ABSTRACT
As the elderly population grows, chronic metabolic dysfunction including obesity and diabetes are becoming increasingly common comorbidities. Hypothalamic inflammation through CNS resident microglia serves as a common pathway between developing obesity and developing systemic aging pathologies. Despite understanding aging as a life-long process involving interactions between individuals and their environment, limited studies address the dynamics of environment interactions with aging or aging therapeutics. We previously demonstrated environmental enrichment (EE) is an effective model for studying improved metabolic health and overall healthspan in mice, which acts through a brain-fat axis. Here we investigated the CSF1R inhibitor PLX5622 (PLX), which depletes microglia, and its effects on metabolic decline in aging in interaction with EE. PLX in combination with EE substantially improved metabolic outcomes in middle-aged female mice over PLX or EE alone. Chronic PLX treatment depleted 75% of microglia from the hypothalamus and reduced markers of inflammation without affecting brain-derived neurotrophic factor levels induced by EE. Adipose tissue remodeling and adipose tissue macrophage modulation were observed in response to CSF1R inhibition, which may contribute to the combined benefits seen in EE with PLX. Our study suggests benefits exist from combined drug and lifestyle interventions in aged animals.
Subject(s)
Adipose Tissue/drug effects , Aging/metabolism , Housing, Animal , Microglia/drug effects , Organic Chemicals/pharmacology , Receptors, Granulocyte-Macrophage Colony-Stimulating Factor/antagonists & inhibitors , Social Environment , Adipose Tissue/metabolism , Animals , Body Composition/drug effects , Body Weight/drug effects , Brain-Derived Neurotrophic Factor/drug effects , Brain-Derived Neurotrophic Factor/genetics , Brain-Derived Neurotrophic Factor/metabolism , Corticotropin-Releasing Hormone/drug effects , Corticotropin-Releasing Hormone/genetics , Corticotropin-Releasing Hormone/metabolism , Female , Glial Fibrillary Acidic Protein/drug effects , Glial Fibrillary Acidic Protein/genetics , Glial Fibrillary Acidic Protein/metabolism , Glucose Tolerance Test , Gonadotropin-Releasing Hormone/drug effects , Gonadotropin-Releasing Hormone/genetics , Gonadotropin-Releasing Hormone/metabolism , Hypothalamus/drug effects , Hypothalamus/metabolism , Inflammation/genetics , Inflammation/metabolism , Macrophages/drug effects , Macrophages/metabolism , Mice , Neuropeptide Y/drug effects , Neuropeptide Y/genetics , Pro-Opiomelanocortin/drug effects , Pro-Opiomelanocortin/genetics , Pro-Opiomelanocortin/metabolism , Protein Kinase Inhibitors/pharmacology , Transcriptome/drug effects , Weight LossABSTRACT
BTBR Tâ¯+â¯Itpr3tf/J (BTBR) mice are an Autism Spectrum Disorder (ASD)-like model that exhibit behavioral and physiological deficits similar to those observed in patients with ASD. While behavioral therapy is a first line of treatment in ASD patients, comparable non-pharmacological treatments are less explored in murine models. Here, we administer a bio-behavioral intervention for BTBR mice by way of environmental enrichment (EE) - an experimental housing paradigm previously shown to improve systemic metabolism, learning/memory, anxious behavior, neurogenesis, locomotion, and immunocompetence in C57BL/6 mice. Juvenile BTBR mice were randomized to standard or EE housing and were subjected to metabolic and behavioral assessments up to 17 weeks. Following EE exposure, we report an EE-induced metabolic and behavioral phenotype. Male BTBR mice responded metabolically to EE, displaying reduced adiposity, increased lean mass, improved glycemic control, and decreased circulating leptin. The gene expressions of brain-derived neurotrophic factor (Bdnf) and its receptor (Ntrk2/TrkB) were upregulated in several brain areas in EE-BTBR males. EE-BTBR females showed modest reduction of adiposity and no changes in glycemic control, circulating leptin, or Bdnf/Ntrk2 gene expression. With regard to behavior, EE resulted in decreased anxiety, and increased social affiliation. Together, these results suggest that EE improves metabolic and behavioral health in BTBR mice.
Subject(s)
Autistic Disorder/metabolism , Autistic Disorder/physiopathology , Autistic Disorder/therapy , Animals , Anxiety , Autism Spectrum Disorder/metabolism , Autism Spectrum Disorder/physiopathology , Autism Spectrum Disorder/therapy , Behavior, Animal/physiology , Brain-Derived Neurotrophic Factor/genetics , Brain-Derived Neurotrophic Factor/metabolism , Disease Models, Animal , Environment , Female , Male , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , Mice , Mice, Inbred Strains , Protein-Tyrosine Kinases/genetics , Protein-Tyrosine Kinases/metabolism , Social BehaviorABSTRACT
Aging is associated with increased central nervous system inflammation, in large part due to dysfunctional microglia. Environmental enrichment (EE) provides a model for studying the dynamics of lifestyle factors in the development of age-related neuroinflammation and microglial dysfunction. EE results in improvements in learning and memory, metabolism, and mental health in a variety of animal models. We recently reported that implementing EE in middle age promotes healthy aging. In the present study, we investigated whether EE influences microglial morphology, and whether EE is associated with changes in expression of microglial and neuroinflammatory markers. Inflammatory cytokines and MHC-II were reduced following 12-month EE in 10-month-old mice. Long-term EE for 7.5 months resulted in broad increases in Iba1 expression in hippocampus, hypothalamus, and amygdala detected by immunohistochemistry. Quantification of microglial morphology reveal both hypertrophy and ramification in these three brain regions, without increases in microglial cell density. These data indicate that long-term EE implemented in middle age results in a microglial state distinct from that of normal aging in standard laboratory housing, in specific brain regions, associated with reduced neuroinflammatory markers and improvement of systemic metabolism.
