Blocking CD40-TRAF6 interactions by small-molecule inhibitor 6860766 ameliorates the complications of diet-induced obesity in mice.

BACKGROUND: Immune processes contribute to the development of obesity and its complications, such as insulin resistance, type 2 diabetes mellitus and cardiovascular disease. Approaches that target the inflammatory response are promising therapeutic strategies for obesity. In this context, we recently demonstrated that the interaction between the costimulatory protein CD40 and its downstream adaptor protein tumor necrosis factor receptor-associated factor 6 (TRAF6) promotes adipose tissue inflammation, insulin resistance and hepatic steatosis in mice in the course of diet-induced obesity (DIO). METHODS: Here we evaluated the effects of a small-molecule inhibitor (SMI) of the CD40-TRAF6 interaction, SMI 6860766, on the development of obesity and its complications in mice that were subjected to DIO. RESULTS: Treatment with SMI 6860766 did not result in differences in weight gain, but improved glucose tolerance. Moreover, SMI 6860766 treatment reduced the amount of CD45(+) leucocytes in the epididymal adipose tissue by 69%. Especially, the number of adipose tissue CD4(+) and CD8(+) T cells, as well as macrophages, was significantly decreased. CONCLUSIONS: Our results indicate that small-molecule-mediated inhibition of the CD40-TRAF6 interaction is a promising therapeutic strategy for the treatment of metabolic complications of obesity by improving glucose tolerance, by reducing the accumulation of immune cells to the adipose tissue and by skewing of the immune response towards a more anti-inflammatory profile.

Peripheral targets in obesity treatment: a comprehensive update.

Obesity is a major epidemic of our time and is associated with diseases such as metabolic syndrome, type 2 diabetes mellitus and atherosclerotic cardiovascular disease. Although weight loss drugs, when accompanied by diet and exercise, could be a very helpful medical tool in treating obese or overweight patients, their usefulness has been questioned due to the complexity of this type of medication, which regards a plethora of issues such as efficacy and safety of the drug and also risks and benefits among different patients. In general, obesity drugs that target peripheral pathophysiological mechanisms can be divided into two main categories. The first category includes anti-obesity agents able to reduce or limit energy absorption, such as pancreatic lipase and microsomal triglyceride transfer protein inhibitors. The second category consists of a heterogeneous group of compounds aiming to decrease fat mass by increasing energy expenditure or by redistributing adipose tissue. Angiogenesis inhibitors, beta-3 receptor agonists, sirtuin-I activators, diazoxide and other molecules belong to this group. The glucagon-like peptide-1 receptor agonists consist the third category of peripheral anti-obesity agents discussed therein. This review aims to provide a general overview of the molecules and substances that are already or could potentially be used as peripheral anti-obesity drugs, the molecular mechanisms by which they act, as well as their current stage of development, production and/or availability.

CD40L stimulates the crosstalk between adipocytes and inflammatory cells.

Macrophages and lymphocytes are implicated in obesity-related adipose tissue inflammation via interactions with adipocytes. Co-stimulatory systems, especially the CD40-CD40L system, play an important role in T cell activation and inflammatory reactions. CD40L was recently shown to promote adipose tissue inflammation in vivo, yet, the mechanisms underlying its function in the intercellular communication between inflammatory cells and adipocytes remain not entirely clear. Here we found that adipocyte stimulation with CD40L increased the expression of CD40, as well as of chemokines, such as MCP-1, CCL4, or CCL5, whereas adipocyte CD40 expression was also stimulated by TNF but not palmitate. Moreover, conditioned media of CD40L-pretreated adipocytes provoked elevated migration of mononuclear cells and increased the expression of inflammatory genes in bone marrow derived mononuclear phagocytes (BMDM) shifting them to an M1-like pro-inflammatory phenotype. Nonetheless, the CD40/CD40L interaction did not contribute to the adhesion between adipocytes and T cells. Together, CD40L stimulates adipocyte chemokine expression, thereby attracting monocytes/macrophages into the adipose tissue. Moreover, CD40L stimulation of adipocytes likely promotes macrophage M1 polarization in the adipose tissue and thereby perpetuation of adipose tissue inflammation.

Lymphocytes in obesity-related adipose tissue inflammation.

Inflammation in the white adipose tissue (WAT) is considered a major player in the development of insulin resistance. The role of macrophages accumulating in the WAT during obesity, promoting WAT inflammation and insulin resistance is well established. In contrast, less is known about the role of lymphocytes. Recent studies have implicated different lymphocyte subsets in WAT inflammation. For instance, cytotoxic CD8(+) T cells infiltrating the WAT may contribute to the recruitment, differentiation and activation of macrophages. On the other hand, a differential role for CD4(+) Th1 and CD4(+) Th2 cells has been suggested. Levels of WAT regulatory T cells decrease during the course of obesity and may represent a crucial factor for the maintenance of insulin sensitivity. Moreover, activation of natural killer T cells, an innate-like T cell population, which recognises lipid antigens, promotes insulin resistance and WAT inflammation. Finally, B cells may infiltrate WAT very early in response to high-fat feeding and worsen glucose metabolism through modulation of T cells and the production of pathogenic antibodies. These interesting new findings however bear controversies and introduce novel, yet unanswered, questions. Here, we review and discuss the impact of the different lymphocyte subsets in obesity-related WAT inflammation and attempt to identify the open questions to be answered by future studies.

CD40 expression and its association with low-grade inflammation in a Greek population of type 1 diabetic juveniles: evidence for differences in CD40 mRNA isoforms expressed by peripheral blood mononuclear cells.

BACKGROUND: CD40 signalling has been associated with the pathogenesis of autoimmune diseases and diseases with low-grade chronic inflammation. OBJECTIVE: To investigate, early in the course of type 1 diabetes (T1DM) patients, the expression of CD40 system components, as well as to explore the association of plasma and urine concentrations of CD40 with known inflammatory markers in T1DM. METHODS: Plasma, urine and peripheral blood mononuclear cells (PBMCs) from 70 T1DM patients without clinically detected chronic complications and 40 healthy controls (HCs) were examined using ELISA, western-blot, semi-quantitative RT-PCR and DNA-sequencing. RESULTS: Patients had significantly higher plasma soluble CD40 (sCD40) levels associated with higher Interleukin-6 (IL-6), matrix metalloproteinase-9 (MMP-9) and CRP levels compared with healthy controls. This difference was also evident between poorly and well-controlled diabetic patients. The elevated plasma sCD40 levels do not appear to be due to diminished renal excretion since sCD40 concentrations in the urine were also elevated, suggesting an increased CD40 production. An upregulation of PBMCs' CD40 was evident in T1DM patients associated with higher sCD40, IL-6 and CRP levels. Furthermore, the main CD40 isoform (isoform-I) was solely expressed in poorly controlled diabetics' PBMCs, who also demonstrated cellular CD40 upregulation, higher plasma CD40, CRP, IL-6 and MMP-9 levels compared with the well-controlled diabetics and the control group, who co-expressed type I and II isoforms. CONCLUSIONS: Homeostatic dysregulation of CD40 and its association with inflammatory markers in T1DM patients, especially in those with poor glycaemic control, implies a pathophysiological role of CD40 in the low-grade inflammatory process in T1DM.

Sex differences in oxidant/antioxidant balance under a chronic mild stress regime.

The deterioration of homeostasis between oxidant/antioxidant species may represent an important mechanism linking psychological stress to cardiovascular risk despite the many sex differences in stress responsiveness. The goal of the present study was to investigate the influence of chronic mild stress (CMS), a widely accepted animal model of depression, on oxidative homeostasis-allostasis markers and sICAM-1, a marker of endothelial injury, in the serum of Wistar rats, by taking into account the effect of sex. After six weeks of exposure to mild unpredictable environmental stressors, both male and female rat groups displayed typical changes in hedonic status (anhedonia), which is a core symptom of human depression. Control female rats had higher (nitrite and nitrate) NOx, lower malondealdehyde (MDA) levels with lower activity of antioxidant enzymes and sICAM-1 levels than did control males. CMS induced oxidant/antioxidant responses in both sexes. Females tended to increase their nitric oxide (NO) levels further, while MDA levels did not reach those of males, thus retaining significantly higher NO bioavailability than in males. Concerning the antioxidant enzymes, CMS-females exhibited significantly higher glutathione peroxidase (GPx) activity and lower glutathione reductase (GR) and superoxide dismutase (SOD) activity compared to CMS-males. The CMS response in females was accompanied by lower sICAM-1 levels than in males, suggesting lower endothelial injury. In conclusion, the results of the present study showed that CMS induces different oxidative stress and compensatory responses in both sexes probably due to differences in the mechanisms regulating oxidant/antioxidant pathways.

In vivo models for heart failure research.

The medical treatment of heart failure (HF) is associated with 50% survival at 5 years, thus being one of the major causes of mortality in Western countries. An understanding of the pathophysiology of HF is essential for the development of novel efficient therapies. Consequently, the use of animal models is indispensable. In addition, the development of new in vivo models of HF is critical for the evaluation of treatments such as gene therapy, mechanical devices and new surgical approaches. However, every animal model has advantages and limitations and none of them is suitable to study all aspects of HF. Besides the technical determinants of a model, species, strain and gender affect the pathophysiology of a given heart pathogenesis and, therefore, have to be considered in each animal model. The most common in vivo models used in cardiology research and in particular in HF remodeling are presented.