Fenretinide (FEN) is a synthetic retinoid that inhibits obesity and insulin resistance in high-fat diet (HFD)-fed mice and completely prevents 3T3-L1 pre-adipocyte differentiation. The aim of this study was to determine the mechanism(s) of FEN action in 3T3-L1 adipocytes and in mice. We used the 3T3-L1 model of adipogenesis, fully differentiated 3T3-L1 adipocytes and adipose tissue from HFD-induced obese mice to investigate the mechanisms of FEN action. We measured expression of adipogenic and retinoid genes by qPCR and activation of nutrient-signalling pathways by western blotting. Global lipid and metabolite analysis was performed and specific ceramide lipid species measured by liquid chromatography-mass spectrometry. We provide direct evidence that FEN inhibits 3T3-L1 adipogenesis via RA-receptor (RAR)-dependent signaling. However, RARα antagonism did not prevent FEN-induced decreases in lipid levels in mature 3T3-L1 adipocytes, suggesting an RAR-independent mechanism. Lipidomics analysis revealed that FEN increased dihydroceramide lipid species 5- to 16-fold in adipocytes, indicating an inhibition of the final step of ceramide biosynthesis. A similar blockade in adipose tissue from FEN-treated obese mice was associated with a complete normalisation of impaired mitochondrial β-oxidation and tricarboxylic acid cycle flux. The FEN catabolite, 4-oxo-N-(4-hydroxyphenyl)retinamide (4-OXO), also decreased lipid accumulation without affecting adipogenesis. FEN and 4-OXO (but not RA) treatment additionally led to the activation of p38-MAPK, peIF2α and autophagy markers in adipocytes. Overall our data reveals FEN utilises both RAR-dependent and -independent pathways to regulate adipocyte biology, both of which may be required for FEN to prevent obesity and insulin resistance in vivo.
This work was supported by the British Heart Foundation Intermediate Basic Research Fellowship FS/09/026/27398 to NM., the Biotechnology and Biological Sciences Research Council doctoral training grant awarded to GDM and the Wellcome Trust and the University of Aberdeen ISSF Fund to NM and LG and The Royal Society (of London) to NM. SRT, BHM, MKD and PDW gratefully acknowledge Highlands and Islands Enterprise, Scottish Funding Council and the European Regional Development Fund for financial support.
The authors thank Tonya Martin (Johnson & Johnson, New Brunswick, NJ), and Urs Thurneer (Cilag AG, Schaffhausen, Switzerland) for the generous gift of Fenretinide to use completely without restriction or obligation.
The authors thank Tonya Martin (Johnson & Johnson, New
Brunswick, NJ), and Urs Thurneer (Cilag AG, Schaffhausen,
Switzerland) for the generous gift of Fenretinide to use completely
without restriction or obligation.
- retinoic acid
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- School of Medicine, Medical Sciences & Nutrition, Cardiometabolic Disease
- School of Medicine, Medical Sciences & Nutrition, Aberdeen Cardiovascular and Diabetes Centre
- School of Medicine, Medical Sciences & Nutrition, Medical Sciences - Senior Lecturer
- School of Medicine, Medical Sciences & Nutrition, Institute of Medical Sciences