Glycine influence on cerebral blood flow parameters in practically healthy individuals evaluated with transcranial Doppler sonography

An insufficient perfusion of the brain tissue can cause a decrease in cognitive functions, and long-term ischemia also leads to emotional and motor disorders. At the same time, check-up of the state of the cerebral blood flow is an important aspect of monitoring the progression of many pathological conditions. The amino acid glycine has been widely used in neurological practice for over 30 years, which helps improve hemodynamic characteristics and metabolic processes in the brain tissue. The aim of the work was to analyze the effect of a sublingual administration of glycine on the cerebral blood flow velocity in practically healthy subjects using transcranial Doppler (TCD) sonography. Material and methods. The pilot randomized controlled study included 20 healthy subjects aged 25 to 65 years, equally divided into 2 groups, one of which took glycine sublingually at a dose of 300 mg/day for 30 days, and the second group was a control group and did not receive the drug. In the first group, a load testing was carried out with 1000 mg of glycine, and in the control group – with 1000 mg of placebo. All the subjects underwent an assessment of the blood flow in the extracranial and intracranial vessels using standard protocols of TCD. Results. In Group I, after a month of glycine intake, the peak systolic (by 11.9 cm/s) and average maximum (by 6.3 cm/s) velocities in the left middle cerebral artery (MCA) increased significantly ( p <0.01), while in the right MCA there was an increase in the peak systolic (by 9.3 cm/s), and diastolic (by 2.8 cm/s) and average maximum (by 5.8 cm/s) velocities. In turn, in the control group, there was no significant increase in velocity. During the load testing with glycine / placebo, the relative increase in the peak systolic velocity in the MCA in the main group was 7.6% [1.2; 10.9], in control group was 1.5% [-3.6; 5.5] ( p =0.03). Conclusion. Glycine intake for 30 days contributes to a reliable improvement in cerebral hemodynamics in healthy individuals, such as an increase in the linear blood flow velocity in the MCA. At the same time, a single dose of 1000 mg of glycine leads to an increase in the peak systolic and average maximum intracranial blood flow velocities up to 10%.