# miRNA changes with ageing and caloric restriction in male rat skeletal muscle: potential roles in muscle cell function

## TL;DR

This study explores how microRNA levels change with age in rat muscle and how caloric restriction can reverse some of these changes, potentially improving muscle function.

## Contribution

The study identifies novel age-related miRNAs and their functional roles in muscle aging, showing how caloric restriction can partially reverse these effects.

## Key findings

- Caloric restriction normalizes over 35% of age-related miRNA changes in rat skeletal muscle.
- Age-upregulated miRNAs target proteins involved in muscle development, metabolism, and longevity pathways like AMPK and autophagy.
- CR is less effective at restoring anti-inflammatory miRNAs that decline with age.

## Abstract

The mechanisms underlying skeletal muscle ageing, whilst poorly understood, are thought to involve dysregulated micro (mi)RNA expression. Using young and aged rat skeletal muscle tissue, we applied high-throughput RNA sequencing to comprehensively study alterations in miRNA expression occurring with age, as well as the impact of caloric restriction (CR) on these changes. Furthermore, the function of the proteins targeted by these age- and CR-associated miRNAs was ascertained. Numerous known and novel age-associated miRNAs were identified of which CR normalised > 35% to youthful levels. Our results suggest miRNAs upregulated with age to downregulate proteins involved in muscle tissue development and metabolism, as well as longevity pathways, such as AMPK and autophagy. Furthermore, our results suggest miRNAs downregulated with age to upregulate pro-inflammatory proteins, particularly those involved in innate immunity as well as the complement and coagulation cascades. Interestingly, CR was particularly effective at normalising miRNAs upregulated with age, rescuing their associated protein-coding genes but was less effective at rescuing anti-inflammatory miRNAs downregulated with age. Lastly, the effects of a specific miRNA, miR-96-5p, identified by our analysis to be upregulated with age, were studied in cultured C2C12 myoblasts. We demonstrated miR-96-5p to decrease cell viability and markers of mitochondrial biogenesis, myogenic differentiation and autophagy. Overall, our results provide novel information regarding how miRNA expression changes in skeletal muscle, as well as the potential functional consequences of these changes and how they are ameliorated by CR.

The online version contains supplementary material available at 10.1007/s10522-025-10336-6.