Metabolism of α-linolenic acid during incubations with strained bovine rumen contents: products and mechanisms

Anne M. Honkanen; Heidi Leskinen; Vesa Toivonen; Nest McKain; Robert John Wallace; Kevin J. Shingfield

doi:10.1017/S0007114516001446

Metabolism of α-linolenic acid during incubations with strained bovine rumen contents: products and mechanisms

Anne M. Honkanen, Heidi Leskinen, Vesa Toivonen, Nest McKain, Robert John Wallace, Kevin J. Shingfield^*

^*Corresponding author for this work

The Rowett Institute of Nutrition and Health

Research output: Contribution to journal › Article › peer-review

26 Citations (Scopus)

Abstract

Description of α-linolenic acid (cis-9,cis-12,cis-15-18 : 3, ALA) metabolism in the rumen is incomplete. Ruminal digesta samples were incubated with ALA and buffer containing water or deuterium oxide to investigate the products and mechanisms of ALA biohydrogenation. Geometric Δ9,11,15-18 : 3 isomers were the main intermediates formed from ALA. An increase in the n+1 isotopomers of Δ9,11,15-18 : 3 was due to ²H labelling at C-13. Isomers of Δ9,11,13-18 : 3, cis-7,cis-12,cis-15-18 : 3 and cis-8,cis-12,cis-15-18 : 3 were also formed. No increase in n+1 isotopomers of Δ7,12,15-18 : 3 or Δ8,12,15-18 : 3 was detected. Enrichment in n+2 isotopomers of 18 : 2 products indicated that ALA metabolism continued via the reduction of 18 : 3 intermediates. Isomers of Δ9,11,15-18 : 3 were reduced to Δ11,15-18 : 2 labelled at C-9 and C-13. ALA resulted in the formation of Δ11,13-18 : 2 and Δ12,14-18 : 2 containing multiple ²H labels. Enrichment of the n+3 isotopomer of Δ12,15-18 : 2 was also detected. Metabolism of ALA during incubations with rumen contents occurs by one of three distinct pathways. Formation of Δ9,11,15-18 : 3 appears to be initiated by H abstraction on C-13. Octadecatrienoic intermediates containing cis-12 and cis-15 double bonds are formed without an apparent H exchange with water. Labelling of Δ9,11,13-18 : 3 was inconclusive, suggesting formation by an alternative mechanism. These findings explain the appearance of several bioactive fatty acids in muscle and milk that influence the nutritional value of ruminant-derived foods.

Original language	English
Pages (from-to)	2093-2105
Number of pages	13
Journal	British Journal of Nutrition
Volume	115
Issue number	12
Early online date	18 Apr 2016
DOIs	https://doi.org/10.1017/S0007114516001446
Publication status	Published - Jun 2016

Bibliographical note

Acknowledgements
The authors gratefully acknowledge and appreciate the technical
assistance of Minna Aalto (Natural Resources Institute
Finland) during lipid analysis. This study was supported in part by core funding from the Finnish Ministry of Agriculture and Forestry, the Scottish Government Rural and Environment Science and Analytical Services Division and a PhD studentship from the Raisio Science Biohydrogenation of α-linolenic acid 2103
Foundation and the August Johannes and Aino Tiura Agricultural
Science Foundations (awarded to A. M. H.). None of the
funders had any role in the experimental design, data analysis
or writing of this article.
The authors’ contributions are as follows: A. M. H. and K. J. S.
designed the study; A. M. H. completed the in vitro incubations;
A. M. H., H. L., R. J. W., N. M., V. T. and K. J. S. contributed to
the analysis of lipids, determination of 2 H enrichment and FA
identification; A. M. H. analysed the data under the supervision
of R. J. W. and K. J. S.; A. M. H. and K. J. S. wrote the manuscript;
R. J. W., N. M. and H. L. provided advice and critically reviewed
the manuscript. All the authors have read and approved the
manuscript content.
There are no conflicts of interest.

Keywords

Biohydrogenation
Conjugated linoleic acid
Conjugated linolenic acid
Linolenic acid
Rumen bacteria

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title = "Metabolism of α-linolenic acid during incubations with strained bovine rumen contents: products and mechanisms",

abstract = "Description of α-linolenic acid (cis-9,cis-12,cis-15-18 : 3, ALA) metabolism in the rumen is incomplete. Ruminal digesta samples were incubated with ALA and buffer containing water or deuterium oxide to investigate the products and mechanisms of ALA biohydrogenation. Geometric Δ9,11,15-18 : 3 isomers were the main intermediates formed from ALA. An increase in the n+1 isotopomers of Δ9,11,15-18 : 3 was due to 2H labelling at C-13. Isomers of Δ9,11,13-18 : 3, cis-7,cis-12,cis-15-18 : 3 and cis-8,cis-12,cis-15-18 : 3 were also formed. No increase in n+1 isotopomers of Δ7,12,15-18 : 3 or Δ8,12,15-18 : 3 was detected. Enrichment in n+2 isotopomers of 18 : 2 products indicated that ALA metabolism continued via the reduction of 18 : 3 intermediates. Isomers of Δ9,11,15-18 : 3 were reduced to Δ11,15-18 : 2 labelled at C-9 and C-13. ALA resulted in the formation of Δ11,13-18 : 2 and Δ12,14-18 : 2 containing multiple 2H labels. Enrichment of the n+3 isotopomer of Δ12,15-18 : 2 was also detected. Metabolism of ALA during incubations with rumen contents occurs by one of three distinct pathways. Formation of Δ9,11,15-18 : 3 appears to be initiated by H abstraction on C-13. Octadecatrienoic intermediates containing cis-12 and cis-15 double bonds are formed without an apparent H exchange with water. Labelling of Δ9,11,13-18 : 3 was inconclusive, suggesting formation by an alternative mechanism. These findings explain the appearance of several bioactive fatty acids in muscle and milk that influence the nutritional value of ruminant-derived foods.",

keywords = "Biohydrogenation, Conjugated linoleic acid, Conjugated linolenic acid, Linolenic acid, Rumen bacteria",

author = "Honkanen, {Anne M.} and Heidi Leskinen and Vesa Toivonen and Nest McKain and Wallace, {Robert John} and Shingfield, {Kevin J.}",

note = "Acknowledgements The authors gratefully acknowledge and appreciate the technical assistance of Minna Aalto (Natural Resources Institute Finland) during lipid analysis. This study was supported in part by core funding from the Finnish Ministry of Agriculture and Forestry, the Scottish Government Rural and Environment Science and Analytical Services Division and a PhD studentship from the Raisio Science Biohydrogenation of α-linolenic acid 2103 Foundation and the August Johannes and Aino Tiura Agricultural Science Foundations (awarded to A. M. H.). None of the funders had any role in the experimental design, data analysis or writing of this article. The authors{\textquoteright} contributions are as follows: A. M. H. and K. J. S. designed the study; A. M. H. completed the in vitro incubations; A. M. H., H. L., R. J. W., N. M., V. T. and K. J. S. contributed to the analysis of lipids, determination of 2 H enrichment and FA identification; A. M. H. analysed the data under the supervision of R. J. W. and K. J. S.; A. M. H. and K. J. S. wrote the manuscript; R. J. W., N. M. and H. L. provided advice and critically reviewed the manuscript. All the authors have read and approved the manuscript content. There are no conflicts of interest.",

year = "2016",

month = jun,

doi = "10.1017/S0007114516001446",

language = "English",

volume = "115",

pages = "2093--2105",

journal = "British Journal of Nutrition",

issn = "0007-1145",

publisher = "Cambridge University Press",

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TY - JOUR

T1 - Metabolism of α-linolenic acid during incubations with strained bovine rumen contents

T2 - products and mechanisms

AU - Honkanen, Anne M.

AU - Leskinen, Heidi

AU - Toivonen, Vesa

AU - McKain, Nest

AU - Wallace, Robert John

AU - Shingfield, Kevin J.

N1 - Acknowledgements The authors gratefully acknowledge and appreciate the technical assistance of Minna Aalto (Natural Resources Institute Finland) during lipid analysis. This study was supported in part by core funding from the Finnish Ministry of Agriculture and Forestry, the Scottish Government Rural and Environment Science and Analytical Services Division and a PhD studentship from the Raisio Science Biohydrogenation of α-linolenic acid 2103 Foundation and the August Johannes and Aino Tiura Agricultural Science Foundations (awarded to A. M. H.). None of the funders had any role in the experimental design, data analysis or writing of this article. The authors’ contributions are as follows: A. M. H. and K. J. S. designed the study; A. M. H. completed the in vitro incubations; A. M. H., H. L., R. J. W., N. M., V. T. and K. J. S. contributed to the analysis of lipids, determination of 2 H enrichment and FA identification; A. M. H. analysed the data under the supervision of R. J. W. and K. J. S.; A. M. H. and K. J. S. wrote the manuscript; R. J. W., N. M. and H. L. provided advice and critically reviewed the manuscript. All the authors have read and approved the manuscript content. There are no conflicts of interest.

PY - 2016/6

Y1 - 2016/6

N2 - Description of α-linolenic acid (cis-9,cis-12,cis-15-18 : 3, ALA) metabolism in the rumen is incomplete. Ruminal digesta samples were incubated with ALA and buffer containing water or deuterium oxide to investigate the products and mechanisms of ALA biohydrogenation. Geometric Δ9,11,15-18 : 3 isomers were the main intermediates formed from ALA. An increase in the n+1 isotopomers of Δ9,11,15-18 : 3 was due to 2H labelling at C-13. Isomers of Δ9,11,13-18 : 3, cis-7,cis-12,cis-15-18 : 3 and cis-8,cis-12,cis-15-18 : 3 were also formed. No increase in n+1 isotopomers of Δ7,12,15-18 : 3 or Δ8,12,15-18 : 3 was detected. Enrichment in n+2 isotopomers of 18 : 2 products indicated that ALA metabolism continued via the reduction of 18 : 3 intermediates. Isomers of Δ9,11,15-18 : 3 were reduced to Δ11,15-18 : 2 labelled at C-9 and C-13. ALA resulted in the formation of Δ11,13-18 : 2 and Δ12,14-18 : 2 containing multiple 2H labels. Enrichment of the n+3 isotopomer of Δ12,15-18 : 2 was also detected. Metabolism of ALA during incubations with rumen contents occurs by one of three distinct pathways. Formation of Δ9,11,15-18 : 3 appears to be initiated by H abstraction on C-13. Octadecatrienoic intermediates containing cis-12 and cis-15 double bonds are formed without an apparent H exchange with water. Labelling of Δ9,11,13-18 : 3 was inconclusive, suggesting formation by an alternative mechanism. These findings explain the appearance of several bioactive fatty acids in muscle and milk that influence the nutritional value of ruminant-derived foods.

AB - Description of α-linolenic acid (cis-9,cis-12,cis-15-18 : 3, ALA) metabolism in the rumen is incomplete. Ruminal digesta samples were incubated with ALA and buffer containing water or deuterium oxide to investigate the products and mechanisms of ALA biohydrogenation. Geometric Δ9,11,15-18 : 3 isomers were the main intermediates formed from ALA. An increase in the n+1 isotopomers of Δ9,11,15-18 : 3 was due to 2H labelling at C-13. Isomers of Δ9,11,13-18 : 3, cis-7,cis-12,cis-15-18 : 3 and cis-8,cis-12,cis-15-18 : 3 were also formed. No increase in n+1 isotopomers of Δ7,12,15-18 : 3 or Δ8,12,15-18 : 3 was detected. Enrichment in n+2 isotopomers of 18 : 2 products indicated that ALA metabolism continued via the reduction of 18 : 3 intermediates. Isomers of Δ9,11,15-18 : 3 were reduced to Δ11,15-18 : 2 labelled at C-9 and C-13. ALA resulted in the formation of Δ11,13-18 : 2 and Δ12,14-18 : 2 containing multiple 2H labels. Enrichment of the n+3 isotopomer of Δ12,15-18 : 2 was also detected. Metabolism of ALA during incubations with rumen contents occurs by one of three distinct pathways. Formation of Δ9,11,15-18 : 3 appears to be initiated by H abstraction on C-13. Octadecatrienoic intermediates containing cis-12 and cis-15 double bonds are formed without an apparent H exchange with water. Labelling of Δ9,11,13-18 : 3 was inconclusive, suggesting formation by an alternative mechanism. These findings explain the appearance of several bioactive fatty acids in muscle and milk that influence the nutritional value of ruminant-derived foods.

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KW - Conjugated linoleic acid

KW - Conjugated linolenic acid

KW - Linolenic acid

KW - Rumen bacteria

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DO - 10.1017/S0007114516001446

M3 - Article

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SN - 0007-1145

VL - 115

SP - 2093

EP - 2105

JO - British Journal of Nutrition

JF - British Journal of Nutrition

IS - 12

ER -

Metabolism of α-linolenic acid during incubations with strained bovine rumen contents: products and mechanisms

Abstract

Bibliographical note

Keywords

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