After discussion with the Data Safety Monitoring Board and NIH, the randomized clinical trial involving metformin vs. placebo is terminated due to slow enrollment in the setting of the COVID-19 pandemic.

This study will investigate if metformin can help people with obesity and high pressures inside their lung blood vessels. Metformin is approved by the U.S. Food and Drug Administration (FDA) to treat diabetes, but metformin is not approved by the FDA to treat pulmonary hypertension.

This study will examine whether Metformin will improve the high pressure inside lung blood vessels in people who are obese. The study will help understand the effect of metformin on pressures inside lung blood vessels.

Obesity can predispose people to develop high pressures inside their lung blood vessels, a condition called pulmonary hypertension, Pulmonary hypertension in turn, can lead to shortness of breath and other health complications such as heart failure. In this study, we seek to identify individuals at risk for the development of high pressures inside lung vessels based on BMI and dyspnea grade 1.

Participants will be screened by echocardiography to estimate pulmonary pressures. Potential participants will undergo invasive cardiopulmonary exercise testing with hemodynamic monitoring, in order to identify individuals with abnormal pulmonary vascular function either at rest or during exercise. Patients who have undergone clinically-indicated cardiopulmonary exercise testing and meet inclusion/exclusion criteria will also be recruited. Those with abnormal pulmonary vascular function will be randomized to receive Metformin or placebo for a total of 3 months under an IND exemption. The primary outcomes include the effect on pulmonary vascular function at rest and during exercise. Secondary outcomes include change in pulmonary artery endothelial cell phenotypes.

Inclusion Criteria:

• Age 30-80 years
• History of obesity and current BMI ≥ 25 kg/ m2 for study volunteers or BMI ≥ 25 kg/ m2 for those with clinically indicated CPET or known HFpEF
• History of Dyspnea (Grade 1 or more)
• Able to provide informed consent and willing to comply with study

Exclusion Criteria:

• History of diabetes mellitus
• History of primary pulmonary arterial hypertension
• History of moderate to severe COPD
• History of severe Obstructive Sleep apnea
• History of renal disease (eGFR< 45 mL/min/1.732)
• History of severe liver disease
• History of cardiovascular disease (recent heart attack or stroke) except known HFpEF
• History of blood clot in lung
• History of Splenectomy
• History of Active Cancer
• Platelets count of < 75,000
• International normalized ration (INR) of > 1.5
• History of recent anemia (HB < 9g/dL)
• Current use of Metformin
• Prior LVEF < 50% on echocardiogram
• Indication of severe valvular disease on echo
• Pregnant or planning to become pregnant in next 4 months
• History of HIV infection

Baseline population includes participants who completed the assigned arm (metformin or placebo) and were included in analysis.

Adverse event data were collected for the metformin and placebo groups over the course of the 3 months on randomized assignment to study drug.

After discussion with the Data Safety Monitoring Board and NIH, the randomized clinical trial involving metformin vs. placebo was terminated due to slow enrollment in the setting of the COVID-19 pandemic, resulting in small numbers of subjects analyzed.