Dietary effect of α-tocopherol and tocotrienols on lipid metabolism and immune function of aged Sprague-Dawley rats

Eight-month-old male Sprague Dawley rats were fed diets containing alpha-tocopherol (Toc) or tocotrienol (T3) mixture (composed of 20.55% alpha-Toc, 21.4% alpha-T3, 36.5% gamma-T3 and other analogs) at the 0.1 or 0.5% level for 3 weeks to examine their dietary effects on lipid metabolism and immune indices. Feeding of alpha-Toc and T3 significantly decreased liver phosphatidylcholine peroxide and serum phospholipid levels. In the regulation of immunoglobulin level, significant increase in serum IgA level was observed in the rats fed alpha-Toc or T3, but the effect on immunoglobulin productivity from spleen and mesenteric lymph node (MLN) was not as marked. Feeding of alpha-Toc and T3 significantly decreased LTB4-releasing activity of peritoneal exudate cells without decreasing arachidonic acid level. The suppression of LTB4 release was more marked in the rats fed 0.1% alpha-Toe or T3 than in these fed them at the 0.5% level. When animals were killed after 10 h of fasting, T3 was detected only in MLN and epidydimal adipose tissue. These results suggest that T3 modulates lipid metabolism and immune functions as well as alpha-Toc, and that MLN and adipose tissue are the main target tissues of T3.