A Preliminary Study Of SRAGE Expression In Critically Ill Patients Of Hyperglycemia And The Effect Of Insulin Therapy On SRAGE Expression

[Background]Stress hyperglycemia represents an important independent prognostic factor in critically ill patients admitted to ICU. However, stress-induced hyperglycemia with critically ill patients distinguished from hyperglycemia patients with diabetes or other secondary hyperglycemia. Compared to critically ill patients without diabetes, the ICU mortality and hospital mortality were significantly decreased in critically ill diabetic patients and the non-diabetic patients benefit more from insulin treatment. The complication incidence of type-2 diabetic patients with hyperglycemia who have had insulin treatment was also lower than non-diabetic patients with stress hyperglycemia. Meta-analysis showed that the hospital mortality of non-diabetic patients with hyperglycemia are 26.7%, obviously higher than diabetes patients (12.5%); and in ICU, the mortality of non-diabetic stress hyperglycemia patients were two times higher than diabetic patients (25.3%:12.8%). These clinical evidence indicate that historically diabetes may be a protecting factor of critically ill patients. The exact mechanism behind the prognosis difference between diabetic and non-diabetic patients is still unknown. Now it’s widely considered that under the stimulation of long-term chronic hyperglycemia, our body may have to adapt with hyperglycemia over time. Having a history of diabetes and prior episodes of hyperglycemia may provide time for the immune system to adapt with hyperglycemia and result in a reduced mortality risk. But there is no relevant study about the essential discuss of this clinical phenomenon.RAGE(receptor for advanced glycation end products,RAGE) is a multiligand member of immunoglobulin superfamily cell-surface receptor. Engagement of ligands with their receptor-RAGE participate in the pathological process of a series of diseases, such as strengthened oxidizing reaction, alteration of cell function and resulting the alteration of the local tissue microenvironment, enhancement of immune response and inflammatory reactions, etc. It has been discovered that ligands-RAGE axes correlated with the pathological process of some chronic diseases, such as diabetes mellitus, cardiovascular disease, tumour and neural degeneration. As a new target spot of disease treatment, RAGE has been followed with interest by numerous researchers, and its subtype’s biological functions gradually arouse attentions. sRAGE is a special subtype of RAGE, which can express biological effects different from RAGE. Acting as a competitor with full RAGE for ligand binding sequester RAGE ligands, sRAGE could restrain the transfer of downstream signals and protect relevant cells from the adverse effect of ligands-RAGE axis’excessive activation. Now, researchers have confirmed that sRAGE is an endogenous protective factor antagonizing the damages induced by RAGE, and it can be considered as a biomarker to reflect the pathological changes. The clinical research about sRAGE mostly focused on patients with chronic disease, and the research of sRAGE with critically ill patients or patients who have acute disease was not clearly observed.Stress hyperglycemia is an important indicator in critical situations and evaluation of prognosis. It has great clinical significance to correct glucose metabolism disorders of critically ill patients in improving the prognosis. Insulin therapy is the main and most effective method of glycemia control in the ICU. With the long-term chronic stimulation of hyperglycemia, AGEs level in diabetic patients is significantly higher than normal people. The chronic accumulation of AGEs in vivo, as well as the loss of the role of AGEs-RAGE axis, is an important cause of diabetes complications. But as an endogenous protection factor, sRAGE has a protective effect in complications of diabetes as well as in macrovasculars. Critically ill patients under stress due to the presence of oxidative stress and inflammation may lead to the generation of a large number of AGEs, which may lead to changes in RAGE and sRAGE levels. Whether there are differences of sRAGE expression between critically ill patients with diabetes and non-diabetic and whether the differences could indicate the prognosis differences or act as a predictor for adverse outcomes, or there is a influence of insulin treatment on sRAGE expression,there are still no such related researches be reported.[Objective]A predesigned analysis was conducted to measure the levels of serum AGEs、 sRAGE and IL-6 in critically ill patients with or without diabetes by time, investigating serum levels of soluble receptor for advanced glycation end products in critically ill patients and the association of sRAGE levels with other clinical markers and prognosis, analyzing the influence of insulin treatment on sRAGE expression and discuss the clinical significance of individualized glucose control, which will intend to provide further theoretical foundation for clinical research of AGEs-RAGE-sRAGE axes.[Method]Prospectively collected samples from 116 critically ill patients with hyperglycemia in ICU. The inclusion criteria were the following:the length of ICU stay is above 7 days, APACHE-Ⅱ grades≥15 and they were above 18 years old; they were not included if they had brain death, end-stage of chronic disease, end-stage of cancer in hopelessly situations. Within these patients,46 patients were diagnosed as type-2 diabete,70 patients were non-diabetes and HbAlc less than 6.5%. Diagnosis of diabetes was based on the history as established by the patient prior to ICU admission. And 25 subjects were used as control with their gender and age matched. Thiese people were at least 18 years old and FPG<6.0mmol/L,2hPG<7.8mmol/L; the exclusion criteria was liver and kidney dysfunction, history of diabetes, cardiovascular disease and tumor. Critically ill patients are divided into diabetic group and non-diabetic group according to with or without history of diabetes. Depending on the blood glucose control targets, patients were randomly divided into two groups, one of which is intensive insulin therapy group, and the other is improved insulin therapy group. The glucose concentration in patients of intensive group will be control in 4.4-6.1mmol/L, while that in improved group will be set in 8-10mmol/L. Blood samples were detected in each group of patients, at the 1st,3rd, and 7th day after they are admitted to hospital. The level of serum AGEs, sRAGE, IL-6, and CRP, as well as other clinical data, biochemical parameters, and general and critical score of patients (APACHE-Ⅱ and SOFA scores) are collected and recorded. In different time points and different insulin treatments, the differences in expression of the serum CRP, IL-6 and AGEs, sRAGE are observed.[Results]1. The average age of critically ill patients with diabetes in critically ill patients is higher than non-diabetic hyperglycemia and normal control group, the difference was statistically significant (F= 7.419, P= 0.001); gender composition of the three groups was not statistically different (x2= 0.072, P= 0.965); the blood glucose, HbAlc, AGEs, sRAGE and IL-6 levels in critically ill patients with diabetes and critically ill patients with non-diabetic were higher than normal control group; the blood glucose, HbAlc, AGEs, sRAGE levels in critically ill patients with diabetes were higher than non-diabetic patients; serum IL-6 levels in critically ill patients with diabetes is less than non-diabetic patients, the differences between the two groups was statistically significant (F= 205.056, P= 0.000; F= 143.967, P= 0.000; F= 42.577, P= 0.000; F= 103.992, P= 0.000; F = 52.226, P= 0.000).2. The disease spectrum between critically ill patients with diabetes and non-diabetic constitute no significant difference(P> 0.05). There were no significant differences of baseline between intensive and improved insulin group for critically ill patients.3. Regression analysis showed that, SOFA score, APACHE-II score, serum Cr and blood levels of AGEs were factors which influenced the sRAGE expression in critically ill patients with diabetes. After eliminating the influence of other factors, AGEs was still the factor influcencing sRAGE expression. SOFA score, serum creatinine and AGEs levels were factors which influence the sRAGE expression of non-diabetic patients, after eliminating the effects of other factors, SOFA score, APACHE-II score and AGEs were still the influencing factors of sRAGE expression. In order to explore grouping factors affecting the expression of sRAGE, a generated consolidated patients were analysised and age, blood glucose, HbAlc, AGEs levels and grouping factor (diabetes mellitus) were influcencing factors of sRAGE expression, after eliminating the effects of factors of various other factors, AGEs and diabetes remain factors influencing sRAGE expression.4. Cox regression survival analysis models showed:APACHE-Ⅱ score, blood glucose, IL-6 and sRAGE were factors which influenced 28-days survival and sRAGE was a protective factor (RR= 0.331, P= 0.037), the other factors were dangerous factors; diabetes had no effect on 28-days survival (P> 0.05).5. The serum CRP, IL-6, and AGEs levels of critically ill diabetes patients in intensive and improved groups were decreasing over time, and the repeated measures analysis of timing differences was statistically significant (F= 15.143, P= 0.000; F= 7.130, P= 0.000; F= 15.371, P= 0.000), but the difference between groups were not significant.6. The level of sRAGE in improved group decreased in the 3rd day compared with that of the 1st day. However, the level in the 7th day increased when compared with that of the 3rd day. The time difference was statistically significant (F= 10.728, P= 0.000). Repeated measures analysis of diabetes in the intensive group, the main time effect of improved group, main grouping effects, and interaction effect in grouping and time were all statistically significant (F= 6.847, P= 0.003; F= 14.136, P= 0.000; F= 10.642, P= 0.000).7. The expression of serum CRP, IL-6, and AGEs in critically ill patients with non-diabetic group declined over time, and the difference was statistically significant (F= 57.810, P= 0.000; F= 34.683, P= 0.000; F= 41.973, P= 0.000).8. The expression of sRAGE declined by time, but the difference was not statistically significant (F= 0.576, P= 0.547). The difference in repeated measures analysis grouping effect, and other parameters between intensive and improved groups was not statistically significant.[Conclusions]1. The serum levels of sRAGE and AGEs were higher in critically ill patients and the elevated sRAGE positively correlated with AGEs, whether with or without diabetes, which means that the elevated serum levels of sRAGE may contribute to the elevated serum levels of AGEs.2. Previous history of diabetes was a factor which could influcence the sRAGE expression.3. High sRAGE level was a protective factor affecting the prognosis of critically ill patients, which maybe a protective factor influencing the prognosis of diabetic critically ill patients.4. The levels of inflammatory factors such as serum IL-6, CRP were declined by time in critically ill patients with or without diabetes.5. The expression of serum AGEs and sRAGE were decreased by time in non-diabetic patients with hyperglycemia of critically ill patients.6. Two different insulin therapies vary greatly in affecting expression of serum sRAGE in critically ill patients with diabetes, Due to the significant difference of serum sRAGE expression between diabetic and non-diabetic patients, it might be more clinical benefit to give different therapy to diabetes patients distinguished from non-diabetic patients.