EMBO J 30 24, 4860–4873 (2011); published online November 15 2011
Human pluripotent stem cells (hPSCs) rely heavily on glycolysis for energy metabolism, and because their mitochondria appear poorly developed, hPSCs have been assumed to be incapable of using oxidative phosphorylation (OxPhos). In this issue, Zhang et al (2011) demonstrate that hPSCs actually possess functional OxPhos machinery, but that the mitochondrial protein UCP2 decouples OxPhos from glycolysis. The study further suggests that regulation of glucose metabolism by UCP2 facilitates hPSC pluripotency and controls hPSC differentiation.