Matters of fiber size and myonuclear domain: does size matter more than age?

TY - JOUR

T1 - Matters of fiber size and myonuclear domain

T2 - does size matter more than age?

AU - Karlsen, Anders

AU - Couppé, Christian

AU - Andersen, Jesper L.

AU - Mikkelsen, Ulla R.

AU - Nielsen, Rie H.

AU - Magnusson, Stig Peter

AU - Kjaer, Michael

AU - Mackey, Abigail

N1 - © 2015 Wiley Periodicals, Inc.

PY - 2015/12/1

Y1 - 2015/12/1

N2 - Introduction: The relationship between fiber size and myonuclear content is poorly understood. Methods: Biopsy cross-sections from young and old trained and untrained healthy individuals were analyzed for fiber area and myonuclei, and 2 fiber-size-dependent cluster analyses were performed. Results: When comparing fibers of similar size, no effect of training or age was found for myonuclear domain. There was a linear relationship between fiber area and myonuclei per fiber (r=0.99; P<0.001) and a non-linear relationship between fiber area and domain (r=0.97-0.99; P<0.0001), with a markedly smaller domain in fibers <3,000 μm2. A higher proportion of type II fibers <3,000 μm2 was observed in the old subjects. Conclusions: These findings suggest that age-related reductions in myonuclear domain size could be explained by the greater proportion of small fibers. The data also highlight the usefulness of determining fiber-size-based clusters for gaining mechanistic insight into the relationship between skeletal muscle fiber size and myonuclear content.

AB - Introduction: The relationship between fiber size and myonuclear content is poorly understood. Methods: Biopsy cross-sections from young and old trained and untrained healthy individuals were analyzed for fiber area and myonuclei, and 2 fiber-size-dependent cluster analyses were performed. Results: When comparing fibers of similar size, no effect of training or age was found for myonuclear domain. There was a linear relationship between fiber area and myonuclei per fiber (r=0.99; P<0.001) and a non-linear relationship between fiber area and domain (r=0.97-0.99; P<0.0001), with a markedly smaller domain in fibers <3,000 μm2. A higher proportion of type II fibers <3,000 μm2 was observed in the old subjects. Conclusions: These findings suggest that age-related reductions in myonuclear domain size could be explained by the greater proportion of small fibers. The data also highlight the usefulness of determining fiber-size-based clusters for gaining mechanistic insight into the relationship between skeletal muscle fiber size and myonuclear content.

U2 - 10.1002/mus.24669

DO - 10.1002/mus.24669

M3 - Journal article

C2 - 25845994

SN - 0148-639X

VL - 52

SP - 1040

EP - 1046

JO - Muscle & Nerve

JF - Muscle & Nerve

IS - 6

ER -