Expression of MicroRNA-200a/b/c in the Mediobasal Hypothalamic Nuclei with Aging.

BACKGROUND: MicroRNAs (miRNAs) belong to small non-coding RNAs that coordinate the expression of cellular genes at the post-transcriptional level. The hypothalamus is a key regulator of homeostasis, biological rhythms and adaptation to different environmental factors. It also participates in the aging regulation. Variations in miRNA expression in the hypothalamus can affect the aging process. OBJECTIVE: Our objective of this study is to examine the expression of miR-200a-3p, miR-200b-3p, miR-200c-3p in the dorsomedial (DMN), ventromedial (VMN) and arcuate (ARN) nuclei of the hypothalamus in male and female rats during aging. METHODS: The expression of miR-200a-3p, miR-200b-3p, and miR-200c-3p in DMN, VMN and ARN was studied by qPCR-RT. The results were presented using the 2-ΔΔCq algorithm. RESULTS: The expression of miR-200a-3p, miR-200b-3p, miR-200c-3p microRNAs decreases with aging in the DMN of males and in the VMN of females. The level of miR-200b-3p expression decreased in aged males in the VMN and females in the DMN. The expression of miR-200c-3p declined in aged males in the ARN and in females in the DMN. The expression of miR-200a-3p, miR-200b-3p, and miR-200c-3p did not change in females in the ARN in aging. CONCLUSION: We found a decrease in the expression of members of the miR-200a-3p, miR-200b-3p, and miR-200c-3p in the tuberal hypothalamic nuclei and their sex differences in aging rats.

Ontogenetic Changes in the Expression of the Lin28 Protein in the Rat Hypothalamic Tuberal Nuclei.

The hypothalamus is a primary regulator of homeostasis, biological rhythms and adaptation to different environment factors. It also participates in the aging regulation. The expression of neurons containing Lin28 was studied by immunohistochemistry in male rats aged 2, 6, 12, and 24 months in the tuberal region of the rat hypothalamus. We have shown for the first time the presence of Lin28-immunoreactive (IR) neurons in the ventromedial nucleus (VMH) and their absence in the dorsomedial and arcuate nuclei in all studied animals. With aging, the percentage of Lin28-IR neurons increases from 37 ± 4.7 in 2-month-old rat until 76 ± 4.6 in 6-month-old and further decreases to 41 ± 7.3 in 12-month-old rat and 28 ± 5.5 in 24-month-old rats. Many VMH Lin28-IR neurons colocalized components of insulin signaling including mTOR, Raptor, PI3K and Akt. The percentage of Lin28/Akt-IR neurons was maximal in 6-month-old and 1-year-old rats compared to 2-month-old and 2-year-old animals. The proportion of Lin28/PI3K-IR neurons significantly increased from 77 ± 1.2 in 2-month-old rat until 99 ± 0.3 in 24-month-old rats and 96-99% of Lin28-IR neurons colocalized mTOR and mTORC1 component Raptor without statistically significant differences in all studied age groups. Thus, Lin28 expresses only in the VMH neurons of the tuberal nuclei of the hypothalamus and the Lin 28 expression changes during the development together with the components of PI3K-Akt-mTOR signaling.