The study will utilize a randomized crossover placebo-controlled study design. Subjects will come to the research laboratory before, during and after the administration of either a placebo or Simvastatin for one month at a standard therapeutic dosage of 40 mg per day. Subjects will be carefully monitored for any adverse effects by examining blood samples at baseline and 4 weeks for markers of liver, kidney, or muscle damage. If the subject's responses to one month of Simvastatin therapy are minimal, such that the decrease in LDL cholesterol is less than 25%, we will ask them to participate in an additional 2 weeks of Simvastatin administration at a dosage of 80 mg per day. During the baseline, the visit at 4 wks, and during the additional visit (if necessary) subjects will undergo the following experimental measurements and procedures, which will take approximately four hours. All measurements and procedures will be performed by the principal investigator and trained research personnel.