Abnormalities of insulin pulsatility and glucose oscillations during meals in obese noninsulin-dependent diabetic patients: effects of weight reduction

Twenty-seven obese patients, including 8 with normal glucose tolerance, 10 with subclinical NIDDM, and 9 with overt noninsulin-dependent diabetes mellitus (NIDDM), were studied before and after prolonged weight loss to assess the effects of the underlying defects of diabetes per se from those of obesity and chronic hyperglycemia on the regulation of pulsatile insulin secretion. Serial measurements of insulin secretion and plasma glucose were obtained during 3 standardized mixed meals consumed over 12 h. Insulin secretion rates were calculated by deconvoluting plasma C peptide levels using a mathematical model for C peptide clearance and kinetic parameters derived individually in each subject. Absolute (nadir to peak) and relative (fold increase above nadir) amplitudes of each insulin secretory pulse and glucose oscillation were calculated. Compared to the obese controls, the subclinical and overt NIDDM patients manifested the following abnormal responses: 1) decreased relative amplitudes of insulin pulses, 2) reduced frequency of glucose oscillations, 3) increased absolute amplitudes of glucose oscillations, 4) decreased temporal concomitance between peaks of insulin pulses and glucose oscillations, 5) reduced correlation between the relative amplitudes of glucose oscillations concomitant with insulin pulses, and 6) temporal disorganization of the insulin pulse profiles. These defects were more severe in the overt NIDDM patients, and weight loss only partially reversed these abnormalities in both NIDDM groups. These findings indicate that beta-cell responsiveness is reduced, and the regulation of insulin secretion is abnormal under physiological conditions in all patients with NIDDM, including those without clinical manifestations of the disease. These abnormalities are not completely normalized with weight loss, even in patients who achieve metabolic control comparable to that in obese controls. The results are consistent with the presence of an inherent beta-cell defect that contributes to secretory derangements in subclinical NIDDM patients. This abnormality precedes frank hyperglycemia and may ultimately contribute to the development of overt NIDDM.     

Human studies with glucagon-like-peptide-1: potential of the gut hormone for clinical use

So far, a wealth of data originating from in vitro or animal experiments has been collected supporting the concept that the gut hormone, glucagon-like peptide-1 (GLP-1) may serve as a model molecule for the design of a new drug for the treatment of diabetes mellitus. This is supported by observations that GLP-1 has potent insulinotropic action in patients with non-insulin-dependent diabetes mellitus (NIDDM). It enhances beta-cell sensitivity to glucose stimulated insulin secretion. GLP-1 may also have a role in the treatment of impaired glucose tolerance, where the beta-cell is already insensitive to changes in plasma glucose concentrations. It may, as has previously been shown in animal models of 'prediabetes', delay the progressive decline in glucose tolerance to NIDDM. The glucose-dependent action of this peptide is an important feature in the treatment of NIDDM as it will protect against hypoglycaemic reactions, the most serious acute side-effect of antidiabetic therapy. Glucose utilization may be enhanced which would improve metabolic control in both NIDDM and IDDM. A glucagon lowering effect will further enhance metabolic control. This article reviews current experiences of the effects of GLP-1 in human studies. It points out the outcomes and limitations of previous trials and discusses future directions for the investigation of its potential use as a new agent in diabetes treatment.     

Beta-cell dysfunction in first-degree relatives of patients with non-insulin-dependent diabetes mellitus

To analyse the relationship between age, glucose tolerance, beta-cell function, and insulin sensitivity in preclinical states of non-insulin-dependent (Type 2) diabetes mellitus (NIDDM), we have done a cross-sectional, age-stratified analysis of 86 non-diabetic first-degree relatives of NIDDM patients and 49 controls with similar age, sex, and BMI. A 5 mg kg ideal body weight-1 min-1 for 60 min of continuous infusion of glucose with model assessment (CIGMA) of serum glucose and C-peptide values at the end of the infusion was used to determine glucose tolerance and beta-cell function. Insulin sensitivity was estimated by modelling basal serum glucose and insulin values. Relatives and controls were divided into tertiles on the basis of age. Relatives had higher basal (5.3 vs 5 mmol l-1, p = 0.02) and achieved serum glucose (9.1 vs 8.4 mmol l-1, p = 0.01), lower beta-cell function (128 vs 145%, p = 0.007), and lower insulin sensitivity (37 vs 43%, p = 0.002). Beta-cell function declined with age in relatives (from 139% in young subjects to 134% in intermediate subjects and to 111% in older subjects, p = 0.002) and this decline was associated with an increase in basal serum glucose (from 5.1 to 5.3 and to 5.7 mmol l-1, p = 0.000) and achieved glucose (from 8.3 to 9.1 and to 9.3 mmol l-1, p = 0.038), without significant changes in insulin sensitivity. These trends were observed even after the exclusion of subjects with mild glucose intolerance. We conclude that both beta-cell dysfunction and insulin resistance are present in first-degree relatives of NIDDM. The progression of beta-cell dysfunction and glucose intolerance with age suggests that beta-cell dysfunction is the key factor in the apparition and progression of the disease.     

Glucagon-like peptide 1 improves the ability of the beta-cell to sense and respond to glucose in subjects with impaired glucose tolerance

Impaired glucose tolerance (IGT) and NIDDM are both associated with an impaired ability of the beta-cell to sense and respond to small changes in plasma glucose concentrations. The aim of this study was to establish if glucagon-like peptide 1 (GLP-1), a natural enteric peptide and potent insulin secretagogue, improves this defect. Two weight-matched groups, one with eight subjects having IGT (2-h glucose, 10.1 +/- 0.3 mmol/l) and another with seven subjects with diet-treated NIDDM (2-h glucose, 14.5 +/- 0.9 mmol/l), were studied on two occasions during a 12-h oscillatory glucose infusion, a sensitive test of the ability of the beta-cell to sense and respond to glucose. Glucose was infused with a mean rate of 4 mg x kg(-1) x min(-1), amplitude 33% above and below the mean rate, and periodicity of 144 min, with infusion of saline or GLP-1 at 0.4 pmol x kg(-1) x min(-1) for 12 h. Mean glucose levels were significantly lower in both groups during the GLP-1 infusion compared with during saline infusion: 9.2 +/- 0.4 vs. 6.4 +/- 0.1 mmol/l in the IGT subjects (P < 0.0004) and 14.6 +/- 1.0 vs. 9.3 +/- 0.7 mmol/l in NIDDM subjects (P < 0.0002). Despite this significant reduction in plasma glucose concentration, insulin secretion rates (ISRs) increased significantly in IGT subjects (513.3 +/- 77.6 vs. 583.1 +/- 100.7 pmol/min; P < 0.03), with a trend toward increasing in NIDDM subjects (561.7 +/- 122.16 vs. 642.8 +/- 128 pmol/min; P = 0.1). These results were compatible with enhanced insulin secretion in the presence of GLP-1. Spectral power was used as a measure of the ability of the beta-cell to secrete insulin in response to small changes in the plasma glucose concentration during the oscillatory infusion. Spectral power for ISR increased from 2.1 +/- 0.9 during saline infusion to 7.4 +/- 1.3 during GLP-1 infusion in IGT subjects (P < 0.004), but was unchanged in NIDDM subjects (1.0 +/- 0.4 to 1.5 +/- 0.6; P = 0.3). We concluded that low dosage GLP-1 improves the ability of the beta-cell to secrete insulin in both IGT and NIDDM subjects, but that the ability to sense and respond to subtle changes in plasma glucose is improved in IGT subjects, with only a variable response in NIDDM subjects. Beta-cell dysfunction was improved by GLP-1 infusion, suggesting that early GLP-1 therapy may preserve beta-cell function in subjects with IGT or mild NIDDM.     

Disruption of IRS-2 causes type 2 diabetes in mice

Human type 2 diabetes is characterized by defects in both insulin action and insulin secretion. It has been difficult to identify a single molecular abnormality underlying these features. Insulin-receptor substrates (IRS proteins) may be involved in type 2 diabetes: they mediate pleiotropic signals initiated by receptors for insulin and other cytokines. Disruption of IRS-1 in mice retards growth, but diabetes does not develop because insulin secretion increases to compensate for the mild resistance to insulin. Here we show that disruption of IRS-2 impairs both peripheral insulin signalling and pancreatic beta-cell function. IRS-2-deficient mice show progressive deterioration of glucose homeostasis because of insulin resistance in the liver and skeletal muscle and a lack of beta-cell compensation for this insulin resistance. Our results indicate that dysfunction of IRS-2 may contribute to the pathophysiology of human type 2 diabetes.     

Defects in insulin secretion and action in women with a history of gestational diabetes

Gestational diabetes mellitus (GDM) is associated with defects in insulin secretion and insulin action, and women with a history of GDM carry a high risk for the development of non-insulin-dependent diabetes mellitus (NIDDM). Assessment of subjects with a history of GDM who are currently normoglycemic should help elucidate some of the underlying defects in insulin secretion or action in the evolution of NIDDM. We have studied 14 women with normal oral glucose tolerance who had a history of GDM. They were compared with a group of control subjects who were matched for both body mass index (BMI) and waist-to-hip ratio (WHR). All subjects underwent tests for the determination of oral glucose tolerance, ultradian oscillations in insulin secretion during a 28-h glucose infusion, insulin secretion in response to intravenous glucose, glucose disappearance after intravenous glucose (Kg), and insulin sensitivity (SI) as measured by the Bergman minimal model method. The BMI in the post-GDM women was similar to that in the control subjects (24.9 +/- 1.2 vs. 25.4 +/- 1.4 kg/m2, respectively), as was the WHR ratio (0.80 +/- 0.01 vs. 0.76 +/- 0.01, respectively). The post-GDM women were slightly older (35.2 +/- 0.9 vs. 32.1 +/- 1.4 years, P = 0.04). The fasting plasma glucose levels were significantly higher in the post-GDM group than in the control group (4.9 +/- 0.1 vs. 4.4 +/- 0.1 mmol/l, respectively, P < 0.001) and remained higher at each of the subsequent determinations during the oral glucose tolerance test, although none had a result indicative of either diabetes or impaired glucose tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pancreatogenic panniculitis

OBJECTIVE: Islet amyloidosis may be one mechanism for pancreatic islet beta-cell loss that is associated with the development of NIDDM. However, the question remains whether chronic overstimulation of insulin and islet amyloid polypeptide (IAPP) secretion in states of insulin resistance could lead to formation of islet amyloidosis and hence NIDDM in some patients. We studied pancreatic islet pathology in congenital generalized lipodystrophy, a genetic syndrome of extreme insulin resistance that may provide some clues. RESEARCH DESIGN AND METHODS: Our patient was a 24-year-old African-American woman with congenital generalized lipodystrophy. Severe acanthosis nigricans was noted in her since age 6. At ages 12 and 16, normal and impaired glucose tolerances, respectively, were noted on oral glucose tolerance tests but were accompanied by extreme fasting and post-prandial hyperinsulnemia. Overt diabetes developed at age 18 and she required approximately 180 U of insulin daily. Immediately after an accidental death at age 24, an autopsy was performed. Pancreatic histology was studied in detail using routine methods and immunohistochemical techniques. RESULTS: Some scarring of the pancreas as a result of previous episodes of acute pancreatitis was observed. Severe amyloidosis was noted in 89% of the islets, sparing those that were rich in pancreatic polypeptide-secreting cells. Amyloid deposits stained intensely on immunostaining with antibodies against amylin. Marked paucity of beta-cells was evident. The ratio of beta- to alpha-cells was reduced to 1:1 (normal ratio approximately 4:1). CONCLUSIONS: These observations suggest that chronic presence of extreme insulin resistance may induce premature and severe islet amyloidosis as well as beta-cell atrophy.     

Cardiovascular risk factors prior to the development of non-insulin-dependent diabetes mellitus in persons with impaired glucose tolerance: the Hoorn Study

The aim of the study was to analyze cardiovascular risk factors as predictors for developing non-insulin-dependent diabetes mellitus (NIDDM) in people with impaired glucose tolerance. A cross-sectional survey of glucose tolerance was conducted in people, aged 50-74, who were randomly selected from the registry of the middle-sized town Hoorn (The Netherlands). Based on the mean values of two oral glucose tolerance tests, people were classified in glucose tolerance categories according to the WHO criteria. The mean follow-up time was 36 months (range 13-55 months). The cumulative incidence of NIDDM was 34% (95% CI 16.9-45.1). In multiple logistic regression analysis, cardiovascular risk factors at baseline did not predict the conversion from impaired glucose tolerance to NIDDM, in contrast with the two-hour plasma glucose level (odds ratio 3.56, p < 0.001) and the fasting proinsulin level, as one of the determinants of beta-cell dysfunction (Odds ratio 2.1, p < 0.05). The baseline HDL-cholesterol level, one of the components of the insulin resistance syndrome, was associated with the conversion from impaired glucose tolerance to normal glucose tolerance (Odds ratio 1.58, p < 0.05). The results of our study seem to support the hypothesis that conversion from impaired glucose tolerance to normal glucose tolerance depends on insulin resistance and the development of NIDDM from impaired glucose tolerance depends on beta-cell dysfunction.     

Amylin as an additional possible pathogenic factor in NIDDM and the insulin resistance syndrome

The syndrome of insulin resistance comprises the following H-phenomena: 1. Hyperinsulinism compensating the inborn postreceptor insulin resistance, 2. Hyperglycaemia-non-insulin-dependent diabetes mellitus, 3. Hyperlipoproteinaemia with android obesity, 4. Hypertension, 5. Hirsutism with the syndrome of polycystic ovaries as a manifestation of a hyperandrogenic situation in the female organism. Molecular syndromes of this syndrome of insulin resistance are obscure. They are the subject of intensive studies because H-phenomena are an aggregation of the main risk factors of atherogenesis. Recently attention is focused also on amylin--a 37 amino acid peptide with a 50% homologous amino acid sequence with a calcitonin-gene--related peptide (CGRP), which is the product of a gene made up of three introns on the 12th chromosome. Amylin acts in the beta-cells of the pancreas as a co-secretion of insulin. If in excess, it is deposited in the form of an amyloid in the beta-cells. In the early stage of NIDDM it alters the physiological response of the beta-cell to glycaemic stimuli and food, in later stages of the disease, after accumulation, it causes apoptosis of the beta-cell and reduces thus the secretory capacity of the Langerhans islets. It is excreted in the urine and thus, if the glomerular filtration is reduced, it cumulates in the blood stream and thus enhances insulin resistance already in the early stages of chronic renal insufficiency, or in diabetic nephropathy. In type II diabetes similarly as insulin levels also amylin levels are elevated, while in type I diabetes with early autoimmune destruction of the beta-cells the insulin and amylin levels are reduced or even zero. Amylin reduces in the muscle, probably by inhibition of glycogen synthase, the insulin stimulated non-oxidative utilization of glucose into muscle glycogen and conversely by stimulation of phosphorylase it stimulates glycogenolysis and thus also lactate production and gluconeogenesis in the liver which all are anti-insulin effects which intensify the insulin resistance of the main target tissues. Amylin, similarly as CGRP or calcitonin, reduces Ca blood levels and has a vasodilatating effect; it reduces the BP but in different minimal and maximal doses and by a different mechanism and via special receptors because the link of amylin to calcitonin receptors is 100 times lower and does not produce a rise of cAMP in the target cell. The effect on the enhancement of insulin resistance in muscle was proved also by direct measurements using an hyperinsulinaemic euglycaemic clamp. After prolongation of the clamp to more than two hours the effect on insulin resistance disappeared, although the hypocalcinaemic effect persisted. Amylin is able by its biological action to modify the secretion as well as the effectiveness of insulin to pathological values. These two characteristics are typical for impaired glucose tolerance in type II diabetes. Studies are under way to find out whether the effect of amylin is involved directly also in the pathogenesis of the other H-phenomena or only via accentuation of hyperinsulinism. In any case amylin is a new link the role of which in the pathogenesis of NIDDM and the syndrome of insulin resistance awaits evaluation. Due to its effect on gastric evacuation it participates also in the postprandial glycaemic control in particular in type I diabetes where it it begins to be used in therapy. Perhaps it will be possible to administer it in these patients along with insulin to improve diabetes compensation.     

Experimental benefit of moxonidine on glucose metabolism and insulin secretion in the fructose-fed rat

OBJECTIVE: Non-insulin-dependent diabetes mellitus (NIDDM) is often associated with hypertension leading to a specifically high cardiovascular risk in these patients. However, there is evidence that insulin resistance and hyperinsulinaemia are not only characteristic for diabetic patients but also for some non-diabetic populations in which a cluster of cardiovascular risk factors is observed (hypertension, hypertriglyceridaemia, obesity). Therefore, hyperinsulinaemia and insulin resistance have been suggested to be of major pathophysiological importance for the development of this syndrome (syndrome X). Since imidazoline receptors are currently considered to be a specific pharmacological target for blood pressure reduction, it is important to know whether and in which way these compounds affect the glucose homoeostasis and insulin release. DESIGN: The influence of moxonidine on glucose tolerance in vivo was determined in healthy control rats, in rats receiving a high fructose diet for 6 weeks to induce insulin resistance, hyperinsulinaemia and hypertension, and in rats receiving in addition to a high fructose diet moxonidine (1.5 mg/kg body weight daily). In vitro, using isolated pancreatic islets of mice, long-lasting effects (chronic) and immediate (acute) effects of moxonidine on beta-cell function were determined by basal and glucose stimulated insulin release in two different experimental systems: (1) islets were exposed for 24 h (37 degrees C) to various concentrations of moxonidine ranging from 1 nmol/l to 1 mmol/l, followed by a washing procedure to remove excess of moxonidine and then used for the beta-cell function test; (2) islet cultures were incubated again with moxonidine for 24 h (37 degrees C) with either 1 nmol/l or 1 micromol/l. In contrast to the first experiments, however, after the washing procedure moxonidine was added at the same concentration as used for preincubation to test its direct effect on beta-cell function. RESULTS: In healthy control rats acute administration of moxonidine in vivo impaired the glucose tolerance in high dosages, which effectively reduced the blood pressure (>1 mg/kg body weight). This effect was, however, smaller that that observed by clonidine. In fructose-fed rats, moxonidine completely prevented the development of insulin resistance, hyperinsulinaemia and hypertension. In vitro, pancreatic islets preincubated with moxonidine exhibited dose-dependently both stimulatory and inhibitory chronic effects on beta-cell function compared with that in controls. Preincubation of islet cultures with moxonidine at concentrations between 1 nmol/l and 1 mmol/l resulted in a reduction of basal insulin release which was very pronounced at concentrations higher than 100 nmol/l. The results obtained for glucose-stimulated insulin release opposed in part those for basal insulin release, since the preincubation with moxonidine up to 10 micromol/l gave rise to an increased insulin release. An additional direct effect of moxonidine with a marked reduction of glucose-stimulated insulin release was observed, however, when moxonidine was present during the preincubation (24 h) and the functional test at a concentration of 1 nmol/l or 1 micromol/l. CONCLUSIONS: Our data suggest that a causal linkage exist between the development of hypertension and insulin resistance/hyperinsulinaemia in the high fructose diet rat model. Since central activation of imidazoline receptors by moxonidine can prevent this syndrome, it follows that an overactivity of the sympathetic nervous system is of major importance. Suppression of this sympathetic overactivity might be an effective approach to reduce hypertension and the concomitant metabolic defect. Therefore, such an interventional strategy could contribute to reduce the cardiovascular risk of NIDDM patients and patients with other forms of insulin resistance/hyperinsulinaemia such as metabolic cardiovascular syndrome.     

Myocardial glucose uptake in patients with NIDDM and stable coronary artery disease

Whole body insulin resistance characterizes patients with NIDDM, but it is not known whether insulin also has impaired ability to stimulate myocardial glucose uptake (MGU) in these patients. This study was designed to evaluate MGU as measured by 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) in patients with NIDDM and stable coronary artery disease (CAD) under standardized metabolic conditions. Eight patients with NIDDM, 11 nondiabetic patients with CAD, and 9 healthy control subjects were enrolled in the study. MGU was quantitated in the normal myocardial regions with [18F]FDG and PET and the whole body glucose disposal by glucose-insulin clamp technique (serum insulin, -430 pmol/l). Plasma glucose and serum insulin concentrations were comparable in all groups during PET studies. The whole body glucose uptake was 45% lower in NIDDM patients (22 +/- 9 micromol x min(-1) X kg(-1) body wt [mean +/- SD]), compared with healthy control subjects (40 +/- 17 micromol x min(-1) x kg(-1) body wt, P < 0.05). In CAD patients, whole body glucose uptake was 30 +/- 9 micromol x min(-1) x kg(-1) body wt (NS between the other groups). MGU was similar in the normal segments in all three groups (69 +/- 28 micromol x min(-1) x 100 g(-1) in NIDDM patients, 72 +/- 17 micromol x min(-1) x 100 g(-1) in CAD patients, and 76 +/- 10 micromol x min(-1) x 100 g(-1) in healthy control subjects, NS). No correlation was found between whole body glucose uptake and MGU. As studied by [18F]FDG PET under stable normoglycemic hyperinsulinemic conditions, MGU is not reduced in patients with NIDDM and CAD in spite of peripheral insulin resistance. These findings suggest that there is no significant defect in MGU in patients with NIDDM.     

Identification of a quantitative trait locus influencing plasma insulin levels after 70% pancreatectomy using the OLETF rat

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for obese-type non-insulin-dependent diabetes mellitus (NIDDM) in humans. The OLETF rat has poor capacity for proliferation of pancreatic beta-cells after partial pancreatectomy, which may be the critical pathogenetic event in NIDDM development. The poor pancreatic beta-cell proliferation in this model is characterized by reduction in beta-cell mass and decrease in insulin content in the remnant pancreas. Our investigation was designed to identify quantitative trait loci (QTLs) responsible for beta-cell mass and plasma insulin levels after partial pancreatectomy by performing a genome-wide scan in an F2 intercross obtained by mating the OLETF and the Fischer-344 (F344) rats. We have identified a suggestive QTL for the plasma insulin levels, near D20Mgh5 on rat chromosome 20, with a maximum lod score of 3.75 which accounts for 20% of the total variance, while no QTLs were detected for beta-cell mass. This chromosome 20 QTL, whose OLETF allele is associated with low plasma insulin levels through acting in an incompletely recessive manner, may affect insulin secretion itself rather than beta-cell proliferation.     

Autoantibodies against CD38 (ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase) that impair glucose-induced insulin secretion in noninsulin- dependent diabetes patients

Cyclic ADP-ribose (cADPR) has been shown to be a mediator for intracellular Ca2+ mobilization for insulin secretion by glucose in pancreatic beta cells, and CD38 shows both ADP-ribosyl cyclase to synthesize cADPR from NAD+ and cADPR hydrolase to hydrolyze cADPR to ADP-ribose. We show here that 13.8% of Japanese non-insulin-dependent diabetes (NIDDM) patients examined have autoantibodies against CD38 and that the sera containing anti-CD38 autoantibodies inhibit the ADP-ribosyl cyclase activity of CD38 (P 相似文献   

Temporal profiles and clinical significance of pulsatile insulin secretion

In this article, recent experiments are reviewed which have addressed the role of oscillatory insulin secretion in the pathophysiology of glucose intolerance and diabetes. The ultradian oscillations of insulin secretion appear to be an integral part of the feedback loop between glucose and insulin secretion and as a result are abnormal in states of glucose intolerance. Treatment of impaired glucose tolerance with troglitazone, a thiazolidinedione that improves insulin sensitivity, leads to an improvement in the ability of the beta-cell to sense and respond to a glucose stimulus restoring the ability of glucose to entrain the ultradian oscillations. The rapid oscillations of insulin secretion appear to be an inherent feature of the cellular mechanisms of insulin secretion since they persist in the isolated perfused pancreas and in perifused islets. These oscillations are paralleled by changes in intracellular Ca2+ and are also abnormal in states of glucose intolerance and diabetes. Available evidence indicates that these alterations are due to decreased expression of voltage-dependent Ca2+ channels on the beta-cell membrane.     

Risk factors for the development of NIDDM in Yonchon County, Korea

OBJECTIVE: To determine the risk factors for the development of NIDDM in Yonchon County of Korea. RESEARCH DESIGN AND METHODS: We studied 1,193 Korean nondiabetic subjects at baseline who participated in a 2-year follow-up study on diabetes in Yonchon County. A 75-g oral glucose tolerance test was performed 2 years after the baseline examination. Age, sex, and anthropometric and metabolic characteristics at baseline were analyzed simultaneously as potential predictors of conversion to NIDDM. We also designed a nested case-control study to determine the role of hyperinsulinemia and/or hyperproinsulinemia in the conversion to NIDDM in patients with newly developed diabetes and control subjects matched for age, sex, BMI, and waist-to-hip-ratio. RESULTS: At 2 years, 67 subjects developed diabetes, as defined by World Health Organization criteria. The age-adjusted incidence was significantly higher in men (6.4%) than in women (3.0%), and the incidence increased as age increased in both sexes. Multiple logistic regression analysis revealed age, male sex, and fasting and 2-h glucose levels to be significant risk factors for the development of NIDDM, whereas waist-to-hip ratio and BMI were not. In a nested case-control study, baseline proinsulin but not insulin levels were significantly higher in subjects who progressed to NIDDM than in those who did not. CONCLUSIONS: In the Korean population, beta-cell dysfunction, as measured by high proinsulin levels, seems to be associated with subsequent development of NIDDM, whereas regional and general obesity and fasting insulin levels, which may be a surrogate for insulin resistance, were not.     

Gestational diabetes mellitus and subsequent development of overt diabetes mellitus

GDM develops in 1-3% of all pregnancies. Women with GDM are characterized by a relatively diminished insulin secretion coupled with a pregnancy-induced insulin resistance primary located in skeletal muscle tissue. The cellular background for this insulin resistance is not known. The binding of insulin to its receptor and the subsequent activation of the insulin receptor tyrosine kinase have significant importance for the cellular effect of insulin. Thus, the pathogenesis to the insulin resistance was studied by investigating insulin receptor binding and tyrosine kinase activity in skeletal muscle biopsies from women with GDM and pregnant controls. No major abnormalities were found in GDM wherefore it is likely that the insulin resistance is caused by intracellular defects distal to the activation of the tyrosine kinase. Glucose tolerance returns to normal postpartum in the majority of women with GDM. However, previous studies, in populations quite different from a Danish population, have shown that women with previous GDM have a high risk of developing overt diabetes mellitus later in life. Hence, we aimed to investigate the prognosis of women with previous GDM with respect to subsequent development of diabetes and also to identify predictive factors for the development of overt diabets in these women. A follow-up study of diet treated GDM women diagnosed during 1978 to 1985 at the Rigshospital, Copenhagen was performed. Glucose tolerance was evaluated in 241 women (81% of the GDM population) 2-11 years after pregnancy. Abnormal glucose tolerance was found in 34.4% of the women (3.7% IDDM, 13.7% NIDDM, 17% IGT) in contrast to a control group where none had diabetes and 5.3% had IGT. Logistic regression analysis identified the following independent risk factors for later development of diabetes: a high fasting glucose level at diagnosis of GDM, a delivery more than 3 weeks before term, and an abnormal OGTT 2 months postpartum. Low insulin secretion at diagnosis of GDM was also an independent risk factor. The presence of ICA and GAD-autoantibodies in pregnancy was associated with later development of IDDM. In another study the following techniques: hyperinsulinaemic euglycaemic clamp, indirect calorimetry and tritiated glucose infusion were used to evaluate insulin sensitivity in glucose tolerant nonobese women with previous GDM and controls. A decreased insulin sensitivity due to a decreased non-oxidative glucose metabolism in skeletal muscle was found in women with previous GDM. Hence, the activity of three key enzymes in intracellular glucose metabolism (GS, HK and PFK) was studied in skeletal muscle biopsies obtained in the basal state and after 3 h hyperinsulinaemia, with the aim to identify the cellular defects causing the decreased insulin sensitivity. However, no abnormalities in enzyme activity was found. The same group of previous GDM women had a relatively reduced insulin secretion evaluated by the IVGTT. A longitudinal study of 91 GDM women showed a relatively reduced insulin secretion to oral glucose in pregnancy, postpartum as well as 5-11 years later. Thus the present review has shown that even nonobese glucose tolerant women with previous GDM are characterized by the metabolic profile of NIDDM i.e. insulin resistance and impaired insulin secretion. Hence, the combination of this finding together with the significantly increased risk for development of diabetes indicates that all women with previous GDM should have a regular assessment of their glucose tolerance in the years after pregnancy. The first OGTT should be performed around 2 months postpartum in order to diagnose women already diabetic and to identify women with the highest risk for later development of overt diabetes. Women with previous GDM comprise a target group for future intervention trials with the aim to prevent or delay development of NIDDM and IDDM.     

Defective pancreatic beta-cell glycolytic signaling in hepatocyte nuclear factor-1alpha-deficient mice

Mutations in the hepatocyte nuclear factor-1alpha (HNF-1alpha) gene cause maturity onset diabetes of the young type 3, a form of type 2 diabetes mellitus. In mice lacking the HNF-1alpha gene, insulin secretion and intracellular calcium ([Ca2+]i) responses were impaired following stimulation with nutrient secretagogues such as glucose and glyceraldehyde but normal with non-nutrient stimuli such as potassium chloride. Patch clamp recordings revealed ATP-sensitive K+ currents (KATP) in beta-cells that were insensitive to suppression by glucose but normally sensitive to ATP. Exposure to mitochondrial substrates suppressed KATP, elevated [Ca2+]i, and corrected the insulin secretion defect. NAD(P)H responses to glucose were substantially reduced, and inhibitors of glycolytic NADH generation reproduced the mutant phenotype in normal islets. Flux of glucose through glycolysis in islets from mutant mice was reduced, as a result of which ATP generation in response to glucose was impaired. We conclude that hepatocyte nuclear factor-1alpha diabetes results from defective beta-cell glycolytic signaling, which is potentially correctable using substrates that bypass the defect.     

Formation of 1,N6-etheno-2''-deoxyadenosine adducts by trans,trans-2, 4-Decadienal

This study was designed to investigate the effect of glucogon-like peptide-1 (GLP-1) on pancreatic beta-cell function in normal, Zucker diabetic fatty (ZDF) rats, a model for non-insulin-dependent diabetes mellitus (NIDDM or type II diabetes) and their heterozygous siblings. Pancreas perfusion and enzyme-linked immunosorbent assay (ELISA) were used to detect the changes in insulin release under fasting and hyperglycemic conditions and following stimulation with GLP-1. Animals from the ZDF/Gmi-fa rats (ZDF) were grouped according to age, sex, and phenotype (obese or lean), and compared with LA lean rats. Glucose stimulation (10 mmol/L) in obese rats showed repressed response in insulin release. Glucose plus GLP-1 stimulation caused increased insulin release in all groups. The degree of this response differed between groups: lean > obese; young > adult; female > male. The LA lean control group was most sensitive, while the ZDF overtly diabetic group had the lowest response. In addition, the pulsatile pattern of insulin secretion was suppressed in ZDF rats, especially in obese groups. These results support the hypothesis that GLP-1 can effectively stimulate insulin secretion. Insulin release was defective in ZDF obese rats and could be partially restored with GLP-1. ZDF lean rats also showed suppression of beta-cell function and there was a difference in beta-cell function related to sex in ZDF strain. This study documents the efficacy of GLP-1 to stimulate insulin release and contributes to our understanding of the pathophysiological mechanisms underlying NIDDM.