Arthroprotective effects of salmon nasal cartilage-derived proteoglycan

 Proteoglycans (PGs) are a group of molecules composed of one or more glycosaminoglycans bound to the core protein. They form the extracellular matrix together with collagen and hyaluronic acid. PG is known to have roles in lubrication and buffering of joint cartilage. With advancing osteoarthritis (OA), the joint cartilage becomes worn, resulting in inflammation and pain. Therefore, preservation of the cartilage components seems to be essential.<br> 　Recently, salmon nasal cartilage-derived proteoglycan (SPG) was developed prompted by knowledge about the method of preparation of “Hizu Namasu (salmon nasal cartilage seasoned with vinegar)”, an item of the local cuisine of Hokkaido, Japan. SPG has been reported to have the effects of improving the skin appearance, suppressing blood glucose elevation, improving the intestinal flora, alleviating the symptoms of rheumatoid arthritis.<br> 　The present study (a randomized placebo-controlled double-blind study) was undertaken to evaluate the effects of ingestion of SPG (10 mg/day) for 16 weeks on the markers of cartilage metabolism, i.e., type II collagen decomposition marker (C1, 2C) and type II collagen synthesis marker (PIICP), in 60 healthy subjects of both sexes experiencing discomfort in their knee joints (mean age 52.4 years, Kellgren-Lawrence grade 0-I). In analysis conducted in subjects with the Japanese Knee Osteoarthritis Measure (JKOM) ≥ 41 and the visual analogue scale (VAS) for knee pain at rest ≥ 1 mm, the SPG group showed a significant reduction of the Δ C1, 2C and a tendency towards reduction of the Δ C1, 2C/PIICP ratio after 16 weeks of ingestion of SPG as compared to the placebo group.<br> 　The STR/Ort mouse (a model of spontaneous-onset OA) is known to develop OA with advancing age, presenting with human OA-like features, such as erosive degeneration and calcification of the joint cartilage and narrowing of the joint space. When STR/Ort mice (32 weeks, male) were orally treated with SPG (10 mg/kg) for 4 weeks and the influence on the knee joint tissue was evaluated by examination of safranin-O stained specimens at the end of the dosing period, SPG was shown to have suppressed cartilage injury and also suppressed the decrease of PG.<br> 　These results suggest that SPG reduces decomposition of cartilage components and improves cartilage metabolism, thus having the potential to protect the joint cartilage.