The metalloprotease ADAMTS4 generates N-truncated Aβ4–x species and marks oligodendrocytes as a source of amyloidogenic peptides in Alzheimer’s disease

Brain accumulation and aggregation of amyloid-β (Aβ) peptides is a critical step in the pathogenesis of Alzheimer’s disease (AD). Full-length Aβ peptides (mainly Aβ1–40 and Aβ1–42) are produced through sequential proteolytic cleavage of the amyloid precursor protein (APP) by β- and γ-secretases. However, studies of autopsy brain samples from AD patients have demonstrated that a large fraction of insoluble Aβ peptides are truncated at the N-terminus, with Aβ4–x peptides being particularly abundant. Aβ4–x peptides are highly aggregation prone, but their origin and any proteases involved in their generation are unknown. We have identified a recognition site for the secreted metalloprotease ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs 4) in the Aβ peptide sequence, which facilitates Aβ4–x peptide generation. Inducible overexpression of ADAMTS4 in HEK293 cells resulted in the secretion of Aβ4–40 but unchanged levels of Aβ1–x peptides. In the 5xFAD mouse model of amyloidosis, Aβ4–x peptides were present not only in amyloid plaque cores and vessel walls, but also in white matter structures co-localized with axonal APP. In the ADAMTS4−/− knockout background, Aβ4–40 levels were reduced confirming a pivotal role of ADAMTS4 in vivo. Surprisingly, in the adult murine brain, ADAMTS4 was exclusively expressed in oligodendrocytes. Cultured oligodendrocytes secreted a variety of Aβ species, but Aβ4–40 peptides were absent in cultures derived from ADAMTS4−/− mice indicating that the enzyme was essential for Aβ4–x production in this cell type. These findings establish an enzymatic mechanism for the generation of Aβ4–x peptides. They further identify oligodendrocytes as a source of these highly amyloidogenic Aβ peptides

Presenilin Is the Molecular Target of Acidic γ-Secretase Modulators in Living Cells

The intramembrane-cleaving protease γ-secretase catalyzes the last step in the generation of toxic amyloid-β (Aβ) peptides and is a principal therapeutic target in Alzheimer's disease. Both preclinical and clinical studies have demonstrated that inhibition of γ-secretase is associated with prohibitive side effects due to suppression of Notch processing and signaling. Potentially safer are γ-secretase modulators (GSMs), which are small molecules that selectively lower generation of the highly amyloidogenic Aβ42 peptides but spare Notch processing. GSMs with nanomolar potency and favorable pharmacological properties have been described, but the molecular mechanism of GSMs remains uncertain and both the substrate amyloid precursor protein (APP) and subunits of the γ-secretase complex have been proposed as the molecular target of GSMs. We have generated a potent photo-probe based on an acidic GSM that lowers Aβ42 generation with an IC50 of 290 nM in cellular assays. By combining in vivo photo-crosslinking with affinity purification, we demonstrated that this probe binds the N-terminal fragment of presenilin (PSEN), the catalytic subunit of the γ-secretase complex, in living cells. Labeling was not observed for APP or any of the other γ-secretase subunits. Binding was readily competed by structurally divergent acidic and non-acidic GSMs suggesting a shared mode of action. These findings indicate that potent acidic GSMs target presenilin to modulate the enzymatic activity of the γ-secretase complex

Ein neues Neutronen-Doppeldiffraktometer

Die Strahlenschutzmessungen, die nach der Aufste.llung der Anlage am Reaktor an der Monochromatorabschirmung durchgeführt wurden, zeigten, daß sie im angelieferten Zustand zur Schwächung des Primärstrahls und der Streustrahlung auf Toleranzdosisleistung in der nächsten Umgebung außerhalb der Abschirmungnicht ausreichte. Es war daher notwendig, die Hauptabschirmung unter Beibehaltung der äußeren Abmessungen durch Auswahl und Kombination geeigneter Abschirmmaterialien zu verbessern bzw. zu ergänzen. Durch die oben beschriebenen Änderungen konnte die Dosisleistung an der Oberfläche der Hauptabschirmung während des Experimentierbetriebes bei Verwendung der Primärkollimatoren vom Typ A und B auf maximal 30 mrem/h an den ungünstigsten Stellen herabgesetzt werden (Abb. 18, 19 und 21). Die Toleranzdosisleistung von 2, 5 mrem/h wird am Rande des Grundgestells erreicht. Bei zusätzlichem Einbau eines Quarzfilters oder bei Benutzung der Primärkollimatoren vom Typ C liegt die Oberflächendosisleistung an allen Stellen unter 4 mrem/h. Einige Daten der Abschirmung sind in der folgenden Tabelle 1 zusammengestellt. Die in diesem Kapitel angegebenen Dosisleistungs-Werte werden z. T. durch das Abschlußprotokoll des Reaktorstrahlenschutzes vom 10. 8. 1966 bestätigt {Tabelle 2). Dem Reaktorstrahlenschutz sei an dieser Stelle für die freundliche Unterstützung bei den Dosisleistungsmessungen gedankt

Central and peripheral endocannabinoids and cognate acylethanolamides in humans: association with race, adiposity, and energy expenditure.

ContextPeripheral and central endocannabinoids and cognate acylethanolamides (AEs) may play important but distinct roles in regulating energy balance.ObjectiveWe hypothesized that in humans central/peripheral endocannabinoids are differently associated with adiposity and energy expenditure and differ by race.DesignWe examined associations of arachindonoylethanolamide, 2-arachidonoylglycerol, palmitoylethanolamide, and oleoylethanolamide (OEA) assayed in plasma and cerebrospinal fluid (CSF) with race, adiposity, and energy expenditure.Setting/participantsIn this monitored clinical inpatient study, CSF was obtained by lumbar puncture in 27 individuals (12 Caucasian, 11 American Indian, and four African-American). Twenty-four hour and sleep energy expenditure were measured by indirect calorimetry in a respiratory chamber.Main outcome measureSamples were analyzed from a previous study originally designed to test a blood-brain barrier leptin transport deficit in human obesity.ResultsCSF (but not peripheral) 2-arachidonoylglycerol was significantly increased in American Indians compared with Caucasians (18.48 ± 6.17 vs. 10.62 ± 4.58 pmol/ml, P < 0.01). In the whole group, peripheral AEs were positively but in CSF negatively associated with adiposity. However, in multivariate models adjusted for the other peripheral and CSF AEs, peripheral arachindonoylethanolamide was the only AE significantly associated with adiposity. Interestingly, CSF OEA concentrations were positively associated with adjusted 24 hour and sleep energy expenditure (r = 0.47, P < 0.05; r = 0.42, P < 0.05), but peripheral OEA was not.ConclusionsThese data indicate a central alteration of the endocannabinoid system in American Indians and furthermore show that AEs in both compartments play an important but distinct role in human energy balance regulation

Central and Peripheral Endocannabinoids and Cognate Acylethanolamides in Humans: Association with Race, Adiposity, and Energy Expenditure

2-Arachidonoylethanolamide is elevated in cerebrospinal fluid (CSF) of American Indians; in plasma, anandamide correlates strongly with adiposity and in CSF oleoylethanolamide is positively associated with energy expenditure

Associations of fatty acids in cerebrospinal fluid with peripheral glucose concentrations and energy metabolism.

Rodent experiments have emphasized a role of central fatty acid (FA) species, such as oleic acid, in regulating peripheral glucose and energy metabolism. Thus, we hypothesized that central FAs are related to peripheral glucose regulation and energy expenditure in humans. To test this we measured FA species profiles in cerebrospinal fluid (CSF) and plasma of 32 individuals who stayed in our clinical inpatient unit for 6 days. Body composition was measured by dual energy X-ray absorptiometry and glucose regulation by an oral glucose test (OGTT) followed by measurements of 24 hour (24EE) and sleep energy expenditure (SLEEP) as well as respiratory quotient (RQ) in a respiratory chamber. CSF was obtained via lumbar punctures; FA concentrations were measured by liquid chromatography/mass spectrometry. As expected, FA concentrations were higher in plasma compared to CSF. Individuals with high concentrations of CSF very-long-chain saturated FAs had lower rates of SLEEP. In the plasma moderate associations of these FAs with higher 24EE were observed. Moreover, CSF monounsaturated long-chain FA (palmitoleic and oleic acid) concentrations were associated with lower RQs and lower glucose area under the curve during the OGTT. Thus, FAs in the CSF strongly correlated with peripheral metabolic traits. These physiological parameters were most specific to long-chain monounsaturated (C16:1, C18:1) and very-long-chain saturated (C24:0, C26:0) FAs.Together with previous animal experiments these initial cross-sectional human data indicate that central FA species are linked to peripheral glucose and energy homeostasis

Associations of Fatty Acids in Cerebrospinal Fluid with Peripheral Glucose Concentrations and Energy Metabolism

Rodent experiments have emphasized a role of central fatty acid (FA) species, such as oleic acid, in regulating peripheral glucose and energy metabolism. Thus, we hypothesized that central FAs are related to peripheral glucose regulation and energy expenditure in humans. To test this we measured FA species profiles in cerebrospinal fluid (CSF) and plasma of 32 individuals who stayed in our clinical inpatient unit for 6 days. Body composition was measured by dual energy X-ray absorptiometry and glucose regulation by an oral glucose test (OGTT) followed by measurements of 24 hour (24EE) and sleep energy expenditure (SLEEP) as well as respiratory quotient (RQ) in a respiratory chamber. CSF was obtained via lumbar punctures; FA concentrations were measured by liquid chromatography/mass spectrometry. As expected, FA concentrations were higher in plasma compared to CSF. Individuals with high concentrations of CSF very-long-chain saturated FAs had lower rates of SLEEP. In the plasma moderate associations of these FAs with higher 24EE were observed. Moreover, CSF monounsaturated long-chain FA (palmitoleic and oleic acid) concentrations were associated with lower RQs and lower glucose area under the curve during the OGTT. Thus, FAs in the CSF strongly correlated with peripheral metabolic traits. These physiological parameters were most specific to long-chain monounsaturated (C16∶1, C18∶1) and very-long-chain saturated (C24∶0, C26∶0) FAs. Conclusions: Together with previous animal experiments these initial cross-sectional human data indicate that central FA species are linked to peripheral glucose and energy homeostasis