Evaluation of a shorter methionine loading test

Area of Science:

• Clinical Biochemistry
• Nutritional Science
• Genetics

Background:

• Hyperhomocysteinemia is a risk factor for various health conditions.
• Accurate identification of hyperhomocysteinemia is crucial for patient management.
• The standard 6-hour methionine loading test is time-consuming.

Purpose of the Study:

• To validate a shorter 3-hour methionine loading test for accuracy in identifying hyperhomocysteinemic patients.
• To investigate determinants of fasting and post-load homocysteine concentrations.
• To assess the impact of MTHFR 677C>T polymorphism on homocysteine levels.

Main Methods:

• Plasma homocysteine levels were measured in women with a history of pre-eclampsia (n=106) after fasting and 3 and 6 hours post-methionine load.
• The 677C>T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, vitamin B6, B12, folate, and creatinine were analyzed.
• Statistical analysis included correlation, agreement assessment, and multiple linear regression.

Main Results:

• Excellent correlation and agreement were found between 3-hour and 6-hour post-load homocysteine concentrations and their changes from fasting levels.
• The methylenetetrahydrofolate reductase (MTHFR) 677 TT genotype, folate, and vitamin B12 were determinants of fasting homocysteine.
• MTHFR 677 TT was the primary determinant of post-load homocysteine, with TT genotype carriers showing >30% higher concentrations.

Conclusions:

• The 3-hour methionine loading test is a valid and accurate alternative to the 6-hour test for identifying hyperhomocysteinemic patients.
• The MTHFR 677C>T polymorphism significantly influences both fasting and post-load homocysteine concentrations.
• This shorter test offers a more efficient approach to diagnosing hyperhomocysteinemia.