Exploring the impact of short daily haemodialysis on muscle strength and bone health in end-stage kidney disease patients

BACKGROUND

Short-daily haemodialysis (SDH) has been strongly recommended over conventional haemodialysis (CHD) for end-stage kidney disease patients, though few studies have directly compared the effects of these two haemodialysis (HD) modalities on clinical variables related to patient's health.

METHODS

We conducted a cross-sectional study in individuals undergoing HD, comparing epidemiological, clinical, metabolic, inflammatory, anthropometric, bone health/metabolism, and skeletal muscle function according to dialysis modality. One-hundred seventy-eight patients (20.8% females, 62 ± 2.5 years old), were analysed in this study, 86 (48%) of whom were undergoing CHD versus 92 (51%) who were undergoing SDH.

RESULTS

SDH patients had significantly higher serum albumin levels (3.93 vs. 3.66 g/dL, P < 0.0001) and higher Kt/v (2.6 vs. 2.38, P < 0.0001). SDH group presented a significantly lower number of erythropoietin-stimulating agents compared with CHD group (percentage: 53.3 vs. 83.7%, P < 0.0001) and had lower levels of serum phosphate (4.9 vs. 5.3 mg/dL, P = 0.004) and parathyroid hormone (PTH) (398.4 vs. 480.4 pg/mL, P < 0.001) compared with CHD patients. In terms of bone health and metabolism, SDH patients had significantly higher total BMD, femur BMD, lumbar BMD, and femoral neck BMD compared with CHD patients (all P < 0.05). SDH patients also had lower anti-osteogenic and inflammatory biomarkers, including FGF23, sclerostin, TNF, IL-18, IL-17a, and C-reactive peptide (all P < 0.05). CHD modality was demonstrated to be a risk factor for low BMD (odds ratio: 4.02; 95% CI: 1.59-10.2, P = 0.003). In terms of skeletal muscle function, SDH patients had significantly higher 6-minute walking test (444.6 vs. 424.9 m, P = 0.04) and higher fat-free mass (52.3 vs. 51.68 kg, P = 0.02) compared with CHD patients. Higher fat-free mass and handgrip strength were associated with a 34% and 23% lower risk of low BMD, respectively. SDH patients had lower levels of the uremic toxin asymmetric dimethyl-l-arginine (ADMA) (1.8 vs. 2.07 μM, P = 0.002) and fasting blood glucose (132.6 vs. 141.7 mg/dL, P < 0.02) than CHD group. SDH patients also displayed higher levels of haemoglobin when compared with CHD group (11.9 vs. 10.2 g/dL, P < 0.0001).

CONCLUSIONS

The present study improves our understanding of the relationship between dialysis modality and clinical variables that may influence HD patient's health. Grip strength and lean mass were positively correlated with bone mineral density in HD patients regardless of dialysis modality. SDH was associated with better bone mineral density, inflammatory profile, and skeletal muscle function when compared with CHD patients. These findings provide more evidence of the clinical benefits of SDH that should be explored in greater detail.

Muscle Sodium Accumulation in Kidney Failure: Physiological Impact and Mitigation Strategies

Skeletal muscle has recently been recognized as a nonosmotic sodium reservoir that buffers dietary sodium. The in-vivo quantification of muscle sodium is based on a novel technology, sodium magnetic resonance imaging. Studies using this technology have shown that muscle sodium accumulation may be a clinical complication of chronic kidney disease (CKD). This review aims to summarize existing evidence on muscle sodium accumulation in patients with CKD and to identify knowledge gaps and topics for further research. The literature examined in this review suggests that muscle sodium accumulation is associated with CKD progression and pathological conditions. However, the causalities between muscle sodium accumulation and its related pathological changes are still elusive mainly because it is still uncertain where and how sodium accumulates in the muscle. More research is needed to address these gaps and determine if muscle sodium is a new intervention target in CKD.

The effect of intradialytic exercise on calcium, phosphorus and parathyroid hormone: a randomized controlled trial

BACKGROUND

Patients with kidney failure experience derangements of circulating markers of mineral metabolism and dysregulation of skeletal and cardiovascular physiology which results in high mortality rate in these patients. This study aimed to evaluate the effect of intradialytic exercise on regulation of these abnormalities in patients receiving chronic hemodialysis (HD).

METHODS

In this randomized controlled trial conducted in an HD center in Iran, adult patients receiving chronic HD were randomized to intradialytic exercise (60 min) in the second hour of thrice weekly dialysis for 6 months (intervention) or no intradialytic exercise (control). The primary outcomes were serum calcium, serum phosphorous and parathyroid hormone levels. Secondary outcomes were serum alkaline phosphatase and calcium-phosphorous product.

RESULTS

The study included 44 participants randomized to intervention (n = 22) or control (n = 22). During the 6-month intervention period, significant between-group changes were observed in all primary and secondary outcomes between the intervention and control groups. Statistical analyses reveal a significant increase in serum calcium (P < 0.05) as well as a significant decrease in serum phosphorous, parathyroid hormone, alkaline phosphatase and calcium-phosphorous product (P < 0.05).

CONCLUSION

Intradialytic exercise performed for at least 60 min during thrice weekly dialysis sessions improves bone mineral metabolism in adult patients receiving HD. Further studies should focus on observing and comparing the effect of different types of exercise on bone mineral disorders and all-cause mortality in HD patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04916743, Registered on 08/06/2021. Registered trial name: The Effect of Intradialytic Exercise on Calcium, Phosphorous and Parathyroid Hormone: A Randomized Controlled Trial.

Patient Perspectives of Skeletal Muscle Cramping in Dialysis: A Focus Group Study

Key Points

This first step demonstrated content validity for a patient-reported outcome measure for skeletal muscle cramping in dialysis. This work lays the foundation for developing a patient-reported outcome measure for regulatory use to assess skeletal muscle cramping in people receiving dialysis.

Background

Skeletal muscle cramping is a common, painful, and debilitating symptom experienced by people receiving dialysis. Neither a standardized, patient-endorsed definition of skeletal muscle cramping nor full understanding of patients' perspectives of skeletal muscle cramping exist. We conducted focus groups, within a Kidney Health Initiative (KHI) project, to elicit skeletal muscle cramping experiences of people receiving dialysis as the basis for patient-reported outcome measure (PROM) development.

Methods

Eligible participants (English-speaking adults aged 18–85 years treated by dialysis and a skeletal muscle cramping episode within 30 days) were purposively recruited from a panel (L&E Research) of people receiving dialysis at home or in-center. Standard qualitative methods were used to conduct virtual 90-minute sessions discussing the following: skeletal muscle cramping clinical characteristics, participants' skeletal muscle cramping experiences, and feedback on a draft skeletal muscle cramping definition and a patient-facing conceptual model developed by the KHI project workgroup. We used qualitative thematic analysis.

Results

There were 20 diverse participants in three focus groups. Universally experienced skeletal muscle cramping attributes differed by dialysis setting in onset, worst pain rating, duration, and timing. Variably experienced attributes (applied to home and in-center dialysis) were gross and fine motor effect, sleep disruption, mood-related themes of fear, and annoyance/frustration/irritability. Avoidance/adaptive behaviors included reluctance or avoiding movement, adjusting what they ate or drink (e.g. , yellow mustard, pickles, pickle juice, and tonic water), heat application, massage, and cannabidiol use. The skeletal muscle cramping definition was endorsed, and insightful suggestions for conceptual model were collected.

Conclusions

This qualitative study of in-center and home patients' skeletal muscle cramping experiences identified universally and variably experienced attributes. The patient-endorsed skeletal muscle cramping definition can serve as a standard for assessment. These results provide the foundation to develop a PROM for regulatory use with people receiving maintenance dialysis who experience skeletal muscle cramping.

Advanced Glycation End Products and Inflammatory Cytokine Profiles in Maintenance Hemodialysis Patients After the Ingestion of a Protein-Dense Meal

OBJECTIVE

The goal of this investigation was to evaluate circulating and skeletal muscle inflammatory biomarkers between maintenance hemodialysis (MHD) and demographic-matched control subjects (CON) before and after ingestion of a protein-rich meal.

DESIGN AND METHODS

CON (n = 8; 50 ± 2 years; 31 ± 1 kg/m2) and MHD patients (n = 8; 56 ± 5 years; 32 ± 2 kg/m2) underwent a basal blood draw and muscle biopsy and serial blood draws after the ingestion of a mixed meal on a nondialysis day. Plasma advanced glycation end products (AGEs) and markers of oxidation were assessed via liquid chromatography-tandem mass spectrometry before and after the meal (+240 min). Circulating inflammatory cytokines and soluble receptors for AGE (sRAGE) isoforms (endogenous secretory RAGEs and cleaved RAGEs) were determined before and after the meal (+240 min). Basal muscle was probed for inflammatory cytokines and protein expression of related signaling components (RAGE, Toll-like receptor 4, oligosaccharyltransferase subunit 48, TIR-domain-containing adapter-inducing interferon-β, total IκBα, and pIκBα).

RESULTS

Basal circulating AGEs were 7- to 343-fold higher (P < .001) in MHD than those in CON, but only MG-H1 increased in CON after the meal (P < .001). There was a group effect (MHD > CON) for total sRAGEs (P = .02) and endogenous secretory RAGEs (P < .001) and a trend for cleaved RAGEs (P=.09), with no meal effect. In addition, there was a group effect (MHD < CON; P < .05) for circulating fractalkine, interleukin (IL)10, IL17A, and IL1β and a trend (P < .10) for IL6 and macrophage inflammatory protein 1 alpha, whereas tumor necrosis factor alpha was higher in MHD (P < .001). In muscle, Toll-like receptor 4 (P = .03), TIR-domain-containing adapter-inducing interferon-β (P = .002), and oligosaccharyltransferase subunit 48 (P = .02) expression was lower in MHD than that in CON, whereas IL6 was higher (P = .01) and IL8 (P = .08) tended to be higher in MHD.

CONCLUSION

Overall, MHD exhibited an exaggerated, circulating, and skeletal muscle inflammatory biomarker environment, and the meal did not appreciably affect the inflammatory status.

Subjective Thirst in Relation to Interdialytic Weight Gain: A Systematic Review of Observational Studies

INTRODUCTION

Hemodialysis (HD) patients are often prescribed salt and fluid-restricted diets to reduce their interdialytic weight gain (IDWG) and prevent chronic volume overload and hypertension. However, adherence to fluid restrictions is poor, which may be due to HD patients' excessive thirst. The purpose of the review is to explore the association between HD patients' subjective thirst and IDWG, which may inform strategies to manage chronic volume overload.

METHODS

We conducted the literature search in Web of Science, Cumulative Index to Nursing and Allied Health Literature, PubMed, and the Cochrane Library, until February 25, 2019. Studies performing statistical tests to assess the association between patients' subjective thirst and IDWG were included.

RESULTS

A total of eighteen studies were included in the systematic review, which measured the relationship between patients' subjective thirst and IDWG. Among them, 14 studies found that different domains of thirst and different units of IDWG are positively associated. Therefore, there is a positive association between the patients' subjective thirst and IDWG. However, the findings should be interpreted cautiously as there was variability in thirst and IDWG measurement techniques, which might influence the estimated relationship in these studies.

DISCUSSION/CONCLUSION

These data suggest that strategies are needed to reduce thirst to control IDWG in HD patients.

Conceptual Framework for Patient-Reported Outcome Measures in Clinical Trials of Skeletal Muscle Cramping Experienced in Dialysis: A Kidney Health Initiative Workgroup Report

Skeletal muscle cramping is a common and bothersome symptom for patients on maintenance dialysis therapy, regardless of modality, and it has not been prioritized for innovative assessments or treatments. Research to prevent or treat skeletal muscle cramping in patients receiving dialysis is hindered by poorly understood pathophysiology, lack of an accepted definition, and the absence of a standardized measurement method. The Kidney Health Initiative, a public-private partnership between the American Society of Nephrology and US Food and Drug Administration, convened a multidisciplinary workgroup to define a set of patient-reported outcome measures for use in clinical trials to test the effect of new dialysis devices, new KRTs, lifestyle/behavioral modifications, and medications on skeletal muscle cramping. Upon determining that foundational work was necessary, the workgroup undertook a multistep process to elicit concepts central to developing the basis for demonstrating content validity of candidate patient-reported outcome measures for skeletal muscle cramping in patients on dialysis. The workgroup sought to (1) create an accepted, patient-endorsed definition for skeletal muscle cramping that applies to all dialysis modalities, (2) construct a conceptual model for developing and evaluating a skeletal muscle cramping-specific patient-reported outcome measure, and (3) identify potential questions from existing patient-reported outcome measures that could be modified or adapted and subsequently tested in the dialysis population. We report the results of the workgroup's efforts, provide our recommendations, and issue a call to action to address the gaps in knowledge and research needs we identified. These action steps are urgently needed to quantify skeletal muscle cramping burden, assess the effect, and measure meaningful changes of new interventions to improve the experience of patients receiving dialysis and suffering from skeletal muscle cramping.

Exercise in Dialysis: Ready for Prime Time?

It is widely acknowledged that patients with end-stage kidney disease receiving maintenance hemodialysis (HD) may benefit from increasing their physical activity levels. Decades of exercise-related clinical trials have demonstrated improvements in various metrics related to dialysis patient's health and quality of life. Yet, the implementation of exercise programs in dialysis clinics today is scarce, and physical inactivity and dysfunction remain a hallmark of the disease. To address this issue, many groups worldwide are beginning to rethink how physical activity and exercise are prescribed in HD patients, as well as how to evaluate the efficacy of these programs. The vast majority of exercise interventions in HD patients have included intradialytic cycling as the predominant or only exercise prescription. Moreover, efficacy has most often been evaluated using standard measures of strength, physical function, and/or traditional cardiovascular disease risk factors (e.g., blood pressure, lipids, etc.). More recently, there has been a greater emphasis on novel intervention approaches that are focused on providing patients with a greater variety of options for exercise and enhanced motivational tools. The benefits of exercise on patient reported outcome measures (PROMs) and other clinically important outcomes are also becoming more prevalent. The purpose of this review was to: (1) critically review the data from several recently published large randomized clinical trials of exercise in HD patients, (2) discuss some of the novel approaches that groups across the world are taking to improve implementation and efficacy of exercise-related interventions in HD, and (3) discuss policy prescriptions that may be needed to continue improving exercise prescriptions for this critically ill patient population. While it may be too early to declare that exercise in dialysis is ready for prime time, exciting advances have been made in recent years, yet more work is needed to realize its full potential.

Global Policy Barriers and Enablers to Exercise and Physical Activity in Kidney Care

OBJECTIVE

Impairment in physical function and physical performance leads to decreased independence and health-related quality of life in people living with chronic kidney disease and end-stage kidney disease. Physical activity and exercise in kidney care are not priorities in policy development. We aimed to identify global policy-related enablers, barriers, and strategies to increase exercise participation and physical activity behavior for people living with kidney disease.

DESIGN AND METHODS

Guided by the Behavior Change Wheel theoretical framework, 50 global renal exercise experts developed policy barriers and enablers to exercise program implementation and physical activity promotion in kidney care. The consensus process consisted of developing themes from renal experts from North America, South America, Continental Europe, United Kingdom, Asia, and Oceania. Strategies to address enablers and barriers were identified by the group, and consensus was achieved.

RESULTS

We found that policies addressing funding, service provision, legislation, regulations, guidelines, the environment, communication, and marketing are required to support people with kidney disease to be physically active, participate in exercise, and improve health-related quality of life. We provide a global perspective and highlight Japanese, Canadian, and other regional examples where policies have been developed to increase renal physical activity and rehabilitation. We present recommendations targeting multiple stakeholders including nephrologists, nurses, allied health clinicians, organizations providing renal care and education, and renal program funders.

CONCLUSIONS

We strongly recommend the nephrology community and people living with kidney disease take action to change policy now, rather than idly waiting for indisputable clinical trial evidence that increasing physical activity, strength, fitness, and function improves the lives of people living with kidney disease.

Depressive Disorders Are Associated With Risk of Falls in People With Chronic Kidney Disease

OBJECTIVES

People with chronic kidney disease (CKD) are at increased risk for falls and fall-related injuries. Depressive disorders (DEP) are common in individuals with CKD and may increase the risk of falls and fall-related injuries. However, not much is known about the relationship between DEP and falls in people with CKD. The purpose of this study was to determine the influence of DEP on the relationship between CKD, falls, and fall-related injuries.

METHOD

Using the Behavioral Risk Factor Surveillance System, we identified 16,574 adults with CKD. Patients with CKD were stratified by history of self-reported DEP (SRDEP), and multivariate logistic regression was conducted to determine the odds for falls and fall-related injuries among those with and without SRDEP.

RESULTS

In unadjusted regression analysis, falls (OR = 2.40, 95% CI = 2.08-2.76) and fall-related injuries (OR = 2.12, 95% CI = 1.72-2.59) were higher in individuals with CKD and history of SRDEP compared to those with CKD and no history of SRDEP. Adjustment for confounders had little effect on the relationship between a history of SRDEP and either falls (AOR = 1.87, 95% CI = 1.60-2.19) or fall-related injuries (AOR = 1.58, 95% CI = 1.26-1.97).

CONCLUSIONS

People with CKD and DEP are at increased odds for falls and fall-related injuries even after adjustment for sociodemographic, lifestyle factors, and comorbidities. Prospective studies are warranted to further understand this relationship, but it may be prudent for clinicians, in particular nurses, to consider fall risk when treating DEP in patients with CKD.

A Comparison of Dietary Intake Between Individuals Undergoing Maintenance Hemodialysis in the United Kingdom and China

OBJECTIVE

Protein-energy wasting is highly prevalent in people with end-stage kidney disease receiving regular hemodialysis. Currently, it is unclear what the optimal nutritional recommendations are, which is further complicated by differences in dietary patterns between countries. The aim of the study was to understand and compare dietary intake between individuals receiving hemodialysis in Leicester, UK and Nantong, China.

METHODS

The study assessed 40 UK and 44 Chinese participants' dietary intake over a period of 14 days using 24-hour diet recall interviews. Nutritional blood parameters were obtained from medical records. Food consumed by participants in the UK and China was analyzed using the Nutritics and Nutrition calculator to quantify nutritional intake.

RESULTS

Energy and protein intake were comparable between UK and Chinese participants, but with both below the recommended daily intake. Potassium intake was higher in UK participants compared to Chinese participants (2,115 [888] versus 1,159 [861] mg/d; P < .001), as was calcium (618 [257] versus 360 [312] mg/d; P < .001) and phosphate intake (927 [485] versus 697 [434] mg/d; P = .007). Vitamin C intake was lower in UK participants compared to their Chinese counterparts (39 [51] versus 64 [42] mg/d; P = .024). Data are reported here as median (interquartile range).

CONCLUSION

Both UK and Chinese hemodialysis participants have insufficient protein and energy in their diet. New strategies are required to increase protein and energy intakes. All participants had inadequate daily intake of vitamins C and D; there may well be a role in the oral supplementation of these vitamins, and further studies are urgently needed.

OUP accepted manuscript

Patients on chronic hemodialysis are counseled to reduce dietary sodium intake to limit their thirst and consequent interdialytic weight gain (IDWG), chronic volume overload and hypertension. Low-sodium dietary trials in hemodialysis are sparse and mostly indicate that dietary education and behavioral counseling are ineffective in reducing sodium intake and IDWG. Additional nutritional restrictions and numerous barriers further complicate dietary adherence. A low-sodium diet may also reduce tissue sodium, which is positively associated with hypertension and left ventricular hypertrophy. A potential alternative or complementary approach to dietary counseling is home delivery of low-sodium meals. Low-sodium meal delivery has demonstrated benefits in patients with hypertension and congestive heart failure but has not been explored or implemented in patients undergoing hemodialysis. The objective of this review is to summarize current strategies to improve volume overload and provide a rationale for low-sodium meal delivery as a novel method to reduce volume-dependent hypertension and tissue sodium accumulation while improving quality of life and other clinical outcomes in patients undergoing hemodialysis.

Effect of Dietary Inulin Supplementation on the Gut Microbiota Composition and Derived Metabolites of Individuals Undergoing Hemodialysis: A Pilot Study

OBJECTIVE

The prebiotic fiber inulin has been studied in individuals undergoing hemodialysis (HD) due to its ability to reduce gut microbiota-derived uremic toxins. However, studies examining the effects of inulin on the gut microbiota and derived metabolites are limited in these patients. We aimed to assess the impact of a 4-week supplementation of inulin on the gut microbiota composition and microbial metabolites of patients on HD.

DESIGN AND METHODS

In a randomized, double-blind, placebo-controlled, crossover study, twelve HD patients (55 ± 10 y, 50% male, 58% Black American, BMI 31.6 ± 8.9 kg/m2, 33% diabetes mellitus) were randomized to consume inulin [10 g/d for females; 15 g/d for males] or maltodextrin [6 g/d for females; 9 g/d for males] for 4 weeks, with a 4-week washout period. We assessed the fecal microbiota composition, fecal metabolites (short-chain fatty acids (SCFA), phenols, and indoles), and plasma indoxyl sulfate and p-cresyl sulfate.

RESULTS

At baseline, factors that explained the gut microbiota variability included BMI category and type of phosphate binder prescribed. Inulin increased the relative abundance of the phylum Verrucomicrobia and its genus Akkermansia (P interaction = 0.045). Inulin and maltodextrin resulted in an increased relative abundance of the phylum Bacteroidetes and its genus Bacteroides (P time = 0.04 and 0.03, respectively). Both treatments increased the fecal acetate and propionate (P time = 0.032 and 0.027, respectively), and there was a trend toward increased fecal butyrate (P time = 0.06). Inulin did not reduce fecal p-cresol or indoles, or plasma concentrations of p-cresyl sulfate or indoxyl sulfate.

CONCLUSIONS

A 4-week supplementation of inulin did not lead to major shifts in the fecal microbiota and gut microbiota-derived metabolites. This may be due to high variability among participants and an unexpected increase in fecal excretion of SCFA with maltodextrin. Larger studies are needed to determine the effects of prebiotic fibers on the gut microbiota and clinical outcomes to justify their use in patients on HD.

Physical Activity and Health in Chronic Kidney Disease

Clinical Background and Epidemiology: Low physical activity is a common phenotype in individuals living with chronic kidney disease (CKD). It increases as renal function declines and is associated with adverse clinical outcomes and a poor quality of life (QOL). Both behavioral and disease-related factors contribute to the low physical activity levels in CKD. CKD has profound negative effects on skeletal muscle structure and function that are related to impairments in mitochondrial function, inflammation, oxidative stress, metabolic acidosis, and other uremia-related factors. These factors promote muscle protein catabolism and wasting, and impair strength, physical performance, and cardiorespiratory fitness. Moreover, the high burden of comorbid disease contributes to patient fatigue, fear of injury, and poor exercise self-efficacy. All of these factors reinforce patient's sedentary behavior, leading to a vicious cycle of disease and disability that further compromises their health and QOL. Data from both observational studies and exercise interventions indicate that increasing levels of physical activity may provide a range of benefits in CKD patients, including attenuating declines in renal function, and improving markers of physical function, cardiovascular disease risk, and QOL. Unfortunately, these results have not led to widespread implementation of exercise programs in CKD, and physical inactivity and poor physical function remain hallmarks of the disease worldwide. Challenges and Solutions: There are many frequently cited barriers to implementing exercise programs in CKD. These include: a lack of training and knowledge about physical activity/exercise prescriptions and interventions among health professionals; inadequate time to implement exercise programs due to other clinical responsibilities; a lack of specific funding and incentives to develop these programs; and a poor quality of the data demonstrating efficacy of exercise. Many CKD patients also are unmotivated to incorporate exercise into their daily lives due to time constraints, depression, and other comorbid diseases, and poor self-efficacy for exercise. Given these barriers, it is not surprising that physical activity/exercise programs have not become a component of standard of care for CKD patients. We discuss several potential solutions to address these barriers, including: (1) providing better education and training for healthcare professionals who provide exercise advise and counselling to individuals with CKD; (2) providing incentives to reimburse payers to develop and maintain exercise programs in CKD; and (3) providing more personalized approaches to exercise prescription and implementation of exercise programs that consider the unique circumstances of individual CKD patients. In summary, low physical activity levels in CKD patients result from a combination of many factors that adversely impact patient's health and QOL. Addressing this problem will require comprehensive intervention strategies that consider both the unique pathophysiology of CKD and the individual circumstances of those living with the disease.

Association between physical activity and mortality in end-stage kidney disease: a systematic review of observational studies

BACKGROUND

End-stage Kidney Disease patients have a high mortality and hospitalization risk. The association of these outcomes with physical activity is described in the general population and in other chronic diseases. However, few studies examining this association have been completed in end-stage Kidney Disease patients, raising the need to systematically review the evidence on the association of physical activity with mortality and hospitalization in this population.

METHODS

Electronic databases (EBSCO, Scopus and Web of Science) and hand search were performed until March 2020 for observational studies reporting the association of physical activity with mortality or hospitalization in adult end-stage Kidney Disease patients on renal replacement therapy (hemodialysis, peritoneal dialysis and kidney transplant). Methodological quality of the included studies was assessed using the Quality in Prognosis Studies tool. The review protocol was registered in PROSPERO (CRD42020155591).

RESULTS

Eleven studies were included: six in hemodialysis, three in kidney transplant, and two in hemodialysis and peritoneal dialysis patients. Physical activity was self-reported, except in one study that used accelerometers. All-cause mortality was addressed in all studies and cardiovascular mortality in three studies. Nine studies reported a significant reduction in all-cause mortality with increased levels of physical activity. Evidence of a dose-response relationship was found. For cardiovascular mortality, a significant reduction was observed in two of the three studies. Only one study investigated the association of physical activity with hospitalization.

CONCLUSIONS

Higher physical activity was associated with reduced mortality in end-stage Kidney Disease patients. Future studies using objective physical activity measures could strengthen these findings. The association of physical activity with hospitalization should be explored in future investigations.

Anabolic Resistance of Muscle Protein Turnover Comes in Various Shapes and Sizes

Anabolic resistance is defined by a blunted stimulation of muscle protein synthesis rates (MPS) to common anabolic stimuli in skeletal muscle tissue such as dietary protein and exercise. Generally, MPS is the target of most exercise and feeding interventions as muscle protein breakdown rates seem to be less responsive to these stimuli. Ultimately, the blunted responsiveness of MPS to dietary protein and exercise underpins the loss of the amount and quality of skeletal muscle mass leading to decrements in physical performance in these populations. The increase of both habitual physical activity (including structured exercise that targets general fitness characteristics) and protein dense food ingestion are frontline strategies utilized to support muscle mass, performance, and health. In this paper, we discuss anabolic resistance as a common denominator underpinning muscle mass loss with aging, obesity, and other disease states. Namely, we discuss the fact that anabolic resistance exists as a dimmer switch, capable of varying from higher to lower levels of resistance, to the main anabolic stimuli of feeding and exercise depending on the population. Moreover, we review the evidence on whether increased physical activity and targeted exercise can be leveraged to restore the sensitivity of skeletal muscle tissue to dietary amino acids regardless of the population.

Muscle-Bone Crosstalk in Chronic Kidney Disease: The Potential Modulatory Effects of Exercise

Chronic kidney disease (CKD) is a prevalent worldwide public burden that increasingly compromises overall health as the disease progresses. Two of the most negatively affected tissues are bone and skeletal muscle, with CKD negatively impacting their structure, function and activity, impairing the quality of life of these patients and contributing to morbidity and mortality. Whereas skeletal health in this population has conventionally been associated with bone and mineral disorders, sarcopenia has been observed to impact skeletal muscle health in CKD. Indeed, bone and muscle tissues are linked anatomically and physiologically, and together regulate functional and metabolic mechanisms. With the initial crosstalk between the skeleton and muscle proposed to explain bone formation through muscle contraction, it is now understood that this communication occurs through the interaction of myokines and osteokines, with the skeletal muscle secretome playing a pivotal role in the regulation of bone activity. Regular exercise has been reported to be beneficial to overall health. Also, the positive regulatory effect that exercise has been proposed to have on bone and muscle anatomical, functional, and metabolic activity has led to the proposal of regular physical exercise as a therapeutic strategy for muscle and bone-related disorders. The detection of bone- and muscle-derived cytokine secretion following physical exercise has strengthened the idea of a cross communication between these organs. Hence, this review presents an overview of the impact of CKD in bone and skeletal muscle, and narrates how these tissues intrinsically communicate with each other, with focus on the potential effect of exercise in the modulation of this intercommunication.

Mindfulness-based Virtual Reality Intervention in Hemodialysis Patients: A Pilot Study on End-user Perceptions and Safety

Background

Virtual reality (VR) is an evolving technology that is becoming a common treatment for pain management and psychologic phobias. Although nonimmersive devices (e.g., the Nintendo Wii) have been previously tested with patients on hemodialysis, no studies to date have used fully immersive VR as a tool for intervention delivery. This pilot trial tests the initial safety, acceptability, and utility of VR during maintenance hemodialysis treatment sessions-particularly, whether VR triggers motion sickness that mimics or negatively effects treatment-related symptoms (e.g., nausea).

Methods

Patients on hemodialysis (n=20) were enrolled in a phase 1 single-arm proof-of-concept trial. While undergoing hemodialysis, participants were exposed to our new Joviality VR program. This 25-minute program delivers mindfulness training and guided meditation using the Oculus Rift head-mounted display. Participants experienced the program on two separate occasions. Before and immediately after exposure, participants recorded motion-related symptoms and related discomfort on the Simulator Sickness Questionnaire. Utility measures included the end-user's ability to be fully immersed in the virtual space, interact with virtual objects, find hardware user friendly, and easily navigate the Joviality program with the System Usability Scale.

Results

Mean age was 55.3 (±13.1) years; 80% male; 60% Black; and mean dialysis vintage was 3.56 (±3.75) years. At the first session, there were significant decreases in treatment and/or motion-related symptoms after VR exposure (22.6 versus 11.2; P=0.03); scores >20 indicate problematic immersion. Hemodialysis end-users reported high levels of immersion in the VR environment and rated the software easy to operate, with average System Usability Scale scores of 82.8 out of 100.

Conclusions

Patients on hemodialysis routinely suffer from fatigue, nausea, lightheadedness, and headaches that often manifest during their dialysis sessions. Our Joviality VR program decreased symptom severity without adverse effects. VR programs may be a safe platform to improve the experience of patients on dialysis.

Working on Wellness: Impact of a Pilot Workplace Wellness Program in a Hemodialysis Center

This article describes the impact of a 12-week workplace wellness program on staff (n = 14) of an outpatient hemodialysis center. The program focused on decreasing dietary sodium and increasing habitual physical activity. The average systolic and diastolic blood pressure of participants decreased by 16.9±21.6 mmHg (p < 0.05) and 4.1±14.0 mmHg (p < 0.05), and body weight decreased by 2.7±1.9kg (p < 0.05). The mean step count at baseline was 7,052±3,278 but increased to 10,388±2,882 (p < 0.05) during a walking challenge. There was a reduction in self-reported barriers to making healthy nutritional changes (p < 0.05) and engaging in habitual physical activity (p < 0.05). Our pilot findings suggest that workplace wellness programs in hemodialysis centers are feasible and effective.

An International Delphi Survey on Exercise Priorities in CKD

Introduction

Defining the role of exercise in chronic kidney disease (CKD) is a top research priority for people with CKD. We aimed to achieve consensus on specific research priorities in exercise and CKD among an international panel of stakeholders.

Methods

Using the Delphi method, patients/caregivers, researchers, clinicians, and policymakers submitted their top research priorities in round 1 and ranked their importance in rounds 2 and 3 using a 9-point Likert scale. The mean, median, and proportion of scores ranked 7 to 9 were calculated. Consensus was defined as priorities that scored above the overall mean and median score within each stakeholder panel. Qualitative description was used to understand participants’ rankings.

Results

Seventy participants (78% response) completed round 1: 15 (21.4%) clinicians, 33 (47.1%) researchers, 13 (18.6%) policymakers, and 9 (12.9%) patients; (85.7%) completed round 3. The top research priorities were defining exercise-related outcomes meaningful to patients, identifying patients’ motivation and perspective towards exercise, understanding the effect of exercise on the risk of institutionalization, mortality, and mobility, and understanding the effect of pre- and post-transplant exercise on postoperative recovery. Themes from the qualitative analysis were individualization, personal experience, and holistic approach to exercise (patients), the need to address common clinical problems (clinicians), developing targeted interventions (researchers), and the importance of evidence-based development versus implementation (policymakers).

Conclusions

Preventing physical disability was a common priority. Policymakers emphasized that more efficacy studies were needed. Other panels expressed the need for holistic and targeted exercise interventions and for outcomes that address common clinical problems.

Pilot study to reduce interdialytic weight gain by provision of low-sodium, home-delivered meals in hemodialysis patients

INTRODUCTION

Patients with kidney failure undergoing maintenance hemodialysis (HD) therapy are routinely counseled to reduce dietary sodium intake to ameliorate sodium retention, volume overload, and hypertension. However, low-sodium diet trials in HD are sparse and indicate that dietary education and behavioral counseling are ineffective in reducing sodium intake. This study aimed to determine whether 4 weeks of low-sodium, home-delivered meals in HD patients reduces interdialytic weight gain (IDWG). Secondary outcomes included changes in dietary sodium intake, thirst, xerostomia, blood pressure, volume overload, and muscle sodium concentration.

METHODS

Twenty HD patients (55 ± 12 years, body mass index [BMI] 40.7 ± 16.6 kg/m² ) were enrolled in this study. Participants followed a usual (control) diet for the first 4 weeks followed by 4 weeks of three low-sodium, home-delivered meals per day. We measured IDWG, hydration status (bioimpedance), standardized blood pressure (BP), food intake (3-day dietary recall), and muscle sodium (magnetic resonance imaging) at baseline (0 M), after the 4-week period of usual diet (1 M), and after the meal intervention (2 M).

FINDINGS

The low-sodium meal intervention significantly reduced IDWG when compared to the control period (-0.82 ± 0.14 kg; 95% confidence interval, -0.55 to -1.08 kg; P < 0.001). There were also 1 month (1 M) to 2 month (2 M) reductions in dietary sodium intake (-1687 ± 297 mg; P < 0.001); thirst score (-4.4 ± 1.3; P = 0.003), xerostomia score (-6.7 ± 1.9; P = 0.002), SBP (-18.0 ± 3.6 mmHg; P < 0.001), DBP (-5.9 ± 2.0 mmHg; P = 0.008), and plasma phosphorus -1.55 ± 0.21 mg/dL; P = 0.005), as well as a 0 M to 2 M reduction in absolute volume overload (-1.08 ± 0.33 L; P = 0.025). However, there were no significant changes in serum or tissue sodium (all P > 0.05).

DISCUSSION

Low-sodium, home-meal delivery appears to be an effective method for improving volume control and blood pressure in HD patients. Future studies with larger sample sizes are needed to examine the long-term effects of home-delivered meals on these outcomes and to assess cost-effectiveness.

Integrin-associated ILK and PINCH1 protein content are reduced in skeletal muscle of maintenance haemodialysis patients

KEY POINTS

Patients with renal failure undergoing maintenance haemodialysis are associated with insulin resistance and protein metabolism dysfunction. Novel research suggests that disruption to the transmembrane protein linkage between the cytoskeleton and the extracellular matrix in skeletal muscle may contribute to reduced amino acid metabolism and insulin resistance in haemodialysis. ILK, PINCH1 and pFAK^Tyr397 were significantly decreased in haemodialysis compared to controls, whereas Rac1 and Akt2 showed no different between groups. Rac1 deletion in the Rac1 knockout model did not alter the expression of integrin-associated proteins. Phenylalanine kinetics were reduced in the haemodialysis group at 30 and 60 min post meal ingestion compared to controls; both groups showed similar levels of insulin sensitivity and β-cell function. Key proteins in the integrin-cytoskeleton linkage are reduced in haemodialysis patients, suggesting for the first time that integrin-associated proteins dysfunction may contribute to reduced phenylalanine flux without affecting insulin resistance in haemodialysis patients.

ABSTRACT

Muscle atrophy, insulin resistance and reduced muscle phosphoinositide 3-kinase-Akt signalling are common characteristics of patients undergoing maintenance haemodialysis (MHD). Disruption to the transmembrane protein linkage between the cytoskeleton and the extracellular matrix in skeletal muscle may contribute to reduced amino acid metabolism and insulin resistance in MHD patients. Eight MHD patients (age: 56 ± 5 years: body mass index: 32 ± 2 kg m^-2 ) and non-diseased controls (age: 50 ± 2 years: body mass index: 31 ± 1 kg m^-2 ) received primed continuous l-[ring-² H₅ ]phenylalanine before consuming a mixed meal. Phenylalanine metabolism was determined using two-compartment modelling. Muscle biopsies were collected prior to the meal and at 300 min postprandially. In a separate experiment, skeletal muscle tissue from muscle-specific Rac1 knockout (Rac1 mKO) was harvested to investigate whether Rac1 depletion disrupted the cytoskeleton-integrin linkage, allowing for cross-model examination of proteins of interest. ILK, PINCH1 and pFAK^Tyr397 were significantly lower in MHD (P < 0.01). Rac1 and Akt showed no difference between groups for the human trial. Rac1 deletion in the Rac1 mKO model did not alter the expression of integrin-associated proteins. Phenylalanine rates of appearance and disappearance, as well as metabolic clearance rates, were lower in the MHD group at 30 and 60 min post meal ingestion compared to controls (P < 0.05). Both groups showed similar levels of insulin sensitivity and β-cell function. Key proteins in the integrin-cytoskeleton linkage are reduced in MHD patients, suggesting for the first time that integrin-associated proteins dysfunction may contribute to reduced phenylalanine flux without affecting insulin resistance in haemodialysis patients.

A Critical Review of Exercise Training in Hemodialysis Patients: Personalized Activity Prescriptions Are Needed

Exercise training appears to have modest or inconsistent benefits in hemodialysis patients. This may be due to the low volume and intensity of exercise often prescribed. To address this, research is needed to evaluate the efficacy of individualized exercise prescriptions as a component of a comprehensive lifestyle intervention strategy that gives patients more autonomy to choose preferred types of physical activity.

Pilot feasibility study examining the effects of a comprehensive volume reduction protocol on hydration status and blood pressure in hemodialysis patients

INTRODUCTION

Chronic volume overload is a persistent problem in hemodialysis (HD) patients. The purpose of this study was to investigate the impacts of comprehensive volume reduction protocol on HD patient's hydration status and blood pressure (BP).

METHODS

Twenty-three HD patients (age = 55.7 ± 13.3 years) completed a 6-month comprehensive volume control protocol consisting of: reducing postdialysis weight; reducing BP medication prescriptions; and weekly intradialytic counseling to reduce dietary sodium intake and interdialytic weight gain (IDWG). The primary outcome was volume overload (VO) measured by bioelectrical impedance spectroscopy. Secondary outcomes included: IDWG, postdialysis weight, estimated dry weight (EDW), dietary sodium intake, BP and BP medication prescriptions.

FINDINGS

From baseline (0M) to 6 months (6M), significant improvements were noted in: VO (0M 3.9 ± 3.9 L vs. 6M 2.6 ± 3.4 L, P = 0.003), postdialysis weight (0M 89.4 ± 23.1 kg vs. 6M 87.6 ± 22.2 kg; P = 0.012), and EDW (0M 89.0 ± 23.2 vs. 6M 86.7 ± 22.5 kg., P = 0.009). There was also a trend for a reduction in monthly averaged IDWG (P = 0.053), and sodium intake (0M 2.9 ± 1.6 vs. 6M 2.3 ± 1.1 g/d, P = 0.125). Neither systolic BP (0M 162 ± 27 vs. 6M 157 ± 23 mmHg, P = 0.405) nor diastolic BP (0M 82 ± 21 vs. 6M 82 ± 19 mmHg, P = 0.960) changed, though there was a significant reduction in the total number of BP medications prescribed (0M 3.0 ± 1.0 vs. 6M 1.5 ± 1.0 BP meds; P = 0.004).

DISCUSSION

Our volume reduction protocol significantly improved HD patient's hydration status. While BP did not change, the reduction in prescribed BP medication number suggests improved BP control. Despite these overall positive findings, the magnitude of change in most variables was modest. Comprehensive changes in HD clinics may be necessary to realize more clinically significant results.

Reply to Comments: Comparison of Methods Study between a Photonic Crystal Biosensor and Certified ELISA to Measure Biomarkers of Iron Deficiency in Chronic Kidney Disease Patients

In this brief note, we respond to the comments made by Dr [...].

A Comparison of Intradialytic versus Out-of-Clinic Exercise Training Programs for Hemodialysis Patients

BACKGROUND

Physical inactivity is prevalent and linked with a variety of unfavorable clinical outcomes in hemodialysis patients. To increase physical activity (PA) and improve quality of life in this population, intradialytic and out-of-clinic exercise interventions have been implemented in many studies. However, there is still a lack of consensus in the literature on which type of exercise intervention is more feasible and effective.

SUMMARY

This review provides a brief overview of intradialytic and out-of-clinic exercise protocols utilized in previous studies. We also examine data related to the feasibility of each approach, and their efficacy for improving cardiovascular health, muscle mass, strength, and physical function. Key Messages: The benefits from most intradialytic and out-of-center exercise training interventions published to date have been modest or inconsistent. Furthermore, neither appears to provide a significant advantage over the other in terms of benefits for cardiovascular health, muscle mass, strength, and physical function. A significant concern is that most intradialytic and out-of-center exercise interventions are mandated exercise prescriptions that include either endurance or resistance training exercises, performed at low-moderate intensities, for a total of 60-135 min of exercise/week. This volume, intensity, and variety of exercise are far less than what is recommended in most PA guidelines. This type of structured activity is also boring for most patients. To enhance the effectiveness of exercise interventions, we suggest using the intradialytic period to provide patients guidance on how they can best incorporate more activity into their lives, based on their individual needs and barriers.

Managing Hyperkalemia: Another Benefit of Exercise in People With Chronic Kidney Disease?

People with chronic kidney disease (CKD) are at increased risk of hyperkalemia, an electrolyte abnormality that can cause serious, sometimes fatal, cardiac arrhythmias. Muscle contraction causes potassium to be released from cells, increasing serum potassium concentrations. However, these effects are transient, and the long-term impact of exercise training on hyperkalemia risk in CKD patients is largely unknown. In this review, we examine the effects of exercise on factors affecting potassium balance in people with CKD, highlighting the potential benefits of regular exercise on hyperkalemia risk in this population. Although regular exercise is already recommended for people with CKD, research examining this hypothesis may lead to novel therapeutic treatments for this life-threatening condition.

Effect of Oral Nutritional Supplementation With and Without Exercise on Nutritional Status and Physical Function of Adult Hemodialysis Patients: A Parallel Controlled Clinical Trial (AVANTE-HEMO Study)

OBJECTIVE

Protein energy wasting affects the nutritional status (NS) and physical function (PF) of dialysis patients. Among the different anabolic strategies to improve NS and PF, oral nutritional supplementation (ONS) and resistance exercise (RE) or aerobic exercise (AE) have been shown to be effective. Nevertheless, the combination of both anabolic strategies has not been completely evaluated. The aim of this study is to assess the effect of exercise combined with ONS versus ONS without exercise during hemodialysis sessions on PF and NS indicators.

METHODS

Young hemodialysis patients (29 ± 9.3 years) with predominantly unknown causes of renal disease (80%) were divided into the following 3 groups during a period of 12 weeks: (1) ONS (n = 15), (2) ONS + RE (n = 15), and (3) ONS + AE (n = 15). Anthropometric, biochemical, PF, and quality of life measurements were recorded at baseline and after 3 months. Repeated measures analysis of variance and effect sizes (Cohen's d) were used to assess the effect of exercise and nutrition (ISRCTN registry 10251828).

RESULTS

At the completion of the study, the ONS and ONS + RE groups exhibited statistically significant increases in body weight, body mass index, and in the percentage of fat mass (P < .05); the greatest effect sizes were observed in the ONS + RE group (d = 0.30 for body weight, d = 0.63 for body mass index, and d = 0.90 for the percentage of fat mass). Groups with RE and AE had statistically significant increases and large effect sizes in the six-minute walk test (RE: d = 0.94, P = .02; AE: d = 1.11, P = .03), sit-to-stand test (RE: d = 0.81, P = .041; AE: d = 1.20, P = .002), timed up and go test (RE: d = 1.04, P = .036; AE: d = 1.6, P = .000), and muscle strength (RE: d = 1.01, P = .000; AE: d = 0.60, P = .003). Regarding quality of life, the ONS + RE group had more areas of improvement at the end of the study, followed by the ONS + AE group. No statistically significant differences were found in the repeated measures ANOVA.

CONCLUSIONS

The combination of exercise with ONS had larger effects on PF than on ONS alone. Further studies to examine the impact of exercise on the effect of oral nutritional supplementation in dialysis patients are indicated.

The association of positive affect and cardiovascular health in Hispanics/Latinos with chronic kidney disease: Results from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

The beneficial influence of positive affect (e.g., joy) remains unexplored in relation to heart health in adults with chronic kidney disease (CKD)-a population at increased risk for poor cardiovascular health (CVH). Therefore, we evaluated the association of positive affect and CVH in a diverse U.S. population of Hispanics/Latinos with CKD. We analyzed cross-sectional data of adults ages 18-74 enrolled between 2008 and 2011 in the Hispanic Community Health Study/Study of Latinos with prevalent CKD (N = 1712). Positively worded items from the Center for Epidemiologic Studies Depression Scale were used to create a composite positive affect score (0-6; higher scores indicate greater positive affect). Prevalent CKD was defined as estimated glomerular filtration <60 ml/min/1.73 m² or urine albumin-to-creatinine ratio ≥30 mg/g. A composite CVH score was calculated using diet, body mass index, physical activity, cholesterol, blood pressure, fasting glucose, and smoking status. Each metric was defined as ideal, intermediate, or poor to compute an additive score. Linear regression was used for continuous scores of CVH and logistic regression for binary treatment (e.g., ≥4 Ideal). In participants with CKD, each unit increase in the positive affect score was associated with higher CVH scores when modeling CVH as a continuous outcome (β = 0.06, 95% CI = 0.01, 0.11). Similarly, a 1-unit increase in positive affect was associated with 1.15 times the odds of having >4 (vs. <4) ideal CVH indicators. Positive affect is associated with favorable CVH profiles in Hispanics/Latinos with CKD. Replication and prospective studies are needed to elucidate whether emotional well-being is a potential therapeutic target for intervention.

Epidemiology of falls and fall-related injuries among middle-aged adults with kidney disease

PURPOSE

Comorbidities, such as kidney disease (CKD), increase the likelihood of falls and fall-related injuries. Despite the focus of most research in this population on older adults, falls are a significant cause of injury throughout adulthood. Therefore, we aimed to describe the epidemiology of falls in middle-aged adults with kidney diseases.

METHODS

We analyzed falls and fall-related injuries among middle-aged adults (45-65 years old) with and without CKD included in the 2014 Behavioral Risk Factor Surveillance System (BRFSS) utilizing multivariate logistic regression and complex sample survey data analysis procedures.

RESULTS

Middle-aged adults with CKD were more likely to suffer a fall (2.30, 95% CI 2.07-2.55) and a fall-related injury (1.54, 95% CI 1.32-1.80) compared to those without CKD. However, only the increased likelihood for falls remained significant after correction for multiple demographic, health, lifestyle, and comorbid conditions (AOR 1.22, 95% CI 1.08-1.39). Among adults with CKD, general health status, smoking, and total comorbidity scores were significant predictors of falls and fall-related injuries (p < 0.05 for all). Furthermore, individual comorbidities such as COPD, asthma, depressive disorders, stroke, and arthritis also predicted falls and fall-related injuries (p < 0.05 for all).

CONCLUSION

Middle-aged adults with CKD were more likely than those without CKD to fall and suffer a fall-related injury. However, injury risk did not remain elevated after accounting for differences between groups. The presence of comorbidities, especially depressive disorders, was associated with increased odds for falls and fall-related injuries. Given the high prevalence of depression among adults with CKD, the relationship between depression and falls warrants further examination.

Sustained exercise programs for hemodialysis patients: The characteristics of successful approaches in Portugal, Canada, Mexico, and Germany

Despite having good intentions, hemodialysis (HD) clinics often fail to sustain exercise programs that they initiate. There are many reasons for this, including a lack of funding, inadequate training of the clinic staff, a lack of exercise professionals to manage the program or train the staff, and the many challenges inherent to exercising a patient population with multiple comorbid diseases. Despite these barriers, there are several outstanding examples of successful exercise programs in HD clinics throughout the world. The aim of this manuscript is to review the characteristics of four successfully sustained HD exercise programs in Portugal, Canada, Mexico, and Germany. We describe the unique approaches they have used to fund and manage their programs, the varied exercise prescriptions they incorporate, the unique challenges they face, and discuss the benefits they have seen. While the programs differ in many regards, a consistent theme is that they each have substantial and committed support from the entire clinic staff, including the nephrologists, administration, nurses, dietitians, and technicians. This suggests that exercise programs in HD clinics can be successfully implemented and sustained provided significant effort is made to foster a culture of physical activity throughout the clinic.

Results from the randomized controlled IHOPE trial suggest no effects of oral protein supplementation and exercise training on physical function in hemodialysis patients

Few long-term studies have assessed whether changes in both diet and exercise can improve the health and quality of life (QOL) of hemodialysis (HD) patients. Here we examined whether 12 months of intradialytic protein supplementation and endurance exercise improves physical function, risk of cardiovascular disease (CVD), and QOL in HD patients in a randomized controlled trial (RCT). A total of 138 HD patients (average age 58 years) were assigned for 12 months to control, intradialytic protein, or protein plus exercise groups. The protein and protein plus exercise groups consumed an oral protein supplement (30 grams of whey) three days/week during dialysis. The protein plus exercise group cycled for 30-45 minutes during dialysis treatment. The primary outcome was change in physical function at 12 months, assessed by a shuttle walk test. Secondary outcomes included arterial stiffness, blood pressure, body composition, muscle strength, markers of nutritional status, and QOL. Assessments were conducted at baseline, 6 and 12 months. In total, 101 patients completed the intervention. There were no significant differences between groups in shuttle walk test performance from baseline to 12 months. There were trends for improvements in some secondary measures of physical function and strength in the protein and protein plus exercise groups at six or 12 months, but these did not reach statistical significance. Thus, our trial did not demonstrate significant improvements in markers of physical function, risk of CVD or QOL after one year of intradialytic oral OPS and aerobic exercise training. More comprehensive lifestyle management may be needed to uncover robust improvements in the health and QOL of HD patients.

Effects of regular endurance exercise on GlycA: Combined analysis of 14 exercise interventions

BACKGROUND AND AIMS

GlycA is a relatively new biomarker for inflammation as well as cardiometabolic disease risk. However, the effect of exercise on GlycA is largely unknown. Therefore, the purpose of this study was to examine the effects of regular exercise on the inflammatory marker GlycA across seven studies and 14 exercise interventions.

METHODS

Nuclear magnetic resonance spectroscopy, specifically signal amplitudes originating from the N-acetyl methyl group protons of the N-acetylglucosamine residues on the glycan branches of glycoproteins, was used to quantify GlycA concentrations. GlycA was measured before and after completion of an exercise intervention in 1568 individuals across seven studies and 14 exercise interventions. Random effects inverse variance weighting models were used to pool effects across interventions.

RESULTS

Combined analysis of unadjusted data showed that regular exercise significantly (p = 2 × 10-6) reduced plasma GlycA (-8.26 ± 1.8 μmol/L). This reduction remained significant (-9.12 ± 1.9 μmol/L, p = 1.22 × 10-6) following adjustment for age, sex, race, baseline BMI, and baseline GlycA. Changes in GlycA were correlated with changes in traditional inflammatory markers, C-reactive protein, interleukin-6, and fibrinogen, however, these correlations were relatively weak (range r: 0.21-0.38, p < 0.0001).

CONCLUSIONS

Regular exercise significantly reduced plasma GlycA across 14 different exercise interventions despite differences in exercise programs and study populations. The current study provides a greater understanding of the use of exercise as a potential therapy for the reduction of systemic inflammation. Further research is needed to understand the mechanisms behind the exercise-related reductions in GlycA.

Effects of acute intradialytic exercise on cardiovascular responses in hemodialysis patients

BACKGROUND

In patients with kidney failure requiring hemodialysis (HD) treatment, intradialytic exercise (IDEX) has been advocated for its feasibility and effectiveness in improving important health outcomes. However, IDEX as an adjunct therapeutic strategy is infrequently implemented, in part due to potential risks of IDEX, especially in patients with chronic volume overload. This study was performed to evaluate the safety of IDEX performed at different time points by examining its effect on intradialytic cardiovascular hemodynamics.

METHODS

In a randomized cross-over study (n = 12), intradialytic changes in brachial, aortic, and cardiac hemodynamics and autonomic function were examined during a HD session; (1) without exercise; (2) with 30 min of IDEX performed in the first hour of treatment; or (3) with 30 min of IDEX in the third hour of treatment.

RESULTS

IDEX during either the first or third hour did not exacerbate hemodynamic instability during treatment regardless of patient's hydrations status. While there were transient increases in stroke volume, cardiac output, and heart rate during IDEX, intradialytic changes in brachial and aortic blood pressure, cardiac hemodynamics, and autonomic function were similar on days with and without IDEX.

CONCLUSION

These results indicate that IDEX does not exacerbate hemodynamic instability during HD, regardless of a patient's hydration status or the timing of exercise.

Dysregulated Handling of Dietary Protein and Muscle Protein Synthesis After Mixed-Meal Ingestion in Maintenance Hemodialysis Patients

Introduction

Skeletal muscle loss is common in patients with renal failure who receive maintenance hemodialysis (MHD) therapy. Regular ingestion of protein-rich meals are recommended to help offset muscle protein loss in MHD patients, but little is known about the anabolic potential of this strategy.

Methods

Eight MHD patients (age: 56 ± 5 years; body mass index [BMI]: 32 ± 2 kg/m²) and 8 nonuremic control subjects (age: 50 ± 2 years: BMI: 31 ± 1 kg/m²) received primed continuous L-[ring-²H₅]phenylalanine and L-[1-¹³C]leucine infusions with blood and muscle biopsy sampling on a nondialysis day. Participants consumed a mixed meal (546 kcal; 20-g protein, 59-g carbohydrates, 26-g fat) with protein provided as L-[5,5,5-²H₃]leucine-labeled eggs.

Results

Circulating dietary amino acid availability was reduced in MHD patients (41 ± 5%) versus control subjects (61 ± 4%; P = 0.03). Basal muscle caspase-3 protein content was elevated (P = 0.03) and large neutral amino acid transporter 1 (LAT1) protein content was reduced (P = 0.02) in MHD patients versus control subjects. Basal muscle protein synthesis (MPS) was ∼2-fold higher in MHD patients (0.030 ± 0.005%/h) versus control subjects (0.014 ± 0.003%/h) (P = 0.01). Meal ingestion failed to increase MPS in MHD patients (absolute change from basal: 0.0003 ± 0.007%/h), but stimulated MPS in control subjects (0.009 ± 0.002%/h; P = 0.004).

Conclusions

MHD patients demonstrated muscle anabolic resistance to meal ingestion. This blunted postprandial MPS response in MHD patients might be related to high basal MPS, which results in a stimulatory ceiling effect and/or reduced plasma dietary amino acid availability after mixed-meal ingestion.

The Relationship Between Intradialytic Nutrition and Gastrointestinal Symptoms Using a Modified Version of the Gastrointestinal Symptom Rating Scale

OBJECTIVE

Intradialytic nutrition has been shown to improve nutritional status in maintenance hemodialysis (HD) patients but remains controversial due in part to concerns over hemodynamic stability and gastrointestinal (GI) distress. There are limited data on the relationship between intradialytic nutrition and GI symptoms, possibly due to the lack of a validated tool. Therefore, we intended to validate a questionnaire to measure GI symptoms associated with a single HD treatment and determine the relationship between intradialytic nutrition and GI symptoms.

DESIGN

Cross-sectional study. Forty-eight maintenance HD patients.

MAIN OUTCOME MEASURE

GI symptoms and dietary intake during HD treatment.

RESULTS

In general, we found acceptable internal consistency (Cronbach's alpha >0.5, exception reflux domain) and repeatability in all 5 domains of a modified version of the Gastrointestinal Symptom Rating Scale. The prevalence of GI symptoms associated with a single HD treatment (generalized score greater than 1) was 54.2, 43.7, 6.2, 41.7, and 45.8% for the abdominal pain, indigestion, reflux, diarrhea, and constipation domains, respectively. More than two-thirds of patients chose to eat during treatment (168.6 ± 165.6 kcal) with the most commonly consumed items being candy, oral supplements, and cookies. There was no difference in GI symptoms among patients who did or did not eat (P > .05). However, the amount of total dietary fat and fiber consumed during treatment was associated with greater indigestion (P < .05) prior to accounting for outliers or multiple comparisons.

CONCLUSION

In this sample, the modified version of the Gastrointestinal Symptom Rating Scale was a generally valid tool for measuring GI symptoms associated with a single HD treatment. Patients who ate during treatment did not experience greater GI symptoms than those who did not; however, high amounts of fat and fiber may be associated with greater GI symptoms. Prospective trials should examine the relationship between GI symptoms and dietary intake during treatment in HD patients.

Comparison of Methods Study between a Photonic Crystal Biosensor and Certified ELISA to Measure Biomarkers of Iron Deficiency in Chronic Kidney Disease Patients

The total analytical error of a photonic crystal (PC) biosensor in the determination of ferritin and soluble transferrin receptor (sTfR) as biomarkers of iron deficiency anemia in chronic kidney disease (CKD) patients was evaluated against certified ELISAs. Antigens were extracted from sera of CKD patients using functionalized iron-oxide nanoparticles (fAb-IONs) followed by magnetic separation. Immuno-complexes were recognized by complementary detection Ab affixed to the PC biosensor surface, and their signals were followed using the BIND instrument. Quantification was conducted against actual protein standards. Total calculated error (TEcalc) was estimated based on systematic (SE) and random error (RE) and compared against total allowed error (TEa) based on established quality specifications. Both detection platforms showed adequate linearity, specificity, and sensitivity for biomarkers. Means, SD, and CV were similar between biomarkers for both detection platforms. Compared to ELISA, inherent imprecision was higher on the PC biosensor for ferritin, but not for sTfR. High SE or RE in the PC biosensor when measuring either biomarker resulted in TEcalc higher than the TEa. This did not influence the diagnostic ability of the PC biosensor to discriminate CKD patients with low iron stores. The performance of the PC biosensor is similar to certified ELISAs; however, optimization is required to reduce TEcalc.

Effect of acute aerobic exercise and histamine receptor blockade on arterial stiffness in African Americans and Caucasians

African Americans (AA) exhibit exaggerated central blood pressure (BP) and arterial stiffness measured by pulse wave velocity (PWV) in response to an acute bout of maximal exercise compared with Caucasians (CA). However, whether potential racial differences exist in central BP, elastic, or muscular arterial distensibility after submaximal aerobic exercise remains unknown. Histamine receptor activation mediates sustained postexercise hyperemia in CA but the effect on arterial stiffness is unknown. This study sought to determine the effects of an acute bout of aerobic exercise on central BP and arterial stiffness and the role of histamine receptors, in AA and CA. Forty-nine (22 AA, 27 CA) young and healthy subjects completed the study. Subjects were randomly assigned to take either histamine receptor antagonist or control placebo. Central blood BP and arterial stiffness measurements were obtained at baseline, and at 30, 60, and 90 min after 45 min of moderate treadmill exercise. AA exhibited greater central diastolic BP, elevated brachial PWV, and local carotid arterial stiffness after an acute bout of submaximal exercise compared with CA, which may contribute to their higher risk of cardiovascular disease. Unexpectedly, histamine receptor blockade did not affect central BP or PWV in AA or CA after exercise, but it may play a role in mediating local carotid arterial stiffness. Furthermore, histamine may mediate postexercise carotid arterial dilation in CA but not in AA. These observations provide evidence that young and healthy AA exhibit an exaggerated hemodynamic response to exercise and attenuated vasodilator response compared with CA.NEW & NOTEWORTHY African Americans are at greater risk for developing cardiovascular disease than Caucasians. We are the first to show that young and healthy African Americans exhibit greater central blood pressure, elevated brachial stiffness, and local carotid arterial stiffness following an acute bout of submaximal exercise compared with Caucasians, which may contribute to their higher risk of cardiovascular disease. Furthermore, African Americans exhibit attenuated vasodilator response compared with Caucasians.

The Impact of Exercise on Statin-Associated Skeletal Muscle Myopathy

HMG-CoA reductase inhibitors (statins) are the most effective pharmacological means of reducing cardiovascular disease risk. The most common side effect of statin use is skeletal muscle myopathy, which may be exacerbated by exercise. Hypercholesterolemia and training status are factors that are rarely considered in the progression of myopathy. The purpose of this study was to determine the extent to which acute and chronic exercise can influence statin-induced myopathy in hypercholesterolemic (ApoE^-/-) mice. Mice either received daily injections of saline or simvastatin (20 mg/kg) while: 1) remaining sedentary (Sed), 2) engaging in daily exercise for two weeks (novel, Nov), or 3) engaging in daily exercise for two weeks after a brief period of training (accustomed, Acct) (2x3 design, n = 60). Cholesterol, activity, strength, and indices of myofiber damage and atrophy were assessed. Running wheel activity declined in both exercise groups receiving statins (statin x time interaction, p<0.05). Cholesterol, grip strength, and maximal isometric force were significantly lower in all groups following statin treatment (statin main effect, p<0.05). Mitochondrial content and myofiber size were increased and 4-HNE was decreased by exercise (statin x exercise interaction, p<0.05), and these beneficial effects were abrogated by statin treatment. Exercise (Acct and Nov) increased atrogin-1 mRNA in combination with statin treatment, yet enhanced fiber damage or atrophy was not observed. The results from this study suggest that exercise (Nov, Acct) does not exacerbate statin-induced myopathy in ApoE^-/- mice, yet statin treatment reduces activity in a manner that prevents muscle from mounting a beneficial adaptive response to training.

Aerobic Exercise Training and Arterial Changes in African Americans versus Caucasians

African Americans (AA) have increased carotid artery intima-media thickness and decreased vascular function compared with their Caucasian (CA) peers. Aerobic exercise prevents and potentially reverses arterial dysfunction.

PURPOSE

The purpose of this study was to examine the effect of 8 wk of moderate- to high-intensity aerobic training in young healthy sedentary AA and CA men and women.

METHODS

Sixty-four healthy volunteers (men, 28; women, 36) with mean age 24 yr underwent measures of arterial structure, function, and blood pressure (BP) variables at baseline, after the 4-wk control period, and 8 wk after training.

RESULTS

There was a significant increase in VO2peak among both groups after exercise training. Brachial systolic BP decreased significantly after the control period in both groups but not after exercise training. Carotid pulse pressure decreased significantly in both groups after exercise training as compared with that in baseline. There was no change in any of the other BP variables. AA had higher intima-media thickness at baseline and after the control period but it significantly decreased after exercise training compared with that of CA. AA had significantly lower baseline forearm blood flow and reactive hyperemia compared with those of CA, but exercise training had no effect on these variables. There was no significant difference in arterial stiffness (central pulse wave velocity) and wave-reflection (augmentation index) between the two groups at any time point.

CONCLUSIONS

This is the first study to show that 8 wk of aerobic exercise training causes significant improvement in the arterial structure in young, healthy AA, making it comparable with the CA and with minimal effects on BP variables.

Rationale and design of a randomized controlled clinical trial of functional electrical stimulation cycling in persons with severe multiple sclerosis

BACKGROUND

This randomized controlled trial (RCT) will examine the efficacy of supervised functional electrical stimulation (FES) cycling on walking performance and physiological function among persons with multiple sclerosis (MS) with severe mobility disability.

METHODS/DESIGN

This RCT will recruit 16 persons with MS that require unilateral or bilateral assistance for ambulation (i.e., Expanded Disability Status Scale (EDSS) score = 6.0-6.5). Participants will be randomized to one of two conditions: supervised FES cycling or passive cycling. The FES cycling condition will involve mild electrical stimulation that will generate an activation pattern that results in cycling the leg ergometer. The passive cycling condition will not provide any electrical stimulation, rather the movement of the pedals will be controlled by the electrical motor. Both conditions will be delivered 3 days/week for the same duration, over 6 months. Primary outcomes will include walking performance assessed as walking speed, endurance, and agility. Secondary outcomes will include physiological function assessed as cardiorespiratory fitness, muscular strength, and balance. Assessments will take place at baseline, mid-point (3-months), and immediately following the intervention (6-months).

DISCUSSION

This study will lay the foundation for the design of a future RCT by: (1) providing effect sizes that can be included in a power analysis for optimal sample size estimation; and (2) identifying cardiorespiratory fitness, muscular strength, and balance (i.e., physiological function) as mechanisms for the beneficial effects of FES cycling on walking performance. This trial will provide important information on a novel exercise rehabilitation therapy for managing walking impairment in persons with severe MS.

Modified Nutritional Recommendations to Improve Dietary Patterns and Outcomes in Hemodialysis Patients

The renal diet has traditionally been regarded as one of the most complex medical nutrition therapies to teach, understand, and implement. Specifically, patients are instructed to limit fruits, vegetables, nuts, legumes, dairy, and whole grains because of both phosphorus and potassium concerns. Furthermore, hemodialysis patients are often encouraged to decrease fluid intake to control interdialytic weight gain. These restrictions can result in frustration, lack of autonomy, and the perception that there is nothing left to eat. It is possible that the traditional renal diet may be liberalized, with a focus on whole foods low in sodium and phosphorus additives, to afford patients greater choices and ultimately improved outcomes. Therefore, the objective of this review is to concisely assess the evidence in support of a renal diet focused primarily on reducing the intake of sodium and inorganic phosphorus. Finally, the limited evidence for restrictions on dietary potassium intake is summarized.