regulation of leptin gene expression in the C6 glioblastoma cell line
Morash B, Johnstone J, Leopold C, Li A, Murphy P, Ur E, Wilkinson M
Division of Endocrinology, Dalhousie University, Nova Scotia, B3H
2Y9, Halifax, Canada
The hormone leptin is implicated in the regulation of appetite and body weight
in rodents, primates and humans.
We reported that the leptin gene (ob) is expressed in the brain, but the factors
which control ob expression in the central nervous system are not known.
We previously showed that brain-derived rat C6 glioblastoma cells express ob
mRNA and protein.
In the present study we examined the regulation of ob expression in C6
Leptin and leptin receptor immunoreactivity was detected in C6 cells, suggesting
a possible autocrine role for leptin.
The identity of the leptin immunoreactivity (OB-ir) in C6 cells was confirmed by
immunoprecipitation and Western blotting using two leptin specific polyclonal
Using RT-PCR analysis a product of the expected size for the short, but not the
long, leptin receptor isoform was detected in C6 cells.
Cells were maintained in serum-free (SF) media for 0-24 h in the presence of
various regulators of leptin expression.
Leptin mRNA levels were significantly higher in cells treated with dbcAMP (1
mM), IGF 1 (100 ng/ml) or insulin (5 microg/ml) compared to SF controls.
In contrast, corticosterone (10(-7)M) reduced leptin mRNA.
In the presence of dbcAMP, C6 cells undergo a dramatic alteration in morphology
which is coincident with an apparent increase in the number of leptin-ir nuclei
and an increase in leptin immunoreactivity.
In contrast to C6 cells, glucocorticoids are reported to increase leptin levels
in adipocytes/adipose tissue, while increases in intracellular cAMP levels are
reported to reduce leptin levels.
Overall, our in vitro data suggest that the regulation of leptin gene expression
in C6 glioblastoma cells is different from that in adipocytes.
PMID: 10940488 [PubMed - indexed for MEDLINE]