Glutamine Oxidation Is Indispensable for Survival of Human Pluripotent Stem Cells

Abstract

Human pluripotent stem cells (hPSCs) are uniquely dependent on aerobic glycolysis to generate ATP. However, the importance of oxidative phosphorylation (OXPHOS) has not been elucidated. Detailed amino acid profiling has revealed that glutamine is indispensable for the survival of hPSCs. Under glucose- and glutamine-depleted conditions, hPSCs quickly died due to the loss of ATP. Metabolome analyses showed that hPSCs oxidized pyruvate poorly and that glutamine was the main energy source for OXPHOS. hPSCs were unable to utilize pyruvate-derived citrate due to negligible expression of aconitase 2 (ACO2) and isocitrate dehydrogenase 2/3 (IDH2/3) and high expression of ATP-citrate lyase. Cardiomyocytes with mature mitochondria were not able to survive without glucose and glutamine, although they were able to use lactate to synthesize pyruvate and glutamate. This distinguishing feature of hPSC metabolism allows preparation of clinical-grade cell sources free of undifferentiated hPSCs, which prevents tumor formation during stem cell therapy.

Proliferation, survival and metabolism: the role of PI3K/AKT/mTOR signalling in pluripotency and cell fate determination

“…In primed human PSCs, metabolism typically proceeds via the glycolytic pathway, which rapidly switches to oxidative phosphorylation upon differentiation (Zhou et al, 2012;Moussaieff et al, 2015). Compared with differentiated cells, which utilise oxidative phosphorylation as the primary metabolic pathway, these PSCs possess largely underdeveloped and immature mitochondria that are few in number, thus maintaining high rates of glycolysis even under aerobic culture conditions, although a recent report found that these cells can nonetheless utilise oxidative phosphorylation for energy generation through glutamine metabolism (Prigione et al, 2010;Varum et al, 2011;Tohyama et al, 2016). This preference for glycolytic metabolism is reminiscent of the Warburg effect in many highly proliferative cancer cells, typified by an increased conversion of pyruvate to lactate.…”

Significant Dietary Changes during Human Evolution and the Development of Cancer: From Cells in Trouble to Cells Causing Trouble

“…As noted earlier, stem cells rely heavily on glycolysis, with high expression of hexokinase II, and use fatty acids and glutamine as the main energy source for OxPhos [169,176]. Similarly, cancer cells take up glucose and glutamine at high rates and convert glucose to lactate through aerobic glycolysis in the presence of oxygen ("Warburg effect"), with high expression of hexokinase II [177].…”

“…Consequently, UCP2 is deeply involved in the regulation of energy metabolism, proliferation and differentiation of hPSCs. It is well established that stem cells heavily rely on glycolysis and use FFA and glutamine as the main energy source for OxPhos [165,169,170]. In stem cells, UCP2 inactivates the pyruvate dehydrogenase complex, thereby shunting substrates such as pyruvate away from glucose oxidation while promoting glycolysis, mediated by expression of high levels of hexokinase II [167,170], and promotes oxidation of alternative substrates such as glutamine and free fatty acids (FFA) [165,170].…”

Recent Progress Using Pluripotent Stem Cells for Cardiac Regenerative Therapy

“…To overcome this, new purification methods utilizing the unique metabolic properties of PSCs and CMs have been developed. 73, 74 When PSC-derived cells were cultured with glucose-depleted culture medium containing abundant lactate, only PSC-CMs survived and CM purity was almost 99%. 73 Recently, this method was models, have suggested the effectiveness of PSC-based therapy.…”