Robert Thayer

Acute and chronic response of skeletal muscle to resistance exercise.

SummarySkeletal muscle tissue is sensitive to the acute and chronic stresses associated with resistance training. These responses are influenced by the structure of resistance activity (i.e. frequency, load and recovery) as well as the training history of the individuals involved. There are histochemical and biochemical data which suggest that resistance training alters the expression of myosin heavy chains (MHCs). Specifically, chronic exposure to bodybuilding and power lifting type activity produces shifts towards the MHC I and IIb isoforms, respectively. However, it is not yet clear which training parameters trigger these differential expressions of MHC isoforms. Interestingly, many programmes undertaken by athletes appear to cause a shift towards the MHC I isoform. Increments in the cross-sectional area of muscle after resistance training can be primarily attributed to fibre hypertrophy. However, there may be an upper limit to this hypertrophy. Furthermore, significant fibre hypertrophy appears to follow the sequence of fast twitch fibre hypertrophy preceding slow twitch fibre hypertrophy. Whilst some indirect measures of fibre number in living humans suggest that there is no interindividual variation, postmortem evidence suggests that there is. There are also animal data arising from investigations using resistance training protocols which suggest that chronic exercise can increase fibre number. Furthermore, satellite cell activity has been linked to myotube formation in the human.However, other animal models (i.e. compensatory hypertrophy) do not support the notion of fibre hyperplasia. Even if hyperplasia does occur, its effect on the cross-sectional area of muscle appears to be small. Phosphagen and glycogen metabolism, whilst important during resistance activity appear not to normally limit the performance of resistance activity. Phosphagen and related enzyme adaptations are affected by the type, structure and duration of resistance training. Whilst endogenous glycogen reserves may be increased with prolonged training, typical isotonic training for less than 6 months does not seem to increase glycolytic enzyme activity. Lipid metabolism may be of some significance in bodybuilding type activity. Thus, not surprisingly, oxidative enzyme adaptations appear to be affected by the structure and perhaps the modality of resistance training. The dilution of mitochondrial volume and endogenous lipid densities appears mainly because of fibre hypertrophy.

Altered metabolism and mitochondrial genome in prostate cancer

Mutations in mitochondrial DNA are frequent in cancer and the accompanying mitochondrial dysfunction and altered intermediary metabolism might contribute to, or signal, tumour pathogenesis. The metabolism of human prostate peripheral zone glandular epithelial cells is unique. Compared with many other soft tissues, these glandular epithelial cells accumulate high concentrations of zinc, which inhibits the activity of m-aconitase, an enzyme involved in citrate metabolism through Krebs cycle. This causes Krebs cycle truncation and accumulation of high concentrations of citrate to be secreted in prostatic fluid. The accumulation of zinc also inhibits terminal oxidation. Therefore, these cells exhibit inefficient energy production. In contrast, malignant transformation of the prostate is associated with an early metabolic switch, leading to decreased zinc accumulation and increased citrate oxidation. The efficient energy production in these transformed cells implies increased electron transport chain activity, increased oxygen consumption, and perhaps, excess reactive oxygen species (ROS) production compared with normal prostate epithelial cells. Because ROS have deleterious effects on DNA, proteins, and lipids, the altered intermediary metabolism may be linked with ROS production and accelerated mitochondrial DNA mutations in prostate cancer.

The effect of exercise intensity on hematuria in healthy male runners.

Abstract The purpose of this study were: (1) to establish the prevalence of exercise-induced hematuria in a group of otherwise healthy male runners (n = 70), and (2) to investigate the role of exercise intensity in those runners who exhibited exercise-related hematuria (n = 10) by evaluating the effect of running and cycling at high and low intensities. The identified and recruited subjects participated in four different exercise protocols: (1) a 60-min treadmill run (RUN) at 90% of anaerobic threshold (Thae), (2) a 60-min leg cycle ergometer ride (BIKE) at 90% of Thae, (3) a 3×400-m sprint (SPRINT), each followed by 4 min of rest or light walking, and (4) 3×60-Wingate leg cycle ergometry tests, each followed by 4 min of rest or light cycling. The study employed a 3×4 (time by protocol) within-subjects design and dependent variables were measured before exercise, 4 min after, and 1 h after exercise, and included measurements of hematuria, proteinuria, urinary pH, serum haptoglobin concentration, serum creatine phosphokinase activity, plasma lactate concentration, and hemoglobin. The 400-m sprint at maximal effort significantly increased both hematuria and proteinuria (P < 0.01). Post-exercise hematuria for the SPRINT protocol was significantly different than that for the BIKE (P < 0.01) and RUN (P < 0.01) protocols. Due to the significant increase in hematuria and proteinuria following the SPRINT protocol, it was concluded that exercise-related changes in renal function were associated with weight-bearing exercise intensity rather than non-weight-bearing exercise duration.

Mitochondrial Genome Deletion Aids in the Identification of False- and True-Negative Prostate Needle Core Biopsy Specimens

We report the usefulness of a 3.4-kb mitochondrial genome deletion (3.4 mtdelta) for molecular definition of benign, malignant, and proximal to malignant (PTM) prostate needle biopsy specimens. The 3.4 mtdelta was identified through long-extension polymerase chain reaction (PCR) analysis of frozen prostate cancer samples. A quantitative PCR assay was developed to measure the levels of the 3.4 mtdelta in clinical samples. For normalization, amplifications of a nuclear target and total mitochondrial DNA were included. Cycle threshold data from these targets were used to calculate a score for each biopsy sample. In a pilot study of 38 benign, 29 malignant, and 41 PTM biopsy specimens, the difference between benign and malignant core biopsy specimens was well differentiated (P & .0001), with PTM indistinguishable from malignant samples (P = .833). Results of a larger study were identical. In comparison with histopathologic examination for benign and malignant samples, the sensitivity and specificity were 80% and 71%, respectively, and the area under a receiver operating characteristic (ROC) curve was 0.83 for the deletion. In a blinded external validation study, the sensitivity and specificity were 83% and 79%, and the area under the ROC curve was 0.87. The 3.4 mtdelta may be useful in defining malignant, benign, and PTM prostate tissues.

Mitochondrial DNA as a potential tool for early cancer detection

The recent surge in mitochondrial research has been driven by the identification of mitochondria-associated diseases and the role of mitochondria in apoptosis. Both of these aspects have identified mitochondrial analysis as a vital component of medical research. Moreover, mitochondria have been implicated in the process of carcinogenesis because of their vital role in energy production, nuclear-cytoplasmic signal integration and control of metabolic pathways. Interestingly, at some point during neoplastic transformation, there is an increase in reactive oxygen species, which damage the mitochondrial genome. This accelerates the somatic mutation rate of mitochondrial DNA. It has been proposed that these mutations may serve as an early indication of potential cancer development and may represent a means for tracking tumour progression. The purpose of this review is to explore the potential utility that these mutations may afford for the identification and monitoring of neoplasia and malignant transformation where appropriate body fluids or non-invasive tissue access is available for mitochondrial DNA recovery. Specifically, prostate, breast, colorectal, skin and lung cancers are discussed.

Facile whole mitochondrial genome resequencing from nipple aspirate fluid using MitoChip v2.0

BackgroundMutations in the mitochondrial genome (mtgenome) have been associated with many disorders, including breast cancer. Nipple aspirate fluid (NAF) from symptomatic women could potentially serve as a minimally invasive sample for breast cancer screening by detecting somatic mutations in this biofluid. This study is aimed at 1) demonstrating the feasibility of NAF recovery from symptomatic women, 2) examining the feasibility of sequencing the entire mitochondrial genome from NAF samples, 3) cross validation of the Human mitochondrial resequencing array 2.0 (MCv2), and 4) assessing the somatic mtDNA mutation rate in benign breast diseases as a potential tool for monitoring early somatic mutations associated with breast cancer.MethodsNAF and blood were obtained from women with symptomatic benign breast conditions, and we successfully assessed the mutation load in the entire mitochondrial genome of 19 of these women. DNA extracts from NAF were sequenced using the mitochondrial resequencing array MCv2 and by capillary electrophoresis (CE) methods as a quality comparison. Sequencing was performed independently at two institutions and the results compared. The germline mtDNA sequence determined using DNA isolated from the patients blood (control) was compared to the mutations present in cellular mtDNA recovered from patients NAF.ResultsFrom the cohort of 28 women recruited for this study, NAF was successfully recovered from 23 participants (82%). Twenty two (96%) of the women produced fluids from both breasts. Twenty NAF samples and corresponding blood were chosen for this study. Except for one NAF sample, the whole mtgenome was successfully amplified using a single primer pair, or three pairs of overlapping primers. Comparison of MCv2 data from the two institutions demonstrates 99.200% concordance. Moreover, MCv2 data was 99.999% identical to CE sequencing, indicating that MCv2 is a reliable method to rapidly sequence the entire mtgenome. Four NAF samples contained somatic mutations.ConclusionWe have demonstrated that NAF is a suitable material for mtDNA sequence analysis using the rapid and reliable MCv2. Somatic mtDNA mutations present in NAF of women with benign breast diseases could potentially be used as risk factors for progression to breast cancer, but this will require a much larger study with clinical follow up.