Division of Nephrology, Chang Gung Memorial Hospital, Keelung, Taiwan; The Graduate Institute of Clinical Medical Sciences, Chang Gung University Medical College, Taoyuan School of Medicine, Taoyuan, Taiwan; College of Medicine, Chang Gung University, Tao-Yuan, Taiwan; Community Medicine Research Center, Keelung Chang Gung Memorial Hospital, Keelung, Taiwan.
Department of Pediatrics, Taipei Medical University Hospital, Taipei, Taiwan; College of Medicine, Taipei Medical University, Taipei, Taiwan.
Clin Nutr ESPEN. 2021 Dec;46:405-415. doi: 10.1016/j.clnesp.2021.08.037. Epub 2021 Oct 4.
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.
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.
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).
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.
慢性肾脏病（CKD）是全球范围内的负担。建议 CKD 患者采用低蛋白饮食（LPD），以避免或推迟透析的开始，并减缓 CKD 的进展。然而，营养失衡和蛋白质能量消耗是主要关注点。基于氨基酸的代谢谱可能提供一种敏感的生物标志物，用于评估接受 LPD 建议的 CKD 患者的营养状况。
我们对接受 LPD 建议的 CKD 3-5 期患者进行了一项横断面研究，以评估 LPD 与传统标志物（包括血浆白蛋白、前白蛋白、转铁蛋白、总铁结合能力）、炎症标志物（包括外周白细胞计数和血浆高敏 C 反应蛋白水平）、身体成分、肌肉力量和身体功能之间的关系，以及新型营养标志物（包括基于氨基酸的代谢谱）在 CKD 3-5 期患者中的应用。
在我们的研究中，共有 73 名 CKD 3-5 期患者，平均年龄约为 71±10 岁。平均每日蛋白摄入量（DPI）约为 0.9±0.3g/kg/天，25 名（34%）患者达到了 DPI<0.8g/kg/天的推荐目标。平均每日热量摄入量（DCI）约为 23±6kcal/kg/天，仅有 11 名（15%）患者达到了推荐的 DCI，即 30-35kcal/kg/天。与未接受 LPD 的 CKD 患者相比，接受 LPD 的患者血红蛋白和白蛋白水平较低，6 分钟步行距离（6MWD）较短，亮氨酸水平较低。多变量分析发现，较低的血红蛋白和亮氨酸水平以及较短的 6MWD 与 LPD 呈负相关且独立相关（均 P<0.05）。然后 ROC 曲线分析发现，亮氨酸血浆水平的最佳截断值为 95.5μM，灵敏度为 60%，特异性为 71%，曲线下面积为 0.646（95%CI：0.512-0.780），可用于预测接受 LPD 的 CKD 患者。
虽然常规接受标准饮食咨询，但我们发现只有 34%的患者接受了 LPD，而大约 85%的 CKD 3-5 期患者的每日热量摄入不足。CKD 患者的低蛋白饮食和每日热量摄入不足与 6MWD 较短、血红蛋白和亮氨酸水平较低有关。血浆亮氨酸水平低于 95.5μM可能预示着这些热量摄入不足的 CKD 3-5 期患者出现肌肉萎缩和营养不良。
