PUT female mice on a diet, and they produce more healthy eggs as they age. Starved worms put reproduction on hold. These surprising discoveries could one day lead to new ways to help older women have children.
and his colleagues at Harvard Medical School in Boston reduced the calorie intake of adult female mice by 40 per cent. By the time the mice were one year old, ancient in mouse reproductive terms, their eggs had fewer abnormal chromosomes than those of mice that ate what they liked. Abnormalities in eggs up the risk of miscarriage and birth defects in both mice and humans.
Year-old, calorie-restricted mice also produced more eggs than normally fed mice when their ovaries were artificially stimulated, and their eggs were more likely to develop into embryos upon fertilisation. Tilly is presenting these results at a in Cambridge, UK, on 3 September. Last year, Tilly鈥檚 team announced that restricting the calorie intake of adult mice extended their reproductive lifespan and increased the chances of their offspring surviving after birth.
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What鈥檚 going on? One possibility is that restricting food affects the interactions between developing eggs and their support cells, says of the University of Edinburgh, UK. Or it could alter the activity of germ-line stem cells, which some think can replenish depleted ovaries under the right conditions.
A new study in worms may provide further insights. and Giana Angelo at the Fred Hutchinson Cancer Research Center in Seattle found that starved, adult nematode worms destroy existing eggs, only to regenerate a new crop from a few remaining stem cells once food returns (Science, ). Van Gilst credits a signalling protein called NHR-49, involved in the metabolic response to fasting: 鈥淚n worms that contained an inactive NHR-49 gene, reproductive recovery and fertility after starvation were severely impaired.鈥�
It has not yet been tested, but a similar process might have evolved in humans 鈥渢o help our ancestors preserve fertility during times of famine鈥�, says Van Gilst. A human protein that might be involved is PPAR gamma, which appears to control the rate of ovulation.
鈥淎 similar process might have evolved in humans to help our ancestors stay fertile during famines鈥�
If fasting does play a role in women鈥檚 fertility as well, the signalling molecules responsible could be identified and manipulated, so as to help treat a variety of fertility problems and perhaps even to extend reproductive life in older women, says Telfer.