University of Southern Denmark
Changes in systemic GDF15 across the adult lifespan and their impact on maximal muscle
power
the Copenhagen Sarcopenia Study
Alcazar, Julian; Frandsen, Ulrik; Prokhorova, Tatyana; Kamper, Rikke S.; Haddock, Bryan;
Aagaard, Per; Suetta, Charlotte
Published in:
Journal of Cachexia, Sarcopenia and Muscle
DOI:
10.1002/jcsm.12823
Publication date:
2021
Document version:
Final published version
Document license:
CC BY-NC-ND
Citation for pulished version (APA):
Alcazar, J., Frandsen, U., Prokhorova, T., Kamper, R. S., Haddock, B., Aagaard, P., & Suetta, C. (2021).
Changes in systemic GDF15 across the adult lifespan and their impact on maximal muscle power: the
Copenhagen Sarcopenia Study. Journal of Cachexia, Sarcopenia and Muscle, 12(6), 1418-1427.
https://doi.org/10.1002/jcsm.12823
Go to publication entry in University of Southern Denmark's Research Portal
Terms of use
This work is brought to you by the University of Southern Denmark.
Unless otherwise specified it has been shared according to the terms for self-archiving.
If no other license is stated, these terms apply:
• You may download this work for personal use only.
• You may not further distribute the material or use it for any profit-making activity or commercial gain
• You may freely distribute the URL identifying this open access version
If you believe that this document breaches copyright please contact us providing details and we will investigate your claim.
Please direct all enquiries to puresupport@bib.sdu.dk
Download date: 20. May. 2023
Journal of Cachexia, Sarcopenia and Muscle (2021)
Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/jcsm.12823
ORIGINAL ARTICLE
Changes in systemic GDF15 across the adult lifespan
and their impact on maximal muscle power: the
Copenhagen Sarcopenia Study
Julian Alcazar1,2,3* , Ulrik Frandsen4, Tatyana Prokhorova4, Rikke S. Kamper3,5, Bryan Haddock6, Per Aagaard4
Charlotte Suetta3,5,7
&
1
GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain; 2CIBER of Frailty and Healthy Aging (CIBERFES), Madrid, Spain; 3CopenAge – Copenhagen
Center for Clinical Age Research, University of Copenhagen, Copenhagen, Denmark; 4Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark,
Odense, Denmark; 5Geriatric Research Unit, Department of Geriatric and Palliative Medicine, Bispebjerg-Frederiksberg University Hospital, Copenhagen, Denmark;
6
Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet University Hospital, Copenhagen, Denmark; 7Geriatric Research Unit, Department of Internal
Medicine, Herlev-Gentofte University Hospital, Copenhagen, Denmark
Abstract
Background Although growth differentiation factor 15 (GDF15) is known to increase with disease and is associated
with low physical performance, the role of GDF15 in normal ageing is still not fully understood. Specifically, the influence of circulating GDF15 on impairments in maximal muscle power (a major contributor to functional limitations) and
the underlying components has not been investigated.
Methods Data from 1305 healthy women and men aged 20 to 93 years from The Copenhagen Sarcopenia Study were
analysed. Circulating levels of GDF15 and markers of inflammation (tumor necrosis factor-alpha, interleukin-6, and
high-sensitivity C-reactive protein) were measured by ELISA (R&D Systems) and multiplex bead-based immunoassays
(Bio-Rad). Relative (normalized to body mass), allometric (normalized to height squared), and specific (normalized to
leg muscle mass) muscle power were assessed by the Nottingham power rig [leg extension power (LEP)] and the 30 s
sit-to-stand (STS) muscle power test. Total body fat, visceral fat, and leg lean mass were assessed by dual energy X-ray
absorptiometry. Leg skeletal muscle index was measured as leg lean mass normalized to body height squared.
Results Systemic levels of GDF15 increased progressively as a function of age in women (1.1 ± 0.4 pg·mL 1·year 1)
and men (3.3 ± 0.6 pg·mL 1·year 1) (both P < 0.05). Notably, GDF15 increased at a faster rate from the age of 65 years
in women (11.5 ± 1.2 pg·mL 1·year 1, P < 0.05) and 70 years in men (19.3 ± 2.3 pg·mL 1·year 1, P < 0.05), resulting
in higher GDF15 levels in men compared with women above the age of 65 years (P < 0.05). Independently of age and
circulatory markers of inflammation, GDF15 was negatively correlated to relative STS power (P < 0.05) but not LEP, in
both women and men. These findings were mainly explained by negative associations of GDF15 with specific STS
power in women and men (both P < 0.05).
Conclusions A J-shaped relationship between age and systemic GDF15 was observed, with men at older age showing
steeper increases and elevated GDF15 levels compared with women. Importantly, circulating GDF15 was independently and negatively associated with relative STS power, supporting the potential role of GDF15 as a sensitive
biomarker of frailty in older people.
Keywords
Growth differentiation factor 15; Sit-to-stand; Leg extension power; Sarcopenia; Frailty
Received: 15 March 2021; Revised: 14 August 2021; Accepted: 7 September 2021
*Correspondence to: Julian Alcazar, GENUD Toledo Research Group, Universidad de Castilla-La Mancha, Toledo, Spain. Phone: +34 925268800 (Ext.: 96808), Email: julian.
alcazar@uclm.es
© 2021 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of Society on Sarcopenia, Cachexia and Wasting Disorders.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium,
provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
2
Introduction
Growth differentiation factor 15 (GDF15) is a cytokine released in response to stress or injury1 that has been identified
as an important biomarker for cardiovascular disease, metabolic disease, cancer, cognitive impairment, mitochondrial
dysfunction, and cachexia.1,2 Increases in circulating levels
of GDF15 with increasing age have been reported in the
literature,3–6 with higher levels related to increased mortality
risk.2,4,7–10 The relationship between circulating GDF15 and
age has been shown to be curvilinear2,10,11; however, the specific age at which GDF15 levels starts to accelerate or
whether these increases are sex specific still need to be
clarified.
Notably, among 1301 circulating proteins measured in a
cohort of older people from the In Chianti study, GDF15
proved to be among the strongest predictors of mobility limitations when assessed at 9 years follow-up.12 Thus, circulating GDF15 is considered a potential core biomarker of frailty
in older people.13,14 Interestingly, a close relationship between GDF15 and another hallmark of ageing, that is, chronic
low-grade inflammation has been demonstrated, but the interplay between these biomarkers and how they contribute
to muscle dysfunction are not fully elucidated.3,9,15,16 The influence of GDF15 on functional ability might be due to its effects on the neuromuscular system, because recent studies
have shown that elevated GDF15 concentrations were related to muscle wasting in intensive care unit patients,17 with
patients demonstrating muscle weakness during their hospital stay also exhibiting increased plasma and muscle mRNA
expression levels of GDF15, respectively, compared with
controls.18 Further, circulating GDF15 levels have been observed to be negatively associated with muscle mass, handgrip strength, and physical performance.2,5,9,19 However, no
knowledge exists about the relationship of circulating
GDF15 with relative muscle power and its underlying components. Importantly, low relative muscle power is a stronger
predictor of mobility limitations, frailty, and disability among
older adults compared with sarcopenia.20 Furthermore, relative muscle power, assessed as maximal leg extension power
(LEP), decreases with age due to changes in allometric (normalized to height squared) muscle power and body mass index (BMI) as observed across the lifespan.21 Specifically,
allometrically scaled muscle power declines with ageing at
annual rates of 1–2% between the age of 40 and 60 years
to reach steeper annual decline rates of 2–4% above the
age of 60 years in both women and men.21 In addition, BMI
has been shown to increase annually 0.3–0.4% from 20 to
~70 years of age, amplifying the annual losses expressed as
maximal relative muscle power normalized to body mass.21
However, the role of GDF15 and the potential relation to
muscle power production have not previously been
investigated.
J. Alcazar et al.
Thus, the aim of the present investigation was (i) to assess
the potential relationship between circulating GDF15, age,
and sex and (ii) to assess the influence of circulating GDF15
on relative muscle power and its underlying components.
Material and methods
Study cohort
The Copenhagen Sarcopenia Study22 is a population-based
cross-sectional study conducted between 2013 and 2016,
whose participants were recruited from a random sample of
20 000 men and women (aged 20 to 101 years) taking part
in the Copenhagen City Heart Study.23 Subjects were invited
to participate in the present investigation using the following
exclusion criteria: pregnancy, acute or chronic medical illness,
surgery within the last 3 months, cancer, medication known
to affect body composition (e.g. corticosteroid administration), and any history of compromised ambulation or
prolonged immobilization. A total of 1305 subjects (729
women and 576 men; aged 20 to 93 years) accepted to participate in the present investigation (Table 1). According to
the data reported elsewhere regarding physical activity
levels24 and functional status,22 the present study participants were considered healthy and physically active. All
participants gave their written informed consent. The study
was performed in accordance with the Helsinki Declaration
and approved by the Ethical Committee of Copenhagen
(H-3-2013-124).
Body composition
A stadiometer and scale device were used to record the
height and body mass of the participants without shoes and
while wearing light clothing. Height (m) was assessed to the
nearest 0.1 cm and body mass (kg) to the nearest 0.1 kg.
BMI was obtained from the ratio between body mass and
height squared (kg·m 2). Total body fat, visceral fat, and legs
lean mass were assessed by dual energy X-ray absorptiometry (iDXA, GE Lunar, Madison, USA) and analysed using commercially available software (Encore software Version 16.0).
Due to the inter-individual variation in these body composition components being highly influenced by body size, leg
skeletal muscle index (legs SMI) was calculated as the ratio
between leg lean mass and height squared (kg·m 2), and
total body fat index and visceral fat index were calculated
as total body fat and visceral fat normalized to height
squared (kg·m 2), respectively.
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
3
GDF15 and muscle power
Table 1 Main characteristics of the study participants per sex and age group
Age (years)
Body mass (kg)
Height (m)
2
BMI (kg·m )
2
Fat index (kg·m )
2
Visceral FI (kg·m )
Inflammation
1
TNF-α (pg·mL )
1
IL-6 (pg·mL )
1
hsCRP (pg·mL )
Young women
(n = 172)
Middle-aged women
(n = 261)
Older women
(n = 296)
Young men
(n = 110)
Middle-aged men
(n = 235)
Older men
(n = 231)
29.9 ± 5.2
64.4 ± 9.7
1.68 ± 0.07
22.7 ± 3.1
6.85 ± 2.43
0.08 ± 0.09
52.5 ± 7.3
69.7 ± 12.0
1.67 ± 0.06
24.9 ± 4.4
8.75 ± 3.53
0.23 ± 0.23
75.1 ± 7.0
67.6 ± 12.2
1.63 ± 0.07
25.5 ± 4.5
9.92 ± 3.36
0.38 ± 0.25
30.0 ± 5.2
83.0 ± 12.4
1.83 ± 0.07
24.8 ± 3.4
5.51 ± 2.52
0.18 ± 0.17
52.7 ± 7.3
85.2 ± 12.0
1.81 ± 0.07
26.1 ± 3.6
7.00 ± 2.61
0.43 ± 0.30
74.1 ± 6.0
82.9 ± 14.9
1.77 ± 0.07
26.5 ± 4.2
8.03 ± 3.00
0.58 ± 0.35
11.3 ± 5.0
0.4 ± 0.4
1.5 ± 3.6
14.6 ± 7.4
0.7 ± 0.4
1.5 ± 2.7
16.6 ± 6.9
0.5 ± 0.7
2.4 ± 4.8
13.0 ± 6.1
0.4 ± 0.3
1.1 ± 1.7
13.7 ± 6.2
0.4 ± 0.4
1.6 ± 3.0
18.6 ± 14.0
0.7 ± 2.4
3.0 ± 8.7
BMI, body mass index. FI, fat index; hsCRP, high-sensitivity C-reactive protein; IL-6, interleukin-6; TNF-α, tumour necrosis factor-alpha.
Data are presented as mean ± standard deviation. Subjects were divided into young (20–39 years), middle-aged (40–64 years) and older
(≥65 years) men and women.
Maximal muscle power
Leg extension power
Maximal LEP was assessed by the Nottingham power rig
(Medical Engineering Unit, University of Nottingham
Medical School, Nottingham, UK).25 This device measures
unilateral lower-limb extension power with the participants
seated in an upright position, their arms folded across the
chest, knees flexed having one foot resting on the floor,
and the other foot positioned on the dynamometer pedal
connected to a flywheel. After two familiarization trials,
the participants were instructed to push the pedal forward
as hard and fast as possible. The test was performed separately on each leg, and measurements were repeated for
each limb until maximal power output could not be increased further. At least five repetitions were performed
with a 30 s resting period between successive attempts.
Strong verbal encouragement and visual feedback were
provided to all study participants to ensure a maximal volitional effort. The highest LEP value was selected for further
analysis.
Sit-to-stand muscle power
The 30 s sit-to-stand (STS) test involves recording the number
of STS repetitions performed continuously by the subjects in
30 s. After the cue ‘ready, set, go!’, participants performed
STS repetitions as rapidly as possible on a standardized armless chair (0.45 m seat height) starting from the sitting position with their buttocks touching the chair to full standing
position with their arms crossed over the chest. A stopwatch
was started simultaneously on the ‘go!’ cue, and it was
stopped when the 30 s time limit was reached. The total
number of completed STS manoeuvres during the 30 s period
was recorded. Strong standardized verbal encouragement
was given throughout the test. The subjects were allowed
to try one to two times with an adequate resting period
(30–60 s) before the definitive STS test was annotated. As
described in details elsewhere,26–28 STS mean muscle power
(W) was calculated as
STS power ¼
Body mass 0:9 g ½Height 0:5
Time
0:5
N of reps
Chair height
where body mass is expressed in kg, body height and chair
height in m, and time in s (30 s in the current setting). Briefly,
0.9 is a coefficient to calculate the proportion of body mass
that is lifted during the STS maneuver, 0.5 in the numerator
is a coefficient to calculate leg length, and 0.5 in the denominator is a coefficient to calculate the relative duration of the
concentric phase in each STS repetition.
Finally, both muscle power measures (LEP and STS power)
were expressed relative to body mass (W·kg 1),20 whereas allometric power (W·m 2) was calculated as the ratio of absolute power and body height squared, and specific power
(W·kg 1) was calculated as the ratio between absolute power
and leg lean mass (one leg for LEP and two legs for STS
power).
Determination of GDF15 and markers of
inflammation
Blood samples were collected from the antecubital vein and
frozen at 80°C after the corresponding procedures for
plasma and serum preparation. Plasma GDF15 was measured
using DuoSet ELISA kits (R&D Systems, USA). Briefly, plates
were pre-coated with capture antibody according to the
manufacturer instructions. Then, 100 μL of pre-cleared
plasma was applied per well and supplemented with equal
volume of DuoSET kit-supplied reagent dilution buffer. Recombinant standard dilution series (5 to 1280 pg·mL 1) were
included. The plates were incubated overnight at 22–24°C. All
consecutive washes, subsequent antibody incubation,
streptavidin-HRP binding, and colorimetric processing were
conducted according to manufacturer instructions. Plates
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
4
J. Alcazar et al.
were examined with a micro-plate reader (EnSpire Multilabel
Reader, Perkin-Elmer, USA) at 450 nm. Calculations were conducted using sigmoidal curve fitting with curve fitted to the
results of the standards measurements on each plate.
Given the relationship between GDF15 and markers of
inflammation,3,9,15,16 plasma tumour necrosis factor-alpha
(TNF-α), interleukin-6 (IL-6), and serum high-sensitivity C-reactive protein (hsCRP) were measured to assess the effects
of GDF15 independently from low-grade inflammatory status.
TNF-α and IL-6 were assessed in plasma using commercially
available multiplex magnetic bead-based immunoassay kits
(Bio-Rad, USA). Serum levels of hsCRP were assessed using
latex-entrenched immune-turbidimetry analyses (Roche Diagnostics, Switzerland).
(Std.) β values] of the basic components of relative muscle
power (i.e. BMI, leg SMI, and specific muscle power) to the
association between GDF15 and relative muscle power (multivariate analysis) was assessed, and again adjusted for age as
well as for age and inflammatory markers. As BMI, total body
fat index, and visceral fat index all are measures of obesity,
only the one parameter showing the greatest association to
GDF15 was included in the final model. All statistical analyses
were performed using SPSS v24 (SPSS Inc., Chicago, Illinois),
and the level of significance was set at α = 0.05 using twotailed testing.
Statistical analysis
Results on LEP, 30 s STS, and GDF15 are presented in Table 2
specified for sex and age groups.
Data are presented as mean ± standard deviation unless otherwise stated. Analyses were performed separately in women
and men. The association between age and plasma GDF15
was assessed by regression analyses. Firstly, linear, quadratic,
and cubic regression models were compared based on the
coefficient of determination (r2) change in order to determine the most suitable regression model based on changes
in F values. Then, segmented (interval confined) regression
analyses were performed to determine whether and at what
boundary age a change in the slope (i.e. altered rate of
change) emerged in the relationship between age and
GDF15. Using an iterative approach several age points were
evaluated (30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 years)
at different age intervals (20–45, 20–50, 25–55, 30–60, 35–
65, 40–70, 45–75, 50–80, 55–85, 60–90, and 65–95 years,
respectively). Subsequently, a single regression model was
created considering the age points at which a statistically significant change in regression slope was observed. Linear
mixed effects models were used to assess differences by
sex and age groups (young: 20.0 to 39.9 years; middle-aged:
40.0 to 64.9 years; and old: ≥65 years), both set as fixed factors, while participants were included as a random factor. The
models were calculated using maximum likelihood estimation
and the best-fitting covariance structure. Pairwise comparisons were conducted applying Bonferroni’s corrections.
For the assessment of the influence of plasma GDF15
levels on relative muscle power and its determining components, a two-step process was followed using linear mixed effect models. First, the unadjusted association (r values) of
plasma GDF15 with relative muscle power and its constitutive
components (i.e. BMI, leg SMI, allometric power, and specific
power) was separately assessed (bivariate analysis), and further adjusted for age as well as for age and inflammatory
markers (TNF-α, hsCRP, and IL-6). The association between
GDF15 and total body fat index and visceral fat index was also
evaluated. Secondly, the partial contribution [standardized
Results
Association between plasma GDF15 and age
Our regression analyses showed a quadratic J-shaped relationship between age and GDF15 in women (r2 = 0.30;
F = 147.061; P < 0.001) (Figure 1A). In addition, segmented
regression analyses yielded two main phases of variation in
GDF15 throughout the adult lifespan in women (r2 = 0.31;
F = 151.901; P < 0.001): GDF15 increased between 20 and
65 years at a rate of 1.1 ± 0.4 pg·mL 1·year 1 (P = 0.017)
and above 65 years at a faster rate of 11.5 ± 1.2 pg·mL 1·year1 (P < 0.001).
Likewise, men demonstrated a cubic J-shaped relationship
between age and GDF15 (r2 = 0.32; F = 83.495; P < 0.001)
(Figure 1B) with segmented regression analyses revealing
two phases of variation in GDF15 (r2 = 0.32; F = 128.694;
P < 0.001) (Figure 1B): GDF15 increased between 20 and
70 years at a rate of 3.3 ± 0.6 pg·mL 1·year 1 (P < 0.001)
while increasing at a steeper rate above the age of 70 years
of 19.3 ± 2.3 pg·mL 1·year 1 (P < 0.001).
There were statistically significant differences by sex in
both phases, with men showing higher rates of age-related
variation in GDF15 compared to women (both P < 0.05)
(Table 2).
Bivariate association of plasma GDF15 with
relative muscle power and its components
Unadjusted r values for the different relationships observed
between GDF15 and relative muscle power (either LEP or
STS power) and its components (i.e. BMI, leg SMI, and allometric and specific power) are reported in Table 3, while adjusted r values are shown in Table 4 for women and Table 5
for men.
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
5
GDF15 and muscle power
Table 2 Lean mass, plasma GDF15, and maximal lower-limb muscle power in young (20–39 years), middle-aged (40–64 years), and older (≥65 years)
women and men
Young women Middle-aged women
2
Leg SMI (kg·m )
1
GDF15 (pg·mL )
STS power
1
Relative (W·kg )
2
Allometric (W·m )
1
Specific (W·kg )
LEP
1
Relative (W·kg )
2
Allometric (W·m )
1
Specific (W·kg )
5.1 ± 0.6
177.1 ± 95.4
5.2 ± 0.6
197.5 ± 88.3
6.3 ± 1.4
142.0 ± 36.1
28.1 ± 5.9
5.1 ± 1.5
a
124.6 ± 35.4
a
24.2 ± 6.4
3.6 ± 0.8
82.0 ± 20.4
32.2 ± 6.8
3.0 ± 0.9
a
73.7 ± 20.1
a
28.6 ± 7.0
Older women
Young men
a,b
4.9 ± 0.6
6.3 ± 0.7*
a,b
323.2 ± 188.8
154.5 ± 58.2
a
3.3 ± 1.1
a,b
82.5 ± 27.5
a,b
16.8 ± 4.9
a
1.9 ± 0.7
a,b
48.1 ± 17.0
a,b
19.6 ± 6.4
Middle-aged men
Older men
6.2 ± 0.7*
a
223.8 ± 107.1
5.8 ± 0.7*
a,b
375.5 ± 242.3*
a,b
7.4 ± 1.5*
183.8 ± 42.0*
29.3 ± 5.6
6.2 ± 1.7*
a
161.0 ± 42.8*
a
26.1 ± 6.6*
a,b
4.7 ± 0.9*
115.4 ± 24.5*
36.9 ± 6.8*
4.0 ± 1.0*
a
104.7 ± 26.5*
a
33.7 ± 7.8*
a,b
a
4.3 ± 1.4*
a,b
112.4 ± 38.3*
a,b
19.4 ± 6.0*
a,b
a
2.7 ± 0.9*
a,b
72.3 ± 24.1*
a,b
24.8 ± 7.7*
a,b
GDF15, growth differentiation factor 15; LEP, leg extension power; SMI, skeletal muscle index; STS, sit-to-stand.
Data are presented as mean ± standard deviation.
*
Significant differences compared to women (P < 0.05).
a
Significant differences compared with young.
b
Significant differences compared with middle-aged.
Figure 1 Trajectories of plasma GDF15 with age in women and men. GDF15, growth differentiation factor 15.
Body mass index and legs skeletal muscle index
In women, there was no association of plasma GDF15 with
BMI or legs SMI after adjusting for age (both r = 0.02 and
P ≥ 0.566) or age and inflammatory markers (both r ≤ 0.06
and P ≥ 0.133) (Table 4). In contrast, both BMI and legs SMI
were significantly associated to plasma GDF15 in men after
adjusting for age (both r = 0.12 and P ≤ 0.015) as well as
age and markers of inflammation (r = 0.16 and 0.15, respectively, both P = 0.002) (Table 5).
Leg extension power
No association was found in women between plasma GDF15
and relative, allometric, or specific LEP when adjusting for age
(all r ≤ 0.06 and P ≥ 0.095) or for age and inflammatory
markers (all r ≤ 0.05 and P ≥ 0.196) (Table 4). Similarly, in
men, there was no association between plasma GDF15 and
relative LEP when adjusting for age (r = 0.06 and P = 0.090)
or for age and inflammatory markers (r = 0.05 and
P = 0.181) (Table 5). However, men demonstrated a negative
association between plasma GDF15 and allometric and specific LEP after adjusting for age (both r = 0.08 to 0.10 and
P ≤ 0.045), and with allometric but not specific LEP after
adjusting for age and inflammatory markers (r = 0.09,
P = 0.034).
Sit-to-stand power
Significant associations between plasma GDF15 and relative,
allometric, and specific STS power were observed in women
after adjusting for either age (all r = 0.09 to 0.12 and
P ≤ 0.004) or age and inflammatory levels (all r = 0.06 to
0.10 and P ≤ 0.045) (Table 4). Similarly, men exhibited significant associations between GDF15 and relative, allometric,
and specific STS power after adjusting for age (all r = 0.10
to 014 and P ≤ 0.009) or age and inflammation status (all
r = 0.07 to 0.12 and P ≤ 0.048) (Table 5).
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
6
J. Alcazar et al.
Table 3 Association between systemic levels of GDF15 and measures of body composition and relative muscle power according to sex and age
Women
Young
BMI
Fat index
Visceral FI
Leg SMI
LEP
Relative
Allometric
Specific
STS power
Relative
Allometric
Specific
Middle-aged
Men
Older
All
Young
Middle-aged
Older
All
0.04
0.03
0.02
0.04
0.11*
0.11*
0.22**
0.01
0.04
0.04
0.03
0.04
0.08**
0.12**
0.20***
0.09**
0.13
0.06
0.18*
0.19*
0.03
0.08
0.13*
0.12*
0.14**
0.11
0.07
0.17**
0.01
0.08
0.17***
0.23***
0.01
0.02
0.01
0.21**
0.16**
0.17**
0.15**
0.17**
0.17**
0.35***
0.34***
0.35***
0.16
0.26**
0.13
0.10
0.10
0.05
0.24***
0.26***
0.24***
0.39***
0.38***
0.36***
0.01
0.02
0.01
0.28***
0.25***
0.25***
0.26***
0.27***
0.29***
0.41***
0.39***
0.40***
0.04
0.04
0.08
0.18**
0.18**
0.13**
0.26***
0.29***
0.24***
0.42***
0.41***
0.38***
BMI, body mass index; FI, fat index; LEP, leg extension power; SMI, skeletal muscle index; STS, sit-to-stand.
Unadjusted bivariate association (r values).
*
P < 0.10,
**
P < 0.05,
***
P < 0.001.
Table 4 Association between systemic levels of GDF15 and measures of body composition and relative muscle power in women adjusted for age and
inflammatory markers
Adjusted for age
r
BMI
Fat index
Visceral FI
Leg SMI
LEP
Relative
Allometric
Specific
STS power
Relative
Allometric
Specific
a
β ± 95% CI
Adjusted for age and inflammatory markers
P
r
a
β ± 95% CI
P
0.02
0.04
0.01
0.02
0.07 ± 0.24
0.08 ± 0.19
0.00 ± 0.01
0.01 ± 0.04
0.566
0.408
0.793
0.699
0.06
0.07
0.04
0.03
0.18 ± 0.23
0.16 ± 0.18
0.01 ± 0.01
0.01 ± 0.04
0.133
0.076
0.303
0.532
0.03
0.05
0.06
0.02 ± 0.04
0.73 ± 1.01
0.30 ± 0.36
0.295
0.155
0.095
0.01
0.04
0.05
0.01 ± 0.04
0.61 ± 1.02
0.24 ± 0.36
0.690
0.244
0.196
0.09
0.11
0.12
0.10 ± 0.07
2.92 ± 1.71
0.55 ± 0.30
0.004
<0.001
<0.001
0.06
0.10
0.10
0.07 ± 0.07
2.58 ± 1.73
0.46 ± 0.31
0.045
0.004
0.003
BMI, body mass index; FI, fat index; LEP, leg extension power; SMI, skeletal muscle index; STS, sit-to-stand.
Adjusted bivariate association (r values).
a
1
Change per each 100 pg·mL increase in GDF15.
Table 5 Association between systemic levels of GDF15 and measures of body composition and relative muscle power in men adjusted for age and
inflammatory markers
Adjusted for age
r
BMI
Fat index
Visceral FI
Leg SMI
LEP
Relative
Allometric
Specific
STS power
Relative
Allometric
Specific
a
β ± 95% CI
Adjusted for age and inflammatory markers
P
r
a
β ± 95% CI
P
0.12
0.10
0.07
0.12
0.24 ± 0.19
0.15 ± 0.14
0.01 ± 0.04
0.05 ± 0.04
0.015
0.042
0.104
0.011
0.16
0.13
0.10
0.15
0.31 ± 0.20
0.20 ± 0.14
0.02 ± 0.02
0.06 ± 0.04
0.002
0.005
0.020
0.002
0.06
0.10
0.08
0.04 ± 0.05
1.66 ± 1.36
0.41 ± 0.40
0.090
0.017
0.045
0.05
0.09
0.07
0.03 ± 0.05
1.50 ± 1.39
0.34 ± 0.41
0.181
0.034
0.110
0.10
0.14
0.11
0.10 ± 0.08
3.65 ± 2.09
0.44 ± 0.32
0.009
<0.001
0.008
0.07
0.12
0.08
0.08 ± 0.08
3.11 ± 2.13
0.34 ± 0.33
0.048
0.004
0.043
BMI, body mass index; FI, fat index; LEP, leg extension power; SMI, skeletal muscle index; STS, sit-to-stand.
Adjusted bivariate association (r values).
a
1
Change per each 100 pg·mL increase in GDF15.
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
7
GDF15 and muscle power
Multivariate association between GDF15 and main
components of relative muscle power
There was a significant association of BMI, legs SMI, and specific STS power with plasma GDF15 in both women (Std.
β = 0.12, 0.13, and 0.37, respectively) and men (Std.
β = 0.21, 0.33, and 0.31, respectively) (all P < 0.001)
(Table 6). Specific STS power (but no other parameters)
remained significantly associated with plasma GDF15 in both
women and men when the model was adjusted for age (Std.
β = 0.16 and 0.12; both P ≤ 0.006). Furthermore, specific
STS power was negatively associated to plasma GDF15 in
women and men after adjusting for age and inflammatory
markers (Std. β = 0.14 and 0.10; both P ≤ 0.034), while
a trend (P = 0.083) was observed for leg SMI in men only
(Std. β = 0.11) (Table 6).
Discussion
The present study investigated the role of GDF15 in normal
ageing, and in particular its relationship to low muscle power,
because the latter is one of the main contributors to impaired
physical function in old adults. The main findings of the present study were (i) a J-shaped relationship was found to exist
between age and GDF15, with men at older age showing
steeper increases and elevated GDF15 levels compared with
women, and (ii) circulating levels of GDF15 were independently and negatively associated to relative STS power in
both men and women.
GDF15 is considered an overall stress-induced cytokine
that is released in response to tissue injury1 and has been
shown to increase during progressive ageing.3–6 However, it
is less clear whether there is a specific stage in life in which
GDF15 increases at an accelerated rate, and differences between women and men are inconsistently reported.2,3,29,30
In the present study, no sex differences in plasma GDF15
were observed before the age of 65 years, from which age
plasma GDF15 levels remained systematically higher in men
compared to women. This observation might explain the disparate conclusions found in the literature. In addition, the sex
differences in plasma GDF15 observed at older age in the
present study could be explained by a greater rate of increase
in GDF15 observed in men compared with women throughout the adult lifespan. In both cases, the increase in circulating GDF15 levels was particularly evident after the sixth
decade of life (65 years in women and 70 years in men).
Notably, elevated levels of circulating GDF15 have been associated with several types of chronic disease and conditions,
including acute and chronic inflammation,31 mitochondrial
dysfunction,2 frailty,32 and all-cause mortality.4 Furthermore,
GDF15 has been inversely associated with physical performance in older people9 and proven to be an independent
predictor of declining physical function.30 In the current
study, plasma GDF15 was negatively associated to relative
STS power, which in turn is a strong predictor of physical performance in older people.12,20 In contrast, no relationship
was observed between GDF15 and maximal LEP. The discrepancy between the two tests may well be related to differing
biomechanical characteristics of the tests. Thus, LEP expresses maximal unilateral lower-limb power produced during an effort lasting <1 s, while STS power expresses
average bilateral lower-limb muscle power exerted during a
continuous 30 s effort. In this sense, the role of GDF15 as a
mitokine15 could explain the present observation of a stronger association with mechanical muscle power exerted during
more sustained efforts. Notably, among the basic components of relative STS muscle power, specific STS power (i.e.
absolute 30 s STS power/leg lean mass) was independently
(negatively) associated with circulating GDF15 levels in both
women and men, indicating that elevated GDF15 levels are
associated with reduced functional muscle quality at old
age (≥65 years).
Table 6 Multivariate association between GDF15 and the basic components of relative muscle power
Women
r
Model 1
BMI
Leg SMI
Specific STS power
Model 2
BMI
Leg SMI
Specific STS power
Model 3
BMI
Leg SMI
Specific STS power
Std. β ± 95% CI
Men
P
0.41
r
Std. β ± 95% CI
P
0.44
0.12 ± 0.11
0.13 ± 0.11
0.37 ± 0.07
<0.001
<0.001
<0.001
0.03 ± 0.11
0.01 ± 0.11
0.16 ± 0.09
0.642
0.875
<0.001
0.09 ± 0.11
0.05 ± 0.11
0.14 ± 0.09
0.124
0.393
0.003
0.49
0.21 ± 0.11
0.33 ± 0.11
0.31 ± 0.08
<0.001
<0.001
<0.001
0.01 ± 0.12
0.09 ± 0.12
0.12 ± 0.09
0.901
0.149
0.006
0.00 ± 0.12
0.11 ± 0.12
0.10 ± 0.09
0.992
0.083
0.034
0.53
0.51
0.54
BMI, body mass index; SMI, skeletal muscle index; STS, sit-to-stand.
Model 1, unadjusted. Model 2, adjusted for age. Model 3, adjusted for age and inflammatory markers (IL-6, TNF-α, and hsCRP).
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
8
These data suggest that the relationship between GDF15
and relative STS power is influenced by the association of
GDF15 with specific STS power (i.e. power production per
unit of muscle mass) in women and men, while legs SMI
might also have a relevant (albeit not significant) role in the
relationship of GDF15 with relative STS power in men. The
different results observed in women and men might be due
to differences in hormone concentrations and changes with
ageing. The greater age-related increase in GDF15 and higher
GDF15 levels at older age noted in men vs. women may explain the stronger association of GDF15 with skeletal muscle
mass (leg lean mass) presently observed in men. This may indicate that greater levels of circulating GDF15 are necessary
to observe a relationship with muscle mass compared with
muscle function. In any case, these sex-specific findings deserve a more thorough investigation in future studies.
Previous studies have tried to elucidate the mechanisms
by which GDF15 could play a role in skeletal muscle metabolism and function. Both plasma and muscle mRNA expression
of GDF15 were found to be higher in intensive care unit patients that developed muscle weakness, which was related
to the inhibition of microRNAs involved in muscle proliferation, differentiation, and recovery.18 A possible mechanism
linking the increased levels of GDF15 with impaired
neuromuscular function with increasing age has recently
been proposed.33 Increased Akt-independent activation of
mTORC1 with ageing has been shown to up-regulate GDF15
gene expression in humans through the activation of the
transcription factor STAT3.33 Concomitantly, GDF15 led to increased caspase 3 activity, while up-regulating autophagic
marker LC3 and inducing increases in protein ubiquitination
and oxidation.33 Of note, this process produced muscle atrophy, loss of type II fibres (especially important for muscle
power production), mitochondrial dysfunction, and reductions in maximal isometric muscle force production and exercise capacity.33 Importantly, in a transgenic mouse model,
these Akt-independent mTORC1-induced degenerative effects were partially reversed by silencing of GDF15.33
Nevertheless, the identification of a peripheral receptor of
GDF15 is needed to better understand its peripheral action
on skeletal muscle mass and neuromuscular function. The
GDNF family alpha-like (GFRAL) receptor has been identified
as a target for GDF15 action in the central nervous system,
participating in the negative regulation of feeding behaviour
in mice.34,35 Interestingly, treatment with a therapeutic antagonistic monoclonal antibody for GDF15-GFRAL reversed
cancer cachexia in mice, which was translated to improved
function.36 However, the evidence on the physiological effects of GDF15 in mice and humans is contradictory. For example, transgenic mice overexpressing GDF15 have
increased lifespan compared with wild-type mice, while elevated circulating GDF15 is an independent predictor of
all-cause mortality in humans.10 In addition, studies conducted in mice have demonstrated a positive role of GDF15
J. Alcazar et al.
in the maintenance of spinal cord motor neurons, preventing
the loss of motor axons and reductions in physical
performance.37 In contrast, circulating GDF15 is negatively
associated with maximal muscle power and physical performance in humans (present data). Regarding these contradictory observations, it is possible that transient peaks in GDF15
may be beneficial (e.g. after a single bout of high-intensity
exercise38), while chronically elevated systemic levels are detrimental to skeletal muscle homeostasis and neuromuscular
function.
Among the limitations of the current study, this was designed as a cross-sectional investigation, and so no direct
cause-effect relationships between GDF15 and maximal
lower-limb muscle power could be established. In addition,
despite including healthy individuals only, it could not be
completely ruled out that some subjects might have had undiagnosed medical conditions, which potentially could have
affected the present results, especially in the oldest age
groups.39 Furthermore, muscle power during the 30 s STS test
was not measured directly, but estimated using an equation,
which on the other hand, has been adequately validated in
previous studies against gold standard instruments.26–28
In conclusion, systemic GDF15 was observed to increase
progressively as a function of age, with a steeper rate of
rise after the sixth decade of life. Further, GDF15 levels increased more rapidly in men compared with women, leading to elevated GDF15 levels in older men compared with
older women. Importantly, circulating GDF15 was independently and negatively associated with relative lower-limb
muscle power produced during maximal functional efforts
(30 s STS), but not during very brief (<1 s) maximal muscle
actions (Nottingham power rig). This association was
mainly due to a negative relationship between GDF15 and
specific muscle power (power normalized to leg lean mass)
in both women and men. The present findings along with
previous evidence reported in the literature support that
GDF15 may serve a future role as a biomarker of frailty
in older people.
Conflict of interest
The authors declare that have no conflict of interest.
Funding
This work was partially supported by the Biomedical Research
Networking Center on Frailty and Healthy Aging (CIBERFES)
and FEDER funds from the European Union (Grant CB16/10/
00477).
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
9
GDF15 and muscle power
Ethical guidelines statement
All authors comply with the Ethical guidelines for authorship
and publishing in the Journal of Cachexia, Sarcopenia and
Muscle.40 This study was approved by the Ethical Committee
of Copenhagen (H-3-2013-124) and was performed in
accordance with the ethical standards laid down in the
1965 Declaration of Helsinki and its later amendments. All
participants gave their informed consent prior to their inclusion in the study.
References
1. Emmerson PJ, Duffin KL, Chintharlapalli S,
Wu X. GDF15 and growth control. Front
Physiol 2018;9:1712.
2. Conte M, Ostan R, Fabbri C, Santoro A,
Guidarelli G, Vitale G, et al. Human aging
and longevity are characterized by high
levels of mitokines. J Gerontol A Biol Sci
Med Sci 2019;74:600–607.
3. Kempf T, Horn-Wichmann R, Brabant G,
Peter T, Allhoff T, Klein G, et al. Circulating
concentrations of growth-differentiation
factor 15 in apparently healthy elderly
individuals and patients with chronic heart
failure as assessed by a new immunoradiometric sandwich assay. Clin Chem
2007;53:284–291.
4. Eggers KM, Kempf T, Wallentin L, Wollert
KC, Lind L. Change in growth differentiation
factor 15 concentrations over time independently
predicts
mortality
in
community-dwelling elderly individuals.
Clin Chem 2013;59:1091–1098.
5. Hofmann M, Halper B, Oesen S, Franzke B,
Stuparits P, Tschan H, et al. Serum
concentrations of insulin-like growth
factor-1, members of the TGF-beta superfamily and follistatin do not reflect different stages of dynapenia and sarcopenia in
elderly women. Exp Gerontol 2015;64:
35–45.
6. Tanaka T, Biancotto A, Moaddel R, Moore
AZ, Gonzalez-Freire M, Aon MA, et al.
Plasma proteomic signature of age in
healthy humans. Aging Cell 2018;17:
e12799.
7. Wang TJ, Wollert KC, Larson MG,
Coglianese E, McCabe EL, Cheng S, et al.
Prognostic utility of novel biomarkers of
cardiovascular stress: the Framingham
Heart Study. Circulation 2012;126:
1596–1604.
8. Wiklund FE, Bennet AM, Magnusson PK,
Eriksson UK, Lindmark F, Wu L, et al.
Macrophage inhibitory cytokine-1 (MIC-1/
GDF15): a new marker of all-cause mortality. Aging Cell 2010;9:1057–1064.
9. Rothenbacher D, Dallmeier D, Christow H,
Koenig W, Denkinger M, Klenk J. Association of growth differentiation factor 15
with other key biomarkers, functional parameters and mortality in communitydwelling older adults. Age Ageing
2019;48:541–546.
10. Johnson AA, Shokhirev MN, Wyss-Coray T,
Lehallier B. Systematic review and analysis
of human proteomics aging studies unveils
a novel proteomic aging clock and identifies key processes that change with age.
Ageing Res Rev 2020;60:101070.
11. Conte M, Martucci M, Mosconi G,
Chiariello A, Cappuccilli M, Totti V, et al.
GDF15 plasma level is inversely associated
with level of physical activity and correlates with markers of inflammation and
muscle weakness. Front Immunol 2020;11.
12. Osawa Y, Semba RD, Fantoni G, Candia J,
Biancotto A, Tanaka T, et al. Plasma proteomic signature of the risk of developing
mobility disability: a 9-year follow-up.
Aging Cell 2020;19:e13132.
13. Cardoso AL, Fernandes A, Aguilar-Pimentel
JA, de Angelis MH, Guedes JR, Brito MA,
et al. Towards frailty biomarkers: candidates from genes and pathways regulated
in aging and age-related diseases. Ageing
Res Rev 2018;47:214–277.
14. Sanchis J, Ruiz V, Bonanad C, Sastre C,
Ruescas A, Díaz M, et al. Growth differentiation factor 15 and geriatric conditions in
acute coronary syndrome. Int J Cardiol
2019;290:15–20.
15. Moon JS, Goeminne LJE, Kim JT, Tian JW,
Kim SH, Nga HT, et al. Growth differentiation factor 15 protects against the
aging-mediated systemic inflammatory response in humans and mice. Aging Cell
2020;19:e13195.
16. Corre J, Hébraud B, Bourin P. Concise review: growth differentiation factor 15 in
pathology: a clinical role? Stem Cells Transl
Med 2013;2:946–952.
17. Bloch SA, Lee JY, Wort SJ, Polkey MI, Kemp
PR, Griffiths MJ. Sustained elevation of circulating growth and differentiation
factor-15 and a dynamic imbalance in mediators of muscle homeostasis are associated with the development of acute
muscle wasting following cardiac surgery.
Crit Care Med 2013;41:982–989.
18. Bloch SA, Lee JY, Syburra T, Rosendahl U,
Griffiths MJ, Kemp PR, et al. Increased
expression of GDF-15 may mediate
ICU-acquired
weakness
by
downregulating muscle microRNAs. Thorax
2015;70:219–228.
19. Patel MS, Lee J, Baz M, Wells CE, Bloch S,
Lewis A, et al. Growth differentiation
factor-15 is associated with muscle mass
in chronic obstructive pulmonary disease
and promotes muscle wasting in vivo. J Cachexia Sarcopenia Muscle 2016;7:436–448.
20. Losa-Reyna J, Alcazar J, Rodríguez-Gómez I,
Alfaro-Acha A, Alegre LM, RodríguezMañas L, et al. Low relative mechanical
power in older adults: an operational definition and algorithm for its application
in the clinical setting. Exp Gerontol
2020;142:111141.
21. Alcazar J, Aagaard P, Haddock B, Kamper
RS, Hansen SK, Prescott E, et al. Age- and
sex-specific changes in lower-limb muscle
power throughout the lifespan. J Gerontol
A Biol Sci Med Sci 2020;75:1369–1378.
22. Suetta C, Haddock B, Alcazar J, Noerst T,
Hansen O, Ludvig H, et al. The Copenhagen
Sarcopenia Study: lean mass, muscle
strength, muscle power and physical function in a Danish cohort aged 20–93 years.
J Cachexia Sarcopenia Muscle 2019;10:
1316–1329.
23. Aguib Y, Al Suwaidi J. The Copenhagen City
Heart Study (Osterbroundersogelsen). Glob
Cardiol Sci Pract 2015;2015:33.
24. Schnorh P. Physical activity in leisure time:
impact on mortality. Dan Med Bull
2009;56:40–71.
25. Bassey EJ, Short AH. A new method for
measuring power output in a single leg extension: feasibility, reliability and validity.
Eur J Appl Physiol Occup Physiol
1990;60:385–390.
26. Alcazar J, Losa-Reyna J, Rodriguez-Lopez C,
Alfaro-Acha A, Rodriguez-Manas L, Ara I, et
al. The sit-to-stand muscle power test: an
easy, inexpensive and portable procedure
to assess muscle power in older people.
Exp Gerontol 2018;112:38–43.
27. Alcazar J, Kamper RS, Aagaard P, Haddock
B, Prescott E, Ara I, et al. Relation between
leg extension power and 30-s sit-to-stand
muscle power in older adults: validation
and translation to functional performance.
Sci Rep 2020;10:16337.
28. Baltasar-Fernandez I, Alcazar J, RodriguezLopez C, Losa-Reyna J, Alonso-Seco M,
Ara I, et al. Sit-to-stand muscle power test:
comparison between estimated and force
plate-derived mechanical power and their
association with physical function in older
adults. Exp Gerontol 2021;145:111213.
29. Semba RD, Gonzalez-Freire M, Tanaka T,
Biancotto A, Zhang P, Shardell M, et al. Elevated plasma growth and differentiation
factor 15 is associated with slower gait
speed and lower physical performance in
healthy community-dwelling adults. J
Gerontol A Biol Sci Med Sci 2020;75:
175–180.
30. Barma M, Khan F, Price RJG, Donnan PT,
Messow CM, Ford I, et al. Association between GDF-15 levels and changes in vascular and physical function in older patients
with hypertension. Aging Clin Exp Res
2017;29:1055–1059.
31. Desmedt S, Desmedt V, De Vos L, Delanghe
JR, Speeckaert R, Speeckaert MM. Growth
differentiation factor 15: a novel biomarker
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823
10
with high clinical potential. Crit Rev Clin
Lab Sci 2019;56:333–350.
32. Arauna D, García F, Rodríguez-Mañas L,
Marrugat J, Sáez C, Alarcón M, et al. Older
adults with frailty syndrome present an altered platelet function and an increased
level of circulating oxidative stress and mitochondrial dysfunction biomarker GDF-15.
Free Radic Biol Med 2020;149:64–71.
33. Tang H, Inoki K, Brooks SV, Okazawa H, Lee
M, Wang J, et al. mTORC1 underlies
age-related muscle fiber damage and loss
by inducing oxidative stress and catabolism. Aging Cell 2019;18:e12943.
34. Emmerson PJ, Wang F, Du Y, Liu Q, Pickard
RT, Gonciarz MD, et al. The metabolic effects of GDF15 are mediated by the orphan
J. Alcazar et al.
receptor GFRAL. Nat Med 2017;23:
1215–1219.
35. Yang L, Chang CC, Sun Z, Madsen D, Zhu H,
Padkjær SB, et al. GFRAL is the receptor for
GDF15 and is required for the anti-obesity
effects of the ligand. Nat Med 2017;23:
1158–1166.
36. Suriben R, Chen M, Higbee J, Oeffinger J,
Ventura R, Li B, et al. Antibody-mediated
inhibition of GDF15-GFRAL activity reverses cancer cachexia in mice. Nat Med
2020;26:1264–1270.
37. Strelau J, Strzelczyk A, Rusu P, Bendner G,
Wiese S, Diella F, et al. Progressive postnatal motoneuron loss in mice lacking GDF15. J Neurosci 2009;29:13640–13648.
38. Kleinert M, Clemmensen C, Sjøberg KA,
Carl CS, Jeppesen JF, Wojtaszewski JFP,
et al. Exercise increases circulating GDF15
in humans. Mol Metab 2018;9:187–191.
39. Conte M, Sabbatinelli J, Chiariello A,
Martucci M, Santoro A, Monti D, et al. Disease-specific plasma levels of mitokines
FGF21, GDF15, and Humanin in type II diabetes and Alzheimer’s disease in comparison with healthy aging. GeroScience
2021;43:985–1001.
40. von Haehling S, Morley JE, Coats AJS, Anker
SD. Ethical guidelines for publishing in the
Journal of Cachexia, Sarcopenia and Muscle: update 2019. J Cachexia Sarcopenia
Muscle 2019;10:1143–1145.
Journal of Cachexia, Sarcopenia and Muscle 2021
DOI: 10.1002/jcsm.12823