Background: CB1 antagonism has potential benefits in the metabolic syndrome, with effects mediated through central orexigenic mechanisms and peripheral action on adipose tissue. We have previously demonstrated the inhibitory effects of CB1 inactivation on preadipocyte proliferation and now extend these studies to in vitro adipogenesis.
Aims: To compare the effects of CB1 agonism and antagonism on differentiation in both preadipocyte cell lines and primary cultures.
Method: Ethical approval was obtained for collection of adipose tissue from patients undergoing elective abdominal surgery. 3T3-L1 (murine), human subcutaneous and omental preadipocytes (isolated by collagenase digest) were used. Cells were cultured in differentiation medium containing PPARγ agonist alone, or supplemented with 100 nM ACEA (CB1 agonist) or AM251 (CB1 antagonist). mRNA was extracted at various time points and reverse transcribed. Differentiation was measured by oil red O staining for lipid accumulation and Q-PCR measurement of transcript expression for CB1, PPARγ, and GPDH (mouse) or LPL (human).
Results: Adipogenesis was confirmed in both 3T3-L1 and human studies by lipid droplet accumulation visible on oil red O staining. In both populations CB1 expression was upregulated during mid-differentiation coincident with the rise in PPARγ. In cell populations cultured in differentiation medium containing PPARγ agonist, ACEA supplementation resulted in increased expression of PPARγ (2-fold), GPDH (2-fold) and LPL (1.5-fold) in comparison to control cell populations. Conversely there was a 50% reduction in transcript expression for GPDH and LPL in populations treated with AM251. No effect was observed in spontaneous differentiation.
Conclusion: These studies suggest that CB1 agonism stimulates induced adipogenesis and CB1 antagonism has an inhibitory effect. These findings support the anti-obesity effects of CB1 antagonist therapy. Our future studies aim to determine the in vitro effects of CB modulation on insulin sensitivity and adipocytokine profile.