Thigh adipose tissue distribution is associated with insulin resistance in obesity and in type 2 diabetes mellitus

Abstract

Background: Adipose tissue (AT) content of the thigh is generally not considered to be associated with insulin resistance (IR), but it is unclear whether the distribution of AT in the thigh is a determinant of IR. Objective: We investigated whether subcompartments of AT within the thigh are determinants of IR. Design: Midthigh AT, muscle composition, and insulin sensitivity were compared in 11 obese patients with type 2 diabetes mellitus (DM); 40 obese, glucose-tolerant (GT) and 15 lean, GT volunteers; and 38 obese subjects who completed a weight-loss program. Midthigh AT area measured with computed tomography was partitioned into 3 components: subcutaneous AT (SCAT), AT beneath the fascia (SFAT), and AT infiltrating muscle groups (IMAT). Muscle attenuation characteristics were determined. Results: Obese DM and obese GT subjects had lower insulin sensitivity than lean GT subjects. SCAT was greater in obesity, yet did not correlate with insulin sensitivity. SFAT was ≈8% of total thigh AT and correlated with insulin sensitivity. IMAT was highest in obese DM, and although it accounted for only ≈3% of thigh AT, it was a strong correlate of insulin sensitivity. Mean attenuation was highest in lean subjects and was associated with higher insulin sensitivity. Weight loss reduced the amount of thigh AT, the proportion of thigh IMAT, and the amount of low-density thigh muscle. Conclusions: SFAT and IMAT are markers of IR in obesity and DM although they are much smaller than SCAT, which does not predict IR. Muscle composition reflecting increased fat content is also associated with IR.