Targeting colonic macrophages improves glycemic control in high-fat diet-induced obesity.

The obesity epidemic continues to worsen worldwide. However, the mechanisms initiating glucose dysregulation in obesity remain poorly understood. We assessed the role that colonic macrophage subpopulations play in glucose homeostasis in mice fed a high-fat diet (HFD). Concurrent with glucose intolerance, pro-inflammatory/monocyte-derived colonic macrophages increased in mice fed a HFD. A link between macrophage numbers and glycemia was established by pharmacological dose-dependent ablation of macrophages. In particular, colon-specific macrophage depletion by intrarectal clodronate liposomes improved glucose tolerance, insulin sensitivity, and insulin secretion capacity. Colonic macrophage activation upon HFD was characterized by an interferon response and a change in mitochondrial metabolism, which converged in mTOR as a common regulator. Colon-specific mTOR inhibition reduced pro-inflammatory macrophages and ameliorated insulin secretion capacity, similar to colon-specific macrophage depletion, but did not affect insulin sensitivity. Thus, pharmacological targeting of colonic macrophages could become a potential therapy in obesity to improve glycemic control.

Obesity in Humans Is Characterized by Gut Inflammation as Shown by Pro-Inflammatory Intestinal Macrophage Accumulation.

Chronic low-grade inflammation is a hallmark of obesity and associated with cardiovascular complications. However, it remains unclear where this inflammation starts. As the gut is constantly exposed to food, gut microbiota, and metabolites, we hypothesized that mucosal immunity triggers an innate inflammatory response in obesity. We characterized five distinct macrophage subpopulations (P1-P5) along the gastrointestinal tract and blood monocyte subpopulations (classical, non-classical, intermediate), which replenish intestinal macrophages, in non-obese (BMI<27kg/m2) and obese individuals (BMI>32kg/m2). To elucidate factors that potentially trigger gut inflammation, we correlated these subpopulations with cardiovascular risk factors and lifestyle behaviors. In obese individuals, we found higher pro-inflammatory macrophages in the stomach, duodenum, and colon. Intermediate blood monocytes were also increased in obesity, suggesting enhanced recruitment to the gut. We identified unhealthy lifestyle habits as potential triggers of gut and systemic inflammation (i.e., low vegetable intake, high processed meat consumption, sedentary lifestyle). Cardiovascular risk factors other than body weight did not affect the innate immune response. Thus, obesity in humans is characterized by gut inflammation as shown by accumulation of pro-inflammatory intestinal macrophages, potentially via recruited blood monocytes. Understanding gut innate immunity in human obesity might open up new targets for immune-modulatory treatments in metabolic disease.

Low Discontinuation Rate of Infliximab Treatment in Steroid-Dependent/Refractory Crohn's Disease Patients.

BACKGROUND: Many patients with moderate to severe Crohn's disease (CD) are treated with infliximab (IFX). As most of these patients experience a long-lasting therapy, the outcome and withdrawal of IFX treatment are important clinical questions. METHODS: In this retrospective study, we analyzed the treatment outcome in moderate to severe CD patients with a steroid-dependent/refractory disease course started on IFX. Withdrawal of IFX was evaluated in patients with deep remission defined as clinical (Harvey-Bradshaw Index ≤4), biochemical (fecal calprotectin [FC] ≤150 µg/g stool) over a period of 2 years, and endoscopic and histological remission before discontinuation of IFX. RESULTS: After induction with IFX, clinical remission was observed in 45/109 patients (41.3%) and clinical response in 61/109 patients (56.0%). Only 8/109 patients (7.3%) achieved deep remission and therefore could be discontinued from IFX therapy. In 4 of these patients (50%), relapse was observed after discontinuation of IFX treatment. FC decreased in these 8 patients in deep remission from 652 ± 168 µg/g stool (mean ± SE) at baseline to 24.9 ± 8.1 µg/g stool at 14 weeks. When compared to patients in deep remission, FC had decreased significantly less at 14 weeks in patients in clinical remission after induction with IFX (n = 31; 154 ± 55 µg/g stool; p = 0.01), in patients with clinical response after induction achieving clinical remission during the maintenance phase (n = 11; 352 ± 67 µg/g stool; p = 0.004), or in patients with chronic active disease course on maintenance therapy (n = 50; 645 ± 93 µg/g stool; p < 0.001). CONCLUSION: A low discontinuation rate was observed for steroid-dependent/refractory moderate to severe CD patients with IFX treatment. As FC showed a more or less pronounced decrease depending on the response to the IFX treatment, monitoring of FC may become a noninvasive tool for tailoring biological therapy in CD patients.

IL26 modulates cytokine response and anti-TNF consumption in Crohn's disease patients with bacterial DNA.

Interleukin IL26 supports killing of microbes and the innate sensing of bacterial-derived DNA (bactDNA). We evaluated the relationship between IL26 serum levels and bactDNA translocation in Crohn's disease (CD). We ran a prospective study on CD patients in remission. IL26 common polymorphisms, serum cytokines and complement protein, amplified-bactDNA, and anti-TNF-α were evaluated. In vitro PBMC analysis was performed. Three hundred and thirteen patients were included (mean CDAI: 83.6 ± 32.8; mean fecal calprotectin: 55.4 ± 35.3 µg/g). A total of 106 patients (33.8%) showed bactDNA and 223 patients (71%) had a varIL26 genotype. BactDNA significantly correlated with increased IL26 levels compared with bactDNA-negative patients. PBMCs from varIL26 patients significantly reduced E. coli killing capacity compared with wtIL26-genotyped patients. The stimulation with a recombinant IL26 protein reduced pro-inflammatory cytokines in response to E. coli in the varIL26 cell supernatants. Serum anti-TNF-α levels in varIL26 vs wtIL26-genotyped patients on biologics were significantly lower in the presence of bactDNA. Cells from varIL26 vs wtIL26-genotyped patients cultured with E. coli DNA and infliximab showed a significant decrease in free anti-TNF-α concentration. A varIL26 genotype was associated with the initiation of anti-TNF-α in CD patients during the 6-month follow-up. IL26 polymorphisms may prevent bactDNA clearance and identify CD patients with a worse inflammatory evolution and response to therapy. KEY MESSAGES: BactDNA translocation in CD is associated with an increased risk of relapse. IL26 is sensitive to bactDNA and modulates the inflammatory response in CD patients. The varIL26 genotype is associated with reduced PMN capacity to kill bacteria. A varIL26 genotype is associated with decreased levels of anti-TNF-α in CD patients. IL26 may help explain the role of bactDNA as a risk factor of flare in CD patients.

Macroscopy predicts tumor progression in gastric cancer: A retrospective patho-historical analysis based on Napoleon Bonaparte's autopsy report.

BACKGROUND: The cause of Napoleon Bonaparte's death remains controversial. Originally suggested to be gastric cancer, whether this was truly neoplastic or a benign lesion has been recently debated. AIMS: To interpret findings of original autopsy reports in light of the current knowledge of gastric cancer and to highlight the significance of accurate macroscopy in modern-day medicine. METHODS: Using original autopsy documents, endoscopic images and data from current literature, Napoleon's gastric situation was reconstructed. In a multicenter collection of 2071 gastric cancer specimens, the relationship between tumor size and features of tumor progression was assessed. RESULTS: Greater tumor size was associated with advanced pT, nodal metastases and Borrmann types 3-4 (p<0.001). The best cut-off for predicting pT3-4 tumors was 6.5cm (AUC 0.8; OR 1.397, 95% CI 1.35-1.446), and 6cm for lymph node metastases (AUC 0.775; OR 1.389, 95% CI 1.338-1.442). The 6cm cut-off of had a positive predictive value of 0.820 for nodal metastases and a negative predictive value of 0.880 for distant metastases. CONCLUSION: This analysis combines Napoleon's autopsy with present-day knowledge to support gastric cancer as his terminal illness and emphasizes the role of macroscopy, which may provide valuable information on gastric cancer progression and aid patient management.

Dendritic cells: the commanders-in-chief of mucosal immune defenses.

PURPOSE OF REVIEW: Intestinal dendritic cells have emerged as key regulators of immunity to pathogens, oral tolerance and intestinal inflammation. Studies have begun to elucidate the regulatory mechanisms responsible for defining region- and compartment-specific phenotypes and functions of dendritic cells in mucosal tissues. RECENT FINDINGS: Specific subsets of dendritic cells appear to be associated with the various routes for antigen acquisition in the intestine. The constant sampling of intestinal antigenic content ensures establishment of tolerance to commensal bacteria and food antigens. Tolerance development to oral antigens is restricted to the mucosal immune system. Other advances have provided insight into the molecular basis of microbial recognition and innate immune responses by intestinal dendritic cells. Differences in the involvement of dendritic cells have begun to emerge in Crohn's disease and ulcerative colitis and link gene regulation in dendritic cells to therapeutic responses. SUMMARY: A major focus of mucosal immunology will be to understand how diverse dendritic cell subsets cooperate in regulating homeostasis and host defense in the different intestinal immune compartments. This will be pivotal to understanding how the mucosal immune system makes the distinction between commensal microbiota, pathogens and self antigens.

CCR6-mediated dendritic cell activation of pathogen-specific T cells in Peyer's patches.

T cell activation by dendritic cells (DCs) is critical to the initiation of adaptive immune responses and protection against pathogens. Here, we demonstrate that a specialized DC subset in Peyer's patches (PPs) mediates the rapid activation of pathogen specific T cells. This DC subset is characterized by the expression of the chemokine receptor CCR6 and is found only in PPs. CCR6(+) DCs were recruited into the dome regions of PPs upon invasion of the follicle associated epithelium (FAE) by an enteric pathogen and were responsible for the rapid local activation of pathogen-specific T cells. CCR6-deficient DCs were unable to respond to bacterial invasion of PPs and failed to initiate T cell activation, resulting in reduced defense against oral infection. Thus, CCR6-dependent regulation of DCs is responsible for localized T cell dependent defense against entero-invasive pathogens.