Uticaj dugotrajne restrikcije hrane na ekspresiju glukokortikoidnog receptora u prednjem mozgu pacova tokom starenja

Abstract

Dugotrajna restrikcija hrane produžava životni vek i odlaže pojavu mnogih bolesti koje sejavljaju sa starenjem. Brojni literaturni podaci ukazuju da kod životinja kojima je unos hranesmanjen izostaje karakterističan starosno-zavistan pad u kognitivnim funkcijama, međutim,mehanizam ovakvog neuroprotektivnog dejstva restrikcije hrane nije u potpunosti razjašnjen. Uisto vreme, kod životinja na dugotrajnoj restrikciji hrane se povećava nivo kortikosterona uplazmi što ukazuje da ovaj tretman deluje kao blagi stresor. Do sada nije ispitivano do kakvihpromena u signalnom putu glukokortikoida dovodi smanjeni unos hrane tokom starenja u mozgu.Centralno polje istraživanja procesa starenja neizbežno podrazumeva ispitivanje promena dokojih dolazi u korteksu i hipokampusu, strukturama mozga koje su ključne za kognitivnefunkcije. Sa druge strane, iste strukture učestvuju u regulaciji HHA ose kao važni regionidelovanja negativne povratne sprege.Cilj doktorske disertacije je da se ispita uloga signalnog puta glukokortikoida u korteksu ihipokampusu pacova tokom starenja i pod uticajem dugotrajne restrikcije hrane.Eksperimentalne životinje (mužjaci pacova soja Wistar) starosti 6 meseci su podeljene u dvegrupe. Prva grupa, označena kao ad libitum (AL), je imala neograničen pristup hrani, dok jedruga grupa (označena kao DR) podvrgnuta režimu redukovane ishrane koji je podrazumevaodobijanje 100% dnevnog unosa hrane AL životinja svakog drugog dana. Životinje su analiziranekada su dostigle starost od 18 i 24 meseca. Životinje stare 6 meseci su predstavljale kontrolnugrupu. Glukokortikoidna signalizacija u ispitivanim strukturama je praćena na prereceptorskomnivou, kao i na nivou ekspresije i aktivacije glukokortikoidnog receptora primenom imunoesej,imunoblot i PCR metoda, kao i imunohistohemijske analize.Rezultati doktorske disertacije pokazuju da tokom starenja dolazi do povećanjakoncentracije kortikosterona u korteksu pacova, dok dugotrajna restrikcija hrane povećava nivokortikosterona u obe ispitivane strukture. Utvrđeno je da nivo ključnog enzima koji u moždanomtkivu reguliše dostupnost kortikosterona za receptore, 11β-HSD1, raste u hipokampusu pacovakoji imaju neograničen pristup hrani. Tretman dugotrajnom restrikcijom hrane dovodi dopovećanja nivoa 11β-HSD1 u korteksu, dok u hipokampusu izostaje efekat na nivo ovog enzima...

Moderate restriction in food intake (dietary restriction, DR) extends the life-span anddelays the onset of many age-related diseases. In addition, food-restricted animals exhibitattenuated cognitive deficits during aging as they perform better in learning and memory tasksthan their ad libitum fed counterparts. At the same time, the animals on chronic food restrictionhave elevated levels of plasma corticosterone, which implies that this treatment could beconsidered as a mild stressor. So far, there are no literature data regarding the effects of foodrestriction on glucocorticoid signaling in the brain during aging and the mechanisms by whichDR exhibits its neuroprotective effects are poorly understood. Two brain regions of interest arecortex and hippocampus, regions particularly prone to age-related changes. The same regions arealso involved in cognition and regulation of the hypothalamic–pituitary–adrenal (HPA) axisactivity.The aim of the present study was to evaluate the effect of long-term food restriction onglucocorticoid signaling pathway in the cortex and hippocampus of rats during aging.Experimental animals (male Wistar rats, 6 months old) were divided into two groups. The ALgroup was fed ad libitum, whereas the food restricted group (DR) received 100% of the meandaily intake of the AL animals every other day. The animals were examined at the age of 18 and24 months. Six-month-old animals were used as a control. Glucocorticoid signaling in specificbrain regions was examined at the pre-receptor level, as well as regarding the level of expressionand glucocorticoid receptor activity by using immunoassays, Western blot, PCR andimmunohistochemistry.The results of this study demonstrate an age-related increase in cortical corticosteroneconcentration. The increase in the hormone level was further detected in DR animals, in bothbrain regions examined. However, 11β-HSD1, a key enzyme in brain tissue that regulates theavailability of corticosterone to its receptors, was increased only in the hippocampi of AL ratsand in the cortex of rats subjected to the long-term food restriction. The most pronouncedchanges in the level of glucocorticoid receptor during aging were observed in the hippocampi of AL animals...