Differential distribution and expression of leptin and the functional leptin receptor in major salivary glands of humans.

Leptin plays a central role in the regulation of food intake and energy expenditure in rodents. However, it has become clear that this hormone has more than only a satiety-inducing function, and that there are other sources of leptin, such as the central nervous system, placenta and the gastrointestinal tract in addition to adipose tIssue. Knowing about the important role of the salivary glands in food intake and digestion, it was the objective of the present study to investigate how leptin and its receptor are expressed and distributed in the major salivary glands of humans. We found leptin distributed throughout the major salivary glands with obvious intracellular concentrations in granula. In contrast, immunostaining for the leptin receptor was found exclusively in the membranes of the glandular cells. A high density of the leptin receptor was localised in the epithelia of the duct lumen. PCR analysis proved the autonomous expression of leptin by the salivary glands independently from adipocytes. Accordingly the long receptor isoform was expressed by any examined tIssue. In the light of recent findings of leptin influencing the growth of rodent salivary glands, the presence and distribution of leptin and its receptor suggests an autocrine role of salivary leptin within the glands.