Abstract
Associations of adipose tissue insulin resistance index (AT-IR, a product of fasting insulin and free fatty acids) with body fat mass and distribution and appendicular skeletal muscle mass (ASM) were compared with results of homeostasis-model assessment-insulin resistance (HOMA-IR) in 284 Japanese female university students and 148 their biological mothers whose BMI averaged <23 kg/m2. Although mothers compared with daughters had higher BMI, body fat percentage and trunk fat to body fat (TF/BF) ratio and lower leg fat to body fat (LF/BF), AT-IR and HOMA-IR did not differ. We had multivariable linear regression analyses which included TF/BF ratio, LF/BF ratio, weight-adjusted ASM (%ASM), height-adjusted ASM index (ASMI), fat mass index (FMI) and body fat percentage. In young women, AT-IR was independently associated with LF/BF ratio (Standardized β [Sβ]: -0.139, p=0.019) and ASMI (Sβ: -0.167, p=0.005). In middle-aged women, LF/BF ratio (Sβ: -0.177, p=0.049) and %ASM (Sβ: -0.205, p=0.02) emerged as independent determinants of AT-IR. HOMA-IR was associated with TF/BF ratio and FMI, a proxy of abdominal and general adiposity, respectively, in both young and middle-aged women. Inverse association of AT-IR with leg fat may support the notion that limited peripheral adipose storage capacity and small skeletal muscle size are important etiological components in insulin-resistant cardiometabolic disease in Japanese women.