Periodontitis induced by Porphyromonas gingivalis drives periodontal microbiota dysbiosis and insulin resistance via an impaired adaptive immune response.

OBJECTIVE: To identify a causal mechanism responsible for the enhancement of insulin resistance and hyperglycaemia following periodontitis in mice fed a fat-enriched diet. DESIGN: We set-up a unique animal model of periodontitis in C57Bl/6 female mice by infecting the periodontal tissue with specific and alive pathogens like Porphyromonas gingivalis (Pg), Fusobacterium nucleatum and Prevotella intermedia. The mice were then fed with a diabetogenic/non-obesogenic fat-enriched diet for up to 3 months. Alveolar bone loss, periodontal microbiota dysbiosis and features of glucose metabolism were quantified. Eventually, adoptive transfer of cervical (regional) and systemic immune cells was performed to demonstrate the causal role of the cervical immune system. RESULTS: Periodontitis induced a periodontal microbiota dysbiosis without mainly affecting gut microbiota. The disease concomitantly impacted on the regional and systemic immune response impairing glucose metabolism. The transfer of cervical lymph-node cells from infected mice to naive recipients guarded against periodontitis-aggravated metabolic disease. A treatment with inactivated Pg prior to the periodontal infection induced specific antibodies against Pg and protected the mouse from periodontitis-induced dysmetabolism. Finally, a 1-month subcutaneous chronic infusion of low rates of lipopolysaccharides from Pg mimicked the impact of periodontitis on immune and metabolic parameters. CONCLUSIONS: We identified that insulin resistance in the high-fat fed mouse is enhanced by pathogen-induced periodontitis. This is caused by an adaptive immune response specifically directed against pathogens and associated with a periodontal dysbiosis.

Mouse and human CD8(+) CD28(low) regulatory T lymphocytes differentiate in the thymus.

Regulatory T (Treg) lymphocytes play a central role in the control of immune responses and so maintain immune tolerance and homeostasis. In mice, expression of the CD8 co-receptor and low levels of the co-stimulatory molecule CD28 characterizes a Treg cell population that exerts potent suppressive function in vitro and efficiently controls experimental immunopathology in vivo. It has remained unclear if CD8(+) CD28(low) Treg cells develop in the thymus or represent a population of chronically activated conventional T cells differentiating into Treg cells in the periphery, as suggested by their CD28(low) phenotype. We demonstrate that functional CD8(+) CD28(low) Treg cells are present in the thymus and that these cells develop locally and are not recirculating from the periphery. Differentiation of CD8(+) CD28(low) Treg cells requires MHC class I expression on radioresistant but not on haematopoietic thymic stromal cells. In contrast to other Treg cells, CD8(+) CD28(low) Treg cells develop simultaneously with CD8(+) CD28(high) conventional T cells. We also identified a novel homologous naive CD8(+) CD28(low) T-cell population with immunosuppressive properties in human blood and thymus. Combined, our data demonstrate that CD8(+) CD28(low) cells can develop in the thymus of mice and suggest that the same is true in humans.

Immuno-microbiota cross and talk: the new paradigm of metabolic diseases.

Over the last decades the rising occurrence of metabolic diseases throughout the world points to the failure of preventive and therapeutic strategies and of the corresponding molecular and physiological concepts. Therefore, a new paradigm needs to be elucidated. Very recently the intimate cross talk of the intestinal microbiota with the host immune system has opened new avenues. The large diversity of the intestinal microbes' genome, i.e. the metagenome, and the extreme plasticity of the immune system provide a unique balance which, when finely tuned, maintains a steady homeostasis. The discovery that a new microbiota repertoire is one of the causes responsible for the onset of metabolic disease suggests that the relationship with the immune system is impaired. Therefore, we here review the recent arguments that support the view that an alteration in the microbiota to host immune system balance leads to an increased translocation of bacterial antigens towards metabolically active tissues, and could result in a chronic inflammatory state and consequently impaired metabolic functions such as insulin resistance, hepatic fat deposition, insulin unresponsiveness, and excessive adipose tissue development. This imbalance could be at the onset of metabolic disease, and therefore the early treatment of the microbiota dysbiosis or immunomodulatory strategies should prevent and slow down the epidemic of metabolic diseases and hence the corresponding lethal cardiovascular consequences.

Autoimmune regulator (AIRE)-deficient CD8+CD28low regulatory T lymphocytes fail to control experimental colitis.

Mutations in the gene encoding the transcription factor autoimmune regulator (AIRE) are responsible for autoimmune polyendocrinopathy candidiasis ectodermal dystrophy syndrome. AIRE directs expression of tissue-restricted antigens in the thymic medulla and in lymph node stromal cells and thereby substantially contributes to induction of immunological tolerance to self-antigens. Data from experimental mouse models showed that AIRE deficiency leads to impaired deletion of autospecific T-cell precursors. However, a potential role for AIRE in the function of regulatory T-cell populations, which are known to play a central role in prevention of immunopathology, has remained elusive. Regulatory T cells of CD8(+)CD28(low) phenotype efficiently control immune responses in experimental autoimmune and colitis models in mice. Here we show that CD8(+)CD28(low) regulatory T lymphocytes from AIRE-deficient mice are transcriptionally and phenotypically normal and exert efficient suppression of in vitro immune responses, but completely fail to prevent experimental colitis in vivo. Our data therefore demonstrate that AIRE plays an important role in the in vivo function of a naturally occurring regulatory T-cell population.

Metagenome and metabolism: the tissue microbiota hypothesis.

Over the last decade, the research community has revealed the role of a new organ: the intestinal microbiota. It is considered as a symbiont that is part of our organism since, at birth, it educates the immune system and contributes to the development of the intestinal vasculature and most probably the nervous system. With the advent of new generation sequencing techniques, a catalogue of genes that belong to this microbiome has been established that lists more than 5 million non-redundant genes called the metagenome. Using germ free mice colonized with the microbiota from different origins, it has been formally demonstrated that the intestinal microbiota causes the onset of metabolic diseases. Further to the role of point mutations in our genome, the microbiota can explain the on-going worldwide pandemic of obesity and diabetes, its dissemination and family inheritance, as well as the diversity of the associated metabolic phenotypes. More recently, the discovery of bacterial DNA within host tissues, such as the liver, the adipose tissue and the blood, which establishes a tissue microbiota, introduces new opportunities to identify targets and predictive biomarkers based on the host to microbiota interaction, as well as to define new strategies for pharmacological, immunomodulatory vaccines and nutritional applications.

Targeting Tumor Angiogenesis with the Selective VEGFR-3 Inhibitor EVT801 in Combination with Cancer Immunotherapy.

The receptor tyrosine kinase VEGFR-3 plays a crucial role in cancer-induced angiogenesis and lymphangiogenesis, promoting tumor development and metastasis. Here, we report the novel VEGFR-3 inhibitor EVT801 that presents a more selective and less toxic profile than two major inhibitors of VEGFRs (i.e., sorafenib and pazopanib). As monotherapy, EVT801 showed a potent antitumor effect in VEGFR-3-positive tumors, and in tumors with VEGFR-3-positive microenvironments. EVT801 suppressed VEGF-C-induced human endothelial cell proliferation in vitro and tumor (lymph)angiogenesis in different tumor mouse models. In addition to reduced tumor growth, EVT801 decreased tumor hypoxia, favored sustained tumor blood vessel homogenization (i.e., leaving fewer and overall larger vessels), and reduced important immunosuppressive cytokines (CCL4, CCL5) and myeloid-derived suppressor cells (MDSC) in circulation. Furthermore, in carcinoma mouse models, the combination of EVT801 with immune checkpoint therapy (ICT) yielded superior outcomes to either single treatment. Moreover, tumor growth inhibition was inversely correlated with levels of CCL4, CCL5, and MDSCs after treatment with EVT801, either alone or combined with ICT. Taken together, EVT801 represents a promising anti(lymph)angiogenic drug for improving ICT response rates in patients with VEGFR-3 positive tumors. Significance: The VEGFR-3 inhibitor EVT801 demonstrates superior selectivity and toxicity profile than other VEGFR-3 tyrosine kinase inhibitors. EVT801 showed potent antitumor effects in VEGFR-3-positive tumors, and tumors with VEGFR-3-positive microenvironments through blood vessel homogenization, and reduction of tumor hypoxia and limited immunosuppression. EVT801 increases immune checkpoint inhibitors' antitumor effects.

CX3CR1 regulates gut microbiota and metabolism. A risk factor of type 2 diabetes.

OBJECTIVE: The intestinal microbiota to immune system crosstalk is a major regulator of metabolism and hence metabolic diseases. An impairment of the chemokine receptor CX3CR1, as a key regulator shaping intestinal microbiota under normal chow feeding, could be one of the early events of dysglycemia. METHODS: We studied the gut microbiota ecology by sequencing the gut and tissue microbiota. We studied its role in energy metabolism in CX3CR1-deficent and control mice using various bioassays notably the glycemic regulation during fasting and the respiratory quotient as two highly sensitive physiological features. We used antibiotics and prebiotics treatments, and germ free mouse colonization. RESULTS: We identify that CX3CR1 disruption impairs gut microbiota ecology and identified a specific signature associated to the genotype. The glycemic control during fasting and the respiratory quotient throughout the day are deeply impaired. A selected four-week prebiotic treatment modifies the dysbiotic microbiota and improves the fasting state glycemic control of the CX3CR1-deficent mice and following a glucose tolerance test. A 4 week antibiotic treatment also improves the glycemic control as well. Eventually, germ free mice colonized with the microbiota from CX3CR1-deficent mice developed glucose intolerance. CONCLUSIONS: CX3CR1 is a molecular mechanism in the control of the gut microbiota ecology ensuring the maintenance of a steady glycemia and energy metabolism. Its impairment could be an early mechanism leading to gut microbiota dysbiosis and the onset of metabolic disease.

Murine CD8+ regulatory T lymphocytes: the new era.

Regulatory T lymphocytes unequivocally play a major role in the maintenance of immunologic homeostasis. The first descriptions of regulatory T lymphocytes concerned CD8(+) cells, but this field was brought into discredit when some of its central tenets turned out to be erroneous. CD4(+) regulatory T cells took over and, with the help of newly developed molecular tools, rapidly were phenotypically and functionally characterized. We now know that these cells control a large variety of immune responses. However some observations of in vitro or in vivo immune regulation could not be explained with CD4(+) regulatory T cell activity and depended on the action of a variety of CD8(+) T cell populations. In recent years, substantial progress has been made in the phenotypic and functional characterization of CD8(+) regulatory T cells. These cells play a role in the control of intestinal immunity, immunopathology, and autoimmunity, as well as in immune privilege of the eye, in oral tolerance, and in prevention of graft-versus-host disease and graft-rejection. The suppressor effector mechanisms used by these cells are in part shared with CD4(+) regulatory T cells and in part unique to this population. We here review the current literature on naturally occurring and experimentally induced murine CD8(+) regulatory T-cell populations.

Corrupted adipose tissue endogenous myelopoiesis initiates diet-induced metabolic disease.

Activation and increased numbers of inflammatory macrophages, in adipose tissue (AT) are deleterious in metabolic diseases. Up to now, AT macrophages (ATM) accumulation was considered to be due to blood infiltration or local proliferation, although the presence of resident hematopoietic stem/progenitor cells (Lin-/Sca+/c-Kit+; LSK phenotype) in the AT (AT-LSK) has been reported. By using transplantation of sorted AT-LSK and gain and loss of function studies we show that some of the inflammatory ATM inducing metabolic disease, originate from resident AT-LSK. Transplantation of AT-LSK sorted from high fat diet-fed (HFD) mice is sufficient to induce ATM accumulation, and to transfer metabolic disease in control mice. Conversely, the transplantation of control AT-LSK improves both AT-inflammation and glucose homeostasis in HFD mice. Our results clearly demonstrate that resident AT-LSK are one of the key point of metabolic disease, and could thus constitute a new promising therapeutic target to fight against metabolic disease.

Gut Microbiota Cool-Down Burning Fat! The Immune Hypothesis.

Obesity is characterized by gut microbiota dysbiosis and reduced thermogenic activity of brown adipose tissue. A recent study reveals that gut microbiota hampers the emergence of thermogenic brown fat cells named beige cells within white fat depots via a mechanism that involves the control of macrophages and eosinophil infiltration.

Triggering the adaptive immune system with commensal gut bacteria protects against insulin resistance and dysglycemia.

OBJECTIVE: To demonstrate that glycemia and insulin resistance are controlled by a mechanism involving the adaptive immune system and gut microbiota crosstalk. METHODS: We triggered the immune system with microbial extracts specifically from the intestinal ileum contents of HFD-diabetic mice by the process of immunization. 35 days later, immunized mice were fed a HFD for up to two months in order to challenge the development of metabolic features. The immune responses were quantified. Eventually, adoptive transfer of immune cells from the microbiota-immunized mice to naïve mice was performed to demonstrate the causality of the microbiota-stimulated adaptive immune system on the development of metabolic disease. The gut microbiota of the immunized HFD-fed mice was characterized in order to demonstrate whether the manipulation of the microbiota to immune system interaction reverses the causal deleterious effect of gut microbiota dysbiosis on metabolic disease. RESULTS: Subcutaneous injection (immunization procedure) of ileum microbial extracts prevented hyperglycemia and insulin resistance in a dose-dependent manner in response to a HFD. The immunization enhanced the proliferation of CD4 and CD8 T cells in lymphoid organs, also increased cytokine production and antibody secretion. As a mechanism explaining the metabolic improvement, the immunization procedure reversed gut microbiota dysbiosis. Finally, adoptive transfer of immune cells from immunized mice improved metabolic features in response to HFD. CONCLUSIONS: Glycemia and insulin sensitivity can be regulated by triggering the adaptive immunity to microbiota interaction. This reduces the gut microbiota dysbiosis induced by a fat-enriched diet.

The Gut Microbiota Regulates Intestinal CD4 T Cells Expressing RORγt and Controls Metabolic Disease.

A high-fat diet (HFD) induces metabolic disease and low-grade metabolic inflammation in response to changes in the intestinal microbiota through as-yet-unknown mechanisms. Here, we show that a HFD-derived ileum microbiota is responsible for a decrease in Th17 cells of the lamina propria in axenic colonized mice. The HFD also changed the expression profiles of intestinal antigen-presenting cells and their ability to generate Th17 cells in vitro. Consistent with these data, the metabolic phenotype was mimicked in RORγt-deficient mice, which lack IL17 and IL22 function, and in the adoptive transfer experiment of T cells from RORγt-deficient mice into Rag1-deficient mice. We conclude that the microbiota of the ileum regulates Th17 cell homeostasis in the small intestine and determines the outcome of metabolic disease.

Defective NOD2 peptidoglycan sensing promotes diet-induced inflammation, dysbiosis, and insulin resistance.

Pattern recognition receptors link metabolite and bacteria-derived inflammation to insulin resistance during obesity. We demonstrate that NOD2 detection of bacterial cell wall peptidoglycan (PGN) regulates metabolic inflammation and insulin sensitivity. An obesity-promoting high-fat diet (HFD) increased NOD2 in hepatocytes and adipocytes, and NOD2(-/-) mice have increased adipose tissue and liver inflammation and exacerbated insulin resistance during a HFD. This effect is independent of altered adiposity or NOD2 in hematopoietic-derived immune cells. Instead, increased metabolic inflammation and insulin resistance in NOD2(-/-) mice is associated with increased commensal bacterial translocation from the gut into adipose tissue and liver. An intact PGN-NOD2 sensing system regulated gut mucosal bacterial colonization and a metabolic tissue dysbiosis that is a potential trigger for increased metabolic inflammation and insulin resistance. Gut dysbiosis in HFD-fed NOD2(-/-) mice is an independent and transmissible factor that contributes to metabolic inflammation and insulin resistance when transferred to WT, germ-free mice. These findings warrant scrutiny of bacterial component detection, dysbiosis, and protective immune responses in the links between inflammatory gut and metabolic diseases, including diabetes.

Changes in lipoprotein kinetics associated with type 2 diabetes affect the distribution of lipopolysaccharides among lipoproteins.

CONTEXT: Lipopolysaccharides (LPSs) are inflammatory components of the outer membrane of Gram-negative bacteria and, in plasma, are mostly associated with lipoproteins. This association is thought to promote their catabolism while reducing their proinflammatory effects. OBJECTIVES: Our aim was to determine the impact of lipoprotein kinetics on plasma LPS distribution and how it may affect patients with type 2 diabetes mellitus (T2DM). DESIGN: We performed a kinetic study in 30 individuals (16 T2DM patients, 14 controls) and analyzed the impact of changes in lipoprotein kinetics on LPS distribution among lipoproteins. RESULTS: Plasma LPS levels in T2DM patients were not different from those in controls, but LPS distribution in the two groups was different. Patients with T2DM had higher LPS-very low-density lipoprotein (VLDL; 31% ± 7% vs 22% ± 11%, P = .002), LPS-high-density lipoprotein (HDL; 29% ± 9% vs 19% ± 10%, P = .015), free (nonlipoprotein bound) LPS (10% ± 4% vs 7% ± 4%, P = .043) and lower LPS-low-density lipoprotein (LDL; 30% ± 13% vs 52% ± 16%, P = .001). In multivariable analysis, VLDL-LPS was associated with HDL-LPS (P < .0001); LDL-LPS was associated with VLDL-LPS (P = .004), and VLDL apolipoprotein (apo) B100 catabolism (P = .002); HDL-LPS was associated with free LPS (P < .0001) and VLDL-LPS (P = .033); free LPS was associated with HDL-LPS (P < .0001). In a patient featuring a dramatic decrease in VLDL catabolism due to apoA-V mutation, LDL-LPS was severely decreased (0.044 EU/mL vs 0.788 EU/mL in controls). The difference between T2DM patients and controls for LDL-LPS fraction was no longer significant after controlling for VLDL apoB100 total fractional catabolic rate. CONCLUSIONS: Our data suggest that in humans, free LPS transfers first to HDL and then to VLDL, whereas the LPS-bound LDL fraction is mainly derived from VLDL catabolism; the latter may hence represent a LPS catabolic pathway. T2DM patients show lower LDL-LPS secondary to reduced VLDL catabolism, which may represent an impaired catabolic pathway.

CD8+CD28- regulatory T lymphocytes prevent experimental inflammatory bowel disease in mice.

BACKGROUND & AIMS: Immune responses to innocuous intestinal antigens appear tightly controlled by regulatory T lymphocytes. While CD4+ T lymphocytes have recently attracted the most attention, CD8+ regulatory T-cell populations are also believed to play an important role in control of mucosal immunity. However, CD8+ regulatory T-cell function has mainly been studied in vitro and no direct in vivo evidence exists that they can control mucosal immune responses. We investigated the capacity of CD8+CD28- T cells to prevent experimental inflammatory bowel disease (IBD) in mice. METHODS: CD8+CD28- regulatory T cells were isolated from unmanipulated mice and tested for their capacity to inhibit T-cell activation in allogeneic mixed lymphocyte cultures in vitro and to prevent IBD induced by injection of CD4+CD45RB(high) cells into syngeneic immunodeficient RAG-2 mutant mice. RESULTS: CD8+CD28- T lymphocytes inhibited proliferation and interferon gamma production by CD4+ responder T cells in vitro. CD8+CD28- regulatory T cells freshly isolated from spleen or gut efficiently prevented IBD induced by transfer of colitogenic T cells into immunodeficient hosts. Regulatory CD8+CD28- T cells incapable of producing interleukin-10 did not prevent colitis. Moreover, IBD induced with colitogenic T cells incapable of responding to transforming growth factor beta could not be prevented with CD8+CD28- regulatory T cells. CD8+CD28+ T cells did not inhibit in vitro or in vivo immune responses. CONCLUSIONS: Our findings show that naturally occurring CD8+CD28- regulatory T lymphocytes can prevent experimental IBD in mice and suggest that these cells may play an important role in control of mucosal immunity.