Morphology and metabolism of human fat cells: a reliability study.

Twenty-three male subjects, 31.7 (mean) +/- 7.4 (s.d.) yr of age, weight 70.7 +/- 9.0 kg and with 13.4 +/- 4.7 percent body fat were submitted twice within a week to biopsies of subcutaneous adipose tissue in the suprailiac region. Two biopsies (sample A and B) were obtained on day 1 and two others (sample C and D) in the contralateral region on day 2. Average fat cell diameter (ACD) was assessed by measuring at least 500 cells per subject. There was no significant difference between day 1 and day 2 for ACD (means 1 = 62.6 +/- 12.2 micron; means 2 = 63.2 +/- 12.3 micron). Intra-class reliability coefficient reached 0.97. ANOVA-RBFD showed no day or sample effects (P greater than 0.05) on ACD. Basal (BL), epinephrine submaximal (10(-5) M) (ESML) and epinephrine maximal (10(-4) M) (EML) stimulated lipolysis have been determined for 18 of these subjects. Intra-class reliabilities were moderately high, reaching 0.71 for BL, 0.83 for ESML and 0.72 for EML, respectively. Controlling the level of activity for 36 h prior to the biopsies resulted, however, in increased coefficients. In this case, intra-class coefficients computed with 11 subjects were 0.99 for BL, 0.88 for ESML and 0.85 for EML. The data demonstrate that ACD and lipolytic capacity can be reliably measured, particularly when activity of subjects is controlled during the 36-h period preceding the biopsies.