Short‐term bed rest‐induced insulin resistance cannot be explained by increased mitochondrial H₂O₂ emission

Abstract

We determined if bed rest increased mitochondrially derived reactive oxygen species and cellular redox stress, contributing to the induction of insulin resistance. Bed rest decreased maximal and submaximal ADP-stimulated mitochondrial respiration. Bed rest did not alter mitochondrial H₂ O₂ emission in the presence of ADP concentrations indicative of resting muscle, the ratio of H₂ O₂ emission to mitochondrial O₂ consumption or markers of oxidative stress The present data suggest strongly that mitochondrial H₂ O₂ does not contribute to bed rest-induced insulin resistance ABSTRACT: Mitochondrial H₂ O₂ has been causally linked to diet-induced insulin resistance, although it remains unclear if muscle disuse similarly increases mitochondrial H₂ O₂ . Therefore, we investigated the potential that an increase in skeletal muscle mitochondrial H₂ O₂ emission, potentially as a result of decreased ADP sensitivity, contributes to cellular redox stress and the induction of insulin resistance during short-term bed rest in 20 healthy males. Bed rest led to a decline in glucose infusion rate during a hyperinsulinaemic-euglycaemic clamp (-42 ± 2%; P < 0.001), and in permeabilized skeletal muscle fibres it decreased OXPHOS protein content (-16 ± 8%) and mitochondrial respiration across a range of ADP concentrations (-13 ± 5%). While bed rest tended to increase maximal mitochondrial H₂ O₂ emission rates (P = 0.053), H₂ O₂ emission in the presence of ADP concentrations indicative of resting muscle, the ratio of H₂ O₂ emission to mitochondrial O₂ consumption, and markers of oxidative stress were not altered following bed rest. Altogether, while bed rest impairs mitochondrial ADP-stimulated respiration, an increase in mitochondrial H₂ O₂ emission does not contribute to the induction of insulin resistance following short-term bed rest.