The Effects of Vitamin C on Acute-Exercise in Postmenopausal Females

Flow-Mediated Dilation (FMD%) - Brachial Artery Endothelial Function

Brachial artery endothelial function will be measured by flow-mediated dilation (FMD) in each participant 5x (at baseline and after 0mg (placebo) 200mg, 500mg, and 1000mg of vitamin C). Participants will be placed in a supine position with their left forearm slightly extended and supinated with legs straight. The brachial artery will be imaged using a high-resolution 7.5MHz linear array transducer at rest, during 5 minutes of forearm occlusion via cuff inflation (250mmHg), and continuously for 2 minutes post-occlusion; an EKG trigger will be used to capture images during end-diastole of the cardiac cycle.

Basal ROS Concentrations - plasma 8-Isoprostane (8-iso) and malondialdehyde (MDA)

A venous blood sample will be collected from a vein in the antecubital fossa. Plasma will be separated out and stored at -80C until concentrations of 8-Isoprostane (8-iso) and malondialdehyde (MDA) are measured via commerically available ELISA kits. ROS concentrations will be measured at 5x points: at baseline and after 0mg (placebo), 200mg, 500mg, and 1000mg of vitamin C

Resting ROS/NO Balance - plasma N-oxides (nitrite and nitrate)

Venous blood samples will be collected from an antecubital fossa vein. Plasma will be separated out and stored at -80C until analysis. Plasma N-oxides (nitrite and nitrate) will be evaluated from the plasma via ozone-based chemiluminescence using a Sievers NOA model 280i. The N-oxides will be compared with the basal ROS also measured to calculate a ROS/NO balance.

Exercise-Induced ROS (plasma 8-Isoprostane (8-iso) and malondialdehyde (MDA)) and NO (plasma nitrate and nitrite)

An intravenous catheter will be placed into a vein in the antecubital fossa. Participants will complete 4 high-intensity exercise sessions (\~200kcals). Each exercise session will be after 3-days of vitamin C supplementation (0mg/placebo, 200mg, 500mg, and 1000mg). Blood will be collected immediately before, immediately after, 15-min after, and 30-min after exercise. Plasma will be separated out and used to evaluate the changes in ROS (plasma 8-Isoprostane (8-iso) and malondialdehyde (MDA)) and NO (plasma nitrate and nitrite) from baseline/rest.

Vitamin C

Blood samples will be collected to evaluate compliance. We will measure vitamin C concentrations after each supplementation phase.

Oral Nitrate Reducing Capacity

Assessment of the oral microbiome's ability to reduce nitrate to nitrite. This will be measured through an unstimulated saliva sample and a rinse of a standard nitrate solution.

Pulse Wave Analysis and Velocity

Brachial artery blood pressures will be obtained using a standard sphygmomanometer. Aortic blood pressures will be obtained using applanation tonometry (SphygmoCor version 8.0, AtCor Medical).

Microvascular Function

Participants will remain in a supine position with their left or right forearm slight extended and supinated. The cuff used for FMD will remain in place and two circular discs will be placed on the participants extended forearm. A laser Doppler imager (Moor Instruments - FLPI2) will be positioned directly over the participants forearm to measure skin blood flow in three different ways: microvascular flow mediated dilation, acetylcholine, and local thermal heating.