| 51. |
- Kim, DI, et al.
(författare)
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PRMT3 regulates hepatic lipogenesis through direct interaction with LXRα
- 2015
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 64:1, s. 60-71
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Tidskriftsartikel (refereegranskat)abstract
- Arginine methylation is responsible for diverse biological functions and is mediated by protein arginine methyltransferases (PRMTs). Nonalcoholic fatty liver disease (NAFLD) is accompanied by excessive hepatic lipogenesis via liver X receptor α (LXRα). Thus we examined the pathophysiological role of PRMTs in NAFLD and their relationship with LXRα. In this study, palmitic acid (PA) treatment increased PRMT3, which is correlated with the elevation of hepatic lipogenic proteins. The expression of lipogenic proteins was increased by PRMT3 overexpression, but decreased by PRMT3 silencing and use of the PRMT3 knockout (KO) mouse embryonic fibroblast cell line. PRMT3 also increased the transcriptional activity of LXRα by directly binding with LXRα in a methylation-independent manner. In addition, PA treatment translocated PRMT3 to the nucleus. In animal models, a high-fat diet increased the LXRα and PRMT3 expressions and binding, which was not observed in LXRα KO mice. Furthermore, increased PRMT3 expression and its binding with LXRα were observed in NAFLD patients. Taken together, LXRα and PRMT3 expression was increased in cellular and mouse models of NAFLD and human patients, and PRMT3 translocated into the nucleus bound with LXRα as a transcriptional cofactor, which induced lipogenesis. In conclusion, PRMT3 translocation by PA is coupled to the binding of LXRα, which is responsible for the onset of fatty liver.
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| 52. |
- Kjobsted, R, et al.
(författare)
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Enhanced Muscle Insulin Sensitivity After Contraction/Exercise Is Mediated by AMPK
- 2017
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 66:3, s. 598-612
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Tidskriftsartikel (refereegranskat)abstract
- Earlier studies have demonstrated that muscle insulin sensitivity to stimulate glucose uptake is enhanced several hours after an acute bout of exercise. Using AICAR, we recently demonstrated that prior activation of AMPK is sufficient to increase insulin sensitivity in mouse skeletal muscle. Here we aimed to determine whether activation of AMPK is also a prerequisite for the ability of muscle contraction to increase insulin sensitivity. We found that prior in situ contraction of m. extensor digitorum longus (EDL) and treadmill exercise increased muscle and whole-body insulin sensitivity in wild-type (WT) mice, respectively. These effects were not found in AMPKα1α2 muscle-specific knockout mice. Prior in situ contraction did not increase insulin sensitivity in m. soleus from either genotype. Improvement in muscle insulin sensitivity was not associated with enhanced glycogen synthase activity or proximal insulin signaling. However, in WT EDL muscle, prior in situ contraction enhanced insulin-stimulated phosphorylation of TBC1D4 Thr649 and Ser711. Such findings are also evident in prior exercised and insulin-sensitized human skeletal muscle. Collectively, our data suggest that the AMPK-TBC1D4 signaling axis is likely mediating the improved muscle insulin sensitivity after contraction/exercise and illuminates an important and physiologically relevant role of AMPK in skeletal muscle.
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| 53. |
- Kjobsted, R, et al.
(författare)
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Prior AICAR stimulation increases insulin sensitivity in mouse skeletal muscle in an AMPK-dependent manner
- 2015
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 64:6, s. 2042-2055
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Tidskriftsartikel (refereegranskat)abstract
- An acute bout of exercise increases glucose uptake in skeletal muscle by an insulin-independent mechanism. In the period after exercise, insulin sensitivity to increased glucose uptake is enhanced. The molecular mechanisms underpinning this phenomenon are poorly understood but appear to involve an increased cell surface abundance of GLUT4. While increased proximal insulin signaling does not seem to mediate this effect, elevated phosphorylation of TBC1D4, a downstream target of both insulin (Akt) and exercise (AMPK) signaling, appears to play a role. The main purpose of this study was to determine whether AMPK activation increases skeletal muscle insulin sensitivity. We found that prior AICAR stimulation of wild-type mouse muscle increases insulin sensitivity to stimulate glucose uptake. However, this was not observed in mice with reduced or ablated AMPK activity in skeletal muscle. Furthermore, prior AICAR stimulation enhanced insulin-stimulated phosphorylation of TBC1D4 at Thr649 and Ser711 in wild-type muscle only. These phosphorylation events were positively correlated with glucose uptake. Our results provide evidence to support that AMPK activation is sufficient to increase skeletal muscle insulin sensitivity. Moreover, TBC1D4 phosphorylation may facilitate the effect of prior AMPK activation to enhance glucose uptake in response to insulin.
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| 54. |
- Komai, Ali, 1987, et al.
(författare)
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White Adipocyte Adiponectin Exocytosis Is Stimulated via beta(3)-Adrenergic Signaling and Activation of Epac1: Catecholamine Resistance in Obesity and Type 2 Diabetes
- 2016
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 65:11, s. 3301-3313
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the physiological regulation of adiponectin exocytosis in health and metabolic disease by a combination of membrane capacitance patch-clamp recordings and biochemical measurements of short-term (30-min incubations) adiponectin secretion. Epinephrine or the beta(3)-adrenergic receptor (AR) agonist CL 316,243 (CL) stimulated adiponectin exocytosis/secretion in cultured 3T3-L1 and in primary subcutaneous mouse adipocytes, and the stimulation was inhibited by the Epac (Exchange Protein directly Activated by cAMP) antagonist ESI-09. The beta(3)AR was highly expressed in cultured and primary adipocytes, whereas other ARs were detected at lower levels. 3T3-L1 and primary adipocytes expressed Epac1, whereas Epac2 was undetectable. Adiponectin secretion could not be stimulated by epinephrine or CL in adipocytes isolated from obese/type 2 diabetic mice, whereas the basal (unstimulated) adiponectin release level was elevated twofold. Gene expression of beta(3)AR and Epac1 was reduced in adipocytes from obese animals, and corresponded to a respective similar to 35% and similar to 30% reduction at the protein level. Small interfering RNA-mediated knockdown of beta(3)AR (similar to 60%) and Epac1 (similar to 50%) was associated with abrogated catecholamine-stimulated adiponectin secretion. We propose that adiponectin exocytosis is stimulated via adrenergic signaling pathways mainly involving beta(3)ARs. We further suggest that adrenergically stimulated adiponectin secretion is disturbed in obesity/type 2 diabetes as a result of the reduced expression of beta(3)ARs and Epac1 in a state we define as "catecholamine resistance."
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| 55. |
- Korol, Sergiy V., et al.
(författare)
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GLP-1 and Exendin-4 Transiently Enhance GABA(A) Receptor-Mediated Synaptic and Tonic Currents in Rat Hippocampal CA3 Pyramidal Neurons
- 2015
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 64:1, s. 79-89
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Tidskriftsartikel (refereegranskat)abstract
- GLP-1 is a hormone that stimulates insulin secretion. Receptors for GLP-1 are also found in the brain, including the hippocampus, the centre for memory and learning. Diabetes mellitus is a risk factor for decreased memory functions. We studied effects of GLP-1 and exendin-4, a GLP-1 receptor agonist, on γ-aminobutyric acid (GABA) signaling in hippocampal CA3 pyramidal neurons. GABA is the main inhibitory neurotransmitter and decreases neuronal excitability. GLP-1 (0.01 – 1 nmol/L) transiently enhanced synaptic and tonic currents and the effects were blocked by exendin(9–39). Ten pmol/L GLP-1 increased both the spontaneous inhibitory postsynaptic current (sIPSC) amplitudes and frequency by a factor of 1.8. In 0.1, 1 nmol/L GLP-1 or 10, 50 or 100 nmol/L exendin-4, only the sIPSC frequency increased. The tonic current was enhanced by 0.01 – 1 nmol/L GLP-1 and by 0.5 – 100 nmol/L exendin-4. When action potentials were inhibited by tetrodotoxin (TTX), IPSCs decreased and currents were no longer potentiated by GLP-1 or exendin-4. In contrast, although the tonic current decreased in TTX, it was still enhanced by GLP-1 or exendin-4. The results demonstrate GLP-1 receptor regulation of hippocampal function and are consistent with GLP-1 receptor agonists enhancing GABAA signaling by pre- and postsynaptic mechanisms.
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| 56. |
- Korsgren, Erik, et al.
(författare)
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An Apparent Deficiency of Lymphatic Capillaries in the Islets of Langerhans in the Human Pancreas
- 2016
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 65:4, s. 1004-1008
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Tidskriftsartikel (refereegranskat)abstract
- The lymphatic system is crucial for efficient immune surveillance and for the maintenance of a physiological pressure in the interstitial space. Even so, almost no information is available concerning the lymph drainage of the islets of Langerhans in the human pancreas. lmmunohistochemical staining allowed us to distinguish lymphatic capillaries from blood capillaries. Almost no lymphatic capillaries were found within the islets in pancreatic biopsy specimens from subjects without diabetes or from subjects with type 1 or type 2 diabetes. Lymphatic capillaries were, however, found at the islet exocrine interface, frequently located along blood capillaries and other fibrotic structures within or close to the islet capsule. Lymphatic capillaries were regularly found in the exocrine pancreas, with small lymphatic vessels located close to and around acini. Larger collecting lymphatic vessels were located in fibrotic septa between the exocrine lobules and adjacent to the ductal system of the pancreas. In summary, we report a pronounced deficiency of lymphatic capillaries in human islets, a finding with implications for immune surveillance and the regulation of interstitial fluid transport in the endocrine pancreas as well as for the pathophysiology of both type 1 and type 2 diabetes.
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| 57. |
- Korsgren, Olle
(författare)
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Islet Encapsulation : Physiological Possibilities and Limitations
- 2017
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Ingår i: Diabetes. - : AMER DIABETES ASSOC. - 0012-1797 .- 1939-327X. ; 66:7, s. 1748-1754
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Tidskriftsartikel (refereegranskat)abstract
- A logical cure for type 1 diabetes (T1D) involves replacing the lost insulin-producing cells with new ones, preferably cells from a well-characterized and unlimited source of human insulin-producing cells. This straightforward and simple solution to provide a cure for T1D is immensely attractive but entails at least two inherent and thus far unresolved hurdles: 1) provision of an unlimited source of functional human insulin-producing cells and 2) prevention of rejection without the side effects of systemic immunosuppression. Generation of transplantable insulin-producing cells from human embryonic stem cells or induced pluripotent stem cells is at present close to reality, and we are currently awaiting the first clinical studies. Focus is now directed to foster development of novel means to control the immune system to enable large-scale clinical application. Encapsulation introduces a physical barrier that prevents access of immune cells to the transplanted cells but also hinders blood vessel ingrowth. Therefore, oxygen, nutrient, and hormonal passage over the encapsulation membrane is solely dependent on diffusion over the immune barrier, contributing to delays in glucose sensing and insulin secretion kinetics. This Perspective focuses on the physiological possibilities and limitations of an encapsulation strategy to establish near-normoglycemia in subjects with T1D, assuming that glucose-responsive insulin-producing cells are available for transplantation.
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| 58. |
- Krischer, Jeffrey P., et al.
(författare)
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The Influence of Type 1 Diabetes Genetic Susceptibility Regions, Age, Sex, and Family History to the Progression from Multiple Autoantibodies to Type 1 Diabetes:A TEDDY Study Report : A TEDDY Study Report
- 2017
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 66:12, s. 3122-3129
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Tidskriftsartikel (refereegranskat)abstract
- This paper seeks to determine whether factors related to autoimmunity risk remain significant after the initiation of two or more diabetes-related autoantibodies and continue to contribute to T1D risk among autoantibody positive children in The Environmental Determinants of Diabetes in the Young (TEDDY) study. Characteristics included are age at multiple autoantibody positivity, sex, selected high-risk HLA-DR-DQ genotypes, relationship to a family member with T1D, autoantibody at seroconversion, INS gene (rs1004446_A), and non-HLA gene polymorphisms identified by the Type 1 Diabetes Genetics Consortium. The risk of progression to T1D was not different among those with or without a family history of T1D (p=0.39) nor HLA-DR-DQ genotypes (p=0.74). Age at developing multiple autoantibodies (HR=0.96 per 1 month increase in age, 95% CI=0.95, 0.97, p<0.001) and the type of first autoantibody (when more than a single autoantibody was the first appearing indication of seroconversion [p=0.006]) were statistically significant. Female sex was also a significant risk factor (p=0.03). Three SNPs were associated with increased diabetes risk (rs10517086_A, [p=0.03], rs1534422_G, [p=0.006], and rs2327832_G in TNFAIP3 [p=0.03]), and one with decreased risk (rs1004446_A in INS, [p=0.006]). The TEDDY data suggest that non-HLA gene polymorphisms may play a different role in the initiation of autoimmunity than they do in progression to T1D once autoimmunity has appeared. The strength of these associations may be related to the age of the population and the high-risk HLA-DR-DQ subtypes studied.
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| 59. |
- Kroeger, Janine, et al.
(författare)
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Circulating Fetuin-A and Risk of Type 2 Diabetes : A Mendelian Randomization Analysis
- 2018
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 67:6, s. 1200-1205
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Tidskriftsartikel (refereegranskat)abstract
- Fetuin-A, a hepatic-origin protein, is strongly positively associated with risk of type 2 diabetes in human observational studies, but it is unknown whether this association is causal. Weaimed to study the potential causal relation of circulating fetuin-A to risk of type 2 diabetes in a Mendelian randomization study with single nucleotide polymorphisms located in the fetuin-A-encoding AHSG gene. We used data from eight European countries of the European Prospective Investigation into Cancer and Nutrition (EPIC)-InterAct case-cohort study including 10,020 incident cases. Plasma fetuin-A concentration was measured in a subset of 965 subcohort participants and 654 case subjects. A genetic score of the AHSG single nucleotide polymorphisms was strongly associated with fetuin-A (28% explained variation). Using the genetic score as instrumental variable of fetuin-A, we observed no significant association of a 50 mu g/mL higher fetuin-A concentration with diabetes risk (hazard ratio 1.02 [95% CI 0.97, 1.07]). Combining our results with those from the DIAbetes Genetics Replication And Meta-analysis (DIAGRAM) consortium (12,171 case subjects) also did not suggest a clear significant relation of fetuin-A with diabetes risk. In conclusion, although there is mechanistic evidence for an effect of fetuin-A on insulin sensitivity and secretion, this study does not support a strong, relevant relationship between circulating fetuin-A and diabetes risk in the general population.
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| 60. |
- Krogvold, Lars, et al.
(författare)
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Detection of a low-grade enteroviral infection in the islets of Langerhans of living patients newly diagnosed with type 1 diabetes
- 2015
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 64:5, s. 1682-1687
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Tidskriftsartikel (refereegranskat)abstract
- The Diabetes Virus Detection study (DiViD) is the first to examine fresh pancreatic tissue at the diagnosis of type 1 diabetes for the presence of viruses. Minimal pancreatic tail resection was performed 3-9 weeks after onset of type 1 diabetes in 6 adult patients (age 24-35 years). The presence of enteroviral capsid protein 1 (VP1) and the expression of class I HLA were investigated by immunohistochemistry. Enterovirus RNA was analyzed from isolated pancreatic islets and from fresh frozen whole pancreatic tissue using PCR and sequencing. Non-diabetic organ donors served as controls. VP1 was detected in the islets of all type 1 diabetes patients (2 of 9 controls). Hyperexpression of class I HLA molecules was found in the islets of all patients (1 of 9 controls). Enterovirus specific RNA sequences were detected in 4 of 6 cases (0 of 6 controls). The results were confirmed in different laboratories. Only 1.7 % of the islets contained VP1 positive cells and the amount of enterovirus RNA was low. The results provides evidence for the presence of enterovirus in pancreatic islets of type 1 diabetic patients, being consistent with the possibility that a low grade enteroviral infection in the pancreatic islets contribute to disease progression in humans.
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