The Effects of Dietary Fat Content and Triacylglycerol Structures on the Vitamin A Storage in Mice

OBJECTIVES: Vitamin A (VA, retinol) is a fat-soluble micronutrient that plays a variety of physiological functions form development to metabolism in humans and animals. The VA metabolism and storage can be affected by many different factors and high fat diet is one of them. As a major dietary lipid component, elevations of dietary intake of triacylglycerol (TAG) are associated with a variety of metabolic abnormalities. The alternation of TAG structure can change its physicochemical features or physiological impacts. We hypothesis that the structure of TAG fatty acyl position may affect the absorption and metabolism of VA in animal body. METHODS: Twenty-seven 6-week-old male C57/BL6J mice at 6 weeks of age were randomly assigned to 3 dietary treatment groups, 1,2-dipalmitoyl-3-oleoylglycerol (PPO, 36% w/w chow diet), 1,3-dipalmitoyl-2-oleoylglycerol (POP, 36% w/w chow diet), and the chow diet control. Mice were fed with assigned diet; their food intake and body weight were measured and record daily. At the end of six-weeks treatment, mice were sacrificed, and liver tissue were collected. Dietary Vitamin A intake for each mouse was calculated based on their food intake and vitamin A content in the chow diet. Vitamin A storage in liver was determined by high performance liquid chromatography. RESULTS: The PPO and POP diets have less VA per unit due to the presence of 36% of pure TAG, which diluted the VA content in the basal chew diet. Mice fed the chew diet had significantly higher VA intake after the adjustment of total net food intake, which is associated with higher usage and storage in the chow fed group than the PPO and POP. The mice in the PPO group have significantly higher VA intake, VA storage in the liver and VA usage than those in the POP group. However, the intake/storage ratio between two high fat diet group is not different. CONCLUSIONS: The VA usage and storage amount are associated with its dietary intakes. The feeding of a high-fat diet reduces the usage of VA due to lowered amounts of VA intakes. The TAG structure can impact the VA intakes because of TAG on metabolism in mice fed a high-fat diet. FUNDING SOURCES: The experiment was conducted at the University of Tennessee, PI Guoxun Chen (Nutrition science) and co-PI Toni Wang (Food Science).