Effects of sleep deprivation: the phosphorus metabolism in the human brain measured by 31P-magnetic resonance spectroscopy

Amide Proton Transfer-Weighted Imaging Detects Hippocampal Proteostasis Disturbance Induced by Sleep Deprivation at 7.0 T MRI

Sleep deprivation leads to hippocampal injury. Proteostasis disturbance is an important mechanism linking sleep deprivation and hippocampal injury. However, identifying noninvasive imaging biomarkers for hippocampal proteostasis disturbance remains challenging. Amide proton transfer-weighted (APTw) imaging is a chemical exchange saturation transfer technique based on the amide protons in proteins and peptides. We aimed to explore the ability of APTw imaging in detecting sleep deprivation-induced hippocampal proteostasis disturbance and its biological significance, as well as its biological basis. In vitro, the feasibility of APTw imaging in detecting changes of the protein state was evaluated, demonstrating that APTw imaging can detect alterations in the protein concentration, conformation, and aggregation state. In vivo, the hippocampal APTw signal declined with increased sleep deprivation time and was significantly lower in sleep-deprived rats than that in normal rats. This signal was positively correlated with the number of surviving neurons counted in Nissl staining and negatively correlated with the expression of glucose-regulated protein 78 evaluated in immunohistochemistry. Differentially expressed proteins in proteostasis network pathways were identified in the hippocampi of normal rats and sleep-deprived rats via mass spectrometry proteomics analysis, providing the biological basis for the change of the hippocampal APTw signal in sleep-deprived rats. These findings demonstrate that APTw imaging can detect hippocampal proteostasis disturbance induced by sleep deprivation and reflect the extent of neuronal injury and endoplasmic reticulum stress.

Impact of spaceflight stressors on behavior and cognition: A molecular, neurochemical, and neurobiological perspective

The response of the human body to multiple spaceflight stressors is complex, but mounting evidence implicate risks to CNS functionality as significant, able to threaten metrics of mission success and longer-term behavioral and neurocognitive health. Prolonged exposure to microgravity, sleep disruption, social isolation, fluid shifts, and ionizing radiation have been shown to disrupt mechanisms of homeostasis and neurobiological well-being. The overarching goal of this review is to document the existing evidence of how the major spaceflight stressors, including radiation, microgravity, isolation/confinement, and sleep deprivation, alone or in combination alter molecular, neurochemical, neurobiological, and plasma metabolite/lipid signatures that may be linked to operationally-relevant behavioral and cognitive performance. While certain brain region-specific and/or systemic alterations titrated in part with neurobiological outcome, variations across model systems, study design, and the conspicuous absence of targeted studies implementing combinations of spaceflight stressors, confounded the identification of specific signatures having direct relevance to human activities in space. Summaries are provided for formulating new research directives and more predictive readouts of portending change in neurobiological function.

Brain bioenergetics during resting wakefulness are related to neurobehavioral deficits in severe obstructive sleep apnea: a 31P magnetic resonance spectroscopy study

Study Objectives

Obstructive sleep apnea (OSA) is a well-established cause of impaired daytime functioning. However, there is a complex inter-individual variability in neurobehavioral performance in OSA patients. We previously reported compromised brain bioenergetics during apneic sleep in severe OSA. In this study, we investigate whether brain bioenergetics during resting wakefulness are related to neurobehavioral performance.

Methods

Patients attended the sleep laboratory in the evening and were kept awake over-night. Repeated testing on the 10-minute psychomotor vigilance task (PVT, at 9 pm, 11 pm, 1 am, 3 am, 5 am) and 30-minute AusEd driving simulator task (9 pm and 5 am) was performed. Brain bioenergetics (inorganic phosphate/adenosine triphosphate ratio, Pi/ATP) were measured in the temporal lobe during resting wakefulness at 7 am in a 1.5T MRI scanner using phosphorus magnetic resonance spectroscopy (31P MRS).

Results

Fifteen males with severe OSA (age 47.7 ± 10.4 years, body mass index [BMI] 34 ± 6.6 kg/m2, apnea hypopnea index [AHI] 79.7 ± 21.8/hour) were investigated. A higher Pi/ATP ratio in the brain (lower phosphorylation potential) was correlated with worse PVT and driving simulator performance across the testing period (PVT lapses: r = 0.632, r2 = 0.399, p = 0.012; and AusEd braking reaction time: r = 0.609, p = 0.016). In contrast, the conventional AHI measure of disease severity was not significantly correlated with performance (PVT lapses: r = -0.084, p = 0.8; and AusEd braking reaction time: r = -0.326, p = 0.2).

Conclusions

Lower phosphorylation potential was associated with worse performance. Compromised brain bioenergetics may in part underlie the neurobehavioral deficits in untreated OSA. We speculate that better brain bioenergetics may explain why some OSA patients are relatively asymptomatic compared with others.

Creatine as a booster for human brain function. How might it work?

Creatine, a naturally occurring nitrogenous organic acid found in animal tissues, has been found to play key roles in the brain including buffering energy supply, improving mitochondrial efficiency, directly acting as an anti-oxidant and acting as a neuroprotectant. Much of the evidence for these roles has been established in vitro or in pre-clinical studies. Here, we examine the roles of creatine and explore the current status of translation of this research into use in humans and the clinic. Some further possibilities for use of creatine in humans are also discussed.

Gray matter-specific changes in brain bioenergetics after acute sleep deprivation: a 31P magnetic resonance spectroscopy study at 4 Tesla

STUDY OBJECTIVES

A principal function of sleep may be restoration of brain energy metabolism caused by the energetic demands of wakefulness. Because energetic demands in the brain are greater in gray than white matter, this study used linear mixed-effects models to examine tissue-type specific changes in high-energy phosphates derived using 31P magnetic resonance spectroscopy (MRS) after sleep deprivation and recovery sleep.

DESIGN

Experimental laboratory study.

SETTING

Outpatient neuroimaging center at a private psychiatric hospital.

PARTICIPANTS

A total of 32 MRS scans performed in eight healthy individuals (mean age 35 y; range 23-51 y).

INTERVENTIONS

Phosphocreatine (PCr) and β-nucleoside triphosphate (NTP) were measured using 31P MRS three dimensional-chemical shift imaging at high field (4 Tesla) after a baseline night of sleep, acute sleep deprivation (SD), and 2 nights of recovery sleep. Novel linear mixed-effects models were constructed using spectral and tissue segmentation data to examine changes in bioenergetics in gray and white matter.

MEASUREMENTS AND RESULTS

PCr increased in gray matter after 2 nights of recovery sleep relative to SD with no significant changes in white matter. Exploratory analyses also demonstrated that increases in PCr were associated with increases in electroencephalographic slow wave activity during recovery sleep. No significant changes in β-NTP were observed.

CONCLUSIONS

These results demonstrate that sleep deprivation and subsequent recovery-induced changes in high-energy phosphates primarily occur in gray matter, and increases in PCr after recovery sleep may be related to sleep homeostasis.

Effects of sleep deprivation on brain bioenergetics, sleep, and cognitive performance in cocaine-dependent individuals

In cocaine-dependent individuals, sleep is disturbed during cocaine use and abstinence, highlighting the importance of examining the behavioral and homeostatic response to acute sleep loss in these individuals. The current study was designed to identify a differential effect of sleep deprivation on brain bioenergetics, cognitive performance, and sleep between cocaine-dependent and healthy control participants. 14 healthy control and 8 cocaine-dependent participants experienced consecutive nights of baseline, total sleep deprivation, and recovery sleep in the research laboratory. Participants underwent ³¹P magnetic resonance spectroscopy (MRS) brain imaging, polysomnography, Continuous Performance Task, and Digit Symbol Substitution Task. Following recovery sleep, ³¹P MRS scans revealed that cocaine-dependent participants exhibited elevated global brain β-NTP (direct measure of adenosine triphosphate), α-NTP, and total NTP levels compared to those of healthy controls. Cocaine-dependent participants performed worse on the Continuous Performance Task and Digit Symbol Substitution Task at baseline compared to healthy control participants, but sleep deprivation did not worsen cognitive performance in either group. Enhancements of brain ATP levels in cocaine dependent participants following recovery sleep may reflect a greater impact of sleep deprivation on sleep homeostasis, which may highlight the importance of monitoring sleep during abstinence and the potential influence of sleep loss in drug relapse.