title: Vagus nerve stimulation increases energy expenditure: relation to brown adipose tissue activity.
abstract: BACKGROUND
  Human brown adipose tissue (BAT) activity is inversely related to obesity and positively related to energy expenditure. BAT is highly innervated and it is suggested the vagus nerve mediates peripheral signals to the central nervous system, there connecting to sympathetic nerves that innervate BAT. Vagus nerve stimulation (VNS) is used for refractory epilepsy, but is also reported to generate weight loss. We hypothesize VNS increases energy expenditure by activating BAT.
  
  
  RESULTS
  Fifteen patients with stable vns therapy (age: 45 ± 10 yrs; body mass index; 25.2 ± 3.5 kg/m(2)) were included between January 2011 and June 2012. Ten subjects were measured twice, once with active and once with inactivated VNS. Five other subjects were measured twice, once with active VNS at room temperature and once with active VNS under cold exposure in order to determine maximal cold-induced BAT activity. BAT activity was assessed by 18-Fluoro-Deoxy-Glucose-Positron-Emission-Tomography-and-Computed-Tomography. Basal metabolic rate (BMR) was significantly higher when VNS was turned on (mean change; +2.2%). Mean BAT activity was not significantly different between active VNS and inactive VNS (BAT SUV(Mean); 0.55 ± 0.25 versus 0.67 ± 0.46, P = 0.619). However, the change in energy expenditure upon VNS intervention (On-Off) was significantly correlated to the change in BAT activity (r = 0.935, P<0.001).
  
  
  CONCLUSIONS
  VNS significantly increases energy expenditure. The observed change in energy expenditure was significantly related to the change in BAT activity. This suggests a role for BAT in the VNS increase in energy expenditure. Chronic VNS may have a beneficial effect on the human energy balance that has potential application for weight management therapy.
  
  
  BACKGROUND
  The study was registered in the Clinical Trial Register under the ClinicalTrials.gov Identifier NCT01491282.
authors.affiliation: Department of Human Biology, School for Nutrition, Toxicology and Metabolism - NUTRIM, Maastricht University Medical Center, Maastricht, The Netherlands ; Department of General Surgery, Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Guy H E J
authors.initials: GH
authors.lastname: Vijgen
authors.forename: Nicole D
authors.initials: ND
authors.lastname: Bouvy
authors.forename: Loes
authors.initials: L
authors.lastname: Leenen
authors.forename: Kim
authors.initials: K
authors.lastname: Rijkers
authors.forename: Erwin
authors.initials: E
authors.lastname: Cornips
authors.forename: Marian
authors.initials: M
authors.lastname: Majoie
authors.forename: Boudewijn
authors.initials: B
authors.lastname: Brans
authors.forename: Wouter D
authors.initials: WD
authors.lastname: van Marken Lichtenbelt
mesh_terms: D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000328:Adult; D000704:Analysis of Variance; D002153:Calorimetry, Indirect; D003080:Cold Temperature; D004734:Energy Metabolism / Q000502:physiology*; D004827:Epilepsy / Q000628:therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D055536:Vagus Nerve Stimulation