Telomere Biology, Erosion, and Age-Related Conditions: Insights from Down Syndrome and Other Telomere-Associated Disorders.

Telomeres play a crucial role in safeguarding DNA integrity. With each cell division, these protective structures undergo shortening, limiting the number of divisions to prevent improper genetic material distribution in aging cells. Senescent cells accumulate in tissues and contribute to age-related changes and decreased regeneration. Various genetic conditions are linked to premature aging and the early onset of age-related disorders. Down syndrome (DS), or chromosome 21 trisomy, is a relatively frequent aneuploidy, having an incidence of 1/1000-1/1100 newborns, and a major cause of intellectual disability. DS individuals exhibit a higher prevalence and earlier onset of age-related disorders, particularly Alzheimer's disease, due to the buildup of beta-amyloid. In DS individuals, telomere erosion occurs at an accelerated rate, caused by the overexpression of numerous genes, and it is associated with various factors, including obesity, inflammation, hormonal fluctuations, physical or emotional stress, higher levels of reactive oxygen species, and autoimmune disorders. Although telomere length in DS children is initially higher than in the general population, their telomeres experience a more rapid shortening process. Developing strategies that target molecular pathways linked to telomere erosion and telomerase activity could become a key point for the therapeutic management of DS individuals.