The function of metabolic state in stemness is poorly understood. Mouse embryonic stem cells (ESC) and epiblast stem cells (EpiSC) are at distinct pluripotent states representing the inner cell mass (ICM) and epiblast embryos. Human embryonic stem cells (hESC) are similar to EpiSC stage. We now show a dramatic metabolic difference between these two stages. EpiSC/hESC are highly glycolytic, while ESC are bivalent in their energy production, dynamically switching from glycolysis to mitochondrial respiration on demand. Despite having a more developed and expanding mitochondrial content, EpiSC/hESC have low mitochondrial respiratory capacity due to low cytochrome c oxidase (COX) expression. Similarly, in vivo epiblasts suppress COX levels. These data reveal EpiSC/ hESC functional similarity to the glycolytic phenotype in cancer (Warburg effect). We further show that hypoxiainducible factor 1a (HIF1a) is sufficient to drive ESC to a glycolytic Activin/Nodal-dependent EpiSC-like stage. This metabolic switch during early stem-cell development may be deterministic.

For nearly a century developmental biologists have recognized that cells from embryos can differ in their potential to differentiate into distinct cell types. Recently, it has been recognized that embryonic stem cells derived from both mice and humans display two stable yet epigenetically distinct states of pluripotency, naïve and primed. We now show that nicotinamide-N-methyl transferase (NNMT) and metabolic state regulate pluripotency in hESCs. Specifically, in naïve hESCs NNMT and its enzymatic product 1-methylnicotinamide (1-MNA) are highly upregulated, and NNMT is required for low SAM levels and H3K27me3 repressive state. NNMT consumes SAM in naïve cells, making it unavailable for histone methylation that represses Wnt and activates HIF pathway in primed hESCs. These data support the hypothesis that the metabolome regulates the epigenetic landscape of the earliest steps in human development.

Gliomas harboring mutations in isocitrate dehydrogenase 1/2 (IDH1/2) have the CpG island methylator phenotype (CIMP) and significantly longer patient survival time than wild-type IDH1/2 (wtIDH1/2) tumors. Although there are many factors underlying the differences in survival between these two tumor types, immune-related differences in cell content are potentially important contributors. In order to investigate the role of IDH mutations in immune response, we created a syngeneic pair mouse model for mutant IDH1 (muIDH1) and wtIDH1 gliomas and demonstrated that muIDH1 mice showed many molecular and clinical similarities to muIDH1 human gliomas, including a 100-fold higher concentration of 2-hydroxygluratate (2-HG), longer survival time, and higher CpG methylation compared with wtIDH1. Also, we showed that IDH1 mutations caused down-regulation of leukocyte chemotaxis, resulting in repression of the tumor-associated immune system. Given that significant infiltration of immune cells such as macrophages, microglia, monocytes, and neutrophils is linked to poor prognosis in many cancer types, these reduced immune infiltrates in muIDH1 glioma tumors may contribute in part to the differences in aggressiveness of the two glioma types.