Interaction Between Inorganic Nitrate Supplementation and Metformin in Individuals With Prediabetes

NCT07131384 | Not Yet Recruiting

• 1 other identifier: 302659
• Study Type: interventional
• Target: 24
• Locations: 0 countries
• Sites: N/A

Brief Summary

This study is examining whether short-term supplementation with inorganic nitrate, in the form of beetroot juice, can enhance blood vessel health, insulin sensitivity, and exercise capacity in individuals with prediabetes. We will be comparing the responses in individuals who are taking metformin to those who are naive to metformin. The results from this study may help identify non-pharmacological interventions in prediabetes.

Conditions

Males; Females; Sedentary; Metformin; Prediabetes

Keywords

Prediabetic Individuals; Exercise Capacity; Vascular health; Inorganic nitrate; Insulin Sensitivity

Outcome Measures

Primary Outcomes (11)

• Vascular Endothelial Function (Pulse wave analysis and velocity [PWA/V])

  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.

  3 days following either active NO3 or placebo without nitrate (following 7-day washout).

• Vascular Endothelial Function (Flow-Mediated Dilation [FMD])

  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.

  3 days following either active NO3 or placebo without nitrate (following 7-day washout).

• Skin microvascular function using post-occlusive reactive hyperemia (PORH)

  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.

  3 days following either active NO3 or placebo without nitrate (following 7-day washout)

• Skin microvascular function: Change in Skin Microvascular Dilation in Response to Local Thermal Heating

  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.

  3 days following either active NO3 or placebo without nitrate (following 7-day washout).

• Skin microvascular function: Change in microvascular dilation in response to acetylcholine (ACh)

  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.

  3 days following either active NO3 or placebo without nitrate (following 7-day washout)

• Oral Glucose Tolerance Test (OGTT)

  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.

  3 days following either active NO3 or placebo without nitrate (following 7-day washout).

• Plasma Nitrate/Nitrite

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

  4 days following either active NO3 or placebo without nitrate (following 7-day washout).

• Cardiorespiratory fitness

  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.

  4 days following either active NO3 or placebo without nitrate (following 7 day washout).

• Exercise time trial to exhaustion (TTE)

  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.

  4 days following either active NO3 or placebo without nitrate (following 7 day washout).

• Tissue oxygenation during exercise (near-infrared spectropscopy [NIRS]

  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.

  4 days following either active NO3 or placebo without nitrate (following 7-day washout).

• Oral nitrate reducing capacity (ONRC)

  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

  4 days following either active NO3 or placebo without nitrate (following 7-day washout).

Secondary Outcomes (3)

• Oral Microbiome

  4 days following either active NO3 or placebo without nitrate (following 7-day washout).

• Biomarker Analyses: Concentration of Inflammatory markers in fasting blood plasma

  Sample collected 4 days post active NO3 juice/placebo and will be analyzed post study completion.

• Biomarker Analyses: Concentration of Oxidative stress markers in fasting blood plasma

  Sample collected 4 days post active NO3 juice/placebo and will be analyzed post study completion.

Study Arms (4)

Active Comparator (Naive to metformin)

EXPERIMENTAL

Participants will supplement with nitrate-rich beetroot juice (BRJ) for 4 days: 6.45 mmol of NO3 in the morning and 6.45 mmol in the evening for 3 days, and 12.9 mmol 2 hours before the lab visit. Supplement order based on randomization and crossover will happen after a minimum of a 7-day washout period.

Dietary Supplement: Dietary Supplement: Inorganic Nitrate (Beetroot juice)

Placebo Comparator (Naive to metformin)

PLACEBO COMPARATOR

Participants will supplement with nitrate-depleted beetroot juice (BRJ) for 4 days: 6.45 mmol of NO3 in the morning and 6.45 mmol in the evening for 3 days, and 12.9 mmol 2 hours before the lab visit. Supplement order based on randomization and crossover will happen after a minimum of a 7-day washout period.

Dietary Supplement: Dietary supplement: Placebo (Nitrate-depleted beetroot juice)

Active Comparator (Taking metformin)

EXPERIMENTAL

Participants will supplement with nitrate-rich beetroot juice (BRJ) for 4 days: 6.45 mmol of NO3 in the morning and 6.45 mmol in the evening for 3 days, and 12.9 mmol 2 hours before the lab visit. Supplement order based on randomization and crossover will happen after a minimum of a 7-day washout period.

Dietary Supplement: Dietary Supplement: Inorganic Nitrate (Beetroot juice)

Placebo Comparator (Taking metformin)

PLACEBO COMPARATOR

Participants will supplement with nitrate-depleted beetroot juice (BRJ) for 4 days: 6.45 mmol of NO3 in the morning and 6.45 mmol in the evening for 3 days, and 12.9 mmol 2 hours before the lab visit. Supplement order based on randomization and crossover will happen after a minimum of a 7-day washout period.

Dietary Supplement: Dietary supplement: Placebo (Nitrate-depleted beetroot juice)

Interventions

Dietary Supplement: Inorganic Nitrate (Beetroot juice) DIETARY_SUPPLEMENT

Participants will be supplemented with inorganic nitrate in the form of beetroot juice for 4 days (12.9 mmol of NO3/day), and their vascular health, insulin sensitivity, and exercise capacity will be measured post-supplementation. This is a randomized crossover design with 2 parallel groups (Group 1: Currently taking metformin, Group 2: Naive to metformin).

Active Comparator (Naive to metformin); Active Comparator (Taking metformin)

Dietary supplement: Placebo (Nitrate-depleted beetroot juice) DIETARY_SUPPLEMENT

Participants will be supplemented with nitrate-depleted beetroot juice for 4 days (\<0.01 mmol NO3/day), and their vascular health, insulin sensitivity, and exercise capacity will be measured post-supplementation. This is a randomized crossover design with 2 parallel groups (Group 1: Currently taking metformin, Group 2: Naive to metformin).

Placebo Comparator (Naive to metformin); Placebo Comparator (Taking metformin)

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• Individuals who can communicate meaningfully with the investigator and can provide written consent.
• Confirmed prediabetic individuals (ages 18-60 years old) (2-hour glucose of 140-199 mg/dL following OGTT test or HbA1c between 5.7-6.4% tested on two occasions within 6 months).
• Taking metformin (stable dose for at least a week) or naïve to metformin
• Sedentary (\<1 day/week of structured exercise)
• Be able to perform exercise on a cycle ergometer without assistance
• Stable medication regimen for the last 6 months
• If female, have a normal menstrual cycle

You may not qualify if:

• Estimated Glomerular filtration rate (GFR) ≤ 45
• Body mass index ≥ 40 Kg/m2
• HbA1c \> 6.4%
• Smokers within the last 5 years
• Has experienced significant weight loss \~3 kg in the last three months or is taking any weight loss drugs
• Current medical condition that prohibits exercising at high intensities
• Currently on hormone replacement of any kind
• History of myocardial infarction, cerebrovascular event, acute or unstable disease other than pre-diabetes or obesity
• Currently taking any of the following medications (calcium channel blockers, statins, ACE or renin inhibitors, angiotensin receptor blockers, organic nitrates (e.g., nitroglycerine) or recent regular use of inorganic nitrates, alpha- or beta-blockers, diuretics, proton pump inhibitors, PDE-5 inhibitors (e.g.,: Cialis, Viagra), or xanthine oxidase inhibitors (e.g.,: Allopurinol))
• Oral antibiotic use within the previous four weeks, including over-the-counter antibacterial mouthwash or a mouthwash containing chlorhexidine and unwilling to discontinue use
• Oral cancer/severe oral disease
• Uncontrolled hypertension (\>140/90)
• Had hysterectomy or oophorectomy
• Fetuses, neonates, children, prisoners, cognitively impaired, non-English speaking participants

Sponsors & Collaborators

• University of Virginia: lead

MeSH Terms

Conditions

Sedentary Behavior; Prediabetic State; Insulin Resistance

Condition Hierarchy (Ancestors)

Behavior; Diabetes Mellitus; Glucose Metabolism Disorders; Metabolic Diseases; Nutritional and Metabolic Diseases; Endocrine System Diseases; Hyperinsulinism

Study Officials

• Arthur Weltman, PhD

  University of Virginia

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Money Ghimire, M.S

CONTACT

4342438677; eta8xd@virginia.edu

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: OTHER
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor

Study Record Dates

• First Submitted: August 6, 2025
• First Posted: August 20, 2025
• Study Start: September 1, 2025
• Primary Completion (Estimated): December 1, 2026
• Study Completion (Estimated): December 1, 2026
• Last Updated: August 26, 2025

Record last verified: 2025-08

Data Sharing

• IPD Sharing: Will not share