Science Interviews

Interview

Fri, 8th Aug 2014

Bears can "turn off" diabetes

Kevin Corbit, Amgen

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New research has shown grizzly bears can become diabetic during their Grizzly bearhibernation, and then simply switch it off again in the spring. This could pave the way to a greater understanding of how to treat diabetes, which is on the rise worldwide. Kevin Corbit gave Georgia Mills the bare necessitiesÖ 

Kevin -   Diabetes is a disease which is generally characterised as having high levels of sugar in your blood.  Now, there are two types of diabetes.  There's type 1 and thatís where your body cannot make the hormone that is responsible for keeping the levels of sugar in your blood normal.  That hormone is called insulin.  And then there's type 2 diabetes in which the body, even though itís either making insulin or receiving insulin through medicine cannot actually respond to that hormone insulin and the blood sugar levels remain high even though the insulin is there.  Type 2 diabetes makes up about 95% of the diabetes and thatís increasing.  Traditionally, it is associated with obesity.

Georgia -   So, to try and look at this, why were you looking at bears?

Kevin -   If you just look at a bear thatís preparing to go in hibernation, one would probably say that is a very obese animal.  But to be sure, we put the bear through some tests that included to try and measure and waist and yes, that was very comical and indeed, the bears do get quite obese before they go into hibernation.

Georgia -   Is this a bad thing or is this necessary for them to survive the winter?

Kevin -   When it comes to the bears, of course, they're getting obese for a specific reason because they're going to lie down for 5 or 6 months and not eat.  In order to survive that long period of fasting, you have to store a whole bunch of fat.  Now, what's interesting is when they get obese as opposed to what we think about in humans, we found that when the bears are most obese, it's actually, when they become most sensitive to insulin, you can almost think about it as an anti-diabetes.  I think that was the first clue that we had stumbled onto something that was quite different between the bears and humans.

Georgia -   Bears get less diabetic when they get obese.  So, thatís the opposite to humans. 

Kevin -   Well, what we think is, one of the other properties of the hormone insulin is, it controls when the body either stores fat or uses fat as a fuel.  So, you can think about this way.  If you were a bear and you are preparing to go into hibernation and you know you're not going to eat for 5 or 6 months, you would want to store every last little molecule fat that you possibly could.  Itís kind of like putting a bunch of money away in your savings account when you know there are economic hard times ahead of you.  So, what insulin does is it instructs the body to not breakdown any fat and to store fat instead.  So, if you wanted to store fat, you would want to be as sensitive to insulin as possible.  In other words, you'd want to be very anti-diabetic.  Indeed, thatís what we find with the obese bears.  Now, if you go and you enter hibernation, you Ė in order to survive Ė have to use the stored fat that you have.  And so, you'd want to prevent the body from responding to insulin.  In other words, you'd want to become diabetic.  In that way, you can breakdown the fat and use it as a fuel source.  Indeed, thatís what we think the bears have evolved: this reversible insulin sensitivity or reversible diabetes if you can think about it that way.  They've evolved it to tell them when to store fat and when to use it as a fuel so they can survive hibernation.

Georgia -   So, these bears can turn diabetes off and on, depending on whether they need to process fat or not.  There's no known cure for diabetes at the moment, but could this be starting off on the right track towards one?

Kevin -   I personally started to really rethink how we are treating diabetic humans.  So, without trying to be too provocative, I think by giving diabetics insulin throughout their lives, in the very early stages, this is a good thing because it does indeed lower blood sugar levels in humans.  But in the long term, I'm afraid that weíre doing more harm than good.  So, if we take a lesson from the bear, if I would inject you with insulin throughout your life, donít forget that one of the things that insulin does is it instructs your body to store fat and not to break it down.  So, if you take it for a long time, what's going to happen is you're going to store more and more fat.  You can think about a cell and your fat tissue like a balloon.  If you keep injecting that with more and more fat, what happens of course is the balloon gets much bigger, and that is obesity.  If you wanted to live in an ideal world to treat a diabetic, you would want to utilise the existing insulin in their blood and just turn up the ability of the cells to respond to that insulin.  Thatís what the bears had figured out and we hope we could translate that to humans.

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