Effect of fibre additions to flatbread flour mixes on glucose kinetics: a randomised controlled trial.

We previously found that guar gum (GG) and chickpea flour (CPF) added to flatbread wheat flour lowered postprandial blood glucose (PPG) and insulin responses dose dependently. However, rates of glucose influx cannot be determined from PPG, which integrates rates of influx, tissue disposal and hepatic glucose production. The objective was to quantify rates of glucose influx and related fluxes as contributors to changes in PPG with GG and CPF additions to wheat-based flatbreads. In a randomised cross-over design, twelve healthy males consumed each of three different 13C-enriched meals: control flatbreads (C), or C incorporating 15 % CPF with either 2 % (GG2) or 4 % (GG4) GG. A dual isotope technique was used to determine the time to reach 50 % absorption of exogenous glucose (T 50 %abs, primary objective), rate of appearance of exogenous glucose (RaE), rate of appearance of total glucose (RaT), endogenous glucose production (EGP) and rate of disappearance of total glucose (RdT). Additional exploratory outcomes included PPG, insulin, glucose-dependent insulinotropic peptide and glucagon-like peptide 1, which were additionally measured over 4 h. Compared with C, GG2 and GG4 had no significant effect on T 50 %abs. However, GG4 significantly reduced 4-h AUC values for RaE, RaT, RdT and EGP, by 11, 14, 14 and 64 %, respectively, whereas GG2 showed minor effects. Effect sizes over 2 and 4 h were similar except for significantly greater reduction in EGP for GG4 at 2 h. In conclusion, a soluble fibre mix added to flatbreads only slightly reduced rates of glucose influx, but more substantially affected rates of postprandial disposal and hepatic glucose production.

Metabolic Profiling Reveals Differences in Plasma Concentrations of Arabinose and Xylose after Consumption of Fiber-Rich Pasta and Wheat Bread with Differential Rates of Systemic Appearance of Exogenous Glucose in Healthy Men.

BACKGROUND: The consumption of products rich in cereal fiber and with a low glycemic index is implicated in a lower risk of metabolic diseases. Previously, we showed that the consumption of fiber-rich pasta compared with bread resulted in a lower rate of appearance of exogenous glucose and a lower glucose clearance rate quantified with a dual-isotope technique, which was in accordance with a lower insulin and glucose-dependent insulinotropic polypeptide response. OBJECTIVE: To gain more insight into the acute metabolic consequences of the consumption of products resulting in differential glucose kinetics, postprandial metabolic profiles were determined. METHODS: In a crossover study, 9 healthy men [mean ± SEM age: 21 ± 0.5 y; mean ± SEM body mass index (kg/m2): 22 ± 0.5] consumed wheat bread (132 g) and fresh pasta (119 g uncooked) enriched with wheat bran (10%) meals. A total of 134 different metabolites in postprandial plasma samples (at -5, 30, 60, 90, 120, and 180 min) were quantified by using a gas chromatography-mass spectrometry-based metabolomics approach (secondary outcomes). Two-factor ANOVA and advanced multivariate statistical analysis (partial least squares) were applied to detect differences between both food products. RESULTS: Forty-two different postprandial metabolite profiles were identified, primarily representing pathways related to protein and energy metabolism, which were on average 8% and 7% lower after the men consumed pasta rather than bread, whereas concentrations of arabinose and xylose were 58% and 53% higher, respectively. Arabinose and xylose are derived from arabinoxylans, which are important components of wheat bran. The higher bioavailability of arabinose and xylose after pasta intake coincided with a lower rate of appearance of glucose and amino acids. We speculate that this higher bioavailability is due to higher degradation of arabinoxylans by small intestinal microbiota, facilitated by the higher viscosity of arabinoxylans after pasta intake than after bread intake. CONCLUSION: This study suggests that wheat bran, depending on the method of processing, can increase the viscosity of the meal bolus in the small intestine and interfere with macronutrient absorption in healthy men, thereby influencing postprandial glucose and insulin responses. This trial was registered at www.controlled-trials.com as ISRCTN42106325.

The structure of wheat bread influences the postprandial metabolic response in healthy men.

Postprandial high glucose and insulin responses after starchy food consumption, associated with an increased risk of developing several metabolic diseases, could possibly be improved by altering food structure. We investigated the influence of a compact food structure; different wheat products with a similar composition were created using different processing conditions. The postprandial glucose kinetics and metabolic response to bread with a compact structure (flat bread, FB) was compared to bread with a porous structure (control bread, CB) in a randomized, crossover study with ten healthy male volunteers. Pasta (PA), with a very compact structure, was used as the control. The rate of appearance of exogenous glucose (RaE), endogenous glucose production, and glucose clearance rate (GCR) was calculated using stable isotopes. Furthermore, postprandial plasma concentrations of glucose, insulin, several intestinal hormones and bile acids were analyzed. The structure of FB was considerably more compact compared to CB, as confirmed by microscopy, XRT analysis (porosity) and density measurements. Consumption of FB resulted in lower peak glucose, insulin and glucose-dependent insulinotropic polypeptide (ns) responses and a slower initial RaE compared to CB. These variables were similar to the PA response, except for RaE which remained slower over a longer period after PA consumption. Interestingly, the GCR after FB was higher than expected based on the insulin response, indicating increased insulin sensitivity or insulin-independent glucose disposal. These results demonstrate that the structure of wheat bread can influence the postprandial metabolic response, with a more compact structure being more beneficial for health. Bread-making technology should be further explored to create healthier products.

Quantitative proteomics analyses of activation states of human THP-1 macrophages.

Macrophages display large functional and phenotypical plasticity. They can adopt a broad range of activation states depending on their microenvironment. Various surface markers are used to characterize these differentially polarized macrophages. However, this is not informative for the functions of the macrophage. In order to have a better understanding of the functional changes of macrophages upon differential polarization, we studied differences in LPS- and IL4-stimulated macrophages. The THP-1 human monocytic cell line, was used as a model system. Cells were labeled, differentiated and stimulated with either LPS or IL-4 in a quantitative SILAC proteomics set-up. The resulting sets of proteins were functionally clustered. LPS-stimulated macrophages show increased secretion of proinflammatory peptides, leading to increased pressure on protein biosynthesis and processing. IL4-stimulated macrophages show upregulation of cell adhesion and extracellular matrix remodeling. Our approach provides an integrated view of polarization-induced functional changes and proves useful for studying functional differences between subsets of macrophages. Moreover, the identified polarization specific proteins may contribute to a better characterization of different activation states in situ and their role in various inflammatory processes.

Cell-based screening assay for anti-inflammatory activity of bioactive compounds.

Excess dietary intake may induce metabolic inflammation which is associated with insulin resistance and cardiovascular disease. Recent evidence indicates that dietary bioactive compounds may diminish metabolic inflammation. To identify anti-inflammatory bioactives, we developed a screening assay using the human H293-NF-κB-RE-luc2P reporter cell line. Under optimised conditions we determined the anti-inflammatory activity of vegetables and purified bioactives, by monitoring their potency to inhibit TNF-α-induced NF-κB activity, as assessed by sensitive chemiluminescence detection in a 96-well assay format. Minced broccoli seedlings reduced NF-κB activity by 16%, while sulphoraphane, the dominant bioactive in broccoli seedlings, inhibited NF-κB activity with an IC50 of 5.11 µmol/l. Short-chain fatty acids also reduced NF-κB activity in the order butyrate>propionate≫acetate with IC50 of 51, 223, and 1300 µmol/l, respectively. The H293-NF-κB-RE-luc2P reporter cell line is a sensitive tool for rapid high-throughput screening for bioactives with anti-inflammatory activity.

Slowly and rapidly digestible starchy foods can elicit a similar glycemic response because of differential tissue glucose uptake in healthy men.

BACKGROUND: Previously we observed that the consumption of pasta and bread resulted in a similar glycemic response, despite a slower intestinal influx rate of glucose from the pasta. Underlying mechanisms of this effect were not clear. OBJECTIVE: The objective was to investigate the differences in glucose kinetics and hormonal response after consumption of products with slow and rapid in vivo starch digestibility but with a similar glycemic response. DESIGN: Ten healthy male volunteers participated in a crossover study and consumed (13)C-enriched wheat bread or pasta while receiving a primed-continuous D-[6,6-(2)H(2)]glucose infusion. The dual-isotope technique enabled calculation of the following glucose kinetics: rate of appearance of exogenous glucose (RaE), endogenous glucose production, and glucose clearance rate (GCR). In addition, postprandial plasma concentrations of glucose, insulin, glucagon, and glucose-dependent insulinotropic polypeptide (GIP) were analyzed. RESULTS: GIP concentrations after pasta consumption were lower than after bread consumption and strongly correlated with the RaE (r = 0.82, P < 0.01). The insulin response was also lower after pasta consumption (P < 0.01). In accordance with the low insulin response, the GCR was lower after pasta consumption, which explained the high glycemic response despite a low RaE. CONCLUSIONS: Slower intestinal uptake of glucose from a starchy food product can result in lower postprandial insulin and GIP concentrations, but not necessarily in a lower glycemic response, because of a slower GCR. Even without being able to reduce postprandial glycemia, products with slowly digestible starch can have beneficial long-term effects. These types of starchy products cannot be identified by using the glycemic index and therefore another classification system may be necessary. This trial was registered at controlled-trials.com as ISRCTN42106325.

Sub-chronic administration of stable GIP analog in mice decreases serum LPL activity and body weight.

GIP receptor knockout mice were shown to be protected from the development of obesity on a high fat diet, suggesting a role of GIP in the development of obesity. In our study we aimed to test the hypothesis if excess of GIP could accelerate development of obesity and to identify GIP gene targets in adipose tissue. Therefore, mice were kept on a chow or a high fat diet and during the last 2 weeks D-Ala(2)-GIP or PBS injections were performed. Afterwards, serum LPL activity and several biochemical parameters (TG, FFA, cholesterol, glucose, insulin, resistin, IL-6, IL-1ß, TNFα, GIP) were measured. Fat tissue was isolated and QPCR was performed for a set of genes involved in energy metabolism and inflammation. A DNA-microarray was used to identify GIP gene targets in adipose tissue of the chow diet group. We found that the D-Ala(2)-GIP injections caused a significant decrease in both body weight and LPL activity compared to controls. Serum biochemical parameters were not affected by D-Ala(2)-GIP, with an exception for resistin and insulin. The set of inflammatory genes were significantly decreased in adipose tissue in the D-Ala(2)-GIP injected animals on a chow diet. A DNA-microarray revealed that APO-genes and CYP-genes were affected by D-Ala(2)-GIP treatment in adipose tissue. These results suggest that the body weight-reducing effect of D-Ala(2)-GIP may be explained by lower LPL activity and insulin serum level. Moreover, the identified GIP candidate gene targets in adipose tissue link GIP action to lipid metabolism exerted by APO and CYP genes.

Regulation of adipokine production in human adipose tissue by propionic acid.

BACKGROUND: Dietary fibre (DF) has been shown to be protective for the development of obesity, insulin resistance and type 2 diabetes. Short-chain fatty acids, produced by colonic fermentation of DF might mediate this beneficial effect. Adipose tissue plays a key role in the regulation of energy homeostasis, therefore, we investigated the influence of the short-chain fatty acid propionic acid (PA) on leptin, adiponectin and resistin production by human omental (OAT) and subcutaneous adipose tissue (SAT). As PA has been shown to be a ligand for G-protein coupled receptor (GPCR) 41 and 43, we investigated the role of GPCR's in PA signalling. MATERIALS AND METHODS: Human OAT and SAT explants were obtained from gynaecological patients who underwent surgery. Explants were incubated for 24 h with PA. Adipokine secretion and mRNA expression were determined using ELISA and RT-PCR respectively. RESULTS: We found that PA significantly stimulated leptin mRNA expression and secretion by OAT and SAT, whereas it had no effect on adiponectin. Furthermore, PA reduced resistin mRNA expression. Leptin induction, but not resistin reduction, was abolished by inhibition of Gi/o-coupled GPCR signalling. Moreover, GPCR41 and GPCR43 mRNA levels were considerably higher in SAT than in OAT. CONCLUSIONS: We demonstrate that PA stimulates expression of the anorexigenic hormone leptin and reduces the pro-inflammatory factor resistin in human adipose tissue depots. This suggests that PA is involved in regulation of human energy metabolism and inflammation and in this way may influence the development of obesity and type 2 diabetes.

Factors related to colonic fermentation of nondigestible carbohydrates of a previous evening meal increase tissue glucose uptake and moderate glucose-associated inflammation.

BACKGROUND: Evening meals that are rich in nondigestible carbohydrates have been shown to lower postprandial glucose concentrations after ingestion of high-glycemic-index breakfasts. This phenomenon is linked to colonic fermentation of nondigestible carbohydrates, but the underlying mechanism is not fully elucidated. OBJECTIVE: We examined the way in which glucose kinetics and related factors change after breakfast as a result of colonic fermentation. DESIGN: In a crossover design, 10 healthy men ingested as an evening meal white wheat bread (WB) or cooked barley kernels (BA) that were rich in nondigestible carbohydrates. In the morning after intake of 50 g (13)C-enriched glucose, the dual-isotope technique was applied to determine glucose kinetics. Plasma insulin, free fatty acid, interleukin-6, tumor necrosis factor-alpha, and short-chain fatty acid concentrations and breath-hydrogen excretion were measured. RESULTS: The plasma glucose response after the glucose drink was 29% lower after the BA evening meal (P = 0.019). The insulin response was the same, whereas mean (+/-SEM) tissue glucose uptake was 30% higher (20.2 +/- 1.9 compared with 15.5 +/- 1.8 mL/2 h; P = 0.016) after the BA evening meal, which indicated higher peripheral insulin sensitivity (P = 0.001). The 4-h mean postprandial interleukin-6 (19.7 +/- 5.1 compared with 5.1 +/- 0.7 pg/mL; P = 0.024) and tumor necrosis factor-alpha (7.8 +/- 2.1 compared with 5.3 +/- 1.6 pg/mL; P = 0.008) concentrations after the glucose drink were higher after the WB evening meal. Butyrate concentrations (P = 0.041) and hydrogen excretion (P = 0.005) were higher in the morning after the BA evening meal. CONCLUSION: In healthy subjects, factors related to colonic fermentation of nondigestible carbohydrates increase peripheral insulin sensitivity and moderate glucose-associated inflammation.

The rate of intestinal glucose absorption is correlated with plasma glucose-dependent insulinotropic polypeptide concentrations in healthy men.

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) both play a role in the control of glucose homeostasis, and GIP is implicated in the regulation of energy storage. The capacity of carbohydrates to induce secretion of these incretin hormones could be one of the factors determining the metabolic quality of different types of carbohydrates. We analyzed the correlation between the rate of intestinal absorption of (starch-derived) glucose and plasma concentrations of GLP-1 and GIP after ingestion of glucose and starchy foods with a different content of rapidly and slowly available glucose. In a crossover study, glucose, insulin, GLP-1, and GIP concentrations were monitored for 6 h after consumption of glucose, uncooked cornstarch (UCCS) or corn pasta in 7 healthy men. All test meals were naturally labeled with 13C. Using a primed, continuous D-[6,6-2H2]glucose infusion, the rate of appearance of exogenous glucose (RaEx) was estimated, reflecting the rate of intestinal glucose absorption. GLP-1 concentrations increased significantly from 180 to 300 min after ingestion of UCCS, the starch product with a high content of slowly available glucose. A high GIP response in the early postprandial phase (15-90 min) occurred after consumption of glucose. There was a strong positive within-subject correlation between RaEx and GIP concentrations (r = 0.73, P < 0.01) across the test meals. Rapidly and slowly digestible carbohydrates differ considerably in their ability to stimulate secretion of incretin hormones; the metabolic consequences of such differences warrant exploration.

Low lactase activity in a small-bowel biopsy specimen: should dietary lactose intake be restricted in children with small intestinal mucosal damage?

OBJECTIVE: Small intestinal mucosal damage can result in decreased lactase activity (LA). When LA is low in a small-bowel biopsy (SBB) specimen, a reduction of dietary lactose intake is usually advised. This is often done by reducing dietary dairy products, which also reduces the intake of calcium, protein and vitamins. Since intestinal damage can have a patchy character and LA varies along the horizontal axis of the small intestine, the relevance of SBB measurement for intestinal LA could be questioned. We compared LA in the SBB with the in vivo capacity to digest lactose using the Lactose Digestion Index (LDI). MATERIAL AND METHODS: LA was measured in 18 children aged 0.8-10.9 years (mean 3.9, SD 2.4) undergoing SBB for various indications. In all children the LDI was determined using the (13)C-lactose/(2)H-glucose test. RESULTS: In 9/18 biopsy specimens LA was low (<10 U/g protein). LDI was normal in 14/18 patients. In 8 out of 9 patients with normal lactase activity, LDI was also normal, while in 6 out of 9 patients LDI was normal despite low LA in the biopsy. In patients with normal LDI, histology was normal in 6/14, in 4/14 mild histological changes (Marsh II) were seen and in 4 patients histological damage was severe (grade III). CONCLUSIONS: In children with small-bowel mucosal damage, lactose digestive capacity can remain high despite low LA and histological changes in an SBB. Extrapolation of LA in SBB specimens to overall lactose digestive capacity may not be reliable. The advice concerning the restriction of intake of dairy products cannot be based on the data of the SBB only.