Prediabetes is a metabolic state that is positioned between normal glucose homeostasis and diabetes mellitus and is associated with an increased risk of developing diabetes mellitus. The criteria that set the boundaries between normal values, impaired fasting glycemia, impaired glucose tolerance and diabetes mellitus are based on calculations of the threshold above which the complications of diabetes appear. Patients who have elevated plasma glucose but are not yet at risk of diabetes-specific chronic complications are not considered diabetic, but enter the group of impaired glucose tolerance or impaired fasting glycemia.

Recently, however, it has become clear that diabetic complications probably begin to develop in earlier phases of impaired glucose homeostasis, as microvascular damage is often present at the time of diagnosis of diabetes. The identification of subclinical changes in macro- and microvascular function in patients without overt diabetes mellitus is of interest in view of the possibilities for earlier therapeutic intervention.

Diabetes mellitus is a significant risk factor for cardiovascular disease. The increased incidence of cardiovascular disease in patients with diabetes is largely attributed to accelerated coronary atherosclerosis, which develops at an earlier age and progresses more rapidly to clinically significant cardiovascular events than in people without diabetes.1 Coronary atherosclerosis is due to the combination of a number of metabolic, hormonal and hemodynamic factors, which often combine with obesity and lead to endothelial dysfunction. Several epidemiological studies have shown that in diabetic patients there is no clear glycemic threshold for cardiovascular risk, which increases gradually from blood glucose levels in nondiabetic range.2 There is evidence that individuals with prediabetes may be at increased risk for developing CVD long before they are diagnosed with diabetes mellitus.

It should be kept in mind that diabetes and prediabetes are the same in the context of dysglycemia and hyperglycemic toxicity.3 The mechanisms by which patients with diabetes and prediabetes develop cardiovascular complications are diverse and related to different factors. These factors include hyperglycemic toxicity, diabetic dyslipidemia, metabolic syndrome, etc., but the pathophysiological mechanisms are similar whether it is diabetes mellitus or prediabetes.4 Insulin resistance per se also increases the risk of cardiovascular disease, even in the absence of hyperglycemia.5 Many different studies confirm the relationship of impaired glucose tolerance with CVD. Even in prediabetic patients, there is an independent association between the coronary calcium score (CAC), a well-known marker of subclinical atherosclerosis, and the presence of impaired glucose tolerance.6 The Honolulu Heart Program found a significant association between impaired glucose tolerance, the incidence of coronary artery disease, and cardiovascular mortality over a 23-year follow-up period, with CVD risk increasing before glucose levels crossed the diagnostic threshold for diabetes.7 In addition, IGT is a significant risk factor for CVD morbidity, as this relationship is independent of the subsequent development of overt diabetes,8., 9., 10. and IGT is associated with increased cardiovascular risk independently of other cardiovascular risk factors.11,12 Studies have demonstrated a significantly higher incidence of cardiovascular events in patients with elevated blood glucose during OGTT.13 This is most likely due to the fact that hyperglycemia induces oxidative stress and endothelial dysfunction, which destabilizes atherosclerotic plaques, which can lead to clinically apparent coronary disease.

A meta-analysis found a linear relationship between increasing blood glucose levels and cardiovascular events, with their incidence beginning to increase at subdiabetic blood glucose levels.14 On the other hand, however, in patients with prediabetes and diabetes mellitus, the increased cardiovascular risk may be largely related to the additional presence of multiple metabolic risk factors other than hyperglycemia per se.15

The aim of the present study was to evaluate the relationship between common carotid artery intima media thickness (CIMT) as an indicator of atherosclerosis in patients with prediabetes and newly diagnosed diabetes mellitus without proven cardiovascular disease and some classical cardio-metabolic risk factors.