Muscle Wasting in Chronic Kidney Disease: Mechanism and Clinical Implications—A Narrative Review

The phase angle before transplantation can predict the status of low muscle mass after kidney transplantation

BACKGROUND

This study aimed to evaluate the association between phase angle, muscle strength, and muscle mass in patients undergoing kidney transplantation.

METHODS

Patients whose pre- and follow-up phase angles were measured after kidney transplantation were enrolled. Phase angle and body composition were measured using a multi-frequency bioimpedance analysis device before and at 7 and 14 days and 3, 6, and 12 months after transplantation. Muscle strength was evaluated using handgrip strength (HGS). Low HGS was defined as < 28 kg in males and < 18 kg in females. Low muscle mass was defined as an appendicular lean mass index of < 7.0 kg/m2 in males and < 5.7 kg/m2 in females.

RESULTS

Eighty-eight patients (mean age 52.3 ± 10.1 years) were analyzed. The mean phase angle of pre-transplantation was 5.0 ± 1.0°. Body fat percentage was significantly higher at 6 and 12 months after transplantation than pre-transplantation (P < 0.0001). Twelve months after kidney transplantation, the prevalence of low HGS decreased (pre-transplantation vs. 12 months post-transplantation: 28.4% vs. 17.0%), and the prevalence of low muscle mass (pre-transplantation vs. 12 months post-transplantation: 21.6% vs. 28.4%) increased. The pre-transplantation phase angle was significantly associated with low muscle mass at 12 months after kidney transplantation (odds ratio [OR]: 0.34; 95% confidence interval [CI]: 0.16-0.72; P = 0.005). The pre-transplantation phase angle was not significantly associated with low HGS (OR: 0.37; 95% CI 0.12-1.17; P = 0.090) 12 months after kidney transplantation.

CONCLUSIONS

Pre-transplantation phase angle can predict muscle mass status 12 months after kidney transplantation.

Whole body resistance training on functional outcomes of patients with Stage 4 or 5 chronic kidney disease: A systematic review

Chronic kidney disease (CKD) causes skeletal muscle wasting, resulting in reduced function and inability to live independently. This systematic review critically appraised the scientific literature regarding the effects of full-body resistance training on clinically-relevant functional capacity measures in CKD. The study population included studies of people with Stage 4 or 5 CKD and a mean age of 40+ years old. Eight databases were searched for eligible studies: Pubmed, Embase, Cochrane, CINAHL, Scopus, Web of Science, MEDLINE, and AGELINE. MeSH terms and keyword combinations were used for screening following the PRISMA conduct. Inclusion criteria were based on PICO principles and no date of publication filter was applied. The intervention was training 2 days/week of structured resistance exercises using major upper and lower muscle groups. Minimum intervention period was 7 weeks. Comparison groups maintained their habitual activity without structured exercise training. Outcome measures of interest were: 6-min walk test, grip strength, timed up-and-go test, and sit-to-stand. Eight randomized controlled trials and one nonequivalent comparison-group study fulfilled the inclusion criteria and underwent data extraction. All studies were of hemodialysis patients. The evidence indicates that full-body resistance exercise significantly improved grip strength, timed up and go and sit to stand tests; metrics associated with enhanced quality and quantity of life.

The association of appendicular skeletal muscle mass with anthropometric, body composition, nutritional, inflammatory, and metabolic variables in non-dialysis-dependent chronic kidney disease men

Background

Muscle atrophy affects more than 50% of patients with chronic kidney disease (CKD) and is associated with increased morbidity and mortality. It is crucial to understand the mechanisms involved in the muscle atrophy in CKD and search for specific determinants of skeletal muscle mass loss, especially those which are available in everyday medical practice. This study aimed to evaluate the association between appendicular skeletal muscle mass (ASM) and anthropometric, body composition, nutritional, inflammatory, metabolic, and kidney function variables in non-dialysis-dependent CKD men.

Methods

A total of 85 men with CKD and eGFR lower than 60 mL/min/1.73 m2 were included in the cross-sectional study: 24 participants with eGFR 59-45 mL/min/1.73 m2, 32 individuals with eGFR 44-30 mL/min/1.73 m2, and 29 men with eGFR ≤29 mL/min/1.73 m2. ASM was estimated by bioimpedance spectroscopy (BIS) with the use of a Body Composition Monitor (BCM). To evaluate ASM from BCM, Lin's algorithm was used. Among anthropometric parameters, height, weight, and body mass index (BMI) were measured. Serum laboratory measurements were grouped into kidney function, nutritional, inflammatory, and metabolic parameters.

Results

ASM was significantly associated with anthropometric and body composition variables. According to the anthropometric parameters, ASM correlated positively with weight, height, and BMI (p < 0.001 and r = 0.913, p < 0.001 and r = 0.560, and p < 0.001 and r = 0.737, respectively). Among body composition variables, ASM correlated significantly and positively with lean tissue mass (LTM) (p < 0.001, r = 0.746), lean tissue index (LTI) (p < 0.001, r = 0.609), fat mass (p < 0.001, r = 0.489), and fat tissue index (FTI) (p < 0.001, r = 0.358). No other statistically significant correlation was found between ASM and kidney, nutritional, metabolic, and inflammatory variables.

Conclusion

In male patients with CKD stages G3-G5 not treated with dialysis, ASM correlates significantly and positively with anthropometric and body composition parameters such as weight, height, BMI, LTM, LTI, fat mass, and FTI. We did not observe such relationship between ASM and kidney function, nutritional, metabolic, and inflammatory variables.

Multidimensional Assessment of Sarcopenia and Sarcopenic Obesity in Geriatric Patients: Creatinine/Cystatin C Ratio Performs Better than Sarcopenia Index

The serum creatinine/cystatin C ratio (CCR) and the sarcopenia index (SI) are novel indicators for sarcopenia, but their accuracy may depend on various confounders. To assess CCR and SI diagnostic accuracy, we studied the clinical and biophysical parameters associated with sarcopenia or sarcopenic obesity. A total of 79 elderly patients (65-99 yrs, 33 females) underwent clinical, anthropometric, body composition, geriatric performance, and blood chemistry evaluation. The CCR and SI accuracy were assessed to identify sarcopenia. Sarcopenia was confirmed in 40.5%, and sarcopenic obesity in 8.9% of the subjects. Sarcopenic patients showed an increased Charlson comorbidity index, cardiovascular disease (CVD) rates and frailty, and decreased physical performance than non-sarcopenic subjects. Patients with sarcopenic obesity had increased body fat and inflammatory markers compared to obese subjects without sarcopenia. Sarcopenia was associated with a decreased CCR and SI. However, when the logistic regression models were adjusted for possible confounders (i.e., age, gender, Charlson comorbidity index, presence of CVD, and frailty score), a significant OR was confirmed for the CCR (OR 0.021, 95% CI 0.00055-0.83) but not for the SI. The AUC for the CCR for sarcopenia discrimination was 0.72. A higher performance was observed in patients without chronic kidney diseases (CKD, AUC 0.83). CCR, more than the SI, is a useful, non-invasive, and cost-effective tool to predict sarcopenia, irrespective of the potential confounders, particularly in subjects without CKD.

Common mouse models of chronic kidney disease are not associated with cachexia

The 5/6 nephrectomy and adenine-induced nephropathy mouse models have been extensively used to study Chronic Kidney Disease (CKD)-related cachexia. One common caveat of these CKD models is the cross-sectional nature of comparisons made versus controls. We here performed a comprehensive longitudinal assessment of body composition and energy metabolism in both models. The most striking finding is that weight loss is largely driven by reduced food intake which promotes rapid loss of lean and fat mass. However, in both models, mice catch up weight and lean mass a few days after the surgery or when they are switched back to standard chow diet. Muscle force and mass are fully recovered and no sign of cachexia is observed. Our data demonstrate that the time-course of kidney failure and weight loss are unrelated in these common CKD models. These data highlight the need to reconsider the relative contribution of direct and indirect mechanisms to muscle wasting observed in CKD.

Association between urinary glyphosate levels and hand grip strength in a representative sample of US adults: NHANES 2013-2014

Introduction

Glyphosate, a widely utilized herbicide globally, has been linked to various health issues, including cancer, birth abnormalities, and reproductive issues. Additionally, there is growing experimental support indicating potential harm to skeletal muscles. Despite this, the impact of glyphosate on human muscle health remains unclear.

Methods

We examined information gathered from the 2013-2014 National Health and Nutrition Examination Survey (NHANES), which included 1466 adults aged 18 or older. Our primary aim was to investigate the relationship between glyphosate exposure and hand grip strength, as well as its influence on lean muscle mass.

Results and discussion

Our investigation uncovered a detrimental correlation between glyphosate exposure and all measures of grip strength, except for the second test of the first hand. Specifically, we observed a statistically significant adverse association between glyphosate exposure and combined grip strength, which is calculated as the sum of the highest readings from both hands (ß coefficient of -2.000, S.E. = 0.891, p = 0.040). We did not observe a significant correlation between glyphosate levels, lean muscle mass, and the likelihood of reaching maximum grip strength meeting sarcopenia criteria. Additionally, we observed an interaction between age and glyphosate, as well as between body mass index (BMI) and glyphosate, concerning the association with combined grip strength. In this comprehensive analysis of NHANES data, our study reveals a potential association between glyphosate exposure and hand grip strength in the adult population. Our findings suggest the need for deeper exploration into the health effects of glyphosate exposure and its impact on muscle strength, shedding light on possible public health concerns.

The Impact of Physical Exercise on microRNAs in Hemodialysis Patients: A Review and a Protocol for an Ancillary Study

Physical inactivity is considered a significant risk factor for mortality and morbidity among chronic hemodialysis (HD) patients. Therefore, physical exercise is recommended in the treatment of HD patients. Although the beneficial effects of physical exercise in HD patients are well-described in the literature, the underlying physiological mechanisms still need to be fully understood. Recently, microRNAs (miRNAs) have emerged as potential mediators of the therapeutic effects of physical exercise in healthy individuals. miRNAs are short, single-stranded, noncoding RNAs involved in gene expression regulation. Specifically, upon forming the RNA-induced silencing complex, miRNAs selectively bind to specific miRNAs within cells, reducing gene expression. miRNAs can be secreted by cells in an accessible form or enclosed within exosomes or extracellular vesicles. They can be detected in various body fluids, including serum (circulating miRNAs), facilitating the study of their diverse expression. Currently, there is no available data regarding the impact of physical exercise on the expression of miRNAs involved in osteogenic differentiation, a fundamental mechanism in the development of vascular calcification, for HD patients. Therefore, we have designed an observational and longitudinal case-control study to evaluate the expression of miR-9 and miR-30b in HD patients participating in a 3-month interdialytic physical exercise program. This paper aims to present the study protocol and review the expression of circulating miRNAs in HD patients and their modulation through physical exercise.

Self-Reported Physical Inactivity and Mood Disturbances in End-Stage Kidney Disease (ESKD) Patients on Chronic Dialysis Treatment

BACKGROUND

Physical inactivity and mood disturbances are key issues in individuals with end-stage kidney disease (ESKD) and may lead to poor clinical outcomes.

METHODS

We performed a pilot, observational study to explore the possible relationships between the self-reported level of physical activity (IPAQ) and the severity of mood disturbances (BDI score) in a cohort of 58 ESKD patients undergoing chronic hemodialysis (HD; n = 30) or peritoneal dialysis (PD; n = 28).

RESULTS

Overall, ESKD patients were severely inactive (median METs: 590 [460-1850]) and the intensity of overall and walking physical activity was mostly low to moderate. HD individuals appeared less active than PD (METs 550 [250-1600] vs. 1080 [750-1730]; p = 0.003) and were also less prone to walking (METs 180 ± 90 vs. 320 ± 100; p = 0.01), while a barely statistical difference was noticed for the time spent sitting. ESKD individuals displayed a median BDI score of 17 [12-21], which indicated, on average, the presence of borderline depression, which was apparently more evident among HD individuals. A strong, inverse correlation was found between self-reported METs and BDI scores (R = -0.78; p < 0.0001), while such scores paralleled the time spent sitting during a weekday (R = 0.45; p = 0.0004) and a weekend day (R = 0.40; p = 0.002).

CONCLUSIONS

In ESKD patients on chronic dialysis, physical inactivity and mood disturbances might be significantly inter-connected, thereby amplifying their relative impact on quality of life, dysautonomia and long-term outcomes. Future studies on larger populations are recommended to confirm these preliminary observations. Promoting strategies to improve fitness, along with greater attention to physiological aspects, should be incorporated into the clinical management of ESKD patients.

Combined use of handgrip strength and hemoglobin as markers of undernutrition in patients with stage 3-5 chronic kidney disease

BACKGROUND AND AIMS

The early identification of undernourished patients with CKD could help instating appropriate nutritional intervention before the full development of the threatening condition known as Protein Energy Wasting (PEW). Handgrip strength (HGS) and blood hemoglobin (Hb) concentration are two parameters considered representative of nutritional status but not included among the criteria for PEW diagnosis. In the present work we investigated whether they could help identifying CKD patients at risk of undernutrition.

METHODS AND RESULTS

We performed a two-step cluster analysis to classify a cohort of 71 stage 3-5 CKD patients, none of which with PEW, according to their Hb concentration and dominant-hand HGS. Two clusters were finely separated using this method. When we compared the two groups for main body composition and nutritional variables by using t-test statistics or Mann-Whitney test, as appropriate, we found significant differences in PhA, ECW/TBW, ASMI, serum iron. Then we stratified our population by gender and performed cluster analysis as well. PhA, ECW/TBW were still significantly different in the two clusters both in M and in F, while serum iron concentration only in males and ASMI only in females.

CONCLUSION

These results suggest that either in male than in female Hb concentration and HGS may distinguish two subgroups of CKD patients with different nutritional status and disease severity. Patient belonging to either of these cluster can be easily identified by using the HGS/Hb ratio which represents the HGS normalized per gr Hb.

Clinical features and molecular mechanism of muscle wasting in end stage renal disease

Muscle wasting in end-stage renal disease (ESRD) is an escalating issue due to the increasing global prevalence of ESRD and its significant clinical impact, including a close association with elevated mortality risk. The phenomenon of muscle wasting in ESRD, which exceeds the rate of muscle loss observed in the normal aging process, arises from multifactorial processes. This review paper aims to provide a comprehensive understanding of muscle wasting in ESRD, covering its epidemiology, underlying molecular mechanisms, and current and emerging therapeutic interventions. It delves into the assessment techniques for muscle mass and function, before exploring the intricate metabolic and molecular pathways that lead to muscle atrophy in ESRD patients. We further discuss various strategies to mitigate muscle wasting, including nutritional, pharmacological, exercise, and physical modalities intervention. This review seeks to provide a solid foundation for future research in this area, fostering a deeper understanding of muscle wasting in ESRD, and paving the way for the development of novel strategies to improve patient outcomes. [BMB Reports 2023; 56(8): 426-438].

Organokines in COVID-19: A Systematic Review

Coronavirus disease 2019 (COVID-19) is a viral infection caused by SARS-CoV-2 that induces a generalized inflammatory state. Organokines (adipokines, osteokines, myokines, hepatokines, and cardiokines) can produce beneficial or harmful effects in this condition. This study aimed to systematically review the role of organokines on COVID-19. PubMed, Embase, Google Scholar, and Cochrane databases were searched, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and 37 studies were selected, comprising more than 2700 individuals infected with the virus. Among COVID-19 patients, organokines have been associated with endothelial dysfunction and multiple organ failure due to augmented cytokines and increased SARS-CoV-2 viremia. Changes in the pattern of organokines secretion can directly or indirectly contribute to aggravating the infection, promoting immune response alterations, and predicting the disease progression. These molecules have the potential to be used as adjuvant biomarkers to predict the severity of the illness and severe outcomes.

Highlights in Pathophysiology of the Musculoskeletal System

The intention of the present Special Issue is to focus on the latest research in the musculoskeletal system, with an emphasis on the molecular mechanisms underlying its pathophysiology, as well as innovative diagnostic tools and therapeutic perspectives [...]

Comparison of Serum Urea, Salivary Urea, and Creatinine Levels in Pre-Dialysis and Post-Dialysis Patients: A Case-Control Study

Background Frequent venepuncture for monitoring of serum urea and creatinine in chronic kidney disease (CKD) patients on dialysis will result in venous damage and infection. In this research, we assessed the feasibility of utilizing salivary samples as a substitute for serum samples in determining the levels of urea and creatinine in patients with CKD undergoing dialysis. Methods The study participants included 50 patients diagnosed with CKD undergoing hemodialysis and an equal number of apparently healthy individuals. We measured the serum and salivary levels of urea and creatinine in normal subjects. CKD patients were also subjected to similar investigations both before and after hemodialysis. Results In our study, we found that the mean value of salivary urea and creatinine are significantly elevated in the case group (salivary urea: 99.56 ± 43.28 mg/dL, salivary creatinine: 1.10 ± 0.83 mg/dL) as compared to the control group (salivary urea: 33.62 ± 23.84 mg/dL, salivary creatinine: 0.15±0.12 mg/dL, p value: <0.001). There was a statistically significant reduction in the mean value of salivary urea and creatinine in the post-dialysis sample (salivary urea: 45.06 ± 30.37 mg/dL, salivary creatinine: 0.43±0.44 mg/dL) compared to the pre-dialysis sample (salivary urea: 99.56 ± 43.28 mg/dL, salivary creatinine: 1.10 ± 0.83 mg/dL; p value: <0.001) in the case group. The salivary urea is significantly positively correlated with serum urea (r value: 0.366, p value: 0.009). But there is no significant correlation seen between salivary and serum creatinine. We have created a cut-off for salivary urea (52.5 mg/dL) to diagnose CKD which has a good sensitivity (84%) and specificity (78%). Conclusion The results of our study suggest that the estimation of salivary urea and creatinine could serve as a non-invasive, alternative marker for the diagnosis of CKD, and benefit in risk-free monitoring of their progress before and after hemodialysis.

Chronic kidney disease-induced muscle atrophy: Molecular mechanisms and promising therapies

Chronic kidney disease (CKD) is a high-risk chronic catabolic disease due to its high morbidity and mortality. CKD is accompanied by many complications, leading to a poor quality of life, and serious complications may even threaten the life of CKD patients. Muscle atrophy is a common complication of CKD. Muscle atrophy and sarcopenia in CKD patients have complex pathways that are related to multiple mechanisms and related factors. This review not only discusses the mechanisms by which inflammation, oxidative stress, mitochondrial dysfunction promote CKD-induced muscle atrophy but also explores other CKD-related complications, such as metabolic acidosis, vitamin D deficiency, anorexia, and excess angiotensin II, as well as other related factors that play a role in CKD muscle atrophy, such as insulin resistance, hormones, hemodialysis, uremic toxins, intestinal flora imbalance, and miRNA. We highlight potential treatments and drugs that can effectively treat CKD-induced muscle atrophy in terms of complication treatment, nutritional supplementation, physical exercise, and drug intervention, thereby helping to improve the prognosis and quality of life of CKD patients.

Muscle plasticity is influenced by renal function and caloric intake through the FGF23-vitamin D axis

Skeletal muscle, the main metabolic engine in the body of vertebrates, is endowed with great plasticity. The association between skeletal muscle plasticity and two highly prevalent health problems: renal dysfunction and obesity, which share etiologic links as well as many comorbidities, is a subject of great relevance. It is important to know how these alterations impact on the structure and function of skeletal muscle because the changes in muscle phenotype have a major influence on the quality of life of the patients. This literature review aims to discuss the influence of a nontraditional axis involving kidney, bone, and muscle on skeletal muscle plasticity. In this axis, the kidneys play a role as the main site for vitamin D activation. Renal disease leads to a direct decrease in 1,25(OH)₂-vitamin D, secondary to reduction in renal functional mass, and has an indirect effect, through phosphate retention, that contributes to stimulate fibroblast growth factor 23 (FGF23) secretion by bone cells. FGF23 downregulates the renal synthesis of 1,25(OH)₂-vitamin D and upregulates its metabolism. Skeletal production of FGF23 is also regulated by caloric intake: it is increased in obesity and decreased by caloric restriction, and these changes impact on 1,25(OH)₂-vitamin D concentrations, which are decreased in obesity and increased after caloric restriction. Thus, both phosphate retention, that develops secondary to renal failure, and caloric intake influence 1,25(OH)₂-vitamin D that in turn plays a key role in muscle anabolism.

Impact of the Nutrition-Inflammation Status on the Functionality of Patients with Chronic Kidney Disease

Functional capacity of chronic kidney disease (CKD) patients is compromised by their nutrition-inflammation status. We evaluated the functional capacity of advanced chronic kidney disease (ACKD) patients and the influence of the nutrition-inflammation status. In a cross-sectional study, which included ACKD patients from the nephrology department of the Hospital Universitario de la Princesa in Madrid, Spain, we assessed: functional capacity with the Short Physical Performance Battery (SPPB) test, interpreting a result <7 in the test as low functionality; body composition with monofrequency bioimpedance; muscular strength with hand grip strength; nutritional and inflammatory status using biochemical parameters and the Malnutrition Inflammation Scale (MIS). A total of 255 patients with ACKD were evaluated, 65.8% were men, their mean age was 70.65 ± 11.97 years and 70.2% of the patients had an age >65 years. The mean score of SPPB was 8.50 ± 2.81 and 76.4% of the patients presented a score ≥7, with a higher percentage in the group of men. The percentage of patients with limitations increased with age. The patients with SPPB values higher than 7 showed high values of albumin and low soluble C-reactive protein (s-CRP) and MIS. We found better functionality in well-nourished patients. A multivariate logistic regression model established an association of high albumin values with a better functional capacity (OR: 0.245 CI: 0.084−0.714 p < 0.010), while another model showed an association between CRP values and decreased functionality (OR: 1.267 CI: 1.007−1.594 p = 0.044). Conclusion: nutritional status and body composition influence on the functional capacity of patients with ACKD.

Uremic Myopathy and Mitochondrial Dysfunction in Kidney Disease

Alterations in muscle structure and function in chronic kidney disease (CKD) patients are associated with poor outcomes. As key organelles in muscle cell homeostasis, mitochondrial metabolism has been studied in the context of muscle dysfunction in CKD. We conducted a study to determine the contribution of oxidative metabolism, glycolysis and fatty acid oxidation to the muscle metabolism in CKD. Mice developed CKD by exposure to adenine in the diet. Muscle of CKD mice showed significant weight loss compared to non-CKD mice, but only extensor digitorum longus (EDL) muscle showed a decreased number of fibers. There was no difference in the proportion of the various muscle fibers in CKD and non-CKD mice. Muscle of CKD mice had decreased expression of proteins associated with oxidative phosphorylation but increased expression of enzymes and transporters associated with glycolysis. In cell culture, myotubes exposed to uremic serum demonstrated decreased oxygen consumption rates (OCR) when glucose was used as substrate, conserved OCR when fatty acids were used and increased lactate production. In conclusion, mice with adenine-induced CKD developed sarcopenia and with increased glycolytic metabolism but without gross changes in fiber structure. In vitro models of uremic myopathy suggest fatty acid utilization is preserved compared to decreased glucose utilization.

Indoxyl Sulfate Might Play a Role in Sarcopenia, While Myostatin Is an Indicator of Muscle Mass in Patients with Chronic Kidney Disease: Analysis from the RECOVERY Study

Serum myostatin and indoxyl sulfate (IS) levels increase with kidney function decline and may function as uremic toxins in chronic kidney disease (CKD)-related sarcopenia. Herein, we analyzed the association between serum myostatin and IS levels and sarcopenia in patients with CKD, by performing a post hoc analysis of baseline data extracted from the RECOVERY study (clinicaltrials.gov: NCT03788252) of 150 patients with CKD. We stratified patients into two groups according to the median value of myostatin (cutoff 4.5 ng/mL) and IS levels (cutoff 0.365 mg/dL). The proportion of patients with sarcopenia was higher in those with high IS levels but lower in those with high myostatin levels. The skeletal muscle mass index (SMI) and handgrip strength (HGS) were significantly lower in patients with high IS levels but significantly higher in patients with high myostatin levels. IS levels showed a negative correlation with glomerular filtration rate (GFR), SMI, and HGS. However, myostatin levels were positively correlated with SMI and HGS, but not with GFR. Sarcopenia was independently associated with age and IS level after adjustment. Increased levels of serum total IS might play a role in sarcopenia, while increased levels of serum myostatin are associated with muscle mass in patients with CKD.