Relationship Between C-peptide And Diabetic Retinopathy In Patients With Type 2 Diabetes Mellitus

ObjectiveThe prevalence of diabetes mellitus is increasing year by year and has become one of global public health issues.Diabetic retinopathy(DR),one of the chronic microvascular complications of diabetes,remains a main cause of blindness in the labor population.A large number of studies at home and abroad have shown that the course of diabetes,glycosylated hemoglobin and systolic blood pressure level are independent risk factors for DR,while the relationship between C-peptide,uric acid,lipid,BMI and DR remains controversial.In recent years,C-peptide has been proved to be an active peptide with important physiological functions and intracellular signal transduction functions,which may play a role in diabetic microvascular diseases.However,there is few studies focus on C-peptide and DR of T2 DM.The purpose of this study is to investigate the correlation between serum C-peptide and Type 2 diabetic retinopathy,and to explore its clinical significance and other risk factors associated with DR.We aim to provide more clinical evidence for preventing and delaying the incidence and development of DR.MethodsThis retrospective study has identified 550 Type 2 diabetic patients who were hospitalized for treatment at Department of Endocrinology and Metabolism of Tianjin Medical University General Hospital from 2013 to 2019.Collect clinical data,including general data: name,gender,age,duration of diabetes,SBP,DBP,BMI,history of hypertension,family history of diabetes,smoking history,and lower limb arterial disease;Laboratory indicators: glycosylated hemoglobin(Hb A1c),total cholesterol(TC),triglyceride(TG),high-density lipoprotein(HDL-C),low-density lipoprotein(LDL-C),serum uric acid(SUA),serum creatinine(SCR),creatinine clearance(CCR),24-hour urinary microalbumin;Oral glucose tolerance test and C-peptide release test were performed,and serum C-peptide were measured after 0h,0.5h,1h,2h and 3h.All patients were examined in the ophthalmic examination room by professionals to complete the non-mydriatic fundus photography.The 550 patients were divided into two groups according to the characteristics of fundus lesions.The group without DR(NDR)and the group with diabetic retinopathy(DR).The DR group was divided into three groups: mild lesion group(NPDR stage I),moderate lesion group(NPDR stage II)and severe lesion group(NPDR stage III and PDR).Statistical Analysis: Using SPSS22.0 to analyze the data.Those variables conformed to the normal distribution were expressed as mean ± standard deviation,while those conformed to the non-normal distribution were expressed as median(P25,P75).The independent sample t-test was used for the comparison of continuous variables with normal distribution between the two groups,while the non-parametric test was used for those non-normal distribution.Continuous variables were compared by using a one way analysis of variance(ANOVA)test while frequency of dichotomous variables was performed by chi-square test analysis.The counting data were expressed as percentages,and the R×C chi-square test was used for inter-group comparisons.Spearman correlation analysis was used to analyze the relationship between C-peptide and other variables.The risk factors of DR were analyzed by Logistic regression model.All P-values were considered significant at P< 0.05.Results1.Overall,264 patients(48.0%)had DR.Patients with DR had higher age,longer duration of diabetes,higher prevalence of hypertension,SBP and 24-hour urinary microalbumin(P<0.05),but lower 2h-postprandial C-peptide(2h CP)(P<0.05)than NDR.There was no significant difference in gender,family history,smoking history,BMI,DBP,lower limb lesions,lipid profile,uric acid,renal function,FPG,2h PG,Hb A1 c,FCP and other biochemical indicators(P >0.05).2.The difference of 24-hour urinary microalbumin between the three groups with mild,moderate and severe lesions was statistically significant(P<0.05).The differences of 2h CP,age at diagnosis of diabetes,SCR,CCR,FPG and PPG between the moderate and severe lesions groups were statistically significant(P<0.05).3.There were statistically significant differences in the prevalence of DR among groups,after delamination of fasting C-peptide and Postprandial 2h CP(P<0.05).4.Univariate Logistic regression analysis showed that age,duration of diabetes,SBP,CCR,2h CP and 24-hour urinary microalbumin were the influencing factors of DR.In the binary multivariate Logistic regression analysis,Hb A1 c and BMI were included in addition to the indicators with significant differences in the single factor.The results showed that: 2h CP was the protective factor for DR,while the duration of diabetes,SBP and 24-hour urinary microalbumin were the risk factors for DR.5.The level of 2h CP was positively correlated with age at diagnosis of diabetes,BMI,FCP,TG and SUA(P<0.05),while was negatively correlated with the duration of diabetes,insulin use rate,FPG,2h PG,Hb A1 c and HDL-C(P<0.05).Conclusion1.Serum C-peptide was correlated with type 2 diabetic retinopathy,and the correlation between postprandial C-peptide and DR was more significant.The higher level of 2h CP was an independent protective factor of DR.Protection of islet function plays an important role in delaying the incidence and development of DR.2.The duration of diabetes,SBP and 24-hour urinary microalbumin are risk factors for DR.