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Lipid metabolism in riboflavin-deficient rats

2. Mitochondrial fatty acid oxidation and the microsomal desaturation pathway

Published online by Cambridge University Press:  09 March 2007

S. E. Olpin  and
C. J. Bates
S. E. Olpin
Affiliation:
Dunn Nutrition Unit, University of Cambridge and Medical Research Council, Cambridge CB4 1XJ
C. J. Bates
Affiliation:
Dunn Nutrition Unit, University of Cambridge and Medical Research Council, Cambridge CB4 1XJ
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Abstract

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1. Oxygen consumption was measured by means of an O2 electrode in mitochondrial suspensions from riboflavin-deficient and pair-fed control rats, using six different substrates. Whereas consumption of O2 by glutamate was only slightly depressed in mitochondria from deficient animals, the consumption of O2 by hexanoate and by palmitoyl-L-carnitine was depressed to approximately half the control value: a highly significant difference. A comparable magnitude of depression was observed for stearoyl-, oleoyl-, and linoleoyl-L-carnitine. There were no major or consistent differences between groups of animals receiving two different types, and two different levels, of fat in their diet.

2. The activity of acyl coenzyme A dehydrogenase (EC 1.3.99.3) in hepatic mitochondrial fragments, measured by cytochrome c reduction with palmitoyl-coenzyme A as substrate, and expressed as maximum velocity (Vmax) With respect to phenazine methosulphate, was also reduced to approximately half the control value in deficient animals.

3. In hepatic microsomes, cytochrome b5 reductase( EC 1.6.2.2) activity was unaffected by riboflavin deficiency, although NADPH-cytochrome c reductase (EC 1.6.2.4) and microsomal flavin content were diminished to approximately half the control values. Acyl CoA (Δ9) desaturase activity (EC 1.14.99.5) was virtually identical in deficient, pair-fed, and ad lib.-fed control groups.

4. It is concluded that the depression of mitochondrial β-oxidation of fatty acids which is observed in riboflavin-deficient animals is not a secondary result of inanition, and may account for the observed changes in fatty acid profiles of triglycerides and phospholipids. Failure of the microsomal fatty acid desaturation system is less likely to be a major consequence of riboflavin deficiency.

Type
Papers on General Nutrition
Information
British Journal of Nutrition , Volume 47 , Issue 3 , May 1982 , pp. 589 - 596
Copyright
Copyright © The Nutrition Society 1982

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