Previous exercise training has a beneficial effect on renal and cardiovascular function in a model of diabetes

Aerobic training increases renal antioxidant defence and reduces angiotensin II levels, mitigating the high mortality in SHR-STZ model

OBJECTVE

The purpose of the research was to investigate the effects of aerobic training on renal function, oxidative stress, intrarenal renin-angiotensin system, and mortality of hypertensive and diabetic (SHR-STZ) rats.

MATERIALS AND METHODS

Blood pressure, creatinine, urea levels, urinary glucose, urine volume, and protein excretion were reduced in trained SHR-STZ rats.

RESULTS

Aerobic training not only attenuated oxidative stress but also elevated the activity of antioxidant enzymes in the kid'ney of SHR-STZ rats. Training increased intrarenal levels of angiotensin-converting enzymes (ACE and ACE2) as well as the neprilysin (NEP) activity, along with decreased intrarenal angiotensin II (Ang II) levels. Aerobic training significantly improved the survival of STZ-SHR rats.

CONCLUSION

The protective role of aerobic training was associated with improvements in the renal antioxidative capacity, reduced urinary protein excretion along with reduced intrarenal Ang II and increased NEP activity. These findings might reflect a better survival under the combined pathological conditions, hypertension, and diabetes.

Renoprotective mechanisms of exercise training against acute and chronic renal diseases - A perspective based on experimental studies

Regular exercise training can lead to several health benefits, reduce mortality risk, and increase life expectancy. On the other hand, a sedentary lifestyle is a known risk factor for chronic diseases and increased mortality. Acute kidney injury (AKI) and chronic kidney disease (CKD) represent a significant global health problem, affecting millions of people worldwide. The progression from AKI to CKD is well-recognized in the literature, and exercise training has emerged as a potential renoprotective strategy. Thus, this article aims to review the main molecular mechanisms underlying the renoprotective actions of exercise training in the context of AKI and CKD, focusing on its antioxidative, anti-inflammatory, anti-apoptotic, anti-fibrotic, and autophagy regulatory effects. For that, bibliographical research was carried out in Medline/PubMed and Scielo databases. Although the pathophysiological mechanisms involved in renal diseases are not fully understood, experimental studies demonstrate that oxidative stress, inflammation, apoptosis, and dysregulation of fibrotic and autophagic processes play central roles in the development of tissue damage. Increasing evidence has suggested that exercise can beneficially modulate these mechanisms, potentially becoming a safe and effective non-pharmacological strategy for kidney health protection and promotion. Thus, the evidence base discussed in this review suggests that an adequate training program emerges as a valuable tool for preserving renal function in experimental animals, mainly through the production of antioxidant enzymes, nitric oxide (NO), irisin, IL-10, and IL-11. Future research can continue to explore these mechanisms to develop specific guidelines for the prescription of exercise training in different populations of patients with kidney diseases.

Benefits of high-intensity interval training compared to continuous training to reduce apoptotic markers in female rats with cisplatin nephrotoxicity - possible modulatory role of IL-11

Apoptotic signaling pathways are involved in acute kidney injury (AKI) induced by the antineoplastic drug cisplatin (Cis). Mechanical stress is known to increase interleukin (IL) -11, a pleiotropic cytokine with antiapoptotic and antinecrotic effects. We compared the impact of high-intensity interval training (HIIT) with low-intensity continuous training (LICT) and moderate-intensity continuous training (MICT) on renal levels of IL-11 and the expression of apoptotic markers in female rats with nephrotoxicity induced by Cis. For that, the animals were divided into five groups (n = 7): control and sedentary (C + S); Cis and sedentary (Cis + S); Cis and LICT (Cis + LICT); Cis and MICT (Cis + MICT) and Cis and HIIT (Cis + HIIT). At the end of 8 weeks of treadmill running, the rats received a single injection of Cis (5 mg/kg), and 7 days later they were euthanized. Serum and kidney samples were collected to assess the blood urea nitrogen (BUN), gene expression of TNF receptor 1 (TNFR1) and 2 (TNFR2), caspase-3, (p38) MAPK (MAPK14), p53, Bax, Bak, Bcl-2, and Bcl-xL, renal levels of IL-11, IL-8, and p53, and immunolocalization of cleaved caspase-3, Bax, Bcl-2, and (p38) MAPK in renal tissue. Our data indicate that all trained groups showed a significant intensity-dependent increase in renal levels of IL-11 associated with reduced local expression of proapoptotic and increased antiapoptotic markers, but these effects were more pronounced with HIIT. So, HIIT appears to provide superior renoprotection than traditional continuous training by modulating apoptotic signaling pathways, and this effect can be related to the increase in renal levels of IL-11.

Enteral gabexate mesilate improves volume requirements and autonomic cardiovascular function after experimental trauma/hemorrhagic shock in the absence of blood reperfusion

The standard of care for fluid resuscitation of trauma/hemorrhagic shock (T/HS) is the infusion of blood. However, in many instances, blood product transfusion may not be feasible. Consequently, crystalloid solutions may be utilized as temporizing cost-effective resuscitation fluids. In this study, we explored an alternative therapeutic strategy of enteral protease inhibition adjunctive to intravenous Lactated Ringer's (LR) reperfusion after T/HS. Male Wistar rats underwent midline laparotomy (trauma) and an enteral catheter was inserted orally and positioned post-pyloric for the infusion of vehicle (Golytely®) with or without the serine protease inhibitor gabexate mesilate (GM) (n=8/group). Hemorrhagic shock was induced by blood removal to reduce the mean arterial blood pressure (MAP) to 35-40 mmHg for 90 minutes, before resuscitation with LR. Animals treated with enteral GM required significantly less crystalloid volume to achieve hemodynamic stability and displayed improvements in both blood pressure and autonomic function (via increased baroreflex sensitivity to vasopressors, heightened vascular sympathetic modulation, elevated levels of circulating catecholamines, and increased α1-adrenergic receptor density) compared to untreated (control) shocked animals. Resistance arteries isolated from healthy donor animals and perfused with plasma from untreated T/HS animals revealed impaired vascular response to the α1 adrenergic agonist phenylephrine and decreased reactivity to sodium nitroprusside that was preserved in the GM-treated group. These findings suggest that blockade of serine proteases within the intestinal lumen in non-blood resuscitated experimental T/HS preserves and enhances peripheral sympathetic modulation, improving hemodynamics. Enteral infusion of gabexate mesilate may be a new and promising approach to the management of trauma/hemorrhagic shock.

The effects of two different dietary regimens during exercise on outcome of experimental acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is a syndrome characterized by rapid loss of excretory function of kidney. Both exercise and some diets have been shown to increase silent information regulator (SIRT1) expression leading to reduction of kidney injury. In this study, the effect of two different diets during exercise on kidney function, oxidative stress, inflammation and also SIRT1 in AKI was investigated.

MATERIALS AND METHODS

A number of rats were randomly divided into four groups; control without exercise, control with exercise, exercise + calorie restriction (CR), and exercise + time restriction (TR). Each group was divided into two subgroups of without AKI and with AKI (six rats in each group). Endurance exercise and diets were implemented before AKI. Serum urea and creatinine, urinary albumin, kidney malondialdehyde (MDA), total antioxidant capacity (TAC), transforming growth factor (TGF-β1), and SIRT1 levels, glomerular filtration rate (GFR) and relative kidney weight were measured before and 24 h after AKI induction.

RESULTS

After induction of kidney injury, serum urea and creatinine, urinary albumin, kidney MDA and TGF-β1 levels increased in rats with both previous exercise and no previous exercise, while GFR, and kidney TAC and SIRT1 levels significantly decreased. These changes after AKI were less in the group with previous exercise than in the group that had no exercise (p <0.001). The TR diet during exercise caused a less increase in serum urea (p <0.01) and creatinine (p <0.01), and urinary albumin (p <0.001) levels after the injury compared to the just exercise group. Also, both CR and TR diets during exercise caused less change in MDA (p <0.001) and TAC (p <0.05, p <0.001, respectively) levels compared to just exercise group.

CONCLUSIONS

The results showed that exercise alone had no effect on preventing function impairment of kidney, oxidative stress, inflammation and also SIRT1 alteration following AKI, although these indexes were less among those with exercise than those without exercise. However, when the CR and TR diets were implemented during exercise, strong renoprotective effects appeared, and the protective effect of TR diet was greater.

BM-MSC-derived small extracellular vesicles (sEV) from trained animals presented nephroprotective potential in unilateralureteral obstruction model

Background:

The efficacy of bone marrow mesenchymal stromal cells (BM-MSC) and its extracellular vesicles has been demonstrated for a broad spectrum of indications, including kidney diseases. However, BM-MSC donor characteristics and their potential are not usually considered. Therefore, the present work aims to evaluate the nephroprotective capacity of sEV secreted by BM-MSC from trained rats inunilateral ureteral obstruction (UUO) model.

Methods:

BM-MSC was characterized by their differentiation potential and immunophenotypic markers. The sEV were isolated by ultracentrifugation and characterized by nanoparticle tracking analysis and western blot. Its miRNA cargo was examined by quantitative PCR analysis for miR-26a, 126a, and 296. Wistar rats were submitted to UUO procedure and concomitantly treated with sEV secreted by BM-MSC from the untrained andtrained rats. The kidney tissue from all groups was evaluated for fibrosis mediators (transforming growth factor beta1 and collagen), CD34-angiogenesis marker, and hypoxia-inducible factor 1 alpha (HIF-1α).

Results:

Treadmill training stimulated in BM-MSC the production of sEV loaded with pro-angiogenic miR-296. The treatment with this sEVin UUO-rats was able to attenuate collagen accumulation and increase CD34 and HIF-1α in the kidney tissue when compared to untrained ones. Tubular proximal cells under hypoxia and exposed to BM-MSC sEV demonstrate accumulation in HIF-1α and NFR-2 (nuclear factor erythroid 2-related factor 2), possibly to mediate the response to hypoxia and oxidative stress, under these conditions.

Conclusion:

The BM-MSC sEV from trained animals presented an increased nephroprotective potential compared to untrained vesicles by carrying 296-angiomiR and contributing to angiogenesis in UUO model.

Resistance exercise shifts the balance of renin-angiotensin system toward ACE2/Ang 1-7 axis and reduces inflammation in the kidney of diabetic rats

AIMS

We aimed to determine whether resistance training (RT) regulates renal renin-angiotensin system (RAS) components and inflammatory mediators in diabetic rats.

MAIN METHODS

Male Wistar rats (3 months old) were randomly assigned into four groups: non-trained (NT), trained (T), non-trained + diabetes (NTD) and trained +diabetes (TD). Diabetes was induced by streptozotocin (50 mg/kg, Sigma Chemical Co., St. Louis, MO, USA), before RT protocol. Trained rats performed RT protocol on a 110-cm ladder (8 ladder climbs, once/day, 5 days/week, 8 weeks), carrying a load corresponding to 50-80% of maximum carrying capacity. Blood glucose, albuminuria and urinary volume were measured. Renal levels of angiotensin peptides (angiotensin I, II and 1-7), inflammatory markers, and also the activities of angiotensin-converting enzyme (ACE) and ACE2 were determined.

KEY FINDINGS

Blood glucose and urinary volume were elevated in diabetic animals, and RT decreased albuminuria, renal Ang I and Ang II levels in diabetic rats. RT shifted the balance of renal RAS toward ACE2/Ang 1-7 axis in TD group, and mitigated the high levels of interleukin (IL)-10, IL-1β and cytokine-induced neutrophil chemoattractant 1 (CINC) in the context of diabetes. Strong positive correlations were found between albuminuria and Ang II, IL-10 and IL-1β. On the other hand, intrarenal Ang 1-7 levels were negatively correlated with IL-10 and IL-1β levels.

SIGNIFICANCE

RT improved kidney function by modulating intrarenal RAS toward ACE2/Ang 1-7 axis and inflammatory cytokines. RT represents a reasonable strategy to improve the renal complications induced by diabetes, counteracting nephropathy-associated maladaptive responses.

Nicotinamide attenuates streptozotocin-induced diabetes complications and increases survival rate in rats: role of autonomic nervous system

BACKGROUND

To evaluate the effect of nicotinamide prior to streptozotocin-induced (STZ) diabetes in baroreflex sensitivity and cardiovascular autonomic modulation, and its association with hemodynamics and metabolic parameters.

METHODS

Methods: Male Wistar rats were divided into control (Cont) and STZ-induced diabetes (Diab). Half of the rats from each group received a single dose of nicotinamide (100 mg/Kg) before STZ injection (Cont+NicA and Diab+NicA). All groups were followed-up for 5 weeks.

RESULTS

Body weight loss of more than 40% was observed in Diab throughout the period (Diab: 271.00 ± 12.74 g; Diab+NicA: 344.62 ± 17.82). Increased glycemia was seen in Diab rats (541.28 ± 18.68 mg/dl) while Diab+NicA group had a slight decrease (440.87 ± 20.96 mg/dl). However, insulin resistance was observed only in Diab. In relation to Cont, heart rate, mean blood pressure and diastolic function were reduced when compared to Diab, together with parasympathetic modulation and baroreflex sensitivity. All of these parameters were improved in Diab+NicA when compared to Diab. Improved baroreflex sensitivity and parasympathetic modulation were correlated with glycemia, insulin resistance, and body weight mass. Additionally, Diab+NicA group increased survival rate.

CONCLUSIONS

Results suggest that the association of nicotinamide in STZ-induced diabetic rats prevents most of the expected derangements mainly by preserving parasympathetic and baroreflex parameters.

High-intensity interval training is more effective than continuous training to reduce inflammation markers in female rats with cisplatin nephrotoxicity

AIMS

Cisplatin (CP) is an antineoplastic widely used in the treatment of various solid tumors, however, its clinical application is limited by nephrotoxicity. Here, we compared the impact of preconditioning with high-intensity interval training (HIIT) with continuous training of low (LIT) and moderate (MIT) intensity on innate immunity markers in female rats with CP-induced acute kidney injury.

MATERIALS AND METHODS

The rats were divided into five groups (n = 7): saline control and sedentary (C + S); CP and sedentary (CP + S); CP and LIT (CP + LIT); CP and MIT (CP + MIT) and CP and HIIT (CP + HIIT). The training intensity was determined by a maximum running test. At the end of training, the rats received a single dose of CP (5 mg/kg), and 7 days later they were euthanized. We evaluated renal function parameters (serum creatinine, glomerular filtration rate and proteinuria), renal structure, macrophage tissue infiltration, immunolocalization of nuclear transcription factor kappa B (NF-κB), renal levels of tumor necrosis factor-alpha (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6), and gene expression of monocyte chemoattractant protein-1 (MCP-1), toll-like receptor 4 (TLR4), and NF-κB in renal tissue.

KEY FINDINGS

Although both MIT and HIIT attenuated the degree of renal injury, only the HIIT prevented changes in renal function. The three training protocols mitigated the increase in expression of all inflammatory markers, however, this effect was more pronounced in HIIT.

SIGNIFICANCE

All training protocols promoted renoprotective actions, but HIIT was more effective in mitigating CP-induced acute kidney injury, in part by modulation of important markers of the innate immune response.

Preventive effect of exercise training on diabetic kidney disease in ovariectomized rats with type 1 diabetes

IMPACT STATEMENT

To date, no studies have been found evaluating the effects of physical exercise on renal function and structure changes in ovariectomized rats with type 1 diabetes. Therefore, this work emerges with an important tool for strengthening and expanding innovative research on exercise with potential for the prevention of renal diseases in ovariectomized diabetic rats, and future development of studies that seek to increase scientific knowledge about the beneficial effects of physical exercise on renal diseases in humans.

Exercise Training Attenuates the Development of Cardiac Autonomic Dysfunction in Diabetic Rats

BACKGROUND/AIM

Exercise training usually complements pharmacological therapy of type 1 diabetes mellitus, however, little is known about its impact on cardiac autonomic neuropathy. Our aim was to evaluate the impact of exercise on electrocardiographic parameters and heart rate variability in diabetic rats.

MATERIALS AND METHODS

Wistar rats were randomly assigned to four groups (n=12): Sedentary control (SC), sedentary diabetic (SD), exercise control (EC), and exercise diabetic (ED). Diabetes was induced by a single intraperitoneal injection of streptozotocin (45 mg/kg). Exercise groups underwent 8 weeks of training on a treadmill. At the end of the study, echocardiography was performed and continuous electrocardiographic recording was obtained by intra-abdominally implanted telemetric devices. Diabetes induction significantly reduced the heart rate and increased the blood glucose level (p<0.001) and R-wave amplitude (p<0.05). Frequency-domain spectral variables were also analyzed. The SD group had a significantly lower absolute high-frequency component (p<0.05) and higher normalized low-frequency component, as well as low-frequency power divided by the high-frequency power ratio when compared to the SC and EC groups (p<0.05). All these diabetes-related adverse changes in heart rate variability parameters were significantly reversed by exercise training (p<0.05). Overall, our study shows that early initiation of systemic exercise training prevents the development of cardiac autonomic neuropathy in rats with type 1 diabetes mellitus, by favorable change in the balance between parasympathetic and sympathetic activity.

Changes in the Complexity of Heart Rate Variability with Exercise Training Measured by Multiscale Entropy-Based Measurements

Quantifying complexity from heart rate variability (HRV) series is a challenging task, and multiscale entropy (MSE), along with its variants, has been demonstrated to be one of the most robust approaches to achieve this goal. Although physical training is known to be beneficial, there is little information about the long-term complexity changes induced by the physical conditioning. The present study aimed to quantify the changes in physiological complexity elicited by physical training through multiscale entropy-based complexity measurements. Rats were subject to a protocol of medium intensity training ( n = 13 ) or a sedentary protocol ( n = 12 ). One-hour HRV series were obtained from all conscious rats five days after the experimental protocol. We estimated MSE, multiscale dispersion entropy (MDE) and multiscale SDiff q from HRV series. Multiscale SDiff q is a recent approach that accounts for entropy differences between a given time series and its shuffled dynamics. From SDiff q , three attributes (q-attributes) were derived, namely SDiff q m a x , q m a x and q z e r o . MSE, MDE and multiscale q-attributes presented similar profiles, except for SDiff q m a x . q m a x showed significant differences between trained and sedentary groups on Time Scales 6 to 20. Results suggest that physical training increases the system complexity and that multiscale q-attributes provide valuable information about the physiological complexity.

Previous Exercise Training Reduces Markers of Renal Oxidative Stress and Inflammation in Streptozotocin-Induced Diabetic Female Rats

The aim of this study is to evaluate the effects of regular moderate exercise training initiated previously or after induction of diabetes mellitus on renal oxidative stress and inflammation in STZ-induced diabetic female rats. For this purpose, Wistar rats were divided into five groups: sedentary control (SC), trained control (TC), sedentary diabetic (SD), trained diabetic (TD), and previously trained diabetic (PTD). Only the PTD group was submitted to treadmill running for 4 weeks previously to DM induction with streptozotocin (40 mg/kg, i.v). After confirming diabetes, the PTD, TD, and TC groups were submitted to eight weeks of exercise training. At the end of the training protocol, we evaluated the following: glycosuria, body weight gain, plasma, renal and urinary levels of nitric oxide and thiobarbituric acid reactive substances, renal glutathione, and immunolocalization of lymphocytes, macrophages, and nuclear factor-kappa B (NF-κB/p65) in the renal cortex. The results showed that exercise training reduced glycosuria, renal TBARS levels, and the number of immune cells in the renal tissue of the TD and PTD groups. Of note, only previous exercise increased weight gain and urinary/renal NO levels and reduced NF-κB (p65) immunostaining in the renal cortex of the PTD group. In conclusion, our study shows that exercise training, especially when initiated previously to diabetes induction, promotes protective effects in diabetic kidney by reduction of renal oxidative stress and inflammation markers in female Wistar rats.

Can regular moderate exercise lead to changes in miRNA-146a and its adapter proteins in the kidney of streptozotocin-induced diabetic male rats?

Objective. The aim of this study was to assess whether microRNA-146a and its adapter proteins TNF receptor associated factor6 (TRAF6) and interleukin-1 receptor-associated kinase-1 (IRAK1) may be changed in the kidney of streptozotocin-induced diabetic rats, following regular moderate exercise.

Methods. Forty adult male Wistar rats were allocated randomly into four groups (n=10), including sedentary control (SC), sedentary diabetic (SD), healthy sixty-day exercise (H60E), and diabetic sixty-day exercise (D60E) groups. Diabetes was induced by an intraperitoneal injection of 60 mg/kg streptozotocin. After 48 h, blood glucose levels >250 mg/dl was included to diabetic rats. After 2 days of diabetes induction, the exercise protocol began. Animals were exposed to 5 days of consecutive treadmill exercise for 60 min/day with the 22 m/min speed for 60 days. The kidneys of the rats were removed and microRNA was extracted from them using the miRCURYTM RNA isolation kit.

Results. In diabetic rats, statistical analysis revealed a significant decrease in miR-146a expression, non-significant decrease in IRAK1 mRNA expression, and non-significant increase in TRAF6 and NF-kB mRNA expression compared to the SC group. Exercise led to a non-significant increase in the expression of miR-146a and NF-kB mRNA in the kidneys of the diabetic group as compared to the SD group, significant increase in TRAF6 and IRAK1 mRNA expression compared to the H60E group, and significant increase in TRAF6 mRNA expression compared to the SD group.

Conclusion. The present data indicate that exercise might be able to help in the prevention in the diabetic nephropathy development.

High Intensity Aerobic Exercise Training Improves Deficits of Cardiovascular Autonomic Function in a Rat Model of Type 1 Diabetes Mellitus with Moderate Hyperglycemia

Indices of cardiovascular autonomic neuropathy (CAN) in experimental models of Type 1 diabetes mellitus (T1DM) are often contrary to clinical data. Here, we investigated whether a relatable insulin-treated model of T1DM would induce deficits in cardiovascular (CV) autonomic function more reflective of clinical results and if exercise training could prevent those deficits. Sixty-four rats were divided into four groups: sedentary control (C), sedentary T1DM (D), control exercise (CX), or T1DM exercise (DX). Diabetes was induced via multiple low-dose injections of streptozotocin and blood glucose was maintained at moderate hyperglycemia (9-17 mM) through insulin supplementation. Exercise training consisted of daily treadmill running for 10 weeks. Compared to C, D had blunted baroreflex sensitivity, increased vascular sympathetic tone, increased serum neuropeptide Y (NPY), and decreased intrinsic heart rate. In contrast, DX differed from D in all measures of CAN (except NPY), including heart rate variability. These findings demonstrate that this T1DM model elicits deficits and exercise-mediated improvements to CV autonomic function which are reflective of clinical T1DM.

Beneficial effects of previous exercise training on renal changes in streptozotocin-induced diabetic female rats

This study evaluated the effects of aerobic exercise performed both previously and after the induction of diabetes mellitus on changes of renal function and structure in streptozotocin-induced diabetic rats. Female wistar rats were divided into five groups: sedentary control (C + Se); trained control (C + Ex); sedentary diabetic (D + Se); trained diabetic (D + Ex) and previously trained diabetic (D + PEx). The previous exercise consisted of treadmill running for four weeks before the induction of diabetes mellitus. After induction of diabetes mellitus with streptozotocin, the D + PEx, D + Ex and C + Ex groups were submitted to eight weeks of aerobic exercise. At the end of the training protocol, we evaluate the serum glucose, insulin and 17β-estradiol levels, renal function and structure, proteinuria, and fibronectin, collagen IV and transforming growth factor beta 1 (TGF-β1) renal expressions. Induction of diabetes mellitus reduced the insulin and did not alter 17β-estradiol levels, and exercise did not affect any of these parameters. Previous exercise training attenuated the loss of body weight, the blood glucose, the increase of glomerular filtration rate and prevented the proteinuria in the D + PEx group compared to D + Se group. Previous exercise also reduced glomerular hypertrophy, tubular and glomerular injury, as well as the expressions of fibronectin and collagen IV. These expressions were associated with reduced expression of TGF-β1. In conclusion, our study shows that regular aerobic exercise especially performed previously to induction of diabetes mellitus improved metabolic control and has renoprotective action on the diabetic kidney.

Microvascular oxygen partial pressure during hyperbaric oxygen in diabetic rat skeletal muscle

Hyperbaric oxygen (HBO) is a major therapeutic treatment for ischemic ulcerations that perforate skin and underlying muscle in diabetic patients. These lesions do not heal effectively, in part, because of the hypoxic microvascular O2 partial pressures (PmvO2 ) resulting from diabetes-induced cardiovascular dysfunction, which alters the dynamic balance between O2 delivery (Q̇o2) and utilization (V̇o2) rates. We tested the hypothesis that HBO in diabetic muscle would exacerbate the hyperoxic PmvO2 dynamics due, in part, to a reduction or slowing of the cardiovascular, sympathetic nervous, and respiratory system responses to acute HBO exposure. Adult male Wistar rats were divided randomly into diabetic (DIA: streptozotocin ip) and healthy (control) groups. A small animal hyperbaric chamber was pressurized with oxygen (100% O2) to 3.0 atmospheres absolute (ATA) at 0.2 ATA/min. Phosphorescence quenching techniques were used to measure PmvO2 in tibialis anterior muscle of anesthetized rats during HBO. Lumbar sympathetic nerve activity (LSNA), heart rate (HR), and respiratory rate (RR) were measured electrophysiologically. During the normobaric hyperoxia and HBO, DIA tibialis anterior PmvO2 increased faster (mean response time, CONT 78 ± 8, DIA 55 ± 8 s, P < 0.05) than CONT. Subsequently, PmvO2 remained elevated at similar levels in CONT and DIA muscles until normobaric normoxic recovery where the DIA PmvO2 retained its hyperoxic level longer than CONT. Sympathetic nervous system and cardiac and respiratory responses to HBO were slower in DIA vs. CONT. Specifically the mean response times for RR (CONT: 6 ± 1 s, DIA: 29 ± 4 s, P < 0.05), HR (CONT: 16 ± 1 s, DIA: 45 ± 5 s, P < 0.05), and LSNA (CONT: 140 ± 16 s, DIA: 247 ± 34 s, P < 0.05) were greater following HBO onset in DIA than CONT. HBO treatment increases tibialis anterior muscle PmvO2 more rapidly and for a longer duration in DIA than CONT, but not to a greater level. Whereas respiratory, cardiovascular, and LSNA responses to HBO are profoundly slowed in DIA, only the cardiovascular arm (via HR) may contribute to the muscle vascular incompetence and these faster PmvO2 kinetics.

Effect of aerobic exercise training on regional blood flow and vascular resistance in diabetic rats

BACKGROUND

Hyperglycemia has been associated with decreased blood flow in various organs, leading to tissue damage and dysfunctions. Exercise training (ET) is known to promote beneficial changes in the autonomic nervous system and may have effects on circulation. The aim of this study was to evaluate coronary and renal blood flows and vascular resistances after ET in diabetic rats.

METHODS

Thirty-two rats were divided into four groups (n = 8): sedentary control (SC), trained control (TC), sedentary diabetic (SD), trained diabetic (TD). Diabetes was induced by an injection of streptozotocin (STZ, 50 mg/kg). The ET was performed on a treadmill for 10 weeks. The blood flows were measured using colored microspheres.

RESULTS

The diabetic groups presented hyperglycemia (blood glucose >350 mg/dL) and ET did not change this parameter. The SD group showed reduced renal blood flow when compared to SC group, and ET was able to normalize this parameter in TD rats (SC: 4.3 ± 0.5; TC: 2.9 ± 0.3; SD: 1.9 ± 0.4; TD: 3.2 ± 0.4 mL/min/g). TD group presented increased coronary blood flow in relation to SD group (SC: 2.3 ± 0.23; TC: 2.8 ± 0.5; SD: 1.2 ± 0.4; TD: 3.0 ± 0.4 mL/min/g). The heart and kidneys vascular resistance were increased in SD group when compared to SC group, and ET was able to reverse these changes.

CONCLUSIONS

Given the relevance of cardiomyopathy and nephropathy in mortality of diabetics, our results demonstrated that ET is effective in improving coronary and renal blood flows and vascular resistances in STZ-diabetic rats, reinforcing the positive role of this approach in preventing hyperglycemia-induced long-term organ damage.

Akt1-mediated fast/glycolytic skeletal muscle growth attenuates renal damage in experimental kidney disease

Muscle wasting is frequently observed in patients with kidney disease, and low muscle strength is associated with poor outcomes in these patients. However, little is known about the effects of skeletal muscle growth per se on kidney diseases. In this study, we utilized a skeletal muscle-specific, inducible Akt1 transgenic (Akt1 TG) mouse model that promotes the growth of functional skeletal muscle independent of exercise to investigate the effects of muscle growth on kidney diseases. Seven days after Akt1 activation in skeletal muscle, renal injury was induced by unilateral ureteral obstruction (UUO) in Akt1 TG and wild-type (WT) control mice. The expression of atrogin-1, an atrophy-inducing gene in skeletal muscle, was upregulated 7 days after UUO in WT mice but not in Akt1 TG mice. UUO-induced renal interstitial fibrosis, tubular injury, apoptosis, and increased expression of inflammatory, fibrosis-related, and adhesion molecule genes were significantly diminished in Akt1 TG mice compared with WT mice. An increase in the activating phosphorylation of eNOS in the kidney accompanied the attenuation of renal damage by myogenic Akt1 activation. Treatment with the NOS inhibitor L-NAME abolished the protective effect of skeletal muscle Akt activation on obstructive kidney disease. In conclusion, Akt1-mediated muscle growth reduces renal damage in a model of obstructive kidney disease. This improvement appears to be mediated by an increase in eNOS signaling in the kidney. Our data support the concept that loss of muscle mass during kidney disease can contribute to renal failure, and maintaining muscle mass may improve clinical outcome.

Low intensity resistance training improves systolic function and cardiovascular autonomic control in diabetic rats

AIMS

We evaluated the effects of low intensity resistance training (RT) on left ventricular (LV) function, baroreflex sensitivity (BRS), and cardiovascular autonomic control of streptozotocin-induced diabetic rats.

METHODS

Male Wistar rats were divided into (n=8 each group): sedentary control (SC), trained control (TC), sedentary diabetic (SD), and trained diabetic (TD). Trained groups underwent low intensity RT (40%-50% 1 repetition maximum) for 10 weeks. Echocardiographic evaluation, arterial pressure (AP), heart rate (HR), BRS, and autonomic measurements were performed.

RESULTS

Diabetes induced an increase in glycemia and a reduction in body weight in diabetics when compared with control animals. Diabetic rats displayed cardiac dysfunction, reduced systolic AP and HR, impaired BRS and autonomic derangement when compared to control rats. RT improved ejection fraction (SD: 68%±1.3% vs. TD: 75%±3.0%) and velocity of circumferential fiber shortening (SD: 0.32±0.02 vs. TD: 0.40±0.01 circ/seg.10(-4)). Trained diabetic rats presented increased AP (+10.2%), HR (+10.4%), and BRS after RT protocol.

CONCLUSIONS

Low intensity RT induced an increase in systolic function in diabetic rats. This may be due to positive LV remodeling and BRS improvement, which may have played an important role in the attenuation of hemodynamic impairment and cardiac autonomic neuropathy in streptozotocin-diabetic rats.

Maternal hyperglycemia leads to fetal cardiac hyperplasia and dysfunction in a rat model

Accelerated fetal myocardial growth with altered cardiac function is a well-documented complication of human diabetic pregnancy, but its pathophysiology is still largely unknown. Our aim was to explore the mechanisms of fetal cardiac remodeling and cardiovascular hemodynamics in a rat model of maternal pregestational streptozotocin-induced hyperglycemia. The hyperglycemic group comprised 107 fetuses (10 dams) and the control group 219 fetuses (20 dams). Fetal cardiac function was assessed serially by Doppler ultrasonography. Fetal cardiac to thoracic area ratio, newborn heart weight, myocardial cell proliferative and apoptotic activities, and cardiac gene expression patterns were determined. Maternal hyperglycemia was associated with increased cardiac size, proliferative, apoptotic and mitotic activities, upregulation of genes encoding A- and B-type natriuretic peptides, myosin heavy chain types 2 and 3, uncoupling proteins 2 and 3, and the angiogenetic tumor necrosis factor receptor superfamily member 12A. The genes encoding Kv channel-interacting protein 2, a regulator of electrical cardiac phenotype, and the insulin-regulated glucose transporter 4 were downregulated. The heart rate was lower in fetuses of hyperglycemic dams. At 13-14 gestational days, 98% of fetuses of hyperglycemic dams had holosystolic atrioventricular valve regurgitation and decreased outflow mean velocity, indicating diminished cardiac output. Maternal hyperglycemia may lead to accelerated fetal myocardial growth by cardiomyocyte hyperplasia. In fetuses of hyperglycemic dams, expression of key genes that control and regulate cardiomyocyte electrophysiological properties, contractility, and metabolism are altered and may lead to major functional and clinical implications on the fetal heart.