Cholesterol Metabolite a Clue to Asia’s Rising Heart Disease

“Another important shift is that it is now happening in younger age groups,” said Associate Professor Rinkoo Dalan, a clinician-scientist at the Nanyang Technological University (NTU) Lee Kong Chian School of Medicine and senior consultant in endocrinology at Tan Tock Seng Hospital. Despite the scale of the problem, large-scale longitudinal studies of cardiovascular risk in Asian populations are few and far between. 

“Asians have unique genetic, dietary and lifestyle factors, so we can’t always generalise from studies done in Western populations,” Assoc Prof Dalan explained. Asian-specific research not only validates Western findings but can uncover new, population-specific insights, she continued. 

Searching for Metabolic Signals 

To address this knowledge gap about the unique features of cardiovascular disease in Asians, researchers led by Dr Nilanjana Sadhu at NTU turned to metabolomics and cardiovascular imaging. Their study, recently published in Nature Cardiovascular Research, examined the relationship between blood metabolites and a well-established marker of atherosclerosis: carotid intima-media thickness (cIMT). Measured via ultrasound, cIMT reflects the thickness of the artery walls in the neck and serves as an indicator of subclinical atherosclerosis. “For every 0.1 millimeter increase in cIMT over the normal range, the risk of heart attack increases by about 10 to 15 percent, and the risk of stroke increases by 13 to 18 percent,” Assoc Prof Dalan said.  

Unlike other methods of screening for the narrowing of arteries associated with heart disease, cIMT does not involve radiation, and its non-invasive nature makes it a practical screening tool for large-scale studies like the Health for Life in Singapore (HELIOS) cohort, part of the national SG100K precision medicine initiative. Meanwhile, metabolites—small molecules that are byproducts of metabolic processes—offer a window into the biochemical activity occurring in the body. Using untargeted mass spectrometry, the team quantified nearly 900 metabolites in blood samples from 8,124 participants in the HELIOS cohort. Of these, 126 were found to be correlated with cIMT. 

“However, correlation does not imply causation,” Dr Sadhu cautions. To determine whether any of these metabolites directly influenced cardiovascular risk, the researchers used a method known as Mendelian randomisation (MR). MR leverages genetic variants as proxies for an exposure—in this case, metabolite levels—thus mimicking a randomized controlled trial. For MR to be valid, the genetic variant must satisfy three criteria: it must be associated with the exposure, not be confounded by other variables, and influence the outcome only through the exposure. 

After extensive sensitivity analyses, one molecule stood out: 3beta-hydroxy-5-cholestenoate (3BH5C), a cholesterol metabolite. Higher genetically predicted levels of 3BH5C were causally linked to reduced risk of coronary artery disease. “It’s a robust signal, and we were able to trace a potentially causal relationship,” Dr Sadhu said. Even more striking was the population-specific nature of the findings. “The effect in Asians is five- to six-fold higher than it is in Europeans,” Dr Sadhu said. Genetic variants associated with the risk of coronary artery disease are more prevalent in Asian populations and further underscores the importance of ethnically diverse research.” 

From Molecule to Mechanism: The Role of FDX1 

3BH5C is produced when cholesterol is metabolised by an enzyme known as CYP27A1. When genetic variants effecting the levels of 3BH5C were mapped to the human genome, they were found to be closely located to the gene for a protein known as ferredoxin-1 (FDX1).  

“Using a technique called co-localisation analysis, we were able to identify variants that change both the level of the metabolite 3BH5C in the blood and expression of FDX1,” Dr Sadhu explained. “How it works is that if there’s a genetic variant that decreases the expression of FDX1, then it changes the enzymatic efficacy of CYP27A1, thus breaking down less cholesterol, which in turn leads to lower synthesis of 3BH5C.” 

To validate this pathway, the researchers conducted experiments in cells known to express CYP27A1, namely hepatocytes and macrophages. When the FDX1 gene was removed by gene editing, production of 3BH5C dropped sharply. Conversely, increasing the expression of FDX1 increased 3BH5C levels and promoted the removal of cholesterol from cells, particularly in macrophages and vascular smooth muscle cells known to be associated with atherosclerotic plaques. 

Addressing the Needs of Asian Patients 

These results suggest that genetic screening for specific FDX1 gene variants could be useful for identifying individuals at a higher risk of developing high cholesterol and coronary artery disease, “We could pursue more aggressive cholesterol reduction in these individuals, and use their FDX1 status to tailor treatments in terms of how much of a given drug to use to make it more safe and effective,” Assoc Prof Dalan said.  

The metabolite 3BH5C itself is also promising as a biomarker, Dr Sadhu added. “The nice thing about looking at metabolites and proteins is that they can be measured in blood samples. Therefore, if a metabolite is causally linked through a certain pathway to a higher risk of an outcome, then you could potentially use it directly as a biomarker for easily stratifying or identifying high risk individuals,” she said. 

As heart disease continues to rise across Asia, cost-effective screening and prevention strategies are essential. “With a huge population and rising rates of chronic disease, precision medicine allows us to identify the right patient, at the right time, for the right intervention,” said Assoc Prof Dalan. “Such precision medicine is an urgent unmet need especially in the realm of cardiovascular disease, which is very heterogeneous and usually linked to multiple genes. Identifying singular genes, like we have done in this paper, can be very powerful to help design diet and lifestyle interventions—and eventually, therapeutics—in a precise way for patients.” 

“Our research demonstrates that it is important to study Asian datasets such as HELIOS, even for something as widely studied as cardiovascular disease,” Dr Sadhu said. “The population-specific findings we have discovered couldn’t have been made using any western dataset, so I’m very excited about what else we will find in the pioneering SG100K dataset.”