Traumatic brain injury (TBI) represents a brain tissue injury caused by
mechanical head injury. TBI is one of the leading causes of death and
disability in the world human population, up to 45 years ...of age. Consequences
of brain injury depend on the location and amount of brain tissue damage, and
can range from mild motor and cognitive impairment, to severe forms of
disability and death. Traumatic brain injury leads to impairment of
blood-brain barrier, resulting in a precisely defined sequence of events in
injured CNS tissue. Two main phases could be distinguished: acute phase,
which is called the primary injury that occurs by direct action of mechanical
forces on the brain tissue and occurs at the time of injury. The events that
followed thereafter are called the secondary injury. Secondary injury occurs
as a result of the initial damage, and includes the processes that lead to
further tissue damage in the days and weeks following injury. These are
primarily inflammatory processes that lead to the death of neurons that
initially were not affected by mechanical injury. It is believed that the
neuronal cell death caused by secondary injury is far greater than the one
caused by primary injury. The fact that most of the processes within the
secondary injury occur relatively late (hours and days following injury)
makes them subject to various therapeutic interventions. For decades, it is
known that food restriction has a beneficial effect on the entire organism by
delaying age-dependent physiological changes and reducing the incidence of
various diseases (cancer, autoimmune disease, Parkinson's and Alzheimer's,
etc). However, only in the last ten years has been to investigate the
influence reduced food intake in the recovery process following injury.
Previous research in this field has shown that several months long food
restriction prior to CNS injury has neuroprotective effects and promotes
functional recovery in several different models of injury. The data
considering effects of DR on different aspects of secondary injury, as well
as secondary neuronal cell death following TBI are still scarce. Therefore,
the aim of this study was to determine whether dietary restriction (DR) can
affect the processes that occur in the brain after injury, primarily, whether
it can influence the process of secondary injury. For the purpose of the
experiment, male Wistar rats 3 months old were divided into two groups, the
ad libitum animals (AL) and the dietary restricted animals (DR). Animals from
the AL group had unlimited access to food throughout the duration of the
experiment, whereas the animals DR groups received 50% of normal daily food
intake. Upon reaching the age of 6 months, the animals were subjected to stub
lesion to the somatosensory cortex, and then were sacrificed at different
time points: control, 2, 7, 14 and 28 day following lesion. In order to
determine the effect of dietary restriction on processes following TBI
following processes were examined: inflammatory processes, secondary
neurodegeneration and neural plasticity. Changes in the temporal and spatial
expression of target mRNA and proteins were examined by using Western blot
analysis, RT-PCR and real-time RT-PCR, histological and immunohistochemical
staining. To determine the effect of dietary restriction on recovery
following TBI genes and proteins involved in the processes of inflammation,
secondary neurodegeneration, as well as those who participate in the
processes of plasticity, were investigated. The results obtained in this
thesis show that dietary restriction significantly changes the brain tissue
response to injury, affecting numerous processes following injury. Namely,
dietary restriction affects the inflammatory process by suppression of
microglial activation, and TNF-α protein induction following injury. Also, DR
acts neuroprotective by suppressing active caspase-3 induction and secondary
neuronal death in the early phase of recovery following brain injury. Dietary
restriction increases the expression of synaptic plasticity proteins GAP-43
and synaptophysin around the site of the injury, with simultaneous
suppression of the activation of astrocytes and reduction of synthesis of
inhibitory proteoglycan - neurocan. Also, DR leads to a prominent increase in
the concentration of corticosterone, and consequent changes in the GR
signaling pathway. Dietary restriction affected the expression of NF-kappaB
transcription factor, as well as the expression of mRNA for Bcl-2 and Bcl-xL,
antiapoptotic genes regulated by mentioned transcription factor. The results
of this study showed that dietary restriction has the capacity to
significantly shape the response of damaged brain tissue by direct impact on
the processes of secondary injury and neural plasticity. Also, these results
point to the possibility of using dietary restriction in clinical practice
for patients who have suffered a brain injury.
Traumatska povreda mozga (engl. traumatic brain injury, TBI) predstavlja
povredu moždanog tkiva uzrokovanu mehaničkom povredom glave. TBI je jedan od
vodećih uzroka smrtnosti i invaliditeta u svetu, u populaciji ljudi do 45
godina starosti. Posledice TBI zavise od lokalizacije i količine oštećenja
moždanog tkiva i mogu varirati od blažih motoričkih i kognitivnih smetnji, pa
sve do težih oblika invaliditeta i smrti. Traumatska povreda mozga dovodi do
narušavanja krvno-moždane barijere, što rezultuje tačno određenim sledom
događaja u povređenom tkivu CNS-a. Naime, akutna faza, označena kao primarna
povreda, nastaje direktnim delovanjem mehaničke sile na moždano tkivo i
javlja se u trenutku povrede. Događaji koji slede nakon toga označeni su kao
sekundarna povreda koja nastaje kao posledica inicijalnog oštećenja, a
obuhvata procese koji dovode do daljeg oštećenja tkiva u danima i nedeljama
nakon povrede. To su pre svega zapaljenski procesi koji dovode do smrti
neurona koji prvobitno nisu bili zahvaćeni mehaničkom povredom. Smatra se da
je broj neurona koji umre usled širenja sekundarne povrede daleko veći od
broja neurona koji strada usled primarne povrede. Činjenica da se većina
procesa u okviru sekundarne povrede odigrava relativno kasno (satima i danima
nakon povrede) čini ih podložnim različitim terapeutskim intervencijama. Već
decenijama je poznato da restrikcija hrane povoljno deluje na čitav organizam
tako što odlaže starosno-zavisne fiziološke promene i smanjuje incidencu
različitih obolenja (kancer, autoimunske bolesti, Parkinsonova i Alchajmerova
bolest, itd.) Međutim, tek u poslednjih desetak godina intenzivno se
istražuje uticaj smanjenog unosa hrane na procese oporavka nakon povrede.
Dosadašnja istraživanja na ovom polju su pokazala da restrikcija hrane u
trajanju od nekoliko meseci pre povrede CNS-a ima neuroprotektivno dejstvo i
promoviše funkcionalni oporavak u nekoliko različitih modela povrede. Efekti
dijetalne restrikcije na različite aspekte sekundarne povrede, kao i na
sekundarnu ćelijsku smrt nakon traumatske povrede mozga još uvek nisu
dovoljno ispitani. Stoga je cilj ovog istraživanja bio je da se utvrdi da li
i u kojoj meri dijetalna restrikcija (DR) može uticati na procese koji se u
mozgu dešavaju nakon povrede, a pre svega, da li može da utiče na procese
sekundarne povrede. Za potrebe eksperimenta, mužjaci pacova Wistar soja stari
3 meseca su podeljeni u dve grupe, ad libitum životinje (AL) i životinje na
restriktivnom režimu ishrane (DR). Životinje iz AL grupe imale su neograničen
pristup hrani tokom čitavog vremena trajanja eksperimenta, dok su životinje
iz DR grupe dobijale 50% normalnog dnevnog unosa hrane. Sa navršenom starošću
od 6 meseci životinje su podvrgnute ubodnoj leziji senzomotorne kore prednjeg
mozga, a zatim su žrtvovane u različitim vremenskim tačkama: kontrola, 2, 7,
14. i 28. dan nakon lezije. Kako bi se utvrdio efekat dijetalne restrikcije
na oporavak nakon traumatske povrede mozga praćeni su procesi inflamacije,
sekundarne neurodegeneracije i neuralne plastičnosti. Primenom metoda Western
blot analize, RT- i PCR-a u realnom vremenu, histološkog bojenja i
imunohistohemije ispitivane su promene u vremenskoj i prostornoj ekspresiji
ciljnih iRNK i proteina, markera ovih procesa. Rezultati dobijeni u okviru
ove disertacije pokazuju da dijetalna restrikcija u značajnoj meri menja
odgovor tkiva mozga na povredu, utičući na brojne procese nakon povrede.
Naime, dobijeni rezultati su pokazali da dijetalna restrikcija utiče na
procese inflamacije suprimirajući aktivaciju mikroglijskih ćelija, kao i
indukciju solubilnog TNF-α proteina nakon povrede. Takođe, DR deluje
neuroprotektivno suprimirajući indukciju aktivne kaspaze-3 i sekundarnu smrt
neurona u ranoj fazi oporavka nakon povrede mozga. Dijetalna restrikcija
povećava ekspresiju proteina sinaptičke plastičnosti GAP-43 i sinaptofizina
oko samog mesta povrede, uz istovremenu supresiju aktivacije astrocita i
smanjenje sinteze inhibitornog proteoglikana neurokana. Takođe, DR dovodi do
izrazitog povećanja koncentracije kortikosterona, kao i posledične promene u
fosforilaciji GR-a, i u nivou 11β-HSD1 proteina nakon povrede. Dijetalna
restrikcija je uticala i na ekspresiju transkripcionog faktora NF-κB, kao i
na ekspresiju iRNK za Bcl-2 i Bcl-xL, antiapoptotskih gena koje reguliše
NF-κB. Rezultati ove studije su pokazali da dijetalna restrikcija ima
kapacitet da u značajnoj meri oblikuje odgovor povređenog tkiva mozga
direktnim uticajem na procese sekundarne povrede, ali i plastičnosti. Takođe,
ovi rezultati ukazuju na mogućnost primene dijetalne restrikcije i u
kliničkoj praksi kod povreda mozga.
Traumatic brain injury (TBI) represents a brain tissue injury caused by
mechanical head injury. TBI is one of the leading causes of death and
disability in the world human population, up to 45 years ...of age. Consequences
of brain injury depend on the location and amount of brain tissue damage, and
can range from mild motor and cognitive impairment, to severe forms of
disability and death. Traumatic brain injury leads to impairment of
blood-brain barrier, resulting in a precisely defined sequence of events in
injured CNS tissue. Two main phases could be distinguished: acute phase,
which is called the primary injury that occurs by direct action of mechanical
forces on the brain tissue and occurs at the time of injury. The events that
followed thereafter are called the secondary injury. Secondary injury occurs
as a result of the initial damage, and includes the processes that lead to
further tissue damage in the days and weeks following injury. These are
primarily inflammatory processes that lead to the death of neurons that
initially were not affected by mechanical injury. It is believed that the
neuronal cell death caused by secondary injury is far greater than the one
caused by primary injury. The fact that most of the processes within the
secondary injury occur relatively late (hours and days following injury)
makes them subject to various therapeutic interventions. For decades, it is
known that food restriction has a beneficial effect on the entire organism by
delaying age-dependent physiological changes and reducing the incidence of
various diseases (cancer, autoimmune disease, Parkinson's and Alzheimer's,
etc). However, only in the last ten years has been to investigate the
influence reduced food intake in the recovery process following injury.
Previous research in this field has shown that several months long food
restriction prior to CNS injury has neuroprotective effects and promotes
functional recovery in several different models of injury. The data
considering effects of DR on different aspects of secondary injury, as well
as secondary neuronal cell death following TBI are still scarce. Therefore,
the aim of this study was to determine whether dietary restriction (DR) can
affect the processes that occur in the brain after injury, primarily, whether
it can influence the process of secondary injury. For the purpose of the
experiment, male Wistar rats 3 months old were divided into two groups, the
ad libitum animals (AL) and the dietary restricted animals (DR). Animals from
the AL group had unlimited access to food throughout the duration of the
experiment, whereas the animals DR groups received 50% of normal daily food
intake. Upon reaching the age of 6 months, the animals were subjected to stub
lesion to the somatosensory cortex, and then were sacrificed at different
time points: control, 2, 7, 14 and 28 day following lesion. In order to
determine the effect of dietary restriction on processes following TBI
following processes were examined: inflammatory processes, secondary
neurodegeneration and neural plasticity. Changes in the temporal and spatial
expression of target mRNA and proteins were examined by using Western blot
analysis, RT-PCR and real-time RT-PCR, histological and immunohistochemical
staining. To determine the effect of dietary restriction on recovery
following TBI genes and proteins involved in the processes of inflammation,
secondary neurodegeneration, as well as those who participate in the
processes of plasticity, were investigated. The results obtained in this
thesis show that dietary restriction significantly changes the brain tissue
response to injury, affecting numerous processes following injury. Namely,
dietary restriction affects the inflammatory process by suppression of
microglial activation, and TNF-α protein induction following injury. Also, DR
acts neuroprotective by suppressing active caspase-3 induction and secondary
neuronal death in the early phase of recovery following brain injury. Dietary
restriction increases the expression of synaptic plasticity proteins GAP-43
and synaptophysin around the site of the injury, with simultaneous
suppression of the activation of astrocytes and reduction of synthesis of
inhibitory proteoglycan - neurocan. Also, DR leads to a prominent increase in
the concentration of corticosterone, and consequent changes in the GR
signaling pathway. Dietary restriction affected the expression of NF-kappaB
transcription factor, as well as the expression of mRNA for Bcl-2 and Bcl-xL,
antiapoptotic genes regulated by mentioned transcription factor. The results
of this study showed that dietary restriction has the capacity to
significantly shape the response of damaged brain tissue by direct impact on
the processes of secondary injury and neural plasticity. Also, these results
point to the possibility of using dietary restriction in clinical practice
for patients who have suffered a brain injury.
Traumatska povreda mozga (engl. traumatic brain injury, TBI) predstavlja
povredu moždanog tkiva uzrokovanu mehaničkom povredom glave. TBI je jedan od
vodećih uzroka smrtnosti i invaliditeta u svetu, u populaciji ljudi do 45
godina starosti. Posledice TBI zavise od lokalizacije i količine oštećenja
moždanog tkiva i mogu varirati od blažih motoričkih i kognitivnih smetnji, pa
sve do težih oblika invaliditeta i smrti. Traumatska povreda mozga dovodi do
narušavanja krvno-moždane barijere, što rezultuje tačno određenim sledom
događaja u povređenom tkivu CNS-a. Naime, akutna faza, označena kao primarna
povreda, nastaje direktnim delovanjem mehaničke sile na moždano tkivo i
javlja se u trenutku povrede. Događaji koji slede nakon toga označeni su kao
sekundarna povreda koja nastaje kao posledica inicijalnog oštećenja, a
obuhvata procese koji dovode do daljeg oštećenja tkiva u danima i nedeljama
nakon povrede. To su pre svega zapaljenski procesi koji dovode do smrti
neurona koji prvobitno nisu bili zahvaćeni mehaničkom povredom. Smatra se da
je broj neurona koji umre usled širenja sekundarne povrede daleko veći od
broja neurona koji strada usled primarne povrede. Činjenica da se većina
procesa u okviru sekundarne povrede odigrava relativno kasno (satima i danima
nakon povrede) čini ih podložnim različitim terapeutskim intervencijama. Već
decenijama je poznato da restrikcija hrane povoljno deluje na čitav organizam
tako što odlaže starosno-zavisne fiziološke promene i smanjuje incidencu
različitih obolenja (kancer, autoimunske bolesti, Parkinsonova i Alchajmerova
bolest, itd.) Međutim, tek u poslednjih desetak godina intenzivno se
istražuje uticaj smanjenog unosa hrane na procese oporavka nakon povrede.
Dosadašnja istraživanja na ovom polju su pokazala da restrikcija hrane u
trajanju od nekoliko meseci pre povrede CNS-a ima neuroprotektivno dejstvo i
promoviše funkcionalni oporavak u nekoliko različitih modela povrede. Efekti
dijetalne restrikcije na različite aspekte sekundarne povrede, kao i na
sekundarnu ćelijsku smrt nakon traumatske povrede mozga još uvek nisu
dovoljno ispitani. Stoga je cilj ovog istraživanja bio je da se utvrdi da li
i u kojoj meri dijetalna restrikcija (DR) može uticati na procese koji se u
mozgu dešavaju nakon povrede, a pre svega, da li može da utiče na procese
sekundarne povrede. Za potrebe eksperimenta, mužjaci pacova Wistar soja stari
3 meseca su podeljeni u dve grupe, ad libitum životinje (AL) i životinje na
restriktivnom režimu ishrane (DR). Životinje iz AL grupe imale su neograničen
pristup hrani tokom čitavog vremena trajanja eksperimenta, dok su životinje
iz DR grupe dobijale 50% normalnog dnevnog unosa hrane. Sa navršenom starošću
od 6 meseci životinje su podvrgnute ubodnoj leziji senzomotorne kore prednjeg
mozga, a zatim su žrtvovane u različitim vremenskim tačkama: kontrola, 2, 7,
14. i 28. dan nakon lezije. Kako bi se utvrdio efekat dijetalne restrikcije
na oporavak nakon traumatske povrede mozga praćeni su procesi inflamacije,
sekundarne neurodegeneracije i neuralne plastičnosti. Primenom metoda Western
blot analize, RT- i PCR-a u realnom vremenu, histološkog bojenja i
imunohistohemije ispitivane su promene u vremenskoj i prostornoj ekspresiji
ciljnih iRNK i proteina, markera ovih procesa. Rezultati dobijeni u okviru
ove disertacije pokazuju da dijetalna restrikcija u značajnoj meri menja
odgovor tkiva mozga na povredu, utičući na brojne procese nakon povrede.
Naime, dobijeni rezultati su pokazali da dijetalna restrikcija utiče na
procese inflamacije suprimirajući aktivaciju mikroglijskih ćelija, kao i
indukciju solubilnog TNF-α proteina nakon povrede. Takođe, DR deluje
neuroprotektivno suprimirajući indukciju aktivne kaspaze-3 i sekundarnu smrt
neurona u ranoj fazi oporavka nakon povrede mozga. Dijetalna restrikcija
povećava ekspresiju proteina sinaptičke plastičnosti GAP-43 i sinaptofizina
oko samog mesta povrede, uz istovremenu supresiju aktivacije astrocita i
smanjenje sinteze inhibitornog proteoglikana neurokana. Takođe, DR dovodi do
izrazitog povećanja koncentracije kortikosterona, kao i posledične promene u
fosforilaciji GR-a, i u nivou 11β-HSD1 proteina nakon povrede. Dijetalna
restrikcija je uticala i na ekspresiju transkripcionog faktora NF-κB, kao i
na ekspresiju iRNK za Bcl-2 i Bcl-xL, antiapoptotskih gena koje reguliše
NF-κB. Rezultati ove studije su pokazali da dijetalna restrikcija ima
kapacitet da u značajnoj meri oblikuje odgovor povređenog tkiva mozga
direktnim uticajem na procese sekundarne povrede, ali i plastičnosti. Takođe,
ovi rezultati ukazuju na mogućnost primene dijetalne restrikcije i u
kliničkoj praksi kod povreda mozga.
Ageing of the central nervous system is associated with a number of changes
that disturb nerve function, especially motor control and cognitive
abilities. It is believed that cognitive disorders in ...aging are consequence
of reduced synaptic plasticity, especially in the cortex and hippocampus,
brain regions extremely important for learning and memory processes. Dominant
factor that can influence aging in general, and therefore the aging of the
brain is reduced diet regime, without malnutrition. In addition to being
known for decades that reduced caloric intake prolongs life span of many
species, including mammals, it is shown that it delays and alleviates
age-dependent changes. Cholesterol is the most abundant lipid in mammalian
cells. By participating in the construction of phospholipid bilayer of
biological membranes, it regulates their fluidity, permeability and rigidity,
and consequently the functional properties of membrane proteins, such as ion
channels and transmmitters receptors. Cholesterol metabolism represents one
aspect of synaptic plasticity, as has been shown that cholesterol is
essential for biogenesis of synaptic vesicles, and vesicle transport, as well
as for proper functional organization of lipid rafts. The brain contains the
most cholesterol of all the organs in the body. Maintenance of cholesterol
homeostasis is essential for proper functioning of the central nervous
system. The aim of this study was to analyze the influence of aging and
long-term dietary restriction on cholesterol metabolism in the rat serum,
cortex and hippocampus. The experiments were performed on 3-, 12-, and
24-month-old male Wistar rats fed ad libitum (AL), or exposed to long term DR
(100% every other day-EOD) starting from the age of 3. At the indicated time
points, the rats were killed by decapitation. The expression of proteins
involved in cholesterol synthesis (HMGCR), transport (ApoE), catabolism
(CYP46) and regulation (LXRα) was determined using Western blot and
immunohistochemistry. The levels of cholesterol, its precursors (lanosterol,
lathosterol, desmosterol) and metabolites (24S-hydroxycholesterol,
27-hydroxycholesterol, cholestanol) were determined by gas
chromatography/mass spectrometry (GC/MS). The same method was used to analyze
the amount of phytosterols, given the increasing use of foods enriched with
plant analogues of cholesterol in human nutrition. Additionally, the link
between cholesterol content and neurotrophin signaling in the rat cortex and
hippocampus was analyzed at protein level. In rat serum cholesterol levels
were increased during ageing, regardless of diet regime. Long-term dietary
restriction counteracted age-dependent increase in the amount of cholesterol
precursors, maintaining their level at the one measured in 3 month old
animals. The same influence of dietary restrictions was detected on the
age-dependent increase in the cholestanol levels. The amount of
24S-hydroxycholesterol remained stable under experimental conditions, while
dietary restriction had no effect on elevated 27-hydroxycholesterol levels
during ageing. Ageing has led to increased phytosterols levels, while reduced
dietary intake maintained their content on control levels measured in
3-month-old animals. During aging, there was a reduction in HMGCR protein in
the rat cortex, regardless of the diet, and reduction in the levels of LXRα
protein, which has been reinforced by dietary restriction. The amount of ApoE
protein was increased during ageing. Dietary restriction in the group of
12-month-old animals acted contrary to aging, reducing the amount of this
protein in relation to age control. CYP46 protein levels were increased in
the group of 24-month-old animals exposed to diet. In the rat hippocampus
aging has caused decreased levels of HMGCR, CYP46 and LXRα proteins,
regardless of the diet. The amount of ApoE protein in the oldest group of
rats that were exposed to dietary restriction was increased in comparison to
age-control, and compared to 3 month old animals. Aging induced slight but
significant increase of cholesterol content in the rat cortex, while there
were no changes in the amount of cholesterol in the hippocampus. With the
exception of lanosterol at 12- month- old AL- fed animals, cholesterol
precursors were less common in aging in both brain regions examined. Dietary
restriction in the group 12mAL animals prevented the increase of lanosterol
amount, keeping it at the level detected in 3-month-old animals. In the
hippocampus of 24-month old animals, reduced diet intake increased
desmosterol amount in relation to age control, although the amount was still
less than that measured in 3-month-old controls. Cholestanol content was
increased during ageing, regardless of diet regime. The levels of
24S-hydroxycholesterol remained stable under experimental conditions,
indicating that experimental conditions had no influence on brain cholesterol
catabolism. Amount of plant sterols in both brain structures was increased
during aging, while the reduced diet intake acted contrary to the aging,
decreasing their levels in relation to age-appropriate controls. Only the
amount of brassicasterol in the cortex did not change in the analyzed
experimental conditions. In the rat cortex ageing influenced increased BDNF
protein levels, and decreased levels of activated receptor pTrkB. Dietary
restriction in the group of 12-month-old animals further increased the amount
of BDNF, while in the oldest group acted contrary to aging, keeping the
amount of this trephine on the control level. At 12-month-old animals dietary
restriction maintained levels of activated receptors at the one measured in
animals aged 3 months. The total receptor in the cortex did not change in the
analyzed conditions. Changes in trephine signaling in the hippocampus during
aging and under the influence of long-term dietary restriction were detected
only through the increase in BDNF protein in the group 12 months old animals
exposed to reduced feeding compared to 3 month old animals. The results
obtained in this thesis showed that the cholesterol metabolism in the rat
cortex and hippocampus have changed during ageing and under the influence of
long-term dietary restriction. The greatest changes were observed at the
level of cholesterol precursors, indicating a reduced rate of cholesterol
synthesis, while the elimination of cholesterol from the brain determined by
its derivate, 24S-hydroxycholesterol, was not altered under the experimental
conditions. Effect of long-term dietary restriction on cholesterol metabolism
was more pronounced in the hippocampus than in the cortex, and was similar to
the impact of reduced dietary intake manifested in the rat serum. The link
between cholesterol and neurotrophine signaling was more evident in the
cortex than in hippocampus. The results of this study showed the capacity of
long-term dietary restriction to influence cholesterol metabolism in the
brain by reducing its synthesis, whereas the amount of cholesterol remained
unchanged, and point to long-term DR as a possible alternative to statin use
for its ability to preserve cholesterol homeostasis in the brain.
Starenje centralnog nervnog sistema (CNS) praćeno je brojnim promenama koje
dovode do narušavanja nervnih funkcija, pre svega kontrole motorike i
kognitivnih sposobnosti. Smatra se da su kognitivni poremećaji tokom starenja
posledica smanjene sinaptičke plastičnosti, naročito u korteksu i
hipokampusu, regionima mozga izuzetno važnim za procese učenja i pamćenja.
Najvažniji faktor sredine kojim se može uticati na starenje uopšte, a samim
tim i na starenje mozga je režim redukovane ishrane, bez pothranjenosti.
Pored toga što se već nekoliko decenija zna da redukovana ishrana produžava
životni vek mnogih vrsta, uključujući i sisare, pokazano je da ona odlaže i
ublažava starosno zavisne promene u nervnom sistemu. Holesterol je
najzastupljeniji lipid u ćelijama sisara. Učestvujući u izgradnji
fosfolipidnog dvosloja bioloških mambrana, on reguliše njihovu fluidnost,
propustljivost i rigidnost, a samim tim i funkcionalna svojstva membranskih
proteina, poput jonskih kanala i transmiterskih receptora. Metabolizam
holesterola predstavlja važan aspekt sinaptičke plastičnosti, jer je pokazano
da je holesterol neophodan za biogenezu i transport sinaptičkih vezikula, kao
i za prvilnu funkcionalnu organizaciju lipidnih ostvaca. Od svih organa u
telu, mozak sadrži najviše holesterola. Održavanje homeostaze holesterola
neophodno je za normalno i neometano funkcionisanje CNS. Cilj ovog
istraživanja bio je da se vidi kako starenje i dugotrajna dijetalna
restrikcija (DR) utuču na metabolizam holesterola u mozgu. Mužjaci pacova
soja Wistar stari 3 meseca (m) bili su podeljeni u dve grupe. Prva grupa,
označena kao ad libitum (AL), dobijala je svakog dana 100% dnevnog unosa
hrane, dok je druga grupa (označena kao DR) stavljena na režim redukovane
ishrane koji je podrazumevao dobijanje 100% dnevnog unosa hrane svakog drugog
dana. Životinje su žrtvovane nakon dostizanja starosti od 12 i 24m. Životinje
stare 3m su predstavljale kontrolnu starosnu grupu. Metabolizam holesterola
određivan je na nivou proteina koji su uključeni u sintezu holesterola
(HMGCR), njegov transport (ApoE), katabolizam (CYP46) i regulaciju (LXRα)
metodom Western blota i imunohistohemijski. Zastupljenost samog holesterola,
njegovih prekursora (lanosterol, latosterol, dezmosterol) i metabolita
(24S-hidroksiholesterol, 27-hidroksiholesterol, holestanol) određena je
gasnom hromatografijom-masenom spektrometrijom (GC-MS). U primenjenim
eksperimentalnim uslovima istom metodom analizirana je i zastupljenost
biljnih sterola u svetlu sve veće upotrebe hrane obogaćene biljnim analozima
holesterola u ljudskoj ishrani. Pored toga, praćena je i veza između sadržaja
holesterola i neurotrofinske signalizacije. Praćenje promena u metabolizam
holesterola pokazalo je da u serumu tokom starenja dolazi do povećanja
količine holesterola,
U članku se kombinirajući elemente gramatike ovisnosti i kognitivne gramatike predlaže (u
rudimentarnom obliku) novi model rečenične strukture u mađarskom, s posebnim osvrtom na
strukturni fokus i ...negaciju. U okviru ovog modela, jezgro sintakse mađarskog jezika se opisuje
pomoću različitih tipova simboličkih relacija (formalno kodiranih semantičkih relacija) izme
đu predikata i njegovih dopuna. Dopunjujući tradicionalni skup relacijskih kategorija {subjekt,
objekt, priloška oznaka} koje su relevantne u mađarskome, uvodi se druga dimenzija
opisa s relacijskim kategorijama {elaborator, proširivač, restriktor} koje se odnose na red riječi i prozodiju. Time se otvara mogućnost novog pristupa strukturnim fokusima i rečeničnom
negatoru u mađarskome koje se interpretira kao poseban tip simboličke relacije predikata.
U skladu s povećanjem broja starijih ljudi u svijetu, fokus znanstvenika usmjeren je na ispitivanje me- hanizama procesa starenja kao i na uspostavljanje strategija / intervencija kako bi se usporilo ...starenje i postigla dugovječnost. Na predkliničkim modelima ispitivanja, najučinkovitija strategija za ovu svrhu, kao i za odgađanje bolesti povezanih s dobi, pokazana je prehrambena intervencija - ograničenje kalo- rija, ali i neki alternativni oblici ograničavanja kalorija. Mogući neželjeni učinci restrikcije još su u fazi ispitivanja, a poznato je da je to općenito teško provesti kod ljudi. Stoga je novo područje istraživanja u gerontologiji postalo otkriće i ispitivanje učinaka spojeva koji oponašaju učinke kalorijske restrikci- je, takozvane mimetike kalorijske restrikcije. Ti spojevi uključuju brojne spojeve prirodnog podrijetla, ali i odobrene lijekove s određenim indikacijama. Ovaj pregled sažima najnovije podatke o poznatim mehanizmima kalorijskog ograničenja i poznatijim mimeticima za ograničenje kalorija.
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