| 1. |
- Davegårdh, Cajsa, et al.
(författare)
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VPS39-deficiency observed in type 2 diabetes impairs muscle stem cell differentiation via altered autophagy and epigenetics
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Insulin resistance and lower muscle quality (strength divided by mass) are hallmarks of type 2 diabetes (T2D). Here, we explore whether alterations in muscle stem cells (myoblasts) from individuals with T2D contribute to these phenotypes. We identify VPS39 as an important regulator of myoblast differentiation and muscle glucose uptake, and VPS39 is downregulated in myoblasts and myotubes from individuals with T2D. We discover a pathway connecting VPS39-deficiency in human myoblasts to impaired autophagy, abnormal epigenetic reprogramming, dysregulation of myogenic regulators, and perturbed differentiation. VPS39 knockdown in human myoblasts has profound effects on autophagic flux, insulin signaling, epigenetic enzymes, DNA methylation and expression of myogenic regulators, and gene sets related to the cell cycle, muscle structure and apoptosis. These data mimic what is observed in myoblasts from individuals with T2D. Furthermore, the muscle of Vps39(+/-) mice display reduced glucose uptake and altered expression of genes regulating autophagy, epigenetic programming, and myogenesis. Overall, VPS39-deficiency contributes to impaired muscle differentiation and reduced glucose uptake. VPS39 thereby offers a therapeutic target for T2D. Insulin resistance and lower muscle strength in relation to mass are hallmarks of type 2 diabetes. Here, the authors report alterations in muscle stem cells from individuals with type 2 diabetes that may contribute to these phenotypes through VPS39 mediated effects on autophagy and epigenetics.
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| 2. |
- Hansson, Björn, et al.
(författare)
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Rosiglitazone drives cavin-2/SDPR expression in adipocytes in a CEBPα-dependent manner
- 2017
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Caveolae are abundant adipocyte surface domains involved in insulin signaling, membrane trafficking and lipid homeostasis. Transcriptional control mechanisms for caveolins and cavins, the building blocks of caveolae, are thus arguably important for adipocyte biology and studies in this area may give insight into insulin resistance and diabetes. Here we addressed the hypothesis that one of the less characterized caveolar components, cavin-2 (SDPR), is controlled by CCAAT/Enhancer Binding Protein (CEBPα) and Peroxisome Proliferator- Activated Receptor Gamma (PPARG). Using human mRNA expression data we found that SDPR correlated with PPARG in several tissues. This was also observed during differentiation of 3T3-L1 fibroblasts into adipocytes. Treatment of 3T3-L1-derived adipocytes with the PPARγ-activator Rosiglitazone increased SDPR and CEBPα expression at both the mRNA and protein levels. Silencing of CEBPα antagonized these effects. Further, adenoviral expression of PPARγ/CEBPα or Rosiglitazone-treatment increased SDPR expression in primary rat adipocytes. The myocardin family coactivator MKL1 was recently shown to regulate SDPR expression in human coronary artery smooth muscle cells. However, we found that actin depolymerization, known to inhibit MKL1 and MKL2, was without effect on SDPR mRNA levels in adipocytes, even though overexpression of MKL1 and MKL2 had the capacity to increase caveolins and cavins and to repress PPARγ/CEBPα. Altogether, this work demonstrates that CEBPα expression and PPARγ-activity promote SDPR transcription and further supports the emerging notion that PPARγ/CEBPα and MKL1/MKL2 are antagonistic in adipocytes.
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| 3. |
- Henriksson, Emma, et al.
(författare)
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SIK2 regulates CRTCs, HDAC4 and glucose uptake in adipocytes
- 2015
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Ingår i: Journal of Cell Science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 128:3, s. 472-486
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Tidskriftsartikel (refereegranskat)abstract
- Salt-inducible kinase 2 (SIK2) is an AMP-activated protein kinase (AMPK) related kinase abundantly expressed in adipose tissue. Our aim was to identify molecular targets and functions of SIK2 in adipocytes, and to address the role of PKA-mediated phosphorylation of SIK2 on Ser358. Modulation of SIK2 in adipocytes resulted in altered phosphorylation of CREB-regulated transcription co-activator 2 (CRTC2), CRTC3 and class IIa histone deacetylase 4 (HDAC4). Furthermore, CRTC2, CRTC3, HDAC4 and protein phosphatase 2A (PP2A) interacted with SIK2, and the binding of CRTCs and PP2A to wild-type but not Ser358Ala SIK2, was reduced by cAMP elevation. Silencing of SIK2 resulted in reduced GLUT4 (also known as SLC2A4) protein levels, whereas cells treated with CRTC2 or HDAC4 siRNA displayed increased levels of GLUT4. Overexpression or pharmacological inhibition of SIK2 resulted in increased and decreased glucose uptake, respectively. We also describe a SIK2-CRTC2-HDAC4 pathway and its regulation in human adipocytes, strengthening the physiological relevance of our findings. Collectively, we demonstrate that SIK2 acts directly on CRTC2, CRTC3 and HDAC4, and that the cAMP-PKA pathway reduces the interaction of SIK2 with CRTCs and PP2A. Downstream, SIK2 increases GLUT4 levels and glucose uptake in adipocytes.
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| 4. |
- Kopietz, Franziska, et al.
(författare)
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AMPK activation by A-769662 and 991 does not affect catecholamine-induced lipolysis in human adipocytes
- 2018
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Ingår i: American Journal of Physiology - Endocrinology and Metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 315:5, s. 1075-1085
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Tidskriftsartikel (refereegranskat)abstract
- Activation of AMP-activated protein kinase (AMPK) is considered an attractive strategy for the treatment of type 2 diabetes. Favorable metabolic effects of AMPK activation are mainly observed in skeletal muscle and liver tissue whereas the effects in human adipose tissue are only poorly understood. Previous studies, which largely employed the AMPK activator 5-aminoimidazole-4-carboxamide-1-D-ribofuranoside (AICAR), suggest an anti-lipolytic role of AMPK in adipocytes. The aim of this work was to re-investigate the role of AMPK in the regulation of lipolysis, using the novel allosteric small-molecule AMPK activators A-769662 and 991, with a focus on human adipocytes. For this purpose, human primary subcutaneous adipocytes were treated with A-769662, 991 or AICAR, as a control, before being stimulated with isoproterenol. AMPK activity status, glycerol release and the phosphorylation of hormone-sensitive lipase (HSL), a key regulator of lipolysis, was then monitored. Our results show that both A-769662 and 991 activated AMPK to a level which was similar to, or greater than that induced by AICAR. In contrast to AICAR, which as expected was anti-lipolytic, neither A-769662 nor 991 affected lipolysis in human adipocytes, although 991 treatment lead to altered HSL phosphorylation. Furthermore, we suggest that HSL Ser660 is an important regulator of lipolytic activity in human adipocytes. These data suggest that the anti-lipolytic effect observed with AICAR in previous studies is, at least to some extent, AMPK-independent.
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| 5. |
- Kopietz, Franziska, et al.
(författare)
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Inhibition of AMPK activity in response to insulin in adipocytes : involvement of AMPK pS485, PDEs, and cellular energy levels
- 2020
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Ingår i: American Journal of Physiology - Endocrinology and Metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 319:3, s. 459-471
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Tidskriftsartikel (refereegranskat)abstract
- Insulin resistance in obesity and type 2 diabetes has been shown to be associated with decreased de novo fatty acid (FA) synthesis in adipose tissue. It is known that insulin can acutely stimulate FA synthesis in adipocytes; however, the mechanisms underlying this effect are unclear. The rate-limiting step in FA synthesis is catalyzed by acetyl-CoA carboxylase (ACC), known to be regulated through inhibitory phosphorylation at S79 by the AMP-activated protein kinase (AMPK). Previous results from our laboratory showed an inhibition of AMPK activity by insulin, which was accompanied by PKB-dependent phosphorylation of AMPK at S485. However, whether the S485 phosphorylation is required for insulin-induced inhibition of AMPK or other mechanisms underlie the reduced kinase activity is not known. To investigate this, primary rat adipocytes were transduced with a recombinant adenovirus encoding AMPK-WT or a nonphosphorylatable AMPK S485A mutant. AMPK activity measurements by Western blot analysis and in vitro kinase assay revealed that WT and S485A AMPK were inhibited to a similar degree by insulin, indicating that AMPK S485 phosphorylation is not required for insulin-induced AMPK inhibition. Further analysis suggested an involvement of decreased AMP-to-ATP ratios in the insulin-induced inhibition of AMPK activity, whereas a possible contribution of phosphodiesterases was excluded. Furthermore, we show that insulin-induced AMPK S485 phosphorylation also occurs in human adipocytes, suggesting it to be of an importance yet to be revealed. Altogether, this study increases our understanding of how insulin regulates AMPK activity, and with that, FA synthesis, in adipose tissue.
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| 6. |
- Ling, Charlotte, et al.
(författare)
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Epigenetic epidemiology and alterations in type 2 diabetes and obesity
- 2022
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Ingår i: Epigenetic epidemiology. - Cham : Springer International Publishing. - 9783030944759 - 9783030944742 ; , s. 445-474
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- ype 2 diabetes (T2D) and obesity are multifactorial and polygenic metabolic diseases. Combinations of genetic and non-genetic risk factors such as risk SNPs, age, unhealthy diets, and physical inactivity increase the risk for these diseases. Emerging data also support a key role for epigenetic mechanisms in the pathogenesis of T2D and obesity. In this chapter, we summarize current knowledge of epigenetic alterations found in individuals with T2D and obesity. We present studies performed in blood, as well as human tissues important for metabolism, i.e., adipose tissue, skeletal muscle, liver, and pancreatic islets. These studies have found differential DNA methylation associated with both T2D and obesity. Although some studies exist, there is still limited information regarding histone modifications in human tissues linked to metabolic diseases. We finally explore how epigenetic mechanisms may be targeted by epigenetic editing and inhibitors of epigenetic enzymes for future therapies and precision medicine in T2D and obesity.
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| 7. |
- Negoita, Florentina, et al.
(författare)
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JUP/plakoglobin is regulated by salt-inducible kinase 2, and is required for insulin-induced signalling and glucose uptake in adipocytes
- 2020
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Ingår i: Cellular Signalling. - : Elsevier BV. - 1873-3913 .- 0898-6568. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Salt-inducible kinase 2 (SIK2) is abundant in adipocytes, but downregulated in adipose tissue from individuals with obesity and insulin resistance. Moreover, SIK isoforms are required for normal insulin signalling and glucose uptake in adipocytes, but the underlying molecular mechanisms are currently not known. The adherens junction protein JUP, also termed plakoglobin or γ-catenin, has recently been reported to promote insulin signalling in muscle cells.OBJECTIVE: The objective of this study was to analyse if JUP is required for insulin signalling in adipocytes and the underlying molecular mechanisms of this regulation.METHODS: Co-expression of SIK2 and JUP mRNA levels in adipose tissue from a human cohort was analysed. siRNA silencing and/or pharmacological inhibition of SIK2, JUP, class IIa HDACs and CRTC2 was employed in 3T3-L1- and primary rat adipocytes. JUP protein expression was analysed by western blot and mRNA levels by qPCR. Insulin signalling was evaluated by western blot as levels of phosphorylated PKB/Akt and AS160, and by monitoring the uptake of 3H-2-deoxyglucose.RESULTS: mRNA expression of SIK2 correlated with that of JUP in human adipose tissue. SIK2 inhibition or silencing resulted in downregulation of JUP mRNA and protein expression in 3T3-L1- and in primary rat adipocytes. Moreover, JUP silencing reduced the expression of PKB and the downstream substrate AS160, and consequently attenuated activity in the insulin signalling pathway, including insulin-induced glucose uptake. The known SIK2 substrates CRTC2 and class IIa HDACs were found to play a role in the SIK-mediated regulation of JUP expression.CONCLUSIONS: These findings identify JUP as a novel player in the regulation of insulin sensitivity in adipocytes, and suggest that changes in JUP expression could contribute to the effect of SIK2 on insulin signalling in these cells.
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| 8. |
- Negoita, Florentina, et al.
(författare)
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Salt-inducible kinase 2 regulates TFEB and is required for autophagic flux in adipocytes
- 2019
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 0006-291X. ; 508:3, s. 775-779
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Tidskriftsartikel (refereegranskat)abstract
- Dysregulation of autophagy has been observed in obesity and type 2 diabetes. Salt-inducible kinase 2 (SIK2), a member of the AMPK-related kinase family, is downregulated in adipocytes from obese or insulin resistant individuals and was previously demonstrated to regulate autophagy in cancer and normal cell lines. The aim of this study was thus to investigate a potential role of SIK2 in the regulation of adipocyte autophagy. To do so, SIK2 siRNA silencing or SIKs pharmacological inhibition of SIK2 was employed in murine differentiated 3T3-L1 adipocytes and autophagic flux was monitored. Our data indicate that SIK2 is required for both autophagic flux and expression of TFEB, the transcription factor that regulates autophagy, in adipocytes. The effect of SIK2 on autophagic flux occurs before the regulation of TFEB protein levels, suggesting different mechanisms whereby SIK2 stimulates autophagy. This study broadens the current knowledge on autophagy regulation and SIK2 function in adipocytes.
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| 9. |
- Nilsson, Emma, et al.
(författare)
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Differential DNA Methylation and Expression of miRNAs in Adipose Tissue From Twin Pairs Discordant for Type 2 Diabetes
- 2021
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Ingår i: Diabetes. - : American Diabetes Association. - 1939-327X .- 0012-1797. ; 70:10, s. 2402-2418
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of type 2 diabetes (T2D) is increasing worldwide, but current treatments have limitations. miRNAs may play a key role in the development of T2D and can be targets for novel therapies. Here, we examined whether T2D is associated with altered expression and DNA methylation of miRNAs using adipose tissue from 14 monozygotic twin pairs discordant for T2D. Four members each of the miR-30 and let-7-families were downregulated in adipose tissue of subjects with T2D versus control subjects, which was confirmed in an independent T2D case-control cohort. Further, DNA methylation of five CpG sites annotated to gene promoters of differentially expressed miRNAs, including miR-30a and let-7a-3, was increased in T2D versus control subjects. Luciferase experiments showed that increased DNA methylation of the miR-30a promoter reduced its transcription in vitro. Silencing of miR-30 in adipocytes resulted in reduced glucose uptake and TBC1D4 phosphorylation; downregulation of genes involved in demethylation and carbohydrate/lipid/amino acid metabolism; and upregulation of immune system genes. In conclusion, T2D is associated with differential DNA methylation and expression of miRNAs in adipose tissue. Downregulation of the miR-30 family may lead to reduced glucose uptake and altered expression of key genes associated with T2D.
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| 10. |
- Parmhed, Sara, et al.
(författare)
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Transformative agreements and their practical impact : a librarian perspective
- 2023
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Ingår i: Insights the UKSG journal. - : Ubiquity Press. - 2048-7754. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- This case study aims at describing how transformative agreements (TAs) have affected our profession with new tasks and workflows at two university libraries in Sweden, namely Karolinska Institutet University Library and Södertörn University Library. TAs are one of the mechanisms by which scientific publications are made open access; they involve moving libraries’ contracts with publishers from payment to read toward payment to publish. We will summarize the status and progress of open access in Sweden, in particular the significant growth of TAs over a short time span. We will then focus on describing how TAs have affected our everyday work and what new tasks they have imposed. We will share our experiences and point out things we find challenging, for example, we will explore questions about eligibility, the verification process, publication types and title changes during the contract period. We will also give some recommendations on how we would prefer the workflows surrounding the TAs to be. Finally, we will share our conclusions and comments about the impact of TAs on the publishing landscape and speculate about what will happen next.
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