Physical activity is linked to later menopause in women and a preserved ovarian egg reserve in female animals. Digest
The ovary is among the first organs to show age-related declines in women. Researchers combined large human datasets with mouse experiments to test whether physical activity might alter that trajectory.
The researchers first examined the relationship between self-reported physical activity and menopause in two large human datasets, then had female mice exercise regularly on a treadmill for one month while controls spent the same sessions on it without running. Afterward, they counted primordial follicles, the dormant follicles that contain immature eggs, and measured a hormone marker of ovarian reserve.
- After accounting for age, women who had not yet reached menopause reported more activity than those who had. Among postmenopausal women, greater activity was associated with a later reported age at menopause.
- Treadmill-trained mice retained roughly 49% more primordial follicles than untrained controls after one month. They also had more total follicles and higher levels of a hormone marker of ovarian reserve.
- Exercise also increased adiponectin, a signaling hormone best known for being released by fat tissue, in blood and ovaries. The ovaries also showed signs of making more of the hormone locally.
- Reducing or removing adiponectin weakened much of the follicle-preserving effect of exercise. The benefit fell by 56% when adiponectin was absent throughout the body and by 76% when it was reduced specifically in the ovaries.
- Activating the adiponectin pathway preserved follicles and prolonged fertility in aging mice.
The ovarian reserve is affected not only by cell death, but by the pace at which primordial follicles begin developing. The mTOR pathway acts like part of the 'go' signal for that transition. Adiponectin pushed in the opposite direction in cultured ovaries, lowering mTOR activity and leaving more follicles dormant. Exercise increased this hormone inside the ovary, and the benefit shrank sharply when local production was reduced. That pattern places ovarian adiponectin as a possible link between physical activity and follicle preservation.
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The ovarian reserve may be finite, but the rate at which it is spent does not appear to be fixed. Exercise may be one factor that influences that decline.