Omega-3 Fatty Acids and Subconcussive Head Impacts

The primary outcome analyses will be comparing group differences (group x time interactions) in blood biomarkers, specifically NF-L (neurofilament light, ), tau (picogram per milliliter), GFAP (glial fibrillary acidic protein; nanograms per milliliter), UCH-L1 (ubiquitin C-terminal hydrolase-L1; picograms per milliliter), and S100B (S100 calcium binding protein B; nanograms per milliliter). The aggregation of all blood biomarkers will provide a comprehensive overview of the biofluid profile of the participant following repetitive head injury.

DTI will be used to derive mean diffusivity (MD; square millimeters per second) and fractional anisotropy (FA; a unitless value that ranges from 0 to 1, 0 = Isotropic, 1= Anisotropic) as indicators joint of axonal integrity (axonal microstructure) and connectivity of white matter tracts by measuring how water molecules move through brain tissues .

Sympathetic Reactivity will be measured by the Cold Pressor Test (CPT). CPT is a general assessment of the ability of the sympathetic nervous system to become activated. The main metric will be changes in mean arterial pressure (MAP) following soccer headings. This test will be performed by submerging a participants hand into cold water for 2 minutes while autonomic and hemodynamic variables are recorded. At each data collection, participants will be instrumented for the measurement of heart rate (electrocardiogram) and continuous blood pressure. Participants will rest quietly for ~10 minutes before the CPT begins. The test takes 2 minutes.

Using the accommodative ruler, a target (14-point letter) will be moved toward the eyes at a rate of 1-2 cm/s. NPC will be recorded when participants report diplopia has occurred, or the tester observes eye misalignment. The assessment will be repeated twice, and the mean near point convergence value will be used for analyses.

The King-Devick test (KDT) consists of a total of 145 saccades while rapidly reading numbers aloud to complete the test. The KDT will be administered on a tablet. The total time (in seconds) will be used for analysis.

NODDI metrics will be derived from the the diffusion tensor images using the NODDI toolbox v1.0 in Matlab. Maps of neurite density (ND), orientation dispersion (OD), and intracellular volume fraction (ICVF) will be generated.

Resting-state connectivity will be examined throughout the whole brain and specific seeded regions including the dorsolateral prefrontal cortex (DLPFC), angular gyrus, and cingulate gyrus.

Spontaneous cardiovagal baroreflex sensitivity (cBRS) will be collected over the last 5 minutes before the CPT. Baroreflex sequences of 4 consecutive cardiac cycles will be captured using WinCPRS software, for which directional changes in the R-R interval and corresponding systolic blood pressure will be identified. Sequences will be detected when changes in systolic blood pressure are ≥1mmHg and the variation in R-R interval is ≥5miliseconds. Only sequences with an R2 ≥0.85 will be deemed acceptable. The mean of the regression slope will be calculated as the cBRS gain and used for analysis

Leading up to and during the cold pressor test (CPT) heart rate will be monitored via 3-lead ECG. Resting-state heart rate variability and spontaneous cardiovagal baroreflex sensitivity (cBRS) will be monitored over the last 5 minutes before the CPT. Using the R-R interval data collected from the ECG recordings during 5 minutes of paced breathing, time domain analyses will be performed to estimate overall heart rate variability and provide insight into cardiac parasympathetic activity.

Cognitive function will be measured using the NIH Toolbox Cognition Battery, which has excellent reliability and validity to measure cognition in young adults, and has construct validity among those with TBI. Multiple forms will minimize learning effects. This battery examines 5 cognitive domains (executive function, episodic memory, language, working memory, and processing speed) and takes 20 minutes to complete on a tablet.

Perfusion imaging will be acquired to examine cerebral blood flow.

Mitochondrial respiration related metabolites, including pyruvate, acetyl-CoA, citrate, isocitrate, alpha-ketogluterate, succinyl-CoA, succinate, fumarate, malate, and oxaloacetate will be assessed on blood samples. The aggregation of all metabolomic data will provide a comprehensive overview of the homeostasis of the participant following repetitive head injury.

Quantitative Susceptibility Mapping of whole brain, as well as regions of interest analysis, will be conducted to inspect the tissue and brain architectural response to head impacts and omega-3 fatty acid supplementation.

Several genetic markers that are known to associate with brain vulnerability will be assessed and regressed against our outcome measures. These genetic markers include, but not limited to, DARC, APOE, KIAA0319, BDNF, TPH2, COMT. Each marker will be compared to the other outcome measures to understand the full effect of the intervention on the genetic markers as a whole.

Participants who meet criteria for ADHD diagnosis will be analyzed to address the interactive effects of DHA+EPA and head impacts in ADHD.