Renal protective effects of chronic exercise and antihypertensive therapy in hypertensive rats with chronic renal failure

Renal Rehabilitation: Present and Future Perspectives

Chronic kidney disease (CKD) is a global health problem. In patients with CKD, exercise endurance is decreased, especially as renal dysfunction advances. This is due to the combined effects of protein-energy wasting, uremic acidosis, and inflammatory cachexia, which lead to sarcopenia and are aggravated by a sedentary lifestyle, resulting in a progressive downward spiral of deconditioning. Renal rehabilitation (RR) is a coordinated, multifaceted intervention designed to optimize a patient's physical, psychological, and social functioning, as well as to stabilize, slow, or even reverse the progression of renal deterioration, improving exercise tolerance and preventing the onset and worsening of heart failure, thereby reducing morbidity and mortality. This review focused on the history and benefits of RR in patients with CKD. Based on current evidence, RR is an effective, feasible, and safe secondary prevention strategy in CKD. RR is a promising model for a new field of rehabilitation. Therefore, efforts to increase RR implementation rates are urgently needed.

Effects of bisphosphonates and treadmill exercise on bone and kidney in adenine-induced chronic kidney disease rats

INTRODUCTION

The increasing prevalence of osteoporosis and chronic kidney disease (CKD) due to the aging of society has highlighted the need for development of effective treatments for elderly patients. This study examined whether the combination of treadmill exercise therapy and alendronate (ALN) can improve bone mineral density (BMD) and bone strength without worsening renal function in adenine-induced CKD model rats.

MATERIALS AND METHODS

8-week-old male Wistar rats (n = 70) were divided into experimental groups based on the treatment protocol, i.e., non-CKD (control), vehicle only (CKD), ALN only, exercise only, and combined ALN plus exercise. A 0.75% adenine diet was used to induce CKD. Groups were killed at either 20 or 30 weeks of age. Comprehensive assessments included serum and urine biochemistry tests, renal histology, bone histomorphometry, BMD measurement, micro-computed tomography examinations, and biomechanical testing.

RESULTS

Blood biochemistry tests, urine analyses and histological evaluations of the kidney demonstrated that ALN treatment did not worsen renal function or kidney fibrosis in moderate-stage CKD model rats. Both ALN and treadmill exercise significantly suppressed bone resorption (p < 0.05-p < 0.01). Moreover, ALN monotherapy and combined ALN and treadmill exercise significantly improved BMD of the lumbar spine and femur, bone microstructure, and trabecular bone strength (p < 0.05-p < 0.01). Treadmill exercise was also shown to decrease cortical porosity at the mid-diaphysis of the femur and improve kidney fibrosis.

CONCLUSION

The combination of ALN and treadmill exercise is effective in improving BMD, the microstructure of trabecular and cortical bone, and bone strength, without compromising renal function in adenine-induced CKD model rats.

Effects of Exercise Training on Mitochondrial Fatty Acid β-Oxidation in the Kidneys of Dahl Salt-Sensitive Rats

Exercise training (Ex) has anti-hypertensive and renal protective effects. In this study, we investigate the effects of Ex on mitochondrial fatty acid metabolism in the kidneys of Dahl salt-sensitive (Dahl-S) rats fed a high-salt (HS) diet. Eight-week-old, male Dahl-S rats were divided into three groups: (1) normal-salt diet, sedentary (NS-Sed), (2) HS diet, sedentary (HS-Sed), and (3) HS-Ex. The NS and HS groups were fed a diet containing 0.6% and 8% NaCl, respectively. The HS-Ex group performed treadmill running for 8 weeks (5 days/week; 60 min/day at 16-20 m/min, 0% gradient). Renal function and the expression of enzymes and regulators of β-oxidation and electron transport chain (ETC) complexes were assessed. HS increased systolic blood pressure and proteinuria, and Ex ameliorated these defects. HS also reduced creatinine clearance, and Ex ameliorated it. HS reduced the renal expression of enzymes of β-oxidation (carnitine palmitoyltransferase type I (CPTI) and acyl-CoA dehydrogenases (CADs)) and the related transcription factors peroxisome proliferator-activated receptor α (PPARα) and PPARγ-coactivator-1α (PGC-1α), and Ex restored this. HS also reduced the renal expression of enzymes in ETC complexes, and Ex restored this expression. Ex ameliorates HS-induced renal damage by upregulating enzymes involved in fatty acid β-oxidation and ETC complexes via increases in PPAR-α and PGC-1α expressions in the kidneys of Dahl-S rats. These results suggest that Ex may have beneficial effects on HS-induced mitochondrial dysfunction in the kidney.

Exercise Training Ameliorates Renal Oxidative Stress in Rats with Chronic Renal Failure

In patients with chronic kidney disease, exercise training with moderate intensity protects renal function and improves mortality. However, the mechanisms of the renal protective effects of exercise training in chronic kidney disease have not been clarified. This study investigated the effects of exercise training on renal NADPH oxidative and xanthine oxidase, which are major sources of reactive oxygen species, in rats with chronic renal failure. Six-week-old, male Sprague–Dawley rats were divided into the sham operation, 5/6 nephrectomy (Nx)+ sedentary, and Nx+ exercise training groups. The Nx+ exercise training group underwent treadmill running. After 12 weeks, systolic blood pressure, renal function, malondialdehyde, renal NADPH oxidase, and xanthine oxidase were examined. Nx induced hypertension, proteinuria, and renal dysfunction, and exercise training attenuated these disorders. Although the plasma levels of malondialdehyde were not different among the group, urinary levels were increased by Nx and decreased by exercise training. Renal activity and expression of NADPH oxidase and xanthine oxidase were increased by Nx and decreased by exercise training. These results indicate that exercise training attenuates hypertension and renal dysfunction and ameliorates NADPH oxidase and xanthine oxidase in rats with chronic renal failure, suggesting that the reduction of reactive oxygen species generation may be involved in the renal protective effects of exercise training.

Effects of Exercise Training on the Renin-Angiotensin System in the Kidneys of Dahl Salt-Sensitive Rats

PURPOSE

Exercise training (Ex) has antihypertensive and renal protective effects; however, the precise mechanisms remain unclear. The renal renin-angiotensin system (RAS) plays a vital role in renal function and pathology. Therefore, we investigated the effects of Ex on the renal RAS components in Dahl salt-sensitive (Dahl-S) rats.

METHODS

Male Dahl-S rats were divided into four groups: normal salt diet + sedentary, normal salt diet + Ex, high-salt diet (HS, 8% NaCl) + sedentary, and HS + Ex. Treadmill running was performed for 8 wk in the Ex groups.

RESULTS

Ex attenuated the HS-induced renal dysfunction and glomerular injury without causing blood pressure alterations. HS increased urinary excretion of both total and intact angiotensinogen. Ex decreased the HS-induced increased urinary excretion of total angiotensinogen. However, it did not change the HS-induced urinary excretion of intact angiotensinogen, indicating reduced intact angiotensinogen cleaving. Ex restored the HS-induced increased angiotensinogen and angiotensin II type 1 receptor expressions in the outer medulla and the HS-induced increased angiotensin-converting enzyme expression in the cortex. Ex restored the HS-induced decreased renin expression in the cortex and outer medulla, and the HS-induced decreased angiotensin-converting enzyme 2, angiotensin II type 2 receptor, and Mas receptor expressions in the outer medulla.

CONCLUSIONS

Ex attenuates HS-induced renal dysfunction, glomerular injury, and renal RAS dysregulation in Dahl-S rats.

The effects of exercise on kidney injury: the role of SIRT1

In patients with kidney injury, muscle mass and strength decrease with altered muscle protein synthesis and degradation along with complications such as inflammation and low physical activity. A treatment strategy to maintain muscle metabolism in kidney injury is important. One of the proposed strategies in this regard is exercise, which in addition to inducing muscle hypertrophy, reducing plasma creatinine and urea and decreasing the severity of tubal injuries, can boost immune function and has anti-inflammatory effects. One of the molecules that have been considered as a target in the treatment of many diseases is silent information regulator 1 (SIRT1). Exercise increases the expression of SIRT1 and improves its activity. Therefore, studies that examined the effect of exercise on kidney injury considering the role of SIRT1 in this effect were reviewed to determine the direction of kidney injury research in future regarding to its prevalence, especially following diabetes, and lack of definitive treatment. In this review, we found that SIRT1 can be one of renoprotective target pathways of exercise. However, further studies are needed to determine the role of SIRT1 in different kidney injuries following exercise according to the type and severity of exercise, and the type of kidney injury.

Osteocrin, a bone-derived humoral factor, exerts a renoprotective role in ischemia-reperfusion injury in mice

Background

Osteocrin (OSTN), a bone-derived humoral factor, was reported to act on heart and bone by potentiating the natriuretic peptide (NP) system. Ostn gene polymorphisms have been associated with renal function decline, but its pathophysiological role in the kidney remains unclear.

Methods

The role of endogenous OSTN was investigated using systemic Ostn-knockout (KO) mice. As a model for OSTN administration, liver-specific Ostn-overexpressing mice crossed with KO (KO-Tg) were generated. These mice were subjected to unilateral ischemia–reperfusion injury (IRI) and renal lesions after 21 days of insult were evaluated. A comprehensive analysis of the Wnt/β-catenin pathway was performed using a polymerase chain reaction (PCR) array. Reporter plasmid-transfected proximal tubular cells (NRK52E) were used to investigate the mechanism by which OSTN affects the pathway.

Results

After injury, KO mice showed marginal worsening of renal fibrosis compared with wild-type mice, with comparable renal atrophy. KO-Tg mice showed significantly ameliorated renal atrophy, fibrosis and tubular injury, together with reduced expressions of fibrosis- and inflammation-related genes. The PCR array showed that the activation of the Wnt/β-catenin pathway was attenuated in KO-Tg mice. The downstream targets Mmp7, Myc and Axin2 showed similar results. MMP7 and Wnt2 were induced in corticomedullary proximal tubules after injury, but not in KO-Tg. In NRK52E, OSTN significantly potentiated the inhibitory effects of NP on transforming growth factor β1–induced activation of the Wnt/β-catenin pathway, which was reproduced by a cyclic guanosine monophosphate analog.

Conclusions

Ectopic Ostn overexpression ameliorated subsequent renal injury following ischemia–reperfusion. OSTN could represent possible renoprotection in acute to chronic kidney disease transition, thus serving as a potential therapeutic strategy.

Chronic Exercise Protects against the Progression of Renal Cyst Growth and Dysfunction in Rats with Polycystic Kidney Disease

Introduction

Polycystic kidney disease (PKD) is a genetic disorder characterized by the progressive enlargement of renal epithelial cysts and renal dysfunction. Previous studies have reported the beneficial effects of chronic exercise on chronic kidney disease. However, the effects of chronic exercise have not been fully examined in PKD patients or models. The effects of chronic exercise on the progression of PKD were investigated in a polycystic kidney (PCK) rat model.

Methods

Six-week-old male PCK rats were divided into a sedentary group and an exercise group. The exercise group underwent forced treadmill exercise for 12 wk (28 m·min⁻¹, 60 min·d⁻¹, 5 d·wk⁻¹). After 12 wk, renal function and histology were examined, and signaling cascades of PKD progression, including arginine vasopressin (AVP), were investigated.

Results

Chronic exercise reduced the excretion of urinary protein, liver-type fatty acid–binding protein, plasma creatinine, urea nitrogen, and increased plasma irisin and urinary AVP excretion. Chronic exercise also slowed renal cyst growth, glomerular damage, and interstitial fibrosis and led to reduced Ki-67 expression. Chronic exercise had no effect on cAMP content but decreased the renal expression of B-Raf and reduced the phosphorylation of extracellular signal-regulated kinase (ERK), mammalian target of rapamycin (mTOR), and S6.

Conclusion

Chronic exercise slows renal cyst growth and damage in PCK rats, despite increasing AVP, with the downregulation of the cAMP/B-Raf/ERK and mTOR/S6 pathways in the kidney of PCK rats.

Effects of Long-Term Exercise on Liver Cyst in Polycystic Liver Disease Model Rats

BACKGROUND

Polycystic liver disease (PLD) is a hereditary liver disease with progressive enlargement of fluid-filled liver cysts, which causes abdominal discomfort and worsens quality of life. Long-term exercise has beneficial effects in various organs, but the effects of long-term exercise on PLD are unclear. Therefore, the aim of this study was to investigate whether long-term exercise inhibits liver cyst formation and fibrosis.

METHODS

Polycystic kidney (PCK) rats, a model of PLD, were randomly divided into a sedentary group and a long-term exercise group, which underwent treadmill running for 12 wk (28 m·min, 60 min·d, 5 d·wk). Sprague-Dawley (SD) rats were set as a control group. After 12 wk, exercise capacity, histology, and signaling cascades of PLD were examined.

RESULTS

Compared with control SD rats, PCK rats showed a low exercise capacity before exercise protocol. After 12 wk, the exercise improved the exercise capacity and ameliorated liver cyst formation and fibrosis. The exercise significantly decreased the number of Ki-67-positive cells; the expression of cystic fibrosis transmembrane conductance regulator, aquaporin 1, transforming growth factor β, and type 1 collagen; and the phosphorylation of extracellular signal-regulated kinase, mammalian target of rapamycin and S6. It also increased the phosphorylation of AMP-activated protein kinase in the liver of PCK rats.

CONCLUSIONS

The present results indicated that long-term moderate-intensity exercise ameliorates liver cyst formation and fibrosis with the inhibition of signaling cascades responsible for cellular proliferation and fibrosis in PCK rats.

Combination of Exercise Training and SOD Mimetic Tempol Enhances Upregulation of Nitric Oxide Synthase in the Kidney of Spontaneously Hypertensive Rats

Both exercise training (Ex) and superoxide dismutase (SOD) mimetic tempol have antihypertensive and renal protective effects in rodent models of several hypertensions. We recently reported that Ex increases nitric oxide (NO) production and the expression levels of endothelial and neuronal NO synthase (eNOS and nNOS) in the kidney and aorta of the spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto rats (WKY). We also found that endogenous hydrogen peroxide (H₂O₂) upregulates the expression levels of eNOS and nNOS in SHR. To elucidate the mechanism of the Ex-upregulated NO system in the kidney, we examined the additive effect of Ex and tempol on the renal NO system in SHR and WKY. Our data showed that, in SHR, both Ex and tempol increase the levels of H₂O₂ and nitrate/nitrite (NOx) in plasma and urine. We also observed an increased renal NOS activity and upregulated expression levels of eNOS and nNOS with decreased NADPH oxidase activity. The effects of the combination of Ex and tempol on these variables were cumulate in SHR. On the other hand, we found that Ex increases these variables with increased renal NADPH oxidase activity, but tempol did not change these variables or affect the Ex-induced upregulation in the activity and expression of NOS in WKY. The SOD activity in the kidney and aorta was activated by tempol only in SHR, but not in WKY; whereas Ex increased SOD activity only in the aorta in both SHR and WKY. These results indicate that Ex-induced endogenous H₂O₂ produced in the blood vessel and other organs outside of the kidney may be carried to the kidney by blood flow and stimulates the NO system in the kidney.

Effects of exercise training on renal interstitial fibrosis and renin-angiotensin system in rats with chronic renal failure

OBJECTIVE

To clarify the mechanisms of the renal protective effects of exercise training, we examined the effects of exercise training on the renal interstitial fibrosis and renin-angiotensin system (RAS) in rats with chronic renal failure.

METHODS

Six-week-old male Sprague-Dawley rats were divided into three groups: sham operation; 5/6 nephrectomy + sedentary; 5/6 nephrectomy + exercise training. The 5/6 nephrectomy + exercise training group underwent treadmill running (20 m/min, 60 min/day, 5 days/week). After 12 weeks, renal function, histology and protein expression of collagen type I, transforming growth factor-β1 (TGF-β1), matrix metalloproteinase (MMP), tissue inhibitors of metalloproteinase (TIMP) and RAS components in the renal cortex were examined.

RESULTS

Exercise training ameliorated the 5/6 nephrectomy-induced hypertension, proteinuria, renal dysfunction, glomerular sclerosis and renal interstitial fibrosis. 5/6 Nephrectomy increased the expression of collagen type I, TGF-β1, MMP-2, MMP-9, TIMP-1, angiotensinogen, angiotensin-converting enzyme (ACE), (pro)renin receptor and angiotensin II type 1 receptor, and exercise training inhibited the 5/6 nephrectomy-increased expression of collagen type I, TGF-β1, TIMP-1, angiotensinogen and ACE expressions. 5/6 Nephrectomy decreased the expression of renin, ACE2, angiotensin II type 2 receptor and Mas receptor, and exercise training inhibited the 5/6 nephrectomy-decreased expressions.

CONCLUSION

These results indicated that exercise training attenuates the progression of glomerular sclerosis and renal interstitial fibrosis in chronic renal failure rats. The renal protective effects of exercise training may be mediated by ameliorating the renal collagen turnover and the exacerbation of renal RAS.

Exercise training delays renal disorders with decreasing oxidative stress and increasing production of 20-hydroxyeicosatetraenoic acid in Dahl salt-sensitive rats

OBJECTIVE

Exercise training has antihypertensive and renoprotective effects in humans and rats. However, the effects of exercise training on renal disorders that occur with salt-sensitive hypertension remains unclear. The study aim was to investigate the effects and mechanisms of exercise training on renal function in a rat model of salt-sensitive hypertension.

METHODS

Six-week-old male Dahl salt-sensitive rats were divided into normal-salt (0.6% NaCl) diet, high-salt (8% NaCl) diet, and high-salt diet with exercise training groups. The high-salt diet with exercise training group underwent daily treadmill running for 8 weeks.

RESULTS

The high-salt diet induced severe hypertension and renal dysfunction. Exercise training significantly improved high-salt diet-induced urinary protein, albumin, and L-type fatty acid-binding protein excretion, and glomerulosclerosis but not renal interstitial fibrosis without changing blood pressure. Exercise training significantly attenuated high-salt diet-induced oxidative stress in the kidneys and decreased high-salt diet-stimulated xanthine oxidoreductase activity but not nicotinamide adenine dinucleotide phosphate oxidase activity. The high-salt diet did not change urinary excretion of 20-hydroxyeicosatetraenoic acid and decreased cytochrome P450 4A protein expression in the kidneys. Exercise training increased urinary 20-hydoroxyeicosatetraenoic acid excretion and renal cytochrome P450 4A protein expression.

CONCLUSION

Exercise training improved renal disorders without lowering blood pressure in Dahl salt-sensitive rats. Exercise training also decreased oxidative stress and increased 20-hydroxyeicosatetraenoic acid production in the kidneys. These results suggest that improvements in oxidative stress and 20-hydroxyeicosatetraenoic acid production may be potential mechanisms by which exercise training improved renal disorders in Dahl salt-sensitive rats.

Association between physical activity and change in renal function in patients after acute myocardial infarction

BACKGROUND

Combined renal dysfunction worsens the subsequent prognosis in patients after acute myocardial infarction (AMI). Therefore, establishing a therapeutic modality to maintain or improve renal function in AMI patients is necessary. This study aimed to elucidate the association between physical activity level and change in renal function in such patients.

DESIGN

Prospective and observational study.

METHODS

We enrolled 41 patients (35 men; average age, 67.5 ± 12.6 years) after AMI onset. Blood biochemistry, urinalysis, and physical function tests were conducted at discharge and 3 months after discharge. Renal function was evaluated based on cystatin C based-estimated glomerular filtration rate (eGFRcys). The number of steps was recorded for 3 months post-discharge. Generalized estimating equations (GEE) was used to test the association between physical activity level and within-patient changes in eGFRcys.

RESULTS

Patients were stratified into low (n = 21; number of steps, 2335 ± 1219 steps/day) and high groups (n = 20; number of steps, 7102 ± 2365 steps/day). eGFRcys significantly increased from baseline to after 3 months in the high group (76.5 ± 13.8 to 83.2 ± 16.0 mL/min/1.73 m2, q = 0.004), whereas no significant change was observed in the low group (65.1 ± 15.9 to 62.2 ± 20.2 mL/min/1.73 m2, q = 0.125). Result of GEE adjusted for potential confounding variables showed a significant positive association between physical activity level and within-patient changes in eGFRcys (p = 0.003). Changes in eGFRcys was -2.9 mL/min/1.73 m2 among low group versus +6.7 mL/min/1.73 m2 among high group.

CONCLUSIONS

Physical activity level was positively associated with changes in renal function, demonstrating that high physical activity may suppress renal function decline in patients after AMI.

Aerobic Exercise Training Alleviates Renal Injury by Interfering with Mitochondrial Function in Type-1 Diabetic Mice

BACKGROUND Diabetic nephropathy was one of the most serious and harmful diabetic complications, characterized by progressive loss of renal function and renal fibrosis. Aerobic exercise training is an important non-pharmacologic method to prevent and treat diabetes mellitus and diabetic complications. MATERIAL AND METHODS Intraperitoneal (i.p.) injection of streptozocin (STZ) was used to construct a type 1 diabetic mouse model. Renal function and mitochondrial function were measured by urinary protein level, Masson staining and ATP, superoxide production, and membrane potential, respectively. The purpose of the research was to explore the effect of aerobic exercise training on renal and renal mitochondrial function, as well as the expression of Sirt1and PGC1α in type-1 diabetic mice. RESULTS Sedentary diabetic mice exhibited increased urinary protein level, blood glucose, and collagen deposition in renal tissues compared with sedentary control mice, which were significantly mitigated by aerobic exercise training. Diabetic mice displayed renal tissue mitochondrial dysfunction (decreased mitochondrial ATP production and membrane potential), as well as increased mitochondrial superoxide production, which were reversed by aerobic exercise. By using Western blot analysis, we identified the decreased expression of Sirt1 and PGC1α in the renal tissue of diabetic mice, which were partly reversed by aerobic exercise training. Data showed that silencing of Sirt1 abrogated the beneficial effect of aerobic exercise training against diabetes-induced mitochondrial abnormalities and renal damage in mice. CONCLUSIONS Aerobic exercise training alleviates diabetes-induced renal injury by improving mitochondrial function.

Effect of free running wheel exercise on renal expression of parathyroid hormone receptor type 1 in spontaneously hypertensive rats

An active lifestyle is generally recommended for hypertensive patients to prevent subsequent end-organ damage. However, experimental data on long-term effects of exercise on hypertension are insufficient and underlying mechanisms are not well understood. This study was aimed to investigate the effect of exercise on renal expression of parathyroid hormone-related protein (PTHrP) and parathyroid hormone receptor type 1 (PTHR1) in spontaneously hypertensive rats (SHR). Twenty-four rats started free running wheel exercise at the age of 1.5 months (pre-hypertensive state) and proceeded for 1.5, 3.0, 6.0, and 10.0 months. Thirty rats kept under standard housing conditions were used as sedentary controls. Kidney function was assessed by measuring plasma creatinine levels and urine albumin-to-creatinine ratios. Renal expression of PTHrP and PTHR1 was analyzed by qRT-PCR and western blot. Renal expression of PTHR1 was markedly increased between the 6th and 10th months in sedentary rats and this increase was significantly lower in SHRs with high physical activity on mRNA (-30%) and protein level (-27%). At the same time, urine albumin-to-creatinine ratio increased (from 65 to 231 mg/g) but somehow lower in exercise performing SHRs (48-196 mg/g). Our data suggest that enhanced exercise, stimulated by allocation of a free running wheel, is associated with lower PTHR1 expression in SHRs and this may contribute to preserved kidney function.

Swimming exercise demonstrates advantages over running exercise in reducing proteinuria and glomerulosclerosis in spontaneously hypertensive rats

Experimental studies in animal models have described the benefits of physical exercise (PE) to kidney diseases associated with hypertension. Land- and water-based exercises induce different responses in renal function. Our aim was to evaluate the renal alterations induced by different environments of PE in spontaneously hypertensive rats (SHRs). The SHRs were divided into sedentary (S), swimming exercise (SE), and running exercise (RE) groups, and were trained for 8 weeks under similar intensities (60 min/day). Arterial pressure (AP) and heart rate (HR) were recorded. The renal function was evaluated through urinary volume at each week of training; sodium and potassium excretions, plasma and urinary osmolarities, glomerular filtration rate (GFR), levels of proteinuria, and renal damage were determined. SE and RE rats presented reduced mean AP, systolic blood pressure, and HR in comparison with S group. SE and RE rats showed higher urine osmolarity compared with S. SE rats showed higher free water clearance (P < 0.01), lower urinary density (P < 0.0001), and increased weekly urine volume (P < 0.05) in comparison with RE and S groups. GFR was increased in both SE and RE rats. The proteinuria of SE (7.0 ± 0.8 mg/24 h) rats was decreased at the 8th week of the PE in comparison with RE (9.6 ± 0.8 mg/24 h) and S (9.8 ± 0.5 mg/24 h) groups. The glomerulosclerosis was reduced in SE rats (P < 0.02). SE produced different response in renal function in comparison with RE, in which only swimming-trained rats had better profile for proteinuria and glomerulosclerosis.

Effect of cardiac rehabilitation on the renal function in chronic kidney disease - Analysis using serum cystatin-C based glomerular filtration rate

Background

Whether an individually determined appropriate level of cardiac rehabilitation (CR) has a favorable effect on the renal function still remains unclarified. The aim of this study was to confirm the effect of CR on the estimated glomerular filtration rate (eGFR) using cystatin C, which is known to be unaffected by physical exercise.

Methods

The study population was comprised of 86 patients (61 males; average age 74 y/o) with a lower-moderate level of chronic kidney disease (CKD) who was admitted to our hospital for treatment of cardiovascular disease (CVD) and who participated in our 3-month CR program. The exercise capacity was assessed by cardiopulmonary exercise testing (CPX) and the eGFR was measured by a formula based on the serum cystatin C concentration (eGFRcys) in each patient both at the beginning and end of the CR.

Results

In the CVD patients with CKD, both the peak oxygen uptake (VO₂) and peak work rate (WR) improved significantly after CR (15.0 ± 3 to 15.8 ± 3 ml/min/kg, p = 0.002. 65.5 ± 21 to 70.2 ± 25 W, p = 0.001). Regarding the renal function, the eGFRcys improved (45.2 ± 11 to 47.3 ± 13 ml/min/1.73 m², p = 0.023), however, the eGFR assessed by the serum creatinine (eGFRcr) did not improve after CR (45.1 ± 12 to 44.9 ± 13 ml/min/1.73 m², p = 0.834).

Conclusions

In CVD patients, a novel CR program significantly improved the exercise capacity. Further, CR was shown to have a favorable effect on the renal function when it was estimated by the eGFRcys.

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Cardiac rehabilitation improved the renal function using serum cystatin C.

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Cardiac rehabilitation didn't change the renal function using serum creatinine.

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Cardiac rehabilitation is most effective on moderate to severe CKD patients.

Transient cardiac dysfunction but elevated cardiac and kidney biomarkers 24 h following an ultra-distance running event in Mexican Tarahumara

Background

The Mexican Tarahumara are accustomed to running ultra-distance races. No data exist on the acute physiological changes following ultra-distance running and physiological-biomarker associations in this population. Thus, we aimed to investigate the acute impact (≤ 24 h) on functional and biochemical changes of the cardiac muscle and biochemical changes associated with kidney function following a 63-km ultra-distance race with an altitude difference of 1800 m in Mexican Tarahumara athletes.

Methods

Ten Tarahumara male athletes (mean ± SD age = 29.9 ± 6.6 years) volunteered to participate in the study. VO₂max was assessed by a sub-maximal step test individually calibrated combining heart rate and accelerometry. Standard transthoracic echocardiography methodology and venipuncture blood tests were carried out at four time points: pre-race, immediately post-race, 6 h, and 24 h post-race.

Results

Estimated mean VO₂max was 54.5 (± 8.8) mL O₂ min⁻¹ kg⁻¹ and average physiological activity intensity was 746 (± 143) J min⁻¹ kg ⁻¹ (~ 11.5 METs). When compared to pre-race values, significant changes in left ventricular ejection fraction (LVEF) and LV end-diastolic volume (− 15%, p < 0.001 for both parameters), cardiac output (39%, p < 0.001), and maximal longitudinal velocity (− 13%, p < 0.009) were seen post-race with LVEF also being decreased at < 6 h post-race (− 8%, p < 0.014). Plasma biomarkers mid-regional pro-atrial natriuretic peptide, copeptin-ultra sensitive, and high-sensitivity cardiac troponin T remained significantly elevated at 24 h post-race, and the two latter were inversely associated with LVEF (p < 0.04). Kidney dysfunction was indicated by increased post-race copeptin-ultra sensitive.

Conclusions

The athletes participating in this study had acute transient cardiac dysfunction as assessed by echocardiography but elevated cardiac and kidney biomarkers at 24 h following a 63-km race with extreme altitude variation.

Electronic supplementary material

The online version of this article (10.1186/s13728-017-0057-5) contains supplementary material, which is available to authorized users.

Chronic Running Exercise Alleviates Early Progression of Nephropathy with Upregulation of Nitric Oxide Synthases and Suppression of Glycation in Zucker Diabetic Rats

Exercise training is known to exert multiple beneficial effects including renal protection in type 2 diabetes mellitus and obesity. However, the mechanisms regulating these actions remain unclear. The present study evaluated the effects of chronic running exercise on the early stage of diabetic nephropathy, focusing on nitric oxide synthase (NOS), oxidative stress and glycation in the kidneys of Zucker diabetic fatty (ZDF) rats. Male ZDF rats (6 weeks old) underwent forced treadmill exercise for 8 weeks (Ex-ZDF). Sedentary ZDF (Sed-ZDF) and Zucker lean (Sed-ZL) rats served as controls. Exercise attenuated hyperglycemia (plasma glucose; 242 ± 43 mg/dL in Sed-ZDF and 115 ± 5 mg/dL in Ex-ZDF) with increased insulin secretion (plasma insulin; 2.3 ± 0.7 and 5.3 ± 0.9 ng/mL), reduced albumin excretion (urine albumin; 492 ± 70 and 176 ± 11 mg/g creatinine) and normalized creatinine clearance (9.7 ± 1.4 and 4.5 ± 0.8 mL/min per body weight) in ZDF rats. Endothelial (e) and neuronal (n) NOS expression in kidneys of Sed-ZDF rats were lower compared with Sed-ZL rats (p<0.01), while both eNOS and nNOS expression were upregulated by exercise (p<0.01). Furthermore, exercise decreased NADPH oxidase activity, p47phox expression (p<0.01) and α-oxoaldehydes (the precursors for advanced glycation end products) (p<0.01) in the kidneys of ZDF rats. Additionally, morphometric evidence indicated renal damage was reduced in response to exercise. These data suggest that upregulation of NOS expression, suppression of NADPH oxidase and α-oxoaldehydes in the kidneys may, at least in part, contribute to the renal protective effects of exercise in the early progression of diabetic nephropathy in ZDF rats. Moreover, this study supports the theory that chronic aerobic exercise could be recommended as an effective non-pharmacological therapy for renoprotection in the early stages of type 2 diabetes mellitus and obesity.

The effects of tai chi on the renal and cardiac functions of patients with chronic kidney and cardiovascular diseases

[Purpose] To assess the effects of Tai Chi on the renal and cardiac functions of patients with chronic kidney disease (CKD) and cardiovascular disease (CVD). [Subjects and Methods] Twenty-one patients with CKD and CVD were randomly divided into control and exercise groups. The exercise group performed Tai Chi training for 30 minutes three to five times a week for 12 weeks, while the control group did not. All patients’ renal and cardiac functions and blood lipid parameters were measured at baseline and after 12 weeks. [Results] The 12 weeks Tai Chi intervention improved the estimated glomerular filtration rate (eGFR), left ventricular ejection fraction (LVEF), and the high density lipoprotein (HDL) level, and decreased the serum creatintine (Scr) level, heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and the total cholesterol (CH), triglyceride (TG) and low density lipoprotein (LDL) levels. The change in eGFR correlated negatively with the changes in CH, TG and LDL, and positively with the change in HDL. In addition, the change in SBP correlated positively with the changes in CH, TG and LDL, and negatively with the change in HDL. [Conclusion] Tai Chi training might improve the renal and cardiac functions of CKD and CVD patients via improved regulation of lipid metabolism.

Daily exercise training protects against albuminuria and angiotensin converting enzyme 2 shedding in db/db diabetic mice

Angiotensin II (Ang II) is involved in induction and progression of renal damage in diabetes. Angiotensin converting enzyme 2 (ACE2) is highly expressed in the kidney and has been shown to be renoprotective by degrading Ang II to Ang-(1-7). A disintegrin and metalloproteinase 17 (ADAM17)-mediated shedding of renal ACE2 contribute to diabetic nephropathy pathogenesis. Lifestyle modification and metformin are recommended as initial therapies for most patients with type 2 diabetes. The aim of this study was to investigate whether exercise training and/or metformin improve glucose homeostasis and albuminuria and downregulate renal ADAM17 and ACE2 shedding in db/db mice. Seven-week-old normal and db/db mice were subjected either to a sedentary existence or exercise training with and without metformin (150 mg/kg per day) for 10 weeks. Exercise training significantly lowered blood glucose, urinary albumin and ACE2 excretion in db/db mice. ADAM17 and ACE2 proteins were co-localized in cortical tubules of the kidney, indicating a possible interaction. Metformin treatment was effective in lowering hyperglycemia only during the first 2 weeks of treatment. Increased renal ADAM17 in 17-week-old db/db mice was corrected by physical exercise but not metformin. In addition, exercise training reduced plasma triglycerides and enhanced insulin levels of db/db mice. In conclusion, exercise training alone and in combination with metformin prevented shedding of renal ACE2 by decreasing ADAM17 protein. Urinary ACE2 could serve as a prognostic tool for the progression of kidney damage and its attenuation by exercise may partially contribute to its renal protection.

Exercise training upregulates nitric oxide synthases in the kidney of rats with chronic heart failure

There is an interaction between heart and kidney diseases, which is a condition termed cardiorenal syndrome. Exercise training has cardioprotective effects, involving upregulation of endothelial (e) nitric oxide synthase (NOS) in the cardiovascular system. However, the effects of exercise training on NOS in the kidney with heart disease are unknown. The aim of the present study was to investigate whether exercise training upregulates NOS in the kidney, left ventricle and aorta of rats with chronic heart failure (CHF). Male Sprague-Dawley rats underwent left coronary artery ligation (LCAL) to induce CHF and were randomly assigned to sedentary or treadmill exercise groups 4 weeks after LCAL. Three days after exercising for 4 weeks, urine samples were collected for 24 h and blood samples were collected following decapitation. Nitric oxide synthase activity and protein expression were examined. Significant interactions between CHF and exercise training were observed on parameters of cardiac and renal function. Exercise training improved cardiac function, decreased plasma B-type natriuretic peptide levels, decreased urinary albumin excretion and increased creatinine clearance in CHF rats. Nitric oxide synthase activity, eNOS expression and neuronal (n) NOS expression were significantly decreased in the left ventricle and kidney of CHF rats. Exercise training significantly increased NOS activity and eNOS and nNOS expression. Upregulation of NOS in the kidney and left ventricle may contribute, in part, to the renal and cardiac protective effects of exercise training in cardiorenal syndrome in CHF rats.

Primary care physicians' own exercise habits influence exercise counseling for patients with chronic kidney disease: a cross-sectional study

BACKGROUND

The appropriate exercise counseling for chronic kidney disease (CKD) patients is crucial to improve their prognosis. There have been few studies about exercise counseling by primary care physicians for CKD patients. We investigated primary care physicians' exercise counseling practices for CKD patients, and the association of these physicians' own exercise habits with exercise counseling.

METHODS

The population of this cross-sectional study was 3310 medical doctors who graduated from Jichi Medical University from 1978 to 2012. The study instrument was a self-administered questionnaire that was mailed in August 2012 to investigate their age class, specialty, workplace, exercise habits, and practices of exercise counseling for CKD.

RESULTS

581 (64.8%) medical doctors practiced the management of CKD among a total of 933 responses. These 581 medical doctors were defined as CKD primary care physicians and their answers were analyzed. CKD primary care physicians' own exercise habits (frequencies and intensities) were as follows: frequencies: daily, 71 (12.1%); ≥ 2-3 times/week, 154 (26.5%); ≥ 1 time/week, 146 (25.1%); and ≤ 1 time/month, 176 (30.2%); intensities: high (≥ 6 Mets), 175 (30.1%); moderate (4-6 Mets), 132 (22.7%); mild (3-4 Mets), 188 (32.3%); very mild (<3 Mets), 47 (8.1%); and none, 37 (6.4%). The CKD primary care physicians' exercise recommendation levels for CKD patients were as follows: high, 31 (5.3%); moderate, 176 (29.7%); low, 256 (44.0%); and none, 92 (15.8%). The CKD primary care physicians' exercise recommendations for CKD patients were significantly related to their own exercise frequency (p < 0.001), but they were not related to their age, specialty, workplace, or exercise intensity.

CONCLUSIONS

CKD primary care physicians' exercise recommendation level for CKD patients was limited. In addition, CKD primary care physicians' own exercise habits influenced the exercise counseling for CKD patients. The establishment of guidelines for exercise by CKD patients and their dissemination among primary care physicians are needed.(University Hospital Medical Information Network Clinical Trial Registry. number, UMIN000011803. Registration date, Sep/19/2013).

Angiotensin Type-1 Receptor Blockade May Not Protect Kidney against Cisplatin-Induced Nephrotoxicity in Rats

Background. Cisplatin (CDDP) is an anticancer drug, which is accompanied with major side effects including nephrotoxicity. We tested two doses of losartan (10 and 20 mg/kg/day) against nephrotoxicity in a rat model treated with daily administration of CDDP (2.5 mg/kg/day). Methods. Five groups of rats were examined. Groups 1 and 2 received losartan 10 and 20 mg/kg/day, i.p, for a period of 10 days. Group 3 received saline for 10 days, but from day 3 the animals received CDDP (2.5 mg/kg/day, i.p) for the next seven days. Groups 4 and 5 received treatment regimen the same as groups 1 and 2, but from day 3 they also received CDDP for the next seven days. At the end of the experiment, blood samples were obtained and the kidneys were removed to undergo pathological investigation and to obtain supernatant from homogenized tissue. Results. CDDP induced nephrotoxicity, but the serum levels of creatinine and blood urea nitrogen were not attenuated by losartan. The pathological findings confirmed that losartan did not have nephroprotective effect in this experimental model. Conclusion. According to the findings, losartan could not improve renal function impaired by toxicity induced by continuous doses of CDDP, and also it worsened the renal failure.

Exercise attenuates renal dysfunction with preservation of myocardial function in chronic kidney disease

Previous studies have suggested that exercise improves renal and cardiac functions in patients with chronic kidney disease. The aim of this study was to evaluate the effects of long-term aerobic swimming exercise with overload on renal and cardiac function in rats with 5/6 nefrectomy (5/6Nx). Eight Wistar rats were placed into 4 groups: Control (C), Control+Exercise (E), Sedentary 5/6Nx (NxS) and 5/6Nx+Exercise (NxE). The rats were subjected to swimming exercise sessions with overload for 30 min five days per week for five weeks. Exercise reduced the effect of 5/6Nx on creatinine clearance compared to the NxS group. In addition, exercise minimized the increase in mean proteinuria compared to the NxS group (96.9±10.0 vs. 51.4±9.9 mg/24 h; p<0.05). Blood pressure was higher in the NxS and NxE groups compared to the C and E groups (216±4 and 178±3 vs. 123±2 and 124±2 mm Hg, p<0.05). In the 200 glomeruli that were evaluated, the NxS group had a higher sclerosis index than did the NxE group (16% vs. 2%, p<0.05). Echocardiography demonstrated a higher anterior wall of the left ventricle (LV) in diastole in the NxS group compared with the C, E and NxE groups. The NxS group also had a higher LV posterior wall in diastole and systole compared with the E group. The developed isometric tension in Lmax of the heart papillary muscle was lower in the NxS group compared with the C, E and NxE groups. These results suggested that exercise in 5/6Nx animals might reduce the progression of renal disease and lessen the cardiovascular impact of a reduction in renal mass.

Exercise training in chronic kidney disease patients

Chronic kidney disease (CKD) is a major public health problem that affects an estimated 1.7 million Australians. Patients with CKD commonly progress to end-stage kidney disease (ESKD) requiring dialysis and/or kidney transplantation. They are at high risk of cardiovascular disease and many die from this prior to reaching ESKD. Few therapies are available to slow CKD progression and reduce cardiovascular morbidity and mortality. The benefit of exercise training has been well demonstrated in a range of disease conditions including ESKD and was recently highlighted by a systematic review in haemodialysis patients and a recent Cochrane review of all stages of CKD. However, the effects of exercise training in patients with CKD have not been extensively investigated. Our systematic search of the literature found only ten clinical trials in this area. The aim of this review is to review these studies, and to discuss the findings, safety considerations and suggest future areas of research. Overall, the majority of the studies are small, non-randomized, non-controlled trials. They have found that exercise training can increase exercise capacity, improve muscle strength and function, decrease blood pressure, and improve inflammation and oxidative stress biomarkers. The effects of exercise training on kidney function, cardiovascular disease and quality of life are unknown. Studies are needed to answer these questions and develop evidence-based exercise training guidelines for individuals with CKD.

Association of sitting time and physical activity with CKD: a cross-sectional study in family practices

BACKGROUND

Chronic kidney disease (CKD) represents a significant and growing health care burden globally. Lifestyle factors, such as physical activity and sitting-related sedentary behavior, have been hypothesized to be directly associated with CKD; however, epidemiologic research is limited.

STUDY DESIGN

Cross-sectional analysis.

SETTING & PARTICIPANTS

A population-level diabetes screening program conducted across 20 family practices in Leicester, United Kingdom, August 2004 to December 2007.

PREDICTORS

Self-reported sitting time and physical activity, obtained using the International Physical Activity Questionnaire.

OUTCOMES & MEASUREMENTS

CKD, defined using NKF-KDOQI (National Kidney Foundation's Kidney Disease Outcomes Quality Initiative) criteria.

RESULTS

6,379 (52% women) individuals were included. Lower levels of sitting time were associated with lower risk of CKD after controlling for physical activity, body mass index, and other potential confounding variables (OR, 0.74 [95% CI, 0.62-0.92] for lowest vs highest tertile). Interaction analysis showed that women trended toward a significantly higher risk of CKD with higher levels of sitting time compared with men. Participating in levels of physical activity that were at least consistent with the minimum recommendations for health was associated with lower risk of CKD. A significant interaction with sex was observed, with men showing a lower risk of CKD with high levels of physical activity compared with women.

LIMITATIONS

Cross-sectional design, self-reported lifestyle data, CKD defined at a single time, and estimated glomerular filtration rate and microalbuminuria were the only measures used to define CKD.

CONCLUSIONS

This study suggests that higher levels of physical activity and lower levels of sitting time are associated with a lower prevalence of CKD independently of each other and other risk factors. However, results may vary by sex, with sitting time being the more important factor in women and physical activity the more important factor in men. These results have important implications for future research.

Exercise in individuals with CKD

There are few studies evaluating exercise in the nondialysis chronic kidney disease (CKD) population. This review covers the rationale for exercise in patients with CKD not requiring dialysis and the effects of exercise training on physical functioning, progression of kidney disease, and cardiovascular risk factors. In addition, we address the issue of the risk of exercise and make recommendations for implementation of exercise in this population. Evidence from uncontrolled studies and small randomized controlled trials shows that exercise training results in improved physical performance and functioning in patients with CKD. In addition, although there are no studies examining cardiovascular outcomes, several studies suggest that cardiovascular risk factors such as hypertension, inflammation, and oxidative stress may be improved with exercise training in this population. Although the current literature does not allow for definitive conclusions about whether exercise training slows the progression of kidney disease, no study has reported worsening of kidney function as a result of exercise training. In the absence of guidelines specific to the CKD population, recent guidelines developed for older individuals and patients with chronic disease should be applied to the CKD population. In sum, exercise appears to be safe in this patient population if begun at moderate intensity and increased gradually. The evidence suggests that the risk of remaining inactive is higher. Patients should be advised to increase their physical activity when possible and be referred to physical therapy or cardiac rehabilitation programs when appropriate.

Physical inactivity and chronic kidney disease in Australian adults: the AusDiab study

BACKGROUND AND AIMS

Physical inactivity is associated with cardiovascular risk however its relationship to chronic kidney disease is largely unknown. We examined the association between leisure-time physical activity and risk of chronic kidney disease in a prospective, population-based cohort of Australians aged ≥ 25 years (AusDiab).

METHODS AND RESULTS

The baseline sample included 10,966 adults (4951 males and 6015 females). From this sample, 6318 participants with complete baseline and 5-year follow-up urinalysis and serum creatinine measurements formed the study population for longitudinal analysis. Self-reported leisure-time physical activity was measured using a validated, interviewer-administered questionnaire. Compared with sufficiently active individuals (≥ 150 min physical activity per week), those who were inactive (0 min/week) were more likely to have albuminuria at baseline (multivariate-adjusted OR=1.34, 95% CI 1.10-1.63). Inactivity (versus sufficient physical activity) was associated with increased age- and sex-adjusted odds of an estimated glomerular filtration rate <3rd percentile (OR=1.30, 95% CI 1.02-1.65), although this was not significant after multivariate adjustment (OR=1.17, 95% CI 0.91-1.50). Obese, inactive individuals were significantly more likely to have albuminuria at baseline (multivariate-adjusted OR=1.74, 95% CI 1.35-2.25), compared with sufficiently active, non-obese individuals. Baseline physical activity status was not significantly associated with longitudinal outcomes.

CONCLUSIONS

Physical inactivity is cross-sectionally associated with albuminuria prevalence, particularly when combined with obesity. Future studies are needed to determine whether this association is causal and the importance of physical activity in CKD prevention.

Exercise therapy correlates with improving renal function through modifying lipid metabolism in patients with cardiovascular disease and chronic kidney disease

BACKGROUND

Patients with cardiovascular disease (CVD) and chronic kidney disease (CKD) are at high risk of cardiovascular mortality, thus therapies to improve renal function should be clinically investigated.

METHODS AND RESULTS

We divided consecutive patients with CVD and CKD (n=19) into exercise (n=10) and non-exercise (n=9) therapy groups. Exercise therapy for 12 weeks significantly improved the anaerobic metabolic threshold (AT-V O₂) and high-density lipoprotein cholesterol (HDL-C) levels, and reduced triglyceride levels. Exercise therapy also improved estimated glomerular filtration rate (eGFR). Change in eGFR correlated significantly and positively with change in AT-V O₂ and HDL-C, and negatively with change in triglyceride levels.

CONCLUSIONS

Exercise therapy correlates with improving renal function in CVD patients with CKD through modifying lipid metabolism. Exercise therapy could be an effective clinical strategy to improve renal function.

Combination of chronic exercise and antihypertensive therapy enhances renoprotective effects in rats with renal ablation

BACKGROUND

We assessed the renal protective effects of treatment with moderate exercise (EX), with EX plus olmesartan (OLS), with EX plus azelnidipine (AZN), and with the three together in a rat model of chronic renal failure (CRF).

METHODS

Male 5/6-nephrectomized Wistar Kyoto (WKY) rats were divided into six groups according to the following treatments for: (i) no EX (C); (ii) moderate EX with treadmill running (20 m/min for 60 min/day, 5 days/week) (EX); (iii) EX+OLS (10 mg/kg/day); (iv) EX+AZN (3 mg/kg/day); (v) EX+OLS (5 mg/kg/day)+AZN (1.5 mg/kg/day); and (vi) sham operation (S). The rats were then treated for 12 weeks.

RESULTS

EX, EX+OLS, EX+AZN, and EX+OLS+AZN showed decreases in the serum creatinine (Scr), an index of glomerular sclerosis (IGS), the relative interstitial volume of the renal cortex (RIV), the number of ED-1 (monoclonal antibody) positive cells (ED1(+)) and the glomerular expression score of alpha-smooth muscle actin (alpha-SMA(+)). EX+OLS, EX+AZN, and EX+OLS+AZN blocked the development of hypertension, increased the number of Wilms' tumor-1 (WT-1) positive cells (WT1(+)); EX+OLS and EX+OLS+AZN blunted the increases in proteinuria. In particular, blood urea nitrogen (BUN), ED1(+), alpha-SMA(+), WT1(+), IGS, and RIV in the EX+OLS+AZN were the lowest among all the nephrectomized groups.

CONCLUSIONS

In the results, simultaneous treatment of EX, OLS, and AZN showed renal protective effects in this rat model suggesting that the treatment may affect the macrophage infiltration to the glomerulus, the fibroblast accumulation in the glomerulus, the mesangial activation, and the podocyte differentiation.

Obesity, Smoking, and Physical Inactivity as Risk Factors for CKD: Are Men More Vulnerable?

BACKGROUND

The incidence of end-stage renal disease is especially high in men, and some studies indicated that smoking is a risk factor for men only. We investigated associations between obesity, smoking, and physical inactivity and chronic kidney disease (CKD) in the general population and whether risk for CKD was restricted to men.

METHODS

This was a cross-sectional health survey of the entire adult population of Nord-Trondelag County, Norway, 1995 to 1997, with a 70.6% participation rate. Glomerular filtration rate (GFR) was estimated in all subjects 20 years and older from calibrated serum creatinine levels by using the simplified Modification of Diet in Renal Disease Study formula, and CKD cases are defined as those with a GFR less than 45 mL/min/1.73 m2 (< 0.75 mL/s).

RESULTS

A total of 30,485 men and 34,708 women were included, and prevalences of GFR less than 45 mL/min/1.73 m2 (< 0.75 mL/s) were 0.8% and 1.1%, respectively. Age- and sex-adjusted logistic regression analyses showed dose-response relations for body mass index, smoking history, and physical activity. Relative risks were 1.77 (95% confidence interval [CI], 1.47 to 2.14) for obesity (body mass index > or = 30 kg/m2), 1.52 (95% CI, 1.13 to 2.06) for smoking (> 25 pack-years), and 2.14 (95% CI, 1.39 to 3.30) for physical inactivity (no or some physical activity in leisure time). For subjects with all these risk factors, relative risk was 5.10 (95% CI, 2.36 to 11.01). These results remained significant after adjusting for other known risk factors. No biological interactions between sex and obesity, smoking, or physical activity were found.

CONCLUSION

Obesity, smoking, and physical inactivity were associated significantly with CKD. Men were not more susceptible to these risk factors than women.

Voluntary Exercise during Chronic Renal Failure in Rats

PURPOSE

Chronic renal failure (CRF) patients often experience a significant degradation in quality of life that is associated with decreased physical fitness. Previous animal studies have used forced running or swimming as modalities to investigate the interactions between exercise and CRF. These modalities generally include stress responses unrelated to the exercise itself. The purpose of the current work was to determine whether, and to what extent, rats experiencing the onset of CRF would participate in voluntary wheel running exercise. An additional objective was to examine physiological parameters related to skeletal muscle and cardiovascular adaptation in the context of CRF and exercise.

METHODS

Groups of rats were assigned to sham-operated or 5/6 nephrectomy groups, and further divided into running or nonrunning subgroups. Blood, heart, and muscle tissues were collected 30 d after the exercise groups were returned to running wheel-equipped cages.

RESULTS

The results demonstrated that rats experiencing the early stages of CRF will voluntarily exercise to the same extent as sham-operated animals (e.g., sham, 7.2+/-0.8 vs CRF, 6.8+/-0.7 km.d). CRF resulted in increased systolic blood pressure that was not normalized by exercise. CRF induced a decrease in hemoglobin concentration that was prevented by exercise. Voluntary running resulted in an apparently nonpathological left ventricular hypertrophy in both the sham-operated and CRF rats. In locomotor skeletal muscles, CRF resulted in a 31% decrease in citrate synthase activity that was completely blunted by voluntary running activity.

CONCLUSION

Rats experiencing the onset of CRF will run voluntarily. This exercise appears to provide some potentially palliative effects on the skeletal muscle and cardiovascular responses to CRF.

Mediation of beta-endorphin in exercise-induced improvement in insulin resistance in obese Zucker rats

BACKGROUND

Aerobic exercise including treadmill running has long been used to successfully treat and/or prevent insulin resistance and type-2 diabetes. Increase of plasma beta-endorphin is observed with exercise. The present study was designed to clarify the role of endogenous beta-endorphin in exercise-induced improvement in insulin resistance.

METHODS

We used a moderate exercise program consisting of treadmill running at 20 m/min and 0% grade for 1 h/day, 7 days/week, for 8 weeks. Plasma glucose concentration was assessed by the glucose oxidase method. The enzyme-linked immunosorbent assay was performed to quantify the plasma level of beta-endorphin-like immunoreactivity (BER). The glucose disposal rate (GDR) was measured by the hyperinsulinemic euglycemic clamp technique. Changes of the insulin signaling in isolated soleus muscle were then detected by immunoprecipitation and immunoblotting.

RESULTS

An increase of plasma BER in parallel with the reduction of plasma glucose was obtained in exercise-trained obese Zucker rats. Different from a marked reduction in sedentary obese rats, the value of insulin-stimulated GDR obtained from the exercised obese rats was reversed to near that of the sedentary lean group, eight weeks after the last period of exercise. This effect of exercise was inhibited by naloxone or naloxonazine at doses sufficient to block opioid micro-receptors. Signaling-related defects in the soleus muscle of sedentary obese Zucker rats, which impaired glucose transporter subtype 4 (GLUT 4), included decreased phosphorylation of insulin receptor substrate (IRS)-1, as well as an attenuated p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3 kinase) and Akt serine phosphorylation. In contrast, exercise training failed to modify the levels of insulin receptor (IR), IRS-1, and IR tyrosine autophosphorylation in obese Zucker rats.

CONCLUSION

Enhanced insulin sensitivity via exercise training might be mediated by endogenous beta-endorphin through an increase of postreceptor insulin signaling related to the IRS-1-associated PI3-kinase step that leads to the enhancement of GLUT 4 translocation and improved glucose disposal in obese Zucker rats.

Effect of high-salt diet or chronic captopril treatment on exercise capacity in normotensive rats

1. We investigated whether chronic suppression of the renin-angiotensin system, which is known to be associated with reductions in microvascular density and vasodilator responsiveness of skeletal muscle, could affect exercise capacity in normotensive rats. 2. Rats were placed on normal rat chow, normal rat chow with captopril (100 mg/kg per day) or a high-salt diet (HS; 4%) for 4 weeks. Following these interventions, rats with indwelling carotid artery catheters were submitted to stepwise increasing exercise on a motor treadmill at a speed of 10, 20 and 30 m/min for 4 min while blood lactate was measured. 3. Blood lactate after exercise at a speed of 20 m/min was significantly higher and the duration during which rats were able to run at a speed of 30 m/min was significantly shorter in captopril-treated rats and rats fed an HS diet compared with control rats. 4. We conclude that chronic treatment with captopril or HS diet could reduce the exercise capacity in inactive normotensive rats, probably through chronic inhibition of the renin-angiotensin system.

INCREASE OF ANTI-OXIDATION BY EXERCISE IN THE LIVER OF OBESE ZUCKER RATS

1. The effects of endurance training on the anti-oxidant status in diabetes were studied using obese Zucker rats. 2. We used a moderate exercise programme consisting of treadmill running at 20 m/min and 0% incline for 1 h/day, 7 days/week, for 8 weeks. At the end of the experimental period, changes in hepatic anti-oxidant enzymes in terms of protein content and mRNA levels were detected using western blotting analysis and northern blotting analysis, respectively. In addition, anti-oxidant enzyme activity was determined. 2. A significant reduction in mRNA levels and the protein content of hepatic Mn-superoxide dismutase (SOD) and glutathione peroxidase (GPx) were observed in non-exercise obese groups, but the mRNA and protein levels of these enzymes were markedly increased after exercise training. In addition, exercise training reversed the decreased enzyme activities of Mn-SOD and GPx in obese Zucker rats. 3. The diabetes-related lowering of the glutathione (GSH) concentration was elevated in exercised obese Zucker rats, indicating a marked effect of regular moderate exercise on the endogenous anti-oxidant system. 4. There were no marked changes in hepatic Cu/Zn-SOD in terms of mRNA levels, protein content and activity in sedentary obese Zucker rats compared with their lean littermates. Endurance training did not modify the gene expression and activity of hepatic Cu/Zn-SOD. 5. The results of the present study suggest that regular moderate exercise could improve the anti-oxidant defence function of Mn-SOD, GPx and GSH in obese Zucker rats.

Down-regulation of hepatic CYP3A in chronic renal insufficiency

PURPOSE

The objective of this study was to investigate the mechanisms underlying the decrease in hepatic clearance of some drugs metabolized by CYP450 enzymes in chronic renal insufficiency (CRI).

METHODS

CRI was induced in male Sprague-Dawley rats (n = 7) by the remnant kidney model (RKM); control animals (C) (n = 12) underwent sham surgery, of which n = 6 rats were pair-fed (CPF) with CRI rats and others (n = 6) had free access to food. Serum creatinine (Scr) and urea nitrogen (SUN) were monitored every 2 weeks. On day 36, livers were isolated, and microsomes were prepared. Catalytic activities were measured through O-demethylation (CYP2D) and N-demethylation of dextromethorphan (CYP3A) and O-deethylation of 7-ethoxyresorufin (CYP1A2). CYP450 protein and mRNA levels were also measured.

RESULTS

Compared with CPF, Scr and SUN levels in CRI rats were increased twofold (p < 0.01) and 2.5-fold (p < 0.01), respectively. No effect on CYP1A2 and CYP2D activities, mRNA, or protein levels was observed between the groups. There was a reduction (41.8 +/- 20%, p < 0.01) in CYP3A activity, mRNA (p < 0.05), and protein levels (p < 0.05) in CRI rats compared to CPF.

CONCLUSIONS

CRI induced by RKM does not have an effect on hepatic CYP1A2 and CYP2D enzymes but does reduce CYP3A activity, probably through down-regulation of CYP3A2.

Effects of losartan combined with exercise training in spontaneously hypertensive rats

We investigate whether combined treatment with losartan, an angiotensin II receptor blocker, and exercise training (ET) in spontaneously hypertensive rats (SHR) would have an additive effect in reducing hypertension and improving baroreflex sensitivity when compared with losartan alone. Male SHR (8 weeks old) were assigned to 3 groups: sedentary placebo (SP, N = 16), sedentary under losartan treatment (SL, N = 11; 10 mg kg-1 day-1, by gavage), and ET under losartan treatment (TL, N = 10). ET was performed on a treadmill 5 days/week for 60 min at 50% of peak VO2, for 18 weeks. Blood pressure (BP) was measured with a catheter inserted into the carotid artery, and cardiac output with a microprobe placed around the ascending aorta. The baroreflex control of heart rate was assessed by administering increasing doses of phenylephrine and sodium nitroprusside (iv). Losartan significantly reduced mean BP (178 16 vs 132 12 mmHg) and left ventricular hypertrophy (2.9 0.4 vs 2.5 0.2 mg/g), and significantly increased baroreflex bradycardia and tachycardia sensitivity (1.0 0.3 vs 1.7 0.5 and 2.0 0.7 vs 3.2 1.7 bpm/mmHg, respectively) in SL compared with SP. However, losartan combined with ET had no additional effect on BP, baroreflex sensitivity or left ventricular hypertrophy when compared with losartan alone. In conclusion, losartan attenuates hypertension and improves baroreflex sensitivity in SHR. However, ET has no synergistic effect on BP in established hypertension when combined with losartan, at least at the dosage used in this investigation.

Effects of a therapy with losartan and quinaprilat on the progression of chronic renal failure in rats after a single dose of uranyl nitrate or 5/6 nephrectomy

The renoprotective effect of losartan and quinaprilat was tested in two different animal models of renal failure [female Wistar rats, single administration of 0.5 mg uranyl nitrate (UN)/100 g body wt. or 5/6 nephrectomy (5/6NX)]. Losartan (1 mg/100 g body weight [wt.]) and quinaprilat (1 mg/100 g body wt.) were administered intraperitoneally, once daily, starting 10 days after UN and one week after 5/6NX till the end of 10 weeks experimental period. Parameters characterizing the therapeutic effect were blood pressure, urinary protein excretion 4 and 10 weeks after the injury, and p-aminohippurate accumulation in renal cortical slices in vitro, hydroxy-proline concentration in renal tissue and morphology at the end of the experiment. Summarizing our results we state: (1) the angiotensin 1 receptor blocker losartan is more effective in UN-treated than in 5/6 NX rats, and (2) the angiotensin converting enzyme inhibitor quinaprilat is more effective than losartan because of the amelioration of blood pressure and OH-proline concentration in renal tissue of UN-treated rats.

Effects of Exercise Training on Glomerular Structure in Fructose-Fed Spontaneously Hypertensive Rats

A high-fructose diet (HFD) has been shown to elevate blood pressure (BP) and to decrease insulin sensitivity in rats. Although running exercise can attenuate these phenomena, its effect on target organ protection is not clear. We investigated whether exercise training has renal protective effects in this model. Nine-week-old spontaneously hypertensive rats were allocated to groups that received HFD or a control diet (control group) for 15 weeks. At the age of 10 weeks, fructose-fed rats were allocated to groups that were given vehicle (FRU group), temocapril, an angiotensin converting enzyme inhibitor (TEM group), exercise training (EX group; treadmill running), or temocapril plus exercise training (TEM+EX group). BP was higher in the FRU group than in the control group. Exercise training tended to decrease BP and temocapril treatment decreased BP significantly. Proteinuria was similar in the five groups. Plasma leptin concentration and epididymal fat weight were lower in the EX and TEM+EX groups than in the FRU group. In the soleus muscle of the FRU group, the composite ratio of type I fiber was decreased and that of type IIa fiber was increased compared with those in the control group. Both temocapril and exercise training restored these ratios. The glomerular sclerosis index (GSI) was higher in the FRU group than in the control group. GSI was decreased equally in the TEM, EX, and TEM+EX groups and was positively correlated with plasma leptin concentration. The results suggest that exercise training ameliorates glomerular sclerosis through mechanisms other than a reduction in BP.