Effects of treadmill exercise on dopaminergic transmission in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mouse model of basal ganglia injury

Effects of a low-resistance, interval bicycling intervention in Parkinson's Disease

Previous studies have shown that people with Parkinson's disease (PD) benefit from a variety of exercise modalities with respect to symptom management and function. Among the possible exercise modalities, speedwork has been identified as a promising strategy, with direct implications for the rate and amplitude of nervous system involvement. Considering that previous speed-based exercise for PD has often been equipment, personnel and/or facility dependent, and often time intensive, our purpose was to develop a population-specific exercise program that could be self-administered with equipment that is readily found in fitness centers or perhaps the home. Fourteen individuals with PD (Hoehn-Yahr (H-Y) stage of 3.0 or less) participated in twelve 30-min sessions of low-resistance interval training on a stationary recumbent bicycle. Motor examination section of the Unified Parkinson's Disease Rating Scale (UPDRS), 10-meter walk (10mW), timed-up-and-go (TUG), functional reach, four-square step test (4SST), nine-hole peg test (9HPT) and simple reaction time scores all exhibited significant improvements (p < 0.05). These results add further support to the practice of speedwork for people with PD and outline a population-amenable program with high feasibility.

Exercise in an animal model of Parkinson's disease: Motor recovery but not restoration of the nigrostriatal pathway

Many clinical studies have reported on the benefits of exercise therapy in patients with Parkinson's disease (PD). Exercise cannot stop the progression of PD or facilitate the recovery of dopamine (DA) neurons in the substantia nigra pars compacta (SNpc) (Bega et al., 2014). To tease apart this paradox, we utilized a progressive MPTP (1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine) mouse model in which we initiated 4weeks of treadmill exercise after the completion of toxin administration (i.e., restoration). We found in our MPTP/exercise (MPTP+EX) group several measures of gait function that recovered compared to the MPTP only group. Although there was a small recovery of tyrosine hydroxylase (TH) positive DA neurons in the SNpc and terminals in the striatum, this increase was not statistically significant. These small changes in TH could not explain the improvement of motor function. The MPTP group had a significant 170% increase in the glycosylated/non-glycosylated dopamine transporter (DAT) and a 200% increase in microglial marker, IBA-1, in the striatum. The MPTP+EX group showed a nearly full recovery of these markers back to the vehicle levels. There was an increase in GLT-1 levels in the striatum due to exercise, with no change in striatal BDNF protein expression. Our data suggest that motor recovery was not prompted by any significant restoration of DA neurons or terminals, but rather the recovery of DAT and dampening the inflammatory response. Although exercise does not promote recovery of nigrostriatal DA, it should be used in conjunction with pharmaceutical methods for controlling PD symptoms.

Treadmill exercise delays the onset of non-motor behaviors and striatal pathology in the CAG140 knock-in mouse model of Huntington's disease

Depression, cognitive impairments, and other neuropsychiatric disturbances are common during the prodromal phase of Huntington's disease (HD) well before the onset of classical motor symptoms of this degenerative disorder. The purpose of this study was to examine the potential impact of physical activity in the form of exercise on a motorized treadmill on non-motor behavioral features including depression-like behavior and cognition in the CAG₁₄₀ knock-in (KI) mouse model of HD. The CAG₁₄₀ KI mouse model has a long lifespan compared to other HD rodent models with HD motor deficits emerging after 12months of age and thus provides the opportunity to investigate early life interventions such as exercise on disease progression. Motorized treadmill running was initiated at 4weeks of age (1h per session, 3 times per week) and continued for 6months. Non-motor behaviors were assessed up to 6months of age and included analysis of depression-like behavior (using the tail-suspension and forced-swim tests) and cognition (using the T-maze and object recognition tests). At both 4 and 6months of age, CAG₁₄₀ KI mice displayed significant depression-like behavior in the forced swim and tail suspension tests and cognitive impairment by deficits in reversal relearning in the T-maze test. These deficits were not evident in mice engaged in treadmill running. In addition, exercise restored striatal dopamine D2 receptor expression and dopamine neurotransmitter levels both reduced in sedentary HD mice. Finally, we examined the pattern of striatal expression of mutant huntingtin (mHTT) protein and showed that the number and intensity of immunohistochemical staining patterns of intranuclear aggregates were significantly reduced with exercise. Altogether these findings begin to address the potential impact of lifestyle and early intervention such as exercise on modifying HD progression.

The many facets of motor learning and their relevance for Parkinson's disease

The final goal of motor learning, a complex process that includes both implicit and explicit (or declarative) components, is the optimization and automatization of motor skills. Motor learning involves different neural networks and neurotransmitters systems depending on the type of task and on the stage of learning. After the first phase of acquisition, a motor skill goes through consolidation (i.e., becoming resistant to interference) and retention, processes in which sleep and long-term potentiation seem to play important roles. The studies of motor learning in Parkinson's disease have yielded controversial results that likely stem from the use of different experimental paradigms. When a task's characteristics, instructions, context, learning phase and type of measures are taken into consideration, it is apparent that, in general, only learning that relies on attentional resources and cognitive strategies is affected by PD, in agreement with the finding of a fronto-striatal deficit in this disease. Levodopa administration does not seem to reverse the learning deficits in PD, while deep brain stimulation of either globus pallidus or subthalamic nucleus appears to be beneficial. Finally and most importantly, patients with PD often show a decrease in retention of newly learned skill, a problem that is present even in the early stages of the disease. A thorough dissection and understanding of the processes involved in motor learning is warranted to provide solid bases for effective medical, surgical and rehabilitative approaches in PD.

Increased neuromuscular consistency in gait and balance after partnered, dance-based rehabilitation in Parkinson's disease

Here we examined changes in muscle coordination associated with improved motor performance after partnered, dance-based rehabilitation in individuals with mild to moderate idiopathic Parkinson's disease. Using motor module (a.k.a. muscle synergy) analysis, we identified changes in the modular control of overground walking and standing reactive balance that accompanied clinically meaningful improvements in behavioral measures of balance, gait, and disease symptoms after 3 wk of daily Adapted Tango classes. In contrast to previous studies that revealed a positive association between motor module number and motor performance, none of the six participants in this pilot study increased motor module number despite improvements in behavioral measures of balance and gait performance. Instead, motor modules were more consistently recruited and distinctly organized immediately after rehabilitation, suggesting more reliable motor output. Furthermore, the pool of motor modules shared between walking and reactive balance increased after rehabilitation, suggesting greater generalizability of motor module function across tasks. Our work is the first to show that motor module distinctness, consistency, and generalizability are more sensitive to improvements in gait and balance function after short-term rehabilitation than motor module number. Moreover, as similar differences in motor module distinctness, consistency, and generalizability have been demonstrated previously in healthy young adults with and without long-term motor training, our work suggests commonalities in the structure of muscle coordination associated with differences in motor performance across the spectrum from motor impairment to expertise.NEW & NOTEWORTHY We demonstrate changes in neuromuscular control of gait and balance in individuals with Parkinson's disease after short-term, dance-based rehabilitation. Our work is the first to show that motor module distinctness, consistency, and generalizability across gait and balance are more sensitive than motor module number to improvements in motor performance following short-term rehabilitation. Our results indicate commonalities in muscle coordination improvements associated with motor skill reacquisition due to rehabilitation and motor skill acquisition in healthy individuals.

Neuroprotective effects of endurance exercise against neuroinflammation in MPTP-induced Parkinson's disease mice

Parkinson's disease (PD) is one of the main degenerative neurological disorders accompanying death of dopaminergic neurons prevalent in aged population. Endurance exercise (EE) has been suggested to confer neurogenesis and mitigate the degree of seriousness of PD. However, underlying molecular mechanisms responsible for exercise-mediated neuroprotection against PD remain largely unknown. Given the relevant interplay between elevated α-synuclein and neuroinflammation in a poor prognosis and vicious progression of PD and anti-inflammatory effects of EE, we hypothesized that EE would reverse motor dysfunction and cell death caused by PD. To this end, we chose a pharmacological model of PD (e.g., chronic injection of neurotoxin MPTP). Young adult male mice (7 weeks old) were randomly divided into three groups: sedentary control (C, n=10), MPTP (M, n=10), and MPTP + endurance exercise (ME, n=10). Our data showed that EE restored motor function impaired by MPTP in parallel with reduced cell death. Strikingly, EE exhibited a significant reduction in α-synuclein protein along with diminished pro-inflammatory cytokines (i.e., TNF-α and IL-1β). Supporting this, EE prevented activation of Toll like receptor 2 (TLR2) downstream signaling cascades such as MyD88, TRAF6 and TAK-1 incurred by in MPTP administration in the striatum. Moreover, EE reestablished tyrosine hydroxylase at levels similar to C group. Taken together, our data suggest that an EE-mediated neuroprotective mechanism against PD underlies anti-neuroinflammation conferred by reduced levels of α-synuclein. Our data provides an important insight into developing a non-pharmacological countermeasure against neuronal degeneration caused by PD.

Premorbid exercise engagement and motor reserve in Parkinson's disease

BACKGROUND

Life-long experiences of cognitive activity could enhance cognitive reserve, which may lead individuals to show less cognitive deficits in Alzheimer's disease, despite similar pathological changes. We performed this study to test whether premorbid physical activity may enhance motor reserve in Parkinson's disease (PD) (i.e., less motor deficits despite similar degrees of dopamine depletion).

METHODS

We assessed engagement in premorbid leisure-time exercise among 102 drug naive PD patients who had been initially diagnosed at our hospital by dopamine transporter scanning. Patients were classified into tertile groups based on the frequency, duration, and intensity of the exercises in which they participated.

RESULTS

Among patients with mild to moderate reductions in striatal dopaminergic activity (above the median dopaminergic activity), the exercise group of the highest tertile showed significantly lower motor scores (i.e., fewer motor deficits, 15.53 ± 6.25), despite similar degrees of dopamine reduction, compared to the combined group of the middle and the lowest tertiles (21.57 ± 8.34, p = 0.01). Nonetheless, the highest tertile group showed a more rapid decline in motor function related to reductions in striatal dopaminergic activity than the other two groups (p = 0.002 with the middle tertile group and p = 0.001 with the lowest tertile group).

CONCLUSIONS

These results suggest that engagement in premorbid exercise acts as a proxy for an active reserve in the motor domain (i.e., motor reserve) in patients with PD.

Influence of aerobic exercise training on the neural correlates of motor learning in Parkinson's disease individuals

BACKGROUND

Aerobic exercise training (AET) has been shown to provide general health benefits, and to improve motor behaviours in particular, in individuals with Parkinson's disease (PD). However, the influence of AET on their motor learning capacities, as well as the change in neural substrates mediating this effect remains to be explored.

OBJECTIVE

In the current study, we employed functional Magnetic Resonance Imaging (fMRI) to assess the effect of a 3-month AET program on the neural correlates of implicit motor sequence learning (MSL).

METHODS

20 healthy controls (HC) and 19 early PD individuals participated in a supervised, high-intensity, stationary recumbent bike training program (3 times/week for 12 weeks). Exercise prescription started at 20 min (+ 5 min/week up to 40 min) based on participant's maximal aerobic power. Before and after the AET program, participants' brain was scanned while performing an implicit version of the serial reaction time task.

RESULTS

Brain data revealed pre-post MSL-related increases in functional activity in the hippocampus, striatum and cerebellum in PD patients, as well as in the striatum in HC individuals. Importantly, the functional brain changes in PD individuals correlated with changes in aerobic fitness: a positive relationship was found with increased activity in the hippocampus and striatum, while a negative relationship was observed with the cerebellar activity.

CONCLUSION

Our results reveal, for the first time, that exercise training produces functional changes in known motor learning related brain structures that are consistent with improved behavioural performance observed in PD patients. As such, AET can be a valuable non-pharmacological intervention to promote, not only physical fitness in early PD, but also better motor learning capacity useful in day-to-day activities through increased plasticity in motor related structures.

Engaging cognitive circuits to promote motor recovery in degenerative disorders. exercise as a learning modality

Exercise and physical activity are fundamental components of a lifestyle essential in maintaining a healthy brain. This is primarily due to the fact that the adult brain maintains a high degree of plasticity and activity is essential for homeostasis throughout life. Plasticity is not lost even in the context of a neurodegenerative disorder, but could be maladaptive thus promoting disease onset and progression. A major breakthrough in treating brain disorders such as Parkinson's disease is to drive neuroplasticity in a direction to improve motor and cognitive dysfunction. The purpose of this short review is to present the evidence from our laboratories that supports neuroplasticity as a potential therapeutic target in treating brain disorders. We consider that the enhancement of motor recovery in both animal models of dopamine depletion and in patients with Parkinson's disease is optimized when cognitive circuits are engaged; in other words, the brain is engaged in a learning modality. Therefore, we propose that to be effective in treating Parkinson's disease, physical therapy must employ both skill-based exercise (to drive specific circuits) and aerobic exercise (to drive the expression of molecules required to strengthen synaptic connections) components to select those neuronal circuits, such as the corticostriatal pathway, necessary to restore proper motor and cognitive behaviors. In the wide spectrum of different forms of exercise, learning as the fundamental modality likely links interventions used to treat patients with Parkinson's disease and may be necessary to drive beneficial neuroplasticity resulting in symptomatic improvement and possible disease modification.

Progressive resistance exercise restores some properties of the triphasic EMG pattern and improves bradykinesia: the PRET-PD randomized clinical trial

In Parkinson's disease (PD), the characteristic triphasic agonist and antagonist muscle activation pattern during ballistic movement is impaired: the number of agonist muscle bursts is increased, and the amplitudes of the agonist and antagonist bursts are reduced. The breakdown of the triphasic electromyographic (EMG) pattern has been hypothesized to underlie bradykinesia in PD. Progressive resistance exercise has been shown to improve clinical measures of bradykinesia, but it is not clear whether the benefits for bradykinesia are accompanied by changes in agonist and antagonist muscle activity. This study examined the spatiotemporal changes in agonist and antagonist muscle activity following 24 mo of progressive resistance exercise and the combined relationship between spatiotemporal muscle activity and strength measures and upper limb bradykinesia. We compared the effects of progressive resistance exercise training (PRET) with a nonprogressive exercise intervention, modified Fitness Counts (mFC), in patients with PD. We randomized 48 participants with mild-to-moderate PD to mFC or PRET. At the study endpoint of 24 mo, participants randomized to PRET compared with mFC had significantly faster movement velocity, accompanied by significant increases in the duration, magnitude, and magnitude normalized to duration of the 1st agonist burst and fewer number of agonist bursts before peak velocity. The antagonist muscle activity was increased relative to baseline but did not differ between groups. Spatiotemporal EMG muscle activity and muscle strength were significantly associated with upper limb bradykinesia. These findings demonstrate that progressive resistance exercise improves upper limb movement velocity and restores some aspects of the triphasic EMG pattern.

Dopamine Replacement Therapy, Learning and Reward Prediction in Parkinson's Disease: Implications for Rehabilitation

The principal feature of Parkinson’s disease (PD) is the impaired ability to acquire and express habitual-automatic actions due to the loss of dopamine in the dorsolateral striatum, the region of the basal ganglia associated with the control of habitual behavior. Dopamine replacement therapy (DRT) compensates for the lack of dopamine, representing the standard treatment for different motor symptoms of PD (such as rigidity, bradykinesia and resting tremor). On the other hand, rehabilitation treatments, exploiting the use of cognitive strategies, feedbacks and external cues, permit to “learn to bypass” the defective basal ganglia (using the dorsolateral area of the prefrontal cortex) allowing the patients to perform correct movements under executive-volitional control. Therefore, DRT and rehabilitation seem to be two complementary and synergistic approaches. Learning and reward are central in rehabilitation: both of these mechanisms are the basis for the success of any rehabilitative treatment. Anyway, it is known that “learning resources” and reward could be negatively influenced from dopaminergic drugs. Furthermore, DRT causes different well-known complications: among these, dyskinesias, motor fluctuations, and dopamine dysregulation syndrome (DDS) are intimately linked with the alteration in the learning and reward mechanisms and could impact seriously on the rehabilitative outcomes. These considerations highlight the need for careful titration of DRT to produce the desired improvement in motor symptoms while minimizing the associated detrimental effects. This is important in order to maximize the motor re-learning based on repetition, reward and practice during rehabilitation. In this scenario, we review the knowledge concerning the interactions between DRT, learning and reward, examine the most impactful DRT side effects and provide suggestions for optimizing rehabilitation in PD.

Exercise during early, but not late abstinence, attenuates subsequent relapse vulnerability in a rat model

Exercise has shown promise as a nonpharmacological intervention for addiction, with evidence suggesting a potential utility for relapse prevention. In humans, exercise as an intervention is typically introduced well after the initiation of abstinence, yet neurobiological data from preclinical studies suggest that it may be more effective if initiated during early abstinence. Here, using rat models, we determined whether the beneficial effects of exercise on relapse vulnerability depends on when exercise is first initiated, during early versus late abstinence. Once rats (n=47) acquired cocaine self-administration, they were given 24-h access to cocaine (1.5 mg/kg per infusion) under a discrete trial procedure (four infusions per hour) for 10 days. The rats then began a 14-day abstinence period in which they had access (2 h per day) to a locked wheel throughout abstinence (sedentary) or an unlocked wheel during early (days 1-7), late (days 8-14) or throughout (days 1-14) abstinence (n=10-14 per group). Cocaine seeking, as assessed under an extinction/cued-induced reinstatement procedure, was examined on day 15 of abstinence. Exercise beginning during early abstinence robustly attenuated subsequent cocaine seeking, and this effect persisted even when exercise ended on the seventh day of abstinence. In contrast, exercise during late abstinence was not effective and these animals displayed high levels of cocaine seeking similar to those observed in sedentary animals. These results indicate that the timing of exercise availability differentially impacts cocaine seeking with results suggesting that exercise during early, but not late, abstinence may provide long-term protection against cocaine relapse.

Physical exercise counteracts MPTP-induced changes in neural precursor cell proliferation in the hippocampus and restores spatial learning but not memory performance in the water maze

Parkinson's disease (PD) is characterized by a continuous loss of dopaminergic neurons in the substantia nigra, which not only leads to characteristic motor symptoms but also to cognitive impairments. Physical exercise has been shown to improve hippocampus-dependent cognitive functions in PD patients. Animal studies have demonstrated the involvement of adult hippocampal neurogenesis in exercise-induced improvements of visuo-spatial learning and memory. Here, we investigated the direct impact of voluntary wheel running on hippocampal neurogenesis and spatial learning and memory in the Morris water maze (MWM) using the1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. We also analyzed striatal and hippocampal dopamine transmission and mRNA expression levels of dopamine receptors. We show that MPTP-induced spatial learning deficits were alleviated by short-term physical exercise but not MPTP-induced spatial memory impairments in either exercise intervention group. Neural precursor proliferation was transiently altered in MPTP-treated mice, while the cell survival was increased by exercise. Dopamine was progressively depleted by MPTP and its turnover altered by exercise. In addition, gene expression of dopamine receptor D1/D5 was transiently upregulated following MPTP treatment but not affected by physical exercise. Our findings suggest that physical exercise benefits spatial learning but not memory performance in the MWM after MPTP-induced dopamine depletion by restoring precursor cell proliferation in the hippocampus and influencing dopamine transmission. This adds to the understanding of cognitive decline and mechanisms for potential improvements by physical exercise in PD patients.

Role of exercise in the treatment of alcohol use disorders

Excessive alcohol use can cause harmful effects on the human body, which are associated with serious health problems, and it can also lead to the development of alcohol use disorders (AUDs). There is certain evidence that physical exercise positively affects excessive alcohol use and the associated problems by leading to reduced alcohol intake. A literature search was conducted using the databases PubMed, Medline and Web of Science. The search terms used as keywords were: Addiction, abuse, alcohol use disorders, exercise training, β-endorphin, opioids, brain, ethanol and alcohol. The current study presents the studies that reported on the use of exercise in the treatment of AUDs between 1970 and 2015. The potential psychological and physiological mechanisms that contribute to the action of exercise were also reviewed, highlighting the role of β-endorphin and the hypothalamic-pituitary-adrenal axis in AUDs and the possible association among physical activity, the endogenous opioid system and the desire for alcohol. Only 11 studies were identified that refer to the effect of exercise on alcohol consumption and/or the associated outcomes. Six of those studies concluded that exercise may have a positive impact towards alcohol consumption, abstinence rates or the urge to drink. One of those studies also indicated that a bout of exercise affects the endogenous opioids, which may be associated with the urge to drink. Another 3 studies indicated that responses to acute exercise in individuals with AUDs are different compared to those in healthy ones. Generally, despite limited research data and often contradictory results, there is certain early promising evidence for the role of exercise as an adjunctive tool in the treatment of AUDs. Physiological and biochemical parameters that would confirm that exercise is safe for individuals with AUDs should be examined in future studies.

Exercise-Mediated Increase in Nigral Tyrosine Hydroxylase Is Accompanied by Increased Nigral GFR-α1 and EAAC1 Expression in Aging Rats

Exercise may alleviate locomotor impairment in Parkinson's disease (PD) or aging. Identifying molecular responses immediately engaged by exercise in the nigrostriatal pathway and allied tissue may reveal critical targets associated with its long-term benefits. In aging, there is loss of tyrosine hydroxylase (TH) and the glial cell line-derived neurotrophic factor (GDNF) receptor, GFR-α1, in the substantia nigra (SN). Exercise can increase GDNF expression, but its effect on GFR-α1 expression is unknown. Infusion of GDNF into striatum or GFR-α1 in SN, respectively, can increase locomotor activity and TH function in SN but not striatum in aged rats. GDNF may also increase glutamate transporter expression, which attenuates TH loss in PD models. We utilized a footshock-free treadmill exercise regimen to determine the immediate impact of short-term exercise on GFR-α1 expression, dopamine regulation, glutamate transporter expression, and glutamate uptake in 18 month old male Brown-Norway/Fischer 344 F1 hybrid rats. GFR-α1 and TH expression significantly increased in SN but not striatum. This exercise regimen did not affect glutamate uptake or glutamate transporter expression in striatum. However, EAAC1 expression increased in SN. These results indicate that nigral GFR-α1 and EAAC1 expression increased in conjunction with increased nigral TH expression following short-term exercise.

Neurotrophic factors in Parkinson's disease are regulated by exercise: Evidence-based practice

We carried out a qualitative review of the literature on the influence of forced or voluntary exercise in Parkinson's Disease (PD)-induced animals, to better understand neural mechanisms and the role of neurotrophic factors (NFs) involved in the improvement of motor behavior. A few studies indicated that forced or voluntary exercise may promote neuroprotection, through upregulation of NF expression, against toxicity of drugs that simulate PD. Forced training, such as treadmill exercise and forced-limb use, adopted in most studies, in addition to voluntary exercise on a running wheel are suitable methods for NFs upregulation.

Initiation of calorie restriction in middle-aged male rats attenuates aging-related motoric decline and bradykinesia without increased striatal dopamine

Aging-related bradykinesia affects ∼ 15% of those reaching age 65 and 50% of those reaching their 80s. Given this high risk and lack of pharmacologic therapeutics, noninvasive lifestyle strategies should be identified to diminish its risk and identify the neurobiological targets to reduce aging-related bradykinesia. Early-life, long-term calorie restriction (CR) attenuates aging-related bradykinesia in rodents. Here, we addressed whether CR initiation at middle age could attenuate aging-related bradykinesia and motoric decline measured as rotarod performance. A 30% CR regimen was implemented for 6 months duration in 12-month-old male Brown-Norway Fischer 344 F1 hybrid rats after establishing individual baseline locomotor activities. Locomotor capacity was assessed every 6 weeks thereafter. The ad libitum group exhibited predictably decreased locomotor activity, except movement speed, out to 18 months of age. In contrast, in the CR group, movement number and horizontal activity did not decrease during the 6-month trial, and aging-related decline in rotarod performance was attenuated. The response to CR was influenced by baseline locomotor activity. The lower the locomotor activity level at baseline, the greater the response to CR. Rats in the lower 50th percentile surpassed their baseline level of activity, whereas rats in the top 50th percentile decreased at 6 weeks and then returned to baseline by 12 weeks of CR. We hypothesized that nigrostriatal dopamine tissue content would be greater in the CR group and observed a modest increase only in substantia nigra with no group differences in striatum, nucleus accumbens, or ventral tegmental area. These results indicate that initiation of CR at middle age may reduce aging-related bradykinesia, and, furthermore, subjects with below average locomotor activity may increase baseline activity. Sustaining nigral dopamine neurotransmission may be one component of preserving locomotor capabilities during aging.

Exercise Therapy for Parkinson's Disease: Pedaling Rate Is Related to Changes in Motor Connectivity

Forced-rate lower-extremity exercise has recently emerged as a potential safe and low-cost therapy for Parkinson's disease (PD). The efficacy is believed to be dependent on pedaling rate, with rates above the subjects' voluntary exercise rates being most beneficial. In this study, we use functional connectivity magnetic resonance imaging (MRI) to further elucidate the mechanism underlying this effect. Twenty-seven PD patients were randomized to complete 8 weeks of forced-rate exercise (FE) or voluntary-rate exercise (VE). Exercise was delivered using a specialized stationary bicycle, which can augment patients' voluntary exercise rates. The FE group received assistance from the cycle. Imaging was conducted at baseline, end of therapy, and after 4 weeks of follow-up. Functional connectivity (FC) was determined via seed-based correlation analysis, using activation-based seeds in the primary motor cortex (M1). The change in FC after exercise was compared using linear correlation with pedaling rate. Results of the correlation analysis showed a strong positive correlation between pedaling rate and change in FC from the most affected M1 to the ipsilateral thalamus. This effect persisted after 4 weeks of follow-up. These results indicate that a plausible mechanism for the therapeutic efficacy of high-rate exercise in PD is that it improves thalamo-cortical connectivity.

The Effects of Exercise on Dopamine Neurotransmission in Parkinson's Disease: Targeting Neuroplasticity to Modulate Basal Ganglia Circuitry

Animal studies have been instrumental in providing evidence for exercise-induced neuroplasticity of corticostriatal circuits that are profoundly affected in Parkinson’s disease. Exercise has been implicated in modulating dopamine and glutamate neurotransmission, altering synaptogenesis, and increasing cerebral blood flow. In addition, recent evidence supports that the type of exercise may have regional effects on brain circuitry, with skilled exercise differentially affecting frontal-striatal related circuits to a greater degree than pure aerobic exercise. Neuroplasticity in models of dopamine depletion will be reviewed with a focus on the influence of exercise on the dorsal lateral striatum and prefrontal related circuitry underlying motor and cognitive impairment in PD. Although clearly more research is needed to address major gaps in our knowledge, we hypothesize that the potential effects of exercise on inducing neuroplasticity in a circuit specific manner may occur through synergistic mechanisms that include the coupling of an increasing neuronal metabolic demand and increased blood flow. Elucidation of these mechanisms may provide important new targets for facilitating brain repair and modifying the course of disease in PD.

The Benefits of Exercise on Structural and Functional Plasticity in the Rodent Hippocampus of Different Disease Models

In this review, the benefits of physical exercise on structural and functional plasticity in the hippocampus are discussed. The evidence is clear that voluntary exercise in rats and mice can lead to increases in hippocampal neurogenesis and enhanced synaptic plasticity which ultimately result in improved performance in hippocampal-dependent tasks. Furthermore, in models of neurological disorders, including fetal alcohol spectrum disorders, traumatic brain injury, stroke, and neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's disease exercise can also elicit beneficial effects on hippocampal function. Ultimately this review highlights the multiple benefits of exercise on hippocampal function in both the healthy and the diseased brain.

Developmental exposure to manganese induces lasting motor and cognitive impairment in rats

Exposure to high manganese (Mn) levels may damage the basal ganglia, leading to a syndrome analogous to Parkinson's disease, with motor and cognitive impairments. The molecular mechanisms underlying Mn neurotoxicity, particularly during development, still deserve further investigation. Herein, we addressed whether early-life Mn exposure affects motor coordination and cognitive function in adulthood and potential underlying mechanisms. Male Wistar rats were exposed intraperitoneally to saline (control) or MnCl2 (5, 10 or 20 mg/kg/day) from post-natal day (PND) 8-12. Behavioral tests were performed on PND 60-65 and biochemical analysis in the striatum and hippocampus were performed on PND14 or PND70. Rats exposed to Mn (10 and 20 mg/kg) performed significantly worse on the rotarod test than controls indicating motor coordination and balance impairments. The object and social recognition tasks were used to evaluate short-term memory. Rats exposed to the highest Mn dose failed to recognize a familiar object when replaced by a novel object as well as to recognize a familiar juvenile rat after a short period of time. However, Mn did not alter olfactory discrimination ability. In addition, Mn-treated rats displayed decreased levels of non-protein thiols (e.g. glutathione) and increased levels of glial fibrillary acidic protein (GFAP) in the striatum. Moreover, Mn significantly increased hippocampal glutathione peroxidase (GPx) activity. These findings demonstrate that acute low-level exposure to Mn during a critical neurodevelopmental period causes cognitive and motor dysfunctions that last into adulthood, that are accompanied by alterations in antioxidant defense system in both the hippocampus and striatum.

Exercise preconditioning improves traumatic brain injury outcomes

PURPOSE

To determine whether 6 weeks of exercise performed prior to traumatic brain injury (TBI) could improve post-TBI behavioral outcomes in mice, and if exercise increases neuroprotective molecules (vascular endothelial growth factor-A [VEGF-A], erythropoietin [EPO], and heme oxygenase-1 [HO-1]) in brain regions responsible for movement (sensorimotor cortex) and memory (hippocampus).

METHODS

120 mice were randomly assigned to one of four groups: (1) no exercise+no TBI (NOEX-NOTBI [n=30]), (2) no exercise+TBI (NOEX-TBI [n=30]), (3) exercise+no TBI (EX-NOTBI [n=30]), and (4) exercise+TBI (EX-TBI [n=30]). The gridwalk task and radial arm water maze were used to evaluate sensorimotor and cognitive function, respectively. Quantitative real time polymerase chain reaction and immunostaining were performed to investigate VEGF-A, EPO, and HO-1 mRNA and protein expression in the right cerebral cortex and ipsilateral hippocampus.

RESULTS

EX-TBI mice displayed reduced post-TBI sensorimotor and cognitive deficits when compared to NOEX-TBI mice. EX-NOTBI and EX-TBI mice showed elevated VEGF-A and EPO mRNA in the cortex and hippocampus, and increased VEGF-A and EPO staining of sensorimotor cortex neurons 1 day post-TBI and/or post-exercise. EX-TBI mice also exhibited increased VEGF-A staining of hippocampal neurons 1 day post-TBI/post-exercise. NOEX-TBI mice demonstrated increased HO-1 mRNA in the cortex (3 days post-TBI) and hippocampus (3 and 7 days post-TBI), but HO-1 was not increased in mice that exercised.

CONCLUSIONS

Improved TBI outcomes following exercise preconditioning are associated with increased expression of specific neuroprotective genes and proteins (VEGF-A and EPO, but not HO-1) in the brain.

Intervention with exercise restores motor deficits but not nigrostriatal loss in a progressive MPTP mouse model of Parkinson's disease

Many studies have investigated exercise therapy in Parkinson's disease (PD) and have shown benefits in improving motor deficits. However, exercise does not slow down the progression of the disease or induce the revival of lost nigrostriatal neurons. To examine the dichotomy of behavioral improvement without the slowing or recovery of dopaminergic cell or terminal loss, we tested exercise therapy in an intervention paradigm where voluntary running wheels were installed half-way through our progressive PD mouse model. In our model, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is administered over 4 weeks with increased doses each week (8, 16, 24, 32-kg/mg). We found that after 4 weeks of MPTP treatment, mice that volunteered to exercise had behavioral recovery in several measures despite the loss of 73% and 53% tyrosine hydroxylase (TH) within the dorsolateral (DL) striatum and the substantia nigra (SN), respectively which was equivalent to the loss seen in the mice that did not exercise but were also administered MPTP for 4 weeks. Mice treated with 4 weeks of MPTP showed a 41% loss of vesicular monoamine transporter II (VMAT2), a 71% increase in the ratio of glycosylated/non-glycosylated dopamine transporter (DAT), and significant increases in glutamate transporters including VGLUT1, GLT-1, and excitatory amino acid carrier 1. MPTP mice that exercised showed recovery of all these biomarkers back to the levels seen in the vehicle group and showed less inflammation compared to the mice treated with MPTP for 4 weeks. Even though we did not measure tissue dopamine (DA) concentration, our data suggest that exercise does not alleviate motor deficits by sparing nigrostriatal neurons, but perhaps by stabilizing the extraneuronal neurotransmitters, as evident by a recovery of DA and glutamate transporters. However, suppressing inflammation could be another mechanism of this locomotor recovery. Although exercise will not be a successful treatment alone, it could supplement other pharmaceutical approaches to PD therapy.

Recruitment of the prefrontal cortex and cerebellum in Parkinsonian rats following skilled aerobic exercise

Exercise modality and complexity play a key role in determining neurorehabilitative outcome in Parkinson's disease (PD). Exercise training (ET) that incorporates both motor skill training and aerobic exercise has been proposed to synergistically improve cognitive and automatic components of motor control in PD patients. Here we introduced such a skilled aerobic ET paradigm in a rat model of dopaminergic deafferentation. Rats with bilateral, intra-striatal 6-hydroxydopamine lesions were exposed to forced ET for 4weeks, either on a simple running wheel (non-skilled aerobic exercise, NSAE) or on a complex wheel with irregularly spaced rungs (skilled aerobic exercise, SAE). Cerebral perfusion was mapped during horizontal treadmill walking or at rest using [(14)C]-iodoantipyrine 1week after the completion of ET. Regional cerebral blood flow (rCBF) was quantified by autoradiography and analyzed in 3-dimensionally reconstructed brains by statistical parametric mapping. SAE compared to NSAE resulted in equal or greater recovery in motor deficits, as well as greater increases in rCBF during walking in the prelimbic area of the prefrontal cortex, broad areas of the somatosensory cortex, and the cerebellum. NSAE compared to SAE animals showed greater activation in the dorsal caudate-putamen and dorsal hippocampus. Seed correlation analysis revealed enhanced functional connectivity in SAE compared to NSAE animals between the prelimbic cortex and motor areas, as well as altered functional connectivity between midline cerebellum and sensorimotor regions. Our study provides the first evidence for functional brain reorganization following skilled aerobic exercise in Parkinsonian rats, and suggests that SAE compared to NSAE results in enhancement of prefrontal cortex- and cerebellum-mediated control of motor function.

Lifelong brain health is a lifelong challenge: from evolutionary principles to empirical evidence

Although the human brain is exceptional in size and information processing capabilities, it is similar to other mammals with regard to the factors that promote its optimal performance. Three such factors are the challenges of physical exercise, food deprivation/fasting, and social/intellectual engagement. Because it evolved, in part, for success in seeking and acquiring food, the brain functions best when the individual is hungry and physically active, as typified by the hungry lion stalking and chasing its prey. Indeed, studies of animal models and human subjects demonstrate robust beneficial effects of regular exercise and intermittent energy restriction/fasting on cognitive function and mood, particularly in the contexts of aging and associated neurodegenerative disorders. Unfortunately, the agricultural revolution and the invention of effort-sparing technologies have resulted in a dramatic reduction or elimination of vigorous exercise and fasting, leaving only intellectual challenges to bolster brain function. In addition to disengaging beneficial adaptive responses in the brain, sedentary overindulgent lifestyles promote obesity, diabetes and cardiovascular disease, all of which may increase the risk of cognitive impairment and Alzheimer's disease. It is therefore important to embrace the reality of the requirements for exercise, intermittent fasting and critical thinking for optimal brain health throughout life, and to recognize the dire consequences for our aging population of failing to implement such brain-healthy lifestyles.

Gallic acid and exercise training improve motor function, nerve conduction velocity but not pain sense reflex after experimental sciatic nerve crush in male rats

OBJECTIVE

The aim of present study was to evaluate the effects of oral administration of gallic acid (GA) for 21 days alone and in combination with exercise on nerve conduction velocity and sensory and motor functions in rats with sciatic nerve crush.

MATERIALS AND METHODS

Seventy adult male Wistar rats (250-300 g) were divided randomly into 7 groups with 10 in each: 1) Control (Cont), 2) Crushed + Vehicle (Cr +Veh), 3-5) Crushed + gallic acid (Cr+GA) (50, 100, and 200 mg/kg/2 mL, orally), 6) Crushed + exercise (Cr+Exe), and 7) Crushed + exercise + effective dose of gallic acid (Cr+Exe +GA200) for 21 days. In order to establish an animal model of sciatic nerve crush, equivalent to 7 kg of force pressed on 2-3 mm of sciatic nerve for 30 s, three times with 30 s intervals. Pain sense reflex in hot plate, motor coordination in rotarod, and sciatic nerve conduction velocity (SNCV) in all groups were tested. Data were analyzed using one-way ANOVA followed by Tukey's post hoc test and p<0.05 has assigned as the significant difference.

RESULTS

Pain threshold was increased significantly in untreated crushed rats while motor function and SNCV were decreased in all groups with nerve crush (p<0.05, p<0.01, p<0.001 vs. control). Pain reflex latency was not changed in treated groups. Motor coordination and SNCV were improved in groups Cr+GA200 and Cr+Exe + GA200 (p<0.05, p<0.01 vs. Cr+Veh).

CONCLUSION

GA, dose-dependently, may have therapeutic potential to improve the peripheral nerve degeneration, which is most likely related, at least in part, to its antioxidant and therapeutic properties.

Physical activity and risk of Parkinson's disease in the Swedish National March Cohort

Physical exercise has been associated with neuroprotective effects in the nigrostriatal dopaminergic system. To examine the impact of physical activity on Parkinson's disease risk prospectively, we followed 43 368 individuals who provided extensive information on physical activity at baseline. We estimated hazard ratios with 95% confidence intervals using Cox proportional hazards regression. During an average of 12.6 years of follow-up, 286 incident Parkinson's disease cases were identified. In males, there was an inverse association with Parkinson's disease for total physical activity (hazard ratio 0.55, 95% confidence interval 0.35-0.87 for medium versus low level), for sum of household, commuting and leisure time exercise (hazard ratio 0.53, 95% confidence interval 0.33-0.85 for high versus low level), and for household and commuting physical activity specifically (hazard ratio 0.50, 95% confidence interval 0.31-0.81 for >6 versus <2 h per week). No association was observed for leisure time exercise or occupational physical activity with Parkinson's disease, among either males or females. Meta-analysis of the present study and five previous prospective studies showed a pooled hazard ratio of 0.66 (95% confidence interval 0.57-0.78) for highest versus lowest physical activity level. Our results indicate that a medium level of physical activity lowers Parkinson's disease risk.

Treadmill exercise improves motor coordination through ameliorating Purkinje cell loss in amyloid beta23-35-induced Alzheimer's disease rats

Alzheimer's disease (AD) is a most common age-related neurodegenerative disease. AD is characterized by a progressive loss of neurons causing cognitive dysfunction. The cerebellum is closely associated with integration of movement, including motor coordination, control, and equilibrium. In the present study, we evaluated the effect of tread-mill exercise on the survival of Purkinje neurons in relation with reactive astrocyte in the cerebellum using Aβ25-35-induced AD rats. AD was induced by a bilateral intracerebroventricular (ICV) injection of Aβ25-35. The rats in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 4 weeks, starting 2 days after Aβ25-35 injection. In the present results, ICV injection of Aβ25-35 deteriorated motor coordination and balance. The number of calbindin-positive cells in the cerebellar vermis was decreased and glial fibrillary acidic protein (GFAP) expression in the cerebellar vermis was increased in the Aβ25-35-induced AD rats. Treadmill exercise improved motor coordination and balance. Treadmill exercise increased the number of Purkinje neurons and suppressed GFAP expression in the cerebellar vermis. The present study demonstrated that treadmill exercises alleviated dysfunction of motor coordination and balance by reduction of Purkinje cell loss through suppressing reactive astrocytes in the cerebellum of AD rats. The present study provides the possibility that treadmill exercise might be an important therapeutic strategy for the symptom improvement of AD patients.

Treadmill exercise activates Nrf2 antioxidant system to protect the nigrostriatal dopaminergic neurons from MPP+ toxicity

Exercise induces oxidative stress, which may activate adaptive antioxidant responses. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the defense of oxidative stress by regulating the expression of antioxidant enzymes, gamma-glutamylcysteine ligase (γGCL) and heme oxygenase-1 (HO-1). We investigated whether treadmill exercise protects dopaminergic neurons by regulating the Nrf2 antioxidant system in a 1-methyl-4-phenylpyridine (MPP(+))-induced parkinsonian rat model. We found that MPP(+) induced early decreases in total glutathione level and Nrf2/γGCLC (catalytic subunit of γGCL) expression, but late upregulation of HO-1 expression in association with loss of nigral dopaminergic neurons and downregulation of tyrosine hydroxylase and dopamine transporter expression in the striatum. Treadmill exercise for 4weeks induced upregulation of Nrf2 and γGCLC expression, and also prevented the MPP(+)-induced downregulation of Nrf2/γGCLC/glutathione, HO-1 upregulation, and nigrostriatal dopaminergic neurodegeneration. Moreover, the protective effect of exercise was blocked by the knockdown of Nrf2 using a lentivirus-carried shNrf2 delivery system. These results demonstrate an essential role of Nrf2 in the exercise-mediated protective effect that exercise enhances the nigrostriatal Nrf2 antioxidant defense capacity to protect dopaminergic neurons against the MPP(+)-induced toxicity.

Healthy body, healthy mind?: the effectiveness of physical activity to treat ADHD in children

Data from animal studies provide convincing evidence that physical exercise enhances brain development and neurobehavioral functioning in areas believed to be impaired in children with attention-deficit/hyperactivity disorder (ADHD). To a lesser but still compelling extent, results from studies in typically developing children and adults indicate beneficial effects of exercise on many of the neurocognitive functions that have been shown to be impaired in children with ADHD. Together, these data provide a strong rationale for why a program of structured physical exercise might serve as an effective intervention for children with ADHD.

Heat shock protein 90 is a potential therapeutic target for ameliorating skeletal muscle abnormalities in Parkinson's disease

Previous studies have confirmed that heat shock protein 90 overexpression can lead to dopaminergic neuronal death. This study was designed to further investigate what effects are produced by heat shock protein 90 after endurance exercise training. Immunohistochemistry results showed that exercise training significantly inhibited heat shock protein 90 overexpression in the soleus and gastrocnemius in Parkinson's disease rats, which is a potential therapeutic target for ameliorating skeletal muscle abnormalities in Parkinson's disease.

Environmental enrichment and brain repair: harnessing the therapeutic effects of cognitive stimulation and physical activity to enhance experience-dependent plasticity

Environmental enrichment (EE) increases levels of novelty and complexity, inducing enhanced sensory, cognitive and motor stimulation. In wild-type rodents, EE has been found to have a range of effects, such as enhancing experience-dependent cellular plasticity and cognitive performance, relative to standard-housed controls. Whilst environmental enrichment is of course a relative term, dependent on the nature of control environmental conditions, epidemiological studies suggest that EE has direct clinical relevance to a range of neurological and psychiatric disorders. EE has been demonstrated to induce beneficial effects in animal models of a wide variety of brain disorders. The first evidence of beneficial effects of EE in a genetically targeted animal model was generated using Huntington's disease transgenic mice. Subsequent studies found that EE was also therapeutic in mouse models of Alzheimer's disease, consistent with epidemiological studies of relevant environmental modifiers. EE has also been found to ameliorate behavioural, cellular and molecular deficits in animal models of various neurological and psychiatric disorders, including Parkinson's disease, stroke, traumatic brain injury, epilepsy, multiple sclerosis, depression, schizophrenia and autism spectrum disorders. This review will focus on the effects of EE observed in animal models of neurodegenerative brain diseases, at molecular, cellular and behavioural levels. The proposal that EE may act synergistically with other approaches, such as drug and cell therapies, to facilitate brain repair will be discussed. I will also discuss the therapeutic potential of 'enviromimetics', drugs which mimic or enhance the therapeutic effects of cognitive activity and physical exercise, for both neuroprotection and brain repair.

Getting to compliance in forced exercise in rodents: a critical standard to evaluate exercise impact in aging-related disorders and disease

There is a major increase in the awareness of the positive impact of exercise on improving several disease states with neurobiological basis; these include improving cognitive function and physical performance. As a result, there is an increase in the number of animal studies employing exercise. It is argued that one intrinsic value of forced exercise is that the investigator has control over the factors that can influence the impact of exercise on behavioral outcomes, notably exercise frequency, duration, and intensity of the exercise regimen. However, compliance in forced exercise regimens may be an issue, particularly if potential confounds of employing foot-shock are to be avoided. It is also important to consider that since most cognitive and locomotor impairments strike in the aged individual, determining impact of exercise on these impairments should consider using aged rodents with a highest possible level of compliance to ensure minimal need for test subjects. Here, the pertinent steps and considerations necessary to achieve nearly 100% compliance to treadmill exercise in an aged rodent model will be presented and discussed. Notwithstanding the particular exercise regimen being employed by the investigator, our protocol should be of use to investigators that are particularly interested in the potential impact of forced exercise on aging-related impairments, including aging-related Parkinsonism and Parkinson's disease.

Voluntary exercise improves performance of a discrimination task through effects on the striatal dopamine system

We have previously demonstrated that voluntary exercise facilitates discrimination learning in a modified T-maze. There is evidence implicating the dorsolateral striatum (DLS) as the substrate for this task. The present experiments examined whether changes in DLS dopamine receptors might underlie the exercise-associated facilitation. Infusing a D1R antagonist into the DLS prior to discrimination learning facilitated the performance of nonexercising rats but not exercising rats. Infusing a D2R antagonist impaired the performance of exercising rats but not nonexercising rats. Exercise-associated facilitation of this task may rely on an exercise-induced decrease in D1R and increase in D2R activation in the DLS.

Omega-3 fatty acids moderate effects of physical activity on cognitive function

Greater amounts of physical activity (PA) and omega-3 fatty acids have both been independently associated with better cognitive performance. Because of the overlapping biological effects of omega-3 fatty acids and PA, fatty acid intake may modify the effects of PA on neurocognitive function. The present study tested this hypothesis by examining whether the ratio of serum omega-6 to omega-3 fatty acid levels would moderate the association between PA and executive and memory functions in 344 participants (Mean age=44.42 years, SD=6.72). The Paffenbarger Physical Activity Questionnaire (PPAQ), serum fatty acid levels, and performance on a standard neuropsychological battery were acquired on all subjects. A principal component analysis reduced the number of cognitive outcomes to three factors: n-back working memory, Trail Making test, and Logical Memory. We found a significant interaction between PA and the ratio of omega-6 to omega-3 fatty acid serum levels on Trail Making performance and n-back performance, such that higher amounts of omega-3 levels offset the deleterious effects of lower amounts of PA. These effects remained significant in a subsample (n=299) controlling for overall dietary fat consumption. There were no significant additive or multiplicative benefits of higher amounts of both omega-3 and PA on cognitive performance. Our results demonstrate that a diet high in omega-3 fatty acids might mitigate the effect of lower levels of PA on cognitive performance. This study illuminates the importance of understanding dietary and PA factors in tandem when exploring their effects on neurocognitive health.

Treadmill exercise ameliorates symptoms of attention deficit/hyperactivity disorder through reducing Purkinje cell loss and astrocytic reaction in spontaneous hypertensive rats

Attention deficit/hyperactivity disorder (ADHD) is a neurobehavioral disorder of cognition. We investigated the effects of treadmill exercise on Purkinje cell and astrocytic reaction in the cerebellum of the ADHD rat. Adult male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKYR) weighing 210± 10 g were used. The animals were randomly divided into four groups (n= 15): control group, ADHD group, ADHD and methylphenidate (MPH)-treated group, ADHD and treadmill exercise group. The rats in the MPH-treated group as a positive control received 1 mg/kg MPH orally once a day for 28 consecutive days. The rats in the treadmill exercise group were made to run on a treadmill for 30 min once a day for 28 days. Motor coordination and balance were determined by vertical pole test. Immunohistochemistry for the expression of calbindinD-28 and glial fibrillary acidic protein (GFAP) in the cerebellar vermis and Western blot for GFAP, Bax, and Bcl-2 were conducted. In the present results, ADHD significantly decreased balance and the number of calbindin-positive cells, while GFAP expression and Bax/Bcl-2 ratio in the cerebellum were significantly increased in the ADHD group compared to the control group (P< 0.05, respectively). In contrast, treadmill exercise and MPH alleviated the ADHD-induced the decrease of balance and the number of calbindine-positive cells, and the increase of GFAP expression and Bax/Bcl-2 ratio in the cerebellum (P< 0.05, respectively). Therefore, the present results suggested that treadmill exercise might exert ameliorating effect on ADHD through reduction of Purkinje cell loss and astrocytic reaction in the cerebellum.

The effects of exercise on cognition in Parkinson's disease: a systematic review

Cognitive impairments are highly prevalent in Parkinson’s disease (PD) and can substantially affect a patient’s quality of life. These impairments remain difficult to manage with current clinical therapies, but exercise has been identified as a possible treatment. The objective of this systematic review was to accumulate and analyze evidence for the effects of exercise on cognition in both animal models of PD and human disease. This systematic review was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement. Fourteen original reports were identified, including six pre-clinical animal studies and eight human clinical studies. These studies used various exercise interventions and evaluated many different outcome measures; therefore, only a qualitative synthesis was performed. The evidence from animal studies supports the role of exercise to improve cognition in humans through the promotion of neuronal proliferation, neuroprotection and neurogenesis. These findings warrant more research to determine what roles these neural mechanisms play in clinical populations. The reports on cognitive changes in clinical studies demonstrate that a range of exercise programs can improve cognition in humans. While each clinical study demonstrated improvements in a marker of cognition, there were limitations in each study, including non-randomized designs and risk of bias. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system was used and the quality of the evidence for human studies were rated from “low” to “moderate” and the strength of the recommendations were rated from “weak” to “strong”. Studies that assessed executive function, compared to general cognitive abilities, received a higher GRADE rating. Overall, this systematic review found that in animal models exercise results in behavioral and corresponding neurobiological changes in the basal ganglia related to cognition. The clinical studies showed that various types of exercise, including aerobic, resistance and dance can improve cognitive function, although the optimal type, amount, mechanisms, and duration of exercise are unclear. With growing support for exercise to improve not only motor symptoms, but also cognitive impairments in PD, health care providers and policy makers should recommend exercise as part of routine management and neurorehabilitation for this disorder.

The Effect of Parkinson Drug Timing on Cardiovascular Response during Treadmill Exercise in a Person with Parkinson Disease and Freezing of Gait

PURPOSE

To examine the response of cerebral oxygenation during treadmill walking in a person with Parkinson disease (PD) who experiences freezing of gait (FOG) and to determine whether the oxygen response was related to the timing of his PD medication. Client Description: A 61-year-old man with PD performed two bouts of treadmill testing on the same day, during the on- and off-phases of his PD medication. Measures and Outcome: The client experienced two FOG episodes during the first testing session (on-phase with hypokinetic movement session). Cerebral oxygen response (measured by near-infrared spectroscopy) was stable until the FOG episodes occurred, at which point it decreased until the FOG episode was over. No electrocardiogram (ECG) changes or lightheadedness were noted; blood pressure (BP) remained stable. During the second exercise testing session (off-phase with dyskinetic movement session), the client did not experience any FOG episodes, and his cerebral oxygen response remained stable. Toward the end of the second testing session, he experienced lightheadedness and a drop in BP of approximately 30 mmHg, along with significant ST segment depression on his ECG.

IMPLICATIONS

Haemodynamic and cerebral oxygen changes occurred that were specific to the timing of the client's PD medication and to his FOG episodes. This case study shows a person with PD demonstrating decreased cerebral oxygenation during FOG, which may be based on his variable response to levodopa medication or may be attributable to as yet unidentified physiologic mechanisms.

Treadmill exercise reverses dendritic spine loss in direct and indirect striatal medium spiny neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease

Exercise has been shown to be beneficial for Parkinson's disease (PD). A major interest in our lab has been to investigate how exercise modulates basal ganglia function and modifies disease progression. Dopamine (DA) depletion leads to loss of dendritic spines within the caudate nucleus and putamen (striatum) in PD and its animal models and contributes to motor impairments. Striatal medium spiny neurons (MSNs) can be delineated into two populations, the dopamine D1 receptor (DA-D1R)-containing MSNs of the direct pathway and dopamine D2 receptor (DA-D2R)-containing MSNs of the indirect pathway. There is evidence to suggest that the DA-D2R-indirect pathway MSNs may be preferentially affected after DA-depletion with a predominate loss of dendritic spine density when compared to MSNs of the DA-D1R-direct pathway in rodents; however, others have reported that both pathways may be affected in primates. The purpose of this study was to investigate the effects of intensive exercise on dendritic spine density and arborization in MSNs of these two pathways in the MPTP mouse model of PD. We found that MPTP led to a decrease in dendritic spine density in both DA-D1R- and DA-D2R-containing MSNs and 30 days of intensive treadmill exercise led to increased dendritic spine density and arborization in MSNs of both pathways. In addition, exercise increased the expression of synaptic proteins PSD-95 and synaptophysin. Taken together these findings support the potential effect of exercise in modifying synaptic connectivity within the DA-depleted striatum and in modifying disease progression in individuals with PD.

Functional reorganization of motor and limbic circuits after exercise training in a rat model of bilateral parkinsonism

Exercise training is widely used for neurorehabilitation of Parkinson's disease (PD). However, little is known about the functional reorganization of the injured brain after long-term aerobic exercise. We examined the effects of 4 weeks of forced running wheel exercise in a rat model of dopaminergic deafferentation (bilateral, dorsal striatal 6-hydroxydopamine lesions). One week after training, cerebral perfusion was mapped during treadmill walking or at rest using [(14)C]-iodoantipyrine autoradiography. Regional cerebral blood flow-related tissue radioactivity (rCBF) was analyzed in three-dimensionally reconstructed brains by statistical parametric mapping. In non-exercised rats, lesions resulted in persistent motor deficits. Compared to sham-lesioned rats, lesioned rats showed altered functional brain activation during walking, including: 1. hypoactivation of the striatum and motor cortex; 2. hyperactivation of non-lesioned areas in the basal ganglia-thalamocortical circuit; 3. functional recruitment of the red nucleus, superior colliculus and somatosensory cortex; 4. hyperactivation of the ventrolateral thalamus, cerebellar vermis and deep nuclei, suggesting recruitment of the cerebellar-thalamocortical circuit; 5. hyperactivation of limbic areas (amygdala, hippocampus, ventral striatum, septum, raphe, insula). These findings show remarkable similarities to imaging findings reported in PD patients. Exercise progressively improved motor deficits in lesioned rats, while increasing activation in dorsal striatum and rostral secondary motor cortex, attenuating a hyperemia of the zona incerta and eliciting a functional reorganization of regions participating in the cerebellar-thalamocortical circuit. Both lesions and exercise increased activation in mesolimbic areas (amygdala, hippocampus, ventral striatum, laterodorsal tegmental n., ventral pallidum), as well as in related paralimbic regions (septum, raphe, insula). Exercise, but not lesioning, resulted in decreases in rCBF in the medial prefrontal cortex (cingulate, prelimbic, infralimbic). Our results in this PD rat model uniquely highlight the breadth of functional reorganizations in motor and limbic circuits following lesion and long-term, aerobic exercise, and provide a framework for understanding the neural substrates underlying exercise-based neurorehabilitation.