Mysid shrimp (Americamysis bahia) have been utilized in routine marine toxicity assessments for decades. While mysids are a well-established model, there a key gaps in understanding how chemical exposure impacts their endocrine systems. Crustacean growth occurs through molting (i.e., shedding old exoskeleton), a process regulated by hormones, primarily ecdysteroids. Ecdysteroids are a class of steroid hormones that share similar chemical structures to vertebrate hormones (i.e., 17β-estradiol and testosterone), which have been suggested to disrupt molting in some invertebrates. Through powerful tools, like transcriptomics, potential genetic biomarkers may be identified following chemical exposure. These biomarkers could provide the basis for future research aimed at screening endocrine disrupting compounds using invertebrate models. The objectives of this work were to 1) assess whether known vertebrate endocrine disruptors (e.g., 17β-estradiol and trenbolone) would induce alterations in molting and growth and, 2) compare gene expression profiles between vertebrate endocrine disruptors and a model ecdysteroid (i.e., ponasterone A) using transcriptomic analysis. Ponasterone A induced predictable alterations in mass, molting, and ecdysteroid-related gene expression, reinforcing both the use of this compound as a positive control and these endpoints for assessing invertebrate endocrine disruptors. Vertebrate endocrine disruptors induced varied responses in the endpoints assessed, but neither acted in a manner comparable to ponasterone A. Future work may investigate the potential for differentially expressed genes identified in the transcriptomic analysis for screening of invertebrate endocrine disruptors.

Metabolic syndrome (MetS) is a cluster of concurrent cardiometabolic risk factors, including increased waist circumference, hypertension, elevated triglyceride level, reduced high-density lipoprotein (HDL) cholesterol level, and hyperglycemia. The key pathophysiology of MetS is insulin resistance, resulting in a disruption of glucose and lipid metabolism in the liver and adipose tissue, which increases the risk of type II diabetes, cardiovascular disease, and stroke. The development of insulin resistance and related conditions is multifaceted, but risk can be mitigated with lifestyle modifications, including improved nutrition. In the US, a typical American diet (TAD) is full of highly processed foods high in saturated fats and refined sugars and is associated with increased insulin resistance and obesity risk. In contrast, adherence to a plant-based Mediterranean diet (MD) rich in unsaturated fats, fiber, and non-refined carbohydrates has been found to reduce disease risk. Despite the contrasting nutritional compositions, the average macronutrient distributions of these two human diet styles are similar (approximately 50% kcal carbohydrates, 15% kcal protein, and 35% kcal fat). Due to the comparable macronutrient ratios but contrasting nutritional composition, direct comparative analysis could uncover metabolic and cellular differences relating to their associated health outcomes.

There are few rodent studies in the literature that directly compare a TAD and MD. Further, studies often utilize a high-fat diet, consisting of 40-60% kcal fat, or individual nutrient supplements, such as olive oil, rather than comprehensive diet models. To address these limitations, our lab developed comprehensive, macronutrient-matched TAD and MD models that more closely mimic human diets in the U.S. and Mediterranean, respectively. A previous study in our lab found that six months of TAD consumption resulted in elevated body weight, increased inflammation, and excess hepatic lipid deposition, in comparison to the MD. Our current study looked to further characterize MetS under this diet model, specifically investigating obesity, insulin resistance, and dyslipidemia markers. Male and female C57BL/6J mice consumed either the TAD or MD from the age of 4 to 7 months. We found that after three months on diet, there were elevations in hepatic steatosis and serum cholesterol levels in both males and females on the TAD. However, other findings suggested early signs of insulin resistance in TAD males, but not females. Future studies will investigate MetS after 6 months on diet to better elucidate insulin resistance development and potential sex differences.

Nick Boehly, Bridey Brown, Emersyn Jorski, Matthew Hale

Texas Christian University, Department of Biology

Previous studies have shown that nutrition plays a key role in influencing epigenetic markers. Additionally, changes in gene expression have been linked to the development of Alzheimer’s disease (AD). However, it is unclear how, and to what effect, nutrition influences changes in the epigenome. To that end, we divided mice into groups and exposed them to two different diets 1) a typical American diet (TAD) and 2) a Mediterranean diet (MD). Although it is known that diet can induce epigenetic modification, it is unknown if these changes are heritable. There has been little research that has focused on the offspring of the mice fed with these diets. Therefore, this experiment will focus on how the diets of parental mice affect their offspring’s methylation patterns of previously identified candidate genes linked to the development of AD. Prefrontal cortex samples from F1 mice, whose parents were exposed to MD or TAD, were removed, and the RNA was extracted and reverse transcribed into cDNA. This cDNA will display levels of expression by 10 distinct genes that have been linked to AD in previous studies. Our goal is to identify correlations between nutrition and the development of AD through modifications of gene expression. Moreover, this data will help illustrate how inheritance of epigenetic modifications can influence gene expression in subsequent generations.

The Trinity River is an important body of water to the state of Texas as it is a source of drinking water for the Dallas-Fort Worth and Houston Metropolitan areas, a popular location for recreational activities, and an ecologically significant habitat for a variety of organisms. Due to its urban location, the Trinity River is subject to potential heavy metal pollution from wastewater treatment plant discharge, road runoff, and industrial activities. Heavy metal exposure has been shown to cause significant adverse impacts on aquatic organisms; thus, this project aimed to evaluate the presence and biological impact of heavy metals in sediment and surface water samples collected from the Trinity River. Water samples collected from the Trinity River were tested for the presence of heavy metals using ICP-OES. Larval fathead minnows were also exposed to sediment and surface water samples collected from the Trinity River and gene expression levels of five biomarkers were measured. Metallothionein was used as a biomarker of exposure to heavy metals, catalase and superoxide dismutase were used as biomarkers of oxidative stress, and heat shock proteins 70 and 90 were used as biomarkers of generalized stress. The results of this study provide insight into the extent of heavy metal contamination in the Trinity River, as well as its potential impact on aquatic life.

As increasing antimicrobial resistance continues to limit treatment options for bacterial infections, several new approaches have sought to avoid the challenges faced by traditional antibiotics. One such approach is targeting virulence factors, which are necessary for pathogens to evade host defenses and establish infection but not for survival outside the host. This strategy could provide an effective form of treatment while reducing selective pressures for bacteria to evolve resistance mechanisms. Studies have shown that the ClpXP proteolytic complex is essential for virulence in Bacillus anthracis and that deletion of the ClpX subunit increases sensitivity to the cell-envelope-targeting antibiotics penicillin and daptomycin as well as the human antimicrobial peptide LL-37. Previously, we used computational modeling to identify commercially available inhibitors of the ClpXP complex and demonstrated that one, ritanserin, mimics the phenotype of a B. anthracis ΔclpX knockout mutant in antimicrobial susceptibility assays. In this study, we evaluated ritanserin in comparison to four other inhibitors identified during the same screen—siramesine, xaliproden, fluspirilene, and R59022—by determining the fractional inhibitory concentration (FIC) index of each when used in combination with penicillin. Notably, all inhibitors used except R59022 have undergone at least phase II clinical trials for other purposes. We found that two out of the three inhibitors with the highest predicted binding affinity, ritanserin and siramesine, exhibited synergistic interaction with penicillin, while the remainder of the interactions were indifferent. Our results further demonstrate the potential of structural biology techniques to identify and repurpose existing drugs for use as novel antibiotics.