Coronary flow reserve (CFR, calculated as the ratio of hyperemic over rest myocardial blood flow) is emerging as a powerful quantitative prognostic imaging marker of clinical cardiovascular risk. CFR provides a robust and reproducible clinical measure of the integrated hemodynamic effects of epicardial coronary artery disease (CAD), diffuse atherosclerosis, and microvascular dysfunction on myocardial tissue perfusion. Inflammation is a key mediator of this constellation of abnormalities, affecting the entire coronary vasculature, but no clinical trial to date has shown that directly reducing inflammation lowers cardiovascular event rates. As such, the recently launched Cardiovascular Inflammation Reduction Trial (CIRT) provides a unique opportunity for mechanistic investigation of the impact of anti-inflammatory therapy on changes in CFR as a reflection of coronary vascular dysfunction, which may precede clinical outcomes, particularly in patients at high-risk of events. The investigators are ideally positioned to examine the impact of inflammation on CFR, having extensive experience in both the quantitation of CFR using clinically-integrated dynamic positron emission tomography (PET) and the ability to assess its association with cardiovascular outcomes. The central hypothesis of this ancillary proposal, CIRT-CFR, is that reducing systemic inflammation using low-dose methotrexate (LDM) will, compared to placebo, quantitatively improve myocardial blood flow and coronary flow reserve as measured by PET over one year, in stable CAD patients with type 2 diabetes or metabolic syndrome enrolled in CIRT. In so doing, improvement in coronary vasoreactivity, endothelial function, and tissue perfusion may have beneficial effects on myocardial mechanics, left ventricular deformation and function and, ultimately, symptoms and prognosis.