How many of you remember The Suite Life of
Zack and Cody? It was a Disney show about two twins who lived
in a hotel and always got in trouble. Zack was the reckless, rebel one. And his twin brother Cody was the sweet, charming,
well-behaved one. However, it’s interesting that they were
twins, identical twins, meaning that their DNA was 100% the same, like literally the
same. Yet they could not be more different. But why? Genes are important. They do define us, to a certain extent. But behavior and environment are also important. The environment can, in a way, shape your
genetics. But, here’s the thing. The environment can have an effect on your
genes, but it doesn’t really change your DNA. The DNA stays the same. What changes is the way your body reads these
genes. These reversible changes in genetics is what
we call epigenetics, a fairly new field of study. What it consists of is, in a nutshell, turning
genes on and off. Identical twins are a scientist's best friend,
for many reasons. For example, to study epigenetics, they could
not be more perfect. It’s two people that are born with the same
genetic material, meaning it allows us to study the impact of the environment and behavior
on development and health. So an interesting fact is that twins when
they are born have practically no difference when it comes to epigenetic tags. Whereas these differences increase the older
they get. And, actually, these differences are stronger
the less of their lifetime that these twins spend together. Let’s use Zack and Cody again for an example. Let’s imagine for a second Zack has an overall
poor health as a consequence of an unhealthy lifestyle. He smokes, he is constantly stressed, and
follows an unhealthy diet. Cody, on the other hand, works out regularly,
doesn’t smoke, and eats healthy. You know where this is going. Chances are, Cody will have an overall healthier
life than his twin brother Zack. But let’s analyze what’s going on on a
genetic level. All of these factors (what Zack and Cody are
exposed to) can cause epigenetic changes. These can have a positive or a rather negative
effect. To understand how epigenetics can affect age,
development, and health, we first need to understand what epigenetics. So, let’s start from the beginning. The basics. Our genetic information is stored in the DNA. The segments in the DNA that contain a specific
set of information are called genes, and they have names like TP53 and stuff. These genes can play a role in many different
processes, like muscle growth, immune system, or tumor formation. But as I just said, literally one second ago,
this is information that is stored in the DNA. If the genes are just sitting there, in the
nucleus of the cells doing nothing, they’re not really doing much. Which means that, in order for them to do
their function, they need to be expressed. In biochemistry, gene expression is the process
by which the instructions in our DNA are converted into a functional product, such as a protein. And here is where epigenetics come into play. Epigenetic changes can affect gene expression,
making a gene able or unable to be expressed, sort of like an on and off switch. This can happen through different mechanisms. So, remember the instructions in our DNA can
be converted into proteins? Well, somebody has got to read this information,
right? This is Peter. Peter reads the DNA so it can be later translated
to protein. For that, Peter needs to attach to the DNA. The epigenetic changes will mostly allow or
prevent Peter to attach to the DNA. The main ones are:
Adding a little chemical group to DNA, so the DNA cannot be read and therefore not expressed. This is called DNA methylation. Histone modification. Some genes are wrapped around proteins called
histones, which makes them inaccessible to Peter. Chemical groups can be added to these histones
for genes to be unwrapped (genes “turned on” → accessible to Peter) or wrapped
(genes “turned off” → inaccessible to Peter). Non-coding RNA. I won’t go into much detail about what non-coding
RNA is because I don’t want to make this video even more complex, but it can also affect
gene expression, but it does so by, for example, attacking Peter, or recruiting other proteins
to do the other things we mentioned before. Epigenetics and lifestyle. Okay, now you know what epigenetics is and
how it works. But what role do they play in our lifestyle? - cough - As stated in a super interesting scientific
Review that I will link down below, there are several lifestyle factors that are suspected
to modify epigenetic patterns, such as diet, obesity, physical activity, tobacco smoking,
alcohol consumption, environmental pollutants, psychological stress, and even working on
night shifts. Let’s talk about food, for example. Back to our Zack and Cody example. Zack, in this imaginary scenario, isn’t
really what you would say a healthy person. He eats tons of fatty food, like, the bad
type. And there is evidence that a diet rich in
polyunsaturated fatty acids could increase the presence of free radicals and oxidative
stress, which have been linked to epigenetic alterations related to even tumor-related
processes. Whereas Cody, super healthy dude, eats tons
of greens and fruits. In particular, he loves soybeans. Why? Because they’re rich in polyphenols. And some of these polyphenols have a positive
epigenetic effect, among so many other benefits. As a matter of fact, soy consumption is correlated
with a reduced risk of hormone-related cancers. Disclaimer, I’m oversimplifying this for
educational purposes. No, you won’t 100% get cancer if you eat
a burger every day. And no, you won’t 100% be the healthiest
person alive if you eat a bowl of soybeans for breakfast every day for the rest of your
life. - cough - Another example is obesity. It is thought that certain foods can alter
DNA methylation and therefore contribute to obesity through epigenetic mechanisms. Physical activity also has an impact on epigenetics. Some scientists believe that physical activity
can increase DNA methylation in genes associated with inflammatory responses. So, higher physical activity can mean more
DNA methylation in these genes, which means less inflammatory response. DNA methylation in these same sequences has
been shown to be related to lower incidence and mortality from ischemic heart disease
and stroke in elderly people. However, we cannot confirm that it is a direct
consequence of physical activity. That will take a little more time and more
evidence to confirm. The Dutch Hunger Winter. Let's talk about one of the most interesting
studies done in the field of epigenetics: the Dutch Hunger Winter. Environment can have an effect on our genes
as early as before we're even born. And the best example of this is the Dutch
Hunger Winter. From 1944 to 1945, the Nazis blocked the food
supply to the Netherlands, resulting in a famine, where 20,000 died of starvation. And the children that were born during this
time were affected not only when they were born, but for their entire lives. As adults, they ended up being more overweight
than average, had higher levels of LDL and cholesterol, also showed higher rates of schizophrenia,
diabetes, and obesity, and even had higher mortality rates after age 68. Scientists studying this tried to find a connecting
pattern, epigenetic tags that they had but their siblings didn’t. And they found a few methyl groups that were
linked both to the famine and to health conditions later in life. This is very interesting for different reasons. First, it implies that stressful conditions
during pregnancy could affect kids before they are even born. And second, if these epigenetic alterations
are really the cause of the health conditions that these people experienced later in life,
which isn’t 100% clear, this could mean that we could detect epigenetic patterns that
can lead to health problems early in life, so we could then treat it and prevent it accordingly. Epigenetics and inheritance So, epigenetics is influenced by a person’s
experiences. Could there be a chance that this is inherited? That things we experience can have an impact
on our genes to such an extent that we can pass it down to our offspring? Could it be that, maybe, Lamarck was right
all along? Well, not exactly. I mean, as unconventional as it may sound,
there is quite significant evidence that epigenetics is indeed inheritable. This is rather new, and it’s something that
scientists are still trying to sort out at this very moment. However, based on the research that I’ve
done for this video, there doesn’t seem to be any real agreement. There’s a group of people that say um hello? epigenetic changes are totally inheritable,
can’t you see? and there is another group that’s like hmm,
it’s not that simple, let’s dig deeper into this. But in any case, if the question is whether
epigenetic changes can be inherited at all, the answer is yes. And this is called transgenerational epigenetic
inheritance. And how can that happen? Well. When the sperm cell and the egg fuse, a process
called reprogramming takes place, in which the cells go back to a blank state, and that
means also deleting all epigenetic tags. However, there is a small number of tags that
go unnoticed, and are, therefore, inherited by the offspring, leading to what we call
parental imprinting. And there are quite some experiments that
suggest this. For example, the agouti mouse, the Överkalix
study, where it was observed that a man’s poor food supply and a woman’s good food
supply can be correlated with their kids having a lower chance of cardiovascular death. It's important to know that, when we talk
about the inheritance of epigenetic changes, we're always referring to germinal cells (sperm
cells and eggs). Any epigenetic alterations that happen in
a muscle cell won't have any impact in your offspring. Let me know if you're interested in the inheritance
of epigenetics and maybe we can do a video about it. Can you imagine a world where we could design
our babies and select the traits we want our our babies to have? Is that even possible? Check this video to find out.
