朱萬(wàn)龍, 謝 靜, 蔡金紅, 王政昆

(云南師范大學(xué) 生命科學(xué)學(xué)院 云南省高校西南山地生態(tài)系統(tǒng)動(dòng)植物生態(tài)適應(yīng)進(jìn)化及保護(hù)重點(diǎn)實(shí)驗(yàn)室, 昆明 650500)

季節(jié)性模擬條件下中緬樹(shù)鼩內(nèi)分泌激素調(diào)節(jié)作用的研究

朱萬(wàn)龍, 謝 靜, 蔡金紅, 王政昆

(云南師范大學(xué) 生命科學(xué)學(xué)院 云南省高校西南山地生態(tài)系統(tǒng)動(dòng)植物生態(tài)適應(yīng)進(jìn)化及保護(hù)重點(diǎn)實(shí)驗(yàn)室, 昆明 650500)

為了闡明內(nèi)分泌激素在中緬樹(shù)鼩體重調(diào)節(jié)中的作用，模擬夏季和冬季環(huán)境，測(cè)定了其血清瘦素含量、胰島素含量和甲狀腺素含量。結(jié)果表明：中緬樹(shù)鼩的血清瘦素水平在模擬冬季環(huán)境中顯著降低；胰島素水平與瘦素水平呈顯著的正相關(guān)，說(shuō)明中緬樹(shù)鼩胰島素能夠正向調(diào)節(jié)和刺激瘦素的分泌；模擬冬季環(huán)境顯著增加甲狀腺素T3含量，從而增強(qiáng)其產(chǎn)熱能力，而模擬夏季環(huán)境對(duì)其影響不大，呈現(xiàn)出降低的趨勢(shì)，在一定程度上減弱了產(chǎn)熱。以上結(jié)果說(shuō)明中緬樹(shù)鼩在季節(jié)性變化過(guò)程中會(huì)通過(guò)調(diào)整內(nèi)分泌激素的含量來(lái)調(diào)節(jié)其能量代謝。

中緬樹(shù)鼩；內(nèi)分泌激素；體重調(diào)節(jié)

小型哺乳動(dòng)物體重的季節(jié)性波動(dòng)主要受到其能量攝入和能量支出的影響[1-2]。隨著體重的變化，動(dòng)物的血清瘦素含量也表現(xiàn)出顯著的季節(jié)波動(dòng)[3]，而且這種季節(jié)波動(dòng)與其能量代謝密切相關(guān)[4]，如動(dòng)物在冬季降低瘦素含量，與此同時(shí)其體重、體脂重量和攝入能在冬季也顯著降低[2]。然而，低溫可以使實(shí)驗(yàn)大鼠和小鼠血清瘦素顯著降低，而其攝入能顯著增加[5-6]。不同動(dòng)物其血清瘦素對(duì)攝入能的調(diào)節(jié)方式不同，暗示著瘦素對(duì)動(dòng)物體重調(diào)節(jié)機(jī)制可能是不一樣的[7]。

研究表明瘦素與胰島素之間存在相互關(guān)系，胰島素可增加瘦素的mRNA表達(dá)，從而增加瘦素的濃度，即瘦素水平與胰島素水平相關(guān)。低溫使得小型哺乳動(dòng)物的產(chǎn)熱能力增加[8]，其重要的生理基礎(chǔ)之一就是甲狀腺功能狀態(tài)或甲狀腺激素的含量發(fā)生了變化[9]，如長(zhǎng)爪沙鼠能耐受極端的高低溫環(huán)境[10]，其產(chǎn)熱能力也隨環(huán)境溫度的急劇變化而改變，其甲狀腺激素的含量也發(fā)生了改變[11]。

中緬樹(shù)鼩為東洋界特有的小型哺乳動(dòng)物，目前關(guān)于其季節(jié)性變化過(guò)程中內(nèi)分泌激素的調(diào)節(jié)作用還沒(méi)有報(bào)道。本研究對(duì)中緬樹(shù)鼩在模擬冬季和夏季環(huán)境中血清瘦素、胰島素、甲狀腺素等激素含量進(jìn)行測(cè)定，最終來(lái)闡明中緬樹(shù)鼩的內(nèi)分泌激素對(duì)其體重調(diào)節(jié)的作用。

1 材料和方法

1.1 動(dòng)物來(lái)源

實(shí)驗(yàn)動(dòng)物捕自云南省昆明市祿勸縣附近灌叢中(海拔1679 m)，動(dòng)物捕回后室溫單籠飼養(yǎng)，定點(diǎn)喂以由玉米面、奶粉、白糖以適當(dāng)比例混合制得熟食，添加少許水，每隔一天加喂蘋(píng)果、梨等水果適量。實(shí)驗(yàn)動(dòng)物均為非繁殖期成年個(gè)體，飼養(yǎng)地點(diǎn)為云南師范大學(xué)生命科學(xué)學(xué)院動(dòng)物飼養(yǎng)房。動(dòng)物適應(yīng)一個(gè)月后進(jìn)行實(shí)驗(yàn)，挑選成年雌性中緬樹(shù)鼩(n=70)，分為兩大組。一組馴化于冬季模擬環(huán)境(5℃，光照為8 L：16D)28 d，于0、7、14、21、28 d處死動(dòng)物(n=7)；另一組馴化于夏季模擬環(huán)境(25℃，光照為16 L：8D)28 d，于0、7、14、21、28 d處死動(dòng)物(n=7)。動(dòng)物處死后，分離血清，測(cè)定其激素含量。每組動(dòng)物實(shí)驗(yàn)前體重差異不顯著。

1.2 內(nèi)分泌激素的測(cè)定

將動(dòng)物處死，取血，4℃靜置1 h，于4℃、4000 r/min離心30 min，吸取上層血清置于-80℃低溫冰箱內(nèi)保存。血清瘦素、甲狀腺激素、促甲狀腺激素、睪酮及褪黑激素含量分別采用對(duì)應(yīng)的放射免疫分析試劑盒(美國(guó)Linco 公司生產(chǎn)) 到昆明醫(yī)學(xué)院第二附屬醫(yī)院進(jìn)行測(cè)定。

1.3 數(shù)據(jù)分析

2 結(jié)果

2.1 體重、血清瘦素含量和胰島素含量

中緬樹(shù)鼩在模擬冬季環(huán)境中，體重顯著增加(F=2.23,P<0.05)，而血清瘦素含量則顯著降低(F=5.21,P<0.01, 圖1)；在模擬夏季環(huán)境中，中緬樹(shù)鼩體重顯著下降 (F=1.95,P<0.05)，血清瘦素濃度差異不顯著(P>0.05, 圖2)。血清胰島素含量在模擬冬季環(huán)境中顯著降低，胰島素含量與瘦素水平呈顯著正相關(guān)(r=0.54,P<0.05, 圖3)。

圖1 模擬冬季環(huán)境中中緬樹(shù)鼩血清瘦素含量的變化

*P<0.05；**P<0.01(與0天比較)

圖2 模擬夏季環(huán)境中中緬樹(shù)鼩血清瘦素含量的變化

圖3 中緬樹(shù)鼩血清瘦素濃度與胰島素的相關(guān)性

2.2 甲狀腺素含量

在模擬冬季環(huán)境中，血清T3濃度顯著增加，T4濃度顯著降低，T3/T4的比率顯著增加(圖4)；血清促甲狀腺素含量較0天增加了44.13%。在模擬夏季環(huán)境中，血清T3和T4濃度變化差異不顯著(P>0.05)，T3/ T4比率顯著降低(F=2.12,P<0.05, 圖5)；血清促甲狀腺素含量較0天減少了27.92%。

圖4 模擬冬季環(huán)境中中緬樹(shù)鼩血清甲狀腺激素含量的變化

*P<0.05; **P<0.01； compared with 0 day

圖5 模擬夏季環(huán)境中中緬樹(shù)鼩血清甲狀腺激素含量的變化

*P<0.05； compared with 0 day

3 討論

瘦素主要由脂肪組織分泌，其在動(dòng)物體重調(diào)節(jié)和能量代謝中起重要的作用[12-14]。本研究結(jié)果表明，模擬冬季環(huán)境顯著降低中緬樹(shù)鼩的血清瘦素水平，而模擬夏季環(huán)境對(duì)其血清瘦素含量沒(méi)有影響。在模擬冬季環(huán)境中，中緬樹(shù)鼩的瘦素含量下降，有利于其增加食物攝入，彌補(bǔ)冷脅迫條件下產(chǎn)熱消耗的增加。胰島素是影響瘦素合成與分泌的最重要的因素[15-16]。胰島素能增強(qiáng)大鼠瘦素含量及分泌[17]，脂肪組織瘦素含量在禁食時(shí)減少而喂養(yǎng)后增加，這與胰島素濃度的變化是相似的，說(shuō)明胰島素可以調(diào)整瘦素的合成與分泌[18]。本研究結(jié)果表明中緬樹(shù)鼩的瘦素與胰島素呈顯著的正相關(guān)，與上述的研究結(jié)果一致，說(shuō)明胰島素能正向的調(diào)節(jié)瘦素的合成與分泌。

甲狀腺激素在動(dòng)物適應(yīng)性產(chǎn)熱中起著重要的作用[19-21]。中緬樹(shù)鼩在模擬冬季環(huán)境中，血清T3濃度顯著增加，T4濃度顯著下降，T3/T4比率顯著增加，動(dòng)物經(jīng)過(guò)冷刺激后，一方面血循環(huán)中T4利用率加速，另一方面外周組織中的T4分布增加，刺激T4在外周組織中脫碘，產(chǎn)生活性更強(qiáng)的T3，這也成為血清T3濃度增加的主要原因，模擬冬季環(huán)境中T3/T4的比率的增加導(dǎo)致產(chǎn)熱能力的增加。在模擬夏季環(huán)境中，中緬樹(shù)鼩血清T3和T4差異不顯著，T3/T4的比率下降，在28 d后達(dá)到顯著水平，說(shuō)明在模擬夏季環(huán)境中其甲狀腺激素刺激產(chǎn)熱的能力有所降低。促甲狀腺激素(thyroid-stimulating hormone, TSH)是由垂體前葉分泌的一種糖蛋白激素，對(duì)甲狀腺組織的生長(zhǎng)、分化等起著非常重要的作用[22-28]。急性冷暴露能夠引起大鼠血清TSH濃度的快速升高[29]。大鼠處于3℃～4℃冷環(huán)境中，血清中的TSH在30 min內(nèi)能夠提高1.5倍[30]。中緬樹(shù)鼩在模擬冬季環(huán)境中促甲狀腺激素水平先上升后下降，可能是因?yàn)榈蜏囟坦庹沾碳ち舜偌谞钕偌に氐姆置?，進(jìn)而提高血清中甲狀腺激素水平，當(dāng)甲狀腺水平達(dá)到一定濃度時(shí)，高水平的甲狀腺激素則通過(guò)下丘腦-垂體-甲狀腺軸的反饋?zhàn)饔茫徛卣{(diào)節(jié)了促甲狀腺激素的分泌，從而維持機(jī)體內(nèi)分泌激素的平衡。

綜上所述，中緬樹(shù)鼩的血清瘦素水平與體重變化趨勢(shì)不同，表現(xiàn)出了一定的特異性，胰島素水平與瘦素水平呈顯著的正相關(guān)，說(shuō)明在中緬樹(shù)鼩中，胰島素能夠正向的調(diào)節(jié)和刺激瘦素的分泌。模擬冬季環(huán)境顯著刺激了甲狀腺素T3含量的增加，從而增強(qiáng)了產(chǎn)熱能力；模擬冬季環(huán)境在前期刺激了促甲狀腺激素的分泌，并通過(guò)下丘腦-垂體-甲狀腺軸調(diào)節(jié)了血清甲狀腺激素的水平，在馴化中期，當(dāng)甲狀腺激素達(dá)到一定濃度后，又通過(guò)下丘腦-垂體-甲狀腺軸反饋抑制了促甲狀腺激素的分泌。內(nèi)分泌激素在中緬樹(shù)鼩季節(jié)性變化過(guò)程中起著非常重要的作用。

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StudyontheroleofendocrinehormoneregulationsinTupaiabelangeriundertheconditionofseasonalsimulationenvironment

ZHU Wan-long, XIE Jing, CAI Jin-hong, WANG Zheng-kun

(Key Laboratory of Ecological Adaptive Evolution and Conservation on Animals-Plants in Southwest Mountain Ecosystem of Yunnan Province Higher Institutes College, School of Life Sciences， Yunnan Normal University, Kunming 650500, China)

In order to investigate the roles of endocrine hormone in the regulation of body mass ofTupaiabelangeri, serum leptin levels, insulin levels, and the levels of thyroid hormone under simulating winter and summer environments were measured. The results showed that serum leptin levels inT.belangeriin simulating winter environment reduced significantly with the acclamation time; insulin levels were significantly correlated to leptin levels, indicating that insulin could positively modulaten and stimulate leptin secretion inT.belangeri; simulating winter environment increased thyroid hormone T3levels significantly, thereby enhancing the heat production capacity, and simulated summer environment had no obvious influence on the thyroid hormone T3levels, but showed a decreasing trend in a certain extent, weakened the heat production. All of these results suggested thatT.belangeriin seasonal change process will be through the adjustment of endocrine hormone levels to regulate the energy metabolism.

Tupaiabelangeri; endocrine hormone; body mass regulation

2016-05-27；

2016-06-06

國(guó)家自然科學(xué)基金項(xiàng)目(編號(hào)：31660121)；云南省應(yīng)用基礎(chǔ)研究計(jì)劃重點(diǎn)項(xiàng)目(編號(hào)：2016FA045);云南師范大學(xué)博士科研啟動(dòng)項(xiàng)目

朱萬(wàn)龍，副教授，研究方向?yàn)閯?dòng)物生理生態(tài)，E-mail: zwl_8307@163.com

10.3969/j.issn.2095-1736.2017.06.042

Q955

A

2095-1736(2017)06-0042-04