Berberine reverses free-fatty-acid-induced insulin resistance in 3T3-L1 adipocytes through targeting IKKbeta.
OBJECTIVE
To investigate the effects and molecular mechanisms of berberine on improving insulin resistance induced by free fatty acids (FFAs) in 3T3-L1 adipocytes.


METHODS
The model of insulin resistance in 3T3-L1 adipocytes was established by adding palmic acid (0.5 mmol/L) to the culture medium. Berberine treatment was performed at the same time. Glucose uptake rate was determined by the 2-deoxy-[(3)H]-D-glucose method. The levels of IkB kinase beta (IKKbeta) Ser(181) phosphorylation, insulin receptor substrate-1(IRS-1) Ser(307) phosphorylation, expression of IKKbeta, IRS-1, nuclear transcription factor kappaB p65 (NF-kappaB p65), phosphatidylinositol-3-kinase p85 (PI-3K p85) and glucose transporter 4 (GLUT4) proteins were detected by Western blotting. The distribution of NF-kappaB p65 proteins inside the adipocytes was observed through confocal laser scanning microscopy (CLSM).


RESULTS
After the intervention of palmic acid for 24 h, the insulin-stimulated glucose transport in 3T3-L1 adipocytes was inhibited by 67%. Meanwhile, the expression of IRS-1 and PI-3K p85 protein was reduced, while the levels of IKKbeta Ser(181) and IRS-1 Ser(307) phosphorylation, and nuclear translocation of NF-kappaB p65 protein were increased. However, the above indexes, which indicated the existence of insulin resistance, were reversed by berberine although the expression of GLUT4, IKKbeta and total NF-kappaB p65 protein were not changed during this study.


CONCLUSIONS
Insulin resistance induced by FFAs in 3T3-L1 adipocytes can be improved by berberine. Berberine reversed free-fatty-acid-induced insulin resistance in 3T3-L1 adipocytes through targeting IKKbeta.
Yi
Ping
P
Department of Integrated Traditional Chinese and Western Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China.
Lu
Fu-Er
FE
Xu
Li-Jun
LJ
Chen
Guang
G
Dong
Hui
H
Wang
Kai-Fu
KF
D041721:3T3-L1 Cells; D021581:Active Transport, Cell Nucleus / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001599:Berberine / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D051550:I-kappa B Kinase / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance / Q000502:physiology*; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D051996:Transcription Factor RelA / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D051996:Transcription Factor RelA; D001599:Berberine; D012694:Serine; D019869:Phosphatidylinositol 3-Kinases; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse; D005947:Glucose