Diet Restriction Slows Neurodegeneration and Extends Lifespan of DNA-Repair-Deficient Mice

DNA damage occurs in human cells at a constant rate. These cells are usually able to repair themselves, but sometimes deficiencies in certain genes cause the repair process to shut down. When damaged DNA isn’t fixed, mutations can occur that cause accelerated aging or cancerous tumors to form (Hoeijmakers, 2009). Scientists at Erasmus University Medical Center in Rotterdam have found a way to slow down the process – at least in mice.

In a study published in Nature, the researchers report that when mice deficient in the DNA-repair genes Ercc1 or Xpg are put on a restricted diet, they experience better overall health and increased lifespans compared to DNA-repair-deficient mice fed a normal diet. They also found significantly lower levels of neurodegeneration in the brains and spinal cords of diet restricted animals compared to controls.

“Here we report that a dietary restriction of 30 percent tripled the median and maximal remaining lifespans of these progeroid mice, strongly retarding numerous aspects of accelerated aging Mice undergoing dietary restriction retained 50 percent more neurons and maintained full motor function far beyond the lifespan of mice fed ad libitum,” (Vermeij, et al 2016).

Since the DNA-repair-deficient mice were already smaller and weaker than normal mice, the Rotterdam researchers wondered whether diet restriction would be beneficial or detrimental to their health. They found that gradually restricting the diets of DNA-repair-deficient mice starting at age seven weeks increased their median lifespans from 10 to 35 weeks in males and 13 to 39 weeks in females as compared to controls.

They also saw significant differences in the levels of neurodegeneration between these two populations. Using Stereo Investigator, they found 50 percent more neurons in the brains of diet-restricted mice compared to those fed a normal diet. They also saw lower levels of cells expressing p53 – a protein expressed in response to DNA damage – in diet-restricted mice.

According to the authors, dietary restriction may not fix defects in DNA repair mechanisms, but it may help to reduce the severity and speed at which the damage occurs.

“Our findings establish the Ercc1 mouse as a powerful model organism for health-sustaining interventions, reveal potential for reducing endogenous DNA damage, facilitate a better understanding of the molecular mechanism of dietary restriction and suggest a role for counterintuitive dietary-restriction-like therapy for human progeroid genome instability syndromes and possibly neurodegeneration in general,” (Vermeij, et al 2016).

Vermeij W.P., Dollé M.E.T., Reiling E., Jaarsma D., Payan-Gomez C, Bombardieri C.R., Wu H., Roks A.J.M., Botter S.M., van der Eerden B.C., Youssef S.A., Kuiper R.V., Nagarajah B., van Oostrom C.T., Brandt R.M.C., Barnhoorn S., Imholz S., Pennings J.L.A., de Bruin A., Gyenis Á., Pothof J, Vijg J, van Steeg H., and Hoeijmakers J.H.J. (2016) Restricted diet delays accelerated aging and genomic stress in DNA repair deficient mice. Nature 537, 427-431, doi:10.1038/nature19329

Hoeijmakers JH (2009) DNA Damage, aging, and cancer. N Engl J Med; 361:1475-1485, DOI: 10.1056/NEJMra0804615

Stock image of DNA used in accordance with the CC0 public domain license.

New Neurons Erase Memories

Dentate gyrus

Neurogenesis occurs in the dentate gyrus, pictured here, from birth through adulthood.

A baby laughs at an elephant at the zoo. A toddler runs across a beach. Small children make memories all the time, but how many will they recall as the years pass? Maybe none at all. The phenomenon is called “infantile amnesia,” and scientists may have pinpointed a reason for why it occurs – neurogenesis.

Researchers at the Hospital for Sick Children in Toronto say that when new brain cells integrate into existing circuitry, they remodel the structure of networks already in place, wiping out the information previously stored there. This process is prevalent in infancy and early childhood because this is the time when new brain cells are being generated faster and more frequently than at any other time in a human being’s life. Humans and other mammals spawn new neurons throughout their lifespans, although the rate of neurogenesis decreases significantly with age.

In their paper, published in Science, the researchers explain how recent studies have focused on how new brain cells can lead to new memories, but the Toronto team speculated that neurogenesis could also wipe away memories. To test their hypothesis, they conducted a series of studies on populations of newborn and adult mice. Neuron development in mice occurs in much the same way as in humans, with rapid cell genesis in infancy that tapers off with age.

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Increased Choline During Pregnancy Improves Learning in Down Syndrome Mice

DCX Cells Counted With Stereo InvestigatorObstetricians and midwifes have long hailed the benefits of folic acid during pregnancy. Now new research offers evidence that choline is another important nutrient for the developing fetus. Found in foods like eggs and cauliflower, choline is known to aid healthy liver function. But in the past few years, studies have shown that the nutrient also plays a role in brain development. One recent study by Velasquez and colleagues claims that increased choline during pregnancy may offer a possible therapy for Down syndrome.

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Study Links Increased Touch to Enhanced Neurogenesis in Adult Mice; Stereo Investigator Used for Quantification

adult_neurogenesis

According to scientists at the Hotchkiss Brain Institute in Calgary, Canada, there is evidence for increased neurogenesis in adult mice reared by two parents. Their study also describes other interesting findings, such as the fact that increased neurogenesis persists in the next generation, or that the effects of differences in rearing affect males and females differently.

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Michigan Scientists Analyze Brain Cells Born During Puberty With Neurolucida

mohr_image

What does it take to survive that tumultuous time called adolescence? Good friends, exercise, and new brain cells.

Scientists at Michigan State University found evidence of neurogenesis in the brains of adolescent hamsters, according to a study published last month in PNAS. The new cells, which became integrated into neural circuits in adulthood, were discovered in the amygdala and connected limbic regions – areas associated with social learning and mating behavior.

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