COMPOSITIONS FOR USE IN THE PREVENTION AND/ OR TREATMENT OF INTELLECTUAL DISABILITY AND NEURODEGENERATIVE DISEASES IN A SUBJECT WITH DOWN SYNDROME

Down syndrome (DS) is a condition caused by total or partial trisomy of chromosome 21, and is characterized by both physical and neurological defects, including mild to severe intellectual disability. In addition, individuals with DS have a high risk of developing neurodegenerative diseases, such as Alzheimer's disease (AD), usually starting at 40 years of age. The recovery of the behavioral and neurophysiological deficit observed following the use of GAB AA receptor (GAB AA-R) inhibitors in mouse models of DS has led to the hypothesis that the intellectual deficit could depend on an imbalance in inhibitory circuits. Most of the data produced so far in mouse models suggests that this imbalance may be attributable to a high number of inhibitory neurons and a higher frequency of inhibitory post-synaptic currents. At the same time, however, evidence to the contrary was also provided: in particular, the imbalance of the inhibitory circuits would cause an increase in the intracellular concentration of chlorine ions (CT) in such a way that, following activation of the GABAA receptor, a flow of Cl- ions from the inside to the outside of the cell would be observed, with consequent depolarization of the neuron and reduced inhibition. Consequently, although alteration of GABAergic transmission is the basis of cognitive retardation in subjects with DS, the causes of this alteration are still unclear and, to date, there are no therapeutic approaches useful for improving cognitive deficit and counteracting the development of neurodegenerative diseases in individuals with DS, particularly in adulthood. Existing products such as GABA-A receptor antagonists or reverse inhibitors are not available in the clinic; when tested on humans they did not reach the primary and secondary endpoints and the study was stopped. Furthermore, the use of broad- spectrum GABAA receptor antagonists has not been approved as they can promote convulsions and anxiety crises. Summary of the invention The present description has the object of providing a composition that is efficient and safe for use in preventing and/or treating intellectual disability and neurodegenerative diseases in a subject with Down syndrome (DS). According to the present description, this object is achieved thanks to the subject specifically indicated in the following claims, which are intended as an integral part of this description. One embodiment of the present description provides a composition for use in the prevention and/or in the treatment of intellectual disability and neurodegenerative diseases in a subject with DS, wherein the composition comprises - as active agent - at least one compound belonging to the class of inhibitors of the enzyme dipeptidyl-peptidase IV (DPP4). The compound belonging to the class of DPP4 inhibitors also belongs to the class of gliptins, and may be selected in the group consisting of sitagliptin, vildagliptin, saxagliptin, linagliptin, gemigliptin, anagliptin, tenegliptin, alogliptin, trelagliptin, omarigliptin, evogliptin, glosogliptin, dutogliptin. The present description also provides a method for treating intellectual disability and neurodegenerative diseases in a subject with DS, the method comprising the step of administering a composition to the subject comprising at least one compound belonging to the class of dipeptidyl-peptidase IV inhibitors (DPP4) as active agent. The composition of the present description has been found to be effective not only in restoring GABAergic transmission and the cognitive deficit, but also in slowing the development of neurodegenerative diseases in subjects with DS, such as Alzheimer's disease, for example. Furthermore, the composition activates a specific molecular mechanism (described below), which in subjects with DS - unlike what has been demonstrated in healthy subjects - has been surprisingly able to promote neuroprotective (and non-neurotoxic) effects.