The gradual deterioration of cognitive functions in Alzheimer’s disease is paralleled by a hierarchical progression of amyloid-beta and tau brain pathology. Recent findings indicate that toxic oligomers of amyloid-beta may cause propagation of pathology in a prion-like manner, although the underlying mechanisms are incompletely understood. Here we show that small extracellular vesicles, exosomes, from Alzheimer patients’ brains contain increased levels of amyloid-beta oligomers and can act as vehicles for the neuron-to-neuron transfer of such toxic species in recipient neurons in culture. Moreover, blocking the formation, secretion or uptake of exosomes was found to reduce both the spread of oligomers and the related toxicity. Taken together, our results imply that exosomes are centrally involved in Alzheimer’s disease and that they could serve as targets for development of new diagnostic and therapeutic principles.Electronic supplementary materialThe online version of this article (10.1007/s00401-018-1868-1) contains supplementary material, which is available to authorized users.

OBJECTIVELong-term data validating glycated hemoglobin (HbA1c) in assessing the risk of type 2 diabetes in children are limited. HbA1c, fasting plasma glucose (FPG), and 2-h postload plasma glucose (2hPG) concentrations were measured in a longitudinal study of American Indians to determine their utility in predicting incident diabetes, all of which is thought to be type 2 in this population.RESEARCH DESIGN AND METHODSIncident diabetes (FPG ≥126 mg/dL [7.0 mmol/L], 2hPG ≥200 mg/dL [11.1 mmol/L], HbA1c ≥6.5% [8 mmol/mol], or clinical diagnosis) was determined in 2,095 children without diabetes ages 10–19 years monitored through age 39, and in 2,005 adults ages 20–39 monitored through age 59. Areas under the receiver operating characteristic (ROC) curve for HbA1c, FPG, and 2hPG in predicting diabetes within 10 years were compared.RESULTSDuring long-term follow-up of children and adolescents who did not initially have diabetes, the incidence rate of subsequent diabetes was fourfold (in boys) as high and more than sevenfold (in girls) as high in those with HbA1c ≥5.7% as in those with HbA1c ≤5.3%—greater rate ratios than experienced by adults in the same HbA1c categories. Analyses of ROCs revealed no significant differences between HbA1c, FPG, and 2hPG in sensitivity and specificity for identifying children and adolescents who later developed diabetes.CONCLUSIONSHbA1c is a useful predictor of diabetes risk in children and can be used to identify prediabetes in children with other type 2 diabetes risk factors with the same predictive value as FPG and 2hPG.

The study has demonstrated that dopamine induces membrane depolarization and a loss of phosphorylation capacity in dose-dependent manner in isolated rat brain mitochondria during extended in vitro incubation and the phenomena are not prevented by oxyradical scavengers or metal chelators. Dopamine effects on brain mitochondria are, however, markedly prevented by reduced glutathione and N-acetyl cysteine and promoted by tyrosinase present in the incubation medium. The results imply that quinone oxidation products of dopamine are involved in mitochondrial damage under this condition. When PC12 cells are exposed to dopamine in varying concentrations (100-400μM) for up to 24h, a pronounced impairment of mitochondrial bio-energetic functions at several levels is observed along with a significant (nearly 40%) loss of cell viability with features of apoptotic nuclear changes and increased activities of caspase 3 and caspase 9 and all these effects of dopamine are remarkably prevented by N-acetyl cysteine. N-acetyl cysteine also blocks nearly completely the dopamine induced increase in reactive oxygen species production and the formation of quinoprotein adducts in mitochondrial fraction within PC12 cells and also the accumulation of quinone products in the culture medium. Clorgyline, an inhibitor of MAO-A, markedly decreases the formation of reactive oxygen species in PC12 cells upon dopamine exposure but has only mild protective actions against quinoprotein adduct formation, mitochondrial dysfunctions, cell death and caspase activation induced by dopamine. The results have indicated that quinone oxidation products and not reactive oxygen species are primarily involved in cytotoxic effects of dopamine and the mitochondrial impairment plays a central role in the latter process. The data have clear implications in the pathogenesis of Parkinson's disease.

a b s t r a c tThis study demonstrates that in vitro incubation of isolated rat brain mitochondria with recombinant human a-synuclein leads to dose-dependent loss of mitochondrial transmembrane potential and phosphorylation capacity. However, a-synuclein does not seem to have any significant effect on the activities of respiratory chain complexes under similar conditions of incubation suggesting that the former may impair mitochondrial bioenergetics by direct effect on mitochondrial membranes. Moreover, the recombinant wild type a-synuclein and different mutant forms (A30P, A53T and E46K) have essentially similar effects on rat brain isolated mitochondria. The results are significant in view of the fact that a-synucleinopathy is involved in the pathogenesis of Parkinson's disease.