Longitudinal association between phosphatidylcholines, neuroimaging measures of Alzheimer's disease pathophysiology, and cognition in the Mayo Clinic Study of Aging

Plasma metabolomics and lipidomics signatures of motoric cognitive risk syndrome in community-dwelling older adults

Introduction

Motoric cognitive risk syndrome (MCR) is characterized by subjective cognitive complaints (SCCs) and slow gait (SG). Metabolomics and lipidomics may potentiate disclosure of the underlying mechanisms of MCR.

Methods

This was a cross-sectional study from the West China Health and Aging Trend cohort study (WCHAT). The operational definition of MCR is the presence of SCCs and SG without dementia or mobility disability. The test and analysis were based on untargeted metabolomics and lipidomics, consensus clustering, lasso regression and 10-fold cross-validation.

Results

This study enrolled 6,031 individuals for clinical analysis and 577 plasma samples for omics analysis. The overall prevalence of MCR was 9.7%, and the prevalence of MCR-only, assessed cognitive impairment-only (CI-only) and MCR-CI were 7.5, 13.3, and 2.1%, respectively. By consensus clustering analysis, MCR-only was clustered into three metabolic subtypes, MCR-I, MCR-II and MCR-III. Clinically, body fat mass (OR = 0.89, CI = 0.82–0.96) was negatively correlated with MCR-I, and comorbidity (OR = 2.19, CI = 1.10–4.38) was positively correlated with MCR-III. Diabetes mellitus had the highest ORs above 1 in MCR-II and MCR-III (OR = 3.18, CI = 1.02–9.91; OR = 2.83, CI = 1.33–6.04, respectively). The risk metabolites of MCR-III showed relatively high similarity with those of cognitive impairment. Notably, L-proline, L-cystine, ADMA, and N1-acetylspermidine were significantly changed in MCR-only, and PC(40:3), SM(32:1), TG(51:3), eicosanoic acid(20:1), methyl-D-galactoside and TG(50:3) contributed most to the prediction model for MCR-III.

Interpretation

Pre-dementia syndrome of MCR has distinct metabolic subtypes, and SCCs and SG may cause different metabolic changes to develop MCR.

The Crucial Roles of Phospholipids in Aging and Lifespan Regulation

Phospholipids are major membrane lipids that consist of lipid bilayers. This basic cellular structure acts as a barrier to protect the cell against various environmental insults and more importantly, enables multiple cellular processes to occur in subcellular compartments. Numerous studies have linked the complexity of membrane lipids to signal transductions, organelle functions, as well as physiological processes, and human diseases. Recently, crucial roles for membrane lipids in the aging process are beginning to emerge. In this study, we summarized current advances in our understanding of the relationship between membrane lipids and aging with an emphasis on phospholipid species. We surveyed how major phospholipid species change with age in different organisms and tissues, and some common patterns of membrane lipid change during aging were proposed. Further, the functions of different phospholipid molecules in regulating healthspan and lifespan, as well as their potential mechanisms of action, were also discussed.

BMI and Allostatic Load Are Directly Associated with Longitudinal Increase in Plasma Neurofilament Light among Urban Middle-Aged Adults

BACKGROUND

Plasma neurofilament light chain (NfL) is a novel biomarker for age-related neurodegenerative disease. We tested whether NfL may be linked to cardiometabolic risk factors, including BMI, the allostatic load (AL) total score (ALtotal), and related AL continuous components (ALcomp). We also tested whether these relations may differ by sex or by race.

METHODS

We used data from the HANDLS (Healthy Aging in Neighborhoods of Diversity across the Life Span) study [n = 608, age at visit 1 (v1: 2004-2009): 30-66 y, 42% male, 58% African American] to investigate associations of initial cardiometabolic risk factors and time-dependent plasma NfL concentrations over 3 visits (2004-2017; mean ± SD follow-up time: 7.72 ± 1.28 y), with outcomes being NfLv1 and annualized change in NfL (δNfL). We used mixed-effects linear regression and structural equations modeling (SM).

RESULTS

BMI was associated with lower initial (γ01 = -0.014 ± 0.002, P < 0.001) but faster increase in plasma NfL over time (γ11 = +0.0012 ± 0.0003, P < 0.001), a pattern replicated for ALtotal. High-sensitivity C-reactive protein (hsCRP), serum total cholesterol, and resting heart rate at v1 were linked with faster plasma NfL increase over time, overall, while being uncorrelated with NfLv1 (e.g., hsCRP × Time, full model: γ11 = +0.004 ± 0.002, P = 0.015). In SM analyses, BMI's association with δNfL was significantly mediated through ALtotal among women [total effect (TE) = +0.0014 ± 0.00038, P < 0.001; indirect effect = +0.00042 ± 0.00019, P = 0.025; mediation proportion = 30%], with only a direct effect (DE) detected among African American adults (TE = +0.0011 ± 0.0004, P = 0.015; DE = +0.0010 ± 0.00048, P = 0.034). The positive associations between ALtotal/BMI and δNfL were mediated through increased glycated hemoglobin (HbA1c) concentrations, overall.

CONCLUSIONS

Cardiometabolic risk factors, particularly elevated HbA1c, should be screened and targeted for neurodegenerative disease, pending comparable longitudinal studies. Other studies examining the clinical utility of plasma NfL as a neurodegeneration marker should account for confounding effects of BMI and AL.

Perturbations in glycerophospholipid levels of PC12 cells after exposure to PCB95 based on targeted lipidomics analysis

Polychlorinated biphenyls (PCBs) are a group of organic chlorine chemicals that can induce various adverse health effects in animals and humans. The toxicology of PCBs is a significant public health concern because of their long-term presence in the environment. Among the 209 PCB congeners, PCB95 has been reported to be neurotoxic, however, there has been limited researches on evaluating whether and how PCB95 affects cellular lipids, the most abundant components of the brain. In this study, PCB95 was found to inhibit cell proliferation at concentrations of 0.1 μM, 2 μM and 10 μM for 120 h. Additionally, there may be a shift in apoptosis to necrosis at 2 μM PCB95 exposure for 24 h. However, lipid peroxidation was found not dominant for PCB95 exposure, especially at the concentrations of 0.1 μM and 2 μM. Because of playing vital roles in cell metabolism, 20 glycerophospholipids in PC12 cells were investigated after exposure to PCB95 for 120 h. The distinctions in the orthogonal projection to latent structures-discriminant analysis (OPLS-DA) models indicated that different concentrations of PCB95 leaded to aberrant glycerophospholipid metabolism. Based on the principles of t-test P-value < 0.05, variable importance at projection (VIP) value >1 and fold change >1, PC (14:0/14:0) and PC (16:0/14:0) were screened as potential biomarkers from all the target glycerophospholipids. This study is the first time that identifies the effects of PCB95 on specific glycerophospholipids in PC12 cells, and the observed changes in glycerophospholipids provides the basis for further evaluation of PCB95-induced neurotoxicity mechanisms.

Associations between cerebrospinal fluid total phosphatidylcholines, neurodegeneration, cognitive decline, and risk of mild cognitive impairment in the Mayo Clinic Study of Aging

It is unclear whether cerebrospinal fluid (CSF) phosphatidylcholines (PCs) are associated with neuroimaging measures of amyloid deposition and neurodegeneration (glucose metabolism, cortical thickness, and hippocampal volume), cognitive decline, or risk of mild cognitive impairment (MCI) among cognitively unimpaired older adults. This study investigated the associations of 19 individual CSF PC concentrations and their total sum with cross-sectional and longitudinal measures of amyloid deposition and neurodegeneration, global and domain-specific cognitive z-scores, and risk of MCI among 655 cognitively unimpaired participants, mean age of 71 years, enrolled in the Mayo Clinic Study of Aging. Neither the CSF total PC concentration nor individual CSF PCs were cross-sectionally or longitudinally associated with neuroimaging measures, cognition, or risk of MCI.

Motoric cognitive risk syndrome: Integration of two early harbingers of dementia in older adults

Dementia is characterized by a long preclinical phase that may last years to decades before the onset of mild cognitive impairment. Slow gait speed and subjective memory complaint commonly co-occur during this preclinical phase, and each is a strong independent predictor of cognitive decline and dementia. Motoric cognitive risk (MCR) syndrome is a pre-dementia syndrome that combines these two early harbingers of dementia. The risk of cognitive decline or dementia is stronger for MCR than for either slow gait speed or subjective memory complaint alone. Slow gait speed and subjective memory complaint have several common risk factors: cardiovascular disease, diabetes mellitus, abnormal cortisol profiles, low vitamin D levels, brain atrophy with decreased hippocampal volume, and increased deposition of beta-amyloid in the brain. The underlying pathogenesis of MCR remains poorly understood. Metabolomics and proteomics have great potential to provide new insights into biological pathways involved in MCR during the long preclinical phase preceding dementia.