| 1. |
- Amrutkar, Manoj, et al.
(författare)
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Genetic Disruption of Protein Kinase STK25 Ameliorates Metabolic Defects in a Diet-Induced Type 2 Diabetes Model
- 2015
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 64:8, s. 2791-2804
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the molecular networks controlling ectopic lipid deposition, glucose tolerance, and insulin sensitivity is essential to identifying new pharmacological approaches to treat type 2 diabetes. We recently identified serine/threonine protein kinase 25 (STK25) as a negative regulator of glucose and insulin homeostasis based on observations in myoblasts with acute depletion of STK25 and in STK25-overexpressing transgenic mice. Here, we challenged Stk25 knockout mice and wild-type littermates with a high-fat diet and showed that STK25 deficiency suppressed development of hyperglycemia and hyperinsulinemia, improved systemic glucose tolerance, reduced hepatic gluconeogenesis, and increased insulin sensitivity. Stk25(-/-) mice were protected from diet-induced liver steatosis accompanied by decreased protein levels of acetyl-CoA carboxylase, a key regulator of both lipid oxidation and synthesis. Lipid accumulation in Stk25(-/-) skeletal muscle was reduced, and expression of enzymes controlling the muscle oxidative capacity (Cpt1, Acox1, Cs, Cycs, Ucp3) and glucose metabolism (Glut1, Glut4, Hk2) was increased. These data are consistent with our previous study of STK25 knockdown in myoblasts and reciprocal to the metabolic phenotype of Stk25 transgenic mice, reinforcing the validity of the results. The findings suggest that STK25 deficiency protects against the metabolic consequences of chronic exposure to dietary lipids and highlight the potential of STK25 antagonists for the treatment of type 2 diabetes.
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| 2. |
- Amrutkar, Manoj, et al.
(författare)
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Protein kinase STK25 controls lipid partitioning in hepatocytes and correlates with liver fat content in humans
- 2016
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 59:2, s. 341-353
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Tidskriftsartikel (refereegranskat)abstract
- Aims/hypothesis Type 2 diabetes is closely associated with pathological lipid accumulation in the liver, which is suggested to actively contribute to the development of insulin resistance. We recently identified serine/threonine protein kinase 25 (STK25) as a regulator of liver steatosis, whole-body glucose tolerance and insulin sensitivity in a mouse model system. The aim of this study was to assess the role of STK25 in the control of lipid metabolism in human liver. Methods Intracellular fat deposition, lipid metabolism and insulin sensitivity were studied in immortalised human hepatocytes (IHHs) and HepG2 hepatocellular carcinoma cells in which STK25 was overexpressed or knocked down by small interfering RNA. The association between STK25 mRNA expression in human liver biopsies and hepatic fat content was analysed. Results Overexpression of STK25 in IHH and HepG2 cells enhanced lipid deposition by suppressing beta-oxidation and triacylglycerol (TAG) secretion, while increasing lipid synthesis. Conversely, knockdown of STK25 attenuated lipid accumulation by stimulating beta-oxidation and TAG secretion, while inhibiting lipid synthesis. Furthermore, TAG hydrolase activity was repressed in hepatocytes overexpressing STK25 and reciprocally increased in cells with STK25 knockdown. Insulin sensitivity was reduced in STK25-overexpressing cells and enhanced in STK25-deficient hepatocytes. We also found a statistically significant positive correlation between STK25 mRNA expression in human liver biopsies and hepatic fat content. Conclusions/interpretation Our data suggest that STK25 regulates lipid partitioning in human liver cells by controlling TAG synthesis as well as lipolytic activity and thereby NEFA release from lipid droplets for beta-oxidation and TAG secretion. Our findings highlight STK25 as a potential drug target for the prevention and treatment of type 2 diabetes.
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| 3. |
- Amrutkar, Manoj
(författare)
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Protein kinase STK25 is a regulator of hepatic lipid partitioning and whole body metabolism
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In past decade, type 2 diabetes (T2D) and associated metabolic complications have become a major global threat for human health with epidemic increase in incidence. Currently available treatments for T2D have several limitations and side effects making it difficult safely reach adequate metabolic control. Therefore, it is important to identify novel therapeutic targets for metabolic regulation, which could complement current treatments for T2D. T2D is closely associated with ectopic lipid deposition. Recent evidence suggests that hepatic lipid deposition is not merely a consequence of the metabolic syndrome but rather that non-alcoholic fatty liver disease (NAFLD), and progression to non-alcoholic steatohepatitis (NASH), exacerbate hepatic and systemic insulin resistance and actively contribute to the pathogenesis of the metabolic syndrome. However, no pharmacological treatment is approved for NAFLD/NASH, to date. Serine/threonine protein kinase 25 (STK25) is broadly expressed in mouse, rat and human tissues. Previous studies by our research group in the rat myoblast cell line L6 by small interfering RNA (siRNA) have shown that STK25 is involved in regulation of glucose uptake and lipid oxidation. Studies presented in this thesis work demonstrate that the transgenic mice overexpressing STK25 challenged with a high-fat diet display a shift in the metabolic balance in peripheral tissues from lipid oxidation to lipid storage, resulting in a systemic insulin resistance. In contrast, Stk25 knockout mice show better-preserved systemic insulin sensitivity via an opposite shift in the metabolic balance in peripheral tissues from lipid storage to lipid utilization. We found that STK25 coats lipid droplets in mouse liver and human hepatocytes. Our studies performed in mouse liver, and in hepatocytes from both mouse and human, suggest that STK25 regulates hepatic lipid partitioning by controlling β-oxidation and very low-density lipoprotein (VLDL)-triacylglycerol (TAG) secretion. Increased activity of STK25 reduces liver lipolytic capacity, which in turn results in lower availability of lipids for hepatic β-oxidation and VLDL-TAG secretion, leading to enhanced lipid storage. Upon inactivation of STK25 reciprocal increase in liver lipolytic capacity, β-oxidation and VLDL-TAG secretion was seen, which likely account for the reduced hepatic lipid storage. We also found a statistically significant positive correlation between STK25 mRNA expression in human liver biopsies and hepatic fat content. Taken together, our studies suggest that inhibition of STK25 enables the reduction of ectopic lipid deposition and improves insulin sensitivity and glucose utilization in peripheral tissues. Our studies highlight STK25 as a potential drug target for prevention and/or treatment of T2D, NAFLD and NASH.
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| 4. |
- Amrutkar, Manoj, et al.
(författare)
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Protein kinase STK25 regulates hepatic lipid partitioning and progression of liver steatosis and NASH
- 2015
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Ingår i: Faseb Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 29:4, s. 1564-1576
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Tidskriftsartikel (refereegranskat)abstract
- Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver disease, and 10% to 20% of NAFLD patients progress to nonalcoholic steatohepatitis (NASH). The molecular pathways controlling progression to NAFLD/NASH remain poorly understood. We recently identified serine/threonine protein kinase 25 (STK25) as a regulator of whole-body insulin and glucose homeostasis. This study investigates the role of STK25 in liver lipid accumulation and NASH. Stk25 transgenic mice challenged with a high-fat diet displayed a dramatic increase in liver steatosis and hepatic insulin resistance compared to wild-type siblings. Focal fibrosis, hepatocellular damage, and inflammation were readily seen in transgenic but not wild-type livers. Transgenic livers displayed reduced beta-oxidation and triacylglycerol secretion, while lipid uptake and synthesis remained unchanged. STK25 was associated with lipid droplets, colocalizing with the main hepatic lipid droplet-coating protein adipose differentiation-related protein, the level of which was increased 3.8 +/- 0.7-fold in transgenic livers (P < 0.01), while a key hepatic lipase, adipose triacylglycerol lipase, was translocated from the lipid droplets surface to the cytoplasm, providing the likely mechanism underlying the effect of STK25. In summary, STK25 is a lipid droplet-associated protein that promotes NAFLD through control of lipid release from the droplets for beta-oxidation and triacylglycerol secretion. STK25 also drives pathogenesis of NASH.
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| 5. |
- Amrutkar, Manoj, et al.
(författare)
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STK25 is a critical determinant in nonalcoholic steatohepatitis.
- 2016
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Ingår i: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - 1530-6860. ; 30:10, s. 3628-3643
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Tidskriftsartikel (refereegranskat)abstract
- Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, and 10-20% of patients with NAFLD progress to nonalcoholic steatohepatitis (NASH) with a high risk of cirrhosis, liver failure, and hepatocellular carcinoma. Despite its high medical importance, the molecular mechanisms controlling progression from simple liver steatosis to NASH remain elusive. We recently identified serine/threonine protein kinase (STK)25 as a critical regulator of ectopic lipid deposition, systemic glucose, and insulin homeostasis. To elucidate the role of STK25 in the development of NASH, we challenged Stk25-knockout and transgenic mice with a methionine and choline-deficient (MCD) diet. We show that Stk25(-/-) mice are protected against MCD-diet-induced NASH, as evidenced by repressed liver steatosis, oxidative damage, inflammation, and fibrosis, whereas Stk25 transgenic mice developed a more severe NASH phenotype, compared with corresponding wild-type littermates. Consistently, NASH features were suppressed in STK25-deficient human hepatocytes cultured in MCD medium, and reciprocally enhanced in STK25-overexpressing cells. We also found a significant positive correlation in human liver biopsies between STK25 expression and NASH development. The study provides evidence for multiple roles of STK25 in NASH pathogenesis and future investigations to address the potential therapeutic relevance of pharmacological STK25 inhibitors in prevention and treatment of NASH are warranted.-Amrutkar, M., Chursa, U., Kern, M., Nuñez-Durán, E., Ståhlman, M., Sütt, S., Borén, J., Johansson, B. R., Marschall, H.-U., Blüher, M., Mahlapuu, M. STK25 is a critical determinant in nonalcoholic steatohepatitis.
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| 6. |
- Cansby, Emmelie, 1984, et al.
(författare)
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Increased expression of STK25 leads to impaired glucose utilization and insulin sensitivity in mice challenged with a high-fat diet.
- 2013
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Ingår i: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - : Wiley. - 1530-6860. ; 27:9, s. 3660-3671
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Tidskriftsartikel (refereegranskat)abstract
- Partial depletion of serine/threonine protein kinase 25 (STK25), a member of the Ste20 superfamily of kinases, increases lipid oxidation and glucose uptake in rodent myoblasts. Here we show that transgenic mice overexpressing STK25, when challenged with a high-fat diet, develop reduced glucose tolerance and insulin sensitivity compared to wild-type siblings, as evidenced by impairment in glucose and insulin tolerance tests as well as in euglycemic-hyperinsulinemic clamp studies. The fasting plasma insulin concentration was elevated in Stk25 transgenic mice compared to wild-type littermates (4.9±0.8 vs. 2.6±0.4 ng/ml after 17 wk on high-fat diet, P<0.05). Overexpression of STK25 decreased energy expenditure during the dark phase of observation (P<0.05), despite increased spontaneous activity. The oxidative capacity of skeletal muscle of transgenic carriers was reduced, as evidenced by altered expression of Cpt1, Acox1, and ACC. Hepatic triglycerides and glycogen were elevated (1.6- and 1.4-fold, respectively; P<0.05) and expression of key enzymes regulating lipogenesis (Fasn), glycogen synthesis (Gck), and gluconeogenesis (G6pc, Fbp1) was increased in the liver of the transgenic mice. Our findings suggest that overexpression of STK25 in conditions of excess dietary fuels associates with a shift in the metabolic balance in peripheral tissues from lipid oxidation to storage, leading to a systemic insulin resistance.-Cansby, E., Amrutkar, M., Mannerås Holm, L., Nerstedt, A., Reyahi, A., Stenfeldt, E., Borén, J., Carlsson, P., Smith, U., Zierath, J.R., Mahlapuu, M. Increased expression of STK25 leads to impaired glucose utilization and insulin sensitivity in mice challenged with a high-fat diet.
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| 7. |
- Cansby, Emmelie, 1984, et al.
(författare)
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Partial hepatic resistance to IL-6-induced inflammation develops in type 2 diabetic mice, while the anti-inflammatory effect of AMPK is maintained
- 2014
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Ingår i: Molecular and Cellular Endocrinology. - : Elsevier BV. - 0303-7207. ; 393:1-2, s. 143-151
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Tidskriftsartikel (refereegranskat)abstract
- Interleukin-6 (IL-6) induces hepatic inflammation and insulin resistance, and therapeutic strategies to counteract the IL-6 action in liver are of high interest. In this study, we demonstrate that acute treatment with AMP-activated protein kinase (AMPK) agonists AICAR and metformin efficiently repressed IL-6-induced hepatic proinflammatory gene expression and activation of STAT3 in a mouse model of diet-induced type 2 diabetes, bringing it back to basal nonstimulated level. Surprisingly, the inflammatory response in liver induced by IL-6 administration in vivo was markedly blunted in the mice fed a high-fat diet, compared to lean chow-fed controls, while this difference was not replicated in vitro in primary hepatocytes derived from these two groups of mice. In summary, our work reveals that partial hepatic IL-6 resistance develops in the mouse model of type 2 diabetes, while the anti-inflammatory action of AMPK is maintained. Systemic factors, rather than differences in intracellular IL-6 receptor signaling, are likely mediating the relative impairment in IL-6 effect.
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| 8. |
- Cansby, Emmelie, 1984, et al.
(författare)
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Protein kinase MST3 modulates lipid homeostasis in hepatocytes and correlates with nonalcoholic steatohepatitis in humans.
- 2019
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Ingår i: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - 1530-6860. ; 33:9, s. 9974-9989
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Tidskriftsartikel (refereegranskat)abstract
- Ectopic lipid storage in the liver is considered the main risk factor for nonalcoholic steatohepatitis (NASH). Understanding the molecular networks controlling hepatocellular lipid deposition is therefore essential for developing new strategies to effectively prevent and treat this complex disease. Here, we describe a new regulator of lipid partitioning in human hepatocytes: mammalian sterile 20-like (MST) 3. We found that MST3 protein coats lipid droplets in mouse and human liver cells. Knockdown of MST3 attenuated lipid accumulation in human hepatocytes by stimulating β-oxidation and triacylglycerol secretion while inhibiting fatty acid influx and lipid synthesis. We also observed that lipogenic gene expression and acetyl-coenzyme A carboxylase protein abundance were reduced in MST3-deficient hepatocytes, providing insight into the molecular mechanisms underlying the decreased lipid storage. Furthermore, MST3 expression was positively correlated with key features of NASH (i.e., hepatic lipid content, lobular inflammation, and hepatocellular ballooning) in human liver biopsies. In summary, our results reveal a role of MST3 in controlling the dynamic metabolic balance of liver lipid catabolism vs. lipid anabolism. Our findings highlight MST3 as a potential drug target for the prevention and treatment of NASH and related complex metabolic diseases.
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| 9. |
- Cansby, Emmelie, 1984, et al.
(författare)
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Targeted Delivery of Stk25 Antisense Oligonucleotides to Hepatocytes Protects Mice Against Nonalcoholic Fatty Liver Disease
- 2019
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Ingår i: CMGH Cellular and Molecular Gastroenterology and Hepatology. - : Elsevier BV. - 2352-345X. ; 7:3, s. 597-618
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims: Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) are emerging as leading causes of liver disease worldwide. Currently, no specific pharmacologic therapy is available for NAFLD/NASH, which has been recognized as one of the major unmet medical needs of the 21st century. Our recent studies in genetic mouse models, human cell lines, and well-characterized patient cohorts have identified serine/threonine protein kinase (STK)25 as a critical regulator of hepatic lipid partitioning and NAFLD/NASH. Here, we studied the metabolic benefit of liver-specific STK25 inhibitors on NAFLD development and progression in a mouse model of diet-induced obesity. Methods: We developed a hepatocyte-specific triantennary N-acetylgalactosamine (GalNAc)-conjugated antisense oligonucleotide (ASO) targeting Stk25 and evaluated its effect on NAFLD features in mice after chronic exposure to dietary lipids. Results: We found that systemic administration of hepatocyte-targeting GalNAc-Stk25 ASO in obese mice effectively ameliorated steatosis, inflammatory infiltration, hepatic stellate cell activation, nutritional fibrosis, and hepatocellular damage in the liver compared with mice treated with GalNAc-conjugated nontargeting ASO, without any systemic toxicity or local tolerability concerns. We also observed protection against high-fat-diet–induced hepatic oxidative stress and improved mitochondrial function with Stk25 ASO treatment in mice. Moreover, GalNAc-Stk25 ASO suppressed lipogenic gene expression and acetyl-CoA carboxylase protein abundance in the liver, providing insight into the molecular mechanisms underlying repression of hepatic steatosis. Conclusions: This study provides in vivo nonclinical proof-of-principle for the metabolic benefit of liver-specific inhibition of STK25 in the context of obesity and warrants future investigations to address the therapeutic potential of GalNAc-Stk25 ASO in the prevention and treatment of NAFLD.
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| 10. |
- Caputo, Mara, et al.
(författare)
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Genetic Ablation of STE20-Type Kinase MST4 Does Not Alleviate Diet-Induced MASLD Susceptibility in Mice
- 2024
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Ingår i: INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES. - 1661-6596 .- 1422-0067. ; 25:4
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic dysfunction-associated steatotic liver disease (MASLD) and its advanced subtype, metabolic dysfunction-associated steatohepatitis (MASH), have emerged as the most common chronic liver disease worldwide, yet there is no targeted pharmacotherapy presently available. This study aimed to investigate the possible in vivo function of STE20-type protein kinase MST4, which was earlier implicated in the regulation of hepatocellular lipotoxic milieu in vitro, in the control of the diet-induced impairment of systemic glucose and insulin homeostasis as well as MASLD susceptibility. Whole-body and liver-specific Mst4 knockout mice were generated by crossbreeding conditional Mst4fl/fl mice with mice expressing Cre recombinase under the Sox2 or Alb promoters, respectively. To replicate the environment in high-risk subjects, Mst4-/- mice and their wild-type littermates were fed a high-fat or a methionine-choline-deficient (MCD) diet. Different in vivo tests were conducted in obese mice to describe the whole-body metabolism. MASLD progression in the liver and lipotoxic damage to adipose tissue, kidney, and skeletal muscle were analyzed by histological and immunofluorescence analysis, biochemical assays, and protein and gene expression profiling. In parallel, intracellular fat storage and oxidative stress were assessed in primary mouse hepatocytes, where MST4 was silenced by small interfering RNA. We found that global MST4 depletion had no effect on body weight or composition, locomotor activity, whole-body glucose tolerance or insulin sensitivity in obese mice. Furthermore, we observed no alterations in lipotoxic injuries to the liver, adipose, kidney, or skeletal muscle tissue in high-fat diet-fed whole-body Mst4-/- vs. wild-type mice. Liver-specific Mst4-/- mice and wild-type littermates displayed a similar severity of MASLD when subjected to an MCD diet, as evidenced by equal levels of steatosis, inflammation, hepatic stellate cell activation, fibrosis, oxidative/ER stress, and apoptosis in the liver. In contrast, the in vitro silencing of MST4 effectively protected primary mouse hepatocytes against ectopic lipid accumulation and oxidative cell injury triggered by exposure to fatty acids. In summary, these results suggest that the genetic ablation of MST4 in mice does not mitigate the initiation or progression of MASLD and has no effect on systemic glucose or insulin homeostasis in the context of nutritional stress. The functional compensation for the genetic loss of MST4 by yet undefined mechanisms may contribute to the apparent discrepancy between in vivo and in vitro phenotypic consequences of MST4 silencing.
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