Nitrites, Skeletal Muscle Mitochondrial Bioenergetics, and Physical Activity in Old Age

Study Overview
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Brief Summary
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This 2-site randomized double blinded controlled trial is to confirm and more definitively clarify the impact of a 12-week course of nitrite versus placebo on mitochondrial bioenergetics in older sedentary adults. This investigator will take an integrative physiology approach to determine the effect of nitrite therapy on a comprehensive assessment of mitochondrial energetics, skeletal muscle vascular function, and whole body physical function (cardiorespiratory function, exercise endurance, strength, balance, and physical activity) and fatigability.

Detailed Description
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Old age is associated with declining skeletal muscle mitochondrial bioenergetics with related decrements in cardiorespiratory fitness (CRF) and physical function that predispose to frailty, disability, and diminished quality of life. While exercise training may moderate and possibly even reverse declines in mitochondrial bioenergetics, potential for such benefit is typically confounded by exercise intolerance with early fatigability that results from the same age-related mitochondrial declines. Consequently, sedentariness is endemic and insidious among the growing population of older adults. This trial is to study the utility of inorganic nitrite salts as a novel means to modify this detrimental pattern. Classic studies demonstrate that nitrite facilitates hypoxic vasodilation in muscle. This investigator's preliminary data suggests that nitrite treatment also augments skeletal muscle mitochondrial bioenergetics in older adults. This investigator proposes improving mitochondrial function will also be reflected in clinical parameters, including CRF as well as broader functional attributes (endurance, strength, and balance) that enable physical activity (PA) and opportunity to mitigate frailty and disability. As such, this application is in line with the National Institute on Aging's mission to develop targeted interventions to prevent and treat age-associated conditions. This multi-disciplinary team has published seminal work indicating that mitochondrial bioenergetics and CRF are significant determinants of physical function in older adults. In parallel efforts, this investigative team showed efficacy of chronic nitrite therapy to improve mitochondrial bioenergetics in older sedentary adults. Only one month of nitrite therapy significantly improved ex vivo assessments of mitochondrial energetics in skeletal muscle biopsies, concomitant with increased skeletal muscle sirtuin-3 expression, a nicotinamide adenine dinucleotide (NAD) dependent lysine deacetylase and key regulator of mitochondrial metabolism. These key data reinforce the premise that nitrite enhances vital mitochondrial metabolism in older adults. Moreover, improvement in muscle energetics in nitrite-treated older adults was linked with increased exercise efficiency as evidenced by reduced oxygen consumption (VO2) during submaximal steady-state walking. This data supports the hypothesis that nitrite will make physical function easier such that physical activity will increase.

Official Title
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Nitrites, Skeletal Muscle Mitochondrial Bioenergetics, and Physical Activity in Old Age

Conditions
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Aging, Sedentary Lifestyle, Frailty

Intervention / Treatment
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* Drug: Placebos
* Drug: 20mg sodium nitrite tid


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age ≥70 years Sedentary (<1 hour/week of volitional exercise activity) Clinically stable (euvolemic; baseline HR <100 bpm) and without hospitalization or invasive cardiac procedure for 6 weeks Exclusion Criteria: Blood pressure <110 or >160/95 mmHg Orthopedic or other chronic condition which limits physical activity or exercise testing assessments If valve replacement has been performed, patient may not be enrolled for 12 months after this procedure Severe peripheral or pulmonary artery disease Anemia: Hgb <11.0 (♂),10.0 (♀) gm/dl Participants with diabetes whose HgbA1c >10.0% Chronic alcohol (>14 drinks ETOH a week) or drug (any cocaine, methamphetamine, and cannabis ≥4 x week) dependency Allergy to lidocaine and red dye Chronic use of oral corticosteroids or other medications that affect muscle function Current use of organic nitrates or phosphodiesterase type 5 (PDE5) inhibitors Unable to hold warfarin, direct-acting oral anticoagulants (DOACs), non-steroidal anti-inflammatory medications (NSAIDs) or aspirin for 3 days prior to muscle biopsy, or to hold thienopyridine medications for 5 days prior to muscle biopsy. Participants unable or unwilling to hold will follow the modified ASA hold plan Any bleeding disorder that would contraindicate biopsy such as history of clinically significant bleeding diathesis (e.g., Hemophilia A or B, Von Willebrand's Disease or congenital Factor VII deficiency) Unstable psychiatric diagnosis that would affect adherence and ability to complete the protocol Dementia or inability to give informed consent or follow study protocol End-stage disease Other chronic unstable disease such as active neoplasm, end stage chronic kidney, liver or other organ disease

Ages Eligible for Study
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Minimum Age: 70 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Parallel assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 20 mg Sodium Nitrite TID Arm<br>Subject is to receive active study drug three times per day during treatment (12 weeks +/- 5 days) period and then after the treatment period (up to 16 weeks total). | Drug: 20mg sodium nitrite tid<br>* Oral, inorganic sodium nitrite capsule at a dose of 20 mg administered three times per day, during the day.<br>|
| Placebo Comparator: Placebo Control Arm<br>Subject is to receive placebo three times per day during treatment period (12 weeks +/- 5 days) and then after the treatment testing period (up to 16 weeks total). | Drug: Placebos<br>* Oral placebo capsule at a dose of 20 mg administered three times per day, during the day.<br>* Other names: Placebo;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Skeletal muscle mitochondrial respiration State 3, Baseline to 12-week change | We will use high resolution respirometry via Oroboros Oxygraph 2k to assess the effects of 12 weeks of inorganic nitrite vs placebo on skeletal muscle mitochondrial respiration from samples obtained via vastus lateralis muscle biopsy. | 12-week course of study drug supplementation, up to 16 weeks total | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Skeletal Muscle adenosine triphosphate (ATP) production, Baseline to 12-week change | Using phosphorus-magnetic resonance spectroscopy, we will measure ATP production and how it will change after 12 weeks (up to 16 weeks) of inorganic nitrite supplementation vs placebo. | 12-week course of study drug supplementation, up to 16 weeks total | 
| Change in cross-sectional area for each fiber type by skeletal muscle microscopy, Baseline to 12-week change | Using microscopy and immmunofluorescence, we will measure the cross-sectional area for each fiber type, relative fiber type number, and relative area composition of each muscle fiber type and mitochondrial content (area/section) after 12 weeks of inorganic nitrite supplementation vs placebo. | 12-week course of study drug supplementation, up to 16 weeks total | 
| Change in relative fiber type number by skeletal muscle microscopy, Baseline to 12-week change | Using microscopy and immmunofluorescence, we will measure the cross-sectional area for each fiber type, relative fiber type number, and relative area composition of each muscle fiber type and mitochondrial content (area/section) after 12 weeks of inorganic nitrite supplementation vs placebo. | 12-week course of study drug supplementation, up to 16 weeks total | 
| Change in relative area composition of each muscle fiber type by skeletal muscle microscopy, Baseline to 12-week change | Using microscopy and immmunofluorescence, we will measure the cross-sectional area for each fiber type, relative fiber type number, and relative area composition of each muscle fiber type and mitochondrial content (area/section) after 12 weeks of inorganic nitrite supplementation vs placebo. | 12-week course of study drug supplementation, up to 16 weeks total | 
| Change in mitochondrial content (area/section) by skeletal muscle microscopy, Baseline to 12-week change | Using microscopy and immmunofluorescence, we will measure the cross-sectional area for each fiber type, relative fiber type number, and relative area composition of each muscle fiber type and mitochondrial content (area/section) after 12 weeks of inorganic nitrite supplementation vs placebo. | 12-week course of study drug supplementation, up to 16 weeks total | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Bioenergetics, 70 and Older, Frailty