Effect of high fat diets on the thermogenic activity of brown adipose tissue in cold-acclimated mice.

The effects of feeding high fat diets on thermogenesis in brown adipose tissue has been investigated in cold-acclimated mice. Two high fat diets of differing fatty acid composition were used, one of which was based on corn oil and the other on beef tallow. After 3 weeks of feeding the diets there was little difference in the weight, protein content and cytochrome oxidase activity of brown adipose tissue (interscapular plus subscapular) of mice fed the high fat diets from those given the low fat stock diet. However, the mice fed the high fat diets showed marked increases in mitochondrial GDP binding and in mitochondrial respiration, consistent with an augmentation in the activity of the proton conductance pathway. This increase in thermogenesis in brown adipose tissue mitochondria occurred without any elevation in digestible energy intake, and is therefore not a response to overfeeding. It is concluded that the activity of the proton conductance pathway in brown adipose tissue of cold-acclimated mice can be modulated by the level of dietary triglyceride independently of energy intake. We suggest that the effect of high fat diets on thermogenesis in brown adipose tissue may relate to the suppressive effects of dietary lipid on fatty acid synthesis in the tissue.