An essential infusion for an essential organ.

Essential amino acid-based parenteral nutrition (PN) was found to be superior to hypertonic dextrose for patients with acute renal failure in a classical randomized trial that was published in 1973. However, subsequent trials were not able to duplicate this finding when this formulation was compared to hypertonic dextrose or to standard amino acid-based PN. As a result, this intervention has not been recommended in various guidelines for the nutrition support of patients with renal failure. However, all of these trials were relatively small, and none of them compared the intervention to a true control group-namely, patients who were not receiving any artificial nutrition. Because no trials have compared any form of artificial nutrition to no nutrition support in patients with acute renal failure, there really is no basis on which to make any level 1 evidence-based recommendation. Furthermore, a close look at all of the trials suggests that the essential amino acid-based formulation may be superior to the other types of intravenous nutrient supplementation to which it was compared. To determine whether this should be offered to patients with acute renal failure, we need data from one or more large, well-designed and executed, low risk of bias randomized trial(s) comparing essential amino acid-based PN to no nutrition therapy.

Reappraisal of the 20th-century version of amino acid metabolism.

In this article, we advocate the radical revision of the 20th-century version of amino acid metabolism as follows. (1) Classic studies on the incorporation of [15N]ammonia into glutamate, once considered to be an epoch-making event, are not distinctive proof of the ability of animals to utilize ammonia for the synthesis of alpha-amino nitrogen. (2) Mammalian glutamate dehydrogenase has been implicated to function as a glutamate-synthesizing enzyme albeit lack of convincing proof. This enzyme, in combination with aminotransferases, is now known to play an exclusive role in the metabolic removal of amino nitrogen and energy production from excess amino acids. (3) Dr. William C Rose's "nutritionally nonessential amino acids" are, of course, essential in cellular metabolism; the nutritional nonessentiality is related to their carbon skeletons, many of which are intermediates of glycolysis or the TCA cycle. Obviously, the prime importance of amino acid nutrition should be the means of obtaining amino nitrogen. (4) Because there is no evidence of the presence of any glutamate-synthesizing enzymes in mammalian tissues, animals must depend on plants and microorganisms for preformed alpha-amino nitrogen. This is analogous to the case of carbohydrates. (5) In contrast, individual essential amino acids, similar to vitamins and essential fatty acids, should be considered important nutrients that must be included regularly in sufficient amounts in the diet.