by Ciara Loughran | Edited by Avani Nooka
Down Syndrome is the most common chromosomal disorder that affects more than 6,000 babies annually. This number has continued to increase, and since 1979 has increased by over 30%. Down Syndrome is an intellectual disability caused by a genetic disorder that affects Chromosome 21. It is also known as Trisomy 21, meaning that individuals with Down Syndrome have a third copy of the twenty-first chromosome. This condition leads to slower cognitive development and faster intellectual decline with aging, along with loss of smell.
The Gonadotropin-Releasing Hormone (GnRH) is a hormone made by the Hypothalamus that is essential for the body to produce reproductive hormones. Recent studies have suggested that this hormone is not only important for reproductive health, but could also have effects in parts of the brain that affect cognition. After learning this information, Vincent Prévot and a team of researchers from the Lille Neuroscience & Cognition laboratory began to study the implications of this hormone as it relates to the cognitive deficits that result from Down Syndrome.
GnRH is found in the brain and partially regulated by 5 strands of microRNA on Chromosome 21. MicroRNA are essential in gene expression. After exploring mouse models with Down Syndrome, the researchers discovered that because there is a genetic altercation on Chromosome 21 in individuals with Down Syndrome, these five strands of microRNA in the mouse models were inactive. This drew the researchers to a conclusion linking this defective hormone with intellectual disabilities.
After conferring with Nelly Pitteloud at the University of Lausanne, a professor studying GnHR as it relates to reproductive health, Prévot decided to try her pulsatile injection therapy on the mouse models. This therapy works to restore function of GnRH, which Prévot hoped would lead to increased cognitive abilities and restoration of smell in the mice. After only 15 days, both cognitive and olfactory improvements were observed.
After observing many successful results in the mouse models, they began a similar treatment on a small group of individuals with Down Syndrome. They first took brain scans and tested cognitive function of 7 male patients between the ages of 20 and 50. Following the protocol from Dr. Pitteloud, they input a pump on the arm of each patient that releases a dose of the needed hormone, GnHR, every 2 hours. This trial lasted for 6 months, and after, they repeated brain scans and testings on the patients. The brain scans demonstrated increased cognitive function in 6 out of the 7 patients and their observations supported this. They noticed improvements in abilities to follow directions and an increased attention span, helping to demonstrate the effectiveness of this trial. However, no improvements in their ability to smell were observed. Additionally, there were no significant side effects which proved promising for future implications of this hormone therapy.
These results can be very beneficial in the future to individuals with Down Syndrome. Following this experiment, the researchers hope to begin a larger study, incorporating more individuals, including females. Ideally, this will not only help those with Down Syndrome, but also other intellectual disabilities.