Ultrasound proxy measures of muscle quality are associated with strength and functional performance in older men

Abstract

Background: Diagnostic musculoskeletal ultrasound has been shown to elicit a hyperechoic response in intramuscular adipose tissue. Skeletal muscle characterized by excessive intramuscular adipose tissue is marked by diminished peak force generation in older adults. Previous study findings also suggest that poor muscle tissue quality, as estimated with ultrasound echogenicity, is associated with functional limitations in older women. In this study, the objective was to determine the association of ultrasound echogenicity with peak muscle torque and functional performance in older male Veterans.

Methods: In this pilot study, we evaluated 12 older, ambulatory Veteran men (age = 63.5 ±11.5 years; BMI: 25.6 ±4.0) who were free of medical conditions associated with weakness, muscle atrophy, or edema. Strength and functional performance were assessed on separate visit days to avoid the effects of acute muscle activity on image echogenicity. Hand grip dynamometry (Jamar, Lafayette Instruments) was used for 3 trials under standardized conditions to obtain the mean peak force values. Peak knee extension torque was measured using an isokinetic dynamometer at 60º/s (Biodex System 4 Pro) following a warm-up set and a familiarization session. Participants completed the timed sit-to-stand test (5 repetitions) without external assistance per the standardized procedure. Habitual and fast gait speeds were recorded during the 6-meter timed walk test using the method validated for older adults by Tiedemann et al (2008). Diagnostic musculoskeletal ultrasound at the mid-femur region of the rectus femoris was completed using B-mode scanning with a 13-6 MHz linear array transducer. Longitudinal ultrasound scans were obtained with the transducer oriented 90º to the muscle bundle. Strength values were expressed as absolute values and also scaled to body weight to account for variations in body size. Tissue quality was measured using grayscale histogram analysis (Adobe Photoshop, ver. 6.0) to quantify the echogenicity of the region of interest. The associations of ultrasound echogenicity with peak muscle torque and functional performance were determined using Pearson correlations.

Results: The sample means for strength included a peak knee extensor torque of 89.6 ±29.7 ft-lbs (scaled, .531 ±.169) and a peak grip force of 89.1 ±20.4 lbs (scaled, .524 ±.090). Habitual and fast walking speeds were 1.11 ±.31 m/s and 1.62 ±.33 m/s, respectively. The timed sit-to-stand test time for the sample was 11.15 ±5.15 s. In examining potential confounders to the data interpretation, age was found to be significantly correlated with scaled knee extensor peak torque and sit-to-stand time (p < .05). Therefore, statistical adjustments were made to account for age in analyses involving the affected variables. Grayscale mean values were inversely related to scaled grip force torque (r = -.64, p = .03) and scaled knee extensor torque (r = -.61, partial correlation adjustment for age, r = -.18; p < .05). Similar magnitude of inverse associations were observed for grayscale mean values and functional performance, including habitual gait speed (r = -.62, p = .04), fast gait speed (r = -.71, p = .02), and the sit-to-stand test (r = .69, partial correlation adjustment for age, r = .30; p = .03).

Conclusions: Our initial results, like those of other investigators, revealed ultrasound echogenicity estimates of tissue quality to be associated with muscle strength in older adults. Moreover, the prior findings that echogenicity is related to functional performance in older women are extended by our current observations in older male Veterans, in whom we found higher mean grayscale values to be associated with lower strength values and slower functional performance. Diminished muscle quality and increased intramuscular adipose tissue are significantly affected by increasing age. Therefore, additional analyses with a younger subset of participants may help to better understand the impact of tissue composition independently of age. Finally, our early findings suggest that the impact of body size on physical performance is also an important consideration in assessing the consequences of poor muscle quality.

Full text

The Journal of Frailty & Aging©
Volume 4, Supplement 1, 2015
61
in the sarcomeric integrity. Even though calpain-3 is a key regulator for the sarcomeric
integrity in atrophic changes, changes of calpain-3 activity by aging have not been well
investigated yet. The purpose of this study is to identify the age-related difference of
atrophied skeletal muscles in view of apoptosis and calpain-3 activity. Methods: Eighteen
young (3 month old) and the equal number of aged (22 month old) male Sprague-
Dawley rats were used. Both young and aged rats were divided by three groups: partial
denervation (PD), hindlimb unweighing (HU), and control. Right sciatic nerves were
injured by experimental crushing for PD. Immobilization by tail suspension was designed
for HU. After 2 and 4 weeks from intervention, rat gastrocnemius muscle tissues of all
groups were obtained by gun biopsy technique. Four outcome parameters were measured
at those periods: 1) The ratio of right gastrocnemius weight to total body weight (GW/
TBW); 2) histological evaluation and morphometric analysis by cross sectional area
(CSA) measurement of myocytes; 3) Apoptotic activity by terminal deoxynucleotidyl
transferase dUTP nick-end labeling (TUNEL) and Western blotting for expressions of
BAX and Bcl-2; and 4) Calpain-3 activity by Western blotting. Results Young rats had
signicantly higher GW/TBW than aged rats in PD and HU groups (P = 0.018 and P =
0.011, respectively). Aged myocytes in PD group showed signicantly smaller CSA than
young ones (1074 ± 121 pixels vs. 1645 ± 263 pixels, P = 0.018) while aged myocytes
had larger CSA than young ones in control group (P = 0.037). In TUNEL assay, aged rats
showed higher apoptotic activity than young rats in PD group (12.0 ± 1.3 % vs. 9.5 ± 1.8
%, P = 0.028). In young HU group, BAX and BAX/Bcl-2 were signicantly decreased (P
= 0.046 and P = 0.028, respectively) from 2 to 4 weeks after intervention. Aged rats had
signicant higher BAXs at 4 weeks after intervention than those of young rats in both PD
and HU groups (P = 0.009 and P = 0.004, respectively). Calpain-3 activity of young rats
was higher than that of aged rats at 4 weeks after two interventions (P = 0.017 in both).
Only young rats showed signicant temporal increases of calpain-3 in both PD (0.810 ±
0.154 to 0.988 ± 0.166, P = 0.046) and HU (0.865 ± 0.118 to 1.097 ± 0.191, P = 0.028)
groups. Conclusion: Atrophied skeletal muscles showed age-dependent different responses
. Although aged muscles maintained higher level of apoptotic activity on muscular atrophic
changes, calpain-3 activity of aged muscles showed diminished reactive responses rather
than young ones.
P31- ANTHROPOMETRIC CHARACTERISTICS OF POSTMENOPAUSAL
WOMEN DEPENDING ON APPENDICULAR SKELETAL MASS. V. Povoroznyuk,
N. Dzerovych, R. Povoroznyuk (Kyiv, Ukraine)
The aim of our study was to evaluate the anthropometric characteristics of the
postmenopausal women depending on their appendicular skeletal mass. Materials and
methods: We’ve examined 8882 women aged 20-89 years (mean age – 56.7±0.14 yrs;
mean height – 162.5±0.07 cm; mean weight – 73.5±0.16 kg), taken anthropometric
measures of 79 examined postmenopausal women aged 40-82 yrs (mean age – 63,53±1,08
yrs, mean height – 157,54±0,79 cm, mean weight – 74,75±1,68 kg). Appendicular skeletal
mass (ASM) was measured at all the four limbs with DXA. We’ve also calculated the
appendicular skeletal mass index (ASMI) according to the formula: ASM/height (kg/m2).
During the quartile analysis, depending on their ASMI parameters, the examined women
were divided into the following groups: Q1 – ASMI < 6,38 kg/m2 (n=20), Q2 – ASMI
= 6,38-6,83 kg/m2 (n=20), Q3 – ASMI = 6,84-7,36 kg/m2 (n=20), Q4 – ASMI > 7,36
kg/m2 (n=19). Anthropometric characteristics of the women were evaluated according
to the V.V. Bunak’s method (1941) modied by P.F. Shaparenko (1994). Lean and fat
masses were measured with DXA using a Prodigy densitometer, GE. Statistical analysis
was performed using the «Statistica 6.0» software. Results: Frequency of sarcopenia in
the group of women aged 65 yrs and older was 7 %. Quartile analysis of women taking
into account their ASMI revealed that the women of Q1 and Q2 groups had the following
anthropometric characteristics signicantly reduced: weight (Q1 – 70,90 kg, Q2 – 70,25
kg, Q3 – 74,75 kg, Q4 – 85,53 kg; F=5,24; р=0,002), neck circumference (Q1 – 350 mm,
Q2 – 357 mm, Q3 – 376 mm, Q4 – 393 mm; F=5,68; р=0,001), abdomen circumference
(Q1 – 846 mm, Q2 – 936 mm, Q3 – 1008 mm, Q4 – 1106 mm; F=11,52; р<0,0001),
shoulder width (Q1 – 903 un., Q2 – 963 un., Q3 – 1029 un., Q4 – 1078 un.; F=2,22;
р=0,09), narrow tibia circumference (Q1 – 221 mm, Q2 – 227 mm, Q3 – 244 mm, Q4 –
248 mm; F=6,44; р=0,0006). We also observed a signicantly lower thorax circumference
in the Q1 group (Q1 – 903 mm, Q2 –963 mm, Q3 – 1029 mm, Q4 – 1079 mm; F=3,82;
р=0,01) in comparison with the women of Q4 group (Q1 – 903 mm, Q2 –963 mm, Q3 –
1029 mm, Q4 – 1079 mm; F=3,82; р=0,01). Conclusion: In women with a lower ASMI
(Q1 and Q2 groups) the following anthropometric characteristics were significantly
lower: weight, neck circumference, abdomen circumference, shoulder width, narrow tibia
circumference. Thus, we can use the anthropometric measures for determining the groups
with the relative risk of sarcopenia and its complications.
P32- ULTRASOUND ECHOGENICITY AT THE RECTUS FEMORIS PREDICTS
ATTENUATION ON COMPUTED TOMOGRAPHY IN THE EVALUATION OF
THIGH TISSUE COMPOSITION. M.O. Harris-Love1, N.A. Avila1,2, B. Adams1,
C. Ismail1, S.H. Zaidi1, C.A. Kassner1, F. Liu1, M.R. Blackman1 (Washington, USA;
2. Bethesda, USA)
Background: Age-related changes in lower extremity skeletal muscle groups may
contribute to functional limitations and compromise independent living in older adults.
Previous investigators have cited diminished muscle quality, estimated via specic force
or tissue composition, as an important contributor to the functional decline observed with
increasing age. The purpose of this investigation was to determine the predictive value of
ultrasound echogenicity of the rectus femoris to estimate thigh tissue composition based
on computed tomography (CT) attenuation levels. Methods: This pilot study featured a
sample of generally healthy, community-dwelling older male Veterans (n = 12, age = 63.5
±11.5 years; BMI: 25.6 ±4.0). Ultrasound images of the dominant-limb rectus femoris
were obtained using B-mode scanning with a 13-6 MHz linear array transducer. Image
capture was completed using the longitudinal view with the ultrasound transducer oriented
90º to the muscle bundle. Image echogenicity was quantied via the mean values from
grayscale histogram analysis of the region of interest (Adobe Photoshop, ver. 6.0). The
mid-femur scanning location on the thigh was marked and identied via a radio-opaque
adhesive tag immediately prior to the CT procedure. Estimates of tissue composition
were obtained with CT scanning using a 10 mm axial image slice (120 kVp, 200 to
250 mA) at the mid-femur location. Intermuscular and visible intramuscular adipose
tissue were segmented from subcutaneous adipose tissue during image post-processing
(ImageJ software, ver. 1.48) using standard tissue attenuation threshold algorithms. The
predictive value of ultrasound echogenicity for CT tissue composition estimates was
determined with univariate linear regression. Results: Ultrasound echogenicity expressed
as grayscale mean values was a signicant predictive variable for several cross-sectional
(CSA) thigh tissue composition estimates. Grayscale mean values were strong predictors
for CSA total adipose tissue and lean mass (R² = 0.86, p < .001). Additionally, the
grayscale measures exhibited signicant predictive value for CSA total intramuscular
adipose tissue (R² = 0.76, p < .005) and intramuscular adipose tissue of the rectus femoris
(R² = 0.80, p < .005). In contrast, the association between grayscale mean values and
CT tissue composition estimates was less robust for CSA subcutaneous adipose tissue
(R² = 0.31, p = .05). Conclusions: Our preliminary findings suggest that portable,
diagnostic, musculoskeletal ultrasound is a useful imaging modality to serve as a proxy
for CT scanning to obtain basic CSA thigh tissue composition estimates. The ultrasound
echogenicity at the recuts femoris, as expressed with grayscale histogram mean values,
may have predictive validity in older men for CSA total and intramuscular adipose tissue
at the mid-femur region of the thigh. Given the discordant declines in muscle mass and
strength in aging adults, and the suspected role of intramuscular adipose tissue in metabolic
dysfunction within this population, readily accessible measures of tissue composition, such
as diagnostic ultrasound, may prove to have utility in geriatric musculoskeletal screening
and assessment. (This study was funded by a Veterans Affairs VISN 5 Pilot Grant award
– Station 688.)
P33- ULTRASOUND PROXY MEASURES OF MUSCLE QUALITY ARE
ASSOCIATED WITH STRENGTH AND FUNCTIONAL PERFORMANCE IN
OLDER MEN. M.O. Harris-Love, B. Adams, C. Ismail, H.J. Hernandez, V. McIntosh,
J. Yang, L. Chacko, M.R. Blackman, B.S. Garra (Washington, USA)
Background: Diagnostic musculoskeletal ultrasound has been shown to elicit a
hyperechoic response in intramuscular adipose tissue. Skeletal muscle characterized by
excessive intramuscular adipose tissue is marked by diminished peak force generation
in older adults. Previous study ndings also suggest that poor muscle tissue quality,
as estimated with ultrasound echogenicity, is associated with functional limitations in
older women. In this study, the objective was to determine the association of ultrasound
echogenicity with peak muscle torque and functional performance in older male Veterans.
Methods: In this pilot study, we evaluated 12 older, ambulatory Veteran men (age =
63.5 ±11.5 years; BMI: 25.6 ±4.0) who were free of medical conditions associated with
weakness, muscle atrophy, or edema. Strength and functional performance were assessed
on separate visit days to avoid the effects of acute muscle activity on image echogenicity.
Hand grip dynamometry (Jamar, Lafayette Instruments) was used for 3 trials under
standardized conditions to obtain the mean peak force values. Peak knee extension
torque was measured using an isokinetic dynamometer at 60º/s (Biodex System 4 Pro)
following a warm-up set and a familiarization session. Participants completed the timed
sit-to-stand test (5 repetitions) without external assistance per the standardized procedure.
Habitual and fast gait speeds were recorded during the 6-meter timed walk test using the
method validated for older adults by Tiedemann et al (2008). Diagnostic musculoskeletal
ultrasound at the mid-femur region of the rectus femoris was completed using B-mode
scanning with a 13-6 MHz linear array transducer. Longitudinal ultrasound scans were
obtained with the transducer oriented 90º to the muscle bundle. Strength values were
expressed as absolute values and also scaled to body weight to account for variations
in body size. Tissue quality was measured using grayscale histogram analysis (Adobe
Photoshop, ver. 6.0) to quantify the echogenicity of the region of interest. The associations
of ultrasound echogenicity with peak muscle torque and functional performance were
determined using Pearson correlations. Results: The sample means for strength included a
peak knee extensor torque of 89.6 ±29.7 ft-lbs (scaled, .531 ±.169) and a peak grip force of
89.1 ±20.4 lbs (scaled, .524 ±.090). Habitual and fast walking speeds were 1.11 ±.31 m/s
and 1.62 ±.33 m/s, respectively. The timed sit-to-stand test time for the sample was 11.15
±5.15 s. In examining potential confounders to the data interpretation, age was found to
be signicantly correlated with scaled knee extensor peak torque and sit-to-stand time (p <
.05). Therefore, statistical adjustments were made to account for age in analyses involving
the affected variables. Grayscale mean values were inversely related to scaled grip force
torque (r = -.64, p = .03) and scaled knee extensor torque (r = -.61, partial correlation
adjustment for age, r = -.18; p < .05). Similar magnitude of inverse associations were
observed for grayscale mean values and functional performance, including habitual gait
speed (r = -.62, p = .04), fast gait speed (r = -.71, p = .02), and the sit-to-stand test (r =
.69, partial correlation adjustment for age, r = .30; p = .03). Conclusions: Our initial
results, like those of other investigators, revealed ultrasound echogenicity estimates
of tissue quality to be associated with muscle strength in older adults. Moreover, the
prior ndings that echogenicity is related to functional performance in older women are
extended by our current observations in older male Veterans, in whom we found higher
mean grayscale values to be associated with lower strength values and slower functional
55