Efficacy, biosafety, and metabolic impacts of feeding mice egg yolks enriched with three bioactive nutrients in different combinations

Background: Docosahexaenoic acid (DHA), 25-hydroxyvitamin D3 (25-OH D3), and astaxanthin (AST) are three bioactive and health-promoting nutrients. We previously enriched eggs with DHA alone and in combination with 25-OH D3 and (or) AST as a novel food source of these nutrients by the public. This study was to determine dietary efficacy, biosafety, and metabolic impacts and mechanisms of feeding these egg yolks with four different enrichments of the three nutrients in mice. Methods: Eighty mice (23- to 40-week-old, n = 8, four males and females each) were divided into two experiments and were fed a sucrose-yeast basal diet with control egg yolk (BD) or one of the four types of enriched yolks (BD + DHA, BD + DHA + 25-OH D3, BD + DHA + AST, and BD + DHA + 25-OH D3 + AST) at recommended (1X, Experiment I) and high dose (5X, Experiment II) for 6 weeks. Concentrations of fatty acids, 25-OH D3, AST, and lipids and expression of genes and proteins related to lipid and vitamin D metabolism in the plasma, liver, and (or) heart were determined. Data within each experiment were analyzed by one-way ANOVA. Results: Compared with BD, the four diets with enriched yolks at the 1X level elevated (P < 0.001, up to 61%) hepatic DHA concentrations. Feeding the enriched yolks at either dose did not affect body weights or plasma glucose and triacylglycerol concentrations. In Experiment I, total cholesterol concentrations were 40% higher (P < 0.05) in the liver of BD + DHA than BD and were 1.5-fold higher (P < 0.05) in the heart of BD + DHA + 25-OH D3 + AST than BD + DHA + 25-OH D3. Compared with BD + DHA, BD + DHA + 25-OH D3 upregulated (P < 0.05) hepatic Dgat1 gene expression by 1.4-fold and hepatic DGAT1 protein expression by 1.7-fold. Conclusions: Feeding mice egg yolks enriched with DHA alone or with other nutrients at two doses (1X and 5X) improved hepatic DHA status and exerted moderate impacts on tissue lipid profiles and the related gene expressions. These eggs may be safe for future human trials.