Protein-energy status

In clinical practice, only a few laboratory tests are of value in tlie assessment of protein-energy status It is particularly important to recognize that serum protein concentrations are not helpful in sick patients with any form of inflammatory process (see Chapter 20). Although serum albumin is often measured and reported as an indicator of protein-energy status, factors such as increased transcapillary escape and reduced hepatic synthesis malce it of little value as a nutritional marker. Serum albumin is, however, a valuable prognostic marker and is frequently used as part of prognostic indices. Short half-life proteins, such as transthyretin (prealbumin) also may be of some limited value in patients with no inflammatory response. 

Shenkin A, Cederblad G, Elia M, Isaksson B. International Federation of Clinical Chemistry. Laboratory assessment of protein-energy status. Clin Chim Acta 1996 253 S5-59. 

Both the overall rate of protein synthesis and the translation of certain specific mRNAs are controlled by agents such as hormones, growth factors, and other extracellular stimuli. As precursors for protein assembly, amino acids also regulate the translational machinery. Because protein synthesis consumes a high proportion of cellular metabolic energy, the energy status of the cell also modulates translation factors. 

Hardie, D. G. 2003. Minireview the AMP-activated protein kinase cascade the key sensor of cellular energy status. Endocrinology 144 5179-5183. 

Ashour MN, Salem SI, El-Gadban HM, et al. Antioxidant status in children with protein-energy malnutrition living in Cairo, Egypt. Eur J Clin Nutr 53 669-673,1999. 

As retinol circulates in plasma as a 1 1 1 complex with RBP and transthyretin, both of these hepatically produced proteins have been measured as an indicator of vitamin A status. RBP has been measured by radial immunodiffusion or nephelometry (see Chapter 20), but its circulating concentration may be limited by inadequate dietary protein, energy, or zinc, all of which are necessary for RBP synthesis. Another confounding factor in the assessment of vitamin A status is the effect of the APR. Both RBP and transthyretin... 

Lee K, Li B, Xi X, Suh Y, Martin RJ. 2005. Role of Neuronal Energy Status in the Regulation of Adenosine 5 -Monopho-sphate-Activated Protein Kinase, Orexigenic Neuropeptides Expression, and Feeding Behavior. Endocrinology 146 3-10,... 

Prealbumin and retinol-binding protein, traditionally sensitive markers of protein-energy malnutrition, may not be as reliable in patients with hepatic failure. Liver failure can cause decreased concentrations of both, independent of nutritional status. Indeed, many of the commonly used markers of nutritional status correlate poorly with body cell mass in those with end-stage liver disease. Midarm muscle circumference and handgrip strength have been found to be the best... 

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],... 

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