Acute nutrition management in the prevention of metabolic illness: A practical approach with glucose polymers

Abstract

Many episodes of metabolic decompensation are triggered by catabolism. Catabolism is a physiologic state in which the body uses internal energetic fuels. It is evoked by lack of nutrition and sufficient calories and enhanced by physiological stressors such as infection. During fasting, metabolism sequentially shifts from use of enteral nutrients during the absorptive stage to glycogenolysis, gluconeogenesis, protein hydrolysis and amino acid oxidation, and lipolysis and fatty acid oxidation. During these processes, intermediates of metabolism are generated resulting in accumulation of toxic intermediaries in many inborn errors of metabolism. These can include organic acids, ammonia, amino acids, such as in maple syrup urine disease, and the accumulation of fatty acyl-CoAs and free fatty acids in fatty acid oxidation disorders. In addition, catabolism can result in a deficiency of an essential energy substrate in inborn errors of metabolism. In glycogen storage diseases, lack of glycogenolysis can result in hypoglycemia, and hypoketonemia occurs in disorders of ketogenesis or fatty acid oxidation. Promotion of anabolism is a key measure in the treatment and prevention of illness in most inborn errors of metabolism. The provision of substrates corrects a deficit, such as glucose in glycogen storage disorders and energy substrates in disorders of fatty acid oxidation and ketogenesis. Anabolism also can decrease accumulating toxic substances by decreasing their production, and by assisting in their removal. Anabolism decreases or halts protein catabolism resulting in reduced generation of ammonia, free amino acids and their metabolites, such as organic acids. During anabolism accumulating metabolites are removed. During the anabolic state, protein synthesis with incorporation of branched chain amino acids helps lower leucine levels in maple syrup urine disease. Free fatty acids are used in triglyceride synthesis, thus lowering them in fatty acid oxidation disorders, and the incorporation of propionyl-CoA in odd-chain length fatty acid synthesis and further into triglycerides removes propionate precursors in propionic acidemia and methylmalonic aciduria. During intercurrent illness in metabolic patients, the resting energy expenditure can be elevated [1], and both protein synthesis and catabolism are increased [2]. Anabolism requires the provision of full caloric support for the immediate period, whereas sustained anabolism beyond 24 h also requires the provision of essential nutrients such as essential ami