Does saliva contain an adiponectin-like imposter?

Objectives: Serum adiponectin is secreted from adipocytes and may influence insulin resistance, inflammation and cardiovascular system. It has anti-inflammatory properties and may exert on obesity and related diseases. Decreased levels of plasma adiponectin were found in obese patients resulting in an increased level of infections, for example periodontitis.
Although adiponectin was considered to be synthesized and secreted exclusively by adipocytes and detected in blood, it is also present in other, less invasive, body fluids such as saliva and gingival crevicular fluid (GCF).
Objectives: this study aims to determine the sources of adiponectin and the challenge of its detection.
Methods: Methods: from healthy adult volunteers, unstimulated whole mouth saliva (UWMS) was collected for 5 minutes; GCF was collected using a periopaper inserted 1 mm below the free gingival margin for 30 seconds. Blood was obtained by a finger prick and collected using sialostrip. Adiponectin was detected by immunoblotting, enzyme linked immunosorbant assay (ELISA), and multiplex array.
Results: Results: in immuno-blotting, after loading samples and standard under heating and reducing conditions, monomer adiponectin was seen at 30KDa in blood and standard. However, in saliva a single positive band was found at different molecular weight of purified adiponectin. ELISA showed positive results in saliva and GCF but not in serum. In contrast multiplex array showed the highest concentration of adiponectin in blood, less in GCF and the least in saliva.
Conclusions: Conclusion: salivary adiponectin has a small contribution from serum via the GCF but there also appears to be a contaminating protein which reacts with several antibodies (in western blots and ELISAs) which is unlikely to be adiponectin. It is yet to be shown whether this imposter has biological activity.