Alzheimer's disease (AD) and osteoporosis are common chronic conditions of aging. Although several studies have reported an association between the 2 conditions, there is limited information on tissue-level mechanisms. In the current study, we performed unbiased proteomics on thoracic vertebral samples collected from female participants enrolled in the religious orders study (ROS) and Rush Memory and Aging Project (MAP) cohorts to assess bone tissue-level changes associated with AD and other dementia-associated neuropathologies. Cognitive functioning and other participant characteristics were collected as part of ROSMAP study visits. Post-mortem evaluations assessed the burden of β-amyloid and paired helical filament tau (PHFtau) tangles, and other common age-related neuropathologies. A total of 45 bone samples were utilized from 19 female participants with a clinical diagnosis of AD dementia and 26 without AD dementia. The association between bone tissue protein abundance and cognition measured proximate to death, as well as neuropathologic indices, were evaluated using linear regression or logistic regression models, as appropriate. Bone tissue abundance of minichromosomal maintenance protein 3 (MCM3) and ubiquitin carboxyl-terminal hydrolase 24 (USP24) were positively associated with cognition and negatively associated with PHFtau tangle density. MCMC3 was also associated with cerebral arteriosclerosis, while USP24 was associated with cerebral amyloid angiopathy. Our findings suggest that processes regulating bone cell division may be involved in the link between brain and bone aging in a relationship that may not be specific to AD.

Background: We examined the cross-sectional relationship between cardiovascular disease (CVD) risk, history of falls, and the number of falls in the past year in the US multicenter MACS/WIHS Combined Cohort Study (2020-2022) of men and women without HIV (MWOH/WWOH) and men and women with HIV (MWH/WWH). Setting/methods: CVD risk was assessed by pooled cohort equation 10-year risk scores and categorized into 4 levels. Self-reported falls outcomes (recent fall, not recent fall, one fall, multiple falls) were assessed using a standardized protocol. Odds ratios of falls were measured using multinomial regression models stratified by sex and adjusted for ethnicity, education attainment, alcohol consumption, body-mass index, fall-risk medications, physical activity, and HIV serostatus. Results: There were 2723 participants, 35% were men (577 MWH, 360 MWOH) with a median age of 58 (IQR: 14) years. Women represented 65% (1271 WWH, 515 WWOH) with a median age of 55 (IQR: 11) years. In sex stratified multinomial adjusted models, among men, high CVD risk (vs. low risk) was significantly associated with a recent fall (vs. never fall) (aOR: 3.12, 95% CI: 1.59 to 6.13) and one fall (vs. no fall) in past year (aOR: 3.66; 95% CI: 1.45 to 9.21). Among women, high CVD risk was only significantly associated with multiple falls (vs. no fall) in past year (aOR: 2.06; 95% CI: 1.24 to 3.43). Conclusion: Our findings highlight the importance of integrating fall-risk assessments into CVD management, particularly for men and women with living with HIV and high CVD risk, and the need for targeted, gender-responsive fall prevention strategies in clinical practice.

Neutron time-of-flight imaging can provide a unique contrast mechanism of crystalline properties. Recently, computed tomography scans using time-of-flight instruments have been used to study structural and spectral characteristics of samples in 3D. To address the challenge of long measurement times associated with hyperspectral neutron computed tomography, the Oak Ridge National Laboratory neutron imaging team has recently demonstrated an autonomous system which can significantly reduce the measurement time by enabling high quality reconstructions from a sparse set of measurements. Some of the core components of such systems are the novel tomographic reconstruction algorithms including those based on artificial intelligence methods. In this work, a new training method is proposed to improve the performance of the artificially intelligent CT reconstruction algorithms. This training method can improve the quality of the reconstruction from very sparse time-of-flight scans. Our method helps hyperspectral tomography systems to obtain high-quality reconstructions with sparse scanning, which can potentially enable hyperspectral neutron computed tomography with reasonable acquisition times and particularly impact research projects which need to scan multiple similar sample beamlines such as the newly constructed VENUS beamline at the Spallation Neutron Source.

Bisphosphonates (BPs) are widely used to treat bone complications, yet their impact on the coupling between resorption and formation during cortical bone remodeling remains incompletely understood. We investigated associations between short-term alendronate treatment and osteoclast morphology, intracortical pore dynamics, and osteoprogenitor organization in a synchronized rat model of endo- and intracortical bone remodeling induced by lactation and dietary calcium restriction. Twenty-four lactating Sprague Dawley rats were randomized to vehicle, alendronate (28 μg/kg, twice weekly), or raloxifene (1 mg/kg, five times weekly) with raloxifene serving as a comparative control, for seven days under a low-calcium diet. Femurs were analyzed by micro-CT, histomorphometry, and multiplex RNA in situ hybridization combined with AI-driven image analysis. Alendronate was associated with a higher proportion of eroded pores (29% vs. 12% in controls) and lower density of formative pores (5.2 vs. 10.0 pores/mm2), indicating a prolonged reversal-resorption phase. Osteoclasts on endocortical surfaces were significantly larger (208 ± 37 μm2vs. 146 ± 46 μm2) and contained more nuclei (2.8 ± 0.40 nuclei vs. 2.2 ± 0.46 nuclei) under alendronate treatment, consistent with enhanced fusion. Osteoprogenitor abundance and spatial organization did not differ between treatment groups. Region-specific structural differences included increased midshaft porosity and larger distal metaphyseal cortical area in alendronate-treated rats. Raloxifene was associated with minimal differences on early remodeling events. Together, these findings support the interpretation that short-term bisphosphonate treatment is associated with early alterations in cortical remodeling dynamics under high-turnover conditions and highlight the importance of site-specific evaluation within defined physiological remodeling contexts.

Abstract Background Approximately 5,000 women living with HIV give birth each year, with perinatal transmission occurring in less than 1% of cases. The World Health Organization (WHO) recommends dolutegravir (DTG) as first and second line antiretroviral therapy (ART), readily crossing the placenta, resulting in persistent exposure throughout development. In adults, DTG-based ART has been linked to metabolic changes, including alterations in bone mineral density and body composition. The effects of DTG exposure on bone development and body composition trajectories in HIV-exposed uninfected (HEU) children are currently unknown. Methods Female C57BL/6J mice (8–10 weeks old) were mated with 3–4-month-old males. Dams were assigned to either dolutegravir/tenofovir disoproxil fumarate/lamivudine (DTG/TDF/3TC) infused pellets (ART) or control pellets from mating until weaning at postnatal day (PND) 28. Offspring body weights were recorded from PND15 to 86. Body composition was assessed using DEXA at PND36 and PND50. At PND28, circulating leptin and adiponectin were measured, and visceral adipose tissue gene expression (leptin and PPARγ) was assessed by qPCR. Results Maternal exposure to DTG-based ART was associated with increased body weight in both sexes, with larger differences in males (PND36: Males 20.28 ± 0.6 g vs 19.16 ± 0.5 g, p = 0.03; Females 17.15 ± 0.4 g vs 16.41 ± 0.3 g, p = 0.05). DEXA analysis demonstrated higher lean mass (PND50: Males 11.5 ± 0.4 cm2 vs 11.0 ± 0.3 cm2, p = 0.04; Females 10.8 ± 0.3 cm2 vs 10.4 ± 0.2 cm2, p = 0.08) and increased fat area (PND50: Males 4.0 ± 0.2 cm2 vs 3.5 ± 0.2 cm2, p = 0.02; Females 3.3 ± 0.1 cm2 vs 3.0 ± 0.1 cm2, p = 0.07) in ART-exposed pups compared to controls. Bone mineral content was elevated in ART-exposed offspring at PND36 and PND50 (PND50: Males 0.55 ± 0.02 g vs 0.48 ± 0.02 g, p = 0.01; Females 0.50 ± 0.01 g vs 0.44 ± 0.01 g, p = 0.02). Serum adiponectin showed a significant increase in ART-treated males (p = 0.02), with a trend toward increased circulating leptin in both treated sex groups. Visceral adipose tissue showed greater adipocyte differentiation in control pups, supported by elevated leptin and PPARγ expression. Conclusion Perinatal exposure to DTG/TDF/3TC during pregnancy and breastfeeding alters growth, body composition and adipose transcriptional profiles in offspring. This suggests maternal ART may shape early-life metabolic programming, highlighting the importance of monitoring outcomes in HEU children.

Abstract Musculoskeletal (MSK) pain is a chronic age-related condition. People with HIV (PWH) report high rates of chronic pain—with MSK pain reported as the most common source—and joints reported as the most common site. As PWH age, MSK-related pain will likely emerge as a growing clinical and quality of life challenge for patients and providers. This review summarizes what is known about MSK pain in PWH and identifies key knowledge gaps. Many well-established risk factors for MSK pain in clinical populations are even more prevalent in PWH, yet few published studies have focused on MSK pain in PWH. Most do not include well-matched comparisons to determine the direct effect of HIV and antiretroviral therapy. It remains unclear how the complex mix of biopsychosocial factors may accelerate or worsen MSK pain onset, severity, and chronicity and in turn, how best to target safe and effective chronic MSK pain management.

PURPOSE OF REVIEW:Osteoporosis and fragility fractures continue to be a concern for aging people living with HIV (PLWH), despite newer antiretroviral (ART) formulations that are associated with reduced bone toxicity. The aim of this review is to evaluate recent literature focusing on estimates of osteoporosis and fractures in various study populations, efficacy of current fracture risk assessment tools, and interventions to improve bone health outcomes. RECENT FINDINGS:Prevalence of low bone mineral density (BMD) remains higher among PLWH globally, with new estimates ranging from 24 to 59%. The FRAX tool underestimates rate of major osteoporotic fractures in PLWH; some studies suggest that modifications can improve accuracy. Bone quality assessments with trabecular bone score may also improve prediction of vertebral fractures in PLWH. Preexposure prophylaxis (PrEP) with TDF/FTC is generally safe for maternal and infant bone health. Denosumab treatment effectively improves bone mass in PLWH. SUMMARY:Despite advancements in ART, osteoporosis and fragility fractures remain common among PLWH. There is a need for continued research on development of fracture risk assessment tools including use of clinical data, imaging studies and biomarkers, and implementation of preventive and treatment strategies for at-risk subgroups.

BACKGROUND:Weight gain is common in treatment naïve people with HIV (PWH) initiating antiretroviral therapy (ART). The mechanisms driving this weight gain are unclear. The current study tested the hypothesis that bone-derived hormones are associated with weight gain with ART initiation and that the associations are antiretroviral (ARV) specific. METHODS:Plasma samples were obtained from the Advancing Clinical Therapeutics Globally (ACTG) study A5260s, in which treatment naïve PWH were initiated on tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) plus either atazanavir/ritonavir (ATV/r), darunavir/ritonavir (DRV/r), or raltegravir (RAL). Plasma levels of bone-derived hormones, undercarboxylated osteocalcin (ucOCN), lipocalin-2 (NGAL), and sclerostin and body weight were measured at baseline and 48-weeks after ART initiation. The associations between change in bone-derived hormones and weight with ART initiation were assessed using linear regression models adjusted for age, sex, race, baseline viral load, and CD4 + cell count change. RESULTS:Increases in ucOCN and decreases in NGAL were associated with weight change in PWH initiating ART. Sclerostin was not associated with weight change. When assessed as a function of ART, both ucOCN and NGAL were associated with weight for participants initiating RAL-based ART, but not ATV/r or DRV/r. After adjustment, the association between ucOCN and weight was no longer significant, while the association with NGAL remained statistically significant in RAL recipients. CONCLUSIONS:This study suggests links between bone-derived hormones and ART induced weight gain in PWH and demonstrates that this relationship is influenced by specific antiretrovirals.

Disclosure: S.M. Cohen: None. J. Sun: None. F.J. Palella: None. J.E. Lake: None. S.L. Koletar: None. N.L. Haw: None. R.D. Ross: None. T.T. Brown: None. Background: People living with HIV (PLWH) experience higher rates of osteoporosis and fractures as they age compared to the general population, though mechanisms connecting HIV to bone loss remain incompletely understood. It is thought that HIV-related chronic inflammation alters bone metabolism—potentially via sclerostin/Wnt/β-catenin signaling, which regulates bone formation, or the RANK-RANK ligand (RANKL)/osteoprotegerin (OPG) axis, which regulates bone resorption. We hypothesized that sclerostin, OPG, and RANKL levels would be altered in PLWH and associated with BMD, inflammation, and HIV-specific factors. Methods: In a sub-study of the Multicenter AIDS Cohort Study, we enrolled 204 men with HIV on antiretroviral therapy (ART) and 204 men without HIV, all aged 50-69 years. Participants underwent dual-energy X-ray absorptiometry (DXA) scans at the lumbar spine (LS), total hip (TH), and femoral neck (FN), morning phlebotomy, and a detailed assessment of osteoporosis risk factors. We used the Wilcoxon Rank-Sum test to compare the two groups and multivariable linear regression to determine associations of sclerostin, OPG, and RANKL concentrations with 1) BMD, 2) inflammatory markers, and 3) HIV-1 viral load and nadir CD4+ count among PLWH. We adjusted for HIV and hepatitis C virus serostatus, demographic and behavioral covariates, osteoporosis risk factors, and ART types. Results: The median age was 60 years and median BMI was 25.3 kg/m2; these were similar by HIV serostatus. Men who were PLWH had significantly lower TH BMD (p=0.03), but LS and FN BMD did not differ between the two groups (LS p=0.86, FN p=0.30). PLWH had higher plasma OPG concentrations (p=0.03), lower RANKL concentrations (p=0.001), and higher soluble TNF-α receptor (sTNF-R) 1 and 2 concentrations (sTNF-R1 p=0.01, sTNF-R2 p<0.001). OPG and RANKL concentrations were both were positively associated with sTNF-R concentrations (OPG vs. sTNF-R1 p<0.001, OPG vs. sTNF-R2 p=0.003, RANKL vs. sTNF-R1 p=0.001, RANKL vs. sTNF-R2 p=0.002). However, OPG and RANKL concentrations were not associated with BMD. Sclerostin concentrations were not associated with sTNF-R concentrations, but lower sclerostin concentrations were associated with lower BMD at all sites regardless of HIV serostatus (LS p<0.001, TH p<0.001, FN p<0.001). Conclusion: Sclerostin concentrations were associated with BMD in men with and without HIV, which suggests that sclerostin is a marker of bone mass and osteocyte number. Circulating concentrations of OPG and RANKL were associated with HIV serostatus and systemic inflammation, but not with bone mineral density, among men with or at risk for HIV. These findings suggest that immune dysfunction in PLWH contributes to dysregulation of the RANK-RANKL/OPG axis, but these changes are not associated with changes in bone mass. Presentation: Saturday, July 12, 2025

Introduction Joint pain is amongst the most common and disabling form of chronic pain globally and is more frequently reported by women than men. Whether joint pain is more prevalent among women with versus without HIV (WWH/WWoH) and differentially contributes to frailty phenotypes and physical, mental, and social functional impairment is unknown. Methods The Common Data Elements (CDE) Pain, Enjoyment, and General Activity (PEG) instrument was used to assess and compare joint pain in Chicago midlife WWH versus WWoH and its association with key outcomes (frailty, depressive symptoms, anxiety, and loneliness) using stepwise multivariable models. Results PEG was assessed in 179 WWH and 81 WWoH. Overall, 42% of women reported moderate/severe pain, which was more commonly reported in WWH than WWoH (44.1 v. 38.3%) but did not reach statistical significance. Women with moderate/severe joint pain, compared to those with no/mild joint pain (58%) were more likely to be pre-frail/frail (aOR 3.05; CI: 1.65-5.63) and report greater depressive symptomology (aOR 2.42; CI: 1.31-4.47), anxiety (aOR 3.38; CI: 1.52-7.43), and loneliness (aOR 1.84; CI: 1.02-3.29). Conclusions Joint pain is highly prevalent in mid-life WWH and WWoH and is associated with greater physical, mental, and social health burdens. Incorporating the PEG as a screening tool in clinical practice may help identify women who would benefit most from joint pain interventions to enhance functional capacity. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The contents of this publication are solely the responsibility of the authors and do not represent the official views of the National Institutes of Health (NIH). MWCCS (Principal Investigators): Atlanta CRS (Cecile Lahiri, Anandi Sheth, and Gina Wingood), U01-HL146241; Baltimore CRS (Todd Brown and Joseph Margolick), U01-HL146201; Bronx CRS (David Hanna and Anjali Sharma), U01-HL146204; Brooklyn CRS (Deborah Gustafson and Tracey Wilson), U01-HL146202; Data Analysis and Coordination Center (Gypsyamber DSouza, Stephen Gange and Elizabeth Topper), U01-HL146193; Chicago-Cook County CRS (Mardge Cohen, Audrey French, and Ryan Ross), U01-HL146245; Chicago-Northwestern CRS (Steven Wolinsky, Frank Palella, and Valentina Stosor), U01-HL146240; Northern California CRS (Bradley Aouizerat, Jennifer Price, and Phyllis Tien), U01-HL146242; Los Angeles CRS (Roger Detels and Matthew Mimiaga), U01-HL146333; Metropolitan Washington CRS (Seble Kassaye and Daniel Merenstein), U01-HL146205; Miami CRS (Maria Alcaide, Claudia Martinez, and Deborah Jones), U01-HL146203; Pittsburgh CRS (Jeremy Martinson and Charles Rinaldo), U01-HL146208; UAB-MS CRS (Mirjam-Colette Kempf, James B. Brock, Emily Levitan, and Deborah Konkle-Parker), U01-HL146192; UNC CRS (M. Bradley Drummond and Michelle Floris-Moore), U01-HL146194. The MWCCS is funded primarily by the National Heart, Lung, and Blood Institute (NHLBI), with additional co-funding from the Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD), National Institute on Aging (NIA), National Institute of Dental & Craniofacial Research (NIDCR), National Institute of Allergy and Infectious Diseases (NIAID), National Institute of Neurological Disorders and Stroke (NINDS), National Institute of Mental Health (NIMH), National Institute on Drug Abuse (NIDA), National Institute of Nursing Research (NINR), National Cancer Institute (NCI), National Institute on Alcohol Abuse and Alcoholism (NIAAA), National Institute on Deafness and Other Communication Disorders (NIDCD), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institute on Minority Health and Health Disparities (NIMHD), and in coordination and alignment with the research priorities of the National Institutes of Health, Office of AIDS Research (OAR). MWCCS data collection is also supported by UL1-TR000004 (UCSF CTSA), UL1-TR003098 (JHU ICTR), UL1-TR001881 (UCLA CTSI), P30-AI-050409 (Atlanta CFAR), P30-AI-073961 (Miami CFAR), P30-AI-050410 (UNC CFAR), P30-AI-027767 (UAB CFAR), P30-AI-124414 (ERC-CFAR), P30-MH-116867 (Miami CHARM), UL1-TR001409 (DC CTSA), KL2-TR001432 (DC CTSA), and TL1-TR001431 (DC CTSA). Further, study specific funding is provided by National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) through R01AR081151 (RDR). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: IRB of Rush University Medical Center gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the MWCCS

As the number of patients undergoing total joint replacement (TJR) surgery increases, so does the number of revision surgeries. One driver of implant failure and subsequent revision surgery is peri-implant osteolysis, which is driven by inflammation-mediated bone loss. IL-6 is an inflammatory cytokine that is elevated during the peri-operative period. Early elevations in IL-6 levels have been linked to osteolysis development. The current study asked whether there is genetic contribution to the IL-6-related peri-operative inflammatory reaction to TJR surgery. Patients undergoing primary TJR (total hip or total knee) provided pre-operative and post-operative blood samples for measurement of the circulating levels of IL-6 and the soluble IL-6 receptor (sIL-6r), as well as evaluation of allele status of three single nucleotide polymorphisms (SNPs) linked to IL-6 or sIL-6r levels - rs2069845, rs2228145, and rs4537545. Circulating sIL-6r levels were associated with allele status in the rs2228145 SNP. More interestingly, allele status in the rs2069845 SNP was associated with the change in circulating IL-6 levels following TJR surgery. Specifically, patients with the A,A allele had increasing levels of IL-6, while those harboring the G,A allele had decreasing levels of IL-6. While implant survival was not assessed, the critical role of IL-6 in peri-implant osteolysis suggests that the rs2069845 allele may influence orthopedic implant success. rs2069845 polymorphisms may be a useful patient-specific marker of inflammatory response to TJR surgery.

Modern antiretroviral therapy (ART) is associated with rapid weight gain, which appears to be antiretroviral-specific. Tenofovir is a nucleoside reverse transcriptase inhibitor commonly employed as a backbone in many ART formulations. Tenofovir alafenamide (TAF) has been associated with significant weight gain in people living with HIV (PLWH) initiating ART. Interestingly, tenofovir disoproxil fumarate (TDF), has no impact on weight or may even be weight suppressive. The current study compared the impact of two tenofovir-based ART formulations on weight and adipose tissue. We utilized a humanized mouse model of HIV-infection and administered two clinically relevant ART combinations TAF/dolutegravir (DTG)/emtricitabine (FTC) and TDF/DTG/FTC. As expected, female mice treated with TAF/DTG/FTC had the greatest weight gain and fat accumulation, as measured by dual energy x-ray absorptiometry (DXA). As ART-induced accumulation of visceral adipose tissue is linked to mortality, we isolated visceral adipose tissue for targeted (qPCR) and non-targeted (RNAseq) gene expression. Mice treated with TAF/DTG/FTC had increased expression of adipocyte differentiation related genes, leptin and PPAR-γ. RNAseq revealed that while the expression patterns for both TAF/DTG/FTC and TDF/DTG/FTC treated mice were similar, there were key differences. Specifically, KEGG pathway analysis indicated that TAF/DTG/FTC treated mice showed suppression of multiple fatty acid metabolism related pathways, while TDF/DTG/FTC treated mice showed evidence for increased thermogenesis. The results suggest that weight gain associated with TAF-based ART may be due to impaired adipocyte mediated lipid handling, while suppressed weight gain with TDF-based ART may be secondary to increased browning of visceral adipocytes, although independent validation is necessary.

OBJECTIVE:The study was to determine the prevalence of baseline risk factors for cardiovascular outcomes and cancer among commercially-insured patients with rheumatoid arthritis (RA) during their first dispensed treatment for either tumor necrosis factor inhibitors (TNFi) or JAK inhibitors (JAKi). METHODS:Patients with RA from August 16, 2019 to March 31, 2022 were identified in the Merative MarketScan Commercial and Medicare databases. The first date that a TNFi or JAKi was dispensed was the index date, and baseline risk factors were assessed among patients continuously eligible for 12 months before the index date. Patients who had the following were stratified into an elevated risk category: age ≥65 years, smoking, or a history of a major adverse cardiovascular event, venous thromboembolism, or cancer. The prevalence of modifiable risk factors was also reported: hypertension, hyperlipidemia, obesity, and diabetes. The crude prevalence and prevalence difference (PD) were reported. RESULTS:A total of 12,673 patients (TNFi [n = 7,748; 61%] and JAKi [n = 4,925; 39%]) met inclusion criteria. The prevalence of elevated risk was the same for all patients using TNFi (n = 2,051; 26%) and JAKi (n = 1,262; 26%). Compared with patients having low risk, patients with an elevated risk also had a higher prevalence of at least one primary modifiable risk factor for both patients using JAKi (79% vs 58%; PD 21%, 95% confidence interval [CI] 18%-24%) and TNFi (81% vs 60%; PD 21%, 95% CI 19%-23%). CONCLUSION:In recent years, JAKi and TNFi were used in similar proportions to treat RA among commercially-insured patients at elevated cardiovascular and cancer risk. Because uncontrolled disease, modifiable comorbidities, and treatment with JAKi are associated with these adverse events, future studies evaluating how practice patterns may be affected by the emergence of safety data will be of value.

Bone mineral density (BMD) loss in people living with HIV occurs with the initiation of combined antiretroviral therapy (cART), particularly with tenofovir disoproxil fumarate (TDF) containing cART. Switching from TDF to abacavir (ABC) or dolutegravir (DTG) leads to increased BMD. Whether BMD gains are due to cessation of TDF or anabolic effects of ABC or DTG is unclear. We investigated the effects of ABC and DTG on osteoblast lineage cells in vitro and in vivo. Primary human osteoblasts and male C57BL/6 mice were treated with individual antiretrovirals (ARVs) or a combination of ABC/DTG/lamivudine (3TC). Nearly all ARVs and cART inhibited osteogenic activity in vitro. Due to the importance of Wnt/beta-catenin in bone formation, we further investigated ARV effects on the Wnt/beta-catenin pathway. ABC, alone and as part of ABC/DTG/3TC, increased osteoblastic beta-catenin activity as indicated by increased TOPFlash activity, hypo-phosphorylated (active) beta-catenin staining, and beta-catenin targeted gene expression. Mice treated with TDF had decreased lumbar spine BMD and trabecular connectivity density in the vertebrae, while those treated with ABC/DTG/3TC reduced cortical area and thickness in the femur. Mice treated with ABC alone had no bone structural changes, increased circulating levels of the bone formation marker, P1NP, and elevated expression of the Wnt/beta-catenin target gene, Lef1, in osteocyte enriched samples. Further, bones from ARV-treated mice were isolated to evaluate ARV distribution. All ARVs were detected in the bone tissue, which was inclusive of bone marrow, but when bone marrow was removed, only TDF, ABC, and DTG were detected at similar to 0.1% of the circulating levels. Overall, our findings demonstrate that ABC activates Wnt/beta-catenin signaling, but whether this leads to increased bone formation requires further study. Assessing the impact of ARVs on bone is critical to informing ARV selection and/or discovery of regimens that do not negatively impact the skeleton.