Previous studies have established the AMP-activated
protein kinase (AMPK) as an upstream regulator of
genes involved in lipid metabolism [16]. The activation
of AMPK leads to the suppression of lipogenesis. Based
on the above promising findings, we speculated that the
effect of GA on cancer cell lipogenesis may mediated
by AMPK signaling. To test this hypothesis, we further
examined the effect of GA on the activity of AMPK
signaling. Immunoblotting results revealed that the
phosphorylation level of AMPK (P-AMPK) in cancer cells
was significantly increased in response to GA treatment
(Figure 5A). To verify GA-inhibited lipogenesis in cancer
cells is mediated by AMPK signaling, siRNA technology
was developed to knockdown AMPK expression. Three
siRNA sequences were designed and the efficiency of
these siRNAs was detected by immunoblotting (Figure
5B). We then chose si-AMPK#1 for further experiments
for its excellent effect to knockdown AMPK expression.
We found that knocking down AMPK expression alone
didn’t affect the expression of FASN, SREBP-1, and
ACC in Panc-1, BxPC-3 and HepG2 cells (Figure 5C);
however, GA prevented these proteins expression was
restored by AMPK knockdown (Figure 5C). Together,
these data suggested that AMPK signaling is involved in
GA suppressed lipogenesis in cancer cells.