The Impacts of ACE Activity according to ACE I/D Polymorphisms on Muscular Functions of People Aged 65

ABSTRACT

OBJECTIVE: To investigate associations between angiotensin-converting enzyme (ACE) polymorphisms and muscle fatigability in 65-year-old Koreans. METHOD: The study participants were 49 Koreans aged 65 years. ACE insertion/deletion (I/D) polymorphisms were determined by polymerase chain reaction and serum ACE activity, by spectrophotometry. Body mass index (BMI), body fat mass (BFM), and lean body mass (LBM) were determined. To evaluate muscle fatigability, dynamic Electromyography was used to measure maximum voluntary isometric contractions (MVICs) of ankle plantar flexor muscles. Patients were seated with their hips flexed at 90degrees, knees fully extended, and ankles at 0degrees. Continuous submaximal VICs (40% MVIC) were then performed, and contraction duration and EMG frequency changes during the initial 2 min were measured. A self-reported physical activity questionnaire was used to evaluate effects of ACE activity levels on muscle fatigability. RESULTS: Among the 49 volunteers, 15 showed II genotype; 22, ID genotype; and 12, DD genotype. Serum ACE activity levels were significantly higher in DD genotype subjects than in II genotype subjects (p<0.05). Furthermore, the duration of submaximal isometric contractions was longer in II and ID genotype subjects than in DD genotype subjects (p<0.05). Dynamic EMG showed significantly lower mean frequency changes in II genotype subjects than in DD genotype subjects (p<0.05). However, LBM, BFM, and BMI were independent of ACE genotypes. CONCLUSION: ACE II genotype subjects showed significantly higher resistant to muscle fatigue than that by DD genotype subjects. However, body composition and BMI showed no correlations with ACE I/D polymorphisms.