Variation Of Regulatory T Cells In The Early Stage Of Obesity And Their Modulation On Macrophage Subtypes In Visceral Adipose Tissue

Objective This study aims to investigate the changes of regulatory T cells (Tregs) and whether Treg could modulate the distribution of macrophage’s subtypes in visceral adipose tissue at the early stage of obesity.Research design and Methods Four-week-old wild-type C57BL/6male mice were placed on either a high-fat diet that derived60%calories from lipids or a chow diet. Metabolic testing was performed evey week of diet. The infiltration of macrophage in visceral adipose and the number of Tregs in spleen was analysed by flow cytometry; serum samples were quantified by ELISA for leptin and insulin; livers were harvest for oil O staining; mRNA samples were evaluated by realtime-PCR for expression of monocyte chemoattractant protein-1(MCP-1). Meanwhile, the HFD mice was treated with rapamycin, and its effect on Tregs stimulation, metabolic, macrophage subtype in viscerel fat tissue were studied.Results①Early stage obesity models were successfully established at20weeks of age in C57BL/6mice. Compared with ND mice, HFD mice had significantly higher body weight (39.05g±2.33g vs31.65g±1.20g, P＜0.05) which is coincident with higher1)epididymal adipose tissue weight (2.12g±0.48g vs0.36g±0.09g, P＜0.05);2) serum leptin level(13.57ng/ml±3.44ng/ml vs4.52ng/ml±0.60ng/ml, P＜0.05);3)adipose infiltration in HFD mice liver. However, there is no statistical difference of blood glucose (8.8mmol/L±0.33mmol/L vs9.3mmol/L±0.80mmol/L, P>0.05) and serum insulin(1.65ng/ml±0.85ng/ml vs1.39ng/ml±0.60ng/ml, P>0.05) between two group.②Macrophages’ infiltration in adipose tissue of HFD mouse gradually increased from2.36%at baseline to8.36%at week10and21.15%at week20, conicident with increses in1)the ratio of M1and M2from0.28to1.80and1.37in the corresponding time;2) MCP-1mRNA levels in epididymal from0.69to1.7and10.96.③The percent of Tregs in spleen showed a decreasing tendency, with6.40%±0.28%at week4, to4.93%±0.71%and4.73%±3.66%at week10and week20.④When treated with rapamycin, the mice showed an increased percent of Treg in spleen, from3.22%to15.30%. Compared to control group, the group intervented with rapamycin showed decreased body weight(27.08g±0.79g vs38.00g±4.74g, P＜0.05) coincided with decreased1)epididymal adipose tissue weight (0.96g±0.09g vs2.05g±0.52g,P＜0.05);2)serum leptin concentration (2.14ng/ml±0.86ng/ml vs13.90ng/ml±2.56ng/ml, P＜0.05);3) blood glucose (8.15mmol/L±0.91mmol/L vs12.15mmol/L±0.47mmol/L, P＜0.05);4) the ratio of M1/M2in epididymal ameliorated to0.48±0.39compared0.98±0.63with the control group.Conclusions Tregs’ decrease at the early stage of obesity may correlate with the infiltration of macrophage and the distribution of it’s subtype in visceral adipose.