Interpretive Summary: 

In some mammals, the major source of heat during cold exposure is a specialized tissue called brown adipose tissue (BAT). Mitochondria in BAT are components of the cell that produce heat as well as energy. This heat production is dependent on many variables including elements such as copper, thyroid hormones and certain chemicals produced by the central nervous system. A lack in any one of these important variables results in the inability of the animal to keep warm when exposed to the cold. We compared rats fed a diet lacking in copper to others either started on a diet lacking in copper then switched to a diet with adequate copper, or maintained on a diet with adequate copper. Rats fed the low copper diet had a decrease in thyroid hormones and a greater loss of body heat when exposed to the cold. In contrast, the rats given supplemental copper after receiving the low copper diet had thyroid hormone levels and body temperatures similar to the rats fed the adequate copper diet. The shape of the inside of the mitochondria changes when there is a lack of copper in the diet. A different change occurs when the animal is exposed to the cold, even in the animals with adequate copper. Inadequate copper in the diet causes changes in the structure of BAT mitochondria that suggest an inability to produce heat. These changes imply that the copper deficient BAT cannot maintain necessary heat production because of its altered mitochondrial structure. These findings will be useful to customers who investigate how nutrients affect energy metabolism. 

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Updated: 1998-12-18