Relationship between metabolism and peripheral blood mononuclear cell mitochondrial complex I activity before and after a short-term refeeding in weight-losing cancer patients

BACKGROUND AND AIMS: Previous investigations showed that mitochondrial complex I activity seems to be a specific marker of dietary malnutrition in human. Since cancer has a more complex etiology than simple calorie deficiency, the aim of this study was to investigate the relationship between mitochondrial complex I activity and cancer. METHODS: Nine cancer patients (CaPs) with weight loss and 14 age-matched healthy volunteers (HVs) were recruited. Body mass index (BMI), body composition as well as resting energy expenditure (REE) and RQ were measured. Mitochondrial complex I activity was measured as described previously in isolated peripheral blood mononuclear cells. Six patients were investigated again after 7 days of refeeding. RESULTS: Weight loss in CaPs was mainly due to a loss of fat mass (FM), while fat-free mass (FFM) was preserved. The RQ was significantly lower in CaPs compared to HVs (P<0.001) and peripheral blood mononuclear cell complex I activity was significantly correlated with the %FM and RQ in CaPs. Furthermore, complex I activity increased significantly after 1 week of refeeding. CONCLUSIONS: Our study showed that mitochondrial complex I activity was inversely correlated to parameters of increased fat oxidation and reduced FM, which are indices of dietary insufficiency rather than loss of lean body mass, which is an index of increased catabolism in cancer.