Metabolic Effects of Switching Kaletra to Boosted Reyataz

• Glucose Trafficking [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  6 month mean and standard deviation for glucose uptake into anterior thigh muscle as measured by FDG/PET scanning during euglycemic hyperinsulinemic clamp. During the hyperinsulinemic conditions of the clamp, glucose and 18-FDG [labeled glucose] are taken up by muscle. The quantity of 18-FDG taken up is measured by the PET scan. Although there are no well-accepted norms for this measurement, a higher value indicates that more glucose is being taken up by (or "trafficked to") muscle. Increased uptake of glucose indicates increased muscle insulin sensitivity.
  
  

• Insulin Sensitivity [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  6 month mean and standard deviation for insulin-stimulated glucose uptake (M) per unit insulin at 120 minutes as measured by euglycemic hyperinsulinemic clamp.
  
  
• Fasting Glucose [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  6 month mean and standard deviation for fasting glucose.
  
  
• Lipid Metabolism - Serum Triglyceride [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  6 month mean and standard deviation for serum triglyceride.
  
  
• Body Composition - Visceral Adipose Tissue [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  6 month mean and standard deviation for visceral adipose tissue (VAT) as measured by single slice computed tomography (CT) scan at the L4 pedicle (pedicle of 4th lumbar vertebra).
  
  
• Immune Parameters -- CD4 Count [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  6 month mean and standard deviation for CD4+ count.
  
  
• Liver Enzymes -- Aspartate Aminotransferase (AST) [ Time Frame: 6 months ] [ Designated as safety issue: Yes ]
  6 month mean and standard deviation for AST.
  
  
• Liver Enzymes -- Alanine Aminotransferase (ALT) [ Time Frame: 6 months ] [ Designated as safety issue: Yes ]
  6 month mean and standard deviation for ALT.
  
  
• Total Bilirubin [ Time Frame: 6 months ] [ Designated as safety issue: Yes ]
  6 month mean and standard deviation for total bilirubin.
  
  

The primary objective of this study is to determine tissue specific glucose trafficking in patients before and after switching from a regimen containing Lopinavir/ritonavir (LPV/r) to one containing atazanavir/ritonavir (ATV/r). Secondary outcome measures of interest will include insulin sensitivity determined by clamp testing, and lipid metabolism and hepatic glucose production assessed using stable isotope techniques. We hypothesize that switching protease inhibitor (PI) to ATV/r from LPV/r will result in direct increases in glucose uptake in muscle and visceral adipose tissue in association with improvements in overall whole body insulin sensitivity compared to remaining on LPV/r. We will complete a prospective randomized trial of Human Immunodeficiency Virus (HIV) infected patients who have been on a stable antiretroviral (ARV) regimen containing LPV/r for at least 6 months and who will be randomized to either switch to a regimen containing ATV/r or remain on LPV/r for 6 months. Each subject will complete Positron Emission Tomography (PET) 18-fluorodeoxyglucose (FDG) imaging during a hyperinsulinemic clamp study at baseline and 6 months after randomization.