High Plasma Concentrations of Sclerostin, an Inhibitor of the Wnt Signaling Pathway, in Young Horses Affected by Osteochondrosis

Osteochondrosis (OC) is a developmental disease in horses with a significant impact on the horse’s welfare and performance. The early disturbance of enchondral ossification progresses to inflammatory and healing process in older horses. Metabolic pathway analysis showed an obvious dysregulation of several signaling pathways related to cartilage formation and cartilage repair such as Wnt/β-catenin, Indian hedgehog and TGF-β signaling pathways. Other regulated genes appeared to be involved in high carbohydrate diet, abnormal insulin metabolism or inflammation. Sclerostin is an osteocyte-secreted soluble antagonist of the Wnt/β-catenin signaling pathway. It is crucial for osteoblast development and activity and is increased in naturally occurring lesions of equine osteochondrosis. The aim of this study is to compare the circulating sclerostin levels between OC-affected (n = 20) and healthy horses (n = 19). A significant linear regression between plasma sclerostin and age is observed especially in the healthy young horses. The mean plasma sclerostin concentration is significantly higher in young horses suffering from osteochondrosis compared to the control horses. These results reinforce the possible role of the Wnt/β-catenin signaling pathway in the OC pathogeny. The inhibition of this essential pathway could disturb the osteo-chondral differentiation. More studies are currently needed to define the eventual clinic interest of plasma sclerostin as future biomarker in bone and cartilage diseases.

Effect of honey on oxidation, chlorination and nitration by purified equine myeloperoxidase

Objective: To evaluate the antioxidant effect of honey using two classical methods generally used, and for the first time to test the effect of honey on the oxidation, chlorination and nitration by purified equine myeloperoxidase (MPO). Methods: The antioxidant activity of three Algerian honey samples (nectar honey, mixed honey and honeydew honey) was evaluated by two classical methods, the ferric- reducing/antioxidant power (FRAP) assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging capacity. Results: Honeydew honey had the highest reducing power and DPPH radical-scavenging activity, whereas nectar honey showed the lowest reducing power and DPPH radical-scavenging activity. All honey samples showed a significant inhibitory effect on the chlorination activity of equine MPO, but honeydew honey was the weakest inhibitor. The three samples were poorly inhibitor on the MPO oxidation and nitration activities, except for nectar honey that exerted an inhibitory effect at the highest tested concentration of 10%. These later results seem to contradict those obtained with DPPH and FRAP. Conclusions: The antioxidant capacity of honey is mainly due to the phenolic compounds and flavonoids it contained. It has been suggested that MPO might be involved in the antioxidant, not pro-oxidant, activity of phenolic compounds.