Microalbuminuria is a well-established risk factor for atherosclerosis in patients with type 2 diabetes (1,2). In this cross-sectional study, we examined the effect of microalbuminuria on the intima-media thickness (IMT) of the carotid arteries, an index of early atherosclerosis (3), in patients with type 2 diabetes.
We studied a total of 120 subjects with type 2 diabetes (60 men and 60 women, aged 61.4 ± 6.8 years, duration of diabetes 10.4 ± 7.7 years, and HbA1c 7.9 ± 1.7% [mean ± SD]) randomly selected from the outpatient diabetes clinic. Microalbuminuria was diagnosed when albumin excretion (measured by radioimmunoassay) was >20 and <200 μg/ml in two of three overnight, timed urine collections. Subjects were divided into two groups based on the presence of microalbuminuria.
All carotid B-mode real-time ultrasound measurements were performed by the same experienced physician, who was blinded to the patient’s urine albumin status. Measurements of the IMT were performed in both the right and left common carotid arteries (CCAs) and internal carotid arteries (ICAs), as previously described (4).
Forty-six (38.3%) subjects had microalbuminuria. There were no significant differences between the study groups in terms of sex, age, blood pressure, BMI, waist-to-hip ratio, duration of diabetes, HbA1c, type of antidiabetic treatment, smoking habit, fasting plasma glucose, insulin, triglycerides or HDL cholesterol, and the use of statins and ACE inhibitors. Plasma total and LDL cholesterol levels were higher in the microalbuminuric group (P < 0.02). The IMT/CCA values were higher in the microalbuminuric group compared with the normoalbuminuric group (0.99 ± 0.14 vs. 0.89 ± 0.15 mm, respectively; P = 0.001), but this was not the case concerning the IMT/ICA values (0.94 ± 0.14 vs. 0.93 ± 0.16 mm, respectively; P = 0.69).
Multivariate analysis, after adjustment for a number of confounding factors, such as age, sex, blood pressure, BMI, waist-to-hip ratio, duration of diabetes, HbA1c, type of antidiabetic treatment, smoking status, plasma lipids, and the use of ACE inhibitors and statins, demonstrated that only the presence and degree of microalbuminuria were independently associated with IMT/CCA (B = 0.01, SE[B] = 0.003, P < 0.0001 and B = 0.0001, SE[B] = 0.00001, P = 0.02, respectively). In addition, it is noteworthy that microalbuminuric patients treated with ACE inhibitors tended to have lower IMT/CCA values than patients not treated with this class of medication (P = 0.06), whereas no such difference was found with the use of statins. The lack of association between microalbuminuria and the IMT/ICA value is explained by the fact that ICAs at the bifurcation are more sensitive to local atherosclerosis and do not necessarily reflect the status of the arterial tree. In nondiabetic subjects, the IMT/CCA shows a graded association with various cardiovascular risk factors and thus can be used as an indicator for the presence of atherosclerosis in other arteries (3).
It is concluded that microalbuminuric subjects with type 2 diabetes have higher IMT/CCA values than normoalbuminuric subjects and that the presence as well as the degree of microalbuminuria are independent predictors of IMT/CCA.