| 1. |
- Nagorny, Cecilia, et al.
(author)
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Distribution of melatonin receptors in murine pancreatic islets.
- 2011
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In: Journal of Pineal Research. - 1600-079X. ; 50, s. 412-417
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Journal article (peer-reviewed)abstract
- Melatonin has multiple receptor-dependent and receptor-independent functions. At the cell membrane, melatonin interacts with its receptors MT1 and MT2, which are expressed in numerous tissues. Genome-wide association studies have recently shown that the MTNR1B/MT2 receptor may be involved in the pathogenesis of type 2 diabetes mellitus. In line with these findings, expression of melatonin receptors has been shown in mouse, rat, and human pancreatic islets. MT1 and MT2 are G-protein-coupled receptors and are proposed to exert inhibitory effects on insulin secretion. Here, we show by immunocytochemistry that these membrane melatonin receptors have distinct locations in the mouse islet. MT1 is expressed in α-cells while MT2 is located to the β-cells. These findings help to unravel the complex machinery underlying melatonin's role in the regulation of islet function.
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| 2. |
- Axelsson, Annika S., et al.
(author)
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Sulforaphane reduces hepatic glucose production and improves glucose control in patients with type 2 diabetes
- 2017
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In: Science Translational Medicine. - : American Association for the Advancement of Science (AAAS). - 1946-6234 .- 1946-6242. ; 9:394
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Journal article (peer-reviewed)abstract
- A potentially useful approach for drug discovery is to connect gene expression profiles of disease-affected tissues ("disease signatures") to drug signatures, but it remains to be shown whether it can be used to identify clinically relevant treatment options. We analyzed coexpression networks and genetic data to identify a disease signature for type 2 diabetes in liver tissue. By interrogating a library of 3800 drug signatures, we identified sulforaphane as a compound that may reverse the disease signature. Sulforaphane suppressed glucose production from hepatic cells by nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2) and decreased expression of key enzymes in gluconeogenesis. Moreover, sulforaphane reversed the disease signature in the livers from diabetic animals and attenuated exaggerated glucose production and glucose intolerance by a magnitude similar to that of metformin. Finally, sulforaphane, provided as concentrated broccoli sprout extract, reduced fasting blood glucose and glycated hemoglobin (HbA1c) in obese patients with dysregulated type 2 diabetes.
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| 3. |
- Kalamajski, Sebastian, et al.
(author)
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Genomic editing of metformin efficacy-associated genetic variants in SLC47A1 does not alter SLC47A1 expression
- 2022
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In: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 31:4, s. 491-498
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Journal article (peer-reviewed)abstract
- Several pharmacogenetics studies have identified an association between a greater metformin-dependent reduction in HbA1c levels and the minor A allele at rs2289669 in intron 10 of SLC47A1, encoding multidrug and toxin extrusion 1 (MATE1), a presumed metformin transporter. It is currently unknown if the rs2289669 locus is a cis-eQTL, which would validate its role as predictor of metformin efficacy. We looked at association between common genetic variants in the SLC47A1 gene region and HbA1c reduction after metformin treatment using locus-wise meta-analysis from the MetGen consortium. CRISPR-Cas9 was applied to perform allele editing of, or genomic deletion around, rs2289669 and of the closely linked rs8065082 in HepG2 cells. The genome-edited cells were evaluated for SLC47A1 expression and splicing. None of the common variants including rs2289669 showed significant association with metformin response. Genomic editing of either rs2289669 or rs8065082 did not alter SLC47A1 expression or splicing. Experimental and in silico analyses show that the rs2289669-containing haploblock does not appear to carry genetic variants that could explain its previously reported association with metformin efficacy.
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| 4. |
- Kumar, Parveen, et al.
(author)
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The transcriptional co-repressor myeloid translocation gene 16 inhibits glycolysis and stimulates mitochondrial respiration.
- 2013
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:7
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Journal article (peer-reviewed)abstract
- The myeloid translocation gene 16 product MTG16 is found in multiple transcription factor-containing complexes as a regulator of gene expression implicated in development and tumorigenesis. A stable Tet-On system for doxycycline-dependent expression of MTG16 was established in B-lymphoblastoid Raji cells to unravel its molecular functions in transformed cells. A noticeable finding was that expression of certain genes involved in tumor cell metabolism including 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 and 4 (PFKFB3 and PFKFB4), and pyruvate dehydrogenase kinase isoenzyme 1 (PDK1) was rapidly diminished when MTG16 was expressed. Furthermore, hypoxia-stimulated production of PFKFB3, PFKFB4 and PDK1 was inhibited by MTG16 expression. The genes in question encode key regulators of glycolysis and its coupling to mitochondrial metabolism and are commonly found to be overexpressed in transformed cells. The MTG16 Nervy Homology Region 2 (NHR2) oligomerization domain and the NHR3 protein-protein interaction domain were required intact for inhibition of PFKFB3, PFKFB4 and PDK1 expression to occur. Expression of MTG16 reduced glycolytic metabolism while mitochondrial respiration and formation of reactive oxygen species increased. The metabolic changes were paralleled by increased phosphorylation of mitogen-activated protein kinases, reduced levels of amino acids and inhibition of proliferation with a decreased fraction of cells in S-phase. Overall, our findings show that MTG16 can serve as a brake on glycolysis, a stimulator of mitochondrial respiration and an inhibitor of cell proliferation. Hence, elevation of MTG16 might have anti-tumor effect.
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| 5. |
- Stenson, Lena, et al.
(author)
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Molecular cloning, genomic organization, and expression of a testicular isoform of hormone-sensitive lipase
- 1996
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In: Genomics. - : Elsevier BV. - 1089-8646 .- 0888-7543. ; 35:3, s. 441-447
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Journal article (peer-reviewed)abstract
- By catalyzing the rate-limiting step in adipose tissue lipolysis, hormone-sensitive lipase (HSL) is an important regulator of energy homeostasis. The role and importance of HSL in tissues other than adipose are poorly understood. We report here the cloning and expression of a testicular isoform, designated HSLtes. Due to an addition of amino acids at the NH2-termini, rat and human HSLtes consist of 1068 and 1076 amino acids, respectively, compared to the 768 and 775 amino acids, respectively, of the adipocyte isoform (HSLadi). A novel exon of 1.2 kb, encoding the human testis-specific amino acids, was isolated and mapped to the HSL gene, 16 kb upstream of the exons encoding HSLadi. The transcribed mRNA of 3.9 kb was specifically expressed in testis. No significant similarity with other known proteins was found for the testis-specific sequence. The amino acid composition differs from the HSLadi sequence, with a notable hydrophilic character and a high content of prolines and glutamines. COS cells, transfected by the 3.9-kb human testis cDNA, expressed a protein of the expected molecular mass (M(r) approximately 120,000) that exhibited catalytic activity similar to that of HSLadi. Immunocytochemistry localized HSL to elongating spermatids and spermatozoa; HSL was not detected in interstitial cells.
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| 6. |
- Adam, Julie, et al.
(author)
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Fumarate Hydratase Deletion in Pancreatic β Cells Leads to Progressive Diabetes
- 2017
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In: Cell Reports. - : Elsevier BV. - 2211-1247. ; 20:13, s. 3135-3148
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Journal article (peer-reviewed)abstract
- We explored the role of the Krebs cycle enzyme fumarate hydratase (FH) in glucose-stimulated insulin secretion (GSIS). Mice lacking Fh1 in pancreatic β cells (Fh1βKO mice) appear normal for 6–8 weeks but then develop progressive glucose intolerance and diabetes. Glucose tolerance is rescued by expression of mitochondrial or cytosolic FH but not by deletion of Hif1α or Nrf2. Progressive hyperglycemia in Fh1βKO mice led to dysregulated metabolism in β cells, a decrease in glucose-induced ATP production, electrical activity, cytoplasmic [Ca2+]i elevation, and GSIS. Fh1 loss resulted in elevated intracellular fumarate, promoting succination of critical cysteines in GAPDH, GMPR, and PARK 7/DJ-1 and cytoplasmic acidification. Intracellular fumarate levels were increased in islets exposed to high glucose and in islets from human donors with type 2 diabetes (T2D). The impaired GSIS in islets from diabetic Fh1βKO mice was ameliorated after culture under normoglycemic conditions. These studies highlight the role of FH and dysregulated mitochondrial metabolism in T2D. Adam et al. have shown that progressive diabetes develops if fumarate hydratase is deleted in mouse pancreatic β cells. Such β cells exhibit elevated fumarate and protein succination and show progressively reduced ATP production and insulin secretion. The depleted insulin response to glucose recovers when diabetic islets are cultured in reduced glucose.
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| 7. |
- Ahlqvist, Emma, et al.
(author)
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Novel subgroups of adult-onset diabetes and their association with outcomes : a data-driven cluster analysis of six variables
- 2018
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In: The Lancet Diabetes and Endocrinology. - 2213-8587 .- 2213-8595. ; 6:5, s. 361-369
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Journal article (peer-reviewed)abstract
- BackgroundDiabetes is presently classified into two main forms, type 1 and type 2 diabetes, but type 2 diabetes in particular is highly heterogeneous. A refined classification could provide a powerful tool to individualise treatment regimens and identify individuals with increased risk of complications at diagnosis.MethodsWe did data-driven cluster analysis (k-means and hierarchical clustering) in patients with newly diagnosed diabetes (n=8980) from the Swedish All New Diabetics in Scania cohort. Clusters were based on six variables (glutamate decarboxylase antibodies, age at diagnosis, BMI, HbA1c, and homoeostatic model assessment 2 estimates of β-cell function and insulin resistance), and were related to prospective data from patient records on development of complications and prescription of medication. Replication was done in three independent cohorts: the Scania Diabetes Registry (n=1466), All New Diabetics in Uppsala (n=844), and Diabetes Registry Vaasa (n=3485). Cox regression and logistic regression were used to compare time to medication, time to reaching the treatment goal, and risk of diabetic complications and genetic associations.FindingsWe identified five replicable clusters of patients with diabetes, which had significantly different patient characteristics and risk of diabetic complications. In particular, individuals in cluster 3 (most resistant to insulin) had significantly higher risk of diabetic kidney disease than individuals in clusters 4 and 5, but had been prescribed similar diabetes treatment. Cluster 2 (insulin deficient) had the highest risk of retinopathy. In support of the clustering, genetic associations in the clusters differed from those seen in traditional type 2 diabetes.InterpretationWe stratified patients into five subgroups with differing disease progression and risk of diabetic complications. This new substratification might eventually help to tailor and target early treatment to patients who would benefit most, thereby representing a first step towards precision medicine in diabetes.
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| 8. |
- Alonso, Lorena, et al.
(author)
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TIGER : The gene expression regulatory variation landscape of human pancreatic islets
- 2021
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In: Cell Reports. - : Elsevier BV. - 2211-1247. ; 37:2
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Journal article (peer-reviewed)abstract
- Genome-wide association studies (GWASs) identified hundreds of signals associated with type 2 diabetes (T2D). To gain insight into their underlying molecular mechanisms, we have created the translational human pancreatic islet genotype tissue-expression resource (TIGER), aggregating >500 human islet genomic datasets from five cohorts in the Horizon 2020 consortium T2DSystems. We impute genotypes using four reference panels and meta-analyze cohorts to improve the coverage of expression quantitative trait loci (eQTL) and develop a method to combine allele-specific expression across samples (cASE). We identify >1 million islet eQTLs, 53 of which colocalize with T2D signals. Among them, a low-frequency allele that reduces T2D risk by half increases CCND2 expression. We identify eight cASE colocalizations, among which we found a T2D-associated SLC30A8 variant. We make all data available through the TIGER portal (http://tiger.bsc.es), which represents a comprehensive human islet genomic data resource to elucidate how genetic variation affects islet function and translates into therapeutic insight and precision medicine for T2D.
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| 9. |
- Andersson, Lotta, et al.
(author)
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Characterization of Stimulus-Secretion Coupling in the Human Pancreatic EndoC-βH1 Beta Cell Line.
- 2015
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:3
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Journal article (peer-reviewed)abstract
- Studies on beta cell metabolism are often conducted in rodent beta cell lines due to the lack of stable human beta cell lines. Recently, a human cell line, EndoC-βH1, was generated. Here we investigate stimulus-secretion coupling in this cell line, and compare it with that in the rat beta cell line, INS-1 832/13, and human islets.
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| 10. |
- Andersson, Lotta E., et al.
(author)
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Glutamine-elicited secretion of glucagon-like peptide 1 is governed by an activated glutamate dehydrogenase
- 2018
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In: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 67:3, s. 372-384
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Journal article (peer-reviewed)abstract
- Glucagon-like peptide 1 (GLP-1), secreted from intestinal L cells, glucose dependently stimulates insulin secretion from β-cells. This glucose dependence prevents hypoglycemia, rendering GLP-1 analogs a useful and safe treatment modality in type 2 diabetes. Although the amino acid glutamine is a potent elicitor of GLP-1 secretion, the responsible mechanism remains unclear. We investigated how GLP-1 secretion is metabolically coupled in L cells (GLUTag) and in vivo inmice using the insulin-secreting cell line INS-1 832/13 as reference. A membrane-permeable glutamate analog (dimethylglutamate [DMG]), acting downstream of electrogenic transporters, elicited similar alterations in metabolism as glutamine in both cell lines. Both DMG and glutamine alone elicited GLP-1 secretion in GLUTag cells and in vivo, whereas activation of glutamate dehydrogenase (GDH) was required to stimulate insulin secretion from INS-1 832/13 cells. Pharmacological inhibition in vivo of GDH blocked secretion of GLP-1 in response to DMG. In conclusion, our results suggest that nonelectrogenic nutrient uptake and metabolism play an important role in L cell stimulus-secretion coupling. Metabolism of glutamine and related analogs by GDH in the L cell may explain why GLP-1 secretion, but not that of insulin, is activated by these secretagogues in vivo.
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