Endocrine Abstracts

Introduction: Type 1 diabetes (T1DM) is one of the most frequent autoimmune and metabolic disorders in childhood and youth, developing due to autoimmune destruction of β-cells, which leads to an absolute insulin deficiency. Accumulating data suggest that gut microbiota (GM) may contribute to the pathogenesis of diabetes influencing the immune response, in which arginine-metabolizing enzymes are involved, particularly arginase. We examined the connection between GM and cytoplasmic and mitochondrial arginase isoforms (AI and AII respectively) in the leukocytes of patients with T1DM.

Materials/Methods: All patients were recruited at the Muratsan University Hospital, Endocrinology Department, Yerevan. Microbiota was examined in feces of participants in the clinical laboratory of «Nork» infectious diseases hospital. Fasting venous blood was taken into 3.8% sodium citrate anticoagulant, mixed with 6% dextran, and leukocytes were isolated by conventional procedures, then the leukocyte cytoplasmic and mitochondrial fractions were prepared by differential centrifugation. 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.

Results: Number of E.coli, Bifidobacterium spp., Lactobacillus 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. E.coli plays 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. Changes in GM were associated with 1.3 and 1.5 fold increase in the activity of cytoplasmic and mitochondrial arginase isoforms in newly-diagnosed T1DM patients and 1.6 and 1.7 fold increase in patients with duration of T1DM more than 1 year. Simultaneously, in the same groups, statistically significant decline in the number of NO metabolites was observed. Arginase is known to 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.

Conclusions: Quantitative and qualitative changes in the content of GM in T1DM patients were recorded, which were associated with arginine metabolism intracellular changes in immune response involved leucocytes. Arginase isoforms stimulation in cytoplasme and mitochondrias of leucocytes in T1DM patients was revealed, associated with a decrease in nitrates level, which indicates the involvement of these processes in pathogenesis of the disease.