| BackgroundObesity is a chronic-metabolic disease caused by a variety of factors, along with high blood insulin level and insulin resistance. It is an important composition of metabolic syndrome. Obesity is characterized by the large volume and increased number of adipose cells, which resulted in the higher percent of fat in body weight and local deposition. Systemic, chronic and low-grade inflammation is the same feature, and it has been confirmed as the key link of obesity and type 2 diabetes complications. The most basic change of obesity is the immune system components, obvious in adipose tissue, skeletal muscle, liver, pancreas and the intestinal tract, cardiovascular system and the peripheral circulation. The functional polarization of CD+4 T subsets has been proved to participate in the development of chronic inflammation much earlier than macrophages, and the harmonious ratio of CD+4 T subsets is more important.GLP-1 is a peptide secreted from intestinal L cells, which can induce insulin secretion of islet β cell. It can combined with glucagon like peptide-1 receptor (GLP-1R) to work. GLP-1 has the capacity in increasing insulin sensitivity, reducing glucose level, inhibiting islet β cells from apoptosis. Besides, GLP-1 has the capacity of decreasing splanchnic adipopexis, anti-inflammation and immune regulation, nerve nutrition and protection.ObjectiveIn the current study, we have evaluated the immune effects of GLP-1 treatment on high-fat induced mice, and demonstrated that GLP-1 can efficiently change the CD+4 subsets and cytokines levels. By cultivating treg cells in vitro, we examine the change of its function. Thus we propose GLP-1 as a potential therapeutic approach in immune regulation of obesity.Methods1. The establishment of high-fat diet induced obese mice model4 weeks of C57BL/6 mice were randomly divided into a high-fat feeding group and normal control group. The modeling process lasted for 16 weeks. The body weight if mice were recorded every week.2. GLP-1 treatment on obese miceWhen the obese model were builted, obese mice model were randomly divided into 3 groups:GLP-1 analogue liraglutide group, transferred normal diet group and high fat diet group. GLP-1 analogue liraglutide were given by intraperitoneal injection into the liraglutide group, and saline were given by the same way into the normal chow diet, high fat diet and transferred normal diet group. During the intervention, body weight of four groups were recorded continuality until the 12th week.3. The effects of GLP-1 on T subsets in obese miceWe used flow cytometry to individually characterize the surface markers of CD4 and related cytokines, distinguish Thl, Th2, treg, Th17 cells, and circle proportion and number of subgroups.4. The effects of GLP-1 on cytokinesEnzyme-linked immunosorbent method was used to detect the level of peripheral cytokines (IFN-y, IL-22, IL-17) to explore GLP-1’s regulation of T cells.5. Metabolic parameters measurement of GLP-1 treatmentBlood lipid (triglyceride, total cholesterol) were measured respectively and fasting glucose were tested after GLP-1 administration. Insulin tolerance test and glucose tolerance test were performed in mice.6. Cultivation of Treg cells in vitroMagnetic bead separation was used to cultivate and expand mice spleen treg cells. The secretion ability of Treg cells were messured by cytokines test. To discuss the effects of GLP-1 on the function of Treg cells.Results1. The change of Th subsets in high-fat induced diet obese mice.The analysis flow cytometry of Th cells found that peripheral inflammatory Th cells ratio of CD4+ T cell had different degree of raise in Th1 and Th17 and anti-inflammatory T cells ratio of CD4+ T cells had different degree of decline in Thl and treg.2. GLP-1 deceases the ratio and number of inflammatory Th cells.After the intervention of GLP-1, the ratio and number of inflammatory Th cells had varying degrees of decline and the ratio and number of anti-inflammatory Th cells had varying degrees of raise.3. GLP-1 deceases the level of pro-inflammatory cytokines.After the intervention of GLP-1, inflammatory cytokines in the peripheral blood serum were deceased. The change of IFN-γ, IL-22 and IL-17 were in correlations with T subsets.4. GLP-1 improve the function of Treg cells in obese mice.Through the classical mixed lymphocyte experiments, we found GLP-1 improved the function of Treg cells in vitro and perfected it.5. GLP-1 treatment improves the metabolic homeostasis of obese mice.Compared with the transferred normal diet group and normal control group, ITT and IPGTT of GLP-1 showed higher insulin sensitivity and glucose tolerance in mice. The plasma cholesterol and triglycerides were statistically different in different groups.Conclusion1. The inflammatory Th cells in peripheral blood of high-fat induced obese mice rise and the anti-inflammatory T cells in peripheral blood of high-fat induced obese mice decline in proportion and function. GLP-1 deceases the ratio and number of inflammatory Th cells and up-regulates the ratio and number of anti-inflammatory T cells.2. GLP-1 deceases the levels of inflammatory cytokines in obese mice and plays a vital role in the regulation of immune system.3. GLP-1 improves the function of Treg cells in vitro and plays a key role in the intervention of chronic inflammation in obesity.4. GLP-1 balances the metabolic homeostasis of high-fat induced obese mice. |
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