Impaired fasting glucose is not a risk factor for atherosclerosis

To determine a new category of dysfunctional glucose homeostasis - impaired fasting glucose (IFG) - introduced by the American Diabetes Association (ADA) and the World Health Organization (WHO) defining those with abnormal but nondiabetic fasting glucose values and with a possible risk for developing diabetes. It is not known whether IFG is a risk factor for atherosclerosis, as is impaired glucose tolerance (IGT).

In this case-control cross-sectional study in which the oral glucose tolerance (75-g OGTT) and the carotid intima-media thickness (IMT) with B mode ultrasound, as a marker of atherosclerosis, were measured, together with HbA1c, lipids, plasminogen activator (PAI), insulin and proinsulin concentrations in blood plasma. Out of 788 subjects of the risk factors in IGT for Atherosclerosis and Diabetes (RIAD) study we found 104 IFG cases that were compared to 104 controls with fasting plasma glucose (FPG)<6.1 mmol/l, matched for age, sex and body mass index. Subjects with 2h postprandial (pp) plasma glucose > or = 11.1 mmol/l were excluded. The rest were subdivided into those with 2h plasma glucose < 7.8 mmol/l (63 pairs, NGT) and those with plasma glucose > 7.8 mmol/l and < 11.1 mmol/l (41 pairs, IGT).

The case and control groups showed no significant differences in the major risk factors except for waist-to-hip ratio (WHR) which was higher in the IFG with NGT. IFG with NGT exhibited significantly higher levels of HbA1c, true insulin and proinsulin. In IFG with IGT, only HbA1c and proinsulin were significantly increased vs. controls. IMT was in the same range for cases and controls in both subgroups. However, IMT mean and IMTmax were significantly increased in IFG with IGT vs. IFG with NGT (0.95 mm vs. 0.80 mm and 1.10 mm vs. 0.90 mm). Cumulative distribution analysis of IMT illustrates that IMT in IFG with IGT is more shifted to higher artery wall thickness than in IFG with NGT.

In our case-control study IFG alone was not related to increased IMT. Only IFG in a combination with IGT exhibited atherosclerotic changes of the carotid arteries. IFG is not analogous to IGT as a risk factor for atherosclerosis.