Richard S. Bruno, PhD, RD

Professor, Human Nutrition Program
The Ohio State University, Columbus, OH

image of Dr. Richard Bruno
Abstract: Dietary recommendations for α-tocopherol, the only essential form of vitamin E, are challenging to meet from food alone. Indeed, >92% of Americans fail to meet recommendations, and α-tocopherol status is likely further compromised by inflammatory responses occurring in metabolic syndrome (MetS). It is therefore important to establish the extent to which MetS increases dietary α-tocopherol requirements due to underlying inflammation that likely impairs α-tocopherol trafficking and metabolism along the gut-liver axis. Our approach entailed a randomized cross-over study in MetS and age- and gender-matched healthy adults in which they ingested encapsulated deuterium-labeled RRR-α-tocopherol (15 mg) with dairy milk beverages containing 0-8 g fat. Pharmacokinetics of labeled α-tocopherol and its physiologic metabolite α-CEHC (carboxyethyl-hydroxychromanol) were then assessed for 72 h using LC-MS. MetS adults had increased circulating oxidized LDL and pro-inflammatory cytokines in association with metabolic endotoxemia. Plasma α-tocopherol absorption, Cmax, and bioavailability (AUC0-72 h) were significantly lower in MetS adults regardless of dairy milk fat content. Their isolated chylomicrons and VLDL also had lower α-tocopherol enrichment, suggesting impaired intestinal and hepatic trafficking of α-tocopherol. MetS adults also had lower circulating and urinary α-CEHC, suggesting inadequate α-tocopherol status to activate P450-mediated metabolism of α-tocopherol. Pharmacokinetic parameters of both α-tocopherol and α-CEHC were correlated with inflammatory responses. Thus, MetS adults have higher dietary requirements to offset inflammatory stress responses that limit α-tocopherol bioavailability by decreasing intestinal absorption and hepatic secretion. This presentation will therefore discuss the potential mechanisms by which MetS impairs α-tocopherol status, and implications for achieving optimal health.