Uremic Sarcopenia: Clinical Evidence and Basic Experimental Approach

Association of endothelial dysfunction and peripheral arterial disease with sarcopenia in chronic kidney disease

BACKGROUND

Endothelial dysfunction and peripheral arterial disease (PAD), which disturb skeletal muscle microperfusion, are highly prevalent in patients with chronic kidney disease (CKD). We evaluated the association of endothelial dysfunction and PAD with sarcopenia in patients with non-dialysis CKD.

METHODS

This cross-sectional study included 420 patients with stages 3-5 non-dialysis CKD aged 69.0 ± 11.8 years. Skeletal muscle index (skeletal muscle mass/height2), handgrip strength, 6-m gait speed and strength of hip flexion and knee extension were measured. Sarcopenia was defined according to the Asian Working Group for Sarcopenia 2019. Endothelial dysfunction and PAD were assessed using the vascular reactivity index (VRI) and ankle-brachial index (ABI), respectively. A VRI < 1.0 was classified as poor endothelial function, and an ABI < 0.9 was defined as PAD. Additionally, endothelial and inflammatory biomarkers, including intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), asymmetric dimethylarginine, endothelin-1 (ET-1) and interleukin-6, were measured in a subgroup of 262 patients.

RESULTS

Among the participants, 103 (24.5%) were classified as having sarcopenia. Compared with patients without sarcopenia, those with sarcopenia had significantly lower ABI (1.04 ± 0.16 vs. 1.08 ± 0.15, P = 0.028 for the right ABI; 1.01 ± 0.16 vs. 1.06 ± 0.16, P = 0.002 for the left ABI) and VRI (0.83 ± 0.57 vs. 1.08 ± 0.56, P < 0.001) and had higher serum levels of ICAM-1 (P < 0.001), VCAM-1 (P = 0.003) and ET-1 (P = 0.037). Multivariate logistic regression revealed that, beyond age and body mass index, the average ABI (odds ratio [OR]: 0.81/0.1 increase; 95% confidence interval [CI]: 0.67-0.98; P = 0.032) and VRI (OR: 0.93/0.1 increase; 95% CI: 0.88-0.98; P = 0.010) were independently associated with sarcopenia. Among the endothelial biomarkers measured, ICAM-1 (OR: 2.47/1-SD increase; 95% CI: 1.62-3.75) and VCAM-1 (OR: 1.91/1-SD increase; 95% CI: 1.27-2.87) were independent predictors of sarcopenia. Group stratification based on the cut-offs of VRI and ABI showed that those with both poor VRI and ABI had the greatest risk for sarcopenia (OR: 4.22; 95% CI: 1.69-10.49), compared with those with normal VRI and ABI.

CONCLUSIONS

Endothelial dysfunction and PAD are independently associated with sarcopenia in patients with stages 3-5 CKD, suggesting the dominant role of vascular dysfunction in sarcopenia.

Skeletal Muscle Injury in Chronic Kidney Disease-From Histologic Changes to Molecular Mechanisms and to Novel Therapies

Chronic kidney disease (CKD) is associated with significant reductions in lean body mass and in the mass of various tissues, including skeletal muscle, which causes fatigue and contributes to high mortality rates. In CKD, the cellular protein turnover is imbalanced, with protein degradation outweighing protein synthesis, leading to a loss of protein and cell mass, which impairs tissue function. As CKD itself, skeletal muscle wasting, or sarcopenia, can have various origins and causes, and both CKD and sarcopenia share common risk factors, such as diabetes, obesity, and age. While these pathologies together with reduced physical performance and malnutrition contribute to muscle loss, they cannot explain all features of CKD-associated sarcopenia. Metabolic acidosis, systemic inflammation, insulin resistance and the accumulation of uremic toxins have been identified as additional factors that occur in CKD and that can contribute to sarcopenia. Here, we discuss the elevation of systemic phosphate levels, also called hyperphosphatemia, and the imbalance in the endocrine regulators of phosphate metabolism as another CKD-associated pathology that can directly and indirectly harm skeletal muscle tissue. To identify causes, affected cell types, and the mechanisms of sarcopenia and thereby novel targets for therapeutic interventions, it is important to first characterize the precise pathologic changes on molecular, cellular, and histologic levels, and to do so in CKD patients as well as in animal models of CKD, which we describe here in detail. We also discuss the currently known pathomechanisms and therapeutic approaches of CKD-associated sarcopenia, as well as the effects of hyperphosphatemia and the novel drug targets it could provide to protect skeletal muscle in CKD.

Definition and evolution of the concept of sarcopenia

Sarcopenia and dynapenia are two terms associated with ageing that respectively define the loss of muscle mass and strength. In 2018, the European Working Group on Sarcopenia in Older People (EWGSOP) introduced the EWGSOP2 diagnostic algorithm for sarcopenia, which integrates both concepts. It consists of 4 sequential steps: screening for sarcopenia, examination of muscle strength, assessment of muscle mass and physical performance; depending on these last 3 aspects sarcopenia is categorised as probable, confirmed, and severe respectively. In the absence of validation of the EWGSOP2 algorithm in various clinical contexts, its use in haemodialysis poses several limitations: (a) low sensitivity of the screening, (b) the techniques that assess muscle mass are not very accessible, reliable, or safe in routine clinical care, (c) the sequential use of the magnitudes that assess dynapenia and muscle mass do not seem to adequately reflect the muscular pathology of the elderly person on dialysis. We reflect on the definition of sarcopenia and the use of more precise terms such as "myopenia" (replacing the classic concept of sarcopenia to designate loss of muscle mass), dynapenia and kratopenia. Prospective evaluation of EWGSOP2 and its comparison with alternatives (i.e. assessment of kratopenia and dynapenia only; steps 2 and 4) is proposed in terms of its applicability in clinical routine, resource consumption, identification of at-risk individuals and impact on events.

Uremia Impedes Skeletal Myocyte Myomixer Expression and Fusogenic Activity: Implication for Uremic Sarcopenia

In patients with chronic kidney disease (CKD), skeletal muscle mass and function are known to occasionally decline. However, the muscle regeneration and differentiation process in uremia has not been extensively studied. In mice with CKD induced by adenine-containing diet, the tibialis anterior muscle injured using a barium chloride injection method recovered poorly as compared to control mice. In the cultured murine skeletal myocytes, stimulation with indoxyl sulfate (IS), a representative uremic toxin, morphologically jeopardized the differentiation, which was counteracted by L-ascorbic acid (L-AsA) treatment. Transcriptome analysis of cultured myocytes identified a set of genes whose expression was down-regulated by IS stimulation but up-regulated by L-AsA treatment. Gene silencing of myomixer, one of the genes in the set, impaired myocyte fusion during differentiation. By contrast, lentiviral overexpression of myomixer compensated for a hypomorphic phenotype caused by IS treatment. The split-luciferase technique demonstrated that IS stimulation negatively affected early myofusion activity that was rescued by L-AsA treatment. Lastly, in mice with CKD compared with control mice, myomixer expression in the muscle tissue in addition to the muscle weight after the injury was reduced, both of which were restored with L-AsA treatment. Collectively, data showed that the uremic milieu impairs the expression of myomixer and impedes the myofusion process. Considering frequent musculoskeletal injuries in uremic patients, defective myocyte fusion followed by delayed muscle damage recovery could underlie their muscle loss and weakness.

The role of ultra-processed food consumption in protein-energy wasting and sarcopenia development in patients with chronic kidney diseases

BACKGROUND

The effect of ultra-processed foods (UPFs) on chronic kidney disease (CKD) has been studied in some studies. The present study aimed to investigate the association between UPF consumption and the risk of protein-energy wasting (PEW) and sarcopenia in patients with CKD in the Iranian population.

METHODS

The current cross-sectional study included 110 patients with CKD referred to two clinics in Shiraz, Iran. The International Society of Renal Nutrition and Metabolism (ISRNM) criteria and the Asian Working Group for Sarcopenia (AWGS) guideline were considered for the diagnosis of PEW and sarcopenia, respectively. The valid semi-quantitative food frequency questionnaire was used to assess participants' dietary intake. The logistic regression was used to examine the association of UPFs with PEW and sarcopenia.

RESULTS

We observed no significant association between sarcopenia and PEW with UPFs in the crude model. After adjusting for confounders, we observed a significantly higher odds of sarcopenia in the upper versus lower median of UPF intake (odds ratio (OR) = 3.59, 95% confidence interval (CI): 1.02-12.62, P = 0.046).

CONCLUSIONS

Our findings suggest a positive relationship between UPF intake and sarcopenia among CKD patients. Therefore, reducing the intake of UPFs may decrease the odds of sarcopenia in patients suffering from CKD.

The Potential Influence of Uremic Toxins on the Homeostasis of Bones and Muscles in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) often experience a high accumulation of protein-bound uremic toxins (PBUTs), specifically indoxyl sulfate (IS) and p-cresyl sulfate (pCS). In the early stages of CKD, the buildup of PBUTs inhibits bone and muscle function. As CKD progresses, elevated PBUT levels further hinder bone turnover and exacerbate muscle wasting. In the late stage of CKD, hyperparathyroidism worsens PBUT-induced muscle damage but can improve low bone turnover. PBUTs play a significant role in reducing both the quantity and quality of bone by affecting osteoblast and osteoclast lineage. IS, in particular, interferes with osteoblastogenesis by activating aryl hydrocarbon receptor (AhR) signaling, which reduces the expression of Runx2 and impedes osteoblast differentiation. High PBUT levels can also reduce calcitriol production, increase the expression of Wnt antagonists (SOST, DKK1), and decrease klotho expression, all of which contribute to low bone turnover disorders. Furthermore, PBUT accumulation leads to continuous muscle protein breakdown through the excessive production of reactive oxygen species (ROS) and inflammatory cytokines. Interactions between muscles and bones, mediated by various factors released from individual tissues, play a crucial role in the mutual modulation of bone and muscle in CKD. Exercise and nutritional therapy have the potential to yield favorable outcomes. Understanding the underlying mechanisms of bone and muscle loss in CKD can aid in developing new therapies for musculoskeletal diseases, particularly those related to bone loss and muscle wasting.

Neurocirculatory regulation and adaptations to exercise in chronic kidney disease

Chronic kidney disease (CKD) is characterized by pronounced exercise intolerance and exaggerated blood pressure reactivity during exercise. Classic mechanisms of exercise intolerance in CKD have been extensively described previously and include uremic myopathy, chronic inflammation, malnutrition, and anemia. We contend that these classic mechanisms only partially explain the exercise intolerance experienced in CKD and that alterations in cardiovascular and autonomic regulation also play a key contributing role. The purpose of this review is to examine the physiological factors that contribute to neurocirculatory dysregulation during exercise and discuss the adaptations that result from regular exercise training in CKD. Key neurocirculatory mechanisms contributing to exercise intolerance in CKD include augmentation of the exercise pressor reflex, aberrations in neurocirculatory control, and increased neurovascular transduction. In addition, we highlight how some contributing factors may be improved through exercise training, with a specific focus on the sympathetic nervous system. Important areas for future work include understanding how the exercise prescription may best be optimized in CKD and how the beneficial effects of exercise training may extend to the brain.

Clinical implications of circulating follistatin-like protein-1 in hemodialysis patients

Follistatin-like protein-1 (FSTL-1) is secreted glycoprotein, which regulates cardiovascular, immune and skeletal system. However, the clinical significance of circulating FSTL-1 levels remains unclear in hemodialysis patients. A total 376 hemodialysis patients were enrolled from June 2016 to March 2020. Plasma FSTL-1 level, inflammatory biomarkers, physical performance, and echocardiographic findings at baseline were examined. Plasma FSTL-1 levels were positively correlated with TNF-α and MCP-1. Handgrip strength showed weak positive correlation in male patients only, and gait speed showed no correlation with FSTL-1 levels. In multivariate linear regression analysis, FSTL-1 level was negatively associated with left ventricular ejection fraction (β =  - 0.36; p = 0.011). The cumulative event rate of the composite of CV event and death, and cumulative event rate of CV events was significantly greater in FSTL-1 tertile 3. In multivariate Cox-regression analysis, FSTL-1 tertile 3 was associated with a 1.80-fold risk for the composite of CV events and death(95% confidence interval (CI) 1.06-3.08), and a 2.28-fold risk for CV events (95% CI 1.15-4.51) after adjustment for multiple variables. In conclusion, high circulating FSTL-1 levels independently predict the composite of CV events and death, and FSTL-1 level was independently associated with left ventricular systolic dysfunction.

A Sarcopenia Index Derived from Malnutrition Parameters in Elderly Haemodialysis Patients

(1) Background: Persons with chronic kidney disease may have sarcopenia characterized by the loss of muscle mass and loss of muscle strength. However, EWGSOP2 criteria to diagnose sarcopenia are technically challenging, especially in elderly persons on hemodialysis. Sarcopenia may be associated with malnutrition. We aimed at defining a sarcopenia index derived from malnutrition parameters for use in elderly haemodialysis patients. (2) Methods: A retrospective study of 60 patients aged 75 to 95 years treated with chronic hemodialysis was conducted. Anthropometric and analytical variables, EWGSOP2 sarcopenia criteria and other nutrition-related variables were collected. Binomial logistic regressions were used to define the combination of anthropometric and nutritional parameters that best predict moderate or severe sarcopenia according to EWGSOP2, and performance for moderate and severe sarcopenia was assessed by the area under the curve (AUC) of receiver operating characteristic (ROC) curves. (3) Results: The combination of loss of strength, loss of muscle mass and low physical performance correlated with malnutrition. We developed regression-equation-related nutrition criteria that predicted moderate sarcopenia (elderly hemodialysis sarcopenia index-moderate, EHSI-M) and severe sarcopenia (EHSI-S) diagnosed according to EWGSOP2 with an AUC of 0.80 and 0.866, respectively. (4) Conclusions: There is a close relationship between nutrition and sarcopenia. The EHSI may identify EWGSOP2-diagnosed sarcopenia from easily accessible anthropometric and nutritional parameters.

Allograft function and muscle mass evolution after kidney transplantation

BACKGROUND

Advanced chronic kidney disease is associated with muscle wasting, but how glomerular filtration rate (GFR) recovery after kidney transplantation is associated with muscle mass is unknown.

METHODS

We took advantage of the simultaneous measurement of GFR (using iohexol plasma clearance; ioGFR) and creatinine excretion rate (a surrogate marker of muscle mass; CER) performed 3 months after transplantation and at a later time point at our institution to investigate the interplay between allograft function, muscle mass, and outcome in kidney transplant recipients.

RESULTS

Between June 2005 and October 2019, 1319 successive kidney transplant recipients (mean age 50.4 ± 14.6; 38.7% female) underwent GFR measurement at our institution 3 months after kidney transplantation. CER (CER₃ ) and ioGFR (ioGFR₃ ) were 7.7 ± 2.6 μmol/min and 53 ± 17.1 mL/min/1.73 m² , respectively. Multivariable analysis identified female gender, older donor and recipient age, reduced body mass index, coronary disease, dialysis history, proteinuria, and reduced ioGFR₃ as independent predictors of low CER₃ (ioGFR₃ : β coefficient 0.19 [95% confidence interval 0.14 to 0.24]). A total of 1165 patients had a subsequent CER measurement after a median follow-up of 9.5 months. Of them, 373 (32%) experienced an increase in CER > 10%, while 222 (19%) showed a CER decrease of more than 10%. Multivariable analysis adjusted for CER₃ and other confounders identified ioGFR₃ as an independent predictor of CER at follow-up (β coefficient 0.11 [95% confidence interval 0.07 to 0.16]). In multivariable Cox analysis, reduced CER at 3 months or at follow-up were consistently associated with mortality (hazard ratio [95% confidence interval] at 3 months: 0.82 [0.74 to 0.91]; at follow-up: 0.79 [0.69 to 0.99]) but not with graft loss.

CONCLUSIONS

Glomerular filtration rate recovery is a determinant of muscle mass variation after kidney transplantation. Early interventions targeting muscle mass gain may be beneficial for kidney transplant recipients.

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.

Sarcopenia and sarcopenic obesity in chronic kidney disease: update on prevalence, outcomes, risk factors and nutrition treatment

PURPOSE OF REVIEW

This review summarizes literature from the last 18 months reporting on sarcopenia (or its components) in chronic kidney disease (CKD).

RECENT FINDINGS

The prevalence of sarcopenia in CKD is reported to be 5-62.5%, with higher rates observed later in the disease. Sarcopenic obesity rates are reported to be 2-23%. Sarcopenia in CKD is associated with increased risk of mortality, cardiovascular disease and vascular calcification. Risk factors include kidney disease itself and the impacts of CKD on lifestyle (reduced physical activity, diet changes). In earlier stages of CKD, if the risks from sarcopenia outweigh the risk of reaching end-stage renal disease, ensuring adequate energy intake combined with modest protein liberalization and physical activity may be indicated. Protein intakes above 1.3 g/kg of body weight per day should be avoided. For dialysis patients, interventions that provide a combination of carbohydrate, protein and fat appear more effective than those that provide protein alone, though it may take as long as 48 weeks for detectable changes in muscle mass.

SUMMARY

Sarcopenia is prevalent in CKD as kidney disease significantly impacts muscle mass and function. Nutrition interventions can improve components of sarcopenia, with an emphasis on adequate energy and protein.

Exercise Reduces the Risk of Chronic Kidney Disease in Individuals with Nonalcoholic Fatty Liver Disease: A Nationwide Cohort Study

AIMS

Recent studies of individuals with nonalcoholic fatty liver disease (NAFLD) have indicated benefits of exercise in improving outcomes. We investigated whether exercise reduces the risk of chronic kidney disease (CKD) in individuals with NAFLD.

METHODS

A total of 7,275 participants from the Korea National Health and Nutrition Examination Survey (KNHANES) cohort, and 40,418 participants with NAFLD from the National Health Insurance Service (NHIS) cohort were included for the cross-sectional and longitudinal analyses, respectively. For the cross-sectional analysis, the primary outcome was prevalent CKD, defined as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73m². For the longitudinal analysis, the primary outcome was incident CKD, defined as the occurrence of eGFR <60 mL/min/1.73m² or proteinuria (≥trace) on two consecutive measurements during follow-up.

RESULTS

In the KNHANES cohort, prevalent CKD was observed in 229 (6.1%), 48 (2.6%), and 36 (2.1%) participants in the 0, 1-2, and ≥3 exercise sessions/week groups, respectively. The likelihood of prevalent CKD was lowest in participants allocated to the ≥3 sessions/week group (adjusted OR 0.49; 95% CI, 0.33-0.71; P<0.001). During a median follow-up of 5.0 years in the NHIS cohort, incident CKD occurred in 1,047 (9.7/1,000 person-years), 188 (7.3/1,000 person-years), and 478 (7.4/1,000 person-years) participants in the 0, 1-2, and ≥3 sessions/week groups, respectively. The risk of incident CKD was lowest in participants allocated to the ≥3 sessions/week group (adjusted HR 0.85; 95% CI, 0.76-0.95; P=0.004).

CONCLUSIONS

Exercise was significantly associated with a reduced risk of both prevalent and incident CKD in individuals with NAFLD.

Effect of Online Home-Based Training on Functional Capacity and Strength in Two CKD Patients: A Case Study

Chronic kidney disease (CKD) is a clinical condition characterized by the loss of kidney function over time, as well as several complications affecting gastrointestinal, cardiovascular, and musculoskeletal systems. Physical exercise seems to induce positive adaptations in CKD patients, without side effects. Usually, these patients show a reduced physical activity and physical performance. The aim of this case-report was to evaluate the effects of an online training protocol on functional capacity and on muscle mass, in CKD stage III patients. Methods: Two CKD (stage III according to KDIGO guidelines) participants (1 female, Patient A; 1 male, Patient B) were enrolled and they performed an online tailored-supervised combined training lasting 12 weeks, including multi-joint strength exercises using TheraBand and an aerobic session at 65–70% of the patients' heart rate reserve. Results: Both patients showed an improving trend on functional capacity (6 minutes walking test: Patient A = +3%; Patient B = +5.3%) and on strength of the upper arms (handgrip strength test-right: Patient A = +13.4%; Patient B = +19.1%; handgrip strength test-left: Patient A = +42.8%; Patient B= +12.9%), as well as a reduction in inflammation and oxidative stress biomarkers. The protocol was feasible, and no side effects were evidenced. These case studies suggest that the online combined training can produce beneficial effects in CKD patients under conservative therapy, by reducing the CKD-related complications and improving the adherence to exercise of this population of patients, overcoming logistic barriers such as transportation, availability of facilities, and working and personal-life schedule.

OUP accepted manuscript

Sarcopaenia is a highly prevalent condition in persons on haemodialysis (HD). In stable very elderly (75–95 years old) persons on chronic HD, we prospectively studied the European Working Group on Sarcopaenia in Older People (EWGSOP2) steps stability over time in 37 controls and their response to a 12-week intradialytic lower limb exercise programme in 23 persons. Overall dropout was 15% and the main cause for dropout was death (8%). Thus 33 controls and 18 exercise participants were evaluated at 12 weeks. In controls, comorbidity, nutrition, dependency and frailty scales, anthropometric assessments, EWGSOP2 step values and the prevalence of suspected, confirmed and severe sarcopaenia as assessed by EWGSOP2 remained stable. In contrast, in persons who completed the exercise programme, a significant improvement in the five times sit-to-stand (STS-5) test was noted at the end of the 12-week exercise programme (19.2 ± 4.9–15.9 ± 5.9 seconds; P = .001), consistent with the lower limb nature of the exercise programme, that persisted 12 weeks after completion of the programme. Exercise also improved the Fried frailty scale (1.7 ± 1.0–1.1 ± 0.6; P = .004). In conclusion, EWGSOP2 steps remain stable in stable very elderly persons on HD and STS-5 is responsive to a short-term intradialytic lower limb exercise programme. These results may help define EWGSOP2-based primary endpoints in future large-scale clinical trials assessing exercise interventions.

The role of potassium in muscle membrane dysfunction in end-stage renal disease

OBJECTIVE

Uremic myopathy is a condition seen in end-stage renal disease (ESRD), characterized by muscle weakness and muscle fatigue, in which the pathophysiology is uncertain. The aim of this study was to assess the role of abnormal serum constituents in ESRD patients by relating them to the excitability properties of the tibialis anterior muscle, at rest and during electrically induced muscle activation, by recording muscle velocity recovery cycles (MVRC) and frequency ramp responses.

METHODS

Eighteen ESRD patients undergoing hemodialysis were evaluated by blood sample, MVRC, and frequency ramp (before and near the end of dialysis treatment), quantitative electromyography, and nerve conduction studies. Patients were compared to 24 control subjects.

RESULTS

In patients, muscle relative refractory period, early supernormality, late supernormality after 5 conditioning stimuli, and latency of the last of 15 and 30 frequency ramp pulses were strongly associated with potassium levels (p < 0.01), showing depolarization before and normalization in the end of hemodialysis.

CONCLUSIONS

In ESRD patients, the muscle membrane is depolarized, mainly due to hyperkalemia.

SIGNIFICANCE

Since normal muscle fatigue has been attributed to potassium-induced depolarization, it seems likely that this mechanism is also a major cause of the exaggerated muscle fatigue and weakness in ESRD patients.

Effectiveness and safety of rehabilitation on minimal change nephrotic syndrome in remission for elderly patients with low activity of daily living: a case report

There are few reports on the rehabilitation of elderly patients with minimal change nephrotic syndrome (MCNS). The purpose of this case study was to evaluate the efficacy and safety of rehabilitation for an elderly patient with MCNS in remission. The patient was an 86-year-old woman. She was admitted to the hospital with a diagnosis of MCNS, and steroid treatment was initiated. She was weaned from dialysis 2 weeks later; however, her activities of daily living (ADL) decreased, and she developed disuse syndrome. After rehabilitation, the patient's ADL, maximum hand grip strength, and gait function improved. There was no recurrence of weight gain or increased proteinuria during rehabilitation, but the estimated glomerular filtration rate decreased. This case suggests that rehabilitation for elderly patients with MCNS in remission can be effective for physical and ADL functions without relapse of MCNS. The effect of exercise therapy on the relationship between exercise therapy and renal function needs to be further investigated by collecting more cases.

Depression and low physical activity are related to sarcopenia in hemodialysis: a single-center study

BACKGROUND

The number of patients who suffer from chronic renal failure (CRF) has widely increased worldwide. Patients with advanced stages of CRF experience a gradual and progressive loss of muscle and fat mass leading to decreased physical activity and mental health problems. The loss of muscle mass in CRF might contribute to the development of sarcopenia. Therefore, this study aimed to explore the prevalence of sarcopenia and to determine the relationship of physical activity and mental state of depression with sarcopenia in hemodialysis patients.

METHODS

A cross-sectional study was designed with a total of 104 male and female with a minimum age of 35 years. Based on the guidelines of the Asian Working Group for Sarcopenia in 2019, gait speed, muscle mass, and handgrip were used to define sarcopenia. In addition, participants were requested to perform a set of questionnaires to evaluate their physical activity and state of depression. Logistic regression analyses were used to explore the risk factors of sarcopenia.

RESULTS

Thirty-four (32.69%) of 104 participants had sarcopenia. Compared to the 70 individuals without sarcopenia, they had a low physical activity and a high depression score (ps < .05). Furthermore, low physical activity and high depression scores in combination with sarcopenia were associated with an increased mortality risk. Low physical activity and high depression scores were also independently associated with sarcopenia in hemodialysis patients after controlling for age (odds ratio = 3.23, and 4.92, respectively).

Indoxyl-Sulfate-Induced Redox Imbalance in Chronic Kidney Disease

The accumulation of the uremic toxin indoxyl sulfate (IS) induces target organ damage in chronic kidney disease (CKD) patients, and causes complications including cardiovascular diseases, renal osteodystrophy, muscle wasting, and anemia. IS stimulates reactive oxygen species (ROS) production in CKD, which impairs glomerular filtration by a direct cytotoxic effect on the mesangial cells. IS further reduces antioxidant capacity in renal proximal tubular cells and contributes to tubulointerstitial injury. IS-induced ROS formation triggers the switching of vascular smooth muscular cells to the osteoblastic phenotype, which induces cardiovascular risk. Low-turnover bone disease seen in early CKD relies on the inhibitory effects of IS on osteoblast viability and differentiation, and osteoblastic signaling via the parathyroid hormone. Excessive ROS and inflammatory cytokine releases caused by IS directly inhibit myocyte growth in muscle wasting via myokines’ effects. Moreover, IS triggers eryptosis via ROS-mediated oxidative stress, and elevates hepcidin levels in order to prevent iron flux in circulation in renal anemia. Thus, IS-induced oxidative stress underlies the mechanisms in CKD-related complications. This review summarizes the underlying mechanisms of how IS mediates oxidative stress in the pathogenesis of CKD’s complications. Furthermore, we also discuss the potential role of oral AST-120 in attenuating IS-mediated oxidative stress after gastrointestinal adsorption of the IS precursor indole.

Associations between frailty, physical performance, and renal biomarkers in older people with advanced chronic kidney disease

Aim

To test whether renal biochemical markers were associated with physical performance and frailty in older people with advanced chronic kidney disease.

Findings

Biochemical markers associated with chronic kidney disease did not consistently associate with baseline physical performance or the rate of change of physical performance measures.

Message

Targeting improvements in renal biochemistry may not be a fruitful way to improve physical function and frailty in older people with advanced chronic kidney disease.

Supplementary Information

The online version of this article (10.1007/s41999-021-00478-4) contains supplementary material, which is available to authorized users.

Purpose

Impaired physical performance and frailty are common in older people with advanced chronic kidney disease but it is unclear which metabolic derangements contribute to these impairments. We, therefore, examined associations between renal biochemical markers and both physical performance and frailty in older people with advanced chronic kidney disease.

Methods

Secondary analysis of data from the BiCARB trial, which enrolled non-dialysing patients aged 60 and over, with chronic kidney disease stage 4/5, with serum bicarbonate < 22 mmol/L. Participants undertook the Short Physical Performance Battery, maximum grip strength and six-minute walk test at baseline, 3, 6, 12 and 24 months. Renal biochemistry (serum creatinine, cystatin C, phosphate, and bicarbonate), haemoglobin, 25-hydroxyvitamin D and NT-pro-B-type natriuretic peptide were measured at baseline. Associations between baseline renal biochemistry and physical performance, and between baseline biochemistry and the monthly rate of change in physical performance were assessed.

Results

We analysed data from 300 participants (mean age 74 years; 86 [29%] women). 148 (49%) were pre-frail, 86 (29%) were frail. In multivariable cross-sectional baseline analyses, only age and BMI were significantly associated with baseline short physical performance battery; age, sex, body mass index, NT-pro-BNP and 25-hydroxyvitamin D were significantly associated with baseline six-minute walk distance. No significant associations were found between biochemical markers and change in physical performance over time, except between baseline 25-hydroxyvitamin D concentration and change in six-minute walk distance.

Conclusions

Biochemical markers associated with chronic kidney disease did not consistently associate with baseline physical performance or the rate of change of physical performance measures.

Trial Registration: ISRCTN09486651

Supplementary Information

The online version of this article (10.1007/s41999-021-00478-4) contains supplementary material, which is available to authorized users.

Uremic Sarcopenia and Its Possible Nutritional Approach

Uremic sarcopenia is a frequent condition present in chronic kidney disease (CKD) patients and is characterized by reduced muscle mass, muscle strength and physical performance. Uremic sarcopenia is related to an increased risk of hospitalization and all-causes mortality. This pathological condition is caused not only by advanced age but also by others factors typical of CKD patients such as metabolic acidosis, hemodialysis therapy, low-grade inflammatory status and inadequate protein-energy intake. Currently, treatments available to ameliorate uremic sarcopenia include nutritional therapy (oral nutritional supplement, inter/intradialytic parenteral nutrition, enteral nutrition, high protein and fiber diet and percutaneous endoscopic gastrectomy) and a personalized program of physical activity. The aim of this review is to analyze the possible benefits induced by nutritional therapy alone or in combination with a personalized program of physical activity, on onset and/or progression of uremic sarcopenia.

25OH Vitamin D Is No Associated with Muscle Function Loss in Adults and Elderly Patients Undergoing Hemodialysis

OBJECTIVES

In patients with chronic kidney disease, sarcopenia is associated with dialysis treatment, accelerated protein catabolism, and high energy demand. Thus, this study aimed to assess the association between 25-OH vitamin D concentrations and muscle function in patients undergoing hemodialysis.

DESIGN

A cross-sectional study.

SETTING

Performed in a hemodialysis clinic.

PARTICIPANTS

79 adult and elderly patients undergoing hemodialysis.

MEASUREMENTS

The sample was divided according to the SARC-F definition, being 55 patients allocated in the SARC-F <4 group and 24 in the SARC-F ≥4 group. Normal 25-OH vitamin D concentrations was considered when ≥30 ng/dL.

RESULTS

Vitamin D concentrations and number of patients with low or normal muscle function did not differ between the groups. There was no correlation between SARC-F and 25-OH vitamin D levels (r: -0.09, p=0.42).

CONCLUSIONS

25-OH vitamin D has no association with muscle function loss in adults and elderly patients undergoing hemodialysis.

Mitochondrial Dysfunction in Kidney Disease and Uremic Sarcopenia

Recently, there has been an increased focus on the influences of mitochondrial dysfunction on various pathologies. Mitochondria are major intracellular organelles with a variety of critical roles, such as adenosine triphosphate production, metabolic modulation, generation of reactive oxygen species, maintenance of intracellular calcium homeostasis, and the regulation of apoptosis. Moreover, mitochondria are attracting attention as a therapeutic target in several diseases. Additionally, a lot of existing agents have been found to have pharmacological effects on mitochondria. This review provides an overview of the mitochondrial change in the kidney and skeletal muscle, which is often complicated with sarcopenia and chronic kidney disease (CKD). Furthermore, the pharmacological effects of therapeutics for CKD on mitochondria are explored.