Figure 3. Loss of AMPK signaling promotes increased biosynthesis.

A) ECAR of control (Cre−, open bar) or AMPKα-null (Cre+, closed bar) MEFs cultured under standard growth conditions. Values shown are the mean ± SEM for samples in quadruplicate. B) Glucose-to-lactate conversion in control (Cre−) or AMPKα-deficient (Cre+) MEFs. Cells were cultured with medium containing uniformly labeled ¹³C-glucose, and enrichment of ¹³C-lactate (m+3) in the extracellular medium was measured at the indicated time points. C) ATP content of control (Cre−) or AMPKα-null (Cre+) MEFs as measured by HPLC. D) AMP:ATP ratios for cells in (C). E) Intracellular citrate levels of control (Cre−) or AMPKα-null (Cre+) MEFs as determined by GC-MS. F) Glucose-derived lipid biosynthesis in control (Cre−) or AMPKα-null (Cre+) MEFs. Cells were incubated with uniformly labeled ¹⁴C-glucose for 72 hours, and radioactive counts in extracted lipids measured. G) Palmitate oxidation by MEFs expressing control (Ctrl) or AMPKα1/α2 shRNAs. MEFs were grown in the presence (+) or absence (−) of glucose for 24 hours, followed by culture with [9,10-³H]-palmitic acid and 200 μM etomoxir. Tritiated water produced from palmitate oxidation was measured. H) Forward scatter (FSC) of control (Cre−, grey histogram) or AMPKα-deficient (Cre+, open histogram) MEFs. *, p<0.05; ***, p<0.001; ****, p<0.0001.