Gordan Lauc is a Professor of Biochemistry and Molecular Biology at the University of Zagreb, Director of the National Centre of Scientific Excellence in Personalised Healthcare, Honorary professor at the Kings College London and member of the Johns Hopkins Society of Scholars. He graduated Molecular Biology in 1992 and got PhD in Biochemistry in 1995 at the University of Zagreb. In 2017 he initiated the launch of the Human Glycome project and is one of its two co-directors. His research team is pioneering high throughput glycomic analysis and the application of glycan biomarkers in the field of precision medicine. By combining glycomic data with extensive genetic, epigenetic, biochemical, and physiological data on over 200,000 individuals they are trying to understand the role of glycans in normal physiology and disease. In 2007 he founded Genos, a biotech company that is currently global leader in high-throughput glycomics. Research in Genos led to the development of the GlycanAge test of biological age.
1. Please can you tell us about your previous work in glycobiology and why the glycome is integral in the aging process?
Glycans are the ultimate layer of molecular complexity. The majority of proteins are modified by the addition of one or more complex oligosaccharides (glycans), which significantly alter their structure and function. However, contrary to polypeptide part of a protein, which is defined by the sequence of nucleotides in the corresponding gene that can be changed only through random mutations, glycans are encoded in a network of dozens of genes and are inherited as complex traits. For example, through a series of genome wide association studies published in the past decade, we mapped a network of over 40 genetic loci that regulate glycosylation of immunoglobulin G. We have shown that the glycosylation of IgG, but also of other proteins, change significantly with age. These findings served as a basis of the first glycan-based biological aging clock also known as glycan clock of aging or glycan age. Change in the glycan clock of aging correlates with chronological age, but not perfectly with median deviation of nine GlycanAge years. The acceleration in glycan aging strongly correlates with biomarker of unhealthy lifestyle, with some individuals being even several decades older in their ‘glycan age,’ then the chronological age. However, a successful lifestyle intervention can even revert the direction of the glycan clock of aging, resulting in people being up to a several decades ‘younger.’
2. Which glycosylated proteins have been identified as risk factors for disease and potential therapeutic targets? Would targeting approaches involve targeting similar glycosylation pathways?
Changes in the IgG glycome composition that happen with aging resemble changes that are present in many age-related diseases, and vice-versa, people suffering from a disease have the glycome that resembles older ‘healthy’ individuals. IgG glycans change up to a decade before the disease is first diagnosed, indicating they may be a part of disease pathobiology. The fact that injecting immunoglobulins from young and healthy individuals (IVIg) in people with inflammatory diseases suppresses inflammation strongly support this hypothesis. Furthermore, in an animal model, we have shown that ‘correcting’ IgG glycome with a dietary supplement N-acetylmannosamine can protect obese mice from developing hypertension. However, targeting glycosylation is not an easy task since in each cell thousands of different proteins are being glycosylated with the same enzymes, thus a more targeted approach will be needed in the majority of cases (beside some terminal cancers, etc.) to avoid unexpected side effects. Fortunately, recently we have shown that the regulatory networks that govern glycosylation can be very different for different proteins, which opens the possibility to target a specific regulatory protein, and not a ubiquitously important glycosyltransferase enzyme.
3. What genetic and proteomic considerations are needed for therapeutic targeting via the glycome in order to tailor a personalized medicine approach?
Glycans are one of the main sources of inter-individual variation. Even the classical ABO blood groups are chemically only a slightly different glycans (as a result of three allelic variants of the ABO gene, A-antigen has terminal N-acetylgalactosamine, B-antigen galactose, and O antigen none of these two monosaccharide residues in its structure). Therefore, personalized approaches will likely be needed for any glycan-based therapeutic approaches. Good example how interfering with glycosylation can have unexpected consequences is the fact that one of the known side effects of the anti-viral drug oseltamivir, which is an analogue of sialic acid, are hallucinations. Unfortunately, we still know very little about inter-individual differences in protein glycosylation, and much more work is needed before we can start to exploit glycosylation as a new therapeutic target.
4. Due to the vast micro- and macroheterogeneity of glycans, their analysis can be challenging. How could current high throughput processes be adapted and optimized in order to increase our understanding of glycans for future targeting and enable wider implementation of this analysis?
Recently, it was reported that a single protein (recombinant acid α-glucosidase) can have over a million different glycoforms. This is an extreme example, but even a simple glycoprotein like IgG can have hundreds of different glycoforms, which is a tremendous analytical challenge. It is unlikely that all these glycoforms are functionally distinct, thus it is important to differentiate alternative glycosylation, which is a regulatory mechanism, from slight differences in structure, which result from the inherent characteristics of the glycosylation pathway. Significant progress in analytical precision, resolution and throughput has been achieved in the last decade and today it is possible to routinely perform glycomics studies on thousands of people. However, it is important to be aware that today’s glycomic studies either focus on a single glycoprotein, or on glycans released from all proteins in a sample, thus analyzing the entire complexity of a glycoproteome is still not possible.
There is significant progress in the development of glycoproteomic methods that can analyze multiple proteins in parallel, but this is probably the maximum for today’s technology, as the analysis of entire glycoproteome cannot be realistically expected without some kind of ‘next generation’ technologies that would significantly surpass today’s sensitivity and separation power. A significant bottleneck in glycoproteomics is the processing of analytical data, as there are not many dedicated software tools to deal with complex data generated by MS analysis of mixtures of many glycopeptides. The complexity of analytical methods and level of technical knowledge required to do these analyses is also one of the reasons why other ‘omics’ have an upper hand at clinical application even in cases when glycomics shows a greater potential.
5. How do the glycosylation modifications of IgG change as a person ages and how does this affect the immune response?
Immunoglobulin G has a conserved glycosylation site in the Fc domain that is essential for function. Without these glycans, IgG does not bind to any of the Fc receptors and cannot activate the immune system. It is fascinating that a slight change in the Fc glycan can completely change a role of immunoglobulins and convert a pro-inflammatory antibody to an anti-inflammatory molecule. In general, young and healthy people have IgG glycans that are larger and have more galactose and sialic acid on the antenna, while old and sick people have much less sialic acid and galactose. Although all mechanistic details are still not fully understood, loss of sialic acid and galactose is known to associate with many different diseases. The change of ‘young’ and ‘anti-inflammatory’ IgG glycome to an ‘old’ and ‘pro-inflammatory’ IgG glycome happens with different pace in different individuals. Part of this difference (approximately 40%) is defined by our genes, while most of the difference in the pace of glycan ‘aging’ is determined by our environment and lifestyle.
6. As IgG glycans are mentioned as a biomarker and functional effector for disease, can glycome testing provide an early warning for age-related disease development?
Numerous studies identified changes in the IgG glycome up to a decade before the disease is diagnosed. Since we know that IgG glycans have an important role in the regulation of low-grade chronic inflammation, which is underlying many complex diseases, monitoring of these glycans can be used as an ‘early warning’ system for the developing disease. However, it is important to note that these changes are frequently not disease-specific, since many inflammatory and cardiometabolic diseases associate with the same type of changes. Therefore, IgG glycans on the level of total IgG mostly cannot be used to diagnose a specific disease, though IgG is a complex molecule and more research on subclass-specific, antigen-specific, and Fab vs. Fc glycosylation could change this drastically. Nevertheless, even on the level of total IgG glycome, it was shown that the acceleration in glycan aging can be reversed by some lifestyle and pharmacological interventions, thus monitoring glycans can be used as a tool for personalized navigation through preventive medicine interventions, i.e. people can check whether a specific intervention is effective at the level of an individual, and not on an imaginary ‘standard person.’ Using glycan biomarkers could also hold a potential to significantly improve specificity of diagnosis or therapy prognosis when combined with other medical diagnostic tools, i.e. radiology or biomolecules such as CA-125.
7. What is a “glycan year” and how does a glycan age measurement differ from other biological clock testing, such as epigenetics?
The GlycanAge clock was developed by the analysis of thousands of individuals of different ages, thus a glycan year is the average change in the IgG glycome composition that happens in a one calendar year in an average individual. In the absence of a significant lifestyle change, the IgG glycome of most of us will change for this single ‘glycan year’ in a calendar year. However, if there is a significant lifestyle change, or a developing disease, the GlycanAge can change for even more than a decade within a single year and this change can be either in the direction of accelerated aging, or in the reverse direction of ‘anti-aging.’ When compared to other aging clocks, there is of course a significant correlation because all these clocks correlate with the chronological age. However, a recent study compared acceleration of aging in different clocks, and there was very little correlation between acceleration of epigenetic and glycan clocks, suggesting that these two clocks measure different aspects of aging. For example, different epigenetic clocks were better at capturing aging of various organs and tissues, while glycan clock of age outperformed most other biological age measures at predicting future hospitalizations.
8. You are involved in the upcoming ‘Reversed: The Race for Longevity‘ TV docuseries, in your opinion, what outstanding question of longevity is the most pressing to answer for future development of therapeutic agents for improving longevity?
I think that longevity, or aging, research is still in its very infancy. We know very little about aging. It is still being debated whether aging is a simple accumulation of damages, or perhaps a genetic program invented to remove old individuals and free resources for the new generations. A key problem with all longevity interventions is that it literally takes a lifetime to see whether a specific intervention works in each individual. Therefore, we cannot use longevity as an outcome in research and need to develop aging biomarkers that will serve as a proxy for longevity. Once relevant aging biomarkers will be developed and validated, it will enable evaluation of different therapeutic agents to prolong both healthspan and lifespan.
Declaration of interest
G Lauc is a founder and CEO of Genos Ltd, a private research institute that is focusing on high-throughput glycomics that holds a number of patents in the field of glycan biomarkers for personalized medicine. He is also a co-founder of GlycanAge Ltd, biotech company that is selling the GlycanAge test of biological age on the global market.
Work in author’s laboratory is supported by European Structural and Investment Funds grant for the Croatian National Centre of Competence in Molecular Diagnostics grant KK.01.2.2.03.0006, Croatian National Centre of Research Excellence in Personalized Healthcare grant KK.01.1.1.01.0010, IRI ‘CardioMetabolic’ grant KK.01.2.1.02.0321, and ERC-Synergy grant ‘GlycanSwitch’ from the European Research Council (grant 101071386).
The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.
The opinions expressed in this interview are those of the Interviewee and do not necessarily reflect the views of the Expert Collection.