Bone turnover markers in children living with HIV remaining on ritonavir-boosted lopinavir or switching to efavirenz.

Introduction: We previously found lower bone mass but similar bone turnover in pre-pubertal children living with HIV (CLWH) on a ritonavir-boosted lopinavir (LPV/r)-based vs. efavirenz-based antiretroviral therapy regimen 2 years after switch. Here, we evaluate if bone turnover differed between the groups close to the time of switch.

Methods: Samples from 108 children remaining on LPV/r and 104 children switched to efavirenz were available for analysis 8 weeks post-randomization. Bone turnover markers, including C-telopeptide of type 1 collagen (CTx), procollagen type-I N-terminal propeptide (P1NP), and osteocalcin were measured. Markers of immune activation were also measured, including IL-6, TNF-alpha, soluble CD14 and high-sensitivity C-reactive protein (CRP).

Results: Eight weeks post-randomization, we did not detect differences in CTx (1.42 vs. 1.44 ng/mL, p = 0.85) or P1NP concentrations (622 vs. 513 ng/mL, p = 0.68) between treatment groups. At 8 weeks, the treatment groups also had similar levels of IL-6, TNF-alpha, soluble CD14 and high-sensitivity CRP. Osteocalcin (ng/mL) was higher in the LPV/r than efavirenz group both at 8 weeks (88.6 vs. 67.3, p = 0.001) and 2 years (67.6 vs. 49.8, p = 0.001).

Conclusions: Overall, we failed to detect difference in bone turnover by P1NP and CTx in virologically-suppressed CLWH on different regimens at a time point close to the switch. We did observe higher levels of total osteocalcin in children remaining on LPV/r compared to children switched to efavirenz. Future studies should focus on uncovering the mechanism and determining whether perturbation in undercarboxylated osteocalcin could explain some of the bone side effects noted with protease inhibitors.