Association between Osteoporosis, Bone Mineral Density Levels and Alzheimer's Disease: A Systematic Review and Meta-analysis

Osteoporosis and Alzheimer´s disease (or Alzheimer´s disease and Osteoporosis)

Alzheimer's disease (AD) and osteoporosis are two diseases that mainly affect elderly people, with increases in the occurrence of cases due to a longer life expectancy. Several epidemiological studies have shown a reciprocal association between both diseases, finding an increase in incidence of osteoporosis in patients with AD, and a higher burden of AD in osteoporotic patients. This epidemiological relationship has motivated the search for molecules, genes, signaling pathways and mechanisms that are related to both pathologies. The mechanisms found in these studies can serve to improve treatments and establish better patient care protocols.

Amyloid-β neuropathology induces bone loss in male mice by suppressing bone formation and enhancing bone resorption

Alzheimer's disease (AD) and osteoporosis often coexist in the elderly. Although observational studies suggest an association between these two diseases, the pathophysiologic link between AD and skeletal health has been poorly defined. We examined the skeletal phenotype of 5xFAD mice, an AD model with accelerated neuron-specific amyloid-β accumulation causing full-blown AD phenotype by the age of 8 months. Micro-computed tomography indicated significantly lower trabecular and cortical bone parameters in 8-month-old male, but not female, 5xFAD mice than sex-matched wild-type littermates. Dynamic histomorphometry revealed reduced bone formation and increased bone resorption, and quantitative RT-PCR showed elevated skeletal RANKL gene expression in 5xFAD males. These mice also had diminished body fat percentage with unaltered lean mass, as determined by dual-energy X-ray absorptiometry (DXA), and elevated Ucp1 mRNA levels in brown adipose tissue, consistent with increased sympathetic tone, which may contribute to the osteopenia observed in 5xFAD males. Nevertheless, no significant changes could be detected between male 5xFAD and wild-type littermates regarding the serum and skeletal concentrations of norepinephrine. Thus, brain-specific amyloid-β pathology is associated with osteopenia and appears to affect both bone formation and bone resorption. Our findings shed new light on the pathophysiologic link between Alzheimer's disease and osteoporosis.

Leveraging electronic health records and knowledge networks for Alzheimer's disease prediction and sex-specific biological insights

Identification of Alzheimer's disease (AD) onset risk can facilitate interventions before irreversible disease progression. We demonstrate that electronic health records from the University of California, San Francisco, followed by knowledge networks (for example, SPOKE) allow for (1) prediction of AD onset and (2) prioritization of biological hypotheses, and (3) contextualization of sex dimorphism. We trained random forest models and predicted AD onset on a cohort of 749 individuals with AD and 250,545 controls with a mean area under the receiver operating characteristic of 0.72 (7 years prior) to 0.81 (1 day prior). We further harnessed matched cohort models to identify conditions with predictive power before AD onset. Knowledge networks highlight shared genes between multiple top predictors and AD (for example, APOE, ACTB, IL6 and INS). Genetic colocalization analysis supports AD association with hyperlipidemia at the APOE locus, as well as a stronger female AD association with osteoporosis at a locus near MS4A6A. We therefore show how clinical data can be utilized for early AD prediction and identification of personalized biological hypotheses.

Unfavorable effects of memantine on the skeletal system in female rats

Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist used in the treatment of Alzheimer's disease (AD). NMDA receptors are expressed on bone cells. The aim of the present study was to investigate the effects of memantine on the rat musculoskeletal system. Taking into account that most of female AD patients are postmenopausal, the study was carried out on intact and ovariectomized (estrogen-deficient) rats. Mature Wistar rats were divided into following groups: non-ovariectomized (NOVX) control rats, NOVX rats treated with memantine, ovariectomized (OVX) control rats, and OVX rats treated with memantine. Memantine (2 mg/kg p.o.) was administered once daily for four weeks, starting one week after ovariectomy. The serum bone turnover marker and cytokine levels, bone density, mass, mineralization, mechanical properties, histomorphometric parameters of compact and cancellous bone, skeletal muscle mass and grip strength were determined. In NOVX rats, memantine slightly decreased the strength of compact bone of the femoral diaphysis (parameters in the yield point) and unfavorably affected histomorphometric parameters of cancellous bone (the femoral epiphysis and metaphysis). In OVX rats, in which estrogen deficiency induced osteoporotic changes, memantine increased the phosphorus content in the femoral bone mineral. No other effects on bone were observed in the memantine-treated OVX rats. In conclusion, the results of the present study indicated slight damaging skeletal effects of memantine in rats with normal estrogen levels.

Effects of Donepezil on the Musculoskeletal System in Female Rats

The extension of human life makes it more and more important to prevent and treat diseases of the elderly, including Alzheimer's disease (AD) and osteoporosis. Little is known about the effects of drugs used in the treatment of AD on the musculoskeletal system. The aim of the present study was to investigate the effects of donepezil, an acetylcholinesterase inhibitor, on the musculoskeletal system in rats with normal and reduced estrogen levels. The study was carried out on four groups of mature female rats: non-ovariectomized (NOVX) control rats, NOVX rats treated with donepezil, ovariectomized (OVX) control rats and OVX rats treated with donepezil. Donepezil (1 mg/kg p.o.) was administered for four weeks, starting one week after the ovariectomy. The serum concentrations of CTX-I, osteocalcin and other biochemical parameters, bone mass, density, mineralization, histomorphometric parameters and mechanical properties, and skeletal muscle mass and strength were examined. Estrogen deficiency increased bone resorption and formation and worsened cancellous bone mechanical properties and histomorphometric parameters. In NOVX rats, donepezil decreased bone volume to tissue volume ratio in the distal femoral metaphysis, increased the serum phosphorus concentration and tended to decrease skeletal muscle strength. No significant bone effects of donepezil were observed in OVX rats. The results of the present study indicate slightly unfavorable effects of donepezil on the musculoskeletal system in rats with normal estrogen levels.

Protective effects of oridonin against osteoporosis by regulating immunity and activating the Wnt3a/β-catenin/VEGF pathway in ovariectomized mice

This study was performed with the aim of investigating the effect of oridonin (ORI) on estrogen deprivation-induced osteoporosis in mice and its mechanism. Animal experiments were used in this work to validate the anti-osteoporotic efficacy of ORI. Morphometric analysis was performed by micro-CT. A special protein meter was used to detect the content of immunoglobulin lgM, immunoglobulin lgG, complement C3 and C4 in the serum of mice. The expression of CD4⁺CD25⁺Foxp3⁺ Treg cell and CD4⁺/CD8⁺ lymphocyte subsets in mice was detected by flow cytometry. ELISA was used to detect the content of insulin-like growth factor (IGF-1), tumor necrosis factor (TNF-α), interleukin-1 (IL-1) and interleukin-6 (IL-6). In addition, key signaling molecules in the Wnt3a/β-catenin signaling pathway were detected by Western blotting. The results showed that compared with the model group, the contents of calcium and phosphorus in the femurs of mice in the ORI groups were increased, and the spleen coefficient was decreased. The ALP activity in the serum of mice in the high and medium dose ORI groups was decreased, and the uterine coefficient was increased. ORI significantly increased the maximum bending load and the maximum bending stress of the femurs of mice, increased the number of trabeculae, and repaired the bone microstructure. At the same time, ORI could significantly increase the levels of immunoglobulin (lgG and lgM) and complement (C3 and C4), increase the activity of peritoneal macrophages in mice, increase the expression of CD4⁺CD25⁺Foxp3⁺ Tregs and CD4⁺/CD8⁺ in the spleen, increase the content of IGF-1, reduce the content of TNF-α, IL-1 and IL-6 and increase the expression levels of VEGF, Wnt3a, p-GSK3β/GSK3β and β-catenin/Lamin in the femoral tissue. These results indicated that ORI might regulate the expression of VEGF through the Wnt3a/β-catenin signaling pathway, improve the immunity of mice, maintain the balance of the immune system, and promote angiogenesis, thereby improving the bone mineral density and bone tissue morphology of mice and playing an anti-osteoporotic role.

Degradation of Bone Quality in a Transgenic Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) patients present with symptoms such as impairment of insulin signaling, chronic inflammation, and oxidative stress. Furthermore, there are comorbidities associated with AD progression. For example, osteoporosis is common with AD wherein patients exhibit reduced mineralization and a risk for fragility fractures. However, there is a lack of understanding on the effects of AD on bone beyond loss of bone density. To this end, we investigated the effects of AD on bone quality using the 5XFAD transgenic mouse model in which 12-month-old 5XFAD mice showed accumulation of amyloid-beta (Aβ42) compared with wild-type (WT) littermates (n = 10/group; 50% female, 50% male). Here, we observed changes in cortical bone but not in cancellous bone quality. Both bone mass and bone quality, measured in femoral samples using imaging (micro-CT, confocal Raman spectroscopy, X-ray diffraction [XRD]), mechanical (fracture tests), and chemical analyses (biochemical assays), were altered in the 5XFAD mice compared with WT. Micro-CT results showed 5XFAD mice had lower volumetric bone mineral density (BMD) and increased endocortical bone loss. XRD results showed decreased mineralization with smaller mineral crystals. Bone matrix compositional properties, from Raman, showed decreased crystallinity along with higher accumulation of glycoxidation products and glycation products, measured biochemically. 5XFAD mice also demonstrated loss of initiation and maximum toughness. We observed that carboxymethyl-lysine (CML) and mineralization correlated with initiation toughness, whereas crystal size and pentosidine (PEN) correlated with maximum toughness, suggesting bone matrix changes predominated by advanced glycation end products (AGEs) and altered/poor mineral quality explained loss of fracture toughness. Our findings highlight two pathways to skeletal fragility in AD through alteration of bone quality: (i) accumulation of AGEs; and (ii) loss of crystallinity, decreased crystal size, and loss of mineralization. We observed that the accumulation of amyloidosis in brain correlated with an increase in several AGEs, consistent with a mechanistic link between elevated Aβ42 levels in the brain and AGE accumulation in bone. © 2022 American Society for Bone and Mineral Research (ASBMR).

Musculoskeletal Deficits and Cognitive Impairment: Epidemiological Evidence and Biological Mechanisms

PURPOSE OF REVIEW

Cognitive impairment is associated with obesity, sarcopenia, and osteoporosis. However, no critical appraisal of the literature on the relationship between musculoskeletal deficits and cognitive impairment, focusing on the epidemiological evidence and biological mechanisms, has been published to date. Herein, we critically evaluate the literature published over the past 3 years, emphasizing interesting and important new findings, and provide an outline of future directions that will improve our understanding of the connections between the brain and the musculoskeletal system.

RECENT FINDINGS

Recent literature suggests that musculoskeletal deficits and cognitive impairment share pathophysiological pathways and risk factors. Cytokines and hormones affect both the brain and the musculoskeletal system; yet, lack of unified definitions and standards makes it difficult to compare studies. Interventions designed to improve musculoskeletal health are plausible means of preventing or slowing cognitive impairment. We highlight several musculoskeletal health interventions that show potential in this regard.

Depression and bone loss as risk factors for cognitive decline: A systematic review and meta-analysis

BACKGROUND

Depression is linked to Alzheimer's disease (AD) but it is unclear whether depression is also associated with cognitive decline in the preclinical phase and mild cognitive impairment (MCI). Previous meta-analyses have only investigated AD as an outcome without accounting for individuals showing cognitive decline that does not meet the diagnostic criteria for AD. Other potentially modifiable risk factors such as bone loss have also been less explored and there remains uncertainty around their temporal relationship with cognitive decline.

AIMS

To conduct a systematic review and meta-analysis investigating depression and bone loss as risk factors for subsequent cognitive decline.

METHODS

A comprehensive search strategy was developed and applied using four databases; MEDLINE Complete, Embase, PsycINFO and CINAHL Complete. The pooled summary effects were estimated as odds ratios with 95% confidence intervals using a random-effects model. The study protocol was registered with PROSPERO (ID: CRD42020159369).

RESULTS

A total of 75 longitudinal cohort studies were identified for meta-analysis, of which 70 examined the impact of depression on cognitive decline and five examined the impact of bone loss. Prior exposure to depression was found to be associated with cognitive score reduction (OR 1.33 95% CI 1.17, 1.51), MCI incidence (OR 1.52 95% CI 1.28, 1.79) and AD incidence (OR 1.79 95% CI 1.46, 2.2). Bone loss was also associated with the incidence of AD (OR=1.81 95% CI 1.28, 2.55).

CONCLUSIONS

Overall, the results support the hypothesis that depression is associated with subsequent cognitive decline. Bone loss was also found to be associated with AD incidence; however, due to the small number of studies, the results should be viewed with caution.

Deep phenotyping of Alzheimer's disease leveraging electronic medical records identifies sex-specific clinical associations

Alzheimer's Disease (AD) is a neurodegenerative disorder that is still not fully understood. Sex modifies AD vulnerability, but the reasons for this are largely unknown. We utilize two independent electronic medical record (EMR) systems across 44,288 patients to perform deep clinical phenotyping and network analysis to gain insight into clinical characteristics and sex-specific clinical associations in AD. Embeddings and network representation of patient diagnoses demonstrate greater comorbidity interactions in AD in comparison to matched controls. Enrichment analysis identifies multiple known and new diagnostic, medication, and lab result associations across the whole cohort and in a sex-stratified analysis. With this data-driven method of phenotyping, we can represent AD complexity and generate hypotheses of clinical factors that can be followed-up for further diagnostic and predictive analyses, mechanistic understanding, or drug repurposing and therapeutic approaches.

Effect of Memantine Treatment and Combination with Vitamin D Supplementation on Body Composition in the APP/PS1 Mouse Model of Alzheimer's Disease Following Chronic Vitamin D Deficiency

BACKGROUND

Vitamin D deficiency and altered body composition are common in Alzheimer's disease (AD). Memantine with vitamin D supplementation can protect cortical axons against amyloid-β exposure and glutamate toxicity.

OBJECTIVE

To study the effects of vitamin D deprivation and subsequent treatment with memantine and vitamin D enrichment on whole-body composition using a mouse model of AD.

METHODS

Male APPswe/PS1dE9 mice were divided into four groups at 2.5 months of age: the control group (n = 14) was fed a standard diet throughout; the remaining mice were started on a vitamin D-deficient diet at month 6. The vitamin D-deficient group (n = 14) remained on the vitamin D-deficient diet for the rest of the study. Of the remaining two groups, one had memantine (n = 14), while the other had both memantine and 10 IU/g vitamin D (n = 14), added to their diet at month 9. Serum 25(OH)D levels measured at months 6, 9, 12, and 15 confirmed vitamin D levels were lower in mice on vitamin D-deficient diets and higher in the vitamin D-supplemented mice. Micro-computed tomography was performed at month 15 to determine whole-body composition.

RESULTS

In mice deprived of vitamin D, memantine increased bone mineral content (8.7% increase, p < 0.01) and absolute skeletal tissue mass (9.3% increase, p < 0.05) and volume (9.2% increase, p < 0.05) relative to controls. This was not observed when memantine treatment was combined with vitamin D enrichment.

CONCLUSION

Combination treatment of vitamin D and memantine had no negative effects on body composition. Future studies should clarify whether vitamin D status impacts the effects of memantine treatment on bone physiology in people with AD.

Aging and direct medical costs of osteoporotic fractures

INTRODUCTION

This study estimated the direct medical costs of osteoporotic fractures from a large claims database in Korea.

MATERIALS AND METHODS

We compared the medical costs of hip, vertebral, and wrist fractures between two age groups (50-64 years vs 65 years and older). We used a generalized linear model to investigate the drivers of osteoporotic fracture medical costs.

RESULTS

Hip fractures had the highest costs, regardless of age, followed by vertebral and wrist. The cost of hip fracture was USD 7285 for those aged 65 years and over and USD 6589 for those aged 50-64 years. The length of hospital days was higher in hip fracture patients, regardless of age, followed by vertebral and wrist. As the number of hospitalizations increased, the medical cost increased by 33.0% (p < 0.0001). Patients older than 65 years who were hospitalized for a fracture had a longer total length of hospital stay, compared to patients aged 50-64, regardlessness of the site of the fracture. The cost of treating fractures among those 65 years and older increased by 31.8% compared to those 50-64 years old (p < 0.0001). The direct medical costs increased by 8.6% as the number of fractures increased (p = 0.041).

CONCLUSIONS

We identified that osteoporotic fracture-related medical costs and hospitalization days increased with age. Interventions are effective in reducing fracture risk the potential to yield substantial cost savings.

Modeling Sympathetic Hyperactivity in Alzheimer's Related Bone Loss

BACKGROUND

A significant subset of patients with Alzheimer's disease (AD) exhibit low bone mineral density and are therefore more fracture-prone, relative to their similarly aged neurotypical counterparts. In addition to chronic immune hyperactivity, behavioral dysregulation of effector peripheral sympathetic neurons-which densely innervate bone and potently modulate bone remodeling-is implicated in this pathological bone reformation.

OBJECTIVE

Thus, there exists a pressing need for a robust in vitro model which allows interrogation of the paracrine interactions between the putative mediators of AD-related osteopenia: sympathetic neurons (SNs) and mesenchymal stem cells (MSCs).

METHODS

Toward this end, activated SN-like PC12 cells and bone marrow derived MSCs were cultured in poly(ethylene glycol) diacrylate (PEGDA) hydrogels in the presence or absence of the AD-relevant inflammatory cytokine tumor necrosis factor alpha (TNF-α) under mono- and co-culture conditions.

RESULTS

PC12s and MSCs exposed separately to TNF-α displayed increased expression of pro-inflammatory mediators and decreased osteopontin (OPN), respectively. These data indicate that TNF-α was capable of inducing a dysregulated state in both cell types consistent with AD. Co-culture of TNF-α-activated PC12s and MSCs further exacerbated pathological behaviors in both cell types. Specifically, PC12s displayed increased secretion of interleukin 6 relative to TNF-α stimulated monoculture controls. Similarly, MSCs demonstrated a further reduction in osteogenic capacity relative to TNF-α stimulated monoculture controls, as illustrated by a significant decrease in OPN and collagen type I alpha I chain.

CONCLUSION

Taken together, these data may indicate that dysregulated sympathetic activity may contribute to AD-related bone loss.

Osteoporosis and cognitive impairment interwoven warning signs: community-based study on older adults-Bushehr Elderly Health (BEH) Program

Cognitive impairment and osteoporosis are frequently seen to coincide in clinical practice. Osteoporosis was higher in elderly populations with cognitive impairment, especially in postmenopausal women. Thus, prophylaxis for osteoporosis, falls, and fractures should be considered as part of the treatment of patients with cognitive impairment.

INTRODUCTION

Cognitive impairment and osteoporosis are two important health concerns among older adults that their possible relationship, concurrent occurrence, and linking mechanism have recently been highlighted. The purpose of this study was to assess the sex-independent association of these two conditions.

MATERIALS AND METHODS

From among 2331 individuals aged ≥ 60 years selected in Bushehr Elderly Health (BEH) Program, Iran; data of 1508 participants were analyzed. Cognitive status was assessed using Category Fluency Test and Mini-cog assessment instrument. Association between osteopenia-osteoporosis and cognitive impairment were assessed using uni- and multivariable logistic regression models.

RESULTS

Osteoporosis was diagnosed in 598 (39.6%) of the participants (58.3% female and 21.9% male, P < 0.001). From among them, 677 (44.9%) had evidence of cognitive impairment (64.5% female and 31.0% male, P < 0.001). Multivariate logistic regressions showed spinal and total hip osteoporosis was associated with 1.83 (CI 95% 1.13-2.96) and 2.24-fold (CI 95% 1.28-3.89) increase in the risk of cognitive impairment among female subjects, respectively. Ordinal logistic regression, on the other hand, revealed cognitive impairment to be associated with 1.42-fold (CI 95% 1.04-1.92) increase in the risk of spinal osteopenia-osteoporosis, 1.5-fold increase in total hip osteoporosis (CI 95% 1.09-2.05), and 1.48-fold increase in general osteoporosis (CI 95% 1.06-2.0).

CONCLUSION

Different degrees of bone loss and cognitive impairment may be a risk factor for each other among women but not in men. It is suggested that the screening, adopting preventive measures for the other condition and regular follow-ups, if needed, could be of utmost importance.

Voxel-Based Morphometry Reveals a Correlation Between Bone Mineral Density Loss and Reduced Cortical Gray Matter Volume in Alzheimer's Disease

Background: Decreased bone mineral density (BMD) was associated with poorer cognitive function and increased risk of Alzheimer's disease (AD). However, objective evidence for the relationship between osteoporosis and AD in humans has not been extensively described. Objectives: We aimed to evaluate the relationships between BMD and the cortical volumes of brain regions vulnerable to AD; hippocampus, parahippocampal gyrus, precuneus, posterior cingulate, and angular gyrus, using voxel-based morphometry (VBM), to investigate the association between bone loss and AD. Methods: A cohort of 149 consecutive elderly participants who complained of memory disturbance underwent high-resolution structural brain magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA). We used SPM12 software to conduct a voxel-based multiple regression analysis to examine the association between femoral neck BMD values and regional gray matter volume (rGMV) on structural T1-weighted MRI. Results: After adjusting for subject age, gender, total brain volume (TBV), and mini-mental state examination (MMSE) scores, the multiple regression analysis showed significant correlations between BMD loss and rGMV decline in the left precuneus, which is an important neural network hub vulnerable to AD. Conclusion: These data suggest that the bone and brain communicate with each other, as in "bone-brain crosstalk," and that control of BMD factors could contribute to cognitive function and help prevent AD.