SLE is an autoimmune disease caused by pathogenic autoantibodies, which may cause multiple organ damages. [16]. It covers a worldwide scale, mostly among Africans and Asians [17]. Because of its heterogeneity, there is still no effective therapy for SLE. At present, the early diagnosis of SLE need more research and clinical experience. In practice, the main diagnostic markers of SLE are antinuclear antibodies, several autoantibodies and complement activation [18]. Patients still have excessive damage accumulation, morbidity and death, which indicates that there are a lot of medical needs in SLE. Previous studies have observed abnormal changes in many proteins and metabolites in patients with SLE. For example, patients with SLE have lower levels of most amino acids, glycolysis and TCA circulating metabolites, and higher levels of fatty acids and markers of oxidative stress [19]. In a study by Rashmi Madda et al, 14 significantly expressed proteins were identified (9 up-regulated and 5 down-regulated). Most proteins, including alpha 2 macroglobulin, complement C4, complement factor H, fibrinogen beta chain, and alpha-1-antitrypsin, play a key role in the pathogenesis of SLE [20]. These studies are helpful for us to understand the pathogenesis of SLE. However, considering the complexity of diseases and the pathological differences between active and inactive diseases, looking for a single biomarker cannot fully understand the pathogenesis of SLE. Most of the previous studies are limited by the analysis platform or sample size, which cannot identify a sufficient number of biomarkers. We used gas chromatography-mass spectrometry and TMT quantitative detection technology for metabonomic and preliminary proteomic analysis. Comprehensive multi-omics analysis will provide new insights into the molecular mechanism of SLE.
We have established three models of SLE preliminary, moderate & severe diagnosis and severe diagnosis. 12 indicators related to SLE diagnosis were screened out from 358 variables by lasso regression analysis, including sex (female), ITIH3, TAG, WBC, LPC, PC and palmitic acid. Previous studies have confirmed that SLE mostly occurs in women of childbearing age, with a male-to-female ratio of about 1:9 [21, 22]. This is consistent with the results of our preliminary diagnostic model analysis. Inter-alpha-trypsin inhibitor (ITI) family is a serine protease inhibitor composed of two precursor proteins, including a light chain (bikunin) and five homologous heavy chains [23]. Different homologous heavy chains constitute a total of five members of ITIH1-5. Different homologous heavy chains constitute five members of ITIH1-5, among which ITIH3 is located in the closely linked region of chromosome 3p21. During the assembly of mature ITI proteins in the liver, ITIH3 undergoes extensive post-translational modification [24], mainly involving C-terminal pruning [25]. Previous studies have shown that ITI is closely related to inflammation, such as colitis [26], pancreatitis [27], Sjögren’s syndrome [28], polyarthritis [29] or sepsis [30]. Our results confirm that ITIH3 is down-regulated in patients with SLE. Leukopenia is one of the important hematological features of SLE. According to the latest diagnostic classification criteria of SLE jointly issued by the European League Against Rheumatism (EULAR) and the American College of Rheumatology (ACR), leukopenia < 4000/mm³scores 3 points in clinical diagnosis. Our statistical results show that the number of WBCs is negatively correlated with SLE, and it can be used to diagnose and distinguish mild patients from moderate and severe patients. Maintaining the dynamic balance of lipid metabolism is a basic feature of normal organisms. The increased level of oxidative stress in patients with SLE leads to the disorder of lipid metabolism in patients with SLE, which is closely related to its pathogenesis [31]. It can be seen in our study that palmitic acid, LPC 15:0(SN2), LPC 22:5, PC (11:0/22:2), PC (9:0/24:2), PC 36:2, PC 44:8e, TAG 57:0 and TAG 48:5 can be used as lipid markers in different degrees of SLE. Palmitic acid, LPC 15:0(SN2), LPC 22:5, PC (11:0/22:2), PC (9:0/24:2), PC 36:2, PC 44:8e, and TAG 48:5 can distinguish mild patients from moderate and severe patients, while palmitic acid, PC (9:0/24:2) and PC 44:8e can further distinguish moderate patients from severe patients. Abnormal lipid metabolism caused by SLE may induce cardiovascular disease, which increases the mortality of patients. Finally, after screening the diagnostic markers, we verify the diagnostic effectiveness of the three models. Complex diseases are generally considered to be caused by the interaction of a variety of environmental exposure factors (macro) and inherent genetic characteristics (micro). Clinical diagnosis alone is increasingly unable to meet the needs of disease diagnosis. Different levels of genetic information in organisms have a relatively large amount of data, which constitute different combinatorial data. Through the comparison of ROC in Fig. 3, it can be seen that clinical and omics co-diagnosis is more effective than simple clinical diagnosis, especially in the diagnosis of severe SLE.
In conclusion, we made a statistical analysis on the demographic characteristics, laboratory indicators, proteomic and metabonomic indicators of patients with SLE, diagnostic markers were screened to provide a reference for the diagnosis of SLE. We have observed changes in many important metabolites in patients with SLE, and multi-omics techniques can identify and quantify various biomolecules in blood and different types of tissues. It accelerates the development of life science research and contributes to a better understanding of the mechanism, diagnosis and treatment of the disease.