1H-[13C]-NMR investigation of brain energy metabolism in zebrafish: Impact of acute ethanol

Abstract

Zebrafish has emerged as an excellent model organism for understanding the biology of the central nervous system. There is limited data pertaining to neurotransmitter energetics in the zebrafish brain. The present study evaluated brain energy metabolism in zebrafish by 1H-[13C]-NMR spectroscopy together with an intracardial administration of [1,6-13C2]glucose. Additionally, the impact of acute ethanol (1% in water) on brain energy metabolism was evaluated. The 13C turnover of brain amino acids from [1,6-13C2]glucose was measured in 1H-[13C]-NMR spectrum of brain tissue extract from 15 min to 90 min. The concentrations of neurometabolites in zebrafish are different than in rats and mice. There is fast incorporation of 13C labels into brain amino acids suggesting rapid glucose metabolism in the zebrafish brain. The incorporation of 13C in [4-13C]glutamate increased linearly until 30 min, and was maintained to a similar level thereafter. This is followed by [4-13C]glutamine and [3-13C]glutamate. The 13C turnover of [2–13C]GABA was much slower, and could attain ∼64% of [4-13C]glutamate labeling even at 90 min. Acute ethanol exposure significantly (p < 0.04) reduced levels of glutamate and NAA in the zebrafish brain. Most interestingly, the amount of 13C label accumulated into [4-13C]glutamate (p = 0.016), [2-13C]GABA (p = 0.016) and [3-13C]glutamate (p = 0.029) was decreased following acute neurotoxicity of ethanol. Moreover, the reduction in [4-13C]glutamine labeling in ethanol exposed fish points towards reduced synaptic transmission in acute ethanol exposed zebrafish. These data suggest that acute ethanol exposure in zebrafish suppresses neurometabolic activity of glutamatergic and GABAergic neurons. Zebrafish exhibited neurometabolism similar to rats, mice and humans, and could be used as an alternate model to study the mechanism of various neurological disorders, and drug screening.