Body's Circadian Rhythm Tightly Entwined With Blood Sugar Control

"Scientists have long struggled to understand the body's biological clock. Its tick-tock wakes us up, reminds us to eat and tells us when to go to bed. But what sets that circadian rhythm?

New research now shows that daily fluctuations in powerful hormones called glucocorticoids directly synchronize the biological clock as an integral part of our mechanism for regulating blood sugar.

'The most surprising part of our findings is that our internal biologic rhythms are embedded directly into another pathway, one that is essential to regulate metabolism,' said senior study author Brian Feldman, MD, PhD, assistant professor of pediatric endocrinology at the Stanford University School of Medicine. Feldman also practices at Lucile Packard Children's Hospital.

The new findings give the first in vivo evidence of a direct link between glucocorticoid hormones and genes that regulate our biological clock. The research may eventually help doctors reduce disabling side effects of glucocorticoid drugs such as prednisone, Feldman said. The work could also help diabetics control their blood sugar levels and may shed light on why night-shift workers are at risk for obesity and diabetes.

The study will be published online Oct. 5 in Proceedings of the National Academy of Sciences. Feldman worked previously at the University of California-San Francisco, where much of the research was conducted.

Feldman's team began their experiments by applying a synthetic glucocorticoid to dishes of mouse and human stem cells to see which genes responded. To the team's surprise, three genes known to control the biological clock changed their activity in a direct response to the hormone."