Disrupted circadian rhythm may cause triglycerides to rise

Aug 03, 2010

When the circadian rhythm gets thrown off, it could come with an unexpected side effect: high triglycerides. The discovery, based on studies in mice with a "broken clock," helps to explain the normal rise and fall in triglycerides, which happens at about the same time each day, according to researchers who report their findings in the August issue of Cell Metabolism.

"We show that the normal up and down [of triglycerides] is lost in clock mutants," said M. Mahmood Hussain of SUNY Downstate Medical Center. "They have high triglycerides all the time." An elevated triglyceride level is a risk factor for atherosclerosis and heart disease.

Several biological, physiological, and behavioral activities show a characteristic recurrence with 24-hour intervals attuned to sunrise and sunset, the researchers explained. That circadian rhythm is driven by the interaction of so-called .

In normal mice, plasma triglycerides double or triple over the course of the day, reaching their lowest point at night when the nocturnal animals eat and are most active, the new report shows. In clock mutants, triglyceride levels don't change; rather, they stay high all the time.

The researchers delved further into the mechanism linking the animal's internal clocks to triglycerides. They found that a core component of the circadian circuitry—a protein known as CLOCK—controls levels of another protein (called microsomal triglyceride transfer protein, or MTP) that helps to ferry triglycerides through the bloodstream. That control takes place via yet another transcription factor.

" and obesity are major metabolic disorders characterized by high plasma lipid concentrations," the researchers conclude. "Plasma lipids are tightly controlled by mechanisms regulating their production and clearance. Here, we show that light-entrained mechanisms involving clock genes also play a role in regulating plasma triglyceride."

If the findings in mice can be extrapolated to humans, it suggests that the effects of drugs designed to lower by acting on MTP might depend on when they are taken each day, the researchers said.

"The dose needed may vary depending on the time of day," Hussain said. "Now we can start to think about [the role of] drug timing in controlling disease states."

The findings also suggest that activities that disrupt the circadian rhythm—staying up until 2:00 a.m. or traveling overseas—might come with real consequences for lipid metabolism, he added.

Explore further: Monitoring the rise and fall of the microbiome

add to favorites email to friend print save as pdf

Related Stories

Study sheds light on triglyceride metabolism

Jul 07, 2010

New findings reported in the July issue of Cell Metabolism are offering new leads as to why some people might suffer from high levels of triglycerides. High triglycerides are a risk factor for atherosclerosis and cardiovascular diseas ...

Link found between immune system and high plasma lipid levels

Apr 12, 2007

Researchers at the University of Chicago have found an unsuspected link between the immune system and high plasma lipid levels (cholesterol and triglycerides in the blood) in mice. The finding could lead to new ways to reduce ...

Circadian rhythm-metabolism link discovered

Jul 24, 2008

UC Irvine researchers have found a molecular link between circadian rhythms – our own body clock – and metabolism. The discovery reveals new possibilities for the treatment of diabetes, obesity and other ...

Recommended for you

Monitoring the rise and fall of the microbiome

32 minutes ago

Trillions of bacteria live in each person's digestive tract. Scientists believe that some of these bacteria help digest food and stave off harmful infections, but their role in human health is not well understood.

Antioxidant biomaterial promotes healing

8 hours ago

When a foreign material like a medical device or surgical implant is put inside the human body, the body always responds. According to Northwestern University's Guillermo Ameer, most of the time, that response can be negative ...

Immune response may cause harm in brain injuries, disorders

10 hours ago

Could the body's own immune system play a role in memory impairment and cognitive dysfunction associated with conditions like chronic epilepsy, Alzheimer's dementia and concussions? Cleveland Clinic researchers believe so, ...

User comments : 0