5071 Impact of Estrogen Replacement Therapy on Bone Health in a Novel Non-human Primate Model of Postmenopausal Women Living with HIV

Abstract Disclosure: K. Sauter: None. D.L. Takahashi: None. G. Webb: None. H. Hofmeister: None. O. Varlamov: None. J. Sacha: None. P. Kievit: None. Current antiretroviral therapy (ART) regimens have rendered HIV a manageable chronic condition rather than a fatal disease, with people who initiate ART soon after infection achieving nearly normal life expectancy. As a consequence of increased survival, more women living with HIV (WLWH) will now undergo menopause and be subject to a disease burden that reflects age along with adverse skeletal consequences of postmenopausal estrogen deficiency. In addition to known bone loss and increased fracture risk in postmenopausal women, ART also causes decreased bone mineral density. Therefore ART-suppressed WLWH may have a compounded detrimental effect on bone due to long-term ART treatment combined with menopause that may be attenuated with estrogen replacement. Eleven rhesus macaques were infected intravenously with SIVmac239M and received ART two weeks post-infection (PI). All animals were ovariectomized (OVX) at 35 weeks PI and received estrogen implants (n=6) or cholesterol implants (n=5). Weekly blood samples were collected and animals were monitored longitudinally for body composition including bone mineral content (BMC) via dual x-ray absorptiometry (DEXA). Infection with SIV caused a significant decrease, -8.2%, in pelvis BMC after 14 days of peak viremia with SIV. These changes were not observed in the BMC of spine or extremities. BMC remained suppressed by ∼7% for an additional 25 weeks PI during ART treatment. Measurement of circulating bone turnover markers (BTMs), osteocalcin and C-terminal telopeptide of type 1 collagen (CTX), decreased post infection without significant improvement after ART suppression. Induction of menopause via OVX and loss of estrogen induced a drastic increase in BTMs with a much larger increase in CTX, indicating potential global bone loss due to OVX. Post-implant, the control animals’ pelvis BMC continued to decrease to -20.9% and pelvis BMD to -9.3% indicating that OVX further exacerbated the effect of SIV and ART. However, animals that received estrogen implants demonstrated marked improvement in both measures to greater than baseline. SIV and subsequent long-term ART negatively impact pelvic BMC and BMD and this effect is compounded by menopause in our model of post-menopausal WLWH. However, estrogen replacement post-menopause may attenuate these detrimental bone effects despite long-term ART treatment. Presentation: 6/1/2024