Overtraining is associated with DNA damage in blood and skeletal muscle cells of Swiss mice

Systemic corticosteroids for the treatment of acute episodes of rhabdomyolysis in lipin-1-deficient patients

Mutations in the LPIN1 gene constitute a major cause of severe rhabdomyolysis (RM). The TLR9 activation prompted us to treat patients with corticosteroids in acute conditions. In patients with LPIN1 mutations, RM and at-risk situations that can trigger RM have been treated in a uniform manner. Since 2015, these patients have also received intravenous corticosteroids. We retrospectively compared data on hospital stays by corticosteroid-treated patients vs. patients not treated with corticosteroids. Nineteen patients were hospitalized. The median number of admissions per patient was 21 overall and did not differ when comparing the 10 corticosteroid-treated patients with the 9 patients not treated with corticosteroids. Four patients in the non-corticosteroid group died during a RM (mean age at death: 5.6 years). There were no deaths in the corticosteroid group. The two groups did not differ significantly in the number of RM episodes. However, for the six patients who had RM and occasionally been treated with corticosteroids, the median number of RM episodes was significantly lower when intravenous steroids had been administered. The peak plasma creatine kinase level and the area under the curve were or tended to be higher in patients treated with corticosteroids-even after the exclusion of deceased patients or focusing on the period after 2015. The median length of stay (10 days overall) was significantly longer for corticosteroid-treated patients but was similar after the exclusion of deceased patients. The absence of deaths and the higher severity of RM observed among corticosteroid-treated patients could suggest that corticotherapy is associated with greater survival.

Muscle endoplasmic reticulum stress in exercise

The endoplasmic reticulum (ER) is an organelle responsible for the post-translational folding and modification of proteins. Under stress conditions, such as physical exercise, there is accumulation of misfolded proteins. The increased load of proteins in the ER results in ER stress, which activates the unfolded protein response (UPR). UPR is comprised of three parallel pathways, responsible for ensuring the quality of secreted proteins. Scientific studies show that resistance or endurance acute physical exercise can induce ER stress and activate the UPR pathways. On the other hand, regular moderate-intensity exercise can attenuate the responses of genes and proteins related to ER stress. However, these positive adaptations do not occur when exercise intensity and volume increase without adequate rest periods, which is observed in overtraining. The current review discusses the frontier-of-knowledge findings on the effects of different acute and chronic physical exercise protocols on skeletal muscle ER stress and its metabolic consequences.

Systematic Review and Meta-Analysis of Endurance Exercise Training Protocols for Mice

Inbred and genetically modified mice are frequently used to investigate the molecular mechanisms responsible for the beneficial adaptations to exercise training. However, published paradigms for exercise training in mice are variable, making comparisons across studies for training efficacy difficult. The purpose of this systematic review and meta-analysis was to characterize the diversity across published treadmill-based endurance exercise training protocols for mice and to identify training protocol parameters that moderate the adaptations to endurance exercise training in mice. Published studies were retrieved from PubMed and EMBASE and reviewed for the following inclusion criteria: inbred mice; inclusion of a sedentary group; and exercise training using a motorized treadmill. Fifty-eight articles met those inclusion criteria and also included a "classical" marker of training efficacy. Outcome measures included changes in exercise performance, V ˙ O_2max, skeletal muscle oxidative enzyme activity, blood lactate levels, or exercise-induced cardiac hypertrophy. The majority of studies were conducted using male mice. Approximately 48% of studies included all information regarding exercise training protocol parameters. Meta-analysis was performed using 105 distinct training groups (i.e., EX-SED pairs). Exercise training had a significant effect on training outcomes, but with high heterogeneity (Hedges' g=1.70, 95% CI=1.47-1.94, Tau²=1.14, I² =80.4%, prediction interval=-0.43-3.84). Heterogeneity was partially explained by subgroup differences in treadmill incline, training duration, exercise performance test type, and outcome variable. Subsequent analyses were performed on subsets of studies based on training outcome, exercise performance, or biochemical markers. Exercise training significantly improved performance outcomes (Hedges' g=1.85, 95% CI=1.55-2.15). Subgroup differences were observed for treadmill incline, training duration, and exercise performance test protocol on improvements in performance. Biochemical markers also changed significantly with training (Hedges' g=1.62, 95% CI=1.14-2.11). Subgroup differences were observed for strain, sex, exercise session time, and training duration. These results demonstrate there is a high degree of heterogeneity across exercise training studies in mice. Training duration had the most significant impact on training outcome. However, the magnitude of the effect of exercise training varies based on the marker used to assess training efficacy.

Excessive treadmill training enhances the insulin signaling pathway and glycogen deposition in mice hearts

Exhaustive and chronic physical exercise leads to peripheral inflammation, which is one of the molecular mechanisms responsible for the impairment of the insulin signaling pathway in the heart. Recently, 3 different running overtraining models performed downhill (OTR/down), uphill (OTR/up), and without inclination (OTR) increased the serum levels of proinflammatory cytokines. This proinflammatory status induced insulin signaling impairment in the skeletal muscle; however, the response of this signaling pathway in the cardiac muscle of overtrained mice was still unknown. Thus, we investigated the effects of OTR/down, OTR/up, and OTR protocols on the protein levels of phosphorylation of insulin receptor β (pIRβ) (Tyr), phosphorylation of protein kinase B (pAkt) (Ser473), plasma membrane glucose transporter-1 (GLUT1) and GLUT4, phosphorylation of insulin receptor substrate-1 (pIRS-1) (Ser307), phosphorylation of IκB kinase α/β) (pIKKα/β (Ser180/181), phosphorylation of p38 mitogen-activated protein kinase (p-p38MAPK) (Thr180/Tyr182), phosphorylation of stress-activated protein kinases-Jun amino-terminal kinases (pSAPK-JNK) (Thr183/Tyr185), and glycogen content in mice hearts. The rodents were divided into naïve (N, sedentary mice), control (CT, sedentary mice submitted to performance evaluations), trained (TR, performed the training protocol), OTR/down, OTR/up, and OTR groups. After the grip force test, the cardiac muscles (ie, left ventricle) were removed and used for immunoblotting and histology. Although the OTR/up and OTR groups exhibited higher cardiac levels of pIRβ (Tyr), only the OTR group exhibited higher cardiac levels of pAkt (Ser473) and plasma membrane GLUT4. On the contrary, the OTR/down group exhibited higher cardiac levels of pIRS-1 (Ser307). The OTR model enhanced the cardiac insulin signaling pathway. All overtraining models increased the left ventricle glycogen content, with this probably acting as a compensatory organ in response to skeletal muscle insulin signaling impairment.

OLIVEIRA L, DE VICENTE LG, FERREIRA GN, DE FREITAS EC, DA SILVA ASR. Uphill Running Excessive Training Increases Gastrocnemius Glycogen Content in C57BL/6 Mice

The main aim of the present investigation was to verify the effects of three overtraining (OT) protocols performed in downhill (OTR/down), uphill (OTR/up) and without inclination (OTR) on the protein levels of Akt (Ser473), AMPKα (Thr172), PGC-1α, plasma membrane GLUT-1 and GLUT-4 as well as on the glycogen contents in mice gastrocnemius. A trained (TR) protocol was used as positive control. Rodents were divided into naïve (N, sedentary mice), control (CT, sedentary mice submitted to the performance evaluations), TR, OTR/down, OTR/up and OTR groups. At the end of the experimental protocols, gastrocnemius samples were removed and used for immunoblotting analysis as well as for glycogen measurements. There was no significant difference between the experimental groups for the protein levels of pAkt (Ser473), pAMPKα (Thr172), PGC-1α, plasma membrane GLUT-1 and GLUT-4. However, the OTR/up protocol exhibited higher contents of glycogen compared to the CT and TR groups. In summary, the OTR/up group increased the gastrocnemius glycogen content without significant changes of pAkt (Ser473), pAMPKα (Thr172), PGC-1α, plasma membrane GLUT-1 and GLUT-4.

Lipocalin2 Protects Human Embryonic Kidney Cells against Cisplatin-Induced Genotoxicity

Cisplatin is one of the most useful chemotherapeutics which performs its cytotoxic effect via accumulation of platinum resulting in oxidative stress, and destruction of cell DNA. This could probably cause secondary cancers in healthy tissues. Lipocalin2 (Lcn2) is a protein which its expression is increased in oxidative stresses. Therefore, the present study was performed to evaluate the protective effects of Lcn2 up-regulation on cisplatin genotoxicity. In order to up-regulate Lcn2 expression, HEK293 cells were transfected with pcDNA3.1-Lcn2 vector. Afterwards, stable cells consistently expressing Lcn2 were selected via screening with G418 antibiotic. Next, overexpression of Lcn2 was evaluated by RT-PCR and ELISA, comparing to the control non-transfected cells. Then, in order to evaluate the cytoprotective effects of Lcn2 overexpression, transfected and non-transfected cells were subjected to cisplatin treatment followed by MTT and alkaline Comet assays. RT-PCR and ELISA assays confirmed up-regulation of Lcn2 by the stable cells. MTT assay of the Lcn2 over-expressing cells showed higher IC50 values comparing to the non-transfected cells. Furthermore, the Comet assay confirmed Lcn2 protective effects on the cisplatin (1 µg/mL) induced genotoxicity. In the present study, for the first time, we showed the protective effect of Lcn2 on cisplatin induced genotoxicity. Therefore, one of the probable mechanisms of Lcn2 cytoprotctive effects under oxidative stress conditions could be due to the prevention of genotoxicity. However, further evaluations in this regard must be considered.

Exercise training dose differentially alters muscle and heart capillary density and metabolic functions in an obese rat with metabolic syndrome

NEW FINDINGS

What is the central question of this study? Regular exercise is recommended as a non-pharmacological approach for the prevention and treatment of metabolic syndrome. However, the impact of different combinations of intensity, duration and frequency of exercise on metabolic syndrome and microvascular density has not been reported. What is the main finding and its importance? We provide evidence on the impact of aerobic exercise dose on metabolic and microvascular alterations in an experimental model of metabolic syndrome induced by high-fat diet. We found that the exercise frequency and duration were the main factors affecting anthropometric and metabolic parameters and microvascular density in the skeletal muscle. Exercise intensity was related only to microvascular density in the heart. We evaluated the effect of the frequency, duration and intensity of exercise training on metabolic parameters and structural capillary density in obese rats with metabolic syndrome. Wistar-Kyoto rats were fed either a standard commercial diet (CON) or a high-fat diet (HFD). Animals that received the HFD were randomly separated into either a sedentary (SED) group or eight different exercise groups that varied according to the frequency, duration and intensity of training. After 12 weeks of aerobic exercise training, the body composition, aerobic capacity, haemodynamic variables, metabolic parameters and capillary density in the heart and skeletal muscle were evaluated. All the exercise training groups showed reduced resting systolic blood pressure and heart rate and normalized fasting glucose. The minimal amount of exercise (90 min per week) produced little effect on metabolic syndrome parameters. A moderate amount of exercise (150 min per week) was required to reduce body weight and improve capillary density. However, only the high amount of exercise (300 min per week) significantly reduced the amount of body fat depots. The three-way ANOVA showed a main effect of exercise frequency and duration for the improvement of metabolic syndrome and capillary density in skeletal muscle. Exercise intensity was a main factor in reversing microvascular rarefaction in the heart.

DNA damage in Wistar Kyoto rats exercised during pregnancy

Purpose:

To evaluate DNA damage levels in pregnant rats undergoing a treadmill exercise program.

Methods:

Wistar Kyoto rats were allocated into two groups (n= 5 animals/group): non-exercise and exercise. The pregnant rats were underwent an exercise protocol on a treadmill throughout pregnancy. Exercise intensity was set at 50% of maximal capacity during maximal exercise testing performed before mating. Body weight, blood pressure and glucose levels, and triglyceride concentration were measured during pregnancy. At day 10 post-natal, the animals were euthanized and maternal blood samples were collected for DNA damage.

Results:

Blood pressure and glucose levels and biochemical measurements showed no significant differences. Increased DNA damage levels were found in exercise group compared to those of non-exercise group (p<0.05).

Conclusion:

The exercise intensity protocol used in the study might have been exhaustive leading to maternal increased DNA damage levels, demonstrating the relevance of an adequate protocol of physical exercise.

Environmental conditions can modulate the links among oxidative stress, age, and longevity

Understanding the links between environmental conditions and longevity remains a major focus in biological research. We examined within-individual changes between early- and mid-adulthood in the circulating levels of four oxidative stress markers linked to ageing, using zebra finches (Taeniopygia guttata): a DNA damage product (8-hydroxy-2'-deoxyguanosine; 8-OHdG), protein carbonyls (PC), non-enzymatic antioxidant capacity (OXY), and superoxide dismutase activity (SOD). We further examined whether such within-individual changes differed among birds living under control (ad lib food) or more challenging environmental conditions (unpredictable food availability), having previously found that the latter increased corticosterone levels when food was absent but improved survival over a three year period. Our key findings were: (i) 8-OHdG and PC increased with age in both environments, with a higher increase in 8-OHdG in the challenging environment; (ii) SOD increased with age in the controls but not in the challenged birds, while the opposite was true for OXY; (iii) control birds with high levels of 8-OHdG died at a younger age, but this was not the case in challenged birds. Our data clearly show that while exposure to the potentially damaging effects of oxidative stress increases with age, environmental conditions can modulate the pace of this age-related change.

Determination of DNA damage and telomerase activity in stanozolol-treated rats

Anabolic androgenic steroids (AAS) are performance-enhancing drugs commonly abused by atheletes. Stanozolol is a synthetic testosterone-derived anabolic steroid. Although it is well known that AAS have several side-effects, there are only few toxicological studies available on the toxic effects and mechanisms of action of stanozolol. The aim of this study was to investigate the genotoxic effects of stanozolol and to determine its effects on telomerase activity in Sprague-Dawley male rats. For this purpose, 34 male rats were divided into 5 groups as follows: i) the control group (n=5); ii) the propylene glycol (PG)-treated group (n=5); iii) the stanozolol-treated group (n=8); iv) the PG-treated group subjected to exercise (n=8); and v) the stanozolol-treated group subjected to exercise (n=8). PG is used as a solvent control in our study. Stanozolol (5 mg/kg) and PG (1 ml/kg) were injected subcutaneously 5 days/week for 28 days. After 28 days, the animals were sacrificed, and DNA damage evaluation (comet assay) and telomerase activity assays were then performed using peripheral blood mononuclear cells (PBMCs). Telomerase activity was measured by using the TeloTAGGG Telomerase PCR ELISA PLUS kit. The results of this study revealed that stanozolol treatment induced DNA damage, while exercise exerted a protective effect. Stanozolol treatment without exercise stimulation was associated with a significant increase in telomerase activity in the PBMCs.

Oxidative Stress in Training, Overtraining and Detraining: from Experimental to Applied Research

According to the hormesis theory, the responses of biological systems to stressors in exercise training may be explained by a U-shaped curve with inactivity and overtraining as the two endpoints. Both of these endpoints decrease physiological functions. Markers of oxidative stress may be important parameters for biological monitoring of athletes. Numerous studies have shown that acute exercise has the potential to induce oxidative stress, but regular exposure to an increased level of prooxidants leads to upregulation of the endogenous antioxidative defence system (ADS) of an athlete. Studies that explored the redox state in athletes during the competitive season showed that the antioxidative status changes depending on the training load and training phase. During the training season, a state of fatigue known as overtraining may occur, which results from an excessive training load. Oxidative stress has been suggested as one of the causes of overtraining syndrome. Based on the existing studies, it can be said that a connection exists, but whether oxidative stress is a cause or a consequence of overtraining is yet to be clarified. Furthermore, detraining (training reduction or cessation) leads to a partial or complete loss of training-induced anatomical, physiological and performance adaptations; therefore, it seems reasonable to assume that changes in ADS are also reversible.

Going retro: Oxidative stress biomarkers in modern redox biology

The field of redox biology is inherently intertwined with oxidative stress biomarkers. Oxidative stress biomarkers have been utilized for many different objectives. Our analysis indicates that oxidative stress biomarkers have several salient applications: (1) diagnosing oxidative stress, (2) pinpointing likely redox components in a physiological or pathological process and (3) estimating the severity, progression and/or regression of a disease. On the contrary, oxidative stress biomarkers do not report on redox signaling. Alternative approaches to gain more mechanistic insights are: (1) measuring molecules that are integrated in pathways linking redox biochemistry with physiology, (2) using the exomarker approach and (3) exploiting -omics techniques. More sophisticated approaches and large trials are needed to establish oxidative stress biomarkers in the clinical setting.

Effects of ozonated autohemotherapy on the antioxidant capacity of Thoroughbred horses

The performance of horses undergoing regular intense exercise is adversely affected by oxidative stress. Thus, it is important to increase antioxidant production in horses in order to reduce oxidative stress. Ozonated autohemotherapy (OAHT) reportedly promotes antioxidant production. This study aimed to evaluate the effects of OAHT on antioxidant capacity. Ten Thoroughbred horses were used in this study. After the OAHT, we collected serum samples and measured biological antioxidant potential (BAP). We found that BAP began to increase after the OAHT and was significantly higher in the OAHT group than at 3 (P<0.01) and 7 days (P<0.05) after OAHT than in the control group at 3 and 7 days after starting collection of blood samples. Therefore, it was shown that OAHT improved the antioxidant capacity of the horses.