old-muscle1

As we age we begin to lose both muscle mass and function and this can impact on our independence, quality of life and metabolic health.

Muscle is important both for locomotion but also maintaining metabolic health. Muscle regulates glucose homeostasis and lipid metabolism.

In this study we aimed to study the turnover of muscle in a chronic setting (six weeks of nutritional and exercise based interventions) in free-living young and elderly men and women, using a novel isotopic approach.

Using D2O (heavy water in which the normal hydrogens are replaced by deuteriums) we can follow the exchange of this isotope into many metabolic pathways including protein, lipid, carbohydrate and nucleic acids (RNA and DNA) over prolonged periods.

Our previous work had demonstrated that elderly muscle was less responsive to nutrition and exercise and we had also shown that both a metabolite of the amino acid leucine and fish oil supplements had positive effects on muscle metabolism.

We therefore validated this new D2O approach and studied the effects of these nutritional supplements or placebo controls on muscle synthesis and growth in a chronic setting.

This work was funded by the Dunhill Medical Trust and The Physiological Society and a Medical Research Council Confidence in Concept award. All clinical, metabolic and molecular physiology is being conducted at the MRC-ARUK Centre for Musculoskeletal Ageing Research.

Milestones

  • Validated the approach for use in humans to study muscle metabolism over periods of days and weeks.
  • The high sensitivity of the analytical approach permits measures of muscle protein synthesis over several hours.
  • Muscle hypertrophy occurs in the early (three weeks) phase of training in the young.
  • Elderly muscles show similar strength improvements to RET, but MPS and mass are unchanged.
  • We can measure both RNA (regulates protein synthesis) and DNA (satellite cell turnover) synthesis in human muscle.
  • We are now applying this technique in a variety of clinical settings, such as the sensitivity and ease of application.
  • The results of the longer term nutritional interventions will be available shortly.
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