O efeito antiproliferativo do calcitriol foi detectado principalmente em linhagens de carcinoma mamário expostas in vitro a alta concentração hormonal (10 - 100nM), que é associado com hipercalcemia em seres humanos. Nossa hipótese era que a administração intratumoral de calcitriol permitiria maior concentração do hormônio e ativação da via genômica. Para testar esta hipótese, um modelo de enxerto tumoral que reproduz o mais próximo das características moleculares do tumor primário, foi estabelecida. As amostras de câncer de mama recolhidos foram enxertados em camundongos nude e depois da sexta semana, semana, os enxertos tumorais foram tratados semanalmente com injeções intra-tumorais de veículo (controle) ou o calcitriol 0,06 mcg (dose que pode permitir que picos séricos de calcitriol na faixa terapêutica prevista) durante seis semanas. A proliferação e apoptose do enxerto tumoral Veículo (controlo) ou o calcitriol 0,06 mcg (dose que pode permitir que o soro de pico, assim como, a expressão dos genes alvos foram avaliadas através de reações imunohistoquímica ou RT-PCR. A expressão de VDR foi detectada em todas as amostras, assim como uma tendência para maior expressão de mRNA CYP24A1 (indução 10-18 vezes) em amostras tratadas com calcitriol, indicando que a via genómica foi induzida pelo hormonio. O elevado índice proliferativo, avaliado pela expressão de Ki67, foi detectado. No entanto, não havia diferenças na expressão de marcadores de proliferação (incorporação de BrdU, Ki67 e CDKN1B expressão) nem marcadores de apoptose (caspase-3 clivada e BCL2 expressão) entre os enxertos tumorais tratados por veículo e calcitriol tratado. Além disso, não houve diferença entre os grupos detectada na expressão de mRNA do CDKN1A. Em resumo, os efeitos antitumorais não foram observados neste modelo de enxerto tumoral. A indução do gene alvo CYP24A1 pode ter em parte impedido os efeito antitumorais da vitamina D / Antiproliferative effects of calcitriol were mainly detected in breast carcinoma lineages exposed in vitro to high hormone concentrations (10-100 nM), which is associated with hypercalcemia in human beings. Our hypothesis was that intra-tumoral administration of calcitriol would allow higher issue concentration of the hormone and activation of the genomic pathway. To test this hypothesis, a tumorgraft model, that more closely reproduces the molecular characteristics of the primary tumor, was established. Freshly collected breast cancer samples were grafted in nude mice and after the 6th week, tumorgrafts were treated weekly with intra-tumoral injections of vehicle (control) or calcitriol 0.06 mcg (dose that may allow peak serum calcitriol levels in the predicted therapeutic range) for six weeks. Tumorgraft proliferation and apoptosis, as well as expression of target genes, were evaluated through immnunohistochemistry reactions or RT-PCR. VDR expression was detected in all samples as well as a trend towards higher expression of CYP24A1 mRNA (10-18 fold induction) in calcitriol treated samples, indicating that the genomic pathway was induced by the hormone. A high proliferative index, evaluated by Ki67 expression, was detected. However, there were neither differences in the expression of proliferation markers (BrdU incorporation, Ki67 and CDKN1B expression) nor in apoptosis markers (cleaved caspase 3 and BCL2 expression) between vehicle and calcitriol treated tumorgrafts. In addition, no difference between groups was detected for the expression of CDKN1A mRNA. In summary, calcitriol antitumoral effects were not observed in this tumorgraft model. Calcitriol induction of the target gene CYP24A1, might have in part, precluded vitamin D antitumoral effects

O efeito antiproliferativo do calcitriol foi detectado principalmente em linhagens de carcinoma mamário expostas in vitro a alta concentração hormonal (10 - 100nM), que é associado com hipercalcemia em seres humanos. Nossa hipótese era que a administração intratumoral de calcitriol permitiria maior concentração do hormônio e ativação da via genômica. Para testar esta hipótese, um modelo de enxerto tumoral que reproduz o mais próximo das características moleculares do tumor primário, foi estabelecida. As amostras de câncer de mama recolhidos foram enxertados em camundongos nude e depois da sexta semana, semana, os enxertos tumorais foram tratados semanalmente com injeções intra-tumorais de veículo (controle) ou o calcitriol 0,06 mcg (dose que pode permitir que picos séricos de calcitriol na faixa terapêutica prevista) durante seis semanas. A proliferação e apoptose do enxerto tumoral Veículo (controlo) ou o calcitriol 0,06 mcg (dose que pode permitir que o soro de pico, assim como, a expressão dos genes alvos foram avaliadas através de reações imunohistoquímica ou RT-PCR. A expressão de VDR foi detectada em todas as amostras, assim como uma tendência para maior expressão de mRNA CYP24A1 (indução 10-18 vezes) em amostras tratadas com calcitriol, indicando que a via genómica foi induzida pelo hormonio. O elevado índice proliferativo, avaliado pela expressão de Ki67, foi detectado. No entanto, não havia diferenças na expressão de marcadores de proliferação (incorporação de BrdU, Ki67 e CDKN1B expressão) nem marcadores de apoptose (caspase-3 clivada e BCL2 expressão) entre os enxertos tumorais tratados por veículo e calcitriol tratado. Além disso, não houve diferença entre os grupos detectada na expressão de mRNA do CDKN1A. Em resumo, os efeitos antitumorais não foram observados neste modelo de enxerto tumoral. A indução do gene alvo CYP24A1 pode ter em parte impedido os efeito antitumorais da vitamina D / Antiproliferative effects of calcitriol were mainly detected in breast carcinoma lineages exposed in vitro to high hormone concentrations (10-100 nM), which is associated with hypercalcemia in human beings. Our hypothesis was that intra-tumoral administration of calcitriol would allow higher issue concentration of the hormone and activation of the genomic pathway. To test this hypothesis, a tumorgraft model, that more closely reproduces the molecular characteristics of the primary tumor, was established. Freshly collected breast cancer samples were grafted in nude mice and after the 6th week, tumorgrafts were treated weekly with intra-tumoral injections of vehicle (control) or calcitriol 0.06 mcg (dose that may allow peak serum calcitriol levels in the predicted therapeutic range) for six weeks. Tumorgraft proliferation and apoptosis, as well as expression of target genes, were evaluated through immnunohistochemistry reactions or RT-PCR. VDR expression was detected in all samples as well as a trend towards higher expression of CYP24A1 mRNA (10-18 fold induction) in calcitriol treated samples, indicating that the genomic pathway was induced by the hormone. A high proliferative index, evaluated by Ki67 expression, was detected. However, there were neither differences in the expression of proliferation markers (BrdU incorporation, Ki67 and CDKN1B expression) nor in apoptosis markers (cleaved caspase 3 and BCL2 expression) between vehicle and calcitriol treated tumorgrafts. In addition, no difference between groups was detected for the expression of CDKN1A mRNA. In summary, calcitriol antitumoral effects were not observed in this tumorgraft model. Calcitriol induction of the target gene CYP24A1, might have in part, precluded vitamin D antitumoral effects

A més del seu paper en la regulació del metabolisme mineral, la vitamina D a través del seu receptor intracel·lular (VDR), juga un paper significatiu en la modulació de la resposta immune. Variants del gen VDR han estat associades amb la vulnerabilitat a malalties infeccioses com la tuberculosis y la lepra i recentment amb la progressió clínica de malalts infectats per VIH-1, la qual cosa posa de manifest el paper que la variabilitat del gen VDR pot jugar en la resposta a agents patògens.El gen CCR5 codifica per a un receptor de citoquines actuant, juntament amb el CD4, com principal correceptor del virus de la immunodeficiència humana tipus I (VIH-1- 1). Variants del gen CCR5 que alteren el patró d'expressió del receptor han estat associades amb la susceptibilitat a la infecció per VIH-1 i progressió a sida.En la present tesi doctoral s'ha caracteritzat l'estructura d´haplotips del gen VDR. Apartir del patró de blocs observat s'han seleccionat cinc variants polimòrfiques localitzades en diferents regions del gen amb la finalitat d'avaluar la seva associació amb la vulnerabilitat a la infecció pel VIH-1 i el ritme de progressió a sida. Els resultat obtinguts indican que l´haplotip GATGL, associat amb una menor funcionalitat de la ruta metabòlica de la vitamina D, confereix protecció a la infecció per VIH-1 seguint un model genètic dominant. Trobem també que el l´haplotip G++GL, relacionat també amb una menor funcionalitat de la ruta metabòlica de la vitamina D, confereix progressió lenta a sida seguint un model dominant. Finalment, trobem que l´haplotip G++AS confereix un major risc de progressió a sida, seguint un model recessiu.A més, hem caracteritzat variants polimòrfiques i l'estructura d'haplotips del gen CCR5. A partir de la caracterització d'aquestes variants es va avaluar la seva associació amb el ritme de progressió a sida en pacients VIH+. Hem trobat que el diplotipo AB, relacionat amb una menor síntesi del receptor CCR5, confereix protecció enfront de la progressió a sida.L'anàlisi conjunta dels gens VDR i CCR5 ens ha permès determinar que els pacients que presenten el genotip combinat G++AS/G++AS (gen VDR) i noAB (gen CCR5) presenten el ritme més ràpid de progressió a sida. Els pacients portadors d'aquest genotip progressen a sida 7 anys abans que els portadors del genotip de protecció G++GL/- (gen VDR) i AB (gen CCR5).Una vegada descrits els haplotipos del gen VDR que presentaven associació. Es va avaluar l'efecte fenotípic del haplotips del gen VDR associats amb infecció i progressió a sida amb els nivells d'expressió del receptor CCR5 i el seu lligat natural RANTES, així com en el balanç Th1/Th2 de pacients VIH+ addictes a droga per via intravenosa (ADVP) i controls sans. No es van detectar diferencies en la síntesi del receptor CCR5 ni en el seu lligant natural RANTES en funció del genotip per a VDR en els pacients VIH+. Tampoc es van detectar diferencies en el balanç Th1/Th2 en funció del genotip per a VDR en pacients VIH+ ADVP. No obstant això, varem trobar que els nivels de CCR5 en membrana varien en funció del genotip per a VDR en els controls sans. Els portadors del diplotip de protecció GL/- presentaven uns nivells inferiors de CCR5 en membrana que aquells que eran portadors del diplotip de risc AS/AS. Podem concloure doncs que en el context de la infecció per VIH-1 i progressió a sida l'acció de la vitamina D exerciria un paper negatiu en quant al control de la infecció viral.La caracterització dels haplotips de VDR i CCR5 podria ser d'utilitat com factor de predicció de la progressió del malalt VIH+. La disponibilitat de vitamina D depèn de factors ambientals com la dieta i de la radiació solar disponible per a la síntesi de vitamina D. Per a entendre l'impacta de la vitamina D en la infecció per VIH-1 i progressió a sida caldria considerar una complexa equació que inclogui factors ambientals, genètics i socials. / Además de su papel en la regulación del metabolismo mineral, la vitamina D a través de su receptor intracelular (VDR), juega un papel significativo en la modulación de la respuesta inmune. Variantes del gen VDR han sido asociadas con la vulnerabilidad a enfermedades infecciosas como tuberculosis o lepra y recientemente con la progresión clínica de enfermos infectados por VIH-1, lo que pone de manifiesto el papel que la variabilidad del gen VDR puede jugar en la respuesta a agentes patógenos.El gen CCR5 codifica para un receptor de citoquinas actuando, junto a CD4, como principal correceptor del virus de la inmunodeficiencia humana tipo I (VIH-1-1). El estudio de variantes en el gen CCR5 que alteren el patrón de expresión del receptor han sido asociadas con variaciones en la respuesta frente a la infección por VIH-1 y progresión a sida.En la presente tesis doctoral se ha caracterizado la estructura de haplotipos del gen VDR. A partir del patrón de bloques observado se han seleccionado cinco variantes polimórficas localizadas en distintas regiones del gen VDR con el fin de evaluar su asociación con la vulnerabilidad a la infección por el VIH-1 y el ritmo de progresión a sida.Encontramos que el haplotipo GATGL del gen VDR, relacionado con una menor funcionalidad de la ruta metabólica de la vitamina D, confiere protección frente a la infección por VIH-1 siguiendo un modelo dominante. Encontramos también que el diplotipo G++GL/- del gen VDR, relacionado con una menor funcionalidad de la ruta metabólica de la vitamina D, confiere protección frente a la progresión a sida siguiendo un modelo dominante. Por último, encontramos que el diplotipo G++AS/G++AS confiere riesgo de progresión a sida siguiendo un modelo recesivo.Además, hemos caracterizado variantes polimórficas y estructura de haplotipos del gen CCR5. A partir de la caracterización de dichas variantes se evaluó su asociación con el ritmo de progresión a sida en pacientes VIH+. Encontramos que el diplotipo AB del gen CCR5, relacionado con una menor síntesis del receptor CCR5 confiere protección frente a la progresión a sida.El análisis de las variantes de los genes VDR y CCR5 nos permitió determinar que los pacientes que presentan el genotipo combinado G++AS/G++AS (gen VDR) y noAB (gen CCR5) presentan el ritmo más rápido de progresión a sida. Los pacientes portadores de dicho genotipo progresan a sida 7 años antes que los portadores del genotipo de protección G++GL/- (gen VDR) y AB (gen CCR5).Una vez descritos los haplotipos del gen VDR que presentaban asociación se determinó su efecto fenotípico en la expresión del receptor CCR5 y su ligado natural RANTES y en el balance Th1/Th2 en pacientes VIH+ adictos a droga por vía intravenosa (ADVP) y controles sanos. No se detectaron variaciones en la síntesis del receptor CCR5 ni en su ligando natural RANTES en función del genotipo para VDR en los pacientes VIH+.Tampoco se detectaron variaciones en el balance Th1/Th2 en función del genotipo para VDR en pacientes VIH+ ADVP. Sin embargo, encontramos que la síntesis del receptor CCR5 varía en función del genotipo para VDR en los controles sanos, siendo menor en los portadores del diplotipo de protección GL/- del gen VDR.Podemos concluir por tanto que en el contexto de la infección por VIH-1 y progresión a sida la acción de la vitamina D ejercería un papel negativo en el control de la infección viral.La caracterización del haplotipo del VDR y CCR5 de las variantes polimórficas analizadas podría servir como factor de predicción de la progresión del enfermo VIH+. Ladisponibilidad de vitamina D depende de factores ambientales como la dieta y la radiación solar disponible para la síntesis de la vitamina D . Para entender el impacto de la vitamina D en la infección por VIH-1 y progresión a sida hay que considerar una compleja ecuación que incluya factores ambientales, genéticos y sociales. / In addition to a important function in the regulation of the mineral metabolism, vitamin D plays a significant role in the modulation of the immune response through its intracellular receptor, VDR. Variants of the VDR gene have been associated with vulnerability to infectious diseases like tuberculosis or leprosy and recently with the clinical progression of patients infected by HIV-1. These facts clearly indicate the importance of VDR variability in the response against pathogenic agents.CCR5 gene codifies for a cytokine receptor protein and is, together with the CD4, the main coreceptor of the virus of the human immunodeficiency type I (HIV-1-1). The study of variants in the CCR5 gene that alter the expression pattern of the receptor has shown that this variation is associated with differences in the response against HIV-1 infection and progression to AIDS.In the present thesis, the structure of haplotypes of the VDR gene has been characterized. From the block pattern observed, five polymorphic variants located in different regions from the VDR gene have been characterized with the purpose of evaluating its association with the vulnerability to infection by the HIV-1 and the rate of progression to AIDS. We have found that haplotype GATGL of the VDR gene, associated with a lower functionality of the metabolic pathway of vitamin D, confers protection from HIV-1 infection following a dominant model. We also found that diplotype G++GL/- of the VDR gene, which also implicates a lower functionality of the metabolic pathway of vitamin D, confers protection from progression to AIDS following a dominant model. Finally, we found that diplotype G++AS/G++AS increase the risk of progression to AIDS, following a recessive model.In addition, we have characterized several polymorphic variants and the structure of haplotypes for the CCR5 gene. Based in the characterization of these variants, we evaluated its association with the rate of progression to AIDS in patients HIV-1. We found that diplotype AB of CCR5 gene, linked to a lower synthesis of receptor CCR5, confers protection from progression to AIDS.The analysis of the variants of VDR and CCR5 genes together allowed us to determine that the patients who present combined genotype G++AS/G++AS (VDR gene) and noAB (CCR5 gene) presents the fastest rate from progression to AIDS. Patients carrying this genotype progress to AIDS 7 years earlier than carriers of protection genotype G++GL/- (VDR gene) and AB (CCR5 gene).Once defined the haplotypes of VDR gene that present association, we determined his phenotypic effect in the expression of receptor CCR5 and his natural ligand RANTES, as well as in the Th1/Th2 balance in intravenous-drugs-users (IVDU) HIV-1 patients and healthy controls. Variations in the synthesis of receptor CCR5 or in his natural ligand RANTES based on the genotype for VDR in patients HIV+ were not detected. Neither were detected variations in the Th1/Th2 based on the genotype for VDR in patients HIV-1 IVDU. Nevertheless, we found that the synthesis of receptor CCR5 varies depending on the genotype for VDR in the healthy controls, being lower in the carriers of the diplotype of protection GL/- of the VDR gene.Therefore, we can conclude that in the context of the infection by HIV-1 and progression to AIDS, vitamin D would play a negative paper in the control of the viral infection.The characterization of the VDR and CCR5 haplotypes for the analyzed polymorphic variants could be a useful factor for predicting progression in HIV+ patient. In addition to the genetic background, different environmental factors as well as behavioral factors could also be considered since the vitamin D availability is dependent of diet and solar radiation D. A complex equation including environmental, genetic and behavioral factors should be proposed to comprehend the impact of vitamin-D3 on HIV-1-1 infection. Our results offer a new scenario to understand the relationship between HIV-1-1 infection and vitamin-D3 metabolism, including dietary supply and synthesis through sunlight exposure.

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Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-06T11:48:54Z No. of bitstreams: 1 arquivototal.pdf: 1508850 bytes, checksum: d542c27a8bd2415bcff28c45c57ad705 (MD5) / Made available in DSpace on 2017-09-06T11:48:54Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1508850 bytes, checksum: d542c27a8bd2415bcff28c45c57ad705 (MD5) Previous issue date: 2015-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Diabetic retinopathy (DR) is an important cause of acquired blindness among diabetics. Clinical factors are related to the risk for DR, in addition, genetic markers have been investigated, among them VDR and MTHFR polymorphisms, however, the impact of rs1801131 and rs1801133 polymorphisms is still inconclusive, while for rs1544410 there is a shortage in the literature. In this work the relationship of polymorphisms rs1544410, rs1801131 and rs1801133 with DR was investigated by cross-sectional study in a sample of 109 individuals with type 2 diabetes (T2DM) duration between 5 and 10 years. After ophthalmological screening a group of 40 affected and 69 unaffected by DR was composed. Genomic DNA was extracted from buccal cells. Genetic data were obtained by PCR-RFLP and analyzed using Fisher's exact test. Blood sample and urine for metabolic markers determinations were obtained in 62 subjects and the mean values were compared to the allele and genotype distribution of rs1544410. There was no association between alleles or genotypes of polymorphisms rs1801131 and rs1801133 with RD. The polymorphic allele b and genotypic group Bb + bb of rs1544410 were more frequent in the affected group with mild significance: [OR 0.5 (95% CI 0.31-0.98) p = 0.0478] and [OR 3.4 (95% CI 1.07-10.9) p = 0.496], respectively. None of the clinical variables were associated with rs1544410 although a trend towards higher values of C-reactive protein in patients allele b has been identified but not statistically significant. In conclusion, this study suggests that the sample investigated rs1544410 polymorphism of the VDR was related to the risk of DR, but not rs1801131 and rs1801133 MTHFR polymorphisms. / A retinopatia diabética (RD) constitui importante causa de cegueira adquirida entre diabéticos. Fatores clínicos estão relacionados ao risco para RD, em adição, diversos marcadores genéticos têm sido investigados, dentre eles, polimorfismos do MTHFR e VDR. Atividade defeituosa desses genes podem atenuar mecanismos implicados na patogenia da RD, no entanto, o impacto dos polimorfismos rs1801131 e rs1801133 ainda é inconclusivo, enquanto que para o rs1544410 há uma escassez de estudos na literatura. Neste trabalho a relação dos polimorfismos rs1801131, rs1801133 e rs1544410 com RD foi investigada por meio de estudo transversal em amostra de 109 indivíduos com tempo de duração de diabetes mellitus tipo 2 (DM2) entre 5 e 10 anos. Após avaliação oftalmológica foi constituído um grupo de 40 afetados e 69 não afetados por RD. DNA genômico foi extraído de células bucais. Os dados genéticos foram obtidos por PCR-RFLP e analisados utilizando o teste exato de Fisher. Coleta de sangue e urina para determinações de marcadores metabólicos foi feita em 62 indivíduos e as médias dos valores foram comparados à distribuição alélica e genotípica do rs1544410. Não houve associação entre alelos ou genótipos dos polimorfismos rs1801131 e rs1801133 com RD. O alelo b e o grupo genotípico Bb+bb do rs1544410 foram mais frequentes no grupo de afetados apresentando leve significância: [OR 0.5 (95% IC 0.31-0.98) p=0,0478] e [OR 3.4 (95% IC 1.07-10.9) p=0,496] respectivamente. Nenhuma das variáveis clínicas estiveram associadas com rs1544410 embora uma tendência para valores maiores de proteína C-reativa em portadores do alelo b tenha sido identificada mas sem significância estatística. Em conclusão este estudo sugere que na amostra estudada o polimorfismo rs1544410 do VDR esteve relacionado ao risco de RD, mas não o rs1801131 e rs1801133 do MTHFR. Palavras-chave: diabetes mellitus tipo 2; MTHFR; retinopatia diabética; VDR.

Nuclear receptors play significant roles in the regulation of transporters and enzymes to balance the level of endogenous molecules and to protect the body from foreign molecules. The vitamin D receptor (VDR) and its natural ligand, 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], was shown to upregulate rat ileal apical sodium dependent bile acid transporter (Asbt) to increase the reclamation of bile acids, ligands of the farnesoid X receptor (FXR). FXR is considered to be an important, negative regulator of the cholesterol metabolizing enzyme, Cyp7a1, which metabolizes cholesterol to bile acids in the liver. In rats, decreased Cyp7a1 and increased P-glycoprotein/multidrug resistance protein 1 (P-gp/Mdr1) expressions pursuant to 1,25(OH)2D3 treatment was viewed as FXR effects in which hepatic VDR protein is poorly expressed. In contrast, changes in rat intestinal and renal transporters such as multidrug resistance associated proteins (Mrp2, Mrp3, and Mrp4), Asbt, and P-gp after administration of 1,25(OH)2D3 were attributed directly as VDR effects due to higher VDR levels expressed in these tissues. Higher VDR expressions were found among mouse hepatocytes compared to those in rats. Hence, fxr(-/-) and fxr(+/+) mouse models were used to discriminate between VDR vs. FXR effects in murine livers. Hepatic Cyp7a1 in mice was found to be upregulated with 1,25(OH)2D3 treatment, via the derepression of the short heterodimer partner (SHP). Putative VDREs, identified in mouse and human SHP promoters, were responsible for the inhibitory effect on SHP. The increase in hepatic Cyp7a1 expression and decreased plasma and liver cholesterol were observed in mice prefed with a Western diet. A strong correlation was found between tissue Cyp7a1 and P-gp changes and 1,25(OH)2D3 plasma and tissue concentrations, confirming that VDR plays an important role in the disposition of xenobiotics and cholesterol metabolism. Moreover, renal and brain Mdr1a/P-gp were found to be directly upregulated by the VDR in mice, and concomitantly, increased renal and brain secretion of digoxin, a P-gp substrate, in vivo. The important observations: the cholesterol lowering and increased brain P-gp efflux activity properties suggest that VDR is a therapeutic target for treatment of hypercholesterolemia and Alzheimer’s diseases, since beta amyloid, precursors of plague, are P-gp substrates.

Nuclear receptors play significant roles in the regulation of transporters and enzymes to balance the level of endogenous molecules and to protect the body from foreign molecules. The vitamin D receptor (VDR) and its natural ligand, 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], was shown to upregulate rat ileal apical sodium dependent bile acid transporter (Asbt) to increase the reclamation of bile acids, ligands of the farnesoid X receptor (FXR). FXR is considered to be an important, negative regulator of the cholesterol metabolizing enzyme, Cyp7a1, which metabolizes cholesterol to bile acids in the liver. In rats, decreased Cyp7a1 and increased P-glycoprotein/multidrug resistance protein 1 (P-gp/Mdr1) expressions pursuant to 1,25(OH)2D3 treatment was viewed as FXR effects in which hepatic VDR protein is poorly expressed. In contrast, changes in rat intestinal and renal transporters such as multidrug resistance associated proteins (Mrp2, Mrp3, and Mrp4), Asbt, and P-gp after administration of 1,25(OH)2D3 were attributed directly as VDR effects due to higher VDR levels expressed in these tissues. Higher VDR expressions were found among mouse hepatocytes compared to those in rats. Hence, fxr(-/-) and fxr(+/+) mouse models were used to discriminate between VDR vs. FXR effects in murine livers. Hepatic Cyp7a1 in mice was found to be upregulated with 1,25(OH)2D3 treatment, via the derepression of the short heterodimer partner (SHP). Putative VDREs, identified in mouse and human SHP promoters, were responsible for the inhibitory effect on SHP. The increase in hepatic Cyp7a1 expression and decreased plasma and liver cholesterol were observed in mice prefed with a Western diet. A strong correlation was found between tissue Cyp7a1 and P-gp changes and 1,25(OH)2D3 plasma and tissue concentrations, confirming that VDR plays an important role in the disposition of xenobiotics and cholesterol metabolism. Moreover, renal and brain Mdr1a/P-gp were found to be directly upregulated by the VDR in mice, and concomitantly, increased renal and brain secretion of digoxin, a P-gp substrate, in vivo. The important observations: the cholesterol lowering and increased brain P-gp efflux activity properties suggest that VDR is a therapeutic target for treatment of hypercholesterolemia and Alzheimer’s diseases, since beta amyloid, precursors of plague, are P-gp substrates.