Profiling of circulating chromosome 21-encoded microRNAs, miR-155, and let-7c, in down syndrome

Background: Down syndrome (DS) is the most common chromosomal survival aneuploidy. The increase in DS life expectancy further heightens the risk of dementia, principally early-onset Alzheimer's disease (AD). AD risk in DS is higher, considering that this population may also develop metabolic diseases such as obesity, dyslipidemias, and diabetes mellitus. The extra genetic material that characterizes DS causes an imbalance in the genetic dosage, including over-expression of AD's key pathophysiological molecules and the gene expression regulators, the microRNAs (miRNAs). Two miRNAs, chromosome 21-encoded, miR-155, and let-7c, are associated with cognitive impairment and dementia in adults; but, expression dynamics and relationship with clinical variables during the DS's lifespan had remained hitherto unexplored.

Methods: The anthropometric, clinical, biochemical, and profile expression of circulating miR-155 and let-7c were analyzed in a population of 52 control and 50 DS subjects divided into the young group (Aged ≤20 years) and the adult group (Aged ≥21 years).

Results: The expression changes for miR-155 were not significant; nevertheless, a negative correlation with HDL-Cholesterol concentrations was observed. Notably, let-7c was over-expressed in DS from young and old ages.

Conclusion: Overall, our results suggest that let-7c plays a role from the early stages of DS's cognitive impairment while overexpression of miR-155 may be related to lipid metabolism changes. Further studies of both miRNAs will shed light on their potential as therapeutic targets to prevent or delay DS's cognitive impairment.