Interaction of Estrogen and Docosahexaenoic Acid on the Maintenance of Hippocampal Neuron Function

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Project title/計畫英文名

Project Number/計畫編號

MOST103-2320-B002-022-MY3

Translated Name/計畫中文名

雌激素和二十二碳六烯酸對維持海馬迴神經功能之交互作用

Project Principal Investigator/計畫主持人

HUI-MIN SU

Funding Organization

National Science and Technology Council

Start date/計畫起

01-08-2016

Expected Completion/計畫迄

12-07-2017

摘要：本計畫在探討雌激素是否對維持海馬迴 docosahexaenoic acid (DHA, 22:6n-3)含量及神經認知功能扮演一重要角色。 DHA 是構成神經細胞膜結構最主要成分，用以維持其正常神經功能表現。然而大鼠海馬迴中 DHA 含量會隨年齡增加而遞減，而人類的阿茲海默氏病人，掌管短期記憶的海馬迴中 DHA 含量亦減少一半，也都伴隨學習記憶能力降低。雌激素和 DHA 均為維持海馬迴記憶學習的重要物質，兩者是否有交互作用，目前不詳。研究發現服用含雌激素避孕藥婦女較未服用者，有較高轉換 18:3n-3 至 DHA 能力，變性手術者，女變男去卵巢後，其血漿 DHA 含量降低，而男變女後補充雌激素，血漿中 DHA 含量隨之升高，停經後婦女補充雌激素，血漿中 DHA 含量較未補充者高，且可有效降低認知退化及減少罹患阿茲海默氏的危險性，顯示雌激素對生物體內 DHA合成及含量扮演一重要角色。利用 6 個月大雌鼠進行兩側卵巢切除手術後，探討是否會影響其 DHA 合成酵素表現，減少 DHA 合成及吸收、及增加 DHA 轉換，而加速其腦區 DHA 流失，影響神經細胞新生、降低記憶學習能力，而魚油或雌激素補充至其 12 個月大時犧牲，應可減緩其發生。初級海馬回神經細胞實驗將更完整探討雌激素添加，促進由[U-13C]-18：3n-3 轉換生成 DHA、增加吸收及減少[U-13C]-DHA 轉換。本計畫可釐清婦女停經後，海馬迴 DHA 含量及學習記憶能力是否會因此而下降，是否可藉由雌激素及魚油補充，減緩其認知退化。並期盼進一步能證實，是否可藉魚油攝取，而非雌激素補充，即能有效減緩認知退化以降低罹患乳癌風險。
Abstract: The aim of this proposal is to determine if estrogen play an essential role in the accumulation of docosahexaenoic acid (DHA, 22:6n-3) on the maintenance of the hippocampal neuron function by conducting studies in ovariectomy (OVX) female rats and primary hippocampal neurons with or without estrogen, progesterone or DHA supplementation. DHA is mainly enriched in neuronal membrane and is essential for normal neurological function. However, hippocampal DHA levels decrease with age in rats and are reduced in the human brain disorder Alzheimer’s disease (AD), that is therefore associated with reduced learning ability in rats and memory loss in AD patients. Estrogen has similar effects to DHA on hippocampal function and it would be interesting to know if there is any interaction between the effects of DHA and estrogen on learning memory function. Women of reproductive age take oral contraceptive containing estradiol have higher 18:3n-3-converted DHA than those without taking oral contraceptive. Plasma DHA levels are increased in male-to-female transsexual subjects receiving estradiol and decreased in female-to-male transsexual subjects who have undergone OVX and are receiving testosterone. But there is still no direct evidence shown in brain for this finding. It is not known whether hippocampal DHA levels would be reduced in postmenopausal women with estrogen deprivation. In addition, postmenopausal women with estrogen replacement therapy have higher plasma DHA levels, delay cognitive decline and reduce AD risk than those without hormone replacement therapy but may increase the risk of breast cancer. It is important to clarify the relationship between DHA and estrogen on the AD prevention in order to provide a better therapy for no risk on both of AD and breast cancer. In the OVX rat study, we hypothesize expression of enzymes involved in the DHA biosynthesis and hippocampal DHA levels would be decreased by OVX and the reducing could be retrieved or avoided by estradiol supplementation. We will determine the DHA biosynthesis, incorporation and turnover in hippocampus with the administration of [U-13C]-18:3n-3 or [U-13C]-22:6n-3. We will evaluate whether OVX may decrease neurogenesis resulted in learning memory loss. While, fish oil or/and estradiol supplementation may retrieve back or avoid those change. 6-month-old female rats will be OVX or sham operation and then feeding n-3 fatty acid-deficient diet supplemented without or with estradiol, progesterone or/and fish oil till sacrificed at age of 12-month-old. The in vivo experiments will be complemented and extended by studies in primary hippocampal neurons to determine the role of estrogen on DHA biosynthesis and turnover. The labeling of fatty acids will be measured in primary hippocampal neurons incubated with [U-13C]-18:3n-3 or [U-13C]-22:6n-3 with or without estradiol or progesterone supplementation. This study should contribute the understanding the effect of estrogen deprivation on hippocampal DHA levels and cognitive behavior, as well as the interaction between DHA and estrogen so as to provide a better strategy for the maintenance of learning memory.

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Interaction of Estrogen and Docosahexaenoic Acid on the Maintenance of Hippocampal Neuron Function

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