Mechanisms for therapeutic correction of dyslipidaemia in insulin resistance and diabetes

Pharmacological Targeting of the Atherogenic Dyslipidemia Complex: The Next Frontier in CVD Prevention Beyond Lowering LDL Cholesterol

Notwithstanding the effectiveness of lowering LDL cholesterol, residual CVD risk remains in high-risk populations, including patients with diabetes, likely contributed to by non-LDL lipid abnormalities. In this Perspectives in Diabetes article, we emphasize that changing demographics and lifestyles over the past few decades have resulted in an epidemic of the "atherogenic dyslipidemia complex," the main features of which include hypertriglyceridemia, low HDL cholesterol levels, qualitative changes in LDL particles, accumulation of remnant lipoproteins, and postprandial hyperlipidemia. We briefly review the underlying pathophysiology of this form of dyslipidemia, in particular its association with insulin resistance, obesity, and type 2 diabetes, and the marked atherogenicity of this condition. We explain the failure of existing classes of therapeutic agents such as fibrates, niacin, and cholesteryl ester transfer protein inhibitors that are known to modify components of the atherogenic dyslipidemia complex. Finally, we discuss targeted repurposing of existing therapies and review promising new therapeutic strategies to modify the atherogenic dyslipidemia complex. We postulate that targeting the central abnormality of the atherogenic dyslipidemia complex, the elevation of triglyceride-rich lipoprotein particles, represents a new frontier in CVD prevention and is likely to prove the most effective strategy in correcting most aspects of the atherogenic dyslipidemia complex, thereby preventing CVD events.

Endothelial dysfunction in diabetes: pathogenesis, significance, and treatment

Type 2 diabetes (T2D) markedly increases the risk of cardiovascular disease. Endothelial dysfunction (ED), an early indicator of diabetic vascular disease, is common in T2D and independently predicts cardiovascular risk. Although the precise pathogenic mechanisms for ED in T2D remain unclear, at inception they probably involve uncoupling of both endothelial nitric oxide synthase activity and mitochondrial oxidative phosphorylation, as well as the activation of vascular nicotinamide adenine dinucleotide phosphate oxidase. The major contributing factors include dyslipoproteinemia, oxidative stress, and inflammation. Therapeutic interventions are designed to target these pathophysiological factors that underlie ED. Therapeutic interventions, including lifestyle changes, antiglycemic agents and lipid-regulating therapies, aim to correct hyperglycemia and atherogenic dyslipidemia and to improve ED. However, high residual cardiovascular risk is seen in both research and clinical practice settings. Well-designed studies of endothelial function in appropriately selected volunteers afford a good opportunity to test new therapeutic interventions, paving the way for clinical trials and utilization in the care of the diabetic patient. However, based on the results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled low-density lipoprotein cholesterol.

Atherogenic dyslipidemia and combination pharmacotherapy in diabetes: recent clinical trials

Patients with type 2 diabetes (T2D) are at a markedly increased risk of cardiovascular disease (CVD). Dyslipidemia is a common risk factor and a strong predictor of CVD in T2D patients. Although statins decrease the incidence of CVD in T2D, residual cardiovascular risk remains high despite the achievement of optimal or near-optimal plasma low-density lipoprotein (LDL) cholesterol concentrations. This may, in part, be due to uncorrected atherogenic dyslipidemia. Hypertriglyceridemia, the driving force behind diabetic dyslipidemia, results from hepatic overproduction and/or delayed clearance of triglyceride-rich lipoproteins. In patients treated with a statin to LDL-cholesterol goals, the addition of ezetimibe, fenofibrate, niacin, or n-3 fatty acid ethyl esters may be required to correct the persistent atherogenic dyslipidemia. Clinical trial evidence describing best practice is limited, but recent data supports the strategy of adding fenofibrate to a statin, and suggests specific benefits in dyslipidemic patients and in the improvement of diabetic retinopathy. However, based on results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled LDL-cholesterol. Further evidence is required to support the role of ezetimibe and n-3 fatty acids in treating residual CVD risk in statin-treated T2D patients.

Atherogenic dyslipidemia and combination pharmacotherapy in diabetes: recent clinical trials

Patients with type 2 diabetes (T2D) are at a markedly increased risk of cardiovascular disease (CVD). Dyslipidemia is a common risk factor and a strong predictor of CVD in T2D patients. Although statins decrease the incidence of CVD in T2D, residual cardiovascular risk remains high despite the achievement of optimal or near-optimal plasma low-density lipoprotein (LDL) cholesterol concentrations. This may, in part, be due to uncorrected atherogenic dyslipidemia. Hypertriglyceridemia, the driving force behind diabetic dyslipidemia, results from hepatic overproduction and/or delayed clearance of triglyceride-rich lipoproteins. In patients treated with a statin to LDL-cholesterol goals, the addition of ezetimibe, fenofibrate, niacin, or n-3 fatty acid ethyl esters may be required to correct the persistent atherogenic dyslipidemia. Clinical trial evidence describing best practice is limited, but recent data supports the strategy of adding fenofibrate to a statin, and suggests specific benefits in dyslipidemic patients and in the improvement of diabetic retinopathy. However, based on results from a recent clinical trial, niacin should not be added to a statin in individuals with low high-density lipoprotein cholesterol and very well controlled LDL-cholesterol. Further evidence is required to support the role of ezetimibe and n-3 fatty acids in treating residual CVD risk in statin-treated T2D patients.

Combination lipid therapy in type 2 diabetes mellitus

INTRODUCTION

A significant drop in cardiovascular risk has been seen in patients with type 2 diabetes treated with statins. However, this cardiovascular risk remains high, compared with nondiabetic individuals. This is partly due to the typical abnormalities of diabetic dyslipidemia - hypertriglyceridemia and decreased high-density lipoprotein cholesterol (HDL-C) - that are uncontrolled by statins. For this reason, combination lipid therapy may be considered in patients with type 2 diabetes.

AREAS COVERED

This review presents the main reasons for a combination lipid therapy in type 2 diabetes and the effects of several drugs, including fibrates, pioglitazone, niacin and omega 3, on diabetic dyslipidemia and the prevention of cardiovascular events. The real cardiovascular benefit of fibrates in patients with type 2 diabetes is not totally clear, but they may produce a significant benefit in patients with type 2 diabetes and diabetic dyslipidemia (hypertriglyceridemia, low HDL-C). Pioglitazone, which reduces triglycerides and increases HDL-C, has been shown to reduce the risk for major cardiovascular events in type 2 diabetes. Niacin and omega 3 fatty acids have a positive effect on diabetic dyslipidemia, but warrants clinical trials to demonstrate a clear cardiovascular benefit in type 2 diabetes.

EXPERT OPINION

Although combination lipid therapy seems to be useful to control diabetic dyslipidemia, the efficacy of such combined therapies on significantly reducing cardiovascular risk has still to be confirmed by additional clinical trials.