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1.  Cholesterol and Statins in Alzheimer’s Disease 
Archives of neurology  2011;68(11):1385-1392.
Substantial evidence has accumulated in support of the hypothesis that elevated cholesterol levels increase the risk of developing Alzheimer’s disease (AD). As a result, much work has been done investigating the potential use of lipid-lowering agents (LLAs), particularly statins, as preventive or therapeutic agents for AD. While epidemiology and preclinical statin research (described in Part 1 of this review) have generally supported an adverse role of high cholesterol regarding AD, human studies of statins (reviewed here) show highly variable outcomes, making it difficult to draw firm conclusions. We identify several confounding factors among the human studies, including differing blood-brain barrier permeabilities among statins, the stage in AD at which statins were administered, and the drugs’ pleiotropic metabolic effects, all of which contribute to the substantial variability observed to date. We recommend that future human studies of this important therapeutic topic 1) take the blood-brain barrier permeabilities of statins into account when analyzing results, 2) include specific analyses of effects on low-density and high-density lipoprotein cholesterol, and most importantly, 3) conduct statin treatment trials solely in mild AD patients, who have the best chance for disease modification.
PMCID: PMC3248784  PMID: 22084122
2.  Cholesterol and Statins in Alzheimer’s Disease 
Archives of neurology  2011;68(10):1239-1244.
Over the past twenty years, evidence has accumulated that high cholesterol levels may increase the risk of developing Alzheimer’s disease (AD). With the global use of statins to treat hypercholesterolemia, this finding has led to the hope that statins could prove useful in treating or preventing AD. However, the results of work on this topic are inconsistent: some studies find beneficial effects, others do not. In this first segment of a two-part review, we examine the complex preclinical and clinical literature on cholesterol and AD. First, we review epidemiological research on cholesterol levels and the risk of AD and discuss the relevance of discrepancies among studies as regards participants’ age and clinical status. Next, we assess studies correlating cholesterol with AD-type neuropathology. The potential molecular mechanisms for cholesterol’s apparent adverse effect on the development of AD are then discussed. Finally, we review preclinical studies of statins and AD. Thus, this first portion of our review provides the background and rationale for investigating statins as potential therapeutic agents in AD patients, the subject of the second part.
PMCID: PMC3211071  PMID: 21987540
3.  Soluble oligomers of amyloid β-protein facilitate hippocampal long-term depression by disrupting neuronal glutamate uptake 
Neuron  2009;62(6):788-801.
In Alzheimer's disease (AD), the insidious impairment of declarative memory coincides with the accumulation of extracellular amyloid-β protein (Aβ) and intraneuronal tau aggregates. Dementia severity correlates strongly with decreased synapse density in hippocampus and cortex. Although numerous studies show that soluble Aβ oligomers inhibit hippocampal long-term potentiation, their role in long-term synaptic depression (LTD) remains unclear. Here, we report that soluble Aβ oligomers from several sources (synthetic, cell culture, human brain extracts) facilitated electrically-evoked LTD in the CA1 region. Aβ-enhanced LTD was mediated by mGluR or NMDAR activity, depending on the induction protocol. Both forms of LTD were prevented by an extracellular glutamate scavenger system. Aβ-facilitated LTD was closely mimicked by the action of the glutamate reuptake inhibitor TBOA, including a shared dependence on extracellular calcium levels and activation of PP2B and GSK-3 signaling. In accord, synaptic glutamate uptake was significantly decreased by soluble Aβ. We conclude that soluble Aβ oligomers perturb synaptic plasticity by altering glutamate recycling at the synapse and promoting synapse depression.
PMCID: PMC2702854  PMID: 19555648
4.  Amyloid β-Protein Dimers Isolated Directly from Alzheimer Brains Impair Synaptic Plasticity and Memory 
Nature medicine  2008;14(8):837-842.
Alzheimer’s disease (AD) constitutes a rising threat to public health. Despite extensive research in cellular and animal models, identifying the pathogenic agent present in the human brain and showing that it confers key features of AD have not been achieved. We extracted soluble amyloid β–protein (Aβ) oligomers directly from the cerebral cortex of typical AD subjects. The oligomers potently inhibited long term potentiation (LTP), enhanced long term depression (LTD), and reduced dendritic spine density in normal rodent hippocampus. Soluble Aβ from AD brain also disrupted the memory of a learned behavior in normal rats. These various effects were specifically attributable to Aβ dimers. Mechanistically, metabotropic glutamate receptors (mGluR) were required for LTD enhancement and NMDA receptors (NMDAR) for spine loss. Co-administering antibodies to the Aβ N-terminus prevented the LTP and LTD deficits, whereas antibodies to the mid-region or C-terminus were less effective. Insoluble amyloid plaque cores from AD cortex did not impair LTP unless they were first solubilized to release Aβ dimers, suggesting that plaque cores are largely inactive but sequester Aβ dimers that are synaptotoxic. We conclude that soluble Aβ oligomers extracted from AD brains potently impair synapse structure and function and that dimers are the smallest synaptotoxic species.
PMCID: PMC2772133  PMID: 18568035

Results 1-4 (4)