Threonine plasma concentration

Goal Normalize plasma concentrations of isoleucine (ILE), valine (VAL), threonine (THR),... 

The neutral amino acids alanine, serine, threonine, asparagine, glutamine, valine, leucine, isoleucine, phenylalanine, tyrosine, tryptophan, histidine and citrulline share a common transporter at the luminal border of the epithelial cells in the renal tubuli and the epithelial cells in the small intestine [16]. In Hartnup disorder an impairment of this transporter leads to hyperexcretion of these neutral amino acids and to intestinal malabsorption. Excretion of tryptophan metabolites kynurenine and N-methyl-nico-tinamide is reduced. Plasma concentrations of the affected amino acids may be low normal or reduced. The inheritance is autosomal recessive. The hph2-deficient mouse has been postulated as a model for Hartnup disorder [17]. Affected persons may be asymptomatic, while some demonstrate pellagra-like photodermatitis or cerebellar ataxia due to a nicotinamide deficiency and respond well to the administration of nicotinamide [16]. 

One of the key components of mammalian signal transduction pathways is protein kinase C (PKC), which is activated by DAG and Ca (40) and phosphorylates serine and threonine residues. PKC contains a catalytic domain containing an ATP-binding site, and a regulatory domain where the sites involved in Ca, DAG and phospholipid binding reside. Whereas the inactive form of PKC is cytosolic, translocation to the plasma membrane is required for activity. This process is controlled by intracellular Ca concentrations. 

Her very low-protein diet was continued, but in order to ensure an adequate supply of essential amino acids for growth she was fed a mixture of the ketoacids of threonine, methionine, leucine, isoleucine and valine. After each feed she again became abnormally drowsy and markedly ketotic, with significant acidosis. Her plasma ammonium ion concentration was within the normal range, and a glucose tolerance test was normal, with a normal increase in insulin secretion after glucose load. 

Table 1. Threonine requirement of 50W5 in early and late gestation based on indicator amino acid and plasma threonine concentration. 

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