Obesity and its associated metabolic morbidities have been and still are on the rise, posing a major challenge to health care systems worldwide. It has become evident over the last decades that a low-grade inflammatory response, primarily proceeding from the adipose tissue (AT), essentially contributes to adiposity-associated comorbidities, most prominently insulin resistance (IR), atherosclerosis and liver diseases. In mouse models, the release of pro-inflammatory cytokines such as TNF-alpha (TNF-α) and interleukin (IL)-1β and the imprinting of immune cells to a pro-inflammatory phenotype in AT play an important role. However, the underlying genetic and molecular determinants are not yet understood in detail. Recent evidence demonstrates that nucleotide-binding and oligomerization domain (NOD)-like receptor (NLR) family proteins, a group of cytosolic pattern recognition receptors (PRR), contribute to the development and control of obesity and obesity-associated inflammatory responses. In this article, we review the current state of research on the role of NLR proteins in obesity and discuss the possible mechanisms leading to and the outcomes of NLR activation in the obesity-associated morbidities IR, type 2 diabetes mellitus (T2DM), atherosclerosis and non-alcoholic fatty liver disease (NAFLD) and discuss emerging ideas about possibilities for NLR-based therapeutic interventions of metabolic diseases.

Background: IL-15 is a promising cytokine for cancer immunotherapy. IL-15 promotes differentiation and homeostasis of innate and adaptive immune cells, and their cytolytic effector functions. The IL-15 receptor is composed of IL-15Rα, IL-15Rβ and the common γ_c chains. IL-15 is also trans-presented as IL-15Rα:IL-15 complex to IL-15Rβ:γ_c on neighboring cells. IL-15Rα is dispensable for early immune response to infections and in autoimmune diabetes. The role of IL-15Rα in antitumor immune responses remains unclear. Methods: In WT, Il15^−/− and Il15ra^−/− mice, we studied the growth of syngeneic tumor cell lines and tumor immune surveillance against endogenous fibrosarcoma induced by methylcholanthrene (MCA). Immune gene signature and total proteome analysis were performed on MCA-induced tumors. Results: Lack of IL-15 or IL-15Rα did not enhance the growth of implanted tumor cell lines, despite reduced immune cell infiltration. MCA-induced tumor incidence was reduced in mice lacking IL-15Rα but not IL-15, although both are required for efficient tumor immunoediting. Il15^−/− and Il15ra^−/− tumors showed reduced Ifng expression but displayed differential modulation of Ifng-responsive genes. Proteome profiles of Il15^−/− tumors, but not tumor-derived cell lines, showed significant reduction in antigen presentation pathways. B16-F10 melanoma cells expressing NLRC5, the IFNγ-induced transcriptional activator of tumor antigen presentation, still required IL-15 but not IL-15Rα for efficient tumor control. Conclusions: Our findings show that IL-15 plays a negligible role in immunosurveillance against spontaneous tumor development, whereas IL-15Rα restrains immunosurveillance. Neither IL-15 nor IL-15Rα have a significant impact on implanted tumor models, although IL-15 facilitates efficient control of highly immunogenic tumors for which IL-15Rα is dispensable.