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Single-cell immunofluorescence assay showing precursor cells maturing into adipose cells full of fat

Precursor cells (blue) mature into adipose cells full of fat (green) with help from hormones, whose levels surge and fall over a day. Credit: Z. Bahrami-Nejad et al/Cell Metab.

Physiology

Why fat piles on when the body’s daily cycles are in disarray

Timing of hormone fluctuations influences fat cells’ development.

Changes in the patterns of hormone production might cause weight gain when circadian rhythms are disrupted.

Hormones called glucocorticoids stimulate the production of mature fat cells. In humans, glucocorticoid levels naturally rise in the morning and fall in the evening, but stress can also elevate them.

To study how glucocorticoid levels relate to weight gain, Mary Teruel at Stanford University in California and her colleagues injected mice with glucocorticoids at varying times of day, but fed all mice the same amount of food. Mice given the hormone late in their wakeful phase gained weight. But mice injected just after they’d woken up — when their glucocorticoid levels were already naturally high — did not.

The results suggest that high glucocorticoid levels at unusual times of day could contribute to weight gain. This could help to explain why stress and disrupted sleep cycles are linked to rising weight.

More Research Highlights...

Monteverde Cloud Forest Preserve, Costa Rica

Mist wafts through the trees at the Monteverde Cloud Forest Biological Preserve in Costa Rica. Cloud forests around the world are threatened by development, wood collection and climate change. Credit: Stefano Paterna/Alamy

Conservation biology

Forests that float in the clouds are drifting away

Tropical cloud forests are safe havens for a vast range of creatures and plants, but they are under siege around the globe.
Illustration of a brown dwarf

A rapidly spinning brown dwarf (pictured, artist’s impression) tends to have narrow atmospheric bands; the faster the spin, the thinner the bands. Credit: NASA/JPL-Caltech

Astronomy and astrophysics

Dim stars that have failed at fusion are masters of spin

Three brown dwarfs whirl on their axes at a dizzying rate that might be close to the celestial speed limit for these bodies.
Aerial photograph of beef cattle standing at the Texana Feeders feedlot in Floresville, Texas

Large-scale facilities such as this feedlot in Floresville, Texas, help to meet the global appetite for beef and other red meat, which remains strong despite the growing consumption of chicken and fish. Credit: Daniel Acker/Bloomberg/Getty

Agriculture

Meat lovers worldwide pay climate little heed

People are eating more poultry and fish — but they’re not giving up their hamburgers.
Midshipmen at dining table eat in formation, CIRCA 1900

Midshipmen in the United States in around 1900. A study found that body-mass index, a gauge of obesity, has increased with the generations during the twentieth century. Credit: Buyenlarge/Getty

Metabolism

A century of US data documents obesity’s racially skewed rise

An analysis also finds that obesity is common at a much younger age among people born in the early 1980s than those born in the late 1950s.
Auroras on Jupiter

Jupiter’s aurora glows blue in this composite image. A newly detected radio signal might be the signature of a similar aurora on a planet in another solar system. Credit: NASA/ESA/J. Nichols, Univ. Leicester

Astronomy and astrophysics

Wiggly signal hints of an aurora on a planet far from the Solar System

A vast radio observatory on Earth detects signals similar to those generated by the aurora on Jupiter.
Members of the "Ice Memory project" extract an ice core piece out of a drill machine

Scientists extract an ice core from the Col du Dome glacier near the top of Mont Blanc in the French Alps. A similar core documents changes in emissions of an ozone-depleting gas. Credit: Philippe Desmazes/AFP/Getty

Atmospheric science

Ice on the Alps’s highest peak details a pollutant’s rise

A glacier on Mont Blanc provides a decades-long record of the use of bromine, which corrodes the ozone layer.
Jumping ant guarding pupae and larvae at the nest

The brain of an Indian jumping worker ant (above, guarding pupae and larvae) becomes smaller if she starts to lay eggs but can regrow to its old size if she stops reproducing. Credit: Martin Dohrn/Nature Picture Library

Neuroscience

Ants shrink their brains for motherhood — but can enlarge them when egg-laying ends

Brain volume plummets in ‘gamergate’ ants that gain the ability to reproduce, but rises again with a fall in fertility.
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