The ginsenoside Rg3 has a stimulatory effect on insulin signaling in L6 myotubes.
The ginsenoside Rg3 is known to have a protective effect against hyperglycemia, obesity and diabetes in vivo. In this study, we examined the effect of Rg3 on insulin signaling and glucose uptake in cultured L6 myotubes. Rg3 increased glucose uptake both in the basal and insulin-induced states of L6 myotubes. Consistent with the increase in glucose uptake, Rg3 stimulated the phosphorylation of IRS-1 and Akt. Interestingly, Rg3 dramatically increased IRS-1 protein levels, while the protein level of Akt was not affected. Rg3 regulated IRS-1 expression at the transcriptional level and also increased the level of GLUT4 mRNA. Treatment of ginsam, in which Rg3 is the major compound of ginsenosides, increased the IRS-1 protein levels in OLEFT rats. In addition, we found that this effect of Rg3 on insulin signaling was not mediated by the AMPK pathway. In conclusion, these results suggest that Rg3 improves insulin signaling and glucose uptake primarily by stimulating the expression of IRS-1 and GLUT4.
Kim
Min
M
Department of Internal Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Republic of Korea.
Ahn
Byung Yong
BY
Lee
Ji Seon
JS
Chung
Sung Soo
SS
Lim
Soo
S
Park
Sang Gyu
SG
Jung
Hye Seung
HS
Lee
Hong Kyu
HK
Park
Kyong Soo
KS
D000091162:AMP-Activated Protein Kinase Kinases; D000818:Animals; D002460:Cell Line; D036145:Ginsenosides / Q000494:pharmacology*; D051275:Glucose Transporter Type 4 / Q000096:biosynthesis; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000096:biosynthesis; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains
D036145:Ginsenosides; D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D012333:RNA, Messenger; C495694:Slc2a4 protein, rat; C097367:ginsenoside Rg3; D011494:Protein Kinases; D000091162:AMP-Activated Protein Kinase Kinases