Identification of the most clinically useful skeletal muscle mass indices pertinent to sarcopenia and physical performance in chronic kidney disease

Aim: Patients with chronic kidney disease (CKD) are characterised by low skeletal muscle mass that negatively impacts physical performance. Operational definitions of ‘low muscle mass’ are inconsistent, and it is unknown how different skeletal muscle mass indices affect the relationship between muscle mass and physical function. Methods: Appendicular skeletal muscle mass (ASM) was measured by dual-energy X-ray absorptiometry in 72 CKD patients. Along with crude ASM, alternative muscle indices were calculated adjusting for height, height-squared, body mass, and BMI. Physical performance was assessed by handgrip strength, sit-to-stand tests, gait speed, the incremental shuttle walk test, and ‘Short Physical Performance Battery’. Results: Prevalence of ‘low muscle mass’ ranged from 26 to 35% of patients depending on the criteria used. The relationship between muscle mass indices and physical function differed for each criteria. Using average coefficients, the association with overall physical function and muscle indices were as follows: crude ASM (r=.258), ASM/height (r=.249), ASM/height-squared (r=.332), ASM/body mass (r=.249) and ASM/BMI (r=.206). Muscle adjusted for markers of adiposity (ASM/body fat %, r=.266; ASM/fat mass, r=.338) provided the best overall associations with physical function. Conclusion: The use of alternative muscle mass indices provide different estimates of ‘low muscle mass’ prevalence, and the strongest (and most useful definition in regard to functional status) involves adjustment for either total or relative body fat. ASM adjusted for adiposity may be physiologically and clinically more relevant in patients with renal disease

Anthropometry-based Equations to Estimate Body Composition: A Suitable Alternative in Renal Transplant Recipients and Patients With Nondialysis Dependent Kidney Disease?

Objective Chronic kidney disease (CKD) patients and renal transplant recipients (RTRs) are characterized by aberrant body composition such as muscle wasting and obesity. It is still unknown which is the most accurate method to estimate body composition in CKD. We investigated the validity of the Hume equation and bioelectrical impedance analysis (BIA) as an estimate of body composition against dual-energy X-ray absorptiometry (DXA) in a cohort of nondialysis dependent (NDD)-CKD and RTRs. Design and methods This was a cross-sectional study with agreement analysis of different assessments of body composition conducted in 61 patients (35 RTRs and 26 NDD-CKD) in a secondary care hospital setting in the UK. Body composition (lean mass [LM], fat mass [FM], and body fat% [BF%]) was assessed using multifrequency BIA and DXA, and estimated using the Hume formula. Method agreement was assessed by intraclass correlation coefficient (ICC), regression, and plotted by Bland and Altman analysis. Results Both BIA and the Hume formula were able to accurately estimate body composition against DXA. In both groups, the BIA overestimated LM (1.7-2.1 kg, ICC .980-.984) and underestimated FM (1.3-2.1 kg, ICC .967-.972) and BF% (3.1-3.8%, ICC .927-.954). The Hume formula also overestimated LM (3.5-3.6 kg, ICC .950-.960) and underestimated BF% (1.9-2.1%, ICC .808-.859). Hume-derived FM was almost identical to DXA in both groups (−0.3 to 0.1 kg, ICC .947-.960). Conclusion Our results demonstrate, in RTR and NDD-CKD patients, that the Hume formula, whose estimation of body composition is based only upon height, body mass, age, and sex, may reliably predict the same parameters obtained by DXA. In addition, BIA also provided similar estimates versus DXA. Thus, the Hume formula and BIA could provide simple and inexpensive means to estimate body composition in renal disease

Quality over quantity? Effects of skeletal muscle myosteatosis and fibrosis on physical functioning in chronic kidney disease

Background Chronic kidney disease (CKD) is characterised by adverse changes in body composition, which are associated with poor clinical outcome and physical functioning. Whilst size is 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-60 (STS-60) test, incremental (ISWT) and endurance shuttle walk tests (ESWT), lower limb and handgrip strength, exercise capacity (VO2peak), and gait speed. Results patients (58.5±14.9) years, 46% female, eGFR 31.1±20.2 mL/min/1.73m2 40 ) were recruited. Lower EI (i.e. higher muscle quality) was significantly associated with better physical performance [STS-60 (r=.363) and ISWT (r=.320)], and greater VO2peak (r=.439). The qualitative rating were closely associated with EI values, and significant differences in function was 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

The influence of acute moderate-to-high intensity aerobic exercise on markers of immune function and microparticles in renal transplant recipients.

Renal transplant recipients (RTRs) and non-dialysis chronic kidney disease (ND-CKD) patients display elevated circulating microparticle (MP) counts, whilst RTRs display immunosuppression-induced infection susceptibility. The impact of aerobic exercise on circulating immune cells and microparticles is unknown in RTRs. Fifteen RTRs (age 52.8±14.5 years, estimated glomerular filtration rate [eGFR] 51.7±19.8 ml/min/1.73m2 [mean ± SD]), 16 ND-CKD patients (54. ± 6.3 years, eGFR 61.9±21.0 ml/min/1.73m2, acting as a uremic control group), and 16 HCs (52.2±16.2 years, eGFR 85.6±6.1 ml/min/1.73m2) completed 20 minutes of walking at 60-70% VO2 peak. Venous blood samples were taken pre, post, and 1h post-exercise. Leukocytes and MPs were assessed using flow cytometry. Exercise increased classical (p = 0.001) and non-classical (p = 0.002) monocyte subset proportions but decreased the intermediate subset (p < 0.001) in all groups. Exercise also decreased the percentage of platelet-derived MPs that expressed tissue factor (TF+) in all groups (p = 0.01), though no other exercise-dependent effects were observed. The exercise-induced reduction in intermediate monocyte percentage suggests an anti-inflammatory effect, though this requires further investigation. The reduction in the percentage of TF+ platelet-derived MPs suggests reduced pro-thrombotic potential, though further functional assays are required. Exercise did not cause aberrant immune cell activation, suggesting its safety from an immunological standpoint (ISRCTN38935454)