Hiroshi Mizuma

Antifatigue effects of coenzyme Q10 during physical fatigue.

OBJECTIVE This study examined the effects of coenzyme Q10 administration on physical fatigue. METHODS In a double-blinded, placebo-controlled, three crossover design, 17 healthy volunteers were randomized to oral coenzyme Q10 (100 or 300 mg/d) or placebo administration for 8 d. As a fatigue-inducing physical task, subjects performed workload trials on a bicycle ergometer at fixed workloads twice for 2 h and then rested for 4 h. During the physical tasks, subjects performed non-workload trials with maximum velocity for 10 s at 30 min (30-min trial) after the start of physical tasks and 30 min before the end of the tasks (210-min trial). RESULTS The change in maximum velocity from the 30- to the 210-min trial in the 300-mg coenzyme Q10-administered group was higher than that in the placebo group. In addition, subjective fatigue sensation measured on a visual analog scale in the 300-mg coenzyme Q10-administered group after the fatigue-inducing physical task and recovery period was alleviated when compared with that in the placebo group. CONCLUSION Oral administration of coenzyme Q10 improved subjective fatigue sensation and physical performance during fatigue-inducing workload trials and might prevent unfavorable conditions as a result of physical fatigue.

Mental and physical fatigue-related biochemical alterations.

OBJECTIVE To confirm fatigue-related biochemical alterations, we measured various parameters just before and after relaxation and fatigue-inducing mental or physical sessions. METHODS Fifty-four healthy volunteers were randomized to perform relaxation and fatigue-inducing mental and physical sessions for 4 h in a double-blind, three-crossover design. Before and after each session, subjects were asked to rate their subjective sensations of fatigue, and blood, saliva, and urine samples were taken. RESULTS After the fatigue-inducing mental and physical sessions, subjective scores of fatigue were increased. After the fatigue-inducing mental session, the vanillylmandelic acid level in urine was higher and plasma valine level was lower than after the relaxation session. In contrast, after the fatigue-inducing physical session, serum citric acid, triacylglycerol, free fatty acid, ketone bodies, total carnitine, acylcarnitine, uric acid, creatine kinase, aspartate aminotransferase, lactate dehydrogenase, cortisol, dehydroepiandrosterone, dehydroepiandrosterone sulfate, plasma branched-chain amino acids, transforming growth factor-beta1 and -beta2, white blood cell and neutrophil counts, saliva cortisol and amylase, and urine vanillylmandelic acid levels were higher and serum free carnitine and plasma total amino acids and alanine levels were lower than those after the relaxation session. CONCLUSION Some mental or physical fatigue-related biochemical changes were determined. Various biochemical alterations reflecting homeostatic perturbation and its responses might be shown. We believe that our results contribute to clarifying the mechanism of fatigue, developing evaluation methods, and establishing a basis for treatment.

Human iPS cell-derived dopaminergic neurons function in a primate Parkinson’s disease model

Induced pluripotent stem cells (iPS cells) are a promising source for a cell-based therapy to treat Parkinson’s disease (PD), in which midbrain dopaminergic neurons progressively degenerate. However, long-term analysis of human iPS cell-derived dopaminergic neurons in primate PD models has never been performed to our knowledge. Here we show that human iPS cell-derived dopaminergic progenitor cells survived and functioned as midbrain dopaminergic neurons in a primate model of PD (Macaca fascicularis) treated with the neurotoxin MPTP. Score-based and video-recording analyses revealed an increase in spontaneous movement of the monkeys after transplantation. Histological studies showed that the mature dopaminergic neurons extended dense neurites into the host striatum; this effect was consistent regardless of whether the cells were derived from patients with PD or from healthy individuals. Cells sorted by the floor plate marker CORIN did not form any tumours in the brains for at least two years. Finally, magnetic resonance imaging and positron emission tomography were used to monitor the survival, expansion and function of the grafted cells as well as the immune response in the host brain. Thus, this preclinical study using a primate model indicates that human iPS cell-derived dopaminergic progenitors are clinically applicable for the treatment of patients with PD.

Establishment of In Vivo Brain Imaging Method in Conscious Mice

In vivo imaging, such as PET, requires restriction of body movements and is generally conducted under sedation by anesthetic agents in studies using laboratory animals. Because anesthetics reduce neural activity and metabolism, physiologic neural functions are difficult to assess in animal PET studies. Therefore, use of an appropriate method in conscious animals is important and is a practical requirement for physiologic in vivo brain imaging studies. Here, we established an in vivo imaging system for conscious mice to reveal the physiologic regional cerebral glucose metabolic rate (rCMRglu) with 18F-FDG PET. Methods: We first developed a head holder to enable brain PET of a conscious mouse. To obtain optimal rCMRglu, we examined the effects of physical and psychologic stresses caused by ambient temperature, intravenous injection, and acclimation to the apparatus and immobile state. Finally, quantitative kinetic analysis was performed for rCMRglu based on a 2-tissue-compartment model with an input function of arterial blood sampling under both conscious and anesthetized (1.5% isoflurane) conditions. Results: Increasing the ambient temperature increased uptake of 18F-FDG in the brain significantly while reducing the uptake in skeletal muscle and brown adipose tissue that was caused by shivering. The reduction of brain 18F-FDG uptake caused by tail holding and manual injection was significantly ameliorated by the use of an automated slow injection. Although brain uptake of 18F-FDG varied at the first session of PET, uptake at the second and subsequent sessions was stable, even after long-term acclimation. After these beneficial changes, brain uptake of 18F-FDG improved significantly, to approximately 260% above the preconditioned state, which is comparable with that obtained in mice that have been allowed to move freely about their home cages. Quantitative kinetic analyses revealed that isoflurane anesthesia lowered rCMRglu in the cerebral cortex, striatum, thalamus, and cerebellum by 66%, 59%, 62%, and 22%, respectively, mainly by reducing the k3 value, a rate constant for phosphorylation by hexokinase. Conclusion: To our knowledge, this is the first study to report quantitative kinetic analysis of rCMRglu in mice that have been conscious throughout PET. This investigation will open avenues for research into in vivo functional brain molecular imaging in both normal and genetically manipulated mice.

Imaging Epigenetic Regulation by Histone Deacetylases in the Brain using PET/MRI with 18F-FAHA

Epigenetic modifications mediated by histone deacetylases (HDACs) play important roles in the mechanisms of different neurologic diseases and HDAC inhibitors (HDACIs) have shown promise in therapy. However, pharmacodynamic profiles of many HDACIs in the brain remain largely unknown due to the lack of validated methods for noninvasive imaging of HDAC expression-activity. In this study, dynamic PET/CT imaging was performed in 4 rhesus macaques using [(18)F]FAHA, a novel HDAC substrate, and [(18)F]fluoroacetate, the major radio-metabolite of [(18)F]FAHA, and fused with corresponding MR images of the brain. Quantification of [(18)F]FAHA accumulation in the brain was performed using a customized dual-tracer pharmacokinetic model. Immunohistochemical analyses of brain tissue revealed the heterogeneity of expression of individual HDACs in different brain structures and cell types and confirmed that PET/CT/MRI with [(18)F]FAHA reflects the level of expression-activity of HDAC class IIa enzymes. Furthermore, PET/CT/MRI with [(18)F]FAHA enabled non-invasive, quantitative assessment of pharmacodynamics of HDAC inhibitor SAHA in the brain.

Developmental Changes in P-Glycoprotein Function in the Blood–Brain Barrier of Nonhuman Primates: PET Study with R-11C-Verapamil and 11C-Oseltamivir

P-glycoprotein (P-gp) plays a pivotal role in limiting the penetration of xenobiotic compounds into the brain at the blood–brain barrier (BBB), where its expression increases with maturation in rats. We investigated developmental changes in P-gp function in the BBB of nonhuman primates using PET with R-11C-verapamil, a PET radiotracer useful for evaluating P-gp function. In addition, developmental changes in the brain penetration of 11C-oseltamivir, a substrate for P-gp, was investigated as practical examples. Methods: PET studies in infant (age, 9 mo), adolescent (age, 24–27 mo), and adult (age, 5.6–6.6 y) rhesus monkeys (Macaca mulatta) were performed with R-11C-verapamil and also with 11C-oseltamivir. Arterial blood samples and PET images were obtained at frequent intervals up to 60 min after administration of the PET tracer. Dynamic imaging data were evaluated by integration plots using data collected within the first 2.5 min after tracer administration. Results: R-11C-verapamil rapidly penetrated the brain, whereas the blood concentration of intact R-11C-verapamil decreased rapidly in all subjects. The maximum brain uptake in infant (0.033% ± 0.007% dose/g of brain) and adolescent (0.020% ± 0.002% dose/g) monkeys was 4.1- and 2.5-fold greater, respectively, than uptake in adults (0.0082% ± 0.0007% dose/g). The clearance of brain R-11C-verapamil uptake in adult monkeys was 0.056 ± 0.010 mL/min/g, significantly lower than that in infants (0.11 ± 0.04 mL/min/g) and adolescents (0.075 ± 0.023 mL/min/g). 11C-oseltamivir showed little brain penetration in adult monkeys, with a clearance of R-11C-verapamil uptake of 0.0072 and 0.0079 mL/min/g, slightly lower than that in infant (0.0097 and 0.0104 mL/min/g) and adolescent (0.0097 and 0.0098 mL/min/g) monkeys. Conclusion: These results suggest that P-gp function in the BBB changes with development in rhesus monkeys, and this change may be closely related to the observed difference in drug responses in the brains of children and adult humans.

Mental fatigue-induced decrease in levels of several plasma amino acids

Summary.To investigate the relation between plasma amino acid levels and mental fatigue, we measured the plasma concentrations of 20 amino acids in 9 healthy volunteers before and after a fatigue-inducing mental task session for 8 hr. As fatigue-inducing mental tasks, the subjects performed an advanced trail making test, a Japanese KANA pick up test, and a mirror drawing test. As a control, 8-hr relaxation session was performed in the same subjects at an interval of 4 weeks. Immediately after the fatigue session, the plasma levels of branched-chain amino acids, tyrosine, cysteine, methionine, lysine, and arginine were below those after a relaxation session. The values for other blood parameters including total protein, albumin, glucose, and total cholesterol did not show any differences between the 2 sessions. These results indicate that mental fatigue may be characterized by a decrease in the plasma level of these amino acids.

Daily oral administration of crocetin attenuates physical fatigue in human subjects

This study compared the effects of placebo with a carotenoid compound, crocetin, as well as an antioxidant, ascorbic acid, on physical fatigue in humans. In this double-blind, placebo-controlled, 3-way crossover study, 14 Japanese healthy volunteers (7 men and 7 women) were randomized to oral administration of crocetin (15 mg), ascorbic acid (3,000 mg), or placebo for 8 days. Subjects performed workload tests on a bicycle ergometer at fixed workloads for 120 minutes at 2 times (a total of 240 minutes) as a fatigue-inducing physical task. During the physical task, subjects performed nonworkload tests at maximum velocity (MV) of 10 seconds at 30 minutes (30-minute test) after the start of the physical task and at 30 minutes before the end of the task (210-minute test). The change in MV from the 30- to the 210-minute test was significantly higher in men who received crocetin compared with men who received placebo (P < .05). This effect of crocetin was specific to males. Administration of ascorbic acid did not change in MV from the 30-minute to the 210-minute test on males or females. These results suggest that daily administration of crocetin may attenuate physical fatigue in men.

Molecular imaging reveals unique degenerative changes in experimental glaucoma.

Experimentally induced changes in the central visual pathway were studied by using positron emission tomography in monkeys with unilateral hypertension glaucoma. In 2-[18F]fluoro-2-deoxy-glucose studies, monocular visual stimulation of the affected eye yielded significantly reduced neural responses in the occipital visuocortical areas. The response reduction was limited to the visual cortex ipsilateral to the affected eye, indicating the unique vulnerability of ipsilateral visual cortex in experimental unilateral glaucoma. In addition, in [11C]PK11195 positron emission tomography and immunohistochemical studies, selective accumulation of activated microglia, a sign of neural degeneration, was found bilaterally in lateral geniculate nuclei. The present findings establish the usefulness of noninvasive molecular imaging for early diagnosis of glaucoma by providing a sharper surrogate end point for an early phase of glaucoma.

Thiamine tetrahydrofurfuryl disulfide improves energy metabolism and physical performance during physical-fatigue loading in rats

Impaired energy metabolism is considered a possible cause of fatigue. The thiamine derivative, thiamine tetrahydrofurfuryl disulfide (TTFD), is prescribed and is also an over-the-counter drug for the attenuation of fatigue. It is readily absorbed from the intestinal tract and converted into thiamine pyrophosphate (TPP), which plays an important role as a cofactor for enzymes of metabolic pathways involved in the production of adenosine triphosphate (ATP). We postulated that TTFD has an anti-fatigue effect by improving energy metabolism during physical-fatigue loading. Here, we initially used the forced swimming test to determine whether daily TTFD or thiamine for 5 days has anti-fatigue effects on weight-loaded rats. The swimming duration of TTFD-, but not of thiamine-treated rats, was significantly longer than that of control rats (P < .05). Based on these findings, we examined changes in the levels of thiamine and its phosphate esters in various organs and the effect of TTFD on ATP levels in skeletal muscle after forced swimming, to determine the cellular mechanisms of the anti-fatigue effect of TTFD. Daily TTFD resulted in a characteristic distribution of thiamine and its phosphate esters in rat skeletal muscle, liver, kidney, heart, brain, and plasma. Furthermore, daily TTFD attenuated the decrease in ATP content in the skeletal muscle caused by forced swimming with a weight load for a defined period (150 s). These results indicate that TTFD exerts anti-fatigue effects by improving energy metabolism during physical fatigue.