Corresponding author: Dr. Chia-Hua Kuo, Laboratory of Exercise Biochemistry, Taipei Physical Education College, 101, Jhongcheng Rd., Sec. 2, Shihlin, Taipei 111, Taiwan, ROC. Tel: +886-2-28718288 ext. 5101, Fax: +886-2-28753383, E-mail: kch@tpec.edu.tw Received: June 25, 2007; Revised: August 23, 2007; Accepted: September 12, 2007. 2008 by The Chinese Physiological Society. ISSN : 0304-4920. http://www.cps.org.tw Chinese Journal of Physiology 51(5): 263-268, 2008 263 Suppression of Age-Dependent Increase in Insulinemia in Early Middle-Aged Females with Exercise Habit Tung-Hsiung Hsu 1 , Yuh-Feng Liu 1 , Shin-Da Lee 2 , Shu-Man Chen 3 , Jo-Ping Lee 2 , Chin-Lung Fang 4 , Te-Chih Liu 1 , and Chia-Hua Kuo 1 1 Laboratory of Exercise Biochemistry Taipei Physical Education College, Taipei 2 Department of Physical Therapy China Medical University, Taichung 3 Committee of General Studies Shih Hsin University, Taipei and 4 Department of Physical Education National Taiwan Normal University, Taipei Taiwan, Republic of China Abstract Circulating insulin concentration has been suggested as a biomarker for human longevity. The goal of the study was to determine the insulin levels under a glucose-challenged condition for the sedentary and physical active females in early middle age. We measured serum insulin levels for following groups: young sedentary (Y-SED, age 19.7 ± 0.2 years), middle-aged sedentary (M-SED, age 42.3 ± 3.1 years), young physically active (Y-EX, age 20.7 ± 0.5 years), and middle-aged physically active (M-EX, age 40.3 ± 2.8 years). Oral glucose tolerance test (OGTT) and insulin measurement were performed under overnight fasted condition. Triglyceride, cholesterol, body mass index (BMI), and waist-to-hip ratio (WHR) were also determined in all subjects. While fasted glucose and insulin levels were not different among 4 groups, glucose and insulin levels under OGTT were greater in the M-SED group than those in the Y-SED group. The M-EX subjects exhibited lower insulin levels on OGTT, as compared to the M-SED group, and were similar to the level of Y-SED. BMI and WHR of the M-SED group were comparable to those of the M-EX group. Triglyceride and cholesterol levels were highly associated with age and WHR but not the level of physical activity. The current study found a substantially greater insulin response on OGTT in the healthy sedentary females aged ~40, as compared to those in the young sedentary and the middle-aged physically active females, independent of weight status. The result of the study also suggests that accumulating 150 min of weekly exercise is sufficient to counteract the adverse effect of age on insulin sensitivity. Key Words: exercise, aging, cholesterol, triglyceride, insulin, glucose tolerance Introduction Insulin, produced by the islets of Langerhans in pancreas, is a major anabolic hormone in human body. The amount of pancreatic insulin output to circulation is a function of circulating glucose and peripheral insulin sensitivity. The blood level of this hormone has recently been suggested as a predictor for human longevity according to the combined results from Baltimore Longitudinal Study of Aging and NIA Primate Aging Study (21), in which the group with greater circulating insulin level exhibits faster rate of age-dependent decline