Metabolomics reveals altered hepatic bile acids, gut microbiome metabolites, and cell membrane lipids associated with marginal vitamin A deficiency in a Mongolian gerbil model

Authors: LA FRANO, MICHAEL - California Polytechnic State University; BRITO, ALEX - First Moscow State Medical University; JOHNSON, CATHERINE - California Polytechnic State University; WILHELMSON, BAYLEE - California Polytechnic State University; GANNON, BRYAN - University Of Wisconsin; FANTER, ROB - California Polytechnic State University; PEDERSEN, THERESA - University Of California, Davis; TANUMIHARDJO, SHERRY - University Of Wisconsin; Newman, John

Submitted to: Molecular Nutrition and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2020
Publication Date: 7/2/2020
Citation: La Frano, M.R., Brito, A., Johnson, C.M., Wilhelmson, B., Gannon, B., Fanter, R.K., Pedersen, T.L., Tanumihardjo, S.A., Newman, J.W. 2020. Metabolomics reveals altered hepatic bile acids, gut microbiome metabolites, and cell membrane lipids associated with marginal vitamin A deficiency in a Mongolian gerbil model. Molecular Nutrition and Food Research. 64(13). https://doi.org/10.1002/mnfr.201901319.
DOI: https://doi.org/10.1002/mnfr.201901319

Interpretive Summary: The current study was designed to increase or understanding of the impacts of vitamin A (VA) deficiency on hepatic metabolism using an accepted rodent model of vitamin A metabolism. After 28 d of VA depletion, male Mongolian gerbils (Meriones unguiculatus) were randomly assigned to experimental diets for 28 d. Groups were fed a white maize-based diet with ~50 µL cottonseed oil vehicle either alone (VA-, n = 10) or containing 40 µg retinyl acetate (VA+, n= 10) for 28 d. Liver retinol levels were measured by high-performance liquid chromatography (HPLC) to assess VA status. Analytical determinations of small molecules associated with metabolism including substrates and products of energy metabolism, those involved with general cellular maintenance, compounds involved in mediating growth and inflammatory responses, and products derived from the gut microflora were determined in post-mortem liver samples by liquid chromatography-mass spectrometry (LC-MS) to assess broad impacts on metabolism. Liver retinol was lower (p<0.001) in the VA- versus VA+ group, with concentrations indicating VA deficiency. Using an array of metabolomics assays, the levels of a total of 300 identified metabolites were assessed. VA deficiency was associated with decreases in bile acids, trimethylamine N-oxide, and a variety of acyl carnitines, phospholipids and sphingomyelins (p <0.05). Components related to DNA biosynthesis and degradation, including purine deoxyribonucleosides, deoxyguanosine, the nucleoside cytidine, and the uracil derivative N-carbomoyl-beta-alanine (p<0.05), were differentially altered. Ultimately, hepatic metabolomics in a VA deficient Gerbil model revealed alterations in markers of the gut microbiome, fatty acid and nucleotide metabolism, and cellular structure and signaling. These results provide significant novel insight into the cascading effects of vitamin a deficiency in mammals.

Technical Abstract: Scope: This study was designed to provide a broad evaluation of the impacts of vitamin A (VA) deficiency on hepatic metabolism in a gerbil model. Methods and results: After 28 d of VA depletion, male Mongolian gerbils (Meriones unguiculatus) were randomly assigned to experimental diets for 28 d. Groups were fed a white maize-based diet with ~50 µL cottonseed oil vehicle either alone (VA-, n = 10) or containing 40 µg retinyl acetate (VA+, n= 10) for 28 d. Liver retinol was measured by high-performance liquid chromatography (HPLC). Primary metabolomics, aminomics, lipidomics, bile acids, oxylipins, ceramides and endocannabinoids were determined in post-mortem liver samples by liquid chromatography-mass spectrometry (LC-MS). Results: Liver retinol was lower (p<0.001) in the VA- versus VA+ group, with concentrations indicating VA deficiency. A total of 300 metabolites were identified. VA deficiency was associated with lower bile acids, trimethylamine N-oxide, and a variety of acyl carnitines, phospholipids and sphingomyelins (p <0.05). Components of DNA, including purine deoxyribonucleosides, deoxyguanosine, the nucleoside cytidine, and the uracil derivative N-carbomoyl-beta-alanine (p<0.05), were differentially altered. Conclusions: Hepatic metabolomics in a VA deficient Gerbil model revealed alterations in markers of the gut microbiome, fatty acid and nucleotide metabolism, and cellular structure and signaling.