A review of the potential therapeutic role of statins in the treatment of Alzheimer's disease: current research and opinion

Rationale and methods for a multicenter clinical trial assessing exercise and intensive vascular risk reduction in preventing dementia (rrAD Study)

Alzheimer's Disease (AD) is an age-related disease with modifiable risk factors such as hypertension, hypercholesterolemia, obesity, and physical inactivity influencing the onset and progression. There is however, no direct evidence that reducing these risk factors prevents or slows AD. The Risk Reduction for Alzheimer's Disease (rrAD) trial is designed to study the independent and combined effects of intensive pharmacological control of blood pressure and cholesterol and exercise training on neurocognitive function. Six hundred and forty cognitively normal older adults age 60 to 85 years with hypertension and increased risk for dementia will be enrolled. Participants are randomized into one of four intervention group for two years: usual care, Intensive Reduction of Vascular Risk factors (IRVR) with blood pressure and cholesterol reduction, exercise training (EX), and IRVR+EX. Neurocognitive function is measured at baseline, 6, 12, 18, and 24 months; brain MRIs are obtained at baseline and 24 months. We hypothesize that both IRVR and EX will improve global cognitive function, while IRVR+EX will provide a greater benefit than either IRVR or EX alone. We also hypothesize that IRVR and EX will slow brain atrophy, improve brain structural and functional connectivity, and improve brain perfusion. Finally, we will explore the mechanisms by which study interventions impact neurocognition and brain. If rrAD interventions are shown to be safe, practical, and successful, our study will have a significant impact on reducing the risks of AD in older adults. NCT Registration: NCT02913664.

Total cholesterol and neuropsychiatric symptoms in Alzheimer's disease: the impact of total cholesterol level and gender

BACKGROUND

Neuropsychiatric symptoms (NPS) in Alzheimer's disease (AD) are a major factor in nursing home placement and a primary cause of stress for caregivers. Elevated cholesterol has been linked to psychiatric disorders and has been shown to be a risk factor for AD and to impact disease progression. The present study investigated the relationship between cholesterol and NPS in AD.

METHODS

Data on cholesterol and NPS from 220 individuals (144 females, 76 males) with mild-to-moderate AD from the Texas Alzheimer's Research and Care Consortium (TARCC) cohort were analyzed. The total number of NPS and symptoms of hyperactivity, psychosis, affect and apathy were evaluated. Groups based on total cholesterol (TC; ≥200 vs. <200 mg/dl) were compared with regard to NPS. The impact of gender was also assessed.

RESULTS

Individuals with high TC had lower MMSE scores as well as significantly more NPS and more symptoms of psychosis. When stratified by gender, males with high TC had significantly more NPS than females with high TC or than males or females with low TC.

CONCLUSION

The role of elevated cholesterol in the occurrence of NPS in AD appears to be gender and symptom specific. A cross-validation of these findings will have implications for possible treatment interventions, especially for males with high TC.

Simvastatin exerts antiamnesic effect in Aβ25-35 -injected mice

AIM AND METHODS

Simvastatin (SV) is reported to improve cognition and slow the progression of Alzheimer's disease (AD). This study explored the mechanisms underlying the antiamnesic effect of SV in AD using behavior tests, histological examination, western blot analysis, and electrophysiological recording technique in AD model mice created by intracerebroventricular injection (i.c.v.) of Aβ25-35 .

RESULTS

Chronic administration of SV (40 mg/kg/day) for 11 days after Aβ25-35 -injection ameliorated the impairment of acquisition performance and probe trail test in Morris water maze task and alternation behavior in Y maze task in Aβ25-35 -mice. Aβ25-35 -induced apoptosis of hippocampal CA1 pyramidal cells and Aβ25-35 -impaired high-frequency stimulation (HFS)-dependent long-term potentiation (LTP) induction in hippocampal Schaffer collaterale-CA1 synapse were rescued by SV-treatment. SV prevented Aβ25-35 -inhibited protein kinase B (Akt) and extracellular signal-related kinase-2 (ERK2) phosphorylation, which was sensitive to α7 nicotinic acetylcholine receptor (α7nAChR) antagonist MLA. SV-induced neuroprotection was attenuated by MLA or phosphatidylinositol-3-kinase (PI3K) antagonist LY294002. SV-rescued LTP induction was blocked by α7nAChR, PI3K or MAPK/ERK kinase (MEK) antagonist. Finally, the antiamnesia of SV in Aβ25-35 -mice was attenuated by blockage of SV-induced neuroprotection or SV-rescued LTP induction.

CONCLUSION

The antiamnesia of SV in Aβ25-35 -mice depends on its neuroprotection and synaptic plasticity improvement.

Statins more than cholesterol lowering agents in Alzheimer disease: their pleiotropic functions as potential therapeutic targets

Alzheimer disease (AD) is a progressive neurodegenerative disorder characterized by severe cognitive impairment, inability to perform activities of daily living and mood changes. Statins, long known to be beneficial in conditions where dyslipidemia occurs by lowering serum cholesterol levels, also have been proposed for use in neurodegenerative conditions, including AD. However, it is not clear that the purported effectiveness of statins in neurodegenerative disorders is directly related to cholesterol-lowering effects of these agents; rather, the pleiotropic functions of statins likely play critical roles. The aim of this review is to provide an overview on the new discoveries about the effects of statin therapy on the oxidative and nitrosative stress levels as well as on the modulation of the heme oxygenase/biliverdin reductase (HO/BVR) system in the brain. We propose a novel mechanism of action for atorvastatin which, through the activation of HO/BVR-A system, may contribute to the neuroprotective effects thus suggesting a potential therapeutic role in AD and potentially accounting for the observation of decreased AD incidence with persons on statin.