title: The effects of dietary weight loss on indices of norepinephrine turnover: modulatory influence of hyperinsulinemia.
abstract: OBJECTIVE
  This study was conducted to examine (1) the effects of dietary weight loss on indices of norepinephrine (NE) turnover and (2) whether baseline hyperinsulinemia modulates sympathetic neural adaptations.
  
  
  METHODS
  Obese individuals aged 56 ± 1 year, BMI 32.5 ± 0.4 kg/m(2) , with metabolic syndrome, underwent a 12-week hypocaloric diet (HCD, n = 39) or no treatment (n = 26). Neurochemical measurements comprised arterial dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylglycol (DHPG), and NE concentrations, the steady-state ratio of [3H]-DHPG to [3H]-NE, as an index of neuronal uptake, and calculated whole-body plasma NE clearance and spillover rates.
  
  
  RESULTS
  Body weight decreased by -7.4 ± 0.5% in HCD group (P < 0.001) and was accompanied by reductions in DOPA, NE, and DHPG averaging -14 ± 5% (P = 0.001), -23 ± 4% (P <0.001), and -5 ± 4% (P = 0.03), respectively. NE spillover rate decreased by -88 ± 39 ng/min (P = 0.01), whereas neuronal uptake and NE plasma clearance were unchanged. Despite similar weight loss, hyperinsulinemic subjects exhibited greater reductions in NE and NE spillover rate, compared to normoinsulinemic subjects (group by time interaction P < 0.05).
  
  
  CONCLUSIONS
  Weight loss is associated with down-regulation of sympathetic nervous activity but no overall alteration in disposition indices. Hyperinsulinemic subjects derive a greater sympathoinhibitory benefit during weight loss.
authors.affiliation: Laboratories of Human Neurotransmitters, Baker IDI Heart & Diabetes Institute, Melbourne, Victoria, Australia.
authors.forename: Nora E
authors.initials: NE
authors.lastname: Straznicky
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Lambert
authors.forename: Mariee T
authors.initials: MT
authors.lastname: Grima
authors.forename: Nina
authors.initials: N
authors.lastname: Eikelis
authors.forename: Katrina
authors.initials: K
authors.lastname: Richards
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Nestel
authors.forename: Tye
authors.initials: T
authors.lastname: Dawood
authors.forename: Kazuko
authors.initials: K
authors.lastname: Masuo
authors.forename: Carolina I
authors.initials: CI
authors.lastname: Sari
authors.forename: John B
authors.initials: JB
authors.lastname: Dixon
authors.forename: Murray D
authors.initials: MD
authors.lastname: Esler
authors.forename: Eldho
authors.initials: E
authors.lastname: Paul
authors.forename: Markus P
authors.initials: MP
authors.lastname: Schlaich
authors.forename: Gavin W
authors.initials: GW
authors.lastname: Lambert
mesh_terms: D015992:Body Mass Index; D004038:Diet, Reducing; D004295:Dihydroxyphenylalanine / Q000097:blood / Q000493:pharmacokinetics; D015536:Down-Regulation; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D006946:Hyperinsulinism / Q000150:complications / Q000378:metabolism*; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications / Q000378:metabolism; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000097:blood / Q000493:pharmacokinetics; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood* / Q000493:pharmacokinetics; D009765:Obesity / Q000150:complications / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000187:drug effects; D015431:Weight Loss / Q000187:drug effects*; D044465:White People
chemical_list: D008734:Methoxyhydroxyphenylglycol; D004295:Dihydroxyphenylalanine; C010117:3,4-dihydroxyphenylglycol; D009638:Norepinephrine