Location: Children's Nutrition Research Center
2022 Annual Report
Objectives
Objective 1: Determine if antinutrients in plant foods impact the gut microbiome.
Subobjective 1A: Using mice feeding studies, analyze the interaction between antinutrient content in plant-based diets and gut microbiota.
Subobjective 1B: Assess the impact of plant-based antinutrient content on animal and human microbiomes using in vitro systems.
Objective 2: Utilize a germ-free murine model to determine the inter-relationships between microbial gut ecology, plant anti-nutrients and host mineral bioavailability.
Approach
Unique plant diets differing in antinutrient content can be used along with 16S ribosomal RNA sequencing to determine how bacterial populations fluctuate as a function of antinutrients. Calcium (Ca) is often sequestered as an oxalate salt making it an 'antinutrient' and bio-unavailable. Medicago truncatula contains insoluble calcium oxalate crystals making it a poor source of dietary Ca. However, a M. truncatula mutant lacking oxalate crystals in the leaf tissue is an excellent source of Ca and allows the preparation of diets that differ in a single plant mutation to be used to analyze the impact of oxalate on the microbiome. Using primary cell culture models from both humans and mice will provide further insights into the impact of antinutrients on microbial composition. Meanwhile, mice reconstituted with either a microbiome associated with an antinutrient replete or antinutrient deficient diet, but consuming equivalent diets, will be analyzed for differences in calcium, iron, and zinc absorption.
Progress Report
This project addresses the dietary impact of antinutrients in plant-based foods on the gut microbiome; a component of the gastrointestinal (GI) tract responsible for the breakdown of complex molecules in food, protection from pathogens, and immune system development. Our hypothesis is that antinutrient-rich plant-based diets modify the microbiome community to alter consumer mineral uptake. As an experimental model, we use mice feeding studies where mice are fed plant diets differing in antinutrient content along with in vitro phenotyping to provide insight into the impact of antinutrients on microbial composition. For these studies, there are two sets of diets used in two different sets of experiments. The first uses Medicago plants +/- the antinutrient calcium oxalate (Ca ox). This diet addresses the role of Ca ox in microbiome composition and Ca bioavailability in the consumer. The second diet uses barley high/low for phytic acid. This diet addresses the role of phytic acid in microbiome composition and zinc (Zn) and iron (Fe) bioavailability in the consumer. For Objective 1, this year we have performed mouse feeding studies with our plant model (Medicago) and isolated fecal samples for microbiome analysis. In November and December of 2021, a pilot study was conducted to access the feasibility for large-scale studies and fecal samples were sent to the Texas Children's Hospital (TCH) Microbiome Center for sequencing in mid-December of 2021. As of the end of June, we are still awaiting the sequencing data from these samples as sequencing is delayed due to the urgency of sequencing COVID-19 variants in the pediatric population. To circumvent this sequencing delay, we initiated another small feeding trial and sent associated fecal samples to the University of Minnesota for sequencing in mid-March of 2022. The rationale here is that other institutions may have fewer sequencing backlogs than at TCH. Currently, these samples have not been processed due to the same issues with COVID-19 sequencing priorities. We anticipate that these sequencing results will be ready in mid-August and analyzed before late September of this year. Further progress with large-scale Medicago feeding studies must wait until we have determined the results from these pilot studies. We continue to amass plant materials for diet preparation and are obtaining preliminary bone density data from the pilot study. For our barley studies associated with Objective 2, we continue to have difficulties obtaining the barley lines to initiate these experiments. With COVID-19 complications, the facility in Idaho could not retrieve USDA, ARS' seed stocks. In early 2021, we collaborated with a company in Yuma, Arizona to grow the barley lines for our feeding studies. This facility had numerous shutdowns this year and the plant material is awaiting processing before being shipped to our lab. Logistical issues with the processing have delayed this shipment however the plant material should be available in this fall.
Accomplishments
