Change in circulating C-reactive protein is not associated with atorvastatin treatment in Alzheimer's disease

Statin Use, Incident Dementia and Alzheimer Disease in Elderly African Americans

OBJECTIVE

To investigate the association between statin use, incident dementia, and Alzheimer disease (AD) in a prospective elderly African American cohort.

DESIGN

Two stage design with a screening interview followed by a comprehensive in-home assessment conducted over an eight-year period. Diagnoses of incident AD and dementia were made by consensus. Statin use was collected at each evaluation. Measurements of low-density lipoprotein cholesterol (LDL), C-reactive protein (CRP) and APOE genotype were obtained from baseline blood samples. Logistic regression models were used to test the association of statin use on incident dementia and AD and its possible association with lipid and CRP levels.

SETTING

Indianapolis, Indiana.

PARTICIPANTS

From an original cohort of 2629 participants, a subsample of 974 African Americans aged >70 years with normal cognition, at least one follow up evaluation, complete statin information, and biomarker availability were included.

MAIN OUTCOME MEASURES

Incident dementia and incident AD.

RESULTS

After controlling for age at diagnosis, sex, education level, presence of the APOE ε4 allele and history of stroke for the incident dementia model, baseline use of statins was associated with a significantly decreased risk of incident dementia (OR=.44, P=.029) and incident AD (OR=.40, P=.029). The significant effect of statin use on reduced AD risk and trend for dementia risk was found only for those participants who reported consistent use over the observational period (incident AD: P=.034; incident dementia: P=.061). Additional models found no significant interaction between baseline statin use, baseline LDL, or CRP level and incident dementia/AD.

CONCLUSIONS

Consistent use of statin medications during eight years of follow-up resulted in significantly reduced risk for incident AD and a trend toward reduced risk for incident dementia.

Systemic inflammation and Alzheimer's disease

A number of studies demonstrate disturbances of the central innate immune system in AD (Alzheimer's disease). In animal and human studies, there is evidence of close communication between systemic and central innate immune systems. Animal models of neurodegeneration show evidence of an exaggerated central innate immune response following systemic inflammation. Clinical studies of AD show evidence of increased cognitive decline and exaggerated sickness behaviour in response to systemic inflammation. Recognition of this communication pathway offers alternative explanations for a number of recognized risk factors in the development and progression of AD and highlights the potential of the manipulation of systemic innate immunity as a novel therapeutic approach.

Systemic and central immunity in Alzheimer's disease: therapeutic implications

Clinical pharmaceutical trials aimed at modulating the immune system in Alzheimer's Disease have largely focused on either dampening down central proinflammatory innate immunity or have manipulated adaptive immunity to facilitate the removal of centrally deposited beta amyloid. To date, these trials have had mixed clinical therapeutic effects. However, a number of clinical studies have demonstrated disturbances of both systemic and central innate immunity in Alzheimer's Disease and attention has been drawn to the close communication pathways between central and systemic immunity. This paper highlights the need to take into account the potential systemic effects of drugs aimed at modulating central immunity and the possibility of developing novel therapeutic approaches based on the manipulation of systemic immunity and its communication with the central nervous system.

A meta-analysis of cytokines in Alzheimer's disease

BACKGROUND

Studies suggest that inflammation is involved in the neurodegenerative cascade leading to Alzheimer's disease (AD) pathology and symptoms. This study sought to quantitatively summarize the clinical cytokine data.

METHODS

Original English language peer-reviewed studies measuring cytokine concentrations in AD and healthy control subjects were included. Mean (± standard deviation) cytokine concentrations for AD and control subjects were extracted.

RESULTS

Forty studies measuring peripheral blood cytokine concentrations and 14 measuring cerebrospinal fluid (CSF) cytokine concentrations were included. In peripheral blood, there were significantly higher concentrations (weighted mean difference [95% confidence interval]) of interleukin (IL)-6 (2.86 [1.68, 4.04] pg/mL, p < .00001, N[AD/control subjects] = 985/680, 14 studies), tumor necrosis factor (TNF)-α (3.25 [.76, 5.74] pg/mL, p = .01, N = 680/447, 14 studies), IL-1β (.55 [.32, .78] pg/mL, p < .00001, N = 574/370, 10 studies), transforming growth factor (TGF)-β (67.23 [28.62, 105.83] pg/mL, p = .0006, N = 190/158, 5 studies), IL-12 (7.60 [5.58, 9.62] pg/mL, p < .00001, N = 148/106, 5 studies), and IL-18 (15.82 [1.98, 29.66] pg/mL, p = .03, N = 131/94, 4 studies) but not of IL-4, IL-8, IL-10, interferon-γ, or C-reactive protein in AD subjects compared with control subjects. There were significantly higher concentrations of TGF-β (7.81 [2.27, 13.35] pg/mL, p =.006, N = 113/114, 5 studies) but not IL-6, TNF-α, and IL-1β in the CSF of AD subjects compared with control subjects.

CONCLUSIONS

These results strengthen the clinical evidence that AD is accompanied by an inflammatory response, particularly higher peripheral concentrations of IL-6, TNF-α, IL-1β, TGF-β, IL-12 and IL-18 and higher CSF concentrations of TGF-β.

Role of HMG-CoA reductase inhibitors in neurological disorders : progress to date

Inhibitors of HMG-CoA reductase (statins) are cholesterol-lowering agents that dramatically reduce morbidity and mortality in patients with established cardiovascular disease. In addition, they exhibit pleiotropic effects that operate independently of lipid modification. Statin administration results in greater nitric oxide bioavailability, improved endothelial function, enhanced cerebral blood flow, immune modulation with anti-inflammatory action, decreased platelet aggregation and antioxidant activity. Some or all of these effects may improve outcome or ameliorate symptoms in neurological disorders. This article examines the potential role of statins in treating stroke, Alzheimer's disease, multiple sclerosis and Parkinson's disease. Studies are ongoing in this controversial area, but there are no firm conclusions. The appropriateness of initiating statin therapy for neurological disorders is not established at this time. The exception is stroke, in which recurrence is significantly reduced by statin therapy.

C-reactive protein and rate of dementia in carriers and non carriers of Apolipoprotein APOE4 genotype

BACKGROUND

Those with an Apolipoprotein APOE4 allele (APOE4) have lower C-reactive protein (CRP) than those without APOE4. Whether APOE4 modifies the effects of CRP on rate of all cause dementia, cognitive impairment or Alzheimer's disease (AD) is not established.

METHODS

All cause dementia and cognitive impairment without dementia (CIND) was determined over five follow up visits from 1998 to 2006 in an ongoing cohort of older Latinos. The association between high sensitivity CRP and dementia/CIND, all cause dementia and Alzheimer's disease by APOE4 status was examined in semi-parametric survival models with covariate adjustments.

RESULTS

CRP was significantly lower among those with APOE4 than in those without. Among those with APOE4, CRP was associated with lower rates of combined dementia/CIND (HR: 0.60, 95% CL: 0.20-0.91, p=0.03) from a fully adjusted model. Among those with no APOE4, there was no effect of CRP on dementia/CIND rates (HR: 0.94, 95% CL: 0.67-1.33).

CONCLUSIONS

Lower CRP in those with APOE4 may reflect immune effects of the APOE4 genotype. Higher CRP in those with APOE4 may be a marker of better immune function, leading to lower rate of dementia and AD.