Effects of dietary fibers on disturbances clustered in the metabolic syndrome

Malt in combination with Lactobacillus rhamnosus increases concentrations of butyric acid in the distal colon and serum in rats compared with other barley products but decreases viable counts of cecal bifidobacteria

Several substances, including glutamine and propionic acid but in particular butyric acid, have been proposed to be important for colonic health. β-Glucans lead to the formation of comparatively high amounts of butyric acid, and germinated barley foodstuff obtained from brewer's spent grain (BSG), containing high amounts of β-glucans and glutamine, has been reported to reduce the inflammatory response in the colon of patients with ulcerative colitis. The present study examines how 3 barley products, whole grain barley, malt, and BSG, affect SCFA in the hindgut and serum of rats and whether the addition of Lactobacillus rhamnosus 271 to each of these diets would have further effects. Amino acids in plasma and the cecal composition of the microbiota were also analyzed. The butyric acid concentration in the distal colon and serum was higher in the malt groups than in the other groups as was the serum concentration of propionic acid. The concentrations of propionic and butyric acids were higher in the cecum and serum of rats given L. rhamnosus than in those not given this strain. The proportion of plasma glutamine and the cecal number of bifidobacteria were lower in the malt groups than in the other groups. L. rhamnosus decreased the number of cecal bifidobacteria, whereas plasma glutamine was unaffected. We conclude that malt together with L. rhamnosus 271 had greater effects on propionic and butyric acid concentrations in rats than the other barley products. This is interesting when developing food with effects on colonic health.

Dietary lignans: physiology and potential for cardiovascular disease risk reduction

The present review of the literature on lignan physiology and lignan intervention and epidemiological studies was conducted to determine if lignans decrease the risks of cardiovascular disease in Western populations. Five intervention studies using flaxseed lignan supplements indicated beneficial associations with C-reactive protein, and a meta-analysis that included these studies also suggested lignans have a lowering effect on plasma total and low-density lipoprotein cholesterol. Three intervention studies using sesamin supplements indicated possible lipid- and blood pressure-lowering associations. Eleven human observational epidemiological studies examined dietary intakes of lignans in relation to cardiovascular disease risk. Five showed decreased risk with either increasing dietary intakes of lignans or increased levels of serum enterolactone (an enterolignan used as a biomarker of lignan intake), five studies were of borderline significance, and one was null. The associations between lignans and decreased risk of cardiovascular disease are promising, but they are yet not well established, perhaps due to low lignan intakes in habitual Western diets. At the higher doses used in intervention studies, associations were more evident.

Butyrate and other short-chain fatty acids as modulators of immunity: what relevance for health?

PURPOSE OF REVIEW

High-fiber diets have been shown to reduce plasma concentrations of inflammation markers. Increased production of fermentation-derived short-chain fatty acids (SCFAs) is one of the factors that could exert these positive effects. This review examines the effects of SCFAs on immune cells and discusses the relevance of their effects on systemic inflammation, as frequently seen in obesity.

RECENT FINDINGS

SCFAs have been shown to reduce chemotaxis and cell adhesion; this effect is dependent on type and concentration of SCFA. In spite of conflicting results, especially butyrate seems to have an anti-inflammatory effect, mediated by signaling pathways like nuclear factor-κB and inhibition of histone deacetylase. The discrepancies in the results could be explained by differences in cell types used and their proliferative and differentiation status.

SUMMARY

SCFAs show anti-inflammatory effects and seem to have the potency to prevent infiltration of immune cells from the bloodstream in, for example, the adipose tissue. In addition, their ability to inhibit the proliferation and activation of T cells and to prevent adhesion of antigen-presenting cells could be important as it recently has been shown that obesity-associated inflammation might be antigen-dependent. More studies with concentrations in micromolar range are needed to approach more physiological concentrations.

Simple advice on lifestyle habits and long-term changes in biomarkers of inflammation and vascular adhesion in healthy middle-aged men

BACKGROUND/OBJECTIVES

Lifestyle habits, vascular function and inflammation are components in the development of cardiovascular disease (CVD). We investigated whether simple advice on dietary and exercise habits given (at a single time point) to hypercholesterolemic men affects circulating biomarkers of inflammation and vascular adhesion.

SUBJECTS/METHODS

In total, 157 men (age 46±5 years) with mild hypercholesterolemia were randomized to four intervention groups, diet (D, n=40), exercise (E, n=39), diet and exercise (DE, n=39) or controls (C, n=39) and serum concentrations of C-reactive protein (CRP), interleukin-6 (IL-6), soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAM-1) and soluble E-selectin (sE-selectin) were quantified at baseline and after a 6-month intervention period.

RESULTS

The intervention applied in this study, that is, simple advice on lifestyle changes given at a single time point, had a modest effect on inflammatory biomarkers and soluble vascular adhesion molecules. The most apparent alterations were found for individuals in group DE, who responded with significant reductions in sICAM-1, -28 (-41 to -14 μg/l) and sE-selectin, -3.6 (-6.9 to -0.3 μg/l) after 6 months. None of the groups had altered their concentrations of sVCAM-1, CRP or IL-6 significantly after the intervention. In all individuals combined, we found changes in apolipoprotein B (apoB) to predict alterations in sICAM-1 (β=0.21) and sE-selectin (β=0.26), independently of changes in inflammation and other adhesion molecules.

CONCLUSIONS

These observations indicate that even small efforts to improve diet and physical activity can influence biomarkers of vascular function in individuals at increased risk for CVD. ApoB was identified as an important determinant of this improvement, which adds further support to the notion of apoB as a critical target in cardiovascular prevention.

Biological effects of propionic acid in humans; metabolism, potential applications and underlying mechanisms

Undigested food is fermented in the colon by the microbiota and gives rise to various microbial metabolites. Short-chain fatty acids (SCFA), including acetic, propionic and butyric acid, are the principal metabolites produced. However, most of the literature focuses on butyrate and to a lesser extent on acetate; consequently, potential effects of propionic acid (PA) on physiology and pathology have long been underestimated. It has been demonstrated that PA lowers fatty acids content in liver and plasma, reduces food intake, exerts immunosuppressive actions and probably improves tissue insulin sensitivity. Thus increased production of PA by the microbiota might be considered beneficial in the context of prevention of obesity and diabetes type 2. The molecular mechanisms by which PA may exert this plethora of physiological effects are slowly being elucidated and include intestinal cyclooxygenase enzyme, the G-protein coupled receptors 41 and 43 and activation of the peroxisome proliferator-activated receptor γ, in turn inhibiting the sentinel transcription factor NF-κB and thus increasing the threshold for inflammatory responses in general. Taken together, PA emerges as a major mediator in the link between nutrition, gut microbiota and physiology.

Canna edulis Ker By-product: Chemical Composition and Characteristics of the Dietary Fiber

Canna edulis Ker by-product was recycled and utilized after starch extraction. The chemical composition, physical properties and antioxidant activity of the by-product were investigated. The by-product was mainly composed of dietary fiber (54.84% measured by AOAC method), and the insoluble dietary fiber constituted the major fraction. Then, the chemical composition of dietary fiber was tested using modified AOAC and Englyst methods. The results showed that dietary fiber was comprised of cellulose, hemicelluloses (including xyloglucans, arabinoxylans and glucuronoxylans), pectin and lignin. Moreover, the by-product contained relatively high content of phenolic compounds and exhibited a moderate antioxidant activity. In addition, the by-product showed both high water-holding capacity (12.5 mL/g) and oil-holding capacity (14 mL/g), and its suspension exhibited controllable viscosity. Therefore, the by-product from C. edulis is not only a source of dietary fiber but also a functional ingredient for food industry.

Fruit and vegetable consumption and proinflammatory gene expression from peripheral blood mononuclear cells in young adults: a translational study

BACKGROUND

Fruits and vegetables are important sources of fiber and nutrients with a recognized antioxidant capacity, which could have beneficial effects on the proinflammatory status as well as some metabolic syndrome and cardiovascular disease features. The current study assessed the potential relationships of fruit and vegetable consumption with the plasma concentrations and mRNA expression values of some proinflammatory markers in young adults.

METHODS

One-hundred and twenty healthy subjects (50 men/70 women; 20.8 +/- 2.6 y; 22.3 +/- 2.8 kg/m2) were enrolled. Experimental determinations included anthropometry, blood pressure and lifestyle features as well as blood biochemical and inflammatory measurements. The mRNA was isolated from peripheral blood mononuclear cells (PBMC) and the gene expression concerning selected inflammatory markers was assessed by quantitative real-time PCR. Nutritional intakes were estimated by a validated semi-quantitative food-frequency questionnaire.

RESULTS

The highest tertile of energy-adjusted fruit and vegetable consumption (>660 g/d) was associated with lower plasma concentrations of C-reactive protein (CRP) and homocysteine and with lower ICAM1, IL1R1, IL6, TNFalpha and NFkappaB1 gene expression in PBMC (P for trend < 0.05), independently of gender, age, energy intake, physical activity, smoking, body mass index, systolic blood pressure and circulating non-esterified fatty acids. In addition, plasma CRP, homocysteine and TNFalpha concentrations and ICAM1, TNFalpha and NFkappaB1 gene expression in PBMC showed a descending trend as increased fiber intake (>19.5 g/d) from fruits and vegetables (P for trend < 0.05). Furthermore, the participants within the higher tertile (>11.8 mmol/d) of dietary total antioxidant capacity showed lower plasma CRP and mRNA values of ICAM1, IL1R1, IL6, TNFalpha and NFkappaB1 genes (P for trend < 0.05). The inverse association between fruit and vegetable consumption and study proinflammatory markers followed the same trend and remained statistically significant, after the inclusion of other foods/nutrients in the linear regression models.

CONCLUSION

A higher fruit and vegetable consumption was independently associated not only with reduced CRP and homocysteine concentrations but also with a lower mRNA expression in PBMC of some relevant proinflammatory markers in healthy young adults.

Prospective study of dietary fiber and risk of chronic obstructive pulmonary disease among US women and men

Little is known about the relation between dietary fiber intake and the incidence of respiratory diseases, especially chronic obstructive pulmonary disease (COPD). The authors investigated this issue among 111,580 US women and men (Nurses' Health Study and Health Professionals Follow-up Study), with 832 cases of newly diagnosed COPD being reported between 1984 and 2000. The cumulative average intake of total fiber and of fiber from specific sources (cereal, fruit, and vegetables) was calculated from food frequency questionnaires and a food composition database and divided into quintiles. After adjustment for 11 factors (age, sex, smoking, energy intake, body mass index, US region, physician visits, physical activity, diabetes, and intakes of omega-3 and cured meat), total dietary fiber intake was negatively associated with risk of newly diagnosed COPD (for highest vs. lowest intake, relative risk = 0.67, 95% confidence interval: 0.50, 0.90; P(trend) = 0.03). For specific fiber sources (cereal, fruit, and vegetables), only cereal fiber was significantly associated with newly diagnosed COPD independently of other fiber sources (for highest vs. lowest intake, relative risk = 0.77, 95% confidence interval: 0.59, 0.99; P(trend) = 0.04). These data suggest that a diet high in fiber, and possibly specifically cereal fiber, may reduce risk of developing COPD.

Effects of oat bran, processed to different molecular weights of beta-glucan, on plasma lipids and caecal formation of SCFA in mice

In the present study, we evaluated the cholesterol-lowering effects of different oat bran (OB) preparations, differing regarding their peak molecular weight (MWp) of beta-glucans (2348, 1311, 241, 56, 21 or < 10 kDa), in C57BL/6NCrl mice. The diets were designed to be atherogenic (0.8 % cholesterol and 0.1 % cholic acid), and they reflected the Western diet pattern (41 % energy fat). All OB preparations that were investigated significantly reduced plasma cholesterol when compared with a cellulose-containing control diet, regardless of the molecular weight of beta-glucan. Moreover, the difference in viscous properties between the processed OB (from 0.11 to 17.7 l/g) did not appear to play a major role in the cholesterol-lowering properties. In addition, there was no correlation between the molecular weight of beta-glucan and the amount of propionic acid formed in caecum. Interestingly, however, there was a significant correlation between the ratio of (propionic acid+butyric acid)/acetic acid and the MWp of beta-glucans: the ratio increased with increasing molecular weight. The results of the present study suggest that the molecular weights and viscous properties of beta-glucan in oat products may not be crucial parameters for their cholesterol-lowering effects.

Relationship between number of metabolic syndrome components and dietary factors in middle-aged and elderly Japanese subjects

Metabolic syndrome (MetS) represents a cluster of risk factors for atherosclerosis and is considered a risk factor for cardiovascular disease. The role of diet in the etiology of MetS is poorly understood, especially among Asian subjects. This cross-sectional study assessed the relationship between diet and the number of MetS components among Japanese men (n=609) and women (n=631). Mean (s.d.) age and body mass index were 57.1 (12.1) years and 22.8 (2.8) kg m(-2) for men and 55.5 (12.0) years and 22.0 (3.0) kg m(-2) for women, respectively. Diet was assessed by a 3-day dietary record that included photographs: 16 nutrients, 11 food groups, and energy % of protein and dietary fat were selected as a dietary index. The definition of MetS was based on modified National Cholesterol Education Program, Adult Treatment Panel III criteria, and the number of clustering MetS components was calculated by adding the presence of each five MetS components. A total of 61 men (10.0%) and 46 women (7.3%) were determined to have MetS. After adjusting for age, energy intake, alcohol intake, smoking status and physical activity, a lower intake of vitamin B6 and dietary fiber in men, and lower intake of calcium, milk and dairy products and higher intake of cereal in women were related to the number of MetS components. These results suggest that some dietary factors were related to the number of MetS components among community-dwelling Japanese men and women.

The dietary quality of persons with heart failure in NHANES 1999-2006

BACKGROUND

Dietary quality may impact heart failure outcomes. However, the current status of the dietary quality of persons with heart failure has not been previously reported.

OBJECTIVE

To describe sodium intake, patient factors associated with sodium intake and overall dietary quality in a national sample of persons with heart failure.

DESIGN

Analysis of repeated cross-sectional probability sample surveys using data from National Health and Nutrition Examination Surveys (NHANES) of 1999-2000, 2001-2002, 2003-2004 and 2005-2006.

PARTICIPANTS

The study sample consisted of 574 persons with self-reported heart failure (mean age = 70 years; 52% women).

MEASUREMENTS

Diet of each survey participant was assessed using single 24 hour recall. Dietary nutrients of interest included sodium, the mainstay of heart failure dietary recommendations, and additionally potassium, calcium, magnesium, fish oils, saturated fat and fiber. Specific dietary goals were based on established guidelines.

RESULTS

Mean sodium intake was 2,719 mg, with 34% consuming less than 2,000 mg per day. Patient factors associated with greater sodium intake included male gender, lower education, lower income and no reported diagnosis of hypertension. Mean potassium intake was 2,367 mg/day, with no differences by type of diuretic used or renal disease status. Adherence rates to established guidelines for other nutrients were 13% for calcium, 10% for magnesium, 2% for fish oils, 13% for saturated fat and 4% for fiber.

CONCLUSIONS

Dietary quality of persons with self-reported heart failure was poor. Public health approaches and clinical dietary interventions are needed for persons with this increasingly prevalent clinical syndrome.

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.

Dietary fiber supplements: effects in obesity and metabolic syndrome and relationship to gastrointestinal functions

Dietary fiber is a term that reflects a heterogeneous group of natural food sources, processed grains, and commercial supplements. Several forms of dietary fiber have been used as complementary or alternative agents in the management of manifestations of the metabolic syndrome, including obesity. Not surprisingly, there is a great variation in the biological efficacy of dietary fiber in the metabolic syndrome and body weight control. Diverse factors and mechanisms have been reported as mediators of the effects of dietary fiber on the metabolic syndrome and obesity. Among this array of mechanisms, the modulation of gastric sensorimotor influences appears to be crucial for the effects of dietary fiber but also quite variable. This report focuses on the role, mechanism of action, and benefits of different forms of fiber and supplements on obesity and the metabolic syndrome, glycemia, dyslipidemia, and cardiovascular risk and explores the effects of dietary fiber on gastric sensorimotor function and satiety in mediating these actions of dietary fiber.

Design and methods for testing a simple dietary message to improve weight loss and dietary quality

BACKGROUND

The current food pyramid guidelines have been criticized because of their complexity and the knowledge required for users to understand the recommendations. Simplification of a dietary message to focus on a single key aspect of dietary quality, e.g., fiber intake, may make the message much easier to comprehend and adhere, such that respondents can achieve greater weight loss, better dietary quality and overall metabolic health.

METHODS AND DESIGN

This is a randomized controlled clinical trial with two equal sized arms. In total, 240 obese adults who meet diagnostic criteria for the metabolic syndrome will be randomized to one of the two conditions: 1) a high fiber diet and 2) the American Heart Association (AHA) diet. In the high fiber diet condition, patients will be given instruction only on achieving daily dietary fiber intake of 30 g or more. In the AHA diet condition, patients will be instructed to make the several dietary changes recommended by the AHA 2006 guidelines. The trial examines participant weight loss and dietary quality as well as changes in components of the metabolic syndrome, inflammatory biomarkers, low-density lipoprotein cholesterol levels, insulin levels, and glycosolated hemoglobin. Potential mediators, i.e., diet adherence and perceived ease of the diet, and the intervention effect on weight change will also be examined.

DISCUSSIONS

The purpose of this paper is to outline the study design and methods for testing the simple message of increasing dietary fiber. If the simple dietary approach is found efficacious for weight loss; and, improves dietary quality, metabolic health, and adherence, it might then be used to develop a simple public health message.

TRIAL REGISTRATION

NCT00911885.

Associations between dietary fiber and inflammation, hepatic function, and risk of type 2 diabetes in older men: potential mechanisms for the benefits of fiber on diabetes risk

OBJECTIVE

To examine the relationship between dietary fiber and the risk of type 2 diabetes in older men and the role of hepatic and inflammatory markers.

RESEARCH DESIGN AND METHODS

The study was performed prospectively and included 3,428 nondiabetic men (age 60-79 years) followed up for 7 years, during which there were 162 incident cases of type 2 diabetes.

RESULTS

Low total dietary fiber (lowest quartile < or =20 g/day) was associated with increased risk of diabetes after adjustment for total calorie intake and potential confounders (relative risk -1.47 [95% CI 1.03-2.11]). This increased risk was seen separately for both low cereal and low vegetable fiber intake. Dietary fiber was inversely associated with inflammatory markers (C-reactive protein, interleukin-6) and with tissue plasminogen activator and gamma-glutamyl transferase. Adjustment for these markers attenuated the increased risk (1.28 [0.88-1.86]).

CONCLUSIONS

Dietary fiber is associated with reduced diabetes risk, which may be partly explained by inflammatory markers and hepatic fat deposition.

Activation of the AMP activated protein kinase by short-chain fatty acids is the main mechanism underlying the beneficial effect of a high fiber diet on the metabolic syndrome

The metabolic syndrome, a cluster of conditions including abdominal obesity, insulin resistance, dyslipidemia, and elevated blood pressure, is a natural consequence of over nutrition and a sedentary lifestyle. The prevalence of the metabolic syndrome has increased to epidemic proportions in the world. The exact pathogenesis of the metabolic syndrome remains unclear, but it is known to be a complex interaction between genetic, metabolic, and environmental factors. Promotion of physical activity and dietary management are still the main methods for the prevention and management of the metabolic syndrome. Numerous experimental and clinical studies have demonstrated the beneficial effects of high fiber diet on the metabolic syndrome. The principal beneficial effects of a fiber-rich diet in these patients are: prevention of obesity, improved glucose levels, and control of the profile of blood lipids. Dietary fiber may also favor the control of arterial blood pressure. How dietary fiber exerts its beneficial effects on the metabolic syndrome is not well understood. AMP activated protein kinase (AMPK) functions as a major cellular fuel gauge and a master regulator of metabolic homeostasis. Several lines of evidence suggest that AMPK can be activated by short-chain fatty acids (SCFA) either directly or indirectly. It is our hypothesis that the main mechanism underlying the beneficial effect of a high fiber diet on the metabolic syndrome is the increased SCFA production in the colon leading to a higher concentration of SCFA in the portal vein, which activates the AMPK in the liver.

Metabolic effects of whole grain wheat and whole grain rye in the C57BL/6J mouse

OBJECTIVE

A diet rich in whole grain cereals is suggested to protect against type 2 diabetes and facilitate body weight regulation. However, little is known about the impact of different cereals and the underlying mechanisms. The objective of this study was to compare the long-term metabolic effects of diets supplemented with whole grain wheat or whole grain rye in the C57BL/6J mouse.

METHODS

Mice were fed the whole grain supplements in a low-fat background diet for 22 wk. Oral and intravenous glucose tolerance tests were performed during the study and in vitro insulin secretion assays were performed at the end of the study. Body weight, energy intake, body fat content, and plasma parameters were measured during the study.

RESULTS

A dietary supplement of whole grain rye suppressed body weight gain and resulted in significantly decreased adiposity, plasma leptin, total plasma cholesterol, and triacylglycerols compared with a supplement of whole grain wheat. Also, a slight improvement in insulin sensitivity was observed in the rye group compared with the wheat group. The decreases in body weight and adiposity were observed in the absence of differences in energy intake.

CONCLUSION

Long-term administration of whole grain rye evokes a different metabolic profile compared with whole grain wheat in the C57BL/6J mouse, the primary difference being that whole grain rye reduces body weight and adiposity compared with whole grain wheat. In addition, whole grain rye slightly improves insulin sensitivity and lowers total plasma cholesterol.

Increased interleukin-10 but unchanged insulin sensitivity after 4 weeks of (1, 3)(1, 6)-beta-glycan consumption in overweight humans

Obesity-induced insulin resistance has been suggested to be a systemic inflammatory condition with activation of the innate immune system. Animal studies indicate that certain dietary fibers such as (1,3)(1,6)-beta-D-glycans (BDG) have potent effects on immune activity such as increasing the antiinflammatory cytokine interleukin-10 (IL-10) and reducing the secretion of inflammatory factors. Therefore, we hypothesized that BDG consumption improves inflammatory markers and insulin sensitivity in overweight and obese subjects with moderately increased levels of C-reactive protein, indicating subclinical inflammation. We screened 180 overweight and obese subjects for moderately increased C-reactive protein levels on 2 or more occasions, in the absence of any signs of acute infection. Twelve of the subjects met all inclusion criteria and were investigated in a randomized, double-blind, placebo-controlled, crossover design for 2 x 4 weeks (washout > or =4 weeks). Subjects ingested capsules containing 3 x 0.5 g of highly purified BDG or 3 x 0.5 g of placebo (waxy maize starch) daily. Maintenance of the normal diet of the participants and the correct intake of the capsules were monitored, using 6 x 3-day food recording and counting of the provided capsules. Predefined outcome measures were BDG-induced changes in pro and antiinflammatory markers in circulating blood and gene expression in adipose tissue and peripheral insulin sensitivity expressed as M value. The BDG consumption for 4 weeks significantly increased both circulating levels and adipose tissue messenger RNA (mRNA) expression of the antiinflammatory cytokine IL-10 in overweight and obese humans. Insulin sensitivity as well as circulating levels and mRNA expression of proinflammatory cytokines were unaffected by BDG treatment. Increased IL-10 after BDG consumption might be a contributing factor to the known beneficial effects of dietary fiber intake.

The influence of dietary fibre source and gender on the postprandial glucose and lipid response in healthy subjects

BACKGROUND

Consumption of soluble dietary fibre is correlated with decreased postprandial glucose and insulin responses and hence has beneficial effects on the metabolic syndrome.

AIM OF THE STUDY

To investigate the effects on postprandial glucose, insulin and triglyceride concentrations of meals enriched with soluble dietary fibres from oats, rye bran, sugar beet fibre or a mixture of these three fibres.

METHODS

Thirteen healthy human volunteers (6 men and 7 women, aged 20-28 years) were included in the study. The subjects came to the study centre once a week after an overnight fast to ingest test meals and a control meal in random order. The meals contained either oat powder (62 g, of which 2.7 soluble fibre), rye bran (31 g, of which 1.7 g soluble fibre), sugar beet fibre (19 g, of which 5 g soluble fibre), a mixture of these three fibres (74 g, of which 1.7 g soluble fibre from each source, giving 5 g soluble fibre) or no added fibre (control) and were all adjusted to contain the same total amount of available carbohydrates. Blood samples were drawn before and every 30 min up to 180 min after the meals.

RESULTS

Meals with rye bran gave a lower postprandial glucose peak when compared with the control meal, and this effect was more pronounced in women compared to men. Oat powder, containing a low amount of total fibre and a high amount of carbohydrates in liquid matrix, gave a higher incremental glucose peak concentration compared to rye bran and sugar beet fibre and higher insulin incremental area under curve compared to control. The oat powder also influenced the effects of the mixed meal, diminishing the glucose-lowering effects. Postprandial triglyceride levels tended to be higher after all fibre-rich meals, but only significant for oat powder and the mixed meal when compared with the control meal.

CONCLUSIONS

Postprandial glucose, insulin and triglyceride concentrations are influenced by dietary fibre-rich meals, depending on fibre source, dose of soluble and total fibre and possibly gender.

Impact of a lignan-rich diet on adiposity and insulin sensitivity in post-menopausal women

There has been a growing interest in lignans, a class of phyto-oestrogens, because of their potentially favourable effects on human health. The aim of the present study was to compare the metabolic profile of post-menopausal women consuming various amounts of dietary lignans. Phyto-oestrogen intake was assessed using a 3-d dietary record analysed with a Canadian food phyto-oestrogen content data table in 115 post-menopausal women (age 56·8 (sd 4·4) years and BMI 28·5 (sd 5·9) kg/m2). Plasma enterolactone (ENL), the major biologically active metabolite of dietary lignans, was determined by time-resolved fluoroimmunoassay. Anthropometrics, abdominal adipose tissue areas (computed tomography), body composition (hydrostatic weighing) and insulin sensitivity (hyperinsulinaemic–euglycaemic clamp) were measured in all women. Women in the high dietary lignan intake subgroup (n 29) had a significantly lower BMI and total body fat mass, as well as a better glucose disposal rate (GDR; P < 0·05), compared with women in the low lignan intake subgroup (n 28). The majority of women with the highest dietary lignan intake were also in the highest quartile of plasma ENL (59 %). Women in the highest ENL quartile had a significantly lower BMI (26·1 (sd 4·4) v. 30·4 (sd 6·9) kg/m2, P < 0·05), total body fat mass (24·8 (sd 9·8) v. 33·3 (sd 13·3) kg, P < 0·05), 2 h postload glycaemia (5·5 (sd 0·9) v. 5·7 (sd 0·8) nmol/l, P < 0·05) and a higher GDR (8·3 (sd 2·7) v. 5·5 (sd 2·8), P < 0·01) compared with women in the lowest ENL quartile. In conclusion, women with the highest ENL concentrations had a better metabolic profile including higher insulin sensitivity and lower adiposity measures.

Downregulation of genes involved in NFkappaB activation in peripheral blood mononuclear cells after weight loss is associated with the improvement of insulin sensitivity in individuals with the metabolic syndrome: the GENOBIN study

AIMS/HYPOTHESIS

The transcription factor nuclear factor-kappa-B (NFkappaB) is implicated in inflammatory responses, obesity and the metabolic syndrome, while immune cells appear to play a central role in mediating insulin resistance and can be used as a model to study inflammation and its relationship with insulin resistance. In peripheral blood mononuclear cells of overweight participants with the metabolic syndrome, we evaluated (1) the effect of diet-induced weight loss on the expression of genes involved in NFkappaB activation and (2) their association with insulin sensitivity. The genes studied were: TNF receptors TNFRSF1A and TNFRSF1B, and IL1R1, TLR4, TLR2, ICAM1, CCL5 and IKBKB.

METHODS

We analysed data from 34 overweight participants with abnormal glucose metabolism and the metabolic syndrome, who were randomised to a weight-reduction (n = 24) or control group (n = 10) for 33 weeks. The mRNA expression was measured using real-time PCR. Measures of insulin and glucose homeostasis were assessed by IVGTT and OGTT.

RESULTS

In general, the genes studied were downregulated after weight loss intervention. The changes in TLR4, TLR2, CCL5 and TNFRSF1A mRNA expression were associated with an increase in insulin sensitivity index independently of the change in waist circumference (p < 0.05). The change in IKBKB expression correlated with most of the changes in gene expression in the weight-reduction group.

CONCLUSIONS/INTERPRETATION

These results suggest that proteins encoded by CCL5, TLR2 and TLR4, and TNFRSF1A might contribute to insulin-resistant states that characterise obesity and the metabolic syndrome.

TRIAL REGISTRATION

ClinicalTrials.gov NCT 00621205.

Effect of mixing dietary fibre (purified lignocellulose or purified pectin) and a corn meal on glucose and insulin responses in healthy horses

The aim of this study was to investigate the effect of the addition of a purified soluble (pectin) and insoluble (lignocellulose) fibre to a starchy meal on post-prandial glucose and insulin responses in healthy horses. Four horses were fed in a randomized order three different diets: (i) cracked corn, (ii) cracked corn mixed with purified lignocellulose, and (iii) cracked corn mixed with purified pectin. Each diet was adjusted to a starch intake of 2 g/kg bodyweight (BW). Lignocellulose was aligned to an intake of 0.2 g/kg BW, and pectin was fed in a dosage of 0.1 g/kg BW. Each period consisted of a 10-day acclimatization to the diet (fed once per day); during this time, the horses were fed 1.2 kg hay/100 kg BW/day. Blood was collected after each acclimatization period before and after the test meal was fed, without any hay. The increase in plasma glucose and insulin, peak values, and area under the curves were similar for all diets. The present findings suggest that adding purified soluble or insoluble fibre to a corn meal does not affect post-prandial glucose and insulin responses in healthy horses. Feeding strategies for horses with a high energy requirement should include a starch reduction per meal, rather than the addition of purified fibre.

Butyrate ingestion improves hepatic glycogen storage in the re-fed rat

Background

Butyrate naturally produced by intestinal fiber fermentation is the main nutrient for colonocytes, but the metabolic effect of the fraction reaching the liver is not totally known. After glycogen hepatic depletion in the 48-hour fasting rat, we monitored the effect of (butyrate 1.90 mg + glucose 14.0 mg)/g body weight versus isocaloric (glucose 18.2 mg/g) or isoglucidic (glucose 14.0 mg/g) control force-feeding on in vivo changes in hepatic glycogen and ATP contents evaluated ex vivo by NMR in the isolated and perfused liver.

Results

The change in glycogen was biphasic with (i) an initial linear period where presence of butyrate in the diet increased (P = 0.05) the net synthesis rate (0.20 ± 0.01 μmol/min.g^-1 liver wet weight, n = 15) versus glucose 14.0 mg/g only (0.16 ± 0.01 μmol/min.g^-1 liver ww, n = 14), and (ii) a plateau of glycogen store followed by a depletion. Butyrate delayed the establishment of the equilibrium between glycogenosynthetic and glycogenolytic fluxes from the 6^th to 8^th hour post-feeding. The maximal glycogen content was then 97.27 ± 10.59 μmol/g liver ww (n = 7) at the 8^th hour, which was significantly higher than with the isocaloric control diet (64.34 ± 8.49 μmol/g, n = 12, P = 0.03) and the isoglucidic control one (49.11 ± 6.35 μmol/g liver ww, n = 6, P = 0.003). After butyrate ingestion, ATP content increased from 0.95 ± 0.29 to a plateau of 2.14 ± 0.23 μmol/g liver ww at the 8^th hour post-feeding (n = 8) [P = 0.04 versus isoglucidic control diet (1.45 ± 0.19 μmol/g, n = 8) but was not different from the isocaloric control diet (1.70 ± 0.18 μmol/g, n = 12)].

Conclusion

The main hepatic effect of butyrate is a sparing effect on glycogen storage explained (i) by competition between butyrate and glucose oxidation, glucose being preferentially directed to glycogenosynthesis during the post-prandial state; and (ii) by a likely reduced glycogenolysis from the newly synthesized glycogen. This first demonstration of the improvement of liver glycogen storage by acute butyrate supply may be an important contribution to explaining the beneficial effects on glucose homeostasis of nutritional supply increasing butyrate amount such as fiber diets.

Glycine regulates the production of pro-inflammatory cytokines in lean and monosodium glutamate-obese mice

Fat tissue plays an important role in the regulation of inflammatory processes. Increased visceral fat has been associated with a higher production of cytokines that triggers a low-grade inflammatory response, which eventually may contribute to the development of insulin resistance. In the present study, we investigated whether glycine, an amino acid that represses the expression in vitro of pro-inflammatory cytokines in Kupffer and 3T3-L1 cells, can affect in vivo cytokine production in lean and monosodium glutamate-induced obese mice (MSG/Ob mice). Our data demonstrate that glycine treatment in lean mice suppressed TNF-alpha transcriptional expression in fat tissue, and serum protein levels of IL-6 were suppressed, while adiponectin levels were increased. In MSG/Ob mice, glycine suppressed TNF-alpha and IL-6 gene expression in fat tissue and significantly reduced protein levels of IL-6, resistin and leptin. To determine the role of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) in the modulation of this inflammatory response evoked by glycine, we examined its expression levels in fat tissue. Glycine clearly increased PPAR-gamma expression in lean mice but not in MSG/Ob mice. Finally, to identify alterations in glucose metabolism by glycine, we also examined insulin levels and other biochemical parameters during an oral glucose tolerance test. Glycine significantly reduced glucose tolerance and raised insulin levels in lean but not in obese mice. In conclusion, our findings suggest that glycine suppresses the pro-inflammatory cytokines production and increases adiponectin secretion in vivo through the activation of PPAR-gamma. Glycine might prevent insulin resistance and associated inflammatory diseases.

Immunomodulatory properties of two wheat bran fractions - aleurone-enriched and crude fractions - in obese mice fed a high fat diet

Several data suggest that fermentable dietary fibers could play a role in the control of obesity and associated metabolic disorders. In mice, dietary fructans, which are extensively fermented in caeco-colon by bifidobacteria, decrease fat mass development and modulate gastrointestinal peptides involved in the control of food intake (namely glucagon-like peptide (GLP)-1). The aim of this study was to compare the effect of two cereal bran fractions isolated from wheat - aleurone-enriched and crude fractions - in a nutritional model of obesity. In a first experiment, we confirmed that 2 weeks of treatment with a high fat (HF) diet is sufficient to exhibit glucose intolerance and to increase adiposity in mice. In the second experiment, mice were fed a HF or a HF diet enriched with 10% wheat bran fractions during 3 weeks. None of the wheat bran fractions modified body weight, adipose tissue mass, glucose or lipid homeostasis. Wheat bran fractions increased bifidobacteria and lactobacilli in the caecal content without any effect on caecal enlargement and on GLP-1 precursor expression in the colon. Furthermore, wheat bran fractions decreased circulating interleukin 6 (IL-6) and CD68 mRNA in the visceral adipose tissue, suggesting a decrease in recruited-tissue macrophages. We propose that specific and early immunomodulatory properties of cereal products with prebiotic properties, may occur in obese mice independently of extensive gut fermentation.

Metabolic effects of dietary fiber consumption and prevention of diabetes

A high dietary fiber (DF) intake is emphasized in the recommendations of most diabetes and nutritional associations. It is accepted that viscous and gel-forming properties of soluble DF inhibit macronutrient absorption, reduce postprandial glucose response, and beneficially influence certain blood lipids. Colonic fermentation of naturally available high fiber foods can also be mainly attributed to soluble DF, whereas no difference between soluble and insoluble DF consumption on the regulation of body weight has been observed. However, in prospective cohort studies, it is primarily insoluble cereal DF and whole grains, and not soluble DF, that is consistently associated with reduced diabetes risk, suggesting that further, unknown mechanisms are likely to be involved. Recent research indicates that DF consumption contributes to a number of unexpected metabolic effects independent from changes in body weight, which include improvement of insulin sensitivity, modulation of the secretion of certain gut hormones, and effects on various metabolic and inflammatory markers that are associated with the metabolic syndrome. In this review, we briefly summarize novel findings from recent interventions and prospective cohort studies. We discuss concepts and potential mechanisms that might contribute to the further understanding of the involved processes.