions later in life. This review discusses these recent findings from a developmental perspective.

Mechanisms of improved glycaemic control after Roux-en-Y gastric bypass

Roux-en-Y gastric bypass (RYGB) greatly improves glycaemic control in morbidly obese patients with type 2 diabetes, in many even before significant weight loss. Understanding the responsible mechanisms may contribute to our knowledge of the pathophysiology of type 2 diabetes and help identify new drug targets or improve surgical techniques. This review summarises the present knowledge based on pathophysiological studies published during the last decade. Taken together, two main mechanisms seem to be responsible for the early improvement in glycaemic control after RYGB: (1) an increase in hepatic insulin sensitivity induced, at least in part, by energy restriction and (2) improved beta cell function associated with an exaggerated postprandial glucagon-like peptide 1 secretion owing to the altered transit of nutrients. Later a weight loss induced improvement in peripheral insulin sensitivity follows.

Bariatric surgery for type 2 diabetes

Bariatric surgery provides substantial, sustained weight loss and major improvements in glycaemic control in severely obese individuals with type 2 diabetes. However, uptake of surgery in eligible patients is poor, and the barriers are difficult to surmount. We examine the indications for and efficacy and safety of conventional bariatric surgical procedures and their effect on glycaemic control in type 2 diabetes. How surgical gastrointestinal interventions achieve these changes is of great research interest, and is evolving rapidly. Old classifications about restriction and malabsorption are inadequate, and we explore understanding of putative mechanisms. Some bariatric procedures improve glycaemic control in people with diabetes beyond that expected for weight loss, and understanding this additional effect could provide insights into the pathogenesis of type 2 diabetes and assist in the development of new procedures, devices, and drugs both for obese and non-obese patients.

Effects of leptin replacement alone and with exendin-4 on food intake and weight regain in weight-reduced diet-induced obese rats

Weight loss in obese humans produces a relative leptin deficiency, which is postulated to activate potent orexigenic and energy conservation mechanisms to restrict weight loss and promote weight regain. Here we determined whether leptin replacement alone or with GLP-1 receptor agonist exendin-4 attenuates weight regain or promotes greater weight loss in weight-reduced diet-induced obese (DIO) rats. Forty percent restriction in daily intake of a high-fat diet in DIO rats for 4 wk reduced body weight by 12%, body fat by 29%, and plasma leptin by 67% and normalized leptin sensitivity. When food restriction ended, body weight, body fat, and plasma leptin increased rapidly. Daily administration of leptin [3-h intraperitoneal (ip) infusions (4 nmol·kg(-1)·h(-1))] at onset and end of dark period for 3 wk did not attenuate hyperphagia and weight regain, nor did it affect mean daily meal sizes or meal numbers. Exendin-4 (50 pmol·kg(-1)·h(-1)) infusions during the same intervals prevented postrestriction hyperphagia and weight regain by normalizing meal size. Coadministration of leptin and exendin-4 did not reduce body weight more than exendin-4 alone. Instead, leptin began to attenuate the inhibitory effects of exendin-4 on food intake, meal size, and weight regain by the end of the second week of administration. Plasma leptin in rats receiving leptin was sevenfold greater than in rats receiving vehicle and 17-fold greater than in rats receiving exendin-4. Together, these results do not support the hypothesis that leptin replacement alone or with exendin-4 attenuates weight regain or promotes greater weight loss in weight-reduced DIO rats.

100 obese patients after laparoscopic adjustable gastric banding - the influence on BMI, gherlin and insulin concentration, parameters of lipid balance and co-morbidities

PURPOSE

Obesity is a widespread health issue caused by chronic impaired balance between energy supply and its expenditure. It leads to gathering of excessive fat tissue and numerous co-morbidities.The aim of this study is to present the influence of laparoscopic adjustable gastric banding (LAGB) on plasma ghrelin, insulin, glucose, triglycerides, total, HDL- and LDL-cholesterol concentration as well as on alanine and aspartate aminotransferase in obese patients and influence on co-morbidities such as type 2 diabetes mellitus, dislipidemy, hypertension and sleep apnea.

MATERIALS AND METHODS

100 obese patients underwent LAGB: 34 men - average age 39.18 ± 12.17 years old and 66 women - average age 37.0 ± 12.6 years old. During 6 months follow-up, particular measurements have been conducted in different time points. Evaluation of body mass loss (%EWL, %EBL) and the homeostatic model assessment insulin resistance (HOMA IR) was conducted. In the same time ghrelin, insulin, glucose, triglycerides, total cholesterol, HDL- and LDL-cholesterol concentration was determined after 7 days, 1, 3 and 6 months after the surgery.

RESULTS

Significant decrease in BMI and HOMA IR was observed as well as in insulin and glucose concentration. Increase in ghrelin concentration in comparison to preoperative values was also stated.

CONCLUSIONS

LAGB leads to significant body mass loss, improvement in patients' general health state and to normalization of metabolic parameters. Improvement or total resolution of type 2 diabetes (T2DM), hypertension and sleep apnea was also noticed.

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.

Insulin resistance and bariatric surgery

The objective of this article is to systematically review the changes in insulin resistance after various types of bariatric surgical procedures. A Pubmed and EMBASE search for studies measuring insulin resistance before and after bariatric surgery was done and all original research articles from 1980 to present (2011) were included. Only the currently widely performed bariatric procedures were included. A meta-analysis of change in HOMA-IR was conducted, grouping studies with similar duration of follow-up. The percentage decrease in HOMA-IR at <=2 weeks, 1 month, 3 months, 6 months, 12 months and >16-18 months was found to be (mean ± standard error) -33.48 ± 5.78, -46.43 ± 6.99, -38.79 ± 9.64, -58.62 ± 7.38, -44.91 ± 7.98 and -67.04 ± 10.78%, respectively. RYGB (gastric bypass) and BPD (biliopancreatic diversion) produced a significant decrease in insulin resistance at 2 weeks after surgery, while LSG (sleeve gastrectomy) was strongly trending. LSG produced an earlier decrease in insulin resistance when compared to LAGB (gastric banding). RYGB, BPD and LSG produce an early decrease in insulin resistance through yet unknown mechanisms.

Vagal innervation of the hepatic portal vein and liver is not necessary for Roux-en-Y gastric bypass surgery-induced hypophagia, weight loss, and hypermetabolism

OBJECTIVE

To determine the role of the common hepatic branch of the abdominal vagus on the beneficial effects of Roux-en-Y gastric bypass (RYGB) on weight loss, food intake, food choice, and energy expenditure in a rat model.

BACKGROUND

Although changes in gut hormone patterns are the leading candidates in RYGB's effects on appetite, weight loss, and reversal of diabetes, a potential role for afferent signaling through the vagal hepatic branch potentially sensing glucose levels in the hepatic portal vein has recently been suggested in a mouse model of RYGB.

METHODS

Male Sprague-Dawley rats underwent either RYGB alone (RYGB; n = 7), RYGB + common hepatic branch vagotomy (RYGB + HV; n = 6), or sham procedure (sham; n = 9). Body weight, body composition, meal patterns, food choice, energy expenditure, and fecal energy loss were monitored up to 3 months after intervention.

RESULTS

Both RYGB and RYGB + HV significantly reduced body weight, adiposity, meal size, and fat preference, and increased satiety, energy expenditure, and respiratory exchange rate compared with sham procedure, and there were no significant differences in these effects between RYGB and RYGB + HV rats.

CONCLUSIONS

Integrity of vagal nerve supply to the liver, hepatic portal vein, and the proximal duodenum provided by the common hepatic branch is not necessary for RYGB to reduce food intake and body weight or increase energy expenditure. Specifically, it is unlikely that a hepatic portal vein glucose sensor signaling RYGB-induced increased intestinal gluconeogenesis to the brain depends on vagal afferent fibers.

A review of studies comparing three laparoscopic procedures in bariatric surgery: sleeve gastrectomy, Roux-en-Y gastric bypass and adjustable gastric banding

Obesity is a major worldwide problem in public health, reaching epidemic proportions in many countries, especially in urbanized regions. Bariatric procedures have been shown to be more effective in the management of morbid obesity, compared to medical treatments in terms of weight loss and its sustainability. The two most commonly performed procedures are laparoscopic Roux-en-Y gastric bypass (LRYGB), laparoscopic adjustable gastric banding (LAGB), and the novel laparoscopic sleeve gastrectomy (LSG). The MEDLINE database (cutoff date September 2010), LILACS, and the Cochrane Library were searched using the key words "gastric bypass," "sleeve gastrectomy," and "gastric banding." Only studies that compared at least two of the laparoscopic procedures were included. Reviews and meta-analysis, editorial letters or comments, case reports, animal or in vitro studies, comparisons with medical treatment, comparisons with open (non-laparoscopic) procedures were excluded. Most studies indicated that LRYGB and LSG could be more effective achieving weight loss than LAGB. However, LAGB seems to be a safer procedure with frequent, but less severe, long-term complications. Although not uniformly reported, a resolution of obesity-related comorbidities was achieved with most bariatric procedures. The three procedures have acceptable efficacy and safety. We believe that patients should be informed in detail on the advantages and disadvantages of each available procedure, possibly in several interviews and always accompanied by a specialized interdisciplinary team, warranting long-term follow-up.

Effect of bypassing the proximal gut on gut hormones involved with glycemic control and weight loss

BACKGROUND

The reported remission of type 2 diabetes in patients undergoing Roux-en-Y gastric bypass has brought the role of the gut in glucose metabolism into focus. Our objective was to explore the differential effects on glucose homeostasis after oral versus gastrostomy glucose loading in patients with Roux-en-Y gastric bypass at an academic health science center.

METHODS

A comparative controlled investigation of oral versus gastrostomy glucose loading in 5 patients who had previously undergone gastric bypass and had a gastrostomy tube placed in the gastric remnant for feeding. A standard glucose load was administered either orally (day 1) or by the gastrostomy tube (day 2). The plasma levels of glucose, insulin, glucagon-like peptide 1 and peptide YY were measured before and after glucose loading.

RESULTS

Exclusion of the proximal small bowel from glucose passage induced greater plasma insulin, glucagon-like peptide 1, and peptide YY responses compared with glucose loading by way of the gastrostomy tube (P <.05).

CONCLUSIONS

Exclusion of glucose passage through the proximal small bowel results in enhanced insulin and gut hormone responses in patients after gastric bypass. The gut plays a central role in glucose metabolism and represents a target for future antidiabetes therapies.

Hypothalamic obesity in patients with craniopharyngioma: treatment approaches and the emerging role of gastric bypass surgery

Hypothalamic obesity is a potential sequela of craniopharyngioma, arising from hypothalamic damage inflicted by either the tumor and/or its treatment. The marked weight gain that characterizes this disorder appears to result from impaired sympathoadrenal activation, parasympathetic dysregulation, and other hormonal and hypothalamic disturbances that upset the balance between energy intake and expenditure. Given hypopituitarism is commonly present, careful management of hormonal deficits is important for weight control in these patients. In addition, diet, exercise, and pharmacotherapy aimed at augmenting sympathetic output, controlling hyperinsulinism, and promoting weight loss have been used to treat this disease, but these measures rarely lead to sustained weight loss. While surgical interventions have not routinely been pursued, emerging data suggests that surgical weight loss interventions including Roux-en-Y gastric bypass can be safely and effectively used for the management of hypothalamic obesity in patients with craniopharyngioma.

Early outcomes of bariatric surgery in patients with metabolic syndrome: an analysis of the bariatric outcomes longitudinal database

BACKGROUND

Metabolic syndrome (MetS) complicating obesity is endemic in the United States.

STUDY DESIGN

Bariatric Outcomes Longitudinal Database, the national database for the American Society for Metabolic and Bariatric Surgery Bariatric Surgery Center of Excellence Program, was queried to identify patients undergoing bariatric surgery from June 2007 through November 2010. MetS was defined as the presence of hypertension, diabetes, and dyslipidemia at presentation for bariatric surgery. Ninety-day and 1-year outcomes were assessed to determine early outcomes in bariatric surgery patients with MetS.

RESULTS

Among 186,576 research-consented patients, 23,106 (12%) were diagnosed with MetS. Patients with MetS were more likely to be male (35% vs 20%; p < 0.0001), older (mean age 54 vs 44 years; p < 0.0001), and Caucasian (81% vs 74%; p < 0.0001). Of the 23,106 MetS patients, more underwent gastric bypass (RYGB) (62%) compared with gastric banding (32%), sleeve gastrectomy (4.5%), and biliopancreactic diversion with duodenal switch (BPD/DS)(1.5%). MetS patients had an increase in serious complications (2.4% vs 1.0%; p < 0.0001), readmissions (6.2% vs 4.7%; p < 0.0001), and mortality (0.3% vs 0.1%; p < 0.0001) within 90 days of operation. After adjusting for sex, age, and body mass index, RYGB patients with MetS had an increased risk of 90-day serious complications compared to RYGB patients without MetS (odds ratio 1.43; 95% CI, 1.27 to 1.61; p < 0.0001). The 12-month remission rate of diabetes was least for gastric banding (28%) compared with the other procedures (RYGB 62%, sleeve gastrectomy 52%, BPD/DS 74%).

CONCLUSIONS

Patients with MetS undergoing bariatric surgery showed dramatic improvement in diabetes 1-year after surgery; however, an adverse 90-day outcome was more common.

Diabetes remission and insulin secretion after gastric bypass in patients with body mass index <35 kg/m2

BACKGROUND

Most morbidly obese patients who undergo gastric bypass experience rapid remission of type 2 diabetes mellitus (T2DM) but the response in non-morbidly obese patients is not clear. This trial prospectively assessed the effect of diabetes remission, glucose metabolism, and the serial changes of insulin secretion after gastric bypass in inadequately controlled T2DM patients with a BMI of 23-35 kg/m(2).

METHODS

A total of 62 consecutive patients with T2DM and a BMI of 23-35 kg/m(2) underwent gastric bypass. Data were prospectively collected before surgery and 1, 4, 12, 26, and 52 weeks and 2 years after surgery. Insulin secretion was measured by insulinogenic index and area under the curve (AUC) during a standard oral glucose tolerance test (OGTT). Remission of type 2 diabetes was defined as fasting glucose level <110 mg/dl and HbA1c <6.0% without any glycemic therapy.

RESULTS

Of the 62 patients, 24 were men and 38 were women (age 43.1 ± 10.8 years). Their preoperative characteristics were as follows: BMI 30.1 ± 3.3 kg/m(2), waist circumference 99.6 ± 9.6 cm, C-peptide 3.1 ± 1.4 ng/ml, and duration of T2DM 5.4 ± 5.1 years. The mean BMI decreased postoperatively to 22.6 ± 2.3 kg/m(2) in 1 year and 23.0 ± 2.7 kg/m(2) in 2 years. The mean HbA1c decreased from 9.7 ± 1.9% to 5.8 ± 0.5% in 1 year and 5.9 ± 0.5% in 2 years. Complete remission of T2DM was achieved in 57% in 1 year and 55% in 2 years after surgery. Before surgery, the OGTT test showed a blunted insulin secretion pattern with an insulinogenic index of 0.1 ± 0.2 and AUC of 2,324 ± 1,015 μIU min/ml. In 1 week after surgery, the insulinogenic index increased to 0.16 and AUC decreased to 1,366 μIU min/ml along with a rapid drop of insulin resistance. The insulinogenic index and AUC gradually increased to 0.27 and 3,220, respectively, 1 year after surgery and remained stable up to 2 years with a very low insulin resistance.

CONCLUSIONS

Laparoscopic gastric bypass facilitates immediate improvement in the glucose metabolism of inadequately controlled non-severe obese T2DM patients, and the benefit is sustained up to 2 years after surgery. The benefit is regulated by the decrease in insulin resistance, increase in early insulin response, and total insulin secretion to glucose load.

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.

Effects of bariatric surgery on food cravings: do food cravings and the consumption of craved foods "normalize" after surgery?

BACKGROUND

The reported effects of bariatric surgery on food cravings have been inconsistent. Moreover, research has been largely limited to sweet cravings, and no study has examined whether surgery patients' cravings differ from those of normal weight (NW) controls. Our objective was to use an empirically validated instrument to examine changes in bariatric surgery patients' frequency of food cravings and consumption of craved foods from before to 3 and 6 months after surgery and to compare surgery patients' frequency of food cravings to those of NW controls. The setting was private hospitals and research center in the United States.

METHODS

Bariatric surgery patients (n = 32) and NW controls (n = 20) completed the Food Cravings Inventory and had their height and weight measured.

RESULTS

Before surgery, the patients reported more overall cravings and cravings for high fat and fast foods and a greater consumption of craved high-fat foods than the NW controls. From before to 3 and 6 months after surgery, the patients had significant reductions in overall cravings for, and consumption of, craved foods, with specific effects for sweets and fast food; however, surgery had virtually no effect on the cravings for high-fat foods. Moreover, high-fat and fast food cravings did not reduce to normative levels. The postoperative patients were less likely to consume craved sweets than NW controls, and the patients' postoperative weight loss was largely unrelated to food cravings.

CONCLUSION

Bariatric surgery is associated with significant reductions in food cravings and consumption of craved foods, with the exception of high-fat foods. Despite these decreases, patients' cravings do not fully reduce to "normative" levels and are not associated with postoperative weight loss.

The role of ghrelin in the control of energy balance

Ghrelin is the only potent orexigenic peptide in circulation. It stimulates food intake and leads to positive energy balance, adipogenesis, and body weight gain. However, the physiological significance of ghrelin in the regulation of energy homeostasis is controversial, since loss of ghrelin function in rodents does not necessarily lead to anorexia and weight loss. In this chapter, we discuss the metabolic function of ghrelin and are highlighting recent findings including the discovery and function of ghrelin-acylating enzyme ghrelin O-acyltransferase (GOAT). Based on available published data, we conclude that ghrelin is a principally important endogenous regulator of energy balance, which however may affect both food intake and systemic metabolism via independent mechanisms. Importantly, ghrelin, when acylated by GOAT, might represent a key molecular link between the sensing of consumed calories and the neuroendocrine control of energy homeostasis. Thus, agents antagonizing the action of ghrelin may have therapeutic potential in the therapy of obesity.

Serum leptin levels are inversely correlated with omental gene expression of adiponectin and markedly decreased after gastric bypass surgery

BACKGROUND

Adipose tissue is the most abundant endocrine tissue in the body, producing leptin, a hormone important in regulating hunger, and adiponectin, a hormone involved in insulin sensitivity and inflammation. This study aimed to assess the impact of gastric bypass surgery (GBS) on leptin levels and its relation to the adipose tissue expression of adiponectin.

METHODS

Omental and subcutaneous adipose tissue and serum were obtained from 40 obese patients undergoing GBS, from 13 patients 1 year or more after GBS, and from 16 non-obese individuals with a body mass index of 20 to 29 kg/m(2). Adiponectin gene expression was measured by quantitative real-time polymerase chain reaction, and the gene expression was normalized for the GAPDH gene. Serum leptin and adiponectin were measured by a high-sensitivity enzymatic assay.

RESULTS

Leptin levels were significantly lower in the post-GBS patients (19.8 ± 6.7) than in the pre-GBS patients (59.0 ± 5.1; P = 0.0001), and similar to those in the non-obese control subjects (18.2 ± 4; P = 0.8). Univariate analysis showed an inverse correlation between serum leptin levels and omental adiponectin gene expression (r = -0.32; P = 0.01).

CONCLUSIONS

Gastric bypass surgery results in resolution of the leptin resistance status that characterizes obese subjects. The study also demonstrated a significant correlation between leptin and adiponectin. This correlation provides preliminary evidence for studying a potential adiponectin-leptin cross-talking that may represent one of the physiologic pathways responsible for the regulation of food intake in humans.

Obesity surgery and gut-brain communication

The prevalence of obesity, and the cluster of serious metabolic diseases it is associated with, continues to rise globally, and hopes for effective treatment with drugs have been considerably set back. Thus, success with bariatric surgeries to induce sustained body weight loss and effectively cure most of the associated co-morbidities appears almost "miraculous" and systematic investigation of the mechanisms at work has gained momentum. Here, we will discuss the basic organization of gut-brain communication and review clinical and pre-clinical investigations on the potential mechanisms by which gastric bypass surgery leads to its beneficial effects on energy balance and glucose homeostasis. Although a lot has been learned regarding changes in energy intake and expenditure, secretion of gut hormones, and improvement in glucose homeostasis, there has not yet been the "breakthrough observation" of identifying a key signaling component common to the beneficial effects of the surgery. However, given the complexity and redundancy of gut-brain signaling and gut signaling to other relevant organs, it is perhaps more realistic to expect a number of key signaling changes that act in concert to bring about the "miracle".

Impact of sustained weight loss achieved through Roux-en-Y gastric bypass or a lifestyle intervention on ghrelin, obestatin, and ghrelin/obestatin ratio in morbidly obese patients

Background

Appetite-regulating hormones seem to play an important role in weight loss after bariatric surgery. Less is known regarding long-term weight loss maintenance. The objective of the study was to evaluate ghrelin and obestatin levels following long-term weight loss achieved through bariatric surgery or a lifestyle intervention in morbidly obese patients.

Methods

The study was cross-sectional in design carried out in a university research center setting. The participants were weight-stable morbidly obese patients who had undergone, on average, 3 years ago, Roux-en-Y gastric bypass (RYGB) surgery (n = 9) or a lifestyle weight loss intervention (n = 8), and patients on a waiting list for bariatric surgery (control group; n = 9). The main outcome measures were fasting/postprandial plasma levels of total ghrelin and obestatin and ghrelin/obestatin ratio.

Results

Fasting ghrelin and obestatin plasma levels were significantly elevated in the RYGB, but not in the lifestyle group, as compared with the control group. There was no statistical significant difference in fasting ghrelin/obestatin ratio among study groups. Ghrelin levels were suppressed after breakfast in all groups, with no significant differences in postprandial levels overtime between them. Obestatin levels did not change postprandially in any of the groups, but the area under the curve was significantly higher in the RYGB than in the control group.

Conclusions

Sustained weight loss maintenance seems to be associated with increased fasting levels of ghrelin and obestatin after RYGB surgery, but not after a lifestyle intervention, while maintaining ghrelin/obestatin ratio. Ghrelin is, therefore, unlikely to contribute to weight loss maintenance after RYGB, and other mechanisms are probably involved.

Comparison of glucostatic parameters after hypocaloric diet or bariatric surgery and equivalent weight loss

Weight-loss independent mechanisms may play an important role in the improvement of glucose homeostasis after Roux-en-Y gastric bypass (RYGB). The objective of this analysis was to determine whether RYGB causes greater improvement in glucostatic parameters as compared with laparoscopic adjustable gastric banding (LAGB) or low calorie diet (LCD) after equivalent weight loss and independent of enteral nutrient passage. Study 1 recruited participants without type 2 diabetes mellitus (T2DM) who underwent LAGB (n = 8) or RYGB (n = 9). Study 2 recruited subjects with T2DM who underwent LCD (n = 7) or RYGB (n = 7). Insulin-supplemented frequently-sampled intravenous glucose tolerance test (fsIVGTT) was performed before and after equivalent weight reduction. MINMOD analysis of insulin sensitivity (Si), acute insulin response to glucose (AIRg) and C-peptide (ACPRg) response to glucose, and insulin secretion normalized to the degree of insulin resistance (disposition index (DI)) were analyzed. Weight loss was comparable in all groups (7.8 ± 0.4%). In Study 1, significant improvement of Si, ACPRg, and DI were observed only after LAGB. In Study 2, Si, ACPRg, and plasma adiponectin increased significantly in the RYGB-DM group but not in LCD. DI improved in both T2DM groups, but the absolute increase was greater after RYGB (258.2 ± 86.6 vs. 55.9 ± 19.9; P < 0.05). Antidiabetic medications were discontinued after RYGB contrasting with 55% reduction in the number of medications after LCD. No intervention affected fasting glucagon-like peptide (GLP)-1, peptide YY (PYY) or ghrelin levels. In conclusion, RYGB produced greater improvement in Si and DI compared with diet at equivalent weight loss in T2DM subjects. Such a beneficial effect was not observed in nondiabetic subjects at this early time-point.

Changes in gastrointestinal hormones and leptin after Roux-en-Y gastric bypass surgery

BACKGROUND

Roux-en-Y gastric bypass (RYGB) imparts long-term weight loss, the mechanisms for which are not well understood. Changes in leptin and gastrointestinal (GI) hormones, including glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and ghrelin, may contribute to the relative success of RYGB compared with conventional weight loss methods. This study evaluated changes in GI hormones and leptin post-RYGB. The study also evaluated whether GI hormones differed after a short-term dose of protein or fat.

METHODS

GLP-1, PYY, ghrelin, and leptin were assessed in 16 women before RYGB and up to 1 year after RYGB. Plasma was collected before and at several times after a short-term equicaloric dose of protein or fat.

RESULTS

GLP-1 area under the curve (AUC) increased at week 6 and 1 year in the fat beverage (FAT-BEV) group compared with baseline. PYY AUC remained elevated at 1 year in the FAT-BEV group. Ghrelin AUC decreased at week 2, week 6, and 1 year in the protein beverage (PRO-BEV) group compared with baseline. Ghrelin AUC was lower in the PRO-BEV group compared with the FAT-BEV group at week 6. Fasted leptin decreased at all visits in both groups and was lower in the FAT-BEV group compared with the PRO-BEV group at 1 year.

CONCLUSIONS

Changes from baseline were evident for all GI hormones and leptin; some differences were evident soon after surgery (ghrelin, leptin), whereas others were maintained long term (GLP-1, PYY, ghrelin, leptin). In response to a short-term stimulus, protein suppressed ghrelin and fat potently stimulated GLP-1 and PYY. Future work in this area is warranted.

Surgical treatment of type 2 diabetes: the surgeon perspective

Type 2 diabetes mellitus (T2DM) is a major health priority globally, having achieved pandemic status in the twenty-first century. Several gastrointestinal procedures that were primarily designed to treat morbid obesity result in dramatic remission of diabetes. Studies in experimental rodent models and humans have shown that the glycemic benefits of surgery are at least in part weight-independent and extend to non-morbidly obese subjects with T2DM. Bariatric procedures differ in their ability to ameliorate type 2 diabetes, with intestinal bypass procedures being more effective than purely restrictive procedures. Several studies have demonstrated that the benefits of bariatric surgery extend beyond amelioration of hyperglycemia and include improvement in other cardiovascular risk factors such as dyslipidemia and hypertension. The safety and cost-effectiveness of bariatric surgery are also well established by several studies. In this paper, the authors present the surgeon perspective on the management of type 2 diabetes focusing on the efficacy, safety and cost-effectiveness of metabolic surgery. The available evidence warrants the inclusion of metabolic surgery in the treatment algorithm of type 2 diabetes.

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.