F Briet1, K N Jeejeebhoy. 1. Department of Medicine, University of Toronto, Ontario, Canada.
Abstract
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. DESIGN: 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. CONCLUSION: Malnutrition decreases activities of mitochondrial complexes, which are restored by protein but not glucose refeeding.
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. DESIGN: 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. CONCLUSION:Malnutrition decreases activities of mitochondrial complexes, which are restored by protein but not glucose refeeding.