An association between glycine and insulin levels is observed in patients with pulmonary tuberculosis and type 2 diabetes

Background & aims: Adequate nutrition from which amino acids are part gives us protection against infectious or metabolic diseases. In particular, glycine has immunomodulatory properties and is a secretagogue of insulin. However, its absorption rate or plasma levels are impaired in bacterial infection or high glucose levels. The aim of this study was to evaluate the association between glycine and insulin plasma levels in patients with pulmonary tuberculosis (PTB) and type 2 diabetes mellitus (DM2). Methods: Plasma levels of insulin and glycine were determined in four groups: 1) patients with PTB; 2) patients with PTB-DM2; 3) household contacts with DM2 (C-DM2), and 4) healthy household contacts (H-C). Likewise, we analyzed the plasma levels of glucose, serine, arginine, lysine, taurine, and glutamic acid. Results: We observed significant differences in the glycine levels between PTB and PTB-DM2 vs C-DM2 and H-C groups (P < 0.05). We observed also important differences in insulin and glucose levels after comparisons between PTB, PTB-DM2, and C-DM2 vs. H-C groups (P < 0.05). A correlation between glycine and insulin levels in the PTB (r = 0.326) and PTB-DM2 (r = 0.318) groups was found. Conclusion: Our results showed a significant association between glycine and insulin plasma levels in patients with PTB and PTB-DM2, which suggests that the determination of glycine levels could be used as a reference test to evaluate both pathologic conditions. An additional support to the above is that significant changes in the glucose levels in these groups were observed, too. (C) 2020 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.