大鼠腦區DHA回復動力效能之研究

Abstract

二十二碳六烯酸（C22：6 n-3, DHA）在腦區及視網膜的發育與功能上扮演ㄧ相當重要的角色。動物的DHA需經由次亞麻油酸（C18：3 n-3, LNA），一種必須脂肪酸代謝轉換而成，或從魚油中直接獲得。本實驗目的在於探討經由富含DHA的魚油補充之後，DHA缺乏大鼠各腦區DHA回復動力比較。母鼠懷孕開始便餵食不含n-3脂肪酸的葵花油飼料（sunflower oil），創造出腦部DHA缺乏的動物，並分別補充0天、5天、10天、20天、30天以及40天的魚油，動物於65天大時犧牲取組織，利用氣相層析儀（Gas Chromatography）進行脂肪酸成份分析。結果發現： 各腦區均出現隨著魚油補充，DHA上升而DPA代償性下降的趨勢。視網膜的DHA回復在5D的魚油補充組就能看到顯著上升，最高可達91％的回復率。而視覺皮質區要在餵食魚油30天以上的組別DHA才會有明顯的增加，40天的魚油補充之後回復率可達九成七。嗅球（olfactory bulb）是與學習相關的重要腦區，control組的嗅球DHA含量佔總脂肪酸的12.2％，經n-3脂肪酸飲食缺乏之後，DHA的流失率有56.3％，至於回復率則是最低的75.6％。與條件學習行為相關的海馬迴（hippocampus）、小腦(cerebellum)等腦區DHA均可完全回復且速度較快，而餵食Chow diet之control組海馬迴DHA含量雖較其他腦區低，但其藉飲食剝奪n-3脂肪酸而造成的流失率最低，補充魚油之後的回復率也最高，推論海馬迴保留DHA的趨勢較強。 综上所述，缺乏DHA的各腦區之回復效率並不相同，具腦區特異性（Regional-specific）。

The deficiency of brain docosahexaenoic acid (C22:6n-3, DHA) is associated with reduced learning ability and cognition. The aim of this study is to measure the dynamics of DHA recovery in various DHA deficient rat brain regions. The DHA deficient rat was created by feeding sunflower oil as n-3 deficient diet for one generation. The pups were supplemented DHA-rich fish oil from 0 up to 40 days. It was found that: The % DHA loss in n-3 deficient rats compared with the chow diet feeding animals was 67% in retina, 61% in cerebellum, 56% in olfactory bulb, 56% in visual cortex, and 50% in hippocampus. Up to 40 days fish oil supplementation, the DHA recovery is 113% in hippocampus, 112% in cerebellum, 97% in visual cortex, 91% in retina, and 76% in olfactory bulb. The T1/2 for the DHA recovery is 16.8 days in cerebellum, 21.7 days in retina, 24.4 days in hippocampus, and 28.5 days in visual cortex, and 37.4 days in olfactory bulb. It was concluded that the hippocampus was a unique area for resistance of DHA deprivation by n-3 deficient diet and high efficiency for DHA recovery followed by fish oil supplementation. It is suggested that brain DHA recovery was region specific.