Regulation of human
androgen biosynthesis is poorly understood. However, detailed knowledge is needed to eventually solve disorders with
androgen dysbalance. We showed that
starvation growth conditions shift steroidogenesis of human adrenal NCI-H295R cells towards
androgen production attributable to decreased
HSD3B2 expression and activity and increased CYP17A1 phosphorylation and
17,20-lyase activity. Generally,
starvation induces stress and energy deprivation that need to be counteracted to maintain proper cell functions.
AMP-activated protein kinase (AMPK) is a master energy sensor that regulates cellular energy balance. AMPK regulates steroidogenesis in the gonad. Therefore, we investigated whether AMPK is also a regulator of adrenal steroidogenesis. We hypothesized that
starvation uses AMPK signaling to enhance
androgen production in NCI-H295R cells. We found that AMPK subunits are expressed in NCI-H295 cells, normal adrenal tissue and human as well as pig ovary cells.
Starvation growth conditions decreased phosphorylation, but not activity of AMPK in NCI-H295 cells. In contrast, the AMPK activator 5-aminoimidazole-4-carboxamide (
AICAR) increased AMPKα phosphorylation and increased CYP17A1-17,20
lyase activity. Compound C (an AMPK inhibitor), directly inhibited CYP17A1 activities and can therefore not be used for AMPK signaling studies in steroidogenesis.
HSD3B2 activity was neither altered by
AICAR nor compound C.
Starvation did not affect mitochondrial respiratory chain function in NCI-H295R cells suggesting that there is no indirect energy effect on AMPK through this avenue. In summary,
starvation-mediated increase of
androgen production in NCI-H295 cells does not seem to be mediated by AMPK signaling. But AMPK activation can enhance
androgen production through a specific increase in CYP17A1-17,20
lyase activity.