A large multi-ancestry GWAS meta-analysis identifies a dominant SIM1-linked locus and multiple genetic connections between electronic health record-defined erectile dysfunction and cardiometabolic, psychiatric, and substance-use traits
0:00Welcome to Base by Base, the papercast that brings genomics to you, wherever you are. Thanks for listening, and don't forget to follow and rate us in your podcast app. Okay, so let's start with a, well, a compelling but maybe uncomfortable reality.
0:15Rectile dysfunction. Right. ED. It affects a massive number of people. I mean, we're talking up to 30% of men over 40. And for decades, the clinical focus has always been on the physical plumbing, you know?
0:28Exactly. The vascular health. Do you smoke? Do you have high blood pressure? Is this just a symptom of type 2 diabetes? It's traditionally seen as a secondary problem, almost like a canary, a coal mine for heart disease.
0:40Yeah. But what if that view is just too narrow? What if the strongest, most fundamental predictors weren't just about your blood vessels, but were written deep in your DNA? And this is where the script absolutely flips.
0:52We're diving into a study that suggests the genetic architecture of ED isn't just linked to heart health. Not at all. It's also tied to some really surprising psychiatric and behavioral traits. Things you would never connect.
1:03We're talking significant genetic overlap with things like opioid use disorder, ADHD, even, even risk taking behaviors. It just raises this immediate question. How can a trait that we define by physical function be so genetically intertwined with complex behavioral disorders?
1:21doesn't seem to make sense. The shared genetic roots here are profound, and they really challenge that simple mechanical explanation of ED. And if that wasn't counterintuitive enough? Wait until you hear this finding.
1:33Genetic liability for ED is positively correlated with the number of children someone has. And their lifetime number of sexual partners. Which just challenges the narrative completely. It really does. It tells us, we aren't just looking at the genetics of, say, inability.
1:49We're looking at the genetics of a complex predisposition. A predisposition that includes what? It seems to include the behavioral motivation to actually seek treatment when these issues come up. So our mission today is to unpack this massive multi-ancestry study.
2:03It analyzed over a 1000000 participants to give us the highest resolution map yet of the genomic complexity behind ED. Before we jump into those intricate connections. We do want to briefly acknowledge the researchers.
2:15Of course. Today, we celebrate the comprehensive work of Yuri Bright, UChen, Joseph D. Deek, and the whole team at Yale School of Medicine, and the VA Connecticut healthcare system. They've really pushed our understanding of the genetics of erectile dysfunction forward in a huge way.
2:31So to ground us, what's the clinical definition we're working with? Okay, so clinically, ED is defined as the inability to achieve and maintain an erection firm enough for satisfactory sexual performance.
2:44And the prevalence is really age dependent, right? Highly. It shoots up from under 10% in younger men to nearly one in 3 men over the age of 30. Physiologically, it's actually a surprisingly delicate process.
2:54It really is. It requires the smooth muscle and the penis to relax, which means decreasing nor adrenaline and crucially increasing a signaling molecule called nitric oxide, NO. And that lets the blood rush in.
3:06Exactly. It fills the erectile tissues. So when that delicate cascade is broken. You have ED. And we know the major physical factors that can disrupt it. Right. Age is the dominant one, of course, but vascular issues, high blood pressure, smoking, those are key.
3:21And type 2 diabetes. T2D is generally considered the strongest risk factor outside of age. The clinical overlap is dramatic. I mean, up to 80% of reported ED cases are individuals who are also grappling with obesity.
3:35But the connection isn't just physical. Clinically, the mental health link is staggering. Oh, it's huge. Individuals with ED have a 77% increased risk of anxiety. A 39% higher odds of depression. And if you look at PTSD, it's 5 times more likely.
3:51Five times. So the psychological distress is just inseparable from the physical mechanism. And that distress is really what creates the urgency for this kind of genetic research. While treatments like PDE 5 inhibitors, you know, the little blue pills are successful for many.
4:07They're not a silver bullet. No. Their success rate plateaus at about 65 to 70%. Which means a huge portion of people don't respond. These substantial 30 to 35% don't respond effectively. And that forces clinicians to look for deeper biological targets that go beyond that nitric oxide pathway.
4:26Okay, so let's unpack how these researchers manage to map this incredibly complex landscape. They leverage the immense statistical power of a genome wide association study, a GWOS. Using data from the All of Us Biobank.
4:40Exactly. And then they combine that with previously published data sets in a massive meta analysis. And the scale here is really what gives the findings their weight. The scale is everything. It gives them statistical certainty.
4:51They achieved an effective sample size of over a 1000000 subjects. A million, wow. Yeah, including over 913,000 subjects of European ancestry and 125,000 of African ancestry. This is, without a doubt, the best powered genetic study of ED to date.
5:08And it's crucial to understand what they are measuring specifically. They called it E-H-R-ED. Electronic health record defined ED. Which is an important distinction. They weren't just relying on casual self-reporting.
5:19No. They included people who had a formal diagnostic code ICD 10 code N52 or who had received a prescription for ED medication. So they were studying people whose condition was severe enough, and concerning enough, to make them seek actual clinical treatment.
5:36Right. And to make sense of all this data, they use some pretty advanced tools. A whole suite of them. But there are 2 that are particularly important for our discussion today. The 1st one being Mendelian randomization or men are.
5:49Right. You can think of it as sort of nature's randomized controlled trial. Because genes are randomly assigned at conception. Exactly. So MRR uses those randomly assigned genetic variants to test for causal relationships between 2 traits.
6:01For example, does the genetic risk for ED cause obesity, or is it the other way around? It helps you figure out the direct of the arrow. Precisely. And the 2nd tool, which gives us some of the most profound insights, is genomic structural equation modeling.
6:15GSEM. GSEM. If MR is about tracing a single causal line. GSEM is about drawing the whole map. It lets researchers organize these highly correlated traits, like depression, T2D, and ED, into a smaller number of underlying genetic factors.
6:32It helps you see the bigger genetic themes. So after this monumental effort, what did they find? Well, the meta analysis was incredibly fruitful. They identified 40 independent risk variants in individuals of European ancestry and 51 cross ancestry variants.
6:48I mean, this single study increased our prior knowledge of the associated coating genes by 50% in the European analysis alone. That's a massive leap. It is. But if we zoom in, one finding really stands above all the others, and that's the sheer strength of the single strongest genetic signal.
7:04Okay. In all of their analyses, the most powerful variants map to a non-coding regulatory region on chromosome 6, a region that controls the SIM one transcription factor. So this one region is like the genetic epicenter of ED risk.
7:18It's the undisputed epicenter. When we talk about significance in genomics, the statistics here were just, they were off the charts. The signal was 100 orders of magnitude stronger than the next closest hit.
7:29So it's basically a guarantee. It essentially guarantees that genetic variations in how Sim one is controlled are fundamental to a person's predisposition for ED. And what's so special about Simone. Simlin is fascinating.
7:42It's deeply involved in the body's weight regulation system. It's a transcription factor that's heavily associated with hyperphagia, which is excessive appetite, and with weight gain and severe obesity.
7:53In both animals and humans. In both, yes. Okay, so beyond Simone, what other candidates popped up? They found a few other compelling ones, ESR one, for instance, which codes for estrogen receptor alpha.
8:04A huge player in reproductive health. A major player. And another one, PHF 21B, which is a gene that's been previously linked to major depressive disorder. Ah, so there's the confirmation of that genetic link to psychiatric risk.
8:17Exactly. And when they looked at the broader correlations, the GWS results confirmed what we see in the clinic. So strong genetic correlations with TTD depression PTSD. Right, which means the genes that predispose you to depression, are also, to some degree, the same genes that predispose you to seeking treatment for ED.
8:35And then there's that paradox we mentioned at the start. They found the strong negative correlation with the age of 1st sexual relations. Meaning a genetic risk for ED correlates with starting sexual activity younger.
8:48And critically, it also showed a positive correlation with the number of children and the number of lifetime sexual partners. So how can a genetic tendency for dysfunction possibly correlate with a more active sexual life?
9:02just doesn't add up on the surface? That's where the advanced causal analysis becomes absolutely essential. So let's start by unpacking that SIM one connection and the link to obesity. Right. Right. Since Simone is such a powerful signal for both traits, the big question is, which one causes the other?
9:19And this is where Mendelian Randomization gives us a really powerful answer. Okay. The MR analysis strongly suggests that the genetic variants associated with EHRED are a much stronger causal factor for morbid obesity than the reverse.
9:32Whoa, okay, say that again. The genes for ED risk are a stronger cause of morbid obesity than the obesity genes are a cause of ED. That completely changes the narrative. It does. We can't just say, oh, obesity causes ED.
9:45Instead, it looks like they spring from the same genetic root. And that root is largely driven by this sim one locus. So the genetic blueprint that predisposes someone to severe ED also, independently, predisposes them to severe weight gain.
9:59Exactly. The ED isn't just a symptom of the obesity. It's a parallel manifestation of the same core genetic vulnerability. So if we expand that out, the genomic structural equation modeling, that overall genetic map.
10:14What did that show us? It gave us this beautiful way to organize all the genetic chaos. It show that the overall genetic architecture of ED isn't just one single thing. It split. It's split into 2 relatively independent major genetic factors.
10:29Isn't that the most exciting finding of the whole study? I think so. So factor 3 is the one we're all familiar with. It's the physical metabolic component. The traditional plumbing problem factor. Exactly.
10:39It includes the genetic risk for TPD, high blood pressure, ischemicar disease, general obesity, all that. But factor one is the profound surprise. It really is. This factor captures the genetic risk for behavioral and psychiatric traits.
10:51Things like substance use disorders. Yes, specifically opioid use disorder and cannabis use disorder. And that's alongside key risk-taking traits like ADHD, and again, the number of lifetime sexual partners.
11:04The implication there is just crystal clear. It is. ED sits at this intersection of genetic risks for 2 totally separate domains, metabolic and vascular health on one side. And complex behavioral dysregulation and risk taking on the other.
11:19So for a subset of patients, their ED is fundamentally driven by the same genetic tendencies that might drive substance use risk. And that distinction is critical for future treatment, right? If your ED is mainly from factor 3, the metabolic side, traditional approaches might work. They might, but if you fall heavily into that factor one bucket, you might need a totally different pharmacological approach, one that targets the neurological underpinning.
11:42And speaking of targets, this kind of genetic identification immediately points toward drug repurposing. Absolutely. The discovery of ESR1, the gene for estrogen receptor alpha, suggests that ER alpha antagonists, drugs like Toramophane or raloxophine, could be effective.
12:00Even though past clinical trials have been mixed? Right. But knowing the precise genetic mechanism driving ED in a specific patient could be what unlocks their utility. But the most novel candidate they identified is an existing drug.
12:13Yes, the NSAIed cullindak. Why Sullandak? Because it has a dual action that hits 2 different targets implicated in ED. Okay, so what's the first one? Well, Solondak is known to inhibit PDE5, just like Viagra or Cialis.
12:26The standard mechanism. But critically, it also targets a gene called CTNNB1 or beta catnan, which they also associated with ED risk. And what's compelling about CTN and B1. What's compelling is it's low enrichment in the amygdala.
12:38The amygdala, a key brain region for emotion and stress. Exactly. That amidable link is huge. Down regulation of beta caten in that region is known to be associated with anxiety and oppressive like behavior.
12:50So Solondak could potentially treat both things at once. That's the idea. It could treat the physical mechanism through PDE 5 inhibition and address the underlying psychogenic component of ED by modulating CTNNB1 expression in the brain.
13:05We have to circle back to that genomic paradox before we finish. The correlation between ED risk and an active sexual life. We do. And the researcher suggests this is a prime example of something called ascertainment bias.
13:18A vital concept in genetic epidemiology. Crucial. Let's break that down Okay. So since the study only included EHRED people who saw treatment. They weren't measuring ED across the entire population. They were only looking at a highly motivated subset.
13:32Precisely. Those were genetically inclined to be highly motivated and sexually active, and also less shy about discussing their health problems. They're the ones who show up in the electronic health records.
13:42And there's genetic evidence for that less shy nature too. A lot of it. There's a strong positive genetic correlation between EHRED and the personality trade of extroversion. So the genes aren't coding for better sexual performance followed by ED.
13:56No, they're coding for personality traits, like openness and motivation, that lead to both a more active lifestyle and the later decision to seek help. Which is how they end up in the EHR cohort for the study.
14:07It's a sociological link disguised as a biological one. Wow. So the overall picture is just incredibly sophisticated. It is. This deep dive confirms that ED is profoundly genetic. It's centered around that powerful SIM1 locus, and it's linked to 2 major separate domains.
14:24Metabolic health and complex behavioral and substance use risk. And this separation into 2 factors is game changing. It really offers hope for that 30 to 35% of patients for whom current treatments just fail.
14:36Right. New targets like SEM one, ESR one, and especially CTN and B one, suggest a future of precision medicine. A future war treatment is tailored to the individual's underlying genetic vulnerability, whether it's factor one or factor 3.
14:49This research is paving the way for targeted prevention. So what does this mean for personalized prevention strategies for men who have a high genetic risk across both these behavioral and metabolic factors.
14:59And should we start screening for ED risk using behavioral metrics, not just blood pressure readings, that's something for you to mull over. This episode was based on an open access article under the CCBY 4.0 license.
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