beta amyloid

Exercise offers protection against Alzheimer's

July 16, 2019

Science Daily/Massachusetts General Hospital

Higher levels of daily physical activity may protect against the cognitive decline and neurodegeneration (brain tissue loss) from Alzheimer's disease (AD) that alters the lives of many older people, researchers from Massachusetts General Hospital (MGH) have found. In a paper in JAMA Neurology, the team also reported that lowering vascular risk factors may offer additional protection against Alzheimer's and delay progression of the devastating disease. The findings from this study will be presented at the Alzheimer's Association International Conference (AAIC) in Los Angeles by the first author of the study, Jennifer Rabin, PhD, now at the University of Toronto, Sunnybrook Research Institute.

 

"One of the most striking findings from our study was that greater physical activity not only appeared to have positive effects on slowing cognitive decline, but also on slowing the rate of brain tissue loss over time in normal people who had high levels of amyloid plaque in the brain," says Jasmeer Chhatwal, MD, PhD of the MGH Department of Neurology, and corresponding author of the study. The report suggests that physical activity might reduce b-amyloid (Ab)-related cortical thinning and preserve gray matter structure in regions of the brain that have been implicated in episodic memory loss and Alzheimer's-related neurodegeneration.

 

The pathophysiological process of AD begins decades before clinical symptoms emerge and is characterized by early accumulation of b-amyloid protein. The MGH study is among the first to demonstrate the protective effects of physical activity and vascular risk management in the "preclinical stage" of Alzheimer's disease, while there is an opportunity to intervene prior to the onset of substantial neuronal loss and clinical impairment. "Because there are currently no disease-modifying therapies for Alzheimer's disease, there is a critical need to identify potential risk-altering factors that might delay progression of the disease," says Chhatwal.

 

The Harvard Aging Brain Study at MGH assessed physical activity in its participants -- 182 normal older adults, including those with elevated b-amyloid who were judged at high-risk of cognitive decline -- through hip-mounted pedometers which counted the number of steps walked during the course of the day.

 

"Beneficial effects were seen at even modest levels of physical activity, but were most prominent at around 8,900 steps, which is only slightly less than the 10,000 many of us strive to achieve daily," notes co-author Reisa Sperling, MD, director of the Center for Alzheimer's Research and Treatment, Brigham and Women's Hospital and Massachusetts General Hospital and co-principal investigator of the Harvard Aging Brain Study.

 

Interventional approaches that target vascular risk factors along with physical exercise have added beneficial properties, she adds, since both operate independently. Vascular risk factors measured by the researchers were drawn from the Framingham Cardiovascular Disease Risk Score Calculator, and include age, sex, weight, smoking/non-smoking, blood pressure, and whether people are on treatment for hypertension.

 

Through ongoing studies MGH is working to characterize other forms of physical activity and lifestyle changes that may help retard the progress of Alzheimer's disease. "Beta amyloid and tau protein build-up certainly set the stage for cognitive impairment in later age, but we shouldn't forget that there are steps we can take now to reduce the risk going forward -- even in people with build-up of these proteins," says Chhatwal. "Alzheimer's disease and the emergence of cognitive decline is multifactorial and demands a multifactorial approach if we hope to change its trajectory."

https://www.sciencedaily.com/releases/2019/07/190716193543.htm

Eating mushrooms may reduce the risk of cognitive decline

March 12, 2019

Science Daily/National University of Singapore

Researchers found that seniors who consume more than two standard portions of mushrooms weekly may have 50 percent reduced odds of having mild cognitive impairment.

 

A team from the Department of Psychological Medicine and Department of Biochemistry at the Yong Loo Lin School of Medicine at the National University of Singapore (NUS) has found that seniors who consume more than two standard portions of mushrooms weekly may have 50 per cent reduced odds of having mild cognitive impairment (MCI).

 

A portion was defined as three quarters of a cup of cooked mushrooms with an average weight of around 150 grams. Two portions would be equivalent to approximately half a plate. While the portion sizes act as a guideline, it was shown that even one small portion of mushrooms a week may still be beneficial to reduce chances of MCI.

 

"This correlation is surprising and encouraging. It seems that a commonly available single ingredient could have a dramatic effect on cognitive decline," said Assistant Professor Lei Feng, who is from the NUS Department of Psychological Medicine, and the lead author of this work.

 

The six-year study, which was conducted from 2011 to 2017, collected data from more than 600 Chinese seniors over the age of 60 living in Singapore. The research was carried out with support from the Life Sciences Institute and the Mind Science Centre at NUS, as well as the Singapore Ministry of Health's National Medical Research Council. The results were published online in the Journal of Alzheimer's Disease on 12 March 2019.

 

Determining MCI in seniors

 

MCI is typically viewed as the stage between the cognitive decline of normal ageing and the more serious decline of dementia. Seniors afflicted with MCI often display some form of memory loss or forgetfulness and may also show deficit on other cognitive function such as language, attention and visuospatial abilities. However, the changes can be subtle, as they do not experience disabling cognitive deficits that affect everyday life activities, which is characteristic of Alzheimer's and other forms of dementia.

 

"People with MCI are still able to carry out their normal daily activities. So, what we had to determine in this study is whether these seniors had poorer performance on standard neuropsychologist tests than other people of the same age and education background," explained Asst Prof Feng. "Neuropsychological tests are specifically designed tasks that can measure various aspects of a person's cognitive abilities. In fact, some of the tests we used in this study are adopted from commonly used IQ test battery, the Wechsler Adult Intelligence Scale (WAIS)."

 

As such, the researchers conducted extensive interviews and tests with the senior citizens to determine an accurate diagnosis. "The interview takes into account demographic information, medical history, psychological factors, and dietary habits. A nurse will measure blood pressure, weight, height, handgrip, and walking speed. They will also do a simple screen test on cognition, depression, anxiety," said Asst Prof Feng.

 

After this, a two-hour standard neuropsychological assessment was performed, along with a dementia rating. The overall results of these tests were discussed in depth with expert psychiatrists involved in the study to get a diagnostic consensus.

 

Mushrooms and cognitive impairment

 

Six commonly consumed mushrooms in Singapore were referenced in the study. They were golden, oyster, shiitake and white button mushrooms, as well as dried and canned mushrooms. However, it is likely that other mushrooms not referenced would also have beneficial effects.

 

The researchers believe the reason for the reduced prevalence of MCI in mushroom eaters may be down to a specific compound found in almost all varieties. "We're very interested in a compound called ergothioneine (ET)," said Dr Irwin Cheah, Senior Research Fellow at the NUS Department of Biochemistry. "ET is a unique antioxidant and anti-inflammatory which humans are unable to synthesise on their own. But it can be obtained from dietary sources, one of the main ones being mushrooms."

 

An earlier study by the team on elderly Singaporeans revealed that plasma levels of ET in participants with MCI were significantly lower than age-matched healthy individuals. The work, which was published in the journal Biochemical and Biophysical Research Communications in 2016, led to the belief that a deficiency in ET may be a risk factor for neurodegeneration, and increasing ET intake through mushroom consumption might possibly promote cognitive health.

 

Other compounds contained within mushrooms may also be advantageous for decreasing the risk of cognitive decline. Certain hericenones, erinacines, scabronines and dictyophorines may promote the synthesis of nerve growth factors. Bioactive compounds in mushrooms may also protect the brain from neurodegeneration by inhibiting production of beta amyloid and phosphorylated tau, and acetylcholinesterase.

 

Next steps

 

The potential next stage of research for the team is to perform a randomised controlled trial with the pure compound of ET and other plant-based ingredients, such as L-theanine and catechins from tea leaves, to determine the efficacy of such phytonutrients in delaying cognitive decline. Such interventional studies will lead to more robust conclusion on causal relationship. In addition, Asst Prof Feng and his team also hope to identify other dietary factors that could be associated with healthy brain ageing and reduced risk of age-related conditions in the future.

https://www.sciencedaily.com/releases/2019/03/190312103702.htm

Midlife cardiovascular risk factors may increase chances of dementia

Study supports link between cognition and vascular health

August 7, 2017

Science Daily/NIH/National Institute of Neurological Disorders and Stroke

A large, long-term study suggests that middle aged Americans who have vascular health risk factors, including diabetes, high blood pressure and smoking, have a greater chance of suffering from dementia later in life.

 

"With an aging population, dementia is becoming a greater health concern. This study supports the importance of controlling vascular risk factors like high blood pressure early in life in an effort to prevent dementia as we age," said Walter J. Koroshetz, M.D., director of NIH's National Institute of Neurological Disorders and Stroke (NINDS), which partially funded the study and created the Mind Your Risks® public health campaign to make people more aware of the link between cardiovascular and brain health. "What's good for the heart is good for the brain," he added.

 

The study was led by Rebecca Gottesman, M.D., Ph.D., professor of neurology at Johns Hopkins University in Baltimore. Her team analyzed the data of 15,744 people who participated in the Atherosclerosis Risk in Communities (ARIC) study, funded by the NIH's National Heart, Lung, and Blood Institute (NHLBI). From 1987-1989, the participants, who were black or white and 45-64 years of age, underwent a battery of medical tests during their initial examinations at one of four centers in four different states. Over the next 25 years they were examined four more times. Cognitive tests of memory and thinking were administered during all but the first and third exams.

 

Her team found that 1,516 participants were diagnosed with dementia during an average of 23 follow-up years. Initially, when they analyzed the influence of factors recorded during the first exams, the researchers found that the chances of dementia increased most strongly with age followed by the presence of APOE4, a gene associated with Alzheimer's disease. Whites with one copy of the APOE4 gene had a greater chance of dementia than blacks. Other factors included race and education: blacks had higher chance of dementia than whites; those who did not graduate from high school were also at higher risk.

 

In agreement with previous studies, an analysis of vascular risk factors showed that participants who had diabetes or high blood pressure, also called hypertension, had a higher chance of developing dementia. In fact, diabetes was almost as strong a predictor of dementia as the presence of the APOE4 gene.

 

Unlike other studies, the researchers discovered a link between dementia and prehypertension, a condition in which blood pressure levels are higher than normal but lower than hypertension. Also, race did not influence the association between dementia and the vascular risk factors they identified. Diabetes, hypertension and prehypertension increased the chances of dementia for white and black participants. Finally, smoking cigarettes exclusively increased the chances of dementia for whites but not blacks.

 

"Our results contribute to a growing body of evidence linking midlife vascular health to dementia," said Dr. Gottesman. "These are modifiable risk factors. Our hope is that by addressing these types of factors early, people can reduce the chances that they will suffer from dementia later in life."

 

Further analysis strengthened the idea that the vascular risk factors identified in this study were linked to dementia. For instance, in order to answer the question of whether having a stroke, which is also associated with the presence of vascular risk factors, may explain these findings, the team reanalyzed the data of participants who did not have a stroke and found similar results. Diabetes, hypertension, prehypertension and smoking increased the risk of dementia for both stroke-free participants and those who had a stroke.

 

Recently, in a separate study partially funded by the NIH's National Institute on Aging, Dr. Gottesman's team analyzed brain scans from a subgroup of ARIC participants who did not have dementia when they entered the study. They found that the presence of one or more vascular risk factors during midlife was associated with higher levels of beta amyloid, a protein that often accumulates in the brains of Alzheimer's patients. This relationship was not affected by the presence of the APOE4 gene and not seen for risk factors present in later life. The presence of vascular risk factors detected in participants older than 65 years of age during the final examination was not associated with greater levels of beta amyloid.

 

"With many years of data from a large and diverse population, the ARIC study is a powerful source of information for medical research," said Jacqueline D. Wright, Dr.P.H., program director at NHLBI. "This epidemiologic study aimed to improve our understanding of atherosclerosis and heart disease and, through the investigators' efforts; it has become a great resource for research on dementia and other diseases of aging. The investments in longitudinal cohort studies like ARIC will benefit all of us for many years to come."

 

In the future, Dr. Gottesman and her team plan to investigate ways in which subclinical, or undiagnosed, vascular problems may influence the brain and why race is associated with dementia.

https://www.sciencedaily.com/releases/2017/08/170807120524.htm

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