Lysine and threonine: essential amino acids important for the connective tissue

Lysine

Lysine is an essential amino acid, which means that our body cannot make it and therefore we must obtain it through our nutrition.

Lysine increases the absorption of calcium in the intestines and limits its evacuation through the urine, which helps maintain healthy bones. Lysine also promotes healthy blood vessels and smooth muscles and limits calcium deposits in the vessels by helping to move calcium from the vessels to the bones.^1,2

In addition, lysine is one of the amino acids necessary for collagen, the protein responsible for the shape and mechanical properties of our tissues. Indeed, lysine is critical for the synthesis of collagen and then for its optimal function. Lysine plays a key role in the structure of collagen, as it acquires many enzymatic modifications (post-translational modifications), particularly those that allow the links in and between collagen chains.³ Lysine also inhibits MPPs, the enzymes responsible for collagen degradation.⁴

These properties make lysine an ally of choice to support wound healing. At the skin level, it facilitates cell proliferation, modulates inflammation and angiogenesis (vascularization) and may even have an antimicrobial action, particularly against herpes, which accelerates healing.^5,6 For bone healing, lysine also accelerates healing by two weeks : it will activate the osteoblasts that form bone, increase calcium and collagen content, promote vascularization and stimulate the secretion of growth factors and insulin (the entry of glucose into cells).^7,8

Finally, lysine may even have some effects on cancer, cataracts, diabetes, hypertension and anxiety.^4,9-13

Threonine

Threonine is also an essential amino acid brought by nutrition. It is very important for the good structure of our tissues, as it is the precursor of glycine, the main amino acid of collagen. In addition, threonine incorporated in collagen plays an important role in the stability of collagen and inter-chain bonds (inter-fibrils of collagen). Threonine is also present in elastin fibres, another structural fibre present in certain connective tissues such as skin and ligaments.^14,15

Threonine also participates in the cellular energy cycle, being the precursor of Acetyl-CoA. Acetyl-CoA may stimulate the immune system and the secretion of neurotransmitters, as well as limit anxiety and the accumulation of fat in the liver.^14,16

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Spallotta, F. et al. Enhancement of lysine acetylation accelerates wound repair. Communicative and Integrative Biology 6, (2013).
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Sulochana, K. N., Punitham, R. & Ramakrishnan, S. Beneficial effect of lysine and amino acids on cataractogenesis in experimental diabetes through possible antiglycation of lens proteins. Experimental Eye Research 67, 597–601 (1998).
Kalogeropoulou, D., LaFave, L., Schweim, K., Gannon, M. C. & Nuttall, F. Q. Lysine ingestion markedly attenuates the glucose response to ingested glucose without a change in insulin response. American Journal of Clinical Nutrition 90, 314–320 (2009).
Vuvor, F., Mohammed, H., Ndanu, T. & Harrison, O. Effect of lysine supplementation on hypertensive men and women in selected peri-urban community in Ghana. BMC Nutrition 3, 67 (2017).
Payen, V. L. et al. (+)-catechin in a 1:2 Complex with lysine inhibits cancer cell migration and metastatic take in mice. Frontiers in Pharmacology 8, (2017).
Smriga, M. et al. Oral treatment with L-lysine and L-arginine reduces anxiety and basal cortisol levels in healthy humans. Biomedical Research 28, 85–90 (2007).
Bird, M. I., Nunn, P. B. & Lord, L. A. J. Formation of glycine and aminoacetone from l-threonine by rat liver mitochondria. BBA – General Subjects 802, 229–236 (1984).
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Boehm, G. et al. Effect of increasing dietary threonine intakes on amino acid metabolism of the central nervous system and peripheral tissues in growing rats. Pediatric Research 44, 900–906 (1998).