Responsiveness to growth hormone administration in hypertrophied skeletal muscle

• Project/Area Number: 18K10814
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 59020:Sports sciences-related
• Research Institution: Nagoya Institute of Technology
• Principal Investigator: Hanai Yoshiteru 名古屋工業大学, 工学研究科, 准教授 (50360730)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000); Fiscal Year 2020: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
• Keywords: 成長ホルモン / 成長ホルモン受容体 / 筋肥大 / GH / IGF-1 / GH受容体 / 骨格筋肥大

Outline of Final Research Achievements

We have studied the growth hormone receptor expression in hypertrophied skeletal muscle.In the present study, to examine whether the reduction of GH receptor gene expression in the early phase of muscle hypertrophy (up to 4 days) affects the responsiveness of skeletal muscle, we externally administered rhGH to hypophisectomized rat with unilatelal compensatory hypertrophy for 4 days.
In the hypertrophied muscle, GH receptor mRNA expression was significantly reduced in hypertrophied muscle compared to the control leg, the IGF-1 mRNA induction was 　comparable.
The reduction of GH receptor expression observed in hypertrophied muscle during the early phase of muscle hypertrophy seems not affect the GH-induced IGF-1 response.

Academic Significance and Societal Importance of the Research Achievements

筋力トレーニングを実施するにあたって、その効率の問題は重要である。筋肥大初期には同化ホルモンである成長ホルモンの受容体の遺伝子発現が肥大筋で低下することが明らかとなっている。本研究では、この成長ホルモンの受容体遺伝子の発現の低下が、実際のGH投与に対する反応性に影響するのか否かについてIGF-1発現の誘導の面から検討を行い、影響は少ないことを明らかにした。
この知見は適切なトレーニング処方を考えるための基礎的成果として有用なものであると考える。