Abstract
The daily amount and quality of protein that should be administered by enteral nutrition in pre-dialysis chronic kidney disease (CKD) patients is a widely studied but still controversial issue. This is due to a compromise between the protein necessary to maintain muscular proteostasis avoiding sarcopenia, and the minimal amount required to prevent uremia and the accumulation of nitrogenous toxic substances in blood because of the renal function limitations. This review underlines some intracellular and extracellular features that should be considered to reconcile those two opposite factors. On one hand, the physiological conditions and usual side effects associated with CKD, mTOR and other proteins and nutrients involved in the regulation of protein synthesis in the muscular tissue are discussed. On the other hand, the main digestive features of the most common proteins used for enteral nutrition formulation (i.e., whey, casein and soy protein) are highlighted, due to the importance of supplying key amino acids to serum and tissues to maintain their concentration above the anabolic threshold needed for active protein synthesis, thereby minimizing the catabolic pathways leading to urea formation.
Highlights
In chronic degenerative diseases related to nitrogen metabolism and excretion, such as chronic kidney disease (CKD), the optimization of the amount of protein ingested in the diet is especially relevant
The occurrence of metabolic disorders and the nature of the amino acid mixture resulting from protein digestion, the general state of the patient and the severity of the CKD implies that proper protein intake should be carefully considered
CKD patients are usually classified into five stages according to Estimated Glomarular Filtration Rate (eGFR) and albuminuria, but for purposes of urea and other nitrogenous molecules, the five stages might be condensed into two large groups
Summary
In chronic degenerative diseases related to nitrogen metabolism and excretion, such as chronic kidney disease (CKD), the optimization of the amount of protein ingested in the diet is especially relevant. This review aims to highlight some metabolic insights on the main factors to be considered for a rational design of protein intakes to preserve muscular proteostasis in pre-dialysis CKD patients under conservative therapy. The goal of this contribution is not the proposal and quantitation of the amount of protein that should be administered, because there are many recommendations from scientific societies and nutrition committees in addition to those mentioned formerly, many others [13–17] and excellent and updated reviews for complying that point [18,19]
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