Endocrine Abstracts

Type 1 diabetes mellitus (T1DM) is one of the most frequent autoimmune disorders in childhood, adolescence and youth, developing due to autoimmune destruction of pancreatic β-cells, which leads to an absolute insulin deficiency. Gut microbiota (GM) is associated with the functions of the body’s immune system, and immune-mediated diseases, including T1DM. However, the exact mechanisms by which GM is involved in the T1DM are still unknown. Accumulating data suggest that GM may contribute to the pathogenesis of diabetes influencing the immune response, in which arginine-metabolizing enzymes are involved, particularly arginase. Here, we examined the connection between gut microbiota and cytoplasmic and mitochondrial arginase isoforms (AI and AII respectively) in the leukocytes of patients with T1DM. The A1 activity is necessary to protect M2 macrophages from inflammation, it is constitutively expressed in human neutrophils and exhibits fungicidal activity, whereas A2 is involved in the production of reactive oxygen species implicating in the oxidative stress and inflammatory processes involved in the T1DM pathophysiology. This offers that arginases can be therapeutic targets in T1DM, and this issue is studied in the presented work. Arginase assay was based on the accumulation of L-ornithine produced by arginase in the reaction mixture during 1-hour incubation and determined by means ninhydrin. Measurement of the nitric oxide stable metabolites in protein-free samples was performed using Griess-Ilosvay reagent. Number of E. coli and Clostridium spp were drastically decreased with a concomitant increase in that of Candida albicans, and a manifestation of Staphilococcus aureus was also observed in T1DM, which may compete with the gut beneficial bacteria. Of note, E. coli and Clostridium spp play a protector role for GM, whereas clinical cultures of C. albicans has detrimental effects causing desquamation of small fragments peptidoglycan layers of cell wall and total destruction of the cytoplasm in lactobacilli. The arginase activity was increased by 2 and 1.6 times in the cytoplasm and mitochondria of leukocytes from T1DM patients as compared respectively to control. Arginase is known contribute to decreased availability of L-Arginine in the organism, and particularly to nitric oxide synthase that may cause a subsequent reduction of NOS/NO production attributed to the pathological processes associated with diabetes. Based on this, the nitrite levels in the leukocyte cytoplasm, mitochondria and blood plasma were examined and in line with other findings it was dropped by 1.9, 2.3 and 1.6 times respectively.