Molecules in blood can make you younger… or older

Healthy Aging

An update on young blood science

In honor of Halloween this week, we’re reviewing the latest science on blood, including which molecules make young folks young… and old folks old. The good news? We older folks will be able to talk any vampire out of choosing us. The even better news? We may be closer to understanding how to regain our youth.

Young blood, good. Young brains, great.

In Nature Neuroscience, Bieri et al. review how molecules in the blood of older versus younger animals influence brain health. Specifically, they summarize which molecules are associated with brain dysfunction and which others may support brain rejuvenation.

First, the Frankenstein experiments.

Your phrase of the week is “heterochronic parabiosis”. This is the process of connecting the circulatory systems of young and old mice to see if younger animals get older, and older animals get younger. Here, Bieri et al. focused on what these studies have taught us about rejuvenating brain health.

So, here’s what we know about aging brains.

As we age, our cognition declines, leading to poorer memory, learning, and mental resilience. At the cellular level, this brain breakdown is caused by the following:

• Fewer synapses and imbalanced signaling between neurons
• Less regeneration of neurons and their protective sheaths (called myelin)
• Higher inflammation and oxidative stress
• Stiffer vessels and a leaky blood-brain barrier

As shown by Villeda et al., when young mice receive old-mouse blood, they develop older brains that have fewer synapses, decreased neurons, and increased inflammation.

That means there’s stuff in our blood that makes our brains age.

So, what in our blood causes our brains to age? Bieri et al. say that it comes down to overactive systemic and local immune responses (aka inflammation). This includes way-too-eager natural killer (NK) cells, T cells, cytokines, and chemokines.

This chronic inflammatory state weakens our blood-brain barrier, and when this barrier is weakened, proinflammatory factors sneak in. The result? Aging brains.

That’s interesting. But can you get to the part of blood that rejuvenates brains?

Fair enough. Encouragingly, studies by Villeda et al. show that old mice infused with young blood have improved brain cognition. They and others also demonstrated that young blood results in more synapses, more new neurons, lower neuroinflammation, and less leaky vessels in older mice. That’s pretty impressive.

Bieri et al. list a variety of factors in the brain that may help to rejuvenate it, including GDF11, osteocalcin, TIMP2, CSF2, THBS4, and SPARCL. These studies are still early, which means that while the science world is making progress in mice, you shouldn’t start shopping for THBS4.

We could drain youthful blood, or just exercise.

We’re joking about taking blood from younger people, of course. Wonderfully, Bieri et al. show that we are likely to gain as much brain-rejuvenating power from exercise as we are from young blood. They provide a robust list of studies showing that exercise raises pro-brain health factors in the blood and brain, like IGF1, GLPD1, and ApoJ. These factors have been associated with:

• Increased neurogenesis
• Lower neuroinflammation
• Improved cognition

Certainly, walking and lifting a few weights is a much easier way to youth-ify our brains. So, let’s do that.