Obesity is a serious medical condition causing various diseases such as
heart disease, type-2 diabetes, and
cancer. Fat cells (adipocytes) play an important role in the generation of energy through hydrolysis of
lipids they accumulate. Therefore, induction of lipolysis (breakdown of
lipids into
fatty acids and
glycerol), is one of the ways to treat
obesity. In the present study, we investigated the lipolytic effect of
widdrol in 3T3-L1 adipocytes and its mechanism.
Widdrol considerably increased the amount of
glycerol released from 3T3-L1 adipocytes into the medium in a time- and dose-dependent manner. To determine the mechanism of this effect, we investigated the alterations in
glycerol release and
protein expression in 3T3-L1 adipocytes treated with
widdrol alone or
widdrol and inhibitors of
proteins involved in the cAMP-dependent pathway or cAMP-independent PKC-MAPK pathway, which are known to induce lipolysis in adipocytes. The
adenylyl cyclase inhibitor
SQ-22536, PLA2 inhibitor
dexamethasone, PI3K inhibitor
wortmannin, and
PKA inhibitor H-89, which were used to investigate the involvement of the cAMP-dependent pathway, did not affect the lipolytic effect of
widdrol.
Widdrol-induced phosphorylation of PKC,
MEK, and ERK, which are related to the PKC-MAPK pathway, and their phosphorylation was inhibited by their inhibitors (
H-7,
U0126, and
PD-98059, respectively). Moreover, the increase in
glycerol release induced by
widdrol was almost completely blocked by PKC,
MEK, and ERK inhibitors. These results suggest that
widdrol induces lipolysis through activation of the PKC-MEK-ERK pathway.