The blood-brain barrier (BBB) comprises the microvasculature network within the brain and has a critical role in maintaining the barrier between the brain tissue and the blood. Proper functionality of the BBB is important in maintaining homeostasis, while disruptions can lead to severe complications. The impact of diet on brain health extends to the BBB. Western diets containing high levels saturated fatty acids, such as lard, increase the risk for neurodegenerative disease and cerebrovascular dysfunction. Whereas fish-oil (FO) diets containing long-chain polyunsaturated fatty acids can form products that reduce inflammation and have been identified to have cerebrovascular benefit. However, the impact of dietary fats on the BBB endothelial cell tight junctions remains unclear. BBB tight junction integrity is governed by key proteins, including claudin-5 (CLDN-5), occludin (OCLN), junctional adhesion molecule-1 (JAM-1) and zonula occludens-1 (ZO-1). This study examined the effect of chronic lard and FO based diets on these key tight junctional proteins. The study further examined the resilience capacity of the BBB tight junctions by inducing an acute inflammatory challenge as a result of the diet treatments. We hypothesized that a long-term diet, rich in polyunsaturated fatty acids, would contribute to increased mRNA and protein expression of the listed critical tight junctional proteins of the blood-brain barrier. Comparatively, a Western diet, containing high saturated fatty acids, would have an overall lower level of mRNA and protein expression. Furthermore, the treatment of chronic Western diet would show enhanced negative effects because of an induced inflammatory event using lipopolysaccharide (LPS). Conversely, a diet rich in Omega-3 fatty acids would be more resilient than the Western Diet at the level of tight junctional integrity.
This study was organized into two different cohort groups, labelled Cohort-1, and Cohort-2. The Cohort-1 set used, 8-week-old, male C57BL/6J mice received a diet containing either 10% lard, 10% FO, 41% lard or 41% FO over 32 weeks. Cortical brain tissue was harvested at conclusion of treatment, with mRNA (RT-qPCR) expression and protein (Western blot) expression analyses performed. Body weights and blood chemistry measures were also evaluated. Two-way ANOVAs performed, with Tukey post-hoc test used to determine if means significantly differed, with significance set at P<0.05. The Cohort-2 set used the exact same study design parameters as Cohort-1, except that the mice in this group were given a 3 mg/kg IP dose of LPS, 24 hours before the blood was collected and the tissue harvested.
In Cohort-1, no differences in mRNA expression were observed across diets for any of the four genes of interest that were analyzed: CLDN-5, OCLN, JAM-1 and ZO-1. These results were also consistent for Cohort-2, in that there were no significant changes in mRNA expression across the diets for any of the target genes. In Cohort-1 for the data for CLDN-5 protein expression showed that there was a significant decrease in the protein expression from 10% lard to 10% fish oil. From 41% lard to 41% fish oil, there showed a trending increase in protein expression. The protein expression of OCLN showed no significant changes across all diets. JAM-1 was not evaluated due to complications in finding am antibody that could produce measurable results. The protein expression for ZO-1 showed significant increases in expression from 10% lard to 10% fish oil. There was also a significant increase from 41% lard to 41% fish oil. In Cohort-2 protein expression showed no significant changes across any of the evaluated proteins, however, some interesting trends were revealed.
The study identified ZO-1 and CLDN-5 protein expression changes within the brain are linked to diet. Data supports that diets high in FO have a greater expression of key tight junctional proteins, which suggests enhanced BBB integrity.
|Commitee:||Sandoval, Karin, Schober, Joseph|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 82/3(E), Masters Abstracts International|
|Keywords:||blood-brain barrier, polyunsaturated fatty acid, RT-qPCR, tight junctional proteins, Western Blotting, Western Diet|
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