Modulating LDL cholesterol and glucose in patients with type 2 diabetes mellitus: targeting the bile acid pathway

Research progress on the relationship between bile acid metabolism and type 2 diabetes mellitus

Bile acids, which are steroid molecules originating from cholesterol and synthesized in the liver, play a pivotal role in regulating glucose metabolism and maintaining energy balance. Upon release into the intestine alongside bile, they activate various nuclear and membrane receptors, influencing crucial processes. These bile acids have emerged as significant contributors to managing type 2 diabetes mellitus, a complex clinical syndrome primarily driven by insulin resistance. Bile acids substantially lower blood glucose levels through multiple pathways: BA-FXR-SHP, BA-FXR-FGFR15/19, BA-TGR5-GLP-1, and BA-TGR5-cAMP. They also impact blood glucose regulation by influencing intestinal flora, endoplasmic reticulum stress, and bitter taste receptors. Collectively, these regulatory mechanisms enhance insulin sensitivity, stimulate insulin secretion, and boost energy expenditure. This review aims to comprehensively explore the interplay between bile acid metabolism and T2DM, focusing on primary regulatory pathways. By examining the latest advancements in our understanding of these interactions, we aim to illuminate potential therapeutic strategies and identify areas for future research. Additionally, this review critically assesses current research limitations to contribute to the effective management of T2DM.

A higher level of total bile acid in early mid-pregnancy is associated with an increased risk of gestational diabetes mellitus: a prospective cohort study in Wuhan, China

PURPOSE

To assess the longitudinal associations between maternal total bile acid (TBA) levels during early mid-pregnancy and the subsequent risk of gestational diabetes mellitus (GDM).

METHODS

In a prospective cohort study, pregnant women who were enrolled prior to gestational week 16 were followed until delivery. TBA levels were tested during weeks 14-18 of gestation. Using logistic regression, we analyzed the associations between quartiles of TBA and GDM based on a 75-g oral glucose tolerance test (OGTT) at 24-28 gestational weeks.

RESULTS

The GDM rate was 7.9% (114/1441). The mean TBA level was higher in women with GDM than in those without GDM (2.1 ± 2.0 vs 1.5 ± 1.0 µmol/L, P = 0.000). The highest TBA level quartile (2.1-10.7 µmol/L) had a 1.78-fold (95% CI 1.01, 3.14) increased risk of GDM compared with that of the lowest quartile (0.0-0.8 µmol/L) after adjusting for pre-pregnancy body mass index (BMI), gestational, age at TBA test and other confounders. High TBA levels were involved in the fasting glucose level rather than that at 1 h and 2 h after OGTT in all participants.

CONCLUSIONS

Pregnant women with higher serum TBA levels during early mid-pregnancy have a higher risk of developing GDM. TBA may be a new risk factor for GDM.

Probucol-poly(meth)acrylate-bile acid nanoparticles increase IL-10, and primary bile acids in prediabetic mice

Aim: Common features in insulin-resistance diabetes include inflammation and liver damage due to bile acid accumulation. Results & methodology: This study aimed to test in vivo pharmacological effects of combining two drugs, ursodeoxycholic acid that has bile acid regulatory effects, and probucol (PB) that has potent anti-oxidative stress effects, using a new poly(meth)acrylate nano-targeting formulation on prediabetic mice. Mice were made diabetic and were fed daily with either PB, nanoencapsulated PB or nanoencapsulated PB-ursodeoxycholic acid before blood, tissues, urine and feces were collected for inflammation and bile acid measurements. The nanoencapsulated PB-ursodeoxycholic acid formulation increased plasma IL-10, and increased the concentration of primary bile acids in the liver and heart. Conclusion: Results suggest potential applications in regulating IL-10 in insulin-resistance prediabetes.

Oral antihyperglycemic treatment options for type 2 diabetes mellitus

Table 3 provides an overview of the oral antihyperglycemic drugs reviewed in this article. A 2011 meta-analysis by Bennett and colleagues found low or insufficient quality of evidence favoring an initial choice of metformin, SUs, glinides, TZDs, or (table see text) DPP-4 inhibitors (alpha-glucosidase inhibitors, bromocriptine mesylate, and SGLT2 inhibitors were not included in this meta-analysis) with regard to the outcomes measures of all-cause mortality, cardiovascular events and mortality, and incidence of microvascular disease (retinopathy, nephropathy, and neuropathy) in previously healthy individuals with newly diagnosed T2DM. Likewise, the Bennett and colleagues meta-analysis judged these drugs to be of roughly equal efficacy with regard to reduction of HbA1c (1%–1.6%) from the pretreatment baseline. The ADOPT clinical trial of 3 different and, at the time, popular, oral monotherapies for T2DM provides support for the consensus recommendation of metformin as first-line therapy. The ADOPT trial showed slightly superior HbA1c reduction for rosiglitazone compared with metformin, which was in turn superior to glyburide. However, significant adverse events, including edema, weight gain, and fractures, were more common in the rosiglitazone-treated patients. The implication of this trial is that the combination of low cost, low risk, minimal adverse effects, and efficacy of metformin justifies use of this agent as the cornerstone of oral drug treatment of T2DM. Judicious use of metformin in groups formerly thought to be at high risk for lactic acidosis (ie, those with CHF, chronic kidney disease [eGFR >30 mL/min/1.73 m2], and the elderly) may be associated with mortality benefit rather than increased risk. Secondary and tertiary add-on drug therapy should be individualized based on cost, personal preferences, and overall treatment goals, taking into account the wishes and priorities of the patient.

Lowering low-density lipoprotein cholesterol levels in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is characterized by hyperglycemia, insulin resistance, and/or progressive loss of β-cell function. T2DM patients are at increased risk of micro- and macrovascular disease, and are often considered as representing an atherosclerotic coronary heart disease (CHD) risk equivalent. Interventions directed at glucose and lipid level control in T2DM patients may reduce micro- and macrovascular disease. The optimal T2DM agent is one that lowers glucose levels with limited risk for hypoglycemia, and with no clinical trial evidence of worsening CHD risk. Lipid-altering drugs should preferably reduce low-density lipoprotein cholesterol and apolipoprotein B (apo B) and have evidence that the mechanism of action reduces CHD risk. Statins reduce low-density lipoprotein cholesterol and apo B and have evidence of improving CHD outcomes, and are thus first-line therapy for the treatment of hypercholesterolemia. In patients who do not achieve optimal lipid levels with statin therapy, or who are intolerant to statin therapy, add-on therapy or alternative therapies may be indicated. Additional available agents to treat hypercholesterolemic patients with T2DM include bile acid sequestrants, fibrates, niacin, and ezetimibe. This review discusses the use of these alternative agents to treat hypercholesterolemia in patients with T2DM, either as monotherapy or in combination with statin therapy.

Advances in pharmacologic therapies for type 2 diabetes

Type 2 diabetes (T2DM) is a multi-causal, heterogeneous and progressive cardiometabolic condition, with an increasing prevalence worldwide. T2DM is associated with multiple comorbidities that may impact patients' quality of life. Treatment is multifactorial, but pharmacologic treatment of hyperglycemia is still regarded as the mainstay of diabetes management. Current established therapies include metformin, sulfonylurea agents and insulin, the long-term use of which was associated with reduced micro- and macrovascular events in the United Kingdom Prospective Diabetes Study. Despite major recent advances in diabetes care, a large proportion of patients remain in poor glycemic control, necessitating the development of new therapeutic options. The recently published position statement of the American Diabetes Association and European Association for the Study of Diabetes for the management of hyperglycemia in T2DM has accommodated this wider range of therapy choices, as it is less prescriptive and advocates an individualized treatment approach, taking into account many relevant patient- and disease-related factors. This review summarizes the updates on various established agents as well as the recent developments with regard to incretin-based therapies, inhibitors of the renal tubular sodium-glucose-linked-transporter-2 and ultra-long acting basal insulin formulations.

Diet1 functions in the FGF15/19 enterohepatic signaling axis to modulate bile acid and lipid levels

We identified a mutation in the Diet1 gene in a mouse strain that is resistant to hyperlipidemia and atherosclerosis. Diet1 encodes a 236 kD protein consisting of tandem low-density lipoprotein receptor and MAM (meprin-A5-protein tyrosine phosphatase mu) domains and is expressed in the enterocytes of the small intestine. Diet1-deficient mice exhibited an elevated bile acid pool size and impaired feedback regulation of hepatic Cyp7a1, which encodes the rate-limiting enzyme in bile acid synthesis. In mouse intestine and in cultured human intestinal cells, Diet1 expression levels influenced the production of fibroblast growth factor 15/19 (FGF15/19), a hormone that signals from the intestine to liver to regulate Cyp7a1. Transgenic expression of Diet1, or adenoviral-mediated Fgf15 expression, restored normal Cyp7a1 regulation in Diet-1-deficient mice. Diet1 and FGF19 proteins exhibited overlapping subcellular localization in cultured intestinal cells. These results establish Diet1 as a control point in enterohepatic bile acid signaling and lipid homeostasis.

Colestilan decreases weight gain by enhanced NEFA incorporation in biliary lipids and fecal lipid excretion

Bile acid sequestrants (BASs) are cholesterol-lowering drugs that also affect hyperglycemia. The mechanism by which BASs exert these and other metabolic effects beyond cholesterol lowering remains poorly understood. The present study aimed to investigate the effects of a BAS, colestilan, on body weight, energy expenditure, and glucose and lipid metabolism and its mechanisms of action in high-fat-fed hyperlipidemic APOE*3 Leiden (E3L) transgenic mice. Mildly insulin-resistant E3L mice were fed a high-fat diet with or without 1.5% colestilan for 8 weeks. Colestilan treatment decreased body weight, visceral and subcutaneous fat, and plasma cholesterol and triglyceride levels but increased food intake. Blood glucose and plasma insulin levels were decreased, and hyperinsulinemic-euglycemic clamp analysis demonstrated improved insulin sensitivity, particularly in peripheral tissues. In addition, colestilan decreased energy expenditure and physical activity, whereas it increased the respiratory exchange ratio, indicating that colestilan induced carbohydrate catabolism. Moreover, kinetic analysis revealed that colestilan increased [(3)H]NEFA incorporation in biliary cholesterol and phospholipids and increased fecal lipid excretion. Gene expression analysis in liver, fat, and muscle supported the above findings. In summary, colestilan decreases weight gain and improves peripheral insulin sensitivity in high-fat-fed E3L mice by enhanced NEFA incorporation in biliary lipids and increased fecal lipid excretion.

TGR5 potentiates GLP-1 secretion in response to anionic exchange resins

Anionic exchange resins are bona fide cholesterol-lowering agents with glycemia lowering actions in diabetic patients. Potentiation of intestinal GLP-1 secretion has been proposed to contribute to the glycemia lowering effect of these non-systemic drugs. Here, we show that resin exposure enhances GLP-1 secretion and improves glycemic control in diet-induced animal models of “diabesity”, effects which are critically dependent on TGR5, a G protein-coupled receptor that is activated by bile acids. We identified the colon as a major source of GLP-1 secretion after resin treatment. Furthermore, we demonstrate that the boost in GLP-1 release by resins is due to both enhanced TGR5-dependent production of the precursor transcript of GLP-1 as well as to the local enrichment of TGR5 agonists in the colon. Thus, TGR5 represents an essential component in the pathway mediating the enhanced GLP-1 release in response to anionic exchange resins.

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.

Bile acid sequestrants: more than simple resins

PURPOSE OF REVIEW

Bile acid sequestrants (BAS) have been used for more than 50 years in the treatment of hypercholesterolemia. The last decade, bile acids are emerging as integrated regulators of metabolism via induction of various signal transduction pathways. Consequently, BAS treatment may exert unexpected side-effects. We discuss a selection of recently published studies that evaluated BAS in several metabolic diseases.

RECENT FINDINGS

Recently, an increasing body of evidence has shown that BAS in addition to ameliorating hypercholesterolemia are also effective in improving glycemic control in patients with type 2 diabetes, although the mechanism is not completely understood. Furthermore, some reports suggested using these compounds to modulate energy expenditure. Many of these effects have been related to the local effects of BAS in the intestine by directly binding bile acids in the intestine or indirectly by interfering with signaling processes.

SUMMARY

A substantial effort is being made by researchers to fully define the mechanism by which BAS improve glycemic control in type 2 diabetic patients. A new challenge will be to confirm in clinical trials the recent discoveries coming from animal experiments suggesting a role for bile acids in energy metabolism.

Bile Acid signaling in liver metabolism and diseases

Obesity, diabetes, and metabolic syndromes are increasingly recognized as health concerns worldwide. Overnutrition and insulin resistance are the major causes of diabetic hyperglycemia and hyperlipidemia in humans. Studies in the past decade provide evidence that bile acids are not just biological detergents facilitating gut nutrient absorption, but also important metabolic regulators of glucose and lipid homeostasis. Pharmacological alteration of bile acid metabolism or bile acid signaling pathways such as using bile acid receptor agonists or bile acid binding resins may be a promising therapeutic strategy for the treatment of obesity and diabetes. On the other hand, bile acid signaling is complex, and the molecular mechanisms mediating the bile acid effects are still not completely understood. This paper will summarize recent advances in our understanding of bile acid signaling in regulation of glucose and lipid metabolism, and the potentials of developing novel therapeutic strategies that target bile acid metabolism for the treatment of metabolic disorders.

Probiotics decreased the bioavailability of the bile acid analog, monoketocholic acid, when coadministered with gliclazide, in healthy but not diabetic rats

In recent studies we showed that gliclazide has no hypoglycemic effect on type 1 diabetic (T1D) rats while MKC does, and their combination exerted a better hypoglycemic effect than MKC alone. We also showed that the most hypoglycemic effect was noticed when T1D rats were treated with probiotics then gavaged with MKC + gliclazide (blood glucose decreased from 24 ± 3 to 10 ± 2 mmol/l). The aim of this study is to investigate the influence of probiotics on MKC pharmacokinetics when coadministered with gliclazide, in T1D rats. 80 male Wistar rats (weight 350 ± 50 g) were randomly allocated into 8 groups (10 rats/group), 4 of which were injected with alloxan (30 mg/kg) to induce T1D. Group 1 was healthy and group 2 was diabetic. Groups 3 (healthy) and 4 (diabetic) were gavaged with probiotics (75 mg/kg) every 12 h for 3 days and 12 h later all groups received a single oral dose of MKC + gliclazide (4 and 20 mg/kg respectively). The remaining 4 groups were treated in the same way but administered MKC + gliclazide via the i.v. route. Blood samples collected from T1D rats prior to MKC + gliclazide revealed that probiotic treatment alone reduced blood glucose levels twofold. When coadministered with gliclazide, the bioavailability of MKC was reduced in healthy rats treated with probiotics but remained the same in diabetic pretreated rats. The decrease in MKC bioavailability, when administered with gliclazide, caused by probiotic treatment in healthy but not diabetic rats suggests that probiotic treatment induced MKC metabolism or impaired its absorption, only in healthy animals. The different MKC bioavailability in healthy and diabetic rats could be explained by different induction of presystemic elimination of MKC in the gut by probiotic treatment.

Clinical Efficacy of Colesevelam in Type 2 Diabetes Mellitus

Purpose: The clinical experience and role in therapy of colesevelam in type 2 diabetes mellitus (T2DM) is discussed. Summary: Colesevelam HCl is a bile acid sequestrant (BAS) with proven efficacy in reducing elevated low-density lipoprotein cholesterol (LDL-C) in patients with primary hyperlipidemia. Colesevelam HCl gained food and drug administration (FDA) approval in 2008 as an adjunct to diet and exercise to improve glycemic control in adults with T2DM. In randomized controlled studies, colesevelam (add-on therapy with metformin, sulfonylureas, and insulin) has shown significant percentage reductions in glycosylated hemoglobin A1c (HbA1c) ranging from 0.5% to 0.54%. Reductions in LDL-C and non-high-density lipoprotein cholesterol (non-HDL-C) ranging from –12.8% to –16.7% and –4.0% to –10.3%, respectively, were also observed. Although no direct comparisons have been made, the safety and tolerability profile of this agent appears to be better than other BAS, with the most common side effects being gastrointestinal related. Conclusion: Colesevelam is effective as an adjunct to diet and exercise to improve glycemic control in adults with T2DM. Due to its effects upon LDL-C and glycemic parameters and favorable safety profile, colesevelam can play a role in an array of T2DM patients.

Advances in the treatment of type 2 diabetes mellitus

There is a rising worldwide prevalence of diabetes, especially type 2 diabetes mellitus (T2DM), which is one of the most challenging health problems in the 21st century. The associated complications of diabetes, such as cardiovascular disease, peripheral vascular disease, stroke, diabetic neuropathy, amputations, renal failure, and blindness result in increasing disability, reduced life expectancy, and enormous health costs. T2DM is a polygenic disease characterized by multiple defects in insulin action in tissues and defects in pancreatic insulin secretion, which eventually leads to loss of pancreatic insulin-secreting cells. The treatment goals for T2DM patients are effective control of blood glucose, blood pressure, and lipids (if elevated) and, ultimately, to avert the serious complications associated with sustained tissue exposure to excessively high glucose concentrations. Prevention and control of diabetes with diet, weight control, and physical activity has been difficult. Treatment of T2DM has centered on increasing insulin levels, either by direct insulin administration or oral agents that promote insulin secretion, improving sensitivity to insulin in tissues, or reducing the rate of carbohydrate absorption from the gastrointestinal tract. This review presents comprehensive and up-to-date information on the mechanism(s) of action, efficacy, pharmacokinetics, pleiotropic effects, drug interactions, and adverse effects of the newer antidiabetic drugs, including (1) peroxisome proliferator-activated-receptor-γ agonists (thiazolidinediones, pioglitazone, and rosiglitazone); (2) the incretin, glucagon-like peptide-) receptor agonists (incretin-mimetics, exenatide. and liraglutide), (3) inhibitors of dipeptidyl-peptidase-4 (incretin enhancers, sitagliptin, and vildagliptin), (4) short-acting, nonsulfonylurea secretagogue, meglitinides (repaglinide and nateglinide), (5) amylin anlog-pramlintide, (6) α-glucosidase inhibitors (miglitol and voglibose), and (7) colesevelam (a bile acid sequestrant). In addition, information is presented on drug candidates in clinical trials, experimental compounds, and some plants used in the traditional treatment of diabetes based on experimental evidence. In the opinion of this reviewer, therapy based on orally active incretins and incretin mimetics with long duration of action that will be efficacious, preserve the β-cell number/function, and block the progression of diabetes will be highly desirable. However, major changes in lifestyle factors such as diet and, especially, exercise will also be needed if the growing burden of diabetes is to be contained.

Pectin from Passiflora edulis shows anti-inflammatory action as well as hypoglycemic and hypotriglyceridemic properties in diabetic rats

Flour made from Passiflora edulis fruit peel has been used in Brazil to treat diabetes. This study evaluated the effects of pectin from P. edulis on rats with alloxan-induced diabetes, on myeloperoxidase release from human neutrophils, and on carrageenan-induced paw edema. In the experiments on carrageenan-induced paw edema, paws were dissected for hematoxylin-eosin staining and immunohistochemistry determinations of tumor necrosis factor-α and inducible nitric oxide synthase. Male Wistar rats were divided into the following groups: diabetic controls and diabetic treated with pectin daily for 5 days (0.5-25 mg/kg orally). Glibenclamide and metformin were used as reference drugs. Forty-eight hours after alloxan administration, blood measures were determined (before treatment) and again 5 days later (after treatment). Pectin decreased blood glucose and triglyceride levels in diabetic rats. Pectin also decreased edema volume and release of myeloperoxidase (0.1-100 μg/mL). It also significantly decreased neutrophil infiltration and partially decreased immunostaining for tumor necrosis factor-α and inducible nitric oxide synthase. In conclusion, these data indicated that pectin, a bioactive compound present in P. edulis, has potential as a useful alternative treatment for type 2 diabetes. Its anti-inflammatory properties are probably involved in its antidiabetic action.

Treatment of dyslipidemia in patients with type 2 diabetes

Type 2 diabetes is associated with significant cardiovascular morbidity and mortality. Although low-density lipoprotein cholesterol levels may be normal in patients with type 2 diabetes, insulin resistance drives a number of changes in lipid metabolism and lipoprotein composition that render low-density lipoprotein cholesterol and other lipoproteins more pathogenic than species found in patients without type 2 diabetes. Dyslipidemia, which affects almost 50% of patients with type 2 diabetes, is a cardiovascular risk factor characterized by elevated triglyceride levels, low high-density lipoprotein cholesterol levels, and a preponderance of small, dense, low-density lipoprotein particles. Early, aggressive pharmacological management is advocated to reduce low-density lipoprotein cholesterol levels, regardless of baseline levels. A number of lipid-lowering agents, including statins, fibrates, niacin, and bile acid sequestrants, are available to target normalization of the entire lipid profile. Despite use of combination and high-dose lipid-lowering agents, many patients with type 2 diabetes do not achieve lipid targets. This review outlines the characteristics and prevalence of dyslipidemia in patients with type 2 diabetes and discusses strategies that may reduce the risk of cardiovascular disease in this population.

Improved glycemic control with colesevelam treatment in patients with type 2 diabetes is not directly associated with changes in bile acid metabolism

Bile acids (BAs) are essential for fat absorption and appear to modulate glucose and energy metabolism. Colesevelam, a BA sequestrant, improves glycemic control in type 2 diabetes mellitus (T2DM). We aimed to characterize the alterations in BA metabolism associated with T2DM and colesevelam treatment and to establish whether metabolic consequences of T2DM and colesevelam are related to changes in BA metabolism. Male subjects with T2DM (n = 16) and controls (n = 12) were matched for age and body mass index. BA pool sizes and synthesis/input rates were determined before and after 2 and 8 weeks of colesevelam treatment. T2DM subjects had higher cholic acid (CA) synthesis rate, higher deoxycholic acid (DCA) input rate, and enlarged DCA pool size. Colesevelam resulted in a preferential increase in CA synthesis in both groups. CA pool size was increased whereas chenodeoxycholic acid and DCA pool sizes were decreased upon treatment. Fasting and postprandial fibroblast growth factor 19 (FGF19) levels did not differ between controls and diabetics, but were decreased by treatment in both groups. Colesevelam treatment reduced hemoglobin A1C by 0.7% (P < 0.01) in diabetics. Yet, no relationships between BA kinetic parameters and changes in glucose metabolism were found in T2DM or with colesevelam treatment.

CONCLUSION

Our results reveal significant changes in BA metabolism in T2DM, particularly affecting CA and DCA. Colesevelam treatment reduced FGF19 signaling associated with increased BA synthesis, particularly of CA, and resulted in a more hydrophilic BA pool without altering total BA pool size. However, these changes could not be related to the improved glycemic control in T2DM.

The effect of colesevelam hydrochloride on insulin sensitivity and secretion in patients with type 2 diabetes: a pilot study

BACKGROUND

This study evaluated the effect of colesevelam hydrochloride on insulin sensitivity, potential binding to glucose, and chronic effect(s) on fasting and postprandial glucose and insulin in patients with type 2 diabetes mellitus.

METHODS

Patients meeting inclusion criteria were withdrawn from all antidiabetes agents for 2 weeks and randomized to colesevelam 3.75 grams/day (n = 17) or placebo (n = 18) for 8 weeks. Hyperinsulinemic-euglycemic clamp studies were performed at baseline (week -1) and weeks 2 and 8. A meal tolerance test was conducted at weeks -1, 0, 2, and 8. The meal tolerance test and study drug were coadministered at week 0 to assess the direct effect of colesevelam on glucose absorption.

RESULTS

Insulin sensitivity as measured by the insulin clamp method did not change, but the Matsuda Index, a measure of whole-body insulin sensitivity calculated from postmeal tolerance test glucose and insulin levels, increased significantly within the colesevelam group from baseline to week 8 with last observation carried forward (P = 0.020). The postprandial area under the curve for glucose decreased with colesevelam versus placebo at weeks 2 and 8 with last observation carried forward (P = 0.012 and P = 0.061, respectively); the area under the curve for insulin did not decrease in concert with the decrease in area under the curve for glucose at week 2 (P = 0.585). Colesevelam had no effect on postmeal tolerance test glucose levels at week 0.

CONCLUSIONS

These results suggest that colesevelam has no effect on peripheral insulin sensitivity or glucose absorption, but may improve glucose control by improving whole-body insulin sensitivity, although not by an acute effect on glucose absorption. CLINICAL TRIAL IDENTIFIER: NCT00361153.

Cholestyramine reverses hyperglycemia and enhances glucose-stimulated glucagon-like peptide 1 release in Zucker diabetic fatty rats

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 glucagon-like 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 beta-cell function. Enhancement in GLP-1 and PYY secretion is an important mechanism for BAS-mediated antidiabetic efficacy.

The Role of Colesevelam Hydrochloride in Hypercholesterolemia and Type 2 Diabetes Mellitus

Objective:

To evaluate the safety and efficacy of colesevelam hydrochloride for the treatment of hypercholesterolemia and type 2 diabetes mellitus.

Data Sources:

Literature retrieval was accessed through MEDLINE/PubMed (1950–March 2010), Web of Science (1980–March 2010), and International Pharmaceutical Abstracts (1977–March 2010) using the terms colesevelam, dyslipidemia, hypercholesterolemia, and type 2 diabetes mellitus. References from publications identified were reviewed for additional resources. In addition, abstracts presented at the most recent (2009) American Diabetes Association, American Association of Clinical Endocrinologists, and European Association for the Study of Diabetes annual meetings were searched for relevant original research.

Study Selection and Data Extraction:

All articles in English identified from the data sources were evaluated. All relevant studies evaluating the safety and efficacy of colesevelam in hypercholesterolemia and/or type 2 diabetes mellitus were included. Priority was placed on data obtained from human randomized controlled trials.

Data Synthesis:

Seventeen clinical trials were reviewed and evaluated. Of the clinical trials evaluating colesevelam in hypercholesterolemia, 3 evaluated monotherapy, 4 evaluated combination therapy with hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, and 6 evaluated combination therapy with other lipid-lowering therapies. In the type 2 diabetes mellitus trials, colesevelam was evaluated in combination with metformin, sulfonylureas, insulin, and rosiglitazone and sitagliptin. A review of the clinical trials provided evidence that colesevelam monotherapy effectively reduces low-density lipoprotein cholesterol (LDL-C). Additionally, the use of colesevelam in combination with other lipid-lowering therapies further reduces LDL-C. Colesevelam also effectively reduces hemoglobin A1c in patients with type 2 diabetes mellitus. The safety and tolerability of colesevelam appear to be improved from that of older-generation bile acid sequestrants, with adverse effects similar to those with placebo in monotherapy and type 2 diabetes mellitus trials.

Conclusions:

Colesevelam is a safe and effective option for the treatment of hypercholesterolemia and type 2 diabetes mellitus. It can fulfill a useful role in combination with HMG-CoA reductase inhibitors for hypercholesterolemia and should be considered in patients with type 2 diabetes mellitus with concomitant hypercholesterolemia.

A review of the response to oral antidiabetes agents in patients with type 2 diabetes

In patients with type 2 diabetes, a progressive decline in glycemic control exacerbates the microvascular (retinopathy, neuropathy, and nephropathy) and macrovascular (cardiovascular disease, stroke, and peripheral arterial disease) complications associated with this disease. In a consensus statement, the American Diabetes Association and the European Association for the Study of Diabetes stated that the main goal of antidiabetes therapy is to achieve glycemic control, defined as a glycated hemoglobin of < 7%, although goals should be individualized to each patient, especially in patients at highest risk of cardiovascular disease events. However, because type 2 diabetes is a progressive disease, the response to oral antidiabetes (OAD) agents declines over time and the majority of patients are unable to maintain glycemic control, thus necessitating additional therapy. This requirement for additional antidiabetes therapies as the disease progresses suggests that more aggressive and earlier use of synergistic therapies may help achieve and prolong glycemic control. This review examines the efficacy of OAD therapies to address the unmet need for prompt and maintained glycemic control to the recommended goal in patients with type 2 diabetes, the factors that can affect the glycemic response to the various classes of OAD agents, and ways in which the management of hyperglycemia can be improved in patients with type 2 diabetes.

Rationale and design of a clinical trial to evaluate metformin and colesevelam HCl as first-line therapy in type 2 diabetes and colesevelam HCl in prediabetes

OBJECTIVE

The complications of type 2 diabetes mellitus (DM) can begin early in the progression from impaired glucose tolerance to type 2 DM. Metformin is recommended as initial drug therapy for managing hyperglycemia in type 2 DM. The bile acid sequestrant colesevelam hydrochloride (HCl) is approved in the United States for glycemic control in adults with type 2 DM. Colesevelam HCl improves glycemic control and reduces low-density lipoprotein-cholesterol in patients inadequately controlled on metformin-, sulfonylurea-, or insulin-based therapy. This trial is designed to evaluate whether initial therapy with metformin + colesevelam HCl provides greater glucose control and additional lipid and lipoprotein benefits, as compared to metformin alone in drug-naïve patients with type 2 DM, and whether treatment with colesevelam HCl has a beneficial effect on lipid and glucose levels in drug-naïve patients with impaired glucose tolerance and/or impaired fasting glucose (prediabetes).

RESEARCH DESIGN AND METHODS

In this multicenter, randomized, double-blind, placebo-controlled, parallel-group trial, drug-naïve patients with type 2 DM will be randomized 1 : 1 to metformin + colesevelam HCl or metformin + matching placebo, while those with prediabetes will be randomized 1 : 1 to colesevelam HCl or placebo, for 16 weeks of treatment. The primary efficacy endpoint will be change in glycosylated hemoglobin (HbA(1c)) in patients with type 2 DM and change in low-density lipoprotein-cholesterol levels in patients with prediabetes.

CONCLUSION

A potential limitation is that there is no direct comparator for the dual glucose- and lipid-lowering effect of colesevelam HCl in the prediabetes cohort. However, results of this trial will help to define the extent to which colesevelam HCl can help improve cardiometabolic risk factors for complications of type 2 DM in the first-line environment, and will also indicate the extent to which early intervention with colesevelam HCl can help to correct metabolic abnormalities associated with prediabetes.