bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered Protein Phosphorylation in Sciatic Nerve From Rats With Streptozocin-Induced Diabetes
Authors: Schrama Loes H , Berti-Mattera Liliana N , Eichberg Joseph
Published: September 2013

The effect of experimental diabetes on the phosphorylation of proteins in the rat sciatic nerve was studied. Nerves from animals made diabetic with streptozocin were incubated in vitro with [32P]orthophosphate and divided into segments from the proximal to the distal end, and proteins from each segment were then separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The principal labeled species were the major myelin proteins, P0, and the basic proteins. After 6 wk of diabetes, the incorporation of isotope into these proteins rose as a function of distance along the nerve in a proximal to distal direction and was significantly higher at the distal end compared with incorporation into nerves from age-matched controls. The overall level of isotope uptake was similar in nerves from diabetic animals and weight-matched controls. The distribution of 32P among proteins also differed in diabetic nerve compared with both control groups in that P0 and the small basic protein accounted for a greater proportion of total label incorporated along the entire length of nerve. In contrast to intact nerve, there was no significant difference in protein phosphorylation when homogenates from normal and diabetic nerve were incubated with [32P]-γ-ATP. The results suggest that abnormal protein phosphorylation, particularly of myelin proteins, is a feature of experimental diabetic neuropathy and that the changes are most pronounced in the distal portion of the nerve.
Developmental Changes in Immunoreactive Content of Novel Pituitary Protein 7B2 in Human Pancreas and Its Identification in Pancreatic Tumors
Authors: Suzuki Hitoshi , Christofides Nicos D , Chretien Michel , Seidah Nabil G , Polak Julia M , Bloom Stephen R
Published: September 2013

Developmental changes in concentration of a novel pituitary protein (7B2) were studied immunochemically in the human pancreas from 20 wk of gestation to 4 mo after birth. The concentrations of 7B2 in pancreatic islet tumors and in nesidioblastosis were investigated also. Significant quantities of 7B2-like immunoreactivity (IR-7B2) were found in all developmental stages studied. The highest concentrations of IR-7B2 were found at term [215.4 ± 40.0 vs. 28.3 ± 4.4 pmol/g (adult levels), P < .001]. A high incidence of elevated IR-7B2 concentration in pancreatic islet tumors and nesidioblastosis was found (10 of 12 insulinomas, 5 of 8 glucagonomas, and in all 3 pancreases with nesidioblastosis). Gel-permeation chromatography on Sephadex G-100 showed two immunoreactive peaks in all extracts studied. The main peak (Kav 0.30) of IR-7B2 corresponded to that found in the porcine pituitary gland. The high incidence of elevated IR-7B2 concentrations in pancreatic islet tumors and the increase in IR-7B2 concentrations in the term pancreas and particularly in nesidioblastosis suggest that the novel protein 7B2 may serve as an islet marker.
Galactose Assimilation in Pups of Diabetic Canine Mothers
Authors: Kliegman Robert M , Morton Sharon
Published: September 2013

The effects of enteric galactose alimentation on neonatal glucose turnover and hepatic glycogen synthesis were investigated in a newborn animal model of diabetic pregnancy. Control pups and pups of diabetic dogs were studied in the basal state and after each group of pups was randomly fed equivalent amounts of galactose or glucose by oral-gastric tubes. Basal fasting blood glucose levels were not statistically different between the groups, whereas basal plasma insulin levels were 2–3 times higher in pups born to diabetic mothers. Blood glucose levels at each time point in response to glucose or galactose feeding in pups of diabetic mothers were not statistically different; however, the rise of plasma insulin concentrations was attenuated in pups of diabetic mothers fed galactose. The increase in the systemic rate of appearance of glucose and in glucose clearance were attenuated in pups of diabetic mothers fed galactose compared with those fed glucose. Hepatic glycogen content was augmented above basal levels in pups of diabetic mothers. Although glycogen synthase activity was not different between glucose-or galactose-fed pups of diabetic mothers, the active component of glycogen phosphorylase was reduced by both glucose and galactose feedings. Galactose alimentation had a greater effect on glycogen phosphorylase than did glucose alimentation. The observed increase in glycogen synthesis and reduced systemic glucose appearance after galactose alimentation could not be accounted for by the previously proposed excess of galactokinase over glucokinase activities when the latter enzyme was assayed at saturation. Indeed, neonatal hepatic glucokinase activity appeared to be induced during diabetic pregnancy. Thus, we hypothesize that galactose may be a more optimal source for neonatal tissue glycogen synthesis than glucose because of preferential direction of galactose carbons tothe glycogen synthetic pathway. For infants of diabetic mothers, enteric availability of galactose, as in lactose-containing milk, may help stabilize blood glucose levels in the absence of a corresponding exaggerated elevation of plasma insulin concentrations.
Strong Association of HLA-DR3/DRw9 Heterozygosity With Early-Onset Insulin-Dependent Diabetes Mellitus in Chinese
Authors: Hawkins Brian R , Lam Karen S L , Ma John T C , Low Louis C K , Cheung Pik To , Serjeantson Susan W , Yeung Rose T T
Published: September 2013

Studies of Caucasian and Japanese patients with insulin-dependent diabetes mellitus (IDDM) have shown that heterozygosity for certain HLA-DR antigens confers a high risk of developing the disease. The HLA antigens of 75 Chinese patients and 100 Chinese controls in Hong Kong were studied to investigate the role of HLA-DR heterozygosity in Chinese individuals. Some of the patients and controls were also tested for allotypic variation in the complement components C2, C4, and BF. Three alleles, Aw33, B17, and DR3, had increased frequencies in patients compared with controls and frequently occurred together in the same phenotype, which suggested their existence as a haplotype. There were no statistically significant differences in complement allotype frequencies between patients and controls, although the C4B null allele seemed to be associated with Aw33, B17, and DR3. No other HLA-DR antigen appeared to be associated with IDDM. However, when the patients were separated on the basis of age at onset, the frequency of DR3/DRw9 heterozygosity was markedly increased in patients presenting in the first decade of life, but there was no increase in patients presenting at >20 yr of age. DRw9 is strongly associated with autoimmune disease in Chinese, whereas DR3 is not. We suggest that the major IDDM susceptibility locus in Chinese is associated with HLA-DR3 and that patients with HLA-DR3 and HLA-DRw9 have an added predisposition to autoimmune disease and therefore develop IDDM earlier than patients without DRw9.
Effect of Age and Sex on Rat Endocrine Pancreas
Authors: Reaven Eve P , Curry Donald L , Reaven Gerald M
Published: September 2013

Maximal glucose-stimulated insulin secretion was quantified in perfused pancreases of 11-wk-old and 12-mo-old female and male rats. In addition, measurements were made of body weight, total pancreatic weight, and percentage of the pancreas occupied by islet tissue. Body weight (mean ± SE) of male rats was greater than that of female rats at both 11 wk (319 ± 3 vs. 237 ± 13 g) and 12 mo (684 ± 17 vs. 376 ± 13 g) of age. Pancreatic weight and percentage of the pancreas occupied by islet tissue were also greater in male rats and increased in approximate proportion to the gain in weight. The first phase and the second phase of maximal glucosestimulated insulin secretion were both qualitatively and quantitatively similar in all four groups of rats. However, because islet cell mass increased with age, maximal glucose-stimulated insulin secretion declined with age in rats of both sexes when expressed per unit islet tissue. Although the fall in insulin secretion (per islet cell mass) with age was observed in perfused pancreases from both male and female rats, the pancreases of female rats contained relatively less islet tissue and secreted more insulin per unit islet cell mass than pancreases of male rats at either age. Thus, there are sex differences in both islet cell structure and function, but the effect of age on endocrine pancreatic function seems to be independent of sex.
Comparison of Glomerular and Mesangial Prostaglandin Synthesis and Glomerular Contraction in Two Rat Models of Diabetes Mellitus
Authors: Barnett Richard , Scharschmidt Linda , Ko Young-Hyeh , Schlondorff Detlef
Published: September 2013

Enhanced prostaglandin production is postulated to contribute to altered vascular reactivity and glomerular hyperfiltration in early insulin-deficient diabetes mellitus. Rats with streptozocin-induced diabetes (STZ-D) show glomerular hyperfiltration and develop renal disease. BB rats with genetic diabetes (BB-D) also hyperfilter but have only minor renal lesions. We therefore compared glomerular and mesangial prostaglandin E2 (PGE2) production and glomerular contractility in response to pressors as a reflection of in vitro vascular reactivity in these models. Glomeruli isolated from rats with 3 wk of STZ-D produced significantly more PGE2 under basal and ionophore A23187-stimulated conditions than those from control rats. Glomeruli from BB-D rats under basal and stimulated conditions, however, generated amounts of PGE2 that were comparable to either those of nondiabetic litter mates or of normal Wistar rats. Mesangial cells cultured from glomeruli of STZ-D, BB-D, and control rats all had identical prostaglandin profiles judged by conversion of [14C]arachidonic acid. They also produced comparable amounts of PGE2 under basal conditions and after stimulation with angiotensin II or A23187, as determined by radioimmunoassay. Planar surface area of glomeruli isolated from control rats showed a dose-dependent decrease in response to angiotensin II (10−11-10−9 M). This response to angiotensin II was at least as great in glomeruli from STZ-D rats. Contraction of glomeruli from control and STZ-D rats was also comparable after vasopressin or norepinephrine. Similarly, glomeruli from BB-D and BB control rats contracted in a comparable fashion to angiotensin II and norepinephrine. We conclude that in vitro PGE2 production is enhanced in glomeruli from STZ-D rats but not in those from BB-D rats, as compared with their respective controls. Because the contractile response of isolated glomeruli to pressors was comparable in all groups, our in vitro results argue against a major role of prostaglandins in the hyperfiltration of diabetes mellitus.
Effect of Stress Hormones on Splanchnic Substrate and Insulin Disposal After Glucose Ingestion in Healthy Humans
Authors: Waldhäusl Werner K , Gasic Slobodan , Bratusch-Marrain Paul , Komjati Martin , Korn Adrienne
Published: September 2013

To compare cortisol and epinephrine action on oral glucose tolerance, healthy humanswere infused with either cortisol (0.1 mg · kg−1 · h−1), epinephrine (5.4 μg · kg−1 · h−1), or saline before and aftera 75-g glucoseload, thereby elevating the respective plasma hormone concentrations into the pathophysiologic range. In the basal state, epinephrine increased arterial concentrations of glucose, β-hydroxybutyrate, and free fatty acids (FFA) as well as splanchnic output of glucose and β-hydroxybutyrate and splanchnic FFA more than cortisol. Postprandially, C-peptide release and hyperinsulinemia were blunted by epinephrine initially and increased less thereafter than during cortisol infusion. The rise in arterial glucose after glucose ingestion as calculated by the area under the curve was more marked (P < .01) after epinephrine [(1.90 ± 0.08 M)150 min] and cortisol [(1.41 ± 0.05 M)150 min] than in the control study [(1.07 ± 0.04 M)150 min]. In parallel, the stress hormones induced an almost identical 24 and 31% rise in mean splanchnic glucose output versus control values (normal, 44.8 ± 2.5; cortisol, 55.3 ± 3.3; epinephrine, 58.9 ± 6.9 g/150 min). The associated rise in arterial concentrations and splanchnic output of insulin above control values was considerably greater during cortisol but unchanged during epinephrine exposure. Epinephrine but not cortisol induced a rise versus the control study in splanchnic uptake of lactate and FFA, as well as in pyruvate output, whereas plasma β-hydroxybutyrate and acetoacetate remained unchanged. The postprandial splanchnic glucose output-to-splanchnic C-peptide output ratio did not differ from normal during epinephrine but was reduced (P < .01) during cortisol administration. Hepatic insulin uptake was proportionate to insulin production rate, whereas hepatic insulin clearance was unaffected by stress hormone action.

We conclude that besides inhibiting adequate insulin release to hyperglycemia, acute epinephrine exposure induces peripheral insulin resistance and increased splanchnic glucose output and lactate uptake. Such insulin resistance seems to be unveiled by normal but inappropriately low postprandial insulin release during epinephrine-induced basal and postprandial hyperglycemia but is partly disguised by secondary hyperinsulinemia after cortisol infusion.
No Evidence For Increased Growth Hormone Responses to Growth Hormone-Releasing Hormone in Patients With Diabetic Retinopathy
Authors: Pietschmann Peter , Schernthaner Guntram , Prskavec Franz , Gisinger Christoph , Freyler Heinz
Published: September 2013

Several studies report increased growth hormone (GH) responses to provocative stimuli in patients with diabetic retinopathy. We studied GH responses to 1 μg/ kg body wt human pancreatic GH-releasing hormone 1-44 (hpGHRH 1-44) in 33 patients with type I diabetes mellitus, 31 patients with type II diabetes mellitus, and 2 control groups (N = 11 and 8). Based on the results of fundoscopy and fluorescein angiography, the diabetic patients were subdivided into 1) patients without diabetic retinopathy, 2) patients with nonproliferative diabetic retinopathy, and 3) patients with proliferative diabetic retinopathy. Growth hormone responses to hpGHRH 1-44 in diabetic patients with proliferative or nonproliferative retinopathy or without retinopathy were not significantly different regardless of the type of diabetes. Remarkably, GH responses to hpGHRH 1-44 in type I diabetic patients without retinopathy were significantly higher than the matched controls. Our data suggest that diabetic retinopathy in type I and in type II diabetes isnot associated with increased GH responsiveness to hpGHRH 1-44, whereas in type I diabetes mellitus without diabetic retinopathy, a GH hyperresponsiveness to hpGHRH seems to occur.
Decreased Uptake of Glucose by Human Forearm During Infusion of Leucine, Isoleucine, or Threonine
Authors: Schwenk W Frederick , Haymond Morey W
Published: September 2013

Competition between glucose and free fatty acids as metabolic fuels is supported by both in vitro and in vivo data, but whether amino acids can also compete with glucose as a source of energy in vivo remains to be established. To determine the effect of increased availability of an amino acid on whole-body glucose flux and glucose carbon uptake by the human forearm, five groups of overnight-fasted normal subjects were infused with either saline, leucine (at 0.5 or 1.0μmol · kg−1 · min−1), isoleucine (0.5 μmol · kg−1 · min−1), or threonine (0.5 μmol · kg−1 · min−1). Plasma glucose concentrations and glucose flux decreased similarly in all groups. No significant changes in forearm output of leucine carbon, isoleucine carbon, or threonine were seen during saline infusion. In contrast, during leucine infusion there was a dose-dependent increase (r = .86, P < .001) in leucine carbon uptake with increased arterial leucine and a-ketoisocaproate concentrations. During infusions of isoleucine and threonine, increases (P < .05) in isoleucine carbon uptake and threonine uptake, respectively, were observed. Glucose uptake by forearm tissues did not change during the saline infusion, but it decreased (P < .05) in all four groups receiving an amino acid infusion. Changes in leucine carbon uptake were strongly correlated (r = −.76, P < .001) with changes in glucose uptake. Therefore, amino acids affect glucose uptake in human forearm tissue and presumably compete as oxidative fuels.
Effect of Anti-la Antibodies, Culture, and Cyclosporin on Prolongation of Canine Islet Allograft Survival
Authors: Alejandro Rodolfo , Latif Zuhair , Noel Jack , Shienvold Frances L , Mintz Daniel H
Published: September 2013

Evidence in rodents suggests that islet pretreatment to reduce islet immunogenicity will also require some form of immunosuppression of the recipient for islet allograft acceptance in highly reactive donor-recipient pairs. We attempted to ascertain whether outbred dogs would also require treatment of both donor islets and the recipient to prolong islet allograft survival. Untreated canine islets are uniformly rejected in 6-10 days in beagles. Tissue culture alone, at 37°C for 7 days, or treatment of freshly prepared islets with antila monoclonal antibodies (MoAbs) (B1F6 + 7.2) did not prolong canine islet allograft survival. Treatment of culture-maintained canine islets with anti-la MoAbs plus complement resulted in prolongation of islet allograft survival for 188 and 368 days in two of seven pancreatectomized nonimmunosuppressed beagles. The administration of low doses of cyclosporin A (CsA) intramuscularly, to recipients of untreated canine islet allografts had no effect on graft survival. By contrast, six of nine CsA-treated recipients of islets that were also treated with anti-la MoAbs (B1F6 + 7.2) plus complement showed prolongation of graft survival. Euglycemia was sustained for 19, 34, 89, and 300 days after the CsA was discontinued (day 30) in four of these animals. Two animals had unstable grafts from the beginning that failed 23 and 29 days after transplantation. Our results indicate that simple maneuvers like short-term tissue culture at 37°C and treatment of freshly isolated islets with anti-la MoAbs and complement are inadequate to prevent rejection in outbred pancreatectomized beagles. In contrast, low-dosage CsA acts synergistically with the in vitro treatment of islets with anti-la MoAbs to prolong islet allograft survival in outbred dogs with induced diabetes mellitus.
Growth Hormone Regulation of Somatomedin C/Insulin-Like Growth Factor I Production and DNA Replication in Fetal Rat Islets in Tissue Culture
Authors: Swenne I , Hill D J , Strain A J , Milner R D G
Published: September 2013

The regulation of DNA replication by growth hormone and the production of somatomedin C/insulin-like growth factor I (SM-C/IGF-I) and insulin by fetal rat islets in culture has been studied. Islets were cultured for 3 days in medium containing 2.7 or 16.7 mM glucose, various concentrations of fetal calf serum (FCS), and 100-1000 ng/ml human growth hormone (GH). DNA replication was determined by incorporation of [3H]thymidine into islet DNA; SM-C/IGF-I and insulin secreted into the medium were measured by specific radioimmunoassays.

Glucose caused a twofold stimulation of islet DNA replication in medium containing ≥ 1% FCS but failed to stimulate DNA replication at lower serum concentrations. In the presence of 16.7 mM glucose, GH (100–1000 ng/ml) stimulated DNA replication at all serum concentrations. In medium containing 2.7 mM glucose, GH was stimulatory only in the presence of 1% FCS.

Somatomedin C/IGF-I release into the culture medium could be detected in all experimental groups. Glucose alone did not affect SM-C/IGF-I release, and in serum concentrations <0.1% FCS, GH also failed to increase the release of the peptide. In medium containing 1% FCS and 16.7 mM glucose, 100–1000 ng/ml GH caused a 50-100% increase in SM-C/IGF-I release into the medium.

Addition of 100 ng/ml exogenous SM-C/IGF-I to medium containing 16.7 mM glucose and 0.1–1.0% FCS caused a twofold stimulation of the islet DNA replication. This effect could be abolished by the addition of an antibody to SM-C/IGF-I. This antibody also significantly reduced GH-stimulated DNA replication, although some stimulation remained in its presence.

Glucose stimulated insulin secretion at all serum concentrations. However, with < 1% FCS in the medium, insulin secretion was markedly reduced and could not be stimulated by the addition of GH. In medium containing 1% FCS and 16.7 mM glucose, 1000 ng/ml GH augmented insulin release almost twofold. We conclude that GH, but not glucose, can stimulate islet cell DNA replication by inducing the local production of SM-C/IGF-I. Apparently, however, part of the stimulation of DNA replication by GH is independent of SM-C/IGF-I and may be related to a direct effect of GH on the islets. Whether the insulin production is augmented via the mediation of somatomedins or by a direct effect of GH remains to be resolved.
Reduced Vital Capacity in Insulin-Dependent Diabetes
Authors: Primhak Robert A , Whincup Graham , Tsanakas John N , Milner Robert D G
Published: September 2013

Spirometry was performed on 88 children with insulindependent diabetes mellitus (IDDM) and 216 healthy controls living in Sheffield. Children with IDDM had significantly lower percentage predicted forced vital capacity (FVC) than did control children or reference norms. There was no evidence that the reduced FVC was confined to a subgroup of children, and there was no correlation with duration of IDDM or glycemic control. A longitudinal study of 27 children with IDDM did not show progressive deterioration in percentage predicted FVC with age. These findings suggest that a tendency toward reduced lung volumes exists in IDDM and may not be a direct result of the metabolic disturbances in the disease.
Studies on Macromolecular Components of Human Glomerular Basement Membrane and Alterations in Diabetes: Decreased Levels of Heparan Sulfate Proteoglycan and Laminin
Authors: Shimomura Hiroyuki , Spiro Robert G
Published: September 2013

Treatment of human glomerular basement membrane (GBM) with 4 M guanidine HCI resulted in a preferential extraction of noncollagenous components including laminin, fibronectin, entactin, and heparan sulfate proteoglycan, whereas effective solubilization of type IV collagen required exposure to denaturing solvents in the presence of reducing agents. The guanidine HCI–solubilized constituents were identified by immunochemical procedures after resolution by polyacrylamide gel electrophoresis, CL-6B filtration, and DEAE-cellulose chromatography. Two immunologically related heparan sulfate proteoglycans (Mr ∼350,000 and 210,000) were observed by electrophoresis, with the higher-molecular-weight form being predominant. An examination of the two proteoglycans after heparitinase digestion or chemical deglycosylation indicated that heparan sulfate chains and other carbohydrate units are attached to core proteins with Mr ∼140,000 and 110,000, respectively.

Radioimmunoassays indicated that human diabetic GBM contained significantly lower (P < .005) amounts of heparan sulfate proteoglycan and laminin with average values that were 30 and 60%, respectively, of nondiabetic controls; the fibronectin content of the diabetic GBM, however, was not significantly different from the normal. These findings, together with previous studies showing increases in GBM collagen, indicate that an alteration in the macromolecular architecture of this basement membrane occurs in diabetes that may be responsible for the filtration defect and the ultimate glomerular occlusion.
Substance P and Somatostatin Content and Transport in Vagus and Sciatic Nerves of the Streptozocin-Induced Diabetic Rat
Authors: MacLean David B
Published: September 2013

Substance P (SP) and somatostatin (SS) are two widely distributed neuropeptides that within the vagus and sciatic nerves are localized predominantly in sensory fibers. The effect of diabetes mellitus on their content or transport in sensory nerves is unknown. With the nerve ligation technique, the peripheral orthograde 24- h transport of both peptides was quantified in the vagus nerve 3 days or 1 mo after induction of streptozocin (STZ) diabetes and in both the vagus and sciatic nerves after diabetes of 3 mo duration. In acute (3-day) diabetics, neuropeptide transport in the vagus was unaltered. After 1 mo, SP transport was significantly increased; content in unligated contralateral nerve was unaltered. Transport of SS was unchanged, and content in contralateral nerve was too low to reliably quantitate. After diabetes of 3-mo duration, transport of both peptides in the vagus nerve was increased in STZ-induced diabetic (STZ-D) rats versus both weightand age-matched controls: SP 474 ± 17 (N = 10) vs. 358 ± 32 (N = 13) pg/24 h, STZ-D rats vs. controls, mean ± SE, P < .03; SS 29 ± 4 vs. 20 ± 3 pg/24 h, STZ-D rats vs. controls, P < .02. In the sciatic nerve, SP transport and content were unaltered. SS content was significantly reduced: 17 ± 3 vs. 30 ± 3 pg/3-mm nerve segment, STZ-D rats vs. controls, P < .01. SS transport in the sciatic nerve of diabetic rats was variably reduced (P < .07), and transport rates were increased (1.41 ± 0.13 vs. 0.96 ±0.10 mm/h, STZ-D rats vs. controls, P = .06), suggesting increased SS turnover within diabetic nerves.

This study indicates that the diabetic state has little short-term adverse effect on neuropeptide synthesis and transport within sensory nerves. Decreased SS content in the sciatic nerve may be a useful marker of early diabetic neuropathy.
Impaired Insulin Secretion Associated With Near Normoglycemia: Study in Normal Rats With 96-h In Vivo Glucose Infusions
Authors: Leahy John L , Cooper Henrietta E , Weir Gordon C
Published: September 2013

We have previously demonstrated impaired glucose influence on insulin secretion in normal rats made overtly hyperglycemic with glucose infusions for 48 h. We examined the effects of a 96-h infusion period. Rats received 30, 35, or 50% glucose or 0.45% NaCI at 2 ml/h. The plasma glucose in the 30 and 35% rats peaked at 24 h but then returned to normal by 72 h. A peak followed by a gradual fall also occurred in the 50% rats, but significant hyperglycemia was maintained throughout. β-Cell responsiveness to glucose was assessed with the perfused pancreas by examining the effect of altering the perfusate glucose concentration on insulin release. Insulin secretion remained intact in the 30% rats, but the response to a glucose increase was blunted in the 35% group and totally absent in the 50% rats. In a second protocol, glucose influence on arginine-stimulated insulin release was tested by adding 10 mM arginine to the perfusate and administering it with 2.8 and 16.7 mM glucose. The ability of the different glucose backgrounds to influence the insulin response decreased as the level of infused glucose rose. On the other hand, when phloridzin was added to 50% glucose during the second 48 h of infusion, glucose modulation of insulin release was completely restored.

These data indicate that during a period of overt hyperglycemia, β-cell defects can fully evolve within 48 h in the rat. Thereafter, they are maintained by the glucose infusion even though the plasma glucose level returns to near normal. Continued minor stimulation of the β-cell may be the responsible factor.
Rate of Glucose Fall Does Not Affect Counterregulatory Hormone Responses to Hypoglycemia in Normal and Diabetic Humans
Authors: Amiel Stephanie A , Simonson Donald C , Tamborlane William V , DeFronzo Ralph A , Sherwin Robert S
Published: September 2013

To test the hypothesis that variations in rate of glucose fall influence counterregulatory hormone responses to hypoglycemia, we have modified the glucose-clamp technique to provide a reproducible hypoglycemic stimulus in normal and type I diabetic subjects that varied only in the rate of glucose fall. Responsive elevations in plasma epinephrine and norepinephrine and in growth hormone, glucagon, and cortisol were not significantly affected by a ninefold change in the rate at which plasma glucose was lowered from 83 ± 1 to 50 ± 1 mg/dl in normal subjects. Similarly, wide variation in the rate of fall produced no substantive differences in counterregulatory hormone responses to hypoglycemia in diabetic subjects. The plasma glucose threshold at which epinephrine release began, determined from the slow-fall studies, was 63 ± 3 mg/dl in normal subjects but exhibited a wide range (48-74 mg/dl). Similar values were found in the diabetics. Thresholds for growth hormone, cortisol, and glucagon were slightly lower, ranging from 45 to 68 mg/dl in the normals. Our data suggest that counterregulatory hormone responses to hypoglycemia are triggered by the glucose level per se and not by its rate of fall. Furthermore, individual differences in glucose thresholds for epinephrine release may contribute to variations in the glucose level associated with hypoglycemic symptoms.
Prevalence of Diabetes and Impaired Glucose Tolerance and Plasma Glucose Levels in U.S. Population Aged 20–74 Yr
Authors: Harris Maureen I , Hadden Wilbur C , Knowler William C , Bennett Peter H
Published: September 2013

The prevalence of physician-diagnosed diabetes and of undiagnosed diabetes and impaired glucose tolerance (IGT) that meet National Diabetes Data Group (NDDG) and World Health Organization (WHO) criteria have been estimated for the U.S. population aged 20–74 yr from the 1976–1980 National Health and Nutrition Examination Survey. This survey included a demographic/medical history questionnaire administered in the participant's home and a detailed examination composed of a physician's exam, special clinical procedures, other tests, and collection of blood and urine specimens. Survey participants were selected from 1970 census data through a stratified multistage probability sampling scheme. Of 17,390 eligible residents aged 20–74 yr, 15,357 (88.3%) participated in the interview and are the basis for estimates of diagnosed diabetes; 11,858 (68%) participated in the exam. A half sample of 5901 examinees was selected to receive a 75-g oral glucose tolerance test (OGTT) performed in the morning after an overnight 10- to 16-h fast. Of these examinees, valid OGTT data were obtained for 3772 people without a medical history of diabetes, and these are the basis for estimates of undiagnosed diabetes and IGT. The major reasons for incomplete OGTT data were inability of participants to attend the examination center in the morning and lack of adherence to the fasting instructions. Despite the relatively low response rates, evidence is presented that data on both the interviewed sample and those receiving the OGTT, when adjusted for the 1970–1980 census characteristics by age, race, sex, income, and geographic location, are representative of the U.S. population. Extrapolation of these data to the U.S. population aged 20–74 yr indicates a total diabetes prevalence of 6.6% by NDDG criteria, or more than 8 million people with diabetes. The prevalence of undiagnosed diabetes (3.2%) was almost equal to that of previously diagnosed diabetes (3.4%). Total rates of diabetes increased with age, from 2.0% at age 20–44 yr to 17.7% at age 65–74 yr. Rates were approximately equal by sex but were greater in Blacks than in Whites. The prevalence of undiagnosed diabetes by WHO criteria (3.4%) was similar to that by NDDG criteria, but the rate of impaired glucose tolerance (11.2%) was more than twice the NDDG estimate (4.6%). Both obesity and parental history of diabetes were associated with significantly higher rates of diabetes and IGT. Fasting plasma glucose was relatively insensitive to age, but 1-h and 2-h post-75-g glucose values increased significantly with age.
Autoimmune Diabetes in NOD Mouse Is L3T4 T-Lymphocyte Dependent
Authors: Wang Yi , Hao Liming , Gill Ronald G , Lafferty Kevin J
Published: September 2013

Cultured BALB/c islets fail to function when transplanted into diabetic nonobesediabetic (NOD) mice; such grafted tissue is rapidly destroyed by disease recurrence. The cellular requirements for this graft damage are unclear. This study was designed to investigate the role of the L3T4+ T-lymphocyte subset in disease recurrence in the NOD mouse. L3T4+ T-lymphocytes were depleted by the in vivo administration of the L3T4-specific monoclonal antibody GK1.5. This treatment reduced the level of L3T4+ T-lymphocytes from an initial 43% of the peripheral blood lymphocytes to 4%. L3T4 levels remained at this low level for ∼2 wk after withdrawal of GK1.5 treatment, after which the L3T4 levels slowly began to increase in the periphery. Grafting of cultured BALB/c islet tissue into GK 1.5-treated diabetic NOD mice resulted in a rapid return to normoglycemia that persisted for 2-4 wk. The gradual return to the hyperglycemic condition roughly correlated with the reappearance of L3T4+ T-lymphocytes in the peripheral circulation. From these findings we conclude that the disease process in the NOD mouse is L3T4 T-lymphocyte dependent.
Quantitative Changes of Cerebral Neocortical Structure in Insulin-Treated Long-Term Streptozocin-lnduced Diabetes in Rats
Authors: Jakobsen Johannes , Sidenius Per , Gundersen H J G , Østerby Ruth
Published: September 2013

The brains of rats with streptozocin-induced diabetes treated with a low-dose insulin regimen (1 IU/day) were studied with morphometric techniques. After 1 yr of diabetes, brain weight decreased slightly (1350 ± 71 vs. 1521 ± 55 mg, 2P < .01) as did the volume of the neocortex (498 ± 36 vs. 567 ± 40 mm3, 2P < .05). A significant loss of neocortical neurons occurred (38 ± 2 × 106 vs. 46 ± 3 × 106, 2P < .01), and the length of the capillary network in the neocortical tissue shortened disproportionately (405 ± 102 vs. 631 ± 47 m, 2P < .01), leading to increased diffusion distance. The mechanisms underlying cerebral loss in this model are unknown, but abnormalities of the vascular supply with prolongation of the route of diffusion might play a role.
Development of Obesity in Zucker Rats: Early Insulin Resistance in Muscles But Normal Sensitivity in White Adipose Tissue
Authors: Pénicaud Luc , Ferré Pascal , Terretaz Jacques , Kinebanyan Marie France , Leturque Armelle , Doré Elizabeth , Girard Jean , Jeanrenaud Bernard , Picon Luc
Published: September 2013

Euglycemic-hyperinsulinemic clamps were performed on 4- and 12-wk-old anesthetized lean and obese Zucker rats. During the clamp studies, total glucose production and utilization were assessed with a 3-[3H]glucose perfusion, whereas local glucose utilization was determined by measuring 2-deoxy-1-[3H]glucose 6-phosphate accumulation in various tissues. In the basal state, 4 wk-old obese rats were hyperinsulinemic (159 ± 8 vs. 82 ± 9 μU/ml), whereas glucose turnover rate was similar to that observed in lean rats (14.9 ± 1.9 vs. 12.5 ± 1.9 mg · min−1 · kg−1). Glucose utilization was identical in skeletal muscles, whereas it was increased in white adipose tissue of obese rats (22 ± 4 vs. 8 ± 2 ng · min−1 · mg−1). At plasma insulin level of 500 μU/ml, glucose production was totally suppressed in both groups, whereas overall glucose utilization was slightly less in 4-wk-old obese than in lean rats. This was due to a reduced stimulation of glucose utilization in skeletal muscles and brown adipose tissue. In contrast, glucose utilization in periovarian white adipose tissue was similarly increased in lean and obese rats. For a maximal insulin concentration (1500 μU/ml), all the differences were abolished between lean and obese young Zucker rats. In older (12-wk-old) obese rats, glucose utilization in various tissues was markedly reduced at maximal insulin level compared with that observed in age-matched lean animals. Thus, a decreased insulin sensitivity in skeletal muscles and brown adipose tissue with a normal insulin sensitivity in white adipose tissue could contribute to the development of obesity in young Zucker rats by preferentially channeling glucose toward this tissue.
Mechanism of Metformin Action in Non-Insulin-Dependent Diabetes
Authors: Jackson Rodwin A , Hawa Mohammed I , Jaspan Jonathan B , Sim Bushra M , DiSilvio Luciana , Featherbe David , Kurtz Antony B
Published: September 2013

The mechanism of action of metformin was studied by comparing glucose turnover before and after a 75-g oral glucose load in 10 nonobese men with noninsulin-dependent diabetes mellitus (NIDDM) during metformin and placebo therapy by the combined application of the forearm and double-isotope techniques. During the study, 9 of the 10 patients were regularly receiving glibenclamide therapy. In 5 of the men, the first study was performed during metformin therapy, and the second study was done during placebo administration; in the other 5 subjects, the order was reversed. The interval between the studies was at least 3 mo. The metformin dosage was 1 g twice daily in 9 of the patients and 850 mg thrice daily in the 10th subject. In the basal state, metformin administration reduced plasma glucose levels from 172 ± 14 to 103 ± 9 mg/dl (P < .005), hepatic glucose output (HGO) from 2.67 ± 0.15 to 2.20 ± 0.20 mg · kg−1 · min−1 (P < .02), and forearm glucose uptake (FGU) from 0.106 ± 0.18 to 0.039 ± 0.016 mg · 100 ml−1 forearm · min−1 (P < .005), whereas insulin (23 ± 6 μU ml) and lactate (1.56 ± 0.18 mM) levels were unchanged. Although the oral glucose tolerance curve (OGTC) was significantly lowered by metformin, the incremental area under the curve and the insulin response were unchanged. The systemic appearance of ingested glucose was unaffected by metformin; 64 ± 2% of the load was recovered peripherally in 3 h. The rise in FGU and total glucose disappearance in 3 h after glucose loading was unaffected by metformin. From 0 to 180 min after glucose loading, HGO was suppressed by 45.3 and 44.5% of the corresponding basal value without and with metformin treatment, respectively. Peak lactate levels were noted 90 min after glucose loading and were increased during metformin treatment from 2.10 ± 0.23 to 2.92 ± 0.32 mM (P < .05).

We conclude that 1) metformin markedly lowers the OGTC in NIDDM; 2) lowering of the OGTC is due entirely to a fall in the basal glucose concentration; and 3) because fasting insulin levels were unchanged, the reduction in basal HGO and fasting glucose concentrations by metformin is the result of a druginduced increase in hepatic insulin sensitivity.
Insulin Binding and Glucose Transport in Adipocytes in Neonatal Streptozocin-Injected Rat Model of Diabetes Mellitus
Authors: Fantus I George , Chayoth Reuben , O'Dea Louis , Marliss Errol B , Yale Jean-François , Grose Mark
Published: September 2013

The neonatal streptozocin (STZ)-injected rat (NSIR) model of diabetes mellitus resembles human non-insulin-dependent diabetes mellitus (NIDDM) with respect to abnormalities in insulin secretory responses. The suggestion that insulin deficiency leads to insulin resistance, a prominent feature of human NIDDM, led us to examine insulin binding and glucose transport in the NSIR during the development of hyperglycemia. Male Wistar rats were injected at 2 days of age with STZ (90 mg/kg i.p.) or vehicle alone. Mild insulin deficiency, reflected by minimally decreased fed plasma insulin concentrations, was apparent at 4 wk (mean ± SE, control vs. NSIR, 2.32 ± 0.19 vs. 1.75 ± 0.21 ng ml) and at 8 wk. Pancreatic insulin content was dramatically reduced in NSIR to 12 and 5% of control values at 4 and 8 wk, respectively (P < .001). Fed plasma glucose concentrations increased in the NSIR between 4 and 5 wk and were significantly elevated at 8 wk (251 ± 25 vs. 527 ± 52 mg/dl, P < .001). 125I-labeled insulin binding showed a progressive increase as a function of adipocyte volume in control and NSIR. Epididymal fat pad weights and adipocyte volumes were significantly decreased in the NSIR. Thus, insulin binding did not differ when expressed per cell number but was increased in NSIR when corrected for cell size (percent specific binding × 102, 8.49 ± 0.96 vs. 11.56 ± 1.08/μl cell vol; P < .05, all ages combined). Insulin-stimulated 3-O-methylglucose transport was similar at 4 wk but significantly decreased in the NSIR at 8 wk (clearance, 272.6 ± 69.2 vs. 106.8 ± 21.0 fl · cell−1 · s−1, P < .05). However, when expressed as fold stimulation above basal or corrected for cell volume, no differences were observed. The abnormalities in insulin action that develop in the NSIR model of diabetes mellitus are characteristic of an insulin-deficient state. Comparison of the features of the insulin resistance demonstrated in this rodent model with those described in human NIDDM reveals both similarities and differences. We suggest that the NSIR model provides an incomplete representation of human NIDDM.
Postchallenge Glucose Concentration and Coronary Heart Disease in Men of Japanese Ancestry: Honolulu Heart Program
Authors: Donahue Richard P , Abbott Robert D , Reed Dwayne M , Yano Katsuhiko
Published: September 2013

Since 1965, the Honolulu Heart Program has followed 8006 men of Japanese ancestry, aged 45–70 yr at study entry, for the development of cardiovascular disease. To investigate the role of glucose concentration 1 h after a 50-g challenge on the risk of fatal coronary heart disease (CHD) and nonfatal myocardial infarction (Ml), 6394 nondiabetic men were followed for 12 yr for the first development of CHD. The rate of fatal CHD increased linearly with amount of glucose. Men in the fourth quintile of postchallenge glucose (157–189 mg/dl) had twice the age-adjusted risk of fatal CHD of those in the lowest quintile (P < .05). Relative risk increased to threefold among those in the top quintile and remained statistically significant after adjustment for other risk factors including body mass, total cholesterol, hypertension, left ventricular hypertrophy, and hematocrit (P < .001). When glucose was considered as a linear term in the proportional hazards model, a highly significant relation was noted with fatal CHD alone and when combined with nonfatal Ml (P < .001). We conclude that a continuously increasing risk gradient exists between postchallenge glucose and subsequent CHD that is independent of other known risk factors.
Hyperglycemia Decreases Glucose Uptake in Type I Diabetes
Authors: Yki-Järvinen Hannele , Helve Eero , Koivisto Veikko A
Published: September 2013

It has recently been postulated that hyperglycemia per se may contribute to insulin resistance in diabetes. To examine this possibility directly, we measured glucose uptake after 24 h of hyperglycemia (281 ±16 mg/dl) and normoglycemia (99 ± 6 mg/dl) in 10 type I (insulin-dependent) diabetic patients (age 33 ± 3 yr, relative body wt 102 ± 3%) treated with continuous subcutaneous insulin infusion. Hyperglycemia was induced by an intravenous glucose infusion, whereas saline was administered during the control day. During both studies the patient received a similar diet and insulin dose. After hyper- and normoglycemia, a primed continuous infusion of insulin (40 mU · m−2 · min−1) was started, and plasma glucose was adjusted to and maintained at 142 ± 2 and 140 ± 2 mg/dl, respectively, during 60–160 min of insulin infusion. The rate of glucose uptake after hyperglycemia averaged 8.3 ± 1.1 mg · kg−1 · min−1, which was lower than the rate after the normoglycemic period (10.1 ± 1.2 mg · kg−1 · min−1, P < .001). In conclusion, short-term hyperglycemia reduces glucose uptake in type I diabetic patients. Thus, part of the glucose or insulin resistance in these patients may be caused by hyperglycemia per se.
Estimation of Endogenous Glucose Production During Hyperinsulinemic-Euglycemic Glucose Clamps: Comparison of Unlabeled and Labeled Exogenous Glucose Infusates
Authors: Finegood Diane T , Bergman Richard N , Vranic Mladen
Published: September 2013

Tracer methodology has been applied extensively to the estimation of endogenous glucose production (Ra) during euglycemic glucose clamps. The accuracy of this approach has been questioned due to the observation of significantly negative estimates for Ra when insulin levels are high. We performed hyperinsulinemic (300 μU/ml)-euglycemic glucose clamps for 180 min in normal dogs and compared the standard approach, an unlabeled exogenous glucose infusate (cold GINF protocol, n = 12), to a new approach in which a tracer (D-[3-3H]glucose) was added to the exogenous glucose used for clamping (hot GINF protocol, n = 10). Plasma glucose, insulin and glucagon concentrations, and glucose infusion rates were similar for the two protocols. Plasma glucose specific activity was 20 ± 1% of basal (at 120–180 min) in the cold GINF studies, and 44 ± 3 to 187 ± 5% of basal in the hot GINF studies. With the one-compartment, fixed pool volume model of Steele, Ra, for the cold GINF studies was –2.4 ± 0.7 mg · min−1 · kg−1 at 25 min and remained significantly negative until 110 min (P < .05). For the hot GINF studies, Ra was never significantly less than zero (P > .05) and was greater than in the cold GINF studies at 20–90 min (P < .05). There was substantially less between-(78%) and within- (40%) experiment variation for the hot GINF studies compared with the cold GINF studies. An alternate approach (regression method) to the application of the one-compartment model, which allows for a variable and estimable effective distribution volume, yielded Ra estimates that were suppressed 60–100% from basal.

In conclusion, the one-compartment, fixed pool volume model of glucose kinetics is inadequate for the estimation of Ra during euglycemic glucose clamps. Two new strategies for estimating Ra from the one-compartment model, the hot GINF protocol and the regression method calculation, yielded more accurate and physiologically plausible estimates of Ra than currently used methodology.
Insulin Suppresses Its Own Secretion In Vivo
Authors: Argoud Georges M , Schade David S , Eaton R Philip
Published: September 2013

This study addressed the controversial question of whether a negative—insulin-feedback loop exists in vivo. We utilized prehepatic insulin production, calculated by computerized deconvolution analysis of peripheral C-peptide concentration, as a measure of endogenous insulin secretion. Prehepatic insulin production was determined in 10 normal men who randomly underwent a control study and two additional studies involving different insulin infusion rates that achieved circulating insulin concentrations within the physiologic range during euglycemic clamps. The results demonstrate a dose-dependent suppression of prehepatic insulin production from 5.8 ± 1.4 mU/min during the control study to 4.0 ± 1.2 and 3.2 ± 0.9 mU/min during plasma insulin levels of 34 ± 4 and 61 ± 6 μU/ml, respectively (P < .05). Therefore, in contrast to recently reported results in vitro, insulin inhibits its own secretion in humans.