bluuebunny/crossref_metadata_2025 huggingface dataset:
Circulating Immune Complexes and Platelet Thromboxane Synthesis in Patients with Insulin-dependent (Type I) Diabetes Mellitus
Authors: Triolo G , Davi' G , Giardina E , Cardella F , Meli F , Grutta A La , Strano A , Bompiani G D
Published: September 2013

Platelets from diabetic subjects with circulating immune complexes (CIC) synthesized greater amounts of thromboxane than did platelets from CIC-negative patients or controls. In view of the known action of CIC on platelet function, a relationship between these two factors may be suggested in the initiation and progression of microangiopathy in diabetes.
Effect of Epinephrine and Somatostatin-induced Insulin Deficiency on Ketone Body Kinetics and Lipolysis in Man
Authors: Weiss M , Keller U , Stauffacher W
Published: September 2013

The effect of elevated plasma epinephrine concentrations (≈800 pg/ml) on ketone body kinetics was determined in postabsorptive normal subjects using primed-continuous infusions of 3-14C-acetoacetate. Infusion of epinephrine (60 ng/kg/min) resulted in a transient increase in total ketone body production to a maximum of 2.5-fold the basal rate within 45 min (P < 0.01 versus controls). Ketone body uptake increased with a delay, compared with production, causing a 2.8-fold increase in total ketone body concentrations (P < 0.05 versus controls). Plasma free fatty acid (FFA) and blood glycerol concentrations increased transiently during epinephrine; their course was similar to that of ketone body production. Epinephrine administration resulted in hyperglycemie, hyperlactatemia, and a modest increase in plasma insulin and glucagon concentrations. To assess epinephrine's effect on ketone body kinetics during lack of insulin, and to avoid epinephrine-induced alterations in plasma insulin and glucagon concentrations, epinephrine was also infused combined with somatostatin (6.5 μg/kg/h). During somatostatin infusion, epinephrine administration resulted in an enhanced and sustained elevation of total ketone body production from 4.4 ± 0.8 to 15.1 ±1.2 μmol/kg/min (P < 0.01 versus somatostatin alone). Ketone body concentrations increased markedly from 310 ± 63 to 1763 ± 137 μmol/L (P < 0.01 versus somatostatin alone); the ketonemic effect was enhanced due to a 40% decrease of the metabolic clearance rate associated with somatostatin infusion. The increase in plasma FFA and blood glycerol concentrations during somatostatin-induced insulin deficiency was transiently enhanced by epinephrine, such that they increased to 3.2- and 5.6-fold their basal values after 45 min, respectively (P < 0.01). Thus, elevation of epinephrine concentrations to levels that are observed in severe stress resulted, in normal man, in a transient increase in lipolysis and ketogenesis. The metabolic clearance of ketone bodies increased initially but remained uninfluenced thereafter. The transient nature of the increase in ketogenesis and lipolysis was in part due to an elevation of plasma insulin levels caused by hyperglycemia. During acute insulin deficiency, epinephrine's effect on ketogenesis was sustained, while the acceleration of lipolysis was again transient, suggesting a direct hepatic ketogenic effect. However, the major influence of epinephrine on ketone body kinetics consisted of an enhancement of ketone body production secondary to an increase in lipolysis and FFA supply for ketogenesis.
The Effect of Salicylates on Nonenzymatic Glycosylation and Thermal Stability of Collagen in Diabetic Rats
Authors: Yue D K , McLennan S , Handelsman D J , Delbridge L , Reeve T , Turtle J R
Published: September 2013

The effects of glucose on the nonenzymatic glycosylation and thermal rupture time of rat tail collagen were examined by (1) in vitro incubation of collagen fibers in glucose and (2) in vivo in diabetic rats. In vitro, glucose caused a dose-dependent rise in both nonenzymatic glycosylation and thermal rupture time and there was a good correlation between these two parameters (r = 0.68, P < 0.0001). Aspirin, a known inhibitor of nonenzymatic glycosylation, was effective in preventing the glucose-induced rise in nonenzymatic glycosylation and thermal rupture time when present at concentrations of 0.78, 1.56, and 3.12 mM. Sodium salicylate at concentrations of 1.56 and 3.12 mM was also effective. In vivo, the nonenzymatic glycosylation and thermal rupture time of collagen fibers were both increased by 2–3-fold in rats with streptozotocin-induced diabetes of 4 wk duration. Aspirin or sodium salicylate treatment for 4 wk (240 mg/kg/day) from the onset of diabetes was able to prevent the rise in thermal rupture time without affecting nonenzymatic glycosylation of collagen or glycosylated hemoglobin levels. Aspirin or sodium salicylate treatment did not have detectable effect on properties of collagen in normal rats. The in vitro findings are consistent with the hypothesis that nonenzymatic glycosylation leads to the increased thermal stability of collagen fibers. The significance of nonenzymatic glycosylation in vivo is less certain, as thermal rupture time can be altered independently. The action of aspirin and sodium salicylate in vivo suggests new therapeutic options in the prevention and treatment of diabetic complications.
The Effects of Biosynthetic Human Proinsulin on Carbohydrate Metabolism
Authors: Revers R R , Henry R , Schmeiser L , Kolterman O , Cohen R , Bergenstal R , Polonsky K , Jaspan J , Rubenstein A , Frank B , Galloway J , Olefsky J M
Published: September 2013

Large quantities of biosynthetic human proinsulin have recently become available through recombinant DNA technology. Since the in vivo effects of human proinsulin have not been studied in man, we compared the dose-response relationship for stimulation of glucose disposal and suppression of hepatic glucose output by proinsulin and insulin. Ten normal subjects were studied using the euglycemic glucose clamp technique. The human proinsulin and insulin infusion rates were chosen to achieve steady-state proinsulin levels 10-fold higher than insulin levels on a molar basis, based on previous observations that porcine proinsulin has ∼10% the potency of insulin. Proinsulin infusion rates of 2.75, 7.5, 22.5, and 45 μg/m2/min were compared with insulin infusion rates of 0.63,1.67, 5, and 10 μg/ m2/min. Primed, continuous infusions of insulin yielded steady-state levels within 25 min, whereas proinsulin levels did not reach a steady state for 120–180 min. The metabolic clearance rate of insulin was 11–12 ml/kg/min at the lower infusion rates but fell to 8.4 ml/kg/min at the highest infusion rate. The metabolic clearance rate of proinsulin was 3.0–3.5 ml/kg/ min at all infusion rates. Dose-response analysis demonstrated that proinsulin-mediated glucose disposal was ∼8% that of insulin. In contrast, proinsulin-mediated suppression of hepatic glucose output was ∼12% that seen with insulin.

We conclude that: (1) primed, continuous infusions of proinsulin and insulin have considerably different kinetics; (2) the metabolic clearance rate of proinsulin is only −28% that of insulin, but the processes responsible for removal of insulin from the circulation are more saturable than those responsible for removal of proinsulin; and (3) proinsulin appears to exert a greater effect on hepatic than on peripheral tissues.
Binding of Insulin to Its Receptor Impairs Recognition by Monoclonal Anti-insulin Antibodies
Authors: Taylor Simeon I , Schroer Joyce A , Marcus-Samuels Bernice , McElduff Aidan , Bender Timothy P
Published: September 2013

The interaction between insulin and its receptor was investigated using both monoclonal and polyclonal anti-insulin antibodies. After covalent cross-linking of 125I-insulin to the insulin receptor on cultured human lymphocytes (IM-9 cells) using disuccinimidyl su berate, we inquired whether the insulin-receptor complex could be immunoprecipitated with anti-insulin antibodies. While a polyclonal guinea pig anti-insulin anti-serum succeeded in immunoprecipitating receptor-bound 125I-insulin, binding to the receptor decreased the avidity of the antiserum for the insulin moiety by a factor of approximately 1000-fold. Sixteen distinct monoclonal murine anti-insulin antibodies were employed to immunoprecipitate receptor-bound 125I-insulin. Of these 16 monoclonal antibodies, only one (antibody 5.9F4) could be shown to recognize receptor-bound 125I-insulin. Moreover, even with antibody 5.9F4, binding of 125I-insulin to its receptor reduced the affinity of the antibody by a factor of 10- to 100-fold.

These data strongly suggest that, when insulin binds to its receptor, the majority of the insulin molecule is unavailable for binding by anti-insulin antibodies. It seems likely that the hormone binding site on the receptor may be very large, thereby allowing for sequestration of the majority of the insulin molecule with relatively little of the hormone remaining exposed.
Isolation of T-Lymphocyte Lines with Specificity for Islet Cell Antigens from Spontaneously Diabetic (Insulin-dependent) Rats
Authors: Prud'homme Gerald J , Fuks Abraham , Colle Eleanor , Guttmann Ronald D
Published: September 2013

T-lymphocyte lines specific for islet cell antigens were isolated from the spleen and pancreas of newly diabetic BB rats or from the related strain BBUF. These cell lines were grown in continuous culture with inter-leukin-2 (IL-2) containing medium for >60 days. Such T-lymphocytes responded by proliferation and IL-2 secretion in the combined presence of islet cell antigens and major histocompatibility (MHC)-matched antigen-presenting cells. By fluorescence-activated cell sorter (FACS) analysis the cells were W3/13+, W3/25+, and 0X8−. Thus, both functionally and by cell-surface-marker analysis they appear to be of the T-helper phenotype. The long-term growth and study of anti-islet T-lymphocyte lines will permit a detailed analysis of the role of T-lymphocytes in the pathogenesis of IDDM.
Altered Responses to Androgen in Diabetic Male Rats
Authors: Jackson Fred L , Hutson James C
Published: September 2013

In male rats, experimentally induced diabetes mellitus has been reported to be associated with reduced serum levels of gonadotropins and testosterone as well as decreased sex accessory organ weights. The purpose of the present study was to determine if the decreased accessory organ weights and gonadotropin levels observed in diabetic animals result from alterations in the ability of target tissues to respond to testosterone. Adult, male, Wistar rats were injected with streptozotocin (STZ) and either maintained as untreated diabetics or treated with daily injections of insulin. Semi-starved animals were included to control for any effects on the reproductive system due to body weight change alone. These three groups, plus intact controls, were maintained for 30 days with one-half of the animals from each group receiving silastic tubing implants of testosterone of various lengths. It was determined that, in uncontrolled diabetic and semi-starved animals, the serum levels of LH, FSH, and testosterone were decreased, as were the weights of seminal vesicles and ventral prostate glands. Insulin treatment restored LH, FSH, and testosterone levels to normal. Sex accessory glands exhibited slight, but significant, recovery in diabetic animals treated with insulin. Implants of testosterone that resulted in physiologic serum levels of testosterone were effective in depressing serum LH and FSH levels as well as in maintaining normal seminal vesicle and ventral prostate weights in control and semi-starved animals. In contrast, the diabetic animals did not respond to testosterone by either inhibition of gonadotropin release or maintenance of sex accessory weights. Insulin-maintained diabetic animals exhibited normal response to testosterone in terms of gonadotropin release; however, insulin treatment had only marginal effects on the response of sex accessory organs. The inability of testosterone to inhibit gonadotropin release or stimulate growth of sex accessory organs in diabetic rats may indicate that a primary reason for reproductive dysfunction in the experimentally induced, diabetic male rat is due to altered actions or accessibility of androgene at the level of the steroid target tissues.
Improved In Vivo Insulin Effect During Continuous Subcutaneous Insulin Infusion in Patients with IDDM
Authors: Beck-Nielsen Henning , Richelsen Bjørn , Hasling Claus , Nielsen Ole Hother , Heding Lise , Sørensen Niels Schwartz
Published: September 2013

It has recently been shown that conventionally treated IDDMs are insulin resistant. Using the insulin clamp technique, we studied the influence of metabolic status on the in vivo insulin effect in these patients. Eleven IDDMs, treated conventionally with diet and insulin for 10.7 ± 5.6 yr, were studied before and after continuous subcutaneous insulin infusion (CSII) treatment (with a portable pump) for 6 mo. We found that conventionally treated diabetic subjects were extremely insulin resistant with regard to peripheral glucose uptake. Glucose uptake, at an insulin concentration of about 80 μU/ml, was 4.3 ± 2.0 mg/kg · min before treatment compared with 11.5 ± 4.0 mg/kg · min in normals (P < 0.01). After pump treatment for 6 mo, metabolic control improved significantly (HbA1c decreased from 8.9 ± 1.9% to 7.4 ± 1.2%, P < 0.01) and, parallel to that, glucose uptake increased about 80% to 7.5 ± 3.5 mg/kg · min (P < 0.01). The mean daily plasma FFA level decreased from 0.32 ± 0.10 mmol/L to 0.21 ± 0.07 mmol/L (P < 0.01); this variable was negatively correlated to the glucose clearance rate (r = –0.62, P < 0.01). There was no statistically significant change in mean daily plasma insulin and plasma growth hormone levels or in 24-h cortisol excretion in the urine (P > 0.1). The insulin binding capacity of serum IgG was also unchanged, and there was no significant relationship between this quantity and glucose clearance rates (r = 0.18, P > 0.1). We conclude that conventionally treated IDDMs are insulin resistant with regard to peripheral glucose uptake. The insulin resistance may, at least in part, be secondary to the abnormal metabolic Status Of these patients.
Plasma β-Thromboglobulin Response to Insulin-induced Hypoglycemia in Type I Diabetic Patients
Authors: Monnier Louis H , Lachkar Hassan , Richard Jean L , Colette Claude , Borgel Dominique , Orsetti André , Mirouze Jacques
Published: September 2013

The effect of an insulin-induced hypoglycemia was examined in 14 type I diabetic patients. After an overnight blood glucose normalization, each patient received an additional intravenous bolus of 3 U regular insulin at 0900 h (time 0). Blood glucose was continuously recorded up to 180 min. Plasma samples were assayed for β-thromboglobulin (βTG, ng/ml), pancreatic glucagon (pg/ml), cortisol (μg/dl), and growth hormone (ng/ml) 30 min before the insulin stress, at time 0, at blood glucose nadir, and at 180 min. The blood glucose fell from a baseline level of 85.0 ± 3.2 mg/dl to a nadir value of 39.2 ± 1.9 mg/dl (P < 0.001) reached at an average time of 41.4 ± 4.9 min. Plasma βTG increased significantly (P < 0.05) during the insulin stress: 93.4 ± 23.7 ng/ml at nadir versus 42.5 ± 5.9 at time 0. Plasma cortisol and growth hormone were significantly increased (P < 0.02 and P < 0.01) at nadir compared with time 0 values. Plasma pancreatic glucagon was higher at nadir than at time 0, but the difference was not significant. The present results indicate that in vivo platelet activation can be triggered by hypoglycemic episodes in insulin-treated diabetic patients.
Age- and Diabetes-related Changes in Tissue Glucose Uptake and Estradiol Accumulation in the C57BL/KsJ Mouse
Authors: Garris David R , Coleman Douglas L , Morgan Carl R
Published: September 2013

The effect of the diabetes (db/db) mutation on the agerelated changes in glucose uptake and estradiol incorporation in peripheral tissues were investigated in C57BL/KsJ mice between 2 and 16 wk of age. Glucose uptake in the uterus, ovaries, pancreas, lung, liver, heart, kidney, and spleen were markedly increased in diabetic mice after the development of the hyperglycemic condition, as compared with control mice. The age-related increase in glucose uptake observed in control mice was enhanced in hyperglycemic (i.e., ≥4 wk of age) animals. In contrast, the diabetes mutation caused a decreased estradiol uptake by the uteri, ovaries, and mesometrial fat pads at 16 wk, while having little effect in nontarget tissues of diabetic mutants. These data indicate that the diabetes mutation enhances glucose uptake, especially in estradiol target tissues (i.e., uterus, ovary), at the same time that estradiol incorporation is depressed. These results suggest that an alteration in glucose utilization by steroid-sensitive reproductive tract tissue may underlie the impaired reproductive ability in these animals. Other peripheral tissues did not demonstrate any remarkable changes in estradiol uptake, but the enhanced carbohydrate metabolism observed may relate to the subsequent age- and diabetes-related changes in tissue structure and function in these animals.
Characterization of the Early Stages of Diabetic Retinopathy by Vitreous Fluorophotometry
Authors: Cunha-Vaz J G , Gray J R , Zeimer R C , Mota M C , Ishimoto B M , Leite E
Published: September 2013

We compared insulin-dependent diabetic patients with minimal (16 eyes of 9 patients) or no retinopathy (45 eyes of 27 patients) to normal volunteers (20 eyes of 12 subjects) using a commercial vitreous fluorophotometer and different procedures for artifact correction. The influence of background autofluorescence was minimized through the use of a software program that subtracted a fluorophotometric scan obtained before administration of fluorescein from that obtained after its injection. We also compared two programs designed to minimize the contribution of the chorioretinal peak spread function to the readings in the vitreous. The fluorescein concentration in the posterior vitreous was then averaged within two different regions. We then assessed the influence of these data-processing methods on the spread of the results of the different groups. The clinical study showed that only the posterior vitreous concentration of fluorescein is relevant in the evaluation of the blood-retinal barrier. However, since there is a gradient of fluorescein concentration in the posterior vitreous, one needs a scanning device so that one can measure at a precise location in front of the retina. The posterior vitreous concentration of fluorescein was significantly increased in diabetic subjects with one or no aneurysms as compared with normals. Moreover, the eyes with minimal retinopathy, as judged by the presence of microaneurysms, had higher values than those without retinopathy. The clear differences among these three groups were not present when the midvitreous values were used. Finally, the concentrations of fluorescein in the anterior chamber were higher in the diabetic subjects with retinopathy than in the normals, but not in the diabetic subjects without retinopathy.
The Effects of Cyclooxygenase and Lipoxygenase Inhibitors on the Collagen Abnormalities of Diabetic Rats
Authors: Yue D K , McLennan S , Handelsman D J , Delbridge L , Reeve T , Turtle J R
Published: September 2013

The importance of cyclooxygenase and lipoxygenase pathways in the determination of collagen abnormalities in diabetes was investigated. Pharmacological agents with antiprostaglandin activity, such as indomethacin, naproxen, and aspirin, were able to prevent the rise in thermal rupture time of tail collagen in diabetic rats. Paracetamol was without effect. The action of indomethacin on diabetic collagen was abolished by concurrent administration of sodium benoxaprofen, an inhibitor of lipoxygenase, to the diabetic rats. Collagen abnormalities in diabetes may be regulated by a balance of the cyclooxygenase and lipoxygenase pathways. Antiprostaglandin agents may have a role in the prevention of some diabetic complications.
Intratesticular Islet Allografts in the Spontaneously Diabetic BB/W Rat
Authors: Selawry Helena , Fajaco Rita , Whittington Karen
Published: September 2013

Thirty-three male BB/W rats with diabetes of 11–145 days duration were divided into 3 groups: (1) six received abdominal, intratesticular islet a I log rafts and no immunosuppression posttransplantation; (2) 15 were similarly grafted and in addition were given four injections of ALS regularly at 10-day intervals for 30 days after transplantation; and (3) 12 rats received scrotal, intratesticular islet allografts and four injections of ALS. The results: (1) in the absence of immunosuppression all six of the rats with abdominal, intratesticular islet allografts became normoglycemic within 2 days after transplantation but in none did graft survival exceed 17 days; (2) a marked prolongation of graft survival of >65–441 days occurred in 13 of the 15 animals with identical intratesticular allografts; (3) sustained immunosuppression was not needed for prolonged islet allograft survival in rats with cryptorchid islet allografts; and (4) only one of the 12 rats with scrotal, intratesticular allografts became normoglycemic whereas 11 remained severely glycosuric. However, on surgical translocation of the grafted testes from the scrotum into the abdominal cavity, the rats promptly became normoglycemic in the absence of any additional therapy.
Time Course of the Lymphopenia in BB Rats: Relation to the Onset of Diabetes
Authors: Yale Jean-François , Grose Mark , Marliss Errol B
Published: September 2013

The spontaneously diabetic BB rat syndrome is associated with a marked lymphopenia, which affects all members of litters of diabetes-prone rats, and may be a necessary condition for the development of the disease. We assessed peripheral blood lymphocyte counts and subsets from birth to 66 days of age with a view to assessing the early time course. At birth, total numbers were decreased, as were total T-cells (monoclonal antibody W3/13 + , with an even greater deficit in OX19 + cells), the helper/inducer subset (W3/25 +), and the suppressor/cytotoxic subset (OX8 +), but la + (B, OX6 +) cells were not reduced. There was a less-thannormal rise in these values with time, and a similar pattern was observed at 66 days. Rats followed thereafter to onset of diabetes showed no differences at 66 days that were predictive of subsequent diabetes development. Another set of rats studied at the same age and again at onset of diabetes showed no changes concurrent with diabetes onset. The data are consistent with a genetically determined defect in lymphocyte numbers that leads to a subnormal rise in circulating cells later in life, and may predispose to another unidentified factor responsible for precipitation of the beta cell cytotoxicity.
In Situ Ultrastructural Demonstration of Cells Bearing la Antigens in the Murine Pancreas
Authors: Farr Andrew G , Anderson Susan K
Published: September 2013

Although an important role has been postulated for class II major histocompatibility gene products in the rejection of transplanted islets, the identity of the cells bearing these molecules within pancreatic tissue has been the topic of some controversy. To clearly define the cell population(s) within the murine pancreas that express la antigens, perfused murine pancreata were processed for the ultrastructural in situ demonstration of la antigens. It was found that la antigen expression was restricted to mononuclear cells adjacent to capillaries throughout the exocrine and endocrine portions of the pancreas. Vascular endothelium and ductular epithelium did not express detectable amounts of la antigens.
Reduced Glomerular Sodium/Potassium Adenosine Triphosphatase Activity in Acute Streptozocin Diabetes and Its Prevention by Oral Sorbinil
Authors: Cohen Margo Panush , Dasmahapatra Amita , Shapiro Edith
Published: September 2013

To explore metabolic changes associated with the sorbitol accumulation and myo-inositol depletion observed in glomeruli of rats with experimental diabetes, we examined total and ouabain-inhibited adenosine triphosphatase (ATPase) activity in glomeruli isolated from control and streptozocin (STZ)-diabetic rats. Glomerular Na/K-ATPase activity (ouabain-inhibited) was significantly reduced in diabetic animals, while total (composite) ATPase activity remained unchanged. Treatment with insulin partially restored the Na/K-ATPase activity. Administration of the aldose reductase inhibitor, sorbinil, which normalizes glomerular contents of both sorbitol and myo-inositol in diabetes, completely prevented the diminution of Na/K-ATPase activity. These results establish that glomerular Na/K-ATPase activity is reduced in acute experimental diabetes. The ability of sorbinil to prevent this decrease suggests that it is related to polyol accumulation and/or myo-inositol depletion, although an effect of the drug unrelated to its aldose reductase inhibiting property has not been excluded. Since increased polyol pathway flux, decreased myo-inositol, and reduced Na/K-ATPase activity have also been described in peripheral nerve, another tissue in which typical diabetic complications characteristically occur,the consequences of these metabolic changes may be implicated in the pathogenesis of diabetic nephropathy.
Effects of Gastric Inhibitory Polypeptide in the Response to Prolonged Parenteral or Enteral Alimentation in Rats
Authors: Baer A R , Dupre J
Published: September 2013

To examine the effects of long-term elevation of plasma gastric inhibitory polypeptide (GIP), the responses to parenteral (PA) or enteral (EA) alimentation were studied in consciousrats with duodenal and venous cannulae. A weight-maintaining liquid diet (84% as glucose, 16% as amino acids) was infused at a constant rate for 6 days by either route, and daily blood samples were taken. A subset of animals receiving PA also received porcine GIP with the infusate (PA plus GIP; plateau plasma immunoreactive GIP, IRGIP, 610 ± 120 pg/ml). With PA, plasma IRGIPdid not change from basal levels, whereas with EA IRGIP rose to virtual plateau levels (mean 530 ±110 pg/ml). In the steady state, plasma immunoreactive insulin (IRI) was significantly lower with EA (mean, 153 ± 5 μU/ml) than with PA (mean, 226 ± 15 μU/ml), which in turn was lower than with PA plus GIP (mean, 375 ± 23 μU/ml, P < 0.001 by ANOVA). A similar ranking of plasma glucose levels occurred in the steady state, with means of 113 ± 7 (EA), 126 ± 3 (PA), and 184 ± 9 (PA plus GIP) mg/dl (P < 0.001 by ANOVA). To assess the response to transient hyperglycemia in the steady state, an intravenous glucose bolus was given to each group on the fifth day. Peak plasma IRI levels did not differ among the three groups; however, the glucose disappearance rate was significantly slower with PA plus GIP compared with either EA or PA. Assuming that porcine GIP did not stimulate glucose production, this peptide appeared to induce hyperinsulinemia with insulin resistance during parenteral alimentation. The contrasting features of relatively low glucose and insulin levels during enteral alimentation associated with high levels of endogenous IRGIP in the blood suggest either (1) that the findings depend on variations of GIP or its actions in the different species, or (2) that mechanisms originating in the intestine act to preserve insulin sensitivity during absorption of nutrients from the gut under physiologic conditions.
Tissue Culture of Human Fetal Pancreas: Development and Function of B-Cells In Vitro and Transplantation of Explants to Nude Mice
Authors: Sandler Stellan , Andersson Arne , Schnell Annika , Mellgren Anders , Tollemar Jan , Borg Håkan , Petersson Birger , Groth Carl-Gustav , Hellerström Claes
Published: September 2013

The present study evaluates the development and function of human fetal B-cells in vitro with a view to using such cells in future attempts for transplantation of human fetal pancreas to diabetic patients. A method previously described in our laboratory for preparing islets in vitro from the fetal rat pancreas has been applied and modified for use with human fetal pancreas. Pancreatic glands of different gestational ages were obtained from 37 consecutive prostaglandin-induced abortions. After a mild collagenase treatment, the partially disintegrated tissue was maintained in culture for 7 days in tissue culture medium RPM1 1640 plus 20% fetal calf serum to permit cell attachment and outgrowth of endocrine cells. In 17 of the 37 consecutively cultured fetal pancreatic glands, islet-like cell clusters were formed. The 20 remaining glands were lost because of either bacterial contamination or lack of viability already before dissection had occurred. Sections of the newly formed cell clusters revealed well-preserved pancreatic cells showing frequent mitotic figures. The tissue exhibited a high rate of (pro)insulin biosynthesis and a modest insulin response to secretory stimuli, suggesting that the mechanism of glucose regulation by the fetal B-cells is not yet fully developed. Electron micrographs showed a large number of granule-containing cells, some of which were identified as B-cells. In nine cases, harvested cell clusters were implanted beneath the kidney capsule of nude mice. When these animals were killed after 2 mo, seven mice showed a considerable growth of the grafts with numerous islet-like structures containing insulin- and glucagon-positive cells. A high replicatory activity of the grafted cells was further supported by the finding of numerous labeled nuclei in autoradiographs of the graft-bearing kidneys. Since no immunocytochemical staining was carried out, the cell replicatory rate is representative for the whole grafted cell population rather than for the endocrine cells. It isconcluded that this improved culture technique provides a suitable system for the study of growthand differentiation of human fetal pancreas and may facilitate the preservation of pancreatic B-cells intended for transplantation.
Insulin-mediated Glucose Uptake in Nondialyzed and Dialyzed Uremic Insulin-dependent Diabetic Subjects
Authors: Schmitz Ole
Published: September 2013

A three-step euglycemic insulin clamp was performed in six matched groups: nine healthy subjects, 10 insulin-dependent diabetic (IDD) subjects with normal kidney function, 10 nondiabetic uremic subjects, six nondialyzed uremic IDD subjects, seven uremic IDD subjects on chronic hemodialysis (HD), and six uremic IDD subjects on chronic ambulatory peritoneal dialysis (CAPD). Insulin was infused sequentially at rates of 0.5 (step 1), 2.0 (step 2), and 4.0 (step 3) mU · kg−1 · min−1. Each dose was given for 120 min; however, in theIDD subjects with fasting hyperglycemia, step 1 of the clamp was slightly extended. Average serumfree insulin levels at steady state ranged from 22 to 342 μU/ml and were comparable in all groups. Step 3 glucose infusion rate (GIR), the last 30 min of the infusion period, was extremely suppressed in nondialyzed uremic IDD subjects, amounting to 53% of that in healthy subjects (7.7 ± 0.7 versus 14.4 ± 0.9 mg · kg−1 · min−1 P < 0.001) indicating severe insulin resistance in peripheral tissues. As expected, step 3 glucose disposal was also reduced in IDD subjects with normal kidney function (12.4 ± 0.6 mg · kg−1 · min−1) and nondiabetic uremic subjects (9.2 ± 0.6 mg · kg−1 · min−1) as compared with healthy subjects (P = 0.06 and P < 0.001, respectively). The pronounced impairment of insulin responsiveness in nondialyzed uremic IDD subjects was almost equal to the sum of the defects in nondiabetic uremic and IDD subjects with normal kidney function. Step 2 of the sequential insulin infusion resulted in differences in GIR between the above-mentioned groups that were analogous to those encountered at the highest insulin infusion rate. During step 1 the average steady-state GIR, reflecting the sum of suppression of glucose production and stimulation of glucose utilization, was more than twofold higher in healthy subjects than in the nondialyzed patient groups. In contrast, the insulin action on Iipoiysis and ketogenesis as assessedby changes in serum NEFA and blood 3-hydroxybutyrate was normal in the patient groups. In the patients treated by HD and CAPD insulin responsiveness (step 3 GIR) was enhanced or tended to be so compared with nondialyzed uremic IDD individuals (9.5 ± 0.7 and 12.2 ± 0.7 mg kg−1 min−1 P = 0.07 and P < 0.001, respectively). Furthermore, GIR at all three steps was significantly higher in the CAPD group than in the HD group (P = 0.08, P < 0.001, and P < 0.03). No difference in degree of azotemia or glycemic and metabolic control wasobserved between the dialyzed groups.

In conclusion, nondialyzed uremic IDD individuals exhibit extreme insulin resistance in peripheral tissue that is probably the result of several intracellular defects. In uremic IDD subjectstreated with CAPD, the insulin-mediated glucose uptake is closer to normal than in IDD subjects on HD. Potentially lower peripheral insulinemia in diabetic CAPD patients having insulin administered intraperitoneally may contribute to this difference.
Virus-induced Murine Diabetes: Enhancement by Immunosuppression
Authors: Gould Cheryl L , McMannama Karyle G , Bigley Nancy J , Giron David J
Published: September 2013

Adult, male ICR Swiss mice are susceptible to the diabetogenic effects of the D-variant of encephalomyocarditis virus (EMC-D) in contrast to adult C3H/HeJ male mice, which are relatively resistant. To date, experimental evidence suggests that the immune system plays a role in the pathogenesis of this infection. We have investigated the potential involvement of the immune system in the pathogenesis of EMC-D-induced diabetes using cyclosporin-A (CyA), a potent immunosuppressive drug. The data show that treatment with CyA results in increased severity and incidence of diabetes in susceptible ICR Swiss mice and induction of diabetes in resistant C3H/HeJ mice. It is concluded that immune mediation probably is not involved in the early pathogenesis of EMC-D-induced diabetes in mice.
Modulation of Adipose Lipoprotein Lipase by Thyroid Hormone and Diabetes: The Significance of the Low T3 State
Authors: Gavin Laurence A , McMahon Francis , Moeller Marie
Published: September 2013

The present study was performed to assess the potential relationship between the low T3 syndrome and hypothyroidism. Comparative studies were performed on the relative effects of diabetes and insulin on heparinreleasable adipose lipoprotein lipase (LPL) in the intact and hypothyroid rat. Hypothyroidism for 10 days (Tx) significantly increased adipose LPL activity (5.8 ± 0.2 μeq/g/h) compared with the activity (3.6 ± 0.4 μeq/g/h) in the normal group. Diabetes for 72 h (streptozocin, STZ, 10 mg/100 g body wt, i.p.) significantly reduced (P < 0.005) adipose LPL activity in the Tx model. However, despite the suppressant effect of diabetes (43 ± 11%), the enzyme activity remained equivalent to the normal group. Insulin stimulated adipose LPL in the Tx-diabetic group. The enzyme demonstrated a synergistic response to insulin and hypothyroidism. Subsequent studies were performed in the intact diabetic rat, a low T3 state. Adipose LPL activity was reduced to a similar degree by diabetes (79 ± 2%) irrespective of the serum T3 concentration. Furthermore, the magnitude of the adipose LPL stimulation by insulin was not modulated by the endogenous serum T3. However, co-treatment of the diabetic group with T3 and insulin blunted the adipose LPL response to insulin. These various modulations in adipose LPL activity were associated with significant but opposite changes in serum triglyceride levels in both the hypothyroid and intact rat.

These studies demonstrate that hypothyroidism counteracts the suppressant effect of diabetes on heparin-releasable rat adipose LPL activity and magnifies the enzyme response to insulin. The synergistic effect of hypothyroidism and insulin on adipose LPL activity suggests that the enzyme responds through different mechanisms. In contrast, the low T3 state associated with diabetes did not influence the adipose LPL response to diabetes or insulin therapy. Thus, the low T3 state in the rat does not reflect hypothyroidism. The low T3 state may, however, have a permissive role as it facilitated the adipose LPL response to insulin in the diabetic rats. Therefore, T3 therapy is contraindicated under these condition.
Insulin-induced Internalization and Replacement of Insulin Receptors in Adipocytes of Rats Adapted to Fat Feeding
Authors: Begum Najma , Tepperman Helen M , Tepperman Jay
Published: September 2013

To elucidate the mechanisms of the previously observed decrease in adipocyte surface insulin binding in fat diet-induced insulin resistance (Ip et al., J. Lipid Res. 1976; 17:588–99), we performed studies on (1) the distribution of insulin receptors between the cell surface and cell interior, and (2) the extent of internalization and recycling of insulin receptors in adipocytes obtained from fat-fed and glucose-fed rats. Intact cell binding and binding to solubilized cells (total) was decreased by 50% in rats fed fat for 7 days when compared with glucose-fed rats. Incubation of adipocytes with insulin in Tris buffer (100 ng/ml) resulted in a 40–60% decrease in cell surface insulin binding capacity. In two separate experiments, it was found that this insulin-induced receptor loss (%) in fat-fed rat adipocyte preparations was either comparable to that of glucosefed rats or somewhat decreased. The degradation of the receptors was not affected, as seen by the lack of difference in the chloroquine effect between the two groups. Incubation of fat cells with insulin in tissue culture medium promoted complete reinsertion of receptors into the cell membrane in glucose-fed rat adipocytes, while fat-fed rat preparations demonstrated a significant decrease (37%) in the extent of reinsertion of insulin receptors. Thus, the decrease in cell surface insulin binding and receptor number in fat-fed rat adipocytes is related to an adaptive decrease in the total receptor content coupled with an impairment in the ability to reinsert insulin receptors from the cell interior after insulin-induced internalization.
Cytosolic Insulin-degrading Activity in Islet-derived Tumor Cell Lines and in Normal Rat Islets
Authors: Bhathena Sam J , Timmers Kim I , Oie Herbert K , Voyles Nancy R , Recant Lillian
Published: September 2013

RIN-m cells, cultured from a rat insulinoma, not only bind and secrete but also degrade insulin (Diabetes 1982; 31:521–31). The insulin-degrading activity resides in the cytosol and is similar to the insulin-specific proteases previously described in muscle and other tissues. It has an apparent Km of 0.15 μM for porcine insulin in crude cell-free extracts, a competitive inhibition constant for proinsulin that is close to the Km, and a lower but measurable affinity for glucagon. The enzyme is inactive at pHs below 6.0, indicating that it is not lysosomal, is completely inhibited by Nethylmaleimide, and exhibits apparent competitive inhibition constants (μM) for the following peptides: desoctapeptide insulin, 0.043; guinea pig insulin, 0.048; proinsulin, 0.64; insulin B-chain, 1.17; glucagon, 7.0; and cyclic somatostatin, 8.6. Highly active insulin-degrading activity was found using cell suspensions of 22 cloned and 8 subcloned cell lines derived from RINm as well as 11 other continuous cell lines derived from a variety of nonislet tissues of rat, mouse, and human origin. Homogenates of the original rat islet tumor and cytosol of normal rat islets also contained insulin-degrading activity. Although insulin protease is present in a variety of tissues, it may have an additional regulatory function in cells that are actively synthesizing, storing, and secreting insulin.
Enhanced Cerebral Substrate Pools in the Fetus and Neonate of the Diabetic Canine Mother
Authors: Kliegman R M , Miettinen E L , Campbell G
Published: September 2013

Energy stores and intermediates of carbohydrate metabolism were investigated in the freeze-clamped cerebral cortex of the fetus and fasted neonate born to a diabetic canine mother. Prior studies in these same pups demonstrated circulating hyperinsulinemia, depressed free fatty acid levels, and attenuated gluconeogenesis. Hepatic and muscle tissue also demonstrated augmented levels of glycogen, triglycerides, and amino acids. In the present investigation, cerebral tissue from these same pups of diabetic mothers also demonstrated enhanced fetal cerebral glucose and glycogen content. After 24 h of neonatal fasting, cerebral glycogen content declined to values lower than in control pups. Cerebral cortical levels of glucoses-phosphate, fructose-6-phosphate, lactate, citrate, α-ketoglutarate, and malate were not altered, while oxaloacetate as higher at 3 and 9 h and fructose-1,6-diphosphate was higher at 9 and 24 h in the IDM pups. Adenine nucleotide levels and the energy charge were equivalent to those in control pups at each time interval. In contrast, cerebral cortical amino acids of the glutamate group were enhanced in the fetus or neonate of the diabetic mother. Cerebral cortical alanine was increased from 3 to 24 h while aspartate and glutamate were augmented in the fetus and fasted IDM newborn pup. Glutamine was increased at 6 and 24 h, while 7-aminobutyrate was elevated in the fetus. Cerebral ammonia concentration was not altered. The augmented stores of cerebral carbohydrate and amino acid pools in the fetus and neonate after maternal canine diabetes may serve as oxidizable substrates for the brain during periods of attenuated systemic fuel availability. This may explain, in part, the paucity of neurodevelopmental sequelae in the hypoglycemic human infant of a diabetic mother.
The Effects of Variations in Percent of Naturally Occurring Complex and Simple Carbohydrates on Plasma Glucose and Insulin Response in Individuals with Non-insulin-dependent Diabetes Mellitus
Authors: Hollenbeck Clarie B , Coulston Ann M , Donner C Christopher , Williams Robin A , Reaven Gerald M
Published: September 2013

In the present study, 12 patients with non-insulin-dependent diabetes mellitus (NIDDM) consumed eucaloric, mixed food diets on three consecutive days. Diets provided 50% of the calories as carbohydrate, 35% as fat, and 15% as protein. The percent of carbohydrate fed as complex (starches) and simple (monoand disaccharides) varied among the 3 days. On day 1, the diet contained 80% of the carbohydrate as complex and 20% as simple (80/20); another contained 50% complex and 50% simple (50/50); and the final diet contained 20% of the carbohydrate as complex and 80% as simple (20/80). All simple carbohydrates represent naturally occurring sugars in fruits, vegetables, and dairy products. No refined sugars were added to any of the diets. The three experimental diets were randomly assigned using a 3 × 3 Latin square design.

Blood was obtained hourly from 0800 to 1700 h for day-long glucose and insulin concentrations, and 24-h urine collections were made for the measurement of urine glucose. Mean (± SEM) day-long glucose concentrations were significantly greater for the 80/20 diet (2245 ± 199 mg/dl · h, P < 0.05) than for either the 50/ 50 (2030 ± 157 mg/dl · h) or the 20/80 diets (2008 ± 160 mg/dl · h). No significant differences were noted between the 50/50 and the 20/80 diets. In contrast, day-long insulin concentrations were not significantly different with 401 ± 62, 370 ± 50, and 369 ± 60 μU/ ml · h on the 80/20, 50/50, and 20/80 diets, respectively. Twenty-four-hour urinary glucose excretion paralleled plasma glucose concentrations. Significant differences were noted when the 80/20 diet (25.1 ± 4.5 g/ 24 h, P < 0.05) was compared with the 20/80 diet (9.7 ± 3.3 g/24 h). Substantial quantitative differences also existed between the 80/20 and 50/50 (12.2 ± 4.5 g7sol;24 h), but these differences did not reach statistical significance.

The results of the present study support the hypothesis that variations in relative proportions of naturally occurring, complex and simple dietary carbohydrate will have no deleterious effect on glycemia in patients with NIDDM. Thus, there seems to be no apparent reason why patients with NIDDM should avoid foods that are high in naturally occurring, simple carbohydrate.
Zinc Supplementation Attenuates Insulin Secretory Activity in Pancreatic Islets of the ob/ob Mouse
Authors: Bēgin-Heick Nicole , Dalpē-Scott Marthe , Rowe Joanne , Heick H M C
Published: September 2013

The purpose of this study was to establish whether a relationship may exist between the hyperinsulinemia, the exaggerated insulin secretion, and the resistance to insulin characteristic of the obese-hyperglycemic syndrome and the zinc status of the ob/ob mouse. To this end, mice were given control and zinc-supplemented diets, and the effects of zinc supplementation on insulin secretion in vivo and in vitro as well as on glucose tolerance were studied. These data were compared with those obtained with oxytetracycline treatment, which is known to ameliorate the insulin sensitivity and glucose tolerance of these animals. The levels of zinc were measured in several tissues of lean and obese mice and the results show that zinc supplementation attenuated the exaggerated insulin secretion in vivo and in vitro without improving the tolerance to glucose. Zinc levels were significantly higher in the tissues of the obese than of the lean mice, with the exception of bone and pancreas. The results suggest a maldistribution of zinc in the tissues of the obese mouse.
Galanin Inhibits Insulin Secretion and Induces Hyperglycemia in Dogs
Authors: McDonald T J , Dupre J , Tatemoto K , Greenberg G R , Radziuk J , Mutt V
Published: September 2013

Intravenous administration of galanin into fasted conscious dogs produced a dose-dependent hyperglycemia accompanied by decreases in plasma insulin levels, but with no elevation of plasma glucagon levels. Galanin infusions produced greater parenteral glucose-induced rises in plasma glucose levels along with markedly blunted insulin responses compared with glucose and insulin responses to control glucose infusions. Immediately after cessation of the galanin infusions, elevation of plasma insulin levels occurred in the basal state and after parenteral glucose loading. These results suggest that galanin's hyperglycemic activity is predominantly mediated by a reversible inhibition of insulin secretion.
Gestational Diabetes Mellitus (GDM): Comparative Evaluation of Two Treatment Regimens, Diet Versus Insulin and Diet
Authors: Persson B , Stangenberg M , Hansson U , Nordlander E
Published: September 2013

Two-hundred and two pregnant women with impaired glucose tolerance were randomized to treatment with diet or diet and insulin by stratified selection. Self-monitoring of blood glucose was performed six times a day, 3 days/wk. Dietary treatment was considered inappropriate if fasting and postprandial blood glucose values exceeded 7 and 9 mmol/L, respectively, in which case insulin therapy was instituted. Insulin doses were adjusted according to blood glucose values, aiming at fasting and postprandial values below 5 and 6.5 mmol/L, respectively. There were no perinatal deaths. The two treatment regimens disclosed no differences regarding achieved degree of maternal blood glucose control, hemoglobin A1c at delivery, obstetric or neonatal complications, infant's size at birth including skinfold thickness, or C-peptide concentration in cord serum. Routine treatment of pregnant women with mild carbohydrate intolerance with insulin seems unnecessary. However, 15 patients (14%) in the diet group needed insulin to achieve acceptable blood glucose control, underlining the importance of monitoring blood glucose to detect those who are at risk of developing overt diabetes.