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, S Peter

AU - Kjaer, Michael

AU - Mackey, Abigail L

N1 - © 2015 Wiley Periodicals, Inc.

PY - 2015/12

Y1 - 2015/12

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 µm(2) . A higher proportion of type II fibers <3,000 µm(2) 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. Muscle Nerve 52: 1040-1046, 2015.

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 µm(2) . A higher proportion of type II fibers <3,000 µm(2) 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. Muscle Nerve 52: 1040-1046, 2015.

U2 - 10.1002/mus.24669

DO - 10.1002/mus.24669

M3 - Journal article

VL - 52

SP - 1040

EP - 1046

JO - Muscle and Nerve

JF - Muscle and Nerve

SN - 0148-639X

IS - 6

ER -