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CASE REPORT article

Front. Nutr., 12 August 2021
Sec. Clinical Nutrition
This article is part of the Research Topic Potentials of Kampo Medicine in Modern Society View all 10 articles

Kampo Medicine Treatment for Advanced Pancreatic Cancer: A Case Series

\nMasayuki Shimizu,Masayuki Shimizu1,2Shin Takayama,,
Shin Takayama2,3,4*Akiko Kikuchi,,Akiko Kikuchi2,3,4Ryutaro Arita,Ryutaro Arita2,3Rie Ono,Rie Ono2,3Kota IshizawaKota Ishizawa3Tadashi Ishii,,Tadashi Ishii2,3,4
  • 1Shimizu Clinic, Sendai, Japan
  • 2Department of Kampo Medicine, Tohoku University Hospital, Sendai, Japan
  • 3Department of Education and Support for Regional Medicine, Tohoku University Hospital, Sendai, Japan
  • 4Department of Kampo and Integrative Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan

Aims: The present report aims to investigate the use of Kampo medicine for advanced pancreatic cancer patients in order to prolong survival.

Methods: We retrospectively reviewed medical records of patients with pancreatic cancer who presented to our Shimizu Clinic from 2000 to 2020. Patients who survived at least twice as long as the initial prognostic estimate were selected and their treatment was reviewed. The Kampo formula and crude drugs were selected according to the Kampo diagnosis and treatment strategy, which included qi and blood supplementation; qi, blood and water smoothing; and inflammation (termed “heat”) and cancer suppression.

Results: Ten patients aged 45–80 years (six males and four females) with stage IV advanced cancer were selected. All patients received hozai, which is a tonic formula, of juzentaihoto (JTT) or hochuekkito (HET) decoction. Anti-cancer crude drugs were included in the decoctions of nine patients. At the first visit, the estimated life expectancy for all patients was no more than 1 year; however, treatment with Western and Kampo medicine led to a relatively long survival period of over 2 years. Three patients were still living at the time of this writing, more than 2, 6, and 14 years after treatment initiation.

Conclusion: Our results suggest that Kampo medicine may be useful for disease control and supportive care for patients with advanced pancreatic cancer.

Introduction

Surgery, radiotherapy, and chemotherapy along with anticancer drugs are the standard Western treatments for pancreatic cancer. However, the therapeutic effects of these treatments are poor in cases of advanced disease, with a 5-year survival rate of 1.3% among patients with advanced pancreatic cancer (1). For patients with advanced cancer who have not responded to Western medicine, an integrated treatment approach using Kampo medicine may be a useful alternative. Kampo medicine is beneficial for the treatment of cancer-related numbness, constipation, anorexia, muscle cramps, and fatigue (2). Given this finding, the Japanese Society for Palliative Medicine has recommended the use of Kampo medicine and crude drugs in combination with Western medicine (3). Improvement of symptoms during cancer treatment may extend the patients' tolerance for longer treatment periods (4, 5).

We previously presented a case of a patient with advanced pancreatic cancer who survived for 7 years after diagnosis without a significant decrease in quality of life (QOL) (6). This initial case demonstrated that Kampo medicine may be useful for disease control and supportive care for patients with advanced pancreatic cancer. To study this idea further, we retrospectively reviewed cases of advanced pancreatic cancer seen in our clinic to summarise and evaluate the efficacy of Kampo treatment for this patient group.

Methods

Medical records of 48 patients with advanced pancreatic cancer who were treated with Kampo medicine in our Shimizu Clinic from the year 2000 to the year 2020 were included in this retrospective review. Ultimately, 10 patients who lived at least twice as long as the estimated prognosis, determined at the time of the first visit, were enrolled for the study. The patients' age, sex, clinical stage of disease at the first visit, life expectancy at the first visit, Western medicine treatment, Kampo medicine treatment, and survival duration were collected from their medical records. The Kampo formula and crude drugs were selected according to the Kampo diagnosis and treatment strategy. This strategy entailed qi and blood supplementation; qi, blood and water smoothing; and inflammation (heat) and cancer suppression. The Kampo formulas of hozai and kuoketsuzai and anti-cancer drugs used for the patients are listed in Table 1. The concentration indicator and composition of each crude drug are regulated by Japanese Pharmacopoeia of Japan version 17th.

TABLE 1
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Table 1. Kampo formula, its constituents, and mechanisms according to prior studies.

Ethical Considerations

This case series was approved by the Institutional Review Board of the Tohoku University Graduate School of Medicine (Institutional Review Board No. 18910).

Results

Ten patients between the ages of 45 and 80 years (six males and four females) with stage IV advanced cancer were selected (Table 2). All Kampo formulas were prescribed as decoctions. All patients received hozai, which is a tonic formula of juzentaihoto (JTT) or hochuekkito (HET). Anti-cancer crude drugs such as Hedyotis diffusa, Scutellaria barbata, and/or Lobelia chinensis were administered to patients 1 through 10, with the exception of patient 9. Patients 1, 2, and 8 received additional Kampo medicine for the relief of chemotherapy-related symptoms. At the first visit, the life expectancy of all patients was limited to no more than 1 year; however, treatment with Western medicine and Kampo medicine led to a relatively long survival period of over 2 years. Three patients undergoing Kampo treatment were still living at the time of this writing, more than 2, 6, and 14 years after treatment initiation.

TABLE 2
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Table 2. Patients with advanced pancreatic cancer who were treated with Kampo medicine and lived at least twice as long as the prognosis determined at the time of initial visit.

Discussion

The cases presented herein indicate that Kampo medicine can be provided for advanced pancreatic cancer treatment as an integrative cancer therapy. Additionally, these cases suggest that Kampo medicine may slow cancer progression and improve the survival rate. The treatment strategy for advanced cancer patients includes supporting vital energy and nutrition, harmonising the immune system and sympathetic condition, suppressing inflammation, and promoting microcirculation and interstitial fluid. These concepts are expressed as balancing qi, blood, and fluid or cold and heat within Kampo theory. Anti-cancer drugs attack cancer cells but also cause body damage, which reduces body recovery and innate immunity. On the other hand, Kampo medicines act on biological reactions and they have a supplementary effect on recovery and reduced immune system. This characteristic is important for striking a balance between offence against cancer and defence for the whole body.

Hozai, such as JTT or HET, are used to support vital energy and nutrition and to harmonise the immune system and sympathetic conditions. The indications for JTT include declined constitution after recovery, fatigue and malaise, anorexia, and anaemia. Additional effects of JTT on suppression of cancer growth, including prevention of malignant progression and tumour cell metastasis (7), upregulation of T cell activity (8), and improving fluorouracil-induced myelosuppression (9) have been reported in several experimental studies. HET has been reported to reduce cancer-related fatigue and improve QOL for cancer patients (21, 22). Additional reported effects of HET on cancer include concomitant enhancement of immunity against tumour development (10); restoration of antitumor T cell responses, and costimulatory molecule expression (11); maintenance of NK cell activity and inhibition of stress mediators (12); inhibition of proinflammatory cytokine production (13); enhancement of cisplatin-induced apoptosis (14); and inhibition of cytokine-mediated apoptosis or necrosis, leading to a reduction of the gastrointestinal side effects of cancer chemotherapy (15); and replenishing B cells after radiotherapy (16). These reports support the possibility of suppressing tumour growth and affecting immunomodulation to reduce inflammation in addition to the original supportive effects for fatigue and malaise. HET also can promote negative conversion of vancomycin-resistant Enterococci or prevent the colonisation of methicillin-resistant Staphylococcus aureus in humans (23, 24). These studies suggested that HET influenced on innate immunity and nutrition status.

Kuoketsuzai, which is a blood stasis-resolving formula such as Keppuchikuoto, has been used for relief of pain caused by blood stasis (25). It stimulates interleukin (IL)-2 and tumor necrosis factor (TNF)-α secretion and improves immune function, resulting in tumour growth suppression (17). For pain control, some crude drugs were added to the formula. Corydalis tuber, a crude drug that contains isoquinoline alkaloids, is used for intractable pain and can be used to manage pain associated with bone metastases.

Some herbal medicines may be added to Kampo treatment due to their anti-cancer effects. H. diffusa is used as an anticancer, antitoxic, and diuretic agent to treat cancers (18). Extracts of S. barbata have inhibitory effects on the growth of several cancers in humans, including lung cancer, gastrointestinal cancers, hepatoma, breast cancer, and chorioepithelioma (19). L. chinensis has anti-inflammatory properties that are attributable to inhibition of inducible nitric oxide synthase, cyclooxygenase-2, TNF-α, and IL-6 via the NF-κB pathway (20). The combination of hozai with anti-cancer crude drugs may support patient condition and inhibit cancer growth, resulting QOL and relatively prolonged survival rate.

In 2019, the 11th revision of the International Statistical Classification of Diseases and Related Health Problems published by the World Health Organisation included a traditional medicine module (26). Following this global trend, recently, most of the clinical practice guidelines in Japan recommended Kampo medicines for symptoms and diseases (2729). Our previous report suggested that integrative medicine combined with Kampo medicine and western medicine can be applied for several intractable symptoms and diseases (6, 3034). Therefore, Kampo treatment may be a helpful tool during advanced pancreatic cancer treatment.

Nowadays, the term “integrative oncology” is used for multidisciplinary cancer treatment. It includes a combination of complementary medicine in conjunction with conventional cancer treatments (35). Complementary medicine and traditional medicine have been incorporated to the contents of the Basic Medical Education: Japanese Specifications WFME (World Federation for Medical Education) Global Standards for Quality Improvement (36). It showed to have an opportunity to contact complementary medicine and traditional medicine in Japan. Furthermore, Model Core Curriculum for Medical Education revised at 2017 included the objectives of outlining the characteristics of Kampo medicine, the indications and pharmacological effects of major Kampo medicines (37). Considering these concepts and educational process, it is important to understand the characteristics of Kampo medicines and use them effectively along with conventional cancer treatments.

This research has some limitations. The study design is a case series; we did not include control or comparison groups. In the retrospective analysis, we did not have complete data of patients' entire clinical course. Thus, we could not compare the factors relating to prognosis between delayed prognosis and poor prognosis. Further, study will be needed to clarify the factors relating to prognosis including Kampo treatment.

In conclusion, Kampo medicine may be useful for disease control and supportive care for patients with advanced pancreatic cancer and may result in a relatively prolonged survival rate.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethics Statement

This case series was approved by the Institutional Review Board of the Tohoku University Graduate School of Medicine (Institutional Review Board No. 18910). Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.

Author Contributions

MS treated patients. MS and ST wrote manuscript. AK, RO, and RA selected patients from medical records. KI and TI revised manuscript. All authors contributed to the article and approved the submitted version.

Funding

This study was supported by Tsumura, a Japanese manufacturer of Kampo medicine.

Conflict of Interest

ST, AK, and TI belong to the Department of Kampo and Integrative Medicine at the Tohoku University School of Medicine. The department received a grant from Tsumura, a Japanese manufacturer of Kampo medicine; however, this grant was used as per Tohoku University rules. Potential conflicts of interest were addressed by the Tohoku University Benefit Reciprocity Committee and managed appropriately.

The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Acknowledgments

We thank Akiko Kuwabara for the clinical coordination.

References

1. Ganjoho.jp [statistics internet page]. Total Cancer Registration Survival Rate in Hospitals such as Cancer Treatment Cooperation Base Hospitals. (2019). Available online at: https://ganjoho.jp/reg_stat/statistics/brochure/hosp_c_reg_surv.html (accessed Febraury 12, 2021).

Google Scholar

2. Iwase S, Yamaguchi T, Miyaji T, Terawaki S, Inui A, Uezono Y. The clinical use of Kampo medicines (traditional Japanese herbal treatments) for controlling cancer patients' symptoms in Japan: a national cross-sectional survey. BMC Complement Altern Med. (2012) 20:222. doi: 10.1186/1472-6882-12-222

PubMed Abstract | CrossRef Full Text | Google Scholar

3. Japanese Society for Palliative Medicine. Clinical Evidence for Complementary and Alternative Therapies in Cancer Patients. Tokyo: Kanehara & Co., Ltd. (2016). Available online at: https://www.jspm.ne.jp/guidelines/cam/2016/pdf/cam01.pdf

Google Scholar

4. Yamakawa J, Motoo Y, Moriya J, Ogawa M, Uenishi H, Akazawa S, et al. Role of Kampo medicine in integrative cancer therapy. Evid Based Complement Alternat Med. (2013) 2013:570848. doi: 10.1155/2013/570848

PubMed Abstract | CrossRef Full Text | Google Scholar

5. Yamakawa J, Motoo Y, Moriya J, Ogawa M, Uenishi H, Akazawa S, et al. Significance of Kampo, traditional Japanese medicine, in supportive care of cancer patients. Evid Based Complement Alternat. Med. (2013) 2013:746486. doi: 10.1155/2013/746486

PubMed Abstract | CrossRef Full Text | Google Scholar

6. Shimizu M, Takayama S, Kikuchi A, Arita R, Ono R, Ishizawa K, et al. Integrative therapy for advanced pancreatic cancer using Kampo and western medicine: a case report. Explore. (2021) 17:255–8. doi: 10.1016/j.explore.2020.07.003

PubMed Abstract | CrossRef Full Text | Google Scholar

7. Saiki I. A Kampo medicine “Juzen-taiho-to”–prevention of malignant progression and metastasis of tumor cells and the mechanism of action. Biol Pharm Bull. (2000) 23:677–88. doi: 10.1248/bpb.23.677

PubMed Abstract | CrossRef Full Text | Google Scholar

8. Ikemoto T, Shimada M, Iwahashi S, Saito Y, Kanamoto M, Mori H, et al. Changes of immunological parameters with administration of Japanese Kampo medicine (Juzen-Taihoto/TJ-48) in patients with advanced pancreatic cancer. Int J Clin Oncol. (2014) 19:81–6. doi: 10.1007/s10147-013-0529-6

PubMed Abstract | CrossRef Full Text | Google Scholar

9. Ogawa K, Omatsu T, Matsumoto C, Tsuchiya N, Yamamoto M, Naito Y, et al. Protective effect of the Japanese traditional medicine juzentaihoto on myelosuppression induced by the anticancer drug TS-1 and identification of a potential biomarker of this effect. BMC Complement Altern Med. (2012) 12:118. doi: 10.1186/1472-6882-12-118

PubMed Abstract | CrossRef Full Text | Google Scholar

10. Harada M, Seta K, Ito O, Tamada K, Li T, Terao H, et al. Concomitant immunity against tumor development is enhanced by the oral administration of a kampo medicine, Hochu-ekki-to (TJ-41: Bu-Zhong-Yi-Qi-Tang). Immunopharmacol Immunotoxicol. (1995) 17:687–703. doi: 10.3109/08923979509037189

PubMed Abstract | CrossRef Full Text | Google Scholar

11. Li T, Tamada K, Abe K, Tada H, Onoe Y, Tatsugami Y, et al. The restoration of the antitumor T cell response from stress-induced suppression using a traditional Chinese herbal medicine Hochu-ekki-to (TJ-41:Bu-Zhong-Yi-Qi-Tang). Immunopharmacology. (1999) 43:11–21. doi: 10.1016/S0162-3109(99)00034-X

PubMed Abstract | CrossRef Full Text | Google Scholar

12. Kimura M, Sasada T, Kanai M, Kawai Y, Yoshida Y, Hayashi E, et al. Preventive effect of a traditional herbal medicine, Hochu-ekki-to, on immunosuppression induced by surgical stress. Surg Today. (2008) 38:316–22. doi: 10.1007/s00595-007-3631-4

PubMed Abstract | CrossRef Full Text | Google Scholar

13. Yae S, Takahashi F, Yae T, Yamaguchi T, Tsukada R, Koike K, et al. Hochuekkito (TJ-41), a Kampo formula, ameliorates cachexia induced by colon 26 adenocarcinoma in mice. Evid Based Complement Alternat Med. (2012) 2012:976926. doi: 10.1155/2012/976926

PubMed Abstract | CrossRef Full Text | Google Scholar

14. Sato T, Kita K, Sato C, Kaneda A. Hochu-ekki-to (Bu-zhong-yi-qi-tang), a herbal medicine, enhances cisplatin-induced apoptosis in HeLa cells. Mol Med Rep. (2015) 12:6215–20. doi: 10.3892/mmr.2015.4137

PubMed Abstract | CrossRef Full Text | Google Scholar

15. Gou KJ, Zeng R, Ma Y, Li AN, Yang K, Yan HX, et al. Traditional uses, phytochemistry, and pharmacology of Persicaria orientalis (L.) Spach - A review. J Ethnopharmacol. (2020) 249:112407. doi: 10.1016/j.jep.2019.112407

PubMed Abstract | CrossRef Full Text | Google Scholar

16. Lee AJ, Lee HJ, Kim JD, Jung HJ, Bae SH, Ryoo SM, et al. Changes of peripheral blood lymphocyte subtypes in patients with end-stage cancer administered localized radiotherapy and bojungikki-tang. Evid Based Complement Alternat Med. (2014) 2014:207613. doi: 10.1155/2014/207613

PubMed Abstract | CrossRef Full Text | Google Scholar

17. Yan-Long H, Song J, Xu X. Study on anti-tumor function of Xue Fu Zhu Yu Decoction. J Mudanjiang Med Coll. (2007) 28:14–5.

Google Scholar

18. Lin CC, Chen JY, Namba T. Development of natural crude drug resources from Taiwan-5-Pharmacognostical studies on Chinese crude drug “Peh-hue-juwa-chi-chhau”. Yakushigaku Zasshi. (1987) 41:180–8.

Google Scholar

19. Yin X1, Zhou J, Jie C, Xing D, Zhang Y. Anticancer activity and mechanism of Scutellaria barbata extract on human lung cancer cell line A549. Life Sci. (2004) 75:2233–44. doi: 10.1016/j.lfs.2004.05.015

PubMed Abstract | CrossRef Full Text | Google Scholar

20. Li KC, Ho YL, Huang GJ, Chang YS. Anti-oxidative and anti-inflammatory effects of Lobelia chinensis in vitro and in vivo. Am J Chin Med. (2015) 43:269–87. doi: 10.1142/S0192415X15500184

PubMed Abstract | CrossRef Full Text | Google Scholar

21. Jeong JS, Ryu BH, Kim JS, Park JW, Choi WC, Yoon SW. Bojungikki-tang for cancer-related fatigue: a pilot randomized clinical trial. Integr Cancer Ther. (2010) 9:331–8. doi: 10.1177/1534735410383170

PubMed Abstract | CrossRef Full Text | Google Scholar

22. Takayama S, Kikuchi A, Makino T, Kainuma M, Namiki T, Ito T. Basic pharmacological mechanisms and clinical evidence of the efficacy of hochuekkito against infectious diseases and its potential for use against COVID-19. Tradit Kampo Med. (2020) 8:3–21. doi: 10.1002/tkm2.1264

CrossRef Full Text | Google Scholar

23. Kohno J, Kawamura T, Kikuchi A, Akaishi T, Takayama S, Ishii T. A Japanese traditional medicine Hochuekkito promotes negative conversion of vancomycin-resistant Enterococci. Sci Rep. (2021) 11:11300. doi: 10.1038/s41598-021-90890-4

PubMed Abstract | CrossRef Full Text | Google Scholar

24. Kitahara M, Takayama S, Akaishi T, Kikuchi A, Ishii T. Hochuekkito can prevent the colonization of methicillin-resistant Staphylococcus aureus in upper respiratory tract of acute stroke patients. Front Pharmacol. (2021) 12:683171. doi: 10.3389/fphar.2021.683171

PubMed Abstract | CrossRef Full Text | Google Scholar

25. Cheolsun H, Yoshiro H, Hideki O, Keigo U, Akio Y, Hirobumi S, et al. A case of prolonged lumbago with severe cold intolerance successfully treated with Keppuchikuoto and Uzushakusekishigan. Kampo Med. (2015) 66:112–8. doi: 10.3937/kampomed.66.112

CrossRef Full Text | Google Scholar

26. Lam WC, Lyu A, Bian Z. ICD-11: impact on traditional Chinese medicine and world healthcare systems. Pharm Med. (2019) 33:373–7. doi: 10.1007/s40290-019-00295-y

PubMed Abstract | CrossRef Full Text | Google Scholar

27. Takayama S, Arita R, Kikuchi A, Ohsawa M, Kaneko S, Ishii T. Clinical practice guidelines and evidence for the efficacy of traditional Japanese herbal medicine (Kampo) in treating geriatric patients. Front Nutr. (2018) 5:66. doi: 10.3389/fnut.2018.00066

PubMed Abstract | CrossRef Full Text | Google Scholar

28. Kojima T, Mizukami K, Tomita N, Arai H, Ohrui T, Eto M, et al. Screening Tool for Older Persons' Appropriate Prescriptions for Japanese: Report of the Japan Geriatrics Society Working Group on “Guidelines for medical treatment and its safety in the elderly.” Geriatr Gerontol Int. (2016) 16:983–1001. doi: 10.1111/ggi.12890

PubMed Abstract | CrossRef Full Text | Google Scholar

29. Takayama S, Iwasaki K. Systematic review of traditional Chinese medicine for geriatrics. Geriatr Gerontol Int. (2017) 17:679–88. doi: 10.1111/ggi.12803

PubMed Abstract | CrossRef Full Text | Google Scholar

30. Takayama S, Arita R, Ohsawa M, Kikuchi A, Yasui H, Makino T, et al. Perspectives on the use of Ninjin'yoeito in modern medicine: a review of randomized controlled trials. Evid Based Complement Alternat Med. (2019) 2019:9590260. doi: 10.1155/2019/9590260

PubMed Abstract | CrossRef Full Text | Google Scholar

31. Takayama S, Kaneko S, Numata T, Kamiya T, Arita R, Saito N, et al. Literature review: herbal medicine treatment after large-scale disasters. Am J Chin Med. (2017) 45:1345–64. 10.1142/S0192415X17500744

PubMed Abstract | Google Scholar

32. Kikuchi A, Shiga Y, Takayama S, Arita R, Maekawa S, Kaneko S, et al. Traditional medicine as a potential treatment for Flammer syndrome. EPMA J. (2017) 8:171–5. doi: 10.1007/s13167-017-0091-9

PubMed Abstract | CrossRef Full Text | Google Scholar

33. Suzuki S, Takayama S, Kikuchi A, Arita R, Abe M, Saito R, et al. Orengedokuto and shosaikoto for intractable intracranial carmustine implant-induced fever in a patient with brain tumor: a case report. Explore. (2020) 17:236–8. doi: 10.1016/j.explore.2020.08.014

PubMed Abstract | CrossRef Full Text | Google Scholar

34. Ohsawa M, Takayama S, Kikuchi A, Arita R, Saito N, Hojo S, et al. Two cases of multiple chemical sensitivity successfully treated with Kampo medicine. Altern Ther Health Med. (2020) 27:54–8.

PubMed Abstract | Google Scholar

35. Witt CM, Balneaves LG, Cardoso MJ, Cohen L, Greenlee H, Johnstone P, et al. A comprehensive definition for integrative oncology. J Natl Cancer Inst Monogr. (2017) 2017:3–8. doi: 10.1093/jncimonographs/lgx012

PubMed Abstract | CrossRef Full Text | Google Scholar

36. Basic Medical Education. Japanese Specifications WFME Global Standards for Quality Improvement. Tokyo: Japan Accreditation Council for Medical Education (2015).

Google Scholar

37. Basic Medical Education. Japanese Specifications WFME Global Standards for Quality Improvement. Ministry of Education, Culture, Sports, Science and Technology. Tokyo: Science, Engineering and Humanities and Social Sciences references (2015).

Google Scholar

Keywords: pancreatic cancer, Kampo medicine, integrative therapy, quality of life, prolong survival

Citation: Shimizu M, Takayama S, Kikuchi A, Arita R, Ono R, Ishizawa K and Ishii T (2021) Kampo Medicine Treatment for Advanced Pancreatic Cancer: A Case Series. Front. Nutr. 8:702812. doi: 10.3389/fnut.2021.702812

Received: 29 April 2021; Accepted: 13 July 2021;
Published: 12 August 2021.

Edited by:

Clelia Madeddu, University of Cagliari, Italy

Reviewed by:

Michihisa Tohda, University of Toyama, Japan
Darukeshwara Joladarashi, Temple University, United States

Copyright © 2021 Shimizu, Takayama, Kikuchi, Arita, Ono, Ishizawa and Ishii. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Shin Takayama, takayama@med.tohoku.ac.jp

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.