Our new study: are muscle capillaries important for muscle mass during aging?
A progressive loss of muscle mass and strength is observed during aging, which is termed sarcopenia. In addition, aging is also accompanied by a loss in capillaries (small blood vessels) that supplies tissues such as muscle with oxygen, nutrients, and growth factors. Is there a connection between muscle mass and capillarization?
In this study, we investigated whether muscle capillarization is related to several muscle mass measurements in healthy older men. Muscle capillarization was measured using immunohistochemistry: we took muscle biopsies, cut them into thin slices, and use antibodies to color certain cell structures. This allowed us to study several structures under the microscope (e.g. fiber size, capillaries, myonuclei etc.).
Using immunohistochemistry, we could quantify capillarization. We expressed capillarization as CFPE index, which is the amount of capillaries surrounding the muscle fibers, corrected for the capillary sharing factor (capillaries are shared between multiple muscle fibers) and the perimeter of the fiber.
We found that capillarization (expressed as CFPE index) significantly correlated with appendicular lean mass. Furthermore, we found the strongest correlation between capillarization and appendicular lean mass divided by BMI, which is often used as a measure of sarcopenia.
This means that the older men with low levels of capillarization (expressed as CFPE index) also had the lowest amount of lean mass.
Now be careful: correlation does not equal causation! This study shows that capillarization and lean mass are related in older people but does not show that low capillarization CAUSES muscle loss. Whether a causal relationship is present remains to be investigated.
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