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Changing meal times may reduce the accumulation of fats in the liver

If the biological clock is not ticking, what causes the cyclic fluctuations in lipid levels? "One of the explanations that came to our mind is that, since food is the main source of fats, and in particular triglycerides, it is possible that the eating habits of the mice play a role here." Says Dr. Yarit Adamovitz, together with colleagues from Dr. Gad Asher's laboratory

holiday dinner. Photo: shutterstock
holiday dinner. Photo: shutterstock

In order to examine the role of the circadian cycle in the accumulation of fats in the liver, the post-doctoral researcher, Dr. Yarit Adamovitz, together with colleagues from the laboratory of Dr. Gad Asher, in the Department of Biological Chemistry, and scientists from the Sanford-Burnham Medical Research Institute in Orlando, hundreds of types of lipids in the mouse liver throughout the day. The scientists discovered that a certain group of fats - triglycerides - shows a circadian behavior: their level in the liver rises about eight hours after sunrise. At the same time, the scientists were surprised to discover that daily fluctuations in triglyceride levels also appear in genetically modified mice, whose biological clock is not functioning. In these mice, the increase in the triglyceride level was delayed by 12 hours compared to the normal mice. "These results were a complete surprise, because one would expect that in a case where the internal clock is not functioning, there would be no cyclical accumulation of triglycerides at all," says Dr. Adamovitz.

If the biological clock is not ticking, what causes the cyclic fluctuations in lipid levels? "One of the explanations that came to our mind is that, since food is the main source of fats, and in particular triglycerides, it is possible that the eating habits of the mice play a role here." Usually the mice consume about 20% of their food during the day, and the rest during the night. The scientists noticed that the mice without the biological clock consume food without a break throughout the day. This observation ruled out the possibility that feeding times are what calibrates the cyclic fluctuations in triglyceride levels. However, when the scientists continued and tested the effect of forced feeding times on normal mice, another surprise awaited them: when the mice consumed the same amount of food that was entirely restricted to the night hours, the overall level of triglycerides in the liver decreased by half. These results raise the possibility that the level of triglycerides in the liver, as well as the timing in which they accumulate, are determined both by the biological clock and by the times of eating. However, the internal mechanism that determines the fluctuations in the amount of triglycerides remains a mystery.

"The dramatic effect of restricting eating to the night hours on lowering the level of triglycerides in the liver, within such a short period of time - ten days - is of medical importance," says Dr. Asher. "Excess fats and excess triglycerides are common diseases characterized by high levels of fats in the blood and liver cells, leading to fatty liver disease and other metabolic diseases. Changing the meal times was able to reduce the accumulation of fats in the liver of the mice effectively and quickly - better than any drug developed to date, and this without considering the side effects associated with the use of those drugs." Mice are of course nocturnal animals, so the phenomenon must first be tested on a reverse schedule, and then the findings regarding humans must be verified.

Time is a central element in any biological system, so these findings may have wider implications for biological research: the circadian clock works even in cells in vitro, so the results of experiments may depend on the time at which the samples were analyzed, or, in the case of animal experiments, on the regimen the feeding. In other words, when it comes to designing experiments, scientists must be aware that timing matters.

3 תגובות

  1. Other variables in the lipid balance are physical activity and alcohol consumption.

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