RESUMO
Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of skin, prostate, colon, and breast as well as leukemia. However, the major side effect of VDR ligands that limits their expanded use and clinical development is hypercalcemia that develops as a result of the action of these compounds mainly on intestine. In order to discover VDR ligands with less hypercalcemia liability, we sought to identify tissue-selective VDR modulators (VDRMs) that act as agonists in some cell types and lack activity in others. Here, we describe LY2108491 and LY2109866 as nonsecosteroidal VDRMs that function as potent agonists in keratinocytes, osteoblasts, and peripheral blood mononuclear cells but show poor activity in intestinal cells. Finally, these nonsecosteroidal VDRMs were less calcemic in vivo, and LY2108491 exhibited more than 270-fold improved therapeutic index over the naturally occurring VDR ligand 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in an in vivo preclinical surrogate model of psoriasis.
Assuntos
Acetatos/farmacologia , Sulfonatos de Arila/farmacologia , Receptores de Calcitriol/metabolismo , Tiofenos/farmacologia , Vitamina D/análogos & derivados , Vitamina D/farmacologia , Acetatos/síntese química , Acetatos/metabolismo , Animais , Sulfonatos de Arila/síntese química , Sulfonatos de Arila/metabolismo , Células CACO-2 , Calcitriol/metabolismo , Calcitriol/farmacologia , Proliferação de Células , Células Cultivadas , Neoplasias do Colo/metabolismo , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Feminino , Humanos , Hipercalcemia/metabolismo , Intestinos , Queratinócitos/efeitos dos fármacos , Queratinócitos/metabolismo , Ligantes , Camundongos , Camundongos Pelados , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Modelos Biológicos , Osteoblastos/efeitos dos fármacos , Osteoblastos/metabolismo , Psoríase/tratamento farmacológico , Ratos , Receptores de Calcitriol/agonistas , Transdução de Sinais , Especificidade da Espécie , Tiofenos/síntese química , Tiofenos/metabolismo , Transcrição Gênica , Células Tumorais Cultivadas , Vitamina D/síntese química , Vitamina D/metabolismoRESUMO
The pyruvate dehydrogenase complex (PDC) functions as an important junction in intermediary metabolism by influencing the utilization of fat versus carbohydrate as a source of fuel. Activation of PDC is achieved by phosphatases, whereas, inactivation is catalyzed by pyruvate dehydrogenase kinases (PDKs). The expression of PDK4 is highly regulated by the glucocorticoid and peroxisome proliferator-activated receptors. We demonstrate that the farnesoid X receptor (FXR; NR1H4), which regulates a variety of genes involved in lipoprotein metabolism, also regulates the expression of PDK4. Treatment of rat hepatoma cells as well as human primary hepatocytes with FXR agonists stimulates the expression of PDK4 to levels comparable to those obtained with glucocorticoids. In addition, treatment of mice with an FXR agonist significantly increased hepatic PDK4 expression, while concomitantly decreasing plasma triglyceride levels. Thus, activation of FXR may suppress glycolysis and enhance oxidation of fatty acids via inactivation of the PDC by increasing PDK4 expression.
Assuntos
Proteínas de Ligação a DNA/fisiologia , Regulação Enzimológica da Expressão Gênica , Proteínas Quinases/biossíntese , Proteínas Quinases/fisiologia , Fatores de Transcrição/fisiologia , Animais , Metabolismo dos Carboidratos , Carcinoma Hepatocelular/metabolismo , Células Cultivadas , Proteínas de Ligação a DNA/metabolismo , Ácidos Graxos/metabolismo , Glucocorticoides/metabolismo , Glucose/metabolismo , Glicólise , Hepatócitos/metabolismo , Humanos , Immunoblotting , Lipoproteínas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Modelos Biológicos , Oxigênio/metabolismo , Receptores Ativados por Proliferador de Peroxissomo/metabolismo , Fosforilação , Proteínas Serina-Treonina Quinases , Piruvato Desidrogenase Quinase de Transferência de Acetil , RNA Mensageiro/metabolismo , Ratos , Receptores Citoplasmáticos e Nucleares , Fatores de Transcrição/metabolismo , Triglicerídeos/sangue , Triglicerídeos/metabolismoRESUMO
The farnesoid X receptor (FXR; NR1H4) is a nuclear hormone receptor that functions as the bile acid receptor. In addition to the critical role FXR plays in bile acid metabolism and transport, it regulates a variety of genes important in lipoprotein metabolism. We demonstrate that FXR also plays a role in carbohydrate metabolism via regulation of phosphoenolpyruvate carboxykinase (PEPCK) gene expression. Treatment of either H4IIE or MH1C1 rat hepatoma cell lines as well as primary rat or human hepatocytes with FXR agonists led to stimulation of PEPCK mRNA expression to levels comparable to those obtained with glucocorticoid receptor agonists. We examined the physiological significance of FXR agonist-induced enhancement of PEPCK expression in primary rat hepatocytes. In addition to inducing PEPCK expression in primary hepatocytes, FXR agonists stimulated glucose output to levels comparable to those observed with a glucocorticoid receptor agonist. Consistent with these observations, treatment of C57BL6 mice with GW4064 significantly increased hepatic PEPCK expression. Activation of FXR initiated a cascade involving induction of peroxisome proliferator-activated receptor alpha and TRB3 expression that is consistent with stimulation of PEPCK gene expression via interference with a pathway that may involve Akt-dependent phosphorylation of Forkhead/winged helix transcription factor (FOXO1). The FXR-peroxisome proliferator-activated receptor alpha-TRB3 pathway was conserved in rat hepatoma cell lines, mice, as well as primary human hepatocytes. Thus, in addition to its role in the regulation of lipid metabolism, FXR regulates carbohydrate metabolism.