Multiple mechanisms involved in diabetes protection by lipopolysaccharide in non-obese diabetic mice

Intracellular galectin-3 is a lipopolysaccharide sensor that promotes glycolysis through mTORC1 activation

How the carbohydrate binding protein galectin-3 might act as a diabetogenic and tumorogenic factor remains to be investigated. Here we report that intracellular galectin-3 interacts with Rag GTPases and Ragulator on lysosomes. We show that galectin-3 senses lipopolysaccharide (LPS) to facilitate the interaction of Rag GTPases and Ragulator, leading to the activation of mTORC1. We find that the lipopolysaccharide/galectin-3-Rag GTPases/Ragulator-mTORC1 axis regulates a cohort of genes including GLUT1, and HK2, and PKM2 that are critically involved in glucose uptake and glycolysis. Indeed, galectin-3 deficiency severely compromises LPS-promoted glycolysis. Importantly, the expression of HK2 is significantly reduced in diabetes patients. In multiple types of cancer including hepatocellular carcinoma (HCC), galectin-3 is highly expressed, and its level of expression is positively correlated with that of HK2 and PKM2 and negatively correlated with the prognosis of HCC patients. Our study unravels that galectin-3 is a sensor of LPS, an important modulator of the mTORC1 signaling, and a critical regulator of glucose metabolism.

The interferon regulatory factors, a double-edged sword, in the pathogenesis of type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease resulted from the unrestrained inflammatory attack towards the insulin-producing islet β cells. Although the exact etiology underlying T1D remains elusive, viral infections, especially those specific strains of enterovirus, are acknowledged as a critical environmental cue involved in the early phase of disease initiation. Viral infections could either directly impede β cell function, or elicit pathological autoinflammatory reactions for β cell killing. Autoimmune responses are bolstered by a massive body of virus-derived exogenous pathogen-associated molecular patterns (PAMPs) and the presence of β cell-derived damage-associated molecular patterns (DAMPs). In particular, the nucleic acid components and the downstream nucleic acid sensing pathways serve as the major effector mechanism. The endogenous retroviral RNA, mitochondrial DNA (mtDNA) and genomic fragments generated by stressed or dying β cells induce host responses reminiscent of viral infection, a phenomenon termed as viral mimicry during the early stage of T1D development. Given that the interferon regulatory factors (IRFs) are considered as hub transcription factors to modulate immune responses relevant to viral infection, we thus sought to summarize the critical role of IRFs in T1D pathogenesis. We discuss with focus for the impact of IRFs on the sensitivity of β cells to cytokine stimulation, the vulnerability of β cells to viral infection/mimicry, and the intensity of immune response. Together, targeting certain IRF members, alone or together with other therapeutics, could be a promising strategy against T1D.

Bate palmas mutant mice as a model of Kabuki syndrome: Higher susceptibility to infections and vocalization impairments?

The recessive mutant mouse bate palmas (bapa) arose from N-ethyl-N-nitrosourea mutagenesis. Previous studies of our group revealed some behavioral impairments and a mutation in the lysine (K)-specific methyltransferase 2D (Kmt2d) gene. Because mutations in the KMT2D gene in humans are mainly responsible for Kabuki syndrome, this study was proposed to validate bapa mice as a model of Kabuki syndrome. Besides other symptoms, Kabuki syndrome is characterized by increased susceptibility to infections and speech impairments, usually diagnosed in the early childhood. Thus, juvenile male and female bapa mice were studied in different developmental stages (prepubertal period and puberty). To induce sickness behavior and to study infection susceptibility responses, lipopolysaccharide (LPS) was used. To study oral communication, ultrasonic vocalizations were evaluated. Behavioral (open-field test) and central (astrocytic glial fibrillary acidic protein [GFAP] and tyrosine hydroxylase [TH]) evaluations were also performed. Control and bapa female mice emitted 31-kHz ultrasounds on prepubertal period when exploring a novel environment, a frequency not yet described for mice, being defined as 31-kHz exploratory vocalizations. Males, LPS, and puberty inhibited these vocalizations. Bapa mice presented increased motor/exploratory behaviors on prepubertal period due to increased striatal TH expression, revealing striatal dopaminergic system hyperactivity. Combining open-field behavior and GFAP expression, bapa mice did not develop LPS tolerance, that is, they remained expressing signs of sickness behavior after LPS challenge, being more susceptible to infectious/inflammatory processes. It was concluded that bapa mice is a robust experimental model of Kabuki syndrome.

Protective effects of sulfated polysaccharides from Lentinula edodes on the lung and liver of MODS mice

In this work, the effects of sulfated polysaccharides from Lentinula edodes (SPLE) on zymosan (ZYM)-induced multiple organ dysfunction syndrome (MODS) mice were investigated. Using the MODS mice model, biochemical works have already shown that in mice treated with SPLE, the lung parameters of GGT, C3 and hs-CRP were down-regulated and the hepatic parameters of TC, TG, ALT and AST, HDLC, LDL-C and VLDL-C were improved, the serum levels of CK, Cr and Amy were decreased, and the levels of inflammatory factors such as TNF-α, IL-1β, IL-6 and IL-10 were also reduced, the activity of antioxidant enzymes SOD and CAT enhanced, and the content of MDA was reduced. In addition, histopathology of the lung and liver confirmed the beneficial effects of SPLE on MODS mice, indicating that SPLE played a role in protecting the organ function of MODS mice. In addition, SPLE was characterized as a sulfated β-glucan linked by β-type glycosidic bonds. These conclusions indicated that SPLE had effective antioxidant and anti-inflammatory activities, and could be used as a functional food and medicine to prevent MODS.

Oral LPS Dosing Induces Local Immunological Changes in the Pancreatic Lymph Nodes in Mice

Lacking the initial contact between the immune system and microbial-associated molecular patterns (MAMPs), such as lipopolysaccharides (LPS), early in life, may be regarded as one of the causal factors of the increasing global increase in the incidence of autoimmune diseases, such as type 1 diabetes (T1D). Previously, a reduced incidence of T1D accompanied by dramatically increased abundances of both the mucin-metabolising bacterium Akkermansia muciniphila, and LPS-carrying Proteobacteria was observed, when vancomycin was given to pups of nonobese diabetic (NOD) mice. While the T1D incidence reducing effect of A. muciniphila has been shown in further studies, little is known as to whether the increased abundance of LPS-carrying bacteria also has a protective effect. Therefore, we fed NOD pups with Eschericia coli LPS orally from birth to weaning, which decreased the gene expressions of TNFα, IL-10, IL-6, IFNγ, IL-1β, IL-2, IL-4, and FoxP3 in the pancreatic lymph nodes, while the same gene expression profile in the spleen was unaffected. However, no significant difference in the incidence of T1D, gut microbiota composition, or ileum expression of the genetic markers of gut permeability, Claudin8, Occludin, Zonulin-1 (Tjp1), Claudin15, Muc1, and Muc2 were observed in relation to LPS ingestion. It is, therefore, concluded that early life oral E. coli LPS has an impact on the local immune response, which, however, did not influence T1D incidence in NOD mice later in life.

Connecting the immune system, systemic chronic inflammation and the gut microbiome: The role of sex

Unresolved low grade systemic inflammation represents the underlying pathological mechanism driving immune and metabolic pathways involved in autoimmune diseases (AID). Mechanistic studies in animal models of AID and observational studies in patients have found alterations in gut microbiota communities and their metabolites, suggesting a microbial contribution to the onset or progression of AID. The gut microbiota and its metabolites have been shown to influence immune functions and immune homeostasis both within the gut and systematically. Microbial derived-short chain fatty acid (SCFA) and bio-transformed bile acid (BA) have been shown to influence the immune system acting as ligands specific cell signaling receptors like GPRCs, TGR5 and FXR, or via epigenetic processes. Similarly, intestinal permeability (leaky gut) and bacterial translocation are important contributors to chronic systemic inflammation and, without repair of the intestinal barrier, might represent a continuous inflammatory stimulus capable of triggering autoimmune processes. Recent studies indicate gender-specific differences in immunity, with the gut microbiota shaping and being concomitantly shaped by the hormonal milieu governing differences between the sexes. A bi-directional cross-talk between microbiota and the endocrine system is emerging with bacteria being able to produce hormones (e.g. serotonin, dopamine and somatostatine), respond to host hormones (e.g. estrogens) and regulate host hormones' homeostasis (e.g by inhibiting gene prolactin transcription or converting glucocorticoids to androgens). We review herein how gut microbiota and its metabolites regulate immune function, intestinal permeability and possibly AID pathological processes. Further, we describe the dysbiosis within the gut microbiota observed in different AID and speculate how restoring gut microbiota composition and its regulatory metabolites by dietary intervention including prebiotics and probiotics could help in preventing or ameliorating AID. Finally, we suggest that, given consistent observations of microbiota dysbiosis associated with AID and the ability of SCFA and BA to regulate intestinal permeability and inflammation, further mechanistic studies, examining how dietary microbiota modulation can protect against AID, hold considerable potential to tackle increased incidence of AID at the population level.

Treatment of experimental autoimmune myasthenia gravis rats with FTY720 and its effect on Th1/Th2 cells

Myasthenia gravis (MG) is an autoimmune neurological disease that is characterized by the expression of anti-acetylcholine receptor (AChR) antibodies. The immune response at AChRs of neuromuscular junction is disrupted in patients with MG, which manifests as skeletal muscle fatigue and is aggravated following periods of activity and alleviated following rest. Although a novel immune suppressant FTY720 drug, which exhibits strong immune suppression efficacy and minor adverse effects, is available, its role and mechanism in MG have not been elucidated. The aim of this study was to investigate the role of FTY720 in MG. A total of 60 healthy female Lewis rats were randomly assigned into 4 groups: Control group, Model group of experimental autoimmune myasthenia gravis (EAMG), 0.5 mg/kg FTY720-treatment EAMG group and 1.0 mg/kg FTY720‑treatment EAMG group. Body weight and symptoms were examined; Lennon score was used to evaluate improvement of clinical symptoms. Reverse transcription‑quantitative polymerase chain reaction and ELISA were used to test the mRNA and protein expression levels, respectively, of the helper T (Th)1 and Th2 cell cytokines, including interleukin (IL)‑2, interferon (IFN)‑γ, IL‑4 and IL‑6 in thymus tissue and serum. FTY720 treatment improved rat MG symptoms, increased body weight and decreased Lennon score. FTY720 treatments also reduced tissue and serum levels of IL‑2, IFN‑γ and IL‑6, but not IL‑4 expression levels. FTY720 suppressed the inflammatory response and improved EAMG symptoms by inhibiting the secretion of inflammatory factors.

Melioidosis

Burkholderia pseudomallei is a Gram-negative environmental bacterium and the aetiological agent of melioidosis, a life-threatening infection that is estimated to account for ∼89,000 deaths per year worldwide. Diabetes mellitus is a major risk factor for melioidosis, and the global diabetes pandemic could increase the number of fatalities caused by melioidosis. Melioidosis is endemic across tropical areas, especially in southeast Asia and northern Australia. Disease manifestations can range from acute septicaemia to chronic infection, as the facultative intracellular lifestyle and virulence factors of B. pseudomallei promote survival and persistence of the pathogen within a broad range of cells, and the bacteria can manipulate the host's immune responses and signalling pathways to escape surveillance. The majority of patients present with sepsis, but specific clinical presentations and their severity vary depending on the route of bacterial entry (skin penetration, inhalation or ingestion), host immune function and bacterial strain and load. Diagnosis is based on clinical and epidemiological features as well as bacterial culture. Treatment requires long-term intravenous and oral antibiotic courses. Delays in treatment due to difficulties in clinical recognition and laboratory diagnosis often lead to poor outcomes and mortality can exceed 40% in some regions. Research into B. pseudomallei is increasing, owing to the biothreat potential of this pathogen and increasing awareness of the disease and its burden; however, better diagnostic tests are needed to improve early confirmation of diagnosis, which would enable better therapeutic efficacy and survival.

Effect of T helper cell 1/T helper cell 2 balance and nuclear factor-κB on white matter injury in premature neonates

Incidence of white matter injury (WMI), which is featured as softening of white matter tissues, has recently increased. Previous studies have demonstrated a close correlation between T helper cell 1 and T helper cell 2 (Th1/Th2) imbalance and nuclear factor‑κB (NF‑κB) with brain disease. Their role in premature WMI, however, remains to be illustrated. Serum samples were collected from 60 premature WMI neonates, plus another control group of 60 premature babies without WMI. Patients were further divided into mild, moderate and severe WMI groups. Reverse transcription quantitative polymerase chain reaction was used to test mRNA expression levels of Th1/Th2 cytokines, including interleukin 2 (IL)‑2, tumor necrosis factor‑α (TNF‑α), IL‑4, IL‑10 and nuclear factor (NF)‑κB, whilst their serum levels were measured by ELISA. Their correlation with disease occurrence and progression were further analysed, to illustrate the effect of Th1/Th2 balance and NF‑κB on pathology of premature WMI. Serum levels of IL‑4 and IL‑10 were significantly decreased in premature WMI babies, whilst IL‑2, TNF‑α and NF‑κB were upregulated (P<0.05 vs. control group). With aggravated disease, IL‑4 and IL‑10 expression was further decreased while IL‑2, TNF‑α and NF‑κB were increased (P<0.05 vs. mild WMI group). Th1 cytokines IL‑2 and TNF‑α and NF‑κB were negatively correlated with Th2 cytokines IL‑4 and IL‑10. Disease severity was positively correlated with IL‑2, TNF‑α and NF‑κB expression, and was negatively correlated with IL‑4 and IL‑10 (P<0.05). Th1/Th2 imbalance and NF‑κB upregulation were observed in WMI pathogenesis, with elevated secretion of Th1 cytokines and decreased Th2 cytokines, suggesting that Th1/Th2 imbalance and NF‑κB upregulation may be a potential indicator for the early diagnosis and treatment of WMI pathogenesis and progression.

LPS priming in early life decreases antigen uptake of dendritic cells via NO production

Immunological mechanisms of hygiene hypothesis are expected to develop a novel strategy for allergy prevention. Although a large number of studies has investigated the relation between allergies and infection, little is known about the influence of the exposure to infections on antigen uptake by dendritic cells (DCs). In this study, we examined the effect of lipopolysaccharide (LPS) priming in early life on the antigen uptake ability of DCs by using an original mouse model. LPS priming in juvenile mice decreased the migration of antigen-capturing CD11c⁺ cells in the lymph nodes, but not in aged mice. Besides, the bone marrow-derived DCs (BMDCs) from juvenile LPS-primed mice had the poor antigen uptake ability, and constitutively produced NO through the inducible nitric oxide synthase (iNOS). Interestingly, the LPS priming-induced poor antigen uptake of BMDCs was mimicked by the NO donor, and recovered by the iNOS inhibitor. Additionally, LPS priming in juvenile mice prevented the allergic reactions, but not in aged mice. Our results suggested that an exposure to infections in early life prevents allergy through the alteration of the BM cells fate that is to induce the differentiation of BM cells into inhibitory DCs such as NO-producing DCs.

Is There a Role for Bioactive Lipids in the Pathobiology of Diabetes Mellitus?

Inflammation, decreased levels of circulating endothelial nitric oxide (eNO) and brain-derived neurotrophic factor (BDNF), altered activity of hypothalamic neurotransmitters (including serotonin and vagal tone) and gut hormones, increased concentrations of free radicals, and imbalance in the levels of bioactive lipids and their pro- and anti-inflammatory metabolites have been suggested to play a role in diabetes mellitus (DM). Type 1 diabetes mellitus (type 1 DM) is due to autoimmune destruction of pancreatic β cells because of enhanced production of IL-6 and tumor necrosis factor-α (TNF-α) and other pro-inflammatory cytokines released by immunocytes infiltrating the pancreas in response to unknown exogenous and endogenous toxin(s). On the other hand, type 2 DM is due to increased peripheral insulin resistance secondary to enhanced production of IL-6 and TNF-α in response to high-fat and/or calorie-rich diet (rich in saturated and trans fats). Type 2 DM is also associated with significant alterations in the production and action of hypothalamic neurotransmitters, eNO, BDNF, free radicals, gut hormones, and vagus nerve activity. Thus, type 1 DM is because of excess production of pro-inflammatory cytokines close to β cells, whereas type 2 DM is due to excess of pro-inflammatory cytokines in the systemic circulation. Hence, methods designed to suppress excess production of pro-inflammatory cytokines may form a new approach to prevent both type 1 and type 2 DM. Roux-en-Y gastric bypass and similar surgeries ameliorate type 2 DM, partly by restoring to normal: gut hormones, hypothalamic neurotransmitters, eNO, vagal activity, gut microbiota, bioactive lipids, BDNF production in the gut and hypothalamus, concentrations of cytokines and free radicals that results in resetting glucose-stimulated insulin production by pancreatic β cells. Our recent studies suggested that bioactive lipids, such as arachidonic acid, eicosapentaneoic acid, and docosahexaenoic acid (which are unsaturated fatty acids) and their anti-inflammatory metabolites: lipoxin A4, resolvins, protectins, and maresins, may have antidiabetic actions. These bioactive lipids have anti-inflammatory actions, enhance eNO, BDNF production, restore hypothalamic dysfunction, enhance vagal tone, modulate production and action of ghrelin, leptin and adiponectin, and influence gut microbiota that may explain their antidiabetic action. These pieces of evidence suggest that methods designed to selectively deliver bioactive lipids to pancreatic β cells, gut, liver, and muscle may prevent type 1 and type 2 DM.

Immune and Metabolic Regulation Mechanism of Dangguiliuhuang Decoction against Insulin Resistance and Hepatic Steatosis

Dangguiliuhuang decoction (DGLHD) is a traditional Chinese medicine (TCM) formula, which mainly consists of angelica, radix rehmanniae, radix rehmanniae praeparata, scutellaria baicalensis, coptis chinensis, astragalus membranaceus, and golden cypress, and used for the treatment of diabetes and some autoimmune diseases. In this study, we explored the potential mechanism of DGLHD against insulin resistance and fatty liver in vivo and in vitro. Our data revealed that DGLHD normalized glucose and insulin level, increased the expression of adiponectin, diminished fat accumulation and lipogenesis, and promoted glucose uptake. Metabolomic analysis also demonstrated that DGLHD decreased isoleucine, adenosine, and cholesterol, increased glutamine levels in liver and visceral adipose tissue (VAT) of ob/ob mice. Importantly, DGLHD promoted the shift of pro-inflammatory to anti-inflammatory cytokines, suppressed T lymphocytes proliferation, and enhanced regulatory T cells (Tregs) differentiation. DGLHD also inhibited dendritic cells (DCs) maturation, attenuated DCs-stimulated T cells proliferation and secretion of IL-12p70 cytokine from DCs, and promoted the interaction of DCs with Tregs. Further studies indicated that the changed PI3K/Akt signaling pathway and elevated PPAR-γ expression were not only observed with the ameliorated glucose and lipid metabolism in adipocytes and hepatocytes, but also exhibited in DCs and T cells by DGLHD. Collectively, our results suggest that DGLHD exerts anti-insulin resistant and antisteatotic effects by improving abnormal immune and metabolic homeostasis. And DGLHD may be a novel approach to the treatment of obesity-related insulin resistance and hepatic steatosis.

Beyond knockout: A novel homodimerization-targeting MyD88 inhibitor prevents and cures type 1 diabetes in NOD mice

INTRODUCTION AND AIMS

Studies have reported that myeloid differentiation factor 88 (MyD88) plays an important role in the development of type 1 diabetes (T1D). The aim of this study was to determine the effects of the self-created MyD88 inhibitor, TJ-M2010-6, in preventing and treating T1D.

METHODS

Molecule docking and co-immunoprecipitation were used to determine the suppressing capability of TJ-M2010-6 on the homodimerization of MyD88. The preventive and therapeutic effects of TJ-M2010-6 were tested in NOD mice.

RESULTS

TJ-M2010-6 interacted with amino acid residues of the MyD88 TIR domain and inhibited MyD88 homodimerization. Continuous administration of TJ-M2010-6 significantly reduced the onset of diabetes during the observation period in NOD mice (36.4% vs. 80%, P<0.01). Although the immediate TJ-M2010-6 treatment group showed a retardation in the rise of their blood glucose level, the delayed treatment group did not show this effect. Mechanism studies have shown that TJ-M2010-6 treatment significantly inhibits insulitis in vivo. In vitro, TJ-M2010-6 inhibited the maturation of DCs, leading to the suppression of T cell activation and inflammatory cytokine secretion.

CONCLUSIONS

These results demonstrated that the strategy targeted at the innate immune system using the MyD88 inhibitor had a profound significance in preventing and treating T1D.

Soluble alpha-enolase activates monocytes by CD14-dependent TLR4 signalling pathway and exhibits a dual function

Rheumatoid arthritis (RA) is the most common form of chronic inflammatory rheumatism. Identifying auto-antigens targeted by RA auto-antibodies is of major interest. Alpha-enolase (ENO1) is considered to be a pivotal auto-antigen in early RA but its pathophysiologic role remains unknown. The main objective of this study was to investigate the in vitro effects of soluble ENO1 on peripheral blood mononuclear cells (PBMC) from healthy donors and RA patients in order to determine the potential pathogenic role of ENO1. ELISA, transcriptomic analysis, experiments of receptor inhibition and flow cytometry analysis were performed to determine the effect, the target cell population and the receptor of ENO1. We showed that ENO1 has the ability to induce early production of pro-inflammatory cytokines and chemokines with delayed production of IL-10 and to activate the innate immune system. We demonstrated that ENO1 binds mainly to monocytes and activates the CD14-dependent TLR4 pathway both in healthy subjects and in RA patients. Our results establish for the first time that ENO1 is able to activate in vitro the CD14-dependent TLR4 pathway on monocytes involving a dual mechanism firstly pro-inflammatory and secondly anti-inflammatory. These results contribute to elucidating the role of this auto-antigen in the pathophysiologic mechanisms of RA.