| Abstract | Objectives: Diabetes mellitus has been associated with increased risk of cognitive decline, dementia, depression and anxiety. The aims of this study were to determine the influence of aging and long-term type 1 diabetes mellitus (DM1) on the rate of adult neurogenesis in subventricular zone of rats, as well as to determine the possible role of DSTYK protein in the adult neurogenesis in subventricular zone of rats as a possible disease mechanism.
Material and Methods: Thirty-five male Sprague-Dawley rats randomly divided into two groups: control or diabetic. DM1 was induced by intraperitoneal injection of streptozotocin (55 mg/kg). DM1 was confirmed by measuring of plasma glucose 4 days after induction. Rats were sacrificed 2 weeks, 6 months and 1 year after induction of the DM1. Tissues of brain were processed for the immunohistochemistry for doublecortin (DCX) alone, or in combination with DSTYK.
Results: For the thick part of the subependymal layer of the SVZ, the percentage of DCX area in the sections from a control group significantly decreased 6 months in comparison to the 2 weeks after the beginning of the experiment (P<0.01). For the thin part of the SVZ we measured the ratios of DCX staining surface to total nuclear surface. At two weeks and at 6 months the differences between the controls and the diabetic rats were not statistically significant. At 1 year there was a significant decrease (P = 0.025) between the controls and diseased animals. We also observed significant increase (P=0.045) comparing neurogenesis at 6 months and 1 year within the within the control group.
DSTYK immunoreactivity was restricted to a wall of the brain blood vessels, the cells of the pia mater, as well as in glia of the white matter in different parts of the brain and spinal cord. In addition, we found expression of DSTYK on a regular base in ependymal cells of the central canal of the spinal cord and lateral ventricles of the brain. We did not find any signs of co-localization of the DSTYK with DCX, a marker for the neuroblasts in any of studied groups of animals.
Conclusion: We concluded that long term experimental DM1 is decreasing neurogenesis in thin part of the SVZ in rat brain, while the short term DM1 did not have influence. Hence, short term studies are not relevant in conclusions for the influence of DM1 on neurogenesis in SVZ of rat. Ageing has an influence on neurogenesis in thick part of the SVZ of the rat brain and pattern of changes is bi-phasic, with initial transient decrease and increase in age of 14 months. DSTYK is expressed in rat brain in neurogenic areas of the SVZ, hence could have role in initial steps of the adult neurogenesis. Since DSTYK is not expressed in neuroblasts, it probably does not have role in their differentiation. |
| Abstract (croatian) | Ciljevi: Šećerna bolest povezana je s povećanim rizikom slabljenja kognitivnih sposobnosti, demencija, depresije i anksioznosti. Ciljevi ovog istraživanja bili su odrediti utjecaj starenja i šećerne bolesti tipa 1 (DM1) na neurogenezu u subventrikularnoj zoni (SVZ) mozga štakora, kao i odrediti moguću ulogu DSTYK u adultnoj neurogenezi u subventrikularnoj zoni, kao moguće mehanizme u nastanku ove bolesti.
Materiali i methode: Trideset pet štakora muškog spola soja Sprague-Dawley podijeljeni su nasumično u dvije skupine: kontrolne i dijabetične životinje. DM1 je izazvan intraperitonealnom aplikacijom streptozotocina (55 mg/kg). DM1 potvrđen je mjerenjem glukoze u plazmi 4 dana nakon indukcije. Štakori su žrtvovani 2 tjedna, 6 mjeseci ili 1 godinu nakon indukcije DM1. Tkiva mozga pripremljena su te obojena imunohistokemijski na doublecortin (DCX) samostalno, ili u kombinaciji s DSTYK.
Rezultati: U debljem području subependimskog sloja SVZ, postotak površine pod DCX u rezovima mozga kontrolnih štakora značajno se smanjio 6 mjeseci, u usporedbi s 2 tjedna nakon početka pokusa (P<0,01). U tanjem dijelu subependimskog sloja SVZ mjerili smo omjer površine pod DCX prema ukupnoj površini jezgara. Dva tjedna i 6 mjeseci nakon početka pokusa nisu pornađene značajne razlike između kontrolnih i dijabetičnih štakora. Dvanaest mjeseci nakon početka pokusa uočen je značajni izražaja DCX u dijabetičnih, u usporedbi s kontrolnim štakorima (P = 0,025). Također je uočen značajni porast izražaja DCX (P=0,045) 12 mjeseci nakon početka pokusa u usporedbi s 6 mjeseci, unutar kontrolne skupine životinja.
Imunoreaktivnost na DSTYK bila je ograničena na stjenke krvnih žila mozga, stanice meke moždane ovojnice (pia mater), kao i na glija stanice u bijeloj tvari različitih dijelova mozga i kralježnične moždine. Nadalje, redovito je pronađen izražaj DSTYK u ependimskim stanicama središnjeg kanala kralježnične moždine i lateralnih komora mozga. Nisu pronađeni znakovi ko-lokalizacije DSTYK s DCX, biljegom neuroblasta, niti u jednoj od istraživanih skupina.
Zaključci: Dugotrajni DM1 smanjuje neurogenezu u tanjem dijelu SVZ mozga štakora, dok kratkotrajni DM1 nije imao nikakvog utjecaja. Stoga se zaključuje kako kratkotrajne studije nisu u potpunosti relevantne za zaključke o utjecaju DM1 na neurogenezu u SVZ štakora. Nadalje, starenje utječe na neurogenezu u debljem dijelu SVZ a uzorak promjena izazvanih starenjem je bifazičan, s početnim prolaznim smanjenjem te porastom u dobi od 14 mjeseci. DSTYK je izražen u neurogenim područjima SVZ štakorskog mozga, te bi stoga mogao imati ulogu u početnim stadijima adultne neurogeneze. Budući da nije izražen u neuroblastima, vjerojatno je da DSTYK nema ulogu u njihovoj diferencijaciji u neurone. |
