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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Davis Electronic Theses and Dissertations (2021)

The postmortem interval (PMI) is one of the most challenging pieces of evidence to obtain in the field of forensic science. In recent years, a novel approach for estimating PMI has been developed based on predictable patterns in microbial community progression found in both mouse models and human cadavers. However, it is unknown if factors that contribute to the composition of the host microbiome (e.g. drug and antibiotic use, immune deficiency, and diet) impact this model’s predictive ability. In the current study, we utilized specific pathogen free (SPF), and germ-free (GF) mice buried in non-sterile and sterile graves to identify sources of variability in microbial community progression. Intestinal contents were collected over the course of a 21-day decomposition period, and bacterial communities were then identified by 16S rRNA sequencing. We found that GF mice remained sterile over the study period, regardless of soil sterility. In contrast, soil sterility had an impact on microbial community dynamics in SPF mice. These data suggest that microbial communities at the time of death influence the entry of environmental microbes and microbial progression. Together, these results show that differences in the host microbiome at the time of death can significantly impact the predictive power of microbial succession in calculating PMI and should be taken into consideration when developing future models.

    Cover page: Contribution of Host and Environmental Microbes in the Decomposition Process
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2021)
    The diet represents one environmental risk factor controlling the progression of type 1 diabetes (T1D) in genetically susceptible individuals. Consequently, understanding which specific nutritional components promote or prevent the development of disease could be used to make dietary recommendations in prediabetic individuals. In the current study, we hypothesized that the immunoregulatory phytochemcial, indole-3-carbinol (I3C) which is found in cruciferous vegetables, will regulate the progression of T1D in nonobese diabetic (NOD) mice. During digestion, I3C is metabolized into ligands for the aryl hydrocarbon receptor (AhR), a transcription factor that when systemically activated prevents T1D. In NOD mice, an I3C-supplemented diet led to strong AhR activation in the small intestine but minimal systemic AhR activity. In the absence of this systemic response, the dietary intervention led to exacerbated insulitis. Consistent with the compartmentalization of AhR activation, dietary I3C did not alter T helper cell differentiation in the spleen or pancreatic draining lymph nodes. Instead, dietary I3C increased the percentage of CD4+RORγt+Foxp3- (Th17 cells) in the lamina propria, intraepithelial layer, and Peyer's patches of the small intestine. The immune modulation in the gut was accompanied by alterations to the intestinal microbiome, with changes in bacterial communities observed within one week of I3C supplementation. A transkingdom network was generated to predict host-microbe interactions that were influenced by dietary I3C. Within the phylum Firmicutes, several genera (Intestinimonas, Ruminiclostridium 9, and unclassified Lachnospiraceae) were negatively regulated by I3C. Using AhR knockout mice, we validated that Intestinimonas is negatively regulated by AhR. I3C-mediated microbial dysbiosis was linked to increases in CD25high Th17 cells. Collectively, these data demonstrate that site of AhR activation and subsequent interactions with the host microbiome are important considerations in developing AhR-targeted interventions for T1D.
      Cover page: Dietary Indole-3-Carbinol Activates AhR in the Gut, Alters Th17-Microbe Interactions, and Exacerbates Insulitis in NOD Mice
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