Subcutaneous Adipose Cell Size and Distribution: Relationship to Insulin Resistance and Body Fat

Metabolic heterogeneity among obese individuals may be attributable to differences in adipose cell size. We sought to clarify this by quantifying adipose cell-size distribution, body fat, and insulin-mediated glucose uptake in overweight/moderately-obese individuals. 148 healthy nondiabetic subjects with BMI 25–38 kg/m(2) underwent subcutaneous adipose tissue biopsies and quantification of insulin-mediated glucose uptake with steady-state plasma glucose concentrations (SSPG) during the modified insulin suppression test. Cell-size distributions were obtained with Beckman Coulter Multisizer. Primary endpoints included % small adipose cells and diameter of large adipose cells. Cell-size and metabolic parameters were compared by regression for the whole group; according to IR and IS subgroups; and by body fat quintile. Both large and small adipose cells were present in nearly equal proportions. Percent small cells was associated with SSPG (r=0.26, p=0.003). Compared to BMI-matched IS individuals, IR counterparts demonstrated fewer, but larger large adipose cells, and a greater proportion of small-to-large adipose cells. Diameter of the large adipose cells was associated with %body fat (r=0.26, p=0.014), female sex (r=0.21, p=0.036), and SSPG (r=0.20, p=0.012). In the highest vs lowest % body fat quintile, adipose cell size increased by only 7% whereas adipose cell number increased by 74%. Recruitment of adipose cells is required for expansion of body fat mass beyond BMI of 25 kg/m(2). Insulin resistance is associated with accumulation of small adipose cells and enlargement of large adipose cells. These data support the notion that impaired adipogenesis may underlie insulin resistance.