Fatty acid profile of linseed and sunflower oils.

<p>The results are expressed as a percentage of the identified fatty acids (n.d.: not detectable, below the level of detection). Only the isomers above the limit of detection were presented in this <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087560#pone-0087560-t001" target="_blank">Table 1</a>.</p

Blood lipids accumulation.

<p>Triglycerides and non-esterified fatty acids (NEFA) were measured just before the Tyloxapol injection (T-30), just before oil force-feeding (T0), ten minutes (T10), 2 hours (T120) and 4 hours (T240) after oil force-feeding in the plasma of mice force-fed with linseed oil (rich in n-3 LnA) or sunflower oil (rich in n-6 LA). Data are mean ± SEM. Linear mixed-effects model followed by contrasts assessed the statistical difference between both the two oil force-feedings and the blood sample times. Differences between linseed oil force-fed mice and sunflower oil force-fed mice were not significant at any of the blood sample times. Grey small superscript letters show significant differences (p<0.05) between blood sample times in linseed oil force-fed mice. Black major superscript letters show significant differences (p<0.05) between the blood sample times in sunflower oil force-fed mice.</p

Fatty acid profile in circulating lipids.

<p>Linoleic acid, α-linolenic acid and PUFA-derived bacterial metabolites in peripheral plasma of mice force-fed with linseed oil (rich in n-3 LnA) or sunflower oil (rich in n-6 LA) at different timing after the force-feeding (10 minutes; 120 minutes and 240 minutes after the force-feeding). Results are expressed as a percentage of identified fatty acids. Data are mean ± SEM. Linear mixed-effects model followed by contrasts assessed the statistical difference between both the two oil force-feedings and the blood sample times. * superscripts show significant differences (p<0.05) between linseed oil force-feeding and sunflower oil force-feeding at each blood sample time. Different small superscript letters show significant differences (p<0.05) between blood sample times in linseed oil force-fed mice. Different capital superscript letters indicate significant differences (p<0.05) between blood sample times in sunflower oil force-fed mice. <i>trans</i>-11,<i>cis</i>-15-18:2 was detected in linseed oil force-fed mice only.</p

Fatty acid profile in intestinal contents.

<p>Linoleic acid, α-linolenic acid and PUFA-derived bacterial metabolites in intestinal contents (jejunum content – ileum content – caecum content and colon content) of mice force-fed with linseed oil (rich in n-3 LnA) or sunflower oil (rich in n-6 LA). Results are expressed as a percentage of identified fatty acids. Data are mean ± SEM. Linear mixed-effects model followed by contrasts assessed the statistical difference between both the two oil force-feedings and the different intestinal contents. * superscripts show significant differences (p<0.05) between linseed oil force-feeding and sunflower oil force-feeding in each intestinal content. Different small superscript letters show significant differences (p<0.05) between intestinal contents in linseed oil force-fed mice. Different capital superscript letters indicate significant differences (p<0.05) between intestinal contents in sunflower oil force-fed mice. <i>trans</i>-11,<i>cis</i>-15-18:2 was detected in linseed oil force-fed mice only.</p

Fatty acid profile in intestinal tissues.

<p>Linoleic acid, α-linolenic acid and PUFA-derived bacterial metabolites in intestinal tissues (jejunum tissue – ileum tissue – caecum tissue and colon tissue) of mice force-fed with linseed oil (rich in n-3 LnA) or sunflower oil (rich in n-6 LA). Results are expressed as a percentage of identified fatty acids. Data are mean ± SEM. Linear mixed-effects model followed by contrasts assessed the statistical difference between both the two oil force-feedings and the different intestinal tissues. * superscripts show significant differences (p<0.05) between linseed oil force-feeding and sunflower oil force-feeding in each intestinal tissue. Different small superscript letters show significant differences (p<0.05) between intestinal tissues in linseed oil force-fed mice. Different capital superscript letters indicate significant differences (p<0.05) between intestinal tissues in sunflower oil force-fed mice. <i>trans</i>-11,<i>cis</i>-15-18:2 was detected in linseed oil force-fed mice only.</p

Proposed metabolic pathway of linoleic acid and α-linolenic acid by murine gut microbiota.

<p>PUFA-derived bacterial metabolites in bold characters were not described in the previous study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087560#pone.0087560-Druart1" target="_blank">[23]</a>.</p

Implication of <i>trans</i>-11,<i>trans</i>-13 conjugated linoleic acid in the development of hepatic steatosis

<div><p>Scope</p><p>Conjugated linoleic acids are linoleic acid isomers found in the diet that can also be produced through bacterial metabolism of polyunsaturated fatty acids. Our objective was to evaluate the contribution of fatty acid metabolites produced from polyunsaturated fatty acids by the gut microbiota <i>in vivo</i> to regulation of hepatic lipid metabolism and steatosis.</p><p>Methods and results</p><p>In mice with depleted n-3 polyunsaturated fatty acids, we observed an accumulation of <i>trans</i>-11,<i>trans</i>-13 CLA and <i>cis</i>-9,<i>cis</i>-11 conjugated linoleic acids in the liver tissue that were associated with an increased triglyceride content and expression of lipogenic genes. We used an <i>in vitro</i> model to evaluate the impact of these two conjugated linoleic acids on hepatic lipid metabolism. In HepG2 cells, we observed that only <i>trans</i>-11,<i>trans</i>-13 conjugated linoleic acids recapitulated triglyceride accumulation and increased lipogenic gene expression, which is a phenomenon that may implicate the nuclear factors sterol regulatory element binding protein 1c (SREBP-1c) and carbohydrate-responsive element-binding protein (ChREBP).</p><p>Conclusion</p><p>The <i>trans</i>-11,<i>trans</i>-13 conjugated linoleic acids can stimulate hepatic lipogenesis, which supports the conclusion that gut microbiota and related metabolites should be considered in the treatment of non-alcoholic liver disease.</p></div

mRNA expression of lipogenic genes in HepG2 cells following CLAs treatment.

<p>HepG2 cells were incubated with bovine serum albumin (BSA) or with 10 μM of LA, <i>cis</i>-9,<i>trans</i>-11 (c9t11) CLA, <i>cis</i>-9,<i>cis</i>-11 (c9c11) CLA or <i>trans</i>-11,<i>trans</i>-13 (t11t13) CLA for 24 h. The mRNA expression of sterol-regulatory element binding protein-1c (SREBP-1c), SREBP-1a, fatty acid synthase (FAS), stearoyl-CoA desaturase 1 (SCD-1), acetyl-CoA carboxylase α (ACCα), and fatty acid elongase 6 (Elolv6) were measured by qPCR and expressed as relative expression. Data are the means ± SEM of 2 independent experiments (n = 6 to 12). Data with no common superscript letter are significantly different (p ≤ 0.05) according to the post-hoc ANOVA statistical analysis.</p

TG content in HepG2 cells following CLAs treatment.

<p>HepG2 cells were incubated with bovine serum albumin (BSA) or with 10 μM of linoleic acid (LA), <i>cis</i>-9,<i>trans</i>-11 (c9ct11) CLA, <i>cis</i>-9,<i>cis</i>-11 (c9c11) CLA or <i>trans</i>-11,<i>trans</i>-13 (t11t13) CLA for 24 h and 72 h. Hepatic TG content was expressed as nmol/mg of protein. Data are the means ± SEM of 2 independent experiments (n = 6). Data with no common superscript letter are significantly different (p ≤ 0.05) according to the post-hoc ANOVA statistical analysis.</p

Hepatic mRNA content and TG levels in mice with depleted n-3 PUFA.

<p>Hepatic mRNA content and TG levels in mice with depleted n-3 PUFA.</p