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Suppression of Very Early Stage Of Adipogenesis by Baicalein, a Plant-Derived Flavonoid through Reduced Akt-C/EBP α -GLUT4 Signaling-Mediated Glucose Uptake in 3T3-L1 Adipocytes

View Article: PubMed Central - PubMed

ABSTRACT

Baicalein has been used as a Chinese medicine, and is an abundant plant flavonoid present in fruits and vegetables. Here, we examined the effects of baicalein in adipogenesis and investigated its molecular mechanism in adipocytes. Baicalein lowered the intracellular lipid accumulation and decreased the transcription levels of the adipocyte-specific genes in mouse 3T3-L1 adipocytes. Glucose uptake mediated by glucose transporter 4 (GLUT4) was reduced, causing down-regulation of the intracellular lipid accumulation. These reductions were also observed even when baicalein was added in only early stage of adipogenesis (0–2 days) of 6-day-adipogenesis. Chromatin immunoprecipitation assay showed that baicalein decreased the binding level of C/EBPα protein to the promoter region of the GLUT4 gene. Phosphorylation of Akt at 1 h after the initiation of adipogenesis was inhibited by the treatment with baicalein. Inhibition during only the first 1.5 h after the initiation of adipogenesis by baicalein or an Akt inhibitor was enough to decrease the lipid contents in the cells undergoing adipocyte differentiation for 6 days. These results indicate that baicalein decreased the intracellular lipid accumulation by down-regulation of glucose uptake via repression of Akt-C/EBPα-GLUT4 signaling in the very early stage of adipogenesis of 3T3-L1 adipocytes.

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Suppressed expression of adipogenesis-related genes in baicalein-treated 3T3-L1 cells.A, Transcription level of the adipogenic genes in baicalein-treated cells. 3T3-L1 cells (undifferentiated cells: U; white columns) were differentiated into adipocytes (differentiated cells: D) for 6 days in DMEM in the absence (gray columns) or presence of baicalein (50 μM; black columns). Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. B, Expression level of the lipogenic genes in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. C, Messenger RNA level of the lipolytic genes in baicalein-treated cells. 3T3-L1 cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. D, Change in glycerol level in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in Materials and Methods. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets.
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pone.0163640.g002: Suppressed expression of adipogenesis-related genes in baicalein-treated 3T3-L1 cells.A, Transcription level of the adipogenic genes in baicalein-treated cells. 3T3-L1 cells (undifferentiated cells: U; white columns) were differentiated into adipocytes (differentiated cells: D) for 6 days in DMEM in the absence (gray columns) or presence of baicalein (50 μM; black columns). Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. B, Expression level of the lipogenic genes in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. C, Messenger RNA level of the lipolytic genes in baicalein-treated cells. 3T3-L1 cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. D, Change in glycerol level in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in Materials and Methods. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets.

Mentions: The transcription levels of the adipogenic genes; i.e., the PPARγ, C/EBPα, fatty acid binding protein 4 (aP2), and GLUT4 genes were elevated approximately 23-, 12-, 299-, and 799-fold, respectively, as compared with the undifferentiated 3T3-L1 cells (Fig 2A). Whereas, when the cells were differentiated into adipose cells for 6 days in medium with baicalein, each of their mRNA levels was decreased to about 28, 18, 18, and 5.1%, respectively, of the vehicle-treated differentiated cells (Fig 2A).


Suppression of Very Early Stage Of Adipogenesis by Baicalein, a Plant-Derived Flavonoid through Reduced Akt-C/EBP α -GLUT4 Signaling-Mediated Glucose Uptake in 3T3-L1 Adipocytes
Suppressed expression of adipogenesis-related genes in baicalein-treated 3T3-L1 cells.A, Transcription level of the adipogenic genes in baicalein-treated cells. 3T3-L1 cells (undifferentiated cells: U; white columns) were differentiated into adipocytes (differentiated cells: D) for 6 days in DMEM in the absence (gray columns) or presence of baicalein (50 μM; black columns). Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. B, Expression level of the lipogenic genes in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. C, Messenger RNA level of the lipolytic genes in baicalein-treated cells. 3T3-L1 cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. D, Change in glycerol level in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in Materials and Methods. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets.
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pone.0163640.g002: Suppressed expression of adipogenesis-related genes in baicalein-treated 3T3-L1 cells.A, Transcription level of the adipogenic genes in baicalein-treated cells. 3T3-L1 cells (undifferentiated cells: U; white columns) were differentiated into adipocytes (differentiated cells: D) for 6 days in DMEM in the absence (gray columns) or presence of baicalein (50 μM; black columns). Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. B, Expression level of the lipogenic genes in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. C, Messenger RNA level of the lipolytic genes in baicalein-treated cells. 3T3-L1 cells were differentiated into adipocytes as described in the legend of Fig 2A. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets. D, Change in glycerol level in baicalein-treated 3T3-L1 cells. Cells were differentiated into adipocytes as described in Materials and Methods. Data are the means ± S.D. from three experiments. **p<0.01, as indicated by the brackets.
Mentions: The transcription levels of the adipogenic genes; i.e., the PPARγ, C/EBPα, fatty acid binding protein 4 (aP2), and GLUT4 genes were elevated approximately 23-, 12-, 299-, and 799-fold, respectively, as compared with the undifferentiated 3T3-L1 cells (Fig 2A). Whereas, when the cells were differentiated into adipose cells for 6 days in medium with baicalein, each of their mRNA levels was decreased to about 28, 18, 18, and 5.1%, respectively, of the vehicle-treated differentiated cells (Fig 2A).

View Article: PubMed Central - PubMed

ABSTRACT

Baicalein has been used as a Chinese medicine, and is an abundant plant flavonoid present in fruits and vegetables. Here, we examined the effects of baicalein in adipogenesis and investigated its molecular mechanism in adipocytes. Baicalein lowered the intracellular lipid accumulation and decreased the transcription levels of the adipocyte-specific genes in mouse 3T3-L1 adipocytes. Glucose uptake mediated by glucose transporter 4 (GLUT4) was reduced, causing down-regulation of the intracellular lipid accumulation. These reductions were also observed even when baicalein was added in only early stage of adipogenesis (0&ndash;2 days) of 6-day-adipogenesis. Chromatin immunoprecipitation assay showed that baicalein decreased the binding level of C/EBP&alpha; protein to the promoter region of the GLUT4 gene. Phosphorylation of Akt at 1 h after the initiation of adipogenesis was inhibited by the treatment with baicalein. Inhibition during only the first 1.5 h after the initiation of adipogenesis by baicalein or an Akt inhibitor was enough to decrease the lipid contents in the cells undergoing adipocyte differentiation for 6 days. These results indicate that baicalein decreased the intracellular lipid accumulation by down-regulation of glucose uptake via repression of Akt-C/EBP&alpha;-GLUT4 signaling in the very early stage of adipogenesis of 3T3-L1 adipocytes.

No MeSH data available.


Related in: MedlinePlus