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Svalastoga P, Kaci A, Molnes J, Solheim MH, Johansson BB, Krogvold L, Skrivarhaug T, Valen E, Johansson S, Molven A, Sagen JV, Søfteland E, Bjørkhaug L, Tjora E, Aukrust I, Njølstad PR. Characterisation of HNF1A variants in paediatric diabetes in Norway using functional and clinical investigations to unmask phenotype and monogenic diabetes. Diabetologia 2023; 66:2226-2237. [PMID: 37798422 PMCID: PMC10627920 DOI: 10.1007/s00125-023-06012-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 06/09/2023] [Indexed: 10/07/2023]
Abstract
AIMS/HYPOTHESIS Correctly diagnosing MODY is important, as individuals with this diagnosis can discontinue insulin injections; however, many people are misdiagnosed. We aimed to develop a robust approach for determining the pathogenicity of variants of uncertain significance in hepatocyte nuclear factor-1 alpha (HNF1A)-MODY and to obtain an accurate estimate of the prevalence of HNF1A-MODY in paediatric cases of diabetes. METHODS We extended our previous screening of the Norwegian Childhood Diabetes Registry by 830 additional samples and comprehensively genotyped HNF1A variants in autoantibody-negative participants using next-generation sequencing. Carriers of pathogenic variants were treated by local healthcare providers, and participants with novel likely pathogenic variants and variants of uncertain significance were enrolled in an investigator-initiated, non-randomised, open-label pilot study (ClinicalTrials.gov registration no. NCT04239586). To identify variants associated with HNF1A-MODY, we functionally characterised their pathogenicity and assessed the carriers' phenotype and treatment response to sulfonylurea. RESULTS In total, 615 autoantibody-negative participants among 4712 cases of paediatric diabetes underwent genetic sequencing, revealing 19 with HNF1A variants. We identified nine carriers with novel variants classified as variants of uncertain significance or likely to be pathogenic, while the remaining ten participants carried five pathogenic variants previously reported. Of the nine carriers with novel variants, six responded favourably to sulfonylurea. Functional investigations revealed their variants to be dysfunctional and demonstrated a correlation with the resulting phenotype, providing evidence for reclassifying these variants as pathogenic. CONCLUSIONS/INTERPRETATION Based on this robust classification, we estimate that the prevalence of HNF1A-MODY is 0.3% in paediatric diabetes. Clinical phenotyping is challenging and functional investigations provide a strong complementary line of evidence. We demonstrate here that combining clinical phenotyping with functional protein studies provides a powerful tool to obtain a precise diagnosis of HNF1A-MODY.
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Affiliation(s)
- Pernille Svalastoga
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Alba Kaci
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
- Center for Laboratory Medicine, Østfold Hospital Trust, Grålum, Norway
| | - Janne Molnes
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
- Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway
| | - Marie H Solheim
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Bente B Johansson
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Lars Krogvold
- Division of Childhood and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
| | - Torild Skrivarhaug
- Division of Childhood and Adolescent Medicine, Oslo University Hospital, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Eivind Valen
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, Norway
| | - Stefan Johansson
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
- Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway
| | - Anders Molven
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
- Department of Pathology, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Jørn V Sagen
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
- Department of Medical Biochemistry and Pharmacology, Haukeland University Hospital, Bergen, Norway
| | - Eirik Søfteland
- Department of Medical Biochemistry and Pharmacology, Haukeland University Hospital, Bergen, Norway
- Department of Medicine, Haukeland University Hospital, Bergen, Norway
| | - Lise Bjørkhaug
- Department of Safety, Chemistry, and Biomedical Laboratory Sciences, Western Norway University of Applied Sciences, Bergen, Norway
| | - Erling Tjora
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
- Children and Youth Clinic, Haukeland University Hospital, Bergen, Norway
| | - Ingvild Aukrust
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway
- Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway
| | - Pål R Njølstad
- Mohn Center for Diabetes Precision Medicine, Department of Clinical Science, University of Bergen, Bergen, Norway.
- Children and Youth Clinic, Haukeland University Hospital, Bergen, Norway.
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Park SH, Helsley RN, Fadhul T, Willoughby JLS, Noetzli L, Tu HC, Solheim MH, Fujisaka S, Pan H, Dreyfuss JM, Bons J, Rose J, King CD, Schilling B, Lusis AJ, Pan C, Gupta M, Kulkarni RN, Fitzgerald K, Kern PA, Divanovic S, Kahn CR, Softic S. Fructose induced KHK-C can increase ER stress independent of its effect on lipogenesis to drive liver disease in diet-induced and genetic models of NAFLD. Metabolism 2023; 145:155591. [PMID: 37230214 PMCID: PMC10752375 DOI: 10.1016/j.metabol.2023.155591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 05/04/2023] [Accepted: 05/10/2023] [Indexed: 05/27/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome, and is estimated to affect one billion individuals worldwide. An increased intake of a high-fat diet (HFD) and sugar-sweetened beverages are risk-factors for NAFLD development, but how their combined intake promotes progression to a more severe form of liver injury is unknown. Here we show that fructose metabolism via ketohexokinase (KHK) C isoform leads to unresolved endoplasmic reticulum (ER) stress when coupled with a HFD intake. Conversely, a liver-specific knockdown of KHK in mice consuming fructose on a HFD is adequate to improve the NAFLD activity score and exert a profound effect on the hepatic transcriptome. Overexpression of KHK-C in cultured hepatocytes is sufficient to induce ER stress in fructose free media. Upregulation of KHK-C is also observed in mice with genetically induced obesity or metabolic dysfunction, whereas KHK knockdown in these mice improves metabolic function. Additionally, in over 100 inbred strains of male or female mice hepatic KHK expression correlates positively with adiposity, insulin resistance, and liver triglycerides. Similarly, in 241 human subjects and their controls, hepatic Khk expression is upregulated in early, but not late stages of NAFLD. In summary, we describe a novel role of KHK-C in triggering ER stress, which offers a mechanistic understanding of how the combined intake of fructose and a HFD propagates the development of metabolic complications.
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Affiliation(s)
- Se-Hyung Park
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Robert N Helsley
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Taghreed Fadhul
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | | | - Leila Noetzli
- Alnylam Pharmaceuticals Inc., Cambridge, MA 02142, USA
| | - Ho-Chou Tu
- Alnylam Pharmaceuticals Inc., Cambridge, MA 02142, USA
| | - Marie H Solheim
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA; Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, 50931 Cologne, Germany
| | - Shiho Fujisaka
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA; First Department of Internal Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Hui Pan
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
| | - Jonathan M Dreyfuss
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
| | - Joanna Bons
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Jacob Rose
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Christina D King
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Birgit Schilling
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Aldons J Lusis
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA, USA
| | - Calvin Pan
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA, USA
| | - Manoj Gupta
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Rohit N Kulkarni
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215, USA
| | | | - Philip A Kern
- Department of Medicine, Division of Endocrinology, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Senad Divanovic
- Department of Pediatrics, University of Cincinnati College of Medicine, Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - C Ronald Kahn
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
| | - Samir Softic
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY 40536, USA; Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA; Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY 40536, USA.
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Park SH, Helsley RN, Fadhul T, Willoughby JL, Noetzli L, Tu HC, Solheim MH, Fujisaka S, Pan H, Dreyfuss JM, Bons J, Rose J, King CD, Schilling B, Lusis AJ, Pan C, Gupta M, Kulkarni RN, Fitzgerald K, Kern PA, Divanovic S, Kahn CR, Softic S. Fructose Induced KHK-C Increases ER Stress and Modulates Hepatic Transcriptome to Drive Liver Disease in Diet-Induced and Genetic Models of NAFLD. bioRxiv 2023:2023.01.27.525605. [PMID: 36747758 PMCID: PMC9900898 DOI: 10.1101/2023.01.27.525605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Non-alcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome, and is estimated to affect one billion individuals worldwide. An increased intake of a high-fat diet (HFD) and sugar-sweetened beverages are risk-factors for NAFLD development, but how their combined intake promotes progression to a more severe form of liver injury is unknown. Here we show that fructose metabolism via ketohexokinase (KHK) C isoform increases endoplasmic reticulum (ER) stress in a dose dependent fashion, so when fructose is coupled with a HFD intake it leads to unresolved ER stress. Conversely, a liver-specific knockdown of KHK in C57BL/6J male mice consuming fructose on a HFD is adequate to improve the NAFLD activity score and exert a profound effect on the hepatic transcriptome. Overexpression of KHK-C in cultured hepatocytes is sufficient to induce ER stress in fructose free media. Upregulation of KHK-C is also observed in genetically obesity ob/ob, db/db and lipodystrophic FIRKO male mice, whereas KHK knockdown in these mice improves metabolic function. Additionally, in over 100 inbred strains of male or female mice hepatic KHK expression correlates positively with adiposity, insulin resistance, and liver triglycerides. Similarly, in 241 human subjects and their controls, hepatic Khk expression is upregulated in early, but not late stages of NAFLD. In summary, we describe a novel role of KHK-C in triggering ER stress, which offers a mechanistic understanding of how the combined intake of fructose and a HFD propagates the development of metabolic complications.
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Affiliation(s)
- Se-Hyung Park
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | - Robert N. Helsley
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | - Taghreed Fadhul
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | | | | | - Ho-Chou Tu
- Alnylam Pharmaceuticals Inc., Cambridge, MA. 02142
| | - Marie H. Solheim
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
- Department of Neuronal Control of Metabolism, Max Planck Institute for Metabolism Research, 50931 Cologne, Germany
| | - Shiho Fujisaka
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
- First Department of Internal Medicine, University of Toyama, Toyama 930-0194, Japan
| | - Hui Pan
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA
| | - Jonathan M. Dreyfuss
- Bioinformatics and Biostatistics Core, Joslin Diabetes Center, Harvard Medical School, Boston, MA
| | - Joanna Bons
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Jacob Rose
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Christina D. King
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Birgit Schilling
- Proteomics and Aging Center, Buck Institute for Research on Aging, Novato, CA 94945
| | - Aldons J. Lusis
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA USA
| | - Calvin Pan
- Department of Medicine/Division of Cardiology, Department of Human Genetics, A2-237 Center for the Health Sciences, University of California, Los Angeles, Los Angeles, CA USA
| | - Manoj Gupta
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center; Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215
| | - Rohit N. Kulkarni
- Section of Islet Cell and Regenerative Biology, Joslin Diabetes Center; Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215
| | | | - Philip A. Kern
- Department of Medicine, Division of Endocrinology, University of Kentucky College of Medicine, Lexington, KY. 40536
| | - Senad Divanovic
- Department of Pediatrics, University of Cincinnati College of Medicine, Division of Immunobiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229
| | - C. Ronald Kahn
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
| | - Samir Softic
- Department of Pediatrics, Division of Pediatric Gastroenterology, University of Kentucky College of Medicine, Lexington, KY. 40536
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA. 02215
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY. 40536
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Fjeld K, Gravdal A, Brekke RS, Alam J, Wilhelm SJ, El Jellas K, Pettersen HN, Lin J, Solheim MH, Steine SJ, Johansson BB, Njølstad PR, Verbeke CS, Xiao X, Lowe ME, Molven A. The genetic risk factor CEL-HYB1 causes proteotoxicity and chronic pancreatitis in mice. Pancreatology 2022; 22:1099-1111. [PMID: 36379850 DOI: 10.1016/j.pan.2022.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 10/31/2022] [Accepted: 11/04/2022] [Indexed: 11/11/2022]
Abstract
BACKGROUND & AIMS The CEL gene encodes the digestive enzyme carboxyl ester lipase. CEL-HYB1, a hybrid allele of CEL and its adjacent pseudogene CELP, is a genetic variant suggested to increase the risk of chronic pancreatitis (CP). Our aim was to develop a mouse model for CEL-HYB1 that enables studies of pancreatic disease mechanisms. METHODS We established a knock-in mouse strain where the variable number of tandem repeat (VNTR) region of the endogenous mouse Cel gene was substituted with the mutated VNTR of the human CEL-HYB1 allele. Heterozygous and homozygous Cel-HYB1 mice and littermate wildtype controls were characterized with respect to pancreatic pathology and function. RESULTS We successfully constructed a mouse model with pancreatic expression of a humanized CEL-HYB1 protein. The Cel-HYB1 mice spontaneously developed features of CP including inflammation, acinar atrophy and fatty replacement, and the phenotype became more pronounced as the animals aged. Moreover, Cel-HYB1 mice were normoglycemic at age 6 months, whereas at 12 months they exhibited impaired glucose tolerance. Immunostaining of pancreatic tissue indicated the formation of CEL protein aggregates, and electron microscopy showed dilated endoplasmic reticulum. Upregulation of the stress marker BiP/GRP78 was seen in pancreatic parenchyma obtained both from Cel-HYB1 animals and from a human CEL-HYB1 carrier. CONCLUSIONS We have developed a new mouse model for CP that confirms the pathogenicity of the human CEL-HYB1 variant. Our findings place CEL-HYB1 in the group of genes that increase CP risk through protein misfolding-dependent pathways.
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Affiliation(s)
- Karianne Fjeld
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway; Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway; Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway.
| | - Anny Gravdal
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway; Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway; Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway
| | - Ranveig S Brekke
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway; Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway; Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway
| | - Jahedul Alam
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway; Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway
| | - Steven J Wilhelm
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA
| | - Khadija El Jellas
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway; Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway
| | - Helene N Pettersen
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway; Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway
| | - Jianguo Lin
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA
| | - Marie H Solheim
- Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway
| | - Solrun J Steine
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Bente B Johansson
- Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway
| | - Pål R Njølstad
- Center for Diabetes Research, Department of Clinical Science, University of Bergen, Norway; Pediatric and Youth Clinic, Haukeland University Hospital, Bergen, Norway
| | - Caroline S Verbeke
- Department of Pathology, Oslo University Hospital Rikshospitalet, Oslo, Norway; Department of Pathology, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Xunjun Xiao
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA
| | - Mark E Lowe
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA
| | - Anders Molven
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway; Department of Pathology, Haukeland University Hospital, Bergen, Norway; Section for Cancer Genomics, Haukeland University Hospital, Bergen, Norway
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Winnay JN, Solheim MH, Sakaguchi M, Njølstad PR, Kahn CR. Inhibition of the PI 3-kinase pathway disrupts the unfolded protein response and reduces sensitivity to ER stress-dependent apoptosis. FASEB J 2020; 34:12521-12532. [PMID: 32744782 DOI: 10.1096/fj.202000892r] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 07/07/2020] [Accepted: 07/07/2020] [Indexed: 01/01/2023]
Abstract
Class Ia phosphoinositide 3-kinases (PI3K) are critical mediators of insulin and growth factor action. We have demonstrated that the p85α regulatory subunit of PI3K modulates the unfolded protein response (UPR) by interacting with and regulating the nuclear translocation of XBP-1s, a transcription factor essential for the UPR. We now show that PI3K activity is required for full activation of the UPR. Pharmacological inhibition of PI3K in cells blunts the ER stress-dependent phosphorylation of IRE1α and PERK, decreases induction of ATF4, CHOP, and XBP-1 and upregulates UPR target genes. Cells expressing a human p85α mutant (R649W) previously shown to inhibit PI3K, exhibit decreased activation of IRE1α and PERK and reduced induction of CHOP and ATF4. Pharmacological inhibition of PI3K, overexpression of a mutant of p85α that lacks the ability to interact with the p110α catalytic subunit (∆p85α) or expression of mutant p85α (R649W) in vivo, decreased UPR-dependent induction of ER stress response genes. Acute tunicamycin treatment of R649W+/- mice revealed reduced induction of UPR target genes in adipose tissue, whereas chronic tunicamycin exposure caused sustained increases in UPR target genes in adipose tissue. Finally, R649W+/- cells exhibited a dramatic resistance to ER stress-dependent apoptosis. These data suggest that PI3K pathway dysfunction causes ER stress that may drive the pathogenesis of several diseases including Type 2 diabetes and various cancers.
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Affiliation(s)
| | - Marie H Solheim
- Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA.,Department of Clinical Science, KG Jebsen Center for Diabetes Research, University of Bergen, Bergen, Norway
| | - Masaji Sakaguchi
- Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA.,Department of Metabolic Medicine, Kumamoto University, Kumamoto, Japan
| | - Pål R Njølstad
- Department of Clinical Science, KG Jebsen Center for Diabetes Research, University of Bergen, Bergen, Norway.,Department of Pediatrics, Haukeland University Hospital, Bergen, Norway
| | - C Ronald Kahn
- Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA
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Solheim MH, Winnay JN, Batista TM, Molven A, Njølstad PR, Kahn CR. Mice Carrying a Dominant-Negative Human PI3K Mutation Are Protected From Obesity and Hepatic Steatosis but Not Diabetes. Diabetes 2018; 67:1297-1309. [PMID: 29724723 PMCID: PMC6014554 DOI: 10.2337/db17-1509] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 04/23/2018] [Indexed: 12/20/2022]
Abstract
Phosphatidylinositol 3-kinase (PI3K) plays a central role in insulin signaling, glucose metabolism, cell growth, cell development, and apoptosis. A heterozygous missense mutation (R649W) in the p85α regulatory subunit gene of PI3K (PIK3R1) has been identified in patients with SHORT (Short stature, Hyperextensibility/Hernia, Ocular depression, Rieger anomaly, and Teething delay) syndrome, a disorder characterized by postnatal growth retardation, insulin resistance, and partial lipodystrophy. Knock-in mice with the same heterozygous mutation mirror the human phenotype. In this study, we show that Pik3r1 R649W knock-in mice fed a high-fat diet (HFD) have reduced weight gain and adipose accumulation. This is accompanied by reduced expression of several genes involved in lipid metabolism. Interestingly, despite the lower level of adiposity, the HFD knock-in mice are more hyperglycemic and more insulin-resistant than HFD-fed control mice. Likewise, when crossed with genetically obese ob/ob mice, the ob/ob mice carrying the heterozygous R649W mutation were protected from obesity and hepatic steatosis but developed a severe diabetic state. Together, our data demonstrate a central role of PI3K in development of obesity and fatty liver disease, separating these effects from the role of PI3K in insulin resistance and the resultant hyperglycemia.
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Affiliation(s)
- Marie H Solheim
- Joslin Diabetes Center and Harvard Medical School, Boston, MA
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway
| | | | | | - Anders Molven
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway
- Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway
- Department of Pathology, Haukeland University Hospital, Bergen, Norway
| | - Pål R Njølstad
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway
- Department of Pediatrics and Adolescent Medicine, Haukeland University Hospital, Bergen, Norway
| | - C Ronald Kahn
- Joslin Diabetes Center and Harvard Medical School, Boston, MA
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Solheim MH, Clermont AC, Winnay JN, Hallstensen E, Molven A, Njølstad PR, Rødahl E, Kahn CR. Iris Malformation and Anterior Segment Dysgenesis in Mice and Humans With a Mutation in PI 3-Kinase. Invest Ophthalmol Vis Sci 2017. [PMID: 28632845 PMCID: PMC5482242 DOI: 10.1167/iovs.16-21347] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Purpose To determine the ocular consequences of a dominant-negative mutation in the p85α subunit of phosphatidylinositol 3-kinase (PIK3R1) using a knock-in mouse model of SHORT syndrome, a syndrome associated with short stature, lipodystrophy, diabetes, and Rieger anomaly in humans. Methods We investigated knock-in mice heterozygous for the SHORT syndrome mutation changing arginine 649 to tryptophan in p85α (PIK3R1) using physical examination, optical coherence tomography (OCT), tonometry, and histopathologic sections from paraffin-embedded eyes, and compared the findings to similar investigations in two human subjects with SHORT syndrome heterozygous for the same mutation. Results While overall eye development was normal with clear cornea and lens, normal anterior chamber volume, normal intraocular pressure, and no changes in the retinal structure, OCT images of the knock-in mouse eyes revealed a significant decrease in thickness and width of the iris resulting in increased pupil area and irregularity of shape. Both human subjects had Rieger anomaly with similar defects including thin irides and irregular pupils, as well as a prominent ring of Schwalbe, goniosynechiae, early cataract formation, and glaucoma. Although the two subjects had had diabetes for more than 30 years, there were no signs of diabetic retinopathy. Conclusions A dominant-negative mutation in the p85α regulatory subunit of PI3K affects development of the iris, and contributes to changes consistent with anterior segment dysgenesis in both humans and mice.
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Affiliation(s)
- Marie H Solheim
- Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, United States 2KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Allen C Clermont
- Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, United States 3Beetham Eye Institute, Boston, Massachusetts, United States
| | - Jonathon N Winnay
- Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, United States
| | | | - Anders Molven
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway 5Department of Clinical Medicine, University of Bergen, Bergen, Norway 6Department of Pathology, Haukeland University Hospital, Bergen, Norway
| | - Pål R Njølstad
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway 7Department of Pediatrics, Haukeland University Hospital, Bergen, Norway
| | - Eyvind Rødahl
- Department of Clinical Medicine, University of Bergen, Bergen, Norway 8Department of Ophthalmology, Haukeland University Hospital, Bergen, Norway
| | - C Ronald Kahn
- Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, United States
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8
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Softic S, Boucher J, Solheim MH, Fujisaka S, Haering MF, Homan EP, Winnay J, Perez-Atayde AR, Kahn CR. Lipodystrophy Due to Adipose Tissue-Specific Insulin Receptor Knockout Results in Progressive NAFLD. Diabetes 2016; 65:2187-200. [PMID: 27207510 PMCID: PMC4955986 DOI: 10.2337/db16-0213] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/29/2016] [Indexed: 02/06/2023]
Abstract
Ectopic lipid accumulation in the liver is an almost universal feature of human and rodent models of generalized lipodystrophy and is also a common feature of type 2 diabetes, obesity, and metabolic syndrome. Here we explore the progression of fatty liver disease using a mouse model of lipodystrophy created by a fat-specific knockout of the insulin receptor (F-IRKO) or both IR and insulin-like growth factor 1 receptor (F-IR/IGFRKO). These mice develop severe lipodystrophy, diabetes, hyperlipidemia, and fatty liver disease within the first weeks of life. By 12 weeks of age, liver demonstrated increased reactive oxygen species, lipid peroxidation, histological evidence of balloon degeneration, and elevated serum alanine aminotransferase and aspartate aminotransferase levels. In these lipodystrophic mice, stored liver lipids can be used for energy production, as indicated by a marked decrease in liver weight with fasting and increased liver fibroblast growth factor 21 expression and intact ketogenesis. By 52 weeks of age, liver accounted for 25% of body weight and showed continued balloon degeneration in addition to inflammation, fibrosis, and highly dysplastic liver nodules. Progression of liver disease was associated with improvement in blood glucose levels, with evidence of altered expression of gluconeogenic and glycolytic enzymes. However, these mice were able to mobilize stored glycogen in response to glucagon. Feeding F-IRKO and F-IR/IGFRKO mice a high-fat diet for 12 weeks accelerated the liver injury and normalization of blood glucose levels. Thus, severe fatty liver disease develops early in lipodystrophic mice and progresses to advanced nonalcoholic steatohepatitis with highly dysplastic liver nodules. The liver injury is propagated by lipotoxicity and is associated with improved blood glucose levels.
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Affiliation(s)
- Samir Softic
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, MA
| | - Jeremie Boucher
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA
| | - Marie H Solheim
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA Department of Clinical Science, KG Jebsen Center for Diabetes Research, University of Bergen, Bergen, Norway
| | - Shiho Fujisaka
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA
| | - Max-Felix Haering
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA
| | - Erica P Homan
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA
| | - Jonathon Winnay
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA
| | - Antonio R Perez-Atayde
- Department of Pathology, Boston Children's Hospital, and Harvard Medical School, Boston, MA
| | - C Ronald Kahn
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, MA
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Winnay JN, Solheim MH, Dirice E, Sakaguchi M, Noh HL, Kang HJ, Takahashi H, Chudasama KK, Kim JK, Molven A, Kahn CR, Njølstad PR. PI3-kinase mutation linked to insulin and growth factor resistance in vivo. J Clin Invest 2016; 126:1401-12. [PMID: 26974159 DOI: 10.1172/jci84005] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 01/28/2016] [Indexed: 12/29/2022] Open
Abstract
The phosphatidylinositol 3-kinase (PI3K) signaling pathway is central to the action of insulin and many growth factors. Heterozygous mutations in the gene encoding the p85α regulatory subunit of PI3K (PIK3R1) have been identified in patients with SHORT syndrome - a disorder characterized by short stature, partial lipodystrophy, and insulin resistance. Here, we evaluated whether SHORT syndrome-associated PIK3R1 mutations account for the pathophysiology that underlies the abnormalities by generating knockin mice that are heterozygous for the Pik3r1Arg649Trp mutation, which is homologous to the mutation found in the majority of affected individuals. Similar to the patients, mutant mice exhibited a reduction in body weight and length, partial lipodystrophy, and systemic insulin resistance. These derangements were associated with a reduced capacity of insulin and other growth factors to activate PI3K in liver, muscle, and fat; marked insulin resistance in liver and fat of mutation-harboring animals; and insulin resistance in vitro in cells derived from these mice. In addition, mutant mice displayed defective insulin secretion and GLP-1 action on islets in vivo and in vitro. These data demonstrate the ability of this heterozygous mutation to alter PI3K activity in vivo and the central role of PI3K in insulin/growth factor action, adipocyte function, and glucose metabolism.
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Negahdar M, Aukrust I, Molnes J, Solheim MH, Johansson BB, Sagen JV, Dahl-Jørgensen K, Kulkarni RN, Søvik O, Flatmark T, Njølstad PR, Bjørkhaug L. GCK-MODY diabetes as a protein misfolding disease: the mutation R275C promotes protein misfolding, self-association and cellular degradation. Mol Cell Endocrinol 2014; 382:55-65. [PMID: 24001579 DOI: 10.1016/j.mce.2013.08.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 08/22/2013] [Accepted: 08/23/2013] [Indexed: 11/28/2022]
Abstract
GCK-MODY, dominantly inherited mild hyperglycemia, is associated with more than 600 mutations in the glucokinase gene. Different molecular mechanisms have been shown to explain GCK-MODY. Here, we report a Pakistani family harboring the glucokinase mutation c.823C>T (p.R275C). The recombinant and in cellulo expressed mutant pancreatic enzyme revealed slightly increased enzyme activity (kcat) and normal affinity for α-D-glucose, and resistance to limited proteolysis by trypsin comparable with wild-type. When stably expressed in HEK293 cells and MIN6 β-cells (at different levels), the mutant protein appeared misfolded and unstable with a propensity to form dimers and aggregates. Its degradation rate was increased, involving the lysosomal and proteasomal quality control systems. On mutation, a hydrogen bond between the R275 side-chain and the carbonyl oxygen of D267 is broken, destabilizing the F260-L271 loop structure and the protein. This promotes the formation of dimers/aggregates and suggests that an increased cellular degradation is the molecular mechanism by which R275C causes GCK-MODY.
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Affiliation(s)
- Maria Negahdar
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
| | - Ingvild Aukrust
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway; Department of Biomedicine, University of Bergen, Bergen, Norway; Section of Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Janne Molnes
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Department of Biomedicine, University of Bergen, Bergen, Norway; Department of Pediatrics, Haukeland University Hospital, Bergen, Norway
| | - Marie H Solheim
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway; Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Bente B Johansson
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway; Department of Pediatrics, Haukeland University Hospital, Bergen, Norway
| | - Jørn V Sagen
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Institute of Medicine, University of Bergen, Bergen, Norway; Hormone Laboratory, Haukeland University Hospital, Bergen, Norway
| | - Knut Dahl-Jørgensen
- Pediatric Department Ullevaal, Oslo University Hospital, Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Rohit N Kulkarni
- Section of Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Oddmund Søvik
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway
| | | | - Pål R Njølstad
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Department of Pediatrics, Haukeland University Hospital, Bergen, Norway.
| | - Lise Bjørkhaug
- KG Jebsen Center for Diabetes Research, Department of Clinical Science, University of Bergen, Bergen, Norway; Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway; Department of Biomedicine, University of Bergen, Bergen, Norway
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