Intracranial administration of transforming growth factor- 3 increases fat oxidation in rats

Yamazaki, Hanae, Masanao Arai, Shigenobu Matsumura, Kazuo Inoue, and Tohru Fushiki. Intracranial administration of transforming growth factor3 increases fat oxidation in rats. Am J Physiol Endocrinol Metab 283: E536–E544, 2002. First published May 28, 2002; 10.1152/ ajpendo.00094.2001.—The effects of intracranial transforming growth factor (TGF)3 on spontaneous motor activity and energy metabolism were examined in rats. After injection of TGF3 into the cisterna magna of the rat, spontaneous motor activity decreased significantly for 1 h. The intracranial injection of TGF3 produced an immediate decrease in respiratory exchange ratio (RER). No significant changes were observed in energy expenditure. TGF3 induced a significant increase in total fat oxidation and a decrease in total carbohydrate oxidation. Furthermore, the serum substrates associated with fat metabolism were significantly altered in rats injected with TGF3. Both lipoprotein lipase activity in skeletal muscle and the concentration of serum ketone bodies increased, suggesting that the increase in fat oxidation caused by TGF3 may have occurred in the liver and muscle. Intracranial injection of TGF3 appeared to evoke a switch in the energy substrates accessed in energy expenditure. These results suggest that the release of TGF3 in the brain by exercise is a signal for regulating energy consumption.