Hikaru Koizumi

Mr. Hikaru Koizumi

orcid

Research Focus & Metrics

Academic Career Length

9Years (2018-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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13 May 2019 in Proceedings of the National Academy of Sciences
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Journal Article
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JYJang Soo Yook
Jang Soo Yook
RRRandeep Rakwal
Randeep Rakwal
JSJunko Shibato
Junko Shibato
KTKanako Takahashi
Kanako Takahashi
HKHikaru Koizumi
Hikaru Koizumi
HSHideaki Soya
Hideaki Soya
Significance: Leptin (LEP), produced and acting in the hippocampus, mediates enhancement by mild exercise (ME) of hippocampus-related memory and neurogenesis, which are further increased by an antioxidant carotenoid, astaxanthin (AX). Both are facilitated by the administration of ME or AX alone. The up-regulation of the LEP gene and LEP protein expression in the hippocampus by ME is further elevated when combined with AX. Consistently, the combined interventions increased hippocampal LEP protein. In LEP-deficient ob/ob mice, LEP replacement in the brain restored the ability of ME+AX to enhance hippocampal function. Thus, a combined lifestyle intervention based on ME, including yoga and tai chi, and specific dietary supplements that include antioxidants may together improve cognition and possibly retard cognitive decline in humans.

1 January 2021 in Biochemical and Biophysical Research Communications
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Journal Article
Closed access
HKHikaru Koizumi
Hikaru Koizumi
THTaichi Hiraga
Taichi Hiraga
LOLeandro K. Oharomari
Leandro K. Oharomari
THToshiaki Hata
Toshiaki Hata
TSTakeru Shima
Takeru Shima
HSHideaki Soya
Hideaki Soya

30 November 2021 in Neuroendocrinology
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Journal Article
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KTKanako Takahashi
Kanako Takahashi
TSTakeru Shima
Takeru Shima
MSMariko Soya
Mariko Soya
JYJang Soo Yook
Jang Soo Yook
HKHikaru Koizumi
Hikaru Koizumi
HSHideaki Soya
Hideaki Soya
Introduction: Exercise becomes a stress when performed at an intensity above the lactate threshold (LT) because at that point the plasma adrenocorticotropic hormone (ACTH), a marker of stress response, increases. It is possible that the exercise-induced ACTH response is regulated at least by arginine vasopressin (AVP) and possibly by corticotropin-releasing hormone (CRH), but this remains unclear. To clarify the involvement of these factors, it is useful to intervene pharmacologically in the regulatory mechanisms, with a physiologically acceptable exercise model. Methods: We used a special stress model of treadmill running (aerobic exercise) for male Wistar rats, which mimic the human physiological response, where plasma ACTH levels increase at just above the LT for 30 min. Animals were administered the AVP V1b receptor antagonist SSR149415 (SSR) and/or the CRH type 1 receptor antagonist CP154526 (CP) intraperitoneally before the exercise, which allowed the monitoring of exercise-induced ACTH response. Immunohistochemical evaluation of activated AVP and CRH neurons with exercise was performed for the animals’ hypothalami. Results: A single injection of either antagonist, SSR or CP, resulted in inhibited ACTH levels after exercise stress. Moreover, the combined injection of SSR and CP strongly suppressed ACTH secretion during treadmill running to a greater extent than each alone. The running-exercise-induced activation of both AVP and CRH neurons in the hypothalamus was also confirmed. Conclusion: These results lead us to hypothesize that AVP and CRH are cooperatively involved in exercise-induced ACTH response just above the LT. This may also reflect the stress response with moderate-intensity exercise in humans.

28 May 2021 in Antioxidants
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Journal Article
Open access
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LOLeandro Kansuke Oharomari
Leandro Kansuke Oharomari
MIMitsushi J IKEMOTO
Mitsushi J IKEMOTO
DHDong Joo Hwang
Dong Joo Hwang
HKHikaru Koizumi
Hikaru Koizumi
HSHideaki Soya
Hideaki Soya
A healthy lifestyle is essential for maintaining physical and mental health. Health promotion, with a particular emphasis on regular exercise and a healthy diet, is one of the emerging trends in healthcare. However, the way in which exercise training and nutrients from dietary intake interact with each other to promote additive, synergistic, or antagonistic effects on physiological functions leading to health promotion, and the possible underlying biomolecular mechanisms of such interactions, remain poorly understood. A healthy diet is characterized by a high intake of various bioactive compounds usually found in natural, organic, and fresh foodstuffs. Among these bioactive compounds, astaxanthin (ASX), a red carotenoid pigment especially found in seafood, has been recognized in the scientific literature as a potential nutraceutical due to its antioxidant, anti-inflammatory, and neurotrophic properties. Therefore, scientists are currently exploring whether this promising nutrient can increase the well-known benefits of exercise on health and disease prevention. Hence, the present review aimed to compile and summarize the current scientific evidence for ASX supplementation in association with exercise regimes, and evaluate the additive or synergistic effects on physiological functions and health when both interventions are combined. The new insights into the combination paradigm of exercise and nutritional supplementation raise awareness of the importance of integrative studies, particularly for future research directions in the field of health and sports nutrition science.

1 July 2018
Verified
Journal Article
Closed access
HSHideaki Soya
Hideaki Soya
MOMasahiro Okamoto
Masahiro Okamoto
YJYook Jangsoo
Yook Jangsoo
HKHikaru Koizumi
Hikaru Koizumi

27 August 2024 in Journal of Infection and Chemotherapy
Verified
Journal Article
Open access
NANobuyuki Ashizawa
Nobuyuki Ashizawa
TTTakahiro Takazono
Takahiro Takazono
KOKenji Ota
Kenji Ota
YIYuya Ito
Yuya Ito
THTatsuro Hirayama
Tatsuro Hirayama
HMHiroshi Mukae
Hiroshi Mukae