bluuebunny/crossref_metadata_2025 huggingface dataset:
Diabetic Autonomic Neuropathy in the BB rat: Ultrastructural and Morphometric Changes in Sympathetic Nerves
Authors: Yagihashi Soroku , Sima Anders A F
Published: September 2013

Autonomic neuropathy occurring in sympathetic nerves of the spontaneously diabetic BB rat has been characterized using ultrastructural and morphometric techniques. Paravertebral thoracic ganglion cells, preganglionic myelinated fibers of the white ramus, and postganglionic unmyelinated fibers of the gray ramus communicans were examined in a longitudinal fashion. The main structural abnormality consisted of expanded axons containing a variety of normal and abnormal subcellular structures, so-called dystrophic axonal changes. These increased with duration of diabetes and were found in close proximity to the somata of ganglion cells, suggesting a preganglionic origin. The ganglion cells showed no alteration in perikaryal or nuclear volume but exhibited decreased number of synapses, which correlated with the progressive increase of dystrophic changes. While no qualitative or quantitative abnormalities could be demonstrated in preganglionic myelinated fibers of the white ramus, postganglionic fibers in the gray ramus showed an increased numberof glycogenosomes, axonal sequestration, and reduction in axonal size. The present findings suggest an axonopathy in sympathetic nerves of the diabetic BB rat.
HLA-DR Antigen Frequencies in a North Indian Type I Diabetic Population
Authors: Bhatia E , Mehra N K , Taneja V , Vaidya M C , Ahuja M M S
Published: September 2013

Eighty-eight North Indian patients with type I, insulindependent diabetes mellitus (IDDM) and 113 unaffected individuals were typed for HLA-DR antigens from DR1 to DR7. The frequency of HLA-DR3 was significantly increased in the patients as compared with the controls (78.4% versus 25.7%, corrected P = 1.68 × 10 −12), the relative risk (RR) of 10.52 being much higher than that reported in the Western IDDM population. HLA-DR2 showed a significant negative association (RR = 0.18, corrected P = 1.03 × 10 −5), but DR4 had no relationship with IDDM in the present study (RR = 1.12, P = 0.12). These results emphasize the differences in HLA-IDDM associations among different ethnic groups.
The Effect of In Vivo Glucose Administration on Human Erythrocyte Ca2+-ATPase Activity and on Enzyme Responsiveness In Vitro to Thyroid Hormone and Calmodulin
Authors: Davis Faith B , Davis Paul J , Nat Gerard , Blas Susan D , Macgillivray Margaret , Gutman Steven , Feldman Mary Jane
Published: September 2013

To characterize endogenous control mechanisms for human erythrocyte membrane Ca2+-ATPase (“calcium pump”) activity, we studied the effect of changes in blood glucose concentration in vivo within the physiologic range on Ca2+-ATPase activity in red cells. Red cells obtained in the course of induced hyperglycemia were also studied to determine susceptibility of membrane Ca2+-ATPase to stimulation in vitro by thyroid hormone and calmodulin, both of which have been shown previously to enhance Ca2+-ATPase activity.

Oral glucose administration (75 g) to eight healthy, adult subjects induced predictable increases in concentrations of blood glucose and immunoreactive insulin. Basal levels of activity of Ca2+-ATPase in red cells obtained after glucose ingestion fell 55% (P < 0.025) by 30 min after glucose with recovery of enzyme activity to levels not significantly different from basal by 60 min. Activity of red cell Ca2+-ATPase at time zero was significantly stimulated in vitro by thyroxine (T4, 10−10 M), triiodo-L-thyronine (T3, 10−10 M), and calmodulin (100 ng/mg membrane protein). In vivo glucose administration led to depression of red cell enzyme responsiveness in vitro to T4 and T3; recovery from this effect did not occur by 120 min after oral administration of glucose. Calmodulin responsiveness of the enzyme in vitro was less significantly reduced in red cells obtained after glucose ingestion.

Intravenous (i.v.) glucose administration (20 g) to five subjects also led to decreased basal enzyme activity (61% of fasting level at 20 min). A significant decrease in response of enzyme to T4 was achieved by 8 min after glucose administration (P < 0.02), with recovery by 60 min. Calmodulin responsiveness showed an insignificant downward trend.

Exposure of red cell membranes to glucose (200 mg/ dl) or insulin (100 nil/ml) in vitro resulted in 26% and 17% reductions, respectively, in basal Ca2+-ATPase activity (P < 0.001), together with a reduction in thyroid hormone stimulation of the enzyme. Tunicamycin, an inhibitor of enzymatic protein glycosylatioh, reversed these in vitro effects of glucose, but not of insulin, on erythrocyte Ca2+-ATPase activity.

These observations are relevant to the interpretation of clinical studies of Ca2+-ATPase activity and to the physiology of the enzyme. Glucose administration predictably decreases Ca2+-ATPase in the human red cell, an alteration in calcium pump activity that would allow pulsing Of Ca2+ into the cell.
Suppression, Stress, and Accommodation of Transplanted Islets of Langerhans
Authors: Merrell Ronald C , Maeda Masamitsu , Basadonna Giacomo , Marincola Francesco , Cobb Luther
Published: September 2013

Successful intrasplenic islet autotransplantation in dogs requires an islet cell mass considerably greater than what might be expected based on studies of subtotal pancreatectomy. Grafts of marginal function ultimately fail, suggesting severe limitations in the capacity of an islet graft to adapt. Accommodation was tested in established intrasplenic grafts by either chronically stressing the graft with mild carbohydrate intolerance induced by exogenous corticosteroids or chronically suppressing the graft with exogenous insulin. After these manipulations, insulin output into the portal vein in response to intravenous (i.v.) glucose was measured and compared with that of normal dogs and dogs receiving islet autografts with no further treatment with either steroids or insulin. Transplanted islets tolerated the two manipulations well in that neither exogenous steroid nor insulin led to failure of the graft as a consequence of either stress or protracted diminished demand. The major determinant of successful islet grafting is the endocrine competence of the initial graft. If that competence is provided at the outset, the graft can adapt to a considerable range of demand for insulin secretion.
An Alteration in Apparent Molecular Weight of the Insulin Receptor from the Human Monocyte Cell Line U-937
Authors: McElduff Aidan , Grunberger George , Gorden Phillip
Published: September 2013

We have studied the structure of the insulin receptor from a human cultured monocyte cell line, U-937. The receptor is composed of alpha and beta subunits as seen in other insulin receptors, but these subunits are of greater apparent molecular weight (alpha 150,000 and beta 102,000) than in typical insulin receptors. Despite this, the U-937 insulin receptor appears to function normally. The alpha subunit binds insulin and the beta subunit is phosphorylated in response to insulin stimulation. Both subunits are expressed in the plasma membrane. Insulin binding isotherms are similar to those seen in IM-9 lymphocytes. Thus, the insulin receptor from U-937 monocytes appears functionally normal despite alterations in molecular weight of the subunits.
Stimulation of Insulin Secretion from Isolated Rat Islets by SaRI 59–801: Relation to cAMP Concentration and Ca2+ Uptake
Authors: Hanson Ronald L , Isaacson Craig M
Published: September 2013

The mechanism of stimulation of insulin release from isolated rat islets by 0.3 mM SaRI 59–801 (DL-α-dimethylaminomethyl-2-[3-ethyl-5-methyl-4-isoxazoyl]-1Hindole- 3-methanol) was investigated, considering cAMP concentration and Ca2+ uptake. Ten millimolar theophylline or 1 mM 1-methyl-3-isobutylxanthine, which inhibit cAMP phosphodiesterase, each greatly increased the stimulation of insulin release by 59–801. Forskolin (0.1 mM), an activator of adenylate cyclase, or 1 mM dibutyryl cAMP also potentiated 59–801, suggesting that 59–801 does not elevate islet cAMP but is potentiated by other compounds that do. Measurement of cAMP in islets by radioimmunoassay confirmed that it was not significantly elevated by 59–801 but was increased sevenfold by forskolin or 1-methyl-3-isobutylxanthine. SaRI 59–801 was not effective in the absence of Ca2+ and presence of 1 mM EGTA. Agents that block entry of Ca2+ into β-cells, verapamil, nifedipine, or CoCl2, inhibited the release of insulin in response to 59–801. Studies of 45Ca2+ uptake by isolated islets revealed an increased uptake in the presence of 59–801 and blockage of this effect by 50 μM verapamil. Thus, the stimulation of insulin secretion by 59–801 appears to involve a stimulation of Ca2+ uptake rather than an increase of cAMP concentration. The mechanism of stimulation of Ca2+ uptake by 59–801 requires further investigation.
Neonatal Rat Islet Cell Cultures Synthesize Insulin-like Growth Factor I
Authors: Romanus Joyce A , Rabinovitch Alexander , Rechler Matthew M
Published: September 2013

Monolayer cultures of islet B-cells were established from neonatal rat pancreas. Serum-free media conditioned by these cultures for 72 h were concentrated and fractionated on Sephadex G-50 at acid pH into a high-molecular-weight pool containing binding protein for insulin-like growth factors (IGFs) and a low-molecular-weight pool containing IGFs. IGF activity in the IGF pool was demonstrated by a specific radioreceptor assay using rat liver plasma membranes and 125I-labeled rat IGF-II. The IGF in islet cell media was characterized further by radioimmunoassays specific for human IGF-I and for rat IGF-II. Islet cell IGF was identified as predominantly IGF-I or a closely related species and not IGF-II. Levels of ∼15–50 ng IGF-I (based on human IGF-I standard)/106 islet cells accumulated in media after 72 h, and presumably represented synthesis by the islet cells. Concentrations of IGF-I attained in culture media, ∼0.1 ng/mf, were sufficient to stimulate [3H]thymidine incorporation into B-cells. Growth hormone did not consistently increase IGF-I synthesis, suggesting that the previously described effects of growth hormone on islet cell replication do not result from stimulation of IGF-I synthesis by islet cells. Thus, although the IGF-I synthesized by islet cells may be a physiologically relevant growth factor for these cells, the mitogenic effects of growth hormone in islet cells appear to be independent and not mediated by IGF-I.
Enhanced Insulin Binding to Blood-Brain Barrier In Vivo and to Brain Microvessels In Vitro in Newborn Rabbits
Authors: Frank H J L , Jankovic-Vokes T , Pardridge W M , Morris W L
Published: September 2013

Insulin is a known growth factor in nonneural tissue, and recent studies have shown that there are insulin receptors throughout the adult and fetal central nervous system. Since insulin has only limited access to the adult brain, this study was undertaken to determine if insulin has increased availability to the newborn brain where it may act as a neonatal brain growth promotor. In vivo brain uptake of 125I-Insulin after a single-pass carotid injection was measured in newborn, 3-wk-old and 11-wk-old (adult) rabbits. The brain uptake index (BUI) relative to a 3HOH reference was 22.0 ± 1.1% (mean ± SEM) for newborn, 12.8 ± 0.6% for 3-wk-old, and 6.5 ± 0.1% for adults. Specific 125I-insulin binding to isolated cerebral microvessels was similarly increased in the newborn (60.6 ± 3.3 %/mg protein) compared with the 3-wk-old (23.8 ± 1.7) and adult animals (13.6 ± 1.9). Scatchard analysis revealed that the difference was due to an increase in receptor number with only minimal changes in the affinity. The increased availability of circulating insulin to the newborn brain was further corroborated by elevated CSF/serum and brain/serum insulin ratios in the newborn versus adult. These results suggest that insulin has increased access to the newborn brain where it may function as a growth factor.
Acute Reversal of the Enhanced Insulin Action in Trained Athletes: Association with Insulin Receptor Changes
Authors: Burstein R , Polychronakos C , Toews C J , MacDougall J D , Guyda H J , Posner B I
Published: September 2013

We studied the effect of aerobic training and detraining on insulin-stimulated glucose disposal and on erythrocyte insulin receptor binding. Seven endurancetrained athletes were studied at 12 h, 60 h, and 7 days after cessation of training and compared with three untrained, age- and weight-matched controls.

The metabolic clearance rate of glucose as measured by the euglycemic clamp technique was 15.6 ± 1 . 8 ml/kg/min (mean ± SEM) in the trained subjects 12 h after the last bout of exercise compared with 7.8 ± 1.2 ml/kg/min in the untrained control group. When the trained subjects refrained from physical training, the metabolic clearance rate decreased to 10.1 ± 1 . 0 ml/kg/min at 60 h and further to 8.5 ± 0.5 ml/kg/min after 7 days of detraining.

The percentage of specific insulin binding to young erythrocytes (density 1.089–1.092), isolated by density gradient centrifugation, decreased from 10.4 ± 0.9 at 12 h after the last exercise to 8.1 ± 0.7%/3 × 109 cells after 60 h of detraining (P < 0.001). The decrease in insulin binding to erythrocytes was almost entirely accounted for by a decrease in the number of insulin receptors.

We conclude that the increase in peripheral insulin action seen in trained athletes is rapidly reversed, possibly by a mechanism separate from other phenomena associated with chronic training. The parallel findings of decreased in vivo insulin action and decreased insulin binding in young erythrocytes suggest that modulation of in vivo insulin response by detraining may be at least partially mediated by changes in insulin receptor number. Isolated young erythrocytes are better indicators of acute insulin receptor modulation than are whole cell preparations.
Hyperproinsulinemia in a Family with a Proposed Defect in Conversion Is Linked to the Insulin Gene
Authors: Elbein S C , Gruppuso P , Schwartz R , Skolnick M , Permutt M A
Published: September 2013

Two previously described pedigrees with familial hyperproinsulinemia have elevated proinsulin conversion intermediates resulting from amino acid substitutions in the proinsulin molecule. In contrast, a third family with elevated levels of an apparently normal proinsulin molecule may have a defect in the converting process. To determine if the defect in this family lies in the insulin gene region, we used restriction fragment length polymorphisms adjacent to the insulin gene to examine cosegregation with hyperproinsulinemia. We demonstrate linkage of hyperproinsulinemia and the insulin gene in this family with a LOD score of 1.8, suggesting that the defect lies in or near the insulin gene. This method has wide applicability in determining whether hyperproinsulinemia or hyperinsulinemia is the result of defects at the insulin gene, and should permit the detection of new defects at or near this locus.
Successful Long-Term Survival of Pancreatic Islet Allografts in Spontaneous or Pancreatectomy-induced Diabetes in Dogs: Cyclosporine-induced Immune Unresponsiveness
Authors: Alejandro Rodolfo , Cutfield Richard , Shienvold Frances L , Latif Zuhair , Mintz Daniel H
Published: September 2013

Nineteen pancreatectomized beagles and three spontaneously diabetic dogs were recipients of canine islet allografts from one or more unrelated donors. The islets, enriched 30–45-fold for endocrine cells and contained in a packed cell volume of <1.5 ml, were engrafted in the livers of recipient animals. Treatment of diabetic recipients with cyclosporine (CsA) was begun 3–5 days before islet transplantation and the initial dosage was adjusted to attain and maintain CsA serum trough levels between 400 and 600 ng/ml. Five dogs with CsA levels less than this (155 ± 35 SEM ng/ml) at the time of transplantation promptly rejected their grafts, whereas rejection was encountered in only 1 of 17 diabetic animals in which the initial level exceeded 400 ng/ml. CsA was discontinued 30, 60, or 90 days after continuous therapy in 10 animals. Graft failure was observed 2 mo after stopping CsA in 1 animal and 5 mo in the other. Eight other islet allograft recipients have sustained fasting euglycemia for 7 and 8 mo in 2 and for at least 2 mo in the remainder.

These results demonstrate that short-term CsA therapy prolongs survival of islet allografts and induces a state of immune unresponsiveness to islet alloantigens in dogs with experimental and spontaneous diabetes. The findings are unique for a nonrodent mammal and thus hold promise that similar results may be achieved for islet allografts of other mammalian species, including humans.
Quantitation of Insulin-stimulated Glucose Disposal in Patients with Non-insulin-dependent Diabetes Mellitus
Authors: Donner C C , Fraze E , Chen Y -D I , Reaven G M
Published: September 2013

Glucose disposal rates (Rd) during an insulin clamp study reflect both basal and insulin-stimulated Rd. To quantify the amount of glucose taken up in response to a known increase ininsulin concentration, two consecutive studies were performed on 10 patients with mild to moderate NIDDM (mean fasting glucose = 146 mg/ dl) and 10 normal subjects. Endogenous insulin secretion was inhibited by somatostatin and plasma glucose level maintained at 180 mg/dl for 5 h. Rd (mg/m2/min) was determined isotopically for 2.5 h at insulin concentrations ∼6 μU/ml and during 2.5 h of physiologic hyperinsulinemia at ∼60 μU/ml (total glucose disposal), with the increase in Rd resulting from the approximate 10-fold elevation of plasma insulin concentration defined as insulin-stimulated glucose disposal. Results showed that the increment in Rd resulting from the elevation of plasma insulin concentration was relatively minor in NIDDM (38 ± 6), increasing from a mean (±SEM) value of 83 ± 8 to 121 ±12. Similar values in normal subjects were 90 ± 7 and 274 ± 26 with an increment of 183 ± 21. Thus, insulin-stimulated glucose uptake in patients with NIDDM was only one-fifth of that in normals, and accounted for only 31% (38 ÷ 121) of total glucose disposal during the clamp study. These data indicate that the majority of previous insulin clamp studies of in vivo insulin action in patients with NIDDM, in which total glucose disposal and insulinstimulated glucose disposal have been equated, have underestimated the magnitude of insulin resistance present in NIDDM. This conclusion is highlighted by the fact that the current study was carried out in patients with relatively mild NIDDM, and the possibility exists that physiologic increments of plasma insulin have essentially no effect on peripheral glucose disposal in patients with moresevere NIDDM.
Enzyme Inducers Improve Insulin Sensitivity in Non-insulin-dependent Diabetic Subjects
Authors: Lahtela Jorma T , Arranto Arno J , Sotaniemi Eero A
Published: September 2013

The reduction in blood glucose in non-insulin-dependent diabetes mellitus (NIDDM) brought about by the use of phenobarbital (PB), a hepatic microsomal enzyme inducer, suggests an improvement in insulin sensitivity. The effect of PB on insulin-mediated glucose metabolism was hence investigated using the euglycemic clamp technique in 10 women with NIDDM aged 56–75 yr. The addition of PB to sulfonylurea therapy, concurrently for 6 wk, reduced fasting blood glucose (BG, from 12.8 ±1.6 to 10.2 ± 3.2 mmol/L, P < 0.01) and immunoreactive insulin (IRI) levels (from 32.4 ± 13.6 to 24.7 ± 9.8 mU/L, P < 0.01), whereas body weight remained unaltered. During the trial, there was a significant change in the glucose disposal rate (M, from 1.27 ± 0.60 to 2.82 ± 0.86 mg/kg/min, P < 0.001), the metabolic clearance rate of glucose (from 0.89 ± 0.41 to 2.24 ± 1.27 ml/kg/min, P < 0.01), the insulin sensitivity index (from 1.10 ± 0.44 to 2.86 ± 1.54 mg kg/min: mU/L × 100, P < 0.001), and the plasma antipyrine clearance rate (from 28.3 ± 11.7 to 51.4 ± 20.2 ml/min, P < 0.001), an in vivo index of liver microsomal enzyme activity. The antipyrine clearance rate correlated with insulin-mediated glucose metabolism (r2 = 0.560, P < 0.01). Thiscorrelation could be interpreted as indicating that, in NIDDM patients, peripheral glucose utilization and the liver microsomal enzyme system share common regulators. Our study suggests a new approach to the improvement of insulin sensitivity in NIDDM patients.
Continuous Subcutaneous Insulin Infusion
Authors:   American Diabetes Association
Published: September 2013

Use of continuous subcutaneous insulin infusion requires continuing available care by skilled professionals, careful selection of patients, meticulous patient monitoring, and provisions for recording and reporting experiences.

Insulin pumps prescribed by a physician within these guidelines are a part of treatment and should be covered by usual payment mechanisms.

Approved: Board of Directors, June 15, 1985.
Synthetic Pancreatic Growth Hormone-Releasing Factor (GRF-40) Stimulates the Secretion of the Endocrine Pancreas
Authors: Hermansen Kjeld , Kappelgaard Anne Marie , Esmann Jørgen , Ørskov Hans
Published: September 2013

The effects on islet hormone secretion of the synthetic replicates of two peptides with potent GH-releasing activity isolated from human pancreatic islet cell tumors (GRF-40 and GRF-44) were studied using the isolated, perfused dog pancreas. GRF-40 produced a dose-dependent stimulation of insulin, glucagon, and somatostatin secretion. The responses to GRF-40 were modified by the prevailing glucose level: higher insulin and somatostatin and lower glucagon responses were obtained at high rather than low glucose. In contrast, GRF-44 did not produce any stimulation of the endocrine pancreas. In vivo GRF-40 and GRF-44 elicited identical pronounced growth hormone responses in the rat. The findings reported here provide support that pancreatic insulin and glucagon are modulated by GRF-40 with somatostatin as its inhibitory counterpart. The question, whether GRF-40 is of physiologic relevance in the regulation of the endocrine pancreas, must await evidence that it is present and releasable from the pancreas.
Effects of Anti-Insulin Receptor Antibodies (AIRA) on Downregulation and Turnover of Insulin Receptors on Cultured Hepatocytes
Authors: Shimoyama R , Shelmet J J , Savage C R , Boden G
Published: September 2013

We have studied the effects of two polyclonal anti-insulin receptor antibodies (AIRA) on insulin receptor downregulation and turnover in rat hepatocytes in primary culture. Downregulation was determined by measurement of insulin binding after acid washing of cells to remove AIRA. Insulin receptor turnover was estimated by measurement of insulin binding after inhibition of synthesis of functional receptors with tunicamycin (0.5 μg/ml). Exposure of hepatocytes to AIRA (both sera were of comparable effectiveness) resulted in progressive, time- and dose-dependent losses of insulin binding (maximal loss was about 55% after 24 h of incubation with AIRA diluted 1:25). Cycloheximide (100 μM) prevented AIRA-mediated downregulation.

The t½ of disappearance of cell surface insulin binding capacity determined with tunicamycin was 8.0 h. Addition of insulin (1000 ng/ml) or AIRA to tunicamycin reduced the t½ to 2.6 h (insulin), 2.2 h (patient B10), and 2.0 h (patient 1). These data suggest that (1) AIRA downregulated insulin receptors on cultured hepatocytes by accelerating their rate of disappearance, (2) inhibition of protein synthesis prevented AIRA-mediated downregulation, and (3) downregulation by AIRA of insulin binding may be partially responsible for the desensitization of target cells to some of the insulinlike actions of these autoantibodies.
Evidence That Cholecystokinin Interacts with Specific Receptors and Regulates Insulin Release in Isolated Rat Islets of Langerhans
Authors: Verspohl Eugen J , Ammon Hermann P T , Williams John A , Goldfine Ira D
Published: September 2013

To determine the nature of the pancreatic islet cell cholecystokinin (CCK) receptor, we studied CCK receptor binding and biologic activity in isolated rat pancreatic islets. Binding of 70 pM 125I-CCK to collagenase-prepared isolated rat pancreatic islets at 24°C was one-half maximal after 5 min and maximal at 60 min. At 60 min, specific binding was 12% of total radioactivity per 100 μg islet protein; nonspecific binding (in the presence of 1 μM CCK 8) was less than 2% of total radioactivity. Unlabeled CCK 33 inhibited labeled hormone binding one-half maximally at 2 nM; Scatchard analysis showed one binding site (Kd, 2.3 ± 0.4 nM; Bmax, 8.1 pmol/mg protein). The agonist selectivity of this binding site was: CCK 8 = CCK 33>desulfated-CCK 8>CCK 4. Two CCK antagonists were studied; N-carbobenzoxy-L-tryptophan was more potent than dibutyryl-cGMP. When the effect of CCK on insulin release from the islets was studied, the order of potency of CCK agonists and antagonists on insulin secretion was the same as the order of their ability to inhibit 125I-CCK binding. The effect of CCK on insulin secretion was dependent on the glucose concentration in the media. CCK had no effect at 5.6 mM glucose and was fully effective at 11.0 mM glucose. These data, therefore, indicate that: (1) specific binding sites for CCK are present in rat pancreatic beta, cells; and (2) CCK acts in concert with glucose to stimulate insulin secretion.
The Glucokinase Glucose Sensor in Human Pancreatic Islet Tissue
Authors: Bedoya F J , Wilson J M , Ghosh A K , Finegold D , Matschinsky F M
Published: September 2013

The enzyme glucokinase controls glucose metabolism in islets and is proposed to be the glucose sensor in pancreatic β-cells. This concept was developed from studies with rodents and it remained to be explored whether it also applies to man. Studies in man were hampered, however, by the difficulty in obtaining wellpreserved pancreatic islet tissue and also because the high activity of hexokinase made it difficult to measure glucokinase. To overcome these obstacles, quantitative histochemical sampling techniques were developed allowing precise dissection of pure human islet tissue and a newly designed radiometric microassay was used, avoiding hexokinase interference, and providing the sensitivity necessary to measure the relatively low glucokinase activity in small samples of tissue obtained from brain-dead tissue donors. The present data indicate that glucokinase is present in human pancreatic islet tissue and is not found in the exocrine pancreas. The enzyme's Vmax with D-glucose as substrate was similar to the Vmax for glucose utilization reported previously for intact, isolated human isletsand the enzyme's Km for D-glucose was about 5 mM. Since glucokinase was also present in islet tissue of hamster, mouse, and rat, it is suggested that the glucokinase-glucose sensor concept has general applicability and that it could explain many aspects of the physiology and pathology of glucose homeostasis. This well-defined pancreatic islet glucokinase-glucose sensor should, therefore, be incorporated in any comprehensive model of glucose homeostasis.
A Human Monoclonal Antibody to Insulin
Authors: Livneh Avi , Avraham Hava , Elias Dana , Sack Joseph , Cohen Irun R , Eshhar Zelig
Published: September 2013

To elucidate the immune aspects of insulin-dependent diabetes mellitus (IDDM), we attempted to generate human monoclonal anti-insulin antibodies by fusing peripheral blood lymphocytes obtained from 10 insulin-treated IDDM patients with cells from a human lymphoblastoid cell line. Hybridomas that secreted immunoglobulins appeared in 9 of 400 wells. One of these hybridomas secreted anti-insulin antibody of the IgM class. The lymphocytic partner of this hybridoma was obtained from an IDDM patient who had undetectable levels of antibodies to insulin in his serum. Thus, by employing the hybridoma technique, it was possible to reveal the presence of insulin-sensitized B-lymphocytes in a patient who was serologically negative for anti-insulin antibodies. The monoclonal antibody recognized intact human insulin and insulins of other species, but not isolated A- and B-chains. This indicates that the antibody was functionally an autoantibody directed to an epitope formed by the native conformation of a highly conserved portion of the insulin molecule. This is the first report of a human hybridoma antibody to insulin.
Hemoglobin South Florida: New Variant With Normal Electrophoretic Pattern Mistaken for Glycosylated Hemoglobin
Authors: Shah S C , Malone J I , Boissel J -P , Kasper T J
Published: September 2013

An 8.75-yr-old Caucasian boy was discovered to have a markedly elevated (14.8%) hemoglobin A1c(HbA1c) as estimated by ion-exchange chromatography (Bio Rex 70). Glycohemoglobin (GHb) measured by a colorimetric method with thiobarbituric acid (TBA) was normal (equivalent to a 6.4% HbA1c). Nondiabetic quantities of GHb were found with affinity chromatography, and the glucose tolerance test was normal. Intensive efforts to identify an abnormal variant hemoglobin by several electrophoretic methods were unsuccessful. A family survey identified a similar abnormality in 11 other individuals, revealing an autosomal-dominant pattern. None of the affected individuals had any other hematologic abnormality. Structural analysis in one family member revealed a new hemoglobin variant (∼45% of the total hemoglobin) with the substitution of methionine for valine at the β-NH2-terminal. In addition, the initiator methionine residue was preserved. Approximately 20% of the variant hemoglobin was modified by acetylation of the NH2-terminal methionine. The modified variant coeluted with HbA1c. We suggest that patients who do not have an explanation for their elevated HbA1c should have GHb measured by the TBA method or affinity chromatography because hemoglobin electrophoresis does not identify this confounding artifact.
Immunohistochemical Colocalization of GABA and Insulin in β-Cells of Rat Islet
Authors: Garry D J , Sorenson R L , Elde R P , Maley B E , Madsen A
Published: September 2013

γ-Aminobutyric acid (GABA) is found in high concentrations in the pancreatic islet. In addition, enzymes regulating the level of GABA (L-glutamate decarboxylase and GABA-α-ketoglutarate transaminase) have been immunohistochemically localized in the medullary cells of the islet. In this study, an immunofluorescence and elution/restaining protocol is used to determine the distribution of GABA and either insulin, glucagon, or somatostatin in a tissue section. GABA was not detected within the islet α- or δ-cells but was determined to be localized within the insulin-containing β-cells.
Presence of ATP-Pyrophosphohydrolase in Mouse Pancreatic Islets
Authors: Capito K , Hansen S E , Hedeskov C J , Thams P
Published: September 2013

The presence of an enzyme that hydrolyzes ATP to AMP and PP1 was demonstrated in a 27,000 × g particulate and supernatant fraction of mouse pancreatic islets. The enzyme was stimulated by addition of Ca2+, Zn2+, and Co2+. Addition of calmodulin or trifluoperazine had no effect. In the presence of Ca2+ and Zn2+, the Michaelis constant (Km) for ATP was 0.1 mM and the maximum velocity (Vmax) was close to 90 nmol · min−1 · mg protein−1. After preincubation of the islets for 30 min with 16.7 mM glucose or 5 mM glucose with 1 mM 3-isobutyl-1-methylxanthine (IBMX), a three- to fourfold increase in enzyme activity was seen. Direct addition of IBMX or CAMP to the enzyme assay also had a small stimulatory effect. Preincubation with the insulin secretagogues leucine and α-ketoisocaproic acid did not affect the enzyme activity. The possible function of the enzyme in pancreatic islets is discussed in relation to hypotheses given for the function of similar enzyme(s) in other tissues.
Blood-Brain Glucose Transfer In Diabetes Mellitus: Decreased Number of Glucose Transporters at Blood-Brain Barrier
Authors: Matthaei S , Horuk R , Olefsky J M
Published: September 2013

This study describes the effects of streptozocin (STZ)- induced diabetes mellitus on the glucose-transporter system of the rat blood-brain barrier. Subcellular membrane fractions, i.e., plasma membranes and high- and low-density microsomes, were prepared from isolated brain microvessels derived from control and diabetic animals. The number of glucose transporters in each of the membrane fractions from both control and diabetic animals was determined by the D-glucose-inhibitable cytochalasin B-binding assay. The total number of glucosetransporters was decreased by 43% in STZ-treated rats compared with controls (35 vs. 115 pmol/mg protein; P < .05). The glucose-transporter number in plasma membranes was decreased by 50%, in highdensity microsomes by 38%, and in low-density microsomes by 45%. Incubation of isolated microvessels from control animals with 7 jiM insulin for 30 min at 37°C led to a cycloheximide-sensitive 27% increase (P < .05) in the number of transporters in high-density microsomes. This insulin effect was significantly diminished to 15% in the diabetic animals (P < .05). In conclusion, 1) STZ-induced diabetes decreases the glucose- transporter number in all subcellular membrane fractions derived from isolated rat brain microvessels, and 2) the insulin-induced increase in de novo synthesis of glucose transporters in brain microvessels is diminished in these chronically diabetic animals.
Aberrant Expression of HLA-DR Antigens by Insulin-Containing β-Cells in Recent-Onset Type I Diabetes MelIitus
Authors: Foulis A K , Farquharson M A
Published: September 2013

The pancreases of 14 children who died of type I diabetes were studied immunohistochemically for aberrant expression of HLA-DR antigens on islet endocrine cells. Two cases in which no residual insulin-secreting β-cells were present had no evidence of HLA-DR expression on endocrine cells. Insulin-containing islets were present in the remainder, and HLA-DR–positive endocrine cells were demonstrable in all of them. Endocrine cells expressing HLA-DR were present in 171 of 630 insulin-containing islets from all the cases. However, HLA-DR–positive endocrine cells were not seen in 2060 insulin-deficient islets, providing evidence that of the four hormone-producing cells in the pancreas only the β-cells expressed HLA-DR. Sections double stained for HLA-DR and the pancreatic hormones confirmed this view. Most islets in which HLA-DR–positive endocrine cells were seen had no evidence of insulitis, suggesting that within an individual islet, aberrant expression of HLA-DR on β-cells may precede the inflammatory infiltrate.
Utilization of Oral Sucrose Load During Exercise in Humans: Effect of the α-Glucosidase Inhibitor Acarbose
Authors: Gerard J , Jandrain B , Pirnay F , Pallikarakis N , Krzentowski G , Lacroix M , Mosora F , Luyckx A S , Lefèbvre P J
Published: September 2013

We investigated the hormonal and metabolic response to a 100-g sucrose load given 15 min after adaptation to moderate-intensity (50% Vmaxo2) long-duration (4-h) exercise in healthy volunteers. The effect of a 100-mg dose of the α-glucosidase inhibitor Acarbose ingested with the sucrose load was also investigated. “Naturally labeled [13C] sucrose” was used to follow the conversion to expired-air CO2 of the sugar ingested by isotope-ratio mass spectrometry. Circulating hormone and metabolite data were obtained in nine subjects, and indirect calorimetry and stable isotope methodology were applied to six of them. Under placebo, 93 ± 4 g sucrose were entirely oxidized during the 4 h of exercise, total carbohydrate utilization was 235 ± 14 g, endogenous carbohydrate utilization was 142 ± 13 g, and total lipid oxidation was 121 ± 7 g. A single oral dose of 100 mg Acarbose ingested with the sucrose load did not significantly modify total carbohydrate (239 ± 2 g/4 h) or lipid (122 ± 6 g/4 h) oxidation. In contrast, sucrose oxidation was reduced to 53 ± 6 g/4 h and endogenous carbohydrate utilization increased to 186 ± 7 g/4 h. Reduction of the rises in blood glucose and fructose and of the increases in plasma insulin and C peptide under Acarbose confirmed these effects, whereas lower circulating levels of alanine suggested a higher rate of gluconeogenesis.

These data show that a 100-g glucose load ingested soon after initiation of exercise is a perfect available metabolic substrate. Furthermore, the simultaneous ingestion of 100 mg Acarbose significantly reduces the availability of sucrose during exercise, a finding that has to be considered if this or other compounds with similar properties are envisaged for the treatment of diabetic patients.
Selective Unresponsiveness of Pancreatic β-Cells to Acute Sulfonylurea Stimulation During Sulfonylurea Therapy in NIDDM
Authors: Karam J H , Sanz N , Salamon E , Nolte M S
Published: September 2013

Patients with non-insulin-dependent diabetes mellitus (NIDDM) who have chronic hyperglycemia lose acute incremental insulin responses to glucose but are able to briskly respond to other β-cell secretagogues. To investigate whether this is a defect specific for glucose or represents a more general phenomenon, we measured the insulin responses to acute intravenous tolbutamide in 10 obese patients with NIDDM both before and during sulfonylurea therapy with tolazamide. Comparable glycemia was achieved with oral dextrose 2 h before intravenous testing. To assess β-cell responsiveness to a nonsulfonylurea secretagogue, 1 mg glucagon was administered intravenously during tolazamide therapy. In seven patients, the mean peak insulin increment 5 or 10 min after intravenous tolbutamide was 54 ± 11 μU/ml when not receiving tolazamide (0.14 ± 1 . 3 μU/ ml) with tolazamide (P < .001), even though serum insulin responded rapidly to intravenous glucagon. In four patients tested for reversibility of their refractoriness to intravenous tolbutamide during chronic tolazamide therapy, the mean peak insulin increment 1 wk after discontinuing tolazamide was 79 ± 22 (μU/ml. A relatively rapid development of refractoriness was documented in four patients who were tested only 12 h after beginning tolazamide therapy; the mean peak insulin increments 5–10 min after intravenous tolbutamide were undetectable (−0.5 (μU/ml), yet responses to intravenous glucagon were evident. In these NIDDM patients, exposure of pancreatic pcells to sustained levels of sulfonylureas induces a reversible state of refractoriness to acute stimulation with sufonylureas but not to another secretagogue. This phenomenon has features in common with the effect of sustained hyperglycemia on desensitization of the β-cell response to intravenous glucose with implications regarding the pathogenesis of NIDDM. More over, it suggests that the insulinotropic effect of sulfonylureas might be more effective, particularly in cases of NIDDM with “secondary failure” to sulfonylureas, if these drugs are administered either on an intermittent schedule or as “pulse” therapy, using a form with a shorter duration of action.
Prevalence of Diabetic Complications in Relation to Risk Factors
Authors: Knuiman M W , Welborn T A , McCann V J , Stanton K G , Constable I J
Published: September 2013

The prevalence of diabetic complications is reported from a cross-sectional study of rural diabetic subjects in Western Australia. Logistic-regression analysis has been used to discover potential risk factors associated with each complication. A distinction has been made between time-related variables (age, age at diagnosis, duration of diabetes) and other risk variables. We have attempted to identify the major time-related risk variables for each complication and then examined the effect of other risk variables after accounting for the major time-related variables. The important time-related variables were found to be duration of diabetes for retinopathy, age for macrovascular disease, duration and age at diagnosis of diabetes for sensory neuropathy, and age for renal impairment. When matched on these important time-related variables, the overall prevalences of complications for insulin-dependent (IDDM) compared wjth non-insulin-dependent (NIDDM) diabetic patients were essentially the same. An exception is renal impairment, for which IDDM patients had a higher prevalence than did NIDDM patients of the same age. After allowing for time-related variables, the analysis also demonstrates positive independent associations between diabetic control (glycosylated hemoglobin) and retinopathy and between diabetic control and macrovascular disease. Plasma cholesterol (positively) and high-density lipoprotein cholesterol (negatively) were related independently to both macrovascular disease and renal impairment. Very few differences in the risk-factor profiles for complications were found for IDDM compared with NIDDM patients after allowing for time-related variables.
Diacylglycerol Modulation of Insulin Receptor From Cultured Human Mononuclear Cells: Effects on Binding and Internalization
Authors: Grunberger G , Iacopetta B , Carpentier J-L , Gorden P
Published: September 2013

Tumor-promoting phorbol esters alter binding of growth factors and hormones to their specific receptors. Action of diacylglycerols, endogenous phorbol ester analogues, on 125I-labeled insulin binding to its receptor from human cells was therefore investigated. A variety of 1,2-diacylglycerols and 1,3-diacylglycerols inhibited 125I-insulin binding to intact human monocytelike (U-937) and lymphoblastoid (IM-9) cells in a dose-, time-, and temperature-dependent manner within 30 sec at 37°C in a fashion analogous to that of the tumor-promoting phorbol diester 12-O-tetradecanoylphorbol-13-acetate (TPA). Inhibition of insulin binding by diacylglycerols, analyzed by Scatchard plot, seems to be due to altered binding affinity of the insulin receptor. Diacylglycerol effects were reversible, were seen regardless of the order of addition of 125I-insulin and diacylglycerols, and were demonstrated only with occupied insulin receptors. Corresponding fatty acids or phospholipids did not affect specific insulin binding to the intact U-937 cells. Diacylglycerols also inhibited binding of 125I-insulin—like growth factor (IGF) I but not that of 125I-human growth hormone (HGH) to the human cells. The non-tumor-promoting phorbols (phorbol, 4-a-phorbol, phorbol-12,13-distearate) did not affect insulin binding to intact cells. Both diacylglycerols and TPA stimulated internalization of 125I-insulin by U-937 and IM-9 cells. The ability of diacylglycerol to mimic the effects of TPA on the insulin receptor supports the concept of diacylglycerols as endogenous phorbol diester analogues even though the sole role of protein kinase C in our system is doubtful. The DAG mediated modulation of the insulin receptor in intact cells might play a role in cell differentiation, proliferation, and tumor promotion through an additional mechanism.
Autoimmunity to Insulin, Beta Cell Dysfunction, and Development of Insulin-dependent Diabetes Mellitus
Authors: Srikanta S , Ricker A T , McCulloch D K , Soeldner J S , Eisenbarth G S , Palmer J P
Published: September 2013

Circulating insulin autoantibodies (INSAAb) were measured in discordant monozygotic twins, first-degree relatives, and other groups at “high risk” for the development of insulin-dependent diabetes mellitus (IDDM), and these results correlated with both islet cell antibody (ICAb) status and beta cell function. INSAAb were positive in 31.6% (12 of 38) ICAb-positive subjects but in only 3.1% (3 of 97) ICAb-negative subjects (X2 = 22.4; P < 0.001). Elevated levels of INSAAb tended to correlate with younger age and were observed in individuals irrespective of the prevailing degree of their beta cell function. Eight of 15 subjects detected to be INSAAb positive have thus far progressed to clinical IDDM (X2 = 18.3; P < 0.001). Thus, autoantibodies reactive with the insulin molecule (1) appear to constitute an additional serologie marker of ongoing autoimmunity and development of IDDM, and (2) may reflect heterogeneity in the pathogenesis of IDDM.
Changes in Islet Cell Composition During Development of Diabetes in Macaca nigra
Authors: Howard Charles F , Bueren Antonia Van
Published: September 2013

The islets of Langerhans in sections from the pancreas tail of Macaca nigra were stained by antiserum to insulin, glucagon, or somatostatin. The area of stained cells per total area of the islets was determined by a computerized photometric method. Insulin of the beta cells occupied 77% of the islet area in nondiabetic (ND) monkeys and decreased to 62% in monkeys in the earliest stages of metabolic deterioration, i.e., hormonally impaired (HI) monkeys. At the later stage of borderline diabetes (BD), monkeys had only 39% of the islet area occupied by insulin and the area was diminished to 1% in diabetic (D) monkeys. Islets in HI monkeys had an unusual pattern in which only the beta cells in the periphery of islets were stained. Glucagon in the alpha cells stained 7% of the islet area in ND monkeys, but the area was almost doubled to 13% in HI monkeys; the percentage decreased to about 5% in BD and 3% in D monkeys. Somatostatin accounted for 5% of the islet area in ND monkeys, was slightly greater at 7% in HI monkeys, and decreased to 3% in BD and 2% in D monkeys. Alterations in percentages of secretory cells correlated with several of the metabolic and clinical Changes.
Variable Relationship Between Peripheral Somatic and Autonomic Neuropathy in Patients with Different Syndromes of Diabetic Polyneuropathy
Authors: Young Robert J , Zhou Yue Qing , Rodriguez Erwin , Prescott Robin J , Ewing David J , Clarke Basil F
Published: September 2013

The relationship between abnormal peripheral nerve electrophysiology and abnormal cardiovascular autonomie function has been studied in four groups of diabetic subjects, comparable with regard to age, duration, and type of diabetes. Thirty-three had no symptoms of neuropathy, 28 had newly developed painful neuropathy, 24 had chronic painful neuropathy, and 21 had painless neuropathy with associated recurrent foot ulcers. In all three symptomatic groups, electrophysiology and autonomie function were more abnormal than in asymptomatic diabetic subjects. There was a significant overall relationship between peripheral nerve (electrophysiologic) and autonomie (cardiovascular reflex) dysfunction. However, when considered by groups, the degree of cardiovascular reflex abnormality was similar in the three symptomatic groups, whereas electrophysiology was appreciably worse in the foot ulcer group than in patients with painful neuropathy. Thus, patients with painful neuropathy had a higher ratio of autonomie (small fiber) abnormality to electrophysiologic (large fiber) abnormality. By contrast, foot ulceration was associated with the worst electrophysiologic (large fiber) abnormality. Heavier alcohol consumption and more severe retinopathy were also related to foot ulceration. In diabetic subjects with symmetrical sensory neuropathy, the relationship between large fiber and small fiber damage is not uniform. We conclude that there may be different etiologie influences on large and small fiber neuropathy in diabetic subjects and that the predominant type of fiber damage may determine the form of the presenting Clinical syndrome.