This study will enroll people with type 2 diabetes. At a series of up to three baseline study visits, participants will have a blood collection, a glucose tolerance test, an echocardiogram to obtain images of the heart, and biopsies of muscle from the thigh and fat from the stomach. All participants will then receive atenolol once a day for 8 weeks. During Week 1, participants will receive a low dose of atenolol. They will then attend a study visit at the end of Week 1, and study researchers will examine how well participants are tolerating the medication. If the atenolol is well tolerated, the dose will be increased. Study researchers will call participants 1 week after any dosage changes to monitor for side effects. Blood collection will occur again at a study visit at Week 4. At Week 8, participants will then attend up to three study visits for repeat baseline testing. Participants will then be slowly tapered off of atenolol over a 1-week period.