Objectives-A low level of high-density lipoprotein (HDL) in plasma has been recognized as an aspect of metabolic syndrome and as a crucial risk factor of cardiovascular events. However, the physiological regulation of plasma HDL levels has not been completely defined. Current studies aim to reveal the contribution of angiopoietin-like protein3 (angptl3), previously known as a plasma suppressor of lipoprotein lipase, to HDL metabolism. Methods and Results-Angptl3-deficient mice showed low plasma HDL cholesterol and HDL phospholipid (PL), and which were increased by ANGPTL3 supplementation via adenovirus. In vitro, ANGPTL3 inhibited the phospholipase activity of endothelial lipase (EL), which hydrolyzes HDL-PL and hence decreases plasma HDL levels, through a putative heparin-binding site in the N-terminal domain of ANGPTL3. Post-heparin plasma in Angptl3-knockout mice had higher phospholipase activity than did that in wild-type mice, suggesting that the activity of endogenous EL is elevated in Angptl3-deficient mice. Furthermore, we established an ELISA system for human ANGPTL3 and found that plasma ANGPTL3 levels significantly correlated with plasma HDL cholesterol and HDL-PL levels in human subjects. Key Words: angptl3 Ⅲ high density lipoprotein Ⅲ endothelial lipase Ⅲ phospholipase Ⅲ triglyceride P lasma concentrations of high-density lipoprotein (HDL) cholesterol are inversely correlated with the risk of atherosclerotic cardiovascular disease. 1 HDL cholesterol levels are low in patients with metabolic disorders, such as obesity, insulin resistance, and diabetes. 2,3 However, the genetic and metabolic factors that regulate HDL metabolism remain to be elucidated. Recently, endothelial lipase (EL) has been recognized as one factor that influences HDL metabolism. EL was originally discovered as a member of the family of triglyceride (TG)-lipases together with lipoprotein lipase (LPL) and hepatic lipase (HL). In contrast to LPL or HL, however, EL has relatively lower triglyceride lipase activity and substantially higher phospholipid lipase activity and can hydrolyze HDL phospholipids (PL). 4 Overexpression of EL in mice resulted in reduced plasma HDL levels and EL knockout mice showed significant increase in HDL levels, [5][6][7] indicating that EL regulates HDL metabolism. Conclusions-Angptl3In the colony of KK mice, characterized by obesity, diabetes mellitus, and hypertriglyceridemia, we recently identified a mutant subgroup of KK/Snk mice with low plasma TG levels despite maintaining the phenotype of obesity and diabetes. Genetic mapping and positional cloning identified the gene of angiopoietin-like protein 3 (Angptl3), which was mutated in the KK/Snk mice. The Angptl3 gene in KK/Snk mice contained a 4-bp nucleotide insertion in exon 6, which caused a premature stop codon attributable to a frameshift, leading to a lack of production of the protein. 8 Angptl3 mRNA is expressed exclusively in the livers of humans and mice. ANGPTL3 protein contains a signal sequence of 18 amino acids at the N terminus, followed b...

We have previously demonstrated that a small molecule inhibitor of bacterial β-glucuronidase (Inh-1; [1-((6,8-dimethyl-2-oxo-1,2-dihydroquinolin-3-yl)-3-(4-ethoxyphenyl)-1-(2-hydroxyethyl)thiourea]) protected mice against diclofenac (DCF)-induced enteropathy. Here we report that Inh-1 was equally protective against small intestinal injury induced by other carboxylic acid-containing non-steroidal anti-inflammatory drugs (NSAIDs), indomethacin (10 mg/kg, ip) and ketoprofen (100 mg/kg, ip).Inh-1 provided complete protection if given prior to DCF (60 mg/kg, ip), and partial protection if administered 3-h post-DCF, suggesting that the temporal window of mucosal protection can be extended for drugs undergoing extensive enterohepatic circulation.Pharmacokinetic analysis of Inh-1 revealed an absolute bioavailability (F) of 21% and a short t1/2 of <1 h. This low F was shown to be due to hepatic first-pass metabolism, as confirmed with the pan-CYP inhibitor, 1-aminobenzotriazole.Using the fluorescent probe 5 (and 6)-carboxy-2′,7′-dichlorofluorescein, we demonstrated that Inh-1 did not interfere with hepatobiliary export of glucuronides in gall bladder-cannulated mice.These data are compatible with the hypothesis that pharmacological inhibition of bacterial β-glucuronidase-mediated cleavage of NSAID glucuronides in the small intestinal lumen can protect against NSAID-induced enteropathy caused by locally high concentrations of NSAID aglycones.

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