Accumulation of microbial DNAs promotes to islet inflammation and β cell abnormalities in obesity in mice

Effects of bacterial extracellular vesicles derived from oral and gastrointestinal pathogens on systemic diseases

Oral microbiota and gastrointestinal microbiota, the two largest microbiomes in the human body, are closely correlated and frequently interact through the oral-gut axis. Recent research has focused on the roles of these microbiomes in human health and diseases. Under normal conditions, probiotics and commensal bacteria can positively impact health. However, altered physiological states may induce dysbiosis, increasing the risk of pathogen colonization. Studies suggest that oral and gastrointestinal pathogens contribute not only to localized diseases at their respective colonized sites but also to the progression of systemic diseases. However, the mechanisms by which bacteria at these local sites are involved in systemic diseases remain elusive. In response to this gap, the focus has shifted to bacterial extracellular vesicles (BEVs), which act as mediators of communication between the microbiota and the host. Numerous studies have reported the targeted delivery of bacterial pathogenic substances from the oral cavity and the gastrointestinal tract to distant organs via BEVs. These pathogenic components subsequently elicit specific cellular responses in target organs, thereby mediating the progression of systemic diseases. This review aims to elucidate the extensive microbial communication via the oral-gut axis, summarize the types and biogenesis mechanisms of BEVs, and highlight the translocation pathways of oral and gastrointestinal BEVs in vivo, as well as the impacts of pathogens-derived BEVs on systemic diseases.

Rosavin improves insulin resistance and alleviates hepatic and kidney damage via modulating the cGAS-STING pathway and autophagy signaling in HFD/STZ-induced T2DM animals

Background: Inflammation-mediated insulin resistance in type 2 diabetes mellitus (T2DM) increases complications, necessitating investigation of its mechanism to find new safe therapies. This study investigated the effect of rosavin on the autophagy and the cGAS-STING pathway-related signatures (ZBP1, STING1, DDX58, LC3B, TNF-α) and on their epigenetic modifiers (miR-1976 and lncRNA AC074117.2) that were identified from in silico analysis in T2DM animals. Methods: A T2DM rat model was established by combining a high-fat diet (HFD) and streptozotocin (STZ). After four weeks from T2DM induction, HFD/STZ-induced T2DM rats were subdivided into an untreated group (T2DM group) and three treated groups which received 10, 20, or 30 mg per kg of R. rosea daily for 4 weeks. Results: The study found that rosavin can affect the cGAS-STING pathway-related RNA signatures by decreasing the expressions of ZBP1, STING1, DDX58, and miR-1976 while increasing the lncRNA AC074117.2 level in the liver, kidney, and adipose tissues. Rosavin prevented further weight loss, reduced serum insulin and glucose, improved insulin resistance and the lipid panel, and mitigated liver and kidney damage compared to the untreated T2DM group. The treatment also resulted in reduced inflammation levels and improved autophagy manifested by decreased immunostaining of TNF-α and increased immunostaining of LC3B in the liver and kidneys of the treated T2DM rats. Conclusion: Rosavin has shown potential in attenuating T2DM, inhibiting inflammation in the liver and kidneys, and improving metabolic disturbances in a T2DM animal model. The observed effect was linked to the activation of autophagy and suppression of the cGAS-STING pathway.

Tissue-resident bacteria in metabolic diseases: emerging evidence and challenges

Although the impact of the gut microbiome on health and disease is well established, there is controversy regarding the presence of microorganisms such as bacteria and their products in organs and tissues. However, recent contamination-aware findings of tissue-resident microbial signatures provide accumulating evidence in support of bacterial translocation in cardiometabolic disease. The latter provides a distinct paradigm for the link between microbial colonizers of mucosal surfaces and host metabolism. In this Perspective, we re-evaluate the concept of tissue-resident bacteria including their role in metabolic low-grade tissue and systemic inflammation. We examine the limitations and challenges associated with studying low bacterial biomass samples and propose experimental and analytical strategies to overcome these issues. Our Perspective aims to encourage further investigation of the mechanisms linking tissue-resident bacteria to host metabolism and their potentially actionable health implications for prevention and treatment.

Gut-Derived Exosomes Mediate the Microbiota Dysbiosis-Induced Spermatogenesis Impairment by Targeting Meioc in Mice

Diseases like obesity and intestinal inflammation diseases are accompanied by dysbiosis of the gut microbiota (DSGM), which leads to various complications, including systemic metabolic disorders. DSGM reportedly impairs the fertility of male mice; however, the regulatory mechanism is unclear. Exosomes are molecular mediators of intercellular communication, but the regulation of spermatogenesis by non-reproductive tissue-originated exosomes remains unknown. The present study shows that DSGM altered the miRNA expression profile of mouse circulating exosomes and impaired spermatogenesis. Moreover, the single-cell sequencing results indicate that circulating exosomes from mice with DSGM impaired spermatogenesis, while circulating exosomes from wild mice improved spermatogenesis by promoting meiosis. Further study demonstrates that DSGM leads to abnormal upregulation of miR-211-5p in gut-derived circulating exosomes, which inhibited the expression of meiosis-specific with coiled-coil domain (Meioc) in the testes and impaired spermatogenesis by disturbing meiosis process. In summary, this study defines the important role of gut-derived exosomes in connecting the "gut-testis" axis.

Small Intestinal Endocrine Cell Derived Exosomal ACE2 Protects Islet β-Cell Function by Inhibiting the Activation of NLRP3 Inflammasome and Reducing β-Cell Pyroptosis

Background

The "gut-islets axis" is an important endocrine signaling axis that regulates islets function by modulating the gut microbiota and endocrine metabolism within the gut. However, the specific mechanisms and roles of the intestine in islets regulation remain unclear. Recent studies investigated that exosomes derived from gut microbiota can transport signals to remotely regulate islets β-cell function, suggesting the possibility of novel signaling pathways mediated by gut exosomes in the regulation of the "gut-islet axis.".

Methods

The exosomes were isolated from the intestinal enteroendocrine cell-line STC-1cells culture supernatants treated with palmitate acid (PA) or BSA. Metabolic stress models were established by separately subjecting MIN6 cells to PA stimulation and feeding mice with a high-fat diet. Intervention with exosomes in vitro and in vivo to assess the biological effects of exosomes on islets β cells under metabolic stress. The Mas receptor antagonist A779 and ACE2ko mice were used to evaluate the role of exosomal ACE2.

Results

We found ACE2, a molecule that plays a crucial role in the regulation of islets function, is abundantly expressed in exosomes derived from STC-1 under physiological normal condition (NCEO). These exosomes cannot only be taken up by β-cells in vitro but also selectively transported to the islets in vivo. Following intervention with NCEXO, both Min6 cells in a lipotoxic environment and mice on a high-fat diet exhibited significant improvements in islets β-cell function and β-cell mass. Further investigations demonstrated that these protective effects are attributed to exosomal ACE2, as ACE2 inhibits NLRP3 inflammasome activation and reduces β-cell pyroptosis.

Conclusion

ACE2-enriched exosomes from the gut can selectively target islets, subsequently inhibiting NLRP3 inflammasome activation and β cell pyroptosis, thereby restoring islets β cell function under metabolic stress. This study provides novel insights into therapeutic strategies for the prevention and treatment of obesity and diabetes.

Immunoregulation in cancer-associated cachexia

BACKGROUND

Cancer-associated cachexia is a multi-organ disorder associated with progressive weight loss due to a variable combination of anorexia, systemic inflammation and excessive energy wasting. Considering the importance of immunoregulation in cachexia, it still lacks a complete understanding of the immunological mechanisms in cachectic progression.

AIM OF REVIEW

Our aim here is to describe the complex immunoregulatory system in cachexia. We summarize the effects and translational potential of the immune system on the development of cancer-associated cachexia and we attempt to conclude with thoughts on precise and integrated therapeutic strategies under the complex immunological context of cachexia.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review is focused on three main key concepts. First, we highlight the inflammatory factors and additional mediators that have been identified to modulate this syndrome. Second, we decipher the potential role of immune checkpoints in tissue wasting. Third, we discuss the multilayered insights in cachexia through the immunometabolic axis, immune-gut axis and immune-nerve axis.

Irisin delays the onset of type 1 diabetes in NOD mice by enhancing intestinal barrier

Type 1 diabetes (T1D), a complex autoimmune disease, is intricately linked to the gut's epithelial barrier function. Emerging evidence emphasizes the role of irisin, an exercise-related hormone, in preserving intestinal integrity. This study investigates whether irisin could delay T1D onset by enhancing the colon intestinal barrier. Impaired colon intestinal barriers were observed in newly diagnosed T1D patients and non-obese diabetic (NOD) mice, worsening with age and accompanied by islet inflammation. Using an LPS-induced colonic inflammation model, a dose-dependent impact of LPS on colon cells irisin expression, secretion, and barrier function was revealed. Exogenous irisin demonstrated remarkable effects, mitigating islet insulitis, enhancing energy expenditure, and alleviating autoimmune symptoms by reducing colon intestinal permeability. Single-cell RNA sequencing (scRNA-seq) highlighted irisin's positive impact on colon epithelial cell clusters, effectively restoring the intestinal barrier. Irisin also selectively modulated bacterial composition, averting potential bacterial translocation. Mechanistically, irisin enhanced colon intestinal barrier tight junction proteins through the AMPK/PI3K/AKT pathway, with FAM120A playing a crucial role. Irisin upregulated MUC3 expression, a protector against damage and inflammation. Harnessing irisin's exercise-mimicking properties suggests therapeutic potential in clinical settings for preventing T1D progression, offering valuable insights into fortifying the colon's intestinal barrier and managing autoimmune conditions associated with T1DM.

The Regulation Role of the Gut-Islets Axis in Diabetes

The gut-islets axis is an important endocrine signaling axis that regulates the function of islets by modulating the gut micro-environment and its endocrine metabolism. The discovery of intestinal hormones, such as GLP-1 and GIP, has established a preliminary link between the gut and the islet, paving the way for the development of GLP-1 receptor agonists based on the regulation theory of the gut-islets axis for diabetes treatment. This discovery has created a new paradigm for diabetes management and rapidly made the regulation theory of the gut-islets axis a focal point of research attention. Recent years, with in-depth study on gut microbiota and the discovery of intestinal-derived extracellular vesicles, the concept of gut endocrine and the regulation theory of the gut-islets axis have been further expanded and updated, offering tremendous research opportunities. The gut-islets axis refers to the complex interplay between the gut and the islet, which plays a crucial role in regulating glucose homeostasis and maintaining metabolic health. The axis involves various components, including gut microbiota, intestinal hormones, amino acids and ACE2, which contribute to the communication and coordination between the gut and the islet.

Restoring SRSF3 in Kupffer cells attenuates obesity-related insulin resistance

BACKGROUND AND AIMS

In obesity, depletion of KCs expressing CRIg (complement receptor of the Ig superfamily) leads to microbial DNA accumulation, which subsequently triggers tissue inflammation and insulin resistance. However, the mechanism underlying obesity-mediated changes in KC complement immune functions is largely unknown.

APPROACH AND RESULTS

Using KC-specific deactivated Cas9 transgenic mice treated with guide RNA, we assessed the effects of restoring CRIg or the serine/arginine-rich splicing factor 3 (SRSF3) abundance on KC functions and metabolic phenotypes in obese mice. The impacts of weight loss on KC responses were evaluated in a diet switch mouse model. The role of SRSF3 in regulating KC functions was also evaluated using KC-specific SRSF3 knockout mice. Here, we report that overexpression of CRIg in KCs of obese mice protects against bacterial DNA accumulation in metabolic tissues. Mechanistically, SRSF3 regulates CRIg expression, which is essential for maintaining the CRIg+ KC population. During obesity, SRSF3 expression decreases, but it is restored with weight loss through a diet switch, normalizing CRIg+ KCs. KC SRSF3 is also repressed in obese human livers. Lack of SRSF3 in KCs in lean and obese mice decreases their CRIg+ population, impairing metabolic parameters. During the diet switch, the benefits of weight loss are compromised due to SRSF3 deficiency. Conversely, SRSF3 overexpression in obese mice preserves CRIg+ KCs and improves metabolic responses.

CONCLUSIONS

Restoring SRSF3 abundance in KCs offers a strategy against obesity-associated tissue inflammation and insulin resistance by preventing bacterial DNA accumulation.

Gut microbiota in overweight and obesity: crosstalk with adipose tissue

Overweight and obesity are characterized by excessive fat mass accumulation produced when energy intake exceeds energy expenditure. One plausible way to control energy expenditure is to modulate thermogenic pathways in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Among the different environmental factors capable of influencing host metabolism and energy balance, the gut microbiota is now considered a key player. Following pioneering studies showing that mice lacking gut microbes (that is, germ-free mice) or depleted of their gut microbiota (that is, using antibiotics) developed less adipose tissue, numerous studies have investigated the complex interactions existing between gut bacteria, some of their membrane components (that is, lipopolysaccharides), and their metabolites (that is, short-chain fatty acids, endocannabinoids, bile acids, aryl hydrocarbon receptor ligands and tryptophan derivatives) as well as their contribution to the browning and/or beiging of WAT and changes in BAT activity. In this Review, we discuss the general physiology of both WAT and BAT. Subsequently, we introduce how gut bacteria and different microbiota-derived metabolites, their receptors and signalling pathways can regulate the development of adipose tissue and its metabolic capacities. Finally, we describe the key challenges in moving from bench to bedside by presenting specific key examples.

The Role of cGAS-STING Signalling in Metabolic Diseases: from Signalling Networks to Targeted Intervention

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) is a crucial innate defence mechanism against viral infection in the innate immune system, as it principally induces the production of type I interferons. Immune responses and metabolic control are inextricably linked, and chronic low-grade inflammation promotes the development of metabolic diseases. The cGAS-STING pathway activated by double-stranded DNA (dsDNA), cyclic dinucleotides (CDNs), endoplasmic reticulum stress (ER stress), mitochondrial stress, and energy imbalance in metabolic cells and immune cells triggers proinflammatory responses and metabolic disorders. Abnormal overactivation of the pathway is closely associated with metabolic diseases such as obesity, nonalcoholic fatty liver disease (NAFLD), insulin resistance and cardiovascular diseases (CVDs). The interaction of cGAS-STING with other pathways, such as the nuclear factor-kappa B (NF-κB), Jun N-terminal kinase (JNK), AMP-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), autophagy, pyroptosis and insulin signalling pathways, is considered an important mechanism by which cGAS-STING regulates inflammation and metabolism. This review focuses on the link between immune responses related to the cGAS-STING pathway and metabolic diseases and cGAS-STING interaction with other pathways for mediating signal input and affecting output. Moreover, potential inhibitors of the cGAS-STING pathway and therapeutic prospects against metabolic diseases are discussed. This review provides a comprehensive perspective on the involvement of STING in immune-related metabolic diseases.

Gut-bacteria derived membrane vesicles and host metabolic health: a narrative review

The intestinal microbiota, consisting of an estimated 10^10-10^11 organisms, regulate physiological processes involved in digestion, metabolism, and immunity. Surprisingly, these intestinal microorganisms have been found to influence tissues that are not directly in contact with the gut, such as adipose tissue, the liver, skeletal muscle, and the brain. This interaction takes place even when intestinal barrier function is uncompromised. An increasing body of evidence suggests that bacterial membrane vesicles (bMVs), in addition to bacterial metabolites such as short-chain fatty acids, are able to mediate effects of the microbiota on these host tissues. The ability of bMVs to dissipate from the intestinal lumen into systemic circulation hereby facilitates the transport and presentation of bacterial components and metabolites to host organs. Importantly, there are indications that the interaction between bMVs and tissues or immune cells may play a role in the etiology of (chronic metabolic) disease. For example, the gut-derived bMV-mediated induction of insulin resistance in skeletal muscle cells and pro-inflammatory signaling by adipocytes possibly underlies diseases such as type 2 diabetes and obesity. Here, we review the current knowledge on bMVs in the microbiota's effects on host energy/substrate metabolism with a focus on etiological roles in the onset and progression of metabolic disease. We furthermore illustrate that vesicle production by bacterial microbiota could potentially be modulated through lifestyle intervention to improve host metabolism.

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.

The Characteristics, Mechanisms and Therapeutics: Exploring the Role of Gut Microbiota in Obesity

Presently, obesity has emerged as a significant global public health concern due to its escalating prevalence and incidence rates. The gut microbiota, being a crucial environmental factor, has emerged as a key player in the etiology of obesity. Nevertheless, the intricate and specific interactions between obesity and gut microbiota, along with the underlying mechanisms, remain incompletely understood. This review comprehensively summarizes the gut microbiota characteristics in obesity, the mechanisms by which it induces obesity, and explores targeted therapies centered on gut microbiota restoration.

Effects of women with gestational diabetes mellitus related weight gain on pregnancy outcomes and its experiences in weight management programs: a mixed-methods systematic review

Introduction

Proper controlling gestational diabetes mellitus (GDM)-related gestational weight gain (GWG) during pregnancy can optimize pregnancy outcomes and improve postpartum glucose homeostasis. This study aimed to explore the existing intervention programs, the effects on pregnancy outcomes, and the experiences of weight management for GDM-related GWG in women with GDM.

Methods

This mixed-methods systematic review was retrieved from nine databases. The retrieval time was from the database construction to September 20, 2023, and all studies were published in English and Chinese. The included records used quantitative, qualitative, or mixed methods and reported original studies of weight-related intervention regimens, effects on pregnancy outcomes, and women's experiences and perceptions. This review used a convergent segregated approach to synthesize and integrate research findings from Joanna Briggs Institute (JBI) mixed-methods systematic reviews.

Results

There were 16 articles that met the inclusion criteria, and the articles came from seven different countries and included 23,997 women with GDM. The meta-analysis pooled outcomes for the incidence of weight gain exceeding the Institute of Medicine (IOM) recommendations after GDM diagnosis to delivery was 0.31% (95% CI 0.21-0.42). The effectiveness of GDM-related weight interventions in reducing weight gain after GDM diagnosis was supported by quantitative evidence. The GDM-related GWG below the IOM recommendations is a protective factor (OR=0.68, 95%CI 0.48-0.97) for large for gestational Age (LGA), and above the IOM recommendations is a risk factor (OR=1.62, 95%CI 1.15-2.27) for LGA. In addition, no significant statistical significance was found in the pooled outcomes of small for gestational age (SGA). Avoiding excessive weight gain helps to optimize neonatal birth weight, pregnancy outcomes, and maternal blood glucose levels. According to qualitative survey results, some women with GDM experienced weight stigma, and a positive relationship between healthcare providers and GDM women helped in weight management.

Conclusion

Following a diagnosis of GDM, weight management interventions positively affected GWG and pregnancy outcomes. In order to improve compliance and safety of weight management in women with GDM, criteria and interventions for weight gain associated with GDM need to be further explored and improved.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=404492, identifier CRD42023404492.

Microbial sensing in the intestine

The gut microbiota plays a key role in host health and disease, particularly through their interactions with the immune system. Intestinal homeostasis is dependent on the symbiotic relationships between the host and the diverse gut microbiota, which is influenced by the highly co-evolved immune-microbiota interactions. The first step of the interaction between the host and the gut microbiota is the sensing of the gut microbes by the host immune system. In this review, we describe the cells of the host immune system and the proteins that sense the components and metabolites of the gut microbes. We further highlight the essential roles of pattern recognition receptors (PRRs), the G protein-coupled receptors (GPCRs), aryl hydrocarbon receptor (AHR) and the nuclear receptors expressed in the intestinal epithelial cells (IECs) and the intestine-resident immune cells. We also discuss the mechanisms by which the disruption of microbial sensing because of genetic or environmental factors causes human diseases such as the inflammatory bowel disease (IBD).

Dysbiotic Gut Microbiota-Derived Metabolites and Their Role in Non-Communicable Diseases

Dysbiosis, generally defined as the disruption to gut microbiota composition or function, is observed in most diseases, including allergies, cancer, metabolic diseases, neurological disorders and diseases associated with autoimmunity. Dysbiosis is commonly associated with reduced levels of beneficial gut microbiota-derived metabolites such as short-chain fatty acids (SCFA) and indoles. Supplementation with these beneficial metabolites, or interventions to increase their microbial production, has been shown to ameliorate a variety of inflammatory diseases. Conversely, the production of gut 'dysbiotic' metabolites or by-products by the gut microbiota may contribute to disease development. This review summarizes the various 'dysbiotic' gut-derived products observed in cardiovascular diseases, cancer, inflammatory bowel disease, metabolic diseases including non-alcoholic steatohepatitis and autoimmune disorders such as multiple sclerosis. The increased production of dysbiotic gut microbial products, including trimethylamine, hydrogen sulphide, products of amino acid metabolism such as p-Cresyl sulphate and phenylacetic acid, and secondary bile acids such as deoxycholic acid, is commonly observed across multiple diseases. The simultaneous increased production of dysbiotic metabolites with the impaired production of beneficial metabolites, commonly associated with a modern lifestyle, may partially explain the high prevalence of inflammatory diseases in western countries.

Roles of bacterial extracellular vesicles in systemic diseases

Accumulating evidence suggests that in various systems, not all bidirectional microbiota-host interactions involve direct cell contact. Bacterial extracellular vesicles (BEVs) may be key participants in this interkingdom crosstalk. BEVs mediate microbiota functions by delivering effector molecules that modulate host signaling pathways, thereby facilitating host-microbe interactions. BEV production during infections by both pathogens and probiotics has been observed in various host tissues. Therefore, these vesicles released by microbiota may have the ability to drive or inhibit disease pathogenesis in different systems within the host. Here, we review the current knowledge of BEVs and particularly emphasize their interactions with the host and the pathogenesis of systemic diseases.

Recent insights of obesity-induced gut and adipose tissue dysbiosis in type 2 diabetes

An imbalance in microbial homeostasis, referred to as dysbiosis, is critically associated with the progression of obesity-induced metabolic disorders including type 2 diabetes (T2D). Alteration in gut microbial diversity and the abundance of pathogenic bacteria disrupt metabolic homeostasis and potentiate chronic inflammation, due to intestinal leakage or release of a diverse range of microbial metabolites. The obesity-associated shifts in gut microbial diversity worsen the triglyceride and cholesterol level that regulates adipogenesis, lipolysis, and fatty acid oxidation. Moreover, an intricate interaction of the gut-brain axis coupled with the altered microbiome profile and microbiome-derived metabolites disrupt bidirectional communication for instigating insulin resistance. Furthermore, a distinct microbial community within visceral adipose tissue is associated with its dysfunction in obese T2D individuals. The specific bacterial signature was found in the mesenteric adipose tissue of T2D patients. Recently, it has been shown that in Crohn's disease, the gut-derived bacterium Clostridium innocuum translocated to the mesenteric adipose tissue and modulates its function by inducing M2 macrophage polarization, increasing adipogenesis, and promoting microbial surveillance. Considering these facts, modulation of microbiota in the gut and adipose tissue could serve as one of the contemporary approaches to manage T2D by using prebiotics, probiotics, or faecal microbial transplantation. Altogether, this review consolidates the current knowledge on gut and adipose tissue dysbiosis and its role in the development and progression of obesity-induced T2D. It emphasizes the significance of the gut microbiota and its metabolites as well as the alteration of adipose tissue microbiome profile for promoting adipose tissue dysfunction, and identifying novel therapeutic strategies, providing valuable insights and directions for future research and potential clinical interventions.

Microbial-host-isozyme analyses reveal microbial DPP4 as a potential antidiabetic target

A mechanistic understanding of how microbial proteins affect the host could yield deeper insights into gut microbiota-host cross-talk. We developed an enzyme activity-screening platform to investigate how gut microbiota-derived enzymes might influence host physiology. We discovered that dipeptidyl peptidase 4 (DPP4) is expressed by specific bacterial taxa of the microbiota. Microbial DPP4 was able to decrease the active glucagon like peptide-1 (GLP-1) and disrupt glucose metabolism in mice with a leaky gut. Furthermore, the current drugs targeting human DPP4, including sitagliptin, had little effect on microbial DPP4. Using high-throughput screening, we identified daurisoline-d4 (Dau-d4) as a selective microbial DPP4 inhibitor that improves glucose tolerance in diabetic mice.

Gut lumen-leaked microbial DNA causes myocardial inflammation and impairs cardiac contractility in ageing mouse heart

Emerging evidence indicates the critical roles of microbiota in mediating host cardiac functions in ageing, however, the mechanisms underlying the communications between microbiota and cardiac cells during the ageing process have not been fully elucidated. Bacterial DNA was enriched in the cardiomyocytes of both ageing humans and mice. Antibiotic treatment remarkably reduced bacterial DNA abundance in ageing mice. Gut microbial DNA containing extracellular vesicles (mEVs) were readily leaked into the bloodstream and infiltrated into cardiomyocytes in ageing mice, causing cardiac microbial DNA enrichment. Vsig4⁺ macrophages efficiently block the spread of gut mEVs whereas Vsig4⁺ cell population was greatly decreased in ageing mice. Gut mEV treatment resulted in cardiac inflammation and a reduction in cardiac contractility in young Vsig4^-/- mice. Microbial DNA depletion attenuated the pathogenic effects of gut mEVs. cGAS/STING signaling is critical for the effects of microbial DNA. Restoring Vsig4⁺ macrophage population in ageing WT mice reduced cardiac microbial DNA abundance and inflammation and improved heart contractility.

Extracellular vesicle-mediated intercellular and interorgan crosstalk of pancreatic islet in health and diabetes

Diabetes mellitus (DM) is a systemic metabolic disease with high mortality and morbidity. Extracellular vesicles (EVs) have emerged as a novel class of signaling molecules, biomarkers and therapeutic agents. EVs-mediated intercellular and interorgan crosstalk of pancreatic islets plays a crucial role in the regulation of insulin secretion of β-cells and insulin action in peripheral insulin target tissues, maintaining glucose homeostasis under physiological conditions, and it's also involved in pathological changes including autoimmune response, insulin resistance and β-cell failure associated with DM. In addition, EVs may serve as biomarkers and therapeutic agents that respectively reflect the status and improve function and viability of pancreatic islets. In this review, we provide an overview of EVs, discuss EVs-mediated intercellular and interorgan crosstalk of pancreatic islet under physiological and diabetic conditions, and summarize the emerging applications of EVs in the diagnosis and treatment of DM. A better understanding of EVs-mediated intercellular and interorgan communication of pancreatic islets will broaden and enrich our knowledge of physiological homeostasis maintenance as well as the development, diagnosis and treatment of DM.

Mechanism of immune attack in the progression of obesity-related type 2 diabetes

Obesity and overweight are widespread issues in adults, children, and adolescents globally, and have caused a noticeable rise in obesity-related complications such as type 2 diabetes mellitus (T2DM). Chronic low-grade inflammation is an important promotor of the pathogenesis of obesity-related T2DM. This proinflammatory activation occurs in multiple organs and tissues. Immune cell-mediated systemic attack is considered to contribute strongly to impaired insulin secretion, insulin resistance, and other metabolic disorders. This review focused on highlighting recent advances and underlying mechanisms of immune cell infiltration and inflammatory responses in the gut, islet, and insulin-targeting organs (adipose tissue, liver, skeletal muscle) in obesity-related T2DM. There is current evidence that both the innate and adaptive immune systems contribute to the development of obesity and T2DM.

Analysis of mRNA-miRNA-lncRNA differential expression in prediabetes/type 2 diabetes mellitus patients as potential players in insulin resistance

Introduction

Type 2 diabetes mellitus (T2DM) is a major global health concern. It usually develops gradually and is frequently preceded by undetectable pre-diabetes mellitus (pre-DM) stage. The purpose of this study was to identify a novel set of seven candidate genes associated with the pathogenesis of insulin resistance (IR) and pre-DM, followed by their experimental validation in patients' serum samples.

Methods

We used the bioinformatics tools and through a two-step process, we first identified and verified two mRNA candidate genes linked to insulin resistance molecular pathogenesis. Second, we identified a non-coding RNAs related to the selected mRNAs and implicated in the insulin resistance molecular pathways followed by pilot study for the RNA panel differential expression in 66 patients with T2DM, 49 individuals with prediabetes and 45 matched controls using real time PCR.

Results

The levels of expression of TMEM173 and CHUK mRNAs, hsa-miR (-611, -5192, and -1976) miRNAs gradually increased from the healthy control group to the prediabetic group, reaching their maximum levels in the T2DM group (p <10-3), whereas the levels of expression of RP4-605O3.4 and AC074117.2 lncRNAs declined gradually from the healthy control group to the prediabetic group, reaching their lowest levels in the T2DM group (p <10-3). TMEM173, CHUK mRNAs, hsa_miR (-611 & -1976) and RP4-605O3.4 lncRNA were useful in distinguishing insulin resistant from insulin sensitive groups. miR_611 together with RP4-605O3.4 exhibited significant difference in good versus poor glycemic control groups.

Discussion

The presented study provides an insight about this RNA based STING/NOD/IR associated panel that could be used for PreDM-T2DM diagnosis and also as a therapeutic target based on the differences of its expression level in the pre-DM and T2DM stages.

Identification of a novel immune checkpoint molecule V-set immunoglobulin domain-containing 4 that leads to impaired immunity infiltration in pancreatic ductal adenocarcinoma

BACKGROUND

Checkpoint-based immunotherapy has failed to elicit responses in the majority of patients with pancreatic cancer. In our study, we aimed to identify the role of a novel immune checkpoint molecule V-set Ig domain-containing 4 (VSIG4) in pancreatic ductal adenocarcinoma (PDAC).

METHODS

Online datasets and tissue microarray (TMA) were utilized to analyze the expression level of VSIG4 and its correlation with clinical parameters in PDAC. CCK8, transwell assay and wound healing assay were applied to explore the function of VSIG4 in vitro. Subcutaneous, orthotopic xenograft and liver metastasis model was established to explore the function of VSIG4 in vivo. TMA analysis and chemotaxis assay were conducted to uncover the effect of VSIG4 on immune infiltration. Histone acetyltransferase (HAT) inhibitors and si-RNA were applied to investigate factors that regulate the expression of VSIG4.

RESULTS

Both mRNA and protein levels of VSIG4 were higher in PDAC than normal pancreas in TCGA, GEO, HPA datasets and our TMA. VSIG4 showed positive correlations with tumor size, T classification and liver metastasis. Patients with higher VSIG4 expression were related to poorer prognosis. VSIG4 knockdown impaired the proliferation and migration ability of pancreatic cancer cells both in vitro and in vivo. Bioinformatics study showed positive correlation between VSIG4 and infiltration of neutrophil and tumor-associated macrophages (TAMs) in PDAC, and it inhibited the secretion of cytokines. According to our TMA panel, high expression of VSIG4 was correlated with fewer infiltration of CD8⁺ T cells. Chemotaxis assay also showed knockdown of VSIG4 increased the recruitment of total T cells and CD8⁺ T cells. HAT inhibitors and knockdown of STAT1 led to decreased expression of VSIG4.

CONCLUSIONS

Our data indicate that VSIG4 contributes to cell proliferation, migration and resistance to immune attack, thus identified as a promising target for PDAC treatment with good prognostic value.

Puerperium experience and lifestyle in women with gestational diabetes mellitus and overweight/obesity in China: A qualitative study

Introduction

Women with overweight or obesity and gestational diabetes mellitus (GDM) are at a high risk of developing type 2 diabetes mellitus (T2DM) and other metabolic diseases. Healthy postpartum lifestyles in women with GDM are important for effectively preventing early T2DM occurrence; however, few studies and guidelines focus in China on this issue.

Aims

This qualitative study aimed to understand the puerperium experience and lifestyle of women with overweight/obesity and GDM.

Methods

A face-to-face, in-depth, and semi-structured interview was conducted using a hermeneutical phenomenology method to collect data that were analyzed through thematic analysis.

Results

Out of 61 recruited women with overweight/obesity and history of GDM, 14 women underwent an interview and provided detailed descriptions of their lifestyle experiences during puerperium. The interview data were used to generate four themes—puerperium dietary behavior, weight perception and “confinement” behavior, family support, disease knowledge, and perceived risk—and nine sub-themes.

Conclusion

Unhealthy lifestyles, misconceptions about food, the conflict between physical activity and confinement behavior, a lack of social and family support, and low awareness of disease risk are all common among overweight/obese women with a history of GDM. Thus, we emphasized that healthcare providers should provide continuous preventive care from pregnancy to postpartum and promote long-term health in high-risk populations with a history of GDM associated with overweight/obesity.

Modified Signaling of Membrane Formyl Peptide Receptors in NADPH-Oxidase Regulation in Obesity-Resistant Mice

The signaling of membrane receptors is modified in obesity characterized by low-grade inflammation. The obesity-resistant state of organisms is poorly understood. We analyzed the generation of reactive oxygen species (ROS) initiated though membrane formyl peptide receptors (Fpr1, Fpr2) in bone-marrow granulocytes of obesity-resistant mice (ORM). A chemiluminescence assay was used to assess NADPH-oxidase-related intensity of ROS generation. ORM were chosen from animals that received high-fat diets and had metric body parameters as controls (standard diet). High spontaneous ROS production was observed in ORM cells. The EC50 for responses to bacterial or mitochondrial peptide N-formyl-MLF was higher in ORM with and without inflammation vs. the same control groups, indicating an insignificant role of high-affinity Fpr1. Increased responses to synthetic peptide WKYMVM (Fpr2 agonist) were observed in controls with acute inflammation, but they were similar in other groups. Fpr2 was possibly partially inactivated in ORM owing to the inflammatory state. Weakened Fpr1 and Fpr2 signaling via MAPKs was revealed in ORM using specific inhibitors for p38, ERK1/2, and JNK. P38 signaling via Fpr2 was lower in ORM with inflammation. Thus, a high-fat diet modified FPRs' role and suppressed MAPK signaling in NADPH-oxidase regulation in ORM. This result can be useful to understand the immunological features of obesity resistance.

The biology of VSIG4: Implications for the treatment of immune-mediated inflammatory diseases and cancer

V-set and immunoglobulin domain containing 4 (VSIG4), a type I transmembrane receptor exclusively expressed in a subset of tissue-resident macrophages, plays a pivotal role in clearing C3-opsonized pathogens and their byproducts from the circulation. VSIG4 maintains immune homeostasis by suppressing the activation of complement pathways or T cells and inducing regulatory T-cell differentiation, thereby inhibiting the development of immune-mediated inflammatory diseases but enhancing cancer progression. Consequently, VSIG4 exhibits a potential therapeutic effect for immune-mediated inflammatory diseases, but also is regarded as a novel target of immune checkpoint inhibition in cancer therapy. Recently, soluble VSIG4, the extracellular domain of VSIG4, shed from the surface of macrophages, has been found to be a biomarker to define macrophage activation-related diseases. This review mainly summarizes recent new findings of VSIG4 in macrophage phagocytosis and immune homeostasis, and discusses its potential diagnostic and therapeutic usage in infection, inflammation, and cancer.

An Overview of Inter-Tissue and Inter-Kingdom Communication Mediated by Extracellular Vesicles in the Regulation of Mammalian Metabolism

Obesity and type 2 diabetes are associated with defects of insulin action in different tissues or alterations in β-cell secretory capacity that may be triggered by environmental challenges, inadequate lifestyle choices, or an underlying genetic predisposition. In addition, recent data shows that obesity may also be caused by perturbations of the gut microbiota, which then affect metabolic function and energy homeostasis in the host. Maintenance of metabolic homeostasis in complex organisms such as mammals requires organismal-level communication, including between the different organs and the gut microbiota. Extracellular vesicles (EVs) have been identified in all domains of life and have emerged as crucial players in inter-organ and inter-kingdom crosstalk. Interestingly, EVs found in edible vegetables or in milk have been shown to influence gut microbiota or tissue function in mammals. Moreover, there is a multidirectional crosstalk mediated by EVs derived from gut microbiota and body organs that has implications for host health. Untangling this complex signaling network may help implement novel therapies for the treatment of metabolic disease.

Therapeutic modulation of V Set and Ig domain-containing 4 (VSIG4) signaling in immune and inflammatory diseases

Inflammation is the result of acute and chronic stresses, caused by emotional or physical trauma, or nutritional or environmental pollutants, and brings serious harm to human life and health. As an important cellular component of the innate immune barrier, the macrophage plays a key role in maintaining tissue homeostasis and promoting tissue repair by controlling infection and resolving inflammation. Several studies suggest that V Set and Ig domain-containing 4 is specifically expressed in tissue macrophages and is associated with a variety of inflammatory diseases. In this paper, we mainly summarize the recent research on V Set and Ig domain-containing 4 structures, functions, function and roles in acute and chronic inflammatory diseases, and provide a novel therapeutic avenue for the treatment of inflammatory diseases, including nervous system, urinary, respiratory and metabolic diseases.

The role of pathogens in diabetes pathogenesis and the potential of immunoproteomics as a diagnostic and prognostic tool

Diabetes mellitus (DM) is a group of metabolic diseases marked by hyperglycemia, which increases the risk of systemic infections. DM patients are at greater risk of hospitalization and mortality from bacterial, viral, and fungal infections. Poor glycemic control can result in skin, blood, bone, urinary, gastrointestinal, and respiratory tract infections and recurrent infections. Therefore, the evidence that infections play a critical role in DM progression and the hazard ratio for a person with DM dying from any infection is higher. Early diagnosis and better glycemic control can help prevent infections and improve treatment outcomes. Perhaps, half (49.7%) of the people living with DM are undiagnosed, resulting in a higher frequency of infections induced by the hyperglycemic milieu that favors immune dysfunction. Novel diagnostic and therapeutic markers for glycemic control and infection prevention are desirable. High-throughput blood-based immunoassays that screen infections and hyperglycemia are required to guide timely interventions and efficiently monitor treatment responses. The present review aims to collect information on the most common infections associated with DM, their origin, pathogenesis, and the potential of immunoproteomics assays in the early diagnosis of the infections. While infections are common in DM, their role in glycemic control and disease pathogenesis is poorly described. Nevertheless, more research is required to identify novel diagnostic and prognostic markers to understand DM pathogenesis and management of infections. Precise monitoring of diabetic infections by immunoproteomics may provide novel insights into disease pathogenesis and healthy prognosis.

Gut microbial DNA and immune checkpoint gene Vsig4/CRIg are key antagonistic players in healthy aging and age-associated development of hypertension and diabetes

Aims

Aging is associated with the development of insulin resistance and hypertension which may stem from inflammation induced by accumulation of toxic bacterial DNA crossing the gut barrier. The aim of this study was to identify factors counter-regulating these processes. Taking advantage of the Chromogranin A (CgA) knockout (CgA-KO) mouse as a model for healthy aging, we have identified Vsig4 (V-set and immunoglobulin domain containing 4) as the critical checkpoint gene in offsetting age-associated hypertension and diabetes.

Methods and Results

The CgA-KO mice display two opposite aging phenotypes: hypertension but heightened insulin sensitivity at young age, whereas the blood pressure normalizes at older age and insulin sensitivity further improves. In comparison, aging WT mice gradually lost glucose tolerance and insulin sensitivity and developed hypertension. The gut barrier, compromised in aging WT mice, was preserved in CgA KO mice leading to major 35-fold protection against bacterial DNA-induced inflammation. Similarly, RNA sequencing showed increased expression of the Vsig4 gene (which removes bacterial DNA) in the liver of 2-yr-old CgA-KO mice, which may account for the very low accumulation of microbial DNA in the heart. The reversal of hypertension in aging CgA-KO mice likely stems from (i) low accumulation of microbial DNA, (ii) decreased spillover of norepinephrine in the heart and kidneys, and (iii) reduced inflammation.

Conclusion

We conclude that healthy aging relies on protection from bacterial DNA and the consequent low inflammation afforded by CgA-KO. Vsig4 also plays a crucial role in "healthy aging" by counteracting age-associated insulin resistance and hypertension.

Potential Mechanisms of Gut-Derived Extracellular Vesicle Participation in Glucose and Lipid Homeostasis

The intestine participates in the regulation of glucose and lipid metabolism in multiple facets. It is the major site of nutrient digestion and absorption, provides the interface as well as docking locus for gut microbiota, and harbors hormone-producing cells scattered throughout the gut epithelium. Intestinal extracellular vesicles are known to influence the local immune response, whereas their roles in glucose and lipid homeostasis have barely been explored. Hence, this current review summarizes the latest knowledge of cargo substances detected in intestinal extracellular vesicles, and connects these molecules with the fine-tuning regulation of glucose and lipid metabolism in liver, muscle, pancreas, and adipose tissue.

β-cell dynamics in type 2 diabetes and in dietary and exercise interventions

Pancreatic β-cell dysfunction and insulin resistance are two of the major causes of type 2 diabetes (T2D). Recent clinical and experimental studies have suggested that the functional capacity of β-cells, particularly in the first phase of insulin secretion, is a primary contributor to the progression of T2D and its associated complications. Pancreatic β-cells undergo dynamic compensation and decompensation processes during the development of T2D, in which metabolic stresses such as endoplasmic reticulum stress, oxidative stress, and inflammatory signals are key regulators of β-cell dynamics. Dietary and exercise interventions have been shown to be effective approaches for the treatment of obesity and T2D, especially in the early stages. Whilst the targeted tissues and underlying mechanisms of dietary and exercise interventions remain somewhat vague, accumulating evidence has implicated the improvement of β-cell functional capacity. In this review, we summarize recent advances in the understanding of the dynamic adaptations of β-cell function in T2D progression and clarify the effects and mechanisms of dietary and exercise interventions on β-cell dysfunction in T2D. This review provides molecular insights into the therapeutic effects of dietary and exercise interventions on T2D, and more importantly, it paves the way for future research on the related underlying mechanisms for developing precision prevention and treatment of T2D.

The Potential Role of Gut Microbial-Derived Exosomes in Metabolic-Associated Fatty Liver Disease: Implications for Treatment

The prevalence and incidence of metabolic-associated fatty liver disease (MAFLD), a clinically heterogeneous disease whose primary clinical therapies include dietary control and exercise therapy, is increasing worldwide and constitutes a significant medical burden. Gut microbes influence the physiopathological processes of the liver through different mechanisms based on the gut-liver axis. Exosomes are essential carriers of intercellular communication. Most previous studies have focused on adipocyte- and hepatocyte-derived exosomes, while the critical role of microbial-derived exosomes and the molecular mechanisms behind them in MAFLD have received little attention. Therefore, we searched and screened the latest relevant studies in the PubMeb database to elucidate the link between microbial-derived exosomes and the pathogenesis of MAFLD, mainly in terms of insulin resistance, intestinal barrier, inflammatory response, lipid metabolism, and liver fibrosis. The aim was to provide a theoretical framework and support for clinical protocols and innovative drug development.

OUP accepted manuscript

Pattern recognition receptors are critical for the sensing of pathogen-associated molecular patterns or danger-associated molecular patterns and subsequent mounting of innate immunity and shaping of adaptive immunity. The identification of 2′3′-cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) synthase (cGAS) as a major cytosolic DNA receptor is a milestone in the field of DNA sensing. The engagement of cGAS by double-stranded DNA from different origins, including invading pathogens, damaged mitochondria, ruptured micronuclei, and genomic DNA results in the generation of cGAMP and activation of stimulator of interferon genes, which thereby activates innate immunity mainly characterized by the activation of type I interferon response. In recent years, great progress has been made in understanding the subcellular localization and novel functions of cGAS. In this review, we particularly focus on summarizing the multifaceted roles of cGAS in regulating senescence, autophagy, cell stemness, apoptosis, angiogenesis, cell proliferation, antitumor effect, DNA replication, DNA damage repair, micronucleophagy, as well as cell metabolism.