Study explores how immune system functions during sleep
November 15, 2016
Science Daily/American Physiological Society (APS)
Researchers have found new insights into sleep’s importance to overall health: it may give the immune system a chance to regroup at a time when the relative risk of infection is low. As the foundation of the human body’s immune system, large quantities of T cells—a type of white blood cell—are present in the bloodstream and are ready to attack viruses and other pathogens that invade the body.
T cells are a type of white blood cells and are the foundation of the human body's immune system. Large quantities of T cells are present in the bloodstream and are ready to attack viruses and other pathogens that invade the body. Even during a deep resting phase, the body is able to release T cells, growth hormones and epinephrine back into circulation to fight pathogens when needed. Researchers conducted a "sleep-wake" study to determine how lack of sleep affects the immune system.
Fourteen young male volunteers with an average age of 25 participated in two 24-hour (8 p.m. to 8 p.m.) studies. In one study, the volunteers were allowed to sleep between 11 p.m. and 7 a.m. During the other study, the men were kept awake for 24 hours. Blood samples were taken from each volunteer at varying intervals (90 minutes to three hours) throughout each 24-hour period.
Among the sleeping group, all measured T cell subsets were reduced within three hours of falling asleep. However, T cell numbers remained high in subjects who were not allowed to sleep. While the research showed that the T cells left the bloodstream, where they went is a mystery. "It is an unsolved question as to where the cells are redistributed during sleep since we cannot follow their migratory route in healthy humans. … There are some hints from previous studies that these cells accumulate in lymph nodes during sleep," the researchers wrote.
The rapid drop in circulating T cells during sleep "show[s] that even one night without sleep affects the adaptive immune system," says first author Luciana Besedovsky. "This … might be one reason why regular sleep is so important for general health."
https://www.sciencedaily.com/releases/2016/11/161115132547.htm
This is your brain on God: Spiritual experiences activate brain reward circuits
November 29, 2016
Science Daily/University of Utah Health Sciences
Religious and spiritual experiences activate the brain reward circuits in much the same way as love, sex, gambling, drugs and music, report researchers.
https://images.sciencedaily.com/2016/11/161129085014_1_540x360.jpg
An fMRI scan shows regions of the brain that become active when devoutly religious study participants have a spiritual experience, including a reward center in the brain, the nucleus accumbens.
Credit: Jeffrey Anderson
"We're just beginning to understand how the brain participates in experiences that believers interpret as spiritual, divine or transcendent," says senior author and neuroradiologist Jeff Anderson. "In the last few years, brain imaging technologies have matured in ways that are letting us approach questions that have been around for millennia."
Specifically, the investigators set out to determine which brain networks are involved in representing spiritual feelings in one group, devout Mormons, by creating an environment that triggered participants to "feel the Spirit." Identifying this feeling of peace and closeness with God in oneself and others is a critically important part of Mormons' lives -- they make decisions based on these feelings; treat them as confirmation of doctrinal principles; and view them as a primary means of communication with the divine.
During fMRI scans, 19 young-adult church members -- including seven females and 12 males -- performed four tasks in response to content meant to evoke spiritual feelings. The hour-long exam included six minutes of rest; six minutes of audiovisual control (a video detailing their church's membership statistics); eight minutes of quotations by Mormon and world religious leaders; eight minutes of reading familiar passages from the Book of Mormon; 12 minutes of audiovisual stimuli (church-produced video of family and Biblical scenes, and other religiously evocative content); and another eight minutes of quotations.
During the initial quotations portion of the exam, participants -- each a former full-time missionary -- were shown a series of quotes, each followed by the question "Are you feeling the spirit?" Participants responded with answers ranging from "not feeling" to "very strongly feeling."
Researchers collected detailed assessments of the feelings of participants, who, almost universally, reported experiencing the kinds of feelings typical of an intense worship service. They described feelings of peace and physical sensations of warmth. Many were in tears by the end of the scan. In one experiment, participants pushed a button when they felt a peak spiritual feeling while watching church-produced stimuli.
"When our study participants were instructed to think about a savior, about being with their families for eternity, about their heavenly rewards, their brains and bodies physically responded," says lead author Michael Ferguson, who carried out the study as a bioengineering graduate student at the University of Utah.
Based on fMRI scans, the researchers found that powerful spiritual feelings were reproducibly associated with activation in the nucleus accumbens, a critical brain region for processing reward. Peak activity occurred about 1-3 seconds before participants pushed the button and was replicated in each of the four tasks. As participants were experiencing peak feelings, their hearts beat faster and their breathing deepened.
In addition to the brain's reward circuits, the researchers found that spiritual feelings were associated with the medial prefrontal cortex, which is a complex brain region that is activated by tasks involving valuation, judgment and moral reasoning. Spiritual feelings also activated brain regions associated with focused attention.
"Religious experience is perhaps the most influential part of how people make decisions that affect all of us, for good and for ill. Understanding what happens in the brain to contribute to those decisions is really important," says Anderson, noting that we don't yet know if believers of other religions would respond the same way. Work by others suggests that the brain responds quite differently to meditative and contemplative practices characteristic of some eastern religions, but so far little is known about the neuroscience of western spiritual practices.
The study is the first initiative of the Religious Brain Project, launched by a group of University of Utah researchers in 2014, which aims to understand how the brain operates in people with deep spiritual and religious beliefs.
https://www.sciencedaily.com/releases/2016/11/161129085014.htm
It's all in the eyes: Women and men really do see things differently
November 28, 2016
Science Daily/University of Queen Mary London
Women and men look at faces and absorb visual information in different ways, which suggests there is a gender difference in understanding visual cues, according to a team of scientists.
https://images.sciencedaily.com/2016/11/161128121211_1_540x360.jpg
This study is the first demonstration of a clear gender difference in how men and women look at faces.
Credit: © puhhha / Fotolia
The researchers used an eye tracking device on almost 500 participants at the Science Museum over a five-week period to monitor and judge how much eye contact they felt comfortable with while looking at a face on a computer screen.
They found that women looked more at the left-hand side of faces and had a strong left eye bias, but that they also explored the face much more than men. The team observed that it was possible to tell the gender of the participant based on the scanning pattern of how they looked at the face with nearly 80 per cent accuracy. Given the very large sample size the researchers suggest this is not due to chance.
Lead author Dr Antoine Coutrot from QMUL's School of Biological and Chemical Sciences said: "This study is the first demonstration of a clear gender difference in how men and women look at faces.
"We are able to establish the gender of the participant based on how they scan the actors' face, and can eliminate that it isn't based on the culture of the participant as nearly 60 nationalities have been tested. We can also eliminate any other observable characteristics like perceived attractiveness or trustworthiness."
The participants were asked to judge how comfortable the amount of eye contact they made with the actor in a Skype-like scenario. Each participant saw the same actor (there were eight in total) during the testing period, which was around 15 minutes. At the end of the session the researchers collected personality information about the participants through questionnaires.
Co-author Dr Isabelle Mareschal also from QMUL's School of Biological and Chemical Sciences added: "There are numerous claims in popular culture that women and men look at things differently -- this is the first demonstration, using eye tracking, to support this claim that they take in visual information in different ways."
The team describe their findings in the Journal of Vision and suggest the gender difference in scanning visual information might impact many research fields, such as autism diagnosis or even everyday behaviours like watching a movie or looking at the road while driving.
The research was funded by the Leverhulme Trust and EPSRC and involved researchers from University College London and University of Nottingham.
https://www.sciencedaily.com/releases/2016/11/161128121211.htm
Can creativity beat death? New study suggests creatives worry less about dying
December 1, 2016
Science Daily/University of Kent
Creative people, such as newly-announced Nobel Prize for Literature winner Bob Dylan, are often thought to be motivated by the desire to leave an enduring cultural legacy. Through their creative work, creatives such as Leonard Cohen and David Bowie continue to live on in our culture even after passing away.
https://images.sciencedaily.com/2016/12/161201114420_1_540x360.jpg
The findings of this study suggest that those who pursue creativity and produce significant creative contributions may benefit from existential security in the face of death.
Credit: © murika / Fotolia
Creative achievement can provide a buffer against being anxious about death, research from psychologists at the University of Kent shows.
Creative people, such as newly-announced Nobel Prize for Literature winner Bob Dylan, are often thought to be motivated by the desire to leave an enduring cultural legacy. Through their creative work, creatives such as Leonard Cohen and David Bowie continue to live on in our culture even after passing away.
Conversely, the destruction of ancient monuments and artefacts in Iraq in 2015 by members of Islamic State could be interpreted as a symbolic act aimed at achieving high negative impact on society through the destruction of a cultural legacy.
Now research, conducted by Rotem Perach, a postgraduate researcher at Kent's School of Psychology under the supervision of Dr Arnaud Wisman, shows that those with high levels of creative ambition and achievement are particularly likely to be more resilient to death concerns.
In what is thought to be the first empirical study of the anxiety-buffering functions of creativity among people for whom creativity constitutes a central part of their cultural worldview, the research analysed findings from a group of 108 students.
The students completed two questionnaires to gauge their level of creative achievement and creative ambition. Those with a record of creative achievement, coupled to high levels of creative ambition, were found to make less death associations in their thought processes after thinking about their own demise in comparison to those in the control condition.
In comparison, among those with low levels of creative ambition -- whatever their record of creative achievement -- thinking about their own mortality did not affect their levels of death-thought accessibility in comparison to controls.
The findings suggest that those who pursue creativity and produce significant creative contributions may benefit from existential security in the face of death.
https://www.sciencedaily.com/releases/2016/12/161201114420.htm
Psychological well-being and physical activity in older adults
December 2, 2016
Science Daily/Chapman University
New findings showed associations between psychological well-being and physical activity in adults ages 50 and older.
"Researchers have long studied how physical activity can lead to improved mood and feelings of well-being," says Julia Boehm, Ph.D., and lead author on the study, "however, less well understood is whether being happy and optimistic might actually encourage a person to be physically active."
Physical activity is a key health behavior linked to better physical and mental functioning, as well as reduced risk of the leading causes of death including cancer and heart disease. Further, psychological well-being is associated with reduced risk of cardiovascular disease, cognitive decline, and mortality. Psychological well-being may be linked with improved health because happier people may be more likely to engage in physical activity.
Rates of physical activity are relatively low among middle-aged adults and decline further in older adulthood -- worsening substantially after age 75 -- so a key challenge is to identify not only modifiable factors that reduce the likelihood of declining activity levels, but also factors that contribute to the initiation and maintenance of physical activity in older age. Interventions that increase the number of people who are physically active may reduce the burden of poor health later in life.
"What we wanted to do in this study was to assess psychological well-being before assessing physical activity to determine if happier adults are more likely to exercise than their less happy peers," said Dr. Boehm.
During the 11-year study, participants were asked about the frequency and intensity of their physical activity both at work and during leisure time and then classified into categories of sedentary activity, low activity, moderate activity, and high activity.
The researchers found that higher psychological well-being at the start of the study was associated with greater levels of physical activity across more than a decade. Moreover, people at the start of the study who had high levels of psychological well-being and who were also physically active initially were less likely to become inactive over time.
"These findings have implications for health care as medical professionals often have difficulty persuading adults to increase physical activity," noted Dr. Boehm. "Results from this study suggest that higher levels of psychological well-being may precede increased physical activity; therefore, it is possible that psychological well-being could be a novel way of not only enhancing psychological health but also increasing physical activity -- which in turn could improve the physical health of a large segment of people in an aging society."
The study included 9,986 English adults over the age of 50 who were assessed up to six times across an average of 11 years. The average age of participants was 63.7 years, with 55 percent of participants being women, and 97 percent of the sample identifying as White.
The paper, called Maintaining Healthy Behavior: a Prospective Study of Psychological Well-Being and Physical Activity, is published in the journal Annals of Behavioral Medicine. Authors were: Dr. Julia Boehm of Chapman University; Eric Kim, Ph.D., Laura Kubzansky, Ph.D, and Jackie Soo, Ph.D., all of Harvard T. H. Chan School of Public Health.
https://www.sciencedaily.com/releases/2016/12/161202101114.htm
Stress-hormone differences identified among gay men
December 3, 2016
Science Daily/New York University
Increased stigma and discrimination can affect circadian HPA-axis functioning, say researchers. The majority of previous studies have been conducted among white heterosexuals, with very little research examining HPA-axis functioning between different minorities. Individuals who identify as both sexual and racial minorities may experience increased stigma and discrimination that can affect this HPA-axis functioning. Now, researchers have examined differences in diurnal cortisol rhythm between young, self-identified, white gay men and black gay men.
Cortisol is a life sustaining adrenal hormone essential to maintaining the natural balance of the body. It is often referred to as "the stress hormone," as cortisol influences, regulates, and modulates many of the changes that occur in the body in response to stress.
Diurnal cortisol studies measure the level of cortisol in the body at various times during the day to examine possible adrenal imbalances. The majority of these diurnal cortisol studies have been conducted among white heterosexuals, with very little research examining HPA-axis functioning between different minorities. However, individuals who identify as both sexual and racial minorities may experience increased stigma and discrimination that can affect this HPA-axis functioning.
To address this need for more expansive research, investigators at the College of Global Public Health (CGPH) Center for Health Identity Behavior & Prevention Studies (CHIBPS), led by Stephanie H. Cook, DrPH, conducted a study, "Cortisol profiles differ by race/ethnicity among young sexual minority men" published in the journal Psychoneuroendocrinology, examining differences in diurnal cortisol rhythm between young, self-identified, white gay men (WGM) and black gay men (BGM).
In the study of healthy men (n=68) with a mean age of twenty-three, Dr. Cook and colleagues utilized a daily diary research design which consisted of researchers collecting four saliva samples daily for five days to measure their cortisol levels at different times of day throughout the week.
"Sexual minorities are more likely to experience discrimination based on their sexual orientation compared to heterosexual individuals," said Dr. Cook. "Recent research shows that sexual orientation-related stress and stigma can modulate HPA-axis reactivity among sexual minority individuals compared to heterosexual individuals."
The research data showed a flattened diurnal cortisol curve between BGM to WGM, with statistically significant differences found in bedtime levels of cortisol. In the current study, the observed flattened diurnal pattern observed among BGM combined with their elevated evening levels suggests less daily variation in cortisol that may be indicative of an unhealthy stress response among BGM.
While beyond the scope of the current analysis, these findings suggest that social factors associated with being a 'double minority' may differentially calibrate circadian HPA-axis functioning in BGM compared to WGM.
"We must conduct additional studies to confirm these study findings because in the current study we cannot make definitive conclusions about our 'double minority' hypothesis because we did not have a majority Black referent group," cautions Dr. Cook. "However, with this being said, we believe this research study presents a first step in understanding differences in the HAP axis functioning among racial/ethnic and sexual minority men."
The current study expands on previous research indicating that those individuals at the intersection of multiple stigmatized identities may indeed experience distinct diurnal cortisol profiles which should be explored further.
"The results of the present study expand health disparities research that has often focused solely on race/ethnic differences by using approaches that assess intersecting identities, which is the cornerstone of the work we undertake at CHIBPS," said Dr. Cook. "This study highlights these disparities and calls for further research on these topics."
https://www.sciencedaily.com/releases/2016/12/161203154538.htm
Short-term sleep deprivation affects heart function
December 2, 2016
Science Daily/Radiological Society of North America
Too little sleep takes a toll on your heart, according to a new study to be presented today at the annual meeting of the Radiological Society of North America (RSNA).
People who work in fire and emergency medical services, medical residencies and other high-stress jobs are often called upon to work 24-hour shifts with little opportunity for sleep. While it is known that extreme fatigue can affect many physical, cognitive and emotional processes, this is the first study to examine how working a 24-hour shift specifically affects cardiac function.
"For the first time, we have shown that short-term sleep deprivation in the context of 24-hour shifts can lead to a significant increase in cardiac contractility, blood pressure and heart rate," said study author Daniel Kuetting, M.D., from the Department of Diagnostic and Interventional Radiology at the University of Bonn in Bonn, Germany.
For the study, Dr. Kuetting and colleagues recruited 20 healthy radiologists, including 19 men and one woman, with a mean age of 31.6 years. Each of the study participants underwent cardiovascular magnetic resonance (CMR) imaging with strain analysis before and after a 24-hour shift with an average of three hours of sleep.
"Cardiac function in the context of sleep deprivation has not previously been investigated with CMR strain analysis, the most sensitive parameter of cardiac contractility," Dr. Kuetting said.
The researchers also collected blood and urine samples from the participants and measured blood pressure and heart rate.
Following short-term sleep deprivation, the participants showed significant increases in mean peak systolic strain (pre = -21.9; post = -23.4), systolic (112.8; 118.5) and diastolic (62.9; 69.2) blood pressure and heart rate (63.0; 68.9). In addition, the participants had significant increases in levels of thyroid stimulating hormone (TSH), thyroid hormones FT3 and FT4, and cortisol, a hormone released by the body in response to stress.
Although the researchers were able to perform follow-up examinations on half of the participants after regular sleep, Dr. Kuetting notes that further study in a larger cohort is needed to determine possible long-term effects of sleep loss.
"The study was designed to investigate real-life work-related sleep deprivation," Dr. Kuetting said. "While the participants were not permitted to consume caffeine or food and beverages containing theobromine, such as chocolate, nuts or tea, we did not take into account factors like individual stress level or environmental stimuli."
As people continue to work longer hours or work at more than one job to make ends meet, it is critical to investigate the detrimental effects of too much work and not enough sleep. Dr. Kuetting believes the results of this pilot study are transferable to other professions in which long periods of uninterrupted labor are common.
"These findings may help us better understand how workload and shift duration affect public health," he said.
https://www.sciencedaily.com/releases/2016/12/161202100943.htm
Avoiding spiritual struggles and existential questions is linked with poorer mental health
December 5, 2016
Science Daily/Case Western Reserve University
Fear of confronting the tensions and conflicts brought on by existential concerns—the “big questions” of life—is linked with poorer mental health, including higher levels of depression, anxiety and difficulty regulating emotions, according to a new study.
"Religious and spiritual struggles -- conflicts with God or religious people, tough questions about faith, morality, and the meaning of life -- these are often taboo topics, and the temptation to push them away is strong," said Julie Exline, professor of psychological sciences at Case Western Reserve and co-author of the research.
"When people avoid these struggles, anxiety and depression tend to be more intense than if they faced these struggles head-on."
People who more fully embrace these struggles with fundamental beliefs and values report better mental health than those who don't, Exline added.
The study, based on a survey of 307 adults about recent life experiences, was published in the Journal of Contextual Behavioral Science.
Among the study's findings:
An unwillingness to accept spiritual struggle could contribute to major social ills, leading to lost opportunities to engage with people of different faith beliefs and backgrounds and come to view them as threatening.
"This avoidance may lead to the rejection of whole groups of people based on their religious differences or perceived incongruence between, for example, their sexuality or gender-based identity and religious teachings," Exline said.
Mental health providers may find it useful to help clients with spiritual struggles face their difficulties in a more proactive way.
"People seem to be more emotionally healthy if they're able to accept troubling thoughts," Exline said. "Looking at spiritual doubts in an objective way seems to help. You may or may not work through them, but at least you can tolerate having them."
Avoidance itself is not a problem; rather, the behavior can become problematic when escaping becomes harmful or contrary to personal goals and sets a rigid pattern of experiencing and responding to the world.
"Regular spiritual avoidance can make it difficult to identify, work toward or experience the qualities that lend a sense of purpose to life," she said.
Using emotional and cognitive energy to push thoughts away will not stop them from continuing to intrude over time.
"Continually being re-visited by these thoughts can create strains on emotional health, especially if a person sees this kind of questioning as morally unacceptable and dangerous," Exline said.
https://www.sciencedaily.com/releases/2016/12/161205111017.htm
Direct link between REM sleep loss, desire for sugary and fatty foods discovered
December 6, 2016
Science Daily/University of Tsukuba
A new method has been used by researchers to produce REM sleep loss in mice along with a chemical-genetic technique to block prefrontal cortex neurons and the behaviors they mediate. As a result, the researchers discovered that inhibiting these neurons reversed the effect of REM sleep loss on sucrose consumption while having no effect on fat consumption.
https://images.sciencedaily.com/2016/12/161206110327_1_540x360.jpg
The medial prefrontal cortex may play a direct role in controlling our desire to consume weight promoting foods, high in sucrose content, when we are lacking sleep.
Credit: © iuricazac / Fotolia
It is not well understood what role sleep loss plays in affecting areas of the brain that control the desire to consume unhealthy foods. A new paper published on December 6 in the journal eLife finds that rapid eye movement (REM) sleep loss leads to increased consumption of unhealthy foods, specifically sucrose and fat. The researchers at the University of Tsukuba's International Institute for Integrative Sleep Medicine (IIIS) used a new method to produce REM sleep loss in mice along with a chemical-genetic technique to block prefrontal cortex neurons and the behaviors they mediate. As a result, the IIIS researchers discovered that inhibiting these neurons reversed the effect of REM sleep loss on sucrose consumption while having no effect on fat consumption.
REM sleep is a unique phase of sleep in mammals that is closely associated with dreaming and characterized by random eye movement and almost complete paralysis of the body. The prefrontal cortex plays a role in judging the palatability of foods through taste, smell and texture. Moreover, persons who are obese tend to have increased activity in the prefrontal cortex when exposed to high calorie foods. "Our results suggest that the medial prefrontal cortex may play a direct role in controlling our desire to consume weight promoting foods, high in sucrose content, when we are lacking sleep," says Kristoph
https://www.sciencedaily.com/releases/2016/12/161206110327.htm
Missing 1-2 hours of sleep doubles crash risk Study reveals the dangers of getting less than 7 hours of sleep
December 6, 2016
Science Daily/AAA
Drivers who miss one to two hours of sleep nearly double their risk for a crash, new research concludes. Drivers who sleep slightly less -- between four and five hours -- have the same risk of crashing that is associated with driving over the legal limit for alcohol.
https://images.sciencedaily.com/2016/12/161206110235_1_540x360.jpg
Drivers missing 2-3 hours of sleep in a 24-hour period more than quadrupled their risk of a crash compared to drivers getting the recommended seven hours of sleep. This is the same crash risk the National Highway Traffic Safety Administration associates with driving over the legal limit for alcohol.
Credit: AAA
"You cannot miss sleep and still expect to be able to safely function behind the wheel," said Dr. David Yang, executive director for the AAA Foundation for Traffic Safety. "Our new research shows that a driver who has slept for less than five hours has a crash risk comparable to someone driving drunk."
The AAA Foundation for Traffic Safety's report, Acute Sleep Deprivation and Risk of Motor Vehicle Crash Involvement, reveals that drivers missing 2-3 hours of sleep in a 24-hour period more than quadrupled their risk of a crash compared to drivers getting the recommended seven hours of sleep. This is the same crash risk the National Highway Traffic Safety Administration associates with driving over the legal limit for alcohol.
The AAA Foundation report found that in a 24-hour period, crash risk for sleep-deprived drivers increased steadily when compared to drivers who slept the recommended seven hours or more:
• Six to seven hours of sleep: 1.3 times the crash risk
• Five to six hours of sleep: 1.9 times the crash risk
• Four to five hours of sleep: 4.3 times the crash risk
• Less than four hours of sleep: 11.5 times the crash risk
While 97 percent of drivers told the AAA Foundation they view drowsy driving as a completely unacceptable behavior that is a serious threat to their safety, nearly one in three admit that at least once in the past month they drove when they were so tired they had a hard time keeping their eyes open.
"Managing a healthy work-life balance can be difficult and far too often we sacrifice our sleep as a result," said Jake Nelson, director of Traffic Safety Advocacy and Research for AAA. "Failing to maintain a healthy sleep schedule could mean putting yourself or others on the road at risk."
Symptoms of drowsy driving can include having trouble keeping eyes open, drifting from lanes or not remembering the last few miles driven. However, more than half of drivers involved in fatigue-related crashes experienced no symptoms before falling asleep behind the wheel. AAA urges drivers to not rely on their bodies to provide warning signs of fatigue and should instead prioritize getting plenty of sleep (at least seven hours) in their daily schedules. For longer trips, drivers should also:
• Travel at times when normally awake
• Schedule a break every two hours or every 100 miles
• Avoid heavy foods
• Travel with an alert passenger and take turns driving
• Avoid medications that cause drowsiness or other impairment
The AAA Foundation report is based on the analysis of a representative sample of 7,234 drivers involved in 4,571 crashes. All data is from the NHTSA's National Motor Vehicle Crash Causation Survey which comprised a representative sample of police-reported crashes that involved at least one vehicle that was towed from the scene and resulted in emergency medical services being dispatched to the scene.
https://www.sciencedaily.com/releases/2016/12/161206110235.htm
Sleeping brain's complex activity mimicked by simple model
New mathematical model could improve understanding of memory consolidation during deep sleep
September 1, 2016
Science Daily/PLOS
Researchers have built and tested a new mathematical model that successfully reproduces complex brain activity during deep sleep, according to a new study.
Recent research has shown that certain patterns of neuronal activity during deep sleep may play an important role in memory consolidation. Michael Schellenberger Costa and Arne Weigenand of the University of Lübeck, Germany, and colleagues set out to build a computational model that could accurately mimic these patterns.
The researchers had previously modeled the activity of the sleeping cortex, the brain's outer layer. However, sleep patterns thought to aid memory arise from interactions between the cortex and the thalamus, a central brain structure. The new model incorporates this thalamocortical coupling, enabling it to successfully mimic memory-related sleep patterns.
Using data from a human sleep study, the researchers confirmed that their new model accurately reproduces brain activity measured by electroencephalography (EEG) during the second and third stages of non-rapid eye movement (NREM) sleep. It also successfully predicts the EEG effects of stimulation techniques known to enhance memory consolidation during sleep.
The new model is a neural mass model, meaning that it approximates and scales up the behavior of a small group of neurons in order to describe a large number of neurons. Compared with other sleep models, many of which are based on the activity of individual neurons, this new model is relatively simple and could aid in future studies of memory consolidation.
"It is fascinating to see that a model incorporating only a few key mechanisms is sufficient to reproduce the complex brain rhythms observed during sleep," say senior authors Thomas Martinetz
How 'super aging' older adults retain youthful memory abilities
September 13, 2016
Science Daily/Massachusetts General Hospital
Some loss of memory is often considered an inevitable part of aging, but new research reveals how some people appear to escape that fate.
The study published in The Journal of Neuroscience is the first step in a research program aimed at understanding how some older adults retain youthful thinking abilities and the brain circuits that support those abilities. The program is led by Bradford Dickerson, MD, director of the Frontotemporal Disorders Unit in the MGH Department of Neurology and Lisa Feldman Barrett, PhD, MGH Department of Psychiatry, who are co-senior authors of the new study.
While most older adults experience a gradual decline in memory ability, some researchers have described older adults -- sometimes called "super agers" -- with unusually resilient memories. For the current study, the MGH team enrolled adults ages 60 to 80 -- 17 of whom performed as well as adults four to five decades younger on memory tests, and 23 with normal results for their age group -- and 41 young adults ages 18 to 35.
"Previous research on super aging has compared people over age 85 to those who are middle aged," says Alexandra Touroutoglou, PhD, MGH Neurology, co-senior author with Dickerson and Barrett. "Our study is exciting because we focused on people around or just after typical retirement age -- mostly in their 60s and 70s -- and investigated those who could remember as well as people in their 20s.
Imaging studies revealed that these super agers had brains with youthful characteristics. While the cortex -- the outermost sheet of brain cells that is critical for many thinking abilities -- and other parts of the brain typically shrink with aging, in the brains of super-agers a number of those regions were comparable in size to those of young adults. "We looked at a set of brain areas known as the default mode network, which has been associated with the ability to learn and remember new information, and found that those areas, particularly the hippocampus and medial prefrontal cortex, were thicker in super agers than in other older adults. In some cases, there was no difference in thickness between super agers and young adults," Touroutoglou says.
Barrett, who is also University Distinguished Professor at Northeastern University, adds, "We also examined a group of regions known as the salience network, which is involved in identifying information that is important and needs attention for specific situations, and also found preserved thickness among super-agers in several regions, including the anterior insula and orbitofrontal cortex."
Critically, the researchers showed not only that super-agers had no shrinkage in these brain networks but also that the size of these regions was correlated with memory ability. One of the strongest correlations between brain size and memory was found in an area at the intersection of the salience and default mode networks. Previous research has shown that this region -- the para-midcingulate cortex -- is an important hub that allows different brain networks to communicate efficiently. "We believe that effective communication between these networks is very important for healthy cognitive aging," Touroutoglou says.
Understanding which factors protect against memory decline could lead to important advances in preventing and treating age-related memory loss and possibly even various forms of dementia, says Dickerson, who is an associate professor of Neurology at Harvard Medical School. "We desperately need to understand how some older adults are able to function very well into their seventh, eight, and ninth decades. This could provide important clues about how to prevent the decline in memory and thinking that accompanies aging in most of us."
Science Daily/SOURCE : https://www.sciencedaily.com/releases/2016/09/160913173303.htm
Brain benefits of aerobic exercise lost to mercury exposure
September 16, 2016
Science Daily/NIH/National Institute of Environmental Health Sciences
Cognitive function improves with aerobic exercise, but not for people exposed to high levels of mercury before birth, according to new research.
Adults with high prenatal exposure to methylmercury, which mainly comes from maternal consumption of fish with high mercury levels, did not experience the faster cognitive processing and better short term memory benefits of exercise that were seen in those with low prenatal methylmercury exposures.
This is one of the first studies to examine how methylmercury exposure in the womb may affect cognitive function in adults. Mercury comes from industrial pollution in the air that falls into the water, where it turns into methylmercury and accumulates in fish. The scientists, based at the Harvard T.H. Chan School of Public Health, suspect that prenatal exposure to methylmercury, known to have toxic effects on the developing brain and nervous system, may limit the ability of nervous system tissues to grow and develop in response to increased aerobic fitness.
"We know that neurodevelopment is a delicate process that is especially sensitive to methylmercury and other environmental toxins, but we are still discovering the lifelong ripple effects of these exposures," said Gwen Collman, Ph.D., director of the NIEHS Division of Extramural Research and Training. "This research points to adult cognitive function as a new area of concern.."
The 197 study participants are from the Faroe Islands, 200 miles north of England, where fish is a major component of the diet. Their health has been followed since they were in the womb in the late 1980s. At age 22, this subset of the original 1,022 participants took part in a follow-up exam that included estimating the participants' VO2 max, or the rate at which they can use oxygen, which increases with aerobic fitness. Also, a range of cognitive tests were performed related to short-term memory, verbal comprehension and knowledge, psychomotor speed, visual processing, long-term storage and retrieval, and cognitive processing speed.
Overall, the researchers found that higher VO2 max values were associated with better neurocognitive function, as expected based on prior research. Cognitive efficiency, which included cognitive processing speed and short term memory, benefitted the most from increased VO2 max.
But when the researchers divided the participants into two groups based on the methylmercury levels in their mothers while they were pregnant, they found that these benefits were confined to the group with the lowest exposure. Participants with prenatal methylmercury levels in the bottom 67 percent, or levels of less than 35 micrograms per liter in umbilical cord blood, still demonstrated better cognitive efficiency with higher VO2 max. However, for participants with higher methylmercury levels, cognitive function did not improve as VO2 max increased.
"We know that aerobic exercise is an important part of a healthy lifestyle, but these findings suggest that early-life exposure to pollutants may reduce the potential benefits," added Collman. "We need to pay special attention to the environment we create for pregnant moms and babies."
The U.S. Food and Drug Administration recommends that children and women of childbearing age eat two to three weekly servings of fish low in mercury as part of a healthy diet. Low mercury fish include salmon, shrimp, pollock, canned light tuna, tilapia, catfish, and cod. Four types of fish should be avoided because of typically high mercury levels -- tilefish from the Gulf of Mexico, shark, swordfish, and king mackerel.
The findings were published Sept. 9 in the journal Environmental Health Perspectives. In addition to NIH funding, the research was supported by the Danish Council for Strategic Research, Programme Commission on Health, Food, and Welfare.
Science Daily/SOURCE :https://www.sciencedaily.com/releases/2016/09/160916120631.htm
How the brain consolidates memories during sleep
October 5, 2016
Science Daily/Ruhr-Universitaet-Bochum
Researchers have studied which brain processes consolidate memories during sleep. They found clear parallels to findings from experimental animal studies.
https://images.sciencedaily.com/2016/10/161005083700_1_540x360.jpg
Hui Zhang analysed the EEG data.
Credit: © RUB, Damian Gorczany
Study with epilepsy patients
Axmacher recorded the brain activity of epilepsy patients who had had electrodes implanted in their brains for medical reasons. The researcher had analyzed EEG data from 13 patients that he had recorded at his former workplace, the Bonn University Hospital.
While the researchers recorded the EEG, the patients first viewed a series of landscape images; then they slept. Later the scientists tested which of the images the test subjects had memorized and which not.
Making nerve cells receptive
Postdoctoral researcher Hui Zhang analyzed the data. The preliminary result: During sleep, the same brain activation patterns occurred as when viewing the landscape photos. This reactivation was particularly related to so-called ripple oscillations in the brain.
Ripples are a specific kind of brain activity. A group of interconnected nerve cells sends out signals at high frequency for a short period of time. In the EEG they appear as a characteristic wave form. One theory is: After a ripple event, a brain area is more receptive for long-term storage of reactivated information.
This was also shown by the current analysis of the patient data. After a ripple there was stronger reactivation than during a comparable time period before a ripple.
Mechanism for learning in sleep
"Individual stimuli, in our case landscape images, are reactivated during sleep, and the ripples seem to actively maintain this reactivation," explains Nikolai Axmacher. However, the researchers found this enhancement mechanism only for the reactivation of those images that were recalled during the final test.
In other words: "When a ripple enhances the reactivation, the image is recalled later," says Axmacher. "We are thus apparently dealing with a mechanism for learning in sleep."
Science Daily/SOURCE :https://www.sciencedaily.com/releases/2016/10/161005083700.htm
Exercise may help ward off memory decline
October 19, 2016
Science Daily/American Academy of Neurology
Exercise may be associated with a small benefit for elderly people who already have memory and thinking problems, according to new research. The research involved people with vascular cognitive impairment, which is the second most common cause of dementia after Alzheimer's disease. In vascular cognitive impairment, problems with memory and thinking skills result from damage to large and small blood vessels in the brain.
The research involved people with vascular cognitive impairment, which is the second most common cause of dementia after Alzheimer's disease. In vascular cognitive impairment, problems with memory and thinking skills result from damage to large and small blood vessels in the brain.
"Studies have shown that exercise can help reduce the risk of developing memory problems, but few studies have looked at whether it can help people who already have these problems get better or keep from getting worse," said study author Teresa Liu-Ambrose, PT, PhD, of the University of British Columbia in Vancouver, Canada.
The study involved 70 people with an average age of about 74 who had mild vascular cognitive impairment. Half of the participants took part in one-hour exercise classes three times a week for six months. The other half received information each month about vascular cognitive impairment and a healthy diet, but no information on physical activity.
All of the participants were tested before the study started, at the end of the study and again six months later on their overall thinking skills, executive function skills such as planning and organizing and how well they could complete their daily activities.
Those who exercised had a small improvement on the test of overall thinking skills compared to those who did not exercise. The scores of those who exercised improved by 1.7 points compared to those who did not exercise.
"This result, while modest, was similar to that seen in previous studies testing the use of drugs for people with vascular cognitive impairment," Liu-Ambrose said. "However, the difference was less than what is considered to be a the minimal clinically important difference of three points."
Six months after the participants stopped the exercise program, their scores were no different than those who did not exercise. Also, there was no difference between the two groups at any point on the tests of executive function skills or daily activities.
Those who exercised also improved compared to the other group in their blood pressure and on a test of how far they could walk in six minutes, which measured overall cardiovascular capacity. These findings are also important to note given that high blood pressure is a risk factor for developing vascular cognitive impairment.
Liu-Ambrose said more studies are needed to determine whether exercise can improve thinking abilities in people with mild vascular cognitive impairment. Because the study sample size was based on detecting a difference on the overall thinking skills test, large samples might be needed to detect differences in specific thinking abilities, such as planning, and everyday skills, such as managing one's finances.
Science Daily/SOURCE : https://www.sciencedaily.com/releases/2016/10/161019162748.htm
How even our brains get 'slacker' as we age
October 24, 2016
Science Daily/Newcastle University
Losing the youthful firmness and elasticity in our skin is one of the first outward signs of aging. Now it seems it's not just our skin that starts to sag, but our brains too.
New research from Newcastle University, UK, in collaboration with the Federal University of Rio de Janeiro, investigated the way the human brain folds and how this 'cortical folding' changes with age.
Linking the change in brain folding to the tension on the cerebral cortex -- the outer layer of neural tissue in our brains -- the team found that as we age, the tension on the cortex appears to decrease. This effect was more pronounced in individuals with Alzheimer's disease.
Publishing their findings in the academic journal PNAS, the team say this new research sheds light on the underlying mechanisms which affect brain folding and could be used in the future to help diagnose brain diseases.
Lead author Dr Yujiang Wang, of Newcastle University, explains, "One of the key features of a mammalian brain is the grooves and folds all over the surface -- a bit like a walnut -- but until now no-one has been able to measure this folding in a consistent way.
"By mapping the brain folding of over 1,000 people, we have shown that our brains fold according to a simple universal law. We also show that a parameter of the law, which is interpreted as the tension on the inside of the cortex, decreases with age.
"In Alzheimer's disease, this effect is observed at an earlier age and is more pronounced. The next step will be to see if there is a way to use the changes in folding as an early indicator of disease."
Common in all mammals
The expansion of the cerebral cortex is the most obvious feature of mammalian brain evolution and is generally accompanied by increasing degrees of folding of the cortical surface.
In the average adult brain, for example, if the cortex of one side -- or hemisphere -- was unfolded and flattened out it would have a surface area of about 100,000 mm2, roughly one and a half times the size of a piece of A4 paper.
Previous research has shown that folding of the cortex across mammalian species follows a universal law -- that is, regardless of size and shape, they all fold in the same way.
However, until now there has been no systematic study demonstrating that the same law holds within a species.
Tension slackens with age
"Our study has shown that we can use this same law to study changes in the human brain," explains Dr Wang, based in Newcastle University's world-leading School of Computing Science.
"From this, we identified a parameter that decreases with age, which we interpret as changing the tension on the cortical surface. It would be similar to the skin. As we age, the tension drops and the skin starts to slacken.
"It has long been known that the size and thickness of the cortex changes with age but the existence of a general law for folding shows us how to combine these quantities into a single measure of folding that can then be compared between genders, age groups and disease states."
Women's brains less folded
The team also found that male and female brains differ in size, surface area, and the degree of folding. Indeed, female brains tend to be slightly less folded than male brains of the same age. Despite this, male and female brains are shown to follow exactly the same law.
"This indicates that for the first time, we have a consistent way of quantifying cortical folding in humans," says Dr Wang.
Throughout the lifespan of healthy individuals, cortical folding changes in the same way in both men and women but in those with Alzheimer's disease the change in the brain folding was significantly different.
She adds: "More work is needed in this area but it does suggest that the effect Alzheimer's disease has on the folding of the brain is akin to premature aging of the cortex."
Science Daily/SOURCE :https://www.sciencedaily.com/releases/2016/10/161024161648.htm
Early supplementation may help offset early-life stress on the adult brain
October 26, 2016
Science Daily/Federation of American Societies for Experimental Biology
Early-life stress has been shown to impair learning and memory in later life, but new research suggests that improved nutrition may help offset the negative effects of this stress. Specifically, using mice, scientists focused on essential micronutrients, including methionine, vitamins B6 and B12, and folic acid, none of which are made by the body and need to be ingested through diet. They found that early-life stress reduces the levels of these nutrients in mouse pups, but supplementation prevented the reduction of methionine levels and even prevented some of the lasting negative effects of early-life stress on later learning and memory in adult offspring.
"Today's children are tomorrow's future," said Aniko Korosi, Ph.D., a researcher involved in the work from the Swammerdam Institute for Life Sciences and the Center for Neuroscience at the University of Amsterdam in Amsterdam, The Netherlands. "We hope that this study can contribute to novel nutritional strategies that help prevent lasting consequences of a stressful childhood on later mental health."
To make their discovery, Korosi and colleagues mimicked a stressful early-life environment during the first week after birth (postnatal days 2-9) for newborn mice and their mothers. Control mice and their mothers were housed in a normal environment. During the stress period, half of the mouse mothers (control and early-life stress) received a standard rodent diet, the other half received a diet that was supplemented with essential micronutrients. The lactating mouse mothers ate the diet and thereby developed elevated micronutrient levels in maternal milk and subsequently in the blood and the brains of their pups. After the initial stress period, all mice received a standard diet and environment. Once the mice became 4 months old, their learning and memory skills were tested in various cognitive/behavioral tasks. Mice that were previously exposed to early-life stress performed worse than control animals and demonstrated poor learning and memory skills. However, stress-exposed mice from mothers that received the supplemented diet performed equally well as the control mice did.
"The field of postnatal nutrition has sometimes taken a back seat to research on the maternal-fetal axis, but of course we cannot ever ignore either," said Thoru Pederson, Ph.D., Editor-in-Chief of The FASEB Journal. "Here we see strikingly beneficial cognitive effects of a sound postnatal diet. The nutrients tested were familiar ones, but the results speak for themselves."
Science Daily/SOURCE : https://www.sciencedaily.com/releases/2016/10/161026105215.htm
Additional benefit of omega-3 fatty acids for the clearance of metabolites from the brain
October 26, 2016
Science Daily/Federation of American Societies for Experimental Biology
Omega-3 polyunsaturated fatty acids, which are found in fish oil, could improve the function of the glymphatic system, which facilitates the clearance of waste from the brain, and promote the clearance of metabolites including amyloid-? peptides, a primary culprit in Alzheimer's disease, report scientists.
To make this discovery, scientists first used transgenic fat-1 mice, which express high endogenous omega-3 polyunsaturated fatty acids (PUFAs) in the brain, to investigate the effect of omega-3 PUFAs on the clearance function of the glymphatic system. Compared to the wild-type mice, the fat-1 mice with enriched endogenous omega-3 PUFAs significantly promote the clearance function of the lymphatic system, including the Aβ clearance from the brain. Wild-type mice were supplemented with fish oil, which contains high concentrations of omega-3 PUFAs, and found that fish oil-supplemented mice also improved the clearance function of the glymphatic system compared to the control mice without fish oil supplementation. Omega-3 PUFAs help maintain the brain homeostasis, which may provide benefits in a number of neurological diseases, such as Alzheimer's disease, traumatic brain injury, and sleep impairment, among others.
"These now-famous fatty acids have been the subject of major studies both in academia and industry. Just when we thought we had heard everything, here is something new, and it is provocative indeed," said Thoru Pederson, Ph.D., Editor-in-Chief of The FASEB Journal. "This study should not turn attention away from the roles of these substances in maintaining vascular health, but neither should they restrict our view. The brain is an extremely vascularized organ, while we might also bear in mind that omega-3 fatty acids may impact neurons, glia, and astrocytes themselves."
Science Daily/SOURCE : https://www.sciencedaily.com/releases/2016/10/161026105336.htm
High blood pressure can impair cognitive function, pose risk for Alzheimer's
October 26, 2016
Science Daily/Loyola University Health System
High blood pressure in middle age can lead to impaired cognition and is a potential risk factor for Alzheimer’s disease, researchers conclude.
Dr. Biller is a member of the multidisciplinary panel of experts that wrote the statement, published in the heart association journal Hypertension. Dr. Biller is chair of the department of neurology of Loyola University Chicago Stritch School of Medicine. The panel is chaired by Constantino Iadecola, MD, of Weill Cornell Medicine and co-chaired by Kristine Yaffe, MD, of the University of California San Francisco.
Dementia affects an estimated 30 to 40 million people worldwide, and the number is expected to triple by 2050 due to an aging population and other factors.
An estimated 80 million people in the United States have hypertension, and the brain is among the organs most affected. Except for age, hypertension is the most important risk factor for vascular problems in the brain that lead to stroke and dementia.
There is consistent evidence that chronic high blood pressure during middle age (40 to 64) is associated with altered cognitive function in both middle age and late life (65 to 84). Cognitive abilities that are affected include memory, speed of processing and executive function (ability to organize thoughts, manage time, make decisions, etc.)
The effect of high blood pressure in late life is less clear. Some studies suggest it's harmful, while other research suggests it may improve cognition. This highlights "the complexities of recommending uniform levels of blood pressure across the life course," the expert panel wrote.
Observational studies have demonstrated that high blood pressure causes atherosclerosis (hardening of the arteries) and other damage to the brain's blood vessels, leading to reduced blood flow to brain cells. But evidence from clinical trials that treating blood pressure improves cognition is not conclusive.
After carefully reviewing available studies, the panel concluded there are not enough data to make evidence-based recommendations. However, judicious treatment of high blood pressure, taking into account goals of care and the patient's individual characteristics, "seems justified to safeguard vascular health and, as a consequence, brain health," the panel concluded.
Science Daily/SOURCE : https://www.sciencedaily.com/releases/2016/10/161026142208.htm
Power outage in the brain may be source of Alzheimer's
Restoring damaged genes linked to mitochondrial function may offer strategy for halting disease advance
November 9, 2016
Science Daily/Arizona State University
In a new study, researchers investigate the role of mitochondria in Alzheimer's disease pathology. Mitochondria act as energy centers for cells and are of central importance in health and disease. The study builds on earlier work suggesting gene mutations affecting mitochondrial function may be critical in the development of the disease.
On Nov. 25, 1901, a 51-year-old woman is admitted to a hospital in Frankfurt, Germany, displaying a bizarre constellation of symptoms. Her behavior is erratic. She shows signs of paranoia as well as auditory hallucinations, disorientation and severe memory impairment. Asked to write her own name, she manages "Mrs.," then lingers over the page, unable to remember the rest. "I have lost myself," she tells the attending physician.
Over time, she will withdraw into her own inscrutable universe, before dying on April 9, 1906.
The tragic case of Auguste Deter might have vanished into the recesses of medical history, but for the following fact: Her doctor, Alois Alzheimer, made a thorough examination of her medical condition, including her excised brain, discovering the telltale amyloid plaques and neurofibrillary tangles characteristic of her illness. Auguste Deter was the first person diagnosed with Alzheimer's disease.
Today, society faces an epidemic of Alzheimer's, with some 5 million afflicted in the U.S. alone. The number is projected to swell to 14 million by midcentury, according to the Centers for Disease Control and Prevention. Of the top 10 leading fatal illnesses, Alzheimer's remains the only one that cannot be prevented, treated or cured.
In new research appearing in the journal Alzheimer's and Dementia, Diego Mastroeni, Paul Coleman and their colleagues at the ASU-Banner Neurodegenerative Disease Research Center (NDRC) and the Biodesign Center for Bioenergetics investigate the role of mitochondria in Alzheimer's disease pathology. Mitochondria act as energy centers for cells and are of central importance in health and disease.
The study builds on earlier work suggesting gene mutations affecting mitochondrial function may be critical in the development -- and pitiless progression -- of the disease.
"Age-related neurodegenerative diseases, like Alzheimer's, progress over a long period of time before they become clinically apparent. The earliest physiological and molecular events are largely unknown," said Mastroeni. "Findings from our laboratory have uncovered early expression changes in nuclear-encoded, but not mitochondrial-encoded mRNAs occurring in one's early 30s, giving us a glimpse into what we suspect are some of the earliest cellular changes in the progression of Alzheimer's disease."
Results of the new study show that specific classes of genes associated with mitochondrial cell respiration display reduced expression levels in patients with Alzheimer's disease, compared with normal patients.
The study also examines gene expression in subjects whose brains show an intermediate level of illness known as mild cognitive impairment. Here, the opposite effect is observed, with relevant genes exhibiting increased levels of expression. The authors suggest this observation may point to some kind of compensatory mechanism in the brain attempting to stave off the disease in its earlier stages.
Further, the study proposes that restoring a specific set of damaged genes linked to mitochondrial function and located in the nuclear DNA of cells may offer a promising strategy for halting the disease's advance.
Assault on identity
Alzheimer's -- the most common form of dementia -- is a progressive, degenerative disease of the brain. While commonly associated with elderly individuals, this devastating illness is now believed to have its origins much earlier, infiltrating the nervous system decades before the onset of clinical symptoms. Indeed, the greatest obstacle to successful treatment of Alzheimer's is the fact that the disease is typically not recognized until its progress has irreparably ravaged the brain.
The disease often begins with mild memory loss, which may interfere with normal conversation. While advancing age remains the leading risk factor for Alzheimer's, some individuals are also genetically predisposed. Other risk factors include high cholesterol, heart disease, stroke and high blood pressure. Today, Alzheimer's is the fifth-leading cause of death in adults 65-85 years old.
Despite the increasingly pronounced effects of dementia, a definitive diagnosis of Alzheimer's disease usually requires the post-mortem examination of brain tissue and identification of two stereotypic symptoms, known as plaques and tangles. More recently, new imaging technology has enabled researchers to detect these symptoms in living brains, though Coleman is cautious about their interpretation:
"Although plaques and tangles remain as the definitive neuropathological hallmark of the disease, plaques do not correlate at all with degree of cognitive impairment in [Alzheimer's] and tangles correlate only slightly," he said. "We further know that plaques and tangles are late comers in the cascade of events that cause the dementia of [Alzheimer's]."
Alzheimer's is believed to account for 60-70 percent of dementia cases. As the disease progresses, symptoms become more severe, including erosion of language ability, physical disorientation and behavioral transformations, often involving the withdrawal from family and society. Over time, bodily functions are lost, ultimately leading to death. Life expectancy for Alzheimer's patients varies, but three to nine years following diagnosis is typical.
Quick energy
Mitochondria -- membrane-bound organelles found in all eukaryotic organisms -- are often called the powerhouses of the cell. Through a process known as oxidative phosphorylation, they produce most of the cell's chemical energy in the form of adenosine triphosphate or ATP.
In addition to supplying cellular energy, mitochondria are involved in cell signaling, cellular differentiation and cell death, as well as in cellular growth and the maintenance of the cell cycle.
Because mitochondria play such an important role in the cell, mitochondrial dysfunction has been implicated in a broad range of illness, including cardiovascular disease, autism, schizophrenia, bipolar disorder, epilepsy, stroke, Lou Gehrig's disease and diabetes along with forms of dementia including Alzheimer's.
Unsurprisingly, defects in mitochondrial function more severely affect energy-hungry organ systems in the body, particularly muscles, the GI tract and the brain -- an organ making up just 2 percent of a person's weight while consuming 20 percent of the body's total energy budget.
Mitochondria are unique among the cell's organelles, as they possess their own DNA, distinct from the DNA contained within the cell's nucleus. This strange state of affairs is due to mitochondrial evolution. Mitochondria are descended from free-living bacteria that colonized other cells some 2 billion years ago. After being incorporated into nucleated cells, these endosymbionts, as they are known, lost much of their original machinery, yet retained their own complement of DNA.
In addition to the role of mitochondrial dysfunction in disease, the gradual degradation of mitochondrial integrity is believed to play a central role in the normal process of aging.
Broken genes
The current study examines tissue from the hippocampus, a structure critical for memory and one severely impacted by the advance of Alzheimer's. Using microarray technology, the authors examined hippocampal tissue from an aging cohort-44 normal brains from 29-99 years of age, 10 with mild cognitive impairment and 18 with Alzheimer's disease.
Gene expression was examined for two sets of genes, 1 encoding mitochondrial DNA and the other, in the nuclear DNA. The two sets of genes both coded for proteins associated with a mitochondrial complex essential for oxidative phosphorylation (OXPHOS), producing energy in the form of ATP for the cell.
Intriguingly, while the mitochondrial genes themselves were largely unaffected, the nuclear genes associated with the OXPHOS complex underwent significant modification, depending on the tissues examined. The microarray data revealed substantial down-regulation of nuclear-encoded OXPHOS genes in Alzheimer's tissue, a finding also found in normally aging brains.
The same genes, however, were up-regulated in the case of mild cognitive impairment, a precursor to Alzheimer's disease. The authors suggest this effect may be due to a compensatory mechanism in the brain in response to early pathology.
The findings are consistent with earlier work establishing that accumulations of amyloid beta (Aβ) in neurons, a hallmark of Alzheimer's, are directly implicated in mitochondrial dysfunction. The pronounced effect on nuclear-encoded but not mitochondrial-encoded OXPHOS genes may point to dysfunctions in the transport of molecules from the cell nucleus to the mitochondria.
"Our work on mitochondria offers the promise of a reliable marker appearing earlier in the course of the disease -- one which more closely correlates with the degree of dementia than the current diagnostic of plaques and tangles," Coleman said.
Precise mechanisms of mitochondrial decline in aging and Alzheimer's have yet to be teased out and will be the focus of continuing research. The study suggests that therapies aimed at restoring function in nuclear-encoded OXPHOS genes may provide an exciting new avenue for treatment of Alzheimer's.
Science Daily/SOURCE :https://www.sciencedaily.com/releases/2016/11/161109175141.htm