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Contini M, Cruz GD, Althoff SF, Freitas MB, Taboga SR, Rafacho A. Heterogeneity in the preferential diet of neotropical bats impacts the pancreatic islet mass and α and β cell distribution. Gen Comp Endocrinol 2024; 348:114449. [PMID: 38216095 DOI: 10.1016/j.ygcen.2024.114449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 01/06/2024] [Accepted: 01/08/2024] [Indexed: 01/14/2024]
Abstract
Whether there is a relationship between bats' dietary patterns and evolutionary endocrine pancreas adaptation is not clearly understood. Aiming to contribute to this topic, we evaluated some metabolic and structural parameters in the following adult bats: the frugivorous Artibeus lituratus, the nectarivorous Anoura caudifer, the hematophagous Desmodus rotundus, and the insectivorous Molossus molossus. A. lituratus and A. caudifer diets consist of high amounts of simple carbohydrates, while D. rotundus and M. molossus diets consist of high amounts of proteins or protein and fat, respectively. In our results, A. lituratus and A. caudifer bats exhibited the highest values of relative islet mass (%), islet density (number of islets per pancreas area), and the lowest values of intestinal length among the four species. When adjusted by the body mass (mg/g of body mass), both D. rotundus and A. caudifer bats exhibited the highest islet mass values among the groups. Blood glucose was similar between A. lituratus, D. rotundus, and M. molossus, with the lowest values for the A. caudifer bats. M. molossus bats had the highest plasma cholesterol values among the studied species but exhibited similar plasma triacylglycerol with D. rotundus and A. caudifer bats. β- and α-cell distribution within A. lituratus, A. caudifer, and M. molossus islets achieved an approximate average value of ∼ 66% and ∼ 28%, respectively, a pattern inverted in D. rotundus islets (53% of α cells and 40% of β cells). A. caudifer and D. rotundus exhibited the highest and the lowest β/α-cells ratio per islet, respectively. We conclude that the macronutrient predominance in each bat-eating niche correlates with the morphophysiological pancreas features being the nectarivorous A. caudifer the species with the highest islet mass per body mass and β/α-cells ratio, while the hematophagous D. rotundus showed the highest α-cells apparatus.
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Affiliation(s)
- M Contini
- Laboratory of Investigation in Chronic Diseases - LIDoC, Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina - UFSC, Florianópolis, Brazil; Multicenter Graduate Program in Physiology, Center of Biological Sciences, Federal University of Santa Catarina - UFSC, Florianópolis, Santa Catarina, Brazil
| | - G D Cruz
- Laboratory of Investigation in Chronic Diseases - LIDoC, Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina - UFSC, Florianópolis, Brazil; Multicenter Graduate Program in Physiology, Center of Biological Sciences, Federal University of Santa Catarina - UFSC, Florianópolis, Santa Catarina, Brazil
| | - S F Althoff
- Biodiversity Graduate Program, Department of Natural Sciences, Fundação Universidade Regional de Blumenau - FURB, Blumenau, Santa Catarina, Brazil
| | - M B Freitas
- Department of Animal Biology, Federal University of Viçosa - UFV, Viçosa, Minas Gerais, Brazil
| | - S R Taboga
- Department of Biological Sciences, Institute of Biosciences, Humanities and Exact Sciences, São Paulo State University (UNESP), São José do Rio Preto, São Paulo, Brazil
| | - A Rafacho
- Laboratory of Investigation in Chronic Diseases - LIDoC, Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina - UFSC, Florianópolis, Brazil; Multicenter Graduate Program in Physiology, Center of Biological Sciences, Federal University of Santa Catarina - UFSC, Florianópolis, Santa Catarina, Brazil.
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Martins JRN, Lopes S, Hurtado HN, da Silva FN, Villard DR, Taboga SR, Souza KLA, Quesada I, Soriano S, Rafacho A. Acute and chronic effects of the organophosphate malathion on the pancreatic α and β cell viability, cell structure, and voltage-gated K + currents. Environ Toxicol Pharmacol 2023; 98:104046. [PMID: 36587778 DOI: 10.1016/j.etap.2022.104046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 12/09/2022] [Accepted: 12/27/2022] [Indexed: 06/17/2023]
Abstract
Studies indicate that the pesticide malathion may have a role in diabetes. Herein, we determined the effects of different concentrations of malathion on survival, ultrastructure, and electrophysiologic islet cell parameters. Acutely, high concentrations of malathion (0.5 or 1 mM) increased cell death in rat islet cells, while low concentrations (0.1 mM) caused signs of cell damage in pancreatic α and β cells. Exposure of RINm5F cells to malathion for 24 or 48 h confirmed the reduction in β-cell viability at lower concentrations (0.001-100 µM). Chronic exposure of mouse pancreatic α and β cells to 3 nM of malathion led to increased voltage-gated K+ (Kv) currents in α-cells. Our findings show a time and concentration dependency for the malathion effect on the reduction of islet cell viability and indicate that pancreatic α cells are more sensitive to malathion effects on Kv currents and cell death.
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Affiliation(s)
- J R N Martins
- Laboratory of Investigation in Chronic Diseases LIDoC, Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina UFSC, Florianópolis, Brazil; Graduate Program in Pharmacology, Center of Biological Sciences, Federal University of Santa Catarina UFSC, Florianópolis, Brazil
| | - S Lopes
- Central Laboratory of Electron Microscopy LCME, PROPESQ, Federal University of Santa Catarina UFSC, Florianópolis, Brazil
| | - H N Hurtado
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain
| | - F N da Silva
- Laboratory of Investigation in Chronic Diseases LIDoC, Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina UFSC, Florianópolis, Brazil; Graduate Program in Pharmacology, Center of Biological Sciences, Federal University of Santa Catarina UFSC, Florianópolis, Brazil
| | - D R Villard
- NUMPEX-BIO, Campus Duque de Caxias, Universidade Federal do Rio de Janeiro (UFRJ), Campus UFRJ Duque de Caxias Prof. Geraldo Cidade, Duque de Caxias 25245-390, Brazil
| | - S R Taboga
- Department of Biological Sciences, Laboratory of Microscopy and Microanalysis, Universidade Estadual Paulista-UNESP, São Paulo, Brazil
| | - K L A Souza
- NUMPEX-BIO, Campus Duque de Caxias, Universidade Federal do Rio de Janeiro (UFRJ), Campus UFRJ Duque de Caxias Prof. Geraldo Cidade, Duque de Caxias 25245-390, Brazil
| | - I Quesada
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, Elche, Spain; Biomedical Research Center in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
| | - S Soriano
- Department of Physiology, Genetics, and Microbiology, University of Alicante, Alicante, Spain; Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, Elche, Spain
| | - A Rafacho
- Laboratory of Investigation in Chronic Diseases LIDoC, Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina UFSC, Florianópolis, Brazil; Graduate Program in Pharmacology, Center of Biological Sciences, Federal University of Santa Catarina UFSC, Florianópolis, Brazil.
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Corrêa C, Filipini R, Mazera M, Rafacho A, Nunes E. Mixed-meal test reveals a worsen phenotypic flexibility correlated to central adiposity in clinically healthy young males. Clin Nutr ESPEN 2020. [DOI: 10.1016/j.clnesp.2020.09.650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
Insulin secretion is mainly regulated by blood glucose concentration. On the other hand, changes in peripheral insulin sensitivity induce compensatory adaptations in pancreatic β-cells to maintain normoglycaemia. Tumour presence causes dramatic alterations in glucose homeostasis and insulin secretion because of the high glucose consumption by the tumour cells. Here, we investigated insulin secretion in solid Ehrlich tumour-bearing mice in association with cachexia. For that, male adult Swiss mice were subcutaneously inoculated with solid Ehrlich tumour cells and sacrificed at 14 days after tumour implantation (SET), while control mice received saline alone (CTL). Insulin secretion, following different stimuli, glucose tolerance, and insulin sensitivity as well as the expression of key proteins involved in insulin secretion was assessed. The SET group showed decreased glycaemia, insulinaemia, hepatic glycogen and body weight, and increased plasma free fatty acids and triglycerides, characteristics of cancer cachexia. A very interesting finding in this study was the development of higher glucose tolerance and insulin sensitivity in SET group. The dose-response curve of insulin secretion to increasing glucose concentrations (2.8-22.2 mM) showed an EC50 of 10 mM glucose for CTL mice and 13 mM glucose for SET mice. Insulin secretion was significantly reduced in SET islets at 30 mM KCl, 100 μM carbachol, 20 mM arginine, and 20 mM leucine. Moreover, AKT, PKA, PKC, and AchRM3 expressions were reduced by 17% to 24% in SET animals. These results, mainly the augmented insulin sensitivity, show that SET is an interesting model to study alterations in pancreatic function and carbohydrate metabolism in cancer cachexia.
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Affiliation(s)
- N M Violato
- Institute of Bioscience, São Paulo State University, Botucatu, SP, Brazil
| | - A Rafacho
- Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianópolis, SC, Brazil
| | - A C Boschero
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, Campinas, SP, Brazil
| | - J R Bosqueiro
- Department of Physical Education, Faculty of Sciences, São Paulo State University, Bauru, SP, Brazil
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Rafacho A, Gonçalves-Neto LM, Ferreira FBD, Protzek AOP, Boschero AC, Nunes EA, Zoccal DB. Glucose homoeostasis in rats exposed to acute intermittent hypoxia. Acta Physiol (Oxf) 2013; 209:77-89. [PMID: 23692825 DOI: 10.1111/apha.12118] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Revised: 01/15/2013] [Accepted: 05/15/2013] [Indexed: 11/29/2022]
Abstract
AIM Chronic exposure to intermittent hypoxia commonly induces the activation of sympathetic tonus and the disruption of glucose homoeostasis. However, the effects of exposure to acute intermittent hypoxia (AIH) on glucose homoeostasis are not yet fully elucidated. Herein, we evaluated parameters related to glucose metabolism in rats exposed to AIH. METHODS Male adult rats were submitted to 10 episodes of hypoxia (6% O2 , for 45 s) interspersed with 5-min intervals of normoxia (21%), while the control (CTL) group was kept in normoxia. RESULTS Acute intermittent hypoxia rats presented higher fasting glycaemia, normal insulinaemia, increased lactataemia and similar serum lipid levels, compared to controls (n = 10, P < 0.05). Additionally, AIH rats exhibited increased glucose tolerance (GT) (n = 10, P < 0.05) and augmented insulin sensitivity (IS) (n = 10, P < 0.05). The p-Akt/Akt protein ratio was increased in the muscle, but not in the liver and adipose tissue of AIH rats (n = 6, P < 0.05). The elevated glycaemia in AIH rats was associated with a reduction in the hepatic glycogen content (n = 10, P < 0.05). Moreover, the AIH-induced increase in blood glucose concentration, as well as reduced hepatic glycogen content, was prevented by prior systemic administration of the β-adrenergic antagonist (P < 0.05). The effects of AIH on glycaemia and Akt phosphorylation were transient and not observed after 60 min. CONCLUSIONS We suggest that AIH induces an increase in blood glucose concentration as a result of hepatic glycogenolysis recruitment through sympathetic activation. The augmentation of GT and IS might be attributed, at least in part, to increased β-adrenergic sympathetic stimulation and Akt protein activation in skeletal muscles, leading to a higher glucose availability and utilization.
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Affiliation(s)
- A. Rafacho
- Department of Physiological Sciences; Centre of Biological Sciences; UFSC - Federal University of de Santa Catarina; Florianópolis; Santa Catarina; Brazil
| | - L. M. Gonçalves-Neto
- Department of Physiological Sciences; Centre of Biological Sciences; UFSC - Federal University of de Santa Catarina; Florianópolis; Santa Catarina; Brazil
| | - F. B. D. Ferreira
- Department of Physiological Sciences; Centre of Biological Sciences; UFSC - Federal University of de Santa Catarina; Florianópolis; Santa Catarina; Brazil
| | - A. O. P. Protzek
- Department of Structural and Functional Biology; Institute of Biology; UNICAMP - State University of Campinas; Campinas; São Paulo; Brazil
| | - A. C. Boschero
- Department of Structural and Functional Biology; Institute of Biology; UNICAMP - State University of Campinas; Campinas; São Paulo; Brazil
| | - E. A. Nunes
- Department of Physiological Sciences; Centre of Biological Sciences; UFSC - Federal University of de Santa Catarina; Florianópolis; Santa Catarina; Brazil
| | - D. B. Zoccal
- Department of Physiological Sciences; Centre of Biological Sciences; UFSC - Federal University of de Santa Catarina; Florianópolis; Santa Catarina; Brazil
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Ribeiro DL, Pinto ME, Rafacho A, Bosqueiro JR, Maeda SY, Anselmo-Franci JA, Taboga SR, Goes RM. High-Fat Diet Obesity Associated With Insulin Resistance Increases Cell Proliferation, Estrogen Receptor, and PI3K Proteins in Rat Ventral Prostate. ACTA ACUST UNITED AC 2012; 33:854-65. [DOI: 10.2164/jandrol.111.016089] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Rafacho A, Abrantes JLF, Ribeiro DL, Paula FM, Pinto ME, Boschero AC, Bosqueiro JR. Morphofunctional alterations in endocrine pancreas of short- and long-term dexamethasone-treated rats. Horm Metab Res 2011; 43:275-81. [PMID: 21225543 DOI: 10.1055/s-0030-1269896] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Long-term dexamethasone therapy may induce peripheral insulin resistance (IR), which in turn elicits increased beta-cell function and proliferation. However, whether such adaptive compensations occur during short-term treatment with dexamethasone is unclear. Here, we compared morphofunctional parameters in endocrine pancreas after short- and long-term dexamethasone administration. Groups of rats received daily i. p. injection of 1 mg/kg b. w. dexamethasone for 1 (DEX-1), 3 (DEX-3), or 5 consecutive days (DEX-5), whilst control rats were saline-treated (CTL). Despite the absence of apparent IR in DEX-1 rats, this group exhibited increased circulating insulin levels and glucose-stimulated insulin secretion (GSIS), compared to the CTL group (p<0.05). Evident IR as well as marked hyperinsulinemia and GSIS, as judged by the static and dynamic insulin secretion values, were observed in DEX-3 and DEX-5 rats (p<0.05). GSIS in islets cultured with 1 μM dexamethasone was lower compared to the control (p<0.05). Marked increases in beta-cell proliferation were observed in DEX-3 and DEX-5 rats, compared to CTL and DEX-1 rats (p<0.05). The alterations observed in DEX-3 rats were more pronounced in DEX-5 rats, which also exhibited a higher content of islet Cdk4 and Cd2 proteins, compared to the CTL group (p<0.05). We conclude that short-term dexamethasone treatment (DEX-1) induces an increase in beta-cell function that does not require the presence of discernible IR. As the treatment continues, the IR develops rapidly, and increased insulin secretion as well as beta-cell hyperplasia is demanded for the appropriate maintenance of glucose homeostasis.
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Affiliation(s)
- A Rafacho
- Department of Physical Education, School of Sciences, UNESP - Universidade Estadual Paulista, Bauru, SP, Brazil.
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Rafacho A, Quallio S, Ribeiro DL, Taboga SR, Paula FMM, Boschero AC, Bosqueiro JR. The adaptive compensations in endocrine pancreas from glucocorticoid-treated rats are reversible after the interruption of treatment. Acta Physiol (Oxf) 2010; 200:223-35. [PMID: 20456283 DOI: 10.1111/j.1748-1716.2010.02146.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM Glucocorticoid administration induces insulin resistance (IR) and enhances islet mass and insulin secretion in rodents and humans. Here, we analysed whether these effects are still present after the interruption of dexamethasone treatment. METHODS Adult Wistar rats were distributed into CTL (daily injection of saline for five consecutive days), DEX (daily injection of 1 mg kg(-1) body wt of dexamethasone for five consecutive days) and DEX(10) (5 days of dexamethasone treatment, followed by a period of 10 days without dexamethasone). RESULTS In vivo experiments indicated that the marked hyperinsulinemia found in DEX rats during fasting and fed states was normalized in the DEX(10) group. Furthermore, the IR and glucose intolerance observed in DEX were restored in DEX(10) rats. Islets from DEX rats secreted more insulin in response to increasing concentrations of glucose and other metabolic and non-metabolic stimuli, compared with that in the CTL group. The insulin secretion for the most compounds studied returned to CTL values in DEX(10) islets. Increased insulin secretion correlated well with the augmentation in β-cell proliferation and mass in DEX rats, and these morphological alterations were normalized in islets from DEX(10) rats. In parallel, the increased levels of proteins involved in β-cell proliferation such as Cd2 and Cdk4 observed in DEX islets were also normalized in DEX(10) islets. CONCLUSION These data strongly support the view that almost all the morphophysiological alterations induced by dexamethasone in the endocrine pancreas are reverted after discontinuation of the treatment. This information is important, considering the frequent use of glucocorticoids in humans.
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Affiliation(s)
- A Rafacho
- Department of Physical Education, School of Sciences, UNESP - Univ. Estadual Paulista, Bauru, São Paulo, Brazil.
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Protzek AOP, Rafacho A, Viscelli BA, Bosqueiro JR, Cappelli AP, Paula FMM, Boschero AC, Pinheiro EC. Insulin and glucose sensitivity, insulin secretion and beta-cell distribution in endocrine pancreas of the fruit bat Artibeus lituratus. Comp Biochem Physiol A Mol Integr Physiol 2010; 157:142-8. [PMID: 20566319 DOI: 10.1016/j.cbpa.2010.05.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 05/28/2010] [Accepted: 05/31/2010] [Indexed: 10/19/2022]
Abstract
The fruit bat Artibeus lituratus absorbs large amounts of glucose in short periods of time and maintains normoglycemia even after a prolonged starvation period. Based on these data, we aimed to investigate various aspects related with glucose homeostasis analyzing: blood glucose and insulin levels, intraperitoneal glucose and insulin tolerance tests (ipGTT and ipITT), glucose-stimulated insulin secretion (2.8, 5.6 or 8.3 mmol/L glucose) in pancreas fragments, cellular distribution of beta cells, and the amount of pAkt/Akt in the pectoral muscle and liver. Blood glucose levels were higher in fed bats (6.88+/-0.5 mmol/L) than fasted bats (4.0+/-0.8 mmol/L), whereas insulin levels were similar in both conditions. The values of the area-under-the curve obtained from ipGTT were significantly higher when bats received 2 (5.5-fold) or 3g/kg glucose (7.5-fold) b.w compared to control (saline). These bats also exhibited a significant decrease of blood glucose values after insulin administration during the ipITT. Insulin secretion from fragments of pancreas under physiological concentrations of glucose (5.6 or 8.3 mmol/L) was similar but higher than in 2.8 mmol/L glucose 1.8- and 2.0-fold, respectively. These bats showed a marked beta-cell distribution along the pancreas, and the pancreatic beta cells are not exclusively located at the central part of the islet. The insulin-induced Akt phosphorylation was more pronounced in the pectoral muscle, compared to liver. The high sensitivity to glucose and insulin, the proper insulin response to glucose, and the presence of an apparent large beta-cell population could represent benefits for the management of high influx of glucose from a carbohydrate-rich meal, which permits appropriate glucose utilization.
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Affiliation(s)
- A O P Protzek
- Department of Physiological Sciences, Institute of Biological Science, University of Brasília, DF, Brazil.
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Rafacho A, Giozzet V, Boschero A, Abrantes J, Cestari T, Carneiro E, Bosqueiro J. Reduced pancreatic β-cell mass is associated with decreased FoxO1 and Erk1/2 protein phosphorylation in low-protein malnourished rats. Braz J Med Biol Res 2009; 42:935-41. [DOI: 10.1590/s0100-879x2009001000010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Accepted: 08/10/2009] [Indexed: 02/01/2023] Open
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Ribeiro DL, Rafacho A, Bosqueiro JR, Taboga SR, Góes RM. Cellular changes in the prostatic stroma of glucocorticoid-treated rats. Cell Tissue Res 2008; 332:499-508. [PMID: 18379825 DOI: 10.1007/s00441-008-0581-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Accepted: 01/10/2008] [Indexed: 11/26/2022]
Abstract
Glucocorticoid hormones (GCs) have been widely used for the treatment of prostate cancer because of their inhibitory property against tumour growth. However, their mechanism of action in the prostate has received little attention. Excess GCs can lead to peripheral insulin resistance resulting in hyperglycaemia and hyperinsulinaemia. Insulin plays an important role as a cellular stimulant and high levels are related to low levels of androgens. Our objective has been to describe the effects of insulin resistance induced by dexamethasone treatment on the morphology of rat ventral prostate. Male adult Wistar rats received daily intraperitoneal injections of dexamethasone or saline for five consecutive days after which the rats were killed and the ventral prostate was removed, weighed and prepared for conventional and transmission electron microscopy (TEM). Dexamethasone treatment resulted in atrophy and decreased proliferative activity of prostatic epithelial cells. TEM analysis revealed changes in the epithelium-stroma interface, with some interruptions in the basement membrane. Fibroblasts showed a secretory phenotype with dilated endoplasmic reticulum. Smooth muscle cells exhibited a contractile pattern with 50% atrophy, an irregular membrane and twisted nuclei. Mitochondrial alterations, such as enlarged size and high electron density in the mitochondrial matrix, were also detected in smooth muscle cells. Insulin resistance induced by dexamethasone is thus associated with epithelial atrophy similar to that described for diabetic rats. However, GCs are responsible for morphological changes in the stromal cell population suggesting the activation of fibroblasts and atrophy of the smooth muscle cells.
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Affiliation(s)
- D L Ribeiro
- Department of Cell Biology, State University of Campinas, UNICAMP, Campinas, Brazil
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Rafacho A, Roma LP, Taboga SR, Boschero AC, Bosqueiro JR. Dexamethasone-induced insulin resistance is associated with increased connexin 36 mRNA and protein expression in pancreatic rat islets. Can J Physiol Pharmacol 2007; 85:536-45. [PMID: 17632589 DOI: 10.1139/y07-037] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Augmented glucose-stimulated insulin secretion (GSIS) is an adaptive mechanism exhibited by pancreatic islets from insulin-resistant animal models. Gap junction proteins have been proposed to contribute to islet function. As such, we investigated the expression of connexin 36 (Cx36), connexin 43 (Cx43), and the glucose transporter Glut2 at mRNA and protein levels in pancreatic islets of dexamethasone (DEX)-induced insulin-resistant rats. Study rats received daily injections of DEX (1 mg/kg body mass, i.p.) for 5 days, whereas control rats (CTL) received saline solution. DEX rats exhibited peripheral insulin resistance, as indicated by the significant postabsorptive insulin levels and by the constant rate for glucose disappearance (KITT). GSIS was significantly higher in DEX islets (1.8-fold in 16.7 mmol/L glucose vs. CTL, p < 0.05). A significant increase of 2.25-fold in islet area was observed in DEX vs. CTL islets (p < 0.05). Cx36 mRNA expression was significantly augmented, Cx43 diminished, and Glut2 mRNA was unaltered in islets of DEX vs. CTL (p < 0.05). Cx36 protein expression was 1.6-fold higher than that of CTL islets (p < 0.05). Glut2 protein expression was unaltered and Cx43 was not detected at the protein level. We conclude that DEX-induced insulin resistance is accompanied by increased GSIS and this may be associated with increase of Cx36 protein expression.
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Affiliation(s)
- A Rafacho
- Department of Physiology and Biophysics, Institute of Biology, State University of Campinas (UNICAMP), Campinas, S.P, Brazil
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