Cardiac hypertrophy in mice submitted to a swimming protocol: influence of training volume and intensity on myocardial renin-angiotensin system

Exercise promotes physiological cardiac hypertrophy and activates the renin-angiotensin system (RAS), which plays an important role in cardiac physiology, both through the classical axis [angiotensin II type 1 receptor (AT1R) activated by angiotensin II (ANG II)] and the alternative axis [proto-oncogene Mas receptor (MASR) activated by angiotensin-(1–7)]. However, very intense exercise could have deleterious effects on the cardiovascular system. We aimed to analyze the cardiac hypertrophy phenotype and the classical and alternative RAS axes in the myocardium of mice submitted to swimming exercises of varying volume and intensity for the development of cardiac hypertrophy. Male Balb/c mice were divided into three groups, sedentary, swimming twice a day without overload (T2), and swimming three times a day with a 2% body weight overload (T3), totaling 6 wk of training. Both training groups developed similar cardiac hypertrophy, but only T3 mice improved their oxidative capacity. We observed that T2 had increased levels of MASR, which was followed by the activation of its main downstream protein AKT; meanwhile, AT1R and its main downstream protein ERK remained unchanged. Furthermore, no change was observed regarding the levels of angiotensin peptides, in either group. In addition, we observed no change in the ratio of expression of the myosin heavy chain β-isoform to that of the α-isoform. Fibrosis was not observed in any of the groups. In conclusion, our results suggest that increasing exercise volume and intensity did not induce a pathological hypertrophy phenotype, but instead improved the oxidative capacity, and this process might have the participation of the RAS alternative axis.

Effect of diacerein on renal function and inflammatory cytokines in participants with type 2 diabetes mellitus and chronic kidney disease: A randomized controlled trial

Diacerein seems to improve metabolic control and reduce inflammatory marker levels in individuals with type 2 diabetes mellitus (Type 2 DM), but for participants with chronic kidney disease (CKD) its effect is unknown. This study aimed to evaluate the effect of diacerein vs. placebo on urinary albumin/creatinine ratio (ACR), glomerular filtration rate (GFR), and inflammatory cytokines in type 2 DM participants with CKD. Blood pressure (BP) and metabolic control were secondary outcomes. This randomized, placebo-controlled, parallel trial of adjuvant treatment of type 2 DM with diacerein enrolled seventy-two participants with CKD, aged 30–80 years, with glycated hemoglobin levels from 53–97 mmol/mol (7.0–11.0%), receiving angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and antidiabetic agents. Participants randomized to diacerein or placebo were followed-up up to 90 days. Both groups had a marked reduction in ACR, but there was no effect on glomerular filtration rate. While the diacerein group had reduced TNF-α levels at the 75th percentile with a borderline significance (P = 0.05), there were no changes in the IL levels at the 75^th percentile.

Diacerein prevented the increase in blood glucose to the level observed in the placebo group (P = 0.04), improving metabolic control by 74%, reducing 24-hour diastolic BP, nighttime systolic and diastolic BP compared to the placebo group. In conclusion, among patients with type 2 DM and CKD, diacerein does not have an effect on ACR or GFR, but slows metabolic control deterioration and is associated with lower nighttime systolic and diastolic blood pressure.

Trial registration: Brazilian Clinical Trials Registry (Registro Brasileiro de Ensaios Clinicos; ReBeC) U1111-1156-0255

Abstract 421: Cardiac Hypertrophy Induced by Swimming Exercise in Mice and the Cardiac Renin-Angiotensin System: The More, the Better?

Cardiac hypertrophy is an adaptive process which is triggered by different mechanism in order to improve blood flow to organism and it may progress as physiological or pathological. Physical exercise offers a wide range hemodynamic stimulus; consequently it may modulate several molecular mechanisms associated to cardiac hypertrophy, for instance the local cardiac renin-angiotensin system (RAS). Thus, the aim of this study was to analyze the classical (ANGII/AT1) and alternative (ANG1-7/MAS) axis of the RAS in the cardiac muscle of mice submitted to exercise with different volumes/intensity training for the development of cardiac hypertrophy. Therefore, male Balb/c mice were divided in three groups: (i) Sedentary (SED), (ii) swimming training twice a day (T2), and (iii) swimming training three times a day with 2% of body weight overload (T3), for six weeks of training. The cardiac hypertrophy was assessed by the left ventricle weight and tibial length (LV/mm) ratio and cardiomyocytes cross-sectional area. Angiotensin peptides were analyzed by HPLC and angiotensin receptor measured by western blotting. We have also analyzed fibrosis by masson’s tricrome and the fetal genes reactivation was assessed by qRT-PCR. Both swimming training induced cardiac hypertrophy, the CHI for groups was T2 (6.34±0.44 mg/mm) and T3 (6.74 ± 0.70 mg/mm) compared to SED (5.55±0.5 mg/mm, p = 0.002). There was no observed change in the levels of angiotensin peptides ANG-I, ANG-II, and ANG1-7 between training groups and sedentary, however when we analyze angiotensin receptors, group T3 showed higher levels of AT1 when compared to SED (p=0.004), while MASR levels was higher in T2 compared to SED (0.017). Further, there was moderate reactivation of fetal genes as evidenced by increased in MHC-β expression observed in T3, but without fibrosis in either group. Our results suggest that increasing volumes/intensity of exercise beyond moderate does not influence the magnitude or the structural phenotype of physiological cardiac hypertrophy. However, it might promote the activation of molecular mechanisms involved in pathological cardiac hypertrophy.

Abstract 318: Vitamin E Affects Pathological Cardiac Hypertrophy and MicroRNAs Expression in Mice

Aims: Vitamin E is a usual antioxidant, but little is known about its effects on cardiac hypertrophy and microRNAs (miRs) expression induced by transverse aortic constriction (TAC) in mice.

Methods and Results: Male Balb/c mice were randomly divided into four cohorts: SHAM ( n= 22), TAC ( n =34), SHAM supplemented with vitamin E (SHAM+VIT, n =22), and TAC supplemented with vitamin E (TAC+VIT, n =34). VIT groups received 200 mg/kg of α-tocopherol once a day, and the other groups received placebo, both by gavage. After 7 and 35 days of surgery analysis of cardiac hypertrophy, fibrosis, miRs and gene expression and carbonyl concentrations in cardiac tissue were performed. Left ventricle mass increased 23% and 35% in 7 and 35 days, respectively, in TAC group, similar data were observed in TAC+VIT group (all p <0.05 vs. SHAM groups). Cardiac fibrosis was increased by TAC surgery as early as 7 days and remained high after 35 days. Still, TAC mice exhibit higher levels of protein damage at 35 days. This pathological phenotype was not seen in animals of the TAC+VIT group. Vitamin E seemed to inhibit cardiac fibrosis and oxidative damage. Moreover, cardiac hypertrophy was followed by increased miR-21 and -499 expression in TAC group, mainly 35 days ( miR-21 : 2.9 ± 0.6 fold vs . SHAM: 1 ± 0.1 fold , miR 499 : 3 ± 0.4 fold vs. 1.1 ± 0.1 fold , p <0.05). However, TAC+VIT mice displayed a different miR expression profile, with decreased miR-21 and - 499 expression ( miR-21 : 0.5 ± 0.1 fold , miR-499 : 0.4 ± 0.1 fold ; TAC vs. p <0.05) and increased miR-210 expression (3.2 ± 0.5 fold vs. TAC: 1.9 ± 0.2 fold, p =0.034). Computational target prediction of these miRs demonstrated that they can be involved in the control of major pathways in the heart disease scenario such as MAPK, mTOR, PI3K-AKT, among others.

Conclusion: TAC model induced pathological cardiac hypertrophy, fibrosis and protein damage followed by changes in miRs expression. Vitamin E supplementation was associated with a different miR expression profile and mitigated the pathological phenotype.

Abstract 317: Physiologic Cardiac Hypertrophy in Mice Reduces mRNA Levels of Myostatin and Autophagy Genes

Myostatin and autophagy are involved in muscle growth regulation. However, there are few studies exploring their role in physiologic cardiac hypertrophy. We evaluated myostatin and autophagy in mice subjected to a swimming protocol to induce physiologic cardiac hypertrophy. Methods: Adult (8 weeks-old) male BALB/c mice ( n =52) were divided in sedentary (S) and trained (T) groups, which were evaluated in 7 (S7 or T7, initial hypertrophy) and 28 (S28 or T28, stablished hypertrophy) days after the start of the protocol. Left ventricular/tibial length ratio (LV/TL) and cardiomyocyte diameter were used to assess cardiac hypertrophy. Gene expression was evaluated by RT-qPCR, while protein expression was analyzed by western blot. Bioinformatic analysis was performed by TargetScan to predict potential miRNAs’ targets and Genemania to create an interaction network between miRNAs and genes. All results were expressed as mean ± SEM and comparisons were performed using the Student T test. Results: Myocardial hypertrophy was confirmed in trained group both by the increase in LV/TL ratio in 28 days (13%, p=0.0001) and cardiomyocyte diameter in 7 days (20%, p=0.04) and 28 days (30%, p=0.002). There was a decrease in myostatin gene expression levels in T7 compared to S7 group (0.8 ± 0.1 vs 1.2 ± 0.1, p=0.01) without changes at day 28. However, there was no difference in mTOR phosphorylation at T7, although it was increased in T28 compared to S28 (397±95 vs 90±23 AU; p=0.02). Autophagic genes showed reduced expression levels in trained groups at both time points (reductions of 19% and 10% for Lc3, 22% and 11% for P62 , 19% and 10% for Beclin1 in T7 and T28, respectively; p<0.05 for all analyses compared to sedentary groups), but there was no difference at protein level. Bioinformatics analysis showed that miR-30a, - 221, -27a/b and 208a/b are possible regulators of autophagic and myostatin genes. Conclusions: Taken together, reduced myostatin during initial hypertrophy and increased mTOR phosphorylation in the established hypertrophic phenotype might favor muscular growth and reduce basal autophagy. Candidate miRNAs identified through bioinformatic analysis might regulate this process, and should be further validated in this scenario.

Oxidative stress in chronic obstructive pulmonary disease patients submitted to a rehabilitation program

Pulmonary rehabilitation (PR) improves physical capacity and health quality in patients with chronic obstructive pulmonary disease (COPD). However, the effect of exercise on oxidative stress markers in COPD patients is only partially known. This study was designed to evaluate the oxidative stress response to long-term exercise in patients with COPD enrolled in a PR program. Fifteen COPD patients (FEV1 < 60%), age between 50 and 60 years, ex-smokers, were separated in two groups: exercise-trained (n=8) and sedentary group (n=7). Exercise consisted of an 8-week conditioning program using a cycle ergometer (three times a week, 1h session). An endurance test (60% of maximal load in an incremental cycle test) was performed before and after PR. Blood samples were obtained at baseline and immediately after each endurance test. We measured the index of lipid peroxidation, thiobarbituric acid reactive species (TBARS), total radical-trapping antioxidant parameter (TRAP) and xanthine oxidase (XO) activity. TRAP was significantly different between the exercise-trained group and sedentary group of COPD patients. Baseline TBARS values were increased after the exercise training program but decreased after the endurance test. XO decrease after effort in the trained and untrained groups. The results suggest that patients with COPD are characterized by increased systemic and pulmonary oxidative stress markers both at rest as well as induced by cardiopulmonary exercise test and that PR program was associated with decreased systemic exercise-induced oxidative damage.

Imbalance in SOD/CAT activities in rat skeletal muscles submitted to treadmill training exercise

The association between physical exercise and oxidative damage in the skeletal musculature has been the focus of many studies in literature, but the balance between superoxide dismutase and catalase activities and its relation to oxidative damage is not well established. Thus, the aim of the present study was to investigate the association between regular treadmill physical exercise, oxidative damage and antioxidant defenses in skeletal muscle of rats. Fifteen male Wistar rats (8-12 months) were randomly separated into two groups (trained n=9 and untrained n=6). Trained rats were treadmill-trained for 12 weeks in progressive exercise (velocity, time, and inclination). Training program consisted in a progressive exercise (10 m/min without inclination for 10 min/day). After 1 week the speed, time and inclination were gradually increased until 17 m/min at 10% for 50 min/day. After the training period animals were killed, and gastrocnemius and quadriceps were surgically removed to the determination of biochemical parameters. Lipid peroxidation, protein oxidative damage, catalase, superoxide dismutase and citrate synthase activities, and muscular glycogen content were measured in the isolated muscles. We demonstrated that there is a different modulation of CAT and SOD in skeletal muscle in trained rats when compared to untrained rats (increased SOD/CAT ratio). TBARS levels were significantly decreased and, in contrast, a significant increase in protein carbonylation was observed. These results suggest a non-described adaptation of skeletal muscle against exercise-induced oxidative stress.

Antioxidant, a pro-oxidant and cytotoxic effects of Achyrocline satureioides extracts

In this study we compared the antioxidant properties of five different extracts of different composition obtained from Achyrocline satureioides' inflorescences (Compositae), a widely used Brazilian folk medicinal herb. All of the extracts presented significant antioxidant potential identified by TRAP assay, which increased in the presence of human plasma. Characterization of the content of flavonoids in each extract showed that the FDP80 (ethanol 80%) and FFr (enriched flavonoid fraction) extracts contained a higher content of flavonoids. Cytotoxicity of the extracts as determined in Sertoli cell culture showed that FDP80 and FFr were highly toxic at most concentrations tested. The extracts induced a significant increase in lipid peroxidation levels in Sertoli cells. These results suggest that medicinal herb extracts that contain higher flavonoid concentrations and shows higher antioxidant protection in vitro might not always produce the greatest benefit.

Treatment with N-acetylcysteine plus deferoxamine protects rats against oxidative stress and improves survival in sepsis*

OBJECTIVE

Oxidative stress plays an important role in the development of multiple organ failure and septic shock. Here we have evaluated the effects of a combination of antioxidants (N-acetylcysteine plus deferoxamine) in a murine model of polymicrobial sepsis induced by cecal ligation and puncture (CLP).

DESIGN

Prospective, randomized, controlled experiment.

SETTING

Animal basic science laboratory.

SUBJECTS

Male Wistar rats, weighing 300-350 g.

INTERVENTIONS

Rats subjected to CLP were treated with either N-acetylcysteine (20 mg/kg, 3 hrs, 6 hrs, 12 hrs, 18 hrs, and 24 hrs after CLP, subcutaneously) plus deferoxamine (20 mg/kg, 3 hrs and 24 hrs after CLP, subcutaneously) or vehicle with or without "basic support" (saline at 50 mL/kg immediately and 12 hrs after CLP plus ceftriaxone at 30 mg/kg and clindamycin 25 mg/kg every 6 hrs).

MEASUREMENTS AND MAIN RESULTS

After 12 hrs, tissue myeloperoxidase (indicator of neutrophil infiltration), thiobarbituric acid reactive species (as a marker of oxidative stress), catalase and superoxide dismutase activities (antioxidant enzymes), and mitochondrial superoxide production (index of uncoupling of electron transfer chain) were measured in major organs involved in septic response. Rats treated with antioxidants had significantly lower myeloperoxidase activity and thiobarbituric acid reactive species formation in all organs studied. Mitochondrial superoxide production was significantly reduced by antioxidant treatment. Furthermore, antioxidants significantly improved the balance between catalase and superoxide dismutase activities. Survival in untreated septic rats was 10%. Survival increased to 40% with fluids and antibiotics. In rats treated only with N-acetylcysteine plus deferoxamine, survival was also significantly improved (47%) in a manner similar to basic support. Survival increased to 66% with basic support with N-acetylcysteine plus deferoxamine.

CONCLUSIONS

Our data provide the first experimental demonstration that N-acetylcysteine plus deferoxamine reduces the consequences of septic shock induced by CLP in the rat, by decreasing oxidative stress and limiting neutrophil infiltration and mitochondrial dysfunction, thereby improving survival.

Neonatal iron exposure induces oxidative stress in adult Wistar rat

Oxidative stress and excess of iron in the brain has been implicated in a variety of acute and chronic neurological conditions. The neonatal period is critical for the establishment of normal iron content in the adult brain. In the present study, the long-term oxidative effects of iron exposure during this period were assessed by treating Wistar rats orally with 0, 7.5 or 15 mg Fe(+2)/kg of body weight on postnatal days 10-12. Thiobarbituric acid reactive species, protein carbonyl, superoxide dismutase activity were measured at the age of 3 months. It was found that there was an increase in thiobarbituric acid reactive species and protein carbonyl in the substantia nigra of iron treated rats. In contrast, oxidative stress in the striatum was decreased. Superoxide dismutase activity was decreased in the substantia nigra iron treated rats. There were no differences in cerebellum measures among the groups. Our results demonstrated that iron supplementation in a critical neonatal period induced oxidative stress and modulated SOD activity in the adult life in selective brain regions.

Imbalance of antioxidant defense in mice lacking cellular prion protein

Prion diseases are fatal neurodegenerative disorders resulting from conformational changes in the prion protein from its normal cellular isoform, PrPC, to the infectious scrapie isoform, PrP(Sc). In spite of many studies, the physiological function of PrPC remains unknown. Recent work shows that PrPC binds Cu2+, internalizing it into the cytoplasm. Since many antioxidant enzymes depend on Cu2+ (e.g., Cu/ZnSOD), their function could be affected in prion diseases. Here we investigate a possible relationship between PrP(C) and the cellular antioxidant systems in different structures isolated from PrPC knockout and wild-type mice by determining oxidative damage in protein and lipids and activity of antioxidant enzymes (CAT, SOD) and stress-adaptive enzymes (ODC). Our results show that, in the absence of PrPC, there is an increased oxidation of lipid and protein in all structures investigated. Decreased SOD activity and changes in CAT/ODC activities were also observed. Taking into account these results, we suggest that the physiological function of PrP(C) is related to cellular antioxidant defenses. Therefore, during development of prion diseases, the whole organism becomes more sensitive to ROS injury, leading to a progressive oxidative disruption of tissues and vital organs, especially the central nervous system.