Differential
Regulation of Long and Short leptin Receptor mRNA by leptin and
Dexamethasone in HepG2 Cells
Liu
Z-J1, Endoh A2, Li R-S2,
Ohzeki T2
1 The Second Affiliated Hospital
Dalian Medical University, Dalian, China
2 Hamamatsu University School of
medicine, Hamamatsu, Japan
Objective: To study the leptin receptor regulation by leptin and
dexamethasone in HepG2 cells.
Methods:
By RT-PCR and DNA sequencing, we demonstrated
for the first time that long leptin receptor (OB-Rb) and short leptin receptor
(OB-Ra) mRNA was expressed in this cell line. Using a quantitative RT-PCR
technique, we quantitated the expression of OB-Rb and OB-Ra mRNA at 24 h
incubation with various concentrations of leptin (10-9- 10-6
M) or dexamethasone (10-9-10-6 M).
Results: leptin (10-7-10-6M) significantly
inhibited the expression of OB-Rb mRNA, with maximum inhibition (to 43% of
control) at 10-6 M. Similarly
the expression of OB-R219.1 and OB-R219.3, two isoforms of OB-Ra, was also
markedly reduced in cells treated with leptin at 10-8- 10-6M,
with maximum decrease (to 44% of control at 10-7M for OB-R219.1,
and to 49% of control at 10-6M for OB-R219.3). In contrast,
dexamethasone (10-8-10-6M) significantly increased
the levels of OB-Rb mRNA, with maximum increase (to 204% of control) at 10-7M,
and the expression of OB-R219.1 and OB-R219.3 mRNA was also markedly
increased at 10-9-10-6M, with maximum increases (to
254% control for OB-R219.1, and to 246% of control for OB-R219.3) at 10-7
M.
Conclusion:
leptin down-regulates the expression of OB-Rb
and OB-Ra mRNA, and dexamethasone up-regulates the expression of OB-Rb and
OB-Ra mRNA in HepG2 cells.