Dietary glycine prevents peptidoglycan polysaccharide-induced reactive arthritis in the rat: role for glycine-gated chloride channel

Li X, Bradford BU, Wheeler MD, Stimpson SA, Pink HM, Brodie TA, Schwab JH, Thurman RG · Infection and Immunity

Ankle swelling rose 2.1 mm in controls but 1.0 mm on glycine, with limp scores of 3.6 against 1.2; blinded histology totalled 14.5 against 7.1, and bone erosion 2.8 against 1.0, with inflammatory infiltration, edema and synovial hyperplasia each lower on glycine. Serum glycine was 0.95 mM on the diet against 0.18 mM. TNF-alpha mRNA was undetectable in glycine-fed joints. The mechanism is immunomodulation via a glycine-gated chloride channel on macrophages — blocked by strychnine — not collagen synthesis.

Population

Rats with peptidoglycan-polysaccharide-induced reactive arthritis

Intervention

Diet with 5% glycine replacing 5% casein, started 3 days before arthritis reactivation and continued through it; five rats per group

Comparator

Nitrogen-balanced control diet

Limitations

Rats, five per group, and an inflammatory/reactive arthritis model rather than osteoarthritis or a cartilage-matrix endpoint. Says nothing about whether dietary glycine builds cartilage; the pathway is anti-inflammatory. NIH-funded; three of the eight authors were at Glaxo-Wellcome.