RESUMEN
Omega-3 polyunsaturated fatty acids (PUFAs) have been proposed to be highly beneficial in Alzheimer's disease (AD). AD pathology is closely linked to an overproduction and accumulation of amyloid-ß (Aß) peptides as extracellular senile plaques in the brain. Total Aß levels are not only dependent on its production by proteolytic processing of the amyloid precursor protein (APP), but also on Aß-clearance mechanisms, including Aß-degrading enzymes. Here we show that the omega-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increase Aß-degradation by affecting insulin-degrading enzyme (IDE), the major Aß-degrading enzyme secreted into the extracellular space of neuronal and microglial cells. The identification of the molecular mechanisms revealed that EPA directly increases IDE enzyme activity and elevates gene expression of IDE. DHA also directly stimulates IDE enzyme activity and affects IDE sorting by increasing exosome release of IDE, resulting in enhanced Aß-degradation in the extracellular milieu. Apart from the known positive effect of DHA in reducing Aß production, EPA and DHA might ameliorate AD pathology by increasing Aß turnover.
Asunto(s)
Péptidos beta-Amiloides/metabolismo , Ácidos Docosahexaenoicos/farmacología , Ácido Eicosapentaenoico/farmacología , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Insulisina/genética , Neuroblastoma/metabolismo , Animales , Western Blotting , Supervivencia Celular/efectos de los fármacos , Insulisina/metabolismo , Ratones , Neuroblastoma/tratamiento farmacológico , Neuroblastoma/genética , Neuroblastoma/patología , Regiones Promotoras Genéticas , ARN Mensajero/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Tumorales CultivadasRESUMEN
Ninety percent of the elderly population has a vitamin D hypovitaminosis, and several lines of evidence suggest that there might be a potential causal link between Alzheimer's disease (AD) and a non-sufficient supply with vitamin D. However, the mechanisms linking AD to vitamin D have not been completely understood. The aim of our study is to elucidate the impact of 25(OH) vitamin D3 on amyloid precursor protein processing in mice and N2A cells utilizing very moderate and physiological vitamin D hypovitaminosis in the range of 20-30% compared to wild-type mice. We found that already under such mild conditions, amyloid-ß peptide (Aß) is significantly increased, which is caused by an increased ß-secretase activity and BACE1 protein level. Additionally, neprilysin (NEP) expression is downregulated resulting in a decreased NEP activity further enhancing the effect of decreased vitamin D on the Aß level. In line with the in vivo findings, corresponding effects were found with N2A cells supplemented with 25(OH) vitamin D3. Our results further strengthen the link between AD and vitamin D3 and suggest that supplementation of vitamin D3 might have a beneficial effect in AD prevention.