Interstitial fluid apolipoprotein A-II: an association with the occurrence of myocardial infarction

A sample of male patients aged 25-64 years, survivors of myocardial infarction (MI) taken from the Lille MONICA register, and age-matched control subjects from the general population were recruited in Lille and its surroundings in the North of France. Diabetics and subjects taking hypolipidemic drugs were excluded from the analysis, so that 73 MI and 144 control subjects were included. Lipids, apolipoprotein (apo) A-I, apo A-II, apo A-IV and apo B, and apo A-I-containing particles such as lipoproteins containing both apo A-I and apo A-II (LpA-I:A-II) and those containing apo A-I but not apo A-II (LpA-I) were measured in interstitial fluid by applying mild suction, and in plasma. Univariate analysis showed that plasma triglycerides, very low density lipoprotein (VLDL)-cholesterol and apo B were significantly higher, while high density lipoprotein (HDL)-cholesterol, apo A-I, LpA-I and LpA-I:A-II were lower in MI survivors compared to controls after adjustment for age, body mass index (BMI), alcohol and tobacco consumption. In interstitial fluid, cholesterol and apo A-II were higher in MI than in controls before adjustment for covariates. However, after adjustment, triglycerides became significant while cholesterol and apo A-II remained significantly higher in MI, at 43.8 and 7.5 mg/dl, respectively, than in control subjects, at 38.6 and 5.9 mg/dl, respectively. Taking into account only the plasma parameters, the multivariate analysis reveals that triglycerides and apo A-I appear to be independent factors indicative of the presence of a MI. When plasma and interstitial fluid parameters were taken together in the multivariate analysis, the measurement of apo A-II in interstitial fluid increased the level of prediction of MI over the information provided by the plasma parameters. These data raise the possibility that interstitial fluid apo A-II levels may be associated with the occurrence of MI.