The endothelium plays an essential role in the regulation of vascular homeostasis and a state of endothelial dysfunction, which develops in the presence of cardiovascular risk factors, may contribute to the development and progression of cardiovascular disease. As such, the measurement of endothelial function, beyond being an experimental tool, may serve as an important tool to complement current risk assessment algorithms in the identification of high-risk patients. Flow-mediated dilation (FMD) is a non-invasive measure of peripheral conduit artery endothelial function that holds great promise. Presently, FMD suffers from methodological heterogeneity and a poor understanding of the various biological components involved in eliciting the dilatory response to a given shear stimulus. We compared both traditional and alternative methods of arterial diameter characterization with regards to their repeatability, nitric oxide-dependency, and their sensitivity in distinguishing between normal and dysfunctional endothelial responses. Our findings emphasize the importance of continuous arterial diameter measurement and suggest that the time to peak FMD is not a useful adjunctive measure of the FMD response. Given that endothelial dysfunction may be of clinical importance, strategies to correct it or prevent it from occurring may be of benefit. The 3-hydroxy-3-methylglutaryl coenzyme A inhibitors are agents that have demonstrated marked cholesterol-independent, endothelial-protective effects. We investigated the ability of rosuvastatin and atorvastatin to protect against endothelial dysfunction associated with ischemia and reperfusion (IR) injury, and chronic nitrate therapy. Using the FMD technique, we demonstrated, for the first time in humans, that acute rosuvastatin administration protects against IR-induced conduit artery endothelial dysfunction. Additionally, we demonstrated that this effect likely occurred by a cyclooxygenase-2-dependent mechanism, which may provide mechanistic insight into the observed cardio-toxicity with cyclooxygenase-2 inhibitors. In contrast, we observed that this endothelial-protective effect was lost upon sustained rosuvastatin administration, which may have important implications regarding the generation of sustained cardioprotective phenotypes. Finally, we demonstrated that atorvastatin co-administration prevented the development of tolerance and endothelial dysfunction associated with continuous transdermal nitroglycerin therapy in humans, likely through an antioxidant mechanism. Future studies are needed in disease patients to determine whether the concept of nitrate tolerance needs reconsideration in the presence of vascular-protective agents.

The endothelium plays an essential role in the regulation of vascular homeostasis and a state of endothelial dysfunction, which develops in the presence of cardiovascular risk factors, may contribute to the development and progression of cardiovascular disease. As such, the measurement of endothelial function, beyond being an experimental tool, may serve as an important tool to complement current risk assessment algorithms in the identification of high-risk patients. Flow-mediated dilation (FMD) is a non-invasive measure of peripheral conduit artery endothelial function that holds great promise. Presently, FMD suffers from methodological heterogeneity and a poor understanding of the various biological components involved in eliciting the dilatory response to a given shear stimulus. We compared both traditional and alternative methods of arterial diameter characterization with regards to their repeatability, nitric oxide-dependency, and their sensitivity in distinguishing between normal and dysfunctional endothelial responses. Our findings emphasize the importance of continuous arterial diameter measurement and suggest that the time to peak FMD is not a useful adjunctive measure of the FMD response. Given that endothelial dysfunction may be of clinical importance, strategies to correct it or prevent it from occurring may be of benefit. The 3-hydroxy-3-methylglutaryl coenzyme A inhibitors are agents that have demonstrated marked cholesterol-independent, endothelial-protective effects. We investigated the ability of rosuvastatin and atorvastatin to protect against endothelial dysfunction associated with ischemia and reperfusion (IR) injury, and chronic nitrate therapy. Using the FMD technique, we demonstrated, for the first time in humans, that acute rosuvastatin administration protects against IR-induced conduit artery endothelial dysfunction. Additionally, we demonstrated that this effect likely occurred by a cyclooxygenase-2-dependent mechanism, which may provide mechanistic insight into the observed cardio-toxicity with cyclooxygenase-2 inhibitors. In contrast, we observed that this endothelial-protective effect was lost upon sustained rosuvastatin administration, which may have important implications regarding the generation of sustained cardioprotective phenotypes. Finally, we demonstrated that atorvastatin co-administration prevented the development of tolerance and endothelial dysfunction associated with continuous transdermal nitroglycerin therapy in humans, likely through an antioxidant mechanism. Future studies are needed in disease patients to determine whether the concept of nitrate tolerance needs reconsideration in the presence of vascular-protective agents.

3-Hydroxy-3-methylglutaryl CoA reductase (HMGR, EC 1.1.1.34) catalyzes the reaction from hydroxymethylglutaryl CoA to mevalonate in the isoprenoid pathway. In solanaceous plants, one class of endproducts of the pathway are sesquiterpenoid phytoalexins, antibiotic compounds produced by plants in response to pathogens. We are interested in the role of the defense-inducible isoforms of HMGR in phytoalexin production and disease resistance. Transgenic tobacco, constitutively expressing the defense-inducible tomato hmgr isogene, hmg2, showed fewer and smaller lesions following tobacco mosaic virus (TMV) inoculation. There is little evidence of phytoalexins acting directly against viruses, but they may reduce the spread of viruses as part of the hypersensitive response resulting in death of the host cell. Transmission electron microscopy of leaf cells of the transgenic plants revealed a larger volume of cytosol and accumulation of electron-dense inclusion bodies within the vacuoles. No structures resembling crystalloid ER or karmellae, caused by overexpression of hmgr in mammalian or yeast cells, respectively, were observed. Similar inclusion bodies were found in the vacuoles of wild-type tobacco leaf cells adjacent to necrotic cells in a TMV lesion. Tobacco expressing a truncated (membrane domain) form of hmg2 did not show enhanced resistance to TMV or any ultrastructural changes, indicating the importance of catalytically active HMG2 in mediating these changes. Sesquiterpene cyclase (a key branch point enzyme controlling sesquiterpene phytoalexin biosynthesis) was not induced and the amount of capsidiol, the tobacco phytoalexin, was not elevated by expression of hmg2. After TMV-inoculation, HMGR activity and the amount of capsidiol were higher in the wild-type than in the transgenic plants. Consequently, the enhanced resistance to TMV was not due to constitutive capsidiol production. The transgenic plants may have been able to produce sesquiterpenoid phytoalexins faster due to constitutive hmg2- expression and restricted the spread of the virus earlier, so that only a few cells were sacrificed. The subcellular localization of the defense-specific HMG2 isoform was determined by tagging tomato hmg2 with a c-myc epitope, and constitutively expressing the construct in transgenic tobacco plants. In non-induced leaves, MYC-HMG2 was found localized in small clusters associated with the ER. In TMV-inoculated leaves MYC-HMG2 co-localized with sesquiterpene cyclase to the vacuolar inclusion bodies suggesting that they may contain a defense-induced, membrane-associated multienzyme complex dedicated to sesquiterpene production. Our results support the hypothesis of the multibranched plant isoprenoid pathway being partly regulated by pathway partitioning. / Ph. D.

The oxysterol, 25-hydroxycholesterol (25-HC), is important for sterol metabolism and emerging evidence suggests that 25-HC plays a more critical role in immunity and infection. However, the precise antiviral mechanism and the target of 25- HC remains unclear. Here efforts were made to investigate the link between viral infection and the triggering of the 25-HC associated interferon (IFN) response, and how this dynamically alters the endogenous level of 3-hydroxy- 3-methylglutaryl-CoA reductase (HMGCR), a key enzyme that catalyses the production of the precursor of cholesterol and oxysterols. In this thesis I have sought to specifically explore the temporal changes and role of HMGCR in DNA virus (cytomegalovirus) and RNA (Influenza) virus infections. I hypothesise that HMGCR is a target for 25-HC associated IFN-mediated host defence against viral infection. To characterise HMGCR and test this hypothesis, the following objectives were defined: (1). To establish an experimental system to quantitatively study the endogenous HMGCR protein level; (2). To investigate the mechanism of the down-regulation of HMGCR involved in the IFN-mediated innate immune response; (3). To study the behaviour of HMGCR in the influenza virus induced 25-HC associated IFN-mediated innate immune response; (4). To study the behaviour of HMGCR in the cytomegalovirus induced 25-HC associated IFN-mediated innate immune response. Chapter 3, describes establishing an experimental system for the quantification of endogenous HMGCR levels. Different protein detection methods, including a modified western blot protocol and immunostaining, were tested. The results of RNA interference of HMGCR demonstrate that under lipid-deficient condition with the supplementation of mevastatin (an HMGCR inhibitor) the modified western blot protocol specifically detects endogenous HMGCR. This chapter lays the foundational work for the temporal analysis and testing the role of HMGCR in infection. In Chapter 4, the mechanism of the degradation of HMGCR following 25-HC and IFN treatments, in wild-type and Ch25h−/− mouse bone marrow derived macrophages (BMDMs), was investigated. Similar to 25-HC, IFN-γ treatment results in the drop of both the transcript and protein abundance of HMGCR in wild-type BMDMs. Differential temporal analysis of RNA and protein alterations and the use of proteasome inhibitors reveals that both 25-HC and IFN-γ lead to a marked reduction of HMGCR protein via a proteasomal degradation mechanism within early times of treatments. Further, the immediate reduction of HMGCR levels induced by IFN-γ was completely abrogated in Ch25h−/− BMDMs. Hence, the reduction of HMGCR following IFN-γ treatment is due to the de novo synthesis in macrophages of 25-HC. However, the decrease of Hmgcr gene expression was observed in not only wild-type but also Ch25h−/− BMDMs, suggesting additional mechanisms for regulating Hmgcr RNA levels. These results demonstrate the mechanism of the down-regulation of HMGCR resulted from the induction of IFN response during viral infection, is only partially due the de novo synthesis of 25-HC. In chapter 5, influenza A virus was used to investigate the role of HMGCR in the IFN-mediated innate immune response. The inhibition of HMGCR by RNA interference inhibited viral growth, suggesting the requirement of HMGCR for optimal intracellular viral growth. Viral infection in wild-type murine BMDMs reduced the endogenous HMGCR levels. However, the reduction of HMGCR at early times was prevented in Ch25h−/− BMDMs. Intriguingly, the decrease of HMGCR at late time points was still observed in Ch25h−/− BMDMs. These results indicate that the down-regulation of HMGCR with influenza virus infection in BMDMs at early times is completely due to the de novo synthesis of 25-HC; whereas at late times alternative pathways or mechanisms exist. Additionally, human epithelial A549 cells and A549/PIV5-V cells that are deficient in STAT1 were used to study the role of IFN pathway in the down-regulation of HMGCR at late times during viral infection. Results from these studies show that at late times the reduction of HMGCR is due to IFN-independent mechanisms. Chapter 6, extends these investigations to the herpes virus murine cytomegalovirus and infection of BMDMs. HMGCR is known to be essential for cytomegaloviral infections and 25-HC, statin and RNAi inhibition of HMGCR restrict viral growth. 25-HC is shown to reduce HMGCR at immediate early times of infection. However, most notably, the down-regulation of HMGCR was also observed in Ch25h−/− BMDMs at late times with murine cytomegalovirus infected BMDMs. These results confirm that alternative pathways or mechanisms exist, playing roles in the crosstalk between cholesterol metabolism and innate immune response. Collectively, this study characterises the role of HMGCR in the 25-HC associated IFN-mediated host defence against viral infection. Results indicate that, in addition to the IFN-mediated host response, alternative pathways or other mechanisms also result in the down-regulation of HMGCR during viral infection. HMGCR is at the crossroad of different pathways or mechanisms, and is therefore not only targeted by 25-HC. Hence, further questions can be addressed from these results: (1). What are the alternative pathways or mechanisms for the down-regulation of HMGCR? (2). How do these pathways or mechanisms work in hosts’ immune system? Answering these questions can contribute to refining the pathway map of innate immunity and understanding the precise role of HMGCR, or even the sterol biosynthesis pathway, in hosts’ immune response against pathogens.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第25356号 / 農博第2622号 / 新制||農||1109(附属図書館) / 京都大学大学院農学研究科食品生物科学専攻 / (主査)教授 井上 和生, 教授 佐々木 努, 准教授 後藤 剛 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

The enzyme 3-Hydroxy-3- Methylglutaryl Coenzyme A Reductase catalyzes the rate limiting step of hepatic cholesterol biosynthesis and is unique among the enzymes in the early part of the pathway in that it is membrane bound. This gives rise to potential regulation of the enzyme through interactions with the endoplasmic reticulum membrane. A purification procedure has been developed which consistently produces enzyme of high specific activity. In order to fully characterize the interactions between HMG-CoA reductase and the lipids in its immediate environment, HMG-CoA reductase was purified to homogeneity and shown to be a protein-lipid complex.

Made available in DSpace on 2016-08-10T10:39:08Z (GMT). No. of bitstreams: 1 STANLEY SILVANO SOUSA.pdf: 1573160 bytes, checksum: 779804c156f10ab50a1b61b85240a0ab (MD5) Previous issue date: 2015-08-27 / The main regulatory enzyme of cholesterol biosynthesis is hydroxyl-methylglutaryl-CoA reductase (HMGCR) and several polymorphisms are described in the gene encoding this enzyme. Currently, associations between genetic polymorphisms and cardiovascular disease are investigated in order to better understand the genetic factors associated with such diseases. The objective of this study was to evaluate the frequency of -911 polymorphism (rs3761740) in the promoter region of HMGCR gene in patients with coronary artery disease (CAD), as well as the possible associations between the resultant genotypes and clinical features of patients with CAD. Genomic DNA isolated from patients blood samples were analyzed for the detection of genetic polymorphism, by using polymerase chain reaction (PCR) analysis and restriction fragment length polymorphism (RFLP). Allele frequencies obtained for the -911 polymorphism (rs3761740) in the promoter region of the HMGCR gene were: A (51.2%) and C (48.8%). The genotype frequencies obtained were: AA (11.9%), AC (78.6%) and CC (9.5%). Significant associations between the diferente genotypes and clinical features of the patients with CAD were not detected in this study. Our results show that -911 polymorphism (rs3761740) in the promoter region of the HMGCR gene was not associated with clinical and laboratory characteristics in patients with coronary artery disease. / A principal enzima regulatória da biossíntese do colesterol é a hidrox-imetilglutaril-CoA redutase (HMGCR) e vários polimorfismos são descritos no gene que codifica esta enzima. Atualmente, associações entre tais polimorfismos genéticos e as doenças cardiovasculares são investigadas no sentido de compreender melhor os fatores genéticos associados a essas doenças. O objetivo deste estudo foi avaliar a frequência do polimorfismo -911(rs3761740) na região promotora do gene da HMGCR em pacientes com doença arterial coronariana (DAC), bem como as possíveis associações entre os genótipos encontrados e os aspectos clínicos dos pacientes com DAC. O DNA genômico isolado das amostras de sangue dos pacientes foi analisado para detecção do polimorfismo genético, por meio da reação em cadeia da polimerase (PCR) e análise de polimorfismos de comprimento de fragmentos de restrição (RFLP). As frequências alélicas obtidas para o polimorfismo -911 (rs3761740) na região promotora do gene HMGCR foram: A (51,2%) e C (48,8%). As frequências genotípicas obtidas foram: AA (11,9%), AC (78,6%) e CC (9,5%). Associações significativas entre os genótipos encontrados e os aspectos clínicos dos pacientes com DAC não foram detectadas neste estudo. Nossos resultados permitem concluir que polimorfismo -911(rs3761740) na região promotora do gene da HMGCR não esteve associado aos aspectos clínicos e laboratoriais em pacientes com doença arterial coronariana.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In Southern Brazil, the plant Campomanesia xanthocarpa Berg. (Myrtaceae), popularly known as guavirova , has been empirically used for its potential effect in reducing blood cholesterol levels. Since there are no scientific data confirming its popular use, the aim of the present study was to investigate the effect of C. xanthocarpa on biochemical, hematological, anthropometrical and oxidative stress parameters in hypercholesterolemic patients. Thirty three patients were selected according to total cholesterol (TC) levels: 200-240 mg/dL, undesirable level (UL), and >240 mg/dL, hypercholesterolemic level (HL). UL or HL patients were randomly divided into control group (CG), which received placebo capsules, and experimental group 250 (EG 250) or 500 (EG 500), which received either 250 or 500 mg of encapsulated C. xanthocarpa. All groups received a cholesterol restriction diet and capsules once a day. The biochemical (TC, triglycerides, HDL, LDL and VLDL), hematological (hematocrit and hemoglobin), anthropometrical (weight and abdominal circumference) and oxidative stress (protein carbonyl) parameters were measured before, 45 and 90 days after the treatment started. There was no alteration on biochemical, hematological, anthropometric or oxidative stress parameters in UL patients of all groups. However, a significant decrease in TC and LDL levels was observed in HL patients from EG 500 group (reduction of 28±3 and 45±4% to levels before treatment) in relation to CG group patients (reduction of 12±2 and 29±4%). Moreover, a significant reduction in oxidative stress was observed in HL patients of EG 250 (51±12%) and EG 500 groups (34±18%) when compared to levels before treatment. A positive correlation between plasma oxidative stress PC and TC levels was observed. Finally, was demonstrated that C. xanthocarpa extract possesses anti-oxidant properties and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitory activity in vitro. Confirming its popular use, the treatment with C. xanthocarpa encapsulated reduced blood TC and LDL levels in hypercholesterolemic patients. Besides its effect on cholesterol levels, this plant reduced the oxidative stress in plasma of hypercholesterolemic patients as well. / No Sul do Brasil, a planta Campomanesia xanthocarpa Berg. (Myrtaceae), popularmente conhecida como guavirova , tem sido empiricamente usada por seu efeito potencial em reduzir os níveis de colesterol sanguíneo. Uma vez que não há dados científicos confirmando seu uso popular, o alvo do presente estudo foi investigar os efeitos da C. xanthocarpa nos parâmetros bioquímicos, hematológicos, antropométricos e de estresse oxidativo em pacientes hipercolesterolêmicos. Trinta e três pacientes foram selecionados de acordo com os níveis de colesterol total (CT): 200-240 mg/dL, níveis indesejáveis (NI), e > 240 mg/dL, níveis hipercolesterolêmicos (NH). Os pacientes NI e NH foram randomicamente divididos em grupo controle (GC), que recebeu cápsulas placebo, e grupo experimental 250 (GE 250) ou 500 (GE 500), que recebeu 250 ou 500 mg de C. xanthocarpa encapsulada. Todos os grupos receberam uma dieta com restrição a colesterol e cápsulas diariamente. Os parâmetros bioquímicos (CT, triacilgliceróis, HDL, LDL e VLDL), hematológicos (hematócrito e hemoglobina), antropométricos (peso e circunferência abdominal) e de estresse oxidativo (proteína carbonilada) foram mensurados antes, 45 e 90 dias depois do tratamento. Não houve nenhum alteração significativa nos parâmetros bioquímico, hematológico, antropométrico e de estresse oxidativo em pacientes NI de todos os grupos. Entretanto, uma redução significativa nos níveis de CT e LDL foi observada em pacientes NH do GE 500 (redução de 28±3 e 45±4% para os níveis antes do tratamento) em relação aos pacientes do GC (redução de 12±2 e 29±4%). Além disso, uma redução significante no estresse oxidativo foi observada em pacientes NH do GE 250 (51±12%) e GE 500 (34±18%) quando comparado com os níveis antes do tratamento. Uma correlação positiva entre os níveis de proteína carbonilada e CT foi observada. Finalmente, foi demonstrado que o extrato de C. xanthocarpa possui propriedade antioxidante e atividade inibitória da 3-hidroxi-3-metilglutaril coenzima A redutase in vitro. Confirmando seu uso popular, o tratamento com C. xanthocarpa reduziu os níveis de CT e LDL sanguíneos em pacientes hipercolesterolêmicos. Além dos seus efeitos nos níveis de colesterol, esta planta reduziu o estresse oxidativo no plasma de pacientes hipercolesterolêmicos.

Dans cette thèse, l’impact du polymorphisme rs3846662 sur l’épissage alternatif de la 3-hydroxy-3-méthylglutaryl coenzyme A réductase (HMGCR) a été investigué in vivo, chez des patients atteints d’hypercholestérolémie familiale (HF) ou de maladie d’Alzheimer (MA). Le premier manuscrit adresse la problématique de la normalisation de la quantification relative des ARNm par PCR quantitative. Les découvertes présentées dans ce manuscrit nous ont permis de déterminer avec un haut niveau de confiance les gènes de référence à utiliser pour la quantification relative des niveaux d’ARNm de l’HMGCR dans des échantillons de sang (troisième manuscrit) et de tissus cérébraux post-mortem (quatrième manuscrit). Dans le deuxième manuscrit, nous démontrons grâce à l’emploi de trois cohortes de patients distinctes, soit la population canadienne française du Québec et les deux populations nord américaines « Alzheimer’s Disease Cooperative Study (ADCS) » et « Alzheimer’s Disease Neuroimaging Initiative (ADNI) », que le génotype AA au locus rs3846662 confère à ces porteurs une protection considérable contre la MA. Les femmes porteuses de ce génotype voient leur risque de MA diminuer de près de 50% et l’âge d’apparition de leurs premiers symptômes retarder de 3.6 ans. Les porteurs de l’allèle à risque APOE4 voient pour leur part leurs niveaux de plaques séniles et dégénérescences neurofibrillaires diminuer significativement en présence du génotype AA. Enfin, les individus atteints de déficit cognitif léger et porteurs à la fois de l’allèle APOE4 et du génotype protecteur AA voient leur risque de convertir vers la MA chuter de 76 à 27%. Dans le troisième manuscrit, nous constatons que les individus atteints d’HF et porteurs du génotype AA ont, contrairement au modèle établi chez les gens normaux, des niveaux plus élevés de cholestérol total et de LDL-C avant traitement comparativement aux porteurs de l’allèle G. Le fait que cette association n’est observée que chez les non porteurs de l’APOE4 et que les femmes porteuses du génotype AA présentent à la fois une augmentation des niveaux d’ARNm totaux et une résistance aux traitements par statines, nous indique que ce génotype influencerait non seulement l’épissage alternatif, mais également la transcription de l’HMGCR. Comme une revue exhaustive de la littérature ne révèle aucune étude abondant dans ce sens, nos résultats suggèrent l’existence de joueurs encore inconnus qui viennent influencer la relation entre le génotype AA, l’épissage alternatif et les niveaux d’ARNm de l’HMGCR. Dans le quatrième manuscrit, l’absence d’associations entre le génotype AA et les niveaux d’ARNm Δ13 ou de protéines HMGCR nous suggère fortement que ce polymorphisme est non fonctionnel dans le SNC affecté par la MA. Une étude approfondie de la littérature nous a permis d’étayer cette hypothèse puisque les niveaux de HNRNPA1, la ribonucléoprotéine influencée par l’allèle au locus rs3846662, sont considérablement réduits dans la MA et le vieillissement. Il est donc proposé que les effets protecteurs contre la MA associés au génotype AA soient le résultat d’une action indirecte sur le processus physiopathologique. / In this thesis, the impact of rs3846662 polymorphism on the alternative splicing of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) was investigated in vivo, in patients with familial hypercholesterolemia (FH) or Alzheimer disease (AD). The first manuscript addresses the issue of normalization in relative quantification of mRNA by quantitative PCR. The findings presented in this manuscript have allowed us to determine with a high level of certainty the appropriate reference genes to use for the relative quantification of HMGCR mRNA levels in blood samples (third manuscript) and postmortem brain tissues (fourth manuscript). In the second manuscript, we demonstrate through the use of three independent cohorts, namely the French Canadian population of Quebec and the two North American populations named "Alzheimer's Disease Cooperative Study (ADCS)" and "Alzheimer's Disease Neuroimaging Initiative (ADNI) ", that the AA genotype at locus rs3846662 confers significant protection against AD. Women carrying this genotype decrease their risk of AD by about 50%, and delay their age of onset of 3.6 years. For their part, individuals carrying both the APOE4 risk allele and the AA genotype have decreased levels of senile plaques and neurofibrillary tangles compared to individuals carrying both the APOE4 and HMGCR G alleles. Finally, individuals suffering from mild cognitive impairment and carrying both the APOE4 risk allele and the protective AA genotype see their risk of converting to AD drop from 76% to 27%. In the third manuscript, contrary to the model described in normal subjects, we discovered that individuals with FH carrying the AA genotype have higher levels of total cholesterol and LDL-C before treatment compared to the carriers of the G allele. This latter association is observed only in non-carriers of the APOE4 risk allele. Furthermore, women carrying the AA genotype have both an increase in total HMGCR mRNA levels and a decrease response to statin treatment. These results suggest the AA genotype has an impact not only on the alternative splicing, but also on the transcription of HMGCR. Since an exhaustive review of the literature has reveal no studies corroborating this hypothesis, our results suggest the existence of yet unknown players influencing the relationships between the AA genotype, alternative splicing and the mRNA levels of HMGCR. In the fourth manuscript, we uncovered no association between the AA genotype and Δ13 mRNA or HMGCR protein levels. This strongly suggests that the rs3846662 polymorphism is not functional in the CNS affected by AD. A thorough study of the literature enabled us to support this hypothesis since the levels of HNRNPA1, the ribonucleoprotein influenced by the allele status at rs3846662 locus, are significantly reduced in AD and aging. Accordingly, we propose that the protective effects of the AA genotype against AD may be mediated through indirect effects on the physiopathology of the disease.