Dietary fatty acids up-regulate the expression of UCP2 in 3T3-L1 preadipocytes

States characterised by elevated plasma fatty acid levels are accompanied b y increased UCP2 expression but the physiological regulation of UCP2 expres sion in white adipose tissue is not fully understood. We used 3T3-L1 preadi pocytes to determine whether various dietary fatty acids (20:5, 18:3, 18:2, 18:1, 18:0) directly regulate UCP2 expression. Physiological concentration s of each class of polyunsaturated fatty acid and the monounsaturated fatty acid dramatically upregulated UCP2 mRNA levels 5- to 8-fold, but the satur ated fatty acid was not so effective (1.5-fold). The up-regulation occurred in a time- and dose-dependent manner, was evident by 4 h and maximum betwe en 18 and 24 h, and was prevented by actinomycin D. Synthetic ligands selec tive for each PPAR isoform did not induce UCP2 expression, which suggests t hat fatty acids might not be acting solely via PPAR transcription factors. In conclusion, dietary unsaturated fatty acids may be physiological signals to alter energy balance by direct induction of UCP2. (C) 2000 Academic Pre ss.