P.31 A multiparametric quantitative NMR study at rest and during exercise in subjects between 22 and 65 years of age: Preliminary results

The progressive decline in muscle strength and performance during ageing negatively affects the quality of life in the elderly and increases the risk of falls, disability and frailty. The age-related loss of muscle mass, strength and quality is a multifactorial process whose mechanisms are incompletely understood. Nuclear magnetic resonance (NMR) allows evaluating anatomical, structural and physiological aspects of muscle tissue non-invasively. Functional NMR also enables, for instance, to image during an exercise paradigm the tissue blood flow (BF) or energy metabolism using ³¹P MR spectroscopy (MRS). Here, we designed a protocol where multiple quantitative and complementary biomarkers were acquired in the lower leg in a single exam. Acquisitions were done at 3 T (Siemens Prisma) on 26 subjects (22 to 65 y.o., 15 women). Variables studied were muscle-specific cross-sectional area (CSA), intramuscular fat fraction (FF), muscle water T1 (T1_H2O) and T2 (T2_H2O ) values; and pH and concentrations of phosphocreatine (PCr), inorganic phosphate (Pi), phosphodiesters (PDE) and phosphomonoesters (PME) in the triceps. Dynamic simultaneous BF, T2* and 31P MRS measurements were done during a 13-min plantar flexion exercise. A linear model and ANOVA using gender and age as fixed factors were used for analysis. Preliminary results showed several statistically significant (p < 0.05) changes related to age: increased T1_H2O and FF in all the lower leg muscles (gastroc. med. & lat., soleus, tibial. ant. & post, peron.); increased PDE/ATP and PME/ATP ratios; and a modest CSA increase of the extensor and fibular muscles (unlike the quadriceps muscles). Pi/PCr at the end of exercise increased with age in male subjects. No other age-related changes were found for functional NMR variables, grip strength or triceps maximal contraction force. Our results show that age-related structural and basal metabolic changes can be observed with a multiparametric NMR approach in the muscle. The ongoing recruitment of additional subjects will allow us to confirm our findings.