Use of Muscle Spectroscopy to Evaluate Mitochondrial Dysfunction in HIV-Infected Patients

Inclusion Criteria Participants in Groups 1 and 2 may be eligible for this study if they: Are at least 18 years old. Participants in Group 1 (HIV-uninfected) may be eligible for this study if they: Are HIV-uninfected within 30 days prior to study entry. Participants in Group 2 (HIV-infected) may be eligible for this study if they: Are HIV infected. Have been taking an NRTI-containing anti-HIV drug regimen for 8 weeks or more prior to study entry. Have a nonexercise venous lactate level greater than 2 times the upper limit of normal (ULN) on 2 repeated measurements. Exclusion Criteria Participants in Groups 1 and 2 may not be eligible for this study if they: Have severe claustrophobia. Have severe symptoms that, in the opinion of the investigator, would interfere with the ability of participants to perform the exercise required for spectroscopy testing. Have hepatitis C or B, within 90 days prior to study entry. Have taken certain drugs within 30 days prior to study entry. Have a medical condition associated with chronic liver disease other than hepatitis C and B. Have consumed excessive amounts of alcohol in the past 12 months. Are pregnant or breast-feeding. Have a foreign object or metal in their body that would impair MRS testing. Have or have had peripheral vascular disease. Weigh 250 lbs or more. Have a family history of mitochondrial disease or have skeletal muscle disease, heart muscle disease, or nervous system conditions without a clearly defined cause that is not related to mitochondria. Participants in Group 1 (HIV-uninfected) may not be eligible for this study if they: Have any active medical condition. Use any prescription drugs, except for vitamins or oral contraceptives.