December 2023 9 Leading Article the production of pro-inflammatory cytokines and other enzymes involved in the destruction of chondrocytes in OA (Simopoulou et al. 2007, Koskinen et al. 2011). Obesity is also linked to other diseases including cardiovascular disease and diabetes mellitus, and it has been hypothesised that OA progression may be worsened by these co-morbidities (Conaghan et al. 2005, Schett et al. 2013). Therefore, weight management is an important factor in OA treatment. Weight loss improved outcomes in terms of joint function, reduced pain and improved QOL for overweight or obese people with knee and hip OA (Messier et al. 2018, Panunzi et al. 2021). These improved clinical outcomes were more pronounced in people who lost more than 10% bodyweight (Atukorala et al. 2016, Messier et al. 2018). In dogs, four studies investigated outcomes in overweight or obese dogs with OA following a weight loss regime (Table 1). Three of these examined outcomes based on weight loss alone. A study involving weight loss in nine overweight and obese dogs with hip OA found a significant improvement in subjective measurements of lameness after 19 weeks, with the dogs losing between 11% and 18% of their bodyweight over the study (Impellizeri et al. 2000). Objective outcomes were used by two studies (Burkholder & Hulse 2000, Marshall et al. 2010). Weight loss led to improved objective measurements of lameness using kinetic gait analysis in 16 dogs with hip OA when body condition score fell from seven or eight out of nine, to four or five out of nine (Burkholder & Hulse 2000). Marshall et al. (2010) found improvements in subjective measurements of lameness, and objective kinetic gait analysis, after a weight loss of 6.1% of bodyweight and 8.85% bodyweight, respectively, in 14 obese dogs with either hip and/or elbow. One published study examined outcomes when physical therapy and weight loss were combined (Mlacnik et al. 2006). The effect of weight reduction and physical therapy (either a home-based physical therapy protocol or intensive programme including transcutaneous electrical nerve stimulation) on lameness was assessed, with greater improvements in the group undergoing weight reduction and intensive physical therapy compared to weight loss alone. These highlighted studies have limitations. Small sample sizes, lack of blinding and lack of control groups limit the level of evidence they provide, although it is difficult to blind owners and assessors to weight loss as it causes a visible change in appearance. However, from the evidence available, it is recommended to maintain a lean body condition in dogs with OA, and pursue a weight loss programme in dogs that are overweight or obese. NUTRACEUTICALS The term “nutraceutical” is defined as “a substance produced in purified or extracted form, which, when administered orally to patients, provides them the necessary elements for their structure and normal function to better their health and well-being” (Boothe 1997). Many nutraceuticals are marketed towards the prevention or treatment of canine OA; however, they are not subject to any regulation due to the lack of evidentiary efficacy reported (Vandeweerd et al. 2012, Comblain et al. 2017). Two previous systematic reviews of veterinary nutraceuticals concluded that there was evidence for clinical efficacy of omega-3 fatty acids in the treatment of canine OA (Vandeweerd et al. 2012, Barbeau-Grégoire et al. 2022), and the more recent of these also found a weak efficacy of collagen (Barbeau-Grégoire et al. 2022). Neither found evidence that glucosamine hydrochloride and chondroitin sulphate provided any beneficial effects in the treatment of canine OA. The most commonly used nutraceuticals are discussed and the evidence behind their efficacy is evaluated. Table 2 details published studies for each of these nutraceuticals Green-lipped mussel (Perna canaliculus) Green-lipped mussel (GLM) is derived from a mussel native to New Zealand and their extract provides essential amino acids, glycoproteins and omega-3 fatty acids. Hielm-Björkman et al. (2009), Soontornvipart et al. (2015) and Vijarnsorn et al. (2019) all demonstrated improvements in clinical outcomes in canine OA by alleviating inflammation and increasing weight-bearing abilities. Furthermore, there has been reported improvement in limb manipulation with a reduction in pain, swelling, crepitus after treatment with GLM in OA dogs (Servet et al. 2006). Dobenecker et al. (2002), however, found no observed effect of adding powdered GLM extract into the animal’s diet and GLM was found to be less effective than carprofen (Hielm-Björkman et al. 2009). Although studies investigating the use of GLM have provided some positive clinical effects in canine OA, there are multiple inconsistencies with respect to the benefits provided. There is currently no recommended dose of GLM, and it is difficult to compare study findings due to different dosages and administration techniques used. Further research is needed to investigate the efficacy of GLM versus non-steroidal anti-inflammatory drugs (NSAIDs) and other pharmaceutical therapies, but also to clarify the optimal dose of GLM to gain improvements in the clinical presentation of OA. Polyunsaturated fatty acids (omega-3) Omega-3 fatty acids modulate the expression and activity of inflammatory biomarkers causing cartilage degradation in OA (Barrouin-Melo et al. 2016, Buddhachat et al. 2017, Adler et al. 2018). Multiple double-blinded randomised studies have found a significant improvement in clinical signs of OA in dogs fed omega-3 supplementation (Fritsch et al. 2010, Roush et al. 2010, Mehler et al. 2016). However, most of these improvements were recorded using subjective methodology, e.g. owner questionnaires using non-validated scoring systems. Both Hielm-Björkman et al. (2012) and Moreau et al. (2013) used objective gait analysis to determine peak vertical force (PVF) and vertical impulse (VI). Moreau et al. (2013) found that the omega-3-infused diet improved locomotor and performance abilities, as well as increased PVF, suggesting that the dogs were inclined to load more weight on the arthritic limbs. Hielm-Björkman et al. (2012) also found greater PVF values and QOL scores, compared to a significant deterioration in veterinary assessments in the placebo group. The study provided evidence that supplementing omega-3 could be used as part of multimodal analgesia for dogs suffering from OA.
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