Is PPARγ a prospective player in HIV-1-associated bone disease?

Lower bone density and microarchitecture alterations in HIV-infected Brazilian men aged 50 years and older are associated with estradiol levels

OBJECTIVE

Combination antiretroviral treatment (cART) allows for longer survival for people living with HIV and hence long-term complications of both disease and treatment are common. Our purpose was to evaluate bone alterations in men living with HIV (MLWH) and receiving cART and to identify associated factors that can be corrected or mitigated.

PATIENTS AND DESIGN

Thirty MLWH and 36 healthy controls (≥50 years) were studied for areal bone mineral density (aBMD) and body composition (dual-energy X-ray absorptiometry), volumetric bone mineral density (vBMD) and bone microstructure (high-resolution peripheral quantitative computed tomography [HR-pQCT]), serum calcium, phosphate, parathyroid hormone, 25(OH)D, testosterone (T), estradiol (E₂ ), glucose, creatinine, and albumin levels.

RESULTS

The proportion of patients classified as osteoporosis (according to the lowest aBMD T-score) was higher among MLWH as compared to controls (17.9% vs. 5.9%, p = .011). The MLWH showed significant alterations in cortical and trabecular bone on HR-pQCT, which were not associated with the duration of HIV infection or cART. These differences in vBMD and bone microstructure seen in HR-pQCT persisted in the nonosteoporotic MLWH as compared to nonosteoporotic control subjects. Body mass index (BMI) and fat mass were lower in MLWH and positively associated with total vBMD, cortical bone area, and thickness. E₂ and E₂ /T ratios were lower in MLWH than in controls and significantly correlated with several cortical and trabecular bone parameters. Multivariate regression analysis entering simultaneously age, BMI, and E₂ defined that E₂ is an independent influence on bone parameters evaluated by HR-pQCT.

CONCLUSION

MLWH have alterations in bone volumetric density and microstructure when compared with controls, irrespective of aBMD, which are associated with lower E₂ and BMI.

Impact of physical exercises on immune function, bone mineral density, and quality of life in people living with HIV/AIDS: a systematic review with meta-analysis

BACKGROUND

Compromised immune function, associated with human immune deficiency virus(HIV) infection, is improved by antiretroviral therapy(ART) which also decreases bone mineral density(BMD), and possibly the quality of life(QoL). However, physical(aerobic/resistance) exercises, were reported to induce reverse effects in uninfected individuals and were appraised in the literature for evidence of similar benefits in people living with HIV/AIDS(PLWHA). The main study objective was to evaluate the impact of physical (aerobic and resistance) exercises on CD4+ count, BMD and QoL in PLWHA.

METHODS

A systematic review was conducted using the Cochrane Collaboration protocol. Searching databases, up to June 2017, only randomized control trials investigating the effects of either aerobic, resistance or a combination of both exercise types with a control/other intervention(s) for a period of at least 4 weeks among adults living with HIV, were included. Two independent reviewers determined the eligibility of the studies. Data were extracted and risk of bias(ROB) was assessed with the Cochrane Collaboration ROB tool. Meta-analyses were conducted using random effect models using the Review Manager(RevMan) computer software.

RESULTS

Nineteen studies met inclusion criteria(n = 491 participants at study completion) comprising male and female with age range 22-66 years. Two meta-analyses across 13 sub-group comparisons were performed. However, there were no RCTs on the impact of physical exercises on BMD in PLWHA. The result showed no significant change in CD4+ count unlike a significant effect of 5.04 point(95%CI:-8.49,-3.74,p = 0.00001) for role activity limitation due to physical health(QoL sub-domain). Overall, the GRADE evidence for this review was of moderate quality.

CONCLUSIONS

There was evidence that engaging in moderate intensity aerobic exercises (55-85% Maximum heart rate-MHR), for 30-60 min, two to five times/week for 6-24 weeks significantly improves role activity limitation due to physical health problems, otherwise physical(aerobic or/and resistance) exercises have no significant effects on CD4+ count and other domains of QoL. Also, there is lack of evidence on the impact of exercises on BMD in PLWHA due to the paucity of RCTs. The moderate grade evidence for this review suggests that further research may likely have an important impact on our confidence in the estimate of effects and may change the estimate.

Integrin subunits αV and β3 promote the osteogenic differentiation of umbilical cord blood mesenchymal stem cells

Human umbilical cord-derived mesenchymal stem cells (hUCMSCs) are multipotent cells that have self-renewal properties and can differentiate into osteocytes, adipocytes, cartilage and extoderm. Bone regeneration and repair are important for the repair of bone injury, skeletal development or continuous remodeling throughout adult life. Thus, investigating the factors influencing osteocyte regeneration from hUCMSCs could be conducive to advancements in skeletal repair and the repair of bone injury. Previous reports have demonstrated that single integrin subunits (αV, β3, α5) and collagen I contribute to the osteogenic differentiation of human mesenchymal stem cells (hMSCs). However, the functions of the vitronectin receptor αV and β3 in the osteogenic differentiation of hUCMSCs and bone regeneration remain unclear. Run-related transcription factor 2 (RUNX2) is considered to be an early osteoblastic gene that is upregulated during the osteogenic differentiation of hUCMSCs. Meanwhile, bone sialoprotein (BSP) and collagen I are the most common early markers of osteoblast differentiation. Herein, we found that the mRNA and protein expression of αV, β3, RUNX2 and collagen I were upregulated during the osteogenic differentiation of hUCMSCs. Overexpression of αV and β3 in hMSCs increased the levels of RUNX2, BSP, and collagen I, decreased the number of adipocytes and promoted the osteogenic differentiation of hUCMSCs. Meanwhile, downregulation of αV and β3 decreased the levels of RUNX2, BSP, and collagen I, increased the number of adipocytes and blocked the osteogenic differentiation of hUCMSCs. In conclusion, the integrin subunits αV and β3 can promote the osteogenic differentiation of hUCMSCs and encourage bone formation.

Magnesium phosphate ceramics incorporating a novel indene compound promote osteoblast differentiation in vitro and bone regeneration in vivo

Incorporating bioactive molecules into synthetic ceramic scaffolds is challenging. In this study, to enhance bone regeneration, a magnesium phosphate (MgP) ceramic scaffold was incorporated with a novel indene compound, KR-34893. KR-34893 induced the deposition of minerals and expression of osteoblast marker genes in primary human bone marrow mesenchymal stem cells (BMSCs) and a mouse osteoblastic MC3T3-E1 cell line. Analysis of the mode of action showed that KR-34893 induced the phosphorylation of MAPK/extracellular signal-regulated kinase and extracellular signal-regulated kinase, and subsequently the expression of bone morphogenetic protein 7, accompanied by SMAD1/5/8 phosphorylation. Accordingly, KR-34893 was incorporated into an MgP scaffold prepared by 3D printing at room temperature, followed by cement reaction. KR-34893-incorporated MgP (KR-MgP) induced the expression of osteoblast differentiation marker genes in vitro. In a rat calvaria defect model, KR-MgP scaffolds enhanced bone regeneration and increased bone volume compared with MgP scaffolds, as assessed by micro-computed tomography and histological analyses. In conclusion, we developed a method for producing osteoinductive MgP scaffolds incorporating a bioactive organic compound, without high temperature sintering. The KR-MgP scaffolds enhanced osteoblast activation in vitro and bone regeneration in vivo.

Protecting bone in long-term HIV positive patients receiving antiretrovirals

INTRODUCTION

As the population of people living with HIV ages, the increase in non-AIDs morbidities is expected to increase in parallel. Maintaining bone health in those with HIV will be an important area of focus for the HIV clinician to prevent the morbidity and mortality associated with fragility fractures, the principal clinical sequela of low bone mineral density (BMD). Rates of fractures and prevalence of low bone mineral density, a risk factor for future fragility fractures, are already increased in the HIV positive population.

AREAS COVERED

This review examines the strategies to maintain bone health in those living with HIV from screening through to managing those with established low BMD or fracture, including the role for choice of or modification of antiretroviral therapy to maintain bone health. Expert commentary: The increasing complexity of managing bone health in the age of succesful antiretroviral therapy and an aging patient population as well as future perspectives which may help achieve the long term aim of minimising the impact of low BMD in those with HIV are discussed and explored.

Bone and vitamin D metabolism in HIV

Human immunodeficiency virus (HIV) infection has progressed to a chronic disease and HIV positive individuals are living longer lives. This has lead to an increase in morbidity and mortality due to secondary issues, one being HIV bone disease. HIV infected pediatric and adult populations have a greater incidence in reduction of BMD as compared to the controls. Osteoporosis has been reported to be present in up to 15 % of HIV positive patients. We are starting to understand the mechanism behind the changes in HIV bone disease. Viral proteins interfere with osteoblastic activity either by direct interaction or by the inflammatory process that they induce. Anti-viral management, including highly active antiretroviral therapy (HAART), protease inhibitors, and nucleoside/nucleotide reverse transcriptase inhibitors (NRTI) also are involved in disrupting proper bone metabolism. Vitamin D levels have strong correlation with bone disease in HIV patients, and are dependent not only to chronic disease state, but interaction of pharmacologic management and inflammatory process as well. Work up of the secondary causes of osteopenia and osteoporosis should be undertaken in all patients. DEXA scan is recommended in all post-menopausal women with HIV, all HIV infected men 50 years of age or older and in those with a history of fragility fractures regardless of age or gender. Preventive measures include adequate nutrition, calcium and Vitamin D intake daily, muscle strengthening and balance exercises to increase BMD and reduce fractures. Bisphosphonates are considered to be the first line for the treatment of HIV associated bone disease. This review will describe how the balanced mechanism of bone metabolism is interrupted by the HIV infection itself, the complications that arise from HIV/AIDS, and its treatment options.

HIV-1 and recombinant gp120 affect the survival and differentiation of human vessel wall-derived mesenchymal stem cells

BACKGROUND

HIV infection elicits the onset of a progressive immunodeficiency and also damages several other organs and tissues such as the CNS, kidney, heart, blood vessels, adipose tissue and bone. In particular, HIV infection has been related to an increased incidence of cardiovascular diseases and derangement in the structure of blood vessels in the absence of classical risk factors. The recent characterization of multipotent mesenchymal cells in the vascular wall, involved in regulating cellular homeostasis, suggests that these cells may be considered a target of HIV pathogenesis. This paper investigated the interaction between HIV-1 and vascular wall resident human mesenchymal stem cells (MSCs).

RESULTS

MSCs were challenged with classical R5 and X4 HIV-1 laboratory strains demonstrating that these strains are able to enter and integrate their retro-transcribed proviral DNA in the host cell genome. Subsequent experiments indicated that HIV-1 strains and recombinant gp120 elicited a reliable increase in apoptosis in sub-confluent MSCs. Since vascular wall MSCs are multipotent cells that may be differentiated towards several cell lineages, we challenged HIV-1 strains and gp120 on MSCs differentiated to adipogenesis and endotheliogenesis. Our experiments showed that the adipogenesis is increased especially by upregulated PPARγ activity whereas the endothelial differentiation induced by VEGF treatment was impaired with a downregulation of endothelial markers such as vWF, Flt-1 and KDR expression. These viral effects in MSC survival and adipogenic or endothelial differentiation were tackled by CD4 blockade suggesting an important role of CD4/gp120 interaction in this context.

CONCLUSIONS

The HIV-related derangement of MSC survival and differentiation may suggest a direct role of HIV infection and gp120 in impaired vessel homeostasis and in genesis of vessel damage observed in HIV-infected patients.

HIV and bone loss

The use of antiretroviral therapy has significantly reduced the number of deaths due to HIV/AIDS. However, no current therapy can suppress the virus completely, and as the HIV-infected population continues to live longer new complications are emerging from the persistence of the virus and use of antiretroviral therapy. This review summarizes the clinical evidence linking HIV-associated osteoporosis to direct infection and antiretroviral therapy (ART) use. The purported molecular mechanisms involved in bone loss are also reviewed. Additionally, recommendations regarding the pharmacologic management of HIV/ART-related osteoporosis are given.