AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 6 1109-R1117, Copyright © 1986 by American Physiological Society
Insulin and metabolic efficiency in rats. I. Effects of sucrose feeding and BAT axotomy
T. J. Bartness, C. J. Billington, A. S. Levine, J. E. Morley, D. M. Brown and N. E. Rowland
The role of insulin and brown adipose tissue (BAT) thermogenesis in
metabolic efficiency (ME, the efficiency of body wt gain) was examined in
rats with varied basal insulin status. Long-lasting insulin was
administered using a protocol that did not alter food intake, yet increased
ME in both groups. Half the rats were fed sucrose to stimulate BAT growth
and thermogenesis. Insulin overrode the exaggerated decrease in ME in
sucrose-fed diabetics, with only partial attenuation in controls.
Interscapular BAT (IBAT) lipoprotein lipase activity was decreased in
diabetic rats, restored by insulin treatment, and not affected in controls.
Sucrose-fed diabetics and controls had their IBAT sham or bilaterally
surgically denervated. Insulin decreased the thermogenic potential of BAT
[cytochrome oxidase activity (COA)] in intact controls and diabetics; in
the latter, insulin restored COA independent of BAT innervation. We
conclude that insulin can increase ME without an associated increase in
energy intake, regardless of basal insulin status, both insulin deficiency
and excess decrease BAT thermogenic potential (COA), and
hyperinsulinemia-induced increases in ME may result from decreased BAT
mitochondrial proliferation.
