TY - JOUR
T1 - Saponarin activates AMPK in a calcium-dependent manner and suppresses gluconeogenesis and increases glucose uptake via phosphorylation of CRTC2 and HDAC5
AU - Seo, Woo Duck
AU - Lee, Ji Hae
AU - Jia, Yaoyao
AU - Wu, Chunyan
AU - Lee, Sung Joon
N1 - Funding Information:
This work was carried out with the support of the ‘ Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ01052801 and PJ010090032015)’, Rural Development Administration (RDA), Republic of Korea.
PY - 2015/11/15
Y1 - 2015/11/15
N2 - This study investigated the molecular mechanism of saponarin, a flavone glucoside, in the regulation of insulin sensitivity. Saponarin suppressed the rate of gluconeogenesis and increased cellular glucose uptake in HepG2 and TE671 cells by regulating AMPK. Using an in vitro kinase assay, we showed that saponarin did not directly interact with the AMPK protein. Instead, saponarin increased intracellular calcium levels and induced AMPK phosphorylation, which was diminished by co-stimulation with STO-609, an inhibitor of CAMKKβ. Transcription of hepatic gluconeogenesis genes was upregulated by nuclear translocation of CRTC2 and HDAC5, coactivators of CREB and FoxO1 transcription factors, respectively. This nuclear translocation was inhibited by increased phosphorylation of CRTC2 and HDAC5 by saponarin-induced AMPK in HepG2 cells and suppression of CREB and FoxO1 transactivation activities in cells stimulated by saponarin. The results from a chromatin immunoprecipitation assay confirmed the reduced binding of CRTC2 on the PEPCK and G6Pase promoters. In TE671 cells, AMPK phosphorylated HDAC5, which suppressed nuclear penetration and upregulated GLUT4 transcription, leading to enhanced glucose uptake. Collectively, these results suggest that saponarin activates AMPK in a calcium-dependent manner, thus regulating gluconeogenesis and glucose uptake.
AB - This study investigated the molecular mechanism of saponarin, a flavone glucoside, in the regulation of insulin sensitivity. Saponarin suppressed the rate of gluconeogenesis and increased cellular glucose uptake in HepG2 and TE671 cells by regulating AMPK. Using an in vitro kinase assay, we showed that saponarin did not directly interact with the AMPK protein. Instead, saponarin increased intracellular calcium levels and induced AMPK phosphorylation, which was diminished by co-stimulation with STO-609, an inhibitor of CAMKKβ. Transcription of hepatic gluconeogenesis genes was upregulated by nuclear translocation of CRTC2 and HDAC5, coactivators of CREB and FoxO1 transcription factors, respectively. This nuclear translocation was inhibited by increased phosphorylation of CRTC2 and HDAC5 by saponarin-induced AMPK in HepG2 cells and suppression of CREB and FoxO1 transactivation activities in cells stimulated by saponarin. The results from a chromatin immunoprecipitation assay confirmed the reduced binding of CRTC2 on the PEPCK and G6Pase promoters. In TE671 cells, AMPK phosphorylated HDAC5, which suppressed nuclear penetration and upregulated GLUT4 transcription, leading to enhanced glucose uptake. Collectively, these results suggest that saponarin activates AMPK in a calcium-dependent manner, thus regulating gluconeogenesis and glucose uptake.
KW - AMPK
KW - Gluconeogenesis
KW - Glucose uptake
KW - Saponarin
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U2 - 10.1016/j.bmcl.2015.09.057
DO - 10.1016/j.bmcl.2015.09.057
M3 - Article
C2 - 26471090
AN - SCOPUS:84945913792
VL - 25
SP - 5237
EP - 5242
JO - Bioorganic and Medicinal Chemistry Letters
JF - Bioorganic and Medicinal Chemistry Letters
SN - 0960-894X
IS - 22
ER -