Investigation of the relationship between apelin hormone response and some physiological parameters in enzootic bovine leukosis virus infected cattle

Apelin is a hormone with lymphangiogenesis potential, associated with tumor growth and lymph node metastasis, and is reported to stimulate tumor vascularization. This study aimed to investigate the response of the apelin hormone in cattle with and without Enzootic Bovine Leukosis (EBL) infection, based on physiological parameters such as breed, age, and body condition score (BCS). A total of 120 Simmental and Montafon cattle of varying ages (<2, 2-8, and >8) and BCS categories (<2, 3-3.5, and >= 4) were included in the study. Serum apelin hormone levels were measured using the ELISA technique in blood samples collected from the neck vein ( Vena jugularis) of the animals. The analysis of mean serum apelin (ng/mL) values revealed that, among EBL-positive cattle, the highest value was 2.77 ng/mL in Simmental cattle aged 2-8 years with a BCS of 3-3.5, while a value of 2.69 ng/mL was observed in Montafon cattle aged >8 years with a BCS of 3-3.5. For EBL-negative cattle, the highest mean serum apelin value was 2.24 ng/mL, recorded in Simmental cattle aged 2-8 years with a BCS of 3-3.5, whereas it was 1.45 ng/mL in Montafon cattle aged >8 years with the same BCS. In conclusion, this study demonstrated for the first time the effect of apelin hormone levels in cattle with or without EBL, depending on physiological parameters such as age, breed, and BCS. It is suggested that the apelin hormone, which is involved in neoplastic lymphocyte cell infiltration in the lymphoreticular tissues of cattle, and plays a role in regulating tumor growth in EBL, a malignant tumor disease, may contribute to eradication programs. Moreover, the evaluated parameters may prove valuable for disease prevention and control strategies.