Effect of hypoenergetic feeding and refeeding on muscle and mononuclear cell activities of mitochondrial complexes I--IV in enterally fed rats.
BACKGROUND
Previous studies suggested that cell energetics are altered by malnutrition.


OBJECTIVE
We hypothesized that nutritional manipulations influence mitochondrial enzyme activities of the electron transport chain in both skeletal muscle and blood mononuclear cells.


METHODS
After a gastrostomy tube was inserted, 44 rats were randomly assigned to 1 of 4 experimental groups: control fed (CF; 364 kJ/d for 7 d), hypoenergetic fed (HF; 92 kJ/d for 7 d), hypoenergetic protein refed (HPR; 92 kJ/d for 7 d and then 129 kJ/d for 1 d), and hypoenergetic glucose refed (HGR; 92 kJ/d for 7 d and then 129 kJ/d for 1 d). The protein and glucose contents of the liquid formulas were different for the HPR and HGR groups. After mitochondria were isolated from the soleus muscle, the activities of complexes I--IV were measured spectrophotometrically. Because of the lack of available tissue, only the activity of complex I was measured in the mononuclear cell extract.


RESULTS
The recovery of complex activities in the CF and HF groups was not significantly different in the mitochondrial fraction of the soleus muscle. Compared with that in the CF group, the activities of complexes I--III in the mitochondrial fraction of the soleus muscle and the activity of complex I in mononuclear cells were significantly lower in the HF group. The activities of complexes I--III in the mitochondrial fraction of the soleus muscle and the activity of complex I in mononuclear cells were significantly higher in the HPR than in the HF group. The activity of complex IV was generally not affected by nutritional manipulations.


CONCLUSIONS
Malnutrition decreases activities of mitochondrial complexes, which are restored by protein but not glucose refeeding.
Briet
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Department of Medicine, University of Toronto, Ontario, Canada.
Jeejeebhoy
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D042967:Electron Transport Complex I; D042963:Electron Transport Complex II; D014450:Electron Transport Complex III / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D004750:Enteral Nutrition; D007963:Leukocytes, Mononuclear / Q000201:enzymology; D008297:Male; D008928:Mitochondria / Q000201:enzymology*; D008931:Mitochondria, Muscle / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000378:metabolism; D018482:Muscle, Skeletal / Q000201:enzymology*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D011502:Protein-Energy Malnutrition / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D012044:Regression Analysis; D013385:Succinate Dehydrogenase / Q000378:metabolism
D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D009097:Multienzyme Complexes; D000255:Adenosine Triphosphate; D010088:Oxidoreductases; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase; D009247:NADH, NADPH Oxidoreductases; D003576:Electron Transport Complex IV; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III