title: The effects of weight loss versus weight loss maintenance on sympathetic nervous system activity and metabolic syndrome components.
abstract: BACKGROUND
  Sympathetic nervous system (SNS) overactivity participates in both the pathogenesis and adverse clinical complications of metabolic syndrome (MetS) obesity.
  
  
  OBJECTIVE
  We conducted a prospective lifestyle intervention trial to compare the effects of active weight loss and extended weight loss maintenance on SNS function and MetS components.
  
  
  METHODS
  Untreated subjects (14 males, four females; mean age, 53 ± 1 yr; body mass index, 30.9 ± 0.9 kg/m(2)) who fulfilled Adult Treatment Panel III criteria were randomized to 12-wk hypocaloric diet alone (n = 8) or together with aerobic exercise training (n = 10). This was followed by a 4-month weight maintenance period. Measurements of muscle sympathetic nerve activity (MSNA) by microneurography, whole-body norepinephrine kinetics, substrate oxidation by indirect calorimetry, baroreflex sensitivity, plasma renin activity (PRA), and MetS components were performed.
  
  
  RESULTS
  Body weight decreased by 9.3 ± 0.8% at wk 12 (P < 0.001), and this was maintained. During active weight loss, norepinephrine spillover rate decreased by 23 ± 16% (P = 0.004), MSNA by 25 ± 3 bursts per 100 heartbeats (P < 0.001), and PRA by 0.25 ± 0.09 ng/ml · h (P = 0.007), whereas baroreflex sensitivity increased by 5.2 ± 2.2 msec/mm Hg (P = 0.005). After weight maintenance, beneficial effects of weight loss on norepinephrine spillover rate were preserved, whereas PRA and MSNA rebounded (by 0.24 ± 0.11 ng/ml · h, P = 0.02; and 20 ± 5 bursts/100 heartbeats, P = 0.0003), and baroreflex sensitivity was attenuated.
  
  
  CONCLUSIONS
  Divergent effects of successful weight loss maintenance on whole-body norepinephrine spillover rate and MSNA suggest organ-specific differentiation in SNS adaptation to weight loss under conditions of negative vs. stable energy balance.
authors.affiliation: Laboratories of Human Neurotransmitters, Baker IDI Heart and Diabetes Institute, P.O. Box 6492, St. Kilda Road Central, Melbourne, Victoria 8008, Australia. Nora.Straznicky@bakeridi.edu.au
authors.forename: Nora E
authors.initials: NE
authors.lastname: Straznicky
authors.forename: Mariee T
authors.initials: MT
authors.lastname: Grima
authors.forename: Nina
authors.initials: N
authors.lastname: Eikelis
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Nestel
authors.forename: Tye
authors.initials: T
authors.lastname: Dawood
authors.forename: Markus P
authors.initials: MP
authors.lastname: Schlaich
authors.forename: Reena
authors.initials: R
authors.lastname: Chopra
authors.forename: Kazuko
authors.initials: K
authors.lastname: Masuo
authors.forename: Murray D
authors.initials: MD
authors.lastname: Esler
authors.forename: Carolina I
authors.initials: CI
authors.lastname: Sari
authors.forename: Gavin W
authors.initials: GW
authors.lastname: Lambert
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Lambert
mesh_terms: D000886:Anthropometry; D017704:Baroreflex / Q000502:physiology; D001835:Body Weight / Q000502:physiology*; D004038:Diet, Reducing; D002149:Energy Intake; D005081:Exercise Therapy; D005260:Female; D006321:Heart / Q000502:physiology; D006801:Humans; D008019:Life Style; D008297:Male; D024821:Metabolic Syndrome / Q000178:diet therapy / Q000503:physiopathology* / Q000628:therapy*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000294:innervation; D009638:Norepinephrine / Q000378:metabolism; D010809:Physical Fitness; D011865:Radioisotope Dilution Technique; D012039:Regional Blood Flow / Q000502:physiology; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D015431:Weight Loss / Q000502:physiology*
chemical_list: D009638:Norepinephrine