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 α-tocopherol (Toc) or tocotrienol (T3) mixture (composed of 20.5% α-Toc, 21.4% α-T3, 36.5% γ-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 α-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 α-Toc or T3, but the effect on immunoglobulin productivity from spleen and mesenteric lymph node (MLN) was not as marked. Feeding of α-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% α-Toc 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 α-Toc, and that MLN and adipose tissue are the main target tissues of T3.