Effects Of Spermidine In Regulating Obesity Based On Inflammation

With the improvement of people’s living standards and lifestyle changes,the proportion of global overweight and obesity is increasing.According to the data of 2014,there were 2.1 billion overweight or obese people globally,accounting for about 30% of the world’s total population.Obesity is an important risk factor for diabetes,hypertension,coronary heart disease,stroke and other diseases.Obesity accounts for about 5% of total mortality of the world.A large number of studies have found that obesity is a low-grade chronic inflammatory state,which can induce insulin resistance and endothelial dysfunction,and further increase the risk of chronic metabolic diseases such as diabetes.In recent years,the anti-inflammatory effects of spermidine have attracted much attention.The aim of our research is to examine whether spermidine regulates obesity by modulating inflammation.The research results will provide new ideas for the improvement of obesity by spermidine,which has important theoretical and practical significance.Objectives:To examine the effects spermidine intervention on obese mice induced by high-fat diet and explore the underlying inflammatory mechanism.Methods:The healthy adult male C57BL/6J strain wild-type mice and TLR2-/-mice were randomly divided into three groups(8 mice in each group):(1)spermidine plus high-fat diet group(SHF): after 10 weeks of spermidine(3m M)drinking water intervention,followed with high-fat diet for 11 weeks;(2)high-fat diet group(HFD): after 10 weeks of regular drinking water,followed with high-fat diet for 11 weeks;(3)normal control group(NC): receiving regular drinking water and regular diet.We adopted a preventive intervention model with a total intervention period of 21 weeks.During the intervention,we weekly recorded mice weight,food and water consumption,and monthly measured fasting blood glucose.After animals were sacrificed,we examined:1.Organ index: at the end of the experiment,we weighed the visceral fat,subcutaneous fat,liver and calculated the organ index.2.Serological indicator: we performed an IPGTT,calculated the area under the curve and measured serum inflammatory cytokines CRP,TNF-α,IL-1β,IL-6,MCP-1,IFN-γ and IL-18 level.3.Blood pressure related indicators: we used the BP-2000 animal non-invasive blood pressure analysis system to measure systolic blood pressure(SBP),diastolic blood pressure(DBP),mean arterial pressure(MBP),and heart rate(HR)in mice.4.HE staining: observation of pathological changes in fat and liver tissue.5.Liver tissue inflammation related indicators: We used Western blot to detect the expression of NLRP3 inflammasome and other related proteins(such as,NLRP3,ASC,IL-18).Results:Effects of spermidine on basic parameters of obese mice induced by high-fat diet:(1)During the experiment,the weight gain of the mice in the SHF group and the HFD group was significantly higher than that in the NC group(p<0.05),and TLR2-/-mice gain significantly more weight than WT mice.(2)The average food intake of the SHF group and the HFD group was significantly lower than that of the NC group(p<0.05),but there was no significant difference in energy intake between these groups.(3)The fat content and fat index of the SHF group and HFD group were significantly higher than that of the NC group(p<0.05),and the SHF group and HFD group of TLR2-/-mice were higher than that of groups of WT mice respectively(p<0.05).However,there was no significant difference in the liver and liver index of WT and TLR2-/-mice.Effects of spermidine on blood glucose and inflammatory factors:(1)After the intervention of high-fat diet,the blood glucose of the SHF group and HFD group of TLR2-/-mice were significantly higher than that of the NC group(p<0.05),and the blood glucose of the SHF group was slightly lower than that of the HFD group.There was no significant difference between the SHF group and the HFD group in WT mice.(2)In glucose tolerance test,either WT or TLR2-/-mice,SHF and HFD group blood glucose area under the curve were significantly higher than that of NC group(p<0.05).The area under the blood glucose curve in the HFD group of the WT mice had a downward trend compared with the SHF group,but there was no significant difference between the SHF group and the HFD group in the TLR2-/-mice.(3)The serum IFN-γ levels of the WT mice in the NC group were higher than that of the HFD group(p<0.05),and the serum IFN-γ level of the TLR2-/-mice in the SHF group was lower than that of the NC group(p<0.05).The inflammatory markers were not significant changed in the rest of the groups.Effects of spermidine on blood pressure and heart rate:(1)In the absence of any intervention,the DBP and MBP of TLR2-/-mice were higher than WT mice(p<0.05).After the high-fat diet intervention,DBP and MBP in WT mice were elevated(p<0.05),indicating that high-fat diet can increase blood pressure in WT mice.(2)The high-fat diet increased the heart rate of WT mice(p<0.05)and did not alter the heart rate of TLR2-/-mice,but the heart rate of TLR2-/-mice in the spermidine intervention group was slightly higher than that of the HFD group.Effects of spermidine on liver and adipose tissue of obese mice induced by high-fat diet:(1)Liver histopathological section results showed that,compared with the NC group,HFD group showed obvious steatosis with a large number of lipid cavitation in the liver cells and significantly reduced hepatic sinusoid;the number of lipid droplets in the SHF group treated with spermidine was significantly reduced,and the cell morphology tends to be normal.(2)Adipose tissue histopathological section results showed that,compared with the NC group,the size of adipocytes in the HFD group was different,and the volume was significantly increased.The size of adipocytes in the SHF group treated with spermidine was significantly reduced.(3)In the liver tissue,compared with NC group,the expression of ASC in SHF group of TLR2-/-mice was significantly decreased(p<0.05),and the expression of IL-18 in HFD group was increased(p<0.05);compared with the HFD group,the expression levels of ASC and IL-18 in the TLR2-/-mice group were significantly decreased(p<0.05),but there was no significant change in the expression of these proteins in WT mice.Conclusions:1.High-fat diet can induce obesity in mice,cause lipid metabolism disorder and hepatic steatosis,TLR2-/-mice are more likely to be obese than WT mice.2.After intervention with spermidine drinking water,impaired glucose tolerance in TLR2-/-obese mice does not improve,even promotes impaired glucose tolerance,which may be related to the loss of TLR2 gene.3.High-fat diet can increase blood pressure and heart rate in WT mice.Spermidine has a tendency to decrease blood pressure in WT mice.However,spermidine has no significant effect on lowering blood pressure and heart rate in high fat diet feeding TLR2-/-mice.4.Spermidine reduced the expression of ASC and IL-18 in the liver of obese mice.It may be through TLR2,down-regulating the expression of NLRP3 inflammasome and its related components to exert anti-inflammatory effects.