Enrollment of participants will be conducted at both Wake Forest and Atrium Health (approximately 40 participants at each site) following assessment of eligibility criteria and willingness to participate in the trial. Eligibility criteria are designed to target the population under study and exclude participants unable to safely take the study intervention or undergo study procedures. Informed consent will be obtained from qualified participants. Participants will complete baseline assessments before masked, random assignment to metformin or placebo. The assigned study medications will be dispensed by the research pharmacy. Participants will take assigned metformin or placebo for a treatment period of 20 weeks, starting at 500mg/day and escalating over the first 3 weeks to a target dose of 1500mg/day. Participants will be contacted every 2 weeks for assessment of adverse events, side effects, and adherence. At week 4, participants will be seen in clinic for safety laboratory assessments. At week 20, participants will complete follow-up assessments by an assessor blinded to treatment group.
Met-PEF will be a randomized, double-blind, placebo-controlled trial to examine the effects of 20 weeks of 1500 mg/day of metformin on physical function, quality of life (QOL), microbiome diversity, leaky gut, and systemic inflammation in patients with 80 older patients with heart failure with preserved ejection fraction (HFpEF).