Role of GATM/creatine as energy reserves in the poll gland and rutting activities in male Bactrian camel.

In the breeding season, male Bactrian camels (Camelus Bactrianus) secrete a large amount of pale-yellow watery secretions with a characteristic odor from the poll glands and spread urine by wagging their tails, which can induce estrus and mating in female camels. However, the compositions of the urine and poll glands secretions during the breeding season are poorly understood. Thus, we investigated the unique secretions of poll glands and identified key metabolites during the breeding season. Neck mane and urine from male camels before and during the breeding season were collected for liquid chromatography-mass spectrometry (LC-MS) analysis to identify differentially expressed metabolites (DEMs). Moreover, poll gland tissue from male camels during breeding periods was collected for LC-MS and data-independent acquisition proteomic analysis to identify the DEMs, differentially expressed proteins, and signaling pathways. Creatine was mainly enriched in the arginine and proline metabolic pathways, highly expressed, and a common metabolite in the poll glands, neck mane, and urine of male Bactrian camels during breeding periods. Immunohistochemical and immunofluorescence assays showed that glycine amidine transferase (GATM) and aldehyde dehydrogenase 18 family member A1 (ALDH18A1), which are closely related to creatine synthesis, were expressed and co-localized in the cytoplasm of poll gland epithelial cells. Quantitative real-time PCR and western blot assays revealed that creatine content and GATM and ALDH18A1 expression levels were significantly increased in the poll glands of active mating camels. These results demonstrate that creatine is a key metabolite in the poll gland secretions and urine of male Bactrian camels during the breeding season and that changes in creatine content are associated with the breeding behavior of male Bactrian camels. This study provides insights into the role of creatine in male Bactrian camels during the breeding season.