Circulation November 20, 2018 Issue

Dr Carolyn
Lam:               
Welcome to Circulation on the Run, your weekly podcast summary
and backstage pass to the journal and its editors. I'm Dr Carolyn
Lam, Associate Editor from the National Heart Center and Duke
National University of Singapore.


                                               
Is there a unique lipoprotein profile for incident peripheral
artery disease as opposed to coronary or cerebral vascular
disease? Well, you're just gonna have to wait for our feature
discussion to find out. That's coming right up after these
summaries.


                                               
Our first original paper this week tells us that gene variance
known to be associated with idiopathic and peripartum
cardiomyopathy are also associated with preeclampsia. First and
corresponding author Dr Gammill from University of Washington and
colleagues studied 181 participants with confirmed preeclampsia
from the Preeclampsia Registry in BioBank. Saliva samples were
collected for DNA isolation and whole exome sequencing was
performed to detect rare variants in 43 genes known to be
associated with cardiomyopathy.


                                               
Results were compared with data from two controlled groups,
unrelated women with a gynecological disorder, sequence using the
same methods and instruments, as well as published variant data
from 33,000 subjects in the Exome Aggregation Consortium.


                                               
The results showed that women who developed preeclampsia are more
likely to carry protein altering mutations in genes associated
with cardiomyopathy, particularly, the TTN gene which encodes the
sarcomeric protein titin. Thus, detecting these gene variants may
allow more specific diagnosis, classification, counseling and
management of women at risk.


                                               
Prior trials have shown that nonsteroidal anti-inflammatory drugs
or NSAIDS confer cardiovascular risk. Now this has been
postulated to be due to enhanced formation of methyl arginines in
the kidney that would limit the action of nitric oxide throughout
the vasculature. However, the next original paper in this week's
journal suggests that this may not be correct. First author, Dr
Ricciotti, corresponding author, Dr FitzGerald from University of
Pennsylvania Perelman School of Medicine and colleagues, used
multiple genetic and pharmacological approaches to disrupt the
COX 2 pathway in mice and analyze plasma from patients taking
NSAIDS.


                                               
However, they did not observe an increase in methyl arginines. In
contrast, they did observe an increase in plasma asymmetric
dimethylarginine or EDMA in mice-rendered hypertensive by
infusion of angiotensin II at a dose that also caused renal
impairment. After a four week washout period following the
infusion of angiotensin II, blood pressure, creatinine, and ADMA
levels all fell back to normal levels.


                                               
Celecoxib-treated mice also exhibited increased ADMA and plasma
creatinine in response to infusion of angiotensin II and their
levels also returned to normal thereafter. Thus, it seems likely
that the previous reported elevations in ADMA reflected renal
dysfunction rather than a direct consequence of COX 2 deletion or
inhibition. The authors end by suggesting that the most plausible
mechanism by which NSAIDS confer a cardiovascular risk, is by
suppression of COX 2 derived cardioprotective prostaglandins such
as Prostacyclin rather than by enhanced formation of methyl
arginines.


                                               
The next original paper identifies new targets with the potential
to prevent vascular malformations in patients with hereditary
hemorrhagic telangiectasia. Co-corresponding authors, Dr Ola and
Eichmann from Yale University School of Medicine and colleagues
looked at SMAD4, which is a downstream effector of transforming
growth factor-beta/bone morphogenetic protein family ligands that
signal via activin-like kinase receptors.


                                               
The authors generated a tamoxifen inducible postnatal endo-fetal
specific SMAD for a mutant mouse and showed that SMAD4 prevented
flow-induced arterial venous malformations by inhibiting casein
kinase II. The uncovered pathways provided novel targets for the
treatment of vascular lesions in hereditary hemorrhagic
telangiectasia related juvenile polyposis patients carrying SMAD4
mutations.


                                               
The next original paper provides important data for the accurate
diagnosis of long QT syndrome. Long QT syndrome can be a
challenging diagnosis partly because the optimal method for QT
assessment is not unequivocally established. QT experts advocate
manual measurements with a tangent or threshold method.


                                               
In today's paper, first and corresponding author, Dr Vink from
Academic Medical Center University of Amsterdam and colleagues,
aimed to assess similarities and differences between these two
methods of QT interval analysis among 1,484 patients with a
confirmed pathogenic variant in either KCNQ1, KCNH2 or SNC5A
genes from 265 families. Both QT measurement methods yielded a
high inter and intra reader validity and a high diagnostic
accuracy.


                                               
Using the same current guideline cutoff of QTC interval 480
milliseconds, both methods had similar specificity but yielded a
different sensitivity. QTC interval cutoff values for the QT
measured by the tangent method was lower compared to that
measured by the threshold method. Plus, values were different
depending on the correction for heart rate, age, and sex.


                                               
The authors provided an adjusted cutoff values specified for
method, correction formula, age, and sex. In addition, a freely
accessible online probability calculator for long QT syndrome at
www.QTcalculator.org has been made available as an aid in the
interpretation of the QT interval.


                                               
The next original paper demonstrates for the first time that
thrombin mediated signaling may play a role in diet-induced
atherogenesis. Co-first authors, Dr Raghavan and Singh,
corresponding author Dr Rao from University of Tennessee Health
Science Center and colleagues, used a mouse model of diet-induced
atherosclerosis and molecular biological approaches and explored
the role of thrombin and its G protein coupled receptor signaling
in diet-induced atherosclerosis.


                                               
They found that thrombin-induced CD36 expression and foam cell
formation required protease activated receptor 1, G alpha 12,
Pyk2, GAB 1, and protein kinase C theta dependent activating
transcription factor 2 activation. Thus, inhibition of thrombin G
protein coupled receptor signaling could be a promising target
for the development of new drugs in reducing the risk of
diet-induced atherogenesis.


                                               
The next study provides insights into the long- term association
of LDL cholesterol with coronary heart disease mortality in
individuals at low tenure risks of atherosclerotic cardiovascular
disease. First and corresponding author, Dr Abdullah, from VA
North Texas Medical Center and UT Southwestern Medical Center and
colleagues studied more than 36,000 subjects in the Cooper Clinic
Longitudinal Study cohort who are at low tenure estimated risk of
atherosclerotic cardiovascular disease. In other words, a low
tenure risk of less than 7.5%. They've followed these patients
for more than two decades.


                                               
Results showed that LDL cholesterol and non-HDL cholesterol at or
above 160 milligrams per deciliter were independently associated
with a 50 to 80% increased relative risk of cardiovascular
disease mortality. The associations between LDL cholesterol and
cardiovascular disease mortality were more robust when follow up
was extended beyond the traditional 10 year estimated risk
period.


                                               
The associations remain significant in those with an estimated
tenure atherosclerotic cardiovascular disease risk of less than
5%. These data suggests that LDL cholesterol levels at or above
160 milligrams per deciliter in individuals deemed to be at low
tenure atherosclerotic cardiovascular risk are associated with
worse long term cardiovascular disease mortality. These findings,
along with other observational data and data extrapolated from
clinical trials, support further consideration of appropriate LDL
cholesterol thresholds for lipid lowering interventions in
individuals categorized as low short-term risk.


                                               
The final paper this week uncovers a novel therapeutic target for
the prevention and treatment of thoracic aortic aneurysms. First
author, Dr Nogi, corresponding author Dr Shimokawa from Tohoku
University Graduate School of Medicine and colleagues, used
genetically modified mice to show a pathogenic role of the small
GTP binding protein, GDP dissociation stimulator in the
development of angiotensin 2 induced thoracic aortic aneurysms
and dissection. Down regulation of this protein contributed to
dysfunction of aortic smooth muscle cells and hence oxidative
stress, and matrix metalloproteinase activities in the
pathogenesis of thoracic aortic aneurysms and dissection.


                                               
Local over expression of this small GTB binding protein GDP
dissociation stimulator around the thoracic aorta inhibited
aortic dilatation and rupture in deficient mice. And that wraps
it up for this week's summaries. Now for our feature discussion.


                                               
Atherosclerosis has been considered a systemic process, meaning
that when we see a disease in one vascular bed, we assume that
that's a risk marker for disease in other vascular territories,
and that they share pathophysiology, they share risk factors.
However, if we think about it, the prior studies have all been
sort of focusing on coronary and cerebral vascular disease, but
today's feature paper changes that a bit because it addresses a
key knowledge gap in peripheral artery disease risk, and
interestingly suggests that there may be a unique lipid profile
that's related to peripheral artery disease.


                                               
This is gonna be an exciting discussion and I have the first
author, Dr Aaron Aday from Vanderbilt University Medical Center
currently. We have our editorialist, Dr Parag Joshi from UT
Southwestern, and our associate editor, Dr Anand Rohatgi from UT
Southwestern. Welcome gentlemen and Aaron, could we start with
you sharing about your study?


Dr Aaron
Aday:                
So, as you mentioned, a lot of the previous epidemiologic data on
atherosclerosis have been primarily in coronary artery disease
and stroke, and when we looked at peripheral artery disease or
PAD, there seemed to be some subtle differences. So for instance,
total cholesterol on HTL cholesterol seemed to be the strongest
risk factors for future peripheral artery disease and in terms of
LDL cholesterol, the data are somewhat mixed. Some have found a
weak association, some have actually found no association. And so
building on that, we wanted to see if using nuclear magnetic
resonance spectroscopy, we could elucidate more details about the
litho protein pathways associated with peripheral artery disease.


                                               
And we did this in the women's health study which is a
prospective cohort study of women free of cardiovascular disease,
the baseline, they were aged 45 and older. And what we've found
in terms of the standards with their profiles, we again found
that there was no association between LDL cholesterol and future
peripheral artery disease, whereas certain standard lipid
measures like HDL cholesterol were strongly associated with PAD,
and then using the Endemol spectroscopy tool, we found that
actually, small LDL particles and total LDL particles were
concentrations of both of those markers, were strong risk factors
for future PAD and other measures like total HDL particle
concentration were even more strongly associated with future PAD
than coronary artery disease.


                                               
So essentially the signature associated with future peripheral
artery disease, had some important differences than that for a
composite of coronary artery disease and stroke.


Dr Carolyn
Lam:               
Aaron thanks for that. That's beautifully described and just so
intriguing. Parag, could you tell us how should we be thinking
about results like this?


Dr Parag
Joshi:                  
It's a great paper and it really highlights a new and unique
approach in that we ... Peripheral artery disease as an isolated
incident event is fairly understudied I guess we could say and
so, this is a really nice paper to start choosing out some of the
risk factors for that. I think overall, when we think of
peripheral arterial disease in general, I think historically,
we've thought of it as similar pathophysiology, you know LDL
particles and perhaps other particles depositing in the arterial
space. But this does highlight some important differences that
might exist and I think one of those seems to be that maybe this
is more a signature of elevated remnant lipoproteins or
triglyceride rich remnant lipoproteins, small dent LDL particles,
low HDL, that sort of metabolic syndrome type patterns that we
look at as a high risk factor that may be more contributory to
peripheral artery disease than coronary disease, or at least more
specific to peripheral artery disease.


                                               
I guess one of my main questions about that from your work Aaron
is, how can we be sure this isn't just a pre-clinical marker of
diabetic patients which we know have this type of pattern?


Dr Aaron
Aday:                
Sure, it's certainly a possibility. I think what's notable in the
cohort, at least a time enrollment. And there was a very little
diabetes and actually there was a much greater prevalent of
metabolic syndrome. So in my mind, it may be more of a metabolic
syndrome specific marker rather than necessarily down the
diabetes pathway, but it's certainly something that needs to be
explored further.


Dr Parag
Joshi:                  
I wonder whether women's health studies such a healthy cohort
that I wonder if this is picking up some signal before the answer
to diabetes or as you said, metabolic syndrome, you know which
certainly suggests an insulin resistance pattern and we know the
association of diabetes with peripheral artery disease is
stronger and so I wonder if this may be a sort of earlier way of
picking that up.


Dr Aaron
Aday:                
It may be. I think one thing to notice is the outcome of
peripheral artery disease that we're using. So it is symptomatic
disease. So, we're not picking up a lot of ulcers that are
developing in the future, it's more the claudication and then
people who've undergone revascularization. Certainly diabetics
have both of those as well but I think that may suggest it's not
fully unexplained by developing diabetes than peripheral artery
disease further down the line.


Dr Parag
Joshi:                  
Yeah that's a great point.


Dr Carolyn
Lam:               
Yeah great questions, great thoughts. Anand, what about you? Did
you have questions too?


Dr Anand
Rohatgi:           
I think from my perspective and thinking about it for circulation
and its readership, we found this really interesting for several
reasons. Number one, I think is, as you all have discussed,
peripheral arterial disease just is not as well characterized and
you can see that here in over 25,000 people, add about a 100 a
bed, so I think in younger folk, it takes a lot of people to
study, to be able to really understand kind of the
pathophysiology of peripheral arterial disease.


                                               
The other thing that they think they really shed some light on is
how this is happening in women in particular and in women, of
course as we know have been understudied in all cardiovascular
diseases, but in particular, diseases like this which are less
common. It's really insightful to see that these lipid
abnormalities in women are contributing to peripheral arterial
disease more so than your typical LDL cholesterol management and
interestingly enough, most of the women who had PAD events in
this study, did not have other cardiovascular events.


                                               
They really just had PAD events exclusively and I thought that
was really intriguing, and the use of this advanced lipoprotein
testing, this NMR modality has been very useful in terms of
biology and research, and I think that's the case here where we
really go under the hood Carolyn, as you said, and get kind of
deep dive, the lipid metalobles on abnormalities. And I think
Parag and Aaron hit the nail in the head that this is really
capturing an insulin resistance of phenotype and what I really
liked about this is, instead of studying people who are 70, 80
years old and a lot of things are sort of clustering, a lot of
diseases are clustering and they're manifesting all at the same
time, it's very hard to tease apart the effective age.


                                               
Here, we captured women in their 50s and middle aged, just as
they have kind of gone through menopause and this adverse
metabolite's phenotype starts to rise in women. And then we could
follow them over time and see what the natural history of that
is, and the women who have this phenotype go on to have this
devastating consequence, this peripheral arterial disease. One of
the questions I had then, Aaron for you is, what do you think the
implications are from these findings? Does it mean that in terms
of diagnostics, we should be doing more advanced testings looking
at LDL and HDL type particles with NMR or some other mortality?
Does it change therapies with new therapies beings studies right
now? What do you think the implications are from your work?


Dr Aaron
Aday:                
That's important right. I think you mentioned this and I see the
inter marked tool in this study, is really a way to try to dig
further into the biology of peripheral artery disease as a form
of atherosclerosis. I think that we already know patients who are
extremely high risk or PAD, those are patients with diabetes,
smoking history, metabolic syndrome et cetera., and as you can
see in a patient population in 28,000 middle aged women who are
pretty healthy, we only had just over a 100 PAD events.


                                               
So, I think even if you were to scale this up in terms of cost,
I'm not sure that that would necessarily be a viable option for
patients, but I think it does suggest that truly focusing on LDL
in a very high-risk patient population, meaning patients with
PAD, or we may not be fully addressing their risk. And so I think
this is a need to highlight that important gap, think about other
therapeutic options and we'll soon have ongoing trials,
triglyceride low in therapy that may be particularly beneficial
in this patient population and so that's how I see this being
used.


Dr Anand
Rohatgi:           
That makes a lot of sense and particular because in middle aged
women like this, your standard risk score algorithms will not
really capture that they're at increased risk, even if they
smoke, just because they're women and they're younger and so, I
think this really is a call to arms to more refined risk
assessment in these women.


Dr Parag
Joshi:                  
Aaron, do you think there's actually a difference in the biology
in the peripheral arteries compared to the coronary and cerebral
vascular beds, or is there data to kind of look at that or maybe
histopathological data to look at that?


Dr Aaron
Aday:                
We know there's a lot of overlaps, so I don't wanna suggest that
PAD is not a former atherosclerosis. I think one limitation is
that the primary animal model for PAD is the hyperCKemia model.
That doesn't fully recapitulate what's happening in a limb with
PAD and so I think that has been one limitation in understanding
the biology. But I think what we're starting to see in some
clinical trials that have come out in the last couple of years or
starting to see a somewhat different signal for therapies in
patients with PAD so for instance, in 48, we actually saw that
there was a greater benefit to LDL lower [inaudible 00:21:00]
inhibitors than for coronary disease. We now have the compass
trial results, again, more events, higher risk among these
patients but for their benefit, add on River Oxodine therapy,
we've seen lymph events or lymph signals in the SGLP2 inhibitor
trials. So, I think we're starting to get a sense that there may
be something else on top of the traditional ascariasis biology
that may be a potential target on down the road.


Dr Parag
Joshi:                  
I think it's really a fascinating biological question of how
these different territories might actually differ in their
pathophysiology. I think it's a really a nice time to look at
this. Also I think, Anand and Aaron both mentioned ongoing
trials. The omega 3 fatty acid trials I think reduce it, will be
soon to be presented and hopefully published in the next month or
so. It would be nice to see if they evaluate peripheral events in
that group, I'm sure they will.


Dr Carolyn
Lam:               
Indeed, these have been just such great thoughts and discussion.
Nothing really much to add there. I suppose I could say something
cheeky like for the first time, and I never thought I'd say it on
the podcast, I feel kind of bad that there are no men included in
this trial but anyway, I just learnt so much from this. I just
wanna thank you gentlemen for a great discussion.


                                               
Thank you, listeners, for joining us today and don't forget to
tune in again next week to Circulation on the Run.