A circum-annual study of the fatty acids of brown adipose tissue triglycerides of
Eptesicus fuscus has demonstrated a rhythmic pattern of change. This is seen as a reciprocal shift of the levels of oleic and linoleic acids.
Oleic acid levels are lower during the summer months and higher in the winter months. Levels of palmitic and linoleic acids
reach maximal values in midsummer and fall significantly during the winter.
Homogenates of brown adipose tissue produce more14CO2 from 1-14C-palmitic acid than from 1-14C-oleic acid when incubated at temperatures below 20C. The formation of14CO2 from either substrate was maximal in the neighborhood of 30C, and the temperature effect was enhanced by stimulation with
DL-carnitine.
It is proposed that the rhythmic change in brown adipose tissue triglyceride composition is a reflection of the different
rates of fatty acid oxidation and the absence of normal food intake for extended periods of time.