GLUL and type 2 diabetes mellitus: Amino acid metabolism plays an important role in diabetes and complications, and branched-chain amino acids may serve as new biomarkers as well as signaling pathways suggesting the risk of DPDs.390,391 Glutamine is a branched-chain amino acid that is synthesized by glutamine synthetase (GS) and hydrolyzed by glutaminase (GLS).392,393 Glutamine levels were negatively associated with BMI and insulin resistance index (HOMA-IR) in men with type 2 diabetes.394 Glutamine in plasma binds the bridging protein GRB-10394 and improves the insulin resistance of cells.