It goes without saying that exercise is good for you. Apart from the obvious benefits related to better physical and cardiovascular health, regular physical exercise can also increase brain health and memory, and has even been shown to reduce the deficits associated with Alzheimer’s Disease. So it may not totally surprise you to learn that exercise can reverse learning and memory deficiencies caused by improper hormone balance during early development. Researchers in Iran (Shafiee et al., 2016) have recently shown that memory deficits caused by maternal hypothyroidism can be undone by aerobic exercise.
Hypothyroidism is a condition in which blood levels of thyroid hormones are consistently lower than normal. This can be concerning as proper levels of thyroid hormones are essential for the development of brain cells in important areas such as the hippocampus, an area of the brain that is crucial for the formation of memory. Maternal hypothyroidism during prenatal development has been shown to decrease levels of brain-derived neurotrophic factor, or BDNF, a protein that promotes proper brain development. Exercise, on the other hand, has been shown to increase levels of BDNF in the hippocampus. Based on this connection to exercise and memory, researchers were curious as to whether deficiencies to the hippocampus in early development could be reversed by physical activity.
To test this theory, researchers gave pregnant rats water that contain PTU, a chemical that is known to suppress thyroid hormone, starting 6 days after conception. The subsequent rat pups were given the same treatment for 21 days post-birth. The treatment rats were then divided into three groups; a group that was given 24-hour access to a running wheel, one group that ran on a treadmill for 30 minutes per day for 14 days, and a group that did not experience any exercise. Any memory improvements caused by exercise were tested by placing rats in a maze and determining if the rats from each group were able to find their way to the target platform more quickly after several consecutive trials. To determine if exercise increased levels of BDNF in the hippocampus, rats from each group were sacrificed and their brains were extracted to test for protein levels within the hippocampus. Using protein assays, a technique that uses coloured labels that bind to specific proteins to measure protein concentrations, researchers examined BDNF levels in control rats that did not experience hypothyroidism or exercise as well as the three experimental rat groups.
Rats that experienced aerobic exercise after maternal and juvenile hypothyroidism showed a marked improvement in memory and learning when compared to rats that had just experienced hypothyroidism. These improvements are echoed by an increased presence of BDNF in the hippocampus of the exercise rats. Increased levels of BDNF were similar in both the rats that experienced the treadmill and wheel running conditions. When compared with the control rats, rats that only experienced hypothyroidism showed a decrease in BDNF levels, while both exercise groups saw BDNF levels that were comparable to the untreated control group. These results further support the idea that hypothyroidism diminishes both memory and BDNF levels, whereas as exercise can have a positive impact on memory and brain cell development. More importantly, this study shows that, by increasing levels of BDNF, exercise can reverse deficits in memory caused by low levels of thyroid hormones during development. This knowledge could help develop therapies to improve cognitive function in children that suffer from hypothyroidism early in life.
Shafiee, S. M., Vafaei, A. A., & Rashidy-Pour, A. (2016). Effects of maternal hypothyroidism during pregnancy on learning, memory and hippocampal BDNF in rat pups: Beneficial effects of exercise. Neuroscience, 329, 151-161.
