Obesity and type II diabetes through night work
Obesity and type II diabetes are typical diseases of affluence in western industrialized countries. What is certain is that an oversupply of unhealthy food is responsible for this. US researchers have now found that certain working methods, such as shift work and too little sleep, also promote the metabolic disorder diabetes. Because whoever works at night and sleeps too little, gets his inner clock out of balance. "In addition, the insulin balance is disturbed," as the researchers at Vanderbilt University in Nashville sum up.
In addition to permanently poor diet, insufficient exercise and family history, US scientists have discovered a new possible cause for diabetes and obesity. If workers on shift work have to work at night and therefore sleep too little, the patient's internal clock and thus the insulin balance are disturbed. "For weight, it is not only important what is eaten, but also when", the scientists report in the journal "Current Biology". A mouse experiment showed that the effects of the hormone insulin change over the course of the day. The same hormone has a major impact on blood sugar levels.
Disruption of daily rhythms provokes insulin resistance However, if the internal clock is continuously disturbed by various daily rhythms, shift workers will very likely develop insulin resistance over time and thus become more susceptible to overweight and obesity. At least that was shown during the laboratory experiment with mice. "The results of the tests can be of great importance in the treatment of diabetes and obesity," explain the study authors. Because the biological clock is currently not included in therapy options for metabolic disorders.
Earlier studies had shown that people who suffer from sleep disorders, for example because they have jet lag or work constantly at night, often suffer from metabolic disorders as a result. In addition, further research showed that special types of so-called clock genes, which are responsible for controlling the internal clock, are linked to diabetes, obesity and hypertension (high blood pressure).
"The insulin effect, which is changed by the hormone in the rhythm, was not investigated sufficiently," says study leader Shu-qun Shi. With the current study, the researchers were able to show that nocturnal mice showed the greatest resistance to insulin during the day. As a result, the blood sugar level was highest in the rodents at that time because less sugar is then transported from the blood. On the other hand, the insulin effect increases at night because the animals are then active and the metabolism is stimulated. This also lowers the blood sugar level. "In genetically modified animals in which the internal clock has been deliberately disturbed, they show insulin resistance during the day and at night," as the authors write.
In the further experimental setup, mice were exposed to permanent light. The biological clock is inevitably lost due to this condition. As a result, the insulin balance also fluctuates. If the animals were also given a high-fat diet, those animals stored more fat than others without permanent light.
Study enables new therapeutic approaches Although it is "normal for the insulin effect to fluctuate during the day," the scientists write, it is natural because "the environment also behaves rhythmically". Living beings that can adjust to these fluctuations can adapt their behavior, their metabolism and their gene activities to the external circumstances. These creatures have much better chances of survival because they can keep their organic functions constant.
Balanced diets that regulate the meal according to a time "cannot stop or reverse the obesity and diabetes epidemic, but they could help fight it," said researcher Carl Johnson. In order to expand the knowledge for therapeutic purposes, further research in this area will take place. (sb)
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