Identification of Biomarkers of Plant-Rich Diets and Carbonyl Stress and Their Associations with Cardiovascular Risk

One potential mechanism through which plant-rich diets reduce chronic disease risk is their high polyphenol content, with flavonoids as the most abundant type, constituting approximately two-thirds of polyphenol intake. Substantial evidence suggests dietary flavonoids play a crucial role in cardiometabolic disease prevention due to their anti-inflammatory and antioxidant effects. However, accurately measuring adherence to a flavonoid-rich eating pattern remains challenging due to limited methods for precise intake assessment. This application aims to identify and validate flavonoid metabolites, particularly those related to carbonyl and oxidative stress, as biomarkers of plant-rich diets through a randomized crossover trial and comprehensive profiling of urinary flavonoid metabolites in cohorts with cardiovascular disease (CVD) outcomes. Specific Aim 1 will assess the dose- and time-dependent formation of flavonoid biomarkers in urine and blood from a randomized crossover trial of low- and high-flavonoid diets among healthy individuals (n=36), using LCMS-based targeted metabolomics to evaluate urinary and plasma flavonoid metabolites, including novel reactive carbonyl species (RCS) conjugated and oxidized flavonoid metabolites. We will investigate whether a flavonoid-rich diet reduces carbonyl stress, measured by RCS and advanced glycation end products (AGEs). Specific Aim 2 involves comprehensive profiling of urinary flavonoid metabolites, utilizing an in-house LCMS database of major dietary flavonoids and new metabolites (~250 compounds), to examine relationships between flavonoid metabolites, carbonyl and oxidative stress biomarkers (RCS and AGEs), and CVD risk among 500 case-control pairs in the Nurses’ Health Study (NHS), 300 pairs in the Hispanic Community Health Study/Study of Latinos (SOL), and 170 pairs of African Americans in the Southern Community Cohort Study (SCCS). We hypothesize that inverse associations between urinary flavonoid biomarkers and CVD risk are partly mediated by RCS and AGEs. These aims are supported by preliminary data from an acute study on RCS-flavonoid conjugate kinetics after consuming flavonoid-rich foods (green tea, soy milk, blueberry) and pilot studies showing our capability to identify urinary biomarkers of flavonoid intake in free-living populations. This project significantly advances precision nutrition by integrating controlled trials with large, diverse cohorts, bridging nutritional epidemiology with cutting-edge metabolomics and CVD biomarkers. One of its novel aspects is the use of a controlled feeding trial to investigate the time- and dose-dependent formation of novel metabolites linked to carbonyl and oxidative stress in response to a high flavonoid diet. By emphasizing overall dietary patterns over individual foods, the project contributes to the formulation of practical dietary guidelines. The inclusion of the SOL and SCCS enhances the racial and ethnic diversity of our study participants, which is crucial for developing effective dietary interventions tailored to the high-risk minority groups. Project Number: 1R01HL178035-01A1 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Frank Hu (+2 co-PIs) | Institution: HARVARD UNIVERSITY D/B/A HARVARD SCHOOL OF PUBLIC HEALTH, BOSTON, MA | Award Amount: $733,785 | Activity Code: R01 | Study Section: Human Studies of Diabetes and Obesity Study Section[HSDO] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01HL17803501A1