Multi-OMICS analyses of frailty and chronic widespread musculoskeletal pain suggest involvement of shared neurological pathways

Multi-omics profiles of chronic low back pain and fibromyalgia-Study protocol

BACKGROUND

Chronic low back pain (CLBP) and fibromyalgia (FM) are leading causes of suffering, disability, and social costs. Current pharmacological treatments do not target molecular mechanisms driving CLBP and FM, and no validated biomarkers are available, hampering the development of effective therapeutics. Omics research has the potential to substantially advance our ability to develop mechanism-specific therapeutics by identifying pathways involved in the pathophysiology of CLBP and FM, and facilitate the development of diagnostic, predictive, and prognostic biomarkers. We will conduct a blood and urine multi-omics study in comprehensively phenotyped and clinically characterized patients with CLBP and FM. Our aims are to identify molecular pathways potentially involved in the pathophysiology of CLBP and FM that would shift the focus of research to the development of target-specific therapeutics, and identify candidate diagnostic, predictive, and prognostic biomarkers.

METHODS

We are conducting a prospective cohort study of adults ≥18 years of age with CLBP (n=100) and FM (n=100), and pain-free controls (n=200). Phenotyping measures include demographics, medication use, pain-related clinical characteristics, physical function, neuropathic components (quantitative sensory tests and DN4 questionnaire), pain facilitation (temporal summation), and psychosocial function as moderator. Blood and urine samples are collected to analyze metabolomics, lipidomics and proteomics. We will integrate the overall omics data to identify common mechanisms and pathways, and associate multi-omics profiles to pain-related clinical characteristics, physical function, indicators of neuropathic pain, and pain facilitation, with psychosocial variables as moderators.

DISCUSSION

Our study addresses the need for a better understanding of the molecular mechanisms underlying chronic low back pain and fibromyalgia. Using a multi-omics approach, we hope to identify converging evidence for potential targets of future therapeutic developments, as well as promising candidate biomarkers for further investigation by biomarker validation studies. We believe that accurate patient phenotyping will be essential for the discovery process, as both conditions are characterized by high heterogeneity and complexity, likely rendering molecular mechanisms phenotype specific.

1H-NMR-based metabolomics identifies disrupted betaine metabolism as distinct serum signature of pre-frailty

Increasing evidence suggests that frailty results from a complex age-associated metabolic decline. Here, we investigated the serum metabolomic profile of a well-characterized cohort of elderly subjects encompassing the whole fit-to-frail continuum. Enrichment analyses revealed a complex dysregulation of amino acids and energy metabolism in both pre-frail and frail participants. Remarkably, upregulated betaine levels emerged as a specific biochemical signature of pre-frail females, holding promise for the development of novel targeted interventions.

Salivary Metabolomics as a Diagnostic Tool: Distinct Metabolic Profiles Across Orofacial Pain Subtypes

Orofacial pain (OFP) includes chronic pain conditions categorized into musculoskeletal (MS), neurovascular (NV), and neuropathic (NP) pain types, encompassing temporomandibular disorders (TMD), migraines, trigeminal neuralgia (TN), post-traumatic neuropathies, and burning mouth syndrome (BMS). These conditions significantly affect quality of life; yet, their underlying metabolic disruptions remain inadequately explored. Salivary metabolomics provides a non-invasive method to investigate biochemical alterations associated with OFP subtypes. This study aimed to identify pain-specific salivary metabolites across chronic OFP types and examine their correlations with clinical characteristics. Saliva samples from 63 OFP patients (TMD, migraines, TN, post-traumatic neuropathies, BMS) and 37 pain-free controls were analyzed using liquid chromatography-mass spectrometry (LC-MS) targeting 28 metabolites linked to pain. Statistical analyses determined significant metabolite changes and associations with pain subtypes and patient characteristics. Among the 28 analyzed metabolites, 18 showed significant differences between OFP patients and controls. Key amino acids, including DL-glutamic acid, DL-aspartic acid, DL-citrulline, spermidine, and DL-ornithine, were significantly elevated in MS, NV, and NP pain types compared to controls. Additionally, DL-glutamine, DL-valine, and DL-phenylalanine were distinctively elevated in TMD and migraine patients. BMS displayed fewer alterations, with significantly lower levels of DL-proline, DL-tryptophan, DL-glutamic acid, DL-asparagine, and DL-aspartic acid compared to other pain types but elevated spermidine levels relative to controls. Salivary metabolomics revealed distinct metabolic alterations in OFP subtypes, providing insights into potential biomarkers for diagnosis and monitoring. These findings offer a foundation for personalized approaches in OFP management, although further research is required to validate and expand these results.

Single-cell metabolomics profiling of somatosensory neurons in various stages of neuropathic pain

Metabolic alterations in the somatosensory cortex (S1) play a crucial role in neuropathic pain development, as evidenced by magnetic resonance spectroscopy and mass spectrometry analyses of brain homogenates. However, investigating metabolic changes in specific neuronal subtypes during neuropathic pain development remains challenging. Here, utilizing a recently developed technique called single-cell mass spectrometry (SCMS), we investigated metabolomic alterations within excitatory glutamatergic neurons located in the primary S1 during various stages of neuropathic pain. Specifically, we induced neuropathic pain in mice using a spared nerve injury (SNI) model and observed activation of glutamatergic neurons in layer II/III of S1 through c-Fos staining and electrophysiology. We profiled metabolic changes and performed pathway enrichment analysis in these neurons by single-cell mass spectrometry during both acute and subchronic phases of SNI. Further analyses revealed metabolites whose alterations significantly correlated with changes in pain thresholds, as well as distinct temporal patterns of metabolite expression during pain progression. From these analyses, we identified several key metabolites (homogentisic acid, phosphatidylcholine, phosphorylcholine, and rhein) and validated their causal roles in pain modulation via pharmacological interventions. Thus, our study provides a valuable resource for elucidating the neurometabolic regulatory mechanisms underlying neuropathic pain from a single-cell perspective.

Innovations in acute and chronic pain biomarkers: enhancing diagnosis and personalized therapy

Pain affects millions worldwide, posing significant challenges in diagnosis and treatment. Despite advances in understanding pain mechanisms, there remains a critical need for validated biomarkers to enhance diagnosis, prognostication, and personalized therapy. This review synthesizes recent advancements in identifying and validating acute and chronic pain biomarkers, including imaging, molecular, sensory, and neurophysiological approaches. We emphasize the emergence of composite, multimodal strategies that integrate psychosocial factors to improve the precision and applicability of biomarkers in chronic pain management. Neuroimaging techniques like MRI and positron emission tomography provide insights into structural and functional abnormalities related to pain, while electrophysiological methods like electroencepholography and magnetoencepholography assess dysfunctional processing in the pain neuroaxis. Molecular biomarkers, including cytokines, proteomics, and metabolites, offer diagnostic and prognostic potential, though extensive validation is needed. Integrating these biomarkers with psychosocial factors into clinical practice can revolutionize pain management by enabling personalized treatment strategies, improving patient outcomes, and potentially reducing healthcare costs. Future directions include the development of composite biomarker signatures, advances in artificial intelligence, and biomarker signature integration into clinical decision support systems. Rigorous validation and standardization efforts are also necessary to ensure these biomarkers are clinically useful. Large-scale collaborative research will be vital to driving progress in this field and implementing these biomarkers in clinical practice. This comprehensive review highlights the potential of biomarkers to transform acute and chronic pain management, offering hope for improved diagnosis, treatment personalization, and patient outcomes.

Association Between Musculoskeletal Pain and Frailty Over Time in Older Adults

BACKGROUND AND PURPOSE

There is a high frequency of frailty in patients with musculoskeletal pain. Pain from osteoarthritis and lower back pain may be associated with frailty. However, the future risk of frailty among older adults with pain remains unclear. Thus, the primary objective of this study was to examine the association between musculoskeletal pain and the risk of becoming prefrail and frail in older adults.

PARTICIPANTS AND METHODS

A secondary analysis was performed using data from baseline and 1-, 2-, 3-, 4-, 6-, and 8-year follow-ups of the Osteoarthritis Initiative (OAI). The OAI recruited participants from 4 clinical sites in the United States, between February 2004 and May 2006. A self-reported questionnaire was used to determine the baseline musculoskeletal pain status in older adults (n = 1780) 65 years and older, including pain in the lower back, hip, knee, and at 2 or more sites. Using the Fried phenotypic criteria, participants were classified as nonfrail, prefrail, and frail at each period over 8 years.

RESULTS

After adjusting for age, sex, race, education, marital status, annual income, smoking status, comorbidities, and body mass index, binary logistic regression modeling using generalized estimating equations revealed that in older adults musculoskeletal pain in the lower back and at multiple sites was associated with a slightly but significantly decreased risk of prefrailty over time (adjusted odds ratio [AOR] = 0.98, 95% CI = 0.95-0.99, P = .019; AOR = 0.96, CI = 0.92-0.99, P = .032). The association between musculoskeletal pain and frailty among older adults was not statistically significant (all P > .05).

CONCLUSIONS

Musculoskeletal pain did not independently significantly increase the risk of prefrailty or frailty over time. It remains possible that when musculoskeletal is combined with other factors, the risk of prefrailty and frailty may be heightened. Further research into the combination of characteristics that best predict prefrailty and frailty, including but not limited to musculoskeletal pain, is warranted.

The vicious cycle of frailty and pain: a two-sided causal relationship revealed

Background

The decline in physiological functions in the older people is frequently accompanied with pain and frailty, yet the causal connection between frailty and pain remains uncertain. In this study, we utilized a two-sample Mendelian randomization (MR) approach to investigate the potential causal association between frailty and pain.

Methods

Two-sample bidirectional MR was conducted using summary data from genome-wide association studies to examine the potential causal relationship between frailty (defined by the frailty index and frailty phenotype) and pain. Summary genome wide association statistics were extracted from populations of European ancestry. We also investigated the causal relationship between frailty and site-specific pain, including joint pain, limb pain, thoracic spine pain and low back pain. Causal effects were estimated using the inverse variance weighting method. Sensitivity analyses were performed to validate the robustness of the results.

Results

Genetic predisposition to frailty was associated with an increased risk of pain (frailty phenotype odds ratio [OR]: 1.73; P = 3.54 × 10-6, frailty index OR: 1.36; P = 2.43 × 10-4). Meanwhile, individuals with a genetic inclination toward pain had a higher risk of developing frailty. Regarding site-specific pain, genetic prediction of the frailty phenotype increased the occurrence risk of joint pain, limb pain and low back pain. Reverse MR analysis further showed that limb pain and low back pain were associated with an increased risk of frailty occurrence.

Conclusion

This study presented evidence supporting a bidirectional causal relationship between frailty and pain. We highlighted the significance of addressing pain to prevent frailty and recommend the inclusion of pain assessment in the evaluation system for frailty.

Multi-Omics Profiles of Chronic Low Back Pain and Fibromyalgia - Study Protocol

Background

Chronic low back pain (CLBP) and fibromyalgia (FM) are leading causes of suffering, disability, and social costs. Current pharmacological treatments do not target molecular mechanisms driving CLBP and FM, and no validated biomarkers are available, hampering the development of effective therapeutics. Omics research has the potential to substantially advance our ability to develop mechanism-specific therapeutics by identifying pathways involved in the pathophysiology of CLBP and FM, and facilitate the development of diagnostic, predictive, and prognostic biomarkers. We will conduct a blood and urine multi-omics study in comprehensively phenotyped and clinically characterized patients with CLBP and FM. Our aims are to identify molecular pathways potentially involved in the pathophysiology of CLBP and FM that would shift the focus of research to the development of target-specific therapeutics, and identify candidate diagnostic, predictive, and prognostic biomarkers.

Methods

We are conducting a prospective cohort study of adults ≥18 years of age with CLBP (n=100) and FM (n=100), and pain-free controls (n=200). Phenotyping measures include demographics, medication use, pain-related clinical characteristics, physical function, neuropathiccomponents (quantitative sensory tests and DN4 questionnaire), pain facilitation (temporal summation), and psychosocial function as moderator. Blood and urine samples are collected to analyze metabolomics, lipidomics and proteomics. We will integrate the overall omics data to identify common mechanisms and pathways, and associate multi-omics profiles to pain-related clinical characteristics, physical function, indicators of neuropathic pain, and pain facilitation, with psychosocial variables as moderators.

Discussion

Our study addresses the need for a better understanding of the molecular mechanisms underlying chronic low back pain and fibromyalgia. Using a multi-omics approach, we hope to identify converging evidence for potential targets of future therapeutic developments, as well as promising candidate biomarkers for further investigation by biomarker validation studies. We believe that accurate patient phenotyping will be essential for the discovery process, as both conditions are characterized by high heterogeneity and complexity, likely rendering molecular mechanisms phenotype specific.

Epigenome-wide analysis of frailty: Results from two European twin cohorts

Epigenetics plays an important role in the aging process, but it is unclear whether epigenetic factors also influence frailty, an age-related state of physiological decline. In this study, we performed a meta-analysis of epigenome-wide association studies in four samples drawn from the Swedish Adoption/Twin Study of Aging (SATSA) and the Longitudinal Study of Aging Danish Twins (LSADT) to explore the association between DNA methylation and frailty. Frailty was defined using the frailty index (FI), and DNA methylation levels were measured in whole blood using Illumina's Infinium HumanMethylation450K and MethylationEPIC arrays. In the meta-analysis consisting of a total of 829 participants, we identified 589 CpG sites that were statistically significantly associated with either the continuous or categorical FI (false discovery rate <0.05). Many of these CpGs have previously been associated with age and age-related diseases. The identified sites were also largely directionally consistent in a longitudinal analysis using mixed-effects models in SATSA, where the participants were followed up to a maximum of 20 years. Moreover, we identified three differentially methylated regions within the MGRN1, MIR596, and TAPBP genes that have been linked to neuronal aging, tumor growth, and immune functions. Furthermore, our meta-analysis results replicated 34 of the 77 previously reported frailty-associated CpGs at p < 0.05. In conclusion, our findings demonstrate robust associations between frailty and DNA methylation levels in 589 novel CpGs, previously unidentified for frailty, and strengthen the role of neuronal/brain pathways in frailty.

Validation of a polygenic risk score for frailty in the Lothian Birth Cohort 1936 and English longitudinal study of ageing

Frailty is a complex trait. Twin studies and high-powered Genome Wide Association Studies conducted in the UK Biobank have demonstrated a strong genetic basis of frailty. The present study utilized summary statistics from a Genome Wide Association Study on the Frailty Index to create and test the predictive power of frailty polygenic risk scores (PRS) in two independent samples - the Lothian Birth Cohort 1936 (LBC1936) and the English Longitudinal Study of Ageing (ELSA) aged 67-84 years. Multiple regression models were built to test the predictive power of frailty PRS at five time points. Frailty PRS significantly predicted frailty, measured via the FI, at all-time points in LBC1936 and ELSA, explaining 2.1% (β = 0.15, 95%CI, 0.085-0.21) and 1.8% (β = 0.14, 95%CI, 0.10-0.17) of the variance, respectively, at age ~ 68/ ~ 70 years (p < 0.001). This work demonstrates that frailty PRS can predict frailty in two independent cohorts, particularly at early ages (~ 68/ ~ 70). PRS have the potential to be valuable instruments for identifying those at risk for frailty and could be important for controlling for genetic confounders in epidemiological studies.

Exploring the metabolomics profile of frailty- a systematic review

Background

Frailty is a multifaceted geriatric syndrome characterized by an increased vulnerability to stressful events. metabolomics studies are valuable tool for better understanding the underlying mechanisms of pathologic conditions. This review aimed to elucidate the metabolomics profile of frailty.

Method

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) 2020 statement. A comprehensive search was conducted across multiple databases. Initially, 5027 results were retrieved, and after removing duplicates, 1838 unique studies were subjected to screening. Subsequently, 248 studies underwent full-text screening, with 21 studies ultimately included in the analysis. Data extraction was performed meticulously by two authors, and the quality of the selected studies was assessed using the Critical Appraisal Skills Program (CASP) checklist.

Results

The findings revealed that certain Branched-chain amino acids (BCAAs) levels were lower in frail subjects compared to robust subjects, while levels of glutamate and glutamine were higher in frail individuals. Moreover, sphingomyelins and phosphatidylcholines (PC) displayed a decreasing trend as frailty advanced. Additionally, other metabolic derivatives, such as carnitine, exhibited significant associations with frailty. These metabolites were primarily interconnected through biochemical pathways related to the tricarboxylic acid and urea cycles. Notably, frailty was associated with a decrease in metabolic derivatives, including carnitine.

Conclusion

This study underscores the intricate relationship between essential metabolites, including amino acids and lipids, and their varying levels in frail individuals compared to their robust counterparts. It provides a comprehensive panel of metabolites, shedding light on their potential associations with frailty and expanding our understanding of this complex syndrome.

The intersection of frailty and metabolism

On average, aging is associated with unfavorable changes in cellular metabolism, which are the processes involved in the storage and expenditure of energy. However, metabolic dysregulation may not occur to the same extent in all older individuals as people age at different rates. Those who are aging rapidly are at increased risk of adverse health outcomes and are said to be "frail." Here, we explore the links between frailty and metabolism, including metabolic contributors and consequences of frailty. We examine how metabolic diseases may modify the degree of frailty in old age and suggest that frailty may predispose toward metabolic disease. Metabolic interventions that can mitigate the degree of frailty in people are reviewed. New treatment strategies developed in animal models that are poised for translation to humans are also considered. We suggest that maintaining a youthful metabolism into older age may be protective against frailty.

Metabolites in aging and aging-relevant diseases: Frailty, sarcopenia and cognitive decline

Aging shows biologically complex features with high individual variability, which reflects the exposure to several stimuli and the adaptation to them. Among them, metabolic changes are well observed as consequences or possible causes of aging. Calorie restriction extends organismal life span in experimental models. Several metabolites; for example, resveratrol or nicotinamide mononucleotide, are reported to mimic calorie restriction effects in vivo. Metabolomic research would be useful to evaluate metabolites as biomarkers in aging-relevant events and to identify metabolic regulation of aging. We recently developed the metabolomic approach for whole blood analysis, which functions as strong tool for this purpose. We review the update findings in aging-relevant metabolites detected by this method. Geriatr Gerontol Int 2024; 24: 44-48.

Exploring causality between bone mineral density and frailty: A bidirectional Mendelian randomization study

OBJECTIVE

The bidirectional correlation between low bone mineral density (BMD) and frailty, despite its extensive documentation, still lacks a conclusive understanding. The objective of this Mendelian randomization (MR) study is to investigate the bidirectional causal relationship between BMD and frailty.

METHODS

We utilized summary statistics data for BMD at different skeletal sites-including heel BMD (e-BMD, N = 40,613), forearm BMD (FA-BMD, N = 8,143), femoral neck BMD (FN-BMD, N = 32,735), and lumbar spine BMD (LS-BMD, N = 28,489), alongside frailty index (FI, N = 175,226) data in participants of European ancestry. MR analysis in our study was conducted using well-established analytical methods, including inverse variance weighted (IVW), weighted median (WM), and MR-Egger approaches.

RESULTS

We observed negative causal estimates between genetically predicted e-BMD (IVW β = - 0.020, 95% confidence interval (CI) = - 0.038, - 0.002, P = 0.029) and FA-BMD (IVW β = -0.035, 95% CI = -0.066, -0.004, P = 0.028) with FI. However, the results did not reach statistical significance after applying the Bonferroni correction, with a significance threshold set at P < 0.0125 (0.05/4). There was no causal effect of FN-BMD (IVW β = - 0.024, 95% CI = -0.052, 0.004, P = 0.088) and LS-BMD (IVW β = - 0.005, 95% CI = -0.034, 0.024, P = 0.749) on FI. In the reverse Mendelian randomization (MR) analysis, we observed no causal effect of FI on BMD at various skeletal sites.

CONCLUSION

Our study provides support for the hypothesis that low BMD may be a potential causal risk factor for frailty, but further research is needed to confirm this relationship. However, our findings did not confirm reverse causality.

Relationship between chronic pain, depressive symptoms, and functional disability in community-dwelling older adults: mediating role of frailty

BACKGROUND

Borim et al. showed that older adults with chronic pain exhibited more depressive symptoms and frailty components. Depressive symptoms were associated with more frailty components, and those with more depressive symptoms and frailty faced greater limitations in IADL performance. Frailty appears to mediate the pathway from chronic pain to functional impairment Chronic pain is directly associated with depressive symptoms and frailty. Chronic pain is not directly associated with functional disability. Depression and frailty are both directly associated with functional disabilities. Frailty mediates the association between chronic pain and functional disability. Depression; Disability evaluation; Frailty; Frail elderly.

OBJECTIVE

To evaluate the direct and indirect effects of chronic pain, depressive symptoms, frailty components, and functional disability through a pathway analysis approach in a sample of community-dwelling older adults.

METHODS

Data of 419 participants were cross-sectionally evaluated for the presence of depressive symptoms (Geriatric Depression Scale [15 items]), physical frailty components (phenotype criteria), chronic pain, and limitations in performing instrumental activities of daily living (functional disability scale by Lawton and Brody). Structural equation modeling via path analysis was used to explore the direct and indirect effects among these four variables. Statistical significance was set at p<0.05.

RESULTS

Of the total participants, 69.8% were women and 59.3% had low education (1-4 years); the mean age was 80.3±4.6 years. Chronic pain and depressive symptoms were directly related and were associated to frailty. The number of frailty components and depressive symptoms were directly associated with functional disability. Frailty had an indirect effect on the association between chronic pain, depressive symptoms, and functional disabilities.

CONCLUSION

The pathway from chronic pain and depressive symptoms to functional disability is potentially mediated by the number of frailty components.

Validation of a polygenic risk score for Frailty in the Lothian Birth Cohort and English Longitudinal Study of Ageing

Frailty is a complex trait. Twin studies and a high-powered Genome Wide Association Study (GWAS) conducted in the UK Biobank have demonstrated a strong genetic basis of frailty. The present study utilized summary statistics from this GWAS to create and test the predictive power of frailty polygenic risk scores (PRS) in two independent samples - the Lothian Birth Cohort 1936 (LBC1936) and the English Longitudinal Study of Ageing (ELSA) aged 67-84 years. Multiple regression models were built to test the predictive power of frailty PRS at five time points. Frailty PRS significantly predicted frailty at all-time points in LBC1936 and ELSA, explaining 2.1% (β = 0.15, 95%CI, 0.085-0.21) and 1.6% (β = 0.14, 95%CI, 0.10-0.17) of the variance, respectively, at age ~68/~70 years (p < 0.001). This work demonstrates that frailty PRS can predict frailty in two independent cohorts, particularly at early ages (~68/~70). PRS have the potential to be valuable instruments for identifying those at risk for frailty and could be important for controlling for genetic confounders in epidemiological studies.

A machine learning based approach towards high-dimensional mediation analysis

Mediation analysis is used to investigate the role of intermediate variables (mediators) that lie in the path between an exposure and an outcome variable. While significant research has focused on developing methods for assessing the influence of mediators on the exposure-outcome relationship, current approaches do not easily extend to settings where the mediator is high-dimensional. These situations are becoming increasingly common with the rapid increase of new applications measuring massive numbers of variables, including brain imaging, genomics, and metabolomics. In this work, we introduce a novel machine learning based method for identifying high dimensional mediators. The proposed algorithm iterates between using a machine learning model to map the high-dimensional mediators onto a lower-dimensional space, and using the predicted values as input in a standard three-variable mediation model. Hence, the machine learning model is trained to maximize the likelihood of the mediation model. Importantly, the proposed algorithm is agnostic to the machine learning model that is used, providing significant flexibility in the types of situations where it can be used. We illustrate the proposed methodology using data from two functional Magnetic Resonance Imaging (fMRI) studies. First, using data from a task-based fMRI study of thermal pain, we combine the proposed algorithm with a deep learning model to detect distributed, network-level brain patterns mediating the relationship between stimulus intensity (temperature) and reported pain at the single trial level. Second, using resting-state fMRI data from the Human Connectome Project, we combine the proposed algorithm with a connectome-based predictive modeling approach to determine brain functional connectivity measures that mediate the relationship between fluid intelligence and working memory accuracy. In both cases, our multivariate mediation model links exposure variables (thermal pain or fluid intelligence), high dimensional brain measures (single-trial brain activation maps or resting-state brain connectivity) and behavioral outcomes (pain report or working memory accuracy) into a single unified model. Using the proposed approach, we are able to identify brain-based measures that simultaneously encode the exposure variable and correlate with the behavioral outcome.

Genetic and Environmental Influences on Longitudinal Frailty Trajectories From Adulthood into Old Age

BACKGROUND

Frailty is a complex, dynamic geriatric condition, but limited evidence has shown how genes and environment may contribute to its longitudinal changes. We sought to investigate sources of individual differences in the longitudinal trajectories of frailty, considering potential selection bias when including a sample of oldest-old twins.

METHODS

Data were from 2 Swedish twin cohort studies: a younger cohort comprising 1 842 adults aged 29-96 years followed up to 15 waves, and an older cohort comprising 654 adults aged ≥79 years followed up to 5 waves. Frailty was measured using the frailty index (FI). Age-based latent growth curve models were used to examine longitudinal trajectories, and extended to a biometric analysis to decompose variability into genetic and environmental etiologies.

RESULTS

A bilinear model with an inflection point at age 75 best described the data, indicating a fourfold to fivefold faster FI increase after 75 years. Twins from the older cohort had significantly higher mean FI at baseline but slower rate of increase afterward. FI level at age 75 was moderately heritable in both men (42%) and women (55%). Genetic influences were relatively stable across age for men and increasing for women, although the most salient amplification in FI variability after age 75 was due to individual-specific environmental influences for both men and women; conclusions were largely consistent when excluding the older cohort.

CONCLUSION

Increased heterogeneity of frailty in late life is mainly attributable to environmental influences, highlighting the importance of targeting environmental risk factors to mitigate frailty in older adults.

Role of obesity in less radiographic correction and worse health-related quality-of-life outcomes following minimally invasive deformity surgery

OBJECTIVE

Minimally invasive surgery (MIS) for adult spinal deformity (ASD) can offer deformity correction with less tissue manipulation and damage. However, the impact of obesity on clinical outcomes and radiographic correction following MIS for ASD is poorly understood. The goal of this study was to determine the role, if any, that obesity has on radiographic correction and health-related quality-of-life measures in MIS for ASD.

METHODS

Data were collected from a multicenter database of MIS for ASD. This was a retrospective review of a prospectively collected database. Patient inclusion criteria were age ≥ 18 years and coronal Cobb angle ≥ 20°, pelvic incidence-lumbar lordosis mismatch ≥ 10°, or sagittal vertical axis (SVA) > 5 cm. A group of patients with body mass index (BMI) < 30 kg/m2 was the control cohort; BMI ≥ 30 kg/m2 was used to define obesity. Obesity cohorts were categorized into BMI 30-34.99 and BMI ≥ 35. All patients had at least 1 year of follow-up. Preoperative and postoperative health-related quality-of-life measures and radiographic parameters, as well as complications, were compared via statistical analysis.

RESULTS

A total of 106 patients were available for analysis (69 control, 17 in the BMI 30-34.99 group, and 20 in the BMI ≥ 35 group). The average BMI was 25.24 kg/m2 for the control group versus 32.46 kg/m2 (p < 0.001) and 39.5 kg/m2 (p < 0.001) for the obese groups. Preoperatively, the BMI 30-34.99 group had significantly more prior spine surgery (70.6% vs 42%, p = 0.04) and worse preoperative numeric rating scale leg scores (7.71 vs 5.08, p = 0.001). Postoperatively, the BMI 30-34.99 cohort had worse Oswestry Disability Index scores (33.86 vs 23.55, p = 0.028), greater improvement in numeric rating scale leg scores (-4.88 vs -2.71, p = 0.012), and worse SVA (51.34 vs 26.98, p = 0.042) at 1 year postoperatively. Preoperatively, the BMI ≥ 35 cohort had significantly worse frailty (4.5 vs 3.27, p = 0.001), Oswestry Disability Index scores (52.9 vs 44.83, p = 0.017), and T1 pelvic angle (26.82 vs 20.71, p = 0.038). Postoperatively, after controlling for differences in frailty, the BMI ≥ 35 cohort had significantly less improvement in their Scoliosis Research Society-22 outcomes questionnaire scores (0.603 vs 1.05, p = 0.025), higher SVA (64.71 vs 25.33, p = 0.015) and T1 pelvic angle (22.76 vs 15.48, p = 0.029), and less change in maximum Cobb angle (-3.93 vs -10.71, p = 0.034) at 1 year. The BMI 30-34.99 cohort had significantly more infections (11.8% vs 0%, p = 0.004). The BMI ≥ 35 cohort had significantly more implant complications (30% vs 11.8%, p = 0.014) and revision surgery within 90 days (5% vs 1.4%, p = 0.034).

CONCLUSIONS

Obese patients who undergo MIS for ASD have less correction of their deformity, worse quality-of-life outcomes, more implant complications and infections, and an increased rate of revision surgery compared with their nonobese counterparts, although both groups benefit from surgery. Appropriate counseling should be provided to obese patients.

Frailty indices based on self-report, blood-based biomarkers and examination-based data in the Canadian Longitudinal Study on Aging

BACKGROUND

Frailty can be operationalised using the deficit accumulation approach, which considers health deficits across multiple domains. We aimed to develop, validate and compare three different frailty indices (FI) constructed from self-reported health measures (FI-Self Report), blood-based biomarkers (FI-Blood) and examination-based assessments (FI-Examination).

METHODS

Up to 30,027 participants aged 45-85 years from the baseline (2011-2015) comprehensive cohort of the Canadian Longitudinal Study on Aging were included in the analyses. Following standard criteria, three FIs were created: a 48-item FI-Self Report, a 23-item FI-Blood and a 47-item FI-Examination. In addition a 118-item FI-Combined was constructed. Mortality status was ascertained in July 2019.

RESULTS

FI-Blood and FI-Examination demonstrated broader distributions than FI-Self Report. FI-Self Report and FI-Blood scores were higher in females, whereas FI-Examination scores were higher in males. All FI scores increased nonlinearly with age and were highest at lower education levels. In sex and age-adjusted models, a 0.01 increase in FI score was associated with a 1.08 [95% confidence interval (CI): 1.07,1.10], 1.05 (1.04,1.06), 1.07 (1.05,1.08) and a 1.13 (1.11,1.16) increased odds of mortality for FI-Self Report, FI-Blood, FI-Examination and FI-Combined, respectively. Inclusion of the three distinct FI types in a single model yielded the best prognostic accuracy and model fit, even compared to the FI-Combined, with all FIs remaining independently associated with mortality.

CONCLUSION

Characteristics of all FIs were largely consistent with previously established FIs. To adequately capture frailty levels and to improve our understanding of the heterogeneity of ageing, FIs should consider multiple types of deficits including self-reported, blood and examination-based measures.

Physiological Systems in Promoting Frailty

Frailty is a complex syndrome affecting a growing sector of the global population as medical developments have advanced human mortality rates across the world. Our current understanding of frailty is derived from studies conducted in the laboratory as well as the clinic, which have generated largely phenotypic information. Far fewer studies have uncovered biological underpinnings driving the onset and progression of frailty, but the stage is set to advance the field with preclinical and clinical assessment tools, multiomics approaches together with physiological and biochemical methodologies. In this article, we provide comprehensive coverage of topics regarding frailty assessment, preclinical models, interventions, and challenges as well as clinical frameworks and prevalence. We also identify central biological mechanisms that may be at play including mitochondrial dysfunction, epigenetic alterations, and oxidative stress that in turn, affect metabolism, stress responses, and endocrine and neuromuscular systems. We review the role of metabolic syndrome, insulin resistance and visceral obesity, focusing on glucose homeostasis, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and nicotinamide adenine dinucleotide (NAD+ ) as critical players influencing the age-related loss of health. We further focus on how immunometabolic dysfunction associates with oxidative stress in promoting sarcopenia, a key contributor to slowness, weakness, and fatigue. We explore the biological mechanisms involved in stem cell exhaustion that affect regeneration and may contribute to the frailty-associated decline in resilience and adaptation to stress. Together, an overview of the interplay of aging biology with genetic, lifestyle, and environmental factors that contribute to frailty, as well as potential therapeutic targets to lower risk and slow the progression of ongoing disease is covered. © 2022 American Physiological Society. Compr Physiol 12:1-46, 2022.

Metabolomics-Based Frailty Biomarkers in Older Chinese Adults

Background/Objectives

Owing to accelerated population aging, health in older adults is becoming increasingly important. Frailty can reflect the health status and disease risks of older adults; however, appropriate biomarkers for early screening of frailty have not been identified. Here, we applied metabolomics to identify frailty biomarkers and potential pathogenic mechanisms of frailty.

Methods

Serum metabolic profiles from 25 frail and 49 non-frail (control) older adults were systematically investigated by liquid chromatography-mass spectrometry-based metabolomics.

Results

We identified 349 metabolites of 46 classes, with four increased and seven decreased metabolites in frail older adults. Pearson correlation analysis identified 11 and 21 metabolites that were positively and negatively correlated with grip strength, and 7 and 76 metabolites that were positively and negatively correlated with gait speed, respectively. Pathway analysis identified 10 metabolite sets and 13 pathways significantly associated with one or more frailty phenotype criteria.

Conclusion

These results revealed the metabolite characteristics of serum in frail older adults. Intermediates of carbohydrate metabolism (e.g., isocitrate, malate, fumarate, cis-aconitate, glucuronate, and pyruvate), saturated fatty acids (e.g., palmitic acid), unsaturated fatty acids (e.g., arachidonate and linoleic acid), and certain essential amino acids (e.g., tryptophan) may be candidate biomarkers for the early diagnosis of frailty. Mitochondrial function disorders, saturated fatty acid-mediated lipotoxicity, aberrant unsaturated fatty acid metabolism, and increased tryptophan degradation could be potential mechanisms of frailty.

Specific Metabolites Involved in Antioxidation and Mitochondrial Function Are Correlated With Frailty in Elderly Men

Background

As an age-related syndrome, frailty may play a central role in poor health among older adults. Sarcopenia overlaps with the physical domain of frailty, and most existing studies have analyzed the associated factors of frailty and sarcopenia as an isolated state. Perturbations in metabolism may play an important role in the presence of frailty or sarcopenia; however, the metabolites associated with frailty, especially overlapping with sarcopenia remain unclear. In this study, we aimed to explore whether amino acids, carnitines, acylcarnitines and lysophosphatidylcholines, as specific panels, are significantly correlated with frailty, especially overlapping with sarcopenia, to gain insight into potential biomarkers and possible biological mechanisms and to facilitate their management.

Methods

We applied a targeted high-performance liquid chromatography-tandem mass spectrometry approach in serum samples from 246 Chinese older men (age 79.2 ± 7.8 years) with frailty (n = 150), non-frailty (n = 96), frailty and sarcopenia (n = 52), non-frail and non-sarcopenic control (n = 85). Frailty was evaluated using Freid phenotype criteria, sarcopenia was defined by diagnostic algorithm of Asian Working Group on Sarcopenia, and the participants were diagnosed as frailty and sarcopenia when they met the evaluation criteria of both frailty and sarcopenia. A panel of 29 metabolomic profiles was assayed and included different classes of amino acids, carnitines, acylcarnitines, and lysophosphatidylcholines (LPCs). Multivariate logistic regression was used to screen the metabolic factors contributing to frailty status, and orthogonal partial least squares discriminant analysis was used to explore important factors and distinguish different groups.

Results

In older men demonstrating the frail phenotype, amino acid perturbations included lower tryptophan and higher glycine levels. With regard to lipid metabolism, the frailty phenotype was characterized by lower concentrations of isovalerylcarnitine (C5), LPC16:0 and LPC18:2, while higher levels of octanoyl-L-carnitine (C8), decanoyl-L-carnitine (C10), dodecanoyl-L-carnitine (C12) and tetradecanoyl-L-carnitine (C14). After adjusting for several clinical confounders, tryptophan, LPC18:2, LPC 16:0 and C5 were negatively correlated with frailty, and C8 and C12 were positively related to frailty. We preliminarily identified metabolic profiles (LPC16:0, LPC18:2, glycine and tryptophan) that may distinguish older men with frailty from those without frailty. Importantly, a set of serum amino acids and LPCs (LPC16:0, LPC18:2, and tryptophan) was characterized in the metabotype of older adults with an overlap of frailty and sarcopenia. The metabolites that were most discriminating of frailty status implied that the underlying mechanism might be involved in antioxidation and mitochondrial dysfunction.

Conclusions

These present metabolic analyses may provide valuable information on the potential biomarkers and possible biological mechanisms of frailty, and overlapping sarcopenia. The findings obtained may offer insight into their management in older adults.

Frailty and pain, human studies and animal models

The hypothesis that pain can predispose to frailty development has been recently investigated in several clinical studies suggesting that frailty and pain may share some mechanisms. Both pain and frailty represent important clinical and social problems and both lack a successful treatment. This circumstance is mainly due to the absence of in-depth knowledge of their pathological mechanisms. Evidence of shared pathways between frailty and pain are preliminary. Indeed, many clinical studies are observational and the impact of pain treatment, and relative pain-relief, on frailty onset and progression has never been investigated. Furthermore, preclinical research on this topic has yet to be performed. Specific researches on the pain-frailty relation are needed. In this narrative review, we will attempt to point out the most relevant findings present in both clinical and preclinical literature on the topic, with particular attention to genetics, epigenetics and inflammation, in order to underline the existing gaps and the potential future interventional strategies. The use of pain and frailty animal models discussed in this review might contribute to research in this area.

Plasmatic Hippuric Acid as a Hallmark of Frailty in an Italian Cohort: The Mediation Effect of Fruit-Vegetable Intake

Frailty syndrome is an age-related condition involving a loss of resilience, susceptibility to adverse health outcomes, and poor quality of life. This study was conducted in the framework of InveCe.Ab, an ongoing longitudinal population-based study. Plasma from 130 older individuals (older adults aged 76–78 years) was analyzed and validated (on 303 participants) using mass spectrometry-based metabolomics approaches. Equivalence tests showed that metabolites from the central cellular metabolic pathways were equivalent in frail and fit participants. Hippuric acid was the only cometabolite that distinguished fit from frail older adults. Logistic regression analysis indicated that high hippuric acid levels are significantly associated with a reduction of the risk of frailty after 4 years. Mediation analysis using a Frailty Index, hippuric acid, and fruit–vegetable intake supported the role of fruit–vegetable consumption in the hippuric acid relationship with the Frailty Index. These data point to low plasma hippuric acid as a plausible hallmark of frailty status, associated with lower fruit–vegetable intakes.

A genome-wide association study of the frailty index highlights brain pathways in ageing

Frailty is a common geriatric syndrome and strongly associated with disability, mortality and hospitalization. Frailty is commonly measured using the frailty index (FI), based on the accumulation of a number of health deficits during the life course. The mechanisms underlying FI are multifactorial and not well understood, but a genetic basis has been suggested with heritability estimates between 30 and 45%. Understanding the genetic determinants and biological mechanisms underpinning FI may help to delay or even prevent frailty. We performed a genome-wide association study (GWAS) meta-analysis of a frailty index in European descent UK Biobank participants (n = 164,610, 60-70 years) and Swedish TwinGene participants (n = 10,616, 41-87 years). FI calculation was based on 49 or 44 self-reported items on symptoms, disabilities and diagnosed diseases for UK Biobank and TwinGene, respectively. 14 loci were associated with the FI (p < 5*10-8 ). Many FI-associated loci have established associations with traits such as body mass index, cardiovascular disease, smoking, HLA proteins, depression and neuroticism; however, one appears to be novel. The estimated single nucleotide polymorphism (SNP) heritability of the FI was 11% (0.11, SE 0.005). In enrichment analysis, genes expressed in the frontal cortex and hippocampus were significantly downregulated (adjusted p < 0.05). We also used Mendelian randomization to identify modifiable traits and exposures that may affect frailty risk, with a higher educational attainment genetic risk score being associated with a lower degree of frailty. Risk of frailty is influenced by many genetic factors, including well-known disease risk factors and mental health, with particular emphasis on pathways in the brain.

Protein C-Mannosylation and C-Mannosyl Tryptophan in Chemical Biology and Medicine

C-Mannosylation is a post-translational modification of proteins in the endoplasmic reticulum. Monomeric α-mannose is attached to specific Trp residues at the first Trp in the Trp-x-x-Trp/Cys (W-x-x-W/C) motif of substrate proteins, by the action of C-mannosyltransferases, DPY19-related gene products. The acceptor substrate proteins are included in the thrombospondin type I repeat (TSR) superfamily, cytokine receptor type I family, and others. Previous studies demonstrated that C-mannosylation plays critical roles in the folding, sorting, and/or secretion of substrate proteins. A C-mannosylation-defective gene mutation was identified in humans as the disease-associated variant affecting a C-mannosylation motif of W-x-x-W of ADAMTSL1, which suggests the involvement of defects in protein C-mannosylation in human diseases such as developmental glaucoma, myopia, and/or retinal defects. On the other hand, monomeric C-mannosyl Trp (C-Man-Trp), a deduced degradation product of C-mannosylated proteins, occurs in cells and extracellular fluids. Several studies showed that the level of C-Man-Trp is upregulated in blood of patients with renal dysfunction, suggesting that the metabolism of C-Man-Trp may be involved in human kidney diseases. Together, protein C-mannosylation is considered to play important roles in the biosynthesis and functions of substrate proteins, and the altered regulation of protein C-manosylation may be involved in the pathophysiology of human diseases. In this review, we consider the biochemical and biomedical knowledge of protein C-mannosylation and C-Man-Trp, and introduce recent studies concerning their significance in biology and medicine.

An association between chronic widespread pain and the gut microbiome

OBJECTIVES

Chronic widespread musculoskeletal pain (CWP) is a characteristic symptom of fibromyalgia, which has been shown to be associated with an altered gut microbiome. Microbiome studies to date have not examined the milder CWP phenotype specifically nor have they explored the role of raised BMI. The aim of this study was to investigate whether the microbiome is abnormal in CWP.

METHODS

CWP was assessed using a standardized screening questionnaire in female volunteers from the TwinsUK cohort including 113 CWP cases and 1623 controls. The stool microbiome was characterized using 16S rRNA amplicon sequencing and amplicon sequence variants, and associations with CWP examined using linear mixed-effects models adjusting for BMI, age, diet, family relatedness and technical factors.

RESULTS

Alpha diversity was significantly lower in CWP cases than controls (Mann-Whitney test, P-values 2.3e-04 and 1.2e-02, for Shannon and Simpson indices respectively). The species Coprococcus comes was significantly depleted in CWP cases (Padj = 3.04e-03). A genome-wide association study (GWAS) performed for C. comes in TwinsUK followed by meta-analysis with three Dutch cohorts (total n = 3521) resulted in nine suggestive regions, with the most convincing on chromosome 4 near the TRAM1L1 gene (rs76957229, P = 7.4e-8). A Mendelian randomization study based on the results of the GWAS did not support a causal role for C. comes on the development of CWP.

CONCLUSIONS

We have demonstrated reduced diversity in the microbiome in CWP, indicating an involvement of the gut microbiota in CWP; prospectively the microbiome may offer therapeutic opportunities for this condition.

The degree of frailty as a translational measure of health in aging

Frailty is a multiply determined, age-related state of increased risk for adverse health outcomes. We review how the degree of frailty conditions the development of late-life diseases and modifies their expression. The risks for frailty range from subcellular damage to social determinants. These risks are often synergistic-circumstances that favor damage also make repair less likely. We explore how age-related damage and decline in repair result in cellular and molecular deficits that scale up to tissue, organ and system levels, where they are jointly expressed as frailty. The degree of frailty can help to explain the distinction between carrying damage and expressing its usual clinical manifestations. Studying people-and animals-who live with frailty, including them in clinical trials and measuring the impact of the degree of frailty are ways to better understand the diseases of old age and to establish best practices for the care of older adults.

Sphingomyelin is involved in multisite musculoskeletal pain: evidence from metabolomic analysis in 2 independent cohorts

ABSTRACT

Metabolic dysfunction has been suggested to be involved in musculoskeletal pain; however, few studies have identified metabolic markers associated with multisite musculoskeletal pain (MSMP). This study sought to identify metabolic marker(s) for MSMP by metabolomic analysis. The Tasmanian Older Adult Cohort Study (TASOAC) provided the discovery cohort with the Newfoundland Osteoarthritis Study (NFOAS) providing the replication cohort. Multisite musculoskeletal pain was assessed by a self-reported pain questionnaire and defined as painful sites ≥4 in both the TASOAC and the NFOAS. Furthermore, MSMP was also defined as painful sites ≥7, whereas non-MSMP was defined as either painful sites <7 or ≤1 in the NFOAS. Serum samples of the TASOAC received metabolic profiling using The Metabolomics Innovation Centre Prime Metabolomics Profiling Assay. The data on the identified metabolites were retrieved from NFOAS metabolomic database for the purpose of replication. A total of 409 participants were included in the TASOAC, 38% of them had MSMP. Among the 143 metabolites assessed, 129 passed quality control and were included in the analysis. Sphingomyelin (SM) C18:1 was significantly associated with MSMP (odds ratio [OR] per log µM increase = 3.96, 95% confidence interval, 1.95-8.22; P = 0.0002). The significance remained in multivariable analysis (OR per log µM increase = 2.70, 95% confidence interval, 1.25-5.95). A total of 610 participants were included in the NFOAS, and the association with SM C18:1 was successfully replicated with 3 MSMP definitions (OR ranging from 1.89 to 2.82; all P < 0.03). Our findings suggest that sphingomyelin metabolism is involved in the pathogenesis of MSMP, and the circulating level of SM C18:1 could serve as a potential marker in the management of MSMP.

A Comprehensive Overview of Activities of Daily Living in Existing Frailty Instruments: A Systematic Literature Search

BACKGROUND AND OBJECTIVES

The relationship between frailty and disability in activities of daily living (ADLs) can be seen in different ways, with disability being-to varying degrees-a characteristic, negative outcome, or predictor of frailty. This conflation of definitions is partly a result of the different frailty tools used in research. Aiming to provide a comprehensive overview, this systematic literature search analyzed (i) if, (ii) to what extent, and (iii) how ADLs are evaluated by frailty instruments.

RESEARCH DESIGN AND METHODS

A search was performed in PubMed, Web of Knowledge, and PsycINFO to identify all frailty instruments, followed by categorization of the ADL items into basic (b-), instrumental (i-), and advanced (a-) ADLs.

RESULTS

In total, 192 articles described 217 frailty instruments, from which 52.1% contained ADL items: 45.2% b-ADLs, 35.0% i-ADLs, and 10.1% a-ADLs. The most commonly included ADL items were bathing (b-ADLs); using transportation (i-ADLs); and semiprofessional work engagement in organized social life or leisure activities (a-ADLs). These instruments all had a multidomain origin (χ 2 = 122.4, p < .001).

DISCUSSION AND IMPLICATIONS

Because 52.1% of all instruments included ADL items, the concepts of frailty and disability appear to be highly entangled. This might lead to circular reasoning, serious concerns regarding contamination, and invalid research results.

Specialized, pro-resolving mediators as potential therapeutic agents for alleviating fibromyalgia symptomatology

OBJECTIVE

To present a hypothesis on a novel strategy in the treatment of fibromyalgia (FM).

DESIGN

A narrative review.

SETTING

FM as a disease remains a challenging concept for numerous reasons, including undefined etiopathogenesis, unclear triggers and unsuccessful treatment modalities. We hypothesize that the inflammatome, the entire set of molecules involved in inflammation, acting as a common pathophysiological instrument of gut dysbiosis, sarcopenia, and neuroinflammation, is one of the major mechanisms underlying FM pathogenesis. In this setup, dysbiosis is proposed as the primary trigger of the inflammatome, sarcopenia as the peripheral nociceptive source, and neuroinflammation as the central mechanism of pain sensitization, transmission and symptomatology of FM. Whereas neuroinflammation is highly-considered as a critical deleterious element in FM pathogenesis, the presumed pathogenic roles of sarcopenia and systemic inflammation remain controversial. Nevertheless, sarcopenia-associated processes and dysbiosis have been recently detected in FM individuals. The prevalence of pro-inflammatory factors in the cerebrospinal fluid and blood has been repeatedly observed in FM individuals, supporting an idea on the role of inflammatome in FM pathogenesis. As such, failed inflammation resolution might be one of the underlying pathogenic mechanisms. In accordance, the application of specialized, inflammation pro-resolving mediators (SPMs) seems most suitable for this goal.

CONCLUSIONS

The capability of various SPMs to prevent and attenuate pain has been repeatedly demonstrated in laboratory animal experiments. Since SPMs suppress inflammation in a manner that does not compromise host defense, they could be attractive and safe candidates for the alleviation of FM symptomatology, probably in combination with anti-dysbiotic medicine.

Whole Blood Metabolomics in Aging Research

Diversity is observed in the wave of global aging because it is a complex biological process exhibiting individual variability. To assess aging physiologically, markers for biological aging are required in addition to the calendar age. From a metabolic perspective, the aging hypothesis includes the mitochondrial hypothesis and the calorie restriction (CR) hypothesis. In experimental models, several compounds or metabolites exert similar lifespan-extending effects, like CR. However, little is known about whether these metabolic modulations are applicable to human longevity, as human aging is greatly affected by a variety of factors, including lifestyle, genetic or epigenetic factors, exposure to stress, diet, and social environment. A comprehensive analysis of the human blood metabolome captures complex changes with individual differences. Moreover, a non-targeted analysis of the whole blood metabolome discloses unexpected aspects of human biology. By using such approaches, markers for aging or aging-relevant conditions were identified. This information should prove valuable for future diagnosis or clinical interventions in diseases relevant to aging.

The potential for complex computational models of aging

The gradual accumulation of damage and dysregulation during the aging of living organisms can be quantified. Even so, the aging process is complex and has multiple interacting physiological scales - from the molecular to cellular to whole tissues. In the face of this complexity, we can significantly advance our understanding of aging with the use of computational models that simulate realistic individual trajectories of health as well as mortality. To do so, they must be systems-level models that incorporate interactions between measurable aspects of age-associated changes. To incorporate individual variability in the aging process, models must be stochastic. To be useful they should also be predictive, and so must be fit or parameterized by data from large populations of aging individuals. In this perspective, we outline where we have been, where we are, and where we hope to go with such computational models of aging. Our focus is on data-driven systems-level models, and on their great potential in aging research.

Metabolomics in chronic pain research

BACKGROUND AND OBJECTIVE

Metabolomics deals with the identification and quantification of small molecules (metabolites) in biological samples. As metabolite levels can reflect normal or altered metabolic pathways, their measurement provides information to improve the understanding, diagnosis and management of diseases. Despite its immense potential, metabolomics applications to pain research have been sparse. This paper describes current metabolomics techniques, reviews published human metabolomics pain research and compares successful metabolomics research in other areas of medicine with the goal of highlighting opportunities offered by metabolomics to advance pain medicine.

DATABASES AND DATA TREATMENT

Non-systematic review.

RESULTS

Our search identified 19 studies that adopted a metabolomics approach in: fibromyalgia (7), chronic widespread pain (4), other musculoskeletal pain conditions (5), neuropathic pain (1), complex regional pain syndrome (1) and pelvic pain (1). The studies used either mass spectrometry or nuclear magnetic resonance. Most are characterized by small sample sizes. Some consistency has been found for alterations in glutamate and testosterone metabolism, and metabolic imbalances caused by the gut microbiome.

CONCLUSIONS

Metabolomics research in chronic pain is in its infancy. Most studies are at the pilot stage. Metabolomics research has been successful in other areas of medicine. These achievements should motivate investigators to expand metabolomics research to improve the understanding of the basic mechanisms of human pain, as well as provide tools to diagnose, predict and monitor chronic pain conditions. Metabolomics research can lead to the identification of biomarkers to support the development and testing of treatments, thereby facilitating personalized pain medicine.

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.

The Metabolomics of Chronic Pain Conditions: A Systematic Review

BACKGROUND

Chronic pain is a significant public health problem in the United States, affecting approximately 100 million people. Yet there is a lack of robust biomarkers for clinical use in chronic pain conditions. Downstream effects of environmental, genomic, and proteomic variations in individuals with chronic pain conditions can be identified and quantified using a metabolomic approach.

AIM/DESIGN

The purpose of this systematic review was to examine the literature for reports of potential metabolomic signatures associated with chronic pain conditions.

METHODS

We searched relevant electronic databases for published studies that used various metabolomic approaches to investigate chronic pain conditions among subjects of all ages.

RESULTS

Our search identified a total of 586 articles, 18 of which are included in this review. The reviewed studies used metabolomics to investigate fibromyalgia (n = 5), osteoarthritis (n = 4), migraine (n = 3), musculoskeletal pain (n = 2), and other chronic pain conditions (n = 1/condition). Results show that several known and newly identified metabolites differ in individuals with chronic pain conditions compared to those without these conditions. These include amino acids (e.g., glutamine, serine, and phenylalanine) and intermediate products (e.g., succinate, citrate, acetylcarnitine, and N-acetylornithine) of pathways that metabolize various macromolecules.

CONCLUSION

Though more high-quality research is needed, this review provides insights into potential biomarkers for future metabolomics studies in people with chronic pain conditions.

Genetics of frailty: A longevity perspective

Frailty is a complex late life phenotype characterized by cumulative declines in multiple physiological systems that increases the risk for disability and mortality. The biological changes associated with aging are risk factors for frailty as well as for complex diseases; whereas longevity is assumed to be an outcome of protective biological mechanisms. Understanding the interplay between biological alterations associated with aging and protective mechanisms associated with longevity in the context of frailty may help guide development of interventions to increase healthspan and promote successful aging. The complexity of these phenotypes and relatively low heritability in studies are the main roadblocks in deciphering genetic mechanisms of these age associated conditions. We review genetic research related to frailty, and discuss the possible intertwined biology of frailty and longevity.

Frailty markers comprise blood metabolites involved in antioxidation, cognition, and mobility

Frailty resulting from age-related deterioration of multiple organ systems displays complex features, including cognitive dysfunction, hypomobility, and impaired daily activity. However, metabolic aspects of frailty remain unclear. We performed untargeted, comprehensive metabolomics of whole blood from 19 frail and nonfrail elderly patients. We identified 22 markers, including 15 for frailty, 6 for cognition, and 12 for hypomobility, most of which are abundant in blood. Frailty markers include 5 of 6 for cognition and 6 of 12 for hypomobility. These overlapping markers include decreased levels of metabolites related to antioxidation, nitrogen, and amino acid metabolism. Ergothioneine, an antioxidant involved in neuronal diseases, declines in frailty. Thus, we reveal essential metabolites linked to the pathogenesis of frailty, including vulnerability to oxidative stress.

As human society ages globally, age-related disorders are becoming increasingly common. Due to decreasing physiological reserves and increasing organ system dysfunction associated with age, frailty affects many elderly people, compromising their ability to cope with acute stressors. Frail elderly people commonly manifest complex clinical symptoms, including cognitive dysfunction, hypomobility, and impaired daily activity, the metabolic basis of which remains poorly understood. We applied untargeted, comprehensive LC-MS metabolomic analysis to human blood from 19 frail and nonfrail elderly patients who were clinically evaluated using the Edmonton Frail Scale, the MoCA-J for cognition, and the TUG for mobility. Among 131 metabolites assayed, we identified 22 markers for frailty, cognition, and hypomobility, most of which were abundant in blood. Frailty markers included 5 of 6 markers specifically related to cognition and 6 of 12 markers associated with hypomobility. These overlapping sets of markers included metabolites related to antioxidation, muscle or nitrogen metabolism, and amino acids, most of which are decreased in frail elderly people. Five frailty-related metabolites that decreased—1,5-anhydroglucitol, acetyl-carnosine, ophthalmic acid, leucine, and isoleucine—have been previously reported as markers of aging, providing a metabolic link between human aging and frailty. Our findings clearly indicate that metabolite profiles efficiently distinguish frailty from nonfrailty. Importantly, the antioxidant ergothioneine, which decreases in frailty, is neuroprotective. Oxidative stress resulting from diminished antioxidant levels could be a key vulnerability for the pathogenesis of frailty, exacerbating illnesses related to human aging.

Fifteen years of progress in understanding frailty and health in aging

The notion of frailty has evolved for more than 15 years. Although there is no consensus definition, frailty reflects a state of increased vulnerability to adverse health outcomes for individuals of the same chronological age. Two commonly used clinical tools, the frailty index and the frailty phenotype, both measure health-related deficits. The frailty index is a ratio of the number of deficits that an individual has accumulated divided by all deficits measured, whereas the phenotype specifies frailty as represented by poor performance in three of five criteria (i.e., weight loss, exhaustion, weakness, slowness, lack of activity). From human studies, animal models of both approaches have been developed and are beginning to shed light on mechanisms underlying frailty, the influence of frailty on disease expression, and new interventions to attenuate frailty. Currently, back-translation to humans is occurring. As we start to understand subcellular mechanisms involved in damage and repair as well as their response to treatment, we will begin to understand the molecular basis of aging and, thus, of frailty.