The New Zealand green-lipped mussel,
(also known as Perna canaliculus, the New Zealand mussel, the greenshell mussel, kuku, and kutai) is a bivalve mollusc in the family Mytilidae. P. canaliculus has great importance as a cultivated species for New Zealand.
This shellfish is economically important to New Zealand. It differs from other mussel species in that it has a dark brown/green shell, a green lip around the edge of the shells and only has one adductor muscle. It is also one of the largest mussel species reaching 240 mm in length.
Green-lipped mussels contain a unique combination of fatty acids. One of these polysaccharides, glycosaminoglycan, is purported to assist in the repair of damaged joint tissues. Studies have also found that Perna canaliculus inhibits the 5-lipoxygenase pathway, which leads to the formation of leukotrienes. Many of the products of these pathways have inflammation-supporting properties.[5] However, a systematic review of current scientific research on supplementation with Green-lipped mussel suggests a lack of compelling evidence for its use in humans with inflammation associated arthritis.

Anti-inflammatory
Arthritis In vitro studies demonstrate anti-inflammatory activity via inhibition of the metabolism of arachidonate and reduced formation of leukotrienes and prostaglandins. In vitro modulation of leukotrienes, cytokines, and immunoglobulin has been demonstrated. Such effects, as well as the inhibition of lipoxygenase and cycloxygenase enzymes, are attributed largely to the polyunsaturated fatty acid content. In addition, the content of chondroitin sulfate, a major component of cartilage matrix and synovial fluid, is of interest.

Animal data
Studies in rats using an adjuvant-induced arthritis model as well as carrageenan-induced rat footpad swelling have generally demonstrated positive anti-inflammatory effects as measured by cytokine and splenocyte protein expression, radiology, paw-swelling, and pain scores. Methodological issues have been noted with route of administration and differing preparations used. Limited studies in dogs with arthritis have been conducted, with reductions in total arthritic scores observed. Improvements in long-term pain and radiological assessments suggest efficacy to be less than that seen with traditional nonsteroidal anti-inflammatory medicines but greater than placebo, suggesting a place in therapy when NSAIDs are contraindicated.

Clinical data
Two systematic reviews have been published; one reviewing osteoarthritis and rheumatoid arthritis trials through 2005, including a highly publicized 1980 trial that reported benefits in patients with rheumatoid arthritis and osteoarthritis, and the other including only osteoarthritis trials through 2007. Generally, clinical trials investigating the use of Perna mussel extracts in arthritis are small and methodologically weak, due to a lack of consistency in product potency and dosing, an absence of placebo or comparator, or use of active placebo. Despite biological plausibility and limited evidence of efficacy in animal studies, there is little compelling evidence to support a therapeutic role for Perna extracts in the treatment or prevention of arthritis.
However, the extract may have a place as adjunctive therapy, because some studies report analgesic effects.

Asthma
eukotrienes are mediators of airway inflammation in asthma. They induce bronchoconstriction and increase mucus secretion and microvascular permeability, allowing infiltration of inflammatory cells (eg, eosinophils, neutrophils) into the airway. Perna mussel extract is thought to prevent this cascade by inhibiting leukotriene production.