Systemic inflammation as a predictor of brain aging: Contributions of physical activity, metabolic risk, and genetic risk

A Metabolic Obesity Profile Is Associated With Decreased Gray Matter Volume in Cognitively Healthy Older Adults

Obesity is a risk factor for cognitive decline and gray matter volume loss in aging. Studies have shown that different metabolic factors, e.g., dysregulated glucose metabolism and systemic inflammation, might mediate this association. Yet, even though these risk factors tend to co-occur, they have mostly been investigated separately, making it difficult to establish their joint contribution to gray matter volume structure in aging. Here, we therefore aimed to determine a metabolic profile of obesity that takes into account different anthropometric and metabolic measures to explain differences in gray matter volume in aging. We included 748 elderly, cognitively healthy participants (age range: 60 - 79 years, BMI range: 17 - 42 kg/m2) of the LIFE-Adult Study. All participants had complete information on body mass index, waist-to-hip ratio, glycated hemoglobin, total blood cholesterol, high-density lipoprotein, interleukin-6, C-reactive protein, adiponectin and leptin. Voxelwise gray matter volume was extracted from T1-weighted images acquired on a 3T Siemens MRI scanner. We used partial least squares correlation to extract latent variables with maximal covariance between anthropometric, metabolic and gray matter volume and applied permutation/bootstrapping and cross-validation to test significance and reliability of the result. We further explored the association of the latent variables with cognitive performance. Permutation tests and cross-validation indicated that the first pair of latent variables was significant and reliable. The metabolic profile was driven by negative contributions from body mass index, waist-to-hip ratio, glycated hemoglobin, C-reactive protein and leptin and a positive contribution from adiponectin. It positively covaried with gray matter volume in temporal, frontal and occipital lobe as well as subcortical regions and cerebellum. This result shows that a metabolic profile characterized by high body fat, visceral adiposity and systemic inflammation is associated with reduced gray matter volume and potentially reduced executive function in older adults. We observed the highest contributions for body weight and fat mass, which indicates that factors underlying sustained energy imbalance, like sedentary lifestyle or intake of energy-dense food, might be important determinants of gray matter structure in aging.

Cytokines are associated with longitudinal changes in cognitive performance among urban adults

BACKGROUND

Chronic systemic inflammation has been positively associated with structural and functional brain changes representing early markers of Alzheimer's Disease (AD) and cognitive decline. The current study examined associations between systemic inflammation and cognitive performance among African-Americans and Whites urban adults.

METHODS

Participants were selected from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study (2004-2013, baseline age: 30-64 y, mean ± SD follow-up time of 4.64 ± 0.93 y, N = 189-222, k = 1.5-1.7 observations/participant). Cytokines known to be positively linked to AD incidence among others were tested against cross-sectional and longitudinal cognitive function, stratifying by age group (≤50 y vs. >50 y), sex and race. A series of mixed-effects regression models were conducted, adjusting for key confounders.

RESULTS

Among key findings, IL1β was positively associated with a faster rate of decline on a test of executive functioning, among older adults (age >50 y, γ₁₁ = +2.49 ± 0.89, p = 0.005), while in the total population, IL-6 was linked to a faster decline on a test of verbal memory (γ₁₁ = -0.011 ± 0.004, p = 0.009). Among younger participants, IL-18 was linked to a poorer performance on a test of attention at baseline (age ≤50 y, γ₀₁ = -0.007 ± 0.0025, p = 0.004) though a slower rate of decline with higher IL-18 was detected for a test of psychomotor speed in older adults (age >50 y, γ₁₁ = +0.0010 ± 0.0004, p = 0.008). Finally, among Whites, unlike among African-Americans, IL-6 was associated with a better baseline performance on two tests of verbal and working memory.

CONCLUSIONS

Cytokines were shown to be associated with age-related cognitive decline among middle-aged and older urban adults in an age group and race-specific manner. Further longitudinal studies are needed to replicate our findings and mediation through relevant biological and psychosocial factors need to be studied as well.

Systemic Levels of Interleukin-6 Correlate With Progression Rate of Geographic Atrophy Secondary to Age-Related Macular Degeneration

Purpose

Geographic atrophy (GA) is a clinical phenotype of late age-related macular degeneration (AMD) with no current treatment available. In this study, we investigated markers of chronic inflammation in plasma of patients with GA and how these relate to progression rate.

Methods

We prospectively included 42 patients with GA, 41 patients with neovascular AMD, and 27 healthy controls. We quantified levels of interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor (TNF) receptor 2, and C-reactive protein (CRP). We adapted an inflammation summary score to cluster conceptually related markers of chronic inflammation. Enlargement rate of the atrophic lesion was measured from fundus autofluorescence images performed at baseline and after 1 year.

Results

Patients with GA showed an increase in proinflammatory markers of IL-6 (P = 0.009), TNF receptor 2 (P = 0.013), and CRP (P = 0.017) compared to healthy controls. We found that IL-8 levels were markedly higher in patients with GA when compared to patients with neovascular AMD (P = 0.013). The inflammation summary score was high in patients with neovascular AMD (P = 0.024), but even higher in patients with GA (<0.001), when compared to healthy controls. GA enlargement was measured in 36 patients, who completed follow-up. Plasma levels of IL-6 had a moderate but significant correlation with GA enlargement rate (R2 = 0.23, P = 0.0035).

Conclusions

Markers of chronic inflammation strongly associates with presence of GA secondary to AMD. Plasma IL-6 possesses predictive ability of progression and constitutes the first known plasma biomarker of disease activity in GA. These findings shed light into a poorly understood clinical phenotype of AMD and highlights the important role of chronic inflammation in GA.

Mediation of the effect of serum uric acid on the risk of developing hypertension: a population-based cohort study

Background

Serum uric acid (SUA) had been associated with incident hypertension, but it is uncertain whether and to what extent the effect of SUA is mediated by other metabolic factors.

Methods

Data from the China Health and Retirement Longitudinal Study (CHARLS) during 2011 to 2015 was employed for this study. A total of 7639 participants aged between 35 and 96 years without hypertension was included. Cox proportional hazards model was used to investigate the association between elevated SUA and hypertension. A mediation model was used to separately explore mediating effects (MEs) of metabolic factors on the association between SUA and incident hypertension.

Results

During a median 4.0 years of follow-up, 2348 individuals were diagnosed with hypertension. After adjustment for metabolic confounders, participants with the highest SUA quartile had a hazard ratio of 1.16 (1.02–1.33) compared with the lowest category for incident hypertension. The association between SUA and incident hypertension were partially mediated by waist circumference (WC; ME = 0.034), body mass index (BMI; ME = 0.016), triglycerides (TG; ME = 0.024), total cholesterol (TC; ME = 0.009), high density lipoprotein cholesterol (HDL-C; ME = 0.009), fasting plasma glucose (FPG; ME = 0.005), and glycated hemoglobin (HbA1c; ME = − 0.002). Additionally, proportional mediation was 32.7% by WC and 15.4% by BMI for obesity indicators; 23.1% by TG, 8.7% by TC, and 8.7% by HDL-C for blood lipid; and 4.8% by FPG and − 1.9% by HbA1c for blood glucose.

Conclusions

The positive association between elevated SUA concentration and hypertension was reconfirmed in a Chinese population. Obesity indicators, blood lipids, and blood glucose may play important mediating roles in the pathways.

Associations between rare microglia-linked Alzheimer's disease risk variants and subcortical brain volumes in young individuals

Introduction

Recent exome sequencing studies have identified three novel risk variants associated with Alzheimer's disease (AD). However, the mechanisms by which these variants confer risk are largely unknown.

Methods

In the present study, the impact of these rare coding variants (in ABI3, PLCG2, and TREM2) on all subcortical volumes is determined in a large sample of young healthy individuals (N = 756–765; aged 22–35 years).

Results

After multiple testing correction (P_CORRECTED < .05), rare variants were associated with basal ganglia volumes (TREM2 and PLCG2 effects within the putamen and pallidum, respectively). Nominal associations between TREM2 and reduced hippocampal and thalamic volumes were also observed.

Discussion

Our observations suggest that rare variants in microglia-mediated immunity pathway may contribute to the subcortical alterations observed in AD cases. These observations provide further evidence that genetic risk for AD may influence the volume of subcortical volumes and increase AD risk in early life processes.

Neuromodulatory Activity of Dietary Phenolics Derived from Corchorus olitorius L

Dietary phenolics are known for their potent antioxidant and anti-inflammatory activities, making them promising candidates for protection against neuroinflammation and neurodegeneration. Hydroalcohol extract of Egyptian species of Corchorus olitorius L. (Co) leaves was investigated for its neuroprotective effects in a lipopolysaccharide-induced neuroinflammatory mouse model. Twenty five metabolites were characterized from the bioactive extract using high-performance liquid chromatography HPLC/PDA/HRESI/MSⁿ , revealing 1,5-dicaffeoylquinic acid (Co11) as one of the major constituents (5.7%), which was isolated and its identity was confirmed by spectral data as first report. Co significantly protected microglia against H₂ O₂ -induced cytotoxicity and immunohistochemistry showed reduced expression of the astrocytic marker, glial fibrillary acidic protein, and the inflammatory marker, cyclooxygenase-2. These findings correlated with significant improvement of cognitive functions and reduction of LPS-induced neurodegeneration in Co-treated mice as revealed by histopathology. The current study shows promising effects of Co in limiting neurodegeneration and cognitive impairment caused by neuroinflammation and glial cell activation. PRACTICAL APPLICATION: Information presented here shed light on the promising effects of Corchorus olitorius (Co) for the modulation of neuroinflammatory pathways improving the neuroinflammation-related neurodegeneration and cognitive decline. This makes Co a promising candidate as a nutraceutical supplement to be used against neuroinflammation-related disorders.

Changes in the levels of 12/15-lipoxygenase, apoptosis-related proteins and inflammatory factors in the cortex of diabetic rats and the neuroprotection of baicalein

This study was designed to investigate the neuroprotective effects of baicalein and the effect of the cortical 12/15-lipoxygenase (12/15-LOX) pathway on diabetic cognitive dysfunction. Our results showed that spatial learning and memory ability, as well as cortex neurons, were significantly impaired after the onset of diabetes. The fasting blood glucose and random blood glucose levels in the model group were significantly higher than those in the normal group. The levels of TG and TC in the plasma of the model group were significantly increased, but there was no significant difference in the LDL level. The insulin content in the plasma of diabetic rats was significantly lower than that of the normal group. The levels of inflammatory factors and 12(S)-HETE were significantly increased in diabetic rats, as were the protein expression levels of cPLA2, 12/15-LOX, p38MAPK, phospho-p38MAPK, caspase-3, caspase-9 and Aβ_1-42; by contrast, protein expression of Bcl-2 was significantly decreased. Administration of baicalein was shown to improve the spatial learning and memory ability and significantly decrease the levels of inflammatory cytokines. However, baicalein did not significantly influence the levels of blood glucose, lipids or insulin in rats. Baicalein treatment significantly protected diabetes rats from neuron death; significantly attenuated the overexpression of cPLA2, 12/15-LOX, p38MAPK, phospho-p38MAPK, caspase-3, caspase-9 and Aβ_1-42; and upregulated the expression of Bcl-2. These findings suggest that baicalein improves the cognitive function of diabetic rats by directly acting in the brain rather than by regulating the levels of blood glucose, lipids or insulin. In addition, baicalein can protect rat cortical neurons from damage caused by diabetes via inhibiting the 12/15-LOX pathway and relieving inflammation and apoptosis of the central nervous system.

Neuroprotective Effect of Dioscin on the Aging Brain

Our previous works have shown that dioscin, a natural product, has various pharmacological activities, however, its role in brain aging has not been reported. In the present study, in vitro H₂O₂-treated PC12 cells and in vivo d-galactose-induced aging rat models were used to evaluate the neuroprotective effect of dioscin on brain aging. The results showed that dioscin increased cell viability and protected PC12 cells against oxidative stress through decreasing reactive oxygen species (ROS) and lactate dehydrogenase (LDH) levels. In vivo, dioscin markedly improved the spatial learning ability and memory of aging rats, reduced the protein carbonyl content and aging cell numbers, restored the levels of superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-Px), malondialdehyde (MDA) and nitric oxide synthase (NOS) in brain tissue, and reversed the histopathological structure changes of nerve cells. Mechanism studies showed that dioscin markedly adjusted the MAPK and Nrf2/ARE signalling pathways to decrease oxidative stress. Additionally, dioscin also significantly decreased inflammation by inhibiting the mRNA or protein levels of TNF-α, IL-1β, IL-6, CYP2E1 and HMGB1. Taken together, these results indicate that dioscin showed neuroprotective effect against brain aging via decreasing oxidative stress and inflammation, which should be developed as an efficient candidate in clinical to treat brain aging in the future.

The Contribution of Genetic Factors to Cognitive Impairment and Dementia: Apolipoprotein E Gene, Gene Interactions, and Polygenic Risk

Alzheimer's disease (AD) is a progressive neurodegenerative disease. Although it has been studied for years, the pathogenesis of AD is still controversial. Genetic factors may play an important role in pathogenesis, with the apolipoprotein E (APOE) gene among the greatest risk factors for AD. In this review, we focus on the influence of genetic factors, including the APOE gene, the interaction between APOE and other genes, and the polygenic risk factors for cognitive function and dementia. The presence of the APOE ε4 allele is associated with increased AD risk and reduced age of AD onset. Accelerated cognitive decline and abnormal internal environment, structure, and function of the brain were also found in ε4 carriers. The effect of the APOE promoter on cognition and the brain was confirmed by some studies, but further investigation is still needed. We also describe the effects of the associations between APOE and other genetic risk factors on cognition and the brain that exhibit a complex gene⁻gene interaction, and we consider the importance of using a polygenic risk score to investigate the association between genetic variance and phenotype.

Neuroanatomical correlates of food addiction symptoms and body mass index in the general population

The food addiction model suggests neurobiological similarities between substance-related and addictive disorders and obesity. While structural brain differences have been consistently reported in these conditions, little is known about the neuroanatomical correlates of food addiction. We therefore aimed to determine whether symptoms of food addiction related to body mass index (BMI), personality, and brain structure in a large population-based sample. Participants of the LIFE-Adult study (n = 625; 20-59 years old, 45% women) answered the Yale Food Addiction Scale (YFAS) and further personality measures, underwent anthropometric assessments and high-resolution 3T-neuroimaging. A higher YFAS symptom score correlated with higher BMI, eating behavior traits, neuroticism, and stress. Higher BMI predicted significantly lower thickness of (pre)frontal, temporal and occipital cortex and increased volume of left nucleus accumbens. In a whole-brain analysis, YFAS symptom score was not associated with significant differences in cortical thickness or subcortical gray matter volumes. A hypothesis-driven Bayes factor analysis suggested a small, additional contribution of YFAS symptom score to lower right lateral orbitofrontal cortex thickness over the effect of BMI. Our study indicates that symptoms of food addiction do not account for the major part of the structural brain differences associated with BMI in the general population. Yet, symptoms of food addiction might explain additional variance in orbitofrontal cortex, a hub area of the reward network. Longitudinal studies implementing both anatomical and functional MRI could further disentangle the neural mechanisms of addictive eating behaviors.

Translating the biology of aging into novel therapeutics for Alzheimer disease

Aging is the leading risk factor for most chronic illnesses of old age, including Alzheimer disease (AD), a progressive neurodegenerative disease with currently no therapies that prevent, slow, or halt disease progression. Like other chronic diseases of old age, the progressive pathology of AD begins decades before the onset of symptoms. Many decades of research in biological gerontology have revealed common processes that are relevant to understanding why the aging brain is vulnerable to AD. In this review, we frame the development of novel therapeutics for AD in the context of biological gerontology. The many therapies currently in development based on biological gerontology principles provide promise for the development of a new generation of therapeutics to prevent and treat AD.

Understanding Structure and Function as a Model for 21st-Century Health Care

Medicine is now at a turning point. The important role of a broader application of the structure-function model in health care is gaining recognition and it may, in fact, be a defining principle that can guide the development of future health care systems. This concept can be applied to the search for solutions to complex health-related issues that span across multiple domains: molecules, cells, tissues, organs, and organ systems. I believe it can equally be applied to a search for solutions to the social issues of our modern era: individual empowerment, relationships between and among people, relationships between and among nations, and population-based global concerns.

Systemic Inflammation Is Associated With Longitudinal Changes in Cognitive Performance Among Urban Adults

Objectives/Background: Systemic inflammation can affect cognitive performance over time. The current study examined associations between systemic inflammation and cognitive performance among African Americans and Whites urban adults, stratifying by sex, and age group and by race. Patients/Methods: Among 1,555-1,719 White and African-American urban adults [Age_base: 30-64y, 2004-2013, mean±SD follow-up time(y): 4.64 ± 0.93y], conducted linear mixed-effects regression models were conducted to test associations of inflammatory markers [C-reactive protein, Erythrocyte Sedimentation Rate (ESR), albumin, iron, and an inflammation composite score (ICS)] with longitudinal cognitive performance. Results: Among key findings, CRP was linked to poorer baseline mental status among younger women (≤50y, γ₀₁ = -0.03 ± 0.01, p = 0.002) and poorer attention in older women (>50y, γ₀₁ = -0.024 ± 0.007, p < 0.004) and African-Americans (γ₀₁ = -0.029 ± 0.008, p < 0.001). ESR was related to faster decline on verbal memory among older men (>50y, γ₁₁ = -0.008 ± 0.003, P = 0.009); with poorer performance on attention tests overall (γ₀₁ = -0.010 ± 0.003, P = 0.003) and among African-Americans (γ₀₁ = -0.013 ± 0.004, P = 0.002); on verbal fluency among older women (>50y,γ₀₁ = -0.037 ± 0.013, P = 0.004) and on executive function: overall (γ₀₁ = +0.62 ± 0.21, P = 0.004), older men (>50y, γ₀₁ = +1.69 ± 0.53, P = 0.001) and African-Americans (γ₀₁ = +0.84 ± 0.28, P = 0.002). Albumin was linked to slower attention decline among older men (>50y, γ₁₁ = +0.329 ± 0.103, P = 0.009), over-time improvement in executive function overall (γ₁₁ = -6.00 ± 2.26, P = 0.008), and better baseline psychomotor speed among African-Americans (γ₀₁ = +0.56 ± 0.19, P = 0.003). Finally, ICS predicted faster decline on visual memory/visuo-constructive abilities among older men (>50y, γ₁₁ = +0.17 ± 0.06, p = 0.003). Conclusion: In sum, strong associations between systemic inflammation and longitudinal cognitive performance were detected, largely among older individuals (>50y) and African-Americans. Randomized trials targeting inflammation are warranted.

Longitudinal serum S100β and brain aging in the Lothian Birth Cohort 1936

Elevated serum and cerebrospinal fluid concentrations of S100β, a protein predominantly found in glia, are associated with intracranial injury and neurodegeneration, although concentrations are also influenced by several other factors. The longitudinal association between serum S100β concentrations and brain health in nonpathological aging is unknown. In a large group (baseline N = 593; longitudinal N = 414) of community-dwelling older adults at ages 73 and 76 years, we examined cross-sectional and parallel longitudinal changes between serum S100β and brain MRI parameters: white matter hyperintensities, perivascular space visibility, white matter fractional anisotropy and mean diffusivity (MD), global atrophy, and gray matter volume. Using bivariate change score structural equation models, correcting for age, sex, diabetes, and hypertension, higher S100β was cross-sectionally associated with poorer general fractional anisotropy (r = -0.150, p = 0.001), which was strongest in the anterior thalamic (r = -0.155, p < 0.001) and cingulum bundles (r = -0.111, p = 0.005), and survived false discovery rate correction. Longitudinally, there were no significant associations between changes in brain imaging parameters and S100β after false discovery rate correction. These data provide some weak evidence that S100β may be an informative biomarker of brain white matter aging.

Evidence of the impact of systemic inflammation on neuroinflammation from a non-bacterial endotoxin animal model

BACKGROUND

Systemic inflammation induces neuroinflammation and cellular changes such as tau phosphorylation to impair cognitive function, including learning and memory. This study uses a single model, laparotomy without any pathogen, to characterize these changes and their responses to anti-inflammatory treatment in the intermediate term.

METHODS

In a two-part experiment, wild-type C57BL/6N mice (male, 3 month old, 25 ± 2 g) were subjected to sevoflurane anesthesia alone or to a laparotomy. Cognitive performance, systemic and neuroinflammatory responses, and tau phosphorylation were evaluated on postoperative days (POD) 1, 3, and 14. The effect of perioperative ibuprofen intervention (60 mg/kg) on these changes was then assessed.

RESULTS

Mice in the laparotomy group displayed memory impairment up to POD 14 with initial high levels of inflammatory cytokines in the liver, frontal cortex (IL-1β, IL-6, and TNF-α), and hippocampus (IL-1β and IL-8). On POD 14, although most circulating and resident cytokine levels returned to normal, a significant number of microglia and astrocytes remained activated in the frontal cortex and microglia in the hippocampus, as well as abnormal tau phosphorylation in these two brain regions. Perioperative ibuprofen improved cognitive performance, attenuated systemic inflammation and glial activation, and suppressed the abnormal tau phosphorylation both in the frontal cortex and hippocampus.

CONCLUSIONS

Our results suggest that (1) cognitive dysfunction is associated with an unbalanced pro-inflammatory and anti-inflammatory response, tauopathy, and gliosis; (2) cognitive dysfunction, gliosis, and tauopathy following laparotomy can persist well beyond the immediate postoperative period; and (3) anti-inflammatory drugs can act rapidly to attenuate inflammatory responses in the brain and negatively modulate neuropathological changes to improve cognition. These findings may have implications for the duration of therapeutic strategies aimed at curtaining cognitive dysfunction following surgery.