Sesamin is known as a specific inhibitor of
Δ-desaturation, the conversion from dihoo-γ-linolenic acid (20: 3(
n-6)) to arachidonic acid (20:4(
n-6)). In the previous paper, we reported that sesamin inhibited
Δ-desaturation of
n-6 fatty acids in rat hepatocytes but not that of
n-3 fatty acids, from 20: 4(
n-3) to 20: 5(
n-3). Then, we studied the effects of sesamin on
Δ-desaturation of
n-6 and
n-3 fatty acids in vivo. Rats were fed two types of diets containing sesamin (0.5% w/w) for 4 weeks as follows: in experiment 1 (Exp. 1) γ-linolenic acid-rich diet and in experiment 2 (Exp. 2) a-linolenic acid-rich diet. The fatty acid composi-tion of liver lipids was compared to those of control groups without sesamin. In both Exps. 1 and 2, sesamin increased the liver weight and phospholipid contents in liver. In Exp. 2, sesamin increased
n-6 fatty acids and decreased
n-3 fatty acids even though the diet was rich in
n-3 fatty acids. Sesamin enhanced the composition ratio of 20: 3(
n-6) in both Exps. 1 and 2. Decrease of
Δ-desaturation index of
n-6 fatty acid, the ratio of 20:4(
n-6)/20: 3(
n-6), by the administration of sesamin suggested that sesamin inhibited the
Δ-desaturation of
n-6 fatty acids in the liver. On the contrary, the
Δ-desaturation index of
n- 3 fatty acids, the ratio of 20: 5(
n-3) to 18: 3(
n-3), was increased by sesamin administration in the liver of rats fed a-linolenic acid-rich diet (Exp. 2). These results sug-gested that sesamin inhibited the
Δ-desaturation of
n-6 fatty acids but not that of
n-3 fatty acids in vivo similarly to results from rat hepatocytes.
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