GC–MS and LC–MS Track Cholesterol in Myelin Damage

Almost all the cholesterol in the brain and spinal cord (more than 99%) is in its "free" form, and about 70% of it sits in myelin, the fatty coating that insulates nerve fibers. In some neurological diseases, however, a different, stored form of cholesterol called cholesterol ester starts to build up. To learn more, chemists at the University of Kansas’ Department of Chemistry studied mice that were genetically engineered so their myelin could be broken down on command. They measured both forms of cholesterol in the mice's brains and spinal cords at three stages (as myelin first forms after birth, as it is destroyed, and as it is rebuilt) using gas chromatography-mass spectrometry with single ion monitoring (GC–MS–SIM) and liquid chromatography–mass spectrometry (LC–MS) to identify and measure molecules by their weight. A paper based on their efforts was published in the journal Molecules.¹

What Is Myelin, and What Role Does Cholesterol Play in It?

Myelin is a fatty coating made of many layers that wraps around sections of nerve fibers, helping nerve signals travel quickly and efficiently. It's much fattier than most cell membranes: about 80% fat and 20% protein, compared with roughly 40% fat and 60% protein in a typical membrane. All that extra fat lets myelin's layers pack together more tightly than ordinary membranes do.^2-4

In the brain and spinal cord, myelin is made by cells called oligodendrocytes, which stretch out their outer membranes to wrap around nerve fibers. How fast these cells can make cholesterol sets the pace for how quickly myelin can grow as the brain develops. When mice were bred so these cells couldn't make their own cholesterol, their myelin formed very poorly, and the mice had trouble with balance and developed tremors.⁵

Almost all cholesterol in the brain is in its free form; less than 1% is in the stored form referred to as cholesterol esters.⁶ Cholesterol makes up about 40% of the fat in myelin and is a key building block that helps hold myelin together.⁷ When myelin is repaired after damage, the new version is less sturdy than the original, partly because it contains less cholesterol.⁸

Cholesterol also serves as the raw material for certain hormones made in the nervous system, which help build and repair myelin and protect nerve cells.⁹

What Did the Researchers Find, and What Comes Next?

The research team found that in healthy mice cholesterol in the brain kept rising steadily until at least 38 weeks of age. In the spinal cord, it rose until the mice were about six weeks old and then held steady from there on. When the myelin was being destroyed, cholesterol in both the brain and spinal cord dropped well below healthy levels, and it never fully bounced back, even after the myelin started to rebuild. At the height of the myelin damage, the cholesterol ester made up about a fifth of the cholesterol measured in the brain and about two-thirds in the spinal cord.¹

The researchers also developed reliable new ways to measure both forms of cholesterol in the nervous system, which will help scientists understand how the body manages cholesterol during disease.¹

“Our measurements,” write the authors of the paper,¹ “highlight key differences between the brain and spinal cord, including the higher concentration of cholesterol in the spinal cord, the continuous increase in brain cholesterol up to 10 months of age, and cholesterol ester dynamics during demyelination.”

In the future, the researchers hope to determine why cholesterol stays low for so long after myelin damage, and why the stored form builds up. If scientists can find ways to protect the nervous system's cholesterol or bring it back to normal levels, that could lead to new treatments for brain diseases and for the myelin breakdown that comes with aging.¹

References

1. Dedunupitiya, D.; Go, E. P.; Witte, T. et al. Cholesterol Quantification in Brain and Spinal Cord During Development, Demyelination, and Remyelination. Molecules 2026, 31 (17), 3033. DOI: 10.3390/molecules31173033
2. Williams, K. A.; Deber, C. M. The Structure and Function of Central Nervous System Myelin. Crit Rev Clin Lab Sci. 1993, 30 (1), 29-64. DOI: 10.3109/10408369309084665
3. Poitelon, Y.; Kopec, A. M.; Belin, S. Myelin Fat Facts: An Overview of Lipids and Fatty Acid Metabolism. Cells 2020, 9 (4), 812. DOI: 10.3390/cells9040812
4. Min, Y.; Kristiansen, K.; Boggs, J. M. et al. Interaction Forces and Adhesion of Supported Myelin Lipid Bilayers Modulated by Myelin Basic Protein. Proc Natl Acad Sci U S A 2009, 106 (9), 3154-315. DOI: 10.1073/pnas.0813110106
5. Saher, G.; Brügger, B.; Lappe-Siefke, C. et al. High Cholesterol Level is Essential for Myelin Membrane Growth. Nat Neurosci. 2005, 8 (4), 468-475. DOI: 10.1038/nn1426
6. Zhang, J.; Liu, Q. Cholesterol Metabolism and Homeostasis in the Brain. Protein Cell. 2015, 6 (4), 254-264. DOI: 10.1007/s13238-014-0131-3
7. O'Brien, J. S. Stability of the Myelin Membrane. Science 1965,147 (3662), 1099-1107. DOI: 10.1126/science.147.3662.1099
8. Nottar Escobar, E. L.; De Silva Mohotti, N.; Manolescu, M. et al. Reduced Cholesterol Alters the Biophysical Properties of Repaired Myelin. Biochim Biophys Acta Mol Cell Biol Lipids 2025, 1870 (5), 159637. DOI: 10.1016/j.bbalip.2025.159637
9. Kalakh, S.; Mouihate, A. The Effects of Neuroactive Steroids on Myelin in Health and Disease. Med Princ Pract. 2024, 33 (3), 198-214. DOI: 10.1159/000537794