Friday, May 11, 2012

Science Friday: Fatty Diets Lead to Bigger Waists & Bigger Brains*

*Not in a good way.

Neuroscientists used to believe new neurons weren’t made in the adult brain. They thought that once our brains are done developing, that’s all we get. We now know this isn’t the case; in very few places in the adult brain, we can detect new neurons being created. One of these areas, the hippocampus, is important for memory. Interestingly, exercise has been shown to increase the number of hippocampal neurons. (This is old news, but still pretty awesome.) Additionally, the subventricular zone has been shown to contain new neurons which incorporate into a pathway important for smell. Recently, Blackshaw and colleagues detected newly born neurons in another area of the brain called the hypothalamus, an area important for the regulation of eating and drinking, among other things.

In this study, the researchers used a special technique that labels neurons that have recently been born so they can be distinguished from neurons that have been around for a while. With this tool, they found a particular type of cell, the tanycyte, to be actively dividing (making new cells) in a region of the adult mouse hypothalamus called the medial eminence. They performed a couple of tests to show the new neurons were active and functional, meaning they had a purpose and were being put to use by the surrounding cells.

High fat, low movement. Blame the hypothalamus.
So what causes this particular brain region to make new cells? Because of the role of this area in food regulation, the researchers fed a group of mice a high fat diet (HFD) and compared them to mice on a normal (low fat) mouse diet. Interestingly, adult mice fed a HFD had a greater number of newly born neurons in the medial eminence than mice on a normal diet. (Younger mice had similar numbers in both diet groups.) This suggests that eating fatty foods increases certain types of neurons in the brain. That doesn't sound so bad, but it's important to see what these new neurons do. To observe their purpose, the researchers used a laser to specifically inhibit these cells and prevent any new neurons from being made. They found that mice without these neurons gained less weight on a HFD, burned more calories, and were more active. Basically, not having these cells is a good thing; these neurons seem like the little devil that sits on your shoulder and tells you to eat. Fatty foods made the mice create these neurons, and in turn the neurons made the mice gain more weight and sit on the mouse couch more. Not a good combination.

This is the first study to suggest adult neurogenesis (creating new neurons) plays a role in weight regulation. What’s interesting to me is the reciprocal relationship between the body and the brain. If we eat stuff that’s bad for us, it affects our* brains in ways that tell us to eat more and move less. It's probably best to eat healthy than try to battle that double whammy. But if you do splurge, resist the urge to sit around all day and get out and be active. That way your hippocampus will grow (better memories!) while your waist and hypothalamus don't. 

*These studies are in mice and shouldn’t be extrapolated to humans. But like all good wannabe scientists, I’m going to anyway.

P.S. Happy birthday to my Dad, the inspiration for my scientific endeavors.

Dream big, 

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