| Introduciton: The immune metabolism disorder induced by stress after severe burn is defined as hypermetabolism due to its severity and persistence,which is associated with sepsis,systemic infection,and multiple organ failure(MOF).The pathological mechanism of hypermetabolism after severe burn is extremely complex.Although some progress has been made in the past in the study of the pathological mechanism of hypermetabolism after severe burns,it is difficult to accurately identify the substantive biological mediators that cause hypermetabolism,so as to explain this pathological mechanism.In recent years,metabolomics studies with high sensitivity,strong stability and high throughput detection have made significant progress in the study of the pathological mechanism of severe burn.Therefore,if metabonomics analysis can be used to study the differences and change rules of endogenous metabolites produced in the hypermetabolic period after severe burn,it can help us to explore the pathological mechanism behind the hypermetabolism of severe burn and explain its relationship with sepsis,systemic infection and MOF.Methods:This study was divided into clinical study and animal experiment.The clinical study was conducted in the Department of Burn and Wound Repair,the First Affiliated Hospital of Anhui Medical University.The burn patients admitted from October 2020 to October 2022 were recruited according to the total burn surface area(TBSA)≤30%,30%<TBS≤50%,50%<TBS≤80%,TBSA>80% of the four different burn areas,ranging from 6 to 10 patients in each group,a total of 37 patients,the serum samples of each enrolled patient were collected 48 h after burn and divided into two groups,group M(TBSA ≤50%)and group S(TBSA>50%),including 17 patients in group M and 20 patients in group S.At the same time,16 non-burn patients were included as the control group(group C)and serum samples were collected and analyzed by ultra-performance liquid chromatography-mass spectrometry(UPLC-MS).At the same time,we collected the clinical data of each enrolled patient upon admission.Six aspects of basal metabolic rate(BMR),blood glucose,glomerular filtration rate(GFR),oxygenation index(Pa O2/Fi O2),total bilirubin(TBIL),acute physiological and chronic health score(APCHE II),sequential organ failure test score(SOFA)were analyzed and compared between the two groups.In animal experiments,four burn rat models with different burn areas of TBSA5%,TBSA20%,TBSA40% and TBSA80% were established,with 6 ～ 8 rats in each group,and they were divided into two groups: group M(TBSA5%,TBSA20%)and group S(TBSA40%,TBSA80%).There were 16 rats in group M and 15 rats in group S,and 6healthy rats were included as control group(group C).Serum samples of the model group and control group were collected 48 h after burn and were analyzed by UPLC-MS for metabolomics studies,so as to verify the reliability of endogenous differential metabolites and their changing trends obtained in clinical experiments.At the same time,we respectively collected the lung,liver,kidney,heart,small intestine and skin tissues of the model group and the healthy control group to make pathological sections.Histopathological analysis was conducted to verify whether the changes of organ tissue injury with severe burn enhancement were consistent with clinical studies and to discover which organ tissue injury was most seriously affected by burn.Results 1.Clinical study(1)There were no differences in age,male-female ratio and body weight between the M group(TBSA≤50%)and the S group(TBSA>50%)(P>0.05).The mean values of BMR,blood glucose,TBIL,APCHE II score and SOFA score of burn patients in group S were higher than those in group M,while the mean values of oxygenation index and GFR were lower than those in group M(P<0.05),and the differences were statistically significant.It indicates that the hypermetabolism level after burn will increase with the increase of the severity of burn,and the hypermetabolism after burn is closely related to multiple organ injury.(2)211 metabolites were obtained by comparing serum metabolomics of burn patients in group M(TBSA ≤ 50%)and group S(TBSA>50%),and 414 metabolites were obtained by comparing serum metabolomics of burn patients in group C(healthy control group)and group M(TBSA≤50%).Among them,128 metabolites from group M and group S showed the same trend of change among group C,group M and group S.(3)36 metabolic pathways were obtained through metabolite enrichment,among which glycerophospholipid metabolism,tryptophan-kynurenine metabolism,catecholamine metabolism and phenylalanine metabolism may be related to immunosuppression,while xanthine-uric acid metabolism may be related to acute kidney injury after burn。2.Animal experiments(1)The serum metabolomics of burn rat models in group M(TBSA5%,TBSA20%)and group S(40%,80%)were compared.231 metabolites were obtained.The serum metabolomics of burn rat models in group C(healthy control group)and group M(TBSA5%,TBSA 20%)were compared.We obtained 155 metabolites,among which 94 metabolites from group M and group S showed the same trend of change among group C,group M and group S.(2)The skin at the burn site of the modeling group was deep second-degree burns,and the damage of kidney,lung,and liver tissues in the modeling group was gradually aggravated with the increase of the burn area,among which the damage of kidney was the most seriously affected by the burn,while the heart and small intestine were not affected by the burn and showed regular damage trend.(3)Through the comparison of human and animal metabolomics data,we found that 27 metabolites appeared in the two experimental results,and 20 of them showed the same trend of change.In addition to the metabolic pathways of glycerophospholipid metabolism,tryptophan-kynurenine metabolism,catecholamine metabolism,phenylalanine metabolism,xanthine-uric acid metabolism,they also involved the citric acid cycle.The glycerophospholipid metabolic pathway is most affected by differential metabolomics,and the disruption of lipid metabolism involved in this metabolic pathway may be associated with immunosuppression and acute kidney injury(AKI)after burn.The overall trend of metabolites is that with the increase of burn severity,the metabolic pathway of citric acid cycle is inhibited.The gradual increase of catecholamines and acylcarnitines suggests the gradual enhancement of hypermetabolism,while the gradual increase of phenylalanine and the gradual decrease of LPC suggest the adverse prognosis caused by the continued development of hypermetabolism.Low levels of tryptophan and high levels of kynurenine suggest overexpression of immune activation,and immunosuppression increases the risk of sepsis,septic shock,and multiple organ failure.The disorder of purine metabolism increases the level of high concentration of xanthine,uric acid deposition in the kidney and various nephrotoxic substances,aggravating AKI after burn.In addition,low levels of LysoPC(16:1(9Z)/0:0)and high levels of choline are the two endogenous metabolites with the highest diagnostic value for burn severity,and their superior performance in ROC curve suggests that they can predict hypermetabolic development after severe burn.conclusion(1)The degree of organ injury after burn is positively correlated with the degree of hypermetabolism after burn,and the kidney injury is the most seriously affected by the hypermetabolism after burn.(2)Increased immunosuppression may be associated with elevated hypermetabolism after burn;(3)Hypermetabolism may lead to immunosuppression and poor prognosis through glycerophospholipid metabolism,tryptophan-kynurenine metabolism,catecholamine metabolism,phenylalanine metabolism.Hypermetabolism may aggravate AKI after burn through xanthine-uric acid pathway;(4)LysoPC(16:1(9Z)/0:0)and choline are endogenous metabolites with the highest diagnostic value for burn severity and can predict high metabolic development after severe burn.(5)The metabolomics method based on UPLC-MS can help us better classify burn patients with different degrees,and the characteristic differential metabolites obtained from it can provide important evidence for personalized treatment of burn patients. |
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