Browsing by Author "Mitchell, Cassie M."

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    Inulin Supplementation Does Not Reduce Plasma Trimethylamine N-Oxide Concentrations in Individuals at Risk for Type 2 Diabetes
    Baugh, Mary Elizabeth; Steele, Cortney N.; Angiletta, Christopher J.; Mitchell, Cassie M.; Neilson, Andrew P.; Davy, Brenda M.; Hulver, Matthew W.; Davy, Kevin P. (MDPI, 2018-06-20)
    Trimethylamine N-oxide (TMAO) is associated with type 2 diabetes (T2DM) and increased risk of adverse cardiovascular events. Prebiotic supplementation has been purported to reduce TMAO production, but whether prebiotics reduce fasting or postprandial TMAO levels is unclear. Sedentary, overweight/obese adults at risk for T2DM (n = 18) were randomized to consume a standardized diet (55% carbohydrate, 30% fat) with 10 g/day of either an inulin supplement or maltodextrin placebo for 6 weeks. Blood samples were obtained in the fasting state and hourly during a 4-h high-fat challenge meal (820 kcal; 25% carbohydrate, 63% fat; 317.4 mg choline, 62.5 mg betaine, 8.1 mg l-carnitine) before and after the diet. Plasma TMAO and trimethylamine (TMA) moieties (choline, l-carnitine, betaine, and γ-butyrobetaine) were measured using isocratic ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). There were no differences in fasting or postprandial TMAO or TMA moieties between the inulin and placebo groups at baseline (all p > 0.05). There were no significant changes in fasting or postprandial plasma TMAO or TMA moiety concentrations following inulin or placebo. These findings suggest that inulin supplementation for 6 weeks did not reduce fasting or postprandial TMAO in individuals at risk for T2DM. Future studies are needed to identify efficacious interventions that reduce plasma TMAO concentrations.
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    Prebiotic Inulin Supplementation and Peripheral Insulin Sensitivity in adults at Elevated Risk for Type 2 Diabetes: A Pilot Randomized Controlled Trial
    Mitchell, Cassie M.; Davy, Brenda M.; Ponder, Monica A.; McMillan, Ryan P.; Hughes, Michael D.; Hulver, Matthew W.; Neilson, Andrew P.; Davy, Kevin P. (MDPI, 2021-09-17)
    Prediabetes affects 84.1 million adults, and many will progress to type 2 diabetes (T2D). The objective of this proof-of-concept trial was to determine the efficacy of inulin supplementation to improve glucose metabolism and reduce T2D risk. Adults (n = 24; BMI: 31.3 ± 2.9 kg/m2; age: 54.4 ± 8.3 years) at risk for T2D were enrolled in this controlled feeding trial and consumed either inulin (10 g/day) or placebo (maltodextrin, 10 g/day) for six weeks. Assessments included peripheral insulin sensitivity, fasting glucose, and insulin, HOMA-IR, in vivo skeletal muscle substrate preference, Bifidobacteria copy number, intestinal permeability, and endotoxin concentrations. Participant retention was 92%. There were no baseline group differences except for fasting insulin (p = 0.003). The magnitude of reduction in fasting insulin concentrations with inulin (p = 0.003, inulin = Δ-2.9, placebo = Δ2.3) was attenuated after adjustment for baseline concentrations (p = 0.04). After adjusting for baseline values, reduction in HOMA-IR with inulin (inulin = Δ-0.40, placebo=Δ0.27; p = 0.004) remained significant. Bifidobacteria 16s increased (p = 0.04; inulin = Δ3.1e9, placebo = Δ-8.9e8) with inulin supplementation. Despite increases in gut Bifidobacteria, inulin supplementation did not improve peripheral insulin sensitivity. These findings question the need for larger investigations of inulin and insulin sensitivity in this population.
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    Prebiotic supplementation with inulin and exercise influence gut microbiome composition and metabolic health
    Mitchell, Cassie M. (Virginia Tech, 2018-04-18)
    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.