title: Characteristics of spinal microglia in aged and obese mice: potential contributions to impaired sensory behavior.
abstract: BACKGROUND
  Both aging and obesity have been recognized widely as health conditions that profoundly affect individuals, families and the society. Aged and obese people often report altered pain responses while underlying mechanisms have not been fully elucidated. We aim to understand whether spinal microglia could potentially contribute to altered sensory behavior in aged and obese population.
  
  
  RESULTS
  In this study, we monitored pain behavior in adult (6 months) and aged (17 months) mice fed with diet containing 10 % or 60 % Kcal fat. The group of young adult (3 months) mice was included as theoretical baseline control. Compared with lean adult animals, diet-induced-obese (DIO) adult, lean and DIO-aged mice showed enhanced painful response to heat and cold stimuli, while exhibiting hyposensitivity to mechanical stimulation. The impact of aging and obesity on microglia properties was evidenced by an increased microglial cell density in the spinal cords, stereotypic morphological changes and polarization towards pro-inflammatory phenotype. Obesity strikingly exacerbated the effect of aging on spinal microglia.
  
  
  CONCLUSIONS
  Aging/obesity altered microglia properties in the spinal cords, which can dysregulate neuron-microglia crosstalk and impair physiological pain signal transmission. The inflammatory functions of microglia have special relevance for understanding of abnormal pain behavior in aged/obese populations.
authors.affiliation: The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada ; Department of Neurology & Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC H3A 2B4 Canada ; Faculty of Dentistry, McGill University, Montreal, QC H3A 0C7 Canada.
authors.forename: SeungHwan
authors.initials: S
authors.lastname: Lee
authors.affiliation: The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada ; Department of Neurology & Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC H3A 2B4 Canada ; Faculty of Dentistry, McGill University, Montreal, QC H3A 0C7 Canada.
authors.forename: YaSi
authors.initials: Y
authors.lastname: Wu
authors.affiliation: The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada ; Department of Neurology & Neurosurgery, Faculty of Medicine, McGill University, Montreal, QC H3A 2B4 Canada ; Faculty of Dentistry, McGill University, Montreal, QC H3A 0C7 Canada.
authors.forename: Xiang Qun
authors.initials: XQ
authors.lastname: Shi
authors.affiliation: The Alan Edwards Centre for Research on Pain, McGill University, 740 Docteur Penfield Ave, Suite 3200C, Montreal, QC H3A 0G1 Canada.
authors.forename: Ji
authors.initials: J
authors.lastname: Zhang
keywords: Aging; Inflammation; Microglia; Obesity; Pain; Spinal cord