13C Natural Abundance of Serum Retinol is a Novel Biomarker for Evaluating Effectiveness of Provitamin A Biofortified Maize and Carrots in Male Mongolian Gerbils

Abstract

BackgroundCrops, such as maize, rice, sorghum, and millet, are being biofortified with provitamin A carotenoids to sustainably ensure adequate vitamin A (VA) intakes. VA assessment can be challenging because serum retinol is homeostatically controlled and more sensitive techniques are resource intensive.ObjectivesThis study investigated serum retinol 13C abundance changes due to natural 13C fractionation in C3 vs. C4 plants as a biomarker to detect provitamin A efficacy from biofortified (orange) maize and carrots.MethodsThe design was a 2×2×2 maize (orange vs. white) by carrot (orange vs. white) by VA fortificant (VA+ vs. VA−) in Mongolian gerbils (n=55), which included a 14‐d VA‐depletion period followed by eight 62‐d treatments (n=5–7/treatment). VA from liver and serum was quantified and purified by HPLC and subsequently analyzed by gas chromatography‐combustion‐ isotope ratio mass spectrometry for 13C abundance.ResultsTreatments significantly affected liver VA concentrations (P<0.0001), but did not affect serum VA concentrations (P=0.64). Serum retinol and liver VA 13C abundance correlated well (R2=0.92, P<0.0001). Serum retinol 13C abundance differentiated control groups consuming white maize and white carrots (−27.1±1.2 δ 13C‰) from those consuming orange maize and white carrots (−21.6±1.4 δ 13C‰, P<0.0001) and those consuming white maize and orange carrots (−30.6±0.7 δ 13C‰, P<0.0001).ConclusionsProvitamin A adoption effectiveness can be evaluated using serum retinol 13C abundance shifts after consumption of provitamin A maize and could likely be used for other C4 plants being biofortified with provitamin A carotenoids (e.g. millet and sorghum). Advantages of this include no extrinsic tracer dose, a single blood sample, and high sensitivity compared with serum retinol.Support or Funding InformationThis work was supported by an endowment to SAT entitled “Friday Chair for Vegetable Processing Research”, USDA Hatch WIS01528 (SAT), California Fresh Carrot Advisory Board (PWS), and HarvestPlus Agreement 5204 (KVP).