Divergent roles for the gut intraepithelial lymphocyte GLP-1R in control of metabolism, microbiota, and T cell-induced inflammation

Gfi1 controls the formation of effector-like CD8+ T cells during chronic infection and cancer

During chronic infection and tumor progression, CD8+ T cells lose their effector functions and become exhausted. These exhausted CD8+ T cells are heterogeneous and comprised of progenitors that give rise to effector-like or terminally-exhausted cells. The precise cues and mechanisms directing subset formation are incompletely understood. Here, we show that growth factor independent-1 (Gfi1) is dynamically regulated in exhausted CD8+ T cells. During chronic LCMV Clone 13 infection, a previously under-described Ly108+CX3CR1+ subset expresses low levels of Gfi1 while other established subsets have high expression. Ly108+CX3CR1+ cells possess distinct chromatin profiles and represent a transitory subset that develops to effector-like and terminally-exhausted cells, a process dependent on Gfi1. Similarly, Gfi1 in tumor-infiltrating CD8+ T cells is required for the formation of terminally differentiated cells and endogenous as well as anti-CTLA-induced anti-tumor responses. Taken together, Gfi1 is a key regulator of the subset formation of exhausted CD8+ T cells.

GLP-1R Agonists and Their Therapeutic Potential in Inflammatory Bowel Disease and Other Immune-Mediated Inflammatory Diseases, a Systematic Review of the Literature

Background/Objectives: GLP-1 receptor agonists (GLP-1RAs) have revolutionized weight loss and shown anti-inflammatory actions in several experimental models of colitis. There has been a wealth of recent data suggesting that GLP-1RA treatment may modify disease outcomes in inflammatory bowel disease (IBD). The aim of this systematic review is to determine if GLP-1RAs can act as a sole or adjunctive agent to induce steroid-free clinical remission in IBD patients. Methods: The PubMed/Medline, Cochrane Clinical Trial, and EMBASE databases were interrogated with a pre-defined search strategy and eligibility criteria to examine the evidence regarding GLP-1RAs' use in IBD and non-IBD immune-mediated inflammatory disease (IMID) patients. Results: While there is a wealth of pre-clinical animal data suggesting that GLP-1RAs can ameliorate experimental colitis, there is a lack of prospective clinical studies on treating active IBD with GLP-1RAs to specifically induce steroid-free clinical remission. Surrogate data on better IBD composite outcomes have been reported with the use of GLP-1RAs, including a lower risk of surgery, hospitalization, corticosteroid use, and/or the initiation of advance therapies. Data from non-IBD IMID patients are only available for the effect of these agonists on psoriatic plaques, with positive signals. Conclusions: The current evidence for the role of GLP-1RAs as a potential anti-inflammatory therapy in IBD is limited, but provides the impetus for much-needed prospective studies and RCTs that include patients with active IBD.

ANMCO statement: semaglutide in the cardio-nephro-metabolic continuum

Semaglutide, a glucagon-like peptide-1 receptor agonist, has emerged as a pivotal therapeutic agent in the management of the cardio-renal-metabolic continuum. Initially developed for glycaemic control in Type 2 diabetes mellitus, its benefits extend far beyond glucose regulation. Clinical trials have demonstrated semaglutide's potential to reduce major adverse cardiovascular events, particularly in overweight/obese patients with high cardiovascular risk, as well as improving functional capacity in patients suffering from heart failure with preserved left ventricular function. Additionally, it has shown promise in improving renal outcomes, such as slowing the progression of albuminuria and reducing the risk of chronic kidney disease in diabetic populations. These effects are likely due to its multifaceted mechanisms, including anti-inflammatory properties, weight reduction, blood pressure lowering, and direct renal protection. This review synthesizes current evidence on semaglutide's role in the interrelated domains of cardiovascular, renal, and metabolic health.

Glucagon-like peptide-1 receptor signaling activation in alveolar type II cells enhances lung development in neonatal rats exposed to hyperoxia

BACKGROUND

Many studies have reported the important role of glucagon-like peptide-1 receptor (GLP-1R) in regulating glucose homeostasis. However, in addition to the pancreas, GLP-1R is distributed in organs such as the lungs. A few researches have reported the mechanism of action of GLP-1R in acute and chronic lung diseases. Nevertheless, its effect on lung development remains unclear. In this research, we aimed to explore the role of GLP-1R in regulating lung development and its potential mechanisms in in vivo and in vitro bronchopulmonary dysplasia (BPD) models.

METHODS

Neonatal Sprague-Dawley rats were divided into hyperoxia (FIO2 = 0.85) and control (FIO2 = 0.21) groups. Lung tissues were extracted at 3, 7, 10, and 14 postnatal days and subjected to hematoxylin and eosin staining for histopathological and morphological observation. Single-cell RNA sequencing was performed to explore the role of GLP-1R in lung development. Western blotting was conducted to assess the expression of GLP-1R, dynamin-related protein 1 (DRP1), and glycolysis-associated enzymes, including phosphofructokinase (PFKM), hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), in the lung tissues, primary alveolar type II (ATII) cells, and RLE-6TN cells. Double immunofluorescence staining was performed to confirm the co-localization of GLP-1R, DRP1, and ATII cells. A Seahorse XF96 metabolic extracellular flux analyzer was used to perform real-time analyses of extracellular acidification rate and oxygen consumption rate in ATII cells isolated from lung tissues and RLE-6TN cells. The adenosine triphosphate (ATP) concentrations in ATII and RLE-6TN cells were measured using an ATP kit. Mitochondria were stained with MitoTracker and observed using HiS-SIM. GLP-1R gene levels in lung tissues, primary ATII cells, and RLE-6TN cells were tested using RT-qPCR. We used MeRIP-qPCR to determine the m6A modification level of GLP-1R mRNA in RLE-6TN cells. A reporter gene was used to verify the modification site and key methyltransferases.

RESULTS

We observed that GLP-1R signaling regulates lung development and plays a key role in ATII cells, particularly after birth. Hyperoxia inhibits GLP-1R protein and gene expression in ATII cells and accelerates BPD development. ATP production decreased and glycolysis levels increased in ATII cells under hyperoxia. Activation of GLP-1R signaling promotes ATP production and downregulates glycolysis by regulating DRP1 induced mitochondria fission. In RLE-6TN cells, we verified that the m6A modification level of GLP-1R mRNA decreased; the modification site was tested by MeRIP-qPCR and was primarily induced by the methyltransferase-like 14 (METTL14).

CONCLUSION

GLP-1R is primarily expressed in ATII cells of neonatal rats and can promote lung development during the early postnatal period. The GLP-1R signaling pathway modulates mitochondrial fission and glucose metabolism in ATII cells under hyperoxia. Hyperoxia can inhibit the activation of GLP-1R by inhibiting m6A methylation during BPD pathogenesis.

GLP-1-based therapies for diabetes, obesity and beyond

Glucagon-like peptide 1 (GLP-1)-based therapies, such as semaglutide and tirzepatide, represent highly effective treatment options for people with type 2 diabetes and obesity, enabling effective control of glucose and weight loss, while reducing cardiovascular and renal morbidity and mortality. The success of these medicines has spurred development of next-generation GLP-1-based drugs, promising greater weight loss, improved tolerability and additional options for the route and frequency of dosing. This Review profiles established and emerging GLP-1-based medicines, discussing optimization of pharmacokinetics and tolerability, engagement of new therapeutically useful pathways and safety aspects. Structurally unique GLP-1-based medicines that achieve substantially greater and rapid weight loss may impact musculoskeletal health, providing a rationale for therapeutics that more selectively target adipose tissue loss while preserving muscle mass and strength. Ongoing clinical trials in peripheral vascular disease, neuropsychiatric and substance use disorders, metabolic liver disease, arthritis, hypertension and neurodegenerative disorders may broaden indications for GLP-1-based therapeutics.

Effects of GLP-1 Analogues and Agonists on the Gut Microbiota: A Systematic Review

BACKGROUND

GLP-1 analogues are a relatively new class of medications that form the cornerstone of diabetes treatment. They possess invaluable glucose-lowering properties without hypoglycemic effects as well as strong cardioprotective effects. The gut microbiome has become the focus of numerous studies, demonstrating its influence not only on the gut but also on the overall well-being of the entire body. However, the effects of GLP-1 analogs on gut microbiota remain uncertain.

SCOPE OF REVIEW

Our systematic review (based on PRISMA guidelines) aimed to gather knowledge on the effects of GLP-1 analogue medications on the composition, richness, and abundance of gut microbiota in both animal and human models.

CONCLUSIONS

Thirty-eight studies were included in this systematic review. GLP-1 analogues have demonstrated a notable impact on the composition, richness, and diversity of gut microbiota. We can conclude, following the obtained research results of our study, that liraglutide promotes the growth of beneficial genera relevant for beneficial metabolic functions. Exenatide and exendin-4 administration showed various effects on the microbiome composition in animal and human studies. In animal models, it increased genera associated with improved metabolism; however, in human models, genera linked to better metabolic functions and escalated inflammation increased. Following dulaglutide administration, increases in Bacteroides, Akkermansia, and Ruminococcus, genera connected to an improved metabolic model, were significant. Finally, varied results were obtained after semaglutide treatment, in which A. muciniphila, known for its positive metabolic functions, increased; however, microbial diversity decreased. Semaglutide treatment provided various results indicating many confounding factors in semaglutide's impact on the gut microbiota. Results varied due to dissimilarities in the studied populations and the duration of the studies. Further research is essential to confirm these findings and to better recognize their implications for the clinical outcomes of patients.

Paeoniflorin: a review of its pharmacology, pharmacokinetics and toxicity in diabetes

The escalating global prevalence of diabetes underscores the urgency of addressing its treatment and associated complications. Paeoniflorin, a monoterpenoid glycoside compound, has garnered substantial attention in recent years owing to its potential therapeutic efficacy in diabetes management. Thus, this study aims to systematically overview the pharmacological effects, pharmacokinetics and toxicity of paeoniflorin in diabetes. Plenty of evidences have verified that paeoniflorin improves diabetes and its complication through reducing blood sugar, enhancing insulin sensitivity, regulating gut microbiota and autophagy, restoration of mitochondrial function, regulation of lipid metabolism, anti-inflammation, anti-oxidative stress, inhibition of apoptosis, immune regulation and so on. Paeoniflorin possess the characteristics of rapid absorption, wide distribution, rapid metabolism and renal excretion. Meanwhile, toxicity studies have suggested that paeoniflorin has low acute toxicity, minimal subacute and chronic toxicity, and no genotoxic or mutational toxic effects. In conclusion, this paper systematically elucidates the potential therapeutic application and safety profile of paeoniflorin in diabetes management.

Gut microbiota regulates gut homeostasis, mucosal immunity and influences immune-related diseases

The intestinal microbiome constitutes a sophisticated and massive ecosystem pivotal for maintaining gastrointestinal equilibrium and mucosal immunity via diverse pathways. The gut microbiota is continuously reshaped by multiple environmental factors, thereby influencing overall wellbeing or predisposing individuals to disease state. Many observations reveal an altered microbiome composition in individuals with autoimmune conditions, coupled with shifts in metabolic profiles, which has spurred ongoing development of therapeutic interventions targeting the microbiome. This review delineates the microbial consortia of the intestine, their role in sustaining gastrointestinal stability, the association between the microbiome and immune-mediated pathologies, and therapeutic modalities focused on microbiome modulation. We emphasize the entire role of the intestinal microbiome in human health and recommend microbiome modulation as a viable strategy for disease prophylaxis and management. However, the application of gut microbiota modification for the treatment of immune-related diseases, such as fecal microbiota transplantation and probiotics, remain quite challenging. Therefore, more research is needed into the role and mechanisms of these therapeutics.

Incretin-based therapeutics for the treatment of neurodegenerative diseases

Neurodegenerative diseases (NDDs) represent a heterogeneous group of disorders characterized by progressive neuronal loss, which results in significant deficits in memory, cognition, motor skills, and sensory functions. As the prevalence of NDDs rises, there is an urgent unmet need for effective therapies. Current drug development approaches primarily target single pathological features of the disease, which could explain the limited efficacy observed in late-stage clinical trials. Originally developed for the treatment of obesity and diabetes, incretin-based therapies, particularly long-acting GLP-1 receptor (GLP-1R) agonists and GLP-1R-gastric inhibitory polypeptide receptor (GIPR) dual agonists, are emerging as promising treatments for NDDs. Despite limited conclusive preclinical evidence, their pleiotropic ability to reduce neuroinflammation, enhance neuronal energy metabolism and promote synaptic plasticity positions them as potential disease-modifying NDD interventions. In anticipation of results from larger clinical trials, continued advances in next-generation incretin mimetics offer the potential for improved brain access and enhanced neuroprotection, paving the way for incretin-based therapies as a future cornerstone in the management of NDDs.

Role of TLRs as signaling cascades to combat infectious diseases: a review

Investigating innate immunity and its signaling transduction is essential to understand inflammation and host defence mechanisms. Toll-like receptors (TLRs), an evolutionarily ancient group of pattern recognition receptors, are crucial for detecting microbial components and initiating immune responses. This review summarizes the mechanisms and outcomes of TLR-mediated signaling, focusing on motifs shared with other immunological pathways, which enhances our understanding of the innate immune system. TLRs recognize molecular patterns in microbial invaders, activate innate immunity and promote antigen-specific adaptive immunity, and each of them triggers unique downstream signaling patterns. Recent advances have highlighted the importance of supramolecular organizing centers (SMOCs) in TLR signaling, ensuring precise cellular responses and pathogen detection. Furthermore, this review illuminates how TLR pathways coordinate metabolism and gene regulation, contributing to adaptive immunity and providing novel insights for next-generation therapeutic strategies. Ongoing studies hold promise for novel treatments against infectious diseases, autoimmune conditions, and cancers.

The immunomodulatory effects of GLP-1 receptor agonists in neurogenerative diseases and ischemic stroke treatment

Glucagon-like peptide-1 (GLP-1) receptor is widely distributed in the digestive system, cardiovascular system, adipose tissue and central nervous system. Numerous GLP-1 receptor-targeting drugs have been investigated in clinical studies for various indications, including type 2 diabetes and obesity (accounts for 70% of the total studies), non-alcoholic steatohepatitis, Alzheimer's disease, and Parkinson's disease. This review presented fundamental information regarding two categories of GLP-1 receptor agonists (GLP-1RAs): peptide-based and small molecule compounds, and elaborated their potential neuroprotective effects by inhibiting neuroinflammation, reducing neuronal apoptosis, and ultimately improving cognitive function in various neurodegenerative diseases. As a new hypoglycemic drug, GLP-1RA has a unique role in reducing the concurrent risk of stroke in T2D patients. Given the infiltration of various peripheral immune cells into brain tissue, particularly in the areas surrounding the infarct lesion, we further investigated the potential immune regulatory mechanisms. GLP-1RA could not only facilitate the M2 polarization of microglia through both direct and indirect pathways, but also modulate the quantity and function of T cell subtypes, including CD4, CD8, and regulatory T cells, resulting into the inhibition of inflammatory responses and the promotion of neuronal regeneration through interleukin-10 secretion. Therefore, we believe that the "Tregs-microglia-neuron/neural precursor cells" axis is instrumental in mediating immune suppression and neuroprotection in the context of ischemic stroke. Given the benefits of rapid diffusion, favorable blood-brain barrier permeability and versatile administration routes, these small molecule compounds will be one of the important candidates of GLP-1RA. We look forward to the further clinical evidence of small molecule GLP-1RA intervention in ischemic stroke or T2D complicated by ischemic stroke.

GLP1 alleviates oleic acid-propelled lipocalin-2 generation by tumor-infiltrating CD8+ T cells to reduce polymorphonuclear MDSC recruitment and enhances viral immunotherapy in pancreatic cancer

Recruitment of polymorphonuclear MDSCs (PMN-MDSCs) in the TME suppresses the antitumor activity of tumor-infiltrating CD8+ T cells (CD8+ TILs). Little is known about the role of antitumoral CD8+ TILs in actively initiating an immune-tolerant microenvironment, particularly in the recruitment of PMN-MDSCs. In this study, we found that immunotherapy-activated CD8+ TILs significantly increased PNM-MDSC infiltration in the TME, resulting in antitumor resistance. When CD8+ T cells are activated, lipocalin-2 (LCN2) expression is strongly upregulated, which significantly enhances PMN-MDSC chemotaxis. Mechanistically, immune activation increased fatty acid synthesis in CD8+ T cells, particularly oleic acid (OA), which induced lysosomal membrane permeabilization, releasing cathepsin B and subsequently activating NF-κB to promote LCN2 expression. Moreover, we showed that glucagon-like peptide 1 (GLP1) effectively inhibited OA synthesis in activated CD8+ T cells, reducing LCN2 production. We then developed a recombinant adenovirus encoding GLP1 (AdV-GLP1), which significantly reduced PMN-MDSC infiltration and reinvigorated the antitumor activity of CD8+ TILs. In various pancreatic cancer models, including subcutaneous, orthotopic, and humanized CDX/PDX models, AdV-GLP1 displayed excellent antitumor efficacy. Our work advances the understanding of how immunotherapy-activated CD8+ TILs initiate PMN-MDSC infiltration and provides a clinically relevant strategy to target this interaction and improve cancer immunotherapy.

Recent advances in incretin-based therapy for MASLD: from single to dual or triple incretin receptor agonists

Clinically effective pharmacological treatment(s) for metabolic dysfunction-associated steatotic liver disease (MASLD) and its progressive form metabolic dysfunction-associated steatohepatitis (MASH) represent a largely unmet need in medicine. Since glucagon-like peptide-1 receptor agonists (GLP-1RAs) have been licensed for the treatment of type 2 diabetes mellitus and obesity, they were one of the first drug classes to be examined in individuals with MASLD/MASH. Successful phase 2 randomised clinical trials with these agents have resulted in progression to phase 3 clinical trials (principally testing the long-term efficacy of subcutaneous semaglutide). Over the last few years, in addition to GLP-1RAs, newer agents with glucose-dependent insulinotropic peptide and/or glucagon receptor agonist functions have been tested, with increasing evidence from phase 2 randomised clinical trials of histological improvements in MASLD/MASH, as well as benefits on MASLD-related extrahepatic complications. Based on this background of evidence, single, dual or triple incretin receptor agonists are becoming an attractive and promising treatment option for MASLD or MASH, particularly in individuals with coexisting obesity or type 2 diabetes mellitus. In this narrative review, we examine the rapidly expanding body of clinical evidence supporting a role of incretin-based pharmacotherapies in delaying or reversing MASH progression. We also discuss the biology of incretins and the putative hepatoprotective mechanisms of incretin-based pharmacotherapies for managing MASLD or MASH.

One step closer to solving the mystery of the anti-inflammatory effects of glucagon-like peptide-1 receptor agonists

Glucagon-like peptide-1 (GLP-1) receptor agonists are antidiabetic drugs that possess a suppressive effect on the progression of atherosclerosis, and it has been thought that their anti-inflammatory effect is involved in their effect, but the detailed mechanism was unknown. Recently, Ben Nasr and colleagues have proposed easily understood mechanism for the anti-inflammatory effect of GLP-1 receptor agonists. They discovered that some normal T cells express GLP-1 receptors on their cell membranes and showed that GLP-1 has an inhibitory effect on T-cell function.

Anorexigenic and anti-inflammatory signaling pathways of semaglutide via the microbiota-gut--brain axis in obese mice

Our study focused on a mouse model of obesity induced by a high-fat diet (HFD). We administered Semaglutide intraperitoneally (Ozempic ®-0.05 mg/Kg-translational dose) every seven days for six weeks. HFD-fed mice had higher blood glucose, lipid profile, and insulin resistance. Moreover, mice fed HFD showed high gut levels of TLR4, NF-kB, TNF-α, IL-1β, and nitrotyrosine and low levels of occludin, indicating intestinal inflammation and permeability, culminating in higher serum levels of IL-1β and LPS. Treatment with semaglutide counteracted the dyslipidemia and insulin resistance, reducing gut and serum inflammatory markers. Structural changes in gut microbiome were determined by 16S rRNA sequencing. Semaglutide reduced the relative abundance of Firmicutes and augmented that of Bacteroidetes. Meanwhile, semaglutide dramatically changed the overall composition and promoted the growth of acetate-producing bacteria (Bacteroides acidifaciens and Blautia coccoides), increasing hypothalamic acetate levels. Semaglutide intervention increased the number of hypothalamic GLP-1R+ neurons that mediate endogenous action on feeding and energy. In addition, semaglutide treatment reversed the hypothalamic neuroinflammation HDF-induced decreasing TLR4/MyD88/NF-κB signaling and JNK and AMPK levels, improving the hypothalamic insulin resistance. Also, semaglutide modulated the intestinal microbiota, promoting the growth of acetate-producing bacteria, inducing high levels of hypothalamic acetate, and increasing GPR43+ /POMC+ neurons. In the ARC, acetate activated the GPR43 and its downstream PI3K-Akt pathway, which activates POMC neurons by repressing the FoxO-1. Thus, among the multifactorial effectors of hypothalamic energy homeostasis, possibly higher levels of acetate derived from the intestinal microbiota contribute to reducing food intake.

Glucagon-Like Peptide-1 Links Ingestion, Homeostasis, and the Heart

Glucagon-like peptide-1 (GLP-1), a hormone released from enteroendocrine cells in the distal small and large intestines in response to nutrients and other stimuli, not only controls eating and insulin release, but is also involved in drinking control as well as renal and cardiovascular functions. Moreover, GLP-1 functions as a central nervous system peptide transmitter, produced by preproglucagon (PPG) neurons in the hindbrain. Intestinal GLP-1 inhibits eating by activating vagal sensory neurons directly, via GLP-1 receptors (GLP-1Rs), but presumably also indirectly, by triggering the release of serotonin from enterochromaffin cells. GLP-1 enhances glucose-dependent insulin release via a vago-vagal reflex and by direct action on beta cells. Finally, intestinal GLP-1 acts on the kidneys to modulate electrolyte and water movements, and on the heart, where it provides numerous benefits, including anti-inflammatory, antiatherogenic, and vasodilatory effects, as well as protection against ischemia/reperfusion injury and arrhythmias. Hindbrain PPG neurons receive multiple inputs and project to many GLP-1R-expressing brain areas involved in reward, autonomic functions, and stress. PPG neuron-derived GLP-1 is involved in the termination of large meals and is implicated in the inhibition of water intake. This review details GLP-1's roles in these interconnected systems, highlighting recent findings and unresolved issues, and integrating them to discuss the physiological and pathological relevance of endogenous GLP-1 in coordinating these functions. As eating poses significant threats to metabolic, fluid, and immune homeostasis, the body needs mechanisms to mitigate these challenges while sustaining essential nutrient intake. Endogenous GLP-1 plays a crucial role in this "ingestive homeostasis."

Immune Dysregulation in Obesity

The immune system plays fundamental roles in maintaining physiological homeostasis. With the increasing prevalence of obesity-a state characterized by chronic inflammation and systemic dyshomeostasis-there is growing scientific and clinical interest in understanding how obesity reshapes immune function. In this review, we propose that obesity is not merely an altered metabolic state but also a fundamentally altered immunological state. We summarize key seminal and recent findings that elucidate how obesity influences immune function, spanning its classical role in microbial defense, its contribution to maladaptive inflammatory diseases such as asthma, and its impact on antitumor immunity. We also explore how obesity modulates immune function within tissue parenchyma, with a particular focus on the role of T cells in adipose tissue. Finally, we consider areas for future research, including investigation of the durable aspects of obesity on immunological function even after weight loss, such as those observed with glucagon-like peptide-1 (GLP-1) receptor agonist treatment. Altogether, this review emphasizes the critical role of systemic metabolism in shaping immune cell functions, with profound implications for tissue homeostasis across various physiological contexts.

Glucose-dependent insulinotropic polypeptide receptor signaling alleviates gut inflammation in mice

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) are gut-derived peptide hormones that potentiate glucose-dependent insulin secretion. The clinical development of GIP receptor-GLP-1 receptor (GIPR-GLP-1R) multiagonists exemplified by tirzepatide and emerging GIPR antagonist-GLP-1R agonist therapeutics such as maritide is increasing interest in the extrapancreatic actions of incretin therapies. Both GLP-1 and GIP modulate inflammation, with GLP-1 also acting locally to alleviate gut inflammation in part through antiinflammatory actions on GLP-1R+ intestinal intraepithelial lymphocytes. In contrast, whether GIP modulates gut inflammation is not known. Here, using gain- and loss-of-function studies, we show that GIP alleviates 5-fluorouracil-induced (5FU-induced) gut inflammation, whereas genetic deletion of Gipr exacerbates the proinflammatory response to 5FU in the murine small bowel (SB). Bone marrow (BM) transplant studies demonstrated that BM-derived Gipr-expressing cells suppress 5FU-induced gut inflammation in the context of global Gipr deficiency. Within the gut, Gipr was localized to nonimmune cells, specifically stromal CD146+ cells. Hence, the extrapancreatic actions of GIPR signaling extend to the attenuation of gut inflammation, findings with potential translational relevance for clinical strategies modulating GIPR action in people with type 2 diabetes or obesity.

The Beneficial Effects of GLP-1 Receptor Agonists Other than Their Anti-Diabetic and Anti-Obesity Properties

As an incretin hormone, Glucagon-like peptide-1 (GLP-1) has obvious effects on blood glucose regulation and weight loss. GLP-1 receptor (GLP-1R) agonists are synthetic products that have similar effects to GLP-1 but are less prone to degradation, and they are widely used in the treatment of type 2 diabetes and obesity. In recent years, different beneficial effects of GLP-1R agonists were discovered, such as reducing ischemia-reperfusion injury, improving the function of various organs, alleviating substance use disorder, affecting tumorigenesis, regulating bone metabolism, changing gut microbiota composition, and prolonging graft survival. Therefore, GLP-1R agonists have great potential for clinical application in various diseases. Here, we briefly summarized the beneficial effects of GLP-1R agonists other than the anti-diabetic and anti-obesity effects.

Glucagon-like peptide-1 agonists: Role of the gut in hypoglycemia unawareness, and the rationale in type 1 diabetes

Type 1 diabetes is increasing and the majority of patients have poor glycemic control. Although advanced technology and nanoparticle use have greatly enhanced insulin delivery and glucose monitoring, weight gain and hypoglycemia remain major challenges and a constant source of concern for patients with type 1 diabetes. Type 1 diabetes shares some pathophysiology with type 2 diabetes, and an overlap has been reported. The above observation created great interest in glucagon-like peptide-1 receptor agonists (GLP-1) as adjuvants for type 1 diabetes. Previous trials confirmed the positive influence of GLP-1 agonists on β cell function. However, hypoglycemia unawareness and dysregulated glucagon response have been previously reported in patients with recurrent hypoglycemia using GLP-1 agonists. Jin et al found that the source of glucagon dysregulation due to GLP-1 agonists resides in the gut. Plausible explanations could be gut nervous system dysregulation or gut microbiota disruption. This review evaluates the potential of GLP-1 agonists in managing type 1 diabetes, particularly focusing on their impact on glycemic control, weight management, and glucagon dysregulation. We provide a broader insight into the problem of type 1 diabetes mellitus management in the light of recent findings and provide future research directions.

The emerging role of gut hormones

The gut is traditionally recognized as the central organ for the digestion and absorption of nutrients, however, it also functions as a significant endocrine organ, secreting a variety of hormones such as glucagon-like peptide 1, serotonin, somatostatin, and glucocorticoids. These gut hormones, produced by specialized intestinal epithelial cells, are crucial not only for digestive processes but also for the regulation of a wide range of physiological functions, including appetite, metabolism, and immune responses. While gut hormones can exert systemic effects, they also play a pivotal role in maintaining local homeostasis within the gut. This review discusses the role of the gut as an endocrine organ, emphasizing the stimuli, the newly discovered functions, and the clinical significance of gut-secreted hormones. Deciphering the emerging role of gut hormones will lead to a better understanding of gut homeostasis, innovative treatments for disorders in the gut, as well as systemic diseases.

Macrophages and T cells in metabolic disorder-associated cancers

Cancer and metabolic disorders have emerged as major global health challenges, reaching epidemic levels in recent decades. Often viewed as separate issues, metabolic disorders are shown by mounting evidence to heighten cancer risk and incidence. The intricacies underlying this connection are still being unraveled and encompass a complex interplay between metabolites, cancer cells and immune cells within the tumour microenvironment (TME). Here, we outline the interplay between metabolic and immune cell dysfunction in the context of three highly prevalent metabolic disorders, namely obesity; two associated liver diseases, metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH); and type 2 diabetes. We focus primarily on macrophages and T cells, the critical roles of which in dictating inflammatory response and immune surveillance in metabolic disorder-associated cancers are widely reported. Moreover, considering the ever-increasing number of patients prescribed with metabolism disorder-altering drugs and diets in recent years, we discuss how these therapies modulate systemic and local immune phenotypes, consequently impacting cancer malignancy. Collectively, unraveling the determinants of metabolic disorder-associated immune landscape and their role in fuelling cancer malignancy will provide a framework essential to therapeutically address these highly prevalent diseases.

Is It Time for a New Algorithm for the Pharmacotherapy of Steroid-Induced Diabetes?

Glucocorticoids (GS) are widely used in multiple medical indications due to their anti-inflammatory, immunosuppressive, and antiproliferative effects. Despite their effectiveness in treating respiratory, skin, joint, renal, and neoplastic diseases, they dysregulate glucose metabolism, leading to steroid-induced diabetes (SID) or a significant increase of glycemia in people with previously diagnosed diabetes. The risk of adverse event development depends on the prior therapy, the duration of the treatment, the form of the drug, and individual factors, i.e., BMI, genetics, and age. Unfortunately, SID and steroid-induced hyperglycemia (SIH) are often overlooked, because the fasting blood glucose level, which is the most commonly used diagnostic test, is insufficient for excluding both conditions. The appropriate control of post-steroid hyperglycemia remains a major challenge in everyday clinical practice. Recently, the most frequently used antidiabetic strategies have been insulin therapy with isophane insulin or multiple injections in the basal-bolus regimen. Alternatively, in patients with lower glycemia, sulphonylureas or glinides were used. Taking into account the pathogenesis of post-steroid-induced hyperglycemia, the initiation of therapy with glucagon-like peptide 1 (GLP-1) analogs and dipeptidyl peptidase 4 (DPP-4) inhibitors should be considered. In this article, we present a universal practical diagnostic algorithm of SID/SIH in patients requiring steroids, in both acute and chronic conditions, and we present a new pharmacotherapy algorithm taking into account the use of all currently available antidiabetic drugs.

Spatiotemporal metabolomic approaches to the cancer-immunity panorama: a methodological perspective

Metabolic reprogramming drives the development of an immunosuppressive tumor microenvironment (TME) through various pathways, contributing to cancer progression and reducing the effectiveness of anticancer immunotherapy. However, our understanding of the metabolic landscape within the tumor-immune context has been limited by conventional metabolic measurements, which have not provided comprehensive insights into the spatiotemporal heterogeneity of metabolism within TME. The emergence of single-cell, spatial, and in vivo metabolomic technologies has now enabled detailed and unbiased analysis, revealing unprecedented spatiotemporal heterogeneity that is particularly valuable in the field of cancer immunology. This review summarizes the methodologies of metabolomics and metabolic regulomics that can be applied to the study of cancer-immunity across single-cell, spatial, and in vivo dimensions, and systematically assesses their benefits and limitations.

The gut microbiota and diabetes: research, translation, and clinical applications - 2023 Diabetes, Diabetes Care, and Diabetologia Expert Forum

This article summarises the state of the science on the role of the gut microbiota (GM) in diabetes from a recent international expert forum organised by Diabetes, Diabetes Care, and Diabetologia, which was held at the European Association for the Study of Diabetes 2023 Annual Meeting in Hamburg, Germany. Forum participants included clinicians and basic scientists who are leading investigators in the field of the intestinal microbiome and metabolism. Their conclusions were as follows: (1) the GM may be involved in the pathophysiology of type 2 diabetes, as microbially produced metabolites associate both positively and negatively with the disease, and mechanistic links of GM functions (e.g. genes for butyrate production) with glucose metabolism have recently emerged through the use of Mendelian randomisation in humans; (2) the highly individualised nature of the GM poses a major research obstacle, and large cohorts and a deep-sequencing metagenomic approach are required for robust assessments of associations and causation; (3) because single time point sampling misses intraindividual GM dynamics, future studies with repeated measures within individuals are needed; and (4) much future research will be required to determine the applicability of this expanding knowledge to diabetes diagnosis and treatment, and novel technologies and improved computational tools will be important to achieve this goal.

GLP-1R agonist therapy and vaccine response: Neglected implications

Glucagon-like peptide-1 receptor agonists (GLP-1RAs), such as semaglutide (Ozempic®), have emerged as effective treatments for diabetes and weight management. However, recent evidence indicates that GLP-1R signalling influences various tissues, including the immune system. Notably, GLP-1 has a short half-life (< 5 minutes) and exists in the picomolar range, while GLP-1RAs like semaglutide have extended half-lives of several days and are administered at supraphysiological doses. This review explores the potential impact of these medications on vaccine efficacy. We examine evidence suggesting that GLP-1RAs may attenuate vaccine responses through direct effects on immune cells and modulation of other tissues. Additionally, we discuss how GLP-1R signalling may create a tolerogenic environment, potentially reducing vaccine immunogenicity. Given the widespread use of GLP-1RAs, it is crucial to understand their impact on immune responses and the translational implications for vaccination outcomes.

The benefits of GLP-1 drugs beyond obesity

Glucagon-like peptide-1-based medicines have weight loss-independent actions.

GLP-1 receptor agonists alleviate colonic inflammation by modulating intestinal microbiota and the function of group 3 innate lymphoid cells

Glucagon-like peptide-1 receptor agonists (GLP-1RAs), which are drugs used for treating type 2 diabetes, have been reported to exert anti-inflammatory effects on inflammatory bowel disease (IBD), the mechanism of which remains elusive. Here, we report that GLP-1RAs ameliorate dextran sulfate sodium (DSS)-induced colitis in both wild-type and T/B-cell-deficient mice through modulating group 3 innate lymphoid cells (ILC3s), a subset of innate lymphoid cells that regulate intestinal immunity. GLP-1RAs promote IL-22 production by ILC3, and the protective effect of GLP-1RAs on DSS-induced colitis was abrogated in ILC3-deficient RORgtgfp/gfp mice. Furthermore, the treatment effect of GLP-RAs on colitis, as well as the generation of IL-22-producing ILC3s by GLP-RAs, is dependent on the gut microbiota. GLP-1RAs increase the abundance of Firmicutes and Proteobacteria in the gut, particularly beneficial bacteria such as Lactobacillus reuteri, and decrease the abundance of enteropathogenic Staphylococcus bacteria. The untargeted gas chromatography (GC)/liquid chromatography (LC)-mass spectrometry (MS) of faecal metabolites further revealed enrichment of N,N-dimethylsphingosine (DMS), an endogenous metabolite derived from sphingosine, in the GLP-1RA-treated group. Strikingly, DMS ameliorates colitis while promoting intestinal IL-22-producing ILC3s. Taken together, our findings show that GLP-1RAs exert a therapeutic effect on colitis possibly by regulating the microbiota-DMS-IL-22+ILC3 axis, highlighting the potential beneficial role of GLP-RAs in inflammatory intestinal disorders with diabetes complications.

Glucagon-like peptide 1 receptor is a T cell-negative costimulatory molecule

Glucagon-like peptide-1 receptor (GLP-1R) is a key regulator of glucose metabolism known to be expressed by pancreatic β cells. We herein investigated the role of GLP-1R on T lymphocytes during immune response. Our data showed that a subset of T lymphocytes expresses GLP-1R, which is upregulated during alloimmune response, similarly to PD-1. When mice received islet or cardiac allotransplantation, an expansion of GLP-1Rpos T cells occurred in the spleen and was found to infiltrate the graft. Additional single-cell RNA sequencing (scRNA-seq) analysis conducted on GLP-1Rpos and GLP-1Rneg CD3+ T cells unveiled the existence of molecular and functional dissimilarities between both subpopulations, as the GLP-1Rpos are mainly composed of exhausted CD8 T cells. GLP-1R acts as a T cell-negative costimulatory molecule, and GLP-1R signaling prolongs allograft survival, mitigates alloimmune response, and reduces T lymphocyte graft infiltration. Notably, GLP-1R antagonism triggered anti-tumor immunity when tested in a preclinical mouse model of colorectal cancer.

Incretin and glucagon receptor polypharmacology in chronic kidney disease

Chronic kidney disease is a debilitating condition associated with significant morbidity and mortality. In recent years, the kidney effects of incretin-based therapies, particularly glucagon-like peptide-1 receptor agonists (GLP-1RAs), have garnered substantial interest in the management of type 2 diabetes and obesity. This review delves into the intricate interactions between the kidney, GLP-1RAs, and glucagon, shedding light on their mechanisms of action and potential kidney benefits. Both GLP-1 and glucagon, known for their opposing roles in regulating glucose homeostasis, improve systemic risk factors affecting the kidney, including adiposity, inflammation, oxidative stress, and endothelial function. Additionally, these hormones and their pharmaceutical mimetics may have a direct impact on the kidney. Clinical studies have provided evidence that incretins, including those incorporating glucagon receptor agonism, are likely to exhibit improved kidney outcomes. Although further research is necessary, receptor polypharmacology holds promise for preserving kidney function through eliciting vasodilatory effects, influencing volume and electrolyte handling, and improving systemic risk factors.

Immunomodulation and inflammation: Role of GLP-1R and GIPR expressing cells within the gut

Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are peptide hormones produced by enteroendocrine cells in the small intestine. Despite being produced in the gut, the leveraging of their role in potentiating glucose-stimulated insulin secretion, also known as the incretin effect, has distracted from discernment of direct intestinal signaling circuits. Both preclinical and clinical evidence have highlighted a role for the incretins in inflammation. In this review, we highlight the discoveries of GLP-1 receptor (GLP-1R)+ natural (TCRαβ and TCRγδ) and induced (TCRαβ+CD4+ cells and TCRαβ+CD8αβ+) intraepithelial lymphocytes. Both endogenous signaling and pharmacological activation of GLP-1R impact local and systemic inflammation, the gut microbiota, whole-body metabolism, as well as the control of GLP-1 bioavailability. While GIPR signaling has been documented to impact hematopoiesis, the impact of these bone marrow-derived cells in gut immunology is not well understood. We uncover gaps in the literature of the evaluation of the impact of sex in these GLP-1R and GIP receptor (GIPR) signaling circuits and provide speculations of the maintenance roles these hormones play within the gut in the fasting-refeeding cycles. GLP-1R agonists and GLP-1R/GIPR agonists are widely used as treatments for diabetes and weight loss, respectively; however, their impact on gut homeostasis has not been fully explored. Advancing our understanding of the roles of GLP-1R and GIPR signaling within the gut at homeostasis as well as metabolic and inflammatory diseases may provide targets to improve disease management.

Anti-Inflammatory Effects of Glucagon-Like Peptide-1 Receptor Agonists via the Neuroimmune Axis

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) have shown efficacy in the treatment of metabolic disease-related complications, partially attributable to their anti-inflammatory properties. However, the specific cell types and pathways involved in these effects were not fully understood. A recent study by Wong et al. demonstrated the importance of the brain GLP-1R in mediating the anti-inflammatory effects of GLP-1RAs in Toll-like receptor and sepsis-mediated inflammation. In this discussion, we review the existing literature on the action of GLP-1RAs in inflammation and explore the implications of these recent findings.

Cyclic Adenosine Monophosphate in Cardiac and Sympathoadrenal GLP-1 Receptor Signaling: Focus on Anti-Inflammatory Effects

Glucagon-like peptide-1 (GLP-1) is a multifunctional incretin hormone with various physiological effects beyond its well-characterized effect of stimulating glucose-dependent insulin secretion in the pancreas. An emerging role for GLP-1 and its receptor, GLP-1R, in brain neuroprotection and in the suppression of inflammation, has been documented in recent years. GLP-1R is a G protein-coupled receptor (GPCR) that couples to Gs proteins that stimulate the production of the second messenger cyclic 3',5'-adenosine monophosphate (cAMP). cAMP, acting through its two main effectors, protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac), exerts several anti-inflammatory (and some pro-inflammatory) effects in cells, depending on the cell type. The present review discusses the cAMP-dependent molecular signaling pathways elicited by the GLP-1R in cardiomyocytes, cardiac fibroblasts, central neurons, and even in adrenal chromaffin cells, with a particular focus on those that lead to anti-inflammatory effects by the GLP-1R. Fully elucidating the role cAMP plays in GLP-1R's anti-inflammatory properties can lead to new and more precise targets for drug development and/or provide the foundation for novel therapeutic combinations of the GLP-1R agonist medications currently on the market with other classes of drugs for additive anti-inflammatory effect.

Advances in Drug Treatments for Companion Animal Obesity

Companion animal obesity has emerged as a significant veterinary health concern globally, with escalating rates posing challenges for preventive and therapeutic interventions. Obesity not only leads to immediate health problems but also contributes to various comorbidities affecting animal well-being and longevity, with consequent emotional and financial burdens on owners. While past treatment strategies have shown limited success, recent breakthroughs in human medicine present new opportunities for addressing this complex issue in companion animals. Here, we discuss the potential of GLP-1 receptor agonists, specifically semaglutide and tirzepatide, already approved for human use, for addressing companion animal obesity. These drugs, originally developed to treat type 2 diabetes in humans and subsequently repurposed to treat obesity, have demonstrated remarkable weight loss effects in rodents, non-human primates and people. Additionally, newer drug combinations have shown even more promising results in clinical trials. Despite current cost and supply challenges, advancements in oral and/or extended-release formulations and increased production may make these drugs more accessible for veterinary use. Thus, these drugs may have utility in companion animal weight management, and future feasibility studies exploring their efficacy and safety in treating companion animal obesity are warranted.

GLP-1R signaling modulates colonic energy metabolism, goblet cell number and survival in the absence of gut microbiota

OBJECTIVES

Gut microbiota increases energy availability through fermentation of dietary fibers to short-chain fatty acids in conventionally raised mice. Energy deficiency in germ-free (GF) mice increases glucagon-like peptide-1 (GLP-1) levels, which slows intestinal transit. To further analyze the role of GLP-1-mediated signaling in this model of energy deficiency, we re-derived mice lacking GLP-1 receptor (GLP-1R KO) as GF.

METHODS

GLP-1R KO mice were rederived as GF through hysterectomy and monitored for 30 weeks. Mice were subjected to rescue experiments either through feeding an energy-rich diet or colonization with a normal cecal microbiota. Histology and intestinal function were assessed at different ages. Intestinal organoids were assessed to investigate stemness.

RESULTS

Unexpectedly, 25% of GF GLP-1R KO mice died before 20 weeks of age, associated with enlarged ceca, increased cecal water content, increased colonic expression of apical ion transporters, reduced number of goblet cells and loss of colonic epithelial integrity. Colonocytes from GLP-1R KO mice were energy-deprived and exhibited increased ER-stress; mitochondrial fragmentation, increased oxygen levels and loss of stemness. Restoring colonic energy levels either by feeding a Western-style diet or colonization with a normal gut microbiota normalized gut phenotypes and prevented lethality.

CONCLUSIONS

Our findings reveal a heretofore unrecognized role for GLP-1R signaling in the maintenance of colonic physiology and survival during energy deprivation.

Intestinal Mucosal Immune Barrier: A Powerful Firewall Against Severe Acute Pancreatitis-Associated Acute Lung Injury via the Gut-Lung Axis

The pathogenesis of severe acute pancreatitis-associated acute lung injury (SAP-ALI), which is the leading cause of mortality among hospitalized patients in the intensive care unit, remains incompletely elucidated. The intestinal mucosal immune barrier is a crucial component of the intestinal epithelial barrier, and its aberrant activation contributes to the induction of sustained pro-inflammatory immune responses, paradoxical intercellular communication, and bacterial translocation. In this review, we firstly provide a comprehensive overview of the composition of the intestinal mucosal immune barrier and its pivotal roles in the pathogenesis of SAP-ALI. Secondly, the mechanisms of its crosstalk with gut microbiota, which is called gut-lung axis, and its effect on SAP-ALI were summarized. Finally, a number of drugs that could enhance the intestinal mucosal immune barrier and exhibit potential anti-SAP-ALI activities were presented, including probiotics, glutamine, enteral nutrition, and traditional Chinese medicine (TCM). The aim is to offer a theoretical framework based on the perspective of the intestinal mucosal immune barrier to protect against SAP-ALI.

Microbiota-gut-brain axis and its therapeutic applications in neurodegenerative diseases

The human gastrointestinal tract is populated with a diverse microbial community. The vast genetic and metabolic potential of the gut microbiome underpins its ubiquity in nearly every aspect of human biology, including health maintenance, development, aging, and disease. The advent of new sequencing technologies and culture-independent methods has allowed researchers to move beyond correlative studies toward mechanistic explorations to shed light on microbiome-host interactions. Evidence has unveiled the bidirectional communication between the gut microbiome and the central nervous system, referred to as the "microbiota-gut-brain axis". The microbiota-gut-brain axis represents an important regulator of glial functions, making it an actionable target to ameliorate the development and progression of neurodegenerative diseases. In this review, we discuss the mechanisms of the microbiota-gut-brain axis in neurodegenerative diseases. As the gut microbiome provides essential cues to microglia, astrocytes, and oligodendrocytes, we examine the communications between gut microbiota and these glial cells during healthy states and neurodegenerative diseases. Subsequently, we discuss the mechanisms of the microbiota-gut-brain axis in neurodegenerative diseases using a metabolite-centric approach, while also examining the role of gut microbiota-related neurotransmitters and gut hormones. Next, we examine the potential of targeting the intestinal barrier, blood-brain barrier, meninges, and peripheral immune system to counteract glial dysfunction in neurodegeneration. Finally, we conclude by assessing the pre-clinical and clinical evidence of probiotics, prebiotics, and fecal microbiota transplantation in neurodegenerative diseases. A thorough comprehension of the microbiota-gut-brain axis will foster the development of effective therapeutic interventions for the management of neurodegenerative diseases.

The suppression of sepsis-induced kidney injury via the knockout of T lymphocytes

Patients with sepsis always have a high mortality rate, and acute kidney injury (AKI) is the main cause of death. It seems obvious that the immune response is involved in this process, but the specific mechanism is unknown, especially the pathogenic role of T cells and B cells needs to be further clarified. Acute kidney injury models induced by lipopolysaccharide were established using T-cell, B-cell, and T&B cell knockout mice to elucidate the role of immune cells in sepsis. Flow cytometry was used to validate the mouse models, and the pathology can confirm renal tubular injury. LPS-induced sepsis caused significant renal pathological damage, Second-generation gene sequencing showed T cells-associated pathway was enriched in sepsis. The renal tubular injury was significantly reduced in T cell and T&B cell knockout mice (BALB/c-nu, Rag1-/-), especially in BALB/c-nu mice, with a decrease in the secretion of inflammatory cytokines in the renal tissue after LPS injection. LPS injection did not produce the same effect after the knockout of B cells. We found that blocking T cells could alleviate inflammation and renal injury caused by sepsis, providing a promising strategy for controlling renal injury.

Central glucagon-like peptide 1 receptor activation inhibits Toll-like receptor agonist-induced inflammation

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert anti-inflammatory effects relevant to the chronic complications of type 2 diabetes. Although GLP-1RAs attenuate T cell-mediated gut and systemic inflammation directly through the gut intraepithelial lymphocyte GLP-1R, how GLP-1RAs inhibit systemic inflammation in the absence of widespread immune expression of the GLP-1R remains uncertain. Here, we show that GLP-1R activation attenuates the induction of plasma tumor necrosis factor alpha (TNF-α) by multiple Toll-like receptor agonists. These actions are not mediated by hematopoietic or endothelial GLP-1Rs but require central neuronal GLP-1Rs. In a cecal slurry model of polymicrobial sepsis, GLP-1RAs similarly require neuronal GLP-1Rs to attenuate detrimental responses associated with sepsis, including sickness, hypothermia, systemic inflammation, and lung injury. Mechanistically, GLP-1R activation leads to reduced TNF-α via α1-adrenergic, δ-opioid, and κ-opioid receptor signaling. These data extend emerging concepts of brain-immune networks and posit a new gut-brain GLP-1R axis for suppression of peripheral inflammation.

The gut ecosystem and immune tolerance

The gastrointestinal tract is home to the largest microbial population in the human body. The gut microbiota plays significant roles in the development of the gut immune system and has a substantial impact on the maintenance of immune tolerance beginning in early life. These microbes interact with the immune system in a dynamic and interdependent manner. They generate immune signals by presenting a vast repertoire of antigenic determinants and microbial metabolites that influence the development, maturation and maintenance of immunological function and homeostasis. At the same time, both the innate and adaptive immune systems are involved in modulating a stable microbial ecosystem between the commensal and pathogenic microorganisms. Hence, the gut microbial population and the host immune system work together to maintain immune homeostasis synergistically. In susceptible hosts, disruption of such a harmonious state can greatly affect human health and lead to various auto-inflammatory and autoimmune disorders. In this review, we discuss our current understanding of the interactions between the gut microbiota and immunity with an emphasis on: a) important players of gut innate and adaptive immunity; b) the contribution of gut microbial metabolites; and c) the effect of disruption of innate and adaptive immunity as well as alteration of gut microbiome on the molecular mechanisms driving autoimmunity in various autoimmune diseases.

Relevance and consequence of chronic inflammation for obesity development

BACKGROUND

Increasing prevalence of morbid obesity accompanied by comorbidities like type 2 diabetes mellitus (T2DM) led to a demand for improving therapeutic strategies and pharmacological intervention options. Apart from genetics, inflammation processes have been hypothesized to be of importance for the development of obesity and related aspects like insulin resistance.

MAIN TEXT

Within this review, we provide an overview of the intricate interplay between chronic inflammation of the adipose tissue and the hypothalamus and the development of obesity. Further understanding of this relationship might improve the understanding of the underlying mechanism and may be of relevance for the establishment of new treatment strategies.

Inulin Inhibits the Inflammatory Response through Modulating Enteric Glial Cell Function in Type 2 Diabetic Mellitus Mice by Reshaping Intestinal Flora

Inulin, a commonly used dietary fiber supplement, is capable of modulating the gut microbiome. Chronic inflammation resulting from metabolic abnormalities and gut flora dysfunction plays a significant role in the development of type 2 diabetes mellitus (T2DM). Our research has demonstrated that inulin administration effectively reduced colonic inflammation in T2DM mice by inducing changes in the gut microbiota and increasing the concentration of butyric acid, which in turn modulated the function of enteric glial cells (EGCs). Experiments conducted on T2DM mice revealed that inulin administration led to an increase in the Bacteroidetes/Firmicutes ratio and the concentration of butyric acid in the colon. The anti-inflammatory effects of altered gastrointestinal flora and its metabolites were further confirmed through fecal microbiota transplantation. Butyric acid was found to inhibit the activation of the κB inhibitor kinase β/nuclear factor κB pathway, regulate the expression levels of interleukin-6 and tumor necrosis factor-α, suppress the abnormal activation of EGCs, and prevent the release of inflammatory factors by EGCs. Similar results were observed in vitro experiments with butyric acid. Our findings demonstrate that inulin, by influencing the intestinal flora, modifies the activity of EGCs to effectively reduce colonic inflammation in T2DM mice.

Incretins and cardiovascular disease: to the heart of type 2 diabetes?

Major cardiovascular outcome trials and real-life observations have proven that glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RAs), regardless of structural GLP-1 homology, exert clinically relevant cardiovascular protection. GLP-1RAs provide cardioprotective benefits through glycaemic and non-glycaemic effects, including improved insulin secretion and action, body-weight loss, blood-pressure lowering and improved lipid profile, as well as via direct effects on the heart and vasculature. These actions are likely combined with anti-inflammatory and antioxidant properties that translate into robust and consistent reductions in atherothrombotic events, particularly in people with type 2 diabetes and established atherosclerotic CVD. GLP-1RAs may also have an impact on obesity and chronic kidney disease, conditions for which cardiovascular risk-reducing options are limited. The available evidence has prompted professional and medical societies to recommend GLP-1RAs for mitigation of the cardiovascular risk in people with type 2 diabetes. This review summarises the clinical evidence for cardiovascular protection with use of GLP-1RAs and the main mechanisms underlying this effect. Moreover, it looks into how the availability of upcoming dual and triple incretin receptor agonists might expand the possibility for cardiovascular protection in people with type 2 diabetes.

Short-chain fatty acids in diseases

Short-chain fatty acids (SCFAs) are the main metabolites produced by bacterial fermentation of dietary fibre in the gastrointestinal tract. The absorption of SCFAs is mediated by substrate transporters, such as monocarboxylate transporter 1 and sodium-coupled monocarboxylate transporter 1, which promote cellular metabolism. An increasing number of studies have implicated metabolites produced by microorganisms as crucial executors of diet-based microbial influence on the host. SCFAs are important fuels for intestinal epithelial cells (IECs) and represent a major carbon flux from the diet, that is decomposed by the gut microbiota. SCFAs play a vital role in multiple molecular biological processes, such as promoting the secretion of glucagon-like peptide-1 by IECs to inhibit the elevation of blood glucose, increasing the expression of G protein-coupled receptors such as GPR41 and GPR43, and inhibiting histone deacetylases, which participate in the regulation of the proliferation, differentiation, and function of IECs. SCFAs affect intestinal motility, barrier function, and host metabolism. Furthermore, SCFAs play important regulatory roles in local, intermediate, and peripheral metabolisms. Acetate, propionate, and butyrate are the major SCFAs, they are involved in the regulation of immunity, apoptosis, inflammation, and lipid metabolism. Herein, we review the diverse functional roles of this major class of bacterial metabolites and reflect on their ability to affect intestine, metabolic, and other diseases. Video Abstract.

Glucagon-like peptide 1 receptor agonists: cardiovascular benefits and mechanisms of action

Type 2 diabetes mellitus (T2DM) and obesity are metabolic disorders characterized by excess cardiovascular risk. Glucagon-like peptide 1 (GLP1) receptor (GLP1R) agonists reduce body weight, glycaemia, blood pressure, postprandial lipaemia and inflammation - actions that could contribute to the reduction of cardiovascular events. Cardiovascular outcome trials (CVOTs) have demonstrated that GLP1R agonists reduce the rates of major adverse cardiovascular events in patients with T2DM. Separate phase III CVOTs of GLP1R agonists are currently being conducted in people living with heart failure with preserved ejection fraction and in those with obesity. Mechanistically, GLP1R is expressed at low levels in the heart and vasculature, raising the possibility that GLP1 might have both direct and indirect actions on the cardiovascular system. In this Review, we summarize the data from CVOTs of GLP1R agonists in patients with T2DM and describe the actions of GLP1R agonists on the heart and blood vessels. We also assess the potential mechanisms that contribute to the reduction in major adverse cardiovascular events in individuals treated with GLP1R agonists and highlight the emerging cardiovascular biology of novel GLP1-based multi-agonists currently in development. Understanding how GLP1R signalling protects the heart and blood vessels will optimize the therapeutic use and development of next-generation GLP1-based therapies with improved cardiovascular safety.

Prenatal lead exposure is negatively associated with the gut microbiome in childhood

Background

Metal exposures are associated with gut microbiome (GM) composition and function, and exposures early in development may be particularly important. Considering the role of the GM in association with many adverse health outcomes, understanding the relationship between prenatal metal exposures and the GM is critically important. However, there is sparse knowledge of the association between prenatal metal exposure and GM later in childhood.

Objectives

This analysis aims to identify associations between prenatal lead (Pb) exposure and GM composition and function in children 9-11 years old.

Methods

Data come from the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) cohort based in Mexico City, Mexico. Prenatal metal concentrations were measured in maternal whole blood drawn during the second and third trimesters of pregnancy. Stool samples collected at 9-11 years old underwent metagenomic sequencing to assess the GM. This analysis uses multiple statistical modeling approaches, including linear regression, permutational analysis of variance, weighted quantile sum regression (WQS), and individual taxa regressions, to estimate the association between maternal blood Pb during pregnancy and multiple aspects of the child GM at 9-11 years old, adjusting for relevant confounders.

Results

Of the 123 child participants in this pilot data analysis, 74 were male and 49 were female. Mean prenatal maternal blood Pb was 33.6 (SE = 2.1) ug/L and 34.9 (SE = 2.1) ug/L at second and third trimesters, respectively. Analysis suggests a consistent negative relationship between prenatal maternal blood Pb and the GM at age 9-11, including measures of alpha and beta diversity, microbiome mixture analysis, and individual taxa. The WQS analysis showed a negative association between prenatal Pb exposure and the gut microbiome, for both second and third trimester exposures (2Tβ = -0.17, 95%CI = [-0.46,0.11]; 3Tβ = -0.17, 95%CI = [-0.44,0.10]). Ruminococcus gnavus, Bifidobacterium longum, Alistipes indistinctus, Bacteroides caccae, and Bifidobacterium bifidum all had weights above the importance threshold from 80% or more of the WQS repeated holdouts in association with both second and third trimester Pb exposure.

Discussion

Pilot data analysis suggests a negative association between prenatal Pb exposure and the gut microbiome later in childhood; however, additional investigation is needed.

Exendin-4 attenuates atherosclerosis progression via controlling hematopoietic stem/progenitor cell proliferation

Beyond glycemic control, applications of glucagon-like peptide-1 receptor (GLP-1r) agonists (GLP-1 RAs) inhibit inflammation and plaque development in murine atherosclerotic models. However, whether they modulate hematopoietic stem/progenitor cells (HSPCs) to prohibit skewed myelopoiesis in hypercholesteremia remains unknown. In this study, GLP-1r expression in fluorescence-activated cell sorting (FACS)-sorted wild-type HSPCs was determined by capillary western blotting. Bone marrow cells (BMCs) of wild-type or GLP-1r-/- mice were transplanted into lethally irradiated low-density lipoprotein receptor deficient (LDLr-/-) recipients followed by high-fat diet (HFD) for chimerism analysis by FACS. In parallel, LDLr-/- mice were placed on HFD for 6 weeks and then treated with saline or Exendin-4 (Ex-4) for another 6 weeks. HSPC frequency and cell cycle were analyzed by FACS, and intracellular metabolite levels were assessed by targeted metabolomics. The results demonstrated that HSPCs expressed GLP-1r and transplantation of GLP-1r-/- BMCs resulted in skewed myelopoiesis in hypercholesterolemic LDLr-/- recipients. In vitro, Ex-4 treatment of FACS-purified HSPCs suppressed cell expansion and granulocyte production induced by LDL. In vivo, Ex-4 treatment inhibited plaque progression, suppressed HSPC proliferation, and modified glycolytic and lipid metabolism in HSPCs of hypercholesteremic LDLr-/- mice. In conclusion, Ex-4 could directly inhibit HSPC proliferation induced by hypercholesteremia.

Prenatal Lead Exposure is Negatively Associated with the Gut Microbiome in Childhood

Background

Metal exposures are associated with gut microbiome (GM) composition and function, and exposures early in development may be particularly important. Considering the role of the GM in association with many adverse health outcomes, understanding the relationship between prenatal metal exposures and the GM is critically important. However, there is sparse knowledge of the association between prenatal metal exposure and GM later in childhood.

Objectives

This analysis aims to identify associations between prenatal lead (Pb) exposure and GM composition and function in children 9-11 years old.

Methods

Data come from the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) cohort based in Mexico City, Mexico. Prenatal metal concentrations were measured in maternal whole blood drawn during the second and third trimesters of pregnancy. Stool samples collected at 9-11 years old underwent metagenomic sequencing to assess the GM. This analysis uses multiple statistical modeling approaches, including linear regression, permutational analysis of variance, weighted quantile sum regression (WQS), and individual taxa regressions, to estimate the association between maternal blood Pb during pregnancy and multiple aspects of the child GM at 9-11 years old, adjusting for relevant confounders.

Results

Of the 123 child participants in this pilot data analysis, 74 were male and 49 were female. Mean prenatal maternal blood Pb was 33.6(SE=2.1) ug/L and 34.9(SE=2.1) ug/L at second and third trimesters, respectively. Analysis suggests a consistent negative relationship between prenatal maternal blood Pb and the GM at age 9-11, including measures of alpha and beta diversity, microbiome mixture analysis, and individual taxa. The WQS analysis showed a negative association between prenatal Pb exposure and the gut microbiome, for both second and third trimester exposures (2Tβ=-0.17,95%CI=[-0.46,0.11]; 3Tβ=-0.17,95%CI=[-0.44,0.10]). Ruminococcus gnavus, Bifidobacterium longum, Alistipes indistinctus, Bacteroides caccae, and Bifidobacterium bifidum all had weights above the importance threshold from 80% or more of the WQS repeated holdouts in association with both second and third trimester Pb exposure.

Discussion

Pilot data analysis suggests a negative association between prenatal Pb exposure and the gut microbiome later in childhood; however, additional investigation is needed.

Beyond the pancreas: contrasting cardiometabolic actions of GIP and GLP1

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP1) exhibit incretin activity, meaning that they potentiate glucose-dependent insulin secretion. The emergence of GIP receptor (GIPR)-GLP1 receptor (GLP1R) co-agonists has fostered growing interest in the actions of GIP and GLP1 in metabolically relevant tissues. Here, we update concepts of how these hormones act beyond the pancreas. The actions of GIP and GLP1 on liver, muscle and adipose tissue, in the control of glucose and lipid homeostasis, are discussed in the context of plausible mechanisms of action. Both the GIPR and GLP1R are expressed in the central nervous system, wherein receptor activation produces anorectic effects enabling weight loss. In preclinical studies, GIP and GLP1 reduce atherosclerosis. Furthermore, GIPR and GLP1R are expressed within the heart and immune system, and GLP1R within the kidney, revealing putative mechanisms linking GIP and GLP1R agonism to cardiorenal protection. We interpret the clinical and mechanistic data obtained for different agents that enable weight loss and glucose control for the treatment of obesity and type 2 diabetes mellitus, respectively, by activating or blocking GIPR signalling, including the GIPR-GLP1R co-agonist tirzepatide, as well as the GIPR antagonist-GLP1R agonist AMG-133. Collectively, we update translational concepts of GIP and GLP1 action, while highlighting gaps, areas of uncertainty and controversies meriting ongoing investigation.