Assessing Neuroinflammation in GWI Using MRS

This proposal is for a Tier 1 (Discovery) study that uses a human, cross-sectional, observational neuroimaging approach to measure neuroinflammation in Gulf War Illness (GWI). A whole-brain magnetic resonance spectroscopic imaging (MRSI) scan will be used to detect multiple markers of neuroinflammation in 30 individuals with GWI and 30 healthy veteran controls. The investigators have fully tested the MRSI scan in several patient groups, and have found strong evidence of neuroinflammation in fibromyalgia and chronic fatigue syndrome - conditions the investigators believe involve abnormal central immune system processing. The investigators have not, however, performed the scan on individuals with GWI. The discovery study will allow investigators to transfer this existing technology to the GWI field. This project meets the core Special Interest of investigating dysregulation between the immune and neurological systems in the brain.

The investigators' central hypothesis is that GWI involves chronic neuroinflammation. The symptoms of GWI (e.g. fatigue, musculoskeletal pain, sleep disturbances, and cognitive dysfunction) overlap heavily with classic cytokine-induced sickness responses. In the case of GWI, microglial cells in the brain can be pushed into a hypersensitized state by toxins or abnormal immune challenges, leading to chronic overproduction of pro-inflammatory factors that result in the primary symptoms of GWI.

To test the central hypothesis, it is necessary to measure neuroinflammation in humans in vivo. However, most techniques are too invasive for use in living individuals. To address that problem, the investigators use an MRSI scan which provides metabolite concentrations in 4,000 separate voxels, giving whole-brain coverage. The scan yields measurements for: Myo-inositol (a marker of glial cell proliferation), lactate (a product of anaerobic metabolism), choline (a sign of cellular breakdown), and N-acetylaspartate (a marker of neuronal health). The scan also provides absolute brain temperature, which is shown to be elevated with severe neuroinflammation. The five main outcomes are as follows:

Myo-inositol (MI): Higher values represent greater microglia proliferation or gliosis.

Lactate (Lac): Higher values represent more severe inflammatory activity.

Choline (Cho): Higher values indicate greater cell turnover (inflammation, gliosis, or demyelination).

NAA: Lower values represent neurodegeneration.

Temperature: Higher values represent greater neuroinflammation. Metabolite and water-reference data will be analyzed using the MIDAS package and thermometry extension41. Absolute brain temperatures (in °C) within each voxel will be calculated by measuring the distance of the temperature-invariant NAA peak from the temperature-variant water peak using the formula: Tbrain = -102.76 × Δwater-NAA + 310.5°C, which has been validated in our scanner to produce reliable readings. Temperature will be expressed on absolute values in °C.

Inclusion criteria

• Between the ages of 46 and 70
• Veterans who meet the Kansas inclusion criteria .The Kansas Inclusion Criteria are a set of the most frequently reported symptoms experienced by Gulf War veterans. This frequency and severity of the symptoms reported by the participant indicate whether the person has Gulf War Illness or not. The Kansas Inclusion Criteria is the gold standard for identifying veterans with GWI in the field. The criteria are attached.
• Present in Persian Gulf between 1990 and August 1991
• Forward deployed (in Iraq or Kuwait)

Exclusion criteria

• Usage of experimental medications, opioid analgesics, psychostimulants (except caffeine), or benzodiazepines
• Uncontrolled diabetes, autoimmune disorders, and thyroid disorders.
• Major cardiovascular illness, cancer, or have any contraindications for MRI (including metallic implants or claustrophobia)