Inhibition of intestinal absorption of cholesterol by ezetimibe or bile acids by SC-435 alters lipoprotein metabolism and extends the lifespan of SR-BI/apoE double knockout mice

SLC10A1 rs2296651 variant (S267F mutation) predicts biochemical traits, hepatitis B virus infection susceptibility and the risk of gallstone disease

Sodium taurocholate co-transporting polypeptide (NTCP), a bile acid transporter, plays a crucial role in regulating bile acid levels and influencing the risk of HBV infection. Genetic variations in the SLC10A1 gene, which encodes NTCP, affect these functions. However, the impact of SLC10A1 gene variants on the metabolic and biochemical traits remained unclear. We aimed to investigate the association of SLC10A1 gene variants with the clinical and biochemical parameters, and the risk of different HBV infection statuses and gallstone disease in the Taiwanese population. Genotyping data from 117,679 Taiwan Biobank participants were analyzed using the Axiom genome-wide CHB arrays. Regional-plot association analysis demonstrated genome-wide significant association between the SLC10A1 rs2296651 genotypes and lipid profile, gamma glutamyl transferase (γGT) level and anti-HBc-positivity. Genotype-phenotype association analyses revealed significantly lower total cholesterol, low-density lipoprotein (LDL) cholesterol and uric acid levels, a higher γGT level and a higher gallstone incidence in rare rs2296651-A allele carrier. Participants with the rs2296651 AA-genotype exhibited significantly lower rates of anti-HBc-positivity and HBsAg-positivity. Compared to those with the GG-genotype, individuals with non-GG-genotypes had reduced risks for various HBV infection statuses: the AA-genotype showed substantially lower risks, while the GA-genotype demonstrated modestly lower risks. Predictive tools also suggested that the rs2296651 variant potentially induced protein damage and pathogenic effects. In conclusion, our data revealed pleiotropic effects of the SLC10A1 rs2296651 genotypes on the levels of biochemical traits and the risk of HBV infection and gallstone disease. This confirms SLC10A1's versatility and implicates its genotypes in predicting both biochemical traits and disease susceptibility.

Therapeutic potential of lipid-lowering probiotics on the atherosclerosis development

Hypercholesterolemia is a critical risk factor for atherosclerosis, mostly attributed to lifestyle behavior such as diet. Recent advances have emphasized the critical effects of gastrointestinal bacteria in the pathology of hypercholesterolemia and atherosclerosis, suggesting that the gastrointestinal microbiome can therefore provide efficient therapeutic targets for preventing and treating atherosclerosis. Thus, interventions, such as probiotic therapy, aimed at altering the bacterial composition introduce a promising therapeutic procedure. In the current review, we will provide an overview of anti-atherogenic probiotics contributing to lipid-lowering, inhibiting atherosclerotic inflammation, and suppressing bacterial atherogenic metabolites.

Metabolic consequences of ileal interruption of the enterohepatic circulation of bile acids

The enterohepatic circulation of bile acids comprises a tightly regulated process of hepatic bile acid secretion, intestinal reabsorption and transport back to the liver. Disruption of this process has significant consequences for gastrointestinal, liver and whole body homeostasis and therefore offers opportunities for therapeutic intervention. In this review we discuss the effects of (pharmacological) interruption of the enterohepatic circulation at different levels. Recently, several studies have been published on ileal interruption of the enterohepatic circulation of bile acids, targeting the apical-sodium dependent bile acid transporter (ASBT, SLC10A2), as therapy for various diseases. However, ambiguous results have been reported and in-depth mechanistic insights are lacking. Here we discuss these novel studies and review the current knowledge on the consequences of ASBT inhibition and its potential effects on physiology and metabolism.

SLC10A1 S267F variant influences susceptibility to HBV infection and reduces cholesterol level by impairing bile acid uptake

The SLC10A1 Ser267Phe (S267F) variant has been reported to severely inhibit hepatitis B virus (HBV) infection and taurocholate transport activity. This study aimed to clarify the effects of this variant on HBV infection and bile acid metabolism. SLC10A1 S267F was genotyped in 2907 HBV-exposed subjects (including HBV persistent carriers and spontaneously recovered subjects) and 1364 unexposed subjects (HBV marker-negative subjects), followed by replication I, comprising 914 exposed subjects and 1123 unexposed subjects, and replication II, comprising 355 children born to HBsAg-positive mothers (226 HBV-infected children and 129 controls). Intriguingly, SLC10A1 AA was observed only in the unexposed group, but not in the exposed group. The SLC10A1 A allele consistently decreased HBV infection risk compared with the G allele (OR = 0.76, 95% CI: 0.64-0.90 in combined samples). In addition, children with the SLC10A1 GA genotype had a reduced risk of perinatal transmission (OR = 0.31, 95% CI: 0.14-0.71). Moreover, unexposed subjects with the SLC10A1 AA genotype exhibited decreased serum total cholesterol and low-density lipoprotein cholesterol compared to those with the GG or GA genotypes (P = 2.975 × 10^-4 and 0.004, respectively). The study highlighted the role of the SLC10A1 S267F variant in the loss of the ability to support HBV infection and taurocholate transport activity. Subjects with the AA genotype may escape from HBV infection and present decreased cholesterol levels as a consequence of impaired bile acid uptake.

Efficient reabsorption of transintestinally excreted cholesterol is a strong determinant for cholesterol disposal in mice

Transintestinal cholesterol excretion (TICE) is a major route for eliminating cholesterol from the body and a potential therapeutic target for hypercholesterolemia. The underlying mechanism, however, is largely unclear, and its contribution to cholesterol disposal from the body is obscured by the counteracting process of intestinal cholesterol reabsorption. To determine the quantity of TICE independent from its reabsorption, we studied two models of decreased intestinal cholesterol absorption. Cholesterol absorption was inhibited either by ezetimibe or, indirectly, by the genetic inactivation of the intestinal apical sodium-dependent bile acid transporter (ASBT; SLC10A2). Both ezetimibe treatment and Asbt inactivation virtually abrogated fractional cholesterol absorption (from 46% to 4% and 6%, respectively). In both models, fecal neutral sterol excretion and net intestinal cholesterol balance were considerably higher than in control mice (5- and 7-fold, respectively), suggesting that, under physiological conditions, TICE is largely reabsorbed. In addition, the net intestinal cholesterol balance was increased to a similar extent but was not further increased when the models were combined, suggesting that the effect on cholesterol reabsorption was already maximal under either condition alone. On the basis of these findings, we hypothesize that the inhibition of cholesterol (re)absorption combined with stimulating TICE will be most effective in increasing cholesterol disposal.

Attenuation of atherogenic apo B-48-dependent hyperlipidemia and high density lipoprotein remodeling induced by vitamin C and E combination and their beneficial effect on lethal ischemic heart disease in mice

Background and aims

Atherosclerotic cardiovascular disease is highly prevalent and its underlying pathogenesis involves dyslipidemia including pro-atherogenic high density lipoprotein (HDL) remodeling. Vitamins C and E have been proposed as atheroprotective agents for cardiovascular disease management. However, their effects and benefits on high density lipoprotein function and remodeling are unknown. In this study, we evaluated the role of vitamin C and E on non HDL lipoproteins as well as HDL function and remodeling, along with their effects on inflammation/oxidation biomarkers and atherosclerosis in atherogenic diet-fed SR-B1 KO/ApoER61^h/h mice.

Methods and results

Mice were pre-treated for 5 weeks before and during atherogenic diet feeding with vitamin C and E added to water and diet, respectively. Compared to a control group, combined vitamin C and E administration reduced serum total cholesterol and triglyceride levels by decreasing apo B-48-containing lipoproteins, remodeled HDL particles by reducing phospholipid as well as increasing PON1 and apo D content, and diminished PLTP activity and levels. Vitamin supplementation improved HDL antioxidant function and lowered serum TNF-α levels. Vitamin C and E combination attenuated atherogenesis and increased lifespan in atherogenic diet-fed SR-B1 KO/ApoER61^h/h mice.

Conclusions

Vitamin C and E administration showed significant lipid metabolism regulating effects, including HDL remodeling and decreased levels of apoB-containing lipoproteins, in mice. In addition, this vitamin supplementation generated a cardioprotective effect in a murine model of severe and lethal atherosclerotic ischemic heart disease.

Rosuvastatin Reduces Aortic Sinus and Coronary Artery Atherosclerosis in SR-B1 (Scavenger Receptor Class B Type 1)/ApoE (Apolipoprotein E) Double Knockout Mice Independently of Plasma Cholesterol Lowering

Supplemental Digital Content is available in the text.

Objective—

Rosuvastatin has been widely used in the primary and secondary prevention of coronary heart disease. However, its antiatherosclerotic properties have not been tested in a mouse model that could mimic human coronary heart disease. The present study was designed to test the effects of rosuvastatin on coronary artery atherosclerosis and myocardial fibrosis in SR-B1 (scavenger receptor class B type 1) and apoE (apolipoprotein E) double knockout mice.

Approach and Results—

Three-week-old SR-B1^−/−/apoE^−/− mice were injected daily with 10 mg/kg of rosuvastatin for 2 weeks. Compared with saline-treated mice, rosuvastatin-treated mice showed increased levels of hepatic PCSK9 (proprotein convertase subtilisin/kexin type-9) and LDLR (low-density lipoprotein receptor) message, increased plasma PCSK9 protein but decreased levels of hepatic LDLR protein and increased plasma total cholesterol associated with apoB (apolipoprotein B) 48-containing lipoproteins. In spite of this, rosuvastatin treatment was associated with decreased atherosclerosis in both the aortic sinus and coronary arteries and reduced platelet accumulation in atherosclerotic coronary arteries. Cardiac fibrosis and cardiomegaly were also attenuated in rosuvastatin-treated SR-B1^−/−/apoE^−/− mice. Two-week treatment with rosuvastatin resulted in significant decreases in markers of oxidized phospholipids in atherosclerotic plaques. In vitro analysis showed that incubation of bone marrow-derived macrophages with rosuvastatin substantially downregulated cluster of differentiation (CD)36 and inhibited oxidized LDL-induced foam cell formation.

Conclusions—

Rosuvastatin protected SR-B1^−/−/apoE^−/− mice against atherosclerosis and platelet accumulation in coronary arteries and attenuated myocardial fibrosis and cardiomegaly, despite increased plasma total cholesterol. The ability of rosuvastatin to reduce oxidized phospholipids in atherosclerotic plaques and inhibit macrophage foam cell formation may have contributed to this protection.

A novel class of apical sodium--dependent bile salt transporter inhibitors: 1-(2,4-bifluorophenyl)-7-dialkylamino-1,8-naphthyridine-3-carboxamides

The apical sodium--dependent bile acid transporter (ASBT) is the main transporter to promote re-absorption of bile acids from the intestinal tract into the enterohepatic circulation. Inhibition of ASBT could increase the excretion of bile acids, thus increasing bile acid synthesis and consequently cholesterol consumption. Therefore, ASBT is an attractive target for developing new cholesterol-lowering drugs. In this report, a series of 1-(2,4-bifluorophenyl)-7-dialkylamino-1,8-naphthyridine-3-carboxamides were designed as inhibitors of ASBT. Most of them demonstrated potency against ASBT transport of bile acids. In particular, compound 4a₁ was found to have the best activity, resulting in 80.1% inhibition of ASBT at 10 μmol/L.

Impact of Inhibiting Ileal Apical versus Basolateral Bile Acid Transport on Cholesterol Metabolism and Atherosclerosis in Mice

BACKGROUND

Bile acid sequestrants have been used for many years to treat hypercholesterolemia by increasing hepatic conversion of cholesterol to bile acids, thereby inducing hepatic LDL receptor expression and clearance of apoB-containing particles. In order to further understand the underlying molecular mechanisms linking gut-liver signaling and cholesterol homeostasis, mouse models defective in ileal apical membrane bile acid transport (Asbt-null) and ileal basolateral membrane bile acid transport (Ostα-null) were studied under basal and hypercholesterolemic conditions.

KEY MESSAGES

Hepatic conversion of cholesterol to bile acids is the major pathway for cholesterol catabolism and a major mechanism for cholesterol elimination. Blocking ileal apical membrane bile acid transport (Asbt-null mice) increases fecal bile acid excretion, hepatic Cyp7a1 expression, and the relative proportion of taurocholate in the bile acid pool, but decreases ileal FGF15 expression, bile acid pool size, and hepatic cholesterol content. In contrast, blocking ileal basolateral membrane bile acid transport (Ostα-null mice) increases ileal FGF15 expression, reduces hepatic Cyp7a1 expression, and increases the proportion of tauro-β-muricholic acid in the bile acid pool. In the hypercholesterolemic apoE-null background, plasma cholesterol levels and measurements of atherosclerosis were reduced in Asbt/apoE-null mice, but not in Ostα/apoE-null mice.

CONCLUSIONS

Blocking the intestinal absorption of bile acids at the apical versus basolateral membrane differentially affects bile acid and cholesterol metabolism, including the development of hypercholesterolemia-associated atherosclerosis. The molecular mechanism likely involves an altered regulation of ileal FGF15 expression.

Structural basis of the alternating-access mechanism in a bile acid transporter

Bile acids are synthesized from cholesterol in hepatocytes and secreted through the biliary tract into the small intestine, where they aid in absorption of lipids and fat-soluble vitamins. Through a process known as enterohepatic recirculation, more than 90% of secreted bile acids are then retrieved from the intestine and returned to the liver for resecretion. In humans, there are two Na(+)-dependent bile acid transporters involved in enterohepatic recirculation, the Na(+)-taurocholate co-transporting polypeptide (NTCP; also known as SLC10A1) expressed in hepatocytes, and the apical sodium-dependent bile acid transporter (ASBT; also known as SLC10A2) expressed on enterocytes in the terminal ileum. In recent years, ASBT has attracted much interest as a potential drug target for treatment of hypercholesterolaemia, because inhibition of ASBT reduces reabsorption of bile acids, thus increasing bile acid synthesis and consequently cholesterol consumption. However, a lack of three-dimensional structures of bile acid transporters hampers our ability to understand the molecular mechanisms of substrate selectivity and transport, and to interpret the wealth of existing functional data. The crystal structure of an ASBT homologue from Neisseria meningitidis (ASBT(NM)) in detergent was reported recently, showing the protein in an inward-open conformation bound to two Na(+) and a taurocholic acid. However, the structural changes that bring bile acid and Na(+) across the membrane are difficult to infer from a single structure. To understand the structural changes associated with the coupled transport of Na(+) and bile acids, here we solved two structures of an ASBT homologue from Yersinia frederiksenii (ASBTYf) in a lipid environment, which reveal that a large rigid-body rotation of a substrate-binding domain gives the conserved 'crossover' region, where two discontinuous helices cross each other, alternating accessibility from either side of the cell membrane. This result has implications for the location and orientation of the bile acid during transport, as well as for the translocation pathway for Na(+).

Inhibition of ileal apical but not basolateral bile acid transport reduces atherosclerosis in apoE⁻/⁻ mice

OBJECTIVE

Interruption of the enterohepatic circulation of bile acids induces hepatic bile acid synthesis, increases hepatic cholesterol demand, and increases clearance of apoB-containing lipoproteins in plasma. Based on these effects, bile acid sequestrants have been used for many years to treat hypercholesterolemia and the associated atherosclerosis. The objective of this study was to determine the effect of blocking ileal apical versus basolateral membrane bile acid transport on the development of hypercholesterolemia and atherosclerosis in mouse models.

METHODS AND RESULTS

ApoE(-/-) and Ldlr(-/-) mice deficient in the apical sodium-dependent bile acid transporter (Asbt) or apoE(-/-) mice deficient in the basolateral bile acid transporter (Ostα) were fed an atherogenic diet for 16 weeks. Bile acid metabolism, cholesterol metabolism, gene expression, and development of atherosclerosis were examined. Mice deficient in Asbt exhibited the classic response to interruption of the enterohepatic circulation of bile acids, including significant reductions in hepatic and plasma cholesterol levels, and reduced aortic cholesteryl ester content. Ileal Fibroblast Growth Factor-15 (FGF15) expression was significantly reduced in Asbt(-/-)apoE(-/-) mice and was inversely correlated with expression of hepatic cholesterol 7-hydroxylase (Cyp7a1). Ileal FGF15 expression was directly correlated with plasma cholesterol levels and aortic cholesterol content. In contrast, plasma and hepatic cholesterol levels and atherosclerosis development were not reduced in apoE(-/-) mice deficient in Ostα.

CONCLUSIONS

Decreases in ileal FGF15, with subsequent increases in hepatic Cyp7a1 expression and bile acid synthesis appear to be necessary for the plasma cholesterol-lowering and atheroprotective effects associated with blocking intestinal bile acid absorption.

The effect of pomegranate extract on coronary artery atherosclerosis in SR-BI/APOE double knockout mice

OBJECTIVES

To examine the effects of pomegranate extract on inflammation and oxidative stress and the development of spontaneous occlusive coronary artery atherosclerosis in the SR-BI/apoE double knockout mouse model of coronary heart disease.

METHODS AND RESULTS

SR-BI/apoE double KO mice were treated for two weeks with pomegranate extract via drinking water, beginning at three weeks of age. Treatment with pomegranate extract increased cholesterol ester content and reduced the abnormally high unesterified/esterified cholesterol ratio of VLDL-sized lipoproteins. Despite the increase in cholesterol levels associated with VLDL-sized particles, pomegranate extract treatment reduced the size of atherosclerotic plaques in the aortic sinus and reduced the proportion of coronary arteries with occlusive atherosclerotic plaques. Treatment with pomegranate extract resulted in substantial reductions in levels of oxidative stress and monocyte chemotactic protein-1 in atherosclerotic plaques in the aortic sinus and coronary arteries. In addition, treatment with pomegranate extract reduced lipid accumulation, macrophage infiltration, levels of monocyte chemotactic protein-1 and fibrosis in the myocardium, attenuated cardiac enlargement and the development of ECG abnormalities in SR-BI/apoE double KO mice.

CONCLUSION

Pomegranate extract reduced aortic sinus and coronary artery atherosclerosis in SR-BI/apoE dKO mice. The atheroprotective effects of pomegranate extract appear to involve reduced oxidative stress and inflammation in the vessel wall despite unaltered systemic markers of inflammation and increased lipoprotein cholesterol in these mice.

Dietary manipulation and social isolation alter disease progression in a murine model of coronary heart disease

BACKGROUND

Mice with a deficiency in the HDL receptor SR-BI and low expression of a modified apolipoprotein E gene (SR-BI KO/ApoeR61(h/h)) called 'HypoE' when fed an atherogenic, 'Paigen' diet develop occlusive, atherosclerotic coronary arterial disease (CHD), myocardial infarctions (MI), and heart dysfunction and die prematurely (50% mortality ~40 days after initiation of this diet). Because few murine models share with HypoE mice these cardinal, human-like, features of CHD, HypoE mice represent a novel, small animal, diet-inducible and genetically tractable model for CHD. To better describe the properties of this model, we have explored the effects of varying the composition and timing of administration of atherogenic diets, as well as social isolation vs. group housing, on these animals.

METHODOLOGY/PRINCIPAL FINDINGS

HypoE mice were maintained on a standard lab chow diet (control) until two months of age. Subsequently they received one of three atherogenic diets (Paigen, Paigen without cholate, Western) or control diet for varying times and were housed in groups or singly, and we determined the plasma cholesterol levels, extent of cardiomegaly and/or survival. The rate of disease progression could be reduced by lowering the severity of the atherogenic diet and accelerated by social isolation. Disease could be induced by Paigen diets either containing or free of cholate. We also established conditions under which CHD could be initiated by an atherogenic diet and then subsequently, by replacing this diet with standard lab chow, hypercholesterolemia could be reduced and progression to early death prevented.

CONCLUSIONS/SIGNIFICANCE

HypoE mice provide a powerful, surgery-free, diet-'titratable' small animal model that can be used to study the onset of recovery from occlusive, atherosclerotic CHD and heart failure due to MI. HypoE mice can be used for the analysis of the effects of environment (diet, social isolation) on a variety of features of cardiovascular disease.

Niemann-pick C1-like 1 (NPC1L1) protein in intestinal and hepatic cholesterol transport

Increased blood cholesterol is an independent risk factor for atherosclerotic cardiovascular disease. Cholesterol homeostasis in the body is controlled mainly by endogenous synthesis, intestinal absorption, and hepatic excretion. Niemann-Pick C1-Like 1 (NPC1L1) is a polytopic transmembrane protein localized at the apical membrane of enterocytes and the canalicular membrane of hepatocytes. It functions as a sterol transporter to mediate intestinal cholesterol absorption and counter-balances hepatobiliary cholesterol excretion. NPC1L1 is the molecular target of ezetimibe, a potent cholesterol absorption inhibitor that is widely used in treating hypercholesterolemia. Recent findings suggest that NPC1L1 deficiency or ezetimibe treatment also prevents diet-induced hepatic steatosis and obesity in addition to reducing blood cholesterol. Future studies should focus on molecular mechanisms underlying NPC1L1-dependent cholesterol transport and elucidation of how a cholesterol transporter modulates the pathogenesis of metabolic diseases.

Statins and cancer: a potential link?

Hypercholesterolemia is a growing health concern in the United States. Pharmacotherapy is increasingly being used to combat the long-term consequences of elevated cholesterol levels. One of the primary pharmacological treatments for hypercholesterolemia is a class of lipid lowering drugs collectively referred to as statins. After introduction of the first statin in 1987, their use quickly became the norm. Recent release of the results from the Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) study unveiled a potential increased risk of cancer and cancer death for individuals taking the well-known drug combination of ezetimibe/simvastatin. Our aim with this review is to look at previous studies to see if any other studies have shown a similar correlation between statins or other lipid-lowering drugs and cancer. The associated studies gathered are reviews, randomized, controlled trials, editorials, and commentaries. We obtained these studies by using electronic searches such as PubMed, Medline, and Cochrane Library. Searches were limited in that certain keywords took precedence, and articles mainly focusing on statins and ezetimibe as opposed to other lipid-lowering drugs were chosen. We have shown that aside from the SEAS study, there are numerous other studies that have also found potential links between statins and various forms of cancer. However, there is also an abundance of literature showing the contrary. Currently, scientific data are slightly in favor of the notion that statins do not cause a significant increase in cancer rates. However, there are many studies that show small correlations between statin use and increased incidence of cancer and therefore, we feel further prospective studies are needed. Whether statins do cause cancer remains uncertain at this point in time.

Loss of PDZK1 causes coronary artery occlusion and myocardial infarction in Paigen diet-fed apolipoprotein E deficient mice

BACKGROUND

PDZK1 is a four PDZ-domain containing protein that binds to the carboxy terminus of the HDL receptor, scavenger receptor class B type I (SR-BI), and regulates its expression, localization and function in a tissue-specific manner. PDZK1 knockout (KO) mice are characterized by a marked reduction of SR-BI protein expression ( approximately 95%) in the liver (lesser or no reduction in other organs) with a concomitant 1.7 fold increase in plasma cholesterol. PDZK1 has been shown to be atheroprotective using the high fat/high cholesterol ('Western') diet-fed murine apolipoprotein E (apoE) KO model of atherosclerosis, presumably because of its role in promoting reverse cholesterol transport via SR-BI.

PRINCIPAL FINDINGS

Here, we have examined the effects of PDZK1 deficiency in apoE KO mice fed with the atherogenic 'Paigen' diet for three months. Relative to apoE KO, PDZK1/apoE double KO (dKO) mice showed increased plasma lipids (33% increase in total cholesterol; 49 % increase in unesterified cholesterol; and 36% increase in phospholipids) and a 26% increase in aortic root lesions. Compared to apoE KO, dKO mice exhibited substantial occlusive coronary artery disease: 375% increase in severe occlusions. Myocardial infarctions, not observed in apoE KO mice (although occasional minimal fibrosis was noted), were seen in 7 of 8 dKO mice, resulting in 12 times greater area of fibrosis in dKO cardiac muscle.

CONCLUSIONS

These results show that Paigen-diet fed PDZK1/apoE dKO mice represent a new animal model useful for studying coronary heart disease and suggest that PDZK1 may represent a valuable target for therapeutic intervention.

Inhibition requirements of the human apical sodium-dependent bile acid transporter (hASBT) using aminopiperidine conjugates of glutamyl-bile acids

PURPOSE

Synthesize aminopiperidine conjugates of glutamyl-bile acids (glu-BAs) and develop a hASBT inhibition model using the conformationally sampled pharmacophore (CSP) approach.

METHODS

glu-BAs aminopiperidine conjugates were synthesized. hASBT inhibition was measured as K(i). A CSP-SAR model was built using structural and physico-chemical descriptors and evaluated via cross-validation.

RESULTS

Twenty-nine aminopiperidine conjugates were synthesized. All inhibited hASBT, with K(i) ranging from 0.95 to 31.8 muM. Amidation of the piperidine nitrogen slightly decreased activity, while replacement by a carbon increased potency. Esterification of the glutamic acid linker had a minor impact, suggesting that a negative charge around C-24 is not required for binding. Three quantitative CSP-SAR models were developed. The best model (r (2) = 0.813, Q (2) = 0.726) included two descriptors: angle between 7-OH, alpha-substituent and centroid of rings B and C, and electrostatic contribution to the solvation free-energy. The model successfully distinguished between compounds with K(i) < 16muM and K(i) > 16muM. Models indicated that hydrophobicity, alpha substituent orientation, and partially compacted side chain conformation promote inhibitory potency. Qualitative CSP-SAR analysis indicated that the presence of an internal salt bridge, resulting in a locked conformation of the side chain, yielded weaker inhibitors.

CONCLUSIONS

Aminopiperidine conjugates of glu-BAs were potent hASBT inhibitors. A predictive and robust CSP-SAR model was developed.