Value of dynamic ³¹P magnetic resonance spectroscopy technique in in vivo assessment of the skeletal muscle mitochondrial function in type 2 diabetes.

BACKGROUND: Phosphorous magnetic resonance spectroscopy ((31)P-MRS) has been successfully applied to study intracellular membrane compounds and high-energy phosphate metabolism. This study aimed to evaluate the capability of dynamic (31)P-MRS for assessing energy metabolism and mitochondrial function in skeletal muscle from type 2 diabetic patients.

METHODS: Dynamic (31)P-MRS was performed on 22 patients with type 2 diabetes and 26 healthy volunteers. Spectra were acquired from quadriceps muscle while subjects were in a state of rest, at exercise and during recovery. The peak areas of inorganic phosphate (Pi), phosphocreatine (PCr), and adenosine triphosphate (ATP) were measured. The concentration of adenosine diphosphate (ADP) and the intracellular pH value were calculated from the biochemistry reaction equilibrium. The time constant and recovery rates of Pi, PCr, and ADP were analyzed using exponential curve fitting.

RESULTS: As compared to healthy controls, type 2 diabetes patients had significantly lower skeletal muscle concentrations of Pi, PCr and β-ATP, and higher levels of ADP and Pi/PCr. During exercise, diabetics experienced a significant Pi peak increase and PCr peak decrease, and once the exercise was completed both Pi and PCr peaks returned to resting levels. Quantitatively, the mean recovery rates of Pi and PCr in diabetes patients were (10.74 ± 1.26) mmol/s and (4.74 ± 2.36) mmol/s, respectively, which was significantly higher than in controls.

CONCLUSIONS: Non-invasive quantitative (31)P-MRS is able to detect energy metabolism inefficiency and mitochondrial function impairment in skeletal muscle of type 2 diabetics.