RESUMO
The recent development and spread of extensively drug-resistant and totally drug-resistant resistant (TDR) strains of Mycobacterium tuberculosis highlight the need for new antitubercular drugs. Protein synthesis inhibitors have played an important role in the treatment of tuberculosis (TB) starting with the inclusion of streptomycin in the first combination therapies. Although parenteral aminoglycosides are a key component of therapy for multidrug-resistant TB, the oxazolidinone linezolid is the only orally available protein synthesis inhibitor that is effective against TB. Here, we show that small-molecule inhibitors of aminoacyl-tRNA synthetases (AARSs), which are known to be excellent antibacterial protein synthesis targets, are orally bioavailable and effective against M. tuberculosis in TB mouse infection models. We applied the oxaborole tRNA-trapping (OBORT) mechanism, which was first developed to target fungal cytoplasmic leucyl-tRNA synthetase (LeuRS), to M. tuberculosis LeuRS. X-ray crystallography was used to guide the design of LeuRS inhibitors that have good biochemical potency and excellent whole-cell activity against M. tuberculosis Importantly, their good oral bioavailability translates into in vivo efficacy in both the acute and chronic mouse models of TB with potency comparable to that of the frontline drug isoniazid.
Assuntos
Antituberculosos/farmacologia , Leucina-tRNA Ligase/antagonistas & inibidores , Mycobacterium tuberculosis/efeitos dos fármacos , Inibidores da Síntese de Proteínas/farmacologia , Administração Oral , Animais , Antituberculosos/administração & dosagem , Antituberculosos/química , Antituberculosos/farmacocinética , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos/métodos , Feminino , Humanos , Leucina-tRNA Ligase/química , Leucina-tRNA Ligase/genética , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Testes de Sensibilidade Microbiana , Mycobacterium smegmatis/efeitos dos fármacos , Mycobacterium smegmatis/genética , Mycobacterium tuberculosis/genética , Inibidores da Síntese de Proteínas/administração & dosagem , Inibidores da Síntese de Proteínas/química , Inibidores da Síntese de Proteínas/farmacocinética , Relação Estrutura-Atividade , Tuberculose/tratamento farmacológico , Células VeroRESUMO
The use of nicotinic acid to treat dyslipidemia is limited by induction of a "flushing" response, mediated in part by the interaction of prostaglandin D(2) (PGD(2)) with its G-protein coupled receptor, DP1 (Ptgdr). The impact of DP1 blockade (genetic or pharmacologic) was assessed in experimental murine models of atherosclerosis. In Ptgdr(-/-)ApoE(-/-) mice versus ApoE(-/-) mice, both fed a high-fat diet, aortic cholesterol content was modestly higher (1.3- to 1.5-fold, P < 0.05) in Ptgdr(-/-)ApoE(-/-) mice at 16 and 24 weeks of age, but not at 32 weeks. In multiple ApoE(-/-) mouse studies, a DP1-specific antagonist, L-655, generally had a neutral to beneficial effect on aortic lipids in the presence or absence of nicotinic acid treatment. In a separate study, a modest increase in some atherosclerotic measures was observed with L-655 treatment in Ldlr(-/-) mice fed a high-fat diet for 8 weeks; however, this effect was not sustained for 16 or 24 weeks. In the same study, treatment with nicotinic acid alone generally decreased plasma and/or aortic lipids, and addition of L-655 did not negate those beneficial effects. These studies demonstrate that inhibition of DP1, with or without nicotinic acid treatment, does not lead to consistent or sustained effects on plaque burden in mouse atherosclerotic models.
Assuntos
Técnicas de Silenciamento de Genes , Niacina/farmacologia , Placa Aterosclerótica/tratamento farmacológico , Placa Aterosclerótica/metabolismo , Receptores Imunológicos/antagonistas & inibidores , Receptores Imunológicos/genética , Receptores de Prostaglandina/antagonistas & inibidores , Receptores de Prostaglandina/genética , Animais , Aorta/efeitos dos fármacos , Aorta/metabolismo , Apolipoproteínas E/deficiência , Colesterol/metabolismo , Interações Medicamentosas , Determinação de Ponto Final , Feminino , Humanos , Masculino , Camundongos , Niacina/uso terapêutico , Placa Aterosclerótica/genética , Receptores Imunológicos/deficiência , Receptores de LDL/deficiência , Receptores de Prostaglandina/deficiência , Receptores de Tromboxano A2 e Prostaglandina H2/metabolismoRESUMO
The mouse is a useful preclinical species for evaluating disease etiology due to the availability of a wide variety of genetically modified strains and the ability to perform disease-modifying manipulations. In order to establish an atrial filtration (AF) model in our laboratory, we profiled several commonly used murine AF models. We initially evaluated a pharmacological model of acute carbachol (CCh) treatment plus atrial burst pacing in C57BL/6 mice. In an effort to observe micro-reentrant circuits indicative of authentic AF, we employed optical mapping imaging in isolated mouse hearts. While CCh reduced atrial refractoriness and increased atrial tachyarrhythmia vulnerability, the left atrial (LA) excitation patterns were rather regular without reentrant circuits or wavelets. Therefore, the atrial tachyarrhythmia resembled high frequency atrial flutter, not typical AF per se. We next examined both a chronic angiotensin II (Ang II) infusion model and the surgical model of transverse aortic constriction (TAC), which have both been reported to induce atrial and ventricular structural changes that serve as a substrates for micro-reentrant AF. Although we observed some extent of atrial remodeling such as fibrosis or enlarged LA diameter, burst pacing-induced atrial tachyarrhythmia vulnerability did not differ from control mice in either model. This again suggested that an AF-like pathophysiology is difficult to demonstrate in the mouse. To continue searching for a valid murine AF model, we studied mice with a cardiac-specific deficiency (KO) in liver kinase B1 (Cardiac-LKB1), which has been reported to exhibit spontaneous AF. Indeed, the electrocardiograms (ECG) of conscious Cardiac-LKB1 KO mice exhibited no P waves and had irregular RR intervals, which are characteristics of AF. Histological evaluation of Cardiac-LKB1 KO mice revealed dilated and fibrotic atria, again consistent with AF. However, atrial electrograms and optical mapping revealed that electrical activity was limited to the sino-atrial node area with no electrical conduction into the atrial myocardium beyond. Thus, Cardiac-LKB1 KO mice have severe atrial myopathy or atrial standstill, but not AF. In summary, the atrial tachyarrhythmias we observed in the four murine models were distinct from typical human AF, which often exhibits micro- or macro-reentrant atrial circuits. Our results suggest that the four murine AF models we examined may not reflect human AF well, and raise a cautionary note for use of those murine models to study AF.
Assuntos
Fibrilação Atrial/fisiopatologia , Modelos Animais de Doenças , Proteínas Quinases Ativadas por AMP/genética , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Flutter Atrial/fisiopatologia , Função do Átrio Esquerdo/fisiologia , Remodelamento Atrial , Carbacol/farmacologia , Estimulação Cardíaca Artificial/efeitos adversos , Eletrocardiografia , Camundongos , Camundongos Endogâmicos C57BL , Miocárdio/patologia , Miócitos Cardíacos/patologia , Taquicardia Ventricular/fisiopatologiaRESUMO
Amino-anthranilic acid derivatives have been identified as a new class of low serum shifted, high affinity full agonists of the human orphan G-protein-coupled receptor GPR109a with improved ADME properties.
Assuntos
Descoberta de Drogas , Receptores Acoplados a Proteínas G/agonistas , Animais , Flúor/química , Humanos , Concentração Inibidora 50 , Camundongos , Estrutura Molecular , Niacina/síntese química , Niacina/química , Niacina/farmacologia , Piridinas/síntese química , Piridinas/química , Ratos , Ratos Sprague-Dawley , Receptores NicotínicosRESUMO
A series of pyrazolyl propionyl cyclohexenamides were discovered as full agonists for the high affinity niacin receptor GPR109A. The structure-activity relationship (SAR) studies were aimed to improve activity on GPR109A, reduce Cytochrome P450 2C8 (CYP2C8) and Cytochrome P450 2C9 (CYP2C9) inhibition, reduce serum shift and improve pharmacokinetic (PK) profiles.
Assuntos
Amidas/química , Cicloexenos/farmacologia , Receptores Acoplados a Proteínas G/agonistas , Animais , Cicloexenos/química , Cicloexenos/farmacocinética , Camundongos , Ratos , Receptores Nicotínicos , Relação Estrutura-AtividadeRESUMO
5-Alkyl and aryl-pyrazole-acids have been identified as a new class of selective, small-molecule, agonists of the human orphan G-protein-coupled receptor GPR109a, a high affinity receptor for the HDL-raising drug nicotinic acid.
Assuntos
Pirazóis/química , Receptores Acoplados a Proteínas G/agonistas , Animais , Ácidos Graxos/metabolismo , Humanos , Camundongos , Niacina/química , Pirazóis/síntese química , Pirazóis/farmacocinética , Receptores Acoplados a Proteínas G/metabolismo , Receptores Nicotínicos/metabolismoRESUMO
Niacin is an effective drug for raising HDL cholesterol. However, niacin must be taken in large doses and significant side effects are often observed, including facial flushing, loss of glucose tolerance, and liver toxicity. An anthranilic acid was identified as an agonist of the niacin receptor. In order to improve efficacy and provide structural diversity, replacements for the anthranilic acid were investigated and several compounds with improved properties were identified.
Assuntos
Niacina/metabolismo , Receptores de Droga/metabolismo , ortoaminobenzoatos/química , Disponibilidade BiológicaRESUMO
Multiprotein complexes are key determinants of Golgi apparatus structure and its capacity for intracellular transport and glycoprotein modification. Three complexes that have previously been partially characterized include (a) the Golgi transport complex (GTC), identified in an in vitro membrane transport assay, (b) the ldlCp complex, identified in analyses of CHO cell mutants with defects in Golgi-associated glycosylation reactions, and (c) the mammalian Sec34 complex, identified by homology to yeast Sec34p, implicated in vesicular transport. We show that these three complexes are identical and rename them the conserved oligomeric Golgi (COG) complex. The COG complex comprises four previously characterized proteins (Cog1/ldlBp, Cog2/ldlCp, Cog3/Sec34, and Cog5/GTC-90), three homologues of yeast Sec34/35 complex subunits (Cog4, -6, and -8), and a previously unidentified Golgi-associated protein (Cog7). EM of ldlB and ldlC mutants established that COG is required for normal Golgi morphology. "Deep etch" EM of purified COG revealed an approximately 37-nm-long structure comprised of two similarly sized globular domains connected by smaller extensions. Consideration of biochemical and genetic data for mammalian COG and its yeast homologue suggests a model for the subunit distribution within this complex, which plays critical roles in Golgi structure and function.
Assuntos
Proteínas Adaptadoras de Transporte Vesicular , Complexo de Golgi/fisiologia , Proteínas/fisiologia , Animais , Proteínas de Transporte/genética , Proteínas de Transporte/fisiologia , Linhagem Celular , Clonagem Molecular , Sequência Conservada , Humanos , Substâncias Macromoleculares , Proteínas de Membrana/fisiologia , Complexos Multiproteicos , Mutação , Conformação Proteica , Subunidades Proteicas , Proteínas/química , Proteínas/genética , Proteínas/isolamento & purificação , Ratos , Proteínas de Saccharomyces cerevisiaeRESUMO
Heavy exercise or oxygen deficit often links with higher levels of arterial lactate and lower levels of plasma free fatty acids (FFA). Treatment with lactate reduces circulating levels of FFA in vivo and lipolysis in adipose tissues in vitro. However, the underlying mechanism has remained unclear. Here we employ pharmacological and genetic approaches to show that GPR81, an orphan G-protein-coupled receptor with relatively restricted expression in the adipose tissues, functions as a receptor for lactate and can mediate an anti-lipolytic effect of lactate. GPR81 may thus function as a sensor of lactate that can modulate the FFA pool under exercise or conditions of oxygen deficit.
Assuntos
Tecido Adiposo/metabolismo , Ácidos Graxos não Esterificados/metabolismo , Ácido Láctico/metabolismo , Lipólise , Receptores Acoplados a Proteínas G/fisiologia , Tecido Adiposo/efeitos dos fármacos , Animais , Células CHO , Cricetinae , Cricetulus , Humanos , Ácido Láctico/farmacologia , Ligantes , Lipólise/efeitos dos fármacos , Lipólise/genética , Camundongos , Receptores Acoplados a Proteínas G/agonistas , Receptores Acoplados a Proteínas G/genética , Receptores Nicotínicos/genética , Receptores Nicotínicos/fisiologia , TransfecçãoRESUMO
Pyrazolopyrimidines were discovered as the first class of allosteric agonists for the high affinity nicotinic acid receptor GPR109A. In addition to its intrinsic activity, compound 9n significantly enhances nicotinic acid binding to the receptor, thereby potentiating the functional efficacy of nicotinic acid.
Assuntos
Agonistas Nicotínicos/síntese química , Agonistas Nicotínicos/farmacologia , Pirazóis/síntese química , Pirazóis/farmacologia , Pirimidinas/síntese química , Pirimidinas/farmacologia , Receptores Acoplados a Proteínas G/agonistas , Sítios de Ligação , Técnicas de Química Combinatória , Humanos , Estrutura Molecular , Niacina/metabolismo , Agonistas Nicotínicos/química , Pirazóis/química , Pirimidinas/química , Receptores Nicotínicos , Relação Estrutura-AtividadeRESUMO
A homology model of the nicotinic acid receptor GPR109A was constructed based on the X-ray crystal structure of bovine rhodopsin. An HTS hit was docked into the homology model. Characterization of the binding pocket by a grid-based surface calculation of the docking model suggested that a larger hydrophobic body plus a polar tail would improve interaction between the ligand and the receptor. The designed compounds were synthesized, and showed significantly improved binding affinity and activation of GPR109A.
Assuntos
Modelos Moleculares , Agonistas Nicotínicos/síntese química , Agonistas Nicotínicos/farmacologia , Receptores Acoplados a Proteínas G/agonistas , ortoaminobenzoatos/síntese química , ortoaminobenzoatos/farmacologia , Sítios de Ligação , Técnicas de Química Combinatória , Humanos , Estrutura Molecular , Niacina/metabolismo , Agonistas Nicotínicos/química , Receptores Nicotínicos , Relação Estrutura-Atividade , ortoaminobenzoatos/químicaRESUMO
The design, synthesis, and biological activity of a series of cycloalkene acid-based niacin receptor agonists are described. This led to the discovery that tetrahydro anthranilic acid is an excellent surrogate for anthranilic acid. Several compounds were identified that were potent against the niacin receptor, had enhanced cytochrome P450 selectivity against subtypes CYP2C8 and CYP2C9, and improved oral exposure in mice.
Assuntos
Cicloexenos/síntese química , Cicloexenos/farmacologia , Ciclopentanos/síntese química , Ciclopentanos/farmacologia , Sistema Enzimático do Citocromo P-450/metabolismo , Agonistas Nicotínicos/síntese química , Agonistas Nicotínicos/farmacologia , ortoaminobenzoatos/síntese química , ortoaminobenzoatos/farmacologia , Animais , Hidrocarboneto de Aril Hidroxilases/efeitos dos fármacos , Cicloexenos/química , Cicloexenos/farmacocinética , Ciclopentanos/química , Ciclopentanos/farmacocinética , Citocromo P-450 CYP2C8 , Citocromo P-450 CYP2C9 , Desenho de Fármacos , Humanos , Camundongos , Agonistas Nicotínicos/química , Antagonistas Nicotínicos/farmacologia , ortoaminobenzoatos/química , ortoaminobenzoatos/farmacocinéticaRESUMO
The "Dsl1p complex" in Saccharomyces cerevisiae, consisting of Dsl1p and Tip20p, is involved in Golgi-ER retrograde transport and it is functionally conserved from yeast to mammalian cells. To further characterize this complex, we analyzed the function of Dsl3p, a protein that interacts with Dsl1p in yeast two hybrids screens. DSL3, recently identified in a genome wide analysis of essential genes as SEC39, encodes a cytosolic protein of 82 kDa that is peripherally associated with membranes derived from the ER. There is strong genetic interaction between DSL3 and other factors required for Golgi-ER retrograde transport. Size exclusion chromatography and affinity purification approaches confirmed that Dsl3p is associated with subunits of the "Dsl1p complex." The complex also includes the Q/t-SNARE proteins, Use1p, Sec20p, and Ufe1p, integral membrane proteins that constitute the trimeric acceptor for R/v-SNAREs on Golgi-derived vesicles at the ER. Using mutants, we performed a detailed analysis of interactions between subunits of the Dsl1p complex and the ER-localized SNARE proteins. This analysis showed that both Dsl1p and Dsl3p are required for the stable interaction of the SNARE Use1p with a central subcomplex consisting of Tip20p and the SNARE proteins Ufe1p and Sec20p.
Assuntos
Proteínas de Transporte/fisiologia , Glicoproteínas/fisiologia , Proteínas de Membrana/fisiologia , Proteínas de Saccharomyces cerevisiae/fisiologia , Saccharomyces cerevisiae/metabolismo , Retículo Endoplasmático/fisiologia , Proteínas de Membrana/genética , Mutação , Reação em Cadeia da Polimerase , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/isolamento & purificação , Proteínas de Transporte VesicularRESUMO
Biaryl anthranilides are reported as potent and selective full agonists for the high affinity niacin receptor GPR109A. The SAR presented outlines approaches to reduce serum shift and both CYPCYP2C8 and CYP2C9 liabilities, while improving PK and maintaining excellent receptor activity. Compound 2i exhibited good in vivo antilipolytic efficacy while providing a significantly improved therapeutic index over vasodilation (flushing) with respect to niacin in the mouse model.
Assuntos
Receptores Acoplados a Proteínas G/agonistas , ortoaminobenzoatos/síntese química , Amidas/síntese química , Amidas/farmacocinética , Amidas/farmacologia , Animais , Hidrocarboneto de Aril Hidroxilases/antagonistas & inibidores , Ligação Competitiva , Células CHO , Cricetinae , Cricetulus , Citocromo P-450 CYP2C8 , Citocromo P-450 CYP2C9 , Humanos , Técnicas In Vitro , Camundongos , Microssomos Hepáticos/metabolismo , Ensaio Radioligante , Receptores Nicotínicos , Relação Estrutura-Atividade , ortoaminobenzoatos/farmacocinética , ortoaminobenzoatos/farmacologiaRESUMO
INTRODUCTION: GPR109A is the receptor mediating both the antilipolytic and vasodilatory effects of nicotinic acid. In order to develop agonists for GPR109A with improved therapeutic indices we have sought to optimize animal models that evaluate both nicotinic acid-mediated inhibition of lipolysis and stimulation of vasodilatation. The rat and the dog have previously been used to study the antilipolytic effects of nicotinic acid, but no optimal vasodilatation model exits in either species. METHODS: We have developed a vasodilatation model in the rat that measures changes in ear perfusion using laser Doppler flowmetry. In the dog, we have developed a model of vasodilatation measuring changes in red color values in the ear, using a spectrocolorimeter. Effects of GPR109A agonists on lipolysis were measured in both species after oral dosing of compounds, and measuring plasma levels of free fatty acids. RESULTS: In both rat and dog, GPR109A agonists induce dose- and time-dependent vasodilatation, similar to that observed in humans. Vasodilatation is inhibited in both species with cyclooxygenase inhibitors or a specific DP1 receptor antagonist, indicating that, as in man, nicotinic acid-induced vasodilatation in rats and dogs is mainly mediated by the release of PGD(2). DISCUSSION: Our results show that both rat and dog are useful models for the characterization of GPR109A agonists. A therapeutic index for GPR109A agonists can be calculated in either species.
Assuntos
Lipólise/efeitos dos fármacos , Agonistas Nicotínicos/farmacologia , Receptores Acoplados a Proteínas G/agonistas , Vasodilatação/efeitos dos fármacos , Animais , Anti-Inflamatórios não Esteroides/administração & dosagem , Anti-Inflamatórios não Esteroides/farmacologia , Cães , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos/métodos , Monitoramento de Medicamentos/métodos , Ácidos Graxos não Esterificados/sangue , Hipolipemiantes/administração & dosagem , Hipolipemiantes/farmacologia , Indometacina/administração & dosagem , Indometacina/farmacologia , Concentração Inibidora 50 , Injeções Subcutâneas , Masculino , Modelos Animais , Niacina/administração & dosagem , Niacina/farmacologia , Agonistas Nicotínicos/administração & dosagem , Pirazinas/administração & dosagem , Pirazinas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores Nicotínicos/metabolismoRESUMO
A urea class of high affinity niacin receptor agonists was discovered. Compound 1a displayed good PK, better in vivo efficacy in reducing FFA in mouse than niacin, and no vasodilation in a mouse model. Compound 1q demonstrated equal affinity to GPR109A as niacin.
Assuntos
Niacina/farmacologia , Receptores Acoplados a Proteínas G/agonistas , Ureia , Animais , Técnicas de Química Combinatória , Humanos , Masculino , Camundongos , Modelos Animais , Estrutura Molecular , Receptores Nicotínicos , Relação Estrutura-Atividade , Ureia/análogos & derivados , Ureia/síntese química , Ureia/química , Ureia/farmacocinética , Vasodilatação/efeitos dos fármacosRESUMO
Diabetes mellitus is one of the major risk factors associated with atherosclerosis and coronary heart disease but the mechanistic links between the disease and atherosclerosis are not well understood. In this study, we investigated the effect of the deletion of the long-form leptin receptor on the progression of atherosclerosis in ApoE-/- mouse. ApoE-/-;db/db double knockout mice as well as ApoE-/-;db/+ and ApoE-/- littermates were generated by crossing ApoE-/- and db/+ mice. On a regular chow diet, ApoE-/-;db/db mice at 20 weeks of age exhibited features typical of type 2 diabetes: obesity, hyperglycemia, hyperinsulinemia and dyslipidemia and had significantly accelerated atherosclerosis compared with their age-matched ApoE-/- littermates as assessed by either the percentage of the aorta bearing lesion (5.3+/-0.9% for ApoE-/-;db/db versus 1.5+/-0.5% for ApoE-/-) or by aortic lipid content ( approximately 1.5-2-fold increase in free cholesterol and approximately 3-4-fold increase in cholesteryl ester). The atherosclerosis in these ApoE-/-;db/db mice was further accelerated by feeding mice with a Western diet and markedly inhibited by fenofibrate with a 2.5- and 5.3-fold reduction of the lesion in male and female mice, respectively. The results from this study demonstrate that type 2 diabetes can accelerate atherogenesis in mice. This mouse model may provide insight into the mechanistic link between type 2 diabetes and atherosclerosis as well as serve as a valuable tool for evaluating therapeutics.
Assuntos
Apolipoproteínas E/genética , Aterosclerose/genética , Modelos Animais de Doenças , Hipercolesterolemia/genética , Camundongos Knockout , Receptores de Superfície Celular/genética , Animais , Aterosclerose/patologia , Aterosclerose/fisiopatologia , Colesterol/sangue , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/fisiopatologia , Angiopatias Diabéticas/genética , Angiopatias Diabéticas/patologia , Angiopatias Diabéticas/fisiopatologia , Feminino , Fenofibrato/farmacologia , Hipercolesterolemia/tratamento farmacológico , Hipercolesterolemia/fisiopatologia , Hipolipemiantes/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Receptores para Leptina , Índice de Gravidade de DoençaRESUMO
G-protein coupled receptor (GPCR) GPR109a is a molecular target for nicotinic acid and is expressed in adipocytes, spleen, and immune cells. Nicotinic acid has long been used for the treatment of dyslipidemia due to its capacity to positively affect serum lipids to a greater extent than other currently marketed drugs. We report a series of tricyclic pyrazole carboxylic acids that are potent and selective agonists of GPR109a. Compound R,R-19a (MK-1903) was advanced through preclinical studies, was well tolerated, and presented no apparent safety concerns. Compound R,R-19a was advanced into a phase 1 clinical trial and produced a robust decrease in plasma free fatty acids. On the basis of these results, R,R-19a was evaluated in a phase 2 study in humans. Because R,R-19a produced only a weak effect on serum lipids as compared with niacin, we conclude that the beneficial effects of niacin are most likely the result of an undefined GPR109a independent pathway.
Assuntos
Ácidos Graxos não Esterificados/sangue , Pirazóis/uso terapêutico , Receptores Acoplados a Proteínas G/agonistas , Animais , Humanos , Hipolipemiantes/farmacocinética , Hipolipemiantes/uso terapêutico , Masculino , Niacina/farmacologia , Pirazóis/síntese química , Pirazóis/farmacocinética , Ratos , Receptores Acoplados a Proteínas G/efeitos dos fármacos , Receptores Nicotínicos/efeitos dos fármacos , Estereoisomerismo , Vasodilatadores/farmacologiaRESUMO
Nicotinic acid (niacin) induces beneficial changes in serum lipoproteins and has been associated with beneficial cardiovascular effects. Niacin reduces low-density lipoprotein, increases high-density lipoprotein, and decreases triglycerides. It is well established that activation of the seven-transmembrane G(i)-coupled receptor GPR109A on Langerhans cells results in release of prostaglandin D2, which mediates the well-known flushing side effect of niacin. Niacin activation of GPR109A on adipocytes also mediates the transient reduction of plasma free fatty acid (FFA) levels characteristic of niacin, which has been long hypothesized to be the mechanism underlying the changes in the serum lipid profile. We tested this "FFA hypothesis" and the hypothesis that niacin lipid efficacy is mediated via GPR109A by dosing mice lacking GPR109A with niacin and testing two novel, full GPR109A agonists, MK-1903 and SCH900271, in three human clinical trials. In mice, the absence of GPR109A had no effect on niacin's lipid efficacy despite complete abrogation of the anti-lipolytic effect. Both MK-1903 and SCH900271 lowered FFAs acutely in humans; however, neither had the expected effects on serum lipids. Chronic FFA suppression was not sustainable via GPR109A agonism with niacin, MK-1903, or SCH900271. We conclude that the GPR109A receptor does not mediate niacin's lipid efficacy, challenging the long-standing FFA hypothesis.
Assuntos
Ácidos Graxos/metabolismo , Niacina/farmacologia , Receptores Acoplados a Proteínas G/metabolismo , Receptores Nicotínicos/metabolismo , Animais , Relação Dose-Resposta a Droga , Ácidos Graxos/sangue , Humanos , Lipólise/efeitos dos fármacos , Lipoproteínas/sangue , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Niacina/administração & dosagem , Pirazóis/farmacologia , Receptores Acoplados a Proteínas G/agonistasRESUMO
Hydrogen sulfide (H(2)S) is a recently discovered gasotransmitter found in mammalian tissues and blood. Treatment with H(2)S donor molecules has shown promising results in preclinical models of inflammatory and cardiovascular diseases. Augmentation of H(2)S levels thus holds promise as a novel therapeutic approach for treatment of disease in man. Cystathionine ß-synthase (CBS) has been shown to catalyze H(2)S production in vitro. CBS enzyme activity is allosterically regulated by the endogenous activator S-adenosyl methionine. This mode of regulation suggests the possibility for designing a small molecule activator of CBS to enhance H(2)S production. This hypothesis, however, has not been directly tested in vivo. We show here that CBS contributes significantly to endogenous H(2)S production in mice: adenovirus mediated over expression of CBS in the liver significantly increased circulating levels of H(2)S, whereas CBS deficiency resulted in reduced levels. We demonstrate that CBS enzyme from endogenous sources can be activated by S-adenosyl methionine to a greater extent compared to recombinant enzyme, suggesting greater potential for activation than previously anticipated. Importantly, we show that circulating H(2)S levels are increased by pharmacological activation of CBS in vivo; i.e. in the presence of the endogenous activator. Together, our data demonstrate that CBS activity partially regulates endogenous H(2)S in mice, and suggest that pharmacological activation of CBS is a promising approach for enhancing endogenous production of H(2)S for the treatment of cardiovascular and other diseases.