Browsing by Subject "Overfeeding"

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Open Access
Caloric restriction reinforces the stem cell pool in the aged brain without affecting overall proliferation status
(Elsevier BV, 2022-11-01) Erbaba, Begün; Macaroğlu, Duygu; Avcı, N. İlgim Ardıç; Ergül , Ayça Arslan; Adams, Michelle M.
Overfeeding (OF) and obesity increase the risk for brain aging and neurodegenerative diseases due to increased oxidative stress and neuroinflammation, which likely contribute to cellular dysfunction. In contrast, caloric restriction (CR) is an intervention known for its effects on extending both life- and health-span. In the current study, the effects on the aging brain of two short-term feeding regimens, OF and CR, were investigated. We applied these diets for 12 weeks to both young and aged zebrafish. We performed protein and mRNA level analysis to examine diet-mediated effects on any potential age-related alterations in the brain. Markers implicated in the regulation of brain aging, cell cycle, proliferation, inflammation, and cytoskeleton were analyzed. The most prominent result observed was a downregulation in the expression levels of the stem cell marker, Sox2, in CR-fed animals as compared to OF-fed fish. Furthermore, our data highlighted significant age-related downregulations in Tp53, Myca, and L-plastin levels. The multivariate analyses of all datasets suggested that as opposed to OF, the adaptive mechanisms increasing lifespan via CR are likely exerting their effects by reinforcing the stem cell pool and downregulating inflammation. The data reveal important therapeutic targets with respect to the state of nutrient uptake for the slowing down of the detrimental effects of aging, resulting in a healthy and extended lifespan, as well as lowering the risk for neurodegenerative disease.
Open Access
Effects of aging, diet and potential genetic interventions on the levels of Smurf2 and its interacting partners in Zebrafish (Danio Rerio) brain
(2020-09) Şaşik, Melek Umay Tüz
Aging is a natural process that is ultimate combination of numerous intrinsic and extrinsic changes in an organism. Contrary the common belief, brain aging is not a loss of neurons while it has been shown that subtle cellular and synaptic alterations have contribution to brain aging. Therefore, the molecular and cellular alterations may give more insight into the brain aging process. There are some hallmarks of aging that are common features in different organisms including genomic instability, telomere attrition, cellular senescence. There are some common factors with the ability to regulate more than one of the hallmarks of aging such as Smurf2. HECTdomain E3 ubiquitin ligase Smurf2 has several roles in the cellular processes for example, telomere attrition and cellular senescence. Moreover, its gene expression is higher in the aged brain. Although there are several publications about Smurf2, most of them focused on its role in cancer. We believed that Smurf2 levels should be examined in terms of brain aging. The first aim of the study was to examine the levels of Smurf2 and its interacting partners across lifespan. Although the Smurf2 protein level was not increased significantly in the whole zebrafish brain, its protein level was upregulated significantly in telencephalon and cerebellum. Also, subcellular protein fractionation demonstrated an enriched Smurf2 level in the cytosolic part. In the case of gene expression levels, smurf2 level was significantly higher in aged whole brain although its expression was downregulated during aging in telencephalon and cerebellum. In addition, the levels of mdm2, ep300a and sirt1 were lower in the aged telencephalon. According to multivariate analysis there is a potential balance between Smurf2-mediated ubiquitination, ep300a-mediated acetylation and Sirt1- mediated deacetylation but with advancing age, this balance may disrupt and other regulatory genes should also take a role to sustain cellular stability. The second aim was to investigate the roles of Smurf2 on brain aging with the help of genetic interventions including inducible knockin, stable knockout or transient knockdown. Since stable knockin and knockout models should be genotyped before further investigations, the genotyping and phenotyping methods were employed to find an efficient and reliable way. Also, transient knockdown via Vivo-morpholino was applied to adult brain and efficient post injection times of two different morpholinos were identified in order to examine the effects of Smurf2 knockdown in both young and old zebrafish. Lastly, it was aimed to examine the effects of non-genetic interventions including dietary regimens and pharmacological compounds on the gene expression of smurf2 and its interacting partners and the levels of the neuronal proteins and proliferation/senescence proteins. The opposing short-term dietary regimens, overfeeding and caloric restriction, were altered the levels of neuronal proteins, HuC and DCAMKL1, and their relation with proliferation and senescence proteins during aging. Also, the gene expression levels of smurf2 and interacting partners except tp53 was not influenced by dietary regimens and aging in terms of whole brain. Also, multivariate analysis indicated that the correlations among smurf2, mdm2, ep300a and sirt1 were conserved in both young and old ages independent to dietary regimen which may imply that the balance between ubiquitination, acetylation and deacetylation is maintained in order to provide cellular stability during aging. Heclin, an inhibitor of HECT E3 ligases, were employed to inhibit Smurf2 activity. Before using in adult zebrafish, heclin was applied to embryos to see its effects. The higher dose of heclin decreased the survival ratio and altered the gene expression levels of downstream gene drastically. So, moderate dose of heclin should be applied to the adult brain and neuronal markers should be examined to observe target effects rather than off-target, unspecific impacts. Taken together, Smurf2 has potential roles during aging and it could be a promising target to delay the brain aging process and probably the onset of age-related cognitive decline.
Open Access
Short-term dietary restriction maintains synaptic plasticity whereas short-term overfeeding alters cellular dynamics in the aged brain: evidence from the zebrafish model organism
(Elsevier, 2021-06-19) Karoğlu-Eravşar, Elif Tuğçe; Tüz Şaşik, Melek Umay; Adams, Michelle
Increased caloric intake (OF) impairs quality of life causing comorbidities with other diseases and cognitive deficits, whereas dietary restriction (DR) increases healthspan by preventing age-related deteriorations. To understand the effects of these opposing dietary regimens on the cellular and synaptic dynamics during brain aging, the zebrafish model, which shows gradual aging like mammals, was utilized. Global changes in cellular and synaptic markers with respect to age and a 12 week dietary regimen of OF and DR demonstrated that aging reduces the levels of the glutamate receptor subunits, GLUR2/3, inhibitory synaptic clustering protein, GEP, synaptic vesicle protein, SYP, and early-differentiated neuronal marker, HuC. DR significantly elevates levels of glutamate receptor subunits, GLUR2/3, and NMDA clustering protein, PSD95, levels, while OF subtly increases the level of the neuronal protein, DCAMKL1. These data suggest that decreased caloric intake within the context of aging has more robust effects on synapses than cellular proteins, whereas OF alters cellular dynamics. Thus, patterns like these should be taken into account for possible translation to human subjects.