Neurobiological markers of exercise-related brain plasticity in older adults

Lactate transport and signaling in the brain: potential therapeutic targets and roles in body-brain interaction

Lactate acts as a 'buffer' between glycolysis and oxidative metabolism. In addition to being exchanged as a fuel by the monocarboxylate transporters (MCTs) between cells and tissues with different glycolytic and oxidative rates, lactate may be a 'volume transmitter' of brain signals. According to some, lactate is a preferred fuel for brain metabolism. Immediately after brain activation, the rate of glycolysis exceeds oxidation, leading to net production of lactate. At physical rest, there is a net efflux of lactate from the brain into the blood stream. But when blood lactate levels rise, such as in physical exercise, there is net influx of lactate from blood to brain, where the lactate is used for energy production and myelin formation. Lactate binds to the lactate receptor GPR81 aka hydroxycarboxylic acid receptor (HCAR1) on brain cells and cerebral blood vessels, and regulates the levels of cAMP. The localization and function of HCAR1 and the three MCTs (MCT1, MCT2, and MCT4) expressed in brain constitute the focus of this review. They are possible targets for new therapeutic drugs and interventions. The author proposes that lactate actions in the brain through MCTs and the lactate receptor underlie part of the favorable effects on the brain resulting from physical exercise.

Age related vascular endothelial function following lifelong sedentariness: positive impact of cardiovascular conditioning without further improvement following low frequency high intensity interval training

Aging is associated with diffuse impairments in vascular endothelial function and traditional aerobic exercise is known to ameliorate these changes. High intensity interval training (HIIT) is effective at improving vascular function in aging men with existing disease, but its effectiveness remains to be demonstrated in otherwise healthy sedentary aging. However, the frequency of commonly used HIIT protocols may be poorly tolerated in older cohorts. Therefore, the present study investigated the effectiveness of lower frequency HIIT (L_fHIIT) on vascular function in a cohort of lifelong sedentary (SED; n =22, age 62.7 ± 5.2 years) men compared with a positive control group of lifelong exercisers (LEX; n = 17, age 61.1 ± 5.4 years). The study consisted of three assessment phases; enrolment to the study (Phase A), following 6 weeks of conditioning exercise in SED (Phase B) and following 6 weeks of low frequency HIIT in both SED and LEX (L_fHIIT; Phase C). Conditioning exercise improved FMD in SED (3.4 ± 1.5% to 4.9 ± 1.1%; P <0.01) such that the difference between groups on enrolment (3.4 ± 1.5% vs. 5.3 ± 1.4%; P <0.01) was abrogated. This was maintained but not further improved following L_fHIIT in SED whilst FMD remained unaffected by L_fHIIT in LEX. In conclusion, L_fHIIT is effective at maintaining improvements in vascular function achieved during conditioning exercise in SED. L_fHIIT is a well‐tolerated and effective exercise mode for reducing cardiovascular risk and maintaining but does not improve vascular function beyond that achieved by conditioning exercise in aging men, irrespective of fitness level.

The effects of low frequency high intensity interval training (HIIT) on vascular endothelial function in lifelong sedentary men remains currently unknown. The present study examined the impact of low frequency HIIT following conditioning exercise on low determinants of vascular endothelial function and angiogenic biomarkers in aging men compared with a positive control group of similarly aged. The major findings of this study indicate that low frequency HIIT is a well‐tolerated and effective exercise mode for reducing cardiovascular risk and maintaining but not improving endothelial function beyond that achieved by conditioning exercise in aging men, irrespective of fitness level.

A meta-analytic review of the effects of exercise on brain-derived neurotrophic factor

Consistent evidence indicates that exercise improves cognition and mood, with preliminary evidence suggesting that brain-derived neurotrophic factor (BDNF) may mediate these effects. The aim of the current meta-analysis was to provide an estimate of the strength of the association between exercise and increased BDNF levels in humans across multiple exercise paradigms. We conducted a meta-analysis of 29 studies (N = 1111 participants) examining the effect of exercise on BDNF levels in three exercise paradigms: (1) a single session of exercise, (2) a session of exercise following a program of regular exercise, and (3) resting BDNF levels following a program of regular exercise. Moderators of this effect were also examined. Results demonstrated a moderate effect size for increases in BDNF following a single session of exercise (Hedges' g = 0.46, p < 0.001). Further, regular exercise intensified the effect of a session of exercise on BDNF levels (Hedges' g = 0.59, p = 0.02). Finally, results indicated a small effect of regular exercise on resting BDNF levels (Hedges' g = 0.27, p = 0.005). When analyzing results across paradigms, sex significantly moderated the effect of exercise on BDNF levels, such that studies with more women showed less BDNF change resulting from exercise. Effect size analysis supports the role of exercise as a strategy for enhancing BDNF activity in humans, but indicates that the magnitude of these effects may be lower in females relative to males.

BDNF mediates improvements in executive function following a 1-year exercise intervention

Executive function declines with age, but engaging in aerobic exercise may attenuate decline. One mechanism by which aerobic exercise may preserve executive function is through the up-regulation of brain-derived neurotropic factor (BDNF), which also declines with age. The present study examined BDNF as a mediator of the effects of a 1-year walking intervention on executive function in 90 older adults (mean age = 66.82). Participants were randomized to a stretching and toning control group or a moderate intensity walking intervention group. BDNF serum levels and performance on a task-switching paradigm were collected at baseline and follow-up. We found that age moderated the effect of intervention group on changes in BDNF levels, with those in the highest age quartile showing the greatest increase in BDNF after 1-year of moderate intensity walking exercise (p = 0.036). The mediation analyses revealed that BDNF mediated the effect of the intervention on task-switch accuracy, but did so as a function of age, such that exercise-induced changes in BDNF mediated the effect of exercise on task-switch performance only for individuals over the age of 71. These results demonstrate that both age and BDNF serum levels are important factors to consider when investigating the mechanisms by which exercise interventions influence cognitive outcomes, particularly in elderly populations.

Cytogenesis in the adult monkey motor cortex: perivascular NG2 cells are the major adult born cell type

We used confocal microscopy and immunohistochemistry (IHC) to look for new cells in the motor cortex of adult macaque monkeys that might form the cellular bases of improved brain function from exercise. Twenty-four female Macaca fascicularis monkeys divided into groups by age (10–12 years, 15–17 years), postexercise survival periods, and controls, received 10 weekly injections of the thymidine analog, bromodeoxyuridine (BrdU) to mark new cells. Sixteen monkeys survived 15 weeks (5 weeks postexercise) and 8 monkeys survived 27 weeks (12 weeks postexercise) after initial BrdU injections. Additionally, five Macaca mulatta female monkeys (∼5.5–7 years) received single injections of BrdU and survived 2 days, 2 weeks, and 6 weeks after BrdU injections. Neural and glial antibodies were used to identify new cell phenotypes and to look for changes in proportions of these cells with respect to time and experimental conditions. No BrdU⁺/DCx⁺ cells were found but about 7.5% of new cells were calretinin-positive (Cr⁺). BrdU⁺/GABA⁺ (gamma-aminobutyric acid) cells were also found but no new Cr⁺ or GABA⁺ cells colabeled with a mature neuron marker, NeuN or chondroitin sulfate antibody, NG2. The proportion of new cells that were NG2⁺ was about 85% for short and long survival monkeys of which two, newly described perivascular phenotypes (Pldv and Elu) and a small percentage of pericytes (2.5%) comprised 44% and 51% of the new NG2⁺ cells, respectively. Proportions of NG2⁺ phenotypes were affected by post-BrdU survival periods, monkey age, and possibly a postexercise sedentary period but no direct effect of exercise was found.

Biological mechanisms underlying the role of physical fitness in health and resilience

Physical fitness, achieved through regular exercise and/or spontaneous physical activity, confers resilience by inducing positive psychological and physiological benefits, blunting stress reactivity, protecting against potentially adverse behavioural and metabolic consequences of stressful events and preventing many chronic diseases. In this review, we discuss the biological mechanisms underlying the beneficial effects of physical fitness on mental and physical health. Physical fitness appears to buffer against stress-related disease owing to its blunting/optimizing effects on hormonal stress responsive systems, such as the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. This blunting appears to contribute to reduced emotional, physiological and metabolic reactivity as well as increased positive mood and well-being. Another mechanism whereby regular exercise and/or physical fitness may confer resilience is through minimizing excessive inflammation. Chronic psychological stress, physical inactivity and abdominal adiposity have been associated with persistent, systemic, low-grade inflammation and exert adverse effects on mental and physical health. The anti-inflammatory effects of regular exercise/activity can promote behavioural and metabolic resilience, and protect against various chronic diseases associated with systemic inflammation. Moreover, exercise may benefit the brain by enhancing growth factor expression and neural plasticity, thereby contributing to improved mood and cognition. In summary, the mechanisms whereby physical fitness promotes increased resilience and well-being and positive psychological and physical health are diverse and complex.

Plasticity of brain and cognition in older adults

Aging is typically related to changes in brain and cognition, but the aging process is heterogeneous and differs between individuals. Recent research has started investigating the influence of cognitive and physical training on cognitive performance, functional brain activity, and brain structure in old age. The functional relevance of neural changes and the interactions among these changes following interventions is still a matter of debate. Here we selectively review research on structural and functional brain correlates of training-induced performance changes in healthy older adults and present exemplary longitudinal intervention studies sorted by the type of training applied (i.e., strategy-based training, process-specific training, and physical exercise). Although many training studies have been conducted recently, within each task domain, the number of studies that used comparable methods and techniques to assess behavioral and neural changes is limited. We suggest that future studies should include a multimodal approach to enhance the understanding of the relation between different levels of brain changes in aging and those changes that result from training. Investigating inter-individual differences in intervention-induced behavioral and neuronal changes would provide more information about who would benefit from a specific intervention and why. In addition, a more systematic examination of the time course of training-related structural and functional changes would improve the current level of knowledge about how learning is implemented in the brain and facilitate our understanding of contradictory results.

Physical activity and cardiorespiratory fitness are beneficial for white matter in low-fit older adults

Physical activity (PA) and cardiorespiratory fitness (CRF) are associated with better cognitive function in late life, but the neural correlates for these relationships are unclear. To study these correlates, we examined the association of both PA and CRF with measures of white matter (WM) integrity in 88 healthy low-fit adults (age 60–78). Using accelerometry, we objectively measured sedentary behavior, light PA, and moderate to vigorous PA (MV-PA) over a week. We showed that greater MV-PA was related to lower volume of WM lesions. The association between PA and WM microstructural integrity (measured with diffusion tensor imaging) was region-specific: light PA was related to temporal WM, while sedentary behavior was associated with lower integrity in the parahippocampal WM. Our findings highlight that engaging in PA of various intensity in parallel with avoiding sedentariness are important in maintaining WM health in older age, supporting public health recommendations that emphasize the importance of active lifestyle.

The effect of exercise on hippocampal volume and neurotrophines in patients with major depression--a randomized clinical trial

BACKGROUND

The hippocampal volume is reduced in patients with major depression. Exercise leads to an increased hippocampal volume in schizophrenia and in healthy old adults. The effect of exercise on hippocampal volume is potentially mediated by brain derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and insulin like growth factor 1 (IGF-1). The aim of this trial was to assess the effect of an aerobic exercise intervention on hippocampal volume and serum BDNF, VEGF, and IGF-1 in patients with major depression.

METHODS

Patients were randomized to an aerobic exercise intervention (n=41) or a control condition (n=38). Both interventions consisted of three supervised sessions per week during a three months period.

RESULTS

Post-intervention the increase in maximal oxygen uptake was 3.90 ml/kg/min (SD 5.1) in the aerobic exercise group and 0.95 ml/kg/min (SD 6.2) in the control group (p=0.03). The hippocampal volume, BDNF, VEGF, or IGF-1 did not differ between the two groups. Post-hoc we found a positive association between change in hippocampal volume and verbal memory (Rho=0.27; p=0.05) and change in hippocampal volume and depressive symptoms (Rho=0.30; p=0.03).

LIMITATIONS

Participation was low in both groups corresponding to an average participation of one session per week.

CONCLUSION

Despite a significant increase in maximal oxygen uptake, a pragmatic exercise intervention did not increase hippocampal volume or resting levels of neurotrophines in out-patients with mild to moderate major depression. Trial identifier: ClinicalTrials.gov (NCT00695552).

Physical activity level and medial temporal health in youth at ultra high-risk for psychosis

A growing body of evidence suggests that moderate to vigorous activity levels can affect quality of life, cognition, and brain structure in patients diagnosed with schizophrenia. However, physical activity has not been systematically studied during the period immediately preceding the onset of psychosis. Given reports of exercise-based neurogenesis in schizophrenia, understanding naturalistic physical activity levels in the prodrome may provide valuable information for early intervention efforts. The present study examined 29 ultra high-risk (UHR) and 27 matched controls to determine relationships between physical activity level, brain structure (hippocampus and parahippocampal gyrus), and symptoms. Participants were assessed with actigraphy for a 5-day period, MRI, and structured clinical interviews. UHR participants showed a greater percentage of time in sedentary behavior while healthy controls spent more time engaged in light to vigorous activity. There was a strong trend to suggest the UHR group showed less total physical activity. The UHR group exhibited smaller medial temporal volumes when compared with healthy controls. Total level of physical activity in the UHR group was moderately correlated with parahippocampal gyri bilaterally (right: r = .44, left: r = .55) and with occupational functioning (r = -.36; of negative symptom domain), but not positive symptomatology. Results suggest that inactivity is associated with medial temporal lobe health. Future studies are needed to determine if symptoms are driving inactivity, which in turn may be affecting the health of the parahippocampal structure and progression of illness. Although causality cannot be determined from the present design, these findings hold important implications for etiological conceptions and suggest promise for an experimental trial.

The effects of poststroke aerobic exercise on neuroplasticity: a systematic review of animal and clinical studies

Aerobic exercise may be a catalyst to promote neuroplasticity and recovery following stroke; however, the optimal methods to measure neuroplasticity and the effects of training parameters have not been fully elucidated. We conducted a systematic review and synthesis of clinical trials and studies in animal models to determine (1) the extent to which aerobic exercise influences poststroke markers of neuroplasticity, (2) the optimal parameters of exercise required to induce beneficial effects, and (3) consistent outcomes in animal models that could help inform the design of future trials. Synthesized findings show that forced exercise at moderate to high intensity increases brain-derived neurotrophic factor (BDNF), insulin-like growth factor-I (IGF-I), nerve growth factor (NGF), and synaptogenesis in multiple brain regions. Dendritic branching was most responsive to moderate rather than intense training. Disparity between clinical stroke and stroke models (timing of initiation of exercise, age, gender) and clinically viable methods to measure neuroplasticity are some of the areas that should be addressed in future research.

The effects of chronic exercise on attentional networks

The aim of this study was to test the hypothesis that chronic physical exercise improves attentional control in young healthy participants. To do this, we compared the performance of physically active and passive participants in the Attentional Network Task, which allows for the assessment of the executive, orienting and alerting networks. The results showed a selective positive effect of exercise on the executive network. These results extend the evidence gathered in children, older adults and certain clinical populations suggesting that exercise can also improve attentional control in healthy young adults.

Effects of diet on brain plasticity in animal and human studies: mind the gap

Dietary interventions have emerged as effective environmental inducers of brain plasticity. Among these dietary interventions, we here highlight the impact of caloric restriction (CR: a consistent reduction of total daily food intake), intermittent fasting (IF, every-other-day feeding), and diet supplementation with polyphenols and polyunsaturated fatty acids (PUFAs) on markers of brain plasticity in animal studies. Moreover, we also discuss epidemiological and intervention studies reporting the effects of CR, IF and dietary polyphenols and PUFAs on learning, memory, and mood. In particular, we evaluate the gap in mechanistic understanding between recent findings from animal studies and those human studies reporting that these dietary factors can benefit cognition, mood, and anxiety, aging, and Alzheimer's disease-with focus on the enhancement of structural and functional plasticity markers in the hippocampus, such as increased expression of neurotrophic factors, synaptic function and adult neurogenesis. Lastly, we discuss some of the obstacles to harnessing the promising effects of diet on brain plasticity in animal studies into effective recommendations and interventions to promote healthy brain function in humans. Together, these data reinforce the important translational concept that diet, a modifiable lifestyle factor, holds the ability to modulate brain health and function.

Physical exercise and vascular endothelial growth factor (VEGF) in elderly: A systematic review

The aim of this study was to conduct a systematic review of studies that verified the effects of physical exercise on vascular endothelial growth factor (VEGF) in elderly.

METHODOLOGY

The bibliographic search was conducted in five database, from 1990 to 2013, with the following keywords and boolean operators: physical exercise OR physical exercise OR physical therapy OR exercise OR training AND VEGF OR vascular endothelial growth factor AND aged OR older OR elderly. The inclusion criteria were: (1) sample including elderly with average age of 60; (2) studies that verified the effects of acute exercise; (3) studies that verified the effects of chronic physical exercise; (4) studies with humans; (5) randomized controlled trials, randomized non-controlled trials, non-randomized controlled trials, non-randomized and non-controlled trials; (6) assessment of VEGF peripheral concentrations.

RESULTS

Ten studies were selected, and that four of them verified an increase of VEGF concentrations after practicing physical exercise and six studies did not verify any change on VEGF concentrations.

CONCLUSION

Different populations found in this study and the different exercise protocols applied in the studies of this review make it difficult to establish parameters of what would be the best type of exercise to promote an increase on the concentrations of VEGF in the elderly. Therefore, we suggest that further studies can be performed, so that we can establish some recommendations for this population.

Physical exercise-induced adult neurogenesis: a good strategy to prevent cognitive decline in neurodegenerative diseases?

Cumulative evidence has indicated that there is an important role for adult hippocampal neurogenesis in cognitive function. With the increasing prevalence of cognitive decline associated with neurodegenerative diseases among the ageing population, physical exercise, a potent enhancer of adult hippocampal neurogenesis, has emerged as a potential preventative strategy/treatment to reduce cognitive decline. Here we review the functional role of adult hippocampal neurogenesis in learning and memory, and how this form of structural plasticity is altered in neurodegenerative diseases known to involve cognitive impairment. We further discuss how physical exercise may contribute to cognitive improvement in the ageing brain by preserving adult neurogenesis, and review the recent approaches for measuring changes in neurogenesis in the live human brain.

Chronic exercise keeps working memory and inhibitory capacities fit

Padilla et al. (2013) recently showed that chronic aerobic exercise in young adults is associated with better inhibitory control as measured by the strategic Stop Signal Task (SST). The aim of the current study was to explore whether better inhibitory abilities, associated with high levels of physical fitness, were also associated with higher working memory capacity (WMC) in young healthy adults. Participants aged between 18 and 30 years and showing different levels of fitness confirmed by the Rockport 1-mile walking fitness test took part in this study. Active and passive participants were administered the SST to measure inhibitory control, and the Automatic Operation Span (AOSPAN) to measure verbal WMC. We first replicated Padilla et al.'s results showing that exercise specifically modulates strategic inhibitory processes. Our results also showed that active participants presented with better WMC than sedentary ones, showing a better capacity to manage simultaneously two verbal tasks and to inhibit interference. The results point to an association between chronic exercise, inhibitory abilities, and WMC. The theoretical relationship between these variables will be discussed.

Brain plasticity and motor practice in cognitive aging

For more than two decades, there have been extensive studies of experience-based neural plasticity exploring effective applications of brain plasticity for cognitive and motor development. Research suggests that human brains continuously undergo structural reorganization and functional changes in response to stimulations or training. From a developmental point of view, the assumption of lifespan brain plasticity has been extended to older adults in terms of the benefits of cognitive training and physical therapy. To summarize recent developments, first, we introduce the concept of neural plasticity from a developmental perspective. Secondly, we note that motor learning often refers to deliberate practice and the resulting performance enhancement and adaptability. We discuss the close interplay between neural plasticity, motor learning and cognitive aging. Thirdly, we review research on motor skill acquisition in older adults with, and without, impairments relative to aging-related cognitive decline. Finally, to enhance future research and application, we highlight the implications of neural plasticity in skills learning and cognitive rehabilitation for the aging population.

A healthy brain in a healthy body: brain network correlates of physical and mental fitness

A healthy lifestyle is an important focus in today's society. The physical benefits of regular exercise are abundantly clear, but physical fitness is also associated with better cognitive performance. How these two factors together relate to characteristics of the brain is still incompletely understood. By applying mathematical concepts from 'network theory', insights in the organization and dynamics of brain functioning can be obtained. We test the hypothesis that neural network organization mediates the association between cardio respiratory fitness (i.e. VO₂ max) and cognitive functioning. A healthy cohort was studied (n = 219, 113 women, age range 41-44 years). Subjects underwent resting-state eyes-closed magneto-encephalography (MEG). Five artifact-free epochs were analyzed and averaged in six frequency bands (delta-gamma). The phase lag index (PLI) was used as a measure of functional connectivity between all sensors. Modularity analysis was performed, and both within and between-module connectivity of each sensor was calculated. Subjects underwent a maximum oxygen uptake (VO₂ max) measurement as an indicator of cardio respiratory fitness. All subjects were tested with a commonly used Dutch intelligence test. Intelligence quotient (IQ) was related to VO₂ max. In addition, VO₂ max was negatively associated with upper alpha and beta band modularity. Particularly increased intermodular connectivity in the beta band was associated with higher VO₂ max and IQ, further indicating a benefit of more global network integration as opposed to local connections. Within-module connectivity showed a spatially varied pattern of correlation, while average connectivity did not show significant results. Mediation analysis was not significant. The occurrence of less modularity in the resting-state is associated with better cardio respiratory fitness, while having increased intermodular connectivity, as opposed to within-module connections, is related to better physical and mental fitness.

Strength training reduces circulating interleukin-6 but not brain-derived neurotrophic factor in community-dwelling elderly individuals

Ageing is associated with a chronic low-grade inflammatory profile (CLIP). Physical exercise could circumvent the deleterious effects of CLIP by influencing circulating inflammatory mediators and neurotrophic growth factors. This study aimed at assessing whether 12 weeks of progressive strength training (PST) influences circulating brain-derived neurotrophic factor (BDNF), interleukin (IL)-6 and IL-10 in elderly individuals. Forty community-dwelling persons aged 62-72 years participated. Twenty participants were assigned to 12-week PST (70-80 % of maximal strength, three times per week). Matched control individuals (n = 20) maintained daily activity levels. Serum was collected for BDNF, IL-6 and IL-10 assay from all participants before and after 12 weeks (for PST subjects 24-48 h after the last training). In PST, muscle strength was significantly improved (+49 % for leg extension, p = 0.039), and basal IL-6 levels significantly reduced (p = 0.001), which remained unchanged in control (p = 0.117). No significant change in BDNF was observed in PST subjects (p = 0.147) or control (p = 0.563). IL-10 was below the detection limit in most subjects. Gender and health status did not influence the results. Our results show that after 12-week PST, muscle performance improved significantly, and basal levels of IL-6 were significantly decreased in older subjects. However, serum BDNF was not altered. The lack of an observable change in BDNF might be due to a short-lived BDNF response, occurring acutely following exercise, which might have been washed out when sampling. Furthermore, blood levels of BDNF may not reflect parallel increases that occur locally in the brain and muscle. These hypotheses need confirmation by further studies.

Metabolic syndrome and colorectal cancer: is hyperinsulinemia/insulin receptor-mediated angiogenesis a critical process?

OBJECTIVE

Components of metabolic syndrome (MS) have been individually linked to colorectal cancer risk and prognosis; however, an understanding of the dominant mechanisms is lacking.

MATERIALS AND METHODS

Twenty-one patients (10 MS; 11 non-MS) with resectable colorectal cancer were prospectively enrolled. Patients were classified for MS by the World Health Organization criteria and tested for circulating vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), insulin-like growth factor-1 (IGF-1), fasting insulin, and tumor expression of IGF-1 receptor (IGF-1R), insulin-receptor (IR) and receptor for advanced glycation end-products (RAGE). Circulating markers were re-tested 6 months after surgery.

RESULTS

The MS group had significantly higher baseline and post-operative fasting insulin levels (p < 0.001 and 0.003). No differences were observed in circulating IL-6, VEGF, IGF-1 and free IGF-1. By immunohistochemistry (IHC), IGF-1R expression was significantly higher in tumor vs. normal tissues (p < 0.001) while IR expression showed no difference. Interestingly, 64% of tumors demonstrated high IR positivity in the vessels within or surrounding the tumor stroma, but not in the vessels away from the tumor. By reverse transcription polymerase chain reaction (RT-PCR), tumor IGF-1R over-expression (80%) was confirmed, but there was no difference between MS and non-MS patients. Tumor RAGE over-expression was found in 67% of patients and was equally distributed between the two groups.

CONCLUSIONS

Hyperinsulinemia was the only significant factor distinguishing patients with colorectal cancer who have MS. The preferential over-expression of IR in the peri-tumoral microvessels suggests that hyperinsulinemia might contribute to colorectal cancer growth by enhancing angiogenesis.

Physical exercise and cognitive performance in the elderly: current perspectives

In an aging population with increasing incidence of dementia and cognitive impairment, strategies are needed to slow age-related decline and reduce disease-related cognitive impairment in older adults. Physical exercise that targets modifiable risk factors and neuroprotective mechanisms may reduce declines in cognitive performance attributed to the normal aging process and protect against changes related to neurodegenerative diseases such as Alzheimer’s disease and other types of dementia. In this review we summarize the role of exercise in neuroprotection and cognitive performance, and provide information related to implementation of physical exercise programs for older adults. Evidence from both animal and human studies supports the role of physical exercise in modifying metabolic, structural, and functional dimensions of the brain and preserving cognitive performance in older adults. The results of observational studies support a dose-dependent neuroprotective relationship between physical exercise and cognitive performance in older adults. Although some clinical trials of exercise interventions demonstrate positive effects of exercise on cognitive performance, other trials show minimal to no effect. Although further research is needed, physical exercise interventions aimed at improving brain health through neuroprotective mechanisms show promise for preserving cognitive performance. Exercise programs that are structured, individualized, higher intensity, longer duration, and multicomponent show promise for preserving cognitive performance in older adults.

Associations between level and change in physical function and brain volumes

BACKGROUND

Higher levels of fitness or physical function are positively associated with cognitive outcomes but the potential underlying mechanisms via brain structure are still to be elucidated in detail. We examined associations between brain structure and physical function (contemporaneous and change over the previous three years) in community-dwelling older adults.

METHODOLOGY/PRINCIPAL FINDINGS

Participants from the Lothian Birth Cohort 1936 (N=694) underwent brain MRI at age 73 years to assess intracranial volume, and the volumes of total brain tissue, ventricles, grey matter, normal-appearing white matter, and white matter lesions. At ages 70 and 73, physical function was assessed by 6-meter walk, grip strength, and forced expiratory volume. A summary 'physical function factor' was derived from the individual measures using principal components analysis. Performance on each individual physical function measure declined across the three year interval (p<0.001). Higher level of physical function at ages 70 and 73 was associated with larger total brain tissue and white matter volumes, and smaller ventricular and white matter lesion volumes (standardized β ranged in magnitude from 0.07 to 0.17, p<0.001 to 0.034). Decline in physical function from age 70 to 73 was associated with smaller white matter volume (0.08, p<0.01, though not after correction for multiple testing), but not with any other brain volumetric measurements.

CONCLUSIONS/SIGNIFICANCE

Physical function was related to brain volumes in community-dwelling older adults: declining physical function was associated with less white matter tissue. Further study is required to explore the detailed mechanisms through which physical function might influence brain structure, and vice versa.

The interplay of stress and sleep impacts BDNF level

Background

Sleep plays a pivotal role in normal biological functions. Sleep loss results in higher stress vulnerability and is often found in mental disorders. There is evidence that brain-derived neurotrophic factor (BDNF) could be a central player in this relationship. Recently, we could demonstrate that subjects suffering from current symptoms of insomnia exhibited significantly decreased serum BDNF levels compared with sleep-healthy controls. In accordance with the paradigm indicating a link between sleep and BDNF, we aimed to investigate if the stress system influences the association between sleep and BDNF.

Methodology/Principal Findings

Participants with current symptoms of insomnia plus a former diagnosis of Restless Legs Syndrome (RLS) and/or Periodic Limb Movement (PLM) and sleep healthy controls were included in the study. They completed questionnaires on sleep (ISI, Insomnia Severity Index) and stress (PSS, Perceived Stress Scale) and provided a blood sample for determination of serum BDNF. We found a significant interaction between stress and insomnia with an impact on serum BDNF levels. Moreover, insomnia severity groups and score on the PSS each revealed a significant main effect on serum BDNF levels. Insomnia severity was associated with increased stress experience affecting serum BDNF levels. Of note, the association between stress and BDNF was only observed in subjects without insomnia. Using a mediation model, sleep was revealed as a mediator of the association between stress experience and serum BDNF levels.

Conclusions

This is the first study to show that the interplay between stress and sleep impacts BDNF levels, suggesting an important role of this relationship in the pathogenesis of stress-associated mental disorders. Hence, we suggest sleep as a key mediator at the connection between stress and BDNF. Whether sleep is maintained or disturbed might explain why some individuals are able to handle a certain stress load while others develop a mental disorder.

Bridging animal and human models of exercise-induced brain plasticity

Significant progress has been made in understanding the neurobiological mechanisms through which exercise protects and restores the brain. In this feature review, we integrate animal and human research, examining physical activity effects across multiple levels of description (neurons up to inter-regional pathways). We evaluate the influence of exercise on hippocampal structure and function, addressing common themes such as spatial memory and pattern separation, brain structure and plasticity, neurotrophic factors, and vasculature. Areas of research focused more within species, such as hippocampal neurogenesis in rodents, also provide crucial insight into the protective role of physical activity. Overall, converging evidence suggests exercise benefits brain function and cognition across the mammalian lifespan, which may translate into reduced risk for Alzheimer's disease (AD) in humans.

Alzheimer's disease clinical and research update for health care practitioners

Of the approximately 6.8 million Americans who have been diagnosed with dementia, over 5 million have been diagnosed with Alzheimer's Disease (AD). Due to the rise in the aging population, these figures are expected to double by 2050. The following paper provides an up-to-date review of clinical issues and relevant research. Research related to the methods of the earliest possible detection of AD is ongoing. Health care professionals should play a critical role in differentially diagnosing AD patients, as well as supporting their families. Novel interventions, including medications, natural supplements, and behavioral techniques, are constantly appearing in the literature. It is necessary for the health practitioner to remain current, regarding AD, as such information will facilitate better care for patients and their families.

Sleep and immune function: glial contributions and consequences of aging

The reciprocal interactions between sleep and immune function are well-studied. Insufficient sleep induces innate immune responses as evidenced by increased expression of pro-inflammatory mediators in the brain and periphery. Conversely, immune challenges upregulate immunomodulator expression, which alters central nervous system-mediated processes and behaviors, including sleep. Recent studies indicate that glial cells, namely microglia and astrocytes, are active contributors to sleep and immune system interactions. Evidence suggests glial regulation of these interactions is mediated, in part, by adenosine and adenosine 5'-triphosphate actions at purinergic type 1 and type 2 receptors. Furthermore, microglia and astrocytes may modulate declines in sleep-wake behavior and immunity observed in aging.