Effects of atazanavir/ritonavir and lopinavir/ritonavir on glucose uptake and insulin sensitivity: demonstrable differences in vitro and clinically.

BACKGROUND

The HIV protease inhibitor (PI) atazanavir does not impair insulin sensitivity acutely but ritonavir and lopinavir induce insulin resistance at therapeutic concentrations.

OBJECTIVE

To test the hypothesis that atazanavir combined with a lower dose of ritonavir would have significantly less effect on glucose metabolism than lopinavir/ritonavir in vitro and clinically.

METHODS

Glucose uptake was measured following insulin stimulation in differentiated human adipocytes in the presence of ritonavir (2 micromol/l) combined with either atazanavir or lopinavir (3-30 micromol/l). These data were examined clinically using the hyperinsulinemic euglycemic clamp and oral glucose tolerance testing (OGTT) in 26 healthy HIV-negative men treated with atazanavir/ritonavir (300/100 mg once daily) and lopinavir/ritonavir (400/100 mg twice daily) for 10 days in a randomized cross-over study.

RESULTS

Atazanavir inhibited glucose uptake in vitro significantly less than lopinavir and ritonavir at all concentrations. Ritonavir (2 micromol/l) combined with either atazanavir or lopinavir (3-30 micromol/l) did not further inhibit glucose uptake. During euglycemic clamp, there was no significant change from baseline insulin sensitivity with atazanavir/ritonavir (P = 0.132), while insulin sensitivity significantly decreased with lopinavir/ritonavir from the baseline (-25%; P < 0.001) and from that seen with atazanavir/ritonavir (-18%; P = 0.023). During OGTT, the HOMA insulin resistance index significantly increased from baseline at 120 min with atazanavir/ritonavir and at 150 min with lopinavir/ritonavir. The area under the curve of glucose increased significantly with lopinavir/ritonavir but not with atazanavir/ritonavir.

CONCLUSIONS

Both glucose uptake in vitro and clinical insulin sensitivity in healthy volunteers demonstrate differential effects on glucose metabolism by the combination PI atazanavir/ritonavir and lopinavir/ritonavir.