Net protein retention

Digestible protein figures are not entirely satisfactory measures of the value of a protein to an animal, because the efficiency with which the absorbed protein is used differs considerably from one source to another. In order to allow for such differences, methods for evaluating proteins, such as the protein efficiency ratio (PER), the net protein retention (NPR) and the gross protein value (GPV), which are based on the growth response of experimental animals to the protein under consideration, have been devised. 

Protein, as well as nonprotein energy (i.e., carbohydrates and fats), must be provided in sufficient amounts to drive protein synthesis and prevent protein-energy deficiency [18]. However, too many nonprotein calories will inCTease weight but not lean body mass, which may be the case in certain patients with inherited metabohc disorders on low protein, high caloric intakes. The type of nonprotein energy can make a difference on protein status. Studies have indicated that carbohydrate (CHO), and not fat, can rednce postprandial protein degradation [19,20]. Net protein utilization improved by 5 % and nitrogen retention by 14 % when carbohydrate was offered. Excess CHO withont protein stimulates post-absorptive proteolysis and protein synthesis [21],... 

Proteins have different biological availabilities in the human body and a number of methods have been introduced to evaluate and measure protein utilisation and retention. Two types of measurements are used to estimate protein quality biological assays and chemical analysis. The most common measures of protein quality included Biological Value (BV), Protein Efficiency Ratio (PER), Net Protein Utilisation (NPU), Amino Acid Score (AAS also known as chemical score, CS), Essential Amino Acid Index (EAAl) and Protein Digestibility Corrected Amino Acids Score (PDCAAS), amongst other procedures and modifications. 

In ABL, an early step in apoB lipoprotein assembly shared by intestinal and liver cells is defective. The net result is near absence of all plasma apoB lipoproteins. ApoB synthesis from a mRNA transcript occurs, but its successful assembly into the mature lipoprotein particle does not. The inability to assemble apoB into lipoproteins was shown to be due to a defect in the mttp gene in affected individuals (Wetterau et al., 1992). Its translational product is an 894-amino acid, 97-kd, polypeptide that exists in the ER complexed with a 55-kd protein disulfide isomerase which is believed to maintain solubility, physiologic activity, and ER retention of the 97-kd peptide. The heterodimeric complex of the 97-kd and 55-kd subunits is referred to as microsomal triglyceride transfer protein (MTP) (Wetterau et al., 1992). 

Many characterized INM proteins have been shown to interact with lamins (Ye et al. 1998). For the subset of putative NETs that share this characteristic, a more definite result can be achieved. As previously discussed, the lamin polymer is insoluble to extraction with detergent and salt therefore retention of NETs in cells extracted with detergent (e.g. 0.5% Triton X-100) prior to fixation for microscopy confirms their direct, or indirect, association with the lamin polymer and NE localization. However, loss of the protein to a pre-extraction with detergent would occur for proteins not tethered to the lamin polymer whether they are normally localized to the INM, ONM, or ER. All eight of the putative NETs originally tested targeted to the NE, but only five remained at the NE after the detergent pre-extraction (Schirmer et al. 2003). 

Daniel, V. A., Leela, R., Doraiswamy, T. R., Rajalakshmi, D., Venkat Rao, S., Swaminathan, M., and Parpia, H. A. B. (1966). The effect of supplementing a poor kaffir com (Sorghum vulgare) diet with L-lysine and DL-threonine on the digestibility coefficient, biological value and net utilization of proteins and retention of nitrogen in children. /. Nutr. Diet. 3,10-14. 

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