Author: Marija Knez
Knez, Marija, 2019 The Role of the LA:DGLA Ratio in Predicting the Zn Status of Humans and Animals, Flinders University, College of Science and Engineering
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Zinc (Zn) is a vital micronutrient for humans, being involved in multiple enzymatic, biochemical and structural processes within the body. Zn deficiency, the main cause of early childhood morbidity and mortality, is a global health problem and is estimated to affect 17% of the world’s population. A precise assessment of the magnitude of Zn deficiency is challenging, as Zn intake and status data for a large number of countries are either outdated or missing. Zn deficiency has been recently recognized as possibly responsible for the expansion of Fe deficiency and Fe deficiency anemia, but there is a lack of information on the mechanism of that interaction. Zn biofortified wheat is a newly developed strategy that aims to contribute to the alleviation of Zn deficiency, yet its efficacy is still awaiting confirmation. A lack of a sensitive and specific Zn biomarker additionally limits the accurate assessment of the magnitude of Zn deficiency and the impact of nutrition intervention strategies, such as biofortification.
This PhD project aims to identify a new biomarker that can act as a reliable and sensitive indicator of Zn status in humans. Additional goals of this research project were to provide an up to date assessment of Zn and Fe intake and status data in an apparently healthy adult population, to investigate the role of Zn in the Fe absorption process and clarify the mechanism by which Zn deficiency contributes to the development of Fe deficiency and Fe deficiency anemia. Finally, the project investigates the effectiveness of Zn biofortified wheat in improving Zn status of consumers.
The linoleic: dihomo-γ-linolenic acid (LA:DGLA) ratio was examined as a potential biomarker of Zn status. The content of plasma phospholipid LA, DGLA and changes in the LA:DGLA ratio were compared to the dietary Zn intake and plasma Zn status in healthy human subjects. Zn and Fe nutritional status of apparently healthy European adults (25-65 years of age) was examined by means of anthropometric, dietary, and biochemical measurements and the relation of usual Zn and Fe dietary intake to Zn and Fe status was investigated. The structure and function of major Zn and Fe transport proteins and Zn and Fe interaction at these sites is comprehensively reviewed to illuminate the mechanism of Zn involvement in the Fe absorption process. The amount of Zn absorbed from Zn biofortified wheat material was estimated using a range of physiological and molecular parameters within an in vivo (Gallus gallus) model of Zn absorption.
This PhD project provided several new contributions to knowledge: it demonstrated that there is a positive link between Zn and Fe for absorption and that the cellular Zn concentrations control Fe absorption processes. A comprehensive model of Zn involvement in the Fe absorption process, both at the local and systemic level, is delivered. In addition, it was revealed that marginal Zn deficiency is present in apparently healthy populations, so regular monitoring is of crucial importance. The core contribution of the work presented within this thesis is the evidence of the responsiveness of the LA:DGLA ratio to dietary Zn modifications in both animals and humans. The ratio can be used as an additional indicator of Zn status.
Finally, it was confirmed that the additional Zn present in biofortified wheat is equally biologically available for absorption as Zn from conventional wheat varieties; consumption of Zn biofortified wheat improved the Zn status of consumers.
Keywords: Zinc, iron, Zn & Fe interaction, dietary intake, Zn biomarker, Zn and Fe status, LA:DGLA, Zn biofortification, wheat
Subject: Biology thesis
Thesis type: Doctor of Philosophy
Completed: 2019
School: College of Science and Engineering
Supervisor: James C.R. Stangoulis