A gene therapy targeting medium-chain acyl-CoA dehydrogenase (MCAD) did not protect against diabetes-induced cardiac pathology.

Diabetic cardiomyopathy describes heart disease in patients with diabetes who have no other cardiac conditions but have a higher risk of developing heart failure. Specific therapies to treat the diabetic heart are limited. A key mechanism involved in the progression of diabetic cardiomyopathy is dysregulation of cardiac energy metabolism. The aim of this study was to determine if increasing the expression of medium-chain acyl-coenzyme A dehydrogenase (MCAD; encoded by Acadm), a key regulator of fatty acid oxidation, could improve the function of the diabetic heart. Male mice were administered streptozotocin to induce diabetes, which led to diastolic dysfunction 8 weeks post-injection. Mice then received cardiac-selective adeno-associated viral vectors encoding MCAD (rAAV6:MCAD) or control AAV and were followed for 8 weeks. In the non-diabetic heart, rAAV6:MCAD increased MCAD expression (mRNA and protein) and increased Acadl and Acadvl, but an increase in MCAD enzyme activity was not detectable. rAAV6:MCAD delivery in the diabetic heart increased MCAD mRNA expression but did not significantly increase protein, activity, or improve diabetes-induced cardiac pathology or molecular metabolic and lipid markers. The uptake of AAV viral vectors was reduced in the diabetic versus non-diabetic heart, which may have implications for the translation of AAV therapies into the clinic. KEY MESSAGES: The effects of increasing MCAD in the diabetic heart are unknown. Delivery of rAAV6:MCAD increased MCAD mRNA and protein, but not enzyme activity, in the non-diabetic heart. Independent of MCAD enzyme activity, rAAV6:MCAD increased Acadl and Acadvl in the non-diabetic heart. Increasing MCAD cardiac gene expression alone was not sufficient to protect against diabetes-induced cardiac pathology. AAV transduction efficiency was reduced in the diabetic heart, which has clinical implications.

The mitochondrial profile in women with polycystic ovary syndrome: impact of exercise.

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting pre-menopausal women and involves metabolic dysregulation. Despite the high prevalence of insulin resistance, the existence of mitochondrial dysregulation and its role in the pathogenesis of PCOS is not clear. Exercise is recommended as the first-line therapy for women with PCOS. In particular, high-intensity interval training (HIIT) is known to improve metabolic health and enhance mitochondrial characteristics. In this narrative review, the existing knowledge of mitochondrial characteristics in skeletal muscle and adipose tissue of women with PCOS and the effect of exercise interventions in ameliorating metabolic and mitochondrial health in these women are discussed. Even though the evidence on mitochondrial dysfunction in PCOS is limited, some studies point to aberrant mitochondrial functions mostly in skeletal muscle, while there is very little research in adipose tissue. Although most exercise intervention studies in PCOS report improvements in metabolic health, they show diverse and inconclusive findings in relation to mitochondrial characteristics. A limitation of the current study is the lack of comprehensive mitochondrial analyses and the diversity in exercise modalities, with only one study investigating the impact of HIIT alone. Therefore, further comprehensive large-scale exercise intervention studies are required to understand the association between metabolic dysfunction and aberrant mitochondrial profile, and the molecular mechanisms underlying the exercise-induced metabolic adaptations in women with PCOS.

Sensitivity to behavioral stress impacts disease pathogenesis in dystrophin-deficient mice.

Mutation to the gene encoding dystrophin can cause Duchenne muscular dystrophy (DMD) and increase the sensitivity to stress in vertebrate species, including the mdx mouse model of DMD. Behavioral stressors can exacerbate some dystrophinopathy phenotypes of mdx skeletal muscle and cause hypotension-induced death. However, we have discovered that a subpopulation of mdx mice present with a wildtype-like response to mild (forced downhill treadmill exercise) and moderate (scruff restraint) behavioral stressors. These "stress-resistant" mdx mice are more physically active, capable of super-activating the hypothalamic-pituitary-adrenal and renin-angiotensin-aldosterone pathways following behavioral stress and they express greater levels of mineralocorticoid and glucocorticoid receptors in striated muscle relative to "stress-sensitive" mdx mice. Stress-resistant mdx mice also presented with a less severe striated muscle histopathology and greater exercise and skeletal muscle oxidative capacity at rest. Most interestingly, female mdx mice were more physically active following behavioral stressors compared to male mdx mice; a response abolished after ovariectomy and rescued with estradiol. We demonstrate that the response to behavioral stress greatly impacts disease severity in mdx mice suggesting the management of stress in patients with DMD be considered as a therapeutic approach to ameliorate disease progression.

Antioxidant supplements and endurance exercise: Current evidence and mechanistic insights.

Antioxidant supplements are commonly consumed by endurance athletes to minimize exercise-induced oxidative stress, with the intention of enhancing recovery and improving performance. There are numerous commercially available nutritional supplements that are targeted to athletes and health enthusiasts that allegedly possess antioxidant properties. However, most of these compounds are poorly investigated with respect to their in vivo redox activity and efficacy in humans. Therefore, this review will firstly provide a background to endurance exercise-related redox signalling and the subsequent adaptations in skeletal muscle and vascular function. The review will then discuss commonly available compounds with purported antioxidant effects for use by athletes. N-acetyl cysteine may be of benefit over the days prior to an endurance event; while chronic intake of combined 1000 mg vitamin C + vitamin E is not recommended during periods of heavy training associated with adaptations in skeletal muscle. Melatonin, vitamin E and α-lipoic acid appear effective at decreasing markers of exercise-induced oxidative stress. However, evidence on their effects on endurance performance are either lacking or not supportive. Catechins, anthocyanins, coenzyme Q10 and vitamin C may improve vascular function, however, evidence is either limited to specific sub-populations and/or does not translate to improved performance. Finally, additional research should clarify the potential benefits of curcumin in improving muscle recovery post intensive exercise; and the potential hampering effects of astaxanthin, selenium and vitamin A on skeletal muscle adaptations to endurance training. Overall, we highlight the lack of supportive evidence for most antioxidant compounds to recommend to athletes.

Optogenetic control of mitochondrial protonmotive force to impact cellular stress resistance.

Mitochondrial respiration generates an electrochemical proton gradient across the mitochondrial inner membrane called protonmotive force (PMF) to drive diverse functions and synthesize ATP. Current techniques to manipulate the PMF are limited to its dissipation; yet, there is no precise and reversible method to increase the PMF. To address this issue, we aimed to use an optogenetic approach and engineered a mitochondria-targeted light-activated proton pump that we name mitochondria-ON (mtON) to selectively increase the PMF in Caenorhabditis elegans. Here we show that mtON photoactivation increases the PMF in a dose-dependent manner, supports ATP synthesis, increases resistance to mitochondrial toxins, and modulates energy-sensing behavior. Moreover, transient mtON activation during hypoxic preconditioning prevents the well-characterized adaptive response of hypoxia resistance. Our results show that optogenetic manipulation of the PMF is a powerful tool to modulate metabolism and cell signaling.

Epigenetic Reprogramming of Immune Cells in Women With PCOS Impact Genes Controlling Reproductive Function.

CONTEXT: Polycystic ovary syndrome (PCOS) is a chronic disease affecting reproductive function and whole-body metabolism. Although the etiology is unclear, emerging evidence indicates that the epigenetics may be a contributing factor. OBJECTIVE: To determine the role of global and genome-wide epigenetic modifications in specific immune cells in PCOS compared with controls and whether these could be related to clinical features of PCOS. DESIGN: Cross-sectional study. PARTICIPANTS: Women with (n = 17) or without PCOS (n = 17). SETTING: Recruited from the general community. MAIN OUTCOME MEASURES: Isolated peripheral blood mononuclear cells were analyzed using multicolor flow cytometry methods to determine global DNA methylation levels in a cell-specific fashion. Transcriptomic and genome-wide DNA methylation analyses were performed on T helper cells using RNA sequencing and reduced representation bisulfite sequencing. RESULTS: Women with PCOS had lower global DNA methylation in monocytes (P = 0.006) and in T helper (P = 0.004), T cytotoxic (P = 0.004), and B cells (P = 0.03). Specific genome-wide DNA methylation analysis of T helper cells from women with PCOS identified 5581 differentially methylated CpG sites. Functional gene ontology enrichment analysis showed that genes located at the proximity of differentially methylated CpG sites belong to pathways related to reproductive function and immune cell function. However, these genes were not altered at the transcriptomic level. CONCLUSIONS: It was shown that PCOS is associated with global and gene-specific DNA methylation remodeling in a cell type-specific manner. Further investigation is warranted to determine whether epigenetic reprogramming of immune cells is important in determining the different phenotypes of PCOS.

Exercise and Mitochondrial Dynamics: Keeping in Shape with ROS and AMPK.

Exercise is a robust stimulus for mitochondrial adaptations in skeletal muscle which consequently plays a central role in enhancing metabolic health. Despite this, the precise molecular events that underpin these beneficial effects remain elusive. In this review, we discuss molecular signals generated during exercise leading to altered mitochondrial morphology and dynamics. In particular, we focus on the interdependence between reactive oxygen species (ROS) and redox homeostasis, the sensing of cellular bioenergetic status via 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK), and the regulation of mitochondrial fission and fusion. Precisely how exercise regulates the network of these responses and their effects on mitochondrial dynamics is not fully understood at present. We highlight the limitations that exist with the techniques currently available, and discuss novel molecular tools to potentially advance the fields of redox biology and mitochondrial bioenergetics. Ultimately, a greater understanding of these processes may lead to novel mitochondria-targeted therapeutic strategies to augment or mimic exercise in order to attenuate or reverse pathophysiology.

BGP-15 Protects against Oxaliplatin-Induced Skeletal Myopathy and Mitochondrial Reactive Oxygen Species Production in Mice.

Chemotherapy is a leading intervention against cancer. Albeit highly effective, chemotherapy has a multitude of deleterious side-effects including skeletal muscle wasting and fatigue, which considerably reduces patient quality of life and survivability. As such, a defense against chemotherapy-induced skeletal muscle dysfunction is required. Here we investigate the effects of oxaliplatin (OXA) treatment in mice on the skeletal muscle and mitochondria, and the capacity for the Poly ADP-ribose polymerase (PARP) inhibitor, BGP-15, to ameliorate any pathological side-effects induced by OXA. To do so, we investigated the effects of 2 weeks of OXA (3 mg/kg) treatment with and without BGP-15 (15 mg/kg). OXA induced a 15% (p < 0.05) reduction in lean tissue mass without significant changes in food consumption or energy expenditure. OXA treatment also altered the muscle architecture, increasing collagen deposition, neutral lipid and Ca2+ accumulation; all of which were ameliorated with BGP-15 adjunct therapy. Here, we are the first to show that OXA penetrates the mitochondria, and, as a possible consequence of this, increases mtROS production. These data correspond with reduced diameter of isolated FDB fibers and shift in the fiber size distribution frequency of TA to the left. There was a tendency for reduction in intramuscular protein content, albeit apparently not via Murf1 (atrophy)- or p62 (autophagy)- dependent pathways. BGP-15 adjunct therapy protected against increased ROS production and improved mitochondrial viability 4-fold and preserved fiber diameter and number. Our study highlights BGP-15 as a potential adjunct therapy to address chemotherapy-induced skeletal muscle and mitochondrial pathology.

Effect of N-acetylcysteine infusion on exercise-induced modulation of insulin sensitivity and signaling pathways in human skeletal muscle.

-Reactive oxygen species (ROS) produced in skeletal muscle may play a role in potentiating the beneficial responses to exercise; however, the effects of exercise-induced ROS on insulin action and protein signaling in humans has not been fully elucidated. Seven healthy, recreationally active participants volunteered for this double-blind, randomized, repeated-measures crossover study. Exercise was undertaken with infusion of saline (CON) or the antioxidant N-acetylcysteine (NAC) to attenuate ROS. Participants performed two 1-h cycling exercise sessions 7-14 days apart, 55 min at 65% V̇o2peak plus 5 min at 85%V̇o2peak, followed 3 h later by a 2-h hyperinsulinemic euglycemic clamp (40 mIU·min(-1)·m(2)) to determine insulin sensitivity. Four muscle biopsies were taken on each trial day, at baseline before NAC infusion (BASE), after exercise (EX), after 3-h recovery (REC), and post-insulin clamp (PI). Exercise, ROS, and insulin action on protein phosphorylation were evaluated with immunoblotting. NAC tended to decrease postexercise markers of the ROS/protein carbonylation ratio by -13.5% (P = 0.08) and increase the GSH/GSSG ratio twofold vs. CON (P < 0.05). Insulin sensitivity was reduced (-5.9%, P < 0.05) by NAC compared with CON without decreased phosphorylation of Akt or AS160. Whereas p-mTOR was not significantly decreased by NAC after EX or REC, phosphorylation of the downstream protein synthesis target kinase p70S6K was blunted by 48% at PI with NAC compared with CON (P < 0.05). We conclude that NAC infusion attenuated muscle ROS and postexercise insulin sensitivity independent of Akt signaling. ROS also played a role in normal p70S6K phosphorylation in response to insulin stimulation in human skeletal muscle.

N-acetylcysteine alters substrate metabolism during high-intensity cycle exercise in well-trained humans.

We investigated the effects of N-acetylcysteine (NAC) on metabolism during fixed work rate high-intensity interval exercise (HIIE) and self-paced 10-min time-trial (TT10) performance. Nine well-trained male cyclists (V̇O2peak, 69.4 ± 5.8 mL · kg(-1) · min(-1); peak power output (PPO), 385 ± 43 W; mean ± SD) participated in a double-blind, repeated-measures, randomised crossover trial. Two trials (NAC supplementation and placebo) were performed 7 days apart consisting of 6 × 5 min HIIE bouts at 82% PPO (316 ± 40 W) separated by 1 min at 100 W, and then after 2 min of recovery at 100 W, TT10 was performed. Expired gases, venous blood, and electromyographic (EMG) data were collected. NAC did not influence blood glutathione but decreased lipid peroxidation compared with the placebo (P < 0.05). Fat oxidation was elevated with NAC compared with the placebo during HIIE bouts 5 and 6 (9.9 ± 8.9 vs. 3.9 ± 4.8 µmol · kg(-1) · min(-1); P < 0.05), as was blood glucose throughout HIIE (4.3 ± 0.6 vs. 3.8 ± 0.6 mmol · L(-1); P < 0.05). Blood lactate was lower with NAC after TT10 (3.3 ± 1.3 vs. 4.2 ± 1.3 mmol · L(-1); P < 0.05). Median EMG frequency of the vastus lateralis was lower with NAC during HIIE (79 ± 10 vs. 85 ± 10 Hz; P < 0.05), but not TT10 (82 ± 11 Hz). Finally, NAC decreased mean power output 4.9% ± 6.6% (effect size = -0.3 ± 0.4, mean ± 90% CI) during TT10 (305 ± 57 W vs. 319 ± 45 W). These data suggest that NAC alters substrate metabolism and muscle fibre type recruitment during HIIE, which is detrimental to time-trial performance.