Systems biology approach to understanding the control of glucose metabolism in healthy and apoptotic neurons

Apoptosis plays a crucial role in sculpting the developing central nervous system (CNS) but can, under certain conditions, contribute to neurodegeneration in the mature CNS. Metabolic disturbances have long been associated with apoptosis-inducing agents, however, the mechanism underlying such changes remains controversial. In this study, our hypotheses was that decreased ATP turnover may bring about other metabolic changes in apoptotic neurons. Accordingly, change in metabolic reactions other than ATP turnover may not be important in the study of apoptotic mechanism. In a living cell, metabolic reactions are highly connected and thus are highly sensitive to kinetic change in one or more reaction, making analysis of direct kinetic change in ATP turnover is experimentally infeasible. For these purposes, a comprehensive detailed map of the control distribution in healthy neurons using the metabolic control analysis was obtained for the first time. This information was important to distinguish the direct kinetic changes caused by the apoptotic stimulus from those occurring indirectly because of changes in the levels of key metabolites to which the reactions respond Our results shokinetic inhibition in ATP consumers (ATC) in response to Apoptosis. However, and despite the observed kinetic inhibition in ATC, this kinetic change could not fully explain the decreased rates of glucose uptake, glycolysis, mitochondrial substrate oxidation and mitochondrial phosphorylation. Kinetic stimulation of the oxidative pentose phosphate pathway by apoptosis was a major contributor to the decrease in glycolysis, while kinetic inhibition of mitochondrial phosphorylation was a major contributor to the decrease in mitochondrial substrate oxidation. Direct inhibition of mitochondrial ATP synthesis coupled with direct activation of mitochondrial proton leak resulted in the neurons becoming more reliant on glycolytic ATP. Direct stimulation of the pentose phosphate pathway as well as proton leak could be consequences of increased oxidative stress that is commonly associated with apoptosis. These findings didn\u27t prove our initial hypotheses, but implying a directly targeted metabolic reactions by apoptotic stimulus. On the other hand, early reactive oxygen species was suggested to stimulate oxidative phase of pentose phosphate pathway oxidative phase of pentose phosphate pathway and proton leak rate which were suggested to play an antioxidant role to maintain neuronal redox status. Despite kinetic activation of oxidative phase of pentose phosphate pathway, glycolysis was stimulated in response to low K stimulus implying a shift of the reliance of ATP sources from mitochondrial to glycolytic