Effect Of High Fat Diet On Adipose Tissue Inflammation In Different Age Mice

BackgroundObesity is metabolic disease that characterized by a chronic, low grade inflammation. Obesity is closely related to the occurrence and development of atherosclerosis, type 2 diabetes, fatty liver, asthma and other diseases. Obesity is influenced by genetic, diet, exercise, age and other factors. With the development of society and the improvement of people’s living standards, high fat diet has becoming a key factor to induce obesity. High fat diet can lead to body weight gain, fat cell size increase, adipose tissue inflammation, and the increase of inflammatory cytokines and immune cells. Insulin sensitivity may improve while the adipose tissue inflammation is decreasing, adipose tissue inflammation results in the occurrence of type 2 diabetes mellitus, so the high-fat diet induced adipose tissue inflammation is very important for the occurrence and development of disease. The effect of high fat diet on adipose tissue inflammation is also affected by age, according to pregnant mice on a high-fat diet may increase the risk of offspring of type 2 diabetes and their offspring increase the inflammation of adipose tissue. The effect of high fat diet on adipose tissue inflammation in different age mice remains unclear.ObjectiveThe same periods high fat diet were given to young mice and adulthood mice, to explore its effect on adipose tissue inflammation in different age mice.Methods1.The establishment of animal model:the 3-week-old C57BL/6 mice (childhood mice) are divided into two groups, a group given normal diet for 14 weeks, a group given high fat diet for 14 weeks. The 12-week-old C57BL/6 mice(adulthood mice) are divided into two groups, one group are given normal diet for 14 weeks, another group are given high fat diet for 14 weeks.2 Body weight change trend:recording their body weight every week.3.Measurement of metabolic indicators:four groups of mice on the high-fat or normal diet for 14 weeks, respectively, then fasting blood glucose, glucose tolerance test and insulin tolerance test are tested.4. Histochemical detection of adipocytes size:four groups of mice in either normal or high fat diet after 14 weeks, the epididymal adipose tissue, subcutaneous adipose tissue, perirenal adipose tissue were stained with hematoxylin and eosin and the calculate the average fat cells of area.5. Using qPCR to detecte the mRNA level of inflammatory cytokines in epididymal adipose tissue of mice.6. Detection of inflammatory immune cells with flow cytometry:minced epididymal adipose tissues of mice and digested them with collagenase, after filtration, staining them with fluorescent antibodies, then detecting the proportion of CD8+ T cells and CD4+ T cell population.7. Histochemical examination of liver lipid accumulation:four groups of mice in normal or high fat diet after 14 weeks, H&E and oil red O staining of liver.ResultsTo explore the effect of high fat diet on adipose tissue inflammation in different age mice.1. Changes in body weight and adipose tissue showed that adulthood mice were more sensitive to high fat diet than young mice, and the volume of the fat cells in the epididymal, subcutaneous and kidney were higher than that of the young mice after 14 weeks high fat diet.2. After the same period after high fat diet, adulthood mice occured more severe inflammation of the epididymal adipose tissue.3. Compared with adulthood mice, the epididymal adipose tissue of young mice can be infiltrated with more CD8+T lymphocytes after 14 weeks high fat diet.4. The results of glucose tolerance test shows that high fat diet can induce the sugar intolerance in adulthood mice compared with that in childhood mice.5. Oil red O staining showed that the liver of childhood and adulthood mice with high fat diet had similar lipid accumulation.conclusionCompared with adulthood mice, the adipose tissue inflammation of childhood mice is more serious after 14 weeks high fat diet.