Hidefumi Kitazawa

Effects of a Novel Y5 Antagonist in Obese Mice: Combination With Food Restriction or Sibutramine

Objective: To further address the function of the Y5 receptor in energy homeostasis, we investigated the effects of a novel spironolactone Y5 antagonist in diet‐induced obese (DIO) mice.

Development of a High-Density Assay for Long-Chain Fatty Acyl-CoA Elongases

We established a convenient assay method for measuring elongation of very long chain fatty acids (ELOVLs) using a Unifilter-96 GF/C plate. The Unifilter GF/C plate preferentially interacts with hydrophobic end products of ELOVLs (i.e., long chain fatty acid), with minimal malonyl-CoA (C2 unit donor for fatty acid elongation) interaction. This new method results in the quick separation and detection of [14C] incorporated end products (e.g., [14C] palmitoyl-CoA) from reaction mixtures containing excessive amounts of [14C] malonyl-CoA. In the Unifilter-96 GF/C plate assay, recombinantly expressed human ELOVLs (i.e., ELOVL1,-2,-3,-5 and -6) displayed appreciable assay windows (>2-fold vs. mock-transfected control), enabling us to conduct comprehensive substrate profiling of ELOVLs. The substrate concentration profile of ELOVL6 in the Unifilter-96 GF/C plate assay is consistent with that obtained from the conventional liquid extraction method, thus, supporting the reliability of the Unifilter-96 GF/C plate assay. We then examined the substrate specificities of ELOVLs in a comprehensive fashion. As previously reported, ELOVL1, -3 and -6 preferably elongated the saturated fatty acyl-CoAs while ELOVL2 and ELOVL5 preferentially elongated the polyunsaturated fatty acyl-CoAs. This further confirms the Unifilter-96 GF/C plate assay reliability. Taken together, our newly developed assay provides a convenient and comprehensive assay platform for ELOVLs, allowing investigators to conduct high density screening and characterization of ELOVLs chemical tools.

Discovery of tetrasubstituted imidazolines as potent and selective neuropeptide Y Y5 receptor antagonists: Reduced human ether-a-go-go related gene potassium channel binding affinity and potent antiobesity effect

A series of novel imidazoline derivatives was synthesized and evaluated as neuropeptide Y (NPY) Y5 receptor antagonists. Optimization of previously reported imidazoline leads, 1a and 1b, was attempted by introduction of substituents at the 5-position on the imidazoline ring and modification of the bis(4-fluorphenyl) moiety. A number of potent derivatives without human ether-a-go-go related gene potassium channel (hERG) activity were identified. Selected compounds, including 2a, were shown to have excellent brain and CSF permeability. Compound 2a displayed a suitable pharmacokinetic profile for chronic in vivo studies and potently inhibited D-Trp(34)NPY-induced acute food intake in rats. Oral administration of 2a resulted in a potent reduction of body weight in a diet-induced obese mouse model.

Discovery of Novel Benzoxazinones as Potent and Orally Active Long Chain Fatty Acid Elongase 6 Inhibitors

A series of benzoxazinones was synthesized and evaluated as novel long chain fatty acid elongase 6 (ELOVL6) inhibitors. Exploration of the SAR of the UHTS lead 1a led to the identification of (S)-1y that possesses a unique chiral quarternary center and a pyrazole ring as critical pharmacophore elements. Compound (S)-1y showed potent and selective inhibitory activity toward human ELOVL6 while displaying potent inhibitory activity toward both mouse ELOVL3 and 6 enzymes. Compound (S)-1y showed acceptable pharmacokinetic profiles after oral dosing in mice. Furthermore, (S)-1y significantly suppressed the elongation of target fatty acids in mouse liver at 30 mg/kg oral dosing.

Discovery and characterization of a novel potent, selective and orally active inhibitor for mammalian ELOVL6

The elongase of long chain fatty acids family 6 (ELOVL6) is a rate-limiting enzyme for the elongation of saturated and monounsaturated long chain fatty acids. ELOVL6 is abundantly expressed in lipogenic tissues such as liver, and its mRNA expression is up-regulated in obese model animals. ELOVL6 deficient mice are protected from high-fat-diet-induced insulin resistance, suggesting that ELOVL6 might be a new therapeutic target for diabetes. We previously identified an indoledione compound, Compound A, as the first inhibitor for mammalian ELOVL6. In this study, we discovered a novel compound, Compound B, and characterized its biochemical and pharmacological properties. Compound B has a more appropriate profile for use as a pharmacological tool compared to Compound A. Chronic treatment with Compound B in model animals, diet-induced obesity (DIO) and KKAy mice, showed significant reduction in hepatic fatty acid composition, suggesting that it effectively inhibits ELOVL6 activity in the liver. However, no improvement in insulin resistance by ELOVL6 inhibition was found in these model animals. Further studies need to address the impact of ELOVL6 inhibition on pharmacological abnormalities in several model animals. This is the first report on pharmacology data from chronic studies using a selective ELOVL6 inhibitor. Compound B appears to be a useful tool to further understand the physiological roles of ELOVL6 and to evaluate the therapeutic potential of ELOVL6 inhibitors.

Synthesis and evaluation of a novel indoledione class of long chain fatty acid elongase 6 (ELOVL6) inhibitors.

Novel indoledione derivatives were synthesized and evaluated as long chain fatty acid elongase 6 (ELOVL6) inhibitors. Systematic optimization of an indole class of lead 1 led to the identification of potent ELOVL6 selective inhibitors. Representative inhibitor 37 showed sustained plasma exposure and good liver penetrability in mice. After oral administration, 37 potently inhibited ELOVL6 activity in the liver in mice.

(-)-Ternatin inhibits adipogenesis and lipid metabolism in 3T3-L1 cells.

(-)-Ternatin, a highly N-methylated cyclic peptide, inhibits fat accumulation in 3T3-L1 cells and reduces fat mass in mice. However, the mechanism for its anti-adipogenic effect has remained unknown. To examine the mechanism used by (-)-ternatin to inhibit adipocyte differentiation, we examined the effects of (-)-ternatin and [l-Ala(4)]ternatin, an inactive analog of (-)-ternatin, on the expression of adipocyte markers and lipogenic enzymes. We found that (-)-ternatin potently reduced mRNA expression of several adipocyte markers in a dose-dependent manner, whereas [l-Ala(4)]ternatin showed no effects. At the immediate early phase, (-)-ternatin, but not [l-Ala(4)]ternatin, reduced the expression of Srebp1c, Fas, Acc2 and C/EBP-alpha while showing no effects on C/EBP-beta and C/EBP-delta. These results suggest that (-)-ternatin affects the mid-to late differentiation stages of adipocytes. Consistent with the decreased expression of lipogenic enzymes, (-)-ternatin potently inhibited triglyceride synthesis. Intriguingly, (-)-ternatin also inhibited triglyceride synthesis in rat primary hepatocytes, suggesting that the potential action sites for (-)-ternatin are shared by adipocytes and liver. Although the target molecule of (-)-ternatin remains unknown, our data suggest that (-)-ternatin and its potential target might provide a new therapeutic approach to metabolic disorders.

5,5-Dimethyl-3-(5-methyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-1-phenyl-3-(trifluoromethyl)-3,5,6,7-tetrahydro-1H-indole-2,4-dione, a potent inhibitor for mammalian elongase of long-chain fatty acids family 6: examination of its potential utility as a pharmacological tool.

Long-chain fatty acid elongases reside in the endoplasmic reticulum and are responsible for the rate-limiting step of the elongation of long-chain fatty acids. The elongase of long-chain fatty acids (ELOVL) family 6 (ELOVL6) is involved in the elongation of saturated and monosaturated fatty acids. Increased expression of ELOVL6 in ob/ob mice suggests a role for ELOVL6 in metabolic disorders. Furthermore, ELOVL6-deficient mice are protected from high-fat diet-induced insulin resistance, which suggests that ELOVL6 might be a new therapeutic target for diabetes. As reported previously, we developed a high-throughput screening system for fatty acid elongases and discovered lead chemicals that possess inhibitory activities against ELOVL6. In the present study, we examined in detail the biochemical and pharmacological properties of 5,5-dimethyl-3-(5-methyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)-1-phenyl-3-(trifluoromethyl)-3,5,6,7-tetrahydro-1H-indole-2,4-dione (Compound-A), a potent inhibitor of ELOVL6. In in vitro assays, Compound-A dose-dependently inhibited mouse and human ELOVL6 and displayed more than 30-fold greater selectivity for ELOVL6 over the other ELOVL family members. In addition, Compound-A effectively reduced the elongation index of fatty acids of hepatocytes, suggesting that Compound-A penetrates the cell wall and inhibits ELOVL6. More importantly, upon oral administration to mice, Compound-A showed high plasma and liver exposure and potently reduced the elongation index of the fatty acids of the liver. This is the first study to report a potent and selective inhibitor of mammalian elongases. Furthermore, Compound-A seems to be a useful tool to further understand the physiological roles of ELOVL6 and to evaluate the therapeutic potential of an ELOVL6 inhibitor.

Synthesis and Biological Evaluation of a Novel 3-Sulfonyl-8-azabicyclo[3.2.1]octane Class of Long Chain Fatty Acid Elongase 6 (ELOVL6) Inhibitors

Long chain fatty acid elongase 6 (ELOVL6) catalyzes the elongation of long chain fatty acyl-CoAs and is a potential target for the treatment of metabolic disorders. The ultrahigh throughput screen of our corporate chemical collections resulted in the identification of a novel 3-sulfonyl-8-azabicyclo[3.2.1]octane class of ELOVL6 inhibitor 1a. Optimization of lead 1a led to the identification of the potent, selective, and orally available ELOVL6 inhibitor 1w.

Synthesis and evaluation of a novel 2-azabicyclo[2.2.2]octane class of long chain fatty acid elongase 6 (ELOVL6) inhibitors

A series of novel 2-azabicyclo[2.2.2]octane derivatives was synthesized and evaluated as long chain fatty acid elongase 6 (ELOVL6) inhibitors. Screening of our corporate chemical collections against ELOVL6 resulted in the identification of lead 1. Exploratory chemistry efforts were applied to lead 1 to identify the orally available, potent, and selective ELOVL6 inhibitor 28a.