An Inserm team at the Lille Neuroscience & Cognition laboratory (Inserm/Université de Lille, Lille University Hospital) has joined forces with its counterparts at Lausanne University Hospital (CHUV) to test the efficacy of GnRH injection therapy in order to improve the cognitive functions of a small group of patients with Down syndrome. First the scientists revealed a dysfunction of the GnRH neurons in an animal model of Down syndrome and its impacts on the cognitive function impairment associated with the condition. Then a pilot study testing GnRH pulsatile injection therapy was conducted in seven patients. The results were promising : the therapy led to improved cognitive function and brain connectivity. This study has been published in Science.
Down syndrome, also known as trisomy 21, affects around one in 800 births and results in a variety of clinical manifestations, including decline in cognitive capacity. With age, 77% of people with the condition experience symptoms similar to those of Alzheimer’s disease. Gradual loss of the ability to smell, typical of neurodegenerative diseases, is also commonly encountered from the prepubertal period, with potential sexual maturation deficits occurring in men.
GnRH-secreting neuron dysfunction identified in Down syndrome
Recent discoveries have suggested that the neurons expressing gonadotropin-releasing hormone (GnRH) — which is known for regulating reproduction via the hypothalamus — could also act on other brain regions with a potential role in other functions, such as cognition.
With this idea in mind, the Lille Neuroscience & Cognition laboratory team led by Inserm Research Director Vincent Prévot studied the mechanism which regulates GnRH in mouse models of Down syndrome.
The laboratory demonstrated that five strands of microRNA regulating the production of this hormone — which are found on chromosome 21 — are dysfunctional. This supernumerary chromosome then leads to abnormalities in the neurons that secrete GnRH. These findings were confirmed at both genetic and cellular levels. The Inserm scientists were able to demonstrate that the progressive cognitive and olfactory deficiencies seen in the mice were closely linked to dysfunctional GnRH secretion.
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