Health
Activating an enzyme known to play a role in the anti-aging benefits of calorie restriction delays the loss of brain cells and preserves cognitive function in mice, according to a study published in the May 22 issue of The Journal of Neuroscience.
The findings could one day guide researchers to discover drug alternatives that slow the progress of age-associated impairments in the brain.
Previous studies have shown that reducing calorie consumption extends the lifespan of a variety of species and decreases the brain changes that often accompany aging and neurodegenerative diseases such as Alzheimer’s.
There is also evidence that caloric restriction activates an enzyme called Sirtuin 1 (SIRT1), which studies suggest offers some protection against age-associated impairments in the brain.
In the current study, Li-Huei Tsai, PhD, Johannes Gräff, PhD, and others at the Picower Institute For Learning and Memory, Massachusetts Institute of Technology, and Howard Hughes Medical Institute, tested whether reducing caloric intake would delay the onset of nerve cell loss that is common in neurodegenerative disease, and if so, whether SIRT1 activation was driving this effect.
The group not only confirmed that caloric restriction delays nerve cell loss, but also found that a drug that activates SIRT1 produces the same effects.
“There has been great interest in finding compounds that mimic the benefits of caloric restriction that could be used to delay the onset of age-associated problems and/or diseases,” said Luigi Puglielli, MD, PhD, who studies aging at the University of Wisconsin, Madison, and was not involved in this study. “If proven safe for humans, this study suggests such a drug could be used as a preventive tool to delay the onset of neurodegeneration associated with several diseases that affect the aging brain,” Puglielli added.
In the study, Tsai’s team first decreased by 30 percent the normal diets of mice genetically engineered to rapidly undergo changes in the brain associated with neurodegeneration. Following three months on the diet, the mice completed several learning and memory tests.
“We not only observed a delay in the onset of neurodegeneration in the calorie-restricted mice, but the animals were spared the learning and memory deficits of mice that did not consume reduced-calorie diets,” Tsai explained.
Curious if they could recreate the benefits of caloric restriction without changing the animals’ diets, the scientists gave a separate group of mice a drug that activates SIRT1.
Similar to what the researchers found in the mice exposed to reduced-calorie diets, the mice that received the drug had less cell loss and better cellular connectivity than the mice that did not receive the drug.
Additionally, the mice that received the drug treatment performed as well as normal mice in learning and memory tests.
“The question now is whether this type of treatment will work in other animal models, whether it’s safe for use over time, and whether it only temporarily slows down the progression of neurodegeneration or stops it altogether,” Tsai said.
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Heart attack or heart failure patients may have a high risk of death or re-admission for a month or longer after leaving the hospital, researchers said at the American Heart Association’s Quality of Care and Outcomes Scientific Sessions 2013.
“The risks of death and re-hospitalization can extend well beyond 30 days after discharge, the time period used by the federal government for measuring hospital performance,” said Kumar Dharmarajan, M.D., M.B.A., lead author of the study and a fellow in cardiology at Columbia University Medical Center in New York City, and visiting scholar at Yale University in New Haven, Conn. “Post-discharge care may be improved when aligned to the periods of greatest risk for patients.”
Researchers examined Medicare data on patients discharged for heart failure (878,963) and heart attack (350,509) and found:
- Within the first year, 41.8 percent of heart failure patients died and 70.3 percent were re-hospitalized.
- Within the first year, 25.9 percent of heart attack patients died and 50.5 percent were re-hospitalized.
- The risk of re-hospitalization after heart failure took more than a month (43 days) to decline 50 percent from its peak level after discharge.
- In the month after a heart attack, the likelihood of death is 21 times higher and the likelihood of hospitalization is 12 times higher than among the general Medicare-age population.
- In the month after hospitalization for heart failure, the likelihood of death is 17 times higher and the likelihood of hospitalization is 16 times higher than among the general Medicare-age population.
“In the weeks after hospital discharge, your risk of death, re-hospitalization and other complications is very high,” Dharmarajan said. “If you feel ill, take it seriously and contact your health care provider.”
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