Discovery of trans-N-[1-(2-fluorophenyl)-3-pyrazolyl]-3-oxospiro[6-azaisobenzofuran-1(3H),1'-cyclohexane]-4'-carboxamide, a potent and orally active neuropeptide Y Y5 receptor antagonist.

A series of trans-3-oxospiro[(aza)isobenzofuran-1(3H),1'-cyclohexane]-4'-carboxamide derivatives were synthesized to identify potent NPY Y5 receptor antagonists. Of the compounds, 21j showed high Y5 binding affinity, metabolic stability and brain and cerebrospinal fluid (CSF) penetration, and low susceptibility to P-glycoprotein transporters. Oral administration of 21j significantly inhibited the Y5 agonist-induced food intake in rats with a minimum effective dose of 1mg/kg. This compound was selected for proof-of-concept studies in human clinical trials.

Comparison of independent and combined chronic anti-obese effects of NPY Y2 receptor agonist, PYY(3-36), and NPY Y5 receptor antagonist in diet-induced obese mice.

Neuropeptide Y (NPY) and its family of peptides are thought to have a major role in the physiological control of energy homeostasis. Among five NPY receptors described, stimulation of the Y2 receptor (Y2R) or inhibition of the Y5 receptor (Y5R) has recently been shown to produce weight-lowering effects in obese rodents. The present study examined and compared the effects of a Y2R agonist, PYY(3-36), and a Y5R antagonist, alone and in combination, on food intake and body weight in diet-induced obese (DIO) mice. Acute intraperitoneal injection of PYY(3-36) dose-dependently reduced spontaneous feeding in lean and DIO mice. In contrast, acute oral administration of the Y5R antagonist had no effect on spontaneous feeding or the anorexigenic effects of PYY(3-36). In a chronic study, subcutaneous infusion of PYY(3-36) (1 mg/kg/day for 14 days) significantly reduced food intake and body weight in DIO mice. The Y5R antagonist (10 mg/kg/day for 14 days, orally) reduced body weight to the same extent as PYY(3-36) without a significant feeding reduction. Combined administration of PYY(3-36) and the Y5R antagonist resulted in a greater body weight reduction than treatment with either agent alone. The combined effects on food intake, body weight, and adiposity are almost the same as a hypothetical sum of the effects of each drug alone. These results illustrate that the combination of a Y2R agonist, PYY(3-36), and a Y5R antagonist resulted in additive effects on body weight and adiposity in DIO mice, suggesting that Y2R stimulation signal and Y5R blockade signal act by distinct pathways.

Hepatic de novo lipogenesis is present in liver-specific ACC1-deficient mice.

Acetyl coenzyme A (acetyl-CoA) carboxylase (ACC) catalyzes carboxylation of acetyl-CoA to form malonyl-CoA. In mammals, two isozymes exist with distinct physiological roles: cytosolic ACC1 participates in de novo lipogenesis (DNL), and mitochondrial ACC2 is involved in negative regulation of mitochondrial beta-oxidation. Since systemic ACC1 null mice were embryonic lethal, to clarify the physiological role of ACC1 in hepatic DNL, we generated the liver-specific ACC1 null mouse by crossbreeding of an Acc1(lox(ex46)) mouse, in which exon 46 of Acc1 was flanked by two loxP sequences and the liver-specific Cre transgenic mouse. In liver-specific ACC1 null mice, neither hepatic Acc1 mRNA nor protein was detected. However, to compensate for ACC1 function, hepatic ACC2 protein and activity were induced 1.4 and 2.2 times, respectively. Surprisingly, hepatic DNL and malonyl-CoA were maintained at the same physiological levels as in wild-type mice. Furthermore, hepatic DNL was completely inhibited by an ACC1/2 dual inhibitor, 5-tetradecyloxyl-2-furancarboxylic acid. These results strongly demonstrate that malonyl-CoA from ACC2 can access fatty acid synthase and become the substrate for the DNL pathway under the unphysiological circumstances that result with ACC1 disruption. Therefore, there does not appear to be strict compartmentalization of malonyl-CoA from either of the ACC isozymes in the liver.

A pair-feeding study reveals that a Y5 antagonist causes weight loss in diet-induced obese mice by modulating food intake and energy expenditure.

Neuropeptide Y (NPY) is thought to have a significant role in the physiological control of energy homeostasis. We recently reported that an NPY Y5 antagonist inhibits body weight gain in diet-induced obese (DIO) mice, with a moderate reduction in food intake. To clarify the mechanism of the antiobesity effects of the Y5 antagonist, we conducted a pair-feeding study in DIO mice. The Y5 antagonist at 100 mg/kg produced a moderate feeding suppression leading to an 18% decrease in body weight, without altering body temperature. In contrast, the pair-fed group showed only a transient weight reduction and a reduced body temperature, thus indicating that the Y5 antagonist stimulates thermogenesis. The Y5 antagonist-treated mice showed an up-regulation of uncoupling protein mRNA in brown adipose tissue (BAT) and white adipose tissue (WAT), suggesting that both BAT and WAT contribute to energy expenditure. Thus, the Y5 antagonist induces its antiobesity effects by acting on both energy intake and expenditure.

Characterization of neuropeptide Y (NPY) Y5 receptor-mediated obesity in mice: chronic intracerebroventricular infusion of D-Trp(34)NPY.

To clarify the role of the neuropeptide Y (NPY) Y5 receptor subtype in energy homeostasis, the effect of the intracerebroventricular infusion of a selective Y5 agonist, D-Trp(34)NPY, was investigated in C57BL/6J mice. Intracerebroventricular infusion of D-Trp(34)NPY (5 and 10 microg/d) produced hyperphagia and body weight gain, accompanied by increased adipose tissue weight, hypercholesterolemia, hyperinsulinemia, and hyperleptinemia. Oral administration of a selective Y5 antagonist at a dose of 100 mg/kg twice a day completely suppressed all of these D-Trp(34)NPY-induced changes, indicating that chronic activation of the Y5 receptor produces hyperphagia and obesity. In addition, D-Trp(34)NPY still resulted in an increase in adipose tissue weight accompanied by hyperleptinemia and hypercholesterolemia, although D-Trp(34)NPY-induced food intake was restricted by pair-feeding. Under the pair-fed condition, D-Trp(34)NPY decreased hormone-sensitive lipase activity in white adipose tissue and uncoupling protein-1 mRNA expression in brown adipose tissue. These findings indicate that Y5-mediated obesity may involve metabolic changes, such as decreased lipolysis and thermogenesis, as well as hyperphagia. Therefore, the Y5 receptor can play a key role in regulating energy homeostasis.

Characterization of MCH-mediated obesity in mice.

Melanin-concentrating hormone (MCH) is a cyclic orexigenic peptide expressed in the lateral hypothalamus. Recently, we demonstrated that chronic intracerebroventricular infusion of MCH induced obesity accompanied by sustained hyperphagia in mice. Here, we analyzed the mechanism of MCH-induced obesity by comparing animals fed ad libitum with pair-fed and control animals. Chronic infusion of MCH significantly increased food intake, body weight, white adipose tissue (WAT) mass, and liver mass in ad libitum-fed mice on a moderately high-fat diet. In addition, a significant increase in lipogenic activity was observed in the WAT of the ad libitum-fed group. Although body weight gain was marginal in the pair-fed group, MCH infusion clearly enhanced the lipogenic activity in liver and WAT. Plasma leptin levels were also increased in the pair-fed group. Furthermore, MCH infusion significantly reduced rectal temperatures in the pair-fed group. In support of these findings, mRNA expression of uncoupling protein-1, acyl-CoA oxidase, and carnitine palmitoyltransferase I, which are key molecules involved in thermogenesis and fatty acid oxidation, were reduced in the brown adipose tissue (BAT) of the pair-fed group, suggesting that MCH infusion might reduce BAT functions. We conclude that the activation of MCH neuronal pathways stimulated adiposity, in part resulting from increased lipogenesis in liver and WAT and reduced energy expenditure in BAT. These findings confirm that modulation of energy homeostasis by MCH may play a critical role in the development of obesity.