We estimated the key molecules related to Type 2 diabetes mellitus (T2DM) in adipose, liver, and muscle tissues, from nonobese diabetic Goto-Kakizaki (GK) rats and their Wistar controls, by computationally analyzing the expression profiles in open source data. With the aid of information from previous reports, Rev-erb alpha in adipose tissue emerged as one of the most plausible candidates. Here, in animal models, including GK rats surgically treated to ameliorate T2DM, we examined the association of Rev-erb alpha in adipose tissue with T2DM progression. After analyses of the Rev-erb alpha mRNA expression in the adipose tissue of our animal models, we compared the Rev-erb alpha protein expression levels in the adipose, liver, and muscle tissues of GK and Wistar controls at the ages of 1 mo (M), 3M, and 6M. The Rev-erb alpha protein levels in adipose tissue showed a distinctive pattern, with the negative correlation of an increasing trend in GK rats, and a decreasing trend in Wistar rats during aging, from those in liver and muscle tissues. Moreover, dysregulation of the circadian Rev-erb alpha expression in the adipose tissue of 6-mo-old GK rats was also observed. In particular, we ameliorated T2DM in GK rats by gastric bypass surgery, and revealed that T2DM amelioration in diabetic GK rats was associated with improved circadian Rev-erb alpha expression, in a comparison between the surgically treated and untreated GK rats. The roles of Rev-erb alpha in adipose tissue were further investigated by observations of Rev-erb alpha-related molecules, with reference to previous reports.