title: Acute cannabinoid receptor type 1 (CB1R) modulation influences insulin sensitivity by an effect outside the central nervous system in mice.
abstract: OBJECTIVE
  Modulation of central nervous system (CNS) and extra-CNS cannabinoid receptor type 1 (CB1R) affects metabolic conditions, independently of weight loss. Here we examined the relative contributions of acute CNS and extra-CNS CB1R modulation on insulin sensitivity using pharmacological gain- and loss-of-function of CB1R in mice.
  
  
  METHODS
  We assessed the effects of acute modulation of CB1R on insulin sensitivity and tissue glucose uptake by administering a CB1R agonist (HU210) and antagonist (AM251) (vs vehicle) i.v. in wild-type mice. In addition, we administered a CB1R agonist (vs vehicle) systemically (i.v.) to Cb1r (also known as Cnr1) knockout (Cb1r (-/-)) mice or intracerebroventricularly (i.c.v.) in wild-type mice to elucidate the peripheral vs CNS-mediated regulatory effect of CB1R on insulin sensitivity.
  
  
  RESULTS
  HU210 induced significant insulin resistance in wild-type mice with a reduction of whole-body glucose disappearance rate and muscle Akt phosphorylation, as well as of glucose uptake by skeletal muscle, but not by adipose tissue, changes that were prevented by pretreatment with AM251. HU210 did not affect insulin sensitivity in Cb1r (-/-) mice, suggesting that the observed effects were mediated through CB1R. HU210 administered i.c.v. did not induce insulin resistance, suggesting that acute stimulation of CNS CB1R was not required for this effect.
  
  
  CONCLUSIONS
  Skeletal muscle insulin sensitivity is affected by acute CB1R modulation. These changes are mediated by extra-CNS CB1R, probably by the receptors in skeletal muscle tissue.
authors.affiliation: Department of Medicine, University of Toronto, Toronto, ON, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Song
authors.forename: R H J
authors.initials: RH
authors.lastname: Bandsma
authors.forename: C
authors.initials: C
authors.lastname: Xiao
authors.forename: L
authors.initials: L
authors.lastname: Xi
authors.forename: W
authors.initials: W
authors.lastname: Shao
authors.forename: T
authors.initials: T
authors.lastname: Jin
authors.forename: G F
authors.initials: GF
authors.lastname: Lewis
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D007333:Insulin Resistance; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; C103505:AM 251; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose