Reactive Oxygen Species Facilitate Adipocyte Differentiation by Accelerating Mitotic Clonal Expansion

Growth-arrested 3T3-L1 preadipocytes rapidly express CCAAT/enhancer-binding protein-β (C/EBPβ) upon hormonal induction of differentiation. However, the DNA binding activity of C/EBPβ is not activated until the cells synchronously reenter S phase during the mitotic clonal expansion (MCE) phase of differentiation. In this period, C/EBPβ is sequentially phosphorylated by MAPK and glycogen synthase kinase-3β, inducing C/EBPβ DNA binding activity and transcription of its target genes. Because the DNA binding activity of C/EBPβ is further enhanced by oxidation in vitro, we investigated how redox state affects C/EBPβ DNA binding and MCE during adipogenesis. When 3T3-L1 cells were treated with H2O2 and hormonal stimuli, differentiation was accelerated with increased expression of peroxisome proliferator-activated receptor γ. Interestingly, cell cycle progression (S to G2/M phase) was markedly enhanced by H2O2, whereas antioxidants caused an S phase arrest during the MCE. H2O2 treatment resulted in the early appearance of a punctate pattern observed by immunofluorescent staining of C/EBPβ, which is a hallmark for C/EBPβ binding to regulatory elements, whereas a short antioxidant treatment rapidly dispersed the centromeric localization of C/EBPβ. Consistently, reactive oxygen species production was increased during 3T3-L1 differentiation. Our results indicate that redox-induced C/EBPβ DNA binding activity, along with the dual phosphorylation of C/EBPβ, is required for the MCE and terminal differentiation of adipocytes. Growth-arrested 3T3-L1 preadipocytes rapidly express CCAAT/enhancer-binding protein-β (C/EBPβ) upon hormonal induction of differentiation. However, the DNA binding activity of C/EBPβ is not activated until the cells synchronously reenter S phase during the mitotic clonal expansion (MCE) phase of differentiation. In this period, C/EBPβ is sequentially phosphorylated by MAPK and glycogen synthase kinase-3β, inducing C/EBPβ DNA binding activity and transcription of its target genes. Because the DNA binding activity of C/EBPβ is further enhanced by oxidation in vitro, we investigated how redox state affects C/EBPβ DNA binding and MCE during adipogenesis. When 3T3-L1 cells were treated with H2O2 and hormonal stimuli, differentiation was accelerated with increased expression of peroxisome proliferator-activated receptor γ. Interestingly, cell cycle progression (S to G2/M phase) was markedly enhanced by H2O2, whereas antioxidants caused an S phase arrest during the MCE. H2O2 treatment resulted in the early appearance of a punctate pattern observed by immunofluorescent staining of C/EBPβ, which is a hallmark for C/EBPβ binding to regulatory elements, whereas a short antioxidant treatment rapidly dispersed the centromeric localization of C/EBPβ. Consistently, reactive oxygen species production was increased during 3T3-L1 differentiation. Our results indicate that redox-induced C/EBPβ DNA binding activity, along with the dual phosphorylation of C/EBPβ, is required for the MCE and terminal differentiation of adipocytes. Adipocyte differentiation involves an elaborate network of transcription factors that regulate the expression of numerous genes responsible for the phenotype of mature adipocytes (1MacDougald O.A. Lane M.D. Annu. Rev. Biochem... 1995; 64: 345-373Google Scholar, 2Farmer S.R. Cell Metab... 2006; 4: 263-273Google Scholar-3Rosen E.D. Walkey C.J. Puigserver P. Spiegelman B.M. Genes Dev... 2000; 14: 1293-1307Google Scholar). Several members of the C/EBP 2The abbreviations used are: C/EBP, CCAAT/enhancer-binding protein; MCE, mitotic clonal expansion; PPAR, peroxisome proliferator-activated receptor; ROS, reactive oxygen species; RSV, resveratrol; MAPK, mitogen-activated protein kinase; GSK, glycogen synthase kinase; DMEM, Dulbecco's modified Eagle's medium; IBMX, 3-isobutyl-1-methylxanthine; FBS, fetal bovine serum; PBS, phosphate-buffered saline; siRNA, small interfering RNA; FACS, fluorescence-activated cell sorting; ChIP, chromatin immunoprecipitation; DCF-DA, 2′,7′-dichlorodihydrofluorescein diacetate; NAC, N-acetyl cysteine; EMSA, electrophoretic mobility shift assay. family as well as PPARγ participate in a transcriptional cascade during adipogenesis (2Farmer S.R. Cell Metab... 2006; 4: 263-273Google Scholar, 4Lane M.D. Tang Q.Q. Jiang M.S. Biochem. Biophys. Res. Commun... 1999; 266: 677-683Google Scholar). Most of our knowledge about transcriptional regulation in adipocytes comes from studies using the murine 3T3-L1 preadipocyte model. The differentiation of growth-arrested 3T3-L1 cells into adipocytes is induced by hormonal stimuli, which immediately causes the expression of C/EBPβ (5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google Scholar, 6Tang Q.Q. Otto T.C. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2003; 100: 850-855Google Scholar-7Mandrup S. Lane M.D. J. Biol. Chem... 1997; 272: 5367-5370Google Scholar). C/EBPβ is thought to initiate mitotic clonal expansion of the preadipocytes and to later coordinate the transcription network by turning on two principal adipogenic factors, C/EBPα and PPARγ (1MacDougald O.A. Lane M.D. Annu. Rev. Biochem... 1995; 64: 345-373Google Scholar, 8Christy R.J. Kaestner K.H. Geiman D.E. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 1991; 88: 2593-2597Google Scholar). Although the expression of C/EBPβ reaches its maximal level within 4 h of induction, the binding of C/EBPβ to DNA and the expression of C/EBPα and PPARγ are only observed after a long lag period (4Lane M.D. Tang Q.Q. Jiang M.S. Biochem. Biophys. Res. Commun... 1999; 266: 677-683Google Scholar, 5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google Scholar). During this period, cells synchronously enter the cell cycle (6Tang Q.Q. Otto T.C. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2003; 100: 850-855Google Scholar, 9Tang Q.Q. Otto T.C. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2003; 100: 44-49Google Scholar), which is accompanied by the nuclear localization of glycogen synthase kinase 3β (GSK3β) (10Tang Q.Q. Gronborg M. Huang H. Kim J.W. Otto T.C. Pandey A. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2005; 102: 9766-9771Google Scholar). A recent investigation has revealed that phosphorylation of C/EBPβ by nuclear GSK3β enhances its DNA binding activity (10Tang Q.Q. Gronborg M. Huang H. Kim J.W. Otto T.C. Pandey A. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2005; 102: 9766-9771Google Scholar). Thr188 of C/EBPβ is phosphorylated by MAPK immediately after its expression is induced and then later by GSK3β on Ser184 or Thr179. The priming phosphorylation of C/EBPβ-Thr188 is maintained throughout S phase and mitotic clonal expansion through the activity of Cdk2-cyclin A after MAPK activity is down-regulated (11Li X. Kim J.W. Gronborg M. Urlaub H. Lane M.D. Tang Q.Q. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 11597-11602Google Scholar). Because the translocation of GSK3β into the nucleus is observed 12–14 h after induction, it has been suggested that the dual phosphorylation of C/EBPβ is associated with the activation of its DNA binding function. This finding has been confirmed in our experiment using highly purified recombinant C/EBPβ (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar). In that study, when recombinant C/EBPβ protein was exposed to mild oxidizing conditions, only doubly phosphorylated C/EBPβ had enhanced DNA binding activity. This suggests that the dual phosphorylation of C/EBPβ leads to a conformational change that facilitates dimerization through its C-terminal leucine zipper domain, rendering the basic DNA-binding region of C/EBPβ accessible to the C/EBP regulatory element on C/EBPα or PPARγ. In this scenario, under oxidizing conditions the monomer-dimer equilibrium of dual phosphorylated C/EBPβ would be shifted toward dimer formation and the binding of the regulatory element to confer the proper level of transcriptional activation (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar). Although the mechanisms by which redox state actively regulates cellular metabolism are not clear, several reports have proposed that oxidative stress is an important element in metabolic diseases. For example, in obesity, fat accumulation is correlated with systemic oxidative stress in humans and mice (13Furukawa S. Fujita T. Shimabukuro M. Iwaki M. Yamada Y. Nakajima Y. Nakayama O. Makishima M. Matsuda M. Shimomura I. J. Clin. Invest... 2004; 114: 1752-1761Google Scholar). Production of reactive oxygen species (ROS) increases selectively in the adipose tissue of obese mice, accompanied by increased expression of NADPH oxidase and decreased expression of antioxidative enzymes. In addition, increased ROS levels are reported to be an important trigger for insulin resistance (14Houstis N. Rosen E.D. Lander E.S. Nature.. 2006; 440: 944-948Google Scholar). Consistent with this, it has been that oxidative stress in mature adipocytes A. A. H. N. and insulin from T. Y. H. H. M. Y. Y. T. Y. J. Clin. Invest... 1997; Scholar). ROS during adipogenesis has been and it has been proposed that insulin and are of H. Biochem. 1995; the mechanisms by which ROS differentiation have not been In this study, we how redox state affects mitotic clonal expansion during differentiation. H2O2 treatment in with hormonal of 3T3-L1 cells caused accelerated cell cycle progression (S to G2/M phase) and the early appearance of punctate observed from the immunofluorescent staining of C/EBPβ. the short antioxidant treatment rapidly dispersed the centromeric localization of C/EBPβ and the mitotic clonal expansion that ROS production is for the mitotic clonal expansion of Our indicate in to the dual phosphorylation of C/EBPβ, redox-induced DNA-binding of C/EBPβ is required for the mitotic clonal expansion and terminal differentiation of adipocytes. Cell and of and preadipocytes were maintained in 3T3-L1 cells were in FBS, and insulin for For differentiation was induced by and insulin for were then and insulin for after which were In H2O2 or N-acetyl or was the of differentiation induction and maintained for Cell were on and staining J.W. Tang Q.Q. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2004; was on cells were with phosphate-buffered and then into and were for and by and then of protein were to and with to C/EBPβ (5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google Scholar), or preadipocytes were with a of in was to and the cells were with using to the The was with for h the induction of differentiation. The modified and were from The are as preadipocytes were induced to as the cells were with PBS, and with cells were with and in the for with staining and A in cells were using a was for and were using cells were on in the as as the cells were with PBS, in for with for on and then in bovine in for were then in C/EBPβ (5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google for by for The cells were in was the of the were with C/EBPβ for 4 h and then with protein for The were and chromatin were from the of the DNA was and or were used as a in using the to the the C/EBP binding In and of C/EBPβ, EMSA, and C/EBPβ protein was and phosphorylated by MAPK and as (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar). For of recombinant protein was with activated MAPK and GSK3β in and for C/EBPβ was treated with of H2O2 for by of were in and to with was as (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar). In binding was The in the C/EBPα is of were with the 2′,7′-dichlorodihydrofluorescein the in was to cells for h under an 3T3-L1 cells were with and in were by the A was used for The was by ROS the of 3T3-L1 growth-arrested 3T3-L1 preadipocytes were induced to by hormonal ROS affects H2O2 was for the to of the differentiation in H2O2 treatment caused enhanced as by which is correlated with PPARγ The H2O2 was when a hormonal insulin from the was The 3T3-L1 cell differentiation was to of levels in the of whereas the of H2O2 markedly enhanced the differentiation in the of The of H2O2 treatment was and observed only in whereas cells not the of H2O2 When preadipocytes were exposed to as or PPARγ expression was and cells not as by staining with the antioxidant N-acetyl had the on staining In an to the by which H2O2 affects 3T3-L1 cell we investigated the expression of C/EBPβ, a of C/EBPα and PPARγ Although PPARγ expression and accumulation were by H2O2 or antioxidant the expression of C/EBPβ was had been that cells from mice clonal terminal that C/EBPβ is required for mitotic clonal expansion (6Tang Q.Q. Otto T.C. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2003; 100: 850-855Google Scholar). Consistently, of C/EBPβ expression the differentiation of 3T3-L1 cells H2O2 treatment not in differentiation when the expression of C/EBPβ was by that C/EBPβ is required for adipogenesis and that the the of C/EBPβ to with the preadipocyte cell This cell is reported to clonal expansion accompanied by DNA and increased cell A. P. Biochem. Biophys. Res. Commun... Scholar, A. Cell 2003; Scholar), which that the differentiation of would be by A was observed with that the ROS is not to 3T3-L1 indicate that ROS the differentiation by the activation of C/EBPβ. ROS Cell into G2/M during we how cell cycle during mitotic clonal expansion are by ROS hormonal growth-arrested 3T3-L1 cells synchronously reenter the cell in the of cells by after h of induction cells a of or the terminal differentiation induced cells are h of (1MacDougald O.A. Lane M.D. Annu. Rev. Biochem... 1995; 64: 345-373Google Scholar). Interestingly, H2O2 treatment caused an in the G2/M during in a In or treatment the progression of the cell that ROS production is required for clonal expansion during adipogenesis. preadipocytes treated with antioxidants were in S phase after h that ROS production is required for progression of cells from S to Consistently, short antioxidant treatment after h of induction cells have S phase) the progression of cells into G2/M phase by h indicate that ROS production is for the S to G2/M during the mitotic clonal expansion of the differentiation or cell cycle progression resulted in decreased cell of induction with The cell cycle was confirmed by the expression of as in that expression of MAPK, and were not by not be that it resulted in accelerated cell cycle H2O2 treatment not to an in cell after clonal that be the of clonal our during the period of mitotic clonal during which cells are highly indicate that ROS production is important for the progression of mitotic clonal expansion during of ROS on cell and expression of A during MCE. on of cells were and to cell were treated with H2O2 or for or as cell were the and to and to the expression of ROS Production with the of have that C/EBPβ is required for mitotic clonal expansion and later for the expression of transcription and PPARγ (6Tang Q.Q. Otto T.C. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2003; 100: 850-855Google Scholar). the early appearance of C/EBPβ protein after the induction of it not to target on DNA until cells enter S C/EBPβ its DNA binding activity, it to in a pattern in studies (5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google Scholar). This pattern is observed from to h S phase) when C/EBPβ is to a phosphorylation by nuclear GSK3β (10Tang Q.Q. Gronborg M. Huang H. Kim J.W. Otto T.C. Pandey A. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2005; 102: 9766-9771Google Scholar). we have reported that the binding activity of C/EBPβ is further enhanced in an oxidative in (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar), we that C/EBPβ binding to would be by in ROS production during adipogenesis. in the immunofluorescent staining pattern of C/EBPβ the h when cells were treated with The was observed when the antioxidant was used the of or after which C/EBPβ is to rapidly the punctate pattern to a nuclear staining pattern A and This that in the of oxidative the equilibrium of C/EBPβ binding is shifted toward DNA to a punctate In when oxidative stress is with C/EBPβ not to DNA been activated by dual the ROS we immunofluorescent of C/EBPβ after the of H2O2 in and h In the differentiation cells to have punctate of C/EBPβ and h whereas H2O2 treatment caused the early appearance of the punctate pattern h This suggests that in the of proper ROS after dual C/EBPβ protein to DNA well to its centromeric C/EBPβ is responsible for mitotic clonal expansion and the activation of the of as C/EBPα and PPARγ. C/EBPβ binding to we the in the or of H2O2 in H2O2 treatment caused increased binding of C/EBPβ to the and and whereas treatment decreased C/EBPβ that C/EBPβ binding to its target is enhanced by ROS The enhanced DNA binding activity of C/EBPβ in to H2O2 treatment was in in using recombinant C/EBPβ had highly purified recombinant C/EBPβ protein using the and and had confirmed the dual phosphorylation of the recombinant C/EBPβ protein by MAPK and GSK3β (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar). had been using (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar), H2O2 treatment caused the dimerization of phosphorylated recombinant C/EBPβ as by H2O2 treatment resulted in increased C/EBPβ DNA binding activity in the results that C/EBPβ binding to its regulatory element is enhanced by ROS, which during differentiation of 3T3-L1 in ROS Production during oxidative stress has been in conditions, have been several to ROS production in mature adipocytes (13Furukawa S. Fujita T. Shimabukuro M. Iwaki M. Yamada Y. Nakajima Y. Nakayama O. Makishima M. Matsuda M. Shimomura I. J. Clin. Invest... 2004; 114: 1752-1761Google Scholar, H. Biochem. 1995; Scholar). However, ROS production has not been during the mitotic clonal expansion of adipocytes. The results that ROS are required for the proper differentiation of preadipocytes and that ROS production be a of the differentiation the that the ROS was important and h after induction we ROS levels with using the during this in ROS production was during mitotic clonal expansion in adipogenesis. ROS was by the of as or not is that ROS production during the h period, then observed that ROS production increases in a and h not that ROS production is a to hormonal and reaches a after which C/EBPβ to DNA which of the hormonal for differentiation is responsible for ROS in it that of the and are required for of ROS in insulin be of on of the results in that cell cycle progression of induced preadipocytes the S to G2/M from its antioxidant activity, has been as a in and the of M. H. N. J. P. P. M. Puigserver P. J. 2006; Scholar, A. S. O. M. S. R.J. P. Puigserver P. Nature.. 2006; Scholar). Although we had confirmed that of our using be using a antioxidant NAC, we not the of the is in the of the cell cycle by ROS, we with or to in the of the S to G2/M by was not by an of E.D. J. Biol. Chem... Scholar), the progression of clonal as by not ROS production during mitotic clonal expansion that affects the cell cycle of adipocytes in a during the mitotic clonal expansion phase of adipogenesis. have suggested that kinase is a target of A. S. O. M. S. R.J. P. Puigserver P. Nature.. 2006; Scholar, M. S. A. X. Jiang M. 2006; Scholar, J. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: Scholar). has been suggested that activation of kinase differentiation J. Biochem. Biophys. Res. Commun... 2005; Scholar, A. S. 2004; Scholar). In our treatment not change the level of ROS production in 3T3-L1 cells that kinase is not in ROS production during adipogenesis. This not the that increased ROS production during mitotic clonal expansion kinase activity, as has been proposed by J. Biochem. Biophys. Res. Commun... 2005; it that mitotic clonal expansion by ROS of the and kinase The differentiation of 3T3-L1 preadipocytes is by hormonal and by the and of transcriptional The of differentiation is arrest a state E.D. Spiegelman B.M. Annu. Rev. Cell 2000; Scholar), and cells not in in the of hormonal until induction of growth-arrested cells of cell as mitotic clonal expansion (1MacDougald O.A. Lane M.D. Annu. Rev. Biochem... 1995; 64: 345-373Google Scholar). preadipocyte as and 3T3-L1 are to a clonal of DNA the differentiation of cells Scholar). the preadipocytes from adipose tissue have been reported to in the of that H. J. Scholar). is preadipocytes from fat have mitotic clonal expansion in E.D. Spiegelman B.M. Annu. Rev. Cell 2000; Scholar, Scholar). is that the mitotic clonal expansion after the from the cell that during the (5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google Scholar), in to the of as PPARγ and after that mitotic clonal expansion and terminal differentiation. it is important to how the during mitotic clonal or not are to cell are associated with terminal differentiation as well as with the expression of C/EBPα and PPARγ. C/EBPβ is of the transcription factors during the mitotic clonal expansion period (4Lane M.D. Tang Q.Q. Jiang M.S. Biochem. Biophys. Res. Commun... 1999; 266: 677-683Google Scholar). During C/EBPβ is immediately upon hormonal and sequentially phosphorylated by MAPK and GSK3β (5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google Scholar, Q.Q. Gronborg M. Huang H. Kim J.W. Otto T.C. Pandey A. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2005; 102: 9766-9771Google Scholar). C/EBPβ DNA binding activity until the protein is phosphorylated by GSK3β h after induction (10Tang Q.Q. Gronborg M. Huang H. Kim J.W. Otto T.C. Pandey A. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2005; 102: 9766-9771Google Scholar). this C/EBPβ to as preadipocytes synchronously enter S phase the of mitotic clonal expansion (5Tang Q.Q. Lane M.D. Genes Dev... 1999; 13: 2231-2241Google Scholar). Because the localization to through C/EBP in centromeric it is thought that the C/EBPβ only after dual phosphorylation by MAPK and the maximal expression of C/EBPβ is h after we were to how C/EBPβ activated by dual phosphorylation using highly purified recombinant C/EBPβ protein (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar). A was proposed in which dual phosphorylation of C/EBPβ caused a conformational change that facilitates formation and rendering the basic region accessible to the C/EBP regulatory In this of we that cells are exposed to an oxidative which enhances C/EBPβ during in In the study, we that adipogenesis is accelerated by ROS which are to C/EBPβ DNA binding activity. ROS production is increased during adipogenesis induced by the within h after differentiation induction This period to the S phase of the mitotic clonal during which C/EBPβ to Interestingly, ROS levels by antioxidant treatment not only the localization of C/EBPβ cell cycle progression into G2/M Although this is not that C/EBPβ is in the S to G2/M it be that short antioxidant treatment dispersed the centromeric localization of C/EBPβ, in to S to G2/M that the activation of C/EBPβ is associated with cell cycle be that C/EBPβ is reported to be for adipogenesis in 3T3-L1 cells and from mice (6Tang Q.Q. Otto T.C. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2003; 100: 850-855Google Scholar), its was by T. N. T. S. 1997; Scholar). mice have to T. N. T. S. 1997; Scholar). In this it was suggested that for the of C/EBPβ, with in the early of adipogenesis in (2Farmer S.R. Cell Metab... 2006; 4: 263-273Google Scholar, E.D. O.A. Rev. Cell 2006; Scholar). to be the ROS on C/EBPβ is to adipogenesis in which is associated with about the of mitotic clonal expansion in E.D. Spiegelman B.M. Annu. Rev. Cell 2000; Scholar, Scholar). stress has been in insulin obesity, and (13Furukawa S. Fujita T. Shimabukuro M. Iwaki M. Yamada Y. Nakajima Y. Nakayama O. Makishima M. Matsuda M. Shimomura I. J. Clin. Invest... 2004; 114: 1752-1761Google Scholar, N. Rosen E.D. Lander E.S. Nature.. 2006; 440: 944-948Google Scholar, A. A. H. N. T. Y. H. H. M. Y. Y. T. Y. J. Clin. Invest... 1997; Scholar). (13Furukawa S. Fujita T. Shimabukuro M. Iwaki M. Yamada Y. Nakajima Y. Nakayama O. Makishima M. Matsuda M. Shimomura I. J. Clin. Invest... 2004; 114: 1752-1761Google have reported that increased oxidative stress in fat is an important of metabolic ROS were reported to have a in of insulin resistance (14Houstis N. Rosen E.D. Lander E.S. Nature.. 2006; 440: 944-948Google Scholar). the is proposed to and NADPH inducing oxidative stress in mature adipocytes J. Kim K.H. T. Y. Kim 2006; Scholar). Our that ROS are important in mitotic clonal expansion during by the in which H2O2 or antioxidant treatment was only for the of the differentiation that in obese mature adipocytes levels of ROS with and (13Furukawa S. Fujita T. Shimabukuro M. Iwaki M. Yamada Y. Nakajima Y. Nakayama O. Makishima M. Matsuda M. Shimomura I. J. Clin. Invest... 2004; 114: 1752-1761Google Scholar), it is that mature adipocytes be of ROS, the differentiation of be by the cycle of increased ROS Although we not the of ROS during MCE, we that insulin be important for the of ROS levels Because preadipocytes not express insulin receptor until of induction M.D. Clin. Biol. Scholar, Lane M.D. Proc. Natl. Acad. Sci. U. S. A... Scholar), be responsible for increased ROS In this it be that insulin from the differentiation IBMX, and caused S phase arrest of the cell J. Cell Biochem... 2004; Scholar). Consistently, our that the in differentiation when hormonal was used was by H2O2 treatment This suggests that preadipocytes are to ROS by in the DNA-binding of C/EBPβ to the clonal and I. P. I. O. T. T. Cell Metab... 2007; reported that is a of adipogenesis and that of C/EBPβ and of PPARγ. oxidase is used to oxidative by in it would be to how is by as well as how affects cell cycle progression in 3T3-L1 In study, we have that in oxidation of C/EBPβ protein markedly enhances the DNA binding activity by formation and conformational change (12Kim J.W. Tang Q.Q. Li X. Lane M.D. Proc. Natl. Acad. Sci. U. S. A... 2007; 104: 1800-1804Google Scholar). Although formation is in is for redox regulation of transcription For example, of the kinase is reported to be a target of oxidative by of A. T. M. J. D.E. Proc. Natl. Acad. Sci. U. S. A... 2006; Scholar). In addition, the transcription is by redox which is to the in the DNA binding of the protein P. S. 1999; 13: Scholar). have been reported for the transcription Y. 1999; Scholar, 1997; Scholar). This protein is activated by a phosphorylation in to in DNA and of target genes. Interestingly, of two within the C-terminal region of resulted in the activation of the transcription a of the protein Y. 1999; Scholar). This that in when in to the it is in the of it has been suggested that are as by the transcription A. S. J. Biol. Chem... Scholar). In the study, the DNA binding activity of C/EBPβ is enhanced in the of H2O2, as by immunofluorescent staining as well as and an of a transcription that be by redox in C/EBPβ is required for the mitotic clonal expansion during differentiation (4Lane M.D. Tang Q.Q. Jiang M.S. Biochem. Biophys. Res. Commun... 1999; 266: 677-683Google and for Li D.E. Y. J. Clin. Invest... 102: Scholar), or the phase S. T. Scholar), and cellular 1991; Scholar). it be to C/EBPβ activation in is caused by of cellular redox how C/EBP family in in be important for the of are to M. Lane and Tang for