Exercise training has been associated with increased mitochondrial content and respiration. However, no study to date has compared in parallel how training at different intensities affects mitochondrial respiration and markers of mitochondrial biogenesis. Twenty-nine healthy men performed 4 wk (12 cycling sessions) of either sprint interval training [SIT; 4-10 3 30-s all-out bouts at ∼200% of peak power output (W Peak )], high-intensity interval training (HIIT; 4-7 3 4-min intervals at ∼90% W Peak ), or sublactate threshold continuous training (STCT; 20-36 min at ∼65% W Peak ). The STCT and HIIT groups were matched for total work. Resting biopsy samples (vastus lateralis) were obtained before and after training. The maximal mitochondrial respiration in permeabilized muscle fibers increased significantly only after SIT (25%). Similarly, the protein content of peroxisome proliferator-activated receptor g coactivator (PGC)-1a, p53, and plant homeodomain finger-containing protein 20 (PHF20) increased only after SIT (60-90%). Conversely, citrate synthase activity, and the protein content of TFAM and subunits of the electron transport system complexes remained unchanged throughout. Our findings suggest that training intensity is an important factor that regulates training-induced changes in mitochondrial respiration and that there is an apparent dissociation between training-induced changes in mitochondrial respiration and mitochondrial content. Moreover, changes in the protein content of PGC-1a, p53, and PHF20 are more strongly associated with training-induced changes in mitochondrial respiration than mitochondrial content.-Granata, C., Oliveira, R. S. F., Little, J. P., Renner, K., Bishop, D. J. Training intensity modulates changes in PGC-1a and p53 protein content and mitochondrial respiration, but not markers of mitochondrial content in human skeletal muscle. FASEB J. 30, 959-970 (2016). www.fasebj.org

A sedentary lifestyle has been linked to a number of metabolic disorders that have been associated with sub-optimal mitochondrial characteristics and an increased risk of premature death. Endurance training can induce an increase in mitochondrial content and/or mitochondrial functional qualities, which are associated with improved health and well-being and longer life expectancy. It is therefore important to better define how manipulating key parameters of an endurance training intervention can influence the content and functionality of the mitochondrial pool. This review focuses on mitochondrial changes taking place following a series of exercise sessions (training-induced mitochondrial adaptations), providing an in-depth analysis of the effects of exercise intensity and training volume on changes in mitochondrial protein synthesis, mitochondrial content and mitochondrial respiratory function. We provide evidence that manipulation of different exercise training variables promotes specific and diverse mitochondrial adaptations. Specifically, we report that training volume may be a critical factor affecting changes in mitochondrial content, whereas relative exercise intensity is an important determinant of changes in mitochondrial respiratory function. As a consequence, a dissociation between training-induced changes in mitochondrial content and mitochondrial respiratory function is often observed. We also provide evidence that exercise-induced changes are not necessarily predictive of training-induced adaptations, we propose possible explanations for the above discrepancies and suggestions for future research.

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Increased mitochondrial content and respiration have both been reported after exercise training. However, no study has directly compared how different training volumes influence mitochondrial respiration and markers of mitochondrial biogenesis. Ten healthy men performed high-intensity interval cycling during 3 consecutive training phases; 4 wk of normal-volume training (NVT; 3/wk), followed by 20 d of high-volume training (HVT; 2/d) and 2 wk of reduced-volume training (RVT; 5 sessions). Resting biopsy samples (vastus lateralis) were obtained at baseline and after each phase. No mitochondrial parameter changed after NVT. After HVT, mitochondrial respiration and citrate synthase activity (∼40-50%), as well as the protein content of electron transport system (ETS) subunits (∼10-40%), and that of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), NRF1, mitochondrial transcription factor A (TFAM), PHF20, and p53 (∼65-170%) all increased compared to baseline; mitochondrial specific respiration remained unchanged. After RVT, all the mitochondrial parameters measured except citrate synthase activity (∼36% above initial) were not significantly different compared to baseline (all P > 0.05). Our findings demonstrate that training volume is an important determinant of training-induced mitochondrial adaptations and highlight the rapid reversibility of human skeletal muscle to a reduction in training volume.-Granata, C., Oliveira, R. S. F., Little, J. P., Renner, K., Bishop, D. J. Mitochondrial adaptations to high-volume exercise training are rapidly reversed after a reduction in training volume in human skeletal muscle.

Abstract:Background: While there is agreement that exercise is a powerful stimulus to increase both

Gene expression analysis by quantitative PCR in skeletal muscle is routine in exercise studies. The reproducibility and reliability of the data fundamentally depend on how the experiments are performed and interpreted. Despite the popularity of the assay, there is a considerable variation in experimental protocols and data analyses from different laboratories, and there is a lack of consistency of proper quality control steps throughout the assay. In this study, we present a number of experiments on various steps of quantitative PCR workflow, and demonstrate how to perform a quantitative PCR experiment with human skeletal muscle samples in an exercise study. We also tested some common mistakes in performing qPCR. Interestingly, we found that mishandling of muscle for a short time span (10 mins) before RNA extraction did not affect RNA quality, and isolated total RNA was preserved for up to one week at room temperature. Demonstrated by our data, use of unstable reference genes lead to substantial differences in the final results. Alternatively, cDNA content can be used for data normalisation; however, complete removal of RNA from cDNA samples is essential for obtaining accurate cDNA content.

In order to improve the leishmanicidal activity of the synthetic cecropin A-melittin hybrid peptide CA(1-7)M(2-9) (KWKLFKKIGAVLKVL-NH 2 ), a systematic study of its acylation with saturated linear fatty acids was carried out. Acylation of the N -7 lysine residue led to a drastic decrease in leishmanicidal activity, whereas acylation at lysine 1, in either the ␣ or the NH 2 group, increased up to 3 times the activity of the peptide against promastigotes and increased up to 15 times the activity of the peptide against amastigotes. Leishmanicidal activity increased with the length of the fatty acid chain, reaching a maximum for the lauroyl analogue (12 carbons). According to the fast kinetics, dissipation of membrane potential, and parasite membrane permeability to the nucleic acid binding probe SYTOX green, the lethal mechanism was directly related to plasma membrane permeabilization.

It is well established that different types of exercise can provide a powerful stimulus for mitochondrial biogenesis. However, there are conflicting findings in the literature, and a consensus has not been reached regarding the efficacy of high-intensity exercise to promote mitochondrial biogenesis in humans. The purpose of this review is to examine current controversies in the field and to highlight some important methodological issues that need to be addressed to resolve existing conflicts.