Zinc deficiency and the desaturation of linoleic acid in rats force-fed fat-free diets |
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Authors: | Klaus Eder Manfred Kirchgessner |
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Institution: | 1. Institut für Ern?hrungsphysiologie der Technischen, Universit?t München, D-85350, Freising, Germany
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Abstract: | Recent studies with rats force-fed zinc-deficient diets containing various types of fat failed to demonstrate a role of zinc
in desaturation of linoleic acid. The present study was conducted to investigate the effect of zinc deficiency on desaturation
of linoleic acid in rats that were initially force-fed fat-free diets to stimulate activity of desaturases. Therefore, rats
were fed zinc-adequate and zinc-deficient fat-free diets for 6 d. After that period, the groups were divided and half of the
rats continued feeding the fat-free diet for another 3.5 d whereas the other half was switched to a fat diet by supplementing
the fat-free diet with 5% safflower oil. In order to assess desaturation of linoleic acid, fatty acid compositions of liver
phosphatidylcholine, ethanolamine, and-serine were considered, particularly levels of individual (n-6) polyunsaturated fatty
acids (PUFA). Levels of total and individual (n-6) PUFA were similar in zinc-adequate and zinc-deficient rats fed the fat-free
diet throughout the experiment. Addition of 5% safflower oil increased levels of total and individual (n-6) PUFA in both zinc-adequate
and zinc-deficient rats. However, total (n-6) PUFA in all types of phospholipids were higher in zinc-adequate rats than in
zinc-deficient rats. Additionally, in zinc-deficient rats there were changes of (n-6) PUFA levels typical for impaired Δ5
and Δ6 desaturation: linoleic acid and dihomo-γ-linolenic acid were elevated; arachidonic acid, docosatetraenoic acid, and
docosapentaenoic were lowered by zinc deficiency. Therefore, the study shows that zinc deficiency impairs desaturation of
linoleic acid in rats force-fed fat-free diets and therefore supports results from former convential zinc deficiency experiments
suggesting a role of zinc for desaturation of linoleic acid. |
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Keywords: | Zinc deficiency force-feeding desaturation liver fat-free diet fatty acid composition rat |
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