Influence of protein intake on the changes in skeletal muscle mass after kidney transplantation.

BACKGROUND & AIMS: Skeletal muscle mass decreases in patients with chronic kidney disease, especially those on dialysis with end-stage kidney disease. On the other hand, the recovery of renal function due to successful kidney transplantation (KT) improves skeletal muscle mass loss. However, low protein intake may influence the changes in skeletal muscle mass after KT. The aim of the present study is to examine the association of the changes in skeletal muscle mass with protein intake in kidney transplant recipients (KTRs). METHODS: A cohort study was conducted in KTRs and living-kidney donors (LKDs). Skeletal muscle mass index (SMI) was measured using bioelectrical impedance analysis before KT and at 1 month and 12 months after KT. Protein intake was calculated with 24-h urine urea nitrogen from the Maroni formula at 12 months after KT. To evaluate the association between protein intake and the changes in SMI during the first year after KT, we performed a multivariable regression analysis adjusted for covariates including age, sex, cumulative glucocorticoids, cumulative hospitalization, diabetes mellitus, and SMI before KT. RESULTS: In KTRs (n = 64), the median SMI was 7.26 kg/m2 before KT, which decreased to 7.01 kg/m2 at 1 month after KT and increased to 7.55 kg/m2 at 12 months after KT. In LKDs (n = 17), the median SMI was 6.24 kg/m2 before KT which increased to 6.40 kg/m2 at 1 month after KT and further increased to 6.95 kg/m2 at 12 months after KT. The changes in SMI during the 1-year period after KT exhibited a positive correlation with protein intake (p = 0.015) after adjustment. The predicted value of protein intake in KTRs, whose values of SMI before KT and at 12 months after KT were the same, was 0.72 g/kg ideal body weight (IBW)/day using the multivariable non-linear regression model. CONCLUSIONS: In KTRs, insufficient protein intake adversely affected the recovery from skeletal muscle mass loss after KT. Therefore, a protein intake of at least more than 0.72 g/kg IBW/day, the predicted value obtained in the present study, might be recommended for KTRs suffering from skeletal muscle mass loss.

Association of sarcopenia with phase angle and body mass index in kidney transplant recipients.

Malnutrition is an important risk factor for the development of sarcopenia. Recently, phase angle (PhA) obtained from the bioelectrical impedance analysis is increasingly becoming known as a nutritional status marker and may be considered a good indicator to identify elderly patients at risk of sarcopenia. In this study, we investigated the prevalence of sarcopenia and the relationship between sarcopenia and PhA or body mass index (BMI) as nutritional factors, and evaluated the discrimination performance of these nutritional factors for sarcopenia in 210 kidney transplant recipients. The median age was 55 years and 11.1% had sarcopenia. This prevalence of sarcopenia was lower than previous reports in kidney transplant recipients, maybe because of the differences in sarcopenia definitions and population demographics such as age, sex, race, and comorbidities. Both PhA and BMI were negatively correlated with sarcopenia after adjusting for age, sex, dialysis vintage, time after transplant, presence of diabetes mellitus, hemoglobin, estimated glomerular filtration rate, and the other nutritional factor. The discrimination performance for PhA and BMI had enough power to detect sarcopenia. These results suggest that PhA and BMI can be used in clinical practice to predict sarcopenia in kidney transplant patients.