Obstructive sleep apnea is associated with altered midbrain chemical concentrations

Area of Science:

• Neuroscience
• Medical Imaging
• Sleep Medicine

Background:

• Obstructive sleep apnea (OSA) is linked to brain structure and function changes.
• The midbrain's role in OSA pathophysiology remains under-explored despite its crucial integrative functions.
• Investigating midbrain chemistry can elucidate mechanisms underlying OSA-related neurological dysfunction.

Purpose of the Study:

• To assess midbrain metabolite concentrations in individuals with OSA compared to healthy controls.
• To explore the relationship between altered midbrain chemistry and OSA-induced physiological disruptions.

Main Methods:

• Utilized accelerated 2D magnetic resonance spectroscopy (2D-MRS), specifically compressed sensing-based 4D echo-planar J-resolved spectroscopic imaging (4D-EP-JRESI).
• Measured midbrain metabolites in 14 OSA patients and 26 healthy controls using high-resolution T1-weighted scans for voxel localization.
• Processed MRS data with custom MATLAB software and calculated metabolite ratios relative to creatine using the ProFit algorithm.

Main Results:

• OSA patients exhibited significantly decreased N-acetylaspartate (NAA), a marker of neuronal viability (p=0.03).
• Elevated levels of glutamate (Glu) (p=0.03), ascorbate (Asc) (p=0.03), and myo-inositol (mI) (p=0.03) were observed in the midbrain of OSA patients.
• No significant differences were found in γ-aminobutyric acid (GABA) or taurine levels between groups.

Conclusions:

• Decreased NAA in the midbrain of OSA patients indicates neuronal injury or dysfunction.
• Increased Glu, Asc, and mI suggest excitotoxic processes, astrocyte activation, and oxidative stress, potentially driven by intermittent hypoxia.
• Altered midbrain metabolite profiles contribute to understanding the neurological deficits associated with obstructive sleep apnea.