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lVl84cLFpgk • How the Hormone Leptin Helps Regulate Appetite I NOVA I PBS
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Kind: captions Language: en Froy fryer has less than 2% body fat although he looks extremely fit it's the lack of fat that makes his muscles stand out is no pattern on his face his cheeks look sunken and his eyes are every second how far you off that way the little bit of fat on my body is behind my eyeballs and on my liver so walking around not having fat it feels like constant needles are poking through the bottom of your shoe you know some of us stand up all day and we're okay with it Troy's not because he has no padding on his feet nothing in between his knees there's no comfort at all it's just unbelievable to watch him struggle troy was born with a normal amount of fat but by age six he began rapidly losing weight despite having a voracious appetite I would go through two or three loaves of bread in one day making 10 sandwiches at a time so I would keep eating and eating and eating until it would hurt if I didn't get that food I would get really upset and really angry about ripped doors off their hinges I actually sent him in for a psych evaluation thinking that there was something wrong because he couldn't take the answer no it's like he was starving [Music] by age 9 Troy was clearly ill doctors were shocked to find that his blood was full of fats and cholesterol symptoms typical of obesity it made no sense until Troy was diagnosed by the genetic disease called lipodystrophy we always think about thinness or something good but in generalized lipodystrophy it's beyond thinness it's actually absolute lack of fat under the skin so the excess energy doesn't have a place to go and that's why Troy was sick with no fat tissue excess calories collected in his liver enlarging and inflaming it and when it got to that point of the doctor saying there's nothing else we could do for you Troy Turner the doctor and said so how and when am I going to die salvation would come from the discovery of a mouse that also couldn't stop eating but unlike Troy this mouse was fact not thin a genetic mutant from a breathing experiment it was nicknamed OB for obese this mouse had a defect in a single gene and the impact of that gene was a mass the weight three times normal and had five times as much fat and that over eight veraciously and genetics is very powerful because what it tells you is that obesity has a biological basis what that basis is required identifying the gene scientists began to hunt for the mutation that made the mouse obese combing through the 2.5 billion letters of its genome they give us an alphabet you spell out letters of the genome there are four letters AG t and see these spell out indirectly proteins and a single spelling error can lead to a defective gene in 1994 after a decade of work Friedman and his collaborators honed in on a gene only found in fat cells that was really the moment of a lifetime I pulled out the film with some vague hope that maybe this would reveal something about the nature of the OB gene and I looked at it and in that instant I knew that we had identified the gene that makes a hormone and that plays a very active role in regulating appetite metabolism and probably other biological systems so if you injected that hormone into the blood of an OB mouse the mouse lost weight it would completely cure the mutation of a OB mouse and over the course of a few weeks depending on the dose you give they'll look indistinguishable for a normal Mouse the hormone was named leptin from the Greek word leftist meaning thin its discovery transformed our view of fact and the biological forces controlling appetite the ob mouse cannot see itself in a mirror and realize that it's hugely obese it thinks it's starving to death because this very critical hormone is not being made by the body and the idea that a hormone produced by fat can control what you think about food in a very important way this is a very radical notion a normal fat cell produces leptin which travels to the brain and signals the hypothalamus the region that determines when and how much we eat high levels of leptin tell your brain about 20 the fat story but low levels to eat and for those like Troy who can't make leptin because they lack fact getting the hormone would be life-saving the starvation was gone within three days of him taking leptin we saved a lot of money the Troy went from eating what three people would eat to eating what a normal person would eat in a day knowing that I was full I'm like wow this is amazing does hurt leptin can't cure Troy's disease but by curbing his hunger it protects his liver leptin does not bring the fat back it just helps to deal with fats absence patients finally can't take a deep breath that they're full and they don't have to worry about eating