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Biomedical subjects

J J Gagliardino

Publications and source records attributed to J J Gagliardino.

At least 19 recordsLinked to original sources

PROPAT: a study to improve the quality and reduce the cost of diabetes care.

OBJECTIVE: In PROPAT we implemented an integrated approach to diabetes care designed to improve the quality and reduce the cost of care. STUDY DESIGN AND METHODS: PROPAT was a case-control study matching patients by age and gender (diabetes:control ratio 1:2) within IOMA, a public employment-based health maintenance organization (HMO) of the Province of Buenos Aires, Argentina. Costs were evaluated using prevalence data from an HMO perspective. We currently report clinical and biochemical data and costs from the first 297 patients enrolled who completed 1 year in PROPAT, and compare them with those derived from control patients. RESULTS: All recommended practices recorded as care provided at baseline increased significantly 1 year after implementing PROPAT, with a parallel significant improvement in several clinical and biochemical parameters, and markedly lower total annual per capita costs. CONCLUSIONS: These results demonstrate that the implementation of a comprehensive diabetes care program can simultaneously improve quality while reducing costs.

Adult↗

Enhanced expression of hexokinase I in pancreatic islets induced by sucrose administration.

Administration of a sucrose-rich diet (SRD) to normal hamsters induces an insulin-resistant state and a significant increase of insulin secretion and beta-cell mass. Islets isolated from these animals had a marked increase in glucose metabolism and glucose-induced insulin secretion, at both low and high glucose concentrations. They also presented increased hexokinase (HK) activity, without measurable changes in glucokinase (GK) activity. In this study we measured HK and GK activity in homogenates of islets isolated from normal control and SRD-fed hamsters, as well as in their particulate and cytosolic fractions. We also measured transcription rate (mRNA by reverse transcriptase PCR) and expression levels (Western blotting) of both enzymes in these islets. We found an increase in HK activity and expression levels, without measurable changes in HK mRNA level in SRD-fed animals. Whereas a similar GK activity was measured in homogenates of islets isolated from both groups, such activity was significantly higher in the cytosolic fraction of SRD islets. On the other hand, GK transcription rate and expression level were similar in both experimental groups. Our results suggest that the increased beta-cell secretory response to low glucose can be partly ascribed to an increased activity of islet HK consecutive to an enhanced expression of the enzyme, while the enhanced response to high glucose could be due to changes in GK compartmentalization.

Animals↗

Hospitalization and re-hospitalization of people with and without diabetes in La Plata, Argentina: comparison of their clinical characteristics and costs.

OBJECTIVE: To examine the prevalence, characteristics, and costs of hospitalization and re-hospitalization of diabetic and non-diabetic patients in La Plata, Argentina, and to compare the data with those of developed countries. RESEARCH DESIGN AND METHODS: We studied all in-hospital registries of diabetic patients enrolled in a health maintenance organization of the Province of Buenos Aires (IOMA, November 1996). For each diabetic patient (127 persons), the characteristics of two other hospitalized non-diabetic patients matched by age and gender were simultaneously recorded. RESULTS: Of the 2200 recorded hospitalizations, 5.8% were for diabetic patients, accounting for 10.5% of the hospitalization cost. Cardiovascular diseases were the major cause of hospitalization in both groups. The per capita hospitalization cost of diabetic patients was significantly higher: 1628.5+/-1754.0 US dollars versus 833+/-842 US dollars; P=0.00002. Percent re-hospitalizations were five and a half times higher in diabetic patients (P=0.0001), and significantly associated with history of severe episodes of acute (odds ratio: 3.61; 95% CI: 1.11-11.70; P=0.03) and chronic (odds ratio: 4.26; 95% CI: 1.60-11.29; P=0.004) complications. CONCLUSIONS: The combination of higher and longer hospitalization rates and frequent re-hospitalizations resulted in increased costs for our diabetic population. Implementation of care programs based on education (for physicians and patients) could effectively decrease current and future costs of the disease.

Aged↗

Islet neogenesis: an apparent key component of long-term pancreas adaptation to increased insulin demand.

This study aimed to determine the relative importance of different functional and morphological pancreatic changes induced by the chronic administration of a sucrose-rich diet (SRD) to maintain normal glucose homeostasis. Male Wistar rats were fed either sucrose (SRD) or starch (CD) for 6 and 12 months. At both periods, serum glucose and triacylglycerol levels were significantly higher (P<0.05; paired and unpaired Student's t-test) in SRD rats. Serum insulin levels were significantly lower in SRD only at 12 months. At 6 months, the insulin secretion dose-response curve in SRD rats showed a shift to the left that was no longer observed at 12 months, when SRD islets decreased their response to 16 mM glucose. At 6 months, SRD rats showed a significant increase in beta-cell volume density (Vvi) and islet cell replication rate, together with a decrease in beta-cell apoptotic rate. Changes were not detected in the percentage of PDX-1- and islet neogenesis associated protein (INGAP)-positive cells. Conversely, at 12 months, there was a significant decrease in beta-cell Vvi and in the percentage of PDX-1-positive cells; the islet cell replication rate was not modified, and the number of apoptotic beta-cells increased significantly. No signs of increased neogenesis or INGAP-positive cells were recorded at any period in SRD rats. Our results show that SRD rats are unable to develop functional and morphological pancreatic reactive changes sufficient to maintain normal glucose and triacylglycerol levels for a long period. Such failure could be ascribed to their inability to increase the rate of neogenesis and of INGAP production.

Adaptation, Physiological↗

Expression of islet neogenesis-associated protein in islets of normal hamsters.

The aim of the present study was to test the possible presence and expression of islet neogenesis-associated protein (INGAP) in islet cells of normal adult hamsters. Pancreata from normal male Syrian hamsters were removed to perform the following studies. (i) Western blot analysis using the cytosolic fraction from homogenates of isolated islets, exocrine tIssue and whole pancreas, and rabbit INGAP-specific antibody. (ii) Immunohistochemical identification of INGAP-positive cells in fixed sections of intact pancreata, fresh and 72 h cultured islets (isolated by collagenase digestion), and smears of exocrine pancreatic cells, using the same INGAP-specific antibody and streptavidin-biotin complex. (iii) RT-PCR using total RNA extracted from isolated islets and from exocrine tIssue as template, and a specific pair of primers. (iv) Control of the sequence of the PCR products. INGAP protein was identified by Western blot in the cytosolic fraction of homogenates from fresh isolated islets, exocrine cells and whole fresh pancreas. INGAP-immunopositive cells were observed in duct, exocrine and islet cells in either fixed intact or digested pancreatic tIssue. INGAP mRNA was identified in samples of total RNA from fresh and cultured isolated islets and from exocrine cells. Our data demonstrate that INGAP is present and expressed in islets and in exocrine pancreatic cells of normal hamsters. The ubiquitous localization of INGAP suggests its possible role in the physiological process of islet growth and its protective effect upon streptozotocin-induced diabetes.

Animals↗

Pancreatic duodenal homeobox-1 and islet neogenesis-associated protein: a possible combined marker of activateable pancreatic cell precursors.

The aim of this work was to study the possible relationship between pancreatic duodenal homeobox-1 (Pdx-1) and islet neogenesis-associated protein (INGAP) during induced islet neogenesis. Pregnant hamsters were fed with (S) and without (C) sucrose, and glycemia, insulin secretion in vitro, and pancreas immunomorphometric parameters were measured in their 7-day-old offspring. S offspring had significantly lower glycemic levels than C animals. Insulin release in response to increasing glucose concentrations in the incubation medium (2-16 mM glucose) did not increase in pancreata from either C or S offspring. However, pancreata from S offspring released more insulin than those from C animals. In S offspring, beta-cell mass, beta-cell replication rate and islet neogenesis increased significantly, with a simultaneous decrease in beta-cell apoptotic rate. INGAP- and Pdx-1-positive cell mass also increased in the islets and among acinar and duct cells. We found two subpopulations of Pdx-1 cells: INGAP-positive and INGAP-negative. Pdx-1/INGAP-positive cells did not stain with insulin, glucagon, somatostatin, pancreatic polypeptide, or neurogenin 3 antibodies. The increment of Pdx-1/INGAP-positive cells represented the major contribution to the Pdx-1 cell mass increase. Such increments varied among pancreas subsectors: ductal>insular>extrainsular. Our results suggested that INGAP participates in the regulation of islet neogenesis, and Pdx-1/INGAP-positive cells represent a new stem cell subpopulation at an early stage of development, highly activateable in neogenesis.

Animals↗

Expression and cellular distribution pattern of plasma membrane calcium pump isoforms in rat pancreatic islets.

This work is aimed at identifying the presence and cellular distribution pattern of plasma membrane calcium pump (PMCA) isoforms in normal rat pancreatic islet. Microsomal fractions of isolated islets and exocrine tissue were analyzed to detect different PMCA isoforms. The cellular distribution pattern of these PMCAs in the islets was also studied in fixed pancreas sections incubated with antibodies against PMCAs and insulin. Antibody 5F10, which reacts with all PMCA variants, showed multiple bands in the blots in the 127-134 kDa region, indicating the presence of several isoforms. Microsomes also reacted positively with specific antibodies for individual PMCA isoforms, generating a band of the expected size. Antibody 5F10 immunocytochemically labeled the plasma cell membrane of both b- and non-b-cells, but predominantly the former. All islet cells were also labeled with antibodies against isoforms 1 and 4, while the antibody reacting with isoform 3 labeled exclusively b-cells. A few b- and non-b-cells were positively labeled with the antibody reacting with PMCA b variant. Negative results were obtained with the antibody against isoform 2. Further studies, together with previous reports on the modulatory effect of insulin secretagogues and blockers upon PMCA activity, may provide evidence of the importance of this particular PMCA expression for islet function under normal and pathological conditions.

Animals↗

Mechanisms involved in the beta-cell mass increase induced by chronic sucrose feeding to normal rats.

The aim of the present study was to clarify the mechanisms by which a sucrose-rich diet (SRD) produces an increase in the pancreatic beta-cell mass in the rat. Normal Wistar rats were fed for 30 weeks either an SRD (SRD rats; 63% wt/wt), or the same diet but with starch instead of sucrose in the same proportion (CD rats). We studied body weight, serum glucose and triacylglycerol levels, endocrine tissue and beta-cell mass, beta-cell replication rate (proliferating cell nuclear antigen; PCNA), islet neogenesis (cytokeratin immunostaining) and beta-cell apoptosis (propidium iodide). Body weight (g) recorded in the SRD rats was significantly (P<0.05) larger than that of the CD group (556.0+/-8.3 vs 470.0+/-13.1). Both serum glucose and triacylglycerol levels (mmol/l) were also significantly higher (P<0.05) in SRD than in CD rats (serum glucose, 8.11+/-0.14 vs 6.62+/-0.17; triacylglycerol, 1.57+/-0.18 vs 0.47+/-0.04). The number of pancreatic islets per unit area increased significantly (P<0.05) in SRD rats (3.29+/-0.1 vs 2.01+/-0.2). A significant increment (2.6 times) in the mass of endocrine tissue was detected in SRD animals, mainly due to an increase in the beta-cell mass (P=0.0025). The islet cell replication rate, measured as the percentage of PCNA-labelled beta cells increased 6.8 times in SRD rats (P<0.03). The number of apoptotic cells in the endocrine pancreas decreased significantly (three times) in the SRD animals (P=0.03). The cytokeratin-positive area did not show significant differences between CD and SRD rats. The increase of beta-cell mass induced by SRD was accomplished by an enhanced replication of beta cells together with a decrease in the rate of beta-cell apoptosis, without any evident participation of islet neogenesis. This pancreatic reaction was unable to maintain serum glucose levels of these rats at the level measured in CD animals.

Animals↗

Effect of an acute glucose overload on Islet cell morphology and secretory function in the toad.

The aim of this work was to study the effect of induced hyperglycemia on islet cell mass and insulin secretion in normal toads. Immunolabeled beta cell area, replication (bromodeoxyuridine) and apoptosis (propidium iodide) rate, islet neogenesis (cytokeratin), and insulin secretion in vitro were measured in adult male specimens of Bufo arenarum during and after interruption of the injection of either a 50% glucose solution (2 g/100 g) or its vehicle for 4 days. Glucose administration caused hyperglycemia (122.6 +/- 16.7 and 508.3 +/- 115.9 mg/dl vs 23.5 +/- 1.26 and 22.8 +/- 1.8 mg/dl, at days 3 and 5, respectively, P < 0.05) and a significant decrease in the number of islets/mm(2) (day 3: 9.7 +/- 0.9 vs 3.3 +/- 0.4, P < 0.05; day 5: 9.4 +/- 0.8 vs 7.4 +/- 0.6; day 9: 9.6 +/- 0.9 vs 6.2 +/- 0.4, P < 0.05) and in the percentage of immunolabeled beta cell area (day 3: 2.07 +/- 0.2 vs 0.5 +/- 0.1%, P < 0.05; day 5: 1.8 +/- 0.1 vs 0.6 +/- 0.1%; day 9: 1.7 +/- 0.1 vs 0.7 +/- 0.1%, P < 0.05). Glucose-injected animals had a simultaneous significantly higher percentage of BrdU-labeled beta cells (day 3: 0.46 +/- 0.02 vs 0.23 +/- 0.03%; day 5: 0.54 +/- 0.13 vs 0.22 +/- 0.02%; day 9: 0.61 +/- 0.0 vs 0.27 +/- 0.05%, P < 0.05) and cytokeratin-labeled endocrine cells (day 3: 0.21 +/- 0.06 vs 0.01 +/- 0.00%; day 5: 0.17 +/- 0.06 vs 0.01 +/- 0.01%; day 9: 1.25 +/- 0.2 vs 0.01 +/- 0.008%, P < 0.05) and a higher rate of apoptotic beta cells (day 3: 0.14 +/- 0.04 vs 0.05 +/- 0.02%; day 5: 0.4 +/- 0.06 vs 0.05 +/- 0.2, P < 0.05; day 9: 0.47 +/- 0.04 vs 0.06 +/- 0.03, P < 0.05). Comparable amounts of insulin were secreted in vitro by both groups in response to 2 mM glucose, whereas there was a significantly reduced response to 8 mM glucose in treated animals (day 3: 73 +/- 12 vs 165 +/- 20%; day 5: 74 +/- 11 vs 204 +/- 18%, P < 0.05). This decreased response to high glucose reverted to normal after removal of the glucose injection. These results show for the first time that short-term hyperglycemia triggers marked morphological and transient secretory changes in the toad pancreas similar in part to those elicited in the pancreas of several mammals. As with other results previously reported, these results support the usefulness of the toad as an alternative easily handled model to study the growth and secretory function of the endocrine pancreas.

Animals↗

[Evaluation of the quality of care for diabetic patients in Latin America].

OBJECTIVE: To make a preliminary diagnosis of the quality of care that individuals with diabetes mellitus (DM) received in participating centers of the QUALIDIAB network in Latin America and the Caribbean, and to assess the potential usefulness of this information as well as the importance of expanding the QUALIDIAB network. METHODS: A total of 13,513 patient records from the QUALIDIAB network were analyzed, from public and private health care entities and from the Social Security systems of Argentina, Brazil, Chile, Colombia, Paraguay, and Uruguay. The study utilized: 1) quality-of-care indicators based on international reference values, 2) patient information on clinical, biochemical, and therapeutic parameters and on the rate of use of diagnostic and therapeutic materials, 3) a computer database program, and 4) a software program for statistical analysis. RESULTS: Among the patients studied, about half of them had suffered from diabetes for 5 years or less; this was true both for persons with type 1 diabetes (DM1) and for those with type 2 diabetes (DM2). Of the persons with DM1, 24% of them had a blood glucose level of < 4.4 mmol/L; this was true for 15% of those with DM2. The proportion of persons with a blood glucose level of > 7.7 mmol/L was 41% among those with DM1 and 57% among those with DM2. The frequencies of association between DM2 and other cardiovascular risk factors were: overweight/obesity, 59%; hypertension, 60%; total cholesterol > 5.5 mmol/L, 53%; high-density lipoprotein cholesterol < 1 mmol/L, 32%; triglycerides > 1.7 mmol/L, 45%; and smoking, 13%. Of the people with DM1, 20% of them had a body mass index < 19 kg/m2, probably reflecting deficient metabolic control and inadequate insulin intake. The systematic checking of metabolic control, other cardiovascular risk factors, and chronic DM complications was inadequate in from 3% to 75% of the cases, depending on the specific aspect considered. According to various patient-therapy-education indicators, only some one-quarter to one-half of the studied patients could play an active, effective role in DM control and treatment. Of the persons with DM1, 50% of them were treated with a mixed dose of insulin (NPH + regular insulin), administered in two daily injections in 43% of the cases. Among the patients, 5% of them received one daily insulin injection, and 9% of them received three daily insulin injections. Of the people with DM2, 13% of them treated it only with diet and 14% just with insulin. Among the patients receiving drug treatment, the oral hypoglycemics most used in monotherapy were sulfonylureas (33%), biguanides (9%), and a combination of these two (14%). Fewer than half of the people with diabetes received drug therapy for the associated cardiovascular risk factors. The frequency of patients' macroangiopathic and microangiopathic complications increased with the duration of their disease. Comparing patients who had had diabetes for 5 years or less with those who had had the illness for more than 20 years, the frequency of renal insufficiency and of amputations was around 7 times as great in the latter group; for peripheral neuropathy, it was 2 times as great, and for stroke 1.6 times as great. CONCLUSIONS: These results show the need to improve the quality of care for diabetic patients in Latin America and the Caribbean, and that QUALIDIAB could help do this. Expanding the QUALIDIAB network will help to more accurately diagnose the quality of that care in the Americas, and it will facilitate interventions aimed at optimizing the care. This, in turn, will improve the quality of life of persons who suffer from diabetes as well as diminish the socioeconomic costs of the disease.

Adolescent↗

Changes induced by sucrose administration on glucose metabolism in pancreatic islets in normal hamsters.

We correlated the changes in glucose-induced insulin secretion with those observed in glucose metabolism and hexokinase/glucokinase activity in islets from normal sucrose-fed hamsters. Blood glucose and insulin levels were measured in normal male hamsters fed with (S5) or without (C5) 10% sucrose in the drinking water for 5 weeks. Isolated islets (collagenase digestion) from both groups of animals were used to study insulin secretion, (14)CO(2) and (3)H(2)O production from D-[U-(14)C]-glucose and D-[5-(3)H]-glucose respectively, with 3.3 or 16.7 mM glucose in the medium, and hexokinase/glucokinase activity (fluorometric assay) in islet homogenates. Whereas S5 and C5 animals had comparable normal blood glucose levels, S5 showed higher insulin levels than C5 hamsters (2.3+/-0.1 vs 0.6+/-0.03 ng/ml, P<0.001). Islets from S5 hamsters released significantly more insulin than C5 islets in the presence of low and high glucose (3.3 mM glucose: 0.77+/-0.04 vs 0.20+/-0.06 pg/ng DNA/min, P<0.001; 16.7 mM glucose: 2.77+/-0.12 vs 0.85+/-0.06 pg/ng DNA/min, P<0.001) and produced significantly higher amounts of (14)CO(2) and (3)H(2)O at both glucose concentrations ((14)CO(2): 3.3 mM glucose: 0.27+/-0.01 vs 0.18+/-0.01, P<0.001; 16.7 mM glucose: 1.44+/-0.15 vs 0.96+/-0.08, P<0.02; (3)H(2)O: 3.3 mM glucose: 0.31+/-0.02 vs 0.15+/-0.01, P<0.001; 16.7 mM glucose: 1.46+/-0.20 vs 0.76+/-0.05 pmol glucose/ng DNA/min, P<0.005). The hexokinase K(m) and V(max) values from S5 animals were significantly higher than those from C5 ones (K(m): 100.14+/-7.01 vs 59.90+/- 3.95 microM, P<0.001; V(max): 0.010+/-0.0005 vs 0.008+/- 0.0006 pmol glucose/ng DNA/min, P<0.02). Conversely, the glucokinase K(m) value from S5 animals was significantly lower than in C5 animals (K(m): 15.31+/-2.64 vs 35.01+/-1.65 mM, P<0.001), whereas V(max) figures were within a comparable range in both groups (V(max): 0.048+/-0.009 vs 0.094+/-0.035 pmol glucose/ng DNA/min, not significant). The glucose phosphorylation ratio measured at 1 and 100 mM (hexokinase/glucokinase ratio) was significantly higher in S5 (0.26+/-0.02) than in C5 animals (0.11+/-0.01, P<0.005), and it was attributable to an increase in the hexokinase activity in S5 animals. In conclusion, sucrose administration increased the hexokinase/glucokinase activity ratio in the islets, which would condition the increase in glucose metabolism by beta-cells, and in beta-cell sensitivity and responsiveness to glucose. These results support the concept that increased hexokinase rather than glucokinase activity causes the beta-cell hypersensitivity to glucose, hexokinase being metabolically more active than glucokinase to up-regulate beta-cell function.

Animals↗

A model educational program for people with type 2 diabetes: a cooperative Latin American implementation study (PEDNID-LA).

OBJECTIVE: To implement an educational program in 10 Latin American countries and to evaluate its effect on the clinical, biochemical, and therapeutic aspects as well as the economic cost of diabetes. RESEARCH DESIGN AND METHODS: Educators from each participating country were previously trained to implement the educational model. The patient population included 446 individuals with type 2 diabetes; all patients were <65 years of age, did not require insulin for metabolic control, did not have severe complications of diabetes or life-limiting illnesses, and had not previously participated in diabetes education courses. Clinical and therapeutic data and the cost of their pharmacological treatment were collected 6 months before participation in the educational program (-6 months), on entry into the program (time 0), and at 4, 8, and 12 months after initiation of the program. RESULTS: All parameters measured had improved significantly (P < 0.001) by 1 year: fasting blood glucose (mean +/- SD) 10.6 +/- 3.5 vs. 8.7 +/- 3.0 mmol/l; HbA(1c) 9.0 +/- 2.0 vs. 7.8 +/- 1.6%; body weight 84.6 +/- 14.7 vs. 81.2 +/- 15.2 kg; systolic blood pressure 149.6 +/- 33.6 vs. 142.9 +/- 18.8 mmHg; total cholesterol 6.1 +/- 1.1 vs. 5.4 +/- 1.0 mmol/l; and triglycerides 2.7 +/- 1.8 vs. 2.1 +/- 1.2 mmol/l. At 12 months, the decrease in pharmacotherapy required for control of diabetes, hypertension, and hyperlipidemia represented a 62% decrease in the annual cost of treatment ($107,939.99 vs. $41,106.30 [U.S.]). After deducting the additional cost of glucosuria monitoring ($30,604), there was still a 34% annual savings. CONCLUSIONS: The beneficial results of this educational model, implemented in 10 Latin American countries, reinforce the value of patient education as an essential part of diabetes care. They also suggest that an educational approach promoting healthy lifestyle habits and patient empowerment is an effective strategy with the potential to decrease the development of complications related to diabetes as well as the socioeconomic costs of the disease.

Adult↗

[Gestational diabetes. Determination of relative importance of risk factors].

The aim of this study was to determine the relative importance of gestational diabetes (GD) risk factors to identify populations at risk. A total of 400 pregnant patients were studied, 200 with confirmed GD diagnosis and 200 controls with risk factors. They regularly attended health-care units belonging to the Ministry of Health of the Province of Buenos Aires, in the context of the Program for the Prevention, Care and Treatment of People with Diabetes of the Province of Buenos Aires (PRODIABA). The following risk factors were evaluated: GD in previous pregnancies, history of diabetes in first degree relatives, age > or = 30 years, BMI > 26, history of fetal macrosomy, perinatal mortality and hypertension during pregnancy. Data analysis was performed with the Program of Statistics in Public Health Epilnfo 6. The association between GD development as a dependent variable and the presence of different risk factors (independent variables) was analyzed with a multiple logistic regression model, determining the logistic probability to develop GD. Results showed that the incidence of risk factors to develop GD is not the same; therefore, they do not have the same predictive value. Overweight or obesity played a key central role, not only for its frequency, but also for its contribution to GD development. Our findings reinforce the importance of multi causal studies as the basis to design and implement prevention strategies for diabetes.

Adult↗

Possible relationship between the B-cell threshold for glucose-induced insulin secretion and blood glucose concentrations in the normal toad.

The aim of this work was to gain information on the possible relationship between basal glycemia in the toad and the B-cell threshold for glucose-induced insulin release. Hence, pieces of pancreas from Bufo arenarum were incubated with 2 to 20 mM glucose or preincubated with 2 mM glucose plus the hexokinase and glucokinase inhibitors (50 mM of 2-deoxyglucose and mannoheptulose, respectively) followed by an incubation with different glucose concentrations. The maximal rate of insulin release occurred at 8 mM glucose, while 50% of the release (K(s50)) was observed at 7 mM glucose. Regardless of the glucose concentration employed, pancreas pieces preincubated with 2-deoxyglucose released less insulin than the corresponding controls. On the other hand, mannoheptulose significantly inhibited the release of insulin at high glucose concentrations, having no effect at low glucose concentrations. The blocking effect of these two inhibitors is the first indirect evidence of the existence of the hexokinase/glucokinase enzymic system in the toad pancreas. Since the activity ratio of this system determines the glucose sensitivity of the insulin secretory mechanism, it is concluded that the possible existence of a higher ratio of these enzymes in toad B cells could explain the particular characteristics of glucose sensitivity in this animal, which in turn may explain its low blood glucose concentration.

Animals↗

A useful model to study the effect of high sugar concentrations upon growth and enzymic activities of toad embryos and larvae.

The aim of this study was to develop an oviparous model suitable for studying the differential effects and mechanisms by which a high concentration of extracellular glucose and other sugars produce diabetes complications, particularly body growth retardation during development. Hence, we studied the experimental conditions necessary to obtain measurable effects of high sugar concentrations (5-mM glucose, mannitol, fructose and galactose) upon body growth and development of Bufo arenarum embryos and larvae, and upon the activity of aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), and alkaline phosphatase (APP). Unfed animals kept in glucose showed lower body weight than controls at all stages, a condition only observed at stage 26 for animals kept in galactose and fructose. All animals reached the same stage of development regardless of the solution in which they were kept. Glucose and fructose significantly decreased the activity of all enzymes tested, while galactose only affected GGT activity. The model provides the first experimental evidence for the deleterious effect exerted in vivo by different sugars upon developing embryos and larvaes of Bufo arenarum. The results prove that this model might help to elucidate the effects and the pathogenic mechanisms of hyperglycemia upon growth and development of embryos exposed to environments with high sugar concentrations. It might also become a useful tool for testing the effectiveness of drugs designed to prevent the deleterious effect of such exposure.

Alkaline Phosphatase↗

Possible relationship between changes in islet neogenesis and islet neogenesis-associated protein-positive cell mass induced by sucrose administration to normal hamsters.

The possible relationship between changes in islet cell mass and in islet neogenesis-associated protein (INGAP)-cell mass induced by sucrose administration to normal hamsters was investigated. Normal hamsters were given sucrose (10% in drinking water) for 5 (S8) or 21 (S24) weeks and compared with control (C) fed hamsters. Serum glucose and insulin levels were measured and quantitative immunocytochemistry of the endocrine pancreas was performed. Serum glucose levels were comparable among the groups, while insulin levels were higher in S hamsters. There was a significant increase in beta-cell mass (P<0.02) and in beta-cell 5-bromo-2'-deoxyuridine index (P<0.01), and a significant decrease in islet volume (P<0.01) only in S8 vs C8 hamsters. Cytokeratin (CK)-labelled cells were detected only in S8 hamsters. INGAP-positive cell mass was significantly larger only in S8 vs C8 hamsters. Endocrine INGAP-positive cells were located at the islet periphery ( approximately 96%), spread within the exocrine pancreas ( approximately 3%), and in ductal cells (<1%) in all groups. INGAP positivity and glucagon co-localization varied according to topographic location and type of treatment. In C8 hamsters, 49.1+/-6. 9% cells were INGAP- and glucagon-positive in the islets, while this percentage decreased by almost half in endocrine extra-insular and ductal cells. In S8 animals, co-expression increased in endocrine extra-insular cells to 36.3+/-9.5%, with similar figures in the islets, decreasing to 19.7+/-6.9% in ductal cells. INGAP-positive cells located at the islet periphery also co-expressed CK. In conclusion, a significant increase of INGAP-positive cell mass was only observed at 8 weeks when neogenesis was present, suggesting that this peptide might participate in the control of islet neogenesis. Thus, INGAP could be a potentially useful tool to treat conditions in which there is a decrease in beta-cell mass.

Animals↗

Quantitative ultrastructural changes induced by sucrose administration in the pancreatic B cells of normal hamsters.

We have previously reported that young male Syrian hamsters receiving a sucrose-rich diet presented increased B-cell replication rate and size. The aim of the present study was to analyze, under the same experimental conditions, the ultrastructural changes in B cells. For this purpose, young male Syrian hamsters were fed with a commercial diet and 10% sucrose in their drinking water (S group) while the control group (C) received the same diet and tap water, for 5 weeks. Samples of the pancreas removed after that period were processed for the immunohistochemical identification of B cells as well as for measuring several ultrastructural parameters. S hamsters showed higher serum insulin levels, while similar serum glucose values were obtained in animals from both groups. The B cells from S group exhibited lesser number of dense secretory granules at expenses of an increase of the pale ones, increased number of both exocytosis profiles and fusion-granule images, as well as enlargement of the intercellular space and mitochondrial area. Marked expansions of this space, limited by junctional complexes, were observed between adjacent B cells. These results would indicate that sucrose administration to normal hamsters not only increases the pancreatic B-cell mass but also induces measurable subcellular changes in the individual B-cell characteristic of an enhanced secretory activity. The present model would represent a useful tool for testing strategies in preventing the damage or promoting the recovery of the pancreatic B cells.

Animals↗