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Background/Objective: Apolipoprotein E (ApoE) has an active part in the pathogenesis of Alzheimer’s disease (AD). Cerebrospinal fluid (CSF) and plasma level alterations have been reported in AD patients. In search of a biomarker potentially predictive of cognitive, functional, or motor decline, we analyzed the CSF to serum ratios of ApoE levels (CSF/serum ApoE) in AD patients in this regard. Methods: Subjects with newly diagnosed AD were followed within a longitudinal observational study (rpAD study). Annual neuropsychological testing and physical examination were performed. Multiple regression analyses were used to determine possible associations of the ApoE CSF/serum concentration ratios and velocity of decline on a variety of cognitive, functional and motor scales (MMSE, iADL, bADL, GDS, UPDRSIII) adjusted for relevant co-variables. Results: CSF/serum ratios of ApoE levels were associated with progression on the UPDRSIII (change of UPDRSIII slope [pt/yr] per unit of ApoE CSF/serum = –0.06, p < 0.01) and instrumental ADL scale (change of iADL slope [pt/yr] per unit of ApoE CSF/serum = 0.01, p = 0.01) (“the lower the ratio, the faster the deterioration” and vice versa). Secondarily, higher age at onset was associated with faster UPDRSIII progression, antidepressant use with faster iADL decline, and better baseline function with more rapid decline on either MMSE, iADL, or GDS scale. Conclusion: Here, CSF/serum ApoE at time of AD diagnosis was shown to be inversely associated with medium-term functional and motor progression. Whether this ratio qualifies for the use as a predictive biomarker must be validated in larger cohort studies over the long term.

The recent discovery of neuronal cell-surface antibodies profoundly expanded the clinical spectrum of paraneoplastic neurological syndromes. Many of these syndromes are associated with impaired cognitive function, a clinical symptom that is of increasing concern in cancer patients. However, the frequency of these antibodies in cancer patients and their relation to clinical syndromes is currently unknown. Here, we investigated the prevalence of neuronal cell-surface antibodies and associated paraneoplastic neurological syndromes in 323 patients with different cancer types and in 105 controls. Cerebrospinal fluid and serum samples were analysed for a large panel of anti-neuronal antibodies and all patients were screened for cognitive deficits. Blood–brain barrier integrity was assessed using the age-normalized albumin cerebrospinal fluid/serum ratio. Anti-neuronal autoantibodies were observed in 24.5% of cancer patients (in contrast to 3.1% in neurological control patients without cancer and 2.5% in healthy controls) and were almost exclusively detected in serum. The majority of antibodies were directed against cell-surface antigens (75.9%), most frequently IgA/IgM isotypes targeting the N-methyl-d-aspartate (NMDA) receptor. Cognitive deficits and cerebellar syndromes were significantly more prevalent in antibody-positive in comparison with antibody-negative patients (21 vs. 7%, p = 2.7 × 10−4; 11 vs. 2%, p = 3.0 × 10−3). Antibody-positive patients with cognitive deficits had a significantly increased albumin cerebrospinal fluid/serum ratio in comparison with antibody-positive patients with other neurological deficits, indicating blood–brain barrier dysfunction (49.1 × 10−3 vs. 12.0 × 10−3; p = 0.036). Our results show that anti-neuronal antibodies have a high prevalence in a wide range of different tumour types and are associated with distinct neurological deficits. Specifically, the results suggest a so far undefined cognitive paraneoplastic syndrome in patients with antibodies targeting neuronal surface antigens and concurrent blood–brain barrier dysfunction. Anti-neuronal antibodies might thus serve as a biomarker for potentially treatment-responsive cognitive impairments in cancer patients.

Weight changes are common in aging and Alzheimer's disease (AD) and postmortem findings suggest a relation between lower body mass index (BMI) and increased AD brain pathology. In the current multicenter study, we tested whether lower BMI is associated with higher core AD brain pathology as assessed by cerebrospinal fluid (CSF)-based biological markers of AD in 751 living subjects: 308 patients with AD, 296 subjects with amnestic mild cognitive impairment (MCI), and 147 elderly healthy controls (HC). Based upon a priori cutoff values on CSF concentration of total tau and beta-amyloid (Aβ(1-42)), subjects were binarized into a group with abnormal CSF biomarker signature (CSF+) and those without (CSF-). Results showed that BMI was significantly lower in the CSF+ when compared with the CSF- group (F = 27.7, df = 746, p0.001). There was no interaction between CSF signature and diagnosis or apolipoprotein E (ApoE) genotype. In conclusion, lower BMI is indicative of AD pathology as assessed with CSF-based biomarkers in demented and nondemented elderly subjects.