Association of plasma biomarkers, p-tau181, glial fibrillary acidic protein, and neurofilament light, with intermediate and long-term clinical Alzheimer's disease risk: Results from a prospective cohort followed over 17 years.

INTRODUCTION: Blood biomarkers for Alzheimer's disease (AD) are the future of AD risk assessment. The aim of this study was to determine the association between plasma-measured phosphorylated tau (p-tau181), glial fibrillary acidic protein (GFAP), and neurofilament light (NfL) levels and risk of clinical AD incidence with consideration to the impact of cardiovascular health. METHODS: Within a community-based cohort, biomarker levels were measured at baseline using single molecule array technology in 768 participants (aged 50-75) followed over 17 years. Associations among biomarkers and AD, vascular dementia, and mixed dementia incidence were assessed. RESULTS: GFAP was associated with clinical AD incidence even more than a decade before diagnosis (9-17 years), while p-tau181 and NfL were associated with more intermediate AD risk (within 9 years). Significant interaction was detected between cardiovascular health and p-tau181/NfL. DISCUSSION: GFAP may be an early AD biomarker increasing before p-tau181 and NfL and the effect modifying role of cardiovascular health should be considered in biomarker risk stratification.

Amyloid-beta misfolding and GFAP predict risk of clinical Alzheimer's disease diagnosis within 17 years.

INTRODUCTION: Blood-based biomarkers for Alzheimer's disease (AD) are urgently needed. Here, four plasma biomarkers were measured at baseline in a community-based cohort followed over 17 years, and the association with clinical AD risk was determined. METHODS: Amyloid beta (Aß) misfolding status as a structure-based biomarker as well as phosphorylated tau 181 (P-tau181), glial fibrillary acidic protein (GFAP), and neurofilament light (NfL) concentration levels were determined at baseline in heparin plasma from 68 participants who were diagnosed with AD and 240 controls without dementia diagnosis throughout follow-up. RESULTS: Aß misfolding exhibited high disease prediction accuracy of AD diagnosis within 17 years. Among the concentration markers, GFAP showed the best performance, followed by NfL and P-tau181. The combination of Aß misfolding and GFAP increased the accuracy. DISCUSSION: Aß misfolding and GFAP showed a strong ability to predict clinical AD risk and may be important early AD risk markers. Aß misfolding illustrated its potential as a prescreening tool for AD risk stratification in older adults.

Genetic predisposition, Aß misfolding in blood plasma, and Alzheimer's disease.

Alzheimer's disease is highly heritable and characterized by amyloid plaques and tau tangles in the brain. The aim of this study was to investigate the association between genetic predisposition, Aß misfolding in blood plasma, a unique marker of Alzheimer associated neuropathological changes, and Alzheimer's disease occurrence within 14 years. Within a German community-based cohort, two polygenic risk scores (clinical Alzheimer's disease and Aß42 based) were calculated, APOE genotype was determined, and Aß misfolding in blood plasma was measured by immuno-infrared sensor in 59 participants diagnosed with Alzheimer's disease during 14 years of follow-up and 581 participants without dementia diagnosis. Associations between each genetic marker and Aß misfolding were assessed through logistic regression and the ability of each genetic marker and Aß misfolding to predict Alzheimer's disease was determined. The Alzheimer's disease polygenic risk score and APOE ε4 presence were associated to Aß misfolding (odds ratio, 95% confidence interval: per standard deviation increase of score: 1.25, 1.03-1.51; APOE ε4 presence: 1.61, 1.04-2.49). No association was evident for the Aß polygenic risk score. All genetic markers were predictive of Alzheimer's disease diagnosis albeit much less so than Aß misfolding (areas under the curve: Aß polygenic risk score: 0.55; AD polygenic risk score: 0.59; APOE ε4: 0.63; Aß misfolding: 0.84). Clinical Alzheimer's genetic risk was associated to early pathological changes (Aß misfolding) measured in blood, however, predicted Alzheimer's disease less accurately than Aß misfolding itself. Genetic predisposition may provide information regarding disease initiation, while Aß misfolding could be important in clinical risk prediction.

Amyloid-ß misfolding as a plasma biomarker indicates risk for future clinical Alzheimer's disease in individuals with subjective cognitive decline.

BACKGROUND: We evaluated Aß misfolding in combination with Aß42/40 ratio as a prognostic tool for future clinical progression to mild cognitive impairment (MCI) or dementia due to Alzheimer's disease (AD) in individuals with subjective cognitive decline (SCD). METHODS: Baseline plasma samples (n = 203) from SCD subjects in the SCIENCe project and Amsterdam Dementia Cohort (age 61 ± 9 years; 57% male, mean follow-up time 2.7 years) were analyzed using immuno-infrared-sensor technology. Within 6 years of follow-up, 22 (11%) individuals progressed to MCI or dementia due to AD. Sensor readout values > 1646 cm- 1 reflected normal Aß folding; readouts at ≤ 1646 cm- 1 reflected low and at < 1644 cm- 1 high misfolding. We used Cox proportional hazard models to quantify Aß misfolding as a prognostic biomarker for progression to MCI and dementia due to AD. The accuracy of the predicted development of MCI/AD was determined by time-dependent receiver operating characteristic (t-ROC) curve analyses that take individual follow-up and conversion times into account. Statistical models were adjusted for age, sex, and APOEε4 status. Additionally, plasma Aß42/40 data measured by SIMOA were statistically analyzed and compared. RESULTS: All 22 patients who converted to MCI or AD-dementia within 6 years exhibited Aß misfolding at baseline. Cox analyses revealed a hazard ratio (HR) of 19 (95% confidence interval [CI] 2.2-157.8) for future conversion of SCD subjects with high misfolding and of 11 (95% CI 1.0-110.1) for those with low misfolding. T-ROC curve analyses yielded an area under the curve (AUC) of 0.94 (95% CI 0.86-1.00; 6-year follow-up) for Aß misfolding in an age, sex, and APOEε4 model. A similar model with plasma Aß42/40 ratio yielded an AUC of 0.92 (95% CI, 0.82-1.00). The AUC increased to 0.99 (95% CI, 0.99-1.00) after inclusion of both Aß misfolding and the Aß42/40 ratio. CONCLUSIONS: A panel of structure- and concentration-based plasma amyloid biomarkers may predict conversion to clinical MCI and dementia due to AD in cognitively unimpaired subjects. These plasma biomarkers provide a noninvasive and cost-effective alternative for screening early AD pathological changes. Follow-up studies and external validation in larger cohorts are in progress for further validation of our findings.

The Effect of (-)-Epigallocatechin-3-Gallate on the Amyloid-ß Secondary Structure.

Amyloid-ß (Aß) is a macromolecular structure of great interest because its misfolding and aggregation, along with changes in the secondary structure, have been correlated with its toxicity in various neurodegenerative diseases. Small drug-like molecules can modulate the amyloid secondary structure and therefore have raised significant interest in applications to active and passive therapies targeting amyloids. In this study, we investigate the interactions of epigallocatechin-3-gallate (EGCG), found in green tea, with Aß polypeptides, using a combination of in vitro immuno-infrared sensor measurements, docking, molecular dynamics simulations, and ab initio calculations. We find that the interactions of EGCG are dominated by only a few residues in the fibrils, including hydrophobic π-π interactions with aromatic rings of side chains and hydrophilic interactions with the backbone of Aß, as confirmed by extended (1-µs-long) molecular dynamics simulations. Immuno-infrared sensor data are consistent with degradation of Aß fibril induced by EGCG and inhibition of Aß fibril and oligomer formation, as manifested by the recovery of the amide-I band of monomeric Aß, which is red-shifted by 26 cm-1 when compared to the amide-I band of the fibrillar form. The shift is rationalized by computations of the infrared spectra of Aß42 model structures, suggesting that the conformational change involves interchain hydrogen bonds in the amyloid fibrils that are broken upon binding of EGCG.

Discovery of three novel sesquiterpene synthases from Streptomyces chartreusis NRRL 3882 and crystal structure of an α-eudesmol synthase.

With more than 50,000 members, terpenoids are one of the most important classes of natural products and show an enormous diversity. Due to their unique odors and specific bioactivities they already find wide application in the flavor, fragrance and pharma industries. Since most terpenoids can only be obtained by natural product extraction, the discovery of biosynthetic genes for the generation of terpene diversity becomes increasingly important. This study describes the discovery of three novel sesquiterpene synthases from Streptomyces chartreusis with preference for the formation of germacradiene-11-ol, α-eudesmol and α-amorphene respectively. The α-eudesmol synthase showed formation of 10-epi-δ-eudesmol and elemol as side products. Eudesmol-isomers are known to have repellent activity, which makes this enzyme a potential catalyst for products for the prevention of mosquito-related disease. The determination of the structure of the apo-enzyme of α-eudesmol synthase from S. chartreusis provides the first structural insights into an eudesmol-forming enzyme.

Transcriptome profiling of the Australian arid-land plant Eremophila serrulata (A.DC.) Druce (Scrophulariaceae) for the identification of monoterpene synthases.

Plant terpenoids are a large and highly diverse class of metabolites with an important role in the immune defense. They find wide industrial application as active pharmaceutical ingredients, aroma and fragrance compounds. Several Eremophila sp. derived terpenoids have been documented. To elucidate the terpenoid metabolism, the transcriptome of juvenile and mature Eremophila serrulata (A.DC.) Druce (Scrophulariaceae) leaves was sequenced and a transcript library was generated. We report on the first transcriptomic dataset of an Eremophila plant. IlluminaMiSeq sequencing (2 × 300 bp) revealed 7,093,266 paired reads, which could be assembled to 34,505 isogroups. To enable detection of terpene biosynthetic genes, leaves were separately treated with methyl jasmonate, a well-documented inducer of plant secondary metabolites. In total, 21 putative terpene synthase genes were detected in the transcriptome data. Two terpene synthase isoenzymatic genes, termed ES01 and ES02, were successfully expressed in E. coli. The resulting proteins catalyzed the conversion of geranyl pyrophosphate, the universal substrate of monoterpene synthases to myrcene and Z-(b)-ocimene, respectively. The transcriptomic data and the discovery of the first terpene synthases from Eremophila serrulata are the initial step for the understanding of the terpene metabolism in this medicinally important plant genus.