Interaction Between Inorganic Nitrate Supplementation and Metformin in Individuals With Prediabetes

PWA/V- These measures will be calculated using the SphygmoCor XCEL system (AtCor Medical). This system will provide arterial stiffness, central, and peripheral pressure waveforms.

FMD- Participants will be placed in a supine position with their left forearm slightly extended and supinated, and their legs straight. The arteries will be imaged using a high-resolution 7.5 MHz linear array transducer at rest, during 5 minutes of forearm occlusion via cuff inflation, and continuously for 3 minutes post-occlusion. An EKG trigger will be used to capture images during the end-diastole of the cardiac cycle.

Skin microvascular function will be measured using Moor Instruments' FLPI-2 laser speckle imaging system. PORH will also be measured during the FMD measurement. Baseline measures will be captured, and the cuff will be inflated for 5 minutes, with the post-occlusion reactive period being measured. The laser positioned above the forearm skin will measure skin blood flow at all these time points.

Skin microvascular function will be measured using Moor Instruments' FLPI-2 laser speckle imaging system. For LTH, ~2 mL of diH2O will be placed on a small disc on the forearm. The solution will be slowly heated to 44 °C. This will allow us to measure the endothelial function of the microcirculation in the skin.

Skin microvascular function will be measured using Moor Instruments' FLPI-2 laser speckle imaging system. For skin ACh iontophoresis, ~2 ml of 2% ACh solution (0.1g of ACh in diH2O and filtered) and low current will be used to deliver small quantities of ACh to the skin. This will allow us to measure the endothelial function of the microcirculation in the skin.

Participants will consume a 75g glucose beverage and then undergo a test to measure insulin, glucose, and C-peptide. A qualified team member will insert a catheter into the antecubital vein for the collection of blood. Blood will be collected at 5 timepoints to estimate insulin sensitivity: before drinking the 75g sugar beverage (0 minutes), and every 30 minutes until the end of the test (120 minutes). Participants will rest in a supine position for the duration of the test.

Plasma samples will be collected to assess changes in plasma nitrate and nitrite following either BRJ or placebo.

Peak aerobic capacity (VO2peak) will be assessed on a cycle ergometer. An IV will be placed and lactate measured during rest and after the completion of every 3-minute stage to determine VO2 at lactate threshold and VO2peak.

Participants will complete a time-to-exhaustion (TTE) test on a cycle ergometer. Participants will begin cycling for 4 minutes at 20 Watts as a warm-up. They will then cycle at a work rate equivalent to 75% of the difference between lactate threshold and VO2peak achieved prior. The TTE test will be terminated when pedal cadence falls ≥ 10 rpm for ≥ 5 sec. When participants reach exhaustion, they will complete a 3-minute unloaded recovery period on the cycle ergometer.

Tissue oxygenation will be captured noninvasively using near-infrared spectrometry (NIRS, PortaMon, Artinis Medical Systems B.V., The Netherlands) positioned on the gastrocnemius (calf) or vastus lateralis (quad) muscle during the VO2peak/lactate test.

To assess the oral microbiome's ability to reduce nitrate to nitrite, the participant will rinse their mouth with a solution of potassium nitrate and ultra-pure water for five minutes. The rinsed solution will be collected into a 50ml Falcon tube. The nitrite concentration will be measured to determine ONRC

In order to assess abundance and classification of nitrate-reducing bacteria, a sample of the oral microbiome will be obtained. The dorsal surface of the tongue will be swabbed using a 6" HydraFlock Sterile Large Flock Swab for 60 seconds (Puritan Medical Products, USA). Additionally, an unstimulated saliva sample (~5ml) will be collected through an unstimulated drool technique. Both swab and saliva samples will be sequenced to analyze bacteria present in the oral microbiome following supplement/placebo.

The investigators plan to assess various markers of inflammation. A fasting blood sample will be collected to measure markers of inflammation.

The investigators plan to assess various markers of oxidative stress. A fasting blood sample will be collected to measure markers of oxidative stress.