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High-resolution respirometry in human permeabilized muscle fibers is extensively used for analysis of mitochondrial adaptions to nutrition and exercise interventions, and is linked to athletic performance. However, the lack of standardization of experimental conditions limits quantitative inter- and intra-laboratory comparisons. In our study, an international team of investigators measured mitochondrial respiration of permeabilized muscle fibers obtained from three biopsies (vastus lateralis) from the same healthy volunteer to avoid inter-individual variability. High-resolution respirometry assays were performed together at the same laboratory to assess whether the heterogenity in published results are due to the effects of respiration media (MiR05 versus Z) with or without the myosin inhibitor blebbistatin at low- and high-oxygen regimes. Our findings reveal significant differences between respiration media for OXPHOS and ETcapacities supported by NADH&succinate-linked substrates at different oxygen concentrations. Respiratory capacities were approximately 1.5-fold higher in MiR05 at high-oxygen regimes compared to medium Z near air saturation. The presence or absence of blebbistatin in human permeabilized muscle fiber preparations was without effect on oxygen flux. Our study constitutes a basis to harmonize and establish optimum experimental conditions for respirometric studies of permeabilized human skeletal muscle fibers to improve reproducibility. [Display omitted] • Understanding muscle energetics' link to athletic performance is crucial. • Harmonizing mitochondrial bioenergetics protocols is critical for inter-study data analysis. • Medium composition and oxygen concentration influence muscle mitochondria respiratory capacity in permeabilized fibers. • Optimizing experimental protocols is pivotal for precise athletic performance evaluation. [ABSTRACT FROM AUTHOR]

Aims Previous data showed that melatonin maintains liver mitochondrial homeostasis during sepsis, but neither the mechanisms underlying mitochondrial dysfunction nor the target of melatonin are known. Main methods Here, we analyzed mitochondrial respiration in isolated mouse liver mitochondria with different substrate combinations (glutamate/malate, glutamate/malate/sucinate or succinate/rotenone) to identify mitochondrial defects and melatonin targets during sepsis. Other bioenergetic parameters including a + a 3 , b , and c + c 1 content, mitochondrial mass, and mitochondrial supercomplexes formation were analyzed. Mitochondrial function was assessed during experimental sepsis induced by cecal ligation and puncture (CLP) in livers of 3 mo. C57BL/6 mice at early and late phases of sepsis, i.e., at 8 and 24 h after sepsis induction. Key findings Septic mice showed mitochondrial injury with a decrease in state 3, respiratory control rate, mitochondrial mass, and cytochrome b and c + c 1 content, which was prevented by melatonin treatment. Mitochondrial dysfunction in sepsis was mainly linked to complex I damage, because complex II was far less impaired. These mitochondria preserved the respiratory supramolecular organization, maintaining their electron transport system capacity. Significance This work strengthens the use of substrate combinations to identify specific respiratory defects and selective melatonin actions in septic mitochondria. Targeting mitochondrial complex I should be a main therapeutical approach in the treatment of sepsis, whereas the use of melatonin should be considered in the therapy of clinical sepsis. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To analyze whether the antioxidant melatonin could reduce the hyperoxidative status in the blood of patients with Duchenne''s muscular dystrophy. Design and methods: Ten patients aged 12.8±0.9years were treated with melatonin (60mg at 21:00h plus 10mg at 09:00h) for 9months, and erythrocyte markers of oxidative stress were determined at 3, 6, and 9months of treatment. Healthy age- and sex-matched subjects served as controls. Results: Prior to treatment, the patients had higher glutathione disulfide/glutathione ratio and higher glutathione transferase and superoxide dismutase activities, and lower glutathione reductase activity than controls. After 3months of melatonin treatment, the hyperoxidative status of these patients was counteracted, being reduced to the normal redox state between 3 and 9months. Conclusion: These results, together with the reduction in the inflammatory process and in muscle injury recently reported in the same patients, support the efficacy of melatonin therapy in DMD patients. [Copyright &y& Elsevier]

Abstract: Mitochondrial complex I inhibition is thought to underlie the neurodegenerative process in Parkinson''s disease (PD). Moreover, an overproduction of nitric oxide due to both cytosolic (iNOS) and mitochondrial (i-mtNOS) inducible nitric oxide synthases causes free radicals generation and oxidative/nitrosative stress, contributing to mitochondrial dysfunction and neuronal cell death. Looking for active molecules against mitochondrial dysfunction and inflammatory response in PD, we show here the effects of four synthetic kynurenines in the MPTP model of PD in mice. After MPTP administration, mitochondria from substantia nigra and, in a lesser extent, from striatum showed a significant increase in i-mtNOS activity, nitric oxide production, oxidative stress, and complex I inhibition. The four kynurenines assayed counteracted the effects of MPTP, reducing iNOS/i-mtNOS activity, and restoring the activity of the complex I. Consequently, the cytosolic and mitochondrial oxidative/nitrosative stress returned to control values. The results suggest that the kynurenines here reported represent a family of synthetic compounds with neuroprotective properties against PD, and that they can serve as templates for the design of new drugs able to target the mitochondria. [Copyright &y& Elsevier]