bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Effects of Sulfonylurea Agents on Glucose Transport in the BC3H-1 Myocyte
Authors: Rogers Bruce J , Standaert Mary L , Pollet Robert J
Published: September 2013

The actions of sulfonylurea agents to increase peripheral glucose disposal have been classically ascribed to an ability to potentiate insulin action. However, in the BC3H-1 cultured muscle cell, tolbutamide, glipizide, and glyburide directly provoked more than a twofold increase in 2-deoxyglucose (2-DG) uptake in a dose-dependent manner in the absence of insulin. Tolbutamide (3 mM) enhanced 2-DG uptake by 130% in the presence or absence of insulin and did not significantly change insulin binding or the sensitivity of the insulin response. The onset of tolbutamidestimulated hexose transport was seen after 30 min and reached a plateau after 12 h. Tolbutamide-stimulated glucose transport was associated with a twofold increase in the Vmax of 2-DG uptake and was completely blocked by 50 μM cytochalasin B, indicating that this action is mediated by increase in cell membrane glucose transporters. We show that sulfonylureas at therapeutic concentrations directly increase glucose transport into muscle cells. Because muscle is the major peripheral target tissue for glucose disposal, these results provide the basis for the therapeutic effect of these agents in improving peripheral glucose disposal in insulin-resistant type II (non-insulindependent) diabetes mellitus.
In Vivo Insulin Action Is Familial Characteristic in Nondiabetic Pima Indians
Authors: Lillioja Stephen , Mott David M , Zawadzki Joanna K , Young Andrew A , Abbott William G H , Knowler William C , Bennett Peter H , Moll Patricia , Bogardus Clifton
Published: September 2013

Non-insulin-dependent diabetes mellitus (NIDDM) is a genetic disorder characterized by two major pathogenic processes: reduced insulin action and a relative or absolute decrease in plasma insulin concentrations. We studied 116 nondiabetic siblings from 45 families to determine if in vivo insulin action showed any aggregation among siblings. Subjects were Pima Indians from the Gila River Indian Community in Arizona who, as a group, have the highest reported incidence and prevalence of NIDDM in the world. In vivo insulin action was determined by the euglycemic-clamp technique at two rates of insulin infusion in each subject with resulting mean plasma insulin concentrations of 119 and 1938 μU/ml. After adjustment for age, sex, and degree of obesity, there was significant aggregation among siblings of in vivo insulin action at the high insulin infusion rate (P < .0001). Family membership independently accounted for ∼34% of the variance in this measure of insulin action. Glucose uptake at the lower insulin infusion rate also showed familial aggregation (P < .01), with family membership independently accounting for ∼15% of the variance of this measurement. We conclude that in vivo insulin action is a familial characteristic. The familial component of insulin action occurs in addition to the effects of obesity, age, and sex on insulin action. Therefore it is not sufficient to simply know that an individual is lean or obese to predict his/her in vivo insulin resistance, because it must also be known whether he/she is from an insulin-resistant or insulin-sensitive family. An alteration of insulin action may be an underlying and potentially genetically determined abnormality in Pima Indians that could help explain the familial aggregation of diabetes in this population. Such a genetic mechanism might also operate in populations with Native American admixture (e.g., Mexicans) as well as other populations.
Evidence of Functional Gastric Inhibitory Polypeptide (GIP) Receptors in Human Insulinoma: Binding of Synthetic Human GIP 1-31 and Activation of Adenylate Cyclase
Authors: Maletti Maura , Altman Jean-Jacques , Hoa Daniele Hui Bon , Carlquist Mats , Rosselin Gabriel
Published: September 2013

Specific gastric inhibitory polypeptide (GIP) receptors were characterized in human benign insulinoma plasma membranes employing [mono-[125l]iodo-Tyr10]- GIP (125I-GIP) as the radioligand. GIP 1-42 inhibited 125I-GIP binding with an IC50 value of −9 M. Scatchard analysis showed two classes of binding sites: a highaffinity site (Kd = 2.23 × −9 M; Bmax = 24 fmol/mg protein) and a low-affinity site (Kd = 8.39 × 10−9 M; Bmax = 118 fmol/mg protein). A synthetic replicate of human GIP 1-31 inhibited 125I-GIP binding with an IC50 value of 10−8 M. The GIP binding sites of human insulinoma were coupled to adenylate cyclase stimulation. GIP 1-31 regulated the adenylate cyclase activity to the same extent as GIP 1-42. The concentrations of GIP required for maximal activity ranged from 10−9 to 10−8 M for either GIP 1-42 or GIP 1-31. The existence of functional GIP receptors in human insulinoma substantiates our recent reports demonstrating the presence of GIP binding sites in transplantable hamster insulinoma and indicates that GIP could exert a direct control of the β-cell function in humans through a purely endocrine pathway.
Effect of Glyburide in Type II Diabetes Mellitus: Studies of Monocyte Membrane Fluidity, Lipid Composition, and Insulin Binding
Authors: Neufeld Naomi D , Harris Michael , Corbo Lucille M , Koduri Aruna
Published: September 2013

Monocyte membrane lipid composition, fluidity, and insulin binding were studied in 10 previously untreated obese type II (non-insulin-dependent) diabetic subjects before and 2-7 days, 1 mo, and 3 mo after glyburide therapy. A significant reduction in fasting blood glucose levels occurred within 1 wk after initiation of therapy in all subjects. Serum insulin levels did not change significantly. After a transient increase at 2-7 days, insulin binding and receptor number decreased to less than pretreatment levels after 3 mo of therapy despite continued improved glycemic control. Molar cholesterol-phospholipid ratios increased significantly at 2-7 days and then reverted to pretreatment levels. A significant positive correlation between insulin binding and cholesterol-phospholipid ratios was seen at all durations of treatment. Membrane microviscosity as measured by fluorescence polarization of the probe diphenylhexatriene was significantly decreased after 3 mo of therapy. The results indicate that the glycemic effect of glyburide represents enhancement of insulin action and occurs independently of membrane insulin receptors.
Cytoadherence of Lymphocytes From Type I Diabetic Subjects to Insulin-Secreting Cells: Marker of Anti-β-Cell Cellular Immunity
Authors: Lang François , Maugendre Didier , Houssaint Elisabeth , Charbonnel Bernard , Sai Pierre
Published: September 2013

We studied the ability of lymphocytes from type I (insulin-dependent) diabetic patients to adhere to murine β-cells. Lymphocytes from 17 recent-onset type I diabetic subjects (<6 mo) displayed enhanced ability to form rosettes with RINm5F cells (P < .001) compared with lymphocytes from 27 healthy subjects forming background rosettes, whereas the number of RIN cytoadherent lymphocytes was unimpaired in 12 type II (non-insulin-dependent) diabetic subjects. This phenomenon tended to decline in 21 subjects with long-standing diabetes (>1 yr) who taken as a group presented a normal number of RIN rosetting lymphocytes. The islet specificity of these diabetic rosettes was confirmed because, compared with controls, lymphocytes from recent-onset type I diabetic subjects also displayed a greater intensity of adherence to normal mouse islets but not to unrelated K562 and TS cell lines. As demonstrated by indirect immunofluorescence studies, these diabetic rosettes contained 54% of T-lymphocytes (OKT3+, OKT4+, or OKT8+), whereas only 20% of T-lymphocytes were found in background rosettes. The high percentage (66%) of la+ cells found in diabetic rosettes suggests that at least some of the cytoadherent T-lymphocytes from recent-onset type I diabetic subjects are activated. Natural killer (NK) cells do not seem to be the major cell type implicated in this phenomenon, because Leu 11+ cells were less represented in diabetic rosettes (25%) than in background rosettes (53%). Moreover, the NK lytic activity of lymphocytes from 12 recent-onset type I diabetic subjects was lower than that of 12 control subjects (21.6 ± 2.8 vs. 31.2 ± 3.3, P < .02) and even inversely correlated to the number of rosetting lymphocytes (r = −.8, P < .005). These diabetic rosettes thus seem to represent a new marker of anti-β-cell cellular immunity in recent-onset type I diabetic subjects, more likely involving activated T-lymphocytes than NK cells.
Development of Rat Embryos Cultured in Glucose-Deficient Media
Authors: Ellington Stephanie K L
Published: September 2013

Embryo-culture techniques were used to study the effects of exposure to glucose-deficient culture media on rat embryos during organogenesis. Embryos and their extraembryonic membranes (explants) were cultured either in control media or in media with low or very low glucose concentrations. At the start of the culture the glucose concentrations were 8.4 ± 0.57, 4.5 ± 0.10, and 3.5 ± 0.07 mM. During the cultures, the explants progressively depleted the glucose in the medium until, after 48 h, the glucose concentrations were reduced to 1.1 ± 0.18, 0.4 ± 0.13, and 0.3 ± 0.02 mM, respectively. At glucose concentrations <2.5 mM, the rate of glucose uptake by the explants progressively decreased, and embryonic growth and differentiation became increasingly retarded. After 48 h in glucose-deficient culture media, embryos had smaller crown-rump lengths, lower protein contents, and fewer somites than embryos from the control media (P < .001). Most of the embryos exposed to the lower glucose concentrations also had severe dysmorphic lesions, especially of the head and branchial arches. The deleterious effects of exposure to low concentrations of glucose on embryonic development appeared not to be reversible. Embryos cultured for 24 h in media with a low concentration of glucose followed by 24 h in control medium grew and developed just as poorly as those cultured for the entire 48 h in the glucose-deficient media.
Defective Vasodilation Response to Exercise in Cutaneous Precapillary Vessels in Diabetic Humans
Authors: Katz Murray A , McNeill George
Published: September 2013

Although anatomic abnormalities in capillary structure are well described in diabetes mellitus, physiologic responses of diabetic microcirculation are less clear. This study addresses whether cutaneous vasodilation occurs normally in diabetic subjects in response to a standard exercise of underlying muscle. The methods involve a washout analysis from forearm skin of the fast-moving isotope 133Xe and the diffusion-limited marker 111ln-diethylenetriamine pentaacetic acid. Twenty-four normotensive type II diabetic patients of age (mean ± SE) 59 ± 1.4 yr were age and weight matched with 24 controls. Control subjects increased flow 50.6 ± 6.4%, which was not different from the increase in diabetic subjects of 52.7 ± 7.6%. Permeability-surface-area product (PS) increased in control subjects from 1.77 ± 0.20 ml · min−1 · 100 g−1 to 3.79 ± 0.50 (2P = .0001), whereas diabetic subjects did not show a change in PS (3.29 ± 0.35 to 2.69 ± 0.31). Resting PS was higher in diabetic than control subjects (P = .0003), perhaps indicating an already recruited capillary bed. During repetitive exercise, control subjects increased capillary density 125 ± 27% (2P = .0001) above basal with a nonsignificant 14 ± 8.4% decrease in mean capillary blood flow. Diabetic subjects responded with a nonsignificant decrease in capillary density and a significant 139 ± 38% increase in capillary blood flow (2P = .001). It is concluded that, although overall vasodilation occurs normally in diabetic cutaneous circulation, the mechanism is different from the normal response in that flow increases by augmentation of capillary flow rather than by recruitment. This is consistent with the thesis promulgated by others that diabetic precapillary vessels have depressed vasodilatory responses or are already maximally vasodilated. The ability of diabetic subjects to vasodilate by augmentation was not correlated with years of diabetes or use of insulin and only slightly negatively correlated with random blood glucose levels (r = −.423, P < .05)
Does Galactose Feeding Provide a Valid Model of Consequences of Exaggerated Polyol-Pathway Flux in Peripheral Nerve in Experimental Diabetes?
Authors: Willars Gary B , Lambourne Julie E , Tomlinson David R
Published: September 2013

This study was designed to examine the effect of exaggerated polyol-pathway flux on sciatic nerve content of polyols, myo-inositol, and water. Rats with streptozocin-induced diabetes of 3- and 12-wk duration and nondiabetic rats fed for 5 days on a diet containing 20% galactose were employed initially. All three conditions showed marked elevation of nerve polyol content, combined with fructose accumulation in the diabetic rats. Galactose-fed rats showed a significant (P < .01) increase in nerve water content of ∼30% (when expressed as water/unit dry wt tissue). Diabetic rats showed no change in nerve water. Both diabetic and galactose-fed rats showed a depletion of nerve free myo-inositol, although the extent of depletion was greater in the latter. All these changes were prevented or attenuated by the aldose reductase inhibitor Statil (IC1128436). When diabetic rats were fed a 20% galactose diet for 5 days, nerves of 3- but not 12-wk diabetic rats showed marked increases in water content. A more mild degree of galactosemia, induced by 5 or 21 days of feeding a diet containing 10% galactose to nondiabetic rats, provoked an increase in nerve water content associated with polyol levels of a similar order to those seen in diabetes. We do not know why polyol-pathway metabolites cause nerve hyperhydration in galactosemia but not in streptozocin-induced diabetes. Such differences urge caution in the use of galactose feeding to model the consequences of exaggerated polyol-pathway flux in nerve to face questions related to neuronal dysfunction in diabetes.
Insulin Response in Individual Tissues of Control and Gold Thioglucose-Obese Mice In Vivo With [1-14C]2-Deoxyglucose
Authors: Cooney Gregory J , Astbury Lyn D , Williams Paul F , Caterson Ian D
Published: September 2013

The dose-response characteristics of several glucoseutilizing tissues (brain, heart, white adipose tissue, brown adipose tissue, and quadriceps muscle) to a single injection of insulin have been compared in control mice and mice made obese with a single injection of gold thioglucose (GTG). Tissue content of [1−14C]2-deoxyglucose 6-phosphate and blood disappearance rate of [1−14C]2-deoxyglucose (2-DG) were measured at nine different insulin doses and used to calculate ratesof 2-DG uptake and phosphorylation in tissues from control and obese mice. The insulin sensitivity of tissues reflected in the ED50 of insulin response varied widely, and brown adipose tissue was the most insulin-sensitive tissue studied. In GTG-obese mice, heart, quadriceps, and brown adipose tissue were insulin resistant (demonstrated by increased ED50), whereas in white adipose tissue, 2-DG phosphorylation was more sensitive to insulin. Brain 2-DG phosphorylation was insulin independent in control and obese animals. The largest decrease in insulin sensitivity in GTG-obese mice was observed in brown adipose tissue. The loss of diet-induced thermogenesis in brown adipose tissue as a result of the hypothalamiclesion in GTG-obese mice could be a major cause of insulin resistance in brown adipose tissue. Because brown adipose tissue can make a major contribution to whole-body glucose utilization, insulin resistance in this tissue may have a significant effect on whole-animal glucose homeostasis in GTG-obese mice.
Opposite Effects of D-Glucose and a Nonmetabolized Analogue of L-Leucine on Respiration and Secretion in Insulin-Producing Tumoral Cells (RINm5F)
Authors: Sener Abdullah , Leclercq-Meyer Viviane , Giroix Marie-Helene , Malaisse Willy J , Hellerström Claes
Published: September 2013

D-Glucose increased the cytosolic NADH%/NAD+ ratio (but not the cytosolic NADPH/NADP+ ratio), augmented O2 uptake, raised the ATP/ADP ratio, decreased 86Rb outflow, and stimulated insulin release in tumoral insulin-producing cells of the RINm5Fline, L-Leucine and 4-methyl-2-oxopentanoate also stimulated insulin secretion. In the RINm5F cells, as in normal islet cells, the nonmetabolized analogue of L-leucine, 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH), activated glutamate dehydrogenase, augmented L-[U−14C]glutamine oxidation, and induced a more reduced state of cytosolic redox couples. However, in sharp contrast to either its effect in normal islet cells or that of D-glucose in the tumoral cells, BCH severely decreased O2 uptake, lowered the ATP/ADP ratio, increased 86Rb outflow, and inhibited insulin release in the RINm5F cells. These findings are interpreted to support the concept that the rate of ATP generation represents an essential determinant of the secretory response of insulin-producing cells to nutrient secretagogues.
Declining Incidence of Persistent Proteinuria in Type I (Insulin-Dependent) Diabetic Patients in Denmark
Authors: Kofoed-Enevoldsen A , Borch-Johnsen K , Kreiner S , Nerup J , Deckert T
Published: September 2013

The decreasing relative mortality among type I (insulin-dependent) diabetic patients during the last 50 years might be related to the incidence of clinical diabetic nephropathy. We therefore followed 2890 type I diabetic patients (1607 males and 1283 females) diagnosed between 1933 and 1972 and before the age of 31, from admission to death, emigration, or January 1, 1984. All patients had been admitted to the Steno Memorial Hospital. Information on development of proteinuria was obtained in 2658 patients (92%). Five hundred twenty-five patients developed proteinuria due to diabetes and 49 developed nondiabetic proteinuria. When comparing patients diagnosed between 1933 and 1942 with those diagnosed between 1953 and 1962, the incidence of proteinuria decreased by 30% (P < .03). This might explain the decrease of relative mortality in type I diabetic patients. The incidence decreased with increasing age at onset but was always highest in males. Insulin dose (U/kg) and diabetes duration at admission did not influence the incidence of proteinuria. The incidence peaked after 15-17 yr of diabetes duration independent of sex, age at diagnosis, or calendar year of diagnosis. However, the majority of patients did not develop proteinuria during 40 yr of diabetes. This suggests individual renal susceptibility to the deleterious effect of hyperglycemia.
Major Histocompatibility Complex Restriction of T-Lymphocyte Responses to Islet Cell Antigens in IDDM Rats
Authors: Prud'Homme Gérald J , Colle Eleanor , Fuks Abraham , Guttmann Ronald D
Published: September 2013

BBUF rats, derived from BB rats, spontaneously develop a form of insulin-dependent diabetes mellitus (IDDM) associated with infiltration of the islets of Langerhans by lymphocytes (insulitis). BBUF rats bear the RT1U major histocompatibility complex (MHC) haplotype that we have shown to be necessary for the expression of this form of IDDM. A T-lymphocyte line obtained from the pancreas of a diabetic rat (UPCC.5) and three T-lymphocyte hybridomas derived by fusing T-lymphocytes of BBUF rats (MUS1.2, MUS1.13, and MUP3.21) respond to islet cell antigens in an MHC-restricted way. UPCC.5 responds to a combination of islet cell antigens (ICAg) and antigen-presenting cells by proliferation, whereas the T-hybridoma responses are detected on the basisof IL-2 production in a similar assay. This study reveals that an antiserum against μhaplotype MHC antigens or a monoclonal antibody against the product of the D class II subregion of the rat MHC could inhibit ICAg recognition. A monoclonal antibody against the product of the B class II MHC subregion of the rat was not inhibitory. These results suggest that RT1.D antigens (analogous to human DR and mouse I-E) restrict islet cell recognition in this rat model of spontaneous IDDM.
Antibodies to Insulin Receptor Followed by Anti-Idiotype: Antibodies to Insulin in Child With Hypoglycemia
Authors: Elias Dana , Cohen Irun R , Shechter Yoram , Spirer Zvi , Golander Avraham
Published: September 2013

A child presenting severe hypoglycemia despite low or normal secretion of insulin was found to have IgM antibodies to the insulin receptor. These antibodies stimulated lipogenesis in fat cells in vitro and competed with insulin for binding to insulin receptors. After treatment with glucocorticoids, the anti-receptor antibodies and the hypoglycemia both disappeared, and antibodies to insulin appeared in the patient's serum. The anti-insulin antibodies were isolated by affinity chromatography and were found to inhibit the antiinsulin- receptor antibodies that were present earlier. The interaction between the patient's anti-insulin antibodies and his anti-receptor antibodies suggests that these two species of antibodies are related as idiotypes and anti-idiotypes. We also studied the interaction of the hypoglycemic patient's anti-receptor antibodies with anti-insulin antibodies of a diabetic patient and with anti-insulin antibodies of mice immunized to insulin. The hypoglycemic patient's antireceptor antibodies were neutralized by the diabetic patient's anti-insulin antibodies, indicating that antiinsulin antibodies with a common idiotype may arise in both diabetes and hypoglycemia. Moreover, mouse anti-insulin antibodies that interacted with mouse antireceptor antibodies neutralized the hypoglycemic patient's anti-receptor antibodies. In contrast, mouse anti-insulin antibodies that did not interact with the mouse anti-receptor antibodies did not neutralize the hypoglycemic patient's anti-receptor antibodies. Thus, the human anti-insulin antibodies share an idiotype with a specific class of mouse anti-insulin antibodies. These findings lead to three conclusions: 7) hypoglycemia of young children can be associated with anti-insulin-receptor antibodies, 2) the anti-idiotypic network may operate in humans to generate autoantibodies to a hormone, and 3) mice and humans can generate networks with common idiotypes.
Morphologic and Functional Changes in Sympathetic Nerve Relationships With Pancreatic α-Cells After Destruction of β-Cells in Rats
Authors: Tominaga Makato , Maruyama Hiroshi , Vasko M R , Baetens Dany , Orci Lelio , Unger Roger H
Published: September 2013

Insulin-dependent diabetes mellitus (IDDM) in humans is accompanied by an attenuation of the response of glucagon to hypoglycemia. To identify an animal model of IDDM with α-cell unresponsiveness to glucopenia in which to pursue morphologic and in vitro functional investigation of the lesion, pancreases isolated from rats with IDDM induced by streptozocin (STZ) or occurring spontaneously in BB/W rats were perfused with buffer containing 150, 25, and 150 mg/dl of glucose. In both forms of IDDM the normal glucagon rise during glucopenia was markedly impaired, suggesting an abnormality comparable to that of human IDDM. Studies of the insular sympathetic apparatus were conducted in these rat models. Electron-microscopic examination of peri-insular nerve endings disclosed no discernible abnormality in either form of rat IDDM. However, morphometric analysis of contacts between [3H]norepinephrine-labeled sympathetic nerve terminals and a-cells in pancreases from STZ-induced diabetic (STZ-D) rats revealed a 65-70% reduction in direct contacts. An 80% reduction in the number of nerve endings (not labeled) in direct contact with αcells was also noted in the BB/W diabetic rats. Norepinephrine reuptake, studied only in the STZ-D group, was not impaired. The availability of local endogenous norepinephrine to α-cells and their sensitivity to exogenous norepinephrine was determined by perfusing 2, 5, or 10 μg/ml of tyramine, a releaser of endogenous norepinephrine, and norepinephrine at a concentration that in pancreases from nondiabetic rats gave a quantitatively similar glucagon response. In STZ-D pancreases, the glucagon response to 10 μg/ml of tyramine was only 11.5% of normal, whereas the response to an equipotent concentration of norepinephrine (0.1 μM) was 55% of normal. These results are consistent with a reduction in both sensitivity to and availability of norepinephrine. The glucagon response of pancreases from BB/W diabetic rats to 10 μg/ml tyramine was 29% of normal, but this was not significantly less than the observed response to a comparable norepinephrine concentration. Consequently, in this group, reduced α-cell sensitivity to norepinephrine alone could have accounted for the reduced response to tyramine. The results suggest that 1) the sympathetic nerve endings are electron-microscopically intact in both spontaneous and insulin-dependent STZ-D rats; 2) there are fewer direct contacts between sympathetic nerve terminals and α-cells in both forms of diabetes; 3) sensitivity of α-cells to perfused norepinephrine is reduced in isolated pancreases of both spontaneously diabetic and STZ-D rats in proportion to reduction in baseline glucagon secretion; and 4) in the STZ-D group, but not in the BB/W diabetic group, there was evidence of reduced availability of locally released norepinephrine based on an α-cell response well below that of an equipotent norepinephrine concentration.
Similar Dose Responsiveness of Hepatic Glycogenolysis and Gluconeogenesis to Glucagon In Vivo
Authors: Stevenson Ralph W , Steiner Kurt E , Davis M A , Hendrick G K , Williams P E , Lacy William W , Brown L , Donahue P , Lacy D B , Cherrington Alan D
Published: September 2013

This study was undertaken to determine whether the dose-dependent effect of glucagon on gluconeogenesis parallels its effect on hepatic glycogenolysis in conscious overnight-fasted dogs. Endogenous insulin and glucagon secretion were inhibited by somatostatin (0.8 μg · kg−1 · min−1), and intraportal replacement infusions of insulin (213 ± 28 (αU kg−1 · min−1) and glucagon (0.65 ng · kg−1 · min−1) were given to maintain basal hormone concentrations for 2 h (12 ± 2 and 108 ± 23 pg/ml, respectively). The glucagon infusion was then increased 2-, 4-, 8-, or 12-fold for 3 h, whereas the rate of insulin infusion was left unchanged. Glucose production (GP) was determined with 3-[3H]glucose, and gluconeogenesis (GNG) was assessed with tracer (U-[14C]alanine conversion to [14C]glucose) and arteriovenous difference (hepatic fractional extraction of alanine, FEA) techniques. Increases in plasma glucagon of 53 ± 8, 199 ± 48, 402 ± 28, and 697 ±149 pg/ml resulted in initial (15- 30 min) increases in GP of 1.1 ± 0.4 (N = 4), 4.9 ± 0.5 (N = 4), 6.5 ± 0.6 (N = 6), and 7.7 ± 1.4 (N = 4) mg kg−1 · min−1, respectively; increases in GNG (∼3 h) of 48 ± 19, 151 ± 50, 161 ± 25, and 157 ± 7%, respectively; and increases in FEA (3 h) of 0.14 ± 0.07, 0.37 ± 0.05, 0.42 ± 0.04, and 0.40 ± 0.17, respectively. In conclusion, GNG and glycogenolysis were similarly sensitive to stimulation by glucagon in vivo, and the dose-response curves were markedly parallel.
Enhanced Peripheral and Splanchnic Insulin Sensitivity in NIDDM Men After Single Bout of Exercise
Authors: Devlin John T , Hirshman Michael , Horton Elizabeth D , Horton Edward S
Published: September 2013

We studied glucose metabolism in non-insulin-dependent diabetic (NIDDM) men with and without glycogendepleting cycle exercise 12 h beforehand and have compared the results to our previous data in lean and obese subjects. Rates of total glucose utilization, glucose oxidation, nonoxidative glucose disposal (NOGD), glucose metabolic clearance rate (MCR), and endogenous glucose production (EGP) were determined with a “two-level” insulin-clamp technique (100-min infusions at 40 and 400 mU · m−2 · min−1) combined with indirect calorimetry and D-3-[3H]glucose infusion. Muscle biopsy specimens from vastus lateralis were analyzed for glycogen content and glycogen synthase activity before and after insulin infusions.

After exercise, NIDDM subjects had muscle glycogen concentrations comparable with those of lean and obese subjects. The activation of glycogen synthase both by prior exercise and insulin infusion was similar to lean controls. After exercise, total glucose disposal was significantly increased during the 40-mU · m−2 · min−1 infusion (P < .05), but the increase observed during the 400-mU · m−2 · min−1 infusion was not significant. These increases after exercise were the result of significantly higher NOGD duringboth levels of insulin infusion. The MCR of glucose during both insulin infusions was reduced in NIDDM compared with lean subjects but was very similar to that in obese nondiabetics. Basal EGP was significantly reduced on the morning after exercise (4.03 ± 0.27 vs. 3.21 ± 0.21 mg · kg−1 fat-free mass · min−1) (P < .05) and associated with significant reductions of fasting plasma glucose (197 ± 12 vs. 164 ± 9 mg/dl). Suppression of EGP by the 40-mU · m−2 · min−1 infusion was also greater on the morning after exercise (54 vs. 90% of basal) (P < .05).

This study demonstrates that a single bout of glycogen-depleting exercise significantly increases periph-eral and splanchnic insulin sensitivity 12–16 h later in NIDDM men. Increased peripheral glucose utilization after exercise is the result of increased NOGD, presumably reflecting increased glucose storage as glycogen. Insulin-stimulated rates of glucose oxidation are decreased after exercise. The lower fasting glucose concentration after exercise is due to decreased EGP rather than increased glucose utilization.
Greater Efficacy of Pulsatile Insulin in Type I Diabetics Critically Depends on Plasma Glucagon Levels
Authors: Paolisso Giuseppe , Sgambato Saverio , Passariello Nicola , Scheen André , D'Onofrio Felice , Lefébvre Pierre J
Published: September 2013

The aim of this study was to investigate the role of plasma glucagon levels on the blood glucose response to intravenous insulin administered continuously or in a pulsatile manner. Six type I diabetic patients proven to have no residual insulin secretion were investigated. Endogenous glucagon secretion was inhibited by a continuous intravenous infusion of somatostatin (100 μg/h) and replaced by exogenous infusions of the hormone at three different rates (7.5, 4.5, and 2.5 μg/h), resulting in three different plasma glucagon steady-state levels (i.e., ≃200, ≃130, and ≃75 pg/ml, respectively). Each subject, in random order and on different days, was infused intravenously with regular human insulin either continuously (0.17 mU · kg−1 · min−1) or with the same amount of insulin infused in a pulsatile manner (0.85 mU · kg−1 · min−1 during 2 min followed by 8 min during which no insulin was infused). At plasma glucagon levels ≃200 pg/ml, blood glucose rose from ∼10 to ∼13 mM without any difference between the two modalities of insulin infusion. For plasma glucagon levels ≃130 pg/ml, plasma glucose remained steady throughout the experiments, but during the last 40 min, plasma glucose levels were significantly lower when insulin was administered intermittently. This greater blood glucose-lowering effect of pulsatile insulin occurred earlier and was more pronounced for plasma glucagon levels averaging 75 pg/ml. We conclude that the greater hypoglycemic effect of insulin administered intravenously in a pulsatile manner in type I diabetics critically depends on plasma glucagon circulating levels.
Progress Toward Standardization of Cytoplasmic Islet Cell–Antibody Assay
Authors: Gleichmann Helga , Bottazzo Gian Franco
Published: September 2013

Cytoplasmic islet cell autoantibodies (ICAs) of 13 coded sera were determined by 26 laboratories. ICAs were determined by 24 laboratories according to a standard protocol based on the conventional indirectimmunofluorescence technique on cryostat sections of human pancreas. In addition, these 24 laboratories had performed any of 8 modifications of the assay. Test samples were titrated to end point, and the results obtained with the different methods were compared with those obtained by the standard protocol. The remaining 2 laboratories used either exclusively pancreatic sections of monkey instead of human as substrate (lab 23) or applied immunohistochemical staining (lab 22).

By following the standard protocol, interlaboratory concordance was >90% for the presence or absence of islet cell antibodies in 7 of the 13 samples circulated. However, a wide variability of titers was recorded, ranging from negative to 128.

Of the modifications, prolonged incubation in the presence of aprotinin was performed by 10 laboratories and was found to improve the sensitivity in 57 of 70 (81%) determinations with samples that had been ICA positive by the standard protocol. Improved sensitivity was also noted by 2 laboratories with sections of monkey pancreas. Acetone-fixed sections, used by 6 laboratories, or a two-color immunofluorescence method, applied by 3 laboratories, did not change the titers in 27 of 35 (77%) and 14 of 25 (56%) determinations with samples that had been ICA positive by the standard protocol. In contrast, heat inactivation of the samples before testing, performed by 5 laboratories, resulted in a decrease in titers in 25 of 39 (64%) determinations. Four laboratories used fluorescein-labeled protein A as reagent and observed a decrease in ICA titers in 22 of 27 (81%) determinations. Complement-fixing antibodies were determined by 20 laboratories and were present in 66 of 136 (48%) determinations with ICA-positive samples, and in general, they were associated with high titers of the latter. Three laboratories reported results obtained by immunohistochemical staining with glucose oxidase, and at this stage, the data indicated the requirement of both method improvement and exchange of reference reagents for interlaboratory comparison.
Pancreatic Somatostatin is a Mediator of Glucagon Inhibition by Hyperglycemia
Authors: Klaff Leslie J , Taborsky Gerald J
Published: September 2013

We have previously shown that a nonimmunoreactive analogue of somatostatin, (D-Ala5, D-Trp8)-somatostatin, differentially inhibits pancreatic somatostatin secretion without inhibiting insulin or glucagon secretion. During normoglycemia, suppression of pancreatic somatostatin with this analogue increases glucagon and insulin secretion, suggesting that pancreatic somatostatin tonically inhibits glucagon and insulin secretion by a paracrine mechanism. In our study, we used this analogue to determine whether endogenous pancreatic somatostatin has a role in the inhibition of glucagon secretion by hyperglycemia. The experiments were performed in pentobarbital-anesthetized, laparotomized dogs. To measure the pancreatic output of somatostatin directly, pancreatic venous blood was sampled from the right lobe of the dog pancreas, and the pancreatic blood flow was measured. In the first set of experiments, glucagon secretion was suppressed by a glucose infusion (200 mg/kg bolus and 20 mg · kg−1 · min−1 i.v.) for 3 h. Plasma glucose rose from 102 ± 6 to 365 ± 34 mg/dl. Pancreatic insulin output increased 10-fold, pancreatic somatostatin output increased from 1.2 ± 0.3 to 3.0 ± 0.8 ng/min, and pancreatic glucagon output was suppressed from 1.4 ± 0.7 to 0.5 ± 0.1 ng/min. After 2 h of gtucose infusion, an infusion of the analogue (5.5 μg/min i.v.) reversed both the stimulation of somatostatin and the suppression of glucagon without significantly changing either the plasma glucose level or the pancreatic insulin output. In a second set of experiments, basal somatostatin output was suppressed by the analogue (5.5 μg/min i.v.) for 15 min before the administration of glucose. Pancreatic somatostatin output decreased from 2.6 ± 0.4 to 1.6 ± 0.3 ng/min, and pancreatic glucagon output rose from 1.2 ± 0.6 to 2.9 ± 0.9 ng/min. Glucose was then infused (200 mg/kg bolus and 20 mg · kg−1 · min−1 i.v.) in combination with the analogue. In response to glucose, somatostatin output rose, and glucagon output was suppressed back toward the original basal levels. Thus, in both sets of experiments, a reciprocal relationship between somatostatin and glucagon secretion was demonstrated regardless of whether the plasma glucose and insulin output changed. These data provide evidence that pancreatic somatostatin is a mediator of the suppression of glucagon during hyperglycemia.
Advanced Diabetic Glomerulopathy: Quantitative Structural Characterization of Nonoccluded Glomeruli
Authors: Østerby Ruth , Gundersen Hans Jørgen G , Nyberg Gudrun , Aurell Mattias
Published: September 2013

Quantitative ultrastructural data were obtained from kidney biopsy material of 12 long-term insulindependent diabetics. All patients had overt diabetic nephropathy with increased urinary albumin excretion and reduced glomerular filtration rate. Renal clearance of 51Cr-EDTA was in the range of 16-50 ml · min−1 · 1.73 m−2. All patients received antihypertensive treatment.

A combined light- and electron-microscope study was performed. A significant proportion of the glomeruli was totally occluded (mean 36%, range 24-67%). Structural data presented relate only to the open, still-functioning glomeruli. Comparison with data previously obtained showed that 1) the thickness of the peripheral basement membrane [647 nm, coefficient of variation (C.V.) 0.22] was more than twice the normal value (310 nm, C.V. 0.08); 2) the width of epithelial foot processes (352 nm, C.V. 0.07) was significantly greater than in normal biopsies (224 nm, C.V. 0.06); and 3) the mean volume of the open glomeruli was markedly increased compared with normal and clearly exceeded that in the early diabetic hypertrophy. Total mesangial volume and total basement membrane material per open glomerulus were increased by 277 and 614%, respectively. However, capillary length and surface per open glomerulus were similar to those observed in early diabetic hypertrophy. These findings suggest that a late glomerular hypertrophy with preservation of capillary surface occurs as a compensatory phenomenon, prolonging renal survival for diabetic nephropathy patients.
Islet Cytotoxicity of Interleukin 1: Influence of Culture Conditions and Islet Donor Characteristics
Authors: Mandrup-Poulsen Thomas , Spinas Giatgen A , Prowse Stephen J , Hansen Birgit S , Jørgensen Dorte W , Bendtzen Klaus , Nielsen Jens Høiriis , Nerup Jørn
Published: September 2013

We recently demonstrated that the macrophage product interleukin 1 (IL-1) is cytotoxic to isolated pancreatic islets and hypothesized that IL-1 is responsible for β-cell destruction in insulin-dependent diabetes mellitus (IDDM). We studied whether the variation in IDDM preponderance with age, sex, and genetic background in vivo is reflected in different susceptibility to IL-1 toxicity of islets in vitro. In addition, we studied the effect of preculture conditions that support endocrine islet cell function and decrease nonendocrine passenger-cell survival on the susceptibility of β-cells to IL-1 because it is unknown whether IL-1 acts directly on β-cells or via passenger cells.

No differences in susceptibility to various doses of IL-1-containing mononuclear cell supernatants were found between islets isolated from newborn or adult rats, male or female rats, or rats of four inbred strains, indicating that age, sex, and genetic background do not influence the susceptibility of the β-cell to IL-1. Preculture of islets for 1-7 days in normal atmosphere and preculture of islet clusters in 95% O2 to delete passenger cells did not affect IL-1-mediated cytotoxicity, suggesting that IL-1 acts directly on β-cells. Increasing the glucose concentration (22 mM) in the culture medium, which is known to protect β-cells against alloxan toxicity, reduced IL-1 toxicity. Five or 25% normal human serum as well as 5% normal rat serum, but not equivalent concentrations of human serum albumin, inhibited IL-1 toxicity, indicating the presence of IL-1 inhibitors, IL-1 antagonists, or β-cell-protecting factors in normal serum. The inhibitory action of serum could be counteracted by increasing the dose of IL-1.
Reduction and Recovery of Plasma 1,5-Anhydro-D-Glucitol Level in Diabetes Mellitus
Authors: Yamanouchi Toshikazu , Akanuma Hiroshi , Asano Tomoichiro , Konishi Chieko , Akaoka Ieo , Akanuma Yasuo
Published: September 2013

The plasma concentration of 1,5-anhydro-D-glucitol (AG) was measured in 135 newly diagnosed patients who were referred for oral glucose tolerance tests. AG concentrations in the nondiabetic patients indicated that the mean value of normal AG concentration was 21.8 μg/ml (SD = 5.9 μg/ml, range 9.6–38.8 μg/ml). This distribution of AG concentration was significantly different from that in patients with impaired glucose tolerance (IGT) (13.3 ± 5.4 μg/ml) and definitely different from that in diabetic patients (2.1 ± 1 . 8 μg/ml). In a standard glucagon test, it was suggested that the decrease of plasma AG was affected not only by glycemic control of the patients but also by pancreatic cell secretory activity. The reduction of AG concentration was more marked in IDDM patients than in NIDDM patients. In longitudinal studies, AG concentration was shown to be sensitive to glycemic control. However, its recovery showed a tendency toward much delay after the improvement of fasting blood glucose or HbA, concentrations. On the other hand, AG concentration showed negligible diurnal change and no immediate change as a result of diet, oral glucose load, or acute shift of the insulin level in both normal and diabetic subjects.
Multiple Aspects of Insulin Resistance: Comparison of Glucose and Intermediary Metabolite Response to Incremental Insulin Infusion in IDDM Subjects of Short and Long Duration
Authors: Singh Baldev M , Palma Marion A , Nattrass Malcolm
Published: September 2013

Glucose and intermediary metabolite responses during incremental insulin infusion (basal, 0.005, 0.01, and 0.05 U · kg−1 · h−1) were examined in IDDM subjects with duration of diabetes of >5 yr (group D5: n = 8, duration 13.5 ± 3.9 yr, mean ± SD) and <1 yr (group D1: n = 8, duration 0.3 ± 0.1 yr) from diagnosis.

Group D5 had significantly elevated basal plasma free-insulin levels (D5 27.4 ± 9.6, D1 15.5 ± 9.4 mU/L; P < .05). Nonetheless, basal blood glucose (D5 13.8 ± 4.8, D1 7.1 ± 1.5 mM; P < .01), plasma nonesterified fatty acid (NEFA) (D5 1.26 ± 0.12, D1 0.89 ± 0.10 mM; P < .01), blood glycerol (D5 0.12 ± 0.05, D1 0.07 ± 0.02 mM; P < .05), and blood ketones (D5 1.25 ± 0.91, D1 0.26 ± 0.20 mM; P < .01) were higher in group D5.

During insulin infusion, group D5 had significantly elevated plasma free-insulin (P < .05) and blood glucose (P < .01) levels. Isotopically determined glucose turnover showed metabolic clearance rates were significantly diminished in group D5 during all insulin infusions, indicating a marked impairment of peripheral glucose metabolism.

In individual subjects the relationship of blood glucose, plasma NEFA, and blood total ketones (log scale) with the simultaneously occurring plasma insulin level (log scale) was linear for each metabolite. At an insulin concentration of 30 mU/L, group D5 had elevated blood glucose (D5 12.4 ± 3.1, D1 4.5 ± 1.0 mM; P < .001), plasma NEFA (D5 0.93 ± 0.26, D1 0.54 ± 0.24 mM; P < .01), and ketone (D5 0.97 ± 0.81, D1 0.07 ± 0.03 mM; P < .02) levels.

The results demonstrate insulin resistance in lipolysis, peripheral glucose metabolism, and possibly hepatic glucose metabolism in long-duration compared with short-duration IDDM.
Treatment With Anti-T-Lymphocyte Antibodies Prevents Induction of Insulitis in Mice Given Multiple Doses of Streptozocin
Authors: Herold Kevan C , Montag Anthony G , Fitch Frank W
Published: September 2013

The importance of T-lymphocytes in the induction of insulitis and hyperglycemia in certain strains of mice treated with multiple subdiabetogenic doses of streptozocin has been a matter of controversy. To understand the role of T-lymphocytes, we treated thymectomized BALB/c ByJ mice with five daily doses of streptozocin (45 mg/kg) and determined the effect of treatment with monoclonal antibodies against T-lymphocyte subsets on the development of diabetes and insulitis. Hyperglycemia (mean glucose of 321 ± 29 vs. 167 ± 15 mg/dl in controls) and insulitis were induced in BALB/c ByJ mice given streptozocin. Thy1.2+, L3T4+, and Lyt2+ cells were all identified within the islets of diabetic mice. There was a relative paucity of L3T4+ cells and an overabundance of Lyt2+ cells compared with the frequency of these cells found in lymphatic tissues or peripheral blood. Treatment with anti-L3T4 or anti-Lyt2 monoclonal antibodies caused a reduction in splenic T-lymphocyte subsets and attenuated the hyperglycemia to 212 ± 14 and 197 ± 16 mg/dl (P < .001 and .01), respectively, compared with controls and prevented the insulitis induced by streptozocin. Our studies support the hypothesis that an immune response is important to the development of multi–low-dose streptozocin diabetes and indicate that treatment with monoclonal antibodies against the L3T4+ or Lyt2+ T-lymphocyte subsets can attenuate this process.
α-Adrenergic Blockade Improves Glucose-Potentiated Insulin Secretion in Non-Insulin-Dependent Diabetes Mellitus
Authors: Broadstone Vasti L , Pfeifer Michael A , Bajaj Vina , Stagner John I , Samols Ellis
Published: September 2013

The impairment of glucose-potentiated insulin secretion present in non-insulin-dependent diabetes mel I it us (NIDDM) can be approximated in normal subjects by an epinephrine infusion. Therefore, we sought to determine the role of the endogenous sympathetic nervous system in glucose-potentiated insulin secretion in both NIDDM (n = 6) and normal (n = 6) subjects. Glucose-potentiated insulin secretion was calculated as the slope of the curve relating increasing ambient glucose levels to the acute insulin response to an intravenous pulse of 5 g of L-arginine. Glucose-potentiated insulin secretion was determined on separate days during α-, β-, and combined α- plus β-adrenergic blockade and compared with a saline control. In. normal subjects, there was no effect of α-, β-, or α- plus β-blockade on the slope of glucose potentiation. In NIDDM, the initially decreased slope of glucose potentiation (0.25 ± 0.06 μU · ml−1 · mg−1 · dl, mean ± SE; P < .01) was not affected by β-blockade but increased during α-blockade (0.91 ± 0.22 μU · ml−1 · mg−1 · dl; P < .05). However, this improvement was abolished by combined α- plus β-blockade (0.32 ± 0.07 μU · ml−1 · mg−1 dl). Plasma norepinephrine was increased above basal levels in both normal (+ 260 ± 89 pg/ml) and NIDDM (+ 438 ± 162 pg/ml) subjects during α-blockade (P < .05 for both). This increase in plasma norepinephrine strongly suggests that there is an increase in synaptic cleft norepinephrine concentration. These results suggest that the increase in glucose-potentiated insulin secretion during α-adrenergic blockade was a result of both a decrease in an endogenous overactive α-adrenergic stimulation and an increase in synaptic cleft norepinephrine levels, which resulted in an increase in islet β-adrenergic stimulation. We suggest that a chronic decrease in islet α-adrenergic stimulation may prove to be a useful adjunct to NIDDM management.
Comparison of Measurement Methods for Capillary Basement Membrane Thickness: Collapsed-Ellipse Technique
Authors: Katz Murray A , Beggs John L , Johnson Peter C
Published: September 2013

Both the grid method of Siperstein et al. (tSIP) and the minimum-points method of Williamson et al. (tWIL) for measurement of capillary basement membrane thickness are inaccurate for assessing mean true membrane thickness of a given section (tTRUE) for various reasons, including errors in selectivity, sensitivity, and geometry. In general, it is agreed that tSIP > tTRUE > tWIL, but estimates of tTRUE beyond this have not been made. In this study, a collapsed-ellipse method for approximating tTRUE is presented that measures thickness by areas (tEA). One hundred-twenty capillaries from the forearm skin of 12 diabetic subjects and 12 age-matched controls were measured to examine these concepts. We found that, whereas tWIL was up to 63% below tTRUE, tEA was 30% too low. Although tSIP, tWIL, and tEA did not distinguish between diabetic and normal subjects, tEA and tWIL measurements had highly predictable and small errors, and tSIP had unpredictable ranges of error, especially when tSIP was low.