Mechanism Of RGN In Lipolysis

Lipolysis is highly regulated by hormone signal,lipid droplet associated protein and lipase.Dyslipidemia can affect energy balance,cause metabolic disorder,obesity and insulin resistance.Fatty triglyceride lipase(ATGL)is the rate limiting enzyme of fat decomposition.It catalyzes the first step of triglyceride(TG)hydrolysis and releases diacylglycerol(DAG)and fatty acids(FA).Hormone sensitive lipase(HSL)catalyzes the second step in the hydrolysis of triglycerides(TG),releasing monoacylglycerides(MG)and fatty acids(FA).ATGL and HSL,as key enzymes of energy homeostasis,mediate lipolysis and are closely related to metabolic disorders.Regucalcin(RGN),also known as calmodulin,participates in the regulation mechanism of lipid metabolism,but the specific role and mechanisms of RGN are not clear.Therefore,this study will identify the mechanism of RGN in triglyceride decomposition.The conclusions are as follows:1.According to the analysis of intracellular triglyceride content,it was found that overexpression of RGN in He La cells induced the decrease of triglyceride content and the increase of glycerol release.Therefore,it was confirmed that RGN affected the metabolism of triglycerides.Further study on the mechanism of RGN mediated triglyceride decomposition showed that under the condition of starvation stimulated lipolysis,the overexpression of RGN could promote the hydrolysis of triglycerides in lipid droplets.2.ATGL is a rate limiting hydrolase for lipolysis.Immunoprecipitation results showed that RGN interacted with ATGL.The results of triglyceride assay and glycerol release assay confirmed that RGN mediated decrease in triglyceride content that attributed to the interaction between ATGL and RGN.RGN promotes the decrease of triglycerides by promoting ATGL mediated lipolysis.3.HSL is the second hydrolase of lipolysis.Immunoprecipitation results showed that RGN interacted with HSL.The results of triglyceride assay and glycerol release assay confirmed that the decrease of triglyceride content induced by RGN was related to HSL interaction.RGN promotes the reduction of triglycerides by promoting HSL mediated lipolysis.Our results found that the efficiency of RGN acts on HSL was not as high as that of RGN on ATGL.4.MGL is the last hydrolase in lipolysis.Immunoprecipitation showed that RGN interacted with MGL.However,the binding site of RGN to MGL is not clear,and whether RGN binds to N-terminal patatin domain needs further experimental verification.Thus,RGN can promote the lipolysis of ATGL through the interaction with ATGL,and then promote the lipolysis,as a positive regulator of lipolysis.Overexpression of RGN in human liver cells can reduce fat accumulation.The interaction of RGN-ATGL,RGN-HSL and RGN-MGL and their discovery in lipolysis and triglyceride decomposition may provide potential therapeutic targets for obesity related metabolic disorders.