In the United States, approximately 30% of adults are obese. Overweight and obesity are associated with the incidence and/or mortality of several cancers. Moreover, there is a growing body of evidence suggesting that measures of obesity are associated with the stage at diagnosis, prognosis and survival of cancer. However, the biological mechanisms underlying these associations are unclear. One hypothesis suggests that obesity might play an important role in angiogenesis. Leptin and vascular endothelial growth factor (VEGF), two proteins produced from adipose tissue, stimulate angiogenesis whereas pigment epithelium-derived factor (PEDF), also produced from adipose tissue, inhibits angiogenesis. Although an association between obesity and circulating leptin is well established there the associations of VEGF and PEDF with overweight or obesity and with leptin are not well understood. Importantly, the measurement of circulating VEGF and PEDF could be confounded by platelet-derived PEDF and VEGF. For the proposed pilot study, we will recruit 100 healthy men and women, aged 21- 50 years who are willing to complete a short sociodemographic and health questionnaire, have their height and weight measured, and who will provide blood samples after a 10 hour fast and two hours later after eating a light, healthful snack. Based on the samples and data collected, we will compare circulating leptin, PEDF and VEGF levels in sample collected from serum, EDTA plasma or platelet poor plasma tubes and between the fasted and non-fasted state. In addition, we will begin to explore the complex associations among PEDF, VEGF, BMI and leptin levels. Results of this study will allow us to establish appropriate blood collection methods for measurement of leptin, PEDF and VEGF, and provide pilot data on the magnitude of associations between the blood biomarkers and obesity. Our long-term goal is to study whether the associations of obesity with cancer risk and prognosis are mediated by leptin, PEDF, and/or VEGF.
