bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic Consequences of Very-Low-Calorie Diet Therapy in Obese Non-insulin-dependent Diabetic and Nondiabetic Subjects
Authors: Henry R R , Wiest-Kent T A , Scheaffer L , Kolterman O G , Olefsky J M
Published: September 2013

To determine the effects of very-low-calorie diets on the metabolic abnormalities of diabetes and obesity, we have studied 10 obese, non-insulin-dependent diabetic (NIDDM) and 5 obese, nondiabetic subjects for 36 days on a metabolic ward during consumption of a liquid diet of 300 kcal/day with 30 g of protein. Rapid improvement occurred in the glycemie indices of the diabetic subjects, with mean (± SEM) fasting plasma glucose falling from 291 ± 21 to 95 ± 6 mg/dl (P < 0.001) and total glycosylated hemoglobin from 13.1 ± 0.7% to 8.8 ± 0.3% (P < 0.001) (normal reference range 5.5–8.5%). Lipid elevations were normalized with plasma triglycerides reduced to <100 mg/dl and total plasma cholesterol to < 150 mg/dl in both groups. Hormonal and substrate responses were also comparable between groups with reductions in insulin and triiodothy-ronine and moderate elevations in blood and urinary ketoacid levels without a corresponding rise in free fatty acids. Electrolyte balance for sodium, potassium, calcium, and phosphorus was initially negative but approached equilibrium by completion of the study. Magnesium, in contrast, remained in positive balance in both groups throughout. Total nitrogen loss varied widely among all subjects, ranging from 70 to 367 g, and showed a strong positive correlation with initial lean body mass (N = 0.83, P < 0.001) and total weight loss (N = 0.87, P < 0.001). The nondiabetic group, which had a significantly greater initial body weight and lean body mass than the diabetic group, also had a significantly greater weight loss of 450 ± 31 g/day compared with 308 ± 19 g/day (P < 0.01) in the diabetic subjects. The composition of the weight lost at completion was similar in both groups and ranged from 21.6% to 31.3% water, 3.9% to 7.8% protein, and 60.9% to 74.5% fat. The contribution of both water and protein progressively decreased and fat increased, resulting in unchanged caloric requirements during the diet. This study demonstrates that short-term treatment with a very-low-calorie diet in both obese diabetic and nondiabetic subjects results in: (1) safe and effective weight loss associated with the normalization of elevated glucose and lipid levels, (2) a large individual variability in total nitrogen loss determined principally by the initial lean body mass, and (3) progressive increments in the contribution of fat to weight loss with stable caloric requirements and no evidence of a hypometabolic response.
Direct Identification of Electrophysiologically Monitored Cells Within Intact Mouse Islets of Langerhans
Authors: Meda P , Santos R M , Atwater I
Published: September 2013

Cells found to be electrically active within microdis-sected mouse islets of Langerhans perifused with high (≥11.1 mM) glucose concentrations were labeled by injecting Lucifer yellow through the recording electrode. After fixation, these cells were located by fluorescence microscopy on sections serially cut throughout the islets and were subsequently identified by immunofluor-orescence staining with specific anti-islet hormone sera. Electrophysiologic control confirmed that the electrode tip had remained within the same cell throughout the experiment and showed that Lucifer yellow labeling did not affect the electrical activity of the impaled cell. Upon individual impalements, Lucifer yellow labeled either the impaled cell alone or this cell and some of its neighbors to which it was dye coupled. Immunofluorescence staining of the Lucifer yellow-labeled cells revealed that glucose-induced electrical activity was recorded from individual B-cells or groups of dye-coupled B-cells as well as from A-cells coupled to B-cellS.
Triglyceride-lowering Effect of Dietary Vitamin E in Streptozocin-induced Diabetic Rats: Increased Lipoprotein Lipase Activity in Livers of Diabetic Rats Fed High Dietary Vitamin E
Authors: Pritchard K A , Patel S T , Karpen C W , Newman H A I , Panganamala R V
Published: September 2013

High vitamin E supplementation in the diets of streptozocin-induced diabetic rats eliminates accumulation of lipid peroxides in the plasma and the liver, returns the plasma triglycerides toward normal levels, and increases the activity of lipoprotein lipase. Vitamin E has no effect on the levels of insulin or glucose. These findings suggest that vitamin E increases the total hepatic triglyceride lipase activity by increasing the lipoprotein lipase activity possibly by protecting the membrane-bound lipase against peroxidative damage.
Hepatic Glycogen Metabolism and Insulin Receptor Status After Long-term Peripheral Insulin Delivery in the Islet-Transplanted Diabetic Rat
Authors: Kruszynska Y T , Home P D , Agius L , Alberti K G M M
Published: September 2013

Severely diabetic (0.15 g/kg streptozocin) rats were transplanted with fetal pancreatic islets (1) under the renal capsule to model peripheral insulin delivery, or (2) into the splenic pulp to model portal delivery. In both groups of transplanted rats, weight gain and blood glucose concentrations were normal. Peripheral insulin delivery abolished the physiologic portal-peripheral insulin concentration gradient but was not associated with peripheral hyperinsulinemia. Incorporation of 3H2O into liver glycogen and the increase in hepatic glycogen concentration after a meal were normal in animals receiving insulin peripherally for 10 wk. Activation of liver glycogen synthase in response to the meal was also normal. Hepatic insulin receptor status in animals with peripheral insulin delivery was identical to that of normal control and splenic pulp islet-transplanted rats. The findings indicate that portal insulin delivery is not a prerequisite for normal hepatic glycogen metabolism in the rat, and that receptor upregulation and increased hepatic extraction of insulin are unlikely to explain the normal hepatic metabolism with peripheral insulin delivery.
The Effect of Oxidation on Sorbitol Pathway Kinetics
Authors: Barnett Patrick A , González R Gilberto , Chylack Leo T , Cheng Hong-Ming
Published: September 2013

The rapid conversion of glucose to sorbitol by aldose reductase and the consequent hyperosmolarity of the cytoplasm has been shown to be the primary cause of the so-called “sugar” or “osmotic” cataract in many animal lenses. It is not as clear, however, that hyperosmolarity is the principal factor in the etiology of cataracts in human diabetic subjects. In fact, the comparatively low activity of aldose reductase in the human lens as compared with several animal lenses, and the osmotically insignificant levels of sorbitol pathway products (sorbitol and fructose), suggest that hyperosmolarity, per se, may not be as important a factor in human cataract formation as it is in animals. We present evidence that the flux of glucose and sorbitol through the rat lens is markedly reduced by oxidative stress (0.1 mM H2O2). Sorbitol accumulation is reduced by 114%, sorbitol turnover is reduced by 78%, sorbitol production is reduced by 90%, fructose accumulation is reduced by 60%, and fructose turnover is reduced by 76% in the presence of 36 mM glucose. H2O2 does not affect glucose turnover, the glucose rate constant, or the ATP level significantly at 36 mM glucose, but at 5.5 mM glucose, 0.2 mM H2O2 leads to a rapid loss of ATP that can be prevented by 0.04 mM sorbinil, an aldose reductase inhibitor. These results suggest that inhibition of aldose reductase by sorbinil renders rat lenses better able to cope with oxidative stress. In the absence of an aldose reductase inhibitor, elevating ambient glucose may render a lens less able to scavenge oxidants by diverting NADPH into sorbitol production. The importance of the rate of flux of glucose through the sorbitol pathway, rather than the absolute concentration of sorbitol or fructose, is stressed in considering the mechanisms underlying complications of diabetes mellitus.
Effects of Insulin on Rat Anterior Pituitary Cells: Inhibition of Growth Hormone Secretion and mRNA Levels
Authors: Yamashita Shunichi , Melmed Shlomo
Published: September 2013

We recently reported that insulin inhibits basal and cortisone- and T3-stimulated GH secretion by GH3 rat pituitary tumor cells. The effects of purified semisynthetic human insulin were therefore tested on long-term GH secretion in normal pituitary cells. Primary monolayer cultures derived from male rat pituitaries were grown in serum-free defined medium. Insulin (7 nM) maximally inhibited basal GH secretion by almost 60% after 72 h, with 50% of maximal GH suppression occuring with 1.75 nM insulin. Insulin receptor antiserum blocked the suppression of GH by 7 nM insulin, but had no effect on the suppression of GH by IGF-I (3.25 nM). GRF (100pM) stimulated GH two- to threefold during 48 h. Insulin (7 nM) prevented the stimulation of GH induced by up to 1 nM GRF (P < 0.01) and this suppression was also selectively blocked by insulin receptor antiserum. The inhibition of GRF-stimulated GH required a lag period of 48 h and the dose of insulin required for 50% inhibition of GRF stimulation was 3.5nM. Insulin did not alter the degradation rate of 125I-GH in these cultures and medium glucose concentrations were not different in control or insulin-treated wells for up to 72 h of incubation. The insulin-induced suppression of GH was also observed when cells were grown in glucose-free medium. Insulin did not nonselectively suppress cell secretion, as PRL secretion was mildly stimulated (P < 0.01) by insulin in the same cultures. Fibroblast growth factor, epidermal growth factor, and insulin A-chain at similar doses did not alter basal or GRFstimulated GH secretion. Northern gel analysis of cell extracts showed that insulin-treated cells exhibited a decrease of the GH mRNA band. Using nitrocellulose dot-blot hybridization of cellular RNA with specific 32P-cDNA for rat GH, insulin suppressed pituitary GH mRNA levels by 56 ± 5% (P < 0.001) after 72 h of incubation. The results show that selective suppression of basal and GRF-stimulated GH secretion by insulin is time and dose dependent. Insulin modulates GH secretion at the level of the somatotroph.
Acetyl-Homocysteine-Thiolactone-Induced Increase of Superoxide Dismutase Counteracts the Effect of Subdiabetogenic Doses of Streptozocin
Authors: Papaccio Gianpaolo , Pisanti Francesco A , Frascatore Sonia
Published: September 2013

Acetyl-homocysteine-thiolactone (CYT) is an organic thio compound that exerts free radical scavenger activity and increases superoxide dismutase (SOD) activity. Administration of 32 mg CYT kg body wt day 30 days in rats increased SOD activity in erythrocytes by 126%, and in pancreatic islets by 202%. Treatment affected only the Cu-Zn fraction of the enzyme. Transmission electron microscope observations showed that the damage to the pancreatic beta cells induced by single or multiple subdiabetogenic doses of streptozocin (STZ) (45 mg/kg body wt) was attenuated in animals treated with CYT. This protective effect was not observed with 65 mg of STZ.

The experimental results seem to support the hypothesis that pancreatic beta cells are particularly vulnerableto the effect of oxygen radicals and that the cytotoxic effect of STZ is related to free radical-induced peroxidation.
Alterations in Physiologic Functions and in Brain Monoamine Content in Streptozocin-Diabetic Rats
Authors: Chu Pin C , Lin Mao T , Shian Lee R , Leu Sou Y
Published: September 2013

In the present study, we used streptozocin (STZ) to induce diabetes in rats and observed alterations in several physiologic functions and in monoamine content of different brain regions. Rats with STZ diabetes displayed a thermoregulatory deficit in the cold. Both the body temperature and metabolic rate of the diabetic animals were reduced at ambient temperatures below 22°C. These diabetic animals had a higher level of the spontaneous pain threshold, but displayed a reduced sensitivity of analgesic responses to morphine injection. In addition, these diabetic animals had a lower level of spontaneous motor activity, but displayed an increased sensitivity of locomotor stimulant responses to amphetamine administration. Biochemical examination revealed that the diabetic animals had a lower serotonin level in both the hypothalamus and the brainstem without changes in the serotonin levels of the corpus striatum. These diabetic animals also had a lower catecholamine level in the hypothalamus, but a higher catecholamine level in the corpus striatum. The alterations in brain monoamine content and in the above-mentioned physiologic parameters were reversed after insulin replacement therapy. The data suggest that alterations in various autonomic, somatosensory, and motor neural functions of untreated STZ-diabetic rats correlated with a reproducible pattern of monoamine content in various brain regions (a pattern that differed from that observed in healthy control rats), and that both the altered neural function and the altered brain monoamine pattern were reversed after insulin therapy.
Modulatory Effect of Glucose, Amino Acids, and Secretin on CCK-8-Induced Somatostatin and Pancreatic Polypeptide Release in Dogs
Authors: Schusdziarra V , Lenz N , Schick R , Maier V
Published: September 2013

Protein- and fat-rich test meals elicit a strong stimulatory effect on postprandial somatostatin (SLI) and pancreatic polypeptide (PP) release, whereas carbohydraterich meals rather attenuate the response of both hormones. Since there is evidence that intestinal hormones might contribute to the postprandial SLI and PP response, it was the aim of the present study to determine in dogs the effect of low-dose cholecystokinin octapeptide (CCK-8) on basal hormone levels and also during a background infusion of amino acids or glucose. In a group of six conscious dogs, sulfated CCK-8 was infused intravenously (i.v.) via a hindleg vein at stepwise increasing infusion rates of 10, 30, and 50 pmol · kg−1 · h. The infusion of CCK was applied during a background infusion of saline (2 ml/min), glucose (0.2 g/min), or an amino acid mixture (8.5%, 2 ml/min). CCK-8 had no effect on plasma insulin and glucagon. levels under all experimental conditions. Plasma SLI levels were significantly stimulated by all doses of CCK. This stimulatory effect was similar during background infusions of either saline, glucose, or amino acids, respectively.

Pancreatic polypeptide (PP) levels rose 200–300 pg/ml during CCK plus saline. This was slightly attenuated by glucose. During CCK plus amino acids, the PP response was augmented to 600–800 pg/ml. Since secretin is also released after the ingestion of a meal and intraduodenal acidification is a potent stimulus not only of secretin but also of gastric and pancreatic SLI release, the effect of secretin was examined additionally. The infusion of secretin (0.03 CU · kg−1 · h) had no effect on basal levels of SLI, PP, insulin, or glucagon and abolished the stimulatory effect of CCK-8 on SLI and PP levels. Interestingly, the concomitant infusion of glucose or amino acids together with secretin restored the stimulatory effect of CCK-8 to those levels observed in the absence of secretin. In conclusion: (1) Postprandial SLI and PP release might in part be due to the stimulatory effect of CCK-8. (2) CCK-induced PP release is attenuated by elevated plasma glucose levels and augmented by elevated levels of circulating amino acids. CCK-induced SLI release remains unaffected by either glucose or amino acids. (3) Low-dose secretin abolishes CCK-8-induced SLI and PP release. Interestingly, circulating nutrients can restore the CCK effect via as yet unknown mechanisms. (4) CCK-8 at the low doses employed has no effect on insulin and glucagon release, suggesting that its primary target cells are the pancreatic PP cells and the gastric and pancreatic D-cells rather than A- and B-cells.
The Diabetes Control and Complications Trial (DCCT): Design and Methodologic Considerations for the Feasibility Phase
Authors:   The DCCT Research Group
Published: September 2013

The Diabetes Control and Complications Trial (DCCT) is a randomized, controlled clinical trial designed to assess the'relationship between glycemic control and the development, progression, or amelioration of early vascular complications in persons with insulin-dependent diabetes mellitus (IDDM). The DCCT consists of two parallel studies: a primary prevention study and a secondary intervention study. The principal outcome in the primary prevention study is the initial appearance and subsequent progression of background retinopathy. In the secondary intervention study, the principal outcome is the progression or amelioration of preexistent minimal retinopathy.

Subjects are randomly assigned to receive either experimental or standard therapy. Experimental therapy involves the use of an intensive insulin regimen designed to maintain near-normal glycemic levels in the absence of severe hypoglycemia. Standard treatment is designed to maintain subjects free of clinical symptoms related to hyper- or hypoglycemia while receiving up to two insulin injections daily.

Two hundred seventy-eight volunteers have been enrolled in 21 centers in the United States and Canada in a preliminary study to assess the feasibility of conducting a full-scale, long-term clinical trial. Based on an external review of the feasibility study results, the DCCT will be expanded to include over 1400 subjects treated for a period of up to 10 yr. This article describes the DCCT and the considerations that led to the choice of specific design features for the feasibility phase.
HLA-DR Associations in Black Type I Diabetics in Nigeria: Further Support for Models of Inheritance
Authors: MacDonald Michael J , Famuyiwa Olufunsho O , Nwabuebo Ishmael A , Bella Andrew F , Junaid T A , Marrari Marilyn , Duquesnoy Rene J
Published: September 2013

The distributions of HLA-A, -B, -(Bw4/Bw6), -C, -DR, -(DRw52/DRw53), and -DQ genes in 19 type I diabetics, 37 type II diabetics, and 13 nondiabetics of the Yoruba tribe in southwestern Nigeria were studied. Because no associations between type II diabetes and HLA were detected in the current study and such associations are not known to exist in most ethnoracial groups, type II diabetics plus nondiabetics were used as a group of controls for the group of type I diabetics. Trends toward associations between increased DR3 (53 versus 30% of controls) and decreased DR2 (21 versus 46% of controls) and type I diabetes were found (0.1 > P >0.05). The strongest HLA association with type I diabetes in Caucasians is usually with DR4. The percent of DR4-positive type I diabetes (11%) was not significantly greater that that in the controls (4%). Because the strong HLA associations with type I diabetes in American Blacks are the same as in Caucasians (i.e., increased DR3 and DR4 and decreased DR2), the genetic contribution (i.e., the lack of an association with DR4) to susceptibility to type I diabetes in most Nigerian Blacks may be different from that in most Caucasians and American Blacks.

Onset of diabetes in most of the type I subjects was after age 20, and type I diabetics were difficult to recruit for the study, in keeping with reports on the rarity of type I diabetes among Blacks in western Africa and reports of DR4, but not DR3, being correlated with an early age of onset in Caucasians. Most cases of type I diabetes in American Blacks have an onset before age 20, and the incidence of type I diabetes in American Blacks is between that in American Blacks and that in Caucasians. Thus, the current data provide additional support for the theory that most type I diabetes occurring in American Blacks is the result of the admixture of a Caucasian-derived susceptibility gene into the American Black gene pool and, in addition, suggest that the susceptibility determinant is associated with DR4.
Acetone Metabolism in Humans During Diabetic Ketoacidosis
Authors: Reichard G A , Skutches C L , Hoeldtke R D , Owen O E
Published: September 2013

Plasma acetone turnover rates were measured with the primed continuous infusion of 2-[14C]acetone in patients with moderate to severe diabetic ketoacidosis. Plasma acetone turnover rates ranged from 1.52 to 15.9 μmol · kg−1 · min−1 (108–1038 n,mol · 1.73 m−2 min−1) and were directly related to the plasma acetone concentrations that ranged from 0.47 to 7.61 mM. The average acetoneturnover rate was 6.45 μmol kg−1 min−1 (533 μmol · 1.73 m−2 min−1), a value twice that obtained in a similar group of diabetic ketoacidotic patients via the single-injection technique of 2-[14C]acetone administration.

Degradation of urine glucose revealed that 14C from administered 2-[14C]acetone was principally located in carbons 1, 2, 5, and 6 of the glucose molecule in five of six patients. This distribution is similar to that expected from 2-[14C]pyruvate, suggesting that acetone was converted to glucose through pyruvate. In one patient, label was located predominantly in glucose carbons 3 and 4, indicating that acetone metabolism maybe different in some patients.

Acetol (1-hydroxyacetone) and 1,2-propanediol (PPD), two possible metabolites of acetone, were detected in plasma of the patients. The concentrations of Acetol ranged from 0 to 0.48 mM and of PPD ranged from 0 to 0.53 mM. The concentrations of each metabolite were directly related to the plasma acetone concentrations.

During the continuous infusion of 2-[14C]acetone, the specific activities of plasma glucose and PPD rose continuously but did not reach constant values. Estimates of theminimal percent plasma glucose and PPD derived from plasma acetone averaged 2.1 and 74%, respectively.
Purification and Characterization of Insulin-Degrading Enzyme From Human Erythrocytes
Authors: Shii Kozui , Yokono Koichi , Baba Shigeaki , Roth Richard A
Published: September 2013

An insulin-degrading enzyme (IDE) was purified from the cytosol of human erythrocytes via the use of ammonium sulfate precipitation and chromatography on columns composed of DEAE-Sephadex, pentylagarose, hydroxylapatite, chromatofocusing resins, and Ultrogel AcA-34. The final preparation was purified >50,000-fold and exhibited a single protein band of Mr = 110,000 on reduced sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Cross-linking of 125I-labeled insulin to the enzyme preparation labeled a protein of the same molecular weight, indicating that this band was in fact the enzyme. Intact insulin, insulin B chain, andglucagon inhibited this cross-linking half-maximally at concentrations of 0.1,1, and 1.5 μM, respectively. Under nondenaturing conditions, the enzyme had an Mr, = 300,000, suggesting that the enzyme may exist under physiological conditions as a dimer or trimer. The purified enzyme was inhibited by both sulfhydrylmodifying reagents and chelating agents, indicating that a free thiol and metal were both required for the activity of the enzyme. The purified enzyme was found to degrade physiological concentrations of intact insulin more rapidly than insulin B chain,although at high substrate concentrations (>1 μM) the enzyme degraded B chain to a greater extent. Additional characteristics of the enzyme were a pl of 5.2 and a pH optimum of 7.0. These properties of the red blood cell (RBC) enzyme were very similar to those reported for IDEs from other tissues. Moreover, a polyclonal antiserum to the IDE from skeletal muscle was found to recognize the RBC enzyme. These results indicate that the human erythrocyte enzyme is very similar tothe enzyme in other tissues and that these cells are a good source of material for purification of the human IDE.
Purification of Putative Insulin-Sensitive cAMP Phosphodiesterase or Its Catalytic Domain From Rat Adipocytes
Authors: Saltiel Alan R , Steigerwalt Ronald W
Published: September 2013

Insulin acutely inhibits the catecholamine-stimulated rise in cAMP levels in fat, liver, and muscle primarily through stimulation of the enzyme cAMP phosphodiesterase (PDE). Adipocytes from rat epidydimal fat pads were exposed to insulin and fractionated by centrifugation. Whereas the cytosolic fraction contained a low-affinity cAMP PDE that was unaffected by insulin, the activity of a high-affinity enzyme residing in a particulate fraction was increased by insulin. This enzyme activity could be solubilized with nonionic detergent and chromatographed on ion exchange followed by chromatofocusing. The resulting enzyme preparation was subjected to sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Silver staining revealed a single band with a molecular weight of 60,000. This apparent molecular weight was verified by calculation of the hydrodynamic properties of the enzyme. Evaluation of its kinetic properties indicated that the enzyme activity residing in this solubilized 60,000-Mr protein exhibited lower affinity than the membrane-bound enzyme but was still specific for cAMP. Activation of this enzyme may be one of the primary mechanisms by which insulin counteracts the effects of adenylate cyclase-stimulating hormones.
Coxsackie Virus B4 Produces Transient Diabetes in Nonhuman Primates
Authors: Yoon Ji-Won , London William T , Curfman Blanche L , Brown Robert L , Notkins Abner Louis
Published: September 2013

Cynomolgus, rhesus, and Cebus monkeys failed to show glucose tolerance or insulin secretion abnormalities after infection with encephalomyocarditis virus or Coxsackie virus B4. Patas monkeys also showed no abnormalities after infection with encephalomyocarditis virus. However, patas monkeys infected with Coxsackie virus B4 or treated first with a subdiabetogenic dose of streptozocin and then infected sequentially with Coxsackie viruses B4 and B3 showed transient elevation of glucose tolerance tests, depressed insulin secretion, and glucose in the urine. Our experiments in nonhuman primates support earlier studies in mice and humans that under certain circumstances, Coxsackie viruses can cause abnormalities in glucose homeostasis.
Modulatory Glucose Effect on Bombesin-Like Immunoreactivity and Gastrin Secretion From Isolated Perfused Rat Stomach
Authors: Schusdziarra V , Schmid R , Classen M
Published: September 2013

Previous studies have demonstrated mostly inhibitory effects of elevated plasma glucose levels on gastric exo- and endocrine as well as motor functions. Because increased plasma glucose levels reduce vagai activity via the central nervous system, it remains unclear if glucose exerts a direct effect on gastric functions. Therefore, our study was designed to determine the effect of acute changes in glucose concentrations on the release of gastrin and bombesin-like immunoreactivity (BLI) from the isolated perfused rat stomach. Acute elevations of pert usate glucose from 100 to 200 mg/dl or from 100 to 300 mg/dl augmented BLI secretion significantly without affecting gastrin release. During an acute decrease from 200 to 30 mg/dl, the secretion of both peptides remained unchanged. When ace-tylcholine was administered to stimulate BLI and gastrin secretion, the elevation of perfusate glucose to 200 mg/dl and the decrease to 30 mg/dl attenuated BLI secretion, whereas gastrin secretion remained unchanged compared with the control experiments at 100 mg/dl glucose. On the other hand, the perfusion of vasoactive intestinal peptide (VIP) and Leu-enkephalin had no effect on BLI and gastrin secretion during 100 mg/dl glucose perfusion, but both peptides elicited a significant stimulatory effect on BLI secretion during a perfusate glucose concentration of 200 mg/dl without affecting gastrin secretion. In conclusion, our study demonstrates first that an acute increase of glucose augments basal BLI secretion. Second, cholinergically induced BLI secretion is attenuated by hypo- and hyperglycemia. Third, hyperglycemia augments BLI secretion in response to the neuropeptides VIP and Leu-enkephalin. Fourth, basal and stimulated gastrin secretion remains unchanged during acute alterations of perfusate glucose levels. Because bombesin is considered to be a putative peptidergic neurotransmitter, the present data indicate that acute changes in glucose levels can affect neuronal activity, not only in the central nervous system, but also in the autonomie nervous system of the stomach. Our findings may be relevant in the study of disturbances of gastrointestinal functions in diabetes mellitus.
Effects of Intracisternal Glucose or Insulin Injections on Glucose Homeostasis in Cat
Authors: Alvarez-Buylla Ramón , Rojas Mireya , Alvarez-Buylla Elena R De , Faría Nancy
Published: September 2013

The injection of glucose (100 mg) into the cisterna magna of intact anesthetized cats elicited immediate glycosurie and natriuresis without significant changes in blood glucose concentration. Immunoreactive insulin (IRI) increased 140% in plasma, and Na+ concentration decreased in cerebrospinal fluid (CSF). After kidney denervation there was a significant decrease in glucose and Na+ concentrations in urine. Control injections with manitol did not elicit changes in the studied parameters. Abdominal vagotomy abolished the rise in IRI levels and the decrease in Na+ concentration in CSF. Vagotomy or adrenalectomy also attenuated the glycosurie and the rise in urine Na+ concentration. The intracisternal injection of insulin (0.5 U/kg) caused first, a decrease in glucose concentration in CSF and afterwards a longer latency in plasma. Again, these responses were significantly attenuated when insulin was administered in vagotomized cats.

These experiments indicate that the nervous system, through the vagi, adrenal glands, and kidneys, plays an important role in glucose homeostasis after increasing glucose or insulin levels in the CSF above physiologic concentrations. The results obtained with a denervated kidney confirm the participation of nervous system in the effector mechanism that brings the sugar and Na+ into the urine. Evidence is presented for an interrelationship between glucose and Na+ concentrations in blood, urine, and CSF.
Glucagon Immunoreactivity and Chromatographic Profiles in Pancreatectomized Humans: Paradoxical Response to Oral Glucose
Authors: Bajorunas D R , Fortner J G , Jaspan J B
Published: September 2013

The nature and origin of plasma immunoreactive glucagon (IRG) after pancreatectomy in humans remains controversial. Low plasma IRG levels and heterogeneity hamper accurate assessment. We studied plasma IRG levels and profiles in 12 patients 2–57 mo after a total pancreatectomy (with antrectomy and duodenectomy) for cancer (N = 9) or chronic pancreatitis (N = 3).

After oral glucose, plasma IRG (with the COOH-terminal-specific 30K glucagon antibody) rose from 59 ± 7 to a peak of 113 ± 17 pg/ml at 60–120 min. Chromatographie profiles revealed four distinct IRG fractions. In every patient a plasma IRG fraction of 9000–15,000 Mr, detectable basally, increased markedly after oral glucose and accounted for the rise in total IRG observed in plasma. Nine of the 12 pancreatectomized subjects had no detectable 3500-Mr glucagon and the remaining 3 had very low levels. For the group as a whole, 3500-Mr IRG comprised 1–2% of the total recovered IRG. Two patients were also studied before pancreatectomy: sup-pressibility of glucagon (Mr 3500) was evident. After surgery this paradoxical response to oral glucose was demonstrated. Reproducibility of these responses was confirmed in two patients studied twice over 2 yr. Diabetic controls without pancreatectomy did not show this response.

The absence or marked reduction of pancreatic glucagon was confirmed in five of the pancreatectomized patients after intravenous arginine or oral protein. Normal basal plasma IRG and profiles, oral glucose sup-pressibility, and arginine stimulation were present in five control patients with unresectable pancreatic malignancies.

These findings suggest that in the chronic 3500-Mr IRG deficient state, a glucagon-related peptide arising from the gut is demonstrable by a paradoxical response to oral glucose. It is speculated that this IRG fraction might be a glucagon precursor.
Encapsulation of Rat Islets of Langerhans Prolongs Xenograft Survival in Diabetic Mice
Authors: O'Shea G M , Sun A M
Published: September 2013

Rat islets encapsulated in alginate-polylysine membranes were implanted intraperitoneally into nonimmu-nosuppressed streptozocin-induced diabetic mice. Diabetes was reversed within 3 days, and the animals remained normoglycemic for up to 144 days, with a mean xenograft survival of 80 days. This was significantly greater than nonencapsulated islets, which functioned for <14 days. The graft survival rate at 50 days was >80%. Xenografts of rat islets encapsulated in alginate-polyornithine membranes also had a prolonged survival rate. This study demonstrates that encapsulation of pancreatic islets in semipermeable membranes can prolong xenograft survival in the absence of immunosuppreSSion.
Prevention of Diabetes in BB Rats: I. Evidence Suggesting a Requirement for Mature T Cells in Bone Marrow Inoculum of Neonatally Injected Rats
Authors: Scott J , Engelhard V H , Curnow R T , Benjamin D C
Published: September 2013

Injection of major histocompatibility complex (MHC)-compatible bone marrow cells from normal animals into neonatal BB rats resulted in a striking decrease in incidence of diabetes and restoration of concanavalin A (ConA) and mixed lymphocyte responses. However, injection of bone marrow cells pretreated with antirat thymocyte antiserum plus complement to remove mature T cells had no effect on incidence of disease, suggesting that mature T cells in the bone marrow inoculum were responsible for prevention of diabetes. Because the decreased incidence of diabetes in rats injected with untreated bone marrow appeared to be unrelated to the extent of lymphopenia in these animals, the involvement of T cells in the onset of diabetes must reflect a defect in the normal function of these cells rather than their absolute number. Approximately 50% of the W3/13+ cells in the spleens of BB rats lacked the OX-8 and W3/25 T cell subset markers. The identity of this W3/13+, OX-8−, W3/25− blank subset remains to be established. Our results, interpreted in light of studies from the other laboratories, suggest the existence of multiple abnormalities in the BB rat, including 1) the presence of T cells as effector or helper cells that augment onset of disease and 2) the absence of a regulatory T cell circuit that could prevent the disease.
Prior Cholecystokinin Exposure Sensitizes Islets of Langerhans to Glucose Stimulation
Authors: Zawalich Walter S , Diaz Victoria A
Published: September 2013

Prior, short-term exposure of isolated perifused islets to cholecystokinin (CCK8S) sensitizes them to subsequent glucose stimulation. This sensitization effect develops quickly and persists long after the removal of CCK8S from the perifusion medium. Continued binding of CCK8S to its receptor on the β-cell and the increase in glucose metabolism noted with glucose stimulation are essential for the full expression of this response. This sensitization process may play an integral role in the postulated incretin effect of the peptide.
Phosphorylation of Purified Insulin Receptor by cAMP Kinase
Authors: Roth Richard A , Beaudoin Jacqueline
Published: September 2013

Highly purified insulin receptor was shown to be a substrate for cAMP kinase. Approximately 1 phosphate was incorporated per molecule of receptor, and the cAMP kinase's affinity for the receptor was at least as high as its affinity for histone. The sites phosphorylated by cAMP kinase seemed distinct from those phosphorylated by the protein kinase C. Phosphorylation by cAMP kinase had no effect on the ability of several monoclonal antibodies to recognize the receptor or on the insulin-binding activity of the receptor. However, cAMP phosphorylation partially inhibited the tyrosine kinase activity of the receptor (∼25%). These results suggest that catecholamine-induced resistance to insulin may be partly due to a direct phosphorylation of the receptor by cAMP kinase and a subsequent inhibition of the ability of the receptor kinase to be activated by insulin.
Do Upper-Body and Centralized Adiposity Measure Different Aspects of Regional Body-Fat Distribution? Relationship to Non-Insulin-Dependent Diabetes Mellitus, Lipids, and Lipoproteins
Authors: Haffner Steven M , Stern Michael P , Hazuda Helen P , Pugh Jacqueline , Patterson Judith K
Published: September 2013

Both central and upper-body adiposity are associated with high rates of type II non-insulin-dependent diabetes mellitus (NIDDM), high triglyceride levels, and low high-density lipoprotein (HDL) cholesterol levels. Previous data have also suggested that central and upperbody adiposity are relatively uncorrelated and hence may measure different aspects of regional body fat distribution. We assessed body mass index (BMI), the ratio of subscapular-to-triceps skinfold (STR), the ratio of waist-to-hip circumference (WHR), lipids, lipoproteins, and glucose tolerance in 738 Mexican Americans (ages 25-64 yr), who participated in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular risk factors. NIDDM was diagnosed according to National Diabetes Data Group criteria. In general, STR and WHR were associated with high NIDDM rates, low HDL cholesterol levels, and high triglyceride levels, although WHR was somewhat more predictive of these than STR. In females, BMI, WHR, and STR all made independent contributions to prediction of NIDDM and HDL cholesterol; in males, WHR and STR both made independent contributions to prediction of triglyceride levels. This suggests that both indices may measure different aspects of body-fat distribution. Investigators should consider measuring both of these indicators of body-fat distribution in studies of diabetes and other cardiovascular risk factors, although if only a single measure is feasible, WHR appears to be preferable.
Differences in Epitope Restriction of Autoantibodies to Native Human Insulin (IAA) and Antibodies to Heterologous Insulin (IA)
Authors: Diaz Jose-Luis , Wilkin Terence
Published: September 2013

The binding profiles of insulin autoantibodies (IAA) and insulin antibodies (IA) to highly purified species variants and fragments of insulin were studied in direct immunospecific enzyme-linked immunosorbent assay (ELISA) and indirect absorption experiments with insulins covalently coupled to Sepharose beads. Five of 10 lAA-containing sera from insulin-naive nondiabetics that bound whole human (H) insulin did not bind whole porcine (P) or whole bovine (B) insulins. These sera bound H insulin B-chain but not P B-chain or desalanated P insulin, suggesting they were dependent on the presence of threonine B30. The other 5 IAA-containing sera bound H, P, B, and desalanated porcine insulins, but only 1 bound isolated B-chains. All 10 IA-containing sera from insulin-treated diabetics bound H, P, B, and desalanated P insulins, but only 1 bound to human (and porcine) B-chain. Further binding studies with ovine, rabbit, rat, and guinea pig insulins confirmed the H (threonine B30) specificity of the 5 IAA-containing sera. B30 residues do not appear to be dominant, however, when insulin is administered exogenously. Instead, IA bind predominantly to Achain or conformational determinants involving both chains. Scatchard analysis of a representative H insulin-specific IAA serum suggested that it contained a single binding affinity, whereas analysis of a representative IA-diabetic serum suggested it contained several different affinities.
Effect on Renal Function of Change From High to Moderate Protein Intake in Type I Diabetic Patients
Authors: Kupin Warren L , Cortes Pedro , Dumler Francis , Feldkamp Carolyn S , Kilates M C , Levin Nathanc W
Published: September 2013

The effects on renal function of moderate restriction in protein intake were studied in 14- to 20-yr-old type I diabetic patients who had no clinical renal disease or hypertension; matched normal subjects served as controls. After assessment of protein intake and renal function, studies were conducted at the completion of each of two consecutive dietary periods of 1 wk. Diets containing 3.5 and 1.5 g · kg−1 · day1 protein were provided during the first and second periods, respectively. Baseline protein intakes were substantial in both controls (1.86 g · kg−1 · day1) and diabetics (2.17 g · kg−1 · day1). Baseline creatinine clearance was increased in diabetics (P < .043). At the end of the highprotein intake period, both diabetics and controls showed similar high values of glomerular filtration rate (GFR) and renal plasma flow (RPF). GFR and RPF decreased markedly (P < .001) and to a similar degree in both groups after normal protein intake. GFR and RPF in diabetics were not higher than in controls at this point, but filtration fraction was increased in diabetics. Albumin excretion rates were similar in both groups and not influenced by renal function changes. GFR and RPF values correlated significantly with the quantity of protein intake, as estimated from the urea nitrogen appearance rate in both groups. The results suggest that the functional response to variations in protein intake is not altered in the diabetic kidney. In addition, increased renal function in diabetics may be related partly to the excessive protein content in commonly prescribed diabetic diets. Moderate dietary protein restriction is an additional approach for the correction of diabetic hyperfiltration.
Relationship Between Renal Function and Metabolic Alterations in Early Streptozocin-Induced Diabetes in Rats
Authors: Cortes Pedro , Dumler Francis , Goldman Jose , Levin Nathan W
Published: September 2013

To investigate the temporal relationship of diabetes-induced renal growth and its associated metabolic alterations to the early development of renal hyperfunction, parallel functional and metabolic studies were performed shortly after the onset of diabetes in rats. Hyperglycemia and hypoinsulinemia were evident 18 h after streptozocin injection, and significant hyperglucagonemia and acidosis were present at 36-48 h. Glomerular filtration rate (GFR), expressed per unit of body weight, first increased at 3 days of diabetes [1.35 ± 0.07 (SE) (N = 14)] and was 18% greater than in controls [1.14 · ± 0.03 ml · min−1 100 g−1 (SE) (N = 38)] (P < .005). Renal enlargement preceded GFR changes, so that GFR per unit of kidney weight was lower at 48 h in diabetics [1.31 ± 0.06 (SE) (N = 16)] than in controls [1.54 ± 0.04 ml · min−1 · g−1 (SE) (N = 38)] (P < .01). Nucleotide and RNA metabolism was studied in the renal cortex after infusion of radiolabeled orotate or adenine. Rate of RNA synthesis, total cellular RNA, and the pools of ATP, UTP, and uridine 5′-diphospho-N-acetyl glucosamine were significantly increased 13–51% in 48-h diabetics. Nucleotide precursor incorporation was significantly increased only in uracil ribonucleotides. The increase in uracil ribonucleotide pool exceeded the degree of cell hypertrophy. Our studies indicate that renal hypertrophy and specific increases in uracil ribonucleotide synthesis precede functional changes in early diabetes. Renal metabolic changes may be the critical primary factors in diabetic nephropathy.
Age-Corrected Empirical Genetic Risk Estimates for First-Degree Relatives of IDDM Patients
Authors: Tillil Hartmut , Köbberling Johannes
Published: September 2013

The families of 554 type I (insulin-dependent) diabetics were genetically analyzed according to probands' sex and age at onset applying a modification of Strömgren's method of age correction. Lifetime recurrence risk of type I diabetes (risk up to age 80 yr) for firstdegree relatives in three consecutive generations was calculated. The overall risk (± 1 SE) for siblings was 6.6 ± 1.1% and for children was 4.9 ± 1.7%. The similar risks among siblings and children argue against a simple autosomal recessive trait. The results do not permit a conclusion about a distinct mode of inheritance. Regardless of age at onset, offspring of male probands always had a higher risk than offspring of female probands. Among all probands, fathers were significantly more often affected with type I diabetes (about twice) than mothers (4.1 ± 0.9 vs. 1.7 ± 0.6%, respectively). The risk for further siblings of the proband was significantly increased in the presence of a type I diabetic parent (25.2 ± 10.3 vs. 5.8 ± 1.0% for remaining probands), indicating a nonrandom clustering of type I diabetes in families. Younger age at onset (<25 yr) was not associated with an increased risk to siblings. Type II diabetes was not more frequent among parents and siblings of type I diabetics than in the general population. The calculated risk estimates are of practical value in genetic counseling and are important for genetic models concerning type I diabetes.
Prolactin Enhances Cell-to-Cell Communication Among β-Cells in Pancreatic Islets
Authors: Michaels Robin L , Sorenson Robert L , Parsons Jonathan A , Sheridan Judson D
Published: September 2013

To determine the role of prolactin in increasing junctional communication among islet β-cells, we studied dye coupling in pancreatic islets exposed to elevated levels of prolactin in vivo and in vitro. Islets were isolated from rats immediately after lactation or from rats bearing mammosomatotropic tumors (MtTW15), conditions involving high levels of prolactin (either 5-fold or 1000-fold control levels, respectively). When β-cells were microinjected with the gap junction permeant dye Lucifer yellow CH, the mean number of dye-coupled cells per injection was ∼10-fold greater than in islets from virgin control rats. As a more direct test of the effects of prolactin on β-cell coupling, islets isolated from virgin rats were treated for 90 min with 500 ng/ml rat prolactin in the presence of low glucose (2.8 mM) and were microinjected with dye. The mean number of dye-coupled cells per injection increased by 6.7-fold over controls with low glucose, demonstrating a direct effect of prolactin on β-cell coupling. In vitro treatment with high glucose (16.7 mM) resulted in a 2.7-fold increase in dye-coupled cells per injection. We discuss the possible relationship between the effects of glucose and of prolactin on coupling.
Loss of Early Phase of Insulin Release in Humans Impairs Glucose Tolerance and Blunts Thermic Effect of Glucose
Authors: Calles-Escandon Jorge , Robbins David C
Published: September 2013

Loss of the early phase of insulin release has been documented in both type I (insulin-dependent) and type II (non-insulin-dependent) diabetes; however, the physiological importanceof this loss is unsettled. We created a model of loss of the early phase of insulin release in normal volunteers. Somatostatin (SRIF) was briefly infused (from −5 to 15 min) during intravenous (IVGTT) and oral (OGTT) glucose tolerance tests. The thermic response to oral glucose was determined under these conditions by indirect calorimetry. Early insulin release was totally blocked during IVGTT and OGTT by SRIF infusion. During the IVGTT, glucose tolerance was deteriorated in association with loss of the early phase of insulin release as indicated by a decrease in the K value (control 1.9 ± 0.36 vs. SRIF 1.1 ± 0.27, P < .001). Higher plasma glucose concentrations were observed during SRIF tests in the OGTT at 60, 90, 120, 150, and 180 min; total glycemic excursion was larger during the SRIF test (9473 ± 3089 mg · dl−1 · 5 h−1) when compared with the control condition (6583 ± 2329 mg dl−1 5 h−1). During the OGTT the total amount of glucose oxidized (control 56 ± 4.2 vs. SRIF 55 ± 3.4 g/5 h) was similar in both conditions, suggesting that nonoxidative pathways of glucose disposal were responsible for the deterioration in glucose tolerance. Surprisingly, we found that glucose-induced thermogenesis was reduced in association with loss of the early phase of insulin release (control 102 ± 21.3 vs. SRIF 72 ± 27.8 J/5 h, P < .001). Thus, loss of the early phase of insulin release is associated with deterioration of glucose tolerance and blunted glucose-induced thermogenesis. These data underscore the key role of the early phase of insulin release in glucose homeostasis and provide a possible mechanism that could lead eventually to obesity and diabetes.