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

NPYR modulation: Potential for the next major advance in obesity and type 2 diabetes management?

The approval of the glucagon-like peptide 1 (GLP-1) mimetics semaglutide and liraglutide for management of obesity, independent of type 2 diabetes (T2DM), has initiated a resurgence of interest in gut-hormone derived peptide therapies for the management of metabolic diseases, but side-effect profile is a concern for these medicines. However, the recent approval of tirzepatide for obesity and T2DM, a glucose-dependent insulinotropic polypeptide (GIP), GLP-1 receptor co-agonist peptide therapy, may provide a somewhat more tolerable option. Despite this, an increasing number of non-incretin alternative peptides are in development for obesity, and it stands to reason that other hormones will take to the limelight in the coming years, such as peptides from the neuropeptide Y family. This narrative review outlines the therapeutic promise of the neuropeptide Y family of peptides, comprising of the 36 amino acid polypeptides neuropeptide Y (NPY), peptide tyrosine-tyrosine (PYY) and pancreatic polypeptide (PP), as well as their derivatives. This family of peptides exerts a number of metabolically relevant effects such as appetite regulation and can influence pancreatic beta-cell survival. Although some of these actions still require full translation to the human setting, potential therapeutic application in obesity and type 2 diabetes is conceivable. However, like GLP-1 and GIP, the endogenous NPY, PYY and PP peptide forms are subject to rapid in vivo degradation and inactivation by the serine peptidase, dipeptidyl-peptidase 4 (DPP-4), and hence require structural modification to prolong circulating half-life. Numerous protective modification strategies are discussed in this regard herein, alongside related impact on biological activity profile and therapeutic promise.

Comparative impact of Roux-en-Y gastric bypass, sleeve gastrectomy or diet alone on beta-cell function in insulin-treated type 2 diabetes patients

Although bariatric surgery is an effective treatment for type 2 diabetes by inducing weight loss and augmenting gut hormone secretion, the immediate effect on beta-cell function itself remains to be elucidated in type 2 diabetes. Therefore, a prospective, randomized trial was performed in 30 patients with insulin-treated type 2 diabetes and a body mass index ≥ 35 kg/m2. Patients were randomly assigned (1:1:1) to Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) in combination with protein-sparing modified fast (PSMF), or to PSMF alone. Eu- and hyperglycemic clamps were performed before and 3 weeks after surgery and/or PSMF initiation. The primary outcome was the evolution of insulin sensitivity and beta-cell function after surgery, calculated using the composite measures of glucose disposal rate, insulin secretion rate, and disposition index (DI). Results revealed that markers of insulin sensitivity increased similarly in all arms (p = 0.43). A higher marker for maximal beta-cell function was observed when comparing SG to PSMF (p = 0.007). The DI showed a clear positive evolution after RYGB and SG, but not after PSMF alone. Altogether, these findings indicate that bariatric surgery results in an immediate beta-cell function recovery in insulin-treated type 2 diabetes.

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.

A Matched Comparative Analysis of Type-2 Diabetes Mellitus Remission Between Roux-en-Y Gastric Bypass and Sleeve Gastrectomy

OBJECTIVE

Multiple scores validate long-term type-2 diabetes mellitus (T2DM) remission after metabolic and bariatric surgery (MBS). However, studies comparing Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) have not adequately controlled for certain parameters, which may influence procedure selection.

METHODS

We conducted a multicenter retrospective review of patients with T2DM who underwent RYGB or SG between 2008 and 2017. Data on demographics, clinical, laboratory, and metabolic values were collected annually for up to 14 years. Each eligible RYGB patient was individually matched to an eligible SG patient based on diabetes severity, weight loss, and follow-up duration.

RESULTS

Among 1149 T2DM patients, 467 were eligible for matching. We found 97 matched pairs who underwent RYGB or SG. RYGB showed significantly higher T2DM remission rates (46.4%) compared to SG (33.0%) after matching. SG patients had higher insulin usage (35.1%) than RYGB patients (20.6%). RYGB patients also experienced greater decreases in HbA1c levels and diabetes medication usage than SG patients.

CONCLUSIONS

RYGB demonstrates higher efficacy for T2DM remission compared to SG, regardless of baseline characteristics, T2DM severity, weight loss, and follow-up duration. Further studies are needed to understand the long-term metabolic effects of MBS and the underlying pathophysiology of T2DM remission after MBS.

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.

G protein-coupled receptors driven intestinal glucagon-like peptide-1 reprogramming for obesity: Hope or hype?

'Globesity' is a foremost challenge to the healthcare system. The limited efficacy and adverse effects of available oral pharmacotherapies pose a significant obstacle in the fight against obesity. The biology of the leading incretin hormone glucagon-like-peptide-1 (GLP-1) has been highly captivated during the last decade owing to its multisystemic pleiotropic clinical outcomes beyond inherent glucoregulatory action. That fostered a pharmaceutical interest in synthetic GLP-1 analogues to tackle type-2 diabetes (T2D), obesity and related complications. Besides, mechanistic insights on metabolic surgeries allude to an incretin-based hormonal combination strategy for weight loss that emerged as a forerunner for the discovery of injectable 'unimolecular poly-incretin-agonist' therapies. Physiologically, intestinal enteroendocrine L-cells (EECs) are the prominent endogenous source of GLP-1 peptide. Despite comprehending the potential of various G protein-coupled receptors (GPCRs) to stimulate endogenous GLP-1 secretion, decades of translational GPCR research have failed to yield regulatory-approved endogenous GLP-1 secretagogue oral therapy. Lately, a dual/poly-GPCR agonism strategy has emerged as an alternative approach to the traditional mono-GPCR concept. This review aims to gain a comprehensive understanding by revisiting the pharmacology of a few potential GPCR-based complementary avenues that have drawn attention to the design of orally active poly-GPCR agonist therapy. The merits, challenges and recent developments that may aid future poly-GPCR drug discovery are critically discussed. Subsequently, we project the mechanism-based therapeutic potential and limitations of oral poly-GPCR agonism strategy to augment intestinal GLP-1 for weight loss. We further extend our discussion to compare the poly-GPCR agonism approach over invasive surgical and injectable GLP-1-based regimens currently in clinical practice for obesity.

Intestinal IL-22RA1 signaling regulates intrinsic and systemic lipid and glucose metabolism to alleviate obesity-associated disorders

IL-22 is critical for ameliorating obesity-induced metabolic disorders. However, it is unknown where IL-22 acts to mediate these outcomes. Here we examine the importance of tissue-specific IL-22RA1 signaling in mediating long-term high fat diet (HFD) driven metabolic disorders. To do so, we generated intestinal epithelium-, liver-, and white adipose tissue (WAT)-specific Il22ra1 knockout and littermate control mice. Intestinal epithelium- and liver-specific IL-22RA1 signaling upregulated systemic glucose metabolism. Intestinal IL-22RA1 signaling also mediated liver and WAT metabolism in a microbiota-dependent manner. We identified an association between Oscillibacter and elevated WAT inflammation, likely induced by Mmp12 expressing macrophages. Mechanistically, transcription of intestinal lipid metabolism genes is regulated by IL-22 and potentially IL-22-induced IL-18. Lastly, we show that Paneth cell-specific IL-22RA1 signaling, in part, mediates systemic glucose metabolism after HFD. Overall, these results elucidate a key role of intestinal epithelium-specific IL-22RA1 signaling in regulating intestinal metabolism and alleviating systemic obesity-associated disorders.

Isomaltulose Enhances GLP-1 and PYY Secretion to a Mixed Meal in People With or Without Type 2 Diabetes as Compared to Saccharose

SCOPE

Secretion of the gut hormones glucagon-like peptide (GLP-1) and peptide YY (PYY) are induced by nutrients reaching the lower small intestine which regulate insulin and glucagon release, inhibit appetite, and may improve β-cell regeneration. The aim is to test the effect of a slowly digested isomaltulose (ISO) compared to the rapidly digested saccharose (SAC) as a snack given 1 h before a standardized mixed meal test (MMT) on GLP-1, PYY, glucose-dependent insulinotropic peptide (GIP), and metabolic responses in participants with or without type 2 diabetes (T2DM).

METHODS AND RESULTS

Fifteen healthy volunteers and 15 patients with T2DM consumed either 50 g ISO or SAC 1 h preload of MMT on nonconsecutive days. Clinical parameters and incretin hormones are measured throughout the whole course of MMT. Administration of 50 g ISO as compared to SAC induced a significant increase in GLP-1, GIP, and PYY responses over 2 h after intake of a typical lunch in healthy controls. Patients with T2DM showed reduced overall responses of GLP-1 and delayed insulin release compared to controls while ISO significantly enhanced the GIP and almost tripled the PYY response compared to SAC.

CONCLUSION

A snack containing ISO markedly enhances the release of the metabolically advantageous gut hormones PYY and GLP-1 and enhances GIP release in response to a subsequent complex meal.

The health benefits of dietary short-chain fatty acids in metabolic diseases

Short-chain fatty acids (SCFAs) are a subset of fatty acids that play crucial roles in maintaining normal physiology and developing metabolic diseases, such as obesity, diabetes, cardiovascular disease, and liver disease. Even though dairy products and vegetable oils are the direct dietary sources of SCFAs, their quantities are highly restricted. SCFAs are produced indirectly through microbial fermentation of fibers. The biological roles of SCFAs in human health and metabolic diseases are mainly due to their receptors, GPR41 and GPR43, FFAR2 and FFAR3. Additionally, it has been demonstrated that SCFAs modulate DNMTs and HDAC activities, inhibit NF-κB-STAT signaling, and regulate G(i/o)βγ-PLC-PKC-PTEN signaling and PPARγ-UCP2-AMPK autophagic signaling, thus mitigating metabolic diseases. Recent studies have uncovered that SCFAs play crucial roles in epigenetic modifications of DNAs, RNAs, and post-translational modifications of proteins, which are critical regulators of metabolic health and diseases. At the same time, dietary recommendations for the purpose of SCFAs have been proposed. The objective of the review is to summarize the most recent research on the role of dietary SCFAs in metabolic diseases, especially the signal transduction of SCFAs in metabolic diseases and their functional efficacy in different backgrounds and models of metabolic diseases, at the same time, to provide dietary and nutritional recommendations for using SCFAs as food ingredients to prevent metabolic diseases.

Dorothy Hodgkin lecture 2023: The enteroendocrine system-Sensors in your guts

Glucagon-like peptide-1 (GLP-1)-based medication is now widely employed in the treatment of type 2 diabetes and obesity. Like other gut hormones, GLP-1 is released from eneteroendocrine cells after a meal and in this review, based on the Dorothy Hodgkin lecture delivered during the annual meeting of Diabetes UK in 2023, I argue that there is sufficient spare capacity of GLP-1 and other gut hormone expressing cells that could be recruited therapeutically. Years of research has revealed several receptors expressed in enteroendocrine cells that could be targeted to stimulate hormone release: although from this research it seems unlikely to find agents that selectively boost GLP-1, release of a mixture of hormones might be the more desirable outcome anyway, given the recent promising results of new peptides combining GLP1-receptor with other gut hormone receptor activation. Alternatively, the fact that GLP-1 and peptideYY (PYY) expressing cells are found in greater density in the ileum might be exploited by increasing the delivery of chyme to the distal small intestine.

Gut microbiota-mediated IL-22 alleviates metabolic inflammation

Low-grade chronic inflammation, also known as metabolic inflammation, promotes the development of metabolic diseases. Increasing evidence suggests that changes in gut microbes and metabolites disrupt the integrity of the gut barrier and exert significant effects on the metabolism of various tissues, including the liver and adipose tissue, thereby contributing to metabolic inflammation. We observed that IL-22 is a key signaling molecule that serves as a bridge between intestinal microbes and the host, effectively alleviating metabolic inflammation by modulating the host immunomodulatory network. Here, we focused on elucidating the underlying mechanisms by which the gut microbiota and their metabolites reduce inflammation via IL-22, highlighting the favorable impact of IL-22 on metabolic inflammation. Furthermore, we discuss the potential of IL-22 as a therapeutic target for the management of metabolic inflammation and related diseases.

Bariatric Surgery and Gut-Brain-Axis Driven Alterations in Cognition and Inflammation

Obesity is associated with systemic inflammation, comorbidities like diabetes, cardiovascular disease and several cancers, cognitive decline and structural and functional brain changes. To treat, or potentially prevent these related comorbidities, individuals with obesity must achieve long-term sustainable weight loss. Often life style interventions, such as dieting and increased physical activity are not successful in achieving long-term weight loss. Meanwhile bariatric surgery has emerged as a safe and effective procedure to treat obesity. Bariatric surgery causes changes in physiological processes, but it is still not fully understood which exact mechanisms are involved. The successful weight loss after bariatric surgery might depend on changes in various energy regulating hormones, such as ghrelin, glucagon-like peptide-1 and peptide YY. Moreover, changes in microbiota composition and white adipose tissue functionality might play a role. Here, we review the effect of obesity on neuroendocrine effects, microbiota composition and adipose tissue and how these may affect inflammation, brain structure and cognition. Finally, we will discuss how these obesity-related changes may improve after bariatric surgery.

Diabetes Remission After LRYGBP With and Without Fundus Resection: a Randomized Clinical Trial

BACKGROUND

Glycemic control, after metabolic surgery, is achieved in two stages, initially with neuroendocrine alterations and in the long-term with sustainable weight loss. The resection of the gastric fundus, as the major site of ghrelin production, is probably related with optimized glucose regulation. The aim of the present study is to investigate whether the modification of laparoscopic Roux-en-Y gastric bypass (LRYGBP) with fundus resection offers superior glycemic control, compared to typical LRYGBP.

MATERIALS AND METHODS

Participants were 24 patients with body mass index (BMI) ≥40kg/m2 and type II diabetes mellitus (T2DM), who were randomly assigned to undergo LRYGBP and LRYGBP with fundus resection (LRYGBP+FR). Gastrointestinal (GI) hormones [ghrelin, glucagon-like-peptide-1 (GLP-1), peptide-YY (PYY)] and glycemic parameters (glucose, insulin, HbA1c, C-peptide, insulinogenic index, HOMA-IR) were measured preoperatively, at 6 and 12 months during an oral glucose tolerance test (OGTT).

RESULTS

Ninety-five percent of patients showed complete remission of T2DM after 12 months. LRYGBP+FR was not related with improved glycemic control, compared to LRYGBP. Ghrelin levels were not significantly reduced at 6 and 12 months after LRYGBP+FR. GLP-1 and PYY levels were remarkably increased postprandially in both groups at 6 and 12 months postoperatively (p<0.01). Patients who underwent LRYGBP+FR achieved a significantly lower BMI at 12 months in comparison to LRYGBP (p<0.05).

CONCLUSION

Fundus resection is not associated with improved glycemic regulation, compared to typical LRYGBP and the significant decrease in BMI after LRYGBP+FR has to be further confirmed with longer follow-up.

Obesity and its comorbidities, current treatment options and future perspectives: Challenging bariatric surgery?

Obesity and its comorbidities, including type 2 diabetes mellitus, cardiovascular disease, heart failure and non-alcoholic liver disease are a major health and economic burden with steadily increasing numbers worldwide. The need for effective pharmacological treatment options is strong, but, until recently, only few drugs have proven sufficient efficacy and safety. This article provides a comprehensive overview of obesity and its comorbidities, with a special focus on organ-specific pathomechanisms. Bariatric surgery as the so far most-effective therapeutic strategy, current pharmacological treatment options and future treatment strategies will be discussed. An increasing knowledge about the gut-brain axis and especially the identification and physiology of incretins unfolds a high number of potential drug candidates with impressive weight-reducing potential. Future multi-modal therapeutic concepts in obesity treatment may surpass the effectivity of bariatric surgery not only with regard to weight loss, but also to associated comorbidities.

A specific gut microbiota signature is associated with an enhanced GLP-1 and GLP-2 secretion and improved metabolic control in patients with type 2 diabetes after metabolic Roux-en-Y gastric bypass

Objective

To determine changes in incretins, systemic inflammation, intestinal permeability and microbiome modifications 12 months after metabolic RYGB (mRYGB) in patients with type 2 diabetes (T2D) and their relationship with metabolic improvement.

Materials and methods

Prospective single-center non-randomized controlled study, including patients with class II-III obesity and T2D undergoing mRYGB. At baseline and one year after surgery we performed body composition measurements, biochemical analysis, a meal tolerance test (MTT) and lipid test (LT) with determination of the area under the curve (AUC) for insulin, C-peptide, GLP-1, GLP-2, and fasting determinations of succinate, zonulin, IL-6 and study of gut microbiota.

Results

Thirteen patients aged 52.6 ± 6.5 years, BMI 39.3 ± 1.4 kg/m2, HbA1c 7.62 ± 1.5% were evaluated. After mRYGB, zonulin decreased and an increase in AUC after MTT was observed for GLP-1 (pre 9371 ± 5973 vs post 15788 ± 8021 pM, P<0.05), GLP-2 (pre 732 ± 182 vs post 1190 ± 447 ng/ml, P<0.001) and C- peptide, as well as after LT. Species belonging to Streptococaceae, Akkermansiacea, Rickenellaceae, Sutterellaceae, Enterobacteriaceae, Oscillospiraceae, Veillonellaceae, Enterobacterales_uc, and Fusobacteriaceae families increased after intervention and correlated positively with AUC of GLP-1 and GLP-2, and negatively with glucose, HbA1c, triglycerides and adiposity markers. Clostridium perfringens and Roseburia sp. 40_7 behaved similarly. In contrast, some species belonging to Lachnospiraceae, Erysipelotricaceae, and Rumnicocaceae families decreased and showed opposite correlations. Higher initial C-peptide was the only predictor for T2D remission, which was achieved in 69% of patients.

Conclusions

Patients with obesity and T2D submitted to mRYGB show an enhanced incretin response, a reduced gut permeability and a metabolic improvement, associated with a specific microbiota signature.

The impacts and mechanisms of dietary proteins on glucose homeostasis and food intake: a pivotal role of gut hormones

Glucose and energy metabolism disorders are the main reasons induced type 2 diabetes (T2D) and obesity. Besides providing energy, dietary nutrients could regulate glucose homeostasis and food intake via intestinal nutrient sensing induced gut hormone secretion. However, reviews regarding intestinal protein sensing are very limited, and no accurate information is available on their underlying mechanisms. Through intestinal protein sensing, dietary proteins regulate glucose homeostasis and food intake by secreting gut hormones, such as glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), peptide YY (PYY) and glucose-dependent insulinotropic polypeptide (GIP). After activating the sensory receptors, such as calcium-sensing receptor (CaSR), peptide transporter-1 (PepT1), and taste 1 receptors (T1Rs), protein digests induced Ca2+ influx and thus triggered gut hormone release. Additionally, research models used to study intestinal protein sensing have been emphasized, especially several innovative models with excellent physiological relevance, such as co-culture cell models, intestinal organoids, and gut-on-a-chips. Lastly, protein-based dietary strategies that stimulate gut hormone secretion and inhibit gut hormone degradation are proposed for regulating glucose homeostasis and food intake.

Diagnosis and management of post-bariatric surgery hypoglycemia

INTRODUCTION

While bariatric surgery remains the most effective treatment for obesity that allows substantial weight loss with improvement and possibly remission of obesity-associated comorbidities, some postoperative complications may occur. Managing physicians need to be familiar with the common problems to ensure timely and effective management. Of these complications, postoperative hypoglycemia is an increasingly recognized complication of bariatric surgery that remains underreported and underdiagnosed.

AREA COVERED

This article highlights the importance of identifying hypoglycemia in patients with a history of bariatric surgery, reviews pathophysiology and addresses available nutritional, pharmacological and surgical management options. Systemic evaluation including careful history taking, confirmation of hypoglycemia and biochemical assessment is essential to establish accurate diagnosis. Understanding the weight-dependent and weight-independent mechanisms of improved postoperative glycemic control can provide better insight into the causes of the exaggerated responses that lead to postoperative hypoglycemia.

EXPERT OPINION

Management of post-operative hypoglycemia can be challenging and requires a multidisciplinary approach. While dietary modification is the mainstay of treatment for most patients, some patients may benefit from pharmacotherapy (e.g. GLP-1 receptor antagonist); Surgery (e.g. reversal of gastric bypass) is reserved for unresponsive severe cases. Additional research is needed to understand the underlying pathophysiology with a primary aim in optimizing diagnostics and treatment options.

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.

Research Progress of Takeda G Protein-Coupled Receptor 5 in Metabolic Syndrome

Bile acids are acknowledged as signaling molecules involved in metabolic syndrome. The Takeda G protein-coupled receptor 5 (TGR5) functions as a significant bile acid receptor. The accumulated evidence suggests that TGR5 involves lipid homeostasis, glucose metabolism, and inflammation regulation. In line with this, recent preclinical studies also demonstrate that TGR5 plays a significant role in the generation and progression of metabolic syndrome, encompassing type 2 diabetes mellitus, obesity, atherosclerosis, and non-alcoholic fatty liver disease (NAFLD). In this review, we discuss the role of TGR5 in metabolic syndrome, illustrating the underlying mechanisms and therapeutic targets.

A peptide triple agonist of GLP-1, neuropeptide Y1, and neuropeptide Y2 receptors promotes glycemic control and weight loss

Mechanisms underlying long-term sustained weight loss and glycemic normalization after obesity surgery include changes in gut hormone levels, including glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). We demonstrate that two peptide biased agonists (GEP44 and GEP12) of the GLP-1, neuropeptide Y1, and neuropeptide Y2 receptors (GLP-1R, Y1-R, and Y2-R, respectively) elicit Y1-R antagonist-controlled, GLP-1R-dependent stimulation of insulin secretion in both rat and human pancreatic islets, thus revealing the counteracting effects of Y1-R and GLP-1R agonism. These agonists also promote insulin-independent Y1-R-mediated glucose uptake in muscle tissue ex vivo and more profound reductions in food intake and body weight than liraglutide when administered to diet-induced obese rats. Our findings support a role for Y1-R signaling in glucoregulation and highlight the therapeutic potential of simultaneous receptor targeting to achieve long-term benefits for millions of patients.

Gut microbiome modified by bariatric surgery improves insulin sensitivity and correlates with increased brown fat activity and energy expenditure

Alterations in the microbiome correlate with improved metabolism in patients following bariatric surgery. While fecal microbiota transplantation (FMT) from obese patients into germ-free (GF) mice has suggested a significant role of the gut microbiome in metabolic improvements following bariatric surgery, causality remains to be confirmed. Here, we perform paired FMT from the same obese patients (BMI > 40; four patients), pre- and 1 or 6 months post-Roux-en-Y gastric bypass (RYGB) surgery, into Western diet-fed GF mice. Mice colonized by FMT from patients' post-surgery stool exhibit significant changes in microbiota composition and metabolomic profiles and, most importantly, improved insulin sensitivity compared with pre-RYGB FMT mice. Mechanistically, mice harboring the post-RYGB microbiome show increased brown fat mass and activity and exhibit increased energy expenditure. Moreover, improvements in immune homeostasis within the white adipose tissue are also observed. Altogether, these findings point to a direct role for the gut microbiome in mediating improved metabolic health post-RYGB surgery.

Effects of bariatric surgery and dietary intervention on insulin resistance and appetite hormones over a 3 year period

To examine an impact of three types of bariatric surgery compared with dietary intervention (DIET), on concurrent changes in Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and appetite hormones over 3 years. Fifty-five adults were studied during phase of weight loss (0-12 months) and during weight stability (12-36 months) post intervention. Measurements of HOMA-IR, fasting and postprandial PYY and GLP1, adiponectin, CRP, RBP4, FGF21 hormones and dual-Xray absorptiometry were performed throughout the study. All surgical groups achieved significant reductions in HOMA-IR with greatest difference between Roux-en-Y gastric bypass and DIET (- 3.7; 95% CI - 5.4, - 2.1; p = 0.001) at 12-36 months. Initial (0-12 months) HOMA-IR values were no different to DIET after adjustment for the lost weight. During 12-36 months, after controlling for treatment procedure and weight, for every twofold increase in postprandial PYY and adiponectin, HOMA-IR decreased by 0.91 (95% CI - 1.71, - 0.11; p = 0.030) and by 0.59 (95% CI - 1.10, - 0.10; p = 0.023) respectively. Initial, non-sustained changes in RBP4 and FGF21 were not associated with HOMA-IR values. While initial rapid weight loss reduces insulin resistance, the enhanced secretions of PYY and adiponectin may contribute to weight-independent improvements in HOMA-IR during weight stability.Clinical trial registration: Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12613000188730.

Somatostatin: From a supporting actor to the protagonist to explain the long-term effect of sleeve gastrectomy on glucose metabolism

BACKGROUND

Bariatric/metabolic surgery has become the most effective treatment against type 2 Diabetes mellitus (T2DM). The role of many gastrointestinal hormones in T2DM has been proposed, but the pathophysiological models described vary greatly depending on the anatomical rearrangements after surgery. We focus on somatostatin as a common factor in two of the most commonly performed surgical procedures in a healthy rodent model. We performed sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) and also an experimental surgery without gastric involvement (intestinal resection of 50 % jejunum-ileum portion -IR50 %).

METHODS

We used five groups of Wistar rats: fasting control, sham-operated, SG-operated, RYGB-operated and IR50-operated. We analysed several parameters 4 and 23 weeks after surgery: plasma SST-14/28 fractions, plasma glucose, insulin release and SST-producing cell expression in the duodenum and pancreatic islets.

RESULTS

Numerous SST-producing cells in the duodenum but a low number in the pancreas and a long-term loss of glucose tolerance were observed in SG and RYGB animals. Additionally, a high plasma SST-28 fraction was found in animals after SG but not after RYGB. Finally, IR50 animals showed no differences versus controls.

CONCLUSIONS

In our SG model the amplitude of insulin response after metabolic surgeries, is mediated by SST-28 plasma levels derived from the proportional compensatory effect of gastric SST-producing tissue ablation. In addition, a strong compensatory response to the surgical loss of gastric SST-producing cells, leads to long-term loss of insulin production after SG but not in the others.

Gastric bypass surgery weight loss-independently induces gut Il-22 release in association with improved glycemic control in obese Zucker fatty rats

Background

Roux-en-Y gastric bypass surgery (RYGB) improves glycemic control in individuals with severe obesity beyond the effects of weight loss alone. To identify potential underlying mechanisms, we asked how equivalent weight loss from RYGB and from chronic caloric restriction impact gut release of the metabolically beneficial cytokine interleukin-22 (Il-22).

Methods

Obese male Zucker fatty rats were randomized into sham-operated (Sham), RYGB, and sham-operated, body weight-matched to RYGB (BWM) groups. Food intake and body weight were measured regularly for 4 weeks. An oral glucose tolerance test (OGTT) was performed on postoperative day 27. Portal vein plasma, systemic plasma, and whole-wall samples from throughout the gut were collected on postoperative day 28. Gut Il-22 mRNA expression was determined by real-time quantitative PCR. Plasma Il-22 levels were determined by enzyme-linked immunosorbant assay (ELISA).

Results

RYGB and BWM rats had lower food intake and body weight as well as superior blood glucose clearing capability compared with Sham rats. RYGB rats also had superior blood glucose clearing capability compared with BWM rats despite having similar body weights and higher food intake. Il-22 mRNA expression was approximately 100-fold higher specifically in the upper jejunum in RYGB rats compared with Sham rats. Il-22 protein was only detectable in portal vein (34.1 ± 9.4 pg/mL) and systemic (46.9 ± 10.5 pg/mL) plasma in RYGB rats. Area under the curve of blood glucose during the OGTT, but not food intake or body weight, negatively correlated with portal vein and systemic plasma Il-22 levels in RYGB rats.

Conclusions

These results suggest that induction of gut Il-22 release might partly account for the weight loss-independent improvements in glycemic control after RYGB, and further support the use of this cytokine for the treatment of metabolic disease.

Metabolic effects of truncal vagotomy when combined with bariatric-metabolic surgery

Bariatric-metabolic surgery (BMS) in patients with obesity frequently leads to remission of concurrent type 2 diabetes mellitus (T2DM), even before body weight loss takes place. This is probably based on the correction of a dysmetabolic cycle in the gastrointestinal physiology of T2DM that includes increased vagus-dependent exocrine pancreatic secretion (EPS) and, hence, amplified digestion and nutrient absorption. The resultant chronic exposure of tissues to high plasma levels of glucose, fatty acids and amino acids causes tissue resistance to the actions of insulin and, at a later stage, β-cell dysfunction and reduction of insulin release. We hypothesize that the addition of a surgical truncal vagotomy (TV) may improve and solidify the beneficial results of BMS on T2DM by stably decreasing EPS, - hence reducing the digestion and absorption of nutrients -, and increasing incretin secretion as a result of increased delivery of unabsorbed nutrients to the distal intestine. This hypothesis is supported by surgical data from gastrointestinal malignancies and peptic ulcer operations that include TV, as well as by vagal blockade studies. We suggest that TV may result in a stable reduction of EPS, and that its combination with the appropriate type of BΜS, may enhance and sustain the salutary effects of the latter on T2DM.

Differential effects of RYGB surgery and best medical treatment for obesity-diabetes on intestinal and islet adaptations in obese-diabetic ZDSD rats

Modification of gut-islet secretions after Roux-En-Y gastric bypass (RYBG) surgery contributes to its metabolic and anti-diabetic benefits. However, there is limited knowledge on tissue-specific hormone distribution post-RYGB surgery and how this compares with best medical treatment (BMT). In the present study, pancreatic and ileal tissues were excised from male Zucker-Diabetic Sprague Dawley (ZDSD) rats 8-weeks after RYGB, BMT (daily oral dosing with metformin 300mg/kg, fenofibrate 100mg/kg, ramipril 1mg/kg, rosuvastatin 10mg/kg and subcutaneous liraglutide 0.2mg/kg) or sham operation (laparotomy). Insulin, glucagon, somatostatin, PYY, GLP-1 and GIP expression patterns were assessed using immunocytochemistry and analyzed using ImageJ. After RYGB and BMT, body weight and plasma glucose were decreased. Intestinal morphometry was unaltered by RYGB, but crypt depth was decreased by BMT. Intestinal PYY cells were increased by both interventions. GLP-1- and GIP-cell counts were unchanged by RYGB but BMT increased ileal GLP-1-cells and decreased those expressing GIP. The intestinal contents of PYY and GLP-1 were significantly enhanced by RYGB, whereas BMT decreased ileal GLP-1. No changes of islet and beta-cell area or proliferation were observed, but the extent of beta-cell apoptosis and islet integrity calculated using circularity index were improved by both treatments. Significantly decreased islet alpha-cell areas were observed in both groups, while beta- and PYY-cell areas were unchanged. RYGB also induced a decrease in islet delta-cell area. PYY and GLP-1 colocalization with glucagon in islets was significantly decreased in both groups, while co-staining of PYY with glucagon was decreased and that with somatostatin increased. These data characterize significant cellular islet and intestinal adaptations following RYGB and BMT associated with amelioration of obesity-diabetes in ZDSD rats. The differential responses observed and particularly those within islets, may provide important clues to the unique ability of RYGB to cause diabetes remission.

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.

Gut Factors Mediating the Physiological Impact of Bariatric Surgery

Despite decades of obesity research and various public health initiatives, obesity remains a major public health concern. Our most drastic but most effective treatment of obesity is bariatric surgery with weight loss and improvements in co-morbidities, including resolution of type 2 diabetes (T2D). However, the mechanisms by which surgery elicits metabolic benefits are still not well understood. One proposed mechanism is through signals generated by the intestine (nutrients, neuronal, and/or endocrine) that communicate nutrient status to the brain. In this review, we discuss the contributions of gut-brain communication to the physiological regulation of body weight and its impact on the success of bariatric surgery. Advancing our understanding of the mechanisms that drive bariatric surgery-induced metabolic benefits will ultimately lead to the identification of novel, less invasive strategies to treat obesity.

Interrupting Prolonged Sitting with Intermittent Walking Increases Postprandial Gut Hormone Responses

INTRODUCTION

Continuous exercise can increase postprandial gut hormone such as glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) responses, but it is unknown whether interrupting prolonged sitting with intermittent walking elicits this effect.

METHOD

Ten participants with central overweight/obesity (7 men and 3 postmenopausal women, 51 ± 5 yr; mean ± SD) completed a randomized crossover study in which they consumed breakfast and lunch in the laboratory while either sitting continuously for the entire 5.5-h period (SIT) or the prolonged sitting interrupted every 20 min by walking briskly (6.4 km·h-1) for 2 min (BREAKS). Blood samples were collected at regular intervals to examine postprandial plasma GLP-1, PYY, and glucose-dependent insulinotropic polypeptide concentrations. Adipose tissue samples were collected at baseline and at the end of the trials to examine changes in net dipeptidyl peptidase 4 secretion from primary explants.

RESULTS

Mean (95% confidence interval) postprandial GLP-1 and PYY incremental area under curve values were elevated by 26% and 31% in the BREAKS trial versus SIT (8.4 [0.7, 16.1] vs 6.7 [-0.8, 14.2], P = 0.001, and 26.9 [8.1, 45.6] vs 20.4 [5.1, 35.8] nmol·330 min·L-1, P = 0.024, respectively) but without any such effect on glucose-dependent insulinotropic polypeptide (P = 0.076) or net adipose tissue dipeptidyl peptidase 4 secretion (P > 0.05).

CONCLUSIONS

Interrupting prolonged sitting with regular short bouts of brisk walking increases postprandial GLP-1 and PYY concentrations in healthy middle-age men and women with central adiposity.

Consistent gut bacterial and short-chain fatty acid signatures in hypoabsorptive bariatric surgeries correlate with metabolic benefits in rats

OBJECTIVE

The study aimed at comparing how changes in the gut microbiota are associated to the beneficial effects of the most clinically efficient hypoabsorptive bariatric procedures, namely Roux-en-Y gastric bypass (RYGB), biliopancreatic diversion with duodenal switch (BPD-DS) and single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S).

METHODS

Diet-induced obese (DIO) male Wistar rats were divided into seven groups. In addition to the groups subjected to RYGB, BPD-DS and SADI-S, the following four control groups were included: SHAM-operated rats fed a high-fat diet (SHAM HF), SHAM fed a low-fat diet (SHAM LF), SHAM HF-pair-weighed to BPD-DS (SHAM HF-PW) and sleeve-gastrectomy (SG) rats. Body weight, food intake, glucose tolerance, insulin sensitivity/resistance, and L-cell secretion were assessed. The gut microbiota (16 S ribosomal RNA gene sequencing) as well as the fecal and cæcal contents of short-chain fatty acids (SCFAs) were also analyzed prior to, and after the surgeries.

RESULTS

The present study demonstrates the beneficial effect of RYGB, BPD-DS and SADI-S on fat mass gain and glucose metabolism in DIO rats. These benefits were proportional to the effect of the surgeries on food digestibility (BPD-DS > SADI-S > RYGB). Notably, hypoabsorptive surgeries led to consonant microbial signatures characterized by decreased abundance of the Ruminococcaceae (Oscillospira and Ruminococcus), Oscillospiraceae (Oscillibacter) and Christensenellaceae, and increased abundance of the Clostridiaceae (Clostridium), Sutterellaceae (Sutterella) and Enterobacteriaceae. The gut bacteria following hypoabsorptive surgeries were associated with higher fecal levels of propionate, butyrate, isobutyrate and isovalerate. Increases in the fecal SCFAs were in turn positively and strongly correlated with the levels of peptide tyrosine-tyrosine (PYY) and with the beneficial effects of the surgery.

CONCLUSION

The present study emphasizes the consistency with which the three major hypoabsorptive bariatric procedures RYGB, BPD-DS and SADI-S create a gut microbial environment capable of producing a SCFA profile favorable to the secretion of PYY and to beneficial metabolic effects.

Weight Loss and Gastrointestinal Hormone Variation Caused by Gastric Artery Embolization: An Updated Analysis Study

OBJECTIVE

Many gastric artery embolizations (GAE) have been performed in recent years. We try to determine whether GAE caused weight loss by decreasing gastrointestinal hormone through the analysis of weight loss and gastrointestinal hormones changes.

METHODS

The PubMed and Medline databases, and the Cochrane Library, were searched using the following keywords. A total of 10 animal trials (n=144), 15 human trials (n=270) were included for analysis. After GAE, we mainly evaluated the changes in body weight loss (BWL) and body mass index (BMI), as well as metabolic indexes, such as blood glucose, lipids, and gastrointestinal hormones levels.

RESULTS

Animal subjects received either chemical or particle embolization, while human subjects only received particle embolization. In animal trials (growing period), the GAE group gained weight significantly slower than the sham-operated group, ghrelin levels decreased. In human trials, GAE brought more weight loss in the early stages, with a trend towards weight recovery after several months that was still lower than baseline levels. Besides weight loss, abnormal metabolic indicators, such as blood glucose and lipids were modified, and the quality of life (QOL) scores of obese patients improved. In addition, weight loss positively correlates with ghrelin.

CONCLUSION

GAE may help people lose weight and become a new minimally invasive and effective surgery for the treatment of modest obesity. Physiologic changes in gastrointestinal tract of gastrointestinal hormones level may be one reason for weight loss in GAE.

Bile acids, gut microbiota and metabolic surgery

Metabolic surgery, or bariatric surgery, is currently the most effective approach for treating obesity and its complications. Vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB) are the top two types of commonly performed metabolic surgery now. The precise mechanisms of how the surgeries work are still unclear, therefore much research has been conducted in this area. Gut hormones such as GLP-1 and PYY have been studied extensively in the context of metabolic surgery because they both participate in satiety and glucose homeostasis. Bile acids, whose functions cover intestinal lipid absorption and various aspects of metabolic regulation via the action of FXR, TGR5, and other bile acid receptors, have also been actively investigated as potential mediators of metabolic surgery. Additionally, gut microbiota and their metabolites have also been studied because they can affect metabolic health. The current review summarizes and compares the recent scientific progress made on identifying the mechanisms of RYGB and VSG. One of the long-term goals of metabolic/bariatric surgery research is to develop new pharmacotherapeutic options for the treatment of obesity and diabetes. Because obesity is a growing health concern worldwide, there is a dire need in developing novel non-invasive treatment options.

Neuropeptide Y1 receptor antagonism protects β-cells and improves glycemic control in type 2 diabetes

OBJECTIVES

Loss of functional β-cell mass is a key factor contributing to poor glycemic control in advanced type 2 diabetes (T2D). We have previously reported that the inhibition of the neuropeptide Y1 receptor improves the islet transplantation outcome in type 1 diabetes (T1D). The aim of this study was to identify the pathophysiological role of the neuropeptide Y (NPY) system in human T2D and further evaluate the therapeutic potential of using the Y1 receptor antagonist BIBO3304 to improve β-cell function and survival in T2D.

METHODS

The gene expression of the NPY system in human islets from nondiabetic subjects and subjects with T2D was determined and correlated with the stimulation index. The glucose-lowering and β-cell-protective effects of BIBO3304, a selective orally bioavailable Y1 receptor antagonist, in high-fat diet (HFD)/multiple low-dose streptozotocin (STZ)-induced and genetically obese (db/db) T2D mouse models were assessed.

RESULTS

In this study, we identified a more than 2-fold increase in NPY1R and its ligand, NPY mRNA expression in human islets from subjects with T2D, which was significantly associated with reduced insulin secretion. Consistently, the pharmacological inhibition of Y1 receptors by BIBO3304 significantly protected β cells from dysfunction and death under multiple diabetogenic conditions in islets. In a preclinical study, we demonstrated that the inhibition of Y1 receptors by BIBO3304 led to reduced adiposity and enhanced insulin action in the skeletal muscle. Importantly, the Y1 receptor antagonist BIBO3304 treatment also improved β-cell function and preserved functional β-cell mass, thereby resulting in better glycemic control in both HFD/multiple low-dose STZ-induced and db/db T2D mice.

CONCLUSIONS

Our results revealed a novel causal link between increased islet NPY-Y1 receptor gene expression and β-cell dysfunction and failure in human T2D, contributing to the understanding of the pathophysiology of T2D. Furthermore, our results demonstrate that the inhibition of the Y1 receptor by BIBO3304 represents a potential β-cell-protective therapy for improving functional β-cell mass and glycemic control in T2D.

Peptide-YY3-36/glucagon-like peptide-1 combination treatment of obese diabetic mice improves insulin sensitivity associated with recovered pancreatic β-cell function and synergistic activation of discrete hypothalamic and brainstem neuronal circuitries

OBJECTIVE

Obesity-linked type 2 diabetes (T2D) is a worldwide health concern and many novel approaches are being considered for its treatment and subsequent prevention of serious comorbidities. Co-administration of glucagon like peptide 1 (Fc-GLP-1) and peptide YY_3-36 (Fc-PYY_3-36) renders a synergistic decrease in energy intake in obese men. However, mechanistic details of the synergy between these peptide agonists and their effects on metabolic homeostasis remain relatively scarce.

METHODS

In this study, we utilized long-acting analogues of GLP-1 and PYY_3-36 (via Fc-peptide conjugation) to better characterize the synergistic pharmacological benefits of their co-administration on body weight and glycaemic regulation in obese and diabetic mouse models. Hyperinsulinemic-euglycemic clamps were used to measure weight-independent effects of Fc-PYY_3-36 + Fc-GLP-1 on insulin action. Fluorescent light sheet microscopy analysis of whole brain was performed to assess activation of brain regions.

RESULTS

Co-administration of long-acting Fc-IgG/peptide conjugates of Fc-GLP-1 and Fc-PYY_3-36 (specific for PYY receptor-2 (Y2R)) resulted in profound weight loss, restored glucose homeostasis, and recovered endogenous β-cell function in two mouse models of obese T2D. Hyperinsulinemic-euglycemic clamps in C57BLKS/J db/db and diet-induced obese Y2R-deficient (Y2RKO) mice indicated Y2R is required for a weight-independent improvement in peripheral insulin sensitivity and enhanced hepatic glycogenesis. Brain cFos staining demonstrated distinct temporal activation of regions of the hypothalamus and hindbrain following Fc-PYY_3-36 + Fc-GLP-1R agonist administration.

CONCLUSIONS

These results reveal a therapeutic approach for obesity/T2D that improved insulin sensitivity and restored endogenous β-cell function. These data also highlight the potential association between the gut-brain axis in control of metabolic homeostasis.

Effect of Bariatric Surgery on Metabolic Diseases and Underlying Mechanisms

Obesity is a highly prevalent public health concern, attributed to multifactorial causes and limited in treatment options. Several comorbidities are closely associated with obesity such as the development of type 2 diabetes mellitus (T2DM), cardiovascular and cerebrovascular diseases, and nonalcoholic fatty liver disease (NAFLD). Bariatric surgery, which can be delivered in multiple forms, has been remarked as an effective treatment to decrease the prevalence of obesity and its associated comorbidities. The different types of bariatric surgery create a variety of new pathways for food to metabolize in the body and truncate the stomach's caliber. As a result, only a small quantity of food is tolerated, and the body mass index noticeably decreases. This review describes the improvements of obesity and its comorbidities following bariatric surgery and their mechanism of improvement. Additionally, endocrine function improvements after bariatric surgery, which contributes to the patients' health improvement, are described, including the role of glucagon-like peptide-1 (GLP-1), fibroblast growth factors 19 and 21 (FGF-19, FGF-21), and pancreatic peptide YY (PYY). Lastly, some of the complications of bariatric surgery, including osteoporosis, iron deficiency/anemia, and diarrhea, as well as their potential mechanisms, are described.

Islet β-cells physiological difference study of old and young mice based on single-cell transcriptomics

AIMS/INTRODUCTION

Body aging is a universal biological process. With aging, cells undergo a series of physiological changes. The main feature is cell proliferation decline, although the cells still have normal functions. Pancreatic β-cells are no exception. However, the physiological senescence of β-cells, and the resulting function and transcriptome changes have rarely attracted attention. The specific senescence phenotype of β-cells remains unknown.

MATERIALS AND METHODS

Pancreatic samples from three female C57BL/6 mice with aged 2.5 months (young) mice and 20 months (old) were digested to a single-cell suspension and analyzed, with 10× Genomics single-cell ribonucleic acid sequencing, β-cells were determined by biosynthesis analysis, and differences between old and young mice were identified.

RESULTS

A total of 47 differential genes with significant and statistical significance were screened in β-cells (fold change >1.5, P < 0.05). In old mice, 27 genes were upregulated and 20 genes were downregulated. Genes Mt1, Mt2, Pyy, Gcg and Pnlip, and mitochondrial genes mt-Nd1, mt-Nd3, mt-Co1, mt-Co2 and mt-Co3 were found to be involved in cellular senescence. Transcription factors Jund and Fos were important regulators of senescence.

CONCLUSIONS

An overall difference was found between the pancreatic β-cells of old and young mice. Transcription factors facilitate transitions between pancreatic β-cells. These findings are worthy of deep exploration, and provide new resources and directions for the research of pancreatic aging in mice.

Plasma GDF15 levels are similar between subjects after bariatric surgery and matched controls and are unaffected by meals

Growth differentiating factor 15 (GDF15) is expressed in the intestine and is one of the most recently identified satiety peptides. The mechanisms controlling its secretion are unclear. The present study investigated whether plasma GDF15 concentrations are meal-related and if potential responses depend on macronutrient type or are affected by previous bariatric surgery. The study included 1) volunteers ingesting rapidly vs. slowly digested carbohydrates (sucrose vs. isomaltose; n = 10), 2) volunteers who had undergone Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) surgery and unoperated matched controls ingesting a liquid mixed meal (n = 9-10 in each group), and 3) individuals with previous RYGB compared with unoperated controls ingesting isocaloric glucose, fat, or protein (n = 6 in each group). Plasma was collected after an overnight fast and up to 6 h after ingestion (≥12 time points). In cohort 1, fasting GDF15 concentrations were ∼480 pg/mL. Concentrations after sucrose or isomaltose intake did not differ from baseline (P = 0.26 to P > 0.99) and total area under the curves (tAUCs were similar between groups (P = 0.77). In cohort 2, fasting GDF15 concentrations were as follows (pg/mL): RYGB = 540 ± 41.4, SG = 477 ± 36.4, and controls = 590 ± 41.8, with no between-group differences (P = 0.73). Concentrations did not increase at any postprandial time point (over all time factor: P = 0.10) and tAUCs were similar between groups (P = 0.73). In cohort 3, fasting plasma GDF15 was similar among the groups (P > 0.99) and neither glucose, fat, nor protein intake consistently increased the concentrations. In conclusion, we find that plasma GDF15 was not stimulated by meal intake and that fasting concentrations did not differ between RYGB-, SG-, and body mass index (BMI)-matched controls when investigated during the weight stable phase after RYGB and SG.NEW & NOTEWORTHY Our combined data show that GDF15 does not increase in response to a liquid meal. Moreover, we show for the first time that ingestion of sucrose, isomaltose, glucose, fat, or protein also does not increase plasma GDF15 concentrations, questioning the role of GDF15 in regulation of food source preference. Finally, we find that neither fasting nor postprandial plasma GDF15 concentrations are increased in individuals with previous bariatric surgery compared with unoperated body mass index (BMI)-matched controls.

Sleeve Gastrectomy and Roux-En-Y Gastric Bypass. Two Sculptors of the Pancreatic Islet

Several surgical procedures are performed for the treatment of obesity. A main outcome of these procedures is the improvement of type 2 diabetes mellitus. Trying to explain this, gastrointestinal hormone levels and their effect on organs involved in carbohydrate metabolism, such as liver, gut, muscle or fat, have been studied intensively after bariatric surgery. These effects on endocrine-cell populations in the pancreas have been less well studied. We gathered the existing data on these pancreatic-cell populations after the two most common types of bariatric surgery, the sleeve gastrectomy (SG) and the roux-en-Y gastric bypass (RYGB), with the aim to explain the pathophysiological mechanisms underlying these surgeries and to improve their outcome.

Theoretical study of the interactions between peptide tyrosine tyrosine [PYY (1-36)], a newly identified modulator in type 2 diabetes pathophysiology, with receptors NPY1R and NPY4R

PURPOSE

Diabetes mellitus is a common condition in the clinically obese. Bariatric surgery is one of the ways to put type 2 diabetes in remission. Recent findings propose the appetite-regulator peptide tyrosine tyrosine (PYY) as a therapeutic option for patients with type 2 diabetes. This novel gut hormone restores impaired insulin and glucagon secretion in pancreatic islets and is implicated in type 2 diabetes reversal after bariatric surgery. The current study elucidates the interactions between PYY and the NPY1R and NPY4R receptors using computational methods.

METHODS

Protein structure prediction, molecular docking simulation, and molecular dynamics (MD) simulation were performed to elucidate the interactions of PYY with NPY1R and NPY4R.

RESULTS

The predicted binding models of PYY-NPY receptors are in agreement with those described in the literature, although different interaction partners are presented for the C-terminal tail of PYY. Non-polar interactions are predicted to drive the formation of the protein complex. The calculated binding energies show that PYY has higher affinity for NPY4R (ΔG_GBSA = -65.08 and ΔG_PBSA = -87.62 kcal/mol) than for NPY1R (ΔG_GBSA = -23.11 and ΔG_PBSA = -50.56 kcal/mol).

CONCLUSIONS

Based on the constructed models, the binding conformations obtained from docking and MD simulation for both the PYY-NPY1R and PYY-NPY4R complexes provide a detailed map of possible interactions. The calculated binding energies show a higher affinity of PYY for NPY4R. These findings may help to understand the mechanisms behind the improvement of diabetes following bariatric surgery.

MECHANISMS IN ENDOCRINOLOGY: The gut-brain axis: regulating energy balance independent of food intake

Obesity is a global pandemic with a large health and economic burden worldwide. Bodyweight is regulated by the ability of the CNS, and especially the hypothalamus, to orchestrate the function of peripheral organs that play a key role in metabolism. Gut hormones play a fundamental role in the regulation of energy balance, as they modulate not only feeding behavior but also energy expenditure and nutrient partitioning. This review examines the recent discoveries about hormones produced in the stomach and gut, which have been reported to regulate food intake and energy expenditure in preclinical models. Some of these hormones act on the hypothalamus to modulate thermogenesis and adiposity in a food intake-independent fashion. Finally, the association of these gut hormones to eating, energy expenditure, and weight loss after bariatric surgery in humans is discussed.

Treatment of type 2 diabetes: challenges, hopes, and anticipated successes

Despite the successful development of new therapies for the treatment of type 2 diabetes, such as glucagon-like peptide-1 (GLP-1) receptor agonists and sodium-glucose cotransporter-2 inhibitors, the search for novel treatment options that can provide better glycaemic control and at reduce complications is a continuous effort. The present Review aims to present an overview of novel targets and mechanisms and focuses on glucose-lowering effects guiding this search and developments. We discuss not only novel developments of insulin therapy (eg, so-called smart insulin preparation with a glucose-dependent mode of action), but also a group of drug classes for which extensive research efforts have not been rewarded with obvious clinical impact. We discuss the potential clinical use of the salutary adipokine adiponectin and the hepatokine fibroblast growth factor (FGF) 21, among others. A GLP-1 peptide receptor agonist (semaglutide) is now available for oral absorption, and small molecules activating GLP-1 receptors appear on the horizon. Bariatric surgery and its accompanying changes in the gut hormonal milieu offer a background for unimolecular peptides interacting with two or more receptors (for GLP-1, glucose-dependent insulinotropic polypeptide, glucagon, and peptide YY) and provide more substantial glycaemic control and bodyweight reduction compared with selective GLP-1 receptor agonists. These and additional approaches will help expand the toolbox of effective medications needed for optimising the treatment of well delineated subgroups of type 2 diabetes or help develop personalised approaches for glucose-lowering drugs based on individual characteristics of our patients.

Established and emerging roles peptide YY (PYY) and exploitation in obesity-diabetes

PURPOSE OF REVIEW

The antiobesity effects of activation of hypothalamic neuropeptide Y2 receptors (NPYR2) by the gut-derived hormone, peptide YY (PYY), are established. However, more recent insight into the biology of PYY has demonstrated remarkable benefits of sustained activation of pancreatic beta-cell NPYR1, that promises to open a new therapeutic avenue in diabetes.

RECENT FINDINGS

The therapeutic applicability of NPYR2 agonists for obesity has been considered for many years. An alternative pathway for the clinical realisation of PYY-based drugs could be related to the development of NPYR1 agonists for treatment of diabetes. Thus, although stimulation of NPYR1 on pancreatic beta-cells has immediate insulinostatic effects, prolonged activation of these receptors leads to well defined beta-cell protective effects, with obvious positive implications for the treatment of diabetes. In this regard, NPYR1-specific, long-acting enzyme resistant PYY analogues, have been recently developed with encouraging preclinical effects observed on pancreatic islet architecture in diabetes. In agreement, the benefits of certain types of bariatric surgeries on beta-cell function and responsiveness have also been linked to elevated PYY secretion and NPY1 receptor activation.

SUMMARY

Enzymatically stable forms of PYY, that selectively activate NPYR1, may have significant potential for preservation of beta-cell mass and the treatment of diabetes.

Weight Loss Following Roux-en-Y Gastric Bypass Causally Implicated with Serum Levels of IL-22: A Mendelian Randomization and Phenome-Wide Association Study

OBJECTIVE

Laparoscopic Roux-en-Y gastric bypass (RYGB) modulates the low-grade inflammatory state associated with severe obesity. This study sought to investigate whether weight loss is causally implicated with changes in serum levels of inflammatory molecules.

METHODS

Using the largest genome-wide association study (n = 1,020 individuals), this study curated five genetic variants associated with weight loss following RYGB. Phenome-wide association studies (PheWAS) were performed to identify other phenotypes associated with these variants. Subsequently, two-sample Mendelian randomization was used to study the causal effects of weight loss on the serum levels of 382 inflammatory proteins (measured in 3,033 individuals). This is the first systematic quasi-experimental investigation of weight loss following RYGB and serum markers of inflammation.

RESULTS

The PheWAS analysis revealed that four of the five variants are associated with phenotypes relating to metabolism and inflammation, including insulin response and levels of C-reactive protein. Two-sample Mendelian randomization of the 382 serum inflammatory markers revealed that weight loss following RYGB increases serum levels of interleukin 22 (IL-22) (beta = 0.021, P < 10-3 ; 95% CI: 0.010-0.031). Sensitivity analyses further supported the results and the causal direction.

CONCLUSIONS

Weight loss following RYGB may cause an increase in IL-22 serum levels, suggesting that weight loss directly contributes to immune modulation following bypass. These results demonstrate the utility of genetic studies to disentangling molecular cause and effect following bariatric surgery.

The role of gut microbiota and amino metabolism in the effects of improvement of islet β-cell function after modified jejunoileal bypass

The change in gut microbiota is an important mechanism of the amelioration of type 2 diabetes mellitus (T2DM) after bariatric surgery. Here, we observe that the modified jejunoileal bypass effectively decreases body weight gain, fasting blood glucose, and lipids level in serum; additionally, islet β-cell function, glucose tolerance, and insulin resistance were markedly ameliorated. The hypoglycemic effect and the improvement in islet β-cell function depend on the changes in gut microbiota structure. modified jejunoileal bypass increases the abundance of gut Escherichia coli and Ruminococcus gnavus and the levels of serum glycine, histidine, and glutamine in T2DM rats; and decreases the abundance of Prevotella copri and the levels of serum branched chain amino acids, which are significantly related to the improvement of islet β-cell function in T2DM rats. Our results suggest that amino acid metabolism may contribute to the islet β-cell function in T2DM rats after modified jejunoileal bypass and that improving gut microbiota composition is a potential therapeutic strategy for T2DM.

Positive Effects of NPY1 Receptor Activation on Islet Structure Are Driven by Pancreatic Alpha- and Beta-Cell Transdifferentiation in Diabetic Mice

Enzymatically stable and specific neuropeptide Y1 receptor (NPYR1) agonists, such as sea lamprey PYY(1-36) (SL-PYY(1-36)), are believed to improve glucose regulation in diabetes by targeting pancreatic islets. In this study, streptozotocin (STZ) diabetic transgenic GluCreERT2 ;ROSA26-eYFP and Ins1Cre/+;Rosa26-eYFP mouse models have been used to study effects of sustained NPYR1 activation on islet cell composition and alpha- and beta-cell lineage transitioning. STZ induced a particularly severe form of diabetes in Ins1Cre/+;Rosa26-eYFP mice, but twice-daily administration (25 nmol/kg) of SL-PYY(1-36) for 11 days consistently improved metabolic status. Blood glucose was decreased (p < 0.05 - p < 0.001) and both fasted plasma and pancreatic insulin significantly increased by SL-PYY(1-36). In both GluCreERT2 ;ROSA26-eYFP and Ins1Cre/+; Rosa26-eYFP mice, STZ provoked characteristic losses (p < 0.05 - p < 0.001) of islet numbers, beta-cell and pancreatic islet areas together with increases in area and central islet location of alpha-cells. With exception of alpha-cell area, these morphological changes were fully, or partially, returned to non-diabetic control levels by SL-PYY(1-36). Interestingly, STZ apparently triggered decreased (p < 0.001) alpha- to beta-cell transition in GluCreERT2 ;ROSA26-eYFP mice, together with increased loss of beta-cell identity in Ins1Cre/+;Rosa26-eYFP mice, but both effects were significantly (p < 0.001) reversed by SL-PYY(1-36). SL-PYY(1-36) also apparently reduced (p < 0.05) beta- to alpha-cell conversion in Ins1Cre/+;Rosa26-eYFP mice and glucagon expressing alpha-cells in GluCreERT2 ;ROSA26-eYFP mice. These data indicate that islet benefits of prolonged NPY1R activation, and especially restoration of beta-cell mass, are observed irrespective of diabetes status, being linked to cell lineage alterations including transdifferentiation of alpha- to beta-cells.

From Entero-Endocrine Cell Biology to Surgical Interventional Therapies for Type 2 Diabetes

The physiological roles of the enteroendocrine system in relation to energy and glucose homeostasis regulation have been extensively studied in the past few decades. Considerable advances were made that enabled to disclose the potential use of gastro-intestinal (GI) hormones to target obesity and type 2 diabetes (T2D). The recognition of the clinical relevance of these discoveries has led the pharmaceutical industry to design several hormone analogues to either to mitigate physiological defects or target pharmacologically T2D.Amongst several advances, a major breakthrough in the field was the unexpected observation that enteroendocrine system modulation to T2D target could be achieved by surgically induced anatomical rearrangement of the GI tract. These findings resulted from the widespread use of bariatric surgery procedures for obesity treatment, which despite initially devised to induce weight loss by limiting the systemic availably of nutrients, are now well recognized to influence GI hormone dynamics in a manner that is highly dependent on the type of anatomical rearrangement produced.This chapter will focus on enteroendocrine system related mechanisms leading to improved glycemic control in T2D after bariatric surgery interventions.

Peptide YY (PYY) Is Associated with Cardiovascular Risk in Patients with Acute Myocardial Infarction

AIMS

Recent studies have found circulating concentrations of the gastrointestinal hormone GLP-1 to be an excellent predictor of cardiovascular risk in patients with myocardial infarction. This illustrates a yet not appreciated crosstalk between the gastrointestinal and cardiovascular systems, which requires further investigation. The gut-derived hormone Peptide YY (PYY) is secreted from the same intestinal L-cells as GLP-1. Relevance of PYY in the context of cardiovascular disease has not been explored. In this study, we aimed to investigate PYY serum concentrations in patients with acute myocardial infarction and to evaluate their association with cardiovascular events.

MATERIAL AND METHODS

PYY levels were assessed in 834 patients presenting with acute myocardial infarction (553 Non-ST-Elevation Myocardial Infarction (NSTEMI) and 281 ST-Elevation Myocardial Infarction (STEMI)) at the time of hospital admission. The composite outcomes of first occurrence of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke (3-P-MACE), and all-cause mortality were assessed with a median follow-up of 338 days.

RESULTS

PYY levels were significantly associated with age and cardiovascular risk factors, including hypertension, diabetes, and kidney function in addition to biomarkers of heart failure (NT-pro BNP) and inflammation (hs-CRP). Further, PYY was significantly associated with 3-P-MACE (HR: 1.7; 95% CI: 1-2.97; p = 0.0495) and all-cause mortality (HR: 2.69; 95% CI: 1.61-4.47; p = 0.0001) by univariable Cox regression analyses, which was however lost after adjusting for multiple confounders.

CONCLUSIONS

PYY levels are associated with parameters of cardiovascular risk as well as cardiovascular events and mortality in patients presenting with acute myocardial infarction. However, this significant association is lost after adjustment for further confounders.

Role of GLP-1 Receptor Agonists in Pediatric Obesity: Benefits, Risks, and Approaches to Patient Selection

PURPOSE OF REVIEW

Effective treatments for pediatric obesity are limited. Glucagon-like peptide-1 receptor (GLP-1R) agonists have emerged as therapeutic agents for obesity in adults and have shown benefits outside of weight loss. Here we explore the evidence for GLP-1R agonist use in pediatric obesity.

RECENT FINDINGS

Emerging evidence suggests that GLP-1R agonists have a role in pediatric obesity treatment. A recently published, randomized, placebo-controlled trial found a greater reduction in BMI z-score (- 0.22 SDs) in adolescents receiving liraglutide compared with placebo. As in adults, gastrointestinal adverse effects were commonly seen. GLP-1R agonists appear to perform favorably compared with other approved pharmacological agents for pediatric obesity. However, heterogeneity in weight loss response, cost, side effects, and need for injections may limit their use in many pediatric patients. Rather than broadly applying this therapy if it is approved, we suggest careful patient selection and monitoring by clinicians pending further studies.

Simulating the Post-gastric Bypass Intestinal Microenvironment Uncovers a Barrier-Stabilizing Role for FXR

Regional changes to the intestinal microenvironment brought about by Roux-en-Y gastric bypass (RYGB) surgery may contribute to some of its potent systemic metabolic benefits through favorably regulating various local cellular processes. Here, we show that the intestinal contents of RYGB-operated compared with sham-operated rats region-dependently confer superior glycemic control to recipient germ-free mice in association with suppression of endotoxemia. Correspondingly, they had direct barrier-stabilizing effects on an intestinal epithelial cell line which, bile-exposed intestinal contents, were partly farnesoid X receptor (FXR)-dependent. Further, circulating fibroblast growth factor 19 levels, a readout of intestinal FXR activation, negatively correlated with endotoxemia severity in longitudinal cohort of RYGB patients. These findings suggest that various host- and/or microbiota-derived luminal factors region-specifically and synergistically stabilize the intestinal epithelial barrier following RYGB through FXR signaling, which could potentially be leveraged to better treat endotoxemia-induced insulin resistance in obesity in a non-invasive and more targeted manner.

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RYGB intestinal contents improve glycemia and suppress endotoxemia in GF mice

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RYGB intestinal contents stabilize barrier function and structure in Caco-2 cells

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This is partly FXR-dependent for bile-exposed intestinal contents only

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Plasma bile acids and FGF19 negatively correlate with endotoxemia in RYGB patients