Short sleep, poor sleep: novel risk factors for obesity and for Type 2 diabetes

A specialist in the effect of circadian rhythms on the endocrine system, Dr. Eve Van Cauter, University of Chicago, has conducted several studies in which short-term sleep restriction damaged the body’s ability to regulate eating by lowering levels of leptin, the hormone that tells the body when it has had enough. In the symposium, Dr. Van Cauter describes other recently published studies from her group, one showing that only three days sleep disruption is sufficient to increase insulin resistance in humans (thus causing the body to need higher levels of insulin) and a large epidemiological study showing that short sleep over a five year period causes an increase in systolic blood pressure.

Energy metabolism during chronic sleep deprivation: sleep less, eat more, don’t gain weight, yet show signs of progression toward diabetes

Dr. Michael Koban, Morgan State University, also reported a new study in which sleep restriction in rats led to glucose intolerance, a prediabetic state in which the blood glucose remains higher than normal after glucose challenge. Significantly, this is the first rodent study of sleep deprivation in which there was no association between glucose dysregulation and weight gain.

The researchers believe that extending sleep restriction will produce more pronounced glucose intolerance in which glucose levels do not return to normal levels for a longer period, thus providing more evidence that not sleeping enough could lead to diabetes in humans. The researchers also are looking for mechanisms to explain the change in metabolism related to sleep deprivation and the dissociation between weight gain and glucose dysregulation and insulin resistance.

Stress-related behaviors and hormone changes after prolonged sleep deprivation – and environmental factors that appear to modify them

Dr. Deborah Suchecki, Universidade Federal de Sao Paulo, described how prolonged sleep deprivation activates the neuroendocrine stress response, as measured by increased blood levels of the stress-related hormones adrenaline, adrenocorticotropic hormone (ACTH), and corticosterone. Earlier studies have shown that sleep restriction in animals can gradually change brain and neuroendocrine systems in ways similar to those seen in stress-related disorders such as depression, while epidemiological studies suggest that sleep restriction may be an important risk factor for cardiovascular and other diseases linked to stress.

CNS changes after chronic sleep deprivation have role in both food intake and metabolism

Dr. Gloria Hoffman, also of Morgan State University, presents studies that explain the role of the central nervous system pathways in stimulating feeding and causing metabolic changes associated with progression to diabetes. Specifically, increased production of the neurotransmitter neuropeptide Y and decreased production of proopiomelanocortiini products in the hypothalamus explain the hyperphagic response.

Although the CNS’s role in regulating metabolic rate is not well understood, she believes that histamine might be involved. Histamine neurons not only affect the maintenance of wakefulness but also are regulators of peripheral metabolism. In sleep deprived rats, elevations in the glucose to insulin ratio were positively correlated with an increase in histamine expression that raises the possibility that a dysregulation of histamine function during impaired sleep might serve to trigger metabolic and other changes leading to diabetes.

The scientists agree that as sleep curtailment becomes more common in industrialized countries it becomes increasingly important to understand how limited or poor quality sleep produces changes that can lead to obesity and diabetes, both epidemic in the developed world. More and more scientists are jumping on board with these lines of investigation, says Dr. Hoffman, and there is an increased demand for information on the part of health professionals and members of the general public, many of whom consider themselves sleep deprived.

On April 22, at the Experimental Biology 2009 meeting in New Orleans, a panel of leading sleep researchers describes recent and new studies in this fast growing field. The session is part of the scientific program of the American Association of Anatomists (AAA).