The metabolic syndrome, LDL particle size, and atherosclerosis - The atherosclerosis and insulin resistance (AIR) study

An operative definition of the metabolic syndrome has been suggested by a w orking group associated with the World Health Organization in 1998. The aim of this study was to examine whether small, low density lipoprotein (LDL) particle size was associated with the metabolic syndrome and with subclinic al atherosclerosis as measured by ultrasound in the carotid and femoral art eries. The study was performed in a population-based sample of clinically h ealthy men (N=391), all 58 years old and not undergoing any treatment with cardiovascular drugs. Exclusion criteria were cardiovascular or other clini cally overt diseases or continuous medication with cardiovascular drugs. Th e results showed that subjects characterized by the metabolic syndrome (n= 62) had a thicker mean intima-media complex (IMT) in both the carotid and f emoral arteries (0.86 versus 0.77 mm, P<0.001, and 1.03 versus 1.00 mm, P=0 .022, respectively) and also lower mean values for LDL particle size (25.78 versus 26.80 nm, respectively, P<0.001) compared with subjects with no ris k factors (n=77). The,group with the metabolic syndrome (n=62) also had hig her mean values for serum cholesterol and heart rate. In the whole study gr oup (N=391), there were significant but weak negative relationships between small LDL particle size, increasing IMT, and increasing cross-sectional in tima-media area of the carotid and femoral arteries and also negative relat ionships between LDL particle size and plaque occurrence and size in the ca rotid and femoral arteries. In summary, this is the first large-scale study to demonstrate a relationship between the clustering of risk factors that constitute the metabolic syndrome and a small LDL particle size pattern and the occurrence of preclinical atherosclerosis in the carotid and femoral a rteries, as assessed by the ultrasound technique, in healthy 58-year-old me n recruited from the general population.