Adiponectin has gained significant attention as a mediator of insulin sensitivity. Recently, two receptors of this adipocyte-secreted hormone, adiponectin receptor I (AdipoR1) and 2 (AdipoR2), have been cloned. To improve Our understanding of the regulation of these receptors in adipocytes, AdipoR1 and AdipoR2 mRNA was measured by quantitative real-time reverse transcription-polymerase chain reaction in brown adipocytes and adipocytes from epigonadal and subcutaneous adipose tissue of C57BL/6 mice as a function of feeding and circadian clocks. AdipoR1 gene expression was higher in brown adipose tissue and epigonadal adipose tissue, but lower in subcutaneous fat in fasted as compared to random-fed mice. In parallel, AdipoR2 mRNA levels were also higher in epigonadal adipose tissue of fasted as compared to fed mice, however, there was no regulation of AdipoR2 mRNA in brown and subcutaneous fat depending on the feeding state. Furthermore, AdipoR2 gene expression was significantly higher in epigonadal as compared to subcutaneous fat. Interestingly, a parallel circadian gene expression pattern for both AdipoR1 and AdipoR2 with lower expression between 20:00 and 06:00 h in brown, epigonadal, and subcutaneous adipose tissue was also found. In conclusion, our results suggest a fat depot specific regulation of AdipoR1 and AdipoR2 gene expression in brown and white fat by fasting. In addition, we have identified a coordinated circadian pattern of AdipoR1 and AdipoR2 gene expression in these tissues. (c) 2005 Elsevier Inc. All rights reserved.