Development of type 2 diabetes (T2D) is preceded by prediabetes, which is a metabolically "atypical" state associated with chronic low-grade inflammation, overweight and obesity, lack of exercise, and detrimental changes to the gut microbiome. Dietary intake and exercise are modifiable lifestyle factors for reducing T2D risk; however, several questions remain unanswered related to the efficacy and role of prebiotics and exercise, and their respective influences on gut microbiome composition, intestinal permeability, insulin sensitivity and metabolic flexibility. Sedentary to recreationally active overweight and obese adults 40-75 years old at-risk for T2D were recruited (n=22) and randomized to either supplementation with inulin, a prebiotic dietary fiber, (10g/d) or maltodextrin while consuming a controlled diet for six weeks. At baseline and week 6, participants completed a stool collection, a 4-sugar probe test, an intravenous glucose tolerance test (IVGTT), and high-fat meal challenge with skeletal muscle biopsies to evaluate changes in the gut microbiome composition, intestinal permeability, insulin sensitivity and metabolic flexibility, respectively. There were no baseline group differences (all p>0.05). Following the intervention, Bifidobacteria operational taxonomic units increased in the intervention group ([placebo: Δ 9.5 ± 27.2 vs inulin: 96.3 ± 35.5][p=0.03]). There were no other group differences over time in any other outcome variables with the exception of changes in metabolic flexibility. Secondarily, a systematic review of literature was conducted to determine the influence of exercise engagement on gut microbiome composition. Overall, exercise interventions appeared to diversify taxa within the Firmicutes phylum, and specifically in several taxa associated with butyrate production and gut barrier function. Due to unclear risk of bias in all studies and low quality of evidence, additional research is needed using well- designed trials. In summary, the respective influences of prebiotics and exercise on human gut microbiome composition and their subsequent effects on metabolic function and disease risk are not well understood. / PHD / Type 2 diabetes (T2D) is common in the United States. Prediabetes occurs before T2D, and goes frequently undiagnosed, yet lifestyle changes (e.g. dietary changes and exercise engagement) may prevent or delay the development of T2D. Gut bacteria is a newer area of research that may have an important role in disease prevention. Several dietary supplements, such as pre- and probiotics, and their influence on gut bacteria have been studied, but the effectiveness of the prebiotic inulin for delaying or preventing T2D is unknown. Additionally the effects of exercise on gut bacteria and its role for T2D prevention is still not well understood. To address these questions, sedentary to recreationally active overweight and obese adults 40-75 years old at increased risk for T2D were recruited (n=22) and randomly assigned to either supplementation with inulin (10g/d) or maltodextrin and all consumed a six week standardized diet. At baseline and week 6, all participants completed a stool collection, a 4-sugar probe test, a high-fat challenge (HFC), and intravenous glucose tolerance test (IVGTT), and changes were evaluated in the gut microbiome, intestinal permeability, and indicators of metabolism, respectively. At week 6 Bifidobacteria, which is associated with improved gut health, increased in the inulin group ([placebo: Δ 9.5 ± 27.2 vs inulin: 96.3 ± 35.5][p=0.03]). There were no other differences over time for any other measurements with the exception muscle metabolism meal response. A systematic review of currently available research was also conducted to determine the influence of exercise engagement on gut microbiome composition. Overall, exercise engagement appeared to increase bacteria that is associated with better gut health. These findings are preliminary, and most evidence is from animal studies. Therefore, more research is needed to confirm these changes in humans. In summary, the roles of prebiotics and exercise on gut bacteria and human health are not well understood.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/94549 |
| Date | 18 April 2018 |
| Creators | Mitchell, Cassie M. |
| Contributors | Human Nutrition, Foods and Exercise, Davy, Brenda M., Hulver, Matthew W., Davy, Kevin P., Neilson, Andrew P. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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