Chapter 2—Other Omics Sciences and Metabolomics

What are Omics?

Advances in scientific technology have made it possible to survey living systems at the tissue and cellular levels by measuring the thousands of molecules that comprise those systems. The high-throughput measurement of these molecules is collectively referred to as “omics.”¹ While there are several types of omics approaches, there are four main omics disciplines that reflect the ever-increasing complexity of living systems, from genetic code to phenotype: genomics, transcriptomics, proteomics, and metabolomics.

Each of these omics disciplines can be studied individually, but biological systems don’t act in a vacuum. Combining different omics disciplines through multi-omics studies² provides a holistic picture of living organisms and systems. Below, we define each of the four major omics disciplines, compare metabolomics to each of the other three, and discuss how studying them synergistically can drive scientific discovery.

Genomics and Metabolomics

Genomics and metabolomics sit at opposite ends of the biological spectrum. Genomics is the study, typically via sequencing, of all of the genetic material in an organism, including single nucleotide polymorphisms (SNPs), indels, gene loss and amplification, and copy number variations (CNVs). In other words, genomics is the study of an organism’s blueprint and any changes to that blueprint that impact the genetic potential. Metabolomics, on the other hand, is the complete set of small molecules present in an organism at a single point in time, measured via mass spectrometry (most commonly) or nuclear magnetic resonance (NMR). In essence, metabolomics is genetic potential in action and can be impacted by literally anything: food, drugs, medications, stress, etc.

It isn’t difficult to imagine how metabolomics and genomics datasets can add important contextual information to one another to elucidate why specific genetic anomalies are associated with specific phenotypes. The integration of genomic and metabolomic data has been extensively used to elucidate metabolite chemical structures, functions, and biosynthetic origins, and several tools have been developed³ to aid such efforts. Genome-metabolome integrations have also proven particularly useful in oncology research, as cancer has critical genetic and metabolomic characteristics. One study⁴ has even used genomics-metabolomics integration to help elucidate why genetic aberrations can be observed in both healthy and cancerous cells and why specific environmental and nutrient cues act as “selectors” during oncogenesis.

Transcriptomics and Metabolomics

While genomics represents an organism’s genetic potential, not all of that potential is enacted. In fact, in humans, only 1.5% to 2% of the genome represents protein-coding genes. Cataloging the complete set of RNA transcripts (typically via microarrays or RNA sequencing) from DNA in a cell, tissue, or organism provides a better idea of which genetic elements have been activated.

Transcriptomics is a powerful tool for cataloging not just expressed genes, but also noncoding RNA elements (ribosomal RNA, messenger RNA, transfer RNA, microRNA, and long noncoding RNA) that may impact gene expression, and how these elements differ in healthy and diseased states. Transcripts often reveal signatures that cannot be detected through genomics approaches alone, such as RNA regulators of driver genes⁵ in oncology. But the presence of a transcript doesn’t always equate to mature, functional protein. Metabolomics, on the other hand, reveals critical information about which genetic instructions have not only been transcribed into RNA but have actually been converted into measurable phenotypes.

Integrated transcriptomics-metabolomics datasets can help demystify the bidirectional and multi-faceted interactions between DNA and RNA elements that lead to observable phenotypes and provide actionable insights into what is going on in a biological system. For example, combining transcriptomics and metabolomics data can make molecular analysis of a blood sample even more comprehensive⁶ when diagnosing disease, and has been proposed as a powerful approach to drive personalized and precision medicine across a range of conditions.

Proteomics and Metabolomics

Proteomics is the most closely related omics technology to metabolomics. It adds another layer of complexity to genomics and transcriptomics by revealing not genetic potential, but which gene products (ie, proteins) have actually been synthesized by an organism. There are several things that can impact whether or not a mature, functional protein is produced by an organism, such as post-translational modifications or environmental toxins and nutrients, which is why combining genomic/transcriptomic and proteomic datasets can reveal important differences between what an organism might be doing and what an organism is actually doing.

Metabolomics is the study of the small molecules in an organism, and some of these are derived from proteins. Yet, there are some key differences between metabolomics and proteomics. First and foremost, proteomics captures information about all proteins produced by an organism, while metabolomics focuses on metabolites alone. Second, while proteomics seeks to understand and describe protein structure and function, metabolomics studies metabolites under given sets of conditions—for example, during drug treatment.

Combined, proteomics and metabolomics provide a complete phenotypic picture. Proteomics reveals which RNA transcripts have yielded mature, functional proteins while metabolomics drills deeper and explores how those proteins act differently under divergent circumstances. Integrated datasets combining proteomics and metabolomics have been used to identify cancer biomarkers⁷ and characterize mechanisms of action⁸ of anti-tumor agents.

Why Multi-omics Approaches Need Metabolomics

As more and more research combines various omic approaches to elucidate the basics of human biology and demystify disease progression, multi-omics is driving advances in human health and disease research. The U.S. market size of single-cell multi-omics alone is expected to exceed $7 billion USD by 2027—and metabolomics plays a critical role in enabling this rapid growth. Metabolomics is the study of specific phenotypes that result from the intricate and complex interaction between the genome, transcriptome, proteome, and the environment. It is the final and critical piece of the puzzle because only it can reveal the result of these complex interactions.

Lipidomics—the large-scale study of pathways and networks of cellular lipids—and glycomics—the systematic study of all glycan (ie, sugar) structures of a given cell, tissue, or organism—are metabolomics “specializations” that are driving a significant proportion of metabolomics’ influence on the overall contribution of multi-omics studies to advancing our understanding of health and disease. These specific metabolites often play critical roles in disease pathogenesis or serve as biomarkers. Sophisticated tools, such as the iKnife⁹, are being developed to aid in diagnosing, treating, and monitoring disease. For example, the iKnife can inform surgeons about the disease status of tissue during procedures by both heating the tissue then performing real-time lipodomics analysis of the resulting smoke.

The iKnife is just one very unique example of the many ways metabolomics is ushering in a new era in our understanding of health and disease. Multi-omics approaches centered on metabolomics as a key component are poised to revolutionize healthcare. Metabolon is positioned at the forefront of this new era in clinical research. The global metabolomics platform, which leverages Metabolon’s unmatched in-house database of over 5,400 small molecules, helps researchers identify pharmacodynamic, efficacy and response biomarkers and reveals changes in key biological pathways. Several companies have already leveraged this platform to improve their clinical trials and ensure successful trials of a variety of therapeutics.

What’s Next?

Now that you understand where metabolomics fits into the multi-omics puzzle, this guide will further explore metabolomics as a technology. In the next chapter, you’ll learn how metabolites are detected and the basic method of generating metabolomics data. Then, in subsequent chapters, we’ll explore some of the most promising academic, industrial, and clinical applications of metabolomics so you can get a better idea of how metabolomics might help propel your own research efforts.

References

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