Effect of Mammalian Target of Rapamycin Inhibition and Other Metabolism Modulating Interventions on the Elderly: Immune, Cognitive, and Functional Consequences

Inhibition of the mTOR pathway by rapamycin (RAPA), an immunosuppressive drug used as adjunct therapy in preventing solid organ allograft rejection, enhances longevity in mice. Importantly, RAPA was efficacious even when initiated in relatively old animals. Thus, it has been suggested that RAPA could be used therapeutically in humans to slow age-associated pathologies. Indeed, improvements in cognition, control of tumorigenesis, and enhancing certain aspects of immunity have been demonstrated in RAPA treated murine models. Moreover, long-term RAPA delivery in older mice is associated with changes in immune reactivity not evident in younger animals. Investigators propose to expand to a larger cohort of older humans to test the hypothesis that RAPA treatment, even in very old individuals, will result in simultaneous improvement in systems known to be negatively affected by aging. Investigators will focus on the immune system, cognition, and physical parameters of healthy aging, such as walking speed. Investigators will recruit healthy volunteers, aged 75-95 years, and randomize them to either RAPA or placebo, controlling for gender, ethnicity, and age. These groups will be used to address the following specific aims: Aim 1. Assess general parameters of immune health before and after RAPA treatment; these include serum inflammatory cytokines, PBMC subsets (naïve vs memory T cells, TREGS, etc.), and polyclonal T cell activation potential. Aim 2. Test the effects of RAPA treatment on responsiveness to a vaccine challenge; both B cell (antibody) and T cell responses will be assessed. Aim 3. Correlate immune function rejuvenation with cognitive and physical function measures in subjects treated with RAPA or placebo. Aim 4. Collect pilot data on effect of RAPA on cardiovascular function. Cognition will be assessed by three different testing tools (EXIT25, SLUMS, and TAPS). Physical performance will be measured by grip strength and 40 foot timed walks, parameters known to correlate with healthy aging. Measures of cardiovascular function (Substudy D) using MRI of the heart to evaluate diastolic function and brain MRI to analyze cerebral blood flow, with measures of pulse wave velocity and endothelial function using laser doppler flowmetry will be performed. In addition to scoring positive outcomes, investigators will assess whether there are adverse changes in clinical laboratory tests that could compromise the safe use of RAPA therapeutically in older individuals. The long-term goal is to assess whether RAPA is safe to use in an elderly population, while also being efficacious in slowing, or even reversing, the aging process.