bluuebunny/crossref_metadata_2025 huggingface dataset:
Hyperglycemia and Microangiopathy in the Eel
Authors: Bendayan Moise , Rasio Eugenio A
Published: September 2013

When female eels, fasting and sexually mature, were progressively adapted to cold water (2–4°C), their blood sugar concentration rose to values averaging 600 mg/dl. Control eels, kept in warm water (18–20°C), had a mean blood sugar concentration of 100 mg/dl. After a period of 5–6 mo, the blood capillaries of the rete mirabile in the swimbladder were examined in both control, low blood sugar eels, and in coldadapted, high blood sugar eels. In the latter, the basal laminae of the capillaries were thickened; their amino acids composition was altered and the in vitro glucose carbon incorporation into basal laminae glycoproteins was increased over a wide range of medium glucose concentrations. Furthermore, the diffusion capacity of the rete, as rqeasured with tracer molecules during steady-state conditions in a countercurrent perfusion system, was increased in the hyperglycemic eel. It is concluded that chronic hyperglycemia in the cold-adapted eel is associated with a microangiopathy characterized by morphologic, biochemical, and functional alterations.
Effect of 1,25 Dihydroxyvitamin D3 on Insulin Secretion
Authors: Clark Samuel A , Stumpf Walter E , Sar Madhabananda
Published: September 2013

Recent autoradiographic studies demonstrated that Bcells concentrate 1,25 (OH)2 D3 in their nuclei, suggesting a genomic action on B-cell function. This study was undertaken to investigate the effects of 1,25 (OH)2 D3 on insulin secretion in vitamin D-deficient rats. Mature vitamin D-deficient rats were injected with 1,25 (OH)2 D3 or the ethanol-isotonic saline vehicle. Administration of 1,25 (OH)2 D3 to 10 rats resulted in a 17 μu/ml (113%) increase in insulin levels and 0.9 mg/dl (16%) increase in plasma calcium. No changes were found in insulin or calcium levels in 5 control rats given vehicle alone. A group of vitamin D-deficient rats with plasma calcium levels of 5.4 ± 0.1 mg/dl had insulin levels that were the same as those observed in a group of vitamin D-deficient rats with plasma calcium levels of 6.3 ± 0.1 mg/dl. The difference in calcium levels between these two groups is similar to the increase in plasma calcium found after 1,25 (OH)2 D3 administration. The results of these studies indicate that 1,25 (OH)2 D3 action on pancreatic B-cells affects insulin secretion. Since insulin increases synthesis of 1,25 (OH)2 D3, the existence of a feedback loop between B-cells and kidney proximal tubule cells is suggested.
Assessment of Insulin Resistance with the Insulin Suppression Test and the Euglycemic Clamp
Authors: Greenfield M S , Doberne L , Kraemer F , Tobey T , Reaven G
Published: September 2013

Insulin resistance was quantified with two different methods in 30 subjects with varying degrees of glucose tolerance. One method, the insulin suppression test, is performed by continuously infusing epinephrine, propranolol, insulin, and glucose. Epinephrine and propranolol suppress endogenous insulin release, and steady-state plasma levels of exogenous insulin and glucose are reached in all individuals. Because the steady-state insulin level is the same in all subjects, the height of the steady-state plasma glucose level provides a direct estimate of insulin resistance. The other method, the euglycemic clamp technique, produces a steady-state level of exogenous hyperinsulinemia by means of a primed and continuous insulin infusion. Glucose is also infused at a rate sufficient to prevent an insulin-induced fall in glucose concentration, and the amount of glucose required to maintain the basal plasma glucose level provides the estimate of insulin resistance. The results indicated that estimates of insulin resistance generated by the two methods were highly correlated (r = 0.93). Furthermore, both methods of assessing insulin resistance indicated that the greater the degree of glucose intolerance, the more severe the insulin resistance. These results serve to further emphasize the importance of insulin resistance in the pathogenesis of hyperglycemia in type II diabetes.
Characterization of Increased Plasma Dopamine-β-Hydroxylase Activity in Rats with Experimental Diabetes
Authors: Schmidt Robert E , Geller David M , Johnson Eugene M
Published: September 2013

Plasma dopamine-β-hydroxylase (pDBH) activity is markedly elevated in chronic experimental streptozotocin (STZ) diabetes in the rat. Several possible explanations, all potentially relevant to the pathophysiology of diabetes, could explain this observation. The objective of this paper was to further delineate the behavior of pDBH in diabetes and examine several possible mechanisms for the increase. Plasma DBH increases within 1 day of STZ administration, is fivefold elevated within 1 wk, and slowly reaches ninefold control values after several months. Similar changes result from alloxan-induced diabetes. The increase in pDBH activity correlates well with the severity of diabetes as assessed by plasma glucose levels. Reversal of the diabetic state with insulin administration or islet cell transplantation results in the decrease of pDBH activity toward normal values. Plasma DBH is not increased in hyperglycemic obese (ob/ob) mice, suggesting a primary dependence of pDBH elevation on reduced levels of insulin and not hyperglycemia per se. Guanethidine-sympathectomized and sympathectomized/adrenal demedullated animals, with 60% and 25% of control levels of pDBH, respectively, show the same percentage increase in pDBH activity with induction of diabetes, thus, the increase in pDBH does not result from a selective activation or dysfunction of the sympathetic nervous system or adrenal medulla in diabetic animals. No evidence is found for the alteration of the kinetic parameters, molecular size, or charge of pDBH in diabetes. Several mechanisms for the increase are considered.
A Major Loss in Islet Mass and B-cell Function Precedes Hyperglycemia in Mice Given Multiple Low Doses of Streptozotocin
Authors: Bonnevie-Nielsen Vagn , Steffes Michael W , Lernmark Åke
Published: September 2013

Streptozotocin (SZ) given in five low doses causes diabetes and an associated lymphocytic infiltration of the pancreatic islets. Using C57BL/KsJ-mice, we demonstrate a reduction in islet number (−38%) and volume (−64%) within 1 day following the last injection of SZ. A substantial fall of insulin secretory capacity (−84%) in the in vitro perfused pancreas matches the reduction in islet cell volume. The parameters of decreased islet function seem to precede the peak of lymphocytic infiltration, occurring 3 days after the last dose of SZ. These functional changes are readily demonstrable before a rise in fasting blood glucose, but they seem to be reflected more readily by a rise in nonfasting blood glucose levels. With development of overt diabetes, as measured by elevated fasting and nonfasting glucose levels, the measures of islet volume and function are reduced to levels only 1–2% of those found in control mice. Taken together, these observations reflect a rapid, islet-toxic effect of SZ that substantially decreases insulin secretory capacity. When islet function falls more than 90%, blood glucose levels begin to reflect the pathophysiologic process. In many aspects, the low-dose SZ model of diabetes parallels the development of diabetes in man. If so, measures other than blood sugar must be developed to identify at an early stage processes reducing islet volume and function.
Somatostatin-like Immunoreactivity in Human Peripheral Plasma Measured by Radioimmunoassay Following Affinity Chromatography
Authors: Tsuda Kinsuke , Sakurai Hideo , Seino Yutaka , Seino Susumu , Tanigawa Keiichiro , Kuzuya Hideshi , Imura Hiroo
Published: September 2013

Somatostatin-like immunoreactivity (SLI) concentrations were determined in human peripheral plasma using affinity chromatography followed by radioimmunoassay. In normal subjects, fasting SLI ranged from 2.9 to 22.0 pg/ml with a mean ± SE value of 10.2 ± 2.1 pg/ml. In totally pancreatectomized or gastrectomized patients, fasting SLI levels were not different from the values in normal subjects. In patients with medullary thyroid carcinoma, fasting SLI ranged from 11.8 to 71.0 pg/ml with a mean of 29.3 ± 12.3 pg/ml, which was significantly higher than normal values (P < 0.01). Following meal ingestion, plasma SLI increased significantly in normal subjects from a basal level of 9.1 ± 2.1 pg/ml to a peak value of 15.4 ± 2.9 pg/ml (P < 0.02). These results indicate that radioimmunoassay combined with affinity chromatography provides an accurate method of measuring SLI in human plasma.
Platelet Survival in Patients with Diabetes Mellitus
Authors: Jones Robert L , Paradise Caroline , Peterson Charles M.
Published: September 2013

Platelet survival by 51chromium labeling was determined in six normal control subjects and in twelve patients with diabetes mellitus, before and after improved glucose control (mean HbA1c 10.5 ± 2.2% and 7.1 ± 1.8%, respectively). Mean platelet survival was 9.47 ± 0.85 days for the normal subjects and 9.04 ± 1.40 and 9.90 ± 1.05 for the diabetic subjects in hyperglycemic and improved glycemic states, respectively. The differences between these values were not statistically significant. However, platelet survivals performed in three diabetic patients who had severe retinal disease requiring photocoagulation were significantly shortened compared with nonsmoking control subjects (P < 0.05) or to patients without severe retinopathy (P < 0.01). These observations imply that measurable changes in in vivo platelet survival occur after the development of small vessel disease. It remains to be determined whether abnormalities described for diabetic platelets in vitro or changes in in vivo platelet physiology contribute to the initiation or propagation of vascular disease in the hyperglycemic individual.
Selective Extravascular Escape of Albumin into the Cerebral Cortex of the Diabetic Rat
Authors: Stauber William T , Ong Shu-Hui , McCuskey Robert S
Published: September 2013

The extravasation of plasma proteins (albumin, IgG, and complement C3) into the cerebral cortex was studied in streptozotocin-induced diabetic rats using im-munohistochemical techniques. The results indicate that albumin, but not IgG or complement C3, selectively enters the cerebral cortex within 2 wk after induction of diabetes. It is suggested that albumin may be an oncotic substance that contributes to diabetic cerebral microangiopathy, astrocytic swelling, and the cerebral edema that occasionally is seen during fluid and insulin therapy of juvenile ketoacidotic diabetes.
Effects of Insulin and Insulin-like Agents on the Glucose Transport System of Cultured Human Fibroblasts
Authors: Berhanu Paulos , Olefsky Jerrold M
Published: September 2013

We have studied the effects of insulin and insulin-like agents on glucose transport by cultured human fibro-blast monolayers. Initial rates of glucose transport were determined by measurement of 2-deoxy-D-glu-cose uptake. At physiologic concentrations, insulin stimulates 2-deoxy-D-glucose transport (average of 50% over basal) with a half-maximally effective insulin concentration of 3.3 ± 0.9 ng/ml. This effect of insulin is rapid and is half-maximal at 10 min and becomes maximal by about 30 min. Kinetic analyses showed that insulin increased the transport Vmax from 7.4 ± 0.9 nmol/min/106 cells to 11.0 ± 1.5 nmol/min/106 cells and had no effect on the Km value (2.5 ± 0.3 mM). While glucose starvation led to a higher overall rate of 2-deoxy-D-glucose transport, the relative stimulation by insulin was the same as in non-glucose-starved cells. Insulin mimickers [insulin-like growth factor (IGF), anti-insulin receptor antibody, and concanavalin A] also stimulate 2-deoxy-D-glucose transport by human fibroblast monolayers in a dose-dependent manner and the maximal effects of IGF and anti-insulin receptor antibody were the same as that of insulin, while the maximal effect of concanavalin A was only 78% of that of insulin. The maximal effects of either insulin and IGF or insulin and anti-insulin receptor antibody were not additive, suggesting that these agents all act via the same glucose transport effector system in human fibroblasts.

In conclusion, human fibroblasts possess an insulin-sensitive glucose transport system that displays many of the characteristics common to other more well studied transport systems. Thus, cultured human fibroblasts can serve as an important model for physiologic studies of insulin action and glucose transport, and for studies of pathophysiologic abnormalities of these processes in cells obtained from patients with various disease states.
The Degree of Sialylation of ApoC-III Is Altered by Diet
Authors: Patsch Wolfgang , Schonfeld Gustav
Published: September 2013

ApoC-III, an apolipoprotein that contains from 0 to 3 or more moles of sialic acid per mole of protein, plays important roles in lipoprotein metabolism. A high carbohydrate diet alters the relative proportions of the variously sialylated isoforms of ApoC-III in the plasma VLDL of man and of rat. Hepatic perfusion experiments in the rat indicate that the diet produces its affects on plasma VLDL by altering the hepatic output of ApoC-III. Diet is a relatively long-term stimulus to VLDL secretion. Our aim was to ascertain whether the changes in ApoC-III sialylation patterns could be reproduced by an acute stimulus to increased hepatic VLDL secretion, i.e., the perfusion of rat livers with media containing high levels of free fatty acid (FFA).

Male Sprague-Dawley rats (∼250 g) were fed either Purina rat meal or a high carbohydrate formula for 3 wk. Livers were perfused with Krebs-Ringers bicarbonate, 3% bovine serum albumin containing either no added FFA, or 200 mg of added oleate. ApoB and ApoC-III3 were measured by radioimmunoassay and lipids by enzymatic assays. Lipoproteins were isolated by preparative or zonal ultracentrifugation. The relative proportions of the various isoforms of ApoC-III were quantified by isoelectric focusing. The carbohydrate diet increased the plasma levels of triglycerides and ApoC-III3 ∼ twofold. The diet also increased the proportions of ApoC-III0 relative to total ApoC-III from 33 to 42%, in plasma VLDL (P < 0.02). Perfusates of livers of carbohydrate-fed rats accumulated VLDL-TG and ApoC-III3 at increased rates (93 versus 211, P < 0.001, and 12.7 versus 23.5, P < 0.05, μg/g/h, respectively) and the relative proportions of perfusate VLDL ApoC-lll were altered: ApoC-III0 rose from 37% to 59% and ApoC-III3 fell from 60% to 38% (P < 0.02 for each). Perfusion of livers of control (meal-fed) animals with 200 mg oleate yielded twofold increases in the rates of accumulation of VLDL-TG over meal fed non-FFA perfused controls and changes in gross VLDL composition that resembled those produced by carbohydrate feeding, but ApoC-III3 levels were not increased and the relative proportions of ApoC-III0, ApoC-III, 2 and ApoC-III3 were not altered. Perfusion of livers of carbohydrate-fed rats with oleate produced fivefold and 2.5-fold increases in the rates of accumulation of VLDL-TG and ApoC-III3, respectively. The proportion of ApoC-III isoforms were identical with those seen in the livers of carbohydrate-fed rats perfused without added oleate. Thus, the changes in ApoC-lll sialylation were related more to diet than to the presence of added FFA, i.e., an acute stimulus did not reproduce the changes seen with diet. These data indicate that the sialylation of ApoC-III is under metabolic control.
Inhibition of Prostaglandin E Synthesis Augments Glucose-induced Insulin Secretion in Cultured Pancreas
Authors: Metz Stewart A , Paul Robertson R , Fujimoto Wilfred Y
Published: September 2013

Monolayer cultures of neonatal rat pancreatic cells were examined to ascertain whether they synthesize prostaglandin E (PGE) and to determine the effects on insulin secretion caused by PGE and drugs that inhibit its synthesis. PGE release into the medium was observed. Sodium salicylate and ibuprofen (at drug concentrations similar to those achieved therapeutically in humans in vivo) inhibited PGE synthesis in a doseresponsive fashion to a maximum of 70–80% inhibition. Inhibition of PGE synthesis was accompanied by augmented insulin secretion. Both PGE synthesis inhibitors shifted the glucose dose-insulin response curves to the left at low glucose concentrations and augmented maximal insulin release at high glucose concentrations. Increments in glucose-induced insulin secretion induced by sodium salicylate correlated well (r = 0.89) with inhibition of PGE synthesis and addition of exogenous PGE1 to the cultures reversed the augmenting effects of the drug on insulin secretion. It is concluded that cultures of pancreatic cells synthesize PGE and that a function of PGE in these cultures appears to be a tonic negative modulation of glucose-induced insulin secretion.
Type II Diabetes and Insulin Resistance: Evidence for Lack of Inherent Cellular Defects in Insulin Sensitivity
Authors: Howard Barbara V , Hidaka Hideki , Ishibashi Fukashi , Fields Rose M , Bennett Peter H
Published: September 2013

To determine if inherent cellular differences in insulin sensitivity account for the insulin resistance of non-insulin- dependent diabetes, the effect of insulin on several aspects of cell glucose metabolism was compared in fibroblasts from diabetics and matched nondiabetic controls. The response of total cell glucose metabolism to insulin was assessed by measurement of 14C-glucose uptake. Insulin stimulated cell glucose incorporation in nondiabetic cells up to twofold with half-maximal stimulation at approximately 3 × 10-9M insulin. This was similar to that observed in diabetic cells. Insulin stimulation of I glycogen synthase activity was also compared in the cells from diabetics and nondiabetics. Both groups demonstrated a threefold increase in %I activity in the presence of insulin with half-maximal stimulation at approximately 2 × 10∼9 M. There were no differences between diabetics and nondiabetics in either magnitude of response or insulin concentration for half-maximal stimulation. Finally, insulin stimulation of hexose transport was compared in the two cell types using 2-deoxyglucose. In both groups hexose transport was elevated approximately 40% over baseline in the fibroblast in the presence of insulin, with half-maximal stimulation at approximately 2 × 10-9 M insulin. No differences were found in insulin action on glucose metabolism in fibroblasts from diabetics and nondiabetics; these results may indicate that there are no inherent differences in cell sensitivity to insulin's glucoregulatory action in non-insulin-dependent diabetics.
Intraportal Glucose Infusion Matched to Oral Glucose Absorption: Lack of Evidence for “Gut Factor” Involvement in Hepatic Glucose Storage
Authors: Bergman Richard N , Beir Jeffrey R , Hourigan Patrick M
Published: September 2013

These studies were designed to test whether a putative gastrointestinal factor (separate from that stimulating insulin release) is involved in the enhancement of liver glycogen storage during oral glucose ingestion. To do this, we compared net hepatic glucose uptake in conscious dogs, following oral glucose administration, with hepatic uptake during intraportal glucose infusion. The rate of intraportal glucose infusion was calculated to match the time course of gut glucose absorption in the oral administration experiments. In control studies, intragastric instillation of tap water [90 ± 2.4 (SE) ml] in four dogs had no effect on basal rates of gastrointestinal (GI) glucose uptake (16 ± 1 mg/min) oe hepatic glucose production (97 ± 3 mq/min). Net basal GI lactate production was equal to GI glucose utilization (P > 0.1); glycolytic conversion of glucose to lactate accounted for all basal GI glucose utilization. In oral experiments, gastric instillation of 1.2 g/kg glucose (N = 8) caused GI glucose absorption to increase within 5 min (P < 0.01). Net glucose absorption from the gut was maximal (355 1.55 mg/min) at 60 min, and was complete at 165–240 min (mean = 186 min). During absorption, liver switched from production to net uptake by 30 min (P < 0.01); production was resumed by 3 h. Total glucose taken up by liver was 7.19 ± 1.8 g (23% oral load). No net metabolism of the instilled glucose to lactate occurred during absorption; GI lactate production was the same during absorption (13.0 ± 5.0 mg/min) as before glucose instillation (11.2 ± 2.0 mg/min; P > 0.45). In intraportal experiments, intraportal glucose infusion (total = 1.09 g/kg) induced liver to take up glucose by 15 min (P < 0.01); total hepatic uptake (4.6 ± 1.5 g) was not significantly different from the oral experiments (P > 0.15). Also, nonsplanchnic glucose uptake was the same in the oral (25.1 ± 2.2) and intraportal (25.2 ± 1.4) studies. The lack of difference between hepatic and extrahepatic fates of administered glucose with oral and intraportal administration indicates that no putative gut factor need be invoked to explain hepatic glycogen deposition during oral glucose, and it seems probable that no such factor exists in the dog.
Diabetes Mellitus Following Pentamidine-induced Hypoglycemia in Humans
Authors: Bouchard Ph , Sai P , Reach G , Caubarrère I , Ganeval D , Assan R
Published: September 2013

Four patients, treated with pentamidine because of Pneumocystis carinii pneumonitis, displayed severe fasting hypoglycemia during this treatment. Diabetes mellitus appeared later, requiring insulin therapy in the three of them who survived more than a few weeks.

The metabolic study, performed in two cases during the hypoglycemic period, demonstrated inappropriately high insulin levels in the postaborptive state. 28 ± 1 μU/ml (blood glucose 41 ± 4 mg/dl) and 86 ± 5 μU/ml (blood glucose 15 ± 5 mg/dl) vs. 15 ± 3 μU/ml in 10 control subjects and 55 ± 3 μU/ml in 6 patients with a verified B-cell tumor, respectively. Poor B-cell secretory responses followed the stimulations by oral glucose (maximal increment over basal: +5 μU/ml vs. +40 μU/ml in control group and +77 μU/ml in the insulinoma group), by i.v. arginine (maximal increment +10 and +28 μU/ml, respectively, vs. +55 in the controls and +90 μU/ml in the insulinoma group) and by i.v. glucagon (+10 and +23 μU/ml, respectively) vs. +40 μU/ml in both the control and the insulinoma groups). Plasma cortisol and glucagon, and the A-cell response to arginine were higher than normal.

These high, nonsuppressible, nonstimulable insulin levels and the sequence of hypoglycemia followed by insulin-dependent diabetes mellitus is consistent with the hypothesis of a selective toxicity turned towards the B-cells. In vitro incubation of islets with pentamidine 10−10 M produced a passive release of insulin, followed by a significant decrease in B-cell response to glucose + theophylline. It is suggested that pentamidine can induce hypoglycemia because of an early cytolytic release of insulin, and then diabetes mellitus because of B-cell destruction and insulin deficiency.
Restoration of Glucose Homeostasis in Insulin-dependent Diabetic Subjects: An Inducible Process
Authors: Foss Milton C , Vlachokosta Fredericka V , Cunningham Lee N , Aoki Thomas T
Published: September 2013

To assess the change in glucose handling capability of diabetic patients regulated with an artificial β-cell, five insulin-dependent diabetic subjects were challenged with a 100-g glucose meal while on conventional (single or split mixed insulin injections) therapy and again after 72 h on an artificial β-cell unit. It was determined that while receiving conventional therapy, the diabetic patient's capacity to oxidize glucose was severely impaired. In addition, glucose storage was markedly reduced. After 72 h on the artificial β-cell unit, the diabetic patient's capacity to oxidize glucose following the ingestion of the glucose meal significantly exceeded that of the control group, and glucose storage returned to normal.

Since the above study did not reveal the amount of time on the artificial β-cell required to restore the glucose processing capability of the diabetic patients to normal, their response to a mixed test meal ingested at noon was monitored while they were on conventional insulin therapy and during four consecutive days that they were on the artificial β-cell. This inquiry revealed a gradual increase in their capacity to oxidize carbohydrate in response to the test meal. In contrast, their ability to store carbohydrate was normalized within 24 h following initiation of artificial β-cell therapy.

These studies clearly reveal that the conventionally treated diabetic patient's capacity to both oxidize and store carbohydrate is severely impaired. Both functions can be restored to normal by the use of the artificial β-cell for 48–72 h. Most importantly, the gradual improvement in carbohydrate oxidation with respect to the daily mixed meal challenge suggests that it is an “inducible” process which requires at least 2–3 days to accomplish. Since the ability to both oxidize and store incoming carbohydrate is essential for glucose homeostasis, these observations may have significant implications for the care of diabetic patients.
Oxytetracycline Treatment Improves the Response to Insulin in the Spontaneously Diabetic (BB) Rat
Authors: Dalpé-Scott Marthe , Heick H M C , Bégin-Heick Nicole
Published: September 2013

Chronic oxytetracycline treatment was found to alter the diabetic status of the spontaneously diabetic rat (BB rat). The treatment led to lowered plasma glucose levels in the fed as well as in the fasted state. These results indicate that the oxytetracycline treatment was effective in lowering the insulin requirements as well as in improving the handling of glucose. The effects of the drug are not secondary to the decreased food intake as a food restricted control group did not show the improvements in glycemia or glucose and insulin tolerance. These results are a further indication that oxytetracycline enhances the response of peripheral tissues to insulin and thus favors better control of glycemia.
Branched Chain Amino Acids as a Major Source of Alanine Nitrogen in Man
Authors: Haymond Morey W , Miles John M
Published: September 2013

In vitro perfusion and incubation studies and recent investigations in dogs suggest that branched chain amino acids (BCAA) may be a major source of alanine nitrogen. To determine the contribution of BCAA nitrogen to the formation of alanine in man, seven postabsorptive adults received prime-dose constant infusions of 15N-leucine, L-[6,6,6-2H3] leucine, and L-[2,3,3,3-2H4] alanine; isotopic enrichment was determined in arterialized venous plasma samples by gas chromatography-mass spectroscopy. At substrate and isotope steady state, alanine flux and the rate of 15N alanine appearance were 5.4 ± 0.3 μmol/kg-min and 32 ± 2 nmol/kg·min, respectively. Leucine nitrogen flux was significantly > that of leucine carbon flux (2.54 ± 0.25 vs. 1.90 ± 0.10 μmol/kg·min, respectively; P < 0.001). The 30% greater flux of leucine nitrogen when compared with leucine carbon suggests significant recycling of the leucine carbon in vivo.

The percent of circulating alanine nitrogen derived from leucine was 12.5 ± 1.5%; however, the rate of leucine nitrogen transferred to alanine was 0.66 ± 0.05 mumol/kg.min, and represents a minimum of 28% of leucine nitrogen going to alanine. On the basis of these data, together with the percent of alanine and leucine in body protein, only 40% of circulating plasma alanine could come from endogenous protein, whereas 60% is derived from de novo synthesis. In addition, at least 20% of the nitrogen required for alanine synthesis is derived solely from leucine following an overnight fast. Therefore, if the contribution of isoleucine and valine nitrogen is similar to that of leucine, the BCAA may contribute to a minimum of 60% of the nitrogen required for alanine synthesis in postabsorptive man.
Glucose-Induced Accumulation of Fructose-2,6-Bisphosphate in Pancreatic Islets
Authors: Malaisse Willy J , Malaisse-Lagae Francine , Sener Abdullah
Published: September 2013

Rat islets contain the acid-labile activator of phosphofructokinase, fructose-2,6-bisphosphate. The islet content in activator is higher in islets exposed to glucose (16.7 mM) than in islets deprived of glucose. The islets display fructose-6-phosphate, 2-kinase activity with a Km for fructose-6-phosphate close to 0.08 mM. Glucose fails to affect the activity of this enzyme. It is proposed that the effect of glucose to increase the islet content of fructose-2,6-bisphosphate is attributable, in part at least, to the glucose-induced increase in the concentration of fructose-6-phosphate in the islet cells.
Dogs with Induced or Spontaneous Diabetes as Models for the Study of Human Diabetes Mellitus
Authors: Engerman Ronald L , Kramer John W
Published: September 2013

Diabetes mellitus can be produced readily in dogs by any of several chemical or surgical methods, and in recent years genetically diabetic dogs have also become available for study. These models are suitable for investigating a wide variety of questions relevant to human diabetes mellitus. Especially noteworthy is the occurrence in diabetic dogs of a number of ocular and other complications typical of human diabetes mellitus. Procedures by which canine models of diabetes may be established or maintained have been outlined in this report.
Yucatan Miniature Swine as a Model for the Study of Human Diabetes Mellitus
Authors: Phillips R W , Panepinto L M , Spangler R , Westmoreland N
Published: September 2013

Two lines of Yucatan miniature swine have been developed by genetic selection for decreased and increased glucose clearance during an i.v. glucose tolerance test. The decreased glucose clearance is due to low peripheral insulin levels usually from a decrease in insulin secretion. In two pigs the decreased peripheral insulin resulted from increased hepatic uptake of insulin. During gestation and lactation, an increased insulin resistance and a diabetic-like state occurs in some animais. When fed a low fiber diet that contains 40% of calories from saturated fat (a typical American diet), Yucatan swine become more glucose intolerant. Seven to ten animals on the diet from the glucose intolerant line showed a glucose tolerance curve that would have been classified as diabetic if they were humans utilizing both intravenous and oral glucose tolerance tests. Miniature swine from this line are available to interested researchers.
Spontaneous Autoimmune Diabetes Mellitus in the BB Rat
Authors: Like Arthur A , Butler Leonard , Williams R Michael , Appel Michael C , Weringer Elora J , Rossini Aldo A
Published: September 2013

The BioBreeding Rat is a recently discovered model of spontaneous diabetes mellitus. Studies to date have revealed the following characteristics of the syndrome: genetic predisposition, equal frequency and severity among males and females, absence of obesity, life sustaining requirement for insulin therapy, lymphocytic insulitis with destruction of pancreatic beta-cells, lymphocytic thyroiditis and the presence of autoantibodies to smooth muscle, thyroid colloid and other cellular antigens. Animals raised in a germ-free environment evidence diabetes with equal frequency and severity. Support for a cell-mediated autoimmune pathogenesis of the diabetic syndrome is derived from the following experiments: administration of antiserum to rat lymphocytes prevents diabetes in susceptible animals and normaliies plasma glucose levels in 36% of diabetic rats; neonatal thymectomy almost completely prevents the occurrence of diabetes. Although the BB rat may not be an appropriate model for studying the vascular complications of diabetes, peripheral nerve functional and ultrastructural defects have been reported and renal glomerular immuneglobulin deposits have been observed in long-term diabetic animals.
Retinopathy in Juvenile-onset Type I Diabetes of Short Duration
Authors: Frank Robert N , Hoffman William H , Podgor Marvin J , Joondeph Howard C , Lewis Richard A , Margherio Raymond R , Nachazel Delbert P , Weiss Harold , Christopherson Kenneth W , Cronin Margaret A
Published: September 2013

We evaluated the prevalence and severity of diabetic retinopathy in 173 juvenile-onset, type I diabetic subjects and 78 nondiabetic controls of similar age, race, and sex distribution by stereoscopic fundus photography and fluorescein angiography, performed by a standardized protocol and evaluated by five expert, masked observers. The overall prevalence of retinopathy was 18% in the diabetic group and 0% in the controls. Retinopathy prevalence increased with duration of diabetes in the diabetic group, with a prevalence of 1% from 0–4 yr after diagnosis, 25% after 5–9 yr, and 67% 10–16 yr after onset of the systemic disease. There was an independent association with age, with little retinopathy before age 15 and a 48% prevalence in older persons. Retinopathy was also found to be independently associated with the following: diabetic “control,” evaluated semiquantitatively but on a masked basis; lens opacities; and frequency of daily insulin injections. Among the 166 diabetic subjects who had both angiography and photography, a retinopathy prevalence of 17% was detected by angiography and 11% by photography. This difference was statistically significant (P = 0.01). This study provides baseline data for use in estimating sample size in controlled trials of therapeutic measures to prevent retinopathy in juvenile diabetic populations. The study also supports the hypothesis that long-term hyperglycemia as well as changes (possibly hormonal in nature) associated with puberty are causally related to diabetic retinopathy.
Sulfonylureas Do Not Affect Insulin Binding or Glycemic Control in Insulin-dependent Diabetics
Authors: Grunberger George , Ryan Janice , Gorden Phillip
Published: September 2013

Sulfonylureas alone are ineffective in the therapy of insulin-independent diabetes mellitus (IDDM). These agents, however, might serve as an adjunct to insulin treatment if they directly affect insulin binding to its receptor. We studied 11 patients with IDDM to determine whether chlorpropamide acts directly on the insulin receptor and whether it could augment the effect of insulin on glycemic control. Mean tracer insulin binding to both peripheral monocytes and erythrocytes in 11 poorly controlled patients was normal. Optimization of glucose control by continuous subcutaneous insulin infusion for 7–10 days did not alter insulin binding to either cell type. Addition of chlorpropamide, 250–500 mg/day for another 7–10 days did not affect any aspect of insulin binding (tracer binding, number of receptor sites, insulin sensitivity, or affinity) in either cell type. Insulin binding was not changed in one patient after 3 days of 250 mg/day of the drug and in another after 500 mg/day over 3 mo. The sulfonylurea, in addition, provides no additive effect with insulin on blood glucose levels or insulin doses required to maintain euglycemia.

We conclude that short-term use of chlorpropamide in addition to insulin in IDDM does not alter insulin binding to circulating monocytes or erythrocytes. In addition, we were unable to show that this agent is a clinically useful adjunct to insulin in IDDM.
A Study of the Structural and Biochemical Development of Human Fetal Islets of Langerhans
Authors: Goldman Hy , Wong Inés , Patel Yogesh C
Published: September 2013

The structural and biochemical ontogeny of 14 mid-trimester (12.0–19.5 wk) human fetal endocrine pancreata were examined. Each pancreas was halved at the region of the isthmus into duodenal (D) and splenic (S) portions, and islets, isolated from each of the two portions, were aliquoted and grouped according to diameter into 4 categories: (1) > 300 μm (2) 300–200 μm (3) 200–100 μm (4) 100 μm.

At all fetal ages, the number of islets isolated from the splenic half was greater than from the duodenal half, and the number of islets increased as their diameter decreased. The mean total cell number per islet for each of the 4 categories are reported: (1)(D) 30,810 (S) 28,450; (2)(D) 10,970 (S) 10,250; (3)(D) 3,390 (S) 3,460; (4)(D) 1,930 (S) 1,840.

Measurement of islet insulin (IRI), glucagon (IRG), and somatostatin (IRS) by radioimmunoassay showed a progressive increase with time in the content of all three hormones in all islets from both halves of the pancreas (with the exception of the smallest islets of <100 μm diameter). After 18 wk, a dramatic increase in the content of all three hormones was observed particularly in the case of the largest (>300 μm) islets. In contrast, pancreatic polypeptide (IRPP) shows no significant increase. With the exception of the smallest islets (100 μm), all splenic-half islets contain a significantly greater content of IRI, IRG, and IRS compared with their duodenal-half match while the content of IRPP is significantly greater in the duodenal-half islets. In addition, all islets with the exception of the largest (>300 μm), contained equal quantities of IRG and IRS and these results were apparent at 12 wk gestation.

These data provide new insights into the ontogeny of individual islet cells during the mid-trimesteric period and serve as a basis for future studies of both normal and abnormal pancreatic development.
Impaired in Vivo Insulin Clearance in Patients With Severe Target-Cell Resistance to Insulin
Authors: Flier J S , Minaker K L , Landsberg L , Young J B , Pallotta J , Rowe J W
Published: September 2013

The concentration of insulin in plasma is determined by both its rate of secretion and its rate of clearance from the plasma compartment. The effect of marked insulin resistance on insulin clearance in vivo has not been determined in man. We have employed the euglycemic insulin clamp technique to measure insulin sensitivity and insulin clearance in 16 control subjects and in 4 subjects with marked target-cell resistance to insulin. Two insulin-resistant patients had reduced receptor concentration on peripheral mononuclear cells, and two patients had normal receptor number and affinity.

During 80-mU/m2/min insulin clamp studies, the clearance rate in each insulin-resistant patient was lower than that in any controls; the mean insulin clearance rate was 511 ± 74 ml/m2/min in control subjects and 205 ml/m2/min (P < 0.001) in insulin-resistant patients. These findings demonstrate an association between marked target-cell resistance to insulin and impaired in vivo insulin clearance, and suggest an important role for receptor-mediated pathways in insulin clearance in vivo.
The Pittsburgh Study of Insulin-Dependent Diabetes Mellitus: Risk for Diabetes Among Relatives of IDDM
Authors: Wagener Diane K , Sacks Jerome M , LaPorte Ronald E , MaCgregor Joan M
Published: September 2013

AN analysis has been made of the family histories of a survey of 1280 cases of IDDM entering Children's Hospital of Pittsburgh between December 31, 1964 and January 1, 1981, discharged on insulin and initial age of onset under 17 yr. Family histories revealed an increased occurrence of IDDM among relatives in the affected families. The risk to siblings was estimated by age-corrected proband exclusion (3.3%) by age 20 and by the Li-Mantel segregation ratio estimator (6.0%). The comparison of these risk measures is discussed. The occurrence of IDDM among the parents is 2.6% and of NIDDM among the parents is 2.4%. A comparison of risk to relatives (parents, sibs, uncles, half-sibs) observed in the Pittsburgh Study to those of six other studies reveal essentially equivalent rates. There is no increased risk to siblings of a diabetic who had an early age of onset. There is an increased risk to siblings of a diabetic (10.5%) in families where at least one parent has insulin-dependent diabetes mellitus (IDDM) and also an increased risk to siblings of a diabetic (8.8%) when at least one parent has non-insulin-dependent diabetes (NIDDM). The average age of onset for second cases in a family is significantly older than age of onset in single case families.
Insulin Treatment Improves the Spontaneous Remission of Neonatal Streptozotocin Diabetes in the Rat
Authors: Portha Bernard , Picon Luc
Published: September 2013

Neonatal rats injected with streptozotocin (STZ, 100 mg/kg) at birth exhibit an acute diabetes that is characterized by a spontaneous and incomplete remission. The short- and long-term effect of exogenous insulin on the course of this neonatal diabetes has been studied. Insulin treatment (20 mU/g body wt./day, for 4 days) diminished the percentage of glycosuric animals on day 5 after birth (10%) as compared with the percentage in the non-insulin-treated diabetics (STZ) (67%). On the 14th day, the body weight and the pancreatic insulin content of insulin-treated animals (STZ + I) were significantly higher than the corresponding values in the STZ animals. Glucose tolerance tests performed sequentially indicated that from 21 days to 7 mo, the plasma insulin response in the (STZ + I) females was clearly increased as compared with that observed in the STZ group. However, it did not reach the insulin response of the controls except in the 21-day-old females and, as a function of age, it declined progressively at variance with the normal age-related pattern. These findings indicate that insulin treatment (sufficient to reduce daily glycosuria) applied during the overtly diabetic period markedly improved the recovery of the insulin stores in the pancreas. Moreover, the long-term effect of the treatment was a long lasting if not permanent improvement of the in vivo insulin response to glucose.
Mathematical Modelling of Cyclic AMP-Ca2+ Interactions in Pancreatic Islets
Authors: Malaisse Willy J , Valverde Isabel , Owen Ann , Verhulst Dirk , Cantraine Francis
Published: September 2013

A mathematical model is proposed to account for the interactions between Ca2+ and cyclic AMP in the process of glucose-induced insulin release. This model allows simulation of experimental findings such as the glucose-induced accumulation of cyclic AMP in islet cells, the calcium dependency of the latter accumulation, the time course of 45Ca net uptake by the islets exposed to glucose and/or a phosphodiesterase inhibitor, the stimulation of insulin release by glucose, the suppression of such a release at low extracellular Ca2+ concentration and its amplification by phosphodiesterase inhibitors, the restoration of a significant secretory response to glucose in islets deprived of Ca2+ but exposed to a phosphodiesterase inhibitor, and the usual relationship between 45Ca net uptake and insulin release. All these data refer to studies performed over a 90-min incubation. The model is not suitable, however, to simulate the rapid response of the islet cells during the first few minutes that follow a change in the environment of the islets.
Effects of Synthetic Human Pancreatic Polypeptide, Synthetic Bovine Pancreatic Polypeptide, and the C-Terminal Hexapeptide on Pancreatic Somatostatin and Glucagon Secretion in the Rat
Authors: Trimble Elisabeth R , Gerber Pietro G , Renold Albert E
Published: September 2013

Synthetic human pancreatic polypeptide stimulated pancreatic somatostatin secretion by isolated rat islets and by the isolated perfused rat pancreas. In contrast, synthetic bovine pancreatic polypeptide and the C-terminal hexapeptide had no effect on somatostatin secretion. Synthetic human pancreatic polypeptide had only a mild stimulatory effect on glucagon secretion at the highest concentration of the peptide used (2.2 × 10−6 M) and in the presence of 16.7 mM glucose.
Comparison Between Continuous Subcutaneous Insulin Infusion and Multiple Injections of Insulin: A One-Year Prospective Study
Authors: Schiffrin A , Belmonte M M
Published: September 2013

Twenty insulin-dependent diabetic patients participated in a 1-yr prospective randomized cross-over study comparing multiple subcutaneous injections (MSI) and continuous subcutaneous insulin infusion (CSII) complemented by home blood glucose monitoring. While 4 patients dropped out early, 16 patients completed the study. Patients had severe insulin deficiency documented by absent C-peptide response to glucagon stimulation. A marked improvement in control was observed when mean blood glucose and glycosylated hemoglobin A1 were compared with conventional therapy. No significant differences in the degree of metabolic control achieved, as measured by mean fasting, preprandial, and postprandial capillary blood glucose (CBG), M values, glycosylated hemoglobin A1 concentration, cholesterol and triglyceride levels were seen between MSI and CSII in the sixteen patients who completed the study. However, individual comparisons showed that fasting CBG and M-values were lower under CSII than MSI in seven patients (P < 0.05). In contrast, two patients exhibited lower M values under MSI than under CSII (P < 0.01), while for the remaining seven patients the results were similar. After completion of the study, two patients went back to conventional insulin therapy, seven patients remained on the pump, and seven patients chose to stay on MSI. In conclusion, on a long-term basis, the two methods can produce comparable levels of blood glucose and glycosylated hemoglobin in ambulatory insulin-dependent diabetics.
Phenytoin Inhibition of Insulin Release: Studies on the Involvement of Ca2+ Fluxes in Rat Pancreatic Islets
Authors: Siegel Eberhard G , Janjic Danilo , Wollheim Claes B
Published: September 2013

The mechanism by which phenytoin inhibits insulin release was studied. Insulin release and 45Ca2+ efflux were measured during perifusion of collagenase isolated rat islets after 2-day maintenance in tissue culture in the presence of a trace amount of 45Ca2+. Islets maintained in the absence of the isotope were used to measure 45Ca2+ uptake over 5 min. Glucose (16.7 mM) induced a biphasic release of insulin, which was accompanied by a biphasic increase in the rate of 45Ca2+ efflux above basal. Phenytoin (80 μM) added during second phase rapidly inhibited insulin release. In contrast, phenytoin added together with glucose failed to affect first phase, but reduced second phase release by 64%. Phenytoin failed to affect basal 45Ca2+ efflux in the presence or absence of Ca2+, nor did it interfere with the inhibitory effect of high glucose on Ca2+ efflux. The drug did not affect basal Ca2+ uptake, but significantly reduced glucose-induced Ca2+ uptake. Glucose utilization was not inhibited by phenytoin. It is suggested that phenytoin inhibits glucose-stimulated insulin release by interfering with Ca2+ uptake via voltage-dependent Ca2+ channels. The pattern of inhibition of insulin release appears to favor this conclusion as the second phase is more dependent on the stimulation of Ca2+ uptake than is the first phase.
Reactions of Biologic Aldehydes with Proteins
Authors: Fantl Wendy J , Stevens Victor J , Peterson Charles M
Published: September 2013

The amino functions of proteins are susceptible to modification by the carbonyl moieties of aldehydes that are found in vivo, such as formaldehyde, glyceraldehyde, acetaldehyde, and glucose.

Formaldehyde reacts fairly nonspecifically with proteins. However, under controlled conditions, it may be used as a structural probe to supply the carbonyl component for the reductive alkylation of proteins. Glyceraldehyde reacts less extensively with proteins, as exemplified by its reaction with hemoglobin, and has therapeutic potential as an antisickling agent.

Recent work has focused on the modification of hemoglobin by acetaldehyde. This primary metabolite of ethanol metabolism is elevated in alcoholics. Clinical studies on fast-chromatographing hemoglobins (hemoglobin A1a–c) have suggested that a novel adduct may be formed in persons abusing alcohol. Alcoholic patients have an elevated concentration of minor hemoglobins but normal or subnormal amounts of glycosylated hemoglobin (hemoglobin A1c) as determined by radioimmunoassay. Acetaldehyde was found to form adducts with hemoglobin (HbAAA), both in vitro and in vivo, leading to a change in Chromatographic properties. Browning occurred with higher concentrations of acetaldehyde. HbAA formation thus provides a potential marker for alcoholism in addition to providing a biochemical hypothesis regarding the secondary sequelae of alcohol intake.