Desnutrin, an Adipocyte Gene Encoding a Novel Patatin Domain-containing Protein, is Induced by Fasting and Glucocorticoids: Ectopic Expression of Desnutrin Increases Triglyceride Hydrolysis

We have used rat cDNA microarrays to identify adipocyte-specific genes that could play an important role in adipocyte differentiation or function. Here, we report the cloning and identification of a 2.0-kb mRNA coding for a putative protein that we have designated as desnutrin. The novel gene is expressed predominantly in adipose tissue, and its expression is induced early during 3T3-L1 adipocyte differentiation. Desnutrin mRNA levels were regulated by the nutritional status of animals, being transiently induced during fasting. In vitro desnutrin gene expression was up-regulated by dexamethasone in a dose-dependent manner but not by cAMP, suggesting that glucocorticoids could mediate the increase in desnutrin mRNA levels observed during fasting. Desnutrin mRNA codes for a 486-amino acid putative protein containing a patatin-like domain, characteristic of many plant acyl hydrolases belonging to the patatin family. Confocal microscopy of enhanced green fluorescent protein-tagged desnutrin protein-transfected cells showed that the fusion protein localized in the cytoplasm. Moreover, cells overexpressing desnutrin by transfection showed an increase in triglyceride hydrolysis. Interestingly, we also found that the desnutrin gene expression level was lower in ob/ob and db/db obese mouse models. Overall, our data suggest that the newly identified desnutrin gene codes for an adipocyte protein that may function as a lipase and play a role in the adaptive response to a low energy state, such as fasting, by providing fatty acids to other tissues for oxidation. In addition, decreased expression of desnutrin in obesity models suggests its possible contribution to the pathophysiology of obesity.