Mitochondrial responses to varying diet quality and quantity: shift in metabolic efficiency and capacity.

Abstract

Many animals experience periods of reduction in food quality and quantity. Metabolic responses of animals to periods of reduction in crucial nutrient and food deprivation may have positive and negative impacts on the animal performance. I will present results on the mitochondrial responses to reduction in omega-3 dietary availability in a marine fish, golden grey mullet (Chelon auratus) and naturally-occurring periods of food deprivation in brown trout (Salmo trutta). We show that mitochondria of fish fed on the low omega 3 highly unsaturated fatty acids (n-3 HUFA) diet had higher mitochondrial efficiency than those of fish maintained on the high n-3 HUFA diet. Yet, mitochondrial efficiency varied up about 2-fold among individuals on the same dietary treatment, resulting in some fish consuming half the oxygen and energy substrate to produce the similar amount of ATP than conspecific on similar diet. In another study, after a 2-week period of fasting, brown trout increased their oxidative phosphorylation (OXPHOS) respiration and decreased proton leakage (LEAK) respiration, suggesting a selective increase in the capacity to produce ATP without a concomitant increase in energy dissipated through proton leakage. However, this was associated with an almost two-fold increase in mitochondrial H2O2 levels. Our results emphasize that (i) shift in energy metabolism in response to food change may help preserve limited resources but potentially come at a cost of increased oxidative stress; (ii) individual variation in mitochondrial efficiency may explain intraspecific variation in response to food changes.