老化、性別及大腦發育期n-3脂肪酸缺乏飲食對大鼠組織重量與腦部二十二碳六烯酸及學習記憶表現之影響

Abstract

二十二碳六烯酸 (docosahexaenoic acid, DHA, C22:6n-3) 是n-3多元不飽和脂肪酸，富含於腦部的神經細胞膜上，影響神經發育與功能，DHA主要於大腦發育期，也就是親代懷孕泌乳時期於子代的腦部大量堆積。根據過去研究顯示，性別、老化及飲食都可能會對腦部DHA含量產生差異，故本實驗主要探討性別、老化及親代懷孕泌乳時期攝取n-3缺乏飼料是否會影響其腦部DHA的含量及學習記憶，並探討對體重、周邊器官及腦部組織重量的影響。 性別方面的實驗，雄鼠與雌鼠終生皆食用chow diet至9個月大。老化及飲食方面的實驗，親代在懷孕泌乳期及其子代雌鼠3個月大前分別食用n-3脂肪酸缺乏飼料以及n-3脂肪酸充足飼料，之後則皆改為攝取n-3脂肪酸缺乏飼料至13個月或17個月大。 本篇論文先使用氣相層析儀火焰離子偵測器與質譜儀偵測器比較大鼠腦部與肝臟脂肪酸分析之結果，發現兩種偵測器在同樣的分析條件下，同一脂肪酸樣品所得出的各脂肪酸百分比結果均相同。在體重、器官及腦部組織重量的實驗中，雄鼠的體重和肝臟較雌鼠的重，下視丘與腦下垂體則是雌鼠較重。而老化雌鼠只會增加體重與肝重。親代懷孕泌乳時期攝取n-3脂肪酸缺乏飼料會造成其雌性子代日後子宮、腎上腺體與腦下垂體重量增加及下視丘減輕。在脂肪酸分析與學習記憶的實驗中，雌鼠老化後其腦部DHA含量無改變。雄鼠與雌鼠腦部DHA含量及空間學習表現皆無差異。大腦發育期若因親代攝取缺乏n-3脂肪酸飼料會降低日後腦部DHA的含量，但在空間學習表現上無差異。 綜合本實驗可知，體重、器官及腦部組織重量會受到性別、老化及大腦發育期n-3脂肪酸缺乏與否等因素影響。大腦發育期缺乏n-3脂肪酸會降低日後腦部DHA含量，然而減少的量並不足以影響學習記憶的表現。

Docosahexaenoic acid (DHA, C22:6n-3) is an n-3 polyunsaturated fatty acid and mainly enriched in the neuronal membranes of brain for the normal neurological function. Most DHA accumulates in the brain during brain development. The aim of this study was to evaluate the effect of gender, aging and n-3 PUFA deficient diet during brain development on the DHA levels in the brain and learning memory as well as the on the body weight, organ and brain tissue weight. To examine the effect of gender, male and female rats fed a chow diet until 9 months old. While exploring the effect of aging and diet, maternal rats during pregnancy and lactation and female offspring before 3 months old fed an n-3 PUFA adequate diet or n-3 PUFA deficient diet. After that, the rats all fed an n-3 PUFA deficient diet until 13 or 17 months old. We used GC-FID and GC-MS for fatty acid analysis of the brain and liver of rats and the results from these two detectors showed no difference. The body and liver weight in female rats were significant higher than those in males, whereas an opposite result was seen for the hypothalamus and pituitary gland. However, brain DHA levels and learning memory performance showed no gender difference. The increase of body and liver weight but no difference in brain DHA levels were observed in aged female rats. The n-3 PUFA deficiency in female rats during brain development resulted in higher weight of uterus, adrenal gland and pituitary gland while lower weight of hypothalamus as well as decreased brain DHA levels, but no effect on the performance of learning memory. This study showed effect of gender, aging and n-3 PUFA deficiency during brain development on the tissue weight. Moreover, n-3 PUFA deficiency during brain development decreased brain DHA levels, but this would not impede learning memory.