Management of people with Type 2 diabetes shared between a specialized outpatient clinic and primary health care is noninferior to management in a specialized outpatient clinic: a randomized, noninferiority trial.

AIM: To evaluate whether management of people with Type 2 diabetes shared between a specialized outpatient clinic and primary health care has noninferior HbA1c outcomes compared with mono-sectorial management in a specialized outpatient clinic. METHODS: A randomized controlled, noninferiority study. People with moderate hyperglycaemia, hypertension and/or incipient complications were eligible for the study. All participants had annual comprehensive check-ups at the outpatient clinic. Quarterly check-ups were conducted by general practitioners (GPs) for the shared care group and by endocrinologists at the outpatient clinic for the control group. The primary outcome was the mean difference in HbA1c from baseline to 12 months of follow-up. The noninferiority margin for HbA1c was 4.4 mmol/mol. RESULTS: A total of 140 people were randomized [age 65.0 ± 0.9 years, HbA1c 52 ± 0.8 mmol/mol (6.9 ± 0.1%), systolic BP 135.6 ± 1.1 mmHg; all mean ± sem]. Peripheral neuropathy was present in 68% of participants and microalbuminuria in 19%; 15% had history of a previous major cardiovascular event. Among study completers (n = 133), HbA1c increased by 2.3 mmol/mol (0.2%) in the shared care group and by 1.0 mmol/mol (0.1%) in the control group, with a between-group difference of 1.3 mmol/mol [90% confidence interval (CI) -1.3, 3.9] (0.1%, 90% CI -0.1, 0.4). Noninferiority was confirmed in both per protocol and intention to treat analyses. CONCLUSION: We found that our shared care programme was noninferior to specialized outpatient management in maintaining glycaemic control in this group of people with Type 2 diabetes. Shared care should be considered for the future diabetes management of Type 2 diabetes.

The effect of insulin dose on the measurement of insulin sensitivity by the minimal model technique. Evidence for saturable insulin transport in humans.

Administration of exogenous insulin during an intravenous glucose tolerance test allows the use of the minimal model technique to determine the insulin sensitivity index in subjects with reduced endogenous insulin responses. To study the effect of different insulin administration protocols, we performed three intravenous glucose tolerance tests in each of seven obese subjects (age, 20-41 yr; body mass index, 30-43 kg/m2). Three different insulin administration protocols were used: a low-dose (0.025 U/kg) infusion given over 10 min, a low-dose (0.025 U/kg) bolus injection, and a high-dose (0.050 U/kg) bolus injection, resulting in peak insulin concentrations of 1,167 +/- 156, 3,014 +/- 483, and 6,596 +/- 547 pM, respectively. The mean insulin sensitivity index was 4.80 +/- 0.95 x 10(-5), 3.56 +/- 0.53 x 10(-5), and 2.42 +/- 0.40 x 10(-5) min-1/pM respectively (chi +/- SEM; P = 0.01). The association of higher peak insulin concentrations with lower measured insulin sensitivity values suggested the presence of a saturable process. Because results were not consistent with the known saturation characteristics of insulin action on tissue, a second saturable site involving the transport of insulin from plasma to interstitium was introduced, leading to a calculated Km of 807 +/- 165 pM for this site, a value near the 1/Kd of the insulin receptor. Thus, the kinetics of insulin action in humans in these studies is consistent with two saturable sites, and supports the hypothesis for transport of insulin to the interstitial space. Saturation may have an impact on minimal model results when high doses of exogenous insulin are given as a bolus, but can be minimized by infusing insulin at a low dose.

Severe insulin-resistant diabetes mellitus in patients with congenital muscle fiber type disproportion myopathy.

Congenital muscle fiber type disproportion myopathy (CFTDM) is a chronic, nonprogressive muscle disorder characterized by universal muscle hypotrophy and growth retardation. Histomorphometric examination of muscle shows a preponderance of smaller than normal type 1 fibers and overall fiber size heterogeneity. Concomitant endocrine dysfunctions have not been described. We report the findings of altered insulin secretion and insulin action in two brothers affected with CFTDM and glucose intolerance as well as in their nonconsanguineous glucose-tolerant parents. Results are compared with those of six normoglycemic control subjects. All study participants underwent an oral glucose tolerance test to estimate insulin secretion. The oldest boy and his parents volunteered for studies of whole-body insulin sensitivity consisting of a 4-h euglycemic hyperinsulinemic clamp in combination with indirect calorimetry. Insulin receptor function and glycogen synthase (GS) activity and expression were examined in biopsies of vastus lateralis muscle. Despite a 45-90-fold increase in both fasting and postprandial serum insulin levels, both CFTDM patients had diabetes mellitus. Clamp studies revealed that the oldest boy had severe insulin resistance of both liver and peripheral tissues. The impaired insulin-stimulated glucose disposal to peripheral tissues was primarily due to reduced nonoxidative glucose metabolism. These changes were paralleled by reduced basal values of muscle GS total activity, allosterical activation of GS by glucose-6-phosphate, GS protein, and GS mRNA. The father expressed a lesser degree of insulin resistance, and studies of muscle insulin receptor function showed a severe impairment of receptor kinase activity. In conclusion, CFTDM is a novel form of severe hyperinsulinemia and insulin resistance. Whether insulin resistance is causally related to the muscle disorder awaits to be clarified.

Insulin-like growth factor-I improves glucose and lipid metabolism in type 2 diabetes mellitus.

Hyperglycemia, hyperinsulinemia, and insulin resistance cause vascular disease in type 2 diabetes mellitus. Dietary treatment alone often fails and oral drugs or insulin enhance hyperinsulinemia. In previous studies, an intravenous bolus of recombinant human insulin-like growth factor-I (rhIGF-I) caused normoglycemia in insulin-resistant diabetics whereas rhIGF-I infusions lowered insulin and lipid levels in healthy humans, suggesting that rhIGF-I is effective in insulin-resistant states. Thus, eight type 2 diabetics on a diet received on five treatment days subcutaneous rhIGF-I (2 x 120 micrograms/kg) after five control days. Fasting and postprandial glucose, insulin, C-peptide, proinsulin, glucagon, triglyceride, insulin-like growth factor-I and -II, and growth hormone levels were determined. RhIGF-I administration increased total IGF-I serum levels 5.3-fold above control. During the control period mean (+/- SD) fasting glucose, insulin, C-peptide, and total triglyceride levels were 11.0 +/- 4.3 mmol/liter, 108 +/- 50 pmol/liter, 793 +/- 250 pmol/liter, and 3.1 +/- 2.7 mmol/liter, respectively, and decreased during treatment to a nadir of 6.6 +/- 2.5 mmol/liter, 47 +/- 18 pmol/liter, 311 +/- 165 pmol/liter, and 1.6 +/- 0.8 mmol/liter (P < 0.01), respectively. Postprandial areas under the glucose, insulin, and C-peptide curve decreased to 77 +/- 13 (P < 0.02), 52 +/- 11, and 60 +/- 9% (P < 0.01) of control, respectively. RhIGF-I decreased the proinsulin/insulin ratio whereas glucagon levels remained unchanged. The magnitude of the effects of rhIGF-I correlated with the respective control levels. Since rhIGF-I appears to improve insulin sensitivity directly and/or indirectly, it may become an interesting tool in type 2 diabetes and other states associated with insulin resistance.

Proinsulin, intact insulin, and fibrinolytic variables and fibrinogen in healthy subjects. A population study.

OBJECTIVE: As high serum insulin predicts impaired fibrinolysis and proinsulin reacts in most conventional insulin assays, we hypothesized that proinsulin could link low fibrinolytic activity and hyperinsulinemic conditions. RESEARCH DESIGN AND METHODS: We explored the relationship between fibrinolysis and plasma fibrinogen on the one hand and specific insulin and proinsulin on the other, in a healthy population sample of 165 men and women, 25-74 years of age, from the Northern Sweden MONICA (Monitoring of Trends and Determinants in Cardiovascular Disease) Study. Specific insulin and proinsulin were measured by enzyme-linked immunosorbent assay. Partial correlation coefficients, adjusted for age and sex, were calculated. RESULTS: Plasma fibrinogen levels were related to insulin (r = 0.25, P < 0.01) and proinsulin (r = 0.29, P < 0.001), as was plasminogen activator inhibitor (PAI)-1 activity (r = 0.36 and r = 0.29, respectively; P < 0.001). Tissue Plasminogen activator (tPA) activity correlated inversely to insulin (r = 0.35, P < 0.001) and proinsulin (r = - 0.36, P < 0.001). In a multivariate analysis taking also smoking and anthropometric and metabolic measurements into account, fasting proinsulin was a significant predictor of high plasma fibrinogen level. Insulin and proinsulin levels were not related to tPA activity. High levels of postload insulin, triglycerides, and diastolic blood pressure, but not proinsulin, predicted high PAI-l activity. CONCLUSIONS: In a healthy population, the relationship previously described between high insulin levels and impaired fibrinolysis is not attributable to confounding from proinsulin. Elevated proinsulin levels are associated with high fibrinogen levels.

Proinsulin immunoreactivity in recent-onset IDDM: the significance of insulin antibodies and insulin autoantibodies.

OBJECTIVE: To study the natural history of fasting proinsulin immunoreactivity (PIM) during the first 30 months of IDDM and its relationship to fasting C-peptide and insulin antibodies. RESEARCH DESIGN AND METHODS: An incidence cohort of 204 consecutive newly diagnosed IDDM patients were followed prospectively, having blood drawn for measurements at diagnosis and at 1, 3, 6, 9, 12, 18, 24, and 30 months. A sensitive enzyme-linked immunosorbent assay was used for the determination of PIM. RESULTS: All patients had detectable fasting PIM in plasma at diagnosis, with a median value and interquartile range of 3.5 pmol/l (2.2-6.2). The median PIM level increased during the first months of IDDM to reach a peak at 9-12 months (9.9-10.3 pmol/l). PIM then declined gradually to 5.6 pmol/l (1.9-13.5) at 30 months without reaching baseline. PIM at each time point was widely scattered in a skewed log-normal distribution without signs of bimodality. After the onset of insulin treatment, median insulin antibody level increased and declined in a similar pattern. Both PIM and antibody level were significantly higher in children and adolescents compared with adults. However, stepwise multiple regression analysis showed that age was only of minor importance for the PIM variation during the study period. Insulin antibody level and fasting C-peptide were the major determinants at 3-30 months, accounting for approximately 40% of the variation (R2). Blood glucose was of minor importance, and insulin dose, HbA1c, and BMI were of no importance. The correlation between fasting PIM and fasting C-peptide improved (R2 doubled) if the insulin antibody level was accounted for. Further, the slope of the correlation curve between PIM and C-peptide increased threefold when antibody binding was > 4%. At diagnosis, insulin autoantibodies could be detected in 19% of the patients. Their presence predicted higher proinsulin at 1-3 months, a higher insulin dose the 1st year, and higher levels of insulin antibodies later in the study. CONCLUSIONS: Circulating insulin antibodies may affect the level of PIM in IDDM, probably by adding a pool of IgG-bound PIM thereby increasing half-life and plasma concentration. This may explain why C-peptide and PIM levels do not change in concert during the 1st years of IDDM. Unlike C-peptide, PIM can not therefore quantitate beta-cell secretion unless the presence of insulin antibodies is ruled out.

Intact proinsulin and beta-cell function in lean and obese subjects with and without type 2 diabetes.

OBJECTIVE: Type 2 diabetes is a heterogeneous disease in which both beta-cell dysfunction and insulin resistance are pathogenetic factors. Disproportionate hyperproinsulinemia (elevated proinsulin/insulin) is another abnormality in type 2 diabetes whose mechanism is unknown. Increased demand due to obesity and/or insulin resistance may result in secretion of immature beta-cell granules with a higher content of intact proinsulin. RESEARCH DESIGN AND METHODS: We investigated the impact of obesity on beta-cell secretion in normal subjects and in type 2 diabetic patients by measuring intact proinsulin, total proinsulin immunoreactivity (PIM), intact insulin, and C-peptide (by radioimmunoassay) by specific enzyme-linked immunosorbent assays in the fasting state and during a 120-min glucagon (1 mg i.v.) stimulation test. Lean (BMI 23.5 +/- 0.3 kg/m2) (LD) and obese (30.1 +/- 0.4 kg/m2) (OD) type 2 diabetic patients matched for fasting glucose (10.2 +/- 0.6 vs. 10.3 +/- 0.4 mmol/l) were compared with age- and BMI-matched lean (22.4 +/- 0.6 kg/m2) (LC) and obese (30.8 +/- 0.9 kg/m2) (OC) normal control subjects. RESULTS: Diabetic patients (LD vs. LC and OD vs. OC) had elevated fasting levels of intact proinsulin 6.6 +/- 1.0 vs. 1.6 +/- 0.3 pmol/l and 7.7 +/- 2.0 vs. 1.2 +/- 0.2 pmol/l; PIM: 19.9 +/- 2.5 vs. 5.4 +/- 1.0 pmol/l and 29.6 +/- 6.1 vs. 6.1 +/- 0.9 pmol/l; and total PIM/intact insulin: 39 +/- 4 vs. 15 +/- 2% and 35 +/- 5 vs. 13 +/- 2%, all P < 0.01. After glucagon stimulation, PIM levels were disproportionately elevated (PIM/intact insulin based on area under the curve analysis) in diabetic patients (LD vs. LC and OD vs. OC): 32.6 +/- 6.7 vs. 9.2 +/- 1.1% and 22.7 +/- 5.2 vs. 9.1 +/- 1.1%, both P < 0.05. Intact insulin and C-peptide net responses were significantly reduced in type 2 diabetic patients, most pronounced in the lean group. The ratio of intact proinsulin to PIM was higher in diabetic patients after stimulation in both LD versus LC: 32 +/- 3 vs. 23 +/- 2%, and OD versus OC: 28 +/- 4 vs. 16 +/- 2%, both P < 0.01. In obese normal subjects, intact proinsulin/PIM was lower both in the fasting state and after glucagon stimulation: OC versus LC: 22 +/- 3 vs. 33 +/- 3% (fasting) and 16 +/- 2 vs. 23 +/- 2% (stimulated), both P < 0.05. CONCLUSIONS: Increased secretory demand from obesity-associated insulin resistance cannot explain elevated intact proinsulin and disproportionate hyperproinsulinemia in type 2 diabetes. This abnormality may be an integrated part of pancreatic beta-cell dysfunction in this disease.

Severe hypoglycaemia during treatment with sulphonylureas in patients with type 2 diabetes in the Capital Region of Denmark.

AIMS: Sulphonylureas (SU) are currently recommended as a well-established second line treatment in guidelines for type 2 diabetes (T2DM). In the Capital Region of Denmark 16,865 patients were given SU as part of their treatment of T2DM in 2010-2011. To what extent SU are associated with hospitalizations due to severe hypoglycaemic episodes, defined as episodes with a need for external assistance, was investigated. The prevalence and characteristics of these patients and potential risk factors were studied. METHODS: ICD-10 diagnosis codes were used to identify patients hospitalized due to hypoglycaemia and T2DM for a period of 2 years (2010-2011). Inclusion criteria were T2DM, hospitalization due to hypoglycaemia and treatment with SU as monotherapy or in combination with other glucose-lowering drugs except insulin treatment. RESULTS: We identified 161 patients fulfilling the inclusion criteria. Their mean age was 76 (53-97) years and 54% were males. Sixty percent of the patients had diabetic complications, including 19% with diabetic nephropathy. The major reason for severe hypoglycaemia was an unchanged dose of SU despite of a significant decline in food intake (45%). In 22% of the patients more than one reason was listed, most commonly a concomitant infection associated with decreased food intake and unchanged dose of SU. CONCLUSION: The incidence of hospital admission-requiring severe hypoglycaemia in patients treated with SU was 0.48 episodes per 100 patient-years of SU-treated patients. It was mainly older patients with diminished food intake, excessive alcohol use or other medications, concomitant infection, and with diabetic complications.

Hyperproinsulinemia in a three-generation Caucasian family due to mutant proinsulin (Arg65-His) not associated with imparied glucose tolerance: the contribution of mutant proinsulin to insulin bioactivity.

Familial hyperproinsulinemia is a genetic abnormality characterized by an increased proportion of proinsulin immunoreactivity in the circulation due to mutations affecting the posttranslational processing of proinsulin. In affected Japanese families, this has been associated with noninsulin-dependent diabetes mellitus or impaired glucose tolerance. A three-generation Caucasian family with hyperproinsulinemia was identified through unexplained hyperinsulinemia in a normal volunteer participating in a metabolic study. High pressure liquid chromatography analysis of fasting plasma revealed a major peak eluting close to the position of proinsulin. Direct sequencing of the proinsulin gene exon 3 showed a heterozygous point mutation (CGT-->CAT) resulting in the substitution of Arg-->His in position 65 (corresponding to the AC cleavage site) in the index case, his mother, and his maternal grandmother. Using specific enzyme-linked immunosorbent assay methods to quantify insulin and proinsulin (including its conversion intermediates), the impact of this mutation on B cell secretion and glucose tolerance was studied. All affected subjects had normal oral glucose tolerance. In the basal state and after oral glucose administration, their proinsulin responses were immense, but intact insulin responses were slightly reduced. However, when calculating insulin bioactivity by assuming 9% activity for mutant Arg65-->His proinsulin, responses in affected subjects were comparable to those in normal subjects. In conclusion, our data demonstrate hyperproinsulinemia in a three-generation Caucasian family due to heterozygous mutant Arg65-->His proinsulin. This was not associated with impaired glucose tolerance. These results suggest that this mutation in the heterozygous state per se does not affect glucose tolerance and that the biological activity of mutant proinsulin contributes to glucose homeostasis in this family. The association of the same mutation with impaired glucose tolerance or diabetes in previous studies may be the result of selection bias or associated conditions (e.g. the genetic background of the kindreds examined).

Disproportionately elevated proinsulin levels reflect the degree of impaired B cell secretory capacity in patients with noninsulin-dependent diabetes mellitus.

An increased proportion of fasting proinsulin (PI) relative to immunoreactive insulin (IRI; increased PI/IRI) occurs in noninsulin-dependent diabetes mellitus (NIDDM). To determine whether the magnitude of the increase in PI/IRI is an indicator of the degree of reduced B cell secretory capacity, we measured fasting plasma glucose, PI, IRI, and PI/IRI and related them to maximal B cell secretory capacity (AIRmax) in 9 subjects with NIDDM [age, 61 +/- 3 yr; body mass index (BMI), 27.5 +/- 1.3 kg/m2; duration of NIDDM, 10.8 +/- 1.8 yr; mean +/- SEM] and in 10 healthy subjects matched for age and BMI (age, 61 +/- 6 yr; BMI, 27.9 +/- 1.5 kg/m2). AIRmax was quantified as the incremental insulin response to i.v. arginine at maximal glycemic potentiation (plasma glucose > 25 mmol/L). Mean fasting plasma glucose was 13.7 +/- 1.4 mmol/L (range, 7.5-18.3 mmol/L) in NIDDM subjects and 5.0 +/- 0.1 mmol/L in the controls. Fasting PI was higher in NIDDM (33.1 +/- 5.2) than in controls (9.4 +/- 2.5 pmol/L; P < 0.01), but IRI levels were similar (93.4 +/- 10.9 vs. 82.8 +/- 23.4 pmol/L; P = NS). The PI/IRI ratio was significantly elevated in NIDDM compared to control subjects (35.9 +/- 4.1% vs. 12.8 +/- 0.8%; P < 0.01). After elevation of the glucose level to 30.3 +/- 0.4 mmol/L (NIDDM) and 30.3 +/- 0.5 mmol/L (controls), AIRmax was quantified as 622 +/- 71 pmol/L in NIDDM and 1997 +/- 315 pmol/L in controls, (P < 0.001). The PI/IRI ratio correlated inversely with AIRmax in the NIDDM patients (r = -0.76; P < 0.01). We conclude that the magnitude of the elevation in fasting PI/IRI is related to the reduction in AIRmax. Thus, the fasting PI/IRI ratio appears to be a marker of the degree of reduced AIRmax in NIDDM.

Disproportionately elevated proinsulin levels precede the onset of insulin-dependent diabetes mellitus in siblings with low first phase insulin responses. The Childhood Diabetes in Finland Study Group.

The objective of this study was to test whether levels of proinsulin immunoreactivity (PIM) relative to those of insulin immunoreactivity (IRI) or C-peptide are changed and related to subclinical beta-cell dysfunction in siblings of insulin-dependent diabetes mellitus (IDDM) patients. Twenty-three siblings, previously found positive for islet cell antibodies and/or insulin autoantibodies, were divided into 2 groups according to their first phase insulin response (FPIR) to i.v. glucose tolerance tests (IVGTTs) sequentially performed during an observation period of 2 yr. Eleven siblings had diminished FPIR on at least 1 occasion (group 1), whereas 12 siblings had a normal FPIR on all occasions studied (group 2). All underwent a further IVGTT (0.5 g glucose/kg BW), and serum samples were taken at 0, 1, 3, 6, 10, 20, 30, 40, 50, and 60 min. The 2 groups had comparable median age, female/male ratio, weight, height, fasting blood glucose, immunoreactive insulin, C-peptide, and insulin autoantibodies levels, but group 1 had significantly higher islet cell antibodies levels. Fasting median PIM/IRI and PIM/C-peptide ratios were 2- to 3-fold higher in group 1 [10.5% (range, 1.8-93.8%) vs. 5.2% (range, 1.9-14.3%) and 3.3% (range, 0.4-23.1%) vs. 1.3% (range, 0.7-2.6%; P < 0.05]. Fasting PIM/C-peptide ratios correlated inversely with FPIRs (rs = -0.68; P < 0.01). During glucose stimulation, maximal responses of IRI and C-peptide were 4-fold lower in group 1, and the time of maximal responses of IRI and C-peptide occurred later in group 1 than in group 2. In contrast, no difference in maximal responses of PIM was found, but the time of maximal responses of PIM occurred later in group 1. Nine of 11 siblings in group 1 presented with IDDM 1-28 months after the test, compared to none in group 2. In group 1 a paradoxical inhibitory response of PIM was observed during the first 6 min of the IVGTT. These data indicate that fasting PIM/IRI and/or PIM/C-peptide ratio reflects subclinical beta-cell dysfunction in prediabetic subjects with evidence of immunological beta-cell assault and suggests that an elevated ratio may be an additional marker for later development of IDDM.

Reduced pancreatic B cell compensation to the insulin resistance of aging: impact on proinsulin and insulin levels.

Type 2 diabetes mellitus is associated with insulin resistance, reduced B cell function, and an increase in the proinsulin (PI) to immunoreactive insulin (IRI) ratio (PI/IRI); the latter is thought to be an indication of B cell dysfunction. Normal aging is associated with insulin resistance and reduced B cell function, but it is not known whether changes in PI and the PI/IRI ratio are also a feature of the aging-associated B cell dysfunction. Therefore, we tested whether the aging-associated changes in insulin sensitivity and B cell function result in changes in PI and IRI levels that are proportionate or whether they are disproportionate as in type 2 diabetes. Twenty-six healthy older (mean +/- SEM age, 67 +/- 1 yr) and 22 younger (28 +/- 1 yr) subjects with similar body mass indexes (27.9 +/- 0.6 vs. 26.3 +/- 1.0 kg/m2) were studied. PI was measured by a RIA recognizing both intact PI and its conversion intermediates. The insulin sensitivity index (SI) was quantified using the minimal model, and B cell function was measured as fasting insulin levels, the acute insulin response to glucose (AIRglucose), and as the acute insulin response to arginine at maximal glycemic potentiation (AIRmax). B cell function was also adjusted for SI based on the known hyperbolic relationship between these two variables. Older and younger subjects had similar fasting glucose (5.3 +/- 0.1 vs. 5.2 +/- 0.1 mmol/L), IRI (83 +/- 8 vs. 76 +/- 9 pmol/L), PI (8.9 +/- 0.8 vs. 10.6 +/- 2.0 pmol/L), and PI/IRI ratio (12.3 +/- 1.3% vs. 13.9 +/- 1.6%; all P = NS) despite a 50% reduction of insulin sensitivity (SI, 1.94 +/- 0.21 vs. 3.88 +/- 0.38 x 10(-5) min(-1)/pmol x L; P < 0.001) and in B cell function [SI x fasting IRI, 139 +/- 18 vs. 244 +/- 24 x 10(-5)(P < 0.001); SI x AIRglucose, 0.75 +/- 0.13 vs. 1.70 +/- 0.15 x 10(-2) min(-1) (P < 0.001); SI x AIRmax, 3.63 +/- 0.53 vs. 6.81 +/- 0.70 x 10(-2) min(-1) (P < 0.001)] in the older subjects. These findings suggest that the B cell dysfunction in older subjects is not associated with disproportionate proinsulinemia. However, in older subjects the B cell response to the insulin resistance of aging is reduced whether measured as fasting levels of PI or IRI or as the acute response to secretagogues. Thus, when examined in terms of the degree of insulin sensitivity, the lower fasting IRI levels in older subjects suggest that the utility of fasting insulin levels as a surrogate measure of insulin resistance in older individuals may be limited.

Proinsulin immunoreactivity in identical twins discordant for noninsulin-dependent diabetes mellitus.

Disproportionate elevation [increased proinsulin/insulin (PI/INS) ratio] of PI immunoreactivity is associated with noninsulin-dependent diabetes mellitus (NIDDM). The nature of this abnormality is not known. To address the question of whether genetic factors contribute to hyperproinsulinemia, we measured fasting levels of PI immunoreactivity, intact INS, and C peptide (CP) in 12 pairs of monozygotic twins discordant for NIDDM for a mean (+/- SEM) period of 9 +/- 3 yr. Thirteen age- and body mass index-matched healthy subjects without any family history of NIDDM acted as controls. The nondiabetic twins had levels of fasting INS, CP, PI, PI/CP, and PI/INS similar to those of control subjects. Fasting levels of PI, and PI/CP and PI/INS ratios were significantly 2- to 3-fold elevated in NIDDM twins compared to those in both nondiabetic twins and control subjects. To investigate whether hyperproinsulinemia in these NIDDM patients was due to a differential elevation of intact PI or conversion intermediates, we analyzed PI profiles in NIDDM twins and normal subjects by high pressure liquid chromatography. PI was heterogeneous and consisted mainly of des(31,32)-PI and intact PI in both NIDDM patients and normal subjects, with no major difference in composition between the groups. Small amounts of des(64,65)-PI (0-11%) were measured in some patients and normal subjects. The results suggest that hyperproinsulinemia is not a genetically determined trait per se in NIDDM. Disproportionately elevated PI levels seem to be related to the actual disease process. Further conversion of intact PI and des(31,32)-PI may be equally impaired in NIDDM.

Proinsulin, C-peptide, and insulin in normal subjects during an 8-h hyperglycemic clamp.

Increased concentrations of proinsulin immunoreactive material (PIM) absolutely or relative to insulin is a characteristic finding in patients with non-insulin-dependent diabetes mellitus (NIDDM). The aim of this study was to test if 8 h or mild hyperglycemia (7-9 mmol/l) in healthy subjects could induce a preferential secretion of PIM from B cells. Serum concentrations of insulin, C-peptide and PIM were measured every 10 min during the 8 h of continuous glucose infusion in nine normal-weight healthy subjects without diabetes among their first-degree relatives. After a gradual rise in B-cell peptides, a steady state was reached. From 4 to 8 h no further difference in insulin, C-peptide or PIM concentration was found. Fasting PIM/C-peptide and PIM/insulin ratios of 0.5% and 2.3% increased during the glucose clamp to levels of 1.4% and 7.6%, respectively. Neither testing the regression slope nor comparing individual time points showed any significant difference for the PIM/C-peptide ratio from 2 to 8 h and for the PIM/insulin ratio from 3 to 8 h. These results do not support the hypothesis that an increased glucose drive per se results in an altered B-cell function with increasing PIM/C-peptide ratio. At least 8 h of mild hyperglycemia in healthy subjects does not progressively alter B-cell function.

Longitudinal study of fasting proinsulin in 148 siblings of patients with insulin-dependent diabetes mellitus. Study Group on Childhood Diabetes in Finland.

OBJECTIVE: To follow proinsulin immunoreactive material (PIM) in healthy siblings from the time of diagnosis of insulin-dependent diabetes mellitus (IDDM) in the proband, for at least 2 years. DESIGN AND METHODS: The study comprised 148 siblings representing 112 families. The siblings were recruited from the nationwide 'Childhood Diabetes in Finland' study and tested for immunological markers. If a sibling was found positive for islet cell antibodies (ICA) or insulin autoantibodies (IAA), PIM sampling was extended beyond 2 years. RESULTS: Of the 148 siblings, 12 developed IDDM 3-53 months after the diagnosis in the proband. Eleven of these siblings exhibited initially normal PIM concentrations. In nine siblings, samples were available both more than 6 months and during the last 6 months before the diagnosis of IDDM; PIM concentrations increased in seven, remained unchanged in one, and decreased in one in the period up to the diagnosis of IDDM (P < 0.05). Median PIM concentration did not change significantly during the examination period of 2 years in the 136 siblings who did not contract IDDM. Constantly increased PIM concentrations were found in 12 of the 136 siblings who did not develop IDDM. These 12 siblings were all ICA negative. CONCLUSION: In healthy siblings of IDDM patients exhibiting an initially low PIM concentration, an abrupt increase in PIM seems to precede the clinical manifestation of IDDM within 0-6 months. However, there were too few patients available to close follow-up to allow calculation of any predictive value of this increase. Persistently increased PIM concentrations were present in some healthy siblings who did not develop IDDM. The reason for that finding remains unclear, but it could be associated with previous B cell damage.

Proportional proinsulin responses in first-degree relatives of patients with type 2 diabetes mellitus.

Elevated fasting proinsulin immunoreactive material (PIM) has previously been found in patients with type 2 (non-insulin-dependent) diabetes mellitus. It is not known whether this is a genetic trait or whether it is related to the manifestation of type 2 diabetes. Neither is it clear whether the raised fasting insulin immunoreactivity previously observed in first-degree relatives of patients with type 2 diabetes is due to raised PIM. Furthermore, it has not been investigated whether first-degree relatives have altered PIM responses to different secretagogues. To study this, PIM, insulin and C-peptide were measured in patients with type 2 diabetes, in their first-degree relatives and in healthy control subjects in the fasting state and in relatives and controls during a hyperglycemic clamp. At the end of the hyperglycemic clamp, 0.5 mg of glucagon was given intravenously to stress the beta cells further. Fasting PIM concentrations were significantly higher in patients with type 2 diabetes (P < 0.05). These patients did not have significantly elevated fasting insulin levels when corrected for PIM. In the relatives, fasting insulin concentrations were elevated but PIM levels were normal suggesting that the increase in fasting insulin concentrations reflected an increase in true insulin. The incremental PIM, insulin and C-peptide responses to glucose and glucagon in the relatives were not different from those in the controls. We conclude that elevated fasting PIM levels in patients with type 2 diabetes seem not to be a genetic trait.(ABSTRACT TRUNCATED AT 250 WORDS)

Low level of tissue plasminogen activator activity in non-diabetic patients with a first myocardial infarction.

OBJECTIVE: To explore the role of tissue plasminogen activator (tPA) activity and plasminogen activator inhibitor type 1 (PAI-1) in survivors of a first myocardial infarction (MI). Insulin and proinsulin were analysed as potential risk factors. DESIGN: Case-control study in northern Sweden. SUBJECTS: A total of 115 patients under 65 years of age with a first MI were enrolled and recalled for further examination 3 months later. Twenty-seven patients were excluded, 17 with known diabetes and 10 who did not come to the follow-up, giving a final number of 88 patients, 73 men and 15 women. Patients were age- and sex-matched with control subjects drawn from the local cohort in the MONICA population survey 1994. MAIN OUTCOME MEASURES: We compared MI patients and controls using univariate and multiple regression analyses including odds ratios (OR). RESULTS: PAI-1 activity, fibrinogen, postload insulin and -proinsulin were significantly higher and tPA activity significantly lower in MI patients in the univariate analysis. In a multiple regression analysis, including also age, sex and cardiovascular risk factors, these parameters were divided in quartiles. The lowest quartile of tPA activity was significantly associated with MI (OR = 19.1; CI 3.0-123) together with the highest quartiles of fibrinogen (OR = 25; CI 5.2-120) but other variables were not. CONCLUSION: Low tPA activity, i.e. low fibrinolytic activity, characterized nondiabetic subjects after a first MI which is not explained by concomitant disturbances in metabolic and anthropometric variables.

Enzyme immunoassay for intact human insulin in serum or plasma.

We describe an enzyme-linked two-site immunoassay for quantitation of intact insulin in human serum and plasma. The method uses two murine monoclonal antibodies that bind to two different epitopes on the insulin molecule. The immunoassay is specific. Human proinsulin is not bound by the antibodies, and the binding of partially processed proinsulin intermediates is believed to be of minor clinical importance. The relative response of human, bovine, and porcine insulin is 1, 1, and 3, respectively. The assay is sensitive (detection limit 5 pmol/L), accurate (101% recovery with 50 pmol/L insulin added to samples, 95% with 100 pmol/L, and 89% with 300 pmol/L), and fast (results within 3 h), and has a high analytical capacity (done in microtiter plates). The working assay range selected is 5-600 pmol/L, corresponding to a clinically useful range. Because of its specificity, this two-site immunoassay gives results that are lower than those obtained by using a competitive radioimmunoassay, both in normal individuals and in non-insulin-dependent diabetics.

Insulin sensitivity and insulin clearance in cystic fibrosis patients with normal and diabetic glucose tolerance.

OBJECTIVE: We studied glucose metabolism and insulin kinetics in cystic fibrosis patients with diabetic and normal glucose tolerance. DESIGN: Measurements of blood glucose and serum free insulin concentrations during hyperinsulinaemic normoglycaemic clamp and post-clamp insulin decay, followed by the calculation of insulin sensitivity (M-value and M/I ratio), insulin clearance rate, serum half-life and apparent distribution space for insulin. SUBJECTS: Cystic fibrosis patients, age range 20-29 years, with diabetes mellitus (n = 10) and normal glucose tolerance (n = 10), and 10 age-matched control subjects. RESULTS: During the glucose clamp, diabetic cystic fibrosis patients needed less glucose than cystic fibrosis patients with normal glucose tolerance and control subjects (M-value), and steady-state serum insulin concentrations were lower in cystic fibrosis patients with diabetic and normal glucose tolerance than in control subjects. The quantity of glucose metabolized per unit of serum insulin concentration (M/I ratio) was similar in the three study groups (median approximately 145 (mumol/kg/min)/(nmol/l); range 70-252). Insulin clearance rates were higher in cystic fibrosis patients with diabetic (24.4 (19.3-29.9) ml/kg/min) and normal (22.6 (14.9-28.4) ml/kg/min) glucose tolerance than in control subjects (17.5 (15.9-24.2) ml/kg/min). Although insulin clearance rates were inversely related to body mass index (R(S) = -0.59, P < 0.001), the higher insulin clearance rates in CF patients cannot be accounted for solely by differences in body mass index since the insulin clearance rates were similarly increased in patients with body mass index above and below 20 kg/m2 (22.7 (14.9-28.4) and 24.4 (19.3-29.9) ml/kg/min, respectively). Serum half-lives for insulin were shorter in cystic fibrosis patients (approximately 4.3 (3.2-7.2) min) than in control subjects (5.9 (3.8-12.5) min), whereas the apparent distribution spaces for insulin were similar in the three study groups (approximately 150 (88-391) ml/kg). CONCLUSIONS: Insulin sensitivity, calculated as the quantity of glucose metabolized per kg body weight per unit of serum insulin concentration, is normal in cystic fibrosis patients with normal glucose tolerance and with well controlled diabetes mellitus. The insulin clearance rate is increased in cystic fibrosis patients with diabetic and normal glucose tolerance, owing to a shorter serum half-life of insulin, whereas the apparent distribution space for insulin is normal.

Separation and quantitation of serum proinsulin and proinsulin intermediates in humans.

Two reversed-phase high-performance liquid chromatographic (RP-HPLC) systems were developed for the separation of human insulin, proinsulin and the major proinsulin intermediates. The individual components were quantified using two enzyme-linked immunosorbent assays for insulin and proinsulin immunore-active material (PIM) after (passive) evaporation of the organic modifier. Serum samples from normal subjects and patients with non-insulin-dependent diabetes mellitus were immunopurified and analysed in one of the RP-HPLC systems. The proportion of PIM relative to insulin immunoreactive material was higher in the diabetic patient compared with that in the normal subject. In both, PIM was heterogeneous, consisting of intact proinsulin and des-proinsulin intermediates.