Lipid synthesis: a thermogenic mechanism in cold-exposed Zucker fa/fa rats.
1. The oxygen consumption and carbon dioxide production of Wistar and Zucker lean (Fa/?) and obese (fa/fa) rats was measured at 4, 10, 20 and 30 degrees C. 2. There was a net synthesis of lipid at the expense of carbohydrate in Wistar rats at 20 degrees C, with active lipid oxidation at 4 degrees C, and increasing heat production at lower temperature. Zucker lean rats also showed this trend. 3. Zucker fa/fa rats synthesized lipid at 4, 10 and 20 degrees C, showing a less marked increase in heat production with lowering temperature. 4. It is postulated that Zucker obese rats synthesize lipids as a way to obtain residual metabolic heat to maintain their body temperature. This is part of a process--fully functional in Wistar and Zucker lean rats, and truncated in Zucker obese rats--in which liver lipogenesis can combine with brown adipose tissue lipolysis to generate enough heat to maintain body functions under a cold environment.
Esteve
M
M
Departament de Bioquímica i Fisiologia, Universitat de Barcelona, Spain.
Rafecas
I
I
Fernández-López
J A
JA
Remesar
X
X
Alemany
M
M
D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D003080:Cold Temperature; D004040:Dietary Carbohydrates / Q000378:metabolism; D004435:Eating / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D008055:Lipids / Q000096:biosynthesis*; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D011924:Rats, Zucker
D004040:Dietary Carbohydrates; D008055:Lipids