Research progress in Alzheimer's disease and bone-brain axis

Healthy Cardiovascular Status Attenuates the Detrimental Association Between Osteosarcopenic Adiposity and Alzheimer's Disease-Related Dementia: A UK Biobank Cohort Study

BACKGROUND

Body composition abnormalities are associated with the risk of Alzheimer's disease-related dementia (ADRD). However, the specific link between osteosarcopenic adiposity (OSA), cardiovascular health (CVH), and ADRD is underexplored. This study examined the association between OSA and ADRD to determine whether optimal CVH could modify this association.

METHODS

We analyzed data from 152 028 UK Biobank participants. OSA-related body composition abnormalities include low bone mineral density, low muscle mass/grip strength, and high body fat percentage. CVH was assessed using the Life's Essential 8 questionnaire. High and low CVH corresponded to the lowest and highest cardiovascular disease risks, respectively. The hazard ratios (HRs) and 95% CIs for ADRD were estimated using Cox proportional hazards models. A secondary analysis included 14 750 participants with brain magnetic resonance imaging data to explore the role of brain structure in the association between OSA and the incidence of ADRD.

RESULTS

After a median follow-up of 14.1 years, 2628 participants (1.73%) developed ADRD. Compared with participants with no body composition abnormalities, the adjusted HRs for ADRD risk for those with 1, 2, and 3 abnormalities were 1.04 (95% CI, 0.95-1.14), 1.17 (95% CI, 1.04-1.31), and 1.46 (95% CI, 1.11-1.92), respectively. We found a significant addictive interaction between CVH and abnormal body components, with a relative excess risk due to interaction (95% CI) of -1.34 (95% CI, -2.11 to -0.57). Gray matter in the hippocampus could mediate these associations, with a mediation proportion of 17.3% (P < 0.001).

CONCLUSIONS

OSA components are positively associated with the risk of ADRD. Maintaining optimal CVH status may mitigate ADRD risk in individuals with OSA.

Research progress on resistance exercise therapy for improving cognitive function in patients with AD and muscle atrophy

Alzheimer's disease (AD) significantly reduces the quality of life of patients and exacerbates the burden on their families and society. Resistance exercise significantly enhances the overall cognitive function of the elderly and patients with AD while positively improving memory, executive function, and muscle strength, reducing fall risks, and alleviating psychological symptoms. As AD is a neurodegenerative disorder, some nerve factors are readily activated and released during exercise. Therefore, several prior studies have concentrated on exploring the molecular mechanisms of resistance exercise and their impact on brain function and neural plasticity. Recent investigations have identified an intrinsic relationship between individuals with AD and the pathological mechanisms of skeletal muscle atrophy, establishing a correlation between patients with AD cognitive level and skeletal muscle content. Resistance exercise primarily targets the skeletal muscle, which improves cognitive impairment in patients with AD by reducing vascular and neuroinflammatory factors and further enhances cognitive function in patients with AD by restoring the structural function of skeletal muscle. Furthermore, the effects of resistance training vary among distinct subgroups of cognitive impairment. Individuals exhibiting lower cognitive function demonstrate more pronounced adaptive responses in physical performance over time. Consequently, further investigation is warranted to determine whether tailored guidelines-such as variations in the frequency and duration of resistance exercise-should be established for patients with varying levels of dementia, in order to optimize the benefits for those experiencing cognitive impairment. This study aimed to review the relationship between AD and skeletal muscle atrophy, the impact of skeletal muscle atrophy on AD cognition, the mechanism by which resistance exercise improves cognition through skeletal muscle improvement, and the optimal resistance exercise mode to elucidate the additional advantages of resistance exercise in treating cognitive function in patients with AD and skeletal muscle atrophy.

Rethinking Depression-Beyond Neurotransmitters: An Integrated Psychoneuroendocrineimmunology Framework for Depression's Pathophysiology and Tailored Treatment

It is known that the effectiveness of drug treatment for depression, ammine deficit based, is largely unsatisfactory. In this review, we examine the proposal of a precision therapy has emerged and has received a strong push by the identification of the role of inflammation in depression. However, precision psychiatry risks being caught in the reductionist trap of searching for the molecular switch that resets the whole system and switches off the disease. This is an illusion since the human being is complex and depression is a systemic and variable disorder. In this study, we show the inadequacy of the reductionist paradigm, and, at the same time, illustrate the superiority of the systemic paradigm centered on psychoneuroendocrineimmunology (PNEI). According to the PNEI paradigm, depression is a disease of the whole human being, caused by different sources working together: psychological, biological, and behavioral. This means knowing the biological and psychological history of the subject, identifying relational and biological crisis factors, and building personalized treatments targeting those factors with the tools of medicine and psychology, which are not reducible to the combination of drugs and psychotherapy. Our proposal presents a paradigm shift that is both theoretical and practical, which enables clinicians to assess patients experiencing depression in a unified way and treat them in an integrated manner.

Bone-brain crosstalk in osteoarthritis: pathophysiology and interventions

Osteoarthritis (OA) is a prevalent articular disorder characterized by joint degeneration and persistent pain; it imposes a significant burden on both individuals and society. While OA has traditionally been viewed as a localized peripheral disorder, recent preclinical and clinical studies have revealed the crucial interconnections between the bone and the brain, highlighting the systemic nature of OA. The neuronal pathway, molecular signaling, circadian rhythms, and genetic underpinnings within the bone-brain axis play vital roles in the complex interplay that contributes to OA initiation and progression. This review explores emerging evidence of the crosstalk between the bone and brain in OA progression, and discusses the potential contributions of the bone-brain axis to the development of effective interventions for managing OA.

Characterization of gene expression profiles in Alzheimer's disease and osteoarthritis: A bioinformatics study

BACKGROUND

Alzheimer's disease (AD) and Osteoarthritis (OA) have been shown to have a close association in previous studies, but the pathogenesis of both diseases are unclear. This study explores the potential common molecular mechanisms between AD and OA through bioinformatics analysis, providing new insights for clinical treatment strategies.

METHODS

The AD and OA-related datasets were downloaded from the gene expression database GEO. The datasets were analyzed to obtain differentially expressed gene (DEG) datasets for OA and AD, respectively. The intersection of these DEGs was analyzed to identify common DEGs (Co-DEGs). Subsequently, the Co-DEGs were enriched, and a protein-protein interaction network was constructed to identify core genes. The expression of these genes was validated in a separate dataset, and their diagnostic value for the diseases was analyzed. In addition, the core genes were analyzed using gene set enrichment analysis and single-gene genome variation analysis.

RESULTS

Analysis of DEGs on gene chips from OA and AD patients revealed significant changes in gene expression patterns. Notably, EFEMP2 and TSPO, genes associated with inflammatory responses, showed lower expression levels in both AD and OA patients, suggesting a downregulation in the pathological backgrounds of these diseases. Additionally, GABARAPL1, which is crucial for the maturation of autophagosomes, was found to be upregulated in both conditions. These findings suggest the potential of these genes as diagnostic biomarkers and potential therapeutic targets. However, to confirm the effectiveness of these genes as therapeutic targets, more in-depth mechanistic studies are needed in the future, particularly to explore the feasibility and specific mechanisms of combating disease progression by regulating the expression of these genes.

CONCLUSIONS

This study suggests that AD and OA shares common molecular mechanisms. The identification of EFEMP2, GABARAPL1, and TSPO as key target genes highlights potential common factors in both diseases. Further investigation into these findings could lead to new candidate targets and treatment directions for AD and OA, offering promising avenues for developing more effective and targeted therapeutic interventions.

Unraveling the impact of blood RANKL and OPG levels on Alzheimer's disease: Independent of bone mineral density and inflammation

INTRODUCTION

Observational studies have revealed a close relationship between reduced bone mineral density (BMD) and Alzheimer's disease (AD) risk. The receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) system, pivotal in regulating bone metabolism, has been implicated in brain function, but the causal impact on AD risk remains unclear.

METHODS

We employed bi-directional Mendelian randomization (MR) and multivariable MR (MVMR) approaches to elucidate the effect of blood soluble RANKL (sRANKL) and OPG levels on AD, assessing whether this influence was independent of BMD and inflammation. Three distinct AD genome-wide association study (GWAS) data sets from the International Genomics of Alzheimer's Project (IGAP), UK Biobank (UKB), and FinnGen were utilized. Summary-level data on blood sRANKL and OPG were sourced from deCODE Genetics.

RESULTS

Genetically predicted per standard deviation (SD) increase in blood sRANKL levels was significantly associated with a reduced risk of AD across all three AD GWAS data sets (IGAP: odds ratio [OR] = 0.82, 95% confidence interval [CI] = 0.72-0.94, p = 0.004; UKB: OR = 0.85, 95% CI = 0.78-0.91, p < 0.001; FinnGen: OR = 0.83, 95% CI = 0.73-0.94, p = 0.004). No significant causal relationship was observed between OPG levels and AD. In addition, there was no causal impact of AD on the blood levels of sRANKL and OPG. MVMR results showed that the inverse association between sRANKL and AD risk persisted after adjusting for BMD and interleukin-1α and chemoattractant protein-1.

DISCUSSION

Our study provides evidence that elevated sRANKL levels are causally linked to a reduced risk of AD, independent of BMD and inflammation. These findings enhance our understanding of the complex interactions between bone metabolism and AD.

Highlights

Blood soluble receptor activator of nuclear factor kappa-B ligand (sRANKL) levels are linked to a reduced risk of Alzheimer's disease (AD).The association between sRANKL levels and AD is independent of bone mineral density (BMD) and inflammation.No causal link exists between blood osteoprotegerin levels and AD.AD does not affect blood levels of sRANKL or osteoprotegerin.