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No Role for Mast Cells in Obesity-Related Metabolic Dysregulation

View Article: PubMed Central - PubMed

ABSTRACT

Obesity-related adipose tissue (AT) inflammation that promotes metabolic dysregulation is associated with increased AT mast cell numbers. Mast cells are potent inducers of inflammatory responses and could potentially contribute to obesity-induced AT inflammation and metabolic dysregulation. Conflicting findings were reported on obesity-related metabolic dysfunction in mast cell-deficient mice, thus creating a controversy that has not been resolved to date. Whereas traditional Kit hypomorphic mast cell-deficient strains featured reduced diet-induced obesity and diabetes, a Kit-independent model of mast cell deficiency, Cpa3Cre/+ mice, displayed no alterations in obesity and insulin sensitivity. Herein, we analyzed diet-induced obesity in Mcpt5-Cre R-DTA mice, in which the lack of mast cells is caused by a principle different from mast cell deficiency in Cpa3Cre/+ mice or Kit mutations. We observed no difference between mast cell-deficient and -proficient mice in diet-induced obesity with regards to weight gain, glucose tolerance, insulin resistance, metabolic parameters, hepatic steatosis, and AT or liver inflammation. We conclude that mast cells play no essential role in obesity and related pathologies.

No MeSH data available.


Related in: MedlinePlus

No difference in AT inflammation between obese mast cell-deficient and -proficient mice. (A–H) The stromal vascular fraction (SVF) of subcutaneous (sAT) and gonadal (gAT) adipose tissue from obese mast cell-deficient and -proficient mice was analyzed by flow cytometry for the accumulation of total macrophages (Mφs) and pro-inflammatory M1-polarized macrophages. The presence of CD3+ T lymphocytes and of T helper CD4+ and cytotoxic CD8+ T cells was analyzed. Student’s t-test was used for statistical analysis; data are expressed as means ± SEM (n = at least 8 mice/group). (A,B) Percentual analysis of macrophage accumulation in the sAT (A) and gAT (B). (C,D) Number of macrophages per gram of sAT (C) and gAT (D). (E,F) Percentual evaluation of T cell accumulation in the sAT (E) and gAT (F). (G,H) Number of T cells per gram of sAT (G) and gAT (H). (I,J) Representative images (Giemsa staining) for the presence of mast cells in the gAT of obese mast cell-deficient and -proficient mice (I). Mast cell deletion was evaluated (J); n = at least 8 mice/group. Mast cells were not present in the AT of Mcpt5-Cre+R-DTA+ mice. *p < 0.05. (K) Quantitative PCR analysis of inflammatory gene expression in the gAT of obese mast cell-deficient and -proficient mice. Data are shown relative to the mast cell-proficient mouse group; 18S RNA was used for normalization. Mann–Whitney U test was used for statistical analysis (n = 8 mice/group).
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Figure 3: No difference in AT inflammation between obese mast cell-deficient and -proficient mice. (A–H) The stromal vascular fraction (SVF) of subcutaneous (sAT) and gonadal (gAT) adipose tissue from obese mast cell-deficient and -proficient mice was analyzed by flow cytometry for the accumulation of total macrophages (Mφs) and pro-inflammatory M1-polarized macrophages. The presence of CD3+ T lymphocytes and of T helper CD4+ and cytotoxic CD8+ T cells was analyzed. Student’s t-test was used for statistical analysis; data are expressed as means ± SEM (n = at least 8 mice/group). (A,B) Percentual analysis of macrophage accumulation in the sAT (A) and gAT (B). (C,D) Number of macrophages per gram of sAT (C) and gAT (D). (E,F) Percentual evaluation of T cell accumulation in the sAT (E) and gAT (F). (G,H) Number of T cells per gram of sAT (G) and gAT (H). (I,J) Representative images (Giemsa staining) for the presence of mast cells in the gAT of obese mast cell-deficient and -proficient mice (I). Mast cell deletion was evaluated (J); n = at least 8 mice/group. Mast cells were not present in the AT of Mcpt5-Cre+R-DTA+ mice. *p < 0.05. (K) Quantitative PCR analysis of inflammatory gene expression in the gAT of obese mast cell-deficient and -proficient mice. Data are shown relative to the mast cell-proficient mouse group; 18S RNA was used for normalization. Mann–Whitney U test was used for statistical analysis (n = 8 mice/group).

Mentions: As mast cells have been previously proposed to contribute to a variety of immune responses (8–10) and especially to obesity-related AT inflammation (12), we next evaluated inflammatory cell accumulation in the AT. Consistent with the findings in mast cell-deficient Cpa3Cre+ mice (16), flow cytometric analysis did not reveal any differences in the accumulation of total Mφs or pro-inflammatory M1-polarized CD11c+ Mφs in the sAT or the gAT between obese Mcpt5-Cre+R-DTA+ mast cell-deficient and obese Cre-negative R-DTA+ control mice (Figures 3A–D). No difference in Mφ accumulation was observed when data were expressed as the percentage of SVF (Figures 3A,B) or when data were expressed as cell numbers per gram of tissue (Figures 3C,D). Similarly, mast cell deficiency did not affect accumulation of total T cell numbers (CD3+ cells), CD4+ T helper cell numbers, or CD8+ cytotoxic T cell numbers in the obese sAT or gAT (Figures 3E–H). Histological analysis of Giemsa-stained sections confirmed the virtual absence of mast cells in gAT of Mcpt5-Cre+R-DTA+ mice (Figures 3I,J). Quantitative PCR analysis of the gAT of obese mast cell-deficient and -proficient mice did not reveal any difference in the expression of cytokines IL-10, IL-1β, IL-6, and TNF and of the chemokine MCP-1 and thus in the inflammatory environment of the AT (Figure 3K). In conclusion, mast cells do not regulate AT inflammation in the course of diet-induced obesity.


No Role for Mast Cells in Obesity-Related Metabolic Dysregulation
No difference in AT inflammation between obese mast cell-deficient and -proficient mice. (A–H) The stromal vascular fraction (SVF) of subcutaneous (sAT) and gonadal (gAT) adipose tissue from obese mast cell-deficient and -proficient mice was analyzed by flow cytometry for the accumulation of total macrophages (Mφs) and pro-inflammatory M1-polarized macrophages. The presence of CD3+ T lymphocytes and of T helper CD4+ and cytotoxic CD8+ T cells was analyzed. Student’s t-test was used for statistical analysis; data are expressed as means ± SEM (n = at least 8 mice/group). (A,B) Percentual analysis of macrophage accumulation in the sAT (A) and gAT (B). (C,D) Number of macrophages per gram of sAT (C) and gAT (D). (E,F) Percentual evaluation of T cell accumulation in the sAT (E) and gAT (F). (G,H) Number of T cells per gram of sAT (G) and gAT (H). (I,J) Representative images (Giemsa staining) for the presence of mast cells in the gAT of obese mast cell-deficient and -proficient mice (I). Mast cell deletion was evaluated (J); n = at least 8 mice/group. Mast cells were not present in the AT of Mcpt5-Cre+R-DTA+ mice. *p < 0.05. (K) Quantitative PCR analysis of inflammatory gene expression in the gAT of obese mast cell-deficient and -proficient mice. Data are shown relative to the mast cell-proficient mouse group; 18S RNA was used for normalization. Mann–Whitney U test was used for statistical analysis (n = 8 mice/group).
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Figure 3: No difference in AT inflammation between obese mast cell-deficient and -proficient mice. (A–H) The stromal vascular fraction (SVF) of subcutaneous (sAT) and gonadal (gAT) adipose tissue from obese mast cell-deficient and -proficient mice was analyzed by flow cytometry for the accumulation of total macrophages (Mφs) and pro-inflammatory M1-polarized macrophages. The presence of CD3+ T lymphocytes and of T helper CD4+ and cytotoxic CD8+ T cells was analyzed. Student’s t-test was used for statistical analysis; data are expressed as means ± SEM (n = at least 8 mice/group). (A,B) Percentual analysis of macrophage accumulation in the sAT (A) and gAT (B). (C,D) Number of macrophages per gram of sAT (C) and gAT (D). (E,F) Percentual evaluation of T cell accumulation in the sAT (E) and gAT (F). (G,H) Number of T cells per gram of sAT (G) and gAT (H). (I,J) Representative images (Giemsa staining) for the presence of mast cells in the gAT of obese mast cell-deficient and -proficient mice (I). Mast cell deletion was evaluated (J); n = at least 8 mice/group. Mast cells were not present in the AT of Mcpt5-Cre+R-DTA+ mice. *p < 0.05. (K) Quantitative PCR analysis of inflammatory gene expression in the gAT of obese mast cell-deficient and -proficient mice. Data are shown relative to the mast cell-proficient mouse group; 18S RNA was used for normalization. Mann–Whitney U test was used for statistical analysis (n = 8 mice/group).
Mentions: As mast cells have been previously proposed to contribute to a variety of immune responses (8–10) and especially to obesity-related AT inflammation (12), we next evaluated inflammatory cell accumulation in the AT. Consistent with the findings in mast cell-deficient Cpa3Cre+ mice (16), flow cytometric analysis did not reveal any differences in the accumulation of total Mφs or pro-inflammatory M1-polarized CD11c+ Mφs in the sAT or the gAT between obese Mcpt5-Cre+R-DTA+ mast cell-deficient and obese Cre-negative R-DTA+ control mice (Figures 3A–D). No difference in Mφ accumulation was observed when data were expressed as the percentage of SVF (Figures 3A,B) or when data were expressed as cell numbers per gram of tissue (Figures 3C,D). Similarly, mast cell deficiency did not affect accumulation of total T cell numbers (CD3+ cells), CD4+ T helper cell numbers, or CD8+ cytotoxic T cell numbers in the obese sAT or gAT (Figures 3E–H). Histological analysis of Giemsa-stained sections confirmed the virtual absence of mast cells in gAT of Mcpt5-Cre+R-DTA+ mice (Figures 3I,J). Quantitative PCR analysis of the gAT of obese mast cell-deficient and -proficient mice did not reveal any difference in the expression of cytokines IL-10, IL-1β, IL-6, and TNF and of the chemokine MCP-1 and thus in the inflammatory environment of the AT (Figure 3K). In conclusion, mast cells do not regulate AT inflammation in the course of diet-induced obesity.

View Article: PubMed Central - PubMed

ABSTRACT

Obesity-related adipose tissue (AT) inflammation that promotes metabolic dysregulation is associated with increased AT mast cell numbers. Mast cells are potent inducers of inflammatory responses and could potentially contribute to obesity-induced AT inflammation and metabolic dysregulation. Conflicting findings were reported on obesity-related metabolic dysfunction in mast cell-deficient mice, thus creating a controversy that has not been resolved to date. Whereas traditional Kit hypomorphic mast cell-deficient strains featured reduced diet-induced obesity and diabetes, a Kit-independent model of mast cell deficiency, Cpa3Cre/+ mice, displayed no alterations in obesity and insulin sensitivity. Herein, we analyzed diet-induced obesity in Mcpt5-Cre R-DTA mice, in which the lack of mast cells is caused by a principle different from mast cell deficiency in Cpa3Cre/+ mice or Kit mutations. We observed no difference between mast cell-deficient and -proficient mice in diet-induced obesity with regards to weight gain, glucose tolerance, insulin resistance, metabolic parameters, hepatic steatosis, and AT or liver inflammation. We conclude that mast cells play no essential role in obesity and related pathologies.

No MeSH data available.


Related in: MedlinePlus