Proteins regulating water retention in salt-sensitive hypertension identified

Friday 25 October 2013

Islamabad, Oct 26 (Newswire): Research conducted by scientists at LSU Health Sciences Center New Orleans has found that two proteins in the brain act as valves to turn the hormone that regulates water retention in the body on and off.

Their findings may lead to advances in treatment for diseases like high blood pressure, congestive heart failure, and cirrhosis of the liver.

Daniel Kapusta, PhD, Professor of Pharmacology at LSU Health Sciences Center New Orleans, and Richard Wainford, PhD, LSUHSC Instructor of Pharmacology, report the role of these brain proteins, called Gaq and Gaz, in producing elevated secretion of the hormone, vasopressin, and water retention in salt-sensitive hypertension, a condition in which blood pressure becomes elevated when salt is consumed. It is estimated that salt-sensitive hypertension occurs in about 26% of Americans with normal blood pressure and in 58% of those whose blood pressure is already high.

"Throughout the day, vasopressin, a peptide hormone produced by the hypothalamus, is released into the circulation from the pituitary gland and plays a vital role as the flood-gate keeper to prevent excessive loss of water from the kidneys," notes Dr. Kapusta.

"Under most conditions, the water-retaining action of vasopressin is vital for survival. However, it has remained essentially a black box as to why, in susceptible individuals, the regulatory mechanisms that control vasopressin secretion cannot turn off when the body already has elevated water content."

For 21-days, the research team fed groups of male salt-resistant and salt-sensitive rats a diet containing either normal or high salt. Then they measured how the treatments influenced the animal's ability to excrete water and how the salt stress altered levels of vasopressin, Gaq and Gaz.

The consumption of high salt triggered a decrease in Gaq proteins in the brain of salt-resistant, but not salt-sensitive, rats. In salt-sensitive rats, the team demonstrated that reducing brain Gaq proteins returned plasma vasopressin to normal levels, decreased salt-induced water retention, and restored the animal's ability to excrete water.

"Our findings are novel and provide evidence that the Gaq sub-unit proteins in the hypothalamus act as a molecular/cellular switch to control the level of vasopressin secretion," says Dr. Wainford.

The researchers concluded that reducing brain Gaq proteins plays a critical counter-regulatory role in preventing the secretion of too much vasopressin in those with salt-resistance and may represent a new therapeutic target in diseases associated with fluid retention.

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'Fruity vegetables' and fish reduce asthma and allergies

Islamabad, Oct 26 (Newswire): Giving children a diet rich in fish and "fruity vegetables" can reduce asthma and allergies, according to a seven-year study of 460 Spanish children.

The findings also reinforce the researchers' earlier findings that a fish-rich diet in pregnancy can help to protect children from asthma and allergies.

"We believe that this is the first study that has assessed the impact of a child's diet on asthma and allergies and also taken into account the food their mother ate during pregnancy" says lead author Dr Leda Chatzi from the Department of Social Medicine at the University of Crete, Greece.

"Because we studied the children from pregnancy to childhood, we were able to include a wide range of elements in our analysis, including maternal diet during pregnancy, breastfeeding, smoking, the mother's health history, parental education and social class."

Researchers followed the progress of the children, on the Spanish island of Menorca, at regular intervals from before they were born until they were six-and-a-half.

They discovered that children who consumed more than 40 grams of "fruity vegetables" a day -- namely tomatoes, eggplants (aubergines), cucumber, green beans and zucchini (courgettes) - were much less likely to suffer from childhood asthma.

And children who consumed more than 60 grams of fish a day also suffered less childhood allergies, echoing the protective effects they experienced when their mothers ate fish during pregnancy.

However the researchers noted that the dietary effects were quite specific and that other fruits and vegetables examined did not provide the same protective effect. Nor did other food groups included in the study, such as dairy products, meat, poultry and bread.

The mothers of 232 boys and 228 girls, who had been recruited during antenatal classes, completed detailed questionnaires on their children's health, weight, diet and any breathing problems every year until their child was six-and-a-half.

90 per cent of the children also underwent allergy testing -- skin prick tests were used to check their response to the six most common allergens, including grass pollen and cats.

The researchers found that just under nine per cent of the children suffered from some degree of wheezing, including six per cent with an allergy-related wheeze. And 17 per cent reacted to at least one of the allergens in the skin prick test.

"After adjusting the results for a wide range of variables, we concluded that the link between symptom-free children and a diet rich in fruity vegetables and fish was statistically significant" says Dr Chatzi.

"The biological mechanisms that underlie the protective affect of these foods is not fully understood, but we btelieve that the fruity vegetables and fish reduce the inflammation associated with asthma and allergies.

"The interesting thing about this study is that it followed a large number of children from the womb to the age of six-and-a-half and incorporated a wide range of dietary, social and health factors" says the Journal's Editor, Professor John Warner, Head of the Department of Paediatrics at Imperial College London.

"It provides parents with specific advice about the health promotion benefits of including fish and fruity vegetables as part of a balanced diet for both their children and the rest of the family."

Reference: "Diet, wheeze and atophy in school children in Menorca, Spain." Chatzi et al. Pediatric Allergy and Immunology. 18, pages 480 to 485. (September 2007).

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Allergies and wheezing illnesses in childhood may be determined in the womb

Islamabad, Oct 26 (Newswire): A child's chances of developing allergies or wheezing is related to how he or she grew at vital stages in the womb, according to scientists from the University of Southampton.

The new research, funded by the Medical Research Council (MRC) and the British Lung Foundation, and undertaken at Southampton General Hospital, reveals that fetuses which develop quickly in early pregnancy but falter later in pregnancy are likely to go on to develop allergies and asthma as children. Scientists believe this is due to changes in the development of their immune system and lungs.

A fetus that grows too slowly in the womb is also more likely to become an infant who wheezes with common colds, possibly as a result of narrower airways in its lungs.

"Childhood allergies and asthma have become an epidemic in developed countries over the last 50 years. This research shows that in order to combat this, we need to understand more about how babies develop in the womb," comments Keith Godfrey, Professor of Epidemiology and Human Development at the University of Southampton and Deputy Director of the NIHR Nutrition Biomedical Research Unit at Southampton General Hospital.

"We already know that a baby's growth in the womb has an important influence on susceptibility to obesity and heart disease in later life, but this research provides some of the most direct evidence yet that changes in how the baby's immune system and lungs develops before birth can predispose them to some of the commonest childhood illnesses."

For the research, published in the journal Thorax, University of Southampton scientists at the MRC Lifecourse Epidemiology Unit based at Southampton General Hospital studied more than 1,500 three year-old children who were taking part in the Southampton Women's Survey, the UK's largest study of women and their offspring. The Survey has studied how a woman's diet and lifestyle before and during pregnancy affects their baby's growth in the womb, and is monitoring how these early life influences determine health and development during childhood.

The team discovered evidence of sensitivity to common allergens (atopy) in 27 per cent of children who had developed quickly in early pregnancy but faltered later in pregnancy, as compared with 4 per cent in those with a slow early growth trajectory and quicker growth in late pregnancy.

Professor Stephen Holgate, from the Medical Research Council, says: "Unravelling the complex interplay between immunity and disease, over the course of a person's life, including before they are even born, is a core part of the MRC's research strategy. Furthering our understanding of the body's natural resilience is critical to developing new advances in the treatment of infectious diseases, autoimmune diseases and allergies."

Ian Jarrold, Research Manager at the British Lung Foundation, adds: "Children's lung health can be complex so this research, funded by the British Lung Foundation, is a considerable step forward in understanding why some children are more likely to develop allergies and asthma.

"The most commonly reported long-term illnesses in children and babies are conditions of the respiratory system. Increasing our understanding of childhood lung conditions is vital for developing new ways of diagnosing and treating lung diseases earlier in life."

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