Impacto da obesidade na amebíase experimental: aspectos imunológicos, bioquímicos e patológicos

Abstract

Amoebiasis is a parasitosis acquired by eating food or water containing the cyst form of Entamoeba histolytica, characterized by a dynamic immune response and great importance in the pathogenesis of the disease. Obesity is characterized by excessive accumulation of body fat, causing metabolic changes that interfere with health status. The metabolic inflammatory state described as metainflammation contributes to insulin resistance, metabolic syndrome and type 2 diabetes. The present study aimed to identify whether obesity is a factor of aggravation or not to the amoebic parasitic infection, under the immunological, biochemical and pathological aspects in an experimental study. Sixty-four (64) gerbils (Meriones unguiculatus) were used, males (16 weeks) distributed in eight groups of eight animals each: Group I - Control without laparotomy (CTWL); Group II - Control with laparotomy (CTWtL); Group III - Infected Control 4 days (INFCT4d); Group IV - Obese without laparotomy (OBWL); Group V - Obese with laparotomy (OBWtL); Group VI - Infected Obese 4 days (INFOB4d), Group VII - Infected Control 11 days (INFCT11d), Group VIII - Infected Obese 11 days (INFOB11d). The animals in the CTWL, CTWtL, INFCT4d and INFCT11d groups were fed a standard diet composed of 64%, 20% and 16% of total calories from carbohydrates, proteins and lipids, respectively and caloric density of 3.9 kcal/g. The animals in the OBWL, OBWtL, INFOB4d and INFOB11d groups received a high-fat diet containing greater amounts of simple sugar and lipids to induce obesity, comprising 36%, 16% and 48% of total calories from carbohydrates, proteins and lipids, respectively and caloric density of 4.9 kcal/g. Before infection and euthanasia, an oral glucose tolerance test was performed. At the end of the 10th experimental week, the animals in the INFCT4d, INFCT11d, INFOB4d and INFOB11d groups were laparatomized and infected on the same day, the CTWtL and OBWtL groups were laparatomized, but not infected, while, the CTWL and OBWL groups were neither laparatomized nor infected. Body weight was measured weekly and food consumption daily. After 4 days of infection and a total of 74 days of experiment, the animals of the groups CTWL, CTWtL, INFCT4d, OBWL, OBWtL and INFOB4d were euthanized. After 11 days of infection and 81 days of experiment, the animals of the INFCT11d and INFOB11d groups were euthanized under the same conditions. Blood, liver, adipose tissues and spleen were collected for further analysis. In serum, levels of total cholesterol, HDL cholesterol, triglycerides, glucose, total proteins and albumin were evaluated. Histopathological analysis, assessment of oxidative stress (TBARS and Catalase), RT-qPCR of cytokines (Il6, Tgfb and Tnf) and myeloproteinase activity (MPO) in the liver were performed. The animals in the INFCT11d and INFOB11d groups were evaluated only under pathological aspects, analysis of cytokines and MPO, in order to comparatively verify the evolution of the amoebic liver abscess. The data were analyzed using the GraphPad Prism software version 7.0 (GraphPad Software, San Diego, CA). The obesity model was successfully reproduced and an insulin resistance profile in the obese was established, regardless of the infection. The association between obesity and E. histolytica significantly altered the glycidic, lipidic metabolism, but did not alter the protein among the infected animals. The infection increased hepatic TBARS concentrations in obese animals, but did not alter the response in adipose tissues. The infection also increased the activity of the antioxidant enzyme in the liver and in the epididymal tissue of obese animals, but had the opposite effect on the mesenteric and retroperitoneal adipose tissues of these animals. Morphometric analyzes showed that obesity associated with 11 days of infection resulted in a reduction of liver abscess in relation to its respective control Infected control for 11 days (OBINF11d 3.05 x 106 1462243 µm2; CTINF11d 1.6 x 107 ± 2793320 µm2) (p <0.05). It should be noted that the longer infection time was significantly associated with a greater degree of reduction in the area of necrosis. The count of trophozoites identified by immunohistochemical reaction was not affected by the infection associated with obesity. The results of the expression of the cytokines demonstrate that Il6 was reduced in the obese groups even infected, Tgfb1 showed a reduction in the levels of expression in the infected obese animals, Tnf presented with greater expression in the infected obese animals and, however, less in relation to the group control. MPO activity was significantly higher in the liver of INFOB11d animals compared to INFCT11d animals. Therefore, based on the findings, the present study concludes that the association of obesity and amoebic liver abscess for a longer period of infection, favored the host when, evidently, it reduced the severity of the injury caused by the parasite E. histolytica.