| 1. |
- Alenkvist, Ida, et al.
(author)
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Absence of Shb impairs insulin secretion by elevated FAK activity in pancreatic islets
- 2014
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In: Journal of Endocrinology. - 0022-0795 .- 1479-6805. ; 223:3, s. 267-275
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Journal article (peer-reviewed)abstract
- The Src homology-2 domain containing protein B (SHB) has previously been shown to function as a pleiotropic adapter protein, conveying signals from receptor tyrosine kinases to intracellular signaling intermediates. The overexpression of Shb in β-cells promotes β-cell proliferation by increased insulin receptor substrate (IRS) and focal adhesion kinase (FAK) activity, whereas Shb deficiency causes moderate glucose intolerance and impaired first-peak insulin secretion. Using an array of techniques, including live-cell imaging, patch-clamping, immunoblotting, and semi-quantitative PCR, we presently investigated the causes of the abnormal insulin secretory characteristics in Shb-knockout mice. Shb-knockout islets displayed an abnormal signaling signature with increased activities of FAK, IRS, and AKT. β-catenin protein expression was elevated and it showed increased nuclear localization. However, there were no major alterations in the gene expression of various proteins involved in the β-cell secretory machinery. Nor was Shb deficiency associated with changes in glucose-induced ATP generation or cytoplasmic Ca(2) (+) handling. In contrast, the glucose-induced rise in cAMP, known to be important for the insulin secretory response, was delayed in the Shb-knockout compared with WT control. Inhibition of FAK increased the submembrane cAMP concentration, implicating FAK activity in the regulation of insulin exocytosis. In conclusion, Shb deficiency causes a chronic increase in β-cell FAK activity that perturbs the normal insulin secretory characteristics of β-cells, suggesting multi-faceted effects of FAK on insulin secretion depending on the mechanism of FAK activation.
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| 2. |
- Blixt, Martin, et al.
(author)
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Pancreatic islets of bank vole show signs of dysfunction after prolonged exposure to high glucose concentrations in vitro
- 2010
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In: Journal of Endocrinology. - 0022-0795 .- 1479-6805. ; 206:1, s. 47-54
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Journal article (peer-reviewed)abstract
- Bank voles develop glucose intolerance/diabetes mellitus when kept in captivity. We have characterized beta-cell function of glucose intolerant/diabetic animals, and found that this animal model has features of both human type 1 and type 2 diabetes. The aim of this study was to study the functional alterations of islets isolated from glucose tolerant bank voles after a prolonged exposure to various glucose concentrations in vitro. For this purpose, pancreatic islets from normal (glucose tolerant) male and female bank voles were cultured at different glucose concentrations (5.6, 11.1 (control), or 28 mM) whereupon islet functions were examined. Overall, islet insulin output was lowered at 5.6 mM glucose, and similar to control, or enhanced after culture in 28 mM glucose. High glucose culture led to decreased insulin contents, but there was no change in islet DNA content and in morphological assessments of cell death, with the latter findings suggesting that the so-called glucotoxicity had not evolved. A slight gender difference was observed in that islets isolated from females exhibited a glucose-regulated (pro) insulin biosynthesis rate and insulin gene expression. In conclusion, we have found that islets isolated from female and male bank voles are affected by glucose concentrations in vitro in that some signs of dysfunction were observed upon high glucose exposure. A minor gender difference was observed suggesting that the islets of the females may more readily adapt to the elevated glucose concentration than islets of the male bank voles. It could be that these in vitro gender differences observed may represent a mechanism underlying the gender difference in diabetes development observed among bank voles. Journal of Endocrinology (2010) 206, 47-54
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| 3. |
- Bäck, Karolina, et al.
(author)
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Insulin and IGF1 receptors in human cardiac microvascular endothelial cells: metabolic, mitogenic and anti-inflammatory effects
- 2012
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In: Journal of Endocrinology. - : Society for Endocrinology. - 0022-0795 .- 1479-6805. ; 215:1, s. 89-96
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Journal article (peer-reviewed)abstract
- Diabetes is associated with microcirculatory dysfunction and heart failure and changes in insulin and IGF1 levels. Whether human cardiac microvascular endothelial cells (HMVEC-Cs) are sensitive to insulin and/or IGF1 is not known. We studied the role of insulin receptors (IRs) and IGF1 receptors (IGF1Rs) in metabolic, mitogenic and anti-inflammatory responses to insulin and IGF1 in HMVEC-Cs and human umbilical vein endothelial cells (HUVECs). IR and IGF1R gene expression was studied using real-time RT-PCR. Receptor protein expression and phosphorylation were determined by western blot and ELISA. Metabolic and mitogenic effects were measured as glucose accumulation and thymidine incorporation. An E-selectin ELISA was used to investigate inflammatory responses. According to gene expression and protein in HMVEC-Cs and HUVECs, IGF1R is more abundant than IR. Immunoprecipitation with anti-IGF1R antibody and immunoblotting with anti-IR antibody and vice versa, showed insulin/IGF1 hybrid receptors in HMVEC-Cs. IGF1 at a concentration of 10(-8) mol/l significantly stimulated phosphorylation of both IGF1R and IR in HMVEC-Cs. In HUVECs IGF1 10(-8) mol/l phosphorylated IGF1R. IGF1 stimulated DNA synthesis at 10(-8) mol/l and glucose accumulation at 10(-7) mol/l in HMVEC-Cs. TNF-alpha dramatically increased E-selectin expression, but no inflammatory or anti-inflammatory effects of insulin, IGF1 or high glucose were seen. We conclude that HMVEC-Cs express more IGF1Rs than IRs, and mainly react to IGF1 due to the predominance of IGF1Rs and insulin/IGF1 hybrid receptors. TNF-alpha has a pronounced pro-inflammatory effect in HMVEC-Cs, which is not counteracted by insulin or IGF1.
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| 4. |
- Farman, Helen H., 1983, et al.
(author)
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Membrane estrogen receptor alpha is essential for estrogen signaling in the male skeleton
- 2018
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In: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 239:3, s. 303-312
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Journal article (peer-reviewed)abstract
- The importance of estrogen receptor alpha (ER alpha) for the regulation of bone mass in males is well established. ERa mediates estrogenic effects both via nuclear and membraneinitiated ER alpha (mER alpha) signaling. The role of mERa signaling for the effects of estrogen on bone in male mice is unknown. To investigate the role of mERa signaling, we have used mice (Nuclear-Only-ER; NOER) with a point mutation (C451A), which results in inhibited trafficking of ER alpha to the plasma membrane. Gonadal-intact male NOER mice had a significantly decreased total body areal bone mineral density (aBMD) compared to WT littermates at 3, 6 and 9 months of age as measured by dual-energy X-ray absorptiometry (DEXA). High-resolution microcomputed tomography (mu CT) analysis of tibia in 3-month-old males demonstrated a decrease in cortical and trabecular thickness in NOER mice compared to WT littermates. As expected, estradiol (E2) treatment of orchidectomized (ORX) WT mice increased total body aBMD, trabecular BV/TV and cortical thickness in tibia compared to placebo treatment. E2 treatment increased these skeletal parameters also in ORX NOER mice. However, the estrogenic responses were significantly decreased in ORX NOER mice compared with ORX WT mice. In conclusion, mER alpha is essential for normal estrogen signaling in both trabecular and cortical bone in male mice. Increased knowledge of estrogen signaling mechanisms in the regulation of the male skeleton may aid in the development of new treatment options for male osteoporosis.
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| 5. |
- Fex, Malin, et al.
(author)
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The pathogenetic role of β-cell mitochondria in type 2 diabetes
- 2018
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In: Journal of Endocrinology. - 0022-0795. ; 236:3, s. 145-149
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Research review (peer-reviewed)abstract
- Mitochondrial metabolism is a major determinant of insulin secretion from pancreatic β-cells. Type 2 diabetes evolves when β-cells fail to release appropriate amounts of insulin in response to glucose. This results in hyperglycemia and metabolic dysregulation. Evidence has recently been mounting that mitochondrial dysfunction plays an important role in these processes. Monogenic dysfunction of mitochondria is a rare condition but causes a type 2 diabetes-like syndrome owing to β-cell failure. Here, we describe novel advances in research on mitochondrial dysfunction in the β-cell in type 2 diabetes, with a focus on human studies. Relevant studies in animal and cell models of the disease are described. Transcriptional and translational regulation in mitochondria are particularly emphasized. The role of metabolic enzymes and pathways and their impact on β-cell function in type 2 diabetes pathophysiology are discussed. The role of genetic variation in mitochondrial function leading to type 2 diabetes is highlighted. We argue that alterations in mitochondria may be a culprit in the pathogenetic processes culminating in type 2 diabetes.
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| 6. |
- Fransson, Liselotte, et al.
(author)
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beta-cell adaptation in a mouse model of glucocorticoid-induced metabolic syndrome
- 2013
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In: Journal of Endocrinology. - : BioScientifica. - 0022-0795 .- 1479-6805. ; 219:3, s. 231-241
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Journal article (peer-reviewed)abstract
- Glucocorticoids (GCs) are stress hormones primarily responsible for mobilizing glucose to the circulation. Due to this effect, insulin resistance and glucose intolerance are concerns in patients with endogenous overproduction of GCs and in patients prescribed GC-based therapy. In addition, hypercortisolemic conditions share many characteristics with the metabolic syndrome. This study reports on a thorough characterization, in terms of glucose control and lipid handling, of a mouse model where corticosterone is given via the drinking water. C57BL/6J mice were treated with corticosterone (100 or 25 mu g/ml) or vehicle in their drinking water for 5 weeks after which they were subjected to insulin or glucose tolerance tests. GC-treated mice displayed increased food intake, body weight gain, and central fat deposit accumulations. In addition, the GC treatment led to dyslipidemia as well as accumulation of ectopic fat in the liver and skeletal muscle, having a substantial negative effect on insulin sensitivity. Also glucose intolerance and hypertension, both part of the metabolic syndrome, were evident in the GC-treated mice. However, the observed effects of corticosterone were reversed after drug removal. Furthermore, this study reveals insights into beta-cell adaptation to the GC-induced insulin resistance. Increased pancreatic islet volume due to cell proliferation, increased insulin secretion capacity, and increased islet chaperone expression were found in GC-treated animals. This model mimics the human metabolic syndrome. It could be a valuable model for studying the complex mechanisms behind the development of the metabolic syndrome and type 2 diabetes, as well as the multifaceted relations between GC excess and disease.
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| 7. |
- Fransson, Liselotte, et al.
(author)
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β-cell adaptation in a mouse model of glucocorticoid-induced metabolic syndrome
- 2013
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In: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 219:3, s. 231-241
-
Journal article (peer-reviewed)abstract
- Glucocorticoids (GCs) are stress hormones primarily responsible for mobilizing glucose to the circulation. Due to this effect, insulin resistance and glucose intolerance are concerns in patients with endogenous overproduction of GCs and in patients prescribed GC-based therapy. In addition, hypercortisolemic conditions share many characteristics with the metabolic syndrome. This study reports on a thorough characterization, in terms of glucose control and lipid handling, of a mouse model where corticosterone is given via the drinking water. C57BL/6J mice were treated with corticosterone (100 or 25 μg/ml) or vehicle in their drinking water for 5 weeks after which they were subjected to insulin or glucose tolerance tests. GC-treated mice displayed increased food intake, body weight gain, and central fat deposit accumulations. In addition, the GC treatment led to dyslipidemia as well as accumulation of ectopic fat in the liver and skeletal muscle, having a substantial negative effect on insulin sensitivity. Also glucose intolerance and hypertension, both part of the metabolic syndrome, were evident in the GC-treated mice. However, the observed effects of corticosterone were reversed after drug removal. Furthermore, this study reveals insights into β-cell adaptation to the GC-induced insulin resistance. Increased pancreatic islet volume due to cell proliferation, increased insulin secretion capacity, and increased islet chaperone expression were found in GC-treated animals. This model mimics the human metabolic syndrome. It could be a valuable model for studying the complex mechanisms behind the development of the metabolic syndrome and type 2 diabetes, as well as the multifaceted relations between GC excess and disease.
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| 8. |
- Funck-Brentano, Thomas, et al.
(author)
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Porcupine inhibitors impair trabecular and cortical bone mass and strength in mice
- 2018
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In: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 238:1, s. 13-23
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Journal article (peer-reviewed)abstract
- WNT signaling is involved in the tumorigenesis of various cancers and regulates bone homeostasis. Palmitoleoylation of WNTs by Porcupine is required for WNT activity. Porcupine inhibitors are under development for cancer therapy. As the possible side effects of Porcupine inhibitors on bone health are unknown, we determined their effects on bone mass and strength. Twelve-week-old C57BL/6N female mice were treated by the Porcupine inhibitors LGK974 (low dose = 3 mg/kg/day; high dose = 6 mg/kg/day) or Wnt-C59 (10 mg/kg/day) or vehicle for 3 weeks. Bone parameters were assessed by serum biomarkers, dual-energy X-ray absorptiometry, mu CT and histomorphometry. Bone strength was measured by the 3-point bending test. The Porcupine inhibitors were well tolerated demonstrated by normal body weight. Both doses of LGK974 and Wnt-C59 reduced total body bone mineral density compared with vehicle treatment (P < 0.001). Cortical thickness of the femur shaft (P < 0.001) and trabecular bone volume fraction in the vertebral body (P < 0.001) were reduced by treatment with LGK974 or Wnt-C59. Porcupine inhibition reduced bone strength in the tibia (P < 0.05). The cortical bone loss was the result of impaired periosteal bone formation and increased endocortical bone resorption and the trabecular bone loss was caused by reduced trabecular bone formation and increased bone resorption. Porcupine inhibitors exert deleterious effects on bone mass and strength caused by a combination of reduced bone formation and increased bone resorption. We suggest that cancer targeted therapies using Porcupine inhibitors may increase the risk of fractures.
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| 9. |
- Grönbladh, Alfhild, et al.
(author)
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GH (Growth hormone) improves spatial memory and reverses certain anabolic androgenic steroid-induced effects in intact rats
- 2013
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In: Journal of Endocrinology. - 0022-0795 .- 1479-6805. ; 216:1, s. 31-41
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Journal article (peer-reviewed)abstract
- Growth hormone (GH) has previously been shown to promote cognitive functions in GH deficient rodents. In this study we report effects of GH on learning and memory in intact rats pretreated with the anabolic androgenic steroid nandrolone. Male Wistar rats received nandrolone decanoate (15 mg/kg) or peanut oil every third day for three weeks and were subsequently treated with recombinant human GH (1.0 IU/kg) or saline for ten consecutive days. During the GH/saline treatment spatial learning and memory were tested in the Morris water maze (MWM). Also, plasma levels of insulin-like growth factor 1 (IGF1) were assessed and the gene expression of the GH receptor, Igf1, and Igf2 in hippocampus and frontal cortex was analyzed. The results demonstrated a significant positive effect of GH on memory functions and increased gene expression of Igf1 in the hippocampus was found in the animals treated with GH. In addition, GH was demonstrated to increase the body weight gain and was able to attenuate the reduced body weight seen in nandrolone treated animals. In general, the rats treated with nandrolone alone did not exhibit any pronounced alteration in memory compared to controls in the MWM, and in many cases GH did not induce any alteration. Regarding target zone crossings, considered to be associated to spatial memory, the difference between GH and steroid treated animals was significant and administration of GH improved this parameter in the latter group. In conclusion, GH improves spatial memory in intact rats and can reverse certain effects induced by AAS (anabolic androgenic steroid).
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| 10. |
- Gustafsson, Karin L., 1987, et al.
(author)
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ER alpha expression in T lymphocytes is dispensable for estrogenic effects in bone
- 2018
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In: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 238:2, s. 129-136
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Journal article (peer-reviewed)abstract
- Estrogen treatment has positive effects on the skeleton, and we have shown that estrogen receptor alpha (ERa) expression in cells of hematopoietic origin contributes to a normal estrogen treatment response in bone tissue. T lymphocytes are implicated in the estrogenic regulation of bone mass, but it is not known whether T lymphocytes are direct estrogen target cells. Therefore, the aim of this study was to determine the importance of ERa expression in T lymphocytes for the estrogenic regulation of the skeleton using female mice lacking ERa expression specifically in T lymphocytes (Lck-ERa-/-) and ERaflox/flox littermate (control) mice. Deletion of ERa expression in T lymphocytes did not affect bone mineral density (BMD) in sham-operated Lck-ERa-/compared to control mice, and ovariectomy (ovx) resulted in a similar decrease in BMD in control and Lck-ERa-/- mice compared to sham-operated mice. Furthermore, estrogen treatment of ovx Lck-ERa-/- led to an increased BMD that was indistinguishable from the increase seen after estrogen treatment of ovx control mice. Detailed analysis of both the appendicular (femur) and axial (vertebrae) skeleton showed that both trabecular and cortical bone parameters responded to a similar extent regardless of the presence of ERa in T lymphocytes. In conclusion, ERa expression in T lymphocytes is dispensable for normal estrogenic regulation of bone mass in female mice.
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