Hyperglycemia Stimulates the Irreversible Catabolism of Branched-Chain Amino Acids and Generation of Ketone Bodies by Cultured Human Astrocytes

Abstract

Astrocytes are considered to possess a noticeable role in brain metabolism and as a partners in neuron-glia cooperation contribute to synthesis, bioconversions and regulation of the flux of substrates for neuronal metabolism. With the aim to investigate to which extend are human astrocytes metabolizing amino acids and by which compounds are they enriching their surrounding we employed the metabolomics analysis of their culture media by 1H-NMR. In addition, we compered the composition of media with either 5 mM or 25 mM glucose. The quantitative analysis of culture media by 1H-NMR revealed that astrocytes readely dispose from their milieu glutamine, branched-chain amino acids, and pyruvate with significantly high rate, while they enrich the culture media with lactate, branched-chain keto acids, citrate, acetate, ketone bodies, and alanine. The hyperglycemia suppressed the capacity of astrocytes to release branched-chain amino acids while stimulating the generation of ketone bodies. Our results highlight the active involvement of astrocytes in metabolism of several amino acids, and the regulation of key metabolic intermediates. The observed metabolic activities of astrocytes provide valuable insights into their roles in supporting neuronal function, brain metabolism, and intercellular metabolic interactions within the brain. Understanding the complex metabolic interactions between astrocytes and neurons is essential for elucidating brain homeostasis and the pathophysiology of neurological disorders.