ビグアニドは,循環型AMPの産生を減少させることで,肝臓のグルカゴン信号伝達を抑制する
Russell A Miller1, Qingwei Chu, Jianxin Xie
1Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Nature
|January 8, 2013
まとめ
2型糖尿病の重要な薬であるメトホルミンは,グルカゴンの作用を阻害することによって,肝臓のグルコース産生を減少させます. これはAMPの蓄積によって発生し,周期的なAMPとタンパク質キナーゼAを阻害し,最終的に血糖を低下させます.
科学分野:
- バイオケミストリー バイオケミストリー
- エンドクリノロジー エンドクリノロジー
- 薬理学 薬理学とは
背景:
- 肝臓のグルコース生成は,断食中の脳機能に不可欠です.
- インスリン抵抗性により,肝臓のグルコース排出抑制が低下し,2型糖尿病では高血糖症を引き起こします.
- ビグアニドは,メトホルミンと同様に,グルコースの生産を減らすための確立された治療法ですが,そのメカニズムは不明です.
研究 の 目的:
- 肝臓のグルコース産生を減少させるメトフォーミンの作用メカニズムを解明する.
- メトフォーミンの血糖低下効果におけるグルカゴン信号伝達の役割を調査する.
- 既存のAMP活性化タンパク質キナーゼ (AMPK) 活性化仮説に異議を唱えるため.
主な方法:
- マウスの肝細胞を用いた実験が行われました.
- AMPと循環型AMP (cAMP) を含む細胞代謝産物に対するメトホルミンの効果を測定した.
- タンパク質キナーゼA (PKA) の活性とその下流リン酸化標的を評価した.
- グルカゴン刺激によるグルコース出力は,メトホルミンと併用して測定された.
主要な成果:
- メトフォーミンは,AMPおよび関連ニュークレオチドの蓄積を肝細胞に誘導した.
- この蓄積はアデニル酸サイクラスを阻害し,cAMPレベルとPKA活性が低下しました.
- メトホルミンはPKA標的のリン酸化を無効化し,グルカゴンに依存したグルコース生成を阻害しました.
- これらの効果は,AMPK活性化とは無関係に観察されました.
結論:
- メトホルミンは,主にAMPK活性化ではなく,グルカゴンのシグナル伝達を阻害することによって作用します.
- AMPの蓄積と,その後のcAMP/PKA経路の阻害は,メトホルミンの血糖低下効果を媒介する.
- これはメトホルミンの新しいメカニズムを提供し,糖尿病の新たな治療目標を示唆しています.
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