bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevention of Diabetes in NOD Mice by Injection of Autoreactive T-Lymphocytes
Authors: Reich Eva-Pia , Scaringe Denise , Yagi Junji , Sherwin Robert S , Janeway Charles A
Published: September 2013

The nonobese diabetic (NOD) mouse develops a high incidence of autoimmune diabetes and is believed to be a good model for insulin-dependent diabetes mellitus (IDDM) in humans. We isolated T-lymphocyte lines from islets of newly diabetic NOD mice, some of which are autoreactive to NOD spleen cells. Because autoreactive T-lymphocytes have been implicated in immune suppression, we injected NOD mice with an autoreactive T-lymphocyte line. The injected mice had a marked decrease in incidence of IDDM compared with control mice. Moreover, their islets showed no insulitis at 1 yr of age. We conclude that autoreactive T-lymphocytes can prevent the development of IDDM in NOD mice. This result suggests that 1) islets contain both effector cells capable of damaging pancreatic β-cells and cells able to regulate this autoimmune response, and 2) development of IDDM depends on the balance between these opposing forces.
Mechanisms of Insulin-Induced Insulin-Receptor Downregulation: Decrease of Receptor Biosynthesis and mRNA Levels
Authors: Okabayashi Yoshinori , Maddux Betty A , McDonald Alexander R , Logsdon Craig D , Williams John A , Goldfine Ira D
Published: September 2013

The influence of insulin on the downregulation of its receptor was studied in AR42J cultured pancreatic acinar cells, a cell line that has been demonstrated to be metabolically responsive to insulin. Downregulation induced by insulin was time and dose dependent. After a 20-h incubation with 1 μM insulin, Scatchard analysis revealed ∼80% loss of insulin receptors. Studies of receptor half-life indicated that treatment with insulin accelerated the degradation of both the α and β-subunits of the insulin receptor by 30–60%. In addition, biosynthetic-labeling studies indicated that insulin inhibited the biosynthesis of the insulin-receptor precursor by >30%. This decreased biosynthesis of the precursor was associated with decreased production of mature receptor subunits. Poly(A)+ RNA was extracted from control cells and cells treated for 24 hwith 100 nM insulin. Slot blots and Northern transfers revealed that insulin induced an ∼ 50% decrease in insulin-receptor mRNA levels. Therefore, these studies indicate that insulin may diminish the concentration of its receptors in target cells by at least two mechanisms: acceleration of receptor degradation and inhibition of receptor biosynthesis at the level of mRNA.
Relative Importance of Extracellular and Intracellular Ca2+ for Acetylcholine Stimulation of Insulin Release in Mouse Islets
Authors: Hermans Michel P , Henquin Jean-Claude
Published: September 2013

Mouse islets were used to study whether mobilization of intracellular Ca2+ is sufficient to account for acetylcholine (ACh) amplification of glucose-induced insulin release. In the presence of 15 mM glucose, the acceleration of 45Ca efflux and insulin release by 1–100μM ACh increased with the concentration of extracellular Ca2+ (0.25–2.5 mM). Low concentrations of the Ca2+-channel blockers D 600 (1 μM) or nifedipine (0.1 μM) partially inhibited glucose-induced insulin release and its amplification by ACh. At higher concentrations, D 600 (25 μM) or nifedipine (2 μM) practically abolished the ionic and secretory effects of 1 μM ACh. However, 100 μM ACh still caused a fast, large, but transient acceleration of 45Ca efflux, accompanied by a small, short-lived release of insulin. Similar results were obtained in a Ca2+-free medium, indicating that this peak of 45Ca efflux reflects Ca2+ mobilization. Addition of nifedipine or omission of Ca2+ during ACh stimulation rapidly and strongly inhibited 45Ca efflux and insulin release. Both glucose and ACh induced 45Ca uptake were inhibited by D 600. Only high concentrations of ACh (100 μM) mobilize enough cellular Ca2+ to trigger a small and transient insulin release when Ca2+ influx is prevented or impossible. A continuous influx ofCa2+ is necessary for low ACh concentrations to increase release and for high concentrations to have a sustained effect. The amplification of release by the neurotransmitter results from a slight enhancement of Ca2+ influx associated with a marked increase in the effectiveness of incoming Ca2+ on the releasing machinery.
In Vitro Effects of Sulfonylurea on Glucose Transport and Translocation of Glucose Transporters in Adipocytes From Streptozocin-Induced Diabetic Rats
Authors: Jacobs David B , Hayes Gary R , Lockwood Dean H
Published: September 2013

The in vitro effects of the sulfonylurea glyburide on insulin binding and action were comparedin adipocytes from control and nonketotic streptozocininduced diabetic rats. Adipose tissue from control and diabetic animals was maintained in the absence or presence of 2 μg/ml glyburidefor 20 h. Insulin binding and insulin-stimulated glucose transport were examined in adipocytes prepared from this tissue. As expected, insulin binding was increased in adipocytes from diabetic animals. Exposure of tissue to glyburide did not influence insulin binding in either control or diabetic cells. Glucose transport activity of diabetic cells, assessed with 2-deoxyglucose, was decreased 30–40% in both the absence (basal) and presence of insulin compared with controls. Glyburide potentiated insulin's effects in both control (15–20%) and diabetic (30–40%) adipocytes. As a result, glucose transport activity in glyburide-treated diabetic cells was restored to a level similar to that of control cells not exposed to the drug. The mechanism by which glyburide potentiatedglucose transport activity was examined with the D-glucose-displaceable cytochalasin B-binding technique to measure glucose-transporter concentration in membranes prepared from control and diabetic adipocytes exposed to the drug. Adipocytes from this model of diabetes are known to have a decreased cellular content of glucose transporters. The concentration of glucose transporters was decreased by 31% in plasma membranes from insulin-treated diabetic cells. There were corresponding decreases in diabetic microsomal and total membrane fractions. There was also a 40% decrease in the translocation of transporters from the microsomes to the plasma membrane in response to insulin in diabetic cells. Glyburide exposure increased the concentration of transporters in plasmamembranes from insulin-treated control and diabetic cells by 18 and 33%, respectively. Glyburide exposure also increased the concentration of glucose transporters in total adipocyte membrane preparations from diabetic but not control animals. Glyburide potentiates insulin-stimulated glucose transport in both control and diabetic adipocytes. In control cells, this effect is due to an increase in the efficiency of the translocation process. In diabetic cells, both cellular transporter content and the translocation process are increased by glyburide.
Total Gastrectomy and Small Intestinal Cholesterol Synthesis in Diabetic Rats
Authors: Feingold Kenneth R , Zeng Qi-Hua , Soued Mounzer , Siperstein Allan , Serio M Kerala , Clark Orlo H , Moser Arthur H
Published: September 2013

Cholesterol synthesis is increased two- to threefold in the small intestine of diabetic rats. We have observed, in three separate experiments, that the characteristic increase in small intestinal cholesterol synthesis (SICS) in diabetic rats was prevented by total gastrectomy. Food intake was increased twofold, and the small intestine hypertrophied in the gastrectomized diabetic animals. In normal animals, total gastrectomy resulted in only a very small increase in intestinal cholesterol synthesis. In hyperphagic lactating animals, total gastrectomy did not prevent the characteristic increase in SICS that is usually observed in this hyperphagic model. These results indicatethat the effects of total gastrectomy on preventing an increase in SICS are relatively specific for the diabetic state. The mechanism by which total gastrectomy prevents the increase in intestinalcholesterol synthesis in diabetic animals is unknown. Vagotomy did not prevent the typical increase in intestinal synthesis in diabetic animals. Additionally, selectively removing either the antrum or fundus of the stomach did not prevent the increase in SICS in diabetic animals, indicating that the inhibition requires the removal of the entire stomach. It can be speculated that the stomach produces a substance that induces the increase in SICS observed in diabetic animals and that total gastrectomy removes this stimulatory substance.
Effects of Basal Insulin Supplementation on Disposition of Mixed Meal in Obese Patients With NIDDM
Authors: McMahon Molly , Marsh H Michael , Rizza Robert A
Published: September 2013

Basal insulin supplementation has been used as a therapy for patients with non-insulin-dependent diabetes mellitus (NIDDM) who require insulin. To determine whether basal insulin supplementation in addition to lowering postabsorptive plasma glucose concentration also improves the postprandial pattern of glucose disposition, glucose metabolism after ingestion of a solid mixed meal was assessed in obese patients with NIDDM before and after treatment with ultralente and compared with glucose metabolism observed in nondiabetic subjects. Splanchnic uptake of ingested glucose clearance was assessed by including [2-3H]glucose (a tracer that only minimally cycles through glycogen) in a solid mixed meal. Postprandial gluconeogenesis was estimated by measuring the rate of incorporation of carbon dioxide into glucose. Net glucose and lipid oxidation were measured by indirect calorimetry. Both splanchnic uptake of ingested glucose (27 ± 1 vs. 14 ± 2 g) and postprandial hepatic glucose release (51 ± 5 vs. 24 ± 3 g) were greater (P < .001) in diabetic than in nondiabetic subjects. Although the percentage of postprandial hepatic glucose release accounted for by glucose synthesis from bicarbonate was similar in the two groups (25 ± 2 vs. 35 ± 5%), the absolute rate was greater in the diabetic patients (13 ± 1 vs. 8 ± 1 g; P < .05). Postprandial glucose oxidation and glucose disposal (measured either isotopically or by the forearm-catheterization technique) were similar in both groups. However, total lipid oxidation was increased in the diabetic patients. (P < .05). Two weeks of basal insulin supplementation lowered fasting glucose concentrations (from 219 ± 22 to 144 ± 21 mg/dl; P < .01) and integrated postprandial glycemic response (from 814 ± 68 to 621 ± 72 min · mg· ml−1) but not to normal. Although circulating insulin concentrations were two- to threefold greater (P < .02) after 3 mo of basal insulin supplementation, the postprandial pattern of glucose metabolism remained essentially the same. Basal insulin supplementation decreased (P < .05) both splanchnic uptake of ingested glucose and hepatic glucose release. The addition of a preprandial injection of soluble insulin to basal insulin supplementation further suppressed (P < .05) postprandial hepatic glucose release, thereby further improving postprandial glucose tolerance. These studies indicate that initial splanchnic glucose clearance, hepatic glucose release, and new glucose synthesis, as well as extrahepatic substrate metabolism, are altered in NIDDM after ingestion of a mixed meal. Basal insulin supplementation improves but does not normalize postprandial glucose metabolism.
Role of Deep Abdominal Fat in the Association Between Regional Adipose Tissue Distribution and Glucose Tolerance in Obese Women
Authors: Després Jean-Pierre , Nadeau André , Tremblay Angelo , Ferland Mario , Moorjani Sital , Lupien Paul J , Thériault Germain , Pinault Sylvie , Bouchard Claude
Published: September 2013

Computed tomography (CT) was used to study the association between adipose tissue localization and glucose tolerance in a sample of 52 premenopausal obese women aged 35.7 ± 5.5 yr (mean ± SD) and with a body fat of 45.9 ± 5.5%. Body-fat mass and the body mass index (BMI) were significantly correlated with plasma glucose, insulin, and connecting peptide (C-peptide) areas after glucose (75 g) ingestion (.40 ≥ r ≤ .51, P < .01). Trunk-fat accumulation and the size of fat cells in the abdomen displayed highly significant correlations with postglucose insulin levels. The C-peptide area was also positively correlated with abdominal fat cell size (r = .76, P < .01) and was more closely associated with the sum of trunk skin folds (r = .59, P <.001) than with the extremity skin folds (r = .29, P < .05). Subcutaneous and deep-abdominal-fat areas measured by CT displayed comparable associations with the plasma insulin area (r = .44 and .49, respectively; P < .001) but marked differences in the associations with glucose tolerance. Indeed, subcutaneous abdominal fat was not significantly correlated with the glucose area, whereas deep abdominal fat showed a significant correlation (r = .57, P < .001) with the glucose area. Midthigh fat deposition measured by CT was not, however, correlated with plasma glucose, insulin, or C-peptide areas. Partial correlation analyses indicated that the effect of accumulation of deep abdominal fat on glucose tolerance was independent from total adiposity and that no association was observed between total adiposity and glucose tolerance after control for accumulation of deep abdominal fat. These results emphasize the importance of deep abdominal fat as an independent correlate of glucose tolerance in obese women.
Molecular Identification of Diabetogenic Viral Gene
Authors: Bae Yong-Soo , Eun Hyone-Myong , Yoon Ji-Won
Published: September 2013

The best evidence that viruses have a causative role in the pathogenesis of insulin-dependent diabetes mellitus comes from experiments in mice infected with encephalomyocarditis (EMC) virus. When SJL/J male mice were inoculated with a highly diabetogenic EMC-D virus, diabetes developed in 95% of the animals. In contrast, none of the mice inoculated with a nondiabetogenic EMC-B virus became diabetic. Tissue culture experiments showed that EMC-B induces considerable amounts of interferon, whereas EMC-D does not. Despite these differences, EMC-D and EMC-B could not be distinguished antigenically by a sensitive plaque-neutralization assay. Furthermore, the buoyant density in CsCI density gradients and the capsid proteins of these two variants on polyacrylamide gels could not be distinguished. Molecular-hybridization studies with radiolabeled DNA complementary to EMC-D and EMC-B RNAs failed to distinguish them. Determination of complete nucleotide sequences of EMC-D and EMC-B revealed that EMC-D (7829 bases) differs from EMC-B (7825 bases) by only 14 nucleotides. The differences consist of two deletions of five nucleotides, one base insertion, and eight point mutations. The first deletion of three nucleotides and the second deletion of two nucleotides are located in the 5'-poly(C) tract and the 3'-end polyadenylation site, respectively. One base insertion in EMC-B occurs in the 5'-noncoding region. The eight point mutations are located in the polyprotein-coding region. Two of them are silent, whereas the other six mutations, one located on the L gene and five on the VP1 gene, introduce amino acid changes. Our findings indicate that a maximum of 14 of 7829 genomic nucleotides are critical in determining the diabetogenicity of EMC virus.
Increased Neuropeptide Y Concentrations in Specific Hypothalamic Regions of Streptozocin-Induced Diabetic Rats
Authors: Williams Gareth , Gill Jaswinder S , Lee Ying C , Cardoso Helena M , Okpere Benjamin E , Bloom Stephen R
Published: September 2013

Untreated streptozocin-induced diabetic (STZ-D) rats have previously been shown to have significantly increased hypothalamic concentrations of neuropeptide Y (NPY), a regulatory peptide that powerfully stimulates eating and drinking and inhibits secretion of several pituitary hormones when injected centrally. Tissue NPY concentrations have been measured by radioimmunoassay in selected hypothalamic regions microdissected from fresh, unfixed brain slices to localize diabetes-associated NPY changes precisely within the hypothalamus. Significant (35–200%) increases in NPY concentrations (P < .01 vs. matched nondiabetic controls) were found in specific hypothalamic regions between 3 and 14 wk after induction of STZ-D. These regions included the paraventricular and ventromedial nuclei and lateral hypothalamic area, major appetite-regulating areas that are sensitive to the hyperphagic and polydipsic actions of NPY. Increased NPYergic activity in these areas may, at least partly, drive the increased eating and drinking characteristic of STZ-D. NPY concentrations were also increased in the arcuate nucleus and medial preoptic area. Because both of these regions are important in modulating pituitary hormone secretion, local NPY increases may be involved in the impaired secretion of luteinizing hormone, thyroid-stimulating hormone, growth hormone, and prolactin known to occur in STZ-D. Our finding of NPY increases in specific hypothalamic nuclei associated with functional changes found in STZ-D suggests that this peptide may have a role in the altered metabolic and neuroendocrine regulation of the syndrome.
Glucagonlike Peptide I (7–37) Actions on Endocrine Pancreas
Authors: Weir Gordon C , Mojsov Svetlana , Hendrick Grant K , Habener Joel F
Published: September 2013

Glucagonlike peptide I (7–37) [GLP-I-(7–37)], encoded with glucagon and glucagonlike peptide II and intervening peptide II in the rat and human glucagon gene, is processed from proglucagon in both pancreas and intestine and is a potent stimulator of insulin secretion. Unequivocal insulin release from the isolated perfused rat pancreas is elicited by a 10−11 M concentration of this peptide, and a weak response is found at 10−12 M. We found that GLP-I-(7–37) is ∼100 times more potent than glucagon in the stimulation of insulin secretion. Insulin release in response to GLP-I-(7–37) is highly dependent on the ambient glucose concentration; no response is detectable at a glucose concentration of 2.8 mM, and at 6.6 and 16.7 mM, insulin release is augmented by 4.7 and 22.8 ng/ml, respectively. The pattern of insulin secretion stimulated by GLP-I-(7–37) is biphasic, with an initial spike followed by a plateau of sustained release. The effects on insulin release of GLP-I-(7–36) amide, a GLP-I analogue, and GLP-I-(7–37) at concentrations of 10−11 M were indistinguishable. We also found that GLP-I-(7–37) at 10−9 M does not influence glucagon secretion and that glucagonlike peptide II and the intervening peptide II, two other peptides encoded by the glucagon gene, have no detectable effects on insulin secretion.
Diabetic Myocardial Infarction: Interaction of Diabetes With Other Preinfarction Risk Factors
Authors: Singer Daniel E , Moulton Anne W , Nathan David M
Published: September 2013

To assess the effect of diabetes on outcome after acute myocardial infarction (MI), we compared a cohort of 228 type II (non-insulin-dependent) diabetic patients who had sustained acute MI with a similar number of nondiabetic patients with MI. Thirty-day mortality was greater in the diabetic group (27 vs. 17%). However, diabetic patients were older and had more cardiovascular disease before MI. Analyses accounting for such baseline risk revealed a complex effect of diabetes. The relative risk (RR) of dying from MI due to diabetes was greatest among patients with lowest baseline risk (RR 7.3) and least among those at highest baseline risk (RR 0.83). These effects were most striking with transmural MI, which was highly lethal for those with diabetes. Analyses with pulmonary edema as the endpoint support the significant risk conferred by diabetes and its interaction with baseline risk. Diabetes is a risk factor for poor outcome after MI, particularly among patients whose pre-MI cardiovascular status otherwise appears normal.
Proliferative Retinopathy in NIDDM: Incidence and Risk Factors in Pima Indians
Authors: Nelson Robert G , Wolfe John A , Horton Mark B , Pettitt David J , Bennett Peter H , Knowler William C
Published: September 2013

The incidence of proliferative diabetic retinopathy was determined in the Pima Indians of the Gila River Indian Community in Arizona. Over 4 yr, this complication developed in 25 of 953 subjects ≥9 yr of age with non-insulin-dependent diabetes. No cases were diagnosed in <35-yr-old subjects, and the incidence was strongly related to the duration of diabetes. The cumulative incidence of proliferative retinopathy after 20 yr duration was 14%. All cases of proliferative retinopathy occurred in subjects with background retinopathy. Younger age at diagnosis of diabetes was associated with a higher incidence of proliferation when subjects with diabetes of similar duration were compared. A higher incidence of proliferative retinopathy, after controlling for age, sex, and diabetes duration, was associated with hypertension, proteinuria, renal insufficiency, absence of Achilles tendon reflex, elevated total serum cholesterol concentration, and insulin therapy.
Cyclophosphamide-Induced Diabetes in NOD/WEHI Mice: Evidence for Suppression in Spontaneous Autoimmune Diabetes Mellitus
Authors: Charlton Brett , Bacelj Angela , Slattery Robyn M , Mandel Thomas E
Published: September 2013

Nonobese diabetic (NOD) mice spontaneously develop a lymphocytic infiltration of pancreatic islets (insulitis) that may progress to overt diabetes. Virtually all NOD/WEHI mice develop insulitis, but very few progress to diabetes. However, cyclophosphamide (CY) can promote the onset of diabetes in NOD mice, including the NOD/WEHI strain. The means by which CY produces diabetes was investigated in NOD/WEHI mice, in which it was hypothesized that active suppression mechanisms prevented the progression from insulitis to diabetes. A study of the time course of insulitis in the islets after CY was given showed that insulitis was initially reduced but rapidly increased over 16 days, and T-lymphocytes were predominant in the lesion. This suggested a compression of the normal time course of the disease seen in NOD mice. CY did not produce diabetes in any of 11 non-NOD strains studied. Fetal isografts in NOD mice given CY several days before were subjected to lymphocytic infiltration and β-cell destruction. These findings suggested that CY was not directly (β-cell toxic and that altered β-cells were not essential for β-cell destruction. This was further demonstrated with subdiabetogenic doses of streptozocin, which significantly damaged β-cells but did not increase the severity of insulitis or induce diabetes as did CY. Most important, the transfer of mononuclear cells from nondiabetic NOD mice to mice given CY prevented diabetes, which indicated that the likely effect of CY was via immunomodulation, possibly by allowing poised effector cells to act on (β-cells. The NOD/WEHI mice appear to have suppressor mechanisms acting to halt the progression of the early insulitis lesion and so preventing diabetes occurring in most mice. We propose that CY removes these suppressors and thereby induces a rapid progression to diabetes by compressing the normal immune destruction process into a 2-wk period. This model affords the opportunity to study the process in ways not practicable in the usual time course of events.
Risk Factors for Progression of Background Retinopathy in Long-Standing IDDM
Authors: Janka Hans U , Warram James H , Rand Lawrence I , Krolewski Andrzej S
Published: September 2013

Risk factors for the development of severe forms of diabetic retinopathy were examined prospectively in a group of 153 patients with long-standing insulin-dependent diabetes mellitus. During a 4-yr follow-up study, 34 individuals progressed to preproliferative and proliferative retinopathy. The risk of progression to severe forms of diabetic retinopathy was determined by the degree of background diabetic retinopathy and several systemic factors. It increased steeply with hemoglobin A1c, declined proportionally with increasing age, and was dramatically different in patients with diastolic blood pressure below versus above 70 mmHg. Although the mechanisms of action of these systemic factors are unclear, the findings emphasize the multifactorial nature of the pathogenesis of severe forms of eye lesions.
Synthesis-Secretion Coupling of Insulin: Effect of Cyclosporin
Authors: Gillison Susan L , Bartlett Stephen T , Curry Donald L
Published: September 2013

This study investigated the effects of cyclosporin (Cs) on insulin secretion and synthesis from the endocrine pancreas. With in vitro perfused pancreases from control and Cs-treated rats (1, 5,10, or 25 mg · kg−1 · day−1 for 2 wk), a dose-response relationship between Cs dose and inhibition of insulin secretion was demonstrated. Examination of the dynamic secretory response to a glucose stimulus (200 mg/dl) over a 3-h perfusion revealed an inhibition of all three secretory phases. Similarly, the ability of the pancreases to synthesize insulin decreased as a function of Cs dose. Reversibility of Cs toxicity on the pancreas was established by 2 wk after cessation of treatment. To evaluate the effect of Cs treatment in vivo, intravenous glucose tolerance tests were performed. Rats treated with 25 mg · kg−1 · day−1 Cs for 2 wk had significantly lower k values (slope of log glucose concentration over time) than controls. At 10 mg · kg−1 · day1, although curves that appeared abnormal were observed, k values were not significantly different from those of controls. In summary, this study demonstrates the profound inhibitory effect of Cs on the endocrine pancreas.
Increased Basal Glucose Production and Utilization in Children With Recent Obesity Versus Adults With Long-Term Obesity
Authors: Bougnères Pierre-François , Artavia-Loria Phraïn , Henry Sixtine , Basdevant Arnaud , Castaño Luis
Published: September 2013

To characterize the abnormalities of glucose homeostasis and insulin action early in the course of human obesity, we studied in vivo glucose kinetics in seven children who were recently massively overweight. At time of study they were gaining weight at a rate of 13.5 ± 1.4 kg/yr. They were compared with six age-matched control subjects. Six adults with long-term obesity and five normal adults were studied in parallel. The obese children and adults were normoglycemic and hyperinsulinemic. We found that glucose production and utilization were remarkably higher in obese children (295 ± 18 mg/min; 7.6 mg · kg−1 lean body mass · min−1) than in control children (129 ± 13 mg/min; 4.4 mg · kg−1 lean body mass · min−1 P < .01) and obese adults (151 ± 8 mg/min; 3.1 ± 0.3 mg · kg−1 lean body mass · min−1 , P < .01). Obese adults had normal rates of glucose production and utilization. Insulin- and non-insulin-mediated glucose uptake, estimated with somatostatin-induced suppression of endogenous insulin secretion, contributed almost equally to the excess glucose utilization observed in the obese children. When studied with the euglycemic-hyperinsulinemic clamp, obese children could not increase glucose disposal to the same extent as normal children and were not able to adequately suppress their endogenous glucose production. Recently obese children are therefore characterized by an increased basal glucose turnover rate and an already established insulin resistance of the liver and probably the skeletal muscles.
Effect of Aspirin Alone and Aspirin Plus Dipyridamole in Early Diabetic Retinopathy: A Multicenter Randomized Controlled Clinical Trial
Authors:   The Damad Study Group
Published: September 2013

In a double-blind randomized controlled clinical trial conducted in two French and two United Kingdom centers, the effect of antiplatelet agents, i.e., aspirin alone (330 mg 3 times daily) or in combination with dipyridamole (75 mg 3 times daily), was tested versus placebo in 475 patients with early diabetic retinopathy. The assessment of retinopathy was based on change in the number of microaneurysms (MAs) present in the macular field, as seen on fluorescein angiograms, over 3 yr. Forty-one patients did not complete the study. At least three readable initial and yearly angiograms were available on 420 patients (266 treated with insulin and 154 not treated); the results reported are based on these patients. The mean yearly increase in definite MAs was similar in insulin-treated and non-insulin-treated diabetic patients. There was no significant difference between the aspirin-alone group (0.69 ± 5.1 mean ± SD, n = 145) and the aspirin-plus-dipyridamole group (0.34 ± 3.0, n = 142). In the placebo group the mean yearly increase (1.44 ± 4.5, n = 133) was significantly higher than in the treated group (P = .02,1-tailed t test). There was a clear relationship between the deterioration in ophthalmological signs and the increase in mean yearly MAs (clinically stable, 0.38 ± 3.96, n = 293; deteriorating, 1.79 ±4.89, n = 127; P = .002, 2-tailed f test). We conclude that aspirin alone and in conjunction with dipyridamole significantly slows the progression of MA evolution in early diabetic retinopathy.
Diabetes, Intermittent Claudication, and Risk of Cardiovascular Events: The Framingham Study
Authors: Brand Frederick N , Abbott Robert D , Kannel William B
Published: September 2013

The impact of diabetes on intermittent claudication was examined in 1813 men and 2504 women with 34-yr follow-up data in the Framingham study. For both sexes, diabetes was associated with a two- to threefold excess risk of intermittent claudication compared with its absence. A pronounced excess risk was also observed in subjects on oral hypoglycemic therapy and in women receiving insulin. Although diabetes was often associated with an atherogenic-risk profile, controlling for age and several concomitant risk factors failed to eliminate the association with intermittent claudication. Those who developed both intermittent claudication and diabetes were at an especially high risk of incident cardiovascular events. In women, the risk of coronary heart disease, stroke, and cardiac failure was increased 3–4 times when diabetes and intermittent claudication occurred together compared with when either condition existed alone. In diabetic men, the presence of intermittent claudication doubled the risk of stroke, and cardiac failure was ∼3 times more likely in subjects with both conditions compared with either alone. We conclude that diabetes is an important risk factor for intermittent claudication, which in turn confers a serious prognosis for subsequent cardiovascular outcomes in the patient with diabetes.
Effects of Aldose Reductase Inhibitor Sorbinil on Neuroaxonal Dystrophy and Levels of myo-inositol and Sorbitol in Sympathetic Autonomic Ganglia of Streptozocin-Induced Diabetic Rats
Authors: Schmidt Robert E , Plurad Santiago B , Sherman William R , Williamson Joseph R , Tilton Ronald G
Published: September 2013

Biochemical and ultrastructural effects of the aldose reductase inhibitor sorbinil were examined in two experimental rat models of chronic diabetic neuropathy: rats with streptozocin-induced diabetes (STZ-D) and rats fed a galactose-enriched diet. The frequency of neuroaxonal dystrophy in the superior mesenteric sympathetic ganglia of rats with untreated 8-mo STZ-D increased sevenfold compared with that in age-matched controls. Animals chronically maintained on a diet containing 50% galactose, however, did not develop neuroaxonal dystrophy in excess of that found in untreated age-matched control rats. Institution of sorbinil therapy at the time of induction of STZ-D decreased, but did not completely normalize, the frequency of neuroaxonal dystrophy without altering the severity of diabetes; this finding is based on measurements of plasma glucose, body weight, food consumption, 24-h urine volume, and levels of glycosylated hemoglobin. Sorbitol levels in the superior cervical sympathetic ganglia (SCG) of untreated 8-mo-diabetic animals increased three- to fourfold compared with levels in controls. The increase in sorbitol content of diabetic SCG was completely prevented by early institution of dietary sorbinil therapy. The myo-inositol content of 8-mo-diabetic SCG was modestly decreased compared with controls. Sorbinil administration improved but did not completely normalize diabetic SCG myo-inositol. The sorbitol content of the SCG, superior mesenteric and celiac sympathetic ganglia, and a major trunk of the superior mesenteric nerve xof short-term (2.5-mo)-diabetic rats increased comparably, but only the diabetic SCG showed a decrease in myo-inositol.
Failure of Insulin Infusion to Stimulate Fractional Muscle Protein Synthesis in Type I Diabetic Patients: Anabolic Effect of Insulin and Decreased Proteolysis
Authors: Pacy Paul J , Nair Kartha S , Ford Charles , Halliday David
Published: September 2013

We evaluated the influence of insulin on fractional mixed skeletal muscle protein synthesis (FMPS) in eight type I (insulin-dependent) diabetic patients in the postabsorptive state. FMPS was calculated from the increment in [13C]leucine in mixed skeletal muscle protein obtained by serial percutaneous needle biopsy during a continuous 8-h intravenous infusion of L-[13C]leucine. We used the plasma [13C]α-aketoisocaproate (representing intracellular leucine labeling) as the precursor pool of protein synthesis for our calculations. FMPS during the insulin treatment (0.0472 ± 0.0046%/h; plasma glucose 4.6 + 1.0 mM) was not different from FMPS during insulin deprivation (0.0499 ±0.0046%/h; plasma glucose 16.4 + 0.5 mM). Using plasma [13C]-α-ketoisocaproate at isotopic plateau for calculation of leucine flux and as the precursor for leucine oxidation, we further confirmed the findings of our group and others that insulin treatment decreases leucine flux, leucine oxidation, and the nonoxidative portion of leucine flux. Our data on direct measurement of FMPS provide further evidence that the anabolic effect of insulin in the postabsorptive type I diabetic patient is mediated via reduction of proteolysis rather than by increasing protein synthesis.
Normalization of Insulin Sensitivity With Lithium in Diabetic Rats
Authors: Rossetti Luciano
Published: September 2013

Lithium salts are commonly used in psychiatric patients and have been shown to have an insulinlike action in vitro. To define the impact of lithium ion on in vivo glucose metabolism, the effect of 2 wk of lithium treatment on plasma glucose and insulin concentrations, insulin-mediated glucose disposal, and skeletal muscle glycogen synthesis in normal and diabetic rats was examined. Our results demonstrated the ability of lithium ions to completely restore insulin sensitivity to normal in diabetic rats. The insulinmimetic activity of the cation seems to be highly specific for the glycogenic pathway in skeletal muscle. These results raise the possibility that lithium ion may prove effective in reversing the defect in glycogen storage that characterizes non-insulin-dependent diabetes mellitus in humans.
Human Monoclonal IgG1 Insulin Autoantibody From Insulin Autoimmune Syndrome Directed at Determinant at Asparagine Site on Insulin B-Chain
Authors: Uchigata Yasuko , Yao Kenshi , Takayama-Hasumi Sumiko , Hirata Yukimasa
Published: September 2013

Purified human insulin autoantibody (IAA) collected from the serum of a man (T.H.) with insulin autoimmune syndrome was characterized. The TH-IAA was found to be of IgG1 (λ-light-chain) subclass. In addition to the single-binding affinity of TH-IAA to human insulin that we have shown in previous studies, the TH-IAA binding to human insulin was completely inhibited by a mouse monoclonal anti-idiotypic antibody against TH-IAA. A competitive inhibition study with various insulins revealed an epitope of human insulin against TH-IAA. These findings suggest that TH-IAA is monoclonal and is directed at a determinant at B-3 (asparagine) on the human insulin B-chain.
Impairment of Spinal Cord Conduction Velocity in Diabetic Rats
Authors: Carsten Ronald E , Whalen L Raymond , Ishii Douglas N
Published: September 2013

Peripheral neuropathy is a common and well-studied complication of diabetes mellitus, but the possibility that central neuropathy is also present has received scant attention. Based on recent evidence showing that insulin has a direct effect on axon formation and neuronal survival in vitro, it was predicted that functional neuropathy would be present in the spinal cord of diabetic animals. Although structural lesions are encountered in the spinal cord of diabetic patients at autopsy, the functional corollaries have essentially remained unstudied. We used a new procedure to study evoked spinal cord potentials in the rat, which revealed a significant retardation in conduction velocity in streptozocin (STZ)-induced diabetic animals. This retardation was not due to a toxic effect of STZ on the involved spinal cord sensory pathways, because insulin infusion prevented the development of spinal cord neuropathy. The kinetics and magnitude of decline in conduction velocity were similar in the spinal cord, saphenous nerve, and common peroneal nerve during the first 2 wk, suggesting that a common mechanism was involved. After 10 wk, a spontaneous improvement in function was observed in the spinal cord and common peroneal nerve but not in the saphenous nerve. Our results support the hypothesis that central nervous system dysfunction can occur along with peripheral sensory neuropathy in diabetes.
Nutritional and Hormonal Regulation of Articular Collagen Production in Diabetic Animals
Authors: Umpierrez Guillermo E , Goldstein Steven , Phillips Lawrence S , Spanheimer Robert G
Published: September 2013

Although changes in collagen production probably play a major role in the connective tissue defects of diabetes, we do not know to what extent these changes are attributable to hormonal/metabolic versus nutritional alterations. To study collagen production as influenced separately by nutrition versus hormonal/metabolic factors, rats were given 50 mg/kg i.v. streptozocin (STZ) (mild weight-gaining diabetes) or 100 mg/kg STZ (severe weight-losing diabetes) and compared with nondiabetic food-restricted rats to match weight changes in diabetic animals. Articular cartilage was incubated with [3H]proline, and uptake of [3H]proline into both collagen and noncollagen proteins was determined with purified bacterial collagenase. Collagen decreased to 49% in mildly diabetic rats and 16% in severely diabetic rats, compared with control rats fed ad libitum and decreased to 85 and 73%, respectively, in food-restricted rats (both P < .01 vs. diabetes). Diabetes induced a greater defect in collagen production than food restriction and a greater decrease in collagen than noncollagen protein production within each group, suggesting a specific effect on collagen. With comparable levels of metabolic severity (glucose, β-hydroxybutyrate), diabetic animals that lost weight produced significantly less collagen than animals that gained weight, suggesting separate mechanisms. Quantitation of the impact of undernutrition on collagen production in diabetes demonstrated that ∼31 to 32% of the defect was due to undernutrition, leaving ∼68–69% of the defect due to the diabetic state. Multivariate analysis of metabolic (glucose, β-hydroxybutyrate), hormonal(insulin, insulinlike growth factor I [IGF-I]), and nutritional (weight change) factors revealed that altered collagen production was correlated only with the degree of weight change (P <.01) in food-restricted animals; reduced collagen production was correlated only with circulating IGF-I (P <.01) in diabetic animals.
Three-Dimensional Imaging of Intact Isolated Islets of Langerhans With Confocal Microscopy
Authors: Brelje T Clark , Scharp David W , Sorenson Robert L
Published: September 2013

We present a new technique for analyzing the three-dimensional structure of intact isolated islets of Langerhans. Adult rat and human islets were stained with whole-mount immunofluorescence techniques and optically sectioned with a confocal microscope. This has several advantages over traditional methods: 1) the technical difficulties in serial sectioning and handling the large numbers of sections are avoided, 2) optical sectioning by confocal microscopy gives improved resolution and strongly suppresses light from out-of-focus structures, and 3) entire islets can be rapidly imaged for the presence of positive staining. This new technique should facilitate the study of the three-dimensional structure of islets of Langerhans.
Effects of Sorbinil on Glomerular Structure and Function in Long-Term–Diabetic Rats
Authors: Mauer S Michael , Steffes Michael W , Azar Silvia , Brown David M
Published: September 2013

We investigated the role of the aldose reductase pathway in the pathogenesis of the nephropathy of rats with severe (non-insulin-treated) streptozocin-induced diabetes of 6 mo duration. The initial experiment included four groups of rats: diabetic and control animals on a 20% protein diet, which were untreated or treated with sorbinil (an aldose reductase inhibitor). Food intake was increased by diabetes but was uninfluenced by sorbinil, whereas urinary urea nitrogen excretion was increased and body weight was decreased by both variables. Glomerular basement membrane (GBM) width was increased by diabetes and decreased by sorbinil. No other structural changes were noted. We speculate that sorbinil could have slowed the abnormal rate of GBM thickening in diabetic rats and the normal increase in GBM width in control rats by inducing a mild catabolic state. The second experiment also involved four groups of rats: diabetic and control animals on a 50% protein diet, which were untreated or treated with sorbinil. In these studies, diabetes was again associated with reduced body weight, but sorbinil had no influence on urinary urea nitrogen. Urinary albumin excretion, which was increased by diabetes, was not affected by sorbinil. GBM width was increased by diabetes, but in contrast to animals on 20% protein diets, the animals on 50% protein diets and treated with sorbinil did not have reduced GBM widths. Mesangial volume fraction was greater in diabetic animals than in controls, and sorbinil largely prevented mesangial expansion in them. Surprisingly, the control animals on the 50% protein diet and given sorbinil had increased mesangial volume fraction compared with control rats on the same diet not given the drug. In these experiments, diabetes was associated with reduced mean arterial blood pressure and renal plasma flow. Filtration fraction was increased in diabetic rats, but glomerular filtration rate was no different from that of controls. The increased filtration fraction was due at least partly to the decreased colloid oncotic pressure in the diabetic rats. Sorbinil did not affect any of these physiological or functional parameters. Thus, sorbinil decreased the rate of mesangial expansion in severely diabetic rats on high-protein intake through other than hemodynamic influences. The mechanism whereby this occurred or whereby this drug caused mesangial expansion in normal animals on a high-protein diet was not explained by these studies.
Effect of Rise in cAMP Levels on Ca2+ Influx Through Voltage-Dependent Ca2+ Channels in HIT Cells: Second-Messenger Synarchy in β-Cells
Authors: Rajan Arun S , Hill Ronald S , Boyd Aubrey E
Published: September 2013

With a glucose-responsive (β-cell line (HIT cells), we tested the hypothesis that the cytosolic free Ca2+ level ([Ca2+],) is an intracellular signal through which a rise in cyclic AMP (cAMP) levels is transmitted to potentiate glucose-stimulated insulin secretion. In these cells, glucose stimulates the acute release of insulin without increasing [Ca2+], or altering cAMP content. Either forskolin or 3-isobutylmethylxanthine (IBMX) potentiated glucose-stimulated insulin secretion and increased cAMP levels. At either a submaximal glucose concentration or maximally stimulatory glucose concentration, both IBMX and forskolin triggered a rapid rise in [Ca2+], (1.9- and 1.5-fold increase over basal levels, respectively). Similarly, glucagon stimulated a 1.3-fold increase in [Ca2+]1 over basal levels. The effect on [Ca2+]1 required glucose and was secondary to Ca2+ influx through voltage-dependent Ca2+ channels because it was blocked by either chelation of extracellular Ca2+ with EGTA or by the Ca2+-channel blockers verapamil and nimodipine. Verapamil also inhibited IBMX potentiation of glucose-stimulated insulin secretion and the IBMX-induced rise in [ca2+]1 in a dose-dependent manner with IC50s of 2 × 10−5 and 4 × 10−6 M, respectively. We conclude that in the β-cell, a rise in cAMP levels increases Ca2+ influx through voltage-dependent Ca2+channels and that this represents a mechanism by which cAMP potentiates glucose-stimulated insulin secretion in β-cells.
Interferon-γ Induces Transcription and Differential Expression of MHC Genes in Rat Insulinoma Cell Line RINm5F
Authors: Ono Santa Jeremy , Colle Eleanor , Guttmann Ronald D , Fuks Abraham
Published: September 2013

We have reported that enhanced levels of class I major histocompatibility complex (MHC) antigen are expressed throughout the islets of prediabetic and newly diabetic BB rats and that the endocrine cells of the islet remained class II negative. In this study we investigated the molecular biology of lymphokine-induced expression of the class I and II MHC genes in subclones of the rat insulinoma cell line RINm5F. Treatment of a particular subclone of RINm5F cells (which are normally class II negative, class I low expressors) with crude lymphokine preparation or various doses of recombinant interferon-γ resulted in enhancement of MHC class I antigen expression but no detectable induction of class II antigen expression. This enhancement of class I antigen expression was a dose-dependent phenomenon and was preceded by a dose-dependent increase in class I–specific RNA. Both class I and II genes were induced at the transcriptional level, as determined by Northern blotting and in vitro nuclear transcription assays, but exhibited strikingly different induction kinetics. Supernatants from concanavalin A–stimulated splenocytes had a similar class I–restricted inductive effect on MHC gene expression. This subclone of RINm5F cells, which exhibits a class I lymphokine response–positive, class II response–negative phenotype, 1) mimics the behavior of β-cells in the prediabetic and newly diabetic pancreas and 2) represents a valuable system for probing the similarities and differences in the lymphokine-mediated induction pathways for class I and II MHC genes.
Peptide-Based Radioimmunoassay for Insulin Receptor: Detection of Insulin-Stimulated Downregulation in IM-9 Lymphocytes
Authors: McFarland K C , Ramachandran J , Grunfeld Carl
Published: September 2013

To overcome the difficulties encountered in quantifying the insulin receptor number by Scatchard analysis, a radioimmunoassay (RIA) for the human insulin receptor (hIR) has been developed that uses an antibody raised against a synthetic peptide (Gly-Lys-Lys-Asn-Gly-Arg-Ile-Leu-Thr-Leu-Pro-Arg-Ser-Asn-Pro-Ser) corresponding to the carboxyl terminal of the hIR. A second peptide (Tyr-Gly-Arg-Ile-Leu-Thr-Leu-Pro-Arg-Ser-Asn-Pro-Ser) was used as a standard and allowed preparation of monoiodinated derivative of theoretical specific activity for use as the radioactive ligand. The assay is specific, highly reproducible, and sensitive, with a detection limit of 10 fmol of receptor. One mole of purified receptor, measured by Scatchard analysis or amino acid analysis, is read as one mole of receptor in the RIA with peptide being the standard. The assay is effective with receptor from multiple sources and could determine the decrease in number of insulin receptors seen in IM-9 lymphocytes after treatment with insulin (downregulation).