Effects of the long-term (17-19 months) feeding of high-iodine eggs on lipid metabolism and thyroid function in rats.

The present paper describes the effects of long-term (17-19 months) feeding of high-iodine eggs on lipid metabolism and thyroid function of rats, and also the effects of inorganic iodine on lipid metabolism. Rats were meal-fed on a diet containing 1% (w/w) of ordinary egg powder (OE diet as control: 35 micrograms I/100 g) or high-iodine egg powder (IE diet: 392 micrograms I/100 g). After the 19-month dietary treatment, rats fed on the IE diet, compared with the controls, showed a higher tissue lipoprotein lipase activity, a lower lipid peroxide level in the brain and a trend toward lower serum triacylglycerol levels and body fat storage without alterations in serum levels of thyroid-related hormones (TSH, T3 and T4). From the results of cold exposure and anti-thyroid drug-treatment conducted on rats fed on the OE and IE diets for 17 months, high-iodine eggs seemed to improve the age-related defects in thermogenic and thyroid hormone responses to cold, and also to result in a resistance to the anti-thyroid drug. The effects of the IE diet on lipid metabolism of rats were partly exhibited by feeding of the OE diet with an equivalent amount of iodine added as KI or KIO3. Thus, it is suggested that iodine ingestion through high-iodine eggs modulates both lipid metabolism and thyroid function in rats.