title: Age-related mitochondrial DNA depletion and the impact on pancreatic Beta cell function.
abstract: Type 2 diabetes is characterised by an age-related decline in insulin secretion. We previously identified a 50% age-related decline in mitochondrial DNA (mtDNA) copy number in isolated human islets. The purpose of this study was to mimic this degree of mtDNA depletion in MIN6 cells to determine whether there is a direct impact on insulin secretion. Transcriptional silencing of mitochondrial transcription factor A, TFAM, decreased mtDNA levels by 40% in MIN6 cells. This level of mtDNA depletion significantly decreased mtDNA gene transcription and translation, resulting in reduced mitochondrial respiratory capacity and ATP production. Glucose-stimulated insulin secretion was impaired following partial mtDNA depletion, but was normalised following treatment with glibenclamide. This confirms that the deficit in the insulin secretory pathway precedes K+ channel closure, indicating that the impact of mtDNA depletion is at the level of mitochondrial respiration. In conclusion, partial mtDNA depletion to a degree comparable to that seen in aged human islets impaired mitochondrial function and directly decreased insulin secretion. Using our model of partial mtDNA depletion following targeted gene silencing of TFAM, we have managed to mimic the degree of mtDNA depletion observed in aged human islets, and have shown how this correlates with impaired insulin secretion. We therefore predict that the age-related mtDNA depletion in human islets is not simply a biomarker of the aging process, but will contribute to the age-related risk of type 2 diabetes.
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Donna L
authors.initials: DL
authors.lastname: Nile
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Audrey E
authors.initials: AE
authors.lastname: Brown
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Meutia A
authors.initials: MA
authors.lastname: Kumaheri
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Helen R
authors.initials: HR
authors.lastname: Blair
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Alison
authors.initials: A
authors.lastname: Heggie
authors.affiliation: Newcastle University Institute for Ageing, Newcastle University, Newcastle upon Tyne, NE4 5PL, United Kingdom.
authors.forename: Satomi
authors.initials: S
authors.lastname: Miwa
authors.affiliation: Department of Obstetrics and Gynaecology, Faculty of Medical and Health Sciences, University of Auckland, Auckland 1142, New Zealand.
authors.forename: Lynsey M
authors.initials: LM
authors.lastname: Cree
authors.affiliation: Wellcome Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, United Kingdom.
authors.forename: Brendan
authors.initials: B
authors.lastname: Payne
authors.affiliation: Wellcome Centre for Mitochondrial Research, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, United Kingdom.
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Chinnery
authors.affiliation: Unilever R&D, Colworth Science Park, Sharnbrook, Bedford, MK44 1LQ, United Kingdom.
authors.forename: Louise
authors.initials: L
authors.lastname: Brown
authors.affiliation: Unilever R&D, Colworth Science Park, Sharnbrook, Bedford, MK44 1LQ, United Kingdom.
authors.forename: David A
authors.initials: DA
authors.lastname: Gunn
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Walker
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004272:DNA, Mitochondrial / Q000187:drug effects / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000503:physiopathology*; D005947:Glucose / Q000494:pharmacology; D006609:High Mobility Group Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013549:Sweetening Agents / Q000494:pharmacology
chemical_list: D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D007328:Insulin; D012333:RNA, Messenger; D013549:Sweetening Agents; C081930:Tfam protein, mouse; D000255:Adenosine Triphosphate; D005947:Glucose