Role of the foregut in the early improvement in glucose tolerance and insulin sensitivity following Roux-en-Y gastric bypass surgery

Gut peptides before and following Roux-En-Y gastric bypass: A systematic review and meta-analysis

A systematic search was conducted in Medline Ovid, Embase, Scopus, and Cochrane Central Register of Controlled Trials up until March 2021 following PRISMA guidelines. Studies included evaluated ghrelin, GLP-1, PYY or appetite sensation via visual analogue scales (VASs) before and after Roux-en-Y gastric bypass (RYGB) in adults. A multilevel model with random effects for study and follow-up time points nested in study was fit to the data. The model included kcal consumption as a covariate and time points as moderators. Among the 2559 articles identified, k = 47 were included, among which k = 19 evaluated ghrelin, k = 40 GLP-1, k = 22 PYY, and k = 8 appetite sensation. Our results indicate that fasting ghrelin levels are decreased 2 weeks post-RYGB (p = 0.005) but do not differ from baseline from 6 weeks to 1-year post-RYGB. Postprandial ghrelin and fasting GLP-1 levels were not different from pre-surgical values. Postprandial levels of GLP-1 increased significantly from 1 week (p < 0.001) to 2 years post-RYGB (p < 0.01) compared with pre-RYGB. Fasting PYY increased at 6 months (p = 0.034) and 1 year (p = 0.029) post-surgery; also, postprandial levels increased up to 1 year (p < 0.01). Insufficient data on appetite sensation were available to be meta-analyzed.

Physiology Reconfigured: How Does Bariatric Surgery Lead to Diabetes Remission?

Bariatric surgery improves glucose homeostasis and glycemic control in patients with type 2 diabetes. Over the past 20 years, a breadth of studies has been conducted in humans and rodents aimed to identify the regulatory nodes responsible for surgical remission of type 2 diabetes. The review herein discusses central mechanisms of type 2 diabetes remission associated with weight loss and surgical modification of the gastrointestinal tract.

Mucosal and hormonal adaptations after Roux-en-Y gastric bypass

The aim of this study was to perform a comprehensive literature review regarding the relevant hormonal and histologic changes observed after Roux-en-Y gastric bypass (RYGB). We aimed to describe the relevant hormonal (glucagon-like peptides 1 and 2 [GLP-1 and GLP-2], peptide YY [PYY], oxyntomodulin [OXM], bile acids [BA], cholecystokinin [CCK], ghrelin, glucagon, gastric inhibitory polypeptide [GIP], and amylin) profiles, as well as the histologic (mucosal cellular) adaptations happening after patients undergo RYGB. Our review compiles the current evidence and furthers the understanding of the rationale behind the food intake regulatory adaptations occurring after RYGB surgery. We identify gaps in the literature where the potential for future investigations and therapeutics may lie. We performed a comprehensive database search without language restrictions looking for RYGB bariatric surgery outcomes in patients with pre- and postoperative blood work hormonal profiling and/or gut mucosal biopsies. We gathered the relevant study results and describe them in this review. Where human findings were lacking, we included animal model studies. The amalgamation of physiologic, metabolic, and cellular adaptations following RYGB is yet to be fully characterized. This constitutes a fundamental aspiration for enhancing and individualizing obesity therapy.

Botulinum Injection Into the Proximal Intestinal Wall of Diet-Induced Obese Mice Leads to Weight Loss and Improves Glucose and Fat Tolerance

Botulinum neurotoxin (available commercially as BOTOX) has been used successfully for treatment of several neuromuscular disorders, including blepharospasm, dystonia, spasticity, and cerebral palsy in children. Our data demonstrate that injection of Botox into the proximal intestinal wall of diet-induced obese (DIO) mice induces weight loss and reduces food intake. This was associated with amelioration of hyperglycemia, hyperlipidemia, and significant improvement of glucose tolerance without alteration of energy expenditure. We also observed accelerated gastrointestinal transit and significant reductions in glucose and lipid absorption, which may account, at least in part, for the observed weight loss and robust metabolic benefits, although possible systemic effects occurring as a consequence of central and/or peripheral signaling cannot be ignored. The observed metabolic benefits were found to be largely independent of weight loss, as demonstrated by pair-feeding experiments. Effects lasted ∼8 weeks, for as long as the half-life of Botox as reported in prior rodent studies. These results have valuable clinical implications. If the observed effects are translatable in humans, this approach could lay the foundation for therapeutic approaches geared toward robust and sustained weight loss, mimicking some of the benefits of bariatric operations without its cost and complications.

Changes in Gastric Inhibitory Polypeptide (GIP) After Roux-en-Y Gastric Bypass in Obese Patients: a Meta-analysis

This meta-analysis aimed to evaluate changes in GIP after RYGB in obese patients. We searched PubMed, EMBASE, and CENTRAL for relevant studies from database inception through July 2021. Articles were eligible for inclusion if they reported pre-operative and post-operative fasting GIP levels. We found fasting GIP levels had a decreasing tendency. The decrease in fasting glucose and postprandial GIP levels was also observed. Subgroup analysis indicated diabetic subjects tended to have a more obvious fasting GIP reduction compared to non-diabetic individuals. Meta-regression showed that the amount of weight loss (% total body weight), gastric pouch volume, alimentary limb length, and biliopancreatic limb length were not related to fasting GIP decrease. Fasting GIP levels decreased significantly after RYGB in obese people, especially in diabetic patients.

Remission of type 2 diabetes after gastrectomy for gastric cancer: diabetes prediction score

BACKGROUND

Although type 2 diabetes (T2D) remission after gastric cancer surgery has been reported, little is known about the predictors of postoperative T2D remission.

METHODS

This study used data from a nationwide cohort provided by the National Health Insurance Service in Korea. We developed a diabetes prediction (DP) score, which predicted postoperative T2D remissions using a logistic regression model based on preoperative variables. We applied machine-learning algorithms [random forest, XGboost, and least absolute shrinkage and selection operator (LASSO) regression] and compared their predictive performances with those of the DP score.

RESULTS

The DP score comprised five parameters: baseline body mass index (< 25 or ≥ 25 kg/m²), surgical procedures (subtotal or total gastrectomy), age (< 65 or ≥ 65 years), fasting plasma glucose levels (≤ 130 or > 130 mg/dL), and antidiabetic medications (combination therapy including sulfonylureas, combination therapy not including sulfonylureas, single sulfonylurea, or single non-sulfonylurea]). The DP score showed a clinically useful predictive performance for T2D remission at 3 years after surgery [training cohort: area under the receiver operating characteristics (AUROC) 0.73, 95% confidence interval (CI), 0.71-0.75; validation cohort: AUROC 0.72, 95% CI 0.69-0.75], which was comparable to that of the machine-learning models (random forest: AUROC 0.71, 95% CI 0.68-0.74; XGboost: AUROC 0.70, 95% CI 0.67-0.73; LASSO regression: AUROC 0.75, 95% CI 0.73-0.78 in the validation cohort). It also predicted the T2D remission at 6 and 9 years after surgery.

CONCLUSIONS

The DP score is a useful scoring system for predicting T2D remission after gastric cancer surgery.

Daily transient coating of the intestine leads to weight loss and improved glucose tolerance

INTRODUCTION

Roux-en-Y gastric bypass surgery (RYGB) has been shown to be the gold standard treatment for obesity associated type-2-diabetes (T2D), however many T2D patients do not qualify or are reluctant to proceed with surgery due to its potential risks and permanent changes to GI anatomy. We have previously described a novel oral formulation, LuCI, that provides a transient coating of the proximal bowel and mimics the effects of RYGB. Herein, we aim to investigate the outcome of chronic LuCI administration on weight and glucose homeostasis.

METHODS

Sprague-Dawley rats on a high fat diet achieving diet-induced obesity (DIO) received 5 weeks of daily LuCI or normal saline as control (n = 8/group). Daily weights and glucose tolerance were monitored throughout the experiment. At 5 weeks, systemic blood was sampled through a surgically placed jugular vein catheter, before and during an intestinal glucose bolus, to investigate changes in key hormones involved in glucose metabolism. To elucidate the effects of LuCI on nutrient absorption, fecal output and food intake were measured simultaneously with the analysis of homogenized stool samples performed using bomb calorimetry.

RESULTS

At 5 weeks, LuCI animals weighted 8.3% less and had lower fasting glucose levels than Controls (77.6 ± 3.8 mg/dl vs. 99.1 ± 2.7 mg/dl, P < 0.001). LuCI-treated animals had lower baseline insulin and HOMA-IR. Post-prandially, LuCI group had increased GLP-1 and GIP secretion following a glucose challenge. Serum lipid analysis revealed lowered LDL levels highlighting the potential to not only improve glucose control but also modify cardiovascular risk. We then investigated whether LuCI's effect on proximal bowel exclusion may play a role in energy balance. Bomb calorimetry analysis suggested that LuCI reduced calorie absorption with no difference in caloric consumption.

CONCLUSION

We demonstrated that LuCI recapitulates the physical and hormonal changes seen after RYGB and can ameliorate weight gain and improve insulin sensitivity in a DIO rat model. Since LuCI's effect is transient and without systemic absorption, LuCI has the potential to be a novel therapy for overweight or obese T2D patients.

Gastric bypass prevents diabetes in genetically modified mice and chemically induced diabetic mice

Obese subjects have increase probabilities of developing type 2 diabetes (T2D). In this study, we sought to determine whether gastric bypass prevents the progression of prediabetes to overt diabetes in genetically modified mice and chemically induced diabetic mice. Roux-en-Y gastric bypass (RYGB) was performed in C57BL/KsJ-db/db null (BKS-db/db,) mice, high-fat diet (HFD)-fed NONcNZO10/LtJ (NZO) mice, C57BL/6 db/db null (B6-db/db) mice and streptozotocin (STZ)-induced diabetic mice. Food consumption, body weight, fat mass, fast blood glucose level, circulating insulin and adiponectin and glucose tolerance test were analyzed. The liver and pancreatic tissues were subjected to H&E and immunohistochemistry staining and islet cells to flow cytometry for apoptotic analysis. RYGB resulted in sustained normoglycemia and improved glucose tolerance in young prediabetic BKS-db/db mice (at the age of 6 weeks with hyperglycemia and normal insulinemia) and HFD-fed NZO and B6-db/db mice. Remarkably, RYGB improved liver steatosis, preserved the pancreatic β-cells and reduced β-cell apoptosis with increases in circulating insulin and adiponectin in young prediabetic BKS-db/db mice. However, RYGB neither reversed hyperglycemia in adult diabetic BKS-db/db mice (12 weeks old) nor attenuated hyperglycemia in STZ-induced diabetic mice. These results demonstrate that gastric bypass improves hyperglycemia in genetically modified prediabetic mice; however, it should be performed prior to β-cells exhaustion.

Foregut Exclusion Enhances Incretin and Insulin Secretion After Roux-en-Y Gastric Bypass in Adults With Type 2 Diabetes

INTRODUCTION

Patients with type 2 diabetes experience resolution of hyperglycemia within days after Roux-en-Y gastric bypass (RYGB) surgery. This is attributed, in part, to enhanced secretion of hindgut factors following exclusion of the gastric remnant and proximal intestine during surgery. However, evidence of the mechanisms of remission remain limited due to the challenges of metabolic evaluation during the early postoperative period. The purpose of this investigation was to determine the role of foregut exclusion in the resolution of type 2 diabetes after RYGB.

METHODS

Patients with type 2 diabetes (n = 15) undergoing RYGB had a gastrostomy tube (G-tube) placed in their gastric remnant at time of surgery. Patients were randomized to receive a mixed meal tolerance test via oral or G-tube feeding immediately prior to and 2 weeks after surgery in a repeated measures crossover design. Plasma glucose, insulin, C-peptide, incretin responses, and indices of meal-stimulated insulin secretion and sensitivity were determined.

RESULTS

Body weight, fat mass, fasting glucose and insulin, and circulating lipids were significantly decreased 2 weeks after surgery. The glycemic response to feeding was reduced as a function of total area under the curve but not after adjustment for the reduction in fasting glucose. Oral feeding significantly enhanced insulin and incretin secretion after RYGB, which was entirely ablated by G-tube feeding.

CONCLUSION

Foregut exclusion accounts for the rise in incretin and insulin secretion but may not fully explain the early improvements in glucose metabolism after RYGB surgery.

Systematic Review and Meta-analysis of the Change in Ghrelin Levels After Roux-en-Y Gastric Bypass

BACKGROUND

Roux-en-Y gastric bypass (RYGB) is considered effective for weight loss and for treatment of many obesity-related metabolic diseases. Ghrelin is an essential orexigenic peptide that plays an indispensable role in controlling body weight and energy homeostasis of post-operative patients. This systematic review and meta-analysis aimed to investigate changes in the level of fasting total ghrelin following RYGB.

METHODS

A systematic literature search of PubMed, EMBASE, and the Cochrane Library until April 2018 with keywords "ghrelin" and "gastric bypass" was performed in accordance with the MOOSE guidelines and PRISMA statement. Three reviewers independently selected the studies and extracted data. Quality assessment of the included studies was undergone. A random effects model was employed to calculate overall effect sizes. Subgroup analyses and meta-regression were subsequently performed.

RESULTS

Sixteen studies with 325 patients were included. We found ghrelin levels had an increasing tendency (SMD = 0.30; 95% CI = 0.04 to 0.57) despite moderate heterogeneity (I² = 58%). Subsequent subgroup analysis indicated that ghrelin levels decreased (SMD = - 0.49; 95% CI = - 0.98 to 0.00) in the short term (≤ 3 months) and increased (SMD = 0.46; 95% CI = 0.22 to 0.69) in the long term (> 3 months) after RYGB. Meta-regression showed that gastric pouch volume, alimentary limb length and biliopancreatic limb length were not associated with changes in ghrelin levels.

CONCLUSION

Fasting total ghrelin levels decreased in the short term (≤ 3 months) and increased in the long term (> 3 months) after RYGB.

Preserving Duodenal-Jejunal (Foregut) Transit Does Not Impair Glucose Tolerance and Diabetes Remission Following Gastric Bypass in Type 2 Diabetes Sprague-Dawley Rat Model

BACKGROUND

Possible mechanisms underlying diabetes remission following Roux-en-Y gastric bypass (RYGB) include eradication of putative factor(s) with duodenal-jejunal bypass.

OBJECTIVE

The objective of this study is to observe the effects of duodenal-jejunal transit on glucose tolerance and diabetes remission in gastric bypass rat model.

METHOD

In order to verify the effect of duodenal-jejunal transit on glucose tolerance and diabetes remission in gastric bypass, 22 type 2 diabetes Sprague-Dawley rat models established through high-fat diet and low-dose streptozotocin (STZ) administered intraperitoneally were assigned to one of three groups: gastric bypass with duodenal-jejunal transit (GB-DJT n = 8), gastric bypass without duodenal-jejunal transit (RYGB n = 8), and sham (n = 6). Body weight, food intake, blood glucose, as well as meal-stimulated insulin, and incretin hormone responses were assessed to ascertain the effect of surgery in all groups. Oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) were conducted three and 7 weeks after surgery.

RESULTS

Comparing our GB-DJT to the RYGB group, we saw no differences in the mean decline in body weight, food intake, and blood glucose 8 weeks after surgery. GB-DJT group exhibited immediate and sustained glucose control throughout the study. Glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP) levels were also significantly increased from preoperative level in the GB-DJT group (p < 0.05). Insulin and GLP-1 area under curve (AUC) as well as improved glycemic excursion on OGTT did not differ between GB-DJT and RYGB groups. Outcomes with sham operation did not differ from preoperative level.

CONCLUSION

Preserving duodenal-jejunal transit does not impede glucose tolerance and diabetes remission after gastric bypass in type-2 diabetes Sprague-Dawley rat model.

GLP-1: Molecular mechanisms and outcomes of a complex signaling system

Meal ingestion provokes the release of hormones and transmitters, which in turn regulate energy homeostasis and feeding behavior. One such hormone, glucagon-like peptide-1 (GLP-1), has received significant attention in the treatment of obesity and diabetes due to its potent incretin effect. In addition to the peripheral actions of GLP-1, this hormone is able to alter behavior through the modulation of multiple neural circuits. Recent work that focused on elucidating the mechanisms and outcomes of GLP-1 neuromodulation led to the discovery of an impressive array of GLP-1 actions. Here, we summarize the many levels at which the GLP-1 signal adapts to different systems, with the goal being to provide a background against which to guide future research.

Metabolic Effects of Bile Acids: Potential Role in Bariatric Surgery

Bariatric surgery is the most effective and durable treatment for morbid obesity, with an unexplained yet beneficial side effect of restoring insulin sensitivity and improving glycemia, often before weight loss is observed. Among the many contributing mechanisms often cited, the altered handling of intestinal bile acids is of considerable therapeutic interest. Here, we review a growing body of literature examining the metabolic effects of bile acids ranging from their physical roles in dietary fat handling within the intestine to their functions as endocrine and paracrine hormones in potentiating responses to bariatric surgery. The roles of 2 important bile acid receptors, Takeda G-protein coupled receptor (also known as G-protein coupled bile acid receptor) and farnesoid X receptor, are highlighted as is downstream signaling through glucagon-like polypeptide 1 and its cognate receptor. Additional improvements in other phenotypes and potential contributions of commensal gut bacteria, such as Akkermansia muciniphila, which are manifest after Roux-en-Y gastric bypass and other emulations, such as gallbladder bile diversion to the ileum, are also discussed.

Early glycemic control and incretin improvement after gastric bypass: the role of oral and gastrostomy route

BACKGROUND

Patients with obesity have a suppressed incretin effect and a consequent imbalance of glycemic homeostasis. Several studies have shown improved type 2 diabetes after Roux-en-Y gastric bypass (RYGB). The mechanisms of early action are linked to caloric restriction, improvement of insulin resistance, pancreatic beta cell function, and the incretin effect of glycogen-like protein 1 and gastric inhibitory polypeptide, but reported data are conflicting.

OBJECTIVE

The objective of this study was to evaluate glycemic metabolism, including the oral glucose tolerance test and enterohormonal profile in the early postoperative period in severely obese patients who underwent RYGB with gastrostomy, comparing the preoperative supply of a standard bolus of nutrient against the postoperative administration through an oral and a gastrostomy route.

SETTING

Clinics Hospital of University of São Paulo, Brazil.

METHODS

Eleven patients with obesity and diabetes underwent RYGB with a gastrostomy performed in the excluded gastric remnant. Patients were given preoperative assessments of glycemic and enterohormone profiles and an oral glucose tolerance test; these were compared with early postoperative assessments after oral and gastrostomy route administrations.

RESULTS

The mean preoperative body mass index of the group was 44.1 ± 6.6 kg/m², mean fasting blood glucose of 194.5 ± 62.4 mg/dL, and glycated hemoglobin 8.7 ± 1.6%. In 77.7% of the patients, there was normalization of the glycemic curve in the early postoperative period as evaluated by the oral glucose tolerance test. Significant decreases in glycemia, insulinemia, and homeostatic model assessment-insulin resistance were also observed, regardless of the route of administration. There was significant increase in glycogen-like protein 1 by the postoperative oral route and reduction of gastric inhibitory polypeptide in both routes. Ghrelin did not change.

CONCLUSION

Glycemia and peripheral insulin resistance reductions were observed in early-postoperative RYGB, independent of the oral or gastrostomy route. Incretin improvement, mediated by glycogen-like protein 1 increased was observed only in the postoperative oral route, while GIP reduced for both routes.

A Meta-Analysis of GLP-1 After Roux-En-Y Gastric Bypass: Impact of Surgical Technique and Measurement Strategy

BACKGROUND

Roux-en-Y gastric bypass (RYGB) is an effective treatment for diabetes. Glucagon-like peptide-1 (GLP-1) is a gut hormone that is important to glucose homeostasis.

OBJECTIVE

This study aimed to assess GLP-1 level and its predictors after RYGB.

METHODS

The study design was a meta-analysis. The data sources were MEDLINE, EMBASE, Web of Science, and the Cochrane Databases. The study selection composed of studies with pre- and post-RYGB levels. The main outcomes were as follows: Primary outcome was the change in postprandial GLP-1 levels after RYGB. Secondary outcomes included the changes in fasting glucose, fasting insulin, and fasting GLP-1 levels after RYGB. Meta-regression to determine predictors of changes in GLP-1 levels was performed. Outcomes were reported using Hedge's g.

RESULTS

Twenty-four studies with 368 patients were included. Postprandial GLP-1 levels increased after RYGB (Hedge's g = 1.29, p < 0.0001), while fasting GLP-1 did not change (p = 0.23). Peak postprandial GLP-1 levels gave the most consistent results (I ² = 9.11). Fasting glucose and insulin levels decreased after RYGB (p < 0.0001). Roux limb length was a significant predictor for amount of GLP-1 increase (β = - 0.01, p = 0.02). Diabetes status, amount of weight loss, length of biliopancreatic limb, and time of measurement were not significant predictors (p > 0.05).

CONCLUSION

Postprandial GLP-1 levels increase after RYGB, while fasting levels remain unchanged. Shorter Roux limb length is associated with greater increase in postprandial GLP-1, which may lead to better glycemic control in this population.

The effect of distal-ileal exclusion after Roux-en-Y gastric bypass on glucose tolerance and GLP-1 response in type-2 diabetes Sprague-Dawley rat model

BACKGROUND

An increase in glucagon-like peptide-1 (GLP-1) mediating early diabetes remission after Roux-en-Y gastric bypass (RYGB) is believed to be associated with distal-ileal stimulation.

OBJECTIVE

To observe the effect of distal-ileal exclusion on glucose tolerance and GLP-1 response after RYGB.

SETTING

Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China.

METHODS

A type 2 diabetes model was created in 40 Sprague-Dawley rats that were randomly assigned to a RYGB group (n = 32) and a sham group (n = 8). Four weeks after surgery, the RYGB group was further divided into the RYGB control group (n = 8) and the distal-ileal exclusion group (RYGB-IEx, n = 24). Rats in the RYGB-IEx group underwent laparotomy, and the last 20 cm of ileum was excluded. An oral glucose tolerance test, insulin tolerance test, and mixed-meal tolerance test conducted preoperatively were repeated in all groups at 4 and 8 weeks postoperatively.

RESULTS

Compared with preoperative level, GLP-1 was significantly increased after RYGB. GLP-1 area under the curve recorded after oral gavage at week 4 postoperatively was significantly higher than the preoperative level (P < .05). GLP-1, insulin area under the curve, and improved glucose-excursion on oral glucose tolerance test 4 weeks after gastric bypass were not reversed at week 8 after distal-ileal exclusion in the RYGB-IEx group. Food intake increased significantly after distal-ileal exclusion in the RYGB-IEx group.

CONCLUSION

These findings suggest that distal-ileal stimulation might not be required for incretin response and diabetes remission after gastric bypass in the type 2 diabetes Sprague-Dawley rat model.

Appetite, Glycemia, and Entero-Insular Hormone Responses Differ Between Oral, Gastric-Remnant, and Duodenal Administration of a Mixed-Meal Test After Roux-en-Y Gastric Bypass

OBJECTIVE

To examine the effect of different feeding routes on appetite and metabolic responses after Roux-en-Y gastric bypass (RYGB).

RESEARCH DESIGN AND METHODS

A standard liquid meal was administered either orally, into the gastric remnant, or intraduodenally 6 months after RYGB. Changes in plasma glucose, insulin, glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), peptide YY (PYY), and appetite were measured pre- and postprandially.

RESULTS

Postprandial GLP-1 and PYY responses were similar, whereas glucose, insulin, and GIP levels differed markedly after oral versus intraduodenal feeding. Intraduodenal feeding prompted an intermediate appetite response (i.e., between oral and intragastric). For postprandial glucose, insulin, and GIP levels, the intraduodenal route was more similar to the intragastric than the oral route. Intragastric administration did not evoke changes in appetite, glucose, or insulin; however, it slightly increased GLP-1 and PYY and moderately increased GIP.

CONCLUSIONS

Appetite and metabolic responses after RYGB depend on the route by which nutrients enter the gastrointestinal tract.

Roux en Y gastric bypass hypoglycemia resolves with gastric feeding or reversal: Confirming a non-pancreatic etiology

OBJECTIVE

Postprandial hypoglycemia is an infrequent but disabling complication of Roux-en-Y gastric bypass (RYGB) surgery. Controversy still exists as to whether the postprandial hyperinsulinemia observed is due to inherent changes in pancreatic β-cell mass or function or to reversible alterations caused by RYGB anatomy. We aimed to determine if gastric feeding or reversal of RYGB would normalize postprandial glucose and hormone excursions in patients with symptomatic hypoglycemia.

METHODS

We completed a prospective study of six patients with severe symptomatic RYGB hypoglycemia who underwent RYGB reversal. An additional subject without hypoglycemia who underwent RYGB reversal was also studied prospectively. Mixed meal tolerance testing (MTT) was done orally (RYGB anatomy), via gastrostomy tube in the excluded stomach in the setting of RYGB, and several months after RYGB reversal.

RESULTS

All subjects reported symptomatic improvement of hypoglycemia after reversal of RYGB. Weight gain after reversal was moderate and variable. Postprandial glucose, insulin, and GLP-1 excursions were significantly diminished with gastric feeding and after reversal. Insulin secretion changed proportional to glucose levels and insulin clearance increased after reversal. Glucagon/insulin ratios were similar throughout study. We further compared the impact of modified sleeve gastrectomy reversal surgery to those with restoration of complete stomach and found no significant differences in weight regain or in postprandial glucose or hormone levels.

CONCLUSIONS

Reversal of RYGB is an effective treatment option for severe postprandial hypoglycemia. The pathophysiology of this disorder is primarily due to RYGB anatomy resulting in altered glucose, gut, and pancreatic hormone levels and decreased insulin clearance, rather than inherent β-cell hyperplasia or hyperfunction.

Impaired Enterohormone Response Following a Liquid Test Meal in Gastrectomized Patients

BACKGROUND

Total gastrectomy (TG) is responsible for symptoms or disturbance of alimentary status (changes in body weight, food intake per meal and frequency of meal per day) which, in turn are responsible for weight loss and malnutrition. The study evaluates the gut hormone responses in totally gastrectomized (TG) patients after a liquid meal test.

METHODS

Twenty total gastrectomized cancer-free patients (12 M, 8 F, 56.4 ± 10.2 years, BMI 21.4 ± 2.2 kg/m2) and 10 healthy volunteers (4 M, 6 F, 48.0 ± 12.7 years, BMI 26.7 ± 3.0 kg/m2 ) drank a liquid meal (1.25 kcal/mL) at the rate of 50 mL/5' min for a maximum of 30 min. Satiety score was assessed and blood sample was taken at different time points.

RESULTS

The time response course, particularly for insulin, glucose-like pepetide-1, and cholecystokinin, significantly differed between TG patients and controls.

CONCLUSIONS

Our results may help to better understand hormone responses triggered by the faster arrival of nutrients in the small bowel and to explain some post-TG symptoms.

Pediatric Nonalcoholic Fatty Liver Disease: the Rise of a Lethal Disease Among Mexican American Hispanic Children

Hispanic children of Mexican origin have a high incidence of NAFLD. Susceptibility has been linked to a combination of factors including an increasing epidemic of obesity in children and adolescents, an allele substitution in the PNPLA3 gene that reduces hepatic lipid catabolism, and an altered microbiome that may increase hepatic endotoxins. The combination of NAFLD and portal vein toxins secondary to an indigenous gut microbiome appear to lead to the early occurrence of NASH, which progresses to cirrhosis and early hepatocellular carcinoma. Early detection and treatment of hepatic changes are needed. Given the success of gastric bypass in reducing body weight, modifying the gut microbiome, and improving NAFLD/NASH in adults, a trial of gastric bypass in predisposed pediatric candidates should be undertaken.

Neuroendocrine mechanisms underlying bariatric surgery: Insights from human studies and animal models

Obesity has reached epidemic proportions and, to date, bariatric surgery remains the only effective treatment for morbid obesity in terms of its capacity to achieve durable weight loss. Bariatric surgery procedures, including Roux-en-Y gastric bypass (RYGB), adjustable gastric banding (AGB) and sleeve gastrectomy (SG), have been the primary procedures conducted over the past decade, with SG increasing in popularity over the past 5 years at the expense of both RYGB and AGB. Although these procedures were initially proposed to function via restrictive or malabsorptive mechanisms, it is now clear that profound physiological changes underlie the metabolic improvements in patients who undergo bariatric surgery. Data generated in human patients and animal models highlight the rapid and sustained changes in gut hormones that coincide with these procedures. Furthermore, recent studies highlight the involvement of the nervous system, specifically the vagus nerve, in mediating the reduction in appetite and food intake following bariatric surgery. What is unclear is where these pathways converge and interact within the gut-brain axis and whether vagally-mediated circuits are sufficient to drive the metabolic sequalae following bariatric surgery.

Neuroendocrine regulation of energy balance: Implications on the development and surgical treatment of obesity

INTRODUCTION

Obesity, a serious public health problem, occurs mainly when food consumption exceeds energy expenditure. Therefore, energy balance depends on the regulation of the hunger-satiety mechanism, which involves interconnection of the central nervous system and peripheral signals from the adipose tissue, pancreas and gastrointestinal tract, generating responses in short-term food intake and long-term energy balance. Increased body fat alters the gut- and adipose-tissue-derived hormone signaling, which promotes modifications in appetite-regulating hormones, decreasing satiety and increasing hunger senses. With the failure of conventional weight loss interventions (dietary treatment, exercise, drugs and lifestyle modifications), bariatric surgeries are well-accepted tools for the treatment of severe obesity, with long-term and sustained weight loss. Bariatric surgeries may cause weight loss due to restriction/malabsorption of nutrients from the anatomical alteration of the gastrointestinal tract that decreases energy intake, but also by other physiological factors associated with better results of the surgical procedure.

OBJECTIVE

This review discusses the neuroendocrine regulation of energy balance, with description of the predominant hormones and peptides involved in the control of energy balance in obesity and all currently available bariatric surgeries.

CONCLUSIONS

According to the findings of our review, bariatric surgeries promote effective and sustained weight loss not only by reducing calorie intake, but also by precipitating changes in appetite control, satiation and satiety, and physiological changes in gut-, neuro- and adipose-tissue-derived hormone signaling.

A new proposed mechanism of action for gastric bypass surgery: Air hypothesis

Roux-en-Y gastric bypass (RYGB) surgery is one of the most effective treatments for obesity and type II diabetes. RYGB was originally believed to work by mechanically restricting caloric intake or causing macronutrient malabsorption. However, such mechanical effects play no role in the remarkable efficacy of gastric bypass. Instead, mounting evidence shows that altered neuroendocrine signaling is responsible for the weight reducing effects of RYGB. The exact mechanism of this surgical response is still a mystery. Here, we propose that RYGB leads to weight loss primarily by inducing a functional shift in the gut microbiome, manifested by a relative expansion of aerobic bacteria numbers in the colon. We point to compelling evidence that gastric bypass changes the function of the microbiome by disrupting intestinal gas homeostasis, causing excessive transit of swallowed air (oxygen) into the colon.

Bile acids and bariatric surgery

Bariatric surgery, specifically Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), are the most effective and durable treatments for morbid obesity and potentially a viable treatment for type 2 diabetes (T2D). The resolution rate of T2D following these procedures is between 40 and 80% and far surpasses that achieved by medical management alone. The molecular basis for this improvement is not entirely understood, but has been attributed in part to the altered enterohepatic circulation of bile acids. In this review we highlight how bile acids potentially contribute to improved lipid and glucose homeostasis, insulin sensitivity and energy expenditure after these procedures. The impact of altered bile acid levels in enterohepatic circulation is also associated with changes in gut microflora, which may further contribute to some of these beneficial effects. We highlight the beneficial effects of experimental surgical procedures in rodents that alter bile secretory flow without gastric restriction or altering nutrient flow. This information suggests a role for bile acids beyond dietary fat emulsification in altering whole body glucose and lipid metabolism strongly, and also suggests emerging roles for the activation of the bile acid receptors farnesoid x receptor (FXR) and G-protein coupled bile acid receptor (TGR5) in these improvements. The limitations of rodent studies and the current state of our understanding is reviewed and the potential effects of bile acids mediating the short- and long-term metabolic improvements after bariatric surgery is critically examined.

Changes in glycemia, insulin and gut hormone responses to a slowly ingested solid low-carbohydrate mixed meal after laparoscopic gastric bypass or band surgery

OBJECTIVE

To evaluate early changes in glycemia, insulin physiology and gut hormone responses to an easily tolerated and slowly ingested solid, low-carbohydrate mixed meal test (MMT) following laparoscopic adjustable gastric banding (LAGB) or Roux-en-Y gastric bypass (RYGB) surgery.

SUBJECTS/METHODS

This was a prospective non-randomized study. Plasma glucose, insulin and c-peptide (to estimate hepatic insulin extraction; %HIE), incretins (GIP, aGLP-1) and pancreatic polypeptide (PP) responses to the MMT were measured at 4-8 weeks before and after surgery in obese, metabolically healthy patients (RYGB=10F or LAGB =7F/1M). Supplementary clamp data on basal endogenous glucose production (EGP) and peripheral insulin action (Rd=rate of glucose disposal) and metabolic clearance rates of insulin (MCR-INS) were available in five of the RYGB patients. Repeated measures were appropriately accounted for in the analyses.

RESULTS

Following LAGB surgery, C-peptide and insulin MMT profiles (P=0.004 and P=0.0005, respectively) were lower with no change in %HIE (P=0.98). In contrast, in RYGB subjects, both fasting glucose and insulin (Δ=-0.66 mmol l^-1, P⩽0.05 and Δ=-44.4 pmol l^-1, P⩽0.05, respectively) decreased, and MMT glucose (P<0.0001) and insulin (P=0.001) but not c-peptide (P= 0.69) decreased. Estimated %HIE increased at fasting (Δ=8.4%, P⩽0.05) and during MMT (P=0.0005). Early (0-20 min) prandial glucose (0.27±0.26 versus 0.006±0.21 mmol l^-1, P⩽0.05) and insulin (63(48, 66) versus 18(12, 24) pmol l^-1, P⩽0.05) responses increased after RYGB. RYGB altered the trajectory of prandial aGLP-1 responses (treatment × trajectory P=0.02), and PP was lower (P<0.0001). Clamp data in a subset of RYGB patients showed early improvement in basal EGP (P=0.001), and MCR-INS (P=0.015).

CONCLUSION

RYGB results in distinctly different changes in plasma glucose, insulin and gut hormone response patterns to a solid, slowly ingested low-carbohydrate MMT versus LAGB. Altered nutrient delivery, along with indirect evidence for changes in hepatic and peripheral insulin physiology, are consistent with the greater early improvement in glycemia observed after RYGB versus LAGB surgery.

Recent advances in metabolic and bariatric surgery

Obesity and its associated medical conditions continue to increase and add significant burden to patients, as well as health-care systems, worldwide. Bariatric surgery is the most effective treatment for severe obesity and its comorbidities, and resolution of diabetes is weight loss-independent in the case of some operations. Although these weight-independent effects are frequently described clinically, the mechanisms behind them are not well understood and remain an intense area of focus in the growing field of metabolic and bariatric surgery. Perceptions of the mechanisms responsible for the beneficial metabolic effects of metabolic/bariatric operations have shifted from being mostly restrictive and malabsorption over the last 10 to 15 years to being more neuro-hormonal in origin. In this review, we describe recent basic and clinical findings of the major clinical procedures (adjustable gastric banding, vertical sleeve gastrectomy, Roux-en-Y gastric bypass, and biliopancreatic diversion) as well as other experimental procedures (ileal interposition and bile diversion) that recapitulate many of the metabolic effects of these complex operations in a simpler fashion. As the role of bile acids and the gut microbiome on metabolism is becoming increasingly well described, their potential roles in these improvements following metabolic surgery are becoming better appreciated. Bile acid and gut microbiome changes, in light of recent developments, are discussed in the context of these surgical procedures, as well as their implications for future study.

Surgical cure for type 2 diabetes by foregut or hindgut operations: a myth or reality? A systematic review

BACKGROUND

Bariatric surgery results in remission of type 2 diabetes mellitus in a significant proportion of patients. Animal research has proposed the foregut and hindgut hypotheses as possible mechanisms of remission of T2DM independent of weight loss. These hypotheses have formed the basis of investigational procedures designed to treat T2DM in non-obese (in addition to obese) patients. The aim of this study was to review the procedures that utilise the foregut and hindgut hypotheses to treat T2DM in humans.

METHODS

A systematic review was conducted to identify the investigational procedures performed in humans that are based on the foregut and hindgut hypotheses and then to assess their outcomes.

RESULTS

Twenty-four studies reported novel procedures to treat T2DM in humans; only ten utilised glycated haemoglobin A1c (HbA1c) in their definition of remission. Reported remission rates were 20-40 % for duodenal-jejunal bypass (DJB), 73-93 % for duodenal-jejunal bypass with sleeve gastrectomy (DJB-SG), 62.5-100 % for duodenal-jejunal bypass sleeve (DJBS) and 47-95.7 % for ileal interposition with sleeve gastrectomy (II-SG). When using a predetermined level of HbA1c to define remission, the remission rates were lower (27, 63, 0 and 65 %) for DJB, DJB-SG, DJBS and II-SG.

CONCLUSIONS

The outcomes of the foregut- and hindgut-based procedures are not better than the outcomes of just one of their components, namely sleeve gastrectomy. The complexity of these procedures in addition to their comparable outcomes to a simpler operation questions their utility.

Mechanisms of surgical control of type 2 diabetes: GLP-1 is key factor

GLP-1 secretion in response to meals is dramatically increased after gastric bypass operations. GLP-1 is a powerful insulinotropic and anorectic hormone, and analogs of GLP-1 are widely used for the treatment of diabetes and recently approved also for obesity treatment. It is, therefore, reasonable to assume that the exaggerated GLP-1 secretion contributes to the antidiabetic and anorectic effects of gastric bypass. Indeed, human experiments with the GLP-1 receptor antagonist, Exendin 9-39, have shown that the improved insulin secretion, which is responsible for part of the antidiabetic effect of the operation, is reduced and or abolished after GLP-1 receptor blockade. Also the postoperative improvement of glucose tolerance is eliminated and or reduced by the antagonist, pointing to a key role for the exaggerated GLP-1 secretion. Indeed, there is evidence that the exaggerated GLP-1 secretion is also responsible for postprandial hypoglycemia sometimes observed after bypass. Other operations (biliopancreatic-diversion and or sleeve gastrectomy) appear to involve different and/or additional mechanisms, and so does experimental bariatric surgery in rodents. However, unlike bypass surgery in humans, the rodent operations are generally associated with increased energy metabolism pointing to an entirely different mechanism of action in the animals.

Surgical treatment of type 2 diabetes in subjects with mild obesity: mechanisms underlying metabolic improvements

BACKGROUND

This study aims to assess the clinical and physiological effects of Roux-en-Y gastric bypass (RYGBP) on type 2 diabetes associated with mild obesity (body mass index [BMI] 30-34.9 kg/m(2)) over 24 months postsurgery.

METHODS

In this prospective trial, 36 mildly obese subjects (19 males) with type 2 diabetes using oral antidiabetic drugs with (n = 24) or without insulin (n = 12) underwent RYGBP. Follow-up was conducted at baseline and 3, 6, 12, and 24 months postsurgery. The following endpoints were considered: changes in HbA1c, fasting glucose and insulin, antidiabetic therapy, BMI, oral glucose insulin sensitivity [OGIS, from meal tolerance test (MTT)], beta-cell secretory function [ΔCP(0-30)/ΔGlu(0-30) (ΔC-peptide/Δglucose ratio, MTT 0-30 min), disposition index (DI = OGIS [Symbol: see text] ΔCP(0-30)/ΔGlu(0-30)], glucagon-like peptide (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) [incremental area under the curve (AUCi)], adiponectin, C-reactive protein, and lipids.

RESULTS

All subjects achieved normal-to-overweight BMI after 3 months. Over 24 months, 31/36 (86 %) subjects presented HbA1c <7 % [complete and partial remission of diabetes in 9/36 (22 %) and 1/36 (3 %), respectively]. Since 3 months postsurgery, improvements were observed in OGIS [290 (174) to 373 (77) ml/min/m(2), P = 0.009], ΔCP(0-30)/ΔGlu(0-30) [0.24 (0.19) to 0.52 (0.34) ng/mg, P = 0.001], DI [7.16 (8.53) to 19.8 (15.4) (ng/mg) (ml/min/m(2)), P = 0.001], GLP-1 AUCi [0.56 (0.64) to 3.97 (3.86) ng/dl [Symbol: see text] 10 min [Symbol: see text] 103, P = 0.000], and GIP AUCi [30.2 (12.6) to 27.0 (20.2) ng/dl [Symbol: see text] 10 min [Symbol: see text] 103, P = 0.004]. At baseline and after 12 months, subjects with diabetes nonremission had longer diabetes duration, higher HbA1c, lower beta-cell secretory function, and higher first 30-min GIP AUCi, compared with those with remission.

CONCLUSIONS

RYGBP improves the glucose metabolism in subjects with type 2 diabetes and mild obesity. This effect is associated with improvement of insulin sensitivity, beta-cell secretory function, and incretin secretion.

GLP-1: a mediator of the beneficial metabolic effects of bariatric surgery?

There has been increasing interest in the role that gut hormones may play in contributing to the physiological changes produced by certain bariatric procedures, such as Roux-en-Y gastric bypass and sleeve gastrectomy. Here, we review the evidence implicating one such gut hormone, glucagon-like peptide-1, as a mediator of the metabolic benefits of these two procedures.

How Durable Are the Effects After Metabolic Surgery?

Bariatric surgery was initially developed as a tool for weight reduction only, but it is gaining popularity because of its remarkable effect on glucose metabolism in morbidly obese and less obese patients. Recent publications have shown the superiority of metabolic surgery over medical treatment for diabetes, creating a new field of clinical research that is currently overflowing in the medical community with outstanding high-quality data. Metabolic surgery is effective in treating diabetes, even in non-morbidly obese patients.

Bile diversion to the distal small intestine has comparable metabolic benefits to bariatric surgery

Roux-en-Y gastric bypass (RYGB) is highly effective in reversing obesity and associated diabetes. Recent observations in humans suggest a contributing role of increased circulating bile acids in mediating such effects. Here we use a diet-induced obesity (DIO) mouse model and compare metabolic remission when bile flow is diverted through a gallbladder anastomosis to jejunum, ileum or duodenum (sham control). We find that only bile diversion to the ileum results in physiologic changes similar to RYGB, including sustained improvements in weight, glucose tolerance and hepatic steatosis despite differential effects on hepatic gene expression. Circulating free fatty acids and triglycerides decrease while bile acids increase, particularly conjugated tauro-β-muricholic acid, an FXR antagonist. Activity of the hepatic FXR/FGF15 signalling axis is reduced and associated with altered gut microbiota. Thus bile diversion, independent of surgical rearrangement of the gastrointestinal tract, imparts significant weight loss accompanied by improved glucose and lipid homeostasis that are hallmarks of RYGB.

Intestinal sweet-sensing pathways and metabolic changes after Roux-en-Y gastric bypass surgery

Studies suggest that improvements in type 2 diabetes (T2D) post- Roux-en-Y gastric bypass (RYGB) surgery are attributable to decreased intestinal glucose absorption capacity mediated by exclusion of sweet taste-sensing pathways in isolated proximal bowel. We probed these pathways in rat models that had undergone RYGB with catheter placement in the biliopancreatic (BP) limb to permit post-RYGB exposure of isolated bowel to sweet taste stimulants. Lean Sprague Dawley (n = 13) and obese Zucker diabetic fatty rats (n = 15) underwent RYGB with BP catheter placement. On postoperative day 11 (POD 11), rats received catheter infusions of saccharin [sweet taste receptor (T1R2/3) agonist] or saline (control). Jejunum was analyzed for changes in glucose transporter/sensor mRNA expression and functional sodium-glucose transporter 1 (SGLT1)-mediated glucose uptake. Saccharin infusion did not alter glucose uptake in the Roux limb of RYGB rats. Intestinal expression of the glucose sensor T1R2 and transporters (SGLT1, glucose transporter 2) was similar in saccharin- vs. saline-infused rats of both strains. However, the abundance of SGLT3b mRNA, a putative glucose sensor, was higher in the common limb vs. BP/Roux limb in both strains of bypassed rats and was significantly decreased in the Roux limb after saccharin infusion. We concluded that failure of BP limb exposure to saccharin to increase Roux limb glucose uptake suggests that isolation of T1R2/3 is unlikely to be involved in metabolic benefits of RYGB, as restimulation failed to reverse changes in intestinal glucose absorption capacity. The altered expression pattern of SGLT3 after RYGB warrants further investigation of its potential involvement in resolution of T2D after RYGB.

Duodenal luminal nutrient sensing

The gastrointestinal mucosa is exposed to numerous chemical substances and microorganisms, including macronutrients, micronutrients, bacteria, endogenous ions, and proteins. The regulation of mucosal protection, digestion, absorption and motility is signaled in part by luminal solutes. Therefore, luminal chemosensing is an important mechanism enabling the mucosa to monitor luminal conditions, such as pH, ion concentrations, nutrient quantity, and microflora. The duodenal mucosa shares luminal nutrient receptors with lingual taste receptors in order to detect the five basic tastes, in addition to essential nutrients, and unwanted chemicals. The recent 'de-orphanization' of nutrient sensing G protein-coupled receptors provides an essential component of the mechanism by which the mucosa senses luminal nutrients. In this review, we will update the mechanisms of and underlying physiological and pathological roles in luminal nutrient sensing, with a main focus on the duodenal mucosa.

Biliopancreatic diversion with duodenal switch improves insulin sensitivity and secretion through caloric restriction

OBJECTIVE

To assess the rapid improvement of insulin sensitivity and β-cell function following biliopancreatic diversion with duodenal switch (BPD-DS) and determine the role played by caloric restriction in these changes.

METHODS

Standard meals were administrated before and on day 3, 4, and 5 after BPD-DS to measure total caloric intake, glucose excursion, insulin sensitivity, and secretion in matched type 2 diabetes and normoglycemic (NG) subjects. In a second set of study, other subjects with type 2 diabetes had the same meal tests prior to and after a 3-day caloric restriction identical to that observed after BPD-DS and then 3 days after actually undergoing BPD-DS.

RESULTS

Improvement of HOMA-IR occurred at day 3 after BPD-DS in diabetes and after 3 days of caloric restriction. The disposition index (DI) improved rapidly in diabetes after BPD-DS and to a similar extent after caloric restriction. DI was higher and did not change after BPD-DS in NG. Changes in glucagon-like peptide-1, gastric inhibitory peptide, peptide tyrosine tyrosine, ghrelin, and pancreatic polypeptide levels were not associated with modulation of DI in the participants.

CONCLUSIONS

Caloric restriction is the major mechanism underlying the early improvement of insulin sensitivity and β-cell function after BPD-DS in type 2 diabetes.

Postprandial metabolite profiles reveal differential nutrient handling after bariatric surgery compared with matched caloric restriction

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery results in exaggerated postprandial insulin and incretin responses and increased susceptibility to hypoglycemia.

OBJECTIVE

We examined whether these features are due to caloric restriction (CR) or altered nutrient handling.

METHODS

We performed comprehensive analysis of postprandial metabolite responses during a 2-hour mixed-meal tolerance (MMT) test in 20 morbidly obese subjects with type 2 diabetes who underwent RYGB surgery or matched CR. Acylcarnitines and amino acids (AAs) were measured using targeted mass spectrometry. A linear mixed model was used to determine the main effect of interventions and interaction term to assess the effect of interventions on postprandial kinetics.

RESULTS

Two weeks after these interventions, several gut hormones (insulin, glucose-dependent insulinotropic polypeptide, and glucagon-like peptide 1), glucose, and multiple AAs, including branched-chain and aromatic species, exhibited a more rapid rate of appearance and clearance in RYGB surgery subjects than in CR subjects during the MMT test. In the RYGB surgery group, changes in leucine/isoleucine, methionine, phenylalanine, and glucagon-like peptide 1 response were associated with changes in insulin response. Levels of alanine, pyruvate, and lactate decreased significantly at the later stages of meal challenge in RYGB surgery subjects but increased with CR.

CONCLUSIONS

RYGB surgery results in improved metabolic flexibility (ie, greater disposal of glucose and AAs and more complete β-oxidation of fatty acids) compared with CR. The changes in the AA kinetics may augment the hormonal responses seen after RYGB surgery. The reduction in key gluconeogenic substrates in the postprandial state may contribute to increased susceptibility to hypoglycemic symptoms in RYGB surgery subjects.

Effects of gastrogastric fistula repair on weight loss and gut hormone levels

BACKGROUND

Weight regain after gastric bypass (GBP) can be associated with a gastrogastric fistula (GGF), in which a channel forms between the gastric pouch and gastric remnant, allowing nutrients to pass through the "old route" rather than bypassing the duodenum. To further understand the mechanisms by which GGF may lead to weight regain, we investigated gut hormone levels in GBP patients with a GGF, before and after repair.

MATERIALS AND METHODS

Seven post-GBP subjects diagnosed with GGF were studied before and 4 months after GGF repair. Another cohort of 22 GBP control subjects without GGF complication were studied before and 1 year post-GBP. All subjects underwent a 50-g oral glucose tolerance test and blood was collected from 0-120 min for glucose, insulin, ghrelin, PYY3-36, GIP, and GLP-1 levels.

RESULTS

Four months after GGF repair subjects lost 6.0 ± 3.9 kg and had significantly increased postprandial PYY3-36 levels. After GGF repair, fasting and postprandial ghrelin levels decreased and were strongly correlated with weight loss. The insulin response to glucose also tended to be increased after GGF repair, however no concomitant increase in GLP-1 was observed. Compared to the post-GBP group, GLP-1 and PYY3-36 levels were significantly lower before GGF repair; however, after GGF repair, PYY3-36 levels were no longer lower than the post-GBP group.

CONCLUSIONS

These data utilize the GGF model to highlight the possible role of duodenal shunting as a mechanism of sustained weight loss after GBP, and lend support to the potential link between blunted satiety peptide release and weight regain.

The effect of selective gut stimulation on glucose metabolism after gastric bypass in the Zucker diabetic fatty rat model

BACKGROUND

Potential mechanisms underlying the antidiabetic effects of Roux-en-Y gastric bypass (RYGB) include altered nutrient exposure in the gut. The aim of this study was to evaluate the effects of selective gut stimulation on glucose metabolism in an obese diabetic rat model.

METHODS

Sixteen male Zucker diabetic fatty rats were randomly assigned to 1 of 2 groups: RYGB with gastrostomy tube (GT) insertion into the excluded stomach or a control group with GT insertion into the stomach. An insulin tolerance test (ITT), oral glucose tolerance test (OGTT), and mixed meal tolerance test (MMTT) were performed before and 14-28 days after surgery. A glucose tolerance test via GT (GTT-GT) and MMTT via GT were performed postoperatively.

RESULTS

Postoperatively, the RYGB group had significant decreases in weight and food intake. Both the ITT and OGTT tests revealed significantly improved glucose tolerance after RYGB. The GTT-GT showed a reversal of the improved glucose tolerance in the RYGB group. In response to meal stimulation, postoperatively, the RYGB group increased glucagon-like peptide 1 (GLP-1) secretion via the oral route and peptide YY secretion by both oral and GT routes.

CONCLUSION

When foregut exposure to nutrients was reversed after RYGB, the improvement in glucose metabolism was abrogated. This model can be extended to identify the role of gut in glucose homeostasis in type 2 diabetes.

Overnutrition stimulates intestinal epithelium proliferation through β-catenin signaling in obese mice

Obesity is a major risk factor for type 2 diabetes and cardiovascular diseases. And overnutrition is a leading cause of obesity. After most nutrients are ingested, they are absorbed in the small intestine. Signals from β-catenin are essential to maintain development of the small intestine and homeostasis. In this study, we used a hyperphagia db/db obese mouse model and a high-fat diet (HFD)-induced obesity mouse model to investigate the effects of overnutrition on intestinal function and β-catenin signaling. The β-catenin protein was upregulated along with inactivation of glycogen synthase kinase (GSK)-3β in the intestines of both db/db and HFD mice. Proliferation of intestinal epithelial stem cells, villi length, nutrient absorption, and body weight also increased in both models. These changes were reversed by caloric restriction in db/db mice and by β-catenin inhibitor JW55 (a small molecule that increases β-catenin degradation) in HFD mice. Parallel, in vitro experiments showed that β-catenin accumulation and cell proliferation stimulated by glucose were blocked by the β-catenin inhibitor FH535. And the GSK-3 inhibitor CHIR98014 in an intestinal epithelial cell line increased β-catenin accumulation and cyclin D1 expression. These results suggested that, besides contribution to intestinal development and homeostasis, GSK-3β/β-catenin signaling plays a central role in intestinal morphological and functional changes in response to overnutrition. Manipulating the GSK-3β/β-catenin signaling pathway in intestinal epithelium might become a therapeutic intervention for obesity induced by overnutrition.

The role of hormonal factors in weight loss and recidivism after bariatric surgery

Substantial heterogeneity exists in weight loss trajectories amongst patients following bariatric surgery. Hormonal factors are postulated to be amongst the contributors to the variation seen. Several hormones involved in hunger, satiety, and energy balance are affected by bariatric surgery, with the alteration in hormonal milieu varying by procedure. Limited research has been conducted to examine potential hormonal mediators of weight loss failure or recidivism following bariatric surgery. While hormonal factors that influence weight loss success following gastric banding have not been identified, data suggest that hormonal factors may be involved in modulating weight loss success following gastric bypass. There may be hormonal mediators involved in determining the weight trajectory following sleeve gastrectomy, though the extremely limited data currently available prohibits definitive conclusions from being drawn. There is great need for future research studies to explore this knowledge gap, as improving this knowledge base could be of benefit to guide clinicians toward understanding the hormonal contributors to a patient's postoperative weight loss failure or recidivism or perhaps be of value in selecting the most appropriate bariatric procedure based on the preoperative hormone milieu. Integrative interdisciplinary approaches exploring these complex interrelationships could potentially increase the explanatory power of such investigations.

Effects of ingestion routes on hormonal and metabolic profiles in gastric-bypassed humans

CONTEXT

Gastric bypass surgery (GBP) results in the rapid resolution of type 2 diabetes. Most studies aiming to explain the underlying mechanisms are limited to data obtained after a postsurgical recovery period, making assessment of confounding influences from, for example, weight loss and altered nutrient intake difficult.

OBJECTIVE

To examine the impact of GBP on hormonal and metabolite profiles under conditions of identical nutrient intake independent of weight loss, we studied GBP patients fitted with a gastrostomy tube to enable the administration of nutrients to bypassed segments of the gut. Thus, this model allowed us to simulate partially the preoperative condition and compare this with the postoperative situation in the same patient.

DESIGN

Patients (n = 4) were first given a mixed meal test (MMT) orally and then via the gastrostomy tube, preceded by overnight and 2-hour fasting, respectively. Blood samples were assessed for hormones and metabolites.

RESULTS

The oral MMT yielded 4.6-fold increase in plasma insulin (P < .05), 2-fold in glucagon-like peptide-1 (P < .05), and 2.5-fold in glucose-dependent insulinotropic peptide (P < .05) plasma levels, compared with the gastrostomy MMT. The changes in hormone levels were accompanied by elevated branched-chain amino acid levels (1.4-2-fold, P < .05) and suppressed fatty acid levels (∼50%, P < .05).

CONCLUSIONS

These data, comparing identical nutrient delivery, demonstrate markedly higher incretin and insulin responses after oral MMT than after gastric MMT, thereby providing a potential explanation for the rapid remission of type 2 diabetes observed after GBP. The simultaneous increase in branched-chain amino acid questions its role as a marker for insulin resistance.

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.

Tissue specificity in fasting glucose utilization in slightly obese diabetic patients submitted to bariatric surgery

OBJECTIVE

The present study was planned to investigate, by means of quantitative FDG-PET, how bariatric surgery (BS) modifies the metabolic pattern of the whole body and different tissues in slightly obese patients with type 2 diabetes mellitus (T2DM).

DESIGN AND METHODS

Before, 1 and 4 months after BS, 21 consecutive slightly obese T2DM patients underwent blood sampling to estimate plasma levels of glucose, insulin, glycosylated hemoglobin. At the same time points, these patients underwent a dynamic (18) F-FDG PET study of thorax and upper abdomen in fasting state and after washout of T2DM therapy. Gjedde-Patlak analysis was applied to estimate glucose uptake in the whole body and in different tissues (myocardium, skeletal back muscle, adipose tissue, and liver).

RESULTS

Surgical intervention quickly lowered levels of both insulin and glucose documenting an amelioration of glucose tolerance. Similarly, skeletal muscle and myocardial glucose uptake significantly increased soon after surgery (P < 0.001 and P < 0.01 at 1 month versus baseline, respectively) and remained substantially stable thereafter. By contrast, glucose uptake slightly decreased from its baseline values in the liver (P < 0.01 at 4 months) while no response could be documented over time in the adipose tissue.

CONCLUSIONS

These findings document that BS-induced modification of glucose homeostasis in slightly obese T2DM patients is mostly due to an increase in muscle glucose consumption. The surgically modified metabolic pattern of these patients might be of interest as a new model to investigate mechanism underlying insulin resistance.