Researchers have discovered that intermittent fasting increases myelin in aged mice, leading to better neural function and coordination.
Crucial proteins and a well-known intervention
Normally, neuronal axons are coated in a protein sheath made of myelin, which is necessary for their proper function [1]. Myelination is most known to be impeded by multiple sclerosis, but it also decreases with aging [2]. It is predominantly formed from two key proteins, myelin basic protein (MBP) and myelin-associated glycoprotein (MAG) [3], and previous work has found that upregulating the expression of these proteins has a beneficial effect on myelination [4].
Other work has found that myelination can be affected by diet and nutrition [5]. However, that work did not focus on these researchers’ chosen intervention: intermittent fasting, which has been found in substantial previous research to have metabolic and anti-inflammatory benefits, particularly in the context of aging [6].
Fasting for 18 hours a day
For their experiments, the researchers used three groups of mice: ten young mice, ten older mice, and eight older mice that had undergone intermittent fasting fof ten weeks, in which they were only allowed to eat for six hours a day. The researchers first began by testing overall markers of physical function: on the wire hanging test, the fasting mice were able to hold on for longer than the old control group, and they trended towards being able to run faster and longer than this group as well.
In a balance beam test, the fasting proved exceptionally potent: the fasting group was able to perform just as well as the young mice, far outpacing their same-aged counterparts. However, cognitive function was found to be unaffected: there was no benefit according to a Y maze test.
Stronger motor signals
A closer look at the mice’s muscles may have revealed why. While the maximum electrical signal strength going from the nerves to the muscles was not significantly affected, the treatment group had higher average signal strength. Looking at the frequency ranges involved revealed that the treatment group could exert more force and could react more quickly than similarly aged mice that were fed freely.
The brain was affected as well. Measuring whole-brain connectivity, the researchers found that the brains of the treated mice were less connected in ten areas but more connected in seven, particularly in places related to motor function and sensory input. Comparing these connection differences to the physical tests, the researchers concluded that these changes may also be responsible for the improvements they found.
Myelin was directly improved
Finally, the researchers looked directly at the myelin in the brain. Interestingly, and possibly of concern, the fasting group had reduced axonal diameters compared to the aged control group, suggesting an increase in degeneration. However, they had substantially more myelin, particularly on their smaller axons. These findings were true for both motor and non-motor portions of the brain, and the researchers note that this has been documented to occur in other animals, including people, who are recovering from demyelinating diseases [5].
Both MBP and MAG were positively affected. The treated mice had significantly more of both proteins in both of the tested areas, although there was no significant increase in MAG in the motor cortex. Myelinated fibers were found to trend towards being more common and longer in the fasting group. Overall, these results suggest that fasting somewhat changes the brain, and the researchers hold that these changes are beneficial.
While this is only a mouse study, it is in line with previous research showing that such dietary interventions may have beneficial effects on the brain. Furthermore, while it may not be appropriate for everyone, intermittent fasting is a freely available intervention. More studies may reveal whether or not it has beneficial effects on the myelin, and muscle coordination, of older people.
Literature
[1] Almeida, R. G., & Lyons, D. A. (2017). On myelinated axon plasticity and neuronal circuit formation and function. Journal of Neuroscience, 37(42), 10023-10034.
[2] Nickel, M., & Gu, C. (2018). Regulation of central nervous system myelination in higher brain functions. Neural plasticity, 2018(1), 6436453.
[3] Deng, S., Shu, S., Zhai, L., Xia, S., Cao, X., Li, H., … & Xu, Y. (2023). Optogenetic stimulation of mPFC alleviates white matter injury‐related cognitive decline after chronic ischemia through adaptive myelination. Advanced science, 10(5), 2202976.
[4] Zhang, Q., Zhu, W., Xu, F., Dai, X., Shi, L., Cai, W., … & Hu, X. (2019). The interleukin-4/PPARγ signaling axis promotes oligodendrocyte differentiation and remyelination after brain injury. PLoS biology, 17(6), e3000330.
[5] Langley, M. R., Triplet, E. M., & Scarisbrick, I. A. (2020). Dietary influence on central nervous system myelin production, injury, and regeneration. Biochimica et Biophysica Acta (BBA)-Molecular Basis of Disease, 1866(7), 165779.
[6] De Cabo, R., & Mattson, M. P. (2019). Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine, 381(26), 2541-2551.
