Optimization and Application of Metabolomic Assays for Analyzing Diet-induced and Gut Microbiota-derived Short-chain Fatty Acids in Mice and Humans

<p><strong>Introduction</strong>: In recent decades, the obesity epidemic worldwide has prompted the need for research targeting disease prevention, treatment, and maintenance. Dietary interventions are one of the primary methods to instill positive nutrition habits into one’s lifestyle. Thus, resistant starch type 4 (RS4), a prebiotic dietary fiber, has been proposed to induce beneficial immunometabolic health outcomes. Currently there is a lack of knowledge on the health outcomes of RS4 in adults with metabolic syndrome (MetS). Goal: The goal of this research was to optimize a metabolomic assay to quantify fecal short chain fatty acids (SCFAs), a byproduct of microbial fermentation in the gut, and to apply this assay to health outcomes of RS4 intervention in an adult population with MetS as well as genetically induced obese mice. <strong>Methods:</strong> An assay was optimized to extract and derivatize fecal SCFA from human stool samples followed by quantification using gas chromatography – mass spectrometry (GC-MS). Retrospective analysis of fecal samples from adults including both men (n=4) and women (n=12) with signs of MetS, collected at four time points throughout an <em>ad libitum</em> dietary intervention of RS4², were processed and quantified. This method was also retrospectively applied to cecum samples of KK.Cg-A^y/a, genetically induced obese mouse model, to quantify the effects of RS4 on cecum SCFA concentrations. 16S rRNA sequencing was performed to study the effect of RS4 on gut microbial composition. Blood biomarkers, glycemic, and lipid viariables, anthropometric measurements, and diet nutrient composition were also studied. <strong>Results</strong>: GC-MS analysis revealed significantly increased SCFAs following RS4 consumption including butyrate, propionate, valerate, isovallerate, and hexanoate. 16S-rRNA gene sequencing revealed a differential abundance of 71 bacterial operational taxonomic units, including the enrichment of three <em>Bacteroides</em> species and one each of <em>Parabacteroides, Oscillospira, Blautia,</em> <em>Ruminococcus, Eubacterium,</em> and <em>Christensenella</em> species in the RS4 group. RS4-specific associations were found between gut microbial composition and SCFA concentrations. Cholesterols, fasting glucose, glycosylated haemoglobin, and proinflammatory markers in the blood as well as waist circumference and % body fat were lower post intervention in the RS4 group compared with the control group. In KK.Cg-Ay/a mice, butyrate was significantly enriched in RS4 fed mice intestinal tissue. Discussion: An optimized method to quantify intestinal and fecal SCFA was created. The biological function of RS4 on gut microbiota in inidividuals with MetS was also identified. Larger studies are needed to fully understand the mechanistic action of RS4 in individuals with metabolic dysfunction for future implications on dietary guidelines.</p>

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - Open Access

Discipline thesis:degree_discipline

Health and Nutritional Sciences

Year dc:date.available

2016

Author dc:creator

• Juenemann, Robert M.

Contributors dc:contributor

• Moul Dey

• GC-MS
• metabolic syndrome
• SCFA
• Medicine and Health Sciences

Licence

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/1123

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-2124