The purpose of this study is to determine if treatment with a drug called fenofibrate, which is a PPAR-alpha agonist and controls how the heart metabolizes fats, will reverse the age-related decline in cardiac fat metabolism and mechanical function.

In older Americans, cardiovascular disease is the leading cause of death and disability. It has been shown recently that with aging the human heart exhibits a decline in myocardial fatty acid utilization (MFAU) and oxidation (MFAO) and that these metabolic changes are paralleled by a decline in mechanical function. It has also been shown that peroxisome proliferator activated receptor alpha (PPAR-alpha) activates the expression of the genes encoding enzymes involved in mitochondrial fatty acid transport and oxidation. There is both indirect and direct evidence that PPAR-alpha-mediated responses decrease with age. Consequently, we hypothesize that changes in fatty acid in the aging heart may be mediated, at least in part, via a decline in PPAR-alpha-mediated responses. Thus, administration of a PPAR-alpha agonist to older humans will result in a shift in cardiac fatty acid metabolism to that more closely seen in younger humans and this shift will be paralleled by an improvement in cardiac mechanical function.

To prove or disprove this hypothesis, we will determine, in aged and young healthy volunteers, whether stimulation of PPAR-alpha using the partial agonist, fenofibrate, shifts myocardial substrate utilization by increasing MFAU and MFAO, and whether these changes are associated with an increase in left ventricular function. Study participants will have 4 clinic visits, each lasting approximately 5 hours.

Inclusion Criteria:

• Aged 60-75 or 21-35
• Normal glucose tolerance test
• Normal plasma fasting lipid panel (fasting total cholesterol less than 220 mg/dL)
• Normal rest/stress echocardiogram
• BMI (body mass index) less than 30 kg/m2
• Must be sedentary (active, but do not engage in regular exercise or jobs that require strenuous exertion)

Exclusion Criteria:

• Coronary artery disease
• High blood pressure
• Current smoker
• Diabetes mellitus
• Cardiovascular disease (signs and symptoms of any kind)
• Pregnant or breastfeeding