New Genetic Study Shows How Belly Fat Differs from Thigh Fat

Researchers have observed that the genes active in a person's belly fat are significantly different from those in the person's thigh fat. 
The findings of the new study could shift the way we approach unwanted belly fat - from banishing it to relocating it.Men tend to store fat in the abdominal area, but don't usually have much in the way of hips or thighs. Women, on the other hand, are more often pear-shaped - storing more fat on their hips and thighs than in the belly. The answer to the question about why are men and women shaped differently still isn't clear, but it's an issue worth investigating, says Steven Smith from Sanford-Burnham Translational Research Institute for Metabolism and Diabetes. 
That's because belly fat is associated with higher risks of heart disease and diabetes. On the other hand, hip and thigh fats don't seem to play a special role in these conditions. 
In the recent study, Smith and colleagues help explain this discrepancy by determining how belly and thigh fat differ genetically. This research might shift common thinking about fat-rather than focusing on how to banish belly fat, perhaps we need to tip the balance in favour of heart-friendly fat in the lower body. 
In that case, the study also provides a first step toward aiming treatments at specific regions of the body, especially those that contribute most to the complications of obesity. 
Smith and colleagues first took fat samples from men and women. Then they compared the genes most active in belly fat to those most active in thigh fat. 
They found that the genes operating in a person's thigh fat are hugely different from those in his or her belly fat. For men, 125 genes are expressed differently in the belly than in the thighs. For women, it's 218 genes. 
The most notable genes that differed are known as homeobox genes. These genes are known for their role in helping shape a developing embryo-determining which cells and organs go where. Many homeobox genes are influenced by hormones such as estrogen. 
Why are these homeobox genes important for fat? 
"We believe these genes actually program those fat cells to respond differently to different hormones and other signals," Smith said. 
In the course of their work, Smith and his team also isolated stem cells from belly and thigh fat and grew them in laboratory dishes. This was a nice control because fat cells in a dish aren't influenced by nerves, hormones, or other outside signals. 
Yet the researchers still saw the same location-specific differences in gene activity in the fat that developed from these stem cells. That result told them that the cells are preprogrammed. 
In other words, belly fat and thigh fat are genetically destined for their final location during development. It's not a difference that's acquired over time, as a result of diet or environmental exposure. 
Medically speaking, says Smith, it's important to understand these differences and how they arise. 
"Even though many women hate having large hips and thighs, that pear shape actually reduces their risk of heart disease and diabetes. In fact, women who have heart attacks tend to have more belly fat than thigh fat," he said. 
The study has been published in the Journal of Clinical Endocrinology and Metabolism.
Source-ANI
 

 

Negative Effect of Exercise

Exercise may be harmful to the hearts of some people, say researchers. A new study analysed data from six exercise studies involving 1,687 regular exercisers to find out the effects of -regular workouts on the heart.
 The results shocked and confused the scientists - in almost one in ten people tested, exercise seemed adversely to affect blood pressure, insulin levels or 'good' HDL cholesterol levels, the Daily Mail reported. 
And in seven percent of people, not just one but two of these risk factors for heart disease were worse as a result of exercise. 
According to lead author Claude Bouchard from Louisiana State University, there is no clear explanation for this effect on a small portion of the population but 'it's not a good sign'. 
Bouchard suspects that it is down to genetics and advises exercisers to have their blood pressure, cholesterol and glucose checked regularly. 
Regular amounts of aerobic exercise like running are known to slow the unhealthy changes to the cardiovascular system that occur with age. 
However, intense and prolonged endurance training for many years - for instance, for marathons or triathlons - could be damaging to the heart. 
Greg Whyte, author of the study from Liverpool John Moores University, said the research found that 50 percent of long-term endurance and ultra-endurance runners, some of whom had been training for 43 years, showed signs of heart damage. 
The study has been published in the journal PLoS One.
Source-ANI
 

Menopause Linked to Declines in Memory and Thinking Skills

According to a study, women who undergo surgical menopause at an earlier age may have an increased risk of decline in memory and thinking skills.The study will be presented at the American Academy of Neurology''s 65th Annual Meeting in San Diego, March 16 to 23, 2013. Early surgical menopause is the removal of both ovaries before natural menopause and often accompanies a hysterectomy.
"While we found a link between surgical menopause and thinking and memory decline, women on longer hormone replacement therapies had slower declines," said study author Riley Bove, MD, with Harvard Medical School in Boston and a member of the American Academy of Neurology. "Since hormone replacement therapy is widely available, our research raises questions as to whether these therapies have a protective effect against cognitive decline and whether women who experience early surgical menopause should be taking hormone replacement therapies afterward." 
The study included 1,837 women between the ages of 53 and 100 participating in the Rush Memory and Aging Project at Rush University Medical Center in Chicago. Of those, 33 percent had undergone surgical menopause. The women were given several types of tests that measured thinking skills and memory. Researchers also recorded age at the start of menstruation, years of menstrual cycles and use and length of hormone replacement therapies. 
The study found that among women who underwent surgical menopause, earlier age of the procedure was associated with a faster decline in long-term memory related to concepts and ideas, in memory that relates to time and places and in overall thinking abilities. The results stayed the same after considering factors such as age, education and smoking. This same association was not seen in women who underwent natural menopause. 
There was also a significant association between age at surgical menopause and the plaques linked to Alzheimer''s disease. 
"Our study warrants further research as the interest in this subject will continue to grow right along with our aging population," said Bove. 
The study was supported by the National Institutes of Health. 
Learn more about cognition at http://www.aan.com/patients. 
The American Academy of Neurology, an association of more than 25,000 neurologists and neuroscience professionals, is dedicated to promoting the highest quality patient-centered neurologic care. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as Alzheimer''s disease, stroke, migraine, multiple sclerosis, brain injury, Parkinson''s disease and epilepsy. 
Source-Newswise 

 

Fetal exposure to PVC plastic chemical linked to obesity in offspring

Exposing pregnant mice to low doses of the chemical tributyltin – which is used in marine hull paint and PVC plastic – can lead to obesity for multiple generations without subsequent exposure, a UC Irvine study has found.After exposing pregnant mice to TBT in concentrations similar to those found in the environment, researchers saw increased body fat, liver fat and fat-specific gene expression in their “children,” “grandchildren” and “great-grandchildren” – none of which had been exposed to the chemical.These findings suggest that early-life exposure to endocrine-disrupting compounds such as TBT can have permanent effects of fat accumulation without further exposure, said study leader Bruce Blumberg, UC Irvine professor of pharmaceutical sciences and developmental & cell biology. These effects appear to be inherited without DNA mutations occurring.The study appears online today in Environmental Health Perspectives, a publication of the National Institute for Environmental Health Sciences.Human exposure to TBT can occur through PVC plastic particles in dust and via leaching of the chemical and other related organotin compounds from PVC pipes and containers.Significant levels of TBT have been reported in house dust – which is particularly relevant for young children who may spend significant time on floors and carpets. Some people are exposed by ingesting seafood contaminated with TBT, which has been used in marine hull paint and is pervasive in the environment.Blumberg categorizes TBT as an obesogen, a class of chemicals that promote obesity by increasing the number of fat cells or the storage of fat in existing cells. He and his colleagues first identified the role of obesogens in a 2006 publication and showed in 2010 that TBT acts in part by modifying the fate of mesenchymal stem cells during development, predisposing them to become fat cells.

Source:UCIrvine News

Choline supplementation during pregnancy presents a new approach to schizophrenia prevention

University of Colorado researchers study choline in infants

 Choline, an essential nutrient similar to the B vitamin and found in foods such as liver, muscle meats, fish, nuts and eggs, when given as a dietary supplement in the last two trimesters of pregnancy and in early infancy, is showing a lower rate of physiological schizophrenic risk factors in infants 33 days old. The study breaks new ground both in its potentially therapeutic findings and in its strategy to target markers of schizophrenia long before the illness itself actually appears. Choline is also being studied for potential benefits in liver disease, including chronic hepatitis and cirrhosis, depression, memory loss, Alzheimer's disease and dementia, and certain types of seizures.
Robert Freedman, MD, professor and chairman of the Department of Psychiatry, University of Colorado School of Medicine and one of the study's authors and Editor of The American Journal of Psychiatry, points out, "Genes associated with schizophrenia are common, so prevention has to be applied to the entire population, and it has to be safe. Basic research indicates that choline supplementation during pregnancy facilitates cognitive functioning in offspring. Our finding that it ameliorates some of the pathophysiology associated with risk for schizophrenia now requires longer-term follow-up to assess whether it decreases risk for the later development of illness as well."
Normally, the brain responds fully to an initial clicking sound but inhibits its response to a second click that follows immediately. In schizophrenia patients, deficient inhibition is common and is related to poor sensory filtering and familial transmission of schizophrenia risk. Since schizophrenia does not usually appear until adolescence, this trait—measurable in infancy—was chosen to represent the illness.
Half the healthy pregnant women in this study took 3,600 milligrams of phosphatidylcholine each morning and 2,700 milligrams each evening; the other half took placebo. After delivery, their infants received 100 milligrams of phosphatidylcholine per day or placebo. Eighty-six percent of infants exposed to pre- and postnatal choline supplementation, compared to 43% of unexposed infants, inhibited the response to repeated sounds, as measured with EEG sensors placed on the baby's head during sleep.
Source: American Journal of Psychiatry

Study finds spiritual care still rare at end of life

Physicians and nurses at four Boston medical centers cited a lack oftraining to explain why they rarely provide spiritual care for terminally ill cancer patients - although most considered it an important part of treatment at the end of life."I was quite surprised that it was really just lack of training that dominated the reasons why," senior author Dr. Tracy Balboni, a radiation oncologist at the Dana-Farber Cancer Institute in Boston, told Reuters Health.Current U.S. palliative care guidelines encourage medical practitioners to pay close attention to religious and spiritual needs that may arise during a patient's end-of-life care.However, the 204 physicians who participated in the study reported providing spiritual care to just 24 percent of their patients. Among 118 nurses, the figure was 31 percent.The 69 patients with advanced cancers who took the survey reported even lower rates, saying 14 percent of nurses and six percent of physicians had provided them some sort of spiritual care.Past research has shown that spiritual care for seriously ill patients improves their quality of life, increases their overall satisfaction with hospital care and decreases aggressive medical treatment, which may in turn result in lower overall health spending."There was a time when nurses and physicians may have said, 'That's not my job,' but I think the tides are changing," said palliative care researcher Betty Ferrell of City of Hope, a cancer research and treatment hospital in Duarte, California."I think we are realizing we can no longer ignore this aspect of care," said Ferrell, a professor of nursing who was not involved in the new study.Yet the reasons why spiritual care is rarely incorporated into patient treatment and dialogue have been poorly understood.To gain more insight, Balboni and her colleagues designed a survey - the first of its kind, to their knowledge - to compare attitudes toward spiritual care across randomly chosen patients, nurses and doctors in oncology departments at four hospitals.The questions were geared toward identifying barriers preventing healthcare professionals from delivering spiritual care, beginning with whether anyone felt it was inappropriate for them to be doing so.The participants' answers indicated that, on the contrary, a majority of providers and patients supported the appropriateness of eight specific examples of spiritual care, such as a doctor or nurse praying with a patient at his or her request or referring the patient to a hospital chaplain.Next, the researchers asked participants to rate previous spiritual care experiences. Again, most ranked these as having a positive impact on care. A fourth possibility offered to nurses and doctors was lack of time."Indeed we found that on average 73 percent reported time to be a significant barrier to spiritual care provision to patients," Balboni told Reuters Health in an email.But those who noted insufficient time as a problem provided spiritual care just as often as those who reported having enough time. That suggested time was not an issue after all, she added.In fact, a lack of training stood out as the biggest barrier to providing spiritual care in this small study.Only 13 percent of doctors and nurses reported having ever received spiritual care training.But those who had training were seven to 11 times more likely to provide spiritual care to their patients than those who hadn't been trained.A lack of "models" for training healthcare professionals to tend to patients' spiritual needs seems to be the underlying problem, Balboni told Reuters Health."There are some basic models, but a rigorously developed spiritual care training model has not been established," she said.Ferrell, who leads End-of-Life Nursing Education Consortium workshops, said such small-scale organized training opportunities are drops in the bucket of a huge unmet training need."We can't practice what we don't know," she said. "Physicians and nurses have never been taught to access and respond to spiritual need."In addition to training, the field of spiritual care needs a clear definition, said Dr. Christina Puchalski, director of the George Washington Institute for Spirituality and Health in Washington, D.C."There is quite a bit of controversy about asking only about religion," Puchalski said. "But previous studies have shown that it's not a patient's particular religious denomination that matters, but what gives meaning and purpose in peoples' lives -things such as family, arts, work, nature, yoga and other values."Puchalski, who invented a basic spiritual assessment questionnaire that is in wide use, added that the study could have benefitted by asking patients if nurses and doctors acted compassionately toward them, which is another example of spiritual care.In a country full of diverse cultures, spiritual care may be intimidating to medical workers, but training can help with that, Ferrell said."For example, if we have a patient who says, 'I'm very devout in my faith and I never make decisions without consulting my rabbi,' then we immediately take that into account - perhaps by giving the patient extra time between procedures," she noted."Patients are telling us spiritual care has to be done with greater intention," Ferrell said.

SOURCE: http://bit.ly/Zm7Fey Journal of Clinical Oncology, online December 17, 2012

Patients rarely told about medication errors: study

In what is likely to come as little surprise, a U.S. study has found that patients and their families are rarely told when hospitals make mistakes with their medicines.Most medication mistakes did not harm patients, the researchers said in a report published in Critical Care Medicine, but those that did were more likely to happen in intensive care units (ICUs) - with ICU patients and their families less likely to be told about errors."For the most part, our findings were in keeping with what the existing literature tells us about the where and how of medication errors in a hospital," said Asad Latif, the study's lead author, in an email to Reuters Health."The most surprising finding was what we do about them, at least in the immediate time around when they occur," added Latif, from the Johns Hopkins University School of Medicine in Baltimore.Using a database of about 840,000 voluntarily reported medication errors from 537 U.S. hospitals between 1999 and 2005, the researchers found that ICUs accounted for about 56,000, or 6.6 percent, of the errors. The rest happened in other units of the hospitals.The vast majority of the mistakes - about 98 percent - didn't lead to a patient being harmed.About four percent of the errors in an ICU, however, did harm a patient, compared with about two percent of errors in non-ICU wards. That's not surprising given the fragile condition of ICU patients and the more intensive treatment they receive, the authors noted.Of errors that may have led to patient deaths, 18 occurred in ICUs and 92 in non-ICU areas of the hospital.In both types, errors of omission - failing to give a patient the medication - were most common. Harmful errors most often involved devices like IV lines and mistakes in calculating medication doses.More than half the time, no actions were taken after an error. In fact, only a third of the hospital staff who made the reported mistakes were immediately told about their errors."And the patient and/or their family is immediately informed when an error occurs barely two percent of the time, despite literature supporting full disclosure and their desire to be promptly informed," Latif said.Research has found that instituting a blame-free reporting system in hospitals increases the number of reported mistakes.Still, Latif said it would be premature for patients and their families to be concerned based just on their findings."Studies like this give us the opportunity to find out how we are actually doing, compared to how we think we are doing," he said."They help us discover associations between the outcomes we are interested in and their potential causes and consequences." 

SOURCE: http://bit.ly/RJVVvfa

Alternative Medicine Use High Amoung Children With Chronic Conditions

According to a recent research, children who see specialists for chronic medical conditions are also using complementary medicine at an increased rate.About 71 per cent of pediatric patients attending various specialty clinics at the Stollery Children's Hospital in Edmonton used alternative medicine, while the rate of use at the Children's Hospital of Eastern Ontario in Ottawa was 42 per cent. Nearly 20 per cent of the families who took part in the study said they never told their physician or pharmacist about concurrently using prescription and alternative medicine. Sunita Vohra, a researcher with the Faculty of Medicine & Dentistry at the U of A, was the lead investigator on the study, which was recently published in the peer-reviewed journal Pediatrics. Her co-investigator was W James King from the University of Ottawa. 
"The children in this study are often given prescription medicines," says Vohra, a pediatrician who works in the Department of Pediatrics and the School of Public Health at the U of A."And many of these children used complementary therapies at the same time or instead of taking prescription medicine. We asked families if they would like to talk about the use of alternative medicine, more than 80 per cent of them said, 'yes, please.' "Right now, these families are getting information about alternative medicine from friends, family and the Internet, but a key place they should be getting this information from is their doctor or another member of their health-care team, who would know about possible drug interactions with prescription medicines."Vohra said the study "identified a gap in communications" in dealing with pediatric patients and their families. 
"It's important to get these conversations going with every patient, especially when you consider it's not widely recognized how common it is for children with chronic illnesses to use alternative medicine," says the Alberta Innovates-Health Solutions scholar. "We need to make sure these families are comfortable telling their specialists they are taking other therapies," she said.Right now, Vohra and her colleagues at the U of A have developed curricula for undergraduate medical students about the use of alternative medicine by pediatric patients, which is considered innovative and novel. Ensuring medical students receive information about alternative medicine is key because it arms them with more knowledge about potential interactions with prescription medicine, says Vohra."Considering parents are saying they want this information, we have an obligation to ensure future physicians have the education and resources they need for these conversations," Vohra says.
Source:University of Alberta Faculty of Medicine & Dentistry  
 

Herbal Remedies May Be Used As an Alternative to HRT for Hot Flashes

A new study has suggested recommending herbal and complementary medicines as an alternative to hormone replacement therapy (HRT) for treating postmenopausal symptoms.The review outlines the advantages and limitations of both pharmacological and herbal and complementary treatments for women with postmenopausal symptoms. 
The menopause is defined as the time after a woman's menstrual periods have ceased (12 months after a woman's final menstrual period). It is associated with an estrogen deficiency and can cause an increase in vasomotor symptoms (hot flushes), genitourinary symptoms (vaginal dryness, sexual dysfunction, frequent urinary tract infections, urinary incontinence), and musculoskeletal symptoms (joint pain) as well as sleep and mood disturbance. 
One of the most common menopausal symptoms is hot flushes; approximately two-thirds of postmenopausal women will experience them, and 20% of women can experience them for up to 15 years, states the review. 
Estrogen deficiency can also lead to longer-term health issues such as cardiovascular disease and osteoporosis. While pharmacological agents are available to treat postmenopausal symptoms, many non-pharmacological treatment options are also available. 
HRT is the most effective treatment of hot flushes, improving symptoms in 80 – 90% of women, says the review. However, the author notes that there are possible health risks associated with HRT, such as links to breast cancer, blood clots, stroke, and cardiovascular problems. 
Due to these possible risks, other treatment options may be equally effective, such as behavior modification and herbal and complimentary medicines, says the author. 
The review states that as many as 50 - 75% of postmenopausal women use herbal options to treat hot flushes, and of the complimentary therapies, soy, red clover and black cohosh have been the most investigated. 
Soy is the most common plant containing estrogen, found naturally in food and supplements. Previous research has shown a reduction in hot flush symptoms with soy ranging from 20 - 55%. Red clover, a legume also containing estrogen, and black cohosh, a plant originating from the eastern United States and Canada, have also been reported to ease postmenopausal symptoms. 
The author of the review recommends these herbal treatments as there are no significant adverse side effects associated with them, as long as they are used in women who do not have a personal history of breast cancer, are not at high risk for breast cancer, and are not taking tamoxifen. However, the review notes that herbal medicines are not regulated in many countries, and therefore the contents of a given product may vary from sample to sample. 
Iris Tong, Director of Women's Primary Care at the Women's Medicine Collaborative, The Warren Alpert Medical School of Brown University, Rhode Island, and author of the review said: 
"Up to 75% of women use herbal and complimentary medicines to treat their postmenopausal symptoms. Therefore, it is vitally important for healthcare providers to be aware of and informed about the non-pharmacological therapies available for women who are experiencing postmenopausal symptoms and who are looking for an alternative to HRT." 
TOG's Editor –in-Chief, Jason Waugh said: 
"Postmenopausal symptoms can be very distressing and it is important to review the advantages and limitations of the non-pharmacological treatments available as well as the pharmacological ones. Even simple behavior modification can make a difference to postmenopausal symptoms, including keeping the room temperature cool, wearing layered clothing, relaxation techniques and smoking cessation.
 
 

New Heart Cells Regenerate in Kids

Children and adolescents too generate new heart muscle cells, say researchers. The first ever finding refutes the long-held belief that the human heart grows only after birth and exclusively because existing cells grow larger, thus opening the way to growing new cells to repair injured hearts.The first ever finding refutes the long-held belief that the human heart grows only after birth and exclusively because existing cells grow larger, thus opening the way to growing new cells to repair injured hearts. 
Beginning in 2009, Bernhard Kuhn and his team from the Boston Children's Hospital looked at specimens from healthy human hearts, aged between 0 to 59 years, the journal Proceedings of the National Academy of Sciences reported. 
Using several lab essays, they documented that cells in these hearts were still dividing after birth, significantly expanding the heart cell numbers, according to a Boston statement. 
The cells regenerated at their highest rates during infancy. Regeneration declined after infancy, rose during the adolescent growth spurt, and continued up until around age 20. 
The findings offer the strongest evidence to date that proliferation of cardiomyocytes (cells making up heart muscle) contributes to growth in healthy young human hearts. 
"For more than 100 years, people have been debating whether human heart muscle cells are generated after birth or whether they simply grow larger," Kuhn said.
Source-IANS
 
 

Diet may not impact certain health outcomes in older persons

Eating diets high in sugar and fat may not affect the health outcomes of older adults ages 75 and up, suggesting that placing people of such advanced age on overly restrictive diets to treat their excess weight or other conditions may have little benefit, according to researchers at Penn State and Geisinger Healthcare System.
"Historically people thought of older persons as tiny and frail," said Gordon Jensen, head of the Department of Nutritional Sciences at Penn State, "but that paradigm has changed for many older persons. Currently, 30 percent or more may be overweight, and by 2030, almost 30 percent are projected to be obese, not just overweight. Recent reports even suggest that there may be survival benefits associated with overweight and mild obesity status among the elderly."
"We all know that adverse dietary patterns, such as a Western diet containing high amounts of fat or a diet containing high amounts of refined sugar, both of which may contribute to obesity, are associated with adverse medical conditions and health outcomes for many people, but until now, the health effects of these types of poor diets have not been characterized for people who live to 75 years of age and older," said Pao Ying Hsao, postdoctoral fellow at Penn State.
The team's research is part of a decades-long collaborative study between Penn State and the Geisinger Healthcare System on the effects of nutritional status and diet on the health of more than 20,000 older people living in Pennsylvania. In the current study, the team followed 449 individuals for five years who were on average 76.5 years old at the beginning of the study.
"This is one of the first studies to examine obesity-related health outcomes and dietary patterns in such aged persons," Jensen said.
At study baseline, the team assessed the participants' dietary patterns by calling each of them by telephone four or five times during a 10-month period and asking them about their diets over the previous 24 hours. The participants were categorized as adhering to one of three different dietary patterns. The "sweets and dairy" pattern was characterized by the largest proportions of energy from baked goods, milk, sweetened coffee and tea and dairy-based desserts, and the lowest intakes of poultry. The "health-conscious" pattern was characterized by relatively higher intakes of pasta, noodles, rice, whole fruit, poultry, nuts, fish and vegetables, and lower intakes of fried vegetables, processed meats and soft drinks. The "Western" pattern was characterized by higher intakes of bread, eggs, fats, fried vegetables, alcohol and soft drinks, and the lowest intakes of milk and whole fruit.
Using outpatient electronic medical records, the researchers identified whether the participants developed cardiovascular disease, diabetes mellitus, hypertension (high blood pressure) and metabolic syndrome during the five-year period. They found no relationship between dietary pattern and prevalence of cardiovascular disease, diabetes, metabolic syndrome or mortality in the participants; however, they did find an increased risk of hypertension in people who followed the "sweets and dairy" pattern.
The results appeared in this month's issue of the Journal of Nutrition Health and Aging.
"We don't know if the participants had been following these dietary patterns their entire adult lives, but we suspect they had been because people don't usually change dietary practices all that much," Jensen said. "The results suggest that if you live to be this old, then there may be little to support the use of overly restrictive dietary prescriptions, especially where food intake may already be inadequate. However, people who live on prudent diets all their lives are likely to have better health outcomes."
Source:Penn State 

Scripps Research Institute Scientists Discover Structure of Protein Essential for Quality Control, Nerve Function

Using an innovative approach, scientists at The Scripps Research Institute (TSRI) have determined the structure of Ltn1, a recently discovered “quality-control” protein that is found in the cells of all plants, fungi and animals.Ltn1 appears to be essential for keeping cells’ protein-making machinery working smoothly. It may also be relevant to human neurodegenerative diseases, for an Ltn1 mutation in mice leads to a motor-neuron disease resembling amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease).“To better understand Ltn1’s mechanism of action, we needed to solve its structure, and that’s what we’ve done here,” said TSRI Associate Professor Claudio Joazeiro.“In addition, this project has brought us a set of structural analysis techniques that we can apply to other exciting problems in biology,” said TSRI Professor Bridget Carragher.Joazeiro and Carragher, along with Clint Potter, also a TSRI professor, are senior authors of the new report, which appears in the online Early Edition of the Proceedings of the National Academy of Sciences the week of January 14, 2013.

Links to Neurodegenerative Disease

Ltn1 first turned up on biologists’ radar screens several years ago when a joint Novartis-Phenomix research team noted that mice with an unknown gene mutation were born normal but suffered from progressive paralysis. The scientists dubbed the animals lister mice, because they listed to one side as they walked. Collaborating with Joazeiro, the Novartis team reported in a 2009 paper that the mutated gene normally codes for a type of enzyme known as an E3 ubiquitin ligase, and that the mouse phenotype was due to a neurodegenerative syndrome resembling ALS.In a study published in the journal Nature the following year, Joazeiro and his postdoctoral research associate Mario H. Bengtson found that the enzyme serves as a crucial quality-control manager for the cellular protein-making factories called ribosomes. Occasionally a ribosome receives miscoded genetic instructions and produces certain types of abnormal proteins, known as “nonstop proteins”— jamming the ribosomal machinery like a wrinkled sheet of paper in an office printer. Bengtson and Joazeiro found that Ltn1 fixes jammed ribosomes by tagging nonstop proteins with ubiquitin molecules, thereby marking them for quick destruction by roving cellular garbage-disposers called proteasomes.“The question for us then was, ‘How does Ltn1 do this?’” said Joazeiro.

Pushing the Boundaries of Electron Microscopy

To help find out, he began a collaboration with Carragher and Potter, who run the National Resource for Automated Molecular Microscopy (NRAMM), an advanced electron microscope facility at TSRI that is funded by the National Institutes of Health’s National Center for Research Resources.Ltn1 was deemed too large for its structure to be determined by current nuclear magnetic resonance (NMR) technology, and, as the scientists know now, too flexible to allow the highly regular crystalline packing needed by X-ray crystallographers. “It’s a very floppy molecule, so it would be hard to crystallize,” said Potter.Advanced electron microscopy offered a way, however. Dmitry Lyumkis, a graduate student in the NRAMM laboratory and first author of the study, took high-resolution images of yeast Ltn1 with an electron microscope. He then used sophisticated image and data processing software to align and average individual images. The technique eliminates much of the random “noise” that obscures single images and produces a sharp 3D picture of the protein.No one has ever used electron microscopy to distinguish so many—more than 20—conformations of such a small protein. “Usually electron microscopists determine no more than two or three conformational states, and they work with protein complexes whose size is in the megadalton range, but Ltn1 is only 180 kilodaltons, an order of magnitude smaller,” Lyumkis said.

An Unusually Flexible Structure

The analysis revealed that Ltn1 has an elongated, double-jointed and extraordinarily flexible structure with two working ends—the N-terminus and C-terminus. “We anticipate that the N-terminus is responsible for association with the ribosome and know that the C-terminus is responsible for the ubiquitylation of nonstop proteins,” said Lyumkis. “We suspect that the high flexibility of this structure is needed for it to work on the variety of nonstop proteins that can get stuck in ribosomes.”One of the next steps for the team is to evaluate Ltn1’s individual segments, which appear to be more rigid, using X-ray crystallography, in order to develop a piece-by-piece atomic-resolution model of the enzyme. Another is to determine the structure of Ltn1 when it is attached to a ribosome and operating on a nonstop protein. Joazeiro notes that a typical yeast cell has nearly 200,000 ribosomes but requires only 200 Ltn1 copies for adequate quality control under normal growth conditions. “Somehow this enzyme can efficiently sense which ribosomes are jammed, and we expect that by solving the joint structure of Ltn1 and a ribosome, we’ll be able to understand how it does this,” he says.Lyumkis, Carragher, Potter and their colleagues at NRAMM also plan to use a similar electron microscopy-based approach to find the structures of other important proteins with highly variable “heterogeneous” conformations. “Heterogeneity has been a big challenge,” said Potter, “and being able to collect this large dataset and do all of this data processing successfully has been a critical breakthrough.”Other contributors to the paper, “Single-particle EM reveals extensive conformationalvariability of the Ltn1 E3 ligase,” were Selom K. Doamekpor and Christopher D. Lima at the Sloan–Kettering Institute; Tasha B. Toro and Matthew D. Petroski of the Sanford-Burnham Medical Research Institute; and Mario H. Bengtson and Joong-Won Lee of TSRI.

Source:Scripps Research Institute