Bile acid sequestrants (BAS) have shown antidiabetic effects in both humans and animals but the underlying mechanism is not clear. In the present study, we evaluated cholestyramine in Zucker diabetic fatty (ZDF) rats. Although control ZDF rats had continuous increases in blood glucose and hemoglobin A1c (HbA1c) and serum glucose and a decrease in serum insulin throughout a 5-week study, the cholestyramine-treated ZDF rats showed a dose-dependent decrease and normalization in serum glucose and HbA1c. An oral glucose tolerance test showed a significant increase in glucose-stimulated glucagonlike peptide 1 (GLP-1), peptide YY (PYY), and insulin release in rats treated with cholestyramine. Quantitative analysis of gene expression indicated that cholestyramine treatment decreased farnesoid X receptor (FXR) activity in the liver and the intestine without liver X receptor (LXR) activation in the liver. Moreover, a combination of an FXR agonist with cholestyramine did not reduce the antihyperglycemic effect over cholestyramine alone, suggesting that the FXR-small heterodimer partner-LXR pathway was not required for the glycemic effects of cholestyramine. In summary, our results demonstrated that cholestyramine could completely reverse hyperglycemia in ZDF rats through improvements in insulin sensitivity and pancreatic ␤-cell function. Enhancement in GLP-1 and PYY secretion is an important mechanism for BAS-mediated antidiabetic efficacy.In the last decade, the traditional view of bile acids as essential players in dietary lipid absorption and cholesterol catabolism has changed. The discovery of bile acids as endogenous ligands for the nuclear receptor farnesoid X receptor (FXR; NR1H4) and the G-protein-coupled bile acid receptor (TGR5; GPBAR1) transformed bile acids from lipid absorption facilitator into autocrine, paracrine, and endocrine factors (Parks et al., 1999;Kawamata et al., 2003). In addition to negative feedback regulation of bile acid synthesis in the liver (Makishima et al., 1999), FXR influences many pathways involved in lipid and glucose metabolism (Lefebvre et al., 2009). FXR agonists have been shown to lower circulating cholesterol, triglycerides, and glucose and improve insulin sensitivity in multiple preclinical models (Duran-Sandoval et al., 2005;Stayrook et al., 2005;Cariou et al., 2006;Ma et al., 2006;Zhang et al., 2006). Similar to FXR, TGR5 mediates some hormonal actions of bile acids, including glucose metabolism. It has been demonstrated that bile acids promote glucagon-like-peptide 1 (GLP-1) secretion through TGR5 in STC-1, a murine enteroendocrine cell line (Katsuma et al., Article, publication date, and citation information can be found at

The apical sodium-dependent bile acid transporter (ASBT) transports bile salts from the lumen of the gastrointestinal (GI) tract to the liver via the portal vein. Multiple pharmaceutical companies have exploited the physiological link between ASBT and hepatic cholesterol metabolism, which led to the clinical investigation of ASBT inhibitors as lipid-lowering agents. While modest lipid effects were demonstrated, the potential utility of ASBT inhibitors for treatment of type 2 diabetes has been relatively unexplored. We initiated a lead optimization effort that focused on the identification of a potent, nonabsorbable ASBT inhibitor starting from the first-generation inhibitor 264W94 (1). Extensive SAR studies culminated in the discovery of GSK2330672 (56) as a highly potent, nonabsorbable ASBT inhibitor which lowers glucose in an animal model of type 2 diabetes and shows excellent developability properties for evaluating the potential therapeutic utility of a nonabsorbable ASBT inhibitor for treatment of patients with type 2 diabetes.

Phospholipase C (PLC) enzymes are an important family of regulatory proteins involved in numerous cellular functions, primarily through hydrolysis of the polar head group from inositol-containing membrane phospholipids. U73122 (1-(6-((17␤-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione), one of only a few small molecules reported to inhibit the activity of these enzymes, has been broadly applied as a pharmacological tool to implicate PLCs in diverse experimental phenotypes. The purpose of this study was to develop a better understanding of molecular interactions between U73122 and PLCs. Hence, the effects of U73122 on human PLC␤3 (hPLC␤3) were evaluated in a cell-free micellar system. Surprisingly, U73122 increased the activity of hPLC␤3 in a concentrationand time-dependent manner; up to an 8-fold increase in enzyme activity was observed with an EC 50 ‫؍‬ 13.6 ؎ 5 M. Activation of hPLC␤3 by U73122 required covalent modification of cysteines as evidenced by the observation that enzyme activation was attenuated by thiol-containing nucleophiles, L-cysteine and glutathione. Mass spectrometric analysis confirmed covalent reaction with U73122 at eight cysteines, although maximum activation was achieved without complete alkylation; the modified residues were identified by LC/MS/MS peptide sequencing. Interestingly, U73122 (10 M) also activated hPLC␥1 (>10-fold) and hPLC␤2 (ϳ2-fold); PLC␦1 was neither activated nor inhibited. Therefore, in contrast to its reported inhibitory potential, U73122 failed to inhibit several purified PLCs. Most of these PLCs were directly activated by U73122, and a simple mechanism for the activation is proposed. These results strongly suggest a need to re-evaluate the use of U73122 as a general inhibitor of PLC isozymes.