The secondary structure change of the Abeta peptide to beta‐sheet was proposed as an early event in Alzheimer's disease. The transition may be used for diagnostics of this disease in an early state. We present an Attenuated Total Reflection (ATR) sensor modified with a specific antibody to extract minute amounts of Abeta peptide out of a complex fluid. Thereby, the Abeta peptide secondary structure was determined in its physiological aqueous environment by FTIR‐difference‐spectroscopy. The presented results open the door for label‐free Alzheimer diagnostics in cerebrospinal fluid or blood. It can be extended to further neurodegenerative diseases.

Here we present a novel assay for the separation and detection of amino-terminal amyloid-β (Aβ) peptide variants by capillary isoelectric focusing (CIEF) immunoassay. Specific amino-terminally truncated Aβ peptides appear to be generated by β-secretase (BACE1)-independent mechanisms and have previously been observed in cerebrospinal fluid (CSF) after BACE1 inhibitor treatment in an animal model. CIEF immunoassay sensitivity is sufficient to detect total Aβ in CSF without preconcentration. To analyze low-abundance amino-terminally truncated Aβ peptides from cell culture supernatants, we developed a CIEF-compatible immunoprecipitation protocol, allowing for selective elution of Aβ peptides with very low background. CIEF immunoassay and immunoprecipitation mass spectrometry analysis identified peptides starting at residue Arg(5) as the main amino-terminal Aβ variants produced in the presence of tripartite BACE1 inhibitor in our cell culture model. The CIEF immunoassay allows for robust relative quantification of Aβ peptide patterns in biological samples. To assess the future possibility of absolute quantification, we have prepared the Aβ peptides Aβ(x-10), Aβ(x-16), and Aβ(5-38(D23S)) by using solid phase peptide synthesis as internal standards for the CIEF immunoassay.

Background: LewisX is a glycan moiety expressed by neural stem cells. Results: LRP1 is a LewisX carrier protein in the mouse CNS; its deletion reduces oligodendrogenesis in the neurosphere model in vitro. Conclusion: Mouse neural stem cell lineage progression requires LRP1. Significance: This is the first study investigating LRP1 in the context of CNS development and neural stem cell biology.

Early detection of dementia in Parkinson disease is a prerequisite for preventive therapeutic approaches. Modified serpinA1 in cerebrospinal fluid (CSF) was suggested as an early biomarker for differentiation between Parkinson patients with (PDD) or without dementia (PD). Within this study we aimed to further explore the diagnostic value of serpinA1. We applied a newly developed nanoscale method for the detection of serpinA1 based on automated capillary isoelectric focusing (CIEF). A clinical sample of 102 subjects including neurologically healthy controls (CON), PD and PDD patients was investigated. Seven serpinA1 isoforms of different charge were detected in CSF from all three diagnostic groups. The mean CSF signals of the most acidic serpinA1 isoform differed significantly (p < 0.01) between PDD (n = 29) and PD (n = 37) or CON (n = 36). Patients above the cut-off of 6.4 have a more than six times higher risk for an association with dementia compared to patients below the cut off. We propose this serpinA1 CIEF-immunoassay as a novel tool in predicting cognitive impairment in PD patients and therefore for patient stratification in therapeutic trials.

Disturbed brain-to-blood elimination of β-amyloid (Aβ) promotes cerebral Aβ accumulation in Alzheimer's disease. Considering that the kidneys are involved in Aβ elimination from the blood, we evaluated how chronic kidney disease (CKD) affects plasma Aβ. In 106 CKD patients stages 3-5 (including 19 patients on hemodialysis and 15 kidney recipients), 53 control subjects with comparable vascular risk profile and 10 kidney donors, plasma Aβ was determined using electrochemiluminescence immunoassay and gel electrophoresis followed by Western blotting. Plasma Aβ increased with CKD stage (control = 182.98 ± 76.73 pg/ml; CKD3A = 248.34 ± 103.77 pg/ml; CKD3B = 259.25 ± 97.74 pg/ml; CKD4 = 489.16 ± 154.16 pg/ml; CKD5 = 721.19 ± 291.69 pg/ml) and was not influenced by hemodialysis (CKD5D = 697.97 ± 265.91 pg/ml). Renal transplantation reduced plasma Aβ (332.57 ± 162.82 pg/ml), whereas kidney donation increased it (251.51 ± 34.34 pg/ml). Gel electrophoresis confirmed stage-dependent elevation namely of Aβ1-40, the most abundant Aβ peptide. In a multivariable regression including age, sex, estimated glomerular filtration rate (eGFR), potassium, hemoglobin, urine urea, and urine total protein, the factors eGFR (β = -0.42, p < 0.001), hemoglobin (β = -0.17, p = 0.020), and urine protein (β = 0.26, p = 0.008) were associated with plasma Aβ. In a regression including age, sex, eGFR, potassium, hemoglobin and the vascular risk factors systolic blood pressure, smoking, LDL, HDL, HbA1c, body mass index, brain-derived natriuretic peptide and fibrinogen, the factors eGFR (β = -0.53, p < 0.001), body mass index (β = -0.17, p = 0.022), and fibrinogen (β = 0.18, p = 0.024) were associated with plasma Aβ. Our results demonstrate a stage-dependent plasma Aβ increase that is augmented by loss of glomerulotubular integrity, low body weight, and inflammation, demonstrating a multifaceted role of renal dysfunction in Aβ retention.