Identification of a nuclear receptor that is activated by farnesol metabolites

Nuclear hormone receptors comprise a superfamily of ligand-modulated transcription factors that mediate the transcriptional activities of steroids, retinoids, and thyroid hormones. A growing number of related proteins have been identified that possess the structural features of hormone receptors, but that lack known ligands. Known as orphan receptors, these proteins represent targets for novel signaling molecules. We have isolated a mammalian orphan receptor that forms a heterodimeric complex with the retinoid X receptor. A screen of candidate ligands identified farnesol and related metabolites as effective activators of this complex. Farnesol metabolites are generated intracellularly and are required for the synthesis of cholesterol, bile acids, steroids, retinoids, and farnesylated proteins. Intermediary metabolites have been recognized as transcriptional regulators in bacteria and yeast. Our results now suggest that metabolite-controlled intracellular signaling systems are utilized by higher organisms.

Effects of physical activity interventions on cognitive and academic performance in children and adolescents: a novel combination of a systematic review and recommendations from an expert panel

OBJECTIVE

To summarise the current evidence on the effects of physical activity (PA) interventions on cognitive and academic performance in children, and formulate research priorities and recommendations.

DESIGN

Systematic review (following PRISMA guidelines) with a methodological quality assessment and an international expert panel. We based the evaluation of the consistency of the scientific evidence on the findings reported in studies rated as of high methodological quality.

DATA SOURCES

PubMed, PsycINFO, Cochrane Central, Web of Science, ERIC, and SPORTDiscus.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

PA-intervention studies in children with at least one cognitive or academic performance assessment.

RESULTS

Eleven (19%) of 58 included intervention studies received a high-quality rating for methodological quality: four assessed effects of PA interventions on cognitive performance, six assessed effects on academic performance, and one on both. All high-quality studies contrasted the effects of additional/adapted PA activities with regular curriculum activities. For cognitive performance 10 of 21 (48%) constructs analysed showed statistically significant beneficial intervention effects of PA, while for academic performance, 15 of 25 (60%) analyses found a significant beneficial effect of PA. Across all five studies assessing PA effects on mathematics, beneficial effects were reported in six out of seven (86%) outcomes. Experts put forward 46 research questions. The most pressing research priority cluster concerned the causality of the relationship between PA and cognitive/academic performance. The remaining clusters pertained to PA characteristics, moderators and mechanisms governing the 'PA-performance' relationship and miscellaneous topics.

CONCLUSION

There is currently inconclusive evidence for the beneficial effects of PA interventions on cognitive and overall academic performance in children. We conclude that there is strong evidence for beneficial effects of PA on maths performance.The expert panel confirmed that more 'high-quality' research is warranted. By prioritising the most important research questions and formulating recommendations we aim to guide researchers in generating high-quality evidence. Our recommendations focus on adequate control groups and sample size, the use of valid and reliable measurement instruments for physical activity and cognitive performance, measurement of compliance and data analysis.

PROSPERO REGISTRATION NUMBER

CRD42017082505.

Acute, intermediate intensity exercise, and speed and accuracy in working memory tasks: a meta-analytical comparison of effects

The purpose of this study was to compare, using meta-analytic techniques, the effect of acute, intermediate intensity exercise on the speed and accuracy of performance of working memory tasks. It was hypothesized that acute, intermediate intensity exercise would have a significant beneficial effect on response time and that effect sizes for response time and accuracy data would differ significantly. Random-effects meta-analysis showed a significant, beneficial effect size for response time, g=-1.41 (p<0.001) but a significant detrimental effect size, g=0.40 (p<0.01), for accuracy. There was a significant difference between effect sizes (Z(diff)=3.85, p<0.001). It was concluded that acute, intermediate intensity exercise has a strong beneficial effect on speed of response in working memory tasks but a low to moderate, detrimental one on accuracy. There was no support for a speed-accuracy trade-off. It was argued that exercise-induced increases in brain concentrations of catecholamines result in faster processing but increases in neural noise may negatively affect accuracy.

Heat stress, plasma concentrations of adrenaline, noradrenaline, 5-hydroxytryptamine and cortisol, mood state and cognitive performance

The primary aims of this paper were to examine the effect of heat stress on working memory, choice reaction time and mood state, and to investigate the relationship between heat induced changes in plasma concentrations of selected neurotransmitters and hormones, and cognition. Heat stress resulted in a deterioration of performance on a central executive task (random movement generation) but not on verbal and spatial recall, and choice reaction time tasks. Perceptions of vigour decreased and fatigue increased following exposure to heat stress. Plasma concentrations of cortisol and 5-hydroxytryptamine significantly increased following exposure to heat. Regression analyses showed that percent body mass loss and change from baseline (Delta) concentrations of cortisol, post-exposure to heat, were significant predictors of Delta random movement generation and Delta fatigue. A secondary purpose was to examine the effect of recovery on cognition and mood. Following recovery, the performance of the central executive task was poorer than pre-treatment. Mood states, catecholamines and 5-hydroxytryptamine concentrations returned to pre-treatment values, but cortisol fell to a level significantly lower. Regression correlations showed that Delta adrenaline and Delta scores, post-recovery, on the central executive task were significantly correlated. Delta noradrenaline correlated significantly with Delta fatigue. It was concluded that heat stress results in deterioration in the performance of central executive tasks and perceptions of mood state, and that this can be predicted by changes in body mass loss and plasma concentrations of the hormones cortisol and adrenaline.

Phytol metabolites are circulating dietary factors that activate the nuclear receptor RXR

RXR is a nuclear receptor that plays a central role in cell signaling by pairing with a host of other receptors. Previously, 9-cis-retinoic acid (9cRA) was defined as a potent RXR activator. Here we describe a unique RXR effector identified from organic extracts of bovine serum by following RXR-dependent transcriptional activity. Structural analyses of material in active fractions pointed to the saturated diterpenoid phytanic acid, which induced RXR-dependent transcription at concentrations between 4 and 64 microM. Although 200 times more potent than phytanic acid, 9cRA was undetectable in equivalent amounts of extract and cannot be present at a concentration that could account for the activity. Phytanic acid, another phytol metabolite, was synthesized and stimulated RXR with a potency and efficacy similar to phytanic acid. These metabolites specifically displaced [3H]-9cRA from RXR with Ki values of 4 microM, indicating that their transcriptional effects are mediated by direct receptor interactions. Phytol metabolites are compelling candidates for physiological effectors, because their RXR binding affinities and activation potencies match their micromolar circulating concentrations. Given their exclusive dietary origin, these chlorophyll metabolites may represent essential nutrients that coordinate cellular metabolism through RXR-dependent signaling pathways.

Dehydration affects brain structure and function in healthy adolescents

It was recently observed that dehydration causes shrinkage of brain tissue and an associated increase in ventricular volume. Negative effects of dehydration on cognitive performance have been shown in some but not all studies, and it has also been reported that an increased perceived effort may be required following dehydration. However, the effects of dehydration on brain function are unknown. We investigated this question using functional magnetic resonance imaging (fMRI) in 10 healthy adolescents (mean age = 16.8, five females). Each subject completed a thermal exercise protocol and nonthermal exercise control condition in a cross-over repeated measures design. Subjects lost more weight via perspiration in the thermal exercise versus the control condition (P < 0.0001), and lateral ventricle enlargement correlated with the reduction in body mass (r = 0.77, P = 0.01). Dehydration following the thermal exercise protocol led to a significantly stronger increase in fronto-parietal blood-oxygen-level-dependent (BOLD) response during an executive function task (Tower of London) than the control condition, whereas cerebral perfusion during rest was not affected. The increase in BOLD response after dehydration was not paralleled by a change in cognitive performance, suggesting an inefficient use of brain metabolic activity following dehydration. This pattern indicates that participants exerted a higher level of neuronal activity in order to achieve the same performance level. Given the limited availability of brain metabolic resources, these findings suggest that prolonged states of reduced water intake may adversely impact executive functions such as planning and visuo-spatial processing.

The effect of exercise on cognitive performance in soccer-specific tests

Two experiments were carried out to examine the effect of moderate and maximal exercise on the cognitive performance of experienced soccer players. Experiment 1 examined the speed and visual search in familiar (game) and unfamiliar (non-game) contexts. Participants had to detect, as quickly as possible, the presence or absence of a ball in tachistoscopically presented slides. Participants were tested at rest and while exercising at 70 and 100% maximum power output. A main effect of exercise intensity was demonstrated and Tukey post-hoc tests showed that performance during maximal exercise was significantly better than in the other two conditions. We concluded that exercise significantly improves speed of visual search. Experiment 2 examined the effects of exercise on speed of search, speed of decision following ball detection, overall speed of decision and accuracy of decision at rest and while exercising at 70 and 100% maximum power output. A repeated-measures multivariate analysis of variance and Tukey post-hoc tests showed that performance during exercise was significantly better than at rest. Observation of the separate univariate analyses of variance demonstrated that most of the variance could be accounted for by overall speed of decision and speed of decision after ball detection. We concluded that exercise induces not only an improvement in a simple task, like speed of visual search, but also an overall increase in speed of information processing. Theories concerning the effect of emotionally induced arousal on cognitive performance do not accurately predict the effect of physically induced arousal on cognitive tasks.

Effect of creatine supplementation and sleep deprivation, with mild exercise, on cognitive and psychomotor performance, mood state, and plasma concentrations of catecholamines and cortisol

RATIONALE

Sleep deprivation has a negative effect on cognitive and psychomotor performance and mood state, partially due to decreases in creatine levels in the brain. Therefore, creatine supplementation should lessen the negative effects of sleep deprivation.

OBJECTIVES

The objective of this study was to examine the effect of creatine supplementation and sleep deprivation, with mild exercise, on cognitive and psychomotor performance, mood state, and plasma concentrations of catecholamines and cortisol.

METHOD

Subjects were divided into a creatine group (n=10) and a placebo group (n=9). They took 5 g of creatine monohydrate or a placebo, dependent on their group, four times a time a day for 7 days, immediately prior to the experiment. The study was double blind. Subjects undertook tests of random movement generation (RMG), verbal and spatial recall, choice reaction time, static balance and mood state pre-test (0 h), after 6, 12 and 24 h of sleep deprivation, with intermittent exercise. They were tested for plasma concentrations of catecholamines and cortisol at 0 and 24 h.

RESULTS

At 24 h, the creatine group demonstrated significantly less change in performance from 0 h (delta) in RMG, choice reaction time, balance and mood state. There were no significant differences between groups in plasma concentrations of catecholamines and cortisol. Norepinephrine and dopamine concentrations were significantly higher at 24 h than 0 h, but cortisol were lower.

CONCLUSIONS

Following 24-h sleep deprivation, creatine supplementation had a positive effect on mood state and tasks that place a heavy stress on the prefrontal cortex.

Effects of acute dehydration on brain morphology in healthy humans

Dehydration can affect brain structure which has important implications for human health. In this study, we measured regional changes in brain structure following acute dehydration. Healthy volunteers received a structural MRI scan before and after an intensive 90-min thermal-exercise dehydration protocol. We used two techniques to determine changes in brain structure: a manual point counting technique using MEASURE, and a fully automated voxelwise analysis using SIENA. After the exercise regime, participants lost (2.2% +/- 0.5%) of their body mass. Using SIENA, we detected expansion of the ventricular system with the largest change occurring in the left lateral ventricle (P = 0.001 corrected for multiple comparisons) but no change in total brain volume (P = 0.13). Using manual point counting, we could not detect any change in ventricular or brain volume, but there was a significant correlation between loss in body mass and third ventricular volume increase (r = 0.79, P = 0.03). These results show ventricular expansion occurs following acute dehydration, and suggest that automated longitudinal voxelwise analysis methods such as SIENA are more sensitive to regional changes in brain volume over time compared with a manual point counting technique.

Specific effects of acute moderate exercise on cognitive control

The main issue of this study was to determine whether cognitive control is affected by acute moderate exercise. Twelve participants [4 females (VO(2 max)=42 ml/kg/min) and 8 males (VO(2 max) = 48 ml/kg/min)] performed a Simon task while cycling at a carefully controlled workload intensity corresponding to their individual ventilatory threshold. The distribution-analytical technique and the delta plot analysis [Ridderinkhof, K. R. (2002). Activation and suppression in conflict tasks: Empirical clarification through distributional analyses. In W. Prinz & B. Hommel (Eds.), Common mechanisms in perception and action. Attention and performance (Vol. 19, pp. 494-519). Oxford: Oxford University Press.] were used to assess the role of selective response inhibition in resolving response conflict. Results showed that cognitive processes appeared to be differently affected by acute moderate exercise. Reaction time results confirmed that performance is better (faster without change in accuracy) when the cognitive task is performed simultaneously with exercise. Between-trial adjustments (post-conflict and post-error) highlighted that cognitive control adjustments are also fully efficient during exercise. However, the effect of congruency (Simon effect) appeared to be more pronounced during exercise compared to rest which suggests that the response inhibition is deteriorated during exercise. The present findings suggest that acute moderate exercise differently affects some specific aspects of cognitive functions.

Creatine Supplementation and Cognitive Performance in Elderly Individuals

The purpose of this study was to examine the effect of creatine supplementation on the cognitive performance of elderly people. Participants were divided into two groups, which were tested on random number generation, forward and backward number and spatial recall, and long-term memory tasks to establish a baseline level. Group 1 (n = 15) were given 5 g four times a day of placebo for 1 week, followed by the same dosage of creatine for the second week. Group 2 (n = 17) were given placebo both weeks. Participants were retested at the end of each week. Results showed a significant effect of creatine supplementation on all tasks except backward number recall. It was concluded that creatine supplementation aids cognition in the elderly.

Effect of exercise on simple reaction times of recreational athletes

To examine the effect of moderate and fatiguing exercise on the simple reaction times of recreational athletes, 12 subjects took a simple reaction-time test while at rest and while cycling on a Monark cycle ergometer at 70% and 100% of maximum workload. To estimate 70% and 100% of maximum workload the subjects underwent a standard incremental test until exhaustion, defined as subjects being unable to maintain the required pedal rate of 70 rpm. Simple reaction time during maximal exercise was significantly slower than in the other two conditions which did not differ significantly from one another. Heart rate and rate of perceived exertion differed significantly for all three conditions.

Creatine supplementation, sleep deprivation, cortisol, melatonin and behavior

The effect of creatine supplementation and sleep deprivation, with intermittent moderate-intensity exercise, on cognitive and psychomotor performance, mood state, effort and salivary concentrations of cortisol and melatonin were examined. Subjects were divided into a creatine supplementation group and a placebo group. They took 5 g of creatine monohydrate or a placebo, dependent on their group, four times a day for 7 days immediately prior to the experiment. They undertook tests examining central executive functioning, short-term memory, choice reaction time, balance, mood state and effort at baseline and following 18-, 24- and 36-h sleep deprivation, with moderate intermittent exercise. Saliva samples were taken prior to each set of tests. A group x time analysis of covariance, with baseline performance the covariate, showed that the creatine group performed significantly (p < 0.05) better than the placebo group on the central executive task but only at 36 h. The creatine group demonstrated a significant (p < 0.01) linear improvement in performance of the central executive task throughout the experiment, while the placebo group showed no significant effects. There were no significant differences between the groups for any of the other variables. A significant (p < 0.001) main effect of time was found for the balance test with a linear improvement being registered. Cortisol concentrations on Day 1 were significantly (p < 0.01) higher than on Day 2. Mood significantly (p < 0.001) deteriorated up to 24 h with no change from 24 to 36 h. Effort at baseline was significantly (p < 0.01) lower than in the other conditions. It was concluded that, during sleep deprivation with moderate-intensity exercise, creatine supplementation only affects performance of complex central executive tasks.

Exercise, plasma catecholamine concentrations and decision-making performance of soccer players on a soccer-specific test

The main aim of this study was to compare the decision-making performance of college soccer players on a soccer-specific, tachistoscopically presented test, at rest and while exercising at their adrenaline threshold and at their maximum power output. These were determined following an incremental test to exhaustion on a cycle ergometer. After the initial maximum power test, participants (n = 9) were allowed 10 habituation trials on the soccer decision-making test. Participants' decision-making performance was tested at rest, while cycling at a power output that had previously been determined to elicit their adrenaline threshold and while cycling at maximum power output. Accuracy and speed of decision were the dependent variables. A one-way repeated-measures analysis of variance showed no significant effect of exercise on accuracy, and showed speed of decision to be significantly affected by exercise. Tukey post-hoc tests showed that speed of decision at rest was significantly slower than in the other two conditions, which did not differ significantly from one another. Based on allocatable resources theories of arousal and performance, we conclude that the adrenaline threshold may be indicative of increases in the resources available to the individual. Furthermore, we considered that exercise at maximum power output may only induce a moderate rather than a high level of arousal.

Effect of acute exercise on cognitive control required during an Eriksen flanker task

This study aimed to determine how cognitive control, engaged in a task requiring selective inhibition, is affected by acute steady-state exercise. An adapted version of the Eriksen flanker task, involving three types of trials that varied according to their level of congruency (congruent trials, stimulus-incongruent trials, and response-incongruent trials) was performed during 2 periods of 20-min cycling at a carefully controlled intensity (50% of maximal aerobic power). The results indicated that moderate exercise improves reaction time (RT) performance on the Eriksen flanker task. This facilitating effect appeared to be neither dependent on the nature of the interference (stimulus level conflict vs. response level conflict) nor on the amount of cognitive control engaged in the task (congruent vs. incongruent trials). Distributional RT analyses did not highlight any sign of impairment in the efficiency of cognitive control.

Anticipation of Professional Soccer Goalkeepers When Facing Right-and Left-Footed Penalty Kicks

The purpose of this study was to examine the anticipation of professional soccer goalkeepers when facing right- and left-footed penalty kicks. Subjects were shown a videotape of 10 right-footed and 10 left-footed penalty kicks. A standard temporal occlusion paradigm was used, with each penalty being presented at 3 occlusion points, 2 frames before foot-ball contact, at the moment of foot-ball contact, and 2 frames after foot-ball contact. A 2-way (foot X occlusion point) analysis of variance (with repeated measures) indicated that anticipation to right-footed kicks was significantly better than that to left-footed kicks. There were no other significant results. Post hoc interviews indicated that the subjects claimed to use angle of approach to the ball, foot position at contact, and hip position at the time of foot-ball contact as the main cues to aid anticipation.

The acute exercise-cognition interaction: From the catecholamines hypothesis to an interoception model

An interoception model for the acute exercise-cognition interaction is presented. During exercise following the norepinephrine threshold, interoceptive feedback induces increased tonic release of extracellular catecholamines, facilitating phasic release hence better cognitive performance of executive functions. When exercise intensity increases to maximum, the nature of task-induced norepinephrine release from the locus coeruleus is dependent on interaction between motivation, perceived effort costs and perceived availability of resources. This is controlled by interaction between the rostral and dorsolateral prefrontal cortices, orbitofrontal cortex, anterior cingulate cortex and anterior insula cortex. If perceived available resources are sufficient to meet predicted effort costs and reward value is high, tonic release from the locus coeruleus is attenuated thus facilitating phasic release, therefore cognition is not inhibited. However, if perceived available resources are insufficient to meet predicted effort costs or reward value is low, tonic release from the locus coeruleus is induced, attenuating phasic release. As a result, cognition is inhibited, although long-term memory and tasks that require switching to new stimuli-response couplings are probably facilitated.

Does acute exercise affect the performance of whole-body, psychomotor skills in an inverted-U fashion? A meta-analytic investigation

The primary purpose of this study was to examine, using meta-analytical measures, whether research into the performance of whole-body, psychomotor tasks following moderate and heavy exercise demonstrates an inverted-U effect. A secondary purpose was to compare the effects of acute exercise on tasks requiring static maintenance of posture versus dynamic, ballistic skills. Moderate intensity exercise was determined as being between 40% and 79% maximum power output (ẆMAX) or equivalent, while ≥80% ẆMAX was considered to be heavy. There was a significant difference (Zdiff=4.29, p=0.001, R(2)=0.42) between the mean effect size for moderate intensity exercise (g=0.15) and that for heavy exercise size (g=-0.86). These data suggest a catastrophe effect during heavy exercise. Mean effect size for static tasks (g=-1.24) was significantly different (Zdiff=3.24, p=0.001, R(2)=0.90) to those for dynamic/ballistic tasks (g=-0.30). The result for the static versus dynamic tasks moderating variables point to perception being more of an issue than peripheral fatigue for maintenance of static posture. The difference between this result and those found in meta-analyses examining the effects of acute exercise on cognition shows that, when perception and action are combined, the complexity of the interaction induces different effects to when cognition is detached from motor performance.

Incremental Exercise, Plasma Concentrations of Catecholamines, Reaction Time, and Motor Time during Performance of a Noncompatible Choice Response Time Task

The primary purpose was to examine the effect of incremental exercise on a noncompatible response time task. Participants ( N = 9) undertook a 4-choice noncompatible response time task under 3 conditions, following rest and during exercise at 70% and 100% of their maximum power output. Reaction and movement times were the dependent variables. Maximum power output had been previously established on an incremental test to exhaustion. A repeated-measures multivariate analysis of variance yielded a significant effect of exercise intensity on the task, but observation of the separate univariate repeated-measures analyses of variance showed that only movement time was significantly affected. Post hoc Tukey tests indicated movement time during maximal intensity exercise was significantly faster than in the other two conditions. The secondary purpose of the study was to assess whether increases in plasma concentrations of adrenaline and nor-adrenaline during exercise and power output would act as predictor variables of reaction and movement times during exercise. Catecholamine concentrations were based on venous blood samples taken during the maximum power output test. None of the variables were significant predictors of reaction time. Only power output was a significant predictor of movement time ( R2 = .24). There was little support for the notion that peripheral concentrations of catecholamines directly induce a central nervous system response.

Performance of a psychomotor skill following rest, exercise at the plasma epinephrine threshold and maximal intensity exercise

The purpose of this study was to examine the effect of exercising at the epinephrine threshold and at Maximum Power Output on the performance of a skill that requires both decision-making and motor performance. Participants (N=12) undertook an incremental test to exhaustion from which their epinephrine threshold and Maximum Power Output were calculated. They were then examined on a soccer skill test following rest and exercise that was previously determined to elicit their epi nephrine threshold and Maximum Power Output. The soccer test examined the participants' speed and accuracy of response. Speed of response was measured by voice reaction time and whole body reaction time. No significant effects of exercise were shown for any of the variables. The need for further research using more complex skill tests and the use of discontinuous exercise protocols, rather than continuous ones, is recommended.