All right friends, welcome back.
So in this lecture, we're going to cover 2 things.
One is Asian glow and the other is pharmacogenomics.
And so, Asian glow or alcohol induced flushing, what we want to do is understand that well enough to explain it to a patient
but also, relate it to something called pharmacogenomics.
And what pharmacogenomics is is the study of how genetic differences can affect drug metabolism and in this case, alcohol metabolism.
And why Asians are more predisposed to getting this alcohol induced flush compared to Caucasians.
So what we can see in this picture here is an Asian before and after drinking alcohol
and the redness that we see here is called alcohol induced flushing. I said Asian glow. It;s sometimes called the Asian flush
and what happens here is you take a sip of beer or any alcohol for that matter and within minutes right,
within 15 minutes, you get this reddening of the face or in the neck that we can see here a little bit.
Maybe some itching on your upper torso and this is a result of genetic differences amongst Asian people.
By the way, I want to give a quick shout out for this picture here.
This is from PLOS which is the Public Library of Science. It's a fantastic non-profit. We can see PLOS here. It's a fantastic, non-profit open access journal for free scientific papers.
So, back to this picture. So what we see here is this alcohol induced flushing and this is common in East Asians.
So it occurs in actually 1/3 of East Asians
and when I say East Asians, I'm referring to Japanese, Taiwanese, or Koreans.
So East Asians and they get this flushing.
And so the first question is why is alcohol causing this and that's kind of a trick question
because surprisingly, the answer is that it's not alcohol that is directly causing this redness
but instead it's a metabolite of alcohol.
So, I'm just going to write here as alcohol and it's not alcohol but instead it's a metabolite of alcohol
and that metabolite my friends is called acetaldehyde.
So let's put acetaldehyde in a little box because this is the key player here. This is what's causing all of our problems.
Interestingly, it's acetaldehyde that is also causing a majority of the hangover effects of alcohol.
So, what's going on?
Well, right here we see this redness of the skin.
So, what's going on is in the periphery near the skin, acetaldehyde is causing the release of things called histamine and prostaglandins.
So, histamine and prostaglandins and so, if we remember from physiology, histamine is a vasodilator
and prostaglandins like PGE2 or the PGD2. This is the specific name of those prostaglandins. These are vasodilators.
So, vasodilators.
And so, what they do is they widen your arteries, your veins and they increase the blood flow to your skin
and remember, blood is obviously red so we increase the blood flow to the skin and we get this facial flushing
and so, this is what's causing the flushing.
So you got to know this.
Histamine is pretty proven to cause this flushing here. Prostaglandins we know that they cause vasodilation as well
And so, the reason you need to know this is because a patient might ask you, "Hey doc, what is causing flushing?"
That's the answer. Histamine and prostaglandins from acetaldehyde.
But what he might also want to know is how can I treat this you know this rag or this reddening that I get, this alcohol induced flushing?
And so, what's happening here is that your answer to him should be,
"Well this is a reaction to a drug and any sort of drug reaction that we get, the best solution is to avoid the offending agent."
So, let's just write here the treatment (Tx or treatment) is no alcohol and alcohol can be abbreviated by ETOH for ethanol
but that's not fair.
What if this patient just wants to have one or two glasses of wine socially but avoid this alcohol induced flush?
Well some research has shown that to treat it, we can use antihistamines.
We know histamines cause the flush so we can use antihistamines to treat it.
And the one most commonly used by people is something called cimetidine which is an H2 blocker.
So, let's just write cimetidine.
That's different than Diphenhydramine which is an H1 blocker but you could actually probably use both.
I did see a paper which talked about both cimetidine and diphenhydramine used together
and that if you took it before you started drinking, you would decrease the flushing in your face.
So, things like you know Pepcid AC or Zantac might help here. That's the H2 blockers.
The other thing is that we know prostaglandins cause some of this flushing.
And so, something that inhibits the production of prostaglandins is our good old friend aspirin.
And so, I'll just write here aspirin decreases the production of prostaglandins.
So, this is the part 1 of our lecture. This is really the underlying principles of Asian glow.
So, we know that 1/3 of East Asians (the Japanese, the Koreans, the Taiwanese) they get this flushing
and it's not a result of alcohol but it's the result of this build up of something called acetaldehyde.
And this leads to the release of histamine and prostaglandins which are vasodilators. More blood goes to the skin.
We are getting flushing and the treatment for it is 1, avoid alcohol but 2, we can use antihistamines to block the histamine effect
or we can use aspirin to decrease the amount of prostaglandins.
So, the next question that a patient might ask you is, "Doctor, why is this happening to me but it's not happening to my Asian wife or to my Asian friends?"
And the real question he's getting at is why do some people get flushing and others don't
and that leads us into pharmacogenomics and something called enzymatic polymorphisms
and that's what we're going to do in the next lecture.