Chronic Low-Grade Inflammation in Childhood Obesity Is Associated with Decreased IL-10 Expression by Monocyte Subsets

Abstract

Chronic low-grade inflammation is related to the development of comorbidities and poor prognosis in obesity. Monocytes are main sources of cytokines and play a pivotal role in inflammation. We evaluated monocyte frequency, phenotype and cytokine profile of monocyte subsets, to determine their association with the pathogenesis of childhood obesity. Children with obesity were evaluated for biochemical and anthropometric parameters. Monocyte subsets were characterized by flow cytometry, considering cytokine production and activation/recognition molecules. Correlation analysis between clinical parameters and immunological data delineated the monocytes contribution for low-grade inflammation. We observed a higher frequency of non-classical monocytes in the childhood obesity group (CO) than normal-weight group (NW). All subsets displayed higher TLR4 expression in CO, but their recognition and antigen presentation functions seem to be diminished due to lower expression of CD40, CD80/86 and HLA-DR. All subsets showed a lower expression of IL-10 in CO and correlation analyses showed changes in IL-10 expression profile. The lower expression of IL-10 may be decisive for the maintenance of the low-grade inflammation status in CO, especially for alterations in non-classical monocytes profile. These cells may contribute to supporting inflammation and loss of regulation in the immune response of children with obesity.

Fig 1

Plasma levels of adiponectin (A), leptin (B) and CRP (C) and dispersion graph of adiponectin versus leptin levels (D) are shown. The groups evaluated were normal-weight (NW; n = 9) and childhood obesity (CO; n = 11). Results in panels A, B and C are presented as mean ± SD. Significant differences (p<0.05) in the charts are identified by p value and connecting lines.

Fig 2. Frequency of monocytes subsets.

(A) Representative gates of flow cytometry for classification of subsets. (B) Frequency of each monocyte subsets in normal-weight (NW; n = 9) and childhood obesity (CO; n = 11). Graphs shown median with interquartile range. Significant differences (p<0.05) in the charts are identified by asterisks and connecting lines.

Fig 3. Evaluation of expression of recognition and activation molecules in monocytes and their subsets.

(A) Expression of recognition molecules was determined by mean fluorescence intensity (MFI). (B) Expression of activation molecules was determined by mean fluorescence intensity (MFI). The groups evaluated were normal-weight (NW; n = 9) and childhood obesity (CO; n = 11). Significant differences (p<0.05) between monocytes subsets, intragroup, are identified by asterisks and connecting lines. Letters represent statistical differences (p<0.05) between the same subset for comparison intergroup. Graphs shown median with interquartile range.

Fig 4. Evaluation of cytokine expression in monocytes and their subsets.

(A) Perceptual of classical monocytes expressing each cytokine. (B) Perceptual of intermediate monocytes expressing each cytokine. (C) Perceptual of non-classical monocytes expressing each cytokine. Graphs show median with interquartile range. Significant differences (p<0.05) are identified by asterisks. (D) Radar graph represent perceptual of each monocytes subsets expressing cytokine. The groups evaluated were normal-weight (NW; n = 9; dispersion points) and childhood obesity (CO; n = 11; bars).

Fig 5. Heatmap for correlations between inflammatory and anti-inflammatory molecules.

Representative heatmap of correlation between recognition/activation molecules and clinical parameters for classical (A), intermediate (B) and non-classical monocytes (C). Representative heatmap of correlation between cytokines and clinical parameters for classical (D), intermediate (E) and non-classical monocytes (F). The groups evaluated were normal-weight (NW; n = 9) and childhood obesity (CO; n = 11).

Fig 6. Correlation networks in monocyte subsets.

Correlations network in normal-weight group (NW; n = 9) for classical (A), intermediate (B) and non-classical monocytes (C). Correlations network in childhood obesity group (CO; n = 11) for classical (D), intermediate (E) and non-classical monocytes (F). All correlations shown in networks are strong, presents r-squared higher than 0.63, and statistical significance defined by p<0.05. The continuous lines represent positive correlation and the traced lines represent the negative correlation.