The purpose of this study was to determine if diet and/or body composition influences resting plasma apelin concentration. Apelin concentration appears to be influenced by the amount of fat in the body and by blood glucose concentration. However, most of the studies that have investigated blood apelin concentration have utilized obese or diabetic subjects. Little is known about how body composition, body fat distribution or diet may influence apelin in apparently healthy, young individuals. More specifically, the purposes of this study were to determine if baseline resting plasma apelin concentration in young, apparently healthy adult subjects is influenced by amount of fat in the body, location of fat, the macronutrient composition in their diet and if the total amount of antioxidant micronutrients (vitamins A, C, E and zinc). The proposed cohort group consisted of twelve apparently healthy young adults between the ages of 18-35.The amount of body fat, body mass index, sagittal diameter and the waist to hip ratio were utilized as covariates to determine if these factors influenced apelin concentration at rest. The data was analyzed to ascertain if there are any relationships with the listed anthropometric measures, the nutrition factors and plasma apelin concentration. Each subject’s body composition was classified via body mass index (BMI), sagittal abdominal diameter (SAD), waist circumference (WC) and 7-site skinfold analysis. In addition, Each subject completed a three day diet record prior to their three visits which were analyzed for total calories, macronutrient percent calories and amount of micronutrient antioxidants; vitamin A, C, E, and zinc. They were instructed on how to log 3 day diet records and were asked to repeat the diets as close as possible on their 2nd and 3rd visits to keep this information as consistent as possible. Significant relationships were found for body composition factors including Siri % body fat (r=0.631, P=0.028*), Brozek % body fat (r=0.642, P=0.024*), and BMI (r=0.649, P=0.022*). Body composition factors showed varied results. A significant association was found between sagittal abdominal diameter and plasma apelin concentrations at rest (r=0.628, p=0.029*), however waist circumference approached significance (r=0.061, P=0.061) and waist-to-hip ratio did not demonstrate a significant relationship (r=0.178, P=0.579). Only two subjects reported consuming high fat diets (>35% of total kilocalorie intake), therefore no relationships could be analyzed regarding plasma apelin concentration at rest and high fat diets. No significant relationships were found between individual micronutrients and plasma apelin concentrations at rest, besides vitamin E (r=0.658, P=0.020*). In conclusion this small cohort of subjects had stable resting plasma apelin levels across visits and does not appear that dietary factors influenced plasma apelin concentrations. In contrast, % BF and SAD suggest that these factors are significantly related to resting plasma apelin, with WC also approaching significance. More research should be done with a larger cohort of subjects including a wider range of diet and anthropometric measures
