Submitted on April 11, 2008
Revised on July 22, 2008
Accepted on July 23, 2008
Adiponectin Secretion and Response is Depot-Dependent in Cultured Human Adipose Tissue
Susan A. Phillips1*, T.P. Ciaraldi2, Debra K. Oh1, Michelle K Savu1, and Robert R. Henry3
1 Veterans Affairs San Diego Healthcare System and The University of California, San Diego
2 University of California, San Diego
3 VA San Diego Healthcare System
* To whom correspondence should be addressed. E-mail: saphillips{at}ucsd.edu.
The subcutaneous (S) and visceral (V) adipose tissue (AT) depots are increasingly recognized as distinct. To test the hypothesis that depot differences exist for adiponectin, fresh and cultured human VAT and SAT from obese type 2 diabetic (T2D) and non-diabetic (ND) subjects was examined to determine whether differences in adiponectin content and secretion occurred as a function of depot studied, diabetic status and response to thiazolidinedione treatment. VAT and SAT was obtained by biopsy and AT explants cultured in defined media for 7-days. Protein expression was assessed by western blot. Adiponectin content of conditioned media was determined by radioimmunoassay. Diabetic status had no effect on adiponectin secretion over d0-2 of culture. In ND SAT, secretion fell over d2-4 but was sustained at greater levels versus T2D SAT. In both ND and T2D VAT, adiponectin secretion was low, similar to T2D SAT. Over the 7d culture period cellular adiponectin increased in ND SAT and VAT. It remained unchanged in T2D SAT and VAT. Pioglitazone increased adiponectin secretion and content in all SAT. Pioglitazone failed to increase adiponectin secretion from either ND or T2D VAT and increased cellular content only in ND VAT. AT depot differences exist in the secretion of adiponectin and responsiveness to thiazolidinedione treatment. These data suggest SAT, not VAT appears to be the major contributor to increased circulating adipopnectin levels in response to pioglitazone treatment.
