| Abstract|| |
The loss of muscle mass and cachexia is commonly seen in hemodialysis (HD) patients and contribute to morbidity and mortality. The exact mechanism of this fact is multifactorial and still unclear. Myostatin, a transforming growth factor-ß family ligand, is released from the skeletal and heart muscle and may be responsible for muscle degradation and atrophy. The aim of this study is evaluation of the relationship between muscle mass and serum myostatin level in chronic HD patients. One hundred and forty HD patients (79 males, 28 diabetic, mean age; 53.96 ± 13.6) were included in this cross-sectional study. Muscle mass measurement was made with dual energy-X ray absorptiometry. Appendicular skeletal muscle index (ASMI) was used as a muscle mass indicator. The anthropometric and biochemistry data were obtained. Serum myostatin levels were determined by an ELISA kit. Serum myostatin levels were elevated when compared to controls (P <0.001), but no significant correlation with ASMI was observed (P = 0.624). ASMI significantly correlated with serum creatinine (P <0.001), creatine phosphokinase (P <0.001), prealbumin (P <0.012), albumin (P <0.039), transferrin (P <0.001), phosphorus (P <0.001), Ca×P (P <0.012), inversely with Kt/V (P <0.001); not with BUN (P = 0.739), parathyroid hormone (P = 0.698), 25-hydroxyvitamin D (P = 0.603), bicarbonate (P = 0.062); such that these parameters also have influence on muscle mass regulation. Our study indicated that myostatin levels were high in HD patients but had no relation with ASMI. Myostatin is a well-known regulator of muscle mass so further studies are needed to demonstrate possible relationship.
|How to cite this article:|
Koyun D, Nergizoglu G, Kir KM. Evaluation of the relationship between muscle mass and serum myostatin levels in chronic hemodialysis patients. Saudi J Kidney Dis Transpl 2018;29:809-15
|How to cite this URL:|
Koyun D, Nergizoglu G, Kir KM. Evaluation of the relationship between muscle mass and serum myostatin levels in chronic hemodialysis patients. Saudi J Kidney Dis Transpl [serial online] 2018 [cited 2019 Nov 18];29:809-15. Available from: http://www.sjkdt.org/text.asp?2018/29/4/809/239648
| Introduction|| |
Loss of muscle mass and cachexia is a increasing public health problem and widely prevalent in patients undergoing chronic hemo-dialysis (HD) and associated with increased falls, hip fractures, hospitalization frequency, and mortality. Causes of the skeletal muscle mass, strength, and function loss appear to be multifactorial; such as malnutrition, neuropathy, inflammation, immobility, hormonal and metobolic changes, but the exact mechanism remains incompletely understood.,, Therefore, attentions tend to new mediators, as myostatin.
Myostatin, a transforming growth factor-ß (TGF-ß) family ligand, is expressed overwhelmingly in the skeletal muscle as a 26-kDa mature glycoprotein. Additively, myostatin is detectable in cardiac muscle modest. Myos-tatin is a secreted protein and active peptid form, responsible for autocrine and paracrine effects, belongs to plasma., Myostatin binds to the activin type IIB receptor on the skeletal muscle membrane with high-affinity and phos-phorylates Smad2 and Smad3 transcription factors, which conjoins Smad4 transcription factors. On the other hand, myostatin blocks Akt/mammalian target of rapamycin pathway, induced by growth-factor signals, thus inhibit protein synthesis. In this way, myostatin leads to abolish skeletal muscle satellite cells proliferation and differentiation. Therefore, myostatin is responsible muscle degradation and atrophy.
The aim of our study is evaluation of the relationship between muscle mass and serum myostatin level in chronic HD patients.
| Materials and Methods|| |
Human subjects and study design
This cross-sectional study was performed in three dialysis units between June 2014 and August 2014. The subjects were 140 HD patients (79 males, 28 diabetic, mean age 53.96 ± 13.6) who had been maintained HD for at least three months, aged between 18 and 85 years. Those who had malignancy, poor general clinical condition or active inflammatory diseases, hospitalized, and surgical operation within three months before enrollment were excluded from the study. Forty healthy adult controls were included to observe myostatin variation. The causes of chronic kidney disease were hypertensive nephrosclerosis and renal vascular disease (25%), diabetic nephropathy (12%), chronic glomerulonephritis (11%), pyelonephritis (7%), polycystic kidney disease (6%), and other or unknown causes (39%). Clinical Research Ethics Committee of Ankara University School of Medicine approved this study (No. 09-391-14), and informed consent was obtained from all individual participants included in the study. All procedures were carried on in accordance to the Helsinki declaration.
Measurement of biochemical and clinical parameters
Demographic data, such as age, gender, etiology of the chronic renal disease comorbid illnesses and drugs, were obtained through patient interviews and confirmed from medical records later. All participants were evaluated for their height, weight, body mass index (BMI). Weight was measured immediately after the HD session. BMI was calculated as weight divided by height squared (kg/m2).
The last one-year serum levels of urea nitrogen (BUN), creatinine, albumin, parathyroid hormone (PTH), calcium (Ca), phosphorus (P), CaxP, Kt/V, and bicarbonate were obtained retrospectively from the past medical records and averaged. Last one month 25-hydroxyvitamin D [25(OH)D3], creatine phos-phokinase (CPK), prealbumin, transferrin. and C-reactive protein (CRP) levels were measured by using routine laboratory methods at the Department of Biochemistry, Ankara University Hospital.
Blood samples were collected before midweek HD session. The plasma was separated within 30 min by centrifuging at 3600 r/min for 15 min at room temperature and kept frozen at –80°C until the analysis of myostatin. Serum myostatin levels were determined by a commercially available ELISA kit (Cloud-Clone Corp, USA lot: L140905197) according to the manufacturer's protocol. The mean minimum detection limit for myostatin was 31 pg/mL.
Skeletal muscle mass assessment
Body composition, regarding lean mass (kg), was assessed by whole-body dual-energy X-ray absorptiometry (DEXA) scans (hologic discovery A-81461). The measurement was performed on the day after dialysis to avoid conditions that would affect volume overload.
Participants with metal implants (prothesis, pacemaker, etc.) not to enter into study. All participants wore a hospital gown, with no footwear and they were asked for remove all jewelry, metal accessories, and other personal effects that could invalidate interpretation of DEXA exam.
Appendicular skeletal muscle index (ASMI), a muscle mass indicator was calculated as the sum of lean mass tissue in both arms and legs divided by body height in m2 (kg/m2). The cutoffs suggested for sarcopenia, which are ≤5.5 kg/m in women and ≤7.3 kg/m2 in men according to ASMI.
| Statistical Analysis|| |
The data were presented as the mean ± standard deviation. Correlations between continuous variables were assessed using Pearson's correlation coefficient. Mann–Whitney U test was used to determine the differences between groups. Statistical analysis was performed with the Statistical Package for Social Sciences (SPSS) version 20.0 for Windows (SPSS Inc., Chicago, IL, USA). P <0.05 was considered statistically significant.
| Results|| |
The demographic and biochemistry characteristics of the 140 participants are shown in [Table 1].
HD patients had significantly elevated serum myostatin level when compared to healthy controls [(40.1 ± 8.3) vs. (2.5 ± 2.4) ng/mL, P <0.001] [Figure 1]. Serum myostatin levels were not significantly correlated with ASMI (r = 0.042, P = 0.624). Sarcopenia prevalence is 37.9%.
|Figure 1: Comparison of serum myostatin levels between the control subjects and the HD patients. P <0.05 is considered significant. |
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When we correlated other parameters which are known associated with muscle mass, we found that ASMI was significantly correlated with creatinine (r = 0.529, P <0.001), CPK (r = 0.305, P <0.001), prealbumin (r = 0.211, P <0.012), albümin (r = 0.2, P <0.039), transferrin (r = 0.430, P <0.001), and P (r =0.389, P <0.001) Ca×P (r = 0.235, P <0.012), but inverse correlation with Kt/V (r = -0.636, P <0.001) [Figure 2]. ASMI showed no significant correlation with BUN (r = 0.033, P = 0.739), PTH (r = 0.033, P = 0.698), [25(OH) D3] (r = -0.044, P = 0.603), bicarbonate (r = -0.158, P = 0.062), Ca (r = 0.055, P = 0.560), and CRP (r =0.115, P = 0.235).
|Figure 2: Correlation between ASMI and CPK (a), Correlation between ASMI and albumin (b), Correlation between ASMI and Ca×P (c), Inverse correlation between ASMI and Kt/V (d) in HD patients. Pearson's correlation coefficient (r) was used. P<0.05 was considered statistically significant|
ASMI: Appendicular skeletal muscle index, CPK: Creatine phosphokinase, HD: Hemodialysis.
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| Discussion|| |
In this study, we showed that the serum myostatin levels were elevated in HD patients when compared to healthy control subjects. Myostatin levels showed no significant relationship with ASMI; whereas ASMI was significantly related to serum creatinine, albumin, prealbumin, P, CaxP, CPK, transferrin, and Kt/V levels.
Muscle mass and strength are important predictors of muscle pathologies in chronic diseases and not be together always. The loss of them involuntarily is defined as sarcopenia. In a study, sarcopenia frequency was 20% incident of 330 HD patients and researchers observed that decreased muscle strength had more influence on mortality than decreased muscle mass. They submitted that low-muscle mass was secondary to the effects of low muscle strength but other factors such as contractile quality, neural activation, systemic inflammation, and underestimated nutritional disorders maybe play a more important part. The prevalence of sarcopenia was 37.9% in our study. This as under rates corroborate the difficulty of uncoupling numerous factors which participate in skeletal musle homeostasis. Their effects are engaged and this complex balance varies from person to person. Therefore, the cruces are finding what plays a key role on skeletal muscle regulation in this disordinance. Through this finding, effective diagnosis methods and therapies will be established to detect and prevent muscle atrophy. Herein, relevance on myostatin increase gradually. Although the existence of the relationship between myostatin and muscle pathologies, furthermore pharmacological inhibition of myostatin to reverse skeletal muscle loss with chronic diseases in experimental research, investigations on this topic are inadequate yet. Zhang et al showed that myostatin blocking with using of anti-myostatin peptibody injection into chronic kidney disease (CKD) mice enhance body mass and prevent muscle atrophy. Yano et al showed that serum myostatin levels tended to rice in the onset stages of CKD. Opposedly Han et al indicated lower myostatin levels in 60 HD patients than healthy participants. Body weight, BMI, muscle mass, and grip strength had a downward tendency in HD patients. They assessed musle mass with bioimpedance analysis (BIA) and found the relation between serum myostatin levels and grip strength, not the muscle mass either.
Researchers found contradictory results between serum myostatin levels and skeletal muscle mass, measured by various methods, in chronic diseases such as diabetes mellitus, chronic obstructive pulmonary disease, heart failure, and end-stage liver disease.,,,, These not only inquire potential pathological role of myostatin but also necessitate an evaluation the validity of muscle mass and strength measuring methods.
Serum myostatin levels have upward tendency in catabolic conditions. In contrast to this, some researchers found that lower or similar levels compared with normal controls. Number of hypotheses can explain this complex findings. First, circulating myostatin concentrations may not necessarily reflect its intramuscular concentrations. Second, other extracellular matrix proteins and pharma-cologic therapies interact with myostatin and myostatin-linked molecules. They may have indirect but precedence over effect than we thought on the regulation of myostatin expression and TGF-ß signaling pathway. Muscle biopsy can be a more superior alternative to clarify this situation., Like patients, serum myostatin levels can also increase in healthy men who received testosterone. Hence, we deduce that myostatin maybe also restrains uncontrolled skeletal muscle mass growth. Recent studies showed that serum myostatin levels were same in older and younger subjects, moreover, outcomes changed in wide range with ELISA-based measurements., Bergen et al used mass spectrometry-based myostatin measurement to annihilate this inconsistency. They found weak but significant association between myostatin and relative ASMI in both gender. Myostatin concentrations had been fluctuated according to age, gender, and being sarcopenia in this study. This research show that myostatin immuno-reactivity bases on also the feature of anti-myostatin antibody in ELISA-based measurements, so not to equal to its bioactivity.
Many methods, such as DEXA, BIA, magnetic resonance, and computed tomography which can also determine body composition measurement beside of anthropometric measures, are utilized to evaluate muscle mass. In this study, we used DEXA, is adopted as a more valuable, safe and robust technique, to measure fat mass and lean mass in HD patients., ASMI is used as a muscle mass indicator instead of total lean mass because extremities have more sceletal muscle and to eliminate the potential impact of visceral muscles in trunk.
Our study differs from others in HD patients with using DEXA for the measurement of muscle mass, investigating other possible causes exhaustively that have impact on muscle mass regulation and sample size. ASMI related to many parameters that but not myostatin in our study. Lots of things can cause this condition. The role of TGF-ß family of signaling ligands, numerous are inapprehensible, vary from cell-to-cell. Myostatin primarily takes an active role in skeletal muscle formation, but its effect on adipose tissue and bone is cloudy. In addition, the clearance of myostatin, a 26-kDa mature glycoprotein, is inadequate because of its molecular weight in HD patients whereas findings in many rat model experiments, conflict with us. This may be due to differences between species.
There are some limitations in our study, including its a cross-sectional study, and the lack of evaluation of muscle strength. These restrict our interpretation power. In conclusion, the present data indicated that myostatin levels were high but had no relation with ASMI in HD patients.
We conclude that serum myostatin levels measurement is not an effective method for a muscle mass regulator in HD population. The impact of myostatin on skeletal muscle homeostasis is testatumso further studies required to reveal possible relationships. Future studies will be planned by using mass spectrometry or myostatin mRNA with skeletal muscle biopsy in dialysis patients if it is as far as possible to control other confounding factors that influence muscle mass.
| Acknowledgments|| |
We are grateful for hemodialysis nurses, department of nuclear medicine technical staff and our participants for their time and effort.
| Source of Support|| |
The study was supported by Ankara Tiplilar Foundation. The funding sources were neither involved in the collection, interpretation, and analysis of the data nor in the decision for the writing and submission of this report for publication. The authors received no specific funding for this work.
Conflict of interest: None declared.
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Dr. Derya Koyun
Department of Internal Medicine, Ankara University School of Medicine, Ankara
[Figure 1], [Figure 2]