ABSTRACT
Reactive oxygen species (ROS) represent a by-product of metabolism and their excess is toxic for hematopoietic stem and progenitor cells (HSPCs). During embryogenesis, a small number of HSPCs are produced from the hemogenic endothelium, before they colonize a transient organ where they expand, for example the fetal liver in mammals. In this study, we use zebrafish to understand the molecular mechanisms that are important in the caudal hematopoietic tissue (equivalent to the mammalian fetal liver) to promote HSPC expansion. High levels of ROS are deleterious for HSPCs in this niche, however this is rescued by addition of antioxidants. We show that Cx41.8 is important to lower ROS levels in HSPCs. We also demonstrate a new role for ifi30, known to be involved in the immune response. In the hematopoietic niche, Ifi30 can recycle oxidized glutathione to allow HSPCs to dampen their levels of ROS, a role that could be conserved in human fetal liver.
Subject(s)
Connexins/genetics , Hematopoietic Stem Cells/metabolism , Oxidative Stress , Oxidoreductases Acting on Sulfur Group Donors/genetics , Signal Transduction/genetics , Stem Cell Niche , Zebrafish Proteins/genetics , Animals , Animals, Genetically Modified , Connexins/metabolism , Embryo, Nonmammalian/cytology , Embryo, Nonmammalian/embryology , Embryo, Nonmammalian/metabolism , Gene Expression Regulation, Developmental , Hematopoietic Stem Cells/cytology , Humans , Microscopy, Confocal , Mutation , Oxidoreductases Acting on Sulfur Group Donors/metabolism , Time-Lapse Imaging/methods , Zebrafish/embryology , Zebrafish/genetics , Zebrafish Proteins/metabolismABSTRACT
It has been suggested that interleukin-6 (IL-6) produced by adipocytes in obesity leads to liver insulin resistance, although this hypothesis has never been definitively tested. Accordingly, we did so by generating adipocyte-specific IL-6-deficient (AdipoIL-6-/-) mice and studying them in the context of diet-induced and genetic obesity. Mice carrying two floxed alleles of IL-6 (C57Bl/6J) were crossed with Cre recombinase-overexpressing mice driven by the adiponectin promoter to generate AdipoIL-6-/- mice. AdipoIL-6-/- and floxed littermate controls were fed a standard chow or high-fat diet (HFD) for 16 wk and comprehensively metabolically phenotyped. In addition to a diet-induced obesity model, we also examined the role of adipocyte-derived IL-6 in a genetic model of obesity and insulin resistance by crossing the AdipoIL-6-/- mice with leptin-deficient (ob/ob) mice. As expected, mice on HFD and ob/ob mice displayed marked weight gain and increased fat mass compared with chow-fed and ob/+ (littermate control) animals, respectively. However, deletion of IL-6 from adipocytes in either model had no effect on glucose tolerance or fasting hyperinsulinemia. We concluded that adipocyte-specific IL-6 does not contribute to whole body glucose intolerance in obese mice.
Subject(s)
Adipocytes/metabolism , Glucose Intolerance/genetics , Interleukin-6/genetics , Obesity/genetics , Weight Gain/genetics , Adiponectin/biosynthesis , Adiponectin/genetics , Adiposity/genetics , Animals , Body Composition/genetics , Diet, High-Fat , Glucose Intolerance/etiology , Insulin Resistance/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Non-alcoholic Fatty Liver Disease/genetics , Non-alcoholic Fatty Liver Disease/pathology , Obesity/complications , Obesity/metabolismABSTRACT
Exercise stimulates the release of molecules into the circulation, supporting the concept that inter-tissue signaling proteins are important mediators of adaptations to exercise. Recognizing that many circulating proteins are packaged in extracellular vesicles (EVs), we employed quantitative proteomic techniques to characterize the exercise-induced secretion of EV-contained proteins. Following a 1-hr bout of cycling exercise in healthy humans, we observed an increase in the circulation of over 300 proteins, with a notable enrichment of several classes of proteins that compose exosomes and small vesicles. Pulse-chase and intravital imaging experiments suggested EVs liberated by exercise have a propensity to localize in the liver and can transfer their protein cargo. Moreover, by employing arteriovenous balance studies across the contracting human limb, we identified several novel candidate myokines, released into circulation independently of classical secretion. These data identify a new paradigm by which tissue crosstalk during exercise can exert systemic biological effects.
