Changes of mitochondrial function and energy transfer enzymes in muscles of mice with deleted wolframin (wfs1) gene

Aim: To assess changes of mitochondrial function and activities of enzymes involved in the transport of energy in different muscles of wfs1 deficient mice. Methods: Mitochondrial function was assayed by high resolution oxygraphy of permeabilized muscle fibers. Respiration related to oxidative phosphorylation was calculated by subtracting initial basal respiration in the presence of pyruvate and malate from respiration with ADP. Proton leak related respiration was found by subtracting residual oxygen consumption with rotenone from basal respiration. The difference between the respiration rates in the presence of ADP+pyruvate+malate and rotenone was considered to represent the activity of Compex I in the electron transfer chain, and the difference between ADP+succinate and rotenone represented the activity of Complex II. Activities of enzymes were measured by spectroscopy of muscle homogenates. Results: Compared to controls, there was no change of proton leak and hexokinase activity in the wfs1 deficient heart and m. soleus, but in m. rectus femoris 16.1-fold (p<0.002) and 1.7-fold (p<0.01) increases were found respectively. However, oxidative phosphorylation was not changed in any muscle group. The Complex I / Complex II ratio was decreased in heart by 15% (p<0.03) and in musculus rectus femoris by 21% (p<0.01). Activities of creatine and adenylate kinase were decreased in m. rectus femoris by 34% (p<0.01) and 48% (p<0.02) respectively. Conclusions: In heart and m. rectus femoris of wfs1 deficient mice the ratio of Complex I and Complex II activities was decreased. In m. rectus femoris of wfs1 deficient mice proton leak and hexokinase activity were increased, but activity of other energy tranfer enzymes was decreased.