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icantly in the early 30s with a steep de-

to 51 years of age (2, 3). This would

surviving age-related atresia (79).

seem to occur, the oocytes that reach

tical models predicting follicle lossthe basis of chronologic age withouting into account biologic markers

The molecular ngerprint obtainedsion prolee aging fe-

male gonad.According to recent studies,g-mdreo-espreserve women from the physical ovulation during reproductive aging changes occurring in the ovary with aing are mostly ovary specic (14). Gerline genes, oocyte-specic genes, anthe intraovarian signaling pathway adown-regulated. Consistent with smatic organs, down-regulation of gen

Received October 19, 2012; revised November 17, 2012; accepted November 19, 2012.C.T. has nothing to disclose. F.A. has nothing to disclose.Reprint requests: Carla Tatone, Ph.D., Department of Life, Health, and Environmental Sciences, Uni-

versity of LAquila, Via Vetoio, 67100 LAquila, Italy (E-mail: carla.tatone@univaq.it).crease beginning after age 35,culminating in the menopause at 50

Although clear perturbations indynamic of follicle growth do not

by the ovarian gene expresprovides a clear picture of thbeen speculated that the premature ag-ing of the ovary when compared withsomatic organs might result from in-creased energy demand for mainte-nance and repair processes in thesoma compartment during aging (1).According to the human biologic clock,female fertility begins to decline signif-

accepted that coping with this issue re-quires a careful reproductive counsel-ing based on accurate predictivemarkers.

It is well established that ovarianfunctional decline is related to thegradual loss of resting follicles and de-creased biologic competence of those

(12). When the concept of oocyte agingas the main determinant of fertility de-cline has become clear (13), researchershave begun to expand investigationsinto the whole ovarian microenviron-ment in search of age-related changeswith potential effects on follicle andoocyte competence.tive success during a denite life stage.According to the evolutionary conceptthat organisms maximize tness bypromoting production of progeny, allo-cation of resources between reproduc-tive and somatic functions is nelyregulated during life (1). Thus, it has

tendency to postpone childbearing tothe fourth decade of life has madereproductive aging an age-related dis-ease that entails careful considerationin our health care systems (5). Giventhe intrapopulation variability of thereproductive life span (6), it is generally

11)reponovamaontakT clock is set to ensure reproduc- can bear children (4). The modern hamper the reproductive process (10,. For decades, research onroductive aging has been focusingthe so-called quantitative aspect ofrian aging, which has led to mathe-female fertility, and its biological and maximize the length of time they chromosomal defects that seriously

he ovary is the main regulator of stress of pregnancy in advanced age are likely to exhibit cellular andgranulosa ceCarla Tatone, Ph.D., and Fernanda Am

Department of Life, Health, and Environm

The development of a competent oocyte inmicroenvironment. On this basis, it is veryperturbations in the whole ovary, we reviewaging. The rst part provides an update ofond part focuses on studies providing evidefunction. With their prolonged half-life anpotentiate the wide spatiotemporal spreada good candidate as a predictive marker anreproductive counseling in aging women. (ciety for Reproductive Medicine.)Key Words: Advanced glycation end prodoxidative stress

Discuss: You can discuss this article withfertstertforum.com/tatonec-follicle-agingFertility and Sterility Vol. 99, No. 1, January 2013 0Copyright 2013 American Society for Reproductivehttp://dx.doi.org/10.1016/j.fertnstert.2012.11.029

12llsrelli, Ph.D.

al Sciences, University of LAquila, LAquila,

ately depends on the maintenance of energly that the oocyte ages as the ovary ages. Starrent knowledge on the involvement of endont ndings that conrm the key role of oxie for the implication of advanced glycationability to act as signaling molecules AGEsoxidative stress. Clinical evidence for th

herapeutic target in new strategies for imprtil Steril 2013;99:127.2013 by America

ts, carbonyl stress, follicle aging, methylgly

uthors and with other ASRM members at hxidative-stress/015-0282/$36.00Medicine, Published by Elsevier Inc.r

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homeostasis in the ovarian and follicularng from the molecular evidence for energynous highly reactive metabolites in follicleive stress in aged granulosa cells. The sec-product (AGE) in aging reproductive dys-y gradually accumulate in the ovary andiew supports the hypothesis that AGE isngo-

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Use your smartphoneto scan this QR codeand connect to thediscussion forum forthis article now.*

* Download a free QR code scanner by searching for QRscanner in your smartphones app store or app marketplace.related to mitochondrial electron trans-port chain is observed and is considered

VOL. 99 NO. 1 / JANUARY 2013

been conrmed by observations in cumulus cells (29). Enzy-

glyoxal in human blood plasma are in the range of 100120life, measurement of ROS levels in the follicle microenviron-ment has led to conicting results about their role in fertility(11). Nevertheless, increasing research in this eld has con-rmed that modulation of ROS levels through ROS scaveng-ing systems may regulate follicular development and/orsurvival. In addition, ROS might be involved in the initiationof apoptosis in antral follicles and are a necessary signal forovulation (22, 23).

More than half a century after the proposal of the freeradical theory of aging (24), research on female reproductiveaging has provided compelling evidence for the key role ofoxidative stress in the age-related decline of ovarian function.In line with previous hypotheses (11), valuable results in thiseld have recently been achieved thanks to amultidisciplinaryapproach based on overall evaluation of the redox state. Inthis regard, relevant ndings are those by Lim and Luderer(25), who revealed signicant age-related increases in oxida-tively damaged lipids, proteins, and DNA in different ovariancompartments, including granulosa cells and ovarian intersti-tial tissue, along with alterations of antioxidant enzyme ex-pression. Further evidence of oxidative stress in the ovariana hallmark of dysregulation of energy homeostasis. It has beenproposed that energy perturbations might be both the causeand the effect of increased production of toxic metabolicbyproducts such as reactive oxygen species (ROS), which canseriously damage biomolecules and impair key regulatorymechanisms (15). On this basis, the process of ovarianaging can be viewed as the progressive and irreversibleaccumulation of damage to macromolecular integrity leadingto loss of metabolic homeostasis and decrease of primaryfunctions.

We review the current state of knowledge about factorsthat can impair ovarian functions with aging by taking intoaccount the hypothesis that increased production of toxic me-tabolites might be relevant to age-related oxidative stress ingranulosa cells (11), the oocytes companion cells throughwhich a continuous cross-talk between the somatic andgerm cell compartments occurs (16, 17). In this context, ourpurpose is to shed some light on the possible role of reactivecarbonyl compounds such as ROS that are toxic byproductsof cellular metabolism.

REACTIVE OXYGEN SPECIES AND OXIDATIVESTRESS IN THE AGING FOLLICLE: A BRIEFUPDATEUnavoidable products of aerobic metabolism, the ROS includesuperoxide anion radicals, hydroxyl radicals, and hydrogenperoxide (18). The main source of ROS is the leakage of elec-trons from the inner mitochondrial membrane during oxida-tive phosphorylation and ATP generation. In steroidogenictissues such as the ovary, steroidogenic cytochrome P450 en-zymes are also relevant sources of ROS (19).

Together, enzymatic and nonenzymatic defense systemspermit cells to live in an oxidative environment, perform nec-essary biochemical processes, and even use ROS as signalingmolecules (20, 21). Given their high reactivity and short half-follicle was obtained by research on stress signaling pathwaysin older granulosa cells (26, 27).

VOL. 99 NO. 1 / JANUARY 2013nM, while cellular concentrations are in the range of 15mM for MG, and 0.11.0 mM for glyoxal. Given its ability toinhibit mitochondrial respiration and proliferation, induceapoptosis and increase ROS production, MG is consideredthe most powerful glycating agent (3234).

Glycation and AGEs

Reactive carbonyl species promote posttranslational modi-cation of proteins by glycation, a nonenzymatic reactionwith free amino groups residing on proteins, lipids, and nu-cleic acids. The early stage of this process involves a complexseries of reactions, often referred to collectively as the Mail-lard reaction, leading to formation of intermediates that arematic activity and protein level of superoxide dismutase(SOD), the enzyme that reacts with superoxide anion radicalsto form oxygen and H2O2, were found to decrease with age,and lower levels of SOD activity are associated with unsuc-cessful IVF outcomes.

CARBONYL REACTIVE SPECIES ANDCARBONYL STRESS IN THE AGING FOLLICLEDicarbonyls: Highly Reactive Toxic Compoundsfrom Cellular Metabolism

Seeking an alternative view to the free radical theory of aging,many researchers have begun to look for reactive endogenousmetabolites other than ROS that have high reactivity with bio-molecules. In this context, attention has been drawn to a het-erogeneous group of low-molecular-weight carbonylsderived frommetabolic processes and, in particular, from gly-colysis (30). Reactive carbonyl species (RCS) share commonfeatures with ROS: they interact with proteins, DNA, andlipids to generate products that contribute to the pathogenesisof diseases across different organ systems. Unlike ROS, RCSare stable and attach to targets far from the site of their for-mation, thereby providing a more deleterious insult to themacromolecular integrity of the cell and extracellular micro-environment (30).

Methylglyoxal (MG) and glyoxal are highly reactive car-bonyls generated from carbohydrate metabolism. They be-long to a class of RCS known as the a-oxoaldehydes andreferred to as dicarbonyls for the presence of two adjacentcarbonyl groups (31). Methylglyoxal is formed from the spon-taneous degradation of glycolytic intermediates and fromother nonenzymatic and enzymatic pathways (32). Glyoxalis formed by lipid peroxidation and degradation of monosac-charides and glycated proteins. Concentrations of MG andCollectively, these studies have identied in older cellsa stress-response signaling pathway leading to up-regulation of glutathione transferase type 1 (GSTT1), an anti-oxidant enzyme that covalently links reactive chemicals withglutathione (GSH) and aids in detoxication of toxic sub-stances (28). Furthermore, previous hypotheses about reducedROS scavenging efciency in the follicular environment have

Fertility and Sterilityinitially reversible but ultimately form stable end-stage ad-ducts called advanced glycation end-products (AGEs) (35,

13

resce (37). For example, MG is known to primarily react with

These observations have given rise to the so-called Maillardtheory or carbonyl stress theory, which proposes that accu-

and reduced intake of nutrients by follicle cells (11). Withtheir prolonged half-life and ability to act as signaling mole-mulation of AGEs accelerates the multisystem functional de-cline that occurs with aging, thus contributing to the agingphenotype.

The Glyoxalase System: The Most PowerfulDefense against Carbonyl Stress and AGE

To counteract the deleterious effects of dicarbonyl overload,a condition referred to as carbonyl stress, organisms haveevolved a series of enzymatic and nonenzymatic defenses.In this regard, the extent of glycation is under control ofthe glyoxalase system (37). Detoxication of MG mainly oc-curs via glyoxalase-1 (GLO1) and glyoxalase-2 (GLO2): GLO1catalyses the formation of S-D-lactoylglutathione from MG,with reduced GSH acting as a cofactor; GLO2 catalyses thehydrolysis of S-D-lactoylglutathione to D-lactate and regener-ates GSH. There is mounting evidence for the key role ofGLO1 activity in prevention of AGE formation. In the modelorganism Caenorhabditis elegans, overexpression of GLO1increases life span by 40%, while RNA interference (RNAi)mediated silencing GLO1 decreases life span by 40% (45).Moreover, poor glyoxalase defense has been observed in oldage and might be one reason for AGE increase in the aged hu-man brain (46).

The Interplay between AGE and Oxidative Stress:The Role of RAGE

The AGEs can be considered as both the trigger and the resultof oxidative stress (47, 48). The latter, in fact, is a key factor inarginin residues to form hydroimidazolones and argpyrimi-dine (38, 39), here referred to as MG-AGEs.

Glycation of proteins is potentially damaging to the pro-teome. Targeting mostly extracellular long-lived proteins,this posttransductional modication impairs protein func-tions and causes trapping and molecular cross-linking (40).These irreversible cross-linked proteins contribute to athero-sclerosis as well as to kidney failure, conditions worsened indiabetes (41). Elevated circulating AGEs are associated withan increased risk of developing many chronic age-related dis-eases (42).

In addition to endogenous AGEs, humans are exposed toAGEs ingested in foods. Exogenously, preparation of food athigh temperatures is reported to facilitate AGE formation (43).Thus, a relevant factor inuencing AGE level in tissues andbody uids is the dietary intake of these glycotoxins. In ex-perimental animal models, reduction of AGE levels either bypharmacologic intervention or reduced dietary intake ofAGEs counteracts systemic and tissue oxidative stress, pre-vents aging-associated disease, and prolongs life span (44).36). These AGEs are heterogeneous substancesa prevalentAGE in vivo is carboxymethyl lysine (CML), a form ofnonuorescent AGE. Other AGEs such as pentosidine arecharacterized by their ability to form cross-links and to uo-

VIEWS AND REVIEWSAGE production because it promotes the last step of advancedglycation (41). Additional mechanisms are involved in the

14cules, AGEs may gradually accumulate in the ovary and po-tentiate the wide spatiotemporal spread of oxidative stress.Prolonged exposure to AGEs during reproductive life maycause subtle oxidative damage in primordial follicles (8) andovarian stroma vessels (54), promoting a gradual increase ofROS in the ovarian microenvironment during folliculogene-sis. These conditions, in turn, may jeopardize granulosa cellmetabolism, assembly of antioxidant defense, and develop-ment of efcient perifollicular vascularization, and endangermaturation, chromosomal constitution, and developmentalcapacity of the oocytes. Decreased antioxidant and antiglyca-tion defenses along with mitochondrial dysfunctions mightbe the driving force for the activation of a positive feedbackloop involving oxidative stress, carbonyl stress, and gradualaccumulation of AGEs, valuable persistent markers of age-related molecular damage in the ovary (Fig. 1).

Initially, this view of follicle aging arose from the ndingof AGE in the human ovarian tissue of young women (55). Byusing a specic antibody, the investigators observed AGE-modied proteins in granulosa cells and theca layers, andfound that RAGE was highly expressed in the ovary in gran-ulosa cells, theca interna, and endothelial and stromal cells.interplay between AGE accumulation and increased ROSlevel. Proteins modied by AGEs exert their action throughactivation of cell responses by interacting with specic cell-surface receptors, such as the receptor for AGEs (RAGE)(49). RAGE is a multiligand member of the immunoglobulinsuperfamily of cell surface. Upon engagement by AGEs,RAGE triggers intracellular signaling pathways, culminatingin the activation of the transcription factor nuclear factorkB(NF-kB), leading to proinammatory gene expression andROS generation (50, 51). The role of RAGE has been studiedin a number of chronic inammatory diseases such asdiabetes, arteriosclerosis, rheumatoid arthritis, inammatorykidney disease, and neurodegenerative disorders (51).Because the gene targets of NF-kB include RAGE genes, theaccumulation of AGEs is associated with an overexpressionof these receptors (52). Moreover, the increased productionof ROS can result in the depletion of GSH and NADPH,which can in turn decrease the activity of GLO1 and therebyincrease the concentration of MG and the formation ofAGEs (53). This positive feedback loop makes AGEformation a valuable persistent marker of increasedproduction of short half-life reactive metabolites.

Involvement of Carbonyl Stress in Follicle Aging

The present overview of mechanisms underlying accumula-tion of molecular damage with aging would provide a frame-work to properly approach the hypothesis of the involvementof carbonyl stress in ovarian aging. Based on the above obser-vations, this theory is intriguing because the potential accu-mulation of AGEs in the human ovary may account fora number of age-related features of ovarian dysfunction, in-cluding impaired vascularization and consequent hypoxiaThe nding of increased levels of AGE in the serum and ovaryof polycystic ovary syndrome (PCOS) patients was viewed as

VOL. 99 NO. 1 / JANUARY 2013

A relevant study has shown that AGEs affect reproduc-tion in a clinical setting. Jinno et al. (68) reported thattherst evidence of AGE involvement in ovarian dysfunctions

FIGURE 1

Some of the possible links in the positive feedback loop by whichoxidative stress and carbonyl stress promote AGE formation duringovarian follicle aging. Decreased antioxidant and antiglycationdefenses along with mitochondrial dysfunctions might be thedriving force for the progressive metabolic impairment duringaging. Altered glucose metabolism can be an additional factorpromoting AGE accumulation.Tatone. Toxic metabolites in follicle aging. Fertil Steril 2013.(55, 56). Moreover, animal studies have identied dietaryglycotoxins in the ovary (57). Finally, an interesting studysearching for a causative link between AGE and cytogenesisin PCOS tissue has provided evidence for a potential role ofAGE signaling in the control of the ovarian extracellularmatrix during follicular development (58).

A possible correlation of AGE with follicle aging was rstreported by an observational study that found increasedlevels of pentosidine in the primordial, primary, and atreticfollicles of premenopausal women (59). However, the rst ev-idence that the mammalian ovary experiences a condition ofcarbonyl stress associated with aging was obtained in themouse model (60): [1] the activity and expression of GLO1 de-creased in aged ovaries, [2] MG-AGE accumulated with agingin specic ovarian compartments, and [3] a preliminary anal-ysis of proteome revealed increased glycation of specicpolypeptides.

Further evidence for the role of AGEs in follicle aging wasprovided by measurements in follicular uid and serum ofsoluble RAGE (s-RAGE), a circulating isoform of RAGE thatcan neutralize the ligand-mediated damage (61). Based onmeasurements in young and reproductive-aged women, theinvestigators suggested that changes in the interplay betweenRAGE and vascular endothelial growth factor (VEGF) may re-sult in reproductive dysfunction in aging women. Indeed,VEGF signaling is deregulated in the follicular microenviron-ment of aged women and may account for alterations in fol-licular vasculature (62).

Notably, assay of MG cytotoxicity in mouse oocytes hasrecently revealed the effects of a possible RCS overload with

VOL. 99 NO. 1 / JANUARY 2013accumulation of some AGEsnamely, pentosidine, carboxy-methyl lysine (CML), and the so-called toxic AGE (TAGE)(69)in follicular uid and in serum correlated negativelywith follicular growth, fertilization, and embryonic develop-ment. They established that serum levels of TAGE above7.24 IU/mL indicated ovarian dysfunction and caused dimin-ished fertility, and that they correlated positively with alteredglucose metabolism, age, and factors related to obesity, dys-lipidemia, hyperglycemia, and insulin resistance.

Targeting AGEs: A Potential Approach forDelaying Follicle Aging

Interventions against carbonyl stress and AGE formation mayoffer potential innovative strategies for saving or rescuingovarian follicle health with aging. In this respect, attentionmust be paid to synthetic compounds with antiglycation ac-tivity as well as to dietary agents and lifestyle. Regardingthe rst issue, a wide range of molecules, including aminoguanidine, metformin, benfotiamine, and pyridoxamine, areunder study as drugs for preventing AGE-related dysfunc-tions. Inhibitors of AGE may act by various mechanisms atdifferent steps of AGE formation and AGE-mediated damagesuch as trapping of reactive carbonyl compounds, AGE cross-link breaking, RAGE blocking, and RAGE-signaling blockingas well as glycemia reduction (7072). Dietary agents havebeen found to be compounds that possess AGE-inhibitor ac-tivity, such as the numerous commonly used medicinal plantsand plant constituents that possess antiglycation activity (73,74). Prominent among them are green tea and its majorbioactive constituents the polyphenol compounds, whichare MG trapping agents more powerful thanaminoguanidine (75). Encouraging studies in animal modelsaging (63, 64). In vivo and in vitro experiments have shownthat MG induced a signicant reduction in the rate ofoocyte maturation, fertilization, and in vitro embryonicdevelopment probably via apoptotic process. Methylglyoxalwas found to cause disturbances in redox regulation anddistribution of mitochondria, aberrant and delayed spindleformation, and DNA damage. The importance ofantiglycation defense in folliculogenesis has been revealedby the nding of Glo1 and Glo2 transcripts in mousecumulus cells and oocytes. Consistent with their role withinthe ovarian follicle, glyoxalase transcripts were found todecrease in ovulated oocytes when compared with oocytesfrom antral follicles. Moreover, aged cumulus cellsexhibited a decreased ability to protect the oocyte from MGtoxicity (64). Together, these ndings suggest that anincreased MG level may contribute to a predisposition toaneuploidy and reduced oocyte developmental potentialwith aging (65, 66). Further evidence for the crucial role ofglyoxalases in the ovary has been provided by the ndingthat dietary glycotoxins and hyperandrogenic statesdecrease GLO1 activity in rat ovaries, possibly contributingto increased AGE accumulation in granulosa cells (67).

Fertility and Sterilityhave recently revealed that further strategies to be takeninto account as anti-AGE measures are reduced intake of

15

concepts, we encourage further investigation of the network

4. Cohen AA. Female post-reproductive lifespan: a general mammalian trait.Biol Rev Camb Philos Soc 2004;79:73350.

VIEWS AND REVIEWS5. Balasch J, Gratacos E. Delayed childbearing: effects on fertility and the out-come of pregnancy. Fetal Diagn Ther 2011;29:26373.

6. Te Velde ER, Pearson PL. The variability of female reproductive ageing. HumReprod Update 2002;8:14154.

7. Faddy MJ. Follicle dynamics during ovarian ageing. Mol Cell Endocrinol2000;163:438.

8. De Bruin JP, DorlandM, Spek ER, Posthuma G, van Haaften M, Looman CW,et al. Age-related changes in the ultrastructure of the resting follicle pool inhuman ovaries. Biol Reprod 2004;70:41924.

9. Broekmans FJ, Soules MR, Fauser BC. Ovarian aging: mechanisms and clin-ical consequences. Endocr Rev 2009;30:46593.

10. Eichenlaub-Ritter U, Vogt E, Yin H, Gosden R. Spindles, mitochondria andinvolving mitochondrial dysfunction, ROS/RCS overload,and relative stress response pathways in the follicle. In thisregard, human granulosa cells from IVF patients mayprovide a valuable model for studying age-related dysfunc-tion in the ovarian microenvironment. Greater understandingof these issues could be helpful in creating innovative strate-gies for counteracting the effects exerted on fertility by age oraging-like insults (i.e., xenobiotics and anticancer drugs).

Acknowledgments: The authors thank Ursula Eichenlaub-Ritter, Riccardo Focarelli, and Giovanna Di Emidio for theirvaluable contribution to the issues discussed and reviewedin our article.

REFERENCES1. Kirkwood TB. Understanding the odd science of aging. Cell 2005;120:

43747.2. Broekmans FJ, Knauff EA, te Velde ER, Macklon NS, Fauser BC. Female re-

productive ageing: current knowledge and future trends. Trends EndocrinolMetab 2007;18:5865.

3. Harlow SD, Gass M, Hall JE, Lobo R, Maki P, Rebar RW, et al. STRAW 10Collaborative Group. Executive summary of the Stages of Reproductive Ag-ingWorkshop 10: addressing the unnished agenda of staging reproduc-tive aging. Fertil Steril 2012;97:84351.glycotoxins (76) and physical exercise. Experiments on mu-rine brains have demonstrated that regular running lowersthe chance of carbonyl stress during aging and reduces mo-lecular damage proles by enhancing activities of MG-scavenging systems (77, 78). The potential of syntheticmolecules, dietary components, modication of diet AGEcontent, and exercise to prevent protein glycation promptsus to hypothesize that these may be exploited forcontrolling AGE accumulation during aging and ovariandysfunction.

FINAL REMARKS AND FUTURE CHALLENGEIn the past few years, the carbonyl stress theory of aging hasgained a great deal of attention from researchers and clini-cians who are involved in female reproductive aging. In themeantime, increased evidence for impaired regulation of en-ergetic metabolism in the aging follicle has been provided byanimal studies showing that caloric restriction or antioxidantsupplementation can prevent loss of oocyte competencethroughout reproductive life (22, 79). Based on theseredox potential in ageing oocytes. Reprod Biomed Online 2004;8:4558.

1611. Tatone C, Amicarelli F, Carbone MC, Monteleone P, Caserta D, Marci R,et al. Cellular and molecular aspects of ovarian follicle ageing. Hum ReprodUpdate 2008;14:13142.

12. Hansen KR, Knowlton NS, Thyer AC, Charleston JS, Soules MR, Klein NA. Anew model of reproductive aging: the decline in ovarian non-growing folli-cle number from birth to menopause. Hum Reprod 2008;23:699708.

13. Sauer MV. The impact of age on reproductive potential: lessons learnedfrom oocyte donation. Maturitas 1998;30:2215.

14. Sharov AA, Falco G, Piao Y, Poosala S, Becker KG, Zonderman AB, et al. Ef-fects of aging and calorie restriction on the global gene expression proles ofmouse testis and ovary. BMC Biol 2008;6:24.

15. Harman D. Free radical theory of aging: an update: increasing the functionallife span. Ann NY Acad Sci 2006;1067:1021.

16. Feuerstein P, Puard V, Chevalier C, Teusan R, Cadoret V, Guerif F, et al. Ge-nomic assessment of human cumulus cell marker genes as predictors of oo-cyte developmental competence: impact of various experimental factors.PLoS One 2012;7:e40449.

17. Gilchrist RB, LaneM, Thompson JG.Oocyte-secreted factors: regulators of cu-mulus cell functionandoocytequality.HumReprodUpdate2008;14:15977.

18. Davies KJ. Oxidative stress: the paradox of aerobic life. Biochem Soc Symp1995;61:131.

19. Finkel T, Holbrook NJ. Oxidants, oxidative stress and the biology of ageing.Nature 2000;408:23947.

20. Halliwell B. Free radicals and antioxidants: updating a personal view. NutrRev 2012;70:25765.

21. Ray PD, Huang BW, Tsuji Y. Reactive oxygen species (ROS) homeostasis andredox regulation in cellular signaling. Cell Signal 2012;24:98190.

22. Selesniemi K, Lee HJ, Muhlhauser A, Tilly JL. Prevention of maternal aging-associated oocyte aneuploidy and meiotic spindle defects in mice by dietaryand genetic strategies. Proc Natl Acad Sci USA 2011;108:1231924.

23. Agarwal A, Aponte-Mellado A, Premkumar BJ, Shaman A, Gupta S. The ef-fects of oxidative stress on female reproduction: a review. Reprod Biol Endo-crinol 2012;10:49.

24. Harman D. Aging: a theory based on free radical and radiation chemistry. JGerontol 1956;11:298300.

25. Lim J, Luderer U. Oxidative damage increases and antioxidant gene expres-sion decreases with aging in the mouse ovary. Biol Reprod 2011;84:77582.

26. Ito M, Muraki M, Takahashi Y, Imai M, Tsukui T, Yamakawa N, et al. Gluta-thione S-transferase theta 1 expressed in granulosa cells as a biomarker foroocyte quality in age-related infertility. Fertil Steril 2008;90:102635.

27. Ito M, Imai M, Muraki M, Miyado K, Qin J, Kyuwa S, et al. GSTT1 is upregu-lated by oxidative stress through p38-MK2 signaling pathway in humangranulosa cells: possible association with mitochondrial activity. Aging2011;3:121323.

28. Devine PJ, Perreault SD, Luderer U. Roles of reactive oxygen species and an-tioxidants in ovarian toxicity. Biol Reprod 2012;86:27.

29. Matos L, Stevenson D, Gomes F, Silva-Carvalho JL, Almeida H. Superoxidedismutase expression in human cumulus oophorus cells. Mol Hum Reprod2009;15:4119.

30. Mano J. Reactive carbonyl species: their production from lipid peroxides, ac-tion in environmental stress, and the detoxicationmechanism. Plant PhysiolBiochem 2012;59:907.

31. Thornalley PJ. Dicarbonyl intermediates in the Maillard reaction. Ann NYAcad Sci 2005;1043:1117.

32. Thornalley PJ. Protein and nucleotide damage by glyoxal and methylglyoxalin physiological systemsrole in ageing and disease. Drug Metabol Drug In-teract 2008;23:12550.

33. Thornalley PJ. Pharmacology of methylglyoxal: formation, modication ofproteins and nucleic acids, and enzymatic detoxicationa role in pathogen-esis and antiproliferative chemotherapy. Gen Pharmacol 1996;27:56573.

34. Amicarelli F, Colafarina S, Cattani F, Cimini A, Di Ilio C, Ceru MP, et al. Scav-enging system efciency is crucial for cell resistance to ROS-mediated meth-ylglyoxal injury. Free Radic Biol Med 2003;35:85671.

35. Dobler D, Ahmed N, Song L, Eboigbodin KE, Thornalley PJ. Increased dicar-bonyl metabolism in endothelial cells in hyperglycemia induces anoikis andimpairs angiogenesis by RGD and GFOGER motif modication. Diabetes

2006;55:19619.

VOL. 99 NO. 1 / JANUARY 2013

Fertility and Sterility36. Peppa M, Uribarri J, Vlassara H. Aging and glycoxidant stress. Hormones2008;7:12332.

37. Thornalley PJ. Glyoxalase Istructure, function and a critical role in the en-zymatic defence against glycation. Biochem Soc Trans 2003;31:13438.

38. Shipanova IN, Glomb MA, Nagaraj RH. Protein modication by methyl-glyoxal: chemical nature and synthetic mechanism of amajor uorescent ad-duct. Arch Biochem Biophys 1997;344:2936.

39. Gomes R, Sousa SilvaM, Quintas A, Cordeiro C, Freire A, Pereira P, et al. Arg-pyrimidine, a methylglyoxal-derived advanced glycation end-product in fa-milial amyloidotic polyneuropathy. Biochem J 2005;385:33945.

40. Rabbani N, Thornalley PJ. Methylglyoxal, glyoxalase 1 and the dicarbonylproteome. Amino Acids 2012;42:113342.

41. Goldin A, Beckman JA, Schmidt AM, Creager MA. Advanced glycation endproducts: sparking the development of diabetic vascular injury. Circulation2006;114:597605.

42. Tessier FJ. The Maillard reaction in the human body: the main discoveriesand factors that affect glycation. Pathol Biol 2010;58:2149.

43. Goldberg T, Cai W, Peppa M, Dardaine V, Baliga BS, Uribarri J, et al. Ad-vanced glycoxidation end products in commonly consumed foods [pub-lished correction appears in J Am Diet Assoc 2005;105:647]. J Am DietAssoc 2004;104:128791.

44. Uribarri J, Cai W, Peppa M, Goodman S, Ferrucci L, Striker G, et al. Circulat-ing glycotoxins and dietary advanced glycation endproducts: two links to in-ammatory response, oxidative stress, and aging. J Gerontol A Biol Sci MedSci 2007;62:42733.

45. Morcos M, Du X, Psterer F, Hutter H, Sayed AA, Thornalley P, et al. Glyox-alase-1 prevents mitochondrial protein modication and enhances lifespanin Caenorhabditis elegans. Aging Cell 2008;7:2609.

46. Kuhla B, Boeck K, Luth HJ, Schmidt A, Weigle B, Schmitz M, et al. Age-de-pendent changes of glyoxalase I expression in human brain. Neurobiol Ag-ing 2006;27:81522.

47. Baynes JW, Thorpe SR. Glycoxidation and lipoxidation in atherogenesis. FreeRadic Biol Med 2000;28:170816.

48. Yin QQ, Dong CF, Dong SQ, Dong XL, Hong Y, Hou XY, et al. AGEs inducecell death via oxidative and endoplasmic reticulum stresses in both humanSH-SY5Y neuroblastoma cells and rat cortical neurons. Cell Mol Neurobiol.Published online June 21, 2012.

49. Bierhaus A, Nawroth PP. Multiple levels of regulation determine the role ofthe receptor for AGE (RAGE) as common soil in inammation, immune re-sponses and diabetes mellitus and its complications. Diabetologia 2009;52:225163.

50. Fleming TH, Humpert PM, Nawroth PP, Bierhaus A. Reactive metabolites andAGE/RAGE-mediated cellular dysfunction affect the aging process: a mini-review. Gerontology 2011;57:43543.

51. Ramasamy R, Yan SF, Schmidt AM. Advanced glycation endproducts: fromprecursors toRAGE: roundand roundwego.AminoAcids 2012;42:115161.

52. Rojas A, Morales MA. Advanced glycation and endothelial functions: a linktowards vascular complications in diabetes. Life Sci 2004;76:71530.

53. Kalapos MP. The tandem of free radicals and methylglyoxal. Chem Biol In-teract 2008;171:25171.

54. Ng EH, Chan CC, Yeung WS, Ho PC. Effect of age on ovarian stromal owmeasured by three-dimensional ultrasound with power Doppler in Chinesewomen with proven fertility. Hum Reprod 2004;19:21327.

55. Diamanti-Kandarakis E, Piperi C, Patsouris E, Korkolopoulou P, Panidis D, Pa-welczyk, et al. Immunohistochemical localization of advanced glycation end-products (AGEs) and their receptor (RAGE) in polycystic and normal ovaries.Histochem Cell Biol 2007;127:5819.

56. Diamanti-Kandarakis E, Katsikis I, Piperi C, Kandaraki E, Piouka A,Papavassiliou AG, et al. Increased serum advanced glycation end-productsis a distinct nding in lean women with polycystic ovary syndrome (PCOS).Clin Endocrinol 2008;69:63441.

57. Diamanti-Kandarakis E, Piperi C, Korkolopoulou P, Kandaraki E, Levidou G,Papalois A, et al. Accumulation of dietary glycotoxins in the reproductive sys-tem of normal female rats. J Mol Med 2007;85:141320.

58. Matsumine M, Shibata N, Ishitani K, Kobayashi M, Ohta H. Pentosidine ac-cumulation in human oocytes and their correlation to age-related apoptosis.

Acta Histochem Cytochem 2008;41:97104.

VOL. 99 NO. 1 / JANUARY 201359. Papachroni KK, Piperi C, Levidou G, Korkolopoulou P, Pawelczyk L, Dia-manti-Kandarakis E, et al. Lysyl oxidase interacts with AGE signalling tomod-ulate collagen synthesis in polycystic ovarian tissue. J Cell Mol Med 2010;14:24609.

60. Tatone C, Carbone MC, Campanella G, Festuccia C, Artini PG, Talesa V,et al. Female reproductive dysfunction during ageing: role of methylglyoxalin the formation of advanced glycation endproducts in ovaries ofreproductively-aged mice. J Biol Regul Homeost Agents 2010;24:6372.

61. Fujii EY, Nakayama M. The measurements of RAGE, VEGF, and AGEs in theplasma and follicular uid of reproductive women: the inuence of aging.Fertil Steril 2010;94:694700.

62. Yeh J, Kim BS, Peresie J. Ovarian vascular endothelial growth factor and vas-cular endothelial growth factor receptor patterns in reproductive aging. Fer-til Steril 2008;89:154656.

63. Chang YJ, Chan WH. Methylglyoxal has injurious effects on maturation ofmouse oocytes, fertilization, and fetal development, via apoptosis. ToxicolLett 2010;193:21723.

64. Tatone C, Heizenrieder T, Di Emidio G, Treffon P, Amicarelli F, Seidel T,et al. Evidence that carbonyl stress by methylglyoxal exposure inducesDNA damage and spindle aberrations, affects mitochondrial integrity inmammalian oocytes and contributes to oocyte ageing. Hum Reprod2011;26:184359.

65. Eichenlaub-Ritter U, Wieczorek M, Luke S, Seidel T. Age related changes inmitochondrial function and new approaches to study redox regulation inmammalian oocytes in response to age or maturation conditions. Mitochon-drion 2011;11:78396.

66. Eichenlaub-Ritter U. Female meiosis and beyond: more questions than an-swers? Reprod Biomed Online 2012;24:58990.

67. Kandaraki E, Chatzigeorgiou A, Piperi C, Palioura E, Palimeri S,Korkolopoulou P, et al. Reduced ovarian glyoxalase-I activity by dietary gly-cotoxins and androgen excess: a causative link to polycystic ovarian syn-drome. Mol Med 2012;18:11839.

68. Jinno M, Takeuchi M, Watanabe A, Teruya K, Hirohama J, Eguchi N, et al.Advanced glycation end-products accumulation compromises embryonicdevelopment and achievement of pregnancy by assisted reproductive tech-nology. Hum Reprod 2011;26:60410.

69. Sato T, Iwaki M, Shimogaito N,Wu X, Yamagishi S, Takeuchi M. TAGE (toxicAGEs) theory in diabetic complications. Curr Mol Med 2006;6:3518.

70. Takeuchi M, Takino J, Yamagishi S. Involvement of the toxic AGEs (TAGE)-RAGE system in the pathogenesis of diabetic vascular complications: a noveltherapeutic strategy. Curr Drug Targets 2010;11:146882.

71. Peyroux J, Sternberg M. Advanced glycation endproducts (AGEs): pharma-cological inhibition in diabetes. Pathol Biol (Paris) 2006;54:40519.

72. Reddy VP, Beyaz A. Inhibitors of the Maillard reaction and AGE breakers astherapeutics for multiple diseases. Drug Discov Today 2006;11:64654.

73. Peng X, Ma J, Chen F, Wang M. Naturally occurring inhibitors againstthe formation of advanced glycation end-products. Food Funct 2011;2:289301.

74. Elosta A, Ghous T, Ahmed N. Natural products as anti-glycation agents: pos-sible therapeutic potential for diabetic complications. Curr Diabetes Rev2012;8:92108.

75. Sang S, Shao X, Bai N, Lo CY, Yang CS, Ho CT. Tea polyphenol()-epigallo-catechin-3-gallate: a new trapping agent of reactive dicarbonyl species.Chem Res Toxicol 2007;20:186270.

76. Vlassara H, Striker GE. AGE restriction in diabetes mellitus: a paradigm shift.Nat Rev Endocrinol 2011 May 24;7:52639.

77. Falone S, DAlessandro A, Mirabilio A, Petruccelli G, Cacchio M, Di Ilio C,et al. Long term running biphasically improves methylglyoxal-related metab-olism, redox homeostasis and neurotrophic support within adult mousebrain cortex. PLoS One 2012;7:e31401.

78. Falone S, DAlessandro A, Mirabilio A, Cacchio M, Di Ilio C, Di Loreto S, et al.Late-onset running biphasically improves redox balance, energy- andmethylglyoxal-related status, as well as SIRT1 expression in mouse hippo-campus. PLoS One 2012;7:e48334.

79. Liu J, Liu M, Ye X, Liu K, Huang J, Wang L, Ji G, Liu N, Tang X, Baltz JM,Keefe DL, Liu L. Delay in oocyte aging in mice by the antioxidant N-acetyl-

l-cysteine (NAC). Hum Reprod 2012;27:141120.

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The aging ovarythe poor granulosa cellsReactive oxygen species and oxidative stress in the aging follicle: a brief updateCarbonyl reactive species and carbonyl stress in the aging follicleDicarbonyls: Highly Reactive Toxic Compounds from Cellular MetabolismGlycation and AGEsThe Glyoxalase System: The Most Powerful Defense against Carbonyl Stress and AGEThe Interplay between AGE and Oxidative Stress: The Role of RAGEInvolvement of Carbonyl Stress in Follicle AgingTargeting AGEs: A Potential Approach for Delaying Follicle Aging

Final remarks and future challengeAcknowledgmentsReferences