ANATOMY
High-fat diets aren't just bad for your hips and your heart - they can also disrupt circadian rhythms, the body's biological clock.
In 2007, Northwestern University scientists reported high-fat diets can shift the internal body clock of mice - causing them to eat when they should be sleeping. It was the rodent equivalent of raiding the refrigerator at night.
Now, Hebrew University of Jerusalem scientists build on that finding with a new study that exposed mice to low- and high-fat diets, with a fasting period at the end. They looked at whether the diets perturb the timing of gene activity involved in the biological clock, or disrupt the timing of a metabolic pathway in the liver.
They found that mice fed a low-fat diet had normal circadian rhythms in the metabolic pathway. Meanwhile, mice on a high-fat diet had a disruption in the activity of genes associated with their internal clock.
Other research has found that disrupting circadian rhythms may lead to obesity or metabolic disorders. The researchers said their findings may reveal "a vicious circle," in which diets high in fat that contribute to obesity also disrupt circadian rhythms - which contributes to obesity.
BOTTOM LINE: It is increasingly clear that diet, like light, affects the biological clock, and research is revealing the underlying mechanisms.
WHAT'S NEXT: Further research may be done to examine the possible repercussions on such things as obesity and sleep disorders.
WHERE TO FIND IT: Endocrinology, Jan. 2009
CAROLYN JOHNSON
Obesity
Researchers study cancer-insulin linkObesity is a known risk factor for breast cancer in postmenopausal women.
Scientists blame fat cells that produce estrogen - itself a risk factor for breast cancer.
But obesity also leads to higher levels of insulin circulating in the blood, a sign of resistance or a weakened responsiveness to insulin.
Researchers led by Marc J. Gunter of Albert Einstein College of Medicine asked whether insulin by itself was linked to breast cancer, based on other research showing that insulin stimulates cell growth in normal breast tissue and breast cancer cells. They analyzed the blood tests of 816 nondiabetic women enrolled in the Women's Health Initiative Observational Study and compared them to data on 835 women also participating in the trial who developed breast cancer after they joined the study. After taking estrogen levels into account, they found that women with the highest insulin levels had a 46 percent greater risk of breast cancer than women with the lowest levels.
BOTTOM LINE: Postmenopausal women who had high insulin levels had a higher risk of breast cancer than similar women with lower levels of insulin.
CAUTIONS: Insulin levels were measured at the beginning of the study and women may have already had breast cancer at a stage too early to be detected.
WHAT'S NEXT: Seeing if lowering insulin levels or estrogen levels may be important in reducing breast cancer risk in postmenopausal women.
WHERE TO FIND IT: Journal of the National Cancer Institute, January issue.
ELIZABETH COONEY
© Copyright 2009 Globe Newspaper Company.
