Browsing by Author "Bomhof, Marc R."

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    Gut microbiota manipulation with prebiotics in patients with non-alcoholic fatty liver disease: a randomized controlled trial protocol
    (BMC Gastroenterology, 2015-12-03) Lambert, Jennifer E.; Parnell, Jill A.; Eksteen, Bertus; Raman, Maitreyi; Bomhof, Marc R.; Rioux, Kevin P.; Madsen, Karen L.; Reimer, Raylene A.
    Background Evidence for the role of the gut microbiome in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) is emerging. Strategies to manipulate the gut microbiota towards a healthier community structure are actively being investigated. Based on their ability to favorably modulate the gut microbiota, prebiotics may provide an inexpensive yet effective dietary treatment for NAFLD. Additionally, prebiotics have established benefits for glucose control and potentially weight control, both advantageous in managing fatty liver disease. Our objective is to evaluate the effects of prebiotic supplementation, adjunct to those achieved with diet-induced weight loss, on heptic injury and liver fat, the gut microbiota, inflammation, glucose tolerance, and satiety in patients with NAFLD. Methods/design In a double blind, placebo controlled, parallel group study, adults (BMI ≥25) with confirmed NAFLD will be randomized to either a 16 g/d prebiotic supplemented group or isocaloric placebo group for 24 weeks (n = 30/group). All participants will receive individualized dietary counseling sessions with a registered dietitian to achieve 10 % weight loss. Primary outcome measures include change in hepatic injury (fibrosis and inflammation) and liver fat. Secondary outcomes include change in body composition, appetite and dietary adherence, glycemic and insulinemic responses and inflammatory cytokines. Mechanisms related to prebiotic-induced changes in gut microbiota (shot-gun sequencing) and their metabolic by-products (volatile organic compounds) and de novo lipogenesis (using deuterium incorporation) will also be investigated. Discussion There are currently no medications or surgical procedures approved for the treatment of NAFLD and weight loss via lifestyle modification remains the cornerstone of current care recommendations. Given that prebiotics target multiple metabolic impairments associated with NAFLD, investigating their ability to modulate the gut microbiota and hepatic health in patients with NAFLD is warranted.
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    Identifying exercise intensity "thresholds": Implications for metabolic responses, performance, and exercise intensity prescription.
    (2019-08-28) Iannetta, Danilo; Murias, Juan M.; Millet, Guillaume Y.; MacIntosh, Brian R.; Paterson, Donald Hugh; Bomhof, Marc R.; Vanhatalo, Anni
    The exercise intensity spectrum, from rest to maximal oxygen uptake (V̇O2max), can be partitioned into three domains of intensity: moderate, heavy, and severe. These domains are demarcated by the lactate threshold (LT) (moderate-to-heavy) and critical power (CP) or maximal lactate steady-state (MLSS) (heavy-to-severe), with the respiratory compensation point (RCP) of the ramp-incremental exercise also being proposed as a marker of the heavy-to-severe boundary of exercise intensity. Although the physiological concepts underpinning these thresholds are well established, methodological issues associated with their determination may lead to inaccuracies and contrasting interpretations regarding their equivalence. The general purpose of this thesis was to find solutions to some of the issues associated with the determination of these “thresholds” and demonstrate why their accurate determination is fundamental in exercise physiology. Using a variety of exercise protocols it was demonstrated that: i) current methods to compute the mean response time (MRT) of V̇O2 during ramp-exercise are inaccurate – the novel method proposed was valid and more reproducible than these methods; ii) exercising slightly above MLSS, although characterized in this study by a stable V̇O2 response, disproportionally impaired maximal exercise capacity; iii) if the V̇O2 dynamics during ramp-incremental exercise are carefully considered, the work rates at RCP and CP/MLSS are not different – refuting the idea that the RCP is not a valid surrogate of the heavy-to-severe boundary of exercise intensity; iv) current methods to prescribe exercise intensity based on fixed-percentage of maximum values (e.g., V̇O2max) do not provide an accurate procedure by which to control exercise intensity. Collectively, these findings provide solutions/explanations to some of the issues related to the correct identification of these exercise thresholds and suggest that their correct identification is of extreme importance when interpreting their physiological implications and to guarantee an accurate exercise intensity prescription.
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    Protective effect of prebiotic and exercise intervention on knee health in a rat model of diet-induced obesity
    (2019-03-07) Rios, Jaqueline Lourdes; Bomhof, Marc R.; Reimer, Raylene A.; Hart, David A.; Collins, Kelsey H.; Herzog, Walter
    Obesity, and associated metabolic syndrome, have been identified as primary risk factors for the development of knee osteoarthritis (OA), representing nearly 60% of the OA patient population. In this study, we sought to determine the effects of prebiotic fibre supplementation, aerobic exercise, and the combination of the two interventions, on the development of metabolic knee osteoarthritis in a high-fat/high-sucrose (HFS) diet-induced rat model of obesity. Twelve-week-old male Sprague-Dawley rats were randomized into five groups: a non-exercising control group fed a standard chow diet, a non-exercising group fed a HFS diet, a non-exercising group fed a HFS diet combined with prebiotic fibre supplement, an exercise group fed a HFS diet, and an exercise group fed a HFS diet combined with prebiotic fibre supplement. Outcome measures included knee joint damage, percent body fat, insulin sensitivity, serum lipid profile, serum endotoxin, serum and synovial fluid cytokines and adipokines, and cecal microbiota. Prebiotic fibre supplementation, aerobic exercise, and the combination of the two interventions completely prevented knee joint damage that is otherwise observed in this rat model of obesity. Prevention of knee damage was associated with a normalization of insulin resistance, leptin levels, dyslipidemia, gut microbiota, and endotoxemia in the HFS-fed rats.