Aims: To study the relations between the metabolic syndrome (MS) and subclinical atherosclerosis in young adults.
Methods and results: International Diabetes Federation (msIDF), National Institute of Health Adult Treatment Panel III (msNCEP), and European Group for the Study of Insulin Resistance (msEGIR) definitions of MS were related to carotid artery intima-media thickness (cIMT), brachial flow-mediated dilatation (FMD), and carotid artery compliance (CAC) in 2163 Finnish adults (aged 32 +/- 5years). All definitions associated with increased cIMT and decreased CAC in both sexes. The cIMT values (mean+/-SD) were 0.576 +/- 0.088 mm in subjects without the syndrome, 0.615 +/- 0.102 mm in msIDF, 0.617 +/- 0.104 mm in msNCEP, and 0.607 +/- 0.097 mm in msEGIR (P < 0.0001). Corresponding CAC values were 2.26 +/- 0.72, 1.76 +/- 0.66, 1.73 +/- 0.66, 1.72 +/- 0.66%/10 mmHg (P < 0.001). Impaired brachial FMD was not related to MS but it modified the relations between MS and cIMT: MS correlated with increased cIMT in subjects with an impaired FMD response (P = 0.003) but not in subjects with an enhanced FMD response (P = 0.75).
Conclusion: All current definitions of MS identify a population of young adults with evidence of increased subclinical atherosclerosis. Impaired brachial endothelial response is not a hallmark of MS in young adults, but the status of endothelial function modifies the association between metabolic risk factors and atherosclerosis.