Management of type 2 diabetes: new and future developments in treatment

The increasing prevalence, variable pathogenesis, progressive natural history, and complications of type 2 diabetes emphasise the urgent need for new treatment strategies. Longacting (eg, once weekly) agonists of the glucagon-like-peptide-1 receptor are advanced in development, and they improve prandial insulin secretion, reduce excess glucagon production, and promote satiety. Trials of inhibitors of dipeptidyl peptidase 4, which enhance the effect of endogenous incretin hormones, are also nearing completion. Novel approaches to glycaemic regulation include use of inhibitors of the sodium-glucose cotransporter 2, which increase renal glucose elimination, and inhibitors of 11β-hydroxysteroid dehydrogenase 1, which reduce the glucocorticoid effects in liver and fat. Insulin-releasing glucokinase activators and pancreatic-G-protein-coupled fatty-acid-receptor agonists, glucagon-receptor antagonists, and metabolic inhibitors of hepatic glucose output are being assessed. Early proof of principle has been shown for compounds that enhance and partly mimic insulin action and replicate some effects of bariatric surgery.

Beyond intestinal soap--bile acids in metabolic control

Over the past decade, it has become apparent that bile acids are involved in a host of activities beyond their classic functions in bile formation and fat absorption. The identification of the farnesoid X receptor (FXR) as a nuclear receptor directly activated by bile acids and the discovery that bile acids are also ligands for the membrane-bound, G-protein coupled bile acid receptor 1 (also known as TGR5) have opened new avenues of research. Both FXR and TGR5 regulate various elements of glucose, lipid and energy metabolism. Consequently, a picture has emerged of bile acids acting as modulators of (postprandial) metabolism. Therefore, strategies that interfere with either bile acid metabolism or signalling cascades mediated by bile acids may represent novel therapeutic approaches for metabolic diseases. Synthetic modulators of FXR have been designed and tested, primarily in animal models. Furthermore, the use of bile acid sequestrants to reduce plasma cholesterol levels has unexpected benefits. For example, treatment of patients with type 2 diabetes mellitus (T2DM) with sequestrants causes substantial reductions in plasma levels of glucose and HbA1c. This Review aims to provide an overview of the molecular mechanisms by which bile acids modulate glucose and energy metabolism, particularly focusing on the glucose-lowering actions of bile acid sequestrants in insulin resistant states and T2DM.

Clinical utility of bile acid sequestrants in the treatment of dyslipidemia: a scientific review

Bile acid sequestrants (BAS) continue to command a position in the treatment of dyslipidemias 25 years after their introduction. Partial diversion of the enterohepatic circulation using BAS depletes the endogenous bile acid pool by approximately 40%, thus stimulating an increase in bile acid synthesis from cholesterol, which lowers low-density lipoprotein cholesterol (LDL-C) by 15 to 26%. Three BAS are currently used for treating hypercholesterolemia in the United States: the conventional sequestrants, cholestyramine and colestipol, and the specifically engineered BAS, colesevelam hydrochloride (HCl). Compared with conventional BAS, colesevelam HCl has enhanced specificity, greater affinity, and higher capacity for binding bile acids, due to its polymer structure engineered for bile acid sequestration. BAS are not absorbed by the intestine and thus have no systemic drug-drug interactions, but may interfere with the absorption of some drugs. Although BAS monotherapy effectively lowers LDL-C, combination therapy, especially with BAS and statins, is becoming increasingly common due to complementary mechanisms of action. Low-dose statin plus BAS combinations lead to greater or similar LDL-C reductions compared with high-dose statin monotherapy and may have a better safety profile. Combinations of BAS with nonstatin lipid-lowering agents, including niacin, fibrates, and cholesterol absorption inhibitors, may be useful in those patients who require intensive lipid-lowering, but are statin intolerant. BAS treatment can significantly reduce coronary artery disease (CAD) progression and the risk of CAD-associated outcomes. It is also becoming clear that BAS and other therapies that manipulate the bile acid synthetic pathway may have clinically useful therapeutic effects on other metabolic disorders including type 2 diabetes.

Colesevelam hydrochloride (cholestagel): a new, potent bile acid sequestrant associated with a low incidence of gastrointestinal side effects

OBJECTIVES

To compare colesevelam hydrochloride (Cholestagel), a nonabsorbed hydrogel with bile acid-sequestering properties, with placebo for its lipid-lowering efficacy, its effects on laboratory and clinical safety parameters, and the incidence of adverse events.

METHODS

Following diet and placebo lead-in periods, placebo or colesevelam was administered at 4 dosages (1.5, 2.25, 3.0, or 3.75 g/d) for 6 weeks with morning and evening meals to men and women with hypercholesterolemia (low-density lipoprotein cholesterol level >4.14 mmol/L [>160 mg/dL]). Patients returned to the clinic every 2 weeks throughout the treatment period for lipid parameter measurements and adverse event assessments. Samples were collected for serum chemistry profiles, hematologic studies, coagulation studies, and vitamin level assessment at baseline and after 6 weeks of treatment.

RESULTS

Among the 149 patients randomized, 137 completed the study. Low-density lipoprotein cholesterol concentrations decreased in a dosage-dependent manner by 0.11 mmol/L (4.2 mg/dL) (1.8%) in the 1.5-g/d colesevelam treatment group and up to 1.01 mmol/L (39 mg/dL) (19.1%) in the 3.75-g/d colesevelam treatment group. Low-density lipoprotein cholesterol concentrations at the end of treatment were significantly reduced from baseline levels in the 3.0- and 3.75-g/d colesevelam treatment groups (P = .01 and P<.001, respectively). Total cholesterol levels demonstrated a similar response to colesevelam treatment, with an 8. 1% decrease from baseline in the 3.75-g/d treatment group (P<.001). High-density lipoprotein cholesterol levels rose significantly in the 3.0- and 3.75-g/d colesevelam treatment groups, by 11.2% (P=.006) and 8.1% (P=.02), respectively. Median triglyceride levels did not change from baseline, nor were there any significant differences between treatment groups. The incidence of adverse events was similar among all groups.

CONCLUSIONS

Colesevelam therapy is effective for lowering low-density lipoprotein cholesterol concentrations in persons with moderate hypercholesterolemia. It lacks the constipating effect of other bile acid sequestrants, demonstrating the potential for increased compliance.

Efficacy and safety of combination simvastatin and colesevelam in patients with primary hypercholesterolemia

PURPOSE

To examine the efficacy and safety of colesevelam hydrochloride, a novel, nonsystemic, lipid-lowering agent, when coadministered with starting doses of simvastatin in a multicenter, randomized, double-blind, placebo-controlled trial.

PATIENTS AND METHODS

Subjects with hypercholesterolemia (plasma low density lipoprotein [LDL] cholesterol level > 160 mg/dL and triglyceride level < or = 300 mg/dL) were randomly assigned to receive daily doses of placebo (n = 33), colesevelam 3.8 g (recommended dose, n = 37), simvastatin 10 mg (n = 35), colesevelam 3.8 g with simvastatin 10 mg (n = 34), colesevelam 2.3 g (low dose, n = 36), simvastatin 20 mg (n = 39), or colesevelam 2.3 g with simvastatin 20 mg (n = 37), for 6 weeks.

RESULTS

Mean LDL cholesterol levels decreased relative to baseline in the placebo group (P < 0.05) and in all active treatment groups (P < 0.0001). For groups treated with combination therapy, the mean reduction in LDL cholesterol level was 42% (-80 mg/dL; P < 0.0001 compared with baseline), which exceeded the reductions for simvastatin 10 mg (-26%, -48 mg/dL) or 20 mg (-34%, -61 mg/dL) alone, or for colesevelam 2.3 g (-8%, -17 mg/dL) or 3.8 g (-16%, -31 mg/dL) alone (P < 0.001). The effects of combination therapy on serum HDL cholesterol and triglyceride levels were similar to those for simvastatin alone. Side effects were similar among treatment groups, and there were no clinically important changes in laboratory parameters.

CONCLUSION

Coadministration of colesevelam and simvastatin was effective and well tolerated, providing additive reductions in LDL cholesterol levels compared with either agent alone.

Results of the glucose-lowering effect of WelChol study (GLOWS): a randomized, double-blind, placebo-controlled pilot study evaluating the effect of colesevelam hydrochloride on glycemic control in subjects with type 2 diabetes

OBJECTIVE

This study evaluated the glycosylated hemoglobin (HbA(1c)-lowering effect of colesevelam hydrochloride, a bile acid sequestrant, in subjects with type 2 diabetes that was inadequately controlled by existing antihyperglycemic therapy.

METHODS

After a 4-week placebo run-in period, subjects with type 2 diabetes and an HbA(1c) value of 7.0% to 10.0% were randomized to receive colesevelam 3.75 g/d or matching placebo for 12 weeks. Subjects' previous oral anti hyperglycemic medication (sulfonylurea and/or metformin) was continued throughout the study. Fasting blood samples were obtained at weeks -5, -1, 0, 1, 4, 8, and 12. The primary efficacy end point was the change in HbA(1c) from baseline to week 12. Secondary end points included changes in fructosamine levels, fasting plasma glucose levels, postprandial glucose level, and meal glucose response (ie, difference between preprandial and postprandial levels), and percent changes in lipid parameters from baseline to week 12.

RESULTS

The 65 randomized subjects (31 colesevelam, 34 placebo) had a mean age of 56.2 years and a mean body mass index of 32.4 kg/m(2); 55.4% were male and 53.8% were white. The difference in least squares (LS) mean (SE) change in HbA(1c) between the colesevelam group and the placebo group was -0.5% (0.18) (P = 0.007). In subjects with a baseline HbAIc > or = 8.0%, the difference in LS mean change in HbA(1c) was -1.0% (0.27) (P = 0.002). Relative to placebo, colesevelam treatment was associated with reductions in levels of fructosamine (-29.0 [10.9] pmol/L; P = 0.011) and postprandial glucose (-31.5 [13.6] mg/dL; P = 0.026). The mean percent change in low-density lipoprotein cholesterol was -9.6% in the colesevelam group, compared with 2.1% in the placebo group (treatment difference, -11.7% [4.2]; P = 0.007); the respective mean percent changes in total cholesterol were -4.0% and 3.4% (treatment difference, -7.3% [3.0]; P = 0.019). Colesevelam also was associated with significant decreases in the percent change in apolipoprotein B (P = 0.003) and low-density lipoprotein particle concentration (P = 0.037). The incidence of treatment-emergent adverse events (TEAEs) was similar in both groups, although treatment-related adverse events were more frequent in the colesevelam group than in the placebo group (29.0% vs 8.8%, respectively). The most frequent TEAEs in the colesevelam group were gastrointestinal disorders (22.6%), primarily constipation (19.4%), compared with an 8.8% incidence of gastrointestinal disorders (0% constipation) in the placebo group. There were no significant changes in body weight or the occurrence of hypoglycemia between treatment groups.

CONCLUSIONS

In these subjects with type 2 diabetes, 12 weeks of colesevelam treatment were associated with significant reductions in HbA(1c) and in fructosamine and postprandial glucose levels compared with placebo. The 2 groups had a similar adverse-event profile, with the exception of an increased incidence of constipation in the colesevelam group. These results suggest that colesevelam may improve both lipid control and glycemic control in patients with type 2 diabetes receiving oral antihyperglycemic medications.

Bile acid sequestrants and the treatment of type 2 diabetes mellitus

Bile acids promote bile formation and facilitate dietary lipid absorption. Animal and human studies showing disturbed bile acid metabolism in diabetes mellitus suggest a link between bile acids and glucose control. Bile acids are activating ligands of the farnesoid X receptor (FXR), a nuclear receptor with an established role in bile acid and lipid metabolism. Evidence suggests a role for FXR also in maintenance of glucose homeostasis. Animal and human studies employing bile acid sequestrants (bile acid binding agents), which interrupt the enterohepatic circulation of bile acids and effectively reduce plasma cholesterol, support a link between bile acid and glucose metabolism. In lipid-lowering trials, bile acid sequestrants, such as colesevelam hydrochloride, colestyramine (cholestyramine) and colestilan (colestimide), have also been shown to lower plasma glucose and glycosylated haemoglobin levels, suggesting the utility of these agents as a potential therapy for type 2 diabetes. In this article, we review the relationship between bile acid metabolism and glucose homeostasis, and present data demonstrating the utility of bile acid sequestrants in the management of diabetes.

Coadministration of colesevelam hydrochloride with atorvastatin lowers LDL cholesterol additively

Colesevelam hydrochloride is a novel, potent, non-absorbed lipid-lowering agent previously shown to reduce low density lipoprotein (LDL) cholesterol. To examine the efficacy and safety of coadministration of colesevelam and atorvastatin, administration of these agents alone or in combination was examined in a double-blind study of 94 hypercholesterolemic men and women (baseline LDL cholesterol > or =160 mg/dl). After 4 weeks on the American Heart Association Step I diet, patients were randomized among five groups: placebo; colesevelam 3.8 g/day; atorvastatin 10 mg/day; coadminstered colesevelam 3.8 g/day plus atorvastatin 10 mg/day; or atorvastatin 80 mg/day. Fasting lipids were measured at screening, baseline and 2 and 4 weeks of treatment. LDL cholesterol decreased by 12-53% in all active treatment groups (P<0.01). LDL cholesterol reductions with combination therapy (48%) were statistically superior to colesevelam (12%) or low-dose atorvastatin (38%) alone (P<0.01), but similar to those achieved with atorvastatin 80 mg/day (53%). Total cholesterol decreased 6-39% in all active treatment groups (P<0.05). High density lipoprotein cholesterol increased significantly for all groups including placebo (P<0.05). Triglycerides decreased in patients taking atorvastatin alone (P<0.05), but were unaffected by colesevelam alone or in combination. The frequency of side effects did not differ among groups. At recommended starting doses of each agent, coadministration of colesevelam and atorvastatin was well tolerated, efficacious and produced additive LDL cholesterol reductions comparable to those observed with the maximum atorvastatin dose.

Colesevelam suppresses hepatic glycogenolysis by TGR5-mediated induction of GLP-1 action in DIO mice

Bile acid sequestrants are nonabsorbable resins designed to treat hypercholesterolemia by preventing ileal uptake of bile acids, thus increasing catabolism of cholesterol into bile acids. However, sequestrants also improve hyperglycemia and hyperinsulinemia through less characterized metabolic and molecular mechanisms. Here, we demonstrate that the bile acid sequestrant, colesevelam, significantly reduced hepatic glucose production by suppressing hepatic glycogenolysis in diet-induced obese mice and that this was partially mediated by activation of the G protein-coupled bile acid receptor TGR5 and glucagon-like peptide-1 (GLP-1) release. A GLP-1 receptor antagonist blocked suppression of hepatic glycogenolysis and blunted but did not eliminate the effect of colesevelam on glycemia. The ability of colesevelam to induce GLP-1, lower glycemia, and spare hepatic glycogen content was compromised in mice lacking TGR5. In vitro assays revealed that bile acid activation of TGR5 initiates a prolonged cAMP signaling cascade and that this signaling was maintained even when the bile acid was complexed to colesevelam. Intestinal TGR5 was most abundantly expressed in the colon, and rectal administration of a colesevelam/bile acid complex was sufficient to induce portal GLP-1 concentration but did not activate the nuclear bile acid receptor farnesoid X receptor (FXR). The beneficial effects of colesevelam on cholesterol metabolism were mediated by FXR and were independent of TGR5/GLP-1. We conclude that colesevelam administration functions through a dual mechanism, which includes TGR5/GLP-1-dependent suppression of hepatic glycogenolysis and FXR-dependent cholesterol reduction.

Effect of bile acid sequestrants on glucose metabolism, hepatic de novo lipogenesis, and cholesterol and bile acid kinetics in type 2 diabetes: a randomised controlled study

AIMS/HYPOTHESIS

The primary aim of this completed multicentre randomised, parallel, double-blind placebo-controlled study was to elucidate the mechanisms of glucose-lowering with colesevelam and secondarily to investigate its effects on lipid metabolism (hepatic de novo lipogenesis, cholesterol and bile acid synthesis).

METHODS

Participants with type 2 diabetes (HbA(1c) 6.7-10.0% [50-86 mmol/mol], fasting glucose <16.7 mmol/l, fasting triacylglycerols <3.9 mmol/l and LDL-cholesterol >1.55 mmol/l) treated with diet and exercise, sulfonylurea, metformin or a combination thereof, were randomised by a central coordinator to either 3.75 g/day colesevelam (n = 30) or placebo (n = 30) for 12 weeks at three clinical sites in the USA. The primary measure was the change from baseline in glucose kinetics with colesevelam compared to placebo treatment. Fasting and postprandial glucose, lipid and bile acid pathways were measured at baseline and post-treatment using stable isotope techniques. Plasma glucose, insulin, total glucagon-like peptide-1 (GLP-1), total glucose-dependent insulinotropic polypeptide (GIP), glucagon and fibroblast growth factor-19 (FGF-19) concentrations were measured during the fasting state and following a meal tolerance test. Data was collected by people blinded to treatment.

RESULTS

Compared with placebo, colesevelam improved HbA(1c) (mean change from baseline of 0.3 [SD 1.1]% for placebo [n = 28] and -0.3 [1.1]% for colesevelam [n = 26]), glucose concentrations, fasting plasma glucose clearance and glycolytic disposal of oral glucose. Colesevelam did not affect gluconeogenesis or appearance rate (absorption) of oral glucose. Fasting endogenous glucose production and glycogenolysis significantly increased with placebo but were unchanged with colesevelam (treatment effect did not reach statistical significance). Compared with placebo, colesevelam increased total GLP-1 and GIP concentrations and improved HOMA-beta cell function while insulin, glucagon and HOMA-insulin resistance were unchanged. Colesevelam increased cholesterol and bile acid synthesis and decreased FGF-19 concentrations. However, no effect was seen on fractional hepatic de novo lipogenesis.

CONCLUSIONS/INTERPRETATION

Colesevelam, a non-absorbed bile acid sequestrant, increased circulating incretins and improved tissue glucose metabolism in both the fasting and postprandial states in a manner different from other approved oral agents.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00596427

FUNDING

The study was funded by Daiichi Sankyo.

Colesevelam lowers glucose and lipid levels in type 2 diabetes: the clinical evidence

Simultaneous control of blood glucose and other risk factors such as hypertension and dyslipidaemia is essential for reducing the risk of complications associated with type 2 diabetes mellitus (T2DM). As relatively few patients with T2DM have their risk factors managed to within the limits recommended by the American Diabetes Association, American College of Endocrinology or National Cholesterol Education Program Adult Treatment Panel III guidelines, treatment that can simultaneously control more than one risk factor is of therapeutic benefit. Clinical studies have shown that bile acid sequestrants have glucose-lowering effects in addition to their low-density lipoprotein cholesterol-lowering effects in patients with T2DM. The bile acid sequestrant colesevelam hydrochloride is approved as an adjunct to antidiabetes therapy for improving glycaemic control in adults with T2DM. This review examines data from three phase III clinical trials that evaluated the glucose- and lipid-lowering effects of colesevelam when added to the existing antidiabetes treatment regimen of patients with T2DM.

Effectiveness of colesevelam hydrochloride in decreasing LDL cholesterol in patients with primary hypercholesterolemia: a 24-week randomized controlled trial

OBJECTIVE

To evaluate the efficacy, tolerability, and safety of colesevelam hydrochloride, a new nonsystemic lipid-lowering agent.

PATIENTS AND METHODS

In this double-blind, placebo-controlled trial performed in 1998, 494 patients with primary hypercholesterolemia (low-density lipoprotein [LDL] cholesterol level > or = 130 mg/dL and < or = 220 mg/dL) were randomized to receive placebo or colesevelam (2.3 g/d, 3.0 g/d, 3.8 g/d, or 4.5 g/d) for 24 weeks. Fasting serum lipid profiles were measured to assess efficacy. Adverse events were monitored, and discontinuation rates and compliance rates were analyzed. The primary outcome measure was the mean absolute change of LDL cholesterol from baseline to the end of the 24-week treatment period.

RESULTS

Colesevelam lowered mean LDL cholesterol levels 9% to 18% in a dose-dependent manner (P<.001), with a median LDL cholesterol reduction of 20% at 4.5 g/d. The reduction in LDL cholesterol levels was maximal after 2 weeks and sustained throughout the study. Mean total cholesterol levels decreased 4% to 10% (P<.001), while median high-density lipoprotein cholesterol levels increased 3% to 4% (P<.001). Median triglyceride levels increased by 5% to 10% in placebo and colesevelam treatment groups relative to baseline (P<.05), but none of these differences were significantly different from placebo. Mean apolipoprotein B levels decreased 6% to 12% in an apparent dose-dependent manner (P<.001). No significant differences occurred in adverse events or discontinuation rates between groups, and compliance rates were between 88% and 92% for all groups.

CONCLUSIONS

Colesevelam was efficacious, decreasing mean LDL cholesterol levels by up to 18%, and well tolerated without serious adverse events.

Low-dose combination therapy with colesevelam hydrochloride and lovastatin effectively decreases low-density lipoprotein cholesterol in patients with primary hypercholesterolemia

BACKGROUND

Colesevelam hydrochloride is a novel, lipid-lowering agent that binds bile acids with high affinity. A multicenter, randomized, double-blind, placebo-controlled, parallel-design study was conducted to assess the efficacy and tolerability of combination low-dose colesevelam and lovastatin treatment in patients with primary hypercholesterolemia.

HYPOTHESIS

Combination therapy with low doses of colesevelam and lovastatin decreases low density (LDL) cholesterol with minimal adverse events.

METHODS

Following a 4- to 6-week dietary lead in, 135 patients were randomized into five groups for a 4-week treatment period: placebo, colesevelam 2.3 g at dinner, lovastatin 10 mg at dinner, the combination of colesevelam and lovastatin given at dinner (dosed together), and combination treatment with colesevelam given at dinner and lovastatin administered at bedtime (dosed apart).

RESULTS

Combination colesevelam and lovastatin treatment decreased LDL cholesterol by 34% (60 mg/dl, p < 0.0001) and 32% (53 mg/dl, p < 0.0001) when colesevelam and lovastatin were dosed together or dosed apart, respectively. Both combination therapies were superior to either agent alone (p < 0.05). Decreases in LDL cholesterol exceeded the combined decreases observed for colesevelam alone (13 mg/dl, 7%) and lovastatin alone (39 mg/dl, 22%). Both combination treatments reduced total cholesterol by 21% (p < 0.0001) and apolipoprotein B by 24% (p < 0.0001). Neither combination treatment significantly altered high-density lipoprotein cholesterol or triglycerides. Adverse side effects were not significantly different among randomized groups.

CONCLUSIONS

Combination colesevelam and lovastatin was efficacious and well tolerated, resulting in additive decreases in LDL cholesterol levels whether or not both agents were administered simultaneously.

Effects of colesevelam hydrochloride on low-density lipoprotein cholesterol and high-sensitivity C-reactive protein when added to statins in patients with hypercholesterolemia

Elevated high-sensitivity C-reactive protein (hs-CRP) levels are associated with an increased risk of atherosclerotic coronary heart disease (CHD). The addition of the bile acid sequestrants, such as colesevelam hydrochloride (HCl), to statins further reduces low-density lipoprotein (LDL) cholesterol levels. However, the effects of approved cholesterol-lowering bile acid sequestrants on hs-CRP have not previously been reported. Three randomized, double-blind, placebo-controlled, parallel, 6-week clinical trials of similar design investigated the efficacy of adding colesevelam HCl to stable simvastatin, atorvastatin, or pravastatin treatment in 204 patients with primary hypercholesterolemia. The primary end point was the mean percent change in the LDL cholesterol levels. Secondary end points included the effects on other lipid parameters and hs-CRP levels. A pooled analysis showed that adding colesevelam HCl to statin therapy significantly lowered LDL cholesterol levels (21 mg/dl or 16% mean reduction from baseline, p = 0.0013, and 11 mg/dl or 9% mean reduction compared with placebo, p = 0.0003). Four times as many patients receiving colesevelam HCl plus a statin achieved a LDL cholesterol target of <100 mg/dl compared with patients receiving a statin plus placebo (39% vs 10%, respectively, p <0.0001). The incidence of mild gastrointestinal adverse effects was slightly higher in the colesevelam HCl plus statin group than in the placebo plus statin group. Finally, the differences in the change in hs-CRP levels with colesevelam HCl plus statin therapy were significant compared with the changes with placebo plus statin (median change -23%, p = 0.0069). In conclusion, this is the first report suggesting that an approved cholesterol-lowering bile acid sequestrant, specifically colesevelam HCl, decreases hs-CRP levels when added to statin therapy.

Drug interactions with colesevelam hydrochloride, a novel, potent lipid-lowering agent

Colesevelam hydrochloride (colesevelam) is a novel, potent, bile acid-binding agent that has been shown to lower LDL cholesterol a mean of 19% at a dose of 3.8 g/d. We studied the pharmacokinetics of colesevelam coadministered with six drugs: digoxin and warfarin, agents with narrow therapeutic indices; sustained-release verapamil and metoprolol; quinidine, an antiarrhythmic with a narrow therapeutic index; and valproic acid, an antiseizure medication. Six individual studies were single-dose, crossover, with or without a 4.5-g dose of colesevelam. Plasma levels were determined using validated analytical methods. Values for the ratio of ln[AUC(0-t)] with and without colesevelam were 107% for quinidine, 102% for valproic acid, 89% for digoxin, 102% for warfarin, 82% for verapamil, and 112% for metoprolol. Values for the ratio of ln[Cmax] with and without colesevelam were 107% for quinidine, 92% for valproic acid, 96% for digoxin, 99% for warfarin, 69% for verapamil, and 112% for metoprolol. The 90% confidence intervals for these ratios and for values of ln[AUC(0-inf)] that could be determined were within the 80-125% range, with the exception of verapamil. In this study, verapamil had great interindividual variability, with a 28-fold range in Cmax and an 11-fold range in AUC(0-t). In summary, pharmacokinetic studies with colesevelam did not show clinically significant effects on absorption of six other coadministered drugs.

The effect of a bile acid sequestrant on glucose metabolism in subjects with type 2 diabetes

We designed an experiment to examine the effect of bile acid sequestration with Colesevelam on fasting and postprandial glucose metabolism in type 2 diabetes. To do so, we tested the hypothesis that Colesevelam increases the disposition index (DI), and this increase is associated with increased glucagon-like peptide-1 (GLP-1) concentrations. Thirty-eight subjects on metformin monotherapy were studied using a double-blind, placebo-controlled, parallel-group design. Subjects were studied before and after 12 weeks of Colesevelam or placebo using a labeled triple-tracer mixed meal to measure the rate of meal appearance (Meal Ra), endogenous glucose production (EGP), and glucose disappearance (Rd). Insulin sensitivity and β-cell responsivity indices were estimated using the oral minimal model and then used to calculate DI. Therapy with Colesevelam was associated with a decrease in fasting (7.0 ± 0.2 vs. 6.6 ± 0.2 mmol/L; P = 0.004) and postprandial glucose concentrations (3,145 ± 138 vs. 2,896 ± 127 mmol/6 h; P = 0.01) in the absence of a change in insulin concentrations. Minimal model-derived indices of insulin secretion and action were unchanged. Postprandial GLP-1 concentrations were not altered by Colesevelam. Although EGP and Rd were unchanged, integrated Meal Ra was decreased by Colesevelam (5,191 ± 204 vs. 5,817 ± 204 μmol/kg/6 h; P = 0.04), suggesting increased splanchnic sequestration of meal-derived glucose.

Pharmacologic options for aggressive low-density lipoprotein cholesterol lowering: benefits versus risks

Lessons from recent end point trials of lipid-lowering drugs indicate that patients at very high risk for coronary artery disease (CAD) benefit from treatment that lowers low-density lipoprotein (LDL) cholesterol plasma levels to < or = 1.81 mmol/L (< or = 70 mg/dL), that patients with > or = 2 risk factors benefit from treatment that lowers plasma LDL cholesterol to <2.59 mmol/L (<100 mg/dL), and that a significant reduction in CAD event rates is most often associated with a minimum plasma LDL cholesterol reduction of 30%. Recently, the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) recommendations were amended to incorporate these lessons. To reach these more aggressive goals and plasma LDL cholesterol reductions, more aggressive therapies will be required. The best way to implement more aggressive therapy is to start with one of the more potent statins, especially atorvastatin or rosuvastatin, or higher doses of other statins. This approach alone is likely to achieve treatment goals in 50% to 80% of patients. For patients needing additional plasma LDL cholesterol lowering, combination therapies will be required. Adding colesevelam, ezetimibe, or niacin to a stable statin regimen will generally provide an additional 10% to 15% lowering of plasma LDL cholesterol. These more potent statins, even when used in higher doses, appear to be safe. The incidence of myopathy and rhabdomyolysis, as documented in long-term clinical trials, is <0.1% and <0.01%, respectively, except for simvastatin, which has a higher incidence of these problems. Less information is available about the safety of lowering levels of plasma LDL cholesterol to < or = 1.81 mmol/L (< or = 70 mg/dL), but an analysis of a recent 2-year-long clinical trial, in which patients had on-treatment plasma LDL cholesterol levels as low as 0.67 mmol/L (26 mg/dL), reported no signals of untoward effects in patients with progressively lower levels.

Neither intestinal sequestration of bile acids nor common bile duct ligation modulate the expression and function of the rat ileal bile acid transporter

The regulatory responses of bile acid (BA) transport in the terminal ileum to perturbations in BA homeostasis are complex, and conflicting results have been reported by different investigators. These studies were designed to examine the response of this system to a reduction in ileal bile salt concentrations at both a functional and molecular level. Common bile duct ligation (BDL) or feeding of a novel bile acid-binding compound, GT31-104HB, for 7 days were used to reduce ileal apical membrane bile salt flux. Apical bile acid transport function was assessed by examining sodium-dependent uptake of [3H]-taurocholate (TC) into brush border membrane vesicles (BBMV). Expression of the apical sodium-dependent bile acid transporter (ASBT) and the ileal lipid-binding protein (ILBP) were assessed by Western blotting with quantitation using [125I]-labeled secondary antibody and a phosphorimager. Neither common BDL nor intestinal sequestration of BA led to a change in ileal bile acid transport function or the expression of the ASBT or the ILBP. These results indicate that a reduction in presentation of bile salts to the apical surface of the terminal ileum does not modulate the expression of the genes involved in their transport.

Colesevelam hydrochloride: a novel bile acid-binding resin

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy, and adverse effects of colesevelam hydrochloride, a bile acid-binding resin.

METHODS

MEDLINE searches (1966-June 2000) and manufacturer prescribing literature were employed to find articles on colesevelam. Additional studies and abstracts were identified from the bibliographies of reviewed literature.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from data sources were evaluated, and all information deemed relevant was included in this review. Priority was given to randomized, double-blind, placebo-controlled studies.

FINDINGS

Colesevelam HCl is a nonabsorbed hydrogel with bile acid sequestrant properties. Monotherapy using colesevelam in once-daily or two divided daily doses of 1.5-4.5 g has produced significant reductions in total cholesterol and low-density lipoprotein (LDL) cholesterol. Mean LDL cholesterol decreases to 20% have been noted when the patient is on 3.75-4.5 g/d. Increases in high-density lipoprotein (HDL) cholesterol have been observed (up to 9%), whereas triglycerides (TG) have increased significantly to 25% in some studies. In unpublished studies, combined use of colesevelam plus hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor have produced greater reductions in LDL cholesterol than either the statin or colesevelam administered alone. The efficacy of colesevelam monotherapy is slightly less than or similar to cholestyramine or colestipol in decreasing LDL cholesterol, although colesevelam is more potent on a gram-to-gram basis. Adverse effects have been minimal with colesevelam in published studies; this suggests an advantage over cholestyramine or colestipol therapy. Colesevelam appears to be more cost-effective than the packet dosage form of the brand formulation of the older bile acid resins. Care in selection of an appropriate agent should be exercised when considering the issues of adverse effects and palatability.

CONCLUSIONS

Colesevelam alone or combined with an HMG-CoA reductase inhibitor is effective in the reduction of total and LDL cholesterol. Since colesevelam is formulated as a tablet, problems with palatability such as with the powder formulation of the bile acid-binding resins are likely to be eliminated.

Bile acid sequestrants in type 2 diabetes: potential effects on GLP1 secretion

Bile acid sequestrants have been used for decades for the treatment of hypercholesterolaemia. Sequestering of bile acids in the intestinal lumen interrupts enterohepatic recirculation of bile acids, which initiate feedback mechanisms on the conversion of cholesterol into bile acids in the liver, thereby lowering cholesterol concentrations in the circulation. In the early 1990s, it was observed that bile acid sequestrants improved glycaemic control in patients with type 2 diabetes. Subsequently, several studies confirmed the finding and recently - despite elusive mechanisms of action - bile acid sequestrants have been approved in the USA for the treatment of type 2 diabetes. Nowadays, bile acids are no longer labelled as simple detergents necessary for lipid digestion and absorption, but are increasingly recognised as metabolic regulators. They are potent hormones, work as signalling molecules on nuclear receptors and G protein-coupled receptors and trigger a myriad of signalling pathways in many target organs. The most described and well-known receptors activated by bile acids are the farnesoid X receptor (nuclear receptor) and the G protein-coupled cell membrane receptor TGR5. Besides controlling bile acid metabolism, these receptors are implicated in lipid, glucose and energy metabolism. Interestingly, activation of TGR5 on enteroendocrine L cells has been suggested to affect secretion of incretin hormones, particularly glucagon-like peptide 1 (GLP1 (GCG)). This review discusses the role of bile acid sequestrants in the treatment of type 2 diabetes, the possible mechanism of action and the role of bile acid-induced secretion of GLP1 via activation of TGR5.

Lipid-lowering effects of colesevelam HCl in combination with ezetimibe

OBJECTIVE

The primary aim of this study was to compare the effect of colesevelam HCl in combination with ezetimibe to ezetimibe monotherapy on low-density lipoprotein cholesterol (LDL-C) levels in subjects with primary hypercholesterolemia.

METHODS

Subjects with primary hypercholesterolemia (N = 86) were enrolled in a multicenter, randomized, double-blind, placebo-controlled, parallel-group study. After a 4- to 8-week washout period, subjects received colesevelam HCl 3.8 g/day plus ezetimibe 10 mg/day or colesevelam HCl placebo plus ezetimibe 10 mg/day for 6 weeks. The primary efficacy endpoint was the mean percent change in LDL-C during randomized treatment. Secondary endpoints included mean absolute change in LDL-C, mean absolute and mean percent change in levels of high-density lipoprotein cholesterol (HDL-C), non-HDL-C, total cholesterol (TC), apolipoprotein (apo) A-I and apo B, and median absolute and percent changes in triglycerides (TG) and high-sensitivity C-reactive protein from baseline to end of treatment. Of the 86 subjects randomized to treatment, 85 were included in the intent-to-treat analysis.

RESULTS

After 6 weeks of treatment, colesevelam HCl plus ezetimibe produced a mean percent change in LDL-C of -32.3% versus -21.4% with ezetimibe monotherapy (p < 0.0001). Colesevelam HCl plus ezetimibe was significantly more effective than ezetimibe alone at producing mean percent reductions in TC, non-HDL-C, and apo B and increases in apo A-I (p < 0.005 for all). Neither treatment regimen resulted in significant changes in median TG levels compared with baseline (p = NS). Both treatments were safe and generally well tolerated.

CONCLUSIONS

Colesevelam HCl plus ezetimibe combination therapy significantly reduced mean LDL-C, TC, non-HDL-C, and apo B levels and increased apo A-I levels (p < 0.005 for all) without significantly increasing median TG levels in hypercholesterolemic subjects compared with ezetimibe alone. Although limited in that atherosclerotic coronary heart disease outcomes were not evaluated, this study demonstrated that combining colesevelam HCl with ezetimibe is a therapeutic option in hypercholesterolemic patients, such as those in whom statins are contraindicated and/or who may have intolerances to statin therapy.

Quantifying bile acid malabsorption helps predict response and tailor sequestrant therapy

Although recognised as a cause of chronic diarrhoea for over forty years, diagnostic tests and treatments for bile acid malabsorption (BAM) remain controversial. Recent National Institute for Health and Care Excellence (NICE) guidelines highlighted the lack of evidence in the field, and called for further research. This retrospective study explores the BAM subtype and severity, the use and response to bile acid sequestrants (BAS) and the prevalence of abnormal colonic histology. 264 selenium-75-labelled homocholic acid conjugated taurine (SeHCAT)-tested patient records were reviewed and the severity and subtype of BAM, presence of colonic histopathology and response to BAS were recorded. 53% of patients tested had BAM, with type-2 BAM in 45% of patients with presumed irritable bowel syndrome. Colonic histological abnormalities were similar overall between patients with (29%) or without (23%) BAM (p = 0.46) and between BAM subtypes, with no significant presence of inflammatory changes. 63% of patients with BAM had a successful BAS response which showed a trend to decreased response with reduced severity. Colestyramine was unsuccessful in 44% (38/87) and 45% of these (17/38) were related to medication intolerance, despite a positive SeHCAT. 47% (7/15) of colestyramine failures had a successful colesevelam response. No patient reported colesevelam intolerance. Quantifying severity of BAM appears to be useful in predicting BAS response. Colesevelam was better tolerated than colestyramine and showed some efficacy in colestyramine failures. Colestyramine failure should not be used to exclude BAM. Colonic histology is of no relevance.

Effectiveness and tolerability of ezetimibe add-on therapy to a bile acid resin-based regimen for hypercholesterolemia

Combination lipid-reducing therapy is increasingly used, particularly for the management of severe or combined dyslipidemia in patients at high risk for coronary heart disease. To assess the potential additive effects of combining the cholesterol absorption inhibitor ezetimibe with a bile acid resin (BAR), a prospective chart review was performed of 40 patients in whom ezetimibe 10 mg/day was added to a stable regimen that included a BAR. At an average follow-up of 107 +/- 57 days, ezetimibe coadministration significantly reduced total cholesterol by 18%, triglycerides by 14%, and low-density lipoprotein cholesterol by 19% (all p < or =0.03), without significantly changing high-density lipoprotein cholesterol, and the combination was well tolerated.

Colesevelam HCl and ezetimibe combination therapy provides effective lipid-lowering in difficult-to-treat patients with hypercholesterolemia

This study investigated the effects of colesevelam hydrochloride (WelChol; Sankyo Pharma, Parsippany, NJ) and ezetimibe (Zetia; Merck/Schering Plough Pharmaceuticals, North Wales, PA), alone and in combination, for the treatment of hypercholesterolemia in patients who were intolerant to, or refused, HMG-Co-A reductase inhibitor (statin) therapy. Combination therapy with colesevelam HCl/ezetimibe resulted in an additional reduction in low-density lipoprotein cholesterol (LDL-C) and non-high-density lipoprotein cholesterol (HDL-C) levels of approximately 20% (P < 0.005) and 16% (P < 0.01), respectively, compared with monotherapy with either agent. Total cholesterol, LDL-C, and non-HDL-C levels were within National Cholesterol Education Program Adult Treatment Panel III target ranges at the end of the combination therapy regimen in 10 of 12 patients. In conclusion, colesevelam HCl/ezetimibe combination therapy appears to be an efficacious and well-tolerated alternative for patients with hypercholesterolemia.

Colesevelam Hydrochloride-Ezetimibe Combination Lipid-Lowering Therapy in Patients with Diabetes or Metabolic Syndrome and a History of Statin Intolerance

OBJECTIVE

To determine the effectiveness and safety of colesevelam hydrochloride (HCl) and ezetimibe combination therapy in statin-intolerant patients with dyslipidemia and diabetes mellitus (DM) or metabolic syndrome (MS).

METHODS

We identified potential study subjects through a computerized text search of patient electronic medical records using the terms colesevelam, WelChol, ezetimibe, and Zetia. Medical records were subsequently reviewed to identify all patients with DM or MS. Baseline total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), non-HDL-C, and triglyceride levels immediately before the initiation of therapy with colesevelam HCl (1.875 g twice a day) or ezetimibe (10 mg daily) were compared with those after a minimum of 3 months of single drug therapy and after a minimum of 3 months of combination therapy. Drug safety was evaluated by review of transaminase levels and reports of side effects or drug discontinuation.

RESULTS

The computerized search initially identified 91 electronic medical records; 16 patients fulfilled all study criteria. Baseline patient demographics included a mean age of 62.5 (+/-11.8) years and a mean body mass index of 31.4 (+/-5.2) kg/m2; 50% of patients were female, 75% had type 2 DM, and 25% had MS. In comparison with baseline, colesevelam HCl-ezetimibe combination therapy was associated with significant reductions in mean levels of total cholesterol (27.5%), LDL-C (42.2%), and non-HDL-C (37.1%). In addition, 50% of patients achieved the National Cholesterol Education Program Adult Treatment Panel III LDL-C target of less than 100 mg/dL. Therapy was well tolerated, with no significant changes in mean transaminase levels, no reports of myalgia, and no discontinuation of therapy.

CONCLUSION

Colesevelam HCl-ezetimibe combination therapy was associated with improved TC, LDL-C, and non-HDL-C lipid profiles and was well tolerated. Such therapy may be a reasonable consideration for statin-intolerant patients with DM or MS who have elevated cholesterol levels.