Abstract MP67: The Association Between Habitual Dietary Sodium and Soluble Cell Adhesion Molecules Among Middle-Aged Male Twins

Abstract

Introduction: Habitual dietary sodium intake is associated with coronary flow reserve, a measure of microvascular function. We investigated the role of habitual dietary sodium in the expression of soluble cell adhesion molecules; these molecules are markers of endothelial dysfunction that are thought to contribute to the development of atherosclerosis. Hypothesis: Habitual dietary sodium is directly associated with soluble vascular cell adhesion molecule-1 (sVCAM-1) and soluble intercellular adhesion molecule-1 (sICAM-1) concentration. Methods: We recruited 475 predominantly healthy middle-aged male twins, including 214 monozygotic and dizygotic twin pairs and 47 unpaired twins, from the Vietnam Era Twin Registry. The twins had no previous history of coronary heart disease. Food intake was assessed using the Willett food-frequency questionnaire. We estimated habitual daily sodium consumption over the previous year from reported food intake. We measured sVCAM-1 and sICAM-1 concentration in blood using commercially available ELISA kits. We also obtained information on demographic characteristics and traditional CVD risk factors, including blood pressure. Mixed-effect regression analysis was used to examine individual-level effects and robust regression analysis was used to examine within-pair differences. Results: The twins’ mean age was 53.4 years (SD = 3.1), and 96% (455 out of 475) were white. An increase in dietary sodium of 1,000 mg/d was associated with a 12.2% higher sVCAM-1 concentration (95% CI: 3.1, 21.2; P = 0.009) after adjustment for total energy intake, various nutritional factors, demographic characteristics, and traditional CVD risk factors. For sICAM-1, the adjusted individual-level effect was only 3.1% and did not achieve statistical significance ( P = 0.39). Across quintiles of sodium consumption, sVCAM-1 concentration was directly associated with dietary sodium ( P for trend = 0.002) with the top quintile (sodium >1,505 mg/d) having a 22.9% higher sVCAM-1 concentration than the bottom quintile (sodium <742 mg/d) after controlling for potential confounders. This association persisted within twin pairs ( P = 0.03), yet differed by zygosity ( P interaction = 0.01). Among dizygotic pairs, a 1,000 mg/d within-pair difference in dietary sodium was associated with a 17.3% higher sVCAM-1 concentration in the twin with higher dietary sodium than in the co-twin with lower dietary sodium ( P = 0.005) after adjustment for potential confounders. Among monozygotic pairs, however, the within-pair difference was only 5.0% per 1,000 mg/d of sodium intake and did not reach statistical significance ( P = 0.25). Conclusions: Habitual dietary sodium is directly associated with sVCAM-1 concentration, a marker of abnormal endothelial function, independent of traditional CVD risk factors. However, shared genetic factors may mediate this association.