Browsing by Subject "High fat diet"

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Open Access
The effects of ER stress on glial cells: evidence from both in vivo and in vitro models
(2022-01) Mutlu, Duygu
Consuming high fat diet for long periods of time increases neuroinflammation, which may result in cognitive decline and loss in memory formation. Excessive free fatty acid influx stresses the ER and mitochondria, two important organelles taking part in protein folding and energy production. The ER responds to stress in part by activating Protein Kinase RNA-like Endoplasmic Reticulum Kinase (PERK) pathway. It has been shown that PERK pathway activation inhibits mitophagy (autophagy of mitochondria) in macrophages. Since microglia are the immune cells of the Central Nervous System (CNS), first I investigated the effects of high fat diet in the cortex of wild type (C57BL/6) and ApoE -/- mice by looking at microglial marker Iba1. Western Blot analysis showed no significant effects of diet and genotype on Iba1 level. I also found that there is no correlation between Iba1 and GFAP (astrocyte marker) levels for these mice. Brain contains many other types of cells and in order to effects of ER stress directly on the microglia, I moved on to the BV2 mouse microglial cell line. There were differential effects of ER stress induction with thapsigargin and palmitate treatments. An increase in ER stress markers such as CHOP and p-IRE1 has been observed with both treatments. While CHOP protein levels could not reach significance, there was an increasing numerical trend. p-IRE1 was marginally significant for both treatments (p=0.087 for thapsigargin and p=0.061 for 100 M palmitate). Mitophagy indicators (Pink1 and p62) were assessed with Western Blot analysis after successful mitochondria isolation from BV2 cells. The data indicated that p62 marginally increased with both palmitate (p=0.61) and thapsigargin (p=0.1) treatments. Following both treatments, very subtle effects of ER stress were observed. This suggests that further experiments examining optimal dosage and duration need to be performed. Overall, the induction of ER stress appears to induce mitophagy and alter microglia, which likely leads to altered cellular and synaptic function.
Open Access
Impacts of high-fat diet and genotype on blood-brain barrier and synaptic integrity in mouse cerebral cortex: an exploration of perk pathway
(2024-09) Şeker, Büşranur
High-fat diet intake can induce hyperlipidemia and result in cognitive decline by causing endoplasmic reticulum stress, decreased blood-brain barrier, and synaptic integrity. The protein kinase R-like endoplasmic reticulum kinase (PERK) pathway is one of the arms of the unfolded protein response, which is activated by endoplasmic reticulum stress. The PERK inhibits the global protein translation while allowing the translation of certain proteins that are involved in inflammation and apoptosis. Due to its apoptotic properties, it is thought that the PERK pathway causes neurodegeneration. To study the effects of hyperlipidemia, a high-fat diet-fed Apoe knock-out mice model (Apoe-/-) is appropriate. Knocking out the Apoe in mice makes the animal model more prone to high-fat diet-induced hyperlipidemia. In the cerebral cortex of these animals, endoplasmic reticulum stress, blood-brain barrier, and synaptic integrity markers are checked at protein and mRNA levels. No changes are observed in the PERK pathway markers besides phosphorylated eukaryotic Initiation Factor 2. Additionally, there is a significant increase in blood-brain barrier marker Claudin-5 levels in Apoe-/- mice fed with a high-fat diet. There is also no significant change in synaptic integrity markers. In the second part, the effects of the PERK pathway inhibition are checked with integrated stress response inhibitor and GSK2606414 in the high-fat diet-fed Apoe-/- mice cerebral cortex. There are no significant alterations in BBB and synaptic integrity when the animals are injected with inhibitors. In conclusion, this study investigates the effects of high-fat diet induced hyperlipidemia in the cerebral cortex of Apoe-/- mice on ER stress, blood-brain barrier, and synaptic integrity. In the cerebral cortex region, the PERK pathway-related ER stress is not observed, and synaptic integrity remained unchanged while the blood-brain barrier is affected. Moreover, the effects of the PERK pathway inhibition are researched, and there is no inhibition effect observed in the cerebral cortex region.