Unique advantages of dynamic l-[11C]methionine PET/CT for assessing the rate of skeletal muscle protein synthesis: A pilot trial in young men

TL;DR

This pilot study explores using dynamic l-[11C]methionine PET/CT as a noninvasive way to assess skeletal muscle protein synthesis in young men.

Contribution

The study demonstrates the potential of dynamic [11C]Met PET/CT for site-specific visualization of muscle protein synthesis.

Findings

Influx constant Ki of [11C]Met was 0.6%–28% higher after yogurt ingestion in 5 of 6 participants.

Significant differences in Ki were observed when analyzing quadriceps and hamstrings separately.

The method shows potential for site-specific and visual assessment of muscle protein synthesis.

Abstract

Although the standard method to evaluate skeletal muscle protein synthesis (MPS) is muscle biopsy, the method is invasive and problematic for multisite use. We conducted a small pilot study in volunteers to investigate changes in MPS according to skeletal muscle site using a noninvasive method in which 6 healthy young men were given yogurt (containing 20 g milk protein) or water, and 1 h later, l-[11C]methionine ([11C]Met) was administered intravenously. Dynamic PET/CT imaging of their thighs was performed for 60 min. The influx constant Ki of [11C]Met in skeletal muscle protein was calculated as an index of MPS using a Patlak plot, and found to be 0.6%–28% higher after ingesting yogurt than after water in 5 of the 6 volunteer participants, but it was 34% lower in the remaining participant. Overall, this indicated no significant increase in Ki after ingesting milk protein. However, when the quadriceps and hamstring muscles were analyzed separately, we found a significant difference in Ki. This demonstrates the potential of visualizing MPS by calculating the Ki for each voxel and reconstructing it as an image, which presents unique advantages of [11C]Met PET/CT for evaluating MPS, such as site-specificity and visualization.

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