The connection between the gut microbiota and the aetiology of obesity and cardiometabolic disorders is increasingly being recognized by clinicians. Our gut microbiota might affect the cardiometabolic phenotype by fermenting indigestible dietary components and thereby producing short-chain fatty acids (SCFA). These SCFA are not only of importance in gut health and as signalling molecules, but might also enter the systemic circulation and directly affect metabolism or the function of peripheral tissues. In this Review, we discuss the effects of three SCFA (acetate, propionate and butyrate) on energy homeostasis and metabolism, as well as how these SCFA can beneficially modulate adipose tissue, skeletal muscle and liver tissue function. As a result, these SCFA contribute to improved glucose homeostasis and insulin sensitivity. Furthermore, we also summarize the increasing evidence for a potential role of SCFA as metabolic targets to prevent and counteract obesity and its associated disorders in glucose metabolism and insulin resistance. However, most data are derived from animal and in vitro studies, and consequently the importance of SCFA and differential SCFA availability in human energy and substrate metabolism remains to be fully established. Well-controlled human intervention studies investigating the role of SCFA on cardiometabolic health are, therefore, eagerly awaited.
Resveratrol is a natural compound that affects energy metabolism and mitochondrial function and serves as a calorie restriction mimetic, at least in animal models of obesity. Here, we treated 11 healthy, obese men with placebo and 150 mg/day resveratrol (resVida) in a randomized double-blind crossover study for 30 days. Resveratrol significantly reduced sleeping and resting metabolic rate. In muscle, resveratrol activated AMPK, increased SIRT1 and PGC-1α protein levels, increased citrate synthase activity without change in mitochondrial content, and improved muscle mitochondrial respiration on a fatty acid-derived substrate. Furthermore, resveratrol elevated intramyocellular lipid levels and decreased intrahepatic lipid content, circulating glucose, triglycerides, alanine-aminotransferase, and inflammation markers. Systolic blood pressure dropped and HOMA index improved after resveratrol. In the postprandial state, adipose tissue lipolysis and plasma fatty acid and glycerol decreased. In conclusion, we demonstrate that 30 days of resveratrol supplementation induces metabolic changes in obese humans, mimicking the effects of calorie restriction.
The intestinal microbiota has been implicated in insulin resistance, although evidence regarding causality in humans is scarce. We therefore studied the effect of lean donor (allogenic) versus own (autologous) fecal microbiota transplantation (FMT) to male recipients with the metabolic syndrome. Whereas we did not observe metabolic changes at 18 weeks after FMT, insulin sensitivity at 6 weeks after allogenic FMT was significantly improved, accompanied by altered microbiota composition. We also observed changes in plasma metabolites such as γ-aminobutyric acid and show that metabolic response upon allogenic FMT (defined as improved insulin sensitivity 6 weeks after FMT) is dependent on decreased fecal microbial diversity at baseline. In conclusion, the beneficial effects of lean donor FMT on glucose metabolism are associated with changes in intestinal microbiota and plasma metabolites and can be predicted based on baseline fecal microbiota composition.
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The importance of chronic low-grade inflammation in the pathology of numerous age-related chronic conditions is now clear. An unresolved inflammatory response is likely to be involved from the early stages of disease development. The present position paper is the most recent in a series produced by the International Life Sciences Institute's European Branch (ILSI Europe). It is co-authored by the speakers from a 2013 workshop led by the Obesity and Diabetes Task Force entitled ‘Low-grade inflammation, a high-grade challenge: biomarkers and modulation by dietary strategies’. The latest research in the areas of acute and chronic inflammation and cardiometabolic, gut and cognitive health is presented along with the cellular and molecular mechanisms underlying inflammation–health/disease associations. The evidence relating diet composition and early-life nutrition to inflammatory status is reviewed. Human epidemiological and intervention data are thus far heavily reliant on the measurement of inflammatory markers in the circulation, and in particular cytokines in the fasting state, which are recognised as an insensitive and highly variable index of tissue inflammation. Potential novel kinetic and integrated approaches to capture inflammatory status in humans are discussed. Such approaches are likely to provide a more discriminating means of quantifying inflammation–health/disease associations, and the ability of diet to positively modulate inflammation and provide the much needed evidence to develop research portfolios that will inform new product development and associated health claims.
Women generally have a higher percentage of body fat than men. Also, women store more fat in the gluteal-femoral region, whereas men store more fat in the visceral (abdominal) depot. This review focuses on differences in regional fatty acid storage, mobilization and oxidation that may contribute to gender-related differences in body fat distribution. There are pronounced regional differences in the regulation of regional fatty acid metabolism between men and women. Firstly, there is evidence that in vivo, catecholamine mediated leg free fatty acid release is lower in women than in men, whereas free fatty acid release from the upper body depots is comparable. These data correspond to in-vitro adipose tissue biopsy data, which indicate a more pronounced difference in catecholamine mediated lipolysis between upper body and lower body fat depots in women than in men. Secondly, free fatty acid release by the upper body subcutaneous fat depots is higher in men than in women, indicating a higher resistance to the antilipolytic effect of meal ingestion in the upper body fat depots in men. Thirdly, there are indications that basal fat oxidation (adjusted for fat free mass) is lower in females as compared to males, thereby contributing to a higher fat storage in women. Finally, postprandial fat storage may be higher in subcutaneous adipose tissue in women than in men, whereas storage in visceral adipose tissue has been hypothesized to be higher in men. All the above differences may play a role in the variation in net regional fat storage between men and women, but the number of in-vivo studies on gender-related differences in fatty acid metabolism is very limited and most findings require confirmation. Furthermore, there is abundant evidence that the proportion of energy derived from fat during exercise is higher in women than in men. With respect to total body fat, this finding seems counterintuitive, as percentage body fat is increased in women. Further studies are necessary to investigate the significance of differences in exercise-induced fat oxidation on 24-h fat balance.
Introduction:Mechanisms for liraglutide-induced weight loss are poorly understood.Objective:We investigated the effects of liraglutide on gastric emptying, glycemic parameters, appetite and energy metabolism in obese non-diabetic individuals.Design:Participants (N=49, 18–75 years, body mass index: 30–40 kg m−2) were randomized to two of three treatments: liraglutide 1.8 mg, 3.0 mg, or placebo in a double-blind, incomplete crossover trial. After 5 weeks, 24-h energy expenditure (EE) and substrate oxidation were measured in a respiratory chamber. Gastric emptying (acetaminophen absorption method), glycemic parameters and appetite were assessed during a 5-h meal test. Ad libitum energy intake during a subsequent lunch was also assessed.Results:Five-hour gastric emptying (AUC0–300 min) was found to be equivalent for liraglutide 1.8 versus 3.0 mg (primary end point), and for both liraglutide doses versus placebo, as 90% confidence intervals for the estimated treatment ratios were contained within the prespecified interval (0.80–1.25). However, 1-h gastric emptying was 23% lower than placebo with liraglutide 3.0 mg (P=0.007), and a nonsignificant 13% lower than placebo with liraglutide 1.8 mg (P=0.14). Both liraglutide doses similarly reduced fasting glucose (0.5–0.6 mmol l−1 versus placebo, P<0.0001), glucose Cmax and 1-h AUC versus placebo; only liraglutide 3.0 mg reduced iAUC0–300 min (by ∼26% versus placebo, P=0.02). Glucagon iAUC0–300 min decreased by ∼30%, and iAUC0–60 min for insulin and C-peptide was ∼20% lower with both liraglutide doses versus placebo. Liraglutide doses similarly increased mean postprandial satiety and fullness ratings, reduced hunger and prospective food consumption and decreased ad libitum energy intake by ∼16%. Liraglutide-associated reductions in EE were partly explained by a decrease in body weight. A relative shift toward increased fat and reduced carbohydrate oxidation was observed with liraglutide. Clinicaltrials.gov ID:NCT00978393. Funding: Novo Nordisk.Conclusion:Gastric emptying AUC0–300 min was equivalent for liraglutide 1.8 and 3.0 mg, and for liraglutide versus placebo, whereas reductions in 1-h gastric emptying of 23% with liraglutide 3.0 mg and 13% with 1.8 mg versus placebo were observed. Liraglutide 3.0 mg improved postprandial glycemia to a greater extent than liraglutide 1.8 mg. Liraglutide-induced weight loss appears to be mediated by reduced appetite and energy intake rather than increased EE.
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