Distinct Metabolic States Can Support Self-Renewal and Lipogenesis in Human Pluripotent Stem Cells under Different Culture Conditions

Abstract

Recent studies have suggested that human pluripotent stem cells (hPSCs) depend primarily on glycolysis and only increase oxidative metabolism during differentiation. Here we demonstrate that both glycolytic and oxidative metabolism can support hPSC growth, and the metabolic phenotype of hPSCs is largely driven by nutrient availability. We comprehensively characterized hPSC metabolism using 13C/2H stable isotope tracing and flux analysis to define the metabolic pathways supporting hPSC bioenergetics and biosynthesis. Whereas glycolytic flux consistently supported hPSC growth, chemically-defined media strongly influenced that state of mitochondrial respiration and fatty acid metabolism. Lipid deficiency dramatically reprogramed pathways associated with fatty acid biosynthesis and NADPH regeneration, altering the mitochondrial function of cells and driving flux through the oxidative pentose phosphate pathway. Lipid supplementation mitigates this metabolic reprograming and increases oxidative metabolism. These results demonstrate that self-renewing hPSCs can present distinct metabolic states and highlight the importance of medium nutrients on mitochondrial function and development.

LKB1 promotes metabolic flexibility in response to energy stress

“…However, LKB1-proficient cells exhibited a significant decrease in M+5 citrate generated via reductive carboxylation compared to LKB1-deficient cells in anchorage-independent conditions (Figure 4G). These results are consistent with the consequences of increased pPDH and decreased pACC in LKB1-deficient cells, as both would be expected to increase the extent of reductive carboxylation (Figure 4A) (Metallo et al, 2012; Zhang et al, 2016). Together, these data suggest that LKB1-proficient cells more effectively maintain oxidative mitochondrial pathway activity in response to anchorage-independent growth.…”

Mitochondria and the dynamic control of stem cell homeostasis

“…Although a glycolytic switch is required for the acquisition of pluripotency, the early phases of iPSC generation are characterized by an initial burst of OXPHOS activity and by the up‐regulation of RC complexes . Mitochondrial metabolism may also be important in the self‐renewal of human PSCs, as its activation is increased when the lipid presence in the media is reduced , further highlighting how nutrients in the environment can shape the metabolic and functional state of stem cells.…”

Metabolism in pluripotency: Both driver and passenger?

“…Glutamine supports PSC survival and expansion by increasing antioxidant glutathione (4) and fueling mitochondrial energy metabolism (12)(13)(14). Glutaminolysis generates tricarboxylic acid (TCA) cycle substrates (12) and supports the mitochondrial inner membrane potential (Δ) required for PSC survival (15).…”