Intracranial administration of transforming growth factor-β3 increases fat oxidation in rats

Abstract

The effects of intracranial transforming growth factor (TGF)-β3 on spontaneous motor activity and energy metabolism were examined in rats. After injection of TGF-β3 into the cisterna magna of the rat, spontaneous motor activity decreased significantly for 1 h. The intracranial injection of TGF-β3 produced an immediate decrease in respiratory exchange ratio (RER). No significant changes were observed in energy expenditure. TGF-β3 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 TGF-β3. Both lipoprotein lipase activity in skeletal muscle and the concentration of serum ketone bodies increased, suggesting that the increase in fat oxidation caused by TGF-β3 may have occurred in the liver and muscle. Intracranial injection of TGF-β3 appeared to evoke a switch in the energy substrates accessed in energy expenditure. These results suggest that the release of TGF-β3 in the brain by exercise is a signal for regulating energy consumption.