Avaliação do transporte transmembrânico de glicose, glutamina e alanil-glutamina em íleo de camundongos nutridos e desnutridos infectados por Escherichia coli enteropatogênica

Abstract

Enteropathogenic Escherichia coli (EPEC) and malnutrition are a major cause of morbidity and mortality in developing countries. The purpose of this study was to evaluate the transport of Na+-glucose, Na+-glutamine and H+-alanyl-glutamine by measurement of short circuit current (Isc) and transepithelial resistance (TR) in the ileum of nourished and malnourished mice infected with EPEC. Albino mice of approximately 35 days of age were subjected to a standard diet or a diet deficient in proteins, lipids and minerals, the Regional Basic Diet (RBD). Of these animals was submitted to acute infection for 3 hours of direct contact with bacteria in isolated intestinal loop. For comparison, the same was done using the commensal bacterium Escherichia coli HS. They were anesthetized with ketamine and xylazine intramuscularly. The ileum was removed, dissected the serous membrane, open with a scalpel, segmented and mounted in Üssing chambers. The total mRNA was extracted and, from this, cDNA was done to analyze if malnutrition caused alterations in gene transcription of transporters as SGLT-1, SN-2, CAT-1, PEPT-1 and CFTR and related proteins to cell junctions such as ZO-1, Claudin-1 and Claudin-2 and occludin. At the same time, immunofluorescence analysis of proteins SGLT-1, SN-1, SN-2 and PEPT-1 were performed. The results showed that EPEC reduced the area of the villi only during malnutrition (1,339 ± 0,1 mm²). But, the basal CCC did not alter (67,41 ± 2,0 μA/ cm²), while EPEC, E. coli HS and malnutrition, when isolated, reduced the basal CCC (65,96 ± 5,1 μA/ cm ², 72,51 ± 7,7 μA/ cm ² and 74,23 ± 5,7 μA/ cm²). However, malnutrition did not change the transport systems of glucose (ΔCCC = 324,7 ± 45,42 µA/cm²), glutamine (ΔCCC = 236.7 ± 43.32 μA/ cm²) and alanyl-glutamine (ΔCCC = 282,6 ± 39,10 μA/ cm²), because occured an increase in gene expression of SGLT-1 and PEPT-1 and increased synthesis of SGLT-1, SN-1, SN-2 and PEPT-1. Already EPEC altered glucose transport (ΔCCC = 102,6 ± 38,3 μA/ cm²), and E. coli HS decreased transport of glucose (ΔCCC = 103,5 ± 106,6 μA/ cm²) and glutamine (ΔCCC = 123,4 ± 106,5 μA/ cm²), whereas in undernourished animals EPEC reduced transport of glutamine (ΔCCC = 62,10 ± 42,7 μA/ cm²), and E. coli HS reduced levels of glucose absorption (ΔCCC = 84,40 ± 178,3 μA/ cm²). Therefore, these substrates may facilitate the recovery of the membrane and alleviate the vicious cycle of malnutrition, infection and diarrhea by increasing absorption (CCC) and the maintenance of normal intestinal permeability (Rt), but before using them for the treatment it is essential to evaluate the nutritional status of the host and the presence of pathogens in their intestinal epithelium.