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Preserved glucose tolerance in high-fat-fed C57BL/6 mice transplanted with PPARgamma-/-, PPARdelta-/-, PPARgammadelta-/-, or LXRalphabeta-/- bone marrow.

Marathe C, Bradley MN, Hong C, Chao L, Wilpitz D, Salazar J, Tontonoz P - J. Lipid Res. (2008)

Bottom Line: Despite their inhibitory effects on inflammatory gene expression, loss of PPARs or LXRs in macrophages did not exert major effects on obesity or glucose tolerance induced by a high-fat diet.These studies suggest that genetic background may be an important modifier of nuclear receptor effects in macrophages.Our results do not exclude a contribution of macrophage PPAR and LXR expression to systemic metabolism in certain contexts, but these factors do not appear to be dominant contributors to glucose tolerance in a high-fat-fed Th1-biased bone marrow transplant model.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Molecular Biology Institute and Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA 90095, USA.

ABSTRACT
Macrophage lipid metabolism and inflammatory responses are both regulated by the nuclear receptors PPAR and LXR. Emerging links between inflammation and metabolic disease progression suggest that PPAR and LXR signaling may alter macrophage function and thereby impact systemic metabolism. In this study, the function of macrophage PPAR and LXR in Th1-biased C57BL/6 mice was tested using a bone marrow transplantation approach with PPARgamma(-/-), PPARdelta(-/-), PPARgammadelta(-/-), and LXRalphabeta(-/-) cells. Despite their inhibitory effects on inflammatory gene expression, loss of PPARs or LXRs in macrophages did not exert major effects on obesity or glucose tolerance induced by a high-fat diet. Treatment with rosiglitazone effectively improved glucose tolerance in mice lacking macrophage PPARgamma, suggesting that cell types other than macrophages are the primary mediators of the anti-diabetic effects of PPARgamma agonists in our model system. C57BL/6 macrophages lacking PPARs or LXRs exhibited normal expression of most alternative activation gene markers, indicating that macrophage alternative activation is not absolutely dependent on these receptors in the C57BL/6 background under the conditions used here. These studies suggest that genetic background may be an important modifier of nuclear receptor effects in macrophages. Our results do not exclude a contribution of macrophage PPAR and LXR expression to systemic metabolism in certain contexts, but these factors do not appear to be dominant contributors to glucose tolerance in a high-fat-fed Th1-biased bone marrow transplant model.

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PPARγ−/−, PPARδ−/−, and PPARγδ−/− macrophages exhibited heightened inflammatory gene expression compared with wild-type cells in vitro. Cells were harvested and pooled from three to five mice per group. The presented data are representative of at least three independent experiments. A: Thioglycollate-elicited wild-type, PPARγ−/−, PPARδ−/−, and PPARγδ−/− peritoneal macrophages were harvested and pretreated with GW7845 (100 nM), GW742 (100 nM), or GW3965 (1 μM) overnight. The cells were then stimulated with LPS (10 ng/ml) for 6 h. PPAR and LXR target genes (aP2 and ABCA1, respectively) were tested to confirm ligand response. B: Macrophages were analyzed for inflammatory gene expression. iNOS was markedly upregulated in macrophages with deleted PPARs; in wild-type cells, treatment with LXR ligands consistently suppressed inflammatory genes, whereas treatment only with PPARγ and not PPARδ ligand resulted in repression. C: Additional inflammatory genes were tested in response to LPS and PPAR ligand treatments. Similar to iNOS, both IL-6 and MCP-1 expression was repressed by PPARγ ligand. However, IL-1β has a different expression profile compared with the other genes and highlights inconsistencies in PPAR signaling in inflammation. Error bars represent SEM.
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fig2: PPARγ−/−, PPARδ−/−, and PPARγδ−/− macrophages exhibited heightened inflammatory gene expression compared with wild-type cells in vitro. Cells were harvested and pooled from three to five mice per group. The presented data are representative of at least three independent experiments. A: Thioglycollate-elicited wild-type, PPARγ−/−, PPARδ−/−, and PPARγδ−/− peritoneal macrophages were harvested and pretreated with GW7845 (100 nM), GW742 (100 nM), or GW3965 (1 μM) overnight. The cells were then stimulated with LPS (10 ng/ml) for 6 h. PPAR and LXR target genes (aP2 and ABCA1, respectively) were tested to confirm ligand response. B: Macrophages were analyzed for inflammatory gene expression. iNOS was markedly upregulated in macrophages with deleted PPARs; in wild-type cells, treatment with LXR ligands consistently suppressed inflammatory genes, whereas treatment only with PPARγ and not PPARδ ligand resulted in repression. C: Additional inflammatory genes were tested in response to LPS and PPAR ligand treatments. Similar to iNOS, both IL-6 and MCP-1 expression was repressed by PPARγ ligand. However, IL-1β has a different expression profile compared with the other genes and highlights inconsistencies in PPAR signaling in inflammation. Error bars represent SEM.

Mentions: Recent work suggests that PPARs mediate inflammatory signaling pathways in macrophages and may affect inflammation associated with insulin resistance (18, 22). To address this issue in our genetic loss-of-function system, thioglycollate-elicited PPARγ−/−, PPARδ−/−, or PPARγδ−/− peritoneal macrophages were isolated and pretreated with either PPAR ligand or LXR ligand overnight. Cells were then stimulated with LPS (10 ng/ml) for 6 h, and inflammatory and receptor target gene was measured by real-time PCR. As shown in Fig. 2A, the PPAR target gene aP2, and the LXR target gene ABCA1, were upregulated in wild-type cells by ligand, confirming proper ligand response. As expected, LXR agonist (GW3965) efficiently suppressed inflammatory gene expression (iNOS). Furthermore, PPARγ ligand (GW7845) repressed IL-6, MCP-1, and iNOS expression in wild-type cells but not in PPARγ- cells (Fig. 2B, C). PPARδ agonist (GW742) had no significant effect on expression of these genes in any genotype.


Preserved glucose tolerance in high-fat-fed C57BL/6 mice transplanted with PPARgamma-/-, PPARdelta-/-, PPARgammadelta-/-, or LXRalphabeta-/- bone marrow.

Marathe C, Bradley MN, Hong C, Chao L, Wilpitz D, Salazar J, Tontonoz P - J. Lipid Res. (2008)

PPARγ−/−, PPARδ−/−, and PPARγδ−/− macrophages exhibited heightened inflammatory gene expression compared with wild-type cells in vitro. Cells were harvested and pooled from three to five mice per group. The presented data are representative of at least three independent experiments. A: Thioglycollate-elicited wild-type, PPARγ−/−, PPARδ−/−, and PPARγδ−/− peritoneal macrophages were harvested and pretreated with GW7845 (100 nM), GW742 (100 nM), or GW3965 (1 μM) overnight. The cells were then stimulated with LPS (10 ng/ml) for 6 h. PPAR and LXR target genes (aP2 and ABCA1, respectively) were tested to confirm ligand response. B: Macrophages were analyzed for inflammatory gene expression. iNOS was markedly upregulated in macrophages with deleted PPARs; in wild-type cells, treatment with LXR ligands consistently suppressed inflammatory genes, whereas treatment only with PPARγ and not PPARδ ligand resulted in repression. C: Additional inflammatory genes were tested in response to LPS and PPAR ligand treatments. Similar to iNOS, both IL-6 and MCP-1 expression was repressed by PPARγ ligand. However, IL-1β has a different expression profile compared with the other genes and highlights inconsistencies in PPAR signaling in inflammation. Error bars represent SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2636915&req=5

fig2: PPARγ−/−, PPARδ−/−, and PPARγδ−/− macrophages exhibited heightened inflammatory gene expression compared with wild-type cells in vitro. Cells were harvested and pooled from three to five mice per group. The presented data are representative of at least three independent experiments. A: Thioglycollate-elicited wild-type, PPARγ−/−, PPARδ−/−, and PPARγδ−/− peritoneal macrophages were harvested and pretreated with GW7845 (100 nM), GW742 (100 nM), or GW3965 (1 μM) overnight. The cells were then stimulated with LPS (10 ng/ml) for 6 h. PPAR and LXR target genes (aP2 and ABCA1, respectively) were tested to confirm ligand response. B: Macrophages were analyzed for inflammatory gene expression. iNOS was markedly upregulated in macrophages with deleted PPARs; in wild-type cells, treatment with LXR ligands consistently suppressed inflammatory genes, whereas treatment only with PPARγ and not PPARδ ligand resulted in repression. C: Additional inflammatory genes were tested in response to LPS and PPAR ligand treatments. Similar to iNOS, both IL-6 and MCP-1 expression was repressed by PPARγ ligand. However, IL-1β has a different expression profile compared with the other genes and highlights inconsistencies in PPAR signaling in inflammation. Error bars represent SEM.
Mentions: Recent work suggests that PPARs mediate inflammatory signaling pathways in macrophages and may affect inflammation associated with insulin resistance (18, 22). To address this issue in our genetic loss-of-function system, thioglycollate-elicited PPARγ−/−, PPARδ−/−, or PPARγδ−/− peritoneal macrophages were isolated and pretreated with either PPAR ligand or LXR ligand overnight. Cells were then stimulated with LPS (10 ng/ml) for 6 h, and inflammatory and receptor target gene was measured by real-time PCR. As shown in Fig. 2A, the PPAR target gene aP2, and the LXR target gene ABCA1, were upregulated in wild-type cells by ligand, confirming proper ligand response. As expected, LXR agonist (GW3965) efficiently suppressed inflammatory gene expression (iNOS). Furthermore, PPARγ ligand (GW7845) repressed IL-6, MCP-1, and iNOS expression in wild-type cells but not in PPARγ- cells (Fig. 2B, C). PPARδ agonist (GW742) had no significant effect on expression of these genes in any genotype.

Bottom Line: Despite their inhibitory effects on inflammatory gene expression, loss of PPARs or LXRs in macrophages did not exert major effects on obesity or glucose tolerance induced by a high-fat diet.These studies suggest that genetic background may be an important modifier of nuclear receptor effects in macrophages.Our results do not exclude a contribution of macrophage PPAR and LXR expression to systemic metabolism in certain contexts, but these factors do not appear to be dominant contributors to glucose tolerance in a high-fat-fed Th1-biased bone marrow transplant model.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Molecular Biology Institute and Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA 90095, USA.

ABSTRACT
Macrophage lipid metabolism and inflammatory responses are both regulated by the nuclear receptors PPAR and LXR. Emerging links between inflammation and metabolic disease progression suggest that PPAR and LXR signaling may alter macrophage function and thereby impact systemic metabolism. In this study, the function of macrophage PPAR and LXR in Th1-biased C57BL/6 mice was tested using a bone marrow transplantation approach with PPARgamma(-/-), PPARdelta(-/-), PPARgammadelta(-/-), and LXRalphabeta(-/-) cells. Despite their inhibitory effects on inflammatory gene expression, loss of PPARs or LXRs in macrophages did not exert major effects on obesity or glucose tolerance induced by a high-fat diet. Treatment with rosiglitazone effectively improved glucose tolerance in mice lacking macrophage PPARgamma, suggesting that cell types other than macrophages are the primary mediators of the anti-diabetic effects of PPARgamma agonists in our model system. C57BL/6 macrophages lacking PPARs or LXRs exhibited normal expression of most alternative activation gene markers, indicating that macrophage alternative activation is not absolutely dependent on these receptors in the C57BL/6 background under the conditions used here. These studies suggest that genetic background may be an important modifier of nuclear receptor effects in macrophages. Our results do not exclude a contribution of macrophage PPAR and LXR expression to systemic metabolism in certain contexts, but these factors do not appear to be dominant contributors to glucose tolerance in a high-fat-fed Th1-biased bone marrow transplant model.

Show MeSH
Related in: MedlinePlus