The preventive effect of greenshell mussel meat against osteoarthritis in vivo : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Health Science At Massey University, Palmerston North, New Zealand

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Osteoarthritis (OA) is identified by progressive cartilage erosion of synovial joints. One of the most prevalent OA phenotypes, metabolic OA (MetOA), is linked to metabolic syndrome (MetS). MetS is a combination of obesity, type II diabetes, hypertension, and hyperlipidemia; the effects of these disorders can lead to the development of MetOA. Osteoporosis is characterised by loss of bone mineral density and is causally linked with a decrease in systemic estrogen levels. As MetS, OA and osteoporosis are all prevalent in postmenopausal women, it is possible they may be causally linked. For example, systemic low-grade inflammation in MetS may trigger inflammation in both joints and bone, which could be further aggravated by high fat/high sugar diet (HFHS)-induced obesity and gut dysbiosis. We hypothesized that chronic inflammation would be correlated with MetOA development and therefore decreasing inflammation would be protective. New Zealand greenshell mussel (GSM) contains anti-inflammatory properties shown to reduce OA symptoms and omega-3 fatty acids shown to reduce the development of post-menopausal osteoporosis. We hypothesized GSM could protect against both MetOA and osteoporosis reducing bone resorption, inhibiting inflammation and/or modulating beneficial gut microbes. In vitro, non-polar GSM lipids demonstrated bone-protective properties and significantly reduced osteoclast differentiation, tartrate-resistant acid phosphatase activity, actin ring formation and gene expression of matrix metalloproteinase, cathepsin K, carbonic anhydrase and nuclear factor of activating T cells 1. In vivo, aging, HFHS and OVX produced a rat model mimicking human MetS. Dietary whole GSM powder provided protection by significantly reducing a biomarker of collagen degradation and subsequent joint damage, as well as improving short-term bone mineral density and lean mass accrual. GSM-induced changes in gut microbiota were not correlated with dysbiosis. No changes in inflammatory markers were found, disproving our initial hypothesis and suggesting that chronic inflammation may not be a critical factor in MetOA. In conclusion, GSM as a dietary intervention may reduce the incidence or progression of MetOA but not via altering systemic inflammation or gut dysbiosis.
Osteoarthritis, Prevention, Alternative treatment, Perna, Therapeutic use, Diseases, Animal models