Hunger hormone enhances sense of smell

An appetite-stimulating hormone causes people and animals to sniff odors more often and with greater sensitivity, according to a new study in the April 13 issue of The Journal of Neuroscience. The findings suggest ghrelin may enhance the ability to find and identify food.

Researchers led by Jenny Tong, MD, and Matthias Tschöp, MD, at the University of Cincinnati found the appetite-related hormone also influences smell. The new study shows ghrelin, made mainly in the stomach, binds to molecules in the brain's olfactory bulb, suggesting the hormone is directly involved in odor processing.
"This new function of ghrelin was unknown prior to our discovery," Tong said. "We think ghrelin is part of an important interface designed to help detect calories in our environment and to link those sensory inputs with the internal regulation of metabolism and body weight."
Previous studies suggested sniffing may help people identify sources of nutrition, particularly during fasts when the sense of smell improves. For this reason, the authors predicted ghrelin, which normally spikes before meals, acts on olfactory regions and leads to behavioral changes — such as sniffing — to help spur food intake.
In this study, Tong and her colleagues measured how rats and people react to different odors. When small amounts of ghrelin were delivered directly to rats' brains, the animals sniffed more often. The ghrelin-treated rats also avoided water with low concentrations of an odor associated with sickness more than untreated rats.
Nine humans who received ghrelin infusions also reacted to stimuli differently. Each volunteer was directed to whiff unperfumed air or baby powder, banana, tomato, or rosemary chicken scents. Participants given ghrelin inhaled more deeply.
Thomas Hummel, MD, of the University of Dresden, an expert in smell and taste who was unaffiliated with the study, noted that the results suggest ghrelin affects odor detection, but not appeal. The volunteers reported no difference in aroma pleasantness.
"Overall, this report seems to confirm that ghrelin is an important modifier of appetite — and eating behavior," Hummel said.


Source : Society for Neuroscience

Accelerated Lab Evolution of Biomolecules Could Yield New Generation of Medicines

ScienceDaily (Apr. 11, 2011) — Scientists at Harvard University have harnessed the prowess of fast-replicating bacterial viruses, also known as phages, to accelerate the evolution of biomolecules in the laboratory. The work, reported in the journal Nature, could ultimately allow the tailoring of custom pharmaceuticals and research tools from lab-grown proteins, nucleic acids, and other such compounds.
The researchers, led by Professor David R. Liu, say their approach -- dubbed phage-assisted continuous evolution, or PACE -- is roughly 100 times faster than conventional laboratory evolution, and far less labor-intensive for scientists.
"Most modern drugs are based on small organic molecules, but biological macromolecules may be better suited as pharmaceuticals in some cases," says Liu, a professor of chemistry and chemical biology at Harvard and an investigator with the Howard Hughes Medical Institute. "Our work provides a new solution to one of the key challenges in the use of macromolecules as research tools or human therapeutics: how to rapidly generate proteins or nucleic acids with desired properties."
Liu and Harvard co-authors Kevin M. Esvelt and Jacob C. Carlson achieved up to 60 rounds of protein evolution every 24 hours by linking laboratory evolution to the life cycle of a virus that infects bacteria. This phage's life cycle of just 10 minutes is among the fastest known. Because this generation time is so brief, the phage makes a perfect vehicle for accelerated protein evolution. The PACE system uses E. coli host cells to produce the resulting proteins, to serve as factories for phage production, and to perform the key selection step that allows phage-carrying genes encoding desired molecules to flourish.
In three separate protein evolution experiments, PACE was able to generate an enzyme with a new target activity within a week, achieving up to 200 rounds of protein evolution during that time. Conventional laboratory evolution methods, Liu says, would require years to complete this many rounds of evolution.
Evolution of biomolecules is also a natural process, of course, but during biological evolution generation times tend to be very long and researchers have no control over the outcomes. Laboratory evolution (also called directed evolution) has been practiced for decades to generate biomolecules with tailor-made properties, but typically proceeds at a rate of about one round of evolution every few days and requires frequent sample manipulation by scientists or technicians during that time.
In addition to not requiring human intervention during the evolutionary process, Liu's new approach uses readily available components and is designed to be resistant to "cheater" molecules that bypass the desired selection process. Researchers can control PACE's selection stringency as well as its mutation rate.
"Laboratory evolution has generated many biomolecules with desired properties, but a single round of mutation, gene expression, screening or selection, and replication typically requires days or longer with frequent human intervention," Liu, Esvelt, and Carlson write in Nature. "Since evolutionary success is dependent on the total number of rounds performed, a means of performing laboratory evolution continuously and rapidly could dramatically enhance its effectiveness."
Among other achievements reported in Nature, Liu and colleagues used PACE to recast an RNA polymerase normally activated by a T7 promoter to recognize a T3 promoter instead. They also evolved polymerases that initiate RNA transcripts with the genetic bases adenine (A) or cytosine (C) instead of the usual guanine (G). In all cases, the PACE-generated enzymes on their new targets matched or exceeded the activity of wild-type enzymes.
This work was supported by the National Institutes of Health, the Howard Hughes Medical Institute, the Hertz Foundation, the National Science Foundation, and the Harvard Chemical Biology Graduate Program.

World's Smallest Wedding Rings: Interlocking Rings of DNA Visible Through Scanning Force Microscope

ScienceDaily (Apr. 12, 2011) — DNA nanotechnology makes use of the ability of natural DNA strains' capacity for self asssembly. Prof. Alexander Heckel and his doctoral student Thorsten Schmidt of Goethe University were able to create two rings of DNA only 18 nanometers in size, and to interlock them like two links in a chain. Such a structure is called catenan, a term derived from the Latin word catena (chain). Schmidt, who got married during the time he was working on the nano-rings, believes that they are probably the world's smallest wedding rings.

From a scientific perspective, the structure is a milestone in the field of DNA nanotechnology, since the two rings of the catenan are, as opposed to the majority of the DNA nano-architectures that have already been realized, not fixed formations, but -- depending on the environmental conditions -- freely pivotable. They are therefore suitable as components of molecular machines or of a molecular motor.

"We still have a long way to go before DNA structures such as the catenan can be used in everyday items," says Prof Alexander Heckel, "but structures of DNA can, in the near future, be used to arrange and study proteins or other molecules that are too small for a direct manipulation, by means of auto-organization." This way, DNA nano-architectures could become a versatile tool for the nanometer world, to which access is difficult.
In the manufacture of DNA nano-architecture, the scientists take advantage of the pairing rules of the four DNA nucleobases, according to which two natural DNA strands can also find each other (in DNA nano-architecture, the base order is without biological significance). An A on one strand pairs with T on the other strand and C is complementary to G. The trick is to create the sequences of the DNA strands involved in such a manner as to ensure that the desired structure builds up on its own without direct intervention on the experimenter's part. If only certain parts of the strands used complement each other, branches and junctions can be created.
As reported by Schmidt and Heckel in the journal Nano Letters, they first created two C-shaped DNA fragments for the catenans. With the help of special molecules that act as sequence-specific glue for the double helix, they arranged the "Cs" in such a ways as to create two junctions, with the open ends of the "Cs" pointing away from each other. The catenan was created by adding two strands that attach to the ends of the two ring fragments, which are still open. Thorsten Schmidt dedicated the publication to his wife Dr Diana Gonçalves Schmidt, who also appreciates the work on scientific level, since she was also a part of Alexander Heckel's work group.
Since they are much smaller than the wavelengths of visible light, the rings cannot be seen with a standard microscope. "You would have to string together about 4000 such rings to even achieve the diameter of a human hair," says Thorsten Schmidt. He therefore displays the catenans with a scanning force microscope, which scans the rings that have been placed on a surface with an extremely fine tip.

Do women really talk more than men?

It's always said that women talk more than men, but here at the Naked Scientists, its hard to get a word in edgeways as Dr Chris is always talking. Now new research from the University of Arizona suggests that men may be just as chatty. The scientists recorded the conversations of 400 Mexican male and female students over 6 years, and logged their words.

In their study, published in the journal Science, the researchers reveal that the women in the study spoke a daily average of 16,215 words during their waking hours, versus an average of 15,669 words for men.

So women do talk more than men, but not by a statistically significant margin. But that's just the average - the team found very large individual differences around this average. For example. among the three most talkative males in the study, one used 47,000 words while the least talkative male spoke just a little more than 500.

Mothers' Hard Work Pays Off With Big Brains for Their Babies

ScienceDaily (Mar. 30, 2011) — Brain growth in babies is linked to the amount of time and energy mothers 'invest', according to new research.

The study of 128 mammal species, including humans, shows that brain growth in babies is determined by the duration of pregnancy and how long they suckle. The Durham University research concludes that the longer the pregnancy and breastfeeding period in mammals, the bigger the baby's brain grows.
The researchers say the findings reinforce the suggestion that breast is best for brain development and add further weight to the World Health Organisation's advice of six months' exclusive breastfeeding followed by continuing breastfeeding up to the age of two or beyond supplemented with solid foods.
The study, published in the Proceedings of the National Academy of Sciences, helps to explain why humans, who suckle their babies for up to three years in addition to their nine-month pregnancies, have such a long period of dependency as this is necessary to support the growth of our enormous 1300cc brains.
In comparison, species such as fallow deer, which are about the same body weight as humans, are only pregnant for seven months with a suckling period of up to six months, resulting in brains of only 220cc, six times smaller than the human brain.
The anthropologists, from Durham's Evolutionary Anthropology Research Group, analysed statistical evidence on brain and body size, maternal investment, and life history variables in mammals, including species such as gorillas, elephants and whales.
They found that brain size relative to body size was most closely linked to maternal investment -- the amount of time a mother spends carrying her offspring in pregnancy and how long she continues to breastfeed. The study shows that length of the pregnancy determines brain size at birth and the period of lactation decides brain growth after birth. It also shows that mothers with higher metabolic rates can afford to fuel faster brain growth in the fetus.
Lead investigator, Professor Robert Barton from Durham University's Department of Anthropology, said: "We already know that large-brained species develop slowly, mature later and have longer lifespans but what has not always been clear is why brains and life histories are related.
"One theory is that large brains increase lifespan by making the animal more generally flexible in its behavioural responses to unpredictable challenges, permitting slower life histories. However, our findings suggest that the slow-down in life histories is directly related to the costs rather than the benefits of growing a large brain. The necessary benefits to offset these costs could come in other ways, such as improving specific perceptual and cognitive abilities, rather than through some generalized flexibility.
"Our findings help us to understand what the implications are of evolutionary changes at different stages, before and after birth, but we now need to do more research to pinpoint exactly how changes to the pre- and postnatal growth phases affect the structure of the brain."
The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and the Natural Environment Research Council (NERC)

Common Dietary Fat and Intestinal Microbes Linked to Heart Disease

ScienceDaily (Apr. 6, 2011) — A new pathway has been discovered that links a common dietary lipid and intestinal microflora with an increased risk of heart disease, according to a Cleveland Clinic study published in the latest issue of Nature.

The study shows that people who eat a diet containing a common nutrient found in animal products (such as eggs, liver and other meats, cheese and other dairy products, fish, shellfish) are not predisposed to cardiovascular disease solely on their genetic make-up, but rather, how the micro-organisms that live in our digestive tracts metabolize a specific lipid -- phosphatidyl choline (also called lecithin). Lecithin and its metabolite, choline, are also found in many commercial baked goods, dietary supplements, and even children's vitamins.
The study examined clinical data from 1,875 patients who were referred for cardiac evaluation, as well as plasma samples from mice. When fed to mice, lecithin and choline were converted to a heart disease-forming product by the intestinal microbes, which promoted fatty plaque deposits to form within arteries (atherosclerosis); in humans, higher blood levels of choline and the heart disease forming microorganism products are strongly associated with increased cardiovascular disease risk.
"When two people both eat a similar diet but one gets heart disease and the other doesn't, we currently think the cardiac disease develops because of their genetic differences; but our studies show that is only a part of the equation," said Stanley Hazen, M.D., Ph.D., Staff in Lerner Research Institute's Department of Cell Biology and the Heart and Vascular Institute's Department of Cardiovascular Medicine and Section Head of Preventive Cardiology & Rehabilitation at Cleveland Clinic, and senior author of the study. "Actually, differences in gut flora metabolism of the diet from one person to another appear to have a big effect on whether one develops heart disease. Gut flora is a filter for our largest environmental exposure -- what we eat."
Dr. Hazen added, "Another remarkable finding is that choline -- a natural semi-essential vitamin -- when taken in excess, promoted atherosclerotic heart disease. Over the past few years we have seen a huge increase in the addition of choline into multi-vitamins -- even in those marketed to our children -- yet it is this same substance that our study shows the gut flora can convert into something that has a direct, negative impact on heart disease risk by forming an atherosclerosis-causing by-product."
In studies of more than 2,000 subjects altogether, blood levels of three metabolites of the dietary lipid lecithin were shown to strongly predict risk for cardiovascular disease: choline (a B-complex vitamin), trimethylamine N-oxide (TMAO, a product that requires gut flora to be produced and is derived from the choline group of the lipid) and betaine (a metabolite of choline).
"The studies identify TMAO as a blood test that can be used in subjects to see who is especially at risk for cardiac disease, and in need of more strict dietary intervention to lower their cardiac risk," Dr. Hazen said.
Healthy amounts of choline, betaine and TMAO are found in many fruits, vegetables and fish. These three metabolites are commonly marketed as direct-to-consumer supplements, supposedly offering increased brain health, weight loss and/or muscle growth.
These compounds also are commonly used as feed additives for cattle, poultry or fish because they may make muscle grow faster; whether muscle from such livestock have higher levels of these compounds remains unknown.
"Knowing that gut flora generates a pro-atherosclerotic metabolite from a common dietary lipid opens up new opportunities for improved diagnostics, prevention and treatment of heart disease," Dr. Hazen said. "These studies suggest we can intelligently design a heart healthy yogurt or other form of probiotic for preventing heart disease in the future. It also appears there is a need for considering the risk vs. benefits of some commonly used supplements."

Self-Made Eye: Formation of Optic Cup from Embryonic Stem Cells

ScienceDaily (Apr. 6, 2011) — Developmental processes are increasingly well-characterized at the molecular and cell biological levels, but how more complex tissues and organs involving the coordinated action of multiple cell types in three dimensions is achieved remains something of a black box. One question of particular interest and importance is whether signaling interactions between neighboring tissues are essential to guiding organogenesis, or whether these can arise autonomously from developmental routines inherent to a given primordial tissue.

Finding answers to these questions will be critical both to a better understanding of embryonic phenomena and to the ability to control the differentiation of cell populations into desired configurations.
A breakthrough new report by Mototsugu Eiraku, deputy leader of the Four-dimensional Tissue Analysis Unit and colleagues in the Laboratory for Neurogenesis and Organogenesis (Group Director, Yoshiki Sasai), as well as the RIKEN VCAD Program, and Kyoto and Osaka Universities, describes how mouse embryonic stem cells (ESCs) are able to differentiate and assemble into an optic cup, capable of giving rise to a tissue exhibiting the stratified structure characteristic of the retina in vivo. Published in Nature, the study used a cutting-edge three-dimensional tissue culture system not only to demonstrate this self-organizing capacity of pluripotent stem cells, but the underlying cell dynamics as well.
The mechanistic basis for the formation of the optic cup, with its complex two-walled structure, has been a longstanding question in embryology. The retina, with its origins in the lateral midbrain, is part of the central nervous system. Its development begins with the formation of the optic vesicle, a pocket of epithelium that deepens and pinches to form the optic cup, which develops a double layer of cells, with pigment epithelium on the outer, and neural retina on the inner wall. It has generally been thought that this transformation is triggered by chemical and physical influences from other tissues, such as lens or cornea, but some, including the father of experimental embryology, Hans Spemann, have suggested that perhaps external induction or force is not necessary.
To resolve this question, Eiraku et al. built on a series of techniques and findings emerging from the use of the SFEBq (serum-free culture of embryoid body-like aggregates) ES cell culture system developed by the Sasai lab, which had previously been used to differentiate these pluripotent stem cells into a wide range of neuronal cell types, including, recently, structurally organized cerebral cortical neurons. By adding extracellular matrix proteins to the SFEBq medium, the group was able to epithelially-organize retinal precursors at high efficiencies by day 7 of culture. One day later, optic vesicle-like structure began to form, followed by bi-layered optic cup-like structures by day 10. The pigmented and neuronal character of the outer and inner layers of cells in these spontaneously formed tissues were confirmed by gene expression, indicating that optic cup development had been recapitulated in vitro, and importantly, in the absence of any external signaling sources, such as from the lens, demonstrating the capacity for self-organization.
They next used multi-photon microscopy to explore the mechanisms behind this process of self-assembly in 3D. They found that after the ES cell-derived retinal precursors differentiated into pigmented epithelial and neuronal layers, the tissue underwent a four step morphological rearrangement on its way to assuming the optic cup structure. When they examined cytoskeletal behaviors in this process, they noted that myosin activity dropped in the region of the epithelium that bend inward to form the cup, giving the flexibility needed to form a pocket driven by expansion of the epithelium through cell division.
Computer simulation of the mechanics behind this revealed that three principal forces can explain the optic cup-forming event. First, the a region of the epithelium must lose rigidity, allowing it to buckle inward, after which cells at the hinge points (defined by the border between presumptive pigment epithelium and neuronal regions) must undergo apical constriction, giving them a wedge-like shape. Once these conditions are met, expansion of the tissue surface by cell division results in further involution of the cup, all of which are very much in line with the experimental findings.
As a final test of the in vitro structure's ability to mirror its embryonic counterpart, Eiraku excised the neuronal layer from the ES cell-derived optic cup and allowed it to develop in 3D cell culture under conditions optimized for spurring neuronal maturation. He found that the retinal neurons underwent active mitosis and ultimately organized into a six-layer stratified and synapse-forming neuronal structure closely resembling that of the post-natal retina.
"What we've been able to do in this study is resolve a nearly century-old problem in embryology, by showing that retinal precursors have the inherent ability to give rise to the complex structure of the optic cup," says Sasai. "It's exciting to think that we are now well on the way to becoming able to generate not only differentiated cell types, but organized tissues from ES and iPS cells, which may open new avenues toward applications in regenerative medicine." Potential applications include regenerative medicine approaches to the treatment of retinal degenerative disorders, such as retinitis pigmentosa.

Men Are From Mars Neuroscientists Find That Men And Women Respond Differently To Stress

April 1, 2008 — Functional magnetic resonance imaging of men and women under stress showed neuroscientists how their brains differed in response to stressful situations. In men, increased blood flow to the left orbitofrontal cortex suggested activation of the "fight or flight" response. In women, stress activated the limbic system, which is associated with emotional responses.
There are many books and movies that highlight the psychological differences between men and women -- Men are From Mars, Women are From Venus, for example; but now, neurologists say they have brain images that prove male and female brains do work differently -- at least under stress.
Same species, different genders … And now, a new high-tech scientific study reveals the differences between men and women may really start at the top. Researchers at the University of Pennsylvania used a high-tech imaging method to scan the brains of 16 men and 16 women. The subjects were placed inside a functional magnetic resonance imaging machine, or fMRI.
"Using this state-of-the art-functional magnetic resonance imaging technique, we try to directly visualize what the human brain does during stress," Jiongjiong Wang, Ph.D., a research assistant professor of radiology and neurology at the University of Pennsylvania in Philadelphia, told Ivanhoe.
Researchers then purposely induced moderate performance stress by asking the men and women to count backward by 13, starting at 1,600. Researchers monitored the subject's heart rate. They also measured the blood flow to the brain and checked for cortisol, a stress hormone.
When the scans were completed, neuroscientists consistently found differences between the men's stressed-out brains and the women's. Men responded with increased blood flow to the right prefrontal cortex, responsible for "fight or flight." Women had increased blood flow to the limbic system, which is also associated with a more nurturing and friendly response.
Doctors say this information may someday lead to a screening process for mood disorders. "In the future, when physicians treat patients -- especially depression, PTSD -- they need to take this into account that really, gender matters," Dr. Wang explains.
Other experts caution that hormones, genetics and environmental factors may influence these results, bringing to light yet another difference between men and women. Neuroscientists say the changes in the brain during stress response also lasted longer in women.
WHAT IS fMRI? Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field rather than X-rays to take clear and detailed pictures of internal organs and tissues. fMRI uses this technology to identify regions of the brain where blood vessels are expanding, chemical changes are taking place, or extra oxygen is being delivered.
These are indications that a particular part of the brain is processing information and giving commands to the body. As a patient performs a particular task, the metabolism will increase in the brain area responsible for that task, changing the signal in the MRI image. So by performing specific tasks that correspond to different functions, scientists can locate the part of the brain that governs that function.
FIGHT OR FLIGHT: Certain events act as "stressors," triggering the nervous system to produce hormones to respond to the perceived danger. Specifically, the adrenal glands produce more adrenaline and cortisol, releasing them into the bloodstream. This speeds up heart and breathing rates, and increases blood pressure and metabolism. These and other physical changes help us to react quickly and effectively under pressure.
This is known as the "stress response," or more commonly, as the "fight or flight response." But if even low levels of stress go on too long, it can be detrimental to one's health. The nervous system remains slightly activated and continues to pump out extra stress hormones over an extended period, leaving the person feeling depleted or overwhelmed, and weakening the body's immune system.
STRESS-REDUCING TIPS: There are several easy, practical things people can do to reduce the amount of stress in their lives. (1) Be realistic and don't try to be perfect, or expect others to be so. (2) Don't over-schedule; cut out an activity or two when you start to feel overwhelmed. (3) Get a good night's sleep. (4) Get regular exercise to manage stress -- just not excessive or compulsive exercise -- and follow a healthy diet. (5) Learn to relax by building time into your schedule for reading or a nice long bath.

Facial Structures of Men and Women Have Become More Similar Over Time

ScienceDaily (Apr. 4, 2011) — Research from North Carolina State University shows that they really don't make women like they used to, at least in Spain. The study, which examined hundreds of Spanish and Portuguese skulls spanning four centuries, shows that differences in the craniofacial features of men and women have become less pronounced.
"Improving our understanding of the craniofacial features of regional groups can help us learn more from skeletal remains, or even help us identify an individual based on his or her remains," says Dr. Ann Ross, an associate professor of anthropology at NC State and principal investigator of the study. The researchers looked at more than 200 skulls dating to 20th and 16th century Spain, as well as approximately 50 skulls from 20th century Portugal.
Researchers found that craniofacial differences between contemporary men and women are less pronounced than they were in the 16th century. The researchers also found that, while craniofacial features for both sexes in Spain have changed over time, the changes have been particularly significant in females. For example, the facial structure of modern Spanish females is much larger than the structure of 16th century females. This difference may stem from improved nutrition or other environmental factors.
The researchers paid particular attention to structural differences between male and female skulls because "this can help us establish the sex of the remains based on their craniofacial features," Ross says -- which is particularly important when an incomplete skeleton is found. "Being able to tell if a skull belonged to a man or woman is useful in both criminal investigation and academic research."
Assessing the 16th century skulls was important to the researchers because it allowed them to determine how the different features of male and female skulls have changed over time. "This has applications for characterizing older remains," Ross says. "Applying 20th century standards to historical remains could be misleading, since sex differences can change over time -- as we showed in this study."
The study also found that the craniofacial sexual differences were very similar between Spanish and Portuguese populations, implying that standards developed for identifying sex in Spanish skulls could also be applied regionally.
A paper describing the research, "Implications of dimorphism, population variation, and secular change in estimating population affinity in the Iberian Peninsula," is forthcoming from the journal Forensic Science International. The paper was co-authored by Ross; Dr. D.H. Ubelaker of the Smithsonian Institution's National Museum of Natural History; and Dr. E.H. Kimmerle of the University of South Florida. The work was funded, in part, by the National Institute of Justice.
NC State's Department of Sociology and Anthropology is part of the university's College of Humanities and Social Sciences.

New evidence links hormone therapy, breast cancer

Sydney, June 2 : Scientists have found new evidence that would further explain that there is a link between use of hormone replacement therapy and breast cancer risk.
A new study has shown that the number of Australian women aged over 50 diagnosed with breast cancer has dropped by 7 per cent with 600 fewer cases between 2001 and 2003, during which there was also a 40 per cent decrease in use of hormone replacement therapy (HRT).
A drop in the number of breast cancer cases with the reduction in hormone therapy use women experiencing menopause may explain the association.
Dr Andrew Penman, CEO at the Cancer Council NSW, said the "findings are great news for women".
"The correlation between the drop in breast cancer cases and HRT use is clear and its importance can't be underestimated," Sydney Morning Herald quoted Dr Penman, as saying.
However, Dr Helen Zorbas, director of the National Breast and Ovarian Cancer Centre said that though the link was "likely" the study did not categorically show a reduction in HRT caused the decrease in cancer rates and did not change the advice to women regarding the use of HRT for the short-term relief of menopausal symptoms such as hot flushes.
"There may be other factors which could be contributing to this decrease in breast cancer incidence," she said.
Zorbas also said that for every 1000 women in their 50s taking HRT over five years, there would be an additional four women diagnosed with breast cancer but the risk returned to normal within a few years of stopping treatment.
"All the data … shows that taking combined HRT does increase the risk for breast cancer with the longer duration of use increasing the risk," she added.
Many women had stopped using HRT after it was found to increase breast cancer rates in the controversial Women's Health Initiative report in 2002. (ANI)