Jaume F. Lalanza

Neurophysiological and epigenetic effects of physical exercise on the aging process.

Aging is a gradual process during which molecular and cellular processes deteriorate progressively, often leading to such pathological conditions as vascular and metabolic disorders and cognitive decline. Although the mechanisms of aging are not yet fully understood, inflammation, oxidative damage, mitochondrial dysfunction, functional alterations in specific neuronal circuits and a restricted degree of apoptosis are involved. Physical exercise improves the efficiency of the capillary system and increases the oxygen supply to the brain, thus enhancing metabolic activity and oxygen intake in neurons, and increases neurotrophin levels and resistance to stress. Regular exercise and an active lifestyle during adulthood have been associated with reduced risk and protective effects for mild cognitive impairment and Alzheimers disease. Similarly, studies in animal models show that physical activity has positive physiological and cognitive effects that correlate with changes in transcriptional profiles. According to numerous studies, epigenetic events that include changes in DNA methylation patterns, histone modification and alterations in microRNA profiles seem to be a signature of aging. Hence, insight into the epigenetic mechanisms involved in the aging process and their modulation through lifestyle interventions such as physical exercise might open new avenues for the development of preventive and therapeutic strategies to treat aging-related diseases.

Long-term treadmill exercise induces neuroprotective molecular changes in rat brain.

Exercise enhances general health. However, its effects on neurodegeneration are controversial, and the molecular pathways in the brain involved in this enhancement are poorly understood. Here, we examined the effect of long-term moderate treadmill training on adult male rat cortex and hippocampus to identify the cellular mechanisms behind the effects of exercise. We compared three animal groups: exercised (30 min/day, 12 m/min, 5 days/wk, 36 wk), handled but nonexercised (treadmill handling procedure, 0 m/min), and sedentary (nonhandled and nonexercised). Moderate long-term exercise induced an increase in IGF-1 levels and also in energy parameters, such as PGC-1α and the OXPHOS system. Moreover, the sirtuin 1 pathway was activated in both the exercised and nonexercised groups but not in sedentary rats. This induction could be a consequence of exercise as well as the handling procedure. To determine whether the long-term moderate treadmill training had neuroprotective effects, we studied tau hyperphosphorylation and GSK3β activation. Our results showed reduced levels of phospho-tau and GSK3β activation mainly in the hippocampus of the exercised animals. In conclusion, in our rodent model, exercise improved several major brain parameters, especially in the hippocampus. These improvements induced the upregulation of sirtuin 1, a protein that extends life, the stimulation of mitochondrial biogenesis, the activation of AMPK, and the prevention of signs of neurodegeneration. These findings are consistent with other reports showing that physical exercise has positive effects on hormesis.

Epigenetic alterations in hippocampus of SAMP8 senescent mice and modulation by voluntary physical exercise.

The senescence-accelerated SAMP8 mouse model displays features of cognitive decline and Alzheimers disease. With the purpose of identifying potential epigenetic markers involved in aging and neurodegeneration, here we analyzed the expression of 84 mature miRNAs, the expression of histone-acetylation regulatory genes and the global histone acetylation in the hippocampus of 8-month-old SAMP8 mice, using SAMR1 mice as control. We also examined the modulation of these parameters by 8 weeks of voluntary exercise. Twenty-one miRNAs were differentially expressed between sedentary SAMP8 and SAMR1 mice and seven miRNAs were responsive to exercise in both strains. SAMP8 mice showed alterations in genes involved in protein acetylation homeostasis such as Sirt1 and Hdac6 and modulation of Hdac3 and Hdac5 gene expression by exercise. Global histone H3 acetylation levels were reduced in SAMP8 compared with SAMR1 mice and reached control levels in response to exercise. In sum, data presented here provide new candidate epigenetic markers for aging and neurodegeneration and suggest that exercise training may prevent or delay some epigenetic alterations associated with accelerated aging.

Long-term physical exercise induces changes in sirtuin 1 pathway and oxidative parameters in adult rat tissues

The protein deacetylase, sirtuin 1, is suggested as a master regulator of exercise-induced beneficial effects. Sirtuin 1 modulates mitochondrial biogenesis, primarily via its ability to deacetylate and activate proliferator-activated receptor-γ coactivator-1α (PGC-1α), interacting with AMPK kinase. Redox cell status can also influence this regulatory axis and together they form an important convergence point in hormesis during the aging process. Here, we tested whether treadmill training (36weeks), as a paradigm of long-term moderate exercise, modifies the AMPK-sirtuin 1-PGC-1α axis and redox balance in rat gastrocnemius muscle, liver and heart. Physical activity induced increases in sirtuin 1 protein levels in all the aged rat tissues studied, as well as total PGC-1α levels. However, no changes in AMPK activation or significant differences in mitochondrial biogenesis (by measuring electron transport chain protein content) were found after exercise training. Parallel to these changes, we observed an improvement of oxidative stress defenses, mainly in muscle, with modification of the antioxidant enzyme machinery resulting in a reduction in lipid peroxidation and protein carbonylation. Thus, we demonstrate that moderate long-term exercise promotes tissue adaptations, increasing muscle, liver and heart sirtuin 1 protein content and activity and increasing PGC-1α protein expression. However, AMPK activation or mitochondrial biogenesis is not modified, but it cannot be discarded that its participation in the adaptive mechanism which prevents the development of the deleterious effects of age.

Effects of a post-weaning cafeteria diet in young rats: metabolic syndrome, reduced activity and low anxiety-like behaviour.

Among adolescents, overweight, obesity and metabolic syndrome are rapidly increasing in recent years as a consequence of unhealthy palatable diets. Animal models of diet-induced obesity have been developed, but little is known about the behavioural patterns produced by the consumption of such diets. The aim of the present study was to determine the behavioural and biochemical effects of a cafeteria diet fed to juvenile male and female rats, as well as to evaluate the possible recovery from these effects by administering standard feeding during the last week of the study. Two groups of male and female rats were fed with either a standard chow diet (ST) or a cafeteria (CAF) diet from weaning and for 8 weeks. A third group of males (CAF withdrawal) was fed with the CAF diet for 7 weeks and the ST in the 8th week. Both males and females developed metabolic syndrome as a consequence of the CAF feeding, showing overweight, higher adiposity and liver weight, increased plasma levels of glucose, insulin and triglycerides, as well as insulin resistance, in comparison with their respective controls. The CAF diet reduced motor activity in all behavioural tests, enhanced exploration, reduced anxiety-like behaviour and increased social interaction; this last effect was more pronounced in females than in males. When compared to animals only fed with a CAF diet, CAF withdrawal increased anxiety in the open field, slightly decreased body weight, and completely recovered the liver weight, insulin sensitivity and the standard levels of glucose, insulin and triglycerides in plasma. In conclusion, a CAF diet fed to young animals for 8 weeks induced obesity and metabolic syndrome, and produced robust behavioural changes in young adult rats, whereas CAF withdrawal in the last week modestly increased anxiety, reversed the metabolic alterations and partially reduced overweight.

Long-Term Exercise Modulates Hippocampal Gene Expression in Senescent Female Mice

The senescence-accelerated SAMP8 mouse is considered a useful non-transgenic model for studying aspects of progressive cognitive decline and Alzheimers disease (AD). Using SAMR1 mice as controls, here we explored the effects of 6 months of voluntary wheel running in 10-month-old female SAMP8 mice. Exercise in SAMP8 mice improved phenotypic features associated with premature aging (i.e., skin color and body tremor) and enhanced vascularization and BDNF gene expression in the hippocampus compared with controls. With the aim of identifying genes involved in brain aging responsive to long-term exercise, we performed whole genome microarray studies in hippocampus from sedentary SAMP8 (P8sed), SAMR1 (R1sed), and exercised SAMP8 (P8run) mice. The genes differentially expressed in P8sed versus R1sed were considered as putative aging markers (i) and those differentially expressed in P8run versus P8sed were considered as genes modulated by exercise (ii). Genes differentially expressed in both comparisons (i and ii) were considered as putative aging genes responsive to physical exercise. We identified 34 genes which met both criteria. Gene ontology analysis revealed that they are mainly involved in functions related to extracellular matrix maintenance. Selected genes were validated by real-time quantitative PCR assays, i.e., collagen type 1 alpha 1 (col1a1), collagen type 1 alpha 2 (col1a2), fibromodulin (fmod), prostaglandin D(2) synthase (ptgds), and aldehyde dehydrogenase (Aldh1a2). As a whole, our study suggests that exercise training during adulthood may prevent or delay gene expression alterations and processes associated with hippocampal aging in at-risk subjects.

Wnt pathway regulation by long-term moderate exercise in rat hippocampus.

An active lifestyle involving regular exercise reduces the deleterious effects of the aging process. At the cerebral level, both synaptic plasticity and neurogenesis are modulated by exercise, although the molecular mechanisms underlying these effects are not clearly understood. In the mature nervous system, the canonical Wnt (Wnt/β-catenin) signaling pathway is implicated in neuroprotection and synaptic plasticity. Here, we examined whether the Wnt pathway could be modulated in adult male rat hippocampus by long-term moderate exercise (treadmill running) or enrichment (handling/environmental stimulation). Sedentary animals showed higher protein levels of the Wnt antagonist, Dkk-1, the lowest levels being found in the exercised group. Although there was no evidence of any changes in activation of the LRP6 receptor, the total levels of LRP6 were higher in exercised and enriched animals. Analysis of some of the components implicated in the phosphorylation of β-catenin, which leads ultimately to its proteasomal degradation, revealed higher levels and activation of Axin1 and GSK-3α/β respectively in sedentary animals. However neither different phosphorylated forms nor total β-catenin protein levels differed between the experimental groups. Higher protein levels of Axin2 and the antiapoptotic protein, Bcl-2, were found with exercise and handling, whereas the proapototic, Bax, was unaffected. Thus, our results suggest activation of the Wnt pathway not only with moderate exercise, but also with the handling of the animals.

Physiological and behavioural consequences of long-term moderate treadmill exercise

The benefits of long-term moderate exercise for health are widely accepted in humans, but few animal studies have been undertaken to characterize the effects of such activity on emotionality and responsiveness to stress. The present study describes the effects of long-term moderate forced treadmill training (36 weeks) on exploratory activity, anxiety-like behaviour, and the resting or stress levels of some physiological variables, including pituitary-adrenal (PA) hormones. Five-week-old male Sprague-Dawley rats were trained on the treadmill (TM) for 36 weeks, using a more moderate training (12m/min, 30min/day, 4-5 days/week) than that currently used in the literature. Two groups were used as controls: a non-handled sedentary (SED) group, receiving no manipulation, and a control (CON) group exposed to a stationary treadmill for the same amount of time as the TM group. In accordance with literature data, TM rats showed lower resting levels of glucose, triglycerides and cholesterol than the other two groups. The TM and CON groups both showed higher ambulation than the SED group in some behavioural tests, without evidence for altered anxiety. Resting levels of adrenocorticotropin (ACTH) and corticosterone did not differ among the groups, but a reduced ACTH response to both a novel environment (mild stressor) and an active escape-avoidance task (severe stressor) was observed in TM rats, whereas changes in corticosterone were modest. The results support the view that the physiological consequences of long-term moderate training are beneficial, including reduced PA responsiveness to stress, even though exercise training did not affect anxiety-like behaviour.

Voluntary exercise promotes beneficial anti-aging mechanisms in SAMP8 female brain.

Regular physical exercise mediates health and longevity promotion involving Sirtuin 1 (SIRT1)-regulated pathways. The anti-aging activity of SIRT1 is achieved, at least in part, by means of fine-tuning the adenosine monophosphate (AMP)-activated protein kinase (AMPK) pathway by preventing the transition of an originally pro-survival program into a pro-aging mechanism. Additionally, SIRT1 promotes mitochondrial function and reduces the production of reactive oxygen species (ROS) through regulating peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), the master controller of mitochondrial biogenesis. Here, by using senescence-accelerated mice prone 8 (SAMP8) as a model for aging, we determined the effect of wheel-running as a paradigm for long-term voluntary exercise on SIRT1-AMPK pathway and mitochondrial functionality measured by oxidative phosphorylation (OXPHOS) complex content in the hippocampus and cortex. We found differential activation of SIRT1 in both tissues and hippocampal-specific activation of AMPK. These findings correlated well with significant changes in OXPHOS in the hippocampal, but not in the cerebral cortex, area. Collectively, the results revealed greater benefits of the exercise in the wheel-running intervention in a murine model of senescence, which was directly related with mitochondrial function and which was mediated through the modulation of SIRT1 and AMPK pathways.

Long-term moderate treadmill exercise promotes stress-coping strategies in male and female rats

Recent evidence has revealed the impact of exercise in alleviating anxiety and mood disorders; however, the exercise protocol that exerts such benefit is far from known. The current study was aimed to assess the effects of long-term moderate exercise on behavioural coping strategies (active vs. passive) and Hypothalamic-Pituitary-Adrenal response in rats. Sprague-Dawley male and female rats were exposed to 32-weeks of treadmill exercise and then tested for two-way active avoidance learning (shuttle-box). Two groups were used as controls: a non-handled sedentary group, receiving no manipulation, and a control group exposed to a stationary treadmill. Female rats displayed shorter escape responses and higher number of avoidance responses, reaching criterion for performance earlier than male rats. In both sexes, exercise shortened escape latencies, increased the total number of avoidances and diminished the number of trials needed to reach criterion for performance. Those effects were greater during acquisition in female rats, but remained over the shuttle-box sessions in treadmill trained male rats. In females, exercise did not change ACTH and corticosterone levels after shuttle-box acquisition. Collectively, treadmill exercise improved active coping strategies in a sex-dependent manner. In a broader context, moderate exercise could serve as a therapeutic intervention for anxiety and mood disorders.