Differential expression of mitomiRs in pancreatic islet cells associated with maternal protein restriction

Mitochondria are central to energy production and cellular homeostasis. Beyond importing diverse RNAs, they also encode hundreds of their own non-coding RNAs, contributing to a complex and dynamic RNA landscape. Early-life nutritional insults, such as fetal and postnatal protein deficiency, can impair mitochondrial function and increase the long-term diabetes risk. However, the mitochondrial non-coding transcriptome of pancreatic islets, particularly its responsiveness to nutritional cues, remains largely unexplored.

We performed RNA sequencing to profile small non-coding RNAs in mitochondrial fractions of islet cells from offspring of rats exposed to low-protein (LP) or control diets during gestation and lactation and employed mRNA-miRNA network analysis to explore the potential regulatory roles of differentially expressed mitomiRs in LP-exposed pups.

Protein deficiency during gestation and lactation led to a profound remodeling of the small non-coding RNA landscape in whole islets, with microRNAs and piRNAs showing the most pronounced changes. In mitochondrial fractions, LP exposure resulted in a striking shift in microRNA composition, with 33 mitomiRs detected in control islets versus 23 in LP-exposed rats, and only 5 shared between groups. Notably, ten mitomiRs were selectively depleted from the cytosol and enriched in mitochondria of LP-exposed islets. Amongst these, miR-10a-5p and miR-126a-5p, are predicted to target genes involved in mitochondrial metabolism and structural organization.

Early-life protein restriction triggers a highly selective reorganization of the mitomiR landscape in pancreatic islets. The identified mitomiRs may serve as regulators of mitochondrial function and intracellular signaling, potentially influencing β-cell metabolic coupling and contributing to diabetes susceptibility.