Effects of high-intensity interval training (HIIT) on skeletal muscle atrophy, function, and myokine profile in diabetic myopathy.

PURPOSE: Diabetes is a metabolic disorder characterized by chronic hyperglycemia due to insulin deficiency and/or loss of its action. Diabetic myopathy causes functional limitations in diabetic patients. The beneficial effects of high-intensity interval training (HIIT) are widely reported. We have hypothesized that HIIT application would prevent the development of diabetic myopathy. METHODS: Male, Wistar albino rats (10 W) were randomly divided into four groups (1)Control(C), (2)Diabetes(DM), (3)Training(HIIT), and (4)Diabetes + Training(DM + HIIT). Streptozotocin(60 mg/kg) was injected for the induction of diabetes. The maximum exercise capacity(MEC) of animals was determined by an incremental load test. HIIT protocol (4 min 85-95 % MEC, 2 min 40-50 % MEC, 6 cycles, 5 days/week) was applied for 8 weeks. In the end, functional parameters, atrophy, and resistance to fatigue in soleus and EDL muscles were evaluated. IL-6, FNDC5, and myonectin levels were measured in EDL, soleus, and serum. RESULTS: We observed atrophy, fatigue sensitivity, and proinflammatory alterations (IL-6 increase) in the EDL samples due to diabetic myopathy which were not observed in the soleus samples. HIIT application prevented the aforementioned detrimental alterations. Both force-frequency response and parallelly the twitch amplitude increased significantly in the DM + HIIT group. Half relaxation time (DT50) increased in both exercising and sedentary diabetics. FNDC5 was significantly higher in the exercising animals in soleus samples. Myonectin was significantly higher in the soleus muscle only in the DM + HIIT group. CONCLUSION: Current findings show that diabetic myopathy develops earlier in glycolytic-fast-twitch fibers(EDL) than in oxidative-slow-twitch fibers(soleus). Furthermore, HIIT application prevents atrophy in skeletal muscle, increases resistance to fatigue, and has an anti-inflammatory effect. NEW FINDINGS: The current study analyzes the myokine profile and skeletal muscle function under the effect of diabetes HIIT-type exercise. We also measured maximal exercise capacity and tailored the exercise program individually according to the result. Diabetic myopathy is an important complication of diabetes yet still, it is not understood completely. Our results show that HIIT-type training would be beneficial in diabetic myopathy but further investigation is needed to understand the whole molecular mechanism.

Effects of aerobic exercise on lipopolysaccharide-induced experimental acute lung injury in the animal model of type 1 diabetes mellitus.

NEW FINDINGS: What is the central question of this study? We evaluated the effects of diabetes and exercise on lipopolysaccharide-induced acute lung injury. By providing a comprehensive analysis of redox status, blood gases and histological parameters, we aimed to contribute to the ongoing debate in the literature. What are the main findings and its importance? We demonstrated the preventive effect of exercise, but diabetes did not alter the severity of acute lung injury. ABSTRACT: Acute lung injury (ALI) is a life-threatening respiratory condition. Diabetes (DM) is a metabolic disease characterized by hyperglycaemia. There is an ongoing debate concerning whether there is a protective effect of diabetes in ALI. Exercise is a special type of physical activity that has numerous beneficial effects. The aim of our study was to investigate the effects of diabetes and exercise on the prognosis of ALI. Male Wistar albino rats were divided into two groups (sedentary and exercise). Both groups were divided into four subgroups: Control, ALI, DM, DM+ALI (n = 6 each). Diabetes was induced by injection of streptozotocin (50 mg/kg i.p.). The maximal exercise capacity was determined with the incremental load test. Animals were exercised on a treadmill for 45 min at 70% of maximal exercise capacity, 5 days a week for 12 weeks. Acute lung injury was induced by intratracheal injection of lipopolysaccharide (100 µg/100 g body weight) 24 h before the end of the experiment. We performed arterial blood gas analysis. Redox status was measured in both plasma and lung tissue. Malondialdehyde and 8-hydroxy-2'-deoxyguanosine levels were measured in lung tissue. Lung tissue was evaluated histologically. Acute lung injury caused significant damage in the lung tissue, which was verified histologically, with an increase in oxidative stress parameters. Exercise prevented the lung damage induced by ALI and reduced oxidative stress in the lung tissue. Diabetes did not alter the magnitude of damage done by ALI. Exercise showed a protective effect against DM and ALI in rats. The effect of DM was insignificant for the prognosis of ALI.

STIM1-Orai1 interaction mediated calcium influx activation contributes to cardiac contractility of insulin-resistant rats.

PURPOSE: Metabolic syndrome (MetS) became a tremendous public health burden in the last decades. Store-operated calcium entry (SOCE) is a unique mechanism that causes a calcium influx, which is triggered by calcium store depletion. MetS-induced alterations in cardiac calcium signaling, especially in SOCE are still unclear. Therefore, we aim to examine the possible role of SOCE and its components (STIM1 and Orai1) in the MetS-induced cardiac remodeling. METHODS: We used male, adult (12 weeks) Wistar albino rats (n = 20). Animals were randomly divided into two groups which were: control (C) and MetS. We gave 33% sucrose solution to animals instead of water for 24 weeks to establish MetS model. In the end, papillary muscle function was evaluated, and various electrophysiological analyses were made in isolated cardiomyocytes. Additionally, STIM1 and Orai1 protein and mRNA expressions were analyzed. RESULTS: We observed a deterioration in contractility in MetS animals and demonstrated the contribution of SOCE by applying a SOCE inhibitor (BTP2). Calcium spark frequency was increased while its amplitude was decreasing in MetS hearts, which was reversed after SOCE inhibition. The amplitude of transient calcium changes in the MetS group was decreased, and it decreased further BTP2 application. Both protein and mRNA levels of STIM1 and Orai1 were increased significantly in MetS hearts. CONCLUSION: Current data indicate the significant contribution of SOCE to cardiac calcium handling in the MetS model. We think MetS-induced SOCE activation is a compensation mechanism that is required for the continuum of proper cardiac functioning, although the activation can also cause cardiac hypertrophy.

Effects of eccentric exercise on different slopes.

OBJECTIVES: Eccentric contraction occurs when the muscle lengthens under tension. Damage-induced responses seen in the muscle after eccentric exercise usually experienced by sedentary individuals. This study aims to investigate muscle damage on different slopes. METHODS: 32 male Wistar albino rats randomly divided into four groups: sedentary, horizontal running, and eccentric exercise (-8°, -16°) groups. Animals ran for 90 min with the speed of 25 m/s for five days. After 48h from the last exercise, rats were sacrificed, and plasma creatine kinase (CK), heat shock protein 70 (HSP70) levels were examined. Plasma and soleus total oxidant/antioxidant status (TOS-TAS) and histological changes of soleus muscle assessed. RESULTS: CK and HSP70 significantly increased in 16° EE group. TOS increased at 16° EE and 8° EE, but oxidative stress index (OSI) was only high at 8° EE group. Mononuclear cell infiltration and the angiogenesis increased in soleus after eccentric exercise, and there was a correlation with slope. Sarcomere breaks were detected in 16° EE group also in a correlation with slope. CONCLUSIONS: Consequently, sedentary individuals are vulnerable to injuries induced by eccentric contraction. Therefore, our study provides information for reconsidering rehabilitation and training programs.

Aerobic exercise has an anxiolytic effect on streptozotocin­induced diabetic rats.

Diabetes is a metabolic disorder characterized by hyperglycemia and impaired insulin secretion or action. Psychological comorbidities, such as depression and anxiety, are more common in people with diabetes. Exercise results in anxiolytic effects, as demonstrated in numerous studies. This study aims to evaluate potential anxiolytic effects of aerobic exercise in streptozotocin (STZ)­induced diabetes. Male Wistar albino rats (n=40) were randomly divided into four groups of control, exercise, diabetes, and diabetes + exercise. Diabetes was induced with a single i.p. injection of STZ. The incremental load test was applied to exercise groups to determine maximal exercise capacity. Rats exercised on a treadmill at 70% of their maximal capacity for 45 min, five days per week for 12 weeks. On the day after the last exercise session the open field test and elevated plus maze test were carried out. Diabetes caused an increase in anxiety level, reflected in stretch­attend posture, self­grooming behaviors, and freezing time, with no significant changes for other behavioral parameters. Training normalized diabetes­induced deteriorations and also induced a significant anxiolytic effect both on diabetic and non­diabetic rats. This effect was observed for all behavioral parameters. The results of the open field test and elevated plus maze were consistent. The current results demonstrated a slight increase in anxiety with diabetes and a prominent anxiolytic effect of aerobic exercise. Considering the conflicting results in exercise­anxiety studies, this study hig hlights the importance of individually designed exercise protocols.

Effects of exercise training on anxiety in diabetic rats.

Diabetes mellitus (DM) is a common health problem, which manifests itself with chronic hyperglycemia and impaired insulin action. The prevalence of anxiety disorders tends to be high in the diabetic population. Exercise has a well-known anxiolytic effect, also demonstrated on rodents, but the effect of exercise on the DM-induced anxiety is still unknown. Female, Wistar albino rats were randomly divided into four groups (n=8) (C; EX; DM; DM+EX). DM was induced by injection (i.p.; 50 mg/kg) of Streptozotocin (STZ). Rats exercised in moderate intensity on the treadmill (15m/min; 5°; 30 min) for 5 weeks. Anxiety-like behavior (ALB) was evaluated by Open field test (OFT) and Elevated Plus Maze (EPM). According to OFT, central time and central entry have increased with in EX but not in DM+EX. There was no difference between C and DM. Central latency time didn't differ among groups. Unsupported rearing increased in both EX and DM+EX. There was no significant decrease in DM. Freezing time was significantly increased in the DM group. Exercise training reduced freezing time both in diabetic and non-diabetic animals. EPM results were similar. Time spent in open arm was increased significantly in exercise groups compared to their sedentary matches, and freezing time data were also parallel to OFT. Our study revealed that diabetes had shown an anxiogenic effect, which was not severe, and it only manifested itself on some behavioral parameters. Exercise training was reduced anxiety-like behavior both in diabetic and non-diabetic rats. However, because of the nature of exercise studies, it is hard to separate the anxiolytic effect of exercise from the alteration of locomotion.

Epoxyeicosatrienoic Acid-Based Therapy Attenuates the Progression of Postischemic Heart Failure in Normotensive Sprague-Dawley but Not in Hypertensive Ren-2 Transgenic Rats.

Epoxyeicosatrienoic acids (EETs) and their analogs have been identified as potent antihypertensive compounds with cardio- and renoprotective actions. Here, we examined the effect of EET-A, an orally active EET analog, and c-AUCB, an inhibitor of the EETs degrading enzyme soluble epoxide hydrolase, on the progression of post-myocardial infarction (MI) heart failure (HF) in normotensive Hannover Sprague-Dawley (HanSD) and in heterozygous Ren-2 transgenic rats (TGR) with angiotensin II-dependent hypertension. Adult male rats (12 weeks old) were subjected to 60-min left anterior descending (LAD) coronary artery occlusion or sham (non-MI) operation. Animals were treated with EET-A and c-AUCB (10 and 1 mg/kg/day, respectively) in drinking water, given alone or combined for 5 weeks starting 24 h after MI induction. Left ventricle (LV) function and geometry were assessed by echocardiography before MI and during the progression of HF. At the end of the study, LV function was determined by catheterization and tissue samples were collected. Ischemic mortality due to the incidence of sustained ventricular fibrillation was significantly higher in TGR than in HanSD rats (35.4 and 17.7%, respectively). MI-induced HF markedly increased LV end-diastolic pressure (Ped) and reduced fractional shortening (FS) and the peak rate of pressure development [+(dP/dt)max] in untreated HanSD compared to sham (non-MI) group [Ped: 30.5 ± 3.3 vs. 9.7 ± 1.3 mmHg; FS: 11.1 ± 1.0 vs. 40.8 ± 0.5%; +(dP/dt)max: 3890 ± 291 vs. 5947 ± 309 mmHg/s]. EET-A and c-AUCB, given alone, tended to improve LV function parameters in HanSD rats. Their combination amplified the cardioprotective effect of single therapy and reached significant differences compared to untreated HanSD controls [Ped: 19.4 ± 2.2 mmHg; FS: 14.9 ± 1.0%; +(dP/dt)max: 5278 ± 255 mmHg/s]. In TGR, MI resulted in the impairment of LV function like HanSD rats. All treatments reduced the increased level of albuminuria in TGR compared to untreated MI group, but neither single nor combined EET-based therapy improved LV function. Our results indicate that EET-based therapy attenuates the progression of post-MI HF in HanSD, but not in TGR, even though they exhibited renoprotective action in TGR hypertensive rats.

Intermittent hypoxia induces beneficial cardiovascular remodeling in left ventricular function of type 1 diabetic rat.

OBJECTIVE: Depressed mechanical activity is a marked complication in diabetics. Hypoxia has properties for novel diagnostic and therapeutic strategies, while intermittent hypoxia (IH) provides early functional and histologic remodeling, including some cardio benefits in early hemodynamic alterations with histologic remodeling and delayed changes in peripheral vasoreactivity. Therefore, we aimed to examine whether IH application presents a cardioprotective effect, via stabilization of hypoxia-inducible factor (HIF) in streptozotocin (STZ)-induced diabetic rat heart. METHODS: Male 10-week-old Wistar rats were randomly assigned as control group (C), IH group, (STZ)-induced diabetic group (DM) and IH applied DM group (DM+IH). Diabetes duration was kept 6 weeks and IH groups were exposed to hypobaric hypoxia at about 70 kPa (including ~14% PO2; 6 h/day for 6-weeks). RESULTS: Depressed left ventricular developed pressure (LVDP) and prolonged contraction and relaxation of Langendorff-perfused hearts, as well as increased total oxidative status from streptozotocin (STZ)-induced diabetic rats were markedly prevented with IH application. IH application induced significant increase in protein expression levels of both HIF-1α and vascular endothelial growth factor (VEGF), in both control and diabetic rat hearts, whereas there were significant decreases in the protein levels of prolyl-4 hydroxylase domain enzymes, PHD2, and PHD3 in diabetic hearts. Furthermore, IH application induced marked increases in protein levels of matrix metalloproteinases, MMP-2 and MMP-9 and capillary density in left ventricle of diabetic rats. CONCLUSION: Overall, we presented how IH application has a beneficial cardiovascular remodeling effect in left ventricular function of diabetic rats, at most, via affecting increased oxidative stress and HIF-VEGF related angiogenesis, providing information on hyperglycemia associated new targets and therapeutic strategies.

Effect of intermittent hypoxia on the cardiac HIF-1/VEGF pathway in experimental type 1 diabetes mellitus.

OBJECTIVE: High altitude and hypoxic preconditioning have cardioprotective effects by increasing coronary vascularity, reducing post-ischemic injury, and improving cardiac function. Our purpose was to examine if intermittent hypoxia treatment has any restoring effects related to the possible role of the HIF-1/VEGF pathway on diabetic cardiomyopathy. METHODS: Wistar Albino male rats (n=34) were divided into four groups: control (C), intermittent hypoxia (IH), diabetes mellitus (DM), and diabetes mellitus plus intermittent hypoxia (DM+IH). Following a streptozotocin (STZ) injection (50 mg/kg, i.p.), blood glucose levels of 250 mg/dL and above were considered as DM. IH and DM+IH groups were exposed to hypoxia 6 h/day for 42 days at a pressure corresponding to 3000 m altitude. Twenty-four hours after the IH protocol, hearts were excised. Hematoxylin and eosin-stained apical parts of the left ventricles were evaluated. Hypoxia inducible factor-1 (HIF-1), vascular endothelial growth factor 164 (VEGF164), and VEGF188 polymerase chain reaction products were run in agarose gel electrophoresis. Band density analysis of UV camera images was performed using Image J. The data were compared by one-way ANOVA, repeated measures two-way ANOVA, and the Kruskal-Wallis test. RESULTS: The percent weight change was lower in the DM group than in the controls (p=0.004). The tissue injury was the highest in the DM group and the least in the IH group. Diabetes decreased, whereas the IH treatment increased the vascularity. A decrease was observed in the VEGF188 mRNA levels in the DM+IH group compared with the C group, but there were no difference in HIF-1α and VEGF164 mRNA levels between the groups. CONCLUSION: The IH treatment restored the diabetic effects on the heart by reducing tissue injury and increasing the capillarity without transcriptional changes in HIF-1/VEGF correspondingly.