The relationship of serum macrophage inhibitory cytokine-1 levels with gray matter volumes in community-dwelling older individuals

GDF15 and its association with cognitive performance over time in a longitudinal study of middle-aged urban adults

Serum GDF15 levels are correlated with multiple neurodegenerative diseases. Few studies have tested this marker's association with middle-aged cognitive performance over time, and whether race affects this association is unknown. We examined associations of initial serum GDF15 concentrations with longitudinal cognitive performance, spanning domains of global mental status, visual and verbal memory, attention, fluency, and executive function in a sub-sample of adults participating in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study (n = 776, Agev1:30-66y, 45.6 % male, 57.0 % African American, 43.0 % below poverty). This analysis consisted of mixed-effects regression models applied to the total selected sample, while also stratifying the analyses by race in the main analyses and further stratifying by sex, age group and poverty status in an exploratory analysis. Our main findings, which passed multiple testing and covariate-adjustment, indicated that GDF15 was associated with poorer baseline performance on several cognitive tests, including animal fluency [overall sample: (Model 1: γ0 ± SE: -0.664 ± 0.208, P < 0.001; Model 2, γ0 ± SE: -0.498 ± 0.217, P < 0.05)]. Among White adults, GDF15 was linked to poorer performance on a brief test of attention (Model 1: γ0 ± SE: -0.426 ± 0.126, P < 0.001; Model 2, γ0 ± SE: -0.281 ± 0.139, P < 0.05); and Trailmaking test, part B (Model 1: γ0 ± SE: +0.129 ± 0.040, P < 0.001; Model 2, γ0 ± SE: +0.089 ± 0.041, P < 0.05), the latter being also linked to higher GDF15 among individuals living below poverty. Among women, GDF15 was associated with poor global mental status (Normalized MMSE: Model 1: γ0 ± SE: -2.617 ± 0.746, P < 0.001; Model 2: γ0 ± SE: -1.729 ± 0.709, P < 0.05). GDF15 was not associated with decline on any of the 11 cognitive test scores considered in ∼ 4 years of follow-up. In sum, we detected cross-sectional associations between GDF15 and cognition, although GDF15 did not predict rate of change in cognitive performance over time among a sample of middle-aged adults. More longitudinal studies are needed to address the clinical utility of this biomarker for early cognitive defects.

Neutrophil to lymphocyte ratio is a transdiagnostic biomarker of depression and structural and functional brain alterations in older adults

The neutrophil to lymphocyte ratio (N:L) is an emergent transdiagnostic biomarker shown to predict peripheral inflammation as well as neuropsychiatric impairment. The afferent signaling of inflammation to the central nervous system has been implicated in the pathophysiology of sickness behavior and depression. Here, the N:L was compared to structural and functional limbic alterations found concomitant with depression within a geriatric cohort. Venous blood was collected for a complete blood count, and magnetic resonance imaging as well as phenotypic data were collected from the 66 community-dwelling older adults (aged 65-86 years). The N:L was regressed on gray matter volume and resting-state functional connectivity (rsFC) of the subgenual anterior cingulate (sgACC). Thresholded parameter estimates were extracted from structural and functional brain scans and bivariate associations tested with scores on the geriatric depression scale. Greater N:L predicted lower volume of hypothalamus and rsFC of sgACC with ventromedial prefrontal cortex. Both parameters were correlated (p < 0.05) with greater symptomology in those reporting moderate to severe levels of depression. These findings support the N:L as a transdiagnostic biomarker of limbic alteration underpinning mood disturbance in non-treated older adults.

Emerging roles of growth differentiation factor-15 in brain disorders (Review)

Brain disorders, such as Alzheimer's and Parkinson's disease and cerebral stroke, are an important contributor to mortality and disability worldwide, where their pathogenesis is currently a topic of intense research. The mechanisms underlying the development of brain disorders are complex and vary widely, including aberrant protein aggregation, ischemic cell necrosis and neuronal dysfunction. Previous studies have found that the expression and function of growth differentiation factor-15 (GDF15) is closely associated with the incidence of brain disorders. GDF15 is a member of the TGFβ superfamily, which is a dimer-structured stress-response protein. The expression of GDF15 is regulated by a number of proteins upstream, including p53, early growth response-1, non-coding RNAs and hormones. In particular, GDF15 has been reported to serve an important role in regulating angiogenesis, apoptosis, lipid metabolism and inflammation. For example, GDF15 can promote angiogenesis by promoting the proliferation of human umbilical vein endothelial cells, apoptosis of prostate cancer cells and fat metabolism in fasted mice, and GDF15 can decrease the inflammatory response of lipopolysaccharide-treated mice. The present article reviews the structure and biosynthesis of GDF15, in addition to the possible roles of GDF15 in Alzheimer's disease, cerebral stroke and Parkinson's disease. The purpose of the present review is to summarize the mechanism underlying the role of GDF15 in various brain disorders, which hopes to provide evidence and guide the prevention and treatment of these debilitating conditions.

Growth Differentiation Factor 15 Is Associated With Alzheimer's Disease Risk

Background

Previous observational studies have suggested that associations exist between growth differentiation factor 15 (GDF-15) and neurodegenerative diseases. We aimed to investigate the causal relationships between GDF-15 and Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS).

Methods

Using summary-level datasets from genome-wide association studies of European ancestry, we performed a two-sample Mendelian randomization (MR) study. Genetic variants significantly associated (p < 5 × 10^–8) with GDF-15 were selected as instrumental variables (n = 5). An inverse-variance weighted method was implemented as the primary MR approach, while weighted median, MR–Egger, leave-one-out analysis, and Cochran’s Q-test were conducted as sensitivity analyses. All analyses were performed using R 3.6.1 with relevant packages.

Results

MR provided evidence for the association of elevated GDF-15 levels with a higher risk of AD (odds ratio = 1.14; 95% confidence interval, 1.04–1.24; p = 0.004). In the reverse direction, Mendelian randomization suggested no causal effect of genetically proxied risk of AD on circulating GDF-15 (p = 0.450). The causal effects of GDF-15 on PD (p = 0.597) or ALS (p = 0.120) were not identified, and the MR results likewise did not support the association of genetic liability to PD or ALS with genetically predicted levels of GDF-15. No evident heterogeneity or horizontal pleiotropy was revealed by multiple sensitivity analyses.

Conclusion

We highlighted the role of GDF-15 in AD as altogether a promising diagnostic marker and a therapeutic target.

Further Evidence of Accelerated Aging in Bipolar Disorder: Focus on GDF-15

Background

Bipolar disorder (BD) is a mood disorder associated with cardiovascular and metabolic diseases and premature aging. Growth differentiation factor 15 (GDF-15) has emerged as a biomarker for cardiovascular risk and aging. Our aim was to compare plasma levels of GDF-15 between BD patients and controls, and to evaluate whether they were associated with clinical parameters.

Methods

Forty-six patients with type I BD (23 in euthymia and 23 in mania) and 33 healthy controls were recruited for this study. Plasma levels of GDF-15 were measured by immunoassay.

Results

The levels of GDF-15 were significantly higher (p < 0.001) in patients with BD in comparison with controls. In patients, GDF-15 levels correlated with age (rho = 0.434; p = 0.003) and illness duration (rho = 0.502; p = 0.001).

Conclusion

Our findings corroborate the view that BD is an illness associated with accelerated aging.

A Meta-Analysis of Genome-Wide Association Studies of Growth Differentiation Factor-15 Concentration in Blood

Blood levels of growth differentiation factor-15 (GDF-15), also known as macrophage inhibitory cytokine-1 (MIC-1), have been associated with various pathological processes and diseases, including cardiovascular disease and cancer. Prior studies suggest genetic factors play a role in regulating blood MIC-1/GDF-15 concentration. In the current study, we conducted the largest genome-wide association study (GWAS) to date using a sample of ∼5,400 community-based Caucasian participants, to determine the genetic variants associated with MIC-1/GDF-15 blood concentration. Conditional and joint (COJO), gene-based association, and gene-set enrichment analyses were also carried out to identify novel loci, genes, and pathways. Consistent with prior results, a locus on chromosome 19, which includes nine single nucleotide polymorphisms (SNPs) (top SNP, rs888663, p = 1.690 × 10^-35), was significantly associated with blood MIC-1/GDF-15 concentration, and explained 21.47% of its variance. COJO analysis showed evidence for two independent signals within this locus. Gene-based analysis confirmed the chromosome 19 locus association and in addition, a putative locus on chromosome 1. Gene-set enrichment analyses showed that the“COPI-mediated anterograde transport” gene-set was associated with MIC-1/GDF15 blood concentration with marginal significance after FDR correction (p = 0.067). In conclusion, a locus on chromosome 19 was associated with MIC-1/GDF-15 blood concentration with genome-wide significance, with evidence for a new locus (chromosome 1). Future studies using independent cohorts are needed to confirm the observed associations especially for the chromosomes 1 locus, and to further investigate and identify the causal SNPs that contribute to MIC-1/GDF-15 levels.

Glycerophospholipid Supplementation as a Potential Intervention for Supporting Cerebral Structure in Older Adults

Modifying nutritional intake through supplementation may be efficacious for altering the trajectory of cerebral structural decline evident with increasing age. To date, there have been a number of clinical trials in older adults whereby chronic supplementation with B vitamins, omega-3 fatty acids, or resveratrol, has been observed to either slow the rate of decline or repair cerebral tissue. There is also some evidence from animal studies indicating that supplementation with glycerophospholipids (GPL) may benefit cerebral structure, though these effects have not yet been investigated in adult humans. Despite this paucity of research, there are a number of factors predicting poorer cerebral structure in older humans, which GPL supplementation appears to beneficially modify or protect against. These include elevated concentrations of homocysteine, unbalanced activity of reactive oxygen species both increasing the risk of oxidative stress, increased concentrations of pro-inflammatory messengers, as well as poorer cardio- and cerebrovascular function. As such, it is hypothesized that GPL supplementation will support cerebral structure in older adults. These cerebral effects may influence cognitive function. The current review aims to provide a theoretical basis for future clinical trials investigating the effects of GPL supplementation on cerebral structural integrity in older adults.

Genetic Variation in S100B Modulates Neural Processing of Visual Scenes in Han Chinese

Spatial navigation is a crucial ability for living. Previous animal studies have shown that the S100B gene is causally related to spatial navigation performance in mice. However, the genetic factors influencing human navigation and its neural substrates remain unclear. Here, we provided the first evidence that the S100B gene modulates neural processing of navigationally relevant scenes in humans. First, with a novel protocol, we demonstrated that the spatial pattern of S100B gene expression in postmortem brains was associated with brain activation pattern for spatial navigation in general, and for scene processing in particular. Further, in a large fMRI cohort of healthy adults of Han Chinese (N = 202), we found that S100B gene polymorphisms modulated scene selectivity in the retrosplenial cortex (RSC) and parahippocampal place area. Finally, the serum levels of S100B protein mediated the association between S100B gene polymorphism and scene selectivity in the RSC. Our study takes the first step toward understanding the neurogenetic mechanism of human spatial navigation and suggests a novel approach to discover candidate genes modulating cognitive functions.

Serum Growth Differentiation Factor 15 in Parkinson Disease

BACKGROUND

Growth differentiation factor 15 (GDF15) has been shown to be protective for dopaminergic neurons in animal and ex vivo experiments. However, little is known about its effect on the human body.

OBJECTIVE

This study investigated associations between serum GDF15 levels and clinical parameters in patients with Parkinson disease (PD).

METHODS

Idiopathic PD patients (n = 104) and age-matched controls (n = 88) were enrolled. Serum GDF15 levels were measured by human enzyme-linked immunosorbent assay. Univariate and multivariate analyses investigated correlations between GDF15 and clinical characteristics, including disease severity by the Unified PD Rating Scale (UPDRS)-III. The diagnostic value of GDF15 was evaluated by receiver-operating characteristic curve (ROC) analysis.

RESULTS

The serum GDF15 levels of the PD patients were significantly higher than those of the healthy controls. In PD patients, serum GDF15 levels in men were significantly higher than in women. GDF15 levels correlated with age, gender, disease duration, and UPDRS-III score. After adjusting for confounding factors, multiple linear regression analysis showed that the serum GDF15 level (β = 0.015, p = 0.001) was an independent risk factor for UPDRS-III score. In ROC analysis, GDF15 achieved an area under the curve of 0.86 for the identification of PD, with a sensitivity of 71.15% and a specificity of 87.50%.

CONCLUSION

GDF15 may be a potential biomarker for the diagnosis and monitoring of motor severity in PD.

Macrophage inhibitory cytokine-1/growth differentiation factor 15 as a marker of cognitive ageing and dementia

PURPOSE OF REVIEW

As a divergent member of the transforming growth factor-β superfamily, macrophage inhibitory cytokine-1 (MIC-1/GDF15) is an autocrine regulatory molecule that plays important roles in diseases, such as cancer and cardiovascular disorders. More recently, this cytokine has been investigated for its contribution to ageing and age-related cognitive decline. This review aims at summarizing existing findings on the relationships of MIC-1/GDF15 with cognition, brain, and dementia in ageing populations and animal models.

RECENT FINDINGS

In community-dwelling samples, higher circulating MIC-1/GDF15 levels were associated with worsening cognitive function and decline from cognitively normal status to mild cognitive impairment or dementia. Higher MIC-1/GDF15 serum levels were also linked to decreased grey matter volumes and white matter integrity. Brain structural changes were shown to mediate the inverse relationships of MIC-1/GDF15 serum levels with cognition. Animal studies indicated that the expression of MIC-1/GDF15 in response to stress was neuroprotective and even promoted neurogenesis.

SUMMARY

From the available findings, MIC-1/GDF15 can be considered as a marker of age-related cognitive decline and brain structural changes. Combining MIC-1/GDF15 with other biomarkers may provide clinical diagnostic and prognostic utility. Threshold effects should be considered in future studies.

An inverse relationship between serum macrophage inhibitory cytokine-1 levels and brain white matter integrity in community-dwelling older individuals

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) is a marker of inflammation that has been associated with atherosclerosis. We have previously demonstrated its relationships with cognitive decline and cerebral gray matter volumes, suggesting its role as a biomarker of cognitive impairment. Considering that it is widely distributed in the brain, and both inflammation and vascular pathology impact on white matter (WM) integrity, we examined the relationship between MIC-1/GDF15 and measures of WM integrity, including WM volumes, mean fractional anisotropy (FA) values and WM hyperintensity (WMH) volumes in a community-dwelling non-demented sample of older individuals (n=327, 70-90 years old). We found that the mean FA values were negatively associated with MIC-1/GDF15 serum levels, after Bonferroni correction. The voxel-wise analysis showed negative relationships between MIC-1/GDF15 serum levels and FA values in corticospinal tract, corpus callosum (including genu, body and splenium parts), superior longitudinal fasciculus, cingulum, as well as anterior and posterior thalamic radiation. Whole brain WMH volumes, especially deep WMH volumes, showed a non-significant trend for a positive association with MIC-1/GDF15 serum levels. The associations between MIC-1/GDF15 serum levels and WM integrity showed a non-significant trend of being stronger for the individuals classified as mild cognitive impairment, compared to the normal ageing participants. The findings suggest that high serum MIC-1/GDF15 levels indicate reduced WM integrity and possibly greater WM pathology.

Associations of Circulating Growth Differentiation Factor-15 and ST2 Concentrations With Subclinical Vascular Brain Injury and Incident Stroke

BACKGROUND AND PURPOSE

Growth differentiation factor-15 (GDF-15) and soluble (s)ST2 are markers of cardiac and vascular stress. We investigated the associations between circulating concentrations of these biomarkers and incident stroke and subclinical vascular brain injury in a sample from the Framingham Offspring cohort.

METHODS

We followed 3374 stroke- and dementia-free individuals (mean age, 59.0±9.7 years; 53% women) attending the Framingham Offspring sixth examination cycle 11.8±3.0 years for incident stroke. A subsample of 2463 individuals underwent brain magnetic resonance imaging and neuropsychological testing ≈4.0±1.7 years after the sixth examination.

RESULTS

After adjustment for traditional cardiovascular risk factors, B-type natriuretic peptide, high-sensitivity C-reactive protein, and urine albumin levels, higher stress biomarker levels were associated cross-sectionally with lower brain volumes (β coefficients for intracranial volume comparing fourth [Q4] versus first biomarker [Q1] quartiles: -0.71% for GDF-15; P=0.002 and 0.47% for sST2; P=0.02) and worse performance on the visual reproduction test (β coefficients for Q4 versus Q1: -0.62 for GDF-15; P=0.009 and -0.40 for sST2; P=0.04). Higher GDF-15 concentrations were also associated with greater log-transformed white-matter hyperintensity volumes (β for Q4 versus Q1=0.19; P=0.01). Prospectively, a total of 203 (6%) individuals developed incident stroke/transient ischemic attack during follow-up. After multivariable adjustment, sST2 remained significantly associated with stroke/transient ischemic attack, hazard ratio for Q4 versus Q1 of 1.76, 95% confidence interval of 1.06 to 2.92, and P=0.03.

CONCLUSIONS

Circulating GDF-15 and sST2 are associated with subclinical brain injury and cognitive impairment. Higher sST2 concentrations are also associated with incident stroke, suggesting potential links between cardiac stress biomarkers and brain injury.