Urinary Levels of Trimethylamine-N-Oxide and Incident Coronary Heart Disease: A Prospective Investigation Among Urban Chinese Adults

Application of Metabolomics to Epidemiological Studies of Atherosclerosis and Cardiovascular Disease

Metabolomics has developed as a powerful tool for investigating the complex pathophysiology underlying atherosclerosis and cardiovascular disease. Many epidemiological studies have applied this technique to accurately and comprehensively assess the effects of environmental factors on health outcomes, which used to be a perpetual challenge. Metabolites are defined as small molecules which are intermediate products of metabolic reactions catalyzed by numerous enzymes occurring within cells. Consequent to both genetic variation and environment, they allow us to explore the gene–environment interactions and to gain a better understanding of multifactorial diseases like cardiovascular disease. This review article highlights the findings of well-known prospective cohort studies around the world that have utilized metabolomics for a wide range of purposes, including biomarker discovery, improving cardiovascular risk prediction and early disease diagnosis, and exploring detailed mechanisms of disease onset and progression. However, technical challenges still exist in applying them clinically. One limitation is due to various analytical platforms that are used based on the judgment of each study; comparative assessments among different platforms need to be conducted in order to correctly interpret and validate each data externally. Secondly, metabolite levels obtained in most high-throughput metabolomics profiling studies are often semiquantitative rather than fully quantitative concentrations, which makes it difficult to compare and combine results among different studies and to determine the levels for practical use. In 2014, the Consortium of Metabolomics Studies was developed, which is expected to take the lead in overcoming these issues.

Diet, the Gut Microbiome and Heart Failure

The collection of microorganisms that live in coexistence within or on the host body has been referred to as the microbiota. In humans, such cohabitation is mostly seen in the gut, mainly in the colon. The gut microbiome is acquired from the environment and is modified mostly by the diet. There are preliminary data to show that gut microbia can directly influence the pathogenetic disease processes in heart failure (HF). HF leads to bowel wall oedema and regional hypoxia, causing a change in the microbial flora of the gut, which can initiate or perpetuate certain pathogenetic process in HF. The structural component of the microbiota itself, such as lipopolysaccharides or the substances produced by the bacteria, such as trimethylamine N-oxide, is implicated in the pathogenesis of HF. This process is termed as the ‘heart–gut axis’ in HF. Manipulating the gut microbia or targeting products from the microbia may become treatment options for HF in future.

Intestinal Microbiota in Cardiovascular Health and Disease: JACC State-of-the-Art Review

Despite major strides in reducing cardiovascular disease (CVD) burden with modification of classic CVD risk factors, significant residual risks remain. Recent discoveries that linked intestinal microbiota and CVD have broadened our understanding of how dietary nutrients may affect cardiovascular health and disease. Although next-generation sequencing techniques can identify gut microbial community participants and provide insights into microbial composition shifts in response to physiological responses and dietary exposures, provisions of prebiotics or probiotics have yet to show therapeutic benefit for CVD. Our evolving understanding of intestinal microbiota-derived physiological modulators (e.g., short-chain fatty acids) and pathogenic mediators (e.g., trimethylamine N-oxide) of host disease susceptibility have created novel potential therapeutic opportunities for improved cardiovascular health. This review discusses the roles of human intestinal microbiota in normal physiology, their associations with CVD susceptibilities, and the potential of modulating intestinal microbiota composition and metabolism as a novel therapeutic target for CVD.

Urinary Levels of Trimethylamine-N-Oxide and Incident Coronary Heart Disease: A Prospective Investigation Among Urban Chinese Adults

Background Trimethylamine-N-oxide ( TMAO ), a diet-derived, gut microbial-host cometabolite, has been associated with adverse cardiovascular outcomes in patient populations; however, evidence is lacking from prospective studies conducted in general populations and non-Western populations. Methods and Results We evaluated urinary levels of TMAO and its precursor metabolites (ie, choline, betaine, and carnitine) in relation to risk of coronary heart disease ( CHD ) among Chinese adults in a nested case-control study, including 275 participants with incident CHD and 275 individually matched controls. We found that urinary TMAO , but not its precursors, was associated with risk of CHD . The odds ratio for the highest versus lowest quartiles of TMAO was 1.91 (95% CI, 1.08-3.35; Ptrend=0.008) after adjusting for CHD risk factors including obesity, diet, lifestyle, and metabolic diseases and 1.75 (95% CI, 0.96-3.18; Ptrend=0.03) after further adjusting for potential confounders or mediators including central obesity, dyslipidemia, inflammation, and intake of seafood and deep-fried meat or fish, which were associated with TMAO level in this study. The odds ratio per standard deviation increase in log- TMAO was 1.30 (95% CI, 1.03-1.63) in the fully adjusted model. A history of diabetes mellitus modified the TMAO - CHD association. A high TMAO level (greater than or equal to versus lower than the median) was associated with odds ratios of 6.21 (95% CI, 1.64-23.6) and 1.56 (95% CI, 1.00-2.43), respectively, among diabetic and nondiabetic participants ( Pinteraction=0.02). Diabetes mellitus status also modified the associations of choline, betaine, and carnitine with risk of CHD ; significant positive associations were found among diabetic participants, but null associations were noted among total and nondiabetic participants. Conclusions Our study suggests that TMAO may accelerate the development of CHD , highlighting the importance of diet-gut microbiota-host interplay in cardiometabolic health.