John Van Camp

Bioavailability of angiotensin I converting enzyme inhibitory peptides

Hypertension or high blood pressure is a significant health problem worldwide. Bioactive peptides that inhibit angiotensin I converting enzyme (ACE) in the cardiovascular system can contribute to the prevention and treatment of hypertension. These ACE inhibitory peptides are derived from many food proteins, especially milk proteins. An ACE inhibitory activity in vitro does not always imply an antihypertensive effect in vivo. Even if it does, it is very difficult to establish a direct relationship between in vitro and in vivo activity. This is mainly due to the bioavailability of the ACE inhibitory peptides after oral administration and the fact that peptides may influence blood pressure by mechanisms other than ACE inhibition. To exert an antihypertensive effect after oral ingestion, ACE inhibitory peptides have to reach the cardiovascular system in an active form. Therefore, they need to remain active during digestion by human proteases and be transported through the intestinal wall into the blood. The bioavailability of some ACE inhibitory peptides has been studied. It is also known that (hydroxy)proline-containing peptides are generally resistant to degradation by digestive enzymes. Peptides can be absorbed intact through the intestine by paracellular and transcellular routes, but the potency of the bioactivity after absorption is inversely correlated to chain length. In addition, some strategies are proposed to increase the bioavailability of ACE inhibitory peptides. Further research into the bioavailability of ACE inhibitory peptides will lead to the development of more effective ACE inhibitory peptides and foods.

Optimisation and validation of an angiotensin-converting enzyme inhibition assay for the screening of bioactive peptides

Angiotensin-converting enzyme (ACE) plays a major role in the regulation of blood pressure. A diagnostic assay to measure angiotensin-converting enzyme (ACE) activity was transformed into an enzyme inhibition assay and optimised, which led to a more sensitive and less expensive assay. By this spectrophotometric method, ACE inhibition is measured using the substrate furanacryloyl-Phe-Gly-Gly and as ACE source rabbit lung acetone extract. The optimised as well as the original ACE inhibition assay were used to verify the ACE inhibitory activity of captopril. The ACE inhibition assay was further validated by enalapril, its active derivative enalaprilat and the ACE-inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg, corresponding to a tryptic fragment of bovine beta-lactoglobulin. Sigmoid curves could be fit adequately to the data points representing ACE inhibition in function of inhibitor concentration. IC(50) values for these compounds corresponded well with literature data. Furthermore, pea and whey protein hydrolysates obtained by digestion with trypsin showed ACE inhibitory activity in the ACE inhibition assay. Hence, this optimised assay is suitable to screen for ACE inhibitory peptides derived from food proteins with a possible antihypertensive effect in vivo.

Consumer perception versus scientific evidence about health benefits and safety risks from fish consumption.

OBJECTIVE To investigate the gap between consumer perception and scientific evidence related to health benefits and safety risks from fish consumption. DESIGN Consumer perceptions from a cross-sectional survey in March 2003 in Belgium were compared with scientific evidence based on a literature review. METHOD A quota sampling procedure was used with age as quota control variable. Subjects completed a self-administered questionnaire including health benefit beliefs from fish, fish content and effect beliefs for nutrients and harmful substances. SUBJECTS Adults (n=429), who were the main person responsible for food purchasing in the household (284 women; 145 men), aged 18-83 years, from different regional, education, family size and income groups. RESULTS Fish is predominantly perceived as a healthy food that reduces risk for coronary heart disease, which corroborates scientific evidence. This perception is stronger among women than among men. In contrast with scientific evidence, 46% of the consumers believe that fish contains dietary fibre, whereas less than one-third is aware that fish contains omega-3 fatty acids and that this nutrient has a positive impact on human health. The gap between perception and evidence is larger among consumers with lower education. In general, consumers are better aware of the content and effect of harmful substances than of nutrients in fish. CONCLUSIONS Despite conclusive evidence about the content and positive effect of omega-3 fatty acids in fish, related consumer awareness and beliefs are poor and often wrong. This study exemplifies the need for nutrition education and more effective communication about the health benefits of fish consumption.

Total and individual carotenoids and phenolic acids content in fresh, refrigerated and processed spinach (Spinacia oleracea L.).

The carotenoid and phenolic acid contents in fresh, stored and processed (blanched, frozen and boiled) spinach were comparatively determined by spectrophotometric and HPLC analyses. The major carotenoids identified after HPLC analysis in saponified samples were lutein (37-53μg/kg), β-carotene (18-31μg/kg), violaxanthin (9-23μg/kg) and neoxanthin (10-22μg/kg). These carotenoids were all affected by storage and/or heating. The content of carotenoids was best preserved after storage for one day at 4°C. The total phenolic content in the fresh spinach was 2088mg GAE/kg FW. After LC-MS analysis three phenolic acids were identified and quantified. These being ortho-coumaric acid (28-60mg/kg FW), ferulic acid (10-35mg/kg) and para-coumaric acid (1-30mg/kg) depending on the sample type. After storage of spinach at different temperatures (4°C or -18°C) the amount of total phenolic compounds decreased by around 20%, while the amount of individual phenolic acids increased by four times on average.

Dietary intakes and food sources of fatty acids for Belgian women, focused on n-6 and n-3 polyunsaturated fatty acids.

The intake of fat, saturated and monounsaturated FA (SFA and MUFA), and omega-6 and omega-3 PUFA has been estimated in 641 Belgian women (age 18-39 y). Their food intake was recorded using a 2-d food diary. The PUFA included were linoleic (LA), alpha-linolenic (LNA), arachidonic (AA), eicosapentaeonoic (EPA), docosapentaenoic (DPA) and docosahexaenoic (DHA) acids. The mean total fat intake corresponded to 34.3% of total energy intake (E). The mean intake of the FA groups corresponded to 13.7%, 13.1%, and 6.0% of E, for SFA, MUFA, and PUFA, respectively. The mean intake of LA was 5.3% of E and of LNA was 0.6% of E, with a mean LA/LNA ratio of 8.7. The mean intake of AA was 0.03% of E. The mean intake of EPA, DPA, and DHA was 0.4%, 0.01%, and 0.06% of E, respectively. According to the Belgian recommendations, the total fat and SFA intake was too high for about three-quarters of the population. The mean LA and overall n-6 PUFA intake corresponded with the recommendation, with part of the population exceeding the upper level. Conversely, the population showed a large deficit for LNA and n-3 PUFA. The major food source for LA and LNA was fats and oils, followed by cereal products. The main sources of long-chain PUFA were fish and seafood, and meat, poultry, and eggs. From a public health perspective, it seems desirable to tackle the problem of low n-3 PUFA intake.

Perceived Importance of Sustainability and Ethics Related to Fish: A Consumer Behavior Perspective

Abstract Although sustainability and ethics are of increasing public importance, little research has been conducted to reveal its association with fish consumer behavior. Cross-sectional data were collected through a postal self-administered survey (June 2005) from a sample of 381 Flemish women aged 20–50 years. Consumers attach high perceived importance to sustainability and ethics related to fish. However, this perceived importance is neither correlated with fish consumption frequency nor with general attitude toward eating fish. Refusing to eat wild fish is grounded in sustainability and ethical concerns, whereas the decision not to eat farmed fish is associated with a lower expected intrinsic quality rather than shaped by importance attached to sustainability and ethical issues.

Influence of the lactokinin Ala-Leu-Pro-Met-His-Ile-Arg (ALPMHIR) on the release of endothelin-1 by endothelial cells.

Milk protein-derived peptides with angiotensin-converting enzyme (ACE) inhibitory activity can reduce blood pressure in hypertensive subjects. The lactokinin Ala-Leu-Pro-Met-His-Ile-Arg (ALPMHIR) is an ACE-inhibitory peptide released by tryptic digestion from the milk protein beta-lactoglobulin. Its ACE-inhibitory activity is 100 times lower than that of captopril. The latter is known to inhibit the release of the vasoconstrictor endothelin-1 (ET-1) by endothelial cells. The effects of ALPMHIR on the endothelium are currently unknown. In this study, the influence of ALPMHIR on release of ET-1 by endothelial cells was investigated. The basal ET-1 release of the cells was reduced by 29% (p<0.01) in the presence of 1 mM ALPMHIR, compared to 42% (p<0.01) for 0.1 mM captopril. Addition of 10 U/ml thrombin to the incubation medium increased the release of ET-1 by 66% (p<0.01). Co-incubation of 10 U/ml thrombin with 1 microM captopril or with 0.1 mM ALPMHIR inhibited the stimulated ET-1 release by 45% (p<0.01) and by 32% (p<0.01), respectively. These data indicate that dietary peptides, such as ALPMHIR, can modulate ET-1 release by endothelial cells. These effects, among other mechanisms, may play a role in the anti-hypertensive effect of milk protein-derived peptides.

The nutritional and toxicological value of organic vegetables: Consumer perception versus scientific evidence

Purpose – The present study aims to explore and compare consumer perception and scientific evidence related to food quality and food safety aspects of organic versus conventional vegetables. Design/methodology/approach – Primary data on consumer perception were gathered in 2006‐2007 through a consumer survey with Flemish adults (n=529) and compared with scientific evidence from literature. Consumers of organic and conventional vegetables were selected by means of a convenience sampling procedure. Subjects were asked to complete a self‐administered questionnaire concerning the perception of the nutritional and toxicological value of organic relative to conventional vegetables. Data processing and analysis included descriptive analysis (frequency distributions), data reduction (Cronbachs alpha test, factor analysis), bivariate analysis (correlations, t‐test, ANOVA) and multivariate analysis (stepwise multiple regression). Findings – It was found that organic vegetables are perceived as containing less contaminants and more nutrients, and as such, being healthier and safer compared to conventional vegetables. However, not enough evidence is currently available in the literature to support or refute such a perception, indicating a certain mismatch between consumer perception and scientific evidence. The gap between perception and evidence is larger among older consumers with children. The perception is stronger when the consumption frequency is higher, but is independent of gender, place of residence (rural or urban), education and income level. Also non‐users, on average, perceive that organic vegetables have a nutritional and toxicological advantage over conventional vegetables. Research limitations/implications – A non‐probability convenience sampling method was applied which limits generalisation of the findings beyond the sample characteristics. Originality/value – This paper is original in comparing consumer perception and scientific facts related to both nutritional and safety aspects of organic versus conventional vegetables.Purpose – Sustainable agriculture implies the ability of agro‐ecosystems to remain productive in the long‐term. It is not easy to point out unambiguously whether or not current production systems meet this sustainability demand. A priori thinking would suggest that organic crops are environmentally favourable, but may ignore the effect of reduced productivity, which shifts the potential impact to other parts of the food provision system. The purpose of this paper is to assess the ecological sustainability of conventional and organic leek production by means of life cycle assessment (LCA).Design/methodology/approach – A cradle‐to‐farm gate LCA is applied, based on real farm data from two research centres. For a consistent comparison, two functional units (FU) were defined: 1ha and 1 kg of leek production.Findings – Assessed on an area basis, organic farming shows a more favourable environmental profile. These overall benefits are strongly reduced when the lower yields are taken into account. Related to org...

Angiotensin-Converting Enzyme Inhibitory Effects by Plant Phenolic Compounds: A Study of Structure Activity Relationships

In this study, 22 phenolic compounds were investigated to inhibit the angiotensin-converting enzyme (ACE). Tannic acid showed the highest activity (IC50 = 230 μM). The IC50 values obtained for phenolic acids and flavonoids ranged between 0.41 and 9.3 mM. QSAR analysis confirmed that the numbers of hydroxyl groups on the benzene ring play an important role for activity of phenolic compounds and that substitution of hydroxyl groups by methoxy groups decreased activity. Docking studies indicated that phenolic acids and flavonoids inhibit ACE via interaction with the zinc ion and this interaction is stabilized by other interactions with amino acids in the active site. Other compounds, such as resveratrol and pyrogallol, may inhibit ACE via interactions with amino acids at the active site, thereby blocking the catalytic activity of ACE. These structure-function relationships are useful for designing new ACE inhibitors and potential blood-pressure-lowering compounds based on phenolic compounds.

The nutritional and toxicological value of organic vegetables

Purpose – The present study aims to explore and compare consumer perception and scientific evidence related to food quality and food safety aspects of organic versus conventional vegetables.Design/methodology/approach – Primary data on consumer perception were gathered in 2006‐2007 through a consumer survey with Flemish adults (n=529) and compared with scientific evidence from literature. Consumers of organic and conventional vegetables were selected by means of a convenience sampling procedure. Subjects were asked to complete a self‐administered questionnaire concerning the perception of the nutritional and toxicological value of organic relative to conventional vegetables. Data processing and analysis included descriptive analysis (frequency distributions), data reduction (Cronbachs alpha test, factor analysis), bivariate analysis (correlations, t‐test, ANOVA) and multivariate analysis (stepwise multiple regression).Findings – It was found that organic vegetables are perceived as containing less contam...