Duodenal-jejunal bypass and jejunectomy improve insulin sensitivity in Goto-Kakizaki diabetic rats without changes in incretins or insulin secretion

Transcriptome atlases of rat brain regions and their adaptation to diabetes resolution following gastrectomy in the Goto-Kakizaki rat

Brain regions drive multiple physiological functions through specific gene expression patterns that adapt to environmental influences, drug treatments and disease conditions. To generate a detailed atlas of the brain transcriptome in the context of diabetes, we carried out RNA sequencing in hypothalamus, hippocampus, brainstem and striatum of the Goto-Kakizaki (GK) rat model of spontaneous type 2 diabetes, which was applied to identify gene transcription adaptation to improved glycemic control following vertical sleeve gastrectomy (VSG) in the GK. Over 19,000 distinct transcripts were detected in the rat brain, including 2794 which were consistently expressed in the four brain regions. Region-specific gene expression was identified in hypothalamus (n = 477), hippocampus (n = 468), brainstem (n = 1173) and striatum (n = 791), resulting in differential regulation of biological processes between regions. Differentially expressed genes between VSG and sham operated rats were only found in the hypothalamus and were predominantly involved in the regulation of endothelium and extracellular matrix. These results provide a detailed atlas of regional gene expression in the diabetic rat brain and suggest that the long term effects of gastrectomy-promoted diabetes remission involve functional changes in the hypothalamus endothelium.

Anti-Incretin Gut Features Induced by Feed Supplementation with Alpha-Amylase: Studies on EPI Pigs

The acini-islet-acinar (AIA) axis concept justifies the anatomical placement of the Langerhans islets within the exocrine pancreatic parenchyma and explains the existence of the pancreas as a single organ. Amylase has been suggested to play a key role as an anti-incretin factor. Oral glucose tolerance tests (OGTT) were performed on 18 piglets in both a healthy (prior to pancreatic duct ligation (PDL) surgery, study Day 10) and an exocrine pancreatic insufficient (EPI) state (30 days after PDL, study Day 48)). Amylase (4000 units/feeding) or Creon® (100,000 units/feeding) was administered to pigs with the morning and evening meals, according to study design randomization, for 37 days following the first OGTT. Blood glucose levels, as well as plasma levels of insulin, GLP-1, and GIP, were measured, and the HOMA-IR index was calculated. EPI status did not affect the area under the curve (AUC) of insulin release, fasting insulin levels, or the HOMA-IR index, while amylase supplementation led to a significant (p < 0.05) decrease in the above-mentioned parameters. At the same time, EPI led to a significant (p < 0.05) increase in GLP-1 levels, and neither amylase nor Creon® supplementation had any effects on this EPI-related increase. Fasting plasma levels of GIP were not affected by EPI; however, the GIP response in EPI and Amylase-treated EPI animals was significantly lower (p < 0.05) when compared to that of the intact, healthy pigs. Orally administered amylase induces gut anti-incretin action, normalizing glucose homeostasis and reducing HOMA-IR as a long-term outcome, thus lowering the risk of diabetes type II development. Amylase has long-lasting anti-incretin effects, and one could consider the existence of a long-lasting gut memory for amylase, which decreases hyperinsulinemia and hyperglycemia for up to 16 h after the last exposure of the gut to amylase.

Hypothesis that alpha-amylase evokes regulatory mechanisms originating in the pancreas, gut and circulation, which govern glucose/insulin homeostasis

The anti-incretin theory involving the abolishment of diabetes type (DT) II by some of methods used in bariatric surgery, first appeared during the early years of the XXI century and considers the existence of anti-incretin substances. However, to date no exogenous or endogenous anti-incretins have been found. Our concept of the acini-islet-acinar axis assumes that insulin intra-pancreatically stimulates alpha-amylase synthesis ("halo phenomenon") and in turn, alpha-amylase reciprocally inhibits insulin production, thus making alpha-amylase a candidate for being an anti-incretin. Additionally, gut as well as plasma alpha-amylase, of pancreatic and other origins, inhibits the appearance of dietary glucose in the blood, lowering the glucose peak after iv or oral glucose loading. This effect of alpha-amylase can be interpreted as an insulin down regulatory mechanism, possibly limiting the depletion of pancreatic beta cells and preventing their failure. Clinical observations agree with the above statements, where patients with high blood alpha-amylase concentrations are seldom obese and seldom develop DT2. Obese-DT2, as well as DT1 patients, usually develop exo-crine pancreatic insufficiency (EPI) and vice versa. Ultimately, DT2 patients develop DT1, when the pancreatic beta cells are exhausted and insulin production ceases. Studies on biliopancreatic diversion (BPD) and on BPD with duodenal switch, a type of bariatric surgery, as well as studies on EPI pigs, allow us to observe and investigate the above-mentioned phenomena of intra-pancreatic interactions.

Mechanisms of bariatric surgery for weight loss and diabetes remission

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

Upper gut heat shock proteins HSP70 and GRP78 promote insulin resistance, hyperglycemia, and non-alcoholic steatohepatitis

A high-fat diet increases the risk of insulin resistance, type-2 diabetes, and non-alcoholic steato-hepatitis. Here we identified two heat-shock proteins, Heat-Shock-Protein70 and Glucose-Regulated Protein78, which are increased in the jejunum of rats on a high-fat diet. We demonstrated a causal link between these proteins and hepatic and whole-body insulin-resistance, as well as the metabolic response to bariatric/metabolic surgery. Long-term continuous infusion of Heat-Shock-Protein70 and Glucose-Regulated Protein78 caused insulin-resistance, hyperglycemia, and non-alcoholic steato-hepatitis in rats on a chow diet, while in rats on a high-fat diet continuous infusion of monoclonal antibodies reversed these phenotypes, mimicking metabolic surgery. Infusion of these proteins or their antibodies was also associated with shifts in fecal microbiota composition. Serum levels of Heat-Shock-Protein70 and Glucose-Regulated Protein78were elevated in patients with non-alcoholic steato-hepatitis, but decreased following metabolic surgery. Understanding the intestinal regulation of metabolism may provide options to reverse metabolic diseases.

The Interaction of Food Allergy and Diabetes: Food Allergy Effects on Diabetic Mice by Intestinal Barrier Destruction and Glucagon-like Peptide 1 Reduction in Jejunum

The increase in food allergies and diabetes leads to the assumption that they are related. This study aimed to (1) verify the interaction between food allergy and diabetes and (2) explore the potential mechanisms by which food allergy promotes diabetes. Female BALB/c mice were grouped into a control group (CK), an ovalbumin-sensitized group (OVA), a diabetes group (STZ), and a diabetic allergic group (STZ + OVA) (Mice were modeled diabetes with STZ first, then were given OVA to model food allergies), and an allergic diabetic group (OVA + STZ) (Mice were modeled food allergies with OVA first, then were given STZ to model diabetes). The results showed that OVA + STZ mice exhibited a more serious Th2 humoral response, and they were more susceptible to diabetes. Furthermore, when the OVA + STZ mice were in the sensitized state, the intestinal barrier function was severely impaired, and mast cell activation was promoted. Moreover, we found that the effect of food allergy on diabetes is related to the inhibition of GLP-1 secretion and the up-regulation of the PI3K/Akt/mTOR/NF-κB P65 signaling pathway in the jejunum. Overall, our results suggest that food allergies have interactions with diabetes, which sheds new light on the importance of food allergies in diabetes.

Role of Proximal Intestinal Glucose Sensing and Metabolism in the Blood Glucose Control in Type 2 Diabetic Rats After Duodenal Jejunal Bypass Surgery

BACKGROUND

Although gastric surgery can significantly improve blood glucose homeostasis in type 2 diabetes mellitus (T2DM), its mechanism remains unclear. This study evaluated the role of intestinal glucose sensing, glucose transport, and metabolism in the alimentary limb (A limb) of T2DM rats after duodenal jejunal bypass (DJB) surgery.

METHODS

A T2DM rat model was induced via a high-glucose high-fat diet and low-dose streptozotocin injection. The diabetic rats were divided into two groups: the DJB surgery (T2DM-DJB) group and the sham surgery (T2DM-Sham) group. Wistar rats were used as wild-type control (Control). Small animal PET was used to assess the change in glucose metabolic status in the intestine. The intestinal villi height and the number of EECs after DJB were evaluated. The expressions of sweet taste receptors (T1R2/T1R3), glucose transporters (SGLT1/GLUT2), and key enzymes involved in glucose metabolism (HK2, PFK2, PKM2, G6Pase, and PCK1) in the A limb after DJB was detected by Western blot and qRT-PCR.

RESULTS

Small animal PET analysis showed the intestinal glucose metabolism increased significantly 6 weeks after DJB surgery. The intestinal villi height and the number of EECs in the A limb 6 weeks after surgery increased significantly in T2DM-DJB rats comparing to T2DM-Sham rats. The mRNA and protein expression of T1R1/T1R3 and SGLT1/GLUT2 were downregulated in DJB-T2DM rats, while enzymes involved in glucose metabolism was upregulated in the A limb in T2DM-DJB rats.

CONCLUSION

Proximal intestinal glucose sensing and metabolism play an important role in blood glucose homeostasis by DJB.

The Effect and Mechanism of Duodenal-Jejunal Bypass to Treat Type 2 Diabetes Mellitus in a Rat Model

OBJECTIVES

Bariatric surgery can treat obesity and T2DM, but the specific mechanism is unknown. This study investigated the effect and possible mechanism of duodenal-jejunal bypass (DJB) to treat T2DM.

METHODS

A T2DM rat model was established using a high-fat, high-sugar diet and a low dose of streptozotocin. DJB surgery and a sham operation (SO) were performed to analyze the effects on glucose homeostasis, lipid metabolism, and inflammation changes. Furthermore, the glucagon-like peptide-1 (GLP-1) in the ileum and the markers of endoplasmic reticulum stress (ERS) in the pancreas were examined after the surgery. The insulinoma cells (INS-1) were divided into three groups; group A was cultured with a normal sugar content (11.1 mmol/L), group B was cultured with fluctuating high glucose (11.1 mmol/L alternating with 33.3 mmol/L), and group C was cultured with fluctuating high glucose and exendin-4 (100 nmol/L). The cells were continuously cultured for 7 days in complete culture medium. The viability of the INS-1 cells was then investigated using the MTT method, apoptosis was detected by flow cytometry, and the ERS markers were detected by Western blot.

RESULTS

The blood glucose, lipids, insulin, and TNF-α were significantly elevated in the T2DM model. A gradual recovery was observed in the DJB group. GLP-1 expression in the distal ileum of the DJB group was significantly higher than that in the T2DM control group (DM) and the SO group (p < 0.05), and the markers of ERS expression in the pancreases of the DJB group decreased significantly more than those of groups DM and SO (p < 0.05). Compared with group A, the cell viability in group B was decreased, and the ERS and apoptosis were increased (p < 0.05). However, compared with group B, the cell viability in group C was improved, and the ERS and apoptosis declined (p < 0.05).

CONCLUSIONS

DJB can be used to treat T2DM in T2DM rats. The mechanism may be that the DJB stimulates the increased expression of GLP-1 on the far side of the ileum, and then, GLP-1 inhibits ERS in the pancreas, reducing the apoptosis of β cells to create a treatment effect in the T2DM rats.

Small intestinal metabolism is central to whole-body insulin resistance

OBJECTIVE

To assess the role of jejunum in insulin resistance in humans and in experimental animals.

DESIGN

Twenty-four subjects undergoing biliopancreatic diversion (BPD) or Roux-en-Y gastric bypass (RYGB) were enrolled. Insulin sensitivity was measured at baseline and at 1 week after surgery using oral glucose minimal model.We excluded the jejunum from intestinal continuity in pigs and created a jejunal loop with its vascular and nerve supply intact accessible from two cutaneous stomas, and reconnected the bowel with an end-to-end anastomosis. Glucose stable isotopes were given in the stomach or in the jejunal loop.In vitro studies using primary porcine and human hepatocytes or myoblasts tested the effects of plasma on gluconeogenesis or glucose uptake and insulin signalling.

RESULTS

Whole-body insulin sensitivity (S_I∙10⁴: 0.54±0.12 before vs 0.82±0.11 after BPD, p=0.024 and 0.41±0.09 before vs 0.65±0.09/pM/min after RYGB, p=not significant) and Glucose Disposition Index increased only after BPD. In pigs, insulin sensitivity was significantly lower when glucose was administered in the jejunal loop than in the stomach (glucose rate of disappearance (R_d) area under the curve (AUC)/insulin AUC∙10: 1.82±0.31 vs 2.96±0.33 mmol/pM/min, p=0.0017).Metabolomics showed a similar pattern before surgery and during jejunal-loop stimulation, pointing to a higher expression of gluconeogenetic substrates, a metabolic signature of impaired insulin sensitivity.A greater hepatocyte phosphoenolpyruvate-carboxykinase and glucose-6-phosphatase gene expression was elicited with plasma from porcine jejunal loop or before surgery compared with plasma from jejunectomy in pigs or jejunal bypass in humans.Stimulation of myoblasts with plasma from porcine jejunal loop or before surgery reduced glucose uptake, Ser473-Akt phosphorylation and GLUT4 expression compared with plasma obtained during gastric glucose administration after jejunectomy in pigs or after jejunal bypass in humans.

CONCLUSION

Proximal gut plays a crucial role in controlling insulin sensitivity through a distinctive metabolic signature involving hepatic gluconeogenesis and muscle insulin resistance. Bypassing the jejunum is beneficial in terms of insulin-mediated glucose disposal in obesity.

TRIAL REGISTRATION NUMBER

NCT03111953.

Small intestine remodeling in male Goto-Kakizaki rats

BACKGROUND

Obesity is associated with the development of insulin resistance (IR) and type-2 diabetes mellitus (T2DM); however, not all patients with T2DM are obese. The Goto-Kakizaki (GK) rat is an experimental model of spontaneous and non-obese T2DM. There is evidence that the intestine contributes to IR development in GK animals. This information prompted us to investigate small intestine remodeling in this animal model.

METHODS

Four-month-old male Wistar (control) and GK rats were utilized for the present study. After removing the small intestine, the duodenum, proximal jejunum, and distal ileum were separated. We then measured villi and muscular and mucosa layer histomorphometry, goblet cells abundance, total myenteric and submucosal neuron populations, and inflammatory marker expression in the small intestinal segments and intestinal transit of both groups of animals.

KEY RESULTS

We found that the GK rats exhibited decreased intestinal area (p < 0.0001), decreased crypt depth in the duodenum (p = 0.01) and ileum (p < 0.0001), increased crypt depth in the jejunum (p < 0.0001), longer villi in the jejunum and ileum (p < 0.0001), thicker villi in the duodenum (p < 0.01) and ileum (p < 0.0001), thicker muscular layers in the duodenum, jejunum, and ileum (p < 0.0001), increased IL-1β concentrations in the duodenum and jejunum (p < 0.05), and increased concentrations of NF-κB p65 in the duodenum (p < 0.01), jejunum and ileum (p < 0.05). We observed high IL-1β reactivity in the muscle layer, myenteric neurons, and glial cells of the experimental group. GK rats also exhibited a significant reduction in submucosal neuron density in the jejunum and ileum, ganglionic hypertrophy in all intestinal segments studied (p < 0.0001), and a slower intestinal transit (about 25%) compared to controls.

CONCLUSIONS

The development of IR and T2DM in GK rats is associated with small intestine remodeling that includes marked alterations in small intestine morphology, local inflammation, and reduced intestinal transit.

DOES EVOLUTIONARY BIOLOGY HELP THE UNDERSTANDING OF METABOLIC SURGERY? A FOCUSED REVIEW

Introduction:

The wide net of physiological issues involved in metabolic surgery is extremely complex. Nonetheless, compared anatomy and phisiology can provide good clues of how digestive tracts are shaped for more or less caloric food, for more or less fiber, for abundance and for scarcity.

Objective:

To review data from Compared Anatomy and Physiology, and in the Evolutionary Sciences that could help in the better comprehension of the metabolic surgery.

Method:

A focused review of the literature selecting information from these three fields of knowledge in databases: Cochrane Library, Medline and SciELO, articles and book chapters in English and Portuguese, between 1955 and 2019, using the headings “GIP, GLP-1, PYY, type 2 diabetes, vertebrates digestive system, hominid evolution, obesity, bariatric surgery “.

Results:

The digestive tract of superior animals shows highly specialized organs to digest and absorb specific diets. In spite of the wide variations of digestive systems, some general rules are observed. The proximal part of the digestive tract, facing the scarcity of sugars, is basically dedicated to generate sugar from different substrates (gluconeogenesis). Basic proximal gut tasks are to proportionally input free sugars, insulin, other fuels and to generate anabolic elements to the blood, some of them obesogenic. To limit the ingestion by satiety, by gastric emptying diminution and to limit the excessive elevation of major fuels (sugar and fat) in the blood are mostly the metabolict asks of the distal gut. A rapid and profound change in human diet composition added large amounts of high glycemic index foods. They seem to have caused an enhancement in the endocrine and metabolic activities of the proximal gut and a reduction in these activities of the distal gut. The most efficient models of metabolic surgery indeed make adjustments in this proximal/distal balance in the gut metabolic activities.

Conclusion:

Metabolic surgery works basically by making adjustments to the proximal and distal gut metabolic activities that resemble the action of natural selection in the development the digestive systems of superior animals.

Dominant gut Prevotella copri in gastrectomised non-obese diabetic Goto-Kakizaki rats improves glucose homeostasis through enhanced FXR signalling

AIMS/HYPOTHESIS

Drug and surgical-based therapies in type 2 diabetes are associated with altered gut microbiota architecture. Here we investigated the role of the gut microbiome in improved glucose homeostasis following bariatric surgery.

METHODS

We carried out gut microbiome analyses in gastrectomised (by vertical sleeve gastrectomy [VSG]) rats of the Goto-Kakizaki (GK) non-obese model of spontaneously occurring type 2 diabetes, followed by physiological studies in the GK rat.

RESULTS

VSG in the GK rat led to permanent improvement of glucose tolerance associated with minor changes in the gut microbiome, mostly characterised by significant enrichment of caecal Prevotella copri. Gut microbiota enrichment with P. copri in GK rats through permissive antibiotic treatment, inoculation of gut microbiota isolated from gastrectomised GK rats, and direct inoculation of P. copri, resulted in significant improvement of glucose tolerance, independent of changes in body weight. Plasma bile acids were increased in GK rats following inoculation with P. copri and P. copri-enriched microbiota from VSG-treated rats; the inoculated GK rats then showed increased liver glycogen and upregulated expression of Fxr (also known as Nr1h4), Srebf1c, Chrebp (also known as Mlxipl) and Il10 and downregulated expression of Cyp7a1.

CONCLUSIONS

Our data underline the impact of intestinal P. copri on improved glucose homeostasis through enhanced bile acid metabolism and farnesoid X receptor (FXR) signalling, which may represent a promising opportunity for novel type 2 diabetes therapeutics.

Anti-incretin effect: The other face of Janus in human glucose homeostasis

The provocative idea that type 2 diabetes (T2D) may be a surgically treated disorder is based on accumulating evidence suggesting impressive remission rates of obesity and diabetes following bariatric surgery interventions. According to the "anti-incretin" theory, ingestion of food in the gastrointestinal (GI) tract, apart from activating the well-described incretin effect, also results in the parallel stimulation of a series of negative feedback mechanisms (anti-incretin effect). The primary goal of these regulations is to counteract the effects of incretins and other postprandial glucose-lowering adaptive mechanisms. Disruption of the equilibrium between incretins and anti-incretins could be an additional pathway leading to the development of insulin resistance and hyperglycemia. This theory provides an alternative theoretical framework to explain the mechanisms behind the optimal effects of metabolic surgery on T2D and underlines the importance of the GI tract in the homeostatic regulation of energy balance in humans. The anti-incretin concept is currently based on a limited amount of evidence and certainly requires further validation by additional studies. The aim of the present review is to discuss and critically evaluate recent evidence on the anti-incretin theory, providing an insight into current state and future perspectives.

The histomorphometric parameters of endocrine pancreas after bariatric surgery in healthy animal models

BACKGROUND

The aim of this study is to describe in depth how different bariatric surgeries affect to the cellularity of β-cells in the pancreatic islet. There are much data regarding the possible physiological mechanisms involved in resolution of type 2 diabetes after bariatric surgery. But these data usually are controversial. We reported a direct influence of bariatric surgical technique on endocrine pancreas cellular turnover. Some surgeries increase proliferation processes of the β-cells. Our objective is to report the histomorphometric mechanism that these techniques stimulate over the cellularity of pancreatic islet.

METHOD

To this purpose, we used adult male Wistar rats to undergo the different techniques. We developed three surgical techniques (Sleeve gastrectomy and Y-Roux Gastric bypass as the most usual bariatric techniques, and a purely malabsorptive technique); moreover two control groups were performed (Sham and fasting controls).

RESULTS

We completed a sequence of morphometric studies to conclude the behaviour of endocrine pancreatic β-cell islet, correlating several histomorphometry parameters.

CONCLUSION

Our purpose was to show a comprehensive interpretation to the consequences that bariatric surgeries had on the pancreatic islets cellularity. Moreover, we included the main tests to report the cellularity in histological samples.

Sleeve Gastrectomy and Roux-en-Y Gastric Bypass Achieve Similar Early Improvements in Beta-cell Function in Obese Patients with Type 2 Diabetes

Bariatric surgery is a treatment option for obese patients with type 2 diabetes mellitus (T2DM). Although sleeve gastrectomy (SG) is growing in favor, some randomized trials show less weight loss and HbA1c improvement compared with Roux-en-Y gastric bypass (RYGB). The study objective was to compare changes in beta-cell function with similar weight loss after SG and RYGB in obese patients with T2DM. Subjects undergoing SG or RYGB were studied with an intravenous glucose tolerance test before surgery and at 5–12% weight loss post-surgery. The primary endpoint was change in the disposition index (DI). Baseline BMI, HbA1c, and diabetes-duration were similar between groups. Mean total weight loss percent was similar (8.4% ± 0.4, p = 0.22) after a period of 21.0 ± 1.7 days. Changes in fasting glucose, acute insulin secretion (AIR), and insulin sensitivity (Si) were similar between groups. Both groups showed increases from baseline to post-surgery in DI (20.2 to 163.3, p = 0.03 for SG; 31.2 to 232.9, p = 0.02 for RYGB) with no significant difference in the change in DI between groups (p = 0.53). Short-term improvements in beta-cell function using an IVGTT were similar between SG and RYGB. It remains unclear if longer-term outcomes are better after RYGB due to greater weight loss and/or other factors.

A Prospective Single-Arm Trial of Modified Long Biliopancreatic and Short Alimentary Limbs Roux-En-Y Gastric Bypass in Type 2 Diabetes Patients with Mild Obesity

BACKGROUND

Type-2 diabetes (T2D) patients with body mass index (BMI) below 35 kg/m² carry lower remission rates than severely obese T2D individuals submitted to "standard limb lengths" Roux-en-Y gastric bypass (RYGB). Mild-obese patients appear to have more severe forms of T2D, where the mechanisms of glycemic control after a standard-RYGB may be insufficient. The elongation of the biliopancreatic limb may lead to greater stimulation of the distal intestine, alterations in bile acids and intestinal microbiota, among other mechanisms, leading to better metabolic outcomes. The aim of this study is to evaluate the safety and efficacy of the RYGB with a biliopancreatic limb of 200 cm in the control of T2D in patients with BMI 30-35 kg/m².

METHODS

From January 2011 to May 2015, 102 T2D patients with BMI from 30 to 34.9 kg/m² underwent laparoscopic RYGB with the biliopancreatic-limb of 200 cm and the alimentary-limb of 50 cm.

RESULTS

There were no deaths or reoperations. The mean follow-up was 28.1 months. The mean BMI dropped from 32.5 to 25.1 kg/m², while the mean fasting glucose decreased from 182.9 to 89.8 mg/dl and the mean glycated hemoglobin (HbA1c) went from 8.7 to 5.2%. During follow-up, 92.2% had their T2D under complete control (HbA1c < 6%, no anti-diabetic medications), while 7.8% were under partial control. Control of hypertension and dyslipidemia were 89.4 and 85.5%, respectively. No patient developed hypoalbuminemia, and there were mild micronutrient deficiencies.

CONCLUSIONS

RYGB with long-biliopancreatic and short-alimentary limbs is safe and seems effective in achieving complete control of T2D in patients with BMIs between 30 and 35 kg/m².

Importance of the gastrointestinal tract in type 2 diabetes. Metabolic surgery is more than just incretin effect

Bariatric and metabolic surgery is creating new concepts about how the intestine assimilates food. Recent studies highlight the role of the gastrointestinal tract in the genesis and evolution of type 2 diabetes. This article has been written to answer frequent questions about metabolic surgery results and the mechanisms of action. For this purpose, a non-systematic search of different databases was carried out, identifying articles published in the last decade referring to the mechanisms of action of metabolic techniques. Understanding these mechanisms will help grasp why some surgeries are more effective than others and why the results can be so disparate among patients undergoing the same surgical approach.

Establishing a successful rat model of duodenal- jejunal bypass: A detailed guide

Gastric bypass surgery, an operation that restricts the stomach and bypasses the duodenum and part of the jejunum, results in major improvement or remission of type 2 diabetes. Duodenual-jejunal bypass was developed by one of the authors (FR) as an experimental, stomach-sparing variant of gastric bypass surgery to investigate weight-independent mechanisms of surgical control of diabetes. Duodenual-jejunal bypass has been shown to improve various aspects of glucose homeostasis in rodents and in humans, thus providing an experimental model for investigating mechanisms of action of surgery and elusive aspects of gastrointestinal physiology. Performing duodenual-jejunal bypass in rodents, however, is associated with a steep learning curve. Here we report our experience with duodenual-jejunal bypass and provide practical tips for successful surgery in rats. Duodenual-jejunal bypass was performed on 50 lean rats as part of a study aimed at investigating the effect of the procedure on the physiologic mechanisms of glucose homeostasis. During the study, we have progressively refined details of anatomic exposure, technical aspects of duodeno-jejunostomy and peri-operative care. We analysed the role of such refinements in improving operative time and post-operative mortality. We found that refinement of exposure methods of the gastro-duodenal junction aimed at minimizing tension on small visceral vasculature, technical aspects of duodeno-jejunal anastomosis and peri-operative management played a major role in improving the survival rate and operative time. Overall, an experimental model of duodenual-jejunal bypass was successfully reproduced. Based on this experience, we describe here what we believe are the most important technical tips to reduce the learning curve for the procedure.

Metabolic surgery improves insulin resistance through the reduction of gut-secreted heat shock proteins

Metabolic surgery improves insulin resistance and is associated with the remission of type 2 diabetes, but the mechanisms involved remain unknown. We find that human jejunal mucosa secretes heat shock proteins (HSPs) in vitro, in particular HSP70 and GRP78. Circulating levels of HSP70 are higher in people resistant to insulin, compared to the healthy and normalize after duodenal-jejunal bypass. Insulin sensitivity negatively correlates with the plasma level of HSP70, while body mass index does not. A high-energy diet increases the circulating levels of HSP70 and insulin resistance. HSP70 stimulates the accumulation of lipid droplets and inhibits Ser473 phosphorylation of Akt and glucose uptake in immortalized liver cells and peripheral blood cells. Serum depleted of HSPs, as well as the serum from the insulin-resistant people subjected to a duodenal-jejunal bypass, reverse these features, identifying gut-secreted HSPs as possible causes of insulin resistance. Duodenal-jejunal bypass might reduce the secretion of HSPs either by shortening the food transit or by decreasing the fat stimulation of endocrine cells.

Effects of Duodenal-Jejunal Exclusion and New Bilio-Pancreatic Diversion on Blood Glucose in Rats with Type 2 Diabetes Mellitus

OBJECTIVE

The current study aimed to investigate the effects of duodenal-jejunal bypass (DJB), new bilio-pancreatic diversion (NBPD), and duodenal-jejunal exclusion (DJE) on blood glucose in rats with type 2 diabetes mellitus (T2DM).

METHODS

Male Sprague Dawley rats were fed with high glucose, high fat food, and intraperitoneally injected with streptozotocin to establish a T2DM animal model. T2DM rats were randomly assigned into 4 groups: a sham group (n = 8), DJB group (n = 9), NBPD group (n = 10), and DJE group (n = 10). Body weight, 2-h postprandial glucose, oral glucose tolerance, fasting serum bile acid, 2-h postprandial serum bile acid, fasting insulin, 2-h postprandial insulin (INS), fasting glucagon-like peptide-1 (GLP-1), and 2-h postprandial GLP-1 were measured before and after surgery.

RESULTS

Six weeks after surgery, the 2-h postprandial glucose in the DJB (16.1 ± 6.7 mmol/L) and NBPD (19.5 ± 5.7 mmol/L) groups decreased significantly compared to the sham group (25.8 ± 4.9 mmol/L) (P < 0.05). There was no significant difference between the DJE (25.0 ± 5.0 mmol/L) and sham groups (P > 0.05). Four weeks after surgery, fasting serum bile acid in the DJB group (60.6 ± 11.4 μmol/L) and NBPD group (54.4 ± 7.64 μmol/L) was significantly higher than that in the sham group (34.3 ± 6.98 μmol/L; P < 0.05). However, fasting GLP-1, 2-h postprandial GLP-1, and insulin remained unchanged at different time points after surgery (P > 0.05). Body weight remained stable after surgery in all 4 groups (P > 0.05).

CONCLUSION

NBPD plays a major role in the therapy of T2DM with DJB. NBPD may significantly increase fasting serum bile acid in T2DM rats, an action that may be one of the mechanisms underlying the therapeutic effects of DJB on T2DM.

Intestinal peptide changes after bariatric and minimally invasive surgery: Relation to diabetes remission

Bariatric surgery is very effective in achieving and maintaining weight loss but it is also associated with improvement of obesity metabolic complications, primarily type 2 diabetes (T2D). Remission of T2D or at least a net improvement of glycemic control persists for at least 5 years. The bypass of duodenum and of the first portion of the jejunum up to the Treitz ligament as in Roux-en-Y Gastric Bypass (RYGB), or the bypass of the duodenum, the entire jejunum and the first tract of the ileum, such as in Bilio-Pancreatic Diversion (BPD), achieve different results on insulin sensitivity. Insulin resistance is the major driver of T2D manifesting long before insulin secretion failure. In fact, T2D development can be prevented by treatment with insulin sensitizing agents. Interestingly, RYGB improves hepatic insulin sensitivity while BPD ameliorates whole-body insulin sensitivity. Two major theories have been advocated to explain the early remission of T2D following RYGB or BPD before a meaningful weight loss takes place, the foregut and the hindgut hypotheses. The former holds that the bypass of the proximal intestine, i.e. duodenum and jejunum, prevents the secretion of signals - including nervous transmitters and hormones - promoting insulin resistance, the latter instead states that the delivery of nutrients directly into the ileum stimulates the secretion of hormones improving glucose disposal. The most studied candidate is Glucagon Like Peptide 1 (GLP1). However, while there is unambiguous evidence that GLP-1 stimulates insulin secretion, its direct action in lowering insulin resistance, independently of the effect on weight loss secondary to its satiety action, is utterly controversial. In this review we examine the effects on T2D and gastrointestinal peptide secretion produced by different types of metabolic surgery and by minimally invasive endoscopic surgery, whose utilization for the treatment of obesity and T2D is gaining wider interest and acceptance.

Is there a Reason Why Obese Patients Choose Either Conservative Treatment or Surgery?

BACKGROUND

The effects of bariatric surgery on excess weight loss (EWL) and comorbidities are proven. Still, a significant number of patients prefer conservative therapy (ConsP).

OBJECTIVES

The goal of this study was to examine why ConsP and patients awaiting bariatric surgery (SurgP) choose which therapy, and to define the differences in their expectations.

SETTING

Prospective study, 1 university hospital, 1 general hospital, Germany.

METHODS

ConsP and SurgP were asked to complete a questionnaire. Statistical analysis including all patients and a BMI-matched cohort was performed using the chi-square and Wilcoxon rank-sum test.

RESULTS

Overall, 151 patients participated in this study (50 ConsP, 101 SurgP, 69.4% females). The mean age was 41.1 years (SD ± 12.2 years). ConsP had a significant lower body mass index (BMI, 44.7 kg/m² vs. 49.3 kg/m², p < 0.01). The educational level was significantly higher in ConsP. SurgP suffered significantly more often from depression (21.6% vs. 36.6%, p = 0.02) and joint pain (45.1% vs. 68.7%, p = 0.02). ConsP completed significantly more diets that were supervised by physicians or considered well-structured (56.3% vs. 31.0%, p = 0.04). SurgP considered their chosen therapy a last resort significantly more often (p < 0.01). A BMI-matched analysis between ConsP and SurgP revealed no significant differences in the prevalence of comorbidities but showed that fear of surgery plays a major role in the decision-making processes of obese patients.

CONCLUSION

A higher BMI and a greater prevalence of comorbidities had driven patients to seek a more radical solution for their obesity, i.e., surgery. The BMI-matched analysis suggests that fear of surgery is a relevant factor in why obese patients do not decide to undergo bariatric surgery lightly.

Salvianolate Reduces Glucose Metabolism Disorders in Dimethylnitrosamine-Induced Cirrhotic Rats

OBJECTIVE

To evaluate the preventive effect of salvianolate (Sal B) on glucose metabolism disorders of dimethylnitrosamine (DMN)-induced cirrhotic rats.

METHODS

Fifty-five Wistar rats were randomly divided into a control group (n=10) and a cirrhotic group (n=45) according to a random number table. Liver cirrhosis was induced by intraperitoneal administration of DMN. The cirrhotic rats were divided into model, Sal B and metformin groups (n=15), respectively. Rats in the model group were given saline, two treatment groups were given Sal B (50 mg/kg), metformin (150 mg/kg) respectively for 28 consecutive days, while rats in the control group were injected 0.9% saline with same volume of vehicle. Body weight was measured everyday. Insulin sensitivity was determined by euglycemic hyperinsulinemic clamp. Organ index, glucose tolerance test (OGTT), and fasting plasma glucose (FPG), fasting insulin (FINS), hepatic glycogen, hydroxyproline (HYP) and liver function were detected at the end of the treatment. Area under the curve (AUC) for OGTT was calculated. Liver and pancreas histology were determined by histopathological examination with hematoxylin and eosin staining (HE), Sirius Red staining and Masson's trichrome staining, respectively. Hepatic expression of α-smooth muscle actin (α-SMA) and collagen (Col I) were evaluated by immunohistochemical staining.

RESULTS

Compared with the model group, Sal B significantly increased body and liver weight, liver-body ratio, glucose infusion rate (GIR), FPG, FINS levels and hepatic glycogen at the end of administration (P<0.05 or P<0.01). Meanwhile, Sal B significantly decreased AUC for OGTT, spleen weight, spleen-body ratio, aminotransferase and HYP level (P<0.05 or P<0.01). Sal B was also effective in alleviating necrosis of liver tissue, suppressing fibrosis progression and inhibiting the expression of α-SMA and Col I in liver. Compared with the metformin group, Sal B had advantages in ameliorating FPG, hepatic glycogen, spleen weight, organ index, liver function and cirrhosis (P<0.05). Metformin increased insulin sensitivity more potently than Sal B (P<0.05).

CONCLUSIONS

Sal B could improve glucose metabolism in cirrhotic rats by protecting hepatic glycogen reserve, increasing insulin sensitivity, and alleviating pancreatic morphology abnormalities. Sal B was clinically potential in preventing glucose metabolism anomalies accompanied with cirrhosis.

The Effects of One-Anastomosis Gastric Bypass on Glucose Metabolism in Goto-Kakizaki Rats

BACKGROUND

The improvement in glucose metabolism after bariatric surgery is well established. The aim of this study was to investigate the hormones and glycemic control in diabetes after a one-anastomosis gastric bypass (OAGB) variant in an animal model of non-obese type 2 diabetes mellitus.

METHODS

Thirty-six Goto-Kakizaki rats were randomly assigned to undergo one of the following procedures: OAGB (18 rats) or sham intervention (18 rats). Each group was subdivided into three additional groups according to the time of surgery (early-12 weeks; intermediate-16 weeks; and late-20 weeks). Weight, fasting glycemia, glucose tolerance test (OGTT), and hormone levels (glucagon, insulin, glucagon-like peptide-1 [GLP-1], and glucose-dependent insulinotropic peptide [GIP]) were measured.

RESULTS

All rats maintained their weight. The OGTT showed a significant improvement in glycemic levels in rats with OAGB in all time groups (p < 0.002, for all groups at 60 min). Insulin levels decreased significantly in all animals with OAGB, but glucagon levels increased (glucagon paradoxical response). GLP-1 and GIP increased in rats with OAGB at all times, but was only statistically significant in the early surgery group of GLP-1 (p < 0.005).

CONCLUSION

OAGB in a non-obese diabetic rat model improves glycemic control, with a significant decrease in glucose and insulin levels. This reduction without weight loss suggests a surgically induced enhancement of pancreatic function. It appears that this improvement occurs, although the GLP-1 levels were significantly increased only in the early stages. The paradoxical response of glucagon should be further evaluated.

Recent advancements in bariatric/metabolic surgery

Obesity and type 2 diabetes mellitus (T2DM) are currently two pan‐endemic health problems worldwide and are associated with considerable increase in morbidity and mortality. Both diseases are closely related and very difficult to control by current medical treatment, including diet, drug therapy and behavioral modification. Bariatric surgery has proven successful in treating not just obesity but also in significantly decreasing overall obesity‐associated morbidities as well as improving quality of life in severely obese patients (body mass index [BMI] >35 kg/m²). A rapid increase in bariatric surgery started in the 2000s when the laparoscopic surgical technique was introduced into this field. Many new procedures had been developed and changed the face of modern bariatric surgery. Recently, bariatric surgery played as gastrointestinal metabolic surgery has been proposed as a new treatment modality for obesity‐related T2DM for patients with BMI >35 kg/m². Strong evidence has demonstrated that bariatric/metabolic surgery is an effective and durable treatment for obese T2DM patients. Bariatric/metabolic surgery is now becoming an important surgical division. The present article examines and discusses recent advancements in bariatric/metabolic surgery and covers four major fields: (i) the rapid increase in numbers and better safety; (ii) new procedures with better outcomes; (iii) from bariatric to metabolic surgery; and (iv) understanding the mechanisms and personalized treatment.

Gastric bypass in the pig increases GIP levels and decreases active GLP-1 levels

Gastric bypass surgery results in remission of type 2 diabetes in the majority of patients. The incretin hormones glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) have been implicated in the observed remission. Most knowledge so far has been generated in obese subjects. To isolate the surgical effects of gastric bypass on metabolism and hormone responses from the confounding influence of obesity, T2D, or food intake, we performed gastric bypass in lean pigs, using sham-operated and pair-fed pigs as controls. Thus, pigs were subjected to Roux-en-Y gastric bypass (RYGB) or sham surgery and oral glucose tolerance tests (OGTT). RYGB pigs and sham pigs exhibited similar basal and 120-min glucose levels in response to the OGTT. However, RYGB pigs had approximately 1.6-fold higher 30-min glucose (p<0.01). Early insulin release (EIR) was enhanced approximately 3.5-fold in the RYGB pigs (p<0.01). Furthermore, GIP release, both acute and sustained release (p<0.001 and p<0.01, respectively), was increased approximately 2.5-fold and 1.4-fold, respectively, in RYGB pigs. Although total GLP-1 release increased approximately 2.1-fold after RYGB (p<0.001), active GLP-1 was 33% lower (p<0.01). Interestingly basal DPP4-activity was approximately 3.2-fold higher in RYGB pigs (p<0.001). In conclusion, RYGB in lean pigs increases the response of GIP, total GLP-1, and insulin, but reduces levels of active GLP-1 in response to an oral glucose load. These data challenge the role of active GLP-1 as a contributor to remission from diabetes after RYGB.

Common Channel Length in Bypass Surgery Does Not Impact T2DM in Diabetic Zucker Rats

INTRODUCTION

Metabolic surgery is known to impact glucose tolerance but the exact mechanism is still unclear. Based on recently-published data, especially the role of the hindgut may require redefinition.

METHODS

Either a loop duodeno-jejunostomy (DJOS) with exclusion of one third of total intestinal length, a loop duodeno-ileostomy (DiOS, exclusion of two thirds), or SHAM operation was performed in 9-week-old Zucker diabetic fatty rats. One, 3, and 6 months after surgery, an oral glucose tolerance test (OGTT) and glucose-stimulated hormone analyses were conducted. Body weight was documented weekly.

RESULTS

DJOS and DiOS animals showed significantly better glucose control in all OGTTs than the SHAM group (two-way ANOVA p < 0.0001). Body weight developed largely parallel in both intervention groups; SHAM animals had gained significantly less weight after 6 months (Mann-Whitney DJOS/DiOS vs. SHAM p < 0.05, DJOS vs. DiOS p > 0.05). Operative interventions had no impact on GLP-1 and GIP levels at any time point (Mann-Whitney p > 0.05 for all). DJOS/DiOS operations could preserve insulin production up to 6 months, while there was already a sharp decline of insulin levels in the SHAM group (Mann-Whitney: DJOS/DiOS vs. SHAM p < 0.05 for all time points). Additionally, insulin sensitivity was improved significantly 1 month postoperative in both intervention groups compared to SHAM (Mann-Whitney DJOS/DiOS vs. SHAM p < 0.05).

CONCLUSION

The data of the current study demonstrate a sharp amelioration of glucose control after duodenal exclusion with unchanged levels of GLP-1 and GIP. Direct or delayed hindgut stimulation had no impact on glucose control in our model.

Endoscopic Duodenal Mucosal Resurfacing for the Treatment of Type 2 Diabetes: 6-Month Interim Analysis From the First-in-Human Proof-of-Concept Study

OBJECTIVE

To assess procedural safety and glycemic indices at 6 months in a first-in-human study of duodenal mucosal resurfacing (DMR), a novel, minimally invasive, upper endoscopic procedure involving hydrothermal ablation of the duodenal mucosa, in patients with type 2 diabetes and HbA_1c ≥7.5% (58 mmol/mol) on one or more oral antidiabetic agents.

RESEARCH DESIGN AND METHODS

Using novel balloon catheters, DMR was conducted on varying lengths of duodenum in anesthetized patients at a single medical center.

RESULTS

A total of 39 patients with type 2 diabetes (screening HbA_1c 9.5% [80 mmol/mol]; BMI 31 kg/m²) were treated and included in the interim efficacy analysis: 28 had a long duodenal segment ablated (LS; ∼9.3 cm treated) and 11 had a short segment ablated (SS; ∼3.4 cm treated). Overall, DMR was well tolerated with minimal gastrointestinal symptoms postprocedure. Three patients experienced duodenal stenosis treated successfully by balloon dilation. HbA_1c was reduced by 1.2% at 6 months in the full cohort (P < 0.001). More potent glycemic effects were observed among the LS cohort, who experienced a 2.5% reduction in mean HbA_1c at 3 months postprocedure vs. 1.2% in the SS group (P < 0.05) and a 1.4% reduction at 6 months vs. 0.7% in the SS group (P = 0.3). This occurred despite net medication reductions in the LS cohort between 0 and 6 months. Among LS patients with a screening HbA_1c of 7.5-10% (58-86 mmol/mol) and on stable antidiabetic medications postprocedure, HbA_1c was reduced by 1.8% at 6 months (P < 0.01).

CONCLUSIONS

Single-procedure DMR elicits a clinically significant improvement in hyperglycemia in patients with type 2 diabetes in the short-term, with acceptable safety and tolerability. Long-term safety, efficacy, and durability and possible mechanisms of action require further investigation.

Lean, but not healthy: the 'metabolically obese, normal-weight' phenotype

PURPOSE OF REVIEW

Obesity is commonly associated with metabolic dysfunction but there are obese persons who are metabolically healthy. On the opposite side of the coin, there are lean persons who carry multiple cardiometabolic risk factors, typically referred to as metabolically obese, normal-weight (MONW). This has called into question our understanding of obesity and metabolic dysfunction, as an appearance of normal weight may mask significant comorbidities and delay health interventions.

RECENT FINDINGS

High heterogeneity in MONW prevalence rates has been observed, with estimates ranging from as low as 5% to as high as 45%. Reasons for this include sample size effects, differences in MONW definition, social and demographic factors, as well as assumptions made in establishing normal weight. MONW study participants are often characterized by excess visceral adipose tissue and ectopic fat deposition, adipose tissue inflammation, altered inflammatory and adipokine profiles, reduced skeletal muscle mass and low cardiorespiratory fitness. However, more often than not, groups of MONW study participants have been somewhat 'fatter' than the control groups of metabolically healthy lean study participants, which in itself could be responsible for some of the observed differences. Very limited data are available regarding interventions to improve metabolic function in MONW study participants.

SUMMARY

There is a need for more research to better understand the characteristics of the MONW phenotype, the cause of metabolic dysfunction in the absence of obesity, and evaluate potential therapies so as to facilitate the establishment of clinical guidelines.

Targeting the gastrointestinal tract to treat type 2 diabetes

The rising global rates of type 2 diabetes and obesity present a significant economic and social burden, underscoring the importance for effective and safe therapeutic options. The success of glucagon-like-peptide-1 receptor agonists in the treatment of type 2 diabetes, along with the potent glucose-lowering effects of bariatric surgery, highlight the gastrointestinal tract as a potential target for diabetes treatment. Furthermore, recent evidence suggests that the gut plays a prominent role in the ability of metformin to lower glucose levels. As such, the current review highlights some of the current and potential pathways in the gut that could be targeted to improve glucose homeostasis, such as changes in nutrient sensing, gut peptides, gut microbiota and bile acids. A better understanding of these pathways will lay the groundwork for novel gut-targeted antidiabetic therapies, some of which have already shown initial promise.

Mechanisms of Diabetes Improvement Following Bariatric/Metabolic Surgery

More than 20 years ago, Pories et al. published a seminal article, "Who Would Have Thought It? An Operation Proves to Be the Most Effective Therapy for Adult-Onset Diabetes Mellitus." This was based on their observation that bariatric surgery rapidly normalized blood glucose levels in obese people with type 2 diabetes mellitus (T2DM), and 10 years later, almost 90% remained diabetes free. Pories et al. suggested that caloric restriction played a key role and that the relative contributions of proximal intestinal nutrient exclusion, rapid distal gut nutrient delivery, and the role of gut hormones required further investigation. These findings of T2DM improvement/remission after bariatric surgery have been widely replicated, together with the observation that bariatric surgery prevents or delays incident T2DM. Over the ensuing two decades, important glucoregulatory roles of the gastrointestinal (GI) tract have been firmly established. However, the physiological and molecular mechanisms underlying the beneficial glycemic effects of bariatric surgery remain incompletely understood. In addition to the mechanisms proposed by Pories et al., changes in bile acid metabolism, GI tract nutrient sensing and glucose utilization, incretins, possible anti-incretin(s), and the intestinal microbiome are implicated. These changes, acting through peripheral and/or central pathways, lead to reduced hepatic glucose production, increased tissue glucose uptake, improved insulin sensitivity, and enhanced β-cell function. A constellation of factors, rather than a single overarching mechanism, likely mediate postoperative glycemic improvement, with the contributing factors varying according to the surgical procedure. Thus, different bariatric/metabolic procedures provide us with experimental tools to probe GI tract physiology. Embracing this approach through the application of detailed phenotyping, genomics, metabolomics, and gut microbiome studies will enhance our understanding of metabolic regulation and help identify novel therapeutic targets.

Expedited Biliopancreatic Juice Flow to the Distal Gut Benefits the Diabetes Control After Duodenal-Jejunal Bypass

BACKGROUND

Serum bile acids (BAs) are elevated after metabolic surgeries including Roux-en-Y gastric bypass (RYGB), ileal transposition (IT), and duodenal-jejunal bypass (DJB). Recently, BAs have emerged as a kind of signaling molecules, which can not only promote glucagon-like peptide-1 (GLP-1) secretion but can also regulate multiple enzymes involved in glucose metabolism. The aim of this study was to investigate whether expedited biliopancreatic juice flow to the distal gut contributes to the increased serum GLP-1 and BAs and benefits the diabetes control after DJB.

METHODS

DJB, long alimentary limb DJB (LDJB), duodenal-jejunal anastomosis (DJA), and sham operation were performed in diabetic rats induced by high-fat diet (HFD) and low dose of streptozotocin (STZ). Body weight, food intake, oral glucose tolerance, insulin tolerance, glucose-stimulated insulin and GLP-1 secretion, fasting serum total bile acids (TBAs), and lipid profiles were measured at indicated time points.

RESULTS

Compared with sham operation, DJA, DJB, and LDJB all achieved rapid and dramatic improvements in glucose tolerance and insulin sensitivity independently of food restriction and weight loss. DJB and LDJB-operated rats exhibited even better glucose tolerance, higher fasting serum TBAs, and higher glucose-stimulated GLP-1 secretion than the DJA group postoperatively. No difference was detected in insulin sensitivity and glucose-stimulated insulin secretion between DJA, DJB, and LDJB groups.

CONCLUSIONS

Expedited biliopancreatic juice flow to the distal gut was associated with augmented GLP-1 secretion and increased fasting serum TBA concentration, which may partly explain the metabolic benefits of DJB.

Bile Diversion in Roux-en-Y Gastric Bypass Modulates Sodium-Dependent Glucose Intestinal Uptake

Gastro-intestinal exclusion by Roux-en-Y gastric bypass (RYGB) improves glucose metabolism, independent of weight loss. Although changes in intestinal bile trafficking have been shown to play a role, the underlying mechanisms are unclear. We performed RYGB in minipigs and showed that the intestinal uptake of ingested glucose is blunted in the bile-deprived alimentary limb (AL). Glucose uptake in the AL was restored by the addition of bile, and this effect was abolished when active glucose intestinal transport was blocked with phlorizin. Sodium-glucose cotransporter 1 remained expressed in the AL, while intraluminal sodium content was markedly decreased. Adding sodium to the AL had the same effect as bile on glucose uptake. It also increased postprandial blood glucose response in conscious minipigs following RYGB. The decrease in intestinal uptake of glucose after RYGB was confirmed in humans. Our results demonstrate that bile diversion affects postprandial glucose metabolism by modulating sodium-glucose intestinal cotransport.

Reconfiguration of the small intestine and diabetes remitting effects of Roux-en-Y gastric bypass surgery

PURPOSE OF REVIEW

Alterations in small intestinal physiology are proposed to play a causative role in the beneficial impact of Roux-en-Y gastric bypass on type 2 diabetes mellitus. The present article describes the key proposed mechanisms implicated with an emphasis on some of the newer findings in the field.

RECENT FINDINGS

Augmented incretin and diminished anti-incretin effects postsurgery are explored and a model proposed that reconciles the hindgut and foregut hypotheses of improved glycaemic control as being complementary rather than mutually exclusive. Synthesis of recent findings on postbypass changes in intestinal glucose handling then follows. Finally an updated view of the role of distal bile diversion and changes in the microbiota on enteroendocrine signalling is presented.

SUMMARY

A series of nonmutually exclusive changes in small intestinal physiology likely make a significant contribution to improved glycaemic control postgastric bypass. Longitudinal data indicate that these effects do not translate into a long-term cure. A number of surgery-induced changes, however, are amenable to device-based and pharmacology-based mimicry, and this is an area for prioritization of future research focus.

Jejunum-ileum circuit procedure improves glucose metabolism in diabetic rats independent of weight loss

OBJECTIVE

To introduce a lower-risk novel surgical procedure to achieve diabetes reversal along with associated hormonal changes.

METHODS

Diabetic rats were randomly assigned to jejunum-ileum circuit (JIC), sham-JIC, ileal interposition (IT), and sham-IT groups. The JIC group included two subgroups: short (JIC-S) and long (JIC-L), based on the length between anastomosis and Treitz ligament (LAT ). The body weight, food intake, blood glucose, glucose and insulin tolerance, and gut hormones were measured. The liver gene expression of glucose transporter 2 (GLUT2) and protein expression of glucose-6-phosphatase (G6P) and phosphoenolpyruvate carboxykinase (PKC) were also measured. Following a dye infusion, nutrient delivery was measured at termination day.

RESULTS

Compared to sham-JIC group, JIC-S group did not reduce body weight or food intake but significantly improved glucose tolerance and insulin resistance. With fast chyme transit, JIC-S not only promoted the secretion of insulin, glucagon-like peptide 1, and peptide YY and decreased leptin, but also upregulated hepatic GLUT2 and downregulated hepatic G6P and PKC. JIC-L group, however, failed to achieve remission of diabetes.

CONCLUSION

JIC-S relieves diabetes independent of weight loss, as it promotes the secretion of anti-diabetic hormones and inhibits hepatic glucose production. The prolonging of LAT , however, diminishes the hypoglycemic effect.

Roux-en Y gastric bypass is superior to duodeno-jejunal bypass in improving glycaemic control in Zucker diabetic fatty rats

BACKGROUND

Whilst weight loss results in many beneficial metabolic consequences, the immediate improvement in glycaemia after Roux-en-Y Gastric bypass (RYGB) remains intriguing. Duodenal jejunal bypass (DJB) induces similar glycaemic effects, while not affecting calorie intake or weight loss. We studied diabetic ZDF(fa/fa) rats to compare the effects of DJB and RYGB operations on glycaemia.

METHODS

Male ZDF(fa/fa) rats, aged 12 weeks underwent RYGB, DJB or sham operations. Unoperated ZDF(fa/fa) and ZDF(fa/+w)ere used as controls. Body weight, food intake, fasting glucose, insulin and gut hormones were measured at baseline and on postoperative days 2, 10 and 35. An oral glucose tolerance test (OGTT) was performed on days 12 and 26.

RESULTS

DJB had similar food intake and body weight to sham-operated and unoperated control ZDF(fa/fa) rats (p = NS), but had lower fasting glucose (p < 0.05). RYGB had lower food intake, body weight and fasting glucose compared to all groups (p < 0.001). DJB prevented the progressive decline in fasting insulin observed in the sham-operated or unoperated ZDF(fa/fa) rats, while RYGB with normalized glycaemia reduced the physiological requirement for raised fasting insulin.

CONCLUSIONS

Bypassing the proximal small bowel with the DJB has mild to moderate body weight independent effects on glucose homeostasis and preservation of fasting insulin levels in the medium term. These effects might be further amplified by the additional anatomical and physiological changes after RYGB.

Glucoregulatory Relevance of Small Intestinal Nutrient Sensing in Physiology, Bariatric Surgery, and Pharmacology

Emerging evidence suggests the gastrointestinal tract plays an important glucoregulatory role. In this perspective, we first review how the intestine senses ingested nutrients, initiating crucial negative feedback mechanisms through a gut-brain neuronal axis to regulate glycemia, mainly via reduction in hepatic glucose production. We then highlight how intestinal energy sensory mechanisms are responsible for the glucose-lowering effects of bariatric surgery, specifically duodenal-jejunal bypass, and the antidiabetic agents metformin and resveratrol. A better understanding of these pathways lays the groundwork for intestinally targeted drug therapy for the treatment of diabetes.

Hormonal signaling in the gut

The gut is anatomically positioned to play a critical role in the regulation of metabolic homeostasis, providing negative feedback via nutrient sensing and local hormonal signaling. Gut hormones, such as cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1), are released following a meal and act on local receptors to regulate glycemia via a neuronal gut-brain axis. Additionally, jejunal nutrient sensing and leptin action are demonstrated to suppress glucose production, and both are required for the rapid antidiabetic effect of duodenal jejunal bypass surgery. Strategies aimed at targeting local gut hormonal signaling pathways may prove to be efficacious therapeutic options to improve glucose control in diabetes.