Nkx6.1 decline accompanies mitochondrial DNA reduction but subtle nucleoid size decrease in pancreatic islet beta-cells of diabetic Goto Kakizaki rats

0485798 - FGÚ 2018 RIV GB eng J - Journal Article
Špaček, Tomáš - Pavluch, Vojtěch - Alán, Lukáš - Capková, Nikola - Engstová, Hana - Dlasková, Andrea - Berková, Z. - Saudek, F. - Ježek, Petr
Nkx6.1 decline accompanies mitochondrial DNA reduction but subtle nucleoid size decrease in pancreatic islet beta-cells of diabetic Goto Kakizaki rats.
Scientific Reports. Roč. 7, Nov 15 (2017), č. článku 15674. ISSN 2045-2322. E-ISSN 2045-2322
R&D Projects: GA ČR(CZ) GA13-02033S; GA ČR(CZ) GA13-06666S; GA MŠMT(CZ) ED1.1.00/02.0109
Institutional support: RVO:67985823
Keywords : GK rat * superresolution fluorescence * microscopy reveals * binding-protein * insulin-release
OECD category: Cell biology
Impact factor: 4.122, year: 2017

Hypertrophic pancreatic islets (PI) of Goto Kakizaki (GK) diabetic rats contain a lower number of beta-cells vs. non-diabetic Wistar rat PI. Remaining beta-cells contain reduced mitochondrial (mt) DNA per nucleus (copy number), probably due to declining mtDNA replication machinery, decreased mt biogenesis or enhanced mitophagy. We confirmed mtDNA copy number decrease down to <30% in PI of one-year-old GK rats. Studying relations to mt nucleoids sizes, we employed 3D superresolution fluorescent photoactivable localization microscopy (FPALM) with lentivirally transduced Eos conjugate of mt single-stranded-DNA-binding protein (mtSSB) or transcription factor TFAM, or by 3D immunocytochemistry. mtSSB (binding transcription or replication nucleoids) contoured “nucleoid ”swhich were smaller by 25% (less diameters >150 nm) in GK beta-cells. Eos-TFAM-visualized nucleoids, composed of 72% localized TFAM, were smaller by 10% (immunochemically by 3%). A theoretical similar to 70% decrease in cell nucleoid number (spatial density) was not observed, rejecting model of single mtDNA per nucleoid. The beta-cell maintenance factor Nkx6.1 mRNA and protein were declining with age (>12-fold, 10 months) and decreasing with fasting hyperglycemia in GK rats, probably predetermining the impaired mtDNA replication (copy number decrease), while spatial expansion of mtDNA kept nucleoids with only smaller sizes than those containing much higher mtDNA in non-diabetic beta-cells.
Permanent Link: http://hdl.handle.net/11104/0281250