A role for AMPK in increased insulin action after serum starvation

Ching JK, Rajguru P, Marupudi N, Banerjee S, Fisher JS. A role for AMPK in increased insulin action after serum starvation. Am J Physiol Cell Physiol 299: C1171-C1179, 2010. First published September 1, 2010; doi:10.1152/ajpcell.00514.2009.-Serum starvation is a common cell culture procedure for increasing cellular response to insulin, though the mechanism for the serum starvation effect is not understood. We hypothesized that factors known to potentiate insulin action [e. g., AMP-activated protein kinase (AMPK) and p38] or to be involved in insulin signaling leading to glucose transport [e. g., Akt, PKC zeta, AS160, and ataxia telangiectasia mutated (ATM)] would be phosphorylated during serum starvation and would be responsible for increased insulin action after serum starvation. L6 myotubes were incubated in serum-containing or serum-free medium for 3 h. Levels of phosphorylated AMPK, Akt, and ATM were greater in serum-starved cells than in control cells. Serum starvation did not affect p38, PKC zeta, or AS160 phosphorylation or insulin-stimulated Akt or AS160 phosphorylation. Insulin had no effect on glucose transport in control cells but caused an increase in glucose uptake for serum-starved cells that was preventable by compound C (an AMPK inhibitor), by expression of dominant negative AMPK (AMPK-DN), and by KU55933 (an ATM inhibitor). ATM protein levels increased during serum starvation, and this increase in ATM was prevented by compound C and AMPK-DN. Thus, it appears that AMPK is required for the serum starvation-related increase in insulin-stimulated glucose transport, with ATM as a possible downstream effector.