メトホルミン関連乳酸アシドーシスは、発症頻度は低いが発症予測は困難であり、また一旦発症すると高い致死率を示すことから、メトホルミン使用における懸念事項である。高乳酸血症は乳酸アシドーシスのリスクと考えられることから、本研究ではメトホルミン治療中の2型糖尿病患者において高乳酸血症の予測因子を後ろ向きに解析した。72例を対象とした解析において、メトホルミン投与量、体格指数（BMI）、γ-グルタミルトランスフェラーゼ（γ-GTP）、尿アルブミン指数が血清乳酸値と有意な相関を示した。これら4因子に年齢を加えて重回帰分析を行ったところ、BMIとγ-GTPがそれぞれ血清乳酸値の独立した予測因子であることが示された。以上より、肥満やγ-GTP高値を示す2型糖尿病患者においてはメトホルミン治療中の高乳酸血症リスクが高いことが示され、血清乳酸値のモニタリングの意義がより大きいものと考えられた。

　Although metformin-associated lactic acidosis is a relatively rare condition, potentially fatal outcomes have long made the use of metformin rather limited to specialized diabetologists in Japan. Since high blood lactate level is an established risk factor for the development of lactic acidosis, we here retrospectively analyzed patients with type 2 diabetes mellitus treated with metformin and explored factors associated with higher serum lactate levels. In 72 consecutive patients, age, BMI, dose and duration of metformin treatment, and blood biochemistry data were retrieved and potential association with serum lactate levels was examined by stratified significance analysis, single correlation analysis and multiple regression analysis. In singly correlation analysis, metformin dose, BMI, γ-glutamyltransferase and spot urinary albumin excretion ratio were significantly correlated with lactate levels. When these four factors and patient age were included as explanatory variables in multiple regression analysis, BMI and γ-glutamyltransferase were the only factors independently correlated with lactate levels. We demonstrate that patients with higher BMI or higher γ-glutamyltransferase levels are at higher risk for hyperlactatemia. Among these patients, therefore, monitoring of serum lactate levels may help to prevent the future development of lactic acidosis.