The circadian clock controls energy homeostasis by regulating circadian expression of proteins involved in metabolism. Disruption of circadian rhythms leads to obesity and metabolic disorders. Little is known regarding the control of the biological clock over adiponectin signaling pathway in adipose tissue, the adiponectin producer, and muscle, an adiponectin target tissue under fasting, low-fat (LF), or high-fat (HF) diet. Mice were fed LF or HF diet for 7 weeks and fasted on the last day. The circadian mRNA expression of clock genes and components of adiponectin metabolic pathway (mAdipoR1, mAdipoR2, mPpar, mPpar, mAmpk, and mAcc) in the muscle and adipose tissue were tested. Using average daily levels of multiple time points around the circadian cycle, we assessed mRNA levels of the different adiponectin signaling components. In addition, serum glucose, adiponectin, and insulin were measured. Under LF diet, adiponectin signaling pathway components exhibited circadian rhythmicity at the mRNA levels. Fasting and HF diet followed by fasting disrupted this circadian expression causing a phase advance or delay, respectively. Changes were also found in the expression levels of adiponectin receptor, mAmpk, mAcc, mPpar, and mPpar reflecting a defect in adiponectin signaling. As both peroxisome proliferator-activated receptor (PPAR) and mAMPK are linked to the core clock mechanism, they could mediate the disruptions seen in clock gene expression under HF diet. In turn, the circadian clock affects the daily rhythm of these adiponectin signaling components.
Maayan Barnea, Zecharia Madar and Oren Froy. High-fat Diet Followed by Fasting Disrupts Circadian Expression of Adiponectin Signaling Pathway in Muscle and Adipose Tissue. Obesity 2009 September Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.