Protein breakdown on whole-body and organ level in non-cachectic tumour-bearing mice undergoing surgery.
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.
Vissers
Yvonne L J
YL
Department of Surgery, Maastricht University and University Hospital Maastricht, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), The Netherlands.
von Meyenfeldt
Maarten F
MF
Argilés
Josep M
JM
Luiking
Yvette C
YC
Dejong
Cornelis H C
CH
Deutz
Nicolaas E P
NE
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
D008762:Methylhistidines; D009124:Muscle Proteins; D011506:Proteins