INSULIN BUT NOT GLUCOSE IS RELATED TO FITNESS AND BODY COMPOSITION IN HEALTHY OLDER ADULTS

80 We examined the relationship between fitness level, body composition, fasting insulin concentration, and glucose area-under-the-curve (GAUC) from an oral glucose tolerance test (OGTT) in healthy older adults. Subjects were 19 females (F) who were not on estrogen (age=67±4.9 yr, Ht=163.0±5.3 cm, Wt=71.2±11.6 kg) and 29 males (M) (age=66.9±4.2 yr, Ht=177.3±7.0 cm, Wt=85.9±11.1 kg) (Mean±SD). Body density was measured by hydrostatic weighing and percent body fat was calculated using the Siri equation. Abdominal visceral fat (AVF) cross-sectional area was determined using single slice CT at L4-L5. Fasting insulin concentration was measured at −30 min. Glucose concentrations during the OGTT (75 g dextrose) were measured every 30 min from −30 to 180 min. GAUC was calculated using the trapezoidal rule. Simple linear regression analysis was performed on each gender separately. In males, the following results were observed: 1) GAUC was not significantly related to AVF, AVF adjusted for fat mass, percent body fat, fat mass, BMI or fitness [as assessed by VO2 peak (ml/kg/min)], 2) fasting insulin level was significantly related to AVF (r=0.49, P=0.007) and fitness (r=−0.38, P=0.04), but not to AVF adjusted for fat mass, BMI, percent body fat, GAUC or fat mass. In females, the following results were observed: 1) GAUC was significantly related to AVF (r=0.54, P=0.02), but not to AVF adjusted for fat mass, percent body fat, fat mass, BMI, or fitness, 2) fasting insulin level was significantly related to AVF (r=0.78, P=0.0002), AVF adjusted for fat mass (r=0.69, P=0.0003), BMI (r=0.7, P=0.0002), fat mass (r=0.69, P=0.003), and GAUC (r=0.47, P=0.05), but not to percent body fat or fitness. We conclude that in healthy older adults, fasting insulin concentration is more strongly related to measures of body composition and fitness than GAUC. Supported in part by NIH grant R01AG10997 and by GCRC grant NIH RR00847