Metabolomic analysis of mouse prefrontal cortex reveals upregulated analytes during wakefulness compared to sleep

Abstract

By identifying endogenous molecules in brain extracellular fluid metabolomics can provide insight into the regulatory mechanisms and functions of sleep. Here we studied how the cortical metabolome changes during sleep, sleep deprivation and spontaneous wakefulness. Mice were implanted with electrodes for chronic sleep/wake recording and with microdialysis probes targeting prefrontal and primary motor cortex. Metabolites were measured using ultra performance liquid chromatography-high resolution mass spectrometry. Sleep/wake changes in metabolites were evaluated using partial least squares discriminant analysis, linear mixed effects model analysis of variance, and machine-learning algorithms. More than 30 known metabolites were reliably detected in most samples. When used by a logistic regression classifier, the profile of these metabolites across sleep, spontaneous wake, and enforced wake was sufficient to assign mice to their correct experimental group (pair-wise) in 80–100% of cases. Eleven of these metabolites showed significantly higher levels in awake than in sleeping mice. Some changes extend previous findings (glutamate, homovanillic acid, lactate, pyruvate, tryptophan, uridine), while others are novel (D-gluconate, N-acetyl-beta-alanine, N-acetylglutamine, orotate, succinate/methylmalonate). The upregulation of the de novo pyrimidine pathway, gluconate shunt and aerobic glycolysis may reflect a wake-dependent need to promote the synthesis of many essential components, from nucleic acids to synaptic membranes.

Neurotransmitter networks in mouse prefrontal cortex are reconfigured by isoflurane anesthesia

“…Machine learning approaches outperform humans in speed and efficiency with which patterns can be detected in very large data sets. The present results encourage application of these analytic techniques to multiple brain regions, to neuroendocrine molecules (Jiang-Xie et al 2019), and to molecules comprising the brain metabolome (Bourdon et al 2018). Over time, the systematic curation of such measures will provide building blocks needed to construct a chemical cartography underlying wakefulness and anesthesia.…”

“…Post hoc evaluation of differences in neurotransmitter concentrations during wakefulness vs. isoflurane anesthesia was provided by Fisher's least significant difference test. Sample sizes were based on previously published, in vivo microdialysis studies of neurotransmitters (Coleman et al 2006;DeMarco et al 2004;Douglas et al 2001Douglas et al , 2002Flint et al 2010;Gettys et al 2013;Van Dort et al 2009;Wathen et al 2012) and metabolomics (Bourdon et al 2018) in B6 mouse. Changes in neurotransmitter concentrations over time were evaluated for each of the eight transmitters by comparing the slopes across the wakefulness sampling period with slopes across the isoflurane sampling period.…”

Metabolomics in Sleep, Insomnia and Sleep Apnea

“…Besides metabolomics studies conducted on plasma and urine samples, animal models have been used to obtain direct information about brain changes due to sleep deprivation. A recent study conducted in mice investigated the metabolome of the prefrontal cortex during sleep, sleep deprivation and spontaneous wakefulness [ 67 ]. Overall, 11 known metabolites were observed to be higher after wakefulness (in most of the cases, after spontaneous as well as enforced wakefulness), whereas no metabolite was found in higher concentrations after sleep.…”

Sleep, brain vascular health and ageing

“…Higher levels of glutamate, along with other metabolomes such as homovanillic acid, lactate, and pyruvate are found in awake mice when compared with sleeping mice. This implies that there is a wake-dependent need to promote synthesis of essential biochemical components (Bourdon et al 2018). Sleep-wake regulation by the basal forebrain requires a balance between excitatory-wake promoting effects mediated by glutamate receptors and inhibitory-sleep promoting effects mediated by adenosine degradation (Yang et al 2018).…”