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AIM: Diet has a profound impact on cardiometabolic health outcomes such as obesity, blood glucose, blood lipids and blood pressure. In recent years, the gut microbiota has emerged as one of several potential key players explaining dietary effects on these outcomes. In this review we aim to summarise current knowledge of interaction between diet and gut microbiota focusing on the gut-derived microbial metabolites short-chain fatty acids and their role in modulating cardiometabolic risk. FINDINGS: Many observational and interventional studies in humans have found that diets rich in fibre or supplemented with prebiotic fibres have a favourable effect on the gut microbiota composition, with increased diversity accompanied by enhancement in short-chain fatty acids and bacteria producing them. High-fat diets, particularly diets high in saturated fatty acids, have shown the opposite effect. Several recent studies indicate that the gut microbiota modulates metabolic responses to diet in, e.g., postprandial blood glucose and blood lipid levels. However, the metabolic responses to dietary interventions, seem to vary depending on individual traits such as age, sex, ethnicity, and existing gut microbiota, as well as genetics. Studies mainly in animal models and cell lines have shown possible pathways through which short-chain fatty acids may mediate these dietary effects on metabolic regulation. Human intervention studies appear to support the favourable effect of short-chain fatty acid in animal studies, but the effects may be modest and vary depending on which cofactors were taken into consideration. CONCLUSION: This is an expanding and active field of research that in the near future is likely to broaden our understanding of the role of the gut microbiota and short-chain fatty acids in modulating metabolic responses to diet. Nevertheless, the findings so far seem to support current dietary guidelines encouraging the intake of fibre rich plant-based foods and discouraging the intake of animal foods rich in saturated fatty acids.

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The aim of the study was to investigate the effect of prebiotic fibres on appetite-regulating hormones, subjective feeling of appetite and energy intake in subjects with type 2 diabetes. Data presented are secondary outcomes of a study investigating the effect of prebiotics on glucagon-like peptide-1 and glycaemic regulation. We conducted a randomised and placebo-controlled crossover trial to evaluate the effects of 16 g/d of inulin-type fructans or a control supplement (maltodextrin) for 6 weeks in randomised order, with a 4-week washout period in-between, on appetite in thirty-five men and women with type 2 diabetes. Data were collected at visits before and after each treatment: plasma concentration of the satiety-related peptides ghrelin and peptide YY (PYY) were assessed during a standardised mixed meal. The subjective sensation of appetite was evaluated in response to an ad libitum lunch by rating the visual analogue scale. Twenty-nine individuals (twelve women) were included in the analyses. Compared to control treatment, the prebiotics did not affect ghrelin (P =0⋅71) or the ratings of hunger (P = 0⋅62), satiety (P = 0⋅56), fullness (P = 0⋅73) or prospective food consumption (P = 0⋅98). Energy intake also did not differ between the treatments. However, the response of PYY increased significantly after the control treatment with mean (sem) 11⋅1 (4⋅3) pg/ml when compared to the prebiotics -0⋅3 (4⋅3) pg/ml (P = 0⋅013). We observed no effect of inulin-type fructans on appetite hormones, subjective feeling of appetite or energy intake in patients with type 2 diabetes.

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AIMS: We aimed to investigate the effect of prebiotic inulin-type fructans (ITF) versus a control supplement on postprandial levels of glucagon-like peptide-1 and -2 (GLP-1 and -2), glucose and insulin in people with type 2 diabetes. METHODS: Adult men and women with type 2 diabetes were randomised in a double-blind, placebo-controlled crossover study. The study participants received 16 g/d ITF and 16 g/d control supplement (maltodextrin) for 6 weeks each in two phases separated by a 4-week washout. A standardised mixed-meal test was performed before and after each intake period. The primary end point was changes in the GLP-1 response, and secondary end points were GLP-2, glucose and insulin responses. Data were analysed using mixed-model analysis. RESULTS: A total of 29 participants were included in the study. Differences between and within the two treatments in estimated area under the curves were not significant. Yet, the predicted means for meal-induced GLP-1 response in plasma showed a 4.8% decline after the prebiotic treatment and an 8.6% increase after the control treatment (difference in changes between the treatments, p < 0.001). Fasting or postprandial glucose, insulin or GLP-2 levels were not changed. CONCLUSIONS: Our findings do not support that ITF improve incretin responses or glucose regulations in this population. Clinicaltrials.gov (NCT02569684).

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The original version of this article unfortunately contained a mistake. The presentation of Fig. 4 was incorrect.

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PURPOSE: Compared to a healthy population, the gut microbiota in type 2 diabetes presents with several unfavourable features that may impair glucose regulation. The aim of this study was to evaluate the prebiotic effect of inulin-type fructans on the faecal microbiota and short-chain fatty acids (SCFA) in patients with type 2 diabetes. METHODS: The study was a placebo controlled crossover study, where 25 patients (15 men) aged 41-71 years consumed 16 g of inulin-type fructans (a mixture of oligofructose and inulin) and 16-g placebo (maltodextrin) for 6 weeks in randomised order. A 4-week washout separated the 6 weeks treatments. The faecal microbiota was analysed by high-throughput 16S rRNA amplicon sequencing and SCFA in faeces were analysed using vacuum distillation followed by gas chromatography. RESULTS: Treatment with inulin-type fructans induced moderate changes in the faecal microbiota composition (1.5%, p = 0.045). A bifidogenic effect was most prominent, with highest positive effect on operational taxonomic units (OTUs) of Bifidobacterium adolescentis, followed by OTUs of Bacteroides. Significantly higher faecal concentrations of total SCFA, acetic acid and propionic acid were detected after prebiotic consumption compared to placebo. The prebiotic fibre had no effects on the concentration of butyric acid or on the overall microbial diversity. CONCLUSION: Six weeks supplementation with inulin-type fructans had a significant bifidogenic effect and induced increased concentrations of faecal SCFA, without changing faecal microbial diversity. Our findings suggest a moderate potential of inulin-type fructans to improve gut microbiota composition and to increase microbial fermentation in type 2 diabetes. TRIAL REGISTRATION: The trial is registered at clinicaltrials.gov (NCT02569684).

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BACKGROUND: Weight regain after bariatric surgery often starts after 1-2 y, but studies evaluating strategies to prevent weight regain are lacking. The aim of this intervention was to evaluate the efficacy of a 2-y-group-based lifestyle intervention starting approximately 2 y after Roux-en-Y gastric bypass (RYGB) compared with usual care on weight regain and related metabolic risk factors. METHODS: A total of 165 patients with a mean of 21 months (range 14-32) after RYGB were randomized to a lifestyle intervention group (LIG) or a usual care group (UCG). Of the 165 participants 86% completed the study. The LIG was offered 16 group meetings over 2 y with focus on healthy diet, physical activity, and behavioural strategies to prevent weight regain, in addition to usual care. RESULTS: Mean (SD) total weight loss at study start was 30.1 ± 8.2%, while weight regain during the intervention was 4.9 ± 7.4 and 4.6 ± 9.2% in the LIG and UCG, respectively (P = 0.84). There were no differences in metabolic risk factors between the groups. The LIG participants attended 8 ± 4 group meetings, with no difference in weight regain between participants with high compared to lower participation. In all the participants, a positive association between weight increase from nadir to study start and weight regain during the intervention was found. Participants who reported physical activity ≥ 150 min/wk had smaller % weight regain compared with less active participants (ß = - 5.2 [SE 2.0, 95% CI - 9.1 to - 1.4]). CONCLUSION: We found no difference in weight regain between LIG and UCG.

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