Future clinical prospects of C-peptide testing in the early diagnosis of gestational diabetes

Gestational diabetes is typically diagnosed in the late second or third trimester of pregnancy.It is one of the most common metabolic disorders among expectant mothers,with potential serious short-and long-term complications for both maternal and offspring health.C-peptide is secreted from pancreatic beta-cells into circulation in equimolar amounts with insulin.It is a useful biomarker to estimate the beta-cell function because it undergoes negligible hepatic clearance and consequently it has a longer half-life compared to insulin.Pregnancy induces increased insulin resistance due to physiological changes in hormonal and metabolic homeostasis.Inadequate compensation by islet beta-cells results in hyperglycemia.The standard oral glucose tolerance test at 24-28 wk of gestation sets the diagnosis.Accumulated evidence from prospective studies indicates a link between early pregnancy C-peptide levels and the risk of subsequent gestational diabetes.Elevated C-peptide levels and surrogate glycemic indices at the beginning of pregnancy could prompt appropriate strategies for secondary prevention.

C-peptide and Diabetic Encephalopathy

With the changes of life style, diabetes and its complications have become a major cause of morbidity and mortality. It is reasonable to anticipate a continued rise in the incidence of diabetes and its complications along with the aging of the population, increase in adult obesity rate, and other risk factors. Diabetic en- cephalopathy is one of the severe microvascular complications of diabetes, characterized by impaired cogni- tive functions, and electrophysiological, neurochemical, and structural abnormalities. It may involve direct neuronal damage caused by intracellular glucose. However, the pathogenesis of this disease is complex and its diagnosis is not very clear. Previous researches have suggested that chronic metabolic alterations, vascular changes, and neuronal apoptosis may play important roles in neuronai loss and damaged cognitive functions. Multiple factors are responsible for neuronal apoptosis, such as disturbed insulin growth factor （IGF） system, hyperglycemia, and the aging process. Recent data suggest that insulin/C-peptide deficiency may exert a primary and key effect in diabetic encephalopathy. Administration of C-peptide partially improves the condition of the IGF system in the brain and prevents neuronal apoptosis in the hippocampus of diabetic patients. Those findings provide a basis for application of C-peptide as a potentially effective therapy for diabetes and diabetic encephalopathy.

C-peptide as a key risk factor for non-alcoholic fatty liver disease in the United States population

AIM To determine whether fasting C-peptide is an independent predictor for non-alcoholic fatty liver disease(NAFLD) in United States population.METHODS Using the National Health and Nutrition Examination Survey(NHANES) 1988-1994, NAFLD participants aged 20 or greater without any other liver diseases were included in this study. Excessive alcohol intake is defined as > 2 drinks per day for males and > 1 drink per day for females. C-peptide and 27 other factors known to be associated with NAFLD(e.g., age, gender, body mass index, waist circumference, race/ethnicity, liver chemistries, and other diabetes tests) were tested in both univariate and multivariate level using logistic regression with a P-value 0.05.RESULTS Of 18825 participants aged ≥ 20, 3235 participants(n = 3235) met inclusion criteria. There were 23 factors associated with NAFLD by univariate analysis. 9 factors, ranked by the highest change in pseudo R2, were found to be significant predictors of NAFLD in multivariate model: waist circumference, fasting C-peptide, natural log of alanine aminotransferase(ALT), total protein, beingMexican American, natural log of glycated hemoglobin, triglyceride level, being non-Hispanic white, and ferritin level. CONCLUSION Together with waist circumference and ALT, fasting C-peptide is among three most important predictors of NAFLD in United States population in the NHANES data set. Further study is needed to validate the clinical utility of fasting C-peptide in diagnosis or monitoring insulin resistance in NAFLD patients.

Pathological consequences of C-peptide deficiency in insulin-dependent diabetes mellitus

Diabetes is associated with several complications such as retinopathy, nephropathy, neuropathy and cardiovascular diseases. Currently, insulin is the main used medication for management of insulin-dependentdiabetes mellitus(type-1 diabetes). In this metabolic syndrome, in addition to decrease of endogenous insulin, the plasma level of connecting peptide(C-peptide) is also reduced due to beta cell destruction. Studies in the past decade have shown that C-peptide is much more than a byproduct of insulin biosynthesis and possess different biological activities. Therefore, it may be possible that C-peptide deficiency be involved, at least in part, in the development of different complications of diabetes. It has been shown that a small level of remaining C-peptide is associated with significant metabolic benefit. The purpose of this review is to describe beneficial effects of C-peptide replacement on pathological features associated with insulin-dependent diabetes. Also, experimental and clinical findings on the effects of C-peptide on wholebody glucose utilization, adipose tissue metabolism and tissues blood flow are summarized and discussed. The hypoglycemic, antilipolytic and vasodilator effects of C-peptide suggest that it may contribute to fine-tuning of the tissues metabolism under different physiologic or pathologic conditions. Therefore, C-peptide replacement together with the classic insulin therapy may prevent, retard, or ameliorate diabetic complications in patients with type-1 diabetes.

Research Progress of C-Peptide and Its Physiological Function

As a product in the process of insulin synthesis, C-peptide’s physiological function is still not very clear. Recent studies have shown that C-peptide has many potential cell targets and has biological effects on a variety of tissue systems in humans and other animals. In this paper, the effects of C-peptide on diabetic complications, reproductive endocrine system, blood system, tissue repair, and neoplastic diseases were reviewed to provide references for further clarification of c-peptide related problems.

Level of Fasting C-Peptide as a Predictor of <i>β</i>-Cell Function in Sudanese Patients with Type 2 Diabetes Mellitus

Objective: In this study, we assessed the level of fasting C-peptide as a predictor of β-cell function and insulin resistance in patients with Type 2 diabetes mellitus (T2DM), Gezira State-Sudan. Methods: In this cross-sectional study, 100 T2DM patients attending the Diabetic patients care Centre were recruited, thirty five patients were males and sixty five were females, the mean age of the patients was 50.29 ± 0.456 years, and body mass index (BMI) was 26.54 ± 0.437. We estimated β-cell function using fasting C-peptide levels;homeostatic model assessment for β-cell function (HOMA-B) and insulin resistance (HOMA-IR) were calculated from C-peptide and fasting blood glucose (FBG). Results: C-peptide was significantly and positively correlated with HOMA-B and HOMA-IR. FBG also showed significant negative correlation with HOMA-B, but was positively and significantly correlated with HOMA-IR. HbA1c was negatively and significantly correlated with HOMA-B. Patients with low C-peptide levels had increased FBG and HbA1c level, while patients with high C-peptide levels were having high HOMA-IR and HOMA-B. Conclusions: Fasting C-peptide is a useful marker of pancreatic β-cell function, and its circulating levels could be used to evaluate insulin secretion and insulin resistance. Moreover, HOMA-IR is an effective index to achieve glycemic control by appropriate pharmacologic treatment of T2DM.

Inverse relationship between glomerular hyperfiltration and C-peptide level in Type 1 diabetes

Background: Increased glomerular filtration rate (GFR) commonly develops in early diabetes and is closely correlated with the development of diabetic nephropathy. Objective: The aim was to study the relationship between GFR, C-peptide level and other parameters at diagnosis of Type 1 diabetes. Methods: We determined GFR, Cpeptide level, glycated hemoglobin (HbA1c), body mass index (BMI) SDS and loss of weight at diagnosis of Type 1 diabetes in 495 children (231 females). Linear and multiple regression analysis was used to test for the associations between GFR and other parameters. Results: In the 495 patients, GFR median (interquartile range) was increased vs normal values (p = 0.0001). GFR was significantly negatively correlated with age (p < 0.001) and C-peptide level (p = 0.001), and positively correlated with weight loss (p = 0.02). The multiple regression analysis showed that age (p = 0.001) and C-peptide level (p = 0.05) were independently and negatively related to GFR. Conclusions: This study shows that, at onset of Type 1 diabetes, higher the GFR, younger the age and lower the C-peptide level are. The role of this hyperfiltration in the development of later nephropathy and the putative preventive effect of C-peptide administration need to be evaluated.

Role of C-Peptide in Relation to Levels of Anti-GAD and Islet Cell Antibodies in Characterizing Types of Diabetes in the Young, in Eastern India

Background: Measuring fasting C-peptide (FCP) and antibodies against Glutamic acid decarboxylase (GADA) and Islet cell antibodies (ICA) are not so commonly explored in children and young adults. Objectives: To assess the levels of FCP, GADA and ICA in subjects below the age of 25 years with DM and compare their levels to differentiate between Autoimmune and Non-Autoimmune Type 1 DM. Methodology: Blood samples of 93 subjects diagnosed with DM, reporting to the tertiary care hospital, were analysed for ICA, GADA and FCP. Receiver operating characteristics (ROC) curves were analysed to check the ability of autoimmune markers, BMI and C-peptide to differentiate between Autoimmune (Ai) and Non-Autoimmune (NonAi) diabetes. Results: 30/93 (32.2%) were positive for anti-GAD ab and/or ICA and categorised as Autoimmune (Ai), the most common antibody being, anti-GAD ab (80%) in them. The level of FCP among Ai compared to NonAi, was significantly low (p 20.75 nmol/l) as a very dependable test for diagnosing Ai, Type 1 DM, in children and young adults. Its sensitivity and specificity are in the range of 86.2% and 96.8% respectively. Low level of C-peptide (Conclusion: This study revealed predominant positivity for anti-GAD ab (80%) among Ai+ patients. ROC analysis shows GADA above 20.75 nmol/l and Fasting C-peptide < 0.36 nmol/l as a good indicator for diagnosing Ai in children and young adults.

地黄水提液对2型糖尿病大鼠proinsulin基因表达的影响

目的:探讨地黄水提液治疗2型糖尿病(2-DM)的分子生物学机制。方法:以半定量RT-PCR法和SDS-聚丙烯酰胺凝胶电泳法分别检测胰岛素原(proinsulin)基因转录及翻译水平的表达。同时观察空腹血糖(FPG)、空腹胰岛素(FINS)的含量,计算胰岛素分泌指数(IS)、β细胞功能指数(HβCI)的变化,来研究不同剂量地黄水提液对上述各指标的影响。结果:与2-DM模型相比,地黄治疗组大鼠proinsulin基因mRNA和蛋白表达显著增高(P<0.01),FPG显著降低,FINS、IS、HβCI升高,差异均有显著性。结论:地黄水提液通过上调2-DM大鼠proinsulin基因mRNA和蛋白表达,可改善胰岛β细胞功能,降低2-DM大鼠血糖。

Significant association of insulin and proinsulin with clustering of cardiovascular risk factors

AIM: To investigate the association between true insulin and proinsulin and clustering of cardiovascular risk factors.METHODS: Based on the random stratified sampling principles, 1196 Chinese people (533 males and 663 females,aged 35-59 years with an average age of 46.69 years) were recruited. Biotin-avidin based double monoclonal antibody ELISA method was used to detect the true insulin and proinsulin, and a risk factor score was set to evaluate individuals according to the number of risk factors.RESULTS: The median (quartile range) of true insulin and proinsulin was 4.91 mIu/L (3.01-7.09 mIu/L) and 3.49 pmol/L (2.14-5.68 pmol/L) respectively, and the true insulin level of female subjects was significantly higher than that of male subjects (P = 0.000), but the level of proinsulin displayed no significant difference between males and females (P = 0.566). The results of covariate ANOVA after age and sex were controlled showed that subjects with any of the risk factors had a significantly higher true insulin level (P = 0.002 for hypercholesterolemia, P = 0.021 for high low-density lipoprotein cholesterol, P = 0.003 for low high-density lipoprotein cholesterol, and P = 0.000 for other risk factors) and proinsulin level (P = 0.001 for low high-density lipoprotein cholesterol, and P = 0.000 for other risk factors)than those with no risk factors. Furthermore, subjects with higher risk factor scores had a higher true insulin and proinsulin level than those with lower risk factor scores (P = 0.000). The multiple linear regression models showed that true insulin and proinsulin were significantly related to cardiovascular risk factor scores respectively (P = 0.000).CONCLUSION: True insulin and proinsulin are significantly associated with the clustering of cardiovascular risk factors.

Level of proinsulin in association with cardiovascular risk factors and sleep snoring

AIM: To explore the relationship between the level of proinsulin with cardiovascular risk factors and sleep snoring.METHODS: Based on the random stratified sampling principle, 1 193 Chinese residents in Pizhou City, Jiangsu Province (530 males and 663 females, aged 35-59 years with an average age of 46.69 years) were recruited. Their sleep snoring habits were investigated. Biotin-avidin based double mAbs ELISA was used to detect specific insulin and proinsulin, and a risk factor score was established to evaluate the individuals according to the number of their risk factors.RESULTS: The results of Spearman correlation analysis and covariate ANOVA analysis after age and sex were controlled, indicated that not only the level of proinsulin (r = 0.156, P = 0.000, F= 5.980 P = 0.000), but also cardiovascular risk factors score (r = 0.194, P = 0.000,F= 11.135, P = 0.000) significantly associated with the frequency of sleep snoring, and the significant relationship between true insulin and frequency of sleep snoring was only shown in the covariate ANOVA analysis (F = 2.868,P = 0.022). The result of multivariate stepwise logistic regression after age, sex, body mass index, waist circumference and true insulin were controlled showed that proinsulin (division by interval of quartile) was an independent risk factor for sleep snoring (OR = 1.220,95%CI: 1.085-1.373, P = 0.001).CONCLUSION: The interaction of cardiovascular risk factors clustering, high proinsulin level and sleep breathing disorder may be a syndrome, which has not been recognized in human beings so far.

Studies on the Renaturation with Simultaneous Purification of Recombinant Human Proinsulin with Unit of Simultaneous Renaturation and Purification of Protein in Semi-preparative Scale

The renaturation and purification of recombinant human proinsulin (rh-proinsulin) expressed in E. coli with the unit of simultaneous renaturation and purification of protein (USRPP) in semi-preparative scale was studied. The result shows that rh-proinsulin extracted with 8.0 mol/L urea can be renatured and purified simultaneously in 45 minutes with the USRPP (1050 mm ID). The purity of rh-proinsulin was found to be more than 90% and the mass recovery to be more than 80%. The renaturation effect of rh-proinsulin with the USRPP was tested by enzyme cleavage for obtaining insulin. In addition, the result was further confirmed with RPLC, SDS-PAGE electrophoresis, and MALDI-TOF, respectively.

25-Hydroxyvitamin D Is Associated with Islet Homeostasis in Type-2 Diabetic Patients with Abdominal Obesity

Objective Isletαcells input is essential for insulin secretion fromβcells.The present study aims to investigate the association between 25-hydroxyvitamin D[25(OH)D]and islet function homeostasis in type-2 diabetes(T2D)patients.Methods A total of 4670 T2D patients from seven communities in Shanghai,China were enrolled.The anthropometric indices,biochemical parameters,serum 25(OH)D,and islet function[including C-peptide(C-p)and glucagon]were measured.Results The fasting plasma glucose(FPG),glycated hemoglobin(HbA1c),glucagon,and C-p levels exhibited a significantly decreasing trend in T2D patients as the 25(OH)D levels increased.Next,the population was divided into two groups:abdominal obesity and non-abdominal obesity groups.After adjustment,the 25(OH)D level was found to be associated with HbA1c,glucagon,and homeostasis model assessment ofβ(HOMA-β)in the non-abdominal obesity group.There was a significant relationship between 25(OH)D and HbA1c,glucagon,HOMA-IR,baseline insulin or C-p in the abdominal obesity group.In the abdominal obesity group,the ordinary least squares(OLS)regression and quantile regression revealed that 25(OH)D was obviously associated with glucagon and fasting C-p levels.In the abdominal obesity group,the moderate analysis revealed a significant interaction effect of 25(OH)D and glucagon on C-p(P=0.0124).Furthermore,the conditional indirect effect of 25(OH)D on the glucagon/C-p ratio was significantly lower at 1 standard deviation(SD)below the mean(P=0.0002),and lower at the mean of the course of diabetes(P=0.0007).Conclusion 25(OH)D was found to be negatively correlated to glucagon and C-p in T2D patients with abdominal obesity.The 25(OH)D influenced C-p in part by influencing glucagon.The effect of 25(OH)D on the glucagon/C-p ratio in T2D patients with abdominal obesity,in terms of islet homeostasis,is influenced by the course of diabetes.

小C肽人胰岛素原类似物(B-Arg-Arg-A)和人胰岛素原(B-C-A)A、B链重组条件的研究

目的 :获得更佳的变复性条件和提高人胰岛素原的重组率。方法 :采用特有的重组方法 ,将小C肽人胰岛素原类似物 (B Arg Arg A)与人胰岛素原 (B C A)进行重组条件的比较。 结果 :发现二者在 pH10 .6左右处重组率达到最大 ,且在相同的条件下B Arg Arg A蛋白质的重组率 (94% )较B C A蛋白质 (82 % )的高。结论 :进一步验证了“胰岛素的A、B链含有足够使二硫键正确配对的结构信息”的论点。

超重及肥胖高血压患者空腹胰岛素、胰岛素原、瘦素水平与高血压的关系

目的 研究超重和肥胖高血压组和超重肥胖正常血压组病人的临床特征和代谢特点 ,比较血清胰岛素、胰岛素原、瘦素水平 ,并探讨这些因素与高血压的关系。方法 选择肥胖 /超重病人 15 2例 ,年龄 2 0～ 6 5岁 ,BMI≥ 2 5。男性 84例 ,女性 78例。高血压组 78例 ,正常血压组 74例。采用HOMA指数评价胰岛素抵抗程度。比较两组间体脂参数、代谢紊乱特点、空腹血清胰岛素、胰岛素原、瘦素水平 ,分析超重及肥胖病人发生高血压的危险因素。结果 两组胰岛素抵抗程度相同 ,高血压组腰臀比增加 ,糖代谢异常、脂代谢异常程度均大于正常血压组 ,胰岛素原水平高于正常血压组。两组之间空腹瘦素水平差异无显著性。超重及肥胖病人的增龄、腰臀比增加、胰岛素原水平、伴糖代谢异常和脂代谢异常是发生高血压的危险因素 ,经BMI校正后这一关系不再显著。结论 肥胖伴高血压病人呈内脏型肥胖趋势 ,糖代谢、脂代谢紊乱的程度高于正常血压组。肥胖病人发生高血压时已存在胰岛细胞受损。瘦素可能对肥胖病人高血压的发生没有重要作用。该组超重和肥胖病人发生高血压的主要危险因素是BMI增高目的 研究超重和肥胖高血压组和超重肥胖正常血压组病人的临床特征和代谢特点 ,比较血清胰岛素、胰岛素原、瘦素水平 ,并探讨这些因素与高?

人血清胰岛素原单克隆抗体夹心酶联免疫法的建立

目的建立灵敏、特异的酶联免疫分析法测定人血清胰岛素原，用以评价胰岛β细胞功能。方法选用可同时与胰岛素原形成夹心结合的抗人C肽单抗和抗人胰岛素单抗，分别包被塑料微孔条作团相抗体和生物素化后作液相抗体，再以亲和素连接的辣根过氧化物酶放大检测信号，通过酶底物显色，判定胰岛素原浓度。结果方法的灵敏度为0．9pmol／L，曲线工作范围0．9～200pmol／L，批内批间变异系数分别小于8．9％和11．2％，平均回收率94％（82％～114％），稀释曲线和标准曲线平行，方法与高浓度的人胰岛素和C肽（5000pmol／L）均未见交叉反应。结论本方法具有灵敏度高、特异性强、操作简便和无同位素污染等优点，适于大批量标本测定胰岛素原及其临床意义的深人探讨。

人胰岛素原类似物(BKRA)基因的合成与表达

为了利用基因工程生产胰岛素，按照已知的人胰岛素Ａ、Ｂ链氨基酸序列和大肠杆菌偏爱的氨基酸密码子设计并合成了人胰岛素原类似物（ＢＫＲＡ）基因，其中以赖（Ｋ）－精（Ｒ）二肽编码区取代人胰岛素原Ｃ肽编码区．为了避免其编码蛋白在大肠杆菌中表达时被降解，通过人工接头将２个ＢＫＲＡ基因串联起来，接头部分氨基酸序列为Ａｒｇ－Ａｒｇ－Ａｓｎ－Ｓｅｒ．将串联的ＢＫＲＡ基因克隆到表达载体ｐＥＴ－２８ａ（＋），实现了在大肠杆菌中的融合表达，表达产物以包含体形式存在，约占细菌总蛋白２４％．表达产物氨基末端具有六组氨酸肽段，以ＨｉＴｒａｐ凝胶进行亲和层析，一步纯化可达纯度９５％以上．放射免疫测定表明，纯化的融合蛋白具有胰岛素抗原活性．

血清胰岛素原在静脉葡萄糖耐量试验中的分泌和释放

目的 研究不同水平的胰岛素抵抗和 β细胞功能状态下的血清胰岛素原水平以及静脉葡萄糖负荷后的胰岛素原分泌情况。 方法 2 5例单纯性肥胖、2 1例糖耐量受损 (IGT)、19例 2型糖尿病 (T2DM )患者和 11名正常对照者在完成静脉葡萄糖耐量试验 (IVGTT)后 ,采用放射免疫测定法 (RIA)测定其血清空腹胰岛素原水平 ,并进行相关性分析。 结果 单纯性肥胖组、IGT组和T2DM组患者的空腹胰岛素原水平明显高于正常对照组 (对照组 ) ,3组间差异无显著意义。葡萄糖负荷后的胰岛素原分泌曲线在 4组中均呈单峰式 ,但高峰在单纯肥胖、IGT组和T2DM组中后移。总的胰岛素原分泌曲线下面积在 3组间差异无显著意义 ,均显著高于对照组。 结论 空腹胰岛素原水平很大程度上取决于机体的胰岛素抵抗和血糖 (空腹或餐后 )的水平。葡萄糖负荷后的胰岛素原释放在胰岛素抵抗人群中显著增加 ,释放高峰后移。单纯肥胖阶段的高胰岛素血症被高胰岛素原血症所修饰 ,预示在该阶段可能已出现

(His)_6-Arg-Arg-人胰岛素原在大肠杆菌中的高效表达(英文)

为了提高胰岛素原的表达量 ,用pQE 40质粒构建了 (His) 6 Arg Arg 人胰岛素原 [(His) 6 Arg Arg humanProinsulin ,RRhPI]的大肠杆菌表达系统。通过培养条件的优化 ,在摇瓶培养的条件下 ,目标产物RRhPI以包涵体形式获得了高效表达 ,每升培养基收获湿菌体约 2 7g ,包涵体 6g(干重 1 .8g) ,RRhPI约5 4 0mg。该水平已超过现有文献报道的摇瓶培养的最高水平。

糖耐量减低人群胰岛β细胞功能的变化

131例正常糖耐量,120例糖耐量减低和107例2型糖尿病患者的研究显示,胰岛素原(PI)呈递增,而胰岛素敏感指数、HOMA-β和△I30/△G30呈递减倾向。肥胖组HOMAβ-,胰岛素、C肽和胰岛素原的曲线下面积均高于非肥胖组。