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

New Lessons from the gut: Studies of the role of gut peptides in weight loss and diabetes resolution after gastric bypass and sleeve gastrectomy

It has been known since 2005 that the secretion of several gut hormones changes radically after gastric bypass operations and, although more moderately, after sleeve gastrectomy but not after gastric banding. It has therefore been speculated that increased secretion of particularly GLP-1 and Peptide YY (PYY), which both inhibit appetite and food intake, may be involved in the weight loss effects of surgery and for improvements in glucose tolerance. Experiments involving inhibition of hormone secretion with somatostatin, blockade of their actions with antagonists, or blockade of hormone formation/activation support this notion. However, differences between results of bypass and sleeve operations indicate that distinct mechanisms may also be involved. Although the reductions in ghrelin secretion after sleeve gastrectomy would seem to provide an obvious explanation, experiments with restoration of ghrelin levels pointed towards effects on insulin secretion and glucose tolerance rather than on food intake. It seems clear that changes in GLP-1 secretion are important for insulin secretion after bypass and appear to be responsible for postbariatric hypoglycemia in glucose-tolerant individuals; however, with time the improvements in insulin sensitivity, which in turn are secondary to the weight loss, may be more important. Changes in bile acid metabolism do not seem to be of particular importance in humans.

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

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

Intestinal Enteroendocrine Cells: Present and Future Druggable Targets

Enteroendocrine cells are specialized secretory lineage cells in the small and large intestines that secrete hormones and peptides in response to luminal contents. The various hormones and peptides can act upon neighboring cells and as part of the endocrine system, circulate systemically via immune cells and the enteric nervous system. Locally, enteroendocrine cells have a major role in gastrointestinal motility, nutrient sensing, and glucose metabolism. Targeting the intestinal enteroendocrine cells or mimicking hormone secretion has been an important field of study in obesity and other metabolic diseases. Studies on the importance of these cells in inflammatory and auto-immune diseases have only recently been reported. The rapid global increase in metabolic and inflammatory diseases suggests that increased understanding and novel therapies are needed. This review will focus on the association between enteroendocrine changes and metabolic and inflammatory disease progression and conclude with the future of enteroendocrine cells as potential druggable targets.

The efficacy of GLP-1RAs for the management of postprandial hypoglycemia following bariatric surgery: a systematic review

OBJECTIVE

Postprandial hyperinsulinemic hypoglycemia with neuroglycopenia is an increasingly recognized complication of Roux-en-Y gastric bypass and gastric sleeve surgery that may detrimentally affect patient quality of life. One likely causal factor is glucagon-like peptide-1 (GLP-1), which has an exaggerated rise following ingestion of carbohydrates after bariatric surgery. This paper sought to assess the role of GLP-1 receptor agonists (GLP-1RAs) in managing postprandial hypoglycemia following bariatric surgery.

METHODS

MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov, and Scopus were systematically and critically appraised for all peer-reviewed publications that suitably fulfilled the inclusion criteria established a priori. This systematic review was developed according to the Preferred Reporting Items for Systematic Review and Meta-Analyses Protocols (PRISMA-P). It followed methods outlined in the Cochrane Handbook for Systematic Reviews of Interventions and is registered with PROSPERO (International Prospective Register of Systematic Reviews; identifier CRD420212716429).

RESULTS AND CONCLUSIONS

Postprandial hyperinsulinemic hypoglycemia remains a notoriously difficult to manage metabolic complication of bariatric surgery. This first, to the authors' knowledge, systematic review presents evidence suggesting that use of GLP-1RAs does not lead to an increase of hypoglycemic episodes, and, although this approach may appear counterintuitive, the findings suggest that GLP-1RAs could reduce the number of postprandial hypoglycemic episodes and improve glycemic variability.

Therapeutic potential of non-starch polysaccharides on type 2 diabetes: from hypoglycemic mechanism to clinical trials

Non-starch polysaccharides (NSPs) have been reported to exert therapeutic potential on managing type 2 diabetes mellitus (T2DM). Various mechanisms have been proposed; however, several studies have not considered the correlations between the anti-T2DM activity of NSPs and their molecular structure. Moreover, the current understanding of the role of NSPs in T2DM treatment is mainly based on in vitro and in vivo data, and more human clinical trials are required to verify the actual efficacy in treating T2DM. The related anti-T2DM mechanisms of NSPs, including regulating insulin action, promoting glucose metabolism and regulating postprandial blood glucose level, anti-inflammatory and regulating gut microbiota (GM), are reviewed. The structure-function relationships are summarized, and the relationships between NSPs structure and anti-T2DM activity from clinical trials are highlighted. The development of anti-T2DM medication or dietary supplements of NSPs could be promoted with an in-depth understanding of the multiple regulatory effects in the treatment/intervention of T2DM.

Gastrointestinal Hormones and β-Cell Function After Gastric Bypass and Sleeve Gastrectomy: A Randomized Controlled Trial (Oseberg)

CONTEXT

Whether Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) differentially affect postprandial gastrointestinal hormones and β-cell function in type 2 diabetes remains unclear.

OBJECTIVE

We aimed to compare gastrointestinal hormones and β-cell function, assessed by an oral glucose tolerance test (OGTT) 5 weeks and 1 year after surgery, hypothesizing higher glucagon-like peptide-1 (GLP-1) levels and greater β-cell response to glucose after RYGB than after SG.

METHODS

This study was a randomized, triple-blind, single-center trial at a tertiary care center in Norway. The primary outcomes were diabetes remission and IVGTT-derived β-cell function. Participants with obesity and type 2 diabetes were allocated (1:1) to RYGB or SG. We measured gastrointestinal hormone profiles and insulin secretion as β-cell glucose sensitivity (β-GS) derived from 180-minute OGTTs.

RESULTS

Participants were 106 patients (67% women), mean (SD) age 48 (10) years. Diabetes remission rates at 1 year were higher after RYGB than after SG (77% vs 48%; P = 0.002). Incremental area under the curve (iAUC0-180) GLP-1 and β-GS increased more after RYGB than after SG, with 1-year between-group difference 1173 pmol/L*min (95% CI, 569-1776; P = 0.0010) and 0.45 pmol/kg/min/mmol (95% CI, 0.15-0.75; P = 0.0032), respectively. After surgery, fasting and postprandial ghrelin levels were higher and decremental AUC0-180 ghrelin, iAUC0-180 glucose-dependent insulinotropic polypeptide, and iAUC0-60 glucagon were greater after RYGB than after SG. Diabetes remission at 1 year was associated with higher β-GS and higher GLP-1 secretion.

CONCLUSION

RYGB was associated with greater improvement in β-cell function and higher postprandial GLP-1 levels than SG.

Is Colectomy Associated with the Risk of Type 2 Diabetes in Patients without Colorectal Cancer? A Population-Based Cohort Study

Type 2 diabetes might be influenced by colonic disease; however, the association between colonic resection and type 2 diabetes has rarely been discussed. This population-based cohort study explored the association between colectomy and type 2 diabetes in patients without colorectal cancer. A total of 642 patients who underwent colectomy for noncancerous diseases at any time between 2000 and 2012 in the National Health Insurance Research Database of Taiwan were enrolled. The enrolled patients were matched with 2568 patients without colectomy at a 1:4 ratio using a propensity score that covered age, sex, and comorbidities. The risk of type 2 diabetes was assessed using a Cox proportional hazards model. The mean (standard deviation) follow-up durations in colectomy cases and non-colectomy controls were 4.9 (4.0) and 5.6 (3.6) years, respectively; 65 (10.1%) colectomy cases and 342 (15.5%) non-colectomy controls developed type 2 diabetes. After adjustment, colectomy cases still exhibited a decreased risk of type 2 diabetes (adjusted HR = 0.80, 95% CI: 0.61–1.04). A stratified analysis for colectomy type indicated that patients who underwent right or transverse colectomy had a significantly lower risk of developing type 2 diabetes (adjusted HR = 0.57, 95% CI: 0.34–0.98). In the present study, colectomy tended to be at a reduced risk of type 2 diabetes in patients without colorectal cancer, and right or transverse colectomies were especially associated with a significantly reduced risk of type 2 diabetes.

GLP-1: 10-year follow-up after Roux-en-Y gastric bypass

PURPOSE

Glucagon-like peptide-1 (GLP-1) is a hormone widely studied in the short-term postoperative follow-up of Roux-en-Y gastric bypass due to its elevation and association with improvement of the glucose metabolism, but there are few studies in 10 years after RYGB follow-up with the same patient.

METHODS

Twenty morbidity obesity patients were submitted to RYGB; these patients were divided into two groups: normal glucose-tolerant morbidly obese patients (NGT) 11 patients and abnormal glucose metabolism morbidly obese patients (AGM) 9 patients. Oral glucose tolerance test (OGTT) was done during four different periods: T1 (first evaluation), T2 (pre-surgery), T3 (9 months after surgery) and T4 (10 years after surgery).

RESULTS

Groups were matched for age and gender, and as NGT and AGM had BMI of 46.31 ± 5.03 kg/m² and 50.87 ± 10.31 kg/m^2. After 10 years of RYGB, they were obesity grade I with BMI for NGT 32.45 ± 4.99 kg/m² and AGM 34.85 ± 4.46 kg/m². Plasma glucose levels decreased NGT group at T4 period had a significant reduction at 120 min after OGTT for NGT 55.49 ± 17.15 mg/dL (p˂0.001). Insulin levels changed from T1 to T4 for the NGT group. GLP-1 curves were statistically different between the NGT and AGM groups. The AGM group had a higher mean for GLP-1 secretion at T4 period and at 30 min of OGTT 63.85 ± 37.98 pmol/L when compared to NGT 50.73 ± 24.82 pmol/L with AGM > NGT with p˂0.001.

CONCLUSION

Evaluation of the same patient during 4 different periods shows that, even with weight regain, after 10-years of RYGB high levels of GLP-1 remained which can be associated with metabolic improvement especially at the NGT group.

Dynamin regulates L cell secretion in human gut

BACKGROUND

The mechanochemical enzyme dynamin mediates endocytosis and regulates neuroendocrine cell exocytosis. Enteroendocrine L cells co-secrete the anorectic gut hormones glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) postprandially and is a potential therapeutic target for metabolic diseases. In the present study, we aimed to determine if dynamin is implicated in human L cell secretion.

METHODS

Western blot was performed on the murine L cell line GLUTag. Static incubation of human colonic mucosae with activators and inhibitors of dynamin was carried out. GLP-1 and PYY contents of the secretion supernatants were assayed using ELISA.

RESULTS AND CONCLUSION

s: Both dynamin I and II are expressed in GLUTag cells. The dynamin activator Ryngo 1-23 evoked significant GLP-1 and PYY release from human colonic mucosae while the dynamin inhibitor Dynole 3-42 significantly inhibited release triggered by known L cell secretagogues. Thus, the cell signaling regulator dynamin is able to bi-directionally regulate L cell hormone secretion in the human gut and may represent a novel target for gastrointestinal-targeted metabolic drug development.

The role of GLP-1 in postprandial glucose metabolism after bariatric surgery: a narrative review of human GLP-1 receptor antagonist studies

The Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) bariatric procedures lead to remission or improvement of type 2 diabetes. A weight loss-independent augmentation of postprandial insulin secretion contributes to the improvement in glycemic control after RYGB and is associated with a ∼10-fold increase in plasma concentrations of the incretin hormone glucagon-like peptide-1 (GLP-1). However, the physiologic importance of the markedly increased postprandial GLP-1 secretion after RYGB has been much debated. The effect of GLP-1 receptor blockade after RYGB has been investigated in 12 studies. The studies indicate a shift toward a more prominent role for GLP-1 in postprandial β-cell function after RYGB. The effect of GLP-1 receptor antagonism on glucose tolerance after RYGB is more complex and is associated with important methodological challenges. The postprandial GLP-1 response is less enhanced after SG compared with RYGB. However, the effect of GLP-1 receptor blockade after SG has been examined in 1 study only and needs further investigation.

Acute effects of delayed-release hydrolyzed pine nut oil on glucose tolerance, incretins, ghrelin and appetite in healthy humans

BACGROUND & AIM

Pinolenic acid, a major component (~20%) of pine nut oil, is a dual agonist of the free fatty acid receptors, FFA1 and FFA4, which may regulate release of incretins and ghrelin from the gut. Here, we investigated the acute effects of hydrolyzed pine nut oil (PNO-FFA), delivered to the small intestine by delayed-release capsules, on glucose tolerance, insulin, incretin and ghrelin secretion, and appetite.

METHODS

In two cross-over studies, we evaluated 3 g unhydrolyzed pine nut oil (PNO-TG) or 3 g PNO-FFA versus no oil in eight healthy, non-obese subjects (study 1), and 3 g PNO-FFA or 6 g PNO-FFA versus no oil in ten healthy, overweight/obese subjects (study 2) in both studies given in delayed-release capsules 30 min prior to a 4-h-oral glucose tolerance test (OGTT). Outcomes were circulating levels of glucose, insulin, GLP-1, GIP, ghrelin, appetite and gastrointestinal tolerability during OGTT.

RESULTS

Both 3 g PNO-FFA in study 1 and 6 g PNO-FFA in study 2 markedly increased GLP-1 levels (p < 0.001) and attenuated ghrelin levels (p < 0.001) during the last 2 h of the OGTT compared with no oil. In study 2, these effects of PNO-FFA were accompanied by an increased satiety and fullness (p < 0.03), and decreased prospective food consumption (p < 0.05). PNO-FFA caused only small reductions in glucose and insulin levels during the first 2 h of the OGTT.

CONCLUSIONS

Our results provide evidence that PNO-FFA delivered to the small intestine by delayed-release capsules may reduce appetite by augmenting GLP-1 release and attenuating ghrelin secretion in the late postprandial state.

CLINICAL TRIAL REGISTRY NUMBERS

NCT03062592 and NCT03305367.

Glucose transporters in the small intestine in health and disease

Absorption of monosaccharides is mainly mediated by Na+-D-glucose cotransporter SGLT1 and the facititative transporters GLUT2 and GLUT5. SGLT1 and GLUT2 are relevant for absorption of D-glucose and D-galactose while GLUT5 is relevant for D-fructose absorption. SGLT1 and GLUT5 are constantly localized in the brush border membrane (BBM) of enterocytes, whereas GLUT2 is localized in the basolateral membrane (BLM) or the BBM plus BLM at low and high luminal D-glucose concentrations, respectively. At high luminal D-glucose, the abundance SGLT1 in the BBM is increased. Hence, D-glucose absorption at low luminal glucose is mediated via SGLT1 in the BBM and GLUT2 in the BLM whereas high-capacity D-glucose absorption at high luminal glucose is mediated by SGLT1 plus GLUT2 in the BBM and GLUT2 in the BLM. The review describes functions and regulations of SGLT1, GLUT2, and GLUT5 in the small intestine including diurnal variations and carbohydrate-dependent regulations. Also, the roles of SGLT1 and GLUT2 for secretion of enterohormones are discussed. Furthermore, diseases are described that are caused by malfunctions of small intestinal monosaccharide transporters, such as glucose-galactose malabsorption, Fanconi syndrome, and fructose intolerance. Moreover, it is reported how diabetes, small intestinal inflammation, parental nutrition, bariatric surgery, and metformin treatment affect expression of monosaccharide transporters in the small intestine. Finally, food components that decrease D-glucose absorption and drugs in development that inhibit or downregulate SGLT1 in the small intestine are compiled. Models for regulations and combined functions of glucose transporters, and for interplay between D-fructose transport and metabolism, are discussed.

Resection of the duodenum causes long-term endocrine and exocrine dysfunction after Whipple procedure for benign tumors - Results of a systematic review and meta-analysis

BACKGROUND

Metabolic dysfunctions after pancreatoduodenectomy (PD) need to be considered when pancreatic head resection is likely to lead to long-term survival.

METHODS

Medline, Embase and Cochrane Library were searched for studies reporting measured data of metabolic function after PD and duodenum-sparing total pancreatic head resection (DPPHR). Data from 23 cohort studies comprising 1019 patients were eligible; 594 and 910 patients were involved in systematic review and meta-analysis, respectively.

RESULTS

The cumulative incidence of postoperative new onset of diabetes mellitus (pNODM) after PD for benign tumors was 46 of 321 patients (14%) measured after follow-up of in mean 36 months postoperatively. New onset of postoperative exocrine insufficiency (PEI) was exhibited by 91 of 209 patients (44%) after PD for benign tumors measured in mean 23 months postoperatively. The meta-analysis indicated pNODM after PD for benign tumor in 32 of 208 patients (15%) and in 10 of 178 patients (6%) after DPPHR (p = 0.007; OR 3.01; (95%CI:1.39-6.49)). PEI was exhibited by 80 of 178 patients (45%) after PD and by 6 of 88 patients (7%) after DPPHR (p < 0.001). GI hormones measured in 194 patients revealed postoperatively a significant impairment of integrated responses of gastrin, motilin, insulin, secretin, PP and GIP (p < 0.050-0.001) after PD. Fasting and stimulated levels of GLP-1 and glucagon levels displayed a significant increase (p < 0.020/p < 0.030). Following DPPHR, responses of gastrin, motilin, secretin and CCK displayed no change compared to preoperative levels.

CONCLUSIONS

After PD, duodenectomy, rather than pancreatic head resection is the main cause for long-term persisting, postoperative new onset of DM and PEI.

ID1-Mediated BMP Signaling Pathway Potentiates Glucagon-Like Peptide-1 Secretion in Response to Nutrient Replenishment

Glucagon-like peptide-1 (GLP-1) is a well-known incretin hormone secreted from enteroendocrinal L cells in response to nutrients, such as glucose and dietary fat, and controls glycemic homeostasis. However, the detailed intracellular mechanisms of how L cells control GLP-1 secretion in response to nutrients still remain unclear. Here, we report that bone morphogenetic protein (BMP) signaling pathway plays a pivotal role to control GLP-1 secretion in response to nutrient replenishment in well-established mouse enteroendocrinal L cells (GLUTag cells). Nutrient starvation dramatically reduced cellular respiration and GLP-1 secretion in GLUTag cells. Transcriptome analysis revealed that nutrient starvation remarkably reduced gene expressions involved in BMP signaling pathway, whereas nutrient replenishment rescued BMP signaling to potentiate GLP-1 secretion. Transient knockdown of inhibitor of DNA binding (ID)1, a well-known target gene of BMP signaling, remarkably reduced GLP-1 secretion. Consistently, LDN193189, an inhibitor of BMP signaling, markedly reduced GLP-1 secretion in L cells. In contrast, BMP4 treatment activated BMP signaling pathway and potentiated GLP-1 secretion in response to nutrient replenishment. Altogether, we demonstrated that BMP signaling pathway is a novel molecular mechanism to control GLP-1 secretion in response to cellular nutrient status. Selective activation of BMP signaling would be a potent therapeutic strategy to stimulate GLP-1 secretion in order to restore glycemic homeostasis.

Brunner's Gland Hyperplasia in a Patient after Roux-Y Gastric Bypass: An Important Pitfall in GLP-1 Receptor Imaging

Severe cases of postprandial hypoglycaemia after bariatric surgery can be a diagnostic and therapeutic challenge. The diagnostic role of ⁶⁸Ga-DOTA-Exendin-4 PET/CT in postbariatric hypoglycaemia for further treatment decisions is unclear. We present a case of a 50-year-old woman with frequent and severe postprandial hypoglycaemic (≤2.5 mmol/L) episodes starting three years after Roux-Y gastric bypass. Despite strict dietary adherence and several medical therapies, the patient remained severely affected, and ⁶⁸Ga-DOTA-Exendin-4 PET/CT was performed to exclude atypical presentation of an insulinoma or nesidioblastosis. No pancreatic abnormalities were found, but intensive tracer accumulation in the first and second part of the duodenum was detected, which proved to be hyperplastic Brunner's glands on histology and were strongly positive for the glucagon-like peptide-1 receptor. This case provides histopathological verification that duodenal ⁶⁸Ga-DOTA-Exendin-4 uptake is caused by uptake in Brunner's glands and points to a potential relationship between bariatric surgery and Brunner's glands.

GIP analogues and the treatment of obesity-diabetes

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

Targeted Analysis of Three Hormonal Systems Identifies Molecules Associated with the Presence and Severity of NAFLD

AIMS

To investigate circulating levels and liver gene expression of 3 hormonal pathways associated with obesity, insulin resistance, and inflammation to identify leads towards potential diagnostic markers and therapeutic targets in patients with nonalcoholic fatty liver disease (NAFLD).

METHODS

We compared circulating levels of (1) proglucagon-derived hormones (glucagon-like peptide [GLP]-1, GLP-2, glicentin, oxyntomodulin, glucagon, major proglucagon fragment [MPGF]), (2) follistatins-activins (follistatin-like [FSTL]3, activin B), (3) IGF axis (insulin-like growth factor [IGF]-1, total and intact IGF binding protein [IGFBP]-3 and IGFBP-4, and pregnancy-associated plasma protein [PAPP]-A) in 2 studies: (1) 18 individuals with early stage NAFLD versus 14 controls (study 1; early NAFLD study) and in (2) 31 individuals with biopsy proven NAFLD (15 with simple steatosis [SS] and 16 with nonalcoholic steatohepatitis [NASH]), vs 50 controls (24 lean and 26 obese) (study 2). Liver gene expression was assessed in 22 subjects (12 controls, 5 NASH, 5 NASH-related cirrhosis).

RESULTS

Patients in early stages of NAFLD demonstrate higher fasting MPGF and lower incremental increase of glicentin during oral glucose tolerance test than controls. In more advanced stages, FSTL3 levels are higher in NASH than simple steatosis and, within NAFLD patients, in those with more severe lobular and portal inflammation. The IGF-1/intact IGFBP-3 ratio is lower in patients with liver fibrosis. Genes encoding follistatin, activin A, activin B, and the IGF-1 receptor are higher in NASH.

CONCLUSION

MPGF and glicentin may be involved in early stages of NAFLD, whereas FSTL3 and IGF-1/intact IGFBP3 in the progression to NASH and liver fibrosis respectively, suggesting potential as diagnostic markers or therapeutic targets.

Secretin release after Roux-en-Y gastric bypass reveals a population of glucose-sensitive S cells in distal small intestine

OBJECTIVES

Gastrointestinal hormones contribute to the beneficial effects of Roux-en-Y gastric bypass surgery (RYGB) on glycemic control. Secretin is secreted from duodenal S cells in response to low luminal pH, but it is unknown whether its secretion is altered after RYGB and if secretin contributes to the postoperative improvement in glycemic control. We hypothesized that secretin secretion increases after RYGB as a result of the diversion of nutrients to more distal parts of the small intestine, and thereby affects islet hormone release.

METHODS

A specific secretin radioimmunoassay was developed, evaluated biochemically, and used to quantify plasma concentrations of secretin in 13 obese individuals before, 1 week after, and 3 months after RYGB. Distribution of secretin and its receptor was assessed by RNA sequencing, mass-spectrometry and in situ hybridization in human and rat tissues. Isolated, perfused rat intestine and pancreas were used to explore the molecular mechanism underlying glucose-induced secretin secretion and to study direct effects of secretin on glucagon, insulin, and somatostatin secretion. Secretin was administered alone or in combination with GLP-1 to non-sedated rats to evaluate effects on glucose regulation.

RESULTS

Plasma postprandial secretin was more than doubled in humans after RYGB (P < 0.001). The distal small intestine harbored secretin expressing cells in both rats and humans. Glucose increased the secretion of secretin in a sodium-glucose cotransporter dependent manner when administered to the distal part but not into the proximal part of the rat small intestine. Secretin stimulated somatostatin secretion (fold change: 1.59, P < 0.05) from the perfused rat pancreas but affected neither insulin (P = 0.2) nor glucagon (P = 0.97) secretion. When administered to rats in vivo, insulin secretion was attenuated and glucagon secretion increased (P = 0.04), while blood glucose peak time was delayed (from 15 to 45 min) and gastric emptying time prolonged (P = 0.004).

CONCLUSIONS

Glucose-sensing secretin cells located in the distal part of the small intestine may contribute to increased plasma concentrations observed after RYGB. The metabolic role of the distal S cells warrants further studies.

Proinsulin associates with poor β-cell function, glucose-dependent insulinotropic peptide, and insulin resistance in persistent type 2 diabetes after Roux-en-Y gastric bypass in humans

BACKGROUND

The determinants of type 2 diabetes (T2D) remission and/or relapse after gastric bypass (RYGB) remain fully unknown. This study characterized β- and α-cell function, in cretin hormone release and insulin sensitivity in individuals with (remitters) or without (non-remitters) diabetes remission after RYGB.

METHODS

This is a cross-sectional study of two distinct cohorts of individuals with or without diabetes remission at least 2 years after RYGB. Each individual underwent-either an oral glucose (remitters) or a mixed meal (non-remitters) test; glucose, proinsulin, insulin, C-peptide, glucagon, incretins and leptin were measured.

RESULTS

Compared to remitters (n = 23), non-remitters (n = 31) were older (mean [±SD] age 56.1 ± 8.2 vs. 46.0 ± 8.9 years, P < 0.001), had longer diabetes duration (13.1 ± 10.1 vs. 2.2 ± 2.4 years, P < 0.001), were further out from the surgery (5.6 ± 3.3 vs. 3.5 ± 1.7 years, P < 0.01), were more insulin resistant (HOMA-IR 4.01 ± 3.65 vs. 2.08 ± 1.22, P < 0.001), but did not differ for body weight. As predicted, remitters had higher β-cell glucose sensitivity (1.95 ± 1.23 vs. 0.86 ± 0.55 pmol/kg/min/mmol, P < 0.001) and disposition index (1.55 ± 1.75 vs 0.33 ± 0.27, P = 0.003), compared to non-remitters, who showed non-suppressibility of glucagon during the oral challenge (time × group P = 0.001). Higher proinsulin (16.55 ± 10.45 vs. 6.62 ± 3.50 PM, P < 0.0001), and proinsulin: C-peptide (40.83 ± 29.43 vs. 17.13 ± 7.16, P < 0.001) were strongly associated with non-remission status, while differences in incretins between remitters and non-remitters were minimal.

CONCLUSIONS

Individual without diabetes remission after gastric bypass have poorer β-cell response and lesser suppression of glucagon to an oral challenge; body weight and incretins differ minimally according to remission status.

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

AIMS

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Gastric Emptying and Distal Gastrectomy Independently Enhance Postprandial Glucagon-Like Peptide-1 Release After a Mixed Meal and Improve Glycemic Control in Subjects Having Undergone Pancreaticoduodenectomy

OBJECTIVES

New-onset diabetes frequently resolves after pancreaticoduodenectomy (PD). Glucagon-like peptide-1 (GLP-1) conceivably is involved as its release is enhanced by rapid gastric emptying and distal bowel exposure to nutrients. We aimed at studying factors associated with GLP-1 release after PD.

METHODS

Fifteen PD subjects with distal gastrectomy (Whipple) and 15 with pylorus preservation were evaluated. A test meal containing 1 g paracetamol to measure gastric emptying was ingested. Blood for the measurement of paracetamol, glucose, insulin, and GLP-1 was drawn at baseline and 10, 20, 30, 60, 90, 120, 150, and 180 minutes thereafter. The Matsuda index of insulin sensitivity was calculated.

RESULTS

In univariate analysis, gastric emptying correlated with GLP-1. Glucagon-like peptide-1 responses to the modes of operation did not differ. Multiple regression analysis confirmed gastric emptying and Whipple versus pylorus-preserving pancreaticoduodenectomy as independent predictors of GLP-1 release. The Matsuda index of insulin sensitivity correlated with GLP-1 concentrations and inversely with body mass index. Patients after Whipple procedure revealed lower glycated hemoglobin as compared with pylorus-preserving pancreaticoduodenectomy.

CONCLUSIONS

Following PD, the postprandial GLP-1 release seems to be enhanced by rapid gastric emptying and to improve insulin sensitivity. Partial gastrectomy versus pylorus preservation enhanced the release of GLP-1, conceivably because of greater distal bowel exposure to undigested nutrients.

Comparison of Human and Murine Enteroendocrine Cells by Transcriptomic and Peptidomic Profiling

Enteroendocrine cells (EECs) produce hormones such as glucagon-like peptide 1 and peptide YY that regulate food absorption, insulin secretion, and appetite. Based on the success of glucagon-like peptide 1-based therapies for type 2 diabetes and obesity, EECs are themselves the focus of drug discovery programs to enhance gut hormone secretion. The aim of this study was to identify the transcriptome and peptidome of human EECs and to provide a cross-species comparison between humans and mice. By RNA sequencing of human EECs purified by flow cytometry after cell fixation and staining, we present a first transcriptomic analysis of human EEC populations and demonstrate a strong correlation with murine counterparts. RNA sequencing was deep enough to enable identification of low-abundance transcripts such as G-protein-coupled receptors and ion channels, revealing expression in human EECs of G-protein-coupled receptors previously found to play roles in postprandial nutrient detection. With liquid chromatography-tandem mass spectrometry, we profiled the gradients of peptide hormones along the human and mouse gut, including their sequences and posttranslational modifications. The transcriptomic and peptidomic profiles of human and mouse EECs and cross-species comparison will be valuable tools for drug discovery programs and for understanding human metabolism and the endocrine impacts of bariatric surgery.

Functional Magnetic Resonance Imaging (fMRI) of Neural Responses to Visual and Auditory Food Stimuli Pre and Post Roux-en-Y Gastric Bypass (RYGB) and Sleeve Gastrectomy (SG)

Of current obesity treatments, bariatric surgery induces the most weight loss. Given the marked increase in the number of bariatric surgeries performed, elucidating the mechanisms of action is a key research goal. We compared whole brain activation in response to high-energy dense (HED) vs. low-energy dense (LED) visual and auditory food cues before and approximately 4 months after Roux-en-Y Gastric Bypass (RYGB) (n = 16) and Sleeve Gastrectomy (SG) (n = 9). We included two control groups: a low-calorie diet weight loss group (WL) (n = 14) and a non-treatment group (NT) (n = 16). Relative to the control groups, the surgery groups showed increased dorsolateral prefrontal cortex (dlPFC) and decreased parahippocampal/fusiform gyrus (PHG/fusiform) activation in response to HED vs. LED, suggesting greater cognitive dietary inhibition and decreased rewarding effects and attention related to HED foods. dlPFC activation was significantly more increased in RYGB vs. SG. We also found that postprandial increases in GLP-1 concentrations (pre to postsurgery) correlated with postsurgical decreases in RYGB brain activity in the inferior temporal gyrus and the right middle occipital gyrus in addition to increases in the right medial prefrontal gyrus/paracingulate for HED > LED stimuli, suggesting involvement of these attention and inhibitory regions in satiety signaling postsurgery.

PYY plays a key role in the resolution of diabetes following bariatric surgery in humans

BACKGROUND

Bariatric surgery leads to early and long-lasting remission of type 2 diabetes (T2D). However, the mechanisms behind this phenomenon remain unclear. Among several factors, gut hormones are thought to be crucial mediators of this effect. Unlike GLP-1, the role of the hormone peptide tyrosine tyrosine (PYY) in bariatric surgery in humans has been limited to appetite regulation and its impact on pancreatic islet secretory function and glucose metabolism remains under-studied.

METHODS

Changes in PYY concentrations were examined in obese patients after bariatric surgery and compared to healthy controls. Human pancreatic islet function was tested upon treatment with sera from patients before and after the surgery, in presence or absence of PYY. Alterations in intra-islet PYY release and insulin secretion were analysed after stimulation with short chain fatty acids (SCFAs), bile acids and the cytokine IL-22.

FINDINGS

We demonstrate that PYY is a key effector of the early recovery of impaired glucose-mediated insulin and glucagon secretion in bariatric surgery. We establish that the short chain fatty acid propionate and bile acids, which are elevated after surgery, can trigger PYY release not only from enteroendocrine cells but also from human pancreatic islets. In addition, we identify IL-22 as a new factor which is modulated by bariatric surgery in humans and which directly regulates PYY expression and release.

INTERPRETATION

This study shows that some major metabolic benefits of bariatric surgery can be emulated ex vivo. Our findings are expected to have a direct impact on the development of new non-surgical therapy for T2D correction.

Glucagon-like peptide 1 (GLP-1) drives postprandial hyperinsulinemic hypoglycemia in pregnant women with a history of Roux-en-Y gastric bypass operation

BACKGROUND

The influential role of incretin hormones on glucose metabolism in patients with a history of Roux-en-Y gastric bypass (RYGB) has been investigated thoroughly, but there has been little examination of the effect of incretins and ectopic lipids on altered glucose profiles, especially severe hypoglycemia in pregnant women with RYGB.

METHODS

In this prospective clinical study, an oral glucose tolerance test (OGTT), an intravenous glucose tolerance test (IVGTT), and continuous glucose monitoring (CGM) were conducted in 25 women with RYGB during pregnancy, 19 of normal weight (NW) and 19 with obesity (OB) between the 24th and the 28th weeks of pregnancy, and 3 to 6 months post-partum. Post-partum, the ectopic lipid content in the liver, heart, and skeletal muscle was analyzed using ¹H-magnetic resonance spectroscopy (¹H-MRS).

RESULTS

RYGB patients presented with major fluctuations in glucose profiles, including a high occurrence of postprandial hyperglycemic spikes and hypoglycemic events during the day, as well as a high risk of hypoglycemic periods during the night (2.9 ± 1.1% vs. 0.1 ± 0.2% in the OB and vs. 0.8 ± 0.6% in the NW groups, p < 0.001). During the extended OGTT, RYGB patients presented with exaggerated expression of GLP-1, which was the main driver of the exaggerated risk of postprandial hypoglycemia in a time-lagged correlation analysis. Basal and dynamic GLP-1 levels were not related to insulin sensitivity, insulin secretion, or beta cell function and did not differ between pregnant women with and without GDM. A lower amount of liver fat (2.34 ± 5.22% vs.5.68 ± 4.42%, p = 0.015), which was positively related to insulin resistance (homeostasis model assessment of insulin resistance, HOMA-IR: rho = 0.61, p = 0.002) and beta-cell function (insulinogenic index: rho = 0.65, p = 0.001), was observed in the RYGB group after delivery in comparison to the OB group.

CONCLUSION

GLP-1 is mainly involved in the regulation of postprandial glucose metabolism and therefore especially in the development of postprandial hypoglycemia in pregnant RYGB patients, who are characterized by major alterations in glucose profiles, and thus in long-term regulation, multiple organ-related mechanisms, such as the lipid content in the liver, must be involved.

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.

Increase in clinically recorded type 2 diabetes after colectomy

The colon hosts gut microbes and glucagon-like peptide 1 secreting cells, both of which influence glucose homeostasis. We tested whether colectomy is associated with development of type 2 diabetes. Using nationwide register data, we identified patients who had undergone total colectomy, partial colectomy, or proctectomy. For each colectomy patient, we selected 15 non-colectomy patients who had undergone other surgeries. Compared with non-colectomy patients, patients with total colectomy (n = 3,793) had a hazard ratio (HR) of clinically recorded type 2 diabetes of 1.40 (95% confidence interval [CI], 1.21 to 1.62; p<0.001). Corresponding HRs after right hemicolectomy (n = 10,989), left hemicolectomy (n = 2,513), and sigmoidectomy (n = 13,927) were 1.08 (95% CI, 0.99 to 1.19; p=0.10), 1.41 (95% CI, 1.19 to 1.67; p<0.001) and 1.30 (95% CI, 1.21 to 1.40; p<0.001), respectively. Although we were not able to adjust for several potential confounders, our findings suggest that the left colon may contribute to maintenance of glucose homeostasis.

Inhibiting RHOA Signaling in Mice Increases Glucose Tolerance and Numbers of Enteroendocrine and Other Secretory Cells in the Intestine

BACKGROUND & AIMS

Glucagon-like peptide 1 (GLP1) is produced by L cells in the intestine, and agonists of the GLP1 receptor are effective in the treatment of diabetes. Levels of GLP1 increase with numbers of L cells. Therefore, agents that increase numbers of L cell might be developed for treatment of diabetes. Ras homologue family member A (RhoA) signaling through Rho-associated coiled-coil-containing protein kinases 1 and 2 (ROCK1 and ROCK2) controls cell differentiation, but it is not clear whether this pathway regulates enteroendocrine differentiation in the intestinal epithelium. We investigated the effects of Y-27632, an inhibitor of ROCK1 and ROCK2, on L-cell differentiation.

METHODS

We collected intestinal tissues from GLU-Venus, GPR41-RFP, and Neurog3-RFP mice, in which the endocrine lineage is fluorescently labeled, for in vitro culture and histologic analysis. Small intestine organoids derived from these mice were cultured with Y-27632 and we measured percentages of L cells, expression of intestinal cell-specific markers, and secretion of GLP1 in medium. Mice were fed a normal chow or a high-fat diet and given Y-27632 or saline (control) and blood samples were collected for measurement of GLP1, insulin, and glucose.

RESULTS

Incubation of intestinal organoids with Y-27632 increased numbers of L cells and secretion of GLP1. These increases were associated with upregulated expression of genes encoding intestinal hormones, neurogenin 3, neurogenic differentiation factor 1, forkhead box A1 and A2, and additional markers of secretory cells. Mice fed the normal chow diet and given Y-27632 had increased numbers of L cells in intestinal tissues, increased plasma levels of GLP1 and insulin, and lower blood levels of glucose compared with mice fed the normal chow diet and given saline. In mice with insulin resistance induced by the high-fat diet, administration of Y-27632 increased secretion of GLP1 and glucose tolerance compared with administration of saline.

CONCLUSIONS

In mouse intestinal organoids, an inhibitor of RhoA signaling increased the differentiation of the secretory lineage and the development of enteroendocrine cells. Inhibitors of RhoA signaling or other strategies to increase numbers of L cells might be developed for treatment of patients with type 2 diabetes or for increasing glucose tolerance.

Incidence of Hypoglycemia After Gastric Bypass vs Sleeve Gastrectomy: A Randomized Trial

CONTEXT

We compared the incidence of hypoglycemia after Roux-en-Y gastric bypass (RYGB) vs sleeve gastrectomy (SG).

DESIGN, SETTING, AND MAIN OUTCOME MEASURES

Randomized, open-label trial conducted at the outpatient obesity clinic in a university hospital in Rome, Italy. The primary aim was the incidence of reactive hypoglycemia (<3.1 mmol/L after 75-g oral glucose load) at 1 year after surgery. Secondary aims were hypoglycemia under everyday life conditions, insulin sensitivity, insulin secretion, and lipid profile.

RESULTS

Of 175 eligible patients, 120 were randomized 1:1 to RYGB or SG; 117 (93%) completed the 12-month follow-up. Reactive hypoglycemia was detected in 14% and 29% of SG and RYGB patients (P = 0.079), respectively, with the effect of treatment in multivariate analysis significant at P = 0.018. Daily hypoglycemic episodes during continuous glucose monitoring did not differ between groups (P = 0.75). Four of 59 RYGB subjects (6.8%) had 1 to 3 hospitalizations for symptomatic hypoglycemia vs 0 in SG. The static β-cell glucose sensitivity index increased after both treatments (P < 0.001), but the dynamic β-cell glucose sensitivity index increased significantly in SG (P = 0.008) and decreased in RYGB (P = 0.004 for time × treatment interaction). Whole-body insulin sensitivity increased about 10-fold in both groups.

CONCLUSIONS

We show that reactive hypoglycemia is no less common after SG and is not a safer option than RYGB, but RYGB is associated with more severe hypoglycemic episodes. This is likely due to the lack of improvement of β-cell sensitivity to changes in circulating glucose after RYGB, which determines an inappropriately high insulin secretion.

COMPARISON OF THE LEVELS OF C-REACTIVE PROTEIN, GLP-1 AND GLP-2 AMONG INDIVIDUALS WITH DIABETES, MORBID OBESITY AND HEALTHY CONTROLS: AN EXPLORATORY STUDY

BACKGROUND

The glucagon-like peptides 1 and 2 (GLP-1/GLP-2) are gut hormones that may directly affect the glucose homeostasis and their activity seems to be significantly affected by chronic inflammation.

OBJECTIVE

To evaluate the postprandial levels of glucagon-like peptides 1 and 2 (GLP-1/GLP-2), C-reactive protein (CRP), and the postprandial glucose and insulin levels among individuals with obesity, type 2 diabetes, and healthy controls.

METHODS

An exploratory cross-sectional study, which involved individuals awaiting for bariatric/metabolic surgery and healthy controls. Postprandial levels of GLP-1, GLP-2, glucose, and insulin were obtained after a standard meal tolerance test. Inflammation was assessed by means of CRP.

RESULTS

There were 30 individuals enrolled in the study, divided into three groups: non-diabetic with morbid obesity (NDO; n=11 individuals), diabetic with mild obesity (T2D; n=12 individuals), and healthy controls (C; n=7 individuals). The mean CRP levels were significantly higher in the NDO group (6.6±4.7 mg/dL) than in the T2D (3.3±2.2 mg/dL) and C groups (2.5±3.2 mg/dL) (P=0.038). The GLP-1 levels following standard meal tolerance test and the area under the curve of GLP-1 did not differ among the three groups. The GLP-2 levels were significantly lower in the NDO and T2D than in the C group following standard meal tolerance test at all the times evaluated. The area under the curve of the GLP-2 was significantly lower in the NDO and T2D groups than in the C group (P=0.05 and P=0.01, respectively).

CONCLUSION

GLP-2 levels were impaired in the individuals with obesity and diabetes. This mechanism seems to be enrolled in preventing the worsening of the glucose homeostasis in these individuals.

Gut as an emerging organ for the treatment of diabetes: focus on mechanism of action of bariatric and endoscopic interventions

Increasing worldwide prevalence of type 2 diabetes mellitus and its accompanying pathologies such as obesity, arterial hypertension and dyslipidemia represents one of the most important challenges of current medicine. Despite intensive efforts, high percentage of patients with type 2 diabetes does not achieve treatment goals and struggle with increasing body weight and poor glucose control. While novel classes of antidiabetic medications such as incretin-based therapies and gliflozins have some favorable characteristics compared to older antidiabetics, the only therapeutic option shown to substantially modify the progression of diabetes or to achieve its remission is bariatric surgery. Its efficacy in the treatment of diabetes is well established, but the exact underlying modes of action are still only partially described. They include restriction of food amount, enhanced passage of chymus into distal part of small intestine with subsequent modification of gastrointestinal hormones and bile acids secretion, neural mechanisms, changes in gut microbiota and many other possible mechanisms underscoring the importance of the gut in the regulation of glucose metabolism. In addition to bariatric surgery, less-invasive endoscopic methods based on the principles of bariatric surgery were introduced and showed promising results. This review highlights the role of the intestine in the regulation of glucose homeostasis focusing on the mechanisms of action of bariatric and especially endoscopic methods of the treatment of diabetes. A better understanding of these mechanisms may lead to less invasive endoscopic treatments of diabetes and obesity that may complement and widen current therapeutic options.

Novel GLP-1/GLP-2 co-agonists display marked effects on gut volume and improves glycemic control in mice

AIM

Analogues of several gastrointestinal peptide hormones have been developed into effective medicines for treatment of diseases such as type 2 diabetes mellitus (T2DM), obesity and short bowel syndrome (SBS). In this study, we aimed to explore whether the combination of glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2) into a potent co-agonist could provide additional benefits compared to existing monotherapies.

METHODS

A short-acting (GUB09-123) and a half-life extended (GUB09-145) GLP-1/GLP-2 co-agonist were generated using solid-phase peptide synthesis and tested for effects on food intake, body weight, glucose homeostasis, and gut proliferation in lean mice and in diabetic db/db mice.

RESULTS

Sub-chronic administration of GUB09-123 to lean mice significantly reduced food intake, improved glucose tolerance, and increased gut volume, superior to monotherapy with the GLP-2 analogue teduglutide. Chronic administration of GUB09-123 to diabetic mice significantly improved glycemic control and showed persistent effects on gastric emptying, superior to monotherapy with the GLP-1 analogue liraglutide. Due to the short-acting nature of the molecule, no effects on body weight were observed, whereas a marked and robust intestinotrophic effect on mainly the small intestine volume and surface area was obtained. In contrast to GUB09-123, sub-chronic administration of a half-life extended GUB09-145 to lean mice caused marked dose-dependent effects on body weight while maintaining its potent intestinotrophic effect.

CONCLUSION

Our data demonstrate that the GLP-1/GLP-2 co-agonists have effects on gut morphometry, showing a marked increase in intestinal volume and mucosal surface area. Furthermore, effects on glucose tolerance and long-term glycemic control are evident. Effects on body weight and gastric emptying are also observed depending on the pharmacokinetic properties of the molecule. We suggest that this novel co-agonistic approach could exemplify a novel concept for treatment of T2DM or SBS.

Mechanisms to Elevate Endogenous GLP-1 Beyond Injectable GLP-1 Analogs and Metabolic Surgery

Therapeutic engineering of glucagon-like peptide 1 (GLP-1) has enabled development of new medicines to treat type 2 diabetes. These injectable analogs achieve robust glycemic control by increasing concentrations of "GLP-1 equivalents" (∼50 pmol/L). Similar levels of endogenous GLP-1 occur after gastric bypass surgery, and mechanistic studies indicate glucose lowering by these procedures is driven by GLP-1. Therefore, because of the remarkable signaling and secretory capacity of the GLP-1 system, we sought to discover mechanisms that increase GLP-1 pharmacologically. To study active GLP-1, glucose-dependent insulinotropic polypeptide receptor (Gipr)-deficient mice receiving background dipeptidyl peptidase 4 (DPP4) inhibitor treatment were characterized as a model for evaluating oral agents that increase circulating GLP-1. A somatostatin receptor 5 antagonist, which blunts inhibition of GLP-1 release, and agonists for TGR5 and GPR40, which stimulate GLP-1 secretion, were investigated alone and in combination with the DPP4 inhibitor sitagliptin; these only modestly increased GLP-1 (∼5-30 pmol/L). However, combining molecules to simultaneously intervene at multiple regulatory nodes synergistically elevated active GLP-1 to unprecedented concentrations (∼300-400 pmol/L), drastically reducing glucose in Gipr null and Lepr^db/db mice in a GLP-1 receptor-dependent manner. Our studies demonstrate that complementary pathways can be engaged to robustly increase GLP-1 without invasive surgical or injection regimens.

Changes in Serum Sphingomyelin After Roux-en-Y Gastric Bypass Surgery Are Related to Diabetes Status

Metabolic surgery is superior to lifestyle intervention in reducing weight and lowering glycemia and recently suggested as treatment for type 2 diabetes mellitus. Especially Roux-en-Y gastric bypass (RYGB) has been focus for much research, but still the mechanisms of action are only partly elucidated. We suggest that several mechanisms might be mediated by sphingolipids like sphingomyelin. We measured serum sphingomyelin before and up to 2 years after RYGB surgery in 220 patients, divided before surgery in one non-diabetic subgroup and two diabetic subgroups, one of which contained patients obtaining remission of type 2 diabetes after RYGB, while patients in the other still had diabetes after RYGB. Pre- and postoperative sphingomyelin levels were compared within and between groups. Sphingomyelin levels were lower in diabetic patients than in non-diabetic patients before surgery. Following RYGB, mean sphingomyelin concentration fell significantly in the non-diabetic subgroup and the preoperative difference between patients with and without diabetes disappeared. Changes in diabetic subgroups were not significant. Relative to bodyweight, an increase in sphingomyelin was seen in all subgroups, irrespective of diabetes status. We conclude that RYGB has a strong influence on sphingomyelin metabolism, as seen reflected in changed serum levels. Most significantly, no differences between the two diabetic subgroups were detected after surgery, which might suggest that patients in both groups still are in a "diabetic state" using the non-diabetic subgroup as a reference.

Assessment of glucose regulation in pregnancy after gastric bypass surgery

AIMS/HYPOTHESIS

Roux-en-Y gastric bypass (RYGB) surgery is characterised by glycaemic variability. Prospective studies of glucose metabolism in pregnancy after RYGB are not available, therefore this study aimed to evaluate physiological alterations in glucose metabolism in pregnancy following RYGB.

METHODS

Sixty-three pregnant women (25 who underwent RYGB, 19 non-operated obese control women and 19 normal weight control women) were included. Frequently sampled 3 h OGTTs and 1 h IVGTTs were performed between 24 and 28 weeks of gestation and, in a subgroup, were repeated at 3-6 months after delivery.

RESULTS

We observed major alterations in glucose kinetics during the OGTT, including an early increase in plasma glucose followed by hypoglycaemia in 90% of women who had previously undergone RYGB. The higher degree of glycaemic variability in this group was accompanied by increased insulin, C-peptide and glucagon concentrations after oral glucose load, whereas no differences in insulin response were observed after parenteral glucose administration (RYGB vs normal weight). IVGTT data suggested improved insulin sensitivity (mean difference 0.226 × 10^-4 min^-1 [pmol/l]^-1 [95% CI 0.104, 0.348]; p < 0.001) and disposition index in pregnancies after RYGB when compared with obese control women. However, subtle alterations in insulin action and beta cell function were still observed when comparing women who had undergone RYGB with the normal-weight control group. Moreover, we observed that fetal growth was associated with maternal glucose nadir levels and insulin secretion in offspring of those who had previously undergone RYGB.

CONCLUSIONS/INTERPRETATION

Pregnancies after RYGB are affected by altered postprandial glucose, insulin and C-peptide dynamics. Insulin sensitivity is improved by RYGB, although subtle alterations in beta cell function are observed. Longitudinal studies are needed to assess potential consequences for fetal development and pregnancy outcomes.

Effect of Roux-en-Y Bariatric Surgery on Lipoproteins, Insulin Resistance, and Systemic and Vascular Inflammation in Obesity and Diabetes

Purpose

Obesity is a major modifiable risk factor for cardiovascular disease. Bariatric surgery is considered to be the most effective treatment option for weight reduction in obese patients with and without type 2 diabetes (T2DM).

Objective

To evaluate changes in lipoproteins, insulin resistance, mediators of systemic and vascular inflammation, and endothelial dysfunction following Roux-en-Y bariatric surgery in obese patients with and without diabetes.

Materials and methods

Lipoproteins, insulin resistance, mediators of systemic and vascular inflammation, and endothelial dysfunction were measured in 37 obese patients with (n = 17) and without (n = 20) T2DM, before and 6 and 12 months after Roux-en-Y bariatric surgery. Two way between subject ANOVA was carried out to study the interaction between independent variables (time since surgery and presence of diabetes) and all dependent variables.

Results

There was a significant effect of time since surgery on (large effect size) weight, body mass index (BMI), waist circumference, triglycerides (TG), small-dense LDL apolipoprotein B (sdLDL ApoB), HOMA-IR, CRP, MCP-1, ICAM-1, E-selectin, P-selectin, leptin, and adiponectin. BMI and waist circumference had the largest impact of time since surgery. The effect of time since surgery was noticed mostly in the first 6 months. Absence of diabetes led to a significantly greater reduction in total cholesterol, low-density lipoprotein cholesterol, and non-high-density lipoprotein cholesterol although the effect size was small to medium. There was a greater reduction in TG and HOMA-IR in patients with diabetes with a small effect size. No patients were lost to follow up.

Conclusion

Lipoproteins, insulin resistance, mediators of systemic and vascular inflammation, and endothelial dysfunction improve mostly 6 months after bariatric surgery in obese patients with and without diabetes.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: NCT02169518. https://clinicaltrials.gov/ct2/show/NCT02169518?term=paraoxonase&cntry1=EU%3AGB&rank=1.

Effect of Gastrogastric Fistula Closure in Type 2 Diabetes

INTRODUCTION

Roux-en-Y gastric bypass (RYGB) has been shown to significantly improve glucose control in patients with type 2 diabetes (T2DM). The formation of a gastrogastric fistula (GGF) allows nutrients to pass through the native route, rather than bypassing the duodenum in typical RYGB configuration. We sought to evaluate the effect of revisional bariatric surgery for known GGF on control of diabetes.

METHODS

A retrospective chart review of a single academic institution was performed to identify patients who had T2DM at the time of corrective surgery for a GGF. Baseline characteristics, and postoperative outcomes including changes in body mass index (BMI), glycated hemoglobin, fasting blood glucose (FBG), and diabetes medications were assessed.

RESULTS

Ten patients were identified with GGF who had T2DM at the time of corrective surgery. Patients had a male-to-female ratio of 2:3, a mean age of 59.2 ± 10 years, a mean baseline BMI of 38.1 ± 17.6 kg/m², and a median duration of 9 years (interquartile range 6-14) from initial RYGB to revision. At a mean follow-up of 14.9 ± 8.5 months, a mean reduction in BMI of 4.9 ± 6 kg/m² was associated with a significant mean reduction in FBG (167.1 ± 88.2 vs. 106.1 ± 20.4 mg/dL, p = 0.04) and number of diabetes medications (1.4 ± 0.8 vs. 0.7 ± 0.7, p = 0.04).

CONCLUSION

In patients with diabetes and GGF, a corrective surgery for closure of fistula and restoration of bypass anatomy results in improvement of glucose control and status of diabetes medications. This finding can highlight the potential metabolic significance of duodenal exclusion.

One-Anastomosis Jejunal Interposition with Gastric Remnant Resection (Branco-Zorron Switch) for Severe Recurrent Hyperinsulinemic Hypoglycemia after Gastric Bypass for Morbid Obesity

BACKGROUND

The anatomical and physiological changes after Roux-en-Y gastric bypass for morbid obesity can lead to severe hyperinsulinemic hypoglycemia with neuroglycopenia in a small percentage of patients. The exact physiologic mechanism is not completely understood. Surgical reversal to the original anatomy and distal or total pancreatectomy are current therapeutic options to reverse the hypoglycemic effect, with substantial associated morbidity. Our group reports a pilot clinical series of a novel surgical technique using one-anastomosis jejunal interposition with gastric remnant resection (Branco-Zorron Switch).

METHODS

Patients with severe symptomatic hyperinsulinemic hypoglycemia refractory to conservative therapy were treated using the technique. The procedure started with resection of the remnant stomach close to pylorus. The alimentary limb was sectioned at 20 cm from the gastrojejunal anastomosis, and the rest of the alimentary limb was resected until the Y-Roux anastomosis. A hand-sutured anastomosis was then performed with the proximal alimentary limb and the remnant antrum.

RESULTS

Four patients were successfully submitted to the procedure with reversal of the symptomatology and normalization of insulin levels, postprandial glucose levels, and oral glucose tolerance test, with a mean follow-up of 24.3 months. Mean operative time was 188 min, and patients recovered without postoperative complications.

CONCLUSION

Patients suffering from severe hyperinsulinemic hypoglycemia after gastric bypass may be efficiently treated by this innovative procedure, avoiding extreme surgical therapy such as pancreatectomy or restoring the gastric anatomy, while still maintaining sustained weight loss. Studies with larger series and longer follow-up are still needed to define the role of this therapy in managing this entity.

Weight Management in Patients with Type 1 Diabetes and Obesity

PURPOSE OF REVIEW

Patients with type 1 diabetes (T1D) are typically viewed as lean individuals. However, recent reports showed that their obesity rate surpassed that of the general population. Patients with T1D who show clinical signs of type 2 diabetes such as obesity and insulin resistance are considered to have "double diabetes." This review explains the mechanisms of weight gain in patients with T1D and how to manage it.

RECENT FINDINGS

Weight management in T1D can be successfully achieved in real-world clinical practice. Nutrition therapy includes reducing energy intake and providing a structured nutrition plan that is lower in carbohydrates and glycemic index and higher in fiber and lean protein. The exercise plan should include combination stretching as well as aerobic and resistance exercises to maintain muscle mass. Dynamic adjustment of insulin doses is necessary during weight management. Addition of anti-obesity medications may be considered. If medical weight reduction is not achieved, bariatric surgery may also be considered.

The Role of PYY in Pancreatic Islet Physiology and Surgical Control of Diabetes

Bariatric surgery in obese individuals leads to rapid and lasting remission of type 2 diabetes (T2D). This phenomenon occurs independently of weight loss possibly via a combination of factors. The incretin hormone GLP-1 has so far been recognised as a critical factor. However, recent data have indicated that elevation in another gut hormone, peptide tyrosine tyrosine (PYY), may drive the beneficial effects of surgery. Here we discuss recent findings on PYY-mediated control of glucose homeostasis and its role in diabetes, in the context of what is known for GLP-1. Identification of factors that increase the expression of PYY following bariatric surgery and elucidation of its role in diabetes reversal may have clinical relevance as a nonsurgical therapy for T2D.

Mechanisms Controlling Glucose-Induced GLP-1 Secretion in Human Small Intestine

Intestinal glucose stimulates secretion of the incretin hormone glucagon-like peptide 1 (GLP-1). The mechanisms underlying this pathway have not been fully investigated in humans. In this study, we showed that a 30-min intraduodenal glucose infusion activated half of all duodenal L cells in humans. This infusion was sufficient to increase plasma GLP-1 levels. With an ex vivo model using human gut tissue specimens, we showed a dose-responsive GLP-1 secretion in the ileum at ≥200 mmol/L glucose. In ex vivo tissue from the duodenum and ileum, but not the colon, 300 mmol/L glucose potently stimulated GLP-1 release. In the ileum, this response was independent of osmotic influences and required delivery of glucose via GLUT2 and mitochondrial metabolism. The requirement of voltage-gated Na⁺ and Ca²⁺ channel activation indicates that membrane depolarization occurs. K_ATP channels do not drive this, as tolbutamide did not trigger release. The sodium-glucose cotransporter 1 (SGLT1) substrate α-MG induced secretion, and the response was blocked by the SGLT1 inhibitor phlorizin or by replacement of extracellular Na⁺ with N-methyl-d-glucamine. This is the first report of the mechanisms underlying glucose-induced GLP-1 secretion from human small intestine. Our findings demonstrate a dominant role of SGLT1 in controlling glucose-stimulated GLP-1 release in human ileal L cells.

Combined Oral Administration of GABA and DPP-4 Inhibitor Prevents Beta Cell Damage and Promotes Beta Cell Regeneration in Mice

γ-aminobutyric acid (GABA) or glucagon-like peptide-1 based drugs, such as sitagliptin (a dipeptidyl peptidase-4 inhibitor), were shown to induce beta cell regenerative effects in various diabetic mouse models. We propose that their combined administration can bring forth an additive therapeutic effect. We tested this hypothesis in a multiple low-dose streptozotocin (STZ)-induced beta cell injury mouse model (MDSD). Male C57BL/6J mice were assigned randomly into four groups: non-treatment diabetic control, GABA, sitagliptin, or GABA plus sitagliptin. Oral drug administration was initiated 1 week before STZ injection and maintained for 6 weeks. GABA or sitagliptin administration decreased ambient blood glucose levels and improved the glucose excursion rate. This was associated with elevated plasma insulin and reduced plasma glucagon levels. Importantly, combined use of GABA and sitagliptin significantly enhanced these effects as compared with each of the monotherapies. An additive effect on reducing water consumption was also observed. Immunohistochemical analyses revealed that combined GABA and sitagliptin therapy was superior in increasing beta cell mass, associated with increased small-size islet numbers, Ki67⁺ and PDX-1⁺ beta cell counts; and reduced Tunel⁺ beta cell counts. Thus, beta cell proliferation was increased, whereas apoptosis was reduced. We also noticed a suppressive effect of GABA or sitagliptin on alpha cell mass, which was not significantly altered by combining the two agents. Although either GABA or sitagliptin administration delays the onset of MDSD, our study indicates that combined use of them produces superior therapeutic outcomes. This is likely due to an amelioration of beta cell proliferation and a decrease of beta cell apoptosis.

Critical role for GLP-1 in symptomatic post-bariatric hypoglycaemia

AIMS/HYPOTHESIS

Post-bariatric hypoglycaemia (PBH) is a rare, but severe, metabolic disorder arising months to years after bariatric surgery. It is characterised by symptomatic postprandial hypoglycaemia, with inappropriately elevated insulin concentrations. The relative contribution of exaggerated incretin hormone signalling to dysregulated insulin secretion and symptomatic hypoglycaemia is a subject of ongoing inquiry. This study was designed to test the hypothesis that PBH and associated symptoms are primarily mediated by glucagon-like peptide-1 (GLP-1).

METHODS

We conducted a double-blinded crossover study wherein eight participants with confirmed PBH were assigned in random order to intravenous infusion of the GLP-1 receptor (GLP-1r) antagonist. Exendin (9-39) (Ex-9), or placebo during an OGTT on two separate days at the Stanford University Clinical and Translational Research Unit. Metabolic, symptomatic and pharmacokinetic variables were evaluated. Results were compared with a cohort of BMI- and glucose-matched non-surgical controls (NSCs).

RESULTS

Infusion of Ex-9 decreased the time to peak glucose and rate of glucose decline during OGTT, and raised the postprandial nadir by over 70%, normalising it relative to NSCs and preventing hypoglycaemia in all PBH participants. Insulin AUC and secretion rate decreased by 57% and 71% respectively, and peak postprandial insulin was normalised relative to NSCs. Autonomic and neuroglycopenic symptoms were significantly reduced during Ex-9 infusion.

CONCLUSIONS/INTERPRETATION

GLP-1r blockade prevented hypoglycaemia in 100% of individuals, normalised beta cell function and reversed neuroglycopenic symptoms, supporting the conclusion that GLP-1 plays a primary role in mediating hyperinsulinaemic hypoglycaemia in PBH. Competitive antagonism at the GLP-1r merits consideration as a therapeutic strategy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02550145.

Duodenal long noncoding RNAs are associated with glycemic control after bariatric surgery in high-fat diet-induced diabetic mice

BACKGROUND

The duodenum plays a role in the mechanism of type 2 diabetes remission after bariatric surgery. Roux-en-Y gastric bypass (RYGB) may change gene expression in the duodenum and metabolism. Long noncoding RNAs (lncRNAs) constitute a novel class of RNAs that regulate gene expression. Little is known about how duodenal lncRNAs respond to RYGB. Logically, studies on the changes of duodenal lncRNAs potentially can lead to an understanding of the mechanisms of bariatric surgery, as well as discovery of antidiabetic drug targets and biomarkers predicting postoperative outcome.

OBJECTIVES

To investigate the expression signature of duodenal lncRNAs associated with glycemic improvement by duodenal-jejunal bypass (DJB), a component of RYGB, on a genome-wide scale in high-fat diet-induced diabetic mice.

SETTING

University medical center.

METHODS

High fat diet-induced diabetic mice were randomized into 2 groups receiving either the DJB or a sham procedure. Microarray was applied to screen the differentially expressed lncRNAs and messenger RNAs (mRNAs) in the duodenum between the DJB and sham groups, and the result was validated by quantitative real-time polymerase chain reaction in another cohort of animals. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to predict the potential lncRNA functions. Based on Pearson correlation analysis, the lncRNA-mRNA and lncRNA-transcription factor (TF) interaction networks were constructed to identify and rank core regulatory lncRNAs and transcription factors.

RESULTS

A total of 301 lncRNAs, including 232 that were upregulated and 69 downregulated (fold change≥2.0), were differentially expressed in the duodenum between the DJB and sham groups. GO enrichment indicated that these lncRNA-coexpressed mRNAs were correlated with biological processes including cell proliferation, digestion, and catabolic and biosynthetic processes. KEGG pathway analysis revealed that in addition to the digestion and absorption signaling pathways, pancreatic secretion- and inflammatory process-related signaling pathways were mostly enriched in the DJB group. In addition, the lncRNA-mRNA interaction network combined with GO and KEGG pathway analysis suggested that as a top-ranked gene, NONMMUG021726 may play an important role in the mechanism of type 2 diabetes remission after DJB.

CONCLUSION

DJB leads to drastic changes in lncRNA and mRNA expressions in the duodenum. The majority of top-ranked lncRNAs and mRNAs have roles in pancreatic secretion and inflammatory processes, implying that bypass of the duodenum may initiate insulin secretion and attenuate inflammation. In addition, modulators of such lncRNAs, most likely NONMMUG021726, have potential to become therapeutic targets or biomarkers for prediction of the outcomes of bariatric surgery.

The impact of EndoBarrier gastrointestinal liner in obese patients with normal glucose tolerance and in patients with type 2 diabetes

AIMS

The duodenal-jejunal bypass sleeve ((DJBS) or EndoBarrier Gastrointestinal Liner) induces weight loss in obese subjects and may improve glucose homeostasis in patients with type 2 diabetes (T2D). To explore the underlying mechanisms, we evaluated postprandial physiology including glucose metabolism, gut hormone secretion, gallbladder emptying, appetite and food intake in patients undergoing DJBS treatment.

MATERIAL AND METHODS

A total of 10 normal glucose-tolerant (NGT) obese subjects and 9 age-, body weight- and body mass index-matched metformin-treated T2D patients underwent a liquid mixed meal test and a subsequent ad libitum meal test before implantation with DJBS and 1 week (1w) and 26 weeks (26w) after implantation.

RESULTS

At 26w, both groups had achieved a weight loss of 6 to 7 kg. Postprandial glucagon-like peptide-1 (GLP-1) and peptide YY responses increased at 1w and 26w, but only in T2D subjects. In contrast, glucose-dependent insulinotropic polypeptide responses were reduced only by DJBS in the NGT group. Postprandial glucose, insulin, C-peptide, glucagon, cholecystokinin and gastrin responses were unaffected by DJBS in both groups. Satiety and fullness sensations were stronger and food intake was reduced at 1w in NGT subjects; no changes in appetite measures or food intake were observed in the T2D group. No effect of DJBS on postprandial gallbladder emptying was observed, and gastric emptying was not delayed.

CONCLUSIONS

DJBS-induced weight loss was associated with only marginal changes in postprandial physiology, which may explain the absence of effect on postprandial glucose metabolism.

Glomerular Hyperfiltration in Diabetes: Mechanisms, Clinical Significance, and Treatment

An absolute, supraphysiologic elevation in GFR is observed early in the natural history in 10%-67% and 6%-73% of patients with type 1 and type 2 diabetes, respectively. Moreover, at the single-nephron level, diabetes-related renal hemodynamic alterations-as an adaptation to reduction in functional nephron mass and/or in response to prevailing metabolic and (neuro)hormonal stimuli-increase glomerular hydraulic pressure and transcapillary convective flux of ultrafiltrate and macromolecules. This phenomenon, known as glomerular hyperfiltration, classically has been hypothesized to predispose to irreversible nephron damage, thereby contributing to initiation and progression of kidney disease in diabetes. However, dedicated studies with appropriate diagnostic measures and clinically relevant end points are warranted to confirm this assumption. In this review, we summarize the hitherto proposed mechanisms involved in diabetic hyperfiltration, focusing on ultrastructural, vascular, and tubular factors. Furthermore, we review available evidence on the clinical significance of hyperfiltration in diabetes and discuss currently available and emerging interventions that may attenuate this renal hemodynamic abnormality. The revived interest in glomerular hyperfiltration as a prognostic and pathophysiologic factor in diabetes may lead to improved and timely detection of (progressive) kidney disease, and could provide new therapeutic opportunities in alleviating the renal burden in this population.