Motoneuron Loss Is Associated With Sarcopenia

doi:10.1016/j.jamda.2014.02.002

Journal of the American Medical Directors Association

Volume 15, Issue 6, June 2014, Pages 435-439

https://doi.org/10.1016/j.jamda.2014.02.002 Get rights and content

Abstract

Objectives

Sarcopenia, age-related muscle wasting, is associated with increased morbidity and mortality in the affected individuals. The pathogenesis of sarcopenia is not yet fully understood. A multifactorial concept is currently favored. The reduced number of motor units as a potential mechanism of muscle mass loss is explored in the present study.

Design

This is a cross-sectional study.

Setting

The participants were community-dwelling older adults.

Participants

The participants were sarcopenic (75) and nonsarcopenic (74) according to the criteria of the European Working Group on Sarcopenia in Older People aged 65 to 94 years.

Measurements

The motor unit number index (MUNIX) of the hypothenar muscle was used to assess the number and size [motor unit size index (MUSIX)] of motor units.

Results

The participants with pathologic MUNIX and MUSIX (n = 23) are significantly more frequently sarcopenic (n = 17, P = .029) than nonsarcopenic (n = 6). The participants with pathologic MUNIX and MUSIX (n = 23) had significantly less muscle mass than the nonsarcopenic controls (P < .001). After adjusting for age and sex, only gait speed has shown no difference between the 2 groups. Pearson's correlation coefficient between MUSIX and the reciprocal value of MUNIX is 0.87 (P < .001).

Conclusions

Sarcopenia induced by a small number of motoneurons can be identified by applying the MUNIX method to the hypothenar muscle. An enlargement of motor units because of motoneuron loss seems to preserve physical performance.

Section snippets

Participants

A total of 75 sarcopenic and 75 nonsarcopenic community-dwelling elderly over the age of 65 were to be recruited for the present investigation. In the first phase, participants were recruited following the publication of a newspaper advertisement. Of the 158 respondents, 70 were ineligible (see below for exclusion criteria) or unwilling to participate in the study. Hence, 88 participants (38 sarcopenic and 50 nonsarcopenic) were recruited for the study in the first phase. In the second phase,

Results

The participants' characteristics are shown in Table 1. Figure 1 shows the relationship between MUNIX and MUSIX in the study participants. Pearson's correlation coefficient between MUSIX and the reciprocal value of MUNIX is 0.87 (P < .001). The solid line in Figure 1 indicates the reciprocal relationship. The upper left cluster shows 23 participants with pathologic MUNIX (<80) and MUSIX (>100μV), 17 of whom belong to the sarcopenic group (3 presarcopenia, 3 sarcopenia, 11 severe sarcopenia); 6

Discussion

In the present study, the MUNIX technique was used to identify a subset of sarcopenic participants by a small quantity of motor units in the hypothenar muscle. In participants with a small quantity of motor units, enlargement of the remaining motor units seems to be a mechanism of compensation and could be a starting point for the pharmacologic treatment of sarcopenia.

Conclusions

It was possible to identify a subset of sarcopenic participants with a low number of motoneurons using the MUNIX methodology. Longitudinal investigations have to show a cause-and-effect relationship between the loss of motoneurons and the onset of sarcopenia. As a small quantity of motor units is combined with an enlargement of the remaining motor units, this mechanism of compensation could be used for pharmacological treatment to increase neural sprouting with the aim of further enlarging the

Acknowledgments

The authors thank Martina Schrodberger for recruiting the study participants and Christine Kokott for performing the laboratory work.

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: The “DISARCO” project was carried out within the Eurostars Programme. The German partners were funded by the German Federal Ministry of Education and Research (BMBF).

: The authors declare no conflicts of interest.

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Original StudyMotoneuron Loss Is Associated With Sarcopenia

Abstract

Objectives

Design

Setting

Participants

Measurements

Results

Conclusions

Section snippets

Participants

Results

Discussion

Conclusions

Acknowledgments

Sarcopenia. Clin Geriatr Med

J Am Med Dir Assoc

J Am Med Dir Assoc

Exp Gerontol

Clin Neurophysiol

Exp Gerontol

J Am Med Dir Assoc

Neurobiol Aging

Neurochirurgie

Exp Gerontol

Evolving concepts on the age-related changes in “muscle quality”

J Cachexia Sarcopenia Muscle

Motor unit number index (MUNIX)

IEEE Trans Biomed Eng

Estimation of skeletal muscle mass by bioelectrical impedance analysis

J Appl Physiol

Prevalence of sarcopenia estimated using a bioelectrical impedance analysis prediction equation in community-dwelling elderly people in Taiwan

J Am Geriatr Soc

Sarcopenia: European consensus on definition and diagnosis: Report of the European Working Group on Sarcopenia in Older People

Age Ageing

Motor unit number index (MUNIX): Principle, method, and findings in healthy subjects and in patients with motor neuron disease

Muscle Nerve

Motor unit number estimates in the tibialis anterior muscle of young, old, and very old men

Muscle Nerve

Original Study
Motoneuron Loss Is Associated With Sarcopenia