Quadriceps mitochondrial DNA quantity, quality, and gene expression after 2 years of calorie restriction: exploratory results from the CALERIE trial.
Level 2 - randomized trial
Exploratory secondary analysis of a randomized controlled trial
PubMed 41886216 · doi:10.1007/s11357-026-02167-1
What was done
This exploratory study analyzed remnant quadriceps muscle biopsy DNA from nonobese participants in the CALERIE trial, a 2-year randomized controlled trial comparing caloric restriction (CR) against an ad libitum (AL) control. Droplet digital PCR was used to quantify nuclear DNA, mitochondrial DNA (mtDNA) copy number, and mtDNA deletion mutations at baseline (n = 93), 12 months (n = 44), and 24 months (n = 31). Investigators compared CR and AL groups and correlated mtDNA measurements with baseline physiological parameters and existing muscle transcriptomic data.
What was found
MtDNA copy number was lower in females (p = 0.0005) and declined over time (p = 0.0001), but showed no statistically significant difference between CR and AL (p = 0.2898) or across age (p = 0.4644). Baseline mtDNA copy number correlated positively with fat-free mass (r = 0.43, p = 2e-05), self-reported energy intake (r = 0.34, p = 0.00077), resting metabolic rate (r = 0.42, p = 0.00261), total energy expenditure (r = 0.31, p = 0.00261), V̇O₂max (r = 0.41, p = 1e-04), and mitochondrial functional gene expression. MtDNA mutation frequency increased with age (p = 0.0041) and weakly inversely correlated with V̇O₂max (r = -0.23, p = 3e-05), but was not significantly altered by CR.
Why it matters
This study provides human trial evidence that two years of moderate calorie restriction does not meaningfully alter quadriceps mtDNA copy number or common deletion mutations in nonobese adults. It also links muscle mtDNA copy number to cardiorespiratory fitness, body composition, and resting energy expenditure.
Limits
The study is an exploratory secondary analysis with substantial longitudinal sample attrition (from 93 at baseline to 31 at 24 months), which limits statistical power to detect small treatment effects. Findings in healthy nonobese participants cannot be directly generalized to older adults or individuals with metabolic disease.
Cited by
- contradicts Eating 15% fewer calories has been shown in multiple randomized trials to have a major impact on boosting mitochondrial health.