Ultrasonographically assessed carotid atherosclerosis in Japanese type 2 diabetic patients: Role of nonesterified fatty acids

Abstract

The aim of the present study was to evaluate the association of carotid atherosclerosis (intimal-medial thickness [IMT] in plaque-free segments and carotid stenosis in plaque segments) with serum nonesterified fatty acids (NEFA) in diabetic and nondiabetic patients. Fifty-one nonobese nonhypertensive Japanese type 2 diabetic patients aged 38 to 83 years (60.0 [plusmn] 1.5 years, mean [plusmn] SEM) and 23 age-matched (60.4 [plusmn] 2.2 years, P = .439; range, 36 to 74 years) and sex-matched nondiabetic subjects were examined. The duration of diabetes was 9.6 [plusmn] 1.0 years. Body mass index (BMI), blood pressure (systolic pressure, diastolic pressure), glycosylated hemoglobin (HbA 1c), and fasting concentrations of plasma glucose, serum lipids (triglycerides, total, and high-density lipoprotein [HDL] cholesterol, low-density lipoprotein [LDL] cholesterol) and serum NEFA were measured. Using high-resolution B-mode ultrasound scan, we measured IMT in plaque-free segments of bilateral common carotid arteries, and the mean of IMT in 2 vessels was used for the analysis. Furthermore, we calculated the degree of stenosis in plaque segments of bilateral common carotid arteries. The degree of carotid stenosis was expressed as a percentage ratio between the area of plaque and that of the lumen using the formula (Lumen Area [minus ] Residual Lumen) [times ] 100. Both the areas were automatically measured by the system on a frozen transverse scanning plane at the site of maximal narrowing. When 2 or more plaques were present in the vessel, only that causing the greatest degree of stenosis was considered for analysis. Univariate regression analyses showed that mean IMT in plaque-free segments was positively correlated with age ( r = .498, P = .0004) and NEFA ( r = .354, P = .0188) in type 2 diabetic patients. The degree of stenosis was positively correlated to age ( r = .422, P = .0028), duration of diabetes ( r = .313, P = .0268) and NEFA ( r = .540, P = .0003) in diabetic patients. Other variables, including BMI and lipid profile, were not associated both with mean IMT in plaque-free segments and the degree of stenosis in plaque segments in our diabetic patients. Multiple regression analyses showed that mean IMT in plaque-free segments was independently associated with age ( P = .0003, F = 15.2), which explained 26.1% of the variability of IMT in our diabetic patients. The degree of stenosis was independently predicted by NEFA ( P = .0047, F = 8.9), which explained 17.2% of the variability of the carotid stenosis in our diabetic patients. In contrast, mean IMT in plaque-free segments was positively correlated to age in nondiabetic subjects ( r = .450, P = .0347). There was, however, no relationship between the degree of stenosis and the variables, including age and NEFA, in nondiabetic subjects. These results indicate that the factors contributing to IMT in plaque-free segments and the degree of carotid stenosis in plaque segments are different in nonobese nonhypertensive Japanese type 2 diabetic patients. IMT in plaque-free segments was independently associated with age both in nondiabetic and diabetic subjects, whereas the serum NEFA level independently predicted the degree of stenosis in plaque segments in our diabetic patients, while not in nondiabetic subjects. Thus, NEFA is considered to be one of the new risk factors responsible for the progression of carotid atherosclerosis in nonobese nonhypertensive Japanese type 2 diabetic patients.