Caloric restriction modifies small RNA profiles and engages age-related molecular pathways in the CALERIE trial

Caloric restriction (CR) extends lifespan and enhances healthspan across species. In humans, the CALERIE Phase 2 trial demonstrated that CR improves inflammation, cardiometabolic health, and molecular aging. To explore underlying mechanisms, we examined CR-induced changes vs. <i>ad libitum</i> (AL) in small non-coding RNAs (smRNAs) across plasma, muscle, and adipose tissue. Using smRNA sequencing, we analyzed microRNAs (miRs) and piwi-interacting RNAs (piRs) over 12 and 24 months, comparing CR levels (%CR) and group assignments (CR vs. AL). We identified 16 smRNAs associated with %CR and 41 with CR vs. AL. Although tissue-specific expression varied, shared pathways emerged, including insulin signaling, circadian rhythm, cell cycle regulation, and stress response. Cross-species analysis revealed 17 miRs altered by CR in both humans and rhesus monkeys. These findings suggest smRNAs are key molecular mediators of CR's effects on aging and longevity, offering insight into biological mechanisms of CR and potential targets for age-related interventions.