Long-echo time MR spectroscopy for skeletal muscle acetylcarnitine detection

Area of Science:

• Biochemistry
• Metabolic Physiology
• Medical Imaging

Background:

• Acetylcarnitine is crucial for metabolic flexibility and insulin sensitivity.
• Current detection methods require tissue biopsy, limiting human studies.
• Noninvasive techniques are needed to assess acetylcarnitine's physiological role.

Purpose of the Study:

• To evaluate long-echo time (TE) proton magnetic resonance spectroscopy (1H-MRS) for measuring skeletal muscle acetylcarnitine.
• To assess acetylcarnitine concentrations across a spectrum of insulin sensitivity.

Main Methods:

• Utilized long-TE 1H-MRS on a clinical 3T scanner.
• Measured skeletal muscle acetylcarnitine in endurance athletes, sedentary lean/obese individuals, and type 2 diabetes mellitus (T2DM) patients.
• Assessed insulin sensitivity via hyperinsulinemic-euglycemic clamp and mitochondrial function via phosphorus-MRS (31P-MRS).

Main Results:

• Successfully detected skeletal muscle acetylcarnitine using the developed 1H-MRS protocol.
• Observed highest insulin sensitivity and mitochondrial function in athletes, lowest in T2DM patients.
• Found a positive correlation between skeletal muscle acetylcarnitine concentration and insulin sensitivity across groups.

Conclusions:

• Long-TE 1H-MRS is a feasible method for measuring skeletal muscle acetylcarnitine on clinical scanners.
• T2DM patients exhibit reduced skeletal muscle acetylcarnitine, potentially contributing to their impaired insulin sensitivity.
• This noninvasive approach can advance understanding of acetylcarnitine's role in human metabolic health.