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TNF-alpha and IL-6 inhibit apolipoprotein A-IV production induced by linoleic acid in human intestinal Caco2 cells.

Li X, Xu M, Liu M, Ji Y, Li Z - J Inflamm (Lond) (2015)

Bottom Line: LA stimulated gene and protein expression of apoA-IV in a dose and time dependent manner.Pre-treatment with the cytokines for 72 h significantly inhibited the increased expression of apoA-IV gene and protein induced by LA.Our data indicate that the pro-inflammatory cytokines may be responsible for the reduced apoA-IV production in response to fat feeding.

View Article: PubMed Central - PubMed

Affiliation: National Local Joint Engineering Research Center of Biodiagnostics and Biotherapy, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710004 China ; Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, 45237-0507 USA.

ABSTRACT

Background: Apolipoprotein A-IV (apoA-IV) is a protein mainly synthesized by enterocytes in the intestine. Its gene expression is suppressed during fasting and stimulated during active fat absorption. Chronic feeding of a high-fat (HF) diet abolishes the differential expression between fasting and fat-feeding and therefore may contribute to diet-induced obesity since apoA-IV is a potent satiety factor. It is well established that the circulating pro-inflammatory cytokines TNF-α and IL-6 are increased by HF feeding.

Methods: To determine whether pro-inflammatory cytokines are involved in the diminished response of apoA-IV gene expression to fat-feeding, different concentrations of linoleic acid (LA), an important dietary fatty acid, was used to stimulate apoA-IV expression in human intestinal Caco2 cells. Cells were pre-treated with or without human recombinant TNF-α, IL-6 or their combination before the addition of LA. Real-time PCR and ELISA were used to detect and quantify RNA transcripts and proteins of apoA-IV and the cytokines.

Results: LA stimulated gene and protein expression of apoA-IV in a dose and time dependent manner. Pre-treatment with the cytokines for 72 h significantly inhibited the increased expression of apoA-IV gene and protein induced by LA. Furthermore, the cytokines, especially TNF-α, also positively up-regulate the cytokine themselves in Caco2 cells.

Conclusions: Our data indicate that the pro-inflammatory cytokines may be responsible for the reduced apoA-IV production in response to fat feeding. Because of apoA-IV's role in satiety, we propose the inhibitory effect of circulating pro-inflammatory cytokines on apoA-IV production contributes to diet-induced obesity.

No MeSH data available.


Related in: MedlinePlus

LA inducedapoA-IVgene expression in Caco2 cells. Differentiated Caco2 cells were supplemented with or without different amount of LA for 24 h (A) or for the indicated time with 1 mM LA (B) up to 24 h. The apoA-IV mRNA levels were measured by real time RT-PCR. The levels of apoA-IV protein released into culture medium from the cells were measured by ELISA (C). ***P <0.001 vs. TC vehicle control.
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Fig1: LA inducedapoA-IVgene expression in Caco2 cells. Differentiated Caco2 cells were supplemented with or without different amount of LA for 24 h (A) or for the indicated time with 1 mM LA (B) up to 24 h. The apoA-IV mRNA levels were measured by real time RT-PCR. The levels of apoA-IV protein released into culture medium from the cells were measured by ELISA (C). ***P <0.001 vs. TC vehicle control.

Mentions: To induce gene expression of apoA-IV in Caco2 cells, the medium of differentiated Caco2 cells was supplemented with LA mixed with TC in the indicated dose and time, as described previously [19]. First, we studied the effect of different concentrations (0.25, 0.5, 1.0 mM) of LA on apoA-IV gene expression after 24 h incubation. As shown in Figure 1A, 0.25 mM of LA was able to enhance apoA-IV gene expression by 1.31 fold, compared with TC vehicle control, although there was no statistically significant difference. 0.5 mM of LA significantly increased apoA-IV mRNA level by 3.3 fold, and 1 mM of LA by 4.42 fold. Second, we determined the time course of apoA-IV gene expression of Caco2 cells after incubation with 1 mM LA for various times (3, 6, 12, and 24 h). As shown in Figure 1B, apoA-IV mRNA level started to increase by 2.34 fold when incubated with LA for 12 h, and increased by 4.42 fold at 24 h, compared with that treated with vehicle controls. Finally, to test whether the apoA-IV protein is also changed with its mRNA levels, we measured the apoA-IV protein levels in the culture medium after the treatment with different amount of LA for 24 h incubation. As presented in Figure 1C, 0.25 mM LA surprisedly showed a maximum effect on apoA-IV protein production, which was stronger than 0.5 mM LA. However, when LA dose increased to 1 mM, its effect on apoA-IV was almost gone. These data indicate that LA up-regulates both apoA-IV mRNA and protein levels in dose-dependent manner, but in different pattern, in the Caco2 cells.Figure 1


TNF-alpha and IL-6 inhibit apolipoprotein A-IV production induced by linoleic acid in human intestinal Caco2 cells.

Li X, Xu M, Liu M, Ji Y, Li Z - J Inflamm (Lond) (2015)

LA inducedapoA-IVgene expression in Caco2 cells. Differentiated Caco2 cells were supplemented with or without different amount of LA for 24 h (A) or for the indicated time with 1 mM LA (B) up to 24 h. The apoA-IV mRNA levels were measured by real time RT-PCR. The levels of apoA-IV protein released into culture medium from the cells were measured by ELISA (C). ***P <0.001 vs. TC vehicle control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4389805&req=5

Fig1: LA inducedapoA-IVgene expression in Caco2 cells. Differentiated Caco2 cells were supplemented with or without different amount of LA for 24 h (A) or for the indicated time with 1 mM LA (B) up to 24 h. The apoA-IV mRNA levels were measured by real time RT-PCR. The levels of apoA-IV protein released into culture medium from the cells were measured by ELISA (C). ***P <0.001 vs. TC vehicle control.
Mentions: To induce gene expression of apoA-IV in Caco2 cells, the medium of differentiated Caco2 cells was supplemented with LA mixed with TC in the indicated dose and time, as described previously [19]. First, we studied the effect of different concentrations (0.25, 0.5, 1.0 mM) of LA on apoA-IV gene expression after 24 h incubation. As shown in Figure 1A, 0.25 mM of LA was able to enhance apoA-IV gene expression by 1.31 fold, compared with TC vehicle control, although there was no statistically significant difference. 0.5 mM of LA significantly increased apoA-IV mRNA level by 3.3 fold, and 1 mM of LA by 4.42 fold. Second, we determined the time course of apoA-IV gene expression of Caco2 cells after incubation with 1 mM LA for various times (3, 6, 12, and 24 h). As shown in Figure 1B, apoA-IV mRNA level started to increase by 2.34 fold when incubated with LA for 12 h, and increased by 4.42 fold at 24 h, compared with that treated with vehicle controls. Finally, to test whether the apoA-IV protein is also changed with its mRNA levels, we measured the apoA-IV protein levels in the culture medium after the treatment with different amount of LA for 24 h incubation. As presented in Figure 1C, 0.25 mM LA surprisedly showed a maximum effect on apoA-IV protein production, which was stronger than 0.5 mM LA. However, when LA dose increased to 1 mM, its effect on apoA-IV was almost gone. These data indicate that LA up-regulates both apoA-IV mRNA and protein levels in dose-dependent manner, but in different pattern, in the Caco2 cells.Figure 1

Bottom Line: LA stimulated gene and protein expression of apoA-IV in a dose and time dependent manner.Pre-treatment with the cytokines for 72 h significantly inhibited the increased expression of apoA-IV gene and protein induced by LA.Our data indicate that the pro-inflammatory cytokines may be responsible for the reduced apoA-IV production in response to fat feeding.

View Article: PubMed Central - PubMed

Affiliation: National Local Joint Engineering Research Center of Biodiagnostics and Biotherapy, The Second Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710004 China ; Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, 45237-0507 USA.

ABSTRACT

Background: Apolipoprotein A-IV (apoA-IV) is a protein mainly synthesized by enterocytes in the intestine. Its gene expression is suppressed during fasting and stimulated during active fat absorption. Chronic feeding of a high-fat (HF) diet abolishes the differential expression between fasting and fat-feeding and therefore may contribute to diet-induced obesity since apoA-IV is a potent satiety factor. It is well established that the circulating pro-inflammatory cytokines TNF-α and IL-6 are increased by HF feeding.

Methods: To determine whether pro-inflammatory cytokines are involved in the diminished response of apoA-IV gene expression to fat-feeding, different concentrations of linoleic acid (LA), an important dietary fatty acid, was used to stimulate apoA-IV expression in human intestinal Caco2 cells. Cells were pre-treated with or without human recombinant TNF-α, IL-6 or their combination before the addition of LA. Real-time PCR and ELISA were used to detect and quantify RNA transcripts and proteins of apoA-IV and the cytokines.

Results: LA stimulated gene and protein expression of apoA-IV in a dose and time dependent manner. Pre-treatment with the cytokines for 72 h significantly inhibited the increased expression of apoA-IV gene and protein induced by LA. Furthermore, the cytokines, especially TNF-α, also positively up-regulate the cytokine themselves in Caco2 cells.

Conclusions: Our data indicate that the pro-inflammatory cytokines may be responsible for the reduced apoA-IV production in response to fat feeding. Because of apoA-IV's role in satiety, we propose the inhibitory effect of circulating pro-inflammatory cytokines on apoA-IV production contributes to diet-induced obesity.

No MeSH data available.


Related in: MedlinePlus