bluuebunny/crossref_metadata_2025 huggingface dataset:
Diminished Glucagon Response to Epinephrine in Physically Trained Diabetic Rats
Authors: Nadeau A , Rousseau-Migneron S , Tancrède G , Jobidon C , Trudel D
Published: September 2013

The effect of physical training on glucose, insulin, and glucagon response to epinephrine was assessed in normal and diabetic rats. Male Wistar rats were injected with streptozocin (STZ, 45 mg/kg) and those presenting 1 wk later a blood glucose value between 250 and 400 mg/dl were retained in the protocol and randomly assigned to a sedentary or trained group. Similar studies were conducted in control animals. Physical training was done on a treadmill according to a 10-wk program. Epinephrine (0.75 fxg/kg/min) was infused intravenously (i.v.) in previously cannulated rats for 1h and arterial blood samples obtained at 15-min intervals for glucose, insulin, and glucagon measurements. Pancreatic insulin and glucagon content was also determined. Basal glucose levels were significantly lower in trained than in sedentary diabetic rats (P < 0.01). The hyperglycemic response to epinephrine was diminished by 19% and 23% in trained control and diabetic animals, respectively, with a faster return to baseline after stopping epinephrine infusion in both trained groups. Although in nondiabetic rats thjs could be related to some diminution in the suppressive effect of epinephrine on insulin secretion, this was not the case in diabetic animals. Moreover, while training did not modify epinephrine-induced glucagon response in control rats, the twofold greater (P < 0.01) glucagon response observed in sedentary diabetic rats was restored to normal in trained diabetic rats. After stopping epinephrine infusion, glucagon levels dropped below the baseline in both groups of trained rats but not in their sedentary counterparts. These effects of training on glucagon response could not be explained by changes in pancreatic glucagon content. These findings suggest that physical training modulates the pancreatic alpha cell response to adrenergic stimulation and/or glucose plus insulin suppression. Diminution in glucagon secretion may thus possibly contribute to the training-induced improvement in the glucose homeostasis of STZ-diabetic rats.
Beta-Endorphin Modulation of the Glucoregulatory Effects of Repeated Epinephrine Infusion in Normal Dogs
Authors: El-Tayeb K M A , Brubaker P L , Vranic M , Lickley H L A
Published: September 2013

Successive epinephrine infusions were used as a partial model to examine hormonal and metabolic responses to repeated stress stimuli. As both the endogenous opiates and epinephrine are released in response to stress, we have also studied interactions between epinephrine and B-endorphin. Epinephrine (0.1 μg/kg · min) was infused for 60 min, followed by a 60-min recovery, a second 60 min of epinephrine, and a 60-min recovery, in nine normal, conscious dogs. In a similar study, B-endorphin (0.06 μg/kg · min) was given 30 min before epinephrine, then continuously infused throughout the study (N = 4 dogs). When epinephrine was infused, levels rose to 600–800 pg/ml. The changes in glucagon, B-endorphin, FFA, and hepatic glucose production were similar during both epinephrine infusions, but there was a diminished insulin response, a greater decrease in glucose metabolic clearance, and a greater increase in plasma glucose with the second epinephrine infusion. When B-endorphin was given, plasma levels increased to 5.3 ng/ml. Compared with the infusion of epinephrine alone, there was a much greater rise in plasma glucose due to greater suppression of glucose metabolic clearance. With the second epinephrine infusion, however, the changes in glucose concentration were not substantially different from those seen during the second infusion of epinephrine alone, as both hepatic glucose production and glucose metabolic clearance were suppressed. B-endorphin diminished the insulin and glucagon responses during the first epinephrine infusion and abolished them during the second, but did not alter the FFA, ACTH, or cortisol responses to epinephrine.

Thus, (1) successive epinephrine infusions appear to desensitize the B-cells, resulting in a greater hypergly-cemic response due to exaggerated suppression of MCR, and (2) B-endorphin (0.06 jig/kg min) attenuated epinephrine's effects on the pancreatic A- and B-cells, and enhanced epinephrine's hyperglycemic effects by potentiating its inhibitory effect on MCR and modulating its stimulatory effects on the liver, through direct and/or indirect mechanisms.
The Effect of Metabolic Control on Hemodynamics in Short-Term Insulin-dependent Diabetic Patients
Authors: Mathiesen E R , Hilsted J , Feldt-Rasmussen B , Bonde-Petersen F , Christensen N J , Parving H -H
Published: September 2013

Hemodynamics variables (heart rate, arterial blood pressure, cardiac output, hepato-splanchnic blood flow, forearm blood flow, and plasma catecholamines) were measured during good (median blood glucose 4.7 mmol/L) and poor (median blood glucose 16.3 mmol/L) metabolic control in eight young, short-term, insulindependent diabetic patients. The measurements were performed twice within 2 wk, in random order. Continuous subcutaneous insulin infusion (CSII) was applied for 1 wk in order to obtain good control. All eight patients had elevated cardiac output (median 9%) and forearm blood flow (median 34%) during poor compared with good metabolic control, P < 0.01. In contrast, hepato-splanchnic blood flow was lower (median 12%) during poor compared with good metabolic control, P < 0.05. Heart rate remained unchanged, while mean arterial blood pressure was slightly higher during poor control, P < 0.05. Five of six patients had elevated plasma noradrenaline concentration during poor metabolic control. Due to the small number of patients investigated, no valid conclusion regarding the activity of the sympathoadrenal system can be drawn.

Our study suggests that both increased cardiac output and reduced hepato-splanchnic blood flow (redistribution) contribute to the elevated blood flow previously demonstrated in various other organs and tissues in diabetic patients during poor metabolic control.
Perifusion of a Clonal Cell Line of Simian Virus 40-Transformed Beta Cells: Insulin Secretory Dynamics in Response to Glucose, 3-Isobutyl-1-Methylxanthine, and Potassium
Authors: Hill Ronald S , Boyd A E
Published: September 2013

A perifusion system for the study of insulin secretory dynamics of a clonal, Simian virus 40-transformed hamster pancreatic beta cell line (HIT cells) is described. After a change from glucose-free to higher glucose levels in the perifusate, insulin secretion increased rapidly in a dose-dependent manner. The pattern of glucose-stimulated insulin release was monophasic and was not sustained during a continued glucose stimulus. Perifusing the cells with low glucose (0.3 mg/ml) before a glucose stimulus of 3.5 mg/ml resulted in more rapid insulin release with lower peak secretory rates than those seen after a glucose-free period. The combined stimulus of high glucose and 100 μM 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, significantly enhanced the acute insulin secretory response and also resulted in a biphasic secretory pattern that was sustained throughout the 60-min stimulation period. Insulin secretion stimulated by IBMX required a nonstimulatory level of glucose in the perifusing media, and, if this requirement was met, the immediate release of insulin was similar to that evoked by high glucose alone. High potassium (40 mM) also triggered a monophasic release of insulin. These studies demonstrate that glucose or high K+, which depolarizes the plasma membrane, and IBMX, an agent presumed to increase intracellular cyclic AMP levels, can signal the acute release of insulin from these beta cells. This cell line is a unique model system for studying the mechanism of insulin secretion.
Influence of Growth Hormone on Overnight Insulin Requirements in Insulin-dependent Diabetes
Authors: Skor Donald A , White Neil H , Thomas Lorraine , Santiago Julio V
Published: September 2013

After a 0100–0300 h nadir, the insulin requirements to maintain blood glucose at 90–110 mg/dl increase substantially in the prebreakfast (0600–0800 h) period in some insulin-dependent diabetic patients (IDDMs). Early insulin-like and delayed insulin-antagonistic effects of physiologic early morning increases in growth hormone (hGH) secretion may account for this variability of overnight insulin requirements. To assess the role of hGH, we studied five IDDMs using a closed-loop insulin infusion device (Biostator, GCIIS). Either saline (C) or somatostatin plus glucagon (SRIF + G) was infused during separate overnight (2400–0800 h) study periods. An infusion of hGH from 2400 to 0130 h was added to SRIF + G infusion during an additional study period (SRIF + G + hGH). In comparison to 0100–0300 h, mean insulin infusion rates required to maintain blood glucose values between 105 and 120 mg/dl during the prebreakfast period increased by 66 ± 25% during C, and 42 ± 12% during SRIF + G when serum growth hormone was suppressed to <0.75 ng/ml. During SRIF + G + hGH, the mean prebreakfast insulin infusion rate increased by 42 ± 11% with a mean peak hGH level of 14.7 ± 5.4 ng/ml at 0130 h. Mean plasma free insulin levels remained constant during the night despite the significantly higher insulin infusion rates between 0600 and 0800 h.

During SRIF + G, insulin requirements remained constant overnight before 0600 h, whereas during both C and SRIF +G + hGH conditions, a nadir was noted between 0100 and 0300 h. Data pooled from 10 overnight, saline infusion studies suggest that the early morning nadir in insulin requirements occurs within 60 min of the peak hGH concentration. We conclude that the physiologic early morning increase in hGH is not an essential component of the prebreakfast increase in insulin requirements. Nocturnal growth hormone secretion may, however, contribute to the early morning nadir in insulin requirements seen in IDDM.
Long-Term Follow-up of Canine Segmental Pancreatic Autografts
Authors: Cutfield Richard G , Polonsky Kenneth , Olson Les , Kyriakides George , Miller Joshua , Mintz Daniel H
Published: September 2013

The functional and morphologic characteristics of freedraining, pancreatic segmental autografts (FDPS) were studied in 8 beagle dogs that had survived longer than 4 yr. After pancreatectomy, animals received FDPS autografts of the left pancreatic limb, representing approximately one-third of the total pancreas with iliac vessel anastamoses. The grafted recipients were given pancreatic enzyme supplements (Viokase). After transplantation (tx), all 8 animals sustained fasting euglycemia with no evidence of microvascular complications. After 4 yr, IVGTT revealed K-values (%/min) that were not significantly different from age-matched controls (2.9 ± 0.5 versus 3.7 ± 0.6, P > 0.05). Mean fasting serum insulin levels were significantly greater in the tx animals (49 ± 5 μU/ml versus 12.2 μU/ml, P < 0.001), although the incremental response to i.v. glucose (0.5 g/kg) was less than in controls (P < 0.05). Mean fasting plasma C-peptide levels (0.09 ± 0.01 pmol/ml versus 0.21 ± 0.5 pmol/ml) and peak C-peptide responses to i.v. glucose were both significantly less than in controls. Sequential pancreatic biopsies up to 2.5 yr post-tx showed atrophy of the exocrine pancreas with coalescence of islets and mild fibrosis that did not progress with time. Immunoperoxidase stains confirmed the presence of insulin, glucagon, and somatostatin within nests of islet cells. Four years after transplantation of FDPS autografts in pancreatectomized dogs, excellent function is retained. The consequences of peripheral hyperinsulinemia remain to be determined.
Long-Term Effect of Diabetes and Pregnancy in the Rat
Authors: Van Assche F A , Aerts L
Published: September 2013

Islet hyperplasia and B-cell degranulation were found in the fetuses of the third generation from mothers (second generation) born to a diabetic mother (first generation) regardless of the origin of the father, while pancreatic islets were normal in fetuses from control mothers, even when the father was an offspring of a diabetic mother. These data support the hypothesis that in our experimental model overstimulation of the fetal endocrine pancreas results in long-term consequences to the third generation.
Screening of High-Risk and General Populations for Gestational Diabetes: Clinical Application and Cost Analysis
Authors: Lavin Justin P
Published: September 2013

Two thousand seventy-seven women attending a university-based prenatal clinic were screened for gestational diabetes. The patients were divided into two groups. Group 1 consisted of 959 patients with historic or clinical factors traditionally employed to identify patients as being at high risk for the occurrence of gestational diabetes. Group 2 consisted of the remaining 1118 patients. The O'Sullivan 50-g 1-h test, with an upper limit of normal for serum glucose of 150 mg/dl, was employed as the initial screening procedure. Patients with an abnormal screening test underwent a 3-h oral glucose tolerance test (GTT) with a 100-g load. The values recommended by the First American Diabetes Association Workshop-Conference on Gestational Diabetes were employed for interpretation. Group 1 patients underwent screening at their initial visit and again at 28 wk gestation. Group 2 patients underwent an identical screening sequence between 28 and 32 wk gestation. Cost analysis was performed.

The prevalences of positive screening tests were 7.2% and 6.1%, and the frequencies of abnormal GTTs were 1.5% and 1.4% among group 1 and group 2 patients, respectively. These rates were not statistically significantly different. Overall, 46.7% and 53.5% of the cases of gestational diabetes were identified among the patients with and without risk factors, respectively. The total cost of the screening program was $9869.00. The cost per patient screened and the cost per case of gestational diabetes identified were $4.75 and $328.96, respectively. These results reemphasize the inadequacy of screening only those patients with traditional risk factors for gestational diabetes and demonstrate the feasibility of implementing a program of universal glucose screening among, a large obstetric population. The observed cost compares favorably with screening tests employed for other diseases during pregnancy.
Consequences of Perturbations of Fetal Fuels in Ovine Pregnancy
Authors: Philipps Anthony F , Rosenkrantz Ted S , Raye John
Published: September 2013

Maternal or fetal substrate infusions into chronically catheterized fetal lambs have recently been performed in order to examine the effects of excessive fetal substrate presentation on fetal metabolism and metabolic rate. The degree of maternal hyperglycemia in this animal model has been shown to relate to the degree of fetal hyperglycemia and to the magnitude of fetal glucose utilization. Series of direct fetal glucose infusions were performed designed to mimic the development of moderate maternal hyperglycemia. These studies suggest that fetal glucose excess stimulates fetal oxidative metabolism with increases in fetal glucose and lactate entry and stimulation of fetal oxygen consumption. If severe, fetal lamb hyperglycemia may result in fetal hypoxia with metabolic acidosis and fetal demise. The metabolic goal of the stimulation of fetal oxidation may relate to increases in fetal activity such as respiration, excessive fetal growth, and other factors, as yet unidentified. Insulin or catecholamines may be mediators of at least some of these events. Chronic infusion studies regarding other potential fetal fuels have not yet been performed. The chronically catheterized glucoseinfused fetal lamb may offer insights into the metabolic derangements observed and suspected in infants born to women with gestational and insulin-requiring diabetes mellitus.
Relationship Between Maternal and Fetal Fuels and Placental Glucose Transfer in Rats with Maternal Diabetes of Varying Severity
Authors: Herrera Emilio , Palacin Manuel , Martin Antonia , Lasuncion Miguel Angel
Published: September 2013

Gestational diabetes mellitus (GDM) is a nonhomogenous entity known to affect fetal development in different ways in both rats and human beings. The degree of severity of diabetes could affect the maternal-fetal transfer of metabolic fuels and consequently influence fetal development. To study this hypothesis, pregnant rats were made diabetic by streptozocin (STZ) treatment (45 mg/kg) at day 7 of gestation and were treated with different daily doses of insulin until the 20th day of gestation, when-they were killed and examined. Differences in plasma glucose levels in the groups studied were not accompanied by differences in plasma glycerol, β-hydroxybutyrate (β-OHB), or total amino acid levels in mothers or their fetuses. Fetal/maternal ratios of these circulating fuels were not modified by maternal diabetes, whereas the glucose level was enhanced in diabetic rats not treated with insulin. Placental glucose transfer was studied directly with a recently reported in situ experimental design and was found to increase linearly with maternal glycemia, independently of whether this was modified by insulin treatment or by acute intravenous (i.v.) infusion of glucose in normal animals. Lactate production by the fetal/placental unit decreased in proportion to the glucose level in the maternal circulation.

The present data indicate that the diabetic condition of the mother rat does not modify the mechanisms of placental transfer of metabolic fuels to the fetus, and that the actual transfer is mainly dependent on the concentrations of these fuels in the maternal circulation. The limited capacity of the fetus to handle the great influx of glucose through the placenta of a highly hyperglycemic mother may aggravate the diabetic condition of the fetus, affecting its subsequent development.
Gestational Diabetes Mellitus: Is Further Improvement Necessary?
Authors: Philipson Elliot H , Kalhan Satish C , Rosen Mortimer G , Edelberg Stuart C , Williams Thomas G , Riha Margo M
Published: September 2013

The maternal antepartum, intrapartum, and neonatal characteristics of 158 patients with gestational diabetes mellitus (GDM) attending a large teaching hospital between 1979 and 1983 were described and compared with a matched nondiabetic control group. The primary cesarean section rate in patients with GDM (18%) was significantly greater than in the control group (11%, P < 0.04). Neonatal macrosomia, as reflected in mean birthweight (P < 0.04), the number of neonates weighing > 4 kg (P < 0.05) and large-for-gestationalage infants (P < 0.05), and the birthweight adjusted for gestational age (K-score, P < 0.01) was significantly increased in the diabetic group.

The characteristics of patients with GDM treated with diet alone and diet and insulin together were examined. The insulin-therapy group was characterized by more patients older than 25 yr (P < 0.01) and a higher mean birthweight (3743 ± 677 g) (P < 0.02) than the dietalone group. This may reflect an increased magnitude of glucose intolerance in the insulin-treated group. Obese patients with GDM delivered heavier neonates than the nonobese patients with GDM (P < 0.01). Although there was no difference between the groups, perinatal mortality was present in this study. These data indicate that the major perinatal morbidity in GDM included increased cesarean section for fetal macrosomia. Early diagnosis with strict diagnostic criteria and rigid antenatal surveillance may result in further improvements in outcome.
Hormonal Responses to Exercise in Diabetic and Nondiabetic Pregnant Patients
Authors: Artal Raul , Wiswell Robert , Romem Yitzhak
Published: September 2013

The hormonal responses to low-level exercise in pregnancy have been studied in 13 insulin-requiring diabetic patients and 42 control subjects.

We found no significant changes in plasma glucose, epinephrine, glucagon, or FFA with this level of exercise in the study group and control subjects; but plasma norepinephrine showed a significant increase with exercise.

This type of exercise appears to be safe and could serve as a model for exercise prescription for attaining improved glucose tolerance in pregnant diabetic women.
The Immunogenicity of New Insulins
Authors: Deckert Torsten
Published: September 2013

Treatment with conventional insulin preparations results in appreciable insulin antibody formation in nearly all subjects. High titers of insulin antibodies are undesirable. They might induce insulin allergy and insulin resistance, and they influence metabolic regulation. Also, lipoatrophy is related to the immunogenicity of insulin preparations. Insulin antibodies are transferred from insulin-treated diabetic mothers to the fetus and contribute to the increase of free plasma insulin in the fetus, thus influencing the development of macrosomia and neonatal hypoglycemia. Therefore, the risk of insulin antibody formation should be reduced. This is possible by using purified, nonbeef insulin preparations. The risk of insulin allergy, insulin resistance, lipoatrophy, and prolonged hypoglycemia in mother and child is reduced by treating pregnant diabetic subjects with purified pork or human insulin preparations. The reduction of insulin requirement that accompanies the change from conventional insulin to purified nonbeef insulin treatment will compensate to some extent for the higher costs of new insulins.
Review: Therapeutic Results of Insulin Therapy in Gestational Diabetes Mellitus
Authors: Kalkhoff Ronald K
Published: September 2013

Most studies of gestational diabetes mellitus (GDM) have reported a marked reduction in perinatal mortality with appropriate dietary regimens and good medical and obstetrical surveillance. Nevertheless, fetal morbidity, including macrosomia, has remained high and appears to be linked to factors other than plasma glucose control. In a review of six investigations in which insulin therapy was combined with an appropriate diet, the incidence of fetal macrosomia was reduced in five studies as compared with diet-only treatments. Again, the improvement did not always correlate with altered plasma glucose profiles. Other studies suggest that maternal plasma substrate disturbances other than glucose may contribute to the development of fetal macrosomia. To what extent insulin administration reduces morbidity by containing circulating maternal fuels, such as lipids and amino acids, in a more normal range remains to be determined. Moreover, the role of diet, maternal obesity, and weight gain during pregnancy adds to the complexity of factors influencing obstetrical outcome in gestational diabetes. Until the relative importance of all of these variables is adequately assessed, criteria for selection of women with pregnancyonset diabetes for insulin therapy are most likely to be based on fasting and postprandial plasma glucose concentrations.
Autoantibodies Against the Insulin Receptor: Dissociation of the Acute Effects of the Antibodies from the Desensitization Seen with Prolonged Exposure
Authors: Grunfeld Carl , Jones Debra S , Shigenaga Judy K
Published: September 2013

The effect of antibodies against the insulin receptor (anti-R) found in a patient with the type B syndrome of insulin resistance and acanthosis nigricans was characterized using 3T3-L1 cultured fat cells. Anti-R acutely mimicked the action of insulin by stimulating deoxyglucose uptake. With more prolonged exposure, this insulinomimetic effect decayed, glucose metabolism returned to basal levels, and the cells became severely resistant to the actions of insulin. As seen with anti-R from a previous patient, desensitization consisted of both a dramatic decrease in the maximal responsiveness of the cells to insulin and a shift in the dose-response curve for insulin-stimulated glucose oxidation.

The acute and chronic effects of anti-R were then compared. The concentration of anti-R required to halfmaximally inhibit insulin binding averaged more than twice that required for half-maximal stimulation of deoxyglucose uptake, consistent with the amount of spare receptors in 3T3-L1 cells. After prolonged exposure, the insulinomimetic activity was completely lost at all concentrations of anti-R, even at those that did not completely induce insulin resistance. Thus, loss of the insulinomimetic activity of anti-R is necessary, but not sufficient, to cause desensitization. Less anti-R was required to desensitize cells to insulin than would have been predicted on the basis of the acute inhibition of binding and the number of spare receptors. In addition, the amount of anti-R required to half-maximally inhibit insulin binding after prolonged exposure was an order of magnitude less than that during acute exposure, implying a progressive loss of insulin receptor binding during antibody-induced desensitization. When cells were treated with subsaturating concentrations of anti-R, insulin binding decreased over a period of several hours.

Finally, an acid wash (capable of dissociating antigen-antibody complexes) could not restore insulin binding after desensitization, but could restore insulin binding if cells were exposed to anti-R at 4°C. These results support the theory that insulin receptors are removed from the cell surface during antibody-induced desensitization.
Do Pancreatic Islets Contain Significant Amounts of Phosphoenolpyruvate Carboxykinase or Ferroactivator Activity?
Authors: MacDonald Michael J , Chang Cheng-Min
Published: September 2013

Phosphoenolpyruvate carboxykinase activity was measured in rat pancreatic islet cytosol and mitochondria. No carboxykinase activity was detected under a variety of conditions, including those that increase phosphoenolpyruvate carboxykinase activity in nonislet tissues, such as starving animals or incubating the islet extracts with Fe2+ or Mn2+ before assaying for enzyme activity. The amounts of islet cytosol protein used exceeded those of liver in companion assays used as controls. It was calculated that if islet phosphoenolpyruvate carboxykinase activity was 0.005 that of liver, or 1 × 10−5 as high as pyruvate kinase activity in islets, it should have been detected in the assays used. Ferroactivator is a protein that permits Fe2+ to activate phosphoenolpyruvate carboxykinase and it is ubiquitous to many tissues that do and even do not contain the carboxykinase. Ferroactivator activity was not detectable in pancreatic islets. Pyruvate kinase, an enzyme that catalyzes a reaction that is essentially the opposite of that catalyzed by phosphoenolpyruvate carboxykinase (i.e., phosphoenolpyruvate formation), is plentiful in islet cytosol. Therefore, even if phosphoenolpyruvate carboxykinase activity is present in pancreatic islets, it is so low that it is unlikely that phosphoenolpyruvate formation would be favored and the contribution of the carboxykinase to intracellular carbohydrate metabolism must be quantitatively unimportant.
An Ascochlorin Derivative, AS-6, Reduces Insulin Resistance in the Genetically Obese Diabetic Mouse, db/db
Authors: Hosokawa Tomoyoshi , Ando Kunio , Tamura Gakuzo
Published: September 2013

An ascochlorin derivative, AS-6, is a new hypoglycemic agent orally active in both obese hyperinsulineroic and insulin-deficient diabetic animal models. AS-6, when given as a 0.025–0.2% admixture in the diet, dose-dependently ameliorated polydipsia, polyuria, and glycosuria in the genetically obese diabetic mouse, C57BL/KsJ db/db, while neither insulin nor tolbutamide showed any beneficial effects. The amelioration by AS-6 was associated with a marked decrease in serum glucose and triglyceride. The effects persisted at least 10 wk, accompanied by a steady decrease in drinking water consumption. The chronic treatment prevented pancreatic islet degeneration, e.g., degranulation of the β-cells, basophilic appearance of the exocrine border around the islets, and small round cell infiltration. The isolated islets from AS-6-treated mice released much more insulin in response to glucose than those from untreated controls. A significant correlation between serum immunoreactive insulin and glucose/triglyceride from both treated and untreated mice suggests that AS-6 restores sensitivity and responsiveness to insulin to the mice.

In fact, the combined treatment with insulin synergistically decreased serum glucose by 50% below AS-6 treatment alone. Furthermore, the epididymal fat pad slices from AS-6-treated db/db mice increased CO2 generation and lipogenesis over the untreated controls, and the glucose metabolic rate (CO2 generation plus lipogenesis from U-[14C]-glucose) in the slices and the serum glucose level inversely correlated at r = 0.8799. These facts indicate that AS-6 reduces insulin resistance in db/db mice.
The Central Biochemistry Laboratory in the Multicenter Kroc Study: Problems and Proposals
Authors: Home Philip D , Alberti K George M M , Rodger N Wilson , Burrin Jacqueline M ,   The Kroc Collaborative Study Group
Published: September 2013

The advantages of a multicenter trial can easily be lost if results from individual centers cannot be safely combined for statistical analysis. One objective of the Kroc Study was to develop methods that would allow valid amalgamation of results from laboratories at the six clinical centers and a central biochemical laboratory at the University of Newcastle upon Tyne. Responsibilities of the local laboratories, in addition to measurement of plasma glucose, creatinine, and glycosylated hemoglobin, were to obtain and prepare samples for measurement of plasma glucose, glycosylated hemoglobin, and serum lipids at the central laboratory, of C-peptide at the University of Chicago, and to collect and prepare samples for measurement of urinary albumin excretion at Guy's Hospital. The central laboratory was additionally to provide a system to ensure the comparability of plasma glucose determinations between and within centers, and to advise on common procedures for sample handling.

Major problems were encountered with sample labeling, dispatch, and transport to the central laboratory. Although central determinations of plasma glucose and serum lipids were still possible in transported specimens, central assay of glycosylated hemoglobin proved inaccurate and useless. Compliance with the plasma glucose quality control program was variable among centers. Although the difference between the centers recording the highest and lowest values was 24.6% of the mean estimate of plasma glucose level, correlation between local and central plasma glucose determinations was good (r = 0.99, see pages 22–26).

From this experience, we suggest that for satisfactory performance of a multicenter trial an individual is given responsibility for coordinating efforts between laboratories, supervising and auditing local procedures of sample preparation and quality control, and ensuring adequate communication between the central laboratory, local centers, and the data collation center. A biochemist at each local laboratory should in turn be personally responsible for the specimens generated by each experiment, and preparation and dispatch of samples to the central laboratory. Duplication of assays of critical variables, namely at local and central laboratories, is recommended. Blood glucose and glycosylated hemoglobin assays should be by a single method using one type of instrument, the methods chosen being selected by their ability to produce reliable and comparable results in different hands.

These measures should minimize the likelihood of loss of critical information due to poor sample management, and the variability inherent in the combined use of biochemical data derived from multiple laboratories.
Observations on Blood Lipid and Intermediary Metabolite Concentrations During Conventional Insulin Treatment or CSII
Authors: Lawson Paul , Home Philip D , Bergenstal Richard ,   The Kroc Collaborative Study Group
Published: September 2013

An objective of The Kroc Collaborative Study Group trial of the feasibility of maintaining improved control of plasma glucose concentrations with continuous subcutaneous insulin infusion (CSII) was to test the nonglycemic aspects of metabolic control in relation to microvascular disease. Serum lipid levels were assessed in the 68 patients completing the 8-mo trial, before and after randomization to conventional insulin treatment (CIT) or CSII. During CSII, fasting serum cholesterol concentrations, normal at baseline (186 ± 7 mg/dl), were unchanged at 4 and 8 mo (183 ± 8 and 186 ± 10 mg/dl). Fasting serum triglyceride concentrations fell on treatment with CSII (baseline 90 ± 12 mg/dl, 8 mo 60 ± 7 mg/dl, P < 0.01), but were unchanged during CIT (baseline 88 ± 8 mg/dl, 8 mo 83 ± 10 mg/dl). Thirty-two patients in three centers had 24-h profiles of intermediary metabolites measured at baseline (0), 4, and 8 mo. Mean 24-h venous blood lactate levels fell during CSII (baseline 1.28 ± 0.12 mmol/L, 4 mo 0.99 ± 0.4 mmol/L, P < 0.05; 8 mo 1.05 ± 0.11 mmol/L), but blood alanine levels were unchanged. Venous blood 3-hydroxybutyrate fell from 0.12 × / ÷ 1.18 mmol/L at baseline to 0.06 × / ÷ 1.22 mmol/L at 8 mo during CSII (P < 0.01), mainly due to decreases at 0400 and 0600 h. Decreases in fasting serum triglyceride levels confirm previous investigations of insulin-dependent diabetic subjects treated with CSII; decreases of venous blood lactate and 3-hydroxybutyrate levels toward normal indicate that these metabolic effects of CSII recognized in short-term studies are sustained over an 8-mo period.
Observations on C-Peptide and Free Insulin in the Blood During Continuous Subcutaneous Insulin Infusion and Conventional Insulin Therapy
Authors: Bergenstal R M , Dupre J , Lawson P M , Rizza R A , Rubenstein A H ,   The Kroc Collaborative Study Group
Published: September 2013

As part of a multicenter trial, 70 individuals with insulin-dependent diabetes were randomized to either conventional insulin therapy (CIT) or continuous subcutaneous insulin infusion (CSII). In order to standardize patient selection in the six participating centers, one of the eligibility criteria was the demonstration that each patient had no residual endogenous insulin secretion as assessed by plasma C-peptide determinations. The patients were of average (± SEM) age of 33.0 ± 1.6 yr, had had diabetes for a mean (±SEM) duration of 17.4 ± 1.1 yr, and had both fasting and postglucagon stimulation C-peptide values of <0.1 pmol/ml, consistent with clinically insignificant endogenous insulin secretion. There was no change in C-peptide response at 4 or 8 mo compared with baseline values, whether or not the patient's glucose control remained unchanged (CIT group) or significantly improved to near-normoglycemia (CSII group). In a subgroup of 34 patients at three centers, the 24-h mean glucose concentration was significantly lower in the CSII group compared with the CIT group at 4 mo (126 ± 10 versus 176 ± 14 mg/dl) and at 8 mo (121 ± 5 versus 183 ± 15 mg/dl) (P < 0.005). Although the 24-h mean serum free immunoreactive insulin levels were shown to be no different at baseline (27.4 ± 3.8 versus 26.2 ± 3.1 μU/ml) or after 4 mo (22.5 ± 3.2 versus 25.6 ± 3.2) or 8 mo (26.5 ± 3.4 versus 28.8 ± 3.4) of CIT or CSII therapy, respectively, the mean increase of free insulin concentrations in relation to the main meals was greater in the CSII group (P < 0.05). The mean serum free insulin levels achieved with both CIT and CSII were significantly greater than the 24-h mean free insulin level obtained in 12 normal subjects (12.2 ± 1.4 μU/ml) (P < 0.001).
Comparison of Stereofundus Photographs in Patients with Insulin-dependent Diabetes During Conventional Insulin Treatment or Continuous Subcutaneous Insulin Infusion
Authors: Canny C L B , Kohner E M , Trautman J , Puklin J , Morse P ,   The Kroc Collaborative Study Group
Published: September 2013

Sixty-five patients with mild to moderate nonproliferative diabetic retinopathy who enrolled in a prospective controlled clinical trial had stereofundus photographs assessed for change over an 8-mo period. The entire study group showed a worsening of retinopathy with time (P < 0.001). The worsening was greater in the pump-treated group (15/32) than in the conventionally treated group (9/33). The significance of this difference ranged from P = 0.67, if changes in mean retinopathy level for each patient were compared, to P = 0.177 if a grading system keyed to the worse eye was compared. The difference in rates of change between treatment groups was found to be related to the baseline mean retinopathy level (P = 0.031), but less significantly so if baseline retinopathy keyed to the worse eye was used as a covariate (P = 0.08). Worsening occurred more frequently in those patients starting with the lower retinopathy levels.

Progression was associated with the appearance of retinal infarcts (cotton-wool spots, soft exudates) and/or intraretinal microvascular abnormalities, with the pump patients showing a significant increase in these individual retinal lesions compared with the conventionally treated patients over 8 mo (P < 0.025).
Eight-Month Correction of Hyperglycemia in Insulin-dependent Diabetes Mellitus Is Associated with a Significant and Sustained Reduction of Urinary Albumin Excretion Rates in Patients with Microalbuminuria
Authors: Bending Jeremy J , Viberti Gian Carlo , Bilous Rudolf W , Keen Harry ,   The Kroc Collaborative Study Group
Published: September 2013

Persistent Albustix-positive proteinuria and subsequent chronic renal failure are frequently encountered in insulin- dependent diabetes mellitus (IDDM). Rates of decline of renal function may be modified by treatment of accompanying hypertension, but studies of the effects of long-term continuous subcutaneous insulin infusion (CSII) on deterioration of renal function provide no statistically significant evidence of benefit of near-normoglycemia. However, short-term studies in IDDM subjects with negative Albustix tests but subclinically raised levels of albumin excretion rate (AER) have shown that treatment with CSII significantly reduces this microalbuminuria. The prospective, controlled 8-mo Kroc Collaborative Study therefore offered the opportunity of examining more protracted effects of CSIIinduced metabolic correction upon microalbuminuria. Twenty-four-hour urine collections obtained at baseline, 4, and 8 mo were available from 59 Albustix-negative patients. β2-microglobulin excretion was normal. The 39 normoalbuminuric (AER < 12 μ/min) patients did not differ from the 20 microalbuminuric (AER elevated between 13.2 and 192.6 μg/min) with respect to distributions of age, sex, and duration of diabetes. In both the normoalbuminuric and the microalbuminuric groups studied at 4 and 8 mo, percent glycosylated hemoglobin (%HbA1) and mean blood glucose were significantly decreased during CSII compared with baseline values, whereas no change occurred in the group continuing their conventional insulin therapy (CIT). AER did not differ between CIT and CSII treatments in the normoalbuminuric group. AER fell significantly in the CSII-treated microalbuminuric patients at 4 (P < 0.05) and 8 (P < 0.01) mo but showed no consistent change in the CIT microalbuminuric group. With respect to responses of patients at particularly high risk of progression to clinical nephropathy (i.e., AER > 30 μ/min), four of four improved during CSII, but only two of six during CIT. These observations demonstrate a sustained reduction of abnormal rates of urinary albumin excretion during therapy designed to achieve near-normoglycemia in IDDM.
Two-Year Experience with Continuous Subcutaneous Insulin Infusion in Relation to Retinopathy and Neuropathy
Authors: Lauritzen Torsten , Frost-Larsen Kim , Larsen Hans-Walther , Deckert Torsten ,   The Steno Study Group
Published: September 2013

Thirty patients with insulin-dependent diabetes mellitus (IDDM) who had advanced background retinopathy were randomized to unchanged conventional treatment (UCT) or to continuous subcutaneous insulin infusion (CSII). They were followed prospectively for 2 yr. The mean blood glucose and hemoglobin A1c (HbA1c) were significantly lower in the CSII group than in the UCT group. The mean blood glucose and HbA1c did not change from the first to the second year in either of the treatment groups in spite of less frequent home-monitoring of blood glucose and less frequent outpatient visits during the second year. Four patients in the CSII group and five in the UCT group developed proliterative retinopathy. However, a marginally significant trend was found toward more frequent improvement of retinal morphology in the CSII group (47%) than in the UCT group (13%). Beat-to-beat variation was found to deteriorate significantly with UCT compared with a nonsignificant improvement with CSII therapy. Vibration sense was unchanged in both treatment groups. It is concluded that near-normal blood glucose levels can be maintained with CSII therapy in spite of less frequent home-monitoring of blood glucose and outpatient visits. Furthermore, established background retinopathy may progress to proliferative retinopathy in spite of 2 yr of near-normal blood glucose levels. However, a marginally significant trend toward more frequent improvement of retinal morphology was found among CSII-treated patients compared with conventionally treated patients. Large-scale, prospective, randomized studies are needed to confirm these results.
Improved Insulin Sensitivity in Patients with Type I Diabetes Mellitus After CSII
Authors: Simonson Donald C , Tamborlane William V , Sherwin Robert S , Smith J Douglas , DeFronzo Ralph A ,   The Kroc Collaborative Study Group
Published: September 2013

Tissue sensitivity to insulin was studied using the euglycemic insulin clamp technique (Δ plasma insulin above basal 90 μU/ml) in eight patients with type I diabetes mellitus (IDDM) before and after 4–8 mo of continuous subcutaneous insulin infusion (CSII) and in 36 age-matched control subjects. Institution of CSII was associated with significant improvements in glycosylated hemoglobin (HbA1) (11.2 ± 0.6% versus 8.1 ± 0.4%; P <0.001) and mean 24-h plasma glucose concentrations (239 ± 23 mg/dl versus 106 ± 18 mg/ dl ; P < 0.001).

Insulin-mediated glucose metabolism in the diabetic patients pre-CSII (3.92 ± 0.36 mg/kg min) was reduced by 44% compared with controls (7.03 ± 0.22 mg/kg min; P < 0.001). After 4–8 mo of improved glycemic control, improved tissue sensitivity to insulin was observed (5.33 ± 0.75 mg/kg·min; P < 0.05 versus pre- CSII). However, insulin-mediated glucose utilization still remained significantly below control values (P < 0.01). During hyperinsulinemia, hepatic glucose production (3-3H-glucose) was suppressed by over 90% in diabetic patients (pre- and post-CSII) and in control subjects.

We conclude that near-normalization of glucose metabolism with CSII partially corrects, but does not restore to normal, insulin-stimulated glucose uptake in IDDM. Our failure to totally reverse the impaired response of peripheral tissues to insulin in IDDM patients may be attributed to inadequate metabolic correction, the peripheral route of insulin administration, or a primary defect in glucose metabolism.
Ketone Body Production and Disposal in Diabetic Ketosis: A Comparison with Fasting Ketosis
Authors: Féry Françoise , Balasse Edmond O
Published: September 2013

This work compares the metabolism of total ketone bodies in 13 insulin-deprived, type I diabetic subjects and 26 control subjects fasted for 15 h to 23 days, with the two groups showing a similar range of ketone body levels (1–12 mM). Ketone turnover rate was measured using a primed, constant infusion of either 14C-acetoacetate or 14C-β-hydroxybutyrate, both tracers yielding comparable results.

The major conclusions of this study are the following: the kinetics of ketone bodies are comparable in the two groups within the range of concentrations tested. The hyperketonemia of fasting and diabetes is primarily caused by an increased production of ketone bodies, but the phenomenon is amplified by a progressive limitation in the ability of tissues to remove ketones from blood as the concentration rises. The inverse relationship between the metabolic clearance and the plasma levels of ketones, which underlies this process, represents a general characteristic of ketone body metabolism that applies to both types of ketosis. A maximal metabolic disposal rate of about 2.3 mmol/min/1.73 m2 is attained in both groups at concentrations of 10–12 mM, which correspond to the highest ketone body levels encountered during prolonged fasting. Thus, up to these levels, there is no evidence for the existence of a ketone body removal defect specific to diabetes.
Effect of Exogenous Phospholipase A2 on Insulin Secretion from Perifused Rat Islets
Authors: Zawalich Walter , Zawalich Kathleen
Published: September 2013

Treatment of isolated, perifused rat islets with exogenous PLA2 in amounts ranging from 1 to 1000 mU/ml caused a dose-dependent increase in the rate of insulin secretion. This effect of PLA2 was rapid and seen in the absence of added exogenous fuel. It differed from glucose-induced insulin release in temporal pattern: high concentrations of PLA2 caused a single phase of secretion, and high levels of glucose caused a biphasic pattern of secretion. Like glucose-induced release, PLA2-induced release was partially dependent on extracellular calcium because D600 caused a significant inhibition of release induced by PLA2 at 5 mU/ml. Concentrations of BW755c and NDGA, inhibitors of both the cyclooxygenase and lipoxygenase or only the lipoxygenase pathways of arachidonic acid metabolism, which completely blocked the insulin secretory response to 10 mM glucose, had no effect on the secretory response to 5 mU/ml of PLA2. These inhibitors also inhibited glucose usage by the islets. Finally, although repeated brief exposure of islets to stimulatory concentrations of glucose lead to a progressive increase in the magnitude of both the first and second phases of insulin secretion, repeated brief exposures to PLA2 lead to a progressive decrease in response to each new exposure. Nonetheless, those islets that had been exposed several times to exogenous PLA2, and no longer displayed a response to a further PLA2 exposure, responded normally to the addition of 10 mM glucose. These results indicate that PLA2 is a potent insulin secretagogue, that it shares some of the characteristics of glucose as a secretagogue, but that in many significant ways differs markedly from glucose in its effects on insulin release from isolated islets.
Production of 12-Hydroxyeicosatetraenoic Acid and Vitamin E Status in Platelets from Type I Human Diabetic Subjects
Authors: Karpen C W , Cataland S , O'Dorisio T M , Panganamala R V
Published: September 2013

Vitamin E content and biosynthesis of 12-hydroxyeicosatetraenoic acid (12-HETE) havebeen measured in platelets from type I diabetic subjects and age- and sex-matched, nondiabetic control subjects. Platelets from diabetic subjects synthesized significantly greater quantities of 12-HETE than did platelets from control subjects when 12-HETE synthesis was induced by thrombin or collagen, either in the presence or absence of indomethacin. Platelet conversion of exogenouslyadded arachidonic acid (AA) to 12-HETE was not significantly different between the diabetic and control groups in the absence of indomethacin, although a small but significant increase in the conversion of AA to 12-HETE was present in the diabetic group platelets when indomethacin was addedto the reaction. Vitamin E content was significantly reduced in platelets from the diabetic subjects, when compared with platelets from the control subjects, although plasma vitamin E levels were not significantly different between the two groups. Thrombin- and collagen-induced platelet 12-HETE synthesis demonstrated a significant negative linear correlation with platelet vitamin E content when measurements from both diabetic and control groups were combined. The above data suggest a relationship between low vitamin E content and increased 12-HETE synthesis in platelets from type I diabetic subjects.