Host — Dan Keller
Hello, and welcome to Episode Ninety-three of Multiple Sclerosis Discovery, the podcast of the MS Discovery Forum. I’m Dan Keller.
Today's interview features Dr. Lilyana Amezcua, an assistant professor of neurology at the University of Southern California in Los Angeles. Part of her work focuses on defining racial disparities in MS, particularly among the Hispanic community. When we met, she said the prevalence of MS among Hispanics in Latin America has been increasing over the past 20 years, and their clinical characteristics are different from those of whites. As Hispanic Americans constitute one of the largest minorities in the U.S. population, she looked into their clinical picture, as well.
Interviewee – Lilyana Amezcua
And so we initially did a first observation in 2011 noting when we examined close to 200 MS patients of Hispanic background self-identified that they were at twice the risk of presenting with optic neuritis and spinal cord problems compared to whites. There is some literature indicating throughout Latin America that these observations could be related to an Asian background. And so when we think about a Hispanic, we think about an umbrella that is related to an intermixing of European, African, and Asian derived background or Native American. So that diversity along with the cultural diversity could have some implications in the way that MS behaves and including risk. And that is one of the theories going around that that's why they don't get MS that much because of an Asian background. However, again, like I mentioned, in the last 20 years more cases have been reported.
Interviewer – Dan Keller
Haven't Asians been reported to have this opticospinal sort of MS? So would that feed into this optic neuritis finding with the Hispanics?
That is correct, and actually a second study of ours that we did several years ago was to actually specifically look for that definition of opticospinal MS. And so what we found within 200 or so patients was that indeed when we applied that definition, very few met that criteria. But irrespective of that, and we made sure that every case was negative for aquaporin 4, which is an antibody that you commonly find in more of the NMO spectrum disorders, that these individuals did not have this aquaporin 4, but yet close to 20% looked like they had spinal cord lesions that could be associated with opticospinal.
So that observation, of course, led us to think, well, okay, we should look further. If we do think that Asian ancestry could be important, would some of those clinical characteristics be associated with that type of global ancestry? And in fact today we have a poster related to taking the population that we just presented and looking at their genetic variants, which are mostly noting that the European genetic variants are also found in the Hispanic, but now going forward and looking at, well, what about global ancestry and their clinical characteristics? And in that poster, that abstract, we find that the higher proportion of Asian background you have, the higher risk of presenting with let's say, an optic neuritis. Now that doesn't necessarily say that this is just specific for optic neuritis, but it could going forward let us know about the mechanism behind optic neuritis, which is also found in MS, also found in NMO, and these optical spinal forms of MS.
How did you go about looking at the genetics of the population?
Going about the genetics actually went back to the fact that when I would say, I'm studying Hispanics, people would ask, what is a Hispanic? And it is true…Hispanic…and so it is defined, you know, when you define it it's well, you can be from Cuba, you can be from Mexico, you can be from the US. But really what links us is…and I say linked us because I'm one of them…is the fact that there is a genetic background that is shared. And there's also cultural aspects that are shared. The cultural aspect is probably going to be important when we start examining the environmental aspects of MS.
What did you find?
We just started basically with vitamin D. We looked at vitamin D levels in Hispanics with MS compared to whites with MS, and we found that significantly lower levels were among the Hispanics. This is not surprising. This is expected, actually, because of the skin coloration and sun exposure probably differences, but it's also widely known that Hispanics would have lower vitamin D levels. Of course, that doesn't answer, well, if they have lower vitamin D levels, if their risk of MS is less, it doesn't give us any explanation. But we know that their vitamin D levels are low.
Other aspects that we have looked at is just examining differences by migration. So we know in MS that migration, usually, depending on when you move from one place to the other and looking at the risk of MS in the underlying country, that will be modified depending on the age of migration. And so of course Hispanics in the US, again, along with their diversity, they're diverse in the fact that there are many that are US born and there are many that are immigrants. So we looked at differences by this, and we found tremendous amount of differences. One was that the US born appears to have an increased risk of developing MS at a younger age. And this again is just validating some of that information that we know about MS in the past, right, coming from a lower prevalent region and being born in a place of higher risk.
But the second was that, which we were surprised, was that the immigrant, despite being here, let's say 25 years, they developed MS after they had emigrated from their country, on average, 15 years later. So that's interesting. That's again calling for us to investigate, what environmental encounters might have they had when coming to this country? And the third was that respective of this, of, you know, disease duration, there was an independent risk factor for the immigrant to develop ambulatory disability at a shorter time. So that's telling us that, again, well, one is differential environmental exposures. But could the immigrant and the US-born also just be two different populations in terms of, again, what does Hispanic mean? That's where we are.
In that sense, could you correlate vitamin D levels or anything else with the amount of European background or indigenous Central and South American background they had?
I think that's an excellent idea. You know, I think that could be done, to look at the US-born versus the immigrant. Now there is a large study conducted by Dr. Langer-Gould that's examining the risk of MS within Hispanics, whites, and African Americans in relationship to vitamin D and their HLA. So that will give us information on vitamin D. But absolutely we know that within Hispanics, we're going to have to separate groups because it's just such a big umbrella.
It's also a big umbrella in terms of cultural background. It's not uniform culture whether you're from the Caribbean or Mexico or born in the US.
Absolutely. So culturally we're going to have to tease that out. And it's simply starts by learning about, well, what are those cultural differences? Which could be from simple perceptions and their access and utilization of care, which needs to be first addressed, or to go forward and then say, well, let's see if there's biological differences. First, I think, you know, between the US-born and the immigrant, the differences could be explained also by sociocultural factors. And those need to be teased out. And then from there look to see, well, is this really a health disparity? Or is it an inherent biological difference of the disease, which we also expect to find.
Do you think that the results you find in this population is going to be more generalizable or relatable and give you some clues into what's going on with anyone who is getting MS or not?
Absolutely. That is the goal. While that diversity is complex, it's also a positive aspect because it will allow you to tease out a lot of those factors. And so within the admixture, of the genetic admixture, one can say, well, you have less European background. But what about that Asian component that is not found in your general European? It doesn't mean that it's not going to be found. Instead of looking for, I guess, a needle in a haystack, you will just be looking it in a block and maybe find something new or lead us to understanding of mechanisms, again, from the optic neuritis and the global ancestry. We are hoping that this is beyond just understanding one population, but understanding MS, which is the target population.
Have we missed anything important?
There is definitely a lot to do, and I think it's an effort that cannot be done alone. And so combining it with different centers that have the same interests and population is what the goal is, is to create a network of centers that are interested in defining this population, to move faster.
Great. Thank you.
Thank you for listening to Episode Ninety-three of Multiple Sclerosis Discovery. This podcast was produced by the MS Discovery Forum, MSDF, the premier source of independent news and information on MS research. Msdiscovery.org is part of the nonprofit Accelerated Cure Project for Multiple Sclerosis. Robert McBurney is our President and CEO, and Hollie Schmidt is Vice President of Scientific Operations.
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For Multiple Sclerosis Discovery, I'm Dan Keller.