Adaptive expression of uncoupling protein 1 in the carp liver and kidney in response to changes in ambient temperature

The expression of uncoupling protein (UCP1) is up-regulated in mammalian brown adipocytes during cold exposure. However, a previous study revealed that UCP1 was highly expressed in the liver of common carps, and that the hepatic expression of UCP1 was down-regulated during cold exposure. The present study examined the effects of temperature on the recovery of UCP1 expression levels and the expression of genes involved in UCP1 transcription in the livers and kidneys of common carps. The hepatic and renal expressions of UCP1 were decreased by acclimation from 22 degrees C to 8 degrees C, and a subsequent increase in the water temperature from 8 degrees C to 28 degrees C recovered the renal, but not hepatic expression of UCP1. Changes in the expression of peroxisome proliferator-activator receptor (PPAR) gamma, retinoid X receptor (RXR) alpha and PPAR gamma co-activator (PGC)-1 alpha, genes that are involved in the expression of UCP1 in mammals, with ambient temperature indicated that the expressions of PPAR gamma and RXR alpha, but not expression of PGC-1 alpha was decreased in response to cold exposure; the hepatic and renal expressions of PPAR gamma and RXR alpha recovered to basal levels with the cessation of cold exposure, although this was not complete for hepatic expression of PPAR gamma. The results of the present study indicate that a unique regulatory mechanism is responsible for the hepatic and renal expressions of carp UCP1 during cold exposure and subsequent reacclimation, and is distinct from that in murine brown adipocytes. (C) 2015 Elsevier Inc. All rights reserved.