The ezetimibe controversy: implications for clinical practice

Ezetimibe reduces cholesterol content and NF-kappaB activation in liver but not in intestinal tissue in guinea pigs

Background

Statins (HMG CoA reductase inhibitors), in addition to reducing circulating cholesterol and incidence of coronary heart disease, also have pleiotropic, anti-inflammatory effects. Patients with chronic liver diseases, non-alcoholic fatty liver disease (NAFLD) or hepatitis C are often excluded from statin therapy because of adverse effects in a small cohort of patients despite increased cardiovascular risk cholesterol. Ezetimibe, which inhibits cholesterol absorption by inhibition of Niemann-Pick C1 like 1 (NPC1L1) protein in the brush border of intestinal cells, has been suggested as a new therapeutic option in these patients.

Methods

Effects of ezetimibe on lipoprotein metabolism, hepatic and intestinal lipid content in guinea pigs, an animal model with a lipoprotein profile and pattern similar to humans were investigated. In order to investigate a possible effect of ezetimibe on cholesterol induced inflammation NF-kappaB activation as an indicator for inflammatory processes in liver and gut tissue was measured.

Results

Lipid enriched diet led to accumulation of lipids in hepatic tissue which caused strong hepatic NF-kappaB activation. Ezetimibe reduced lipid diet induced increase of circulating cholesterol by about 77% and prevent hepatic NF-kappaB activation almost completely. In contrast in intestinal cells Ezetimibe, though lowering diet induced cholesterol accumulation, increased triglyceride content and subsequent NF-kappaB activation.

Conclusion

In summary these data show, that ezetimibe effectively reduced diet induced circulating cholesterol levels, hepatic lipid accumulation and inflammatory response in our guinea pig model. However this drug elicited a local inflammatory response in intestinal tissue. Whether these diverse effects of ezetimibe on inflammatory parameters such as NF-kappaB have clinical relevance remains to be determined.

Current drug treatment of hyperlipidemia in older adults

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death, especially in older adults. Managing modifiable risk factors (e.g., hyperlipidemia, hypertension) remains the primary approach to prevent ASCVD events and ASCVD-related mortality. Statins are generally considered one of the most effective approaches to reduce ASCVD risk, especially for secondary prevention, yet remain underutilized in older adults. The evidence to support statin therapy in older adults is less robust than in their younger counterparts, especially in individuals aged 75 years and older. Recent lipid guidelines have raised this concern, yet statin therapy is recommended in 'at risk' older adults. Determining which older adults should receive statin therapy for primary prevention of ASCVD is challenging, as the currently available risk estimation tools are of limited use in those aged over 75 years. Furthermore, non-statin therapies have been de-emphasized in recent clinical practice guidelines and remain understudied in the older adult population. This is unfortunate given that older adults are less likely to tolerate moderate- to high-intensity statins. Non-statin therapies could be viable options in this population if more was understood about their ability to lower ASCVD risk and safety profiles. Nevertheless, lipid-lowering agents remain an integral component of the overall strategy to reduce atherogenic burden in older adults. Future research in this area should aim to enroll more older adults in clinical trials, determine the utility of ASCVD risk estimation for primary prevention, and investigate the role of non-statin therapies in this population.

Animal models of diabetic macrovascular complications: key players in the development of new therapeutic approaches

Diabetes mellitus is a lifelong, incapacitating metabolic disease associated with chronic macrovascular complications (coronary heart disease, stroke, and peripheral vascular disease) and microvascular disorders leading to damage of the kidneys (nephropathy) and eyes (retinopathy). Based on the current trends, the rising prevalence of diabetes worldwide will lead to increased cardiovascular morbidity and mortality. Therefore, novel means to prevent and treat these complications are needed. Under the auspices of the IMI (Innovative Medicines Initiative), the SUMMIT (SUrrogate markers for Micro- and Macrovascular hard end points for Innovative diabetes Tools) consortium is working on the development of novel animal models that better replicate vascular complications of diabetes and on the characterization of the available models. In the past years, with the high level of genomic information available and more advanced molecular tools, a very large number of models has been created. Selecting the right model for a specific study is not a trivial task and will have an impact on the study results and their interpretation. This review gathers information on the available experimental animal models of diabetic macrovascular complications and evaluates their pros and cons for research purposes as well as for drug development.

Berberine decreases cholesterol levels in rats through multiple mechanisms, including inhibition of cholesterol absorption

OBJECTIVE

The objective was to determine the mechanisms of action of berberine (BBR) on cholesterol homeostasis using in vivo and in vitro models.

METHODS

Male Sprague-Dawley rats were fed the AIN-93G diet (normal control) or modified AIN-93G diet containing 28% fat, 2% cholesterol and 0.5% cholic acid with treatment of 0 (atherogenic control), 50, 100, and 150 mg/kg·d of BBR, respectively by gavaging in water for 8 weeks. Cholesterol absorption rate was measured with the dual stable isotope ratio method, and plasma lipids were determined using the enzymatic methods. Gene and protein expressions of Acyl-coenzyme A:cholesterol acyltransferase-2 were analyzed in vivo and in vitro. Cholesterol micellarization, uptake and permeability were determined in vitro.

RESULTS

Rats on the atherogenic diet showed significantly hypercholesterolemic characteristics compared to normal control rats. Treatment with BBR in rats on the atherogenic diet reduced plasma total cholesterol and nonHDL cholesterol levels by 29%-33% and 31%-41%, respectively, with no significant differences being observed among the three doses. The fractional dietary cholesterol absorption rate was decreased by 40%-51%. Rats fed the atherogenic diet showed lower plasma triacylglycerol levels, and no changes were observed after the BBR treatment. BBR interfered with cholesterol micellarization, decreased cholesterol uptake by Caco-2 cells and permeability through Caco-2 monolayer. BBR also inhibited the gene and protein expressions of acyl-coenzyme A cholesterol acyltransferease-2 in the small intestine and Caco-2 cells.

CONCLUSION

BBR lowered blood cholesterol levels at least in part through inhibiting the intestinal absorption and further by interfering with intraluminal cholesterol micellarization and decreasing enterocyte cholesterol uptake and secretion.

Effect of ezetimibe on major atherosclerotic disease events and all-cause mortality

Despite ezetimibe's ability to reduce serum cholesterol levels, there are concerns over its vascular effects and whether it prevents or ameliorates atherosclerotic disease (AD). The aims of this study were to estimate the effect of ezetimibe use on major AD events and all-cause mortality and to compare these associations to those observed for hydroxymethylglutaryl coenzyme A reductase inhibitor (statin) use. A total of 367 new ezetimibe users were identified from November 1, 2002, to December 31, 2009. These subjects were aged ≥18 years and had no previous statin use. One to 4 statin user matches were identified for each ezetimibe user, resulting in a total of 1,238 closely matched statin users. Pharmacy data and drug dosage information were used to estimate a moving window of ezetimibe and statin exposure for each day of study follow-up. The primary outcome was a composite of major AD events (coronary heart disease, cerebrovascular disease, and peripheral vascular disease events) and all-cause death. Ezetimibe use (odds ratio 0.33, 95% confidence interval 0.13 to 0.86) and statin use (odds ratio 0.61, 95% confidence interval 0.36 to 1.04) were associated with reductions in the likelihood of the composite outcome. These protective associations were most significant for cerebrovascular disease events and all-cause death. Subgroup analyses by gender, race or ethnicity, history of AD, diabetes status, and estimated renal function showed consistent estimates across strata, with no significant differences between ezetimibe and statin use. In conclusion, ezetimibe appeared to have a protective effect on major AD events and all-cause death that was not significantly different from that observed for statin use.

Ezetimibe/simvastatin: a guide to its clinical use in hypercholesterolemia

Ezetimibe/simvastatin therapy combines two lipid-lowering compounds with complementary mechanisms of action, thereby blocking the two sources of plasma cholesterol and improving lipid profiles. Ezetimibe/simvastatin is an effective and generally well tolerated adjunct to dietary therapy for markedly reducing low-density lipoprotein cholesterol (LDL-C) levels and improving other lipid parameters across diverse patient populations. Dual treatment with ezetimibe/simvastatin is more effective than monotherapy with an HMG-CoA reductase inhibitor (statin), and the addition of ezetimibe to current statin therapy is more effective than doubling the statin dose.

Multidisciplinary pharmacotherapeutic options for nonalcoholic Fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are multidisciplinary liver diseases that often accompany type 2 diabetes or metabolic syndrome, which are characterized by insulin resistance. Therefore, effective treatment of type 2 diabetes and metabolic syndrome should target not only the cardiometabolic abnormalities, but also the associated liver disorders. In the last decade, it has been shown that metformin, thiazolidinediones, vitamin E, ezetimibe, n-3 polyunsaturated fatty acids, renin-angiotensin system (RAS) blockers, and antiobesity drugs may improve hepatic pathophysiological disorders as well as clinical parameters. Accordingly, insulin sensitizers, antioxidative agents, Niemann-Pick C1-like 1 (NPC1L1) inhibitors, RAS blockers, and drugs that target the central nervous system may represent candidate pharmacotherapies for NAFLD and possibly NASH. However, the efficacy, safety, and tolerability of long-term treatment (potentially for many years) with these drugs have not been fully established. Furthermore, clinical trials have not comprehensively examined the efficacy of lipid-lowering drugs (i.e., statins, fibrates, and NPC1L1 inhibitors) for the treatment of NAFLD. Although clinical evidence for RAS blockers and incretin-based agents (GLP-1 analogs and dipeptidyl peptidase-4 inhibitors) is also lacking, these agents are promising in terms of their insulin-sensitizing and anti-inflammatory effects without causing weight gain.