Potential prebiotic activity of oligosaccharides obtained by enzymatic conversion of durum wheat insoluble dietary fibre into soluble dietary fibre

Background and aims: Epidemiological evidence indicates that cereal dietary fibre (DF) may have several cardiovascular health benefits. The underlying mechanisms have not yet been elucidated. Here, the potential nutritional effects of physico-chemical. properties modifications of durum wheat dietary fibre (DWF) induced by enzyme treatment have been investigated. Methods and results: The conversion of the highly polymerised insoluble dietary fibre into soluble feruloyl oligosaccharides of DWF was achieved by a tailored enzymatic treatment. The in vitro fermentation and release of ferulic acid by intestinal microbiota from DWF before and after the enzymatic treatment were assessed using a gut model validated to mimic the human colonic microbial environment. Results demonstrated that, compared to DWF, the enzyme-treated DWF (ETD-WF) stimulated the growth of bifidobacteria and lactobacilli. Concurrently, the release of free ferulic acid by ET-DWF was almost three times higher respect to the control. No effect on the formation of short chain fatty acids was observed. Conclusions: The conversion of insoluble dietary fibre from cereals into soluble dietary fibre generated a gut microbial fermentation that supported bifidobacteria and lactobacilli. The concurrent increase in free ferulic acid from the enzyme-treated DWF might result in a higher plasma ferulic acid concentration which could be one of the reasons for the health benefits reported for dietary fibre in cardiovascular diseases. (c) 2008 Elsevier B.V. All rights reserved.

ApoE genotype, cardiovascular risk and responsiveness to dietary fat manipulation

Cardiovascular risk is determined by the complex interactions between genetic and environmental factors. The apoE genotype represents the most-widely-studied single nucleotide polymorphism in relation to CVD risk, with >3600 publications cited in PubMed. Although originally described as a mediator of lipoprotein metabolism, the lipoprotein-independent functions of apoE are being increasingly recognised, with limited data available on the potential impact of genotype on these metabolic processes. Furthermore, although meta-analyses suggest that apoE4 carriers may have a 40-50% increased CVD risk, the associations reported in individual studies are highly heterogeneous and it is recognised that environmental factors such as smoking status and dietary fat composition influence genotype-phenotype associations. However, information is often derived from observational studies or small intervention trials in which retrospective genotyping of the cohort results in small group sizes in the rarer E2 and E4 subgroups. Either larger well-standardised intervention trials or smaller trials with prospective recruitment according to apoE genotype are needed to fully establish the impact of diet on genotype-CVD associations and to establish the potential of dietary strategies such as reduced total fat, saturated fat, or increased antioxidant intakes to counteract the increased CVD burden in apoE4 carriers.

Lack of effect of dietary n-6 : n-3 PUFA ratio on plasma lipids and markers of insulin responses in Indian Asians living in the UK

Background: Indian Asians living in Western Countries have an over 50% increased risk of coronary heart disease (CHD) relative to their Caucasians counterparts. The atherogenic lipoprotein phenotype (ALP), which is more prevalent in this ethnic group, may in part explain the increased risk. A low dietary long chain n-3 fatty acid (LC n-3 PUFA) intake and a high dietary n-6 PUFA intake and n-6:n-3 PUFA ratio in Indian Asians have been proposed as contributors to the increased ALP incidence and CHD risk in this subgroup. Aim: To examine the impact of dietary n-6:n-3 PUFA ratio on membrane fatty acid composition, blood lipid levels and markers of insulin sensitivity in Indian Asians living in the UK. Methods: Twenty-nine males were assigned to either a moderate or high n-6:n-3 PUFA (9 or 16) diet for 6 weeks. Fasting blood samples were collected at baseline and 6 weeks for analysis of triglycerides, total-, LDL- and HDL- cholesterol, non-esterified fatty acids, glucose, insulin, markers of insulin sensitivity and C-reactive protein. Results: Group mean saturated fatty acid, MUFA, n-6 PUFA and n-3 PUFA on the moderate and high n-6:n-3 PUFA diets were 26 g/d, 43 g/d, 15 g/d, 2 g/d and 25 g/d, 25 g/d, 28 g/d, 2 g/d respectively. A significantly lower total membrane n-3 PUFA and a trend towards lower EPA and DHA levels were observed following the high n-6:n-3 PUFA diet. However no significant effect of treatment on plasma lipids was evident. There was a trend towards a loss of insulin sensitivity on the high n-6:n-3 PUFA diet, with the increase in fasting insulin (P = 0.04) and HOMA IR [(insulin x glucose)/22.5] (P = 0.02) reaching significance. Conclusion: The results of the current study suggest that, within the context of a western diet, it is unlikely that dietary n-6:n-3 PUFA ratio has any major impact on the levels of LC n-3 PUFA in membrane phospholipids or have any major clinically relevant impact on insulin sensitivity and its associated dyslipidaemia.

Dietary fat composition and cardiovascular disease

Cardiovascular disease (CVD), which includes coronary heart disease and stroke, remains the major killer in the EU, being responsible for 42% of total mortality. The amount and composition of dietary fat is arguably the most important dietary factor contributing to disease risk. A significant body of consistent evidence indicates that a decrease in dietary saturated fat:unsaturated (polyunsaturated + monounsaturated) ratio and an increased intake of long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) found in fish, is cardioprotective. Furthermore, although the evidence is currently less convincing, such a strategy is also likely to improve insulin sensitivity, the central metabolic defect in diabetes. Currently in the UK only 12% of men, 17% of women and 8% of children have an SFA intakes <10% of energy. The average intake of LC n-3 PUFA is <0.2 g/day, which is less than half the current conservative recommendation of a minimum of 0.45 g/day. Public health strategies to reverse these dietary fatty acid imbalances, aimed at educating and motivating the consumer and making affordable and acceptable food products with an ‘enhanced’ fatty acid profile more widely available, must remain a public health priority in the ‘fight’ against CVD.

Dietary glycated protein modulates the colonic microbiota towards a more detrimental composition in ulcerative colitis patients and non-ulcerative colitis subjects

Aim: To investigate the effect of native, heated and glycated bovine serum albumin (BSA) on the ulcerative colitis (UC) and non-UC colonic microbiota in vitro. Methods and Results: Continuous flow culture (CFC) models of the human colonic microbiota inoculated with faeces from UC and non-UC volunteers were maintained on BSA as growth substrate. Changes in bacterial populations and short-chain fatty acids were determined. UC and non-UC microbiota differed significantly in microbial populations, with elevated numbers of sulfate-reducing bacteria (SRB) and clostridia in the microbiota from UC patients. Compared with native BSA, glycated BSA modulated the gut microbiota of UC patients in vitro towards a more detrimental community structure with significant increases in putatively harmful bacteria (clostridia, bacteroides and SRB; P < 0.009) and decreases in dominant and putatively beneficial bacterial groups (eubacteria and bifidobacteria; P < 0.0004). The levels of beneficial short-chain fatty acids were significantly decreased by heated or glycated BSA, but were increased significantly by native BSA. Conclusion: The UC colonic microbiota maintained in CFC was significantly modified by glycated BSA. Significance and Impact of the Study: Results suggest that dietary glycated protein may impact upon the composition and activity of the colonic microbiota, an important environmental variable in UC.

Flavonoids and cognitive function: a review of human randomized controlled trial studies and recommendations for future studies

Evidence in support of the neuroprotective effects of flavonoids has increased significantly in recent years, although to date much of this evidence has emerged from animal rather than human studies. Nonetheless, with a view to making recommendations for future good practice, we review 15 existing human dietary intervention studies that have examined the effects of particular types of flavonoid on cognitive performance. The studies employed a total of 55 different cognitive tests covering a broad range of cognitive domains. Most studies incorporated at least one measure of executive function/working memory, with nine reporting significant improvements in performance as a function of flavonoid supplementation compared to a control group. However, some domains were overlooked completely (e.g. implicit memory, prospective memory), and for the most part there was little consistency in terms of the particular cognitive tests used making across study comparisons difficult. Furthermore, there was some confusion concerning what aspects of cognitive function particular tests were actually measuring. Overall, while initial results are encouraging, future studies need to pay careful attention when selecting cognitive measures, especially in terms of ensuring that tasks are actually sensitive enough to detect treatment effects.

Functional food, blood lipids and cardiovascular disease. Part 1: probiotics

For the past 20 years, the focuses of public health strategies for reducing the risk of cardiovascular disease (CVD) have been aimed at lowering cholesterol levels. However recent findings have highlighted not only cholesterol but also triacylglycerol as a lipid risk factor for CVD. Dietary strategies which are able to reduce these circulating lipid levels, but which are able to offer long-term efficacy comparable with effective drug treatments, are currently being sought. One dietary strategy that has been proposed to benefit the lipid profile involves the supplementation of the diet with probiotics (Part 1), prebiotics and synbiotics (Part 2), which are mechanisms to improve the health of the host by supplementation and/or fortification of certain health promoting gut bacteria. Probiotics in the form of fermented milk products have been shown to have cholesterol-lowering properties, whereas non-digestible fermentable prebiotics have been shown to reduce triacylglycerol levels in animal studies. However in humans studies, there have been inconsistent findings with respect to changes in lipid levels with both prebiotics and probiotics although on the whole there have been favourable outcomes.

Symposium on 'nutrition interventions in high-risk groups' - CVD risk in South Asians: the importance of defining adiposity and influence of dietary polyunsaturated fat

The prevalence of the metabolic syndrome (MetS), CVD and type 2 diabetes (T2D) is known to be higher in populations from the Indian subcontinent compared with the general UK population. While identification of this increased risk is crucial to allow for effective treatment, there is controversy over the applicability of diagnostic criteria, and particularly measures of adiposity in ethnic minorities. Diagnostic cut-offs for BMI and waist circumference have been largely derived from predominantly white Caucasian populations and, therefore, have been inappropriate and not transferable to Asian groups. Many Asian populations, particularly South Asians, have a higher total and central adiposity for a similar body weight compared with matched Caucasians and greater CVD risk associated with a lower BMI. Although the causes of CVD and T2D are multi-factorial, diet is thought to make a substantial contribution to the development of these diseases. Low dietary intakes and tissue levels of long-chain (LC) n-3 PUFA in South Asian populations have been linked to high-risk abnormalities in the MetS. Conversely, increasing the dietary intake of LC n-3 PUFA in South Asians has proved an effective strategy for correcting such abnormalities as dyslipidaemia in the MetS. Appropriate diagnostic criteria that include a modified definition of adiposity must be in place to facilitate the early detection and thus targeted treatment of increased risk in ethnic minorities.

Dietary, physiological, genetic and pathological influences on postprandial lipid metabolism

Most of diurnal time is spent in a postprandial state due to successive meal intakes during the day. As long as the meals contain enough fat, a transient increase in triacylglycerolaemia and a change in lipoprotein pattern occurs. The extent and kinetics of such postprandial changes are highly variable and are modulated by numerous factors. This review focuses on factors affecting postprandial lipoprotein metabolism and genes, their variability and their relationship with intermediate phenotypes and risk of CHD. Postprandial lipoprotein metabolism is modulated by background dietary pattern as well as meal composition (fat amount and type, carbohydrate, protein, fibre, alcohol) and several lifestyle conditions (physical activity, tobacco use), physiological factors (age, gender, menopausal status) and pathological conditions (obesity, insulin resistance, diabetes mellitus). The roles of many genes have been explored in order to establish the possible implications of their variability in lipid metabolism and CHD risk. The postprandial lipid response has been shown to be modified by polymorphisms within the genes for apo A-I, A-IV, AN, E, B, C-I and C-III, lipoprotein lipase, hepatic lipase, fatty acid binding and transport proteins, microsomal trigyceride transfer protein and scavenger receptor class B type I. Overall, the variability in postprandial response is important and complex, and the interactions between nutrients or dietary or meal compositions and gene variants need further investigation. The extent of present knowledge and needs for future studies are discussed in light of ongoing developments in nutrigenetics.

Vitamin E supplementation, cereal feed type and consumer sensory perceptions of poultry meat quality

Lipid oxidation leads to meat spoilage and has been reported to cause adverse changes in the flavour and texture of poultry meat. Vitamin E has been found to be effective in delaying lipid oxidation. The aim of this study was to determine whether the vitamin E supplementation of chicken feed influences the consumers' perception of the quality of chicken meat under normal display and storage conditions. Untrained consumers (n 32) evaluated cooked breast meat from chickens (both corn fed and wheat fed) supplemented with 75 250 or 500 mg/kg vitamin E and after storage at 4&DEG; C for 4 and 7 d. Factorial analysis found an interaction between vitamin E treatment and storage day upon the perceived juiciness (P = 0.023) and tenderness (P = 0.041) of the chicken meat. Perceptions of quality relative to vitamin E level were more evident on day 4 than day 7. When the two cereal types were compared, the time-related subgroup effects were observed only in meat from corn-fed chickens supplemented with either 75 or 250 mg/kg, which was perceived to be juicier (P = 0.018) and more tender (P = 0.020) than that supplemented at the 500 mg/kg level. These results imply that the two lower concentrations of vitamin E have some advantages over 500 mg/kg, but for optimal consumer acceptance of corn-fed chicken meat, we suggest that 250 mg/kg vitamin E should be added to corn-fed poultry feed. There was no evidence to suggest any advantages in changing the current amount of vitamin E (75 mg/kg) used to rear wheat-fed birds.

Functional food, blood lipids and cardiovascular disease. Part 2: prebiotics and synbiotics

For the past 20 years, the focuses of public health strategies for reducing the risk of cardiovascular disease (CVD) have been aimed at lowering cholesterol levels. However, recent findings have highlighted not only cholesterol but also triacylglycerol as a lipid risk factor for CVD. Dietary strategies which are able to reduce these Circulating lipid levels, but which are able to offer longterm efficacy comparable with effective drug treatments, are currently being sought. One dietary strategy that has been proposed to benefit the lipid profile involves the supplementation of the diet with probiotics (Part 1) prebiotics and synbiotics (Part 2), which are mechanisms to improve the health of the host by supplementation and/or fortification of certain health promoting gut bacteria. Probiotics in the form of fermented milk products have been shown to have cholesterol-lowering properties, whereas non-digestible fermentable prebiotics have been shown to reduce triacylglycerol levels in animal studies, However, in human studies, there have been inconsistent findings with respect to changes in lipid levels with both prebiotics and probiotics although on the whole there have been favourable outcomes.

Apolipoprotein E genotype and alpha-tocopherol modulate amyloid precursor protein metabolism and cell cycle regulation

Apolipoprotein E4 (apoE4) genotype is associated with an increased risk for Alzheimer's disease (AD). This is thought to be in part attributable to an impact of apoE genotype on the processing of the transmembrane amyloid precursor protein (APP) thereby contributing to amyloid beta peptide formation in apoE4 carriers, which is a primary patho-physiological feature of AD. As apoE and alphato-copherol (alpha-toc) have been shown to modulate membrane bilayer properties and hippocampal gene expression, we studied the effect of apoE genotype on APP metabolism and cell cycle regulation in response to dietary a-toc. ApoE3 and apoE4 transgenic mice were fed a diet low (VE) or high (+VE) in vitamin E (3 and 235 mg alpha-toe/kg diet, respectively) for 12 weeks. Cholesterol levels and membrane fluidity were not different in synaptosomal plasma membranes isolated from brains of apoE3 and apoE4 mice (-VE and +VE). Non-amyloidogenic alpha-secretase mRNA concentration and activity were significantly higher in brains of apoE3 relative to apoE4 mice irrespective of the dietary a-toe supply, while amyloidogenic beta-secretase and gamma-secretase remained unchanged. Relative mRNA concentration of cell cycle related proteins were modulated differentially by dietary a-toc supplementation in apoE3 and apoE4 mice, suggesting genotype-dependent signalling effects on cell cycle regulation.

Ingestion of quercetin inhibits platelet aggregation and essential components of the collagen-stimulated platelet activation pathway in humans

Background: Quercetin, a flavonoid present in the human diet, which is found in high levels in onions, apples, tea and wine, has been shown previously to inhibit platelet aggregation and signaling in vitro. Consequently, it has been proposed that quercetin may contribute to the protective effects against cardiovascular disease of a diet rich in fruit and vegetables. Objectives: A pilot human dietary intervention study was designed to investigate the relationship between the ingestion of dietary quercetin and platelet function. Methods: Human subjects ingested either 150 mg or 300 mg quercetin-4'-O-beta-D-glucoside Supplement to determine the systemic availability of quercetin. Platelets were isolated from subjects to analyse collagen-stimulated cell signaling and aggregation. Results: Plasma quercetin concentrations peaked at 4.66 mum (+/-0.77) and 9.72mum (+/-1.38) 30min after ingestion of 150-mg and 300-mg doses of quercefin-4'-O-beta-D-glucoside, respectively, demonstrating that quercetin was bioavailable, with plasma concentrations attained in the range known to affect platelet function in vitro. Platelet aggregation was inhibited 30 and 120 min after ingestion of both doses of quercetin-4'-O-beta-D-glucoside. Correspondingly, collagen-stimulated tyrosine phosphorylation of total platelet proteins was inhibited. This was accorripanied by reduced tyrosine phosphorylation of the tyrosine kinase Syk and phospholipase Cgamma2, components of the platelet glycoprotein VI collagen receptor signaling pathway. Conclusions: This study provides new evidence of the relatively high systemic availability of quercetin in the form of quercetin-4'-O-beta-D-glucoside by supplementation, and implicates quercetin as a dietary inhibitor of platelet cell signaling and thrombus formation.