Exercise as an anabolic intervention in patients with end-stage renal disease

Physician knowledge, attitudes, and practices regarding physical activity restrictions in pediatric hemodialysis patients

INTRODUCTION

Epidemiologic studies of physical activity among pediatric hemodialysis (HD) patients are lacking. A sedentary lifestyle in End-Stage Kidney Disease is associated with a higher cardiovascular mortality risk. In those patients receiving HD, time spent on dialysis and restrictions on physical activity due to access also contribute. No consensus exists regarding physical activity restrictions based on vascular access type. The aim of this study was to describe the patterns of physical activity restrictions imposed by pediatric nephrologists on pediatric HD patients and to understand the basis for these restrictions.

METHODS

We conducted a cross-sectional study involving US pediatric nephrologists using an anonymized survey through Pediatric Nephrology Research Consortium. The survey consisted of 19 items, 6 questions detailed physician characteristics with the subsequent 13 addressing physical activity restrictions.

FINDINGS

A total of 35 responses (35% response rate) were received. The average years in practice after fellowship was 11.5 years. Significant restrictions were placed on physical activity and water exposure. None of the participants reported accesses damage or loss that was attributed to physical activity and sport participation. Physicians practice is based on their personal experience, standard practice at their HD center, and clinical practices they were taught.

DISCUSSION

There is no consensus among pediatric nephrologists about allowable physical activity in children receiving HD. Due to the lack of objective data, individual physician beliefs have been utilized to restrict activities in the absence of any deleterious effects to accesses. This survey clearly demonstrates the need for more prospective and detailed studies to develop guidelines regarding physical activity and dialysis access in order to optimize quality of care in these children.

Molecular mechanisms of post-burn muscle wasting and the therapeutic potential of physical exercise

After a severe burn injury, a systemic stress response activates metabolic and inflammatory derangements that, among other, leads to muscle mass loss (muscle wasting). These negative effects on skeletal muscle continue for several months or years and are aggravated by short-term and long-term disuse. The dynamic balance between muscle protein synthesis and muscle protein breakdown (proteolysis) is regulated by complex signalling pathways that leads to an overall negative protein balance in skeletal muscle after a burn injury. Research concerning these molecular mechanisms is still scarce and inconclusive, understanding of which, if any, molecular mechanisms contribute to muscle wasting is of fundamental importance in designing of therapeutic interventions for burn patients as well. This review not only summarizes our present knowledge of the molecular mechanisms that underpin muscle protein balance but also summarizes the effects of exercise on muscle wasting post-burn as promising strategy to counteract the detrimental effects on skeletal muscle. Future research focusing on the pathways causing post-burn muscle wasting and the different effects of exercise on them is needed to confirm this hypothesis and to lay the foundation of therapeutic strategies.

Nutritional Assessment of Adult Patients Undergoing Maintenance Hemodialysis in the Gaza Strip

Malnutrition is a common condition in patients undergoing hemodialysis (HD), and it is associated with increased morbidity and mortality. The main objective of the study was to evaluate the nutritional status of patients on maintenance HD. After applying eligibility criteria, 141 HD patients attending major governmental dialysis centers were randomly recruited in this cross-sectional study and assessed for nutritional status using the Patient-Generated Subjective Global Assessment (PG-SGA) tool. The PG-SGA categorizes patients as well-nourished, moderately malnourished, and severely malnourished. Different anthropometric measurements, laboratory investigations, blood pressure measurements, and 24-h dietary recall were collected from each patient. According to PG- SGA results, 78% of patients were moderately malnourished and 22% of patients were severely malnourished. The mean body mass index was 27.8 kg/m2, and 5.7% of patients were underweight. There were significant differences in the mid-upper arm muscle circumference (P = 0.020) between the PG-SGA groups. The total energy and protein intake were significantly (P <0.001) less than the recommended dietary intake by 1268.9 kcal and 41.4 g, respectively. The albumin level in 37.6% of patients was less than the normal level, and the results indicated that there were significant differences in serum iron (P = 0.022) between the moderately and severely malnourished patients. The results of this study indicated that all HD patients were suffering from different degrees of malnutrition and, unfortunately, most of their energy and nutrient intake was far less than the requirements, which might be the reason why they face nutritional and health risks.

Effect of Intradialytic Oral Nutritional Supplementation with or without Exercise Improves Muscle Mass Quality and Physical Function in Hemodialysis Patients: A Pilot Study

Background: Oral nutritional supplementation (ONS) with or without exercise (EX) could improve muscle mass (MM) in chronic kidney disease. Methods: Patients were randomized into two groups: (1) ONS and (2) ONS + EX. Thigh muscle area (cm²) and intramuscular lipid content via attenuation were evaluated at baseline and 6 months with computed tomography (CT) to measure MM quantity and quality. Physical function was measured by six-minute walk test (6 MWT), gait speed, handgrip strength (HGS), and Time Up and Go test (TUG) at baseline and 3 and 6 months. Results: The ONS group (n= 14) showed statistically significant improvement in gait speed and HGS; ONS + EX group (n = 10) showed differences in gait speed, in 6 MWT, and HGS. In the ANOVA (3 times × 2 groups), no differences were observed between groups. Greater effect sizes in favor to ONS + EX group were observed in the 6 MWT (d = 1.02) and TUG test (d = 0.63). Muscle quality at six months revealed a significant trend in favor of the EX-group (p = 0.054). Conclusions: Both groups had improved physical function, and greater effect sizes were seen in the ONS + EX group for the 6 MWT and TUG test. Neither MM quantity or quality was improved in either group.

Muscle Status Response to Oral Nutritional Supplementation in Hemodialysis Patients With Protein Energy Wasting: A Multi-Center Randomized, Open Label-Controlled Trial

Background: Muscle wasting, observed in patients with end-stage kidney disease and protein energy wasting (PEW), is associated with increased mortality for those on hemodialysis (HD). Oral nutritional supplementation (ONS) and nutrition counseling (NC) are treatment options for PEW but research targeting muscle status, as an outcome metric, is limited.

Aim: We compared the effects of combined treatment (ONS + NC) vs. NC alone on muscle status and nutritional parameters in HD patients with PEW.

Methods: This multi-center randomized, open label-controlled trial, registered under ClinicalTrials.gov (Identifier no. NCT04789031), recruited 56 HD patients identified with PEW using the International Society of Renal Nutrition and Metabolism criteria. Patients were randomly allocated to intervention (ONS + NC, n = 29) and control (NC, n = 27) groups. The ONS + NC received commercial renal-specific ONS providing 475 kcal and 21.7 g of protein daily for 6 months. Both groups also received standard NC during the study period. Differences in quadriceps muscle status assessed using ultrasound (US) imaging, arm muscle area and circumference, bio-impedance spectroscopy (BIS), and handgrip strength (HGS) methods were analyzed using the generalized linear model for repeated measures.

Results: Muscle indices as per US metrics indicated significance (p < 0.001) for group × time interaction only in the ONS + NC group, with increases by 8.3 and 7.7% for quadriceps muscle thickness and 4.5% for cross-sectional area (all p < 0.05). This effect was not observed for arm muscle area and circumference, BIS metrics and HGS in both the groups. ONS + NC compared to NC demonstrated increased dry weight (p = 0.039), mid-thigh girth (p = 0.004), serum prealbumin (p = 0.005), normalized protein catabolic rate (p = 0.025), and dietary intakes (p < 0.001), along with lower malnutrition–inflammation score (MIS) (p = 0.041). At the end of the study, lesser patients in the ONS + NC group were diagnosed with PEW (24.1%, p = 0.008) as they had achieved dietary adequacy with ONS provision.

Conclusion: Combination of ONS with NC was effective in treating PEW and contributed to a gain in the muscle status as assessed by the US, suggesting that the treatment for PEW requires nutritional optimization via ONS.

A Systematic Review of the Acute Effects of Hemodialysis on Skeletal Muscle Perfusion, Metabolism, and Function

Introduction

The underlying mechanisms of skeletal muscle wasting in hemodialysis patients are complex. We performed a systematic review to summarize evidence on whether hemodialysis has acute effects on skeletal muscle perfusion, metabolism, and function.

Methods

The protocol was registered on PROSPERO (Registration number CRD42018103682). A systematic search was performed in MEDLINE, PubMed, Cochrane, Embase, Scopus, and Web of Science. Citation, reference list, and gray literature searches were also performed. Studies were selected in 2 stages: title and abstract review, then full-text review.

Results

A total of 65 full-text articles were reviewed, and 14 studies were eligible for inclusion. No studies were identified that assessed muscle perfusion during dialysis. Two studies used near-infrared spectroscopy to indirectly measure skeletal muscle oxygen consumption, which increased during dialysis in 1 study but only in patients with diabetes in the second. Metabolism was examined in 9 studies. A number of acute metabolic changes were reported (e.g., caspase-3 activity, polyubiquitin, and interleukin-6 protein increased in response to hemodialysis) as was a net negative protein balance over the dialysis session. Three studies examining muscle function did not produce consistent findings.

Conclusion

Gaps remain in understanding the acute effects of hemodialysis on skeletal muscle, particularly for changes in perfusion and function, although there does appear to be an acute effect on muscle metabolism.

The association of exercise and sedentary behaviours with incident end-stage renal disease: the Southern Community Cohort Study

OBJECTIVE

To examine whether lifestyle factors, including sedentary time and physical activity, could independently contribute to risk of end-stage renal disease (ESRD).

STUDY DESIGN

Case-cohort study.

SETTING

South-eastern USA.

PARTICIPANTS

The Southern Community Cohort Study recruited ~86 000 black and white participants from 2002 to 2009. We assembled a case cohort of 692 incident ESRD cases and a probability sample of 4113 participants.

PREDICTORS

Sedentary time was calculated as hours/day from daily sitting activities. Physical activity was calculated as metabolic equivalent (MET)-hours/day from engagement in light, moderate and vigorous activities.

OUTCOMES

Incident ESRD.

RESULTS

At baseline, among the subcohort, mean (SD) age was 52 (8.6) years, and median (25th, 75th centile) estimated glomerular filtration rate (eGFR) was 102.8 (85.9-117.9) mL/min/1.73 m². Medians (25th-75th centile) for sedentary time and physical activity were 8.0 (5.5-12.0) hours/day and 17.2 (8.7-31.9) MET-hours/day, respectively. Median follow-up was 9.4 years. We observed significant interactions between eGFR and both physical activity and sedentary behaviour (p<0.001). The partial effect plot of the association between physical activity and log relative hazard of ESRD suggests that ESRD risk decreases as physical activity increases when eGFR is 90 mL/min/1.73 m². The inverse association is most pronounced at physical activity levels >27 MET-hours/day. High levels of sitting time were associated with increased ESRD risk only among those with reduced kidney function (eGFR ≤30 mL/min/1.73 m²); this association was attenuated after excluding the first 2 years of follow-up.

CONCLUSIONS

In a population with a high prevalence of chronic kidney disease risk factors such as hypertension and diabetes, physical activity appears to be associated with reduced risk of ESRD among those with preserved kidney function. A positive association between sitting time and ESRD observed among those with advanced kidney disease is likely due to reverse causation.

The association between six month intra-dialytic resistance training and muscle strength or physical performance in patients with maintenance hemodialysis: a multicenter retrospective observational study

Background

Reduced muscle strength and physical performance are prevalent in patients of maintenance hemodialysis (MHD), and deleterious changes in these parameters are associated with increased mortality.

Methods

This retrospective observational study included 306 patients, who received a 6-month resistance exercise program during hemodialysis, three times per week on an outpatient basis. The training protocol consisted of two sets of 10 repetitions of knee extension, hip abduction, and hip flexion, using an elastic band in a sitting or supine position. Primary outcome measures included muscle strength, measured by percent knee extension muscle power to dry body weight (pKEMP-dBW), and physical performance, measured by short physical performance battery (SPPB). The adjusted mean differences in these variables during the 6 months were estimated using a multivariate linear regression model.

Results

The mean age with standard deviation was 70 ± 11 years. One hundred and sixty patients (52.3%) were men and the dry weight was 55.6 ± 11.3 kg. Sarcopenia, defined as SPPB ≤8, was present in 21.4% patients. Their hemodialysis adequacy was acceptable, with a Kt/V of 1.65 ± 0.29, and their nutritional status was good, with a normalized protein catabolism rate of 0.89 ± 0.18 g/kg/day. During the 6 months, both pKEMP-dBW and SPPB showed a slight but significant increase with an adjusted mean difference of 2.8 (95% confidence interval 1.3–4.3, p <  0.001) and 0.6 (0.4–0.9, p <  0.001), respectively.

Conclusions

Six-month resistance training was associated with improved muscle strength and physical performance in patients with MHD.

Effects of intradialytic resistance training on physical activity in daily life, muscle strength, physical capacity and quality of life in hemodialysis patients: a randomized clinical trial

Purpose: We evaluated the effects of supervised intradialytic resistance training on physical activity in daily life (PADL), muscle strength, physical capacity and quality of life (QoL) in hemodialysis patients.Methods: Twenty-four hemodialysis patients were randomly assigned to either a 12-weeks moderate-intensity resistance training or a control period. An accelerometer evaluated PADL for seven consecutive days, measuring the time spent in different activities and positions of daily routine and the number of steps taken. Muscle strength, physical capacity and QoL were evaluated.Results: After 12 weeks of training, we did not find significant difference (post-pre values) in walking time (-1.2 ± 18.3 vs. -9.2 ± 13.1 min/day); standing time (-10.2 ± 28.6 vs. 3.2 ± 20.1 min/day); sitting time (20.8 ± 58.9 vs. -30.0 ± 53.0 min/day); lying down time (-9.3 ± 57.9 vs. 34.6 ± 54.0 min/day); number of steps taken [-147 (1834) vs. -454 (2066)] and muscle strength in training and control group, respectively. There was a significant increase in the six-minute walking test distance (48.8 ± 35.9 vs. 6.9 ± 45.9 m, p < 0.05) and some domains of QoL in the training compared to the control group.Conclusions: PADL was not modified after 12 weeks of intradialytic resistance training in hemodialysis patients. However, the exercise program was able to increase the physical capacity and some domains of QoL.Implications for rehabilitationPhysical activity in daily life was not modified after 12 weeks of intradialytic resistance training in hemodialysis patients.The exercise program was able to increase the physical capacity, efficacy of dialysis and some domains of quality of life in hemodialysis patients.The protocol used in this study was safe since no complications were observed during and after resistance training.These results should be interpreted with caution because we applied a moderate resistance training in both lower limbs and in the contralateral arteriovenous fistula upper limb, using perceived exertion by Borg scale to exercise prescription. Moreover, the safety protocol evaluation was not conducted.

Sarcopenia, cachexia, and muscle performance in heart failure: Review update 2016

Cachexia in the context of heart failure (HF) has been termed cardiac cachexia, and represents a progressive involuntary weight loss. Cachexia is mainly the result of an imbalance in the homeostasis of muscle protein synthesis and degradation due to a lower activity of protein synthesis pathways and an over-activation of protein degradation. In addition, muscle wasting leads to of impaired functional capacity, even after adjusting for clinical relevant variables in patients with HF. However, there is no sufficient therapeutic strategy in muscle wasting in HF patients and very few studies in animal models. Exercise training represents a promising intervention that can prevent or even reverse the process of muscle wasting, and worsening the muscle function and performance in HF with muscle wasting and cachexia. The pathological mechanisms and effective therapeutic approach of cardiac cachexia remain uncertain, because of the difficulty to establish animal cardiac cachexia models, thus novel animal models are warranted. Furthermore, the use of improved animal models will lead to a better understanding of the pathways that modulate muscle wasting and therapeutics of muscle wasting of cardiac cachexia.

The Gut in Older Patients on Peritoneal Dialysis

Age-related changes in gastrointestinal symptoms need to be considered in peritoneal dialysis (PD) patients. A diminishing appetite is associated with aging and may be exacerbated by renal failure and PD treatment, meaning that attention to dietary adequacy is important in the older patient. Constipation and its treatment may increase the risk of peritonitis, but is important for comfort as well as trouble-free dialysis. Diverticulosis increases with age, and whilst there may be ethnic differences in the patterns of this condition, there is conflicting evidence regarding the risks of peritonitis associated with asymptomatic disease. Hernias, urinary incontinence, and prolapse are also common and made worse by PD, so it is important to know about these issues prior to starting. Whilst data around these topics are scant and some studies conflicting, further understanding these issues and considering mitigation strategies may improve technique survival and quality of life.

Skeletal muscle wasting in cachexia and sarcopenia: molecular pathophysiology and impact of exercise training

Skeletal muscle provides a fundamental basis for human function, enabling locomotion and respiration. Transmission of external stimuli to intracellular effector proteins via signalling pathways is a highly regulated and controlled process that determines muscle mass by balancing protein synthesis and protein degradation. An impaired balance between protein synthesis and breakdown leads to the development of specific myopathies. Sarcopenia and cachexia represent two distinct muscle wasting diseases characterized by inflammation and oxidative stress, where specific regulating molecules associated with wasting are either activated (e.g. members of the ubiquitin-proteasome system and myostatin) or repressed (e.g. insulin-like growth factor 1 and PGC-1α). At present, no therapeutic interventions are established to successfully treat muscle wasting in sarcopenia and cachexia. Exercise training, however, represents an intervention that can attenuate or even reverse the process of muscle wasting, by exerting anti-inflammatory and anti-oxidative effects that are able to attenuate signalling pathways associated with protein degradation and activate molecules associated with protein synthesis. This review will therefore discuss the molecular mechanisms associated with the pathology of muscle wasting in both sarcopenia and cachexia, as well as highlighting the intracellular effects of exercise training in attenuating the debilitating loss of muscle mass in these specific conditions.

Resistance exercise: an effective strategy to reverse muscle wasting in hemodialysis patients?

Muscle wasting is a common complication afflicting maintenance hemodialysis (HD) patients, and it is associated with decreased muscle function, exercise performance, physical function, and quality of life. Meanwhile, numerous epidemiologic studies have consistently shown that greater muscle mass (ascertained by body anthropometry surrogates, body composition tests such as dual x-ray absorptiometry, and/or serum creatinine in patients with little to no residual kidney function) is associated with increased survival in this population. The pathophysiology of muscle wasting in HD patients is complex and may be caused by poor dietary intake, catabolic effects of dialysis therapy, hormonal alterations (e.g., decreased levels or resistance to anabolic hormones, increased levels of catabolic hormones), inflammation, metabolic acidosis, and concurrent comorbidities. Muscle disuse resulting from low physical activity is an important yet under-appreciated risk factor for muscle wasting. Intra-dialytic resistance exercise training has been suggested as a potential strategy to correct and/or prevent this complication in HD patients, but prior studies examining this exercise modality as an anabolic intervention have shown mixed results. In a recently published 12-week randomized controlled trial of a novel intra-dialytic progressive resistance exercise training (PRET) program vs. control therapy conducted in HD and non-HD patients, PRET resulted in increased muscle volume and strength in both groups. At this time, further study is needed to determine if anabolic improvements imparted by resistance exercise translates into improved physical function and quality of life, decreased hospitalization and mortality risk, and greater cost-effectiveness in HD patients.

Resistance training in hemodialysis patients: a review

PURPOSE

Few studies have examined the role of resistance training (RT) in chronic kidney patients on hemodialysis (HD). This study reviews the literature about resistance exercise for patients on HD and describes protocols and clinical outcomes.

METHODS

A search of the MEDLINE database found 21 eligible publications, of which 14 studies applied only RT and 7 combined RT and aerobic training.

FINDINGS

Regarding the period of exercise training, 14 studies applied intradialytic exercise. The main outcome reported was muscle strength, which was assessed through knee strength and handgrip measures.

CONCLUSIONS

All studies reviewed presented at least one significant result in relation to biochemical parameters, physical capacity, strength, body composition, or quality of life.

CLINICAL RELEVANCE

This review demonstrates that RT improves muscle strength, some biochemical parameters, and quality of life of the HD patients.

Exercise limitation following transplantation

Organ transplantation is one of the medical miracles or the 20th century. It has the capacity to substantially improve exercise performance and quality of life in patients who are severely limited with chronic organ failure. We focus on the most commonly performed solid-organ transplants and describe peak exercise performance following recovery from transplantation. Across all of the common transplants, evaluated significant reduction in VO2peak is seen (typically renal and liver 65%-80% with heart and/or lung 50%-60% of predicted). Those with the lowest VO2peak pretransplant have the lowest VO2peak posttransplant. Overall very few patients have a VO2peak in the normal range. Investigation of the cause of the reduction of VO2peak has identified many factors pre- and posttransplant that may contribute. These include organ-specific factors in the otherwise well-functioning allograft (e.g., chronotropic incompetence in heart transplantation) as well as allograft dysfunction itself (e.g., chronic lung allograft dysfunction). However, looking across all transplants, a pattern emerges. A low muscle mass with qualitative change in large exercising skeletal muscle groups is seen pretransplant. Many factor posttransplant aggravate these changes or prevent them recovering, especially calcineurin antagonist drugs which are key immunosuppressing agents. This results in the reduction of VO2peak despite restoration of near normal function of the initially failing organ system. As such organ transplantation has provided an experiment of nature that has focused our attention on an important confounder of chronic organ failure-skeletal muscle dysfunction.

A patient with CKD and poor nutritional status

Protein energy wasting is common in patients with CKD and ESRD and is associated with adverse clinical outcomes, such as increased rates of hospitalization and death, in these patients. A multitude of factors can affect the nutritional and metabolic status of patients with CKD, including decreased dietary nutrient intake, catabolic effects of renal replacement therapy, systemic inflammation, metabolic and hormonal derangements, and comorbid conditions (such as diabetes and depression). Unique aspects of CKD also confound reliable assessment of nutritional status, further complicating management of this comorbid condition. In patients in whom preventive measures and oral dietary intake from regular meals cannot help them maintain adequate nutritional status, nutritional supplementation, administered orally, enterally, or parenterally, is effective in replenishing protein and energy stores. The advantages of oral nutritional supplements include proven efficacy, safety, and compliance. Anabolic steroids and exercise, with nutritional supplementation or alone, improve protein stores and represent potential additional approaches for the treatment of PEW. There are several emerging novel therapies, such as appetite stimulants, anti-inflammatory interventions, and anabolic agents.

Glomerular filtration rate after a 12-wk resistance exercise program with post-exercise protein ingestion in community dwelling elderly

OBJECTIVE

Increased protein intake and resistance exercise can be beneficial for maintenance of lean body mass (LBM) in older adults. However, these factors could also negatively affect renal function. We investigated changes in renal function after a 12-wk resistance exercise program combined with protein supplementation in community dwelling older adults.

METHODS

Patients (N = 237, 73.7 ± 5.7 y, 58.2% female) participated in a 12-wk resistance exercise program (3 times/wk) designed to increase strength and muscle mass of major muscle groups. Participants were randomly assigned to one of three dietary supplements consumed directly after training: whey protein drink (20 g whey protein, 20 g carbohydrates), milk protein drink (20 g milk protein, 20 g carbohydrates), or carbohydrate drink (40 g carbohydrates). Renal function was estimated as glomerular filtration rate (GFR, Cockcroft-Gault formula), and dietary intake was measured as 3-d-weighed food record at baseline and endpoint.

RESULTS

During the intervention, energy intake did not increase. Carbohydrate intake increased in the carbohydrate group and protein intake increased in the milk group, both approximately in accordance with the supplementation. In the whey group, protein intake did not increase, but carbohydrate intake did. GFR increased after the intervention (+4.4 mL/min/1.73 m2; P < 0.001), and the changes were similar in men and women or in the age quartiles. Changes in GFR at endpoint were not associated with LBM, dietary supplements, or total protein intake.

CONCLUSIONS

A 12-wk resistance exercise program combined with protein supplementation in community dwelling older adults does not negatively affect GFR. The supplementation had only minor effects on total dietary intake.

Physical Activity in the Prevention of Chronic Kidney Disease

Chronic kidney disease (CKD) is an important risk factor for cardiovascular disease (CVD) and mortality. The increase in CKD in recent decades has paralleled increases in obesity, diabetes, and the metabolic syndrome. Physical inactivity is a modifiable risk factor that may affect the development and course of CKD. It is well established that exercise training improves a number of metabolic factors, including blood pressure and insulin resistance, which would be expected to preserve renal function as well as lower CVD risk. Epidemiological studies have suggested that partaking in vigorous physical activity may protect against kidney disease. However, to date few studies have rigorously measured physical activity levels. Instead, investigators have relied on subjective measures of physical activity and patient recall. This is particularly problematic when attempting to capture low- and very-low-intensity physical activity and in quantifying sedentary behavior. Improvements in vascular endothelial function, insulin sensitivity, adipocytokine profiles, and oxidative stress likely mediate the benefits of physical activity on the kidney. While formal exercise recommendations have been published for diabetes and hypertension, guidelines regarding the optimal type, frequency, intensity and duration of physical activity for preventing CKD have yet to be formalized.