Effects of salmon calcitonin and omega – 3 fatty acids on selected biomarkers in experimental diabetic – osteoarthritic rats

Decades back, there were reports on the pathogenic association between diabetes mellitus (DM) and osteoarthritis (OA). Moreover, it was recently reported that in the presence of DM, OA worsens glycaemic control, and that various symptoms of these disease conditions offset each other. Therefore, the present study investigated the effects of salmon calcitonin (Sct) and/or omega–3 fatty acids (N-3: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); EPA/DHA ratio = 3/2) on known biochemical markers in diabetic-knee osteoarthritic rats. Diabetes was induced by the administration of streptozotocin (65 mg/kg) and nicotinamide (110 mg/kg), while, knee OA was induced by the intra-articular injection of 4 mg of sodium monoiodoacetate. Thereafter, N-3 were administered at 200 mg/kg/day, while Sct was administered at 2.5 and 5.0 IU/kg/day for four weeks. The results showed that the induced diabetic-osteoarthritic condition featured imbalances of lipid metabolism, pro-inflammatory and hyperglycaemic responses. After N-3 administration, there were significant hypercalcaemic, hypoglycaemic, and insulin releasing effects. Moreover, N-3 significantly elevated glycogenesis in the hepatic tissue and nitric oxide synthesis. However, Sct significantly contradicted all these effects in a dose-dependent and non-dose dependent measures. Nevertheless, both therapies demonstrated non-additive effects on cortisol, interleukin-6, lipid profile, and uric acid. In conclusion, the co-administration of Sct and N-3, and not the single therapy, could be preferably used in the management of diabetic-osteoarthritic state.