title: Protein breakdown on whole-body and organ level in non-cachectic tumour-bearing mice undergoing surgery.
abstract: OBJECTIVE
  Since both cancer and surgery are known to alter protein turnover, we investigated how the presence of tumour affects post-operative protein breakdown.
  
  
  METHODS
  Controls and tumour-bearing non-cachectic mice were studied, both with and without laparotomy (n=8 per group). One day after laparotomy, stable isotopes of phenylalanine and 3-methylhistidine were used in a steady-state protocol to assess total protein breakdown on whole-body level and in muscle, intestines, liver and kidney, in addition to whole-body myofibrillar protein breakdown and body composition. Proteasomal chymotrypsin-like activity was measured to determine activity of the ATP-dependent ubiquitin pathway.
  
  
  RESULTS
  On whole-body level, the presence of tumour increased total protein breakdown from 47+/-6 to 58+/-4 nmol/10 g/min (p<0.05) and myofibrillar protein breakdown from 0.70+/-0.04 to 1.22+/-0.14 nmol/10 g/min (p<0.05) without affecting protein breakdown in organs, body composition or proteasomal activity. Laparotomy increased myofibrillar protein breakdown in controls (from 0.70+/-0.04 to 0.98+/-0.12 nmol/10 g/min, p<0.05) and tumour-bearing mice (from 1.22+/-0.14 to 1.54+/-0.22 nmol/10 g/min, p=0.15) to a similar extent.
  
  
  CONCLUSIONS
  Whole-body total protein breakdown, total protein breakdown across organs, body composition or proteasomal activity were not affected by laparotomy. Tumour-bearing mice had increased total and myofibrillar protein breakdown on whole-body level even before weight loss was obvious. However, this did not affect the post-operative response in protein breakdown or body composition.
authors.affiliation: Department of Surgery, Maastricht University and University Hospital Maastricht, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), The Netherlands.
authors.forename: Yvonne L J
authors.initials: YL
authors.lastname: Vissers
authors.forename: Maarten F
authors.initials: MF
authors.lastname: von Meyenfeldt
authors.forename: Josep M
authors.initials: JM
authors.lastname: Argilés
authors.forename: Yvette C
authors.initials: YC
authors.lastname: Luiking
authors.forename: Cornelis H C
authors.initials: CH
authors.lastname: Dejong
authors.forename: Nicolaas E P
authors.initials: NE
authors.lastname: Deutz
mesh_terms: D000818:Animals; D001823:Body Composition; D004734:Energy Metabolism / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007813:Laparotomy; D008099:Liver / Q000378:metabolism; D008297:Male; D008762:Methylhistidines / Q000378:metabolism; D051379:Mice; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism; D009374:Neoplasms, Experimental / Q000378:metabolism*; D009928:Organ Specificity; D011184:Postoperative Period; D011506:Proteins / Q000378:metabolism*; D011897:Random Allocation
chemical_list: D008762:Methylhistidines; D009124:Muscle Proteins; D011506:Proteins