Comparative Study On Clinical Feature,Pathology,Genetic Mutation And Proteomics Of Sporadic Inclusion Body Myositis And Hereditary Inclusion Body Myopathy

BackgroundsSporadic inclusion body myositis（s-IBM）is a kind of idiopathic inflammatory myopathy affects mainly middle-aged and elderly male.It is characterized by insidious onset,chronic progressive myasthenia and muscle atrophy.The weakness of quadriceps femoris is common in s-IBM patients.Hereditary inclusion body myopathy（h-IBM）is an autosomal dominant or recessive hereditary disease.GNE myopathy（UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase myopathy,GNEM）is the most common type of h-IBM.It usually onsets in early adulthood.The manifestations of h-IBM include progressive foot drop,limb weakness,and relatively less involvement of quadriceps femoris.However,the clinical manifestations of s-IBM and h-IBM are non-specific,leading to difficulties in differential diagnosis between the two kinds of diseases.Due to the limitations in clinical resources and diagnostic accuracy,the domestic research status of s-IBM and h-IBM has the following three characteristics:firstly,there are many potential patients with misdiagnoses and missed diagnoses;secondly,most of the studies are focused on the clinical and pathological analysis,and the exploration of protein level and pathogenesis is relatively shallow;thirdly,there is no systematic comparative study of the two diseases.According to the reports from domestic and foreign literature,the formation of rimmed vacuoles is often accompanied by abnormal protein degradation pathways.So it is of great value to clarify the protein expression changes and the corresponding function alterations in s-IBM and h-IBM,for elucidating their pathogenesis,searching for biological markers and providing possible therapeutic approaches in the future.Objectives1.30 s-IBM patients and 20 h-IBM patients represented by GNEM were studied using clinical data analysis and muscle enzyme histochemistry,and their characteristics were compared in order to provide more evidence for clinical diagnosis and differential diagnosis.2.Gene screening for h-IBM patients was carried out by second-generation sequencing technology to analyze the mutation characteristics of GNE gene in a Chinese population.3.Using iTRAQ technology,the proteomic characteristics of s-IBM and h-IBM were analyzed and compared to provide candidate proteins as biological markers.Methods1.The clinical characteristics were compared between 30 patients diagnosed as s-IBM and 20 patients diagnosed as h-IBM,who underwent muscle biopsy in our hospital between January 2003 and December 2018.2.the pathomorphological features of skeletal muscle in s-IBM and h-IBM patients were observed and compared by enzyme histochemical staining.3.the genetic mutations in h-IBM patients were Screened and analyzed by using second-generation sequencing technology.4.the proteomic characteristics of three normal controls,three s-IBM and three h-IBM patients were analyzed and compared Using iTRAQ technology.Results1.The average onset age of s-IBM patients was（53.23±7.37）years old,and that of GNEM patients was（26.00±8.07）years old.The age of onset of s-IBM was significantly older than that of GNEM（P=0.000）;Four limbs involvement was most common in s-IBM patients.GNEM patients were often affected by lower limb involvement（P=0.030）.s-IBM was more likely to have quadriceps atrophy than GNEM（P=0.010）and lower extremity muscle strength.Left and right asymmetry（P=0.033）,tibialis anterior muscle involvement was lighter（P=0.001）;s-IBM patients with upper extremity involvement weremore common in the distal end than in the proximal end,while GNEM patients had no significant difference in the far proximal end（P=0.009）;s-IBM patients with lower extremity involvement were more common in the proximal end than in the distal end,while GNEM patients were more common in the distal end than in the proximal end（P=0.001）;The level of serum CK of s-IBM patients was slightly lower than that of patients with GNEM（P=0.027）;14 patients who had used a large number of regular glucocorticoids therapy and 6 patients who had been treated with intravenous immunoglobulin had no significant improvement,and 3 GNEM patients who had used a large number of regular glucocorticoids treatment also had no significant improvement.2.There were five pathological differences observed:（1）A majority of the rimmed vacuoles found in the s-IBM patients resembled cracks,whereas the GNEM patients（P=0.001）had round or oval vacuoles.（2）A majority of the rimmed vacuoles that were located in the periphery of the atrophic muscle fibers of the s-IBM patients.The patients with GNEM had a majority of the rimmed vacuoles in the center of the atrophic muscle fibers（P=0.000）.（3）The patients with s-IBM had basophilic granules in the rimmed vacuoles,which appeared to be fine granules that were sand-like particles.The GNEM patients had coarse granules（P=0.000）.（4）The proportion of mononuclear cells invasion of muscle fibers was larger in the s-IBM patients than the GNEM patients（P=0.049）.（5）The percentage of inflammatory cell infiltration in muscle fibers of patients with s-IBM was higher than that of patients with GNEM（P=0.003）.3.Twenty-four gene mutations were detected in 20 patients with GNEM,eight of which were not reported in HGMDpro database,c.1619-2A>C,c.1559A>G,c.1711₁712del,c.556T>C,c.1634-1G>C,c.1897G>T,c.1205dupT and c.733A>G respectively.4.Compared with the normal control group,124 proteins were identified in s-IBM patients.The proteins were involved in important pathways such as carbon metabolism,glycolysis,gluconeogenesis and Alzheimer’s disease.Among the 124 proteins,there were 24 mitochondrial-related proteins,suggesting abnormal mitochondrial function.Compared with the normal control group,70 proteins were identified in GNEM patients.These proteins were involved in the calcium signaling pathway,glycolysis,gluconeogenesis and tight junction.Twenty-five differential proteins were identified between s-IBM and GNEM,which were mainly related to oxidative stress and involved in the regulation of longevity.Conclusions1.There are several non-specific differences in clinical manifestations between s-IBM and h-IBM.2.Immunotherapy ineffective in s-IBM and h-IBM patients3.There were significant differences in the morphologies of the rimmed vacuoles between s-IBM and h-IBM patients.4.Eight GNE gene mutations were found which were not reported in HGMDpro database.5.The difference in protein expression between s-IBM and h-IBM is mainly related to oxidative stress.