ABSTRACT
Leucine is an essential branched-chain amino acid that acts as a substrate for protein synthesis and as a signaling molecule. Leucine not incorporated into muscle protein is ultimately oxidized through intermediates such as ß-hydroxy-ß-methylbutyrate (HMB) which itself is reported to enhance muscle mass and function in rats and humans. HMB has been reported in the plasma following oral leucine administration in sheep and pigs but not in Sprague-Dawley rats, the standard preclinical model. Therefore, we conducted radiolabeled absorption, distribution, metabolism and excretion (ADME) studies in rats using a low (3 mg/kg) or high dose (1,000 mg/kg) of (14)C-leucine. Blood, tissue, and urine samples were analyzed for (14)C-leucine and its metabolites by HPLC-MS. Our results show for the first time that (14)C-HMB appears in plasma and urine of rats following an oral dose of (14)C-leucine. (14)C-leucine appears in plasma as (14)C-α-ketoisocaproic acid (KIC) with a slower time course than (14)C-HMB, a putative product of KIC. Further, two novel metabolites of leucine were detected in urine, N-acetyl leucine and glycyl leucine. Mass balance studies demonstrate that excretory routes accounted for no more than 0.9 % of the radiolabel and approximately 61 % of the dose was recovered in the carcass. Approximately 65 % of the dose was recovered in total, suggesting that approximately one-third of the leucine dose is oxidized to CO2. In conclusion, this study demonstrates endogenous production of HMB from leucine in adult rats, a standard preclinical model used to guide design of clinical trials in nutrition.
Subject(s)
Dipeptides/urine , Keto Acids/blood , Leucine/analogs & derivatives , Leucine/pharmacokinetics , Valerates/blood , Animals , Biological Transport , Carbon Radioisotopes , Chromatography, High Pressure Liquid , Dipeptides/blood , Intestinal Absorption/physiology , Keto Acids/urine , Leucine/blood , Leucine/urine , Male , Mass Spectrometry , Oxidation-Reduction , Rats , Rats, Sprague-Dawley , Valerates/urineABSTRACT
A series of potent 2-carboxychromone-based melanin-concentrating hormone receptor 1 (MCHr1) antagonists were synthesized and evaluated for hERG (human Ether-a-go-go Related Gene) channel affinity and functional blockade. Basic dialkylamine-terminated analogs were found to weakly bind the hERG channel and provided marked improvement in a functional patch-clamp assay versus previously reported antagonists of the series.
Subject(s)
Amides/pharmacology , Chromones/pharmacology , Ether-A-Go-Go Potassium Channels/metabolism , Receptors, Pituitary Hormone/antagonists & inhibitors , Animals , Ether-A-Go-Go Potassium Channels/drug effects , Humans , Inhibitory Concentration 50 , Mice , Obesity/drug therapy , Patch-Clamp Techniques , PharmacokineticsABSTRACT
The incorporation of constrained tertiary amines into an existing class of N-benzyl-4-aminopiperidinyl chromone-based MCHr1 antagonists led to the identification of a series of chiral racemic compounds that displayed good to excellent functional potency, binding affinity, and selectivity over the hERG channel. Further separation of two distinct chiral racemic compounds into their corresponding pairs of enantiomers revealed a considerable selectivity for MCHr1 for one configuration, in addition to a striking difference in oral exposure between one pair of enantiomers in diet-induced obese mice. Oral administration of the most potent compound in this class in the same animal model led to significant reduction of fat mass in a semi-chronic model for weight loss.
Subject(s)
Chromones/chemical synthesis , Chromones/pharmacology , Piperidines/chemical synthesis , Piperidines/pharmacology , Receptors, Somatostatin/antagonists & inhibitors , Animals , Anti-Obesity Agents/chemical synthesis , Anti-Obesity Agents/pharmacology , Appetite Depressants/pharmacology , Body Weight/drug effects , Brain/metabolism , Cell Line , Diet , Dietary Fats , Ether-A-Go-Go Potassium Channels/drug effects , Fenfluramine/pharmacology , Indicators and Reagents , Mice , Molecular Conformation , Potassium Channel Blockers/chemical synthesis , Potassium Channel Blockers/pharmacology , Structure-Activity RelationshipABSTRACT
Evaluation of multiple structurally distinct series of melanin concentrating hormone receptor 1 antagonists in an anesthetized rat cardiovascualar assay led to the identification of a chromone-2-carboxamide series as having excellent safety against the chosen cardiovascular endpoints at high drug concentrations in the plasma and brain. Optimization of this series led to considerable improvements in affinity, functional potency, and pharmacokinetic profile. This led to the identification of a 7-fluorochromone-2-carboxamide (22) that was orally efficacious in a diet-induced obese mouse model, retained a favorable cardiovascular profile in rat, and demonstrated dramatic improvement in effects on mean arterial pressure in our dog cardiovascular model compared to other series reported by our group. However, this analogue also led to prolongation of the QT interval in the dog that was linked to affinity for hERG channel and unexpectedly potent functional blockade of this ion channel.
Subject(s)
Benzodioxoles/pharmacology , Cardiovascular Diseases/chemically induced , Chromones/pharmacology , Receptors, Somatostatin/antagonists & inhibitors , Acylation , Animals , Area Under Curve , Benzodioxoles/pharmacokinetics , Benzodioxoles/toxicity , Blood Pressure/drug effects , Body Weight/drug effects , Calcium/metabolism , Cell Line , Chromones/pharmacokinetics , Chromones/toxicity , Dogs , Electrocardiography/drug effects , Female , Half-Life , Heart Rate/drug effects , Indicators and Reagents , Mice , Mice, Inbred C57BL , Potassium Channels/drug effects , Potassium Channels/metabolism , Rats , Rats, Sprague-Dawley , Structure-Activity RelationshipABSTRACT
A series of metabolically stable butyrolactam 11beta-HSD1 inhibitors have been synthesized and biologically evaluated. These compounds exhibit excellent HSD1 potency and HSD2 selectivity, pharmacokinetic, and pharmacodynamic profiles.
Subject(s)
11-beta-Hydroxysteroid Dehydrogenase Type 1/antagonists & inhibitors , Lactams/pharmacology , Administration, Oral , Animals , Humans , Lactams/administration & dosage , Lactams/chemical synthesis , Lactams/pharmacokinetics , Metabolic Syndrome/drug therapy , MiceABSTRACT
The discovery and pharmacological evaluation of potent, selective, and orally bioavailable growth hormone secretagogue receptor (GHS-R) antagonists are reported. Previously, 2,4-diaminopyrimidine-based GHS-R antagonists reported from our laboratories have been shown to be dihydrofolate reductase (DHFR) inhibitors. By comparing the X-ray crystal structure of DHFR docked with our GHS-R antagonists and GHS-R modeling, we designed and synthesized a series of potent and DHFR selective GHS-R antagonists with good pharmacokinetic (PK) profiles. An amide derivative 13d (Ca2+ flux IC50 = 188 nM, [brain]/[plasma] = 0.97 @ 8 h in rat) showed a 10% decrease in 24 h food intake in rats, and over 5% body weight reduction after 14-day oral treatment in diet-induced obese (DIO) mice. In comparison, a urea derivative 14c (Ca2+ flux IC50 = 7 nM, [brain]/[plasma] = 0.0 in DIO) failed to show significant effect on food intake in the acute feeding DIO model. These observations demonstrated for the first time that peripheral GHS-R blockage with small molecule GHS-R antagonists might not be sufficient for suppressing appetite and inducing body weight reduction.
Subject(s)
Aminopyridines/chemical synthesis , Anti-Obesity Agents/chemical synthesis , Receptors, G-Protein-Coupled/antagonists & inhibitors , Administration, Oral , Amides/chemical synthesis , Amides/pharmacology , Aminopyridines/pharmacology , Animals , Anti-Obesity Agents/pharmacology , Appetite Depressants/chemical synthesis , Appetite Depressants/pharmacology , Biological Availability , Body Weight/drug effects , Cell Line , Crystallography, X-Ray , Eating/drug effects , Humans , Male , Mice , Mice, Inbred C57BL , Mice, Obese , Models, Molecular , Molecular Structure , Rats , Rats, Sprague-Dawley , Receptors, Ghrelin , Structure-Activity Relationship , Urea/analogs & derivatives , Urea/chemical synthesis , Urea/pharmacologyABSTRACT
Dexfenfluramine (DEX) and sibutramine (SIB) are effective antiobesity agents. Their effects on weight control and hormone profile have not been previously studied in diet-switched diet-induced obese (DIO) mice, in which treatment is initiated upon cessation of a low-fat diet and resumption of a high-fat diet. Furthermore, their effects on circulating ghrelin in obese humans or in animal models of obesity have not yet been reported. Male C57Bl/6J DIO mice after 16 wk on a high-fat diet (HF, 60 kcal% fat) were switched to a low-fat diet (LF, 10 kcal% fat) for 50 d. HF diet resumed concurrently with treatment for 28 d with DEX 3 and 10 mg/kg, twice a day (BID); SIB 5 mg/kg BID; or vehicle. Rapid weight regain ensued in vehicle-treated DIO mice. DEX or SIB treatment significantly blunted the body weight gain. Caloric intake was decreased acutely by DEX or SIB vs vehicle during the first 2 d treatment, but returned to control after 5 d. At the end of study, epididymal fat weight and whole body fat mass determined by DEXA scan were decreased by DEX 10 mg/kg, and whole body lean mass decreased with DEX 3 mg/kg treatment. Circulating ghrelin on d 28 was increased with either DEX 3 or 10 mg/kg treatment, while growth hormone and insulin were decreased. Leptin was also decreased in the DEX 10 mg/kg group. SIB did not significantly affect fat mass, ghrelin, growth hormone, insulin, or leptin. Mice chronically fed LF diet maintained a lower caloric intake, gained less weight and fat mass than diet-switched mice, and had higher ghrelin and lower insulin and leptin. In summary, weight regain in diet-switched DIO mice is delayed with either DEX or SIB treatment. DEX treatment of diet-switched DIO mice decreased growth hormone, insulin, leptin, fat mass, lean mass, and increased ghrelin, while SIB only decreased body weight.
Subject(s)
Anti-Obesity Agents/pharmacology , Cyclobutanes/pharmacology , Dexfenfluramine/pharmacology , Obesity/drug therapy , Animals , Body Weight/drug effects , Diet, Fat-Restricted , Ghrelin , Growth Hormone/blood , Male , Mice , Obesity/etiology , Obesity/prevention & control , Peptide Hormones/blood , Thinness/blood , Weight Gain/drug effectsABSTRACT
Ghrelin, a gut-derived orexigenic hormone, is an endogenous ligand of the growth hormone secretagogue receptor (GHS-R). Centrally administered ghrelin has been shown to cause hunger and increase food intake in rodents. Inhibition of ghrelin actions with ghrelin antibody, peptidyl GHS-R antagonists, and antisense oligonucleosides resulted in weight loss and food intake decrease in rodents. Here we report the effects of GHS-R antagonists, some of which were potent, selective, and orally bioavailable. A structure-activity relationship study led to the discovery of 8a, which was effective in decreasing food intake and body weight in several acute rat studies.
Subject(s)
Pyrimidines/pharmacology , Receptors, G-Protein-Coupled/antagonists & inhibitors , Animals , CHO Cells , Cricetinae , Drug Evaluation, Preclinical , Humans , Ligands , Molecular Structure , Pyrimidines/chemical synthesis , Pyrimidines/chemistry , Receptors, Ghrelin , Stereoisomerism , Structure-Activity Relationship , Time FactorsABSTRACT
The synthesis and biological evaluation of novel 3-amino indazole melanin concentrating hormone receptor-1 antagonists are reported, several of which demonstrated functional activity of less than 100nM. Compounds 19 and 28, two of the more potent compounds identified in this study, were characterized by high exposure in the brain and demonstrated robust efficacy when dosed in diet-induced obese mice.
Subject(s)
Anti-Obesity Agents/chemical synthesis , Anti-Obesity Agents/pharmacology , Indazoles/chemical synthesis , Indazoles/pharmacology , Receptors, Somatostatin/antagonists & inhibitors , Administration, Oral , Animals , Anti-Obesity Agents/administration & dosage , Humans , Indazoles/administration & dosage , Mice , Piperidines/chemistry , Tissue DistributionABSTRACT
4-(1-Benzo[1,3]dioxol-5-ylmethylpiperidine-4-ylmethyl)-6-chlorochromen-2-one (7) is a potent, orally bioavailable melanin concentrating hormone receptor 1 (MCHr1) antagonist that causes dose-dependent weight loss in diet-induced obese mice. Further evaluation of 7 in an anesthetized dog model of cardiovascular safety revealed adverse hemodynamic effects at a plasma concentration comparable to the minimally effective therapeutic concentration. These results highlight the need for scrutiny of the cardiovascular safety profile of MCHr1 antagonists.
Subject(s)
Coumarins/chemical synthesis , Piperidines/chemical synthesis , Receptors, Pituitary Hormone/antagonists & inhibitors , Receptors, Somatostatin/antagonists & inhibitors , Administration, Oral , Animals , Anti-Obesity Agents/adverse effects , Anti-Obesity Agents/chemical synthesis , Anti-Obesity Agents/pharmacology , Biological Availability , Blood Pressure/drug effects , Brain/metabolism , Cell Line, Tumor , Coumarins/adverse effects , Coumarins/pharmacology , Dogs , Eating/drug effects , Energy Metabolism , Humans , Male , Mice , Mice, Obese , Myocardial Contraction/drug effects , Piperidines/adverse effects , Piperidines/pharmacology , Radioligand Assay , Structure-Activity RelationshipABSTRACT
Several potent and efficacious MCHr1 antagonists containing an ortho-amino benzamide or nicotinamide chemotype have been identified, exemplified by 28 and 50.
Subject(s)
Niacinamide/analogs & derivatives , Receptors, Somatostatin/antagonists & inhibitors , ortho-Aminobenzoates/chemical synthesis , Animals , Benzamides/chemical synthesis , Benzamides/pharmacokinetics , Benzamides/pharmacology , Inhibitory Concentration 50 , Mice , Mice, Inbred Strains , Niacinamide/pharmacokinetics , Niacinamide/pharmacology , Pharmacokinetics , Receptors, Somatostatin/agonists , Structure-Activity Relationship , Tissue Distribution , ortho-Aminobenzoates/pharmacokinetics , ortho-Aminobenzoates/pharmacologyABSTRACT
A series of urea-based N-1-(2-aminoethyl)-indazoles was synthesized and evaluated for melanin-concentrating hormone receptor 1 (MCHr1) antagonism in both binding and functional assays. Several compounds that acted as MCHr1 antagonists were identified, and optimization afforded a compound with excellent binding affinity, good functional potency, and oral efficacy in a chronic model for weight loss in diet-induced obese mice.
Subject(s)
Indazoles/chemical synthesis , Indazoles/pharmacology , Obesity/drug therapy , Receptors, Somatostatin/antagonists & inhibitors , Urea/chemistry , Animals , Indazoles/chemistry , Indazoles/therapeutic use , Mice , Structure-Activity RelationshipABSTRACT
Optimization of a high-throughput screening hit against melanin-concentrating hormone receptor 1 (MCHr1) led to the discovery of 2-(4-benzyloxy-phenyl)-N-[1-(2-pyrrolidin-1-yl-ethyl)-1H-indazol-6-yl]acetamide (7a). This compound was found to be a high-affinity ligand for MCHr1 and a potent inhibitor of MCH-mediated Ca(2+) release, showed good plasma and CNS exposure upon oral dosing in diet-induced obese mice, and is the first reported MCHr1 antagonist that is efficacious upon oral dosing in a chronic model of weight loss.
Subject(s)
Acetamides/chemical synthesis , Anti-Obesity Agents/chemical synthesis , Indazoles/chemical synthesis , Obesity/drug therapy , Pyrrolidines/chemical synthesis , Receptors, Somatostatin/antagonists & inhibitors , Acetamides/pharmacokinetics , Acetamides/pharmacology , Administration, Oral , Animals , Anti-Obesity Agents/pharmacokinetics , Anti-Obesity Agents/pharmacology , Binding, Competitive , Brain/metabolism , Calcium/metabolism , Chronic Disease , Indazoles/pharmacokinetics , Indazoles/pharmacology , Mice , Pyrrolidines/pharmacokinetics , Pyrrolidines/pharmacology , Radioligand Assay , Structure-Activity Relationship , Tissue DistributionABSTRACT
Histamine affects homeostatic mechanisms, including food and water consumption, by acting on central nervous system (CNS) receptors. Presynaptic histamine H(3) receptors regulate release of histamine and other neurotransmitters, and histamine H(3) receptor antagonists enhance neurotransmitter release. A-331440 [4'-[3-(3(R)-(dimethylamino)-pyrrolidin-1-yl)-propoxy]-biphenyl-4-carbonitrile] is a histamine H(3) receptor antagonist which binds potently and selectively to both human and rat histamine H(3) receptors (K(i)<==25 nM). Mice were stabilized on a high-fat diet (45 kcal % lard) prior to 28-day oral b.i.d. dosing for measurement of obesity-related parameters. A-331440 administered at 0.5 mg/kg had no significant effect on weight, whereas 5 mg/kg decreased weight comparably to dexfenfluramine (10 mg/kg). A-331440 administered at 15 mg/kg reduced weight to a level comparable to mice on the low-fat diet. The two higher doses reduced body fat and the highest dose also normalized an insulin tolerance test. These data show that the histamine H(3) receptor antagonist, A-331440, has potential as an antiobesity agent.