Effects of acute or prolonged exposure to leptin on hepatic glucose oxidation.
OBJECTIVE
To observe the short-term and long-term effects of leptin on hepatic glucose oxidation and glucokinase gene expression.


METHODS
Rat hepatic cell line BRL was incubated with leptin of different doses (range from 10 ng/ml-200 ng/ml) for 1 h or 24 h. Glucose oxidation was determined by liquid scintillation counting. Glucokinase gene expression (corrected by beta-actin) was determined by reverse transcription semi-quantitative polymerase chain reaction.


RESULTS
Treatment with leptin 10 ng/ml for 1 h had no significant effects on glucose oxidation in hepatic cells. However, at the doses ranging from 50 ng/ml to 200 ng/ml, leptin significantly inhibited glucose oxidation. These effects disappeared when the hepatic cells were exposed to leptin for 24 h. Glucokinase mRNA expression was reduced significantly after both 1 h and 24 h exposure to leptin (100 ng/ml) as compared to that of the control group.


CONCLUSIONS
A low dose of leptin has no significant effect on glucose oxidation in hepatic cells. A relatively high dose of leptin has an acute inhibitory effect on the glucose oxidation in hepatic cells. This effect may likely involve the inhibition of glucokinase gene expression. The inhibitory effect on glucose oxidation is transient and disappears with prolonged exposure time.
Cao
X
X
Department of Endocrinology, First Affiliated Hospital, Sun Yat-sen University of Medical Sciences, Guangzhou 510080, China. tncxp@gzsums.edu.cn
Fu
Z
Z
Ming
W
W
Yang
R
R
Cheng
H
H
D000818:Animals; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005941:Glucokinase / Q000235:genetics; D005947:Glucose / Q000378:metabolism*; D020738:Leptin / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013997:Time Factors
D020738:Leptin; D012333:RNA, Messenger; D005941:Glucokinase; D005947:Glucose