Clinical Utility and Cross-Reactivity of Insulin and C-Peptide Assays by the Lumipulse G1200 System

BACKGROUND: Measurement of insulin and C-peptide concentrations is important for deciding whether insulin treatment is required in diabetic patients. We aimed to investigate the analytical performance of insulin and C-peptide assays using the Lumipulse G1200 system (Fujirebio Inc., Tokyo, Japan). METHODS: We examined the precision, linearity, and cross-reactivity of insulin and C-peptide using five insulin analogues and purified proinsulin. A method comparison was conducted between the Lumipulse G1200 and Roche E170 (Roche Diagnostics, Mannheim, Germany) systems in 200 diabetic patients on insulin treatment. Reference intervals for insulin and C-peptide concentrations were determined in 279 healthy individuals. RESULTS: For insulin and C-peptide assays, within-laboratory precision (% CV) was 3.78–4.14 and 2.89–3.35%, respectively. The linearity of the insulin assay in the range of 0–2,778 pmol/L was R2=0.9997, and that of the C-peptide assay in the range of 0–10 nmol/L was R2=0.9996. The correlation coefficient (r) between the Roche E170 and Lumipulse G1200 results was 0.943 (P < 0.001) for insulin and 0.996 (P < 0.001) for C-peptide. The mean differences in insulin and C-peptide between Lumipulse G1200 and the Roche E170 were 19.4 pmol/L and 0.2 nmol/L, respectively. None of the insulin analogues or proinsulin showed significant cross-reactivity with the Lumipulse G1200. Reference intervals of insulin and C-peptide were 7.64–70.14 pmol/L and 0.17–0.85 nmol/L, respectively. CONCLUSIONS: Insulin and C-peptide tests on the Lumipulse G1200 show adequate analytical performance and are expected to be acceptable for use in clinical areas.

Structural Analysis of Recombinant Human Preproinsulins by Structure Prediction, Molecular Dynamics, and Protein-Protein Docking

More effective production of human insulin is important, because insulin is the main medication that is used to treat multiple types of diabetes and because many people are suffering from diabetes. The current system of insulin production is based on recombinant DNA technology, and the expression vector is composed of a preproinsulin sequence that is a fused form of an artificial leader peptide and the native proinsulin. It has been reported that the sequence of the leader peptide affects the production of insulin. To analyze how the leader peptide affects the maturation of insulin structurally, we adapted several in silico simulations using 13 artificial proinsulin sequences. Three-dimensional structures of models were predicted and compared. Although their sequences had few differences, the predicted structures were somewhat different. The structures were refined by molecular dynamics simulation, and the energy of each model was estimated. Then, protein-protein docking between the models and trypsin was carried out to compare how efficiently the protease could access the cleavage sites of the proinsulin models. The results showed some concordance with experimental results that have been reported; so, we expect our analysis will be used to predict the optimized sequence of artificial proinsulin for more effective production.

Mesenchymal Stem Cell Differentiation into Adipocytes Is Equally Induced by Insulin and Proinsulin In Vitro

BACKGROUND AND OBJECTIVES: In advanced β-cell dysfunction, proinsulin is increasingly replacing insulin as major component of the secretion product. It has been speculated that proinsulin has at least the same adipogenic potency than insulin, leading to an increased tendency of lipid tissue formation in patients with late stage β-cell dysfunction. METHODS AND RESULTS: Mesenchymal stem cells obtained from liposuction material were grown in differentiation media containing insulin (0.01 μmol), proinsulin (0.01 μmol) or insulin+proinsulin (each 0.005 μmol). Cell culture supernatants were taken from these experiments and an untreated control at weeks 1, 2, and 3, and were stored at −80°C until analysis. Cell differentiation was microscopically supervised and adiponectin concentrations were measured as marker for differentiation into mature lipid cells. This experiment was repeated three times. No growth of lipid cells and no change in adiponectin values was observed in the negative control group (after 7/14/12 days: 3.2±0.5/3.3±0.1/4.4±0.5 ng/ml/12 h). A continuous differentiation into mature adipocytes (also confirmed by Red-Oil-staining) and a corresponding increase in adiponectin values was observed in the experiments with insulin (3.6±1.9/5.1±1.4/13.3±1.5 ng/ml/12 h; p < 0.05 week 1 vs. week 3) and proinsulin (3.3±1.2/3.5±0.3/12.2±1.2 ng/ml/12 h; p < 0.05). Comparable effects were seen with the insulin/proinsulin combination. CONCLUSIONS: Proinsulin has the same adipogenic potential than insulin in vitro. Proinsulin has only 10~20% of the glucose-lowering effect of insulin. It can be speculated that the adipogenic potential of proinsulin may be a large contributor to the increased body weight problems in patients with type 2 diabetes and advanced β-cell dysfunction.

Hiperinsulinismo endógeno: dois desafios diagnósticos / Endogenous hyperinsulinism: two diagnostic challenges

A hipoglicemia em um adulto aparentemente saudável é um achado raro na prática clínica que exige uma investigação exaustiva da causa. A identificação de glicemia plasmática diminuída associada a concentrações plasmáticas de insulina e peptídeo-C não suprimidos deverá levar à exclusão de causas raras de hipoglicemia, entre elas, doença das células betapancreáticas e hipoglicemia autoimune. Neste artigo, descrevemos dois casos de hipoglicemia associada a hiperinsulinismo endógeno, cujas causas são pouco habituais na prática clínica. A propósito desses casos clínicos revemos aspectos importantes de diagnósticos e tratamento da hipoglicemia no contexto de hiperinsulinismo endógeno.

Hypoglycemia in apparently healthy adults is a rare finding in clinical practice requiring a thorough investigation of the cause. During the investigation, identification of hypoglycemia associated with inappropriately high levels of insulin and C-peptide should prompt the exclusion of rare causes of hypoglycemia, including pancreatic islet-cells disease and autoimmune hypoglycemia. In this paper, we describe two cases of hypoglycemia associated with endogenous hyperinsulinism, whose causes are uncommon in clinical practice, and review important aspects of the diagnosis and treatment of hyperinsulinemic hypoglycemia.

Carboxypeptidase-beta from Bubalus bubalus pancreas: purification, properties and MALDI-TOF monitored activation of proinsulin

Carboxypeptidase-B [E.C 3.4.17.2] catalyzes the hydrolysis of peptides and esters at C-terminus of arginine and lysine residues. Our study describes the large scale purification, N-terminal sequence analysis and physiochemical properties of pancreatic enzyme from river buffalo [Bubalus bubalis]. The enzyme was purified up to 71 folds by anionexchange chromatography with 21% final recovery. Purified enzyme displayed two bands on SDS-PAGE with molecular weights of 9 kDa and 26 kDa respectively, the N-terminal sequence of later was EFLDKLDFYV. The enzyme has shown optimum activity at pH 9.0 and 40°C. The K[M], Kcat and K[cat]/K[M] values of purified carboxypeptidase-B with Hippuryl-LArg are 30 micro M, 72sec[-1] and 2.4x10[5] M[-1] sec[-1] respectively. A computer based model for the structure of enzyme was proposed by chromatographic studies of component fragments and N-terminal sequence. The enzyme purified in the present study was free of carboxypeptidase A and endoprotease contamination. It was efficiently used in the processing of recombinant buffalo proinsulin, in combination with trypsin. Activation of proinsulin was monitored by MALDI-TOF analysis of peptides before and after the action of enzymes

Hypothyroidism decreases proinsulin gene expression and the attachment of its mRNA and eEF1A protein to the actin cytoskeleton of INS-1E cells

The actions of thyroid hormone (TH) on pancreatic beta cells have not been thoroughly explored, with current knowledge being limited to the modulation of insulin secretion in response to glucose, and beta cell viability by regulation of pro-mitotic and pro-apoptotic factors. Therefore, the effects of TH on proinsulin gene expression are not known. This led us to measure: a) proinsulin mRNA expression, b) proinsulin transcripts and eEF1A protein binding to the actin cytoskeleton, c) actin cytoskeleton arrangement, and d) proinsulin mRNA poly(A) tail length modulation in INS-1E cells cultured in different media containing: i) normal fetal bovine serum - FBS (control); ii) normal FBS plus 1 µM or 10 nM T3, for 12 h, and iii) FBS depleted of TH for 24 h (Tx). A decrease in proinsulin mRNA content and attachment to the cytoskeleton were observed in hypothyroid (Tx) beta cells. The amount of eEF1A protein anchored to the cytoskeleton was also reduced in hypothyroidism, and it is worth mentioning that eEF1A is essential to attach transcripts to the cytoskeleton, which might modulate their stability and rate of translation. Proinsulin poly(A) tail length and cytoskeleton arrangement remained unchanged in hypothyroidism. T3 treatment of control cells for 12 h did not induce any changes in the parameters studied. The data indicate that TH is important for proinsulin mRNA expression and translation, since its total amount and attachment to the cytoskeleton are decreased in hypothyroid beta cells, providing evidence that effects of TH on carbohydrate metabolism also include the control of proinsulin gene expression.

Effects of hepatic insulin gene therapy on enteric neuropathy in STZ-diabetic mice / 中南大学学报(医学版)

OBJECTIVE@#To evaluate the effect of hepatic insulin gene therapy on diabetic enteric neuropathy.@*METHODS@#Mice were randomly allocated into 3 groups: a normal control group, a diabetic group, and a diabetic gene therapy group. Diabetes were induced by penial vein injection of streptozocin (STZ). The gene therapy group received hepatic insulin gene therapy while the other 2 groups only received an empty virus expressing green fluorescent protein. Random blood glucose, body weight growth, gastric emptying, total bowel length, absolute and relative bowel transit, electric field stimulation of colon smooth muscle, colon nuclei staining and counting were measured.@*RESULTS@#We successully established a mouse model of diabetic enteric neuropathy which manifests as: 8 weeks of continuous hyperglycemia,increased total bowel length, decreased relative bowel transit, impaired colon smooth muscle relaxation and loss of inhibitory neurons in colon. Through gene therapy, the above indexes were normalized or ameliorated, suggesting hepatic insulin gene therapy is capable of preventing diabetic enteric neuropathy.@*CONCLUSION@#Hepatic insulin gene therapy can prevent STZ induced diabetic enteric neuropathy.

Translation: Executive Summary: Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus

BACKGROUND: Multiple laboratory tests are used in the diagnosis and management of patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially. APPROACH: An expert committee compiled evidencebased recommendations for the use of laboratory analysis in patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. A draft of the guidelines was posted on the Internet, and the document was modified in response to comments. The guidelines were reviewed by the joint Evidence-Based Laboratory Medicine Committee of the AACC and the National Academy of Clinical Biochemistry and were accepted after revisions by the Professional Practice Committee and subsequent approval by the Executive Committee of the American Diabetes Association. CONTENT: In addition to the long-standing criteria based on measurement of venous plasma glucose, diabetes can be diagnosed by demonstrating increased hemoglobin A1c (HbA1c) concentrations in the blood. Monitoring of glycemic control is performed by the patients measuring their own plasma or blood glucose with meters and by laboratory analysis of Hb A1c. The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed. SUMMARY: The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are found to have minimal clinical value at the present time, and measurement of them is not recommended.

Recombination of RegIII-proinsulin-pBudCE4.1 plasmid and its therapeutic effect on STZ-induced type 1 diabetes mellitus / 药学学报

The aim of this study is to investigate the therapeutic effect of RegIII-proinsulin-pBudCE4.1 plasmid on streptozotocin (STZ)-induced type 1 diabetes mellitus and its underlying mechanisms. The model of type 1 diabetes mellitus was established by intraperitoneal injections of STZ (40 mg kg(-1)) to Balb/c mice for five consecutive days. Then, ten type 1 diabetic mice were intramuscularly injected with 100 microg RegIII-proinsulin-pBudCE4.1 plasmid for 4 weeks (one time/week) and the blood glucose levels were monitored every week; whereas another ten diabetic mice served as negative control group were injected with pBudCE4.1 vector at the same dose. Normal control and model control mice were treated with normal saline at identical volume under the same way. Western blotting, MTT assay, ELISA, HE staining and Tunel assay were applied to explore the underlying mechanisms. Results showed that RegIII-proinsulin-pBudCE4.1 plasmid ameliorated the hyperglycemia symptoms in diabetic mouse remarkably. It induced an immunological tolerance state in type 1 diabetic mice by inhibiting the proliferation of splenic lymphocytes and recovering Th1/Th2 balance evidenced by MTT and ELISA analysis. Furthermore, it elevated insulin concentration in the serum of type 1 diabetic mice and promoted the regeneration of beta cells supported by the results of HE staining and Tunel assay. In conclusion, RegIII-proinsulin-pBudCE4.1 plasmid possesses powerful anti-diabetic ability, which may be involved in the inducing of immunological tolerance and enhancing beta cells recovery.

[Effects of conjugated linoleic acid on insulin sensitivity and diabetes markers in type 2 diabetic patients]

Some cell culture and animal studies have reported that Conjugated Linoleic Acids [CLAs] have several health related benefits. CLAs have been shown to have antiadipogenic, antiatherogenic, antidiabetogenic and anti-inflammatory properties. While increase in insulin resistance with 10-trans, 12-cis isomer of CLA was reported in some animal studies, there are controversial results about a 50:50 isomer mixture. The object of the present study was to determine the effect of CLAs supplementation [providing equal proportions of c9, t11 and t10, c12 - CLA] on plasma glucose, insulin, proinsulin, C-peptide, insulin sensitivity, insulin resistance, beta cell function and HbA1c in patients with type 2 diabetes mellitus. The study was performed as an 8-week randomized double-blind, placebo-controlled parallel intervention. Participants were 39 [19 men and 20 women] type 2 diabetic subjects [35 to 50 Y, BMI >25 and <30], stratified according to sex, age and BMI into two groups. Group one were given 3.0 g CLA/d [3x1 g capsules, a 50:50 isomer blend of c9, t11 and t10, c12 CLA] and, group 2 took CLA placebos [soy bean oil] for 8 weeks. Blood sample collection after fasting and 2 hours after a standard breakfast, was done before and after the intervention in order to determine insulin, glucose, pre insulin, c-peptide and HbA1c levels. No significant differences were seen in fasting and postprandial glucose, insulin, proinsulin, C- peptide and HbA1c levels between groups or in insulin resistance, insulin sensitivity, beta cell function and beta cell responsiveness. CLA supplementation has no effects on diabetes glucose level and insulin function and its prescription is not recommended

Frequency Of Pancreatic Beta-Cell Autoimmunity Markers In Patients With Autoimmune Thyroid Disease / Frecuencia de marcadores de autoinmunidad beta pancreática en pacientes con enfermedad tiroidea autoinmune

A total of 305 ambulatory patients recruited at the Division of Endocrinology, Hospital de Clínicas, University of Buenos Aires, with autoimmune thyroid disease (AITD) were studied to search for associations between autoimmune thyroid disease and presence of serum markers of autoimmune diabetes mellitus. Screening for markers of pancreatic beta-cell autoimmunity was performed by radioligand binding assays (RBA) as follows: autoantibodies to glutamic acid decarboxylase (GADA) and proinsulin (PAA) were determined in all sera, whereas autoantibodies to protein tyrosine phosphatase (IA-2A) and insulin (IAA) were additionally measured in 200 sera randomly selected from the total collection. In addition, every GADA positive serum among the remaining 105 sera was systematically tested for the presence of IA-2A and IAA. In the cohort of 305 AITD patients 22 (7.2%) were previously diagnosed as type 1, type 2 or insulin-requiring type 2 diabetics. Ten of these patients presented serum marker positivity specific for β-cell autoantigens and 12 were marker negative. On the other hand, considering the majority of non-diabetic AITD patients (n=283), β-cell marker positivity was detected in 17 individuals (6.0%). The prevalence of autoimmune diabetes markers was much higher in the studied population than in the general population utilized as a control group, and GADA was the most frequent marker.

Se investigó la asociación entre enfermedad tiroidea autoinmune y la presencia de marcadores séricos de diabetes mellitus en 305 pacientes ambulatorios con enfermedad tiroidea autoinmune reclutados en la División Endocrinología. La búsqueda de marcadores de autoinmunidad contra las células beta pancreáticas se realizó por la técnica de unión de radioligandos (RBA) como se detalla a continuación: se determinaron autoanticuerpos contra la decarboxilasa del ácido glutámico (GADA) y proinsulina (PAA) en todos los sueros, mientras que los anticuerpos contra la proteína tirosina fosfatasa (IA-2A) e insulina (IAA) fueron medidos en 200 de estos sueros tomados al azar de la colección total. Además, en los restantes 105 pacientes, la presencia de IA-2A y IAA fue evaluada en todos los sueros positivos para GADA. Del grupo de 305 pacientes con enfermedad tiroidea autoinmune 22 (7.2%) fueron diagnosticados previamente como diabéticos tipo 1, tipo 2 o tipo 2 insulino-requirientes. Diez de ellos presentaron positividad para marcadores específicos de autoantígenos de célula β, en tanto 12 fueron negativos. Por otra parte, en 17 de los 283 pacientes (6.0%) con enfermedad tiroidea autoimmune y sin diagnóstico previo de diabetes, se detectó positividad para marcadores de célula β. La prevalencia de marcadores de autoinmunidad asociados a diabetes fue mayor en la población estudiada que en la población general usada como grupo control, siendo GADA el marcador más frecuente.

role of proinsulin in gestational diabetes mellitus

To look for any increase in proinsulin or proinsulin/insulin ratio in women suffering GDM as an additional factor to their insulin resistance state during pregnancy; and to test for its reversibility in the post partum period. The study was conducted on 30 pregnant age matched women in their second or third trimester and 10 age matched non pregnant normoglycemic women as a reference group. The pregnant women were divided into 3 groups each of ten as follow: normoglycemic women with normal OGTT as a control group, obese women with GDM and lean women with GDM. All women were subjected to full history taking and complete clinical examination. The following parameters were measured: diagnostic OGTT using 100 gm glucose, fasting serum proinsulin, fasting serum insulin, serum C-peptide, proinsulin/insulin ratio and insulin sensitivity. All these tests were repeated 4-8 weeks postpartum. The results of the study revealed that the serum levels of proinsulin and the proinsulin/insulin ratio were significantly higher in obese and lean women with GDM than the control and reference groups during pregnancy and also after delivery. The insulin sensitivity index was significantly lower and the relative resistance for insulin was significantly higher in GDM women compared with normal glucose tolerant pregnant women during pregnancy, while after delivery the sensitivity index was significantly higher than during pregnancy in GDM women as well as pregnant women with normal OGTT. The mean values of C-peptide were significantly higher in GDM patients versus control and reference groups during pregnancy. After delivery these mean values of C-peptide were significantly lower than during pregnancy in the three pregnant studied groups. Women with GOM are characterized by elevated serum proinsulin concentrations and increased proinsulin/insulin ratio which reflect beta-cell decompensation. These precursors molecules might thus serve as a marker for the disease and potentially even identify the subjects of high risk for development of type 2 diabetes. Also, it may be possible to detect such beta-cell stress earlier in pregnancy and to use this phenomena in the assistance of better prediction of GDM

Study on the Optimum Conditions For the Expression Of Human Recombinant Proinsulin In E.Coli - BL21(DE3) with pET - 28a(+) Vector

Introduction: There are thousands of diabetes sufferers worldwide. In addition, there is an increased trend in Vietnam due to economic development, increased population, lifespan, and changing lifestyle. Insulin is a hormone, which is a natural protein. It plays an important role in the transformation of glucose in human and animal blood. Note, while insulin has not been produced in Vietnam, the production of recombinant Proinsulin is a premise for insulin. This study is based on a successful design of pET - 28a (+) Vector with recombinant Proinsulin codified gene.\r\n', u'Objectives: To define the human proinsulin codified gene and study the optimum conditions for the expression of proinsulin. \r\n', u'Subjects and method: To discover the appropriate conditions for the expression of proinsulin, including initial cell density, cultural temperature, IPTG concentration, and expression time. The product of the expression was confirmed by Sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SOS - PAGE) and reconfirmed by Western blotting with His - Tag antibody. \r\n', u'Results: Proinsulin expression was successfully proved by SOS - PAGE and Western blotting. Four appropriate conditions for the expression were confirmed as highlighted in the Conclusion. \r\n', u'Conclusion: The appropriate conditions for expression of proinsulin: cell density was 00600 0.6 - 1.0; the cultural temperature was 300C; IPTG concentration was 0.4 mM; the length of the culture time was 20 hours. \r\n', u'

Association between proinsulin, insulin, proinsulin/insulin ratio, and insulin resistance status with the metabolic syndrome

The Metabolic Syndrome (MS) constitutes an independent risk factor of cardiovascular disease. There is evidence that proinsulin blood levels and the proinsulin/insulin ratio are associated to the MS. The purpose of this study was to compare proinsulin and insulin, insulin resistance index, and the proinsulin/insulin ratio as predictors of MS. This is a cross-sectional study involving 440 men and 556 women with a mean age of 24 years. Diagnosis of MS was made according to the National Cholesterol Education Program Adult Treatment Panel III. Blood levels of insulin and proinsulin were measured, and the insulin resistance status was estimated using the homeostatic model assessment (HOMA-IR). The prevalence of MS was 10.1 percent. HOMA-IR was the best MS risk factor for both women and men (OR = 2.04; 95 percent CI: 1.68-2.48 and 1.09; 95 percent CI: 1.05-1.13, respectively). HOMA-IR presented the best positive predictive value for MS: 22 percent and 36 percent for men and women, respectively, and was the best MS indicator. The proinsulin/insulin ratio did not show significant association with MS. HOMA-IR, proinsulin, and insulin presented good negative predictive values for both genders that could be used to identify an at-risk population.

A síndrome metabólica (SM) constitui um fator de risco independente para doenças cardiovasculares. Existem evidências de que níveis sangüíneos de proinsulina e o índice proinsulina/insulina estão associados com a presença da SM. O objetivo deste trabalho foi comparar proinsulina e insulina, índice de resistência insulínica e o fator proinsulina/insulina para predizer a presença da SM. Este é um estudo transversal envolvendo 440 homens e 556 mulheres com média de 24 anos de idade. O diagnóstico da SM foi feito de acordo com o Painel III do programa de tratamento nacional educacional de colesterol para adultos. Níveis sangüíneos de insulina e proinsulina foram medidos, o índice de resistência insulínica foi estimado através do modelo de avaliação hemostático (HOMA-IR). A prevalência da SM foi de 10 por cento. HOMA-IR demonstrou ser o melhor fator de risco da SM em homens e mulheres (OR = 2,04; 95 por cento CI: 1,68-2,48 e 1,09; 95 por cento CI: 1,05-1,13, respectivamente). HOMA-IR apresentou o melhor valor preditivo positivo para SM: 22 por cento e 36 por cento para homens e mulheres, respectivamente, e foi o melhor indicador da SM. O índice proinsulina/insulina não apresentou associação significativa com SM. HOMA-IR, proinsulina e insulina apresentaram bons valores preditivos negativos para ambos sexos, o que poderia ser usado para identificar uma população de risco.

Expression of human proinsulin gene in pet 28A (+) vector and escherichia coli BL21 (DE3)

Background: Insulin is a hormone produced by the beta \r\n', u'cells of the pancreas that permits glucose to enter cells and \r\n', u'helps the body use glucose for energy. Insulin controls the \r\n', u'amount of glucose in the blood. Insulin is produced by recombinant protein technology. Expression of human proinsulin is the first step to express insulin. Objectives:To express successfully human proinsulin gene in pET 28a vector and E.coli BL21 (DE3). Subjects and method: Human proinsulin gene was applied from human pencreas cDNA by PCR using specific PINS primer pairs which contained sites for BamH I, Xho I. Proinsulin gene was cloned into pET 28a (+) vector to form recombinant vector pET 28a-PINS then transformed into E.coli BL21 (DE3) host strain to make pET 28a-PINS/ BL21 (DE3) clone. The clone was cultured and induced by IPTG (1mM). Recombine protein was analysed by SDS-PAGE. Results: Expression vector pET 28a-PINS was constructed successfully. Proinsulin protein expressed in E.coli BL21 (DE3) was purified by ProPond-Resin (Amersham). Conclusion: Human proinsulin was produced successfully using pET 28a-PINS/ BL21 (DE3) system.\r\n', u'

Association of adipocytokines (leptin, adiponectin TNF-alpha), insulin and proinsulin with diabetes--the Mumbai Obesity Project [MOP].

Asian Indians have a unique phenotype characterized by increased abdominal obesity and visceral fat despite low body mass index [BMI]. Though studies have indicated some adipocytokines to be associated with diabetes and obesity in Indians, there are virtually no studies relating adipocytokines and proinsulin with diabetes and obesity in Asian Indians. In this study we looked at adipocytokines--leptin, adiponectin and tumour necrosis factor-a [TNF-alpha] and insulin and proinsulin in subjects with diabetes and obesity. Thirty five diabetic subjects and 50 healthy controls were recruited for the study. Leptin [p=0.002J and adiponectin levels [p=0.011] were lower and proinsulin values higher [p<0.001] in diabetic subjects compared to non-diabetic subjects. In addition, leptin [p<0.001] and proinsulin [p<0.001] were higher and adiponectin [p<0.001] lower, in obese subjects compared to non-obese subjects. TNF-alpha failed to show any significant difference between the study groups. Leptin and proinsulin showed a significant and positive correlation with BMI [p<0.001] and waist circumference [p<0.001]. Adiponectin showed an inverse correlation with BMI [p=0.050] and waist circumference [p=0.002]. Proinsulin showed a significant negative association with adiponectin [p=0.002]. Logistic regression analysis revealed leptin to be negatively associated [Odds ratio [OR]: 0.864, 95% confidence interval [95% CI]: 0.775 -0.963, p=0.008] and proinsulin [OR: 1.567, 95% CI: 1.246-1.971, p<0.001] to be positively associated with diabetes even after adjusting for age, gender and BMI. Leptin [OR: 1.365, 95% CI: 1.170-1.592, p<0.001] and proinsulin [OR: 1.617, 95% CI: 1.218 -2.147, p=0.001] showed a significant positive association with obesity, while adiponectin [OR: 0.927, 95% CI: 0.865 - 0.995, p=0.035] had a significant inverse association. Linear regression analysis revealed that adiponectin is inversely associated with proinsulin even after the addition of age, gender and diabetes status [beta= -0.61, p=0.033] into the model. In conclusion, in urban Asian Indians in western India, proinsulin levels showed a positive association, while leptin and adiponectin showed a negative association with diabetes. With regard to obesity, leptin and proinsulin had a positive association, while adiponectin had a negative association. Proinsulin levels showed an inverse association with adiponectin indicating a possible link between insulin secretion and insulin resistance.

Blood levels of true insulin and immunoreactive insulin in evaluating beta-cell function with arginine stimulation test / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the difference between serum true insulin (TI) and immunoreactive insulin (IRI) in evaluating islet beta-cell function and insulin resistance.</p><p><b>METHODS</b>The arginine stimulation test was performed in 141 individuals, including 35 with normal glucose tolerance (NGT) and 106 with type 2 diabetes (T2DM). Plasma glucose (PG), TI, IRI and proinsulin (PI) levels were measured; the incremental value of TI/PG, (TI+PI)/PG and IRI/PG (delta TI/PG, delta(TI+PI)/PG and deltaIRI/PG) and the area under curve of TI/PG, (TI+PI)/PG and IRI/PG (AUC [TI/PG], AUC[(TI+PI)/PG] and AUC [IRI/PG]) after arginine stimulation were calculated to evaluate beta-cell function.</p><p><b>RESULT</b>There were positive correlations of delta TI/PG with delta (TI+PI)/PG and delta IRI/PG in both NGT and T2DM patients (r=0.68 - 0.99, P<0.01). The similar correlations of AUC [TI/PG] with AUC [(TI+PI)/PG] and AUC [IRI/PG] were also shown (r=0.62 - 0.99, P<0.01). delta TI/PG was correlated with AUC [TI/PG] in two groups (NGT r=0.96, T2DM r=0.82, P<0.01). HOMA-IRTI, HOMA-IR(TI+PI) and HOMA-IRIRI in T2DM were higher than those in NGT (P<0.01). After arginine stimulation T2DM subjects mainly presented insulin resistance and decreased insulin secretion.</p><p><b>CONCLUSION</b>The determination of TI may be more accurate than IRI in evaluating beta-cell function and insulin resistance.</p>

Cloning of CTB-PROIN fusion gene and its expression in Escherichia coli / 生物工程学报

A fusion gene CTB-PROIN, in which Proinsulin gene was fused to the 3' end of CTB gene by a hinge peptide 'GPGP', was constructed and cloned into pET-30a(+) to obtain a prokaryotic expression vector pETCPI. Subsequently the recombinant plasmid pETCPI was transformed into E. coli stain BL21 (DE3). After induced by IPTG, the expression product was analyzed by sodium dodecyl sulphate-polyacrylamide gel (15%) electrophoresis (SDS-PAGE), and its result indicated that the recombinant protein CTB-PROIN was expressed and accumulated as inclusion bodies. The recombinant CTB-PROIN protein accumulated to the level of 25% of total bacterial proteins. After inclusion bodies was denaturalized and refolded in vitro, significant assembly of monomers had occurred, and the recombinant protein represented assembled pentamers. The results of western blotting analysis also demonstrated that the fusion protein could be recognized by the anti-CT and anti-insulin antibody, respectively. In addition, the result of the CTB-PROIN-GM1 binding assay, that the protein could bind to monosialoganglioside specifically, showed it possesed biological activity in vitro. These results provided the possibility of developing a cheaper and more efficient oral vaccine for type I diabetes using such constructs.

Obtención de 35 S-proinsulina humana recombinante y su aplicación en un ensayo radiométrico combinado: Utilidad del método desarrollado para predecir el requerimiento de insulina en pacientes diabéticos adultos / Obtaining of 35 recombinant human S-proinsulina and its application in a combined radiometric test: Utility of the developed method to predict the insulin requirement in adult diabetic patients

Los autoanticuerpos anti glutamano decarboxilasa y anti insulina/proinsulina(GADA e IAA/PAA)tienen valor predictivo del requerimiento insulínico en pacientes diabéticos con comienzo clínico en edad adulta. En este trabajo se desarrolló un nuevo trazador 35 S-Proinsulina y se lo utilizó en un ensayo de unión de radioligando combinado con el trazador 35 S-GAD para la determinación simultñanea de GADA y PAA (RBA-combi). Se aplico el ensayo a 85 pacientes infanto-juveniles con diabetes tipo 1, a 98 pacientes con comienzo clínico en edad adulta y a 53 controles normales. El 100% de los pacientes con diabetes tipo 1 con al menos un marcador positivo, y el 17,7% de los que eran negativos para ambos marcadores, fueron positivos por el RBA-combi(RBA-comi+). El 100% de los pacientes adultos PAA+(GADA+ o GADA-) el 92,3% de los pacientes GADA+/PAA-, y el 1,3% de los pacientes GADA-/PAA-, fueron RBA-combi+. El 88.9% de los pacientes adultos RBA-combi+evolucionaron a requerimiento insulínico. En conclusión, el nuevo trazador 35 S-Proinsulina fue apto para su utilización en el método radiométrico combinado, permitiendo la detección simultánea de los marcadores GADA Y PAA. El RBA- combi es una herramienta valiosa para detectar procesos autoinmunes asociados a un futuro requerimiento insulínico, en pacientes diabéticos adultos.