ABSTRACT
During evolution, mitochondrial DNA haplogroups of arctic populations may have been selected for lower coupling of mitochondrial respiration to ATP production in favor of higher heat production. We show that mitochondrial coupling in skeletal muscle of traditional and westernized Inuit habituating northern Greenland is identical to Danes of western Europe haplogroups. Biochemical coupling efficiency was preserved across variations in diet, muscle fiber type, and uncoupling protein-3 content. Mitochondrial phenotype displayed plasticity in relation to lifestyle and environment. Untrained Inuit and Danes had identical capacities to oxidize fat substrate in arm muscle, which increased in Danes during the 42 days of acclimation to exercise, approaching the higher level of the Inuit hunters. A common pattern emerges of mitochondrial acclimatization and evolutionary adaptation in humans at high latitude and high altitude where economy of locomotion may be optimized by preservation of biochemical coupling efficiency at modest mitochondrial density, when submaximum performance is uncoupled from VO2max and maximum capacities of oxidative phosphorylation.
Subject(s)
Deltoid Muscle/metabolism , Inuit , Mitochondria, Muscle/metabolism , Oxidative Phosphorylation , Quadriceps Muscle/metabolism , White People , Adenosine Triphosphate/biosynthesis , Adult , Cell Respiration , Cold Temperature , DNA, Mitochondrial , Deltoid Muscle/cytology , Denmark/ethnology , Fatty Acids/metabolism , Female , Greenland/ethnology , Haplotypes , Humans , Inuit/genetics , Ion Channels/metabolism , Male , Mitochondrial Proteins/metabolism , Oxidation-Reduction , Oxygen Consumption , Quadriceps Muscle/cytology , Seasons , Skiing/physiology , Thermogenesis , Uncoupling Protein 3 , White People/geneticsABSTRACT
Previous studies have investigated if cryopreservation is a viable approach for functional mitochondrial analysis. Different tissues have been studied, and conflicting results have been published. The aim of the present study was to investigate if mitochondria in human skeletal muscle maintain functionality after long term cryopreservation (1 year). Skeletal muscle samples were preserved in dimethyl sulfoxide (DMSO) for later analysis. Human skeletal muscle fibres were thawed and permeabilised with saponin, and mitochondrial respiration was measured by high-resolution respirometry. The capacity of oxidative phosphorylation was significantly (P < 0.05) reduced in cryopreserved human skeletal muscle samples. Cryopreservation impaired respiration with substrates linked to Complex I more than for Complex II (P < 0.05). Addition of cytochrome c revealed an increase in respiration indicating cytochrome c loss from the mitochondria. The results from this study demonstrate that normal mitochondrial functionality is not maintained in cryopreserved human skeletal muscle samples.
