Colesevelam

Metabolites Linking the Gut Microbiome with Risk for Type 2 Diabetes

PURPOSE OF REVIEW

An increasing body of evidence suggests that the gut microbiome influences the pathogenesis of insulin resistance and type 2 diabetes (T2D). In this review, we will discuss the latest findings regarding the mechanisms linking the gut microbiome and microbial metabolites with T2D and therapeutic approaches based on the gut microbiota for the prevention and treatment of T2D.

RECENT FINDINGS

Alterations in the gut microbial composition are associated with the risk of T2D. The gut microbiota can metabolize dietary- and host-derived factors to produce numerous microbial metabolites, which are involved in metabolic processes modulating nutrition and energy harvest, gut barrier function, systemic inflammation, and glucose metabolism. Microbial metabolites are important mediators of microbial-host crosstalk impacting host glucose metabolism. Furthermore, microbiome-based interventions may have beneficial effects on glycemic control. Future research is required to develop personalized T2D therapy based on microbial composition and/or metabolites.

Colesevelam hydrochloride: evidence for its use in the treatment of hypercholesterolemia and type 2 diabetes mellitus with insights into mechanism of action

Colesevelam hydrochloride is a molecularly engineered, second-generation bile acid sequestrant demonstrating enhanced specificity for bile acids which has been approved for use as adjunctive therapy to diet and exercise as monotherapy or in combination with a β-hydroxymethylglutaryl-coenzyme A reductase inhibitor for the reduction of elevated low-density lipoprotein cholesterol in patients with primary hypercholesterolemia. It is also the only lipid-lowering agent currently available in the United States which has been approved for use as adjunctive therapy in patients with type 2 diabetes mellitus whose glycemia remains inadequately controlled on therapy with metformin, sulfonylurea, or insulin. With the recent emphasis upon drug safety by the Food and Drug Administration and various consumer agencies, it is fitting that the role of nonsystemic lipid-lowering therapies such as bile acid sequestrants – with nearly 90 years of in-class, clinically safe experience – should be reexamined. This paper presents information on the major pharmacologic effects of colesevelam, including a discussion of recent data derived from both in vitro and in vivo rodent and human studies, which shed light on the putative mechanisms involved.

Colesevelam: in pediatric patients with heterozygous familial hypercholesterolemia

Colesevelam hydrochloride (colesevelam), a non-absorbed, synthetic, lipid-lowering polymer, is a bile acid sequestrant. Colesevelam binds with high affinity to bile acids within the gastrointestinal tract, thereby inhibiting the reabsorption of bile acids, resulting in decreases in serum low-density lipoprotein cholesterol (LDL-C) levels. Colesevelam is available as tablets and as powder for oral suspension. At dosages of 3.75 g once daily or 1.875 g twice daily, colesevelam is approved in the US for the treatment of pediatric patients aged 10-17 years with heterozygous familial hypercholesterolemia. Colesevelam may be administered as monotherapy or in combination with an HMG-CoA reductase inhibitor (statin). A 32-week trial was conducted and consisted of a stablilization period ( approximately 4 weeks), a randomized period (8 weeks), an open-label period (18 weeks), and a 2-week follow-up period. In the 8-week, randomized, double-blind, placebo-controlled period of the trial, colesevelam (tablets), as monotherapy or with a statin, was an effective treatment for pediatric patients with heterozygous familial hypercholesterolemia. At week 8, recipients of colesevelam 3.75 g/day had significant percentage reductions from baseline in mean LDL-C levels (primary endpoint) compared with placebo recipients. Significant beneficial treatment effects for colesevelam 3.75 g/day versus placebo were also reported for several other lipid/lipoprotein parameters at week 8 of the study. The reported treatment effects on lipid/lipoprotein parameters were maintained over a subsequent 18-week, open-label, noncomparative period, when all patients received colesevelam 3.75 g/day. Colesevelam 3.75 g/day was generally well tolerated for up to 26 weeks by pediatric patients with heterozygous familial hypercholesterolemia.

Novel pathways for glycaemic control in type 2 diabetes: focus on bile acid modulation

Type 2 diabetes is a common disorder with high risk of macrovascular and microvascular complications. These complications are largely driven by hyperglycaemia, dyslipidaemia and hypertension, for which aggressive treatment is thus warranted. Achieving and maintaining control of all three risk factors is especially difficult, however, and new therapeutic approaches could be useful. Bile acids have a well-established and important role in cholesterol homeostasis. Normally, their levels are maintained primarily by ileal reabsorption and enterohepatic recycling. Bile acid sequestrants bind bile acids in the intestine, reduce this recycling and deplete the bile acid pool, thereby stimulating use of hepatic cholesterol for bile acid synthesis, which leads to accelerated removal of LDL from the plasma and a decrease in LDL-cholesterol levels. Interestingly, recent evidence suggests that bile acid sequestrants can lower glucose levels to a clinically meaningful degree. This review presents this evidence and the possible mechanisms by which these glucose-lowering effects occur and discusses the apparently unique ability of bile acid sequestrants among lipid-lowering agents to significantly improve two cardiovascular risk factors, hyperglycaemia and dyslipidaemia. There is renewed interest in the use of bile acid sequestrants in individuals with type 2 diabetes, most of whom would benefit from additional reductions in both LDL-cholesterol and glycaemia.

Emerging antidyslipidemic drugs

BACKGROUND

Many patients at high risk for coronary heart disease (CHD) fail to reach target lipid levels with currently available medications, and a small but clinically relevant proportion of patients experience adverse effects. Thus, additional pharmaceutical strategies are required to fill these gaps in efficacy and tolerability.

OBJECTIVE

To provide an overview of both current and emerging antidyslipidemic drugs.

METHODS

For the current antidyslipidemic drugs, we focus primarily on statins, bile acid sequestrants, fibrates, ezetimibe, and niacin. Emerging antidyslipidemic drugs herein discussed were identified by searching the Pharmaprojects database for 'hypercholesterolemia drugs' (Phase II or Phase III), 'HDL-based therapies', and 'PCSK9 inhibition'.

RESULTS/CONCLUSIONS

Combinations of currently existing medications are most easily applicable. Meanwhile, strategies to raise HDL-C rely on a deep understanding of the complexity of HDL metabolism. Furthermore, novel approaches to further reduce LDL-C warrant careful evaluation of benefit-risk ratio. Finally, the medical community will have to rely on late-phase CHD outcome studies as the final arbiter of clinical application for any new antidyslipidemia treatment.

Colesevelam: a review of its use in hypercholesterolemia

Colesevelam hydrochloride (Cholestagel, WelChol is an orally administered, non-absorbable, polymeric, bile-acid-binding agent with a higher affinity for glycocholic acid in vitro and greater capacity for binding bile acids in vivo than other bile-acid-binding agents. In randomized controlled trials in patients with primary hypercholesterolemia, colesevelam monotherapy reduced mean serum low-density lipoprotein-cholesterol (LDL-C) levels by 9-19%. In combination with an HMG-CoA reductase inhibitor (statin) or fenofibrate, colesevelam induced additive reductions in LDL-C 10-16% greater than those achieved by monotherapy with a statin (in patients with primary hypercholesterolemia) or fenofibrate (in patients with mixed hyperlipidemia). Colesevelam was generally well tolerated, with a relatively low incidence of gastrointestinal adverse events and a high compliance rate. Thus, colesevelam provides a useful addition to primary therapy with statins in the treatment of primary hypercholesterolemia, or fenofibrate in the treatment of mixed hyperlipidemia.

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.

Novel non-systemic inhibitor of ileal apical Na+-dependent bile acid transporter reduces serum cholesterol levels in hamsters and monkeys

1-{7-[(1-(3,5-Diethoxyphenyl)-3-{[(3,5-difluorophenyl)(ethyl)amino]carbonyl}-4-oxo-1,4-dihydroquinolin-7-yl)oxy]heptyl}-1-methylpiperidinium bromide, R-146224, is a potent, specific ileum apical sodium-dependent bile acid transporter (ASBT) inhibitor; concentrations required for 50% inhibition of [3H]taurocholate uptake in human ASBT-expressing HEK-293 cells and hamster ileum tissues were 0.023 and 0.73 microM, respectively. In bile-fistula rats, biliary and urinary excretion 48 h after 10 mg/kg [14C]R-146224, were 1.49+/-1.75% and 0.14+/-0.05%, respectively, demonstrating extremely low absorption. In hamsters, R-146224 dose-dependently reduced gallbladder bile [3H]taurocholate uptake (ED50: 2.8 mg/kg). In basal diet-fed hamsters, 14-day 30-100 mg/kg R-146224 dose-dependently reduced serum total cholesterol (approximately 40%), high density lipoprotein (HDL) cholesterol (approximately 37%), non-HDL cholesterols (approximately 20%), and phospholipids (approximately 20%), without affecting serum triglycerides, associated with reduced free and esterified liver cholesterol contents. In normocholesterolemic cynomolgus monkeys, R-146224 specifically reduced non-HDL cholesterol. In human ileum specimens, R-146224 dose-dependently inhibited [3H]taurocholate uptake. Potent non-systemic ASBT inhibitor R-146224 decreases bile acid reabsorption by inhibiting the ileal bile acid active transport system, resulting in hypolipidemic activity.

Effect of Colesevelam HCl on Single-Dose Fenofibrate Pharmacokinetics

OBJECTIVE

The primary aim of this study was to determine whether there is an effect of colesevelam HCl (WelChol; Sankyo Pharma Inc., Parsippany, NJ, USA) on fenofibric acid (active metabolite of fenofibrate, TriCor, Abbott Laboratories, North Chicago, IL, USA) pharmacokinetics following single-dose fenofibrate when colesevelam HCl and fenofibrate are administered concomitantly, or when colesevelam HCl is administered 4 hours following fenofibrate therapy.

METHODS

Thirty healthy volunteers were enrolled in a randomised, open-label, three-way crossover, drug interaction study. Subjects received one of three treatments at each of three dose administration periods: (i) treatment A -- fenofibrate 160 mg plus colesevelam HCl 3750 mg (6 x 625 mg tablets) administered with breakfast; (ii) treatment B -- fenofibrate 160 mg administered with breakfast, followed 4 hours later by colesevelam HCl 3750 mg (6 x 625 mg tablets) administered with lunch; or (iii) treatment C -- fenofibrate 160 mg administered with breakfast. Treatments were separated by a 10-day washout period. Blood samples were collected at predetermined time intervals, both before and after drug administration. Plasma concentrations of fenofibrate and fenofibric acid were measured using a validated liquid chromatography/mass spectroscopy/mass spectroscopy method.

RESULTS

Area under the concentration-time curve (AUC) from time zero to the timepoint of the lowest quantifiable concentration (AUCt), AUC from time zero to infinity (AUCinfinity) and maximum plasma concentration (Cmax) for fenofibric acid were 92.1%, 93.9% and 79.8%, respectively, of control values when colesevelam HCl and fenofibrate were coadministered with breakfast; and 91.9%, 93.9% and 99.1%, respectively, when fenofibrate was administered followed 4 hours later by administration of colesevelam HCl. The 90% confidence intervals for the ratios of geometric means for AUCt, AUCinfinity and Cmax comparing the three treatments were contained within the 80-125% equivalence range, with the exception of Cmax for treatment A. Coadministration of fenofibrate with colesevelam HCl resulted in an approximate 20% reduction in Cmax of the active metabolite (fenofibric acid). There were no significant differences in the time to Cmax, elimination rate constant or elimination half-life between any of the treatment groups.

CONCLUSIONS

Colesevelam HCl had no significant effect on fenofibrate bioavailability when administered either concomitantly with fenofibrate or 4 hours after fenofibrate.