Metformin for HIV Inflammation

Inclusion Criteria: * HIV+ * on suppressive ART stable for \> 1 year * Age \> 45 years * Ability and willingness to provide written informed consent Exclusion Criteria: * Uncontrolled chronic medical condition or cancer * Acute illness within 2 weeks of entry * Diagnosis of diabetes or impaired fasting glucose * Chronic diarrhea * Known hypersensitivity or contraindication to metformin use * Hepatitis C co-infection * Serum B12 level below the reference normal range as listed by the commercial laboratory (Diagnostic Laboratory Services) * Pregnancy, or intent to become pregnant * Any immunomodulator, HIV vaccine, any other vaccine, or investigational therapy within 30 days of study entry. * Current or past history of coronary artery disease or congestive heart failure * Resting heart rate \> 100 beats/min * Presence of conduction abnormalities or pathologic arrhythmia on EKG * The following lab values: Hemoglobin \< 9.0 g/dL; Absolute neutrophil count \< 1000/μL; Platelet count \< 50,000/μL; and AST (SGOT) and ALT (SGPT) \> 5x ULN * Calculated creatinine clearance (Cockcroft and Gault) \< 60 ml/min * Patients over 450 lbs * History of iodine allergy or X-ray contrast allergy * History of allergy to metoprolol * Active or recent past history (within past 2 years) of illicit substance or alcohol use or abuse which, in the judgment of the Investigator, will interfere with the patient's ability to comply with the protocol requirements * Patients in whom there are other reasons that the CAC/CTA procedure is contra-indicated or who are at higher risk of adverse events * Patients, who, in the opinion of the Investigator, are unable to comply with the dosing schedule and protocol evaluation or for whom the study may not be advisable