Healthy News for Healthy Nation

ScienceDaily (July 17, 2008) — Researchers in Ohio and New Mexico are reporting an advance in the quest for a fast, sensitive test to detect flu viruses — one that requires no refrigeration and can be used in remote areas of the world where new flu viruses often emerge. Their new method is the first to use sugar molecules rather than antibodies.

In the new study, Jurgen Schmidt, Suri Iyer, and colleagues point out that conventional tests for flu viruses — including bird flu — rely on antibodies, proteins produced by the immune system, to recognize viruses. But antibody-based tests can be expensive and require refrigeration to remain stable.

Their solution involved development of artificial forms of sialic acid, a sugar molecule found on the surface of cells that flu viruses attach to when they attack humans. In laboratory tests, the researchers showed that their highly-selective artificial sugars could be used to quickly capture and recognize two common strains of influenza viruses, H1N1, which infects birds, and H3N2, which infects pigs and humans.

They used the molecules to differentiate between 2 strains (Sydney and Beijing) commonly found in human infections without isolating the viral RNA or surface glycoproteins. The sugars remain stable for several months, can be produced in large quantities, and exhibit extended shelf life.

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ScienceDaily (July 17, 2008) — Diet can strongly influence how long you live and your reproductive success, but now scientists have discovered that what works for males can be very different for females.

In the first study of its kind, the researchers have shown that gender plays a major role in determining which diet is better suited to promoting longer life or better reproductive success.

In the evolutionary “battle of the sexes”, traits that benefit males are costly when expressed in females and vice versa. This conflict may have implications for human diet, aging and reproduction, says a team of scientists from UNSW, the University of Sydney and Massey University.

“When it comes to choosing the right diet, we need to look more closely to the individual, their sex and their reproductive stage in life,” says Associate Professor Rob Brooks, Director of the Evolution and Ecology Research Centre at the University of New South Wales. “It may be, for example, that women in their child-bearing years need a different diet to those who are post-menopausal.

“It also underlines the important lesson that what we want to eat or, if you like, what we’re programmed to eat, is not necessarily best for us.” The researchers are conducting long-term studies on Australian black field crickets and have discovered that the lifespan of both males and females is maximised on high-carbohydrate, low-protein diets, they say in the latest issue of Current Biology.

But reproductive success differs dramatically between the sexes when the carbohydrate-protein balance is changed: males live longest and have the greatest reproductive success with a diet that favours carbohydrates to protein by eight-to-one, whereas females have greatest success when the ratio is just one-to-one. Given a choice, however, females eat only a small amount more protein than males. The shared ability to sense and choose food dooms both males and females to eat a diet that is a compromise between what is best for each sex.

“Male and female crickets maximise their fitness on different diets,” says UNSW’s Dr Alexei Maklakov, the study’s lead author. “Despite that, the dietary preferences of the sexes are very similar. Instead of selecting foods in a sex-specific manner, males and females select ‘intermediate’ diets that are less than optimal for both sexes.

The researchers believe the sexes share most of their genes and this fact can constrain the evolution of sex differences in traits such as diet choice, because many of the same genes are likely to be responsible for trait expression in both sexes.

Significance for humans — “Men and women invest differently in reproduction, a difference that is even more marked than that between male and female crickets,” says Rob Brooks. “Think of the tremendous amounts of energy and protein required of a mother in carrying a baby to term and breastfeeding. We also know that men and women need to eat different diets - think of the careful attention we pay to what expectant mothers eat.

“What men and women need to eat might be more dramatically different than we had realised. However, men and women eat very similar diets and our results suggest that our tastes and food preferences could be a shared compromise, as they are in crickets.”

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ScienceDaily (July 18, 2008) — Obesity and common weight gain share a genetic basis. Professor Philippe Froguel, from Imperial College in Great Britain, and his team from the laboratoire Génomique et physiologie moléculaire des maladies métaboliques (CNRS/ Université Lille 2 / Institut Pasteur de Lille), in collaboration with teams from Inserm and Danish, Swiss and German partners, have discovered a new obesity gene that plays an essential role in the maturation of several key hormones that control food intake.

Mutations in this gene increase the risk of severe obesity and can lead to excessive weight.

The gene PCSK1 produces an enzyme called proconvertase 1 which activates several hormones and circulating peptides that are essential to life and are involved in controlling appetite – examples include insulin, glucagon (and derivatives such as GLP1, a new treatment for type 2 diabetes) and proopiomelanocortin (which makes a person feel full).

This enzyme had been previously identified as being almost completely ineffective in three obese patients with abnormalities in intestinal functioning.

The French-British team became interested in the frequent mutations in the gene PCSK1 which modify the structure of proconvertase 1. They showed that the enzyme activity in the mutated gene is intermediate between what was seen in the three obese patients and that of a non-mutated gene. These mutations increase the risk of becoming severely obese and have contributed to weight gain in, among others, French, Swiss, and Danish populations. Carriers of mutations of the PCSK1 gene also have a tendency to be hypoglycemic after meals due to insulin abnormalities linked to this mutation.

This discovery shows that apparently minor abnormalities in a key enzyme for the maturation of several hormones involved in controlling appetite (insulin, GLP1, melanocortin) are enough to significantly increase the risk of severe obesity and to lead to excessive weight in the general population.

After the early 2008 discovery that frequent variants in the melanocortin 4 receptor play a role in obesity (also published in Nature Genetics), the French-British team demonstrated that severe obesity and common weight gain have a common genetic base principally linked to defects in the complex hormone system (including some hormones produced by the intestine) and in specific receptors in certain areas of the brain that regulate food intake and satiation. At a time when the prevalence of morbid obesity (body-mass index greater than 40 kg/m2) has doubled in the past decade, these results highlight the importance of early dietary control to prevent and reduce obesity.

This study was carried out thanks to volunteers from families with obese children.

Authors:  Michael Benzinou, John W M Creemers, Helene Choquet, Stephane Lobbens, Christian Dina, Emmanuelle Durand, Audrey Guerardel, Philippe Boutin, Beatrice Jouret, Barbara Heude, Beverley Balkau, Jean Tichet, Michel Marre, Natascha Potoczna, Fritz Horber, Catherine Le Stunff, Sebastien Czernichow, Annelli Sandbaek, Torsten Lauritzen, Knut Borch-Johnsen, Gitte Andersen, Wieland Kiess, Antje Ko¨rner, Peter Kovacs, Peter Jacobson, Lena M S Carlsson, Andrew J Walley, Torben Jørgensen, Torben Hansen, Oluf Pedersen, David Meyre & Philippe Froguel.

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ScienceDaily (July 19, 2008) — Following a low-sodium diet does not appear to have any appreciable impact on asthma control, according to new research.

Contrary to past studies — which have suggested a link between low-sodium diets and improved asthma control — a new study by researchers at The University of Nottingham found no evidence that cutting back on salt helps patients with their symptoms.

Dr Zara Pogson, clinical research fellow at The University of Nottingham, said: “Despite the clear benefit of a low-sodium diet on cardiovascular risk factors, there is no therapeutic benefit in the use of a low-sodium diet…on asthma control in our study population.”

Nearly 200 subjects completed the study which compared the effect of changes in bronchial reactivity — a measure of asthma activity — on asthma patients who followed a strict low-sodium diet. Each subject either received sodium supplements to approximate normal sodium intake of 80 millimoles per litre (mmol) a day, or placebo tablets, for six weeks.

Dr Pogson and colleagues hypothesized that the subjects on the low sodium intake would show improved clinical control of asthma symptoms based on a test of asthma activity, measures of lung function, asthma symptoms and use of asthma medication. Contrary to their hypothesis, however, they detected no differences in any measures of asthma between the groups.

“We observed no difference in the outcome measures related to asthma activity in adults with asthma and bronchial reactivity who adopted a low-sodium diet for six weeks compared with those who did not, despite a final difference in daily sodium excretion of 50 mmol,” wrote Dr Pogson.

While past studies have suggested a link between low-sodium diets and improved asthma control, none were as large or tightly controlled as this study, suggesting that their findings may have been artifacts of study design rather than reflective of a true therapeutic benefit.

“We were disappointed that a simple measure, such as a decrease in sodium intake, does not result in improvements in asthma control,” said Dr Pogson. “We therefore cannot advise people with asthma to alter their sodium intake to improve control of their asthma, despite the fact that a low-sodium diet improves cardiovascular risk factors. This study suggests that further dietary research in asthma should be directed to factors other than sodium.”

According to Asthma UK, 5.2 million people in the UK have asthma — and 50 per cent of these people have severe asthma symptoms that have a major impact on their daily lives.

The results of the randomised, double-blind, placebo-controlled trial were published in the second issue for July of the American Journal of Respiratory and Critical Care Medicine by the American Thoracic Society.

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