Association of frailty with the serine protease HtrA1 in older adults

Mid-life plasma proteins associated with late-life prefrailty and frailty: a proteomic analysis

Physical frailty is a syndrome that typically manifests in later life, although the pathogenic process causing physical frailty likely begins decades earlier. To date, few studies have examined the biological signatures in mid-life associated with physical frailty later in life. Among 4,189 middle-aged participants (57.8 ± 5.0 years, 55.8% women) from the Atherosclerosis Risk in Community (ARIC) study, we evaluated the associations of 4,955 plasma proteins (log 2-transformed and standardized) measured using the SomaScan platform with their frailty status approximately 20 years later. Using multinomial logistic regression models adjusting for demographics, health behaviors, kidney function, total cholesterol, and comorbidities, 12 and 221 proteins were associated with prefrailty and frailty in later life, respectively (FDR p < 0.05). Top frailty-associated proteins included neurocan core protein (NCAN, OR = 0.66), fatty acid-binding protein heart (FABP3, OR = 1.62) and adipocyte (FABP4, OR = 1.65), as well proteins involved in the contactin-1 (CNTN1), toll-like receptor 5 (TLR5), and neurogenic locus notch homolog protein 1 (NOTCH1) signaling pathway relevant to skeletal muscle regeneration, myelination, and inflammation. Pathway analyses suggest midlife dysregulation of inflammation, metabolism, extracellular matrix, angiogenesis, and lysosomal autophagy among those at risk for late-life frailty. After further adjusting for midlife body mass index (BMI) - an established frailty risk factor - only CNTN1 (OR = 0.75) remained significantly associated with frailty. Post-hoc analyses demonstrated that the top 41 midlife frailty-associated proteins mediate 32% of the association between mid-life BMI and late-life frailty. Our findings provide new insights into frailty etiology earlier in the life course, enhancing the potential for prevention.

Progress in the Study of the Role and Mechanism of HTRA1 in Diseases Related to Vascular Abnormalities

High temperature requirement A1 (HTRA1) is a member of the serine protease family, comprising four structural domains: IGFBP domain, Kazal domain, protease domain and PDZ domain. HTRA1 encodes a serine protease, a secreted protein that is widely expressed in the vasculature. HTRA1 regulates a wide range of physiological processes through its proteolytic activity, and is also involved in a variety of vascular abnormalities-related diseases. This article reviews the role of HTRA1 in the development of vascular abnormalities-related hereditary cerebral small vessel disease (CSVD), age-related macular degeneration (AMD), tumors and other diseases. Through relevant research advances to understand the role of HTRA1 in regulating signaling pathways or refolding, translocation, degradation of extracellular matrix (ECM) proteins, thus directly or indirectly regulating angiogenesis, vascular remodeling, and playing an important role in vascular homeostasis, further understanding the mechanism of HTRA1's role in vascular abnormality-related diseases is important for HTRA1 to be used as a therapeutic target in related diseases.

The Potential Role of Spa Therapy in Managing Frailty in Rheumatic Patients: A Scoping Review

Frailty is not limited to the elderly, as patients with rheumatic diseases can also experience this condition. The present scoping review aimed to investigate the possibility of using the health resort setting as an alternative location for managing rheumatic patients with frailty. The research resulted in finding several in vitro, in vivo, and clinical studies, resulting in evidence supporting the effectiveness of spa treatments in reducing pain, improving function, and managing comorbidity in rheumatic diseases. Additionally, spa treatments were demonstrated to modulate the MAPK/ERK pathway and the NF-kB pathway's activation and to reduce proinflammatory molecules' secretion in rheumatic diseases, thus suggesting their potential effective role in the regulation of inflammaging in frailty. Moreover, the health resort setting may offer potential resources to reduce risk factors, such as drug consumption, inactivity, and disease severity, and may serve as a setting for developing prevention protocols for frailty. Future research should explore innovative approaches, such as exercise training and early diagnostics, for the overall management of frailty in rheumatic patients in the spa setting.

Inhibiting HIF-1 signaling alleviates HTRA1-induced RPE senescence in retinal degeneration

BACKGROUND

Age-related macular degeneration (AMD), characterized by the degeneration of retinal pigment epithelium (RPE) and photoreceptors, is the leading cause of irreversible vision impairment among the elderly. RPE senescence is an important contributor to AMD and has become a potential target for AMD therapy. HTRA1 is one of the most significant susceptibility genes in AMD, however, the correlation between HTRA1 and RPE senescence hasn't been investigated in the pathogenesis of AMD.

METHODS

Western blotting and immunohistochemistry were used to detect HTRA1 expression in WT and transgenic mice overexpressing human HTRA1 (hHTRA1-Tg mice). RT-qPCR was used to detect the SASP in hHTRA1-Tg mice and ARPE-19 cells infected with HTRA1. TEM, SA-β-gal was used to detect the mitochondria and senescence in RPE. Retinal degeneration of mice was investigated by fundus photography, FFA, SD-OCT and ERG. The RNA-Seq dataset of ARPE-19 cells treated with adv-HTRA1 versus adv-NC were analyzed. Mitochondrial respiration and glycolytic capacity in ARPE-19 cells were measured using OCR and ECAR. Hypoxia of ARPE-19 cells was detected using EF5 Hypoxia Detection Kit. KC7F2 was used to reduce the HIF1α expression both in vitro and in vivo.

RESULTS

In our study, we found that RPE senescence was facilitated in hHTRA1-Tg mice. And hHTRA1-Tg mice became more susceptible to NaIO₃ in the development of oxidative stress-induced retinal degeneration. Similarly, overexpression of HTRA1 in ARPE-19 cells accelerated cellular senescence. Our RNA-seq revealed an overlap between HTRA1-induced differentially expressed genes associated with aging and those involved in mitochondrial function and hypoxia response in ARPE-19 cells. HTRA1 overexpression in ARPE-19 cells impaired mitochondrial function and augmented glycolytic capacity. Importantly, upregulation of HTRA1 remarkably activated HIF-1 signaling, shown as promoting HIF1α expression which mainly located in the nucleus. HIF1α translation inhibitor KC7F2 significantly prevented HTRA1-induced cellular senescence in ARPE-19 cells, as well as improved the visual function in hHTRA1-Tg mice treated with NaIO₃.

CONCLUSIONS

Our study showed elevated HTRA1 contributes to the pathogenesis of AMD by promoting cellular senescence in RPE through damaging mitochondrial function and activating HIF-1 signaling. It also pointed out that inhibition of HIF-1 signaling might serve as a potential therapeutic strategy for AMD. Video Abstract.

Shotgun proteomics of extracellular matrix in late senescent human dermal fibroblasts reveals a down-regulated fibronectin-centered network

Extracellular matrix (ECM) proteins play a pivotal role in cell growth and differentiation. To characterize aged ECM proteins, we compared the proteomes by shotgun method of young (passage #15) and late senescent (passage #40) human dermal fibroblasts (HDFs) using SDS-PAGE coupled with LC–MS/MS. The relative abundance of identified proteins was determined using mol% of individual proteins as a semi-quantitative index. Fifteen ECM proteins including apolipoprotein B (APOB) and high-temperature requirement factor 1 (HTRA1) were up-regulated, whereas 50 proteins including fibronectin 1 (FN1) and vitronectin (VTN) were down-regulated in late senescent HDFs. The identified ECM proteins combined with plasma membrane were queried to construct the protein–protein interaction network using Ingenuity Pathways Analysis, resulting in a distinct FN1-centered network. Of differentially abundant ECM proteins in shotgun proteomics, the protein levels of FN1, VTN, APOB, and HTRA1 were verified by immunoblot analysis. The results suggest that the aging process in HDFs might be finally involved in the impaired FN1 regulatory ECM network combined with altered interaction of neighboring proteins. Shotgun proteomics of highly aged HDFs provides insight for further studies of late senescence-related alterations in ECM proteins.

The multifaced role of HtrA1 in the development of joint and skeletal disorders

HtrA1 (High temperature requirement A1) family proteins include four members, widely conserved from prokaryotes to eukaryotes, named HtrA1, HtrA2, HtrA3 and HtrA4. HtrA1 is a serine protease involved in a variety of biological functions regulating many signaling pathways degrading specific components and playing key roles in many human diseases such as neurodegenerative disorders, pregnancy complications and cancer. Due to its role in the breakdown of many ExtraCellular Matrix (ECM) components of articular cartilage such as fibronectin, decorin and aggrecan, HtrA1 encouraged many researches on studying its role in several skeletal diseases (SDs). These studies were further inspired by the fact that HtrA1 is able to regulate the signaling of one of the most important cytokines involved in SDs, the TGFβ-1. This review aims to summarize the data currently available on the role of HtrA1 in skeletal diseases such as Osteoporosis, Rheumatoid Arthritis, Osteoarthritis and Intervertebral Disc Degeneration (IDD). The use of HtrA1 as a marker of frailty in geriatric medicine would represent a powerful tool for identifying older individuals at risk of developing skeletal disorders, evaluating an appropriate intervention to improve quality care in these people avoiding or improving age-related SDs in the elderly population.

Placental HTRA1 cleaves α1-antitrypsin to generate a NET-inhibitory peptide

Neutrophil extracellular traps (NETs) are important components of innate immunity. Neonatal neutrophils (polymorphonuclear leukocytes [PMNs]) fail to form NETs due to circulating NET-inhibitory peptides (NIPs), cleavage fragments of α1-antitrypsin (A1AT). How fetal and neonatal blood NIPs are generated remains unknown, however. The placenta expresses high-temperature requirement serine protease A1 (HTRA1) during fetal development, which can cleave A1AT. We hypothesized that placentally expressed HTRA1 regulates the formation of NIPs and that NET competency changed in PMNs isolated from neonatal HTRA1 knockout mice (HTRA1-/-). We found that umbilical cord blood plasma has elevated HTRA1 levels compared with adult plasma and that recombinant and placenta-eluted HTRA1 cleaves A1AT to generate an A1AT cleavage fragment (A1ATM383S-CF) of molecular weight similar to previously identified NIPs that block NET formation by adult neutrophils. We showed that neonatal mouse pup plasma contains A1AT fragments that inhibit NET formation by PMNs isolated from adult mice, indicating that NIP generation during gestation is conserved across species. Lipopolysaccharide-stimulated PMNs isolated from HTRA1+/+ littermate control pups exhibit delayed NET formation after birth. However, plasma from HTRA1-/- pups had no detectable NIPs, and PMNs from HTRA1-/- pups became NET competent earlier after birth compared with HTRA1+/+ littermate controls. Finally, in the cecal slurry model of neonatal sepsis, A1ATM383S-CF improved survival in C57BL/6 pups by preventing pathogenic NET formation. Our data indicate that placentally expressed HTRA1 is a serine protease that cleaves A1AT in utero to generate NIPs that regulate NET formation by human and mouse PMNs.

Effects of Low-Speed and High-Speed Resistance Training Programs on Frailty Status, Physical Performance, Cognitive Function, and Blood Pressure in Prefrail and Frail Older Adults

Aim: The current study investigated the effects of low-speed resistance training (LSRT) and high-speed resistance training (HSRT) on frailty status, physical performance, cognitive function and blood pressure in pre-frail and frail older people.

Material and Methods: Sixty older adults, 32 prefrail and 28 frail, were randomly allocated into LSRT, HSRT, and control group (CG). Before and after intervention periods frailty status, blood pressure, heart rate, and a set of physical performance capabilities and cognitive domains were assessed. Exercise interventions occurred over 16 weeks and included four resistance exercises with 4–8 sets of 4–10 repetitions at moderate intensity.

Results: The prevalence of frailty criteria in prefrail and frail older adults were reduced after both LSRT and HSRT. In prefrail, LSRT significantly improved lower-limb muscle strength, while mobility was only improved after HSRT. Muscle power and dual-task performance were significantly increased in both LSRT and HSRT. In frail, LSRT and HSRT similarly improved lower-limb muscle strength and power. However, exclusive improvements in dual-task were observed after LSRT. Memory was significantly increased in prefrail and frail, regardless of the type of resistance training. No significant changes were observed in blood pressure and heart rate.

Conclusion: Findings of the present study indicated that both LSRT and HSRT reversed frailty status and improved physical performance in prefrail and frail older adults. Notably, different patterns of improvement were observed among RT protocols. Regarding frailty status, LSRT seemed to be more effective in reverse prefrailty and frailty when compared to HSRT. Greater improvements in muscle strength and power were also observed after LSRT, while HSRT produced superior increases in mobility and dual-task performance. One-leg stand performance was significantly reduced in LSRT, but not HSRT and CG, after 16 weeks. In contrast, RT programs similarly improved verbal memory in prefrail. Finally, no changes in blood pressure and heart rate were observed, regardless of the type of RT.

Trial Registration: The protocol was approved by the University of Campinas Human Research Ethics Committee (Protocol No. 20021919.7.0000.5404) and retrospectively registered at ClinicalTrials.gov Protocol Registration and Results System: NCT04868071.

Identification of biomarkers for physical frailty and sarcopenia through a new multi-marker approach: results from the BIOSPHERE study

Physical frailty and sarcopenia (PF&S) is a prototypical geriatric condition characterized by reduced physical function and low muscle mass. The aim of the present study was to provide an initial selection of biomarkers for PF&S using a novel multivariate analytic strategy. Two-hundred community-dwellers, 100 with PF&S and 100 non-physically frail, non-sarcopenic (nonPF&S) controls aged 70 and older were enrolled as part of the BIOmarkers associated with Sarcopenia and Physical frailty in EldeRly pErsons (BIOSPHERE) study. A panel of 74 serum analytes involved in inflammation, muscle growth and remodeling, neuromuscular junction damage, and amino acid metabolism was assayed. Biomarker selection was accomplished through sequential and orthogonalized covariance selection (SO-CovSel) analysis. Separate SO-CovSel models were constructed for the whole study population and for the two genders. The model with the best prediction ability obtained with the smallest number of variables was built using seven biomolecules. This model allowed correct classification of 80.6 ± 5.3% PF&S participants and 79.9 ± 5.1% nonPF&S controls. The PF&S biomarker profile was characterized by higher serum levels of asparagine, aspartic acid, and citrulline. Higher serum concentrations of platelet-derived growth factor BB, heat shock protein 72 (Hsp72), myeloperoxidase, and α-aminobutyric acid defined the profile of nonPF&S participants. Gender-specific SO-CovSel models identified a "core" biomarker profile of PF&S, characterized by higher serum levels of aspartic acid and Hsp72 and lower concentrations of macrophage inflammatory protein 1β, with peculiar signatures in men and women.SO-CovSel analysis allowed identifying a set of potential biomarkers for PF&S. The adoption of such an innovative multivariate approach could help address the complex pathophysiology of PF&S, translate biomarker discovery from bench to bedside, and unveil novel targets for interventions.

Cross-sectional associations among P3NP, HtrA, Hsp70, Apelin and sarcopenia in Taiwanese population

BACKGROUND

Sarcopenia is a multifactorial pathophysiologic condition of skeletal muscle mass and muscle strength associated with aging. However, biomarkers for predicting the occurrence of sarcopenia are rarely discussed in recent studies. The aim of the study was to elucidate the relationship between sarcopenia and several pertinent biomarkers.

METHODS

Using the Gene Expression Omnibus (GEO) profiles of the National Center for Biotechnology Information, the associations between mRNA expression of biomarkers and sarcopenia were explored, including high temperature requirement serine protease A1 (HtrA1), procollagen type III N-terminal peptide (P3NP), apelin, and heat shock proteins 70 (Hsp72). We enrolled 408 community-dwelling adults aged 65 years and older with sarcopenia and nonsarcopenia based on the algorithm proposed by the Asian Working Group for Sarcopenia (AWGS). Muscle strength is identified by hand grip strength using an analogue isometric dynamometer. Muscle mass is estimated by skeletal mass index (SMI) using a bioelectrical impedance analysis. Physical performance is measured by gait speed using 6 m walking distance. The associations between these biomarkers and sarcopenia were determined using receiver operating characteristic (ROC) curve analysis and multivariate regression models.

RESULTS

From the GEO profiles, the sarcopenia gene set variation analysis score was correlated significantly with the mRNA expression of APLNR (p < 0.001) and HSPA2 (p < 0.001). In our study, apelin was significantly associated with decreased hand grip strength with β values of - 0.137 (95%CI: - 0.229, - 0.046) in men. P3NP and HtrA1 were significantly associated with increased SMI with β values of 0.081 (95%CI: 0.010, 0.153) and 0.005 (95%CI: 0.001, 0.009) in men, respectively. Apelin and HtrA1 were inversely associated with the presence of sarcopenia with an OR of 0.543 (95%CI: 0.397-0.743) and 0.003 (95%CI: 0.001-0.890) after full adjustment. The cutoff point of HtrA1 was associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778) in men. The cutoff point of apelin was negatively associated with the presence of sarcopenia with an OR of 0.254 (95%CI: 0.083-0.778).

CONCLUSION

Our study highlights that P3NP, HtrA, and apelin are useful for diagnosis of sarcopenia in the clinical setting.

Frailty is not associated with hypertension, blood pressure or antihypertensive medication in community-dwelling older adults: A cross-sectional comparison across 3 frailty instruments

AIM

The present study investigated whether hypertension, blood pressure, and antihypertensive therapy were associated with frailty status in community-dwelling older adults. In addition, we tested whether such associations were consistent across different frailty instruments.

MATERIAL AND METHODS

Two-hundred older adults were enrolled in the study. Participant frailty status was determined according to a modified physical frailty phenotype (mFP), the FRAIL scale, and the Study of Osteoporotic Fracture (SOF) index. Blood pressure was assessed three times, in three different days, and mean values were used in the final analysis. Information pertaining to disease conditions and antihypertensive therapy were collected by two researchers through self-report and careful review of medical charts.

RESULTS

No significant differences in hemodynamic parameters, hypertension diagnosis, and antihypertensive therapy were observed across frailty statuses, regardless of the frailty assessment tool used.

CONCLUSION

Findings of the present study indicate that hypertension, blood pressure levels and antihypertensive medication were not cross-sectionally associated with frailty status in cognitively preserved community-dwelling older adults with low prevalence of comorbidities, regardless of the tool used for frailty identification.

The 10q26 Risk Haplotype of Age-Related Macular Degeneration Aggravates Subretinal Inflammation by Impairing Monocyte Elimination

A minor haplotype of the 10q26 locus conveys the strongest genetic risk for age-related macular degeneration (AMD). Here, we examined the mechanisms underlying this susceptibility. We found that monocytes from homozygous carriers of the 10q26 AMD-risk haplotype expressed high amounts of the serine peptidase HTRA1, and HTRA1 located to mononuclear phagocytes (MPs) in eyes of non-carriers with AMD. HTRA1 induced the persistence of monocytes in the subretinal space and exacerbated pathogenic inflammation by hydrolyzing thrombospondin 1 (TSP1), which separated the two CD47-binding sites within TSP1 that are necessary for efficient CD47 activation. This HTRA1-induced inhibition of CD47 signaling induced the expression of pro-inflammatory osteopontin (OPN). OPN expression increased in early monocyte-derived macrophages in 10q26 risk carriers. In models of subretinal inflammation and AMD, OPN deletion or pharmacological inhibition reversed HTRA1-induced pathogenic MP persistence. Our findings argue for the therapeutic potential of CD47 agonists and OPN inhibitors for the treatment of AMD.

Omics biomarkers for frailty in older adults

Frailty is a clinical state characterized by an age-related unsteady state of the body, a decline in physiological function, and an increased vulnerability to adverse outcomes. Early diagnosis of frailty is important for improving the quality of life in older adults and promoting healthy aging. The biological mechanisms underlying frailty have been extensively studied in recent years. Combining assessment tools and biomarkers can facilitate the early diagnosis of frailty. However, there is a lack of stable and reliable frailty-related biomarkers for use in clinical practice. Advances in the multi-omics platforms have provided new information on the molecular mechanisms underlying frailty. Thus, identifying biomarkers using omics-based approaches helps explore the physiological mechanisms underlying frailty, and aids the evaluation of the risk of frailty development and progression. This article reviews the current status of frailty biomarkers from the genomics, transcriptomics, proteomics, and metabolomics perspectives.

Circulating biomarkers characterizing physical frailty: CRP, hemoglobin, albumin, 25OHD and free testosterone as best biomarkers. Results of a meta-analysis

INTRODUCTION

During aging, individuals can be classified as being in one of 3 different states: robust, frail or dependent. Frailty is described as reversible, so early detection offers the potential of returning the subject to a robust status. There are multiple clinical frailty scales but no gold standard and frailty is not systematically assessed in clinicians' daily practice. Reliable biomarkers of frailty are lacking, however, while their identification and systematic use would make this simple scale a useful clinical tool.

OBJECTIVE

To conduct a review of the literature concerning the biomarkers associated with frailty and to compare in a meta-analysis the plasmatic values of each biomarker in the frail with the robust group.

RESULTS

503 articles were identified on PubMed, 467 on Scopus and 369 on Web Of Science. 67 articles were included, collecting a total of 32,934 robust subjects and 6864 frail subjects. C-reactive protein (CRP) (Standardized Mean Difference (SMD): 0.49 CI 95% [0.37-0.61]) was significantly higher in the frail group whereas hemoglobin (SMD: -0.67[-0.90; -0.44]), albumin (SMD: -0.62[-0.84; -0.41]), 25-hydroxyvitamin D (25OHD) (SMD: -0.43 [-0.64; -0.21]) and, in men, free testosterone (SMD: -0.77 [-1.05; -0.49]) were significantly lower in the frail group.

CONCLUSION

We found 5 biomarkers that were associated with frailty (CRP, hemoglobin, albumin, 25OHD and free testosterone in men) belonging to multiple physiological systems. Further cohort studies are needed to verify their ability to screen for frailty.

Protein-Related Dietary Parameters and Frailty Status in Older Community-Dwellers across Different Frailty Instruments

The present study investigated the associations between frailty status and (a) daily protein intake, (b) daily body weight-adjusted protein intake, (c) branched-chain amino acid (BCAA) consumption, (d) evenness of protein distribution across main meals, (e) number of daily meals providing at least 30 g of protein, and (f) number of daily meals providing at least 0.4 g protein/kg of body weight in community-dwelling older adults. The relationship between frailty status and protein-related dietary parameters was explored across different frailty assessment tools. Two hundred older adults were enrolled in the study. Participant frailty status was determined according to a modified Fried’s frailty phenotype (mFP), the FRAIL scale, and the Study of Osteoporotic Fracture (SOF) index. Diet was assessed by 24-h dietary recall, while diet composition was estimated using a nutritional software. A frailty instrument-dependent relationship was observed between frailty status and protein-related dietary parameters. Protein consumption was associated with frailty status only in participants identified as frail according to the mFP. In addition, protein and BCAA intake was found to be greater in robust and pre-frail participants relative to their frail counterparts. Our findings suggest that the association between frailty and protein-related dietary parameters is tool dependent. Specifically, protein and BCAA consumption appears to be lower only in older adults identified as frail by the mFP.

HtrA1 serine protease expression levels on age-related macular degeneration (AMD) patients in Yogyakarta

This research aims to investigate the HtrA1 serine protease circulating level of Age-related Macular Degeneration (AMD) patients in Yogyakarta, Indonesia. This study was conducted from January to August 2019 which included 38 AMD patients and 16 Non-AMD patients/controls (two groups). Baseline data and blood sample were collected. ELISA assay was used to measure the HtrA1 serine protease circulating level on both groups. SNP genotyping of rs10490924 was using restriction enzyme digestion. This study used The IBM SPSS® version 24 (Chicago, The USA) to determine the relationship between HtrA1 expression level and AMD incidence. AMD patients had higher HtrA1 serine protease level (35.31) than controls (30.08). However, there is no association found between HtrA1 serine protease level and AMD incidence (p-value>0.05, CI 95 %). However, HtrA1 serine protease did not associate positively to AMD incidence in Yogyakarta samples. Further analysis by grouping AMD patient based on the rs10490924 genotype show no statistical correlation between HTRA1 to the incidence of AMD. This result might be due to the lack of samples in the study groups. Future studies with larger number of samples are advised to better see the association between Htra1 serine protease level and AMD incidence.

Frailty biomarkers in humans and rodents: Current approaches and future advances

Even though they would have great benefit across research and clinical fields, currently there are no accepted biomarkers of frailty. Cross-sectional studies in humans have identified promising candidates including inflammatory markers such as IL-6, immune markers such as WBC count, clinical markers such as albumin, endocrine markers such as vitamin D, oxidative stress markers such as isoprostanes, proteins such as BDNF and epigenetic markers such as DNA methylation, but there are limitations to the current state of the research. Future approaches to the identification of frailty biomarkers should include longitudinal studies, studies using animal models of frailty, studies incorporating novel biomarkers combined into composite panels, and studies investigating sex differences and potential overlap between markers of biological age and frailty.

Deep Profiling of the Aggregated Proteome in Alzheimer's Disease: From Pathology to Disease Mechanisms

Hallmarks of Alzheimer’s disease (AD), a progressive neurodegenerative disease causing dementia, include protein aggregates such as amyloid beta plaques and tau neurofibrillary tangles in a patient’s brain. Understanding the complete composition and structure of protein aggregates in AD can shed light on the as-yet unidentified underlying mechanisms of AD development and progression. Biochemical isolation of aggregates coupled with mass spectrometry (MS) provides a comprehensive proteomic analysis of aggregates in AD. Dissection of these AD-specific aggregate components, such as U1 small nuclear ribonucleoprotein complex (U1 snRNP), provides novel insights into the deregulation of RNA splicing in the disease. In this review, we summarize the methodologies of laser capture microdissection (LCM) and differential extraction to analyze the aggregated proteomes in AD samples, and discuss the derived novel insights that may contribute to AD pathogenesis.

The "BIOmarkers associated with Sarcopenia and PHysical frailty in EldeRly pErsons" (BIOSPHERE) study: Rationale, design and methods

Sarcopenia, the progressive and generalised loss of muscle mass and strength/function, is a major health issue in older adults given its high prevalence and burdensome clinical implications. Over the years, this condition has been endorsed as a marker for discriminating biological from chronological age. However, the absence of a unified operational definition has hampered its full appreciation by healthcare providers, researchers and policy-makers. In addition to this unsolved debate, the complexity of musculoskeletal ageing represents a major challenge to the identification of clinically meaningful biomarkers. Here, we illustrate the advantages of biomarker discovery procedures in muscle ageing based on multivariate methodologies as an alternative approach to traditional single-marker strategies. The rationale, design and methods of the "BIOmarkers associated with Sarcopenia and PHysical frailty in EldeRly pErsons" (BIOSPHERE) study are described as an application of a multi-marker strategy for the development of biomarkers for the newly operationalised Physical Frailty & Sarcopenia condition.

Changes in the detergent-insoluble brain proteome linked to amyloid and tau in Alzheimer's Disease progression

Despite a key role of amyloid-beta (Aβ) in Alzheimer's disease (AD), mechanisms that link Aβ plaques to tau neurofibrillary tangles and cognitive decline still remain poorly understood. The purpose of this study was to quantify proteins in the sarkosyl-insoluble brain proteome correlated with Aβ and tau insolubility in the asymptomatic phase of AD (AsymAD) and through mild cognitive impairment (MCI) and symptomatic AD. Employing label-free mass spectrometry-based proteomics, we quantified 2711 sarkosyl-insoluble proteins across the prefrontal cortex from 35 individual cases representing control, AsymAD, MCI and AD. Significant enrichment of Aβ and tau in AD was observed, which correlated with neuropathological measurements of plaque and tau tangle density, respectively. Pairwise correlation coefficients were also determined for all quantified proteins to Aβ and tau, across the 35 cases. Notably, six of the ten most correlated proteins to Aβ were U1 small nuclear ribonucleoproteins (U1 snRNPs). Three of these U1 snRNPs (U1A, SmD and U1-70K) also correlated with tau consistent with their association with tangle pathology in AD. Thus, proteins that cross-correlate with both Aβ and tau, including specific U1 snRNPs, may have potential mechanistic roles in linking Aβ plaques to tau tangle pathology during AD progression.

Role of HTRA1 in bone formation and regeneration: In vitro and in vivo evaluation

The role of mammalian high temperature requirement protease A1 (HTRA1) in somatic stem cell differentiation and mineralized matrix formation remains controversial, having been demonstrated to impart either anti- or pro-osteogenic effects, depending on the in vitro cell model used. The aim of this study was therefore to further evaluate the role of HTRA1 in regulating the differentiation potential and lineage commitment of murine mesenchymal stem cells in vitro, and to assess its influence on bone structure and regeneration in vivo. Our results demonstrated that short hairpin RNA-mediated ablation of Htra1 in the murine mesenchymal cell line C3H10T1/2 increased the expression of several osteogenic gene markers, and significantly enhanced matrix mineralization in response to BMP-2 stimulation. These effects were concomitant with decreases in the expression of chondrogenic gene markers, and increases in adipogenic gene expression and lipid accrual. Despite the profound effects of loss-of-function of HTRA1 on this in vitro osteochondral model, these were not reproduced in vivo, where bone microarchitecture and regeneration in 16-week-old Htra1-knockout mice remained unaltered as compared to wild-type controls. By comparison, analysis of femurs from 52-week-old mice revealed that bone structure was better preserved in Htra1-knockout mice than age-matched wild-type controls. These findings therefore provide additional insights into the role played by HTRA1 in regulating mesenchymal stem cell differentiation, and offer opportunities for improving our understanding of how this multifunctional protease may act to influence bone quality.