Direct comparison of the acute in vivo effects of HIV protease inhibitors on peripheral glucose disposal

Abstract

The clinical use of HIV protease inhibitors (PIs) is associated with the development of peripheral insulin resistance. The incidence and degree of impaired glucose tolerance observed in treated patients vary considerably between drugs, however. To compare the ability of HIV PIs to alter peripheral glucose disposal acutely in a genetically identical model system at therapeutically relevant drug levels, healthy lean male rats previously naive to PI exposure were given ritonavir, amprenavir, lopinavir/ritonavir (4:1), or atazanavir by continuous intravenous infusion to achieve steady state drug levels of 10 or 25 muM rapidly. Under euglycemic hyperinsulinemic clamp conditions, a dose-dependent reduction in the peripheral glucose disposal rate (Rd) was observed with all the PIs except atazanavir. The rank order of sensitivity was ritonavir, lopinavir, and then amprenavir. Changes in skeletal muscle and heart 2-deoxyglucose (2-DOG) uptake correlated with reductions in Rd. All 3 of these PIs also produced significant reductions in 2-DOG uptake into primary rat adipocytes in vitro. Atazanavir had no effect on glucose uptake in vitro or in vivo. The in vivo potency of PIs to impair peripheral glucose disposal acutely correlates with the degree of insulin resistance observed in HIV-infected patients receiving these drugs. Preclinical testing of novel candidate PIs in a rodent model system may be useful in identifying the future risk of altering glucose homeostasis.

FIGURE 1.

Acute effects of PIs on adipocyte glucose uptake. Each of the indicated PIs was added to insulin-stimulated primary rat adipocytes 1 minute before adding 50 mM of [3H]-2-DOG. Cells were incubated for 1 minute at 37°C with gentle agitation before quenching the reaction by separating the cells and reaction mixture through dinonylphalate as described in the Methods section. Panels A and B represent separate sets of experiments. A, Lopinavir/ritonavir samples contained 2.5 and 6.25 mM of ritonavir together with 10 and 25 mM of lopinavir, respectively. Each data point represents the mean ± SE of 4 assays. *Statistical significance relative to vehicle-treated controls (P < 0.001, analysis of variance of the mean).

FIGURE 2.

Acute effects of PIs on peripheral glucose disposal. Euglycemic-hyperinsulinemic clamps were performed using 10 mU · kg^-1 · min^-1 of insulin. PIs were administered by constant intravenous infusion to maintain drug levels of 5 to 10 mM for “therapeutic” doses and 25 to 35 mM for “high” doses (see Table 1). Data represent the mean ± SE of 4 independent experiments per group. *P < 0.0001 as determined by analysis of variance of the mean.

FIGURE 3.

Acute effects of PIs on muscle glucose uptake. [3H]-DOG was injected into the arterial catheters 30 minutes before the conclusion of the euglycemic-hyperinsulinemic clamp experiments. Muscles were removed from the rats immediately after euthanasia and were analyzed for accumulation of radio-labeled 2-DOG-6-phosphate, as described in the Methods section. A, Soleus muscle. B, EDL muscle. C, Cardiac tissue. Rg' indicates glucose metabolism index. Values represent the means ± SE of 4 independent experiments. *P < 0.05 as determined by analysis of variance of the mean.