Isomers of conjugated linoleic acids are synthesized via different mechanisms in ruminal digesta and bacteria

Wallace, Robert John; McKain, Nest; Shingfield, Kevin J.; Devillard, Estelle

doi:10.1194/jlr.m700271-jlr200

Cited by 154 publications

(164 citation statements)

References 48 publications

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“…Concentrations of trans-10,cis-12-CLA were too low in the mixed microbiota to make an assessment of labelling, but data from incubations of LA with pure cultures indicated that the labelling of trans-10,cis-12-CLA was much lower compared with RA. This is a pattern that has been observed previously in pure and mixed cultures of ruminal bacteria (Kepler et al, 1971;Wallace et al, 2007).…”

Section: Fatty Acid Biohydrogenation By Human Gut Bacteriasupporting

confidence: 63%

Mechanism of conjugated linoleic acid and vaccenic acid formation in human faecal suspensions and pure cultures of intestinal bacteria

McIntosh¹,

Shingfield

Devillard³

et al. 2009

Microbiology

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Faecal bacteria from four human donors and six species of human intestinal bacteria known to metabolize linoleic acid (LA) were incubated with LA in deuterium oxide-enriched medium to investigate the mechanisms of conjugated linoleic acid (CLA) and vaccenic acid (VA) formation. The main CLA products in faecal suspensions, rumenic acid (cis-9,trans-11-CLA; RA) and trans-9,trans-11-CLA, were labelled at C-13, as were other 9,11 geometric isomers. Traces of trans-10,cis-12-CLA formed were labelled to a much lower extent. In pure culture, Bifidobacterium breve NCFB 2258 formed labelled RA and trans-9,trans-11-CLA, while Butyrivibrio fibrisolvens 16.4, Roseburia hominis A2-183 T , Roseburia inulinivorans A2-192 T and Ruminococcus obeumlike strain A2-162 converted LA to VA, labelled in a manner indicating that VA was formed via C-13-labelled RA. Propionibacterium freudenreichii subsp. shermanii DSM 4902 T , a possible probiotic, formed mainly RA with smaller amounts of trans-10,cis-12-CLA and trans-9,trans-11-CLA, labelled the same as in the mixed microbiota. Ricinoleic acid (12-OH-cis-9-18 : 1) did not form CLA in the mixed microbiota, in contrast to CLA formation described for Lactobacillus plantarum. These results were similar to those reported for the mixed microbiota of the rumen. Thus, although the bacterial genera and species responsible for biohydrogenation in the rumen and the human intestine differ, and a second route of RA formation via a 10-OH-18 : 1 is present in the intestine, the overall labelling patterns of different CLA isomers formation are common to both gut ecosystems. A hydrogen-abstraction enzymic mechanism is proposed that may explain the role of a 10-OH-18 : 1 intermediate in 9,11-CLA formation in pure and mixed cultures.

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Section: Fatty Acid Biohydrogenation By Human Gut Bacteriasupporting

confidence: 63%

Mechanism of conjugated linoleic acid and vaccenic acid formation in human faecal suspensions and pure cultures of intestinal bacteria

McIntosh¹,

Shingfield

Devillard³

et al. 2009

Microbiology

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“…Fish oil or marine algal oil rich in long chain polyunsaturated fatty acids (PUFA) in the diet are known to inhibit the complete biohydrogenation of C18 unsaturated fatty acids resulting in an increase in ruminal trans 18:1 and trans 18:2 outflow Kim et al, 2008;Lee et al, 2008). Incubations with rumen micro-organisms have shown that eicosapentaenoic acid (EPA; cis-5, cis-8, cis-11, cis-14, cis-17 20:5) and docosahexaenoic acid (DHA; Figure 2 Putative pathways describing cis-9, cis-12 18:2 metabolism in the rumen (adapted from Harfoot and Hazlewood, 1988;Hudson et al, 1998;Wallace et al, 2007;Shingfield et al, 2008a). Arrows with solid lines highlight the major biohydrogenation pathway, whereas arrows with dashed lines describe the formation of minor fatty acid metabolites.…”

Section: Ruminal Lipid Metabolismmentioning

confidence: 99%

“…Trans-10, cis-12 CLA formed during the isomerization of LA (Wallace et al, 2007) is the only biohydrogenation intermediate to have been infused at the abomasum over a range of doses and shown unequivocally to inhibit milk fat synthesis in the bovine. Often increases in ruminal trans-10, cis-12 CLA production have been considered as the cause of MFD, but direct measurements indicate that ruminal outflow of trans-10, cis-12 CLA in lactating cows is less than 1.5 g/day (Shingfield and Griinari, 2007; Table 3).…”

Section: Role Of Ruminal Biohydrogenation On Mammary Lipogenesis In Tmentioning

confidence: 99%

Role of trans fatty acids in the nutritional regulation of mammary lipogenesis in ruminants

Shingfield

Bernard

Leroux

et al. 2010

Animal

336

427

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Fat is an important constituent contributing to the organoleptic, processing and physical properties of ruminant milk. Understanding the regulation of milk fat synthesis is central to the development of nutritional strategies to enhance the nutritional value of milk, decrease milk energy secretion and improve the energy balance of lactating ruminants. Nutrition is the major environmental factor regulating the concentration and composition of fat in ruminant milk. Feeding low-fibre/high-starch diets and/or lipid supplements rich in polyunsaturated fatty acids induce milk fat depression (MFD) in the bovine, typically increase milk fat secretion in the caprine, whereas limited data in sheep suggest that the responses are more similar to the goat than the cow. Following the observation that reductions in milk fat synthesis during diet-induced MFD are associated with increases in the concentration of specific trans fatty acids in milk, the biohydrogenation theory of MFD was proposed, which attributes the causal mechanism to altered ruminal lipid metabolism leading to increased formation of specific biohydrogenation intermediates that exert anti-lipogenic effects. Trans-10, cis-12 conjugated linoleic acid (CLA) is the only biohydrogenation intermediate to have been infused at the abomasum over a range of experimental doses (1.25 to 14.0 g/day) and shown unequivocally to inhibit milk fat synthesis in ruminants. However, increases in ruminal trans-10, cis-12 CLA formation do not explain entirely diet-induced MFD, suggesting that other biohydrogenation intermediates and/or other mechanisms may also be involved. Experiments involving abomasal infusions (g/day) in lactating cows have provided evidence that cis-10, trans-12 CLA (1.2), trans-9, cis-11 CLA (5.0) and trans-10 18:1 (92.1) may also exert anti-lipogenic effects. Use of molecular-based approaches have demonstrated that mammary abundance of transcripts encoding for key lipogenic genes are reduced during MFD in the bovine, changes that are accompanied by decrease in sterol response element binding protein 1 (SREBP1) and alterations in the expression of genes related to the SREBP1 pathway. Recent studies indicate that transcription of one or more adipogenic genes is increased in subcutaneous adipose tissue in cows during acute or chronic MFD. Feeding diets of similar composition do not induce MFD or substantially alter mammary lipogenic gene expression in the goat. The available data suggests that variation in mammary fatty acid secretion and lipogenic responses to changes in diet composition between ruminants reflect inherent interspecies differences in ruminal lipid metabolism and mammary specific regulation of cellular processes and key lipogenic enzymes involved in the synthesis of milk fat triacylglycerides.Keywords: milk fat, trans fatty acids, gene expression, lipogenesis, ruminants ImplicationsUnderstanding the regulation of milk fat synthesis is central to the development of nutritional strategies to enhance the nutritional value of milk, decrease milk-energ...

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“…Most dietary FA are esterified, and they are almost completely hydrolyzed to free FA in the rumen. Unsaturated free FA are then isomerized (double-bond position or orientation changed) and reduced (saturation of double bond), although the exact mechanisms are not well established (Wallace et al, 2007). The resulting saturated FA and some of the biohydrogenation intermediates escape the rumen and are subsequently absorbed.…”

Section: Biohydrogenation Intermediatesmentioning

confidence: 99%

Recent advances in the regulation of milk fat synthesis

Harvatine

Boisclair

Bauman

2009

Animal

268

272

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In addition to its economic value, milk fat is responsible for many of milk's characteristics and can be markedly affected by diet. Diet-induced milk fat depression (MFD) was first described over a century ago and remains a common problem observed under both intensive and extensive management. The biohydrogenation theory established that MFD is caused by an inhibition of mammary synthesis of milk fat by specific fatty acids (FA) produced as intermediates in ruminal biohydrogenation. During MFD, lipogenic capacity and transcription of key lipid synthesis genes in the mammary gland are down-regulated in a coordinated manner. Our investigations have established that expressions of sterol response element-binding protein 1 (SREBP1) and SREBP-activation proteins are down-regulated during MFD. Importantly, key lipogenic enzymes are transcriptionally regulated via SREBP1. Collectively, these results provide strong evidence for SREBP1 as a central signaling pathway in the regulation of mammary FA synthesis. Spot 14 is also down-regulated during MFD, consistent with a lipogenic role for this novel nuclear protein. In addition, SREBP1c and Spot 14 knock-out mice exhibit reduced milk fat similar to the magnitude and pattern of MFD in the cow. Application of molecular biology approaches has provided the latest chapter in the regulation of milk fat synthesis and is reviewed along with a brief background in nutritional regulation of milk fat synthesis in ruminants.

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Isomers of conjugated linoleic acids are synthesized via different mechanisms in ruminal digesta and bacteria

Cited by 154 publications

References 48 publications

Mechanism of conjugated linoleic acid and vaccenic acid formation in human faecal suspensions and pure cultures of intestinal bacteria

Mechanism of conjugated linoleic acid and vaccenic acid formation in human faecal suspensions and pure cultures of intestinal bacteria

Role of trans fatty acids in the nutritional regulation of mammary lipogenesis in ruminants

Recent advances in the regulation of milk fat synthesis

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