A randomized control trial to establish the feasibility and safety of rapamycin treatment in an older human cohort: Immunological, physical performance, and cognitive effects.

Inhibition of the mechanistic target of rapamycin (mTOR) pathway by rapamycin (RAPA), an FDA-approved immunosuppressive drug used as a clinical therapy to prevent solid organ allograft rejection, enhances longevity in mice. Importantly, RAPA was efficacious even when initiated in relatively old animals, suggesting that mTOR inhibition could potentially slow the progression of aging-associated pathologies in older humans (Harrison et al., 2009; Miller et al., 2011). However, the safety and tolerability of RAPA in older human subjects have not yet been demonstrated. Towards this end, we undertook a placebo-controlled pilot study in 25 generally healthy older adults (aged 70-95 years); subjects were randomized to receive either 1 mg RAPA or placebo daily. Although three subjects withdrew, 11 RAPA and 14 controls completed at least 8 weeks of treatment and were included in the analysis. We monitored for changes that would indicate detrimental effects of RAPA treatment on metabolism, including both standard clinical laboratory assays (CBC, CMP, HbA1c) and oral glucose tolerance tests (OGTTs). We also monitored parameters typically associated with aging that could potentially be modified by RAPA; these included cognitive function which was assessed by three different tools: Executive Interview-25 (EXIT25); Saint Louis University Mental Status Exam (SLUMS); and Texas Assessment of Processing Speed (TAPS). In addition, physical performance was measured by handgrip strength and 40-foot timed walks. Lastly, changes in general parameters of healthy immune aging, including serum pro-inflammatory cytokine levels and blood cell subsets, were assessed. Five subjects reported potential adverse side effects; in the RAPA group, these were limited to facial rash (1 subject), stomatitis (1 subject) and gastrointestinal issues (2 subjects) whereas placebo treated subjects only reported stomatitis (1 subject). Although no other adverse events were reported, statistically significant decrements in several erythrocyte parameters including hemoglobin (HgB) and hematocrit (Hct) as well as in red blood cell count (RBC), red blood cell distribution width (RDW), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) were observed in the RAPA-treatment group. None of these changes manifested clinically significant effects during the short duration of this study. Similarly, no changes were noted in any other clinical laboratory, cognitive, physical performance, or self-perceived health status measure over the study period. Immune parameters were largely unchanged as well, possibly due to the advanced ages of the cohort (70-93 years; mean age 80.5). RAPA-associated increases in a myeloid cell subset and in TREGS were detected, but changes in most other PBMC cell subsets were not statistically significant. Importantly, the OGTTs revealed no RAPA-induced change in blood glucose concentration, insulin secretion, and insulin sensitivity. Thus, based on the results of our pilot study, it appears that short-term RAPA treatment can be used safely in older persons who are otherwise healthy; a trial with a larger sample size and longer treatment duration is warranted.

NF-kappaB elements associated with the Stat6 site in the germline gamma1 immunoglobulin promoter are not necessary for the transcriptional response to CD40 ligand.

Both germline transcription and switch recombination of heavy chain genes are likely to be regulated by cis elements binding transcription factors in the promoter regions of germline immunoglobulin genes. To identify cis-acting elements important in germline transcription of the murine gamma1 heavy chain gene, we have used a transgenic approach. Seventeen kb gamma1 immunoglobulin transgenes with mutations in three NF-kappaB sites in the gamma1 proximal promoter, a putative CD40 response element, are expressed well. Compared to wild-type transgenes, there is no deficiency in the expression of the transgenes with mutations of the three NF-kappaB sites after induction of splenic B cells with IL-4 alone, CD40L, or CD40L + IL-4. There may be a small reduction in the response of these mutant transgenes after induction with LPS + IL-4. We also prepared transgenes that were truncated at -150 (rather than -2100) and therefore included the wild-type Stat6 binding site at -123 and the three wild-type NF-kappaB sites. Nevertheless, gamma1 germline transcripts were not expressed from these transgenes. We conclude that the three proximal NF-kappaB sites are dispensable for expression of gamma1 germline transcripts under most conditions. However, cis-acting elements distal to -150 must be critical to this transcription.