Matching Items (4)
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- All Subjects: Vitamin D
- Creators: Hackney Price, Jennifer
Description
Vitamin D, a bioactive lipid and essential nutrient, is obtained by humans through either endogenous synthesis in response to UV light exposure or via nutritional intake. Once activated to its hormonal form, vitamin D binds to and activates the nuclear vitamin D receptor (VDR). Activation of VDR is known to modulate gene transcription in vitamin D target tissues such as kidney, colon, and bone; however, less is known about the ability of VDR to respond to "nutritional modulators". One such potential VDR modulator is resveratrol, a plant-derived polyphenol and potent antioxidant nutrient that also functions as a chemopreventative. Resveratrol is known to activate sirtuin-1, a deacetylase enzyme with potential anti-aging properties. This study explores the potential for resveratrol, an anticancer nutraceutical, to upregulate VDR activity through its effector protein, sirtuin-1. Furthermore, due to its putative interactions with several intracellular signaling pathways, klotho has been proposed as an anti-aging protein and tumor suppressor gene, while the Wnt/β-catenin signaling pathway drives enhanced cellular proliferation leading to numerous types of cancers, especially colorectal neoplasia. Thus, the ability of klotho to cooperate with vitamin D to inhibit oncogenic β-catenin signaling was also analyzed. The experiments and resultant data presented in this thesis explore the potential role of VDR as a physiologically relevant nutritional sensor in human cells. This novel study reveals the importance of nutrient modulation of the VDR system by vitamin D and resveratrol and how this might represent a molecular mechanism that is responsible for the putative anti-cancer actions of vitamin D. Furthermore, this study enhances our understanding of how vitamin D/VDR and resveratrol interact with klotho and how this interaction affects β-catenin signaling to mitigate oncogenic growth and differentiation. This works demonstrates that the vitamin D hormone serves as a likely chemopreventive agent for various types of cancers through control of anti-oxidation and cellular proliferation pathways via its nuclear receptor. Our results also indicate the potential for resveratrol, an anticancer nutraceutical, to upregulate VDR activity through SIRT1. Furthermore, the novel data presented in this work illustrate that klotho, an anti-aging protein, cooperates with vitamin D to synergistically inhibit oncogenic β-catenin signaling. Ultimately, this study enhances our understating of the molecular pathways that underpin nutritional chemoprevention, and how modulation of these pathways via dietary intervention may lead to advances in public health strategies to eventually curb carcinogenesis.
ContributorsKhan, Zainab (Author) / Jurutka, Peter (Thesis director) / Hackney Price, Jennifer (Committee member) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Colchicine is a chemical known for inhibiting mitosis during eukaryotic cellular reproduction by halting the tubulin formation necessary for the division of the chromosomes. The meristem is the primary source of mitosis in developing flowering plants, and it was the focus of our research to determine if the hindrance of mitosis would interfere with the production of capsaicinoids within pungent pepper plants. Moruga Scorpion peppers have one of the world's highest concentration of capsaicinoids with Scoville Heat Units (SHU) averaging 1.2 million SHU (Bannister, 2012). The highest concentration of these capsaicinoids are within the placental and endocarp regions of the fruit, which are the primary location for capsaicinoid biosynthesis (Aza-Gonzalez & Nunez-Palenius, 2010). Hindering mitosis from the earliest stage of development could lead to phenotypic abnormalities within those placental and endocarp regions, quite possibly through the mechanism of the induced polyploidy. In many cases, this polymerization interference is beneficial in cultivating plants with characterized polyploidy due to its desired increased size of fruits and leaves. Due to the lethal nature of colchicine, there is threshold of effectiveness where it may induce polyploidy or it may result in fatality. This first stage of this research sought to determine which lethal dose was required to elicit a polyploid response or lead to seed unviability. The second stage was analyzing capsaicin concentration within the fruit of the mature dosed plants to determine whether there was an effect on the capsaicinoids, and whether polyploidy played a role in those effects. The final inspection of this research was in germinating the seeds from the hottest F1 pepper that had developed the fruit the slowest of all the doses, and determining whether there were any effects on the germination or seedling development.
ContributorsKeppler, Lydia Jacqueline (Author) / Cahill, Thomas (Thesis director) / Sweat, Ken G. (Committee member) / Hackney Price, Jennifer (Committee member) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
The significance of hormonal vitamin D in the numerous facets of health stresses the importance of elucidating the molecular mechanism(s) associated with 1,25D-VDR signaling modulators (e.g., resveratrol and sirtuin-1). Resveratrol (Res), a natural antioxidant, is a potent activator of NAD-dependent deacetylase sirtuin-1 (SIRT-1), an enzyme associated with longevity in animal models. This present study employed mammalian 2-hybrid (M2H) and vitamin D responsive element (VDRE)-based transcriptional assays to investigate the potential effects of Res and SIRT-1 on VDR signal transduction. Results from VDRE-based assays indicate that Res and SIRT-1 potentiate 1,25D-VDR activity via cell-and-promoter-specific pathways. In addition, 1,25D displacement experiments revealed an increase in VDR-bound radiolabeled 1,25D in the presence of Res, suggesting that Res may potentiate VDR transactivation by stimulating 1,25D binding. M2H assays in HEK293 cells were then utilized to assess levels of interaction between VDR and VDR comodulators, including RXR, SRC-1, and DRIP-205. Both Res and SIRT-1 increased the ability of VDR to associate with RXR; however, SRC-1 and DRIP-205 interactions were not enhanced. The activity of a novel, non-acetylatable VDR mutant, K413R, was probed revealing that K413R possesses amplified transactivation capacity over wild-type VDR. A SIRT-1 inhibitor, EX-527, was used to suppress endogenous SIRT-1, resulting in significantly decreased VDR transactivation. Finally, qPCR results in HEK293 cells revealed that the 1,25D-mediated induction of CYP24A1, an endogenous VDR target gene, was enhanced (85%) by SIRT-1 while Res increased CYP24A1 expression by 294%. The combination of 1,25D, SIRT-1, and Res amplified CYP24A1 expression by 326% over 1,25D, although this effect did not reach statistical significance when compared to the Res only treated group. We conclude that acetylation of VDR comprises a negative feedback loop that attenuates 1,25D-VDR signaling. This loop is suppressed by resveratrol/SIRT-1-catalyzed deacetylation of VDR, restoring VDR activity. The two compounds, 1,25-dihydroxyvitamin D (1,25D, vitamin D) and 5-hydroxytryptamine (5-HT, serotonin), have been proposed to play a significant role in abnormal social behavior associated with psychological conditions including autism spectrum disorders (ASDs) and depression; however, the mechanism underlying these associations has yet to be elucidated. Deficiencies in 1,25D or 5-HT have been linked to the increased incidence of ASDs. Thus, examining the modulation of genes involved in 5-HT biosynthesis, reuptake, and degradation is fundamental in linking low 1,25D levels to the increased incidence of psychiatric disorders. We propose that 1,25D regulates tryptophan hydroxylase-2 (TPH2), the initial and rate-limiting enzyme in the biosynthetic pathway of 5-HT. In order to evaluate the regulation of TPH2 in neuronal cells, three formulations of media were examined to optimize the cell culture conditions necessary for growth and morphology of embryonic rat medullary raphe (B14) serotonergic neurons. Next, quantitative real time-PCR (qPCR) was utilized to examine TPH2 expression in cultured human glioblastoma (U-87) cells and rat serotonergic neurons (B-14). Human TPH2 mRNA in U-87 cells was induced dose-dependently resulting in a 2.4-fold increase at 10 nM 1,25D. Strikingly, TPH2 mRNA in B-14 cells was observed to be 26- to 86-fold upregulated at 10 nM 1,25D; however, 1 nM and 100 nM 1,25D elicited significantly smaller inductions (8-fold and 1.2-fold, respectively).
ContributorsSabir, Marya Sabah (Author) / Jurutka, Peter (Thesis director) / Hackney Price, Jennifer (Committee member) / Sandrin, Todd R. (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
Vitamin D3 (cholecalciferol) is an essential micronutrient that plays a key role in developmental growth and lifespan in mammals. However, few studies have shown how vitamin D3 plays its vital functions in arthropods. Here, we examined the effects of full (13.3 IU/mL) and half dose (6.65 IU/mL) vitamin D3 on the growth and lifespan of Drosophila melanogaster. Vitamin B12 is another micronutrient that shows decreases absorption in elderly patients and might be linked to symptoms associated with aging rather than lifespan, but again, the effects of vitamin B12 supplementation in arthropods is poorly characterized. Results showed that both full and half doses of vitamin D3 and B12 do not significantly alter the timing of pupariation or adult eclosion. Similarly, the mortality rate of adult D. melanogaster exposed to vitamin B12 or higher doses of vitamin D3 was not significantly decreased or increased. However, a low dose of vitamin D3 did significantly lower the mortality rate of D. melanogaster. The genetic composition of Drosophila for vitamin B12 and D metabolism showed similarities in humans. However, there are no biological evidences if these genes are functional thus, this may explain the results of this study.
ContributorsRebonza, Edzel May Suico (Author) / Hackney Price, Jennifer (Thesis director) / Jurutka, Peter (Committee member) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05