bluuebunny/crossref_metadata_2025 huggingface dataset:
Reverse Hemolytic Plaque Assay Study of Luteinizing and Follicle-Stimulating Hormone and Thyrotropin Secretion in Diabetic Rat Pituitary Glands
Authors: Rossi Giovanni L , Bestetti Gilberto E , Tontis Dimitrios K , Varini Martine
Published: September 2013

Numerous studies indicate that an impaired hypothalamopituitary axis plays an important role in reproductive and thyroid disorders in diabetic humans and animal models. Yet, several questions about the pathogenesis of these diabetic complications have not been answered. To evaluate the basal secretion of single gonadotrophs and thyrotrophs in vitro, uncultured pituitary cells from control rats and 1-mo streptozocin-induced diabetic (STZ-D) rats were studied with a reverse hemolytic plaque assay and morphometry. After light-microscopy immunocytochemistry for gonadotropin and thyrotropin (TSH), we recorded the ratio of plaqueforming to non—plaque-forming cells. The area of plaques produced by luteinizing hormone (LH), folliclestimulating hormone (FSH), and TSH cells and the area of plaque-forming and non—plaque-forming cells were clearly smaller in diabetic than control rats. The plaque area, however, was more severely reduced than the cell area. The percentage of LH-, FSH-, and TSHimmunoreactive plaque-forming cells was greatly decreased in diabetic compared with control animals. In conclusion, our findings demonstrate that the LH-, FSH-, and TSH-secreting cells of diabetic rats released less hormone and were less numerous than the corresponding cells of control rats. Thus, several pathogenetic mechanisms might be involved in reduced gonadotropin and TSH release at the cellular level: 1) anatomical lesions of organelles involved in glycoprotein hormone synthesis and secretion, possibly due to insulin deficiency; 2) decreased gonadotropin-releasing hormone (GnRH) and thyrotropin-releasing hormone (TRH) receptors on pituitary cells; 3) inadequate GnRH and TRH stimulation; 4) high plasma corticosterone levels; or 5) a combination of points 1–4.
Effects of Fish Oil Supplementation on Glucose and Lipid Metabolism in NIDDM
Authors: Borkman Mark , Chisholm Donald J , Furler Stuart M , Storlien Leonard H , Kraegen Edward W , Simons Leon A , Chesterman Colin N
Published: September 2013

Fish oils, containing omega-3 fatty acids (ω3FAs), favorably influence plasma lipoproteins in nondiabetic humans and prevent the development of insulin resistance induced by fat feeding in rats. We studied the effects of fish oils in 10 subjects (aged 42–65 yr) with mild non-insulin-dependent diabetes mellitus (NIDDM). Subjects were fed a standard diabetic diet plus 1) no supplementation (baseline), 2) 10 g fish oil concentrate (30% ω3FAs) daily, and 3) 10 g safflower oil daily over separate 3-wk periods, the latter two supplements being given in radom order by use of a double-blind crossover design. At the end of each diet period, fasting blood glucose (FBG), insulin, and lipids were measured, and insulin sensitivity was assessed with a hyperinsulinemic-euglycemic clamp performed with [3-3H]glucose. FBG increased 14% during fish oil and 11% during safflower oil supplementation compared with baseline (P < .05), whereas body weight, fasting serum insulin levels, and insulin sensitivity were unchanged. The absolute increase in FBG during each supplementation period correlated with the baseline FBG (fish oil, r = .83, P < .005; safflower oil, r = .75, P = .012). Fasting plasma triglyceride levels decreased during fish oil supplementation in the 4 subjects with baseline hypertriglyceridemia (>2 mM) but were not significantly reduced overall. There was no significant change in fasting plasma total, high-density lipoprotein, and low-density lipoprotein cholesterol levels. In summary, dietary fish oil supplementation adversely affected glycemic control in NIDDM subjects without producing significant beneficial effects on plasma lipids. The effect of safflower oil supplementation was not significantly different from fish oil, suggesting that the negative effects on glucose metabolism may be related to the extra energy or fat intake. These data indicate that fish oil supplementation should be used with caution in subjects with NIDDM.
Postreceptor Effects of Sulfonylurea on Skeletal Muscle Glycogen Synthase Activity in Type II Diabetic Patients
Authors: Friis Jens , Schmitz Ole , Sørensen Niels Schwartz , Pedersen Oluf
Published: September 2013

To elucidate the subcellular mechanism of action of sulfonylurea on glucose utilization of skeletal muscle, we studied nine newly diagnosed patients with type II (non-insulin-dependent) diabetes. Examinations were performed before and after 8 wk of gliclazide therapy. Gliclazide treatment was associated with improved glycemie control and enhanced pancreatic β-cell responses to meal stimulation. During euglycemic insulin clamps, insulin-inhibited endogenous glucose production was improved after gliclazide therapy. Moreover, mean (±SE) glucose disposal rate increased from 3.2 ± 0.7 to 4.8 ± 0.8 and from 7.9 ± 0.9 to 10.4 ± 0.9 mg · kg1 · min−1 at in vivo plasma insulin levels of ∼75 and ∼320 mU/L, respectively. In addition, insulin-receptor function and glycogen synthase activity were analyzed in skeletal muscle biopsies obtained in seven patients. The biopsies were obtained during basal insulinemia and hyperinsulinemia (∼320 mU/L) before and after treatment. Insulin receptors purified with wheat-germ agglutinin showed unchanged insulin-binding properties and unchanged receptor kinase function with respect to basal and insulin-stimulated phosphorylation of exogenous peptide poly(Glu80Tyr20). Gliclazide treatment had no effect on the maximal activities of glycogen synthase. Moreover, in biopsies obtained at basal insulinemia, the half-maximal activation constant for glucose 6-phosphate (A0.5) was identical before and after therapy (0.54 ± 0.05 vs. 0.54 ± 0.05 mM, respectively, NS). However, in biopsies obtained at hyperinsulinemia, A0.5 was 0.30 ± 0.05 vs. 0.20 ± 0.02 mM before and after gliclazide therapy, P < .04. In conclusion, this study indicates that gliclazide, in addition to its splanchnic effects, may enhance insulin-stimulated peripheral glucose metabolism through a potentiation of insulin action on skeletal muscle glycogen synthase by a mechanism distal to the insulin-receptor kinase.
Peripheral Neuropathy in Diabetic Monkeys
Authors: Cornblath David R , Hillman Michael A , Striffler John S , Herman Charles N , Hansen Barbara C
Published: September 2013

Peripheral neuropathy is a significant complication of human diabetes and a source of morbidity. Appropriate experimental models may aid in understanding its pathogenesis and in developing therapeutic strategies. We sought to determine whether spontaneously diabetic obese adult monkeys developed peripheral neuropathy and whether it occurred early or late in relation to the onset of hyperglycemia. We studied nerve conduction in both motor (peroneal, median, and ulnar) and sensory (median and ulnar) nerves in 13 adult male rhesus monkeys, 4 overtly diabetic and 9 nondiabetic (mean age 21 ± 2 and 16 ± 2 yr, respectively, NS; mean fasting plasma glucose 14.5 ± 3.4 and 4.4 ± 0.6 mM, P = .001). The diabetic animals had significantly reduced motor conduction velocities and prolonged F-wave latencies. Motor-evoked amplitudes did not differ. In the diabetic monkeys, nerve conduction times were increased in motor fibers, which could be identified as early as 2 yr after the onset of hyperglycemia. These abnormalities are similar to those seen in humans and suggest further study of these animals as a primate model of human diabetic neuropathy.
Effects of High Glucose on Insulin Secretion by Isolated Rat Islets and Purified β-Cells and Possible Role of Glycosylation
Authors: Purrello Francesco , Vetri Mario , Gatta Concetta , Gullo Damiano , Vigneri Riccardo
Published: September 2013

We investigated the effect of 24 h of exposure to various glucose concentrations on insulin secretion by isolated rat pancreatic islets and purified rat β-cells. Compared with islets cultured with standard medium (5.5 mM glucose), islets cultured with 16.7 mM glucose showed a higher basal insulin release (means ± SE, 3.0 ± 0.5 vs. 0.7 ± 0.2%, n = 8, P < .005) and reduced glucose-stimulated insulin secretion (2.4 ± 0.3 vs. 5.8 ± 0.4%, n = 8, P < .005). Similar results were also obtained with purified β-cells. The effect of high glucose was time dependent (present after 12 h, maximal after 24 h) and reversible: when islets cultured with high glucose were transferred to standard medium, normal responsiveness to glucose was restored within 8 h and normal basal release within 24 h. Mannitol, 3-O-methylglucose, and 2-deoxyglucose were not able to mimic the effects of glucose. Islets or purified β-cells cultured in the presence of high glucose had a normal response when stimulated with glyburide, dibutyryl cyclic AMP, and isobutylmethylxanthine. Tunicamycin, an inhibitor of N-terminal glycosylation, prevented glucose-induced desensitization when added during 24 h of islet culture with 16.7 mM glucose. Swainsonine, another agent that influences glycosylation, had a similar effect. Our study indicates 1) that 24 h of exposure to high glucose induces a specific and reversible impairment of insulin secretion in response to glucose, 2) that this is a direct effect of glucose on β-cells, and 3) that islet glucose metabolism and glycosylation processes may play a critical role in determining glucose desensitization.
Epidemiological Correlates of Diabetic Neuropathy: Report From Pittsburgh Epidemiology of Diabetes Complications Study
Authors: Maser Raelene E , Steenkiste Ann R , Dorman Janice S , Nielsen Viggo Kamp , Bass Eric B , Manjoo Qurashia , Drash Allan L , Becker Dorothy J , Kuller Lewis H , Greene Douglas A , Orchard Trevor J
Published: September 2013

The natural history of diabetic neuropathy and its risk factors are not well understood, apart from the recognition that prevalence increases with duration and, in many studies, degree of glycemia. The role of potential risk factors was therefore evaluated in a cross-sectional analysis from the baseline examination of the Pittsburgh Epidemiology of Diabetes Complications Study. We present results from the first 400 subjects seen at baseline examination. Neuropathy was determined by a trained internist with a standardized examination and was defined as the presence of at least two of three criteria: abnormal sensory or motor signs, symptoms consistent with neuropathy, and decreased tendon reflexes. The prevalence of neuropathy in this cohort was 34% (18%, 18-29 yr old, 58% ≥30 yr old) with no difference by sex. By focusing on subjects s 18 yr old, all significant univariate variables (e.g., duration, glycosylated hemoglobin [HbAJ) were analyzed in 3 multiple logistic regression models: all subjects ≥18 yr old and separating the same subjects into two groups based on age (18-29 and 2:30 yr). Duration, HbA1, smoking status, and high-density lipoprotein cholesterol were found to be associated with neuropathy in the models for the ≥18-yr-old group and the ≥30-yr-old group. In the 18- to 29-yr-old group, duration, HbA1, and hypertension status were found to be significantly associated with neuropathy. There was a univariate association of neuropathy with macrovascular disease, nephropathy, and retinopathy. Macrovascular disease, although borderline significant, remained in the original logistic model for the ≥18-yr-old subjects. The addition of either retinopathy or nephropathy to the original logistic model for the 18- to 29-yr-old subjects resulted in a statistically significantly improved fit (of model to data), suggesting that these complications may be a marker for something beyond the risk factors described. The results suggest that traditional cardiovascular risk factors (e.g., lipids and smoking) are important determinants of distal symmetric polyneuropathy and if confirmed in prospective follow-up, open new avenues to the prevention of diabetic neuropathy.
Ganglioside Expression in Human Pancreatic Islets
Authors: Dotta Francesco , Colman Peter G , Lombardi Daniela , Scharp David W , Andreani Domenico , Pontieri Giuseppe M , Mario Umberto Di , Lenti Luisa , Eisenbarth George S , Nayak Ramesh C
Published: September 2013

Recent biochemical studies have shown that the cytoplasmic islet cell–antibody autoantigen has properties of a monosialoganglioside (GM). To characterize islet glycolipids and ascertain whether islets express unique gangliosides, we determined the pattern of ganglioside expression in whole human pancreas and isolated human islets using high-performance liquid chromatography (HPLC) and high-performance thin-layer chromatography (HPTLC). The major gangliosides detected in glycolipid extracts of whole human pancreas were GM3, GD3 (disialoganglioside), and in a lesser amount, a GD1a-comigrating ganglioside. In contrast to whole human pancreas, isolated human islets were found to predominantly express GM3, an acidic glycolipid comigrating with GM2, and a ganglioside with mobility between GM2 and GM1 by both HPLC and HPTLC. Quantitation of the major ganglioside UV peaks seen on HPLC gave the following results. In whole pancreas, GM3 represented 66.7% of total gangliosides detected; an asialoglycolipid comigrating with GM2, 2.0%; a ganglioside migrating between GM2 and GM1, 2.6%; GD3, 22.6%; and a GD1a-comigrating ganglioside, 6.1%. In isolated islets, these components were found at the following levels: GM3, 14.9%; GM2-comigrating glycolipid, 74.2%; a ganglioside migrating between GM2 and GM1, 9.8%; GD3, 1.1%; and the GD1a-comigrating ganglioside, not detectable.
Effects of Glucagonlike Peptide l-(7–36) on Release of Insulin, Glucagon, and Somatostatin by Rat Pancreatic Islet Cell Monolayer Cultures
Authors: D'Alessio David A , Fujimoto Wilfred Y , Ensinck John W
Published: September 2013

Glucagonlike peptide I (GLP-I-(7–36)) is cleaved from proglucagon in ileal epithelial cells and increases in human plasma after nutrient ingestion. This peptide has been shown to stimulate insulin secretion in vitro and in vivo and thus potentially acts as an incretin. To characterize its action on islet cells, the release of insulin, glucagon, and somatostatin by rat pancreatic islet monolayer cultures at varying concentrations of GLP-I-(7–36) was measured. The interaction of GLP-I-(7–36) with nutrient substrates was assessed by adding amino acids and differing glucose concentrations to the cultures. Islet cell cultures (n = 5) were incubated for 1 h in medium containing 1.67 or 16.7 mM glucose or 1.67 mM glucose supplemented with amino acids and GLP-I-(7–36) at 10−13−10−7 M. Hormone release was compared with control cultures containing no GLP-I-(7–36); 1.67−16.7 mM glucose with and without GLP-I-(7–36) at 10−11 M; and 1.67, 3.3, 8.3, or 11.1 mM glucose alone or supplemented with amino acids, GLP-I-(7–36) 10−11 M, or both amino acids and GLP-I-(7–36). In medium with 1.67 or 16.7 mM glucose or 1.67 mM glucose and amino acids, GLP-I-(7–36) increased insulin secretion two- to threefold over control at concentrations of 10−9, 10−11, and 10−12 M, respectively. In medium with increasing concentrations of glucose, GLP-I-(7–36) at 10−11 M significantly increased insulin secretion at glucose concentrations ≥3.34 mM. Amino acids and GLP-I-(7–36) combined caused insulin secretion by the monolayer cultures at low glucose concentrations, whereas neither GLP-I-(7–36) nor amino acids alone were stimulatory. At higher glucose concentrations, amino acids and GLP-I-(7–36) together evoked greater insulin release than amino acids or GLP-I-(7–36) alone. With 16.7 mM glucose and GLP-I-(7–36) at 10−9 M, somatostatin release was increased by 40%. Glucagon release was not affected by any concentration of GLP-I-(7–36). Thus, the effect of GLP-I-(7–36) is enhanced in the presence of amino acids and glucose and, at putative physiological levels, is specific for pancreatic β-cells. We conclude that GLP-I-(7–36) is a potent insulinotropin that may be a physiological humoral modulator of nutrient-stimulated insulin secretion.
Effects of Brief Exposure to Insulin-Induced Hypoglycemic Serum During Organogenesis in Rat Embryo Culture
Authors: Akazawa Mihoko , Akazawa Shoichi , Hashimoto Masumi , Akashi Masaharu , Yamazaki Hironori , Tahara Daigo , Yamamoto Hidefumi , Yamaguchi Yoshihiko , Nakanishi Toshiaki , Nagataki Shigenobu
Published: September 2013

We have previously shown that long-term exposure to medium containing insulin-induced hypoglycemic serum during the early phase of organogenesis can adversely affect embryonic development in rat embryo culture and that these effects were mediated through the interruption of glycolytic flux that constituted the principal pathway at this embryonic stage. Further experiments were performed to examine whether brief exposure to the hypoglycemic medium during critical developmental periods would have adverse effects on embryogenesis during embryo culture not only in normal but also in high glucose concentrations. Rat embryos in the early head-fold stage (9.5 days gestation) were grown in vitro for 48 h until neural tube closure occurred; dysmorphogenic lesions were not elicited in either the basal culture medium containing 6.6 mM glucose (control medium) or the hyperglycemic medium supplemented with glucose at a concentration of 33.3 mM. Hypoglycemic mediums (2.2−2.5 mM glucose) were prepared from the serum of rats given insulin intraperitoneally. Postimplantation embryos (in early neural tube formation) were briefly exposed (1 h) to hypoglycemic medium on day 10.3 of gestation during the basal culture. After exposure to the hypoglycemic medium for 1 h during culture in the control medium, embryos showed minor growth retardation and dysmorphogenic lesions (7.1% open neural pores). Exposure to the hypoglycemic medium for 1 h during culture in hyperglycemic medium supplemented with a subteratogenic concentration of glucose (33.3 mM) resulted in greater growth retardation and increased occurrence of dysmorphogenic lesions (17.3% open neural pores). These results indicate that even brief exposure to hypoglycemia can adversely affect embryogenesis at the critical developmental period, and these effects are enhanced when embryos are cultured in hyperglycemic medium.
Dendritic Cells and Scavenger Macrophages in Pancreatic Islets of Prediabetic BB Rats
Authors: Voorbij Hieronymus A M , Jeucken Pieter H M , Kabel Peter J , Haan Meeny De , Drexhage Hemmo A
Published: September 2013

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease whose notorious pathologic feature is insulitis accompanied by destruction of β-cells. In this morphological study, we examined the pancreatic events during the onset of diabetes in spontaneously diabetic BB/Organon rats. Dendritic cells were the first cells to accumulate around the islets, followed by lymphocytes. Scavenger macrophages and MHC class II-positive β-cells were only seen late in the disease. These observations suggest a role for antigen-presenting dendritic cells in the onset of the β-cell-specific autoimmune reaction and emphasize the necessity to distinguish between the several monocyte-macrophage subtypes in studies on the pathogenesis of IDDM.
Characterization of Endothelin Receptors and Effects of Endothelin on Diacylglycerol and Protein Kinase C in Retinal Capillary Pericytes
Authors: Lee Tian-Shing , Hu Kang-Quan , Chao Ting , King George L
Published: September 2013

Retinal capillary pericyte is a cell type selectively lost in early diabetic retinopathy. The physiological function of pericytes is not yet clearly identified, although it probably has contractile properties. We determined the specific binding of endothelin 1, a 21–amino acid peptide with potent vasoconstrictive action, and the stimulation of diacylglycerol/protein kinase C (DAG/PKC) pathway in cultured retinal capillary pericytes by endothelin. A single specific binding site for 125I-labeled endothelin was identified, with an apparent Kd of 1.3 nM and a maximal binding capacity of ∼1–2 × 105 sites/cell. Endothelin (100 nM) increased total cellular DAG content by 15% at 5 min and 24% at 10 min. When pericytes were labeled isotopically with [3H]glycerol, endothelin stimulated [3H]DAG formation by 100% at 10 min and 88% at 30 min. After 10 min of endothelin treatment, PKC activities were increased by 60 and 100% in the membranous and cytosolic pools, respectively. We conclude that bovine retinal capillary pericytes possess numerous high-affinity specific binding sites for endothelin that mediate the action of endothelin by the stimulation of the DAG/PKC pathway in pericytes. These findings suggest that endothelin is a regulator of the contractile properties of pericytes, which may be adversely affected in diabetic retinopathy.
In Vitro and In Vivo Stability of Electrode Potentials in Needle-Type Glucose Sensors: Influence of Needle Material
Authors: Velho G , Froguel P , Sternberg R , Thevenot D R , Reach G
Published: September 2013

Enzymatic glucose sensors are based on the amperometric detection of an oxidable species generated during the oxydation of glucose by glucose oxidase. This measurement usually requires a working electrode (anode), an auxiliary electrode (cathode), and a reference electrode, the function ofthe latter being to keep constant the working potential of the anode, which is responsible for current generation. However, in the needle-type glucose sensors proposed so far, the reference electrode is missing, and its function is performed by the auxiliary electrode. We investigated, in vitro and in vivo in rats, the ability of several cathode-needle materials to behave as a reference electrode in two-electrode glucose sensors, i.e., to present a stable auxiliary electrode potential. In vitro, when glucose concentration was raised from 0 to 30 mM, the auxiliary potential of both gold- and silvercoated sensors presented a cathodic drift, whereas that of silver/silver chloride-coated sensors remained stable. In vivo, during insulin-induced hypoglycemia (5.9–2.4 mM), the auxiliary potentials of all sensors remained stable, whereas during glucose infusion (mean blood glucose concentration 11.2 mM), the auxiliary potentials of both gold- and silver-coated sensors presented an anodic drift, whereas those of silver/silver chloride-coated sensors remained stable. We also indirectly quantified the changes in sensor response induced by variations in the working potential in vitro and in vivo, simulating those that might be produced by a drift in the auxiliary potential. Such changes in the working potential could bring about a 30% unspecific variationin sensor response. We conclude that improvements in sensor analytical characteristics should be obtained with silver/silverchloride—coated cathodes.
Characterization of Voltage-Dependent Ca2+ Channels in β-Cell Line
Authors: Keahey Holly H , Rajan Arun S , Boyd Aubrey E , Kunze Diana L
Published: September 2013

Although there is compelling pharmacological evidence based on Ca2+-channel antagonist studies suggesting that the voltage-dependent Ca2+ channels regulate insulin release, no direct comparison with Ca2+ currents exists. This is particularly important because of the recent demonstration in other cell types of one and possibly two Ca2+ channels that are insensitive to Ca2+-channel antagonists, the dihydropyridines and the phenylalkylamines. Using an SV40-transformed pancreatic β-cell line (HIT cells), we determined how voltage-dependent Ca2+ channels are involved in stimulus-secretion coupling. Ca2+ currents were measured with the tight-seal technique for wholecell recording. The cytosolic free-Ca2+ concentration ([Ca2+]1) was followed with the fluorescent probe Fura 2, and the measurements were compared with insulin secretion stimulated by depolarizing the cells with K+. The Ca2+ current contained two components: arapidly decaying current activated at –50 to –40 mV that decayed with a time constant of 25 ms anda very slowly decaying component activated at –40 mV. Both components were sensitive to the Ca2+-channel antagonist nimodipine. There is excellent agreement in the concentration of nimodipine that inhibited Ca2+ current and the increase in [Ca2+1], in response to K+ depolarization (IC50 of 15 and 6 nM, respectively). Nimodipine inhibited insulin release over a similar dose-response range with an IC50of 1.5 × 10 9 M. These studies indicate that the increase in [Ca2+1], in response to β-cell depolarization can be accounted for by the influx of this ion through a single class of dihydropyridine-sensitive Ca2+ channels in the cell membrane.
Modification of Tissue-Factor mRNA and Protein Response to Thrombin and Interleukin 1 by High Glucose in Cultured Human Endothelial Cells
Authors: Boeri Daria , Almus Fanny E , Maiello Michele , Cagliero Enrico , Rao L Vijaya Mohan , Lorenzi Mara
Published: September 2013

Because diabetic vascular disease is accompanied by a state of hypercoagulability, manifested by increased thrombin activity and foci of intravascular coagulation, we investigated whether a specific procoagulant property of the endothelium—production and surface expression of tissue factor—is modified by elevated glucose concentrations. In unperturbed human vascular endothelial cells, tissue factor mRNA and expression of the functional protein were undetectable and werenot induced by 10–12 days of exposure to 30 mM glucose. In thrombin-stimulated cultures, tissuefactor expression was related inversely to cellular density, with confluent cultures producing (per 105 cells) half the amount of tissue factor measured in sparse cultures. Cells exposed to high glucose and studied when cell number and thymidine incorporation were identical to control cells manifested increased tissue-factor mRNA level and functional protein production in response to thrombin (P = .002). This effect was not attributable to hypertonicity and was not observed after short exposure to high glucose. In contrast, the tissue-factor response to interleukin 1, a modulator of endothelial function in the context of host defense, was decreased in cells cultured in high glucose (P = .04). These findings indicate that exposure to high glucose can alter tissue-factor gene expression in perturbed vascular endothelium. The reciprocal effects of high glucose on the tissue-factor response to thrombin and interleukin 1 points to different pathwaysof tissue-factor stimulation by the two agents and suggests functional consequences pertinent to the increased thrombin activity and compromised host-defense mechanisms observed in diabetes.
Successful Reversal of Diabetes in Nude Rats by Transplantation of Isolated Adult Human Islets of Langerhans
Authors: Lake Stephen P , Chamberlain Julie , Bassett P Drew , London Nick J M , Walczak Karen , Bell Peter R F , James Roger F L
Published: September 2013

A method is described in which the viability of isolated adult human islets of Langerhans can be assessed in vivo. The Rowett nude rat, made diabetic with streptozocin (STZ), has been used as the islet recipient in these studies. Although these animals are athymic and are able to accept xenogeneic grafts for prolonged periods, they are very susceptible to dehydration and infection oncemade diabetic. Therefore, a considerably shortened diabetes induction period was used. The basis of the study was to prepare pure adult human pancreatic islets that were cultured for 48 h. Nude rats were given 80 mg/kg i.v. STZ during islet isolation and were transplanted with 800–1000 islets under the renal capsule at 48 h. To monitor islet function, animals were bled regularly for random blood glucose measurements and were given a glucose tolerance test at day 20. The kidney containing the graft was removed on day 21 to allow histological assessment of the graft and to confirm that glucose control was due to the transplanted islets and was not secondary to reversion of the animal's own islets. Seven rats were transplanted, and five were deemed to have received viable human islets. Two rats that received islets from the same donor did not reverse their diabetes and were found by histology to have vacuolated islet structures with scant insulin-staining tissue under the kidney capsule. This method allows a definitive judgment of the ability of isolated adult human islets to reverse diabetes.
Unaltered Class II Histocompatibility Antigens and Pathogenesis of IDDM in BB Rats
Authors: Holowachuk Eugene W , Greer Mary K
Published: September 2013

The BB rat spontaneously develops insulin-dependent diabetes mellitus (IDDM) as an autoimmune abnormality involving the class II molecules of the major histocompatibility complex (MHC). The rat MHC (RT1 complex) encodes two class II loci, RT1 .B and RT1.D. The possibility that variant or unique class II MHC molecules may be associated with IDDM susceptibility was directly examined by determining the nucleotide sequences of class II mRNAs and/or cDNAs from the diabetes-prone (DP) BB rat, the diabetes-resistant (DR) BB rat, the normal histocompatible Wistar-Furth (WF) rat, and the Lewis rat. Sequence analysis indicates that the β-chains of the RT1.B and RT1.D molecules of the u haplotype from DP-BB, DR-BB, and WF rats are identical but that they are different fromother rat alleles and published mouse class II sequences. At the nucleotide level, the NH2-terminal domain of RTI.Dp of the BB and WF rats differs by a single silent nucleotide substitution. Comparisons with the sequences of the Lewis rat indicate hypervariable allelic differences and that the u and / haplotypes are remarkably similar. These findings establish that the class II molecules of the DP-BB rat are not variant or unique and that unaltered class II molecules of the u haplotype support the autoimmune response in the BB rat.
Morning Insulin Requirements: Critique of Dawn and Meal Phenomena
Authors: Blackard William G , Barlascini Cornelius O , Clore John N , Nestler John E
Published: September 2013

Morning insulin resistance has frequently been invoked to explain early-morning increases in both basal and breakfast-associated insulin requirements in diabetic patients. This increase in insulin requirements and plasma glucose from 0600 to 0900, when compared with midnight to 0600, has been termed the dawn phenomenon. We believe that the increased need for insulin in the morning has been misinterpreted. Data are reviewed that suggest the major perturbation overnight is a sleep-associated fall in hepatic glucose output, with a return to basal production rates on arousal in the morning. Moreover, the apparent increased insulin requirement for breakfast compared with lunch or supper (meal phenomenon) appears to be related more to lack of residual insulin effect from a preceding meal than to any putative morning insulin resistance. Thus, we found little evidence to support morning insulin resistance as a cause of either the dawn phenomenon (more appropriately designated the sleep phenomenon) or the meal phenomenon. A proper understanding of these phenomena is essential to the management of diabetic patients receiving insulin.
Effect of Isologous and Autologous Insulin Antibodies on In Vivo Bioavailability and Metabolic Fate of Immune-Complexed Insulin in Lou/M Rats
Authors: Arquilla Edward R , McDougall Brenda R , Stenger David P
Published: September 2013

The in vivo bioavailability, distribution, and metabolic fate of 125I-labeled insulin complexed to isologous and autologous antibodies were studied in inbred Lou/M rats. There was an impaired bioavailability of the 125I-insulin bound to the isologous and autologous antibodies. Very little of the 125I-insulin in these immune complexes could bind to insulin receptors on hepatocytes or renal tubular cells and be degraded, because the amounts of 125I from degraded 125I-insulin in the blood or secreted into the stomach were markedly attenuated in both cases for at least 30 min after injection. There was a simultaneous accumulation of 125I-insulin immune complexes in the liver and the kidneys of Lou/M rats injected with ,25I-insulin complexed with isologous antibodies or when insulin-immunized Lou/M rats were injected with 125I-insulin during the same interval. The impaired bioavailability of immune-complexed insulin and altered distribution of radioactivity due to the accumulation of immune complexes in the liver and kidney were also observed in previous experiments in which Lewis rats were injected with xenogenic guinea pig and homologous insulin antibodies. These observations are therefore submitted as evidence that the Lou/M rat is a valid model in which to study the bioavailability of insulin immune complexed to isologous, homologous, and xenogenic antibodies and the metabolic fate of the respective insulin-antibody immune complexes.
Gemfibrozil Alone and in Combination With Lovastatin for Treatment of Hypertriglyceridemia in NIDDM
Authors: Garg Abhimanyu , Grundy Scott M
Published: September 2013

Hypertriglyceridemic patients with non-insulin-dependent diabetes mellitus (NIDDM) have an increased risk of coronary heart disease (CHD) and acute pancreatitis. To examine the potential of hypolipidemic drugs for therapy of lipoprotein abnormalities in NIDDM, 10 patients maintaining marked (plasma triglycerides >500 mg/dl) and 6 with moderate (plasma triglycerides 250–500 mg/dl) hypertriglyceridemia, despite good glycemic control, were studied in two phases. In the first phase, gemfibrozil alone (600 mg twice daily) was compared with a placebo, and in the second phase a combination of gemfibrozil and lovastatin (20 mg twice daily) was compared with gemfibrozil alone in a randomized, double-blind, placebo-controlled crossover study. In markedly hypertriglyceridemic patients, gemfibrozil reduced plasma triglycerides by 52% and very-low-density lipoprotein cholesterol (VLDL-chol) by 55% and increased high-density lipoprotein cholesterol by 23% compared with a placebo. However, low-density lipoprotein cholesterol (LDL-chol) levels increased (42%), and LDL apolipoprotein B (apoB) levels remained unchanged. Addition of lovastatin to gemfibrozil effectively reduced total cholesterol (25%), LDL-chol (30%), and LDL-apoB (19%). Lovastatin further reduced plasma triglycerides (11%) and VLDL-chol (27%). However, in moderately hypertriglyceridemic patients, gemfibrozil or the combination therapy did not seem to offer benefits over the previously reported study with lovastatin alone. Glycemic control was maintained throughout the study. In conclusion, the beneficial effects of the combination therapy on lipoprotein levels in markedly hypertriglyceridemic NIDDM patients could decrease the risk of development of both acute pancreatitis and CHD.
Oxygen Free-Radical Scavengers and Immune Destruction of Murine Islets in Allograft Rejection and Multiple Low-Dose Streptozocin-Induced Insulitis
Authors: Mendola Jose , Wright James R , Lacy Paul E
Published: September 2013

We examined the effects of desferrioxamine (DFX), a potent inhibitor of the formation of oxygen-derived hydroxyl radicals, and nicotinamide (NIC), a poly(ADP-ribose) synthetase inhibitor and a weak free-radical scavenger, on two models of immune destruction of murine islets [i.e., allograft rejection and multiple low-dose streptozocin (STZ)-induced insulitis]. Freshly isolated or low-temperature-cultured BALB/cJ islets were transplanted beneath the kidney capsules of C57BL/6J recipients. The recipients were treated with NIC alone (500 mg · kg−1 · day−1), DFX alone (4.2 mg/day × 14 days), or NIC + DFX. Only recipients treated with NIC + DFX, receiving cultured islets, showed a mean graft survival time significantly longer than control mice receiving freshly isolated or cultured islets. Control CD-1 mice treated with multiple low doses of STZ developed insulitis and diabetes. Treatment with NIC alone, DFX alone, or NIC + DFX decreased the severity of hyperglycemia relative to the controls. Treatment with DFX alone was more effective than NIC alone or NIC + DFX. Only the group treated with DFX alone had a lower incidence of diabetes (mean plasma glucose level >200 mg/dl) than the controls after 4 wk. Histologically, islets from control mice showed severe insulitis, islet destruction, and absence of stainable insulin, whereas islets from DFX-treated mice showed only mild peri-insulitis and a relative preservation of β-cell granulation. Our study showed that NIC and DFX partially protect islets from immune destruction in allograft rejection and in low-dose STZ-induced insulitis. Apparently, hydroxyl radicals play important roles in both of these models.
Erythrocytes and Glucose Homeostasis in Rats
Authors: Guarner Verónica , Alvarez-Buylla Ramó
Published: September 2013

The capacity of erythrocytes to modify their glycogen stores to compensate for changes in glucose concentration in plasma was studied. Experiments in vitro and in vivo demonstrated that erythrocytes absorbed and incorporated glucose into their glycogen stores when glucose concentration in the medium was high and liberated it when the concentration was low. Epinephrine administration inhibited glucose absorption by erythrocytes, and in its presence, erythrocytes liberated glucose from their glycogen stores, being unable to compensate for this rise in glucose concentration in plasma. Similar results were obtained when endogenous secretion of epinephrine was enhanced by carotid sinus-chemoreceptor stimulation. Insulin had no effect on the capacity of erythrocytes to absorb glucose. These data suggest a role for erythrocytes in the transport of glucose to different regions in the organism's circulation and in the regulation of glucose concentration in plasma.
Metabolite-Regulated ATP-Sensitive K+ Channel in Human Pancreatic Islet Cells
Authors: Misler Stanley , Gee William M , Gillis Kevin D , Scharp David W , Falke Lee C
Published: September 2013

In patch-clamped surface cells of human islets, we identified an inwardly rectifying, voltage-independent K+ channel that may be a crucial link between substrate metabolism and depolarization-induced insulin secretion. It is the major channel open at rest. It closes on exposure of the cell to secretagogue concentrations of glucose or other metabolic fuels and oral hypoglycemic sulfonylureas but reopens on addition of either a metabolic inhibitor that prevents substrate utilization or the hyperglycemic sulfonamide diazoxide. Onset of electrical activity coincides with channel closure by the secretagogues. In excised patches, the activity of this channel is inhibited at its cytoplasmic surface by ATP. These results suggest that in humans, as in rodents, 1) rises in cytoplasmic ATP levels during substrate metabolism trigger K+-channel closure and cell depolarization and 2) clinically useful sulfonamides modulate glucose-induced insulin secretion, in part by affecting a readily identifiable resting conductance pathway for K+.
Contribution of α- and β-Receptors to Ketogenic and Lipolytic Effects of Norepinephrine in Humans
Authors: Keller Ulrich , Weiss Markus , Stauffacher Werner
Published: September 2013

To assess the effects of α- and β-adrenergic-receptor activation on ketone body kinetics and lipolysis in humans, five groups of overnight-fasted subjects were studied. Group 1 (n = 7) received norepinephrine (NE) to activate α- and β-receptors, resulting in plasma NE concentrations of 1.5 ± 0.19 ng/ml; group 2 (n = 7) received NE plus β-blockade; group 3 (n = 7) NE plus α-blockade; group 4 (n = 6) NE plus α- and β-blockade; and group 5 (n = 6) saline. Plasma insulin and glucagon concentrations were maintained constant by infusion of somatostatin with insulin and glucagon replacements. Infusion of NE for 170 min resulted in an increase in total ketone body production ([3-14C]acetoacetate infusions) to 8.5 ± 1.3 vs. 3.9 ± 0.6 μmol · kg−1 · min−1 (P < .01) in saline controls and in an increase in plasma free fatty acids (FFAs) to 1120 ± 102 vs. 526 ± 115 μM (P < .01) in controls. α-Blockade during NE infusion enhanced the lipolytic effect of NE, because plasma FFA increased to 1981 ± 204 vs. 1301 ± 146 μ after 45 min (P < .002), and the ketogenic effect was augmented (14.3 ± 1.7 vs. 5.6 ± 0.9 μmol · kg1 · min−1) after 60 min (P < .001). In contrast, β-blockade abolished the ketogenic and lipolytic effects of NE to those observed in saline controls. Combined α- and β-blockade during NE infusion was without significant effect on ketone body kinetics and plasma FFA. The results indicate that modulation of circulating FFA concentrations plays a predominant role in the acute and α- and β- adrenergic regulation of ketone body production in humans. Because plasma NE concentrations achieved in this study were similar to those observed in severe stress and in diabetic ketoacidosis, the data suggest that in these conditions the lipolytic and ketogenic effects of NE result from β-adrenergic timulation, which is restrained in part by α-adrenergic inhibition.
Long-Term Study of Normal Kidneys Transplanted Into Patients With Type I Diabetes
Authors: Mauer S Michael , Goetz Frederick C , McHugh Lois E , Sutherland David E R , Barbosa Jose , Najarian John S , Steffes Michael W
Published: September 2013

We examined the rate of development of the lesions of diabetic nephropathy in transplanted kidneys residing for 6–14 yr in type I (insulin-dependent) diabetic kidney-allograft recipients. Although each recipient had end-stage diabetic nephropathy with his/her own kidneys, there was marked variability in the rate of development of mesangial expansion observed in the transplanted kidneys. The progression of glomerular pathology, including widening of the glomerular basement membrane and expansion of the mesangium, did not correlate significantly with several potential risk factors (e.g., donor source—cadaver or living related, histocompatibility match, age of the recipient or donor, age at onset of diabetes, duration of diabetes before renal failure, immunosuppressive drug dose, blood pressure, and severity of lesions of chronic rejection). However, there was a direct albeit imprecise relationship between the index of mesangial expansion at the final biopsy and the index of glycemic control (r = .61, P < .01). These observations suggest that currently unknown factor(s) may modulate the progression of diabetic renal disease, even in a population that had uniformly demonstrated nephropathy risk. Our data support the hypothesis that in addition to glycemic control per se, there are risk factors intrinsic to the kidney itself.
Abnormal Action of Catecholamines on Lipolysis in Adipocytes of Type I Diabetic Patients Treated With Insulin
Authors: Wahrenberg Hans , Lönnqvist Fredrik , Engfeldt Peter , Arner Peter
Published: September 2013

Catecholamine-induced lipolysis was investigated in adipocytes obtained before and after 30 min of exercise from 10 insulin-treated type I (insulin-dependent) diabetic men and 10 male matched control subjects. The α2-adrenoceptor-mediated antilipolytic effect of catecholamines was normal, but the β-adrenoceptor-mediated lipolytic sensitivity was increased 10-fold (P < .01) in diabetic subjects before and after exercise. The latter correlated inversely (r > .7) with the circulating norepinephrine level, which was significantly reduced in diabetic subjects. Basal lipolysis and lipolysis activated at different steps distal to the β-receptor were similar in the two groups. There was no major change in the total number of β- and α-adrenoceptors in the diabetic patients. However, the proportion of high-affinity β-adrenoceptors was significantly increased in these patients compared with control subjects. In the diabetic patients, ∼50% of the β-adrenoceptors were in a high-affinity state, compared to ∼30% in the control subjects (P < .025). In diabetic subjects there was an enhanced plasma glycerol response to exercise, despite a blunted plasma norepinephrine response. The data suggest enhanced sensitivity of catecholamine-induced lipolysis in type I diabetes due to an increase in the number of high-affinity (i.e., coupled) β-adrenoceptors in fat cells. This mechanism may be due to low levels of circulating norepinephrine and may also explain the exaggerated lipolytic response to exercise in the diabetic state.
Phasic Effects of Glucose, p-Hydroxymercuribenzoate, and Lysophosphatidylcholine on Insulin Secretion from HIT Cells
Authors: Fujimoto Wilfred Y , Teague Jeanette
Published: September 2013

Monolayer cultures of HIT cells were superfused to examine phasic insulin secretion. A Diphasic pattern of insulin secretion was observed when cells were stimulated with a constant glucose concentration as low as 0.28 mM, with increasing stimulation at 0.56,1.7, and 5.6 mM glucose. Higher glucose concentrations did not increase insulin secretion. In the absence of glucose, p-hydroxymercuribenzoate (15, 30, and 50 μM), which blocks the reacylation of lysophospholipids with arachidonic acid, also evoked a concentration-dependent biphasic release of insulin. Lysophosphatidylcholine (50, 75, and 100 μg/ml) also caused a concentration-dependent biphasic release of insulin in the absence of glucose. These observations were similar to those previously reported for superfused monolayer culture of rat islet cells and suggest that the HIT cell is a β-cell line that may be valuable in the further examination of the relationships among glucose, phospholipid metabolism, and insulin secretion. The data are consistent with the hypothesis that glucose-stimulated release of lysophospholipids may be important in initiation of the biphasic pattern of glucose-stimulated insulin release.
Effect of Interferon on Glucose Tolerance and Insulin Sensitivity
Authors: Koivisto Veikko A , Pelkonen Risto , Cantell Kari
Published: September 2013

Many viral infections induce interferon (IFN) production and cause insulin resistance. To examine the causal relationship between IFN and insulin resistance, we injected natural human leukocyte IFN-α (3 × 106 IU, i.m.) twice overnight in eight healthy subjects and determined oral (OGT) and intravenous (IVGT) glucose tolerance and sensitivity to insulin (287 nmol or 40 mU · m−2 · min−1 euglycemic insulin clamp) the following morning. IFN caused mild influenzalike symptoms and induced a rise in circulating glucose, insulin, hydrocortisone (cortisol), growth hormone, and glucagon concentrations (P < .05–.001). In the OGT test, the area under the glucose curve was 2.6-fold greater (P < .02), and the disappearance rate of intravenously administered glucose was reduced by 28% (P < .05) after IFN administration. The impairment in OGT and IVGT occurred despite augmented insulin response. Insulin-stimulated glucose disposal was reduced by 22% (P < .005), and insulin clearance increased by 18% (P < .02) after IFN administration. When the insulin-clamp study was repeated in patients with steady-state hyperinsulinemia that was 12% higher (P < .005) after IFN, the glucose disposal rate was still reduced by 15% (P < .01). These data indicate that IFN 1) stimulates counterregulatory hormone secretion, 2) impairs glucose tolerance and insulin sensitivity, and 3) stimulates insulin clearance. Thus, IFN may be involved in the development of insulin resistance during viral infections.