Category: Natural chemicals
Introduction and description
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Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. As an essential amino acid, threonine is not synthesized in humans, and needs to be present in proteins in the diet. Adult humans require about 20 mg/kg body weight/day.
Threonine was the last of the 20 common proteinogenic amino acids to be discovered. It was discovered in 1936 by William Cumming Rose, collaborating with Curtis Meyer.
Deficiency and overdose
The inter-dependency of amino acids means that a sort of cascade of illness can occur from deficiency or overdose in any one of the amino acids, not just threonine. It is known that plasma serine and threonine concentrations are elevated in rats chronically fed an essential amino acid deficient diet. Rats fed a lysine or valine deficient diet for 4 weeks, for example, induced marked elevation of hepatic serine and threonine levels PMID: 18584286
Lack of this essential amino acid, does not just affect human beings, it appears to affect other animals, birds and even fish. In one study, for example, threonine deficiency depressed the disease resistance, and impaired immune and physical barriers in fish . Threonine deficiency also decreased the ability of fish to combat enteritis, and it down-regulated the transcript abundances of liver-expressed antimicrobial peptide and up-regulated intestinal pro-inflammatory cytokines.
Threonine is incorporated into intestinal mucosal proteins and synthesis of secretory glycoproteins. Therefore, it has an important function in neonatal gut barrier integrity. In a study to determine how much threonine is needed by a baby, it was found that the mean threonine requirement was estimated to be 68 mg · kg · day with an upper and lower 95% confidence interval of 104 and 32 mg · kg · day, respectively (r = 0.37). This determined threonine requirement is extremely close to the existing requirement recommendations (∼90% of the present World Health Organization requirement guidelines).
It should be noted that mother’s milk contains the requisite amount, but Infant formula preparations presently on the market, can contain up to twice as much threonine as recommended. Overdose of any chemical is dangerous and may lead to health problems, as such the threonine intake in formula-fed infants may need to be reduced considerably, or better the mother breast feeds the infant. [PMID: 25844708]
In general threonine deficiency appears to affect the intestinal integrity of most animals, birds and fish.
In one study on chickens “Overall, Thr deficiency worsened the detrimental effects of combined feed withdrawal and coccidial infection on growth performance and oocyst shedding by impairing intestinal morphology, barrier function, lymphocyte profiles and their cytokine expressions. PMID: 27993179”
There is also some indication that threoline deficiency may also result in lactation failure
“In conclusion, [animals]with the adequate threonine intake were more able to conserve dietary amino acids to support foetal and maternal tissue gain. Deficient or ST threonine intake may induce a delay in changes in progesterone and prolactin concentrations during the prepartum period impeding the transition from pregnancy to lactation. PMID: 29327380”
For adults, foods high in threonine include cottage cheese, poultry, fish, meat, lentils, Black turtle bean and Sesame seeds.