Long-term calorie restriction has small effect on DNA methylation measure of rate of aging

In a recent letter published in natural agingresearchers assessed the impact of calorie restriction (CR) on biological aging among the comprehensive evaluation of long-term effects of reduced energy intake (CALERIE) participants in the randomized controlled trial.

Background

Several therapies have been identified to increase biological aging in humans. Intervention trials take months to years for clinical translation, but age-related processes take years to decades to cause disease. Metrics that can summarize age-associated alterations in biological pathways can overcome the challenge. Quantification measures of biological age that can estimate future disease, morbidity and death and also detect short-term age-associated changes could be used as alternative endpoints in interventional aging trials. .

According to the geroscience hypothesis, therapies capable of delaying or reversing age-related molecular changes could prevent or delay the onset of chronic diseases and increase lifespan. Caloric restriction by reducing caloric intake without altering the intake of important nutrients could alter age-related molecular changes such as deoxyribonucleic acid (DNA) methylation (mDNA) and, therefore, increase the duration of life.

About the trial

In the present study, the researchers reported the results of the CALERIE trial, which was performed to assess the impact of restricting caloric intake by 25.0% over two years in healthy adult individuals with a body mass index <27.90 kg m⁻²composed of men aged 21-50 and premenopausal women aged 21-47).

The CALERIE trial was conducted at three clinical centers in the United States to provide therapy with known anti-aging properties in animals. The trial included 220 non-obese adults, randomized 2:1 to follow a 25.0% calorie restriction diet (intervention) and optional diets (control) diets for two years.

CR levels were quantified based on energy requirements (determined semi-annually based on two-week periods of doubly labeled water (DLW)). Blood mDNA analysis information was obtained for 197 people, of whom 128 and 69 people were on CR diets and control diets, respectively. DNA methylation tests were performed using blood samples from participants in the CALERIE randomized controlled clinical trial, and the data was merged with secondary information from the clinical trial.

Biological aging was measured based on changes in blood DNA methylation using previously published algorithms based on the molecular changes underlying the gradual system integration losses associated with age . First-generation mDNA clocks, such as the Horvath clock and the Hannum clock, have been used to compare samples from individuals of different ages.

Intention-to-treat (ITT) analysis was performed using second-generation DNA methylation clocks such as GrimAge and PhenoAge which improved the quantification of aging by emphasizing differences in risk of death rather than age-related differences, and the third-generation DunedinPACE clock to measure the speed of aging, using the repeated measures covariance analysis (ANCOVA) method.

DNAm PC/PC clocks were used to assess test-retest reliability. Follow-up evaluations of dose-response effects and effects of treatment on treated (TOT) were conducted one year and two years after the intervention. TOT effects were assessed using the instrumental variables (IV) approach. Study participants also received individual and intensive group behavioral counseling sessions once a week. Sensitivity analyzes assessed alterations in leukocyte counts by CALERIE therapy and sex-based differences in therapy effects. The magnitude of weight loss was compared to an estimated weight loss trajectory of 16% weight loss in one year with subsequent maintenance.

Results

The average age of study participants was 38.0 years, 77.0% of them were Caucasian, and 70.0% of them were female. The proposed methods for quantifying biological aging used in the study could estimate health deterioration and mortality associated with aging. The CALERIE intervention delayed aging as determined using the DunedinPACE DNA methylation clock, but significant age-associated alterations measured using the PhenoAge and GrimAge clocks did not occur. not been observed. Therapeutic effects were weak; however, the modest delay in aging observed could have a profound impact on public health.

CR treatment reduced participants’ DunedinPACE within one year, with the effect maintained for two years. No dose-response effect was observed using GrimAge and PhenoAge clocks; however, individuals achieving greater CR experienced deeper DunedinPACE reductions. Sensitivity analysis gave similar results. DunedinPACE has shown high test-retest reliability and strong correlation with aging parameters in validation studies.

Most participants in the CALERIE trial were unable to achieve the prescribed calorie restriction of 25%. Despite imperfect compliance, participants in the therapy group showed considerable weight loss and associated alterations in body composition, with improved cardiovascular health and delayed age-related physiological alterations.

Conclusion

Overall, the study results showed that the CALERIE trial intervention delayed the aging process, as determined by the DunedinPACE clock, while the DNA methylation clocks GrimAge and PhenoAge were not significantly affected by CR.

The results supported the geroscience hypothesis and highlighted DunedinPACE as a reliable measure of aging for further clinical trials. However, long-term follow-up evaluations are needed to determine if CR-induced reductions in DunedinPACE might translate to longer lifespan and prevent disease.