According to previous studies, an elevated level of the protein amino acid homocysteine (in a condition called hyperhomocysteinemia) can hinder fracture healing. Because the essential amino acid methionine is a precursor of homocysteine and an important component in the biosynthesis of cysteine, researchers at the University of Saarland in Germany investigated if excess levels of methionine would also affect rate of bone repair.
Methionine also plays a key part in the biosynthesis of carnitine, taurine, lecithin, phosphatidylcholine and other phospholipids. An error in the conversion of methionine can lead to atherosclerosis, when fatty materials accumulate on artery walls and can cause inflammation.
For the experiment, researchers Joerg Holstein et al. divided 25 mice into two groups. One group received a diet high in methionine while the other group received a control diet that was equivalent in calories. Three weeks after methionine supplementation, the researchers anesthetized the mice using ketamine and xylazine.
They then fractured the right femur of each mouse. Four weeks after fracture, the researchers analyzed the healing process using histomorphometry and biomechanical testing. Blood samples were also taken to determine level of serum homocysteine.
The effect of amino acid methionine on bone healing
At the end of the study, Holstein, et al., found an increased level of homocysteine in the methionine group when compared to the control. Results from biomechanical testing showed no significant difference between the groups in bending stiffness of the healed bones. Results from histomorphometry analyses also did not show any significant difference between the two groups in size or tissue composition of the callus.
Based on these findings, the researchers conclude that excess methionine intake does not have a significant effect on bone repair in mice.
They further suggest that hyperhomocysteinemia does not pose a risk for inhibited fracture healing and that dietary methionine may even help regulate osteoblasts, cells that are responsible for bone formation.
They believe that additional testing will reveal the role methionine plays in bone healing.