Screening for muscle wasting and dysfunction in patients with chronic kidney disease

Reduced skeletal muscle expression of mitochondrial-derived peptides humanin and MOTS-C and Nrf2 in chronic kidney disease

Advanced chronic kidney disease (CKD) is characterized by a premature aging phenotype of multifactorial origin. Mitochondrial dysfunction is prevalent in CKD and has been proposed as a major contributor to poor muscle function. Although the mitochondria-derived peptides (MDPs) humanin and mitochondrial open reading frame of 12S rRNA-c (MOTS-c) are involved in cell survival, suppression of apoptosis, and glucose control, the implications of MDP in CKD are unknown. We investigated humanin and MOTS-c protein expression in skeletal muscle and serum levels in CKD at stage 5 (glomerular filtration rate: <15 ml/min) patients and age-matched controls with normal renal function. Whereas circulating levels of humanin were increased in CKD, local muscle expression was reduced. In contrast, MOTS-c levels were reduced in both skeletal muscle and serum in CKD. Humanin in serum correlated positively to circulating TNF levels. Reduced MDP levels in skeletal muscle were associated with lower mitochondrial density and evidence of oxidative stress. These results indicate a differential regulation of MDPs in CKD and suggest an alternative site for humanin production than skeletal muscle in the uremic milieu. MDP levels were linked to systemic inflammation and evidence of oxidative stress in the muscle, two hallmark features of premature aging and uremia.

Sarcopenia and relationships between muscle mass, measured glomerular filtration rate and physical function in patients with chronic kidney disease stages 3-5

Background

Sarcopenia and poor physical function are common in patients with chronic kidney disease (CKD). Our aim was to investigate the relationships between muscle mass and measured glomerular filtration rate (GFR) and between muscle mass and strength and balance, respectively, in patients with CKD stages 3-5.

Methods

This is a baseline data analysis of a randomized controlled clinical trial. A total of 148 adult patients with an estimated GFR <30 mL/min/1.72 m2, not on renal replacement therapy, irrespective of the number of comorbidities were included from the Department of Nephrology, Skåne University Hospital, Lund, from 2011 to 2016. Body composition was measured by dual-energy X-ray absorptiometry (DEXA). GFR was measured by iohexol clearance. Balance was measured by functional reach and the Berg balance test and strength by handgrip strength and isometric quadriceps strength.

Results

Measured GFR ranged from 8 to 55 mL/min/1.73 m2. Lean mass (P < 0.05), fat mass (P < 0.05), appendicular skeletal muscle (P < 0.001) and appendicular skeletal muscle index (P < 0.05) were associated with GFR. Functional reach was associated with leg lean mass (P < 0.05) and the Berg balance test score was associated with trunk lean mass (P < 0.05). Handgrip strength was associated with arm lean mass (P < 0.001). Isometric quadriceps strength was associated with leg lean mass (P < 0.001). More men (44%) suffered from low muscle mass than women (22%), whereas more women (36%) suffered from low muscle strength than men (26%). However, when combining both, men (16%) suffered from sarcopenia to a greater extent than women (8%).

Conclusions

Among patients with CKD stages 3-5, loss of lean body mass, especially appendicular skeletal muscle, was significantly related to GFR decline. Two important markers of physical function, balance and strength, were significantly related to muscle mass. Moreover, men were more prone to sarcopenia than women during kidney function decline.

Ultrasound assessment of muscle mass in response to exercise training in chronic kidney disease: a comparison with MRI

BACKGROUND

Chronic kidney disease (CKD) is a catabolic condition associated with muscle wasting and dysfunction, which associates with morbidity and mortality. There is a need for simple techniques capable of monitoring changes in muscle size with disease progression and in response to interventions aiming to increase muscle mass and function. Ultrasound is one such technique; however, it is unknown how well changes in muscle cross-sectional area (CSA) measured using ultrasound relate to changes in whole muscle volume measured using magnetic resonance imaging. We tested whether rectus femoris CSA (RF-CSA) could be used as a valid indication of changes in quadriceps muscle volume as a single measure of muscle size and following a 12 week exercise intervention that resulted in muscle hypertrophy.

METHODS

Secondary analysis of data was collected from the ExTra CKD study (ISRCTN 36489137). Quadriceps muscle size was assessed from 36 patients with non-dialysis CKD before and after 12 weeks of supervised exercise that resulted in muscle hypertrophy.

RESULTS

Strong positive correlations were observed between RF-CSA and quadriceps volume at baseline (r² = 0.815, CI 0.661 to 0.903; P < 0.001) and following 12 week exercise (r² = 0.845, CI 0.700 to 0.923; P < 0.001). A moderate positive association was also observed between changes in RF-CSA and quadriceps following exercise training (rho = 0.441, CI 0.085 to 0.697; P = 0.015). Bland-Altman analysis revealed a small bias (bias 0.6% ± 12.5) between the mean percentage changes in RF-CSA and quadriceps volume but wide limits of agreement from -24 to 25.

CONCLUSIONS

Rectus femoris CSA appears to be a reliable index of total quadriceps volume as a simple measure of muscle size, both as a single observation and in response to exercise training in non-dialysis CKD patients.

Quantitative Assessment of Muscular Stiffness in Children With Chronic Kidney Disease Using Acoustic Radiation Force Impulse Ultrasound Elastography

ABSTRACT

The aim of this study was to evaluate the feasibility of quantitative analysis of muscle stiffness in the rectus femoris muscle (RFM) by acoustic radiation force impulse (ARFI) ultrasound elastography in children with chronic kidney disease (CKD). Twenty-three children with CKD and 22 healthy children participated in the study in our radiology department. The strength of each CKD group and healthy group participants' tight extensors was assessed by a physiatrist using a handheld dynamometer. Acoustic radiation force impulse was used to measure the shear wave velocities (SWVs) of the RFM. The mean SWV value of the RFM correlated with the strengths of the tight extensors in the CKD and healthy groups. The mean ± SD SWV values of the RFM in the CKD group for the right (n = 23) and left sides (n = 21) were 1.23 ± 0.25 and 1.26 ± 0.30 m/s, respectively. The mean ± SD SWV values of the RFM in the healthy group for the right (n = 23) and left sides (n = 21) were 1.62 ± 0.33 and 1.65 ± 0.35 m/s, respectively. The SWV of the RFM significantly decreased in the patients with CKD when compared with controls (P < 0.001). The SWV values were not correlated to the handheld dynamometry. The interobserver agreement expressed as the interclass correlation coefficient was 0.65 (95% confidence interval, 0.33-0.84; P < 0.001). The acoustic radiation force impulse demonstrates a difference in RFM muscle stiffness between the CKD and healthy groups. This method is a feasible imaging method for the noninvasive assessment of muscle weakness in children with CKD.

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.

Chronic Kidney Disease is Associated with Physical Impairment

Background

Physical impairment or frailty due to sarcopaenia is common in patients with chronic kidney disease and those receiving dialysis. This study examined the association between muscle weakness and kidney function in Japanese patients with chronic kidney disease.

Methods

A total of 23 stable outpatients were enrolled in the study. Several indices were used to assess muscle function; hand grip strength, isometric knee extension strength, Timed Up and Go test (TUG), and the short physical performance battery. The relationships between these indices and estimated glomerular filtration rate (eGFR) as a measure of kidney function were analysed statistically.

Results

Patients' characteristics were as follows: mean age 73.9 years (standard deviation (SD) 13); 12 males, 11 females; body mass index (BMI) 22.5 kg/m² (SD 3.2); serum creatinine (sCr) 4.6 mg/ dl (SD 3.7); estimated glomerular filtration rate (eGFR) 19.1 ml/min (SD 16). Their physical performance indices were: hand grip strength 20.8 kg (SD 7.9); isometric knee extension strength 19.1 kgf/kg (SD 10.6); TUG 14.9 s (SD 6.0); and short physical performance battery score 7.0 (SD 4.3). Multiple regression analysis adjusted for age revealed significant associations between isometric knee extension strength/body weight and eGFR (F [2,19] = 8.38, p = 0.002) and TUG and eGFR (F=4.98 [2,18], p = 0.02).

Conclusion

Deterioration in muscle function or maintenance of posture is associated with chronic kidney disease.

Thumb adductor muscle thickness used in the nutritional assessment of chronic kidney disease patients under conservative treatment

INTRODUCTION

Evaluate the association between the thumb adductor muscle thickness and the patient's nutritional status, and propose cutoff points for muscle mass depletion in elderly patients with chronic kidney disease (CKD) under conservative treatment. Epidemiological and cross-sectional study, including patients with CKD stages 3 to 5, older than 60 years. Socioeconomic, clinical, physical activity and anthropometric data was obtained. TAMT was described and compared according to CKD stage, socioeconomic data, physical activity, nutritional status and correlated with age, glomerular filtration rate and anthropometric variables. Receiver Operating Characteristic (ROC) curves were produced, considering the lean tissue index classification as reference. The cut-off point was defined by the Youden index.

RESULTS

We evaluated 137 individuals. The TAMT was lower in malnourished and/or depleted muscle mass individuals; among males it was higher among those who practiced physical activities (p <0.05). This measure was moderately correlated with BMI, calf and brachial circumferences, lean body tissue, lean tissue index and body cell mass (r <0.7); negatively with age (r = -0.34). The ROC curve analysis determined cut points of 15.33 mm for females and 20.33 mm for males, with 72.22% and 62.50% accuracy, respectively.

CONCLUSION

TAMT is used to estimate muscle mass and we suggest the cutoff point is useful to rule out the likelihood of muscle mass depletion. It is recommended that it be used in a complementary way in nutritional assessment.

Body composition is associated with clinical outcomes in patients with non-dialysis-dependent chronic kidney disease

An inverse relationship between body mass index (BMI) and mortality (the obesity paradox) has been found in patients with non-dialysis-dependent chronic kidney disease (CKD). However, it is unclear whether increased muscle mass or body fat confers the survival advantage. To resolve this we investigated the impact of body makeup on a composite outcome of death or cardiovascular events in a prospective cohort of 326 patients with stage 3-5 CKD not yet on dialysis. Lean mass and body fat were determined using the Body Composition Monitor, a multifrequency bioimpedance spectroscopy device, and were expressed as the lean tissue or fat tissue index, respectively. Patients were stratified as High (above median) or Low (below median) BMI, High or Low lean tissue index, or as High or Low fat tissue index. During a median follow-up of 4.6 years, there were 40 deaths and 68 cardiovascular events. In Cox proportional hazards models, a High lean tissue index, but not High BMI or High fat tissue index, predicted a lower risk of both the composite or its component outcomes (reference: below median). When patients were further stratified into four distinct body composition groups based on both the lean and fat tissue index, only the High lean/fat tissue index group had a significantly lower risk of the composite outcome (hazard ratio 0.36, 95% confidence interval 0.14-0.87; reference: Low lean/fat tissue index group). Thus, the lean tissue index can provide better risk prediction than the BMI alone in non-dialysis-dependent patients with CKD. The High lean/fat tissue index appears to be associated with best outcomes. An optimal body composition for improving the prognosis of CKD needs to be determined.

Prevalence and Correlates of Sarcopenia among Elderly CKD Outpatients on Tertiary Care

Background: Sarcopenia is a widespread concern in chronic kidney disease (CKD) as well in elderly patients and is one of the main reasons why low-protein diets for this population are controversial. The aim of this study was to assess the prevalence and correlates of sarcopenia among elderly male patients affected by CKD followed up in an outpatient nephrology clinic, where moderate protein restriction (0.6–0.8 g/Kg/day) is routinely recommended to patients in CKD stage 3b-5 not on dialysis. Methods: This observational study included 80 clinically-stable male out-patients aged >60, affected by stage 3b-4 CKD. Forty patients aged ≥75 (older seniors) were compared to the other forty patients aged 60–74 (younger seniors). All patients underwent a comprehensive nutritional and functional assessment. Results: Older seniors showed lower serum albumin, hand-grip strength, body mass index (BMI), skeletal muscle mass, and resting energy expenditure. Protein intake was significantly lower in older seniors whereas energy intake was similar. Average daily physical activity was lower in the older seniors than in the younger ones. Sarcopenia was more prevalent in older than in younger seniors. Among older seniors, sarcopenic and non-sarcopenic ones differed in age and performance on the Six-Minute Walk test, whereas the estimated glomerular filtration rate (eGFR), biochemistry, dietary protein, and energy intakes were similar. Conclusions: Older senior CKD male patients have lower muscle mass, muscle strength, and physical capacity and activity levels, with a higher prevalence of sarcopenia than younger patients. This occurs at the same residual renal function and metabolic profile and protein intake. Energy intake was at the target in both subgroups. In this CKD cohort, sarcopenia was associated with age and physical capacity, but not with eGFR or dietary intakes.

Satellite cell function, intramuscular inflammation and exercise in chronic kidney disease

Skeletal muscle wasting is a common feature of chronic kidney disease (CKD) and is clinically relevant due to associations with quality of life, physical functioning, mortality and a number of comorbidities. Satellite cells (SCs) are a population of skeletal muscle progenitor cells responsible for accrual and maintenance of muscle mass by providing new nuclei to myofibres. Recent evidence from animal models and human studies indicates CKD may negatively affect SC abundance and function in response to stimuli such as exercise and damage. The aim of this review is to collate recent literature on the effect of CKD on SCs, with a particular focus on the myogenic response to exercise in this population. Exercise is widely recognized as important for the maintenance of healthy skeletal muscle mass and is increasingly advocated in the care of a number of chronic conditions. Therefore a greater understanding of the impact of uraemia upon SCs and the possible altered myogenic response in CKD is required to inform strategies to prevent uraemic cachexia.

Wasting in Chronic Kidney Disease – a Complex Issue

Chronic kidney disease (CKD) has become a global health burden and is associated with increased morbidity and mortality. In particular, wasting is highly prevalent in later stages of the illness with muscle loss being a common problem. The aetiology and progression of this wasting is complex and multiple states have been identified linked to wasting in CKD. These include: ‘malnutrition’, ‘disease-related malnutrition’, ‘protein-energy wasting’, ‘cachexia’, ‘sarcopenia’, ‘frailty’ and ‘muscle wasting’. The purpose of this paper is to review these terms in the context of CKD. Common features include weight loss, loss of muscle mass and muscle function principally driven by CKD disease specific factors and inflammatory mediators. Disease-related malnutrition would appear to be a more appropriate term for CKD than malnutrition as it take in to consideration disease specific factors such as inflammation for example.  Frailty is commonly associated with age-related decline in physiological function. Development of novel screening tools measuring across multiple domains of nutritional status, muscle and physical function may be useful in CKD. Research into potential treatments are currently underway with focus on multi-modal therapies including nutrition, resistance training and anabolic drugs such as myostatin blockade and selective androgen receptor modulators. A better understanding of different states and terms may help guide assessment and treatment opportunities for patients.

Quantitative assessment of erector spinae muscles in patients with Mycobacterium avium complex lung disease

BACKGROUND AND OBJECTIVE

No reports exist regarding skeletal muscle involvement in patients with Mycobacterium avium complex lung disease (MAC-LD). The cross-sectional area of the erector spinae muscles (ESM_CSA) reflects physical activity and can be assessed by computed tomography (CT). We investigated the relationship between ESM_CSA and physiological parameters and prognosis in MAC-LD patients.

MATERIAL AND METHODS

In this prospective observational study, the ESM_CSA was measured on single-slice axial CT images. MAC-LD patients and sex- and age-matched controls (non-MAC-LD participants) were evaluated. We evaluated the relationship between the ESM_CSA and physiological parameters and prognosis.

RESULTS

A total of 260 patients (209 female; median age, 69 years; 190 with nodular/bronchiectatic disease; 74 with cavitary lesions) were enrolled. The ESM_CSA was not different between MAC-LD patients and controls. In MAC-LD patients, the ESM_CSA was significantly associated with age, body mass index (BMI), pulmonary function, CT severity, and health-related quality of life (HRQL). Multivariate Cox proportional hazards analyses revealed that an ESM_CSA < -1 standard derivation (hazards ratio [HR], 2.76; P = 0.047) was significantly associated with all-cause mortality, along with BMI < 18.5 kg/m² (HR, 3.67; P = 0.02) and presence of cavitary lesions (HR, 5.84; P = 0.001). However, the ESM_CSA was not significantly associated with all-cause mortality when current treatment status, % predicted functional vital capacity, and forced expiratory volume in 1 s were added to the analyses.

CONCLUSIONS

Although the prognostic impact was limited, ESM_CSA was significantly associated with HRQL and prognostic physiological parameters, such as BMI and pulmonary function.

Electrically stimulated acupuncture increases renal blood flow through exosome-carried miR-181

Acupuncture with low-frequency electrical stimulation (Acu/LFES) can prevent muscle atrophy by increasing muscle protein anabolism in mouse models of chronic kidney disease. During the treatment of muscle wasting, we found that Acu/LFES on the gastrocnemius muscle of the leg enhances renal blood flow. We also found that Acu/LFES increases exosome abundance and alters exosome-associated microRNA expression in the circulation. When exosome secretion was blocked using GW4869, the Acu/LFES-induced increase in renal blood flow was limited. This provided evidence that the increased renal blood flow is exosome mediated. To identify how exosomes regulate renal blood flow, we performed microRNA deep sequencing in exosomes isolated from treated and untreated mouse serum and found that the 34 microRNAs are altered by Acu/LFES. In particular, miR-181d-5p is increased in the serum exosome of Acu/LFES-treated mice. In silico searching suggested that miR-181d-5p could target angiotensinogen. Using a luciferase reporter assay, we demonstrated that miR-181 directly inhibits angiotensinogen. When Acu/LFES-treated muscle was excised and incubated in culture medium, we found that the amount of exosomes and miR-181d-5p was increased in the medium providing evidence that Acu/LFES can increase miR-181 secretion. We conclude that Acu/LFES on leg hindlimb increases miR-181 in serum exosome leading to increased renal blood flow. This study provides important new insights about the mechanism(s) by which acupuncture may regulation of muscle-organ cross talk through exosome-derived microRNA.

Physical inactivity and protein energy wasting play independent roles in muscle weakness in maintenance haemodialysis patients

Background

Muscle weakness is associated with increased mortality risk in chronic haemodialysis (CHD) patients. Protein energy wasting (PEW) and low physical activity could impair muscle quality and contribute to muscle weakness beyond muscle wasting in these patients. Aim of this study was to assess clinical and biological parameters involved in the reduction of muscle strength of CHD patients.

Methods

One hundred and twenty-three CHD patients (80 males, 43 females; 68,8 [57.9–78.8] y.o.) were included in this study. Maximal voluntary force (MVF) of quadriceps was assessed using a belt-stabilized hand-held dynamometer. Muscle quality was evaluated by muscle specific torque, defined as the strength per unit of muscle mass. Muscle mass was estimated using lean tissue index (LTI), skeletal muscle mass (SMM) assessed by bioelectrical impedance analysis and creatinine index (CI). Voorrips questionnaire was used to estimate physical activity. Criteria for the diagnosis of PEW were serum albumin, body mass index < 23 kg/m², creatinine index < 18.82 mg/kg/d and low dietary protein intake estimated by nPCR < 0.80g/kg/d.

Results

MVF was 76.1 [58.2–111.7] N.m. and was associated with CI (β = 5.3 [2.2–8.4], p = 0.001), LTI (β = 2.8 [0.6–5.1], p = 0.013), Voorrips score (β = 17.4 [2.9–31.9], p = 0.02) and serum albumin (β = 1.9 [0.5–3.2], p = 0.006). Only serum albumin (β = 0.09 [0.03–0.15], p = 0.003), Voorrips score (β = 0.8 [0.2–1.5], p = 0.005) and CI (β = 0.2 [0.1–0.3], p<0.001) remained associated with muscle specific torque. Thirty patients have dynapenia defined as impaired MVF with maintained SMM and were younger with high hs-CRP (p = 0.001), PEW criteria (p<0.001) and low Voorrips score (p = 0.001), and reduced dialysis vintage (p<0.046).

Conclusions

Beyond atrophy, physical inactivity and PEW conspire to impair muscle strength and specific torque in CHD patients and could be related to muscle quality.

Trial registration

ClinicalTrials.gov NCT02806089

Chronic kidney disease: considerations for monitoring skeletal muscle health and prescribing resistance exercise

Skeletal muscle wasting has gained interest as a primary consequence of chronic kidney disease (CKD) due to the relationship between skeletal muscle mass, mortality and major adverse cardiovascular events in this population. The combination of reductions in physical function, skeletal muscle performance and skeletal muscle mass places individuals with CKD at greater risk of sarcopenia. Therefore the monitoring of skeletal muscle composition and function may provide clinical insight into disease progression. Dual-energy X-ray absorptiometry and bioelectrical impedance analysis are frequently used to estimate body composition in people with CKD within clinical research environments, however, their translation into clinical practice has been limited. Proxy measures of skeletal muscle quality can be obtained using diagnostic ultrasound, providing a cost-effective and accessible imaging modality to aid further clinical research regarding changes in muscle composition. Clinicians and practitioners should evaluate the strengths and limitations of the available technology to determine which devices are most appropriate given their respective circumstances. Progressive resistance exercise has been shown to improve skeletal muscle hypertrophy of the lower extremities, muscular strength and health-related quality of life in end-stage renal disease, with limited evidence available in CKD predialysis. Fundamental principles (i.e. specificity, overload, variation, reversibility, individuality) can be used in the development of more advanced programs focused on improving specific neuromuscular and functional outcomes. Future research is needed to determine the applicability of skeletal muscle monitoring in clinical settings and the feasibility and efficacy of more advanced resistance exercise approaches in those with CKD predialysis.

Diagnostic Usefulness of the Protein Energy Wasting Score in Prevalent Hemodialysis Patients

OBJECTIVE

To study whether the score proposed by the International Society of Renal Nutrition and Metabolism to define the protein energy wasting (PEW) syndrome has diagnostic validity in patients undergoing dialysis.

DESIGN AND METHODS

Cross-sectional study including 468 prevalent hemodialysis patients from Canary Islands, Spain. Individual PEW syndrome criteria and the number of PEW syndrome categories were related to other objective markers of PEW using linear and logistic regression analyses: subjective global assessment, handgrip strength, bioimpedance-assessed body composition, and levels of high-sensitivity C-reactive protein.

RESULTS

Study participants (34% women) had a median age of 66 years, 37 months of maintenance dialysis, and 50% were diabetics. About 23% of patients had PEW (≥3 PEW categories), and 68% were at risk of PEW (1-2 PEW categories). Low prealbumin was the most frequently found derangement (52% of cases), followed by low albumin (46%), and low protein intake (35%). Across higher number of PEW syndrome categories, patients showed a longer dialysis vintage and had lower creatinine, triglycerides, and transferrin (P for trend <.001 for all). All nutritional assessments not included in the PEW definition worsened across higher number of PEW categories. In multivariable regression analyses, there was a linear inverse relationship between muscle and fat mass as well as handgrip strength with the number of PEW syndrome categories. Likewise, the proportion of subjective global assessment-defined malnutrition and serum concentration of C-reactive protein gradually increased despite adjustment for confounders (P for trend <.05 for all).

CONCLUSION

The PEW score reflects systemic inflammation, malnutrition and wasting among dialysis patients and may thus be used for diagnostic purposes.

Obesity Paradox in Advanced Kidney Disease: From Bedside to the Bench

While obesity is associated with a variety of complications including diabetes, hypertension, cardiovascular disease and premature death, observational studies have also found that obesity and increasing body mass index (BMI) can be linked with improved survival in certain patient populations, including those with conditions marked by protein-energy wasting and dysmetabolism that ultimately lead to cachexia. The latter observations have been reported in various clinical settings including end-stage renal disease (ESRD) and have been described as the "obesity paradox" or "reverse epidemiology", engendering controversy. While some have attributed the obesity paradox to residual confounding in an effort to "debunk" these observations, recent experimental discoveries provide biologically plausible mechanisms in which higher BMI can be linked to longevity in certain groups of patients. In addition, sophisticated epidemiologic methods that extensively adjusted for confounding have found that the obesity paradox remains robust in ESRD. Furthermore, novel hypotheses suggest that weight loss and cachexia can be linked to adverse outcomes including cardiomyopathy, arrhythmias, sudden death and poor outcomes. Therefore, the survival benefit observed in obese ESRD patients can at least partly be derived from mechanisms that protect against inefficient energy utilization, cachexia and protein-energy wasting. Given that in ESRD patients, treatment of traditional risk factors has failed to alter outcomes, detailed translational studies of the obesity paradox may help identify innovative pathways that can be targeted to improve survival. We have reviewed recent clinical evidence detailing the association of BMI with outcomes in patients with chronic kidney disease, including ESRD, and discuss potential mechanisms underlying the obesity paradox with potential for clinical applicability.

Quality over quantity? Association of skeletal muscle myosteatosis and myofibrosis on physical function in chronic kidney disease

Background

Chronic kidney disease (CKD) is characterized by adverse changes in body composition, which are associated with poor clinical outcome and physical functioning. Whilst size is the key for muscle functioning, changes in muscle quality specifically increase in intramuscular fat infiltration (myosteatosis) and fibrosis (myofibrosis) may be important. We investigated the role of muscle quality and size on physical performance in non-dialysis CKD patients.

Methods

Ultrasound (US) images of the rectus femoris (RF) were obtained. Muscle quality was assessed using echo intensity (EI), and qualitatively using Heckmatt’s visual rating scale. Muscle size was obtained from RF cross-sectional area (RF-CSA). Physical function was measured by the sit-to-stand-60s (STS-60) test, incremental (ISWT) and endurance shuttle walk tests, lower limb and handgrip strength, exercise capacity (VO2peak) and gait speed.

Results

A total of 61 patients (58.5 ± 14.9 years, 46% female, estimated glomerular filtration rate 31.1 ± 20.2 mL/min/1.73 m2) were recruited. Lower EI (i.e. higher muscle quality) was significantly associated with better physical performance [STS-60 (r = 0.363) and ISWT (r = 0.320)], and greater VO2peak (r = 0.439). The qualitative rating was closely associated with EI values, and significant differences in function were seen between the ratings. RF-CSA was a better predictor of performance than muscle quality.

Conclusions

In CKD, increased US-derived EI was negatively correlated with physical performance; however, muscle size remains the largest predictor of physical function. Therefore, in addition to the loss of muscle size, muscle quality should be considered an important factor that may contribute to deficits in mobility and function in CKD. Interventions such as exercise could improve both of these factors.

Differences in the prevalence of sarcopenia in peritoneal dialysis patients using hand grip strength and appendicular lean mass: depends upon guideline definitions

BACKGROUND

Peritoneal dialysis (PD) patients with sarcopenia have increased risk of mortality. There is consensus that sarcopenia should combine assessments of muscle function and mass. We wished to determine the effect of using different operational definitions in PD patients.

METHODS

Hand grip strength (HGS) and segmental bioimpedance derived appendicular lean mass (ALM) were measured and the prevalence of sarcopenia determined using the Foundation for the National Institutes of Health Sarcopenia Project (FNIH), European Working Group on Sarcopenia Older Persons (EWGSOP), and Asian Working Group on Sarcopenia (AWGS) definitions.

RESULTS

We studied 155 PD patients, 95 men (61.3%), mean age 63.0 ± 14.9 years, 37.4% diabetic, treated by PD 9 (3-20) months with a HGS of 22.5 (15.5-30.2) kg, weight 73.6 ± 16.6 kg, % body fat 31.4 ± 4.2, and ALM index 7.52 ± 1.40 kg/m². More patients were defined with muscle weakness using the EWGSOP compared to the FNIH criteria (X² = 6.8, p = 0.009), whereas fewer patients met the EWGSOP criteria for muscle wasting compared to FNIH body mass index adjustment (X² = 7.7, p = 0.006). However, when combining both criteria, there was no difference in the prevalence of sarcopenia between the different recommended definitions (11-15.5%).

CONCLUSION

We report a much lower prevalence of sarcopenia compared to studies in haemodialysis patients. Although there may be an element of patient selection bias, PD patients are not subject to changes in hydration and electrolytes with haemodialysis, which can affect HGS and muscle mass measurements. Using HGS and segmental bioimpedance we found similar prevalence of sarcopenia using EWGSOP, FNIH, AWGS definitions.

Relation of Lean Body Mass and Muscle Performance to Serum Creatinine Concentration in Hemodialysis Patients

INTRODUCTION

Serum creatinine concentration is an important uremic marker and predictor of survival in dialysis patients. This cross-sectional case-control study was made to quantitatively describe the relation between lean body mass (LBM), physical performance measures, and serum creatinine values.

METHODS

Ninety hemodialysis patients and 106 controls were measured by bioimpedance spectroscopy, handgrip strength, sit-to-stand test, and biochemical serum tests. Univariate and multivariate general linear models were used to analyze quantitative relations.

RESULTS

At univariate regression LBM accounted for 13.6% variability of serum creatinine concentration. In adjusted analyses with age, height, and body mass, LBM persisted as the only significant predictor of midweek predialysis serum creatinine concentration. Physical performance measures handgrip strength and sit-to-stand performance did not improve prediction of serum creatinine. With addition of serum urea concentration and residual diuresis the predictive value of the regression model improved to account for 45% of serum creatinine variability. Each kg of LBM was associated with 7.7 μmol/l increase in creatinine concentration (95% CI 3.4-12.1, p=0.001).

CONCLUSION

Bioimpedance derived LBM has a significant linear relation with predialysis serum creatinine concentrations. Hereby described quantitative relation should help clinicians to better evaluate observed creatinine concentrations of hemodialysis patients when bioimpedance derived LBM is available.

Risk of hospitalization associated with body mass index and weight changes among prevalent haemodialysis patients

The impact of body mass index (BMI) and body weight on hospitalization rates in haemodialysis patients is unknown. This study hypothesizes that being either underweight or obese is associated with a higher hospitalization rate. Observational study of 6296 European haemodialysis patients with prospective data collection and follow-up every six months for three years (COSMOS study). The risk of being hospitalized was estimated by a time-dependent Cox regression model and the annual risk (incidence rate ratios, IRR) by Poisson regression. We considered weight loss, weight gain and stable weight. Weight change analyses were also performed after patient stratification according to their baseline BMI. A total of 3096 patients were hospitalized at least once with 9731 hospitalizations in total. The hospitalization incidence (fully adjusted IRR 1.28, 95% CI [1.18-1.39]) was higher among underweight patients (BMI <20kg/m²) than patients of normal weight (BMI 20-25kg/m²), while the incidence of overweight (0.88 [0.83-0.93]) and obese patients (≥30kg/m², 0.85 [0.79-0.92]) was lower. Weight gain was associated with a reduced risk of hospitalization. Conversely, weight loss was associated with a higher hospitalization rate, particularly in underweight patients (IRR 2.85 [2.33-3.47]). Underweight haemodialysis patients were at increased risk of hospitalization, while overweight and obese patients were less likely to be hospitalized. Short-term weight loss in underweight individuals was associated with a strikingly high hospitalization rate.

Noninvasive evaluation of muscle mass by ultrasonography of quadriceps femoris muscle in End-Stage Renal Disease patients on hemodialysis

BACKGROUND & AIMS

Protein-Energy Wasting (PEW) is a pathological condition of renal patients with advanced Chronic Kidney Disease characterized by a progressive reduction of energy and protein assets. Nutritional status assessment, especially for what concerns muscle mass, is essential for both the identification of patients at risk for the development of PEW, as well as monitoring the effects of nutritional interventions. Ultrasound methods are easily applicable at the bedside for quantitative assessment of skeletal muscle. The present study was aimed at evaluating quadriceps rectus femoris thickness (QRFT) and quadriceps vastus intermedius thickness (QVIT) in patients on chronic hemodialysis.

METHODS

This was a prospective observational study. Three groups of adult patients were studied: young healthy subjects, well-nourished hospitalized patients with normal renal function, and End-Stage Renal Disease patients on hemodialysis (ESRD-HD). QRFT and QVIT were measured at two sites bilaterally (8 measures/patient) and were compared between groups, and also between subgroups of ESRD-HD patients stratified on the basis of conventional nutritional status parameters.

RESULTS

We enrolled 35 healthy subjects, 30 hospitalized patients, and 121 ESRD-HD patients on hemodialysis. QRFT and QVIT of ESRD patients on hemodialysis were lower than those of both control groups (P < 0.001). After stratifying ESRD patients into subgroups based on nutritional variable cut-offs commonly used to define PEW in this clinical setting (BMI [≥ 23 vs <23 kg/m²], albumin [≥3.8 vs <3.8 g/dL]) and malnutrition inflammation score (MIS) status (<6 vs ≥6), QRFT and QVIT of patients with worse nutritional status were significantly lower than those of well-nourished ESRD-HD patients (P value range: <0.001 to <0.05).

CONCLUSION

Skeletal muscle ultrasound is a simple and easily applicable bedside technique in the dialysis units, and could represent an adequate tool for the identification of patients with reduced muscle mass.

Protein Losses and Urea Nitrogen Underestimate Total Nitrogen Losses in Peritoneal Dialysis and Hemodialysis Patients

OBJECTIVE

Muscle wasting is associated with increased mortality and is commonly reported in dialysis patients. Hemodialysis (HD) and peritoneal dialysis (PD) treatments lead to protein losses in effluent dialysate. We wished to determine whether changes in current dialysis practice had increased therapy-associated nitrogen losses.

DESIGN

Cross-sectional cohort study.

METHODS

Measurement of total protein, urea and total nitrogen in effluent dialysate from 24-hour collections from PD patients, and during haemodiafiltration (HDF) and haemodialysis (HD) sessions.

SUBJECTS

One hundred eight adult dialysis patients.

INTERVENTION

Peritoneal dialysis, high-flux haemodialysis and haemodiafiltration.

MAIN OUTCOME MEASURE

Total nitrogen and protein losses.

RESULTS

Dialysate protein losses were measured in 68 PD and 40 HD patients. Sessional losses of urea (13.9 [9.2-21.1] vs. 4.8 [2.8-7.8] g); protein (8.6 [7.2-11.1] vs. 6.7 [3.9-11.1] g); and nitrogen (11.5 [8.7-17.7] vs. 4.9 [2.6-9.5] g) were all greater for HD than PD, P < .001. Protein-derived nitrogen was 71.9 (54.4-110.4) g for HD and 30.8 (16.1-59.6) g for PD. Weekly protein losses were lower with HD 25.9 (21.5-33.4) versus 46.6 (27-77.6) g/week, but nitrogen losses were similar. We found no difference between high-flux HD and HDF: urea (13.5 [8.8-20.6] vs. 15.3 [10.5-25.5] g); protein (8.8 [7.3-12.2] vs. 7.6 [5.8-9.0] g); and total nitrogen (11.6 [8.3-17.3] vs. 10.8 [8.9-22.5] g). Urea nitrogen (UN) only accounted for 45.1 (38.3-51.0)% PD and 63.0 (55.3-62.4)% HD of total nitrogen losses.

CONCLUSION

Although sessional losses of protein and UN were greater with HD, weekly losses were similar between modalities. We found no differences between HD and HDF. However, total nitrogen losses were much greater than the combination of protein and UN, suggesting greater nutritional losses with dialysis than previously reported.

Differences in the prevalence of sarcopenia in haemodialysis patients: the effects of gender and ethnicity

BACKGROUND

There is no universal consensus definition of sarcopenia, although there is agreement that sarcopenia is a risk factor for mortality in haemodialysis (HD) patients. We aimed to determine the effect of using different operational definitions in a multiracial group of HD patients.

METHODS

We measured hand grip strength (HGS) and appendicular lean mass (ALM) by segmental bioimpedance using the Foundation for the National Institutes of Health Sarcopenia Project (FNIH), European Working Group on Sarcopenia (EWGS) and Asian Working Group on Sarcopenia definitions for HGS weakness and loss of appendicular lean mass.

RESULTS

In total, there were 600 HD patients: 373 men (62.2%), mean (SD) age 66.3 (14.7) years, 45.6% diabetic, ethnicity: 281 (48.5%) White, 167 (27.8%) Asian and 149 (24.8%) Black. On HGS criteria, 90.5% of Asian women and 88.5% of Asian men were weak according to EWGS compared to 62.3% of Black women and 52.5% of Black men and 64.5% of White women and 69.1% of White men by FNIH criteria (P < 0.001). On adding appendicular lean mass, the prevalence of sarcopenia was 68.3% for Asian, 27.1% for Black and 36.6% for White women by FNIH and 59.6% Asian, 21.3% Black and 39.9% White men by EWGS criteria.

CONCLUSIONS

Current definitions of sarcopenia report a greater prevalence of muscle weakness compared to appendicular muscle loss in female compared to male HD patients and this is greater for Asian compared to Black and White patients. Because HGS weakness is a greater risk for death, definitions of sarcopenia may underestimate risk in HD patients.

Muscle mass assessment by computed tomography in chronic kidney disease patients: agreement with surrogate methods

BACKGROUND/OBJECTIVES

Patients with chronic kidney disease (CKD) are subjected to muscle wasting. Therefore, it is important to investigate surrogate methods that enable the assessment of muscle mass loss in the clinical setting. We aimed to analyze the agreement between computed tomography (CT) and surrogate methods for the assessment of muscle mass in non-dialysis CKD patients.

SUBJECTS/METHODS

Cross-sectional study including 233 non-dialysis patients on CKD stages 3 to 5 (61 ± 11 years; 64% men; glomerular filtration rate 22 (14-33) mL/min/1.73 m²). The muscle mass was evaluated by CT and bioelectrical impedance, skinfold thicknesses, midarm muscle circumference (MAMC), the predictive equations of Janssen and Baumgartner and the physical examination of muscle atrophy from the subjective global assessment.

RESULTS

In males, the MAMC showed the best agreement with CT as indicated by the kappa test (k = 0.57, P < 0.01), sensitivity (S = 68%), specificity (S = 89%) and accuracy (area under the curve-AUC = 0.78), followed by the Baumgartner equation (kappa = 0.46, P < 0.01; sensitivity = 60%; specificity = 87% and AUC = 0.73). In female, the Baumgartner equation showed the best agreement with CT (kappa = 0.43, P < 0.01; sensitivity = 57%; specificity = 86% and AUC = 0.71).

CONCLUSIONS

The MAMC and Baumgartner equation showed the best agreement with CT for the assessment of muscle mass in non-dialysis CKD patients.

Comparing Western and Eastern criteria for sarcopenia and their association with survival in patients with pancreatic cancer

BACKGROUND & AIMS

Sarcopenia and cachexia are associated with pancreatic cancer and serve as important adverse prognostic factors. Body composition can be analyzed by routine computed tomography (CT) for cancer staging and has been used to study many types of cancer. The CT measurements are robust, but the diagnostic criteria for sarcopenia vary among different studies. Age, sex and race are important factors that affect muscle and fat masses. This study aimed to analyze the effect of different sarcopenia diagnostic criteria on the prognosis of patients with pancreatic cancer.

METHODS

Patients with newly diagnosed pancreatic cancer at National Taiwan University Hospital between October 2013 and October 2016 were retrospectively reviewed in this study. Body composition was assessed using cross-sectional CT images to calculate the total skeletal muscle (TSM) index. The concordance and interobserver variability of the TSM measurements were evaluated using both the Western criteria and the Eastern criteria. Kaplan-Meier analyses and the Cox proportional hazard ratio with two different diagnostic criteria for sarcopenia were used to compare the effect on overall survival (OS).

RESULTS

A total of 146 patients with pancreatic cancer were enrolled. The TSM index measured by the Western institute was highly correlated with that measured by the Eastern institute (r = 0.953, p < 0.001). The prevalence of sarcopenia in the patient group at baseline was 66.4% (97/146) by the Western criteria and 11.0% (16/146) by the Eastern criteria, and only low agreement was found between the Western and Eastern criteria (Kappa value = 0.028, p = 0.149). Patients who were sarcopenic by the Western criteria showed no significant difference in OS versus those who were not sarcopenic (p = 0.807). However, patients who were sarcopenic by the Eastern criteria showed a significant difference in OS versus those who were not sarcopenic in a univariate analysis (p = 0.008) and multivariate analysis after adjustment for AJCC stage (p = 0.014).

CONCLUSIONS

Our study demonstrates that different diagnostic criteria may result in different diagnoses and that sarcopenia is an important poor prognostic factor for pancreatic cancer when appropriate diagnostic criteria are selected.

Muscle Atrophy in Chronic Kidney Disease

The renal damage and loss of kidney function that characterize chronic kidney disease (CKD) cause several complex systemic alterations that affect muscular homeostasis, leading to loss of muscle mass and, ultimately, to muscle atrophy. CKD-induced muscle atrophy is highly prevalent and, in association with common CKD comorbidities, is responsible for the reduction of physical capacity, functional independence, and an increase in the number of hospitalizations and mortality rates. Thus, this chapter summarizes current knowledge about the complex interactions between CKD factors and the pathophysiological mechanisms that induce muscle atrophy that, despite growing interest, are not yet fully understood. The current treatments of CKD-induced muscle atrophy are multidisciplinary, including correction of metabolic acidosis, nutritional supplementation, reducing insulin resistance, administration of androgenic steroids, resisted and aerobic exercise, neuromuscular electrical stimulation, and inspiratory muscle training. However, further studies are still needed to strengthen the comprehension of CKD-induced muscle atrophy and the better treatment strategies.

Hand grip strength measurement in haemodialysis patients: before or after the session?

Background

Hand grip strength (HGS) is a key measurement in the assessment of frailty phenotype in haemodialysis patients. However, the measurement is not very standardized, and notably, current data on the potential impact of a haemodialysis session on the results are both limited and controversial. In the present analysis, we compared HGS results before and after a haemodialysis session in 101 patients.

Methods

In the current observational study, HGS has been measured in adult haemodialysis patients on the same day, first before connection to the dialysis machine and then just after disconnection. At each timing, measurements were repeated three times with an interval of 5 s between measurements and the higher value was used for analysis.

Results

One hundred and one patients (64% men) with a median (interquartile range, 25th percentile; 75th percentile) age of 66 (46; 76) years were included. In the whole population, a significant decline in HGS was observed after dialysis, with an absolute median decline of − 4 (0; −6) kg and a relative median difference of −11 (0; −20)%. These differences were observed in both genders and were independent of the baseline HGS value.

Conclusions

Our results suggest that the timing (before or after the dialysis session) of hand grip assessment is clinically relevant and should be taken into account in clinical practice and also in epidemiological and clinical studies.

Vitamin D, a modulator of musculoskeletal health in chronic kidney disease

The spectrum of activity of vitamin D goes beyond calcium and bone homeostasis, and growing evidence suggests that vitamin D contributes to maintain musculoskeletal health in healthy subjects as well as in patients with chronic kidney disease (CKD), who display the combination of bone metabolism disorder, muscle wasting, and weakness. Here, we review how vitamin D represents a pathway in which bone and muscle may interact. In vitro studies have confirmed that the vitamin D receptor is present on muscle, describing the mechanisms whereby vitamin D directly affects skeletal muscle. These include genomic and non-genomic (rapid) effects, regulating cellular differentiation and proliferation. Observational studies have shown that circulating 25-hydroxyvitamin D levels correlate with the clinical symptoms and muscle morphological changes observed in CKD patients. Vitamin D deficiency has been linked to low bone formation rate and bone mineral density, with an increased risk of skeletal fractures. The impact of low vitamin D status on skeletal muscle may also affect muscle metabolic pathways, including its sensitivity to insulin. Although some interventional studies have shown that vitamin D may improve physical performance and protect against the development of histological and radiological signs of hyperparathyroidism, evidence is still insufficient to draw definitive conclusions.

Association of handgrip strength with hospitalization, cardiovascular events, and mortality in Japanese patients with type 2 diabetes

Handgrip strength is useful for the diagnosis of sarcopenia. We examined the associations of handgrip strength with all-cause mortality, cardiovascular events, and hospitalization in patients with type 2 diabetes. From April 2013 to December 2015, we conducted a retrospective cohort study to examine patients with type 2 diabetes whose handgrip strength was measured at our hospital. All patients were followed up until May 2016. A total of 1,282 patients (63.8 ± 13.9 years) were enrolled and followed up for 2.36 ± 0.73 years. During the follow-up period, 20 patients (1.6%) died, 14 (1.1%) experienced cardiovascular events, and 556 (43.4%) were admitted to our hospital for any diseases. Multiple regression analyses revealed that handgrip strength was favorably associated with abdominal obesity and renal function. Moreover, Cox proportional hazard analyses with adjustment for potential confounding variables revealed that handgrip strength was significantly associated with occurrence of CVD events and hospitalization in all subjects. In addition, handgrip strength was significantly associated with mortality and hospitalization in men and with hospitalization in women. Handgrip strength could be a prognostic indicator for health as well as a diagnostic marker of skeletal muscle mass loss in Japanese patients with type 2 diabetes.

Sarcopenia is associated with incident albuminuria in patients with type 2 diabetes: A retrospective observational study

Sarcopenia, defined as age‐related loss of skeletal muscle mass and function, increases the risk of albuminuria. However, it has still unknown whether sarcopenia could increase the risk for the progression of albuminuria. A total 238 patients with type 2 diabetes (mean age 64 ± 12 years; 39.2% women) were studied in the present retrospective observational study. The prevalence of sarcopenia was 17.6%. During the median follow‐up period of 2.6 years, albuminuria was measured 5.8 ± 1.8 times, and progression of albuminuria was observed in 14.9% of patients with normoalbuminuria, as was 11.5% in those with microalbuminuria. Sarcopenia was significantly associated with both progression (hazard ratio 2.61, 95% confidence interval 1.08–6.31, P = 0.034) and regression (hazard ratio 0.23, 95% confidence interval 0.05–0.98, P = 0.048) of albuminuria by multivariate Cox regression analysis. The present data suggest that sarcopenia is an important determinant of both progression and regression of albuminuria in patients with type 2 diabetes.

Standardized Method to Measure Muscle Force at the Bedside in Hemodialysis Patients

OBJECTIVES

In hemodialysis, diminution of muscle strength constitutes a major prognostic factor of mortality. Currently, measurement of quadriceps isometric maximal voluntary force (MVF) represents the reference method to investigate muscle strength. However, reduction of MVF is rarely detected in these patients due to the absence of portative bedside tools in clinical practice. The purposes of this study were therefore to assess the agreement of a belt-stabilized handheld dynamometer (HHD) with the dynamometer chair (reference method) and to determine intratester and intertester reliability of the quadriceps MVF measurements using belt-stabilized HHD in healthy subjects and in hemodialysis patients.

DESIGN

Repeated-measures cross-sectional study.

SETTING

Clinical and academic hospital.

PARTICIPANTS

Fifty-three healthy adult subjects (23 males, 36.5 + 12.5 y.o.) and 21 hemodialysis patients (14 males, 72.4 + 13.3 y.o., dialysis vintage 30 + 75.1 months).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE

MVF measurements were assessed with belt-stabilized HHD and dynamometer chair, by two independent investigators. The agreement between the two devices would be quantified using the Bland-Altman 95% limits of agreement (LOA) method and the Spearman correlation.

RESULTS

For healthy subjects and hemodialysis patients, Spearman coefficients between belt-stabilized HHD and dynamometer chair were 0.63 and 0.75, respectively (P < .05). In hemodialysis group, reliability was excellent for both the intratester and intertester reliability R² = 0.85 (P < .01) and R² = 0.90 (P < .01), respectively. In all individuals, the mean difference between the dynamometer chair and the belt-stabilized HHD was -13.07 ± 21.77 N.m. (P < .001). The LOA for the upper and the lower was 29.59 and -55.73 N.m., respectively.

CONCLUSION

In healthy subjects and in hemodialysis patients, the belt-stabilized HHD dynamometer appears as a valid and reliable method to measure in clinical practice isometric MVF of quadriceps in hemodialysis patients. Therefore, the belt-stabilized HHD appears as a suitable and a relevant diagnostic tool for the identification of muscle dysfunction in hemodialysis patients.

Sarcopenia and its individual criteria are associated, in part, with mortality among patients on hemodialysis

The relative importance of sarcopenia and its individual components as independent predictors of mortality in the dialysis population has not been determined. We estimated whole-body muscle mass using pre-dialysis bioimpedance spectroscopy measurements in 645 ACTIVE/ADIPOSE-enrolled prevalent hemodialysis patients from San Francisco and Atlanta. Low muscle mass was defined as two standard deviations below sex-specific means for young adults from NHANES and indexed to height², body weight, body surface area, or body mass index. We evaluated the association of sarcopenia (low muscle mass) by four indexing methods, weak hand grip strength, and slow gait speed with mortality. Seventy-eight deaths were observed during a mean follow-up of 1.9 years. Sarcopenia was not significantly associated with mortality after adjusting for covariates. No muscle mass criteria were associated with death, regardless of indexing metrics. In contrast, having weak grip strength or slow walking speed was associated with mortality in the adjusted model. Only gait slowness significantly improved the predictive accuracy for death with an increase in C-statistic from 0.63 to 0.68. However, both gait slowness and hand grip weakness significantly improved the net reclassification index compared to models without performance measures (50.5% for slowness and 33.7% for weakness), whereas models with muscle size did not. Neither sarcopenia nor low muscle mass by itself was a better predictor of mortality than functional limitation alone in patients receiving hemodialysis. Thus, physical performance measures, including slow gait speed and weak hand grip strength, were associated with mortality even after adjustment for muscle size and other confounders.

Characterization of deficits across the spectrum of motor abilities in dialysis patients and the impact of sarcopenic overweight and obesity

BACKGROUND & AIMS

Physical performance deficits in kidney failure predict mortality and quality of life. We aimed to quantify deficits in multiple motor abilities, investigate associations of lean and fat tissue content with test results and analyzed performance of sarcopenic individuals with adipose tissue excess.

METHODS

Ninety hemodialysis patients and 140 healthy controls performed 6-minute walk test, gait speed measurement, sit-to-stand and time up and go tests, upper extremity handgrip and tapping tests, Stork balance and forward bend flexibility tests. Human Activity Profile questionnaire was used to assess habitual activity. Body composition was measured by bioimpedance analysis.

RESULTS

Relative performance deficit of dialysis patients in age, sex, height and comorbidity adjusted estimated marginal means was largest for balance and flexibility (-52 and -33%), followed by lower extremity deficits in sit-to-stand, time up and go and 6-minute walk tests (-29, -19 and -15%, respectively), p < 0.05 for all comparisons. Upper extremity performance was less affected. Lean tissue index associated significantly positively with five and fat tissue index associated significantly negatively with two out of nine tests. Sarcopenic overweight and obese individuals exhibited significant deficits mainly in lower extremity tests with worse composite lower extremity score when compared to other categories of body composition.

CONCLUSIONS

Patients with hemodialysis treated kidney failure have largest functional deficits in balance, flexibility and lower extremity functions. Lean and fat mass associate oppositely with physical performance measures and individuals at unfavorable extremes of these indices express significantly impaired lower extremity functions.

11C-L-methyl methionine dynamic PET/CT of skeletal muscle: response to protein supplementation compared to L-[ring 13C6] phenylalanine infusion with serial muscle biopsy

Objective

The objective of this study was to determine if clinical dynamic PET/CT imaging with ¹¹C-L-methyl-methionine (¹¹C-MET) in healthy older women can provide an estimate of tissue-level post-absorptive and post-prandial skeletal muscle protein synthesis that is consistent with the more traditional method of calculating fractional synthesis rate (FSR) of muscle protein synthesis from skeletal muscle biopsies obtained during an infusion of L-[ring ¹³C₆] phenylalanine (¹³C₆-Phe).

Methods

Healthy older women (73 ± 5 years) completed both dynamic PET/CT imaging with ¹¹C-MET and a stable isotope infusion of ¹³C₆-Phe with biopsies to measure the skeletal muscle protein synthetic response to 25 g of a whey protein supplement. Graphical estimation of the Patlak coefficient K_i from analysis of the dynamic PET/CT images was employed as a measure of incorporation of 11 C-MET in the mid-thigh muscle bundle.

Results

Post-prandial values [mean ± standard error of the mean (SEM)] were higher than post-absorptive values for both K_i (0.0095 ± 0.001 vs. 0.00785 ± 0.001 min⁻¹, p < 0.05) and FSR (0.083 ± 0.008 vs. 0.049 ± 0.006%/h, p < 0.001) in response to the whey protein supplement. The percent increase in K_i and FSR in response to the whey protein supplement was significantly correlated (r = 0.79, p = 0.015).

Conclusions

Dynamic PET/CT imaging with ¹¹C-MET provides an estimate of the post-prandial anabolic response that is consistent with a traditional, invasive stable isotope, and muscle biopsy approach. These results support the potential future use of ¹¹C-MET imaging as a non-invasive method for assessing conditions affecting skeletal muscle protein synthesis.

Sarcopenia among patients receiving hemodialysis: weighing the evidence

BACKGROUND

There is no consensus on how best to define low muscle mass in patients with end-stage renal disease. Use of muscle mass normalized to height-squared has been suggested by geriatric societies but may underestimate sarcopenia, particularly in the setting of excess adiposity. We compared four definitions of low muscle mass in a prevalent hemodialysis cohort.

METHODS

ACTIVE/ADIPOSE enrolled prevalent patients receiving hemodialysis from the San Francisco and Atlanta areas from June 2009 to August 2011. Whole-body muscle mass was estimated using bioelectrical impedance spectroscopy, performed before a midweek dialysis session (n = 645; age 56.7 ± 14.5 years, 41% women). We defined low muscle mass as muscle mass of 2SD or more below sex-specific bioelectrical impedance spectroscopy-derived means for young adults (18-49 years) from National Health and Nutrition Examination Survey and indexed to height² , body weight (percentage), body surface area (BSA) by the DuBois formula, or Quételet's body mass index (BMI). We compared prevalence of low muscle mass among the four methods and assessed their correlation with strength and physical performance.

RESULTS

The prevalence of low muscle mass ranged from 8 to 32%. Muscle mass indexed to height² classified the smallest percentage of patients as having low muscle mass, particularly among women, whereas indexing by BSA classified the largest percentage. Low muscle mass/height² was present almost exclusively among normal or underweight patients, whereas indexing to body weight and BMI classified more overweight and obese patients as having low muscle mass. Handgrip strength was lower among those with low muscle mass by all methods except height² . Handgrip strength was directly and modestly correlated with muscle mass normalized by percentage of body weight, BSA, and BMI (ρ = 0.43, 0.56, and, 0.64, respectively) and less so with muscle/height² (ρ = 0.31, P < 0.001). The difference in grip strength among patients with low vs. normal muscle mass was largest according to muscle/BMI (-6.84 kg, 95% CI -8.66 to -5.02, P < 0.001). There were significant direct correlations of gait speed with muscle mass indexed to percentage of body weight, BSA, and BMI but not with muscle mass indexed to height² .

CONCLUSIONS

Skeletal muscle mass normalized to height² may underestimate the prevalence of low muscle mass, particularly among overweight and obese patients on hemodialysis. Valid detection of sarcopenia among obese patients receiving hemodialysis requires adjustment for body size.

The diagnosis of sarcopenia is mainly driven by muscle mass in hemodialysis patients

BACKGROUND & AIMS

Sarcopenia is a well-known complication of protein energy wasting in hemodialysis patients. Its diagnosis requires measurements of muscle mass and muscle function. Few studies have reported its prevalence in hemodialysis patients. In this study, we report the prevalence of sarcopenia in this population and evaluate the performance of other parameters for its diagnosis.

METHODS

In this observational cross-sectional study, data from hemodialysis patients from our nephrology department were recorded. Body composition measured by bioimpedancemetry analysis and muscle strength measured by handgrip were recorded. Normal values for sarcopenia were those recommended by the European Working Group on Sarcopenia in Older People (EWGSOP).

RESULTS

The median age (interquartile range) of the 111 patients was 77.5 (70.8-84.8) years. A large majority of 88.3% (n = 98) of patients had a low muscle strength; a low muscle mass index was present in 33.3% (n = 37) of the population. Finally, 31.5% (n = 35) of patients had sarcopenia. These latter were older, had longer dialysis vintage, lower BMI, mid-arm circumference and mid-leg circumference, and a lower prealbumin. The best parameter predicting sarcopenia was BMI (ROC curve AUC of 0.79 [0.68-0.91] (p < 0.001) in men and 0.81 [0.68-0.93] (p = 0.003) in women). Mid-arm circumference predicted sarcopenia, but was less accurate than BMI. Mid-leg circumference predicted sarcopenia only in men. Predialysis creatinine or creatinine index could not predict sarcopenia.

CONCLUSIONS

We report a 31.5% prevalence of sarcopenia in hemodialysis patients. The diagnosis of sarcopenia was mainly driven by muscle mass measurement because muscle strength is low in the large majority of hemodialysis patients.

Protein-energy wasting and nutritional supplementation in patients with end-stage renal disease on hemodialysis

BACKGROUND & AIMS

Protein-Energy Wasting (PEW) is the depletion of protein/energy stores observed in the most advanced stages of Chronic Kidney Disease (CKD). PEW is highly prevalent among patients on chronic dialysis, and is associated with adverse clinical outcomes, high morbidity/mortality rates and increased healthcare costs. This narrative review was aimed at exploring the pathophysiology of PEW in end-stage renal disease (ESRD) on hemodialysis. The main aspects of nutritional status evaluation, intervention and monitoring in this clinical setting were described, as well as the current approaches for the prevention and treatment of ESRD-related PEW.

METHODS

An exhaustive literature search was performed, in order to identify the relevant studies describing the epidemiology, pathogenesis, nutritional intervention and outcome of PEW in ESRD on hemodialysis.

RESULTS AND CONCLUSION

The pathogenesis of PEW is multifactorial. Loss of appetite, reduced intake of nutrients and altered lean body mass anabolism/catabolism play a key role. Nutritional approach to PEW should be based on a careful and periodic assessment of nutritional status and on timely dietary counseling. When protein and energy intakes are reduced, nutritional supplementation by means of specific oral formulations administered during the hemodialysis session may be the first-step intervention, and represents a valid nutritional approach to PEW prevention and treatment since it is easy, effective and safe. Omega-3 fatty acids and fibers, now included in commercially available preparations for renal patients, could lend relevant added value to macronutrient supplementation. When oral supplementation fails, intradialytic parenteral nutrition can be implemented in selected patients.