title: Alterations in hypothalamic gene expression following Roux-en-Y gastric bypass.
abstract: OBJECTIVE
  The role of the central nervous system in mediating metabolic effects of Roux-en-Y gastric bypass (RYGB) surgery is poorly understood. Using a rat model of RYGB, we aimed to identify changes in gene expression of key hypothalamic neuropeptides known to be involved in the regulation of energy balance.
  
  
  METHODS
  Lean male Sprague-Dawley rats underwent either RYGB or sham surgery. Body weight and food intake were monitored bi-weekly for 60 days post-surgery. In situ hybridization mRNA analysis of hypothalamic AgRP, NPY, CART, POMC and MCH was applied to RYGB and sham animals and compared with ad libitum fed and food-restricted rats. Furthermore, in situ hybridization mRNA analysis of dopaminergic transmission markers (TH and DAT) was applied in the midbrain.
  
  
  RESULTS
  RYGB surgery significantly reduced body weight and intake of a highly palatable diet but increased chow consumption compared with sham operated controls. In the arcuate nucleus, RYGB surgery increased mRNA levels of orexigenic AgRP and NPY, whereas no change was observed in anorexigenic CART and POMC mRNA levels. A similar pattern was seen in food-restricted versus ad libitum fed rats. In contrast to a significant increase of orexigenic MCH mRNA levels in food-restricted animals, RYGB did not change MCH expression in the lateral hypothalamus. In the VTA, RYGB surgery induced a reduction in mRNA levels of TH and DAT, whereas no changes were observed in the substantia nigra relative to sham surgery.
  
  
  CONCLUSIONS
  RYGB surgery increases the mRNA levels of hunger-associated signaling markers in the rat arcuate nucleus without concomitantly increasing downstream MCH expression in the lateral hypothalamus, suggesting that RYGB surgery puts a brake on orexigenic hypothalamic output signals. In addition, down-regulation of midbrain TH and DAT expression suggests that altered dopaminergic activity also contributes to the reduced intake of palatable food in RYGB rats.
authors.affiliation: Gubra, Agern Alle 1, 2970 Hørsholm, Denmark; Department of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark. Electronic address: pb@gubra.dk.
authors.forename: Pernille
authors.initials: P
authors.lastname: Barkholt
authors.affiliation: Gubra, Agern Alle 1, 2970 Hørsholm, Denmark.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Pedersen
authors.affiliation: Department of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen N, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Hay-Schmidt
authors.affiliation: Gubra, Agern Alle 1, 2970 Hørsholm, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Jelsing
authors.affiliation: Gubra, Agern Alle 1, 2970 Hørsholm, Denmark.
authors.forename: Henrik H
authors.initials: HH
authors.lastname: Hansen
authors.affiliation: Gubra, Agern Alle 1, 2970 Hørsholm, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Vrang
keywords: Energy homeostasis; Hedonic; Hypothalamus; Mesolimbic pathway; Roux-en-Y gastric bypass