Glycine is one of the components of creatine which helps increase muscle growth and energy during exercise (29). When metabolised it acts as an amino acid and regulates blood sugar levels which can also control that amount of sugar released into the blood (30).
29 – Hultman, E., Soderlund, K., Timmons, J. A., Cederblad, G., & Greenhaff, P. L. (1996). Muscle creatine loading in men. Journal of Applied Physiology, 81(1), 232-237.
30 – Felig, P., & Wahren, J. (1971). Influence of endogenous insulin secretion on splanchnic glucose and amino acid metabolism in man. Journal of Clinical Investigation, 50(8), 1702.