生長分化因子11在衰老中的研究進展

趙素潔， 陸 怡， 吳曉琰

復旦大學附屬華山醫院老年病科，上海 200040

·綜 述·

生長分化因子11在衰老中的研究進展

趙素潔， 陸 怡， 吳曉琰*

復旦大學附屬華山醫院老年病科，上海 200040

生長分化因子11(growth differentiation factor 11, GDF11)是轉化生長因子β(transforming growth factor-β，TGF-β)家族的一員。GDF11在多種器官和組織中表達。生長發育期間，GDF11通過可逆性地阻滯細胞周期來調節發育進程；在衰老方面，GDF11可延緩心臟、骨骼肌、大腦、骨骼、血管等多個器官和組織的衰老進程。本文就GDF11在生長發育及衰老中的作用及其機制作一綜述，以期為GDF11在衰老方面的研究提供指導。

生長分化因子11；衰老；轉化生長因子β

轉化生長因子β(transforming growth factor-β，TGF-β)家族可以分為4個亞類：轉化生長因子類(TGFs)；激活素類(activins)；骨形成蛋白類(BMPs)；生長分化因子類(GDFs)，如GDF11和其結構類似物GDF8；其他，如抗苗勒氏管激素(AMH)和GDF15[1]。與TGF-β家族其他成員一樣，GDF11和GDF8的前體在細胞內合成后以成熟信號肽形式分泌到細胞外，與相應細胞膜表面的Ⅰ型、Ⅱ型受體結合后活化細胞質內的信號分子，并將信號傳遞給細胞核，進而調控基因的表達。GDF11和GDF8可結合Ⅰ型受體中的激活素受體B(activin typeⅠreceptor B, ActRⅠB)、轉化生長因子Ⅰ型受體(TGF-β receptor Ⅰ，TβRⅠ)，Ⅱ型受體中的激活素受體A(activin typeⅡreceptor A， ActRⅡA)、激活素受體B(activin typeⅡreceptor B，ActRⅡB)。GDF11和GDF8在細胞質中激活的信號分子為Smad2/3 (smart mothers against decapentaplegic-2 and -3，Smad2/3)。細胞膜接受膜外信號分子傳遞的信號后選擇性磷酸化Smad2/3，Smad2/3把信號傳遞給細胞核，從基因水平調控細胞的一系列生物活動[1-2]。

TGF-β家族在衰老方面發揮著至關重要的作用[3-4]。阻滯GDF11的同源類似物GDF8可以改善小鼠衰老相關的肌肉萎縮，并增加其胰島素敏感性[5]。近年來，研究[6]發現TGF-β/Smad通路通過激活p21基因誘導細胞周期阻滯來干預哺乳動物胚胎發育期間的程序性衰老。

1 GDF11與GDF8的調節因子

TGF-β家族種類繁多，配體遠多于受體，信號有條不紊的傳遞依賴多種調控因子。人GDF11前體蛋白有407個氨基酸，其二聚體由兩個GDF11單體組成，每個單體由109個氨基酸組成，成熟GDF11即為酶切后的GDF11前體C端成熟區[7]。GDF11可以通過誘導機體產生卵泡抑素(follistatin，FST)來建立負反饋調節[8]。FST通過活化周期素依賴性激酶2/4(cyclin-dependent kinase2/4, cdk2/4)，上調細胞周期蛋白D1基因(cyclinD1)，下調p21基因，進而抑制Smad2/3磷酸化，減弱GDF11對肌源性祖細胞(myosphere-derived progenitor cells ，MDPCs)的抑制作用[9]。生長分化因子相關血清蛋白(growth and differentiation factor-associated serum protein，GASP)包括GASP 1和GASP2，是GDF11/GDF8的天然抑制信號分子[2]。GASP、FST與GDF11相協調共同參與機體的發育[1-2,8]。

2 GDF11對組織器官生長發育及衰老的作用

GDF11基因作為1種保守基因，廣泛參與機體生長發育的調控，在衰老中的作用雖有爭議，但大部分研究顯示其有抗衰老作用(表1)。

表1 GDF11對生長發育及衰老的作用

2.1 GDF11對心肌、骨骼肌的作用 2013年，哈佛醫學院研究團隊[10]通過外科手術使高齡小鼠與低齡小鼠共用一套血液循環，發現循環中的GDF11可緩解高齡小鼠的心肌肥大。他們還發現小鼠循環中的GDF11隨著年齡增長濃度降低[10,31]。在3月齡小鼠體內，GDF11的mRNA表達量由高到低分別為脾、胸腺、腎、視網膜、骨骼肌、小腦、前腦、骨髓、心臟、小腸、肺、肝，且脾的表達量明顯高于其他組織[31]。按照0.1 mg/kg給高齡小鼠注射外源性重組GDF11蛋白(recombinant GDF11，rGDF11)，結果發現衛星細胞的比例明顯增加，小鼠肌纖維結構得到改善[14]。與GDF11結構相似的GDF8在小鼠、牛、羊骨骼肌的生長中發揮明顯的抑制作用[32]。

2.2 GDF11對神經系統的作用 GDF11對神經發育的調節大多是抑制性作用，并呈現一定的時空特異性，即在不同組織及不同發育階段，GDF11對細胞增殖的作用不同。在胚胎視網膜發育階段，GDF11通過調節祖細胞中影響視網膜神經節細胞(retinal ganglion cell，RGC)發生的Math5基因表達來間接影響RGC的發育[30]。在胚胎嗅神經發生過程中，GDF11則是通過上調細胞周期依賴的激酶抑制劑p27激酶抑制蛋白1(p27 kinase inhibition protein1，p27Kip1)的水平來可逆性誘導定向祖細胞的周期阻滯，從而調節RGC的發育[18]。

然而，與GDF11胚胎神經發育期間的抑制性調節作用不同，研究[19]發現，GDF11對衰老大腦則起促進神經再生的作用。22個月齡小鼠連續注射GDF11 4周后，共聚焦顯微鏡成像顯示大腦室下區(subventricula zone，SVZ)神經細胞數量增多，此外血管數目和血容量明顯增加。之后，該研究團隊發現，GDF11可促進高齡小鼠嗅神經及血管重建[19]；共生模型的老年小鼠神經髓鞘得到修復和再生[16]；低齡小鼠的血液有改善高齡小鼠認知的作用[33]。研究[17]發現，通過給阿爾茨海默病(Alzheimer′s disease，AD)小鼠移植低齡小鼠富含GDF11的脾臟，可以緩解其認知和記憶能力減退。

對脊髓發育影響的研究[34]發現，GDF11可能經GDF11-Smad2通路調控同源盒基因(Hox)在脊髓中的表達區域及延喙尾軸在脊髓尾部的位置；而FST作為GDF11的抑制性因素參與靶基因的調控。

2.3 GDF11對血液循環系統的作用 應用酶聯免疫吸附法(enzyme linked immunosorbent assay，ELISA)、LC-MS/MS等多種方法檢測，在小鼠、大鼠、馬、羊等多種動物中已檢測到GDF11。但是，血液中GDF11的濃度與年齡的關系目前沒有定論[10,31]。研究[26-27]發現，在血液透析患者體內，血清GDF11高濃度與低血紅蛋白濃度有關；GDF11-ActRⅡB-Smad2/3 通路參與紅系造血，并與血液透析患者促紅細胞生成素(erythropoietin，EPO)無效性貧血有關。國內有研究[35]報道，骨髓增生異常綜合征(myelodysplastic syndromes, MDS)患者血液中的GDF11濃度明顯高于健康人。此外，小鼠脾臟中GDF11高表達[31]可能與脾臟本身儲存大量的血小板有關。

有關GDF11與貧血關系的研究較深入。靶作用GDF11及其相關信號分子在治療β-地中海貧血方面已經取得明顯的進展[26-29]。GDF11-ActRⅡA通路與β-地中海貧血的病情進展有密切的關系，GDF11在有核紅細胞中高表達，促進終末期骨髓無效造血；人體GDF11及TGF-βs阻斷劑RAP-011、RAP-536(對應小鼠體內的ACE-011、ACE-536)，可以捕獲ActRⅡA配體，阻滯GDF11-ActRⅡA通路，達到改善貧血的效果[28]。

2.4 GDF11對血管的作用 國內關于人臍靜脈內皮細胞(human umbilical vein endothelial cells，HUVECs)的研究[36]表明，GDF11(50 ng/mL)處理細胞48 h可激活Smad1/5/8和Smad2/3信號通路，增加HUVECs中的NADPH氧化酶(NOX4)、磷酸化的c-Jun氨基末端激酶(p-JNK)和磷酸化的絲裂原活化蛋白激酶(p-AMPK)的含量；GDF11處理24 h后，噻唑藍(MTT)實驗檢測顯示，細胞活性增加，72 h后細胞活性降低，但GDF11沒有改變細胞增殖和遷移能力。有研究[37]報道，GDF11可促進內皮祖細胞 (endothelial progenitor cells, EPCs) 分化，利于血管形成。GDF11能促進腦內毛細血管再生[19]。

2.5 GDF11對其他組織的作用 研究[38]發現，在小鼠胚胎中，NGN3+內分泌祖細胞表達GDF11；GDF11通過抑制神經原素3(neurogenin 3，NGN3)的表達來調節胰島細胞分化。GDF11-Smad2通路參與胰島β細胞的成熟，并影響胰島β細胞的數目[24]。GDF11與糖尿病的發生和發展也有密切聯系。2015年，骨骼衰老相關的研究[21]發現，GDF11一方面可調節間充質干細胞(MSC)向脂肪細胞和成骨細胞分化的百分比，另一方面通過降低過氧化物酶體增生物激活受體-γ(peroxisome proliferators-activated receptor-γ，PPAR-γ)及促進其類泛素化來緩解骨質疏松。

3 總結與展望

GDF11通過調控祖細胞基因表達或通過可逆性阻滯對已分化細胞周期來影響機體發育，并在多個器官的衰老進程發揮作用。多項報道提示，GDF11在胚胎神經、骨骼、肌肉發生期間通過GDF11-ActRⅡA/ActRⅡB-Smad或GDF11-TβRⅠ-Smad通路發揮反饋性抑制作用[8,20,39-40]。GDF11在神經發生、血管生成及動脈粥樣硬化過程中[19,37]發揮的作用使GDF11通路有望成為治療老年癡呆、高血壓、心血管疾病、糖尿病等疾病的新靶點。干預GDF11與其類似物GDF8有望成為治療衰老相關的心肌肥大、肌肉萎縮等疾病的新思路。

細胞衰老本質是由各種原因導致的不可逆的細胞周期阻滯，這些原因可以是端粒縮短、DNA損傷及強烈的致癌信號等，且細胞衰老也機體免于產生腫瘤的一個保護因素[41]。GDF11通過抑制細胞從G1期向S期轉變的進程來抑制MDPCs增殖[9]；通過可逆性地誘導嗅神經細胞周期阻滯來調節神經發育[18]。臨床研究[42]發現，GDF11高水平與結腸癌患者預后差緊密相關，結腸癌組織中高表達的GDF11可能與TGF-β有相似作用，即將腫瘤細胞周期阻滯在G1期。TGF-β激活p21通路引起的細胞周期阻滯參與哺乳動物胚胎發育期間細胞的程序性衰老[6]。

GDF11對機體的生長發育及衰老的調控貫穿自發育起始的整個生命歷程。GDF11及TGF-β家族信號網絡與衰老有密切的聯系，干預GDF11及TGF-β家族信號通路有望延緩衰老，相關機制有待更加深入的探索。

[1] YADIN D, KNAUS P, MUELLER T D. Structural insights into BMP receptors: specificity, activation and inhibition[J]. Cytokine Growth Factor Rev, 2016, 27: 13-34.

[2] WALKER R G, POGGIOLI T, KATSIMPARDI L, et al. Biochemistry and biology of GDF11 and myostatin: similarities, differences, and questions for future investigation[J]. Circ Res, 2016, 118(7): 1125-1141.

[3] HE Y, ZHANG H, YUNG A, et al. ALK5-dependent TGF-βsignaling is a major determinant of late-stage adult neurogenesis[J]. Nat Neurosci, 2014, 17(7): 943-952.

[4] TESSEUR I, ZOU K, ESPOSITO L, et al. Deficiency in neuronal TGF-beta signaling promotes neurodegeneration and Alzheimer's pathology[J]. J Clin Invest, 2006, 116(11): 3060-3069.

[5] CAMPOREZ J P, PETERSEN M C, ABUDUKADIER A, et al. Anti-myostatin antibody increases muscle mass and strength and improves insulin sensitivity in old mice[J]. Proc Natl Acad Sci U S A, 2016, 113(8): 2212-2217.

[7] WALKER R G, POGGIOLI T, KATSIMPARDI L, et al. Biochemistry and biology of GDF11 and myostatin: similarities, differences, and questions for future investigation[J]. Circ Res, 2016, 118(7): 1125-1141; discussion 1142.

[8] GAMER L W, COX K A, SMALL C, et al. Gdf11 is a negative regulator of chondrogenesis and myogenesis in the developing chick limb[J]. Dev Biol, 2001, 229(2): 407-420.

[9] NOMURA T, UEYAMA T, ASHIHARA E, et al. Skeletal muscle-derived progenitors capable of differentiating into cardiomyocytes proliferate through myostatin-independent TGF-beta family signaling[J]. Biochem Biophys Res Commun, 2008, 365(4): 863-869.

[10] LOFFREDO F S, STEINHAUSER M L, JAY S M, et al. Growth differentiation factor 11 is a circulating factor that reverses age-related cardiac hypertrophy[J]. Cell, 2013, 153(4): 828-839.

[11] SMITH S C, ZHANG X X, ZHANG X Y, et al. GDF11 does not rescue aging-related pathological hypertrophy[J]. Circ Res, 2015, 117(11): 926-932.

[12] MCPHERRON A C, HUYNH T V, LEE S J. Redundancy of myostatin and growth/differentiation factor 11 function[J]. BMC Dev Biol, 2009, 9: 24.

[13] SINHA M, JANG Y C, OH J, et al. Restoring systemic GDF11 levels reverses age-related dysfunction in mouse skeletal muscle[J]. Science, 2014, 344(6184): 649-652.

[14] RINALDI F, ZHANG Y, MONDRAGON-GONZALEZ R, et al. Treatment with rGDF11 does not improve the dystrophic muscle pathology of mdx mice[J]. Skelet Muscle, 2016, 6: 21.

[15] EGERMAN M A, CADENA S M, GILBERT J A, et al. GDF11 increases with age and inhibits skeletal muscle regeneration[J]. Cell Metab, 2015, 22(1): 164-174.

[16] RUCKH J M, ZHAO J W, SHADRACH J L, et al. Rejuvenation of regeneration in the aging central nervous system[J]. Cell Stem Cell, 2012, 10(1): 96-103.

[17] WANG F, SHEN X, LI S, et al. Splenocytes derived from young WT mice prevent AD progression in APPswe/PSENldE9 transgenic mice[J]. Oncotarget, 2015, 6(25): 20851-20862.

[18] WU H H, IVKOVIC S, MURRAY R C, et al. Autoregulation of neurogenesis by GDF11[J]. Neuron, 2003, 37(2): 197-207.

[19] KATSIMPARDI L, LITTERMAN N K, SCHEIN P A, et al. Vascular and neurogenic rejuvenation of the aging mouse brain by young systemic factors[J]. Science, 2014, 344(6184): 630-634.

[20] MCPHERRON A C, LAWLER A M, LEE S J. Regulation of anterior/posterior patterning of the axial skeleton by growth/differentiation factor 11[J]. Nat Genet, 1999, 22(3): 260-264.

[21] ZHANG Y, SHAO J, WANG Z, et al. Growth differentiation factor 11 is a protective factor for osteoblastogenesis by targeting PPARgamma[J]. Gene, 2015, 557(2): 209-214.

[22] ESQUELA A F, LEE S J. Regulation of metanephric kidney development by growth/differentiation factor 11[J]. Dev Biol, 2003, 257(2): 356-370.

[23] DICHMANN D S, YASSIN H, SERUP P. Analysis of pancreatic endocrine development in GDF11-deficient mice[J]. Dev Dyn, 2006, 235(11): 3016-3025.

[24] HARMON E B, APELQVIST A A, SMART N G, et al. GDF11 modulates NGN3+ islet progenitor cell number and promotes beta-cell differentiation in pancreas development[J]. Development, 2004, 131(24): 6163-6174.

[25] SCHAFER M J, ATKINSON E J, VANDERBOOM P M, et al. Quantification of GDF11 and myostatin in human aging and cardiovascular disease[J]. Cell Metabolism, 2016, 23(6): 1207-1215.

[26] YAMAGISHI S, MATSUI T, KUROKAWA Y, et al. Serum levels of growth differentiation factor 11 are independently associated with low hemoglobin values in hemodialysis patients[J]. Biores Open Access, 2016, 5(1): 155-158.

[27] SURAGANI R N, CADENA S M, CAWLEY S M, et al. Transforming growth factor-beta superfamily ligand trap ACE-536 corrects anemia by promoting late-stage erythropoiesis[J]. Nat Med, 2014, 20(4): 408-414.

[28] DUSSIOT M, MACIEL T T, FRICOT A, et al. An activin receptorⅡA ligand trap corrects ineffective erythropoiesis in β-thalassemia[J]. Nat Med, 2014, 20(4): 398-407.

[29] ARLET J B, DUSSIOT M, MOURA I C, et al.Novel players in β-thalassemia dyserythropoiesis and new therapeutic strategies[J]. Curr Opin Hematol, 2016, 23(3): 181-188.

[30] KIM J, WU H H, LANDER A D, et al. GDF11 controls the timing of progenitor cell competence in developing retina[J]. Science, 2005, 308(5730): 1927-1930.

[31] POGGIOLI T, VUJIC A, YANG P, et al. Circulating growth differentiation factor 11/8 levels decline with age[J]. Circ Res, 2016, 118(1): 29-37.

[32] LEE S J. Extracellular regulation of myostatin: a molecular rheostat for muscle mass[J]. Immunol Endocr Metab Agents Med Chem, 2010, 10: 183-194.

[33] VILLEDA S A, PLAMBECK K E, MIDDELDORP J, et al. Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice[J]. Nat Med, 2014, 20(6): 659-663.

[34] LIU J P. The function of growth/differentiation factor 11 (Gdf11) in rostrocaudal patterning of the developing spinal cord[J]. Development, 2006, 133(15):2865-2874.

[35] HAN Y, WANG H, FU R, et al. GDF11 level in patients with myelodysplastic syndrome and its clinical significance[J]. Zhonghua Yi Xue Za Zhi, 2016, 96(8): 620-624.

[36] ZHANG Y H, CHENG F, DU X T, et al. GDF11/BMP11 activates both smad1/5/8 and smad2/3 signals but shows no significant effect on proliferation and migration of human umbilical vein endothelial cells[J]. Oncotarget, 2016, 7(11): 12063-12074.

[37] FINKENZELLER G, STARK G B, STRASSBURG S. Growth differentiation factor 11 supports migration and sprouting of endothelial progenitor cells[J]. J Surg Res, 2015, 198(1): 50-56.

[38] SHIMAJIRI Y, KOSAKA Y, SCHEEL D W, et al. A mouse model for monitoring islet cell genesis and developing therapies for diabetes[J]. Dis Model Mech, 2011, 4(2): 268-276.

[39] MCPHERRON A C, LAWLER A M, LEE S J. Regulation of skeletal muscle mass in mice by a new TGF-beta superfamily member[J]. Nature, 1997, 387(6628): 83-90.

[40] ANDERSSON O, REISSMANN E, IBEZ C F. Growth differentiation factor 11 signals through the transforming growth factor-beta receptor ALK5 to regionalize the anterior-posterior axis[J]. EMBO Rep, 2006, 7(8): 831-837.

[41] COLLADO M, BLASCO M A, SERRANO M. Cellular senescence in cancer and aging[J]. Cell, 2007, 130(2): 223-233.

[42] YOKOE T, OHMACHI T, INOUE H, et al. Clinical significance of growth differentiation factor 11 in colorectal cancer[J]. Int J Oncol, 2007, 31(5): 1097-1101.

[本文編輯] 姬靜芳

Advances on aging of growth differentiation factor 11

ZHAO Su-jie，LU Yi，WU Xiao-yan*

Department of Gerontology，Huashan Hospital，Shanghai Medical College of Fudan University, Shanghai 200040，China

Growth differentiation factor 11(GDF11), a member of the transforming growth factor β(TGF-β)family, is widely expressed in many tissues. GDF11 regulates multiple developmental processes by reversing cell cycle arrest and reverses the aging process of many tissues including heart, skeletal muscle, brain, bone and blood vessels. In this article, we review the role of GDF11 in aging considering the TGF-β family signaling pathway and the mechanism of GDF11 in growth and development.

GDF11; aging; transforming growth factor-β

2016-11-01 [接受日期] 2017-04-14

上海市科學技術委員會重點項目科技創新行動(10431904000). Supported by the Key Program of Science and Technology Commission of Shanghai (10431904000).

趙素潔, 碩士生, 住院醫師. E-mail：sujiezhao2014@163.com

*通信作者(Corresponding author). Tel: 021-52887270, E-mail：wxygtj@ aliyun.com

10.12025/j.issn.1008-6358.2017.20161017

R 592

A