“People think that fat is fat. But it’s much more complicated than that,” says Dr Mary Doherty of the University of the Highlands and Islands’ Lipidomics Research Facility. We’re discussing her rapidly growing research field, lipidomics. Once shunted to the side by investment in other omics, lipidomics has seen increasing attention from biotech and pharma companies in recent years. Interest, from both academic and industry perspectives, has been reignited in the incredible diversity of lipids throughout our body.
Lipids are a hugely influential class of molecules. Extending far beyond the triglyceride fats, lipids fulfil several key roles. As Doherty explains, “Lipids are everywhere in your body - they form the membrane of your cells, they act as signaling molecules and they help drive and resolve inflammatory responses. Lipids are important in many organs particularly the brain and nervous system”.
Mass Spectrometry: A Lean Technique to Study Lipids
To study this diversity of molecules, lipodomists (a really smooth sounding job title) need to use analytical techniques that can perform targeted analysis of particular molecules as well as provide a global assessment of the lipidome, the totality of lipids within our cells. To this end, labs like Doherty’s rely on mass spectrometry (MS), the workhorse of the field. Doherty’s lab has several different mass spectrometers, each fulfilling a different analytical role. “We have high resolution LC-MS/MS systems that are employed to profile populations of lipids. We also have triple quadrupole platforms, that are used for the targeted analysis of lipids. When we know what we are looking for in sample we can operate the mass spectrometer to detect specific and obtain detailed quantitative information” In addition, we have a standard GC-MS (a mass spectrometer coupled to a gas chromatograph) which we use for the analysis of fatty acids and cholesterol.”
The extraordinary complexity of the lipidome has driven better and smarter machinery into labs. Lipids can generally be organized into 8 categories, but each of these categories includes a huge range of subspecies. Fatty acids, for example, are a major category that have one function as the building blocks for glycerophospholipids, integral molecules in the membranes that hold our cells together. There’s quite a few species of glycerophospholipids. Roughly 30,000, in fact. The star player in Doherty’s MS fleet is a machine that is capable of ion mobility analysis – an essential trick for in-depth analysis, as Doherty says, “A lot of lipids have the same mass and are isobaric, but ion mobility allows us to tease out different structures. It allows us to separate lipids in the gas phase before we put them into the instrument, which we can’t do on the other instruments.”
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These advances in lipidomics are benefiting players outside of academia as well. Lipotype GmbH, spun out from the laboratories of Prof. Dr. Kai Simons and Dr. Andrej Shevchenko of the Max-Planck-Institute of Molecular Cell Biology and Genetics in 2012, offer specialized lipid analysis services. Dr. Christian Klose, Head of Research and Development at Lipotype, explains that these services are in demand from several quarters: “People or companies or research groups that have had nothing to do with lipids are now coming across them, and don't know how to access this class of molecules in a quantitative or qualitative way. They are faced with questions like “How do I find out what lipids I have in my sample?” or “Does my drug induce changes to lipid metabolism?”.
Shotgun Lipodomics: Breaking Down (and Speeding up) Lipidomics
Lipotype’s favored analysis technique, shotgun lipidomics, is another example of the advances in technology that have powered the current lipidomics boom.
The shotgun approach shares a name with the genome sequencing technique made famous by J Craig Venter but is very much still a MS-based method. “The shotgun approach is a direct infusion approach and that means that we do not do any liquid chromatography to separate lipid classes, but you take the organic extract, which you obtain from any biological material that you could think of - and shoot it directly into the MS, no pre-separation required,” explains Klose.
This addresses the need for faster analysis and quick turnaround times sought by Lipotype’s customers in industry.
These advances in technology are fueling, and are fueled by, breakthroughs in how researchers are using and thinking about lipids. Dr Laura Bindila, Head of the Endocannabinoids/Lipidomics Facility at University Medical Center Mainz, highlights the value of lipids as a predictive tool for disease: ““Lipids change in the patient often before symptoms occur or other markers change, meaning if we focus on lipids we can anticipate certain aspects of disease”. Bindila’s recent research has focused on endocannabinoids, lipid-based neurotransmitters, signaling lipids, and their precursors that are expressed throughout the central and peripheral nervous system. Modulation of these lipids may have potentially therapeutic roles in everything from cardiac disease to neurological disease and psychiatric disorders, so it’s unsurprising that there has been increased interest from industry.
Lipidomics: Fit for the Future?
There is still a way to go for lipidomics. Klose personally feels that the hardware and software solutions available are sufficient to power the next few years of research and thinks the next big leap will be to standardize protocols across labs. “Almost every lab has a slightly different method running, in both academic and industrial labs, so everybody does it in their own way. The standardization of results is something we would like to see developed so we can make the data across different labs more comparable than it is now and that goes hand in hand with an overall increase in the quality of the data. It is also an important aspect when it comes to the potential uses of the technology- not just in R&D purposes and the pre-clinical phase, but also when it comes to using the technology for diagnostics purposes.”
Once more regular and high-quality data is produced, lipid research will certainly not be shackled by a lack of ideas: Bindila highlights interesting work into epilepsy where the fatty acid palmitoylethanolamide was administered to epileptic mice. Seizure intensity was significantly reduced, and palmitoylethanolamide also promoted neuroprotective and anti-inflammatory pathways, although the exact mechanism by which it achieves still awaits discovery.
Doherty for one is excited for the future of her field: “With the advancement of analytical technologies we can see a lot more of the lipidome; there are still a lot of unknowns about lipids and so many interesting things about these molecules in the body to understand and only now are we beginning to get a handle of what is going on.”