WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT Association of UDP-glucuronosyltransferase 1A1 (UGT1A1) genetic polymorphisms *6 and *28 with reduced clearance of SN-38 and severe neutropenia in irinotecan therapy was demonstrated in Japanese cancer patients. * The detailed gene structure of CES1 has been characterized. * Possible functional SNPs in the promoter region have been reported. WHAT THIS STUDY ADDS * Association of functional CES1 gene number with AUC ratio [(SN-38 + SN-38G)/irinotecan], an in vivo index of CES activity, was observed in patients with irinotecan monotherapy. * No significant effects of major CES1 SNPs on irinotecan PK were detected. AIMS Human carboxylesterase 1 (CES1) hydrolyzes irinotecan to produce an active metabolite SN-38 in the liver. The human CES1 gene family consists of two functional genes, CES1A1 (1A1) and CES1A2 (1A2), which are located tail-to-tail on chromosome 16q13-q22.1 (CES1A2-1A1). The pseudogene CES1A3 (1A3) and a chimeric CES1A1 variant (var1A1) are also found as polymorphic isoforms of 1A2 and 1A1, respectively. In this study, roles of CES1 genotypes and major SNPs in irinotecan pharmacokinetics were investigated in Japanese cancer patients. METHODS CES1A diplotypes [combinations of haplotypes A (1A3-1A1), B (1A2-1A1), C (1A3-var1A1) and D (1A2-var1A1)] and the major SNPs (-75T>G and -30G>A in 1A1, and -816A>C in 1A2 and 1A3) were determined in 177 Japanese cancer patients. Associations of CES1 genotypes, number of functional CES1 genes (1A1, 1A2 and var1A1) and major SNPs, with the AUC ratio of (SN-38 + SN-38G)/irinotecan, a parameter of in vivo CES activity, were analyzed for 58 patients treated with irinotecan monotherapy. RESULTS The median AUC ratio of patients having three or four functional CES1 genes (diplotypes A/B, A/D or B/C, C/D, B/B and B/D; n= 35) was 1.24-fold of that in patients with two functional CES1 genes (diplotypes A/A, A/C and C/C; n= 23) [median (25th-75th percentiles): 0.31 (0.25-0.38) vs. 0.25 (0.20-0.32), P= 0.0134]. No significant effects of var1A1 and the major SNPs examined were observed. CONCLUSION This study suggests a gene-dose effect of functional CES1A genes on SN-38 formation in irinotecan-treated Japanese cancer patients.
Title: [Isolation of pancreatic lipase activity-inhibitory component of spirulina platensis and it reduce postprandial triacylglycerolemia] Han LK, Li DX, Xiang L, Gong XJ, Kondo Y, Suzuki I, Okuda H Ref: Yakugaku Zasshi, 126:43, 2006 : PubMed
In the process of investigating the hypolipidemic effects of Spirulina platensis, we found that the aqueous extract of S. platensis may inhibit the intestinal absorption of dietary fat by inhibiting pancreatic lipase activity. The aqueous extract of S. platensis (500 m/kg) reduced the elevation of rat plasma triacylglycerol levels after oral administration of the lipid emulsion 2 h after administration. To clarify the hypolipidemic effects of S. platensis, the active component was isolated and designated 1'-O-(palmitonyl)-2'-O-(caprylonyl) glyceryl-beta-alpha-D-galactopyranoside (glycolipid H-b2). Glycolipid H-b2 was found to inhibit pancreatic lipase activity in a dose-dependent manner. The fractions containing glycolipid H-b2 (250 mg/kg) reduced the elevation of rat plasma triacylglycerol levels after oral administration of the lipid emulsion 2 h after administration. Furthermore, we examined the effects of phycocyanin isolated from S. platensis on pancreatic lipase activity. Phycocyanin inhibited the pancreatic lipase activity in a dose-dependent manner. These results suggest that the inhibitory effects of S. platensis on postprandial triacylglycerolemia may be due in part to the inhibition of pancreatic lipase activity by glycolipid H-b2 and phycocyanin.
Title: New biologically active triterpenoid saponins from Scabiosa tschiliensis Zheng Q, Koike K, Han LK, Okuda H, Nikaido T Ref: Journal of Natural Products, 67:604, 2004 : PubMed
Eleven new triterpenoid saponins, scabiosaponins A-K (1-11), and hookerosides A (12) and B (13) were isolated from the whole plants of Scabiosa tschiliensis. The structures of the new compounds were established on the basis of extensive NMR (DEPT, DQF-COSY, HETCOR, TOCSY, HMQC, HMQC-TOCSY, HMBC, and NOESY) and MS studies coupled with chemical degradations. The biological activity of compounds 1-10, 12, and 13 and prosapogenin 1b were examined against pancreatic lipase. Scabiosaponins E, F, G, I (5, 6, 7, 9), hookerosides A, B (12, 13), and prosapogenin 1b all exhibited strong inhibition of pancreatic lipase in vitro.
The oral administration of pectin to rats reduced and delayed the peak plasma triacylglycerol concentration. Pectin inhibited the hydrolysis of trioleoylglycerol emulsified with soybean phosphatidylcholine by pancreatic, carboxylester, and lingual lipases in a concentration-dependent manner. However, the effective concentration of pectin for lingual lipase was 100 times lower than that for pancreatic lipase. Pectin did not inhibit the tributyrin- and p-nitrophenylbutyrate-hydrolyzing activities by pancreatic and carboxylester lipase. When low molecular weight pectin was assayed, pectin at a molecular weight of 90,000 (MW 90) most strongly inhibited three lipase activities. When the effect of pH on pectin inhibition was analyzed using pancreatic lipase, strong inhibition was observed at an acidic pH (below pH 7.0). In the assay system, the pancreatic lipase protein levels in the supernatant and fat layer were estimated by Western blotting with an anti-pancreatic lipase antibody. Pectin reduced the amount of pancreatic lipase protein in the fat layer in a concentration-dependent manner and concomitantly increased that in the supernatant. These results suggest that pectin may interact with emulsified substrates and inhibit the adsorption of lipase to the surface of substrate emulsion.
Title: Effects of mutations of a glutamine residue in loop D of the alpha7 nicotinic acetylcholine receptor on agonist profiles for neonicotinoid insecticides and related ligands Shimomura M, Okuda H, Matsuda K, Komai K, Akamatsu M, Sattelle DB Ref: British Journal of Pharmacology, 137:162, 2002 : PubMed
1. Neonicotinoid insecticides are agonists of insect nicotinic acetylcholine receptors (AChRs) and show selective toxicity for insects over vertebrates. To elucidate the molecular basis of the selectivity, amino acid residues influencing neonicotinoid sensitivity were investigated by site-directed mutagenesis of the chicken alpha7 nicotinic AChR subunit, based on the crystal structure of an ACh binding protein (AChBP). 2. In the ligand binding site of AChBP, Q55 in loop D is close to Y164 in loop F that corresponds to G189 of the alpha7 nicotinic receptor. Since Q55 of AChBP is preserved as Q79 in the alpha7 nicotinic receptor and the G189D and G189E mutations have been found to reduce the neonicotinoid sensitivity, we investigated effects of Q79E, Q79K and Q79R mutations on the neonicotinoid sensitivity of the alpha7 receptor expressed in Xenopus laevis oocytes to evaluate contributions of the glutamine residue to nicotinic AChR-neonicotinoid interactions. 3. The Q79E mutation markedly reduced neonicotinoid sensitivity of the alpha7 nicotinic AChR whereas the Q79K and Q79R mutations increased sensitivity, suggesting electronic interactions of the neonicotinoids with the added residues. 4. By contrast, the Q79E mutation scarcely influenced responses of the alpha7 nicotinic receptor to ACh, (-)-nicotine and desnitro-imidacloprid (DN-IMI), an imidacloprid derivative lacking the nitro group, whereas the Q79K and Q79R mutations reduced the sensitivity to these ligands. The results indicate that the glutamine residue of the alpha7 nicotinic receptor is likely to be located close to the nitro group of the insecticides in the nicotinic receptor-insecticide complex.
Title: Hydrolysis of cholesteryl oleate liquid crystals by hormone-sensitive lipase Tsujita T, Okuda H Ref: J Biochem, 113:264, 1993 : PubMed
Cholesteryl oleate liquid crystals were prepared by sonication as a model of lipid droplets accumulated in foam cells derived from macrophages. These liquid crystals were spherical and showed an anisotropic cross image. Hormone-sensitive lipase from bovine adipose tissue hydrolyzed these liquid crystals optimally at pH 6.8. The Km for the liquid crystals was about 8 times that for vesicles or emulsified cholesteryl oleate. The Vmax for the liquid crystals was the same as that for the emulsified substrate and 6 times that for the vesicle substrate. Phospholipid inhibited cholesteryl oleate hydrolysis in a concentration-dependent fashion, phosphatidylserine being especially inhibitory. The effect of phospholipids on the activity changed upon their incorporation into the cholesteryl oleate liquid crystals, phosphatidylethanolamine increasing the activity to about twice that of the control. These results suggest that hormone-sensitive lipase hydrolyzes cholesteryl oleate liquid crystals as a model of endogenous lipid droplets and its activities are affected by phospholipids.
Title: Hepatic triacylglycerol lipase in circulating blood of normal and tumor-bearing mice and its hydrolysis of very-low-density lipoprotein and synthetic acylglycerols Masuno H, Okuda H Ref: Biochimica & Biophysica Acta, 879:339, 1986 : PubMed
A large amount of triacylglycerol lipase activity was present in the circulating blood of normal mice, and this activity decreased with development of Sarcoma 180 inoculated intraperitoneally. Triacylglycerol lipase in plasma of both normal and tumor-bearing mice was retained on the heparin-Sepharose columns and over 90% of the activity was eluted with 0.75 M NaCl. This enzyme had similar properties to hepatic triacylglycerol lipase and hydrolyzed very-low-density lipoprotein (VLDL)-triacylglycerol. Hepatic triacylglycerol lipase in plasma of normal mice hydrolyzed tricaprin and trilaurin most readily and better than 1-monoacylglycerols with the same acyl chain length. The hydrolyzing activities decreased with increase in the acyl chain length. The activity toward triolein was also higher than that toward 1-monoolein. 1-Monomyristin was hydrolyzed better than trimyristin. In contrast, hepatic triacylglycerol lipase in plasma of mice on day 4 after tumor inoculation hydrolyzed 1-monoacylglycerols better than triacylglycerols with the same acyl chain length. Hydrolysis of triolein by hepatic triacylglycerol lipase in plasma of both normal and tumor-bearing mice was reduced in the presence of 1-monoacylglycerols in the reaction mixture. The orders of their inhibitory effects coincided with the orders of the hydrolyzing activities toward 1-monoacylglycerols.
