Tick, tock, a β-cell clock

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Abstract
The daily light–dark cycle affects many aspects of normal physiology through the activity of circadian clocks. It emerges that the pancreas has a clock of its own, which responds to energy fluctuations. During periods of feeding, pancreatic islets secrete insulin to maintain glucose homeostasis — a rhythmic process that is disturbed in people with diabetes. Experiments in mice now show that the pancreatic islets contain their own biological clock, which orchestrates insulin secretion during the sleep–wake cycle. The transcription factors CLOCK and BMAL1 are vital for this process, and mice with defective copies of the genes Clock and Bmal1 develop hypoinsulinaemia and diabetes. By demonstrating that a local tissue clock integrates circadian and metabolic signals in pancreatic β-cells, this work suggests that circadian analyses are crucial for deeper understanding of metabolic phenotypes, as well as for the treatment of metabolic diseases such as type 2 diabetes.