ADIPOCYTE TURNOVER: RELEVANCE TO HUMAN ADIPOSE TISSUE MORPHOLOGY

Abstract

Objective: Adipose tissue may contain few large adipocytes (hypertrophy) or many small adipocytes (hyperplasia). We investigated factors of putative importance for adipose tissue morphology.

Research Design And Methods: Subcutaneous adipocyte size and total fat mass were compared in 764 subjects with body mass index 18-60 kg/m². A morphology value was defined as the difference between the measured adipocyte volume and the expected volume given by a curve-line fit, for a given body fat mass and was related to insulin values. In 35 subjects, in vivo adipocyte turnover was measured by exploiting incorporation of atmospheric¹⁴C into DNA.

Results: Occurrence of hyperplasia (negative morphology value) or hypertrophy (positive morphology value) was independent of gender and body weight but correlated with fasting plasma insulin levels and insulin sensitivity, independently from adipocyte volume (beta coefficient=0.3, p<0.0001). Total adipocyte number and morphology were negatively related (r=-0.66); i.e. the total adipocyte number was greatest in pronounced hyperplasia and smallest in pronounced hypertrophy. The absolute number of new adipocytes generated each year was 70% lower (p<0.001) in hypertrophy than in hyperplasia and individual values for adipocyte generation and morphology were strongly related (r=0.7; p<0.001). The relative death rate (about 10% per year) or mean age of adipocytes (about 10 years) was not correlated with morphology.

Conclusions: Adipose tissue morphology correlates with insulin measures and is linked to the total adipocyte number independently of gender and the body fat level. Low generation rates of adipocytes associate with adipose tissue hypertrophy whereas high rates associate with adipose hyperplasia.