Effect of malnutrition and short-term refeeding on peripheral blood mononuclear cell mitochondrial complex I activity in humans

Background: Previous investigations in rats have shown that the first enzyme of the mitochondrial electron transport chain (complex 1) is altered in peripheral blood mononuclear cells (PBMCs) and muscle by dietary manipulations. Objective: We hypothesized that similar changes would occur in human PBMCs as a result of dietary malnutrition and short-term refeeding irrespective of the presence or absence of active inflammatory bowel disease (IBD). Design: Fourteen malnourished patients with active IBD, 13 malnourished patients without IBD, and 42 healthy subjects were investigated. Complex I activity, body mass index, body composition, energy and protein intakes, and resting energy expenditure were measured. Five patients without IBD and 6 patients with IBD were investigated after 7 d of refeeding. Results: In patients without IBD, weight loss was mainly due to a loss of fat mass. In contrast, weight loss in IBD patients was due to a loss of both fat-free mass and fat mass. Complex I activity was reduced to the same degree in both groups of patients and was significantly lower than that observed in healthy subjects. In both groups of patients, complex I activity correlated significantly with body weight, body mass index, percentage weight loss, and fat mass. Complex I activity increased significantly after 1 wk of refeeding in both groups of patients before observed changes of measured nutritional assessment indexes. Conclusion: Our study showed that mitochondrial complex I activity measured in PBMCs seems to be a specific marker of dietary malnutrition and responds rapidly to refeeding.