Die Auswirkungen von α-Tocopherol und α-Tocotrienol auf die amyloidogene Prozessierung und Cholesterinhomöostase im Rahmen der Alzheimer Krankheit

Die Alzheimer Erkrankung (engl. Alzheimer‘s disease, AD) stellt die weltweit häufigste Ursache für Demenz dar. Amyloid-Plaques und neurofibrilläre Bündel (engl. neurofibrillary tangles, NFTs) bilden eine entscheidende Komponente der Pathogenese, der erstmals von Alois Alzheimer beschriebenen Erkrankung. Extrazelluläres Amyloid oder auch neuritische Plaques bestehen aus aggregierten Amyloid β (Aβ)-Proteinen. Diese entstehen durch die proteolytische Prozessierung des Amyloid Vorläufer Proteins (engl. amyloid-precusor-protein, APP). APP, welches unter anderem von Neuronen exprimiert wird, ist ein Typ-I-Transmembraneprotein, dessen genaue Funktion noch nicht gänzlich geklärt ist. Die hydrophobe transmembrane Domäne des APP beinhaltet die Aβ-Sequenz, welche im Rahmen der proteolytischen Prozessierung von APP durch die Aspartyl-Proteasen β- und γ-Sekretase freigesetzt wird. Darüber hinaus spielen reaktive Sauerstoffspezies (engl. reactive oxygen species, ROS) ebenfalls eine entscheidende Rolle in der Pathogenese chronischer Erkrankungen, zu welche auch AD zählt. Auch die Cholesterinhomöostase trägt maßgeblich zur Pathogenese der AD bei. Hypercholesterinämie ist ein bekannter Risikofaktor verschiedener chronischer Erkrankungen und wird mit einer Förderung von Inflammationsprozessen, oxidativem Stress, sowie einer erhöhten Freisetzung von Aβ aus APP in Zusammenhang gebracht. In zahlreichen früheren Studien konnte gezeigt werden, dass Vitamin E ein hohes antioxidatives, Cholesterin-senkendes sowie antiinflammatorisches Potenzial besitzt, weshalb es als neuroprotektive Substanz im Zusammenhang mit verschiedenen neurodegenerativen Erkrankungen untersucht wurde. Bezüglich AD zeigte sich innerhalb epidemiologischer Studien ein verringertes Erkrankungsrisiko. Im Rahmen randomisierter, kontrollierter Studien konnten diese Effekte jedoch nicht reproduziert werden, weshalb Vitamin E als diätische Therapieoption kontrovers diskutiert wird. Als Ursache für die inkongruente Studienlage wird häufig das unterschiedliche Studiendesign angeführt. Ziel dieser Arbeit ist es die Wirkung der Vitamin E-Derivate α-Tocopherol (α-TP) und α-Tocotrienol (α-TT) auf die amyloidogene Prozessierung, die Beseitigung von ROS sowie den Cholesterinspiegel zu untersuchen, um ein detaillierteres Wirkprofil des Vitamins im Rahmen von AD zu erhalten und gegebenenfalls anteilige Ursachen der widersprüchlichen Studienlage zu erkennen. Aufgrund des hohen antioxidativen Potenzials von α-TP sowie der ausführlichen bisherigen Studienlage zu diesem wurde das Vitamin E-Derivat im Rahmen dieser Arbeit verwendet. Tocotrienole (TTs) zeichnen sich durch ihre ausgeprägten Cholesterin-senkenden Eigenschaften über die Beeinflussung des SREBP (engl. sterol regulatory element-binding protein, „Sterol-regulierendes Element bindendes Protein“) /SCAP (engl. SREBP cleavage activating protein, „SREBP-Spaltung-aktivierendes Protein“)-Systems aus, was sie zu einem interessanten Substanz bei der Suche nach ernährungsbezogener Beeinflussung der AD Pathogenese macht. Aus diesem Grund wurde α-Tocotrienol (α-TT) in dieser Arbeit ausgewählt, um den Effekt der beiden Vitamin E-Derivate im Rahmen der durchgeführten Experimente vergleichen zu können. Zur Untersuchung des Effekts von α-TP und α-TT auf die amyloidogene Prozessierung wurden humane Neuroblastomzellen verwendet. Es zeigte sich eine Erhöhung des Gesamt-Aβ sowohl durch die Inkubation mit α-TP als auch α-TT. Zur weiteren Aufschlüsselung des hierfür zugrundeliegenden Mechanismus erfolgte die Untersuchung der Aktivität der β- und γ- Sekretase unter Einfluss der Vitamin E-Derivate. Es ergab sich eine erhöhte Aktivität der Sekretasen. Dass dieser ein direkter Effekt von α-TP und α-TT zugrunde liegen könnte, ergaben die Untersuchung der Sekretaseaktivität in post-nukleären Fraktionen, sowie die Analyse der Expression der den Sekretasen zugrundeliegenden Gene. Der Abbau von Aβ trägt maßgeblich zur Aβ-Homöostase und dem generellen Aβ-Aufkommen bei. Unter dem Einfluss von α-TP und α-TT zeigte sich eine Reduktion der Degradation, woraus sich schließen lässt, dass die Erhöhung des Gesamt-Aβ neben der Aktivierung der Aβ-produzierenden Enzyme auch auf eine Reduktion des Aβ-Abbaus zurückzuführen sein könnte. Durch die Verwendung von Insulin als kompetitiven Inhibitor des Insulin-degradierenden Enzyms (engl. insulin degrading enzyme, IDE), welches maßgeblich am Aβ-Abbau beteiligt ist, war keine Beeinflussung der Degradation nach Inkubation mit α-TT zu verzeichnen. Hieraus lässt sich schlussfolgern, dass der Einfluss von α-TT über einen Mechanismus zustande kommt, bei welchem IDE eine entscheidende Rolle spielt. Bei der Untersuchung des Effekts der Vitamin E Derivate auf den Cholesterinspiegel zeige sich eine deutliche Dominanz des Cholesterin-senkenden Effekts von α-TT im Vergleich mit α-TP. Darüber hinaus zeigte sich hierbei eine stärkere Senkung des Gesamt-Cholesterins als des freien Cholesterins, was vermuten lässt, dass der Cholesterin-senkende-Effekt des α-TTs vor allem über verestertes Cholesterin erfolgt. Aufgrund der Wechselwirkungen von Aβ und ROS ist die antioxidative Rolle der Vitamin E-Derivate im Rahmen von AD entscheidend. Die Untersuchung der antioxidativen Eigenschaften erfolgte durch eine Behandlung der humanen Neuroblastomzellen mit hochreaktiven Sauerstoffspezies (engl. highly-reactive oxygen species, hROS) und H2O2 induziertem hROS. Durch die Inkubation mit den Vitamin E-Derivaten erfolgte eine Reduktion der Oxidantien. Der Effekt von α-TT auf hROS war im Vergleich mit α-TP stärker ausgeprägt. Die Ergebnisse dieser Arbeit verdeutlichen die vielfältigen Effekte von Vitamin E-Derivaten im Rahmen von AD. Durch sowohl vorteilhafte Eigenschaften wie die Senkung des Cholesterinspiegels und hROS, als auch nachteilige Eigenschaften wie die Induktion der Aβ-Synthese und Reduktion der Aβ-Degradation wird deutlich, dass eine unreflektierte Supplementation von Vitamin E nicht für jeden Patienten geeignet ist. Vielmehr sind das metabolische Profil sowie das Erkrankungsstadium im Sinne von personalisierter Medizin mit einzubeziehen. So könnten Patienten mit einem hohen Cholesterinspiegel vorwiegend von dem Cholesterin-senkenden Effekt des Vitamin Es profitieren, während eine Vitamin E-Zufuhr bei Patienten mit geringem oder normwertigem Cholesterinspiegel weniger Vorteile birgt.The influence of α-Tocopherol and α-Tocotrienol on the amyloidogenic processing and cholesterol homeostasis in Alzheimer’s disease Alzheimer’s disease (AD) is the world’s most common cause of dementia. It is characterised by amyloid plaques and neurofibrillary tangles, as crucial parts of the disease pathogenesis. The extracellular amyloid plaques contain aggregates of amyloid-β (Aβ), generated by sequential proteolytic processing of the amyloid precursor protein (APP). The type 1 transmembrane protein APP is expressed by neurons and other cells, yet its function remains unclear. The hydrophobic transmembrane domain of APP includes the Aβ sequence that is released via amyloidogenic processing through β- and γ-secretase activity. Besides Aβ, reactive oxygen species are a significant part of AD pathogenesis, since they induce Aβ synthesis, inflammation, and neurodegeneration. Furthermore, the cholesterol homeostasis plays a critical role in AD pathogenesis. Hypercholesteremia is a well-known risk factor in multiple chronic diseases as well as AD. It’s associated with induced inflammation, oxidative stress and an increased Aβ synthesis. Vitamin E shows relevant antioxidative potential as well as cholesterol lowering effects in early studies. Therefore, studies focussed on evaluating its neuroprotective properties regarding neurodegenerative diseases. Regarding AD, there was a reduced risk of disease development. However, these promising effects could not be substantiated in randomized, controlled studies, leading to a controversy in terms of vitamin E as a therapeutic option in AD. Vastly variable study-designs could be a reason for these inhomogeneous results. The aim of this work was to evaluate the effect of α-Tocopherol (α-TP) and α-Tocotrienol (α-TT) on the amyloidogenic processing, reduction of ROS and cholesterol homeostasis to gain a detailed knowledge on the impact of vitamin E in AD and potentially find further reasons for inconsistencies in former studies. Due to its high antioxidative properties α-TP was so far in the focus of science and is likely the most studied form of vitamin E. Therefore, it was used in this work. Tocotrienols (TTs), however, are unique due to their cholesterol-lowering effects by modifying the sterol regulatory element-binding protein (SREBP)/ SREBP-cleavage activating protein (SCAP)-system. This renders them an attractive target in the search for a diet-based AD therapy. Therefore α-Tocotrienol (α-TT) was used in this work as well aiming to facilitate a comparison between the two vitamin E forms. To evaluate the effects of α-TP and α-TT on the amyloidogenic processing, human neuroblastoma cells were used. There was an increase in total Aβ following the incubation with α-TP and α-TT. To further break down this mechanism, the β- and γ-secretase activity was measured, revealing an increased activity for both enzymes. Since there was a similar effect in postnuclear fractions but nearly no alteration on a genetic level, a direct effect of α-TP and α-TT on the enzymes was suggested. Degradation of Aβ constitutes another important component of Aβ-homeostasis. Aβ-degradation was decreased due to α-TP and α-TT treatment, therefore contributing to the observed rise in total Aβ. When using insulin as a competitive inhibitor of the insulin degrading enzyme (IDE), which is one of the major enzymes involved in Aβ-degradation, there was no effect following α-TT incubation, suggesting an IDE-mediated mechanism of reduced Aβ-degradation. When evaluating the effects of α-TP and α-TT on cholesterol levels, there was a reduction of cholesterol especially after α-TT treatment. Furthermore, there was a pronounced reduction of total cholesterol in comparison to free cholesterol suggesting a connection between the cholesterol-lowering effect and cholesterol esters. Due to the interaction between ROS and Aβ, vitamin E forms are a promising target in AD therapy since they are potent antioxidants. To evaluate the antioxidative effects of the vitamin E forms, human neuroblastoma cells were treated with highly-reactive oxygen species (hROS) and H2O2 induced hROS as well as α-TP and α-TT. There was a reduction in oxygens, especially through α-TT regarding hROS. These results evidence the versatile effects of vitamin E forms on AD. Favourable characteristics like cholesterol-lowering and ROS-reducing properties alongside detrimental effects like induced Aβ synthesis and reduced Aβ-degradation suggest that Vitamin E supplementation is not suitable for every patient. In the framework of personalized medicine, the patient’s metabolic profile and state of the disease should be taken into consideration. Patients with hypercholesterolemia might profit from the cholesterol-lowering effects, while patients with normal cholesterol levels are solely exposed to unfavourable characteristics

Effect of Caffeine and Other Methylxanthines on Aβ-Homeostasis in SH-SY5Y Cells

Methylxanthines (MTX) are alkaloids derived from the purine-base xanthine. Whereas especially caffeine, the most prominent known MTX, has been formerly assessed to be detrimental, this point of view has changed substantially. MTXs are discussed to have beneficial properties in neurodegenerative diseases, however, the mechanisms of action are not completely understood. Here we investigate the effect of the naturally occurring caffeine, theobromine and theophylline and the synthetic propentofylline and pentoxifylline on processes involved in Alzheimer’s disease (AD). All MTXs decreased amyloid-β (Aβ) level by shifting the amyloid precursor protein (APP) processing from the Aβ-producing amyloidogenic to the non-amyloidogenic pathway. The α-secretase activity was elevated whereas β-secretase activity was decreased. Breaking down the molecular mechanism, caffeine increased protein stability of the major α-secretase ADAM10, downregulated BACE1 expression and directly decreased β-secretase activity. Additionally, APP expression was reduced. In line with literature, MTXs reduced oxidative stress, decreased cholesterol and a decreased in Aβ1-42 aggregation. In conclusion, all MTXs act via the pleiotropic mechanism resulting in decreased Aβ and show beneficial properties with respect to AD in neuroblastoma cells. However, the observed effect strength was moderate, suggesting that MTXs should be integrated in a healthy diet rather than be used exclusively to treat or prevent AD

Tocotrienol Affects Oxidative Stress, Cholesterol Homeostasis and the Amyloidogenic Pathway in Neuroblastoma Cells: Consequences for Alzheimer’s Disease

One of the characteristics of Alzheimer´s disease (AD) is an increased amyloid load and an enhanced level of reactive oxidative species (ROS). Vitamin E has known beneficial neuroprotective effects, and previously, some studies suggested that vitamin E is associated with a reduced risk of AD due to its antioxidative properties. However, epidemiological studies and nutritional approaches of vitamin E treatment are controversial. Here, we investigate the effect of α-tocotrienol, which belongs to the group of vitamin E, on AD-relevant processes in neuronal cell lines. In line with the literature, α-tocotrienol reduced the ROS level in SH-SY5Y cells. In the presence of tocotrienols, cholesterol and cholesterol esters, which have been shown to be risk factors in AD, were decreased. Besides the unambiguous positive effects of tocotrienol, amyloid-β (Aβ) levels were increased accompanied by an increase in the activity of enzymes responsible for Aβ production. Proteins and gene expression of the secretases and their components remained unchanged, whereas tocotrienol accelerates enzyme activity in cell-free assays. Besides enhanced Aβ production, tocotrienols inhibited Aβ degradation in neuro 2a (N2a)-cells. Our results might help to understand the controversial findings of vitamin E studies and demonstrate that besides the known positive neuroprotective properties, tocotrienols also have negative characteristics with respect to AD

Vitamin D and Its Analogues Decrease Amyloid-β (Aβ) Formation and Increase Aβ-Degradation

Alzheimer’s disease (AD) is characterized by extracellular plaques in the brain, mainly consisting of amyloid-β (Aβ), as derived from sequential cleavage of the amyloid precursor protein. Epidemiological studies suggest a tight link between hypovitaminosis of the secosteroid vitamin D and AD. Besides decreased vitamin D level in AD patients, an effect of vitamin D on Aβ-homeostasis is discussed. However, the exact underlying mechanisms remain to be elucidated and nothing is known about the potential effect of vitamin D analogues. Here we systematically investigate the effect of vitamin D and therapeutically used analogues (maxacalcitol, calcipotriol, alfacalcidol, paricalcitol, doxercalciferol) on AD-relevant mechanisms. D2 and D3 analogues decreased Aβ-production and increased Aβ-degradation in neuroblastoma cells or vitamin D deficient mouse brains. Effects were mediated by affecting the Aβ-producing enzymes BACE1 and γ-secretase. A reduced secretase activity was accompanied by a decreased BACE1 protein level and nicastrin expression, an essential component of the γ-secretase. Vitamin D and analogues decreased β-secretase activity, not only in mouse brains with mild vitamin D hypovitaminosis, but also in non-deficient mouse brains. Our results further strengthen the link between AD and vitamin D, suggesting that supplementation of vitamin D or vitamin D analogues might have beneficial effects in AD prevention

Real-world evidence on siponimod treatment in patients with secondary progressive multiple sclerosis

BACKGROUND: Therapeutic options targeting inflammation in multiple sclerosis (MS) have evolved rapidly for relapsing–remitting MS, whereas few therapies are available for progressive forms of MS, in particular secondary progressive MS (SPMS). The approval of siponimod for SPMS has allowed for optimism in the otherwise discouraging therapeutic landscape. METHODS: We conducted a retrospective, multicenter, non-interventional study analyzing the efficacy and safety of siponimod under real-world conditions in 227 SPMS patients. According to the retrospective study framework, data was acquired at prespecified time points. Clinical readouts were assessed every three months. Disease progression was determined as increase in expanded disability status scale (EDSS), radiological progression, or the occurrence of new relapses under treatment. For safety analyses, adverse events (AE) and reasons for discontinuation were documented. The collected data points were analyzed at baseline and after 6, 12 and 18 months. However, data were predominately collected at the 6- and 12-month time points as many patients were lost to follow-up. In a group consisting of 41 patients, a more detailed investigation regarding disease progression was conducted, including data from measurement of cognitive and motoric functions. RESULTS: Under siponimod therapy, 64.8% of patients experienced sustained clinical disease stability at 12 months. Out of the stable patients 21.4% of patients improved. Of the remaining patients, 31.5% experienced EDSS progression, 3.7% worsened without meeting the threshold for progression. Relapses occurred in 7.4%. Radiological disease activity was detected in 24.1% of patients after six months of treatment and in 29.6% of patients at 12 months follow-up. The in-depth cohort consisting of 41 patients demonstrated no substantial changes in cognitive abilities measured by Paced Auditory Serial Addition Test and Symbol Digit Modalities Test or motoric functions measured with Timed 25-Foot Walk, 100-m timed test, and 9-Hole Peg Test throughout the 12-month study period. Radiological assessment showed a stable volume of white and grey matter, as well as a stable lesion count at 12 months follow-up. AE were observed in nearly half of the included patients, with lymphopenia being the most common. Due to disease progression or AE, 31.2% of patients discontinued therapy. CONCLUSION: Treatment with siponimod had an overall stabilizing effect regarding clinical and radiological outcome measures. However, there is a need for more intensive treatment management and monitoring to identify disease progression and AE. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s42466-022-00219-3

Mind the gap: acute bilateral vocal cord palsy in CIDP after extending the IVIG treatment interval?

Cranial nerve involvement is rarely seen in chronic inflammatory demyelinating polyneuropathy (CIDP). We present a patient diagnosed with CIDP who was in a stable medical condition under long-term treatment with intravenous immunoglobulin (IVIG) every five weeks for more than seven years. Following a 12-day delay in the patient’s regular IVIG therapy, he developed acute bilateral vocal cord palsy. The patient had to be intubated and tracheostomized because of acute respiratory distress. Weaning from mechanical ventilation was complicated due to pneumonia. After antibiotic treatment and restarting IVIG therapy vocal cord palsy rapidly improved allowing for subsequent decannulation. Although coincidence between treatment delay and symptom development does not prove definitive causality this case report may serve as a reminder how time critical IVIG therapy can be for sufficient symptom control. Moreover, it provides evidence that IVIG therapy may be effective for the treatment of cranial nerve symptoms in CIDP

Effect of Caffeine and Other Methylxanthines on Aβ-Homeostasis in SH-SY5Y Cells

Methylxanthines (MTX) are alkaloids derived from the purine-base xanthine. Whereas especially caffeine, the most prominent known MTX, has been formerly assessed to be detrimental, this point of view has changed substantially. MTXs are discussed to have beneficial properties in neurodegenerative diseases, however, the mechanisms of action are not completely understood. Here we investigate the effect of the naturally occurring caffeine, theobromine and theophylline and the synthetic propentofylline and pentoxifylline on processes involved in Alzheimer’s disease (AD). All MTXs decreased amyloid-β (Aβ) level by shifting the amyloid precursor protein (APP) processing from the Aβ-producing amyloidogenic to the non-amyloidogenic pathway. The α-secretase activity was elevated whereas β-secretase activity was decreased. Breaking down the molecular mechanism, caffeine increased protein stability of the major α-secretase ADAM10, downregulated BACE1 expression and directly decreased β-secretase activity. Additionally, APP expression was reduced. In line with literature, MTXs reduced oxidative stress, decreased cholesterol and a decreased in Aβ1-42 aggregation. In conclusion, all MTXs act via the pleiotropic mechanism resulting in decreased Aβ and show beneficial properties with respect to AD in neuroblastoma cells. However, the observed effect strength was moderate, suggesting that MTXs should be integrated in a healthy diet rather than be used exclusively to treat or prevent AD

Myositis in Germany: epidemiological insights over 15 years from 2005 to 2019

Abstract Background The medical care of patients with myositis is a great challenge in clinical practice. This is due to the rarity of these disease, the complexity of diagnosis and management as well as the lack of systematic analyses. Objectives Therefore, the aim of this project was to obtain an overview of the current care of myositis patients in Germany and to evaluate epidemiological trends in recent years. Methods In collaboration with BARMER Insurance, retrospective analysis of outpatient and inpatient data from an average of approximately 8.7 million insured patients between January 2005 and December 2019 was performed using ICD-10 codes for myositis for identification of relevant data. In addition, a comparative analysis was performed between myositis patients and an age-matched comparison group from other populations insured by BARMER. Results 45,800 BARMER-insured individuals received a diagnosis of myositis during the observation period, with a relatively stable prevalence throughout. With regard to comorbidities, a significantly higher rate of cardiovascular disease as well as neoplasm was observed compared to the control group within the BARMER-insured population. In addition, myositis patients suffer more frequently from psychiatric disorders, such as depression and somatoform disorders. However, the ICD-10 catalogue only includes the specific coding of “dermatomyositis” and “polymyositis” and thus does not allow for a sufficient analysis of all idiopathic inflammatory myopathies subtypes. Conclusion The current data provide a comprehensive epidemiological analysis of myositis in Germany, highlighting the multimorbidity of myositis patients. This underlines the need for multidisciplinary management. However, the ICD-10 codes currently still in use do not allow for specific analysis of the subtypes of myositis. The upcoming ICD-11 coding may improve future analyses in this regard

NK Cell Patterns in Idiopathic Inflammatory Myopathies with Pulmonary Affection

International audienceBackground: Pulmonary affection (PA) is associated with a substantial increase in morbidity and mortality in patients with idiopathic inflammatory myopathies (IIM). However, the underlying immune mechanisms of PA remain enigmatic and prompt deeper immunological analyses. Importantly, the Janus-faced role of natural killer (NK) cells, capable of pro-inflammatory as well as regulatory effects, might be of interest for the pathophysiologic understanding of PA in IIM. Methods: To extend our understanding of immunological alterations in IIM patients with PA, we compared the signatures of NK cells in peripheral blood using multi-color flow cytometry in IIM patients with (n = 12, of which anti-synthetase syndrome = 8 and dermatomyositis = 4) or without PA (n = 12).Results: We did not observe any significant differences for B cells, CD4, and CD8 T cells, while total NK cell numbers in IIM patients with PA were reduced compared to non-PA patients. NK cell alterations were driven by a particular decrease of CD56dim NK cells, while CD56bright NK cells remained unchanged. Comparisons of the cell surface expression of a large panel of NK receptors revealed an increased mean fluorescence intensity of NKG2D+ on NK cells from patients with PA compared with non-PA patients, especially on the CD56dim subset. NKG2D+ and NKp46+ cell surface levels were associated with reduced vital capacity, serving as a surrogate marker for clinical severity of PA.Conclusion: Our data illustrate that PA in IIM is associated with alterations of the NK cell repertoire, suggesting a relevant contribution of NK cells in certain IIMs, which might pave the way for NK cell-targeted therapeutic approaches

Tocotrienol Affects Oxidative Stress, Cholesterol Homeostasis and the Amyloidogenic Pathway in Neuroblastoma Cells: Consequences for Alzheimer’s Disease

One of the characteristics of Alzheimer´s disease (AD) is an increased amyloid load and an enhanced level of reactive oxidative species (ROS). Vitamin E has known beneficial neuroprotective effects, and previously, some studies suggested that vitamin E is associated with a reduced risk of AD due to its antioxidative properties. However, epidemiological studies and nutritional approaches of vitamin E treatment are controversial. Here, we investigate the effect of α-tocotrienol, which belongs to the group of vitamin E, on AD-relevant processes in neuronal cell lines. In line with the literature, α-tocotrienol reduced the ROS level in SH-SY5Y cells. In the presence of tocotrienols, cholesterol and cholesterol esters, which have been shown to be risk factors in AD, were decreased. Besides the unambiguous positive effects of tocotrienol, amyloid-β (Aβ) levels were increased accompanied by an increase in the activity of enzymes responsible for Aβ production. Proteins and gene expression of the secretases and their components remained unchanged, whereas tocotrienol accelerates enzyme activity in cell-free assays. Besides enhanced Aβ production, tocotrienols inhibited Aβ degradation in neuro 2a (N2a)-cells. Our results might help to understand the controversial findings of vitamin E studies and demonstrate that besides the known positive neuroprotective properties, tocotrienols also have negative characteristics with respect to AD