The association between low protein diet and body composition, muscle function, inflammation, and amino acid-based metabolic profile in chronic kidney disease stage 3–5 patients

Background: Chronic kidney disease (CKD) is a global burden in the world. Low protein diet (LPD) recommendation is suggested in CKD patients to avoid or defer dialysis initiation and slow down CKD progression. However, nutritional imbalance and protein energy wasting represent key worries. The amino acid-based metabolic profile may provide a sensitive biomarker to evaluate CKD patients' nutrition status with LPD recommendations. Methods: We conducted a cross-sectional study in CKD stage 3–5 patients who had received LPD recommendation to evaluate the association between LPD and traditional markers (including plasma levels of albumin, pre-albumin, transferrin, total iron-binding capacity), inflammation markers (including peripheral leukocyte count and plasma levels of high-sensitivity C-reactive protein), body composition, muscle strength, and physical function, and novel nutrition markers (including amino acid-based metabolic profile) in CKD stage 3–5 patients. Results: In our study CKD stage 3–5 patients with the total number of 73, the mean age was around 71 ± 10 years old. The mean daily protein intake (DPI) was around 0.9 ± 0.3 g/kg/day and 25 (34%) patients met the recommended goal of DPI <0.8 g/kg/day. The mean daily calorie intake (DCI) was around 23 ± 6 kcal/kg/day, with only 11 (15%) patients met the recommend DCI with 30–35 kcal/kg/day. Compared to CKD patients with non-LPD, patients with LPD had significantly lower hemoglobin and albumin levels, shorter 6-min walking distance (6MWD), and lower leucine levels. Multivariable analysis found that lower hemoglobin and leucine levels, and shorter 6MWD were negatively and independently associated with LPD (all p < 0.05). Then ROC curve analysis found that the optimal cut-off value of leucine plasma levels was 95.5 μM with 60% sensitivity and 71% specificity to predict those CKD patients with LPD with the area under the curve of 0.646 (95% CI: 0.512–0.780). Conclusion: LPD attainment was noted in 34% patients and most of CKD stage 3–5 patients (around 85%) had inadequate daily calorie intake although receiving standard dietary counseling routinely. A low protein diet and inadequate daily calorie intake in CKD patients were associated with shorter 6MWD, and lower hemoglobin and leucine levels. Plasma leucine levels lower than 95.5 μM may be a herald for muscle wasting and malnutrition in these CKD stage 3–5 patients with inadequate calorie intake.