Biomarkers of aging in frailty and age-associated disorders: State of the art and future perspective

Elevated Circulating Procathepsin L as a Potential Biomarker of Inflamm-aging

Inflamm-aging is a condition of low-grade and chronic systemic inflammation characterized by a systemic increase in multiple inflammatory biomarkers such as tumor necrosis factor (TNF), interleukin 6 (IL-6), C-reactive protein (CRP), and CXCL9 (MIG) in experimental and clinical settings. However, despite the recent identification of extracellular procathepsin L (pCTS-L) as a novel mediator of inflammatory diseases such as sepsis, its possible role in inflamm-aging was previously not investigated. In the present study, we compared blood levels of pCTS-L and other 62 cytokines and chemokines between young and aged Balb/C mice by Western blotting and Cytokine Antibody Arrays. In light of the surprising finding of a marked increase in blood pCTS-L levels in aged mice, we propose that blood pCTS-L levels may serve as another biomarker of inflamm-aging. Given the capacity of pCTS-L in inducing various cytokines (e.g., TNF and IL-6), it will be important to test the hypothetic role of pCTS-L in inflamm-aging under experimental and clinical conditions.

The Association between Circulating Cytokines and Body Composition in Frail Patients with Cardiovascular Disease

The burden of cardiovascular disease and the percentage of frail patients in the aging population will increase. This study aims to assess the circulating levels of several cytokines in frail patients. This is an ancillary analysis of the FRAPICA trial. The ratio of men/women changed from robust through frail groups from 3:1 to 1:2. The groups are comparable in terms of age and body measurements analysis (weight, height, and BMI), yet the frail patients have significantly reduced fat-free mass, and more often have been diagnosed with diabetes. Frail patients have higher fibroblast growth factor basic (FGF basic) and follistatin levels (borderline significance). In multiple linear regression modeling of fat-free mass, we identified FGF basic, osteopontin, stem cell factor, soluble suppression of tumorigenicity 2, soluble epidermal growth factor receptor, soluble human epidermal growth factor receptor 2, follistatin, prolactin, soluble interleukin 6 receptor alfa, platelet endothelial cell adhesion molecule 1, soluble vascular endothelial cell growth factor receptor 1, leptin, soluble angiopoietin/tyrosine kinase 2, and granulocyte colony-stimulating factor. We have identified a few cytokines that correlate with fat-free mass, a hallmark of frailty. They comprise the kinins implicated in bone and muscle metabolism, fibrosis, vascular wall function, inflammation, endocrine function, or regulation of bone marrow integrity.

Plasma GFAP, NfL and pTau 181 detect preclinical stages of dementia

Background

Plasma biomarkers are preferable to invasive and expensive diagnostic tools, such as neuroimaging and lumbar puncture that are gold standard in the clinical management of Alzheimer's Disease (AD). Here, we investigated plasma Glial Fibrillary Acidic Protein (GFAP), Neurofilament Light Chain (NfL) and Phosphorylated-tau-181 (pTau 181) in AD and in its early stages: Subjective cognitive decline (SCD) and Mild cognitive impairment (MCI).

Material and methods

This study included 152 patients (42 SCD, 74 MCI and 36 AD). All patients underwent comprehensive clinical and neurological assessment. Blood samples were collected for Apolipoprotein E (APOE) genotyping and plasma biomarker (GFAP, NfL, and pTau 181) measurements. Forty-three patients (7 SCD, 27 MCI, and 9 AD) underwent a follow-up (FU) visit after 2 years, and a second plasma sample was collected. Plasma biomarker levels were detected using the Simoa SR-X technology (Quanterix Corp.). Statistical analysis was performed using SPSS software version 28 (IBM SPSS Statistics). Statistical significance was set at p < 0.05.

Results

GFAP, NfL and pTau 181 levels in plasma were lower in SCD and MCI than in AD patients. In particular, plasma GFAP levels were statistically significant different between SCD and AD (p=0.003), and between MCI and AD (p=0.032). Plasma NfL was different in SCD vs MCI (p=0.026), SCD vs AD (p<0.001), SCD vs AD FU (p<0.001), SCD FU vs AD (p=0.033), SCD FU vs AD FU (p=0.011), MCI vs AD (p=0.002), MCI FU vs AD (p=0.003), MCI FU vs AD FU (p=0.003) and MCI vs AD FU (p=0.003). Plasma pTau 181 concentration was significantly different between SCD and AD (p=0.001), MCI and AD (p=0.026), MCI FU and AD (p=0.020). In APOE ϵ4 carriers, a statistically significant increase in plasma NfL (p<0.001) and pTau 181 levels was found (p=0.014). Moreover, an association emerged between age at disease onset and plasma GFAP (p = 0.021) and pTau181 (p < 0.001) levels.

Discussion and conclusions

Plasma GFAP, NfL and pTau 181 are promising biomarkers in the diagnosis of the prodromic stages and prognosis of dementia.

Association between different skeletal muscle mass indices, physical function, and inflammation in obese pre-frail older adults

OBJECTIVES

There is lack of consensus on measurement of muscle mass and quality in obese older adults. We aim to evaluate the association of four muscle mass indices (appendicular skeletal muscle mass (ASM) over height2(ASMIht), ASM/weight (ASMwt), ASM/body fat percentage (ASMbfp)and ASM/body mass index (BMI) ASMIbmi) with physical function and inflammation in pre-frail obese older adults.

METHODS

Cross-sectional study of 407 community dwelling pre-frail older adults. Data on demographics, cognition, and physical function(gait speed, handgrip strength (HGS) and Short Physical Performance Battery (SPPB) test), body composition and inflammation biomarkers were collected. Participants were analysed based on BMI tertiles(T1 lowest,T3 highest).

RESULTS

The mean age was 72.67 years, mean BMI 25.42 kg/m2 and 59.5 % were females. Participants in T3 had a mean BMI of 30.75 kg/m2, younger with lower education levels, multimorbidity, polypharmacy and lower prevalence of sarcopenia. In BMI T3, ASMIbmi was significantly associated with EQ-5D index (β 0.53, 95 % CI 0.04 to 1.03, p = 0.033),HGS (β 5.28, 95 % CI 0.27 to 10.29, p = 0.039), SPPB (β 2.19, 95 % CI 0.47 to 3.91, p = 0.013) and IL-6 (β -4.13, 95 % CI -7.46 to -0.81, p = 0.017). ASMIwt was associated with EQ-5D index (β 0.17, 95 % CI 0.02 - 0.33, p = 0.047). ASMbfp was associated with HGS (β 6.97, 95 % CI 0.051 to 13.92, p = 0.049). There was significant association of HGS with all muscle mass indices in BMI T2, and ASMbfpin BMI T1.

CONCLUSION

ASMIbmi was significantly associated with SPPB, HGS, EQ-5D index and IL-6 in BMI T3. ASMbfp was associated with HGS in all the tertiles. Our results need further validation at population level.

Assessing causal associations between neurodegenerative diseases and neurological tumors with biological aging: a bidirectional Mendelian randomization study

Background

Aging is a significant risk factor for many neurodegenerative diseases and neurological tumors. Previous studies indicate that the frailty index, facial aging, telomere length (TL), and epigenetic aging clock acceleration are commonly used biological aging proxy indicators. This study aims to comprehensively explore potential relationships between biological aging and neurodegenerative diseases and neurological tumors by integrating various biological aging proxy indicators, employing Mendelian randomization (MR) analysis.

Methods

Two-sample bidirectional MR analyses were conducted using genome-wide association study (GWAS) data. Summary statistics for various neurodegenerative diseases and neurological tumors, along with biological aging proxy indicators, were obtained from extensive meta-analyses of GWAS. Genetic single-nucleotide polymorphisms (SNPs) associated with the exposures were used as instrumental variables, assessing causal relationships between three neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis), two benign neurological tumors (vestibular schwannoma and meningioma), one malignant neurological tumor (glioma), and four biological aging indicators (frailty index, facial aging, TL, and epigenetic aging clock acceleration). Sensitivity analyses were also performed.

Results

Our analysis revealed that genetically predicted longer TL reduces the risk of Alzheimer's disease but increases the risk of vestibular schwannoma and glioma (All Glioma, GBM, non-GBM). In addition, there is a suggestive causal relationship between some diseases (PD and GBM) and DNA methylation GrimAge acceleration. Causal relationships between biological aging proxy indicators and other neurodegenerative diseases and neurological tumors were not observed.

Conclusion

Building upon prior investigations into the causal relationships between telomeres and neurodegenerative diseases and neurological tumors, our study validates these findings using larger GWAS data and demonstrates, for the first time, that Parkinson's disease and GBM may promote epigenetic age acceleration. Our research provides new insights and evidence into the causal relationships between biological aging and the risk of neurodegenerative diseases and neurological tumors.