Endocrine Abstracts

Objective: Endocannabinoids (CBs) are novel lipid mediators that modulate appetitive behaviour and energy metabolism. The overactivation of the endocannabinoid system plays an important role in obesity. Endocannabinoids may regulate the lipid metabolism through their receptors (CB1 and CB2) in liver and adipose tissue. 11β-hydroxysteroid dehydrogenase (11β-HSD1) type 1 regulates the local availability of active glucocorticoid, potent inductors of adipogenic differentiation. We hypothesized that CBs are involved in adipogenesis and investigated whether this occurs via 11β-HSD1 modulation.

Materials and methods: Of 3T3-L1 cells were either differentiated with a cocktail containing dexamethasone+IBMX+insulin, or with insulin alone and treated with anandamide (AEA 100 nM–10 mcM) for 48–96 h. Gene expression was analyzed by reverse transcription followed by PCR with specific murine primers for 11β-HSD1 and beta-actin as housekeeping gene. 11β-HSD1 activity was measured as [3H]-cortisone into [3H]-cortisol conversion estimated by TLC separation and beta-scanning.

Results: At day 7 of differentiation, with cocktail and insulin, AEA stimulates 11β-HSD1 expression compared to control (+30.4±0.08% AEA vs C, P=0.005) and induces a slight increase of its enzymatic activity (+15.3±3.5% AEA vs C). In presence of insulin alone, AEA strongly increases 11β-HSD1 mRNA levels of three times when compared to C (P<0.0012). In mature adipocytes AEA increases significantly 11β-HSD1 activity (+77.1±36.1% AEA vs C, P=0.0002) and mRNA levels (+21±0.51% AEA vs C, P=0.01). Preliminary results show that selective CB1 blockade is not effective in antagonizing AEA, whereas by itself seems to affect 11β-HSD1. CB2 blockade properly antagonizes the effects on 11β-HSD1.

Conclusions: CBs influence the expression and activity of 11β-HSD1 during adipogenesis, by promoting adipocytes maturation even in cells not receiving differentiation cocktail. Therefore, CBs not only has a lipogenic effect in mature adipocytes, but also induce adipogenesis in differentiating cells. The interplays between CB1 and CB2 seem to be involved in this process.