bluuebunny/crossref_metadata_2025 huggingface dataset:
Maternal Enteroviral Infection During Pregnancy as a Risk Factor for ChildHood IDDM: A Population-Based Case-Control Study
Authors: Dahlquist Gisela G , Ivarsson Sten , Lindberg Bengt , Forsgren Marianne
Published: September 2013

Using the nationwide childhood-onset diabetes register in Sweden, we were able to trace children who contracted diabetes before the age of 15 years and who were born at a specific hospital in Sweden where maternal sera from delivery had been stored during the years 1969-1989. Sera obtained at delivery from 57 mothers of diabetic children were compared with sera from 203 mothers of control subjects who were delivered at the same hospital during the same time period. The sera were analyzed blindly using a group-specific enzyme-linked immunosorbent assay for enteroviral IgG and IgM antibodies before and after urea wash as an avidity test. On the same plates, IgG antibodies to herpes, mumps, and toxoplasmosis were analyzed. The mean absorbance values of enteroviral IgG antibodies against enteroviral antigens (echo30, coxsackie B5, and echo9) were significantly higher among mothers whose children later developed diabetes (P = 0.002, P = 0.02, and P = 0.04, respectively). When reduction in activity after urea wash, indicating recently formed antibodies, was compared, the differences were even more pronounced (P < 0.001 for all three antigens). No significant differences were found for antibodies against herpes (all types), herpes type 2, mumps, or toxoplasmosis. When IgM activity and/or a significant decrease in avidity index, an indication of recent enterovirus infection, was used as a risk exposure, the odds ratio standardized for year of birth (95% confidence interval) was 3.19 (1.39–7.30). We conclude that the results of this study indicate that enteroviral infection during pregnancy is a risk factor for childhood-onset diabetes in the offspring. Whether one or several viruses in the enterovirus group are responsible remains to be discovered.
Athletes With IDDM Exhibit Impaired Metabolic Control and Increased Lipid utilization With No Increase in Insulin Sensitivity
Authors: Ebeling Pertti , Tuominen Juha A , Bourey Raymond , Koranyi Laszlo , Koivisto Veikko A
Published: September 2013

Physical exercise is traditionally recommended to diabetic patients as part of their treatment. Although healthy athletes exhibit enhanced skeletal muscle insulin sensitivity, the metabolic effects of vigorous training in patients with insulin-dependent diabetes mellitus (IDDM) are not known. This study was designed to examine the effects of competitive sports on fuel homeostasis and insulin sensitivity in athletes with IDDM. We studied 11 athletes and 12 matched sedentary men with IDDM. In each subject, we measured glycemic control, insulin-stimulated glucose uptake in the whole body and forearm, rates of glucose and lipid oxidation, and muscle glycogen, glycogen synthase, and glucose transport protein (GLUT4) concentrations. The athletes had higher VO2max (52 ± 1 vs. 42 ± 1 ml.kg−1 · min−1, P < 0.001) and HbA1c levels (8.4 ± 0.4 vs. 7.2 ± 0.2%, P < 0.05) than sedentary patients, but took smaller insulin doses (41 ± 3 vs. 53 ± 3 U/day, P < 0.05). The insulin-stimulated rates of whole-body and forearm glucose uptake and glucose oxidation were similar in the two groups, whereas both energy expenditure and lipid oxidation were increased in the athletes. Lipid oxidation correlated inversely with glycogen synthase activity. The mean glucose arterialized venous blood-deep venous blood (A-V) difference during the insulin infusion (60-240 min) correlated with the whole-body glucose disposal throughout the insulin infusion (after 60 min, r > 0.73, P < 0.001 for all 30-min periods). This association is accounted for by the relationship between glucose A-V difference and nonoxidative glucose disposal. Muscle glycogen and GLUT4 protein contents were not different in the two groups. In conclusion, in athletes with IDDM: 1) competitive exercise performed at variable schedules and intensities leads to a decrease in required insulin dose, impairment of metabolic control, and increase in lipid utilization; 2) insulin sensitivity is not enhanced; and 3) glucose A-V difference, not blood flow, is the major determinant of body sensitivity to insulin. Thus, more intense glucose monitoring and education may be required for the maintenance of good control in patients with IDDM involved in competitive sports.
Lack of Relationship Between an Insertion/Deletion Polymorphism in the Angiotensin I–Converting Enzyme Gene and Diabetic Nephropathy and Proliferative Retinopathy in IDDM Patients
Authors: Tarnow Lise , Cambien François , Rossing Peter , Nielsen Flemming S , Hansen Birgitte V , Lecerf Laure , Poirier Odette , Danilov Sergei , Parving Hans-Henrik
Published: September 2013

Genotypic abnormalities of the renin-angiotensin system have been suggested as a risk factor for the development of diabetic nephropathy and proliferative retinopathy. We studied the relationship between an insertion(I)/deletion (D) polymorphism in the angiotensin-converting enzyme (ACE) gene in insulin-dependent diabetes mellitus (IDDM) patients with diabetic nephropathy (121 men and 77 women, age 40.9 ± 10 years, diabetes duration 27 ± 8 years) and in IDDM patients with normoalbuminuria (118 men and 74 women, age 42.7 ± 10 years, diabetes duration 26 ± 8 years). A total of 155 patients (40%) had proliferative retinopathy, and 67 patients (17%) had no diabetic retinopathy. There was no difference in genotype distribution between IDDM patients with diabetic nephropathy and those with normoalbuminuria: 63 (32%)/95 (48%)/40 (20%) vs. 67 (35%)/77 (41%)/46 (24%) had DD/ID/II genotypes, respectively. Patients with nephropathy had higher plasma ACE levels (609 [151–1,504] ³g/l) compared with patients with normoalbuminuria (428 [55–1,630] ³g/l) (P < 0.001). Multiple linear regression analysis revealed that the plasma ACE level in patients with nephropathy is partially determined by ACE/ID polymorphism, mean arterial blood pressure, and glomerular filtration rate (r2 = 0.30, P < 0.001). There was no difference in genotype distribution between IDDM patients with proliferative retinopathy and those without diabetic retinopathy: 52 (34%)/74 (48%)/29 (19%) vs. 26 (39%)/25 (37%)/16 (24%) had DD/ID/II genotypes, respectively. There was also no difference in plasma ACE concentration detected among patients with no, simplex, or proliferative retinopathy. We conclude that the ACE/ID polymorphism does not contribute to the genetic susceptibility to diabetic nephropathy and proliferative retinopathy, whereas the raised plasma ACE concentration may play a role in the initiation and progression of diabetic nephropathy in Caucasian IDDM patients.
Myocardial Glucose Uptake Evaluated by Positron Emission Tomography and Fluorodeoxyglucose During Hyperglycemic Clamp in IDDM Patients: Role of Free Fatty Acid and Insulin Levels
Authors: Monti Lucilla D , Lucignani Giovanni , Landoni Claudio , Moresco Rosa M , Piatti Piermarco , Stefani Ilario , Pozza Guido , Fazio Ferruccio
Published: September 2013

Myocardial and whole-body glucose metabolism was assessed in 19 insulin-dependent diabetes mellitus (IDDM) patients. A hyperglycemic clamp was performed 1) in the absence of insulin at free fatty acid (FFA) levels of 1.0 mmol/l (test 1); 2) in the absence of insulin at low FFA levels (0.1 mmol/l) by means of a lipid-lowering drug, acipimox (test 2); 3) during insulin infusion to achieve systemic levels of 400 pmol/l and FFA levels of 0.1 mmol/l (test 3); and 4) at the insulin levels of test 3 but increasing FFA to 1.0 mmol/l by means of heparin and intralipid infusion (test 4). Myocardial glucose uptake was measured by positron emission tomography (PET) and 2-[18F]fluoro-2-deoxy-D-glucose. Whole-body glucose uptake was measured in the four conditions by the glucose infusion rate during the PET scanning period. Myocardial glucose uptakes were 40.3 ± 18.0, 395.5 ± 139.6, 852.2 ± 99.1, and 1,388.4 ± 199.1 μmol · kg tissue−1 · min−1 (mean ± SD) and whole-body glucose uptakes were 10.1 ± 2.3, 10.1 ± 3.4, 42.8 ± 5.8, and 30.5 ± 5.6 μmol · kg body wt−1 · min−1 during tests 1, 2, 3, and 4, respectively. Thus, in IDDM patients without coronary artery disease under the condition of hyperglycemia, an increase of myocardial glucose uptake was obtained either by lowering of FFA levels during hypoinsulinemia or by an increase in FFA levels during hyperinsulinemia. In both conditions no significant changes of whole-body glucose uptake were demonstrated.
Myocardial m-[123I]Iodobenzylguanidine Scintigraphy for the Assessment of Adrenergic Cardiac Innervation in Patients With IDDM: Comparison With Cardiovascular Reflex Tests and Relationship to Left Ventricular Function
Authors: Kreiner Gerhard , Wolzt Michael , Fasching Peter , Leitha Thomas , Edlmayer Alexandra , Korn Asdrienne , Waldhäusl Werner , Dudczak Robert
Published: September 2013

Cardiac imaging using m-[123I]iodobenzylguanidine (mIBG) reflects sympathetic myocardial innervation. In patients with insulin-dependent diabetes mellitus (IDDM), the following were studied: 1) the prevalence of derangements of cardiac autonomic innervation as detected by mIBG scintigraphy in comparison with cardiovascular reflex tests and 2) the relationship between adrenergic cardiac innervation and left ventricular (LV) function. Twenty-four patients with IDDM without overt heart disease were studied after silent coronary artery disease was excluded by 201Tl scintigraphy. Cardiac innervation was evaluated by both mIBG scintigraphy (tomographic imaging) and cardiovascular reflex tests. Systolic (ejection fraction [EF] percentage) and diastolic (peak filling rate [PFR] defined as end-diastolic volumes per second [EDV/s]) LV function were determined by equilibrium radionuclide angiography at rest and during bicycle exercise. mIBG scintigraphy was also performed in 10 control subjects. All control subjects exhibited a normal myocardial mIBG distribution. Among diabetic patients, only six had normal mIBG scans (group 1), whereas 18 had evidence of regional adrenergic denervation (group 2). Reflex tests suggested cardiac autonomic neuropathy in only seven of these patients (P < 0.01 vs. mIBG). All patients had a normal EF at rest. However, group 2 showed an impaired response to exercise as indicated by a smaller increase in EF (5 ± 6 vs. 13 ± 5%, P < 0.05) and a lower PFR (5.9 ± 0.8 vs. 7.3 ± 1.2 EDV/s, P < 0.01). Myocardial mIBG scintigraphy reveals that in patients with IDDM, sympathetic myocardial dysinnervation is much more common than previously thought. Furthermore, subclinical LV dysfunction is related to derangements of adrenergic cardiac innervation.
Comparison of Estimates of Insulin Sensitivity From Minimal Model Analysis of the Insulin-Modified Frequently Sampled Intravenous Glucose Tolerance Test and the Isoglycemic Hyperinsulinemic Clamp in Subjects With NIDDM
Authors: Coates Philip A , Luzio Stephen D , Brunel Patrick , Owens David R
Published: September 2013

Minimal model (MINMOD) analysis of the frequently sampled intravenous glucose tolerance test (FSIVGTT) is dependent on an adequate insulin response to the glucose load. As this is characteristically deficient in subjects with non-insulin-dependent diabetes mellitus (NIDDM), the technique has been modified by the use of an intravenous bolus of insulin. Previous validation of this modification in humans has relied on agreement between insulin sensitivity indexes (SI) estimated from tolbutamide- and insulin-modified tests and not on direct comparison with estimates derived from the isoglycemic glucose clamp. We have compared estimates of insulin sensitivity derived from minimal modeling of a 4-h insulin-modified FSIVGTT and the glucose clamp in subjects with NIDDM. Twelve subjects underwent an insulin-modified FSIVGTT and an isoglycemic hyperinsulinemic clamp in random order 2–4 weeks apart. Fasting plasma glucose (8.4 vs. 9.0 mmol/l) and immunoreactive insulin (IRI) concentrations (104.5 vs. 101.5 pmol/l) were not different between the 2 study days. SI(clamp) was derived from the steady-state glucose infusion rate during the 3rd h of the clamp, corrected for the ambient insulin and glucose concentrations. SI(ivgtt) was derived using MINMOD. SI(ivgtt) was 1.06 ± 0.18 min−1 · mU−1 · ml × 104, and mean SI(clamp) was 4.97 ± 0.69 l · min−1/pmol · 1−1 × 104 (mean ± SE). SI(ivgtt) was positively correlated with SI(clamp) (r = 0.73, P = 0.004) and negatively correlated with body mass index (r = −0.7, P = 0.005) and fasting IRI(ivgtt) (r = −0.64, P = 0.008). In summary, MINMOD analysis of the insulin-modified FSIVGTT provides a valid measure of insulin sensitivity in subjects with NIDDM.
Okadaic Acid, Vanadate, and Phenylarsine Oxide Stimulate 2-Deoxyglucose Transport in Insulin-Resistant Human Skeletal Muscle
Authors: Carey Julie O , Azevedo John L , Morris Patricia G , Pories Walter J , Dohm G Lynis
Published: September 2013

In response to insulin, several proteins are phosphorylated on tyrosine and on serine/threonine residues. Decreased phosphorylation of signaling peptides by a defective insulin receptor kinase may be a cause of insulin resistance. Accordingly, inhibition of the appropriate phosphatases might increase the phosphorylation state of these signaling peptides and thereby elicit increased glucose transport. The purpose of this study was to examine the effect of the serine/threonine phosphatase inhibitor okadaic acid and the tyrosine phosphatase inhibitors phenylarsine oxide and vanadate on 2-deoxyglucose transport in insulin-resistant human skeletal muscle. All three phosphatase inhibitors stimulated 2-deoxyglucose transport in insulin-resistant skeletal muscle. These data suggest that these compounds have bypassed a defect in at least one of the signaling pathways leading to glucose transport. Furthermore, maximal transport rates induced by the simultaneous presence of insulin and phosphatase inhibitor in insulin-resistant muscle were equal to insulin-stimulated rates in lean control subjects. However, both vanadate alone and vanadate plus insulin stimulated 2-deoxyglucose transport significantly more in insulin-sensitive tissue than in insulin-resistant tissue. These results demonstrate that although vanadate is able to stimulate glucose transport in insulin-resistant muscle, it is not able to normalize transport to the same rate achieved in insulin-sensitive muscle.
The β-Cell in Diabetes: From Molecular Genetics to Clinical Research
Authors: Polonsky Kenneth S
Published: September 2013

Pancreatic insulin secretion rates can be accurately derived by mathematical deconvolution of peripheral C-peptide concentrations either by using individual C-peptide kinetic parameters obtained by analysis of the decay curve of biosynthetic human C-peptide or by using published group parameters with appropriate adjustments for age and degree of obesity. Since the cross-reactivity of proinsulin and related peptides is low (< 10%) in many C-peptide assays, this experimental approach avoids the spurious increase in insulin immunoreactivity resulting from cross-reactivity with proinsulin and related peptides in the insulin assay. Application of this technique has demonstrated that the phenotypic expression of β-cell dysfunction differs in subjects with different genetic mechanisms of non-insulin-dependent diabetes mellitus (NIDDM). Subjects who have maturity-onset diabetes of the young (MODY) due to mutations in the glucokinase gene demonstrate different patterns of altered insulin secretion when compared with subjects who have mutations in the MODY1 gene on chromosome 20. Glucokinase mutations affect the ability of the β-cell to detect and respond to small increases in glucose above the basal level. However, compensatory mechanisms operative in vivo, which include a priming effect of glucose on insulin secretion, limit the severity of the observed insulin secretory defect, resulting in a generally mild clinical course in these subjects. In contrast, mutations in the MODY1 gene are associated with an inability to increase insulin secretion as the plasma glucose concentration increases above 7–8 mmol/l and the normal priming effect of glucose on insulin secretion is lost. These characteristics of the dose-response relationships between glucose and insulin secretion result in a more severe degree of hyperglycemia than observed in subjects with glucokinase mutations, and these subjects more frequently need insulin treatment. These alterations are evident in prediabetic subjects with normal glucose levels who carry the MODY1 mutation, suggesting that defective β-cell function is the primary pathogenetic defect in the diabetic syndrome in these subjects. Studies performed in the classic form of NIDDM demonstrate that subjects with mild glucose intolerance and normal fasting glucose concentrations and glycosylated hemoglobin levels consistently demonstrate defective β-cell function. These results are consistent with studies in the Zucker diabetic fatty rat, an animal model of NIDDM in which prediabetic animals demonstrate extensive alterations in expression of multiple genes involved in the regulation of insulin secretion. It thus appears that abnormal β-cell function is present at a relatively early stage in the evolution of NIDDM, even before the onset of overt hyperglycemia.
Microvascular Function in Human Diabetes: A Physiological Perspective
Authors: Tooke John E
Published: September 2013

The late complications of diabetes represent in large part microvascular dysfunction. The development of techniques to measure microvascular function has resulted in a clearer picture of the stages of development of microangiopathy and the key pathophysiological processes involved. Considerable evidence supports the hemodynamic hypothesis of pathogenesis, which argues that early insulin-dependent diabetes is characterized by increased microvascular pressure and flow. Resultant injury to the microvascular endothelium causes adaptive microvascular sclerosis contributing to a loss of vasodilatory reserve and autoregulatory capacity with increasing disease duration. High susceptibility to microangiopathy appears to be characterized by both high capillary pressure and increased permeability, although the interrelationship between these variables needs to be better defined. In normotensive non-insulin-dependent diabetes subjects, a different pattern of microvascular functional abnormalities is apparent; it is hypothesized that these differences represent the impact of a prediabetic insulin-resistant phase on microvascular behavior and may in part explain the differential expression of vascular pathology in the two major types of diabetes. The physiological framework that has been defined reveals those pivotal processes upon which scientific attention should be centered and facilitates the generation of plausible molecular and cellular mechanisms that fit the physiological facts.
Unchanged Incidence of Diabetic Nephropathy in IDDM Patients
Authors: Rossing Peter , Rossing Kasper , Jacobsen Peter , Parving Hans-Henrik
Published: September 2013

Recently, a dramatic decline in the cumulative incidence of diabetic nephropathy (<10% after 25 years of diabetes) has been reported in insulin-dependent diabetes mellitus (IDDM) patients diagnosed before the age of 15 years between 1961 and 1980. In a clinic-based study, we assessed recent trends in the incidence of diabetic nephropathy. All 356 patients in whom IDDM was diagnosed before the age of 41 years between 1965 and 1979, identified in 1984, were followed until 1991 or until death. All patients were Caucasians and resided in Copenhagen. The cumulative incidences (life-table method) of diabetic nephropathy (urinary albumin excretion ≥300 mg/24 h in two out of three consecutive samples) after 15 years of diabetes and in 1991 were 18 ± 4 and 35 ± 5% (cumulative incidence ± SE; onset of diabetes 1965–1969, n = 113), 20 ± 4 and 35 ± 5% (onset of diabetes 1970–1974, n = 130), and 16 ± 5& (onset of diabetes 1975–1979, n = 113), respectively (NS at 15 years). The prevalence of persistent microalbuminuria (31–299 mg/24 h) at time of follow-up was 24% (95% confidence interval: 16–33) in the group with onset of diabetes in 1965–1969, 28% (20–36) with onset of diabetes in 1970–1974, and 19% (13–28) with onset of diabetes in 1975–1979 (NS). The mean ± SE HbAlc measured yearly beginning in 1984 was higher in patients with nephropathy (9.4 ± 0.1%) and persistent microalbuminuria (8.9 ± 0.1%) than in patients with normoalbuminuria (8.5 ± 0.1%; P < 0.001). Our study revealed no evidence suggesting a so-called calendar effect, i.e., declining cumulative incidence of diabetic nephropathy with increasing calendar year of diabetes onset. The lack of calendar effect may in part be explained by poor metabolic control and a high and unchanged prevalence of smoking (58–71%).
Expression of Intercellular Adhesion Molecule 1 on Pancreatic β-Cells Accelerates β-Cell Destruction by Cytotoxic T-Cells in Murine Autoimmune Diabetes
Authors: Yagi Nrorio , Yokono Koichi , Amano Kazuhiko , Nagata Masao , Tsukamoto Kazuya , Hasegawa Yutaka , Yoneda Ryoji , Okamoto Naoko , Moriyama Hiroaki , Miki Masatoshi , Tominaga Yoichi , Miyazaki Jun-ich , Yagita Hideo , Okumura Ko , Mizoguchi Akira , Miki Akinori , Ide Chizuka , Maeda Sakan , Kasuga Masato
Published: September 2013

Intercellular adhesion molecule 1 (ICAM-1) plays an important role in the pathogenesis of insulin-dependent diabetes mellitus (IDDM) by being involved in the extravasation of lymphocytes from the circulation into the inflamed pancreas. However, the mechanism of β-cell destruction by which expression of ICAM-1 on β-cells may facilitate adhesion of effector cells still remains to be elucidated. Several lines of evidence suggest that this adhesion molecule is involved in the destruction of pancreatic β-cells by killer lymphocytes in the NOD mouse, which shows an autoimmune diabetic syndrome similar to that of human IDDM. Immunohistochemical study under light microscopy demonstrated that all of the mononuclear cells infiltrating the islets strongly expressed ICAM-1 and leukocyte function-associated antigen 1 (LFA-1), a counterreceptor of ICAM-1, whereas ICAM-1 expression on islet cells was not apparent. However, immunohistochemical staining under electron microscopy revealed that islet β-cells adjacent to infiltrating lymphocytes were clearly stained by an anti-ICAM-1 monoclonal antibody (mAb). Flow cytometric analysis showed that the ICAM-1 expression on NOD islet cells and NOD-derived insulinoma cells (MIN6N8a) was inducible by interferon (IFN)-γ or tumor necrosis factor-α. These cytokines had an additive effect on the ICAM-1 induction. Susceptibility of MIN6N8a cells to lysis by a NOD islet-derived CD8+ cytotoxic T-cell clone was greatly enhanced by IFN-γ pretreatment, and this enhancement was abolished by anti-ICAM-1 and anti-LFA-1 mAbs. When both mAbs were administered into NOD mice with spontaneous or adoptively transferred diabetes, the development of diabetes was significantly prevented. These results suggest that cytokines secreted by isletinfiltrating mononuclear cells could induce the ICAM-1 expression on γ-cells, which accelerates the γ-cell destruction by cytotoxic T-cells. Therefore, immunointervention of the ICAM-l/LFA-1 pathway would be an excellent strategy to prevent human IDDM.
Bone Loss and Bone Turnover in Diabetes
Authors: Krakauer Jesse C , Mckenna Malachi J , Fenn Buderer Nancy , Rao D Sudhaker , Whitehouse Fred W , Parfitt A Michael
Published: September 2013

There have been conflicting reports about the effect of diabetes on bone density. In 1978, we studied 109 patients, 46 with type I and 63 with type II diabetes; ∼12 years later we restudied 35 of the 66 surviving patients. In the original study, radial bone density did not differ significantly between patients with either type of diabetes but was significantly lower than in nondiabetic control subjects. In eight osteopenic patients, bone formation rate and other histological indexes of osteoblast recruitment and function were markedly depressed compared with those in nondiabetic control subjects. In patients remeasured ∼2.5 years (41 patients) and ∼12.5 years (35 patients) after baseline, bone loss had continued at the expected rate in patients with type I diabetes, with maintenance of the same deficit, but was slower than expected in patients with type II diabetes, such that the initial deficit had been completely corrected. In six of the eight patients who had undergone bone biopsy, one with type I and five with type II diabetes, the mean bone mineral density z-score of the spine and femoral neck ∼12 years later was >0 and in one subject was significantly higher than normal at both sites. Based on these data and on previous studies, we propose that in patients with diabetes, low bone formation retards bone accumulation during growth, metabolic effects of poor glycemic control lead to increased bone resorption and bone loss in young adults, and low bone turnover retards agerelated bone loss. These effects account for low bone density in young patients with type I diabetes and normal or increased bone density in older patients with type II diabetes.
Formation of Immunochemical Advanced Glycosylation End Products Precedes and Correlates With Early Manifestations of Renal and Retinal Disease in Diabetes
Authors: Beisswenger Paul J , Makita Zenji , Curphey Thomas J , Moore Lynn L , Jean Smith , Brinck-Johnsen Truls , Bucala Richard , Vlassara Helen
Published: September 2013

Elevated levels of advanced glycosylation end products (AGEs) have been found in multiple tissues in association with diabetic vascular complications and during the microalbuminuric phase of diabetic nephropathy. In this study, we have used an AGE-specific enzyme-linked immunosorbent assay (ELISA) to measure skin AGEs to determine whether elevated levels can be detected before the onset of overt microangiopathy. Subjects with type I diabetes (n = 48) were graded for the degree of nephropathy (normal [23], microalbuminuria [12], or macroalbuminuria [12]) and retinopathy (none [13], background [20], or proliferative [15]). Subgroups with a premicroalbuminuric phase of albumin excretion (≤28 mg/24 h, n = 27) or with the earliest stages of retinopathy (n = 27) were identified. A significant increase in tissue AGEs was found as urinary albumin increased during the premicroalbuminuric phase of nephropathy even when the data were adjusted for age and duration of diabetes (P = 0.005). Immunoreactive AGEs also increased as normal renal status advanced to microalbuminuria and macroalbuminuria (P = 0.0001 across groups). Significant elevation of AGEs was also found in association with the earliest stages of clinically evident retinopathy (early background versus minimal grades). In addition, higher AGE levels were found in subjects with proliferative retinopathy when compared with those with less severe retinopathy (P < 0.004 across groups). In contrast, no significant differences were found in tissue AGE levels between groups with or without early retinopathy based on pentosidine or fluorescent AGE measurements, although fluorescent AGEs correlated with albumin excretion. In conclusion, levels of collagen-linked AGEs, when measured by an AGE-specific ELISA, reveal a correlation with preclinical stages of diabetic nephropathy and early retinopathy not indicated by other methods and may prove useful as early markers of microangiopathy in type I diabetes.
The Pseudotetrasaccharide Acarbose Inhibits Pancreatic Islet Glucan-1,4-α-glucosidase Activity in Parallel With a Suppressive Action on Glucose-Induced Insulin Release
Authors: Salehi Albert , Panagiotidis Georgios , Borg L A Håkan , Lundquist Ingmar
Published: September 2013

The pseudotetrasaccharide acarbose, previously known as a potent inhibitor of intestinal α-glucoside hydrolases, was investigated with regard to its influence on islet lysosomal enzyme activities and the insulin secretory processes. We observed that acarbose was a potent inhibitor of mouse islet lysosomal acid glucan-l,4-α-glucosidase activity, EC50 ∼5 μmol/l, as well as of acid α-glucosidase activity. In contrast, acarbose did not influence other lysosomal enzyme activities such as acid phosphatase and N-acetyl-β-D-glucosaminidase. Neutral a-glucosidase (endoplasmic reticulum) was only moderately inhibited in homogenate and was unaffected in intact islets. Incubation of isolated mouse islets with acarbose revealed that the pseudotetrasaccharide was a strong inhibitor of glucose-induced insulin secretion, EC50 ∼500 nmol/1, and a significant inhibition was already observed at a concentration of acarbose as low as 100 nmol/1. The acarbose analogue maltotetrose did not influence either glucoseinduced insulin release or islet lysosomal enzyme activities. Further, acarbose as well as two other α-glucoside hydrolase inhibitors, the deoxynojirimycin derivatives miglitol and emiglitate, did not affect islet glucose oxidation at low or high glucose levels. Acarbose also inhibited insulin release induced by the sulfonylurea glibenclamide, whereas insulin secretion stimulated by the cholinergic muscarinic agonist carbachol or the phosphodiesterase inhibitor isobutylmethylxanthine was unaffected by the drug. Moreover, complementary in vivo experiments showed that pretreatment of mice with acarbose to allow for endocytosis of the compound markedly suppressed the insulin secretory response to an intravenous glucose load. In contrast, acute intravenous injection of acarbose did not influence insulin secretion (no membrane effect) either when injected alone or when injected together with glucose. Since the action of acarbose is known to be restricted to the vacuolar apparatus, the present results, together with previous observations, suggest that an activation of the acid glucan-l,4-α-glucosidase and the lysosomal system may serve as one of several transduction signals for insulin release stimulated by glucose and glibenclamide.
Lipotoxicity in the Pathogenesis of Obesity-Dependent NIDDM: Genetic and Clinical Implications
Authors: Unger Roger H
Published: September 2013

We review evidence that increased tissue levels of fatty acyl CoA cause the β-cell abnormalities of nondiabetic obesity and ultimately result in obesity-dependent diabetes. Nondiabetic obesity in Zucker rats is characterized by hypersecretion of insulin at normal fasting and subfasting glucose concentrations. This is a result of β-cell hyperplasia and increased low Km glucose usage and oxidation. These abnormalities, the hyperinsulinemia, the hyperplasia of β-cells, i.e., its in vitro equivalent, enhanced bromodeoxyuridine incorporation, and the increased low Km glucose usage can be induced by culturing normal islets with 2 mmol/l free fatty acids (FFAs). Once obese Zucker diabetic fatty rats become diabetic, glucose-stimulated insulin secretion (GSIS) is absent and β-cell GLUT2 reduced. Islet triglyceride (TG) content is increased 10-fold, probably reflecting increased FFA delivery (plasma FFA levels > 1.5 mmol/l) beginning about 2 weeks before the onset of diabetes. These β-cell abnormalities, GSIS loss, GLUT2 loss, and TG accumulation, are prevented by reducing plasma FFAs by caloric restriction and by nicotinamide injection. The loss of GSIS and the accumulation of TGs, but not the GLUT2 loss, can be induced in vitro in normal islets cultured in a 2 mmol/l FFA-containing medium, but prediabetic islets seem far more vulnerable to FFA-induced functional impairment and TG accumulation. It is proposed that in uncomplicated obesity, increased lipid availability (FFA levels <1.5 mmol/1) induces both hyperinsulinemia and insulin resistance in parallel fashion, thereby maintaining normoglycemia. A further increase in substrate overload impairs β-cell compensation for insulin resistance and hyperglycemia appears.
Excessive Secretion of Insulin Precursors Characterizes and Predicts Gestational Diabetes
Authors: Swinn Robert A , Wareham Nicholas J , Gregory Robert , Curling Victoria , Clark Penelope M , Dalton Kevin J , Edwards Owen M , O'Rahilly Stephen
Published: September 2013

Using assays that specifically measure insulin, intact proinsulin, and 32,33 split proinsulin, we examined the β-cell secretory response to an oral glucose tolerance test (OGTT) in 64 women with gestational diabetes mellitus (GDM) and 154 pregnant normoglycemic control subjects of comparable age and body mass index. Women with GDM were characterized by a lower 30-min insulin increment (40.8 [34.9–47.6] vs. 58.6 [53.6–64] pmol insulin/mmol glucose, P < 0.001; geometric mean [95% confidence interval]) and a higher plasma insulin level at 120 min (702 [610–808] vs. 444 [400–492] pmol/l, P < 0.001). 32,33 split proinsulin levels were elevated in GDM patients in both fasting (9.1 [7.3–11.4] vs. 6.7 [6.0–7.5] pmol/l, P < 0.02) and 120-min (75.2 [62.9–90.0] vs. 52.2 [46.7–58.3] pmol/l, P < 0.001) samples, respectively. Intact proinsulin levels were significantly elevated at 120 min in the women with GDM (21.3 [18.1–25.1] vs. 14.8 [13.4–16.3] pmol/l, P < 0.001). Thus, the qualitative abnormalities of insulin secretion in GDM patients (low 30-min insulin increment, high 120-min plasma insulin, and elevated 32,33 split proinsulin) are similar to those seen in nonpregnant subjects with impaired glucose tolerance. To determine whether measures of proinsulinlike molecules (PLMs) might assist in the prediction of GDM, women who had a 1-h glucose level of >7.7 mmol/1 after a 50-g glucose challenge at 28–32 weeks’ gestation had insulin and PLMs measured in the 1-h sample. The percentage of total insulin-like molecules accounted for by proinsulin-like molecules (%PLM) was significantly raised in those women in whom a subsequent OGTT showed GDM versus those in whom a later OGTT was normal (13.9 [11.5–16.7] vs. 10.3 [9.6–11.2]% P = 0.003). In a logistic regression analysis, %PLM at screening was more strongly associated with later GDM than age, obesity, the degree of hyperglycemia at screening, or any individual insulin or PLM variable at the screening test. Incorporation of a measure of %PLM in the routine 50-g screening test has the potential for improving the predictive power of screening tests for GDM.
Insulin Action and Glucose Metabolism in Nondiabetic Control and NIDDM Subjects: Comparison Using Human Skeletal Muscle Cell Cultures
Authors: Henry Robert R , Abrams Leslie , Nikoulina Svetlana , Ciaraldi Theodore P
Published: September 2013

Myoblasts from human skeletal muscle were isolated from needle biopsy samples of vastus lateralis and fused to differentiated multinucleated myotubes. Specific high-affinity insulin and insulin-like growth factor I (IGF-I) binding, glucose transporter proteins GLUT1 and GLUT4, glycogen synthase and pyruvate dehydrogenase proteins, and their specific mRNAs were identified in fused myotubes. Insulin and IGF-I stimulated 2-deoxyglucose uptake twofold with half-maximal stimulation by insulin at 0.98 ± 0.12 nmol/l and maximal stimulation at 17.5 nmol/l. Acute insulin treatment (33 nmol/1) doubled glycogen synthase activity and glucose incorporation into glycogen while increasing pyruvate dehydrogenase ∼30%. In cells cultured from NIDDM subjects, both basal (6.9 ± 1.0 vs. 13.0 ± 1.7 pmol · mg protein−1 · min−1) and acute insulin-stimulated transport (13.5 ± 2.0 vs. 22.4 ± 1.3 pmol · mg protein−1 · min–1) were significantly reduced compared with nondiabetic control subjects (both P ≤ 0.005). GLUT1 protein content of total membranes from NIDDM subjects was decreased compared with control subjects, while GLUT4 levels were similar between groups. A significant correlation (r = 0.65, P ≤ 0.05) was present when maximal rates of insulin-stimulated glucose transport in cell culture from subjects were compared with their corresponding in vivo glucose disposal determined by hyperinsulinemic glucose clamp. In summary, differentiated human skeletal muscle cultures exhibit biochemical and molecular features of insulin-stimulated glucose transport and intracellular enzyme activity comparable with the in vivo situation. Defective insulin-stimulated glucose transport persists in muscle cultures from NIDDM subjects and resembles the reduced insulin-mediated glucose uptake present in vivo. We conclude that this technique provides a relevant cellular model to study insulin action and glucose metabolism in normal subjects and determine the mechanisms of insulin resistance in NIDDM.
Kinetics of Insulin Action In Vivo: Identification of Rate-Limiting Steps
Authors: Miles Philip D G , Levisetti Matteo , Reichart Donna , Khoursheed Mousa , Moossa A R , Olefsky Jerrold M
Published: September 2013

To examine the kinetic steps in insulin's in vivo action, we have assessed the temporal relationship between arterial insulin, interstitial insulin, glucose disposal rate (GDR), and insulin receptor kinase (IRK) activity in muscle and between portal insulin, hepatic glucose production (HGP), and IRK activity in liver. Interstitial insulin, as measured by lymph-insulin concentration (muscle only), and IRK activity were used as independent methods to determine the arrival of insulin at its tissue site of action. Euglycemic clamps were conducted in seven mongrel dogs and consisted of an activation phase with a venous insulin infusion (7.2 nmol · kg−1 · min−1,100 min) and a deactivation phase. Liver and muscle biopsies were taken to assess IRK activity. Arterial, portal, and lymph insulin rose to 636 ± 12, 558 ± 18, and 402 ± 24 pmol/1, respectively. GDR increased from 13.9 ± 0.6 to 41.7 ± 2.8, and HGP declined from 14.4 ± 0.6 to 1.1 ± 0.6 μmol · kg−1 · min−1. Muscle and liver IRK activity increased significantly from 5.9 ± 0.9 to 14.6 ± 0.6 and 5.5 ± 0.7 to 23.7 ± 1.9 fmol P/fmol insulin receptor (IR), respectively. The time to half-maximum response (t½a) for stimulation of GDR (19.8 ± 4.8 min) and suppression of HGP (21.5 ± 3.7 min) were similar. The t½a for stimulation of GDR, muscle IRK, and rise in lymph insulin were not significantly different from one another and were all markedly greater than that for the approach to steady state of arterial insulin (2.3 ± 1.2 min, P < 0.01). The t½a for portal insulin (1.8 ± 0.8 min) was less than that for activation of liver IRK (11.3 ± 4.3, P < 0.05), which in turn was less than that for suppression of HGP (21.5 ± 3.7 min, P < 0.05). In skeletal muscle, the delay in insulin-stimulated GDR occurs before IR binding and is due to the time required for plasma insulin to gain access to the interstitial compartment. In liver, however, identification of the site(s) of delay in insulin's effects to suppress HGP is dependent on whether insulin acts directly or indirectly on the liver. If its action is direct, there are two separate sites of delay: a prereceptor and a postreceptor delay. If, however, insulin's effect on suppressing HGP is indirect, then a single extrahepatic site of delay is likely, which represents the time-limiting step of insulin's ability to stimulate GDR and suppress HGP. Then, the locus of the site involves transendothelial passage of insulin to the interstitial space.
DR-BB Rat Thymus Contains Thymocyte Populations Predisposed to Autoreactivity
Authors: Whalen Barbara J , Rossini Aldo A , Mordes John P , Greiner Dale L
Published: September 2013

We have induced autoimmune insulin-dependent diabetes mellitus (IDDM) in athymic WAG rats by transfusing thymocytes from histocompatible phenotypically normal rats of the DR-BB strain. DR-BB rats rarely develop spontaneous IDDM, but readily become hyperglycemic if depleted in vivo of regulatory T-cells that express the RT6.1 maturational alloantigen. Successful adoptive transfer of IDDM by DR-BB thymocytes required that the athymic recipients be depleted of emerging populations of donor-origin RT6.1+ T-cells. Thymocytes from both normal and RT6-depleted diabetic DR donors were equally capable of transferring autoimmunity. In contrast, thymocytes from normal histocompatible YOS rats failed to transfer IDDM. The autoreactive potential of DR-BB rat thymocytes was minimal from birth to 4 weeks of age and then increased substantially at 8–9 weeks of age. These results demonstrate that the DR-BB rat thymus harbors abnormal cell populations predisposed to autoreactivity. The data localize the developmental defect leading to diabetes in the BB rat to an abnormal intrathymic selection process.
The Relationship of Glycemic Exposure (HbA1c) to the Risk of Development and Progression of Retinopathy in the Diabetes Control and Complications Trial
Authors:   The Diabetes Control and Complications Trial Research Group
Published: September 2013

The Diabetes Control and Complications Trial (DCCT) demonstrated that a regimen of intensive therapy aimed at maintaining near-normal blood glucose values markedly reduces the risks of development or progression of retinopathy and other complications of insulin-dependent diabetes mellitus (IDDM) when compared with a conventional treatment regimen. This report presents an epidemiological assessment of the association between levels of glycemic exposure (HbA1c) before and during the DCCT with the risk of retinopathy progression within each treatment group. The initial level of HbA1c observed at eligibility screening as an index of pre-DCCT glycemia and the duration of IDDM on entry were the dominant baseline predictors of the risk of progression. The shorter the duration of IDDM on entry, the greater were the benefits of intensive therapy. In each treatment group, the mean HbA1c during the trial was the dominant predictor of retinopathy progression, and the risk gradients were similar in the two groups; a 10% lower HbA1c (e.g., 8 vs. 7.2%) is associated with a 43% lower risk in the intensive group and a 45% lower risk in the conventional group. These risk gradients applied over the observed range of HbA1c values and were unaffected by adjustment for other covariates. Over the range of HbA1c achieved by DCCT intensive therapy, there does not appear to be a level of glycemia below which the risks of retinopathy progression are eliminated. The change in risk over time, however, differed significantly between the treatment groups, the risk increasing with time in the study in the conventional group but remaining relatively constant in the intensive group. The risks were compounded by a multiplicative effect of the level of HbA1c with the duration of exposure (time in study). Total glycemic exposure was the dominant factor associated with the risk of retinopathy progression. When examined simultaneously within each treatment group, each of the components of pre-DCCT glycemic exposure (screening HbA1c value and IDDM duration) and glycemic exposure during the DCCT (mean HbA1c, time in study, and their interaction) were significantly associated with risk of retinopathy progression. Similar results also apply to other retinopathic, nephropathic, and neuropathic outcomes. The recommendation of the DCCT remains that intensive therapy with the goal of achieving near-normal glycemia should be implemented as early as possible in as many IDDM patients as is safely possible.
Insulin Secretory Defect in Zucker fa/fa Rats Is Improved by Ameliorating Insulin Resistance
Authors: de Souza Christopher J , Yu Jen H , Robinson Deborah D , Ulrich Roger G , Meglasson Martin D
Published: September 2013

The role of insulin resistance in the impaired glucosestimulated insulin release of Zucker fatty rats was investigated using the insulin-sensitizing thiazolidinedione drug pioglitazone. Fatty rats had fasting hyperinsulinemia yet a blunted secretory response to intravenous glucose compared with lean age-matched controls. Islets from fatty rats secreted less insulin (based on islet DNA) in response to high glucose than islets from lean rats but secreted normal amounts of insulin when tolbutamide or α-ketoisocaproic acid (α-KIC) was the stimulus. Administering pioglitazone for 9 days diminished basal hyperinsulinemia and increased the insulin response to high glucose by fatty rats but not by lean controls. Pioglitazone pretreatment augmented the secretory response by isolated islets to high glucose, α-KIC, and tolbutamide. Augmentation of islet insulin release was not associated with reduced plasma glucose concentration, suggesting that altered glycemia was not involved. Pancreas and islet insulin content was greater in fatty rats than in lean controls and was decreased by pioglitazone; hence, insulin stores and glucose-stimulated insulin release did not correlate. Pioglitazone treatment did not affect the rate of islet glucose usage or ATP/ADP in the presence of 2.75 or 16 mmol/1 glucose. These data indicate that ameliorating insulin resistance reverses defective glucosestimulated insulin release by Zucker fa/fa rats. After pioglitazone administration, insulin secretion may be augmented by increased generation of a metabolic coupling factor from glucose or at a later step in the secretory process that is common to both glucose and nonglucose secretagogues.
Elevated Levels of Authentic Plasma Hydroperoxides in NIDDM
Authors: Nourooz-Zadeh Jaffar , Tajaddini-Sarmadi Javad , McCarthy Sue , Betteridge D John , Wolff Simon P
Published: September 2013

Using a precise technique for measuring authentic plasma lipid hydroperoxides (ROOHs), we show that individuals with non-insulin-dependent diabetes mellitus (NIDDM) have higher levels of ROOH than do control subjects. ROOHs were measured by the ferrous oxidation with xylenol orange assay coupled with the selective ROOH reductant triphenylphosphine. Formation of the ferric xylenol orange complex was determined at 560 nm and calibrated against H2O2. For 22 individuals with NIDDM, a concentration of 9.04 ± 4.3 μmol/l (mean ± SD) ROOH was recorded. This concentration was higher (P < 0.0005 by separate-variance t test) than that of plasma ROOHs from control subjects (3.76 ± 2.48 μmol/l). There was no difference between concentrations of plasma malondialdehyde measured as thiobarbituric acid–reactive material (TBARM) in NIDDM or control subjects (1.00 ± 0.70 vs. 1.21 ± 0.62 μmol/l, respectively; P > 0.1). A trend to lower vitamin E levels in the NIDDM group (9.03 ± 3.31 vs. 10.31 ± 5.02 μg/ml in control subjects) failed to achieve significance at the 95% confidence level. Plasma ROOHs in the diabetic group did not correlate with total plasma cholesterol, triglyceride, fasting glucose, HbA1, vitamin E, or TBARM levels. These data indicate that measurement of authentic ROOHs shows NIDDM to be associated with oxidative stress, which may be unrelated to abnormalities in lipid metabolism and glycemic control.