Development of a Specific Competitive ELISA for Plasma Adropin Levels and Its Application to Investigating Energy Homeostasis in Mice

Adropin is a 43-amino acid peptide that is highly conserved among mammals. First identified in the mouse liver in 2008, adropin is broadly expressed throughout the body and has been implicated in various pathological conditions, including obesity, altered food intake, insulin resistance, glucose intolerance, and other disorders related to energy metabolism. However, its precise physiological role remains unclear. In this study, we developed a specific competitive enzyme-linked immunosorbent assay (ELISA) for adropin using an in-house generated anti-adropin polyclonal antibody. We then examined plasma adropin levels in mice under different energy metabolic conditions: fed a normal diet, subjected to short-term fasting, and fed a long-term high-fat diet. In addition, we assessed hepatic and hypothalamic expression of Enho mRNA, which encodes adropin. We observed a wide range of plasma adropin levels, spanning from those in normal healthy mice on a high-fat diet to preclinical and obese diabetic mice. Both plasma adropin concentrations and hepatic Enho mRNA expression increased in response to feeding and high-fat diet intake. Multiple regression analysis revealed a significant negative correlation between plasma adropin and plasma glucagon concentrations. These findings suggest that adropin secretion is modulated by the peripheral hormone glucagon and may contribute to the maintenance of energy metabolic homeostasis. In conclusion, the ELISA developed in this study provides a useful and reliable tool for investigating the mechanisms underlying energy metabolism.