| 1. |
- Esguerra, Jonathan L.S., et al.
(författare)
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Glucocorticoid induces human beta cell dysfunction by involving riborepressor GAS5 LincRNA
- 2020
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Ingår i: Molecular Metabolism. - : Elsevier BV. - 2212-8778. ; 32, s. 160-167
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Tidskriftsartikel (refereegranskat)abstract
- Objective: A widely recognized metabolic side effect of glucocorticoid (GC) therapy is steroid-induced diabetes mellitus (DM). However, studies on the molecular basis of GC-induced pancreatic beta cell dysfunction in human beta cells are lacking. The significance of non-coding RNAs in various cellular processes is emerging. In this study, we aimed to show the direct negative impact of GC on beta cell function and elucidate the role of riborepressor GAS5 lincRNA in the GC signaling pathway in human pancreatic beta cells. Methods: Patients undergoing two weeks of high-dose prednisolone therapy were monitored for C-peptide levels. Human pancreatic islets and the human beta cell line EndoC-βH1 were incubated in pharmacological concentrations of dexamethasone. The GAS5 level was modulated using anti-sense LNA gapmeR or short oligonucleotides with GAS5 HREM (hormone response element motif). Immunoblotting and/or real-time PCR were used to assess changes in protein and RNA expression, respectively. Functional characterization included glucose-stimulated insulin secretion and apoptosis assays. Correlation analysis was performed on RNAseq data of human pancreatic islets. Results: We found reduced C-peptide levels in patients undergoing high-dose GC therapy. Human islets and the human beta cell line EndoC-βH1 exposed to GC exhibited reduced insulin secretion and increased apoptosis. Concomitantly, reduced expression of important beta cell transcription factors, PDX1 and NKX6-1, as well as exocytotic protein SYT13 were observed. The expression of the glucocorticoid receptor was decreased, while that of serum and glucocorticoid-regulated kinase 1 (SGK1) was elevated. The expression of these genes was found to significantly correlate with GAS5 in human islet transcriptomics data. Increasing GAS5 levels using GAS5 HREM alleviated the inhibitory effects of dexamethasone on insulin secretion. Conclusions: The direct adverse effect of glucocorticoid in human beta cell function is mediated via important beta cell proteins and components of the GC signaling pathway in an intricate interplay with GAS5 lincRNA, a potentially novel therapeutic target to counter GC-mediated beta cell dysfunction.
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| 2. |
- Nagao, Mototsugu, et al.
(författare)
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Diagnostic potential of miR-483 family for IGF-II producing non-islet cell tumor hypoglycemia
- 2021
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Ingår i: European Journal of Endocrinology. - 1479-683X. ; 184:1, s. 41-49
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Tidskriftsartikel (refereegranskat)abstract
- Objective: In insulin-like growth factor II (IGF-II) producing non-islet cell tumor hypoglycemia (NICTH), high molecular weight forms of IGF-II (big IGF-II) are produced as a cause of spontaneous hypoglycemia. MicroRNA (miRNA)-483 family, encoded in an intron lesion of IGF2 gene, is suggested to be co-expressed with IGF-II. Here, we tested whether serum miR-483-5p and -3p levels are associated with the presence of big IGF-II in NICTH. Design: Serum samples from patients who were suspected to have IGF-II producing NICTH (n = 42) were tested. MiR-483-5p and -3p levels were evaluated using quantitative PCR. IGF-II level was analyzed using ELISA. The presence of big IGF-II was identified by Western blotting. Results: Big IGF-II was detected in the sera of 32 patients. MiR-483-5p (P = 0.0015) and -3p (P = 0.027) levels were significantly higher in sera with big IGF-II (n = 32) than in those without (n = 10), whereas serum IGF-II level (P = 0.055) was not significantly different between the groups. The median serum concentration of miR-483-5p was ~10 times higher than that of miR-483-3p. Although a strong correlation was observed between the two miRNAs (r = 0.844, P < 0.0001), but neither of which was correlated with serum IGF-II level. The areas under the receiver operating characteristic curves of miR-483-5p (0.853) and -3p (0.722) were higher than that of IGF-II (0.694) for detecting the presence of big IGF-II. Conclusion: The associations of serum miR-483-5p and -3p levels with the presence of big IGF-II suggest the diagnostic potential of these miRNAs for IGF-II producing NICTH.
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| 3. |
- Nagao, Mototsugu, et al.
(författare)
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Potential Protection Against Type 2 Diabetes in Obesity Through Lower CD36 Expression and Improved Exocytosis in β-Cells
- 2020
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 69:6, s. 1193-1205
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is a risk factor for type 2 diabetes (T2D); however, not all obese individuals develop the disease. In this study, we aimed to investigate the cause of differential insulin secretion capacity of pancreatic islets from donors with T2D and non-T2D (ND), especially obese donors (BMI ≥30 kg/m2). Islets from obese donors with T2D had reduced insulin secretion, decreased β-cell exocytosis, and higher expression of fatty acid translocase CD36. We tested the hypothesis that CD36 is a key molecule in the reduced insulin secretion capacity. Indeed, CD36 overexpression led to decreased insulin secretion, impaired exocytosis, and reduced granule docking. This was accompanied by reduced expression of the exocytotic proteins SNAP25, STXBP1, and VAMP2, likely because CD36 induced downregulation of the insulin receptor substrate (IRS) proteins, suppressed the insulin-signaling phosphatidylinositol 3-kinase/AKT pathway, and increased nuclear localization of the transcription factor FoxO1. CD36 antibody treatment of the human β-cell line EndoC-βH1 increased IRS1 and exocytotic protein levels, improved granule docking, and enhanced insulin secretion. Our results demonstrate that β-cells from obese donors with T2D have dysfunctional exocytosis likely due to an abnormal lipid handling represented by differential CD36 expression. Hence, CD36 could be a key molecule to limit β-cell function in T2D associated with obesity.
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| 4. |
- Nagao, Mototsugu, et al.
(författare)
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Selectively Bred Diabetes Models : GK Rats, NSY Mice, and ON Mice
- 2020
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Ingår i: Animal Models of Diabetes. Methods in Molecular Biology. - New York, NY : Springer US. - 1940-6029. - 9781071603857 - 9781071603840 ; 2128, s. 25-54
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Bokkapitel (refereegranskat)abstract
- The polygenic background of selectively bred diabetes models mimics the etiology of type 2 diabetes. So far, three different rodent models (Goto-Kakizaki rats, Nagoya-Shibata-Yasuda mice, and Oikawa-Nagao mice) have been established in the diabetes research field by continuous selective breeding for glucose tolerance from outbred rodent stocks. The origin of hyperglycemia in these rodents is mainly insulin secretion deficiency from the pancreatic β-cells and mild insulin resistance in insulin target organs. In this chapter, we summarize backgrounds and phenotypes of these rodent models to highlight their importance in diabetes research. Then, we introduce experimental methodologies to evaluate β-cell exocytosis as a putative common defect observed in these rodent models.
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