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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.