Singapore’s “SLING”

Why focus on lipids?

Anne K Bendt: Coming from a proteomics and transcriptomics background, I used to consider lipids “the slime” you tried to get rid of! I was amazed to discover that lipids constitute 50 percent of the brain, and that popping a painkiller directly influences lipid signaling.

Amaury Cazenave Gassiot: I came to the lipidomics field almost accidentally after my PhD in analytical chemistry, and never left. The analytical challenges brought up by lipids, their chemical diversity, and the potential they offer – for instance in clinical research – are of tremendous interest to me.

Federico Torta: My interest in lipidomics grew from my interest in mass spectrometry, and proteomics in particular. A few years ago I was looking for new and exciting applications of MS, and the lipidomics field seemed an obvious choice. As I learnt more about lipids, I realized how ubiquitous these molecules are and how many important roles they play in biology.

Markus Wenk: I was motivated by a single question: “Why are there so many different lipids in nature?”

Why are lipid metabolites deserving of their own “omics”?

FT: Once seen as enemies of a healthy life, lipids are essential players in any biological process. Hence, if we want to understand the inner workings of an organism, we need to measure not just proteins but lipids too.

ACG: As Federico says, lipids have a bad press for a long time, but it is becoming increasingly clear that the picture is more complex. Current clinical tests measure cholesterol and total triglycerides, but there are thousands of individual molecular species or lipids in a drop of blood… We need to understand what they are and what they do.

AKB: The size of the lipidome is still not well understood. Why are there so many different lipid molecules? What is the degree of sheer randomness versus functionality, especially given that subtle differences in molecular fine structures have been shown to have effects on their immunomodulatory properties? Differences in the lipid repertoires of pathogens and their human hosts have already been exploited; for example, as targets for more selective antibiotics and as pathogen-specific diagnostic biomarkers.

What makes lipidomic analysis so complex?

ACG: The chemical diversity of lipids is staggering. Under a single mass spectrometric peak, even measured in a high-resolution instrument, many lipids can be hidden, in the form of isomers. Many techniques, therefore, including relatively new ones (such as ion mobility and on-line chemical reactions – ozonolysis, for example), are needed to obtain more detailed information. The use of shotgun, LC, GC, SFC, high-resolution MS or low-resolution MS/MS should be determined by what kind of lipids you are looking at, what level of information you require, and what your application is.

FT: The extreme heterogeneity of their chemistry means the number of lipid species has so far been quantified in the hundreds of thousands. These different molecules have different properties and characteristics and it is impossible to measure all of them at once. The complexity is reflected by the proliferation of methods and techniques used to characterize different classes separately, compared with proteomics, where the spectrum of analytical methods might be smaller. Many different lipids can be generated by the same enzyme, making the biological investigation more complex.

AKB: Proteins consist of known amino acids and a number of post-translational modifications, whereas lipids have vastly diverse chemistries, with a large number of isobaric compounds complicating their characterization. They also cover an extensive dynamic range, from low-abundance signaling molecules to bulk lipids, further complicating their comprehensive extraction. Plus, we still don’t have good databases.

Interest in lipidomics has risen steeply in the last 20 years – why?

AKB: With the increasing focus on personalized health and preventive monitoring, there is a growing interest in lipids as indicators for the status of health and disease, prompting investments by manufacturers (instruments, medical devices), big data and service providers. Though this increasing attention is great for the overall awareness and growth of the field, we must be aware of immature solutions (such as lipid biomarker panels) that are marketed only to fulfill business interests.

FT: I believe the development of analytical technology used to measure lipids, especially mass spectrometry, has played a major role. Once researchers could accurately measure lipids, they began to realize how important they are in biology. The fact that many lipids are also bioactive molecules that can be used as disease treatments/biomarkers or as active components in nutritional interventions has also fueled business growth around lipidomics – which is positive for the field as it brings more possibilities, new ideas and new players. Perhaps our task as scientists in the field is to watch this growth closely, to avoid the false claims and promises that can arise when business takes over science…

ACG: I would concur with Federico here. We have been told for decades to avoid certain kinds of fats and favor others, but were these recommendations based on good science?

MW: As Federico says, lipidomics is an area of growth driven by technological advances. Better analytics inevitably leads to new opportunities, be they in scientific discovery or applications. The latter part of this process – the translational aspects beyond descriptive biochemistry – will require considerable additional efforts and time to mature successfully.

What’s next for your group?

FT: Higher throughput and more quantitative approaches, with integration of different fields (lipidomics, proteomics, genomics) and different expertise (biologists, physicians, data engineers).

AKB: I will drive our efforts towards clinical mass spec, through engagement of key stakeholders from lipidomics R&D, data integration and clinicians. We aim to establish clinical utility for select lipid markers, and work closely with the intended “end users,” toward needs-driven assays for routine applications.

ACG: As Federico mentioned, our future lies in teaming up with other specialties. Whether it be a MS-based lab test for a specific disease, or a better understanding of how lipid metabolism affects health outcomes, we are definitely moving toward more pre-clinical and clinical work.

What analytical techniques will have the greatest impact over the next 10 years?

AKB: The currently available technologies are great tools for R&D applications because of their sensitivity, specificity and versatility. However, in clinical diagnostics, where reliability, turnaround time and of course costs are crucial, further development towards robustness, ease of use and automation are crucial.

FT: Instruments have reached an amazing level of resolution and sensitivity, but more time will have to be invested in separations (ion mobility is a very exciting application), robustness and data analytics.

ACG: Current analytical workflows are robust enough and identify lipids of interest with enough precision that we can hope to usefully roll them out to clinical application. However, new techniques that will enable us to discriminate between lipid isomers could potentially shed new light on specific diseases.

How do you expect to see our understanding of lipids evolve?

FT: I expect us to gain a little more understanding of the molecular aspects of life – this would be a giant step in scientific knowledge. 

MW: Hopefully, we will gain better insights into how the oceans of different lipid molecules interact at the molecular as well as organismal level. The former will contribute to our fundamental understanding of membrane biology, the latter will give us a more fine-grained picture of lipid transport and metabolism relevant to medicine.

AKB: I would like to see the perception of lipids in health to shift from foe to friend, with an increasing awareness of how we can take specific actions to improve health and disease outcomes.

ACG: A better understanding of lipids will bring us better diagnostics and better health outcomes. But a better understanding of the chemistry of life in its own right is a worthy pursuit!

Anne K Bendt is Associate Director of SLING and Principal Investigator at the Life Sciences Institute at the National University of Singapore.

Amaury Cazenave Gassiot is Research Assistant Professor, SLING, Department of Biochemistry, YLL School of Medicine, National University of Singapore.

Federico Torta is Research Assistant Professor, SLING, Department of Biochemistry, YLL School of Medicine, National University of Singapore.

Markus Wenk is Director of SLING and Head, Department of Biochemistry at the National University of Singapore.