Mechanism of action of bile acid sequestrants and other lipid-lowering drugs

Therapeutic potential of herbal medicine for the management of hyperlipidemia: latest updates

Hyperlipidemia, the most common form of dyslipidemia, is the main source of cardiovascular disorders, characterized by elevated level of total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) with high-density lipoprotein cholesterol (HDL-C) in peripheral blood. It is caused by a defect in lipid metabolism in the surface of Apoprotein C-II or a defect in lipoprotein lipase activity as well as reported in genetic, dietary and environmental factors. Several electronic databases were investigated as information sources, including Google Scholar, PubMed, Web of Science, Scopus, ScienceDirect, SpringerLink, Semantic Scholar, MEDLINE and CNKI Scholar. The current review focused on the risk factors of dyslipidemia, synthetic medication with their side effects and different types of medicinal plants having significant potential for the management of hyperlipidemia. The management of hyperlipidemia mostly involves a constant decrease in lipid level using different remedial drugs like statin, fibrate, bile acid sequestrates and niacin. However, this extensive review suggested that the consequences of these drugs are arguable, due to their numerous adverse effects. The selected parts of herb plants are used intact or their extracts containing active phytoconstituents to regulate the lipids in blood level. It was also noted that the Chinese herbal medicine and combination therapy is promising for the lowering of hyperlipidemia. This review intends to provide a scientific base for future endeavors, such as in-depth biological and chemical investigations into previously researched topics.

Cellular and Molecular Aspects of Managing Familial Hypercholesterolemia: Recent and Emerging Therapeutic Approaches

Familial hypercholesterolemia (FH) as a high-frequency genetic disorder is diagnosed based on family and/or patient's history of coronary heart disease (CHD) or some other atherosclerotic disease, LDL-C levels and/or clinical signs such as tendonous xantomata, arcus cornealis before age 45 years as well as functional mutation in the LDLR, apoB or PCSK9 gene. Its clinical features are detectable since early childhood. Early diagnosis and timely treatment increase life expectancy in most patients with FH. Current FH therapies decrease the level of low-density lipoprotein up to ≥50% from baseline with diet, pharmacotherapeutic treatment, lipid apheresis, and liver transplantation. The cornerstone of medical therapy is the use of more potent statins in higher doses, to which often ezetimibe has to be added, but some FH patients do not achieve the target LDL-C with this therapy Therefore, besides these and the most recent but already established therapeutic approaches including PCSK9 inhibitors, inclisiran, and bempedoic acid, new therapies are on the horizon such as gene therapy, CRISPR/Cas9 strategy etc. This paper focuses on cellular and molecular potential strategies for the treatment of FH.

Modulation of Bile Acid Metabolism to Improve Plasma Lipid and Lipoprotein Profiles

New drugs targeting bile acid metabolism are currently being evaluated in clinical studies for their potential to treat cholestatic liver diseases, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Changes in bile acid metabolism, however, translate into an alteration of plasma cholesterol and triglyceride concentrations, which may also affect cardiovascular outcomes in such patients. This review attempts to gain insight into this matter and improve our understanding of the interactions between bile acid and lipid metabolism. Bile acid sequestrants (BAS), which bind bile acids in the intestine and promote their faecal excretion, have long been used in the clinic to reduce LDL cholesterol and, thereby, atherosclerotic cardiovascular disease (ASCVD) risk. However, BAS modestly but consistently increase plasma triglycerides, which is considered a causal risk factor for ASCVD. Like BAS, inhibitors of the apical sodium-dependent bile acid transporter (ASBTi’s) reduce intestinal bile acid absorption. ASBTi’s show effects that are quite similar to those obtained with BAS, which is anticipated when considering that accelerated faecal loss of bile acids is compensated by an increased hepatic synthesis of bile acids from cholesterol. Oppositely, treatment with farnesoid X receptor agonists, resulting in inhibition of bile acid synthesis, appears to be associated with increased LDL cholesterol. In conclusion, the increasing efforts to employ drugs that intervene in bile acid metabolism and signalling pathways for the treatment of metabolic diseases such as NAFLD warrants reinforcing interactions between the bile acid and lipid and lipoprotein research fields. This review may be considered as the first step in this process.

Circulating bile acids concentration is predictive of coronary artery disease in human

Synthetized by the liver and metabolized by the gut microbiota, BA are involved in metabolic liver diseases that are associated with cardiovascular disorders. Animal models of atheroma documented a powerful anti-atherosclerotic effect of bile acids (BA). This prospective study examined whether variations in circulating BA are predictive of coronary artery disease (CAD) in human. Consecutive patients undergoing coronary angiography were enrolled. Circulating and fecal BA were measured by high pressure liquid chromatography and tandem mass spectrometry. Of 406 screened patients, 80 were prospectively included and divided in two groups with (n = 45) and without (n = 35) CAD. The mean serum concentration of total BA was twice lower in patients with, versus without CAD (P = 0.005). Adjusted for gender and age, this decrease was an independent predictor of CAD. In a subgroup of 17 patients, statin therapy doubled the serum BA concentration. Decreased serum concentrations of BA were predictors of CAD in humans. A subgroup analysis showed a possible correction by statins. With respect to the anti-atherosclerotic effect of BA in animal models, and their role in human lipid metabolism, this study describe a new metabolic disturbance associated to CAD in human.

Can You Trust Your Gut? Implicating a Disrupted Intestinal Microbiome in the Progression of NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of disorders, ranging from fatty liver to a more insulin resistant, inflammatory and fibrotic state collectively termed non-alcoholic steatohepatitis (NASH). In the United States, 30%-40% of the adult population has fatty liver and 3%-12% has NASH, making it a major public health concern. Consumption of diets high in fat, obesity and Type II diabetes (T2D) are well-established risk factors; however, there is a growing body of literature suggesting a role for the gut microbiome in the development and progression of NAFLD. The gut microbiota is separated from the body by a monolayer of intestinal epithelial cells (IECs) that line the small intestine and colon. The IEC layer is exposed to luminal contents, participates in selective uptake of nutrients and acts as a barrier to passive paracellular permeability of luminal contents through the expression of tight junctions (TJs) between adjacent IECs. A dysbiotic gut microbiome also leads to decreased gut barrier function by disrupting TJs and the gut vascular barrier (GVB), thus exposing the liver to microbial endotoxins. These endotoxins activate hepatic Toll-like receptors (TLRs), further promoting the progression of fatty liver to a more inflammatory and fibrotic NASH phenotype. This review will summarize major findings pertaining to aforementioned gut-liver interactions and its role in the pathophysiology of NAFLD.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY GUIDELINES FOR MANAGEMENT OF DYSLIPIDEMIA AND PREVENTION OF CARDIOVASCULAR DISEASE

OBJECTIVE

The development of these guidelines is mandated by the American Association of Clinical Endocrinologists (AACE) Board of Directors and American College of Endocrinology (ACE) Board of Trustees and adheres with published AACE protocols for the standardized production of clinical practice guidelines (CPGs).

METHODS

Recommendations are based on diligent reviews of the clinical evidence with transparent incorporation of subjective factors, according to established AACE/ACE guidelines for guidelines protocols.

RESULTS

The Executive Summary of this document contains 87 recommendations of which 45 are Grade A (51.7%), 18 are Grade B (20.7%), 15 are Grade C (17.2%), and 9 (10.3%) are Grade D. These detailed, evidence-based recommendations allow for nuance-based clinical decision-making that addresses multiple aspects of real-world medical care. The evidence base presented in the subsequent Appendix provides relevant supporting information for Executive Summary Recommendations. This update contains 695 citations of which 203 (29.2 %) are EL 1 (strong), 137 (19.7%) are EL 2 (intermediate), 119 (17.1%) are EL 3 (weak), and 236 (34.0%) are EL 4 (no clinical evidence).

CONCLUSION

This CPG is a practical tool that endocrinologists, other health care professionals, health-related organizations, and regulatory bodies can use to reduce the risks and consequences of dyslipidemia. It provides guidance on screening, risk assessment, and treatment recommendations for a range of individuals with various lipid disorders. The recommendations emphasize the importance of treating low-density lipoprotein cholesterol (LDL-C) in some individuals to lower goals than previously endorsed and support the measurement of coronary artery calcium scores and inflammatory markers to help stratify risk. Special consideration is given to individuals with diabetes, familial hypercholesterolemia, women, and youth with dyslipidemia. Both clinical and cost-effectiveness data are provided to support treatment decisions.

ABBREVIATIONS

4S = Scandinavian Simvastatin Survival Study A1C = glycated hemoglobin AACE = American Association of Clinical Endocrinologists AAP = American Academy of Pediatrics ACC = American College of Cardiology ACE = American College of Endocrinology ACS = acute coronary syndrome ADMIT = Arterial Disease Multiple Intervention Trial ADVENT = Assessment of Diabetes Control and Evaluation of the Efficacy of Niaspan Trial AFCAPS/TexCAPS = Air Force/Texas Coronary Atherosclerosis Prevention Study AHA = American Heart Association AHRQ = Agency for Healthcare Research and Quality AIM-HIGH = Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides trial ASCVD = atherosclerotic cardiovascular disease ATP = Adult Treatment Panel apo = apolipoprotein BEL = best evidence level BIP = Bezafibrate Infarction Prevention trial BMI = body mass index CABG = coronary artery bypass graft CAC = coronary artery calcification CARDS = Collaborative Atorvastatin Diabetes Study CDP = Coronary Drug Project trial CI = confidence interval CIMT = carotid intimal media thickness CKD = chronic kidney disease CPG(s) = clinical practice guideline(s) CRP = C-reactive protein CTT = Cholesterol Treatment Trialists CV = cerebrovascular CVA = cerebrovascular accident EL = evidence level FH = familial hypercholesterolemia FIELD = Secondary Endpoints from the Fenofibrate Intervention and Event Lowering in Diabetes trial FOURIER = Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects With Elevated Risk trial HATS = HDL-Atherosclerosis Treatment Study HDL-C = high-density lipoprotein cholesterol HeFH = heterozygous familial hypercholesterolemia HHS = Helsinki Heart Study HIV = human immunodeficiency virus HoFH = homozygous familial hypercholesterolemia HPS = Heart Protection Study HPS2-THRIVE = Treatment of HDL to Reduce the Incidence of Vascular Events trial HR = hazard ratio HRT = hormone replacement therapy hsCRP = high-sensitivity CRP IMPROVE-IT = Improved Reduction of Outcomes: Vytorin Efficacy International Trial IRAS = Insulin Resistance Atherosclerosis Study JUPITER = Justification for the Use of Statins in Primary Prevention: An Intervention Trial Evaluating Rosuvastatin LDL-C = low-density lipoprotein cholesterol Lp-PLA2 = lipoprotein-associated phospholipase A2 MACE = major cardiovascular events MESA = Multi-Ethnic Study of Atherosclerosis MetS = metabolic syndrome MI = myocardial infarction MRFIT = Multiple Risk Factor Intervention Trial NCEP = National Cholesterol Education Program NHLBI = National Heart, Lung, and Blood Institute PCOS = polycystic ovary syndrome PCSK9 = proprotein convertase subtilisin/kexin type 9 Post CABG = Post Coronary Artery Bypass Graft trial PROSPER = Prospective Study of Pravastatin in the Elderly at Risk trial QALY = quality-adjusted life-year ROC = receiver-operator characteristic SOC = standard of care SHARP = Study of Heart and Renal Protection T1DM = type 1 diabetes mellitus T2DM = type 2 diabetes mellitus TG = triglycerides TNT = Treating to New Targets trial VA-HIT = Veterans Affairs High-Density Lipoprotein Cholesterol Intervention Trial VLDL-C = very low-density lipoprotein cholesterol WHI = Women's Health Initiative.

Structural Basis of Bioactivity of Food Peptides in Promoting Metabolic Health

Bioactive peptides have many structural features that enable them to become functional in controlling several biological processes in the body, especially those related to metabolic health. This chapter provides an overview of the multiple targets of food-derived peptides against metabolic health problems (e.g., hypertension, dyslipidemia, hyperglycemia, oxidative stress) and discusses the importance of structural chemistry in determining the bioactivities of peptides and protein hydrolysates.

Grape Seed Procyanidins and Cholestyramine Differentially Alter Bile Acid and Cholesterol Homeostatic Gene Expression in Mouse Intestine and Liver

Bile acid (BA) sequestrants, lipid-lowering agents, may be prescribed as a monotherapy or combination therapy to reduce the risk of coronary artery disease. Over 33% of adults in the United States use complementary and alternative medicine strategies, and we recently reported that grape seed procyanidin extract (GSPE) reduces enterohepatic BA recirculation as a means to reduce serum triglyceride (TG) levels. The current study was therefore designed to assess the effects on BA, cholesterol and TG homeostatic gene expression following co-administration with GSPE and the BA sequestrant, cholestyramine (CHY). Eight-week old male C57BL/6 mice were treated for 4 weeks with either a control or 2% CHY-supplemented diet, after which, they were administered vehicle or GSPE for 14 hours. Liver and intestines were harvested and gene expression was analyzed. BA, cholesterol, non-esterified fatty acid and TG levels were also analyzed in serum and feces. Results reveal that GSPE treatment alone, and co-administration with CHY, regulates BA, cholesterol and TG metabolism differently than CHY administration alone. Notably, GSPE decreased intestinal apical sodium-dependent bile acid transporter (Asbt) gene expression, while CHY significantly induced expression. Administration with GSPE or CHY robustly induced hepatic BA biosynthetic gene expression, especially cholesterol 7α-hydroxylase (Cyp7a1), compared to control, while co-administration further enhanced expression. Treatment with CHY induced both intestinal and hepatic cholesterologenic gene expression, while co-administration with GSPE attenuated the CHY-induced increase in the liver but not intestine. CHY also induced hepatic lipogenic gene expression, which was attenuated by co-administration with GSPE. Consequently, a 25% decrease in serum TG levels was observed in the CHY+GSPE group, compared to the CHY group. Collectively, this study presents novel evidence demonstrating that GSPE provides additive and complementary efficacy as a lipid-lowering combination therapy in conjunction with CHY by attenuating hepatic cholesterol synthesis, enhancing BA biosynthesis and decreasing lipogenesis, which warrants further investigation.

Nanoparticulate carrier system: a novel treatment approach for hyperlipidemia

Hyperlipidemia is a prevailing risk factor that leads to development and progression of atherosclerosis and consequently cardiovascular diseases. Several antihyperlipidemic drugs are having various disadvantages such as low water solubility and poor bioavailabilty due to presystemic gastrointestinal clearance. Thus, there is a considerable need for the development of efficient delivery methods and carriers. This review focuses on the importance and role of various nanoparticulate systems as carrier for antihyperlipidemic drugs in the treatment of hyperlipidemia. Some nanoparticle technology-based products are approved by FDA for effective treatment of hyperlipidemia, namely Tricor® by Abbott Laboratories (Chicago, IL, USA) and Triglide® by Skye Pharma (London, UK). Efforts to address each of these issues are going on, and should remain the focus on the future studies and look forward to many more clinical products in the future.

Mitotane-induced hyperlipidemia: a retrospective cohort study

Limited data are available about mitotane-nduced hyperlipidemia. We retrospectively analyzed lipid data in 38 patients with adrenocortical carcinoma (ACC) who received mitotane therapy with emphasis on HDL cholesterol (HDL-c) and clinical predictors of lipid changes. At baseline, the mean levels of HDL-c, LDL-c, and triglycerides were 53.3 mg/dL, 114.4 mg/dL, and 149 mg/dL, respectively. HDL-c, LDL-c, and triglyceride concentrations significantly increased with mitotane therapy to a mean HDL peak (HDL-P) of 86.3 mg/dL (P < 0.001), a mean LDL peak of 160.1 mg/dL (P < 0.001), and a mean triglyceride peak (Tg-P) of 216.7 mg/dL (P = 0.042). HDL-P positively correlated with mitotane concentration (r = 0.52, P < 0.001), while LDL-P levels and Tg-P did not. Gender, body mass index, cortisol overproduction, baseline levels of HDL-c, and triglyceride did not predict change in HDL-c. Similar changes were noticed in subgroup analysis after excluding patients who were using lipid-lowering agents. In conclusion, in ACC patients, mitotane caused significant increases in HDL-c that may counteract the deleterious atherosclerotic effects of LDL-c and Tg rise. Understanding the mechanism of HDL change may lead to the discovery of novel HDL-c-elevating drugs.

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.

Role of colesevelam in managing heterozygous familial hypercholesterolemia in adolescents and children

BACKGROUND

Colesevelam hydrochloride is a synthetic, nonsystemically absorbed polymer that functions as a bile acid sequestrant for the treatment of hypercholesterolemia. Recently, colesevelam was investigated for the treatment of heterozygous familial hypercholesterolemia (HeFH) in the pediatric/adolescent population aged 10-17 years.

OBJECTIVE

The purpose of this article is to review the disease state of HeFH in children and adolescents, review the pharmacologic mechanism of action, kinetics, and safety profile of colesevelam, analyze the results of a recent clinical trial of colesevelam in the pediatric/adolescent HeFH population, and discuss the role of colesevelam as a viable treatment option for HeFH.

METHODS

A literature search using Medline (1966-03 May 2010), PubMed (1950-03 May 2010), Science Direct (1994-03 May 2010), and International Pharmaceutical Abstracts (2004-2010) was performed using the search term colesevelam. English language, original research, and review articles were examined, and citations from these articles were also assessed. The manufacturer's prescribing information and the Food and Drug Administration review of the new drug application for the powder formulation were also examined.

RESULTS

A 32-week trial was performed investigating the efficacy of colesevelam as monotherapy or combination therapy with a stable statin regimen. Upon completion of the trial, significant benefits were found in regard to the treatment of HeFH and the lowering of low-density lipoprotein cholesterol, total cholesterol, and other secondary measures. Safety and tolerability were also examined throughout the duration of the clinical trial, with adverse drug reactions considered mild in severity.

CONCLUSION

Colesevelam has been shown to reduce low-density lipoprotein cholesterol levels significantly in pediatric/adolescent patients with HeFH, while maintaining a mild side effect profile. Although further research would be beneficial for long-term effects in this population, colesevelam should be considered when developing a treatment regimen for HeFH in the pediatric/adolescent population.

Absorption and excretion of colestilan in healthy subjects

Colestilan, an anion-exchange resin binding both phosphate and bile-acid anions, is under development for the treatment of hyperphosphataemia and dyslipidaemia, which occur in the majority of end-stage renal disease patients. This study using 14C-colestilan was conducted to investigate the absorption and excretion of colestilan in humans. Following a 28-day run-in period with administration of colestilan 3 g three times daily, 12 subjects received a single oral dose of 14C-colestilan 100 mg (approximately 4.0 MBq) and colestilan 3 g under fasted conditions on the morning of day 1. A total of 9 g of colestilan was administered three times daily on days 1-4. Total radioactivity levels in whole blood (at 4, 8, 12 and 24 hours and then at 24-hour intervals) and in the urine and faeces (from 0 to 24 hours and then at 24-hour intervals) were monitored up to 216 hours postdose (day 10). Total radioactivity measured in all whole-blood samples was below the lower limit of quantification (0.025 microg equivalent of 14C-labelled colestilan/mL of whole blood). Total radioactivity assessed in all urine samples was also below the lower limit of quantification (0.003 microg equivalent/mL for urine), except at 0-24 hours postdose, when 0.01% of the radioactive dose was excreted by all subjects. This level was below the predetermined water soluble impurity level of 0.04%. The mean cumulative excretion of total radioactivity in the faeces was 99.66% by 216 hours postdose, excluding one subject with incomplete collection of faecal samples. These results demonstrate that colestilan is not absorbed from the gastrointestinal tract and is completely excreted in the faeces.

Rational approach to the treatment for heterozygous familial hypercholesterolemia in childhood and adolescence: a review

Atherosclerosis represents a disease that begins in childhood and in which LDL cholesterol plays a pivotal role for the development of the pathology. Children and adolescents with high cholesterol levels are more likely than their peers to present cholesterol elevation as adults. The identification of genetic dyslipidemias associated with premature cardiovascular disease is crucial during childhood to delay or prevent the atherosclerotic process. Guidelines for the diagnosis and treatment of hypercholesterolemia during pediatric age are available from the National Cholesterol Education Program. A heart-healthy diet should begin at the age of 2 yr and a large number of studies have demonstrated no adverse effects on nutritional status, growth, pubertal development, and psychological aspects in children and adolescents limiting total and saturated fat intake. Pharmacotherapy should be considered in children over 10 yr of age when LDL cholesterol concentrations remain very high despite severe dietary therapy, especially when multiple risk factors are present. The only lipid-lowering drugs recommended up to now for childhood and adolescence are resins reported to be effective and well tolerated, although compliance is very poor because of unpalatability. The use of statins is increasing and seems to be effective and safe in children, even if studies enrolled a small number of patients and evaluated efficacy and safety for short-term periods. Recently, an interesting drug represented by ezetimibe has been found that may provide cholesterol-lowering additive to that reached with statin treatment. This review provides an update on recent advances in the diagnosis, therapy, and follow-up of familial hypercholesterolemia during pediatric age and adolescence.

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.

Colesevelam: Potential Uses for the Newest Bile Resin

Colesevelam is the newest bile resin with a unique chemical structure. It binds to bile acids with higher affinity than traditional bile acid sequestrants and has fewer gastrointestinal side effects and drug interactions. Colesevelam is safe and efficacious alone or in combination with HMG-CoA reductase inhibitors (statins) in reducing low-density lipoprotein cholesterol (LDL-C) levels. Despite this, the role of colesevelam in the treatment of hyperlipidemia remains limited, particularly in the face of new lipid lowering agents. As guidelines for cholesterol control become more stringent, the need to maximize therapeutic benefit through combination therapy will become increasingly more important. Colesevelam has a dose-sparing effect on statin therapy, potentially decreasing the risk of unwanted side effects or drug-drug interactions associated with statin use. This makes colesevelam a viable option for addition to a statin regimen when goal LDL-C levels cannot be achieved with a statin alone. Additionally, anecdotal reports indicate that colesevelam may have potential benefits in certain patient populations that cannot tolerate other lipid lowering therapies, including organ transplant recipients, cholestatic liver disesase, and end-stage renal disease. By recognizing the potential utility of colesevelam, clinicians can better manage those patients who are not able to tolerate first-line therapies.

Cross-Over Trial of Intensive Monotherapy With Atorvastatin and Combined Therapy With Atorvastatin and Colestimide for Japanese Familial Hypercholesterolemia

BACKGROUND

In familial hypercholesterolemia (FH), low-density lipoprotein-cholesterol (LDL-C)-lowering therapy is important to avoid predisposition to coronary artery disease. This study investigated the advantages of combined therapy with atorvastatin and colestimide vs intensive monotherapy with atorvastatin.

METHODS AND RESULTS

The trial used a randomized cross-over design consisting of 2 16-week periods of open-label drug therapy. Among the 24 initial patients, 17 heterozygous FH patients (age: 54.1 years; 5 males) were enrolled after 20 mg/day atorvastatin failed to achieve their target level. The patients received 20 mg/day atorvastatin and 3 g/day colestimide or 40 mg/day atorvastatin. Fifteen patients completed the trial and their LDL-C reduced from 5.07 +/- 1.10 mmol/L to 3.76 +/- 0.90 mmol/L with the combined therapy and to 3.81 +/- 0.50 mmol/L with the intensive monotherapy. Although the 2 therapies showed comparable mean effects for decreasing LDL-C, similar adverse reaction and cost, each therapy was predominantly more effective in some patients than in others. The triglyceride and high-density lipoprotein cholesterol levels were similar in both therapies.

CONCLUSIONS

To achieve the therapeutic target of LDL-C level for refractory FH, the LDL-C-lowering therapy selected can be either intensive monotherapy or combined therapy as the next to standard statin therapy.

Familial hypercholesterolemia--improving treatment and meeting guidelines

Familial hypercholesterolemia (FH) is a common, inherited disorder that affects around one in 500 individuals in the heterozygous form. By the year 2001, more people in the US had FH than were infected by the human immunodeficiency virus. The disease is caused by mutations within the low-density lipoprotein (LDL) receptor gene. FH is associated with elevated plasma LDL-cholesterol (LDL-C) levels, xanthomatosis, early onset of atherosclerosis and premature cardiac death. Patients with heterozygous FH commonly have plasma LDL-C levels that are two-fold higher than normal, while homozygotes have four- to five-fold elevations in plasma LDL-C. Although FH patients have a high risk of developing premature coronary heart disease (CHD), they remain underdiagnosed and undertreated. Early detection of FH is critical to prolonging the life of these patients. Once identified, patients with heterozygous FH can be placed on a diet and drug management program. As the most efficacious and well-tolerated agents, hydroxy methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are usually the drugs of first choice; bile acid sequestrants, niacin, and occasionally fibrates may be used as supplemental agents. Statins may also provide a realistic option for the treatment of some FH homozygotes with genes that produce partially functional LDL receptors. However, a number of patients are still failing to reach treatment guidelines even with the most effective of the currently available statins. The development of new more efficacious statins or the use of new combination therapies such as statins with the cholesterol absorption inhibitor, ezetimibe may help to reduce the current problem of undertreatment in FH patients.

Effects of polyphenolic fraction of silymarin on lipoprotein profile in rats fed cholesterol-rich diets

To study the influence of polymerised polyphenolics (PP), a fraction of silymarin (SM), on lipids and oxidant status, rats were fed high-cholesterol (1%), high-fat (10%) diets containing either lard fat (LFD) rich in saturated/monounsaturated fatty acids, or currant oil (COD) rich in polyunsaturated fatty acids. PP and SM were administered as dietary supplements (0.1-0.5-1.0%) for 3 weeks. PP (1%) decreased cholesterol (C) in VLDL (from 0.72+/-0.08 mmol l(-1) in LFD control to 0.35+/-0.07 mmol l(-1), P<0.01, and from 0.33+/-0.05 mmol l(-1) in COD control to 0.09+/-0.02 mmol l(-1), P<0.001), and increased HDL-C/VLDL-C ratio, however, without effect on the total plasma C and LDL-C. Liver C content (LFD 19.32+/-1.50 micromol g(-1), COD 18.64+/-2.13 micromol g(-1), N.S.) decreased after PP (1%) to 12.24+/-0.76 micromol g(-1), P<0.01, and 8.78+/-0.95 micromol g(-1), P<0.001, respectively. Triacylglycerols (TAG) in plasma and VLDL decreased after PP in the LFD group only, which displayed higher TAG levels than the COD group. Likewise, LFD caused a higher liver TAG content than did COD (31.16+/-3.00 micromol g(-1) versus 17.31+/-1.48 micromol g(-1), P<0.01), and PP (1%) decreased liver TAG only in rats fed LFD (19.55+/-2.43 micromol g(-1), P<0.02). Blood glutathione (GSH) increased after PP (1%) in the LFD group from 0.97+/-0.11 to 1.54+/-0.19 mmol l(-1) (P<0.05) and in the COD group from 0.58+/-0.15 to 1.23+/-0.10 mmol l(-1) (P<0.01), while liver GSH and plasma TBARS did not change. On principle, effects of PP were dose-dependent and parallel to SM. These results suggest that the polyphenolic fraction of SM positively modifies lipoprotein profile, counteracts the development of fatty liver and ameliorates an antioxidant status in circulation.

Management of dyslipidemia

The 2 principal approaches to management of dyslipidemias are lifestyle intervention and lipid-modifying drug therapy. Recent revisions to the American Heart Association's dietary guidelines for reducing cardiovascular disease emphasize an overall healthy eating pattern and maintenance of appropriate body weight, together with achieving a desirable blood pressure and a desirable lipoprotein profile. New National Cholesterol Education Program treatment guidelines include a scoring system for calculating coronary heart disease (CHD) risk that is adapted from the Framingham Heart Study, as well as a category of CHD risk equivalents (e.g., diabetes) that will encourage more aggressive therapeutic intervention for individuals at high short-term risk for CHD, even in the absence of clinically evident coronary disease. Classes of lipid-modifying drugs include bile acid sequestrants (resins), fibrates, and statins, with each class exerting different effects on the lipid profile. Nicotinic acid (niacin) is also an approved lipid-modifying agent. The armamentarium for treating lipid disorders and atherosclerosis now includes statins that can decrease low-density lipoprotein (LDL) cholesterol levels by up to 55%, as well as a resin with improved tolerability. In patients with high levels of LDL cholesterol and triglycerides, together with low concentrations of high-density lipoprotein cholesterol, combination therapy may be effective. Moreover, researchers are currently investigating the development of drugs directed at molecular targets, including cholesterol esterification and accumulation in macrophage foam cells (e.g., inhibiting acyl-coenzyme A : cholesterol acyltransferase), degradation of atherosclerotic plaque (e.g., decreasing the expression of matrix metalloproteinases), and reverse cholesterol transport (e.g., stimulating ATP-binding cassette transporter A1).

Development and validation of a cholate binding capacity method for DMP 504, a bile acid sequestrant

DMP 504, a highly cross-linked insoluble polymer, is a bile acid sequestrant developed by the DuPont Pharmaceuticals Company for serum cholesterol reduction. Since DMP 504 is insoluble, it was necessary to develop unique specific analytical methods to measure and control the quality of different lots of the drug. Since the mechanism of action of DMP 504 is believed to be by sequestration of bile acids, the in-vitro binding capacity of the polymer for cholic acid was chosen as a surrogate of in-vivo performance and used to assess potency of the compound. In this method, individual aliquots of DMP 504 at three different levels were incubated with a cholate solution of known concentration. The residual cholate solution was filtered and analyzed by a reversed-phase HPLC method using refractive index detection. When the bound cholate was plotted versus the mass of DMP 504, the resulting curve was linear. The slope of this curve is the cholate binding capacity of DMP 504. This method has been shown to be precise and robust. Precision of the method was shown to have an RSD of 2.0% with injection precision of 0.4% and stability of cholate solutions up to 73 h. It is also a unique binding capacity method due to its multi-point determination, and it has been shown to be a suitable quality control method for ensuring lot-to-lot consistency of drug substance.

Improving compliance in your dyslipidemic patient: an evidence-based approach

PURPOSE

To synthesize the evidence from landmark clinical studies of lipid-lowering pharmacotherapy and nurse management of hyperlipidemia, discuss issues related to nonadherence, and proposes strategies for achieving long-term cholesterol control.

DATA SOURCES

All publications of lipid-lowering clinical trials related to pharmacotherapy for dyslipidemias were accessed from a thorough Medline Search and reviewed by two nurse experts.

CONCLUSIONS

Randomized controlled studies provide compelling evidence that reduction of blood cholesterol with pharmacotherapy reduces both first and subsequent coronary events. Nonetheless, inadequate provider and patient adherence to guidelines for lipid lowering remains prevalent. Studies show that nurses provide safe and effective care for patients with abnormal lipids.

IMPLICATIONS

This article assists nurse practitioners in playing an active role in the implementation of the National Cholesterol Education Program Adult Treatment Panel III Report to be released in Spring 2001, where a strong emphasis will be placed on multidisciplinary approaches and adherence.

Absorption, distribution and excretion of GT31-104, a novel bile acid sequestrant, in rats and dogs after acute and subchronic administration

The absorption, distribution, and excretion of GT31-104, a novel bile acid sequestrant, was studied in rats and dogs after both acute and subchronic oral administration. The polyallylamine backbone of GT31-104 was labeled with tritium and one of the alkyl side chains was labeled with 14C. The mean blood and plasma concentration of [3H, 14C]GT31-104 in rats, in both treatment regimens, was negligible at all time points, with the highest amount observed being 0.69 microgram eq/g blood; in dogs the mean blood and plasma concentration of [3H, 14C]GT31-104 was below the limit of quantitation (< 0.001% total dose) at all time points. In both rats and dogs, the mean total urinary excretion of [3H, 14C]GT31-104 was approximately 0.06% of the total dose. The fecal excretion data indicates that both 3H- and 14C-derived radioactivity was excreted entirely in the feces. Mean total radioactivity excreted in the feces ranged from approximately 95 to 105% in the rats and 92 to 102% in the dogs. Across the different treatment regimens, in both species, tissue concentrations were negligible (< 0.01% total dose) and no differences in tissue profile were noted, indicating that there was no effect of pretreatment on [3H, 14C]GT31-104 absorption. GT31-104 was extracted with water, and the water-soluble portion contained radioactivity that would correlate to approximately 0.19% of the 3H dose and 0.41% of the 14C dose; this portion probably accounted for the negligible radioactivity observed systemically. Analysis of gastrointestinal (GI) tract tissues with contents indicated that GT31-104 is rapidly cleared from the GI tract. These data indicate that GT31-104 is not absorbed from the GI tract in rats and dogs.

Evaluation of cultured hamster hepatocytes as an experimental model for the study of very low density lipoprotein secretion

The secretion of triacylglycerol, cholesterol and cholesteryl ester in very low density lipoprotein (VLDL) by cultured hamster hepatocytes was studied, and the results compared with those obtained previously using cultured rat hepatocytes and the human hepatoma cell line HepG2. The hamster cells secreted apolipoprotein B and VLDL triacylglycerol, cholesterol and cholesteryl ester linearly during 24 h in culture, and this time period was used in all experiments. Addition of oleate (1 mM) to the culture medium resulted in increased secretion of triacylglycerol, but cholesterol ester output were unchanged. Triacylglycerol secretion was also increased in the presence of lipogenic substrates (10 mM lactate + 1 mM pyruvate) plus dexamethasone (1 microM), but not with either of these agents alone. Inhibition of cholesterol synthesis in the hamster cells by incubation with mevinolin (2 micrograms/ml) did not change VLDL lipid secretion, but stimulation using mevalonate lactone resulted in decreased triacylglycerol output. Manipulation of the rate of cholesterol esterification in the hepatocytes by inhibiting or stimulating the activity of acyl coenzyme A cholesterol:acyl transferase using the inhibitor Dup128 (25 microM) and 25-hydroxycholesterol (50 microM), respectively, had no effect on the secretion of VLDL lipid. In the presence of 1 mM oleate plus 25-hydroxycholesterol, however, a rise in the output of triacylglycerol and cholesteryl ester was observed. Hepatocytes prepared from hamsters fed 2% cholestyramine secreted significantly less triacylglycerol than those from animals given the control diet, but cholesterol and cholesteryl ester output were unchanged, despite a decrease of about 40% in the total cholesterol content of the cells. These results show that the secretion of lipid in VLDL in hamster hepatocytes differs from that in rat and human liver in its response to dietary cholestyramine, and from rat hepatocytes and HepG2 cells in its response to changes in the rate of lipogenesis and cholesterol synthesis and esterification. Overall, hamster hepatocytes appear to be less susceptible to modification the rate of hepatic VLDL secretion, and should provide a useful additional tool for the investigation of this process.

The hypocholesterolemic effect of an antacid containing aluminum hydroxide

STUDY OBJECTIVE

To evaluate the efficacy, safety, and hypocholesterolemic effect of an aluminum hydroxide-containing antacid in hypercholesterolemic individuals.

DESIGN

A prospective, randomized, double-masked, placebo-controlled phase of 2 months' duration, followed by an open-design treatment phase of 2 months' duration and a washout phase of 2 months' duration.

SETTING

Family practice clinics of two rural communities (kibbutzim) in Israel.

PATIENTS

Fifty-six men and women with hypercholesterolemia (type IIa or IIb). Fifty individuals completed the study.

INTERVENTION

After 2 months of dietary modification (low-fat, low-cholesterol diet), the participants were randomized into two matched groups. Group 1 (28 participants) was treated for 2 months with a chewable antacid tablet containing simethicone, magnesium hydroxide, and 113 mg of aluminum hydroxide per tablet, at a dose of two tablets four times daily. Group 2 (22 participants) was given a similar number of placebo tablets for 2 months. During the following 2 months, both groups received the antacid at the above dose.

MEASUREMENTS AND MAIN RESULTS

Lipoprotein levels were evaluated at baseline and every 2 months thereafter for 6 months. Compared with pretreatment levels, Group 1 experienced a decrease in low-density lipoprotein cholesterol (LDL-C) of 9.8% after 2 months (p less than 0.001) and 18.5% after 4 months (p less than 0.001). Compared with Group 2, the decrease in LDL-C in Group 1 was 6.2% at the end of the 2-month double-masked, placebo phase. Although the high-density lipoprotein cholesterol (HDL-C) was also reduced in Group 1 at the end of 4 months of therapy (10.2%), the HDL-C/LDL-C ratio increased by 13% during the same interval (p less than 0.05). The treatment was well tolerated, with minimal side effects.

CONCLUSIONS

An aluminum hydroxide-containing antacid reduces LDL-C in hypercholesterolemic individuals. Although HDL-C was also reduced to a lesser extent, the overall atherogenic index was improved. Further studies should be conducted to evaluate the long-term safety and efficacy of antacids containing aluminum hydroxide in hypercholesterolemic patients.

Bile acid sequestrants

The bile acid sequestrants, cholestyramine and colestipol, are the drugs of choice for the treatment of patients with hypercholesterolemia caused by increases in LDL-cholesterol levels without concurrent hypertriglyceridemia (type IIA and type IIB hyperlipoproteinemia). Longitudinal clinical studies with these drugs have shown their ability to slow the progression of atherosclerosis and to limit the consequences of the disease. Bile acid sequestrants can be used with other lipid-lowering drugs such as nicotinic acid or HMG CoA reductase inhibitors, to maximize the cholesterol-lowering effects. The side effect profile of the bile acid sequestrants is tolerable, with most complaints related to effects on the gastrointestinal tract and the bulkiness of the resins.