Different adipose tissue territories show distinct morphological and functional features. In this sense, several metabolic pathways respond in a deposit-specific manner to the same stimulus. Melatonin modulates various metabolic processes (lipolysis and lipogenesis) in adipose tissue (AT). However, it remains unknown if the transcriptional expression of enzymes involved in these biochemical pathways exhibits a circadian pattern and if melatonin influences it in retroperitoneal (RP) fat.
For this, male Wistar rats (10 weeks old) were divided into Sham-operated (Control) or Pinealectomized (Pinx) groups. Four weeks after surgery, the animals were euthanized by decapitation every 4 h over 24 h, the RP fat was removed and processed for mRNA expression analysis by RT-qPCR. ANOVA (one- and two-way) and cosinor adjustments were used to evaluate possible time-dependent differential expression for each gene in each group and between them.
The expression of Atgl, Fasn and Lhs was significantly altered by the time main effect, while no difference was observed between the groups (treatment main effect) according the two-way ANOVA. Besides the evidence of time main effect, none of the metabolic genes evaluated displayed a circadian cosinoidal pattern in Control rats. Surprisingly, the mRNA expression of Atgl and Lhs showed a circadian rhythymicity only in Pinx animals.
Taking together, these findings demonstrate that the transcript expression of enzymes related to the lipid metabolism does not display a circadian cosinoidal pattern in RP fat, contrasting the previous observation in other adipose deposits, but reinforcing that each adipose territory has functional specificities and differential sensitivity to melatonin.