Glucose-induced responses of insulin and gastric inhibitory polypeptide in various animal models

In order to clarify the role of gastric inhibitory polypeptide (GIP) in an enteroinsular axis, 19 healthy mongrel dogs were divided into following groups: 5 normal dogs (N), 4 dogs with gastrojejunostomy (GJ), 5 dogs with duodenal fistula (D) and 5 vagotomized dogs (V). Four weeks after the operation glucose was administered orally or intraduodenally in a conscious state. In group D, glucose administration was repeated under atropine injection (A). Glucose-induced response of plasma GIP was exaggerated in all the groups compared with group N. The regression equation reported by Lauritsen and Moody was obtained in each dog from the ratio of plasma insulin to blood glucose and from plasma GIP. The slope of the regression line was elevated in group GJ and reduced in group V. However, groups D and A did not reveal any difference in the slope of the regression line compared with group N. From the present study, it might be concluded that the B-values in Lauritsen and Moody's equation indicates the sensitivity of the B cell in the pancreatic islet and that GIP secretion plays an important role in the glucose-induced insulin response even in the conditions with various surgical modifications.     

Transgenic rescue of GATA-1-deficient mice with GATA-1 lacking a FOG-1 association site phenocopies patients with X-linked thrombocytopenia

Association of GATA-1 and its cofactor Friend of GATA-1 (FOG-1) is essential for erythroid and megakaryocyte development. To assess functions of GATA-1-FOG-1 association during mouse development, we used the GATA-1 hematopoietic regulatory domain to generate transgenic mouse lines expressing a mutant GATA-1, which contains a substitution of glycine 205 for valine (V205G) that abrogates its association with FOG-1. We examined whether the transgenic expression of mutant GATA-1 rescues GATA-1 germ line mutants from embryonic lethality. In high-expressor lines we observed that the GATA-1(V205G) rescues GATA-1-deficient mice from embryonic lethality at the expected frequency, revealing that excess GATA-1(V205G) can eliminate the lethal anemia that is due to GATA-1 deficiency. In contrast, transgene expression comparable to the endogenous GATA-1 level resulted in much lower frequency of rescue, indicating that the GATA-1-FOG-1 association is critical for normal embryonic hematopoiesis. Rescued mice in these analyses exhibit thrombocytopenia and display dysregulated proliferation and impaired cytoplasmic maturation of megakaryocytes. Although anemia is not observed under steady-state conditions, stress erythropoiesis is attenuated in the rescued mice. Our findings reveal an indispensable role for the association of GATA-1 and FOG-1 during late-stage megakaryopoiesis and provide a unique model for X-linked thrombocytopenia with inherited GATA-1 mutation.     

Hepatic steatosis and the elevated plasma insulin level in patients with endogenous hypertriglyceridemia

Among 31 nonobese or obese patients with endogenous hypertriglyceridemia, hepatic steatosis was found by histologic examination of the biopsied specimen in 17 patients, and it was severe in six patients. They had no history of excessive alcohol intake. Chemical analysis revealed that the lipid accumulated in the liver was triglyceride. The hypertriglyceridemic patients, with or without histologic steatosis, showed significantly increased responses of both plasma insulin and blood glucose to oral glucose load compared with control subjects. The responses were more exaggerated in the hypertriglyceridemic patients with steatosis than in the hypertriglyceridemic patients without steatosis. Analysis of correlations between five variables (liver triglyceride, plasma insulin, blood glucose, body weight index, and serum triglyceride) was done on 15 subjects whose liver triglyceride values were quantified, and highly significant correlations were found between liver triglyceride and plasma insulin, blood glucose, or body weight index. A stepwise multiple regression analysis performed on the five variables with liver triglyceride as the dependent variable revealed that the plasma insulin level was the most closely related variable, and the blood glucose level the next. The prediction equation for liver triglyceride as a function of plasma insulin and blood glucose levels (r = 0.91, p < 0.001) accounted for 84% of the total variance of liver triglyceride. It was shown that the decay of intravenously injected insulin in plasma was not delayed in the hypertriglyceridemic patients with steatosis, while the insulin sensitivity examined after intravenous insulin injection significantly decreased in the hypertriglyceridemic patients with or without steatosis, thus suggesting that the hyperinsulinemia in the hypertriglyceridemic patients was due to an increased insulin secretion associated with the decrease in the insulin sensitivity. Therefore, the elevated plasma insulin and blood glucose levels—or the insulin insensitivity by itself—might be the essential abnormalities in patients with endogenous hypertriglyceridemia, which, in extreme cases, might lead to massive triglyceride accumulation in the liver.     

Development of a resonant‐type microwave reactor and its application to the synthesis of positron emission tomography radiopharmaceuticals

Microwave technology has been successfully applied to enhance the effectiveness of radiolabeling reactions. The use of a microwave as a source of heat energy can allow chemical reactions to proceed over much shorter reaction times and in higher yields than they would do under conventional thermal conditions. A microwave reactor developed by Resonance Instrument Inc. (Model 520/521) and CEM (PETWave) has been used exclusively for the synthesis of radiolabeled agents for positron emission tomography by numerous groups throughout the world. In this study, we have developed a novel resonant‐type microwave reactor powered by a solid‐state device and confirmed that this system can focus microwave power on a small amount of reaction solution. Furthermore, we have demonstrated the rapid and facile radiosynthesis of 16α‐[¹⁸F]fluoroestradiol, 4‐[¹⁸F]fluoro‐N‐[2‐(1‐methoxyphenyl)‐1‐piperazinyl]ethyl‐N‐2‐pyridinylbenzamide, and N‐succinimidyl 4‐[¹⁸F]fluorobenzoate using our newly developed microwave reactor.     

Influence of vagotomy upon GIP release in patients with peptic ulcer

Twenty-two vagotomized peptic ulcer patients were studied on the influence of vagotomy on the release of GIP. Moreover, the relationship between acid output and GIP release was analyzed. These patients underwent one of the three types of operation; truncal vagotomy with pyloroplasty (TV + P) selective vagotomy with pyloroplasty (SV + P) and selective vagotomy with antrectomy (SV + A). Before and after surgery, a gastric juice study and an oral glucose tolerance test were performed on separate days. Maximum acid output in response to tetragastrin correlated significantly with integrated GIP response after oral glucose loading. In the SV + P group, the response of GIP was slightly greater after surgery. In the SV + A group, the integrated GIP response diminished postoperatively, although, after surgery, GIP reached its peak sooner. The integrated GIP response was greater in the SV + P group than in the TV + P group. The response of GIP was less in the SV + A group than in the SV + P group. These changes were insignificant. In conclusion, it is presumed that GIP release is affected by gastric acid, gastric emptying time, intestinal transit time and vagal nerve action.     

The role of aminogenic glucagon secretion in blood glucose homeostasis

Hyperaminoacidemia is a powerful stimulus of pancreatic glucagon secretion. These studies were designed to elucidate the role of aminogenic hyperglucagonemia in glucoregulation. Conscious dogs with previously implanted indwelling venous catheters were employed. The results support the view that a role of glucagon is to limit blood glucose decline during hyperaminoacidemia.First, a significant negative correlation between the area of glucagon increment during the 1st 20 min of a 10 amino acid infusion and the maximum fall in glucose concentration was observed. Second, when endogenous glucagon secretion was suppressed by means of a continuous glucose infusion, hyperaminoacidemia induced a maximal glucose decline which averaged 35 mg/100 ml, differing significantly from mean maximal fall of 3 mg/100 ml, which normally occurs in the presence of endogenous hyperglucagonemia. Third, when, during hyperglycemic suppression of endogenous glucagon secretion, 50 mmug of exogenous glucagon/min was infused via the mesenteric vein with the amino acids, the fall in glucose was reduced to an average of 5 mg/100 ml. Similarly when pancreozymin, administered during the combined infusion of glucose and amino acids, overcame glucose suppression of endogenous glucagon secretion, plasma glucose did not fall.Similar results were obtained when aminogenic hyperglucagonemia was prevented by other means. Hyperlipacidemia, induced by infusing a triglyceride emulsion and giving heparin injections, also suppressed aminogenic hyperglucagonemia in two of four experiments; in these two dogs glucose fell 15 and 11 mg/100 ml. In a final group of experiments, the canine pancreas was resected except for the uncinate process, which is virtually devoid of alpha-cells. In two dogs, in which this procedure resulted in zero portal venous glucagon levels, the administration of amino acids and/or pancreozymin resulted in a glucose decline of 14 and 16 mg/100 ml, despite the reduced beta-cell population resulting from the subtotal pancreotectomy.It thus appears that the secretion of pancreatic glucagon during hyperaminoacidemia in association with insulin secretion, serves to limit the decline of glucose concentration.     

Evaluation of new criteria for diagnosis of diabetes mellitus based on follow-up study of borderline diabetes

In order to evaluate the validity of recently proposed criteria for diagnosis of diabetes mellitus, a retrospective study was performed in 315 patients with borderline diabetes, who were selected from approximately 4,000 outpatients under treatment for more than three years. They were divided into two groups, BI and BII, according to the 2-hr blood glucose level in the 50 g glucose tolerance test (GTT): BI between 100 and 135 mg/100 ml and BII between 135 and 195 mg/100 ml. In group BI, glucose tolerance was deteriorated in 38 of 75 patients (51%) and converted to diabetes mellitus in 21 patients (28%). In group BII, 78 among 232 patients (34%) developed diabetes mellitus. Furthermore, in 85% of the 99 cases of the conversion to diabetes mellitus from borderline diabetes, it occurred within 5 years. Diabetic retinopathy was observed in 25 of 72 patients (35%) in group BI and in 60 of 212 patients (28%) in group BII. More than two thirds of the patients with diabetic retinopathy observed in the borderline diabetes developed their retinopathy within 5 years. Normal insulin response during GTT was proved only in 21% and 17% among groups BI and BII, respectively. These results indicate that the patients with borderline diabetes BI as well as BII, are closely related with diabetes mellitus, and that the patients with impaired glucose tolerance should be treated with diet restriction as in diabetes mellitus.     

Identification of functional endothelial progenitor cells suitable for the treatment of ischemic tissue using human umbilical cord blood

Umbilical cord blood (UCB) has been used as a potential source of various kinds of stem cells, including hematopoietic stem cells, mesenchymal stem cells, and endothelial progenitor cells (EPCs), for a variety of cell therapies. Recently, EPCs were introduced for restoring vascularization in ischemic tissues. An appropriate procedure for isolating EPCs from UCB is a key issue for improving therapeutic efficacy and eliminating the unexpected expansion of nonessential cells. Here we report a novel method for isolating EPCs from UCB by a combination of negative immunoselection and cell culture techniques. In addition, we divided EPCs into 2 subpopulations according to the aldehyde dehydrogenase (ALDH) activity. We found that EPCs with low ALDH activity (Alde-Low) possess a greater ability to proliferate and migrate compared to those with high ALDH activity (Alde-High). Moreover, hypoxia-inducible factor proteins are up-regulated and VEGF, CXCR4, and GLUT-1 mRNAs are increased in Alde-Low EPCs under hypoxic conditions, while the response was not significant in Alde-High EPCs. In fact, the introduction of Alde-Low EPCs significantly reduced tissue damage in ischemia in a mouse flap model. Thus, the introduction of Alde-Low EPCs may be a potential strategy for inducing rapid neovascularization and subsequent regeneration of ischemic tissues.