Sigurdardottir V, Fagerberg B, Hulthe J (Sahlgrenska University Hospital, Göteborg University, Gothenburg, Sweden). Circulating oxidized low‐density lipoprotein (LDL) is associated with risk factors of the metabolic syndrome and LDL size in clinically healthy 58‐year‐old men (AIR study). J Intern Med 2002; 252: 440–447.

Objectives. Hypothetically the atherogenic effect of the metabolic syndrome may be mediated through the increased occurrence of small LDL‐particles which are easily modified to atherogenic oxidized LDL (ox‐LDL). The aim of this study was to test this concept by examining the association between circulating ox‐LDL, LDL‐particle size, and the metabolic syndrome.

Design and results. A population‐based sample of clinically healthy 58‐year‐old men (n = 391) was recruited. Ox‐LDL was measured by ELISA (specific monoclonal antibody, mAb‐4E6) and LDL‐particle size by gradient gel electrophoresis. The results showed that ox‐LDL significantly correlated to factors constituting the metabolic syndrome; triglycerides (r = 0.43), plasma insulin (r = 0.20), body mass index (r = 0.20), waist‐to‐hip ratio (r = 0.21) and HDL (r = −0.24); (P < 0.001). Ox‐LDL correlated also to LDL‐particle size (r = −0.42), Apo‐B (r = 0.70), LDL (r = 0.65); (P < 0.001) and, furthermore, with Apo A‐1 (r = −0.13) and heart rate (r = 0.13); (P < 0.01).

Conclusion. The metabolic syndrome was accompanied by high plasma ox‐LDL concentrations compared with those without the syndrome. Ox‐LDL levels were associated with most of the risk factors constituting the metabolic syndrome and was, in addition related to small LDL‐particle size. To our knowledge the present study is the first one to demonstrate that circulating ox‐LDL levels are associated with small LDL‐particle size in a population representative sample of clinically healthy middle‐aged men. The high degree of intercorrelation amongst several factors makes it difficult to clarify the independent role of any specific factor.