bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimal Effects of Phorbol Esters on Glucose Transport and Insulin Sensitivity of Rat Skeletal Muscle
Authors: Sowell Margaret O , Treutelaar Mary K , Burant Charles F , Buse Maria G
Published: September 2013

Protein kinase C (PKC) has been suggested as a mediator of insulin's effect on glucose transport, and PKC-mediated modulation of tyrosine kinase activity in the insulin receptor has been implicated in regulating the insulin sensitivity of tissues. Because skeletal muscle is a major target of insulin action, we examined the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA), 1-oleoyl-2-acetyl-rac-glycerol, and dioctanoyl diacylglycerol, known activators of PKC, on glucose metabolism in rat skeletal muscles. In contrast to results reported for other tissues, incubation of muscles with PKC activators produced only small increases in glucose transport and had minimal effects on the ability of insulin to stimulate transport. However, TPA treatment of muscles produced a significant decrease in basal glycogen synthesis. Incubation of muscles with TPA did not affect insulin binding or the tyrosine kinase activity of partially purified insulin receptors measured under basal conditions or after stimulation by insulin in situ or in vitro. Our findings do not support activation of PKC as a major mechanism for regulating glucose uptake or insulin receptor activity in skeletal muscle. However, the data do not rule out the possibility that glucose transport in skeletal muscle may respond to physiological activators of PKC.
Proteinuria and Activated T-Lymphocytes in Diabetic Nephropathy
Authors: Bending Jeremy J , Lobo-Yeo Ava , Vergani Diego , Viberti GianCarlo
Published: September 2013

The reasons for the presence of activated T-lymphocytes (ATL) in some long-standing insulin-dependent diabetic (IDDM) patients are unknown. These cells have been implicated in the genesis of proteinuria in some forms of immune-mediated renal disease. We measured ATL in 18 IDDM patients with diabetic nephropathy, 10 with nonnephrotic proteinuria (total urinary protein excretion rate >0.5 and <3.5 g/24 h) and 8 with nephrotic proteinuria (total urinary protein excretion rate > 3.5 g/24 h), and in 17 age-, sex-, and duration-of-diabetes–matched diabetic control subjects without clinical proteinuria (total urinary protein <0.5 g/24 h). T-lymphocytes purified from peripheral blood were stained by direct immunofluorescence with the fluorescein-labeled monoclonal antibody anti-HLA-DR. Absolute number and percent of DR-positive T-lymphocytes were significantly higher in patients with nonnephrotic proteinuria (median and range 162 × 106/ml, 40–320 × 106/ml; 13.9%, 8.1–19.4%) compared with nonproteinuric control subjects (81 × 106/ml, 2–240 × 106/ml, P < .05; 6.2%, 0–13.1%, P < .01). In 8 patients with nephrotic proteinuria, absolute and percent DR-positive T-lymphocytes tended to be lower (36 × 106/ml, 14–56 × 106/ml; 3.4%, 1.1–5.4%) than in nonproteinuric control subjects. An increased number of activated T-lymphocytes may be part of an immune-mediated process associated with the development of proteinuria in diabetic nephropathy. In advanced renal disease with nephrotic proteinuria, this immune process may become exhausted.
Role of Host Immune System in BB/Wor Rat: Predisposition to Diabetes Resides in Bone Marrow
Authors: Nakano Koji , Mordes John P , Handler Eugene S , Greiner Dale L , Rossini Aldo A
Published: September 2013

The role of the immune system in the development of autoimmune diabetes mellitus in the BB/Wor rat was studied with bone marrow transplantation methodology. In the first experiment, diabetes-prone (DP) and diabetes-resistant (DR) BB/Wor rats were irradiated and reconstituted with bone marrow to create both reciprocal (DP donor → DR host; DR donor → DP host) and syngeneic (DR → DR; DP → DP) histocompatible chimeras. Both susceptibility and resistance to subsequent spontaneous diabetes in these chimeras were found to be a function of the type of donor bone marrow transplanted and not the genetic background of the host. In a second experiment, rats from three strains that share the RT1u major histocompatibility complex haplotype of the BB/Wor and rats from three non-RT1u strains were lethally irradiated and reconstituted with DP BB/Wor bone marrow. To rapidly induce diabetes and/or insulitis, they were then injected with mitogen-activated spleen cells from acutely diabetic DP BB/Wor donors, with standard passive-transfer methods. Diabetes and pancreatic insulitis were observed in RT1u recipients, whereas non-RT1u rats developed insulitis but not diabetes. The data suggest that predisposition to spontaneous diabetes in BB rats resides in bone marrow cells.
Modulation of Insulin Activity by Hydrochloride Salts
Authors: Agharanya Julius C
Published: September 2013

The influence of hydrochloride salts of various amino acids and other drugs on the activity of exogenously administered insulin was studied in the rat. Insulin activity was assessed in terms of insulin's effects on lowering of blood glucose and nonesterified fatty acids (NEFA), release of adrenaline (epinephrine) from the adrenal medulla, and the elevation of urinary catecholamines. Insulin alone produced a 60–70% fall in blood glucose and NEFA, 70% depletion of adrenal epinephrine, a 10-fold increase in urinary epinephrine, and a 2-fold elevation of adrenal dopamine. Concurrent administration of hydrochloride salts completely abolished all clinical manifestations that usually accompany insulin injection. Serum glucose and NEFA remained unchanged, the fall in adrenal epinephrine was blocked, and the increase in urinary catecholamines was abolished. These data suggest that certain hydrochloride salts possess an anti-insulin property. They decrease tissue responsiveness to insulin, thus rendering its action ineffective. The implication of these findings on the treatment of diabetic subjects requiring insulin therapy is discussed.
Autoradiographic Evidence for Insulin and Insulin-Like Growth Factor Binding to Early Mouse Embryos
Authors: Mattson Britta A , Rosenblum I Y , Smith Robert M , Heyner Susan
Published: September 2013

Insulin binding to mouse oocytes and preimplantation embryos was assessed by light-microscopic autoradiography. Significant insulin binding was present on the cells of morulae and increased twofold at the blastocyst stage of development. Insulin binding was markedly decreased by native insulin and to a lesser extent by insulin-like growth factors (IGFs). No specific insulin binding was detected on oocytes or embryos throughout the eight-cell stage. Specific binding of IGF-I and IGF-II was also observed on the cells of blastocyst outgrowths. The findings demonstrate that specific binding of insulin and IGF is temporally expressed on the cells of pre- and peri-implantation mouse embryos. These results confirm and extend our previous immunofluorescence study.
Day-Long Integrated Serum Insulin and C-Peptide Profiles in Patients With NIDDM: Correlation With Urinary C-Peptide Excretion
Authors: Garvey W Timothy , Olefsky Jerrold M , Rubenstein Arthur H , Kolterman Orville G
Published: September 2013

To determine whether non-insulin-dependent diabetes mellitus (NIDDM) is characterized by day-long hypoinsulinemia, we measured 24-h serum profiles for glucose, insulin, and C-peptide by use of a constant-rate blood-withdrawal technique in diabetic and control subjects fed isocaloric meals. When only lean subjects were considered, diabetic subjects (relative body weight 0.99 ± 0.3) and control subjects (relative body weight 0.95 ± 0.03) had similar 24-h integrated serum insulin concentrations (13.4 ± 2.5 vs. 16.1 ± 2.0 μU/ml, P NS) due to the offsetting effects of increased basal levels and decreased postprandial responses in NIDDM. In contrast, both basal and meal-stimulated insulin levels were decreased in obese NIDDM subjects (relative body weight 1.39 ± 0.07) compared with obese control subjects (relative body weight 1.60 ± 0.08), resulting in a 61% reduction in the 24-h integrated insulin value (18.7 ± 1.5 vs. 48.4 ± 13.7 μU/ml). Thus, the capacity to increase 24-h integrated serum insulin as a function of relative body weight was impaired in NIDDM subjects (r = 0.27, P NS) compared with control subjects (r = .70, P < .01). In contrast, 24-h integrated C-peptide was decreased (P < .01) in both lean (0.92 ± 0.13 pM/ml) and obese (1.52 ± 0.19 pM/ml) NIDDM patients compared with the respective control groups (1.50 ± 0.13 and 3.03 ± 0.44 pM/ml). The molar ratio of 24-h integrated C-peptide to insulin was diminished in lean but not obese NIDDM compared with control subjects. A 3-wk period of intensive insulin therapy led to normalization of the mean 24-h integrated insulin (but not integrated serum C-peptide) value in NIDDM compared with a control group that had an identical mean relative body weight. The 24-h urinary C-peptide measured on the same day as the serum profile was correlated (P < .01) with both the 24-h integrated serum insulin (r = .69) and C-peptide (r = .67) concentrations in control subjects but not in NIDDM subjects (r = .20 and .04, respectively, P NS). Additionally, the urinary clearance of C-peptide was increased in NIDDM (38.1 ± 7.8 vs. 20.4 ± 1.7 ml/min in control subjects, P < .05) and varied with treatment status (26.0 ± 4.6 ml/min after insulin therapy). We conclude that in NIDDM, 1) lean but not obese untreated patients can have normal 24-h integrated serum insulin values due to the combination of high fasting and decreased postprandial levels, 2) 24-h integrated C-peptide values are decreased in both lean and obese patients, 3) intensive therapy normalizes 24-h integrated serum insulin but not C-peptide levels, and 4) urinary Cpeptide per se cannot be used as an index of insulin secretion because urinary C-peptide clearance is elevated and varies with treatment status.
Plasma Lipolytic Activity: Relationship to Postheparin Lipolytic Activity and Evidence for Metabolic Regulation
Authors: Eckel Robert H , Goldberg Ira J , Steiner LaDonna , Yost Trudy J , Paterniti James R
Published: September 2013

Lipolytic activity was measured in human plasma without prior administration of intravenous heparin. Eluted from heparin-Sepharose in a barbital buffer containing 6 mg/ml heparin, plasma lipolytic activities in 20 subjects were distributed between hepatic triglyceride lipase (HTGL, mean ± SE 60.6 ± 4.6%) and extrahepatic lipoprotein lipase (LPL, 39.4 ± 4.6%). Confirmation of the identities of HTGL and LPL was provided by inhibitory antisera. Preheparin LPL activity was absent in plasma from a patient with type I hyperlipoproteinemia. Both preheparin HTGL and LPL activities correlated with the respective activities measured in plasma obtained 15 min after intravenous injection of heparin (rs = + .774 and +.685, respectively; n = 12). Evidence for the metabolic regulation of preheparin lipases was provided by measurement of significant increases in LPL and HTGL activities after oral glucose ingestion. Overall, preheparin plasma HTGL and LPL activities may reflect ongoing lipoprotein lipolytic activity in tissue beds, and because these measurements do not require the administration of intravenous heparin, they should prove useful for additional studies of short-term regulation of the lipases.
Binding of Cytoplasmic Islet Cell Antibodies Is Blocked by Human Pancreatic Glycolipid Extracts
Authors: Colman Peter G , Nayak Ramesh C , Campbell Iain L , Eisenbarth George S
Published: September 2013

With biochemical and enzymatic treatment of frozen sections of pancreas, we have previously shown that cytoplasmic islet cell antibodies (ICAs) react with carbohydrate determinants of islet cell glycoconjugates. As a first step toward purifying these glycoconjugates, human pancreas tissue was extracted in a mixture of chloroform and methanol, and the glycolipids were obtained by effecting a Folch partition. The protein pellet, lipid fraction, and glycolipid fraction so obtained were assessed for their ability to block the binding of ICAs to frozen sections of human pancreas, the effect being quantitated with a photometer. Only the glycolipid extract could block ICA binding, and blocking was dose dependent. Subfractionation of the glycolipid extract by hydrophobic interaction on C18 cartridges demonstrated that blocking activity resided in the fraction bound and eluted with methanol, consistent with the autoantigen being a glycolipid. Furthermore, the binding of an anti-islet cell ganglioside monoclonal antibody, 3G5, could be blocked with these extracts, whereas the binding of an anti-islet cell protein monoclonal antibody, 4F2, was unaffected. The major gangliosides of the pancreas were seen to be GM3 and GD3 by thin-layer chromatography (TLC). Fractions scraped and eluted from TLC plates were tested for their ability to block ICA binding to pancreatic sections. Neither GM3- nor GD3-containing fractions could block ICA binding; however, a fraction containing minor pancreatic gangliosides (including GM2) of monosialoganglioside mobility was a potent inhibitor of ICA binding to pancreas sections. TLC of a chloroform-methanol extract of human islets demonstrated that islets differentially express monosialogangliosides (especially GM2). These findings suggest that the islet cell autoantigen in frozen sections is a glycolipid migrating with a mobility characteristic of a monosialoganglioside.
Insulin Resistance by Uncleaved Insulin Proreceptor: Emergence of Binding Site by Trypsin
Authors: Kobayashi Masashi , Sasaoka Toshiyasu , Takata Yasumitsu , Hisatomi Akitaka , Shigeta Yukio
Published: September 2013

Two sisters presented with severe insulin resistance and markedly decreased insulin binding to erythrocytes, cultured fibroblasts, and transformed lymphocytes. The dose-response curve of insulin-stimulated amino acid uptake in the fibroblasts was shifted to the right. The molecular weight of the insulin receptor on the transformed lymphocytes from the patients was 210,000 and could not be dissociated to α- and β-subunits by dithiothreitol treatment. However, the proreceptor was cleaved by trypsin, and this led to production of a 135,000-Mr α-subunit. Insulin binding to the trypsin-treated cells increased to the normal level, and insulin action was normalized. These results suggest that the failure of proreceptor cleavage produces hormone-resistant states and that a proreceptor syndrome may be a unique disease entity for hormone resistance.
Influence of Circulating Epinephrine on Absorption of Subcutaneously Injected Insulin
Authors: Fernqvist Eva , Gunnarsson Rolf , Linde Birgitta
Published: September 2013

Effects of epinephrine (Epi) infusion on the absorption of subcutaneously injected 125I-labeled soluble human insulin (10 U) from the thigh or the abdomen were studied in 16 healthy subjects and from the thigh in 10 insulin-dependent diabetic (IDDM) patients. Epi was infused at 0.3 (high dose) or 0.1 (low dose; healthy subjects) nmol · kg−1 · min−1 i.v., resulting in arterial plasma Epi levels of ∼6 and 2 nM, respectively. Saline was infused on a control day. Insulin absorption was measured as disappearance of radioactivity from the injection site and as appearance of plasma immunoreactive insulin (IRI). Adipose tissue blood flow was measured with the 133Xe clearance technique. First-order disappearance rate constants of 125I from the thigh depot decreased ∼40–50% during the high dose of Epi compared with control (P < .001). The corresponding decrease from the abdominal depot was ∼40% (P < .001), whereas no significant change was found during the low Epi dose. IRI fell compared with control in all groups at the high Epi dose. The Epi-induced depression of insulin absorption occurred despite unaltered or even slightly increased subcutaneous blood flow. The results indicate that circulating Epi at levels seen during moderate physical stress depresses the absorption of soluble insulin from subcutaneous injection sites to an extent that might be important for glycemic control in IDDM patients. Furthermore, dissociation is found between changes in insulin absorption and subcutaneous blood flow during Epi infusion, suggesting that factors other than blood flow may also influence the absorption of subcutaneously injected insulin.
Changes in Low-Km cAMP Phosphodiesterase Activity in Liver Golgi Fractions from Hyper- and Hypoinsulinemic Rats
Authors: Benelli Chantal , Lopez Soledad , Desbuquois Bernard , Achagiotis Christiane
Published: September 2013

Acute insulin treatment in rats has recently been shown to cause a rapid increase in liver low-Km cAMP phosphodiesterase (PDE) activity, which selectively affects Golgi fractions. To assess the physiological significance of this observation, the cAMP PDE activity associated with liver Golgi fractions has been measured in genetically obese Zucker rats, which spontaneously develop hyperinsulinemia, in rats receiving a continuous infusion of insulin, and in rats treated with anti-insulin serum. In genetically obese Zucker rats, a significant increase in Golgi-associated cAMP PDE relative to age-matched lean animals occurred after 3 wk, coinciding with the development of hyperinsulinemia. This change was maximal at 5–8 wk and affected the light (Gl) and intermediate (Gi) GolGi fractions (100–110% increase) to a greater extent than the heavy (Gh) fraction (30% increase). After 7 wk, despite the further increase in insulinemia, the increase in GolGi-associated cAMP PDE became progressively less marked, and at 18 wk it was no longer detectable except in Gh, suggesting the development of a hepatic insulin resistance. Infusion of insulin through chronically implanted intracardiac catheters led to a 30–50% increase in GolGi-associated cAMP PDE, which occurred earlier in Gi (3 h) than in Gh (7 h) and persisted for > 96 h. Injection of anti-insulin serum led to a 30–50% decrease in GolGi-associated cAMP PDE, which occurred sequentially in Gl (5 min), Gi (15 min), and Gh (30 min) and affected predominantly Gl and Gh. These results suggest that the cAMP PDE associated with GolGi fractions is a physioloGical effector of plasma insulin in vivo.
HLA Class I and II Antigens in South African Indians With NIDDM
Authors: Omar Mahomed A K , Hammond Michael G , Motala Ayesha A , Seedat Mahomed A
Published: September 2013

The relationship between the HLA system and non-insulin-dependent diabetes mellitus (NIDDM) in South African Indians, a migrant Indian group, was evaluated by testing HLA-A, -B, and -C antigens in 184 patients and 1444 control subjects and HLA-DR antigens in 104 patients and 330 control subjects. There was a significant increase in the frequency of HLA-Bw61 in patients compared with control subjects (27.7 vs. 18%, P = .00155), although the degree of association was not very strong (relative risk 1.7). A similar association has been noted in Fiji Indians, another migrant Indian group. However, no relationship could be established at the DR locus. It is suggested that the relatively high frequency of the Bw61 allele in South African Indians could, in the presence of some environmental factor like obesity, confer increased susceptibility to NIDDM.
Effect of Bacitracin on Binding and Processing of Insulin by Established Renal Cell Line
Authors: Yagil Chana , Frank Bruce H , Rabkin Ralph
Published: September 2013

The effect of bacitracin on the binding and processing of 125I-labeled insulin was studied in a proximal tubular epithelium-like opossum kidney cell line. This cultured cell line handles insulin in a manner comparable to the in vivo situation, which requires membrane binding, internalization, and intracellular degradation. The addition of bacitracin inhibited insulin degradation significantly and delayed the time of appearance of products in the medium (22 min) compared with control cells (14 min). Maximum total cell-associated radioactivity increased from 1.5 ± 0.19% in the control cells to 2.5 ± 0.17% in the treated cells. Separation of cell membrane from internalized radioactivity was achieved by acid washing and showed no change in membrane-bound radioactivity or rate of internalization, but a significant increase in intracellular radioactivity was noted. Gel-filtration chromatography revealed that this was due to an accumulation of chromatographically intact insulin. Accordingly, we conclude that bacitracin inhibits insulin degradation in cultured kidney cells by perturbing the intracellular processing of insulin, not by altering the binding or internalization of the hormone or by inhibiting the release of small degradation products. Because of the multiple actions of this agent, the exact site in these kidney cells at which intracellular degradation is inhibited remains to be established. However, in contrast to studies with lysosomes isolated from cells of other tissues, this study showed that when lysosomes isolated from rat renal cortex were exposed to bacitracin, insulin degradation was inhibited markedly (81%).
Diabetic Retinopathy in Mexican Americans and Non-Hispanic Whites
Authors: Haffner Steven M , Fong Donald , Stern Michael P , Pugh Jacqueline A , Hazuda Helen P , Patterson Judith K , Van Heuven W A J , Klein Ronald
Published: September 2013

Mexican Americans (MAs) have a threefold greater prevalence of non-insulin-dependent diabetes mellitus (NIDDM) than non-Hispanic Whites (NHWs). Because MA diabetic subjects have greater hyperglycemia and an earlier age of onset than NHW diabetic subjects, we postulated that diabetic MAs might also have more severe diabetic retinopathy. Stereoscopic retinal photographs of the seven standard fields of each eye were taken in 257 MAs and 56 NHWs with NIDDM. The photographs were read by the University of Wisconsin Fundus Photographic Reading Center and graded with standardized criteria. The MAs had a nonsignificantly increased risk of retinopathy relative to the NHWs [odds ratio (OR) = 1.71; 95% confidence interval (CI) = (0.93, 3.17)]. The risk of severe retinopathy (proliferative or preproliferative) relative to background or no retinopathy was significantly greater in MAs than in NHWs [OR = 2.37; 95% CI = (1.04, 5.39)]. After control by logistic regression for duration of disease, severity of hyperglycemia, age, and systolic blood pressure, MAs still had an increased risk of severe retinopathy relative to NHWs [OR = 3.18; 95% CI = (1.32, 7.66)]. Severe retinopathy was related to duration of disease, hyperglycemia, and insulin therapy in both ethnic groups. Previously diagnosed MA diabetic subjects also had an increased prevalence of any retinopathy [OR = 2.39; 95% CI = (1.63, 3.50)] and severe retinopathy [OR = 3.21 ; 95% CI = (2.24, 4.59)] relative to previously diagnosed White diabetic subjects (n = 896) from Wisconsin. The combination of an increased prevalence of NIDDM in MAs plus an increased severity of retinopathy in those MAs who have diabetes suggests that a major public health effort should be made to screen this ethnic group for retinopathy.
Prospective Study of Predictors of β-Cell Survival in Type I Diabetes
Authors: Schiffrin Alicia , Suissa Samy , Poussier Philip , Guttmann Ronald , Weitzner Gabriel
Published: September 2013

We conducted a prospective study to describe the course of the pancreatic β-cell function from the time of clinical diagnosis of insulin-dependent (type I) diabetes to determine whether DR type, presence of islet cell antibodies (ICA), presence of insulin antibodies (IA), age at onset, and sex could help in the prediction of residual endogenous insulin secretion. A cohort of 68 children was followed for 18 mo after diagnosis of type I diabetes. The outcome variables selected for analysis were 1)serum C-peptide peak concentration after a Sustacal meal, 2) time of disappearance of the serum C-peptide response, and 3) time after diagnosis at which the maximal serum C-peptide response was observed. After institution of insulin therapy, serum C-peptide peak concentrations rose temporarily for 1–6 mo and declined thereafter. Multivariate analysis of the data showed that DR type (P = .2488) and presence of IA (P = .1604) had no effect on serum C-peptide over time, but sex (P = .0146), age at onset (P = .0002), and presence of ICA (P = .0147) significantly contributed to the variation of serum C-peptide over time. Furthermore, age at onset, presence of ICA, and sex were also the only significant predictors of the time of disappearance of the β-cell function. The relative risks of β-cell-function disappearance were 0.87 (P = .0015), 9.43 (P = .0181), and 2.25 (P = .0468), respectively. In conclusion, there are distinct variations in the natural course of the β-cell function in type I diabetes. β-Cell-function survival is significantly shortened the younger the subject is at disease onset, if ICA are present at diagnosis, and if the subject is male.
Administration of Silica Particles or Anti-Lyt2 Antibody Prevents β-Cell Destruction in NOD Mice Given Cyclophosphamide
Authors: Charlton Brett , Bacelj Angela , Mandel Thomas E
Published: September 2013

The cellular pathway of β-cell destruction in type I (insulin-dependent) diabetes is still undefined. L3T4+ T-lymphocytes have a role in both the initiation of insulitis and in recurrent disease in transplanted allogeneic islets in nonobese diabetic (NOD) mice. The roles of macrophages and Lyt2+ T-lymphocytes in β-cell destruction were studied in cyclophosphamide-induced diabetic NOD mice with silica particles and a rat anti-Lyt2 monoclonal antibody. After administration of cyclophosphamide, 10 of 26 untreated mice and 1 of 21 anti-Lyt2-treated mice became diabetic. Insulitis was significantly reduced in anti-Lyt2-treated mice, and immunocytochemical staining showed a lack of Lyt2+ cells. Only 1 of 19 silica-treated mice became diabetic, compared to 8 of 19 control mice. This study demonstrates that both Lyt2+ T-lymphocytes and macrophages are necessary, but not sufficient, for β-cell destruction in NOD mice. Therefore, we propose that macrophages present β-cell antigen to L3T4+ cells, which induce cytotoxic Lyt2+ cells to specifically destroy β-cells.
Immunological Abnormalities in Insulin Receptors on Cultured EBV-Transformed Lymphocytes From Insulin-Resistant Patient With Leprechaunism
Authors: Cama Alessandro , Marcus-Samuels Bernice , Taylor Simeon I
Published: September 2013

Defects in insulin-receptor structure can impair insulin-receptor function. We have previously identified qualitative abnormalities in insulin binding to insulin receptors from an insulin-resistant patient (Lep/Ark-1). The defects in insulin binding are probably caused by a defect in receptor structure. In this study, we used immunological probes to investigate the structural defect(s) responsible for the abnormal function. Several anti-receptor antibodies were impaired in their abilities to bind to the insulin receptor of Lep/Ark-1. For example, monoclonal antibody MoAb-51 was much less effective in inhibiting binding to insulin receptors from Lep/Ark-1 (ID50 70 nM) than to those of normal subjects (ID50 8 nM). In addition, there was a 10-fold reduction of the avidity with which human polyclonal antibody B-d immunoprecipitated the patient's insulin receptors. The avidity of antibody B-10 was also reduced, although to a lesser extent. In contrast, several site-specific antibodies against epitopes on the β-subunit of the receptor bound to receptors from Lep/Ark-1 with normal avidity. The data with monoclonal and polyclonal antibodies are consistent with the hypothesis that the structural defect resides in the extracellular domain of this patient's insulin receptor. The normal immunoreactivity of two putative phosphorylation sites on the β-subunit with site-specific antibodies gives further support to the conclusion that this patient's receptors have normal tyrosine kinase activity.
Observations on Offspring of Mice Made Diabetic With Streptozocin
Authors: Steele E J
Published: September 2013

My objective was to determine the effect of streptozocin (STZ)-induced diabetes in male inbred mice on nonfasting blood glucose levels and body weights of offspring. Hyperglycemia was induced in CBA/H male mice by either multiple subdiabetogenic doses (MD) of STZ (5 doses/day of 50 mg STZ/kg body wt) or by a single high sublethal (SD) dose (200 mg STZ/kg body wt). Females were made diabetic by the multiple low-dose procedure. The following matings were set up: SD males with normal (NOR) females; MD males with NOR females; NOR males with MD females; MD males with MD females. Controls were matings of NOR males with NOR females. Among the first cohort of litters was born one female from the cross of an SD male with an NOR female who became spontaneously hyperglycemic at 5 wk of age; the female progeny of this cross had significantly lower body weights. All other progeny groups were normoglycemic (up to 5 wk) and had normal body weights. Test progeny weaned in the second and subsequent cohorts of litters were also normoglycemic. The major effect in this progeny group was on body weight; diabetic fathers (particularly MD males) mated with NOR females produced offspring with significantly higher juvenile body weights than the controls (increase of ∼0.5 g). These body-weight distributions also appeared more homogeneous than the more variable body-weight distribution of the controls. In contrast, MD mothers (mated with NOR males) produced second-cohort offspring with significantly lower average body weights (decrease of ∼1–2 g) than the controls. However, if MD females were mated with MD males, the second-cohort offspring had body-weight distributions that approached those observed in control progeny or in progeny where the father alone was diabetic. The mechanism and biological significance of this complex STZ-induced paternal transmission effect is unknown, although general possibilities are discussed.
Interaction of Sulfonylureas With Pancreatic β-Cells: A Study With Glyburide
Authors: Gorus Frans K , Schuit Frans C , Veld Peter A In't , Gepts Willy , Pipeleers Daniel G
Published: September 2013

In this study on purified rat pancreatic β-cells, we show that the second-generation sulfonylurea glyburide stimulates insulin release through a direct interaction with the β-cells. During static incubations, 2 μM glyburide releases 0.16 pg insulin per β-cell, which corresponds to a half-maximal glucose stimulation. This effect occurs independently from the glucose-recognition unit, being detectable at both nonstimulatory and stimulatory glucose concentrations and proceeding without alterations in the rate of glucose oxidation. The secretagogue action of glyburide appears not to be mediated through cAMP but is potentiated by cAMP-generating substances such as glucagon (10−8 M; 0.31 pg insulin released per β-cell). Its 10-fold higher potency in isolated islets is attributed to the markedly higher cAMP levels that are maintained in islet β-cells under the influence of locally released glucagon. Perifused pancreatic β-cells respond to glyburide with a biphasic insulin release. After removal of the drug, the cells continue to secrete insulin at the same rate for ≥ 30 min. This prolonged secretory activity coincides with a cellular accumulation of the drug, primarily in association with membranes of secretory vesicles and mitochondria. Tolbutamide also stimulates insulin release from pure β-cells, but it is less powerful on a molar basis and does not lead to a sustained hormone release after its removal from the extracellular medium. We conclude that the hypoglycemic action of glyburide is at least partly the result of a direct interaction with pancreatic β-cells. The insulin-releasing action of the drug has been shown to occur independently of both the nutrient-dependent and the cAMP-generating regulatory units but to vary markedly with the cellular cAMP content and with the prolonged and possibly intracellular actions of the drug.
Incidence of IDDM in Montreal by Ethnic Group and by Social Class and Comparisons With Ethnic Groups Living Elsewhere
Authors: Siemiatycki Jack , Colle Eleanor , Campbell Sally , Dewar Ron , Aubert Denis , Belmonte Mimi M
Published: September 2013

We examined the incidence of insulin-dependent diabetes mellitus (IDDM) among children aged 0–14 yr in Montreal by social class and by ethnic group from 1971 to 1985. There was a slightly higher risk in wealthier as opposed to poorer classes. This income gradient was more marked in younger than in older children. Children of French extraction had about two-thirds the risk of IDDM of children of other origins, mainly British and other European. This mimics the patterns of risk in Europe, where France is reported to have lower rates than does Britain and Scandinavia. The absolute levels of risks among French Canadian and Jewish Canadian children were about double those reported from France and Israel, respectively. These various results are compatible with the hypothesis that both genetic and environmental factors influence IDDM risk.
Cyclo(His-Pro) Concentration: Changes in Brain Striatum of Hyperglycemic Rat
Authors: Mori Masatomo , Iriuchijima Tokuji , Yamada Masanobu
Published: September 2013

We scrutinized whether the hyperglycemic status changed the concentration of prototype neuropeptides cyclo(His-Pro) and thyrotropin-releasing hormone (TRH) in the rat brain. Streptozocin-induced hyperglycemia caused a significant increase in cyclo(His-Pro) concentration in the striatum but not in the other brain regions, whereas TRH concentration in any brain region did not differ between control and hyperglycemic groups. Insulin injection normalized blood glucose level and prevented an increase in cyclo(His-Pro) concentration after hyperglycemia. These data indicate that hyperglycemia causes a profound alteration in cyclo(His-Pro) concentration in the rat brain striatum.
Use of Liposomes to Introduce Substances Into Pancreatic Islet Cells
Authors: Welsh Nils , Hallberg Anders , Sandler Stellan , Hellerström Claes
Published: September 2013

The liposome technique is widely used to transport substances that cannot normally traverse the plasma membrane into the cell. The interactions of liposomes with the plasma membrane of pancreatic islet cells have not previously been studied. We evaluate the suitability of the liposome technique for introducing substances into the pancreatic β-cell to which the cell membrane is impermeable. Liposomes were synthesized with an ether-injection method, and the cell-liposomal interactions were investigated by means of radioactive labeling and the fluorescent aqueous space marker 6-carboxyfluorescein. Experiments were performed on freshly isolated mouse pancreatic islets and on free islet cell preparations. With fluorescence microscopy, liposomes were observed to fuse spontaneously with islet cells, and the corresponding internalized volumes were quantified with spectrofluorometric measurements. The liposome association with islets and islet cell suspensions, as assessed by radioactive labeling, was found to increase with the liposome concentration. The effects of liposome membrane lipid composition on the fusion rate were found to be decreased in the presence of glucolipid. In addition, polyethylene glycol failed to affect the liposomal uptake. Freshly isolated islets incubated with liposomes containing glucose 6-phosphate were observed to release slightly more insulin than islets incubated with “empty” liposomes. In conclusion, liposomes fuse spontaneously with islet cells in vitro, and the uptake of liposomes is regulated by the lipid composition of the liposomal bilayer and the amount of liposomes present. The function of the β-cell can be altered with the liposome technique, e.g., by addition of biologically active molecules such as glucose 6-phosphate.
Diet-Induced Type II Diabetes in C57BL/6J Mice
Authors: Surwit Richard S , Kuhn Cynthia M , Cochrane Christina , McCubbin James A , Feinglos Mark N
Published: September 2013

We investigated the effects of diet-induced obesity on glucose metabolism in two strains of mice, C57BL/6J and A/J. Twenty animals from each strain received ad libitum exposure to a high–fat high-simple-carbohydrate diet or standard Purina Rodent Chow for 6 mo. Exposure to the high-fat, high-simple-carbohydrate, low-fiber diet produced obesity in both A/J and C57BL/6J mice. Whereas obesity was associated with only moderate glucose intolerance and insulin resistance in A/J mice, obese C57BL/6J mice showed clear-cut diabetes with fasting blood glucose levels of >240 mg/dl and blood insulin levels of >150 μU/ml. C57BL/6J mice showed larger glycemic responses to stress and epinephrine in the lean state than AJ mice, and these responses were exaggerated by obesity. These data suggest that the C57BL/6J mouse carries a genetic predisposition to develop non-insulin-dependent (type II) diabetes. Futhermore, altered glycemic response to adrenergic stimulation may be a biologic marker for this genetic predisposition to develop type II diabetes.
Inhibition of Insulin-Stimulated Glucose Transport by Factor Extracted From Serum of Insulin-Resistant Patient
Authors: Misbin Robert I , Green Allan , Alvarez Idania M , Almira Ernesto C , Dohm G Lynis , Caro Jose F
Published: September 2013

We report a 31-yr-old nondiabetic male patient with acanthosis nigricans whose hyperinsulinemia and insulin resistance could not be explained by anti-receptor antibodies or by an intrinsic defect of insulin binding to his cells. An acid-alcohol extract of the patient's serum contained a factor that inhibited insulin-stimulated glucose transport in rat adipocytes. Low levels of the factor could be detected in 9 of 13 unselected patients with non-insulin-dependent diabetes. The factor was heat stable and resistant to treatment with acid, base, and various lytic enzymes. It eluted from a Bio-Gel β-2 column with an apparent molecular weight of 300. The factor also inhibited stimulation of glucose transport in adipocytes by the insulin mimickers hydrogen peroxide and sodium vanadate. In vitro incubation of rat soleus muscles in the presence of the factor resulted in inhibition of insulin-stimulated glucose transport. The factor enhanced 125I-labeled insulin binding in both adipocytes and muscle. A preparation of insulin receptors obtained from muscles incubated with serum factor showed increased binding of 125I-insulin to the α-subunit of the insulin receptor. Autophosphorylation of the β-subunit and phosphorylation of exogenous substrate were increased in the receptor preparation obtained from muscles that had been incubated with serum factor. However, the increase in kinase activity was approximately the same as the increase in binding activity. No difference in kinase activity was observed when assayed under conditions in which 125I-insulin binding activity had been equalized. These results suggest that insulin resistance in this patient was due to a circulating factor of low molecular weight that uncoupled insulin stimulation of glucose transport from receptor binding and phosphorylation. The factor appears to increase the binding activity of the α-subunit of the insulin receptor without affecting the kinase activity of the β-subunit.
Long-Term Follow-Up of Polyneuropathy in Diabetic Kidney Transplant Recipients
Authors: Van Der Vliet J Adam , Navarro Xavier , Kennedy William R , Goetz Frederick C , Barbosa Jose J , Sutherland David E R , Najarian John S
Published: September 2013

Nerve conduction and electromyography (EMG) of insulin-dependent (type I) diabetic patients with end-stage nephropathy was studied before and up to 10 yr after kidney transplantation (KTx). A series of nondiabetic KTx patients served as a comparison group. Motor nerve conduction velocity (NCV) was measured in the ulnar, median, peroneal, and tibial nerves; sensory NCV was measured in the median nerve. EMG was performed in the first dorsal interosseus, flexor carpi radialis, anterior tibialis, and gastrocnemius muscles. In 68 pre-KTx diabetic patients, the mean NCV was below normal in all nerves, and the mean amplitudes of the evoked muscle action potential (MAP) were low normal in the upper extremity and below normal in the lower extremity. The values of the comparison group were within the normal range. At 1 (n = 57), 5 (n = 23), and 10 (n = 10) yr after KTx, the mean NCV of the diabetic patients remained essentially unchanged, but MAP amplitudes of all muscles had declined. EMG revealed progression of the denervation process, especially in muscles of the lower extremities. We conclude that diabetic neuropathy continues to progress by a progressive axonal loss after correction of uremia by KTx.
Effect of Hyperglycemia on Pain Perception and on Efficacy of Morphine Analgesia in Rats
Authors: Raz Itmar , Hasdai David , Seltzer Zeev , Melmed Raphael N
Published: September 2013

The effect exerted by different hyperglycemic states on the pain threshold and on the analgesic potential of morphine was studied in male Sabra rats with the hot plate device. Hyperglycemia induced by an intraperitoneal injection of 0.014 mol/kg glucose or an acute or chronic diabetic state induced by streptozocin injection did not significantly alter the pain threshold. However, states of acute and chronic diabetes markedly blunted the analgesic effect of morphine (5 mg/kg). Sabra rats maintained on a cocktail of glucose-saccharin, thought to activate the release of endogenous opioids, demonstrated an increased pain threshold and rapidly developed resistance to the analgesic effect of morphine. Previous studies have shown that glucose in high concentration may interfere with the interaction of morphine on the opiate receptor. The influence of the diabetic state on β-endorphin synthesis and concentration in the central nervous system is another factor that might change pain perception in diabetes. We propose that in diabetes, generally, the pain threshold is adequately maintained, despite the antagonistic effect of glucose, partly due to a compensatory increased secretion of endogenous opioid peptides. We hypothesize that in patients with chronic painful diabetic neuropathy, these normal analgesic response mechanisms may be overwhelmed either by an excess of nociceptive impulses from diseased peripheral nerves or conceivably by a failure of endogenous opioid secretory response to the hyperglycemia.
Effect of Vitamin E Supplementation on Platelet Thromboxane A2 Production in Type I Diabetic Patients: Double-Blind Crossover Trial
Authors: Gisinger Christoph , Jeremy Jamie , Speiser Paul , Mikhailidis Dimitri , Dandona Paresh , Schernthaner Guntram
Published: September 2013

Vitamin E deficiency is associated with increased platelet aggregation, which can be normalized through vitamin E supplementation. In diabetes, increased platelet thromboxane A2 (TXA2) production is correlated with decreased platelet vitamin E content. We therefore investigated the effect of 400 mg DL-α-tocopherol acetate daily for 4 wk on ADP- and collagen-induced platelet aggregation and platelet TXA2 production in 22 type I (insulin-dependent) diabetic patients without macroangiopathy and with no or only minimal microangiopathy by a double-blind placebo-controlled crossover study. Platelet aggregation was induced in platelet-rich plasma by two or three different concentrations of ADP and collagen. TXA2 was measured by the stable spontaneous breakdown product thromboxane B2 by a specific radioimmunoassay. Whereas metabolic control remained unchanged during the study period, platelet TXA2 production was significantly (P < .05 and P < .01) reduced at each ADP concentration and at two of three collagen concentrations. Because increased TXA2 production of diabetic platelets is thought to play an important pathogenetic role in diabetic angiopathy, we conclude that vitamin E treatment could be beneficial with respect to platelet–vessel-wall interaction and thus might be promising for the prevention of diabetic angiopathy.
Phosphoinositide Hydrolysis and Insulin Release From Isolated Perifused Rat Islets: Studies With Glucose
Authors: Zawalich Walter S , Zawalich Kathleen C
Published: September 2013

The ability of glucose to promote the hydrolysis of pre I a be led [2-3H]inositol-containing phosphoinositides (PI) was assessed by measuring the efflux of 3H in response to glucose and the accumulation of labeled inositol phosphates. The inclusion of nonradioactive inositol (1 mM) in the perifusion medium dramatically improved our ability to monitor glucose-induced increases in 3H efflux. Efflux studies with this method revealed the following. 1) 3H efflux is significantly greater at 7 than at 2.75 mM glucose, and this parallels a small but significant increase in insulin secretion. 2) D-manno-Heptulose reduces 3H efflux with 7 mM glucose to a level approximating that seen in the presence of 2.75 mM glucose and has no effect on 3H efflux with 2.75 mM glucose. 3) In the presence of 20 mM glucose plus 1 mM inositol, 3H efflux is rapid and biphasic, a response that parallels the timing and amplitude of the biphasic pattern of insulin secretion. Direct measurements of labeled inositol and inositol phosphate levels in islets revealed the following. 4) After 50 min of perifusion with 2.75 or 7 mM glucose, labeled inositol phosphates were significantly greater with 7 mM glucose. 5) In response to 20 mM glucose alone, islet levels of free inositol, inositol monophosphate (IP,), and inositol bisphosphate (IP2) increased. 6) In response to 20 mM glucose plus 1 mM cold inositol, islet levels of free inositol increased, whereas islet levels of IP1, IP2, and inositol trisphosphate (IP3) were reduced compared with values obtained with 20 mM glucose alone. 7) In response to perifusion with 20 mM glucose, IP3 accumulation was biphasic in nature, and this response precedes the biphasic pattern of both insulin output and 3H efflux by several minutes. These results suggest that PI hydrolysis in islets is tightly regulated by the ambient glucose level and that second-messenger signals generated by activation of this pathway may contribute to the biphasic pattern of glucose-induced insulin secretion.
Release of Glomerular Heparan-35SO4 Proteoglycan by Heparin From Glomeruli of Streptozocin-Induced Diabetic Rats
Authors: Klein David J , Oegema Theodore R , Brown David M
Published: September 2013

Abnormalities in the incorporation of heparan sulfate proteoglycan into the glomerular basement membrane have been implicated in the pathogenesis of various proteinuric states, including diabetes mellitus. To understand further the interactions between proteoglycans and glomerular extracellular matrices, glomeruli were isolated from normal and streptozocin-induced diabetic rats after in vivo exposure to 35S-labeled sulfate and were treated with heparin in vitro. Heparin treatment released a unique heparan sulfate proteoglycan from glomerular cell surface or extracellular matrix proteoglycan receptors. Another, smaller heparan sulfate proteoglycan was the most abundant proteoglycan released into medium and was released constitutively in medium with or without added heparin. While the two heparin-extracted proteoglycans copurified on anion-exchange and gelfiltration chromatographic columns, they were resolved by composite 0.6% agarose–1.8% polyacrylamide gel electrophoresis. Glomeruli from diabetic rats contained decreased proportions of the heparin-releasable heparan sulfate proteoglycan and more constitutively released heparan sulfate proteoglycan. The apparent molecular weight and intrinsic charge of the heparin-released proteoglycan mixture and the apparent molecular weight and sulfation pattern of their 35S-labeled glycosaminoglycan chains after nitrous acid deaminative cleavage were similar in the two groups. A brief trypsin digestion of heparin-treated glomeruli released proportionately less integral membrane and extracellular matrix 35S-labeled proteoglycans and 35S-labeled glycopeptides from diabetic glomeruli than from control glomeruli. Elution of these 35S-labeled macromolecules from anion-exchange columns and migration in agarose-polyacrylamide gels were similar in the two groups. Abnormalities in proteoglycan-matrix interactions or proteoglycan processing may account for changes in the proportions of heparin- and trypsin-extracted proteoglycan compartments in diabetes