The purpose of this study is to assess the efficacy of supplementation with the mitochondria-targeted antioxidant, mitoquinone (MitoQ), for improving physiological function (vascular, motor, and cognitive) in middle-aged and older adults.

Overall, the proposed research project has the long-term potential to influence clinical practice by establishing novel therapies for treating multiple domains of age-associated physiological dysfunction and thereby reducing the risk of clinical disease and disability.

Inclusion Criteria:

• Women will be confirmed as postmenopausal (either natural or surgical) based on cessation of menses for >1 year.
• Ability to provide informed consent
• Baseline brachial flow-mediated dilation (FMD) < 6%Δ (rationale: non-invasive screening to ensure exclusion of subjects with exceptionally high baseline endothelial function.
• Ability to perform motor and cognitive tests (e.g., can rise from a chair, walk for 2 min, climb 10 stairs)
• Willing to accept random assignment to condition

Exclusion Criteria:

• Current smoking
• Having past or present alcohol dependence or abuse, as defined by the American Psychiatry Association, Diagnostic and Statistical Manual of Mental Disorders
• Body mass index (BMI) >40 kg/m2 (FMD measurements can be inaccurate in severely obese patients)
• Chronic clinical diseases (e.g., coronary artery/peripheral artery/cerebrovascular diseases, diabetes, chronic kidney disease requiring dialysis, neurological disorders or diseases that may affect motor/cognitive functions [multiple sclerosis, Parkinson's disease, polio, Alzheimer's disease, dementia or other brain diseases of aging]), except hypertension and hyperlipidemia
• Regular vigorous aerobic/endurance exercise (>3 vigorous bouts/week).
• Not weight stable in the prior 3 months (>2 kg weight change) or unwilling to remain weight stable throughout study (rationale: recent weight change or weight loss can influence vascular function.
• Current treatment or recent cessation (< 3 mo) of hormone replacement therapy
• Moderate or severe peripheral artery disease (ankle-brachial index <0.7).
• A graded exercise test will be performed by all subjects, if there is physician concern or an adverse event, the subject will not participate in a maximal oxygen consumption (VO2max) test (this will be determined in accordance with stated contraindications for exercise testing provided by the American Heart Association).
• Thyroid disease that is not controlled by medications or <3 month's use of a particular medication and/or dosage (uncontrolled thyroid diseases are associated with alterations in vascular function).