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- Genre: Doctoral Dissertation
Description
High fiber diets have been associated with improved cardiometabolic health with specific efforts to lower circulating levels of low-density lipoprotein (LDL cholesterol). Whole grain and grain-based foods are major contributors of dietary fiber in the American diet, of which wheat has been extensively studied. Corn, however, has not been well studied for its cholesterol-lowering properties. Further, the mechanisms by which grains improve cardiometabolic health require further exploration with regard to the human microbiome. The objective of this single-blind randomized controlled, crossover trial was to assess the impact of three different corn flours (whole grain, refined, and bran-enhanced refined flour mixture) on serum LDL cholesterol and the gut microbiota diversity and composition. Twenty-three participants were recruited, between the ages of 18-70 with hypercholesterolemia (Male = 10, Female = 13, LDL >120 mg/dL) who were not taking any cholesterol-lowering medications. Participants consumed each flour mixture for 4 weeks prepared as muffins and pita breads. At the beginning and end of each 4-week period serum for cholesterol assessment, anthropometrics, and stool samples were obtained. Serum cholesterol was assessed using a clinical analyzer. Stool samples were processed, and microbial DNA extracted and sequenced based on the 16S rRNA gene. A generalized linear model demonstrated a significant treatment effect (p=0.016) on LDL cholesterol and explained a majority of the variance (R-squared= 0.89). Post hoc tests revealed bran-enhanced refined flour had a significant effect on cholesterol in comparison to whole grain flour (p=0.001). No statistically significant differences were observed for gut microbial community composition (Jaccard and weighted Unifrac) after corn consumption. However, relative abundance analysis (LEfSE) identified Mycobacterium celatum (p=0.048 FDR=0.975) as a potential marker of post-corn consumption with this microbe being differentially less abundant following bran-enhanced flour treatment. These data suggest that corn flour consumption may be beneficial for individuals with hypercholesterolemia but the role of gut microbiota in this relationship requires further exploration, especially given the small sample size. Further research and analysis of a fully powered cohort is needed to more accurately describe the associations and potential mechanisms of corn-derived dietary fiber on circulating LDL cholesterol and the gut microbiota.
ContributorsWilson, Shannon L (Author) / Whisner, Corrie M (Thesis advisor) / Sears, Dorothy (Committee member) / Buman, Matthew (Committee member) / Dickinson, Jared (Committee member) / Zhu, Qiyun (Committee member) / Arizona State University (Publisher)
Created2022
Description
Obesity is one of the most challenging health conditions of our time, characterized by complex interactions between behavioral, environmental, and genetic factors. These interactions lead to a distinctive obese phenotype. Twenty years ago, the gut microbiota (GM) was postulated as a significant factor contributing to the obese phenotype and associated metabolic disturbances. Exercise had shown to improve and revert the metabolic abnormalities in obese individuals. Also, genistein has a suggested potential anti-obesogenic effect. Studying the dynamic interaction of the GM with relevant organs in metabolic homeostasis is crucial for the design of new long-term therapies to treat obesity. The purpose of this experimental study is to examine exercise (Exe), genistein (Gen), and their combined intervention (Exe + Gen) effects on GM composition and musculoskeletal mitochondrial oxidative function in diet-induced obese mice. Also, this study aims to explore the association between gut microbial diversity and mitochondrial oxidative capacity. 132 adult male (n=63) and female (n= 69) C57BL/6 mice were randomized to one of five interventions for twelve weeks: control (n= 27), high fat diet (HFD; n=26), HFD + Exe (n=28), HFD + Gen (n=27), or HFD + Exe + Gen (n=24). All HFD drinking water was supplemented with 42g sugar/L. Fecal pellets were collected, DNA extracted, and measured the microbial composition by sequencing the V4 of the 16S rRNA gene with Illumina. The mitochondrial oxidative capacity was assessed by measuring the enzymatic kinetic activity of the citrate synthase (CS) of forty-nine mice. This study found that Exe groups had a significantly higher bacterial richness compared to HFD + Gen or HFD group. Exe + Gen showed the synergistic effect to drive the GM towards the control group´s GM composition as we found Ruminococcus significantly more abundant in the HFD + Exe + Gen than the rest of the HFD groups. The study did not find preventive capacity in either of the interventions on the CS activity. Therefore, further research is needed to confirm the synergistic effect of Exe, Exe, and Gen on the gut bacterial richness and the capacity to prevent HFD-induced deleterious effect on GM and mitochondrial oxidative capacity.
ContributorsOrtega Santos, Carmen Patricia (Author) / Whisner, Corrie M (Thesis advisor) / Dickinson, Jared M (Committee member) / Katsanos, Christos (Committee member) / Gu, Haiwei (Committee member) / Liu, Li (Committee member) / Al-Nakkash, Layla (Committee member) / Arizona State University (Publisher)
Created2021