Limits...
The macrophage A2B adenosine receptor regulates tissue insulin sensitivity.

Johnston-Cox H, Eisenstein AS, Koupenova M, Carroll S, Ravid K - PLoS ONE (2014)

Bottom Line: High fat diet (HFD)-induced type 2 diabetes continues to be an epidemic with significant risk for various pathologies.As the A2bAR is expressed in different tissues, here, we provide the first lead to cellular mechanism by demonstrating that the receptor's influence on tissue insulin sensitivity is mediated via its expression in macrophages.The molecular mechanism for this effect involves A2bAR-mediated changes in cyclic adenosine monophosphate in macrophages, reducing the expression and release of inflammatory cytokines, which downregulate insulin receptor-2.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America; Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts, United States of America.

ABSTRACT
High fat diet (HFD)-induced type 2 diabetes continues to be an epidemic with significant risk for various pathologies. Previously, we identified the A2b adenosine receptor (A2bAR), an established regulator of inflammation, as a regulator of HFD-induced insulin resistance. In particular, HFD was associated with vast upregulation of liver A2bAR in control mice, and while mice lacking this receptor showed augmented liver inflammation and tissue insulin resistance. As the A2bAR is expressed in different tissues, here, we provide the first lead to cellular mechanism by demonstrating that the receptor's influence on tissue insulin sensitivity is mediated via its expression in macrophages. This was shown using a newly generated transgenic mouse model expressing the A2bAR gene in the macrophage lineage on an otherwise A2bAR background. Reinstatement of macrophage A2bAR expression in A2bAR mice fed HFD restored insulin tolerance and tissue insulin signaling to the level of control mice. The molecular mechanism for this effect involves A2bAR-mediated changes in cyclic adenosine monophosphate in macrophages, reducing the expression and release of inflammatory cytokines, which downregulate insulin receptor-2. Thus, our results illustrate that macrophage A2bAR signaling is needed and sufficient for relaying the protective effect of the A2bAR against HFD-induced tissue inflammation and insulin resistance in mice.

Show MeSH

Related in: MedlinePlus

Effect of restoration of macrophage A2bAR on adipose tissue.Visceral (epididymal) adipose tissue was collected from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD as described in the methods. A-C,E. Relative mRNA expression was determined using the ΔΔCT method with normalization to 18s rRNA. A. mRNA expression of TNF-α in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0345. B. mRNA expression of IL-6 in visceral fat. A2bAR KO (n = 7) vs WT (n = 7) p-value  = 0.0073; A2bAR KO vs CD68-Tg (n = 7) p-value  = 0.0141. C. mRNA expression of MCP1 in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0232. D. Visceral adipose tissue from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD was fixed in 4% paraformaldehyde and paraffin-embedded. Sections immunostained with the macrophage marker F4/80. Representative sections for each genotype at a magnification of 200x and 400x. Arrows point to crown-like structures. E. mRNA expression of IRS-2 in visceral fat. CD68-Tg (n = 8) vs A2bAR KO (n = 8) p-value  = 0.0115, WT (n = 6) vs A2bAR KO p-value  = 0.0358. F. Western blot analysis of visceral fat; one representative (of 3 sets) WT, CD68-Tg and A2bAR KO group shown at 15 minutes post-insulin injection, following 16 weeks of HFD. WT to A2bAR KO: IRS-2 p-value  = 0.0411, SREBP-1 p-value  = 0.0103. CD68-Tg to A2bAR KO: IRS-2 p-value  = 0.0305, SREBP-1 p-value  = 0.0459. Data are averages ± SD. *Student two-tail t-test assuming equal variance was found significant only when p-value <0.05.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4043770&req=5

pone-0098775-g005: Effect of restoration of macrophage A2bAR on adipose tissue.Visceral (epididymal) adipose tissue was collected from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD as described in the methods. A-C,E. Relative mRNA expression was determined using the ΔΔCT method with normalization to 18s rRNA. A. mRNA expression of TNF-α in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0345. B. mRNA expression of IL-6 in visceral fat. A2bAR KO (n = 7) vs WT (n = 7) p-value  = 0.0073; A2bAR KO vs CD68-Tg (n = 7) p-value  = 0.0141. C. mRNA expression of MCP1 in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0232. D. Visceral adipose tissue from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD was fixed in 4% paraformaldehyde and paraffin-embedded. Sections immunostained with the macrophage marker F4/80. Representative sections for each genotype at a magnification of 200x and 400x. Arrows point to crown-like structures. E. mRNA expression of IRS-2 in visceral fat. CD68-Tg (n = 8) vs A2bAR KO (n = 8) p-value  = 0.0115, WT (n = 6) vs A2bAR KO p-value  = 0.0358. F. Western blot analysis of visceral fat; one representative (of 3 sets) WT, CD68-Tg and A2bAR KO group shown at 15 minutes post-insulin injection, following 16 weeks of HFD. WT to A2bAR KO: IRS-2 p-value  = 0.0411, SREBP-1 p-value  = 0.0103. CD68-Tg to A2bAR KO: IRS-2 p-value  = 0.0305, SREBP-1 p-value  = 0.0459. Data are averages ± SD. *Student two-tail t-test assuming equal variance was found significant only when p-value <0.05.

Mentions: As adipose tissue macrophages have been reported to influence glucose homeostasis [47]–[49], we expected that restoration of A2bAR in macrophages might also affect fat tissue metabolic function. Much like in the liver, we found reduced TNF-α and IL-6 mRNA levels in the adipose tissue from CD68-Tg mice as compared to A2bAR KO mice (Figure 5A,B). In addition, as compared to adipose tissue from A2bAR KO mice, that from CD68-Tg mice showed lower expression of MCP1 (Figure 5C), a macrophage chemokine, as well as reduced crown-like structures (Figure 5D). As in the liver, adipose tissue IRS-2 and SREBP-1 levels were restored in CD68-Tg mice to that of WT mice (Figure 5E,F).


The macrophage A2B adenosine receptor regulates tissue insulin sensitivity.

Johnston-Cox H, Eisenstein AS, Koupenova M, Carroll S, Ravid K - PLoS ONE (2014)

Effect of restoration of macrophage A2bAR on adipose tissue.Visceral (epididymal) adipose tissue was collected from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD as described in the methods. A-C,E. Relative mRNA expression was determined using the ΔΔCT method with normalization to 18s rRNA. A. mRNA expression of TNF-α in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0345. B. mRNA expression of IL-6 in visceral fat. A2bAR KO (n = 7) vs WT (n = 7) p-value  = 0.0073; A2bAR KO vs CD68-Tg (n = 7) p-value  = 0.0141. C. mRNA expression of MCP1 in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0232. D. Visceral adipose tissue from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD was fixed in 4% paraformaldehyde and paraffin-embedded. Sections immunostained with the macrophage marker F4/80. Representative sections for each genotype at a magnification of 200x and 400x. Arrows point to crown-like structures. E. mRNA expression of IRS-2 in visceral fat. CD68-Tg (n = 8) vs A2bAR KO (n = 8) p-value  = 0.0115, WT (n = 6) vs A2bAR KO p-value  = 0.0358. F. Western blot analysis of visceral fat; one representative (of 3 sets) WT, CD68-Tg and A2bAR KO group shown at 15 minutes post-insulin injection, following 16 weeks of HFD. WT to A2bAR KO: IRS-2 p-value  = 0.0411, SREBP-1 p-value  = 0.0103. CD68-Tg to A2bAR KO: IRS-2 p-value  = 0.0305, SREBP-1 p-value  = 0.0459. Data are averages ± SD. *Student two-tail t-test assuming equal variance was found significant only when p-value <0.05.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4043770&req=5

pone-0098775-g005: Effect of restoration of macrophage A2bAR on adipose tissue.Visceral (epididymal) adipose tissue was collected from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD as described in the methods. A-C,E. Relative mRNA expression was determined using the ΔΔCT method with normalization to 18s rRNA. A. mRNA expression of TNF-α in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0345. B. mRNA expression of IL-6 in visceral fat. A2bAR KO (n = 7) vs WT (n = 7) p-value  = 0.0073; A2bAR KO vs CD68-Tg (n = 7) p-value  = 0.0141. C. mRNA expression of MCP1 in visceral fat. A2bAR KO (n = 7) vs CD68-Tg (n = 9) p-value  = 0.0232. D. Visceral adipose tissue from WT, A2bAR KO, and CD68-Tg mice after 16 weeks of HFD was fixed in 4% paraformaldehyde and paraffin-embedded. Sections immunostained with the macrophage marker F4/80. Representative sections for each genotype at a magnification of 200x and 400x. Arrows point to crown-like structures. E. mRNA expression of IRS-2 in visceral fat. CD68-Tg (n = 8) vs A2bAR KO (n = 8) p-value  = 0.0115, WT (n = 6) vs A2bAR KO p-value  = 0.0358. F. Western blot analysis of visceral fat; one representative (of 3 sets) WT, CD68-Tg and A2bAR KO group shown at 15 minutes post-insulin injection, following 16 weeks of HFD. WT to A2bAR KO: IRS-2 p-value  = 0.0411, SREBP-1 p-value  = 0.0103. CD68-Tg to A2bAR KO: IRS-2 p-value  = 0.0305, SREBP-1 p-value  = 0.0459. Data are averages ± SD. *Student two-tail t-test assuming equal variance was found significant only when p-value <0.05.
Mentions: As adipose tissue macrophages have been reported to influence glucose homeostasis [47]–[49], we expected that restoration of A2bAR in macrophages might also affect fat tissue metabolic function. Much like in the liver, we found reduced TNF-α and IL-6 mRNA levels in the adipose tissue from CD68-Tg mice as compared to A2bAR KO mice (Figure 5A,B). In addition, as compared to adipose tissue from A2bAR KO mice, that from CD68-Tg mice showed lower expression of MCP1 (Figure 5C), a macrophage chemokine, as well as reduced crown-like structures (Figure 5D). As in the liver, adipose tissue IRS-2 and SREBP-1 levels were restored in CD68-Tg mice to that of WT mice (Figure 5E,F).

Bottom Line: High fat diet (HFD)-induced type 2 diabetes continues to be an epidemic with significant risk for various pathologies.As the A2bAR is expressed in different tissues, here, we provide the first lead to cellular mechanism by demonstrating that the receptor's influence on tissue insulin sensitivity is mediated via its expression in macrophages.The molecular mechanism for this effect involves A2bAR-mediated changes in cyclic adenosine monophosphate in macrophages, reducing the expression and release of inflammatory cytokines, which downregulate insulin receptor-2.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America; Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts, United States of America.

ABSTRACT
High fat diet (HFD)-induced type 2 diabetes continues to be an epidemic with significant risk for various pathologies. Previously, we identified the A2b adenosine receptor (A2bAR), an established regulator of inflammation, as a regulator of HFD-induced insulin resistance. In particular, HFD was associated with vast upregulation of liver A2bAR in control mice, and while mice lacking this receptor showed augmented liver inflammation and tissue insulin resistance. As the A2bAR is expressed in different tissues, here, we provide the first lead to cellular mechanism by demonstrating that the receptor's influence on tissue insulin sensitivity is mediated via its expression in macrophages. This was shown using a newly generated transgenic mouse model expressing the A2bAR gene in the macrophage lineage on an otherwise A2bAR background. Reinstatement of macrophage A2bAR expression in A2bAR mice fed HFD restored insulin tolerance and tissue insulin signaling to the level of control mice. The molecular mechanism for this effect involves A2bAR-mediated changes in cyclic adenosine monophosphate in macrophages, reducing the expression and release of inflammatory cytokines, which downregulate insulin receptor-2. Thus, our results illustrate that macrophage A2bAR signaling is needed and sufficient for relaying the protective effect of the A2bAR against HFD-induced tissue inflammation and insulin resistance in mice.

Show MeSH
Related in: MedlinePlus