Diabetes mellitus

Why is type 2 diabetes mellitus a high-risk condition for coronary heart disease?

Persons with type 2 diabetes mellitus are between two and four times more likely than non-diabetics to develop CVD and two thirds of the patients with type 2 diabetes die from cardiovascular causes. Risk is increased in diabetes for several reasons:

1. About eight in ten type 2 diabetics have hypertension and six in ten show atherogenic diabetic dyslipidemia (Table 1), characterized by elevated plasma triglycerides, low levels of HDL cholesterol, an increased number of small, dense LDL particles and elevated plasma apolipoprotein B. This atherogenic dyslipidemic state is a component of a cluster of atherogenic, prothrombotic and inflammatory abnormalities that is often found in individuals with insulin resistance and is sometimes referred to as the metabolic syndrome. Contrary to popular belief, LDL cholesterol levels in patients with type 2 diabetes mellitus (or type 1 diabetes mellitus) are not different from those in the general population.
2. Chronic hyperglycemia produces glycation of lipoproteins, which then cannot be metabolized normally and exhibit a prolonged residence time in the circulation. Chronic hyperglycemia also generates free radicals, potentiating oxidative stress and leading to production of protein adducts called advanced glycation end products. These can harm the vascular wall and initiate a chronic inflammatory response.
3. Cardiovascular risk is particularly high in patients with diabetes mellitus who exhibit microalbuminuria, frank proteinuria or renal impairment. Persons with type 2 diabetes mellitus who suffer an MI show increased mortality both immediately and in the long term. Late diagnosis and thus poor prognosis is also contributed to by the fact that MI in persons with diabetes may be painless due to the presence of autonomic neuropathy.

Table 1. Characteristics of the diabetic dyslipidemic profile.