High glycine concentration increases collagen synthesis by articular chondrocytes in vitro: acute glycine deficiency could be an important cause of osteoarthritis

de Paz-Lugo P, Lupiáñez JA, Meléndez-Hevia E · Amino Acids

Glycine at 1.5 mM raised type II collagen synthesis by cultured bovine chondrocytes about 225% over control at fifteen days, and kept raising it up to 7 mM. Proline and lysine reached comparable peaks at lower concentrations — 0.6 and 0.85 mM — and then fell away, standing at one-half and one-third of glycine's effect by 1.5 mM. Aspartate and isoleucine, run as control amino acids, did nothing at any concentration, which is what makes the effect specific. Supports the glycine-limitation hypothesis at the cell level.

Population

Cultured bovine articular chondrocytes

Intervention

Culture medium enriched with glycine, proline, or lysine at graded concentrations

Limitations

Bovine cells in a dish, from three animals, in monolayer rather than in cartilage; culture glycine concentrations exceed normal human plasma levels of 0.25-0.5 mM, though the authors argue 10 g/day of dietary glycine would reach them. Authors are the originators of the hypothesis being tested. The abstract's '60-75%' appears nowhere in the results or the discussion, both of which report an effect several times that size.