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Dietary supplementation with n-3 polyunsaturated fatty acids (n-3 PUFA) reduces amyloid-β (Aβ) and tau pathology and improves cognitive performance in animal models of Alzheimer's disease (AD). To exclude confounding variables associated with the diet, we crossed 3 × Tg-AD mice (modeling AD neuropathology) with transgenic Fat-1 mice that express the fat-1 gene encoding a PUFA desaturase, which endogenously produces n-3 PUFA from n-6 PUFA. The expression of fat-1 shifted the n-3:n-6 PUFA ratio upward in the brain (+11%, p < 0.001), including docosahexaenoic acid (DHA; +5%, p < 0.001) in 20 month-old mice. The expression of fat-1 decreased the levels of soluble Aβ₄₂ (-41%, p < 0.01) at 20 months without reducing the level of insoluble forms of Aβ₄₀ and Aβ₄₂ in the brain of 3 × Tg-AD mice. The 3 × Tg-AD/Fat-1 mice exhibited lower cortical levels of both soluble (-25%, p < 0.05) and insoluble phosphorylated tau (-55%, p < 0.05) compared to 3 × Tg-AD mice, but only in 20 month-old animals. Whereas a decrease of calcium/calmodulin-dependent protein kinase II was observed in 3 × Tg-AD/Fat-1 mice (-039%, p < 0.05), altered tau phosphorylation could not be related to changes in glycogen synthase kinase 3β, cyclin-dependent kinase 5, or protein phosphatase type 2A enzymatic activity. In addition, the expression of the fat-1 transgene prevented the increase of glial fibrillary acidic protein (-37%, p < 0.01) observed in 20 month-old 3 × Tg-AD mice. In conclusion, the expression of fat-1 in 3 × Tg-AD mice increases brain DHA and induces biomarker changes that are consistent with a beneficial effect against an AD-like neuropathology.

To investigate the mRNA expression of the dendritic spine protein drebrin in Alzheimer's disease (AD), we performed post-mortem in situ hybridization studies in brain sections from 20 AD patients and 21 controls. AD diagnosis was confirmed by decreased drebrin protein and increased Abeta(40) (+464%; P < 0.05), Abeta(42) (+369%; P < 0.0001), Abeta(42/40) ratio (+226%; P < 0.01), total tau (+2,725%; P < 0.0001), and paired helical filament tau (PHFtau; +867%; P < 0.001) compared with controls. We found significant decreases in drebrin mRNA in the parietal cortex (-27%; P < 0.01), the temporal cortex (-22%; P < 0.05), and the hippocampus (-25%; P < 0.05) of AD patients compared with controls. Cortical levels of drebrin mRNA correlated positively with soluble total tau (r(2) = +0.244) but negatively with duration of symptoms (r(2) = -0.357) and PHFtau (r(2) = -0.248). Drebrin mRNA levels were correlated to a lesser degree with the drebrin protein content (r(2) = +0.136) and with sim2 (r(2) = +0.176), a potential modulator of drebrin transcription. Our results suggest that the down-regulation of drebrin mRNA expression plays an important role in AD and is closely related to the progression of the disease.

The present data suggest that our new PSIL formulation combines molecular features required for targeted gene therapy including high DNA encapsulation efficiencies and vector-specific transient transfection capacity.

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