bluuebunny/crossref_metadata_2025_split huggingface dataset:
β-Hydroxybutyrate Increases the Insulin Sensitivity of Adipocyte Glucose Transport at a Postreceptor Level
Authors: Green Allan , Bustillos Dalia P , Misbin Robert I 
Published: September 2013

The effect of insulin on glucose transport (2-deoxyglucose uptake) in adipocytes was measured in the absence and in the presence of 10 mM sodium-DL-β-hydroxybutyrate. The ketone body had little or no effect on the basal or the maximally insulin-stimulated rate of transport. However, β-hydroxybutyrate potentiated the effect of submaximal concentrations of insulin, i.e., it resulted in a leftward shift in the dose-response curve. The half-maximally effective concentration of insulin was decreased by approximately 30% from 0.58 ng/ml to 0.40 ng/ml. β-Hydroxybutyrate caused a slight (approximately 10%) increase in 125I-insulin binding to the cells. To determine whether this small increase in insulin binding is responsible for the increased insulin sensitivity in the presence of the ketone, two mimickers of insulin action were used: a serum containing anti-insulin receptor antibodies and hydrogen peroxide. β-Hydroxybutyrate increased the sensitivity of glucose transport to stimulation by the anti-receptor antibody, demonstrating that insulin itself does not have to be present. β-Hydroxybutyrate also potentiated the effect of hydrogen peroxide (which acts at a level distal to the insulin receptor) even in cells that had been depleted of insulin receptors by trypsin treatment. Therefore, β-hydroxybutyrate acts, at least partly, at a post-insulin receptor level.
Adenosine increases the insulin sensitivity of adipocytes. β-Hydroxybutyrate increased the sensitivity of the cells: (1) in the presence of a maximally effective concentration of adenosine (50 μM), (2) in the presence of adenosine deaminase (10 μg/ml), and (3) in the presence of adenosine deaminase plus a maximally effective concentration of the adenosine analogue, N6-phenylisopropyl adenosine (1 μ). Therefore, β-hydroxybutyrate appears to act independently from, and by a different mechanism to adenosine.
Hypoglycemic Brain Injury in the Rat: Correlation of Density of Brain Damage with the EEG Isoelectric Time: A Quantitative Study
Authors: Auer Roland N , Olsson Yngve , Siesjö Bo K 
Published: September 2013

Thirty-eight male Wistar rats were exposed to insulin-induced hypoglycemia resulting in periods of cerebral isoelectricity ranging from 10 to 60 min. Plasma glucose levels during cerebral isoelectricity ranged from 0.12 mM to 1.36 mM. Control rats were injected with insulin, but hypoglycemia was terminated with glucose at the stage of large δ-wave EEG slowing. After recovery, the rats were allowed to wake up and survive for 1 wk.
The number of dying neurons was assessed with acid-fuchsin/cresyl-violet-stained, whole-brain, sub-serial sections using direct visual counting of acido-philic, cytoclastic neurons. Brains from control rats that were not allowed to become isoelectric showed no dying neurons. Ten minutes of cerebral isoelectricity produced very minimal brain damage. The density of neuronal necrosis was positively related to the number of minutes of cerebral isoelectricity up to the maximum examined period of 60 min, but showed no correlation with the blood sugar levels.
The cerebral cortex, hippocampus, caudate nucleus, spinal cord, and, to a lesser extent, cerebellar Purkinje cells were affected. The distribution of neuronal necrosis was not identical with that seen in ischemia, but, rather, suggested a CSF-borne neurotoxin operant in contributing to the pathogenesis of neuronal necrosis in hypoglycemie brain damage.
Neuronal death does not occur in hypoglycemia unless the EEG becomes isoelectric, whatever the blood sugar level. Serious brain damage does not occur until electrocerebral silence has been established for at least several minutes. Neuronal death accelerates after 30 min of EEG isoelectricity in the rat. Most animals recovered well after up to 40 min of cerebral isoelectricity.
In Vitro Characterization of Biosynthetic Human Proinsulin
Authors: Podlecki D A , Frank B H , Olefsky J M 
Published: September 2013

The binding and biologic properties of human proinsulin produced by recombinant DNA technology have been determined. The biosynthetic human proinsulin was iodinated using lactoperoxidase and subsequently purified by HPLC to yield the [(125I)TyrA14]-proinsulin isomer.
Using isolated rat adipocytes, biosynthetic human proinsulin was shown to have approximately 11% of the binding potency of native insulin. At 16°C and 37°C, the ED50 values of biosynthetic human proinsulin were 3.7 nM and 15 nM, respectively, which was significantly different from the insulin values of 0.4 nM and 1.7 nM, respectively. Kinetic analysis suggested that the decreased affinity of biosynthetic human proinsulin was due primarily to a decreased association rate rather than an increased dissociation rate. Similar to insulin, biosynthetic human proinsulin exhibited a decreased half-time of dissociation in the presence of insulin (16.7 nM) or proinsulin (111 nM); however, this negative cooperative effect was lost in the presence of high concentrations of proinsulin (11 μM).
Biologic potency, assessed by measuring glucose transport in rat adipocytes, showed that biosynthetic human proinsulin had 10% of the biologic activity of insulin, suggesting close coupling between binding to receptors and membrane generated cellular response.
By extracting cell surface bound proinsulin with acidic buffer, the amount of 125I-proinsulin that internalized following binding to surface receptors was measured. At equilibrium, 55% of the cell-associated radioactivity was internalized at 37°C. When chloroquine-treated (200 μM) cells were incubated with 125I-proinsulin at 37°C, a 1.5-fold increase in the amount of intra-cellular proinsulin was observed at 1 h. This suggests that like insulin, chloroquine treatment augments the intracellular accumulation of proinsulin by inhibiting intracellular processing of internalized proinsulin.
In conclusion, (1) biosynthetic human proinsulin exhibits ∼ 10% of the binding and biologic potency of native insulin in adipocytes, (2) despite its decreased affinity for surface receptors, proinsulin is readily internalized by adipocytes, where it is degraded by a chloroquine-sensitive pathway.
Insulin and Glucagon Regulate Cytosolic Phosphoenolpyruvate Carboxykinase (GTP) mRNA in Rat Liver
Authors: Beale Elmus , Andreone Teresa , Koch Stephen , Granner Mark , Granner Daryl 
Published: September 2013

Insulin causes a 7–10-fold decrease of both the mRNA that codes for rat hepatic phosphoenolpyruvate carboxykinase (mRNAPEPCK) and of PEPCK synthesis, provided the animals are made diabetic and fed chow. mRNAPEPCK, measured either by in vitro translation or cDNA hybridization, decreases with a half-time of 30–60 min after insulin treatment. This coordinant decrease, which approximates the half-life of mRNAPEPCK measured in a variety of situations, suggests that insulin acts by decreasing mRNAPEPCK production, and that the hormone does not alter the activity of a fixed amount of this RNA, or enhance its degradation.
Glucagon results in a ninefold induction of mRNAPEPCK. Half-maximal induction occurs with doses between 20–75 μg/100 g body wt and occurs within 30–45 min. Maximal induction requires 150 μg/100 g body wt and occurs about 80 min after a single glucagon injection. N6,O2' -dibutyryl cAMP and a cAMP analogue that is not metabolized, 8-(4-chlorophenylthio)cAMP, induce mRNAPEPCK as effectively as glucagon and with similar kinetics. Since sodium butyrate, adenosine, and dibutyryl cGMP are ineffective inducers, cAMP appears to be the active agent in the hepatocyte.
Glucose-induced Changes in Histochemically Determined Ca2+ in B-cell Granules, 45Ca Uptake, and Total Ca2+ of Rat Pancreatic Islets
Authors: Wolters G H J , Pasma A , Wiegman J B , Konijnendijk W 
Published: September 2013

Rat pancreatic islets contain an ionized or readily ionizable calcium fraction that can be determined by the metallochromic indicator glyoxal-bis-(2-hydroxyanil) (GBHA). This calcium fraction is mainly localized in the secretory granules. The relationship between the effects of glucose on 45Ca uptake and on this ionized calcium fraction was investigated. In addition, the effects of glucose on total islet calcium content were also studied. Stimulation of isolated islets for 30 min with 15 mM glucose in the presence of 2.5 mM CaCl2 increased the 45Ca uptake but decreased the GBHA-Ca content, while the total calcium content was not affected. Deletion of CaCl2 caused, at 2.5 mM glucose, an abrupt decrease of GBHA-Ca, which did not occur at 15 mM glucose. Total islet calcium content decreased slowly at 2.5 mM glucose, but this was not significantly affected by glucose stimulation. Islet GBHA-Ca can be reduced by 70% and total islet calcium by 30% by means of washing with calcium-free buffer. Reintroduction of calcium at 2.5 mM glucose partly restored, but glucose 15 mM completely restored, the GBHA-Ca level within 5 min. The total calcium content was restored within 15 min independent of the glucose concentration. The increase of the islet calcium content equalled the 45Ca uptake at 2.5 mM glucose. The 45Ca uptake at 15 mM glucose was higher than the increase of the islet calcium content.
The results indicate that the intragranular Ca2+ pool, as measured by GBHA, is rapidly and dramatically altered by glucose stimulation. The glucose-induced changes of this Ca2+ fraction are not directly related to changes of the 45Ca uptake or the total islet calcium content. It is suggested that intracellular factors, particularly cAMP (production of which is Ca2+ dependent) and Na+ concentration, alter the amount of granular Ca2+.
Development of Early Lesions of Microangiopathy in Chronically Diabetic Monkeys
Authors: Yasuda H , Harano Y , Kosugi K , Nakano T , Suzuki M , Tsuruoka Y , Taniguchi Y , Nishimori T , Kikkawa R , Shigeta Y 
Published: September 2013

A chronic diabetic state was produced in Macaca fuscatus, and these diabetic monkeys were kept without insulin treatment for up to 25 mo. The metabolic derangements were characterized by hyperglycemia, insulinopenia, hyperglucagonemia, ketonemia, and hyperlipidemia. Significant thickening of the capillary basement membrane of the gastrocnemius muscle was observed in the chronically diabetic monkeys, and became obvious in the course of diabetic state; 732 ± 35 Å in controls, 750± 58 Å in diabetic monkeys with duration of 4 mo, and 1165 ± 112 Å in those with duration of more than 11 mo. In addition to duration of the diabetic state, severity of hyperglycemia is also thought to play an important role in the capillary basement membrane thickening judging from the fact that diabetic monkeys with constant hyperglycemia showed a greater membrane thickening. Ultrastructural alterations, such as significant thickening of glomerular basement membrane and increase of mesangial matrix, were observed in kidney as well.
These results indicate that diabetic microangiopathy has been produced by metabolic derangements characterized by chronic hyperglycemia, insulinopenia, and hyperlipidemia.
Downregulation Occurs Normally in Cultured Epstein-Barr Virus-transformed Lymphocytes from Patients with Extreme Insulin Resistance: Discrepancy Between Downregulation In Vivo and In Vitro
Authors: Wagman Lawrence D , Lambert Scott S , McElduff Aidan , Roth Jesse , Gorden Phillip , Taylor Simeon I 
Published: September 2013

Levels of fasting plasma insulin are generally inversely correlated with125I-insulin binding to circulating blood cells. In disease states associated with hyperinsulinemia (e.g., obesity and non-insulin-dependent diabetes mellitus), 125I-insulin binding is usually low. In contrast, 125I-insulin binding to circulating cells may be normal in patients with certain forms of extreme insulin resistance despite marked hyperinsulinemia. To explain this paradox, it has been proposed that postbinding defects in insulin action may give rise to defects in downregulation. We have employed cultured Epstein-Barr virus (EBV)-transformed lymphocytes from eight patients with extreme insulin resistance to address the question of whether there is a defect in the downregulation process in vitro.
In this cell type, insulin leads to a decrease in the number of insulin receptors on the cell surface by accelerating the rate of degradation of insulin receptors. We could not detect any abnormality in in vitro downregulation with cultured EBV-transformed lymphocytes from insulin-resistant patients. The apparent discrepancy between the in vivo and in vitro studies raises the possibility that some factor in the patient's internal milieu may prevent insulin-induced downregulation. An alternative possible explanation might be that the mechanism of downregulation in vitro differs from the mechanism whereby receptor number is regulated in vivo in insulin's target cells.
A Postbinding Inhibitor of Insulin Action: Increased Concentrations in the Plasma of Non-insulin-dependent Diabetic Subjects
Authors: Dean Brian , Peluso Ivana , Harrison Len C 
Published: September 2013

“Postreceptor” insulin resistance in persons with non-insulin-dependent diabetes (NIDDM) could be due to an intrinsic defect in insulin-sensitive pathways or to the action of a circulating inhibitor. Since evidence for the former is lacking, we have addressed the question of a circulating inhibitor by examining the effect of plasma and plasma extracts from NIDDM subjects on the lipogenic response of rat adipocytes to insulin.
A majority (77%) of plasma samples (1:20 dilution) from unselected, treated NIDDM subjects (N = 69) inhibited insulin-stimulated conversion of 3-3H-glucose to 3H-lipid in rat adipocytes to a greater extent than did control samples (N = 24). The mean ± SD inhibition by NIDDM plasma (81 ± 21%) was significantly greater (P &lt; 0.01) than by control plasma (50 ± 14%). Diabetic and, to a lesser degree, control plasma both caused a significant decrease in the maximal response of lipogenesis to insulin. Inhibitory activity was extracted into acid/ethanol, present in the flow of a Seppak C18 column, heat-stable (56°C for 30 min [plasma], 80°C for 30 min [acid/ethanol]), resistant to proteases, and dialyzable through 1000-dalton-mol wt exclusion dialysis tubing. The inhibition by NIDDM plasma or partially purified inhibitor could not be explained by the presence of insulin antibodies, insulin receptor antibodies, other inhibitors of insulin binding, or the concentrations of known counterregulatory factors. There was no correlation between inhibitory activity and plasma glucose (r = 0.26), insulin (r = 0.33), C-peptide (r = 0.26), or HbA1c(r = 0.26).
Our findings suggest that a humoral inhibitor of postreceptor insulin action is present in increased concentrations in the plasma of NIDDM subjects. The nature of this inhibitory activity and its pathophysiologic significance deserve further investigation.
Glibenclamide Stimulates and Glucose Inhibits Glucagon Release Induced by Calcium Deprivation
Authors: Grill V , Nylén A , Östenson C G , Efendić S 
Published: September 2013

The effects of low extracellular calcium levels on glibenclamide- and glucose-induced A-, B-, and D-cell secretion were investigated using the perfused pancreas preparation of the rat. At normal (2.6 mM) calcium, glucagon secretion was unaffected by glibenclamide (1 μg/ml) and transiently suppressed by glucose (6.7 and 16.7 mM). Reduction of extracellular calcium to 0.24 mM promptly and persistently enhanced glucagon secretion in the presence of 3.3 mM glucose; this effect of low calcium was, however, diminished (P &lt; 0.001) by 54% and 61% when the glucose concentration was increased to 6.7 and 16.7 mM, respectively. In contrast, glibenclamide enhanced the glucagon response to calcium reduction, a twofold stimulation by the drug being observed at all glucose concentrations.
Reduction of calcium to 0.24 mM failed to inhibit first-phase glibenclamide or glucose-induced insulin release; second phase was, however, inhibited whether induced by glibenclamide (in the presence of 6.7 mM glucose) or by glucose 16.7 mM per se. Reduction of calcium uniformly and completely abolished glibenclamide and glucose-induced somatostatin responses. It is concluded that: (1) the glucagon response induced by calcium deprivation is inhibited by glucose but potentiated by glibenclamide, and (2) reversal of a D-cell paracrine effect could underlie the glibenclamide effect.
Assessment of Perfusion in the Diabetic Foot by Regional Transcutaneous Oximetry
Authors: Hauser Carl J , Klein Stanley R , Mehringer C Mark , Appel Paul , Shoemaker William C 
Published: September 2013

Regional transcutaneous oximetry is a new, noninvasive diagnostic technique for the investigation of peripheral vascular disease (PVD) that uses differences in limb and trunk transcutaneous PO2 to assess the adequacy of local perfusion. The application of such measurements would be of great importance in diabetes, in which limb ischemia is commonly difficult to assess. A group of diabetic subjects with symptomatic PVD was studied with regional oximetry, Doppler-assisted blood pressure measurements, and arteriography. Doppler studies correlated poorly to symptom grade and angiographie data, while oximetry clearly demonstrated limb hypoxia under the functional conditions appropriate to the patients’ clinical symptomatology. The superiority of oximetry to Doppler studies was highly significant (X2 = 12.64, P &lt; 0.001). Regional transcutaneous oximetry should therefore be the non-invasive diagnostic test of choice in the initial evaluation of the diabetic limb for PVD.
Because of its dependence on the adequacy of local oxygenation, transcutaneous oximetry is a powerful tool for investigation of the pathophysiology of PVD and will, in the future, have wide-ranging applications to the diagnosis and therapy of PVD.
Marked Improvement in Carbohydrate and Lipid Metabolism in Diabetic Australian Aborigines After Temporary Reversion to Traditional Lifestyle
Authors: O'dea Kerin 
Published: September 2013

The rationale for the present study was that temporarily reversing the urbanization process in diabetic Aborigines should improve all aspects of their carbohydrate and lipid metabolism that are linked to insulin resistance. Ten full-blood, diabetic Aborigines from the Mowanjum Community (Derby, Western Australia) agreed to be tested before and after living for 7 wk as hunter-gatherers in their traditional country in northwestern Australia. They were middle aged (53.9 ±1.8 yr) and overweight (81.9 ± 3.4 kg), and all lost weight steadily over the 7-wk period (average, 8 kg). A detailed analysis of food intake over 2 wk revealed a low-energy intake (1200 kcal/person/day). Despite the high contribution of animal food to the total energy intake (64%), the diet was low in total fat (13%) due to the very low fat content of wild animals.
Oral glucose tolerance tests (75 g glucose) were conducted in the urban setting and repeated at the end of 7 wk of traditional lifestyle. The marked improvement in glucose was due to both a fall in fasting glucose (11.6 ± 1.2 mM before, 6.6 ± 0.8 mM after) and an improvement in postprandial glucose clearance (incremental area under the glucose curve: 15.0 ±1.2 mmol/ L/h before, 11.7 ± 1.2 mmol/L/h after). Fasting plasma insulin concentration fell (23 ± 2 mU/L before, 12 ± 1 mU/L after) and the insulin response to glucose improved (incremental area under the insulin curve: 61 ± 18 mU/L/h before, 104 ± 21 mU/L/h after). The marked fall in fasting plasma triglycerides (4.0 ± 0.5 mM before, 1.2 ± 0.1 mM after) was due largely to the fall in VLDL triglyceride concentration (2.31 ± 0.31 mM before, 0.20 ± 0.03 mM after).
In conclusion, the major metabolic abnormalities of type II diabetes were either greatly improved or completely normalized in this group of Aborigines by relatively short reversal of the urbanization process. At least three factors known to improve insulin sensitivity (weight loss, low-fat diet, and increased physical activity) were operating in this study and would have contributed to the metabolic changes observed.
Functional Correlates of Reduced Central Conduction Velocity in Diabetic Subjects
Authors: Donald M W , Erdahl D L William , Surridge D H C , Monga T N , Lawson J S , Bird C E , Letemendia F J J 
Published: September 2013

In a previous publication, we presented evidence of slowed conduction speed in the central nervous systems of insulin-dependent diabetic subjects, manifest in a delay in the latency of the brainstem auditory-evoked response (BAER). In this article, we present the results of a multivariate study conducted on a larger sample of 50 insulin-dependent, adult diabetic subjects. The purpose of the study was to determine some of the functional correlates of the BAER delay; each patient received an assessment of the BAER, the late auditory-evoked potential (EP), the conduction velocities of the sural, median, and common peroneal nerves, and intellectual and emotional function, in addition to neurologic and audiologie examinations. A nondiabetic control group was matched with the diabetic group as to age and sex.
The results indicated a delay in the latency of wave V, and in interpeak latencies I–III and I–V, of the BAER. The most reliable effect was on interpeak latency I–V; this suggested that the locus of the delay was in the central auditory projections, rather than in the acoustic nerve. In addition, BAER waves I, II, III, IV, and V were reduced in amplitude, as was the Ni component of the late auditory EP; the most reliable reduction in amplitude was in wave V. The effect was similar in magnitude for males and females, relative to their counterparts in the control group.
The slowed BAER response appeared early in the disease and was not related to the duration of insulin treatment. It was correlated with a chronic loss of energy and the presence of sexual dysfunction. It was not correlated with intellectual deterioration, clinical signs of peripheral or autonomie neuropathy, recent blood sugar regulation, or current blood sugar levels. The results of this study confirm the presence of abnormalities in the central nervous systems of diabetic subjects, and suggest that the BAER technique may prove useful in detecting early signs of central diabetic neuropathy.
Identification of Insulin Variants in Patients with Hyperinsulinemia by Reversed-Phase, High-Performance Liquid Chromatography
Authors: Seino Susumu , Funakoshi Akihiro , Fu Zu Zhi , Vinik Aaron 
Published: September 2013

We have characterized the molecular forms of circulating insulins in patients with hyperinsulinemia of diverse etiology. We have also compared the efficacy of various chromatographic conditions using reversedphase (RP) HPLC. Using 0.2% trifluoroacetic acid (TFA) and triethylamine (TEA) with acetonitrile as the organic modifier, at an elution rate of 0.17%/min, porcine, bovine, and human insulins could be easily separated as well as abnormal insulins in the plasma of a patient (J.R.) with hyperinsulinemia of unknown etiology. When the reversed-phase C18 column was changed and a gradient of 0.33%/min was used, the abnormal insulin in patient J.R. could not be separated. By changing the solvent system to acetonitrile and isopropanol (vohvol, 3:1) containing 0.1% TFA, omitting the TEA, and using a gentle gradient of 0.1%/min, various semisynthetic analogues of human insulin could be easily separated and the abnormal insulin could be identified in the plasma of the patient J.R. Abnormal insulin was also found in a patient with MEN-I, but in contrast, the insulins in eight patients with benign sporadic insulinomas appeared to be normal.
These results suggest that certain hyperinsulinemic states may be associated with an abnormal insulin and that RP-HPLC is useful for identification of insulin variants in the circulation. However, the conditions of RPHPLC may be critical if the abnormalities of the insulin are subtle.