bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Chronic Intravascular Blood Glucose Sensor in Dogs
Authors: Armour Jon C , Lucisano Joseph Y , McKean Brian D , Gough David A
Published: September 2013

An intravenous glucose sensor was implanted in six dogs for 1–15 wk. The glucose sensor is a flexible cylinder, ∼0.2 cm diam and 30 cm long, with a tip containing immobilized glucose oxidase and catalase coupled to a potentiostatic O2 sensor. The sensor and a similar O2 reference sensor were implanted in the superior vena cava near the entrance of the right atrium. The sensor response was conveyed externally either by a telemetry system implanted nearby, surgically accessed leads, or chronically maintained percutaneous leads. Summing over the six implants, there was a total implantation period of 333 days during which glucose sensors were functional on demand. The sensor response showed agreement with conventionally assayed blood samples after accounting for a response lag. Sensor response to glucose showed little change over the implant period. Biocompatibility, enzyme lifetime, O2 availability, O2 sensor stability, and biochemical interference were not limitations. Results demonstrated that this sensor can function effectively as an implant in dogs for a period of months and has the potential for long-term operation.
Mild Hypoglycemia and Impairment of Brain Stem and Cortical Evoked Potentials in Healthy Subjects
Authors: Jones Timothy W , McCarthy Gregory , Tamborlane William V , Caprio Sonia , Roessler Elizabeth , Kraemer Deborah , Starick-Zych Kathleen , Allison Truett , Boulware Susan D , Sherwin Robert S
Published: September 2013

To evaluate the impact of mild hypoglycemia on CNS function in healthy adults, we measured brain stem auditory evoked potentials and P300 potentials (elicited by cognitive processing of auditory stimuli) during hypoglycemic or euglycemic insulin clamps (80 mU · m−2 · min−1). In the hypoglycemic clamp study (n = 8), plasma glucose was allowed to fall from 4.6 to 3 mM in hourly ∼0.5-mM steps and subsequently returned to euglycemic baseline levels. In the euglycemic clamp study (n = 8), plasma glucose was maintained at baseline levels throughout. Neither brain stem nor P300 responses changed during the euglycemic control study; symptoms and counterregulatory hormones were also unaffected. During the hypoglycemia study, epinephrine and growth hormone rose once plasma glucose reached 3.4 ± 0.1 mM. Brain stem and P300 potentials remained unchanged until the 3-mM glucose step, when neurophysiological changes suddenly developed in conjunction with reported symptoms. At this glucose level, the wave V component of the brain stem potential was selectively altered in 7 of 8 subjects. Furthermore, P300 latency significantly increased, and amplitude diminished. Changes in both brain stem and cortical (P300) responses reversed when euglycemia was restored. We conclude that modest reductions in plasma glucose (to 3 mM) produce marked alterations in both brain stem and cortical responses to auditory stimuli. These changes in neural function appear at the same time as symptoms and follow rather than precede the rise in counterregulatory hormones during hypoglycemia. Our data suggest that the adverse effects of mild hypoglycemia on brain function are not limited to higher centers but also involve the brain stem.
Recognition of Hypertension and Abnormal Blood Pressure Burden With Ambulatory Blood Pressure Recordings in Type I Diabetes Mellitus
Authors: Wiegmann Thomas B , Herron Kristine G , Chonko Arnold M , MacDougall Margaret L , Moore Wayne V
Published: September 2013

Ambulatory blood pressure (AMBP) measurements were obtained at 20-min intervals for 24 h in 25 subjects with insulin-dependent (type I) diabetes mellitus and 21 control subjects. The diabetic patients had normal kidney function (glomerular filtration rate 112.1 ± 7.2 ml · min−1 · 1.73 m−2, renal plasma flow 459.0 ± 23.4 ml · min−1 · 1.73 m−2) and were normotensive according to standard sphygmomanometer examinations. Mean ± SE AMBP (systolic/diastolic in mmHg) measurements in diabetic patients (24 h, 131.7/77.2 ± 2.9/1.8; 0600–2200, 132.3/78.4 ± 2.9/3.4; 2200–0600, 125.1/75.7 ± 3.9/3.4) significantly exceeded control values during all times (24 h, 121.8/70.3 ± 2.9/1.9; 0600–2200, 120.7/71.8 ± 2.6/2.0; 2200–0600, 108.2/61.5 ± 6.6/2.7). Mean 24-h AMBP exceeded 135/85 mmHg in 49% of diabetic patients. The same threshold of 135/85 mmHg was used to determine the prevalence of abnormal measurements per time period (pressure burden). Pressure burden was increased twofold in diabetic patients compared with control subjects. Mean AMBP was significantly reduced at night in control subjects but not in diabetic patients. Changes in blood pressure were not related to kidney function in diabetic patients. AMBP recordings uncovered an increased prevalence of abnormal mean blood pressure, increased pressure burden, and a lack of diurnal variation of blood pressure in subjects with type I diabetes mellitus. These findings have important implications for early intervention strategies in diabetes mellitus because AMBP recordings correlate well with end-organ damage.
Relationship Between Blood Pressure and Urinary Albumin Excretion in Development of Microalbuminuria
Authors: Mathiesen Elisabeth R , Rønn Birgitte , Jensen Tonny , Storm Bente , Deckert Torsten
Published: September 2013

Two hundred nine consecutive normotensive insulindependent diabetic (IDDM) patients were followed prospectively from November 1982 to January 1988. Patient urinary albumin excretion rate (UAE) had to be normal (<30 mg/24 h) on at least two occasions before inclusion in the study. Patients were aged 18–50 yr with a duration of diabetes of 10–30 yr. UAE was measured every 4 mo, and supine blood pressure was measured annually. Two hundred five patients completed the study. Five years later, 15 patients had developed persistent microalbuminuria with median UAE >30 mg/24 h for at least 2 yr (group 2), and 190 patients stayed normoalbuminuric (group 1). Although within normal range, initial UAE was significantly elevated in group 2 compared with group 1 (mean 19 mg/24 h [range 15–23 mg/24 h] vs. 11 mg/24 h [10–12], 95% confidence interval [Cl], P < 0.001). Initially, there was no difference in blood pressure between group 2 (mean systolic 122 mmHg [117–127], diastolic 80 mmHg [76–84]) and group 1 (mean 126 mmHg [124–128], 79 mmHg [78–80], 95% Cl), and a significant increase in diastolic blood pressure could first be detected during the 3rd yr of persistent microalbuminuria (mean systolic 132 mmHg [124–140], diastolic 85 mmHg [81–89] vs. 128 mmHg [126–130], 79 mmHg [78–80], P < 0.05). Initial hemoglobin A1c was significantly elevated in group 2 compared with group 1 (9.6% [8.8–10.4] vs. 8.5% [8.3–8.7], P < 0.01). Regarding sex, age, duration of diabetes, insulin dose, height, weight, or inverse serum creatinine, no significant differences were seen between the groups. No increase in UAE or blood pressure was detected in group 1, although 38% had experienced at least one elevated UAE during the 5-yr follow-up. Thus, a significant elevation in UAE precedes the increase of systemic blood pressure during the development of nephropathy in IDDM.
Modulation of Hemodynamic and Vascular Filtration Changes in Diabetic Rats by Dietary myo-inositol
Authors: Pugliese Giuseppe , Tilton Ronald G , Speedy Amanda , Santarelli Elettra , Eades Donald M , Province Michael A , Kilo Charles , Sherman William R , Williamson Joseph R
Published: September 2013

To assess the potential of myo-inositol-supplemented diets to prevent diabetes-induced vascular functional changes, we examined the effects of diets supplemented with 0.5,1, or 2% myo-inositol on blood flow and vascular filtration function in nondiabetic control rats and rats with streptozocin-induced diabetes (STZ-D). After 1 mo of diabetes and dietary myo-inositol supplementation, 1) 131I-labeled bovine serum albumin (BSA) permeation of vessels was assessed in multiple tissues, 2) glomerular filtration rate (GFR) was estimated as renal plasma clearance of 57Co-labeled EDTA, 3) regional blood flows were measured with 15-μm 85Sr-labeled microspheres, and 4) endogenous albumin and IgG urinary excretion rates were quantified by radial immunodiffusion assay. In STZ-D rats, 131I-BSA tissue clearance increased significantly (2- to 4-fold) in the anterior uvea, choroid-sclera, retina, sciatic nerve, aorta, new granulation tissue, diaphragm, and kidney but was unchanged in skin, forelimb muscle, and heart, myo-inositol-supplemented diets reduced diabetes-induced increases in 131I-BSA clearance (in a dose-dependent manner) in all tissues; however, only in new granulation tissue and diaphragm did the 2% myo-inositol diet completely normalize vascular albumin permeation. Diabetes-induced increases in GFR and in urinary albumin and IgG excretion were also substantially reduced or normalized by dietary myo-inositol supplements. Increased blood flow in anterior uvea, choroid-sclera, kidney, new granulation tissue, and skeletal muscle in STZ-D rats also was substantially reduced or normalized by the 2% myo-inositol diet, myo-inositol had minimal if any effects on the above parameters in control rats. These observations indicate that diabetes-induced increases in regional blood flow, 131I-BSA permeation, GFR, and urinary protein excretion can be markedly reduced or normalized by consumption of myo-inositol-supplemented diets that raise plasma myo-inositol levels approximately fivefold. The failure of the 2% myo-inositol diet to normalize GFR and blood flow and albumin permeation in several tissues despite markedly elevated plasma myo-inositol levels and normal or elevated tissue myo-inositol levels indicates that if vascular functional changes in these tissues are linked to altered myo-inositol levels, they are resistant to normalization by elevation of plasma myo-inositol levels. These results suggest that other factors independent of changes in relative or absolute tissue myo-inositol levels may play an important role in the pathogenesis of diabetes-induced vascular functional changes in these tissues. The finding that myo-inositol-supplemented diets had no effect on body weight gain, renal hypertrophy, or urine volume indicates that these changes were not linked to imbalances in myo-inositol metabolism.
Differential Effects of IGF-I and Insulin on Glucoregulation and Fat Metabolism in Depancreatized Dogs
Authors: Giacca Adria , Gupta Rajiv , Efendic Suad , Hall Kerstin , Skottner Anna , Lickley Lavina , Vranic Mladen
Published: September 2013

The effects of equipotent glucose-lowering doses of insulinlike growth factor I (IGF-I) and insulin on tracer-determined glucose kinetics and several metabolites were compared in 14 experiments (7 in each group) in fasted, totally depancreatized dogs. This model prevented variations in insulin secretion induced by IGF-I and permitted evaluation of the effects of IGF-I on extrapancreatic glucagon. Steady-state moderate hyperglycemia (9.9 ± 0.2 mM) was maintained by a subbasal intraportal infusion of insulin (1.29 ± 0.17 pmol · kg−1 · min−1). This was continued throughout the experiment, allowing evaluation of IGF-I effects on insulin clearance. Human recombinant IGF-I or insulin was given intravenously as a primed infusion for 90 min, followed by a 50-min recovery period. The dose of IGF-I was a 2.6-nmol/kg bolus plus 57.4 pmol · kg−1 · min−1. The insulin dose required to induce the same plasma glucose decline as IGF-I (44 ± 6 vs. 43 ± 5%, NS) was 9–12 times lower (0.06-nmol/kg bolus + 6.4 ± 0.6 pmol · kg−1 · min−1). However, the mechanism of this decline differed with IGF-I and insulin; glucose production was much less suppressed (25 ± 9 vs. 42 ± 11%, P < 0.001) and glucose utilization was more stimulated (68 ± 18 vs. 38 ± 19%, P < 0.05) with IGF-I. Lactate and pyruvate increased significantly with IGF-I (by 85 ± 28 and 123 ± 83%, respectively) but not with insulin. Glycerol and free-fatty acid levels decreased much less with IGF-I than insulin (29 ± 16 vs. 52 ± 5%, P < 0.05, and 36 ± 10 vs. 56 ± 8%, P < 0.01). β-Hydroxybutyrate, alanine, and glucagon decreased similarly with IGF-I or insulin by 60, 20, and 20%, respectively. Plasma insulin was not affected by IGF-I administration (92.6 ± 8.5 vs. 92.6 ± 10.1 pM). In conclusion, in insulin-infused depancreatized dogs, 1) IGF-I is 8–11% as potent as insulin as a glucose-lowering agent on a molar basis, 2) IGF-I does not affect insulin clearance at doses effective in lowering plasma glucose, and 3) equipotent glucose-lowering doses of IGF-I and insulin have very different effects on both glucose kinetics and lipolysis. This suggests that the IGF-I-insulin potency ratio in vivo is higher in muscle than liver or adipose tissue. Therefore, insulinlike effects of supraphysiological doses of IGF-I can be mediated not only through the insulin but also the IGF-I receptor.
Diabetes-Related Changes in Chromatin Structure of Brain, Liver, and Intestinal Epithelium
Authors: Hartnell Joan M , Storrie Michele C , Mooradian Arshag D
Published: September 2013

To determine whether diabetes alters chromatin structure in vivo, fluorometric analysis of alkali-induced DNA unwinding was carried out in various tissues of streptozocin-induced diabetic ratsand genetically obese diabetic (dbldb) mice. When zero-order kinetics were used to analyze the data, the percentage of double-stranded DNA (%dsDNA) unwinding in brain, liver, and intestinalepithelium of diabetic rats maintained for 4 wk was significantly reduced compared with vehicle-injected control rats (%dsDNA 0.37 ± 0.05 vs. 0.73 ± 0.02 for brain, 0.59 ± 0.1vs. 0.84 ± 0.02 for liver, and 0.58 ± 0.07 vs. 0.90 ± 0.13 for intestinal epithelium). Insulin treatment of diabetic rats normalized the rate of DNA unwinding in liver (0.82 ± 0.09 %dsDNA/min) and intestinal epithelium (1.05 ± 0.09 %dsDNA/min), but the increase in the unwinding rate of brain DNA (0.51 ± 0.06 %dsDNA/min) did not achieve control values. Similarly, alkali-induced DNA unwinding was significantly slower in brain and liver of db/db mice compared with homozygote controls. When first-order kinetics were used to analyze the data, fractional rate constants of DNA unwinding in brain and liver of diabetic rats or mice were significantly smaller than observed in nondiabetic control animals. The fractional rate constant of DNA unwinding in intestinal epithelium was not altered with diabetes. We conclude that chronic uncontrolled hyperglycemia can alter chromatin structure in vivo.
Increased Liver Glucose-Transporter Protein and mRNA in Streptozocin-Induced Diabetic Rats
Authors: Oka Yoshitomo , Asano Tomoichiro , Shibasaki Yoshikazu , Lin Jiann-Liang , Tsukuda Katsunori , Akanuma Yasuo , Takaku Fumimaro
Published: September 2013

The effect of insulin-deficient diabetic states on the rat liver glucose-transporter (L-transporter isoform) protein and mRNA levels were studied. Rats were injected with 65 mg/kg streptozocin to induce diabetes and were maintained for 10 days and then treated with or without insulin for the next 5 days. The L-transporter isoform with apparent Mr of 55,000 was observed to be increased approximately twofold in the membranes from liver homogenates of diabetic rats compared with control rats when assessed by Western blot analysis with an anti-peptide antibody directed against rat L-transporter isoform. Insulin treatment of diabetic rats decreased the amount of L-transporter isoform protein toward levels observed in nondiabetic rats. Northern blot analysis demonstrated similar alterations in the rat L-transporter isoform mRNA that paralleled the changes observed in the L-transporter isoform protein. The increased levels of the L-transporter isoform protein and mRNA in diabetic rats are in marked contrast to the effects of insulin deficiency in rat adipocytes, which specifically decrease the amount of the adipocyte glucose-transporter isoform protein and mRNA. These results suggest that glucose-transporter isoforms in rat liver and adipocytes are regulated by different mechanisms and that an increased synthesis of the L-transporter isoform may contribute to the increased glucose output that occurs from the liver during insulin deficiency.
Possible Role for Increased C4b-Binding–Protein Level in Acquired Protein S Deficiency in Type I Diabetes
Authors: Ceriello Antonio , Giugliano Dario , Quatraro Antonio , Marchi Egidio , Barbanti Miriam , Lefebvre Pierre
Published: September 2013

In this study, total protein S (PS) immunological levels, free-PS and C4b-binding–protein (C4bBP) concentrations, and PS functional activity were investigated in insulin-dependent (type I) diabetic patients and compared with nondiabetic subjects. Mean total PS antigen concentration was not different between diabetic patients and nondiabetic subjects, whereas free-PS levels and PS functional activity were significantly reduced in diabetic patients. C4bBP was increased in diabetic patients and correlated with HbA1 levels. This study shows that type I diabetic patients have depressed free PS and PS activity despite the presence of normal total PS concentration and suggests that this phenomenon is probably linked to the increase of circulating C4bBP.
Bone and Mineral Metabolism in BB Rats With Long-Term Diabetes: Decreased Bone Turnover and Osteoporosis
Authors: Verhaeghe Johan , Herck Erik Van , Visser Walter J , Suiker Astrid M H , Thomasset Monique , Einhorn Thomas A , Faierman Eial , Bouillon Roger
Published: September 2013

The effect of long-term diabetes mellitus on bone and mineral metabolism was studied in BB rats. Diabetic rats were treated with 1 U of long-acting insulin every other day for 12 wk and compared with nondiabetic littermates. Urinary calcium excretion was increased > 10-fold, but serum total and diffusible calcium remained normal. Serum concentrations of both 1α,25-dihydroxyvitamin D3 and vitamin D–binding protein were significantly decreased in diabetic rats. The intestinal calbindin-D 9K concentration was decreased by nearly 50%, and active duodenal calcium absorption was totally abolished. Trabecular bone volume measured in the tibial metaphysis was decreased by 44%, and the osteoblast and osteoid surfaces were <10% of values observed in control rats, whereas the osteoclast surface was unchanged by diabetes. The daily bone formation (bone mineral apposition rate) measured by labeling twice with calcein was decreased by 86% in diabetic rats. The serum concentration of osteocalcin, a biochemical marker of osteoblast function, was similarly decreased (mean ± SE 23 ± 3 and 62 ± 4 μg/L in diabetic [n = 15] and nondiabetic [n = 15] rats, respectively). Serum osteocalcin was significantly correlated with the serum concentration of insulinlike growth factor I (r = 0.89, P < 0.001). Bone strength measured as the energy needed to fracture the femur was markedly decreased (5.3 ±1.4 and 8.4 ± 1.3 N · m · degree in diabetic and nondiabetic rats, respectively; P < 0.01). These histological, chemical, and biomechanical data clearly indicate that long-standing diabetes in BB rats results in severe low-turnover osteoporosis probably related to decreased osteoblast recruitment and/or function.
Free–Fatty Acid Inhibition of Insulin Binding, Degradation, and Action in Isolated Rat Hepatocytes
Authors: Svedberg Jan , Björntorp Per , Smith Ulf , Lönnroth Peter
Published: September 2013

The effect of free fatty acids (FFAs) on insulin binding and action was investigated in isolated rat hepatocytes. Oleic acid (0.4 mM) added to the cells rapidly (within 45 min) reduced insulin binding and degradation (each by 45%; P < 0.001, n = 7) without changing the apparent receptor affinity. The effect was concentration dependent; a half-maximal inhibitory effect occurred at 0.150 ± 0.050 mM (mean ± SE). Oleic acid exerted no effect on insulin binding in energy-depleted (KCN-treated) cells. Oleic, palmitic, stearic, palmitoleic, and eicosapentaenoic acids were equally effective in reducing insulin binding. FFA did not change insulin binding to partially purified insulin receptors, thus excluding a direct effect on the insulin receptor. Furthermore, binding to partially purified receptors from solubilized cells pretreated with 0.2 mM oleic acid was not changed, indicating the effect of FFA in intact cells is on the rate of receptor internalization and/or recycling. Concomitant with the effect on insulin binding, oleic acid elicited a concentration-dependent reduction in nonstimulated cellular [14C]aminoisobutyric acid uptake (AIB; 29 ± 8%, P <0.05) and decreased the maximal effect of insulin (39 ± 7%, P < 0.05). Thus, in a concentration-dependent manner, different fatty acids can reduce the number of binding sites for insulin and the degradation of insulin by isolated liver cells. Basal and insulin-stimulated AIB transport was reduced, suggesting the presence of postbinding perturbations. These data suggest that FFA exerts an important modulating effect on insulin action in the liver.
Diabetic Autonomic Neuropathy in BB Rats and Effect of ARI Treatment on Heart-Rate Variability and Vagus Nerve Structure
Authors: Zhang Wei-Xian , Chakrabarti Subrata , Greene Douglas A , Sima Anders A F
Published: September 2013

The preventive effect of the aldose reductase inhibitor (ARI) ponalrestat on heart-rate variability and the development of autonomie neuropathy in the vagus nerve was investigated in the spontaneously diabetic BB rat. ARI treatment completely prevented the characteristic decrease in heart-rate variability and axonal atrophy of the vagus nerve for 4 mo in hyperglycemic BB rats. After 6 mo of treatment, the preventive effect on heart-rate variability was partial, and the vagus nerve demonstrated an increase in regenerating myelinated and unmyelinated fibers. These data suggest that autonomie neuropathy involving the vagus nerve is metabolically induced by demonstrating that inhibition of the polyol pathway significantly delays the occurrence of functional and structural autonomie neuropathy despite the presence of hyperglycemia.
Effect of Streptozocin-Induced Diabetes on Insulin-Receptor Tyrosine Kinase Activity in Obese Zucker Rats
Authors: Slieker Lawrence J , Roberts Edda F , Shaw Walter N , Johnson William T
Published: September 2013

We examined insulin binding, insulin-stimulated autophosphorylation, and phosphorylation of poly(GIu · Na,Tyr)4:1 by liver and skeletal muscle insulin receptor from lean, obese, and obese streptozocin-induced diabetic Zucker rats. Induction of diabetes with streptozocin (30 mg/kg) lowered the fasting insulin level from 11.4 to 3.8 ng/ml, which was not significantly greater than the lean control level. Autophosphorylation and tyrosine kinase activity of liver insulin receptors were increased 70–100% in the obese control group (relative to lean rats), but diabetes reversed this hyperresponsiveness to insulin. In muscle, obesity was associated with a 40–50% decrease in autophosphorylation and tyrosine kinase activity, which was also reversed in the diabetic state. Autophosphorylation and tyrosine kinase activity were significantly correlated in liver and muscle and were also correlated with fasting insulin levels. These data suggest that insulin-receptor tyrosine kinase activity is regulated differently in liver and muscle and that the abnormalities in kinase activity associated with the obese Zucker rat are at least partly secondary to hyperinsulinemia.
Evidence of Cosecretion of Islet Amyloid Polypeptide and Insulin by β-Cells
Authors: Kahn Steven E , D'Alessio David A , Schwartz Michael W , Fujimoto Wilfred Y , Ensinck John W , Taborsky Gerald J , Porte Daniel
Published: September 2013

Islet amyloid polypeptide (IAPP) has been identified as the major constituent of the pancreatic amyloid of non-insulin-dependent diabetes mellitus (NIDDM) and is also present in normal β-cell secretory granules. To determine whether IAPP is a pancreatic secretory product, we measured the quantity of lAPP-like immunoreactivity (IAPP-LI), insulin, and glucagon released into 5 ml of incubation medium during a 2-h incubation of monolayer cultures (n = 5) of neonatal (3- to 5-day-old) Sprague-Dawley rat pancreases under three conditions: 1.67 mM glucose, 16.7 mM glucose, and 16.7 mM glucose plus 10 mM arginine and 0.1 mM isobutylmethylxanthine (IBMX). The quantity of IAPP-LI, insulin, and glucagon in the cell extract was also determined. Mean ± SE IAPP-LI in the incubation medium increased from 0.041 ± 0.003 pmol in 1.67 mM glucose to 0.168 ± 0.029 pmol in 16.7 mM glucose (P < 0.05) and 1.02 ± 0.06 pmol in 16.7 mM glucose plus arginine and IBMX (P < 0.05 vs. 1.67 or 16.7 mM glucose). Insulin secretion increased similarly from 4.34 ± 0.27 to 20.2 ± 0.6 pmol (P < 0.05) and then to 135 ± 5 pmol (P < 0.05 vs. 1.67 or 16.7 mM glucose). Glucagon release tended to decrease with the increase in glucose concentration (0.39 ± 0.01 vs. 0.33 ± 0.02 pmol, P < 0.1), whereas with the addition of arginine and IBMX to high glucose, glucagon release increased to 1.32 ± 0.03 pmol (P < 0.05 vs. 1.67 or 16.7 mM glucose). Thus, the molar proportion of IAPP-LI to insulin secreted in low glucose was ∼1% and did not differ significantly with stimulation (0.95 ± 0.08 vs. 0.84 ± 0.15 vs. 0.76 ± 0.05%). In contrast, there was no constant proportional relationship between the release of IAPP-LI and glucagon (10.6 ± 0.8 vs. 51.3 ± 8.7 vs. 77.5 ± 5.2%). After incubation in 1.67 mM glucose, the extracted cells contained 3.7 ± 0.2 pmol IAPP-LI, 944 ± 25 pmol insulin, and 28.2 ±1.5 pmol glucagon. After maximal stimulation, the fractional release of IAPP-LI was 26.7 ± 0.7% vs. 14.7 ± 0.6% of insulin and 4.4 ± 0.2% of glucagon. These data indicate that nondiabetic neonatal rat islet cultures contain IAPP-LI and release it after stimulation by glucose and nonglucose secretagogues. Furthermore, the data suggest that IAPP-LI is a product of the β-cell, which coreleases it with insulin in a molar ratio of ∼1.100.
Islet Amyloid Polypeptide Response to Glucose, Insulin, and Somatostatin Analogue Administration
Authors: Mitsukawa Tomohiro , Takemura Jiro , Asai Junko , Nakazato Masamitsu , Kangawa Kenji , Matsuo Hisayuki , Matsukura Shigeru
Published: September 2013

We determined islet amyloid polypeptide (IAPP) response in plasma to oral and intravenous glucose administration and intravenous insulin injection in nondiabetic subjects. Moreover, we studied the effect of somatostatin analogue SMS 201-995 on glucose-induced IAPP secretion in nondiabetic subjects. Plasma IAPP concentration was determined by radioimmunoassay. Oral administration of 75 g glucose (n = 8) significantly increased plasma IAPP levels from 4.5 ± 0.7 to 14.0 ± 1.7 pM (P < 0.01) 60 min after administration. Intravenous administration of 10 g glucose (n = 7) also caused a significant increase in plasma IAPP from 5.0 ± 0.4 to 11.6 ± 0.9 pM (P < 0.01) 5 min after injection. Plasma IAPP significantly decreased from 5.1 ± 0.4 to 2.9 ± 0.4 pM (P < 0.01) 60 min after intravenous insulin injection (n = 8). Pretreatment with SMS 201-995 completely abolished IAPP and insulin secretion to intravenous glucose injection. A significant correlation was found between plasma IAPP and insulin levels in oral and intravenous glucose administration and between plasma IAPP and C-peptide levels during insulin-induced hypoglycemia. These results suggest that IAPP is cosecreted with insulin in response to a glucose load and secretion of IAPP is inhibited by hypoglycemia and somatostatin. IAPP may serve as a novel pancreatic hormone to control carbohydrate metabolism.
Effects of Long-Term Aldose Reductase Inhibition on Development of Experimental Diabetic Neuropathy: Ultrastructural and Morphometric Studies of Sural Nerve in Streptozocin-Induced Diabetic Rats
Authors: Yagihashi Soroku , Kamijo Mikiko , Ido Yasuo , Mirrlees Donald J
Published: September 2013

There is controversy over the efficacy of aldose reductase inhibitors in preventing the development of peripheral nerve lesions in experimental diabetes. This study was designed to show whether long-term (28-wk) inhibition of aldose reductase by ponalrestat influences structural changes in peripheral sensory nerve in rats with chronic streptozocin-induced diabetes. Sciatic nerve levels of sorbitol and fructose were significantly reduced but not completely normalized by ponalrestat treatment, myo-lnositol levels, which tended to decrease in diabetic rats, were significantly increased by ponalrestat treatment and exceeded the level in nondiabetic control rats (P < 0.01). Ponalrestat treatment significantly increased nerve conduction velocity over the 28 wk of treatment (P < 0.05), but levels remained well below those of control rats. Structural analysis of sural nerve of diabetic rats disclosed significant preventive effects of ponalrestat on the reduction in myelinated nerve fiber size and fiber occupancy. Axon-fiber size ratio was also preserved in the ponalrestat-treated group. However, diffuse deposition of glycogen and increased glycogenosomes within axons were not influenced by ponalrestat treatment. In contrast to the effect on myelinated nerve fibers, morphometry of unmyelinated nerve fibers did not reveal a significant effect of ponalrestat treatment. These results suggest that chronic treatment with an aldose reductase inhibitor has beneficial effects on the peripheral sensory nerve of experimentally diabetic rats. The effects were primarily on myelinated rather than unmyelinated nerve fibers.
Effects of Meal Ingestion on Plasma Amylin Concentration in NIDDM and Nondiabetic Humans
Authors: Butler Peter C , Chou Joanne , Carter W Bradford , Wang Yeng-Nung , Bu Bing-Hong , Chang Ding , Chang Jaw-Kang , Rizza Robert A
Published: September 2013

Recent interest has focused on the potential role of amylin in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM). This 37-amino acid peptide is found in extracellular amyloid deposits in ∼50% of pancreatic islets of patients with NIDDM and has been shown to inhibit skeletal muscle glycogen synthesis in vitro. Immunocytochemical studies have colocalized amylin and insulin within β-cell secretory granules in nondiabetic humans, provoking the following questions. Is amylin cosecreted with insulin? Are circulating amylin concentrations higher in patients with NIDDM either before or after food ingestion? To answer these questions, we developed a sensitive and specific immunoassay to measure plasma concentrations of amylin in humans. Use of this assay indicated that, in lean nondiabetic subjects, glucose ingestion resulted in an increase (P < 0.001) in the plasma concentration of amylin (from 2.03 ± 0.22 to 3.78 ± 0.39 pM) and insulin (from 48.3 ± 3.1 to 265 ± 44 pM). There was a significant correlation between the concentrations of insulin and amylin (r = 0.74, P < 0.001) and the increase in insulin and amylin concentration (r = 0.65, P < 0.005). Fasting concentrations of amylin did not differ in diabetic and weight-matched nondiabetic subjects and showed a similar pattern of change after ingestion of a mixed meal. We conclude that amylin is secreted in response to ingestion of either glucose or a mixed meal and circulates at concentrations that do not differ in patients with NIDDM and nondiabetic subjects. It remains to be determined whether amylin at physiological concentrations influences carbohydrate metabolism and if so whether its effects differ in diabetic and nondiabetic humans.
Plasma C-Peptide Levels and Clinical Remissions in Recent-Onset Type I Diabetic Patients Treated With Cyclosporin A and Insulin
Authors: Assan Roger , Feutren Gilles , Sirmai Jean , Laborie Christine , Boitard Christian , Vexiau Patrick , Rostu Hubert Du , Roder Michel , Figoni Martine , Vague Philippe , Hors Jacques , Bach Jean-François
Published: September 2013

Remission from insulin dependency in insulin-treated recent-onset type I (insulin-dependent) diabetic patients can result from a partial recovery of insulin secretion, an improvement in tissue sensitivity to insulin, or both. The same hypothesis must be analyzed when remission occurs in cyclosporin A (CsA)-treated patients. In this study, plasma C-peptide levels were serially measured in the basal state and after stimulation in 219 recent-onset type I diabetic patients; 129 received CsA, and all patients were similarly monitored and insulin treated. The results were analyzed in view of the occurrence of remission. Remission was defined as good metabolic control in the absence of hypoglycemic treatment for ≥1 mo. Remission occurred in 44% of the CsA-treated group and lasted for mean ± SE 10.0 ± 0.9 mo vs. 21.6% in the non-CsA-treated group with a duration of 4.4 ± 0.8 mo. Plasma C-peptide levels were initially dramatically lower than normal in both groups in the basal and stimulated states. C-peptide levels increased significantly later, at 3 and 6 mo, in both groups. C-peptide values were proportional to the rates of remission in both groups. In the non-CsA-treated group, C-peptide levels later decreased, and these patients inexorably relapsed to insulin dependency. In contrast, in the CsA-treated group, the initial recovery in insulin secretory capacity was maintained over the 18–24 mo of the study. Furthermore, higher remission rates and longer-lasting remission were obtained in patients who reached higher C-peptide levels at the 3rd mo of treatment. Conversely, a progressive decrease in C-peptide values followed interuption of CsA treatment in some patients who had previously maintained some C-peptide secretory capacity. Our results support the hypothesis of an efficient suspension by CsA of the progressive deterioration of islets. The maintenance of β-cell secretory capacity by CsA plus insulin was better than by insulin alone. However, C-peptide concentrations remained lower than normal in patients in remission. An improvement in sensitivity to insulin may have also contributed to the development of remission.
Metabolic Effects of Reducing Rate of Glucose Ingestion by Single Bolus Versus Continuous Sipping
Authors: Jenkins David J A , Wolever Thomas M S , Ocana Anthony M , Vuksan Vladimir , Cunnane Stephen C , Jenkins Mark , Wong Gerald S , Singer William , Bloom Stephen R , Blendis Lawrence M , Josse Robert G
Published: September 2013

Modifying the rate of absorption has been proposed as a therapeutic principle of specific relevance to diabetes. To demonstrate clearly the metabolic benefits that might result from reducing the rate of nutrient delivery, nine healthy volunteers took 50 g glucose in 700 ml water on two occasions: over 5–10 min (bolus) and at a constant rate over 3.5 h (sipping). Despite similar 4-h blood glucose areas, large reductions were seen in serum insulin (54 ± 10%, P < 0.001) and C-peptide (47 ± 12%, P < 0.01) areas after sipping, together with lower gastric inhibitory polypeptide and enteroglucagon levels and urinary catecholamine output. There was also prolonged suppression of plasma glucagon, growth hormone, and free-fatty acid (FFA) levels after sipping, whereas these levels rose 3–4 h after the glucose bolus. An intravenous glucose tolerance test at 4 h demonstrated a 48 ± 10% (P < 0.01) more rapid decline in blood glucose (Kg) after sipping than after the bolus. Furthermore, FFA and total branched-chain amino acid levels as additional markers of insulin action were lower over this period despite similar absolute levels of insulin and C-peptide. These findings indicate that prolonging the rate of glucose absorption enhances insulin economy and glucose disposal.
Correction of Altered Metabolic Activities in Sciatic Nerves of Streptozocin-Induced Diabetic Rats: Effect of Ganglioside Treatment
Authors: Bianchi Roberto , Berti-Mattera Liliana N , Fiori Mario G , Eichberg Joseph
Published: September 2013

The effect of ganglioside administration to nondiabetic and streptozocin-induced diabetic rats on sciatic nerve Na+-K+-ATPase, polyphosphoinositide (PPI) turnover, and protein phosphorylation was investigated. Gangliosides were injected (10 mg/kg body wt i.p.) for 10 or 30 days beginning 20 days after induction of diabetes. Na+-K+-ATPase activity was reduced nearly 50% in diabetic nerve and was restored to normal by both ganglioside treatments. The elevated levels of fructose and sorbitol and depressed content of myo-inositol in diabetic nerve were unaffected by 30 days of ganglioside treatment, indicating that the restoration of Na+-K+-ATPase activity is not dependent on normal concentrations of these compounds. In the same nerves, 32P incorporation into phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-phosphate increased 73–76 and 39–53%, respectively, in diabetic compared with nondiabetic tissue. Ganglioside administration abolished the elevated labeling of PPIs after 30 days but was ineffective after only 10 days. Neither ganglioside regimen was able to reverse enhanced phosphorylation of the major peripheral nerve myelin protein P0· The finding that gangliosides can more quickly correct the effects of diabetes on Na+-K+-ATPase activity than on PPI turnover suggests that the mechanisms underlying these two phenomena are not closely related and are distinct from the sequence of events responsible for altered myelin protein phosphorylation.
Prevention of Diabetes-Increased Aging Effect on Rat Collagen-Linked Fluorescence by Aminoguanidine and Rutin
Authors: Odetti Patrizio R , Borgoglio Antonella , Pascale Angelo De , Rolandi Ranieri , Adezati Luciano
Published: September 2013

Products from the advanced Maillard reaction, which increase during aging and diabetes, may contribute to the development of the typical pathology of aging and diabetes. These compounds are detectable only by their characteristic fluorescence, and few data based on long-term studies are available. For this reason, we studied subcutaneous skin collagen fluorescence in 57 nondiabetic (10- to 110-wk-old) and 74 streptozocin-induced diabetic (10- to 22-wk-old) rats. An exponential increase (r = 0.969, P < 0.001) of collagen-linked fluorescence (excitation at 370 nm, emission at 440 nm) was observed with aging; after a lag, diabetes induced an earlier dramatic elevation of the fluorescence, suggesting a more complicated phenomenon than simple accumulation. To prevent such increases, the effects of 1 g · kg∼1 · day−1 aminoguanidine, suggested to be an inhibitor of the advanced glycosylation reaction, and 1 g · kg−1 · day−1 rutin, an aldose reductase inhibitor, in drinking water were tested. Both treatments had a significant lowering effect on collagen fluorescence in diabetic rats. The mechanisms by which aminoguanidine and rutin prevent the accumulation of fluorescence are unknown, but these observations raise the question of whether they could be identical. If fluorescence is a marker for age-related pathologies and diabetic sequelae, aminoguanidine and rutin could have therapeutic effects in their prevention.
Laminin Alterations After In Vitro Nonenzymatic Glycosylation
Authors: Charonis Aristidis S , Reger Lorrel A , Dege Jay E , Kouzi-Koliakos Kokkona , Furcht Leo T , Wohlhueter Robert M , Tsilibary Effie C
Published: September 2013

Laminin, a basement membrane protein derived from the matrix of the Engelbreth-Holm-Swarm murine tumor, was nonenzymatically glycosylated in vitro in the presence of increasing glucose concentrations. The amount of glucose incorporated per laminin molecule was shown to be proportional to the molarity of glucose used. Nonenzymatic glycosylation resulted in formation of cross-links and alterations of the cruciform shape of laminin molecules; these alterations were dramatic when high concentrations of glucose were used. One of the functions of laminin, the process of self-assembly, was shown to be impaired after in vitro nonenzymatic glycosylation. Glucose incorporation resulted in a dramatic decrease of long-to-long laminin dimers, which normally form during the initial steps of assembly. Furthermore, nonenzymatic glycosylation of laminin reduced its ability to self-associate into complexes larger than dimers, as judged by turbidimetry. The observed decrease of maximal turbidity was proportional to the degree of nonenzymatic glycosylation. Aminoguanidine, which has been suggested to inhibit cross-link formation, was shown to restore to a large extent the shape of laminin, the percentage of long-to-long arm dimers, and the maximal turbidity when included in the mixtures of laminin and glucose. These data suggest that structural and functional alterations of laminin may be primarily due to formation of crosslinks. Such modifications of laminin (along with our basement membrane components) may contribute to the morphological and physiological changes observed in basement membranes under diabetic conditions.
Hypoglycmic Thresholds for Cognitive Dysfunction in Humans
Authors: Blackman John D , Towle Vernon L , Lewis Gary F , Spire Jean-Paul , Polonsky Kenneth S
Published: September 2013

Nineteen healthy adult volunteers were studied to define the nature of and threshold for the cognitive dysfunction that occurs during insulin-induced hypoglycemia. The P300 cerebral event-related potential is an electrophysiological correlate of cognitive decision-making processes that can be measured in response to either an auditory or visual stimulus. P300 and reaction time (RT) were recorded from a visual stimulus under euglycemic conditions and at plasma glucose concentrations of 3.3 and 2.6 mM during insulin infusion in 10 subjects. Reducing plasma glucose levels to 3.3 mM was not associated with an increase in either the latency or amplitude of the P300 component or a change in RT. However, further lowering of plasma glucose to 2.6 mM resulted in an increase in the latency of P300 and a prolongation in RT. Similar changes were seen for the auditory P300 in experiments performed on 9 additional subjects in which both auditory and visual stimuli were presented. The prolongation of P300 did not correct immediately when plasma glucose was raised to basal levels with intravenous glucose but returned to normal 45–75 min later, after ingestion of a carbohydrate-containing meal. Analysis of another event-related potential, P140 (a measure of the sensory processes), showed no change in response to hypoglycemia. Prolongation of RT paralleled the prolongation of P300 latency, suggesting that motor processes were not altered. Therefore, hypoglycemia appears to induce abnormalities in decision-making processes. This study shows that 1) insulin-induced hypoglycemia results in cognitive dysfunction when plasma glucose is between 3.3 and 2.6 mM on average, 2)decision-making processes rather than sensory or motor processes appear to be predominantly affected, 3)both auditory or visual P300 and RT were affected, 4) recovery of the cortical dysfunction may lag behind the return of plasma glucose to normal by 45–75 min, and 5) individual sensitivity to the adverse effects of hypoglycemia on cortical function appears to exist, but the physiological basis of this finding is not known.
Improvement With Metformin in Insulin Internalizaron and Processing in Monocytes From NIDDM Patients
Authors: Benzi Luca , Trischitta Vincenzo , Ciccarone Annamaria , Cecchetti Paolo , Brunetti Antonio , Squatrito Sebastiano , Marchetti Piero , Vigneri Riccardo , Navalesi Renzo
Published: September 2013

This study investigateci the relative effect of obesity alone and in combination with non-insulin-dependent diabetes mellitus (NIDDM) on the intracellular processing of insulin and evaluated the effect of metformin therapy on this process. Monocytes from 11 obese hyperinsulinemic subjects, 13 obese hyperinsulinemic NIDDM patients, and 7 nondiabetic control subjects were incubated with A14-125I-labeled insulin for 60 min at 37°C, and intracellular insulin degradation was characterized by high-performance liquid chromatography. Total cell-associated insulin (insulin binding) and internalized and degraded insulin were decreased in obese subjects and significantly decreased in obese NIDDM patients compared with nondiabetic control subjects. In NIDDM patients, intracellular insulin degradation was inversely correlated with fasting plasma glucose (P < 0.01). Eight obese subjects and 9 obese NIDDM patients were restudied after 4 wk of therapy with metformin (850 mg twice a day). Plasma levels of the drug were superimposable in the two groups. Metformin therapy did not change glucose and insulin levels in obese subjects but caused a decrease in blood glucose in obese NIDDM patients. Total cell-associated radioactivity (insulin binding) significantly increased in both groups (P < 0.01). On the contrary, internalized radioactivity increased (0.83 ± 0.3 vs. 1.31 ± 0.35%, P < 0.01), and similarly, insulin degradation was enhanced (54.6 ± 8.9 vs. 74.22 ± 9.15%, P< 0.01) only in monocytes from obese NIDDM patients. However, the levels of these parameters were still lower than in control subjects (internalization, 2.94 ± 0.68%; degradation, 93.03 ± 3.7%). Plasma metformin concentrations showed a significant correlation with total cell-associated radioactivity in obese subjects (P < 0.01) and obese NIDDM patients (P < 0.05). Moreover, in obese NIDDM patients, a significant correlation (P < 0.01) was found between the decrease in fasting plasma glucose and the increase in A14-125I-insulin degradation by monocytes. These data suggest that 1)NIDDM significantly worsens the abnormality of intracellular insulin processing present in obesity; 2) metformin therapy could increase total cell-associated radioactivity, probably with a concentration-dependent effect, independently from its clinical effectiveness; 3) metformin therapy enhances intracellular insulin processing only in cells from obese NIDDM patients, suggesting that the underlying abnormalities may actually be different in these two groups of patients; and 4) the correlation observed in NIDDM patients between the improvement in intracellular insulin degradation and the decrease of plasma glucose levels raises the possibility that metformin-induced degradation changes have a role in insulin action.
Insulitis and Diabetes in NOD Mice Reduced by Prophylactic Insulin Therapy
Authors: Atkinson Mark A , Maclaren Noel K , Luchetta Roberto
Published: September 2013

Intensive insulin therapy in patients with recently diagnosed insulin-dependent diabetes mellitus (IDDM) has been reported to result in a prolonged increase in endogenous insulin-secreting capacity. Because the clinical onset of IDDM occurs only after most insulinsecreting β-cells have been destroyed, we tested whether prophylactic insulin therapy might prevent IDDM in nonobese diabetic (NOD) mice. One hundred fourteen NOD mice were randomized at weaning into a protamine zinc pork insulin-treated (I) group or a placebo-treated (P) group given insulin diluent. All insulin treatments were adjusted to the maximum tolerable dosages and continued until 180 days of age. The cumulative IDDM frequency within the female I group was significantly less (3 of 34, 8%) than in female P controls (17 of 26, 65%; P < 0.0001). This beneficial effect was limited to females, however, because the frequency of IDDM in male I mice (3 of 32, 9%) was not significantly different from the frequency in male P controls (1 of 22, 5%; P < 0.5). Pancreatic histological examinations of nondiabetic animals revealed that insulin treatment resulted in significant reductions in islet cell inflammation and damage and improvements in insulin content. In summary, NOD mice given insulin therapy from weaning until 180 days of age had significantly lower frequencies of diabetes and pancreatic insulitis than sex-matched control littermates treated with insulin diluent. These results suggest that prophylactic insulin therapy to prevent IDDM in humans should be considered for clinical trials.