Diet-Genetic Interactions – Metabolic Pathways Influenced by Intake of Dietary Compounds

National Cancer Institute, Frederick MD

Investigators

Abstract

The primary purpose of this research is to determine if smokers have higher levels of beta-apo-13-carotenone than nonsmokers or former smokers. This Inter-Agency Agreement will capitalize on the joint expertise of the NCI DCP NSRG and the USDA Beltsville Human Nutrition Research Center to conduct human research related to the role of diet in cancer prevention. The USDA aims to analyze the blood of smokers obtained from commercial and other sources (such as Prostate Lung Colon Ovarian Screening, ATBC, and CARET Trials) to examine and corroborate the findings in preclinical models. The testing hypothesis is that smokers will have a higher concentration of beta-apo-13-carotenone than non- or former smokers. The methods and standards are available to USDA and the team is fully equipped to do these analyses that are a natural follow-up to the published studies on healthy non-smoker. The identification of the elevated formation of beta-apo-13-carotenone in smokers but not in normal nonsmoking subjects will help explain the unexpected lung cancer increase in previous trials (the beta-carotene blood levels in smokers in these trials were orders of magnitude higher than the normal physiological range). USDA will obtain standards and adapt the novel methodology for analysis of beta-apo-13-carotenone by LC-MS/MS. Once the method is vetted, USDA will obtain blood from smokers, either through commercial sources or other sources. Carotenoids and metabolites will be extracted from plasma samples by liquid-liquid extraction, and the resulting extract will be concentrated then injected onto an Agilent 6490 liquid chromatograph with a triple quadrupole mass spectrometer detector fitted with an atmospheric pressure chemical ionization source for measurement of beta-apo-13-carotenone. The same extract will also be injected onto an HPLC with a photodiode array detector for analysis of carotenoids and vitamin A. Both instruments will be fitted with a C30 reverse phase HPLC column, which will provide maximum separation of the carotenoid species and analytes, and separation will be achieved with a gradient mobile phase comprised of methanol, water, and methyl tertiary butyl ether. Analyte concentrations will be determined against an external standard curve. Resulting carotenoid and beta-apo-13-carotenone concentrations in plasma of smokers and nonsmokers will be compared.