Given the steady increase in the number of Americans who are developing type 2 diabetes, researchers are now investigating a wide range of environmental and lifestyle factors to determine how much of the statistical increase of the disease is being caused by behavior and not genetics. One new study has implicated both diet and work habits as factors in type 2 diabetes.
A new study entitled “Dietary Iron Controls Circadian Hepatic Glucose Metabolism through Heme Synthesis” published in the online issue of Diabetes journal shows that circadian regulated glucose metabolism in the liver is controlled by dietary iron intake. Thus, people who do shift work may have an increased risk for diabetes if they also ingest iron-rich foods regularly.
Circadian rhythm is driven by the circadian clock, our internal clock that controls a wide range of biological processes, such as resting/activity rhythms, feeding/fasting rhythms, and hormonal secretion, according to a 24-hour oscillation. A paradigm of the circadian control of metabolism is the glucose homeostasis. Recent studies showed circadian rhythm in the liver regulates glucose homeostasis, and its disruption is associated with the development of type two diabetes.
Since dietary intake impacts the circadian clock, in this study, a team of researchers at the Department of Biochemistry and Department of Internal Medicine, University of Utah, Salt Lake City determined the effects of dietary iron on circadian gluconeogenesis. The authors fed mice with iron and found that dietary iron affects circadian glucose metabolism. Further studies showed that dietary iron induced increased levels of heme — a component of hemoglobin, responsible for oxygen transport in the blood. Previous studies showed heme could bind circadian proteins. Accordingly, the authors found that heme bound to circadian proteins increased their activity promoting liver glucose control. While this capacity is important when set in accordance with livers’ circadian cycle, it will be disruptive if induced outside the natural cycle. This is the case with night-workers.
Thus, Donald McClain, study last author noted, “When a shift worker eats foods high in iron at night it could exacerbate the lack of synchronization between the clock in the liver and the main one in the brain.”