The Expression Of PPARα And ACOT2 In Lipid Storage Myopathy.

Lipid storage myopathy (LSMT) is one of metabolic diseases asT Tlong chainT Tfattyacids(LCFA)T Tmetabolism disordersT Tcaused byT TabnormalT TdepositsT Tin theT TmuscletissueT. It was first diagnosed in 1969 by Bradley. Most of LSM are autosomalrecessive. The clinical manifestations varied, mainly as progressive muscleweakness and repeated episodes of rhabdomyolysis in proximal limbs. Thedisorders of LCFA metabolism in LSM include defects of transport andoxidation of exogenous fatty acid in the mitochondria (such as primarycarnitine deficiency, Carnitine palmitoyl transferase II deficiency,Carnitine/acylcarnitine translocase deficiency, et al.) and defects ofendogenous triglycerides catabolism (such as neutral lipid storage disease withichthyosis, neutral lipid storage disease with myopathy, et al.). LSM typediagnosis depends on detection of biochemical and molecular aspects. It isdifficult with clinical application. The ultimate diagnosis must rely onmuscle biopsy.Peroxisome proliferator-activated receptorα(PPARα) is a member of anuclear hormone receptor superfamily (PPARs), other members includePPARβand PPARγ. PPARs are a class of ligand regulated transcriptionfactors activated by agonist ligands. Fatty acid and its metabolites areendogenous PPARαligands. Lipid lowering drugs fenofibrates already widelyused in the treatment of hyperlipidemia are synthetic ligands. PPARαmainlyregulate some enzymes involved inβ-oxidation pathway in peroxisomal andmitochondrial such as acetyl coenzyme A oxidase, acyl coenzyme A synthase,carnitine palm-Acyltransferase and so on. PPARαare widely involved in lipidmetabolism, inflammation, heart disease, fatty degeneration of liver andformation of hepatoma.Acyl-CoA thioesteras-2 (ACOT2), also known as acyl coenzyme A hydrolase, has been named as mitochondrial thioesterase-1 (MTE-1) before.ACOT2 is abundantly expressed in tissues engaged in high rates of fatty acidoxidation, such as liver, brown adipose tissue, skeletal muscle and heart. Itincludes 12 members named as ACOT1 to ACOT12.T Among them, TACOT2 islocated in mitochondria. It can hydrolyze LCFA^-CoA molecules inmitochondria to corresponding LCFA^- and CoA, the formula is as followes:LCFA^-CoA+H₂O→LCFA^- + CoA.In 2006, Lamar K. proposed a hypothesis about LCFA generation andtransport system in mitochondria. In mitochondrial, LCFA is hydrolyzed intocorresponding LCFA^- and CoA under the action of ACOT2. Then LCFA^- istransferred out of mitochondria by uncoupling protein 3 (UCP3) which islocated in the inner mitochondrial membrane while CoA is free to transfer outof mitochondria. The systerm was believed to promoteβ-oxidation inmitochondria. Some other experiments have conformed this hypothesis. Inrecent years, experiments showed that PPARαregulated the expression of notonly ACOT2, but also UCP3 and many experiments are carried based onabove.As LSM is autosomal recessive, it is often focused on the geneticsub-type and pathological diagnosis. But what changes has happened indeed invivo to LSM patients is seldom reported. The disorders of LCFA metabolismin LSM include defects of transport and oxidation of exogenous fatty acid inthe mitochondria and defects of endogenous triglycerides catabolism. But here,we proposed a new method for classification of LSM. That is, according to ourtesting some proteins involved in LCFA generation and transport system inmitochondria, we can make a conclusion primarily whether the LCFAtransportation is increased or decreased. LSM is very important for us to studymitochondrial LCFA metabolism and LCFA generation and transport systemin mitochondria.T Furthermore, Tcombained with detecting the expression ofPPARαof LSM, we can explore what LCFA metabolism disorder hashappende in LSM in more aspects.Objective:The experiment is to detect the expression of ACOT2 and PPARαof LSM, explore what LCFA metabolism disorder indeed hashappened in LSM, conform whether the LCFA generation and export systemin mitochondria is impaired and finally judge the classification of LSM.Methods:Our study include two groups: LSM as the observation groupwhile normal as the control group pathologically. Using Western-blot analysisto detect the expression of ACOT2 and PPARα. The data was analyzed bySPSS13.0 between the two groups using two independent samples t test andthe level of significance was set at P＜0.05.Results:Expression of ACOT2 is increased, significantly higher thannormal (P<0.05), but peroxisome proliferator-activated receptor-α(PPARα)expression was not significantly different compared with the control group(P> 0.05).Conclusion:TACOT2T Texpression ofT Tlipid storage myopathyT is TincreasedsignificantlyT, TcomparedT Twith the normalT Texpression ofT TtheT TPPARαT which is Tnotsignificantly changed.T LCFA metabolism disorder exists in LSM and TACOT2participate in it. TLCFA generation and export system in mitochondriaT in LSMis impaired. Acorrding to the upregulation of ACOT2 ,we can conclude thatthe transportation of LCFA to TmitochondriaT is increased. The expression ofUCP3 is not changed make us think that PPARαmay not participate in theLCFA metabolism disorder in LSM.