Honey propolis ingredient may protect cyclists against heat stress
A recent study by scientists from Taiwan and published in the Journal of Food Science
suggests that caffeic acid phenetheyl ester (CAPE), an active ingredient of honey propolis, may protect blood cells of athletes, such as cyclists, against heat stress.
Aerobic and endurance exercise such as cycling can cause an increase in core body temperature as well as greatly increasing production in the body of reactive oxygen species such as the superoxide anion, hydrogen peroxide and hydroxyl radicals. Heat stress is known to reduce endurance capacity. Hyperthermia (muscle temperatures up to 45oC and core body temperature up to 44oC) and the generation of free radicals can lead to physical damage induced by exercise.
Honey bee propolis has long been used as an alternative medicine and previous studies have shown that an active ingredient of propolis, CAPE, shows a wide range of biological properties including antioxidant effects, antiviral action, prevention of reperfusion injury and anti-cancer effects. Given these properties, Chen et al sought to investigate whether an antioxidant could reduce or prevent the generation of free radicals induced by hyperthermia, and if CAPE could prevent hyperthermia-induced damage.
Thirty male competitive cyclists were recruited, all of whom had undergone endurance training for between 2 and 4 years prior to the study but had not taken part in any competitions or intensive training in the four months immediately before the study. Subjects rested quietly for 30 minutes and blood samples were taken. Mononuclear cells (MNCs) from the blood of each subject were separated and divided into five groups. Group A, the control group was incubated at 37oC for 1 hr. Group B was incubated at 37oC for 30 minutes followed by 1 hr at 43oC. Group C was incubated with 1 µg/ml CAPE for 30 minutes at 37oC and 1hr at 43oC. Groups D and E were handled as for group C but with 2 µg/ml and 4 µg/ml CAPE respectively. Following treatment cells were incubated at 37oC until analysis.
The number of cultured viable MNCs in each group was counted 24hrs after treatment. A surviving fraction of MNC was calculated by dividing the number of viable cells in the group by the number of viable cells in the control group after this period. The percentages of dead monocytes and lymphocytes were calculated for each group. Levels of intracellular glutathione (GSH) and superoxide anions were assessed and measured.
The surviving fraction of MNC after 24 hrs in group B (hyperthermia alone) and group E (hyperthermia and higher dose CAPE) were 72.5% and 97.8% respectively. Chen et al claim this shows the protective effect of CAPE on hyperthermia-induced cell death. They also note the effect shows a dose dependent pattern. They further state that the percentage of dead monocytes and lymphocytes were much higher in group B than group A but not in the CAPE treated groups. It was also demonstrated that CAPE inhibited the over-production of superoxide caused by hyperthermia and that this, again, showed a dose dependency. The increase in the levels of intracellular superoxide was also reversed in a dose dependent manner by CAPE. Finally, intracellular GSH levels in cells in group B were decreased compared to group A. Pre-treatment with CAPE reversed this decrease but only in lymphocytes.
In conclusion Chen and his co-workers suggest their findings show CAPE offers effective protection against hyperthermia-induced oxidative stress and injury in MNC from cyclists. They suggest that this effect may be the result of the antioxidant activity of CAPE. They state that they discovered that hyperthermia not only increased the production of superoxide but also decreased intercellular GSH. They found that CAPE was able to return this unbalanced state to nearly normal and rescued MNC from hyperthermia-induced cell death. Whilst they note that this implies CAPE may be preventing immunosuppression, they believe that the protective effect of CAPE against hyperthermia stress needs further investigation.
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Nut consumption may lower CVD risk in diabetic women
A cohort study published in the Journal of Nutrition has evaluated the relationship between nuts and peanut butter consumption and cardiovascular disease (CVD), including coronary heart disease (CHD) and stroke amongst a group of women with type 2 diabetes.
Although nuts are high in fat and calories, previous studies have found that a high consumption has been associated with a reduced risk of CVD. Macronutrients and micronutrients contained in nuts have been found to provide health benefits. Peanuts are proportionally low in saturated fat and high in mono- and polyunsaturated fats which have been shown to improve the blood lipid profile by lowering LDL cholesterol. This study by Li et al from the Harvard Medical School and Harvard School of Public Heath also examined plasma lipids or markers of inflammation to see if nuts influenced the risk of CVD.
The participants of this study were women who were also members of the Nurses’ Health Study. This was carried out from 1980 to 2002 and participants were 6309 women, all with type 2 diabetes. 1171 of these participants also provided blood samples. Participants reported their average frequency of consuming selected foods at commonly used portion sizes including nuts and peanut butter (portion size 28g/1oz and 16g/1 tablespoon respectively) and using a questionnaire starting in 1980 and subsequently every two years. Women were classified into four exposure groups depending on their frequency of nuts and peanut butter consumption, namely almost never, 1-3 serving/month to less than 1 serving a week, 1-4 servings a week and at least five servings a week. Nutrient intake was calculated using consumption frequency and specified portion size. Cardiovascular endpoints, including fatal CHD, non fatal myocardial infarction (MI), stroke and coronary bypass surgery were recorded and where blood samples were provided these were analysed for variety compounds including total cholesterol, triacylglycerols and plasma lipid. Participants also completed a questionnaire every two years assessing a variety of factors including physical activity, smoking, alcohol consumption, menopausal status, duration of diabetes, and hypertension.
Li et al reported 634 cases of CVD endpoints between 1980 and 2002. They discovered that women who, at baseline, consumed more nuts and peanut butter tended to be leaner, more physically active and to smoke less. They reported that these women were less hypertensive and had a slightly longer duration of diabetes. Women in the highest consumption group had higher total energy, polyunsaturated fat, red meat, fruit and vegetable intakes as well as a significantly lower glycaemic load than those in the other groups. The researchers discovered that frequent nut and peanut butter consumption was inversely associated with total CVD risk (after adjustments for age). This association was found to be stronger amongst vegetarians who had higher nut consumption than non vegetarians. Those women in the highest consumption group had a CVD and MI risk lower by 44% than those in the “almost never” group but no significant linear trend across increasing consumption was found. Li et al also found those women in the highest consumption group had significantly lower LDL cholesterol, non-HDL cholesterol and total cholesterol concentrations than those in other groups. No association between HDL cholesterol and nut and peanut butter consumption was found, nor did consumption appear to be associated with those inflammatory markers measured in the blood.
Li et al note that their results agree with and extend previous studies by showing that frequent nut consumption is beneficial for women with diabetes who are at increased risk of CVD. The authors of the study note that as well as improvements in blood lipid levels there are other possible mechanisms by which nut and peanut butter consumption may provide a cardio-protective effect. These include decreased lipoprotein oxidation, inhibition of inflammation, decreasing insulin resistance and improving endothelial function. The authors conclude that although their study has several limitations including possible misreporting of consumption by participants, they say that they would expect this to bias the result toward a null effect. They believe it has many strengths including a large sample size and long duration of follow up. They indicate that their data supports a role for the regular consumption of nuts for patients with diabetes to reduce the risk of CVD.
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New shrimp allergen identified
In the United States shellfish are one of the main causes of food allergy, yet despite the frequency and severity of allergic reactions few options are available for treatment, and avoidance is the only therapy. For this reason it is necessary to develop better diagnostic and therapeutic options for shellfish allergy. With this in mind, a team based at the Mount Sinai School of Medicine in New York, have focussed on the characterisation and production of new recombinant shrimp allergens for use as diagnostic and immunotherapeutic agents.
In their introduction, Rosalia Ayuso and her colleagues explain that shellfish allergy is a long-lasting and potentially life-threatening disorder which is said to affect as many as 1 in 50 Americans. Although the black tiger shrimp (Panaeus monodon) is the most widely cultured prawn species in the world, the Pacific white shrimp (Litopenaeus vannamei, also in fact a prawn) is the species of choice in the Western hemisphere. These two species account for 80% of all farmed shrimp.
Until recently the allergenic reactivity of shrimp had been attributed to the protein tropomyosin. However, in 2008, Ayuso et al. found that myosin light chain (MLC), Lit v 3, was also allergenic, especially in children. (JACI, 2008, 122: 795-802). But although the IgE recognition of MLC in boiled shrimp extract was very intense, the recombinant protein was recognised significantly less strongly. This led the authors to speculate as to whether another IgE-binding protein of a similar molecular weight might be present.
Sera from fifty two subjects with shrimp allergy (23 children and 29 adults) were used for the current study. They had exhibited immediate allergic reactions after ingestion of shrimp and had elevated levels of serum IgE to shrimp. Extracts were prepared from raw and boiled tail muscle of Pacific white shrimp. Proteins from the extracts were separated by SDS-PAGE and protein identification performed from 1- and 2-dimensional gels stained with Simply Blue SafeStain. Proteins of interest were excised and subjected to tryptic digestion. Immunoblots for detection of IgE binding were performed with the raw and boiled shrimp extracts. Membranes were incubated with the sera from the shrimp-allergic subjects. This demonstrated IgE binding by 31 of the 52 sera to a 20-kd shrimp protein. Tryptic digests from this 20-kd IgE-binding protein were analysed by LC-MS/MS and showed it to be a sarcoplasmic calcium-binding protein (SCP). DNA encoding for this protein was obtained from a shrimp DNA library, amplified by PCR and cloned into an expression vector (E. coli). The recombinant SCP produced in this way was tested against the allergic subjects’ sera.
Results showed that the recombinant SCP was recognised by serum IgE from 20 of the 52 subjects, 17 of whom were children. Mediator release (measured as beta-hexosaminidase in rat basophilic leukaemia cells) in a few subjects, induced by recombinant SCP, was shown to be higher than that induced by recombinant tropomyosin. So in conclusion the authors claim to have identified and cloned a new shrimp allergen, Lit v 4.0101, a sarcoplasmic calcium-binding protein, which appeared to be of particular importance in children with this type of allergy.
RSSL’s DNA and Protein Laboratory carries out allergen testing using immunological, DNA and distillation techniques, depending on the allergen to be detected. Detection limits are in the range 0.1 – 10 mg allergen/kg of sample for almond, Brazil nut, macadamia nut, peanut, walnut, hazelnut, cashew nut, pistachio nut, pecan nut, pine nut and chestnut. Celery, celeriac, black mustard, lupin and kiwi allergens can also be detected by DNA methods, as can crustacean allergens. The laboratory also uses a range of UKAS accredited immunological procedures for the detection of allergens including gluten, peanut, hazelnut, almonds, soya, egg, milk, lactose, sesame and histamine. Distillation and titration methods are used for the determination of sulphur dioxide and sulphites. For more information please contact Customer Services on Freefone 0800 243482 or e-mail enquiries@rssl.com.
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Pesticides Residues Monitoring fourth quarter of 2008
The UK’s Pesticides Residues Committee (PRC) has just published two new reports. One records the results of its pesticides monitoring programme for the final quarter of 2008. The other gives details of the pesticide residues found in produce supplied under the Government’s School Fruit & Vegetable Scheme (SFVS).
The PRC’s fourth quarterly report for 2008 (232 pages) covered 1518 samples of 28 different foods. These were apples, beans in pods, bread, carrots, celery, chillies, Chinese cabbage, cooking oils, courgettes, cucumber, duck, grapes, infant food, lettuce, melon, milk, nuts, oily fish, oranges, parsnip, pears, peppers, potatoes, prawns, sausages, spinach, tomato products and yams. The results showed that only 33 samples contained residues above the maximum permitted levels, including yams, apples, chilli peppers, cucumbers, beans in pods and grapes. It is pointed out that some of the samples analysed for this report were collected after 1 September 2008, a date on which new EU legislation came into force in the form of Regulation 396/2005/EC, with further details of maximum residue levels (MRLs) contained in Regulation 149/2008, Annexes II, III and IV (398 pages). This legislation recognises that produce treated before this date is not subject to the new MRLs, and the PRC has indicated that the MRLs in place before 1 September 2008 would apply to produce sampled throughout 2008.
In 2007 the maximum number of pesticides that were looked for in the survey was 200, with a reporting limit of 0.02 mg/kg. For the 2008 survey, the range of pesticides looked for has been expended to 240 and the reporting limit reduced in most cases to 0.01 mg/kg.
Monitoring carried out by the PRC has also confirmed that fresh produce supplied to schoolchildren as part of the School Fruit & Vegetable Scheme (SFVS) is consistently safe to eat. Results from the latest testing programme for the Autumn Term in 2008 indicated that all samples either contained no detectable residues or residues below the maximum residue level (MRL). (More comments at FreshInfo.com (30/06/09).
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Starvation diet lengthens life span
Food e-News has reported on several occasions on research which shows that caloric restriction can increase lifespan in a number of species. The latest work carried out at the Salk Institute in California, US on the roundworm (Caenorhabditis elegans) has identified a pivotal role for two enzymes which work together. The enzymes are referred to as WWP-1 (a ubiquitin ligase) and UBC-18 (a ubiquitin conjugating enzyme).
Although health factors such as obesity influence life expectancy, genetic factors are also central to the ageing process. So far three genetic networks are known to be involved in extending youthfulness. These involve insulin/insulin growth factor-1 (a regulator of metabolism and growth), the mitochondria (the energy generating part of the cell), and dietary restriction. Although it may seem some evolutionary distance from a roundworm to a human, scientists have found that the WWP-1 pathway is highly conserved between worms and mammals. When Andrea Carrano began her investigations she found that humans had three copies of WWP-1 which would make it difficult to study. Since C. elegans contains only one copy, Carrano began to work with Professor Andrew Dillon at Salk, who was already working on the ageing process using C. elegans.
In an article in Nature.com (24/06/09) Andrea Carrano, Andrew Dillon and their colleagues describe how they found that HECT (homologous to E6AP carboxy terminus) E3 ubiquitin ligase WWP-1 was a positive regulator of lifespan in C.elegans in response to dietary restriction. The over-expression of WWP-1 in the worms extended their lifespan by up to 20% under conditions of ad libitum feeding. However in worms manipulated to over-express WWP-1 lacking in catalytic activity, the lifespan extending characteristic was lost, proving the central role of the ubiquitin ligase in longevity. The Salk research also indicated that UBC-18, a ubiquitin conjugating enzyme was also essential for diet-restriction-induced longevity. Over-expression of UBC-18 alone was not sufficient to extend the worm’s lifespan, but depleting it appeared to negate the effects of caloric restriction. Ubiquitin ligases work in tandem with ubiquitin conjugating enzymes to attach a chain of ubiquitin molecules to other proteins. This usually tags the proteins ready for destruction, although it can also act as a regulatory signal.
Commenting on the research, Professor Dillon said that elucidating the role of these two enzymes brings scientists closer to understanding the receptor that receives the signal for throwing the cellular switch to promote a longer lifespan. Identifying this receptor might mean that drugs could be designed to mimic that signal and lead to new treatments for age-related diseases. (Summary in Eurekalert.org 24/06/09).
An outline of the cell’s ubquitin system is given in Nature, with further links to scientific articles giving further information. Also a review entitled “Aging and survival: the genetics of life span extension by dietary restriction “ by Mair and Dillin appeared in the Annual Reviews of Biochemistry, 2008, 77: 727-754.
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Sweetness perception could vary with ethnicity
Research conducted by three different groups and published in the Current Biology charts the discovery of a particular gene variant that could affect sweetness perception among different ethnic groups, raising the possibility of more targeted flavour profiling of foods. Europeans are among the most sugar-sensitive people in the world, the analysis concludes.
The study, conducted by a team led by Dennis Drayna at the National Institute on Deafness and Other Communication Disorders presented a group of 144 people (92 European, 37 Asian and 15 African) with nine solutions containing varying amounts of table sugar (sucrose) in amounts varying from 0 to 4 per cent (4 per cent being intensely sweet). The solutions were arranged by the volunteers in order of their perceived sweetness numerous times, and from these, the researchers calculated a sucrose sensitivity score for each person. They saw differences of up to 16 per cent. This data was then set against a wider analysis of the worldwide sweetness taste receptor genes. Human sweet taste perception is mediated by the heterodimeric G protein-coupled receptor encoded by the TAS1R2 and TAS1R3 genes. The results of the study show that the vast majority of people in the UK, France, Italy and Russia have a tandem of genetic variations in a sugar-sensing gene that allows them to detect trace levels of sweetness. Around the world, populations that live at northern latitudes carry these genetic variations at far higher frequencies than tropical-living people.
Although the gene variants were most common in Europeans, they were also widespread in Japanese, Palestinian, Han Chinese and other Middle Eastern and Asian populations. Low-sensitivity variations were most prevalent among the several different African populations that the team examined. But since other great apes appear to have the low sensitivity version, the changes probably occurred sometime after the common ancestor of humans and chimpanzees split, roughly six million years ago. One explanation for the variation in sensitivity observed could have been a dearth of sweet fruits and vegetables beyond the tropics. This might have favoured increased sugar sensitivity to help find energy rich carbohydrates in local food plants.
The researchers hope that the study will be used to help inform discussion of behavioural differences and their role in the global obesity epidemic. It is suggested that if people are more taste-sensitive to carbohydrates, their gut could also be more sensitive to carbohydrates. It is posited that the existing differences could be based on evolutionary changes. It is hypothesized that the ability to taste sugars at lower concentrations was one of the critical factors for human survival in cold geographical regions. As a result, evolutionary pressure led to high sweet sensitivity gene variants becoming more prevalent in non-tropical regions. The results of this research will be of interest for food and beverage manufacturers in creating more geographically targeted marketing. (Fushan et al. Current Biology, article in press, doi:10.1016/j.cub.2009.06.015. Summary in New Scientist 27/06/09).
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Dietary carotenoids may lower risk of invasive breast cancer
Laura Mignone and colleagues from the Harvard School of Public Health, US, looking at the correlation between dietary consumption of certain classes of vitamins and nutrients in fruits and vegetables, suggest that a high consumption of carotenoids may reduce the risk of premenopausal breast cancer, particularly in smokers. A recent article in the International Journal of Cancer details their study examining the association of carotenoid consumption and breast cancers.
A series of review articles have indicated that carotenoids have a protective influence on certain cancers in animals, and therefore may also have the same effect in humans. Carotenoids are plant pigments that can be found in yellow and orange vegetables and fruits and in dark green leafy vegetables. In an interview with Reuters Health Mignone points out that carotenoids are strong antioxidants and may play a role in protecting the body from the various carcinogens to which people are exposed. Indeed, hypothesised mechanisms for the protective properties of carotenoids against cancer include their potential antiproliferative and antioxidant properties. Specific carotenoids such as β-carotene, α-carotene and β-cryptoxanthin possess retinoic acid activity and are able to influence cell differentiation. Others, such as lutein and zeaxanthin are able to reduce cell proliferation despite not having any retinoic acid activity. The other proposed mechanism involves the inhibition of estrogen signalling by 17β-estradiol that may alleviate the effects of hormone-dependent malignancies.
The study by Mignone and colleagues involved examining the association between consumption of carotenoids and breast cancer in a large population-based case-control study of women (pre and postmenopausal). An inverse association was observed among premenopausal women for high levels of vitamin A, β-carotene, α-carotene and lutein/zeaxanthin. The results indicated that the risk of premenopausal breast cancer was reduced with the consumption of carotenoid rich vegetables such as carrots, kales and green leafy vegetables. Higher intake of the above mentioned carotenoids and vitamin A from food was associated with statistically lower risk among premenopausal women. Contrastingly, this was not observed in postmenopausal women.
The authors state that it is unclear why the association between carotenoids and breast cancer is limited to premenopausal women, although it may be related to the increasing cell turnover in breast epithelium under the influence of cyclic ovarian estrogen exposure. Other risk factors considered by the study include smoking and the known oxidative stress induced by tobacco smoke. Considering this, it is suggested that premenopausal women, particularly smokers, might benefit from increasing their dietary intake of carotenoid-rich vegetables to at least two servings each day, which might reduce the risk of breast cancer by 17%.
RSSL's Functional Ingredients Laboratory can determine physiologically active compounds, including flavanols and other polyphenols and other phytochemicals in a range of fruits, vegetables, herbals and dietary supplements. For more information contact Customer Services on Freefone 0800 243482 or e-mail enquiries@rssl.com
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