Journal of Applied Physiology, Vol 57, Issue 4 1120-1125, Copyright © 1984 by American Physiological Society
Effects of cell size and exercise on glucose uptake and metabolism in adipocytes of female rats
B. W. Craig and P. J. Foley
The purpose of this study was to attain a better understanding of how the
adipocyte transports and metabolizes glucose with and without the influence
of exercise training. Rates of 2-deoxyglucose and glucose oxidation, using
[1-14C]-and [6-14C]glucose, were measured in adipocytes from
exercise-trained and sedentary control female rats of the same age. The
trained animals were exercised by swimming, 6 h/day, 5 days/wk for 10 wk.
The fat cells of the sedentary rats were significantly larger (P less than
0.005) than the trained animals and had very low rates of glucose uptake
and [1-14C]- and [6-14C]glucose oxidation. The adipocytes of the trained
rats were very responsive to insulin with 2-deoxyglucose rates seven times
higher than those of the control animals and [1-14C]- and [6-14C]-glucose
oxidation rates 14- and 13-fold (respectively) larger than control values.
Comparisons of the data from exercised animals to younger sedentary rats
indicates that glucose oxidation remains normal in the adipocytes of the
trained animals whereas glucose transport is greatly improved. If the older
sedentary controls are compared to younger animals, it can be seen that as
the cell enlarges it loses its ability to take up or metabolize glucose.
The combination of a loss in glucose transporting capacity with cellular
enlargement and an increase in glucose uptake with exercise training
suggests that movement of glucose across the cell membrane may be a
limiting factor in glucose utilization in fat cells.
