With regard to our primary endpoint, neither total bilirubin nor ATV status was significantly associated with FMD of the brachial artery. This is consistent with both the study by Flammer et al. and the SABAR (Switch to Atazanavir and Brachial Artery Reactivity) study by Murphy et al., which showed that switching to ATV from another PI, whether boosted with ritonavir or not, did not improve endothelial function measured using FMD after 24 weeks, despite significant improvement in lipid levels [13, 14]. It is conceivable that the effect of a modest increase in bilirubin in this population is masked by the ongoing heightened

inflammation resulting from chronic HIV infection. Indeed, with potent ART, inflammation and endothelial dysfunction do improve [18, 19], but not to SB431542 research buy normal levels, when compared with HIV-uninfected individuals [2, 19]. Further, participants included in this study did not have extremely elevated total bilirubin levels (median 1.8 mg/dL; IQR 1.1–2.6 mg/dL; minimum 0.3 mg/dL and maximum 5 mg/dL). Although seeing an effect with extreme hyperbilirubinaemia would be mechanistically intriguing, this would have uncertain clinical relevance. Another consideration is that the antioxidant effect of elevated bilirubin was outweighed by the oxidative stress induced by ART [20]. Although a different method for measuring endothelial function

was used, our results are Staurosporine mouse incongruent with the study by Dekker et al., in which ATV-induced hyperbilirubinaemia did improve endothelium-dependent vasodilation measured using forearm blood flow response to acetylcholine in participants with type II diabetes mellitus after 3 days [11]. In our study, perhaps an effect would have been seen if FMD had been measured earlier after ATV was initiated [median (IQR) duration on ATV in our study was 28.5 (16.8–47.7) months]. The clinical implication of a solely transient acute effect would also be questionable, however. Another consideration is that endothelial dysfunction is more pronounced in subjects with diabetes mellitus

than in our Benzatropine HIV-infected population and is why an effect was seen in this potentially higher risk group. To better assess whether the degree of endothelial dysfunction played a role in the association between total bilirubin level and FMD in our study, the correlation between total bilirubin level and FMD in those with the lowest FMD (FMD less than the median FMD of 3.3%) was determined. Total bilirubin was not correlated with FMD in this subgroup (Spearman correlation coefficient = 0.13; P = 0.38). With regard to our secondary endpoints, neither total bilirubin nor ATV status was associated with markers of inflammation, coagulation or oxidation, with the exception of fibrinogen. Fibrinogen levels were higher among participants taking ATV. This result is consistent with a study by Madden et al., where PI use was associated with elevated fibrinogen levels.