Poster Sessions

Biophys-3

Junghyo Jo

J. Jo, O. Gavrilova, S. Pack, W. Jou, S. Mueller, A. Sumner, S. Cushman, V. Periwal

Hypertrophy and/or hyperplasia: Dynamics of adipose tissue growth

Adipose tissue grows by two mechanisms: hyperplasia (cell number increase) and hypertrophy (cell size increase). How do genetics and diet affect the relative contributions of these two mechanisms to the growth of adipose tissue in obesity? In this study, the size distributions of epididymal adipose cells from two mouse strains, FVB/N and C57/Bl6, were measured by the Beckman-Coulter Multisizer after 2, 4, and 12 weeks under regular and high fat feeding conditions. The total fat pad cell number was estimated from the epididymal fat pad mass and the normalized cell-size distribution. To address adipose tissue growth precisely, we propose a mathematical model describing the evolution of the adipose cell-size distributions according to the increase of fat mass. It considers the recruitment of new adipose cells and their subsequent development. Our model can describe all the size distributions of different strains and diet regimes by adjusting model parameters. The differences in parameter values can explain the strain differences between obesity-resistant FVB/N mice and obesity-prone C57/Bl6 mice, as well as the effect of chow (low fat) and high fat diets on adipose tissue growth in these two strains. Compared to the FVB/N strain, the C57/Bl6 strain has higher recruitment of small adipocytes. This hyperplastic growth in both strains is enhanced by high fat diet. Moreover, high fat feeding increases the rate of adipose cell size growth, independent of strain, reflecting the increase in calories requiring storage. Additionally, high fat diet induces a dramatic increase in the rate at which adipose cell size spreads in both strains. This may reflect increased triglyceride turnover.