bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth of Neonatal Islet Transplants in the Spontaneously Diabetic BB/Wor Rat
Authors: Serie Janet R , Cooper Hanna N , Kemmer Kathleen A , Hegre Orion D
Published: September 2013

We have previously shown that culture-isolated neonatal islets are able to survive both rejection and the recurrence of autoimmunity in the spontaneously diabetic BB/Wor rat. In trials designed to demonstrate the MHC restriction of the autoimmune response in this model, we discovered that neonatal islet graftsfrom diabetic BB rats appeared larger than grafts from nondiabetic controls. This study was undertaken to quantify the mass difference seen in this original study and to determine the characteristics of graft growth in more highly controlled trials. Grafts from diabetic animals in the original study were significantly larger than those from nondiabetic animals (81 ± 36 vs. 238 ± 216 μg, P = 0.01). These findings were supported by results from a second series of experiments, in which the mean growth index of grafts from diabetic animals was 7.25 ± 4.91, whereas that from nondiabetic animals was 2.5 ± 1.15 (P = 0.011). Three animals in this study were reversed of hyperglycemia: two had normal and one had a subdiabetic ip GTTs. These three rats received 97, 317, and 408 ng of islet tissue that increased in mass to 1790, 3270, and 4107 fig, respectively. Nuclear/total cell area percentages were the same in diabetic and nondiabetic grafts (P = 0.76), suggesting that the increase in mass was attributable primarily to proliferation rather than hypertrophy. Limited studies that use BrDU incorporation support this conclusion. High glucose levels have been shown to stimulate β-cell replication in fetal, neonatal, and adult islets and may be the stimulus for enhanced graft growth in this model. This study shows that small, immunomodulated neonatal grafts placed in the diabetic environment of the spontaneously diabetic BB/Wor rat can increase in mass >10-fold and can ameliorate the symptoms of diabetes.
Cerebral Taurine Transport Is Increased During Streptozocin-Induced Diabetes in Rats
Authors: Trachtman Howard , Futterweit Stephen , Sturman John A
Published: September 2013

Taurine is a cerebral osmolyte whose intracellular content changes in parallel with plasma osmolality. We conducted experiments to assess whether cerebral taurine transport is modified during chronic hyperglycemia. Rats with STZ-induced diabetes were studied after 1 wk of sustained hyperglycemia. Cerebral taurine uptake in synaptosomes (metabolically active nerve terminal vesicles) was measured using a rapid filtration technique. The synaptosomes were isolated by homogenization of the brain and purification on discontinuous Ficoll gradients (n = 8 synaptosome preparations). Diabetic rats (n = 13) displayed a 15–25% increase in synaptosomal taurine uptake compared with normoglycemic control animals (n = 12) at all time points assayed between 5 and 120 min. Thus, after a 30-min incubation, cerebral taurine uptake increased from a contro level of 3.53 ± 0.23 to 4.10 ± 0.24 μmol/mg protein (n = 10) in hyperglycemic rats, P < 0.03. The magnitude of the plasma-to-brain cell taurine gradient was unchanged in diabetic animals. The intrasynaptosomal taurine concentration (∼2μ μM) and taurine efflux from the synaptosomes were no different in hyperglycemic versus control rats; effluxmounted to <2.5% of the uptake value at corresponding time points. Maximal brain taurine uptake under both control and experimental hyperglycemic conditions required the presence of external Na+ and Cl−. Synaptosomal taurine transporwas reduced by competing β-amino acids such as β-alanine, β-aminoisobutyric acid, and hypotaurine (P < 0.01). Addition of oubain and the anionic binding site inhibitors, 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid and 4,4'diisothio-cyanatostilbene-2,2'-disulfonic acid, also decreased cerebral taurine uptake under normoglycemic and hyperglycemic conditions (P < 0.01). The increased synaptosomaltaurine uptake by diabetic rats was not a result of generalized membrane dysfunction because glycine transport was not elevated in hyperglycemic rats. The enhanced transport rate was attributable to a 35 and 81% increase in the Vmax of the high- and low-affinity taurine transporters, respectively (P < 0.01), without significant change in the Km of the carrier systems. Treatment of hyperglycemic rats (n = 5) with ultra-long-acting insulin to normalize the serum glucose concentration restored synaptosomal taurine uptake to the level observed in normoglycemic controls. The effect of insulin was attributable to correction of hyperglycemia, because addition of insulin (500 mU/ml) to the in vitro assay system did not alter synaptosomal taurine uptake. We conclude that taurine uptake into the brain is enhanced during chronic hyperglycemia in order to expand the cytosolic pool of this osmoprotective molecule and limit brain cell shrinkage during this hyperosmolal condition. This adaptation in taurine transport, mediated by increased activity of the β-amino acid carrier system, is reversible because insulin therapy that achieves euglycemia prevents the change.
Identification and Characterization of Aldose Reductase in Cultured Rat Mesangial Cells
Authors: Kikkawa Ryuichi , Umemura Kisaburo , Haneda Masakazu , Kajiwara Nobuyuki , Maeda Shiro , Nishimura Chihiro , Shigeta Yukio
Published: September 2013

Although the enhanced activity of the polyol pathway has been detected in diabetic glomeruli, the intraglomerular localization of this pathway has not yet been well defined. In this study, we attempted to identify aldose reductase, a key enzyme of the polyol pathway, in cultured rat mesangial cells and to characterize the properties of this enzyme using enzymological and immunological methods. When the aldose reductase (DL-glyceraldehyde-reducing) activity was analyzed in mesangial cell extract, the Lineweaver-Burk plot showed concave downward curvature, and the Michaelis constant was 0.83 mM DL-glyceraldehyde, and this activity was noncompetitively inhibited by an aldose reductase inhibitor, ICI-128,436. The enzyme activity was enhanced by the addition of sulfate ion and partially suppressed by barbital. The enzyme cross-reacted with the antisera against rat lens and testis aldose reductases on Ouchterlony plate, and migrated to the region of molecular weight of about 36,500 Da on Western blotting. The presence of aldose reductase mRNA was also confirmed by Northern analysis using cDNA for rat aldose reductase, 10Q. From these results, it was concluded that the aldose reductase may exist in rat glomerular mesangial cells and may play a role in the development of diabetic glomerulopathy, though the coexistence of aldehyde reductase(s) may not be fully ruled out.
Attenuated Fibrinolysis and Accelerated Atherogenesis in Type II Diabetic Patients
Authors: Schneider David J , Nordt Thomas K , Sobel Burton E
Published: September 2013

Patients with hyperinsulinemia, defined by increased concentrations of IRI in plasma, experience increased cardiovascular mortality. In type II diabetic patients, the increase in IRI may reflect, in part, not only insulin but also proinsulinemia as a result of impaired conversion of proinsulin to insulin by pancreatic β-cells. High IRI is accompanied by attenuation of endogenous fibrinolytic activity and increased plasma PAI-1, the primary physiological inhibitor of t-PA. Concordant increases of plasma PAI-1 and plasma IRI appear to reflect direct effects of insulin and proinsulin on the synthesis and secretion of PAI-1 by endothelial and liver cells as judged from results of studies in vitro. Because attenuated fibrinolysis may predispose to thrombosis, the increased exposure of luminal surfaces of vessels to atherogenic, clot-associated mitogens and chemoattractants may activate macrophages and potentiate proliferation of vascular smooth muscle cells. Accordingly, increased concentrations of plasma IRI may contribute to macrovascular disease in diabetic patients by Impairing endogenous fibrinolysis.
Increased Proinsulin/Insulin Ratio in Pancreas Extracts of Hyperglycemic Rats
Authors: Leahy Jack L
Published: September 2013

The plasma ratio of proinsulin/insulin is raised in people with NIDDM. A relative hypersecretion of proinsulin is thought to be the cause, because pancreas extracts from diabetic rats have a raised proinsulin/insulin ratio. We tested the hypothesis that the pancreatic proinsulin/insulin mismatch results from hyperglycemia-induced β-cell degranulation. Normal rats made hyperglycemic with 48-h glucose infusions had a raised pancreatic percentage of proinsulin. In contrast, rats infused with enough glucose to induce compensatory hyperinsulinemia without changing the plasma glucose level had a normal percentage of proinsulin. The raised percentage of proinsulin in the hyperglycemic rats reflected a reduction in pancreatic insulin content. Administering an inhibitor of insulin release, diazoxide, to hyperglycemic rats blocked the fall in pancreatic insulin content and prevented the rise in the percentage of proinsulin. Normal rats infused with tolbutamide for 3 days and enough glucose to maintain euglycemia had a 50% reduction in pancreatic insulin content. The β-cell degranulation from this nonhyperglycemic mechanism resulted in a raised pancreatic percentage of proinsulin. In summary, chronic hyperglycemia causes β-cell degranulation primarily because of hyperstimulated insulin release. The net result is a rise in the ratio of immature (proinsulin-rich) to mature (insulin-rich) granules, which is reflected as an increased relative proportion of proinsulin. Mobilization of these proinsulin-enriched granules may explain the relative hypersecretion of proinsulin that occurs with diabetes.
Insulin Secretory Function in Relation to Transplanted Islet Mass in STZ-Induced Diabetic Rats
Authors: Tobin Brian W , Lewis Jamie T , Chen Dawn Z X , Finegood Diane T
Published: September 2013

In vivo insulin secretion was quantified as the AIRg or AIRa in islet-transplanted rats. Male Wistar-Furth rats previously made diabetic by STZ administration (55 mg/kg) were transplanted with 500,1000, 2000, or 3000 islets infused into the portal vein (n = 12–14 per group) and were compared with sham-treated controls (CN, n = 16). At 4–5 wk posttransplantation, no significant differences were noted in the FPG or fasting plasma insulin of the experimental groups (P > 0.05). Body weight, however, was 10% less (P < 0.05) in rats receiving 500 islets than in controls, indicating an effect of β-cell deficiency on growth rates. To determine the relationship between islet mass and insulin secretion, we measured AIRg after a 0.3 g/kg glucose bolus in fasted conscious animals. A significant correlation was observed between the AIRg and islet number (r = 0.61, P = 0.0001), and both 500- and 1000-islet groups could be differentiated from controls by ANOVA (500: 8%; 1000: 12% of controls; P < 0.05). During a glycemic potentiation protocol, AIRa was measured at basal and elevated blood glucose (∼16 mM). At neither basal nor elevated blood glucose was AIRa correlated with islet number (basal r = 0.0622, P = 0.7834; elevated r = 0.3133, P = 0.1667). None of the groups could be differentiated by ANOVA (elevated 500: 37%; 1000, 68% of controls; P > 0.05). Although this study illustrates that AIRa may be better preserved in islet-transplanted rats, AIRg is the better correlate of islet number. This study is thefirst to demonstrate that the acute insulin secretory response to glucose is proportional to the number of transplanted islets. This model of graded insulin secretory response allows for predetermination of a wide range of insulin secretory function in animals with fasting normoglycemia.
Reduced Motor Nerve Conduction Velocity and Na+-K+-ATPase Activity in Rats Maintained on L-Fucose Diet: Reversal by myo-Inositol Supplementation
Authors: Yorek Mark A , Wiese Thomas J , Davidson Eric P , Dunlap Joyce A , Stefani Mark R , Conner Corinne E , Lattimer Sarah A , Kamijo Mikiko , Greene Douglas A , Sima Anders A F
Published: September 2013

L-Fucose is a monosaccharide that occurs in low concentrations in normal serum but has been shown to be increased in diabetic individuals. In cultured mammalian cells, L-fucose is a potent competitive inhibitor of myo-inositol transport. Abnormal myo-inositol metabolism has been proposed to be a factor in the development of diabetic complications. To test the hypothesis that myo-inositol deficiency may be responsible for the electrophysiological and biological defects in diabetic neuropathy, rats were fed a diet containing 10 or 20% L-fucose for a period of 6 wk. After 3 wk, the L-fucose diets in two groups of rats were supplemented with 1% myo-inositol. At the end of the study protocol, motor nerve conduction velocity, sciatic nerve tissue Na+-K+-ATPase activity, and myo-inositol content were determined. These results were compared with those of STZ-induced diabetic rats fed either a normal diet or a diet containing 1% myo-inositol or with those given 450 mg/kg body wt of sorbinil. Serum L-fucose levels were significantly increased in rats fed a diet containing 10 or 20% L-fucose. In comparison, the serum L-fucose levels in the diabetic rats were increased to a lesser extent. Motor nerve conduction velocity was significantly slower in rats fed a 10 or 20% L-fucose diet. Sciatic nerve composite and ouabain-sensitive Na+-K+-ATPase activity and myo-inositol content was also significantly decreased. Supplementation of 1% myo-inositol to the L-fucose-containing diet restored nerve myo-inositol levels and significantly improved Na+-K+-ATPase activity and motor nerve conduction velocity. In diabetic rats, similar changes were prevented by treatment with myo-inositol or sorbinil. These observations suggest that myo-inositol deficiency may be a major factor in the development of neural defects associated with acute diabetic neuropathy.
Chronic Exposure of Rat Fat Cells to Insulin Enhances Lipolysis and Activation of Partially Purified Hormone-Sensitive Lipase
Authors: Kang Ellen S , Betts Dennis , Fain John N , Bahouth Suleiman W , Myers Linda K
Published: September 2013

The activity of adipose tissue hormone-sensitive lipase in animals with hyperinsulinemia has been reported to be increased compared with that in control animals. We examined whether this results from a direct effect of insulin on the tissue and whether it is accompanied by alteration in the regulation of lipolysis. When rat epididymal fat pads are incubated in culture medium with bovine serum albumin for 2–4 h with 2 ng/ml or 50 µU/ml of insulin, hormone-sensitive lipase activity in the postµsomal supernatant fraction after acid precipitation and activation with ATP-Mg2+ increases significantly compared with preparations from tissues incubated with the vehicle. The specific activities of hormone-sensitive lipase in sonicates of adipocytes after primary culture with insulin at concentrations from 10 to 4000 ng/ml (250 µU to 100 mU/ml) increase in an insulin-dose-related manner. Lipolysis in response to 10−7 M isoproterenol also increases in an insulin-dose-dependent manner. Enhancement of isoproterenol-mediated lipolysis is not attributable to a difference in the triglyceride content of the cells. Lipolysis caused by the β-agonist could be completely blocked by the simultaneous presence of insulin in both control and insulin-treated cells reflecting normal responsiveness of both types of cells to the acute effect of insulin. Although an increase in lipolysis is seen with norepinephrine and growth hormone after insulin treatment, other lipolytic agents such as ACTH, thyrotropin, and glucagon evoke similar responses in insulin-treated and control cells. The simultaneous presence of growth hormone and insulin during the 16-h culture results in additive effects on the subsequent response of the cells to 10−7 M isoproterenol compared with the responses of the cells cultured with each hormone alone. β-Agonist-mediated cAMP accumulation in the presence of Ro-20.1724, a specific phosphodiesterase inhibitor, is significantly higher in cells cultured in the presence of insulin than in control cells. Forskolin (1–25 µM) increases the lipolytic responses of insulin-treated cells compared with control cells, but the maximal response of the insulin-treated cells to forskolin is lower than that to isoproterenol. We conclude that changes produced by chronic insulin treatment involve more than one site along the lipolytic cascade.
Ethnicity and Polycystic Ovary Syndrome are Associated With Independent and Additive Decreases in Insulin Action in Caribbean-Hispanic Women
Authors: Dunaif Andrea , Sorbara Lynn , Delson Roberta , Green Georgette
Published: September 2013

This study was conducted to determine the impact of polycystic ovary syndrome and ethnicity on insulin action. Thirteen Caribbean-Hispanic and 10 non-Hispanic white polycystic ovary syndrome women were compared with 5 Caribbean-Hispanic and 8 non-Hispanic white normal women matched for age, weight, and body composition. All subjects underwent a 2-h 75 g oral glucose tolerance test and euglycemic glucose clamp study with a 40 mU.m−2 · min−1 insulin dose. Hepatic glucose production was determined basally and throughout the euglycemic clamp study. Polycystic ovary syndrome was associated with significant increases in fasting insulin levels (P < 0.05) and in 2-h postglucose-load glucose and insulin levels (P < 0.001). Ethnicity was not associated with any changes in these parameters. Polycystic ovary syndrome but not ethnicity was also associated with hepatic insulin resistance, because significant (P < 0.05) residual hepatic glucose production occurred during the euglycemic clamp in the polycystic ovary syndrome women. However, significant independent effects existed for both polycystic ovary syndrome (P < 0.01) and ethnicity (P < 0.05) that resulted in decreased insulin-mediated glucose disposal. Similarly, significant independent effects of polycystic ovary syndrome (P < 0.005) and ethnicity (P < 0.05) occurred, resulting in increased steady-state insulin levels during the euglycemic clamp. This appeared to be, in part, secondary to a decrease in the metabolic clearance rate of insulin associated with ethnicity (P < 0.05). We conclude that polycystic ovary syndrome and ethnicity result in independent and additive decreases in insulin sensitivity in Caribbean-Hispanic women. Insulin resistance resulting in hyperinsulinemia may account for the increased prevalence of both polycystic ovary syndrome and of NIDDM in Caribbean-Hispanic women.
Tolerance to IDDM Induced by CD4 Antibodies in Nonobese Diabetic Mice is Reversed by Cyclophosphamide
Authors: Parish Nicole M , Hutchings Patricia R , Waldmann Herman , Cooke Anne
Published: September 2013

IDDM can be induced in nonobese diabetic (NOD) mice in several ways, including high doses of cyclophosphamide and transfer of diabetic spleen cells to sublethally irradiated recipients. It has previously been established that transferred diabetes can be prevented by treatment with a nondepleting CD4 monoclonal antibody; however, we report herein that cyclophosphamide-induced diabetes also can be prevented using this antibody. The protection induced by CD4 monoclonal antibody to transferred diabetes is maintained for a long period after cessation of antibody treatment. However, cyclophosphamide can abrogate this induced tolerance and we report that this abrogation does not require new T-cells. During the course of the experimental work described, we observed that the thymus had a suppressive effect on the expression of transferred disease. Mice that were depleted of their peripheral T-cells showed a doubling of the time for disease expression if they were euthymic, compared with thymectomized mice.
Alcohol Intake Impairs Glucose Counterregulation During Acute Insulin-Induced Hypoglycemia in IDDM Patients: Evidence for a Critical Role of Free Fatty Acids
Authors: Avogaro Angelo , Beltramello Piero , Gnudi Luigi , Maran Anna , Valerio Anna , Miola Marina , Marin Narciso , Crepaldi Cristina , Confortin Loris , Costa Franco , MacDonald Ian , Tiengo Antonio
Published: September 2013

In this study, we assessed the effects of alcohol intake on glucose counterregulation in response to acute insulin-induced hypoglycemia in IDDM patients and in normal control subjects. Nine euglycemic IDDM patients and 9 normal control subjects were studied. After a baseline period, insulin (0.15 U/kg) was administered subcutaneously to induce hypoglycemia. Each IDDM patient was studied 3 times. In the first study, alcohol was orally administered as wine. In the second (control) study, water was administered instead of wine. In the third study, wine was given; however, a continuous infusion of heparin plus intralipid was administered to prevent the fall in plasma free fatty acid. Normal control subjects underwent only the alcohol and the control studies. In IDDM patients alcohol intake impairs, whereas in normal subjects it supports glucose counterregulation. Alcohol intake is associated with normal catecholamine responses in both IDDM diabetic patients and normal subjects. In both IDDM patients and normal subjects, hepatic glucose production in the recovery phase of the alcohol study was normal. Plasma glucose rate of disappearance was significantly increased by alcohol intake in IDDM (13.72 ± 0.82 vs. 11.84 ± 0.53 μmol · kg−1 · min−1; P < 0.05). Alcohol intake in both normal subjects and IDDM patients decreased plasma free fatty acid (267 ± 22 vs. 156 ± 20 μM; P < 0.01 and 356 ± 29 vs. 96 ± 12 μM; P < 0.01). We hypothesized that in IDDM patients, deficient glucose recovery during alcohol intake is the result of the ability of alcohol to depress lipolysis.
Cytoplasmic Islet Cell Antibodies Recognize Distinct Islet Antigens in IDDM But Not in Stiff Man Syndrome
Authors: Richter Wiltrud , Seissler Jochen , Northemann Wolfgang , Wolfahrt Sonja , Meinck Hans-Michael , Scherbaum Werner A
Published: September 2013

Cytoplasmic islet cell antibodies are well-established predictive markers of IDDM. Although target molecules of ICA have been suggested to be gangliosides, human monoclonal ICA of the immunoglobulin G class (MICA 1xyd6) produced from a patient with newly diagnosed IDDM recognized glutamate decarboxylase as a target antigen. Here we analyzed the possible heterogeneity of target antigens of ICA by subtracting the GAD-specific ICA staining from total ICA staining of sera. This was achieved 1) by preabsorption of ICA+ sera with recombinant GAD65 and/or GAD67 expressed in a baculovirus system and 2) by ICA analysis of sera on mouse pancreas, as GAD antibodies do not stain mouse islets in the immunofluorescence test. We show that 24 of 25 sera from newly diagnosed patients with IDDM recognize islet antigens besides GAD. In contrast, GAD was the only islet antigen recognized by ICA from 7 sera from patients with stiff man syndrome. Two of these sera, however, recognized antigens besides GAD in Purkinje cells. In patients with IDDM, non-GAD ICA were diverse. One group, found in 64% of the sera, stained human and mouse islets, whereas the other group of non-GAD ICA was human specific. Therefore, mouse islets distinguish two groups of non-GAD ICA and lack additional target epitopes of ICA besides GAD. Longitudinal analysis of 6 sera from nondiabetic ICA+ individuals revealed that mouse-reactive ICA may appear closer to clinical onset of IDDM in some individuals. Mouse-reactive ICAs, however, remained absent in 36% of the patients at diagnosis of IDDM.
Meticulous Prevention of Hypoglycemia Normalizes the Glycemic Thresholds and Magnitude of Most of Neuroendocrine Responses to, Symptoms of, and Cognitive Function During Hypoglycemia in Intensively Treated Patients With Short-Term IDDM
Authors: Fanelli Carmine G , Epifano Lucilla , Rambotti Aanna Maria , Pampanelli Simone , Di Vincenzo Antonio , Modarelli Francesco , Lepore Mauro , Annibale Bruno , Ciofetta Marco , Bottini Paolo , Porcellati Francesca , Scionti Luciano , Santeusanio Fausto , Brunetti Paolo , Geremia B Bolli
Published: September 2013

To test the hypothesis that hypoglycemia unawareness is largely secondary to recurrent therapeutic hypoglycemia in IDDM, we assessed neuroendocrine and symptom responses and cognitive function in 8 patients with short-term IDDM (7 yr) and hypoglycemia unawareness. Patients were assessed during a stepped hypoglycemic clamp, before and after 2 wk and 3 mo of meticulous prevention of hypoglycemia, which resulted in a decreased frequency of hypoglycemia (0.49 ± 0.05 to 0.045 ± 0.03 episodes/patient-day) and an increase in HbA1c (5.8 ± 0.3 to 6.9 ± 0.2%) (P < 0.05). We also studied 12 nondiabetic volunteer subjects. At baseline, lower than normal symptom and neuroendocrine responses occurred at lower than normal plasma glucose, and cognitive function deteriorated only marginally during hypoglycemia. After 2 wk of hypoglycemia prevention, the magnitude of symptom and neuroendocrine responses (with the exception of glucagon and norepinephrine) nearly normalized, and cognitive function deteriorated at the same glycemic threshold and to the same extent as in nondiabetic volunteer subjects. At 3 mo, the glycemic thresholds of symptom and neuroendocrine responses normalized, and surprisingly, some of the responses of glucagon recovered. We concluded that hypoglycemia unawareness in IDDM is largely reversible and that intensive insulin therapy and a program of intensive education may substantially prevent hypoglycemia and at the same time maintain the glycemic targets of intensive insulin therapy, at least in patients with IDDM of short duration.
A Second Pathway for Regeneration of Adult Exocrine and Endocrine Pancreas: A Possible Recapitulation of Embryonic Development
Authors: Bonner-Weir Susan , Baxter Leslie A , Schuppin George T , Smith Fannie E
Published: September 2013

Substantial regeneration of both the endocrine and exocrine pancreas occurs after a 90% partial pancreatectomy in the young adult rat. We have reported previously that replication of preexisting islet and exocrine cells is enhanced 3- to 4-fold. Here, we report a second pathway of regeneration, that of proliferation and differentiation of precursor cells in the ductal epithelium. As shown with in vivo pulse labeling using 5-bromo-2′-deoxyuridine, an expansion of the ductal epithelium occurs. Proliferation is seen first in the common pancreatic duct and sequentially in smaller ducts of the ductal tree as focal areas of proliferation small ductules form. By 60 h after pancreatectomy, only these focal areas show heavy 5-bromo-2′-deoxyuridine staining. These proliferating ductules comprise 12.8% of the pancreatic volume at 3 days after pancreatectomy but are uncommon at 7 days after pancreatectomy. Coincident with the appearance and disappearance of these regions was a 3.5-fold increased growth of the pancreatic remnant compared with its equivalent of sham animals. These small ductules differentiate into new pancreatic islets and exocrine tissue, forming new lobules of pancreas that are indistinguishable from the preexisting ones. This second pathway of rapid regeneration recapitulates embryonic development in its pattern of ductal proliferation and subsequent differentiation. Furthermore, these studies provide evidence of the presence of precursor/stem cells in the adult pancreas.
Primary Prevention of Diabetes Mellitus by Prevention of Obesity in Monkeys
Authors: Hansen Barbara C , Bodkin Noni L
Published: September 2013

Many, but not all, adult rhesus monkeys spontaneously develop significant increases in body fat mass, and many, but not all, progress to develop overt adult-onset type II diabetes. The purpose of this study was to determine whether both an increase in body fat and onset of diabetes could be simultaneously prevented through long-term maintenance of stable normal adult body weight by caloric titration. Eight adult male monkeys were provided a complete normal chow diet, but with daily amounts restricted and titrated on a weekly basis to maintain a constant body weight (weight-stabilized group). This regimen has been continued for 5–9 yr (mean ± SD of 7 ± 0.5 yr) with monkeys attaining the age of 17.9 ± 0.6 yr and with maintenance of normal body fat (17.7 ± 1.8%). The age-matched ad libitum fed group (18.1 ± 0.2 yr of age) consisted of 19 monkeys maintained under identical laboratory conditions and diet, but with food available ad libitum. Results showed weight-stabilized monkeys weighed significantly < ad libitum fed monkeys (10.4 ± 0.2 vs. 16.1 ± 0.7 kg, respectively, P < 0.05) and had significantly better glucose tolerance as measured by Kglucose (glucose disappearance rate) (3.9 ± 0.3 vs. 2.4 ± 0.2, P ± 0.05). Of the 19 ad libitum fed age-matched monkeys, 4 were overtly diabetic, and 6 others had significantly reduced glucose tolerance. Hyperinsulinemia did not develop in the weight-stabilized group, and β-cell response to glucose remained normal; both were significantly different from the exaggerated levels of the ad libitum fed group (P < 0.05). This form of obesity-associated type II diabetes and impaired glucose tolerance, thus, appears to be completely prevented or onset indefinitely delayed by sustained caloric restriction and maintenance of normal body composition.
Driving Decrements in Type I Diabetes During Moderate Hypoglycemia
Authors: Cox Daniel J , Gonder-Frederick Linda , Clarke William
Published: September 2013

Diabetic hypoglycemia produces cognitive-motor slowing, which is assumed to increase risk of automobile crashes. This study investigated driving decrements during and after hypoglycemia, and the patients' awareness of driving decrements. We used a randomized, single-blind, crossover design and conducted the study at the University of Virginia's General Clinical Research Center. We studied a volunteer sample of 27 consecutive adult type I diabetic patients who responded to newspaper ads. Two dropped out (final n = 25). Mean age (± SD) was 35.9 ± 14 yr. Diabetes history was 14.6 ± 10.5 yr, with HbA1 of 10.8 ± 2.9%. Driving experience was 19 ± 13.2 yr. Participants drove a state-of-the-art driving simulator on two consecutive days: Control day involved four euglycemia (mean blood glucose, 6.3 ± 0.89 mM) driving tests; experimental day involved testing at euglycemia, mild hypoglycemia (mean blood glucose, 3.6 ± 0.33 mM), moderate hypoglycemia (mean blood glucose, 2.6 ± 0.28 mM), and again at euglycemia. Patients were blind to blood glucose manipulations and levels. Driving performance was not disrupted at mild hypoglycemia nor after recovery from moderate hypoglycemia. Moderate hypoglycemia disrupted steering, causing more swerving (P < 0.03), spinning (P < 0.03), time over midline (P < 0.05), and time off road (P < 0.01). It also resulted in an apparent compensatory slowing, with more very slow driving (P < 0.04). Global driving performance decrements were observed in 35% of the patients, only 50% of whom stated they would not drive under similar conditions. Driving decrements were unrelated to demographic, disease, or driving history variables. Between 3.6 and 2.6 mM, driving performance was disrupted and not reliably recognized by our patients.
Somatostatin Inhibits Insulin-Gene Expression Through a Posttranscriptional Mechanism in a Hamster Islet Cell Line
Authors: Philippe Jacques
Published: September 2013

Insulin secretion is regulated by the interplay of nutrients, local intraislet factors, and hormones. Nutrients involved in the positive control of insulin secretion, such as glucose and amino acid, also act on insulin biosynthesis. SRIF is one of the most potent inhibitors of insulin secretion. To determine whether SRIF also regulates insulin biosynthesis, we studied its effects on insulin-gene expression. SRIF decreases steady-state insulin mRNA levels in a clonal hamster islet cell line, HIT-T15, in a dose- and time-dependent manner; this decrease does not occur at the transcriptional level but essentially at a posttranscriptional level. We conclude that SRIF not only modulates insulin secretion but also affects insulin-gene expression.
Dynamics of Hepatic and Peripheral Insulin Effects Suggest Common Rate-Limiting Step In Vivo
Authors: Bradley David C , Poulin Renee A , Bergman Richard N
Published: September 2013

This study compares the dynamics and sensitivity of hepatic and peripheral insulin action in conscious dogs. Glucose turnover was measured simultaneously by HOT GINF tracer methodology and by hepatic AV differences. SRIF was infused during euglycemic clamps to suppress endogenous insulin and glucagon secretion. Basal plasma glucagon levels were recreated by intraportal replacement (2 ng · min−1 · kg−1), and insulin was infused intraportally at 0, 3, 6, 10, or 20 pmol · min−1 · kg−1 for 3 h. Steady-state HGO and NHGO were suppressed by insulin with EC50s of 164 and 95 pM, respectively. As expected, these were lower than the EC50 for Rd stimulation (516 pM), demonstrating greater hepatic than peripheral insulin sensitivity. In contrast to sensitivity, dynamics for suppression of HGO and NHGO and for stimulation of Rd by insulin were indistinguishable: half-times averaged 43 ± 5, 42 ± 9, and 45 ± 5 min, respectively (P > 0.77). For all three variables, the half-time of insulin effect was independent of insulin dose (P > 0.26). The striking similarity of the time courses for suppression of glucose production and stimulation of glucose uptake suggests that both effects are secondary manifestations of a single, rate-limiting phenomenon. We hypothesize this single gateway to Insulin action is transendothelial insulin transport, which we previously have shown to be rate limiting for insulin's effect on glucose uptake in vivo.
Effects of Epinephrine on Insulin Secretion and Action in Humans: Interaction With Aging
Authors: Morrow Linda A , Morganroth Greg S , Herman William H , Bergman Richard N , Halter Jeffrey B
Published: September 2013

This study was designed to define the effects on glucose metabolism of small increases of plasma EPI, comparable to increases observed during physiological sympathoadrenal activation. This study was also designed to determine the effects of EPI on glucose metabolism in older adults, in whom changes in adrenergic responsiveness of several tissues were described. Tolbutamide-boosted IVGTTs were performed during intravenous infusions of saline (control) or EPI at 2.7, 5.5, and 10.9 mmol/min to achieve physiological levels of EPI in 7 young subjects (19–26 yr of age) and 7 old subjects (62–75 yr of age), all with a normal screening OGTT. IVGTT results were analyzed to determine the AIR and with the minimal model method of Bergman to determine SI and SG. A significant fall was observed in AIR, SI, and SG for all subjects, even with the lowest dose of EPI, which resulted in only a two- to threefold increase in plasma EPI. Older subjects had a delayed recovery from hyperglycemia during the EPI infusions, although we detected no significant differences between the young and old subjects in the ability of EPI to alter either acute phase insulin secretion or insulin action. In contrast, the impairment of SG by EPI appeared to be greater in the elderly. We conclude that small increases of plasma EPI can significantly affect determinants of glucose tolerance in both young and old people.
A New Model for the Study of Mild Diabetes During Pregnancy: Syngeneic Islet-Transplanted STZ-Induced Diabetic Rats
Authors: Ryan Edmond A , Tobin Brian W , Tang Jiping , Finegood Diane T
Published: September 2013

Diabetes during pregnancy carries short- and long-term consequences for the offspring. Improved obstetrical and diabetic care has resulted in decreased morbidity and mortality in the neonate of the diabetic mother. Mild hyperglycemia is still found in both IDDM pregnant women and women with GDM. The long-term consequences of exposure to mild hyperglycemia in utero remain to be determined. In an effort to develop an appropriate animal model of mild diabetes during pregnancy, we mated female STZ-induced diabetic rats previously transplanted with specific numbers of islets of Langerhans (2500,1000, 700, or 500 islets). Diabetic and nondiabetic sham-transplanted control groups also were studied. During pregnancy, the plasma glucose levels in the diabetic rats and the group receiving 500 islets (26.5 ± 1.1 and 10.0 ± 0.8 mM, respectively) were significantly greater than in control animals (5.4 ± 0.5 mM, P < 0.0001). The mean glucose levels in rats receiving 700 or 1000 transplanted islets (6.8 ± 0.2 and 6.5 ± 0.2 mM) also were significantly greater than in control animals (P < 0.001). No difference was evident between control rats and the group receiving 2500 islets (5.8 ± 0.2 mM). No gross congenital abnormalities were apparent in the offspring. The pup plasma glucose was significantly greater in the offspring of dams receiving either none (diabetic) or 500 islets (10.6 ± 0.7 and 11.1 ± 1.1 mM, respectively) compared with the offspring of nondiabetic control dams (4.4 ± 0.3 mM, P < 0.0001). The pup pancreatic insulin content was lower in the offspring of diabetic animals than in control animals (4.9 ± 0.3 vs. 15.2 ± 0.5 nM/mg, P < 0.0001), but no difference was found between the offspring of islet-transplanted dams compared with control offspring. In summary, the STZ-induced diabetic rat transplanted with a specified number of islets of Langerhans is a promising new animal model for the study of mild to moderate hyperglycemia during pregnancy. This model should be useful for study of the longer term consequences of diabetes during pregnancy.
Insulin Stimulates Production and Secretion of Endothelin From Bovine Endothelial Cells
Authors: Hu Ren-Ming , Levin Ellis R , Pedram Ali , Frank Harrison J L
Published: September 2013

Endothelin, a vasoconstrictor peptide secreted from endothelial cells, has been thought to play a role in various forms of vascular disease. Diabetes mellitus is well known for its association with accelerated atherosclerosis and microvascular damage. Although the basis for the vessel insult is multifactorial, hyperinsulinemia is thought to contribute by an unknown mechanism. In this study, we sought to determine whether insulin stimulates the production and secretion of ET-1 as a possible basis for the association of hyperinsulinemia and vascular disease. We demonstrated that insulin significantly stimulates the gene expression and secretion of ET-1 from cultured BAEC, and that insulin increases ET-1 mRNA expressed in BBCEC. Insulin caused a maximal twofold inducement above control ET-1 mRNA expression in a dose-related fashion in BAEC. The increased mRNA resulted from increased transcription, as determined by nuclear run-off studies. Increased ET-1 mRNA was seen after 4 h of incubation with insulin: the peak occurred at 6–8 h and persisted for 24 h. Insulin caused as much as a fourfold stimulation of ET-1 secretion from BAEC in a dose-related fashion, including a twofold increase at a physiological concentration (10−9 M): The increase began at 1 h of incubation and continued for the entire 24-h incubation period. The insulin-induced increases in both ET-1 mRNA and ET-1 protein secretion were significantly attenuated by genistein, a tyrosine kinase inhibitor. This stimulation probably occurred through the insulin receptor, because IGF-1 had no effect on ET-1 gene expression or secretion from these cells. Actinomycin-D inhibited the stimulation of ET-1 mRNA by insulin, whereas cycloheximide caused a superinducement of insulin's effect. Rats implanted with subcutaneous insulin pellets for 10 days had markedly elevated plasma ET levels, confirming a stimulatory role for insulin in vivo, in both diabetic and normal rodents. This study suggests that circulating hyperinsulinemia might induce the production and secretion of ET-1, a powerful endogenous vasoconstrictor and mitogen for the vascular smooth muscle cell. This interaction could underlie the increased vascular disease characteristic of hyperinsulinemic diabetic states.
Do Blacks With NIDDM Have an Insulin-Resistance Syndrome?
Authors: Chaiken Rochelle L , Ann Banerji Mary , Huey Howard , Lebovitz Harold E
Published: September 2013

NIDDM has been postulated to be a component of a more generalized metabolic syndrome, Syndrome X, caused by insulin resistance. Although the components of the syndrome include glucose intolerance, hypertension, increased TG, and decreased HDL cholesterol, their relationship to insulin resistance and/or hyperinsulinemia is controversial. Recent investigations have shown racial differences in the relationship between insulin resistance and BP in nondiabetic populations. We assessed the relationship between insulin resistance and the other components of the syndrome in 37 black men and 53 black women with NIDDM. Insulin sensitivity was determined by measuring glucose disposal with the euglycemic insulin clamp technique with a 1 mU · kg−1 · min−1 insulin infusion. We also determined fasting lipid profiles and BP. In this group of black men and women with NIDDM, 30% were insulin sensitive, and 70% were insulin resistant. No correlation existed between insulin sensitivity and sBP or dBP in either sex. Fasting serum TGs were inversely correlated with insulin sensitivity for both men (r = −0.401, P = 0.02) and women (r = −0.366, P = 0.008). Serum HDL cholesterol was highly correlated with insulin sensitivity for men (r = 0.421, P = 0.01) but not for women (r = 0.071, P = 0.62). Fasting serum TG levels and serum HDL-cholesterol levels were highly correlated in an inverse relationship in men (r = −0.368, P = 0.03), but not women (r = −0.199, P = 0.17). In summary, BP does not correlate with insulin resistance in blacks with NIDDM. Normal insulin sensitivity occurs in 33% of black men and 25% of black women with NIDDM. In black women with NIDDM, serum HDL cholesterol does not correlate with either insulin sensitivity or fasting serum TGs. The data fail to support a major association of insulin resistance with metabolic abnormalities in black women with NIDDM and show only a weak association in black men with NIDDM.
Syndromes of Insulin Resistance in the Rat: Inducement by Diet and Amelioration with Benfluorex
Authors: Storlien Leonard H , Oakes Nicholas D , Pan David A , Kusunoki Masataka , Jenkins Arthur B
Published: September 2013

Insulin resistance, mainly in skeletal muscle, is linked to a cluster of prevalent diseases including NIDDM, dyslipidemias, hypertension, and cardiovascular disease. To determine if an oversupply of lipid is associated with the development of skeletal muscle insulin resistance, we examined the effect of the hypolipidemic agent benfluorex in dietary models of insulin resistance. Adult, male Wistar rats were divided into six groups and maintained for 4 wk on diets high in complex carbohydrate, fructose or fat, with or without 50 mg · kg−1 · day−1 of benfluorex, given orally. Insulin action was assessed using a hyperinsulinemic (∼ 100 mU/L) euglycemic clamp, with 2-deoxyglucose tracer for individual tissue evaluation, in chronically cannulated conscious animals. Compared with starch feeding, fructose and fat feeding significantly impaired insulin action at the whole-body level (–46% and –41%, respectively, both P < 0.001), as well as in individual skeletal muscles. Fructose feeding increased circulating TGs (by 80%, P < 0.01) but not skeletal muscle TGs; whereas, fat feeding increased skeletal muscle TGs (by 59%, P < 0.01) but not circulating TGs. With benfluorex, however, diet had no effect on circulating and storage TGs; and development of skeletal muscle insulin resistance in the two diet groups was prevented. Feeding fructose but not fat significantly increased mean arterial BP (by 13%, P < 0.05), an effect prevented by benfluorex. These effects support the hypothesis that the development of muscle insulin resistance in these models is linked to local or systemic oversupply of lipid. These diet models—and the parallel effect of benfluorex on insulin resistance, lipids, and hypertension—may prove useful in the search for the mechanisms that underlie the human disorders associated with insulin resistance.
An Insulinlike Growth Factor I-Resistant State in Cartilage of Diabetic Rats Is Ameliorated by Hypophysectomy: Possible Role of Metabolism
Authors: Kelley Kevin M , Russell Sharon M , Matteucci Mark L , Nicoll Charless S
Published: September 2013

This study investigated the effect of IDDM on cartilage anabolic activity in rats. Rats were injected with STZ to induce IDDM, were hypophysectomized, or were injected with STZ and hypophysectomized. After 14 days, control (intact and sham-Hx) and Hx rats were normoglycemic, whereas the rats with IDDM exhibited hyperglycemia and glycosuria. The HxDb rats, however, had normal blood glucose levels and no glycosuria. Both growth, serum levels of IGF-I, and basal cartilage 35SO4 incorporation measured in vitro were decreased in the Hx, IDDM, and HxDb groups. IGF-I added in vitro significantly stimulated 35SO4 incorporation by cartilage explants from control and Hx animals, whereas explants from the animals with IDDM were unresponsive. Explants from the HxDb rats, however, were stimulated by IGF-I in a dose-related manner. Because Hx corrected the glycemic status of the IDDM rats and restored cartilage responsiveness to IGF-I, a second set of experiments was undertaken to further investigate the relationship between cellular metabolism and anabolic activity in cartilage. Cartilage explants from rats fasted for 48 h showed significantly decreased basal 35SO4 incorporation, which was as low as that in explants from rats with severe IDDM. Whereas explants from the IDDM rats were completely unresponsive, those from the fasted rats (and fed rats) were significantly stimulated by the added IGF-I. However, incubation in the presence of 2-D-G, which causes intracellular glucopenia, or in the absence of glucose, completely blocked the anabolic response to IGF-I in otherwise responsive tissues. In conclusion, an important component of diabetic growth inhibition appears to be tissue resistance to the anabolic action of IGF-I, a condition that is correctable by Hx and that may be a result of metabolic impairment at the tissue level.
Granulocyte-Colony Stimulating Factor Improves an Impaired Bactericidal Function in Neutrophils From STZ-Induced Diabetic Rats
Authors: Sato Nariyuki , Shimizu Hiroyuki
Published: September 2013

To evaluate whether G-CSF improves an impaired production of oxygen-derived free radicals in diabetic neutrophils, we studied the effect of G-CSF on chemiluminescence amplified by a luciferin analog (CLA-DCL) and luminol (L-DCL) in response to fMLP in neutrophils from STZ-induced diabetic rats. Both CLA-DCL and L-DCL in diabetic neutrophils were significantly reduced, and L-DCL was more sensitive to this inhibition than CLA-DCL. G-CSF did not change the basal chemiluminescence in either control or diabetic neutrophils, but it apparently primed CLA-DCL and L-DCL. Although, in diabetic neutrophils, the priming effect of G-CSF to both CLA-DCL and L-DCL was less compared with that in control neutrophils, L-DCL was more sensitive than CLA-DCL to this priming effect. Because bacterial infection is still an important cause of morbidity and mortality in diabetic patients, these data suggest that G-CSF may be useful as a drug to prevent the aggravation of bacterial infection in diabetic patients.