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Loss of BMP receptor type 1A in murine adipose tissue attenuates age-related onset of insulin resistance.

Schulz TJ, Graja A, Huang TL, Xue R, An D, Poehle-Kronawitter S, Lynes MD, Tolkachov A, O'Sullivan LE, Hirshman MF, Schupp M, Goodyear LJ, Mishina Y, Tseng YH - Diabetologia (2016)

Bottom Line: Conditional deletion of Bmpr1a using the aP2 (also known as Fabp4)-Cre strain resulted in a complex phenotype.Moreover, knockouts displayed significant reduction of variables of adipose tissue inflammation.Co-cultivation of macrophages with pre-adipocytes lacking Bmpr1a markedly reduced expression of proinflammatory genes.

View Article: PubMed Central - PubMed

Affiliation: German Institute of Human Nutrition (DIfE), Department of Adipocyte Development and Nutrition, 114-116, Arthur-Scheunert Allee, 14558, Potsdam-Nuthetal, Germany. Tim.Schulz@dife.de.

ABSTRACT

Aims/hypothesis: Adipose tissue dysfunction is a prime risk factor for the development of metabolic disease. Bone morphogenetic proteins (BMPs) have previously been implicated in adipocyte formation. Here, we investigate the role of BMP signalling in adipose tissue health and systemic glucose homeostasis.

Methods: We employed the Cre/loxP system to generate mouse models with conditional ablation of BMP receptor 1A in differentiating and mature adipocytes, as well as tissue-resident myeloid cells. Metabolic variables were assessed by glucose and insulin tolerance testing, insulin-stimulated glucose uptake and gene expression analysis.

Results: Conditional deletion of Bmpr1a using the aP2 (also known as Fabp4)-Cre strain resulted in a complex phenotype. Knockout mice were clearly resistant to age-related impairment of insulin sensitivity during normal and high-fat-diet feeding and showed significantly improved insulin-stimulated glucose uptake in brown adipose tissue and skeletal muscle. Moreover, knockouts displayed significant reduction of variables of adipose tissue inflammation. Deletion of Bmpr1a in myeloid cells had no impact on insulin sensitivity, while ablation of Bmpr1a in mature adipocytes partially recapitulated the initial phenotype from aP2-Cre driven deletion. Co-cultivation of macrophages with pre-adipocytes lacking Bmpr1a markedly reduced expression of proinflammatory genes.

Conclusions/interpretation: Our findings show that altered BMP signalling in adipose tissue affects the tissue's metabolic properties and systemic insulin resistance by altering the pattern of immune cell infiltration. The phenotype is due to ablation of Bmpr1a specifically in pre-adipocytes and maturing adipocytes rather than an immune cell-autonomous effect. Mechanistically, we provide evidence for a BMP-mediated direct crosstalk between pre-adipocytes and macrophages.

No MeSH data available.


Related in: MedlinePlus

Loss of Bmpr1a in adipocytes, but not myeloid cells, reduces macrophage infiltration. (a) Gene expression analysis of Bmpr1a mRNA in bone marrow of mice with LysM-Cre-driven deletion of Bmpr1a (LysM-Bmpr1a-KO). White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (b) mRNA levels of leptin and macrophage infiltration markers Cd68 and Mcp1 in WAT depots of LysM-Bmpr1a-KO mice. White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (c) ITT in HFD-fed LysM-Bmpr1a-KO mice at 52 weeks of age. Squares, control mice; diamonds, LysM-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 mice/group). (d) Bmpr1a mRNA levels in WAT depots of knockout mice with Adipoq-Cre-driven deletion of Bmpr1a (Adipoq-Bmpr1a-KO). White bars, control mice; black bars, Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). (e) mRNA levels of leptin and macrophage infiltration markers Cd68, Mcp1 and Cd11c in WAT of Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). ***p < 0.001, †p = 0.078, ‡p = 0.084, §p = 0.096, ¶p = 0.097 compared with control mice of the same treatment group and/or tissue type. qPCR, quantitative real-time PCR
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Fig4: Loss of Bmpr1a in adipocytes, but not myeloid cells, reduces macrophage infiltration. (a) Gene expression analysis of Bmpr1a mRNA in bone marrow of mice with LysM-Cre-driven deletion of Bmpr1a (LysM-Bmpr1a-KO). White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (b) mRNA levels of leptin and macrophage infiltration markers Cd68 and Mcp1 in WAT depots of LysM-Bmpr1a-KO mice. White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (c) ITT in HFD-fed LysM-Bmpr1a-KO mice at 52 weeks of age. Squares, control mice; diamonds, LysM-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 mice/group). (d) Bmpr1a mRNA levels in WAT depots of knockout mice with Adipoq-Cre-driven deletion of Bmpr1a (Adipoq-Bmpr1a-KO). White bars, control mice; black bars, Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). (e) mRNA levels of leptin and macrophage infiltration markers Cd68, Mcp1 and Cd11c in WAT of Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). ***p < 0.001, †p = 0.078, ‡p = 0.084, §p = 0.096, ¶p = 0.097 compared with control mice of the same treatment group and/or tissue type. qPCR, quantitative real-time PCR

Mentions: Previous studies have demonstrated that aP2 is also expressed in cell types other than adipocytes. Specifically, it is also expressed in macrophages, where aP2 plays a role in foam cell formation [33]. These findings raise the possibility that use of aP2-Cre may also result in gene deletion in macrophages infiltrating the adipose tissue. While this possibility is still valid, a recent study using the same aP2-Cre strain as us showed no Cre-mediated recombination in adipose tissue macrophages [34]. Consistent with this report, Bmpr1a mRNA levels were not changed in macrophages sorted from WAT of aP2-Bmpr1a-KO mice when compared with WAT from control mice (ESM Fig. 9). Nevertheless, to determine whether loss of BMP signalling in macrophages could still be responsible for reduced adipose tissue macrophage infiltration and improved insulin sensitivity, we generated a mouse model with myeloid-specific ablation of BMP receptor 1A (BMPR1A) using the LysM (also known as Lyz2)-Cre mouse strain [35]. Efficient ablation of BMPR1A expression was observed in tissues with a high content of myeloid cells, such as bone marrow, in LysM-Bmpr1a-KO mice (Fig. 4a). In this strain, body and tissue weights were unchanged (data not shown) and gene expression levels of Lep, Cd68 and Mcp1, which were significantly decreased in the aP2-Bmpr1a-KO mice, were unchanged in iWAT and eWAT of 5-month-old mice (Fig. 4b). Moreover, insulin sensitivity was not altered in 12-month-old LysM-Bmpr1a-KO mice compared with control mice under high-fat feeding (Fig. 4c). Hence, the improved insulin sensitivity in aP2-Bmpr1a-KO mice cannot be attributed to deletion of Bmpr1a in macrophages.Fig. 4


Loss of BMP receptor type 1A in murine adipose tissue attenuates age-related onset of insulin resistance.

Schulz TJ, Graja A, Huang TL, Xue R, An D, Poehle-Kronawitter S, Lynes MD, Tolkachov A, O'Sullivan LE, Hirshman MF, Schupp M, Goodyear LJ, Mishina Y, Tseng YH - Diabetologia (2016)

Loss of Bmpr1a in adipocytes, but not myeloid cells, reduces macrophage infiltration. (a) Gene expression analysis of Bmpr1a mRNA in bone marrow of mice with LysM-Cre-driven deletion of Bmpr1a (LysM-Bmpr1a-KO). White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (b) mRNA levels of leptin and macrophage infiltration markers Cd68 and Mcp1 in WAT depots of LysM-Bmpr1a-KO mice. White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (c) ITT in HFD-fed LysM-Bmpr1a-KO mice at 52 weeks of age. Squares, control mice; diamonds, LysM-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 mice/group). (d) Bmpr1a mRNA levels in WAT depots of knockout mice with Adipoq-Cre-driven deletion of Bmpr1a (Adipoq-Bmpr1a-KO). White bars, control mice; black bars, Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). (e) mRNA levels of leptin and macrophage infiltration markers Cd68, Mcp1 and Cd11c in WAT of Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). ***p < 0.001, †p = 0.078, ‡p = 0.084, §p = 0.096, ¶p = 0.097 compared with control mice of the same treatment group and/or tissue type. qPCR, quantitative real-time PCR
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Fig4: Loss of Bmpr1a in adipocytes, but not myeloid cells, reduces macrophage infiltration. (a) Gene expression analysis of Bmpr1a mRNA in bone marrow of mice with LysM-Cre-driven deletion of Bmpr1a (LysM-Bmpr1a-KO). White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (b) mRNA levels of leptin and macrophage infiltration markers Cd68 and Mcp1 in WAT depots of LysM-Bmpr1a-KO mice. White bars, control mice; grey bars, LysM-Bmpr1a-knockout mice. Data are shown as means ± SEM (n = 3/group). (c) ITT in HFD-fed LysM-Bmpr1a-KO mice at 52 weeks of age. Squares, control mice; diamonds, LysM-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 mice/group). (d) Bmpr1a mRNA levels in WAT depots of knockout mice with Adipoq-Cre-driven deletion of Bmpr1a (Adipoq-Bmpr1a-KO). White bars, control mice; black bars, Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). (e) mRNA levels of leptin and macrophage infiltration markers Cd68, Mcp1 and Cd11c in WAT of Adipoq-Bmpr1a-KO mice. Data are shown as means ± SEM (n = 7 for control and n = 6 for knockout). ***p < 0.001, †p = 0.078, ‡p = 0.084, §p = 0.096, ¶p = 0.097 compared with control mice of the same treatment group and/or tissue type. qPCR, quantitative real-time PCR
Mentions: Previous studies have demonstrated that aP2 is also expressed in cell types other than adipocytes. Specifically, it is also expressed in macrophages, where aP2 plays a role in foam cell formation [33]. These findings raise the possibility that use of aP2-Cre may also result in gene deletion in macrophages infiltrating the adipose tissue. While this possibility is still valid, a recent study using the same aP2-Cre strain as us showed no Cre-mediated recombination in adipose tissue macrophages [34]. Consistent with this report, Bmpr1a mRNA levels were not changed in macrophages sorted from WAT of aP2-Bmpr1a-KO mice when compared with WAT from control mice (ESM Fig. 9). Nevertheless, to determine whether loss of BMP signalling in macrophages could still be responsible for reduced adipose tissue macrophage infiltration and improved insulin sensitivity, we generated a mouse model with myeloid-specific ablation of BMP receptor 1A (BMPR1A) using the LysM (also known as Lyz2)-Cre mouse strain [35]. Efficient ablation of BMPR1A expression was observed in tissues with a high content of myeloid cells, such as bone marrow, in LysM-Bmpr1a-KO mice (Fig. 4a). In this strain, body and tissue weights were unchanged (data not shown) and gene expression levels of Lep, Cd68 and Mcp1, which were significantly decreased in the aP2-Bmpr1a-KO mice, were unchanged in iWAT and eWAT of 5-month-old mice (Fig. 4b). Moreover, insulin sensitivity was not altered in 12-month-old LysM-Bmpr1a-KO mice compared with control mice under high-fat feeding (Fig. 4c). Hence, the improved insulin sensitivity in aP2-Bmpr1a-KO mice cannot be attributed to deletion of Bmpr1a in macrophages.Fig. 4

Bottom Line: Conditional deletion of Bmpr1a using the aP2 (also known as Fabp4)-Cre strain resulted in a complex phenotype.Moreover, knockouts displayed significant reduction of variables of adipose tissue inflammation.Co-cultivation of macrophages with pre-adipocytes lacking Bmpr1a markedly reduced expression of proinflammatory genes.

View Article: PubMed Central - PubMed

Affiliation: German Institute of Human Nutrition (DIfE), Department of Adipocyte Development and Nutrition, 114-116, Arthur-Scheunert Allee, 14558, Potsdam-Nuthetal, Germany. Tim.Schulz@dife.de.

ABSTRACT

Aims/hypothesis: Adipose tissue dysfunction is a prime risk factor for the development of metabolic disease. Bone morphogenetic proteins (BMPs) have previously been implicated in adipocyte formation. Here, we investigate the role of BMP signalling in adipose tissue health and systemic glucose homeostasis.

Methods: We employed the Cre/loxP system to generate mouse models with conditional ablation of BMP receptor 1A in differentiating and mature adipocytes, as well as tissue-resident myeloid cells. Metabolic variables were assessed by glucose and insulin tolerance testing, insulin-stimulated glucose uptake and gene expression analysis.

Results: Conditional deletion of Bmpr1a using the aP2 (also known as Fabp4)-Cre strain resulted in a complex phenotype. Knockout mice were clearly resistant to age-related impairment of insulin sensitivity during normal and high-fat-diet feeding and showed significantly improved insulin-stimulated glucose uptake in brown adipose tissue and skeletal muscle. Moreover, knockouts displayed significant reduction of variables of adipose tissue inflammation. Deletion of Bmpr1a in myeloid cells had no impact on insulin sensitivity, while ablation of Bmpr1a in mature adipocytes partially recapitulated the initial phenotype from aP2-Cre driven deletion. Co-cultivation of macrophages with pre-adipocytes lacking Bmpr1a markedly reduced expression of proinflammatory genes.

Conclusions/interpretation: Our findings show that altered BMP signalling in adipose tissue affects the tissue's metabolic properties and systemic insulin resistance by altering the pattern of immune cell infiltration. The phenotype is due to ablation of Bmpr1a specifically in pre-adipocytes and maturing adipocytes rather than an immune cell-autonomous effect. Mechanistically, we provide evidence for a BMP-mediated direct crosstalk between pre-adipocytes and macrophages.

No MeSH data available.


Related in: MedlinePlus