The number of older adults is projected to increase dramatically by 2050. Aging-related diseases and conditions still seriously compromise the quality of life among most older adults. Several pharmaceutical agents, such as metformin, have been tested to extend lifespan and delay aging-related diseases and dysfunctions in mice. Metformin, a biguanide antidiabetic drug, reduces the risk for developing type-2 diabetes in persons at risk by over one-third with few adverse effects (e.g., gastrointestinal irritation). Metformin prevents type-2 diabetes primarily through decreasing hepatic glucose synthesis, as well as enhancing insulin sensitivity and increasing peripheral glucose uptake. The molecular mechanisms remain unclear, although a number of potential mechanism such as activation of AMP-activated protein kinase (AMPK) and inhibition of mitochondrial glycerophosphate dehydrogenase have been proposed. The fact that metformin treatment in persons with type-2 diabetes has been associated with reduced risk of other aging-related diseases and conditions, including cardiovascular disease, cancer and cognitive decline supports the possibility of the beneficial effects of metformin on healthy aging. It is imperative to capitalize on these leads to extend health span among older adults.
To translate animal findings to human intervention trials, appropriate aging biomarkers are needed. Methylomic and transcriptomic profiles in relevant cells may reflect molecular features that mediate effects of both genetic and environmental factors on aging-related functional decline and disease. The roles of monocytes have been implicated in development of many aging-related diseases such as cardiovascular disease, cancer and neurodegenerative disease. In a cross-sectional association study of 1,200 monocyte samples, we identified 1,794 age-associated methylation sites and 2,704 age-associated transcripts, which were over-represented in two networks (autophagy and oxidative phosphorylation) and suggestive of decline in those functions with age. Both autophagy and oxidative phosphorylation are considered as key contributors to the aging process, and their dysfunctions have been linked to aging-related diseases. Changes in these aging-related omic biomarkers may be early indicators of cellular damage or disruption that eventually leads to age-related dysfunctions. Assessment of these aging biomarkers in response to therapeutic intervention may also provide molecular insight for personalizing treatment. The investigators propose a pilot study to examine changes in aging-related omic profiles after 3 months of metformin treatment in 35 monocyte samples from older adults using a randomized, double-blind, placebo-controlled crossover study design.
Our overarching goal of the pilot study is to evaluate the utility of using the aging-related omic biomarkers as an indicator of pharmacologic responses in the anti-aging therapeutic intervention trials through the following specific aims. Although this pilot study does not have sufficient power to definitively test all the aims, it will provide essential preliminary data for developing a full scale research program.
* Aim 1A: To test the effects of the metformin treatment on transcriptomic profiles and related functional changes in human monocytes,
* Aim 1B: To explore the effects of the metformin treatment on methylomic profiles in human monocytes,
* Aim 2: To investigate the longitudinal relationship between transcriptional and functional changes in human monocytes during the metformin treatment and
* Aim 3: To test the effects of the metformin treatment on frailty and other aging-related physical and cognitive measures and investigate the longitudinal relationship between these changes and transcriptional changes.
A randomized, double-blind, placebo-controlled crossover trial in 30 participants using metformin and matching placebo will be used. In the absence of a treatment by sequence interaction effect, this design can increase study power for evaluating treatment effects by allowing each participant to be his/her own control. The period effect may be minimum because the primary outcomes, methylation and transcriptional measures, are relatively stable overtime.
