Endocrine Abstracts

Introduction: Incidence of type 1 diabetes mellitus (T1DM) is rising steadily around the globe, including Armenia. It is one of the most common autoimmune and metabolic disorders in pediatric population, resulting from autoimmune destruction of pancreatic β-cells leading to insulin deficiency. Gut microbiota (GM) is reportedly involved in the pathogenesis of T1DM likely by influencing the immune response with the help of arginine-metabolizing enzymes. Arginase is known to contribute to decreased availability of L-Arginine, particularly to nitric oxide synthase, which may cause a subsequent reduction of Nitric oxide synthases/nitric oxide (NOS/NO) production attributed to the pathological processes associated with diabetes. Here, we aimed to investigate the correlation between GM and cytoplasmic and mitochondrial arginase isoforms in peripheral leukocytes of patients with T1DM.

Materials and methods: All T1DM patients (n = 108) and healthy controls (n = 108) were recruited at the Muratsan University Hospital, Department of Endocrinology, Yerevan, Armenia. GM was evaluated in the feces of all participants. Qualitative and quantitative examination of the intestinal microflora was performed by sowing fecal samples in appropriate nutritional environments. Fasting peripheral blood was draw into 3.8% sodium citrate anticoagulant, mixed with 6% dextran, and peripheral leukocytes were isolated by conventional procedures. 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 of ninhydrin. Measurement of the nitric oxide stable metabolites in protein-free samples was performed using Griess-Ilosvay reagent.

Results: In T1DM patients, colony numbersof E. coli (P < 0,001), Bifidobacterium spp. (P < 0.002), Lactobacillus spp. (P < 0,0002) were drastically decreased with a concomitant increase of Candida albicans (P < 0.003), and a manifestation of Staphilococcus (P < 0.0001) aureus was also observed. Changes in GM were associated with 1.3 and 1.5 fold increase intheactivity of cytoplasmic and mitochondrial arginase isoforms respectivelyin newly diagnosed T1DM patients, and 1.6 and 1.7 fold increase in patients with duration of T1DM more than 1 year.

Conclusion: Quantitative and qualitative changes in the content of GMin T1DM patients were observed. These were associated with changes in arginine metabolism in peripheral leucocytes. Increase in the activity of arginase isoforms in cytoplasmand mitochondrias of leucocytes in T1DM patients was revealed, associated with a decrease in nitrates level, suggesting the involvement of these processes in pathogenesis of T1DM.