Sasaki, Hironobu



School of Medicine, Center for Preventive Medicine (Shinanomachi)


Project Assistant Professor (Non-tenured)/Project Research Associate (Non-tenured)/Project Instructor (Non-tenured)

Academic Background 【 Display / hide

  • 2007.04

    Keio University

    University, Graduated

  • 2017.04

    Keio University

    Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide

  • Bachelor of Medicine, Keio University, 2013.03

  • Doctor of Medicine, Keio University, Coursework, 2021.03

    Associations of birthweight and history of childhood obesity with beta cell mass in Japanese adults

Licenses and Qualifications 【 Display / hide

  • Board Certified Member of the Japanese Society of Internal Medicine, 2016.09

  • the Japan Medical Association (JMA)-certified Sports Medicine Physician, 2017.03

  • the Japan Medical Association (JMA)-certified Occupational Physician, 2019.07

  • Fellow of the Japan Diabetes Society, 2019.11

  • Approved Doctor by the Japan Association for Diabetes Education and Care, 2019.12

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Research Areas 【 Display / hide

  • Life Science / Metabolism and endocrinology (human islet research)

Research Keywords 【 Display / hide

  • Diabetes


Papers 【 Display / hide

  • Increased alpha cell to beta cell ratio in patients with pancreatic cancer

    Tami Tsuchiya, Yoshifumi Saisho, Jun Inaishi, Hironobu Sasaki, Midori Sato, Masaru Nishikawa, Yohei Masugi, Taketo Yamada, Hiroshi Itoh

    Endocrine journal (Japan Endocrine Society)   2022.08

    Research paper (scientific journal), Joint Work, Accepted,  ISSN  0918-8959

     View Summary

    The development of pancreatic cancer (PC) is associated with worsening of glucose tolerance. However, there is limited information about the effects of PC on islet morphology. The aim of this study was to elucidate changes in alpha and beta cell mass in patients with PC. We enrolled 30 autopsy cases with death due to PC (9 with diabetes; DM) and 31 age- and BMI-matched autopsy cases without PC (controls, 12 with DM). Tumor-free pancreatic sections were stained for insulin and glucagon, and fractional beta cell (BCA) and alpha cell area (ACA) were quantified. In addition, expression of de-differentiation markers, i.e., ALDH1A3 and UCN3, was qualitatively evaluated. The pancreas of subjects with PC showed atrophic and fibrotic changes. There was no significant difference in BCA in subjects with PC compared to controls (1.53 ± 1.26% vs. 0.95 ± 0.42%, p = 0.07). However, ACA and ACA to BCA ratio were significantly higher in subjects with PC compared to controls (2.48 ± 2.39% vs. 0.53 ± 0.26% and 1.94 ± 1.93 vs. 0.59 ± 0.26, respectively, both p < 0.001). Increased ACA to BCA ratio was observed in subjects with PC irrespective of the presence of DM. Qualitative evaluation of ALDH1A3 and UCN3 expression showed no significant difference between the groups. In conclusion, in subjects with PC, alpha to beta cell mass ratio is increased, which may contribute to the increased risk of worsening glucose metabolism. Further studies are warranted to elucidate the mechanisms of increased alpha to beta cell mass in patients with PC.

  • Could the development of COVID-19 vaccine-induced type 1 diabetes be explained by a simple mechanism?

    Hironobu Sasaki, Arata Itoh, Hiroshi Itoh

    Diabetes & Metabolism (Elsevier BV)  48 ( 4 ) 101338 2022.07

    Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  1262-3636

  • Newly developed type 1 diabetes after coronavirus disease 2019 vaccination: A case report

    Hironobu Sasaki, Arata Itoh, Yasuhiro Watanabe, Yuya Nakajima, Yoshifumi Saisho, Junichiro Irie, Shu Meguro, Hiroshi Itoh

    Journal of Diabetes Investigation (John Wiley & Sons)  13 ( 6 ) 1105 - 1108 2022.06

    Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  2040-1116

     View Summary

    The vaccine for the coronavirus disease 2019 (COVID-19) has been reported to potentially cause or worsen diabetes. A 73-year-old Japanese woman received two doses of Moderna COVID-19 vaccine. Four weeks after the second vaccination, her glycemic control began to deteriorate, and 8 weeks after the second vaccination, the patient was diagnosed with new-onset type 1 diabetes that was strongly positive for autoantibodies and showed a disease-susceptible human leukocyte antigen haplotype, DRB1*04:05:01-DQB1*04:01:01. The glucagon stimulation test suggested an insulin-dependent state, and induction of intensive insulin therapy brought about fair glycemic control. The time period from the COVID-19 vaccination to the development of type 1 diabetes was relatively longer than to the onset or exacerbation of type 2 diabetes, as previously reported, suggesting the complicated immunological mechanisms for the destruction of β-cells associated with the vaccination. In recipients with the disease-susceptible haplotypes, one should be cautious about autoimmune responses for several months after the vaccination.

  • Dipeptidyl peptidase-4 inhibitors and beta cell mass in Japanese adults with type 2 diabetes

    Hironobu Sasaki, Yoshifumi Saisho, Hiroshi Itoh

    Endocrine Practice (Elsevier BV)  28 ( 5 ) 563 - 564 2022.05

    Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  1530-891X

  • Changes in glycemic variability, gastric emptying and vascular endothelial function after switching from twice-daily to once-weekly exenatide in patients with type 2 diabetes: a subpopulation analysis of the twin-exenatide study

    Jun Inaishi, Yoshifumi Saisho, Yuusuke Watanabe, Tami Tsuchiya, Hironobu Sasaki, Tatsuhiro Masaoka, Hiroshi Itoh

    BMC Endocrine Disorders (BioMed Central)  22 ( 1 ) 20 2022.01

    Research paper (scientific journal), Joint Work, Accepted

     View Summary

    Background: We investigated the changes in blood glucose fluctuation, gastric emptying, and vascular endothelial function by switching from an exenatide twice-daily formulation (BID) to a once-weekly formulation (QW) since the evaluation of postprandial glucose excursion and glycemic variability (GV) by continuous glucose monitoring (CGM) after switching was lacking. Methods: Twenty-nine patients with type 2 diabetes treated with exenatide BID were included in this study and switched to exenatide QW for 24 weeks. GV assessed by CGM, gastric emptying (by 13 C-acetate breath test) and vascular endothelial function (by reactive hyperemia - peripheral arterial tonometry) were evaluated at baseline and 24 weeks after switching. Results: HbA1c decreased significantly from the baseline to week 24, while postprandial glucose levels after breakfast and dinner significantly increased (both P <0.05). However, the increases in GV indices were modest and not statistically significant at week 24. Vascular endothelial function was also not significantly changed after switching (P >0.05). Gastric emptying was significantly accelerated at week 24 (Tmax 83.4 ± 12.1 min vs. 58.2 ± 16.4 min) (P <0.001) and correlated with increased postprandial glucose levels after breakfast and dinner (both P <0.05). Conclusions: Despite the increase in postprandial glucose associated with accelerated gastric emptying after switching from exenatide BID to QW, change in GV was modest and no significant deterioration in vascular endothelial function was observed after switching. These results support the superiority of treatment with exenatide QW over exenatide BID in clinical practice; however, attention should be paid to the monitoring and management of postprandial glucose levels when selecting exenatide QW. Trial registration: Clinical trial registry number; UMIN000016390 and jRCTs031180320. Approval date of Registry and the Registration: December 12, 2014.

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Awards 【 Display / hide

  • Medical Research Encouragement Prize

    2021.12, Tokyo Medical Association

    Type of Award: Award from publisher, newspaper, foundation, etc.

  • Young Investigator Award

    2021.05, the Japan Diabetes Society

    Type of Award: Award from Japanese society, conference, symposium, etc.

  • Clinical Investigator Award

    2020.10, the Hormone Station of Japan

    Type of Award: Award from publisher, newspaper, foundation, etc.


Committee Experiences 【 Display / hide

  • 2020

    Reviewer Board Member of the Japanese Society of Internal Medicine