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Now, for a long time people thought that was a passive energy storage reservoir.
很长一段时间以来，人们都以为棕色脂肪组织只是一个被动的储能库。
It was a useful source of emergency calories, but otherwise it didn't serve any larger function.
能在紧急情况下有效地保障卡路里供应，其他时候并不会起太大作用。
These days, we know that's not true.
如今我们已经知道，事实并不是这样。
Especially when we consider its role in the endocrine system.
尤其是考虑到它在内分泌系统中的作用就显得更重要了。
This is a system that handles hormones including the sex hormones like estrogen and testosterone.
内分泌系统是一个处理各种激素的系统，包括雌激素、睾酮等性激素。
But also other hormones that have effects on parts of the body that aren't that.
除了这些激素，影响身体其他部位的激素也属于这个系统。
Before scientists name any of the specific hormones,
在科学家给各种激素命名之前，
they suspected there might be something floating around the blood
他们就曾怀疑，血液周围是不是有什么呈漂浮状态的东西，
that signaled energy levels to the central nervous system.
会向中枢神经系统发送机体能量水平的信号。
One of the first big moments in this concept was back in the early 70s with an experiment on obese and diabetic mice.
“激素”这一概念早期比较重大的发现可以追溯到70年代初，当时，科学家们拿肥胖小白鼠和糖尿病小白鼠做了一项实验。
See, scientists can breed mice with different genetic profiles, or genotypes.
要知道，科学家是可以培育出不同基因图谱或基因型的小白鼠的。
That results in predictably physically different mice or phenotypes of mice.
这样培育出来的小白鼠的生理特征，或者说表型都是可以直接预测的。
In this case, a tweak in the ob gene part of the mouse's genotype results in an obese Mouse.
这种情况下，调整小白鼠性状中的肥胖基因就会改变小白鼠的肥胖程度。
Its phenotype.
也就是会改变它们的表型。
This makes sure that the test subjects are as consistent as possible.
这就确保了测试结果与预期能够尽可能的吻合。
During the experiment, mice were stitched together in an experimental condition called parabiosis,
实验过程中，他们将两只小白鼠拼接到了一起，这种实验条件就是所谓的“连体共生”实验，
meaning certain aspects of their anatomy, including their circulatory systems, were connected.
意思就是，两只小白鼠的某些解剖特征，包括它们的循环系统都是相互连通的。
This style of experiment used to be more common in the 60s and 70s
这类实验六七十年代的时候做得比较多，
and it led to some big breakthroughs in our understanding of hormones and in the immune system.
也正是因为这些实验，我们对激素和免疫系统的理解才有了各项重大突破。
The experimenters at the time set up four parabiotic scenarios.
研究人员设置了四个准生物场景。
An obese Mouse joins to a normal healthy Mouse,
肥胖小白鼠搭正常健康小白鼠，
a diabetic Mouse joins to an obese Mouse,
糖尿病小白鼠搭肥胖小白鼠，
now an obese with an obese and finally normal with normal as controls.
肥胖小白鼠搭肥胖小白鼠，最后一组是对照组，正常小白鼠搭正常小白鼠。
It was common for some of the mice to die during the experiment.
实验过程中有小白鼠死亡是很正常的。
And in the diabetic obese combo, the obese mouse tended to get hypoglycemia and died.
糖尿病+肥胖的组合中的肥胖小白鼠就大多都会低血糖而死。
But most of the mice in the other conditions survived.
但其他组的大部分小白鼠都活下来了。
Meaning almost all of the obese-obese combinations made it and both partners gained weight quickly.
这就意味着几乎所有肥胖+肥胖的组合都成功了，而且双方的体重都出现了迅速上涨的趋势。
On the other hand the obese-normal combinations also survived and gained weight,
另一边，肥胖+正常的组合也活下来并增加体重了，
but to a lesser degree than the obese-obese mice.
但程度没有肥胖+肥胖那一组那么明显。
So to the researchers, that meant that the normal mice
对研究人员而言，这就意味着正常小白鼠
were secreting some kind of hormone that regulates food consumption into the bloodstream of their obese partner.
悄无声息地将调解食物消耗的激素输送到了肥胖小伙伴的血液里。
Now, every hormone needs a receptor, and this hormone's main source of receptors was in the hypothalamus.
要知道，每种激素都是需要受体的，而调控食物消耗的这种激素的受体主要位于下丘脑内。
A portion of the brain that signals the release of a bunch of other hormones too.
下丘脑不仅要负责示意调控食物消耗的这种激素的分泌，还要负责示意一系列其他激素的分泌。
Now here's the big payoff.
接下来，丰厚的回报来了。
That parabiotic mouse study gave researchers a substance to look for what they called a satiety factor,
通过这一连体共生鼠实验，研究人员发现了一种用来观察他们所谓的“饱腹因子”的物质，
that OB gene that resulted in obese mice had also been shown to make a specific protein.
实验表明，导致小白鼠肥胖的肥胖基因也会制造一种特定的蛋白质。
And in 1994, that hormone was discovered and named leptin.
1994年，研究人员终于找出了这一激素，将其命名为“瘦素”。
It's a hormone released from adipocytes that tells our bodies we have enough energy and we're not starving.
它是脂肪细胞释放的一种激素，意思是告诉我们，我们的身体已经有足够的能量，已经不会挨饿了。
Adipocytes will give off different amounts of leptin depending on how much fat mass we have,
脂肪细胞会根据我们脂肪量的多少，根据我们的营养状况
our nutritional status plus a few other factors.
加上其他一些因素释放不同量的瘦素。
Leptin's main job is to signal that you have enough energy stores, not excess energy stores.
瘦素的主要工作是示意你的机体你的体内已经储备了足够，而不是过量的能量。
So when you don't eat enough or you're losing weight,
所以，当你吃的不够多，或是在减肥的时候，
lower leptin levels are a signal to your brain that it should eat more.
较低的瘦素水平就会通知你的大脑，你还需要吃东西。
That's one of the reasons that diets are largely pointless.
所以说节食在很大程度上都是没必要的。
Your body will literally adjust to tell you to eat more.
因为你的身体会自行调节，告诉你你得再吃点儿东西。
Leptin is involved in a few other things too.
除此之外，瘦素也会参与人体的其他活动。
Like immune function regulation and bone development.
比如免疫功能的调节啊，骨骼发育等等。
And leptin isn't the only hormone that fat tissue makes.
不仅如此，瘦素也不是脂肪组织分泌的唯一一种激素。
It also makes a hormone that helps regulate blood sugar called adiponectin,
脂肪组织还会分泌帮助我们调节血糖的一种名为“脂连素”的激素，
and a bunch of enzymes that can modify steroid hormones like estrogen and testosterone.
以及一系列可以调节类固醇激素(如雌激素和睾酮)的酶。
That's especially useful if you're a person with ovaries and in menopause.
如果你是一个有卵巢且正处于更年期的人，脂肪组织就更重要了。
Up to a hundred percent of circulating estrogen comes from adipose tissue for postmenopausal women.
因为绝经后的女性体内循环的雌激素几乎全部都来源于脂肪组织。
As if the energy stored and hormone production wasn't enough, fat is also a useful source for stem cells.
就算你觉得储存能量和分泌激素这两个功能还不够重要，脂肪也是干细胞的重要来源。
Stem cells can become other types of cells and show promise as treatments in the future.
干细胞能发育成其他类型的细胞，在医疗方面也有着广阔的前景。
And in the last few years, scientists around the world have figured out ways to take that tissue and turn them into stem cells.
过去的几年里，国际社会的科学家已经找到了提取脂肪组织并将其转化为干细胞的方法。
This is called induced pluripotent C.
这就是所谓的“诱导性多能干细胞”。
If you take a mature cell and transform it into a cell that can become their cell types,
如果我们能将一个成熟的细胞转化成它的类型细胞就好了，
that's great since we have plenty of adipose tissue in our bodies and it's easily accessible with a little bit of liposuction.
因为我们体内有大量的脂肪组织，只要做一点吸脂手术就可以很容易地取到脂肪组织。
This also makes sure that the stem cells are compatible with the recipients immune system,
这也确保了干细胞与受体的免疫系统能够兼容，
since they came from the recipients body in the first place.
因为移植的干细胞本来就是从受体身上取下来的。
But this is all relatively new science.
问题是，这些研究都还比较新颖不够成熟。
And there's ongoing research to figure out best practices for fat derived stem cells.
研究人员还在继续研究将脂肪细胞转化成干细胞怎么转化最好。
Plus, there's still more to learn about fat's role in the endocrine system.
另外，脂肪在内分泌系统中的作用我们也还需要做进一步了解。
My goal with this episode was to show you that fat is incredibly valuable to our bodies.
做这期视频，我就是想告诉大家脂肪对我们的身体有着极其重要的价值。
Fat is part of what makes us human and it's worth celebrating how cool this organ is.
脂肪也是造就我们的功臣之一，它值得我们加以歌颂表扬。
Thanks for watching this episode of seeker human and appreciating the body with us.
感谢大家收看本期视频，和我们一起欣赏我们的身体。
I'm Patrick Kelly.
我是Patrick Kelly。
