Glucagon Reduces Neutrophil Migration and Increases Susceptibility to Sepsis in Diabetic Mice.

Sepsis is one of the most common comorbidities observed in diabetic patients, associated with a deficient innate immune response. Recently, we have shown that glucagon possesses anti-inflammatory properties. In this study, we investigated if hyperglucagonemia triggered by diabetes might reduce the migration of neutrophils, increasing sepsis susceptibility. 21 days after diabetes induction by intravenous injection of alloxan, we induced moderate sepsis in Swiss-Webster mice through cecum ligation and puncture (CLP). The glucagon receptor (GcgR) antagonist des-his1-[Glu9]-glucagon amide was injected intraperitoneally 24h and 1h before CLP. We also tested the effect of glucagon on CXCL1/KC-induced neutrophil migration to the peritoneal cavity in mice. Neutrophil chemotaxis in vitro was tested using transwell plates, and the expression of total PKA and phospho-PKA was evaluated by western blot. GcgR antagonist restored neutrophil migration, reduced CFU numbers in the peritoneal cavity and improved survival rate of diabetic mice after CLP procedure, however, the treatment did no alter hyperglycemia, CXCL1/KC plasma levels and blood neutrophilia. In addition, glucagon inhibited CXCL1/KC-induced neutrophil migration to the peritoneal cavity of non-diabetic mice. Glucagon also decreased the chemotaxis of neutrophils triggered by CXCL1/KC, PAF, or fMLP in vitro. The inhibitory action of glucagon occurred in parallel with the reduction of CXCL1/KC-induced actin polymerization in neutrophils in vitro, but not CD11a and CD11b translocation to cell surface. The suppressor effect of glucagon on CXCL1/KC-induced neutrophil chemotaxis in vitro was reversed by pre-treatment with GcgR antagonist and adenylyl cyclase or PKA inhibitors. Glucagon also increased PKA phosphorylation directly in neutrophils in vitro. Furthermore, glucagon impaired zymosan-A-induced ROS production by neutrophils in vitro. Human neutrophil chemotaxis and adherence to endothelial cells in vitro were inhibited by glucagon treatment. According to our results, this inhibition was independent of CD11a and CD11b translocation to neutrophil surface or neutrophil release of CXCL8/IL-8. Altogether, our results suggest that glucagon may be involved in the reduction of neutrophil migration and increased susceptibility to sepsis in diabetic mice. This work collaborates with better understanding of the increased susceptibility and worsening of sepsis in diabetics, which can contribute to the development of new effective therapeutic strategies for diabetic septic patients.

Preclinical relevance of probiotics in type 2 diabetes: A systematic review.

Type 2 diabetes (T2DM) is among the most prevalent metabolic diseases in the world and may result in several long-term complications. The crosstalk between gut microbiota and host metabolism is closely related to T2DM. Currently, fragmented data hamper defining the relationship between probiotics and T2DM. This systematic review aimed at investigating the effects of probiotics on T2DM in animal models. We systematically reviewed preclinical evidences using PubMed/MEDLINE and Scopus databases, recovering 24 original articles published until September 27th, 2019. This systematic review was performed according to PRISMA guidelines. We included experimental studies with animal models reporting the effects of probiotics on T2DM. Studies were sorted by characteristics of publications, animal models, performed analyses, probiotic used and interventions. Bias analysis and methodological quality assessments were examined through the SYRCLE's Risk of Bias tool. Probiotics improved T2DM in 96% of the studies. Most studies (96%) used Lactobacillus strains, and all of them led to improved glycaemia. All studies used rodents as models, and male animals were preferred over females. Results suggest that probiotics have a beneficial effect in T2DM animals and could be used as a supporting alternative in the disease treatment. Considering a detailed evaluation of the reporting and methodological quality, the current preclinical evidence is at high risk of bias. We hope that our critical analysis will be useful in mitigating the sources of bias in further studies.

Gut microbiota translocation to the pancreatic lymph nodes triggers NOD2 activation and contributes to T1D onset.

Type 1 diabetes (T1D) is an autoimmune disease that is triggered by both genetic and environmental factors, resulting in the destruction of pancreatic ß cells. The disruption of the intestinal epithelial barrier and consequent escape of microbial products may be one of these environmental triggers. However, the immune receptors that are activated in this context remain elusive. We show here that during streptozotocin (STZ)-induced T1D, the nucleotide-binding oligomerization domain containing 2 (NOD2), but not NOD1, participates in the pathogenesis of the disease by inducing T helper 1 (Th1) and Th17 cells in the pancreatic LNs (PLNs) and pancreas. Additionally, STZ-injected wild-type (WT) diabetic mice displayed an altered gut microbiota compared with vehicle-injected WT mice, together with the translocation of bacteria to the PLNs. Interestingly, WT mice treated with broad-spectrum antibiotics (Abx) were fully protected from STZ-induced T1D, which correlated with the abrogation of bacterial translocation to the PLNs. Notably, when Abx-treated STZ-injected WT mice received the NOD2 ligand muramyl dipeptide, both hyperglycemia and the proinflammatory immune response were restored. Our results demonstrate that the recognition of bacterial products by NOD2 inside the PLNs contributes to T1D development, establishing a new putative target for intervention during the early stages of the disease.

Imbalanced Macrophage and Dendritic Cell Activations in Response to Candida albicans in a Murine Model of Diabetes Mellitus.

Bloodstream infections caused by Candida species are responsible for high morbidity and mortality, and diabetes mellitus (DM) is an important underlying disease in candidemia episodes. Although DM patients show an enhanced proinflammatory profile, they are highly susceptible to mycobacterial and mycotic infections. Attempting to understand this paradox, we investigated if imbalanced macrophage and dendritic cell (DC) activations could be associated to high incidence and/or severity of Candida albicans infection in the hypoinsulinemia-hyperglycemia (HH) milieu. HH alloxan-induced mice were infected with C. albicans and peritoneal aderent phagocytes were co-cultured with or without lipopolyssaccharide or heat-killed C. albicans, and the production of cytotoxic metabolites, cytokines, and chemokines was evaluated. We also evaluated the surface expression of MHC-II and CD86 in splenic DCs. Our findings showed that both uninfected and C. albicans-infected HH mice showed less production of CCL2 and reduced expression of CD86 by peritoneal phagocytes and splenic DCs, respectively.

Aminoguanidine treatment increased NOX2 response in diabetic rats: Improved phagocytosis and killing of Candida albicans by neutrophils.

In this study, we show that aminoguanidine (AMG), an inhibitor of protein glycation, increases the NOX2 (phagocyte NADPH oxidase) response and microbicidal activity by neutrophils, regardless of diabetic status. The non-enzymatic glycation of proteins, yielding irreversible advanced glycation end products (AGEs), is involved in the development of diabetes complications, including alterations of signaling pathways and the generation of reactive oxygen species by phagocytes. The phagocytes produce ROS (reactive oxygen species) through activation of the NOX2 complex, which generates superoxide. The purpose of this study was to evaluate the effect of hyperglycemia and the glycation of proteins on the NOX2 activity of neutrophils and its implications for cellular physiology, with a focus on the microbicidal activity of these cells. We treated diabetic rats with AMG and evaluated neutrophil ROS generation and Candida albicans killing ability. We observed a large increase in the microbicidal activity of peritoneal neutrophils from AMG-treated rats. The increase was independent of diabetic status and myeloperoxidase activity. Collectively, our results suggest that AMG has an immunomodulator role that triggers an increase in the microbicidal response of neutrophils mainly related to reactive oxygen species production by NOX2.

Immunomodulation and nitric oxide restoration by a probiotic and its activity in gut and peritoneal macrophages in diabetic rats.

BACKGROUND: The hyperglycemia leads to increased oxidative stress, causing lipid peroxidation and imbalance in the immune system. AIMS: To investigate the effect of Kefir - a probiotic containing different strains - on metabolic parameters, cytokines, nitric oxide (NO) production, phagocytic activity of peritoneal macrophages and intestinal modulation in diabetes. METHODS: Wistar rats received injection of streptozotocin (45 mg/kg, intravenously) and diabetes was defined as glycemia ≥200 mg/dL. The animals were distributed in four groups: control (CTL); control Kefir (CTLK); diabetic (DM); diabetic Kefir (DMK). Kefir was given at 1.8 mL/day by gavage, started on the 5th day of diabetes, during 8 weeks. The animals were allocated in metabolic cages, pre and post treatment with Kefir, for measurement of the metabolic parameters, such as water intake, food intake, diuresis, glycemia, body mass, insulin and lipid profile, these last two were only measured at the end of Kefir protocol. After treatment, the animals were euthanized and the peritoneal cavity was prepared, resident macrophages were collected and cultured for analysis of the phagocytic activity, cytokines (IL-10, TNF-α, IL-17, IL-1ß) and NO. The intestinal modulation was performed by the quantification of Peyer's patches (PP) in the small intestine. The data were presented as mean ± SEM, with significance of p < 0.05. RESULTS: DM when compared to CTL showed increase in water intake (133 ± 7 vs. 28 ± 1 mL, p < 0.0001), food intake (40 ± 2 vs. 16 ± 1 g, p < 0.0001), diuresis (102 ± 5 vs. 13 ± 1 mL, p < 0.0001) and glycemia (567 ± 12 vs. 84 ± 3 mg/dL, p < 0.0001), while in DMK group all these metabolic parameters were decreased (96 ± 14; 36 ± 1; 86 ± 7 and 407 ± 19, respectively, p < 0.0001), presenting increase of body mass (42 ± 5 vs. 16 ± 4Δ, p < 0.0001) and insulin levels (0.3 ± 0.8 vs. 0.1 ± 0.04 ng/mL, p < 0.0001) compared to DM. The lipid profile of the diabetic groups showed tendency to increase compared to the respective controls. In relation to function of peritoneal macrophages, DMK group vs. DM showed improvement in phagocytic capacity (70 ± 5 vs. 51 ± 7%, p = 0,0023) and increased concentration of all the cytokines analyzed (pg/mL), as IL-10 (926 ± 69 vs. 556 ± 92, p = 0.0004), TNF-α (178 ± 20 vs. 109 ± 20, p = 0.005), IL-17 (33 ± 1 vs. 9 ± 1, p = 0.0001) and IL-1ß (102 ± 14 vs. 70 ± 5, p = 0.0129), after 24 h of LPS stimulation; including NO bioavailability after 24 h (102 ± 9 vs. 66 ± 5 µM/mL, p = 0.0029) or 48 h (143 ± 8 vs. 119 ± 4 µM/mL, p = 0.0102) of LPS stimulation. Moreover, the number of PP in the whole small intestine of DMK group was also increased as compared to DM (22 ± 1 vs. 18 ± 1, p = 0.0292). CONCLUSION: These results show that Kefir has a potential to modulate the immune response and activate peritoneal macrophages in diabetic animals, which suggests that it could enhance the immunocompetence of patients affected by diabetes mellitus. The hypoglycemic effect of this probiotic could be used as a tool to control glycemia, reducing or delaying the onset of complications associated with this disease.

Histamine h2 receptor signaling in the pathogenesis of sepsis: studies in a murine diabetes model.

Type 1 diabetes enhances susceptibility to infection and favors the sepsis development. In addition, diabetic mice produced higher levels of histamine in several tissues and in the blood after LPS stimulation than nondiabetic mice. In this study, we aimed to explore the role of mast cells (MCs) and histamine in neutrophil migration and, consequently, infection control in diabetic mice with mild sepsis (MS) induced by cecum ligation and puncture. We used female BALB/c, MC-sufficient (WB/B6), MC-deficient (W/W(v)), and NOD mice. Diabetic mice given MS displayed 100% mortality within 24 h, whereas all nondiabetic mice survived for at least 5 d. The mortality rate of diabetic mice was reduced to 57% after the depletion of MC granules with compound 48/80. Moreover, this pretreatment increased neutrophil migration to the focus of infection, which reduced systemic inflammatory response and bacteremia. The downregulation of CXCR2 and upregulation of G protein-coupled receptor kinase 2 in neutrophils was prevented by pretreatment of diabetic mice given MS with compound 48/80. In addition, blocking the histamine H2 receptor restored neutrophil migration, enhanced CXCR2 expression, decreased bacteremia, and improved sepsis survival in alloxan-induced diabetic and spontaneous NOD mice. Finally, diabetic W/W(v) mice had neutrophil migration to the peritoneal cavity, increased CXCR2 expression, and reduced bacteremia compared with diabetic WB/B6 mice. These results demonstrate that histamine released by MCs reduces diabetic host resistance to septic peritonitis in mice.

Spontaneous periodontitis development in diabetic rats involves an unrestricted expression of inflammatory cytokines and tissue destructive factors in the absence of major changes in commensal oral microbiota.

Diabetes mellitus is a heterogeneous group of disorders, in which hyperglycemia is a main feature. The objective was to evaluate the involvement of RAGE, inflammatory cytokines, and metalloproteinases in spontaneous periodontitis triggered by diabetes induction. Immunohistochemical procedures for MMP-2, MMP-9, TNF-α, IL-1ß, IL-6, RANKL, and RAGE were performed in rats after 1, 3, 6, 9, and 12 months of diabetes induction. Total DNA was extracted from paraffin-embedded tissues and evaluated by Real-TimePCR for 16S total bacterial load and specific periodontopathogens. Our data did not demonstrate differences in microbiological patterns between groups. In diabetic groups, an increase in RAGE-positive cells was detected at 6, 9, and 12 months, while TNF-alpha-stained cells were more prevalent at 6 and 12 months. In experimental groups, IL-ß-positive cells were increased after 12 months, IL-6 stained cells were increased at 9 and 12 months, and RANKL-positive cells at 9 months. Diabetes resulted in widespread expression of RAGE, followed by expression of proinflammatory mediators, without major alterations in oral microbial profile. The pervasive expression of cytokines suggests that spontaneous periodontitis development may be independent of microbial stimulation and may be triggered by diabetes-driven imbalance of homeostasis.