Circadian rhythms are the body’s ‘clock’ that regulates expression and activity of enzymes and hormones involved in metabolism The researchers at The Hebrew University of Israel noted that disruption of the circadian rhythms may lead to obesity and metabolic disorders. Such disorders may include hormone imbalance, psychological and sleep disorders, some forms of cancer, and obesity.
The study findings, if relevant to humans, would show a cause and effect relation between diet and biological clock imbalance.
Dr Oren Froy and colleagues from the Institute of Biochemistry, Food Science and Nutrition set out to uncover whether the biological clock controls the adiponectin signaling pathway in the liver of mice. Adiponectin is a protein hormone that is involves in glucose and fat metabolism, and is secreted from fat tissues known as adipocytes.
They wanted to know whether this control is affected by fasting and/or a high fat diet in a mouse model.
The experiments showed that “under low-fat diet, adiponectin signaling component pathways exhibited circadian rhythmicity”. However they noted that this circadian expression was altered by both fasting and a high fat diet.
In the case of fasting, phases were advanced; with the high fat diet, they were they were delayed.
In addition, levels of adenosine monophosphate-activated protein kinase (a protein involved in fatty acid metabolism) were high during fasting and low during the high fat diet.
“Changes in the phase and daily rhythm of clock genes and components of adiponextin signaling pathways as a result of HF diet may lead to obesity and may explain the disruption of other clock-controlled output systems, such as blood pressure and sleep/wake cycle, usually associated with metabolic disorders,” wrote Froy and collegues.
The study involved feeding mice either a low-fat diet or a high-fat diet, then put them on a one-day fast. They then measured components of the adiponectin metabolic pathway at the RNA, protein and enzyme activity level, as well as serum levels of glucose, adiponectin and insulin.
Endocrinology Vol. 150, No. 1 161-168
“High-Fat Diet Delays and Fasting Advances the Circadian Expression of Adiponectin Signaling Components in Mouse Liver”
Authors: Maayan Barnea, Zecharia Madar and Oren Froy