David Kitts


Relevant Degree Programs


Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - Nov 2020)
Major chlorogenic acid isomers present in coffee are modulators of redox biology and inflammation in Caco-2 cells (2018)

Chlorogenic acid (CGA) is a general term used to describe the most abundant group of phenolic acids in coffee. 3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA are major CGAs in coffee; but only 5-CQA has been thoroughly studied. The first objective of this thesis was to study interactions between major CGA isomers and chemical changes in coffee brew that affect antioxidant activity noted for coffee. The second overall objective was to study the potential of these six major CGA isomers in modulating oxidative stress and inflammation using a human intestinal Caco-2 cell line. The findings from Chapter 2 suggested that the other five CGA isomers (4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA) together account for more than 50% of the total CGA in coffee and contributed to the antioxidant activity of coffee brew. Chapter 3 and 4 addressed the research question of whether these major CGA isomers have a modulating effect on oxidative stress and inflammation in human intestinal Caco-2 cell line. Caco-2 cells were first incubated with, or without, individual CGA isomers, followed by a phorbol 12-myristate 13-acetate plus human interferon gamma challenge. Biomarkers of oxidative stress (intracellular ROS and GSH/GSSG) and inflammation (IL-8) were measured. The results demonstrated that CGA isomers scavenged intracellular ROS in inflamed Caco-2 cells, mitigated the drop in GSH/GSSG ratio and attenuated IL-8 secretion. Dicaffeoylquinic acids (3,4-diCQA, 3,5-diCQA, and 4,5-diCQA) had a relatively stronger capacity to evoke protection compared to caffeoylquinic acids (3-CQA, 4-CQA, and 5-CQA). To elucidate the possible mechanism underlying these actions, the effects of CGA isomers on the nuclear factor kappa B signaling pathway, mitogen-activated protein kinase cascades, and nuclear factor (erythroid-derived 2)-like 2 signaling pathway were further investigated. In conclusion, structural differences in six CGA isomers were found to correspond to differences in antioxidant and anti-inflammation activities. CGA isomers attenuate oxidative stress and inflammation in Caco-2 cells by triggering changes in redox biology parameters, lead to an up-regulation of nuclear factor kappa B signaling at very early stage, mitigation of p38 phosphorylation and up-regulation of antioxidant genes in an intermediate stage, and activation of Nrf2 signaling at a much later stage.

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Characterization of food chain-derived Listeria monocytogenes and the role of Listeria genomic island (LGI1) in virulence, survival, and tolerance to food-related stress (2014)

The presence of Listeria spp. and L. monocytogenes (Lm) was investigated in provincially inspected food processing and retail facilities in British Columbia. Lm (n=56) was recovered in food processing environment (FPE) of dairy, meat and fish facilities, and in ready-to-eat fish products. The majority of Lm belonged to listeriosis causing serotypes 1/2a and 4b. Isolate fingerprinting revealed 14 sequence types, and 38 pulsotypes, with 66% of Lm possessing the full-length inlA, a causally linked virulence determinant. Unexpectedly, 4b serotypes more readily acquired point mutations leading to rifampicin resistance compared to other serotypes (p
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Role of Tocopherol isoforms in modulation of oxidative and inflammatory respsonses in Caco-2 and FHs 74 int intestinal cell lines (2013)

Vitamin (vit) E comprises 8 isoforms, of which only α-tocopherol (Toc) has been thoroughly investigated. Other vit E isoforms, particularly γ-Toc and δ-Toc, however are present in significant amounts in the North American diet. The effect of α-Toc, γ-Toc and δ-Toc in modulating oxidative status and inflammatory responses in adult-derived Caco-2 and fetal-derived FHs 74 Int intestinal cell lines were thus determined. Toc isoforms were effective antioxidants that protected against peroxyl radical-induced membrane oxidation in both cell lines in an isoform-dependent manner (δ-Toc>γ-To>α-Toc). Nevertheless, Toc isoforms exhibited differential modulation of inflammatory response in the two cell lines, in that Toc isoforms suppressed IFNγ/PMA-induced IL8 expression in Caco-2 cells, but promoted an inflammatory response in FHs 74 Int cells. Modulation of IL8 expression by Toc isoforms corresponded with an efficacy of Toc to modulate NfκB pro-inflammatory and Nrf-2 antioxidant enzyme signaling pathways. Non-α-Toc isoforms promoted Nrf-2 activation in both cell lines. Alpha-Toc and γ-Toc mitigated IFNγ/PMA-induced NfκB activation in Caco-2 cells while non-α-Toc isoforms promoted NfκB activation in FHs 74 Int cells. The pro-oxidant activity of δ-Toc corresponded to its lower ability to suppress IFNγ/PMA-induced IL8 expression and NfκB activation, but enhanced the Nrf-2 signal in Caco-2 cells. One key difference between the effect of Toc isoforms on modulation of NfκB and Nrf-2 signaling was that non-α-Toc isoforms down-regulated the gene expression of glutamate cysteine ligase, the rate-limiting enzyme in glutathione biosynthesis, in FHs 74 Int, but not in Caco-2 cells. This was supported by a reduced (P
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Characterization of antioxidant and anti-inflammatory activities of Maillard reaction products derived from sugar-amino acid models (2011)

Maillard reaction products (MRPs) are produced when reducing sugars react with amino acids, peptides or proteins in heat-processed foods. The overall objective of this research was to isolate and identify MRPs that exhibit antioxidant and anti-inflammatory activities, from different sugar-amino acid model systems comprised of fructose, glucose or ribose, each with glycine (Fru-Gly, Glu-Gly and Rib-Gly) or lysine (Fru-Lys, Glu-Lys and Rib-Lys), respectively. The development of peroxyl radical scavenging activity was found to be positively correlated (r = 0.893-0.905, P
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Master's Student Supervision (2010 - 2018)
Coffee constituents and modulation of antioxidant status in caco-2 cells (2010)

Coffee contains biologically active components which may affect chronic disease risk.These biologically active components include caffeine, cafestol and kahweol, andantioxidants such as chlorogenic acids and Maillard reaction products (MRPs) that aregenerated during roasting. Although MRPs are regarded as being the most abundantgroup of antioxidants present in coffee, the mechanism underlying the antioxidant effectsof coffee MRPs in both in vitro and in biological systems has yet to be elucidated.In this study, the in vitro antioxidant properties of roasted and non-roasted coffee extracts(Coffea arabica L.) were tested using oxygen radical absorbance capacity (ORAC),Trolox equivalent antioxidant capacity (TEAC) and reducing power assays. MRPs wereshown to be the prevailing antioxidants in roasted coffee extracts. The mechanisms of theantioxidant action associated with coffee MRPs involve the hydrogen atom transfer (HAT)mechanism and the single electron transfer (SET) mechanism.The biological effects of MRPs derived from coffee extracts on the enzymatic antioxidantdefense in human colon adenocarcinoma Caco-2 cells were also investigated. Noinduction of antioxidant enzyme activities of catalase, glutathione peroxidase, glutathionereductase and superoxide dismutase were observed in Caco-2 cells after exposure tocoffee MRPs, except for an increased glutathione peroxidase activity after 24 h exposure.In contrast, significantly decreased activities of catalase and glutathione peroxidase, and areduced glutathione content were observed in Caco-2 cells after treatment with coffeeMRPs (p
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