A possible link between lack of sleep (insomnia) and obesity has been traced to hypocretin/orexin cells in the hypothalamus region of the brain that are easily excited and sensitive to stress, according to Yale School of Medicine researchers.

They reported in the April issue of Cell Metabolism that if these neurons are over-activated by stress, "they may support sustained arousal, triggering sleeplessness, leading to overeating.

"The more stress you have, the lower the threshold becomes for exciting these hypocretin neurons," said lead author Tamas Horvath, associate professor in the Departments of Obstetrics, Gynecology & Reproductive Sciences (Ob/Gyn) and Neurobiology at Yale School of Medicine.

Horvath and co-author Xiao-Bing Gao, assistant professor in Ob/Gyn, studied hypocretin/orexin neurons in mice using electrophysiology and electron microscopy. They found a unique, previously un-described organization of inputs on hypocretin neurons in which excitatory nerve junctions outnumber inhibitory contacts by almost 10 fold. Stressors such as fasting further excite these neurons.

"This unique wiring and acute stress-induced plasticity of the hypocretin neurons correlates well with its involvement in the control of arousal and alertness, which are vital to survival," said Horvath. "But it may also be an underlying cause of insomnia and associated metabolic disturbances, including obesity. In addition, insomnia is characteristic of perimenopause (early onset of menopause), which may lead to increased prevalence of obesity in postmenopausal women."

Horvath said "people with weight and sleep problems could benefit from cutting back on stressful aspects of their lives, rather than trying to specifically medicate either insomnia or obesity."

Other sources: Medical Week staff