Collaborative Atorvastatin Diabetes Study Research Articles

Statins for all patients with type 2 diabetes: not so soon

In this issue of The Lancet, Helen Colhoun and colleagues report the results of the Collaborative Atorvastatin Diabetes Study (CARDS), and document the efficacy and safety of low-dose atorvastatin treatment in primary prevention of coronary heart disease in patients with type 2 diabetes at high-risk of coronary heart disease. Since our first report of the efficacy of statin therapy in lowering lipid concentrations in patients with type 2 diabetes,1 clinical trial evidence has accumulated in support of statins as the primary lipid-lowering drugs for these patients.

Clinical trials and lipid guidelines for type II diabetes.

The management of dyslipidemia in adults with diabetes is receiving more attention. However, there is a paucity of large, prospective, randomized outcome trials designed for diabetic patients. Diabetic dyslipidemia is characterized by an increase in triglyceride levels, low high-density lipoprotein (HDL) cholesterol concentrations, and small, dense low-density lipoprotein (LDL) particles. The treatment goals include an LDL cholesterol less than 100 mg/dL, triglyceride level less than 150 mg/dL, and an HDL greater than 40 mg/dL for men and more than 50 mg/dL for women. In the Diabetic Atherosclerosis Intervention Study, fenofibrate resulted in a 42% less increase in the percent stenosis, as assessed by quantitative coronary arteriography. The Heart Protection Study documented the unambiguous benefit of simvastatin in reducing all-cause mortality among 5963 diabetic patients. The Lescol Intervention Prevention Study observed a reduction in major adverse cardiac events in diabetics undergoing percutaneous intervention who received fluvastatin. The Veterans Affairs HDL Cholesterol Intervention Trial reported a reduction in major coronary events among 627 diabetic patients with low HDL cholesterol who sustained a myocardial infarction. The Fenofibrate Intervention and Event Lowering in Diabetics (FIELD) Trial (n = 9795), the Action to Control Cardiovascular Risk in Diabetes (ACCORD, n = 10,000), the Atorvastatin Study for Prevention of Coronary Heart Disease Endpoints in Non Insulin Dependent Diabetes Mellitus (ASPEN, n = 2421), and the Collaborative Atorvastatin Diabetes Study (CARDS, n = 2140) will provide the prospective outcome data that are needed for the management of patients. Combination drug therapy will be necessary to achieve treatment goals. Careful monitoring will be required to avoid myositis and hepatotoxicity.

Lipoprotein abnormalities and their consequences for patients with type 2 diabetes.

Dyslipidaemia is common in patients with Type 2 diabetes and is held to be responsible for considerable CVD-related morbidity and mortality. Patients with Type 2 diabetes are at high risk from complications associated with atherosclerosis and should therefore receive preventive interventions. At the level of the adipocyte, impaired insulin action leads to increased rates of intracellular hydrolysis of triglycerides with the release of NEFA. The rise in NEFA provides substrate for the liver that, in the presence of impaired insulin action and relative insulin deficiency, is associated with complex alterations in plasma lipids: * Plasma VLDL levels are raised. (i). Increased VLDL levels are associated with post-prandial hyperlipidaemia that is compounded by impaired LPL activity. The latter may be independently associated with CAD. (ii). Remnant particles can deliver more cholesterol to macrophages than LDL-C particles. Thrombogenic alterations in the coagulation system also ensue from hypertriglyceridaemia. * Plasma HDL-C levels are reduced. (i). The reduction in cardioprotective HDL-C means a reduction of cholesterol efflux from the tissues--the first step in reverse cholesterol transport to the liver from peripheral tissues. (ii). The antioxidant and antiatherogenic activities of HDL-C are reduced when circulating levels are low. * LDL-C particles become small and dense. Small, dense LDL-C particles are held to be more atherogenic than their larger, buoyant counterparts because they (a) are more liable to oxidation and (b) may more readily adhere to and subsequently invade the arterial wall. The atherogenicity of LDL-C may also be enhanced by nonenzymatic glycation. Metabolic and lipid abnormalities can often be improved with lifestyle changes, including dietary modification, weight loss, smoking cessation and increased exercise. Although attainment of better glycaemic control may improve diabetic dyslipidaemia, pharmacological intervention is usually required. Several large-scale clinical trials, including 4S and more recently HPS, have clearly demonstrated the benefits of statins in reducing cardiovascular events. By virtue of their high absolute risk of CVD, many patients with Type 2 diabetes may achieve a greater risk reduction than their non-diabetic counterparts. For example, in 4S there was a 43% reduction in total mortality risk among patients with diabetes compared with 29% for non-diabetics and a reduced risk of MI by 55% vs. 32% for diabetic and non-diabetics, respectively. In the diabetic subgroup in HPS, there were reductions of approximately 25-30% in the risk of first major vascular events. More recently, the lipid-lowering arm of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) was halted early because of a significant reduction in cardiovascular events compared with placebo. Surprisingly an analysis of subgroups failed to show significance among the diabetic population, although the sample size, shortened follow-up period and higher drop-in statin use among diabetics on placebo may have affected results. The Collaborative Atorvastatin Diabetes Study (CARDS), involving 2800 patients with Type 2 diabetes, was halted 2 years early in June 2003 because patients allocated atorvastatin had significant reductions in MI, stroke and surgical procedures compared with those receiving placebo. The UKPDS demonstrated that the appearance and progression of certain microvascular complications of Type 2 diabetes could be reduced by treatment directed at hyperglycaemia and hypertension. In addition, correction of dyslipidaemia in patients with diabetes is important in reducing the high toll from macrovascular disease. The subjects in the HPS had similar lipid profiles to the participants in UKPDS, suggesting that additional benefit would accrue from a therapeutic assault on the main cardiovascular risk factors simultaneously. We now have firm evidence that appropriate use of statins in patients with Type 2 diabetes can significantly reduce cardiovascular morbidity and mortality.

What does the future hold for diabetic dyslipidaemia?

Preliminary evidence from trials with the HMG-CoA reductase inhibitors (statins), simvastatin and pravastatin, suggests that aggressive treatment of diabetic dyslipidaemia will reduce coronary events. Questions regarding the prevention of cardiovascular events in diabetic patients are now being addressed in prospectively designed trials. The first question is, can aggressive treatment of dyslipidaemia lead to primary prevention of cardiovascular events in patients with type 2 diabetes? This is being addressed in the ongoing Atorvastatin Study for the Prevention of coronary heart disease Endpoints in NIDDM (ASPEN) and the Collaborative AtoRvastatin Diabetes Study (CARDS). These trials will randomize over 4000 patients with type 2 diabetes and no previous myocardial infarction to either atorvastatin or placebo for 4 years. The second question is, are there benefits for aggressive lipid lowering to levels below those recommended in current treatment guidelines, i.e. is lower better? Results from the recent Atorvastatin VErsus Revascularization Treatment (AVERT) trial suggest this to be the case. AVERT showed that, in stable coronary heart disease patients who had been referred for revascularization, aggressive lowering of low density lipoprotein (LDL) cholesterol with atorvastatin 80 mg/day (to a mean level of 2.0 mmol/L [77 mg/dL]) reduced the incidence of ischaemic events by 36% compared with angioplasty and usual care (which reduced LDL cholesterol to 3.1 mmol/L [119 mg/dL]). The 36% reduction in events with atorvastatin versus angioplasty and usual care trended towards significance (p=0.048). The benefits of aggressive lipid-lowering therapy are also being investigated in the ongoing Treating to New Targets (TNT) and Incremental Decrease in Endpoints through Aggressive Lipid lowering (IDEAL) trials. These studies will more closely examine the benefits of treating diabetic dyslipidaemia, and will determine how aggressively this abnormal lipid profile should be treated.

The UKPDS: implications for the dyslipidaemic patient.

The UK Prospective Diabetes Study (UKPDS) is the largest intervention trial to date of patients with type 2 diabetes, involving 5102 newly diagnosed diabetic patients. Results showed that 59% of patient deaths were from cardiovascular disease. While intensive treatment of glucose produced a significant 25% reduction in microvascular endpoints compared with diet only (p=0.0099), patients with type 2 diabetes usually have a lipid profile that is highly atherogenic. In the UKPDS, intensive treatment of hyperglycaemia and hypertension did not improve lipid levels. In patients without diabetes, lipid-lowering therapy has been shown to reduce the risk of cardiovascular events in both primary and secondary prevention trials. Currently, a number of large-scale trials of lipid-lowering therapy in patients with diabetes are ongoing. For example, the Lipids in Diabetes Study will determine whether lipid lowering with a statin or fibrate can substantially reduce cardiovascular morbidity and mortality in 5000 patients with type 2 diabetes. The Atorvastatin Study for the Prevention of coronary heart disease ENdpoints (ASPEN) is comparing double-blind treatment with atorvastatin and placebo in 2250 US diabetic patients without coronary heart disease, while a sister trial in the UK, the Collaborative AtoRvastatin Diabetes Study (CARDS), is enrolling 1820 diabetic patients. The results from these trials may provide information that which will help determine the future management of diabetic dyslipidaemia.