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Title: Factors influencing the Δ6-desaturation of linoleic acid
Author: Brown, Jonathan E.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1995
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The role of dietary cholesterol on both linolenic acid Δ6-desaturation and tissue fatty acid composition was assessed. Cholesterol enrichment increased Δ6-desaturation activity and this was reflected in the increased product-precursor ratio of γ-linolenic to linoleic acid in microsomal phospholipids. However, the total amount of long chain polyunsaturated fatty acids derived from linoleic acid, including arachidonic acid, was reduced in cholesterol fed rats, suggesting an impaired Δ5-desaturase. The increased activity of liver microsomal Δ6-desaturase was not associated with any significant changes to adipose tissue n-6 fatty acid composition. Further studies were conducted to elucidate possible reasons for the disparity between the present and published studies on the effect of cholesterol. Cholesterol feeding was carried out in grouped and isolated rats and microsomal Δ6-desaturase reassessed. Although stress caused by isolation reduced Δ6-desaturase activity, dietary cholesterol increased its activity again. This was observed under both saturating and non-saturating substrate conditions with a good correlation observed between the two. Levels of non-esterified fatty acids in the microsomal preparations were not different between the four groups, indicating that this was not the explanation for the lower activity of Δ6-desaturase reported by others. The effect of dietary cholesterol on the in vivo metabolism of linoleic acid was subsequently pursued to investigate whether this differed from that demonstrated in vitro. The overall metabolism of linoleic acid, assessed on the basis of the decline in the specific activity of linoleic acid with time, was decreased by cholesterol feeding, whilst Δ6-desaturase activity of isolated liver microsomes increased in one experiment and no change was found in the remaining experiments.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available