Determinants of mild fasting hypertriglyceridaemia in non-insulin-dependent diabetes

Factors contributing to fasting hypertriglyceridaemia were studied in 20 patients with non-insulin-dependent diabetes--nine with normal triglyceride concentrations [fasting triglyceride 0.94 (range 0.58-1.23) mmol l-1] and eleven with mild fasting hypertriglyceridaemia [fasting triglyceride 2.4 (1.82-4.0) mmol l-1]. The patients with hypertriglyceridaemia were more obese [body mass index 29.0 (24.6-33.8) vs. 25.7 (21.9-30.1) kg m-2, P less than 0.05] and demonstrated impaired glucose disposal in response to exogenous insulin at isoglycaemia [insulin sensitivity index, SIp 0.7 (0.27-2.5) vs. 2.4 (0.62-5.1) ml m-2 min per mU l-1, P less than 0.001]. Basal non-esterified fatty acid (NEFA) and glycerol concentrations were higher and were suppressed to a lesser extent during isoglycaemic hyperinsulinaemia. Fasting glucose and apolipoprotein B concentrations were higher in the hypertriglyceridaemic patients, but lipoprotein lipase activities were similar in the two groups. When the effect of obesity was removed (by weight-matching six normotriglyceridaemic with seven hypertriglyceridaemic patients) basal NEFA and glycerol concentrations and the suppression of NEFA in response to insulin remained significantly different between the two groups. We propose that defects in both the glucoregulatory and antilipolytic actions of insulin contribute to mild fasting hypertriglyceridaemia in NIDDM, and that these defects cannot be attributed solely to obesity. These disorders of insulin action may also have important implications for the postprandial metabolism of triglyceride-rich lipoproteins and hence atherogenesis.     

Kinetics of circulating endogenous insulin, C-peptide, and proinsulin in fasting nondiabetic man

Plasma concentrations of insulin, C-peptide, and proinsulin were measured in different vascular beds in order to determine renal, hepatic, and systemic kinetics of the endogenous peptides in the fasting condition. Nineteen nondiabetic subjects were studied, two were normal, nine had minor vascular disorders, four had cirrhosis without organic kidney disease, and four had organic kidney disease with moderately decreased glomerular filtration rate. In subjects without organic kidney disease the arteriorenal venous extraction ratios of insulin, C-peptide, and proinsulin were mean 0.27, 0.20, and 0.21, respectively (n = 14). These values were significantly reduced in kidneys with organic disease. Renal plasma clearance values of insulin, C-peptide, and proinsulin were mean 113, 87, and 90 mL/min, respectively (n = 6). Urinary clearances were substantially lower (0.8, 13, 3.5 mL/min, respectively), indicating that a significant degradation of these peptides also takes place in the normal kidney. In subjects without liver disease the estimated hepatic extraction ratio of insulin was mean 0.48, under the assumption that no C-peptide is removed by the liver. Endogenously released insulin was removed from plasma in kidney, liver, and elsewhere in the approximate proportion 10%:65%:25%, whereas, C-peptide was removed by one half in kidney and the other half elsewhere. The overall metabolic clearance rates of insulin and C-peptide were estimated to be 15 and 4.5 mL/min/kg, respectively. The results indicate that the kidney contributes substantially to removal of insulin, C-peptide, an proinsulin, mainly by degradation, less by urinary excretion.     

Rosiglitazone, but not glyburide, reduces circulating proinsulin and the proinsulin:insulin ratio in type 2 diabetes

An elevation in the ratio of proinsulin (PI) to immunoreactive insulin (IRI) is inversely related to beta-cell function in type 2 diabetes, and increased PI is an independent risk factor for coronary heart disease. An objective of the present studies was to assess the effects of the thiazolidinedione insulin sensitizer, rosiglitazone, on indirect markers of beta-cell function and cardiovascular risk in people with type 2 diabetes by measuring plasma PI and the PI:IRI ratio. Parameters of insulin processing, including plasma PI and PI:IRI ratios, were determined in type 2 diabetes patients enrolled in two randomized double-blind studies comparing the effects of rosiglitazone (4 or 8 mg/d) with placebo (study 1, 26-wk treatment) or the sulfonylurea glyburide (study 2, 52-wk treatment). Treatment with rosiglitazone for 26 wk (study 1) produced significant dose-dependent decreases in both plasma PI concentrations (18-29%) and the PI:IRI ratio compared with baseline (7-14%) and placebo (19-29%) (P < 0.001). A significant increase in the PI:IRI ratio in placebo-treated patients occurred (P < 0.001). In study 2, rosiglitazone also significantly reduced both plasma PI and the PI:IRI ratio compared with baseline (P < 0.001). In contrast, glyburide significantly increased both plasma PI (45%; P < 0.001) and the PI:IRI ratio (10%) (P < 0.05 vs. baseline). These results show that rosiglitazone and glyburide have differential effects on absolute PI levels and the PI:IRI ratio in people with type 2 diabetes.     

Relative hypoleptinaemia in women with mild gestational diabetes mellitus.

AIMS: There is increasing evidence suggesting that leptin plays a major role in the regulation of energy homeostasis, as well as in the neuroendocrine and reproductive systems. Leptin is synthesized in the human placenta. The aim of this study was to relate serum leptin levels during pregnancy to glucose tolerance, body mass index (BMI) and specific metabolic variables, such as specific insulin and proinsulin. METHODS: A 2-h 75 g oral glucose tolerance test was performed in 221 pregnant women at 22-29 weeks of gestation (median 25th week). Serum leptin was measured using a radioimmunoassay. In 49 women, sequential leptin measurements were performed (during pregnancy and post partum (median 5 months)). RESULTS: During pregnancy serum leptin was significantly related to body weight (r = 0.49), BMI (r = 0.51), fasting immunoreactive insulin (r = 0.46), specific insulin (r = 0.43) and proinsulin (r = 0.29) (all P-values <0.0001). In women with mild gestational diabetes (GDM, n = 55), leptin levels were lower compared to women with normal glucose tolerance (n = 166) after adjusting for BMI and fasting insulin (26.9 vs. 19.4 ng/ml, P = 0.0001). Leptin was significantly higher during pregnancy compared to post partum (mean +/- SE: 24.3+/-1.5 vs. 19.6+/-1.6 ng/ml, P = 0.0003), even after adjustment for changes in BMI and changes in fasting insulin (P = 0.013). CONCLUSIONS: Leptin levels are elevated in pregnancy. Women with mild GDM presented with relative hypoleptinaemia compared to women with normal glucose tolerance.     

Serum proinsulin in normal and gestational diabetic pregnancy

Summary The concentration of proinsulin-like components (PLC) in serum has been determined by gel filtration on samples obtained from eight normal pregnant women and eight nonobese gestational diabetics. The normal women were investigated early in pregnancy and all subjects were investigated in mid pregnancy, late pregnancy, and postpartum. At each occasion, samples were obtained after an overnight fast and after glucose ingestion. In both groups, the concentration of PLC in serum after overnight fast rose with gestation as well as after glucose ingestion, but there were no significant differences between mean levels of PLC of the normals and the gestational diabetics. With gestation, serum insulin rose in parallel with PLC in either group. The proportion of total insulin immunoreactivity composed by PLC thus remained constant and, furthermore, the proportions of PLC in gestation were equal to those observed postpartum. Four to six weeks after delivery, the basal concentration of PLC in serum was higher in the gestational diabetics than in the normals, whereas the concentrations of insulin were equal. Since the biological potency of proinsulin is much less than that of insulin, the results exclude the possibility that the decrease of glucose tolerance in normal pregnant women and gestational diabetics is due to an increased concentration of proinsulin in serum.     

Abnormalities of proinsulin processing in functioning insulinomas: clinical implications

OBJECTIVE: Abnormal proinsulin processing in insulinomas may result in secretory granules containing both insulin and proinsulin, a finding not encountered in healthy beta-cells. The aim of this study was to test whether such abnormalities in the proinsulin to insulin conversion have clinical implications in patients with hypoglycaemic disorders. DESIGN: Case-series. PATIENTS AND METHODS: Fifteen patients with histologically confirmed insulinoma and two patients with islet cell hyperplasia were included. The immunohistochemical distribution pattern of proinsulin within the tumour cells was classified as Golgi pattern (predominantly perinuclear immunolabelling) or diffuse pattern (immunolabelling in the periphery of the cells, indicating the presence of proinsulin in secretory granules). Data obtained from the 72-h fast and arterial calcium stimulation and hepatic venous sampling (ASVS) test were related to the morphological classification. RESULTS: Six insulinomas exhibited a diffuse proinsulin distribution pattern, while nine insulinomas and two islet cell hyperplasias disclosed a Golgi pattern. Median proinsulin concentrations at the termination of the fast tended to be higher in patients with the diffuse proinsulin distribution pattern than in patients with the Golgi pattern (86.9 vs. 18.8 pmol/l, P = 0.07). Higher insulin (P < 0.005) and proinsulin (P < 0.05) concentrations were significantly correlated with earlier occurrence of hypoglycaemia during the prolonged fast. During the ASVS test, tumours with the diffuse proinsulin distribution pattern exhibited a higher increase in both insulin (median, 37.3- vs. 10.5-fold, P < 0.05) and proinsulin (6.3- vs. 1.6 fold, P < 0.005) concentrations following calcium stimulation than the tumours with the Golgi pattern. CONCLUSIONS: Abnormalities in the proinsulin to insulin conversion in patients with insulinomas and islet cell hyperplasia correlate with impaired regulation of both insulin and proinsulin secretion during the prolonged fast as well as the ASVS test.     

Diabetes screening after gestational diabetes mellitus: poor performance of fasting plasma glucose

Abstract. Gestational diabetes mellitus (GDM) is an established risk factor for the development of overt diabetes. Since the change in diagnostic criteria for diabetes in 1997, it is unclear whether there should be any preference for fasting or post-glucose challenge blood glucose in diagnosing diabetes after GDM. The study aimed at assessing the usefulness of both diagnostic methods in women after GDM. The study enrolled 193 women with previous GDM. Women who did not have a current diagnosis of diabetes were screened for impaired fasting glucose (IFG) and for glucose intolerance with an oral 75-g glucose tolerance test. A total of 45 (23.3%) subjects declared to be already diabetic. Of the 148 non-diabetic subjects, 141 (95.3%) had normal fasting plasma glucose, whereas four (2.8%) had IFG (i.e. FPG6.1 and <7.0 mmol/l) and 3 (2.5%) had FPG7.0 mmol/l. Upon OGTT, among the 141 subjects with normal FPG, 6 (4.3%) were diagnosed with diabetes and 23 (16.3%) with impaired glucose tolerance (IGT); the remaining 112 (79.5%) had normal glucose tolerance. Three out of four subjects with IFG had IGT. The sensitivities of fasting criteria for diagnosis of diabetes and IFG/IGT were 14.3% (95% CI, 8.0%–37.2%) and 17.1% (95% CI, 8.6%–19.8%), respectively. The specificities were 98.6% (95% CI, 97.9%–99.7%) and 99.1% (95% CI, 96.5%–100%), respectively. The kappa for diabetes diagnosis was 0.177 (95% CI, 0.018–0.507). For women with previous GDM, the sensitivity of the new criteria based upon fasting plasma glucose is unacceptably low. In addition, the two sets of criteria are not interchangeable. Therefore, we suggest full glucose tolerance diagnostic procedures in women after GDM, including assessment of post-glucose challenge values.     

Correspondence between first-trimester fasting glycaemia,and oral glucose tolerance test in gestational diabetes diagnosis

AimTo evaluate the correspondence between first-trimester fasting glycaemia and the results of the OGTT in diagnosing gestational diabetes (GDM).MethodsThe medical records of all consecutive women who had undergone a diagnostic OGTT, performed according to the IADPSG, during the past year were retrospectively reviewed. All first-trimester fasting glucose values greater or equal to 5.1 mmol/L (92 mg/dL), recommended as a diagnostic value, were also verified for each patient in this cohort. Moreover, a ROC curve and a multiple logistic-regression model were constructed to calculate the predictive capability of this cut-off value in diagnosing GDM.ResultsIn our population of 738 eligible pregnant women, an 11.9% prevalence of GDM was revealed by OGTT. However, when the first-trimester fasting glucose value for each patient was retrospectively considered, there were a further 29 patients who should have been diagnosed as GDM cases (glycaemia ≥ 5.1 mmol/L), although their OGTT was normal. Yet, when the value of fasting glucose was considered not diagnostic, but only predictive, an AUC of 0.614 (95% CI: 0.544–0.684) and an aOR of 7.1 (95% CI: 3.8–13.1) was obtained in these patients compared with the reference group (fasting glucose < 5.1 mmol/L).ConclusionThere was no complete correspondence in diagnosing GDM between the first-trimester fasting glucose value and the results of a 2-h 75-g OGTT performed early in the third trimester. However, albeit not diagnostic, a fasting glucose value greater or equal to 5.1 mmol/L may be considered a highly predictive risk factor for GDM.     

Electrophoretic characterization of circulating human proinsulin and insulin

Summary The serum proinsulin and insulin components of normal weight subjects treated with tolbutamide, or glucose and tolbutamide, were shown to be homogeneous on both Sephadex filtration and polyacrylamide gel electrophoresis. Serum of obese subjects treated with glucose and tolbutamide contained, in addition to proinsulin and insulin, two intermediate species when electrophoresed on polyacrylamide gel, i.e., desdipeptide proinsulin and diarginyl insulin. It is suggested that, 1. the conversion of proinsulin to insulin proceeds via these intermediates under physiological conditions, and 2. intermediates may appear in the circulation with excessive elevations of plasma immunoreactive insulin materials.Supported by VA Funds and NIH Grant # AM 11578.     

Proinsulin in pregnant women with normal glucose tolerance or mild gestational diabetes mellitus.

Pregnancy is characterized by peripheral insulin resistance, which is physiologically compensated by an increase in insulin secretion. Type 2 diabetes and impaired glucose tolerance (IGT) have been associated with an inappropriate increase in insulin precursors, namely proinsulin. The aim of this study was to determine levels of proinsulin (PI), specific insulin (SI) and the proinsulin-to-specific insulin (PI/SI) ratio in consecutive pregnant women (n = 209) with normal glucose tolerance (NGT), as assessed by a 2h oral glucose tolerance test, and with mild gestational diabetes (GDM), in comparison to 32 healthy, non-pregnant women. Furthermore, we related these variables to surrogate markers of insulin resistance and insulin secretion. We found no significant differences in the levels of PI and the PI/ SI ratio between pregnant and non-pregnant women (PI: 5.0 +/- 3.6 vs. 4.8 +/- 3.5 pmol/L, p = NS), and between pregnant women with mild GDM and NGT (PI: 5.4 +/- 2.4 vs. 4.9 +/- 3.9 pmol/L, p = NS). SI was elevated in women with mild GDM (112.2 +/- 47.3 vs. 94.8 +/- 43.0 pmol/L in NGT, p=0.02). PI was related to fasting glucose (r = 0.17, p < 0.02), but not post-load glucose levels, and to fasting insulin [specific insulin: r = 0.67, p = 0.0001; total immunoreactive insulin (IRI): r = 0.69, p = 0.0001], as well as post-load insulin levels (IRI at 120 min: r = 0.18, p < 0.03). The PI/SI ratio showed no association with fasting or post-load glucose or insulin levels. Pregnant women presented with a metabolic pattern suggestive of enhanced insulin resistance, namely increased fasting and post-load insulin levels. In women with mild GDM, fasting and post-load hyperglycemia, as well as an additional increase in insulin resistance was found. Group differences weakened when accounting for differences in body weight. The data of the present study suggest that in normal pregnancy as well as mild GDM metabolic alterations including enhanced insulin resistance and hyperglycemia do not result in an increase in circulating levels of proinsulin, both in absolute terms and relative to levels of specific insulin, as indicated by the proinsulin-to-specific insulin ratio.     

Association of fasting glucagon and proinsulin concentrations with insulin resistance

Aims/hypothesis Hyperproinsulinaemia and relative hyperglucagonaemia are features of type 2 diabetes. We hypothesised that raised fasting glucagon and proinsulin concentrations may be associated with insulin resistance (IR) in non-diabetic individuals. Methods We measured IR [by a euglycaemic–hyperinsulinaemic (240 pmol min⁻¹ m⁻²) clamp technique] in 1,296 non-diabetic (on a 75 g OGTT) individuals [716 women and 579 men, mean age 44 years, BMI 26 kg/m² (range 18–44 kg/m²)] recruited at 19 centres in 14 European countries. IR was related to fasting proinsulin or pancreatic glucagon concentrations in univariate and multivariate analyses. Given its known relationship to IR, serum adiponectin was used as a positive control. Results In either sex, both glucagon and proinsulin were directly related to IR, while adiponectin was negatively associated with it (all p < 0.0001). In multivariate models, controlling for known determinants of insulin sensitivity (i.e. sex, age, BMI and glucose tolerance) as well as factors potentially affecting glucagon and proinsulin (i.e. fasting plasma glucose and C-peptide concentrations), glucagon and proinsulin were still positively associated, and adiponectin was negatively associated, with IR. Finally, when these associations were tested as the probability that individuals in the top IR quartile would have hormone levels in the top quartile of their distribution independently of covariates, the odds ratio was ∼2 for both glucagon (p = 0.05) and proinsulin (p = 0.02) and 0.36 for adiponectin (p < 0.0001). Conclusions/interpretation Whole-body IR is independently associated with raised fasting plasma glucagon and proinsulin concentrations, possibly as a result of IR at the level of alpha cells and beta cells in pancreatic islets. Electronic supplementary material The online version of this article (doi:) contains a list of the European Group for the Study of Insulin Resistance RISC investigators, which is available to authorised users.     

Serum proinsulin levels at fasting and after oral glucose load in patients with Type 2 (non-insulin-dependent) diabetes mellitus

Summary A simple and sensitive human proinsulin radioimmunoassay system was developed using guinea pig antiproinsulin serum, which cross-reacted neither with human insulin nor C-peptide. The recognition site of the antiserum seems to be located near the junction between the B chain and C-peptide. With this assay system, we studied the serum proinsulin concentration at fasting and after an oral 100 g glucose load in 25 healthy subjects, 21 subjects with impaired glucose tolerance and 40 patients with Type 2 (non-insulin-dependent) diabetes mellitus. At fasting, serum proinsulin was 5.8±3.3 pmol/l in normal subjects as compared to 9.5±6.9 pmol/l (p<0.05) in subjects with impaired glucose tolerance and 12.6±7.5 pmol/l (p<0.001) in diabetic patients. The molar ratio of proinsulin to insulin was also increased in subjects with impaired glucose tolerance or diabetes compared to control subjects. After a 100 g oral glucose load, serum proinsulin increased more slowly than insulin. The proinsulin response after an oral glucose load was augmented in subjects with impaired glucose tolerance and diabetes, while the insulin response decreased with the elevation of fasting plasma glucose. Diabetic patients with high fasting plasma glucose had a very poor insulin response, but the proinsulin response was similar to control subjects. There was a linear correlation between summed proinsulin values and summed insulin values, but the slope of the regression line was steeper in diabetic patients than in control subjects. There was a relative increase in serum proinsulin both in subjects with impaired glucose tolerance and diabetic patients. We suggest that B cells may release ‘immature’ granules richer in proinsulin content as well as mature granules in the over-stimulated state.     

Preliminary report: circulating levels of the adipokine vaspin in gestational diabetes mellitus and preeclampsia

The objective of the study was to investigate serum levels of the insulin-sensitizing adipokine vaspin in patients with gestational diabetes mellitus (GDM) and preeclampsia (PE) as compared with healthy controls of similar gestational age. Vaspin serum levels were quantified by enzyme-linked immunosorbent assay in control (n = 102), GDM (n = 40), and PE (n = 22) subjects. Median maternal vaspin concentrations were not significantly different in GDM, PE, and control subjects. Furthermore, vaspin did not significantly correlate to clinical and biochemical measures of renal function, glucose, and lipid metabolism, as well as inflammation. Circulating vaspin levels are not significantly different between GDM, PE, and control subjects and do not correlate with insulin sensitivity in pregnant subjects.     

Impaired circulating glucagon-like peptide-1 response to oral glucose in women with previous gestational diabetes

BACKGROUND AND OBJECTIVE: Women with previous gestational diabetes (pGDM) are at risk of developing Type 2 diabetes. Glucagon-like peptide-1 (GLP-1) potentiates the insulin response to oral glucose, and its secretion is diminished in Type 2 diabetes. The aim of the study was to see if decreased GLP-1 secretion might be an early abnormality in the progression to Type 2 diabetes and would therefore be diminished in women with pGDM. PATIENTS AND METHODS: Eleven women with pGDM and previously documented normal glucose tolerance and 11 control women underwent a 75 g oral glucose tolerance test (OGTT). Circulating plasma glucose, insulin, nonesterified fatty acids (NEFA) and GLP-1 concentrations were sampled. RESULTS: One of the women with pGDM had impaired glucose tolerance and was excluded from the study. All other women had normal glucose tolerance. The women with pGDM had higher fasting glucose concentrations than controls (5.1; 4.9-5.3 vs. 4.8; 4.4-5.1 mmol/l, median; interquartile range, P = 0.04) and greater circulating glucose area under the curve (AUC) following the oral glucose load (930; 818-1015 vs. 668; 584-737 min x mmol/l, P = 0.0007). Fasting insulin concentrations and total insulin AUC were similar. The initial (0-30 min) insulin response was decreased in the pGDM women (AUC 3981; 2783-4795 vs. 6167; 5009-8145 min x pmol/l, P = 0.05). The initial (0-30 min) GLP-1 response was reduced in the pGDM women (AUC 816; 663-984 vs. 1163; 872-2024 min x pmol/l, P = 0.02). CONCLUSION: A reduced initial GLP-1 response to oral glucose may therefore be an early abnormality in the progression to Type 2 diabetes.     

Visfatin concentration is decreased in women with gestational diabetes mellitus in the third trimester

Our aim is to investigate visfatin concentration and its relationship to glycated hemoglobin (HbA1c), insulin resistance, lipid parameters, and neonatal birth weight in women with gestational diabetes mellitus (GDM). In our study group, there were 47 women with GDM and 31 women with normal glucose tolerance (NGT) between 33-39 weeks of gestation. Plasma visfatin levels were significantly decreased in pregnant women with GDM compared to those with NGT (p=0.001). Homeostasis model assessment-insulin resistance (HOMA-IR) levels were higher in the GDM group than in the NGT group (p=0.006). In all subjects, plasma visfatin levels were negatively correlated with HOMA-IR, post-prandial blood glucose, triglycerides, and VLDL cholesterol (p<0.05). We did not observe any statistically significant correlation between the plasma visfatin levels and the selected parameters in the GDM group, but in the NGT group plasma visfatin levels were negatively correlated with HOMA-IR (r=-0.36, p=0.04). There was no correlation between visfatin concentrations and fetal birth weight in either group (p>0.05). By regression analysis, having GDM was found to be the only significant determinant (t=3.5, p=0.001) of visfatin concentration (R=0.39, r2=0.15). We conclude that women with GDM have significantly decreased visfatin concentrations in the third trimester. Future studies are required to establish the exact role of visfatin in the pathogenesis of GDM.     

Diagnostic value of dysregulated microribonucleic acids in the placenta and circulating exosomes in gestational diabetes mellitus

Aims/IntroductionDifferentially expressed microribonucleic acids (miRNAs) in the placenta and circulating exosomes are of diagnostic value for gestational diabetes mellitus (GDM). In a cross‐sectional study, we identified miRNAs expressed both in the placenta and circulating exosomes of pregnant women with GDM, and estimated their diagnostic value.Materials and MethodsNext‐generation sequencing was used to identify miRNAs in the placenta that were differentially expressed between GDM and normal glucose tolerance pregnancies. Quantitative polymerase chain reaction was used to validate the identified targets. Western blot and transmission electron microscopy were used to validate exosomes. Univariate logistic regression analysis was used to establish diagnostic models based on miRNAs expression, and the diagnostic value was estimated using the receiver operator characteristic curve.ResultsWe identified 157 dysregulated miRNAs in the placental tissue obtained from GDM pregnancies. Of these, miRNA‐125b was downregulated (P < 0.001), whereas miRNA‐144 was upregulated (P < 0.001). The patterns of these two miRNAs remained the same in circulating exosomes from GDM pregnancies (all P < 0.001). miRNA‐144 levels in the circulating exosomes negatively correlated with body mass index both before pregnancy (P = 0.018) and before delivery (P = 0.039), and positively correlated with blood glucose at 1 h, estimated using the oral glucose tolerance test (P = 0.044). The area under curve for the established diagnostic model was 0.898, which was higher than blood glucose levels at 0 h.ConclusionsThese findings suggest that miRNA‐125b and miRNA‐144 are consistently dysregulated in circulating exosomes and the placenta from GDM pregnancies, and are of excellent diagnostic value for GDM.     

Abnormal proinsulin/c-peptide ratio in juvenile diabetes

Summary B-cell function was studied in 20 diabetic children, with an age at onset of diabetes between 1–16 years (8.8 ± 4.0). Serum samples were taken before the first insulin injection and after 1, 3, 6, 9 and in a few patients after 18 months. At 3, 9, and 18 months the patients were also given a standardized breakfast load. Serum proinsulin, C-peptide, IRI and insulin antibodies (IgG) were determined. At onset 19 patients had measurable C-peptide (0.22 ± 0.17 pmol/ml; range 0.05–0.58). Proinsulin varied between 0.000–0.25 pmol/ml (0.069 ± 0.071) and at onset amounted to 31.3 ± 29.4 (0–100)% of C-peptide as compared to 3.3 ± 1.1 (1.7–6.6) in non-diabetics. A long partial remission was significantly correlated to a low proinsulin/C-peptide ratio at onset. In patients with low fasting proinsulin and no insulin antibodies, breakfast stimulation was accompanied by an increased proinsulin release at 3 and 9 months. The results suggest that abnormal proinsulin secretion is a feature of the ‘B-cell exhaustion’ complex in juvenile-onset diabetes.