Type 2 Diabetes
Conditions
Brief summary
The purpose of this study is to use a randomized, double-blind, placebo controlled study design to comprehensively investigate the impact of 8-weeks of dietary nitrate supplementation on skeletal muscle blood flow, mitochondrial function, and exercise capacity in patients with type 2 diabetes (T2D).
Detailed description
Patients with type 2 diabetes (T2D) demonstrate a reduced exercise capacity, a powerful predictor of cardiovascular mortality, which may be due to reductions in skeletal muscle perfusion and mitochondrial dysfunction. Nitric oxide (NO) is a key molecule involved in in the regulation of blood flow to contracting muscles, as well as a critical mediator in mitochondrial respiration. However, there appears to be a decreased enzymatic synthesis of NO and an overall reduction of bioavailable NO in patients with T2D, which likely contributes to the reduced exercise capacity and tolerance. Accumulating evidence suggests that exogenous nitrate supplementation is an effective option for increasing NO bioavailability in vivo. The purpose of the proposal is to use a randomized, double-blind, placebo controlled study design to comprehensively investigate the impact of 8-weeks of dietary nitrate supplementation on skeletal muscle blood flow, mitochondrial function, and exercise capacity in patients with T2D. The central hypothesis is that increasing NO bioavailability via dietary nitrate supplementation in patients with T2D will lead to improved oxygen delivery and utilization during exercise. To address this hypothesis a highly mechanistic and translational experimental strategy will be used to explore whether increased NO bioavailability via dietary nitrate supplementation improves skeletal muscle perfusion during exercise (Aim 1), enhances mitochondrial biogenesis and function (Aim 2), and improves exercise capacity and efficiency (Aim 3). Collectively, these studies will provide important mechanistic insight into the therapeutic potential of dietary nitrate supplementation for improving skeletal muscle blood flow, mitochondrial function and exercise capacity in patients with T2D.
Interventions
DIETARY_SUPPLEMENTSuper Beets
Nitrate rich beetroot powder (10g/day) for 8 weeks
OTHERSuper Beets Placebo
Nitrate deficient beetroot powder (10g/day) for 8 weeks
Sponsors
American Diabetes Association
Darren P Casey
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Eligibility
Sex/Gender
ALL
Age
40 Years to 77 Years
Healthy volunteers
Yes
Inclusion criteria
For 50 patients with documented Type 2 diabetes Inclusion Criteria: * Willing and able to provide written, signed informed consent after the nature of the study has been explained, and prior to any research-related procedures. * Age is \> or = 40 and \< or = 77 years of age * Documented Type 2 diabetes
Exclusion criteria
* diagnosis of type 2 diabetes \< 3 years prior to enrollment * HbA1c \<6.0% or \>10.0% * body mass index \> 42 kg/m2 * incident cardiovascular events in the last year (heart attack, stroke) * symptomatic coronary artery disease and/or heart failure * uncontrolled hypertension * hypotension (resting systolic BP \< 90 mmHg) * renal impairment with creatinine clearance (eGFR) of \<50 ml/min * smoking or history of smoking within past one year * use of medication which contain nitrates * use of anti-coagulant drugs * use of anti-platelet drugs * participation in research studies in which medications or interventions are given which would potentially alter subject responses in the current study For 15 age- and weight-matched nondiabetic control subjects Inclusion Criteria: * Willing and able to provide written, signed informed consent after the nature of the study has been explained, and prior to any research-related procedures. * Age is \> or = 40 and \< or = 77 years of age
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Maximal Exercise Capacity (VO2max) | Pre and post 8 weeks of dietary nitrate supplementation | A 12-lead ECG, symptom limited cardiopulmonary exercise testing with gas exchange measurements will be performed on a cycle ergometer using a ramp protocol to determine maximal aerobic capacity (VO2max) and exercise efficiency. |
| Change in Skeletal Muscle Perfusion During Exercise | Pre and post 8 weeks of dietary nitrate supplementation | Forearm blood flow will be determined using Doppler ultrasound during rhythmic forearm exercise. |
| Change in Skeletal Muscle Mitochondrial Function | Pre and post 8 weeks of dietary nitrate supplementation | Muscle biopsies were obtained from the vastus lateralis using a Bergstrom needle with suction under local anesthesia, which will yield \ 200-250mg of tissue. Mitochondrial function was assessed as follows: Fiber bundles were chemically permeabilized with saponin and mitochondrial respiration was analyzed by in situ high-resolution respirometry at 37°. |
Countries
United States
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Beetroot Crystals (Nitrate) Participants will receive a nitrate rich beetroot powder (10g/day) for 8 weeks.
Super Beets: Nitrate rich beetroot powder (10g/day) for 8 weeks | 20 |
| Placebo (Beetroot Powder, no Nitrate) Participants will receive a beetroot powder placebo (no nitrate) for 8 weeks.
Super Beets Placebo: Nitrate deficient beetroot powder (10g/day) for 8 weeks | 19 |
| Nondiabetic Control Subjects All pre supplementation measures and study visits will be performed in a group of 15 nondiabetic control subjects to allow us to 1) quantify the degree of impairment in T2D prior to intervention and 2) assess the effectiveness of the nitrate therapy in restoring the primary outcome measures back to 'normal'. Nondiabetic controls will not receive an 8-week beetroot supplementation. | 15 |
| Total | 54 |
Baseline characteristics
| Characteristic | Placebo (Beetroot Powder, no Nitrate) | Nondiabetic Control Subjects | Beetroot Crystals (Nitrate) | Total |
|---|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical >=65 years | 5 Participants | 4 Participants | 8 Participants | 17 Participants |
| Age, Categorical Between 18 and 65 years | 14 Participants | 11 Participants | 12 Participants | 37 Participants |
| Age, Continuous | 58.7 years STANDARD_DEVIATION 8.8 | 60.2 years STANDARD_DEVIATION 9.2 | 58.4 years STANDARD_DEVIATION 9.7 | 59.2 years STANDARD_DEVIATION 9.1 |
| Race and Ethnicity Not Collected | — | — | — | 0 Participants |
| Region of Enrollment United States | 19 participants | 15 participants | 20 participants | 54 participants |
| Sex: Female, Male Female | 5 Participants | 5 Participants | 5 Participants | 15 Participants |
| Sex: Female, Male Male | 14 Participants | 10 Participants | 15 Participants | 39 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk |
|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 20 | 0 / 19 | 0 / 15 |
| other Total, other adverse events | 0 / 20 | 0 / 19 | 0 / 15 |
| serious Total, serious adverse events | 0 / 20 | 0 / 19 | 0 / 15 |
Outcome results
Primary
Change in Skeletal Muscle Mitochondrial Function
Muscle biopsies were obtained from the vastus lateralis using a Bergstrom needle with suction under local anesthesia, which will yield \ 200-250mg of tissue. Mitochondrial function was assessed as follows: Fiber bundles were chemically permeabilized with saponin and mitochondrial respiration was analyzed by in situ high-resolution respirometry at 37°.
Time frame: Pre and post 8 weeks of dietary nitrate supplementation
Population: Final number of participants studied with muscle biopsies was smaller than the total number of subjects enrolled in the study. The lower number was influenced by: (i) subjects not consenting to the muscle biopsy procedure; or (ii) technical problems (ex: not enough muscle tissue and/or extensive proportion of intramuscular fat obtained).~Nondiabetic control subjects only had muscle biopsies performed at one time point (same time point as pre measurements for T2D subjects).
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Beetroot Crystals (Nitrate) | Change in Skeletal Muscle Mitochondrial Function | CHO-supported respiration - Pre | 64.6 Oxygen Flux, JO2 (pmol/(s*mg)) | Standard Deviation 22.2 |
| Beetroot Crystals (Nitrate) | Change in Skeletal Muscle Mitochondrial Function | CHO-supported respiration - Post | 75.4 Oxygen Flux, JO2 (pmol/(s*mg)) | Standard Deviation 16.4 |
| Placebo (Beetroot Powder, no Nitrate) | Change in Skeletal Muscle Mitochondrial Function | CHO-supported respiration - Pre | 71.0 Oxygen Flux, JO2 (pmol/(s*mg)) | Standard Deviation 20.5 |
| Placebo (Beetroot Powder, no Nitrate) | Change in Skeletal Muscle Mitochondrial Function | CHO-supported respiration - Post | 59.8 Oxygen Flux, JO2 (pmol/(s*mg)) | Standard Deviation 11.1 |
| Nondiabetic Control Subjects | Change in Skeletal Muscle Mitochondrial Function | CHO-supported respiration - Pre | 87.5 Oxygen Flux, JO2 (pmol/(s*mg)) | Standard Deviation 21.5 |
Primary
Change in Skeletal Muscle Perfusion During Exercise
Forearm blood flow will be determined using Doppler ultrasound during rhythmic forearm exercise.
Time frame: Pre and post 8 weeks of dietary nitrate supplementation
Population: Nondiabetic control subjects only completed rhythmic forearm exercise and forearm blood flow measurements at one study visit (same time point as pre measurements for T2D subjects).
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Beetroot Crystals (Nitrate) | Change in Skeletal Muscle Perfusion During Exercise | Forearm Blood Flow - pre supplementation | 156 ml/min | Standard Deviation 69 |
| Beetroot Crystals (Nitrate) | Change in Skeletal Muscle Perfusion During Exercise | Forearm Blood Flow - post supplementation | 175 ml/min | Standard Deviation 73 |
| Placebo (Beetroot Powder, no Nitrate) | Change in Skeletal Muscle Perfusion During Exercise | Forearm Blood Flow - pre supplementation | 143 ml/min | Standard Deviation 69 |
| Placebo (Beetroot Powder, no Nitrate) | Change in Skeletal Muscle Perfusion During Exercise | Forearm Blood Flow - post supplementation | 143 ml/min | Standard Deviation 66 |
| Nondiabetic Control Subjects | Change in Skeletal Muscle Perfusion During Exercise | Forearm Blood Flow - pre supplementation | 200 ml/min | Standard Deviation 64 |
Primary
Maximal Exercise Capacity (VO2max)
A 12-lead ECG, symptom limited cardiopulmonary exercise testing with gas exchange measurements will be performed on a cycle ergometer using a ramp protocol to determine maximal aerobic capacity (VO2max) and exercise efficiency.
Time frame: Pre and post 8 weeks of dietary nitrate supplementation
Population: One subject in the nitrate group did not reach maximal criteria during testing. Therefore, VO2max data was analyzed only in 18 participants in the nitrate group. Nondiabetic control subjects only completed VO2max testing once (same time point as pre measurements for T2D subjects).
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Beetroot Crystals (Nitrate) | Maximal Exercise Capacity (VO2max) | VO2max - Pre supplementation | 20.7 mL/kg/min | Standard Deviation 7 |
| Beetroot Crystals (Nitrate) | Maximal Exercise Capacity (VO2max) | VO2max - Post supplementation | 21.9 mL/kg/min | Standard Deviation 7.4 |
| Placebo (Beetroot Powder, no Nitrate) | Maximal Exercise Capacity (VO2max) | VO2max - Pre supplementation | 20.0 mL/kg/min | Standard Deviation 4.2 |
| Placebo (Beetroot Powder, no Nitrate) | Maximal Exercise Capacity (VO2max) | VO2max - Post supplementation | 19.7 mL/kg/min | Standard Deviation 4.6 |
| Nondiabetic Control Subjects | Maximal Exercise Capacity (VO2max) | VO2max - Pre supplementation | 27.6 mL/kg/min | Standard Deviation 8.7 |