Effects of Roux-en-Y gastric bypass surgery on fasting and postprandial concentrations of plasma ghrelin, peptide YY, and insulin

Comparison of the effectiveness of four bariatric surgery procedures in obese patients with type 2 diabetes: a retrospective study

AIM

The aim of the present retrospective study was to evaluate the efficacy of four bariatric surgical procedures to induce diabetes remission and lower cardiovascular risk factors in diabetic obese patients. Moreover, the influence of surgery on weight evolution in the diabetic population was compared with that observed in a nondiabetic matched population.

METHODS

Among 970 patients who were operated on in our center since 2001, 81 patients were identified as type 2 diabetes. Laparoscopic adjustable gastric banding (GB), intervention type Mason (MA), gastric bypass (RYGB), and sleeve gastrectomy (SG) were performed, respectively, in 25%, 17%, 28%, and 30% of this diabetic population.

RESULTS

The resolution rate of diabetes one year after surgery was significantly higher after SG than GB (62.5% versus 20%, P < 0.01), but not significantly different between SG and RYGB. In terms of LDL-cholesterol reduction, RYGB was equivalent to SG and superior to CGMA or GB. Considering the other cardiovascular risk factors, there was no significant difference according to surgical procedures. The weight loss was not statistically different between diabetic and nondiabetic matched patients regardless of the surgical procedures used.

CONCLUSION

Our data confirm that the efficacy of surgery to treat diabetes is variable among the diverse procedures and SG might be an interesting option in this context.

Recombinant human leptin does not alter gut hormone levels after gastric bypass but may attenuate sweet cravings

Bariatric surgery improves glucose homeostasis and alters gut hormones partly independent of weight loss. Leptin plays a role in these processes; levels are decreased following bariatric surgery, creating a relative leptin insufficiency. We previously showed that leptin administration in a weight-reduced state after Roux-en-Y gastric bypass (RYGB) caused no further weight loss. Here, we discuss the impact of leptin administration on gut hormones, glucostasis, and appetite. Weight stable women after RYGB were randomized to receive placebo or recombinant human metreleptin (0.05 mg/kg twice daily). At weeks 0 and 16, a liquid meal challenge was performed. Glucose, insulin, C-peptide, GLP-1, PYY, glucagon, and ghrelin (total, acyl, and desacyl) were measured fasting and postprandially. Appetite was assessed using a visual analog scale. Mean post-op period was 53 ± 2.3 months; mean BMI was 34.6 ± 0.2 kg/m(2). At 16 weeks, there was no significant change in weight within or between groups. Fasting PYY was significantly different between groups and the leptin group had lower sweets craving at week 16 than the placebo group (P < 0.05). No other differences were observed. Leptin replacement does not alter gut hormones or glucostasis but may diminish sweet cravings compared to placebo in this population of post-RYGB women.

The sum of many parts: potential mechanisms for improvement in glucose homeostasis after bariatric surgery

Bariatric surgery has emerged as the most durably effective treatment of type 2 diabetes (DM). However, the mechanisms governing improvement in glucose homeostasis have yet to be fully elucidated. In this review we discuss the various types of surgical interventions and the multitude of factors that potentially mediate the effects on glycemia, such as altered delivery of nutrients to the distal ileum, duodenal exclusion, gut hormone changes, bile acid reabsorption, and amino acid metabolism. Accumulating evidence that some of these changes seem to be independent of weight loss questions the rationale of using body mass index as the major indication for surgery in diabetic patients. Understanding the complex mechanisms and interactions underlying improved glycemic control could lead to novel therapeutic targets and would also allow for greater individualization of therapy and optimization of surgical outcomes.

An intragastric balloon produces large weight losses in the absence of a change in ghrelin or peptide YY

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT?: The development of obesity is a multi-factorial process that results in an alteration in the neuroendocrine hormones that help regulate appetite and body weight. Weight loss has been shown to alter this neuroendocrine balance so as to promote weight regain. An intragastric balloon is an effective method to achieve significant weight loss in obese patients and is well suited for those patients who are looking for an alternative to lifestyle modification alone, and those who are not ready or suitable for surgical intervention. Limited research has shown that the weight loss achieved with an intragastric balloon is mediated by altered secretion of the hormones that regulate appetite and weight. WHAT DOES THIS STUDY ADD?: There are currently limited data on the effects of intragastric balloons on appetite and weight-related hormones. In the current study, we have investigated a broad range of gut hormones and adipokines and their response to weight loss induced by differing methods, and the subsequent effect this may have on weight regain. This is an important research area as novel therapies and long-term strategies are needed to counteract the unfavourable changes to the neuroendocrine control of appetite and satiety associated with diet-induced weight loss. This study aims to determine the effect of weight loss achieved with different methods on fasting levels of appetite hormones. Sixty-six obese adults with metabolic syndrome were randomized to intragastric balloon (IGB) for 6 months, with a 12-month behavioural modification programme (IGB group, 'IGBG') or a 12-month behavioural modification programme alone (control group, 'CG'). Anthropometric assessments and blood samples were taken every 3 months and total ghrelin, peptide YY (PYY), adiponectin and leptin were measured. Significant weight-loss differences favouring the IGBG were evident between groups at all time points. Ghrelin increased when the IGB was in situ (+39.3 pmol L(-1) vs. baseline) and returned to baseline after its removal (-34.7 pmol L(-1) ). Adiponectin and PYY levels remained stable in the IGBG, with transient increases noted in the CG. There were no significant between-group differences for ghrelin, PYY or adiponectin. In the IGBG, despite a decrease in leptin at 6 months (-11.7 ng mL(-1) ), levels increased to baseline after IGB removal (-3.7 ng mL(-1) ). In summary, weight loss associated with the IGB did not alter fasting levels of PYY or adiponectin. There was a return of ghrelin and leptin levels to baseline values after IGB removal. No compensatory rise in ghrelin was evident in either group 12 months after initial weight reduction, suggesting that such treatment strategies may lead to better long-term sustainable weight loss.

Role of proximal gut exclusion from food on glucose homeostasis in patients with Type 2 diabetes

AIMS

To report Type 2 diabetes-related outcomes after the implantation of a duodenal-jejunal bypass liner device and to investigate the role of proximal gut exclusion from food in glucose homeostasis using the model of this device.

METHODS

Sixteen patients with Type 2 diabetes and BMI <36 kg/m(2) were evaluated before and 1, 12 and 52 weeks after duodenal-jejunal bypass liner implantation and 26 weeks after explantation. Mixed-meal tolerance tests were conducted over a period of 120 min and glucose, insulin and C-peptide levels were measured. The Matsuda index and the homeostatic model of assessment of insulin resistance were used for the estimation of insulin sensitivity and insulin resistance. The insulin secretion rate was calculated using deconvolution of C-peptide levels.

RESULTS

Body weight decreased by 1.3 kg after 1 week and by 2.4 kg after 52 weeks (P < 0.001). One year after duodenal-jejunal bypass liner implantation, the mean (sem) HbA(1c) level decreased from 71.3 (2.4) mmol/mol (8.6[0.2]%) to 58.1 (4.4) mmol/mol (7.5 [0.4]%) and mean (sem) fasting glucose levels decreased from 203.3 (13.5) mg/dl to 155.1 (13.1) mg/dl (both P < 0.001). Insulin sensitivity improved by >50% as early as 1 week after implantation as measured by the Matsuda index and the homeostatic model of assessment of insulin resistance (P < 0.001), but there was a trend towards deterioration in all the above-mentioned variables 26 weeks after explantation. Fasting insulin levels, insulin area under the curve, fasting C-peptide, C-peptide area under the curve, fasting insulin and total insulin secretion rates did not change during the duodenal-jejunal bypass liner implantation period or after explantation.

CONCLUSIONS

The duodenal-jejunal bypass liner improves glycaemia in overweight and obese patients with Type 2 diabetes by rapidly improving insulin sensitivity. A reduction in hepatic glucose output is the most likely explanation for this improvement.

Improved acylated ghrelin suppression at 2 years in obese patients with type 2 diabetes: effects of bariatric surgery vs standard medical therapy

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) produces more durable glycemic control than sleeve gastrectomy (SG) or intensive medical therapy (IMT). However, the contribution of acylated ghrelin (AG), a gluco-regulatory/appetite hormone, to improve glucose metabolism and body composition in patients with type 2 diabetes (T2D) following RYGB is unknown.

DESIGN

STAMPEDE (Surgical Treatment and Medication Potentially Eradicate Diabetes Efficiently) was a prospective, randomized controlled trial.

SUBJECTS

Fifty-three (body mass index: 36±3 kg m(-2), age: 49±9 years) poorly controlled patients with T2D (HbA1c (glycated hemoglobin): 9.7±2%) were randomized to IMT, IMT+RYGB or IMT+SG and underwent a mixed-meal tolerance test at baseline, 12, and 24 months for evaluation of AG suppression (postprandial minus fasting) and beta-cell function (oral disposition index; glucose-stimulated insulin secretion × Matsuda index). Total/android body fat (dual-energy X-ray absorptiometry) was also assessed.

RESULTS

RYGB and SG reduced body fat comparably (15-23 kg) at 12 and 24 months, whereas IMT had no effect. Beta-cell function increased 5.8-fold in RYGB and was greater than IMT at 24 months (P<0.001). However, there was no difference in insulin secretion between SG vs IMT at 24 months (P=0.32). Fasting AG was reduced fourfold following SG (P<0.01) and did not change with RYGB or IMT at 24 months. AG suppression improved more following RYGB than SG or IMT at 24 months (P=0.01 vs SG, P=0.07 vs IMT). At 24 months, AG suppression was associated with increased postprandial glucagon-like peptide-1 (r=-0.32, P<0.02) and decreased android fat (r=0.38; P<0.006).

CONCLUSIONS

Enhanced AG suppression persists for up to 2 years after RYGB, and this effect is associated with decreased android obesity and improved insulin secretion. Together, these findings suggest that AG suppression is partly responsible for the improved glucose control after RYGB surgery.

Moving beyond energy homeostasis: new roles for glucagon-like peptide-1 in food and drug reward

Glucagon-like peptide-1 (GLP-1), a hormone and neuropeptide, is known to regulate energy homeostasis in part through an established central role in controlling food intake. Historically this central role has largely been attributed to GLP-1 receptor signaling in the brainstem and hypothalamus. However, emerging data indicate that GLP-1 also contributes to non-homeostatic regulation of food reward and motivated behaviors in brain reward centers, including the ventral tegmental area and nucleus accumbens. The hypothesis that GLP-1 signaling modulates reward circuitry has provided the impetus for studies demonstrating that GLP-1 attenuates reward for psychostimulants and alcohol. Here, we examine current evidence for GLP-1-mediated regulation of food and drug reward and use these findings to hypothesize mechanisms of action within brain reward centers.

The endocrinology of food intake

Many questions must be considered with regard to consuming food, including when to eat, what to eat and how much to eat. Although eating is often thought to be a homeostatic behaviour, little evidence exists to suggest that eating is an automatic response to an acute shortage of energy. Instead, food intake can be considered as an integrated response over a prolonged period of time that maintains the levels of energy stored in adipocytes. When we eat is generally determined by habit, convenience or opportunity rather than need, and meals are preceded by a neurally-controlled coordinated secretion of numerous hormones that prime the digestive system for the anticipated caloric load. How much we eat is determined by satiation hormones that are secreted in response to ingested nutrients, and these signals are in turn modified by adiposity hormones that indicate the fat content of the body. In addition, many nonhomeostatic factors, including stress, learning, palatability and social influences, interact with other controllers of food intake. If a choice of food is available, what we eat is based on pleasure and past experience. This article reviews the hormones that mediate and influence these processes.

Very low-calorie diet mimics the early beneficial effect of Roux-en-Y gastric bypass on insulin sensitivity and β-cell Function in type 2 diabetic patients

Marked improvement in glycemic control occurs in patients with type 2 diabetes mellitus shortly after Roux-en-Y gastric bypass surgery (RYGB) and before there is major weight loss. The objective of this study was to determine whether the magnitude of this change is primarily due to caloric restriction or is unique to the surgical procedure. We studied eleven subjects who underwent RYGB and fourteen subjects mean-matched for BMI, HbA1c, and diabetes duration who were admitted to our inpatient research unit and given a very low-calorie diet (VLCD) of 500 kcal/day with a macronutrient content similar to that consumed by patients after RYGB. Frequently sampled intravenous glucose tolerance tests were performed before and after interventions. Both groups lost an equivalent amount of weight over a mean study period of 21 days. Insulin sensitivity, acute insulin secretion after intravenous glucose administration, and β-cell function as determined by disposition index improved to a similar extent in both groups. Likewise, changes in fasting glucose and fructosamine levels were similar. Based on these data, VLCD improves insulin sensitivity and β-cell function just as well as RYGB in the short term.

The gut microbiota elicits a profound metabolic reorientation in the mouse jejunal mucosa during conventionalisation

OBJECTIVE

Proper interactions between the intestinal mucosa, gut microbiota and nutrient flow are required to establish homoeostasis of the host. Since the proximal part of the small intestine is the first region where these interactions occur, and since most of the nutrient absorption occurs in the jejunum, it is important to understand the dynamics of metabolic responses of the mucosa in this intestinal region.

DESIGN

Germ-free mice aged 8-10 weeks were conventionalised with faecal microbiota, and responses of the jejunal mucosa to bacterial colonisation were followed over a 30-day time course. Combined transcriptome, histology, (1)H NMR metabonomics and microbiota phylogenetic profiling analyses were used.

RESULTS

The jejunal mucosa showed a two-phase response to the colonising microbiota. The acute-phase response, which had already started 1 day after conventionalisation, involved repression of the cell cycle and parts of the basal metabolism. The secondary-phase response, which was consolidated during conventionalisation (days 4-30), was characterised by a metabolic shift from an oxidative energy supply to anabolic metabolism, as inferred from the tissue transcriptome and metabonome changes. Detailed transcriptome analysis identified tissue transcriptional signatures for the dynamic control of the metabolic reorientation in the jejunum. The molecular components identified in the response signatures have known roles in human metabolic disorders, including insulin sensitivity and type 2 diabetes mellitus.

CONCLUSION

This study elucidates the dynamic jejunal response to the microbiota and supports a prominent role for the jejunum in metabolic control, including glucose and energy homoeostasis. The molecular signatures of this process may help to find risk markers in the declining insulin sensitivity seen in human type 2 diabetes mellitus, for instance.

Pharmacological inhibition to examine the role of DGAT1 in dietary lipid absorption in rodents and humans

Alterations in fat metabolism, in particular elevated plasma concentrations of free fatty acids and triglycerides (TG), have been implicated in the pathogenesis of Type 2 diabetes, obesity, and cardiovascular disease. Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1), a member of the large family of membrane-bound O-acyltransferases, catalyzes the final step in triacylglycerol formation. In the intestine, DGAT1 is one of the acyltransferases responsible for the reesterficiation of dietary TG. Following a single dose of a selective pharmacological inhibitor of DGAT1, PF-04620110, a dose-dependent inhibition of TG and vitamin A absorption postprandially was demonstrated in rodents and human subjects. In C57/BL6J mice, acute DGAT1 inhibition alters the temporal and spatial pattern of dietary lipid absorption. To understand the impact of DGAT1 inhibition on enterocyte lipid metabolism, lipomic profiling was performed in rat intestine and plasma as well as human plasma. DGAT1 inhibition causes an enrichment of polyunsaturated fatty acids within the TG class of lipids. This pharmacological intervention gives us insight as to the role of DGAT1 in human dietary lipid absorption.

Comparison of postprandial profiles of ghrelin, active GLP-1, and total PYY to meals varying in fat and carbohydrate and their association with hunger and the phases of satiety

CONTEXT

The relationship between postprandial peptides at circulating physiological levels and short-term appetite control is not well understood.

OBJECTIVE

The purpose of this study was first to compare the postprandial profiles of ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) after isoenergetic meals differing in fat and carbohydrate content and second to examine the relationships between ghrelin, GLP-1, and PYY with hunger, fullness, and energy intake.

DESIGN

Plasma was collected before and periodically after the meals for 180 minutes, after which time ad libitum food was provided. Simultaneous ratings of hunger and fullness were tracked for 180 minutes through phases identified as early (0-60 minutes) and late (60-180 minutes) satiety.

SETTING

This study was conducted at the Psychobiology and Energy Balance Research Unit, University of Leeds.

PARTICIPANTS

The participants were 16 healthy overweight/obese adults.

MAIN OUTCOME MEASURES

Changes in hunger and fullness and metabolic markers were indicators of the impact of the meals on satiety.

RESULTS

Ghrelin was influenced similarly by the 2 meals [F(1, 12) = 0.658, P = .433] and was significantly associated with changes in hunger (P < .05), which in turn correlated with food intake (P < .05). GLP-1 and PYY increased more by the high-fat meal [F(1, 15) = 5.099 and F(1, 14) = 5.226, P < .05]. GLP-1 was negatively associated with hunger in the late satiety phase and with energy intake (P < .05), but the PYY profile was not associated with hunger or fullness, nor was PYY associated with food intake.

CONCLUSIONS

The results demonstrate that under these conditions, these peptides respond differently to ingested nutrients. Ghrelin and GLP-1, but not PYY, were associated with short-term control of appetite over the measurement period.

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.

Metabolic effects of Roux-en-Y gastric bypass in obese adolescents and young adults

Weight loss surgery is an increasingly common treatment option for obese adolescents, but data are limited regarding the metabolic effects of surgical weight loss procedures. We performed a retrospective review of the electronic medical record to determine metabolic outcomes for 24 adolescents and young adults ages 15 to 22 years undergoing Roux-en-Y gastric bypass from 2009 to 2011 as well as 24 age-, sex-, and BMI-matched controls. During a median follow-up of 6 months after Roux-en-Y gastric bypass, fasting glucose, hemoglobin A1c, low-density lipoprotein, triglyceride, and high-sensitivity C-reactive protein decreased significantly. Changes in these measures were not significantly associated with age or extent of weight loss.

From gut changes to type 2 diabetes remission after gastric bypass surgeries

Increasing evidence suggests that the gut may influence the host's metabolism and ultimately change the outcomes of type 2 diabetes mellitus (T2DM). We review the evidence on the relationship between the gut and T2DM remission after gastric bypass surgery, and discuss the potential mechanisms underlying the above relationship: gut anatomical rearrangement, microbial composition changes, altered gut cells, and gut hormone modulation. However, the exact changes and their relative importance in the metabolic improvements after gastric bypass surgery remain to be further clarified. Elucidating the precise metabolic mechanisms of T2DM resolution after bypass surgery will help to reveal the molecular mechanisms of pathogenesis, and facilitate the development of novel diagnoses and preventative interventions for this common disease.

Acute peripheral GLP-1 receptor agonism or antagonism does not alter energy expenditure in rats after Roux-en-Y gastric bypass

Compared to traditional weight loss strategies, the compensatory decrease in energy expenditure in response to body weight loss is markedly attenuated after Roux-en-Y gastric bypass surgery (RYGB). Because basal and postprandial levels of glucagon-like peptide-1 (GLP-1) are increased after RYGB surgery, and because GLP-1 has been shown to increase energy expenditure, we investigated if increased GLP-1 levels are involved in the alterations in energy expenditure after RYGB. Adult male Wistar rats were randomized for RYGB (n=8) or sham surgery (n=17). Part of the sham-operated rats were food restricted and body weight-matched (n=8) to the RYGB animals. The effects of acute subcutaneous administration of the GLP-1 antagonist Exendin (9-39) (Ex-9, 30μg/kg) or the GLP-1 agonist Exendin-4 (Ex-4, 5μg/kg), respectively, on energy expenditure were tested using indirect calorimetry. We found that Ex-9 increased food intake in RYGB, but not in sham-operated rats. Energy expenditure was lower in RYGB and sham-operated body weight-matched rats compared to sham-operated ad libitum fed rats, but significantly higher in RYGB rats compared to sham-operated body weight-matched rats. There was no effect of Ex-9 treatment on energy expenditure in either group of animals. Similarly, Ex-4 decreased food intake more in RYGB than in sham-operated rats, but Ex-4 did not modulate energy expenditure in any surgical group. We conclude that acute modulation of GLP-1 signaling is not directly involved in altered energy expenditure after RYGB surgery in rats.

Diabetes Mellitus: New Challenges and Innovative Therapies

Diabetes is a common chronic disease affecting an estimated 285 million adults worldwide. The rising incidence of diabetes, metabolic syndrome, and subsequent vascular diseases is a major public health problem in industrialized countries. This chapter summarizes current pharmacological approaches to treat diabetes mellitus and focuses on novel therapies for diabetes mellitus that are under development.

There is great potential for developing a new generation of therapeutics that offer better control of diabetes, its co-morbidities and its complications. Preclinical results are discussed for new approaches including AMPK activation, the FGF21 target, cell therapy approaches, adiponectin mimetics and novel insulin formulations. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications.

In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality of life in the near future.

The defence of body weight: a physiological basis for weight regain after weight loss

Although weight loss can usually be achieved by restricting food intake, the majority of dieters regain weight over the long-term. In the hypothalamus, hormonal signals from the gastrointestinal tract, adipose tissue and other peripheral sites are integrated to influence appetite and energy expenditure. Diet-induced weight loss is accompanied by several physiological changes which encourage weight regain, including alterations in energy expenditure, substrate metabolism and hormone pathways involved in appetite regulation, many of which persist beyond the initial weight loss period. Safe effective long-term strategies to overcome these physiological changes are needed to help facilitate maintenance of weight loss. The present review, which focuses on data from human studies, begins with an outline of body weight regulation to provide the context for the subsequent discussion of short- and long-term physiological changes which accompany diet-induced weight loss.

Role of RACK1 in the differential proliferative effects of neuropeptide Y(1-36) and peptide YY(1-36) in SHR vs. WKY preglomerular vascular smooth muscle cells

Previous studies show that neuropeptide Y(1-36) (NPY(1-36)) and peptide YY(1-36) (PYY(1-36)), by engaging Y1 receptors, stimulate proliferation of spontaneous hypertensive rat (SHR) preglomerular vascular smooth muscle cells (PGVSMCs). In contrast, these peptides have little effect on proliferation of Wistar-Kyoto (WKY) PGVSMCs. Why SHR and WKY PGVSMCs differ in this regard is unknown. Because receptor for activated C kinase 1 (RACK1) can modulate cell proliferation, we tested the hypothesis that differences in RACK1 levels/localization may explain the differential response of SHR vs. WKY PGVSMCs to NPY(1-36) and PYY(1-36). Western blotting for RACK1 in subcellular fractions of cultured SHR and WKY PGVSMCs demonstrated increased levels of RACK1 in the membrane and cytoskeletal subcellular fractions of SHR vs. WKY PGVSMCs. NPY(1-36) and PYY(1-36) stimulated proliferation of SHR PGVSMCs, and siRNA knockdown of RACK1 abrogated this effect. Neither NPY(1-36) nor PYY(1-36) stimulated the proliferation of WKY PGVSMCs. However, in WKY PGVSMCs treated with a RACK1 plasmid, both NPY(1-36) and PYY(1-36) stimulated proliferation. In SHR PGVSMCs, inhibitors of the G(i)/phospholipase C/PKC pathway (a pathway known to be organized by RACK1) attenuated the ability of NPY(1-36) to stimulate the proliferation of SHR PGVSMCs. Our results suggest that RACK1 modulates the ability of PGVSMCs to respond to the proliferative actions of NPY(1-36) and PYY(1-36)and differences in RACK1 levels/localization account for, in part, differential proliferative responses to NPY(1-36) and PYY(1-36) in SHR vs. WKY PGVSMCs. Because dipeptidyl peptidase IV inhibitors increase NPY(1-36) and PYY(1-36) levels, our findings have implications for the use of such drugs in diabetic patients.

Update on the Mechanisms Facilitating Weight Loss and Resolution of Type 2 Diabetes Following Bariatric Surgery

The prevalence of type 2 diabetes mellitus (T2DM) and obesity is steadily increasingworldwide. To fight the twin pandemics of obesity and T2DM, clinicians need everytool they can get. Major, durable weight loss is uncommon with medical andbehavioral approaches; many diabetes drugs promote weight gain, while using themto obtain better blood glucose profiles increases the risk of hypoglycemia. Bariatricsurgery seems to be the most effective method for promoting major and durableweight loss in obese subjects, leading also to ameliorations of obesity-associated comorbidities,especially T2DM. Currently, indications for bariatric surgery includemorbidly obese patients or patients with a body mass index (BMI) >35 withsignificant co-morbidities. Currently, bariatric surgery (also referred to as“metabolic surgery”) is advocated for the treatment of T2DM even in overweightsubjects who do not meet the current BMI criteria. This review examines the currentevidence regarding the mechanisms of T2DM resolution following bariatric surgery.

Long-term results of a randomized clinical trial comparing Roux-en-Y gastric bypass with vertical banded gastroplasty

BACKGROUND

The long-term results of Roux-en-$\hbox{Y}$ gastric bypass (gastric bypass) and vertical banded gastroplasty (VBG) from randomized studies have not been described in detail.

METHODS

Patients were randomized to gastric bypass or VBG. Body mass index (BMI), body composition, eating habits and gastrointestinal hormones were reviewed after 6 years. The frequency of reoperation was assessed up to 10 years after surgery.

RESULTS

Sixty-six (80 per cent) of the 82 subjects randomized were assessed for weight and BMI 6 years after surgery, 30 (81 per cent) in the gastric bypass group and 36 (80 per cent) in the VBG group. Intention-to-treat analysis demonstrated greater weight loss after gastric bypass compared with VBG, 6 years after surgery: BMI reduced from 41·8 (95 per cent confidence interval 41·3 to 42·3) to 30·3 (28·6 to 32·0) kg/m(2) for gastric bypass and from 42·3 (42·8 to 44·8) to 32·9 (31·3 to 34·5) kg/m(2) for VBG (P = 0·036). Gastric bypass caused a larger loss of fat mass (P = 0·026) and better preservation of lean tissue (P = 0·009). Patients having a gastric bypass had greater postprandial responses to the satiety hormones glucagon-like peptide 1 and peptide YY (P = 0·003 and P = 0·004 respectively). Ghrelin levels did not differ between the groups. Patients with a gastric bypass maintained a lower intake of fat compared with those having VBG (P = 0·013). Some 89 per cent of patients who initially had VBG had undergone, or were scheduled for, conversion to gastric bypass at latest follow-up.

CONCLUSION

Gastric bypass was superior to VBG regarding weight loss, body composition, dietary composition and postprandial satiety hormone responses.

Partial small bowel resection with sleeve gastrectomy increases adiponectin levels and improves glucose homeostasis in obese rodents with type 2 diabetes

BACKGROUND

The aim of this study was to examine the effect of small bowel resection with and without sleeve gastrectomy on glucose homeostasis in an obese rodent model of type 2 diabetes.

METHODS

Zucker diabetic fatty rats were randomized into three surgical groups: Sham, small bowel resection, and small bowel resection with sleeve gastrectomy (BRSG). Weight and fasting glucose levels were measured at randomization and monitored after surgery. Oral glucose tolerance testing was performed at baseline and 45 days after surgery to assess glucose homeostasis and peptide changes.

RESULTS

At baseline, all animals exhibited impaired glucose tolerance and showed no difference in weight or fasting (area under the curve) AUC(glucose). At sacrifice, Sham animals weighed more than BRSG animals (p = 0.047). At day 45, the Sham group experienced a significant increase in AUC(glucose) compared to baseline (p = 0.02), whereas there was no difference in AUC(glucose) in either surgical group at any time point: BR (p = 0.58) and BRSG (p = 0.56). Single-factor ANOVA showed a significant difference in AUC(glucose) of p = 0.004 between groups postoperatively: Sham (50,745 ± 11,170) versus BR (23,865 ± 432.6) (p = 0.01); Sham versus BRSG (28,710 ± 3188.8) (p = 0.02). There was no difference in plasma insulin, GLP-1, or adiponectin levels before surgery, although 45 days following surgery adiponectin levels where higher in the BRSG group (p = 0.004).

CONCLUSIONS

Partial small bowel resection improved glucose tolerance independent of weight. The combination of small bowel resection and sleeve gastrectomy leads to an increase in adiponectin levels, which may contribute to improved glucose homeostasis.

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.

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.

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.

Roux-en-Y gastric bypass operation in rats

Currently, the most effective therapy for the treatment of morbid obesity to induce significant and maintained body weight loss with a proven mortality benefit is bariatric surgery. Consequently, there has been a steady rise in the number of bariatric operations done worldwide in recent years with the Roux-en-Y gastric bypass (gastric bypass) being the most commonly performed operation. Against this background, it is important to understand the physiological mechanisms by which gastric bypass induces and maintains body weight loss. These mechanisms are yet not fully understood, but may include reduced hunger and increased satiation, increased energy expenditure, altered preference for food high in fat and sugar, altered salt and water handling of the kidney as well as alterations in gut microbiota. Such changes seen after gastric bypass may at least partly stem from how the surgery alters the hormonal milieu because gastric bypass increases the postprandial release of peptide-YY (PYY) and glucagon-like-peptide-1 (GLP-1), hormones that are released by the gut in the presence of nutrients and that reduce eating. During the last two decades numerous studies using rats have been carried out to further investigate physiological changes after gastric bypass. The gastric bypass rat model has proven to be a valuable experimental tool not least as it closely mimics the time profile and magnitude of human weight loss, but also allows researchers to control and manipulate critical anatomic and physiologic factors including the use of appropriate controls. Consequently, there is a wide array of rat gastric bypass models available in the literature reviewed elsewhere in more detail. The description of the exact surgical technique of these models varies widely and differs e.g. in terms of pouch size, limb lengths, and the preservation of the vagal nerve. If reported, mortality rates seem to range from 0 to 35%. Furthermore, surgery has been carried out almost exclusively in male rats of different strains and ages. Pre- and postoperative diets also varied significantly. Technical and experimental variations in published gastric bypass rat models complicate the comparison and identification of potential physiological mechanisms involved in gastric bypass. There is no clear evidence that any of these models is superior, but there is an emerging need for standardization of the procedure to achieve consistent and comparable data. This article therefore aims to summarize and discuss technical and experimental details of our previously validated and published gastric bypass rat model.

The preliminary clinical experience with laparoscopic duodenojejunal bypass for treatment of type 2 diabetes mellitus in non-morbidly obese patients: the 1-year result in a single institute

BACKGROUND

Although various bariatric surgeries are widely known for their effect of ameliorating type 2 diabetes mellitus (T2DM), there are only a few reports demonstrating the effect of duodenojejunal bypass on T2DM. The aim of this study was to evaluate and report the clinical effects of laparoscopic duodenojejunal bypass (LDJB) in non-morbidly obese patients with T2DM.

METHODS

Twelve non-morbidly obese patients with T2DM underwent LDJB. Changes in fasting blood glucose, body mass index glycosylated hemoglobin (HbA1c), and dose of antidiabetic medications were recorded prospectively during a 1-year period.

RESULTS

Reduction in HbA1c occurred 3 months after surgery and was maintained up to 1 year, and hyperglycemia was reversed within 1 month after surgery and remained controlled at 12 months. BMI decreased significantly 1 month after surgery and then remained steady through the year. Three patients (25.0 %) stopped antidiabetic medication, seven (58.3 %) patients maintained or decreased doses, and two (16.7 %) increased doses. Seven (58.3 %) patients had a decline in HbA1c.

CONCLUSION

LDJB demonstrated a glycemic control effect up to 1 year on T2DM in non-morbidly obese patients.

Influence of gastrectomy for stomach cancer on type 2 diabetes mellitus for patients with a body mass index less than 30 kg/m(2)

Purpose

The impressive effect of LRYGBP on mildly obese patients (30 kg/m² < BMI < 35 kg/m²) with T2DM raises the argument for lowering the threshold for surgical intervention to non-obesity (BMI < 30 kg/m²). The goal of this study was to evaluate the effect of gastrectomy on non-obese patients with T2DM and what preoperative clinical factors are associated with postoperative long term improvement.

Methods

In this retrospective review, we analyzed the change in diabetic status in 75 patients with gastric cancer undergoing three different gastrectomies in a single institution from June 1996 to September 2009. Pre- and postoperative fasting blood glucose, serum hemoglobin A1c and diabetic medication requirements were compared. The demographic data and other biochemical markers were also collected.

Results

At an average follow-up of 35.0 ± 25.9 months, we collected the data of 75 patients and evaluated the change of diabetes status. There was no resolution of diabetes in Billroth-I (B-I) group, and 45.2% of patients improved whereas the resolution rate of Billroth-II (B-II) and RY group was 22.2% and 23.5% and 85.2% and 88.2%, respectively. The improvement rate of diabetes mellitus (DM) status was 7.46 times higher in B-II than in B-I patients. The method of reconstruction is the most powerful factor and severity and duration of diabetes showed significant clinical factors for the improvement of the disease after surgery.

Conclusion

According to these results, foregut-bypass procedure may improve the type 2 DM better than can be explained by the effect of weight loss only. Diabetes remission is significantly higher in those with duration of diabetes less than 5 years.

Gastric stimulation for weight loss

The prevalence of obesity is growing to epidemic proportions, and there is clearly a need for minimally invasive therapies with few adverse effects that allow for sustained weight loss. Behavior and lifestyle therapy are safe treatments for obesity in the short term, but the durability of the weight loss is limited. Although promising obesity drugs are in development, the currently available drugs lack efficacy or have unacceptable side effects. Surgery leads to long-term weight loss, but it is associated with morbidity and mortality. Gastric electrical stimulation (GES) has received increasing attention as a potential tool for treating obesity and gastrointestinal dysmotility disorders. GES is a promising, minimally invasive, safe, and effective method for treating obesity. External gastric pacing is aimed at alteration of the motility of the gastrointestinal tract in a way that will alter absorption due to alteration of transit time. In addition, data from animal models and preliminary data from human trials suggest a role for the gut-brain axis in the mechanism of GES. This may involve alteration of secretion of hormones associated with hunger or satiety. Patient selection for gastric stimulation therapy seems to be an important determinant of the treatment’s outcome. Here, we review the current status, potential mechanisms of action, and possible future applications of gastric stimulation for obesity.

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.

Type 2 diabetes mellitus: a possible surgically reversible intestinal dysfunction

Type 2 diabetes mellitus (T2DM) is a global public health problem often associated with obesity. Bariatric surgery is effective for treating serious obesity, and techniques involving intestinal bypass have metabolic benefits, such as complete and early remission of T2DM. We present a literature review of the possible mechanisms of early normalization of glycemic homeostasis after bariatric surgery, including intestinal gluconeogenesis, increased antidiabetogenic signals from L cells located in the distal small intestine, and impaired secretion of diabetogenic signals in the upper part of the small intestine. Adding to these potential mechanisms, unknown factors that regulate insulin sensitivity may be involved and altered by bariatric surgery. This review discusses the various hypotheses about the mechanisms of glycemic control after bariatric surgery involving intestinal bypass. Further research is essential to better understand these mechanisms and to identify potential new mechanisms that might help in developing less invasive and safer alternatives for the treatment of T2DM and reveal novel pharmaceutical targets for glycemic control.

Role of bariatric-metabolic surgery in the treatment of obese type 2 diabetes with body mass index <35 kg/m2: a literature review

Bariatric surgery has been used to treat type 2 diabetes mellitus (T2DM); however, its efficacy is still debatable. This literature review analyzed articles that evaluated the effects of bariatric surgery in treatment of T2DM in obese patients with a body mass index (BMI) of <35 kg/m(2). A paired t test was applied for the analysis of pre- and postintervention mean BMI, fasting plasma glucose (FPG), and glycosylated hemoglobin (A1c) values. A significant (P<0.001) reduction in BMI (from 29.95±0.51 kg/m(2) to 24.83±0.44 kg/m(2)), FPG (from 207.86±8.51 mg/dL to 113.54±4.93 mg/dL), and A1c (from 8.89±0.15% to 6.35±0.18%) was observed in 29 articles (n=675). T2DM resolution (A1c <7% without antidiabetes medication) was achieved in 84.0% (n=567) of the subjects. T2DM remission, control, and improvement were observed in 55.41%, 28.59%, and 14.37%, respectively. Only 1.63% (n=11) of the subjects presented similar or worse glycemic control after the surgery. T2DM remission (A1c <6% without antidiabetes medication) was higher after mini-gastric bypass (72.22%) and laparoscopic/Roux-en-Y gastric bypass (70.43%). According to the Foregut and Hindgut Hypotheses, T2DM results from the imbalance between the incretins and diabetogenic signals. The procedures that remove the proximal intestine and do ileal transposition contribute to the increase of glucagon-like peptide-1 levels and improvement of insulin sensitivity. These findings provide preliminary evidence of the benefits of bariatric-metabolic surgery on glycemic control of T2DM obese subjects with a BMI of <35 kg/m(2). However, more clinical trials are needed to investigate the metabolic effects of bariatric surgery in T2DM remission on pre-obese and obese class I patients.

A synergy between incretin effect and intestinal gluconeogenesis accounting for the rapid metabolic benefits of gastric bypass surgery

The early improvement of glucose control taking place shortly after gastric bypass surgery in obese diabetic patients has long been mysterious. A recent study in mice has highlighted some specific mechanisms underlying this phenomenon. The specificity of gastric bypass in obese diabetic mice relates to major changes in the sensations of hunger and to rapid improvement of glucose parameters. The induction of intestinal gluconeogenesis plays a major role in diminishing hunger, and in restoring insulin sensitivity of endogenous glucose production. In parallel, the restoration of the secretion of glucagon-like peptide 1 and insulin plays a key additional role, in this context of recovered insulin sensitivity, to improve postprandial glucose tolerance. Therefore, a synergy between an incretin effect and intestinal gluconeogenesis is a key feature accounting for the rapid improvement of glucose control in obese diabetic patients after bypass surgery.

Roux-en-Y gastric bypass-induced improvement of glucose tolerance and insulin resistance in type 2 diabetic rats are mediated by glucagon-like peptide-1

BACKGROUND

The aim of this study was to investigate the effects of Roux-en-Y gastric bypass (RYGB) on glucose tolerance and insulin resistance in type 2 diabetic rats and the possible mechanisms involved in this process.

METHODS

Thirty Goto-Kakizaki (GK) rats were randomly divided into three groups: RYGB operation, sham operation, and food restriction groups. Ten Wistar rats were used as non-diabetic control. The body weight and food consumption of rats were recorded 1 week before or every week after surgery. The fasting blood sugar and oral glucose tolerance test were performed using blood glucose meter. The levels of plasma insulin or glucagon-like peptide-1 (GLP-1) were evaluated by enzyme-linked immunosorbent assay. The insulin resistance was quantified using homeostasis model assessment method. The expression of GLP-1 receptor, Bcl-2, Bax, and caspase-3 was determined by Western blotting.

RESULTS

Our results revealed that RYGB efficiently improved both glucose tolerance and insulin resistance in GK diabetic rats by upregulating GLP-1/GLP-1R expression. In addition, GLP-1R agonist exendin-4 dose-dependently increased insulin secretion in RIN-m5F cells and regulated the proliferation and apoptosis of these cells.

CONCLUSIONS

RYGB provides a valuable therapeutic option for patients with type 2 diabetes. GLP-1 may contribute to the regulation of pancreatic β-cell function through its receptor following RYGB.

Probing the mechanisms of the metabolic effects of weight loss surgery in humans using a novel mouse model system

BACKGROUND

Gastrointestinal weight loss surgery, especially Roux-en-Y gastric bypass (RYGB), is the most effective treatment for severe obesity. RYGB is associated with a remarkable decrease in the rate of death from obesity-related complications, such as diabetes mellitus, coronary artery disease, and cancer. Dissecting the mechanisms of RYGB effects could augment our understanding about the pathogenesis of obesity and its complications.

OBJECTIVES AND METHODS

In this study, we describe in detail a mouse model of RYGB that closely reproduces the surgical steps of the human procedure.

RESULTS

We show that RYGB in mice has the same effects as in human patients, proving the high translational validity of this model system. We present an intraoperative video to facilitate the widespread use of this complex and difficult method.

CONCLUSIONS

The study of the mechanisms of RYGB using this model system can greatly facilitate our understanding about the effects of RYGB in human patients. The reverse engineering of the physiological mechanisms of RYGB could lead to discovery of new, effective, and less invasive treatments.

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.

Effect of weight loss after gastric bypass surgery on thyroid function in euthyroid people with morbid obesity

Obesity is positively associated with serum thyrotropin (TSH) concentrations at the high end of the normal range. The relationship between weight loss and thyroid function is less clear and studies to date have yielded inconsistent results. Our aim was to describe changes in thyroid function in obese people in relation to durable and significant weight loss after Roux-en-Y gastric bypass (RYGB) surgery. We recorded percentage of excess weight loss (% EWL), serum TSH and free thyroxine (fT4) before and median 4.5, 15 and 24 months after RYGB in 55 euthyroid patients with morbid obesity ranging in age from 18 to 64 years in a retrospective cohort analysis in a university hospital in Greater Manchester. Mean ± standard error preoperative weight was 135.13 ± 4.23 kg and BMI 48.08 ± 1.58 kg m(-2) . Patients attained nadir %EWL of 68% by median 15 months after RYGB. TSH was 2.00 ± 0.14 mU L(-1) at baseline and 2.02 ± 0.22 mU L(-1) at 24 months after RYGB (non-significant). Baseline fT4 was 13.46 ± 0.28 pmol L(-1) , and increased significantly to 15.14 ± 0.55 pmol L(-1) at 24 months (P < 0.004). In conclusion, we report that weight loss after RYGB was accompanied by significant increase in serum fT4 but no change in TSH concentrations. Further study to elucidate the effect of significant weight loss on the thyroid axis is required.

Appetite regulation and weight control: the role of gut hormones

The overwhelming increase in the prevalence of overweight and obesity in recent years represents one of the greatest threats to the health of the developed world. Among current treatments, however, gastrointestinal (GI) surgery remains the only approach capable of achieving significant weight loss results with long-term sustainability. As the obesity prevalence approaches epidemic proportions, the necessity to unravel the mechanisms regulating appetite control has garnered significant attention. It is well known that physical activity and food intake regulation are the two most important factors involved in body weight control. To regulate food intake, the brain must alter appetite. With this realization has come increased efforts to understand the intricate interplay between gut hormones and the central nervous system, and the role of these peptides in food intake regulation through appetite modulation. This review discusses the central mechanisms involved in body weight regulation and explores a suite of well characterized and intensely investigated anorexigenic and orexigenic gut hormones. Their appetite-regulating capabilities, post-GI surgery physiology and emerging potential as anti-obesity therapeutics are then reviewed.

Increased energy expenditure in gastric bypass rats is not caused by activated brown adipose tissue

OBJECTIVE

To investigate whether gastric bypass induces a higher activity of brown adipose tissue and greater levels of the brown adipose tissue-specific protein uncoupling protein-1 (UCP-1) in rats.

METHODS

Gastric bypass rats and sham-operated controls (each n = 8) underwent whole body (1)H-MR spectroscopy for analysis of body composition and (18)F-fluorodeoxyglucose positron emission tomography combined with computed tomography ((18)F-FDG PET/CT) imaging for measurement of the metabolic activity of brown adipose tissue. Brown adipose tissue was harvested and weighed, and UCP-1 mRNA content was measured by Northern Blot technique.

RESULTS

Gastric bypass rats had a significantly lower percentage of whole body adipose tissue mass compared to sham-operated rats (p = 0.001). There was no difference in brown adipose tissue activity between the two groups (standardised uptake value sham 2.81 ± 0.58 vs. bypass 2.56 ± 0.46 ; p = 0.73). Furthermore, there was no difference in the UCP-1 mRNA content of brown adipose tissue between the two groups (sham 49.5 ± 13.2 vs. bypass 43.7 ± 13.1; p = 0.77).

CONCLUSION

Gastric bypass does not increase the activity of brown adipose tissue in rats suggesting that other mechanisms are involved to explain the increased energy expenditure after bypass surgery. Our results cannot justify the radiation dose of (18)F-FDG PET/CT studies in humans to determine potential changes in brown adipose tissue after gastric bypass surgery.

Gastrostomy tube placement in gastric remnant at gastric bypass: a rat model for selective gut stimulation

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery achieves high remission rates of type 2 diabetes mellitus in obese diabetic patients. It has been hypothesized that the changes in bowel nutrient exposure after RYGB results in altered release of gut hormones and improved glucose homeostasis. Our objective was to assess the feasibility of, and report on, our technique and initial experience with selective gut stimulation in a gastric bypass rat model at an academic medical center in the United States.

METHODS

We performed RYGB with simultaneous placement of a gastrostomy tube in the excluded gastric remnant in 8 obese Sprague-Dawley rats. A second group of 8 obese Sprague-Dawley rats underwent gastrostomy tube placement without gastric bypass and served as the controls. Each rat was tested for oral glucose tolerance preoperatively. On postoperative days 14 and 28, glucose tolerance was re-evaluated using the oral and gastrostomy tube routes.

RESULTS

The gastrostomy tubes were successfully inserted in all the rats with no tube-related complications. The area under the curve after oral glucose gavage decreased significantly after gastric bypass (P = .01 at 14 d and P = .003 at 28 d). The gastric remnant glucose gavage after RYGB essentially reversed the effects of surgery on glucose metabolism. The areas under the curve showed no significant differences in the control group between the preoperative and postoperative oral or tube results.

CONCLUSION

Placing a gastrostomy tube into the gastric remnant at RYGB in a rat model is technically feasible. Our initial findings support the role of duodenal exclusion in improving glucose metabolism after RYGB.

Gastrointestinal hormones, energy balance and bariatric surgery

Despite increasing understanding of the changes in gastrointestinal and central neuroendocrine signaling following gastric bypass surgery (GBP) in morbidly obese patients, the mechanisms underlying weight loss and weight loss maintenance are not completely understood. Changes in energy expenditure are increasingly recognized as an important factor contributing to weight loss and metabolic effects in patients following GBP surgery. Experimental data regarding changes in energy balance following metabolic surgery in animal models suggest increased energy expenditure postoperatively as an important factor in the process of weight loss. However, the underlying neuroendocrine mechanisms are not well understood, and data regarding changes in energy expenditure in humans after GBP are inconsistent because of heterogenic patient populations and variable techniques. Nevertheless, a growing body of knowledge and understanding of the complex entero-neurohumoral interaction with its consequences in appetite, satiety and energy expenditure will help reveal the mechanisms of weight loss and weight loss maintenance following GBP surgery. Here we review how gastrointestinal hormones potentially regulate energy balance, and summarize current available experimental and clinical data on energy expenditure following obesity surgery.

Pancreatic polypeptide meal response may predict gastric band-induced weight loss

BACKGROUND

Unknown hormonal and neural satiety signals are thought to drive sustainable weight loss following laparoscopic adjustable gastric banding (LAGB). The objective of this study was to investigate whether the structurally related satiety hormones pancreatic polypeptide (PP) and peptide YY (PYY) influence total percentage weight loss after LAGB.

METHODS

A cross-sectional study examined 17 postoperative individuals who had already achieved a mean of 28% LAGB-induced weight loss (range, 10-38%). A prospective study assessed plasma PP and PYY meal responses in 16 obese individuals prior to LAGB.

RESULTS

In the cross-sectional study, individuals with higher weight loss had lower PP meal responses (2-h AUC, R = -0.60, p = 0.01) and lower fasting PYY levels (R = -0.55, p = 0.02). In the prospective study, subsequent mean weight loss was 20% (range, 5-50%) after a mean of 53 months. Low preoperative PP meal response (2-h AUC) predicted significantly higher subsequent weight loss after LAGB (R = -0.56, p = 0.024). The eight individuals with the lowest PP meal response lost more weight than the eight with the highest PP meal response (median 25% vs. 14%, p = 0.004). When compared across all three groups, mean PP meal responses did not differ. Fasting PYY levels, however, were significantly lower in the postoperative group compared to the group tested pre-operatively, or the BMI-matched controls (-30%, p = 0.03).

CONCLUSIONS

PYY appears reduced in proportion to weight loss following LAGB, possibly representing attempted orexigenic homeostatic compensation. Although PP responses appear unchanged by weight loss status, low PP meal response may predict higher weight loss. PP meal response may be a biological marker that could predict an individual's susceptibility to the mechanism underlying LAGB-induced weight loss.

A role for metalloendopeptidases in the breakdown of the gut hormone, PYY 3-36

Peptide YY(3-36) (PYY(3-36)) is a gut hormone that acts on Y2 receptors to reduce appetite. Obese humans are sensitive to the anorectic effects of PYY(3-36) and display a blunted postprandial rise in PYY(3-36). Bariatric surgery results in increased circulating PYY-immunoreactivity, which appears to play a role in postoperative weight loss. The utility of PYY(3-36) as an antiobesity treatment is limited by its short circulating half-life. Insight into the mechanisms by which PYY(3-36) is degraded may aid design of long-acting PYY(3-36) analogues or enzyme inhibitor therapies. We aimed to investigate the role of metalloendopeptidases in PYY(3-36) degradation and determine whether modulation of these enzymes enhanced PYY(3-36) plasma levels and bioactivity in vivo. Degradation and resultant cleavage products of PYY(3-36) were characterized after incubation with neprilysin and meprin β and with a kidney brush border preparation in vitro. Specific metalloendopeptidase inhibitors were coadministered with PYY(3-36) to mice and subsequent PYY(3-36) plasma levels and bioactivity determined. Meprin β cleaves PYY(3-36) at multiple conserved acidic sites. Blocking the actions of meprin β prevents the degradative effect of kidney brush borders on PYY(3-36). In mice, pretreatment with actinonin significantly prolonged the anorectic effect of PYY(3-36) and maintained higher PYY(3-36) plasma levels than treatment with PYY(3-36) alone. These studies suggest that inhibiting the degradation of PYY(3-36) using specific inhibitor therapies and/or the design of analogues resistant to cleavage by meprins may be useful to antiobesity therapeutics.

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".