Physical Exercise Retards the Development of Chronic Nephropathy in the Ageing Rat as Efficiently as Food Restriction Does

Beneficial effects of time and energy restriction diets on the development of experimental acute kidney injury in Rat: Bax/Bcl-2 and histopathological evaluation

People's lifestyles and, especially, their eating habits affect their health and the functioning of the organs in their bodies, including the kidneys. One's diet influences the cells' responses to stressful conditions such as acute kidney injury (AKI). This study aims to determine the preconditioning effects of four different diets: energy restriction (ER) diet, time restriction (TR) eating, intermittent fasting (IF), and high-fat diet (HF) on histopathological indices of the kidney as well as the molecules involved in apoptosis during AKI. Adult male rats underwent ER, TR, IF, and HF diets for eight weeks. Then, AKI was induced, and renal function indices, histopathological indices, and molecules involved in apoptosis were measured. In animals with AKI, urinary albumin excretion, serum urea, creatinine and, Bax/Bcl-2 ratio increased in the kidney, while renal eGFR decreased. ER and TR diets improved renal parameters and prevented an increase in the Bax/Bcl-2 ratio. The IF diet improved renal parameters but had no effect on the Bax/Bcl-2 ratio. On the other hand, the HF diet worsened renal function and increased the Bax/Bcl-2 ratio. Histopathological examination also showed improved kidney conditions in the ER and TR groups and more damage in the HF group. This study demonstrated that ER and TR diets have renoprotective effects on AKI and possibly cause the resistance of kidney cells to damage by reducing the Bax/Bcl-2 ratio and improving apoptotic conditions.

The effect of two types of diet on apoptosis indexes, lipid profile and histopathological outcome in acute kidney injury during exercise

Background

Exercise and some pre-AKI diets have been shown to improve injury, apoptosis, and lipid profile. In this study, the effect of two different diets along with exercise training on acute kidney injury (AKI) was investigated. 

Materials and methods

Laboratory rats were randomly divided into four groups of control, standard diet + exercise, exercise + calorie restriction (CR) and exercise + time restriction (TR). Each group was divided into two subgroups of AKI and no AKI. The animals received endurance training and diet regimens before AKI. Fasting blood glucose, serum creatinine, Bcl-2-associated X protein (Bax), B-cell lymphoma 2 (Bcl2) and histopathological outcome of renal tissue as well as serum lipid profile of animals were assessed 24 h after AKI. 

Results

The percentage of changes in renal Bcl2 and Bax after AKI in the group with previous exercise was lower than the group without previous exercise (p < 0.01). After induction of AKI, serum lipid profile changed in non-exercised rats (p < 0.001). Also, after injury, fasting blood glucose levels increased in non-exercised rats (p < 0.05). After injury, the start of both CR and TR diets during exercise caused less change in Bcl2 and Bax of non-exercised rats compared to exercised rats (p < 0.001). CR diet along with exercise improved lipid profile, and also CR diet along exercise decreased fasting blood glucose levels (p < 0.001). Also, both the CR and TR diets during exercise caused fewer changes in histopathological outcome after AKI.

Conclusion

Exercise alone decreased changes in apoptotic and histopathological indexes, fasting blood glucose, as well as lipid profile of rats after AKI. Reduction of apoptosis and improvement of histopathological outcome after AKI appeared more when CR and TR diets were commenced during exercise. The reduction of lipid profile changes was more pronounced in the group that received CR diet during exercise.

Angiotensin II blockade: how its molecular targets may signal to mitochondria and slow aging. Coincidences with calorie restriction and mTOR inhibition

Caloric restriction (CR), renin angiotensin system blockade (RAS-bl), and rapamycin-mediated mechanistic target of rapamycin (mTOR) inhibition increase survival and retard aging across species. Previously, we have summarized CR and RAS-bl's converging effects, and the mitochondrial function changes associated with their physiological benefits. mTOR inhibition and enhanced sirtuin and KLOTHO signaling contribute to the benefits of CR in aging. mTORC1/mTORC2 complexes contribute to cell growth and metabolic regulation. Prolonged mTORC1 activation may lead to age-related disease progression; thus, rapamycin-mediated mTOR inhibition and CR may extend lifespan and retard aging through mTORC1 interference. Sirtuins by deacetylating histone and transcription-related proteins modulate signaling and survival pathways and mitochondrial functioning. CR regulates several mammalian sirtuins favoring their role in aging regulation. KLOTHO/fibroblast growth factor 23 (FGF23) contribute to control Ca(2+), phosphate, and vitamin D metabolism, and their dysregulation may participate in age-related disease. Here we review how mTOR inhibition extends lifespan, how KLOTHO functions as an aging suppressor, how sirtuins mediate longevity, how vitamin D loss may contribute to age-related disease, and how they relate to mitochondrial function. Also, we discuss how RAS-bl downregulates mTOR and upregulates KLOTHO, sirtuin, and vitamin D receptor expression, suggesting that at least some of RAS-bl benefits in aging are mediated through the modulation of mTOR, KLOTHO, and sirtuin expression and vitamin D signaling, paralleling CR actions in age retardation. Concluding, the available evidence endorses the idea that RAS-bl is among the interventions that may turn out to provide relief to the spreading issue of age-associated chronic disease.

Cardiac function is preserved following 4 weeks of voluntary wheel running in a rodent model of chronic kidney disease

The purpose of this investigation was to determine the effect of 4 wk of voluntary wheel running on cardiac performance in the 5/6 ablation-infarction (AI) rat model of chronic kidney disease (CKD). We hypothesized that voluntary wheel running would be effective in preserving cardiac function in AI. Male Sprague-Dawley rats were divided into three study groups: 1) sham, sedentary nondiseased control; 2) AI-SED, sedentary AI; and 3) AI-WR, wheel-running AI. Animals were maintained over a total period of 8 wk following AI and sham surgery. The 8-wk period included 4 wk of disease development followed by a 4-wk voluntary wheel-running intervention/sedentary control period. Cardiac performance was assessed using an isolated working heart preparation. Left ventricular (LV) tissue was used for biochemical tissue analysis. In addition, soleus muscle citrate synthase activity was measured. AI-WR rats performed a low volume of exercise, running an average of 13 ± 2 km, which resulted in citrate synthase activity not different from that in sham animals. Isolated AI-SED hearts demonstrated impaired cardiac performance at baseline and in response to preload/afterload manipulations. Conversely, cardiac function was preserved in AI-WR vs. sham hearts. LV nitrite + nitrate and expression of LV nitric oxide (NO) synthase isoforms 2 and 3 in AI-WR were not different from those of sham rats. In addition, LV H2O2 in AI-WR was similar to that of sham and associated with increased expression of LV superoxide-dismutase-2 and glutathione peroxidase-1/2. The findings of the current study suggest that a low-volume exercise intervention is sufficient to maintain cardiac performance in rats with CKD, potentially through a mechanism related to improved redox homeostasis and increased NO.

[Mild stress as a means to modulate aging: from fly to human?]

Hormesis is the phenomenon by which adaptive responses to low doses of otherwise harmful conditions improve the functional ability of organisms. Some mild stresses have beneficial effects on longevity, aging and resistance to strong stresses (heat or cold shocks, infection) in Drosophila flies. Studies on rodents are indeed scarce but mild stress seems to be effective in humans because, for instance, patients suffering from angina have a higher survival when confronted with a heart attack. A few studies, in less tragic situations however, suggest that mild stress could have positive effects in elderly people. Performing more experiments on the effects of mild stress in humans would help to know whether it could be used in therapy or to improve healthspan of elderly.

Twelve weeks of treadmill exercise does not alter age-dependent chronic kidney disease in the Fisher 344 male rat

The ageing kidney exhibits slowly developing chronic kidney disease (CKD) and is associated with nitric oxide (NO) deficiency and increased oxidative stress. The impact of exercise on the ageing kidney is not well understood. Here, we determined whether 12 weeks of treadmill exercise can influence age-dependent CKD in old (22-24 months) Fisher 344 (F344) male rats by comparing sedentary (SED) and exercise (EX) trained rats; young (3 months) rats were also studied. In addition to renal structure and function, we assessed protein levels of various isoforms of the NO synthases (NOS) and superoxide dismutase (SOD) enzymes as well as markers of oxidative stress, in kidney cortex and medulla. Renal function as determined by plasma creatinine, proteinuria, and glomerular structural injury worsened with age and was unaffected by exercise. Ageing also increased the protein abundance of neuronal NOSβ and p22phox while decreasing extracellular (EC) and copper/zinc (CuZn) SOD, in kidney cortex and medulla. H(2)O(2) content and nitrotyrosine abundance also increased in the kidney with age. None of these age-related changes were altered with exercise. However, exercise did increase renal cortical endothelial (e)NOS and EC SOD in young rats. Data indicate that exercise-induced increases in eNOS and EC SOD seen in young rats are lost with age. We conclude that chronic exercise is ineffective in reversing age-dependent CKD in the male F344 rat.

Angiotensin II blockade: a strategy to slow ageing by protecting mitochondria?

Protein and lipid oxidation-mainly by mitochondrial reactive oxygen species (mtROS)-was proposed as a crucial determinant of health and lifespan. Angiotensin II (Ang II) enhances ROS production by activating NAD(P)H oxidase and uncoupling endothelial nitric oxide synthase (NOS). Ang II also stimulates mtROS production, which depresses mitochondrial energy metabolism. In rodents, renin-angiotensin system blockade (RAS blockade) increases survival and prevents age-associated changes. RAS blockade reduces mtROS and enhances mitochondrial content and function. This suggests that Ang II contributes to the ageing process by prompting mitochondrial dysfunction. Since Ang II is a pleiotropic peptide, the age-protecting effects of RAS blockade are expected to involve a variety of other mechanisms. Caloric restriction (CR)-an age-retarding intervention in humans and animals-and RAS blockade display a number of converging effects, i.e. they delay the manifestations of hypertension, diabetes, nephropathy, cardiovascular disease, and cancer; increase body temperature; reduce body weight, plasma glucose, insulin, and insulin-like growth factor-1; ameliorate insulin sensitivity; lower protein, lipid, and DNA oxidation, and mitochondrial H(2)O(2) production; and increase uncoupling protein-2 and sirtuin expression. A number of these overlapping effects involve changes in mitochondrial function. In CR, peroxisome proliferator-activated receptors (PPARs) seem to contribute to age-retardation partly by regulating mitochondrial function. RAS inhibition up-regulates PPARs; therefore, it is feasible that PPAR modulation is pivotal for mitochondrial protection by RAS blockade during rodent ageing. Other potential mechanisms that may underlie RAS blockade's mitochondrial benefits are TGF-β down-regulation and up-regulation of Klotho and sirtuins. In conclusion, the available data suggest that RAS blockade deserves further research efforts to establish its role as a potential tool to mitigate the growing problem of age-associated chronic disease.

Running has a negative effect on bone metabolism and proinflammatory status in male aged rats

Animal models for male osteoporosis are scarce. This study aimed at identifying the impact of different living conditions on bone structure and metabolism as well as the inflammatory status in a rat model of age-related male osteoporosis. Bone mineral density, bone histomorphometric data, ex vivo osteoclast generation, and bone metabolism serum marker as well as intracellular cytokine expressions were evaluated in 23-month-old male Sprague-Dawley rats subjected to different housing conditions from the age of 5 months. Running rats were housed individually and were exercised voluntarily in running wheels attached to their cages. Dieting rats were housed individually, too, but were fed to pair weight with the running rats. Walking rats were exercised mildly by use of a treadmill (800m/day, 5 days a week) and social rats were kept as four in a cage and fed ad libitum. Whereas no marked differences could be found for bone mineral density, trabecular bone volume as well as trabecular bone surface were diminished in walking rats. The ex vivo osteoclast generation assay revealed no significant differences between groups. Osteoblasts of running rats were not only decreased in number, but displayed also a lower activity as indicated by decreased serum osteocalcin levels. Osteoclast activity was increased in the same group as indicated by elevated CTX (c-terminal telopeptide of type I collagen) levels. Additionally, production of tumor necrosis factor (TNF)-alpha and interferone (IFN)-gamma by CD8(+) T cells was elevated in running rats. In conclusion, running has a negative effect on bone metabolism and proinflammatory status in male aged rats.

Influence of physical exercise and food restriction on the biomechanical properties of the femur of ageing male rats

BACKGROUND

Voluntary running in wheels as well as food reduction increase the life spans of rats. Disparate parameters such as the collagen biomarker of ageing and the development of kidney pathologies are decreased by voluntary exercise. There are few reports on the influence of physical exercise and food restriction on the skeleton of male rats. Most investigations initiated rather short-term interventions in 4- to 5-week-old animals and thus studied more the influence of growth than the influence of ageing on the skeleton.

OBJECTIVE

To compare the effects of physical exercise and food restriction on the biomechanical properties of bone tissue of ageing male rats with the interventions starting at the age of 5 months with the end point at 23 months. This enables the study of the influence of these interventions on the ageing of the skeleton.

METHODS

Five groups of male Sprague-Dawley rats were used: baseline (BL), voluntarily running in wheels (RW), food restriction to attain pair weight with RW animals (PW), forced running in treadmills (TM), and sedentary controls (SE). The biomechanical properties of femoral neck, diaphysis, and distal metaphysis were measured.

RESULTS

While the body weights and fat-free mass increased from BL to SE group, the occiput-sacrum length did not increase and the length of the femur increased marginally. These lengths were slightly retarded in RW and PW groups compared to the SE group. The strength of the distal femoral metaphysis decreased from BL to SE group. This decrease was counteracted by physical exercise (RW and TM groups) as well as by food restriction (PW group). In contrast, the strength of the femoral mid-diaphysis did not differ between BL and SE groups.

CONCLUSIONS

The distal metaphysis in the male rat femur is more prone to decreasing biomechanical strength than the diaphysis during ageing. Physical exercise, when started at the age of 5 months, when the skeleton has reached its adult size, is somewhat effective in counteracting these changes. There is also some retarding effect of food restriction.

Impact of moderate physical exercise--in comparison with dietary restrictions--on age-associated decline in cell-mediated immunity of Sprague-Dawley rats

BACKGROUND AND AIMS

Moderate physical exercise and dietary restriction have both been demonstrated to delay some of the adverse effects of aging. In order to elucidate similarities or dissimilarities in their mode of action on the aging immune system in a comparative setting, we examined significant parameters of cell-mediated immunity in Sprague- Dawley rats.

METHODS

Male Sprague-Dawley rats, housed individually, were divided into four groups, living from 5 months (baseline group BL) up to 15, 19 and 23 months of age as follows: voluntary running in wheels (RW), food restricted by feeding to pair weight with RW animals (PW), forced running on treadmills (TM), and sedentary controls with ad libitum access to food (S1). White blood cell counts, capacity for lymphocyte proliferation in response to Concanavalin A, and interleukin-2 (IL-2) plasma concentrations were determined.

RESULTS

White blood cell counts and the cell numbers of lymphocytes, neutrophil and eosinophil granulocytes were significantly lower in the older RW and PW groups. We observed influences of forced exercise on lymphocyte proliferation: blastogenic reactivity was higher in TM animals compared with RW and PW animals at 23 months of age. Exclusively for RW animals, we found lower plasma concentrations of IL-2 at 23 months.

CONCLUSIONS

Our data support the idea that moderate physical exercise modulates age-associated decline in the cell-mediated immunity of old Sprague-Dawley rats significantly more than corresponding dietary restrictions.