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E Montanya

Publications and source records attributed to E Montanya.

14 recordsLinked to original sources
PubMed2001

Increased islet DNA synthesis and glucose-derived lipid and amino acid production in association with beta-cell hyperproliferation in normoglycaemic 60 % pancreatectomy rats.

AIMS/HYPOTHESIS: Glycaemia does not change following a 60 % pancreatectomy in rats because of enhanced beta-cell function and proliferation (so-called beta-cell adaptation). We previously studied these rats 4 weeks after surgery and showed hypersensitization of glucose-induced insulin secretion because of increased glucokinase activity. In this study of 60 % pancreatectomy rats 5 days after surgery, when beta-cell proliferation increased threefold, we investigated whether increases in glucose metabolism enhance the production of glucose-derived lipid, amino acids and DNA. METHODS: Isolated islets from 60 % pancreatectomy and sham-operated control rats 5 days or 4 weeks after surgery were studied. RESULTS: Five days after 60 % pancreatectomy surgery, islet glucose phosphorylation increased threefold, but overall glucose usage increased only twofold. The glucose-6-phosphate (G6P) concentration thus doubled, resulting in a sixfold increase in G6P metabolism through the pentose phosphate shunt (PPS). The pentose phosphate shunt generates ribose-5-phosphate for nucleotide synthesis, and DNA synthesis doubled in the partial pancreatectomy islets. In contrast, partial pancreatectomy rats 4 weeks after surgery had a smaller increase in glucokinase activity and their islet glucose-6-phosphate concentration and pentose phosphate shunt activity were equal to that of the control rats. DNA synthesis and beta-cell proliferation, based on BrdU incorporation were close to normal. Another consequence of the heightened glucose metabolism in the 5-day partial pancreatectomy islets was twofold increase in production of glucose-derived lipid and the amino acids, alanine and glutamate. CONCLUSIONS/INTERPRETATION: The enhanced glucokinase activity in 60 % pancreatectomy rats supports the compensatory beta-cell hyperproliferation by increasing production of glucose-derived DNA, lipids and amino acids.

Alanine↗
PubMed2001

Stem cells and diabetes.

Diabetes mellitus is a metabolic disorder affecting 2-5% of the population. Transplantation of isolated islets of Langerhans from donor pancreata could be a cure for diabetes; however, such an approach is limited by the scarcity of the transplantation material and the long-term side effects of immunosuppressive therapy. These problems may be overcome by using a renewable source of cells, such as islet cells derived from stem cells. Stem cells are defined as clonogenic cells capable of both self-renewal and multilineage differentiation. This mean that these cells can be expanded in vivo or in vitro and differentiated to produce the desired cell type. There exist several sources of stem cells that have been demonstrated to give rise to pluripotent cell lines: 1) embryonic stem cells; 2) embryonic germ cells; 3) embryonic carcinoma cells; and 4) adult stem cells. By using in vitro differentiation and selection protocols, embryonic stem cells can be guided into specific cell lineages and selected by applying genetic selection when a marker gene is expressed. Recently, differentiation and cell selection protocols have been used to generate embryonic stem cell-derived insulin-secreting cells that normalise blood glucose when transplanted into diabetic animals. Some recent reports suggest that functional plasticity of adult stem cells may be greater than expected. The use of adult stem cells will circumvent the ethical dilemma surrounding embryonic stem cells and will allow autotransplantation. These investigations have increased the expectations that cell therapy could be one of the solutions to diabetes.

Cell Differentiation↗
PubMed2000

Engineering pancreatic islets.

Pancreatic islets are neuroendocrine organs that control blood glucose homeostasis. The precise interplay of a heterogeneous group of cell populations (beta, alpha, delta and PP cells) results in the fine-tuned release of counterbalanced hormones (insulin, glucagon, somatostatin and pancreatic polypeptide respectively). Under the premises of detailed knowledge of the physiological basis underlying this behaviour, two lines of investigation might be inferred: generating computational and operational models to explain and predict this behaviour and engineering islet cells to reconstruct pancreatic endocrine function. Whilst the former is being fuelled by new computational strategies, giving biophysicists the possibility of modelling a system in which new "emergent" properties appear, the latter is benefiting from the useful tools and strategic knowledge achieved by molecular, cell and developmental biologists. This includes using tumour cell lines, engineering islet cell precursors, knowledge of the mechanisms of differentiation, regeneration and growth and, finally, therapeutic cloning of human tissues. Gaining deep physiological understanding of the basis governing these processes is instrumental for engineering new pancreatic islets.

Animals↗
PubMed2000

Linear correlation between beta-cell mass and body weight throughout the lifespan in Lewis rats: role of beta-cell hyperplasia and hypertrophy.

We determined the beta-cell replicative rate, beta-cell apoptosis, cross-sectional beta-cell area, and pancreatic beta-cell mass throughout the entire postweaning lifespan (months 1, 3, 7, 10, 15, and 20) of Lewis rats. Beta-cell replication was progressively reduced in the initial months of life but remained stable after month 7 (month 1, 0.99 +/- 0.10%; month 3, 0.24 +/- 0.04%; month 7, 0.12 +/- 0.02%; month 10, 0.14 +/- 0.02%; month 15, 0.10 +/- 0.03%; month 20, 0.13 +/- 0.03%; analysis of variance [ANOVA], P < 0.001). Beta-cell apoptosis was low and did not change significantly from month 1 to 20 of life. Cross-sectional area of individual beta-cells increased progressively in the initial months, remained stable from month 7 to 15, and increased again on month 20. The estimated number of beta-cells per pancreas, calculated as the ratio of total beta-cell mass to individual beta-cell mass, tripled from month 1 to 7 but did not change significantly thereafter. Beta-cell mass increased approximately 8 times from month 1 to 20 (month 1, 2.04 +/- 0.28 mg; month 20, 15.5 +/- 2.32 mg; ANOVA, P < 0.001) and showed a strong and significant linear correlation with body weight (r = 0.98, P < 0.001). In summary, we have shown that beta-cell replication was maintained throughout the lifespan in normal rats, clearly establishing that the beta-cell birth rate does not fall to 0, even in very old rats. Beta-cell mass increased throughout the lifespan, closely matching the increment in total body weight at any time point. This increment was selective for beta-cells, since the growth of the endocrine non-beta-cell mass was limited to the initial months of life. Both beta-cell hypertrophy and hyperplasia contributed to increased beta-cell mass in young animals, but only beta-cell hypertrophy was responsible for the increased beta-cell mass found in old animals. This study provides a global perspective for understanding the dynamics of beta-cell mass in young, adult, and aged animals.

Aging↗
PubMed1999

Mechanisms of glucose hypersensitivity in beta-cells from normoglycemic, partially pancreatectomized mice.

Increased beta-cell sensitivity to glucose precedes the loss of glucose-induced insulin secretion in diabetic animals. Changes at the level of beta-cell glucose sensor have been described in these situations, but it is not clear whether they fully account for the increased insulin secretion. Using a euglycemic-normolipidemic 60% pancreatectomized (60%-Px) mouse model, we have studied the ionic mechanisms responsible for increased beta-cell glucose sensitivity. Two weeks after Px (Px14 group), Px mice maintained normoglycemia with a reduced beta-cell mass (0.88 +/- 0.18 mg) compared with control mice (1.41 +/- 0.21 mg). At this stage, the dose-response curve for glucose-induced insulin release showed a significant displacement to the left (P < 0.001). Islets from the Px14 group showed oscillatory electrical activity and cytosolic Ca2+ ([Ca2+]i) oscillations in response to glucose concentrations of 5.6 mmol/l compared with islets from the control group at 11.1 mmol/l. All the above changes were fully reversible both in vitro (after 48-h culture of islets from the Px14 group) and in vivo (after regeneration of beta-cell mass in islets studied 60 days after Px). No significant differences in the input resistance and ATP inhibition of ATP-sensitive K+ (K(ATP)) channels were found between beta-cells from the Px14 and control groups. The dose-response curve for glucose-induced MTT (C,N-diphenyl-N''-4,5-dimethyl thiazol 2 yl tetrazolium bromide) reduction showed a significant displacement to the left in islets from the Px14 group (P < 0.001). These results indicate that increased glucose sensitivity in terms of insulin secretion and Ca2+ signaling was not due to intrinsic modifications of K(ATP) channel properties, and suggest that the changes are most likely to be found in the glucose metabolism.

Adenosine Triphosphate↗
PubMed1998

[Prevalence of nephropathy in type I diabetes].

BACKGROUND: Diabetic nephropathy is a serious complication of diabetes, of which there are few epidemiological data in Spain. The aim of this study is to determine diabetic nephropathy prevalence in a group of patients with type I diabetes mellitus, representative of the population of Barcelona, Spain, evaluating several risk factors related with its development. PATIENTS AND METHODS: 639 patients (296 males and 343 women), from 6 hospitals, selected according with the diabetes duration (194 between 5 and 9 years [group I], 227 between 10 and 19 years [group II] and 218 with 20 years or more [group III]) were studied. In all patients urinary albumin excretion and plasma levels of creatinine, HbA1c, cholesterol and triglycerides were determined. The presence of retinopathy, neuropathy, vasculopathy and tobacco consumption were also evaluated. RESULTS: The prevalence of diabetic nephropathy increased with longer diabetes duration (8.1% [CI: 4.3-11.9] in group I, 24.7% [CI: 19.1-30.3] in group II and 44.7% [CI: 38.1-51.3] in group III), as well as that of hypertension, diabetes complications, cholesterol and triglycerides plasma levels. Related to people with normal renal function, after logistic regression, microalbuminuria was associated with hypertension and longer diabetes duration. Clinical nephropathy (macroalbuminuria + renal failure) to hypertension, longer duration, hypertriglyceridemia, male sex and tobacco consumption. CONCLUSIONS: The prevalence of diabetic nephropathy in Barcelona area is high and similar to that observed in other european regions. Its existence is associated with other diabetic complications. In addition to the classic risk factors, tobacco consumption must also be considered as a factor for diabetic nephropathy.

Adult↗
PubMed1998

Normoglycemia restores beta-cell replicative response to glucose in transplanted islets exposed to chronic hyperglycemia.

We studied the effects of chronic hyperglycemia on beta-cell replication and mass in transplanted (Tx) islets. Five groups of streptozocin-induced diabetic C57Bl/6 mice were transplanted with 100 (Tx-100) syngeneic islets, an insufficient beta-cell mass to restore normoglycemia. Groups 1 and 2 remained hyperglycemic throughout the study; after 30 days of hyperglycemia, a second transplantation of 250 islets (Tx-250) restored normoglycemia in groups 3, 4, and 5. Tx-250 was harvested on day 60 in all three groups, and transient mild hyperglycemia developed (10-12 days); thereafter, Tx-100 maintained blood glucose values in the normal range. Tx-100 was harvested 14 (group 1), 60 (groups 2 and 3), 74 (group 4), and 90 (group 5) days after transplantation. Hyperglycemia increased beta-cell replication after 14 days (group 1: 1.26 +/- 0.18%, P < 0.05) but not after 60 days (group 2: 0.59 +/- 0.13%) compared with islets exposed to normoglycemia (group 3: 0.51 +/- 0.07%) (analysis of variance [ANOVA], P < 0.0002). beta-cell replication in group 4 increased after Tx-250 harvesting (0.94 +/- 0.16%, P < 0.05). The initially Tx beta-cell mass (0.21 +/- 0.014 mg) was progressively reduced in hyperglycemic groups (group 1: 0.13 +/- 0.020 mg; group 2: 0.048 +/- 0.012 mg; P < 0.05) (ANOVA, P = 0.0001). Restoration of normoglycemia after Tx-250 did not modify beta-cell mass in Tx-100 grafts (group 3: 0.076 +/- 0.008 mg). However, after Tx-250 harvesting, beta-cell mass increased progressively (group 4: 0.11 +/- 0.018 mg; group 5: 0.14 +/- 0.026 mg, P < 0.05), although it was still reduced compared with the initially Tx beta-cell mass (P < 0.05). In summary, Tx islets exposed to severe chronic hyperglycemia showed a limited beta-cell replication and a progressive reduction in beta-cell mass. With normoglycemia, the Tx beta-cells recovered the replicative response to glucose and partially restored the initially Tx beta-cell mass, indicating that normoglycemia, even after long-term hyperglycemia, has a beneficial effect in islet transplantation.

Animals↗
PubMed1997

[The influence of clinical presentation and metabolic control of insulin dependent diabetes in the evolution of residual insulin secretion. A prospective study at five years].

BACKGROUND: To study the influence of clinical, metabolic and immunological parameters during the first years of the evolution of insulin-dependent diabetes mellitus (IDDM) on the long-term residual insulin secretion (IS). PATIENTS AND METHODS: 186 IDDM subjects diagnosed from 1986 to 1993 were included; 135 subjects have completed a two year follow-up, and 57 have completed a five year follow-up. The influence of individual characteristics at diagnosis (age, sex, clinical presentation, islet-cell antibodies) and during the first two years of follow-up (IS, metabolic control) on IS at five years was evaluated by multiple linear regression. Differences between groups were evaluated by non-parametric tests. RESULTS: 18 patients had a significant insulin secretion at five years (post-glucagon C-peptide > or = 0.15 nmol/l). They showed minor significant differences in sex (77.7 vs 48.7% of males, p = 0.03), duration of symptoms (12.9 vs 7.2 weeks, p = 0.01), ketoacidosis at diagnosis (23.3 vs 46.1%, p = 0.07) and ICA positivity at diagnosis (41.1 vs 69.4%, p = 0.05). They also had a better metabolic control (8.8 vs 10.8% of HbA1, p < 0.001) with lss insulin (0.48 vs 0.71 Ul/kg, p < 0.001) during the first two years of evolution. Initial IS was similar, but differences became significant at 6 months. In the multivariate analysis, only metabolic control during the second year of evolution (p = 0.008), ketoacidosis at diagnosis (p = 0.026) and sex (p = 0.026) had an independent influence on IS at five years. A more intensified therapeutic approach introduced in 1990 induced a better metabolic control and higher IS during the first years of follow-up. CONCLUSION: The absence of ketoacidosis at diagnosis and a good metabolic control during the first two years can have a positive influence in the long-term preservation of IS in IDDM patients.

Adult↗
PubMed1997

Improved outcome of islet transplantation in insulin-treated diabetic mice: effects on beta-cell mass and function.

Insulin treatment may improve the outcome of islet transplantation. To determine the effects of insulin treatment on transplanted islets, 4 groups of streptozotocin-diabetic C57BL/6 mice were transplanted with 100 islets, an insufficient beta-cell mass to restore normoglycaemia. Groups 1 (n = 12) and 2 (n = 12), were kept normoglycaemic with insulin treatment from day 10 before transplantation to day 14 after transplantation; groups 3 (n = 12) and 4 (n = 18), were not treated with insulin. Grafts were harvested 14 (groups 1 and 3) or 60 (groups 2 and 4) days after transplantation and beta-cell mass and replication were measured. When insulin was discontinued all mice maintained normoglycaemia; in contrast, non-insulin-treated groups remained hyperglycaemic throughout the study. Fourteen days after transplantation the beta-cell mass was reduced both in group 1 (0.09 +/- 0.01 mg) and group 3 (0.14 +/- 0.02 mg) compared to the initially transplanted mass (0.22 +/- 0.02 mg, p < 0.01); beta-cell replication and area did not change in group 1, but were increased in group 3. Insulin content, expressed as a function of beta-cell mass, was maintained in group 1 grafts (12.5 +/- 2.0 micrograms/mg), but was severely reduced in group 3 (1.0 +/- 0.2 micrograms/mg) compared to non-transplanted islets (20.4 +/- 3.3 micrograms/mg). In group 2, beta-cell mass increased when insulin was discontinued; 60 days after transplantation beta-cell mass was similar to the initially transplanted mass (0.23 +/- 0.04 mg), glucose levels after an intraperitoneal glucose challenge were normal, and insulin content was preserved (19.6 +/- 2.7 micrograms/mg). In contrast, beta-cell mass was progressively reduced in group 4 (0.08 +/- 0.02 mg, p < 0.001). In summary, insulin treatment reduced the beta-cell mass needed to achieve normoglycaemia in islet transplantation. Islets transplanted to insulin-treated mice showed better beta-cell function, preserved insulin content, and were able to increase their beta-cell mass to meet an increased functional demand.

Animals↗
PubMed1997

Improved metabolic control preserved beta-cell function two years after diagnosis of insulin-dependent diabetes mellitus.

To determine whether improved metabolic control during the first two years of insulin-dependent diabetes (IDDM) modified beta cell function, we studied 108 subjects with recent-onset IDDM diagnosed between March 1986 and April 1992 and followed up prospectively for 2 years. Two insulin regimens were used: 1) conventional insulin treatment (CIT) (1986-90, n = 67) involving a mixture of regular and intermediate insulin before breakfast and dinner; and 2) intensive insulin treatment (IIT) (1990-92, n = 41) providing regular insulin before breakfast and lunch, and a mixture of regular and long-acting insulin before dinner. Glucagon-stimulated C-peptide was determined at diagnosis and at 3, 6, 12 and 24 months. Both groups had similar clinical, metabolic and immunological characteristics at diagnosis. The IIT group had better metabolic control at any given time-point after diagnosis (mean HbA1 during follow-up in CIT: 9.86 +/- 0.28%; IIT: 8.18 +/- 0.04%; p < 0.001) (normal < 9.0%). C-peptide was increased in the IIT group 3 and 6 months after diagnosis (month 0: 0.36 +/- 0.05 nmol/l; month 6: 0.55 +/- 0.06 nmol/l; p < 0.006), but not in the CIT group (month 0: 0.39 +/- 0.04 nmol/l; month 6: 0.45 +/- 0.04 nmol/l; p = NS). Two years after diagnosis, the IIT group maintained initial C-peptide secretion (2 years: 0.37 +/- 0.04 nmol/l) whereas C-peptide was reduced in the CIT group (2 years: 0.23 +/- 0.06 nmol/l) compared to the initial value (p < 0.001) or to that of the IIT group (p = 0.017). Thus, sustained improvement in metabolic control with IIT resulted in better beta-cell function during the first two years after IDDM diagnosis.

Adult↗
PubMed1997

[Assessment of prognosis factors in the cure of Cushing's disease surgically treated via a +septotransphenoidal approach].

INTRODUCTION: In Cushing's disease (CD) pituitary surgery or radiotherapy has been proposed by some authors, when plasmatic cortisol after surgery is not clearly low. AIM: To assess if the different prognostic factors, specially plasmatic cortisol seven days after surgery and/or hypocortisolism phase are predictive of the CD outcome. METHODS: From 1988, 11 women with CD underwent 13 transsphenoidal microsurgery, because two patients relapsed. The mean age of patients was 27 years (11-52). Plasmatic cortisol was measured seven days after pituitary surgery, and since 45 days, every three-six months, basal plasmatic cortisol and after ACTH and urinary free cortisol were determined. RESULTS: Follow-up evaluations ranged from 18-84 months (median, 38 months). After pituitary surgery in 13 cases the cumulative remission was 100%, two cases relapsed. In 10 cases plasmatic cortisol seven days after surgery was less than 137 nmol/l and in three cases higher than 137 nmol/l. Three cases did not presented hypocortisolism phase. The two patients who relapsed, one was after eight months of pituitary surgery an previously showed low plasmatic cortisol and the other relapse 25 months after pituitary surgery without low cortisol plasmatic levels. CONCLUSION: Remission in CD can happen either low or normal plasmatic cortisol levels seven days posttreatment or without hypocortisolism phase. Ours findings ascribe new importance to the different presentations after treatment of CD, and patients with these findings are not a risk for relapse and pituitary surgery or irradiation would not be early indicated.

Adolescent↗
PubMedDate not supplied

Optimal insulin treatment in syngeneic islet transplantation.

Insulin-induced normoglycemia has shown to have a beneficial effect on the outcome of pancreatic islets transplanted to diabetic recipients. The aim of the study was to identify the insulin treatment that can maximize its beneficial effect on islet transplants. Six groups of streptozotocin diabetic C57Bl/6 mice were transplanted (Tx) with 100 syngeneic islets, an insufficient beta cell mass to restore normoglycemia, and were treated with insulin as follows: group 1 (n = 9): from day 10 before Tx to day 14 after Tx; group 2 (n = 11): from day 6 before Tx to Tx day; group 3 (n = 11): from Tx day to day 6 after Tx; group 4 (n = 7): from Tx day to day 14 after Tx; group 5 (n = 8): from day 10 to day 24 after Tx; group 6 (n = 18): Tx mice were not treated with insulin. Sixty days after Tx, normoglycemia was achieved in 100% of mice in groups 1, 4, and 5, in 73% of mice in group 2, and in only 45% and 33% of mice in groups 3 and 6, respectively (p < 0.01). Intraperitoneal glucose tolerance, determined only in normoglycemic mice, was similar in groups 1, 2, 4, and normal controls. In contrast, normoglycemic mice from groups 3, 5, and 6, exposed to more severe and prolonged hyperglycemia after Tx, showed higher glucose values after glucose injection, suggesting that hyperglycemia had a long-lasting deleterious effect on transplanted beta cell function. The initially transplanted beta cell mass was maintained in the grafts of normoglycemic mice, but was severely reduced in hyperglycemic mice. Transplanted beta cell mass was similar in normoglycemic groups with normal or impaired glucose tolerance, indicating that impaired glucose tolerance was not due to reduced beta cell mass. In summary, the beneficial effect of insulin-induced normoglycemia on transplanted islets was maximal when insulin treatment was maintained the initial 14 days after transplantation. Exposure to sustained hyperglycemia initially after transplantation had a long-lasting deleterious effect on transplanted islets.

Animals↗