Irisin/FNDC5: A participant in camel metabolism

The quantification, localization, production, function, and regulation of irisin/FNDC5 in camel species have not been previously studied. The objective of this study was to detect the irisin content in Arabian camel blood and tissues and study the gene expression of FNDC5 and PGC-1α in camel skeletal muscles and white adipose tissue depots under basal conditions. To monitor if exercise influences blood and tissue irisin protein levels as well as FNDC5 and PGC-1α gene expression levels, we analyzed irisin concentrations in the serum, skeletal muscles (soleus and gastrocnemius), and white adipose tissues (hump, subcutaneous, visceral, epididymal, and perirenal) in both control (n = 6) and exercised group (n = 6) using ELISA and determined the cellular localization of irisin/FNDC5 and the mRNA levels of FNDC5 and PGC-1α in skeletal muscles and adipose tissues via immunohistochemistry and real-time PCR, respectively. The possible regulatory roles of exercise on some hormones and metabolites as well as the detection of links between serum irisin and other circulating hormones (insulin, leptin, and cortisol) and metabolites (glucose, free fatty acids, triglycerides, and ATP) were explored for the first time in camels. Our results indicated that exercise induces tissue-specific regulation of the camel irisin, FNDC5, and PGC-1α levels, which subsequently regulates the circulating irisin level. Significant associations were detected between the levels of irisin/FNDC5/PGC-1α in camels and the metabolic and hormonal responses to exercise. Our study suggested that irisin regulates, or is regulated by, glucose, FFA, insulin, leptin, and cortisol in camels. The novel results of the present study will serve as baseline data for camels

FNDC5 Gene Expression in the Smooth Muscles of Dromedary Camels (Camelus dromedarius)

Irisin is a recently reported adipo-myokine. It is synthesized after the proteolytic cleavage of its precursor, fibronectin type III domain-containing protein 5 (FNDC5) prior to its release into the circulation. Currently, it is unknown whether irisin/FNDC5 exists in the tissues of camel species. Our findings demonstrated for the first time the existence of mRNA transcripts for FNDC5 gene in the dromedary camel smooth muscles, as determined by RT-PCR analysis and showed predominant localization of irisin/FNDC5 protein in the visceral and vascular smooth muscle cells of dromedary camels, as assessed by immunohistochemical analysis. The present study suggests that irisin/FNDC5 possibly has physiological role(s) in the contractility and motility of the camel intestinal smooth muscle cells as well as it might be implicated in the maintenance and control of blood pressure in camels. These important factors could contribute to the distinct biological characteristics of dromedary camels for adaptation to harsh environmental conditions