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V Nacher

Publications and source records attributed to V Nacher.

11 recordsLinked to original sources
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↗
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↗
PubMed1996

Diminished fraction of blockable ATP-sensitive K+ channels in islets transplanted into diabetic mice.

The reasons for the poor outcome of islet transplantation in diabetic patients are not well known; a better understanding of the pathophysiology of transplanted islets is needed. To study the mechanism coupling secretagogue stimuli with insulin release in transplanted islets, we determined the effects of glucose, tolbutamide, and carbamylcholine on the beta-cell membrane potential and cytosolic calcium concentrations ([Ca2+]i) of islets syngeneically transplanted into normal and streptozocin-induced diabetic mice. In both groups, normoglycemia was maintained after transplantation. Islets transplanted into normal recipients showed similar changes in beta-cell membrane potential and [Ca2+]i oscillations to those in control islets. In contrast, when islets were transplanted into diabetic mice, bursts of electrical activity were triggered at lower glucose concentrations (5.6 mmol/l) than in control islets (11 mmol/l), and maximal electrical activity was achieved at lower glucose concentrations (11 mmol/l) than in control islets (22 mmol/l). When membrane potential was plotted as a function of glucose concentration, the dose-response curve was shifted to the left. Compared with control islets, glucose-induced [Ca2+]i oscillations were broader in duration (22.3 +/- 0.6 s vs. 118.1 +/- 12.6 s; P < 0.01) and higher in amplitude (135 +/- 36 nmol/l vs. 352 +/- 36 nmol/l; P < 0.01). Glucose supersensitivity was attributed to a resting decrease in the fraction of blockable ATP-sensitive K+ (K+(ATP)) channels in transplanted islets that maintained normoglycemia with a limited beta-cell mass.

Adenosine Triphosphate↗
PubMed1996

Ketoacidosis at diagnosis is predictive of lower residual beta-cell function and poor metabolic control in type 1 diabetes.

To determine the factors at diagnosis predictive of changes in residual beta-cell function and metabolic control in Type 1 diabetes, 125 patients older than 7 years of age consecutively diagnosed between March 1986 and June 1991 were followed prospectively for two years. The effect of age, gender and the presence of ketoacidosis (DKA) and islet-cell antibodies (ICA) on beta-cell function, metabolic control and insulin requirements were studied by multivariate analysis of variance (repeated measurements over time) in 90 patients who completed follow-up. DKA had an independent negative effect on residual beta-cell function over time (p = 0.001). ICA-positive patients had lower residual beta-cell function at the end of follow-up (p < 0.05), but overall differences were not significant. DKA and younger age had an independent negative influence on metabolic control (p < 0.05) and insulin requirements (p < 0.001) over time. It is concluded that residual beta-cell function in Type 1 diabetic patients two years after diagnosis was independently influenced by DKA and ICA at diagnosis. Moreover, DKA and age influenced metabolic control and could thus be used to predict those patients with rapidly deteriorating metabolic control who might benefit from a more intensive therapeutic approach.

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↗