Promotion of lipid storage rather than of thermogenic competence by fetal versus newborn calf serum in primary cultures of brown adipocytes

On the Validity of Adipogenic Cell Lines as Model Systems for Browning Processes: In Authentic Brown, Brite/Beige, and White Preadipocytes, There is No Cell-Autonomous Thermogenic Recruitment by Green Tea Compounds

The potential ability of nutritional compounds to induce or enhance the browning of adipocytes has attracted large interest as a workable means of combatting the obesity epidemic. Green tea compounds are discussed as such inducers of an enhanced thermogenic capacity and activity. However, the cell-autonomous effects of green tea compounds on adipocytes have until now only been demonstrated in adipogenic cell lines (3T3-L1 and 3T3-F442A), i.e., cells of undefined tissue lineage. In this study, we examine the ability of green tea compounds to cell-autonomously induce thermogenic recruitment in authentic brown and brite/beige adipocytes in vitro. In primary brown adipocytes, the green tea compounds suppressed basal UCP1 gene expression, and there was no positive interaction between the compounds and adrenergic stimulation. In white adipocytes, green tea compounds decreased both basal and norepinephrine-induced UCP1 mRNA levels, and this was associated with the suppression of cell differentiation, indicated by reduced lipogenic gene expression and lipid accumulation. A lack of interaction between rosiglitazone and green tea compounds suggests that the green tea compounds do not directly interact with the PPARγ pathway. We conclude that there is a negative effect of the green tea compounds on basal UCP1 gene expression, in both brown and white primary adipocytes, in contrast to the positive effects earlier reported from studies in adipogenic cell lines. We posit that the epigenetic status of the adipogenic cell lines is fundamentally different from that of genuine brown and white adipocytes, reflected, e.g., in several-thousand-fold differences in UCP1 gene expression levels. Thus, results obtained with adipogenic cell lines cannot unreservedly be extrapolated as being relevant for authentic effects in brown and white adipocytes. We suggest that this conclusion can be of general concern for studies attempting to establish physiologically relevant cell-autonomous effects.

Human Adipose Tissue Cryopreservation: Impact of Different Calf Serum Concentrations on Tissue Viability

Adipose tissue, which is harvested in large quantities during liposuction, has no blood supply and becomes necrotic within a few hours, if not immediately transplanted. Cryopreservation of adipose tissue allows these samples to be stored and used in diverse fundamental experiments, especially in fat-grafting animal tests that could provide a theoretical basis for clinical applications. Traditionally, fetal bovine serum (FBS) has been added as a cryoprotectant (CPA) to maintain the maximum viability of different tissues after freezing and thawing. Calf serum (CS) comes from the same species as FBS but is more economical compared with FBS-containing medium. The optimal concentration of CS in CPA for banking adipose tissue has not been studied. Here, we studied the cell survival rate, cell viability, tissue structural integrity, number of adipose-derived stem cells and blood vessels, and survival after transplantation into nude mice via ultrastructural evaluation of adipose tissue cryopreserved for 6 months in condition A (60% CS, 15% dimethyl sulfoxide [DMSO], 25% Dulbecco's modified Eagle's medium [DMEM]) and condition B (30% CS, 15% DMSO, 55% DMEM). Our results indicate that CS in addition to CPA results in adequate preservation of adipose tissue, especially when a higher concentration of CS (60%) is used in the CPA.