Daily Amino Acid Supplementation for People With Parkinson's Disease

Amino Acid bioavailability (Lysine, Tryptophan, Arginine, Glutamate, Leucine, Taurine, Glutathione)

Circulating amino acid concentrations will be measured from blood samples using high performance liquid chromatography using a solid phase column specifically designed to test amino acids (e.g. 00F-4435-E0, Phenomenex, USA) along with appropriate column guards (e.g. AJ0-7597 \& KJ0-4282, Phenomenex, USA) and liquid phases. This analysis will be performed at the Laboratory of Mass Spectroscopy and Omics Analysis.

Oxidative stress

Oxidative stress will be measured using a total antioxidant power test (e.g. ab65329, ABCAM, USA). It is a quantitative bioassay and will be performed using the laboratory facilities.

Oxidative stress

Oxidative stress will be assessed with reduced/oxidized glutathione assays (e.g. ab138881, ABCAM, USA). It is a quantitative bioassay and will be assessed using laboratory facilities.

Body composition: Bioelectrical impedance

Body composition will be assessed using a multi-spectral bioelectrical impedance (Mediana i55, Mediana, South Korea). During this test participants will clean their feet and hands using a sanitary wipe and then stand barefoot on the impedance machine while holding two electrodes. Then a small and imperceivable multi-spectral electrical current will be sent between limbs which the machine will use to estimate the fat content and distribution based on the resistance (i.e., impedance) of this current.

Body composition: Ultrasound & Shear Wave Elastography (Tissue Organization & Fibrosis)

A trained (\>20 hr. logged research scanning) ultrasound researcher will use an ultrasound (ACUSON Sequoia, Siemens Healthineers, USA) to assess muscle thickness of the primary knee extensors (quadriceps femoris) and the plantar flexors (gastrocnemius and soleus) as well as their tendons. Longitudinal panoramic 2D ultrasound will be used to measure muscle fascicle length and angle of each muscle. To assess tissue composition of these muscles shear-wave elastography will be used to measure localized muscle stiffness based on propagation of a concentrated acoustic shear (push-pull) wave applied to the center of the muscle.

Physical function: Physical activity

Participants will be sent a research-grade activity monitor, Actigraph GT9X device, in the standard mail at their residence. After receiving the device, participants will engage in a telephone or virtual meeting with a research assistant to learn how to use the device. (approximately 30-40 minutes). Participants will be asked to wear the activity monitor for 7 days prior to the first baseline visit. They will be asked to continuously wear the device on their wrist for the 7 days. Participants will return the device in a pre-paid envelope. The same procedure will occur at the conclusion of the intervention for a post-intervention assessment.

Physical function: Balance (Mini Balance Evaluation System Test)

This test assesses balance impairments across 14 items consisting of dynamic balance, anticipatory postural adjustments, reactive postural control, sensory orientation and dynamic gait. The total score ranges from 0 to 28, with each item scored on a scale from 0 to 2 with higher scores indicating better balance.