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Abundance of gut Prevotella at baseline and metabolic response to barley prebiotics.
Sandberg, J, Kovatcheva-Datchary, P, Björck, I, Bäckhed, F, Nilsson, A
European journal of nutrition. 2019;(6):2365-2376
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Abstract
PURPOSE We previously showed that short-term intervention with barley kernel bread (BKB) improved glucose tolerance. However, glucose tolerance was not improved in a subset of individuals (non-responders) who were characterized by a low Prevotella/Bacteroides ratio. The purpose of the present study was to investigate if the baseline Prevotella/Bacteroides ratio can be used to stratify metabolic responders and non-responders to barley dietary fiber (DF). METHODS Fecal samples were collected from 99 healthy humans with BMI < 28 kg/m2 between 50 and 70 years old. The abundance of fecal Prevotella and Bacteroides was quantified with 16S rRNA quantitative PCR. 33 subjects were grouped in three groups: subjects with highest Prevotella/Bacteroides ratios, "HP", n = 12; subjects with lowest Prevotella/Bacteroides ratios, "LP", n = 13; and subjects with high abundance of both measured bacteria, HPB, n = 8. A 3-day randomized crossover intervention with BKB and white wheat bread (control) was performed. Cardiometabolic test variables were analyzed the next day following a standardized breakfast. RESULTS The BKB intervention lowered the blood glucose responses to the breakfast independently of Prevotella/Bacteroides ratios (P < 0.01). However, independently of intervention, the HP group displayed an overall lower insulin response and lower IL-6 concentrations compared with the LP group (P < 0.05). Furthermore, the groups HP and HPB showed lower hunger sensations compared to the LP group (P < 0.05). CONCLUSIONS Here we show that the abundance of gut Prevotella and Bacteroides at baseline did not stratify metabolic responders and non-responders to barley DF intervention. However, our results indicate the importance of gut microbiota in host metabolic regulation, further suggesting that higher Prevotella/Bacteroides ratio may be favorable. CLINICALTRIALS. GOV ID NCT02427555.
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Effects of GI vs content of cereal fibre of the evening meal on glucose tolerance at a subsequent standardized breakfast.
Nilsson, A, Ostman, E, Preston, T, Björck, I
European journal of clinical nutrition. 2008;(6):712-20
Abstract
OBJECTIVE To investigate if the improved glucose tolerance previously observed at breakfast following an evening meal with boiled barley kernels derives from colonic events related to the fermentation of the elevated amounts of indigestible carbohydrates present and/or from the low-GI features. SUBJECTS/METHODS Twenty healthy volunteers aged 19-30 years. DESIGN High-GI white wheat bread (WWB), WWB+barley dietary fibre (DF) corresponding to the DF content of barley kernels, low-GI spaghetti+ barley DF, spaghetti+double amounts of barley DF (2(*)DF), spaghetti+oat DF, or whole grain barley flour porridge, were provided as late evening meals. At a subsequent standardised WWB breakfast, B-glucose, s-insulin, p-SCFA, p-FFA, and breath hydrogen (H(2)) were measured. RESULTS The B-glucose response (incremental areas under the curves (IAUC) 0-120 min and total areas under the curves 0-180 min) to the standardized breakfast was significantly lower after consuming spaghetti+2*DF in the evening compared with barley porridge (P=0.012). The spaghetti+2*DF meal also resulted in the highest breath H(2) excretion (P<0.02). The glucose IAUC (0-120 min) after the standardized breakfast was positively correlated to fasting p-FFA (r=0.29, P<0.02), and the total glucose area (0-180 min) was negatively correlated to the p-propionate level (0-30 min) (r=-0.24, P<0.02). CONCLUSIONS The prolonged digestive and absorptive phase per se, like with a low-glycaemic index (GI) spaghetti evening meal, did not induce overnight benefits on glucose tolerance. Addition of barley DF in high amounts (2*DF) was required to improve overnight glucose tolerance. The correlations observed between glycaemia and p-propionate implicate colonic fermentation as a modulator of glucose tolerance through a mechanism leading to suppressed free fatty acids levels. It is proposed that the overnight benefits on glucose tolerance previously reported for boiled barley kernels is mediated through colonic fermentation of the prebiotic carbohydrates present in this product.