THE ASSOCIATION BETWEEN MUSCLE FIBER SIZE,FIBER TYPE AND BODY COMPOSITION IN

MEN WITH SARCOPENIA1Asta Mastaviciute*, 2Arvydas Laurinavicius, 1Vidmantas Alekna, 1Marija Tamulaitiene, 2Donatas Petroska, 3Vaidile Strazdiene

1 Vilnius University, Faculty of Medicine; 2 National Center of Pathology, Vilnius, Lithuania; 3 State Research Institute Centre For Innovative Medicine; Vilnius, Lithuania

OBJECTIVEThis study was designed to analyze the association between muscle fiber lenght, fiber area, I/II fibers types and regional body composition in sarcopenic men.

CONCLUSIONThis study showed that sarcopenic men possessed fewer fiber type II com-

pared with fiber type I. Muscle fiber size, not fiber type, was positively cor-related with leg muscle mass and leg bone mineral density, although no such associations was observed with leg fat mass.

BACKGROUNDAge-associated changes in types I/II human skeletal muscle fibers and regional body fat, lean mass and bone mineral density (BMD) were detected either in cross-

sectional or in longitudinal studies. The data about relationship between muscle fiber size, fiber type and regional body composition are limited in the elderly men.

MATERIAL AND METHODSThis cross-sectional study included 30 community-dwelling, ambulatory men

(mean age 72.2 ± 7.5 y). Exclusion criteria were metabolic or endocrine disor-ders known to affect musculoskeletal system, taking any medication known to affect muscle or bone metabolism. All participants answered face-to-face ques-tionnaires addressing medical history, lifestyle habits and medications use. Writ-ten informed consent was obtained from each participant. Physical examination was performed. Dual-energy X-ray absorptiometry (iDXA, GE Lunar) was used to measure leg muscle mass and leg fat mass separately, leg BMD. Muscle biop-sies from m. vastus lateralis were taken and histomorphometric parameters were

measured by adenosine triphosphate and merosin staining and image analysis, including muscle fiber length, muscle fiber area, type I and type II muscle fibers percentage (1 picture). Sarcopenia was defined when appendicular skeletal mus-cle mass divided by stature squared was less than 7.26 kg/m2. Statistical analysis was carried out using SPSS version 18.0 for Windows. Pearson’s correlation coef-ficient was determined to assess associations between muscle size, muscle fibers type and regional body composition components. All tests were two-tailed, with significance accepted at p value was <0.05

We haven‘t found significant relationship between leg fat mass and fiber size. No any association was found between fiber type and body composition in sarcopenic men.

ACNOWLEDGMENTSWe are grateful to the elderly men who took part in this study. We thank the technicians at the National Osteoporosis Center (Vilnius, Lithuania) personnel.

RESULTSMean leg fat mass (6.34 ± 2.13 kg), leg muscle mass (17.62 ± 2.68 kg), leg BMD

(1.311 ± 0.161 g/cm²) were measured in sarcopenic men. Mean muscle fiber length (220.69 ± 25.15 µm), fiber area (2492.96 ± 615.96 µm2). Sixty one percentage I type fibers and 39% II type fibers were estimated.

The correlations between muscle fibers morphometric parameters and body compostion in sarcopenic men (table 1).

BMD – bone mineral density;

Table 1. The correlations between muscle fibers morphometric parameters and leg muscle mass, leg bone mineral density in sarcopenic men

Characteristics,units of measurements

Correlation coefficient(r) p

Muscle fiber length (µm)

Leg muscle mass (kg) 0.7 0.001

Leg BMD (g/cm2) 0.6 0.04

Muscle fiber area (µm2)

Leg muscle mass (kg) 0.7 0.026

*Contact address: asta.mastaviciute@osteo.lt

1 picture. Muscle fibers stained by merosin