Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/50979
標題: 去氫雄表固酮: 食物中抗氧化物對組織含量, 抗氧化活性和其毒性之影響
DHEA:Effects of dietary antioxidants on tissue contents, antioxidative activity and toxicity
作者: 黃喜波
NG, Hee Poh
關鍵字: dehydroepiandrosterone;去氫雄表固酮;vitamin E;selenium;toxicity;red cells;rats;維生素 E;硒;毒性;紅血球;大鼠
出版社: 食品科學系
摘要: 
人體的循環體液中,存有一種含量豐富的腎上腺質素(adrenal steroid
hormone),即去氫表雄固酮 (DHEA, dehydroepiandrosterone)。DHEA是
雄性和雌性激素的前驅物,其含量在二十五歲達到巔峰,此後便隨年齡上
升而含量下降,在七、八十歲時,含量約只有二十五歲時的10 %,所以
DHEA曾被認為與老化有關。此種DHEA隨年齡變化之現象是否與氧化傷害或
體內抗氧化能力降低所造成,是本論文所要探討的重點之一。此外,有不
少報導指出補充DHEA具有許多功能,如抗肥胖、抗癌和抗心血管疾病。然
而,也有報導指出DHEA可能具有致癌性或改變G6PD (glucose
6-phosphate dehydrogenase)的活性和促進脂質過氧化的副作用。為了探
討DHEA含量是否與體內抗氧化能力有關以及DHEA是否具有毒性或抗氧化性
,本研究論文共分成三部份:( I ) 探討維生素E和硒對大鼠體內之DHEA
含量的影響;( II ) 探討攝食中缺乏或補充適量的維生素E之大鼠在注射
DHEA一週後,DHEA是否具有毒性;( III ) 探討DHEA在試管試驗中(37℃,
反應一小時)造成人體紅血球細胞溶血的機制。此三部份的實驗模式和結
果如下: ( I ) 探討維生素E和硒對大鼠體內之DHEA含量的影響
:以雄性 SD (Spraque-Dawley)大鼠(約四週大)餵食有、無硒元素以及缺
乏、適量(30 IU/kg diet)以及高量(200 IU/kg diet) 維生素E等六大組
進行實驗。結果顯示餵食硒和高量維生素 E 顯著增加大鼠之睪丸相對重
量。如所預料,攝食含硒飼料的大鼠血清glutathione peroxidase活性遠
高於攝食缺乏硒飼料的大鼠。在腎上腺,餵食硒和維生素E明顯增加DHEA
的含量,但是攝食高量的維生素E並沒有較高的DHEA含量。硒和維生素E對
於DHEA的含量兩者並無交互的影響。攝食30 IU/kg的維生素E顯著的增加
大鼠腦部的DHEA含量,但攝食200IU/kg的維生素E並沒有較高的DHEA含量
。相同的,只有攝食具有維生素E飼料,才會影響大鼠血清中的DHEA含量
。以上結果說明年輕大鼠組織和血清中的DHEA含量主要是受到攝食維生素
E的飼料所影響。 ( II ) 食物中維生素E在DHEA短期的毒性對大
鼠之影響:四週齡之SD大鼠被餵食缺乏或足夠維生素E (30 IU/kg)飼料四
週後,以腹腔注射方式給予DHEA一週。結果顯示經注射100 mg DHEA/kg
bw七天後缺乏維生素E之大鼠的體重顯著性降低。DHEA的劑量與肝和腎之
相對重量( g/100 g bw)具有正相關係,然而攝食維生素E之大鼠的組織重
量之增加並不具有劑量關係。同時此研究發現腎上腺之相對重量只在攝食
缺乏維生素E之大鼠才有顯著性的增加。DHEA顯著性增加肝中的NPSH和TSH
含量,但此種作用並不具有劑量關係和不受維生素E的影響。在ALT(
alanine aminotransferase)活性方面,只有在缺乏維生素E之大鼠經注
射100 mg DHEA/kg,其肝中ALT的才會具顯著的增加。在缺乏維生素E之大
鼠,DHEA降低其GST (Glutathione S-transferase)的活性程度大於維生
素E足夠之大鼠。相對的,DHEA增加攝食缺乏維生素E之大鼠的肝中G6PD活
性程度大於攝食足夠維生素E之大鼠。DHEA和食物中維生素E可降低肝中in
vivo 和in vitro (以100 mM FeCl3反應之誘發)的脂質過氧化,但DHEA只
有在維生素E缺乏下才具有顯著性的抑制。此一研究說明了大鼠經注射七
天後,DHEA之毒性包括增加肝、腎和腎上腺的重量以及促進肝中某些酵素
活性的改變。在缺乏維生素E的大鼠中,DHEA使血漿中之ALT活性顯著上昇
,同時對肝中的酵素活性之改變 亦大於食用足量維生素E之大鼠。只有在
維生素E缺乏下,DHEA才有抑制肝中脂質過氧化的能力。這些結果說明了
DHEA可能具一些抗氧化性,但是當維生素E足夠時,DHEA之抗氧化性會受
到掩蓋。 ( III ) 探討DHEA在試管試驗中造成人體紅血球之溶血
機制:在試管試驗中 (37℃, 反應一小時),DHEA會造成人體紅血球之溶
血,其溶血程度與DHEA成正比,而在2mM DHEA下會達到70 %的溶血。2 mM
DHEA所誘導之溶血過程相當快速,而且不遷涉到血紅素(hemoglobin) 氧
化和脂質過氧化的反應。在溶血試驗中也不會因加入EDTA、catalase、
superoxide dismutase、glucose、和自由基捕捉劑包括mannitol、
dimethylsulfoxide 或a-tocopherol而減低溶血程度,此結果顯示溶血反
應為非氧化機制所造成。經由紅血球細胞與2 mM DHEA反應一小時後,在
光學顯微鏡下紅血球細胞膜明顯變厚和變形(deformity),此種結果說明
了DHEA可能嵌入紅血球細胞膜使細胞膜結構改變,而造成溶血。
綜合上述實驗結果,年輕大鼠組織內DHEA的含量會受到維生素E和硒的影
響。可能的原因是體內的抗氧化能力可保護組織抵抗自由基的傷害。相反
的,當缺乏抗氧化劑時,體內組織因受到自由基的傷害而造成組織中DHEA
之生產與累積量受損。因此補充抗化劑時可防止組織中DHEA含量受自由基
的氧化傷害。另一方面,在補充DHEA時應當注意高劑量DHEA的負面影響。
同時,在補充DHEA的方式應當注意以靜脈注射時,可能會造成溶血的現象
。此外,本研究結果顯示DHEA本身是一種微弱的抗氧化劑,其也會改變體
內抗氧化酵素的活性,但這些機制迄今未明。

Abstract human bodies contain an affluent adrenal
steroid, dehydroepiandrosterone (DHEA) which is the precursor
of both male and female sex hormones. DHEA reaches the highest
level at approximately 25 years of age and declines dramatically
afterwards, with only approximately 10 % DHEA remaining at the
age of 70 or 80. In addition, the hormone may postpone and even
reverse aging process. Whether this phenomenon is affected by
oxidative stress and antioxidative ability was an important
point of investigation of this thesis. DHEA has also been shown
to have a variety of physiological functions against obesity,
cancer and atherosclerosis. However DHEA has also been shown to
be involved in carcinogenesis or to alter G6PD activities and
enhance lipid peroxidation. To determine the effect of dietary
antioxidants on the tissue contents and the toxicity and
antioxidative activity of DHEA, three studies were conducted in
: ( I ) effect of dietary selenium and vitamin E on tissue and
serum levels of dehydroepiandrosterone in rats; ( II ) dietary
vitamin E modifies in vivo toxicity of dehydroepiandrosterone in
rats; ( III ) hemolytic effects of dehydroepiandrosterone in
vitro. The three studies are : ( I ) Effect of dietary
selenium and vitamin E on tissue and serum levels of
dehydroepiandrosterone in rats: Male Sprague-Dawley rats (4-wk
old) were fed diets deficient in or supplemented with 0.2 ppm Se
with or without adequate (30 IU/kg diet) and high (200 IU/kg
diet) levels of vitamin E for six weeks. The results showed that
both Se and vitamin E supplementation significantly increased
the relative testis weight. As expected, serum glutathione
peroxidase activity was high in Se-supplemented rats and very
low in Se-deficient rats. In the adrenal, the concentration of
DHEA was significantly increased by supplementation of either
dietary Se or vitamin E. However, high vitamin E did not further
increase the adrenal DHEA level, and there was no interaction
between the two dietary factors. Dietary vitamin E at 30 IU/kg
significantly increased brain DHEA levels in rats fed Se-
deficient but not Se-adequate diets while high vitamin E did not
further increase the DHEA levels. Similarly, the serum DHEA
level was only affected by dietary vitamin E, whose effect was
not dependent on Se. The results demonstrate that tissue and
serum levels of DHEA are mainly affected by dietary vitamin E
which at levels beyond 30 IU/kg afforded no additional
steroidogenic effect in young rats. ( II ) Dietary vitamin
E modifies in vivo toxicity of dehydroepiandrosterone in rats:
Male Sprague-Dawley rats (4-wk old) were fed vitamin E-deficient
or vitamin E-adequate (30 IU/kg) diet for four weeks before
being injected i.p. with DHEA for one week. The results showed
that DHEA injected at 100 mg/kg for 7 days significantly
decreased body weights of vitamin E-deficient rats. DHEA dose-
dependently increased the relative liver and kidney weights
(g/100 g body weight) regardless of dietary vitamin E status
while the relative adrenal weight was increased by the steroid
only in vitamin E-deficient rats. DHEA significantly increased
hepatic NPSH and TSH contents but the effect was not dose-
dependent or was affected by vitamin E. DHEA injected at 100 mg/
Kg significantly increased plasma ALT activity in vitamin E-
deficient rats only. DHEA decreased (P < 0.05) hepatic GST
activity in vitamin E-deficient rats to a greater extent than in
vitamin E-sufficient rats. By contrast, DHEA increased (P <
0.05) hepatic G6PD activity in vitamin E-deficient rats to a
greater extent than in vitamin E-sufficient rats. Both the in
vivo and in vitro lipid peroxidation of liver (induced by
incubation with 100 mM FeCl3) were significantly decreased by
DHEA injection and by dietary vitamin E, but the effect of DHEA
was only significant in the vitamin E-deficient rats. The
present study demonstrates that injection with DHEA for 7 days
results in overt toxicity including increased weights of liver,
kidney and adrenal and altered hepatic enzyme activities.
Dietary vitamin E deficiency led to elevated plasma ALT activity
induced by DHEA and to greater changes in hepatic enzymes
assayed. That DHEA inhibited hepatic lipid peroxidation only in
vitamin E-deficient rats suggests that the steroid may have some
antioxidant activity which is masked by vitamin E when the
latter is sufficient. ( III ) Hemolytic effects of
dehydroepiandrosterone in vitro: DHEA induced lysis of human red
blood cells (RBCs) in a concentration-dependent manner, with ca.
70 % hemolysis at 2 mM DHEA at 37℃ for 1 hr. Hemolysis induced
by 2 mM DHEA was rapid and involved neither hemoglobin oxidation
nor lipid peroxidation. The hemolysis was also not inhibited by
addition of EDTA, catalase, superoxide dismutase, glucose, or a
radical scavenger including mannitol, dimethylsulfoxide and a-
tocopherol, indicating a non-oxidative mechanism. RBCs stored
overnight before incubation with DHEA were hemolyzed to a lesser
extent than the freshly prepared RBCs. Light microscopy of the
fresh RBCs following 1-h incubation with 2 mM DHEA revealed
thickened and cup-shaped deformity of the membranes, suggesting
a change in the membrane structure possibly due to the
intercalation of the steroid into the membranes. The
results of above studies demonstrated that the DHEA contents of
tissues were affected by vitamin E and selenium in young rats,
it may be the activities of antioxidants protected tissues
against the stress of free radicals. In contrast, tissues were
attacted by free radicals when the tissues were deficient
antioxidants, and it was diminished the production or contents
of DHEA .Therefore, supplementation of antioxidants may be
avoided the contents of DHEA diminished by oxidative stress. In
the other hand, when supplementation of DHEA must be pay
attention to negative effect on high doses of DHEA. And it must
be careful the type of supplemetation of DHEA especially the i.v
injection, because it may be cause the hemolysis. In this study,
the results demonstated that DHEA is a weak antioxidants, it
altered the activities of antioxidative enzyme in vivo, but the
mechanism is not clear.
URI: http://hdl.handle.net/11455/50979
Appears in Collections:食品暨應用生物科技學系

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