April 27, 2005
Mutant Mice With Disrupted Sleep Habits Get Fat

Irregular sleep patterns may be contributing to human problems with obesity, high cholesterol. and other ills.

Staying up past bedtime, skipping meals, and snacking constantly all add up to weight gain, fatty livers, and high cholesterol levels for an unlucky group of mice whose internal biological clocks are genetically disrupted.

Researchers at Northwestern University and the Howard Hughes Medical Institute have identified wide-ranging molecular and behavioral changes in mice that have a faulty circadian system. In people, similar changes in body fat and metabolic activity are known as metabolic syndrome, which can lead to cardiovascular disease and type 2 diabetes.

Lots of things go wrong metabolically when mice don't sleep regularly.

The Clock mutant mice lost both their alarm clocks and their internal dinner bells. Mice typically sleep during the day and then eat a meal at the beginning and at the end of their active nocturnal day, akin to breakfast and dinner. Instead, the Clock mutant mice skipped their meals, stayed awake far into the usual rest time, and snacked often.

The insomniac mice also were a little more sluggish, as measured by infrared sensors in their cages. The researchers removed the exercise wheels normally used to gauge mouse activity, because regular spins can help the mice reset their biological clocks, just as a daily walk might help a person sleep better at night.

In repeated round-the-clock measurements, the researchers found signs of further trouble emerging in the mice's early adult months. The circadian-challenged mice developed high cholesterol, high triglycerides, high blood sugar, low insulin, bloated fat cells, and lipid-engorged liver cells. Some of these changes appeared to be independent of the weight gain, Bass said.

So then does artificial light contribute to human obesity? Probably. Note that exercise helps mice reset their biological clocks. Could be that lack of exercise causes people to stay up too late and also to eat too much, and have lousy blood lipid and sugar profiles.

Also see my previous post "Sleep A Lot To Avoid Burn-Out From Stress And To Stay Skinny".

Share |      Randall Parker, 2005 April 27 02:17 AM  Brain Appetite


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