TY  - JOUR
A1  - Maass, Anne
A1  - Düzel, Sandra
A1  - Brigadski, Tanja
A1  - Goerke, Monique
A1  - Becke, Andreas
A1  - Sobieray, Uwe
A1  - Neumann, Katja
A1  - Lövdén, Martin
A1  - Lindenberger, Ulman
A1  - Bäckman, Lars
A1  - Braun-Dullaeus, Rüdiger
A1  - Ahrens, Dörte
A1  - Heinze, Hans-Jochen
A1  - Müller, Notger G.
A1  - Lessmann, Volkmar
A1  - Sendtner, Michael
A1  - Düzel, Emrah
T1  - Relationships of peripheral IGF-1, VEGF and BDNF levels to exercise-related changes in memory, hippocampal perfusion and volumes in older adults
JF  - NeuroImage
N2  - Animal models point towards a key role of brain-derived neurotrophic factor (BDNF), insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor (VEGF) in mediating exercise-induced structural and functional changes in the hippocampus. Recently, also platelet derived growth factor-C (PDGF-C) has been shown to promote blood vessel growth and neuronal survival. Moreover, reductions of these neurotrophic and angiogenic factors in old age have been related to hippocampal atrophy, decreased vascularization and cognitive decline. In a 3-month aerobic exercise study, forty healthy older humans (60 to 77 years) were pseudo-randomly assigned to either an aerobic exercise group (indoor treadmill, n = 21) or to a control group (indoor progressive-muscle relaxation/stretching, n = 19). As reported recently, we found evidence for fitness-related perfusion changes of the aged human hippocampus that were closely linked to changes in episodic memory function. Here, we test whether peripheral levels of BDNF, IGF-I, VEGF or PDGF-C are related to changes in hippocampal blood flow, volume and memory performance. Growth factor levels were not significantly affected by exercise, and their changes were not related to changes in fitness or perfusion. However, changes in IGF-I levels were positively correlated with hippocampal volume changes (derived by manual volumetry and voxel-based morphometry) and late verbal recall performance, a relationship that seemed to be independent of fitness, perfusion or their changes over time. These preliminary findings link IGF-I levels to hippocampal volume changes and putatively hippocampus-dependent memory changes that seem to occur over time independently of exercise. We discuss methodological shortcomings of our study and potential differences in the temporal dynamics of how IGF-1, VEGF and BDNF may be affected by exercise and to what extent these differences may have led to the negative findings reported here.
KW  - Exercise
KW  - Neurotrophic factors
KW  - Hippocampus
KW  - Vascular plasticity
KW  - Aging
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-189219
VL  - 131
ER  - 
TY  - JOUR
A1  - Wencker, Freya D. R
A1  - Marincola, Gabriella
A1  - Schoenfelder, Sonja M. K.
A1  - Maaß, Sandra
A1  - Becher, Dörte
A1  - Ziebuhr, Wilma
T1  - Another layer of complexity in Staphylococcus aureus methionine biosynthesis control: unusual RNase III-driven T-box riboswitch cleavage determines met operon mRNA stability and decay
JF  - Nucleic Acids Research
N2  - In Staphylococcus aureus, de novo methionine biosynthesis is regulated by a unique hierarchical pathway involving stringent-response controlled CodY repression in combination with a T-box riboswitch and RNA decay. The T-box riboswitch residing in the 5′ untranslated region (met leader RNA) of the S. aureus metICFE-mdh operon controls downstream gene transcription upon interaction with uncharged methionyl-tRNA. met leader and metICFE-mdh (m)RNAs undergo RNase-mediated degradation in a process whose molecular details are poorly understood. Here we determined the secondary structure of the met leader RNA and found the element to harbor, beyond other conserved T-box riboswitch structural features, a terminator helix which is target for RNase III endoribonucleolytic cleavage. As the terminator is a thermodynamically highly stable structure, it also forms posttranscriptionally in met leader/ metICFE-mdh read-through transcripts. Cleavage by RNase III releases the met leader from metICFE-mdh mRNA and initiates RNase J-mediated degradation of the mRNA from the 5′-end. Of note, metICFE-mdh mRNA stability varies over the length of the transcript with a longer lifespan towards the 3′-end. The obtained data suggest that coordinated RNA decay represents another checkpoint in a complex regulatory network that adjusts costly methionine biosynthesis to current metabolic requirements.
KW  - allelic replacement
KW  - expression
KW  - translation
KW  - mechanism
KW  - acid
KW  - endoribonuclease
KW  - antitermination
KW  - transcription
KW  - proteins
KW  - geometry
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259029
VL  - 49
IS  - 4
ER  -