Study On Relationship Between Type 2 Diabetes Mellitus And Autophagic-Lysosomal System

Objective:Autophagic-lysosmal system involves degradation of cellular components and macromolecular substances through lysosomal digestion,which is a specific vital phenomenon in eukaryotic cells.Autophagy plays an important role in cell growth,development and disease.Autophagy functions widely in normal physiological processes,cellular defense mechanism under certain circumstances and pathological processes.Excessive or reduced autophagy cause a great number of diseases.Accumulating evidence shows that autophagy has been associated to cancer, neurodegenerative diseases,invasion of pathogenic microorganisms and other diseases.To date,very few studies have been reported on the association between autophagic-lysosomal system and type 2 diabetes.Some studies have revealed the quantitaty and functional changes of autophagic-lysosomal system in the patients with T2DM,suggesting its role in the pathogenesis and development of T2DM.However,negatvie efftects have also been reported,indicting the comlex effects of the system.This study was designed to investigate the quantity changes of the autophagic-lysosomal system in the T2DM patients and explore its role in the onset and development of T2DM.The results will provide a theoretical basis for understaning the etiology and developing novel intervention and treatment measures for the disease.Methods:From Dec.2007 to Apr.2008,we collected blood samples of T2DM patients,without or with diabetic microangiopathy,in the Endocrinology Department of Affiliated Hospital of Jining Medical College.Healthy volunteers as normal control were from the hospital physical-examination center.We employed case-control method with 3 groups:normal control(40 cases),T2MD patients(40 cases),T2MD patients with microangiopathy(40 cases).Blood samples were collected and the leukocytes were isolated.Cellular protein and total RNA were parepared for western blotting and RT-PCR,respectively.All data were analysed with software SPSS13.0 and P value＜0.05 set as statistically significant.Results:The results of western blotting and RT-PCR showed that the LC3 protein levels and LC3 gene expression levels were significantly decreased in T2DM patient group and T2DM patients with with microangiopathy group,compared with normal controls,indicating that autophagosome formation were reduced.There was not significant difference between T2DM pateint group and T2DM patient with microangiopathy group.However,we did not observe the differences of LAMP-2 protein level and LAMP-2 gene expresion levels among these three groups.Logistic analyses showed that age,FBG,TG,TC and LDL were significantly positively correlated with the onset of T2DM,but uric acid were significantly negative correlated with them.Conclusions:Our study showed that number and formation of autophagosome were associated with the pathogeneis,development of T2DM and its complications, suggesting that autophagosomes has protective effects in T2DM patients.As the formation and number of autophagosome were reduced and the damaged cell organelles in the pancreaticβ-cell could not be cleared promptly,theβ-cell functions are not well maintained in T2DM patients.As a result,uncleared and damaged mitochondria and swelled endoplasmic reticulum ofβ-cell may reduce its ability to produce insulin.Although LAMP-2 protein,a mark of lysosomes,were decreased in T2DM patients,but there was no significant difference among the three groups, which may be related to the great variation of lysosomes.Lysosomes not only fuse with autophagosome,but also directly digest both endogenous and exogenous macromolecules.Therefore,the assocition of lysosomes and T2DM can not be ruled out and needs to be further investigated.In addition,age,obesity,high blood sugar and high blood lipids were the risk factors for the onset of T2DM.