Neurogranin and BACE1 in CSF as Potential Biomarkers Differentiating Depression with Cognitive Deficits from Early Alzheimer’s Disease: A Pilot Study

Background/Aims: Major depressive disorder (MDD) can cooccur with early Alzheimer’s disease (AD) or may cause memory problems independently of AD. Previous studies have suggested that the AD-related cerebrospinal fluid (CSF) biomarkers tau and Aβ(1–42) could help discriminate between early AD and depression unrelated to AD. Moreover, the postsynaptic protein neurogranin and presynaptic BACE1 have increasingly gained attention as potential new AD biomarkers, but they have not yet been investigated concerning depression. Methods: Using ELISAs, we studied CSF neurogranin and BACE1 levels in patients with mild (n = 21) and moderate (n = 19) AD, as well as in MDD patients with (n = 20) and without (n = 20) cognitive deficits. The clinical examinations included analyses of t-tau, Aβ(1–42), and Aβ(1–40), besides neuropsychological tests and cranial magnetic resonance imaging. Depressive symptom severity was assessed using the Geriatric Depression Scale (GDS). Results: Along with classic AD biomarkers, neurogranin and BACE1 CSF levels differed between moderate AD and MDD (p ≤ 0.01). MDD associated with cognitive deficits was distinguished from mild AD through the CSF neurogranin/BACE1 ratio (p < 0.05), which was strongly correlated with GDS scores (ρ = –0.656; p < 0.01). Conclusion: The neurogranin/BACE1 ratio in CSF can distinguish between depression and AD among patients with similar cognitive deficits, along with the classic AD biomarkers. Further longitudinal studies are ongoing to identify which biomarkers have prognostic value

Proteome profiling in cerebrospinal fluid reveals novel biomarkers of Alzheimer's disease

Neurodegenerative diseases are a growing burden, and there is an urgent need for better biomarkers for diagnosis, prognosis, and treatment efficacy. Structural and functional brain alterations are reflected in the protein composition of cerebrospinal fluid (CSF). Alzheimer's disease (AD) patients have higher CSF levels of tau, but we lack knowledge of systems-wide changes of CSF protein levels that accompany AD. Here, we present a highly reproducible mass spectrometry (MS)-based proteomics workflow for the in-depth analysis of CSF from minimal sample amounts. From three independent studies (197 individuals), we characterize differences in proteins by AD status (> 1,000 proteins, CV < 20%). Proteins with previous links to neurodegeneration such as tau, SOD1, and PARK7 differed most strongly by AD status, providing strong positive controls for our approach. CSF proteome changes in Alzheimer's disease prove to be widespread and often correlated with tau concentrations. Our unbiased screen also reveals a consistent glycolytic signature across our cohorts and a recent study. Machine learning suggests clinical utility of this proteomic signature

Long-term stability and age-dependence of six regulatory serum proteins

Aim: The development of biomarker-based diagnostic procedures often relies on samples stored for several years. We aimed to investigate the influence of storage time and patient age on six neuroregulatory and immunoregulatory serum biomarkers. Materials & methods: We quantified six biomarkers in serum from 151 individuals using ELISA. Serum was stored at -80°C for up to 9.5 years. Results: When associating storage time with biomarker values, BDNF, VEGF-A and TGF-β1 showed a significant increase over time; IGF-1, MCP-1 and IL-18 did not. Associating participant age with biomarkers, only IL-18 in Alzheimer's disease patients showed a significant increase. Conclusion: Storage time can influence results of biomarkers in human serum. This needs to be considered when assessing samples stored for several years. Keywords: Alzheimer’s disease; age-dependence; biobanking; biomarkers; blood serum; cognitive impairment; long-term storage; neuroinflammation; neuroprotection; storage time

Comparison of diagnostic routines for suspected Alzheimer’s disease patients in US–American and German primary care supplement

Aim: Thorough diagnostics are a prerequisite for the optimal treatment of Alzheimer’s disease (AD). Biomarker-based diagnostics are standard in academia, data on practitioners’ diagnostic workups is scarce. Materials & methods: Surveys in German and US healthcare providers (HCP) were conducted regarding diagnostics in presumed AD patients. A subsample of 153 German and 88 US professionals was analyzed in detail. Results: Fewer German physicians conduct AD diagnostics themselves compared with US colleagues (67% vs 99%; p Conclusion: Diagnostic routines for suspected AD patients differ between German and US–American healthcare providers. Plain language summary: It is important to conduct the best-possible tests to come to a correct diagnosis of Alzheimer’s disease (AD). This ensures choosing the optimal treatment. In academic surroundings such as specialized memory clinics, so called biomarkers (found for example in blood) are an important component in finding the correct diagnosis. However, there is limited data on the methods healthcare providers (HCP) use in their everyday clinical practice. With this study, we aimed to get a clearer picture of the differences in the diagnostic routines for potential AD patients implemented by HCPs in two highincome countries, Germany and the USA. We conducted two surveys in 500 German and 100 US HCPs on their AD-diagnostic routines. A comparable subsample of 153 German and 88 US professionals was analyzed in detail.We found that fewer German physicians conduct AD diagnostics themselves compared with their US–American colleagues (67% vs 99%). The other way around, German doctors more often order diagnostics at other institutions (65% vs 45%). However, there were no significant differences in the type of diagnostic procedures ordered at other institutions. In conclusion, diagnostic routines for suspected AD patients differ between German and US–American healthcare providers, such as biomarkerbased diagnostics, which German physicians significantly perform less often.</p

Temperature and nitric oxide control spontaneous calcium transients in astrocytes.

Transient spontaneous increases in the intracellular Ca2+ concentration have been frequently observed in astrocytes in cell culture and in acutely isolated slices from several brain regions. Recent in vivo experiments, however, reported only a low frequency of spontaneous Ca2+ events in astrocytes. Since the ex vivo experiments were usually performed at temperatures lower than physiological body temperature, we addressed the question whether temperature could influence the spontaneous Ca2+ activity in astrocytes. Indeed, comparing the frequency and spike width of spontaneous Ca2+ transients in astrocytes at temperatures between 20 and 37 degrees C in culture as well as in acute cortical slices from mouse brain, revealed that spontaneous Ca2+ responses occurred frequently at low temperature and became less frequent at higher temperature. Moreover, the single Ca2+ events had a longer duration at low temperature. We found that nitric oxide (NO) mimicked the increase in spontaneous Ca2+ activity and that an NO-synthase inhibitor attenuated the effect of lowering the temperature. Thus, temperature and NO are major determinants of spontaneous astrocytic Ca2+ signalling

Activity‐dependent ATP‐waves in the mouse neocortex are independent from astrocytic calcium waves

In the corpus callosum, astrocytic calcium waves propagate via a mechanism involving ATP-release but not gap junctional coupling. In the present study, we report for the neocortex that calcium wave propagation depends on functional astrocytic gap junctions but is still accompanied by ATP-release. In acute slices obtained from the neocortex of mice deficient for astrocytic expression of connexin43, the calcium wave did not propagate. In contrast, in the corpus callosum and hippocampus of these mice, the wave propagated as in control animals. In addition to calcium wave propagation in astrocytes, ATP-release was recorded as a calcium signal from ‘sniffer cells’, a cell line expressing high-affinity purinergic receptors placed on the surface of the slice. The astrocyte calcium wave in the neocortex was accompanied by calcium signals in the ‘sniffer cell’ population. In the connexin43-deficient mice we recorded calcium signals from sniffer cells also in the absence of an astrocytic calcium wave. Our findings indicate that astrocytes propagate calcium signals by two separate mechanisms depending on the brain region and that ATP release can propagate within the neocortex independent from calcium waves

Apolipoprotein E4 disrupts the neuroprotective action of sortilin in neuronal lipid metabolism and endocannabinoid signaling

INTRODUCTION: ApoE is a carrier for brain lipids and the most important genetic risk factor for Alzheimer’s disease (AD). ApoE binds the receptor sortilin which mediates uptake of apoE-bound cargo into neurons. The significance of this uptake route for brain lipid homeostasis and AD risk seen with apoE4, but not apoE3, remains unresolved. METHODS: Combining neurolipidomics in patient specimens with functional studies in mouse models, we interrogated apoE isoform-specific functions for sortilin in brain lipid metabolism and AD. RESULTS: Sortilin directs uptake and conversion of polyunsaturated fatty acids into endocannabinoids, lipid-based neurotransmitters that act through nuclear receptors to sustain neuroprotective gene expression in the brain. This sortilin function requires apoE3, but is disrupted by binding of apoE4, impairing endocannabinoid signaling and increasing amyloidogenic processing. DISCUSSION: We uncovered the significance of neuronal apoE receptor sortilin in facilitating neuroprotective actions of brain lipids, and its relevance for AD risk seen with apoE4