bluuebunny/crossref_metadata_2025 huggingface dataset:
High Plasma Free Fatty Acid Levels Contribute to the Hypersomatostatinemia of Insulin Deficiency
Authors: Wasada Taro , Howard Barbara , McCorkle Kay , Harris Virginia , Unger Roger H
Published: September 2013

High plasma levels of free fatty acids (FFA) stimulate the secretion of splanchnic somatostatin, and both are elevated in insulin deficiency. To determine if the hypersomatostatinemia of insulin deficiency is secondary to high FFA levels, plasma somatostatin-like immunoreactivity (SLI) was measured in a group of insulin- deprived alloxan-diabetic dogs during nicotinic acid-induced lowering of their elevated plasma FFA to normal, and in a group of nondiabetic dogs during nicotinic acid-induced lowering of their FFA to subnormal values. In insulin-deprived diabetic dogs, nicotinic acid reduced plasma FFA from 1.07 ± 0.2 (M ± SE) mmol/L to 0.6 ± 0.1 mmol/L (P < 0.02), approximately the basal FFA level in normal dogs. This was accompanied by a significant decline in plasma SLI levels from a mean baseline of 247 ±15 pg/ml to a mean nadir of 199 ± 10 pg/ml (P < 0.005). The latter was, nevertheless, significantly above the basal SLI level of the nondiabetic dogs. In contrast, in normal dogs, nicotinic acid-induced reduction in FFA from 0.54 ± 0.02 mmol/L to 0.24 ± 0.03 mmol/ (P < 0.001) was associated with only a small and inconsistent decrease in SLI. These findings suggest that the hypersomatostatinemia of insulin-deficient alloxan-diabetic dogs is, in part, secondary to high plasma FFA levels.
Effects of Experimental Diabetes and Insulin on Cyclic AMP Phosphodiesterase and its Protein Activator in Rat Adipose Tissue
Authors: Solomon Solomon S , Palazzolo Marjorie , McPherson Janet , Smoake Al
Published: September 2013

Streptozotocin-induced diabetes in the rat has been shown to decrease and insulin to increase the activity of cyclic AMP phosphodiesterase (PDE) in adipose tissue. Protein activator (PA), a substance of low molecular weight, is essential for full activity of some component phosphodiesterases. A significant decrease in protein activator level (60% of control) is found in the 13,000 × g boiled supernatant from streptozotocin-diabetic rat adipose tissue. When diabetic animals are treated with insulin 24 h following the induction of diabetes, protein activator is restored to 80% of the normal control level; when diabetic animals are immediately treated with insulin, the levels of protein activator are not reduced (98% of control). Hence, insulin is capable of reversing both the decrease in protein activator and phosphodiesterase activity seen with diabetes. When partially purified supernatant from diabetic animal fat is chromatographed on a DEAE Sephacel column, the untreated diabetics show inhibition, whereas insulin-treated diabetics show maximal stimulation of the low Km cyclic AMP phosphodiesterase. Protein activator and an inhibitor are readily separated when adipose tissue homogenate is centrifuged at 13,000 × g and the boiled supernatant is passed over a DEAE Sephacel column.

Diabetes is associated with a decrease in both cyclic AMP phosphodiesterase and protein activator activity, both of which are restored to normal by administration of insulin. We also report the presence of an inhibitor of activator, which is increased in streptozotocin diabetes. All of these components appear to play a role in the pathophysiology of diabetes.
Effect of pH and 3-Hydroxybutyrate on Insulin Binding and Action in Cultured Human Fibroblasts
Authors: Hidaka Hideki , Howard Barbara V , Ishibashi Fukashi , Kosmakos Frank C , Craig James W , Bennett Peter H , Larner Joseph
Published: September 2013

The influence of pH and 3-hydroxybutyrate on insulin binding and action has been studied in cultured human fibroblasts. When the pH of the incubation medium was decreased from 7.6 to 6.8, insulin stimulation of glycogen synthase and total glucose uptake was decreased. The decreased pH induced both an increase in the insulin concentration for half-maximal response, and a decrease in maximal responsiveness. When insulin binding was measured at lower pH, receptor affinity was decreased. The effect of 3-hydroxybutyrate on insulin binding and action was assessed at pH 7.4 and 6.9. In the presence of 3-hydroxybutyrate, insulin binding increased, but insulin action on glycogen synthase and total glucose uptake was unaffected. The data show that insulin action is impaired at lower pH. The decreased sensitivity is probably related to the decrease in insulin binding affinity at lower pH, but decreased maximal responsiveness implies that postreceptor components are also affected by lower pH. The results also suggest that 3-hydroxybutyrate induced a dissociation between binding and response, since an increase of insulin binding was not accompanied by changes in the regulation of glycogen synthase and total glucose uptake.
Effect of Islet-Activating Protein (IAP), Purified from the Culture Medium of Bordetella pertussis, on the Secretion of Immunoreactive Insulin and Glucagon in Normal, Alloxan-Treated, and Depancreatized Dogs
Authors: Yoshida Toshihide , Nakamura Yoshio , Nakano Koji , Kondo Motoharu
Published: September 2013

Islet-activating protein (IAP) is a new active substance purified from the culture medium of Bordetella pertussis. This active protein possesses a molecular weight of 77,000 and an isoelectric point of pH 7.8. The nature of IAP action is characterized by the enhancement of insulin secretory response to glucose and other stimuli. In this experiment, the effect of IAP on the secretion of immunoreactive insulin (IRI) and glucagon (IRG) was investigated in conscious normal, alloxan-treated, and depancreatized dogs. On the 8th day after IAP injection, in normal and alloxan-treated dogs during the infusion of arginine or glucose, the plasma glucose level was lower and the IRI level was significantly higher compared with the saline controls. The IRG level showed no significant difference between IAP and saline control groups of normal dogs, but in alloxan-treated dogs the IRG level was significantly lower when compared with the saline control. This effect of IAP disappeared on the 30th day after injection in normal and alloxan-treated dogs. However, in depancreatized dogs, there was no effect on plasma glucose and gastrointestinal IRG levels. Anti-IAP antibody was not detected by PHA before or after IAP injection in any dogs, although a marked increase of heart rate was observed. These findings suggest that (1) IAP had an insulinotropic effect in dogs, (2) insulin deficiency induced by alloxan was partially overcome by IAP, (3) the effect of IAP on glucagon secretion might be secondarily related to the enhancement of insulin secretion, although a direct glucagon-lowering effect in alloxan-treated dogs could not be excluded, (4) a single administration of IAP did not produce anti-IAP antibody, and (5) an increase of heart rate was observed after IAP injection.
Comparison of Oral Glucose Tolerance Tests and Mixed Meals in Patients with Apparent Idiopathic Postabsorptive Hypoglycemia: Absence of Hypoglycemia After Meals
Authors: Arthur Charles M , Hofeldt Fred , Shackelford Annelie , Waldeck Nancy , Dodson Leonard E , Bunker Donna , Coggins Julian T , Eichner Harvey
Published: September 2013

The relationship between symptoms of idiopathic postabsorptive hypoglycemia and glucose homeosta-sis was evaluated by giving oral glucose tolerance tests (OGTT) and mixed meals to 18 patients and 16 controls. Chemical hypoglycemia after OGTT occurred as often in patients referred because of possible hypoglycemia symptoms, 18 out of 80 (23%), as in controls, 4 out of 16 (25%). After glucose, patients showed both clinical and chemical hypoglycemia (mean ± SE plasma glucose, 48 ± 3 mg/dl), but insulin, glu-cagon, and growth hormone responses were similar to controls. After mixed meals, no chemical hypoglycemia occurred in patients (mean plasma glucose, 79 ± 3 mg/dl), yet 14 out of 18 (78%) had symptoms and/or signs consistent with hypoglycemia. No abnormality of glucose homeostasis was observed after meals that could account for symptoms or signs experienced by patients with idiopathic postabsorptive hypoglycemia. Since factors other than hypoglycemia appear to be involved, the disorder should be termed the idiopathic postprandial syndrome to avoid the connotation of chemical hypoglycemia.
Renal Function and Effects of Partial Rehydration During Diabetic Ketoacidosis
Authors: Owen Oliver E , Hamilton Licht J , Sapir Daniel G
Published: September 2013

Although diabetic ketoacidosis is characterized by increased renal excretion of glucose, ketone bodies, and nitrogenous compounds, there are few quantitative studies pertaining to renal function during this state. Therefore, renal function was studied in 10 adult patients in moderate to severe diabetic ketoacidosis before insulin administration. Admission plasma concentrations were: glucose 21.4 (9.2–39.4) mM or 386 (166–710) mg/dl, acetoacetate 3.0 (1.3–7.4) mM, beta-hydroxybutyrate 7.9 (2.9–15.2) mM, acetone 4.4 (1.3–8.9) mM, and HCO3 12.8 (9.5–17.8) mM. Arterial blood pH was 7.28 (7.21–7.38). Partial rehydration was achieved with 0.45% saline. Inulin was used to measure GFR. Renal clearance of acetoacetate, beta-hydroxybutyrate, acetone, glucose, and urinary excretion of nitrogenous compounds were determined.

Partial rehydration reduced plasma glucose concentration, primarily because of renal excretion, amounting to 384 ± 73 μmol/min or 69 ± 13 mg/min. Partial rehydration had no effect on plasma ketone bodies, on bicarbonate or urea concentrations, or on arterial pH. Partial rehydration had no effect on ketone body or nitrogenous compound excretory rates.

Reabsorptive rates of acetoacetate, beta-hydroxybutyrate, acetone, and glucose increased linearly with their filtered loads, and no maximal renal tubular transport rates were demonstrated for any ketone body or glucose. Because renal absorption of ketone bodies was less than 100%, ketonuria increased as filtered loads increase. Unlike ketone bodies, glucose reabsorptive rate was directly related to GFR.

Total renal excretion of nitrogen in the forms of urea, ammonium, creatinine, and uric acid amounted to 16 ± 2 mg/min. This huge loss of body nitrogen reflected ongoing protein catabolism and not heightened renal excretion of preformed compounds, as the plasma concentrations of urea, creatinine, and uric acid did not change during the study. Urea nitrogen accounted for 12 ± 2 mg/min (72%) of the total nitrogen excreted. Ammonium excretion was markedly augmented, ranging from 76 to 537 μmol/min, and was inversely related to arterial pH.

We conclude that the fall in plasma glucose concentration is primarily caused by renal glucose excretion, and that the absence of a maximal renal tubular reab-sorption rate for either acetoacetate (AcAc) or beta-hydroxybutyrate (β-OHB) serves to mitigate urinary losses of sodium and potassium during diabetic ketoacidosis.
Dissociation of the Effects of Vincristine on Stimulated Insulin Release and the Pancreatic β-Cell Microtubular Structures in the Intact Rat
Authors: Shah Jayendra H , Stevens Bernard , Sorensen Bonita J
Published: September 2013

We have recently shown that in the intact rat, at 10 min after vincristine treatment, glucose-induced insulin release and glucose tolerance were potentiated, but at 60 and 120 min after vincristine treatment, glucose- induced insulin release and glucose tolerance were significantly impaired. The present study further evaluated the mechanisms of these observations by examining the in vivo effect of vincristine on (1) the pancreatic β-cell microtubular structures and (2) insulin release in response to arginine, an insulin secretogogue other than glucose. In the first series of studies, the pancreases were removed from the rats at 60 and 120 min after vincristine (0.15 mg/kg; i.v.) or vehicle (control) administration for electron microscopy. Morphometric analysis revealed that the number of β- cell microtubules was similar in the vincristinetreated and the control rats. Furthermore, the mean microtubular length in vincristine-treated rats was also similar to that observed in the control rats. In the next series of studies, at 10, 60, or 120 min after vincristine (0.15 mg/kg; i.v.), insulin levels in response to an i.v. arginine pulse were similar in the vincristinetreated and in the control rats at all time intervals between 2 and 30 min. A parallel study once again demonstrated that glucose-induced insulin release and glucose tolerance were significantly impaired at 120 min after vincristine treatment. These findings indicate that (1) In the intact rat, inhibition of glucose-induced insulin release by vincristine occurs in the absence of any demonstrable changes in the β-cell microtubular structure; and (2) even though vincristine inhibits glucose-induced insulin release, it has no effect on arginine-induced insulin release. Therefore, in the intact rat, the inhibition of glucose-induced insulin release by vincristine may be mediated via mechanisms other than microtubular disruption.
Neonatal Pig Pseudo-Islets: A Product of Selective Aggregation
Authors: Britt L D , Stojeba P C , Scharp C R , Greider M H , Scharp D W
Published: September 2013

Pseudo-islets have been formed from single cell preparations of neonatal porcine pancreas by selective aggregation using the gyrotational tissue culture method for 7 days. Small, distinct aggregates present on the second day of culture gradually enlarged by the seventh day and at that time were taken off for assessment of secreting capabilities and cell type identification. Provocative stimulation and immunocytochemical examination confirmed viable, well-preserved pseudo-islets which contain all four islet cell types. Neonatal pig pseudo-islet formation will allow us to pursue the suitability and growth potential of this source of islet tissue under appropriate immunoaltered conditions as a xenograft source for future transplantation studies.
Defective Hydroxylation of Phenformin as a Determinant of Drug Toxicity
Authors: Bosisio E , Galli Kienle M , Galli G , Ciconali M , Negri A , Sessa A , Morosati S , Sirtori C R
Published: September 2013

The kinetics of phenformin and its metabolite, p-hydroxyphenethylbiguanide, was studied in eight diabetic patients with varying degrees of renal impairment. Plasma and urinary phenformin and p-hydroxyphenethylbiguanide levels were determined by the multiple selected ion monitoring technique. Phenformin half-lives were unrelated to the degree of renal impairment, whereas reduced renal clearances of inulin and creatinine were significantly correlated with a prolonged half-life of the metabolite. The excretion of p-hydroxyphenethylbiguanide was quite variable (between 4.9% and 27% of total urinary drug loss), probably due to a genetic polymorphism of hepatic mechanisms for hydroxylation. A reduced formation of the metabolite was concomitant with marked increases in the amount of circulating phenformin. A positive reciprocal correlation was detected between areas under the plasma curve of phenformin and both the renal clearance of the unchanged drug and the percentage of metabolite formation. A reduced hydroxylation of phenformin seems, therefore, to be responsible for the high plasma levels of the drug previously described in toxic patients.
Differential Response to Infusions of Highly Purified and Conventional Bovine and Porcine Insulins
Authors: Nosadini R , Noy G , Kurtz A B , Alberti K G M M
Published: September 2013

The glucose clamp technique allows quantification of tissue sensitivity to insulin without modulation by the effects of hypoglycemia. The amount of glucose infused to maintain euglycemia during an insulin infusion gives a direct measure of tissue sensitivity. We have used this technique to compare the metabolic effects of highly purified porcine, highly purified bovine, and conventional insulins in diabetic subjects: (A) a group normally taking conventional bovine insulin, and (B) diabetics who had originally been treated with conventional bovine insulin and had changed to highly purified porcine insulin. Subjects were studied while attached to the Biostator with blood glucose values clamped at the basal level during a 2-h insulin infusion (0.01 U/kg/h). Both groups of diabetics received significantly more glucose in the first hour of the monocomponent porcine insulin infusion than during the same period either of conventional or of highly purified bovine insulin infusion. Highly purified porcine insulin infusion was also associated with a more rapid fall in blood ketone body concentrations.

Highly purified porcine insulin infusion was accompanied by a greater and earlier increase in free insulin concentrations. All diabetics had antibodies to insulin but no differential antibody binding of beef and pork insulin was found in the two groups of patients. Thus, use of highly purified porcine insulin is associated with a more rapid onset of action and a greater initial increment in free insulin values.
Effect of Ethanol, Acetaldehyde, and Acetate on Insulin and Glucagon Secretion in the Perfused Rat Pancreas
Authors: Tiengo A , Valerio A , Molinari M , Meneghel A , Lapolla A
Published: September 2013

The effects of varying concentrations of ethanol (1,10, and 30 mM) and its metabolites (1 mM acetate and 1 and 10 mM acetaldehyde) on insulin and glucagon secretion induced by glucose (11.1 mM) and arginine (20 mM) were studied in isolated perfused pancreas of Sprague-Dawley rats

Ethanol and its metabolites did not significantly modify basal secretion of the two hormones. Ethanol reduced glucose-induced insulin secretion by means of a dose-related effect. Arginine-induced insulin output did not seem to be influenced to any significant degree. Acetate and acetaldehyde significantly inhibited glucose and arginine-induced insulin secretion. While ethanol (10 and 30 mM) did not modify glucagon output during arginine perfusion, acetate and acetaldehyde markedly enhanced it.

The block of insulin secretion and the increased secretion of glucagon could explain the diabetogenic effect of ethanol demonstrated in vivo. The mechanism by which ethanol acts on the pancreatic β- and α-cells is discussed.
Insulin Inhibits Somatostatin-Like Immunoreactivity Release Stimulated by Intragastric HCI
Authors: Rouiller Dominique , Schusdziarra Volker , Unger Roger H
Published: September 2013

To determine the effect of an increase in insulin levels within the range occuring under physiologic conditions on the protein- and acid-induced release of splanchnic somatostatin, insulin was infused in dogs for 1 h following the intragastric instillation of a neutral protein load (20% liver extract at pH 7), a weak stimulus of somatostatin-like immunoreactivity (SLI), and after an intragastric HCI, a strong stimulus of SLI release, instilled 30 min later. Insulin levels between 50 and 60 μU/ml significantly reduced the rise in peripheral venous SLI levels elicited by the acid load from a mean integrated incremental value of 1705 ±182 pg/ml in controls to 840 ± 312 in the insulininfused group (P < 0.05). Prevention of the insulininduced hypoglycemia and the secondary rise in glucagon, a known stimulus of pancreatic somatostatin secretion, by means of a concomitant infusion of glucose, did not modify the reduction in acid-induced increase in plasma SLI concentration associated with hyperinsulinemia. Insulin-glucose infusion significantly lowered the SLI in the pancreaticoduodenal vein, and in the gastroepiploic vein draining the antrum (P < 0.02; P < 0.05), but not in the short gastric veins draining the fundus of the stomach in response to the acid load. It is concluded that a physiologic elevation of insulin levels causes significantly reduced response of SLI to an intragastric acid load in dogs. This reduction is explained by a diminished increment of SLI in the venous effluent of the pancreas and the antrum.
Regional Localization of Cerebral Edema Following Fluid and Insulin Therapy in Streptozotocin-Diabetic Rats
Authors: Tornheim Patricia A
Published: September 2013

To evaluate the location and early time course for development of cerebral edema following therapy for diabetes, streptozotocin-diabetic rats were subjected to constant i.v. infusion with saline and regular insulin. At the end of 1, 2, and 5 h of therapy, these rats were killed and tested for density of the cerebral cortex, subcortical white matter, caudate-putamen, thalamus, and medulla. Density data from treated animals were compared with those from control animals. From these data, change in brain tissue volume as water was calculated.

Diabetic animals killed after 1 h of fluid and insulin therapy demonstrated a modest increase in brain water content of all areas tested except white matter. Following 2 h of therapy, all regions tested were edematous, with a magnitude of edema that was similar to that seen at 1 h. After 5 h of therapy, there was further increase in water content of the cerebral cortex, but not the other regions examined. Treatment with saline alone did not result in central overhydration.

The findings of this study suggest that aggressive therapy with fluids and insulin, but not fluid alone, results in global overhydration of the brains of diabetic animals. Prolonged fluid and insulin treatment with a return of blood glucose to normal values causes further and preferential accumulation of edema fluid in the cerebral cortex.
Increase of Plasma Acetaldehyde: An Objective Indicator of the Chlorpropamide Alcohol Flush
Authors: Jerntorp Peter , Öhlin Hans , Bergström Bengt , Almér Lars-Olof
Published: September 2013

Chlorpropamide alcohol flushing (CPAF) in non-insulin-dependent diabetics (NIDDs) has been reported to be associated with a lower tendency to develop late complications. The flush was thought to be mediated by enkephalins and prostaglandins. Early studies could not correlate CPAF to increased levels of acetaldehyde in blood and the flush was not regarded as an antabuse-like reaction.

In this study, the increase of plasma acetaldehyde during the flush in 13 CPAF positive diabetics was significantly (P < 0.005) higher than in 13 CPAF negative diabetics during a CPAF challenge test. The increase of plasma acetaldehyde was reduced to the level of CPAF negative diabetics in three CPAF positive diabetics when they were exposed to alcohol without premedication with chlorpropamide and they did not flush. The normal breakdown of ethanol to acetic acid via acetaldehyde appears to be inhibited by chlorpropamide in the flushers. Acetaldehyde measurement is an objective method to study the chlorpropamide alcohol flush and it appears superior to the measurement of skin temperature.
Metabolic Control of Prevention of Nephropathy by 2-Tetradecylglycidate in the Diabetic Mouse (db/db)
Authors: Lee Stanly M , Tutwiler Gene , Bressler Rubin , Kircher Charles H
Published: September 2013

The genetically diabetic mouse (db/db) exhibits hyperphagia, progressive weight gain, hyperglycemia, and hyperinsulinemia during the first few months of life during which time characteristic pathologic changes occur in several organ systems including the kidney. The extent to which long chain fatty acid oxidation (LCFAO) contributes to excessive gluconeogenesis and hyperglycemia in these animals in unknown. Therefore, the synthetic fatty acid analogue 2-tetradeclyglycidate (TDHA), a potent inhibitor of LCFAO, was given orally to db/db mice to evaluate its capacity to control the blood glucose and prevent their diabetic nephropathy. Five groups of diabetic mice (N = 6) were assigned to receive TDGA in a dose of 5, 10, and 25 mg/kg/day, vehicle (tragacanth), or nothing (control). TDGA had no observable effects on food intake or growth patterns. Drug-treated animals had significant lowering of fasting glucose at 0 and 4 h after dosing during the midportion of the study (2–6 wk). In the latter part of the study (wk 8–11), blood glucose 4 h after dosing was lowered in mice given 10 and 25 free fatty acids. Animals receiving TDGA 25 mg/kg/day exhibited significant inhibition of immunopathologic changes in the kidney. Heart weight was significantly increased in mice receiving TDGA 25 mg/kg/day, and the total amount of myocardial carnitine content was increased in all three drug-treated groups. Increased tissue deposition of lipid was not apparent on histologic examination of liver in drug-treated animals.

Inhibition of long chain fat oxidation in the db/db mouse results in significant lowering of blood glucose, and decreases the renal immunopathologic features of diabetic nephropathy in this animal model.
Genetic and Immunologic Factors in Microvascular Disease in Type I Insulin-Dependent Diabetes
Authors: Bodansky H J , Wolf Eva , Cudworth A G , Dean Betty M , Nineham Lynn J , Bottazzo G F , Matthews Judith A , Kurtz A B , Kohner Eva M
Published: September 2013

A detailed study of 133 subjects with insulin-dependent (type I) diabetes with severe microvascular disease has failed to substantiate the hypothesis that HLA factors influence the predisposition to this type of complication. A significant association between proliferative retinopathy and raised levels of circulating immune complexes was found. The distribution of insulin-binding levels in serum was similar to that in patients without complications. There was no correlation between insulin binding and the presence of immune complexes and no evidence was found that these complexes contained anti-insulin, anti-nuclear, or organ-specific antibodies.

The distribution of insulin-binding levels in these subjects with diabetes of long duration was similar to that observed in 270 subjects with juvenile-onset short-duration type I diabetes. When the data were combined, significant associations between HLA-B8 and low/absent insulin binding levels and B7 with moderate/high insulin-binding levels were observed. HLA-BW62 was not associated with either high or low insulin-binding capacity.

It is concluded that HLA genetic factors, insulinbinding capacity, and autoimmunity are unrelated to the pathogenesis of microvascular disease. Raised levels of circulating immune complexes may well be secondary to widespread tissue damage in diabetes of long duration.
Other Potentially Useful Rodents as Models for the Study of Human Diabetes Mellitus
Authors: Coleman Douglas L
Published: September 2013

There are several other rodent models, not described in the previous papers, that are also suitable for studies of human diabetes mellitus. All have advantages and disadvantages depending on the type of investigation being undertaken. The most useful models and the characteristics which could make them valuable in diabetes research are described.
Metabolic and Underlying Causes of Diabetes Mellitus
Authors: Grodsky Gerold M , Anderson Carol E , Coleman Douglas L , Craighead John E , Gerritsen George C , Hansen Carl T , Herberg Lieselotte , Howard Charles F , Lernmark Ake , Matschinsky Franz M , Rayfield Elliot , Riley William J , Rossini Aldo A
Published: September 2013

It is emphasized that animai models should be used to study specific genotypic or phenotypic expressions associated with diabetes rather than assuming a single animal model can reflect diverse forms of the human disease. Diabetic and normal animals are reviewed on the basis of their usefulness as models of genetic, viral, and chemically induced diabetes, including the often associated immune phenomena. Characteristics of spontaneously diabetic animals with and without obesity are also described with an emphasis on both genetics and metabolic derangements.

Recommendations for future animal experimentation include: more longitudinal studies evaluating the role of sex, prenatal environment, diet, and viral or chemical attack on B-cell function; characterization of the immune phenomena associated with B-cell lesions (and insulitis) in diabetic and immunologically incompetent lines; clarification of relationships between obesity and islet-ceil function with emphasis on the role of fuel metabolism, vitamins, and minerals; and, finally, the development of new models with specific genetic aberrations placed in normal or diabetic lines.
Ocular Complications
Authors: Engerman Ronald , Finkelstein Daniel , Aguirre Gustavo , Diddie Kenneth R , Fox Richard R , Frank Robert N , Varma Shambhu D
Published: September 2013

Ocular complications of diabetes in humans are reviewed briefly, and experimental models available for study of the complications are described. Potentially suitable models include not only diabetic animals, but also nondiabetic animals in which analogous lesions have been demonstrated. Many abnormalities of the lens, cornea, iris, and retina comparable to those of diabetes in humans may be observed in diabetic animals, although all abnormalities are not necessarily observed in every species. Retinal changes, in particular, may occur in diabetic animals of several species, but only in large animals (dogs, primates) have saccular capillary aneurysms been reproduced consistently, together with other retinal changes typical of diabetes in humans. A few examples of the uses of animal models are offered, and attention is called to a lack of animal models of proliferative diabetic retinqpathy and of rubeosis iridiS.
Influence of Age on Clearance of Insulin in Man
Authors: Minaker K L , Rowe J W , Tonino R , Pallotta J A
Published: September 2013

With advancing age, glucose-induced insulin release is decreased in vitro, yet circulating insulin levels after glucose challenge are not decreased in the elderly. Age-related changes in insulin clearance may contribute to this discrepancy. We employed the 2-h euglycemic clamp technique to examine insulin clearance (C1) during steady-state insulin infusions (N = 53) at rates of 20, 80, and 200 mU/m2/min in healthy young (N = 16, age range 22–37 yr, relative weight 1.07 ± 0.03) and old (N = 10, age range 63–77 yr, relative weight 1.14 ± 0.03) men. Steady-state insulin levels were statistically significantly higher (P < 0.01) in the elderly at each infusion rate. C1 was 40% lower (p < 0.01) in the infusion rate. There was no effect of increasing relative weight on C1 within age groups. Within each age group, C1 was similar in insulin infusion rates of 20 and 80 mU/m2/min (young P < 0.05, old P < 0.001), implying a saturable system for insulin clearance. Alterations in C1 contribute to changes in insulin levels with age and may reconcile the discrepancy between in vivo and in vitro studies of glucose-induced insulin release. These results indicate the value of evaluating C1 as one determinant of circulating insulin level in states of abnormal insulin physiology.
Metabolism of Cholesterol and Plasma Triglycerides in Nonketotic Diabetes Mellitus
Authors: Abrams Jeffrey J , Ginsberg Henry , Grundy Scott M
Published: September 2013

The metabolism of cholesterol and plasma triglycerides (TG) was studied in 14 diabetic men: these patients did not have marked obesity nor did they develop ketoacidosis without insulin. Before insulin therapy, measurements were made of (1) plasma lipoproteins, (2) postheparin lipolytic enzymes, (3) turnover to TG in very-low-density lipoproteins (VLDL) and chylomicrons, (4) cholesterol balance, and (5) biliary lipids. After baseline measurements, the patients were treated with enough long-acting insulin to maintain their fasting plasma glucose in the range of 100–125 mg/dl. When plasma glucose and lipid levels reached a new steady state, all of the above measurements were repeated. Before insulin, most patients had fasting hypertriglyceridemia. This was due mainly to overproduction of VLDL-TG. Insulin therapy lowered both synthesis and concentrations of VLDLTG to near normal. Also, patients with normotriglyceridemia, both before and during insulin therapy, had essentially normal clearance of chylomicrons. Those with high fasting TG had delayed clearance of chylomicrons, but clearance returned to normal in most with insulin therapy. Postheparin lipolytic enzymes were not decreased. Before insulin, synthesis rates of cholesterol and bile acids usually were greater than normal, and bile commonly was supersaturated with cholesterol. During insulin therapy, synthesis of both cholesterol and bile acids remained elevated, possibly because of imperfect control of hyperglycemia. Furthermore, saturation of bile with cholesterol was accentuated by insulin therapy.
Postreceptor Defects Causing Insulin Resistance in Normoinsulinemic Non-insulin-dependent Diabetes Mellitus
Authors: Bolinder Jan , Östman Jan , Arner Peter
Published: September 2013

The mechanisms of the diminished hypoglycemic response to insulin in non-insulin-dependent diabetes mellitus (NIDDM) with normal levels of circulating plasma insulin were investigated. Specific binding of mono-125I (Tyr A14)-insulin to isolated adipocytes and effects of insulin (5–10,000 μU/ml) on glucose oxidation and lipolysis were determined simultaneously in subcutaneous adipose tissue of seven healthy subjects of normal weight and seven untreated NIDDM patients with normal plasma insulin levels. The two groups were matched for age, sex, and body weight. Insulin binding, measured in terms of receptor number and affinity, was normal in NIDDM, the total number of receptors averaging 350,000 per cell. Neither sensitivity nor the maximum antilipolytic effect of insulin was altered in NIDDM patients as compared with control subjects; the insulin concentration producing half the maximum effect (ED50) was 10 μU/ml. As regards the effect of insulin on glucose oxidation, for the control subjects ED50 was 30 μU/ml, whereas in NIDDM patients, insulin exerted no stimulatory effect. The results obtained suggest that the effect of insulin on glucose utilization in normoinsulinemic NIDDM may be diminished in spite of normal insulin binding to receptors. The resistance may be due solely to postreceptor defects, and does not involve antilipolysis.
Evidence for an Intrahepatic Contribution to the Waning Effect of Glucagon on Glucose Production in the Conscious Dog
Authors: Cherrington Alan D , Diamond Michael P , Green Donald R , Williams Phillip E
Published: September 2013

We previously showed that infusion of glucagon at four times the basal rate into conscious dogs given somatostatin and basal replacement amounts of insulin caused hyperglycemia (217 ± 15 mg/dl) for at least 3 h and an initial increment in hepatic glucose production of 5.5 ± 0.8 mg/kg · min. After 3 h, however, the effect of hyperglucagonemia on glucose production had declined by 85%. The aim of the present study was to determine the importance of hyperglycemia in the “downregulation” of the action of glucagon.

Six overnight-fasted conscious dogs were given somatostatin (0.8 μg/kg · min) plus basal intraportal replacement amounts of insulin (263 μU/kg · min) and glucagon (0.65 ng/kg · min). Hyperglycemia (276 ± 12 md/dl) was established after 2 h by the infusion of exogenous glucose. The glucagon infusion rate was then increased fourfold 1 h later, so that the plasma glucagon level rose from 95 ± 16 to 227 ± 35 pg/ml. The glucose concentration was maintained at a fixed value despite the increase in glucagon by decreasing the glucose infusion rate by an amount equal to the increase in endogenous glucose production induced by the hormone. Glucose production was measured using a primed infusion of 3H-glucose. With the insulin (11 ± 2 μU/ml) and glucose levels fixed, the elevation in glucagon caused an initial increment of 5.1 ± 0.7 mg/kg · min in glucose production which was followed by a fall of only 2.5 · 0.4 mg/kg · min (50%) over the next 3 h. Thus, when the plasma glucagon level is raised fourfold under conditions in which insulin mobilization cannot occur, the effect of hyperglucagonemia on glucose production will be partially offset by the resulting hyperglycemia and partly inhibited by an hepatic factor(s).
Selective Binding of Fluoresceinated-Avidin to A-Cells of Sectioned Pancreas
Authors: Rowley R F , Eisenbarth G S
Published: September 2013

Fluoresceinated-avidin (FITC-avidin) was observed to bind specifically to a subset of pancreatic islet cells in sections of both human and rat pancreas. FITC-avidin binding was inhibited by excess unlabeled avidin, and by biotin, but not by glucagon, somatostatin, or insulin. Labeling of islets with anti-insulin, anti-glucagon, anti-somatostatin, and anti-human pancreatic polypeptide antibodies showed the avidin binding subset to correspond to islet cells identified by anti-glucagon antibody. Conversely, avidin reacted with no insulin, somatostatin, or cells containing HPP. We conclude that avidin localizes specifically to A-islet cells. Binding may be to a biotin-containing enzyme within the A-cells, but the precise molecular site of binding is currently unidentified.
Reticuloendothelial Hyperphagocytosis Occurs in Streptozotocin-Diabetic Rats: Studies with Colloidal Carbon, Albumin Microaggregates, and Soluble Fibrin Monomers
Authors: Cornell Robert P
Published: September 2013

In contrast to previous studies of diabetic humans and animals, which reported unchanged or depressed function, reticuloendothelial system (RES) hyperphagocytosis of colloidal carbon, 125I-albumin microaggregates, and 125I-fibrin monomers were observed in rats as early as 14 days after the induction of diabetes with streptozotocin (STZ). The fact that enhanced phagocytosis by RE macrophages was prevented by chronic insulin replacement therapy indicates that the diabetic internal environment of hyperglycemia and hypoinsulinemia was perhaps responsible for the observed changes. Experiments involving organ localization of intravenously administered particles, perfusion of isolated livers, and microscopic examination of the liver all suggested that increased Kupffer cell activity was the primary event in RES hyperphagocytosis by STZ-diabetic rats. Both hypertrophy and hyperplasia of Kupffer cells were apparent in livers of STZ-diabetic animals as evidenced by photomicrographs and hepatic cell quantification. Plasma fibronectin, which binds fibrin monomers to RE macrophages before phagocytosis, was significantly decreased in the circulation of STZ-diabetic rats, but the level of cell-associated fibronectin was not measured. Renal localization of urea-soluble 125I-fibrin monomers exceeded splenic and pulmonary uptake in normal control rats and was enhanced in animals with STZ-diabetes. Changes in fibronectin levels, fibrin monomer localization, and Kupffer cell size and numbers in experimental diabetes in rats may have implications for the pathogenesis of vascular disease involving phagocytic mesangial and foam cells in diabetic humans.
Alterations in the Basement Membrane (Heparan Sulfate) Proteoglycan in Diabetic Mice
Authors: Rohrbach David H , Hassell John R , Kleinman Hynda K , Martin George R
Published: September 2013

We have grown the EHS (Engelbreth-Holm, Swarm) tumor in normal and genetically diabetic mice (db/db) and measured some components of basement membrane produced in the tumor. These studies showed similar amounts of total protein in control and diabetic tissue and similar patterns of proteins on SDS gel electrophoresis of extracts of the tissue. Laminin, a basement membrane specific glycoprotein utilized as an attachment factor by epithelial cells, was present in increased amounts in diabetic tissue. In contrast, the amount of BM-1 (heparan sulfate) proteoglycan was reduced. Less 35S-sulfate was incorporated into this proteoglycan, and the proteoglycan, but not its component glycosaminoglycans, was heterogeneous in size. The data indicate that either the synthesis of proteoglycan was decreased or its degradation was increased in diabetic tissue. Since the heparan sulfate proteoglycan serves to block the passage of anionic macromolecules through the basement membrane, decreased levels could account for the increased porosity of diabetic basement membrane. Compensatory synthesis of the basement membrane components to restore normal permeability could account for the thickened basement membranes observed in diabetes.
Nonenzymatic Glucosylation of Low-Density Lipoprotein Alters Its Biologic Activity
Authors: Witztum Joseph L , Mahoney Eileen M , Branks Michael J , Fisher Milton , Elam Richard , Steinberg Daniel
Published: September 2013

Human low-density lipoprotein (LDL) was glucosylated by incubation in vitro with glucose (20–80 mM) with or without addition of cyanoborohydride. The incorporation of covalently bound glucose was linear over time, and amino acid analysis showed the presence of glucosyllysine residues. The glucosylated LDL (glc LDL) moved more rapidly than normal LDL on agarose electrophoresis.

The rate of degradation of 125I-labeled glucosylated LDL (glc LDL) by cultured human fibroblasts was reduced compared with that of native 125I-LDL, the difference increasing with extent of glucosylation. Effects were seen with blockage of as few as 6–15﹪ of the LDL lysine residues; high-affinity degradation was completely lost when one-third of the lysine residues were blocked. Conjugation of LDL with glucose-6-phosphate also blocked high-affinity uptake and degradation. Whereas native LDL uptake inhibited the activity of β-hydroxy-β-methylglutaryl coenzyme A reductase and stimulated acyl coenzyme A:cholesterol acyltransferase activity, glc LDL had no effects on these enzymes. The fractional catabolic rate of glc LDL in guinea pigs was reduced. Degradation of glc LDL by mouse peritoneal macrophages was not significantly faster than that of native LDL. Finally, the presence of glc LDL in human plasma was demonstrated. Preliminary data show that 1.3﹪ of lysine residues in normal LDL and 2–5.3﹪ of lysines in diabetic LDL were glucosylated. Since, like other plasma proteins, LDL undergoes glucosylation in diabetes, its turnover and sites of catabolism may differ from normal and this may be relevant to the accelerated atherosclerosis of diabetes.
HLA Antigens, Cytoplasmic Islet Cell Antibodies, and Carbohydrate Tolerance in Families of Children with Insulin-dependent Diabetes Mellitus
Authors: Ginsberg-Fellner Fredda , Dobersen Michael J , Witt Mary E , Rayfield Elliot J , Rubinstein Pablo , Notkins Abner L
Published: September 2013

Cytoplasmic pancreatic islet cell antibodies were found in 21﹪ of 244 unaffected first degree relatives of type I diabetic patients. Twenty-five percent of HLA-identical, 35﹪ of HLA-haploidentical, 16﹪ of HLA-nonidentical siblings, and 14﹪ of parents were ICA-positive. In the HLA-identical sibs, irrespective of ICA, and in the 18 ICA-positive parents but not the other groups, increased plasma glucose levels were observed after the administration of glucose. In most children, these were associated with reduced insulin levels, while in the adults elevated insulin responses were noted. In 48﹪ of the ICA-positive children and 84﹪ of the ICA-positive parents, other evidence of “autoimmunity” was obtained either by history or by testing for specific autoantibodies. Two of the originally unaffected HLA-identical and ICA-positive siblings developed diabetes during the course of the study. These findings, plus previously reported data in families with two diabetic sibs demonstrating that the empiric risk for developing IDDM is of the order of 30﹪ for HLA-identical sibs but < 5﹪ for those that are HLA-haploidentical, suggest that HLA-identity may be a useful predictor of potential type I diabetes. The presence of ICA may, at times, portend the need for future antidiabetic therapy but prospective studies must be continued to fully elucidate this relationship.
Transplantation Without Immunosuppression
Authors: Faustman Denise , Lacy Paul E , Davie Joseph M
Published: September 2013

Exciting new findings have been reported in the past few years that indicate that islets can he transplanted successfully across major histocompatibility harriers without the continuous use of imrnunosuppressive agents by techniques designed to eliminate passenger leukocytes, in vitro culture of donor islets either at a low temperature (24°C) with a single injection of anti-lymphocyte serum or culture of megaislets in the presence of 95% O2 before transplantation permitted the successful transplantation of islet allograft and xenografts (rat to mouse). Definitive evidence in support of the passenger leukocyte concept has been obtained recently. Mouse islet cells have been shown to express the class I antigens of the H-2 complex, but do not express la antigens. Treatment of fresh mouse islets with specific anti-la sera and complement completely prevented rejection of islets transplanted across a major histocompatibility barrier. These findings indicate that la-positive cells (possibly dendritic cells) are primarily responsible for the initiation of immune rejection of the transplants. This is of particular importance with respect to the eventual transplantation of islets into human diabetics since it may be feasible to utilize antisera to HLA-DR antigens for pretreatment of islets before transplantation. In addition, these new developments may also be applicable to the transplantation of other organs such as the parathyroid, heart, kidney, liver, and skin.
Immunocytochemical Localization of HLA-DR in Human Islets of Langerhans
Authors: Alejandro Rodolfo , Shienvold Frances Litz , Hajek Shirley Vaerewyck , Ryan Una , Miller Joshua , Mintz Daniel H
Published: September 2013

Previous reports of allogeneic transplantation studies in rodents have postulated that the primary carriers of la antigen in islets of Langerhans are passenger leukocytes. We sought to demonstrate directly the localization of the analogous human antigen, HLA-DR, in islet-enriched fractions (IEFs), utilizing a nonpolymorphic monoclonal anti-DR (αDR) antibody.

The presence of DR in the IEFs was first demonstrated by radioimmunobinding assay. Light microscopic immunocytochemistry, in frozen sections of intact (unfixed) human pancreas, revealed a staining pattern suggestive of a vascular distribution of DR in islets.

Ultrastructural localization of DR was then carried out by indirect immunoperoxidase labeling in the presence of NaN3 (to prevent internalization of bound αDR). The major site of DR expression in the islet was the endothelial cell surface. Endocrine cells were entirely devoid of αDR binding. Nonislet endothelium was also heavily labeled, but acinar and ductal cells were completely negative. Leukocytes bound αDR but were relatively rare in the IEFs. Human islets, therefore, clearly express HLA-DR, but predominantly on insular endothelial cells. Isolation of pure endocrine cell populations, specifically free of endothelium, would appear to be a rational approach to reducing immunogenicity in allogeneic transplantation.
Survival of Intrasplenically Implanted Islets in Mice with Experimental Insulitis and Hyperglycemia
Authors: Sandler Stellan , Andersson Arne
Published: September 2013

Injections of repeated, subdiabetogenic doses of streptozotocin to C57BL/KsJ mice induced a slowly developing hyperglycemia and pancreatic insulitis similar to that observed in human type I diabetes. It was found that the hyperglycemia could be normalized in these animals by the intrasplenic implantation of syngeneic islets. This could be achieved both 9 and 14 days after the first streptozotocin injection. At the first time point there was a severe insulitis in the pancreas of the recipient. When animals that had been cured by an intrasplenic islet implant were given three subdiabetogenic booster-doses of streptozotocin, they reverted to hyperglycemia. This suggests that cell-mediated immune reactions are of etiologic significance in this diabetes model, since mice made diabetic by a single large dose of streptozotocin and subsequently cured by islet transplantation remained unaffected by the booster-dose administration of streptozotocin.

To test the hypothesis that the β-cell destruction induced by streptozotocin is the triggering mechanism for the insulitis process, syngeneic islets were implanted into the spleen after being exposed in vitro to a weak streptozotocin concentration. This treatment led to normoglycemia in only two of seven alloxan-di-abetic recipients. Streptozotocin-treated islets implanted into normoglycemic recipients were recovered intact in the spleens, and pancreatic islet morphology was not influenced by this treatment.

The present data do not speak against ongoing attempts to cure human diabetics with islet cell transplantation despite the fact that islet lesions that may reflect immunologic mechanisms are encountered in type I diabetes.