Coagulation and inflammatory markers in Alzheimer's and vascular dementia

Elevated plasma fibrin D-dimer as a risk factor for vascular dementia: the Three-City cohort study

BACKGROUND

Hemostatic biomarkers have been associated with coronary heart disease (CHD) and stroke. However, few studies have investigated these associations in the elderly. Moreover, vascular factors may be involved in dementia. Data on the relationship between hemostatic biomarkers and dementia remain scarce.

OBJECTIVES

Our study aimed to investigate the relationship between hemostatic biomarkers and the risk of CHD, stroke and dementia in an elderly population.

PATIENTS/METHODS

In the Three-City cohort study including men and women aged > or = 65, we investigated the association of fibrinogen, D-dimer and von Willebrand factor with the 4-year incidence of arterial disease (CHD, n = 199; and stroke, n = 111) and dementia (n = 218). Measurements were performed for all cases and for a random sample of the entire cohort (n = 1254). Hazards ratios (HR) compared the last quintile with the first of each parameter's distribution and P-values refer to the test for linear trend across quintiles.

RESULTS

Elevated fibrinogen was associated with the risk of CHD and myocardial infarction (HR = 2.20, P < 0.05 and 2.45 P < 0.05, respectively). Moreover, high D-dimer was associated with the risk of CHD among younger subjects (aged < 75, HR = 3.64, P < 0.01) but not older subjects (P for interaction = 0.01). Furthermore, the risk of vascular dementia (VaD) increased with D-dimer level (HR = 3.05, P < 0.01).

CONCLUSIONS

In the elderly, elevated fibrinogen and D-dimer levels were associated with incident arterial disease. In addition, high D-dimer level could represent a new risk factor for VaD.

Elevated C-reactive protein levels are associated with prevalent dementia in the oldest-old

BACKGROUND

C-reactive protein (CRP) is a nonspecific marker of inflammation that is increased in the brain and serum of patients with Alzheimer's disease (AD), and has been associated with increased risk of developing dementia. Inflammation increases with age, and the number of people reaching age 90 years and older is growing, making the association between inflammation and dementia increasingly relevant. Using a cross-sectional design, we examined whether high levels of serum CRP are associated with increased odds of prevalent dementia in the oldest-old.

METHODS

Serum CRP levels of 305 participants (mean age +/- standard deviation, 94.3 +/- 2.9 years) from the 90+ Study, a longitudinal cohort study of people aged 90 years and older, were evaluated with respect to all-cause dementia. Levels of CRP were divided into three categories: undetectable (<0.5 mg/dL), detectable (0.5-0.7 mg/dL), and elevated (> or =0.8 mg/dL). Odds ratios (ORs) were calculated using logistic regression, and were adjusted for covariates.

RESULTS

Relative to participants with undetectable CRP levels, participants with detectable or elevated CRP levels had increased odds of all-cause dementia (detectable: OR, 3.0; 95% confidence interval, 1.2-7.3; elevated: OR, 5.0; 95% confidence interval, 1.9-12.9). When participants were subdivided by gender, significantly increased ORs were seen only in women.

CONCLUSIONS

In the oldest-old, high CRP levels are associated with increased odds of all-cause dementia, particularly in women. Prospective studies are necessary to confirm whether increased CRP levels are associated with an increased risk of developing dementia in this age group.

Fibrinogen, a possible key player in Alzheimer's disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by progressive loss of cognitive function and subsequent death. Since the first case of this disease was diagnosed one century ago, much effort has been dedicated to find a cure. However, even though progress has been made in the knowledge of the pathogenesis of this disease, an effective treatment has not been found. Therefore, new approaches are needed urgently. AD patients have an abnormal cerebral vasculature and brain hypoperfusion, and a large body of research, including some from our lab, implicates cerebrovascular dysfunction as a contributing factor to AD. Reducing fibrinogen, a circulating protein critical in hemostasis, provides a significant decrease in the neurovascular damage, blood-brain barrier permeability and neuroinflammation present in AD. These studies implicate fibrinogen as a possible contributor to AD.

The relation of genetic and environmental factors to systemic inflammatory biomarker concentrations

BACKGROUND

Environmental and genetic correlates of inflammatory marker variability are incompletely understood. In the family-based Framingham Heart Study, we investigated heritability and candidate gene associations of systemic inflammatory biomarkers.

METHODS AND RESULTS

In offspring participants (n=3710), we examined 11 inflammatory biomarkers (CD40 ligand, C-reactive protein, intercellular adhesion molecule-1, interleukin-6, urinary isoprostanes, monocyte chemoattractant protein-1, myeloperoxidase, P-selectin, tumor necrosis factor-alpha, tumor necrosis factor receptor II, fibrinogen). Heritability and bivariate genetic and environmental correlations were assessed by Sequential Oligogenic Linkage Analysis routines in 1012 family members. We examined 1943 tagging single-nucleotide polymorphisms in 233 inflammatory pathway genes with >or=5 minor allele carriers using a general genetic linear model. Clinical correlates explained 2.4% (CD40 ligand) to 28.5% (C-reactive protein) of the variability in inflammatory biomarkers. Estimated heritability ranged from 10.9% (isoprostanes) to 44.8% (P-selectin). Most correlations between biomarkers were weak although statistically significant. A total of 45 single-nucleotide polymorphism-biomarker associations met the q-value threshold of 0.25. Novel top single-nucleotide polymorphisms were observed in ICAM1 gene in relation to intercellular adhesion molecule-1 concentrations (rs1799969, P=1.32 x 10(-8)) and MPO in relation to myeloperoxidase (rs28730837, P=1.9 x 10(-5)). Lowest P values for trans-acting single-nucleotide polymorphisms were observed for APCS with monocyte chemoattractant protein-1 concentrations (rs1374486, P=1.01 x 10(-7)) and confirmed for IL6R with interleukin-6 concentrations (rs8192284, P=3.36 x 10(-5)). Novel potential candidates (APCS, MPO) need to be replicated.

CONCLUSIONS

Our community-based data support the relevance of clinical and genetic factors for explaining variation in inflammatory biomarker traits.

Plasma fibrinogen is associated with cognitive decline and risk for dementia in patients with mild cognitive impairment

This study was aimed to investigate the relationship between plasma fibrinogen level and risk for cognitive decline and dementia in patients with mild cognitive impairment (MCI). Elderly patients with suspected cognitive impairment were screened and evaluated periodically. One hundred and eighty-five patients who met the criteria for MCI were enrolled. Blood coagulation functions and plasma fibrinogen levels were measured at baseline. Hyperfibrinogenaemia was defined as plasma fibrinogen > or =3.0 g/l. Global cognitive function was assessed serially with Mini-Mental State Examination (MMSE). The enrolled patients were followed for 2 years to observe if dementia was developed. There were 185 patients diagnosed as MCI, of which 17 (9.2%) deceased, 15 (8.1%) lost to follow-up, and 68 (36.8%) developed dementia during follow-up. Mean of MMSE score of the enrolled patients declined significantly during follow-up (22.0 +/- 3.0 vs. 18.1 +/- 5.8, p < 0.001). Patients with hyperfibrinogenaemia at baseline had greater MMSE decrement during follow-up than patients with normal fibrinogen level (-5.4 +/- 5.4 vs. -3.5 +/- 4.5, p < 0.05). Linear regression indicated that plasma fibrinogen level was associated with cognitive decline (R = 0.17, p < 0.05). Patients with hyperfibrinogenaemia had an increased risk for dementia and vascular dementia compared with patients with normal level of plasma fibrinogen (log rank test, p < 0.05). There was a trend that hyperfibrinogenaemia also increased risk for dementia of Alzheimer's type (p = 0.061). It can be concluded that plasma fibrinogen level may be associated with cognitive decline, and hyperfibrinogenaemia may increase risk for dementia in patients with MCI.

Brain type carnosinase in dementia: a pilot study

Background

The pathological processes underlying dementia are poorly understood and so are the markers which identify them. Carnosinase is a dipeptidase found almost exclusively in brain and serum. Carnosinase and its substrate carnosine have been linked to neuropathophysiological processes.

Methods

Carnosinase activity was measured by a flourometric method in 37 patients attending a Geriatric Outpatient Clinic. There were 17 patients without dementia, 13 had Alzheimer's disease (AD) and 7 had mixed dementia (MD).

Results

The range of serum carnosinase activity for patients without dementia was 14.5 – 78.5 μmol/ml/h. There was no difference in carnosinase activity between patients without dementia (40.3 ± 15.2 μmol/ml/h) and patients with AD (44.4 ± 12.4 μmol/ml/h) or MD (26.6 ± 15 μmol/ml/h). However, levels in the MD group were significantly lower than the AD group (p = 0.01). This difference remained significant after adjusting for gender, MMSE score, exercise, but not age, one at a time and all combined. The effect of other medical conditions did not remove the significance between the AD and MD groups. The MD group, but not the AD group, demonstrated a significant trend with carnosinase activity decreasing with duration of disease (from first recorded date of diagnosis to date of blood collection) (r = -0.76, p = 0.049). There was no association with carnosinase activity and MMSE score in the AD or MD group. Both AD and MD patients on any dementia medication (donepezil, galantamine, memantine) had higher carnosinase activity compared to those not taking a dementia medication. Carnosinase activity was higher in patients who regularly exercised (n = 20) compared to those who did not exercise regularly (n = 17)(p = 0.006).

Conclusion

This exploratory study has shown altered activities of the enzyme carnosinase in patients with dementia.

Fibrinogen gamma-A chain precursor in CSF: a candidate biomarker for Alzheimer's disease

BACKGROUND

Cerebrospinal fluid (CSF) may be valuable for exploring protein markers for the diagnosis of Alzheimer's disease (AD). The prospect of early detection and treatment, to slow progression, holds hope for aging populations with increased average lifespan. The aim of the present study was to investigate candidate CSF biological markers in patients with mild cognitive impairment (MCI) and AD and compare them with age-matched normal control subjects.

METHODS

We applied proteomics approaches to analyze CSF samples derived from 27 patients with AD, 3 subjects with MCI and 30 controls. The AD group was subdivided into three groups by clinical severity according to clinical dementia rating (CDR), a well known clinical scale for dementia.

RESULTS

We demonstrated an elevated level of fibrinogen gamma-A chain precursor protein in CSF from patients with mild cognitive impairment and AD compared to the age-matched normal subjects. Moreover, its expression was more prominent in the AD group than in the MCI and correlated with disease severity and progression. In contrast, fibrinogen gamma-A chain precursor protein was detected very low in the age-matched normal group.

CONCLUSION

These findings suggest that the CSF level of fibrinogen gamma-A chain precursor may be a candidate biomarker for AD.

Cognitive decline and markers of inflammation and hemostasis: the Edinburgh Artery Study

OBJECTIVES

To determine whether circulating markers of activated inflammation and hemostasis are associated with cognitive decline in older people.

DESIGN

Prospective cohort study (Edinburgh Artery Study).

SETTING

Eleven general practices in Edinburgh, Scotland.

PARTICIPANTS

A sample of 452 men and women followed for 16 years.

MEASUREMENTS

Biomarker data were collected in 1987/88, and cognitive assessment was first conducted in 1998/99, when the mean age of the sample +/- standard deviation was 73.1+/-5.0), and subsequently in 2002/03. Information was obtained on verbal declarative memory (Wechsler Logical Memory Test (LMT)), nonverbal reasoning (Raven's Standard Progressive Matrices), verbal fluency (Verbal Fluency Test), information processing speed (Wechsler Digit Symbol Test), and a general cognitive factor representing the variance common to the individual test scores.

RESULTS

In age-adjusted analyses, plasma fibrinogen, interleukin-6 (IL-6), and intercellular adhesion molecule 1 (ICAM-1) were negatively associated with performance on all cognitive measures in 2002/03 except the LMT (correlation coefficients from -0.10 to -0.24). In multivariate analyses controlling for demographic characteristics, depression, and cardiovascular morbidity and risk factors, fibrinogen independently predicted 4-year decline in nonverbal reasoning (P<.05). Also, when cognitive change was estimated from peak prior level, IL-6 turned out to be inversely related to decline in information processing speed (P<.05). Similarly, ICAM-1 was associated with a greater decline in general cognitive ability (P<.05) and nonverbal ability (P<.05).

CONCLUSION

Systemic markers of inflammation and hemostasis are associated with a progressive decline in general and specific cognitive abilities in older people, independent of major vascular comorbidity.